Correlated Spectral and Temporal Variability in the High-Energy Emission from Blazars

Blazar flare data show energy-dependent lags and correlated variability between optical/X-ray and GeV-TeV energies, and follow characteristic trajectories when plotted in the spectral-index/flux plane. This behavior is qualitatively explained if nonthermal electrons are injected over a finite time interval in the comoving plasma frame and cool by radiative processes. Numerical results are presented which show the importance of the effects of synchrotron self-Compton cooling and plasmoid deceleration. The use of INTEGRAL to advance our understanding of these systems is discussed.Comment: 8 pages, 5 figures, uses epsf.sty, rotate.sty Invited paper in "The Extreme Universe," 3rd INTEGRAL Workshop, 14-18 September 1998, Taorimina, Ital

Effects of vibration and shock on the performance of gas-bearing space-power Brayton cycle turbomachinery. Part 4: Suppression of rotor-bearing system vibrations through flexible bearing support damping

A bearing damper, operating on the support flexure of a pivoted pad in a tilting-pad type gas-lubricated journal bearing, has been designed, built, and tested under externally-applied random vibrations. The NASA Brayton Rotating Unit (BRU), a 36,000 rpm, 10-Kwe turbogenerator had previously been subjected in the MTI Vibration Test Laboratory to external random vibrations, and vibration response data had been recorded and analyzed for amplitude distribution and frequency content at a number of locations in the machine. Based on data from that evaluation, a piston-type damper was designed and developed for each of the two flexibly-supported journal bearing pads (one in each of the two three-pad bearings). A modified BRU, with dampers installed, has been re-tested under random vibration conditions. Root-mean-square vibration amplitudes were determined from the test data, and displacement power spectral density analyses have been performed. Results of these data reduction efforts have been compared with vibration tolerance limits. Results of the tests indicate significant reductions in vibration levels in the bearing gas-lubricant films, particularly in the rigidly-mounted pads. The utility of the gas-lubricated damper for limiting rotor-bearing system vibrations in high-speed turbomachinery has thus been demonstrated

Unitary chiral dynamics in J/ΨJ/\Psi decays into VPPVPP and the role of the scalar mesons

We make a theoretical study of the \J decays into $\omega\pi\pi$, $\phi\pi\pi$, $\omega K \bar{K}$ and $\phi K\bar{K}$ using the techniques of the chiral unitary approach stressing the important role of the scalar resonances dynamically generated through the final state interaction of the two pseudoscalar mesons. We also discuss the importance of new mechanisms with intermediate exchange of vector and axial-vector mesons and the role played by the OZI rule in the \J\phi\pi\pi vertex, quantifying its effects. The results nicely reproduce the experimental data for the invariant mass distributions in all the channels considered.Comment: Prepared for the 10th International Symposium on Meson-Nucleon Physics and the Structure of the Nucleo

Testing Gaussian random hypothesis with the cosmic microwave background temperature anisotropies in the three-year WMAP data

We test the hypothesis that the temperature of the cosmic microwave background is consistent with a Gaussian random field defined on the celestial sphere, using de-biased internal linear combination (DILC) map produced from the 3-year WMAP data. We test the phases for spherical harmonic modes with l <= 10 (which should be the cleanest) for their uniformity, randomness, and correlation with those of the foreground templates. The phases themselves are consistent with a uniform distribution, but not for l <= 5, and the differences between phases are not consistent with uniformity. For l=3 and l=6, the phases of the CMB maps cross-correlate with the foregrounds, suggestion the presence of residual contamination in the DLC map even on these large scales. We also use a one-dimensional Fourier representation to assemble a_lm into the \Delta T_l(\phi) for each l mode, and test the positions of the resulting maxima and minima for consistency with uniformity randomness on the unit circle. The results show significant departures at the 0.5% level, with the one-dimensional peaks being concentrated around \phi=180 degs. This strongly significant alignment with the Galactic meridian, together with the cross-correlation of DILC phases with the foreground maps, strongly suggests that even the lowest spherical harmonic modes in the map are significantly contaminated with foreground radiation.Comment: submitted to ApJL, one paragraph is added in Section 3 and some more in the Referenc

High Rayleigh number convection with double diffusive fingers

An electrodeposition cell is used to sustain a destabilizing concentration difference of copper ions in aqueous solution between the top and bottom boundaries of the cell. The resulting convecting motion is analogous to Rayleigh-B\'enard convection at high Prandtl numbers. In addition, a stabilizing temperature gradient is imposed across the cell. Even for thermal buoyancy two orders of magnitude smaller than chemical buoyancy, the presence of the weak stabilizing gradient has a profound effect on the convection pattern. Double diffusive fingers appear in all cases. The size of these fingers and the flow velocities are independent of the height of the cell, but they depend on the ion concentration difference between top and bottom boundaries as well as on the imposed temperature gradient. The scaling of the mass transport is compatible with previous results on double diffusive convection

Long-Distance Contributions to D^0-D^0bar Mixing Parameters

Long-distance contributions to the $D^0$-$\bar D^0$ mixing parameters $x$ and $y$ are evaluated using latest data on hadronic $D^0$ decays. In particular, we take on two-body $D \to PP$ and $VP$ decays to evaluate the contributions of two-body intermediate states because they account for $\sim 50$ of hadronic $D^0$ decays. Use of the diagrammatic approach has been made to estimate yet-observed decay modes. We find that $y$ is of order a few $\times 10^{-3}$ and $x$ of order $10^{-3}$ from hadronic $PP$ and $VP$ modes. These are in good agreement with the latest direct measurement of $D^0$-$\bar D^0$ mixing parameters using the $D^0 \to K_S \pi^+\pi^-$ and $K_S K^+ K^-$ decays by BaBar. We estimate the contribution to $y$ from the $VV$ modes using the factorization model and comment on the single-particle resonance effects and contributions from other two-body modes involving even-parity states.Comment: 18 pages and 1 figure; footnotes and references added; to appear in Phys. Rev.

Spin injection from perpendicular magnetized ferromagnetic δ\delta-MnGa into (Al,Ga)As heterostructures

Electrical spin injection from ferromagnetic $\delta$-MnGa into an (Al,Ga)As p-i-n light emitting diode (LED) is demonstrated. The $\delta$-MnGa layers show strong perpendicular magnetocrystalline anisotropy, enabling detection of spin injection at remanence without an applied magnetic field. The bias and temperature dependence of the spin injection are found to be qualitatively similar to Fe-based spin LED devices. A Hanle effect is observed and demonstrates complete depolarization of spins in the semiconductor in a transverse magnetic field.Comment: 4 pages, 3 figure

The wonder years: what can primary school children teach us about immunity to Mycobacterium tuberculosis?

In high burden settings, the risk of infection with Mycobacterium tuberculosis increases throughout childhood due to cumulative exposure. However, the risk of progressing from tuberculosis (TB) infection to disease varies by age. Young children (<5 years) have high risk of disease progression following infection. The risk falls in primary school children (5 to <10 years), but rises again during puberty. TB disease phenotype also varies by age: generally, young children have intrathoracic lymph node disease or disseminated disease, while adolescents (10 to <20 years) have adult-type pulmonary disease. TB risk also exhibits a gender difference: compared to adolescent boys, adolescent girls have an earlier rise in disease progression risk and higher TB incidence until early adulthood. Understanding why primary school children, during what we term the “Wonder Years,” have low TB risk has implications for vaccine development, therapeutic interventions, and diagnostics. To understand why this group is at low risk, we need a better comprehension of why younger children and adolescents have higher risks, and why risk varies by gender. Immunological response to M. tuberculosis is central to these issues. Host response at key stages in the immunopathological interaction with M. tuberculosis influences risk and disease phenotype. Cell numbers and function change dramatically with age and sexual maturation. Young children have poorly functioning innate cells and a Th2 skew. During the “Wonder Years,” there is a lymphocyte predominance and a Th1 skew. During puberty, neutrophils become more central to host response, and CD4+ T cells increase in number. Sex hormones (dehydroepiandrosterone, adiponectin, leptin, oestradiol, progesterone, and testosterone) profoundly affect immunity. Compared to girls, boys have a stronger Th1 profile and increased numbers of CD8+ T cells and NK cells. Girls are more Th2-skewed and elicit more enhanced inflammatory responses. Non-immunological factors (including exposure intensity, behavior, and co-infections) may impact disease. However, given the consistent patterns seen across time and geography, these factors likely are less central. Strategies to protect children and adolescents from TB may need to differ by age and sex. Further work is required to better understand the contribution of age and sex to M. tuberculosis immunity

On the Antenna Beam Shape Reconstruction Using Planet Transit

The calibration of the in-flight antenna beam shape and possible beamdegradation is one of the most crucial tasks for the upcoming Planck mission. We examine several effects which could significantly influence the in-flight main beam calibration using planet transit: the problems of the variability of the Jupiter's flux, the antenna temperature and passing of the planets through the main beam. We estimate these effects on the antenna beam shape calibration and calculate the limits on the main beam and far sidelobe measurements, using observations of Jupiter and Saturn. We also discuss possible effects of degradation of the mirror surfaces and specify corresponding parameters which can help us to determine these effects.Comment: 10 pages, 8 figure

Photoemission studies of Ga1−x_{1-x}Mnx_{x}As: Mn-concentration dependent properties

Using angle-resolved photoemission, we have investigated the development of the electronic structure and the Fermi level pinnning in Ga$_{1-x}$Mn$_{x}$As with Mn concentrations in the range 1--6%. We find that the Mn-induced changes in the valence-band spectra depend strongly on the Mn concentration, suggesting that the interaction between the Mn ions is more complex than assumed in earlier studies. The relative position of the Fermi level is also found to be concentration-dependent. In particular we find that for concentrations around 3.5--5% it is located very close to the valence-band maximum, which is in the range where metallic conductivity has been reported in earlier studies. For concentration outside this range, larger as well as smaller, the Fermi level is found to be pinned at about 0.15 eV higher energy.Comment: REVTeX style; 7 pages, 3 figure