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  • 1
    ISSN: 1432-1920
    Keywords: Brain tumours ; Ultrasonography ; Computed tomography ; Stereotactic biopsy ; Transcranial colour-coded real time sonography ; Glloma ; Central nervous system ; Duplex sonography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Transcranial colour-coded real-time sonography (TCCS) was carried out in 25 patients with brain tumours to determine whether this noninvasive method provides additional information about the extent of solid tumour, its differentiation from oedema, and its tissue components. All 25 patients had serial computed tomography (CT)-guided stereotactic biopsies. Comparison of ultrasound, CT and histological findings revealed that the vast majority of contrast enhancing areas on CT were hyperechogenic (32/33; 97%) and contained tumour tissue (29/32; 91%). Hyperechogenic areas always represented solid tumour (23/23 patients), even when CT showed low density non-enhancing lesions. In lestons hypoechogenic on TCCS and low density on CT, histology consistently revealed necrotic tumour (7/7). Biopsies obtained from parenchyma with normal echogenicity revealed tumour in only 3 of 16 speciemens. Despite the high specificity of TCCS in the differentiation of tumour components, its sensitivity to tumour was inferior to that of CT (24/25; 96%). TCCS thus allows noninvasive preoperative identification of tumour tissue and its extent setting.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Ocean dynamics 46 (1994), S. 263-275 
    ISSN: 1616-7228
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung Die Sauerstoff-Bedingungen in der unteren Wasserschicht eines Schelfmeeres werden im allgemeinen durch die O2-Konzentration dicht über dem Meeresboden charakterisiert, weil diese für die Boden-Organismen besonders wichtig ist und am Boden häufig O2-Mangel herrscht. Für andere Umwelt-Aspekte muß man die gesamte Wassersäule in die Betrachtung einbeziehen. Daher wird ein neuer Sauerstoffmangel-Index vorgeschlagen. Er ist definiert durch das Sauerstoff-Defizit in der Schicht zwischen dem Meersboden und der Tiefe mit 100% O2-Sättigung. Beide Indexe ergänzen einander. Sie können angewendet werden a) zur Beurteilung der aktuellen Sauerstoff-Situation b) zur Erkennung von zeitlichen Veränderungen und Trends c) zum Vergleich der der Sauerstoff-Bedingungen in verschiedenen Gebieten. Zum Vergleich von Stationen mit unterschiedlichen Wassertiefen wird der Sauerstoffmangel-Index auf die Wassertiefe bezogen. Die Indexe werden anhand von praktischen Beispielen aus der südwestlichen Ostsee erläutert.
    Notes: Summary Usually, the oxygen conditions in the lower water layer of a shelf sea area are characterized by the oxygen concentration immediately above the bottom, because this concentration is essential for the bottom living organisms, and as there may be a high oxygen demand due to benthic respiration For other environmental aspects, however, the vertical distribution in the whole water column must be taken into account. So, a new oxygen deficiency index is proposed. It is difined by the oxygen deficit in the layer between the bottom and the depth witl: 100% oxygen saturation, Both indexes complement each other. They can be used for a) Characterizing the actual oxygen situation, b) recongnizing temporal changes and trends, c) comparing the oxygen conditions in different areas. For comparison of stations with different depths, the oxygen dificiency index is related to (=divided by) the water depth. Some examples are given for temporal variations and trends and for spatial differences of the oxygen situation in the south-western Baltic Sea.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 273 (1994), S. 171-178 
    ISSN: 1573-5117
    Keywords: Trichoptera ; scrapers ; selectivity ; food quality ; periphyton ; detritus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Feeding selectivity by five epilithic, case-building trichopteran species from a first-order stream was examined using laboratory experiments. Larvae had the choice of three food types: periphyton and detritus from the stream, and nettle broth as an ‘artificial’ food source. Food type influenced the microdistribution of these species. Larvae were able to distinguish between different food types and showed species-specific responses to the various types of food. Drusus annulatus, Micrasema longulum and Apatania fimbriata favoured periphyton, while Agapetus fuscipes and Silo pallipes showed no preference for periphyton over detritus. Four of the five species examined (Apatania fimbriata was the exception) tended to avoid nettle broth. The complexity of foraging behaviour was illustrated by M. longulum. Given a choice between detritus, periphyton and periphyton with the addition of moss, they clearly preferred the latter food type, scraping mostly on the epiphytic algae. Proportions of a given species selecting periphyton were correlated with percentage areas of algae in the gut contents of that species in the field. D. annulatus, M. longulum and A. fimbriata showed the greatest preference for periphyton, and consumed the highest proportions of algae in the field. A. fuscipes and S. pallipes often selected detritus, and these species had the lowest proportions of algae, and the highest proportions of detritus, in their guts.
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  • 4
    ISSN: 0044-2313
    Keywords: (1,2-dimethoxyethane-O,O′)lithium methylphosphanide ; (2,5,8-trioxanonane-O2,O5)lithium methylphosphanide ; catena-poly(lithium-organylphosphanide) ; X-ray structure determination ; meso-helix ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Metal Derivatives of Molecular Compounds. VIII. catena-Poly[(2,5,8-trioxanonane-O2,O5) lithium-methylphosphanide]  -  a Compound with a meso-Helix StructureStudies of Fritz et al. [10] showed methylphosphane to be lithiated at -60°C in 1,2-dimethoxyethane or bis(2-methoxyethyl) ether solution by stoichiometric amounts of lithium n-butanide in n-hexane. After removing the hydrocarbons almost completely by distillation and cooling the solutions to -60°C again, colourless square crystals of (1,2-dimethoxyethane-O,O′)lithium (1) and (2,5,8-trioxanonane-O2,O5)lithium methylphosphanide (2) precipitate. As shown by an X-ray structure determination (monoclinic, P21/n; a = 805.5(1); b = 1820.6(2); c = 851.5(1) pm; β = 116.76(1)° at -100 ± 3°C; Z = 4 formula units; R = 0.034) complex 2 forms a polymer which has the shape of an up to now scarcely noted meso-helix. Four-coordinated lithium is bound to two phosphorus (P—Li 252.9 and 253.2 pm; P—Li—P 131.8°; Li—P—Li 132.1°) and to two oxygen atoms (Li—O 203.9 and 206.8; O … O 270.7 pm; O—Li—O 82.5°) of the inherently tridentate 2,5,8-trioxanonane ligand. As compared to the standard value (185 pm) the P—C distance (187.4 pm) is slightly lengthened. Structure determinations of (2,5,8-trioxanonane-O2,O5,O8) lithium 1-(phenylsulfonyl)alkyl compounds published some years ago [26, 27], allow a comparison of molecular parameters characteristic for the twofold or threefold coordinating chelate ligand.
    Notes: Nach Untersuchungen von Fritz u. a. [10] wird in 1,2-Dimethoxyethan oder Bis(2-methoxyethyl)ether Zur einfacheren Beschreibung der Koordination am Lithium wählen wir beim Bis(2-methoxyethyl)ether (diglyme) das Synonym 2,5,8-Trioxanonan. 1,2-Bis(dimethylamino)ethan (tmeda), Tetrahydrofuran (thf), 1,2-Dimethoxyethan (dme), Diethylether (OEt2) gelöstes Methylphosphan bei -60°C durch Lithium-n-butanid in n-Hexan metalliert. Beim Abkühlen der von Kohlenwasserstoffen weitgehend befreiten Ansätze auf wiederum -60°C kristallisiert (1,2-Dimethoxyethan-O,O′)lithium- (1) bzw. (2,5,8-Trioxanonan-O2,O5) lithium-methylphosphanid (2) in farblosen Quadern aus. Nach einer Röntgenstrukturanalyse (monoklin, P21/n; a = 805,5(1); b = 1 820,6(2); c = 851,5(1)pm; β = 116,76(1)° bei -100 ± 3°C; Z = 4 Formeleinheiten; R = 0,034) liegt Komplex 2 als Polymer in der bislang wenig beachteten achiralen Abfolge einer „meso-Helix“ vor. Lithium weist mit Bindungen zu zwei Phosphor- (P—Li 252,9 und 253,2 pm; P—Li—P 131,8°; Li—P—Li 132,1°) und zu nur zwei Sauerstoffatomen (Li—O 203,9 und 206,8; O … O 270,7 pm; O—Li—O 82,5°) des a priori dreizähnigen 2,5,8-Trioxanonan-Liganden ebenso wie Phosphor die Koordinationszahl 4 auf. Der P—C-Abstand ist mit 187,4 pm gegenüber dem Standard (185 pm) geringfügig verlängert. Vor einigen Jahren veröffentlichte Strukturen [26, 27] von (2,5,8-Trioxanonan-O2,O5,O8)- lithium-1-(phenylsulfonyl)alkyl-Verbindungen ermöglichen einen Vergleich charakteristischer Molekülparameter im zwei-oder dreifach koordinierenden Chelatliganden.
    Additional Material: 4 Ill.
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  • 5
    ISSN: 0044-2313
    Keywords: Bis[1,2-bis(dimethylamino)ethane-N,N′]lithium disilylphosphanide ; [Li(tmeda)2]+ cation(1) ; [(H3Si)2P]- anion ; X-ray structure determination ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Metal Derivatives of Molecular Compounds. VII. Bis[1,2-bis(dimethylamino)ethane-N,N′]lithium Disilylphosphanide  -  Synthesis and StructureCrystalline lithium phosphanides studied so far show a remarkably high diversity of structure types dependent on the ligands at lithium and the substituents at phosphorus. Bis[1,2-bis(dimethylamino)ethane-N,N′]lithium disilylphosphanide (1) discussed here, belongs to the up to now small group of compounds which are ionic in the solid state. It is best prepared from silylphosphane by twofold lithiation with lithium dimethylphosphanide first and subsequent monosilylation with silyl trifluoromethanesulfonate, followed by complexation. As found by X-ray structure determination (wR = 0.038) on crystals obtained from diethyl ether {monoclinic; space group P21/c; a = 897.8(1); b = 1 673.6(2); c = 1 466.8(1) pm; β = 90.73(1)° at -100 ± 3°C; Z = 4 formula units}, the lithium cation is tetrahedrally coordinated by four nitrogen atoms of two 1,2-bis(dimethylamino)ethane molecules. Characteristic parameters of the disilylphosphanide anion are a shortened average P—Si bond length of 217 pm (standard value 225 pm) and a Si—P—Si angle of 92.3°.
    Notes: Untersuchungen an kristallinen Lithiumphosphaniden ergeben in Abhängigkeit von den Liganden am Lithium- und den Substituenten am Phosphoratom eine überraschend große Strukturviefalt. Das aus Silylphosphan durch zweifache Lithinierung mit Lithium-dimethylphosphanid, nachfolgende einfache Silylierung mit Silyl-trifluormethansulfonat und anschließende Komplexierung gut zugängliche Bis[1,2-bis(dimethylamino)ethan-N,N′]lithium-disilylphosphanid (1) gehört zur bislang kleinen Gruppe der im Festkörper ionisch vorliegenden Verbindungen. Nach einer Röntgenstruktur-analyse (wR = 0,038) an den aus Diethylether isolierten Kristallen {monoklin; Raumgruppe P21/c; a = 897,8(1); b = 1 673,6(2); c = 1 466,8(1) pm; β = 90,73(1)° bei -100 ± 3°C; Z = 4 Formeleinheiten} ist Lithium verzerrt tetraedrisch von vier Stickstoffatomen aus zwei 1,2-Bis(dimethyl-amino)ethan-Molekülen umgeben. Das Disilylphosphanid-Anion weist einen gegenüber dem Standard von 225 auf 217 pm verkürzten mittleren P—Si-Abstand und einen Si—P—Si-Winkel von 92,3° auf.
    Additional Material: 3 Ill.
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  • 6
    ISSN: 0044-2313
    Keywords: Lithium cyanotrimethylsilylamide ; (tetrahydrofuran)lithium cyanotrimethylsilylamide ; polymeric lithium amide ; X-ray structure determination ; vibrational spectra ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Metal Derivatives of Molecular Compounds. VI. Lithium and (Tetrahydrofuran)lithium Cyanotrimethylsilylamide  -  Syntheses and StructuresAt different temperatures N,N′-bis(trimethylsilyl)carbodiimide (1) and lithium methanide react either under addition or substitution. When compound 1, however, is treated at -40°C with an equimolar amount of (1,2-dimethoxyethane-O,O′)lithium phosphanide (2) in 1,2-dimethoxyethane, only exchange of one trimethylsilyl group versus lithium is observed and in addition to phosphane and tris(trimethylsilyl)phosphane a very pure lithium derivative insoluble in n-pentane can be isolated. The vibrational spectra prove the compound to be lithium cyanotrimethylsilylamide (3).Recrystallization from tetrahydrofuran (+40/+20°C) yields (tetrahydrofuran)lithium cyanotrimethylsilylamide (3′). As shown by an X-ray structure analysis {C2/c; a = 2 261.1(5); b = 1 106.4(2); c = 1 045.9(2) pm; β = 113.63(1)°; Z = 8 formula units}, compound 3′ is polymeric in the solid state. Coordinative Li—N2′ bonds allow a head-to-tail addition of two monomeric units each to give an eight-membered heterocycle with two linear N1—C2≡N2 fragments (N1—C2 126.1; C2≡N2 117.5; N1—Si 171.4; Li—N1 203.2; Li—N2′ 206.1 pm; C2—N1—Li 109.0; N1—Li—N2′ 115.9; N2≡C2—N1 177.2°). Forming planar four-membered Li—N2—Li—N2 rings (Li—N2″″ 198.3 pm; Li′—N2—Li″ 80.3; N2′—Li—N2″″ 99.5°) these heterocycles polymerize to slightly folded tapes.
    Notes: N,N′-Bis(trimethylsilyl)carbodiimid (1) und Lithiummethanid reagieren in Abhängigkeit von der Temperatur sowohl unter Addition als auch Substitution. Wird Verbindung 1 jedoch mit der äquimolaren Menge (1,2-Dimethoxyethan-O,O′)lithium-phosphanid (2) bei -40°C in 1,2-Dimethoxyethan umgesetzt, so erhält man unter Austausch einer Trimethylsilyl-Gruppe gegen Lithium neben Phosphan und Tris(trimethylsilyl)phosphan ein sehr reines, in n-Pentan unlösliches Monosubstitutionsprodukt. Nach Aussage der Schwingungsspektren liegt Lithium-cyantrimethylsilylamid (3) vor.Kühlt man eine bei +40°C gesättigte Lösung von Verbindung 3 in Tetrahydrofuran auf Zimmertemperatur ab, so kristallisiert (Tetrahydrofuran)lithium-cyantrimethylsilylamid (3′) aus. Nach den Ergebnissen der Röntgenstrukturanalyse {C2/c; a = 2261,1(5); b = 1 106,4(2); c = 1 045,9(2) pm; β = 113,63(1)°; Z = 8 Formeleinheiten} liegt ein Polymer vor. Je zwei monomere Einheiten bauen zunächst über koordinative Li—N2′-Bindungen achtgliedrige Heterozyklen mit linearen N1—C2≡N2-Fragmenten auf (N1—C2 126,1; C2≡N2 117,5; N1—Si 171,4; Li—N1 203,2; Li—N2′ 206,1 pm; C2—N1—Li 109,0; N1—Li—N2′ 115,9; N2≡C2—N1 177,2°); diese fügen sich unter Ausbildung planarer viergliedriger Li—N2—Li—N2-Ringe (Li—N2″″ 198,3 pm; Li′—N2—Li″ 80,3; N2′—Li—N2″″ 99,5°) zu einem schwach gewellten Band zusammen.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 405-417 
    ISSN: 0044-2313
    Keywords: Tris(1,2-dimethoxyethane-O,O′)lithium 2λ3-phosphaethynylsulfanide ; [P≡C—S]--anion ; [Li(dme)3]+-cation ; heteroatom-substituted λ3-phosphaalkynes ; nmr and ir data ; X-ray structure determination ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Alkylidynephosphanes and -arsanes. I [P ≡ C—S]-[Li(dme)3]+ - Synthesis and StructureO,O′-Diethyl thiocarbonate and bis(tetrahydrofuran)-lithium bis(trimethylsilyl)phosphanide dissolved in 1,2-dimethoxyethane, react below 0°C to give ethoxy trimethylsilane and tris(1,2-dimethoxyethane-O,O′)lithium 2λ3-phosphaethynylsulfanide - [P≡C—S]- [Li(dme)3]+ - (1a). Apart from bis(trimethylsilyl)sulfane or carbon oxide sulfide, dark red concentrated solutions of λ3-phosphaalkyne 1 are also obtained from reactions of carbon disulfide with bis(tetrahydrofuran)-lithium bis(trimethylsilyl)phosphanide or with the homologous lithoxy-methylidynephosphane (2) [1]. The ir spectrum shows two absorptions at 1762 and 747 cm-1 characteristic for the P≡C and C—S stretching vibrations. The nmr parameters {δ(31P) - 121.3; δ(13C) 190.8 ppm; 1JCP 18.2 Hz} resemble much more values of diorganylamino-2λ3-phosphaalkynes than those of bis(1,2-dimethoxyethane-O,O′)lithoxy-methylidyne-phosphane (2a). As found by an X-ray structure analysis (P21/c; a = 1192.6(16); b = 1239.1(19); c = 1414.8(26) pm; β = 105.91(13)° at -100 ± 3°C; Z = 4 formula units; wR = 0.064) of pale yellow crystals (mp. + 16°C) isolated from the reaction with O,O′-diethyl thiocarbonate, the solid is built up of separate [P≡C—S]- and [Li(dme)3]+ ions. Typical bond lengths and angles are: P≡C 155.5(11); C—S 162.0(11); Li—O 206.4(17) to 220.3(20) pm; P≡C—S 178.9(7)°.
    Notes: O,O′-Diethylthiocarbonat setzt sich mit Bis-(tetrahydrofuran)lithium-bis(trimethylsilyl)phosphanid in 1,2-Dimethoxyethan unterhalb 0°C zu Ethoxy-trimethylsilan und Tris(1,2-dimethoxyethan-O,O′)lithium-2λ3-phosphaethinylsulfanid - [P≡C—S]-[Li(dme)3]+ - (1a)1,2-Dimethoxyethan (dme); Tetrahydrofuran (thf); Bis(2-methoxyethyl)ether (diglyme). Den λ3-Phosphaalkinen P≡C—S—Li und P≡C—O—Li werden unabhängig vom Gehalt an koordinierendem Solvens und der Konstitution die Ziffern 1 und 2 zugeordnet; bei den röntgenstrukturanalytisch untersuchten Komplexen [P≡C—S]-[Li(dme)3]+ und P≡C—O—Li(dme)2 kommt das Suffix a hinzu. um. Das als dunkelrote, konzentrierte Lösung erhaltene λ3-Phosphaalkin 1 entsteht neben Bis(trimethylsilyl)sulfan bzw. Kohlenstoffoxidsulfid auch bei den Umsetzungen von Kohlenstoffdisulfid mit Bis(tetrahydrofuran)lithium-bis(trimethylsilyl)phosphanid oder dem homologen Lithoxy-methylidinphosphan P≡C—O—Li (2) [1]. Das IR-Spektrum weist die für eine P≡C- und C—S-Valenzschwingung charakteristischen Absorptionen bei 1762 und 747 cm-1 auf; die NMR-Parameter {δ(31P) - 121,3; δ(13C) 190,8 ppm; 1JCP 18,2 Hz} gleichen mehr den Werten der Diorganylamino-2λ3-phosphaalkine als des Bis(1,2-dimethoxyethan-O,O′)-lithoxy-methylidinphosphans (2a). Nach den Ergebnissen einer Röntgenstrukturanalyse (P21/c; a = 1192,6(16); b = 1239,1(19); c = 1414,8(26) pm; β = 105,91(13)° bei -100 ± 3°C; Z = 4 Formeleinheiten; wR = 0,064) an blaßgelben, aus einem Ansatz mit O,O′-Diethylthiocarbonat isolierten Kristallen (Schmp. + 16°C) liegen im Festkörper getrennte [P≡C—S]-- und [Li(dme)3]+-Ionen vor. Charakteristische Bindungslängen und -winkel sind: P≡C 155,5(11); C—S 162,0(11); Li—O 206,4(17) bis 220,3(20) pm; P≡C—S 178,9(7)°.
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