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The structure of bitumen/SBS polymer blends and both physical and in situ chemically reacted has been characterized using cryo-scanning electron microscopy. This low-temperature technique has allowed the extension of infrared and fluorescence microscopy studies to a higher resolving power. The microstructure has been imaged at a submicrometer scale. The distribution of the polymer nanoparticles throughout the bitumen matrix has been followed during its fabrication at the high temperature state. The in situ chemically reacted polymer-modified bitumen shows a very good polymer distribution homogeneity compared with the physical blend.

This study was designed to evaluate the influence of body position during neurosurgical and cerebrovascular operations on regional cerebral oxygen saturation (rSO2). Awake volunteers (group I; n = 14), anesthetized patients (group II; n = 48) undergoing lumbar discectomy, and 12 patients undergoing carotid endarterectomy (group III) with internal carotid artery (ICA) stenosis were studied. Anesthesia in the patient groups was performed with sevoflurane (1.1 Vol% insp.) in N2O2/O2 mixture (FiO2 0.4) rSO2 was monitored with a INVOS 4100 cerebral oxymeter (Somanetics Corporation, Troy, MI). Measurements were done in all groups in supine position with head turned to the right and left side. Furthermore, in groups I and II, rSO2 was measured in right lateral, left lateral, prone, or sitting position. In each position the parameters were registered at three times (1, 3, and 5 min after taking up the position). In the healthy volunteers, the mean rSO2 values of both hemispheres were 71.3 +/- 5.0%. No significant changes of rSO2 were found interhemispherical and upon turning the head to both sides or positioning to the prone and both lateral positions. After assuming the sitting position, the decrease of rSO2 was not significant. In group II, rSO2 decreased significantly in the sitting position. In group III, baseline readings for rSO2 obtained from the side of ICA stenosis were significantly lower, compared to the contralateral side. After turning the head to the ipsilateral side, this difference diminished. In contrast, turning the head toward the contralateral side, the rSO2 difference remained nearly constant, both values decreasing constantly throughout the observation period. In conclusion, after different positioning maneuvers awake and under anesthesia, alterations of rSO2 can be registrated by near-infrared spectroscopy (NIRS).

Bulk YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) material with single-domain grains up to 35 mm in diameter was prepared by a modified melt-texture process. Trapped fields of 1.1 T at 77 K and of 9 T at 43 K were obtained In zinc-doped YBCO material showing a pronounced peak effect in the field dependence of the critical current density. Very high trapped fields up to 11.4 T have been achieved at 17 K in YBCO material with improved mechanical properties. The tensile strength of this material was enhanced by the addition of silver. Additionally, a stainless steel tube was used in order to strengthen the sample against the magnetic tensile stresses. For application of YBCO samples in superconducting magnetic bearings, it is difficult to magnetize the superconductor to the maximum storable field. The authors present results on magnetizing the YBCO samples by applying pulsed magnetic fields.

The previously introduced modified melt crystallization process (MMCP) has been applied to prepare single grain YBCO bulk material with Zn partially substituting for Cu. Hole doping was controlled by an appropriate oxidizing treatment of the as-grown bulk. A field induced pinning was indicated by a well pronounced peak of the critical current density jc in the jc vs. H relationship for the maximal oxidized (overdoped) material containing Zn, whereas pure overdoped YBCO shows no peak effect. The peak effect for Zn-doped YBCO appearing for T=77 K at a relatively high field of about 3 T can be attributed to pair breaking by locally induced magnetic moments due to in plane Zn for Cu substitution. Besides high quality of the bulk YBCO, the peak effect is the reason for the trapped field as large as 1.12 T at 77 K in the cylinder of only 25 mm in diameter.

Nitrite and nitrate are used as additives in the food industry to provide color and taste and to control undesirable gas and flavor production by anaerobic bacteria by virtue of their antimicrobial properties. The analytical method that has been widely used to determine nitrite and nitrate involves the use of toxic cadmium. In response to a request from the Nordic Committee on Food Analysis, a study was performed to obtain an alternative chromatographic method to determine residual nitrite and nitrate in meat products. The study was done in 3 stages: (1) comparative evaluation of the performance of 3 liquid chromatographic methods, (2) internal validation of the selected ion chromatographic method, and (3) a collaborative study in which 17 laboratories from European countries participated. Furthermore, the applicability of the method to matrixes other than meat and meat products was demonstrated. The results of the collaborative study show that the European Prestandard prENV 12014-4 is well suited for the determination of nitrite and nitrate in different foods (e.g., meat products, vegetables, baby food, and cheese). The limits of detection for nitrite and nitrate ions are 1 and 10 mg/kg, respectively. Recoveries of residual nitrite/nitrate ranged from 96 to 108%. Repeatability and reproducibility were satisfactory.

Epidermodysplasia verruciformis-associated human papillomaviruses (EV-HPVs) are possibly involved in the development of actinic keratoses and may play a part in the pathogenesis of squamous cell carcinoma (SCC) of the skin, as the DNA of these viruses is frequently detected in biopsies of such lesions. Properly designed epidemiological studies, using serological tests to investigate the role of infection with EV-HPVs in cutaneous oncogenesis, are still rare. An IgG-specific enzyme-linked immunosorbent assay using virus-like particles composed of the major capsid protein L1 of the EV-specific HPV 8 (HPV 8 VLPs) was developed and used to test the seroprevalence of HPV 8 in 114 inhabitants of a tropical island, of whom 13 had developed SCC, and 19 had developed basal cell carcinoma. Gender, age, eye and hair colour, sun exposure and number of actinic keratoses were recorded for all individuals. The presence of antibodies against HPV 8 VLPs was associated with the development of large numbers of actinic keratoses. After adjusting for gender, age, eye and hair colour, and sun exposure, the odds ratio to develop 37 (the median in this dataset) or more actinic keratoses in the presence of antibodies against HPV 8 VLPs was 2.3 (95% confidence interval: 1.0; 5.3), Similarly, after adjustment for the same factors, the presence of these antibodies was associated with SCC with an odds ratio of 3.1 (0.74; 13.3), but the small number of individuals with SCC does not permit any definite conclusions. The presence of these antibodies did not appear to be associated with basal cell carcinoma as, after adjustment for the same factors, the odds ratio was 0.73 (0.23; 2.4). This study provides serological evidence that infection with EV-HPVs may play a part in the pathogenesis of actinic keratoses. The role of EV-HPVs in the development of SCC, however, remains to be elucidated.

The radiative improved (RI) mode is a tokamak regime offering many attractive reactor features. In the article, the RI mode of TEXTOR-94 is shown to follow the same scaling as the linear ohmic confinement regime and is thus identified as one of the most fundamental tokamak operational regimes. The current understanding derived from experiments and modelling of the conditions necessary for sustaining the mode is reviewed, as are the mechanisms leading to L-RI mode transition. The article discusses the compatibility of high impurity seeding with the low central power density of a burning reactor, as well as RI mode properties at and beyond the Greenwald density.

Abstract This study describes a new method, based on accelerometry, which quantifies tremor activity and posture continuously. A total of 25 right-handed patients with Parkinson's disease were recorded in a rest condition and in a postural tremor test, and during 24-h ambulatory monitoring. The tremor parameters, such as amplitude, frequency, and occurrence (percent of time), were derived by joint amplitude-frequency analysis. The DC components of multi-channel accelerometry allowed the detection of posture. A repeated measurement MANOVA was used to test the effects of posture and night-day differences in tremor activity. Further issues included consistencies of amplitude measurements across hands, between tasks, and between segments of recordings. Findings indicated an increase between resting tremor and postural tremor in the three tremor parameters, an increase under distraction, and enhanced activity in sitting compared to standing/walking. The best predictions of daytime monitoring measures, based on resting measures, were made for left hand tremor. This methodology is suitable for the detection of diurnal changes in tremor activity, especially amplitude changes, and for the psychophysiological investigation of enhanced tremor caused by task demands and emotional reactions.

Superconducting properties and magnetic ordering of pseudoquaternary Tb x Er 1− x Ni 2 B 2 C intermetallic compounds have been investigated by susceptibility, resistivity and magnetization measurements on polycrystalline samples. Tb-rich compounds display an additional metamagnetic transition which can be suppressed by magnetic fields as low as 50 mT. A sizable reduction of the saturation magnetization of pseudoquaternary compounds is observed with a minimum located near x =0.5. T c decreases with increasing Tb fraction up to x ≈0.25, where superconductivity breaks down. The effect of composition fluctuations within the homogeneity range of the compound leads to two different types of materials with distinct T c for a given Tb/Er ratio. A depression of T N with decreasing Tb content is observed.

The specific features of the density and total pressure (the sum of magnetic and gas-kinetic pressures) behavior in the process of forced (by the example of propagation of a magnetic acoustic wave in the vicinity of the X-point) and spontaneous (by the example of development of a helical Thirring mode) reconnection are considered. It is shown that the total pressure distribution depends weakly on the initial value of the gas-kinetic pressure, the strength of the z-component of the magnetic field, and the thermal conductivity in a wide range of parameters. The character of density distribution is determined only by the thermal conductivity. It is also shown that the behavior of the total pressure and density in the case of spontaneous reconnection weakly depends on the thermal conductivity, in contrast to the forced case.

Based on thermoanalytic investigations a melt crystallization process was developed with reduced process temperatures and process times to produce YBCO/Ag monoliths (d=26 mm) achieving the homogenous distribution of small sized Ag inclusions. The mechanical properties are improved, but the superconducting properties at 77 K, B/sub 0/ (480 mT) and F/sub N/ (40 N) are slightly reduced compared with YBCO monoliths without an addition of Ag (750 mT and 65 N). The maximum trapped flux was increased to the value B/sub 0/ 9.4 T at 26.5 K, instead of 8.4 T in the Ag-free bulk monolith.

Bulk melt textured YBCO material with single-domain grains up to 35 mm in diameter was prepared by a modified melt-texture process. The maximum trapped field B/sub o/ measured in the 1 mm gap between two single-grain disks was found to increase from 1.2 T at 75 K up to 9.6 T at 46 K, which is the highest trapped field achieved in nonirradiated samples. A strong exponential decrease of the trapped field with increasing temperature found in most of the cases can be explained by flux creep within the framework of collective pinning assuming weak pinning. A weaker B/sub o/(T) dependence and higher B/sub o/ values at temperatures between 55 and 75 K were observed in newly processed YBCO material. A pronounced peak effect found in the field dependence of the critical current density suggests strong pinning in this material. For applications of YBCO samples in superconducting magnetic bearings, an effective method for magnetizing the superconductor is required. Results of magnetizing YBCO samples by applying pulsed magnetic fields are presented.

The Hall effect in ${\mathrm{LuNi}}_{2}{\mathrm{B}}_{2}\mathrm{C}$ and ${\mathrm{YNi}}_{2}{\mathrm{B}}_{2}\mathrm{C}$ borocarbides has been investigated in normal and superconducting mixed states. The Hall resistivity ${\ensuremath{\rho}}_{\mathrm{xy}}$ for both compounds is negative in the normal as well as in the mixed state and has no sign reversal below ${T}_{c}$ typical for high-${T}_{c}$ superconductors. In the mixed state the behavior of both systems is quite similar. The scaling relation ${\ensuremath{\rho}}_{\mathrm{xy}}\ensuremath{\sim}{\ensuremath{\rho}}_{\mathrm{xx}}^{\ensuremath{\beta}}$ $({\ensuremath{\rho}}_{\mathrm{xx}}$ is the longitudinal resistivity) was found with $\ensuremath{\beta}=2.0$ and 2.1 for annealed Lu- and Y-based compounds, respectively. The scaling exponent $\ensuremath{\beta}$ decreases with increasing degree of disorder and can be varied by annealing. This is attributed to a variation of the strength of flux pinning. In the normal state weakly temperature dependent Hall coefficients were observed for both compounds. A distinct nonlinearity in the ${\ensuremath{\rho}}_{\mathrm{xy}}$ dependence on field H was found for ${\mathrm{LuNi}}_{2}{\mathrm{B}}_{2}\mathrm{C}$ in the normal state below 40 K, accompanied by a large magnetoresistance (MR) reaching $+90%$ for $H=160\mathrm{kOe}$ at $T=20\mathrm{K}.$ At the same time for ${\mathrm{YNi}}_{2}{\mathrm{B}}_{2}\mathrm{C}$ only linear ${\ensuremath{\rho}}_{\mathrm{xy}}(H)$ dependences were observed in the normal state with an approximately three times lower MR value. This difference in the normal-state behavior of the very similar Lu- and Y-based borocarbides seems to be connected with the difference in the topology of the Fermi surface of these compounds.

Parkinson's disease (PD) is one of the most common neurodegenerative disorders affecting about 1% of Western populations older than age 50. The pathological hallmark of PD are Lewy bodies, that is, intracytoplasmic inclusion bodies in affected neurons of the substantia nigra. Recently, α-synuclein (α-SYN) has been identified as the main component of Lewy bodies in sporadic PD, suggesting involvement in neurodegeneration via protein accumulation. The partially overlapping pathology of PD and Alzheimer's disease, as well as striking structural similarities of α-SYN and apolipoprotein E, which is a major risk factor for late-onset Alzheimer's disease, prompted us to investigate the influence of different α-SYN and apolipoprotein E alleles for developing sporadic PD. We performed association studies in 193 German PD patients and 200 healthy control subjects matched for age, sex, and origin. A polymorphism in the promoter region of the α-SYN gene (NACP-Rep1) as well as of the closely linked DNA markers D4S1647 and D4S1628 revealed significant differences in the allelic distributions between PD patients and the control group. Furthermore, the Apoe4 allele but not the Th1/E47 promoter polymorphism of the apolipoprotein E gene was significantly more frequent among early-onset PD patients (age at onset

After analysis of useful frequencies for DAB (digital audio broadcasting) transmission and the signal levels in CATV (cable television)-networks given, we discuss the theoretical requirements for a cable-type DAB receiver. We show the nature of the digital part and its influence on the characteristics of the receiver's RF-stages. The influence of filters, of nonlinear effects and noise on the receiver's overall performance are discussed. Finally, we present a level diagram for the receiver's stages and discuss data as measured.

Superconducting and magnetic properties as well as the lattice structure of polycrystalline Ho x La 1− x Ni 2 B 2 C samples have been studied by susceptibility, X-ray, and neutron diffraction measurements, respectively. A miscibility gap has been found between x =0.4 and x =0.7 if the samples are prepared by standard arc-melting. Samples in this concentration range have been successfully prepared by melt-spinning. All samples exhibit the LuNi 2 B 2 C-type structure and the lattice parameters depend linearly on the La content. Already a low lanthanum concentration of about 10% leads to a rapid depression of T c from 8.5 K to 2 K. Furthermore this concentration leads to a complete depression of the a -axis modulated incommensurate antiferromagnetic structure. Two other magnetic structures, one with commensurate (0 0 1) and one with incommensurate wave vector (0 0 0.915) were found to be less sensitive to the La concentration. The neutron-diffraction peak intensities connected to these structures decrease with increasing La content and disappear at x =0.75 (commensurate structure) and x =0.55 (incommensurate structure). A comparison with Ho x R 1− x Ni 2 B 2 C compounds (R=Y, Lu) shows that these two magnetic structures are influenced in different way by the size of the nonmagnetic rare-earth ion R. No size effect was observed for the magnetic ordering temperature of the commensurate antiferromagnetic structure, whereas the incommensurate spiral structure along c -axis was found to be sensitive to the difference in the size of the R and the Ho ions.

The nonpathogenic Fusarium oxysporum strain Fo47 is an effective biocontrol agent against Fusarium wilt of tomato caused by F. oxysporum f. sp. lycopersici. Inoculant delivery protocols in which plants were exposed to Fo47 prior to challenge with the pathogen, so as to promote the strain's ability to induce resistance to Fusarium wilt in tomato, were assessed. In rockwool microcosms, the biocontrol efficacy of Fo47 (inoculated at sowing) against F. oxysporum f. sp. lycopersici Fol8 (race O) was not improved following a second inoculation of the biocontrol strain at transplanting (i.e., when plants became exposed to the pathogen) or using inoculum levels of Fo47 higher than 10 4 conidia/ml of nutrient solution. In natural soil microcosms (with Fo47 applied into potting mix prior to sowing and to roots at transplanting), effective control of Fusarium wilt required inoculum levels of 10 5 conidia of Fo47/ml. Strain Fo47 was also studied in greenhouse microplots in which soil was artificially infested with the pathogenic strain Fol8. Fo47 delayed the progression of the disease in each of the two years and also improved final plant health in the second year. The protective effect of Fo47 resulted in a significant increase in the yield of first-grade tomatoes in the first year. Treatments did not influence yield in the second year. The results of this investigation illustrate how a biocontrol fungus can be used at a moderate inoculum level to obtain disease control under commercial conditions. It is hypothesized that this was achieved by making use of the ability of the biocontrol agent to induce resistance to Fusarium wilt in tomato.

We present a overivew of the present knowledge of the electronic structure of selected properties of quaternary intermetallic rare earth transition metal borocarbides and related boronitride compounds. The calculated highly anisotropic Fermi surfaces exhibit clear similarities such as nested regions but also significant distinctions. Electrons from the nested parts of the Fermi surface affect several properties in the superconducting state. We report theoretical calculations which emphasize the relevance of these electrons to the mechanism of superconductivity. Structural parameters for ScNi2B2C derived from total energy calculation allow to discriminate confilicting experimental structural calculation results with various electronic spectroscopies such as X-ray absorption spectroscopy (XAS). The excellent agreement with the XAS data suggests a minor importance of correlation effects compared with the cuprate super-conductors. Thermodynamic properties of these systems are analyzed within the multi-band Eliashberg theory with special emphasis on the upper critical field (H c2 (T) and the specific heat. In particular, the unusual positive curvature of H c2 (T) near T c observed for high-quality single crystals, polycrystalline samples of YNi2B2C, LuNi2B2C as well as to a somewhat reduced extent also for the mixed system Y1−x LuxNi2B2C is explained microscopically. The values of H c2 (T) and of its positive curvature near T c are intrinsic quantities generic for such samples. Both quantities decrease with growing disorder and thus provide a direct measure of the sample quality.

Electrical resistivity ρ(T), specific heat Cp(T), magnetic susceptibility χ(T), and magnetization M(H) have been measured for polycrystalline PrNi2B2C. Maxima in Cp(T) and |dχ(T)/dT| dependencies were found at TN≈ 4.3 K connected with AFM ordering observed earlier by neutron diffraction. The Sommerfeld coefficient is at least 250 mJ/mol K2. The values of TNfor PrNi2B2Cand |dTc/dx| for Y1−xPrxNi2B2C were found to be much larger than estimated by the de Gennes scaling from the Gd-based borocar-bides. These facts as well as anomalous decrease of ρ(T) found below 20K are connected with moderate heavy fermion behaviour of antiferromagnetic PrNi2B2C.

The suppression of superconductivity of pseudo-quaternary R{sub x}Y{sub 1{minus}x}Ni{sub 2}B{sub 2}C compounds in the dilute limit was found to be mainly caused by magnetic pair-breaking in the case of the heavy rare-earth elements (R = Tm, Er, Ho, Dy, Tb, Gd) and by lattice distortions in the case of the light rare-earth elements (R = Pr, Nd) resulting from the large difference of the ionic radii between the Y host ions and the R impurity ones.

It was shown that the Hall resistivity {rho}{sub xy} for LuNi{sub 2}B{sub 2}C and YNi{sub 2}B{sub 2}C is negative in the normal and mixed states and has no sign reversal below {Tc}. In the mixed state the scaling relation {rho}{sub xy} {approximately} {rho}{sub xx}{sup {beta}} ({rho}{sub xx} is the longitudinal resistivity) was found for both compounds with {beta} {approx} 2.0. In the normal state a distinct nonlinearity in the {rho}{sub xy}(H) dependence, accompanied by a large magnetoresistance, was found below 40 K only for LuNi{sub 2}B{sub 2}C. The difference in the behavior of Lu- and Y-based borocarbides seems to be connected with the difference in the Fermi surfaces of these compounds.

YBCO bulk materials were crystallized by a multi-seeded melt growth process. Up to four biaxial oriented Sm-123 seeds were placed on the top of rectangular shaped YBCO bars (up to ). The oriented grown single grains are joined by partially coherent grain boundaries with an improved current transport capability and high levitation forces with overall values of 55-65 N. Segregation of nonsuperconducting rest melt and microcracks limit the current transport across the grain boundary.

With reference to the problem of the development of tiring instability in a helical geometry it is shown that, as distinct from traditional gas dynamics, in plasma dynamics the incompressibility approximation cannot generally be used for describing slow flows. This is associated with the fact that several types of disturbances whose interaction results in possible density variations of the order of unity can propagate in plasma.

A planar Mach probe to measure the Mach number and the flow vector with respect to the magnetic field in the edge plasma of e.g. a tokamak is being proposed. The probe is constructed as a double probe and the saturation ion current is measured as function of the angle of rotation of the probe surface normal with respect to the magnetic field. The saturation current as function of the angle is calculated by taking a drifted Maxwellian distribution for ions and an effective size of the probe depending on the angle. From the ratio of the saturation currents for plus and minus biases respectively and from the envelope of the saturation current with respect to the rotation angle, the Mach number and the flow vector can be determined.

A fast camera system is being prepared for the TEXTOR tokamak for the investigation of magnetohydrodynamics (MHD) instabilities. The camera will consist of a scintillator screen for conversion of x rays into visible light, a fiberoptic cable for transport of the visible images out of the Textor magnetic field, an electrostatic image converter for amplification and demagnification of the images, and a fast charge-coupled device (CCD) camera for capturing and storing the image data. The purpose of our camera is two-dimensional imaging of magnetic islands and the structure of MHD instabilities. In order to increase the signal intensity and simultaneously reduce statistical noise, we maximize the diameter of the scintillator screen to 100 mm. For good time response, we use fast scintillators and phosphors, and plan to employ a 1 MHz framing CCD camera. MHD events having an amplitude larger than 1% can be observed with a time resolution of 100 kHz and a spatial resolution of 3 cm. In the future, the camera will be used on the Large Helical Device in Japan. (C) 1999 American Institute of Physics. [S0034-6748(99)62201-8].

In patients with lesions of the cervical spine, direct laryngoscopy for endotracheal intubation entails the risk of injuring the spinal cord. In an attempt to avoid this complication, the authors used flexible fiberoptic nasal intubation in a series of 327 patients with cervical lesions undergoing elective neurosurgical procedures. The nasal route was preferred for laryngeal intubation because it is easier than the oral route and a restraining collar or halo device does not impair the intubating maneuver. Bronchoscopic intubation was possible in all patients. In 12 patients (3.6%), anatomic abnormalities prevented transnasal insertion of the endotracheal tube, and transoral fiberoptic intubation was necessary. Endotracheal intubation was graded as slightly difficult in 85 patients (26%). The minimal peripheral oxygen saturation during intubation exceeded 90% in 289 patients (88%). In the other 38 patients, the mean O2 saturation was 84.2+/-4.3% (range, 72-89%). Intubation was well tolerated by all patients and none had recall of the procedure. Cervical stabilizers did not have to be removed for intubation in any patient. None of the patients had postoperative neurologic deficits attributable to the intubation procedure. The authors consider fiberoptic transnasal intubation to be a useful alternative to direct laryngoscopic tracheal intubation in patients undergoing elective surgical procedures on the cervical spine to avoid potential injury to the cervical spinal cord.

Binary (Nd, Sm)-Ba-Cu-O superconductors with Tc of 96 K and a high irreversibility field up to 8 T have been fabricated in air via a newly developed technique. The initial composition was controlled by using binary (Nd, Sm)2BaO4 as an addition. In comparison with both NdBaCuO and YBaCuO melt-textured superconductors, the present composition showed a remarkable enhancement of critical current densities in an intermediate field regime (1-3 T). Microstructural observations and compositional analysis showed that the distributions of Nd and Sm in the (Nd, Sm)-123 matrix were homogeneous while the atomic ratio between these two rare earth elements was inconsistent with that in the nominal composition. These new characteristics were thought to cohere with the different solubilities between Nd and Sm in the liquid phase. Finally, trapped magnetic field mapping showed a single-domain shape of the trapped field, which indicated the growth of a single grain in the samples.

The electronic structure of tetragonal (RC(N))m(TB)2, m=1−3, compounds, with R= Y,Lu,La, T=Ni,Pt is studied. Total and partial densities of states N(E) are calculated and compared with orbital resolved x-ray absorption data. Special attention is paid to the structure of N(E) near the Fermi-level and its consequences for thermodynamic properties in the superconducting and the normal states. A medium el-ph coupling constant 0.5≤λ≤ 1.2 is found. There is no simple correlation between N(0) and Tc. The analysis of the upper critical field reveals the presence of at least two groups of electrons with quite different Fermi velocities vFin accord with dHvA data, and with calculated distributions of vFaround the Fermi surface

The effect of alloying on magnetic ordering and superconducting properties of pseudoquaternary Tb x Y 1− x Ni 2 B 2 C intermetallic compounds has been investigated by susceptibility and resistivity measurements on polycrystalline samples. The single phase nature of the samples was proven by high-temperature DTA, X-ray and electron microprobe methods. Antiferromagnetic ordering and a depression of the Neel temperature with decreasing Tb content have been revealed for x >0.45. For lower Tb concentrations x T C increases with increasing Y fraction. The magnetic susceptibility χ ( T ) of TbNi 2 B 2 C shows a maximum at T N =15.5 K, passes through a minimum with decreasing temperature, and rises toward a second maximum near 5.5 K. This second maximum was ascribed to weak ferromagnetic ordering which has been confirmed by magnetic hysteresis effects. For decreasing Tb content the ferromagnetic ordering temperature was found to shift to lower temperatures and to disappear for x

Global transport measurements and local Hall-probe array measurements of a section of silver clad BSCCO tape, are reported. Transport measurements are in good agreement with the `brick wall' model. The induction profiles obtained from magnetic measurements agree with the assumption of a uniform bulk current at low (40–60 K) temperatures. At higher temperatures and relatively high fields (700 G and up) local measurements seem to reveal the existence of surface currents. These currents are the result of small current loops, flowing within the grains, which result in a net current only at the edges of the sample. Thus, the local magnetic measurements do not agree with global transport ones, and we contend that the `brick wall' model aptly describes the flow of transport currents, but fails to describe the flow of currents induced by an external magnetic field.

The temperature dependence of magnetic ordering and the superconducting transition have been studied for polycrystalline Ho x Lu 1− x Ni 2 B 2 C compounds by susceptibility and resistivity measurements as well as neutron diffraction. For Ho concentrations in the range 0⩽ x ⩽0.7, the superconducting transition temperature, T c , decreases from 16.5 K at x =0 linearly with increasing x and, consequently, with increasing effective de Gennes factor. This is in accordance with a generalized Abrikosov–Gor'kov theory. At x =0.7, T c reaches 8.5 K i.e. the value of HoNi 2 B 2 C. Pair breaking by the Ho magnetic moments is stronger in Ho x Lu 1− x Ni 2 B 2 C compared to Ho x Y 1− x Ni 2 B 2 C. This is attributed to the difference between the lattice constants of the Ho–Y and the Ho–Lu systems resulting in different electronic structure parameters. A complete breakdown of the scaling behaviour of T c occurs for x >0.7, where T c becomes independent of the effective de Gennes factor. In this range of x re-entrant behaviour and the presence of an incommensurate a -axis, modulated antiferromagnetic structures have been observed below a characteristic temperature T m . Commensurate and incommensurate c -axis modulated antiferromagnetic structures that are observed both in the Ho–Y and the Ho–Lu systems coexist with superconductivity.

The superconducting transition temperature T c , the temperature dependence of the upper critical field H c2 ( T ), and the lattice structure of polycrystalline Y x Lu 1− x Ni 2 B 2 C samples have been studied by susceptibility, resistivity, and X-ray measurements, respectively. All samples exhibit the same LuNi 2 B 2 C-type structure and the lattice parameters depend linearly on the yttrium content. The residual resistivity ratio (RRR) decreases steeply first for slight deviations from both pure stoichiometric limiting contents and then saturates at a low level in a broad plateau in between 0.1 x T c ( x ) and H c2 ( x ) at fixed T change nearly parabolically. The H c2 ( T )-curves show a positive curvature for all samples. This dependence can be described within a broad temperature region 0.3 T c T ≤0.95 T c by a simple and convenient empirical expression H c2 ( T )∝(1− T / T c ) α . The parameter α >1 describing the positive curvature of H c2 ( T ) characterizes the sample quality and decreases with increasing disorder in the Y x Lu 1− x Ni 2 B 2 C samples. However, the case of complete disorder (dirty limit) where α =1 is not reached yet in the investigated samples. The nonmonotonous dependence of T c and H c2 upon x is attributed to partial disorder within the Y–Lu basis layers. Together with the RRR-saturation they reflect the complex multiband character of the materials under consideration.

Small double pancake coils with a 15 mm bore were fabricated from Ag sheathed multifilamentary Bi-2223 tapes by the 'wind and react' technique. The electric insulation between the turns consists of an alumina screen print paste. In a double pancake coil with a total tape length of 73 m, a magnetic field of 1.34 T was generated at liquid helium temperature. The technique for the fabrication of the test coils was optimized in order to achieve the critical current density of the tapes in the coils. The critical current in different sections of the coils was controlled by electric field vs. current measurements. Correlations between the filament structure of the tapes and critical bending diameter of the tapes in the coil are discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.

The development of the tearing instability is studied in the presence of a high toroidal magnetic field and a high plasma conductivity. The variation of the plasma density is shown to be significant in this case.

It is not absolutely necessary for DAB (digital audio broadcasting) signals to be inserted into CATV (cable television) networks within the CATV frequency range. Because the signals are robust they can also be transmitted beyond the usual boundaries of the usual frequency range. This paper includes a discussion of experimental results and a design for a DAB converter.

A patent foramen ovale (PFO) is the most common cause of paradoxical air embolism during neurosurgical procedures in the posterior fossa in the sitting position in both adults and children. To detect right-to-left shunting, we performed Doppler color-flow imaging preoperatively in 30 children scheduled for neurosurgical procedures in the sitting position. A PFO was diagnosed on the basis of color alterations indicating an immediate blood shunt through a PFO. Six of 30 children (20%) had a PFO; in 4 of these children the sitting position then was avoided, and 2 children were operated on in a special supine position with minimal elevation of the head. Venous air embolism occurred in 9 of 24 (37%) children operated on in the sitting position and in none of the 6 children operated on in a nonsitting position. We conclude that Doppler color-flow mapping could be a useful noninvasive technique to screen children scheduled for neurosurgery in the sitting position for the presence of a PFO.

■ Abstract Insidious onset of mild, unspecific, sensitive, vegetative, psychopathological, cognitive and perceptive disturbances, i. e., visual and olfactory dysfunction, with a resulting change of personal behavior, i. e., reduced stress tolerance, precede the initially intermittently occurring motor symptoms in patients with Parkinson's disease (PD). Novel neuropathological findings suggest an expansion pattern of the neurodegenerative process beyond the nigral dopaminergic neurons with the initial event located outside the brain. This underlines the clinical concept of an initial premotor phase, which starts in non-dopaminergic areas in PD. Moreover a more global general understanding of chronic neurodegeneration enables the performance of clinical trials on neuro-protection, since there is increasing evidence that diagnosis of PD at the threshold of onset of motor symptoms or cognitive symptoms in Alzheimer's disease is too late. Such an earlier diagnosis of chronic neurodegeneration will allow a more convincing demonstration of the efficacy of a neuroprotective or disease modifying compound. It will also support the concept of a clinically effective pharmacological intervention on a disease process, which is also more and more demanded by the health authorities for drug approval.

In this paper hyperbolic partial differential equations with random coefficients are discussed. Such random partial differential equations appear for instance in traffic flow problems as well as in many physical processes in random media. Two types of models are presented: The first has a time-dependent coefficient modeled by the Ornstein–Uhlenbeck process. The second has a random field coefficient with a given covariance in space. For the former a formula for the exact solution in terms of moments is derived. In both cases stable numerical schemes are introduced to solve these random partial differential equations. Simulation results including convergence studies conclude the theoretical findings.

To evaluate the influence of compost on soil fertility and plant growth, several medium term and long term field experiments with composts were conducted in different crops. In two maize experiments, one in a sandy and one in a loamy soil, the influence of different composts and digestates on soil parameters and plant growth were investigated. All products increased pH of the soil and improved the biological soil activity (e.g., enzymatic activities). Immature compost immobilized nitrogen and reduced plant growth. Organic nitrogen fertilizer added during cultivation, could compensate the growth depression. A full factorial experiment in a 2-years-old organic apple orchard was conducted from 2001-2007. The factors tested in all 9 possible combinations were: i) biowaste compost, ii) commercial organic N-fertilizer, iii) foliar N-fertilizer. In spring, the highest values for mineralized N (Nmin) in the tree strip were found in the treatment with commercial organic N-fertilizer, with addition of compost it was 75%, and biowaste compost alone reached 50% of this value on average, whereas unfertilized plots had the lowest but still sufficient values for the same tree performance and fruit nutrition as fertilized plots. In the DOK long-term field trial, three farming systems are compared since 1978: i) mineral and organic fertilisers, synthetic pesticides; ii) organic fertilisers, mechanical weeding and biological disease and pest control; and iii) composted manure and bio-dynamic preparations. A conventional system with mineral fertilisers only and an unfertilized treatment serve as controls. Soil fertility mirrored by soil biological parameters, soil biodiversity and soil organic matter are higher in the organic systems and render these systems less dependent from external inputs.

The multi-channel HCN-polarimeter on TEXTOR-94 has been used to measure the plasma current density for a wide range of operation/confinement conditions. The characteristic features of the safety factor profiles in discharges with edge-radiation cooling and the application of different heating scenarios together with a strong impurity influx will be described. The stabilization of sawteeth and changes in the MHD behaviour of the plasma is related to modifications of the current density profile.

Low-energy cluster beam deposition (LECBD) has been used to synthesize cermets with controlled size nanoparticles. In the In - system, this technique allows the formation of In nanograins uniformly distributed in the insulating matrix. Optical spectra in the range 2 to 6 eV present plasmon resonance bands which have been interpreted by Mie and Maxwell-Garnett theories. XPS measurements have shown an oxidation of a fraction of the indium particles.

High quality melt textured YBCO samples have been prepared on a modified MTG route. A trapped magnetic field of 8.5 T at 51.5 K was measured in the gap of 1 mm in a mini-magnet from two YBCO cylinders (d=26 mm, h=12 mm). At 77 K, each single domain cylinder traps more than 600 mT and the levitation pressure of 15 N/cm/sup 2/ in a distance of 0.5 mm was achieved by a 0.4 T SmCo magnet. The thermodynamic background of the preparation method is outlined. A thermodynamic approach to control growth and stoichiometry y in the alternative material Nd/sub 1+y/Ba/sub 2-y/Cu/sub 3/O/sub x/ is discussed. Critical currents of 46 kA/cm/sup 2/ (77 K) have been achieved by a modified recipe.

Silver sheathed Bi-2223 tapes have been investigated by transport and magnetization measurements in the temperature range between 4.2 K and 77 K for magnetic fields up to 12 T. The superconducting current through the tape can be explained by assuming a network of platelike grains coupled by weak links. At high temperatures the critical current is governed by flux creep of pancake vortices within the grains. At temperatures below 40 K this intragrain critical current exceeds the intergrain Josephson current leading to a weak link limitation in the tape. In this picture the differences between critical transport and magnetization currents can be explained by a reduction of the geometrical length scale of current loops. An improvement of the weak link current density is observed in multifilamentary wires and tapes with AgCu sheath material.

Bulk melt textured YBCO materials in the shape of disks are being developed for use as trapped field magnets and in superconducting bearings. The trapped field in the gap between two disks of 26 mm in diameter reached maximum values of 1 T at 77 K and of 8.5 T at 51.5 K. A superconducting magnetic bearing has been built up of two YBCO rings and two concentric NdFeB ring magnets between them. A static levitation force of 25 N and values of the axial and radial stiffnesses of 15 N/mm and 10 N/mm, respectively, have been achieved for this bearing in the working position. A high speed motor with two superconducting magnetic bearings of this kind has been tested at 77 K.

An overview of the results obtained so far for the radiative I-mode regime on the upgraded Torus Experiment for Technology Oriented Research (TEXTOR-94) [Proceedings of die 16th IEEE Symposium on Fusion Engineering (Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1995), Vol. 1, p. 470] is given. This regime is obtained under quasistationary conditions with edge neon seeding in a pumped limiter tokamak with circular cross section. It combines high confinement and high beta (up to a normalized beta, beta(n) = 2) with low edge q values (down to q(a) = 2.8) and high density even above the Greenwald limit together with dominant edge radiative heat exhaust, and therefore shows promise for the future of fusion research. Bulk and edge properties of these discharges an described, and a detailed account is given of the energy and particle confinement and their scaling. Energy confinement scales linearly with density as for the nonsaturated Ohmic Neo-Alcator scaling, but the usual degradation with total power remains. No deleterious effects of the neon seeding on fusion reactivity and plasma stability have been observed. (C) 1997 American Institute of Physics.