162 research outputs found
Revealing the structure of the outer disks of Be stars
Context. The structure of the inner parts of Be star disks (20 stellar radii)
is well explained by the viscous decretion disk (VDD) model, which is able to
reproduce the observable properties of most of the objects studied so far. The
outer parts, on the ther hand, are not observationally well-explored, as they
are observable only at radio wavelengths. A steepening of the spectral slope
somewhere between infrared and radio wavelengths was reported for several Be
stars that were previously detected in the radio, but a convincing physical
explanation for this trend has not yet been provided. Aims. We test the VDD
model predictions for the extended parts of a sample of six Be disks that have
been observed in the radio to address the question of whether the observed
turndown in the spectral energy distribution (SED) can be explained in the
framework of the VDD model, including recent theoretical development for
truncated Be disks in binary systems. Methods. We combine new multi-wavelength
radio observations from the Karl. G. Jansky Very Large Array (JVLA) and Atacama
Pathfinder Experiment (APEX) with previously published radio data and archival
SED measurements at ultraviolet, visual, and infrared wavelengths. The density
structure of the disks, including their outer parts, is constrained by
radiative transfer modeling of the observed spectrum using VDD model
predictions. In the VDD model we include the presumed effects of possible tidal
influence from faint binary companions. Results. For 5 out of 6 studied stars,
the observed SED shows strong signs of SED turndown between far-IR and radio
wavelengths. A VDD model that extends to large distances closely reproduces the
observed SEDs up to far IR wavelengths, but fails to reproduce the radio SED.
... (abstract continues but did not fit here)Comment: 20 pages, 8 figure
Impairment of the catalytic activity of Escherichia coli ribonucleic acid polymerase by a unique reaction of 4-chloro-7-nitrobenzofurazan
Noncovalent and Nonspecific Molecular Interactions of Polymers with Multiwalled Carbon Nanotubes
Evolution of the capsular gene locus of Streptococcus pneumoniae serogroup 6
Streptococcus pneumoniae expressing serogroup 6 capsules frequently causes pneumococcal infections and the evolutionary origins of the serogroup 6 strains have been extensively studied. However, these studies were performed when serogroup 6 had only two known members (serotypes 6A and 6B) and before the two new members (serotypes 6C and 6D) expressing wciNβ were found. We have therefore reinvestigated the evolutionary origins of serogroup 6 by examining the profiles of the capsule gene loci and the multilocus sequence types (MLSTs) of many serogroup 6 isolates from several continents. We confirmed that there are two classes of cps locus sequences for serogroup 6 isolates. In our study, class 2 cps sequences were limited to a few serotype 6B isolates. Neighbour-joining analysis of cps sequence profiles showed a distinct clade for 6C and moderately distinct clades for class 1 6A and 6B sequences. The serotype 6D cps profile was found within the class 1 6B clade, suggesting that it was created by recombination between 6C and 6B cps loci. Interestingly, all 6C isolates also had a unique wzy allele with a 6 bp deletion. This suggests that serotype switching to 6C involves the transfer of a large (>4 kb) gene segment that includes both the wciNβ allele and the ‘short’ wzy allele. The MLST studies of serotype 6C isolates suggest that the 6C cps locus is incorporated into many different pneumococcal genomic backgrounds but that, interestingly, 6C cps may have preferentially entered strains of the same genomic backgrounds as those of serotype 6A
Microfabricated recessed disk microelectrodes: characterization in static and convective solutions
Construction and characterization of microfabricated recessed disk microelectrodes (RDMs) of 14 and 55 µm diameter are reported. Hybrid blamers were constructed by fusion of vesicles of dimyristoylphosphatidyl choline (DMPC), which forms the top layer, with ethanol-rinsed SAMs of hexadecanethiol on gold, which form the bottom layer. Gramicidin A was included in the modifying solutions to incorporate it into hybrid blamers
Multilayer microcavity devices and methods
Microcavities and micropores that are microscopic (\u3c1 \u3emm) in width and depth and contain any number of individually-addressable electrodes separated by insulators along the walls of each cavity are described. The conducting materials, and the insulator materials can be deposited alternately onto a starting substrate, which is typically an oxidized silicon wafer or polyimide film, but may be any substrate that shows good adhesion to the materials layered on it. The cavities are etched through these layers, perpendicular to the plane of the substrate, exposing the layers at their edges. Pores may be carved entirely through the device
Carbon Nanotubes with Covalently Linked Porphyrin Antennae: Photoinduced Electron Transfer
UKMenCar4: A cross-sectional survey of asymptomatic meningococcal carriage amongst UK adolescents at a period of low invasive meningococcal disease incidence.
Carriage of Neisseria meningitidis, the meningococcus, is a prerequisite for invasive meningococcal disease (IMD), a potentially devastating infection that disproportionately afflicts infants and children. Humans are the sole known reservoir for the meningococcus, and it is carried asymptomatically in the nasopharynx of ~10% of the population. Rates of carriage are dependent on age of the host and social and behavioural factors. In the UK, meningococcal carriage has been studied through large, multi-centre carriage surveys of adolescents in 1999, 2000, and 2001, demonstrating carriage can be affected by immunisation with the capsular group C meningococcal conjugate vaccine, inducing population immunity against carriage. Fifteen years after these surveys were carried out, invasive meningococcal disease incidence had declined from a peak in 1999. The UKMenCar4 study was conducted in 2014/15 to investigate rates of carriage amongst the adolescent population during a period of low disease incidence. The protocols and methodology used to perform UKMenCar4, a large carriage survey, are described here
Renal cell cancer without a renal primary
Renal cell carcinoma has been increasing in incidence over the past two decades. Men are affected more than women and metastatic disease at presentation occurs in up to one third of patients. Metastasis can occur to virtually any organ, and involvement of multiple organs is not uncommon. To date, no reports have been found of metastatic disease without a renal primary. We present a case of renal cell cancer initially presenting as a subcutaneous mass with subsequent pancreatic and parotid gland metastases in absence of a primary renal source
- …