919 research outputs found
A novel and precise time domain description of MOSFET low frequency noise due to random telegraph signals
Nowadays, random telegraph signals play an important role in integrated
circuit performance variability, leading for instance to failures in memory
circuits. This problem is related to the successive captures and emissions of
electrons at the many traps stochastically distributed at the silicon-oxide
(Si-SiO2) interface of MOS transistors. In this paper we propose a novel
analytical and numerical approach to statistically describe the fluctuations of
current due to random telegraph signal in time domain. Our results include two
distinct situations: when the density of interface trap density is uniform in
energy, and when it is an u-shape curve as prescribed in literature, here
described as simple quadratic function. We establish formulas for relative
error as function of the parameters related to capture and emission
probabilities. For a complete analysis experimental u-shape curves are used and
compared with the theoretical aproach
Undergraduate geotechnical engineering education of the 21st century
Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal.Peer ReviewedPostprint (author's final draft
Logarithmic behavior of degradation dynamics in metal--oxide semiconductor devices
In this paper the authors describe a theoretical simple statistical modelling
of relaxation process in metal-oxide semiconductor devices that governs its
degradation. Basically, starting from an initial state where a given number of
traps are occupied, the dynamics of the relaxation process is measured
calculating the density of occupied traps and its fluctuations (second moment)
as function of time. Our theoretical results show a universal logarithmic law
for the density of occupied traps , i.e., the degradation is logarithmic and its amplitude depends on the
temperature and Fermi Level of device. Our approach reduces the work to the
averages determined by simple binomial sums that are corroborated by our Monte
Carlo simulations and by experimental results from literature, which bear in
mind enlightening elucidations about the physics of degradation of
semiconductor devices of our modern life
Recombinant protein expression by targeting pre-selected chromosomal loci
<p>Abstract</p> <p>Background</p> <p>Recombinant protein expression in mammalian cells is mostly achieved by stable integration of transgenes into the chromosomal DNA of established cell lines. The chromosomal surroundings have strong influences on the expression of transgenes. The exploitation of defined loci by targeting expression constructs with different regulatory elements is an approach to design high level expression systems. Further, this allows to evaluate the impact of chromosomal surroundings on distinct vector constructs.</p> <p>Results</p> <p>We explored antibody expression upon targeting diverse expression constructs into previously tagged loci in CHO-K1 and HEK293 cells that exhibit high reporter gene expression. These loci were selected by random transfer of reporter cassettes and subsequent screening. Both, retroviral infection and plasmid transfection with eGFP or antibody expression cassettes were employed for tagging. The tagged cell clones were screened for expression and single copy integration. Cell clones producing > 20 pg/cell in 24 hours could be identified. Selected integration sites that had been flanked with heterologous recombinase target sites (FRTs) were targeted by Flp recombinase mediated cassette exchange (RMCE). The results give proof of principle for consistent protein expression upon RMCE. Upon targeting antibody expression cassettes 90-100% of all resulting cell clones showed correct integration. Antibody production was found to be highly consistent within the individual cell clones as expected from their isogenic nature. However, the nature and orientation of expression control elements revealed to be critical. The impact of different promoters was examined with the tag-and-targeting approach. For each of the chosen promoters high expression sites were identified. However, each site supported the chosen promoters to a different extent, indicating that the strength of a particular promoter is dominantly defined by its chromosomal context.</p> <p>Conclusion</p> <p>RMCE provides a powerful method to specifically design vectors for optimized gene expression with high accuracy. Upon considering the specific requirements of chromosomal sites this method provides a unique tool to exploit such sites for predictable expression of biotechnologically relevant proteins such as antibodies.</p
Técnicas probabilísticas para análise de yield em nível elétrico usando propagação de erros e derivadas numéricas
Em tecnologias nanométricas, variações nos parâmetros CMOS são um desafio para o projeto de circuitos com yield apropriado. Neste trabalho nós propomos uma metodologia eficiente e precisa para a modelagem estatística de circuitos. Propagação de erros e técnicas numéricas são aplicadas para a modelagem em nível elétrico de variações aleatórias e sistemáticas durante o processo de fabricação. O modelo considera covariâncias entre os parâmetros e correlação espacial, e tem como saída os estimadores estatísticos que podem ser usados em ferramentas de mais alto nível, tais como ferramentas de análise estatística de atraso (SSTA). Além disso, desenvolvemos uma metodologia para a análise quantitativa da contribuição de cada parâmetro para a variância da resposta do circuito. Como estudos de caso, modelamos o yield de uma memória SRAM e uma porta NOR dinâmica de pré-carga. No primeiro, consideramos o impacto do comprimento do canal e da tensão de limiar no tempo de acesso da célula de memória SRAM. Nós desenvolvemos um modelo probabilístico para o atraso de uma NOR dinâmica com keeperb estático, considerando variações na largura do canal e na tensão de limiar. Comparamos os resultados calculados pela metodologia proposta com dados estatístico obtidos a partir de simulações Monte Carlo. Reportamos ganho de desempenho de 70×, com um erro menor que 1%
Subclinical thyroid dysfunction and the risk for fractures: a systematic review and meta-analysis.
BACKGROUND: Data on the association between subclinical thyroid dysfunction and fractures conflict.
PURPOSE: To assess the risk for hip and nonspine fractures associated with subclinical thyroid dysfunction among prospective cohorts.
DATA SOURCES: Search of MEDLINE and EMBASE (1946 to 16 March 2014) and reference lists of retrieved articles without language restriction.
STUDY SELECTION: Two physicians screened and identified prospective cohorts that measured thyroid function and followed participants to assess fracture outcomes.
DATA EXTRACTION: One reviewer extracted data using a standardized protocol, and another verified data. Both reviewers independently assessed methodological quality of the studies.
DATA SYNTHESIS: The 7 population-based cohorts of heterogeneous quality included 50,245 participants with 1966 hip and 3281 nonspine fractures. In random-effects models that included the 5 higher-quality studies, the pooled adjusted hazard ratios (HRs) of participants with subclinical hyperthyroidism versus euthyrodism were 1.38 (95% CI, 0.92 to 2.07) for hip fractures and 1.20 (CI, 0.83 to 1.72) for nonspine fractures without statistical heterogeneity (P = 0.82 and 0.52, respectively; I2= 0%). Pooled estimates for the 7 cohorts were 1.26 (CI, 0.96 to 1.65) for hip fractures and 1.16 (CI, 0.95 to 1.42) for nonspine fractures. When thyroxine recipients were excluded, the HRs for participants with subclinical hyperthyroidism were 2.16 (CI, 0.87 to 5.37) for hip fractures and 1.43 (CI, 0.73 to 2.78) for nonspine fractures. For participants with subclinical hypothyroidism, HRs from higher-quality studies were 1.12 (CI, 0.83 to 1.51) for hip fractures and 1.04 (CI, 0.76 to 1.42) for nonspine fractures (P for heterogeneity = 0.69 and 0.88, respectively; I2 = 0%).
LIMITATIONS: Selective reporting cannot be excluded. Adjustment for potential common confounders varied and was not adequately done across all studies.
CONCLUSION: Subclinical hyperthyroidism might be associated with an increased risk for hip and nonspine fractures, but additional large, high-quality studies are needed.
PRIMARY FUNDING SOURCE: Swiss National Science Foundation
Low Frequency Noise Considerations for CMOS Analog Circuit Design
Abstract: This paper gives an overview on 1/f-noise issues relevant for today's CMOS analog circuit design. The device-to-circuit relation of noise and the relevant operating conditions are reviewed. Modeling of the biasing dependence of 1/f-noise amplitude including large signal and statistical effects are discussed. The noise corner frequency 1 is shown to increase with CMOS technology scaling, and statistical effects are shown to even scale worse compared to the 1/fnoise. Moreover circuit design measures against noise are investigated. Finally, reliability issues concerning 1/f-noise in analog circuits are reviewed
Antlia Dwarf Galaxy: Distance, quantitative morphology and recent formation history via statistical field correction
We apply a statistical field correction technique originally designed to
determine membership of high redshift galaxy clusters to Hubble Space Telescope
imaging of the Antlia Dwarf Galaxy; a galaxy at the very edge of the Local
Group. Using the tip of the red giant branch standard candle method coupled
with a simple Sobel edge detection filter we find a new distance to Antlia of
1.31 +/- 0.03 Mpc. For the first time for a Local Group Member, we compute the
concentration, asymmetry and clumpiness (CAS) quantitative morphology
parameters for Antlia from the distribution of resolved stars in the HST/ACS
field, corrected with a new method for contaminants and complement these
parameters with the Gini coefficient (G) and the second order moment of the
brightest 20 per cent of the flux (M_20). We show that it is a classic dwarf
elliptical (C = 2.0, A = 0.063, S = 0.077, G = 0.39 and M_20 = -1.17 in the
F814W band), but has an appreciable blue stellar population at its core,
confirming on-going star-formation. The values of asymmetry and clumpiness, as
well as Gini and M_20 are consistent with an undisturbed galaxy. Although our
analysis suggests that Antlia may not be tidally influenced by NGC 3109 it does
not necessarily preclude such interaction.Comment: Accepted for publication in MNRA
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