Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1985-1989  (11)
  • 1955-1959
  • 1940-1944
  • 1880-1889
  • 1870-1879
  • 1989  (11)
  • 1
    Electronic Resource
    Electronic Resource
    An electron spin-echo envelope modulation study of the lowest triplet state of pyridine-d5: Spin-density distribution and structure (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 6549-6565 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Recently we have shown that the lowest triplet state (T0) of pyridine, incorporated in a single crystal of benzene, may be studied by electron spin-echo (ESE) spectroscopy. From the nitrogen hyperfine structure in the ESE detected electron paramagnetic resonance (EPR) spectra, we were able to conclude that pyridine, a planar molecule in the ground state, becomes nonplanar upon excitation into T0. Here we report the results of a detailed investigation of this distortion and of the electronic nature of the lowest triplet state of pyridine-d5. We have performed electron spin–echo envelope modulation (ESEEM) spectroscopy. From the modulation spectra, the electron-nuclear double resonance (ENDOR) frequencies corresponding to the various deuterium nuclei are obtained. Analysis of the dependence of these frequencies on the orientation of the magnetic field with respect to the triplet fine-structure axes system allows for a determination of the deuterium hyperfine and quadrupole tensors. From these tensors and the known nitrogen hyperfine tensor, the structure and spin-density distribution of pyridine in its lowest triplet state are deduced. Pyridine adopts upon excitation into T0 a boatlike structure, in which the nitrogen atom is tilted by about 40° with respect to the plane through the ortho- and meta-carbon atoms and the para-carbon/para-deuterium fragment by about 10° with respect to this plane. Thereby the hybridization of the ortho-carbon atomic orbitals strongly deviates from that for aromatic hydrocarbons and becomes almost sp3; the hybridization of the atomic orbitals on the other carbon atoms changes much less, while the nitrogen atomic orbitals remain sp2 hybridized. Approximately half of the spin density is found to be localized on the nitrogen atom with a remarkable distribution over the atomic orbitals: the π orbital carries 40%, the n orbital 10%. The rest of the spin density is distributed over the para- (30%) and ortho-carbon atoms (10% each). The lowest triplet state of pyridine is neither an nπ* state nor a ππ* state, but a state of mixed character as the result of a strong vibronic coupling between the 3B1 (nπ*) and 3A1 (ππ*) states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457374
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Absorption cross sections, saturated vapor pressures, sublimation energies, and evaporation energies of some organic laser dye vapors (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 1403-1409 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new technique of transmission measurement of overheated dye vapors is applied to determine absolute absorption cross-section spectra of three active dyes for vapor phase dye lasers. The investigated compounds are 1,4-di[2-(5-phenyloxazolyl)]-benzene (POPOP), 1,4-di[2-(4-methyl-5-phenyl-oxazolyl)]-benzene (dimethyl-POPOP), and 2,5-diphenylfuran (PPF). The vapor absorption spectra are compared with liquid solution spectra in order to obtain information on the dye–solvent interaction. The saturated vapor densities are determined by transmission measurements after knowing the absolute absorption cross-section spectra. The latent heats of sublimation, evaporation, and melting are derived by analyzing the dependences of the saturated vapor densities on the vapor temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457152
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Magnetic and optical properties of triplet excitons and traps in 1,4-dibromobenzene (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 1521-1527 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An optical and magnetic resonance study on neat 1,4-dibromobenzene crystals shows that the molecules in their lowest triplet state are distorted into a chair-like shape and confirms previous conclusions about the one-dimensional character of the triplet excitons. From a study of the phosphorescence spectrum at various temperatures it is found that the band width of the triplet excitons is (−1.0±0.15) cm−1 and that the k=0 state is at the bottom of the band.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457112
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Host examination walk and oviposition site selection ofTrichogramma minutum: Studies on spherical hosts (1989)
    Springer
    Journal of insect behavior 2 (1989), S. 143-171 
    Details
    ISSN: 1572-8889
    Keywords: host examination ; host recognition ; locomotion ; parasitoid ; Trichogramma minutum ; oviposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The host examination behavior of the parasitoid wasp Trichogramma minutumon spherical Manduca sextahosts is described. The mean walking speed during host examination was 0.64 ± 0.03 mm s −1 and is independent of wasp size. The paths taken by the wasps are not evenly distributed over the host surface; the majority of time is spent below 45 ° latitude. The distribution of oviposition sites is also nonrandom with respect to latitude and is not influenced by phototaxic and geotaxic responses. The initial transit made by the wasps over the host surface is a straight path which frequently passes across the highest point on the host. The length and duration of the initial transit are independent of wasp body length. However, stride length and stepping rates are proportional to wasp body length, and small wasps take more steps to complete their initial transit. The roles of the examination walk in host recognition and host volume measurement by Trichogrammaare also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01053289
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Positive interpolation with rational splines (1989)
    Springer
    BIT 29 (1989), S. 140-147 
    Details
    ISSN: 1572-9125
    Keywords: AMS(MOS) 65D07 ; 41A15
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A method is presented for the construction of positive rational splines of continuity classC 2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01932711
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Evidence for an osteoblast-activating factor in a patient with peripheral T-cell lymphoma and osteosclerosis (1989)
    Springer
    Journal of molecular medicine 67 (1989), S. 402-407 
    Details
    ISSN: 1432-1440
    Keywords: T-cell lymphoma ; Osteosclerosis ; Lymphokines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A patient with peripheral T-cell Lymphoma and aquired, systemic osteosclerosis is described. Bone histology showed a spectacular activation of osteoblasts accompanyed by massive new bone formation. Alkaline phosphatase in serum was elevated and increased to 〉2000 U/l when the lymphoma became refractory to chemotherapy. In the patient's serum an osteoblast-activating factor could be demonstrated using a rat osteogenic osteosarcoma cell line (ROS 17/2.8). The factor was absent during remission of the tumor. We conclude that osteosclerosis was a paraneoplastic syndrome in this patient due to the secretion of an osteoblast-stimulating factor by the T-cell lymphoma. This situation is similar to the secretion of osteoclast-activating factors described in B-cell lymphomas, particularly multiple myeloma. The characterization of such a factor could be of therapeutic relevance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01711269
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    The clinical effect of felodipine and nifedipine in Raynaud's phenomenon (1989)
    Springer
    European journal of clinical pharmacology 37 (1989), S. 191-192 
    Details
    ISSN: 1432-1041
    Keywords: felodipine ; nifedipine ; clinical trial ; Raynaud's phenomenon ; adverse effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Sixteen patients participated in a double-blind cross-over trial comparing the effect of two dosages of the new calcium entry blocker, felodipine, with nifedipine in the treatment of Raynaud's phenomenon. The effect was evaluated using a symptom recording system. As no difference was found between the 3 treatments, the lower dose of felodipine (10 mg) may be preferable as only one dose per day is necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00558230
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Characterization of the binding parameters of3H-nitrendipine as a Ca2+-channel blocker in the myocardial membrane of the infarction region of mini-pigs (1989)
    Springer
    The protein journal 8 (1989), S. 446-448 
    Details
    ISSN: 1573-4943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01674320
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Surface acoustic wave measurements of a superconducting granular lead film in a magnetic field (1989)
    Springer
    Journal of low temperature physics 76 (1989), S. 191-197 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements of the dc resistance and surface acoustic wave attenuation have been made in a granular superconducting lead film which was subjected to an externally applied magnetic field. Resistance and attenuation curves were obtained as a function of temperature for fixed magnetic field as well as function of magnetic field for fixed temperature. The resistance and attenuation data are discussed within the context of a percolation description of granular superconducting films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00681584
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Über Phospholkomplexe einiger 3d-ÜbergangselementeProfessor Kurt Issleib zum 70. Geburtstage am 19. November 1989 gewidmet (1989)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 578 (1989), S. 81-88 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On Phosphole Complexes of 3d Transition MetalsThe 2-ethoxy-, 2-cyclohexanoxy-, 2-phenoxy-, 2-(4′-methylphenoxy)- and 2-(4′-chlorphenoxy)-benzo[1,3,2]-dioxaphospholcomplexes of chromium(III), iron(II), cobalt(II), and nickel(II) are synthesized and characterized by N.M.R., I.R. and U.V.-VIS spectroscopy and by magnetic investigations. When titanium(IV) ore copper(II) halides are used redox-reactions can be observed. The corresponding copper(I) complexes are isolated.
    Notes: Es werden 2-Ethoxy-, 2-Cyclohexanoxy-, 2-Phenoxy-, 2-(4′-Methylphenoxy)- und 2-(4′-Chlorphenoxy)benzo[1,3,2]dioxaphospholkomplexe des Chrom(III), Eisen(II), Cobalt(II) und Nickel(II) synthetisiert und mittels NMR-, IR- und UV-VIS-Spektroskopie sowie durch magnetische Untersuchungen charakterisiert. Im Falle des Titan(IV) und des Kupfer(II) werden Redoxreaktionen beobachtet, es werden entsprechende Kupfer(I)-Komplexe isoliert und im Falle des 2-(4′-Chlorphenoxy)-benzol[1,3,2]dioxaphospholliganden der Kupfer(II)-Komplex nachgewiesen.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19895780110
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...