1,093 research outputs found
Smarter Simulation Placement of Kilonova Light Curve Models for Computationally Inexpensive Surrogate Model Creation
The first detected binary neutron star merger GW170817 allowed for the simultaneous detection of gravitational and electromagnetic waves which started the era of multi-messenger astrophysics. The existence of an electromagnetic counterpart to a compact object merger allowed for a significantly deeper analysis of the merger event and much tighter resultant constraints on existing physical models of neutron stars, nuclear physics, and the Universe itself.
Multi-messenger analysis requires sophisticated source modeling. For the foreseeable future, demanding computational resource costs will result in a sparse availability of state-of-the-art neutron star merger light curve simulations. Astrophysical inference can proceed using an alternate approach of creating computationally cheaper surrogate models based on the aforementioned state-of-the-art simulations.
The work presented here focuses on the creation and interpolation of a library of light curve simulations suitable for the generation of surrogate models capable of conveying useful astrophysical information. It addresses the necessity of switching from grid-based simulation placement to an error-maximization approach which identifies the least understood regions of parameter space. Interpolation is introduced as the connecting factor between the long-term goal of surrogate model creation and the new simulation placement mechanism. Finally, a discussion about the iterative process of simulation placement using interpolation outputs describes how each new simulation brings the library one step closer to serving as a surrogate model training set
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PS-BBICS: Pulse stretching bulk built-in current sensor for on-chip measurement of single event transients
The bulk built-in current sensor (BBICS) is a cost-effective solution for detection of energetic particle strikes in integrated circuits. With an appropriate number of BBICSs distributed across the chip, the soft error locations can be identified, and the dynamic fault-tolerant mechanisms can be activated locally to correct the soft errors in the affected logic. In this work, we introduce a pulse stretching BBICS (PS-BBICS) constructed by connecting a standard BBICS and a custom-designed pulse stretching cell. The aim of PS-BBICS is to enable the on-chip measurement of the single event transient (SET) pulse width, allowing to detect the linear energy transfer (LET) of incident particles, and thus assess more accurately the radiation conditions. Based on Spectre simulations, we have shown that for the LET from 1 to 100 MeV cm2 mg−1, the SET pulse width detected by PS-BBICS varies by 620–800 ps. The threshold LET of PS-BBICS increases linearly with the number of monitored inverters, and it is around 1.7 MeV cm2 mg−1 for ten monitored inverters. On the other hand, the SET pulse width is independent of the number of monitored inverters for LET > 4 MeV cm2 mg−1. It was shown that supply voltage, temperature and process variations have strong impact on the response of PS-BBICS
The effects of valsartan on cardiac function and pro-oxidative parameters in the streptozotocin-induced diabetic rat heart
© 2020, University of Kragujevac, Faculty of Science. All rights reserved. Diabetes mellitus is a major risk factor for cardiovascular diseases, while cardiovascular diseases are a leading cause of morbidity and mortality worldwide. The renin–angiotensin– aldosterone system controls renal, cardiovascular, adrenal function and regulates fluid and electrolyte balance as well as blood pressure. Because of his role, inhibition of renin-angiotensin-aldosteron system is another therapy approach that reduces the risk of diabetes and cardiovascular disease. In this study, our goal was to evaluate effect of valsartan,as inhibitor of angiotensin II receptor type 1, on cardiac tissue and function, with focus on cardiodynamic and oxidative stress. The present study was carried out on 20 adult male Wistar albino rats (8 week old and with body masses of 180-200 g). Rats were divided randomly into 2 groups (10 animals per group). Healthy animals treated with 1 μM of valsartan and streptozotocin-induced diabetic animals perfused with 1 μM of valsartan 4 weeks after the induction of diabetes. Our results demonstrated that acute application of valsartan has different effect on cardiodynamics in rat heart of diabetic and healthy animals but did not improve cardiac function in hy-perglycemia-induced changes. A challenge for further investi-gations are studies with chronic or acute administration, alone or in combination with other angiotensin-converting-enzyme inhibitor in various models of diabetes
Interpolated kilonova spectra models: necessity for a phenomenological, blue component in the fitting of AT2017gfo spectra
In this work, we present a simple interpolation methodology for spectroscopic
time series, based on conventional interpolation techniques (random forests)
implemented in widely-available libraries. We demonstrate that our existing
library of simulations is sufficient for training, producing interpolated
spectra that respond sensitively to varied ejecta parameter, post-merger time,
and viewing angle inputs. We compare our interpolated spectra to the AT2017gfo
spectral data, and find parameters similar to our previous inferences using
broadband light curves. However, the spectral observations have significant
systematic short-wavelength residuals relative to our models, which we cannot
explain within our existing framework. Similar to previous studies, we argue
that an additional blue component is required. We consider a radioactive
heating source as a third component characterized by light, slow-moving,
lanthanide-free ejecta with , c,
and cm/g. When included as part of our radiative
transfer simulations, our choice of third component reprocesses blue photons
into lower energies, having the opposite effect and further accentuating the
blue-underluminosity disparity in our simulations. As such, we are unable to
overcome short-wavelength deficits at later times using an additional
radioactive heating component, indicating the need for a more sophisticated
modeling treatment.Comment: 11 pages, 7 figures, presenting at April APS session F13.0000
Predicting the effect of chemical factors on the pH of crystallisation trials
In macromolecular crystallisation, success is often dependent on the pH of the experiment. However, little is known about the pH of reagents used and it is generally assumed that the pH of the experiment will closely match that of any buffering chemical in the solution. We use a large data set of experimentally measured solution pH values to show that this assumption can be very wrong and generate a model which can be used to successfully predict the overall solution pH of a crystallisation experiment. Further, we investigate the time dependence of the pH of some polyethylene glycol polymers widely used in protein crystallisation under different storage conditions
Tools to Ease the Choice and Design of Protein Crystallisation Experiments
The process of macromolecular crystallisation almost always begins by setting up crystallisation trials using commercial or other premade screens, followed by cycles of optimisation where the crystallisation cocktails are focused towards a particular small region of chemical space. The screening process is relatively straightforward, but still requires an understanding of the plethora of commercially available screens. Optimisation is complicated by requiring both the design and preparation of the appropriate secondary screens. Software has been developed in the C3 lab to aid the process of choosing initial screens, to analyse the results of the initial trials, and to design and describe how to prepare optimisation screens
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Analysis of Single Event Transient Effects in Standard Delay Cells Based on Decoupling Capacitors
Single Event Transients (SETs), i.e., voltage glitches induced in combinational logic as a result of the passage of energetic particles, represent an increasingly critical reliability threat for modern complementary metal oxide semiconductor (CMOS) integrated circuits (ICs) employed in space missions. In rad-hard ICs implemented with standard digital cells, special design techniques should be applied to reduce the Soft Error Rate (SER) due to SETs. To this end, it is essential to consider the SET robustness of individual standard cells. Among the wide range of logic cells available in standard cell libraries, the standard delay cells (SDCs) implemented with the skew-sized inverters are exceptionally vulnerable to SETs. Namely, the SET pulses induced in these cells may be hundreds of picoseconds longer than those in other standard cells. In this work, an alternative design of a SDC based on two inverters and two decoupling capacitors is introduced. Electrical simulations have shown that the propagation delay and SET robustness of the proposed delay cell are strongly influenced by the transistor sizes and supply voltage, while the impact of temperature is moderate. The proposed design is more tolerant to SETs than the SDCs with skew-sized inverters, and occupies less area compared to the hardening configurations based on partial and complete duplication. Due to the low transistor count (only six transistors), the proposed delay cell could also be used as a SET filter
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