Long-Ranged Orientational Order in Dipolar Fluids

Recently Groh and Dietrich claimed the thermodynamic state of a dipolar fluid depends on the shape of the fluid's container. For example, a homogeneous fluid in a short fat container would phase separate when transferred to a tall skinny container of identical volume and temperature. Their calculation thus lacks a thermodynamic limit. We show that removal of demagnetizing fields restores the true, shape independent, thermodynamic limit. As a consequence, spontaneously magnetized liquids display inhomogeneous magnetization textures.Comment: 3 pages, LaTex, no figures. Submitted as comment to PRL, May 199

Inhomogeneous magnetization in dipolar ferromagnetic liquids

At high densities fluids of strongly dipolar spherical particles exhibit spontaneous long-ranged orientational order. Typically, due to demagnetization effects induced by the long range of the dipolar interactions, the magnetization structure is spatially inhomogeneous and depends on the shape of the sample. We determine this structure for a cubic sample by the free minimization of an appropriate microscopic density functional using simulated annealing. We find a vortex structure resembling four domains separated by four domain walls whose thickness increases proportional to the system size L. There are indications that for large L the whole configuration scales with the system size. Near the axis of the mainly planar vortex structure the direction of the magnetization escapes into the third dimension or, at higher temperatures, the absolute value of the magnetization is strongly reduced. Thus the orientational order is characterized by two point defects at the top and the bottom of the sample, respectively. The equilibrium structure in an external field and the transition to a homogeneous magnetization for strong fields are analyzed, too.Comment: 17 postscript figures included, submitted to Phys. Rev.

Ferromagnetic Liquid Thin Films Under Applied Field

Theoretical calculations, computer simulations and experiments indicate the possible existence of a ferromagnetic liquid state, although definitive experimental evidence is lacking. Should such a state exist, demagnetization effects would force a nontrivial magnetization texture. Since liquid droplets are deformable, the droplet shape is coupled with the magnetization texture. In a thin-film geometry in zero applied field, the droplet has a circular shape and a rotating magnetization texture with a point vortex at the center. We calculate the elongation and magnetization texture of such ferromagnetic thin film liquid droplet confined between two parallel plates under a weak applied magnetic field. The vortex stretches into a domain wall and exchange forces break the reflection symmetry. This behavior contrasts qualitatively and quantitatively with the elongation of paramagnetic thin films.Comment: 10 pages, 4 figures, Submitted to Phys. Rev.

Magnetic Properties of Fe-49Co-2V Alloy and Pure Fe at Room and Elevated Temperatures

The National Aeronautics and Space Administration (NASA) has a need for soft magnetic materials for fission power and ion propulsion systems. In this work the magnetic properties of the soft magnetic materials Hiperco 50 (Fe-49wt%Cr-2V) and CMI-C (commercially pure magnetic iron) were examined at various temperatures up to 600 C. Toroidal Hiperco 50 samples were made from stacks of 0.35 mm thick sheet, toroidal CMI-C specimens were machined out of solid bar stock, and both were heat treated prior to testing. The magnetic properties of a Hiperco 50 sample were measured at various temperatures up to 600 C and then again after returning to room temperature; the magnetic properties of CMI-C were tested at temperatures up to 400 C. For Hiperco 50 coercivity decreased as temperature increased, and remained low upon returning to room temperature; maximum permeability improved (increased) with increasing temperature and was dramatically improved upon returning to room temperature; remanence was not significantly affected by temperature; flux density at H = 0.1 kA/m increased slightly with increasing temperature, and was about 20% higher upon returning to room temperature; flux density at H = 0.5 kA/m was insensitive to temperature. It appears that the properties of Hiperco 50 improved with increasing temperature due to grain growth. There was no significant magnetic property difference between annealed and aged CMI-C iron material; permeability tended to decrease with increasing temperature; the approximate decline in the permeability at 400 C compared to room temperature was 30%; saturation flux density, B(sub S), was approximately equal for all temperatures below 400 C; B(sub S) was lower at 400 C

The sudden appearance of CO emission in LHA 115-S 65

Molecular emission has been detected in several Magellanic Cloud B[e] supergiants. In this Letter, we report on the detection of CO band head emission in the B[e] supergiant LHA 115-S 65, and present a K-band near-infrared spectrum obtained with the Spectrograph for INtegral Field Observation in the Near-Infrared (SINFONI; R=4500) on the ESO VLT UT4 telescope. The observed molecular band head emission in S 65 is quite surprising in light of a previous non-detection by McGregor et al. 1989, as well as a high resolution (R=50000) Gemini/Phoenix spectrum of this star taken nine months earlier showing no emission. Based on analysis of the optical spectrum by Kraus et al. 2010, we suspect that the sudden appearance of molecular emission could be due to density build up in an outflowing viscous disk, as seen for Be stars. This new discovery, combined with variability in two other similar evolved massive stars, indicates an evolutionary link between B[e] supergiants and LBVs.Comment: Letter accepted for publication in MNRAS. 5 pages, 2 figures, 1 tabl

Cellular expression, trafficking, and function of two isoforms of human ULBP5/RAET1G

Background: The activating immunoreceptor NKG2D is expressed on Natural Killer (NK) cells and subsets of T cells. NKG2D contributes to anti-tumour and anti-viral immune responses in vitro and in vivo. The ligands for NKG2D in humans are diverse proteins of the MIC and ULBP/RAET families that are upregulated on the surface of virally infected cells and tumours. Two splicing variants of ULBP5/RAET1G have been cloned previously, but not extensively characterised. Methodology/Principal Findings: We pursue a number of approaches to characterise the expression, trafficking, and function of the two isoforms of ULBP5/RAET1G. We show that both transcripts are frequently expressed in cell lines derived from epithelial cancers, and in primary breast cancers. The full-length transcript, RAET1G1, is predicted to encode a molecule with transmembrane and cytoplasmic domains that are unique amongst NKG2D ligands. Using specific anti-RAET1G1 antiserum to stain tissue microarrays we show that RAET1G1 expression is highly restricted in normal tissues. RAET1G1 was expressed at a low level in normal gastrointestinal epithelial cells in a similar pattern to MICA. Both RAET1G1 and MICA showed increased expression in the gut of patients with celiac disease. In contrast to healthy tissues the RAET1G1 antiserum stained a wide variety or different primary tumour sections. Both endogenously expressed and transfected RAET1G1 was mainly found inside the cell, with a minority of the protein reaching the cell surface. Conversely the truncated splicing variant of RAET1G2 was shown to encode a soluble molecule that could be secreted from cells. Secreted RAET1G2 was shown to downregulate NKG2D receptor expression on NK cells and hence may represent a novel tumour immune evasion strategy. Conclusions/Significance: We demonstrate that the expression patterns of ULBP5RAET1G are very similar to the well-characterised NKG2D ligand, MICA. However the two isoforms of ULBP5/RAET1G have very different cellular localisations that are likely to reflect unique functionality

Orientational Ordering in Spatially Disordered Dipolar Systems

This letter addresses basic questions concerning ferroelectric order in positionally disordered dipolar materials. Three models distinguished by dipole vectors which have one, two or three components are studied by computer simulation. Randomly frozen and dynamically disordered media are considered. It is shown that ferroelectric order is possible in spatially random systems, but that its existence is very sensitive to the dipole vector dimensionality and the motion of the medium. A physical analysis of our results provides significant insight into the nature of ferroelectric transitions.Comment: 4 pages twocolumn LATEX style. 4 POSTSCRIPT figures available from [email protected]

Normally occurring NKG2D+CD4+ T cells are immunosuppressive and inversely correlated with disease activity in juvenile-onset lupus

The NKG2D receptor stimulates natural killer cell and T cell responses upon engagement of ligands associated with malignancies and certain autoimmune diseases. However, conditions of persistent NKG2D ligand expression can lead to immunosuppression. In cancer patients, tumor expression and shedding of the MHC class I–related chain A (MICA) ligand of NKG2D drives proliferative expansions of NKG2D+CD4+ T cells that produce interleukin-10 (IL-10) and transforming growth factor-β, as well as Fas ligand, which inhibits bystander T cell proliferation in vitro. Here, we show that increased frequencies of functionally equivalent NKG2D+CD4+ T cells are inversely correlated with disease activity in juvenile-onset systemic lupus erythematosus (SLE), suggesting that these T cells may have regulatory effects. The NKG2D+CD4+ T cells correspond to a normally occurring small CD4 T cell subset that is autoreactive, primed to produce IL-10, and clearly distinct from proinflammatory and cytolytic CD4 T cells with cytokine-induced NKG2D expression that occur in rheumatoid arthritis and Crohn's disease. As classical regulatory T cell functions are typically impaired in SLE, it may be clinically significant that the immunosuppressive NKG2D+CD4+ T cells appear functionally uncompromised in this disease