Showing papers by "University of Cologne published in 1978"
TL;DR: Heteroclitic property as well as the presence of λ, μ and γ1 chains are characteristic for primary anti‐NP sera of C57BL/6 mice.
Abstract: Spleen cells from C57BL/6 mice sensitized to the hapten (4-hydroxy-3-nitrophenyl)acetyl (NP) were hybridized with myeloma cells, and a variety of hybrid cell lines was isolated which secreted homogeneous anti-NP antibodies. The antibodies were purified by affinity chromatography and their chain composition, affinity and fine specificity were determined. All antibodies recovered from the primary immune response carried λ light and μ or γ1 heavy chains. Their variable portions were nonidentical but similar in terms of hapten-binding specificity with a higher affinity for the cross-reacting haptens (4-hydroxy-3,5-dinitro-phenyl)acetyl (NNP) and (4-hydroxy-5-iodo-3-nitro-phenyl)acetyl (NIP) than for the homologous hapten NP. This heteroclitic property as well as the presence of λ, μ and γ1 chains are characteristic for primary anti-NP sera of C57BL/6 mice.
In contrast, four families of anti-NP antibodies, each with a characteristic fine specificity pattern, were found among the hybrid cell antibodies derived from the hyperimmune anti-NP response. The antibodies of one of these families were related to the antibodies recovered from the primary immune response in that they were heteroclitic and carried λ light chains. All members of the other groups expressed k chains and were nonheteroclitic.
The finding of well-defined antibody families in this system and the isolation of their members enable us to approach the problem of V gene expression and diversification in a new way.
285 citations
TL;DR: Using weak beam electron microscopy the stacking fault energy (SFE) of III-V compounds was determined by measuring the dissociation width of edge dislocations as discussed by the authors, which was corrected for the lattice parameters in meV/atom for GaAs, GaP, GaSb, InAs, InP, and InSb.
Abstract: Using weak beam electron microscopy the stacking fault energy (SFE) of III-V compounds is determined by measuring the dissociation width of edge dislocations. The SFE corrected for the lattice parameters is given in meV/atom for GaAs, GaP, GaSb, InAs, InP, and InSb. As expected there is a strong correlation of the SFE with the ionicity of the bond. The different plasticity of the compounds is traced back to different dislocation velocities.
Mit Weak-Beam-Elektronenmikroskopie wird die Stapelfehlerenergie (SFE) von III-V-Verbindungen durch Messung der Aufspaltungsweite von Stufenversetzungen bestimmt. Die SFE, korrigiert fur die Gitterparameter, wird in meV/Atom angegeben fur GaAs, GaP, GaSb, InAs, InP und InSb. Wie erwartet gibt es eine starke Abhangigkeit der SFE von der Ionizitat der Bindung. Die unterschiedliche Plastizitat der Verbindungen wird auf verschieden grose Versetzungsgeschwindigkeiten zuruckgefuhrt.
276 citations
TL;DR: A way of generating restriction endonuclease cleavage sites by single base changes derived after in vitro methylation of single-stranded DNA is described.
Abstract: RESTRICTION endonucleases recognise specific sequences in DNA, and these endonucleases, especially those which generate cohesive ends, have been widely used to clone DNA1. However, many DNAs lack sequences which are recognised by endonucleases such as EcoRI, HindIII or BamHI. A general method of overcoming this problem has been described recently2. This approach involves the synthesis of oligonucleotides sensitive to a specific endonuclease and the blunt end ligation of these molecules to the DNA to be cloned. In contrast, we sought a method which avoids the insertion of additional nucleotides into a DNA sequence, but depends on direct modification of DNA. If a DNA sequence differs in only one base pair from the recognition sequence of a restriction endonuclease, a particular change of this base pair will generate the proper sequence. Here we describe a way of generating restriction endonuclease cleavage sites by single base changes derived after in vitro methylation of single-stranded DNA.
204 citations
TL;DR: In this paper, specific heat measurements of (La1−xCeghazi x )Al2 samples, with 1.5 a/o≦x≦100 a/O, performed in magnetic fields of up to 5 T between 0.3 and 10 K, are reported.
Abstract: We report on specific heat measurements of (La1−x
Ce
x
)Al2 samples, with 1.5 a/o≦x≦100 a/o, performed in magnetic fields of up to 5 T between 0.3 and 10 K. In the Ce rich alloys, and especially in CeAl2, aλ-type peak of an antiferromagnetic phase transition, and at lower temperatures spin waves and very large electronic contributions are clearly visible. In higher magnetic fields, that is when antiferromagnetic order can be suppressed, the specific heat of the alloys exhibits a broadened Schottky peak. All these phenomena add up tok ln 2, i.e. to the correct entropy change per single Ce3+ ion in itsΓ
7 crystal field ground state. We interpret experimental results as an interplay between cooperative magnetism and the single-ion Kondo effect which describes a gradual turning off of one magnetic moment. The broadening of the Schottky peak is directly related to the Kondo temperatureT
K
, which we determine with a simple “resonance level model”.T
K
increases by an order of magnitude whenx increases from 1.5 a/o to 100 a/o. This is interpreted as caused by a lattice contraction. A quadraticx dependence of the Neel temperature suggests that (forT≲T
K
) stable Ce moments can only exist through pair interactions. The very large (and almost field independent) specific heat term linear in temperature with a coefficientγ=135 mJ/K2 mole for CeAl2 is attributed to the Kondo effect—still present in the antiferromagnetically ordered state. Our evaluation of the experimental data is backed by a molecular field theory for a simplified antiferromagnetic structure combined with the simplest possible Kondo theory.
176 citations
TL;DR: Analysis of the integration patterns of Ad12 DNA in the four hamster lines investigated reveals that some of the viral DNA molecules are fragmented prior to or during integration, which is compatible with, but does not prove, the notion that at least a portion of theiral DNA sequences, is integrated into repetitive sequences, or else that the integrated viral sequences have been amplified after integration.
166 citations
TL;DR: The derivation of three cloned hybrid cell lines which synthesise antibodies detecting different public antigenic specificities of the mouse H–2 complex are reported, which can be grown in the mouse as ascites tumours and obtained contain large quantities of homogeneous anti-H–2 antibodies.
Abstract: HYBRIDISATION of a myeloma cell line with hyperimmunised spleen cells can provide hybrid cell lines secreting monoclonal antibodies of predefined specificity1,2. Lines have thus been established which secrete homogeneous antibodies against antigens such as sheep red blood cells1, the hapten 2,4,6-trinitrophenyl2, influenza virus3, horse red blood cells, the haptens (4-hydroxy-3-nitrophenyl)acetyl and (4-hydroxy-5-iodo-3-nitrophenyl)acetyl, group A streptococcal carbohydrate, hen egg lysozyme, chicken γ globulin, the synthetic polypeptide poly-L-(Tyr, Glu)-poly-D,L-Ala-poly-L-Lys4 and antigens encoded by the major histocompatibility complex (MHC) of the rat5. We report here the derivation of three cloned hybrid cell lines which synthesise antibodies detecting different public antigenic specificities of the mouse H–2 complex. These hybrid cell lines can be grown in the mouse as ascites tumours, and the ascites fluids obtained contain large quantities of homogeneous anti-H–2 antibodies.
162 citations
TL;DR: The lactose carrier protein, coded for by the Y gene, is readily identified upon lac operon induction in strains carrying the plasmid and comprises about 15% of the cytoplasmic membrane protein synthesized in the first generation after induction, compared with a wild type strain induced under the same conditions.
Abstract: The isolation and properties of a hybrid plasmid carrying the Y gene of the lac operon of Escherichia coli are described. The lactose carrier protein, coded for by the Y gene, is readily identified upon lac operon induction in strains carrying the plasmid. The protein comprises about 15% of the cytoplasmic membrane protein synthesized in the first generation after induction, compared with a wild type strain induced under the same conditions where lactose carrier protein comprises 1.4% of the cytoplasmic membrane protein.
146 citations
TL;DR: Antigen‐independent cooperation between T and B lymphocytes is demonstrated in vitro in two different experimental protocols, such that only those B cells respond that secrete antibody with the A5A idiotype.
Abstract: Antigen-independent cooperation between T and B lymphocytes is demonstrated in vitro in two different experimental protocols: (a) B cells from A/J mice immunized in vivo either with Group A streptococcal vaccine (Strep.A) or with the IgG1 fraction of guinea pig anti-idiotypic antibody to the A5A idiotype, mature into plaque-forming cells (PFC) with specificity for Group A streptococcal carbohydrate (A-CHO) during a 4-day culture together with T cells from A/J mice immunized in vivo with A5A idiotypic antibody. (b) B cells from A/J mice immunized in vivo with Strep.A generate PFC specific for A-CHO when cultured in the presence of small concentrations of anti-A5A idiotypic antibody and of T cells primed with Strep.A. In both cases, antigenindependent cooperation is idiotypically selective, such that only those B cells respond that secrete antibody with the A5A idiotype.
The data are interpreted to suggest that, in addition to antigen-specific helper cells, idiotype-specific may participate in antibody responses, and that the latter type of help may be responsible for the idiotypic selectivity in T-B cooperation observed previously. Furthermore, idiotype-specific cooperation may be a means to generate and maintain B cell diversity during the evolution and ontogeny of the immune system.
135 citations
TL;DR: In this article, the Lagrange multiplier which effects this constraint, the hypermomentum current, is closely related to the constraint "force" which keeps space-time Riemannian.
Abstract: Within the confines of conventional general relativity, variational principles are analyzed in which the metric tensor and the asymmetric linear connection are varied independently. The constraint that space-time remain Riemannian is introduced by means of the Lagrange multiplier technique. The Lagrange multiplier which effects this constraint, the hypermomentum current, is closely related to the constraint “force” which keeps space-time Riemannian and should be a measure for the violation of the Riemannian constraint at the microscopic level.
128 citations
TL;DR: In this paper, the frequency-dependent dipole moment and the radiation emission spectrum for a small particle located above a metal film were calculated and a resonance structure associated with a localized surface plasma mode at a frequency corresponding to the peak in the structure observed in the emission spectra.
Abstract: A resonancelike structure has been reported in the frequency spectrum of light emitted from small-particle tunnel junctions. Here we present a calculation of the frequency-dependent dipole moment and the radiation emission spectrum for a small particle located above a metal film. The dipole moment exhibits a resonance structure associated with a localized surface plasma mode at a frequency corresponding to the peak in the structure observed in the emission spectra.
TL;DR: A fast iterative method for solving the solution of parabolic control problems by a system of two equations parabolic with respect to opposite orientations is proposed.
Abstract: The solution of parabolic control problems is characterized by a system of two equations parabolic with respect to opposite orientations. In this paper a fast iterative method for solving such problems is proposed.
TL;DR: In this article, a comparative study of the numerical behavior of different algorithms for solving quadratic assignment problems is presented, where branch and bound algorithms are briefly discussed and starting procedures are described and compared by means of numerical results.
Abstract: This paper contains a comparative study of the numerical behavior of different algorithms for solving quadratic assignment problems. After the formulation of the problem, branch and bound algorithms are briefly discussed. Then, starting procedures are described and compared by means of numerical results. Modifications of branch and bound procedures for obtaining good suboptimal solutions are treated in the next section. Subsequently, numerical results with the Gaschutz-Ahrens algorithm are reported. In the last section, exchange algorithms are discussed, and it is pointed out how they can be combined efficiently with the Gaschutz-Ahrens procedure and the perturbation method. All suboptimal solutions found in the literature could be improved by these combined methods. In the appendix, test examples and the best known solutions are listed.
TL;DR: In the framework of Poincare gauge field theory, this paper showed that a certain quadratic Lagrangian has three limits: (1) a weak-field limit with a newtonian and a "confinement" potential, (2) a general relativistic limit including the Schwarzschild solution, and (3) the unphysical limit of a riemannian model of spacetime with a curvature-square lagrangian.
TL;DR: A multi-grid method is applied to Helmholtz's equation (Dirichlet boundary data) in a general region and to a differential equation with variable coefficients subject to arbitrary boundary conditions.
Abstract: Multi-grid methods are characterized by the simultaneous use of additional auxiliary grids corresponding to coarser step widths. Contrary to usual iterative methods the speed of convergence is very fast and does not tend to one if the step size approaches zero. The computational amount of one iteration is proportional toN, the number of grid points. Thus, a solution with accuracy ɛ requires 0 (|log ɛ|N) operations. In this paper we apply a multi-grid method to Helmholtz's equation (Dirichlet boundary data) in a general region and to a differential equation with variable coefficients subject to arbitrary boundary conditions.
TL;DR: Blue-green algae are presumably of limited value in projects of solar energy conversion to form molecular hydrogen, because H2-formation by intact cells is found to be catalyzed exclusively by nitrogenase, and the enzyme is characterized with respect to its specifity towards electron donors and acceptors.
TL;DR: It is suggested that the inducing factor acts bimodally by inducing pedal disc development and by eliminating a head inhibitor originating from the basal end of the bud in the induction of polyp formation.
Abstract: Scyphistomae of Cassiopea andromeda Forskal, 1775 containing symbiontic zooxanthellae did not develop medusae at a constant temperature of ∼20°C, but monodisc strobilation was initiated after transfer of the polyps to ∼24°C. After release of the ephyrae and regeneration of the hypostome and tentacular region, the recovered polyps either produced vegetative buds or entered a new strobilation phase. Formation of motile, planula-like buds was not found to be indicative of unfavourable environmental conditions. Intensity of budding was positively correlated with available food and with increase of temperature. Budding was negatively correlated with the number of polyps maintained per dish and with the conditioning of the sea water. Under optimal feeding and temperature conditions, polyps could simultaneously produce chains of buds at 2 to 4 budding regions. Settlement and development of buds into scyphistomae was suppressed in pasteurized sea water and in pasteurized sea water containing antibiotics, but polyps developed from buds in the presence of algal material taken from the aquarium, debris or egg shells of Artemia salina, or on glass slides which had been incubated in used A. salina culture medium. Several species of marine bacteria were detected after staining these slides. One, a Gramnegative coccoid rod, which was identified as a nonpathogenic Vibrio species, was isolated, cultivated as a pure strain, and was proved to induce the development of C. andromeda buds into polyps. Millipore filter-plates coated with Vibrio sp. cells grown in suspension culture were ineffectual, but diluted filtrate initiated polyp morphogenesis. The inducing factor is obviously not a constituent of the bacterial cell surface, but is a product of growing Vibrio sp. cells released into the medium. This product was found to be relatively heat-stable and dialyzable. As to the basic mechanism involved in the induction of polyp formation, it is suggested that the inducing factor (s) acts bimodally by inducing pedal disc development and by eliminating a head inhibitor originating from the basal end of the bud. The life history, and various aspects of medusa-formation and of vegetative reproduction in scyphozoans are reviewed and discussed with particular reference to rhizostome species. Special attention has been paid to some reports of larval metamorphosis controlled by marine bacteria.
TL;DR: The results confirmed that initiation of therapy at the onset of menstruation was followed by an immediate and significant decrease in luteal PG in three out of five women receiving 5 mg.
TL;DR: In this paper, the electrical resistivity, thermal conductivity, and the thermoelectric power were measured on the anomalous CeCu2Si2 compound and on the reference compound, and it was shown that resistivity and temperature dependences were in accord with those found in otherd band metals.
Abstract: We report measurements of the electrical resistivityρ, the thermal conductivityk and the thermoelectric powerS between 1.5K and 300K on the anomalous CeCu2Si2 compound and on LaCu2Si2 as reference compound. For LaCu2Si2 the temperature dependences ofρ andS are in accord with those found in otherd band metals. For CeCu2Si2 the observed resistivity (ρ≃220 µΩ cm at 200K) leads to a very short electronic mean free path which is of the order of the Ce-Ce spacing. Correspondingly,k is almost identical with the phonon contributionk
p
. Below 20K, resistivity and thermoelectric power strongly suggest Fermi liquid behavior with a “degeneracy temperature” between 20K and 40K. Above 200K, bothρ andS decrease proportionally to −ln(T/1 K).
TL;DR: The results show that in procaryotic organisms the diversity in diglyceride portions of lipids is reduced as compared to eucaryotic organism, but nevertheless does exist.
Abstract: The main glycerolipids (monogalactosyl-, digalactosyl-, sulphoquinovosyl diacylglycerol, phosphatidylglycerol) from five blue-green algae (Microcystis, Anabaena, Nostoc, Oscillatoria, Tolypothrix) were analyzed for fatty acid composition, occurrence of diglyceride species and positional distribution of fatty acids between thesn-1- andsn-2-position of glycerol In contrast to eucaryotic plants biosynthetically closely related lipids (monogalactosyl-, digalactosyl-, trigalactosyl diacylglycerol) show nearly identical diglyceride moieties, whereas sulphoquinovosyl diacylglycerol and phosphatidylglycerol are separated from galactolipids by composition as well as occurrence of fatty acids On the other hand the positional distribution of fatty acids in all lipids is controlled exclusively by chain length and not by degree of unsaturation with C18-fatty acids at thesn-1- and C16-fatty acids at thesn-2-position These results show that in procaryotic organisms the diversity in diglyceride portions of lipids is reduced as compared to eucaryotic organisms, but nevertheless does exist
TL;DR: In patients with early stromal invasion or microcarcinoma, a restricted cancer therapy may be possible, just as in patients with carcinoma in situ, if intraluminal tumor invasion is demonstrated in the diagnostic biopsy, an additional lymphadenectomy is advisable.
TL;DR: The topologically singular lattice structure around a spiral dislocation scatters electrons in a manner much different from the deformation-potential scattering as discussed by the authors, which does not cause a perpendicular resistivity, but in a dirty limit a specific dislocation resistivity does exist, whose relaxation time per unit length of dislocation is of the order ofℏ/(Fermi energy).
Abstract: The topologically singular lattice structure around a spiral dislocation scatters electrons in a manner much different from the deformation-potential-scattering. Thet-matrix is represented ast(k, k′)=t0 sin (kz/2) exp (±i Θkk′/2)/sin (Θkk′/2) with the scattering angleΘkk′, the componentkz of the wave vector parallel to the dislocation, andt0≅(Fermi energy). This kind of scattering alone does not cause a perpendicular resistivity, but in a dirty limit a specific dislocation resistivity does exist, whose relaxation time per unit length of dislocation is of the order ofℏ/(Fermi energy).
TL;DR: An efficient method for solving Linear Bottleneck Assignment problems is described, which starts with a heuristically determined partial assignment and shortest augmenting paths are constructed with the aid of a modification of the algorithm of Dijkstra.
Abstract: An efficient method for solving Linear Bottleneck Assignment problems is described. The method starts with a heuristically determined partial assignment. Then shortest augmenting paths are constructed with the aid of a modification of the algorithm of Dijkstra. Comprehensive numerical investigations are reported and discussed. A FORTRAN IV subroutine can be found in the appendix.
TL;DR: The infinite unitary irreducible spinor representations of the hadron algebra of hadron excitations are embedded in a global π(4,R)$ with intrinsic dilation, shear, and spin pieces in its hypermomentum current as mentioned in this paper.
Abstract: The infinite unitary irreducible spinor representations of the $\mathrm{SL}(3,R)$ algebra of hadron excitations are embedded in a global $\mathrm{GA}(4,R)$ with intrinsic dilation, shear, and spin pieces in its hypermomentum current (i.e., the affine generalization of angular momentum). When gauged over a space with a local Minkowski metric, $\mathrm{GA}(4,R)$ reproduces the metric-affine theory of gravity, in which the intrinsic hypermomentum is coupled to the connection, and the energy-momentum to the tetrad.
TL;DR: In this paper, the Hartree-Fock approximation of the periodic Anderson model for a lattice of magnetic ions is investigated in Hartree Fock approximation, and the effect of hybridization leading to reduced magnetic moments strongly depends on the position of the localized f levels relative to the conduction band.
Abstract: The periodic Anderson model for a lattice of magnetic ions is investigated in Hartree-Fock approximation. Attention is paid to different solutions of the self-consistency equations corresponding to ferromagnetic or antiferromagnetic ordering of the local magnetic moments. The effect of hybridization leading to reduced magnetic moments strongly depends on the position of the localizedf levels relative to the conduction band. For paramagnetic solutions with a non-integer value for thef level occupation number comparison is made with properties of intermediate valence rare earth compounds. The mean-field results for the susceptibility and specific heat agree with essential features found for these substances.
TL;DR: In this article, the Hartree-Fock model was extended by the hybridization between the localized electron states and the conduction band states, and the occupation number of the localized levels always varies continuously with the level energy for nonvanishing hybridization.
TL;DR: The phase relationship between the semilunar rhythm and the semi-monthly zeitgeber cycle is a population-specific property as demonstrated by stocks from two locations with different tidal schedules (Helgoland and Normandy).
TL;DR: A new murine cell line is described which is continuously producing high amounts of IgE antibodies with anti-ovalbumin (OA) specificity, which is indispensable for several important applications to future studies on the origin and mechanism of allergic processes.
Abstract: SINCE the identification of IgE antibodies as mediators of allergic reactions by Ishizaka et al.1 extensive work has been done to purify this new type of immunoglobulin from the serum of allergic patients and animals However, all attempts so far have been limited by the very low serum concentration of these reaginic antibodies This difficulty has been partly overcome with the detection of the extremely rarely occurring IgE-producing myelomas of the human2 and the rat3, although IgE myelomas of other species are lacking Moreover, none of the available IgE-myeloma proteins has a known allergenic specificity, which is indispensable for several important applications to future studies on the origin and mechanism of allergic processes Here we describe a new murine cell line which is continuously producing high amounts of IgE antibodies with anti-ovalbumin (OA) specificity This cell line was generated by cell fusion of murine myeloma cells with spleen cells from OA-hyperimmunised mice following the cell hybridisation technique developed by Kohler and Milstein4.
TL;DR: In this article, the authors investigated the temperature dependence of the Auger-lifetime of n-Hg1−xCdxTe for several values of bandgap and of extrinsic carrier-concentration nex in the whole range between room and He-temperatures.
Abstract: The temperature dependence of the Auger-lifetime of n-Hg1−xCdxTe is investigated both theoretically and experimentally for several values of bandgap and of extrinsic carrier-concentration nex in the whole range between room and He-temperatures. For semiconducting compounds a pronounced minimum of the lifetime between 10 and 50K and an exponential increase at still lower temperatures are found. The position of the minimum and the exponent depend mainly on the value of the bandgap and on the ratio of the conduction- and valenceband effective masses. Apart from the extended temperature range, which does not allow the use of classical statistics, our calculation differs from earlier work in so far, as we take the band energies and the overlap integrals of conduction- and valenceband Bloch-functions from a k·p-calculation. For semiconducting compounds, we compare the results with those obtained from an estimate of the overlap integrals given by Antoncik and Landsberg. Whereas both results are compatible at high temperatures, characteristic differences occur at low temperatures, where we find the lifetime to be proportional to n ex −8 3 rather than to nex−2. For semimetallic compounds we calculate a weakly temperature dependent Auger-time of the order of 0.1–1 nsec.