Energy spectrum and transport properties of the two-dimensional t-J model

1992

Abstract The formation of a ferromagnetically ordered region around a hole in the two-dimensional t-J model is investigated. The energy bands characterized by different values of the z-component of the total spin are analysed. A strong anisotropy of the lower-energy bands is found. For intermediate coupling of additionally included optical phonons, this anisotropy leads to a large polaronic state with an anisotropic envelope oriented along the plane diagonals. In the strong-coupling case the competition between the hole-magnon and the hole-phonon interactions prevents the formation of ferrons. Owing to the large effective mass in both cases, the hole transport takes place via hopping, with …

Distribution and coexistence of chromogranin A-, serotonin-and pancreastatin-like immunoreactivity in endocrine-like cells of the human anal canal

1992

The comparative distribution and coexistence of chromogranin A (CGA)-, serotonin (5-hydroxytryptamine; 5-HT)- and pancreastatin (PST)-like immunoreactivity in endocrine-like cells of the human anal canal was investigated by light-microscopic immunocytochemistry. The largest population of colorectal endocrine-like cells consisted of CGA-immunoreactive (ir) cells, followed by the 5-HT-ir and PST-ir cell population. In the anal transitional zone (ATZ), CGA- and 5-HT-immunoreactivity was equally distributed; ir-PST was confined to a smaller endocrine-like cell population. In the squamous zone and the perianal skin, Merkel cells in the basal layer of the epidermis and hair follicles exhibited ir…

Study of Fe−Ti and Fe−TiN interfaces by conversion electron Mössbauer spectroscopy

1992

Titanium and titanium nitride-iron interfaces obtained by PVD coated thin films of Ti and TiN onto argon plasma etched iron substrates at various temperatures and negative bias were studied by use of CEMS. It was found that intermixing to Ti with Fe resulted in the appearance of an amorphous FeTi1−x phase. Furthermore, a comparison of CEM spectra of samples before and after heating in UHV has shown rather strong influence of thermal treatments on Fe/Ti as well as Fe/TiN interfaces.

Antihypertensive efficacy and effects of nitrendipine on cardiac and renal hemodynamics in mild to moderate hypertensive patients: Randomized control…

1992

In this study antihypertensive efficacy, safety, and the effects of short-term nitrendipine administration on central and renal hemodynamics were evaluated in mild to moderate hypertensives. Our final goal was to ascertain whether the reduction in blood pressure induced by nitrendipine treatment was associated with maintained renal function. After a run-in period with placebo, 26 hypertensives without cardiac or renal disease were randomly assigned to a double-blind 8-week controlled trial with nitrendipine (N) 20 mg once a day (13 pts) or hydrochlorothiazide (HCT) 25 mg once a day (13 pts). Renal hemodynamic measurements included effective renal plasma flow (ERPF) and glomerular filtration…

Polymeric gegenions induced variability and mobility of amphiphilic supramolecular structures on solid substrates

1992

Abstract The micromorphological variations of amphiphilic L -glutamate derivatives at air-substrate interfaces due to an adjacent mobile polymer matrix have been investigated via fluorescence microscopy. Adjusted monolayers of the L -glutamate derivatives have been transferred by LB technique out of different aggregation states onto various substrates. The substrates have been prepared by successive polymer preadsorption to the solid support. The influence of the adjacent polymer layers on the domain morphology as a function of water content and temperature has been examined intensively. Moreover, reversible domain changes induced by temperature variation of the transferred films have been …

Coherent and incoherent electron transport along a disordered chain

1992

Abstract The Landauer-Buttiker approach is used to describe electron transport along a chain of scatterers which allow elastic as well as inelastic processes. The inelastic scattering takes place via side branches, coupling the chain to electron reservoirs which serve as a heat bath. In this approach, coherent and dissipative transport can be treated in a unified manner, and the suppression of quantum coherence effects for increasing coupling to the heat bath can be described. The influence of disorder on the transmission properties can be characterized by an appropriate coherence length in addition to the decay of the coherence due to dissipation.

Spontaneous domain formation of phospholipase A2 at interfaces: fluorescence microscopy of the interaction of phospholipase A2 with mixed monolayers …

1992

Abstract Fluorescence microscopy has recently been proven to be an ideal tool to investigated the specific interaction of phospholipase A 2 with oriented substrate monolayers. Using a dual labeling technique, it could be shown that phospholipase A 2 can specifically attack and hydrolyze solid analogous l -α-DPPC domains. After a critical extent of monolayer hydrolysis the enzyme itself starts to aggregate forming regular shaped protein domains (Grainger et al. (1990) Biochim. Biophys. Acta 1023. 365–379). In order to confirm that the existence of hydrolysis products in the mononlayer is necessary for the observed aggregation of phospholipase A 2 , mixed monolayers of d - and l -α-DPPC, l -α…

Influence of stretch-shortening cycle on mechanical behaviour of triceps surae during hopping.

1992

Six subjects performed a first series of vertical plantar flexions and a second series of vertical rebounds, both involving muscle triceps surae exclusively. Vertical displacements, vertical forces and ankle angles were recorded during the entire work period of 60 seconds per series. In addition, expired gases were collected during the test and recovery for determination of the energy expenditure. Triceps surae was mechanically modelled with a contractile component and with an elastic component. Mechanical behaviour and work of the different muscle components were determined in both series. The net muscular efficiency calculated from the work performed by the centre of gravity was 17.5 +/- …

Microwave muffle furnace assisted decomposition of vegetable samples for flame atomic spectrometric determination of Ca, Mg, K, Fe, Mn and Zn

1992

Calcium, magnesium, potassium, iron, manganese and zinc can be accurately determined in vegetable samples by flame atomic absorption and flame emission spectrophotometry after a previous dry ashing of the sample in a microwave muffle furnace. This treatment is carried out in 45 min using a new accessory developed by us to obtain high temperatures on a domestic microwave oven. Sample ashes, obtained in the muffle, are diluted with nitric acid and the obtained slurry is introduced directly into an air-C2H2 flame for the analysis of Fe, Mn, and Zn, or injected into a double-channel FIA manifold to determine Ca, Mg and K. The obtained results agree with those certified and also with those obtai…

A one-dimensional simulation of the interaction between land surface processes and the atmosphere

1992

A one-dimensional soil-vegetation model is developed for future incorporation into a mesoscale model. The interaction of land surface processes with the overlying atmosphere is treated in terms of three coupled balance equations describing the energy and moisture transfer at the ground and the energy state of the vegetation layer. For a complete description of the interaction, the coupled processes of heat and moisture transport within the soil are included as a multilayer soil model. As model verification, successful reproductions of the observed energy fluxes over vegetated surfaces from the HAPEX-MOBILHY experiment in southwestern France and from the LOTREX-10E/HIBE88 field experiment in…

Effect of Prime and Target Repetition on Lexical Decision Time

1992

On a prime-target lexical decision task we manipulated the relatedness between prime and target (semantically related or unrelated), the number of repetitions (from 1 to 5), the type of the repeated stimulus (only the prime, only the target, or both), and the stimulus onset asynchrony (within a range of automatic activation from 60 to 400 msec.) to find whether semantic and repetition priming are additive (or interact), and whether there is episodic priming in an automatic, nonconscious way. Analysis showed repetition and semantic priming were additive rather than interactive. No episodic automatic priming was found. Results are discussed in terms of the predictions made from the main theo…

DNA-DNA hybridization and ribotyping of Acidovorax delafieldii isolates from eels and aquatic environments

1992

Eleven strains of Acidovorax isolated from a freshwater lake and from healthy and diseased European eels in a hatchery were investigated by genotypic methods. DNA-DNA slot blot hybridization confirmed the identity of all strains as A. delafieldii. Isolates were heterogeneous in EcoR1 ribopatterns with four types recognizable. Most freshwater and healthy eel strains had the same ribotype but differed from the disease-associated strains. Typical ribopatterns of A. delafieldii contained 1·3, 1·5, and 3·2 kb fragments which provided useful additional taxonomic markers for species identification.

Simulation Analysis of the Influence of Hemodialysis Control Parameters on Exchange Processes during Therapy

1992

The effect of dialysis control parameters (dialysate composition, ultrafiltration rate, blood flow rate) on the patient's internal milieu were studied using a mathematical model for the description of the dynamic exchange processes during hemodialysis. This model simulates the electrolyte and water distribution, the acid-base and the oxygenation state as well as the ventilation. The dialysate sodium concentration affects mainly the intra-/ extracellular water and the potassium distribution. The dialysate bicarbonate and acetate concentrations control the acid-base state and the electrolyte distribution (sodium and potassium). In addition, the dialysate acetate concentration has a strong ef…

VALIDATING SCREENING INSTRUMENTS FOR NEUROEPIDEMIOLOGIC SURVEYS - EXPERIENCE IN SICILY

1992

In a hospital setting in Sicily, we assessed a screening instrument developed for a prevalence survey of parkinsonism, peripheral neuropathies, stroke, and epilepsy. The subjects consisted of (1) hospital patients with any of the above-mentioned diseases, to investigate sensitivity; and (2) hospital visitors free of all these diseases, to investigate specificity. The standard for comparison was a clinical evaluation based on specified criteria. Trained interviewers administered the screening instrument, asking subjects to answer symptom questions and to perform simple physical tasks. For the questions and tasks together, the sensitivity estimates were 100% for parkinsonism (n = 21), 96% for…

Spin correlations at the Z peak. A probe to the Z′ mass

1992

Abstract The interactions of a new heavy gauge boson are fixed by its coupling to matter and by its mass and its mixing with the Z 0 . Until now LEP has only constrained the Z′ mixing. However, there is one observable (and only one), the P - and T -odd transverse-normal spin correlation in ττ production, which fully and independently of its mixing measures the Z′ mass at the Z peak. For M z′ ∼ 130 GeV the Z′ contribution to this observable is typically of the same order as the standard model contribution.

Neurochemical anatomy of the mammalian spinal cord: Functional implications

1992

The nucleotide and deduced amino acid structures of sheep and pig fetuin. Common structural features of the mammalian fetuin family

1992

This study was initiated to gain further insight into the structural features of the mammalian fetuin family. The cDNA structures of sheep and pig fetuin were determined. The cDNA insert encoding sheep (pig) fetuin comprised 1550 (1470) nucleotides, including 54 (46) nucleotides encoding a signal peptide of 18 (15) residues and 1038 (1041) nucleotides encoding the 346 (347) amino acids of the mature plasma protein. The predicted amino-terminal sequence of the mature pig fetuin was confirmed by the amino-terminal sequence of the purified protein. However, two alternative sheep amino-terminal sequences were found in fetuin purified from the plasma of a single sheep fetus; the minor product wa…

Isotope shifts and nuclear-charge radii in singly ionizedCa40–48

1992

The isotope shifts in the resonance lines 4${\mathit{s}}_{1/2}$\ensuremath{\rightarrow}4${\mathit{p}}_{1/2,3/2}$ in Ca ii have been measured for the isotopes $^{40\mathrm{\ensuremath{-}}48}\mathrm{Ca}$ by fast-ion-beam collinear laser spectroscopy. Atomic many-body perturbation theory was then used to calculate the electronic factor for the field shift, giving F=-285(3) MHz/${\mathrm{fm}}^{2}$. The estimate of the uncertainty in F is based on the agreement at the level of 1% for the 4s and 4p hyperfine structures obtained using the same wave functions which include core polarization and pair correlation to all orders. The theoretical value is in excellent agreement with the result F=-283(6)…

4,4′‐Distyrylazobenzol als Mesogen

1992

4,4′-Distyrylazobenzene as Mesogen From 3,4-dihydroxybenzaldehyde (1) the tetraalkoxy-substituted 4,4′-distyrylazobenzenes (E,E,E)-5a – c are synthesized. A similar reaction sequence leads from ethyl 3,4,5-trihydroxy-benzoate (6) to the hexaalkoxy-substituted 4,4′-distyrylazobenzenes (E,E,E)-11 b, c. With the exception of 5a all products show thermotropic LC properties. Smectic phases have been characterized by polarizing microscopy and by differential scanning calorimetry.

Kinetics of domain growth in finite Ising strips

1992

Abstract Monte Carlo simulations are presented for the kinetics of ordering of the two-dimensional nearest-neighbor Ising models in an L x M geometry with two free boundaries of length M ⪢ L . This geometry models a “terrace” of width L on regularly stepped surfaces, adatoms adsorbed on neighboring terraces being assumed to be noninteracting. Starting out with an initially random configuration of the atoms in the lattice gas at coverage θ = 1 2 in the square lattice, quenching experiments to temperatures in the range 0.85⩽ T / T c ⩽1 are considered, assuming a dynamics of the Glauber model type (no conservation laws being operative). At T c the ordering behavior can be described in terms of…

A Mössbauer spectroscopic study of salt lake sediments from Qaidam basin

1992

Mossbauer spectroscopy, X-ray diffractometry and chemical fractionation have been used to study the clay smaples in sediments of Charhan playa and Qinghai lake. The spectral components of the Mossbauer spectra of the samples are attributed to Fe2+ ions in chlorite and siderite, Fe3+ ions in clay minerals and hematite, and partly in amorphous ferric hydroxides. The essential difference in the mineral composition of the sediments of both lakes is the presence of siderite in the samples of Char han playa, whereas it is absent in the samples of Qinghai lake. The fraction of the amorphous ferric hydroxides is higher in the sediments of Qinghai lake. Total Fe2+/Fe3+ ratios increase with sediment …

Substituted Dibenzothiophenes I: Synthesis, Chromatography, Mass Spectrometry and Structure Elucidation by1H NMR Spectroscopy

1992

Abstract Some polychlorinated and polymethylated dibenzothiophenes have been synthesized to serve as model compounds in environmental analysis. In order to obtain pure isomers, the synthesis mixtures have been fractionated with reversed-phase high performance liquid chromatography. In spite of a high sensitivity, mass spectrometry does not provide any reliable way to determine the precise structures of different isomers. Therefore, 1H NMR spectroscopy has been utilized as an aid in their analysis. The structures for two isomeric tetramethyldibenzothiophenes could be suggested on the basis of their 1H NMR spectra. Also some proposals for possible structures of two isomeric trimethyldibenzoth…

The third planet

1992

This paper examines the conceptions of planetary phenomena related to temperature change as held by primary school teacher trainees at the Department of Teacher Education of Jyvaskyla University. The data were collected by means of an essay test, supplemented by interviews. The results show that very few students have internalized these phenomena in accordance with present‐day scientific concepts. The significance of the Earth's sphericity seems particularly obscure. The influence of the angle of inclination of the Earth's axis is misunderstood. Similarly, temperature differences are erroneously attributed to the distance from the sun of the Earth or of a particular place. The students do n…

Electro-optical spectroscopy on aggregated chromophore systems in Langmuir-Blodgett films

1992

Linear and quadratic Stark spectra were measured on LB films that contained a hydrophobically substituted cyanine chromophore in binary mixtures with arachidic acid. The external field was applied normal or parallel to the film surface on samples with different internal symmetry. It was found that the orientation of the symmetry axis of the dye molecule is close to the surface normal. A significant number of molecules, 5–10%, are flipped head-to-tail from the main orientation. Parallel to the film surface, large polarizability changes on electronic excitation, Δα ∼ 1000 A3, were observed that reflect electron delocalization over aggregates. At low dye concentrations, large internal electric…

Shear flow characterization of blends containing liquid crystal polymers

1992

A simple phenomenological approach is proposed in order to predict the presence of minima in the viscosity-composition curves of blends of thermoplastic with liquid crystal polymer (LCP). When the viscosity of the liquid crystal polymer is larger than that of the thermoplastic matrix, a minimum is observed. A possible explanation of the presence of yield stress in the flow curves of these blends is also given.

On the peptidergic hypothesis for non-adrenergic non-cholinergic innervation in the rat duodenum

1992

1. The nature of the non-adrenergic, non-cholinergic (NANC) transmitter was studied in vitro in the rat duodenum, by use of an isometric-isovolumic preparation. 2. Electrical field stimulation (EFS) induced a tetrodotoxin (TTX)-sensitive fall both in luminal pressure and in isometric tension. 3. Neurotensin (NT) induced TTX-insensitive inhibitory responses similar to those induced by EFS. Vasoactive intestinal peptide (VIP) caused a delayed, slow, concentration-dependent, TTX-insensitive inhibitory effect, detected only by a change in luminal pressure. 4. alpha-chymotrypsin prevented the NT- and VIP-induced inhibitory effects and antagonized the response to EFS. 5. Apamin antagonized the EF…

Dactylogyrus (Monogenea) communities on the gills of roach in three lakes in Central Finland

1992

SUMMARYDactylogyrus (Monogenea) species were studied on the gills of roach (Rutilus rutilus) from a total of 293 fish in 3 interconnected lakes in Central Finland. One of the lakes is eutrophic and polluted by a paper and pulp mill, one is eutrophic and one is oligotrophic. Nine Dactylogyrus species were found. The structure of the monogenean communities was analysed at the component and infracommunity level and the Dactylogyrus fauna of the lakes was compared. Although it was found that the component communities tended to be very similar there were also differences. The abundance and diversity were highest in the polluted lake; the infracommunities of this lake were considerably more often…

Formation, phase composition, and transformations of Langmuir-Blodgett multi- and monolayers containing Fe

1992

Mono- and multilayers of ferric stearate were formed by the Langmuir-Blodgett technique. Thermodesorption of the hydrocarbon chains results in well defined thin oxidic films. Their reduction to Fe2+ and α-Fe was followed by conversion electron Mossbauer spectroscopy. Resonance lines can be observed even if the Fe coverage is less than one monolayer.

Purinoceptor-mediated modulation by endogenous and exogenous agonists of stimulation-evoked [3H]noradrenaline release on rat iris.

1992

To investigate whether endogenous purinoceptor agonists affect the sympathetic neurotransmission in the rat isolated iris, and to classify the purinoceptors modulating exocytotic [3H]-noradrenaline release, we have determined the effect of adenosine receptor antagonists on, and the relative potency of selected agonists in modulating, the field stimulation-evoked (3 Hz, 2 min) [3H]-noradrenaline overflow. In addition, the apparent affinity constants of 8-phenyltheophylline (8-PT) and 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) in antagonizing the prejunctional effects of purinoceptor agonists were estimated. The relatively A1-selective DPCPX 10 and 100 nmol/l increased the evoked [3H]-noradre…

Strukturen von [Me4Sb]2[MeSbI4]MeSbI2, und [Me4Sb]I. Darstellung von Me3Sb · MeSbI2 und farbwechsel bei Me4Sb2 · Me2SbBr

1992

Abstract The crystal structures of the complex [Me 4 Sb] 2 [MeSbI 4 ] ( 1 ) and its precursors MeSbI 2 ( 2 ) and [Me 4 Sb]I ( 3 ) are reported. In 1 there are tetrahedral cations and square pyramidal anions with Sb-I distances of 290–320 pm. The structure of 2 contains MeSbI 2 molecules. They associate via iodine bridges to form linear chains with alternating short and long Sb-I distances. The coordination around antimony is distorted tetragonal pyramidal. The tetrahedral coordination of the ions in 3 results in the formation of a wurtzite type structure with antimony-iodine distances of 406 and 435 pm. The novel adducts Me 3 Sb·Me 2 SbI 2 ( 4 ) and Me 2 SbSbMe 2 ·Me 2 SbBr ( 5 ) are formed…

Clinical relevance of vegetation localization by transoesophageal echocardiography in infective endocarditis

1992

Infective endocarditis is associated with significant morbidity and mortality, with valvular destruction and congestive heart failure being more common in patients with echocardiographically discernible vegetations. The transoesophageal approach affords consistently high quality images with excellent structural resolution. Two-hundred and eighty-one patients with clinically suspected infective endocarditis were studied, to evaluate the prognostic value of ascertaining the site of vegetations. Among them were 118 patients with vegetations attached to the aortic or mitral valve. These patients were followed for a mean period of 14 months. Mitral valve vegetations were associated with a signif…

Flashlamp-pumped Ti:Sapphire laser with different rods grown by Czochralski and Verneuil methods

1992

The design and the development of a flashlamp-pumped Ti:Sapphire laser is described. Design criteria are discussed and performance improvements using different types of fluorescent UV converters or filters, such as organic dyes or doped glass are presented. We have tested different laser rods at various Ti-concentrations obtained by Verneuil or Czochralski growth techniques. The maximum laser output energy of 540 mJ with a differential efficiency up to 1% was achieved by using only a pyrex filter surrounding the laser rod.

Therapeutic management of elderly hypertensives with concomitant ischaemic heart disease.

1992

CHARACTERISTICS OF ELDERLY HYPERTENSIVES: Hypertension is most prevalent in older patients and is associated with increasing morbidity and mortality with age. Elderly hypertensives often suffer from concomitant diseases, such as ischaemic heart disease, caused by age-induced modifications to the cardiovascular system, haemodynamic function and neurohormone activity. THERAPEUTIC MANAGEMENT: Therapeutic management of elderly hypertensives with concomitant ischaemic heart disease must take account of the pharmacodynamic and pharmacokinetic changes that occur in older subjects and drugs should be selected for their efficacy in both diseases. Since elderly subjects often metabolize drugs more sl…

A large area detector for high-energy neutrons

1992

Abstract We present design studies, results of test measurements, and Monte Carlo simulations which served as a basis for the realization of a large area neutron detector (LAND). It has a front area of 2m×2m and a depth of 1 m, and features a multilayer structure of passive converter and active scintillator material. The detector is subdivided in independently operating paddles which allow time-of-flight and position measurement. An energy resolution of ΔT n / T n =5.3% for a flight path of 15 m and an overall detection efficiency of ϵ ≈ 1 is anticipated for neutrons with T n ≈ 1 GeV. The operation of LAND at the SIS facility of GSI is described.

Selective inhibition of calcium entry induced by benzylisoquinolines in rat smooth muscle.

1992

Abstract The mechanism of relaxant activity of six benzylisoquinolines was examined in order to determine the minimal structural requirements that enable these compounds to have either a non-specific action like papaverine or an inhibitory activity on calcium entry via potential-operated channels. All the alkaloids tested totally or partially relaxed KCl-depolarized rat uterus and inhibited oxytocin-induced rhythmic contractions. Only glaucine and laudanosine inhibited K+-induced uterine contractions more than oxytocin-induced uterine contractions. In Ca+-free medium, sustained contractions induced by oxytocin or vanadate were relaxed by the alkaloids tested except for glaucine and laudanos…

Two-neutron removal reactions for very neutron-rich nuclei

1992

Abstract The two-neutron removal reactions of beams of 11 Li, 14 Be and 8 He upon Be, Ni and Au targets were studied at 30 MeV/u. The cross sections and the neutron forward angular distributions were measured; they correlate strongly with the two-neutron separation energy of the projectile. Even though the coverage of the neutron detectors was limited, a rough neutron-neutron distribution could be extracted. A simplified interpretation of the data is presented.