Substituenteneffekte auf azido-tetrazolo-gleichgewichte elektronische und sterische effekte bei s-triazolo[4,3-c]tetrazolo[1,5-a]pyrimidinen1

The azido tetrazolo valence isomerism of twenty 9-methyl-s-triazolo[4,3-c]tetrazolo[1,5-a]pyrimidines with different substituents at position 5 has been studied by means of ¹H NMR spectroscopy. All the compounds have been found to be tetrazoles in the solid state and in (CD₃)₂SO solution; in CF₃COOH azido and tetrazolo isomers are in equilibrium. From equilibrium constants K and thermodynamic data determined it is concluded that in this series K depends on both electronic effects and steric requirements of the 5-substituents. A linear relation between K and σ was found for 5-arylderivatives because ΔS° keeps approximately constant and the substituent mainly operates on ΔH°.     

Codings of graphs with binary edge labels

LetG(V,E) be a graph. A mappingf:E{0,1} ^m is called a (binary) coding ofG, if the induced mapping , assigns different vectors to the vertices. For the Boolean sum,f is called aB-code, and for the mod 2 sum anM-code. Letm _B (G) resp.m _M (G) be the smallest lengthm for whichB-codes resp.M-codes are possible. Trivially,m _B (G),m _M (G) log₂|V|. Improving results of Z. Tuza we showm _B (G)log₂|V| + 1,m _M (G)log₂|V|+4.     

Topologische Affine Ebenen Mit Nichtstetigem Parallelismus

In this paper, we present a general method of constructing topological affine planes having non-continuous parallelism. We prove that a topological affine plane E with point set L ^k ×L ^k , and with a special K-algebraic slope has a topological affine subplane with non-continuous parallelism (Satz 4.6). Here, K is a real-closed subfield of a real-closed field L. The crucial tools needed to make our method work are the notion of a slope and the notion of K-algebraicity, a concept which is introduced and intensively studied here. As an application of our general method, we obtain in Section 5 affine Salzmann planes with lines being bent countably infinitely often admitting a subplane with non-continuous parallelism. This provides a negative answer to a question posed by H. Salzmann [13, p. 52].     

Zur Kennzeichnung der Lorentz-Transformationen

Let (V, f) be a real Minkowski space of any, not necessarily finite, dimension, and letd be the corresponding distance function (taking negative values for timelike distances). Then the following statement (among others) is proved: If ? :V →V is a surjective mapping such that $$d(P,Q) = a \Leftrightarrow d(P^\varphi ,Q^\varphi ) = a\forall P,Q \in V$$ is true for some fixeda εR,a<0, then ? is a Lorentz transformation (including a possible translation).     

Structure and properties of polystyrene-polyethylene interpenetrating polymer network (ipn)-like systems

A series of samples of polystyrene (PS) –polyethylene (PE) interpenetrating polymer network (IPN)–like system was prepared by synthesis in situ. The measurement of uniaxial compression modulus of the IPN samples was used for the determination of mean molar mass of the polymer chain between two junction points of the polymer network – M̌_C. The electron microscopic records gave an evidence about two phase structure of the IPN samples. Generally, the crystalline part of PE network in all IPN investigated samples is relatively low. The influence of the concentration of crosslinking agent on mechanical behaviour of the IPN samples was studied.     

Raman spectroscopy in high polymer research and production

The mechanism of RAMAN scattering depends on molecular polarizability changes and therefore this method is especially useful for the study of non-polar bonds. This is shown by reviewing some analytical applications. Knowledge on polymer structure was especially promoted by studies of the lowest-frequency bending modes, of correlation splittings in case of crystallinity, and by measurements on depolarization of the laser light. RAMAN spectroscopy has possibilities for in-situ and multi-method measurements. Newer developments serving the polymer sciences are surface enhanced RAMAN scattering and the RAMAN spectroscopy of electroconducting polymers.     

Recognition hysteresis of the acetylcholine receptor of torpedo Californica

The nicotinic acetylcholine receptor (nAcChR) of the electric organ of Torpedo californica fish exhibits a pronounced hysteresis loop in the high affinity binding of the neurotransmitter acetylcholine (AcCh). When increasing amounts of AcCh are added (pulse mode) an extremely long-lived, metastable conformer distribution is obtained (lower hysteresis branch) between low affinity AcCh binding states (R_l) and high (R_h) and very high (R_vh) affinity states. Dialysis conditions always lead to the equilibrium binding curve (upper hysteresis branch; K̄_A = 5 × 10⁻⁹M, 4°C; one A bound to the R-monomer of M_r ≈ 290 000). Cyclic, pulse mode addition and dilution of AcCh results in scanning loops within the main hysteresis. The kinetic analysis of the changes in free and bound AcCh during the open-system conditions of dialysis, that releases the metastability, shows that the AcCh (A) binding proceeds along an induced-fit pathway according to A+R_h ⇋ AR_n ⇋ AR_vh. The rate constant of the step AR_h → AR_vh is k₂ = 6 × 10⁻³s⁻¹ and that of the reverse step is k₋₂ = 3 × 10⁻⁴s⁻¹. Direct binding of A to free R_vh can be excluded. Therefore, the state R_vh does not preexist, it is induced and only stable, as AR_vh, by bound AcCh. The metastability can be described in terms of long-lived AR_vh ·R₁ hybrid dimers. Physiologically, the metastable hybrid may be viewed as a saving device: the functionally important, channel-active R₁ conformer is, at low AcCh-concentrations [A] < 1μM, prevented to convert to the desensitized states R_h and AR_vh. Furtheron, AcCh enhances the phosphorylation of phosphatidyl inositol and the auto-phosphorylation of the receptor. If the AcCh binding hysteresis causes a phosphorylation hysteresis the desensitized nAcChR may serve as a memory molecule of the transsynaptic information signalling of the neurotransmission.     

Statistical experiments and their conical measures

Summary In the theory of functional analytic comparison of statistical experiments (started by L. LeCam) one can characterize equivalence classes of experiments by conical measures (in the sense of G. Choquet). We begin with a short proof of the (known) fact that any conical measure with normed resultant belongs to an experiment class. Then we are concerned with the special case of dominated experiments which are characterized by the extendability of their conical measures to finite concrete measures. These results are in close connection with a paper of E.N. Torgersen (Mixtures and products of dominated experiments. Ann. Statist. 5, 44–64 (1977)).After this we study class properties of experiments which are expressible in terms of their conical measures. Simple examples are domination, existence of bounded densities and compactness. It follows the investigation of a more profound class property which we call extremality and which generalizes the concept of an experiment with a sufficient and boundedly complete subalgebra. Finally we prove that the extreme points of the compact convex set of conical measures with normed resultant are just the conical measures of the extremal experiments.