2,497 publications from this institution
Very low bit error rate (BER) requirements for the operation of a high-speed link system require a very precise analysis of the link performance in order to prevent unrealistic specifications on both IC design and communication algorithm development. This paper presents the analysis of the noise and distortion sources in a high-speed link system, and their impact on the choice and effectiveness of different communication techniques. Phase-locked loop and clock-and-data recovery loop modeling is also described. It is shown that the most dominant noise and distortion sources are colored and bounded, as opposed to standard unbounded Gaussian white noise assumptions, which yield large errors in the estimation of the link performance and comparison of different signaling techniques. With very low BER requirements, shape of probability distribution of noise and distortion sources and their correlations, are much more important than just their total power, which contrasts the standard analysis in communication systems.
The language and conceptual framework of "research reproducibility" are nonstandard and unsettled across the sciences.In this Perspective, we review an array of explicit and implicit definitions of reproducibility and related terminology, and discuss how to avoid potential misunderstandings when these terms are used as a surrogate for "truth.
Summary Objective We studied the entire agenda of randomized clinical trials in pulmonary hypertension ( PH ) using sociological methods. We explored the geometry of the PH network to interpret the evidence on multiple competing treatments for the same indication. Design We searched MEDLINE , Embase and Cochrane Library Databases for published studies. We queried clinicaltrials.gov and WHO International Clinical Trials Registry platform for non‐published studies. Results We found 75 randomized trials (41 published [n = 4136 participants] and 34 registered unpublished [planned n = 3470 participants]). Of the published randomized studies, all used placebo as the comparator arm except for two nonindustry‐sponsored comparisons between phosphodiestearase‐5 ( PDE ‐5) inhibitors and endothelin receptor antagonists ( ERA ), and one study comparing two different regimens of treprostinil. Similarly, only five unpublished/ongoing trials used an active PH treatment as comparator ( PDE ‐5 inhibitors versus ERA (n = 3), different doses of sildenafil (n = 1) and two formulations of epoprostenol (n = 1). Of the 75 trials, 47 were sponsored by the manufacturer of the tested active product(s), and only two trials were sponsored by two companies comparing their products. Conclusions The relative merits of different treatment options are not directly known, as there are very few head‐to‐head comparisons. A limited number of ongoing studies are using active FDA ‐approved PH ‐treatments for comparison. This lack of information can be overcome by carefully designing comparative effectiveness trials.
Simple models for the delay, power, and area of a static random access memory (SRAM) are used to determine the optimal organizations for an SRAM and study the scaling of their speed and power with size and technology. The delay is found to increase by about one gate delay for every doubling of the RAM size up to 1 Mb, beyond which the interconnect delay becomes an increasingly significant fraction of the total delay. With technology scaling, the nonscaling of threshold mismatches in the sense amplifiers is found to significantly impact the total delay in generations of 0.1 /spl mu/m and below.
We examine two multiple-context schemes in the context of scalable shared-memory multiprocessors. The blocked scheme switches between contexts at cache misses. The proposed interleaved scheme switches between available contexts on a cycle-by-cycle basis, while providing full pipeline interlocks for good single-context performance. We show the interleaved scheme to have a performance advantage over the blocked scheme due to its ability to hide pipeline dependencies and reduce the context switch cost. We also show that, while the implementation of the interleaved scheme is more complex, this complexity is not overwhelming.
Importance: The Global Burden of Disease (GBD) reports widely used estimates of mortality and disability-adjusted life-years (DALYs) and related risk factors. However, the overall reliability of these estimates between GBD iterations has not been assessed. Objective: To evaluate the instability and inconsistency of GBD risk factor estimates for mortality and DALYs across GBD iterations. Data Sources: GBD risk factor collaboration estimates extracted from the published tables of GBD iterations and the Institute for Health Metrics and Evaluation repository. Study Selection: GBD risk factor collaboration publications published for 2010 through 2023. Data Extraction and Synthesis: Death and DALY estimates were manually extracted by 1 reviewer with independent validation of a random sample of 100 by another with no discrepancies. Risk factor naming was harmonized across iterations to ensure comparability; those with inconsistent definitions were excluded. Main Outcomes and Measures: Fluctuations were calculated for numbers of deaths and DALYs for each risk factor across GBD iterations during the study period (2010-2023) and between the original and subsequently revised estimates for each year (1990-2021). Differences were expressed as a ratio of the minimum to maximum range to the mean (R:M) and coefficient of variation. Detail analyses assessed diet and low physical activity. Point estimates were compared to the previous iterations' estimates 95% uncertainty intervals (95% UI) for GBD 2019, 2021, and 2023. Results: Across GBD iterations from 2010 to 2023, the median (range) R:M was 0.8 (0-3.8) for deaths, and 0.7 (0.1-3.3) for DALYs. Level 2 dietary and child and maternal malnutrition death estimates showed high instability (R:M >1 for 9 of 16 and 4 of 8 risks, respectively). When comparing original estimates with GBD 2019, 2021, and 2023 estimates for the same years, the median R:M was 0.4 (0-2.9) for both deaths and DALYs. The coefficient of variation was greater than 0.2 for 336 of 675 death estimates (50%). Specifically, 70% to 96% of point estimates for red meat, sugar-sweetened beverages, fruits, vegetables, and seafood omega-3 fatty acids in GBD 2021 fell outside the GBD 2019 95% UI. In GBD 2023, only diet high in trans fats had more than half of point estimates outside the GBD 2021 95% UI. Conclusions and Relevance: This meta-epidemiological assessment indicates that GBD estimates are substantially unstable, particularly for behavioral risks, making them unlikely to simply reflect genuine changes over time, and warranting caution in interpretation.
Article Free Access Share on Clustered voltage scaling technique for low-power design Authors: Kimiyoshi Usami Toshiba Corp., 580-1, Horikawa-cho, Saiwai-ku, Kawasaki, Japan and Stanford University, Stanford, CA Toshiba Corp., 580-1, Horikawa-cho, Saiwai-ku, Kawasaki, Japan and Stanford University, Stanford, CAView Profile , Mark Horowitz Stanford University, Stanford, CA Stanford University, Stanford, CAView Profile Authors Info & Claims ISLPED '95: Proceedings of the 1995 international symposium on Low power designApril 1995 Pages 3–8https://doi.org/10.1145/224081.224083Online:23 April 1995Publication History 338citation1,972DownloadsMetricsTotal Citations338Total Downloads1,972Last 12 Months53Last 6 weeks11 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF
Citation metrics are widely used and misused. We have created a publicly available database of 100,000 top scientists that provides standardized information on citations, h-index, coauthorship-adjusted hm-index, citations to papers in different authorship positions, and a composite indicator. Separate data are shown for career-long and single-year impact. Metrics with and without self-citations and ratio of citations to citing papers are given. Scientists are classified into 22 scientific fields and 176 subfields. Field- and subfield-specific percentiles are also provided for all scientists who have published at least five papers. Career-long data are updated to end of 2017 and to end of 2018 for comparison.
Trials that are unregistered, unfinished, unpublished, unreachable, or simply irrelevant Randomized controlled trials are the gold standard tool for evaluating interventions. Nevertheless, the utility of this excellent tool is contingent on how it is used. Chapman and colleagues (doi:10.1136/bmj.g6870) show this in a sample of 395 trials relevant to surgical practice that were registered in ClincialTrials.gov between 2008 and 2009.1 By the end of 2013, 21% were discontinued, 34% of those that were completed were not published, and for 77% of the trials that had uncertain fate no way existed to reach investigators to find what had happened to them. This work adds to several other empirical evaluations showing that evidence from randomized controlled trials is wasted at multiple stages from conception to publication and beyond.2 3 4 5 6 7 8 9 10 11 12 Many trials are entirely lost, as they are not even registered. Substantial diversity probably exists across specialties, countries, and settings. Overall, in a survey conducted in 2012, only 30% of journal editors requested or encouraged trial registration.2 Among registered trials, a sizeable fraction are never completed. In some cases, discontinuation may be the best …
ABSTRACT Background Perceived trustworthiness of research may be influenced by factors beyond the risk of bias, including study-related characteristics, research context, and external circumstances. Identifying these factors is essential for gauging the credibility of non-randomized studies of interventions (NRSIs) as they are interpreted and used in systematic reviews, and for improving their design to ensure that they provide reliable evidence for decision-making. Our objective was to identify factors, not covered in risk of bias assessment tools, that could influence the trustworthiness of NRSIs. Methods We conducted a cross-sectional survey of international experts. We defined trustworthiness as the proper, justified or rational trust in the study findings. Using convenience sampling, we recruited participants who were top-cited scientists in the field of epidemiology, members of the Cochrane Bias Group and Cochrane Non-Randomized Studies Methods Group, authors of initiatives related to observational studies and corresponding authors of NRSIs. Through an online survey, we asked them to identify factors that they believe could influence the trustworthiness of NRSIs. We analyzed qualitative data using an inductive thematic approach. We first coded the responses, which were redefined into factors and grouped under themes. We summarized findings in frequencies and percentages. Results 130 participants out of 1488 contacted completed the survey. Of the 130 participants, 40 (31%) were methodologists and 61 (47%) had 21-40 years of experience in research. The level of expertise in NRSIs ranged from intermediate (35%) to advanced (30%) and expert (30%).We identified a total of 56 factors, with a median of 6 factors per participant (IQR 3; 9, range 0-20). We grouped the factors under 20 domains, when relevant, and eventually under eight overarching themes: Open Science (e.g., transparency, registration), Research Question (e.g., appropriate rationale and hypothesis), Study Methodology (e.g., study design, participants, statistical considerations), Data Source (e.g., quality), Findings and Interpretation (e.g., plausibility of effect estimate), Writing (e.g., appropriate writing), Oversight (e.g., investigators, journal), and Artificial Intelligence (e.g., no suspicion of use in writing or synthesis). Conclusions Our findings provide insight to gauge and improve the quality and uptake of NRSIs, with important implications for strengthening evidence-based decision-making in both research and practice.
ABSTRACT Importance COVID-19 has resulted in massive production, publication and wide dissemination of clinical studies trying to identify effective treatments. However, several widely touted treatments failed to show effectiveness in large well-done randomized controlled trials (RCTs). Objective To evaluate for COVID-19 treatments that showed no benefits in subsequent large RCTs how many of their most-cited clinical studies had declared favorable results for these interventions. Methods Scopus (last update December 23, 2021) identified articles on lopinavir-ritonavir, hydroxycholoroquine/azithromycin, remdesivir, convalescent plasma, colchicine or interferon (index interventions) that represented clinical trials and that had received >150 citations. Their conclusions were assessed and correlated with study design features. The ten most recent citations for the most-cited article on each index intervention were examined on whether they were critical to the highly-cited study. Altmetric scores were also obtained. Findings 40 articles of clinical studies on these index interventions had received >150 citations (7 exceeded 1,000 citations). 20/40 (50%) had favorable conclusions and 4 were equivocal. Highly-cited articles with favorable conclusions were rarely RCTs while those without favorable conclusions were mostly RCTs (3/20 vs 15/20, p=0.0003). Only 1 RCT with favorable conclusions had sample size >160. Citation counts correlated strongly with Altmetric scores, in particular news items. Only 9 (15%) of 60 recent citations to the most highly-cited studies with favorable or equivocal conclusions were critical to the highly-cited study. Conclusion Many clinical studies with favorable conclusions for largely ineffective COVID-19 treatments are uncritically heavily cited and disseminated. Early observational studies and small randomized trials may cause spurious claims of effectiveness that get perpetuated.
Abstract Objective To assess the impact of the Fcγ receptor type IIa (FcγRIIa)–R/H131 polymorphism on the risk for systemic lupus erythematosus (SLE) and development of lupus nephritis. Methods A meta‐analysis was performed based on the Medline and Embase databases (last retrieval August 2001), assessment of bibliographies of pertinent articles, and additional data gathered after contact with primary investigators. Results A total of 25 comparisons from 17 studies involving R/H131 genotyping of 1,405 patients with lupus nephritis, 1,709 SLE patients without nephritis, and 2,580 non‐SLE controls were included. No association between RR genotype and risk of lupus nephritis relative to both other genotypes (odds ratio [OR] 1.05, 95% confidence interval [95% CI] 0.88–1.27) was demonstrated in the total meta‐analysis or in any racial subgroup. The RR genotype was more frequent in SLE patients as a whole (OR 1.30, 95% CI 1.10–1.52) and in SLE patients without nephritis (OR 1.27, 95% CI 1.04–1.55) compared with disease‐free controls. A potential dose–response relation between the R131 allele and the risk of SLE was also identified, with an OR of 1.23 for RR versus RH (95% CI 1.03–1.46). The OR was 1.55 for RR versus HH (95% CI 1.21–1.98). There was no significant heterogeneity between racial subgroups. The population‐attributable fractions of SLE cases due to the FcγRIIa‐R131 allele were 13%, 40%, and 24% in subjects of European, African, and Asian descent, respectively. Conclusion The FcγRIIa‐R/H131 polymorphism represents a significant risk factor for SLE but has no clear effect on susceptibility for lupus nephritis.
In a collaboration of 7 European and United States prospective studies, 44 cases of vertical human immunodeficiency virus type 1 (HIV-1) transmission were identified among 1202 women with RNA virus loads <1000 copies/mL at delivery or at the measurement closest to delivery. For mothers receiving antiretroviral treatment during pregnancy or at the time of delivery (or both), there was a 1.0% transmission rate (8 of 834; 95% confidence interval [CI], 0.4%-1.9%), compared with 9.8% (36 of 368; 95% CI, 7.0%-13.4%) for untreated mothers (risk ratio, 0.10; 95% CI, 0.05-0.21). In multivariate analysis adjusting for study, transmission was lower with antiretroviral treatment (odds ratio [OR], 0.10; P<.001), cesarean section (OR, 0.30; P=.022), greater birth weight (P=.003), and higher CD4 cell count (P=.039). In 12 of 44 cases, multiple RNA measurements were obtained during pregnancy or at the time of delivery or within 4 months after giving birth; in 10 of the 12 cases, the geometric mean virus load was >500 copies/mL. Perinatal HIV-1 transmission occurs in only 1% of treated women with RNA virus loads <1000 copies/mL and may be almost eliminated with antiretroviral prophylaxis accompanied by suppression of maternal viremia.
