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The cycloadducts 6 and 7 of tricyc1o[4.1.0.0 2 ,7)hepta- 3,4-diene (~) with styrene and 1,3-butadiene rearrange to unusual products on thermolysis, namely the cycloheptatriene derivatives ~ and 10. 1-0xa-3,4-cyclohexadiene (20) is generated smoothly from 6,6-dichloro-3-oxabicyclo[3.1.0]hexane (22) and n-butyllithium. 1-0xa-2,3-cyclohexadiene (11) is formed from 6-exo-bromo-6-endo-fluoro-2-oxabicyclo[ 3.1.0]hexane (30) and methyllithium. In the presence of activated olefins, this reaction provides an efficient route to 28 and 33 - 38, the trapping products of 21. Interestingly, [2+2]-cycloadditions do not take place at the same double bond of 21 as [4+2]-cycloadditions. The reactions of 1,3-cyclopentadiene and indene with bromofluorocarbene afford 6-exo-bromo-6-endo-fluorobicyclo[3.1.0]hex-2-ene (50) and its benzo derivative ~, respectively. On treatment of these compounds with methyl lithium in the presence of styrene, the interception products 53 and 47 of 1,2,4-cyc10- hexatriene (44) and its benzo derivative 43, respectively, are formed in good yields.
Umsetzung von 6,6-Dichlor-2-oxabicyclo[3.1.0)hexan (4a) in Styrol mit n-Butyllithium lieferte neben Polystyrol und t-Chlor-1- pbenylhexan (6) in geringer Ausbeute die Tet~hydrocyclobutapyrane 5, die Abfangprodukte des aus 4a generierten t-Oxa-2,3- cyclobexadiens (3). Das unbeständige 6,6-Dibrom-2-oxabicyclo( J.l.O]hexan (4b) wurde bei -60°C erzeugt un~ bei -30°C mit Methyllithium in Gegenwart von Styrol umgesetzt, woraus die Produkte 5 mit 24% Ausbeute hervorgingen. Als bei 20°C beständige Quelle für 3 erwies sich exo-6-Brom-e~o-6-fluor-2-oxabicyclo[ J.t.O]bexan (9), das aus 2,3-Dihydrofuran und Bromßuorcarben mit 25% Ausbeute bereitet wurde. Behandlung von 9 in Styrol, <X-Methylstyrol, 1,3-Butadien, 2,3-Dimet~yl-!,3-butadien, Furan und 2,5-Dimethylfuran mit Methyllithium ergab Abfangprodukte von 3 mit Ausbeuten von 31-80%. Dabei entstanden mit den Styrolen und überwiegend auch mit den l ,3-Butadienen (2 + 2]-Cycloaddukte als Diastereomerengemische, nämlich 5, ll, 13 und 15. Die Furane lieferten ausschließlieb [4 + 2]-Cycloaddukte (17 und 18), die 1,3-Butadiene nur mit einem kleinen Anteil (14 und 16). [2 + 2]- und [4 + 2]-Cycloadditionen zeigen eine unterschiedliche Chemoselektivität. Während erstere die Enolether- Doppelbindung von 3 nutzen, finden letztere an der vom Sauerstoffatom entfernteren Doppelbindung statt. Das als 1 : IGemisch aus exo- und endo-Isomeren anfallende Produkt 5 lieferte beim Erhitzen auf l50°C ein 20:1: 1-Gemiseh aus exo- und endo-5 sowie dem Strukturisomeren 19. Thermolyse· des 2: 1-Gemisches aus 13 und 14 erbrachte ein 2: 1-Gemiscb aus 14 und dem Tetrahydro-1-benzopyran 20.
No abstract available
Nichtbindende Wechselwirkungen in zwei 7-Spirotetracyclo[4.1.0.0\(^{2,4}\).0\(^{3,5}\)]heptanen
(1989)
Die Reaktion von Tetrachlordiazocyclopentadien mit Be.nzvalen (2) ergab das Fulven-Derivat 3. Dagegen führten die Umsetzungen von Diazoßuoren und 5-Diazo-10,1 1-dihydro-SH-dibenzo[ a.d]cyclohepten mit 2 zu den erwarteten Spiro-1-pyrazolinen 4 bzw. 5. Die photolytische Abspaltung von Stickstoff aus 4 und 5 lieferte die Spirotetracycloheptane 6 bzw. 7. Die Röntgenstrukturanalyse von 6 beweist einen engen Kontakt zwischen je eineßl Wasserstoffatom der Tetracycloheptan- und der Fluoren-Einheit. Dieser kurze Abstand (2.15 A) ruft Winkelaufweitungen hervor und wird auch als Grund für starke Entschirmungen der betreffenden Protonen und eine formal über sieben Bindungen reichende 0.6-Hz-Kopplung zwischen ihnen angesehen. 7 ist das erste chiralc Tetracyclohcptan. Ursache dafür ist eine nichtebene Konformation des Siebenrings, der bei Raumtemperatur nicht invertiert. Auf der Basis von NOE-Messungen gelang die Zuordnung der tH-NMR-Signale von 6 und 7.
This article gives an overview of possibilities for the assessment offacial behavior. With regard to validity, results from a longitudinal study of 36 depressed patients and nine controls as weil as often schizophrenic patients and their relatives will be referred to. These results are used to illustrate the following principles which have to be taken into account when studying facial behavior: a) communication strongly facilitates facial expression, b) activation of facial behavior follows the "principle of least effort", and c) the principle of individual specificity applies to the association of nonverbal behavior and mood states. Making allowance for these principles has, among others, consequences a) for situations or conditions under which to asses behavior (specifically conditions of communication), b) for data analysis (e.g., dealing with frequent and rare events), and c) for empirical or experimental strategies (e.g., aggregation of single-case longitudinal comparisons). From the results on facial behavior during depression it can be concluded that the nonverbal reaction tendencies of endogenous and neurotic depressed patients differ. Moreover, the differential behavioral pattems observed cast doubt on the assumption of a homogeneity of affects in depression. Taking into account the conditions which govern it, facial behavior has proved to be a valid and, especially, a differential indicator for pathoIogic affective states and their changes. Given the fact that a psychiatric illness generally incorporates emotional problems it is more than surprising that little attention has been paid to the systematic study of emotional behavior. Some of the reasons for this will be clarified in the following.
No abstract available
No abstract available
Large-scale multireference configuration interaction (MRD-CI) calculations in a quite flexible AO basis are employed to study the energy hypersurface for the reaction intermediate FC\(_2\)H\(_4\) • The reaction F + C\(_2\)H\(_4\) -> FC\(_2\)H\(_4\) as weil as the 1,2 migration of the fluorine atom in FC\(_2\)H\(_4\) is investigated. In addition the rotation around the CC bond in the optimum conformation is studied. The absolute minimum in the potential energy is found for the asymmetric structure but the symmetric structure is also found to be stable with respect to the dissociation, so that a shuttling of the fluorine atom is in principle possible but highly unlikely because ( l) the activation energy is high ( II 5-130 kJ fmol) and the saddle point lies only 4(}-50 kJ jmol below the dissociation Iimit of F + C\(_2\)H\(_4\) and (2) the competitive motion, i.e., rotation around the CC axis, is nearly free (I 1-17 kJ/mol).
The hyperfine coupling constants for the \(^3\)Σ\(-\) ground state of the NH molecule are determined by configuration interaction calculations whereby the infl.uence of polarization functions as weil as of the configuration space on the spin polarization mechanism is analysed. The dipolar part Au(N) and Au(H) can be obtained very reliably without much computational effort (A .. (N) == -45·3 MHz and A"(H) = -62·3 MHz). The value for the isotropic contribution a1.., in the best AO basis and MRD-CI treatment is - 64·5 MHz for H and 16·6 MHz for nitrogen compared to the corresponding experimental quantities of -66 MHz and 19 MHz respectively. Their determination depends on a subtle balance of the lu, 2u and 3u shell correlation description, whereby the dominant contribution to a1..,(H) results from the 2u shell. It is shown that the often good agreement of a110 values with experiment in a small basis singledouble configuration interaction treatment results from a cancellation of two errors.
Multi-reference configuration interaction calculations employing various orbital transformations are undertaken to obtain the isotropic hyperfine coupling constant a\(_{iso\) in nitrogen and a\(_{iso\) (H) in the CH molecule. The natural orbital (NO) basis is found to be more effective than the simple RHF-MO basis; the most obvious is a basis of spin natural orbitals (SNO). It is found that a\(_{iso\) is approached from opposite sides in the NO and 2s shell SNO basis if the CI expansion is increased. Both results are within a few percent of the full CI Iimit for the nitrogen atorn (in the given AO basis) and the experimental value for Hin the CH radical. Various features ofthe SNO are discussed.
At early developmental stages (embryonic day 7, E7), chick paravertebral sympathetic ganglia contain a cell population that divides in culture while expressing various neuronal properties. In an attempt to identify factors that control neuronal proliferation, we found that ciliary neurotrophic factor (CNTF) specifically inhibits the proliferation of those cells expressing neuronal markers. In addition, CNTF affects the differentiation of sympathetic ganglion cells by inducing the expression of vasoactive intestinal peptide immunoreactivity (VIP-IR). After 1 day in culture, tyrosine hydroxylase immunoreactivity (TH-I R) was expressed by about 86% of the cells whereas VIP-IR was virtually absent. In the presence of CNTF, 50%-60% of the cells expressed VIP-IR after 4 days in culture; however, none of the cells expressed VIP-IR in the absence of CNTF. These results, and the demonstration of cells that express both VIP and TH-IR, indicate that VIP is induced in cells that initially express tyrosine hydroxylase. The findings suggest a potential role for CNTF as a factor affecting the proliferation and differentiation of developing sympathetic neurons.
We have previously reported that analgesic doses of morphine accelerate mortality of rats exposed to hemorrhage (Feuerstein and Siren: Circ Shock 19:293-300, 1986). To study the potential mechanisms involved in this phenomenon, rats were chronically implanted with catheters in the femoral vessels and morphine (1.5 or 5 mg/kg) was administered 30 min or 24 hr after bleeding (8.5 mll300 g over 5 min) while arterial blood pressure and heart rate were continuously monitored. Furthermore, the effect of morphine (5 mg/kg) on cardiac output (CO) response to hemorrhage was studied in rats chronically equipped with a mini thermistor for CO monitoring by a thermodilution technique. In addition, plasma catecholamines (HPLC), plasma renin activity (PRA, RIA), vasopressin (RIA), pH, and blood gases were also determined. Morphine administration 30 min after hemorrhage produced a pressor response and tachycardia which were in marked contrast to its depressor effect in intact rats. Morphine elevated PRA and epinephrine but not vasopressin, while blood pH and gases showed no consistent change as compared to salinetreated hemorrhaged rats. Morphine given after the bleeding resulted in enhanced cardiac depression in response to a second bleed of 2 m1l300 g. Our data suggest that activation of pressor mechanisms by morphine during hypovolemic hypotension might enhance vasoconstriction in essential organs, depress cardiac function, and further reduce effective tissue perfusion.
In the humid tropics of SE Asia there are some 14 myrmecophytic species of the pioneer tree genus Macaranga (Euphorbiaceae). In Peninsular Malaysia a close association exists between the trees and the small, non-stinging myrmicine Crema togas ter borneensis. These ants feed mainly on food bodies provided by the plants and have their colonies inside the hollow intemodes. In a ten months field study we were able to demonstrate for four Macaranga species (M. triloba, M. hypoleuca, M. hosei, M. hulletti) that host plants also benefit considerably from ant-occupation. Ants do not contribute to the nutrient demands of their host plant, they do, however, protect it against herbivores and plant competition. Cleaning behaviour of the ants results in the removal of potential herbivores already in their earliest developmental stages. Strong aggressiveness and a mass recruiting system enable the ants to defend the host plant against many herbivorous insects. This results in a significant decrease in leaf damage due to herbivores on ant-occupied compared to ant-free myrmecophytes as well as compared to non-myrmecophytic Macaranga species. Most important is the ants' defense of the host plant against plant competitors, especially vines, which are abundant in the well-lit pioneer habitats where Macaranga grows. Ants bite off any foreign plant part coming into contact with their host plant. Both ant-free myrmecophytes and non-myrmecophytic Macaranga species had a significantly higher incidence of vine growth than specimens with active ant colonies. This may be a factor of considerable importance allowing Macaranga plants to grow at sites of strongest competition.