57Co emission studies of cupric oxide

1990

Results on the incorporation, valence and spin states of Fe(Co) in CuO (with reference to similar studies on high temperature superconductors) and coupling of the Fe(Co) moment to the Cu magnetism in CuO are presented. Freshly prepared57Co: CuO shows two quadrupole doublets D1 and D2 withQ.S. of 2.49 and 1.52,I.S. of 0.35 and 0.70 mm/s and relative abundance of 74% and 26%, respectively at room temperature, the abundance being dependent on time in a sample exposed to ambient conditions and reaching 38 to 62% fifteen months after preparation. Below,TN=2251K, a typical combined magnetic-quadrupole interaction pattern is observed with a single saturation magnetic hfs of 25.6 T, central shift o…

New time-differential Mössbauer emission measurements on the high-spin→low-spin relaxation in [57Co/Co(phen)3](ClO4)2

1990

Using our new spectrometer for time-differential Mossbauer emission spectroscopy we reinvestigated the high-spin→low-spin relaxation following the57Co(EC)57Fe process in [57Co/Co(phen)3](ClO4)2 (phen=1,10-phenanthroline). In contrast to former investigations we found a temperature dependent initial population less than 1 for the metastable high-spin states. The results and the data evaluation method are presented.

Heterogeneity of P2-Purinoceptors in Brain Circulation

1990

The existence of P2-purinoceptors in the cerebrovascular bed was examined by testing the effects of ATP and its stable analog, α,β-methylene-ATP, on CBF in the unanesthetized goat as well as on isometric tension in isolated goat middle cerebral artery. When injected directly into the cerebral circulation, ATP increased and α,β-methylene-ATP decreased CBF. Indomethacin did not modify either of these effects. The vasoconstrictor action of α,β-methylene-ATP was reduced by nicardipine. “In vitro,” both ATP and α,β-methylene-ATP contracted the cerebral arteries at resting tone, but the analog was more potent than ATP. Repeated application of α,β-methylene-ATP as well as indomethacin significant…

Oxidative halogenation of substituted pyrroles with cu(II). Part I. Bromination of some 3-acetylpyrroles

1990

3-Acetylpyrroles are brominated with copper(II) bromide. The reaction afforded almost quantitatively only nuclear monobromination. Evidence for the structures of final compounds was by mass spectrometry, 1 H-nuclear magnetic resonance, ir, and elemental analysis

Icems and dcems study of Fe layers evaporated onto Al and Si

1990

Thin layers of57Fe (2.5 nm, 10 nm and 70 nm thickness), vacuum evaporated onto Al and Si plates, have been investigated by conversion electron Mossbauer spectroscopy (CEMS). The measurements were performed employing both a proportional counter and a channeltron for conventional and ultrahigh-vacuum integral CEMS (UHV-ICEMS) studies, respectively, and a channeltron for depth-selective CEMS (DCEMS). The phase analysis of the layers on base of experimental results has indicated the presence of metallic iron and one or two iron compounds, ascribed to iron reaction products formed with the residual gas during evaporation. These products are most likely rather stable iron nitrides, are more or le…

Effects of GABA on hypothalamic histamine neurons in vitro

1990

Oxidative halogenation of substituted pyrroles with cu(II). Part II. Bromination of some ethyl 3-pyrrolecarboxylates and corresponding acids

1990

Ethyl 3-pyrrolecarboxylates and their corresponding acids are brominated with copper(II) bromide. The reaction afforded at 0°, with high-yield nuclear monobromination.

Neuronal markers in the rodent pineal gland ? an immunohistochemical investigation

1990

Although some embryological and morphological features speak in favour of a neuronal character of rodent pinealocytes, histochemistry and ultrastructure let this issue appear controversial. Using antibodies to different neurofilaments, the neural adhesion molecule L1, synaptophysin and tubulin as neuronal markers, the pineal glands of rat and guinea-pig were studied by means of immunofluorescence. Neurofilament-immunoreactivity was present in some rat pineal nerve fibers and in the majority of guinea-pig pinealocytes, L1 decorated rat intrapineal nerve fibers, synaptophysin was almost ubiquitously distributed in the pineal of both species, while tubulin-immunofluorescence was seen in nerve …

Vitamin A deficiency increases noise susceptibility in guinea pigs.

1990

The effect of vitamin A deficiency in guinea pigs on noise-induced temporary threshold shift (TTS) was evaluated after short (15 min) acoustic overstimulation with a moderate (90 dB) broad-band white noise. Some guinea pigs were fed ad libitum a purified diet deficient in vitamin A (VAD group) until biochemical signs of deficiency occurred. A second, control group (VA group) received the same diet as well as 100 IU vitamin A daily by pharyngeal tube. Cochlear potentials were recorded by special computerized equipment using implanted electrodes. Before acoustic stimulation, a baseline value was determined with a test stimulus [90 dBA (A-filter according to usual DIN instructions)] correspond…

The state of iron in andalusite

1990

Iron in andalusite (Al2SiO5) with concentrations of 1.5 … 4.3 wt-% has been reported in the literature to occupy mainly Al1 sites as Fe3+, and only small portions occupy Al2 sites as Fe3+ and Fe2+. In no case a magnetic hyperfine splitting has been found at temperatures above 77 K.

Random analysis of geometrically non-linear FE modelled structures under seismic actions

1990

Abstract In the framework of the finite element (FE) method, by using the “total Lagrangian approach”, the stochastic analysis of geometrically non-linear structures subjected to seismic inputs is performed. For this purpose the equations of motion are written with the non-linear contribution in an explicit representation, as pseudo-forces, and with the ground motion modelled as a filtered non-stationary white noise Gaussian process, using a Tajimi-Kanai-like filter. Then equations for the moments of the response are obtained by extending the classical Ito's rule to vectors of random processes. The equations of motion, and the equations for moments, obtained here, show a perfect formal simi…

Study of very thin oxide layers by conversion and Auger electrons

1990

Oxidic layers as thin as 20–30 A on α-Fe and stainless steel are studied by57Fe-DCEMS with K-conversion electrons and ICEMS. No indication of a vanishingf-factor could be found. Mossbauer spectra, recorded by use of LMM-Auger electrons (AEMS) and by electrons emitted with energies below 15 eV (LEEMS), contain information on the surface layer as well as on the bulk material, showing that part of these electrons are due to secondary effects and the high escape depths of K-conversion electrons.

Volumes and compressibilities of pentanol in aqueous alkyltrimethylammonium bromide solutions at different temperatures

1990

Speed of sound and density properties of ternary water-tetradecyltrimethylammonium bromide-pentanol system at 15, 25 and 35°C and of water-hexadecyltrimethylammonium bromide-pentanol system at 25, 35 and 45°C were measured at fixed alcohol concentration as a function of surfactant concentration. The apparent molar volumes Vϕ,R and isentropic compressibilities Kϕ,RS of pentanol in micellar solutions as a function of the surfactant concentration show irregular behavior which depends on the alkyl chain length of the surfactant and tends to disappear with increasing temperature. These anomalies are ascribed to micellar transitions. For both surfactants at high concentrations, Vϕ,R decrease and …

Conversion electron Mössbauer study of vacuum and thermally treated vivianite

1990

Natural vivianite samples were studied by Mossbauer transmission and conversion electron spectroscopy. The intensities of ferrous doublets in vivianite and the widths of the resonance lines depend strongly on the origin of the samples, on their preparation history, and on exposures in vacuo as well as on thermal treatments. An additional ferrous doublet appearing in samples after vacuum treatment can be ascribed to a tetrahydrate phosphate phase appearing at the surface due to dehydration. Heating at 413 K in dry air for periods of 15–240 min causes a higher oxidation and decomposition rate at the surface region than in the bulk of vivianite. All results do not confirm the assumption publis…

Recombination studies of photodissociated MbCO by Mössbauer spectroscopy at low temperatures

1990

Rebinding of carbonmonoxide to myoglobin after photodissociation has been studied by Mossbauer spectroscopy at 57.6 K and below for up to 9 days. The time dependence is reproduced by a set of exponentials representing a distribution of activation enthalpies. A shift to smaller values of these activation enthalpies and of the preexponential factor compared to optical studies at higher temperatures has been observed as well as pumping into long-living states.

Synthesis and crystal structure of Na1+xV4P4O17(OH) (x ≈ 1.44)

1990

Abstract Hydrothermal synthesis starting from Na0.46VOPO4 · 1.58H2O leads to a new mixed-valence sodium vanadium phosphate: Na2.44V4P4O17(OH) (orthorhombic, space group Pnma; Z = 4; a = 13.723(5) A, b = 6.314(2) A, c = 16.139(4) A; R = 0.032 for 2659 reflections). In this phase, the interconnection of three complex types of infinite chains, built from VO6 octahedra and PO4 tetrahedra, sometimes edgeshared, defines tunnels partly occupied by a portion of the sodium atoms.

Crystallographic study of a family of Cs2BX4compounds

1990

Abstract Five compounds of the Cs2BX4 family with B = Zn, Co, Cu and X = Cl, Br were grown and studied. They belong to Pnma space group with 4 formula units per cell. From the full determination of the structure it appears that the ZnX4 tetrahedra are almost regular while the CuX4 tetrahedra are strongly distorted. This seems to be due to a strong Jahn-Teller effect induced by the Cu ions. This remark is extended to other compounds of the general family A2BX4.

Including long-distance effects in theKL−KSmass splitting

1990

In the framework of the standard model we propose an approach to the computation of the {ital K}{sub {ital L}}-{ital K}{sub {ital S}} mass difference which does not rely on an effective local Hamiltonian. Using partial conservation of axial-vector current, low-momentum Ward identities, and working at leading order in 1/{ital N}{sub {ital c}}, we relate box diagrams to others where strong interactions can be resummed. After subtracting the {ital K}-to-vacuum transitions, an expression involving only hadronic quantities is obtained. A numerical evaluation is performed by using a method of analytic continuation from the high-energy behavior given by QCD. The resulting contribution is found sma…

Quantitative Bestimmung der Hirnperfusion mit Hilfe der digitalen Subtraktionsangiographie (DSA)

1990

In a search for a reliable and relatively non-invasive method for quantifying cerebral perfusion, we examined the possible role of DSA. By using special software, it is possible to demonstrate vascular morphology and obtain functional data concerning blood flow. Regions of interest are used for obtaining time-density curves and these are evaluated by a formula designed by Meier and Zierler. Perfusion through the arterial territory in both cerebral hemispheres was correlated with the clinical symptoms of the patients and with the morphological findings. Difficulties and problems are described and discussed.

Radiation forces and the formation of planetary systems

1990

We briefly support on some new results about the influence of the rotation and finite size of a stellar radiation source on dust particle orbits, emphasizing the possibility of stable orbits, in the equatorial plane, for dust sizes near the radiation pressure limit.

Dynamics of protein-water systems revealed by Rayleigh scattering of Mössbauer radiation (RSMR)

1990

A critical review of recent studies of protein dynamics by the RSMR technique is given. The main approximations in quantitative analyses of RSMR data are discussed and conclusions about dynamical properties of protein and interprotein water, deduced from experiments, are described.

Accretion disc evolution in cataclysmic variables (the 1988 international time project in La Palma

1990

A summary of data collected during a sixty night international campaign devoted to cataclysmic variables is presented.

Electrostatic model and NMR results for EFG tensors in tetragonal BaTiO3

1990

Abstract We present 47,49Ti and 135,137Ba NMR second-order quadrupolar rotation patterns in a tetragonal single domain crystal of BaTiO3. These data will be analysed in terms of a ionic polarizable point multipole model.

Investigations on day-night differences of vesicle densities in synapses of the rat suprachiasmatic nucleus

1990

The present study was conducted to test whether the well-known circadian alterations in physiological and metabolical parameters of the hypothalamic suprachiasmatic nucleus (SCN) are accompanied by day-night differences in the number of vesicles in intrinsic synapses of the nucleus. Two groups of 5 adult male rats each were killed at mid-light or mid-dark, respectively, by perfusion with Karnovsky's fluid. The SCN were removed and processed for routine electron microscopy. In medial parts of the nucleus, synapses were characterized as being of Gray type I (asymmetrical), Gray type II (symmetrical) or of intermediate form, and the vesicles per synaptic profile (VPSP) were counted over a defi…

Partial molar volumes and compressibilities of alkyltrimethylammonium bromides

1990

Density and ultrasound measurements were performed for dodecyl- and tetradecyltrimethylammonium bromide at 15, 25 and 35°C and for hexadecyltrimethylammonium bromide at 25, 35 and 45°C over a wide concentration region. From these and previously reported data, partial molar volumes and isentropic and isothermal compressibilities were derived as a function of the surfactant concentration. It is shown that by increasing the surfactant concentration the apparent molar volumes and compressibilities increase according to the expected behavior of surfactant solutions. However, anomalies are displayed in plots of apparent molar compressibility of tetradecyltrimethylammonium bromide and of the speed…

Parallel simulation of dense two-dimensional polymer systems

1990

Abstract We present a parallel algorithm for the simulation of dense lattice polymer systems. The algorithm will be given for a two-dimensional system although the algorithm can be generalized to higher dimensions. We discuss timing results and applications.

Characterization of Diesel Soot by Sedimentation Field Flow Fractionation

1990

Three-dimensional singletons

1990

The three-dimensional analog of singleton gauge theory turns out to be related to the topological gauge theory of Schwartz and Witten. It is a fully-fledged gauge theory, though it involves only a single scalar field. Real, physical degrees of freedom propagate in 3-space, but they are ‘confined’ in the sense that they cannot be detected locally. The physical Hamiltonian density is not zero, but it is concentrated on the boundary at spatial infinity. This boundary surface, a torus, supports a two-dimensional conformal field theory.

Failure of endodontic treatment due to a palatal gingival groove in a maxillary lateral incisor with talon cusp and two root canals.

1990

A case is presented in which endodontic treatment of a maxillary lateral incisor with a talon cusp and two root canals failed following a mistaken diagnosis. What was first diagnosed as an endodontic lesion was, in all probability, a primary periodontal lesion caused by the advance of bacteria from the gingival crevice to the apex along the radicular groove between the main tooth and the talon cusp.

Selected dissociation‐ and correlation‐consistent configuration interaction by a perturbative criterion

1990

We propose a perturbative criterion to select the most important dissociation‐ or correlation‐consistent type of contributions to perform generalized valence bond‐configuration interaction (GVB‐CI) calculations, dissociation‐consistent configuration interaction (DCCI) or correlation‐consistent configuration interaction (CCCI) approach, respectively. The procedure presented is computationally less demanding than the CCCI proposed by Goddard and co‐workers. To ensure the distance consistency of the MOs used, the nonvalence virtual orbitals are obtained by a projection technique. The results obtained for a few test calculations show the ability of the suggested approach to get close results to…

The influence of different generations of computer algorithms on diabetes control

1990

With all control schedules, the management of diabetes is possible using Skyler's algorithm. In general, those control algorithms which do not allow the individual adaptation to changing conditions lead to overinsulinisation. So-called meal-related algorithms do usually minimise the fluctuations in blood sugar. The introduction of self-adapting algorithms, detecting peripheral insulin resistance, may further improve metabolic diabetes control.

Temperature Dependence of Irradiation-Induced Magnetic Flux Loss in Nd 2 Fe 14 B Permanent Magnets

1990

Nd2Fe14B permanent magnets were irradiated with 20 MeV protons at 300 K and at 15 K, and the flux loss was measured as a function of the irradiation dose. The results show that at 15 K the Nd2Fe14B magnets can withstand particle radiation at least 1000 times more than at room temperature.

Zur Diagnostik atherosklerotischer Läsionen der extrakraniellen Arteria carotis mit Duplexsonographie und IA-DSA

1990

Fifty patients were studied prospectively. The extracranial portions of the carotid arteries were examined by duplex sonography and IA-DSA in order to demonstrate haemodynamically significant stenoses or plaques which might give rise to emboli and the findings compared with the pathologic specimens. The results indicate high sensitivity (up to 90%) for more than 75% detection of stenoses. On the other hand ulceration was diagnosed sonographically with an accuracy of 66% and plaque hemorrhage with an accuracy of 56%.

Conductivity and light-induced absorption in BaTiO3

1990

A charge transport model including deep and shallow traps explains both the nonlinear relation between photoconductivity and light intensity and the light-induced absorption in BaTiO3. A correlation between measurements of photoconductivity and light-induced absorption as a function of temperature yields parameters for the shallow center, among them thermal activation energy and generation rate.

Studies of the spontaneous motility and the effect of histamine on isolated myometrial strips of the nonpregnant human uterus: the influence of vario…

1990

We investigated the spontaneous uterine activity of isolated corpus uteri myometrial strips from 30 patients with nonpathologic myometrium, 26 patients with uterine myoma, 23 patients with uterine adenomyosis, and three patients with uterine malignancy. We also investigated the influence of these conditions on the response of the uterus to histamine. The results show the same qualitative cyclic changes of the spontaneous motility of isolated myometrial strips throughout the menstrual cycle in all the abnormalities studied. These changes are characterized by a low amplitude and high frequency of spontaneous contractions in the proliferative phase and lower frequency with higher amplitude of …

A multicompartment model for open-loop control of glucose in insulin-dependent diabetics

1990

This paper describes a model that has been developed for individually adjusted therapy management in insulin-dependent diabetics. The multicompartment model considers all relevant aspects of glucose kinetics and its dependence on insulin. The structure of the model reflects that of the physiological system. Its parameters can be classified into (a) general parameters that are independent of the individual, (b) classifying parameters that are related systematically to the individual, and (c) distinguishing parameters. Classifying parameters allow a very convenient adjustment to relevant features of the individual like sex, age, body weight and length. The model can be employed in open-loop c…