Modeling the interstellar aromatic infrared bands with co-added spectra of PAHs

The observed variations in profiles of the interstellar aromatic infrared bands correlate with the object type and are indicative of PAH populations existing i n different sources. Spectroscopic studies on PAHs can provide tools for the int erpretation of variations accompanying the AIBs. As the observed spectra results from a mix of possible species in the region attempt is made to model this comp osite spectra by co-adding emissions from PAHs in different size groups. Theoretical IR data of PAHs having 10 to 96 carbon atoms is used to obtain emis sion spectra. The models are taken in size groups making up of small, medium and large PAHs. The models show good profile match with observations for the 7.7 $\mu m$ complex having sub-features at 7.6 and 7.8 $\mu m$. The 7.6 $\mu m$ sub-feature dominates in the spectra of medium sized PAH cations matching observations from UV rich interstellar environments. The 7.8 $\mu m$ component is more intense in the spectra of large PAH cations (model III) correlating with observations from benign astrophysical regions. A possible interpretation for the observations of $C-H$ out-of-plane bend modes and the weak outliers on the blue side of the intense 11.2 $\mu m$ band is proposed. The models provide pointers to possible PAH populations in different regions.Comment: accepted for publication in A&

1-[2-(2,6-Dichloro­benz­yloxy)-2-(2-fur­yl)eth­yl]-1H-benzimidazole

In the mol­ecule of the title compound, C20H16Cl2N2O2, the planar benzimidazole ring system is oriented with respect to the furan and dichloro­benzene rings at dihedral angles of 53.39 (6) and 31.04 (5)°, respectively. In the crystal structure, inter­molecular C—H⋯Cl hydrogen bonds link the mol­ecules into centrosymmetric R 2 2(8) dimers. These dimers are connected via a C—H⋯π contact between the benzimidazole and the furan rings, and π–π contacts between the benz­imidazole and dichloro­benzene ring systems [centroid–centroid distances = 3.505 (1), 3.567 (1), 3.505 (1) and 3.567 (1) Å]

1-{2-Phenyl-2-[4-(trifluoro­meth­yl)­benzyl­oxy]eth­yl}-1H-benzimidazole

The asymmetric unit of the crystal structure of the title compound, C23H19F3N2O, contains two independent mol­ecules. In the two mol­ecules the planar benzimidazole ring systems are oriented with respect to the phen­yl/trifluoro­methyl­benzene rings at dihedral angles of 9.62 (6)/78.63 (7) and 2.53 (8)/83.83 (9)°. In the crystal structure, inter­molecular C—H⋯N hydrogen bonds link the mol­ecules into R 2 2(6) dimers. The mol­ecules are elongated along [001] and stacked along the b axis

1-[2-(3,4-Dichloro­benz­yloxy)-2-phenyl­ethyl]-1H-benzimidazole

In the mol­ecule of the title compound, C22H18Cl2N2O, the planar benzimidazole ring system is oriented with respect to the phenyl and dichloro­benzene rings at dihedral angles of 12.73 (3) and 36.57 (4)°, respectively. The dihedral angle between the dichloro­benzene and phenyl rings is 29.95 (6)°. There are C—H⋯π contacts between the benzimidazole and dichloro­benzene rings, between the benzimidazole and phenyl rings, and between a methylene group and the dichlorobenzene ring

Reduced capacity of antibodies from patients infected with human immunodeficiency virus type 1 (HIV-1) group O to neutralize primary isolates of HIV-1 group M viruses

Neutralizing antibody patterns in sera of persons infected with human immunodeficiency virus type 1 (HIV-1) groups M and a to their homologous and heterologous primary isolates were determined in a peripheral blood mononuclear cell-based neutralization assay and correlated with their ability to bind to V3 loop synthetic peptides. Most HIV-1 group M sera (9/16) neutralized HIV-1 group a viruses, whereas fewer group a sera (3/13) only weakly neutralized HIV-1 group M viruses. Group M sera neutralizing HIV-1 group a viruses neutralized other HIV-1 group M viruses with titers of 1:10-1:1280. V3 loop binding capacity of sera did not reflect their neutralizing capacity of the homologous isolate. Despite the reduced neutralizing capacity of group a-infected patients ' sera to group M viruses, some group M- infected patients ' sera neutralized both HIV-1 group M and a isolates, suggesting that they share some conserved neutralizing epitopes. Nucleic acid sequence analysis of the envelope gene of hu-man immunodeficiency virus type 1 (HIV-1) isolates has thus far distinguished at least 8 subtypes, A-H [1-3], which to-gether are referred to as HIV-1 group M (for major). However, the relevance of these genetic subtypes in terms of neutraliza

Sedimentary DNA from a submerged site reveals wheat in the British Isles 8000 years ago

YesThe Mesolithic-to-Neolithic transition marked the time when a hunter-gatherer economy gave way to agriculture, coinciding with rising sea levels. Bouldnor Cliff, is a submarine archaeological site off the Isle of Wight in the United Kingdom that has a well-preserved Mesolithic paleosol dated to 8000 years before the present. We analyzed a core obtained from sealed sediments, combining evidence from microgeomorphology and microfossils with sedimentary ancient DNA (sedaDNA) analyses to reconstruct floral and faunal changes during the occupation of this site, before it was submerged. In agreement with palynological analyses, the sedaDNA sequences suggest a mixed habitat of oak forest and herbaceous plants. However, they also provide evidence of wheat 2000 years earlier than mainland Britain and 400 years earlier than proximate European sites. These results suggest that sophisticated social networks linked the Neolithic front in southern Europe to the Mesolithic peoples of northern Europe

Direct detection of a flared disk around a young massive star HD200775 and its 10 to 1000AU scale properties

We made mid-infrared observations of the 10Msun Herbig Be star HD200775 with the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the 8.2m Subaru Telescope. We discovered diffuse emission of an elliptical shape extended in the north-south direction inabout 1000AU radius around unresolved excess emission. The diffuse emission is perpendicular to the cavity wall formed by the past outflow activity and is parallel to the projected major axis of the central close binary orbit. The centers of the ellipse contours of the diffuse emission are shifted from the stellar position and the amount of the shift increases as the contour brightness level decreases. The diffuse emission is well explained in all of geometry, size, and configuration by an inclined flared disk where only its surface emits the mid-infrared photons. Our results give the first well-resolved infrared disk images around a massive star and strongly support that HD200775 is formed through the disk accretion. The disk survives the main accretion phase and shows a structure similar to that around lower-mass stars with 'disk atmosphere'. At the same time, the disk also shows properties characteristic to massive stars such as photoevaporation traced by the 3.4mm free-free emission and unusual silicate emission with a peak at 9.2micron, which is shorter than that of many astronomical objects. It provides a good place to compare the disk properties between massive and lower-mass stars.Comment: 18 pages, 8 figures, accepted by The Astrophysical Journa

Theory of Magneto--Acoustic Transport in Modulated Quantum Hall Systems Near ν=1/2\nu=1/2

Motivated by the experimental results of Willett et al [Phys.Rev. Lett., {\bf 78}, 4478 (1997)] we develop a magneto-transport theory for the response of a two dimensional electron gas (2DEG) in the Fractional Quantum Hall Regime near Landau level filling factor $\nu = 1/2$ to the surface acoustic wave (SAW) in the presence of an added periodic density modulation. We assume there exists a Composite Fermion Fermi Surface (CF-FS) at $\nu = 1/2$, and we show that the deformation of the (CF-FS) due to the density modulation can be at the origin of the observed transport anomalies for the experimental conditions. Our analysis is carried out particularly for the non-local case which corresponds to the SAW experiments. We introduce a new model of a deformed CF-FS. The model permits us to explain anomalous features of the response of the modulated 2DEG to the SAW near $\nu = 1/2:$ namely the nonlinear wave vector dependence of the electron conductivity, the appearance of peaks in the SAW velocity shift and attenuation and the anisotropy of the effect, all of which originate from contributions to the conductivity tensor due to the regions of the CF-FS which are flattened by the applied modulation.Comment: 13 pages, 4 figures, the published versio