1,912 research outputs found
An Extinction Study of the Taurus Dark Cloud Complex
We present a study of the detailed distribution of extinction in a region of
the Taurus dark cloud complex. Our study uses new BVR images of the region,
spectral classification data for 95 stars, and IRAS Sky Survey Atlas (ISSA) 60
and 100 micron images. We study the extinction of the region in four different
ways, and we present the first inter-comparison of all these methods, which
are: 1) using the color excess of background stars for which spectral types are
known; 2) using the ISSA 60 and 100 micron images; 3) using star counts; and 4)
using an optical (V and R) version of the average color excess method used by
Lada et al. (1994). We find that all four methods give generally similar
results, with important exceptions. To study the structure in the dust
distribution, we compare the ISSA extinction and the extinction measured for
individual stars. From the comparison, we conclude that in the relatively low
extinction regions studied, with 0.9 < A_V < 3.0 mag (away from filamentary
dark clouds and IRAS cores), there are no fluctuations in the dust column
density greater than 45% (at the 99.7% confidence level), on scales smaller
than 0.2 pc. We also report the discovery of a previously unknown stellar
cluster behind the Taurus dark cloud near R.A 4h19m00s, Dec. 27:30:00 (B1950)Comment: 49 pages (which include 6 pages of tables and 6 pages of figures
Sperm mobility: mechanisms of fertilizing efficiency, genetic variation and phenotypic relationship with male status in the domestic fowl, Gallus gallus domesticus
When females are sexually promiscuous, sexual selection continues after insemination through sperm
competition and cryptic female choice, and male traits conveying an advantage in competitive fertilization
are selected for. Although individual male and ejaculate traits are known to influence paternity in a competitive
scenario, multiple mechanisms co-occur and interact to determine paternity. The way in which
different traits interact with each other and the mechanisms through which their heritability is maintained
despite selection remain unresolved. In the promiscuous fowl, paternity is determined by the number of
sperm inseminated into a female, which is mediated by male social dominance, and by the quality of the
sperm inseminated, measured as sperm mobility. Here we show that: (i) the number of sperm inseminated
determines how many sperm reach the female sperm-storage sites, and that sperm mobility mediates the
fertilizing efficiency of inseminated sperm, mainly by determining the rate at which sperm are released
from the female storage sites, (ii) like social status, sperm mobility is heritable, and (iii) subdominant
males are significantly more likely to have higher sperm mobility than dominant males. This study indicates
that although the functions of social status and sperm mobility are highly interdependent, the lack of
phenotypic integration of these traits may maintain the variability of male fitness and heritability of fertilizing
efficiency
Dual Requirement for Yeast hnRNP Nab2p in mRNA poly(A) Tail Length Control and Nuclear Export
Recent studies of mRNA export factors have provided additional evidence for a mechanistic link between mRNA 3âČâend formation and nuclear export. Here, we identify Nab2p as a nuclear poly(A)âbinding protein required for both poly(A) tail length control and nuclear export of mRNA. Loss of NAB2 expression leads to hyperadenylation and nuclear accumulation of poly(A)+ RNA but, in contrast to mRNA export mutants, these defects can be uncoupled in a nab2 mutant strain. Previous studies have implicated the cytoplasmic poly(A) tailâbinding protein Pab1p in poly(A) tail length control during polyadenylation. Although cells are viable in the absence of NAB2 expression when PAB1 is overexpressed, Pab1p fails to resolve the nab2Î hyperadenylation defect even when Pab1p is tagged with a nuclear localization sequence and targeted to the nucleus. These results indicate that Nab2p is essential for poly(A) tail length control in vivo, and we demonstrate that Nab2p activates polyadenylation, while inhibiting hyperadenylation, in the absence of Pab1p in vitro. We propose that Nab2p provides an important link between the termination of mRNA polyadenylation and nuclear export
Cortical mapping with navigated transcranial magnetic stimulation in low-grade glioma surgery
Transcranial magnetic stimulation (TMS) is a promising method for both investigation and therapeutic treatment of psychiatric and neurologic disorders and, more recently, for brain mapping. This study describes the application of navigated TMS for motor cortex mapping in patients with a brain tumor located close to the precentral gyrus
Generalized Electromagnetic fields in Chiral Medium
The time dependent Dirac-Maxwell's Equations in presence of electric and
magnetic sources are written in chiral media and the solutions for the
classical problem are obtained in unique simple and consistent manner. The
quaternion reformulation of generalized electromagnetic fields in chiral media
has also been developed in compact, simple and consistent manner
Modelling of the radiative properties of an opaque porous ceramic layer
Solid Oxide Fuel Cells (SOFCs) operate at temperatures above 1,100 K where radiation effects can be significant. Therefore, an accurate thermal model of an SOFC requires the inclusion of the contribution of thermal radiation. This implies that the thermal radiative properties of the oxide ceramics used in the design of SOFCs must be known. However, little information can be found in the literature concerning their operating temperatures. On the other hand, several types of ceramics with different chemical compositions and microstructures for designing efficient cells are now being tested. This is a situation where the use of a numerical tool making possible the prediction of the thermal radiative properties of SOFC materials, whatever their chemical composition and microstructure are, may be a decisive help. Using this method, first attempts to predict the radiative properties of a lanthanum nickelate porous layer deposited onto an yttria stabilized zirconium substrate can be reported
Quaternionic and Octonionic Spinors. A Classification
Quaternionic and octonionic realizations of Clifford algebras and spinors are
classified and explicitly constructed in terms of recursive formulas. The most
general free dynamics in arbitrary signature space-times for both quaternionic
and octonionic spinors is presented. In the octonionic case we further provide
a systematic list of results and tables expressing, e.g., the relations of the
octonionic Clifford algebras with the cosets over the Lorentz algebras,
the identities satisfied by the higher-rank antisymmetric octonionic tensors
and so on. Applications of these results range from the classification of
octonionic generalized supersymmetries, the construction of octonionic
superstrings, as well as the investigations concerning the recently discovered
octonionic -superalgebra and its superconformal extension.Comment: 24 pages, LaTe
Effectiveness of The Wikipedia Collaboration of Dental Schools' Training Programme:a new Paradigm for Teaching and Learning of Evidence-Based Dentistry
BASCD-Borrow Foundation Early Career Poster Award Winning Entry 2019 Background: The Wikipedia Collaboration of Dental Schools (WCODS) is a student-led initiative that aims to publish high quality scientific, evidence-based dental content on the Wikipedia online encyclopaedia by equipping its members to use research, critical appraisal and writing skills to create accurate content. In 2019, the Collaboration launched a standardised training programme developed by Wikimediatrained committee members, academic dental school staff and the Cochrane Oral Health global community. Objective: To evaluate the effectiveness of this training programme in ensuring WCODS editors follow the processes underpinning Evidence-Based Dentistry (EBD). Method: A cohort of dental students and staff (n=136) from six dental schools in the UK and Malaysia took part in a standardised and structured training programme at the annual WCODS training meeting. Participantsâ abilities and their perceived levels of confidence in carrying out critical analysis of the literature were measured using pre- and post-training surveys, and competency assessments. Results: Participantsâ skills in conducting literature searches, critical appraisal of the findings and creating and editing a Wikipedia page improved after training. Conclusion: The training programme provided participants with the skill set and confidence to apply best practice to create and edit Wikipedia entries. This Collaboration intends to recruit more contributors to improve global oral health literacy using the free online Wikipedia encyclopaedia. Keywords: Wikipedia, Evidence-Based Dentistry, Curriculum, Dental Students, Dentistry, Training Programm
Cosmology, Oscillating Physics and Oscilllating Biology
According to recent reports there is an excess correlation and an apparent
regularity in the galaxy one-dimensional polar distribution with a
characteristic scale of 128 Mpc. This aparent spatial periodicity can
be naturally explained by a time oscillation of the gravitational constant .
On the other hand, periodic growth features of bivalve and coral fossiles
appear to show a periodic component in the time dependence of the number of
days per year. In this letter we show that a time oscillating gravitational
constant with similar period and amplitude can explain such a feature.Comment: 9 pages. latex using revtex. This revised version is supposed to be
free of e-mail nois
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