8,059 research outputs found
The Close Binary Fraction of Dwarf M Stars
We describe a search for close spectroscopic dwarf M star binaries using data from the Sloan Digital Sky Survey to address the question of the rate of occurrence of multiplicity in M dwarfs. We use a template-fitting technique to measure radial velocities from 145,888 individual spectra obtained for a magnitude-limited sample of 39,543 M dwarfs. Typically, the three or four spectra observed for each star are separated in time by less than four hours, but for ~17% of the stars, the individual observations span more than two days. In these cases we are sensitive to large-amplitude radial velocity variations on timescales comparable to the separation between the observations. We use a control sample of objects having observations taken within a four-hour period to make an empirical estimate of the underlying radial velocity error distribution and simulate our detection efficiency for a wide range of binary star systems. We find the frequency of binaries among the dwarf M stars with a < 0.4 AU to be 3%-4%. Comparison with other samples of binary stars demonstrates that the close binary fraction, like the total binary fraction, is an increasing function of primary mass
The unusual distribution of molecular gas and star formation in Arp 140
We investigate the atomic and molecular interstellar medium and star
formation of NGC 275, the late-type spiral galaxy in Arp 140, which is
interacting with NGC 274, an early-type system. The atomic gas (HI)
observations reveal a tidal tail from NGC 275 which extends many optical radii
beyond the interacting pair. The HI morphology implies a prograde encounter
between the galaxy pair approximately 1.5 x 10**8 years ago. The Halpha
emission from NGC 275 indicates clumpy irregular star-formation, clumpiness
which is mirrored by the underlying mass distribution as traced by the Ks-band
emission. The molecular gas distribution is striking in its anti-correlation
with the {HII regions. Despite the evolved nature of NGC 275's interaction and
its barred potential, neither the molecular gas nor the star formation are
centrally concentrated. We suggest that this structure results from stochastic
star formation leading to preferential consumption of the gas in certain
regions of the galaxy. In contrast to the often assumed picture of interacting
galaxies, NGC 275, which appears to be close to merger, does not display
enhanced or centrally concentrated star formation. If the eventual merger is to
lead to a significant burst of star formation it must be preceded by a
significant conversion of atomic to molecular gas as at the current rate of
star formation all the molecular gas will be exhausted by the time the merger
is complete.Comment: 13 paper, accepted my Monthly Notices of the Royal Astronomical
Societ
Natural Populations of Woodchuck Hepatitis Virus Contain Variant Precore and Core Sequences Including a Premature Stop Codon in the Epsilon Motif
We have determined a consensus sequence and the type and the frequency of spontaneous sequence variations in the woodchuck hepatitis virus (WHV) precore gene and the 5' region of the core gene in 101 serum samples from 53 naturally WHV-infected woodchucks by polymerase chain reaction sequencing. Twenty of the 53 woodchucks were found to have variant sequences. Ten patterns of variant sequences were identified in these 20 animals. WHV sequences from 4 woodchucks had 1 nucleotide change, 3 had 2 nucleotide changes and 3 had 3 nucleotide changes. The nucleotide changes were not randomly distributed, but were limited to only 8 sites. Four sites were in the epsilon motif of the precore gene and four were in the 5' region of the core gene. Sixteen of the 53 (30%) woodchucks had precore sequence variants. All altered sites were analogous to previously described mutations in hepatitis B virus. There was a nucleotide change at nucleotide 2016 in codon 29 of the precore region that produced a stop codon in 4 animals. This site is analogous to a common hepatitis B virus e antigen mutation. The sequence from the initial blood samples from 3 of 4 animals with this stop codon producing variant appeared to be the consensus sequence; however, in later samples the variant occurred as a mixed infection with the consensus sequence. The mixed infections were chronic and the proportion of the variant sequence was maintained or increased in the course of infection. In the fourth animal only the variant was found and it persisted for over 14 months of infection. WHV appears to be a valuable model for the study of the structure and function of the hepadnavirus precore region
Management preferences in stage I non-seminomatous germ cell tumours of the testis: an investigation among patients, controls and oncologists.
Increasingly, treatment choices leading to the same survival outcome can be offered to cancer patients (e.g. mastectomy or conservative surgery in early breast cancer). Two approaches available for post-orchidectomy, stage I patients with non-seminomatous germ cell tumours of the testis (NSGCTT), particularly those at high risk of relapse, include immediate adjuvant chemotherapy (two courses) or surveillance, with chemotherapy (typically four courses) given only on relapse. The aim of this study was to investigate which approach patients prefer. Questionnaires were given to newly diagnosed NSGCTT patients, to patients with previous experience of the two options and to non-cancer controls, including specialist testicular tumour oncologists. Participants were asked to choose between immediate chemotherapy, surveillance or for the doctor to decide, at recurrence risk levels ranging from 10% to 90%. Questionnaires were returned by 207 subjects in nine different groups. The risk thresholds at which subjects' management preference changed, within apparently homogeneous groups, varied greatly, although at least one subject in each group selected adjuvant chemotherapy at the lowest (10%) level of risk. Subjects tended to favour options of which they had previous experience. Cancer patients wanted the doctor to decide more frequently than controls. The wide variability observed makes it difficult to predict which option an individual will select. Personality factors and personal circumstances, other than specific experience and knowledge, are obviously influential. Many patients would prefer their doctor to decide, but variability among oncologists is as great as that among their patients
Industry 4.0 â LabVIEW Based Industrial IoT Condition Monitoring System
As a result of a substantial shift in focus towards a more digital industry, multiple sectors of industry are now realising the potential of Industry 4.0 and Internet of Things (IoT) technology. The manufacturing industry in particular is subject to unexpected machine downtime from component wear over an extended period. With Industrial IoT (IIoT) technology implemented, there is the potential for gathering large quantities of data, which can be used for preventative maintenance. This research article addresses some of the technological requirements for developing an IoT industrial condition monitoring network, whose composition makes use of wireless devices along with conventional wired methods to enable a series of data capture and control operations in amongst a network of nodes. To provide a platform to host these operations, the industry standard fieldbus protocol Modbus TCP was used in conjunction with the LabVIEW development environment, where a bespoke graphical user interface was developed to provide control and a visual representation of the data collected. In addition, one of the nodes acted as the output for hardware displays, which in turn correlated the alarm status of the user interface. By using industry standard communication protocols, it was also possible to enable connectivity between real industry hardware, further extending the capabilities of the system
Spontaneous time reversal symmetry breaking in the pseudogap state of high-Tc superconductors
When matter undergoes a phase transition from one state to another, usually a
change in symmetry is observed, as some of the symmetries exhibited are said to
be spontaneously broken. The superconducting phase transition in the underdoped
high-Tc superconductors is rather unusual, in that it is not a mean-field
transition as other superconducting transitions are. Instead, it is observed
that a pseudo-gap in the electronic excitation spectrum appears at temperatures
T* higher than Tc, while phase coherence, and superconductivity, are
established at Tc (Refs. 1, 2). One would then wish to understand if T* is just
a crossover, controlled by fluctuations in order which will set in at the lower
Tc (Refs. 3, 4), or whether some symmetry is spontaneously broken at T* (Refs.
5-10). Here, using angle-resolved photoemission with circularly polarized
light, we find that, in the pseudogap state, left-circularly polarized photons
give a different photocurrent than right-circularly polarized photons, and
therefore the state below T* is rather unusual, in that it breaks time reversal
symmetry11. This observation of a phase transition at T* provides the answer to
a major mystery of the phase diagram of the cuprates. The appearance of the
anomalies below T* must be related to the order parameter that sets in at this
characteristic temperature .Comment: 11 pages, 4 figure
Successful ageing in an area of deprivation: Part 1âA qualitative exploration of the role of life experiences in good health in old age
Objectives: To determine the life histories and current circumstances of healthy and unhealthy older people who share an ecology marked by relative deprivation and generally poor health.
Study design: In-depth interview study with a qualitative analysis.
Methods: Matched pairs of healthy and unhealthy âagersâ were interviewed face-to-face. Healthy ageing was assessed in terms of hospital morbidity and self-reported health. Study participants consisted of 22 pairs (44 individuals), aged 72â89 years, matched for sex, age and deprivation category, and currently resident in the West of Scotland. All study participants were survivors of the Paisley/Renfrew (MIDSPAN) survey, a longitudinal study commenced in 1972 with continuous recording of morbidity and mortality since.
Detailed life histories were obtained which focused on family, residence, employment, leisure and health. This information was supplemented by more focused data on âcritical incidentsâ, financial situation and position in social hierarchies.
Results: Data provided rich insights into life histories and current circumstances but no differences were found between healthy and unhealthy agers.
Conclusions: It is important to understand what differentiates individuals who have lived in circumstances characterized by relative deprivation and poor health, yet have aged healthily. This study collected rich and detailed qualitative data. Yet, no important differences were detected between healthy and unhealthy agers. This is an important negative result as it suggests that the phenomenon of healthy ageing and the factors that promote healthy ageing over a lifetime are so complex that they will require even more detailed studies to disentangle
- âŠ