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Showing papers by "University of Bremen published in 1983"


Journal ArticleDOI
TL;DR: It is argued that the best measure of evolutionary adaptation is the persistence of this autopoietic system, which allows organisms to compensate environmental, and even genetic, perturbations without having to change morphologically.

255 citations


Journal ArticleDOI
TL;DR: In this paper, the retention behavior of phenylureas, s-triazines and phenoxycarbonic acid derivatives in a reversed-phase high-performance liquid chromatographic (RPLC) system has been examined.

170 citations


Book ChapterDOI
01 Jan 1983
TL;DR: In this article, the problems and results of qualitative theory of stochastic dynamical systems are discussed, focusing on the general nature of a solution on the entire time interval (asymptotic or long-term behavior) without solving the equation.
Abstract: Publisher Summary This chapter presents the problems and results of the qualitative theory of stochastic dynamical systems. Qualitative theory studies the general nature of a solution in the entire time interval. Attention has been attracted mainly by the white noise case, in particular, by nondegenerate diffusion processes. The methods used were mainly Lyapunov function techniques and the interrelation between Markov processes and deterministic partial differential equations. White noise is a generalized Gaussian stationary process with constant spectral density on the whole real line. Qualitative theory studies the general nature of a solution on the entire time interval (asymptotic or long-term behavior) without solving the equation.

112 citations


Journal ArticleDOI
TL;DR: In this article, a Fourier transform ion cyclotron resonance spectrometer (FT ICR) utilizing a superconducting magnet was described, where a narrow-band ultrahigh resolution and a wide-band medium resolution mode can be used.

111 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that these structures are not numerical artefacts but properties of the solution manifold of Eq. (1.1) and that they can explain normal and pathological behavior of control systems in the physiology of blood cell production and respiration.

105 citations


Journal ArticleDOI
01 Nov 1983-Planta
TL;DR: The results of this study indicate that (1) the vascular parenchyma cells are able to retrieve at least sucrose from the vessels and transfer it to the thick-walled sieve tubes, (2) the thickness of the sieves are not involved in long-distance transport, and (3) the thin-walling sieves tubes are capable themselves of accumulating sucrose and photosynthates from the apoplast, without the companion cells serving as intermediary cells.
Abstract: Microautoradiographs showed that [14C]sucrose taken up in the xylem of small and intermediate (longitudinal) vascular bundles of Zea mays leaf strips was quickly accumulated by vascular parenchyma cells abutting the vessels. The first sieve tubes to exhibit 14C-labeling during the [14C]sucrose experiments were thick-walled sieve tubes contiguous to the more heavily labeled vascular parenchyma cells. (These two cell types typically have numerous plasmodesmatal connections.) With increasing [14C]sucrose feeding periods, greater proportions of thick- and thin-walled sieve tubes became labeled, but few of the labeled thin-walled sieve tubes were associated with labeled companion cells. (Only the thin-walled sieve tubes are associated with companion cells.) When portions of leaf strips were exposed to 14CO2 for 5 min, the vascular parenchyma cells-regardless of their location in relation to the vessels or sieve tubes-were the most consistently labeled cells of small and intermediate bundles, and label (14C-photosynthate) appeared in a greater proportion of thin-walled sieve tubes than thick-walled sieve tubes. After a 5-min chase with 12CO2, the thin-walled sieve tubes were more heavily labeled than any other cell type of the leaf. After a 10-min chase with 12CO2, the thin-walled sieve tubes were even more heavily labeled. The companion cells generally were less heavily labeled than their associated thin-walled sieve tubes. Although all of the thick-walled sieve tubes were labeled in portions of leaf strips fed 14CO2 for 5 min and given a 10-min 12CO2 chase, only five of 72 vascular bundles below the 14CO2-exposed portions contained labeled thick-walled sieve tubes. Moreover, the few labeled thick-walledsieve tubes of the “transport region” always abutted 14C-labeled vascular parenchyma cells. The results of this study indicate that (1) the vascular parenchyma cells are able to retrieve at least sucrose from the vessels and transfer it to the thick-walled sieve tubes, (2) the thick-walled sieve tubes are not involved in long-distance transport, and (3) the thin-walled sieve tubes are capable themselves of accumulating sucrose and photosynthates from the apoplast, without the companion cells serving as intermediary cells.

90 citations


Book ChapterDOI
01 Jan 1983
TL;DR: In this article, a review of metal chelates where the metal atom is surrounded by a planar ligand is presented, where the coordinative and covalent binding of the chelate in a polymer chain is described in detail.
Abstract: The topic of this review concentrates on those metal chelates where the metal atom is surrounded by a planar ligand: porphyrins, phthalocyanines, hemiporphyrazines (hexaazocyclanes), tetraaza(14)annulenes, bis(1,2-dioximes), and Schiff'base chelates (salens). The coordinative (through the metal atom) and covalent (through the ligand and metal atom) binding of the chelate in a polymer chain is described in detail. Binding of small molecules as oxygen and catalytic activity are the main promising properties. Then the covalent and coordinative incorporation of the chelate through the metal atom in the polymer chain is discussed. Electrical conductivity and thermal properties are further main interesting aspects of such polymers. Finally, this review deals with polymeric chelates with covalent introduction of the chelate through the ligand in the main chain. These polymeric chelates and their ligands show other interesting features, such as electrical conductivity, small molecule binding, catalytic and electrocatalytic properties.

69 citations


Journal ArticleDOI
01 Nov 1983
TL;DR: An efficient computer method is developed for the generation of all 2n sets of GRM coefficients of an n-variable Boolean function and a metric is calculated from which the minimum cost set according to some criterion may be selected.
Abstract: Application of exclusive-OR logic design suffers from a lack of straightforward design methods. Recently a procedure using generalised Reed-Muller (GRM) coefficient maps has been proposed. Based on this approach, an efficient computer method is developed for the generation of all 2n sets of GRM coefficients of an n-variable Boolean function. Along with the coefficients a metric may be calculated from which the minimum cost set according to some criterion may be selected. The method requires a storage of 2n bits and an average of 2n-1 + n/2 ExOR single-bit operations per set of GRM coefficients.

66 citations


Journal ArticleDOI
TL;DR: The substrate specificity of beef heart phosphodiesters activity and of the phosphodiesterase activity at the cell surface of the cellular slime mold Dictyostelium discoideum has been investigated, indicating that binding of the substrate to the enzyme and ring opening are two separate steps in the hydrolysis of cAMP.
Abstract: The substrate specificity of beef heart phosphodiesterase activity and of the phosphodiesterase activity at the cell surface of the cellular slime mold Dictyostelium discoideum has been investigated by measuring the apparent Km and maximal velocity (V) of 24 derivatives of adenosine 3',5'-monophosphate (cAMP). Several analogs have increased Km values, but unaltered V values if compared to cAMP; also the contrary (unaltered Km and reduced V) has been observed, indicating that binding of the substrate to the enzyme and ring opening are two separate steps in the hydrolysis of cAMP. cAMP is bound to the beef heart phosphodiesterase by dipole-induced dipole interactions between the adenine moiety and an aromatic amino acid, and possibly by a hydrogen bond between the enzyme and one of the exocyclic oxygen atoms; a cyclic phosphate ring is not required to obtain binding. cAMP is bound to the slime mold enzyme via a hydrogen bond at the 3'-oxygen atom, and probably via a hydrogen bond with one of the exocyclic oxygen atoms. A cyclic phosphate ring is necessary to obtain binding to the enzyme. A specific interaction (polar or hydrophobic) between the base moiety and the enzyme has not been demonstrated. A negative charge on the phosphate moiety is not required for binding of cAMP to either enzyme. The catalytic reaction in both enzymes is restricted to the phosphorus atom and to the exocyclic oxygen atoms. Substitution of the negatively charged oxygen atom by an uncharged dimethylamino group in axial or equatorial position renders the compound non-hydrolyzable. Substitution of an exocyclic oxygen by a sulphur atom reduces the rate of the catalytic reaction about 100-fold if sulphur is placed in axial position and more than 10000-fold if sulphur is placed in equatorial position. A reaction mechanism for the enzymatic hydrolysis of cAMP is proposed.

59 citations


Journal ArticleDOI
TL;DR: Different procedures to calculate dimensionless numbers that are ratios between the maximum rate of substrate conversion and the maximum rates of substrate transfer are described and compared with respect to their potential use to predict experimental data.

58 citations


Book ChapterDOI
01 Jan 1983
TL;DR: Since 1970, the number of U.S. college and university students choosing to major in mathematics has declined sharply as discussed by the authors, and many conjectures about the causes of this decline have been made.
Abstract: Since 1970 the number of U.S. college and university students choosing to major in mathematics has declined sharply. There are several sources of data describing this decline and many conjectures about the causes. The situation is summarized in two sections of the paper below.

Journal ArticleDOI
TL;DR: In this paper, the authors measured neutron time-of-flight spectra from 90 MeV protons and 140 MeV alpha particles bombarding thin targets of Al, Ni, Zr, and Bi at laboratory angles between 20 and 135 degrees.
Abstract: We measured neutron time-of-flight spectra from 90 MeV protons and 140 MeV alpha particles bombarding thin targets of Al, Ni, Zr, and Bi at laboratory angles between 20\ifmmode^\circ\else\textdegree\fi{} and 135\ifmmode^\circ\else\textdegree\fi{}. The lowenergy (5 to 45 MeV) portions of the spectra were measured with 5 cm diameter by 5 cm deep NE-213 counters at 1 m flight paths with n-$\ensuremath{\gamma}$ pulse-shape discrimination. The high-energy (35 to 150 MeV) portions of the spectra were measured with 12.7 cm diameter by 10.2 cm deep NE-102 counters at flight paths of 2.0 to 5.0 m. The proton-induced measured neutron spectra reveal three distinct energy regions: a low-energy evaporation region, a high-energy region dominated by the quasifree scattering process, and an intermediate-energy region dominated by multistep, preequilibrium processes. In the latter two regions, the spectra show strong angular dependence. The alpha-particle induced neutron spectra show these same distinct energy regions plus an exponential falloff above the beam energy per nucleon. The neutron spectra are compared with earlier proton spectra produced also by 90 MeV protons and 140 MeV alpha particles. It is observed that the high-energy portions of the forward-angle neutron and proton cross sections are in ratios consistent with the idea that single nucleon-nucleon scattering dominates. For the heavy-mass targets, the low-energy evaporation regions show neutron yields larger than proton yields. The proton-to-neutron ratios observed in the high-energy continua are interpreted with a quasifree calculation fitted simultaneously to the proton and the neutron spectra. Preequilibrium calculations with the exciton model and the hybrid model reproduce the shape of the experimental angle-integrated energy spectra down to lower energies than the quasifree calculations. The exciton model calculations underestimate the magnitudes of the cross sections, while the hybrid model provides better absolute agreement. One of the preequilibrium calculations uses the method of Mantzouranis and Weidenm\"uller to predict angular distributions; we find that the predicted angular distributions overestimate the neutron yields at forward angles. The intranuclear-cascade model predicts proton-to-neutron ratios much smaller than experimentally observed in the high-energy forward-angle continua.NUCLEAR REACTIONS $^{27}\mathrm{Al}$, $^{58}\mathrm{Ni}$, $^{90}\mathrm{Zr}$, $^{209}\mathrm{Bi}$(p,n), ($\ensuremath{\alpha}$, n), ${E}_{\mathrm{p}}=90$ MeV; ${E}_{\ensuremath{\alpha}}=140$ MeV; ${\ensuremath{\theta}}_{L}=20\ifmmode^\circ\else\textdegree\fi{}\ensuremath{-}135\ifmmode^\circ\else\textdegree\fi{}$; measured $\frac{{d}^{2}\ensuremath{\sigma}}{d\ensuremath{\Omega}\mathrm{dE}}$; compared with available experimental proton spectra and with theoretical calculations including PWIA quasifree scattering, preequilibrium exciton, geometry-dependent hybrid, and intranuclear-cascade models.

Journal ArticleDOI
TL;DR: The findings suggest that glycoproteins and in particular the neuron-specific 200 kD glycoprotein, are related to morphological differentiation processes, mainly to cellular adhesion and neurite outgrowth.

Journal ArticleDOI
TL;DR: The adduct H3N · PF5 (1) is obtained in 8% yield from the reaction of NH3 with PF5, in 41% yield, however, from HF and (F2PPN)3 as mentioned in this paper.
Abstract: Das Addukt H3N · PF5 (1) wird in 8proz. Ausbeute bei der Reaktion von H3N mit PF5 und in 41proz. Ausbeute durch Umsetzung von wasserfreiem HF mit (F2PN)3 erhalten. Die Rontgenstrukturanalyse ergibt eine nur wenig verzerrte oktaedrische Geometrie mit einem PN-Bindungsabstand von 1.842 A. Aus den 1H-, 19F- und 31P-NMR-Spektren konnen die Kopplungen 14N-H, 14N-P-F(cis) und 14N-P entnommen werden. Synthesis and X-Ray Structure Analysis of Ammonia-Phosphorus Pentafluoride (1/1) The adduct H3N · PF5 (1) is obtained in 8% yield from the reaction of NH3 with PF5, in 41% yield, however, from HF and (F2PPN)3. The x-ray structure analysis shows only slightly distorted octahedral geometry at phosphorus with a PN bond length of 1.842 A. 14N-H, 14N-P-F(cis), and 14N-P coupling constants are found in the 1H, 19F, and 31P NMR spectra.

Journal ArticleDOI
TL;DR: In this article, a Galerkin scheme with a continuation method was proposed for the effective computation and continuation of periodic solutions of the parametrized differential delay equation x[xdot](t) [email protected]@?(x(t-1)), @l > 0, where @? is an odd, continuous, and nonlinear function satisfying [emailprotected]? (x)>0 for all x 0.

Journal ArticleDOI
TL;DR: In this article, low molecular and polymeric Schiff's base chelates were synthesized from Z-2,3-diamino-2-butene dinitrile (3), the corresponding o-hydroxyaldehydes, and Co(II), Ni, or Cu(II) acetate.
Abstract: Various low molecular and polymeric Schiff's base chelates 9 – 13, 15 – 19, and 22 were synthesized from Z-2,3-diamino-2-butene dinitrile (3), the corresponding o-hydroxyaldehydes, and Co(II), Ni(II), or Cu(II) acetate. Their IR, UV, and MS data are discussed. The cobalt containing Schiff's base chelates including the polymeric ones, were found to be effective catalysts for the isomerization of quadricyclane (24) into norbornadiene (23). First results are reported.

Journal ArticleDOI
J. Wolfart1
TL;DR: In this paper, a Fuchsian triangle group and an elliptic fixed point of δ are defined, and a basis of automorphic forms with expansions with expansions is given.
Abstract: LetΔ⊂SL2 Open image in new window denote a Fuchsian triangle group andA an elliptic fixed point of δ. For any weightk and any multiplier systemv whose values are roots of unity, there is a basis of automorphic forms with expansions $$f\left( z \right) = \left( {z - \bar A} \right)^{ - k} \sum\limits_{n = 0}^\infty {r_n b^n } \left( {\frac{{z - A}}{{z - A}}} \right)^n ,$$

Journal ArticleDOI
TL;DR: As expected, it was found that cranial nerves IX and X and spinal nerve 1 supplied the muscles involved in tongue movement and both functionally related and phylogenetically determined routes were found.
Abstract: Innervation of the tongue and associated musculature in plethodontid salamanders was studied using Palmgren stained sectioned materials, fresh dissection, and whole mounts of experimental specimens treated with horseradish peroxidase (HRP). Species studied were chosen to represent modes of tongue projection recognized by Lombard and Wake ('77). Special attention was given to species of the genera Plethodon, Batrachoseps, Pseudoeurycea, and Hydromantes, but representatives of other genera were investigated. As expected we found that cranial nerves IX and X and spinal nerve 1 supplied the muscles involved in tongue movement. The peripheral courses of the nerves were traced, and both functionally related and phylogenetically determined routes were found. As relative projection length increases, the nerves supplying the tongue tip also increase in length. When the tongue is at rest the long nerves are stored in coils. The coil of ramus lingualis lies between the ceratobranchials, but that of ramus hypoglossus is more variable, although constant within a species. Ramus hypoglossus bifurcates into separate branches to tongue and anterior musculature of the floor of the mouth. In generalized, presumably primitive, modes the bifurcation and coiling are far anterior. In most of the tongue projection modes bifurcation is relatively posterior, but in one, bifurcation is anterior, but coiling is relatively posterior in position. The most unusual condition is in Hydromantes, in which bifurcation is relatively posterior and a coiled ramus hypoglossus joins a coiled ramus lingualis to form a unique, coiled common ramus to the tongue tip. Hydromantes has the greatest projection distance of any salamander.

Journal ArticleDOI
TL;DR: In this paper, substitution silica gels were analyzed to determine the nature of their ligands and the determinations revealed structural differences between products of the same ligand type, especially for ion exchangers.

Journal ArticleDOI
TL;DR: Probenecid included in the perfusate abolished transtubular secretion and inhibited the metabolism of PCPT-cyclic AMP, suggesting that cyclicAMP analogs penetrate the renal cell at the peritubular membrane by an organic acid transport system.

Journal ArticleDOI
TL;DR: Polyphthalocyanine coatings on different metal substrates (Ti, Cu, Fe, Ni) were obtained by in situ synthesis with 1,2,4,5-tetracyanobenzene.

Journal ArticleDOI
TL;DR: In this paper, a qualitative theory for multidimensional stochastic dynamical models is presented where the random influences may be white or colored, i.e. a (possibly bounded) diffusion process.

Journal ArticleDOI
TL;DR: Serum samples from four tribal Populations--Chaudhuri, Kotwalia, Vasava, Gamit-living in Gujarat (Northwest India) were tested for transferrin subtypes and some interesting racial differences in the distribution of gene frequencies emerge.
Abstract: Serum samples from four tribal Populations--Chaudhuri, Kotwalia, Vasava, Gamit-living in Gujarat (Northwest India) were tested for transferrin subtypes. The results are compared with those reported for other Indian populations. Reviewing all the hitherto published Tf subtype data some interesting racial differences in the distribution of gene frequencies emerge. A possible geographical distribution pattern of the variants is explored.

Journal ArticleDOI
01 Dec 1983
TL;DR: In this article, the depolarisation ratio and the excitation profiles of some prominent Raman lines of the oxyhaemoglobin spectrum (1,375 cm-1, 1,583 cm- 1, 1 638 cm 1) have been measured as functions of the exciting laser frequency.
Abstract: The depolarisation ratio and the excitation profiles of some prominent Raman lines of the oxyhaemoglobin spectrum (1,375 cm-1, 1,583 cm-1, 1,638 cm-1) have been measured as functions of the exciting laser frequency. The depolarisation ratio shows a complicated minimum-maximum structure in the preresonant region between Soret- and β-band of the optical spectrum, which depends on the pH-value of the solution. These dispersion curves are interpreted by fifth-order Loudon theory of the polarisability tensor including static distortions of the haem group, which lower its symmetry from the ideal D4h-symmetry, and enhancement by a second, non-Raman-active phonon. The fitting constants needed to fit the experimental data are related to static distortions of A1g, B1g, B2g, and A2g` symmetry types and thus give information on the symmetry lowering from D4h. The variation of the fitting constants with the pH-value of the solution is interpreted to be caused by protonation/deprotonation processes of titrable amino acid groups contributing to the alkaline and acid Bohr effect. The protonation changes the electrostatic interaction energies in the globular protein and destabilises the salt bridge between His(HC3)β and Asp(FG1)β in the R-state. These processes induce distortions of the haem group via haem-apoprotein interactions. Our results give no indication for a dominant role of the covalent Fe2+-N[His(F8)] bond in this process. They are in agreement, however, with the allosteric model of Hopfield, which assumes all interactions to be evenly distributed all over the protein molecule.

Journal ArticleDOI
TL;DR: In this article, the reaction of RMgCl [R = (Me3Si)2CH] with SbCl3 affords RSbCl2, and R2SbCl reacts with RLi to yield R3Sb, while R′SbC] is synthesized from R′Li and SbC.

Journal ArticleDOI
TL;DR: The cGMP analogues showed linear competitive inhibition with respect to cAMP (adenosine 3',5'-monophosphate) as substrate, suggesting that, for that enzyme, the catalytic site was sensitive to a guanine-type cyclic nucleotide structure.
Abstract: Cyclic nucleotide derivatives have been used as a tool to characterize distinct catalytic sites on phosphodiesterase enzyme forms: the cGMP-stimulated enzyme from rat liver and the calmodulin-sensitive enzyme from rat or bovine brain. Under appropriate assay conditions, the analogues showed linear competitive inhibition with respect to cAMP (adenosine 3',5'-monophosphate) as substrate. The inhibition sequence of the fully activated cGMP-stimulated phosphodiesterase was identical to the inhibition sequence of the desensitized enzyme, i.e. the enzyme which has lost its ability to be stimulated by cGMP. The inhibition pattern could, therefore, not be attributed to competition with cGMP at an allosteric-activating site. Also, the inhibition sequence of the calmodulin-sensitive phosphodiesterase was maintained whether activity was basal or fully stimulated by calmodulin. When cAMP and cGMP, with identical chemical ligands substituted at the same position, were compared as inhibitors of the calmodulin-sensitive phosphodiesterase, the cGMP analogues were always the more potent suggesting that, for that enzyme, the catalytic site was sensitive to a guanine-type cyclic nucleotide structure. Comparing the two phosphodiesterases, it was possible to establish both similar and specific inhibitor potencies of cyclic nucleotide derivatives. In particular, the two enzymes exhibited large differences in analogue specificity modified at C-6, 6-chloropurine 3',5'-monophosphate or purine 3',5'-monophosphate.

Journal ArticleDOI
Besslich1
TL;DR: A class of invertible fast in-place transformations is developed based on indexing elements of an array of 2n data so that adjacent elements have Hamming distance 1.
Abstract: The elements of an array of 2n data are indexed so that adjacent elements have Hamming distance 1. Based on this indexing a class of invertible fast in-place transformations is developed. The transform coefficients depend on the Hamming distance between the indexes of input data. A class of similar transformations exists in the Walsh-Hadamard domain. Three transform operations are discussed in detail: dyadic shift transform, a subsuming and averaging transformation and a weighting operation. Applications of the method are in the processing of Boolean and fuzzy switching functions, image analysis, etc.

Journal ArticleDOI
TL;DR: In this paper, necessary graph-theoretic conditions are presented for a parametrized system to have structurally fixed modus under output feedback of some arbitrarily specified pattern, which are formulated by the aid of a new graph which represents the couplings inherent in the system as well as the admissible feedback pattern.
Abstract: Several necessary graph-theoretic conditions are presented for a parametrized system nut to have structurally fixed modus under output feedback of some arbitrarily specified pattern. The criteria are formulated by the aid of a new graph which represents the couplings inherent in the system as well as the admissible feedback pattern. For the special class of structured systems, the conditions turn out to be also sufficient

Journal ArticleDOI
TL;DR: In this article, the spirocyclic bipyramide with the stereochemical active free electron pair in equatorial position is analyzed and the difference in length of the axial PO bonds is 0.25 A.
Abstract: Durch Saure-Base-Reaktion des Hydrophosphorans 9 mit Triethylamin entsteht das spirocyclische Phosphoranid 10, welches durch Methyliodid zu dem Phosphoran 7P-methyliert und durch Trimethylsilyliodid zu dem Phosphit 12O-silyliert wird. Die Rontgenstrukturanalyse von 10 ergibt eine stark verzerrte trigonale Bipyramide, in der das freie Elektronenpaar in aquatorialer Position sterisch wirksam wird. Die axialen PO-Bindungen weisen einen Langenunterschied von 0.25 A auf. In Losung liegt 10 offenbar im Gleichgewicht mit dem monocyclischen Phosphitalkoxid 10a vor. Structure and Synthesis of a Spirocyclic Phosphoranide Anion: Model of an Intermediate in a SN2(P) Reaction In an acid-base reaction the hydrophosphorane 9 reacts with triethylamine to give the spirocyclic phosphoranide 10, which is P-methylated by methyl iodide to form phosphorane 7 and O-silylated by trimethylsilyl iodide to form phosphite 12. The X-ray structure analysis of 10 shows a highly distorted trigonal bipyramide with the stereochemical active free electron pair in equatorial position. The difference in length of the axial PO bonds is 0.25 A. There is evidence for an equilibrium of 10 with the monocyclic phosphite alkoxide 10a in solution.

Journal ArticleDOI
TL;DR: In this paper, a method was developed for discussion of the brownian movement of a rotator in a periodic potential to calculate the transient behaviour when the linear approximation of the Debye theory is discarded.