Suppression of lattice doubling in quasi-skutterudite La3Rh4Sn13: a comparison of temperature and hydrostatic pressure routes.

We present structural properties at different temperatures and high-pressure (HP) of La3Rh4Sn13 which is one of the interesting systems in the Remika phase RE3Rh4Sn13 (RE = Sr, Ca, La, Pr, Ce) quasi-skutterudite series using synchrotron diffraction. Data at ambient conditions revealed the presence of several weak reflections, which could be accounted only with a superlattice I* structure (I4132) with lattice parameter a ~19.457 Å. However, above 350 K, a complete suppression of the weak superlattice reflections of the I*  structure is observed. Data at higher temperatures is found to be well described by the I structure (Pm-3n) having half the lattice parameter compared to the I* structure. HP-XRPD at ambient temperature showed that pressures greater than 7.5 GPa result in similar suppression of the weak I* superlattice reflections. Data at higher pressures is found to be well described by the I structure (Pm-3n), similar to the high-temperature phase. HP Raman measurements demonstrated changes that seem to be consistent with a locally more ordered structure as in the case of the I* à I transition. Our findings on La3Rh4Sn13 open up new avenues to study unexplored HP phenomena, especially the superconductivity in these Remika phase quasi-skutterudites.

Insight into intrinsic ferromagnetism in quasi-2D Cr5-yTe8.

Cr5Te8is a half metal with 2D van der Waals ferromagnetic structure and its magnetic properties can be tuned by changing the proportionality of Cr and Te. We report an investigation of magnetization and magnetic anisotropy near the critical transition region of a Cr5-yTe8single crystal with the static and dynamic probes, to unravel the nature of field-dependent spin-spin interactions. The magnetic transition temperatureTCincreasing from 255 K (at near zero-field) to 279 K (at 65 kOe along theab-plane) has been identified. Accordingly, a phase diagram of field versus transition temperature has been established. From the analysis of the field dependence of the critical behavior, we provided evidence that the scenario of 2D Heisenberg-type interactions can be employed to interpret the field-dependent magnetic transitions in Te-rich Cr4.8Te8. The precise picture for the field-reduced spin-spin interaction range has been obtained. The conclusion drawn from the present study demonstrated that Cr4.8Te8is a promising candidate for the spintronic applications with a tunable magnetic transition temperature.

Nodeless superconductivity in the cage-type superconductor Sc5Ru6Sn18 with preserved time-reversal symmetry.

We report the single-crystal synthesis and detailed investigations of the cage-type superconductor Sc5Ru6Sn18, using powder x-ray diffraction (XRD), magnetization, specific-heat and muon-spin relaxation (µSR) measurements. Sc5Ru6Sn18 crystallizes in a tetragonal structure (space group I41/acd) with lattice parameters a = 1.387(3) nm and c = 2.641(5) nm. Both DC and AC magnetization measurements prove the type-II superconductivity in Sc5Ru6Sn18 with T c ≈ 3.5(1) K, a lower critical field [Formula: see text] = 157(9) Oe and an upper critical field, [Formula: see text] = 26(1) kOe. The zero-field electronic specific-heat data are well fitted using a single-gap BCS model, with [Formula: see text] = 0.64(1) meV. The Sommerfeld constant γ varies linearly with the applied magnetic field, indicating s-wave superconductivity in Sc5Ru6Sn18. Specific-heat and transverse-field (TF) µSR measurements reveal that Sc5Ru6Sn18 is a superconductor with strong electron-phonon coupling, with TF-µSR also suggesting a single-gap s-wave character of the superconductivity. Furthermore, zero-field µSR measurements do not detect spontaneous magnetic fields below T c, hence implying that time-reversal symmetry is preserved in Sc5Ru6Sn18.

ARTEMIS Observations of Solar Wind Proton Scattering off the Lunar Surface.

We study the scattering of solar wind protons off the lunar surface, using ion observations collected over 6 years by the ARTEMIS satellites at the Moon. We show the average scattered proton energy spectra, directional scattering distributions, and scattering efficiency, for different solar wind incidence angles and impact speeds. We find that the protons have a scattering distribution that is similar to existing empirical models for scattered hydrogen energetic neutral atoms, with a peak in the backward direction (toward the Sun). We provide a revised model for the scattered proton energy spectrum. We evaluate the positive to neutral charge state ratio by comparing the proton spectrum with existing models for scattered hydrogen. The positive to neutral ratio increases with increasing exit speed from the surface but decreases with increasing impact speed. Combined, these counteracting effects result in a scattering efficiency that decreases from ~0.5% at 300 km/s solar wind speed to ~0.3% at 600 km/s solar wind speed.

Magnetic correlations in the intermetallic antiferromagnet Nd3Co4Sn13.

Specific heat, magnetic susceptibility, and neutron scattering have been used to investigate the nature of the spin system in the antiferromagnet Nd3Co4Sn13. At room temperature Nd3Co4Sn13 has a cubic, Pm-3n structure similar to Yb3Rh4Sn13. Antiferromagnetic interactions between, Nd3+ ions dominate the magnetic character of this sample and at 2.4 K the Nd spins enter a long range order state with a magnetic propagation vector q = (0 0 0) with an ordered moment of 1.78(2) µB at 1.5 K. The magnetic Bragg intensity grows very slowly below 1 K, reaching ~2.4 µB at 350 mK. The average magnetic Nd3+ configuration corresponds to the 3D irreducible representation Γ7. This magnetic structure can be viewed as three sublattices of antiferromagnetic spin chains coupled with each other in the 120°-configuration. A well-defined magnetic excitation was measured around the 1 1 1 zone centre and the resulting dispersion curve is appropriate for an antiferromagnet with a gap of 0.20(1) meV.

Electronic and atomic structures of the Sr3Ir4Sn13 single crystal: A possible charge density wave material.

X-ray scattering (XRS), x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) spectroscopic techniques were used to study the electronic and atomic structures of the high-quality Sr3Ir4Sn13 (SIS) single crystal below and above the transition temperature (T* ≈ 147 K). The evolution of a series of modulated satellite peaks below the transition temperature in the XRS experiment indicated the formation of a possible charge density wave (CDW) in the (110) plane. The EXAFS phase derivative analysis supports the CDW-like formation by revealing different bond distances [Sn1(2)-Sn2] below and above T* in the (110) plane. XANES spectra at the Ir L3-edge and Sn K-edge demonstrated an increase (decrease) in the unoccupied (occupied) density of Ir 5d-derived states and a nearly constant density of Sn 5p-derived states at temperatures T < T* in the (110) plane. These observations clearly suggest that the Ir 5d-derived states are closely related to the anomalous resistivity transition. Accordingly, a close relationship exists between local electronic and atomic structures and the CDW-like phase in the SIS single crystal.

ARTEMIS observations of the solar wind proton scattering function from lunar crustal magnetic anomalies.

Despite their small scales, lunar crustal magnetic fields are routinely associated with observations of reflected and/or backstreaming populations of solar wind protons. Solar wind proton reflection locally reduces the rate of space weathering of the lunar regolith, depresses local sputtering rates of neutrals into the lunar exosphere, and can trigger electromagnetic waves and small-scale collisionless shocks in the near-lunar space plasma environment. Thus, knowledge of both the magnitude and scattering function of solar wind protons from magnetic anomalies is crucial in understanding a wide variety of planetary phenomena at the Moon. We have compiled 5.5 years of ARTEMIS (Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun) observations of reflected protons at the Moon and used a Liouville tracing method to ascertain each proton's reflection location and scattering angles. We find that solar wind proton reflection is largely correlated with crustal magnetic field strength, with anomalies such as South Pole/Aitken Basin (SPA), Mare Marginis, and Gerasimovich reflecting on average 5-12% of the solar wind flux while the unmagnetized surface reflects between 0.1 and 1% in charged form. We present the scattering function of solar wind protons off of the SPA anomaly, showing that the scattering transitions from isotropic at low solar zenith angles to strongly forward scattering at solar zenith angles near 90°. Such scattering is consistent with simulations that have suggested electrostatic fields as the primary mechanism for solar wind proton reflection from crustal magnetic anomalies.

Distribution and solar wind control of compressional solar wind-magnetic anomaly interactions observed at the Moon by ARTEMIS.

A statistical investigation of 5 years of observations from the two-probe Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) mission reveals that strong compressional interactions occur infrequently at high altitudes near the ecliptic but can form in a wide range of solar wind conditions and can occur up to two lunar radii downstream from the lunar limb. The compressional events, some of which may represent small-scale collisionless shocks ("limb shocks"), occur in both steady and variable interplanetary magnetic field (IMF) conditions, with those forming in steady IMF well organized by the location of lunar remanent crustal magnetization. The events observed by ARTEMIS have similarities to ion foreshock phenomena, and those observed in variable IMF conditions may result from either local lunar interactions or distant terrestrial foreshock interactions. Observed velocity deflections associated with compressional events are always outward from the lunar wake, regardless of location and solar wind conditions. However, events for which the observed velocity deflection is parallel to the upstream motional electric field form in distinctly different solar wind conditions and locations than events with antiparallel deflections. Consideration of the momentum transfer between incoming and reflected solar wind populations helps explain the observed characteristics of the different groups of events.

Electrical and thermal transport properties of intermetallic RCoGe2 (R = Ce and La) compounds.

To investigate the electronic structure of the intermetallic compound CeCoGe2, we performed electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) measurements in a temperature range of 10-300 K. For comparison, the non-magnetic counterpart LaCoGe2 is also studied. It is found that CeCoGe2 exhibits a broad maximum in the S(T) near 75 K, at which the sudden drop in the ρ(T) is observed. Temperature-dependent electrical resistivity and the Seebeck coefficient of CeCoGe2 can be described well by a two-band model, which reveals the signature of Kondo scattering in CeCoGe2. On the other hand, a typical metallic-like behavior is seen in the non-magnetic LaCoGe2 from the ρ(T) and S(T) studies. Analysis of the thermal conductivity indicates that the electronic contribution dominates thermal transport above 100 K in both CeCoGe2 and LaCoGe2. In addition, it is found that the variation in low-temperature lattice thermal conductivity of CeCoGe2 as compared to that of LaCoGe2 is most likely due to the phonon-point-defect scattering.

The effect of Al/Si ratio on the transport properties of the layered intermetallic compound CaAl(2)Si(2).

We report the results of the electrical resistivity and Seebeck coefficient as well as thermal conductivity measurements on the stoichiometric CaAl(2)Si(2) and non-stoichiometric CaAl(1.75)Si(2.25), CaAl(1.9)Si(2.1), CaAl(2.1)Si(1.9), and CaAl(2.25)Si(1.75) compounds in the temperature range 10-300 K. It has been found that the magnitude of electrical resistivity decreases for the non-stoichiometric samples, attributed to the shift of Fermi energy from the dip of the density of states as a consequence of the changed Si/Al content. In addition, a systematic change in the magnitude of Seebeck coefficient as a function of Al/Si concentration has been observed. The results have been associated with the effect of hole/electron doping on the Fermi level density of states. A detailed analysis of the electrical resistivity and Seebeck coefficient suggests the presence of two types of charge carrier and the temperature dependent changes in their mobility. From the thermal conductivity results, we correlated the extent of disorder and Al/Si ratio with various thermal scattering mechanisms in the investigated temperature range.

Weak charge-density-wave transition in LaAgSb(2) investigated by transport, thermal, and NMR studies.

We report a study of the charge-density-wave (CDW) behavior in LaAgSb(2) by means of electrical resistivity, Seebeck coefficient, thermal conductivity, specific heat, and nuclear magnetic resonance (NMR) measurements. Except for the Seebeck coefficient, apparent indications of CDW ordering at around 207 K were noticed in the physical quantities investigated. On the other hand, all measured physical properties are insensitive to the second CDW formation (∼184 K), as the transition character is considerably weaker than the high-temperature one. Further, analyses of the thermal conductivity and NMR Knight shift data revealed that the observed variations are essentially of electronic origin. The present findings are in good agreement with the previous results, indicating that the high-temperature CDW ordering is associated with a small gapping of the Fermi surface with a minor periodic displacement of the crystal lattice in LaAgSb(2).

Distinct T-cell clonal expansion in the vicinity of tumor cells in plasmacytoma.

BACKGROUND: Although various clinical observations suggested that myeloma cell growth might be modulated by the immune system, evidence supporting the in situ immunogenicity of myeloma cells remains scarce. The authors reasoned that if there is any specific T-cell/tumor cell interaction in myeloma, it is most likely reflected in the T-cell population in the vicinity of the tumor cells. METHODS: The authors used a molecular method to compare the T-cell populations in the vicinity of tumor cells with those in the peripheral blood in patients with plasmacytomas and multiple myeloma. RESULTS: Six patients were studied. When compared with the peripheral blood from the corresponding patients, T cells in the vicinity of tumor cells in five of the six patients showed significant contraction of the T-cell receptor (TCR) Vbeta repertoire. In addition to this, the T cells isolated from the sites of the tumor cells from four of these five patients also demonstrated significant increase in the number of TCR Vbeta gene families with restricted number of CDR3 size peaks and loss of the normal CDR3 size gaussian distribution pattern. These findings were observed in patients who experienced recurrence after allogeneic stem cell transplantation and also in those who had autologous stem cell transplant. They also were found in previously untreated myeloma patients. In all six patients, distinct TCR Vbeta recurring transcripts indicative of a T-cell clonal expansion were found in the vicinity of the tumor cells and either absent or detected at only a low frequency in the peripheral blood. CONCLUSIONS: Our results provide evidence for an in situ local T-cell clonal expansion in the vicinity of tumor cells and support the presence of specific T-cell/tumor cell interaction in myeloma.

An automated method for the analysis of T-cell receptor repertoires. Rapid RT-PCR fragment length analysis of the T-cell receptor beta chain complementarity-determining region 3.

The examination of T-cell receptor (TCR) repertoires has an important role in the study of lymphoproliferative disorders and autoimmune diseases. Analysis of the complementarity-determining region 3 (CDR3) of the TCR beta chain is used to assess the clonality of T-cell populations. We developed a rapid fluorescence-based method for CDR3 length analysis of expressed TCR gene families. TCR beta chain complementary DNA is amplified by a nested polymerase chain reaction with V beta family-specific oligonucleotide primers and a fluorochrome-labeled C beta primer. The polymerase chain reaction products were analyzed on a compact automated DNA sequencing system (OpenGene system, Visible Genetics, Toronto, Ontario). To demonstrate the usefulness of our technique, we examined the CDR3 length distribution of peripheral blood T cells from a healthy subject, intestinal T cells from a patient with ulcerative colitis, and the T-cell leukemia cell line Jurkat. The analysis revealed polyclonal, oligoclonal, and monoclonal CDR3 distributions, respectively, for the 3 T-cell populations. Our new method shows virtually identical CDR3 length patterns compared with the traditional radioisotope-based method. The new technique offers the convenience of rapid throughput, nonradioactive labeling, and quality data analysis.

Human peritoneal B-1 cells and the influence of continuous ambulatory peritoneal dialysis on peritoneal and peripheral blood mononuclear cell (PBMC) composition and immunoglobulin levels.

In mice, peritoneal B cells are composed of a unique B-1 cell population which can repopulate the intestinal lamina propria with IgA-producing cells, as well as contribute to the majority of serum IgM. In this study, peritoneal lymphocytes from patients starting continuous ambulatory peritoneal dialysis (CAPD) and from women undergoing bilateral tubal ligation (BTL) were analysed for the presence of a B-1 cell population as well as the expression of potential homing receptors. Up to 63% of the peritoneal B cells express surface antigen CD5, and most peritoneal lymphocytes express the mucosal homing receptors, alpha4 beta7 and alphaE beta7. When analysing serial samples collected from patients from the beginning of dialysis to 1 year, no marked changes were observed in serum or salivary immunoglobulin levels, although the peritoneal lymphocyte population was reduced by 50%. These data suggest that the phenotype of human peritoneal B-1 cells is similar to that of mice, but the contributions to the immune system may differ.

Overexpression of full- or partial-length MAP4 stabilizes microtubules and alters cell growth.

To investigate the in vivo functions of MAP4, a microtubule-associated protein expressed almost ubiquitously in vertebrate cells, we prepared stably transfected clonal mouse Ltk- cell lines expressing full-length MAP4 (L-MAP4 cells) or its MT-binding domain (L-MTB cells). Although transfectants showed no dramatic defect in morphology, organellar distribution, or level of MT polymer, as compared to naive Ltk- cells or L-MOCK cells (transfected with vector alone), MTs in L-MAP4 and L-MTB cells showed greater stability than those in control cells, as monitored by the level of post-translationally detyrosinated alpha-tubulin and by a quantitative nocodazole-resistance assay. In vivo, the MT-binding domain of MAP4 stabilized MTs less potently than full-length MAP4, in contrast to the equivalent efficacy demonstrated in studies of in vitro MT polymerization (Aizawa et al. (1991), J. Biol. Chem. 266, 9841-9846), L-MAP4 and L-MTB cells grew significantly more slowly than control cells; this growth inhibition was not due to mitotic arrest or cell death. L-MAP4 and L-MTB cells also exhibited greater tolerance to the MT-depolymerizing agent, nocodazole, but not to the MT-polymerizing agent, Taxol. Our results demonstrate that MAP4 and its MT-binding domain are capable of MT stabilization in vivo, and that increasing the intracellular level of MAP4 affects cell growth parameters.

Characterization of a cowpox-like orthopox virus which had caused a lethal infection in man.

In August 1990 an orthopox virus (OPV) had been isolated from a severe case of a generalized infection with lethal outcome in an immunosuppressed 18-year-old man. In this communication we present a detailed characterization of the causative virus strain. Based on distinct epitope configurations detected by various monoclonal antibodies the isolate could be differentiated from other OPV species and was classified as a cowpox virus (CP). This classification was confirmed by a species-specific PCR assay and by establishing physical maps for the restriction enzymes HindIII and XhoI. Based on serological data of neutralization assays, blocking-ELISAs and Western blotting analysis evidence is provided that the infection had been acquired from a stray cat.

Calciphylaxis mimicking skin lesions of connective tissue diseases.

Calciphylaxis is a rare condition found in patients with end-stage renal disease and secondary hyperparathyroidism. We describe two cases of prominent cutaneous manifestations of calciphylaxis in which skin lesions were refractory to topical treatments. We also include a brief description of calciphylaxis.

Traumatic cycloplegia and myopic anisometropia.

The pathogenesis of myopia and the mechanism of atropine in preventing myopic progression have long been widely discussed. Recent studies with animals have pointed to the possible role of the muscarinic receptor of the retina itself in regulating eye growth. This paper stresses that, for myopia in humans, the importance of accommodation still holds. Twenty-five recovered cases of previous traumatic hyphema, occurring under age 16, were collected. For four or more years, the patients were examined for ocular refraction, axial length, intraocular pressure, gonioscopy and accommodation time; the latter was measured with an accommodo-polyrecorder. Data from injured eyes and fellow eyes were compared and analyzed. The results indicated that, in the injured eyes the refractive status was invariably less myopic than in the fellow eye, and was not related to intraocular pressure. In injured eyes the accommodation time was highly correlated with the extent of angle recess. And the difference of anisometropia was also related to the extent of angle recess. These observations showed that there was a significant correlation between the degree of myopic anisometropia and the impairment of accommodation.

The course of myopia in children with mild retinopathy of prematurity.

The courses of spherical equivalent in patients (n = 62) who had mild, non-cicatricial retinopathy of prematurity (ROP), and in those without a history of ROP (n = 25) were modeled as a linear function of age; an exponential model was also considered. A few (n = 5) without ROP have abnormal courses characterized by hyperopia in early infancy; none have poor acuity. Although the majority of patients with ROP have courses indistinguishable from those of term born controls, 27 (43.5%) have abnormal courses, most of which are toward myopia. Optotype acuities were significantly poorer among the ROP patients with abnormal than normal refractive courses. Thus abnormal refractive development and acuity deficits are associated in eyes that have had mild ROP.

Differential expression of alternatively spliced forms of MAP4: a repertoire of structurally different microtubule-binding domains.

We previously reported that the microtubule (MT)-binding domain of microtubule-associated protein 4 (MAP4) contains three 18-amino acid imperfect repeats that are homologous to the repeats found in the MT-binding domains of the neuronal MAPs, MAP2 and tau [Chapin, S. J., & Bulinski, J. C. (1991) J. Cell Sci. 98, 27-36]. Here we report the isolation of clones encoding additional isoforms of MAP4, which differ in the number of repeated elements contained within their MT-binding domains. In addition to clones encoding three repeats, we isolated clones encoding a four-repeat isoform, whose MT-binding domain bears a striking similarity to the four-repeat isoform of tau. Other MAP4 clones that we isolated encode five repeats. The additional repeat in the five-repeat isoform of MAP4 is quite unusual in its amino acid sequence; this unusual repeat was also found by Aizawa et al. [Aizawa, H., et al. (1990) J. Biol. Chem. 265, 13849-13855] among the repeats encoded by bovine MAP4 clones possessing four repeats. In humans, MAP4 was recently shown to be encoded by a single-copy gene [West, R. R., et al. (1991) J. Biol. Chem. 266, 21886-21896]; we demonstrated that the human MAP4 gene is located on human chromosome 3p21. Expression of multiple MAP4 isoforms from this gene, which appears to result from alternative RNA splicing, was investigated by RNase protection analysis of mammalian cell lines and rat tissues. The five-repeat isoform was the only form detectable in most cell lines, and it was the most abundant isoform expressed in rat lung, liver, kidney, spleen, and testis. However, in rat brain, heart, and skeletal muscle, although the five-repeat isoform was expressed at all developmental stages examined, the tau-like four-repeat isoform was also expressed, and its expression increased during development. The three-repeat isoform was expressed in heart and, to a lesser extent, in brain, skeletal muscle, and lung. Our results demonstrate that several different MAP4 isoforms are expressed in the rat in different tissues and at various developmental stages. Furthermore, our data suggest that differential expression of MAP4 isoforms possessing distinct MT-binding domains may be involved in the changes in MT dynamics or function that are known to accompany differentiation.