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We report the results of magnetoresistance and magnetization measurements on single crystal EuB{sub 6} for temperatures above and below the ferromagnetic ordering temperatures T{sub C}{sup +}=15.3 K and T{sub C}{sup {minus}}=12.5 K, in magnetic fields as large as 30 T. Shubnikov{endash}de Haas and de Haas{endash}van Alphen oscillations were observed with four fundamental frequencies. By comparison to band-structure calculations, we ascribe the orbits to small pockets of electrons and holes, centered at the {ital X} points. The effective masses and extremal areas of the pockets are in good agreement with the predictions of band-structure calculations. We conclude that EuB{sub 6} is an intrinsic semimetal and not a doped insulator. The intrinsic carrier concentration is 1.2{times}10{sup 20} cm{sup {minus}3}, although our sample is somewhat uncompensated, with a 65{percent} surplus of holes. There is no appreciable modification to the Fermi-surface dimensions or carrier masses with the onset of ferromagnetism. {copyright} {ital 1999} {ital The American Physical Society}

This article describes the behavior of Cernox™ zirconium oxynitride film temperature sensors from Lake Shore Cryotronics, Inc. in magnetic fields up to 32 T at temperatures between 2 and 286 K. Results from a number of sensors with different dimensionless temperature sensitivities and from different production batches are analyzed and compared with previous results on carbon-glass sensors that extend to 19 T. In that field range, the Cernox™ sensors appear to be a real alternative to carbon glass. Furthermore, the magnitude of their uncorrected error, ΔT/T, is smaller than other sensors at most temperatures in fields less than 20 T, and their temperature correctabilities appear to apply to off-the-shelf sensors with dimensionless temperature sensitivities in the range of −0.74 to −1.9. The sensors show a negligible (

We present the results of the high magnetic field studies of properties of two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures grown over high-pressure bulk GaN, sapphire, and insulating SiC substrates. The experimental results include the low field Hall measurements, cyclotron resonance measurements, and cryogenic temperature Quantum Hall Effect studies as well as room-temperature characteristics of High Electron Mobility Transistors fabricated on all these substrates. The room temperature high field measurements allow us to clearly separate the contributions of a parasitic parallel conduction from 2DEG conduction in all investigated heterostructures.The magnetotransport measurements are performed in the magnetic fields up to 30 Tesla for temperatures between 50mK-300K. This high magnetic field in combination with very high mobilities (over 60.000 cm2/Vs) in the sample on the bulk GaN substrates allow us to observe features related both to cyclotron resonance and spin splitting. The temperature dependence of this splitting determines the spin and cyclotron resonance energy gaps and, in combination with cyclotron resonance and tilted field experiments, allows us to determine the complete energy structure of 2DEG conduction band. We also present the first experimental results showing so called “the exchange enhancement” of the energy gaps between spin Landau levels.

Twenty-one asymptomatic adults who had recently received multiple polysaccharide, live viral, and protein-derived vaccines were identified as being infected with human immunodeficiency virus (HIV). The mean subject age was 24 years (range 18-33); 20 of 21 (95%) were male. The mean T4 count was 523/mm3 with a mean T4/T8 ratio of 0.6. Serologic responses to immunization with meningococcus group C, adenovirus types 4 and 7, tetanus, and diphtheria were evaluated for the HIV seropositive subjects and were compared with the responses of similarly vaccinated age-, sex-, and race-matched HIV-seronegative controls. Significantly fewer (p less than 0.03) HIV subjects responded to meningococcus C (bactericidal antibody) and adenovirus 4 (neutralizing antibody) vaccines than did normals; the HIV-infected subjects who did respond produced functional antibody comparable to that of normals. Booster responses of HIV subjects to tetanus and diphtheria were comparable to those of normals. HIV-infected vaccine nonresponders did not differ from HIV-infected responders in total white blood cell, T4, T4/T8, total serum IgG, or delayed-type hypersensitivity skin test reactivity. All HIV subjects had negative cultures for live vaccine viruses (rubella, measles, adenovirus, and poliovirus). Postimmunization, no clinically apparent adverse reactions to vaccination were detected.

A clonal cell line exhibiting many of the properties of skeletal muscle has been derived from embryonic BDIX rat heart tissue. Multinucleated myotubes, formed by fusion of mononucleated myoblasts, simultaneously contract and produce regenerative action potentials in response to electrical stimulation or iontophoretic application of acetylcholine. The acetylcholine response is inhibited by 1−3 × 10 −7 M d -tubocurarine, 10 −7 g/ml α-neurotoxin or 1 × 10 −4 M atropine. The specific activities of the enzymes myokinase and creatine phosphokinase (CPK) increase 3-fold and 20-fold, respectively, after myotube formation, but only CPK activity parallels the extent of fusion. Exponentially dividing myoblasts synthesize a predominantly brain-type CPK isoenzyme while fused myotubes synthesize a muscle type CPK isoenzyme. Electron microscopic analysis reveals that the myotubes contain elaborately branched tubular systems and numerous bundles of thick filaments with distinct M-bands. Some of the thick filament bundles are associated with thin filaments and organized into sarcomere-like structures with faint Z-regions, but no distinct Z-bands are observed.

Two clonal cell lines have been derived from the thoracic aorta of embryonic rats. Both of these cell lines, at some stage of their development possess membranes capable of generating overshooting action potentials spontaneously. Contiguous cells of each of these lines are electrically coupled. Ultrastructural analysis consistently reveals the presence of rows of pinocytotic vesicles, a well-developed rough endoplasmic reticulum, massive tracts of thin filaments oriented parallel to the longitudinal axis of the cell and randomly dispersed intermediate sized filaments. The specific activities of the enzymes myokinase and creatine phosphokinase (CPK) increase 3- to 5-fold after growth has ceased. These two cell lines synthesize a muscle type CPK isoenzyme after the cessation of cell division. It is concluded that these cell lines proliferate as myoblasts and develop into cells which phenotypically resemble smooth muscle. A third clonal cell line, from fetal rat aorta, with properties of both smooth and skeletal muscle, is also described.

An anomalous magnetic behavior has been observed in rare-earch-rich metallic glasses of the composition ${({R}_{75}{\mathrm{Au}}_{25})}_{100\ensuremath{-}x}{\mathrm{B}}_{x}$ where $R$ denotes Pr, Gd, Tb, Er and $x=0,10$. The observed hysteresis in all samples except Gd at liquid-helium temperatures is due to the large anisotropy which develops below the ordering temperature. High-field-magnetization measurements up to 220 kOe were used to determine the spontaneous magnetization and the magnetic anisotropy constant which was found to be of order ${10}^{8}$ erg/${\mathrm{cm}}^{3}$ for the Tb and Er glasses. These parameters were used together with the observed remanence ratio to examine the high coercive fields in terms of recently proposed models of random anisotropy.

IgA purified from the sera of patients convalescing from disseminated group C meningococcal disease induced human monocyte-mediated anti-meningococcal activity in vitro in the absence of complement. Both IgA- and IgG-dependent activity were directed against the group C meningococcal polysaccharide (Csss) capsule. The amount of IgA that was effective bound less than 1 ng of Csss. Antibacterial activity was dependent upon the length and the temperature of the test incubation and on the concentration of monocytes. The implications of this mechanism for local cell-mediated antibacterial immunity are discussed.

Measurements of the low-temperature specific heat, both in 0- and 7-T applied field, and magnetic susceptibility on polycrystalline, unannealed single-crystal and annealed single-crystal samples of UA${\mathrm{l}}_{2}$ show no sample dependence for these properties to \ifmmode\pm\else\textpm\fi{}5%, in contrast to recent results for Ti${\mathrm{Be}}_{2}$. Measurements of the specific heat of the annealed single crystal of UA${\mathrm{l}}_{2}$ from 2 to 23 K in fields to 12.5 T and from 4 to 16 K in fields to 17 T indicate a partial (\ensuremath{\sim}40%) suppression of the spin-fluctuation contribution, which occurs at 2 K in 12.5 T, and the possible existence of a small competing effect which increases the specific heat with increasing field above 4 K. These results are compared with recent magnetization and magnetoresistivity results which indicate suppression of spin fluctuations in UA${\mathrm{l}}_{2}$ between 15 and 20 T.

The characteristics of carbon‐glass resistance thermometers for temperatures from 2.15 to 320 K and in magnetic fields of up to 19 T are described. The results from nine thermometers made from six different batches of raw material are combined to produce mean values that may be used to correct a ’’typical’’ thermometer at 19 T to within ±0.1% in temperatures between 30 and 320 K, and to within ±1% between 2.15 and 30 K. All nine sensors show a small orientation dependence of their magnetoresistance at 77 K; two out of four tested have an experimentally significant dependence at 4.2 K. The temperature error corresponding to the magnetoresistance of a miniature precision platinum resistance thermometer at 19 T is less than for carbon‐glass sensors above 77 K. New recommendations are made for the optimum use of low‐temperature thermometers in high magnetic fields.

The successful application of the Kerr magneto‐optic technique to observe magnetic domains in orthoferrite single crystals is described. A series of photographs portray domain developments in thick samples of YFeO3 and HoFeO3 similar to those previously revealed in thin, transparent sections by the Faraday effect. Quantitative measurements of the normal, polar Kerr rotation for the two orthoferrites are reported for several wavelengths, and an apparatus for making such measurements is described.

The purpose of this study was to examine the state of a thin type-I superconductor in a magnetic field to determine its dependence on the specimen thickness and on the value of the Ginzburg-Landau parameter κ. Three materials (aluminum, indium, and In0.99Pb0.01) with values of the Ginzburg-Landau parameter ranging from 0.19 to 0.34 were studied. Specimen thicknesses ranged from 200 to 200,000 A. All of the materials studied were type-I or nonlocal superconductors in the bulk. Yet, it has been predicted that they would behave in ways characteristic of type-II or local superconductors if the specimen were sufficiently thin. For intermediate thicknesses the specimens were expected to be in one of many possible states. We have inferred from critical field studies that the structure of the intermediate state in thin type-I superconductors is equivalent to the type-II vortex state for very thin films (d ≪ ξ0), and to the type-I macroscopic domain state for very thick films d ≳ 2ξ(t). For thicknesses between these limits the intermediate-state structure takes on many forms as the area of each normal domain and the amount of flux threading it increases with increasing thickness.

A dc magnetic field of 33.6±0.3 T was produced in a hybrid magnet whose central field was enhanced by a 3.5 T contribution from holmium pole pieces. The working (sample) volume was a 2‐mm gap between the 19‐mm‐diam×32‐mm‐long pole pieces tapered to 12‐mm‐diam faces. The magnetic field was measured with high‐field/low‐temperature Hall‐effect sensors whose reproducibility and linearity made practical an extrapolation technique for fields above 30 T. Three superconducting samples with previously measured upper critical fields were used as calibration check points.

The laboratory provides a wide variety of magnets and equipment to about 250 experimenters involved in ≈ 100 programs each year; these account for over 100 publications covering a broad scientific spectrum. The hybrid magnet has surpassed 1500 hours of operation and recently attained a field of 31.8 T.

Previously reported temperature increases above 4.2 K in an immersion geometry in liquid 4He at fields >19 T have been verified and examined. Magnetic forces (B dB/dx) above a threshold level of ∼21 T2/cm were found to trap 4He bubbles near the center of the field. Significant heat input to the region (from conduction, radiation, etc.) can then raise the temperature by as much as several kelvins. Thus, measurements at very high B dB/dx should not depend on vapor pressure thermometry. To assure temperature accuracy and stability, the temperature should be measured directly at the sample position.

Five cases of disseminated meningococcal disease due to serogroup W135 Neisseria meningitidis are presented. The cases ranged in age from 16 months to 23 years, and spanned a clinical spectrum from mild meningitis without rash or evidence of meningococcal septicemia to severe meningoencephalitis with fulminant meningococcemia, disseminated intravascular coagulation, and death. These cases demonstrate that serogroup W135 N meningitidis is fully pathogenic for man and capable of producing the full spectrum of disseminated meningococcal disease associated with other serogroups. Since this serogroup has recently emerged as a significant cause of disease in Europe, attention should be focused on the correct serogroup designation of strains of N meningitidis isolated from clinical material and reported as "nongroupable" by clinical laboratories, so that additional clinical and epidemiologic information may be obtained.

Five neuronal and a large collection of putative glial cell lines from the rat central nervous system have been established in clonal cell culture and partially characterised. These cells shed new light on the distribution of neurotransmitter synthesis and brain-specific antigens among nerve and glia.

By using a hemagglutination-inhibition assay, certain lots of purified group A meningococcal polysaccharide vaccines were found to contain trace amounts of group C polysaccharide (0.032 to 0.128%). Young adult human volunteers inoculated with these vaccines showed a very poor group C serum anti-polysaccharide antibody response as determined by a radioactive antigen-binding assay. Two weeks later volunteers were given a 50-mug subcutaneous injection of purified group C polysaccharide. Serum specimens obtained 1 month later showed a significant suppression of group C antibody response in comparison with subjects who had initially received group A vaccines which were free of group C antigen. The observed hyporesponsiveness may represent an example of immunologic tolerance in man.

Serogroup Y and W135 Neisseria meningitidis capsular polysaccharide vaccines were tested as monovalent and divalent preparations in groups of 10 adult human volunteers at a dose of 50 (monovalent) or 100 micrograms (divalent) injected subcutaneously. Reactogenicity was low for the group Y vaccine and the group Y-W135 combined vaccine; 3 of 10 volunteers developed systemic reactions after group W135 vaccination. All three vaccines induced significant homologous and heterologous binding and bactericidal antibody. Except for group W135 bactericidal antibody, homologous responses exceeded heterologous responses, and divalent and monovalent vaccines induced equivalent homologous responses. Homologous bactericidal antibody responses were maintained for 4 weeks in 85% of group W135 vaccinates and in 100% of group Y vaccinates. Bactericidal antibody was induced in 11 of 11 group Y and 12 of 15 group W135 volunteers without preexisting respective bactericidal activities, regardless of which vaccine they received. For all three vaccines, antibody levels declined only slightly over 6 months. Prevaccination antibody levels positively affected postvaccination binding antibody levels, but not bactericidal levels.

1. Electrophysiological properties of the rat chromaffin cell were studied using intracellular recording techniques. 2. The resting potential in the chromaffin cell was -49 +/- 6 mV (mean +/- S.D., n = 14) in standard saline containing 10 mM-Ca whereas that in Na-free saline was -63 +/- 9 mV (n = 17). At rest, the membrane has a substantial Na permeability. 3. Action potentials were evoked by passing current through the recording electrode. In standard saline the major fraction of the action potential disappeared either upon omission of external Na ions from standard saline or addition of 1 muM tetrodotoxin (TTX). We conclude that action potentials in the chromaffin cell are due mainly to an increase in the permeability of the membrane to Na ions. 4. Small but significant regenerative action potentials were observed in Na-free saline, and when Ca in Na-free saline was replaced by Ba, prolonged action potentials occurred. We conclude that action potentials in the chromaffin cell also have a Ca component. 5. Iontophoretic application of acetylcholine (ACh) produced a transient membrane depolarization in standard saline. 6. Spontaneous action potentials were recorded extracellularly by microsuction electrodes. They occurred at a rate of 0-05-0-1/sec in almost all cells. 7. When the perfusion fluid contained 3 x 10(-7) M to 10(-4) M ACh the spike frequency increased up to about 2/sec. This stimulatory effect of ACh was blocked by 10(-7) M atropine but not by 10(-3) M hexamethonium nor by 10(-5) M-d-tubocurarine. 8. The importance of Ca entry during action potentials for catecholamine secretion is discussed

A series of murine monoclonal antibodies to serotype 2 and serotype 15 strains of Neisseria meningitidis were produced which were specific for outer membrane proteins of classes 1, 2, 3, and 5. A panel of eight monoclonal antibodies that exhibited a high degree of serotype specificity when reacted with prototype strains of known serotype were selected for study. Each of the corresponding epitopes was localized on a specific outer membrane protein by means of immunoprecipitation, electroblotting, or both. The serotype 2a-, 2b-, and 2c-specific antibodies bound to the class 2 protein, the serotype 15-specific antibody bound to the class 3 protein, two antibodies (3-1-P1.2 and 3-1-P1.16) bound to class 1 proteins, and two antibodies (1-1-P5.1 and 3-1-P5.2) bound to class 5 proteins. Six of these monoclonal antibodies were used in a spot-blot procedure to survey 122 case isolates (groups B, C, Y, and W135) and 363 carrier isolates (all serogroups) for the presence of the 2a, 2b, 2c, 15, P1.2, and P1.16 epitopes. A total of 66% of the case isolates and 30% of the carrier isolates reacted with one or more of the monoclonal antibodies. The use of monoclonal antibodies for serotyping of meningococci appears to be feasible and easy and appears to have significant advantages over the use of polyclonal typing sera.

For the measurement of temperatures between 1 K and 300 K, there are available a wide variety of sensors and several dc, ac, and pulse techniques. The choice of measurement system depends on a number of factors, including the required precision, cost, speed of response, sensor size and availability, and the effect of high magnetic fields. When the most significant of those factors have been identified and quantified, it should then be possible to select the thermometer(s) that best meet those requirements. To aid in the selection procedures, some pertinent characteristics of a number of useful thermometers are presented. A brief discussion of high magnetic field sensors useful at low temperatures is included.

Over the past 4 years 19 lots of group C polysaccharide vaccine and five lots of group A polysaccharide vaccine have been tested for their immunogenicity in man. For each lot tested, groups of 18 to 50 men received 50 μg of vaccine subcutaneously. Sera were obtained prior to and 2 weeks after vaccination. The analytical and serological methods used in these studies were Sepharose 4B chromatography for the estimation of molecular size, the radioactive antigen binding assay, and the indirect hemagglutination (IHA) test for measuring the antibody response. Results have shown that the radioactive antigen binding assay is preferable to the IHA test as a measure of antibody response. Group C meningococcal vaccines have been highly stable when stored at 4 C in powdered form. All lots of group C vaccine tested to date have been of equal potency, with molecular weight varying from 520,000 to 2,000,000. Group A polysaccharides have been found to be unstable after 2 years of storage at 4 C. Optimal antibody response to the group A vaccines appears to be directly related to the molecular size of the preparation.

We present the results of high magnetic field (up to 30 T) and temperature (50 mK-80 K) dependent transport measurements on a 2DEG in GaN/AlGaN heterojunctions. A high mobility (above 60000 cm(2) V-1 s(-1) at 4 K) 2DEG was obtained by MBE growth of dislocation free GaN and AlGaN layers on semi-insulating bulk GaN substrates. A cyclotron gap and spin splitting are observed. Results from two studies are reported: (i) a tilted field experiment determining the 2DEG g*-factor from the angular modulation of the amplitude of SdH oscillations; (ii) quantum Hall effect measurements determining the activation energies for spin and cyclotron energy gaps at even and odd filling factors. The observed 'cyclotron gap' enhancement is attributed to the effect of electron-electron interaction and it is estimated using the model of a 2D-screened Coulomb potential. The analytic result for the enhancement of the,cyclotron gap' yields an addition to the activation energy, epsilon(even)(x) approximate to kappa(h) over bar omega(c), K = 1.06 roota(2)n(e), which is proportional to the magnetic field and resembles the mass renormalization.

We report accurate measurements of the specific heat of zone-refined, high-purity Pd between 6 and 17 K in fields of 10, 15, and 20 T. The change of the specific heat of this Pd in 20 T, averaged over the 14 different temperatures of measurement, compared with zero-field measurements at the same temperatures, is +1.0%. Within our limits of error ( +- 2%), the results directly contradict previous specific heat results on Pd in fields to 11 T by Hsiang et al.