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  • 1995-1999  (1.265)
  • 1995  (1.265)
  • Engineering General  (737)
  • Atomic, Molecular and Optical Physics  (370)
  • crystal structure  (158)
  • Nuclear reactions
Datenquelle
Materialart
Erscheinungszeitraum
  • 1995-1999  (1.265)
Jahr
Schlagwörter
  • 1
    Digitale Medien
    Digitale Medien
    α-Iminohydroxylamine-α-aminonitrone tautomerism: a 1∶1 mixture of two tautomeric forms in crystals of N-(4,5-dihydro-1H-imidazol-2-yl)-N-phenyl-hydroxylamine (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 813-821 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Tautomerism ; hydrogen bonding ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Crystals consisting of two distinct chemical entities, tautomers of each other, in exact 1∶1 ratio, have been obtained and their structure determined by X-ray analysis. The crystals of C9H11N3·C9H11N3 are monoclinic,P21/c,a=15.674(3),b=17.085(3),c=13.758(3)Å, β=90.78(2)°,Z=8. There are two hydroxylamine and two aminonitrone molecules in the asymmetric unit. Hydrogen bonds connect those molecules into chiral layers. Layers of opposite chirality alternate andthe crystal is centrosymmetric as a whole. Within those layers chains of tautomers joined by very strong O−H... O and strong N−H... N bonds can be recognized. Proton transfer along those chains with simultaneous rearrangement of π-bonds within the molecules would result in interconversion of tautomers and would affect chirality of the layer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01671076
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  • 2
    Digitale Medien
    Digitale Medien
    Dialkylimidazolium-sodium chloroaluminate ternary salt system: phase diagram and crystal structure (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 57-62 
    Details
    ISSN: 1572-8854
    Schlagwort(e): phase diagram ; buffered chloroaluminate ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The phase diagram of the buffered neutral aluminum chloride + 1-ethyl-3-methyl-1H-imidazolium chloride + sodium chloride (AlCl3-EMIC-NaCl) ternary melt system can be represented by a binary phase diagram composed of (EMI)AlCl4 and NaAlCl4. In the binary phase diagram, the salts are liquid at, or near, room temperature for a wide range of compositions. At the 1∶1 composition, the congruently melting compound (EMI)(Na)(AlCl4)2 with m.p.=36.7°C is formed. Crystals of this mixed organic-inorganic salt were grown for single crystal x-ray diffraction analysis. The compound crystalizes in the space group $$P\bar 1$$ with lattice parametersa=10.321(1) Å,b=10.895(3) Å,c=9.284(4) Å, α=98.31(2)°, β=100.83(4)°, γ=101.95(3)°. Data collected at −120°C gave final residuals ofR=0.037 andR w=0.045 using 2713 observed reflections. The packing diagram reveals Na+ ion zig-zag chains running along thea-axis with each Na+ surrounded by four AlCl 4 − units, reminiscent of NaAlCl4. The AlCl 4 − ions form a distorted square planar coordination sphere around Na+ at an average Na−Al distance of 3.76(4) Å. Using a sodium ionic radius of 1.16 Å, a new AlCl 4 − ionic radius of 2.60 Å is calculated. This radius is 0.21 Å shorter than the reported thermodynamic radius.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01667037
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  • 3
    Digitale Medien
    Digitale Medien
    Antifungal copyrine alkaloids: crystal structure of 3-methylsampangine (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 223-226 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Antifungal alkaloids ; 3-methylsampangine ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract 3-Methylsampangine, C16H10N2O, crystallizes in the monoclinic space group P21/c witha=7.260(3),b=10.697(5),c=15.342(6) Å, and β=102.69(4). All nonhydrogen atoms of this potent antifungal agent are planar to within 0.082 Å. The title compound exhibits potentin vitro antifungal activity againstC. neoformans, C. albicans andA. fumigatus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665173
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  • 4
    Digitale Medien
    Digitale Medien
    Crystal structure of decacalcium tetrapotassium hexakis (pyrophosphate) nonahydrate (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 219-222 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Calcium phosphate ; calcium pyrophosphate ; calcium potassium pyrophosphate ; crystal structure ; layer-type structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The crystal structure of Ca10K4(P2O7)6·9H2O has been determined by single crystal X-ray diffraction. Crystals are hexagonal, space group P63cm witha=11.761(1),c=9.770(1) Å, andZ=1. The structure was refined toR=0.028 andR w=0.037 for 468 reflections withI≥3σ(I). The structure consists of a compact assembly of Ca and P2O7 ions arranged in layers perpendicular to thec-axis in a hexagonal array with relatively large open channels along thec-axis. The K ions and the water molecules are located in these open channels and are disordered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665172
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  • 5
    Digitale Medien
    Digitale Medien
    Unusual occurrence of photooxidation of a cage diol (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 295-298 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Cage-diol ; crystal structure ; photooxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract An unusual photooxidation was noted upon photolytic cage closure of a substituted tricyclo[6.2.1.02.7]undecane-exo, exo-diol. The resultant compound, which may be regarded as a mono-reduced pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione, was characterizedvia X-ray crystallography. This species could be reduced to the tricyclo[6.2.1.02,7]undecane-endo, exo-diol under conditions previously shown to be inert for the parent dione.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01796053
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  • 6
    Digitale Medien
    Digitale Medien
    Crystal and molecular structure of 6,7-benzo-3,4 (1,4-dimethoxy-2,3-naphtho)-1,5-dioxosuberane (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 379-382 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Benzonaphthodioxosuberane ; crystal structure ; radermachol
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The crystal and molecular structure of the title compound (2) C21H16O4 has been determined by an X-ray analysis, by direct methods from diffractometer data and refined by full-matrix least squares. The compound (2) crystallizes in the space group P21/a, with cell parameters:a=36.432(5),b=5.512(3),c=8.269(5) Å, β=108.0(3)°,z=4,D c =1.397 g/cm−3,R=7.8 for 1136 observed reflections. The conformation of the tetracyclic ring system shows a folding of two planar parts of the carbon skeleton about an axis passing thorough C8 and C16 of the seven membered ring C.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665273
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  • 7
    Digitale Medien
    Digitale Medien
    Synthesis and structural characterization of [Au2Pd14(μ3-CO)7(μ2-CO)2(PMe3)11](PF6)2—An icosahedrally-based high nuclearity mixed metal cluster (1995)
    Springer
    Journal of cluster science 6 (1995), S. 71-91 
    Details
    ISSN: 1572-8862
    Schlagwort(e): Palladium ; gold ; cluster ; phosphine ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract [Au2Pd14(μ3-CO)7(μ2-CO)2(PMe3)11](PF6)2 has been synthesized from [Pd8(CO)8(PMe3)7] and AuCl(PCy3) in the presence of TIPF6. It has been characterised on the basis of mass spectrometry, infrared and NMR spectroscopy, and a single crystal X-ray diffraction study. The structure is based on a palladium-centered Au2Pd11 icosahedron which shares an edge with a Pd5 trigonal bipyramid.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01175837
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  • 8
    Digitale Medien
    Digitale Medien
    The synthesis and reactivity of the heptanuclear dianion [Os7(CO)20]2− including the synthesis and structural characterizations of the compounds [Os7(CO)20(AuPEt)3 2] and [Os8(CO)20(η6-C6H6] (1995)
    Springer
    Journal of cluster science 6 (1995), S. 163-173 
    Details
    ISSN: 1572-8862
    Schlagwort(e): Cluster carbonyl ; osmium ; gold ; arene ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Reduction of the heptaosmium cluster [Os7(CO)21] With [Et4N][NH4) gives the cluster dianion [Os7(CO)20]2−,1, in high yield. The reaction of the dianion with [AuPR 3Cl] (R=Et or Ph) in the presence of TlPF6 forms [Os7((CO)20(AuPR 3)2] [R=Et (2a);R = Ph(2b)] in 80% yield, while the corresponding reaction with (Os(C6H6)(CH3CN)3]2+ gives [Os8(CO)20 (η 6-C6H6)] (3) in reasonable yield (ca. 30%). The dianion,1, and the clusters2 and3 have been fully characterized by bout spectroscopic and crystallographic methods. The crystal structure of the [Ph4P]+ salt of1 shows that the metals in the anion adopt a capped octahedral geometry, with all twenty carbonyl ligands in terminal sites. The metal core geometry in2a is best described as a tricapped octahedron, and is based on the structure of the dianion1 with two adjacent octahedral faces capped by the Au atoms of the two AuPEt3 groups. In a similar fashion, the geometry of3 is related to that of1 with the addition of an Os(C6H6) unit capped to a triangular face, to give a bicapped octahedral framework.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01175843
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  • 9
    Digitale Medien
    Digitale Medien
    Synthesis and characterization of the undecaosmium carbido carbonyl cluster: Crystal and molecular structures of [N(PPh3)2][Os11C(CO)27(μ-Cl)] (1995)
    Springer
    Journal of cluster science 6 (1995), S. 343-346 
    Details
    ISSN: 1572-8862
    Schlagwort(e): Undecaosmium carbido cluster ; µ-bridged chlorol preparation ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A chloro-derivative of undecaosmium carbido cluster [Os11C(CO)27(µ-Cl)]-1 anion has been prepared and fully characterized by spectroscopic and crystallographic methods. The structure1 is an important intermediate for the conversion of [Os11C(CO)27]2 2 dianion to [OS10C(CO)24]2-3 dianion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01169700
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  • 10
    Digitale Medien
    Digitale Medien
    Synthesis, chemical, and electrochemical characterization of the [Ag13{μ3-Fe(CO)4}] n− (n = 3, 4, 5) cluster anions: X-Ray structural determination of [N(PPh3)2]3 [Ag12(μ12-Ag){μ3Fe(CO)4}8]1 (1995)
    Springer
    Journal of cluster science 6 (1995), S. 107-123 
    Details
    ISSN: 1572-8862
    Schlagwort(e): Silver ; iron ; carbonyl ; cluster ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The oxidation of the [Fe(CO)4]2− dianion with Ag+ salts occurs through a particularinner-sphere mechanism, which involves an intermediate cascade of silver clusters stabilized by Fe(CO)4 ligands. The last detectable Ag-Fe cluster of the sequence is the [Ag13{μ-Fe(CO)4}8]3− trianion, which has been selectively obtained by using ca. 1.7 equivalents of Ag+ per mole of [Fe(CO)4]2−. The [Ag13{μ-Fe(CO)4}8]3−- trianion has been isolated in a crystalline state with several quaternary cations, and has been characterized by X-ray diffraction studies of its bis(triphenylphosphine)iminium salt. [N(PPh3)2]3 [Ag13{μ 3-Fe(CO)4}8]·2(CH3)2CO, monoclinic, space group P21 (No.4),a = 16.284(2) Å,b =18.767(5) Å,c = 25.905(4) Å,β = 90.46(1)°,V = 7916(3) Å3,Z = 2,R = 0.0324. The molecular structure of the anion consists of a centered cuboctahedron of silver atoms with the triangular faces capped by Fe(CO)4 units. Chemical reduction of ( Ag13{μ 3-Fe(CO)4}8]3− affords the corresponding [Ag13{μ 3-Fe(CO)4)8]4−, which in turn gives [Ag13{μ 3-Fe(CO)4)8]5− and [Ag6{μ 3-Fe(CO)4}4]– upon further reduction. Electrochemical investigations confirm the reversibility of the [Ag13{μ 3-Fe(CO)4}8]3−/4− redox change. Furthermore, in spite of some electrode poisoning effects, evidence of the existence of the [Ag13{μ 3-Fe(CO)4}8]5− pentaanion was obtained. The yet structurally uncharacterized [Ag6{μ 3-Fe(CO)4)4]2− dianion is quantitatively obtained by reaction of [Fe(CO)4]2− with ca. 1.5 equivalents of Ag+ or by addition of one equivalent of Ag+ to solutions of the [Ag5{Fe(CO)4}4]3− trianion. All attempts to isolate its quaternary salts as crystalline materials failed owing to formation of amorphous insoluble precipitates. The above series ofμ 3-Fe(CO)4 octa-capped cuboctahedral Ag13 clusters can be envisioned as the Ag+ . Ag and Ag− cryptates of the [Ag12{μ}3-Fe(CO)4}8]4− cryptand. respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01175839
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  • 11
    Digitale Medien
    Digitale Medien
    The synthesis and structural characterization of Os3(CO)8[Si(OMe)3][μ-PMe2(C6H4](μ-H)2: An unusual unsaturated triosmium cluster complex (1995)
    Springer
    Journal of cluster science 6 (1995), S. 437-447 
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    ISSN: 1572-8862
    Schlagwort(e): Osmium ; unsaturated cluster ; ortho-metallation ; siloxyl ligand ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The reaction of Os3(CO)10(NCMe)[Si(OMe)3](μ-H),1, with PMe2Ph yielded the new complex Os3(CO)10(PMe2Ph)[Si(OMe)3](μ-H),2 by substitution of the MeCn ligand with the phosphine ligand. When heated to 125°C compound2 was decarbonylated and transformed into the new unsaturated cluster complex Os3(CO)8[μ-PMe2(C6H4)][Si(OMe)3](μ-H)2,3 in 54% yield. Compound3 was characterized by a single crystal X-ray diffraction analysis, osmium bonds. The phenyl ring of the phosphine ligand has undergoneortho-metallation by a neighboring metal atom. A terminally coordinated Si(OMe)3 ligand is coordinated to the third osmium atom. The cluster is unsaturated by the amount of 2 electrons, and there is an open coordination site on the siloxyl substituted osmium atom that is partially filled by a weak interaction with one of the π-bonds of theortho-metalled phenyl ring. Complex3 reacts with CO at 1 atm to reform compound2 in 85% yield in 5 h at 40°C. Crystal Data: for3: space group = P21/n,a = 9.911(2) Å,b = 18.451(6) Å,c = 14.872(2) Å,β = 95.64(2)°,Z = 4, 1994 reflections,R = 0.028.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01165472
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  • 12
    Digitale Medien
    Digitale Medien
    Doubly-bridged binuclear complexes of oxomolybdenum(V) and oxotungsten(V) containing sexadentate ligands (1995)
    Springer
    Journal of cluster science 6 (1995), S. 549-566 
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    ISSN: 1572-8862
    Schlagwort(e): Molybdenum ; tungsten ; di-μ-oxo bridge ; sexadentate ligands ; asymmetric distortion ; stereoselectivity ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Binuclear oxomolybdenum(V) and oxotungsten(V) complexes of the type, [M 2(O)2(μ-X)(μ-X 1)]”, where M=Mo, W;X.X 1=O, S; L=edta, pdta (n=2-), tpen, tppn (n=2+) (edta4– =ethylenediaminetetraacetate(4–), pdta=R- orR,S-propylenediaminetetraacetate(4–), tpen=N,N,N 1,N1-tetrakis(2-pyridyhnethyl)-ethylenediamine, and tppn=R- orR,S-N,N,N 1,N1-tetrakis(2-pyridylmethyl)-propylenediami ne) are reviewed with respect to their preparation, structure, spectroscopic properties, reactivities, and in particular asymmetric distortion around the bicyclo [4.1.1 ] type core and stereoselectivity related to this distortion,
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01165773
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  • 13
    Digitale Medien
    Digitale Medien
    Comparison of the crystal structure and molecular models of N,N-diisobutyl-2-(octylphenylphosphinyl)acetamide (CMPO) (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 43-49 
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    ISSN: 1572-8854
    Schlagwort(e): Molecular mechanics ; molecular dynamics ; MNDO ; CMPO ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The crystal structure of N,N-diisobutyl-2-(octylphenylphosphinyl)acetamide, or CMPO was recently determined. The compound crystallizes in the space group P21/c witha=13.446(6),b=22.280(7),c=17.217(7) Å, β=92.07(4)°, andD calc=1.05 g/cm3 forZ=8 @20°C). Molecular mechanics, molecular dynamics, and MNDO calculations were also performed on CMPO utilizing the SYBYL1 suite of programs. The results from these calculations are compared to the crystal structure and to similar calculations performed on CMPO using ALCHEMY2,3. In general, the results from the calculations agree fairly well with the parameters from the crystal structure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01666193
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  • 14
    Digitale Medien
    Digitale Medien
    Mercury(II) complex with terpyridine: structure of the 2∶1 solvate of [Hg(terpy)2](CF3SO3)2 with acetone (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 453-458 
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    ISSN: 1572-8854
    Schlagwort(e): Mercury(II) terpyridine complex ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract [Hg(terpy)2](CF3SO3)2·0.5(CH3)2CO crystallizes in the triclinic $$P\bar 1$$ space group witha=14.631(6),b=15.258(4),c=18.785(7) Å, α=69.66(2), β=70.72(1), γ=88.55(1)°. The crystal structure consists of two independent [Hg(terpy)2]2+ cations, four trifluoromethanesulfonate anions and an acetone molecule in the asymmetric unit. Each mercury atom is coordinated by two tridentate terpyridine ligands forming an irregular six-coordination polyhedron. The Hg−N bond lengths range from 2.27(2) to 2.53(2) Å.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665700
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  • 15
    Digitale Medien
    Digitale Medien
    Crystal structures of twoN-substituted 2-thioxo-1,3-dithiole-4-carboxamides (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 463-467 
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    ISSN: 1572-8854
    Schlagwort(e): 1,3-dithiole-4-carboxamides ; resonance effect ; short intramolecular S...O contact ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The two closely related compoundsN,N-dimethyl 5-(methylthio)-2-thioxo-1,3-dithiole-4-carboxamide1 andN-(p-methoxy-phenyl)-N-methyl 5-(methylthio)-2-thioxo-1,3-dithiole-4-carboxamide2 have been characterized by X-ray crystal structure determination. Crystal data for1: triclinic, $$P\bar 1$$ ,a=6.767(1),b=12.594(2),c=6.648(1) Å, α=101.38(1), β=93.37(2), γ=79.62(1)°,V=546.2 Å3,Z=2. Crystal data for2: monoclinic, Cc,a=19.836(4),b=6.057(1),c=15.860(3) Å, β=127.61(3)°,V=1509.5Å3,Z=4. The molecular structures of1 and2 show remarkable differences concerning the conformational behavior. These differences are related to the nature of the substituents at the nitrogen atom. The presence of an aromatic system in2 leads to an almost planar arrangement of the α-oxoketene dithioacetal moiety. This effect is accompanied by a short intramolecular S...O contact of 2.648(2) Å. In the absence of an aromatic system, as is the case for compound1, neither a resonance effect along the α-oxoketene dithioacetal fragment nor a short S...O distance is observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665702
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  • 16
    Digitale Medien
    Digitale Medien
    The crystal structure of a heterobimetallic crown ether complex: [Na(dibenzo-18-crown-6)][FeCl4] (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 579-582 
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    ISSN: 1572-8854
    Schlagwort(e): Dibenzo-18-crown-6 ; hetero bimetallic ; crown ether ; crystal structure ; ferric chloride
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Slow evaporation of a solution of ferric chloride and dibenzo-18-crown-6 in 3∶1 CH3CN∶CH3OH produced single crystals of the title complex. This heterobimetallic crown ether complex, [Na(dibenzo-18-crown-6)][FeCl4], crystallizes in the monoclinic space group P2t/n with cell parameters (at 22°C)a=14.608(6),b=10.466(9),c=17.276(9)Å, β=91.47(6)°, andD calc=1.46 g cm−3 for Z=4. The structure consists of discrete ions with the shortest Na ... Cl distance a lengthy contact of 3.56(1)Å. The average Na...O separation is 2.69(3)Å. The [FeCl4]− anion exhibits a distorted tetrahedral geometry with an average Fe−Cl bond length of 2.16(2)Å.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01667027
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  • 17
    Digitale Medien
    Digitale Medien
    Nucleophilic additions of primary and secondary amines to pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 633-640 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Amines ; crystal structure ; pentacycloundecane-8,11-dione
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The crystal structures of three compounds formedvia nucleophilic attack of a heterocyclic secondary amine on PCU-8,11-dione, with the concomitant intramolecular attack of one keto oxygen on the carbon of the other ketone, are presented. In all three compounds, the bridging oxygen contains substantial p-character, and the bonds to the “attacking” nitrogen are significantly shorter than would be expected.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665969
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  • 18
    Digitale Medien
    Digitale Medien
    X-ray structure of sesterterpene, 16β-acetoxy-24-methyl-12,24-dioxoscalaran-25-al (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 765-768 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Sesterterpene ; scalaran ; crystal structure ; marine compound
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The molecular geometry of a tetracyclic sesterterpene has been determined by X-ray diffraction. The conformation of the aldehyde group as observed in the crystal structure supports the rationalization for the absence of aldehyde proton coupling in the nmr spectra of the compound. Crystal data: C28H42O5, M.W.=458.6; orthorhombic, P212121;a=10.797(2),b=29.270(9),c=8.033(1)Å,V=2538.7Å3,Dx=1.199 g cm−3;R=0.045 for 2287 observed reflections.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01670333
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  • 19
    Digitale Medien
    Digitale Medien
    Synthesis of a chiral calixarene: 5,11,17,23-tetra (tert-butyl)-25,27-bis[((+)-camphor-10-sulfonyl)-oxy]-calix[4]arene-26,28-diol: crystal and molecular structure of its (1∶2) complex with toluene (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 401-406 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Calixarene ; complex ; crystal structure ; chirality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The title compound was obtained by treatment ofp-tert-butylcalix[4]arene with (+) camphorsulfonyl chloride in triethylamine and toluene. A (1∶2) complex with toluene has been found. Its structure has been determined by X-ray crystallography. Crystals are triclinic with space group P1,a=16.426(3),b=18.553(3),c=13.661(2) Å, α=94.78(2), β=110.76(2), γ=72.83(2)°,V=3720(2) Å3,d c =1.127 g/cm3 Z=2. Refinement based on 10495 observed reflections led to a finalR value of 0.100. The two independent molecules of calixarene in the asymmetric unit are in the cone conformation and the calixarene cavities are empty. The guest molecule occupies the interhost space. The norborane skelton of (+) camphorsulfonyl group is the same as ones found in literature. Only van der Waals interactions exist between the host and the guest molecules.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665277
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  • 20
    Digitale Medien
    Digitale Medien
    Synthesis and structure of a seven electron triangular cluster complex [Mo3S4Cl3(dppe)2(PEt3] (1995)
    Springer
    Journal of cluster science 6 (1995), S. 523-532 
    Details
    ISSN: 1572-8862
    Schlagwort(e): Molybdenum ; reduction ; seven-electron triangular cluster ; bridging sulfide ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The triangular six-electron cluster complex [Mo3S4Cl4(PEt3) x (thf)5] produced by the excision reaction of Mo3S7Cl4 with triethypholsphine is reduced by magnesium at − 20°C. Subsequent addition of dppe (=1,2-his(diphenylphosphino)ethane) to the reduced species affords a seven-electron triangular cluster complex [Mo3S4Cl3(dppe)2(PEt3)]. The complex crystallizes in the space groupCm witha=17.170(6),b-19.878(6),c = 13.289(5)β = 121.73(2)°,V = 3858(2) A3, andZ = 2. The structure shows an almost equilateral triangle of three molybdenum atoms capped by a Sulfur atom and bridged by three sulfur atoms. The Mo Mo distances, ranging from 2.804(1) to 2.809(1) A are elongated ca. 0.04 A as compared with lose of a six-electron cluster complex with drape ligands. Two molybdenum atoms have a chlorine and a dppe ligands, and the other molybdenum atom bas a chlorine and a triethylphosphine ligands. The UV-Vis spectrum has a characteristic broad hand centered at 1410 n m, which is not observed for six-electron clusters. The ESR spectrum indicates the presence of an unpaired electron consistent with the formulation of the compound as a seven-electron cluster.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01165771
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  • 21
    Digitale Medien
    Digitale Medien
    Linear and Nonlinear Optical Properties Of Racemic (±)2-(α-Methylbenzylamino)-5-Nitropyridine Single Crystals (1995)
    Springer
    Optical review 2 (1995), S. 128-131 
    Details
    ISSN: 1349-9432
    Schlagwort(e): organic crystal ; racemic form ; second-harmonic generation ; refractive index ; nonlinear optical coefficient ; crystal structure ; oriented-gas model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Linear and nonlinear optical properties of racemic (±)2-(α-methylbenzylamino)-5-nitropyridine ((±)MBANP) single crystals have been comprehensively investigated and compared with those of the enantiomorph (–)2-(α-methylbenzylamino)-5-nitropyridine ((–)MBANP) crystals. (±)MBANP crystal exhibits very high chemical and physical stability, but relatively small nonlinear optical coefficients (d31 = 6.8 pm/V, d32 = 4.7 pm/V, d33 = 0.84 pm/V). A comparison between the nonlinear optical coefficients of (±)MBANP and (–)MBANP demonstrates the validity of the oriented-gas model in molecular crystals that neglects all the contributions from intermolecular interaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s10043-995-0128-5
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  • 22
    Digitale Medien
    Digitale Medien
    The synthesis and X-Ray crystallographic analysis of a stable norbornadienone: 17-Oxo-7,16-methano-7,16-diphenylcyclopenta[d,e]tribenzo[a,h,j]anthracene (1995)
    Springer
    Structural chemistry 6 (1995), S. 167-173 
    Details
    ISSN: 1572-9001
    Schlagwort(e): MM3 ; PM3 ; MMX ; crystal structure ; norbonadienone ; distorted compound
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The reaction of 4,5-didehydroacenaphthene with phencyclone yields the title compound, a stable dibenzo-fused norbornadienone (8). The X-ray structure of8 is presented and compared with the structure predicted from a MM3, PM3, and a MMX calculation. Thermal decomposition of 8 produces, 7,16-diphenylcyclopenta[d,e]tribenzo[a,h,j]anthracene (9), a hydrocarbon that is computed to have a significantly twisted polycyclic aromatic skeleton with 19 kcal/mole of strain energy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02286444
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  • 23
    Digitale Medien
    Digitale Medien
    Molecular Structure of 5-Methylchrysene-7,8-dihydro-7,8-trans-(e, e)-diol (1995)
    Springer
    Structural chemistry 6 (1995), S. 57-63 
    Details
    ISSN: 1572-9001
    Schlagwort(e): Hydrogen bonding ; carcinogen ; polycyclic aromatic hydrocarbon derivative ; dihydrodiol ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The crystal structure of the weak carcinogen 5-methylchrysene-7,8-dihydro-7,8-trans-(e,e)-diol is reported. This molecule contains a distorted bay region as a result of the presence of the 5-methyl group as found in 5-methylchrysene and 5,6- and 5, 12-dimethylchrysene. One torsion angle in this bay region is 20
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02263528
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  • 24
    Digitale Medien
    Digitale Medien
    Synthesis and structure of 13- and 26-membered crown ethers, derivatives of resorcinol (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 2353-2360 
    Details
    ISSN: 1573-9171
    Schlagwort(e): resorcinol-based crown ethers ; crystal structure ; intramolecular nonbonded C-H...O contacts
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract 13- and 26-Membered crown ethers have been synthesized based on resorcinol and 1,8-dichloro-3,6-dioxaoctane. The products with substituents in the benzene ring have been prepared by alkylation of 13-membered crown ether. Complexing properties of the macrocycles have been studied with the use of ion-selective membrane electrodes. The structures of 13- and 26-membered crown ethers have been established by X-ray structural analysis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00713607
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  • 25
    Digitale Medien
    Digitale Medien
    Oxidation of 1-hydrazino-3,3-dimethyl-3,4-dihydroisoquinoline. X-ray, spectroscopic, and quantum-chemical study of the structure of 3,3-dimethyl-3,4-dihydroisocarbostyryl azine (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 2364-2370 
    Details
    ISSN: 1573-9171
    Schlagwort(e): dihydroisoquinoline derivatives ; crystal structure ; electronic, IR, and1H NMR spectra ; quantum-chemical calculation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract 3,3-Dimethyl-3,4-dihydroisocarbostyryl azine (2) has been synthesized by oxidation of l-hydrazino-3,3-dimethyl-3,4-dihydroisoquinoline (1). The crystal and molecular structures of compound 2 were determined. It has been established that in the solid state, compound2 exists as an azine tautomer. The IR, electronic, and NMR spectral data indicate that in solution the tautomeric form of2 does not change. A possible mechanism of the oxidation of1 to2 is suggested.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00713609
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  • 26
    Digitale Medien
    Digitale Medien
    Crystal Structure of 2-Debenzoyl, 2-Acetoxy Paclitaxel (Taxol®): Conformation of the Paclitaxel Side-Chain (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 337-341 
    Details
    ISSN: 1573-904X
    Schlagwort(e): 2-debenzoyl, 2-acetoxy paclitaxel ; docetaxel ; paclitaxel side-chain ; crystal structure ; solid state conformation ; intramolecular hydrogen bonding ; intermolecular hydrogen bonding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Crystals of the C2-acetate analog of paclitaxel, grown from a mixture of isopropyl alcohol and methanol, belong to the space group P2l with a = 9.058(3), b = 18.306(5), c = 15.043(1) Å, β = 97.09(1)°, Z = 2, V = 2475.1(9)Å3, D calc = 1.269 gcm−3 and µ = 0.75 cm−1. The structure was determined by direct methods and refined to R(F) = 0.054 and wR(F) = 0.057 for 605 variables and 3496 observed reflections. The paclitaxel side chain possesses a conformation similar to that observed in the crystal structure of docetaxel (Taxotere®). A three dimensional network of hydrogen bonds is formed through solvent molecules and stabilizes the crystal lattice.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1016236014766
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  • 27
    Digitale Medien
    Digitale Medien
    Structure ofp-tetrakis-(4-nitrophenylazo)calix[4]-arene-4-picoline (1∶4) complex (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 22 (1995), S. 33-40 
    Details
    ISSN: 1573-1111
    Schlagwort(e): Calixarene-dye ; crystal structure ; inclusion compound
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The structure of thep-tetrakis-(4-nitrophenylazo)calix[4]arene-4-picoline (1∶4) complex has been determined by X-ray crystallography. Crystals are monoclinic, space groupC2/c,a=24.9097) Å,b=8.425(6) Å,c=33.81(1) Å, β=101.13(2)°,D c =1.330 g/cm3,Z=4, finalR value =0.067. The cone conformation adopted by this azocalixarene is disturbed by the positions of the picoline molecules. Two of them are inside the macorocycle cavity and the two others are outside.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00706496
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  • 28
    Digitale Medien
    Digitale Medien
    New synthesis and complexing properties ofp-tert-butyldihomooxacalix[4]arene. Structure of its 1∶2 complex with tetrahydrofuran (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 22 (1995), S. 119-130 
    Details
    ISSN: 1573-1111
    Schlagwort(e): Calixarene ; complexation ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A new method is described for the synthesis of isolatedp-tert-butyldihomooxacalix[4]arene (CALO) with a 24% yield. The ability of CALO to form complexes in the solid state with small neutral molecules has been studied; the potential guests were common solvents bearing various chemical functions. The powder obtained after evaporation of the solvent has been characterized by the X-ray powder diffraction technique. Analysis of the patterns shows the non-complexation of linear alkanes and alcohols, but formation of complexes when the guest is cyclic or when it bears an amine or a ketone function. As illustration of the possible arrangement of molecules in complexes, the structure of the 1:2 complex with tetrahydrofuran (THF) is presented: the crystals are monoclinic, space groupP21/c,a=9.459(2) Å,b=17.286(2) Å,c=30.469(6) Å, β=92.52(2)o,V=4977(2) Å3,Z=4,D c=1.099 Mg m−3, λ=1.54178 Å, μ=5.6 cm−1,R=0.086 for 3590 reflections withF〉4σ (F); one of the THF molecules is inside the cavity of the macrocycle, while the other, in the interhost space, exhibits disorder. In the CALO molecule, three out of the fourtert-butyl groups are disordered which may induce the disorder of the THF molecule.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00707687
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  • 29
    Digitale Medien
    Digitale Medien
    Inclusion compounds of (±) gossypol. Structure of the gossypol-n-valeric acid (1/2) coordinato-clathrate (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 22 (1995), S. 187-201 
    Details
    ISSN: 1573-1111
    Schlagwort(e): Inclusion compounds ; gossypol ; crystal structure ; hydrogen bonds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The crystal structure of the inclusion compound of gossypol withn-valeric acid as a guest molecule has been determined by X-ray structure analysis. The crystals of C30H30O8·(C5H10O2)2, are triclinic, space group $$P\bar 1$$ ,a=6.912(2),b=14.506(3),c=19.387(4) Å, α=78.85(2)°, β=83.92(3)°, γ=86.78(3)°V=1895(1) Å3,Z=2,D x=1.267 g cm−3, μ (CuK α)=0.768 mm−1,T=292 K. The structure has been solved by direct methods on intensity data collected for a twinned crystal and refined to the finalR value of 0.062 for 1606 observed reflections and 470 refined parameters. Gossypol-n-valeric acid (1/2) coordinato-clathrate is not isostructural with any of the previously investigated gossypol inclusion compounds but shows some structural similarities to gossypol-acetic acid (1/1). The host and one of the carboxylic acid molecules are connected via hydrogen bonds into molecular assemblies of a column type which are further bonded to centrosymmetric dimers of the secondn-valeric acid molecule. In effect, host and guest molecules are assembled into layer-type H-bonded aggregates. Structural features common to gossypol-n-valeric acid (1/2) and other earlier reported gossypol inclusion compounds are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00707082
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  • 30
    Digitale Medien
    Digitale Medien
    Lattice dynamics of (Ba/K)BiO3 (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 595-598 
    Details
    ISSN: 1572-9605
    Schlagwort(e): (Ba/K)BiO3 ; lattice dynamics ; electron phonon coupling ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract The Lattice dynamics of Ba.6K.4BiO3 was investigated by inelastic neutron scattering on a superconducting single crystal (T c =26 K (midpoint)). At low frequencies the dispersion curves are very similar to those observed in BaPb.75Bi.25O3. Differences were found in the bond bending vibrations of the BiO6 octahedra which indicate that the binding in the K-doped compound is more ionic. Rather anomalous features were observed in the high frequency Bi-O bond stretching vibrations which resemble those observed in the high T c cuprates La1.85Sr.15CuO4 and YBa2Cu3O7. The observed frequency shifts are interpreted as the consequence from a strong electron phonon coupling. The data are compared to the results obtained on non superconducting Ba.98K.02BiO3.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00727434
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  • 31
    Digitale Medien
    Digitale Medien
    Binding geometry of α-helices that recognize DNA (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 525-535 
    Details
    ISSN: 0887-3585
    Schlagwort(e): DNA-protein interaction ; crystal structure ; transcription factor ; gene regulation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Many transcription factors have an α-helix that binds to DNA bases in a specific fashion. The DNA-binding geometry of these recognition helices varies substantially. We define a set of parameters to describe the binding geometry of recognition helices and analyze specific stereochemical elements that determine particular geometries. Because the convex surface of the helix must fit into the concave surface of the DNA major groove, the number of degrees of freedom of the recognition helix is reduced from a possible six to a single angle, which we call α. The chemically interacting DNA bases and amino acid residues must lie along a common line and have the same spacing along it. This pairing of base positions with residue positions seems to restrict the binding geometry further to a set of discrete values for α. © 1995 Wiley-Liss, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.340230407
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  • 32
    Digitale Medien
    Digitale Medien
    Effect of Humidity-Dependent Changes in Crystal Structure on the Solid-State Fluorescence Properties of a New HMG-CoA Reductase Inhibitor (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 556-559 
    Details
    ISSN: 1573-904X
    Schlagwort(e): HMG-CoA reductase inhibitor ; SQ-33600 ; crystal structure ; hydrates ; solid-state fluorescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract It has been shown previously that the disodium salt of a new HMG-CoA reductase inhibitor (SQ-33600) is capable of existing as a number of hydrate species [1]. Three crystalline solid hydrates and one liquid crystalline phase have been identified, each having a definite stability over a defined range of humidity. These forms have been found to exhibit varying fluorescence properties in their respective solid states, with differences in bandshapes and intensities being noted for each. These spectral variations have been correlated with the known pseudopolymorphism of the compound.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1016206130213
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  • 33
    Digitale Medien
    Digitale Medien
    The 7.25-hydrate oftert-butylamine. A semi-clathrate and complex variant of the cubic 12 Å structure type (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 22 (1995), S. 145-154 
    Details
    ISSN: 1573-1111
    Schlagwort(e): tert-Butylamine 7.25 H2O ; amine hydrate ; semi-clathrate ; clathrate hydrate ; hydrate ; hydrogen bonding ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Of the various hydrates oftert-butylamine, the title compound has been identified as the second-highest, melting incongruently at −19°C. Its crystal structure (orthorhombic, space groupPca21,Z=32 formula units per unit cell,a=24.80,b=16.440,c=25.29 Å) and the exact composition have been determined from X-ray diffraction at −150°C. The hydrate is a rather complex semi-clathrate, with the amine molecules not merely encaged, but also hydrogen-bonded, in a three-dimensional water host structure, which in turn is not fully four-connected. Nevertheless, it bears a clear relationship to the basic and genuine clathrate-hydrate cubic 12 Å type.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00707689
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  • 34
    Digitale Medien
    Digitale Medien
    Crystal structure of supramolecular complexes formed by 18-crown-6 andcis-anti-cis-dicyclohexano-18-crown-6 (host) with 3,4-diaminofurazane (guest) (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 23 (1995), S. 181-193 
    Details
    ISSN: 1573-1111
    Schlagwort(e): 18-crown-6 ; diaminofurazane ; crystal structure ; host-guest complexes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract An X-ray—diffraction study is reported for two molecular complexes containing 3,4-diamino-1,2,5-oxadiazole as guest (G) with 18-crown-6 (18-C-6) andcis-anti-cis-dicyclohexano-18-crown-6 (DCH-6B) as host. Both complexes are of the polymeric-chain structure with the guest molecule bridging two crown neighbours. ComplexI: [18-C-6*G*H2O], 1∶1∶1, monoclinic,P21/n,a=8.171(1),b=15.042(2),c=16.209(6) Å, β=101.15(2)°, finalR-factor 0.068. ComplexII: [DCH-6B*G], 1∶1, monoclinicC2/c,a=21.212(4),b=9.380(2),c=13.049(3) Å, β=108.61(3)°, finalR 0.047.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00709576
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  • 35
    Digitale Medien
    Digitale Medien
    TheO, O′-dibenzoyl derivative of (R, R)-tartaric acid as a host compound for simple organic ethers (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 22 (1995), S. 211-219 
    Details
    ISSN: 1573-1111
    Schlagwort(e): (R, R)-Tartaric acid derivatives ; host-guest compounds ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract TheO, O′-dibenzoyl derivative of (R, R)-tartaric acid shows a good inclusion ability for diethyl and di-n-propol ethers. The two crystalline inclusion compounds have 1:1 stoichiometry and reveal isomorphous structures. Hydrogen bonded host molecules form chains running along thez axis of the unit cell and guest molecules join to these chains by short O−H...O hydrogen bonds. Hydrogen bonding in the crystals is characterized by a C(7)D first-order network. The ether molecules are in a fully extended conformation. They are accommodated in channel-like voids running along thex axis. Atomic displacement parameters are significantly larger for diethyl ether than for the di-n-propyl ether molecule reflecting less dense packing for this inclusion compound.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00707084
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  • 36
    Digitale Medien
    Digitale Medien
    Crystal and molecular structures of binuclear caesium complexes with 1,3-calix[4]-bis-crown-6 and 1,3-calix[4]-bis-benzo-crown-6 (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 23 (1995), S. 305-312 
    Details
    ISSN: 1573-1111
    Schlagwort(e): Bridged calix[4]arene ; caesium complex ; ditopic receptor ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The crystal structures of two binuclear complexes between caesium and 1,3-calix[4]-bis-crowns have been determined. Cs2 Bis-benzoC6(NO3)2. 3CHCl3 (1) in whichBis-benzoC6 is 1,3-calix[4]-bis-benzo-crown-6, crystallizes in the orthorhombic system: space groupPca2 1 a=19.513(10),b=15.382(5),c=23.708(9) Å,V=7116(5) Å3,Z=4. Refinement led to a final conventionalR value of 0.065 for 2321 reflections. The structure of (1) is analogous to those already reported withBis-C6, (in whichBis-C6 is, 1,3-calix[4]-bis-crown-6) and NO 3 − as a counter-ion. Cs2 Bis-C6(NCS)2 (2) crystallizes in the monoclinic system: space, groupC2 a=36.57(2),b=11.47(1),c=13.65(1) Å, β=109.03(5)°.,V=5415(6) Å3,Z=4. Refinement led to a final conventionalR value of 0.063 for 2227 reflections. Compound (2) is made of dimers bridged by a disordered NCS− ion. The crown ether chain conformations are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00707934
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  • 37
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    Digitale Medien
    Analytical solutions of mass transport problems for error estimation of finite/infinite element methods (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 13-23 
    Details
    ISSN: 1069-8299
    Schlagwort(e): mass transport problems ; error estimation ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: In order to make an exact estimation of discretization error for finite/infinite element methods, it is necessary to develop analytical solutions for some transient mass transport problems in infinite media. These transient mass transport problems may be viewed as the benchmark problems for the discretization error estimation of a new numerical method so that they generally have the following characteristics: (1) their initial and boundary conditions can be exactly modelled by the finite/infinite element method; (2) their solutions can be rigorously expressed in a closed form. In this paper, several of the aforementioned problems have been constructed and solved mathematically for transient mass transport problems in both 1D and 2D infinite media.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110104
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  • 38
    Digitale Medien
    Digitale Medien
    Solution of the differential Riccati equation using the transmission line modelling (TLM) technique (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 25-32 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Riccati equation ; transmission line modelling ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: In this communication, the application of the transmission line modelling (TLM) technique to the solution of the differential Riccati equation is described. A comparison is made between the TLM, fourth-order Runge-Kutta and the first-order Gear methods, for the case where one is applying the Kalman filter to the estimation of a voltage in a passive analogue circuit. In the particular example studied, the state equation is second-order. It is found that, when the system is underdamped, the fourth-order Runge-Kutta method has the best performance, followed by the TLM method. When the system is overdamped and stiff, the TLM method yields results that are closest to the analytical solution. Finally, a discussion is presented of the effects of errors in the TLM solution of the Riccati equation on the accuracy of the solution to the continuous Kalman filter estimation equation.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110105
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  • 39
    Digitale Medien
    Digitale Medien
    Influence of contact area on service life of gears with crack in tooth root (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 49-58 
    Details
    ISSN: 1069-8299
    Schlagwort(e): gears ; fracture mechanics ; service life ; fatigue process ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The paper describes the influence of contact area on the service life of dynamically loaded gears with a crack in a tooth root. Numerical results obtained with the finite element method using the program package BERSAFE are compared with the experimental results obtained on the universal testing machine INSTRON 1255. Numerical and experimental results are in good agreement. The analysis shows that the contact area directly influences the speed and direction of the crack propagation and the service life of the gear with a crack in a tooth root.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110108
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  • 40
    Digitale Medien
    Digitale Medien
    Transverse shear correction factors for laminates in cylindrical bending (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 41-47 
    Details
    ISSN: 1069-8299
    Schlagwort(e): shear correction ; laminates ; cylindrical bending hypothesis ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Mindlin-type plate and shell finite elements are the most widely used ones in the analysis of laminated composite structures. In the commercially available finite element programs, the transverse shear correction factors for these elements are usually the same as for structures made of isotropic materials. In the paper the shear correction factors are determined using energy principles for general laminates in cylindrical bending. Results for various materials and laminates are presented.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110107
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  • 41
    Digitale Medien
    Digitale Medien
    A B-spline finite element method for the regularized long wave equation (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 59-68 
    Details
    ISSN: 1069-8299
    Schlagwort(e): RLW equation ; finite elements ; splines ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A B-spline finite element method is used to solve the regularized long wave equation numerically. This approach involves a Galerkin method with quadratic B-spline finite elements so that there is continuity of the dependent variable and its first derivative throughout the solution range. Time integration of the resulting system of ordinary differential equations is effected using a Crank-Nicolson approximation. Standard problems are used to validate the algorithm, which is then used to model the smooth development of an undular bore.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110109
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  • 42
    Digitale Medien
    Digitale Medien
    Modified calculation of the dissipation term in thermoplastic finite element equations (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 69-72 
    Details
    ISSN: 1069-8299
    Schlagwort(e): finite element method ; thermoplasticity ; internal dissipation ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: In the paper, a simple modification of the internal dissipation term in coupled thermoplastic finite element equations is presented. A modified form of the heat capacity and the thermomechanical coupling matrices are derived. These modifications are based on a decomposition of the internal dissipation term into two parts, which depend on the total strain rate and the rate of temperature change, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110110
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  • 43
    Digitale Medien
    Digitale Medien
    Conference diary (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 91-92 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110112
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  • 44
    Digitale Medien
    Digitale Medien
    Announcements (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 93-94 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110113
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  • 45
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    Digitale Medien
    On boundary conditions for unbounded flows (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 179-185 
    Details
    ISSN: 1069-8299
    Schlagwort(e): finite elements ; fluid flow ; open boundaries ; Sommerfield boundary conditions ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: We examine a method to impose boundary conditions on arbitrary boundaries, introduced to make domains of infinite extent finite for the purpose of numerical calculations, when a finite element discretization based on linear, bilinear or trilinear elements is used, in one, two or three dimensions, respectively. In particular, we look at the so-called ‘free’ boundary condition, which consists in retaining the boundary integrals generated by the weighted-residuals formulation along the open boundaries and adding them to the stiffness matrix. We show that this procedure is exactly equivalent to imposing on the boundary nodes a Sommerfeld radiation condition in one dimension, and a slightly modified form of the Sommerfeld boundary condition in two and three dimensions. We also show that the procedure is not applicable to the purely elliptic case.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110211
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  • 46
    Digitale Medien
    Digitale Medien
    Announcements (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 189-190 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110213
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  • 47
    Digitale Medien
    Digitale Medien
    Conference diary (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 187-188 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110212
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  • 48
    Digitale Medien
    Digitale Medien
    Masthead (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995) 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110301
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  • 49
    Digitale Medien
    Digitale Medien
    Structural improvement of planar triangulations: Some constraints and practical issues (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 191-198 
    Details
    ISSN: 1069-8299
    Schlagwort(e): triangulations ; mesh relaxation ; computational geometry ; planar mesh generation ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Recent advances in planar mesh generation of arbitrary domains incorporate methods for placing points as well as connecting them into a triangulation. Postprocessing techniques such as Laplacian smoothing and mesh relaxation enhance the shape of triangles in these meshes but do not address the construction of meshes near boundaries or provide a criterion to determine the number of interior points of the initial triangulation. The paper addresses these issues by investigating the construction of degree-6 triangulations, the primary goal of the mesh relaxation method.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110302
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  • 50
    Digitale Medien
    Digitale Medien
    Distributed finite element structural analysis using the client-server model (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 227-233 
    Details
    ISSN: 1069-8299
    Schlagwort(e): finite element analysis ; distributed computing ; structures ; client-server model ; remote procedure calls ; structural mechanics ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The paper presents a distributed computing approach for concurrent finite element analysis of truss structures. The client-server model of distributed computation is applied to the plane frame finite element algorithm and implemented on SUN workstations. The remote procedure call combined with the ability to create threads of computation allows one to efficiently implement distributed and concurrent programs. The present approach is demonstrated through a typical truss structure to illustrate the details of the implementation. This approach can be used for very large finite element systems.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110305
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  • 51
    Digitale Medien
    Digitale Medien
    Fluid flows around turbomachinery using an explicit pseudo-temporal Euler FEM (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 199-211 
    Details
    ISSN: 1069-8299
    Schlagwort(e): SUPG ; Petrov-Galerkin methods ; finite elements ; explicit scheme ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: This work is devoted to the simulation by finite elements of nearly incompressible inviscid flows in real 3D geometries, by means of an Euler code based on the SUPG (streamline upwind Petrov-Galerkin) method, explicit forward Euler pseudo-temporal time integration and periodic and absorbing boundary conditions, among other features. The main goal is the application to flow around turbomachinery, with special emphasis on the performance analysis of a given machine, that involves several numerical computations at different operation points. Finally, these results are summarized in the form of characteristic curves.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110303
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  • 52
    Digitale Medien
    Digitale Medien
    A posteriori finite element method error estimates for fourth-order problems (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 213-226 
    Details
    ISSN: 1069-8299
    Schlagwort(e): a posteriori error estimates ; asymptotic exactness ; finite elements ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A posteriori error estimation for typical Euler-Bernoulli beam bending problems is developed using a recovery operator based on a smoothing technique that is applied in the context of one-dimensional fourth-order problems. The development exploits a discrete superconvergence property of the ‘bending moments’ of the trial space interpolant of a polynomial solution of sufficiently low degree at certain Gauss points, and the superconvegence property of the energy norm difference of the trial space interpolant (of the weak solution) and the finite element approximation. An asymptotically exact error estimator is developed.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110304
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  • 53
    Digitale Medien
    Digitale Medien
    A superposition method for the solution of crack problems (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 243-254 
    Details
    ISSN: 1069-8299
    Schlagwort(e): fracture ; boundary elements ; superposition ; stress intensity factor ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: We discuss a two-step superposition method for calculating linear elastic stress intensity factors. The procedure requires the solution to the full cracked problem and the solution to a problem on the same mesh assuming the singularity due to a crack tip in an infinite region. We show that this is equivalent to the well known subtraction of singularity method if the two solutions are characterized by crack tip stress. The advantages of our procedure are that no modifications need to be made to a standard computer program and that once one singular solution is available on a given cracked mesh, solutions with different boundary conditions on the same mesh may be obtained in one step without including any singular crack effects. The mesh required to represent the singular crack tip field may also be studied independently of the complete problem. The additional computational cost of a two-step procedure is minimal since the solution matrix from step one may be reused with a new right-hand side. Numerical experiments using the boundary element method demonstrate the high accuracy and simplicity of the superposition approach.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110307
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  • 54
    Digitale Medien
    Digitale Medien
    Selecting upwind parameters for improved iterative performance (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 235-242 
    Details
    ISSN: 1069-8299
    Schlagwort(e): upwinding ; iterative methods ; convection-diffusion ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The effect of upwinding on iterative performance of convection-diffusion problems is investigated. An analysis of the iterative method considered here leads to a criterion for selecting the optimal upwinding parameter to improve iterative performance for a class of two-dimensional convection-diffusion problems. Supporting numerical experiments are presented.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110306
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  • 55
    Digitale Medien
    Digitale Medien
    A numerical solution for dynamic interaction between rigid wheel and flexible beam (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 267-279 
    Details
    ISSN: 1069-8299
    Schlagwort(e): dynamic interaction ; rigid wheel ; flexible beam ; contact force ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: A numerical method is presented for the analysis of dynamic interaction between rigid wheel and flexible beam. In contrast to traditional approaches, the wheel nominal motion as well as the contact force are considered here as unknowns. The correct contact force between the wheel and the beam is computed by iteratively reducing the constraint error towards zero, and a simple time integration is employed for the solution of equations of motion. Convergence of the iterative scheme is analysed, and numerical simulations are conducted to demonstrate the accuracy of the solution.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110309
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  • 56
    Digitale Medien
    Digitale Medien
    The h-, p- and hp-versions of the BEM in elasticity: Numerical results (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 255-265 
    Details
    ISSN: 1069-8299
    Schlagwort(e): boundary element method ; error estimation ; hp-version ; Galerkin BEM ; numerical results ; elasticity ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The paper investigates the convergence of the h-, p- and hp-versions of a variational symmetric boundary element method (BEM) in plane elasticity by numerical experiments. The study discusses mixed boundary value problems on polygonal domains, i.e. problems for which the exact solution is analytic except in a finite number of points. The convergence of the error in energy norm is displayed for all versions of the BEM. All results are also compared with those obtained by the corresponding finite element methods. The theoretically predicted asymptotic convergence rates for all versions of the method can be observed in the numerical experiments. A comparison of computer times is given as well.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110308
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  • 57
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    Digitale Medien
    Background to bench marks, edited by G. E. O. Davies, R. T. Fenner and R. W. Lewis, NAFEMS, Birniehill, East Kilbride, Glasgow. ISBN 1 874376 10 7 (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 281-282 
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    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110310
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  • 58
    Digitale Medien
    Digitale Medien
    Conference diary (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 283-284 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110311
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  • 59
    Digitale Medien
    Digitale Medien
    Announcements (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 285-286 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110312
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  • 60
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    Digitale Medien
    Masthead (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995) 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110401
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  • 61
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    Digitale Medien
    On the eigenvalues basic to the analytical solution of convective heat transfer with axial diffusion effects (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 287-296 
    Details
    ISSN: 1069-8299
    Schlagwort(e): eigenvalues ; integral transforms ; analytical methods ; convection ; Sturm-Liouville system ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The integral transform method is employed in the analytical solution of the non-classical eigenvalue problem that appears in connection with the analysis of forced convection in ducts, including the effect of fluid heat diffusion in the axial direction. The related eigenfunctions are expanded in terms of eigenfunctions from a simpler auxiliary eigenvalue problem, and the original eigenvalues are determined from the associated matrix eigensystem analysis. Convergence rates of the proposed solutions are illustrated and reference results established for different values of the governing parameters.
    Zusätzliches Material: 4 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110402
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  • 62
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    Digitale Medien
    Permanent heavy waves in circular-shaped channels (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 355-362 
    Details
    ISSN: 1069-8299
    Schlagwort(e): permanent heavy waves ; circular shaped channels ; conformal mapping ; Fatou's method ; Levi-Civita's decomposition ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Because of the earth's curvature, all existing channels have a curvature. E. Zeidler gave an existence and uniqueness proof for permanent heavy and capillar-heavy waves in such circular shaped channels. Based on this proof and on a general computational method for constructing the solutions numerically, the case of permanent heavy waves in circular-shaped channels is considered in this work.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110409
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  • 63
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    Digitale Medien
    Introduction to finite and boundary element methods for engineers, by G. Beer and J. O. Watson, John Wiley and Sons, Chichester, U.K. ISBN 0-471-92813-5. £29.95/$49.95, Program disk £19.95 (extra) (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 373-374 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110411
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  • 64
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    Digitale Medien
    Conference diary (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 375-377 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110412
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  • 65
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    Digitale Medien
    Masthead (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995) 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110501
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  • 66
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    Digitale Medien
    Announcements (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 379-381 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110413
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  • 67
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    Digitale Medien
    On the convergence of the generalized matrix multisplitting relaxed methods (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 363-371 
    Details
    ISSN: 1069-8299
    Schlagwort(e): matrix multisplitting ; relaxed method ; convergence ; divergence ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: In this paper, I discuss the convergence and divergence rates for a class of generalized matrix multisplitting relaxation methods in a detailed manner. In particular, when the coefficient matrix is an L-matrix, I obtain several sufficient and necessary conditions ensuring the convergence of these methods.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110410
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  • 68
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    Digitale Medien
    An independent refinement and integration procedure in multiregion finite element analysis (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 383-390 
    Details
    ISSN: 1069-8299
    Schlagwort(e): finite elements analyses ; global and local analyses ; multiregion ; interfaces ; interpolation functions ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: An independent refinement and integration procedure is developed to couple together independently modelled (global and local) regions in a single analysis. The finite element models can have different levels of refinement and the nodes along the interface between them need not coincide with one another. A spline interpolation function that satisfies the linear isotropic plate-bending differential equation is used to relate the local model interface nodal displacements to the global model interface displacements. The proposed independent refinement and integration procedure is validated by applying it to problems involving in-plane and out-of-plane deformations.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110502
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  • 69
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    Digitale Medien
    A quadratic boundary element for potential problems in 2D with no numerical integration (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 391-401 
    Details
    ISSN: 1069-8299
    Schlagwort(e): boundary element method ; two-dimensional potential problems ; logarithmic kernel ; derivative kernal ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Both the logarithmic and derivative kernel integrations for potential problems, solved with quadratic isoparametric boundary elements, contain quartic functions of the integration parameter. It is shown that such functions can be written as the product of two quadratic functions with real coefficients. The derivative kernel integration is then represented as the sum of two integrals, which can be evaluated analytically. The logarithmic kernel integration can be similarly split but needs a Taylor series expansion of the Jacobian of the integration to enable analytical integration. The use of this Taylor series expansion means that the method presented is limited to problems involving weakly curved elements.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110503
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  • 70
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    Digitale Medien
    The variationally correct rate of convergence for a two-noded beam element, or why residual bending flexibility correction is an extravariational trick (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 403-407 
    Details
    ISSN: 1069-8299
    Schlagwort(e): finite element method ; residual bending flexibility ; convergence ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: In this paper I re-examine the mechanics of the residual bending flexibility correction and show that it is an extravariational trick.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110504
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  • 71
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    Digitale Medien
    Discrete element dynamic response of elastoplastic shells subjected to impulsive loading (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 417-426 
    Details
    ISSN: 1069-8299
    Schlagwort(e): discrete elements ; dynamic analysis ; impact ; impulsive loads ; elastoplastic response ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The determination of the dynamic response of plate and shell structures is carried out employing a discrete representation of the continuum, associated with an explicit integration scheme in the time domain. Comparisons with experimental results certify the accuracy and reliability of the proposed method.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110506
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  • 72
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    Digitale Medien
    Masthead (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995) 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110701
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  • 73
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    Digitale Medien
    Announcements (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 547-548 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110610
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  • 74
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    Digitale Medien
    Direct application of constraints to symmetric algebraic systems (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 563-573 
    Details
    ISSN: 1069-8299
    Schlagwort(e): constraints ; boundary conditions ; rigid inclusions ; inextensibility ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Constraints arise naturally in the context of rigid inclusions, incompressibility, inextensible fibres and deformed finite elements. Typical methods for handling constraints in the governing matrix equation include Lagrange multipliers, penalty weights and elimination of variables. Each procedure has a particular undesirable feature. Proposed here is an approach in which each constraint is handled directly and sequentially through a modification of the rows and columns of the governing matrix and force vector. Positive definiteness, symmetry and the dimensions of the matrix remain unchanged. Elementary examples involving both the static and dynamic response of a bar are given to illustrate the procedure.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110703
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  • 75
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    Digitale Medien
    Hierarchic and mixed-interpolated finite elements for Reissner-Mindlin problems (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 549-562 
    Details
    ISSN: 1069-8299
    Schlagwort(e): plate problem ; Reissner-Mindlin ; finite elements ; hierarchic elements ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The focus of the present work is directed towards the construction of a family of special finite elements for the numerical solution of the Reissner-Mindlin plate problem. The model describes the deformation of a plate when transverse shear deformation is taken into account. The model is widely used for thin to moderately thick plates. Despite its simple formulation, the numerical approximation is not straightforward. When standard low-order finite elements are used for the approximation the solution degenerates very rapidly for small thickness (locking phenomenon). To overcome such behaviour, non-standard formulations of the problem are usually combined with low-order finite elements to weaken or possibly eliminate the locking of the numerical solution.In recent years high-order finite elements have been introduced and successfully applied in several fields. Previously we have constructed a family of hierarchic high-order finite elements to solve the Reissner-Mindlin problem in its plain formulation. The locking was strongly reduced but was still active for very thin plates. Meanwhile some mixed-interpolated finite elements have been developed and shown to be locking free. In this paper we combine the two approaches, namely, the hierarchic high-order elements and the mixed-interpolated elements. The result is a family of special finite elements that exhibits both properties of convergence and robustness.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110702
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  • 76
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    Digitale Medien
    Comments on ‘transverse shear correction factors for laminates in cylindrical bending’ (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 629-629 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110709
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  • 77
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    Digitale Medien
    Conference diary (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 631-632 
    Details
    ISSN: 1069-8299
    Schlagwort(e): Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640110711
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  • 78
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    Digitale Medien
    Smooth modelling of the normal vector by using C0-continuous lagrange elements in BEM (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 981-993 
    Details
    ISSN: 1069-8299
    Schlagwort(e): boundary element method ; boundary geometry ; smooth modelling ; Lagrange elements ; Overhauser elements ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The paper reveals the conditions under which the approximations of the normal vector and global coordinates of interior points of two segments on a smooth contour can fail using the C1-continuous Overhauser elements. A new continuous modelling of the normal vector is developed using the standard Lagrange elements. The derivation is consistent with the assumptions employed in the boundary element method formulations of potential problems. Test numerical examples are considered in order to analyse the accuracy of the approximations based on the use of standard C0-continuous elements, Overhauser C1-continuous elements and the proposed ‘smooth’ C0 elements.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640111204
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  • 79
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    Digitale Medien
    An accurate numerical algorithm for advective transport (1995)
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 1039-1045 
    Details
    ISSN: 1069-8299
    Schlagwort(e): pure advection ; Lagrangian treatment ; control volume ; QUICKEST scheme ; large Courant numbers ; accuracy ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Mathematik , Technik allgemein
    Notizen: The paper describes a new numerical algorithm for pure advection at large Courant numbers. The DISCUS scheme uses an accurate and proven control volume algorithm (QUICKEST) within a Lagrangian treatment of advection. By being in sympathy with the information flow dictated by characteristic lines, the scheme performs exceedingly well at Courant numbers greater than one. In contrast to existing Lagrangian schemes which use the characteristics to determine the grid points from which concentrations are interpolated, in DISCUS the characteristics are used to determine the appropriate location for the control volume. The scheme is of comparable accuracy to Eulerian schemes at Courant numbers less than one, but it increasingly outperforms them as the Courant number increases. Indeed, the results reported illustrate the futility of using an Eulerian scheme at high Courant numbers.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cnm.1640111210
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  • 80
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    Digitale Medien
    Absolute configurations and conformations of the opioid agonist and antagonist enantiomers of picenadol (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 518-525 
    Details
    ISSN: 0899-0042
    Schlagwort(e): crystal structure ; molecular mechanics ; MM2-87 ; opioid ligand model ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The absolute configurations of the enantiomers of the opiod picenadol [cis-1,3-dimethyl-4-propyl-4-propyl-4-(3-hydroxyphenyl)piperidine; cis-3-methyl, 4-propyl] have been determined by an X-ray crystallographic study of the chloride salt of the (+)-enantiomer. The agonist (+)-enantiomer and the antagonist (-)-enantiomer were found to have the 3R, 4R and 3S, 4S absolute configurations, respectively. The conformational properties of the enantiomers were also examined with MM2-87 calculations. There was good agreement between the computed global minimum and the crystallographic structure with the phenyl ring approximately bisecting the piperidine ring by both methods. This orientation of the phenyl ring differs from that of related opioids such as the phenylmorphans, prodines, meperidine, and ketobemidone in which the phenyl ring tends to eclipse one edge of the piperidine ring. Because the phenyl ring bisects the piperidine ring in picenadol, there is little difference in the three-dimensional orientations of the phenyl rings of the two enantiomers when one superimposes the piperidine rings. The agonist (+)-enantiomer is ambiguous with respect to an opioid ligand model, which suggests that agonist activity requires a specific range of dihedral angles for the phenyl ring. While the global minimum of the agonist is not consistent with the model, a second conformer that is only 1.2 kcal/mol above the global minimum is consistent. An alternative explanation is that agonist or antagonist activity is solely due to the presence of the 3-methyl group on the different edges of the piperidine ring. MM2-87 calculations were also performed on the opioid agonist des-3-methyl analog of picenadol and the closely related trans-1,3,4-trimethyl-4-(3-hydroxyphenyl)piperidines (trans-3-methyl, 4-methyl) in which both enantiomers are opioid antagonists. The conformational properties of these compounds are consistent with the ligand model. © 1995 Wiley-Liss, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530070705
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  • 81
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    Digitale Medien
    In3Ti2Br9: Jahn-Teller Unstable Indium(I) and Antiferromagnetically Coupled Titanium(III) Atoms (1995)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 1 (1995), S. 118-123 
    Details
    ISSN: 0947-6539
    Schlagwort(e): antiferromagnetic exchange ; crystal structure ; indium compounds ; Jahn-Teller distortion ; titanium compounds ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Dark green crystals of In3Ti2Br9 have been synthesized from elemental Ti and molten InBr3 at 450°C. The X-ray diffractional characterization by means of single-crystal and powder Rietveld refinement reveals a hexagonal crystal structure (a = 738.2(2), c = 1813.9(3) pm; P63/mmc, Z = 2) of Cs3Cr2Cl9 type, containing Ti2Br3-9 dimers and univalent indium cations. Self-consistent, semiempirical band structure calculations show the structural distortions of the two monovalent indium cations to arise from a second-order Jahn-Teller instability. The new compound's magnetic susceptibility and microscopic antiferromagnetic exchange are analyzed by using a Bleaney-Bowers ansatz.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chem.19950010205
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  • 82
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    Digitale Medien
    Phase Relationships in the N2O3/N2O4 System and Crystal Structures of N2O3 (1995)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 1 (1995), S. 389-393 
    Details
    ISSN: 0947-6539
    Schlagwort(e): crystal structure ; differential thermal analysis ; nitrogen oxides ; phase transitions ; twinning ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Mixtures of N2O3 and N2O4 have been prepared from measured volumes of NO and O2. Phase relationships in the system N2O3/N2O4, which depend on the composition of the samples and on the temperature, were studied by the Guinier technique and differential thermal analysis. Single crystals of phases A and B of N2O3 were grown in situ on a diffractometer and studied at temperatures between -107 and -170°C by X-ray diffraction. The structure analysis of A-N2O3 (tetragonal, space group I41/a, T = -170°C, a = 1625.57 (16), c = 880.49(13) pm, Z = 32, R1 = 0.051 for 1030 unique reflections) is hampered by twinning and additional disorder of one of two crystallographically independent molecules. B-N2O3 is nicely ordered with one molecule in the asymmetric unit (orthorhombic, space group P212121, T = -160°C, a = 506.86(4), b = 647.96(5), c = 863.26(6) pm, Z = 4, R1 = 0.023 for 1352 unique reflections). The most interesting features of the N2O3 molecule are its planarity and the extraordinarily long N—N bond (189.0(1) pm).
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chem.19950010610
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  • 83
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    Digitale Medien
    Reactions of the “Naked” Fluoride Ion: Syntheses and Structures of SeF62- and BrF6- (1995)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 1 (1995), S. 261-265 
    Details
    ISSN: 0947-6539
    Schlagwort(e): crystal structure ; fluorides ; hexafluorobromate(V) ; hexafluoroselenate(IV) ; naked fluoride ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 1,1,3,3,5,5-Hexamethylpiperidinium fluoride (pip+F-) and 1,2-dimethylpropyltrimethylammonium fluoride have been prepared. They dissolve in fluorohydrocarbons (CH2F2, CF3-CHF-CF3, CHF3) even at very low temperatures. The nature of these solutions is indicated by the crystal structure of the adduct pip+F-·4CH2F2, which shows (C)H…F bridging. The high fluoride activity is exemplified by the previously unknown reaction between SeF5- and F- to yield SeF62-. The salt pip+BrF6- is obtained by a metathesis reaction of Cs+BrF6- with pip+F-. The distortion of the SeF62- structure from octahedral symmetry is intermediate between IF6- (strongly distorted) and BrF6- (octahedral). The electron-pair repulsion model is checked against these results.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chem.19950010410
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  • 84
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    Digitale Medien
    Metal-Mediated Synthesis of Multidomain Ligands - A New Strategy for Metallosupramolecular Chemistry (1995)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 1 (1995), S. 360-367 
    Details
    ISSN: 0947-6539
    Schlagwort(e): crystal structure ; polynuclear ; complexes ; ruthenium compounds ; supramolecular chemistry ; terpyridines ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The bridging ligand bis{4′-(2,2′:6′,2″-terpyridinyl)}ether (1) can be prepared in 69% yield from the reaction of 4′-chloro-2,2′:6′,2″-terpyridine (3) with 2,2′:6′,2″-terpyridin-4′(1′H)-one (2) in Me2NCHO in the presence of KOH. More conveniently, complexes of 1 can be prepared in situ by the reaction of 2 with a ruthenium(II) complex of 3 in the presence of K2CO3. This methodology has been developed for the synthesis of a range of mono-, di-, tri- and hexanuclear complexes with a variety of Xtpy (Xtpy = 4′-substituted 2,2′:6′,2″-terpyridine) terminator ligands. The molecular structure of 1 (a = 9.623(2), b = 11.241(1), c = 11.828(1) Å; space group P1; α = 93.064(9), β = 107.072(14), γ = 99.088(14)°; Z = 2, R = 0.0450, Rw = 0.0577) has been determined. The generality of the methodology may ultimately be limited by the sensitivity of the ether-linkage in 1 to attack by nucleophiles.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chem.19950010606
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  • 85
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    Digitale Medien
    Molecular structure and conformational analysis of chirai (−)-3-(4-bromobenzylidene)-1-isopropyl-2-methoxy-4-methylcyclohexene (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 2331-2336 
    Details
    ISSN: 1573-9171
    Schlagwort(e): molecular structure ; conformational analysis ; crystal structure ; X-ray structural analysis ; molecular mechanics ; (−)-3-(4-bromobenzylidene)-l-isopropyl-2-methoxy-4-methylcyclohexene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract (−)-3-(4-Bromobenzylidene)-1-isopropyl-2-methoxy-4-methylcyclohexene, capable of inducing spiral supramolecular ordering when introduced to nematic and some smectic mesophases, has been studied by an X-ray structural analysis. The crystals are orthorhombic; at 20 °Ca = 6.055(1),b = 13.282(3),c=20.734(4) Å,V=1668(1) Å3,d calc = 1.380 g cm−3, space groupP2 12121 Z=4. The cyclohexene ring has a conformation intermediate between a sofa and a half-chair. The methyl and methoxyl groups are in asyn orientation with respect to the mean plane of the cycle. The angle between the plane of the aryl substituent and the exocyclic double bond is 33°. The observed distortions of bond angles at unsaturated carbon atoms are typical of derivatives of benzylidenecyclohexene. Molecular mechanics calculations demonstrated that the conformation observed in the crystalline state is not the most favorable, and this conformation is stabilized through intermolecular interactions upon stacking in crystals. It was shown that the relative orientation of the methyl and methoxyl groups as well as the orientation of the aryl substituent substantially affect the conformation of the cyclohexene ring.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00713603
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  • 86
    Digitale Medien
    Digitale Medien
    Chiral β-hydroxycarbonyl compounds based on (−)-menthone: structure and behavior in liquid crystalline systems (1995)
    Springer
    Russian chemical bulletin 44 (1995), S. 1200-1209 
    Details
    ISSN: 1573-9171
    Schlagwort(e): stereoisomeric 2-(1′-biphenyl-4-yl-1′-hydroxy)methyl-p-menthan-3-ones ; molecular structure ; X-ray structural analysis ; crystal structure ; conformational analysis ; molecular mechanics ; hydrogen bond ; induced cholesteric liquid crystals ; twisting power
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract It has been established by X-ray structural analysis that 2-(1′-biphenyl-4-yl-1′-hydroxy)methyl-p-menthan-3-one, one of the products of the reaction of (−)-menthone triisopropyloxytitanium enolate with 4-phenylbenzaldehyde, has a 1R,2S,4S,1′S configuration. In crystals, this β-hydroxyketone adopts a chair conformation with equatorial methyl and isopropyl groups and an axial 2-(1′-biphenyl-4-yl-1′-hydroxy)methyl substituent. Unlike the stereoisomeric compound with the 1R,2S,4S,1′S configuration, the exocyclic fragment of which has an intramolecular 〉C=O...H-O- hydrogen bond in crystals and solutions, in the crystals of the 1R,2S,4S,1′S ketol under study, molecules are linked by a network of cooperative -O-H...O-H...O-H... hydrogen bonds. Based on the results of molecular mechanics calculations and experimental data of1H NMR and IR spectroscopy, conformations of molecules of this compound, which are in equilibrium in solution, have been characterized. Based on data on spatial structures of stereoisomeric β-hydroxyketones and the character of H-bonds formed by these compounds, the characteristic features of the effect of these chiral alloying additives on the supramolecular structure and macroscopic properties of liquid crystalline systems have been interpreted.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00700889
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  • 87
    Digitale Medien
    Digitale Medien
    Effective core potentials and the structures of metallocenes (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 53 (1995), S. 309-319 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The use of effective core potentials in the calculation of the geometrical parameters of the ferrocene molecule and its heavier analogs is reported. It is shown that a critical factor in these calculations is the efective core-core (ECC) potential and, in the absence of ECCs for first-row atoms that are involved in short bonds, calculations of the geometrical parameters are not reliable. Good agreement with experimental geometries may be obtained by using the Los Alamos ECPs for atoms of the second and higher rows of the periodic table at the MP2 level. DFT calculations have been performed and found to give numerical results comparable to MP2 in the same basis. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 8 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560530307
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  • 88
    Digitale Medien
    Digitale Medien
    Cubic-grid Gaussian basis sets for electron scattering calculations. II. Matrix elements (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 53 (1995), S. 431-436 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In this article, we report an efficient computational procedure for electron scattering matrix elements in the previously developed cubic-grid Gaussian basis sets. The Green function matrix elements derived for the cubic-grid basis set are simpler and easier to calculate than are those available in the literature for conventional Gaussian basis sets. Special features of the cubic-grid basis sets may also be exploited for a very efficient computation of Coulomb and exchange integrals. Inelastic scattering amplitudes for vibrational excitations may be efficiently calcualted in the harmonic approximation by numerical differention of the T-matrix elements. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560530409
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  • 89
    Digitale Medien
    Digitale Medien
    In memory of professor Masao Kotani (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 53 (1995), S. 451-454 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560530411
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  • 90
    Digitale Medien
    Digitale Medien
    Cubic-grid Gaussian basis sets for electron scattering calculations. III. Effect of basis-set translation and size on the calculated cross section (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 53 (1995), S. 437-450 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Previously developed cubic-grid basis sets of various sizes were used for the calculation of cross sections for elastic and inelastic electron scattering by the He and Ne atoms and the H2O molecule by the T-matrix expansion method. The aim was to test the invariance of calculated cross sections with respect to the translation of the target molecule and to examine the effect of basis-set size on the results. We also present a simple procedure for accounting for long-range interactions from the part of space that lies outside the volume that contains the cubic-grid basis set. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560530410
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  • 91
    Digitale Medien
    Digitale Medien
    Announcement (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 53 (1995), S. 455-456 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560530412
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  • 92
    Digitale Medien
    Digitale Medien
    Measures of distance for atomic charge and momentum densities and their relationship to physical properties (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 53 (1995), S. 627-633 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Atomic charge and momentum densities of 91 atoms (He—U) are classified in terms of their L1, L2, and entropic measures of distance from the densities of the preceding atoms. The relationship between these distances and the first ionization energies is also considered. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560530606
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  • 93
    Digitale Medien
    Digitale Medien
    Self-consistent methods for the treatment of low-lying molecular vibrations (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 53 (1995), S. 635-649 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The subject of this article is the self-consistent-field (SCF) treatment of low-lying molecular vibrations in molecules subject to solvent effects and light atom migration. The analyses use a Cartesian Gaussian basis and Gaussian functional expansions of potential energy operators. The objective of the work was to establish approximate and practical methods of analysis of vibrational degrees of freedom in molecules that build on and compare well with the highly accurate treatments of vibrations in small molecular systems of the past decade. An application to a system in which hydrogen bonding contributes the major anharmonic effect illustrates the method. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560530607
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  • 94
    Digitale Medien
    Digitale Medien
    The evaluation of matrix elements in the analysis of anharmonic molecular vibrations: Optimized expansions and quadratures (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 53 (1995), S. 663-677 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: This article presents methods for computing matrix elements with Cartesian Gaussian wave functions of potential energy operators that depend on functions of the form (r-r0)n exp[-a(r - r0)] as well as matrix elements of the class of polynomial many-body potentials developed by Murrell et al. The matrix elements arise in the analyses of anharmonic vibrations in molecules. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560530609
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  • 95
    Digitale Medien
    Digitale Medien
    The PPP model of alternant cyclic polyenes with modified boundary conditions (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 55 (1995), S. 347-359 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The extension of the PPP Hamiltonian for alternant cyclic polyenes to noninteger values of the pseudomomentum by imposing modified boundary conditions is discussed in detail. It is shown that a computer program for periodic boundary conditions can be easily adapted to the new boundary conditions. Full CI computations are carried out for some low-lying states of the PPP model of altemant cyclic polyenes (CH)N, (N even) at half-filling. The energy values obtained by using periodic (Bloch) and antiperiodic (Möbius) orbitals are used to perform energy extrapolations for N → ∞. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560550406
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  • 96
    Digitale Medien
    Digitale Medien
    Masthead (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 55 (1995) 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560550501
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  • 97
    Digitale Medien
    Digitale Medien
    Matrix elements for Ĵ2 and Ĵz operators over explicitly correlated Cartesian Gaussian functions (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 55 (1995), S. 367-376 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: General formalism for evaluation of multiparticle integrals involving J̌2 and J̌z operators over explicitly correlated Cartesian Gaussian functions is presented. The integrals are expressed in terms of the general overlap integrals. An explicitly correlated Cartesian Gaussian function is a product of spherical orbital Gaussian functions, powers of the Cartesian coordinates of the particle, and exponential Gaussian factors, which depend on interparticular distances. This development is relevant to both adiabatic and nonadiabatic calculations of energy and properties of multiparticle systems. © 1995 John Wiley & Sons, Inc.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560550502
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  • 98
    Digitale Medien
    Digitale Medien
    Ab initio study of molecular g-tensors (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 55 (1995), S. 377-392 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The molecular g-tensors for the molecules NO2, CO2-, C3H5, H2CO+, and NF3+ are calculated at the unrestricted Hartree-Fock (UHF) level using the Rayleigh-Schrödinger perturbation approach. All one-electron terms have been evaluated, including the relativistic mass correction, the one-electron spin-Zeeman gauge correction, and a second-order term involving the spin-orbit coupling and the orbital-Zeeman interaction. The relative importance of the first-order terms is found to be quite substantial. For first-row molecules, their total contribution is often of the same order of magnitude as of the second-order contribution, in some instances even larger. A study on the basis-set dependence of these g-tensors has been conducted. At this level, the most important basis-set criterion is shown to be a satisfactory description of the valence regions. Finally, the gauge dependence of these g-tensor calculations has been systematically studied. This dependence seems to be substantially reduced for basis sets which include polarization functions. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560550503
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  • 99
    Digitale Medien
    Digitale Medien
    SINDO1 calculations of vibrational frequencies of adsorbed molecules (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 55 (1995), S. 411-417 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A scaling procedure is used for the force constants generated by the SINDO1 method in internal coordinates to achieve better agreement with experimental frequencies of molecules. The procedure is subsequently used to calculate frequency shifts for adsorbed molecules. The results for CO2 and CO adsorption at NaCl cluster surfaces are in good agreement with experimental data. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560550505
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  • 100
    Digitale Medien
    Digitale Medien
    Ab initio studies of the electronic structure of Be93, Be105, Be111, and Be123 clusters (1995)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 55 (1995), S. 393-410 
    Details
    ISSN: 0020-7608
    Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Ab initio self-consistent-field calculations are reported for electronic states of beryllium clusters comprised of 93, 105, 111, and 123 atoms. The respective clusters correspond to coordination shells 12-15 of a central Be atom with internuclear separations derived from the lattice constants of the bulk metal. Ab initio effective core potentials have been employed to replace the 1 s electrons, thereby reducing the complexity of the calculations. In addition, use of the full D3h point group symmetry of the clusters results in a substantial reduction of the numbers of two-electron integrals that must be computed and processed. Binding energies, orbital energies, electric field gradient, nuclear-electrostatic potential, diamagnetic shielding constant, second moments, and Mulliken populations are calculated for selected electronic states. Calculated binding energies when compared among the different clusters as well as to smaller and larger fragments from earlier studies provide evidence for the onset of convergence to the Hartree-Fock limit of the bulk. Lowest-state ionization potentials are consistently above and agree to within 14% of the experimental workfunction. The net charge on the central beryllium atom decreases toward zero. The variability of observed bulklike behavior for the different properties indicates that the transition between cluster and bulklike behavior is not sharp and depends on the quantity of interest. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/qua.560550504
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