Comparison between unipolar and bipolar single phase grid-connected inverters for PV applications

An inverter is essential for the interfacing of photovoltaic panels with the AC network. There are many possible inverter topologies and inverter switching schemes and each one will have its own relative advantages and disadvantages. Efficiency and output current distortion are two important factors governing the choice of inverter system. In this paper, it is argued that current controlled inverters offer significant advantages from the point of view of minimisation of current distortion. Two inverter switching strategies are explored in detail. These are the unipolar current controlled inverter and the bipolar current controlled inverter. With respect to low frequency distortion, previously published works provide theoretical arguments in favour of bipolar switching. On the other hand it has also been argued that the unipolar switched inverter offers reduced switching losses and generates less EMI. On efficiency grounds, it appears that the unipolar switched inverter has an advantage. However, experimental results presented in this paper show that the level of low frequency current distortion in the unipolar switched inverter is such that it can only comply with Australian Standard 4777.2 above a minimum output current. On the other hand it is shown that at the same current levels bipolar switching results in reduced low frequency harmonics

The Fermi GBM Gamma-Ray Burst Spectral Catalog: Four Years Of Data

In this catalog we present the updated set of spectral analyses of GRBs detected by the Fermi Gamma-Ray Burst Monitor (GBM) during its first four years of operation. It contains two types of spectra, time-integrated spectral fits and spectral fits at the brightest time bin, from 943 triggered GRBs. Four different spectral models were fitted to the data, resulting in a compendium of more than 7500 spectra. The analysis was performed similarly, but not identically to Goldstein et al. 2012. All 487 GRBs from the first two years have been re-fitted using the same methodology as that of the 456 GRBs in years three and four. We describe, in detail, our procedure and criteria for the analysis, and present the results in the form of parameter distributions both for the observer-frame and rest-frame quantities. The data files containing the complete results are available from the High-Energy Astrophysics Science Archive Research Center (HEASARC).Comment: Accepted for publication in ApJ

Dietary inflammatory index (DII) and risk of prostate cancer in a case–control study among Black and White US Veteran men

© 2019, Springer Nature America, Inc. Background: We hypothesized a pro-inflammatory diet would be associated with higher prostate cancer (PC) risk. Methods: We prospectively recruited incident PC cases (n = 254) and controls (n = 328) at the Durham Veteran Affairs, from 2007 to 2018. From a self-completed 61-item Food Frequency Questionnaire, we calculated dietary inflammatory index (DII ® ) scores with and without supplements. We examined the association between DII scores with and without supplements and overall PC risk using logistic regression and risk of low-grade PC (grade group 1) and high-grade PC (grade group 2–5) with multinomial logistic regression. Results: Cases were more likely to be Black (58 vs. 42%), had higher PSA (6.4 vs. 0.8 ng/ml), lower BMI (29.1 vs. 30.6 kg/m 2 ) and were older (64 vs. 62 years) versus controls (all p \u3c 0.01). Both black controls and cases had higher DII scores with and without supplements, though the DII scores with supplements in controls was not significant. On multivariable analysis, there were no associations between DII with or without supplements and overall PC risk (p-trend = 0.14, p-trend = 0.09, respectively) or low-grade PC (p-trend = 0.72, p-trend = 0.47, respectively). Higher DII scores with (p-trend = 0.04) and without supplements (p = 0.08) were associated with high-grade PC, though the association for DII without supplements was not significant. Conclusions: A pro-inflammatory diet was more common among Black men and associated with high-grade PC in our case–control study. The degree to which a pro-inflammatory diet contributes to PC race disparities warrants further study. If confirmed, studies should test whether a low-inflammatory diet can prevent high-grade PC, particularly among Black men

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

Pan-cancer analysis of whole genomes

Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale(1-3). Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4-5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter(4); identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation(5,6); analyses timings and patterns of tumour evolution(7); describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity(8,9); and evaluates a range of more-specialized features of cancer genomes(8,10-18).Peer reviewe

More than smell - COVID-19 is associated with severe impairment of smell, taste, and chemesthesis

Recent anecdotal and scientific reports have provided evidence of a link between COVID-19 and chemosensory impairments, such as anosmia. However, these reports have downplayed or failed to distinguish potential effects on taste, ignored chemesthesis, and generally lacked quantitative measurements. Here, we report the development, implementation, and initial results of a multilingual, international questionnaire to assess self-reported quantity and quality of perception in 3 distinct chemosensory modalities (smell, taste, and chemesthesis) before and during COVID-19. In the first 11 days after questionnaire launch, 4039 participants (2913 women, 1118 men, and 8 others, aged 19-79) reported a COVID-19 diagnosis either via laboratory tests or clinical assessment. Importantly, smell, taste, and chemesthetic function were each significantly reduced compared to their status before the disease. Difference scores (maximum possible change ±100) revealed a mean reduction of smell (-79.7 ± 28.7, mean ± standard deviation), taste (-69.0 ± 32.6), and chemesthetic (-37.3 ± 36.2) function during COVID-19. Qualitative changes in olfactory ability (parosmia and phantosmia) were relatively rare and correlated with smell loss. Importantly, perceived nasal obstruction did not account for smell loss. Furthermore, chemosensory impairments were similar between participants in the laboratory test and clinical assessment groups. These results show that COVID-19-associated chemosensory impairment is not limited to smell but also affects taste and chemesthesis. The multimodal impact of COVID-19 and the lack of perceived nasal obstruction suggest that severe acute respiratory syndrome coronavirus strain 2 (SARS-CoV-2) infection may disrupt sensory-neural mechanisms. © 2020 The Author(s) 2020. Published by Oxford University Press. All rights reserved

Development of a GPC Chromatograms Decomposition Method for Identifying and Quantifying the Degradation of SBS Polymer Modified Bitumen

SBS polymer modified bitumen (SPMB) can notably improve the performance of asphalt pavement and is widely employed on the surface layer of pavements. However, SBS polymer is sensitive to ageing and its degradation evolution is difficult to be quantitatively characterized due to the overlapping of GPC chromatograms. In this research, a chromatogram decomposition method (CDM) is proposed based on a combination of experimental quantitative analysis and mathematical deconvolution methods, which target simultaneous identification and quantification of degraded SBS polymers in SPMB. According to the experimental and analysis results, the overlapped chromatograph peaks of 24 different SPMB binders (different SBS contents, base bitumen types and ageing levels) were successfully decomposed and the degraded SBS polymer was quantitively analyzed by the CDM method. Meanwhile, the CDM analysis parameters of SPMB binders demonstrated a good correlation with the rheological characterization results, indicating the validity of the proposed CDM method. These results revealed the degradation process of SBS polymer during the aging of SPMB, and also provide a promising analytical strategy for the polymer modified bitumen with overlapped GPC chromatograms.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Pavement Engineerin

Low-Temperature and Fatigue Characteristics of Degraded Crumb Rubber-Modified Bitumen before and after Aging

The high viscosity and poor storage stability of crumb rubber-modified asphalt (CRMA) can be partially addressed by the appropriate degree of degradation of the crumb rubber modifier. However, the low-Temperature and fatigue characteristics of degraded crumb rubber-modified bitumen (DCRMB) in different aging states are not well understood. In this study, two types of DCRMB-namely, terminal blend rubberized asphalt (TBRA) and terminal blend hybrid asphalt (TBHA)-were prepared with sulfur, styrene-butadiene-styrene (SBS) polymer, and crumb rubber (CR). All DCRMB binders were short-Term aged with a rolling thin film oven test (RTFOT) and long-Term aged with a pressure aging vessel (PAV). Afterward, a bending beam rheometer (BBR) test and a linear amplitude sweep (LAS) test were conducted to characterize the low-Temperature and fatigue properties of DCRMB binders at different aging degrees, respectively. Based on the rheological test results, several conclusions can be drawn. First, the BBR results indicated that the increase in CR content led to a slight increase in creep rate and a significant decrease in stiffness. Especially in PAV aging, the low-Temperature properties of DCRMB were much better than those of neat asphalt. Meanwhile, DCRMB demonstrated an advantage over neat asphalt in integrity and fatigue resistance before and after aging. Finally, based on correlation analysis, the LAS test is recommended for evaluating the fatigue properties of DCRMB before and after aging. Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Pavement Engineerin

Aging Characteristics of Rubber Modified Bitumen Mixed with Sulfur after Terminal Blend Process

The influence of sulfur on the chemical, rheological, and aging resistance of terminal blend rubberized bitumen (TBRB) was studied. TB hybrid bitumen (TBHB) was prepared from with different sulfur contents (0.1, 0.2, 0.3, 0.4 wt%) and TBRB prepared with neat bitumen and crumb rubbers at 20% content. TBHB binders were aged by rolling thin film oven test (RTFOT) and pressure aging vessel (PAV), respectively. The chemical composition of TBHB binders was monitored by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR). Rheological properties of all TBHB samples were tested. Chemical composition results show that TBHB can inhibit the degradation of polybutadiene compared with TBRB in the RTFOT stage, and the polybutadiene degradation is the main process of TBHB in the RTFOT stage, while the TBHB is mainly desulfurized after PAV aging. Meanwhile, the increase in sulfur content in the TBHB can improve the desulfurization degree of the TBHB binder after PAV. TBRB containing sulfur can improve the mechanical properties and elasticity and reduce the hardening degree during aging. Moreover, blending sulfur into the TBRB caused a lower complex modulus aging index after aging, which indicates that TBHB has superior aging resistancePavement Engineerin

Influence of SBS on the Aging Properties of High-Content Terminal Blend Rubber Modified Asphalt

The goal of this study was to investigate the effect of styrene-butadiene-styrene (SBS) polymer on the aging properties of high-content terminal blend rubber modified asphalt (HCTBMA). All asphalt was tested for chemo-rheological properties using an attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) test, temperature sweep test, frequency sweep tests, and multiple stress creep recovery (MSCR) test. According to ATR-FTIR observations, SBS can retard the oxidation effect of HCTBMA during short-term aging, but its inhibitory effect is reduced during long-term aging. Furthermore, aging aggravates the degree of desulfurization of crumb rubber in HCTBMA as the SBS content increases. Compared with HCTBMA, neat asphalt has a lower elasticity at high temperatures and a higher elasticity at low temperatures. The addition of SBS to HCTBMA improves the elasticity of the material. The elasticity of HCTBMA decreases and then increases after aging, and SBS can reduce the aging degree of HCTBMA after aging. Moreover, based on Pearson correlation analysis, the correlation between the desulfurization of rubber and the degradation of polybutadiene in HCTBMA during aging is high.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Pavement Engineerin