7440 research outputs found
Sort by
Sgr A* and its environment : low-mass star formation, the origin of X-ray gas and collimated outflow
No full textWe present high-resolution multiwavelength radio continuum images of the region within 150″ of Sgr A*, revealing a number of new extended features and stellar sources in this region. First, we detect a continuous 2″ east-west ridge of radio emission, linking Sgr A* and a cluster of stars associated with IRS 13 N and IRS 13E. The ridge suggests that an outflow of east-west blob-like structures is emerging from Sgr A*. In particular, we find arc-like radio structures within the ridge with morphologies suggestive of photoevaporative protoplanetary disks. We use infrared Ks and L′ fluxes to show that the emission has similar characteristics to those of a protoplanetary disk irradiated by the intense radiation field at the Galactic center. This suggests that star formation has taken place within the S-cluster 2″ from Sgr A*. We suggest that the diffuse X-ray emission associated with Sgr A* is due to an expanding hot wind produced by the mass loss from B-type main sequence stars, and/or the disks of photoevaporation of low mass young stellar objects (YSOs) at a rate of ~10⁻⁶ M⊙ yr⁻¹. The proposed model naturally reduces the inferred accretion rate and is an alternative to the inflow–outflow style models to explain the underluminous nature of Sgr A*. Second, on a scale of 5″ from Sgr A*, we detect new cometary radio and infrared sources at a position angle PA ~ 50° which is similar to that of two other cometary sources X3 and X7, all of which face Sgr A*. In addition, we detect a striking tower of radio emission at a PA ~ 50°-60° along the major axis of the Sgr A East supernova remnant shell on a scale of 150″ from Sgr A*. We suggest that the cometary sources and the tower feature are tracing interaction sites of a mildly relativistic jet from Sgr A* with the atmosphere of stars and the nonthermal Sgr A East shell at a PA ~ 50°-60° with Ṁ ~ 1 × 10⁻⁷ M⊙ yr⁻¹, and opening angle 10°. Lastly, we suggest that the east–west ridge of radio emission traces an outflow that is potentially associated with past flaring activity from Sgr A*. The position angle of the outflow driven by flaring activity is close to -90°.25 page(s
The Innovative progressive aspect of Black South African English
No full textConflicting findings are reported for New Englishes and Learner Englishes: similarities are identified mainly on psycholinguistic grounds and differences on sociolinguistic grounds. This article offers an analysis of the progressive form in Black South African English, in which the interaction between gradual increases in proficiency and normative interventions by explicit feedback and editing of published texts is examined to establish the route towards conventionalisation of innovative features. The results indicate that one innovative feature, the extension of the progressive to longer time spans, becomes established as a feature of the variety, but other potential innovations gradually disappear under normative influence and with increased proficiency. Innovations are likely to be accepted if they are insufficiently salient to be targeted for normative correction and sufficiently present in the written and spoken input to become entrenched in the grammatical representations of learners as they turn into advanced users of the New English.24 page(s
Molecular determinants and interaction data of cyclic peptide inhibitor with the extracellular domain of TrkB receptor
No full textTrkB is a high affinity receptor for the brain derived neurotrophic factor (BDNF) and its phosphorylation stimulates activation of several intracellular signalling pathways linked to cellular growth, differentiation and maintenance. Identification of various activators and inhibitors of the TrkB receptor and greater understanding their binding mechanisms is critical to elucidate the biochemical and pharmacological pathways and analyse various protein crystallization studies. The data presented here is related to the research article entitled "Brain Derived neurotrophic factor is involved in the regulation of glycogen synthase kinase 3β (GSK3β) signalling" [1]. Cyclotraxin B (CTXB) is a disulphide bridge linked cyclic peptide molecule that interacts with TrkB receptor and inhibits the BDNF/TrkB downstream signalling. This article reports for the first time binding mechanism and interaction parameters of CTXB with the TrkB receptor. The molecular model of CTXB has been generated and it's docking with TrkB domain carried out to determine the critical residues involved in the protein peptide interaction.7 page(s
On the accuracy of long-period Rayleigh waves extracted from ambient noise
No full textThe aim of this paper is to assess the accuracy of the long-period (50–250 s) surface waves extracted from cross-correlation functions (CCF) of ambient noise. First, we compare waveforms of Empirical Green's functions (EGF) converted from CCF with their synthetics, and also compare seismograms from a ground truth earthquake with their synthetics, through numerical simulations using a common 3-D model. We then quantify the accuracy of EGFs by comparing two sets of time-shifts between the observed waveforms and the synthetics: one set for the ground truth earthquake and the other set for EGFs. Second, we compare Rayleigh wave phase velocity dispersion measurements from ambient noise and those from earthquake data in both global and regional studies. Through these comparisons, we conclude that both the dispersion curves and waveforms from noise data are consistent with their counterparts from earthquake data in the long-period band. The long-period surface waves from ambient noise are as accurate as those from earthquake data, and can be included in both global and regional ambient noise tomography and provide complementary data to constrain the lithospheric and asthenospheric structures.8 page(s
Reading damaged scripts : partial packet recovery based on compressive sensing for efficient random linear coded transmission
No full textRandom linear coding (RLC) can improve the performance of multicast transmissions in terms of throughput and energy efficiency. However, RLC and linear codes in general cannot necessarily attain the optimal performance in arbitrary networks. In this regard, partial packet recovery can be considered as a nonlinear strategy to complement such approaches for more general networks. In this paper, we propose a partial packet recovery scheme that benefits from the sparsity of bit errors in partially corrupted RLC packets. As opposed to many previous schemes, it performs without introducing preliminary checksums or preambles, demanding physical layer soft information, or requesting post-redundancy from the transmitter. It relies only on algebraic coding and data processing techniques, the existing knowledge at the receiver, and the conventional acknowledgment messages in RLC. By reconstructing and utilizing the partially corrupted packets that are usually discarded, it can reduce the average number of transmitted RLC packets required for successful decoding by typically 50%, which improves throughput and energy efficiency at the transmitter. We formulate our partial packet recovery in the form of a sparse recovery problem, present its different solutions using compressive sensing theory, discuss their complexity, and present and evaluate a Markov chain model for its performance.15 page(s
Quantitative assessment of knee effusion-synovitis in older adults : association with knee structural abnormalities
No full textObjective: To describe the natural history of quantitatively measured knee effusion-synovitis and the longitudinal associations between effusion-synovitis and knee structural factors, including cartilage defects, cartilage volume, subchondral bone marrow lesions, and meniscal pathology, in older adults. Methods: A total of 406 subjects (with a mean age of 63 years, 50% women) were randomly selected at baseline and followed up 2.7 years later. T2- or T1-weighted fat saturation magnetic resonance imaging was used to assess knee effusion-synovitis maximal area, cartilage defects, cartilage volume, bone marrow lesions, and meniscal pathology at baseline and follow-up. Multivariable generalized linear regression was performed to analyze the associations between the maximal area of effusion-synovitis and other joint structural factors after adjustment for age, sex, body mass index, tibial bone area, and/or radiographic osteoarthritis (OA). Results: Over 2.7 years of follow-up, the size of effusion-synovitis increased in 29%, remained stable in 50%, and decreased in 22% of the participants. Baseline effusion-synovitis maximal area was significantly associated with changes in knee cartilage defects (β = 0.18 [95% confidence interval (95% CI)] 0.07, 0.29), bone marrow lesions (β = 0.17 [95% CI 0.05, 0.30]), and cartilage volume (β = -0.40 [95% CI -0.71, -0.09]) but not with change in meniscal pathology. In contrast, baseline structural measures were not associated with change or increase in effusion-synovitis maximal area. Conclusion: Our findings indicate that knee effusion-synovitis is not static in older adults. It is predictive of, but not predicted by, other structural abnormalities, suggesting a potential role in early knee OA changes.8 page(s
Tschermak fractionation in calc-alkaline magmas : the Eocene Sabzevar volcanism (NE Iran)
No full textCalc-alkaline arc magmatism at convergent plate margins is volumetrically dominated by metaluminous andesites. Many studies highlighted the importance of differentiation via fractionation processes of arc magmas, but only in the last decades, it has been demonstrated that not all rock-forming minerals may affect the evolution of calc-alkaline suites. In particular, a major role exerted by Al-rich hornblende amphibole as fractionating mineral phase has been documented in many volcanic arc settings. The aim of this work is to understand the role of the Tschermak molecule (CaAlAlSiO₆) hosted in the hornblende and plagioclase fractionation assemblage in driving magma differentiation in calc-alkaline magmatic suites. We explore this issue by applying replenishment–fractional crystallization (RFC) and rare earth element–Rayleigh fractional crystallization (REE-FC) modeling to the Sabzevar Eocene (ca. 45–47 Ma) calc-alkaline volcanism of NE Central Iran, where hornblende-controlled fractionation has been demonstrated. Major element mass balance modeling indicates RFC dominated by a fractionating assemblage made of Hbl₅₂.₀₋₅₂.₅ + Pl₄₄.₁₋₄₄.₂ + Ttn₃.₃₋₃.₉ (phases are expressed on total crystallized assemblage). REE-FC modeling shows, instead, a lower degree of fractionation with respect to RFC models that is interpreted as due to hornblende and plagioclase resorption by the residual melt. Calculations demonstrate that fractionation of the Tschermak molecule can readily produce dacite and rhyolite magmas starting from a calc-alkaline andesite source (FC = ca. 30 %). In particular, the Tschermak molecule controls both the heavy rare earth elements (HREE) and light rare earth element (LREE) budgets in calc-alkaline differentiation trends.12 page(s
Proteomic identification of the lactate dehydrogenase A in a radioresistant prostate cancer xenograft mouse model for improving radiotherapy
No full textRadioresistance is a major challenge for prostate cancer (CaP) metastasis and recurrence after radiotherapy. This study aimed to identify potential protein markers and signaling pathways associated with radioresistance using a PC-3 radioresistant (RR) subcutaneous xenograft mouse model and verify the radiosensitization effect from a selected potential candidate. PC-3RR and PC-3 xenograft tumors were established and differential protein expression profiles from two groups of xenografts were analyzed using liquid chromatography tandem-mass spectrometry. One selected glycolysis marker, lactate dehydrogenase A (LDHA) was validated, and further investigated for its role in CaP radioresistance. We found that 378 proteins and 51 pathways were significantly differentially expressed between PC-3RR and PC-3 xenograft tumors, and that the glycolysis pathway is closely linked with CaP radioresistance. In addition, we also demonstrated that knock down of LDHA with siRNA or inhibition of LDHA activity with a LDHA specific inhibitor (FX-11), could sensitize PC-3RR cells to radiotherapy with reduced epithelial-mesenchymal transition, hypoxia, DNA repair ability and autophagy, as well as increased DNA double strand breaks and apoptosis. In summary, we identified a list of potential RR protein markers and important signaling pathways from a PC-3RR xenograft mouse model, and demonstrate that targeting LDHA combined with radiotherapy could increase radiosensitivity in RR CaP cells, suggesting that LDHA is an ideal therapeutic target to develop combination therapy for overcoming CaP radioresistance.17 page(s
The Impact of ethics review on a research-led university curriculum : results of a qualitative study in Australia
No full textIn the human sciences, a student research-centered pedagogy is constrained by institutional ethics review, yet there is little research on the impact of ethics review on research-led teaching. This article documents a range of ways that Australian universities are responding to ethics review of undergraduate human research. Forty teachers and administrators were interviewed at 14 universities using purposive sampling to document the range of ways teachers are avoiding ethics review or incorporating it into their curriculum. Some reported halting undergraduate research or evading ethics review, regarding it as meaningless bureaucracy divorced from actual ethical thinking. Those who incorporated ethics review into student research did so by collaborating with administrators. Institutions can facilitate research-led teaching by designing dedicated forms and decentralized review procedures for student research.11 page(s
How to analyze the Visual Analogue Scale : myths, truths and clinical relevance
No full textBackground and aims: The Visual Analogue Scale (VAS) is a popular tool for the measurement of pain. A variety of statistical methods are employed for its analysis as an outcome measure, not all of them optimal or appropriate. An issue which has attracted much discussion in the literature is whether VAS is at a ratio or ordinal level of measurement. This decision has an influence on the appropriate method of analysis. The aim of this article is to provide an overview of current practice in the analysis of VAS scores, to propose a method of analysis which avoids the shortcomings of more traditional approaches, and to provide best practice recommendations for the analysis of VAS scores. Methods: We report on the current usage of statistical methods, which fall broadly into two categories: those that assume a probability distribution for VAS, and those that do not. We give an overview of these methods, and propose continuous ordinal regression, an extension of current ordinal regression methodology, which is appropriate for VAS at an ordinal level of measurement. We demonstrate the analysis of a published data set using a variety of methods, and use simulation to compare the power of the various methods to detect treatment differences, in differing pain situations. Results: We demonstrate that continuous ordinal regression provides the most powerful statistical analysis under a variety of conditions. Conclusions and Implications: We recommend that in the situation in which no covariates besides treatment group are included in the analysis, distribution-free methods (Wilcoxon, Mann–Whitney) be used, as their power is indistinguishable from that of the proposed method. In the situation in which there are covariates which affect VAS, the proposed method is optimal. However, in this case, if the VAS scores are not concentrated around either extreme of the scale, normal-distribution methods (t-test, linear regression) are almost as powerful, and are recommended as a pragmatic choice. In the case of small sample size and VAS skewed to either extreme of the scale, the proposed method has vastly superior power to other methods.9 page(s