Transient dynamics and structure of optimal excitations in thermocapillary spreading: Precursor film model

Linearized modal stability theory has shown that the thermocapillary spreading of a liquid film on a homogeneous, completely wetting surface can produce a rivulet instability at the advancing front due to formation of a capillary ridge. Mechanisms that drain fluid from the ridge can stabilize the flow against rivulet formation. Numerical predictions from this analysis for the film speed, shape, and most unstable wavelength agree remarkably well with experimental measurements even though the linearized disturbance operator is non-normal, which allows transient growth of perturbations. Our previous studies using a more generalized nonmodal stability analysis for contact lines models describing partially wetting liquids (i.e., either boundary slip or van der Waals interactions) have shown that the transient amplification is not sufficient to affect the predictions of eigenvalue analysis. In this work we complete examination of the various contact line models by studying the influence of an infinite and flat precursor film, which is the most commonly employed contact line model for completely wetting films. The maximum amplification of arbitrary disturbances and the optimal initial excitations that elicit the maximum growth over a specified time, which quantify the sensitivity of the film to perturbations of different structure, are presented. While the modal results for the three different contact line models are essentially indistinguishable, the transient dynamics and maximum possible amplification differ, which suggests different transient dynamics for completely and partially wetting films. These differences are explained by the structure of the computed optimal excitations, which provides further basis for understanding the agreement between experiment and predictions of conventional modal analysis

Synthetic X-ray light curves of BL Lacs from relativistic hydrodynamic simulations

We present the results of relativistic hydrodynamic simulations of the collision of two dense shells in a uniform external medium, as envisaged in the internal shock model for BL Lac jets. The non-thermal radiation produced by highly energetic electrons injected at the relativistic shocks is computed following their temporal and spatial evolution. The acceleration of electrons at the relativistic shocks is parametrized using two different models and the corresponding X-ray light curves are computed. We find that the interaction time scale of the two shells is influenced by an interaction with the external medium. For the chosen parameter sets, the efficiency of the collision in converting dissipated kinetic energy into the observed X-ray radiation is of the order of one percent.Comment: 22 pages, 6 figures, accepted to A&

Gamma-ray Spectral Evolution of NGC1275 Observed with Fermi-LAT

We report on a detailed investigation of the high-energy gamma-ray emission from NGC\,1275, a well-known radio galaxy hosted by a giant elliptical located at the center of the nearby Perseus cluster. With the increased photon statistics, the center of the gamma-ray emitting region is now measured to be separated by only 0.46' from the nucleus of NGC1275, well within the 95% confidence error circle with radius ~1.5'. Early Fermi-LAT observations revealed a significant decade-timescale brightening of NGC1275 at GeV photon energies, with a flux about seven times higher than the one implied by the upper limit from previous EGRET observations. With the accumulation of one-year of Fermi-LAT all-sky-survey exposure, we now detect flux and spectral variations of this source on month timescales, as reported in this paper. The average >100 MeV gamma-ray spectrum of NGC1275 shows a possible deviation from a simple power-law shape, indicating a spectral cut-off around an observed photon energy of E = 42.2+-19.6 GeV, with an average flux of F = (2.31+-0.13) X 10^{-7} ph/cm^2/s and a power-law photon index, Gamma = 2.13+-0.02. The largest gamma-ray flaring event was observed in April--May 2009 and was accompanied by significant spectral variability above E > 1-2 GeV. The gamma-ray activity of NGC1275 during this flare can be described by a hysteresis behavior in the flux versus photon index plane. The highest energy photon associated with the gamma-ray source was detected at the very end of the observation, with the observed energy of E = 67.4GeV and an angular separation of about 2.4' from the nucleus. In this paper we present the details of the Fermi-LAT data analysis, and briefly discuss the implications of the observed gamma-ray spectral evolution of NGC1275 in the context of gamma-ray blazar sources in general.Comment: 20 pages, 6 figures, accepted for publication in the Ap

Volume contraction at the Jahn-Teller transition of LaMnO3_3

We have studied the volume collapse of LaMnO$_3$ at the Jahn- Teller (JT) transition temperature T$_{JT}$=750 K which has recently been found in high temperature powder x- ray and neutron diffraction experiments. We construct a model Hamiltonian involving the pseudospin of Mn$^{3+}$ e$_g$ states, the staggered JT distortion and the volume strain coordinate. We show that the anharmonic coupling between these primary and secondary order parameters leads to the first order JT phase transition associated with a comparatively large reduction of the unit cell volume of $\Delta$V/V$\simeq$ 10$^{-2}$. We explain the temperature dependence of JT distortions and volume strain and discuss the volume change as function of the anharmonic coupling constant. A continuous change to a second order transition as function of model parameters is obtained. This behaviour is also observed under Ba doping.Comment: 5 pages, 4 figure

DNA adjuvants for potent mucosal immunity

In order to develop safe vaccines for effective mucosal immunity to major pulmonary bacterial infections, one must consider appropriate vaccine antigens (Ags), delivery systems and nontoxic molecular adjuvants. Such vaccine constructs can induce Ag-specific immune responses which provide effective protection from mucosal infections. In particular, it has been shown that adjuvant-based mucosal vaccine preparations are relatively easy to construct by simply mixing the adjuvant with the bacterial Ag, and the resulting vaccine can elicit protective immunity. We have studied DNA-based nasal adjuvants targeting mucosal dendritic cells (DCs) in order to induce Ag-specific mucosal and systemic immune responses that provide essential protection against microbial pathogens which invade our mucosal surfaces. In this review, we initially introduce a plasmid encoding the cDNA of Flt3 ligand (pFL), a molecule which is a growth factor for DCs as an effective adjuvant for mucosal immunity to pneumococcal infections. Next, we discuss the potential of adding unmethylated CpG oligodeoxynucleotide together with pFL together with a pneumococcal Ag for protection from pneumococcal infections. To do this, we have used pneumococcal surface protein A as vaccine for the restoration of mucosal immunity in aging. Further, we have also used our nasal pFL adjuvant system with phosphorylcholine-keyhole limpet hemocyanin (PC-KLH) in pneumococcal vaccine development, to successfully induce complete protection from nasal carriage by Streptococcus pneumoniae. Finally, we discuss the possibility that anti-PC antibodies induced by nasal delivery of pFL plus PC-KLH may play a protective role for prevention of atherogenesis and thus block the subsequent development of cardiovascular disease

Kiloparsec-Scale Jets in FR I Radio Galaxies and the Gamma-Ray Background

We discuss the contribution of kiloparsec-scale jets in FR I radio galaxies to the diffuse gamma-ray background radiation. The analyzed gamma-ray emission comes from inverse-Compton scattering of starlight photon fields by the ultrarelativistic electrons whose synchrotron radiation is detected from such sources at radio, optical and X-ray energies. We find that these objects, under the minimum-power hypothesis (corresponding to a magnetic field of 300 muG in the brightest knots of these jets), can contribute about one percent to the extragalactic gamma-ray background measured by EGRET. We point out that this result already indicates that the magnetic fields in kpc-scale jets of low-power radio galaxies are not likely to be smaller than 10 muG on average, as otherwise the extragalactic gamma-ray background would be overproduced.Comment: 18 pages, 3 figures included. ApJ accepte

Human T‐cell lymphotrophic virus in solid‐organ transplant recipients: Guidelines from the American society of transplantation infectious diseases community of practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of Human T‐cell lymphotrophic virus 1 (HTLV)‐1 in the pre‐ and post‐transplant period. HTLV‐1 is an oncogenic human retrovirus rare in North America but endemic in the Caribbean and parts of Africa, South America, Asia, and Oceania. While most infected persons do not develop disease, <5% will develop adult T‐cell leukemia/lymphoma or neurological disease. No proven antiviral treatment for established HTLV‐1 infection is available. The effect of immunosuppression on the development of HTLV‐1‐associated disease in asymptomatically infected recipients is not well characterized, and HTLV‐1‐infected individuals should be counseled that immunosuppression may increase the risk of developing HTLV‐1‐associated disease and they should be monitored post‐transplant for HTLV‐1‐associated disease. Currently approved screening assays do not distinguish between HTLV‐1 and HTLV‐2, and routine screening of deceased donors without risk factors in low seroprevalence areas is likely to result in significant organ wastage and is not recommended. Targeted screening of donors with risk factors for HTLV‐1 infection and of living donors (as time is available to perform confirmatory tests) is reasonable.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151899/1/ctr13575.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151899/2/ctr13575_am.pd

Spin current and magneto-electric effect in non-collinear magnets

A new microscopic mechanism of the magneto-electric (ME) effect based on the spin supercurrent is theoretically presented for non-collinear magnets. The close analogy between the superconductors (charge current) and magnets (spin current) is drawn to derive the distribution of the spin supercurrent and the resultant electric polarization. Application to the spiral spin structure is discussed.Comment: 5 pages, 2 figure

Surface-acoustic-wave-driven luminescence from a lateral p-n junction

The authors report surface-acoustic-wave-driven luminescence from a lateral p-n junction formed by molecular beam epitaxy regrowth of a modulation doped GaAs/AlGaAs quantum well on a patterned GaAs substrate. Surface-acoustic-wave-driven transport is demonstrated by peaks in the electrical current and light emission from the GaAs quantum well at the resonant frequency of the transducer. This type of junction offers high carrier mobility and scalability. The demonstration of surface-acoustic-wave luminescence is a significant step towards single-photon applications in quantum computation and quantum cryptography.Comment: 4 pages, 3 figure