Showing papers by "Academy of Sciences of the Czech Republic published in 1981"

Role of the B-G-region antigen in the humoral immune response to the B-F-region antigen of chicken MHC

Abstract: In the chicken MHC there exist two regions, designated F and G, which were separated by crossing-over. The F region contains genes controlling all functions characteristic of the MHC. So far only one gene has been assigned to the G region and it is responsible for the presence of an RBC antigen. When cross-immunizing animals of the congenic lines CB and CC with erythrocytes, we have found that both F- and G-specific antibodies were produced. By using the recombinant haplotypes Br1 and Br2 we were able to dissociate the F from the G antigen and immunize with them separately. It was found that production of F antibodies required the copresence of the G antigen, whereas G antibodies were formed regardless of the presence of absence of the F-region antigen. It could be demonstrated that a prerequisite of the role of the G antigen with respect to the F antigen was the localization of both antigens on the same erythrocyte. Possible mechanisms underlying this phenomenon are discussed.

Ferromagnetic resonance in amorphous (FeNi)80P10B10 alloys I. Alloys with high curie temperature

Abstract: FMR measurements at room temperature on amorphous (Fe1–xNix)80P10B10 thin wires in the frequency range from 9.2 to 70 GHz are reported. In alloys with Curie temperatures well above the room temperature (x ≦ 0.7) saturation magnetic polarization Js, g-factor, effective anisotropy field HK and Landau-Lifshitz damping parameter λ are determined. The value of the spectroscopic splitting factor g = 2.09 is independent of composition x. For the alloys with x ≦ 0.4 the damping parameter λ is proportional to Js. Comparison with crystalline FeNi alloys shows that topological disorder has little effect on quenching of the orbital moment as well as on the relaxation mechanism in these amorphous alloys. Zimmertemperaturmessungen der ferromagnetischen Resonanz an amorphen dunnen (Fe1–xNix)80P10B10 Drahten im Frequenzbereich von 9.2 bis 70 GHz werden beschrieben. Die gesattigte magnetische Polarisation Js, g-Faktoren, das effektive Feld der Anisotropie HK und der Landau-Lifshitz-Parameter der Dampfung λ werden bestimmt fur die Legierungen (x ≦ 0,7), deren Curie-Temperaturen viel hoher als Zimmertemperatur sind. Die Grose des spektroskopischen Aufspaltungsfaktors g = 2,09 ist von der Zusammensetzung x unabhangig. Fur die Legierungen mit x ≦ 0,4 ist der Parameter der Dampfung Js proportional. Der Vergleich mit den kristallinen FeNi-Legierungen zeigt, das die topologische Unordnung das Einfrieren des Orbitalmoments und den Relaxationsmechanismus in diesen amorphen Legierungen nur sehr wenig beeinflust.

A bibliography of statistical tolerance regions

Abstract: This bibiliography (completing the previous one, JILEK 1981a) contains about 130 references dealing with statistical tolerance regions. References are classified according to the type of probability distribution concerned and according to some other criteria as well

Statistical properties of brillouin scattering

Abstract: The complete normal quantum characteristic function is calculated from which fluctuations in photon and phonon modes as well as the correlations among them are obtained. They are particularly discussed from the point of view of antibunching assuming that the phonon and the photon modes are initially coherent.

The age structure of populations of Saccharomyces cerevisiae

Abstract: A discrete deterministic model is described for the growth of an age-structured population of yeast, Saccharomyces cerevisiae, incorporating recent information on the asymmetry of cell division and control of the cell cycle in this species. Solutions are obtained for the age structure of the population at equilibrium, and for the equilibrium distribution of relative frequency of cells through the cell cycle. The model is applied to experimental data on the changing age structure of nonequilibrium populations of yeast. The model predicts well both the transient behavior and the equilibrium structure of such populations. It is shown that the asymmetry of cell division explains (1) the excess of newly formed daughter cells in the population as compared to the frequency of older cells and (2) the damped oscillations in the frequencies of cells of different ages as demographic equilibrium is approached.

Ferromagnetic resonance in amorphous (FeNi)80P10B10 alloys. II. Resonance near the curie temperature

Abstract: Ferromagnetic resonance at room temperature is measured on amorphous (Fe1−xNix)80P10B10 very thin wires with 0.74 ≦ x ≦ 0.84. FMR measurements in the frequency range from 9.2 to 70 GHz are supplemented by static measurements of magnetization. With increasing Ni content, x, the Curie temperature decreases passing room temperature at approximately x = 0.80. Near this composition the resonance linewidth rapidly increases and its frequency dependence significantly changes. FMR data in the vicinity of Tc can be explained by a combination of two relaxation terms in the equation of motion and a g-factor dependent on applied magnetic field. Ferromagnetische Resonanz an sehr dannen amorphen (Fe1−xNix)80P10B10-Drahten wird fur 0,74 ≦ x ≦ 0,84 bei Zimmertemperatur gemessen. Die FMR Messungen im Frequenzbereich von 9,2 bis 70 GHz werden durch statische Messungen der Magnetisierung erganzt. Die Curie-Temperatur fallt mit steigendem Ni-Gehalt, sie ist nahe der Zimmertemperatur annahernd x = 0,80. In der Nahe dieser Zusammensetzung wachst die Resonanzlinienbreite sehr schnell und ihre fre-quenzabhangigkeit andert sich wesentlich. Die FMR-Angaben in der Umgebung von Tc kann man mit Hilfe einer Kombination von zwei Relaxationsgliedern der Bewegungsgleichung und eines vom auseren Magnetfeld abhangigen g-Faktors erklaren.

Theory of the Auger Spectra of Narrow-Band Metals with Impurities

Abstract: The intraatomic CVV Auger spectrum for a single impurity in a perfect crystal with an initially filled band is investigated. The impurity is characterized by its atomic level Δ and the contact pair interaction U of electrons (Wolff-Clogston model). The exact solution of the problem is found. The spectrum may consist of three parts: (i) band of the two-hole extended states, (ii) isolated localized two-hole states, and (iii) band of mixed two-hole states, in which one hole is localized, and the other one is in an extended state. The band of extended states is present in all cases, the localized and mixed states appear simultaneously for a certain value of |Δ|. The condition for the existence of bound states is derived, and the theory is numerically illustrated for a simple bandstructure model. Das inneratomare CVV-Augerspektrum fur eine einzelne Storstelle in einem Idealkristall mit einem anfangs besetzten Energieband wird untersucht. Die Storstelle wird durch ihr Atomniveau Δ und durch die Kontaktpaarwechselwirkung U der Elektronen (Wolff-Clogston-Modell) charakterisiert. Zu diesem Problem wird eine exakte Losung gefunden. Das Spektrum kann aus drei Teilen bestehen: (i) Band des ausgedehnten Zweilochzustandes, (ii) des isoliert lokalisierten Zweilochzustandes und (iii) Band des gemischten Zweilochzustandes, wobei das eine Loch lokalisiert und das andere ein ausgedehnter Zustand ist. Das Band des ausgedehnten Zustandes ist in allen Fallen anwesend, die lokalisierten und gemischten Zustande erscheinen simultan fur einen gewissen Wert |Δ|. Die Bedingung fur die Existenz des gebundenen Zustandes wird abgeleitet, und die Theorie fur ein einfaches Bandstrukturmodell wird numerisch dargestellt.

Internal conversion of valence shell electrons: Measurement and analysis for the 10.84 keV transition in206Bi

Abstract: Conversion electrons of the 10.84 keV transition in206Bi were measured with the iron-free magnetic spectrometer. The conversion line of the valence shell was observed to be narrower than those of the inner ones. The computer program which optimizes the line profiles given numerically is outlined and used for the spectrum analysis. The studied transition was proved to be pure M1 with the nuclear structure parameterλ=1.7±0.7. The internal conversion coefficients were calculated using the relativistic Hartree-Fock model for neutral atoms as well as various isolated ions. Altogether, 15 different valence-shell configurations were considered. The prediction for the 6s 1 2/2 configuration (Bi3+) is in accord with the measured conversion intensities. This is consistent with probable chemical form Bi2O3 of bismuth atoms in the radioactive source.

Evidence for direct mechanism in the128Te(n,γ)129Te reaction at thermal neutron energies

Abstract: Spectra of γ-rays following thermal neutron capture in128Te have been measured. Partial cross section for the radiative transitions to eight129Te levels with ln=1 have been determined. The experimental data are in a very good quantitative agreement with the theory of direct capture by Lane and Lynn.

Polymerization of lactams, 39. Condensation as side reaction in the anionic polymerization of 2‐pyrrolidone

Abstract: Polymerization mixtures before extraction and extracted polymers prepared by the anionic polymerization of 2-pyrrolidone with various initiating systems were characterized by their content of β-ketoamide structures (5) as a measure of side reactions of the propagation sites by condensation. With N-acyllactams, used as activators, the content of these structures 5 in poly(2-pyrrolidone) was found to increase proportionally to the polymerization time, which may have a negative effect on the thermal stability of the polymer.

Mechanism of induced plastic anisotropy on polycrystalline metals

Abstract: Induced plastic anisotropy is demonstrated by precise tension-torsion experiments on thin-walled polycrystalline tubes. After a sudden change of the deformation mode (e.g. tension to torsion) the stress direction delays with respect to the direction of the strain increment. This delay effect is interpreted in terms of the theory of plasticity of a polycrystal. A good qualitative agreement between experimental results and theoretical predictions is achieved. There are indications that the main mechanism responsible for induced plastic anisotropy is the internal stress arising among plastically deformed grains in the polycrystalline aggregate. Induzierte plastische Anisotropie wird durch genaue Zug-Drehungs-Experimente an dunnwandigen polykristallinen Rohren demonstriert. Nach plotzlicher Anderung des Deformationsmodus (z. B. Zug in Drehung) verzogert sich die Spannungsrichtung in Richtung des Verformungsinkrementes. Dieser verzogerte Effekt wird durch die Plastizitatstheorie des Polykristalles interpretiert. Eine gute qualitative Ubereinstimmung zwischen experimentellen Ergebnissen und den theoretischen Voraussetzungen wird erreicht. Es gibt Anzeichen, das der fur die induzierte plastische Anisotropie verantwortliche Hauptmechanismus die innere Spannung ist, die von den plastisch deformierten Kornern in den pol ykristallinen Aggregaten herruhrt.

Genetic regulation of antibody response to sheep red blood cells: isoelectric focusing analysis of sera of well responding strain A/J and poorly responding strain B10 mice.

Abstract: Isoelectric focusing (IEF) on a thin layer of polyacrylamide gel revealed that strain A/J produces antibodies with pI values distributed over the whole assayed pH range (pH 5.05–7.75), while strain B10 produces antibodies of a limited heterogeneity with pI values distributed between pH 6.3 and 7.5. The analysis of sera of congenic resistant (CR) and recombinant strains showed that haplotype H-2a is associated with wide-heterogeneity antibodies, while the presence of haplotype H-2b is associated with the occurrence of limited-heterogeneity antibodies. Thus a gene located within the I region of the major histocompatibility complex (MHC) may affect the degree of heterogeneity of the anti-sheep red blood cell (SRBC) response. The gene is transmitted to the F1 generation as a dominant trait. After administration of endotoxin (LPS LT2, 10 μg/mouse) to the B10 mice, antibodies with pI values below pH 6.3 and above 7.5 appear in the serum; the heterogeneity of these antibodies resembles that of the A/J strain spectrotype.

Optimized growth conditions of GaN epitaxial layers

Abstract: Optimized growth conditions of the epitaxial GaN layers on the (0001) oriented sapphire substrates in the Ga/HCl/NH3/H2 system have been proposed. The corresponding growth rate varied about the value 0.5 μm · min−1. The study of surface morphology and X-ray diffraction have confirmed the single crystalline character of the layers even though the surface shows a faceted structure. The c/a ratio calculated from our measured data of the lattice parameters was found 1.624 which is relatively close to the ideal close-packed wurtzite structure value. The cathodoluminescent spectra of the layers with a sufficient thickness were characterized by a peak at 3.35 eV having a halfwidth of about 0.2 eV. Es werden die optimierten Wachstumsbedingungen von epitaktischen GaN-Schichten auf (0001)-orientierten Saphirsubstraten im System Ga/HCl/NH3/H2 vorgeschlagen. Die entsprechende Wachstumsgeschwindigkeit schwankte um den Wert 0.5 μm · min−1. Das Studium der Oberflachenmorphologie sowie das der Rontgenbeugung bestatigten den einkristallinen Charakter der Schichten, wenn auch die Oberflache eine facettenartige Struktur zeigte. Die aus unseren Meswerten der Gitterparameter berechnete Relation c/a wurde mit 1.624 festgestellt. Sie entspricht mit guter Genauigkeit dem Wert einer idealen Wurtzitstruktur. Die Katodolumineszenzspektren der Schichten genugender Dicke wurden durch ein Maximum bei 3.35 eV charakterisiert, mit einer Halbwertsbreite von ungefahr 0.2 eV.

Magnetic structure of amorphous (Fe1−xMnx)75 P15C10 alloys

Abstract: The magnetic properties of amorphous (Fe1−xMnx)75P15C10 (z = 0 to 0.3) are studied by Mossbauer spectroscopy and magnetization and susceptibility measurements. By deviations in the Arrott-Belov-Kouvel plots from linearity the system can be characterized as a magnetically inhomogeneous one. The observed low field behaviour, the very large hysteresis effects, and the cusp in the χ versus T curve for x = 0.3 point to the existence of a mixture of a ferromagnetic phase with a spin-cluster glass. Die magnetischen Eigenschaften von amorphem (Fe1−xMnx)75P15C10 (x = 0 bis 0.3) werden mittels Mossbauer-Spektroskopie sowie Magnetisierungs- und Suszeptibilitatsmessungen untersucht. Abweichungen der Arrott-Belov-Kouvel-Kurven von der Linearitat zeigen, das es sich um ein magnetisch inhomogenes System handelt. Die fur x = 0,3 beobachtete Magnetisierungsschleife, die sehr grosen Hystereseeffekte und das Maximum in der Temperaturabhangigkeit der magnetischen Suszeptibilitat weisen auf die Koexistenz einer ferromagnetischen Phase mit einem Spincluster-Glas hin.

Doping of amorphous silicon by ion implantation: Electrical, optical and photoelectrical properties

Abstract: Results of electrical, optical and photoelectrical properties of a-Si and a-Si(H) doped by means of ion implantation of Ga and N respectively show that the hydrogenated Si can be doped with higher efficiency. Ga seems to be built in the amorphous network as an acceptor and N in the form of (Si-N)x complexes.

Photostructural changes in some ternary Ge-Sb-S chalcogenide layers

Abstract: The changes of optical transmission and of the index of refraction were studied in flash evaporated Ge-Sb-S layers. Photobleaching, photodarkening and photoinduced crystallization were observed depending on the composition of layers. The effects are qualitatively explained using the idea of photoinduced atoms and/or chemical bonds rearrangement.

Quantum oscillations of the thermogalvanomagnetic transport coefficients: CPA model calculation

Abstract: The Kubo formula and the CPA averaging procedure are used to express the thermogalvanomagnetic coefficients for the electrons described by the parabolic dispersion law and scattered by the zero-range randomly distributed static impurities. Their dependence on the magnetic fields is calculated numerically, and the results are compared with the approximate treatment based on the Poisson summation formula.

The effect of shear stress on the screw dislocation core in bcc metals

Abstract: The screw dislocation core structure in bcc metals under an external shear stress is investigated using the model of generalized splitting as an approximation of the Peierls-Nabarro model of screw dislocation dissociated on three {110} slip planes. The shear stress for which the core structure in this model is unstable is found.

Simple Two‐Band s–d Model for Ferromagnetic Semiconductors with Hybridization. II. Further Development and Optical Properties

Abstract: The two-band model of electronic states proposed previously for the conduction band of some types of ferromagnetic semiconductors like chromium chalkospinels is discussed and used to prove the significance of the higher order spin-flip processes. On the basis of this model a simple valence-to-conduction band absorption is investigated at a level of the self-consistent CPA. The inadequacy of such mechanism for the explanation of the absorption edge at least in CdCr2Se4 is shown. The lowest order mean-field approach to the d-states is illustrated to yield a spurious agreement with the experiment. Das fruher fur das Leitungsband einiger ferromagnetischer Halbleiter wie Chromchalkospinell vorgeschlagene Zweibandmodell der Elektronenzustande wird diskutiert und zur Uberprufung der Bedeutung der Spin-Flip-Prozesse hoherer Ordnung benutzt. Auf der Grundlage dieses Modells wird eine einfache Valenzband–Leitungsband-Absorption auf dem Niveau einer selbstkonsistenten CPA untersucht. Es wird gezeigt, das die Annahme eines derartigen Mechanismus fur die Erklarung der Absorptionskante wenigstens fur CdCr2Se4 nicht ausreichend ist. Der Beitrag niedrigster Ordnung des mittleren Feldes zu den d-Zustanden ergibt keine Ubereinstimmung mit dem Experiment.