Valve interstitial cells induce donor-specific T-cell anergy

AbstractObjectives: Valve allografts produce an immune response, which can influence their performance. The exact role of the interaction between recipient T cells and the different cellular components of the donor valve in stimulating an immune response is not known. Therefore the T-cell response to valve endothelial and interstitial cells was investigated in vitro. Methods: Valve endothelial and interstitial cells were characterized for cell-surface molecules before and after interferon γ treatment by means of a panel of specific monoclonal antibodies and flow cytometry. The proliferative response of highly purified T lymphocytes was used to assess the immunogenicity of cultured valve endothelial and interstitial cells. This was further investigated by using a 2-step tolerance-induction protocol. Results: Valve endothelial and interstitial cells express similar levels of human leukocyte antigens and adhesion and costimulatory molecules, which are either induced or upregulated after interferon γ treatment. T-cell responses to endothelial cells were detected after interferon γ treatment, but responses to interferon γ–treated interstitial cells were not detected. This lack of response resulted in the induction of T-cell anergy, which was reversed by the presence of the costimulatory molecule B7-1. Conclusions: Although valve endothelial and interstitial cells express a similar range of cell-surface molecules, it is only the endothelial cells that are immunogenic. In addition, we have shown that these 2 cell types interact in a donorspecific manner to orchestrate the immune response and therefore may have clinical relevance in the allogeneic response of the heart valve recipients.J Thorac Cardiovasc Surg 2001;122:129-3

Plasma fluctuations in crossed electric and magnetic fields

An experimental study has been made of the high-amplitude electrical fluctuations associated with a gas discharge in a strong magnetic field.Hydrogen, helium, argon, and nitrogen gas were used at pressures from 0.3 to 100 micronsThe power spectrum on plasma probes was investigated for various values of magnetic field, gas pressure, and power input to the discharge.For the range of frequencies studied (0.5 to 4000 megacycles per second), the spectrum shows a continuous high level that increases in amplitude with decreasing pressures at all frequencies and increases with increasing magnetic field at low frequencies.A sharp dip in the spectrum was observed near the ion cyclotron frequency for discharges in hydrogen and helium. The velocity and direction of propagation for the low frequency fluctuations were determined by cross-correlating the potential variations on two neighboring probes. These fluctuations appear to propagate in the direction of the electron drift and at a velocity somewhat less than the Lorentz drift velocity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32512/1/0000602.pd

Testing Rotational Mixing Predictions with New Boron Abundances in Main Sequence B-type Stars

(Abridged) New boron abundances for seven main-sequence B-type stars are determined from HST STIS spectroscopy around the BIII 2066A line. Boron abundances provide a unique and critical test of stellar evolution models that include rotational mixing since boron is destroyed in the surface layers of stars through shallow mixing long before other elements are mixed from the stellar interior through deep mixing. Boron abundances range from 12+log(B/H) = 1.0 to 2.2. The boron abundances are compared to the published values of their stellar nitrogen abundances (all have 12+log(N/H) < 7.8, i.e., they do not show significant CNO-mixing) and to their host cluster ages (4 to 16 Myr) to investigate the predictions from models of massive star evolution with rotational mixing effects (Heger & Langer 2000). Only three stars (out of 34) deviate from the model predictions, including HD36591, HD205021, and HD30836. These three stars suggest that rotational mixing could be more efficient than currently modelled at the highest rotation rates.Comment: 10 figures, 7 tables; accepted for publication in the Astrophysical Journa

Unusual magnetic-field dependence of partially frustrated triangular ordering in manganese tricyanomethanide

Manganese tricyanomethanide, Mn[C(CN)3]2, consists of two interpenetrating three-dimensional rutile-like networks. In each network, the tridentate C(CN)3- anion gives rise to superexchange interactions between the Mn2+ ions (S=5/2) that can be mapped onto the "row model" for partially frustrated triangular magnets. We present heat capacity measurements that reveal a phase transition at T_N = 1.18K, indicative of magnetic ordering. The zero-field magnetically ordered structure was solved from neutron powder diffraction data taken between 0.04 and 1.2 K. It consists of an incommensurate spiral with a temperature independent propagation vector Q=(2Q 0 0)=(+/-0.622 0 0), where different signs relate to the two different networks. This corresponds to (+/-0.311 +/-0.311 0) in a quasi-hexagonal representation. The ordered moment mu=3.3mu_B is about 2/3 of the full Mn2+ moment. From the values of T_N and Q, the exchange parameters J/k = 0.15 K and J'/J = 0.749 are estimated. The magnetic-field dependence of the intensity of the Bragg reflection, measured for external fields H||Q, indicates the presence of three different magnetic phases. We associate them with the incommensurate spiral (H < 13.5 kOe), an intermediate phase (13.5 kOe 16 kOe) proposed for related compounds. For increasing fields, Q continuously approaches the value 1/3, corresponding to the commensurate magnetic structure of the fully frustrated triangular lattice. This value is reached at H_c = 19 kOe. At this point, the field-dependence reverses and Q adopts a value of 0.327 at 26 kOe, the highest field applied in the experiment. Except for H_c, the magnetic ordering is incommensurate in all three magnetic phases of Mn[C(CN)3]2.Comment: accepted for publication in J. Phys.: Condens. Matte

An Optical Study of BG Geminorum: An Ellipsoidal Binary with an Unseen Primar Star

We describe optical photometric and spectroscopic observations of the bright variable BG Geminorum. Optical photometry shows a pronounced ellipsoidal variation of the K0 I secondary, with amplitudes of ~0.5 mag at VRI and a period of 91.645 days. A deep primary eclipse is visible for wavelengths < 4400A; a shallower secondary eclipse is present at longer wavelengths. Eclipse timings and the radial velocity curve of the K0 secondary star indicate an interacting binary where a lobe-filling secondary, M_2 ~ 0.5 Msun, transfers material into a extended disk around a massive primary, M_1 ~ 4.5 Msun. The primary star is either an early B-type star or a black hole. If it did contain a black hole, BG Gem would be the longest period black hole binary known by a factor of 10, as well as the only eclipsing black hole binary system.Comment: 27 pages, includes 8 figures and 5 tables, accepted to A

The HgMn Binary Star Phi Herculis: Detection and Properties of the Secondary and Revision of the Elemental Abundances of the Primary

Observations of the Mercury-Manganese star Phi Herculis with the Navy Prototype Optical Interferometer (NPOI) conclusively reveal the previously unseen companion in this single-lined binary system. The NPOI data were used to predict a spectral type of A8V for the secondary star Phi Her B. This prediction was subsequently confirmed by spectroscopic observations obtained at the Dominion Astrophysical Observatory. Phi Her B is rotating at 50 +/-3 km/sec, in contrast to the 8 km/sec lines of Phi Her A. Recognizing the lines from the secondary permits one to separate them from those of the primary. The abundance analysis of Phi Her A shows an abundance pattern similar to those of other HgMn stars with Al being very underabundant and Sc, Cr, Mn, Zn, Ga, Sr, Y, Zr, Ba, Ce, and Hg being very overabundant.Comment: Accepted to ApJ, 45 pages, 11 figure

Assessing the probability of introduction and transmission of lumpy skin disease virus within the United Kingdom

Several emerging exotic diseases are currently oscillating on the eastern borders of the European Union (EU) including the bovine pathogen Lumpy skin disease virus (LSDV). Given the recent transboundary spread of LSDV into the EU, assessing the probability of further expansion is an important part of EU surveillance and can inform policy regarding risk mitigation priorities. This qualitative assessment focuses on the probability of introduction and onward transmission of LSDV into the United Kingdom (UK) for the time period June 2017 to June 2018. Overall the probability of introduction was considered, at most, to be very low. The probability of onward transmission was considered highest for vector mediated routes either via contact of an infected vector with susceptible cattle or contact of a competent native vector with an infected cattle. Factors with high uncertainty were identified to emphasise their impact on the assessment conclusions and for future research requirements. Medium to high uncertainty surrounds the probability of introduction to the UK via several of the routes assessed, in particular, the species of vectors involved and the illegal/legal import of meat and milk products; all estimates made consequential to these probabilities are therefore underpinned by high uncertainty. Whilst the assessment was UK centric the knowledge gaps are relevant to the probability of introduction and spread of LSDV in any geographical region. The value of estimating uncertainty lies in the identification of research required to make conclusions more robust

Electronic Structure of Transition-Metal Dicyanamides Me[N(CN)2_2]2_2 (Me = Mn, Fe, Co, Ni, Cu)

The electronic structure of Me[N(CN)$_2$]$_2$ (Me=Mn, Fe, Co, Ni, Cu) molecular magnets has been investigated using x-ray emission spectroscopy (XES) and x-ray photoelectron spectroscopy (XPS) as well as theoretical density-functional-based methods. Both theory and experiments show that the top of the valence band is dominated by Me 3d bands, while a strong hybridization between C 2p and N 2p states determines the valence band electronic structure away from the top. The 2p contributions from non-equivalent nitrogen sites have been identified using resonant inelastic x-ray scattering spectroscopy with the excitation energy tuned near the N 1s threshold. The binding energy of the Me 3d bands and the hybridization between N 2p and Me 3d states both increase in going across the row from Me = Mn to Me = Cu. Localization of the Cu 3d states also leads to weak screening of Cu 2p and 3s states, which accounts for shifts in the core 2p and 3s spectra of the transition metal atoms. Calculations indicate that the ground-state magnetic ordering, which varies across the series is largely dependent on the occupation of the metal 3d shell and that structural differences in the superexchange pathways for different compounds play a secondary role.Comment: 20 pages, 11 figures, 2 table

Interferometric Observations of the Hierarchical Triple System Algol

Algol is a triple stellar system consisting of a close semidetached binary orbited by a third object. Due to the disputed spatial orientation of the close pair, the third body perturbation of this pair is a subject of much research. In this study, we determine the spatial orientation of the close pair orbital plane using the CHARA Array, a six-element optical/IR interferometer located on Mount Wilson, and state-of-the-art e-EVN interferometric techniques. We find that the longitude of the line of nodes for the close pair is \Omega_1=48\degr\pm2\degr and the mutual inclination of the orbital planes of the close and the wide pairs is 95\degr\pm3\degr. This latter value differs by 5\degr from the formerly known 100\degr which would imply a very fast inclination variation of the system, not borne out by the photometric observations. We also investigated the dynamics of the system with numerical integration of the equations of motions using our result as an initial condition. We found large variations in the inclination of the close pair (its amplitude \sim 170\degr) with a period of about 20 millennia. This result is in good agreement with the photometrically observed change of amplitude in Algol's primary minimum.Comment: ApJ, in press. This is the accepted version; will be changed with the final version later (minor language corrections