Evidence for enhanced persistent emission during sub-Eddington thermonuclear bursts

The standard approach for time-resolved X-ray spectral analysis of thermonuclear bursts involves subtraction of the pre-burst emission as background. This approach implicitly assumes that the persistent flux remains constant throughout the burst. We reanalyzed 332 photospheric radius expansion bursts observed from 40 sources by the Rossi X-ray Timing Explorer, introducing a multiplicative factor $f_a$ to the persistent emission contribution in our spectral fits. We found that for the majority of spectra the best-fit value of $f_a$ is significantly greater than 1, suggesting that the persistent emission typically increases during a burst. Elevated $f_a$ values were not found solely during the radius expansion interval of the burst, but were also measured in the cooling tail. The modified model results in a lower average value of the $\chi^2$ fit statistic, indicating superior spectral fits, but not yet to the level of formal statistical consistency for all the spectra. We interpret the elevated $f_a$ values as an increase of the mass accretion rate onto the neutron star during the burst, likely arising from the effects of Poynting-Robertson drag on the disk material. We measured an inverse correlation of $f_a$ with the persistent flux, consistent with theoretical models of the disc response. We suggest that this modified approach may provide more accurate burst spectral parameters, as well as offering a probe of the accretion disk structure.Comment: 15 pages, 9 figure

Evidence for accretion rate change during type I X-ray bursts

The standard approach for time-resolved X-ray spectral analysis of thermonuclear bursts involves subtraction of the pre-burst emission as background. This approach implicitly assumes that the persistent flux remains constant throughout the burst. We reanalyzed 332 photospheric radius expansion bursts observed from 40 sources by the Rossi X-ray Timing Explorer, introducing a multiplicative factor $f_a$ to the persistent emission contribution in our spectral fits. We found that for the majority of spectra the best-fit value of $f_a$ is significantly greater than 1, suggesting that the persistent emission typically increases during a burst. Elevated $f_a$ values were not found solely during the radius expansion interval of the burst, but were also measured in the cooling tail. The modified model results in a lower average value of the $\chi^2$ fit statistic, indicating superior spectral fits, but not yet to the level of formal statistical consistency for all the spectra. We interpret the elevated $f_a$ values as an increase of the mass accretion rate onto the neutron star during the burst, likely arising from the effects of Poynting-Robertson drag on the disk material. We measured an inverse correlation of $f_a$ with the persistent flux, consistent with theoretical models of the disc response. We suggest that this modified approach may provide more accurate burst spectral parameters, as well as offering a probe of the accretion disk structure.Comment: 15 pages, 12 figures, 4 table

Local Quasiconvexity of Groups acting on Small Cancellation Complexes

Given a group acting cellularly and cocompactly on a simply-connected 2-complex, we provide a criterion establishing that all finitely generated subgroups have quasiconvex orbits. This work generalizes the "perimeter method". As an application, we show that high-powered one-relator products A \ast B / \nclose{r^n} are coherent if $A$ and $B$ are coherent.Comment: version 1. 14 pages, 4 figure

Accelerated Neural Networks on OpenCL Devices Using SYCL-DNN

Over the past few years machine learning has seen a renewed explosion of interest, following a number of studies showing the effectiveness of neural networks in a range of tasks which had previously been considered incredibly hard. Neural networks' effectiveness in the fields of image recognition and natural language processing stems primarily from the vast amounts of data available to companies and researchers, coupled with the huge amounts of compute power available in modern accelerators such as GPUs, FPGAs and ASICs. There are a number of approaches available to developers for utilizing GPGPU technologies such as SYCL, OpenCL and CUDA, however many applications require the same low level mathematical routines. Libraries dedicated to accelerating these common routines allow developers to easily make full use of the available hardware without requiring low level knowledge of the hardware themselves, however such libraries are often provided by hardware manufacturers for specific hardware such as cuDNN for Nvidia hardware or MIOpen for AMD hardware. SYCL-DNN is a new open-source library dedicated to providing accelerated routines for neural network operations which are hardware and vendor agnostic. Built on top of the SYCL open standard and written entirely in standard C++, SYCL-DNN allows a user to easily accelerate neural network code for a wide range of hardware using a modern C++ interface. The library is tested on AMD's OpenCL for GPU, Intel's OpenCL for CPU and GPU, ARM's OpenCL for Mali GPUs as well as ComputeAorta's OpenCL for R-Car CV engine and host CPU. In this talk we will present performance figures for SYCL-DNN on this range of hardware, and discuss how high performance was achieved on such a varied set of accelerators with such different hardware features.Comment: 4 pages, 3 figures. In International Workshop on OpenCL (IWOCL '19), May 13-15, 2019, Bosto

Grammars Compete Late: Evidence from Embedded Passives

One of the biggest problems for variationist approaches to syntactic variation is the question of where such variation occurs in the grammar, and what type of variation is allowed. Kroch (1994) suggests that syntactic variables are a result of Competing Grammars, in which grammars that derive differing surface outputs are in competition and selected by the speaker. In this paper, I observe an implicit prediction of the Competing Grammars viewpoint as typically described: material above the variable cannot condition variation. I test this prediction in a variationist study of embedded passives (the ëneeds washedí construction) in Pittsburghese, and show that material above the variable does condition variation. This finding suggests that a look-ahead problem arises if a grammar in competition is selected prior to derivation of the variable. To solve this, I propose that both grammars are initially derived, and that the derivation transferred to LF and PF is chosen in Spell-Out from the two possibilities. Grammars still compete; however, the competition selects a variant later than previously thought

A Freezing Approach to the Ish-Construction in English

The English affix -ish has historically been a derivational morpheme that creates adjectives denoting approximation to the root. In this paper, I introduce a novel use of ish in English, in which it may appear following VP/PP and a pause, even when no adjective is present. I assert that this novel use is a syntactic construction, and provide an analysis of the syntax of the ish-construction. Based on facts from clefting, Sluicing, and incompatibility with NPI-licensing, I show that ish is TP-Internal and triggers island effects. Because it appears to the right of the island in the surface structure, I propose an analysis drawing from Müller\u27s (1998) discussion of Freezing, by which moved objects cannot be extracted from. I argue that ish Merges above the VP/PP it modifies, which then moves past ish to derive the surface structure. I provide evidence from Raising constructions that support predictions made by such an analysis

Altering the stability of the Cdc8 overlap region modulates the ability of this tropomyosin to bind cooperatively to actin and regulate myosin.

Tropomyosin (Tm) is an evolutionarily conserved ?-helical coiled-coil protein, dimers of which form end-to-end polymers capable of associating with and stabilising actin-filaments and regulate myosin function. The fission yeast, Schizosaccharomyces pombe, possesses a single essential Tm, Cdc8, which can be acetylated on its amino terminal methionine to increase its affinity for actin and enhance its ability to regulate myosin function. We have designed and generated a number of novel Cdc8 mutant proteins with amino terminal substitutions to explore how stability of the Cdc8-polymer overlap region affects the regulatory function of this Tm. By correlating the stability of each protein, its propensity to form stable polymers, its ability to associate with actin and to regulate myosin, we have shown the stability of the amino terminal of the Cdc8 ?-helix is crucial for Tm function. In addition we have identified a novel Cdc8 mutant with increased amino-terminal stability, dimers of which are capable of forming Tm-polymers significantly longer than the wild-type protein. This protein had a reduced affinity for actin with respect to wild type, and was unable to regulate actomyosin interactions. The data presented here are consistent with acetylation providing a mechanism for modulating the formation and stability of Cdc8 polymers within the fission yeast cell. The data also provide evidence for a mechanism in which Tm dimers form end-to-end polymers on the actin-filament, consistent with a cooperative model for Tm binding to actin

Emt Driven By Tgf-B Is A Significant Mediator Of Stenosis In Tissue Engineered Vascular Grafts

The development of an autologous tissue engineered vascular graft (TEVG) holds great promise for improving outcomes in congenital heart surgery. The first clinical trial showed that this approach is safe and effective but that the primary mode of failure is stenosis. In a C57BL/6 mouse model of unseeded TEVGs implanted as inferior vena cava interposition grafts, neovessels form in 2 weeks and patent grafts show endothelial and smooth muscle cell (SMC) layers, but occluded grafts show accumulation of SMCs. This suggests stenosis results from abnormal SMC in-growth in the neointima. Studies on fibrosis have shown that resident endothelial cells (EC) contribute to fibroblast accumulation through endothelial-mesenchymal transition (EMT). We utilized transgenic EC lineage-tracing mouse models to track the occurrence of EMT in our TEVG and found an increased percentage of cells co-expressing LacZ and smooth muscle actin in occluded grafts, suggesting that EMT contributes to occlusion in our TEVG. We hypothesized that ECs in our TEVG undergo EMT driven by TGF-B to contribute to stenosis. Immunohistochemistry and qRT-PCR showed higher expression of TGF-B in occluded compared to patent grafts. In vivo expression of a soluble FGF trap virus to increase TGF-B signaling and thus increase EMT was found to result in a significantly increased stenosis rate in our TEVG. We next modulated this pathway by intraperitoneal administration of a small molecule inhibitor of TGF-B receptor type 1 (SB431542). Grafts from treated mice had significantly increased patency rates and internal diameters at 2 weeks compared to controls while maintaining normal neovessel architecture. We then designed a novel local delivery system for this TGF-B R1 inhibitor in our grafts and showed that local drug delivery inhibits stenosis without cell seeding and maintains normal neovessel formation. These results suggest that EMT under the control of TGF-B is a significant mediator of stenosis and that modulation of this pathway by local drug delivery might be useful in next generation TEVGs

Exploring the Uses of ShellBag Data within the Windows 7 Registry.

Digital forensic examiners are faced with the task of recreating a user’s actions for auditing purposes. ShellBag data from the registry is critical to the reproduction of these actions in a Microsoft Windows 7 operating system, because ShellBag data contains a listing of folders and files contained within a specific folder. Once an understanding of the structure of ShellBag data in a Windows 7 operating system is reached, this data can be parsed to create a timeline of user actions on a given machine