Showing papers by "University of Würzburg published in 1975"

Incidence of Listeria monocytogenes in nature.

Abstract: During a research project on the occurrence of Listeria monocytogenes 194 strains were isolated in southern West Germany during the years 1972 to 1974:154 from soil and plant samples (20.3%), 16 from feces of deer and stag (15.7%), 9 from old moldy fodder and wildlife feeding grounds (27.2%), and 8 from birds (17.3%). The highest number of isolates was obtained from uncultivated fields. The beta-hemolytic serovars 1/2b and 4b were were predominant; other serovars (some of them identified for the first time), including nonhemolyzing strains, have been encountered frequently. It is suggested that Listeria monocytogenes is a saprophytic organism which lives in a plant-soil environment and therefore can be contracted by humans and animals via many possible routes from many sources.

Metabolism of trichloroethylene in man. III. Interaction of trichloroethylene and ethanol.

Abstract: Volunteers inhaled a constant concentration of 50 ppm trichloroethylene (Tri) for 6 hrs per day on 5 consecutive days. Simultaneous ethanol (EtOH) ingestion (blood level 0.6 %.) inhibits the metabolization of Tri to triehloroethanol (TCE) and trichloroacetic acid (TCA) by 40 % on the average. Oxidation of Tri to TCA does not occur as long as EtOH is present. During this time period the blood Tri-concentration increases 21/2-fold, that in the expired air rising 4-fold, as compared to Tri inhalation without EtOH. TCE glucuronidation is not subject to inhibition. On concurrent inhalation of Tri, the EtOH and acetaldehyde levels are slightly increased over the control values without Tri. The mechanisms underlying the alternate inhibition of mixed-function oxygenases and aldehyde dehydrogenase on simultaneous intake of Tri and EtOH are discussed. The intolerance reaction occurring on combined exposure to Tri and EtOH can be interpreted as an accumulation of Tri in the CNS resulting from the complete depression of Tri oxidation.

The role of air humidity and leaf temperature in controlling stomatal resistance of Prunus armeniaca L. under desert conditions : II. The significance of leaf water status and internal carbon dioxide concentration.

Abstract: The gas exchange of the apricot (Prunus armeniaca L.) growing in the runoff farm at Avdat (Negev, Israel) was measured during its growing period using temperature- and humidity-controlled chambers. Water potentials of the xylem were measured with a pressure bomb, and the mesophyll internal CO2 concentration was calculated from simultaneous measurements of net photosynthesis and transpiration.

Concepts of microdosimetry

Abstract: This is the second part of an investigation of microdosimetric concepts relevant to numerical calculations. Two different types of distributions of the microdosimetric quantities are discussed. The sampling procedures are considered, which lead from the initial pattern of energy transfer, the so-called inchoate distribution, to the distribution of specific energy and thier mean values. The dependences of the distribution of specific energy on absorbed dose is related to the sampling procedures.

Induction of drug metabolism in man after rifampicin treatment measured by increased hexobarbital and tolbutamide clearance.

Abstract: Five healthy volunteers took 1.2 g rifampicin daily for 8 days, and before and afterwards each received hexobarbital (7.32 mg/kg) and tolbutamide (20 mg/kg) by i.v. infusion on two consecutive days. The plasma concentrations of the two drugs were determined during and after infusion. The average elimination half-life of hexobarbital had decreased from 325 to 122 min and of tolbutamide from 418 to 183 min following rifampicin treatment. It was calculated that the metabolic clearance of hexobarbital had increased about three-fold and that of tolbutamide more than two-fold. Significant changes in the distribution kinetics of the two drugs were not observed. The results suggest that rifampicin is capable of inducing drug metabolism in man, which leads to an increased rate of elimination of drugs that undergo biotransformation in the liver.

A third signal in B cell activation given by TRF.

Abstract: There is a wealth of experimental evidence supporting the idea that T cells have to intervene in the immune response to many antigens to ensure an optimal antibody response (Reviewed in Greaves et al. 1973). We have addressed our work to the question at whicli step of B cell activation this intervention is necessary. An in vitro culture system (Mishell & Dutton 1967) was applied using spleen cells of thie functionally athymic nu/nu mice and heterologous blood cells as antigens. SRBC can operationally be defined as T cell dependent antigens since the IgM immune response in T cell deprived cultures is far from the optimal response obtained in the presence of T cells (Schimpl & Wecker 1970). In an attempt to restore the immune response in T cell deprived cultures with thymocytes we found that allogeneic thymocytes were greatly superior to syngeneic ones (Schimpl & Wecker 1971). Subsequent experiments showed that the effect could be ascribed to a soluble factor produced by allogeneically or Concanavalin A (Con A) stimulated T cells (Schimpl & Wecker 1972, Wecker et al. 1974). Soluble mediators with similar T cell replacing activities have now been described by many different groups (Dutton et al. 1971, Doria et al. 1972, Gorczynski et al. 1972, Feldmann & Basten 1972, Britton 1972, Sjoberg et al. 1972, Gisler et al. 1973, Rubin et al. 1973, Waldmann & Munro 1973, Watson 1973, Kishimoto & Ishizaka 1973, Amerding & Katz 1974), some factors being obtained from T cells, activated by antigen in vivo and incubated with the same antigen in vitro. The assumption imderlying all further considerations is that such mediators are regularly produced upon stimulation of T cells and that they

Oxygen supply and uptake in the liver and the intestine.

Abstract: The oxygen supply to the liver was found to be dependent on the total blood flow only and not on the ratio of arterial to portal contribution. The mean value of O2-uptake in the liver, related to a blood flow of 110 ml/min - 100 g liver, amounted to 6.08 +/- 0.2 ml O2/min - 100 g liver (mean +/- S.E.M.). O2-uptake of the intestine was found to be 1.95 +/- 0.13 ml O2/min - 100 g tissue, related to a normal blood flow of 50 ml/min - 100 g tissue. With low oxygen supply O2 extraction in the liver reaches values of 97%, whereas the intestinal extraction does not surpass 75%. A rise in oxygen supply surmounting normal values does not increase the O2-consumption. Contrary to the intestinal circulation the liver showed no postocclusive vasodilatation. The oxygen debt was payed back by a greater extraction. The portal oxygen supply to the liver can markedly increase due to intestinal metabolic hyperemia. High O2-extraction capacity, rather than vasodilatation, is the main mechanism for matching hepatic oxygen supply with requirements. The hepatic venous blood may leave the liver with an extremely low O2-content.

13 C‐NMR‐Spektren von Bicyclo[n.1.0]kohlenwasserstoffen

Abstract: Die 13C-NMR-Spektren einer Reihe gespannter polycyclischer Verbindungen werden vorgelegt und zusammen mit publizierten Spektren von Vergleichssubstanzen diskutiert. In einigen Systemen uben Cyclopropanringe Effekte auf die chemischen Verschiebungen bestimmter Kohlenstoffe aus, die zur Konformationsanalyse von Bicyclo[3.1.0]hexanen nutzlich sind. Gemas einer qualitativen MO-Betrachtung sowie MINDO/2- und ab-initio-Berechnungen werden diese Einflusse durch Elektronendichteveranderungen an diesen Zentren hervorgerufen. Die bekannte Beziehung zwischen 13CH-Kopplungskonstanten und der Ringspannung liefert Aussagen uber die Spannungsenergie in endo-endo'-uberbruckten Bicyclo[1.1.0]butanen. Am Tetracyclo[4.1.0.02,4.03,5]-heptan (1) wurden 13C13C-Kopplungskonstanten bestimmt. 13C N. M. R. Spectra of Bicyclo[n.1.0]hydrocarbons The 13C n. m. r. spectra of a series of strained polycyclic compounds are presented and discussed in comparison with the spectra of related substances given in the literature. In some systems effects of cyclopropane rings on the chemical shift of certain carbons are observed, which can be applied in the conformational analysis of bicyclo[3.1.0]hexanes. According to a qualitative MO argument as well as MINDO/2 and ab initio calculations these effects are caused by changes of the electron density at the centres concerned. The well known correlation between 13CH coupling constants and ring strain provides information on the strain energy in endo-endo'-bridged bicyclo[1.1.0]butanes. 13C13C coupling constants were determined in tetracyclo[4.1.0.02,4.03,5]-heptane (1).

Application of multiple shooting to the numerical solution of optimal control problems with bounded state variables

Abstract: Algorithms for the numerical solution of optimal control problems with bounded state variables are developed. Two main cases are considered: either the control variable appears nonlinearly or the control variable appears linearly. In the first case, an extremal are touching the boundary or containing a boundary arc, is shown to satisfy a suitable two-point boundary value problem. In the second case, a numerical idea for solving the problem in statespace is presented which dispenses with the Lagrange-multipliers. Three numerical examples are discussed illustrating the efficiency of the different algorithms. The encountered two-point boundary value problems are solved with the method of multiple shooting.

Pharmacokinetics of hexobarbital in acute hepatitis and after apparent recovery.

Abstract: The pharmacokinetics of hexobarbital were studied in 13 patients with acute hepatitis. Hexobarbital sodium was administered by zero order intravenous (iv) infusion, and plasma concentrations were determined regularly by gas chromatography. For each patient the data were fitted according to 2-compartment kinetics. The results were compared to those obtained for 14 healthy volunteers. The elimination half-life of hexobarbital was 490 +/- 186 min in the hepatitis patients and 261 +/- 69 min in the control group. Clearance was significantly reduced in the hepatitis group, whereas the volume of distribution at steady state was not significantly altered. For some patients the initial distribution volume was reduced. In 6 patients the experiment with hexobarbital was repeated after apparent recovery from hepatitis as judged by normal transaminase and bilirubin levels. Generally the half-life of hexobarbital was shorter and the clearance value was higher than during the acute illness, but the values had not yet returned to normal. Clinical recovery from liver disease is not accompanied by corresponding recovery of drug-metabolizing capability.

The role of air humidity and temperature in controlling stomatal resistance of Prunus armeniaca L. under desert conditions : III. The effect on water use efficiency.

Abstract: Measurements of CO2 and water vapor exchange were performed on Prunus armeniaca L. with humidity- and temperature-controlled chambers under the climatic conditions of a desert habitat. In apricot, the stomatal response to changes in temperature and water-vapor concentration difference between leaf and air (WD) significantly determined the rates of gas exchange during the day (parts I and II). The effect of climate-controlled stomatal response on the transpiration/net photosynthesis (T/P)-ratio was analyzed and simulated using experiments conducted at constant temperature and/or humidity conditions for input parameters. The measured values of the T/P-ratio at naturally varying conditions of humidity and temperature were compared with calculated results of a model in which it was assumed, (1) that stomata and photosynthetic activity are not affected by air humidity and temperature, (2) that the stomata only respond with a constant photosynthetic activity to changes in WD, and (3) that the stomata respond to both, leaf temperature and air humidity with a constant photosynthetic activity. These simulations facilitated an analysis of the naturally observed changes in the T/P-ratio.The calculated T/P-ratios were very small if the simulation assumed that stomata only respond to WD at a constant photosynthetic activity. These low predicted values of the T/P-ratio were not obtained under natural conditions, since an increase in WD during the day was correlated with a temperature rise which tended to open stomata and change the photosynthetic activity. Humidity induced stomatal closure did appear to substantially reduce T/P-ratios.The measured T/P-ratio changed considerably during the year. The lowest T/P-ratios were obtained in the middle of the dry season at a time when stomata responded strongly to air humidity and when optimum of photosynthesis was reached at high temperatures. The daily average T/P-ratio calculated from the daily sum of P and T showed little change during the seasons. A high T/P-ratio was also observed at reduced rates of gas exchange. The T/P-ratios of apricot were compared with different species in different environments.

The pH dependence of SO2 damage to lichens.

Abstract: In order to determine the influence of the hydrogen-ion concentration on the damage exerted to lichens by sulfur dioxide gas, thalli of the species Hypogymnia physodes and Xanthoria parietina were submerged in buffer solutions of pH 2 to pH 8 and subsequently exposed to SO2 gas. Net photosynthesis was employed as a criterion of vitality.

Determination of the Complete Amino-Acid Sequence of Protein S4 from Escherichia coli Ribosomes

Abstract: After digestion of protein S4 with trypsin, all 32 tryptic peptides were isolated. Their amino acid compositions were analyzed and the sequence of the amino acids within the tryptic peptides was determined by means of a solid-phase peptide sequenator and by exopeptidases. Alignment of the tryptic peptides was established by analyzing and partially sequencing peptides isolated after digestion of the S4 protein with cnymotrypsin, thermolysin and a glutamic-acid-specific protease. Further information about the alignment of peptides came from treatment of S4 with CNBr and with a lysine-modifying reagent. Protein S4 consists of 203 amino acids (Asp8, Asn8, Thr6, Ser10, Glu16, Gln10, Pro6, Gly15, Ala18, Val16, Cys1, Met3, Ile8, Leu20, Tyr8, Phe4, His3, Lys20, Arg22 and Trp1) and has a molecular weight of 22550. The basic amino acids are clustered in five regions. Many short repetitions mainly with charged amino acids occur. A prediction is made for regions with α-helices and with β-sheets.

Malonyl and palmityl transferase-less mutants of the yeast fatty-acid-synthetase complex.

Abstract: 146 independently isolated mutants of the fatty acid synthetase gene locus fas 1 were subdivided into six different complementation groups. Three of these groups, Va, Vb and Vd, have not been described before. The mutant fatty acid synthetases isolated from representatives of complementation group Vb were specifically deficient in two component enzymes at the same time, the malonyl and palmityl transferases. Among more than 180 fas 1 and fas 2 mutants systematically screened for malonyl and palmityl transferase activities no mutant was found affected in only one of these two fatty acid synthetase component enzymes. From this it is concluded that both transfer reactions are catalyzed by the same enzyme. In any malonyl transferase-less fatty acid synthetase, neither of the two known malonyl binding sites, i.e. enzyme-bound pantetheine and the non-thiol binding site, accepts malonate. This indicates that malonate is transferred to both groups by the same enzyme. So far, no acetyl transferase-less fas mutants have been characterized. On the other hand, the mutants of two fas 1 complementation groups, Va and Vd, though negative in overall fatty acid synthetase activity had no deficiency in any of the known component enzymes which can be tested in vitro. A possible interrelationship between both findings is discussed.

The temperature-related photosynthetic capacity of plants under desert conditions : II. Possible controlling mechanisms for the seasonal changes of the photosynthetic response to temperature.

Abstract: In a previous paper seasonal shifts of the temperature optimum (OP) and of the upper temperature compensation point (CP) of net photosynthesis were described for Hammada scoparia growing wild, and for Prunus armeniaca cultivated in the Negev Desert (Israel). In this paper the relationships between these shifts and the microclimatic conditions, plant-water relations, and plant development are studied.The energy budged of the thin, round photosynthesizing stems of H. scoparia growing in an open desert habitat differes from that of the broad leaves of P. armeniaca within the orchard. This explains the fact that daily maximum temperatures of the apricot increased until August and September, whereas maximum temperatures of H. scoparia reached a peak in May and June and decreased thereafter during the second half of the growing season.For H. scoparia a correspondence was found between the daily maximum tissue temperatures (and also the average temperatures of the warmest periods of the day) and the seasonal changes of the OP and CP values. This may indicate that the shifts in the temperature sensitivity of net photosynthesis of this plant are adaptations to the temperature conditions of the plant. This, however, cannot be the case for P. armeniaca, where during the second part of the growing season a period of rising leaf temperatures coincides with a period of decreasing OP and CP values. Therefore, the seasonal changes of the temperature dependence of net photosynthesis of P. armeniaca could not always be considered an adaptation to the prevailing temperature conditions of the plant. In this case, the changes in temperature sensitivity of photosynthesis could be due to developmental processes such as aging. In both lants the seasonal changes of the OP and CP values correspond to changes of the daily photoperiod and to changes of the daily average light intensity. It appears possible that this correlation indicates a causal relationship.

Sterische Wechselwirkungen im Innern cyclischer Verbindungen, XXII. No2,CO2R,SO2R,SCH3 und C6H5 als intraanulare Substituenten

Abstract: Durch dynamische 1H-NMR-Spektroskopie wird die Raumbeanspruchung der folgenden, in neuen Ringverbindungen aromatisch gebundenen Gruppen miteinander und mit fruher untersuchten Substituenten verglichen: NO2, CO2CH3, SO2CH3, SCH3, C6H5. Der „Gesamt-Raumbedarf” der intraanularen Nitrogruppe wird etwas kleiner als der von Methyl gefunden. Der Platz-bedarf der Methylesterfunktion ist betrachtlich groser. Der Methylthiorest ist voluminoser als die OCH3-Gruppe, aber deutlich kleiner als SO2CH3. Isochronie-Effekte verhindern entsprechende Messungen fur die unsubstituierte Phenylgruppe. Sterische Einflusse durch intraanulare Substituenten bestimmen auch die statische und dynamische Stereochemie neuer [2.2]- und [3.3]Phane mit diesen intraanularen Substituenten. Steric Interactions of Inner Atoms in Cyclic Compounds, XXII. NO2, CO2R, SO2R, SCH3 and C6H5 as Intraanular Substituents Dynamic 1H-n.m.r. spectroscopy permits the comparison of the steric requirements of several substituents in new ring compounds, e.g. the NO2, CO2CH3, SO2CH3, SCH3, and C6H H5 groups. The „overall spatial requirement” of NO2 is found to be slightly smaller than that of the CH3 group. CO2CH3 and SO2CH3 are bulkier than NO2 and SCH3, the latter exceeding OCH3 as well. Isochrony effects prevent analogous measurements for the phenyl group. Steric factors also control the static and dynamic stereochemistry of new intraanularly substituted [2.2]- and [3.3]Phanes.

Galvanomagnetic Properties of Bi2Se3with Free Carrier Densities below 5 × 1017 cm−3

Abstract: Bi2Se3, Bi2Te3, and Sb2Te3 tend to grow non-stoichiometric, the defects causing high free carrier densities. Here it was achieved, in the case of Bi2Se3, to produce crystals of n-and p-type conductivity showing concentrations down to 4 × 1016 cm−3. The temperature and magnetic field dependences of their galvanomagnetic properties are investigated. At low magnetic fields and low temperatures negative magnetoresistance occurs, at high magnetic fields no saturation of the positive magnetoresistance is observed which is assumed to originate from the influence of an impurity conduction band. The temperature dependence of the Hall constant enables the evaluation of the energy gap for thermal excitations to (160 ± 10) meV for T 0. The temperature dependence of the mobility between about 50 and 200 K supports the assumption of dominating scattering of the free carriers by acoustical phonons in this temperature range. Bi2Se3, Bi2Te3 und Sb2Te3 neigen zu einem unstochiometrischen Wachstum, wobei die Defekte hohe Dichten freier Ladungstrager verursachen. Hier gelang es,im Falle von Bi2Se3, Kristalle mit n-undp-Leitungstypzu erzeugen, die Tragerkonzentrationen bis hinab zu 4 × 1016 cm−3 aufwiesen. Die Temperatur- und Magnetfeldabhangigkeiten der galvanomagnetischen Eigenschaften werden untersucht. Bei kleinen magnetischen Flusdichten und niedrigen Temperaturen wird eine negative Magnetowiderstandsanderung gefunden, bei hohen Feldern fehlt jedes Anzeichen einer Sattigung der positiven Magnetowiderstandsanderung, was auf den Einflus eines Storleitungsbandes zuruckgefuhrt wird. Die Tempera-turabhangigkeitder Hallkonstante ermoglicht die Auswertung der kleiusten Bandlucke fur thermische Anregungen zu (160 ± 10) meV fur T 0. Die Temperaturabhangigkeit der Beweglichkeit zwischen etwa 50 und 200 K unterstutzt die Annahme einer uberwiegen-den Streuung der freien Ladungstrager durch akustische Phononen in diesem Temperatur-bereich.

Theg-factor of the conduction electrons in Bi2Se3

Abstract: The oscillatory part of the magneto-resistance (Shubnikov-de Haas effect) was investigated on n-Bi2Se3 single crystals with carrier concentrations between 5 × 1017 and 1 × 1018cm−3 in the temperature range from 1.6 to 4.2 K in pulsed magnetic fields up to 35 T (350 kG) magnetic induction. Most experiments were performed for the magnetic induction B parallel to the trigonal axis c of the crystals, where the smallest cyclotron mass mc and a parabolic e(κ) relation is present. No spin-splitting of the Shubnikov-de Haas resistivity extrema is observed at high quantum numbers. At low quantum numbers the influence of spin-splitting causes a shift of the resistivity extrema and an additional maximum, which should not be present for M = gmc/(2m0) ≪ 1. A calculation of the magnetoresistance in quantizing magnetic fields based on Kubo's theory for a field-independent carrier concentration enables the determination of the expression M = gmc/(2m0) = 2 with ±5% uncertainty for B‖ c. The absolute value of the g-factor is evaluated hence as (32 ± 3) for B‖ c. For arbitrary crystal orientation in the magnetic field M may be assumed to be constant within the error margin, the g-factor being consequently smaller for B ⟂ c: g ⟂ = (23 ± 3). Der oszillatorische Anteil der Magneto-Widerstandsanderung (Shubnikov-de Haas-Effekt) wurde an n-Bi2Se3-Einkristallen mit Ladungstragerkonzentrationen zwischen 5×l017 and 1×1018 cm−3 im Temperaturbereich von 1,6 bis 4,2 K in gepulsten Magnet-feldern bis zu 35 T (350 kG) Flusdichte untersucht. Die meisten Experimente wurden fur B‖ c (B Vektor der magnetischen Flusdichte, c trigonale Achae der Kristalle) durchgefuhrt, wo die kleinste Zyklotronmasse mc bei parabolischer e(κ)-Beziehung vorliegt. Bei hohen Quantenzahlen wird keine Spin-Aufspaltung der Shubnikov-de Haas-Widerstandsextrema beobachtet. Bei kleinen Quantenzahlen bewirkt der Einflus der Spin-Aufspaltung eine Verschiebung der Widerstandsextrema und ein zusatzliches Maximum, das fur M = gmc/(2m0) ≪ 1 nicht vorhanden sein sollte. Eine Berechnung des Magnetowiderstandes in quantisierenden Magnetfeldern auf der Grundlage der Kuboschen Theorie mit der Annahme einer magnetfeld-unabhangigen Elektronenkonzentration erlaubt die Bestimmung des Ausdrucks M = gmc/(2m0) = 2 mit einer Unsicherheit von ±5% fur B‖ c. Der Absolutbetrag des g-Faktors wird hieraus zu. (32 ± 3) fur B‖ c ausgewertet. Fur beliebige Kristallorientierungen im Magnetfeld kann M innerhalb der Fehlergrenzen als konstant angenommen werden, der g-Faktor hat daher fur B ⟂ c einen kleineren Wert: g ⟂ = (23±3).

Methylkobaltverbindungen mit nicht chelatisierenden Liganden, III: Dimethyltris (trimethylphosphin)kobalt(II) und seine Derivate

Abstract: Bei der Reduktion von Kobaltdichlorid mit Natriumamalgam oder Magnesium in Athern wird in Gegenwart von Trimethylphosphin paramagnetisches L4Co (L(CH3)3P) gebildet. Als Zwischenstufe der Reduktion wird ein komplexes Kobalt(I)-chlorid der Formel L3CoCl (L (CH3)3P) isoliert. Dieses entsteht quantitativ aus L4Co und wasserfreiem Kobaltchlorid. Mit LiCH3 wird daraus die Titelverbindung L4CoCH3 dargestellt. Ihre CoC-Bindung wird durch Protonensauren unter Methanentwicklung gelost, wobei z. B. das Kobalt(I)-acetylid L4CoC CC6H5 bzw. Polymere der Formel Co(OR)2(RCH3, CH3, C2H5, Si(CH3)3, C6H5) entstehen. Carbonylierung und Decarbonylierung unter Normalbedingungen liefert [L2(CO2Co]2, L3(CO)CoCH3 und L 2(CO)2CoCOCH3. Gegenuber L4Co ist neben Acetylchlorid sogar noch Acetanhydrid zu einer oxidativen Additionsreaktion befahigt. L4CoCH3 ist stark reduzierend und reagiert sogar mit CO2. Die oxidative Addition von CH3X (XBr. j) fuhrt in die Reihe der neuartigen Methylkobalt Methylkobalt(III)-Komplexe. – Die Protonenresonanz der CoCH3-Gruppe zeigt bei variabler Temperatur die enge Verwandtschaft im dynamischen Verhalten der isosteren Verbindungen L4CoCH3 und [L4NiCH3]+. Methylcobalt Compounds with Non-chelating Ligands, I. Methyltetrakis(trimethylphosphine)cobalt and its Derivatives In the presence of trimethylphosphine, cobalt dichloride is reduced with sodium amalgam or magnesium in ethers to give paramagnetic L4Co (L(CH3)3P). As an intermediate of this reduction a complex cobalt(I) halide of the formula L3CoCl (L(CH3)3P) could be isolated which also arises quantitatively from L4Co and anhydrous cobalt dichloride. L3CoCl is converted into the title compound L4CoCH3 by LiCH3. The CoCbond of this species is cleaved by protic acids with liberation of methane. Thus, e. g. a cobalt(I) acetylide L4CoC CC6H5, or polymers of the formula Co(OR)2(RCH3, C2H 5, Si(CH3)3, C6H5) are formed. Carbonylation and decarbonylation under normal pressure lead to [L2(CO)2Co]2, L3(CO)CoCH3, and L2(CO)2CoCOCH3. L4Co undergoes oxidative addition with acetyl chloride and even with acetic anhydride. As a strong reducing agent l4CoCH 3 attacks CO2 to give a carbonyl complex. Addition of CH3X (XBr,J) leads to novel methylcobalt(III) complexes. – The temperature dependence of the 1H n.m.r. of the CoCH3resonance reveals a strong relationship in the fluxional behaviour of the isosteric species L 4CoCH3and [L4NiCH3]+.

Force velocity relationships in vascular smooth muscle. The influence of temperature.

Abstract: Force velocity relationships of isolated vascular smooth muscle preparations were examined in the tetanized rat portal--anterior mesenteric vein by means of afterloaded isotonic contractions. Lowering of the temperature from 37 degrees C to 25 degrees C caused an average decrease of the follwoing parameters: maximal velocity of shortening at zero load from 0.51 to 0.28 muscle length/sec; maximal rate of tension increase (dT/dt) from 847 to 362 dyn/sec; mechanical tension developed at the maximum of dT/dt from 43 to 34% of the peak force generation; constant b of Hill's equation from 0.18 to 0.09 muscle length/sec. The latency was prolonged from 0.33 to 0.56 sec, and the time-to-maximum of dT/dt from 0.9 to 1.6 sec. Between 27 degrees C and 37 degrees C the following Q10 values were calculated: for the maximal velocity of shortening at zero load 1.56; for the maximal rate of tension increase 1.88; for the latency 1.63. No distinct influence of temperature could be observed on the extent of isotonic shortening at zero load (3.69 muscle length at 37 degrees C), on the extent of peak force generation (1107 dyn at 37 degrees C), and on constant a of Hill's equation (0.35 at 37 degrees C). It is concluded that parameters of contraction velocity in vascular smooth muscle depend on temperature, whereas the extent of contraction is independent of temperature. These findings are discussed in connection with the theory of the sliding-filament mechanism.

Seasonal and diurnal courses of water relations of the arido-active plant Hammada scoparia in the Negev desert

Abstract: The photosynthesizing branches of Hammada scoparia, one of the typical dwarf shrubs of the Negev desert, undergo a seasonal change from succulent to xeromorphic anatomy. This trend is accompanied by a marked decrease of water content and of total water Ψ plant and osmotic Ψ π plant potential. Irrigated plants do not show such transitions. The daily courses of Ψ plant and Ψ π plant showed minima around noon and a tendency for maxima before sunrise. Turgor pressure Ψ plant reached minima around noon and became negative (until ca.-10 bars). Generally, Ψ plant decreases with increasing water vapour concentration difference between plant and air (WD) in the first half of the day, and in the second half the reversal of this trend occurs. Mostly smaller increments of Ψ plant were correlated with larger increases in WD which lead to the conclusion that stomates closed enough to maintain transpiration at a constant value. Non-irrigated and irrigated plants showed different hysteresis loops of relation between Ψ plant and WD. Regulatory reduction of transpiration appears largely independently of Ψ plant which is in spring and with irrigated plants on a high level, with non-irrigated plants in summer on a low level. In summer the continous but decreasing drop of Ψ plant with increasing WD was interpreted as caused by a change in soil or root resistance. Independent of the seasonal state and of the Ψ plant level, H. scoparia regulates its water status within limited ranges of Ψ plant changes: the irrigated plants on a higher level, the non-irrigated on a lower level of Ψ plant . The water contents of the tissues of H. scoparia are linearily related to Ψ plant as well as Ψ plant . Steeper slopes with non-irrigated plants in summer than with spring palnts and with irrigated plants during the whole season signify that in the latter a certain increment in turgor pressure corresponds to a large gain in water content while in the non-irrigated summer plants it varies only little for an identical change in Ψ plant . This behaviour of non-irrigated wild plants apparently is due to the change of the elastic properties of the tissues in the assimilating branches.

Organogold‐Chemie, XV. Gold(I)‐Verbindungen einfacher Phosphor‐ylide

Abstract: Alkyl(phosphin)gold(I)-Komplexe reagieren rasch und vollstandig mit Phosphor-yliden unter Verdrangung der Phosphine vom Goldatom und Bildung neuartiger, ungewohnlich stabiler Alkylgold-ylid-Komplexe. Prototyp dieser Produkte ist CH3AuCH2P(CH3)3 (1) mit zwei AuC-σ-Bindungen. Auch silylierte Alkylgold-Komplexe (CH3)3SiCH2AuPR3 und silylierte Ylide (CH3)3PCHSi(CH3)3 geben diese Reaktion. (Phosphin)gold(I)-halogenide addieren Phosphor-ylide unter stufenweiser Substitution des Halogens und des Phosphins. Dabei entstehen oniumstabilisierte Alkylgoldsalze der Typen [(CH3)3P CH2 Au P(CH3)3]X und (CH3)3P CH2 Au CH2 P(CH3)3X etc. Organogold Chemistry, XV. Gold(I) Compounds of Simple Phosphorus Ylides Alkyl(phosphine)gold(I) complexes react rapidly and quantitatively with phosphorus ylides with displacement of the phosphine to give novel alkylgold ylide complexes of unusual stability. CH3AuCH2P(CH3)3, with its two AuC σ-bonds, is a prototype of these reaction products. Silylated alkylgold complexes (CH3)3SiCH2AuPR3 and silylated ylides also give this reaction. — (Phosphine)gold(I) halides add phosphorus ylides with stepwise substitution of the halogen and phosphine ligands and formation of onium-stabilized alkylgold salts of the type [(CH3)3P CH2 Au P(CH3)3]X and [(CH3)3P CH2 Au CH2 P(CH3)3]X.

Absolute electron impactK-ionization cross sections of titanium and nickel (≦50 keV)

Abstract: The absoluteK-ionization cross sections of Ti and Ni by electron impact (impact energy ≦50 keV) was measured detecting the X-rays emitted by thin solid film targets of known mass thickness with a flow proportional counter. The experimental method, especially the correction procedures and the measurements are described, the results compared with calculations in different theoretical approaches. For impact energies aboveE0/EK>1.5 (EK=K-shell ionization energy) a systematic deviation of about +20% occurs in comparison with the best agreeing calculations of M.R.H. Rudge and S.B. Schwartz. A fit to Drawin's empirical formula reveals that the measurements are approximated better than ±10 % within the range of comparison.

On Optimal Control Problems with Bounded State Variables and Control Appearing Linearly

Abstract: Necessary conditions for the junction of interior arcs and boundary arcs of an optimal control are given. These conditions are based on necessary conditions for the switching function holding at junction points or contact points with the state boundary. The junction theorems obtained are similar to junction theorems in singular control problems.