1,519 research outputs found
Molecule sublimation as a tracer of protostellar accretion: Evidence for accretion bursts from high angular resolution C18O images
The accretion histories of embedded protostars are an integral part of
descriptions of their physical and chemical evolution. In particular, are the
accretion rates smoothly declining from the earlier toward later stages or in
fact characterized by variations such as intermittent bursts? We aim to
characterize the impact of possible accretion variations in a sample of
embedded protostars by measuring the size of the inner regions of their
envelopes where CO is sublimated and relate those to their temperature profiles
dictated by their current luminosities. Using observations from the
Submillimeter Array we measure the extents of the emission from the C18O
isotopologue toward 16 deeply embedded protostars. We compare these
measurements to the predicted extent of the emission given the current
luminosities of the sources through dust and line radiative transfer
calculations. Eight out of sixteen sources show more extended C18O emission
than predicted by the models. The modeling shows that the likely culprit for
these signatures is sublimation due to increases in luminosities of the sources
by about a factor five or more during the recent 10,000 years - the time it
takes for CO to freeze-out again on dust grains. For four of those sources the
increase would have had to have been a factor 10 or more. The compact emission
seen toward the other half of the sample suggests that C18O only sublimates
when the temperature exceeds 30 K - as one would expect if CO is mixed with H2O
in the grain ice-mantles. The small-number statistics from this survey suggest
that protostars undergo significant bursts about once every 20,000 years. This
also illustrates the importance of taking the physical evolutionary histories
into account for descriptions of the chemical structures of embedded
protostars.Comment: Accepted by A&A; 11 pages, 5 figure
Matrix metalloproteinase activities and their relationship with collagen remodelling in tendon pathology
Our aim was to correlate the activity of matrix metalloproteinases (MMPs) with denaturation and the turnover of collagen in normal and pathological human tendons. MMPs were extracted from ruptured supraspinatus tendons (n=10), macroscopically normal (âcontrolâ) supraspinatus tendons (n=29) and normal short head of biceps brachii tendons (n=24). Enzyme activity was measured using fluorogenic substrates selective for MMP-1, MMP-3 and enzymes with gelatinolytic activity (MMP-2, MMP-9 and MMP-13). Collagen denaturation was determined by a-chymotrypsin digestion. Protein turnover was determined by measuring the percentage of d-aspartic acid (% d-Asp). Zymography was conducted to identity specific gelatinases. MMP-1 activity was higher in ruptured supraspinatus compared to control supraspinatus and normal biceps brachii tendons (70.9, 26.4 and 11.5 fmol/mg tendon, respectively;
Which regime works best in social welfare?:Comparing outcomes of eight Dutch RCT experiments
Current technological innovations (automation, robotization, digitization, AI, big data) may have adverse employment effects notably for the low skilled welfare recipients. They face reduced chances for getting access to secure and fairly paid jobs also while two in three lack the basic qualifications needed to acquire the lowest level jobs, let alone that also more than one third consider themselves unfit to work due to serious physical or mental health issues. Therefore, eight Dutch municipalities (Deventer, Groningen, Nijmegen, Tilburg, Utrecht, Wageningen, Apeldoorn-Epe, Oss) started in the fall of 2017 and early 2018 a two-year long unique randomized control trial (RCT) to test three alternative regimes for people on welfare in which more than 5,000 recipients participated2. The treatments set up were (1) exemption/selfmanagement, that is exemption of the application obligations and rendering more trust and autonomy to the recipient for self-management, (2) intensive or tailored support, that is providing tailored and intensified counselling support to improve claimantsâ work and social participation opportunities (e.g., in education, training or volunteer work) and (3) earnings release, that is rewarding welfare claimants for finding work by allowing participants to keep a larger part of their earnings on top of their benefit (work bonus). The experiments share some features of participation and basic income approaches even though their design and implementation are rather different. We found no evidence that the alternative welfare regimes have reduced employment effects compared to âworkfareâ regimes. In some municipalities we find small positive significant effects on parttime and fulltime employment and on peopleâs self-efficacy, social trust and trust in caseworkerâ support. No significant positive effects were found on health and wellbeing. The use of field experiments for testing the outcomes of alternative welfare regimes provides new avenues for welfare state policy in an era of rapid technological and economic change
Anomalous Change Point Detection Using Probabilistic Predictive Coding
Change point detection (CPD) and anomaly detection (AD) are essential techniques in various fields to identify abrupt changes or abnormal data instances. However, existing methods are often constrained to univariate data, face scalability challenges with large datasets due to computational demands, and experience reduced performance with high-dimensional or intricate data, as well as hidden anomalies. Furthermore, they often lack interpretability and adaptability to domain-specific knowledge, which limits their versatility across different fields. In this work, we propose a deep learning-based CPD/AD method called Probabilistic Predictive Coding (PPC) that jointly learns to encode sequential data to low dimensional latent space representations and to predict the subsequent data representations as well as the corresponding prediction uncertainties. The model parameters are optimized with maximum likelihood estimation by comparing these predictions with the true encodings. At the time of application, the true and predicted encodings are used to determine the probability of conformity, an interpretable and meaningful anomaly score. Furthermore, our approach has linear time complexity, scalability issues are prevented, and the method can easily be adjusted to a wide range of data types and intricate applications. We demonstrate the effectiveness and adaptability of our proposed method across synthetic time series experiments, image data, and real-world magnetic resonance spectroscopic imaging data
Further evidence of the involvement of the Wnt signaling pathway in Dupuytren's disease
Genetic background plays an important role in the development of Dupuytren's disease. A genome-wide association study (GWAS) showed that nine loci are associated with the disease, six of which contain genes that are involved in Wnt signaling (WNT2, WNT4, WNT7B, RSPO2, SFRP4, SULF1). To obtain insight in the role of these genes, we performed expression studies on affected and unaffected patient's tissues. Surgically obtained nodules and cords from eight Dupuytren's patients were compared to patient-matched control tissue (unaffected transverse palmar fascia). The Wnt-related genes found in the GWAS, the classical Wnt-downstream protein beta-catenin, as well as (myo) fibroblast markers were analyzed using real-time qPCR and immunohistochemical stainings for mRNA levels and protein levels, respectively. The collagen-coding genes COL1A1 and COL3A1 were highly upregulated on mRNA level, both in cords and nodules. Three Wnt-related genes were found to be differently regulated compared to control tissue: WNT2 was downregulated in nodules, WNT7B was upregulated in nodules, and SFRP4 was upregulated in nodules and cords. Immunohistochemistry revealed significantly less staining of Wnt2 in cords, but significantly more staining for Wnt7b in nodules. There was significantly more staining of alpha-SMA in nodules and cord and beta-catenin in nodules than in control tissue. We found differences in expression, both at mRNA and protein level, in several Wnt-related genes found earlier to be associated with Dupuytren's disease. Of these, Wnt7b was upregulated and found in close association with both alpha-SMA and beta-catenin expressing cells, making it a candidate pro-fibrotic mediator in Dupuytren's disease
On the Lagrangian Realization of Non-Critical -Strings
A large class of non-critical string theories with extended worldsheet gauge
symmetry are described by two coupled, gauged Wess-Zumino-Witten Models. We
give a detailed analysis of the gauge invariant action and in particular the
gauge fixing procedure and the resulting BRST symmetries. The results are
applied to the example of strings.Comment: 19 pages, LaTeX (REVTEX macro's
Diapycnal mixing across the photic zone of the NEÂ Atlantic
Variable physical conditions such as vertical turbulent exchange, internal wave, and mesoscale eddy action affect the availability of light and nutrients for phytoplankton (unicellular algae) growth. It is hypothesized that changes in ocean temperature may affect ocean vertical density stratification, which may hamper vertical exchange. In order to quantify variations in physical conditions in the northeast Atlantic Ocean, we sampled a latitudinal transect along 17â±â5ââW between 30 and 63ââN in summer. A shipborne conductivityâtemperatureâdepth (CTD) instrumented package was used with a custom-made modification of the pump inlet to minimize detrimental effects of ship motions on its data. Thorpe-scale analysis was used to establish turbulence values for the upper 500âm from three to six profiles obtained in a short CTD yo-yo, 3 to 5âh after local sunrise. From south to north, average temperature decreased together with stratification while turbulence values weakly increased or remained constant. Vertical turbulent nutrient fluxes did not vary significantly with stratification and latitude. This apparent lack of correspondence between turbulent mixing and temperature is likely due to internal waves breaking (increased stratification can support more internal waves), acting as a potential feedback mechanism. As this feedback mechanism mediates potential physical environment changes in temperature, global surface ocean warming may not affect the vertical nutrient fluxes to a large degree. We urge modellers to test this deduction as it could imply that the future summer phytoplankton productivity in stratified oligotrophic waters would experience little alterations in nutrient input from deeper waters
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