Vacuum-UV spectroscopy of interstellar ice analogs. II. Absorption cross-sections of nonpolar ice molecules

Dust grains in cold circumstellar regions and dark-cloud interiors at 10-20 K are covered by ice mantles. A nonthermal desorption mechanism is invoked to explain the presence of gas-phase molecules in these environments, such as the photodesorption induced by irradiation of ice due to secondary ultraviolet photons. To quantify the effects of ice photoprocessing, an estimate of the photon absorption in ice mantles is required. In a recent work, we reported the vacuum-ultraviolet (VUV) absorption cross sections of nonpolar molecules in the solid phase. The aim was to estimate the VUV-absorption cross sections of nonpolar molecular ice components, including CH4, CO2, N2, and O2. The column densities of the ice samples deposited at 8 K were measured in situ by infrared spectroscopy in transmittance. VUV spectra of the ice samples were collected in the 120-160 nm (10.33-7.74 eV) range using a commercial microwave-discharged hydrogen flow lamp. We found that, as expected, solid N2 has the lowest VUV-absorption cross section, which about three orders of magnitude lower than that of other species such as O2, which is also homonuclear. Methane (CH4) ice presents a high absorption near Ly-alpha (121.6 nm) and does not absorb below 148 nm. Estimating the ice absorption cross sections is essential for models of ice photoprocessing and allows estimating the ice photodesorption rates as the number of photodesorbed molecules per absorbed photon in the ice.Comment: 9 pages, 6 figures, 7 table

Larkin-Ovchinnikov-Fulde-Ferrell phase in the superconductor (TMTSF)2ClO4: Theory versus experiment

We consider a formation of the Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase in a quasi-one-dimensional (Q1D) conductor in a magnetic field, parallel to its conducting chains, where we take into account both the paramagnetic spin-splitting and orbital destructive effects against superconductivity. We show that, due to a relative weakness of the orbital effects in a Q1D case, the LOFF phase appears in (TMTSF)$_2$ClO$_4$ superconductor for real values of its Q1D band parameters. We compare our theoretical calculations with the recent experimental data by Y. Maeno's group [S. Yonezawa et al., Phys. Rev. Lett. \textbf{100}, 117002 (2008)] and show that there is a good qualitative and quantitative agreement between the theory and experimental data.Comment: 4 pages, 1 figur

Experimental verification of strong rotational dependence of fluorescence and predissociation yield in the b ¹Πᵤ(v = 1) level of ¹⁴N₂

New, rotationally resolved fluorescence-excitation spectra confirm coupled-channel Schrödinger-equation predictions of strong rotational dependence of the fluorescence and predissociation yields in the b(v = 1) level of ¹⁴N₂.This work was supported by the National Science Foundation grant AST-0906158 and the Australian Research Council grants DP0558962, DP0773050, and LX0882438

The Cerenkov effect revisited: from swimming ducks to zero modes in gravitational analogs

We present an interdisciplinary review of the generalized Cerenkov emission of radiation from uniformly moving sources in the different contexts of classical electromagnetism, superfluid hydrodynamics, and classical hydrodynamics. The details of each specific physical systems enter our theory via the dispersion law of the excitations. A geometrical recipe to obtain the emission patterns in both real and wavevector space from the geometrical shape of the dispersion law is discussed and applied to a number of cases of current experimental interest. Some consequences of these emission processes onto the stability of condensed-matter analogs of gravitational systems are finally illustrated.Comment: Lecture Notes at the IX SIGRAV School on "Analogue Gravity" in Como, Italy from May 16th-21th, 201

Antimatter from the cosmological baryogenesis and the anisotropies and polarization of the CMB radiation

We discuss the hypotheses that cosmological baryon asymmetry and entropy were produced in the early Universe by phase transition of the scalar fields in the framework of spontaneous baryogenesis scenario. We show that annihilation of the matter-antimatter clouds during the cosmological hydrogen recombination could distort of the CMB anisotropies and polarization by delay of the recombination. After recombination the annihilation of the antibaryonic clouds (ABC) and baryonic matter can produce peak-like reionization at the high redshifts before formation of quasars and early galaxy formation. We discuss the constraints on the parameters of spontaneous baryogenesis scenario by the recent WMAP CMB anisotropy and polarization data and on possible manifestation of the antimatter clouds in the upcoming PLANCK data.Comment: PRD in press with minor change

Some exact and numerical results for plane steady sheared flow of an incompressible inviscid fluid

Analytical and numerical solutions are presented for the steady flow of an inviscid fluid about symmetric lifting profiles at an angle of attack in a plane sheared onset flow for which conformal mapping plays a critical role. For uniform shear (i.e. the onset flow speed varies linearly with position) in two dimensions, the disturbance field is potential and hence a solution based on the conformal transformation technique may be constructed. The Moriya transformation, which employs a leading-term transformation coefficient that stretches and rotates the field at great distances from the foil (as distinct from other classical transformations which leave the far field unchanged) is used and, with a limited number of terms selected for the transformation, a simple elegant solution is obtained that may be easily evaluated at arbitrary points on the foil contour. An additional investigation is reported for the field solution -- involving a locally similar but globally non-uniform sheared onset flow -- about one of the foils for which a simple O-type grid is analytically generated from the mapping function. These data indicate that the uniform-shear solution overpredicts the lift and surface speed on the suction side of the foil relative to the more realistic onset flow: the numerical solution predicts surface speeds that generally lie between those for the uniform flow and the uniformly sheared flow solutions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29989/1/0000356.pd

Decrease in seroprevalence of Hepatitis A after the implementation of nationwide disposable tableware use in Taiwan

<p>Abstract</p> <p>Background</p> <p>Taiwan is an endemic area of viral hepatitis, including hepatitis A, which is transmitted mainly from the fecal-oral route. In order to reduce the transmission through food intake, the government implemented a policy of nationwide disposal tableware use in public eating places in 1982. We conducted a study to estimate the seroprevalence of Hepatitis A in a group of workers in Taiwan in 2005, determine the risk factors, and compare seroprevalence to published estimates in Taiwan to evaluate changes in the seroprevalence after the implementation of the nationwide disposal tableware use.</p> <p>Methods</p> <p>We recruited workers of an industrial park during their annual health examinations in 2005 and measured their anti-hepatitis A virus IgG titer using microparticle enzyme immunoassay. We compared the seroprevalence across different birth cohorts within the study population and also analyzed data from previous studies.</p> <p>Results</p> <p>The overall sero-positive rate was 22.0% in the 11,777 participants. The rate was much lower among those who were covered by the program since birth (born after 1982) in comparison with those who were not (2.7% vs. 25.3%, p < 0.001). From the analyses of data from pervious studies, we found the age-specific rates were similar in cohorts born in or after 1982 across studies conducted in different time periods but decreased with the calendar year in cohorts born before 1982. In particular, the age-specific seroprevalence dropped to less than one third in a three-year period among those who were born around 1982.</p> <p>Conclusions</p> <p>Data from both the current and previous studies in different time periods supported the effectiveness of disposal tableware in preventing the transmission of hepatitis A.</p

Using Web Search Query Data to Monitor Dengue Epidemics: A New Model for Neglected Tropical Disease Surveillance

A variety of obstacles, including bureaucracy and lack of resources, delay detection and reporting of dengue and exist in many countries where the disease is a major public health threat. Surveillance efforts have turned to modern data sources such as Internet usage data. People often seek health-related information online and it has been found that the frequency of, for example, influenza-related web searches as a whole rises as the number of people sick with influenza rises. Tools have been developed to help track influenza epidemics by finding patterns in certain web search activity. However, few have evaluated whether this approach would also be effective for other diseases, especially those that affect many people, that have severe consequences, or for which there is no vaccine. In this study, we found that aggregated, anonymized Google search query data were also capable of tracking dengue activity in Bolivia, Brazil, India, Indonesia and Singapore. Whereas traditional dengue data from official sources are often not available until after a long delay, web search query data is available for analysis within a day. Therefore, because it could potentially provide earlier warnings, these data represent a valuable complement to traditional dengue surveillance

Scanned Probe Oxidation onp-GaAs(100) Surface with an Atomic Force Microscopy

Locally anodic oxidation has been performed to fabricate the nanoscale oxide structures onp-GaAs(100) surface, by using an atomic force microscopy (AFM) with the conventional and carbon nanotube (CNT)-attached probes. The results can be utilized to fabricate the oxide nanodots under ambient conditions in noncontact mode. To investigate the conversion of GaAs to oxides, micro-Auger analysis was employed to analyze the chemical compositions. The growth kinetics and the associated mechanism of the oxide nanodots were studied under DC voltages. With the CNT-attached probe the initial growth rate of oxide nanodots is in the order of ~300 nm/s, which is ~15 times larger than that obtained by using the conventional one. The oxide nanodots cease to grow practically as the electric field strength is reduced to the threshold value of ~2 × 107 V cm−1. In addition, results indicate that the height of oxide nanodots is significantly enhanced with an AC voltage for both types of probes. The influence of the AC voltages on controlling the dynamics of the AFM-induced nanooxidation is discussed