3,539 research outputs found
Interaction Effect of Social Isolation and High Dose Corticosteroid on Neurogenesis and Emotional Behavior
published_or_final_versio
Photoinduced Dehydrogenation of Defects in Undoped a-Si:H Using Positron Annihilation Spectroscopy
We report changes in variable-energy positron annihilation spectroscopy measurements on undoped hydrogenated amorphous silicon films after light soaking. The change, seen predominantly in the high momentum band of the annihilation radiation, is not reversed by thermal annealing. We suggest, following recent models of the Staebler-Wronski effect, that light exposure induces hydrogen trapped in vacancylikc detects to become mobile in the Si network. The observations place constraints on models of hydrogen motion fitting macroscopic Staebler-Wronski effect kinetics and may help to achieve a definitive description of metastability in a-Si:H.published_or_final_versio
New Experimental Limits on Macroscopic Forces Below 100 Microns
Results of an experimental search for new macroscopic forces with Yukawa
range between 5 and 500 microns are presented. The experiment uses 1 kHz
mechanical oscillators as test masses with a stiff conducting shield between
them to suppress backgrounds. No signal is observed above the instrumental
thermal noise after 22 hours of integration time. These results provide the
strongest limits to date between 10 and 100 microns, improve on previous limits
by as much as three orders of magnitude, and rule out half of the remaining
parameter space for predictions of string-inspired models with low-energy
supersymmetry breaking. New forces of four times gravitational strength or
greater are excluded at the 95% confidence level for interaction ranges between
200 and 500 microns.Comment: 25 Pages, 7 Figures: Minor Correction
Dendritic Spine Shape Analysis: A Clustering Perspective
Functional properties of neurons are strongly coupled with their morphology.
Changes in neuronal activity alter morphological characteristics of dendritic
spines. First step towards understanding the structure-function relationship is
to group spines into main spine classes reported in the literature. Shape
analysis of dendritic spines can help neuroscientists understand the underlying
relationships. Due to unavailability of reliable automated tools, this analysis
is currently performed manually which is a time-intensive and subjective task.
Several studies on spine shape classification have been reported in the
literature, however, there is an on-going debate on whether distinct spine
shape classes exist or whether spines should be modeled through a continuum of
shape variations. Another challenge is the subjectivity and bias that is
introduced due to the supervised nature of classification approaches. In this
paper, we aim to address these issues by presenting a clustering perspective.
In this context, clustering may serve both confirmation of known patterns and
discovery of new ones. We perform cluster analysis on two-photon microscopic
images of spines using morphological, shape, and appearance based features and
gain insights into the spine shape analysis problem. We use histogram of
oriented gradients (HOG), disjunctive normal shape models (DNSM), morphological
features, and intensity profile based features for cluster analysis. We use
x-means to perform cluster analysis that selects the number of clusters
automatically using the Bayesian information criterion (BIC). For all features,
this analysis produces 4 clusters and we observe the formation of at least one
cluster consisting of spines which are difficult to be assigned to a known
class. This observation supports the argument of intermediate shape types.Comment: Accepted for BioImageComputing workshop at ECCV 201
Interface characterisation and internal electric field evaluation of a-Si:H pin solar cell by variable energy positron annhilation spectroscopy
Symposium Theme: Amorphous and microcrystalline silicon technologyBy means of the slow positron beam Doppler-broadening technique, the depth profile of microvoids across a p-i-n double junction solar cell has been resolved. VEPFIT fitting results indicate an approximately uniform density of the defects throughout the solar cell, but with an enhanced concentration at all of the interfaces possibly due to network mismatch. In order to evaluate the internal electric field, Variable Energy Positron Annihilation Spectroscopy (VEPAS) measurements have been performed on a single junction pin solar cell at different biases. The internal electric field effect on positrons has also been examined in terms of the bias dependence of positron drift in a-Si:H single junction pin solar cell.published_or_final_versio
Identification of vacancy-like defects in high-rate grown a-Si before and after ligh soaking by vepas
Symposium Theme: Amorphous and microcrystalline silicon technologyWe show how positron annihilation can distinguish vacancies in undoped hydrogenated amorphous silicon by performing Variable Energy Positron Annihilation Spectroscopy experiments before and after light soaking. We find that vacancy clusters, di-vacancies and a new type of single vacancies are created in undoped as-grown a-Si:H thin film by light illumination. The fact that the vacancy clusters are eliminated by the thermal annealing suggests that the Staebler-Wronski effect is closely related to vacancy clusters in a-Si:H material. The creation of vacancy clusters and redistribution of di-vacancies and even single vacancies probably result in photo-induced structural changes in this material.published_or_final_versio
Formation of Complex and Unstable Chromosomal Translocations in Yeast
Genome instability, associated with chromosome breakage syndromes and most human
cancers, is still poorly understood. In the yeast Saccharomyces
cerevisiae, numerous genes with roles in the preservation of genome
integrity have been identified. DNA-damage-checkpoint-deficient yeast cells that
lack Sgs1, a RecQ-like DNA helicase related to the human
Bloom's-syndrome-associated helicase BLM, show an increased rate of
genome instability, and we have previously shown that they accumulate recurring
chromosomal translocations between three similar genes, CAN1,
LYP1 and ALP1. Here, the chromosomal
location, copy number and sequence similarity of the translocation targets
ALP1 and LYP1 were altered to gain insight
into the formation of complex translocations. Among 844 clones with chromosomal
rearrangements, 93 with various types of simple and complex translocations
involving CAN1, LYP1 and ALP1
were identified. Breakpoint sequencing and mapping showed that the formation of
complex translocation types is strictly dependent on the location of the
initiating DNA break and revealed that complex translocations arise via a
combination of interchromosomal translocation and template-switching, as well as
from unstable dicentric intermediates. Template-switching occurred between
sequences on the same chromosome, but was inhibited if the genes were
transferred to different chromosomes. Unstable dicentric translocations
continuously gave rise to clones with multiple translocations in various
combinations, reminiscent of intratumor heterogeneity in human cancers. Base
substitutions and evidence of DNA slippage near rearrangement breakpoints
revealed that translocation formation can be accompanied by point mutations, and
their presence in different translocation types within the same clone provides
evidence that some of the different translocation types are derived from each
other rather than being formed de novo. These findings provide
insight into eukaryotic genome instability, especially the formation of
translocations and the sources of intraclonal heterogeneity, both of which are
often associated with human cancers
Opinions on registering trial details: a survey of academic researchers
<p>Abstract</p> <p>Background</p> <p>The World Health Organization (WHO) has established a set of items related to study design and administrative information that should build the minimum set of data in a study register. A more comprehensive data set for registration is currently developed by the Ottawa Group. Since nothing is known about the attitudes of academic researchers towards prospective study registration, we surveyed academic researchers about their opinion regarding the registration of study details proposed by the WHO and the Ottawa Group.</p> <p>Methods</p> <p>This was a web-based survey of academic researchers currently running an investigator-initiated clinical study which is registered with clinicaltrials.gov. In July 2006 we contacted 1299 principal investigators of clinical studies by e-mail explaining the purpose of the survey and a link to access a 52-item questionnaire based on the proposed minimum data set by the Ottawa Group. Two reminder e-mails were sent each two weeks apart. Association between willingness to disclose study details and study phase was assessed using the chi-squared test for trend. To explore the potential influence of non-response bias we used logistic regression to assess associations between factors associated with non-response and the willingness to register study details.</p> <p>Results</p> <p>Overall response was low as only 282/1299 (22%) principal investigators participated in the survey. Disclosing study documents, in particular the study protocol and financial agreements, was found to be most problematic with only 31% of respondents willing to disclose these publicly. Consequently, only 34/282 (12%) agreed to disclose all details proposed by the Ottawa Group. Logistic regression indicated no association between characteristics of non-responders and willingness to disclose details.</p> <p>Conclusion</p> <p>Principal investigators of non-industry sponsored studies are reluctant to disclose all data items proposed by the Ottawa Group. Disclosing the study protocol and financial agreements was found to be most problematic. Future discussions on trial registration should not only focus on industry but also on academic researchers.</p
Cytoplasmic PML promotes TGF-β-associated epithelial–mesenchymal transition and invasion in prostate cancer
Epithelial–mesenchymal transition (EMT) is a key event that is involved in the invasion and dissemination of cancer cells. Although typically considered as having tumour-suppressive properties, transforming growth factor (TGF)-β signalling is altered during cancer and has been associated with the invasion of cancer cells and metastasis. In this study, we report a previously unknown role for the cytoplasmic promyelocytic leukaemia (cPML) tumour suppressor in TGF-β signalling-induced regulation of prostate cancer-associated EMT and invasion. We demonstrate that cPML promotes a mesenchymal phenotype and increases the invasiveness of prostate cancer cells. This event is associated with activation of TGF-β canonical signalling pathway through the induction of Sma and Mad related family 2 and 3 (SMAD2 and SMAD3) phosphorylation. Furthermore, the cytoplasmic localization of promyelocytic leukaemia (PML) is mediated by its nuclear export in a chromosomal maintenance 1 (CRM1)-dependent manner. This was clinically tested in prostate cancer tissue and shown that cytoplasmic PML and CRM1 co-expression correlates with reduced disease-specific survival. In summary, we provide evidence of dysfunctional TGF-β signalling occurring at an early stage in prostate cancer. We show that this disease pathway is mediated by cPML and CRM1 and results in a more aggressive cancer cell phenotype. We propose that the targeting of this pathway could be therapeutically exploited for clinical benefit
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