Showing papers by "Ludwig Maximilian University of Munich published in 1974"

Quantitative measurement of food selection : A modification of the forage ratio and Ivlev's electivity index

Abstract: The forage ratio and Ivlev's electivity index are common measures to quantify food selection but the values of both indices depend not only on the extent of selection but also on the relative abundances of the food types in the environment. They are therefore useless when food types with different relative abundances are compared, or when the relation between selection and relative abundance is studied. Modified versions of both indices are proposed which are based directly on the rates of decrement (mortality) of the food due to feeding, and are independent of the relative abundance.

Model for Brillouin Scattering in Amorphous Solids

Abstract: An elastic continuum model is presented for Brillouin scattering by an amorphous solid. The assumption that light scatters on distorted plane wave acoustic phonons leads to the prediction that the scattered intensity plotted as a function of the frequency transfer Ωo consists of the usual Brillouin peaks plus a background which, a t room temperature, goes like Ωo; for small Ωo, but rises less steeply for larger Ωo, and may even bend over within the range of the validity of the model, depending on the correlation lengths for spatial fluctuations due to disorder and on the speeds of sound. For the case of a-Si, additional results are obtained with the help of existing experimental measurements. Es wird die Brillouinstreuung in a morphen Snbstanzen an einem elastischen Kontinuums-modell diskutiert. Die Annahme, das Licht an durch deformierte ebene Wellen beschriebenen akustischen Phononen gestreut wird, fiihrt zu folgenden Aussagen. Die Streuintensitiit als Funktion der Frequenzverschiebung besteht aus den ublichen Brillouin-Peaks und einem Hintergrund, der, bei Raumtemperaturen, fur kleine Ωo proportional zu Ω 2o ist. Mit wachsendem Ω o wachst der Hintergrund dam schwacher als Ω2o. Jc nach den Werten der Korrelationslangen fur raumliche Fluktuationen und der Schallgeschwindigkeiten kanner im Giiltigkeitsbereich des Modells sogar nach Erreichen eines Maximums wieder abfallen. ZusaItzliche Aussagen werden fur den Fall von a-Si unter Ausnutzung existierender Messungen gemacht.

The Tryptophan → Ommochrome Pathway in Insects

Abstract: Publisher Summary This chapter assembles data, which contribute to a physiological understanding of this pathway in insects, to appraise the role of ommochromes in insect life, and the relation of tryptophan metabolism to insect development. Tryptophan is an outstanding amino acid. It has the highest molecular weight of all amino acids occurring in proteins, and comprises, in its indolyl moiety, a system capable of donating electrons and; therefore, liable to form complexes with a range of other molecules. Molecular interactions have been observed between tryptophan and nucleic acids, and a variety of other molecules of biological importance. Organisms have taken advantage of the potentialities of this molecule and have transformed it into a wide range of biologically active compounds. In these, either the indole ring or its benzene nucleus are retained, the latter also being recast into the pyridine ring. In insects, a major product of tryptophan degradation is a group of 10 to 15 pigments, the ommochromes. Being brownish-yellow, bright red or dark violet-purple, these pigments produce the deep tinge of insect eyes and contribute to the brilliant coloration of many species.

Auf dem Weg zu Carben‐ und Carbin‐Komplexen (Nobel‐Vortrag)

Abstract: Alfred Nobel hat einmal im Gesprach zu einem Freund gesagt, er wolle den Traumern unter den Wissenschaftlern helfen. Das den Traumern im Reiche der Chemie auch in Zukunft ein Platz erhalten bleibe, ist der Wunsch der Nobel-Preistrager fur Chemie des Jahres 1973.

Decoding the Language of the Bee

Abstract: Some 60 years ago, many biologists thought that bees and other insects were totally color-blind animals. I was unable to believe it. For the bright colors of flowers can be understood only as an adaptation to color-sensitive visitors. This was the beginning of experiments on the color sense of the bee (I). On a table outdoors I placed a colored paper between papers of different shades of gray and on it I laid a small glass dish filled with sugar syrup. Bees from a nearby hive could be trained to recognize this color and demonstrated their ability to distinguish it from shades of gray. To prevent too great a gathering of bees, I instituted breaks between feedings. After these breaks, only sporadic scout bees came to the empty bowl and flew back home; the feeding table remained deserted. If a scout bee, however, found the bowl filled and returned home successfully, within a few minutes the entire forager group was back. Had she reported her findings to the hive? This question subsequently became the starting point for further investigations. In order that the behavior of foragers could be seen after their return to the hive, a small colony was placed in an observation hive with glass windows, and a feeding bowl was placed next to it. The individual foragers were marked with colored dots, that is, numbered according to a certain system. Now an astonishing picture could be seen in the observation hive: Even before the returning bees turned over the contents of their honey sack to other bees, they ran over the comb in close circles, alternately to the right and the left. This round dance caused the numbered bees moving behind them to undertake a new excursion to the feeding place. But foragers from one hive do not always fly to the same feeding source. Foraging groups form: One may collect from dandelions, another from clover, and a third from forget-me-nots. Even in flowering plants the food supply often becomes scarce, and a “feeding break” ensues. Were the bees in the experiment able to alert those very same foragers who were at the bowl with them? Did they know each other individually? To settle the question, I installed two feeding places at which two groups from the same observation hive collected separately. During a feeding break, both groups stayed on the honey-comb and mingled with each other. Then one of the bowls was refilled. The bees coming from the filled bowl alerted by their dances not only their own group but also bees of the second group, which responded by flying to their customary feeding place where they investigated the empty bowl. However, the natural stopping places of bees are not glass bowls but flowers. Therefore, the experiment was modified; one of two groups of bees collected food from linden blossoms, the other one from robinias. Now the picture

Structural aspects of initial psoriatic lesions

Abstract: A total of 32 pin-sized lesions were excised in 29 patients with psoriasis vulgaris. The specimens were prepared for light and electron microscopy.

Investigation of neutron deficient nuclei in the region 28<N, Z <50 with the help of heavy ion compound reactions

Abstract: In-beamγ ray spectroscopy withγ singles spectra,γγ coincidences andγ ray angular distributions has been performed with several target-projectile combinations:natCa +32S,natCa +40Ca,54Fe +14N,58Ni +12C,58Ni +14N,66Zn +16O,68Zn +16O Level schemes of66Ge,68Ge,69As,70Se,74Kr,80Sr and82Sr have been deduced The following level energies and spin-parity assignments have been found:66Ge: 9574 keV, 2+; 16937; 21747, (4+); 36857; 42075;68Ge: 10158, 2+; 17779, 2+; 22679, 4+; 24288, 3(+); 26491, 3−; 35823, (5−); 36493, (5−); 36962, (6+); 38833, (6−); 40544, (7−); 44546; 48373;69As: 982; 1646;7896;8632; 1306;2160;22104;28315;32583;32635;39911;51957;70Se: 9454, 2+; 16009; 20394, (4+);74Kr: 4557, 2+; 10135, (4+); 17815;80Sr: 3854, 2+; 9802, (4+); 17632, (6+);82Sr: 5734, 2+; 13285,(4+); 22296,(6+) γ ray activity spectra have been measured after the bombardment of natural Ca with32S The half-life of the new isotope69Se has been found to be 27±3 sec Recoil distance Doppler-shift measurements have been performed with the reactions62,64Ni,66zn(16O, 2n)76, 78 Kr,80Sr The following half-lives have been determined:76Kr: 4238 keV, 2+, 37±5 psec; 10342,4+, 57±16;78Kr: 4553, 2+, 25±3; 11200, 4+, 38±1;80Sr: 3854, 2+, 44±6 The energy and half-life systematics of the first excited state of even-even nuclei suggest a maximum of nuclear deformation in the region 28≦N, Z≦50 near 38 76 Sr38 or 40 78 Zr38

Identification of the Iron-Ligand Vibration of Oxyhemoglobin

Abstract: obse rva t ion t h a t l eadt rea ted h u m i c acids t end to form dist inc t ive aggregates , whereas u n t r e a t e d h u m i c acids do not . The obse rved d i sappea rance of the b road carboxyl ic-ac id shoulder a t 2 700 to 2 300 cm -~ and t he increased ca rboxy la t e abso rp t ion a t 1 400 to t 380 cm -1 revealed t h a t lead fo rms sa l ts w i th acid ca rboxyl groups , t h u s ind ica t ing t h a t lead f ixa t ion b y h u m i c acids involves qu i te d i f ferent t ypes of b inding. A fu r t he r e x p e r i m e n t showed t h a t p H condi t ions s t rong ly inf luence lead f ixa t ion (Table 2), t h u s conf i rming the resu l t s ind ica ted above. This jus t i f ies t he a s s u m p t i o n tha t , a t low pH, g roups of low ac id i ty t ake less pa r t in lead f ixat ion. L ead sa l ts fo rmed unde r these condi t ions are t h u s more polar and more readi ly ionized.

Investigations on the specificity of the Limulus test for the detection of endotoxin.

Abstract: Lysates obtained from amoebocytes of Limulus polyphemus, the horseshoe crab, showed gel formation after the addition of bacterial endotoxin. In contrast to living gram-negative bacteria, viable gram-positive microorganisms did not cause gelation of lysate. Nevertheless, peptidoglycan isolated from the cell walls of various gram-positive organisms did induce the reaction. However, the activity of peptidoglycan was 1,000 to 400,000 times less than that of Escherichia coli lipopolysaccharide. After exposure to lysozyme, peptidoglycan no longer gelled amoebocyte lysate, therefore apparently excluding endotoxin contamination. Gelation of amoebocyte lysate by endotoxin or peptidoglycan was inhibited by different concentrations of sodium polystyrolsulfonate. Whereas these studies confirm the specificity of the Limulus test for bacterial endotoxins, they also indicate that other substances of bacterial origin should be investigated for their ability to gel amoebocyte lysate.

13C‐NMR‐Spektren von π‐Komplexen des Indens zur Bestimmung der Haptoeigenschaften von Liganden

Abstract: Die Analyse der 13C-NMR-Spektren von Inden und einigen π-Komplexen des Indens erlaubt, zwischen h6-, h5- und h3-Verbindungen zu unterscheiden. Insbesondere wird die Struktur von Bis(h3-indenyl)nickel geklart und uber eine verbesserte Synthese dieser Verbindung berichtet. 13C N.M.R. Spectra of Indene π-Complexes and their Use for the Determination of Ligand Haptoproperties The analysis of the 13C n.m.r.spectra of indene and some indene π-complexes allows to distinguish between h6-, h5-, and h3-compounds. In particular the structure of bis(h3-indenyl)-nickel is determined and an improved synthesis of this compound is reported.

Kernresonanzspektroskopische Untersuchungen an Borverbindungen, VII. 11B- und 14N- Kernresonanzstudien an tetrakoordinierten Bor-Stickstoff-Verbindungen

Abstract: Die chemischen Verschiebungen δ11B und δ14N einer grosen Zahl von tetrakoordinierten Bor-Stickstoff-Verbindungen werden mitgeteilt und diskutiert. Es besteht eine nahezu lineare Korrelation zwischen den δ14N- bzw. δ11B-Werten der R3B-Addukte (RH, CH3) aliphatischer Amine und den δ13C-Daten der mit diesen Addukten isoelektronischen und isosteren Alkanen. Auserdem geben die δ14N- und δ11B-Daten von R3B-Addukten (RH, CH3, C2H5) mit N-Heteroaromaten (Azinen, Azolen) Auskunft uber ihre Stabilitat und Struktur. Nuclear Magnetic Resonance Studies on Boron Compounds, VII. 11B and 14N N.M.R. Studies on Tetracoordinated Boron Nitrogen Compounds 11B and 14N chemical shifts for many tetracoordinated boron nitrogen compounds are reported and discussed. There is a nearly linear relationship for δ14N or δ11B of R3B adducts (RH, CH3) of aliphatic amines and δ13C of alkanes isoelectronic and isosteric with these adducts. Furthermore, δ14N and δ11B data of R3B adducts (RH, CH3, C2H5) of N-heteroaromatic systems (azines, azoles) give information related to their stability and structure.

Dinitrogen‐Transition Metal Complexes: Synthesis, Properties, and Significance

Abstract: Compared to the large number of CO complexes, N2 complexes are still rare In certain cases they may be formed from N2 gas and metal compounds under physiological conditions, and are therefore frequently considered as possible intermediates in N2 assimilation However, despite numerous attempts it has not yet been possible to reduce the N2 ligand of a fully characterized N2 complex to NH3 This negative evidence recently prompted the discoverers of the first dinitrogen complex, the [Ru(NH3)5N2]2⊕ ion isolated in 1965, to express doubt whether such complexes really do play a part in the enzymatic reduction of N2 The latest findings nevertheless incline toward a somewhat more optimistic view Thus, the mild partial reduction of the N2 ligand in metal complexes with inert gas configuration, hitherto considered nonreducible, justifies the hope that a suitable system permitting the catalytic reduction of molecular nitrogen under normal conditions will one day be found Even apart from any technical potential, the N2 complexes constitute an interesting chapter of modern inorganic chemistry

Nonlinear voltage dependence of excitatory synaptic current in crayfish muscle

Abstract: Excitatory postsynaptic currents (EPSCs) were measured as clamp current of muscle fibers or by focal extracellular recording. In the control bathing solution the voltage dependence of the EPSC was nearly linear in the potential range between −160 to −40 mV, in most experiments the slope of this relation decreased at potentials more negative than the resting potential. In 5×Ca++ solution at potentials more negative than −70 to −100 mV the slope of the current voltage relation of the EPSC was zero or negative. The reversal potentials for the EPSCs, extrapolated from the current voltage relation, were at +33 mV (S.D.±32 mV) both in 1×Ca++ and in 5×Ca++ solution. The declining phase of EPSCs was slowed by depolarization and shortened by hyperpolarization, its time constant increasing by about 100% between −160 mV and −40 mV. Excitatory postsynaptic currents also were elicited by glutamate-pulses (g-EPSCs). In 1×Ca++ and in 5×Ca++ solutions the amplitude of the g-EPSCs showed a voltage dependence like that of the EPSCs. In 10×Ca++ solution (10% normal Na+) synaptic current was reduced to about 50%. The current voltage relation was very flat and showed a negative slope for high negative potentials. It is concluded that Na+-, Ca++- and K+-ions contribute to the EPSC. Synaptic sodium and/or calcium conductance seems to decrease at potentials more negative than the resting potential.

A three-dimensional atomic model of the murein layer of bacteria.

Abstract: X-Ray diffraction, infrared spectra and density of murein, the rigid component of almost all bacterial cell walls, were measured using gram-negative (Spirillum serpens) and gram-positive (Lactobacillus plantarum) strains. X-Ray diffraction of dried foils of murein showed Debye-Scherrer rings, indicating periodicities of 0.93 to 1.00 and 0.44 nm. The comparison of the infrared spectra of chitin and murein showed that their amide I and amide II bands have the same frequencies. With isopycnic density-gradient centrifugation of murein a density of ϱ= 1.46 g × cm−3 was observed. Based on these data, on theoretical considerations and on model building the following structure of murein is proposed: the structure of the glycan chains in murein is similar to that of chitin and cellulose. The peptides consisting of alternating d- and l-amino acids have the 2.27 helical conformation. They are linked to the carbohydrate chains through their N-terminus and form two hydrogen bonds with the sugar residues. This linkage causes an angle of about 150° between the carbohydrate and peptide chains.

Application of Green's functions to excitations accompanying photoionization in atoms and molecules

Abstract: The method of Green's one-particle functions is used to explain excitations with simultaneous ionization in atoms and molecules. The relative intensities of satellite lines in the photoelectron spectra, which arise due to excitations accompanying photoionization, are found to be simply related to the pole strengths of the Green's functions. For the water molecule many such satellite lines are calculated to be in the region of 25–80 eV binding energy.

New Technique for the Measurement of Lifetimes of Heavy-Ion Inner-Shell Vacancies

Abstract: We report a new technique for the measurement of short lifetimes (${10}^{\ensuremath{-}14}$ sec) of innershell vacancies in heavy-ion projectiles moving through thin, solid targets. The technique is applicable whenever the yield of projectile x rays does not increase in proportion to target thickness. Lifetime values of 1.5\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}14}$ and 3.3\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}14}$ sec have been found for $K\ensuremath{\alpha}$ and $K\ensuremath{\beta}$ transitions, respectively, in highly stripped sulfur ions.

Übergangsmetall‐Carben‐Komplexe, LXVIII. Synthese von cis‐ und trans‐Tetracarbonyl(carben)(phosphin)‐Komplexen von Chrom(0) und Wolfram(0)

Abstract: Bei der thermischen Umsetzung von tertiaren Phosphinen PX3 [X3(CH3)3, (C2H5)3, (n-C4H9)3, (n-C8H17)3, (C3H7)3, (C6H11)2C6H5, (C6H5)2C2H5)3, (p-C6H4CH3)3- (p-C6H4F)3, (m-C 6H4F)3] mit Pentacarbonyl(carben)-Komplexen von Chrom (0) und Wolfram(0), (CO)5Cr[(R′)R″] und (CO)5W[ C(R′)R″] (R′OCH3, OC2H5; R″CH3, C2H5, i-C3H7, C6H5), erhalt man im Temperaturbereich zwischen 60 und 80°C unter CO-Abspaltung sowohl die cis-als auch die trans-Isomeren der Tetracarbonyl(carben)-(phosphin)-Komplexe (CO)4M(PR3)[C(R′)R″]. desgleichen bei photochemischer Reaktion bei Raumtemperatur. Bei photochemischer Umsetzung bei tiefen Temperaturen und fur R′NH2 oder NHCH3 fallen jedoch nur die cis-Verbindungen an. Die Konstitutionen der gelben bis roten, diamagnetischen Verbindungen wurden analytisch und spektroskopisch gesichert. Transition Metal Carbene Complexes, LXVIII. Synthesis of cis- and trans-Tetracarbonyl(carbene)(phosphine) Complexes of Chromium(0) and Tungsten(0) Thermal reaction in the range 60 to 80°C and photochemical reaction at room temperature of tertiary phosphines PX3 [X3(CH3)3, (C2H5)3, (n-C8H17)3, (i-c3H7)3, (C6H11)3, (C2H5)2C6H5, (C6H5)2 C2H5, (C6H5)3, (p-C6H4CH3)3, (p-C6H4F)3, (m-C6H4F)3] with pentacarbony(carbene) complexes of chromium (0) and tungsten (0), (CO)5Cr[C(R′)R″] and (CO)4M(PR3)[C(R′)R″] and trans-(CO)4M(PR3)[C(R′)R″]. Photochemical reaction at low temperatures and in the case where R′NH2 and NHCH3, yields only the cis-isomers. The structures of the yellow to red, diamagnetic compounds were established by analyses and spectra.

Cation exchange reactions and layer solvate complexes of ternary phases MxMoS2

Abstract: Layer intercalation compounds of molybdenum disulphide with alkali and alkali-earth metals show cation exchange behaviour after decomposition with water or aqueous ammonia. Mono- and divalent inorganic and organic cations can be taken into exchange positions in the interlayer space of the MoS 2 crystals. The interlayer distance depends on the type of cation exchanged and on cation hydration. Intracrystalline swelling of the compounds is observed with a whole series of polar inorganic and organic molecules. The cation exchange phenomena are explained in terms of the reduction of a part of the Mo(IV) atoms in the sulphide layers by alkali metal. Oxidation and heating restore the original MoS 2 lattice.