174 research outputs found
PSweight: An R Package for Propensity Score Weighting Analysis
Propensity score weighting is an important tool for comparative effectiveness
research.Besides the inverse probability of treatment weights (IPW), recent
development has introduced a general class of balancing weights, corresponding
to alternative target populations and estimands. In particular, the overlap
weights (OW) lead to optimal covariate balance and estimation efficiency, and a
target population of scientific and policy interest. We develop the R package
PSweight to provide a comprehensive design and analysis platform for causal
inference based on propensity score weighting. PSweight supports (i) a variety
of balancing weights, (ii) binary and multiple treatments,(iii) simple and
augmented weighting estimators, (iv) nuisance-adjusted sandwich variances,
and(v) ratio estimands. PSweight also provides diagnostic tables and graphs for
covariate balance assessment. We demonstrate the functionality of the package
using a data example from the NationalChild Development Survey (NCDS), where we
evaluate the causal effect of educational attainment on income.Comment: 18 pages, 3 figures, 5 table
Enhanced multi-colour gating for the generation of high-power isolated attosecond pulses
Isolated attosecond pulses (IAP) generated by high-order harmonic generation
are valuable tools that enable dynamics to be studied on the attosecond time
scale. The applicability of these IAP would be widened drastically by
increasing their energy. Here we analyze the potential of using multi-colour
driving pulses for temporally gating the attosecond pulse generation process.
We devise how this approach can enable the generation of IAP with the available
high-energy kHz-repetition-rate Ytterbium-based laser amplifiers (delivering
180-fs, 1030-nm pulses). We show theoretically that this requires a
three-colour field composed of the fundamental and its second harmonic as well
as a lower-frequency auxiliary component. We present pulse characterization
measurements of such auxiliary pulses generated directly by white-light seeded
OPA with the required significantly shorter pulse duration than the that of the
fundamental. This, combined with our recent experimental results on
three-colour waveform synthesis [Phys. Rev. X 4, 021028 (2014)], proves that
the theoretically considered multi-colour drivers for IAP generation can be
realized with existing high-power laser technology. The high-energy driver
pulses, combined with the strongly enhanced single-atom-level conversion
efficiency we observe in our calculations, thus make multi-colour drivers prime
candidates for the development of unprecedented high-energy IAP sources in the
near future
Role of a Genetic Variant on the 15q25.1 Lung Cancer Susceptibility Locus in Smoking-Associated Nasopharyngeal Carcinoma
Background: The 15q25.1 lung cancer susceptibility locus, containing CHRNA5, could modify lung cancer susceptibility and multiple smoking related phenotypes. However, no studies have investigated the association between CHRNA5 rs3841324, which has been proven to have the highest association with CHRNA5 mRNA expression, and the risk of other smoking-associated cancers, except lung cancer. In the current study we examined the association between rs3841324 and susceptibility to smoking-associated nasopharyngeal carcinoma (NPC).
Methods: In this case-control study we genotyped the CHRNA5 rs3841324 polymorphism with 400 NPC cases and 491 healthy controls who were Han Chinese and frequency-matched by age (Ā±5 years), gender, and alcohol consumption. Univariate and multivariate logistic regression analyses were used to calculate the odds ratio (OR) and 95% confidence intervals (95% CI)
Solitary beam propagation in a nonlinear optical resonator enables high-efficiency pulse compression and mode self-cleaning
Generating intense ultrashort pulses with high-quality spatial modes is
crucial for ultrafast and strong-field science. This can be accomplished by
controlling propagation of femtosecond pulses under the influence of Kerr
nonlinearity and achieving stable propagation with high intensity. In this
work, we propose that the generation of spatial solitons in periodic layered
Kerr media can provide an optimum condition for supercontinuum generation and
pulse compression using multiple thin plates. With both the experimental and
theoretical investigations, we successfully identify these solitary modes and
reveal a universal relationship between the beam size and the critical
nonlinear phase. Space-time coupling is shown to strongly influence the
spectral, spatial and temporal profiles of femtosecond pulses. Taking advantage
of the unique characters of these solitary modes, we demonstrate single-stage
supercontinuum generation and compression of femtosecond pulses from initially
170 fs down to 22 fs with an efficiency ~90%. We also provide evidence of
efficient mode self-cleaning which suggests rich spatial-temporal
self-organization processes of laser beams in a nonlinear resonator
Helicity-Selective Enhancement and Polarization Control of Attosecond High Harmonic Waveforms Driven by Bichromatic Circularly Polarized Laser Fields
source of bright, circularly polarized, extreme ultraviolet, and soft x-ray beams, where the individual harmonics themselves are completely circularly polarized. Here, we demonstrate the ability to preferentially select either the right or left circularly polarized harmonics simply by adjusting the relative intensity ratio of the bichromatic circularly polarized driving laser field. In the frequency domain, this significantly enhances the harmonic orders that rotate in the same direction as the higher-intensity driving laser. In the time domain, this helicity-dependent enhancement corresponds to control over the polarization of the resulting attosecond waveforms. This helicity control enables the generation of circularly polarized high harmonics with a user-defined polarization of the underlying attosecond bursts. In the future, this technique should allow for the production of bright highly elliptical harmonic supercontinua as well as the generation of isolated elliptically polarized attosecond pulses.H. K. and M. M. graciously acknowledge support from the Department of Energy BES Award No. DE-FG02- 99ER14982 for the experimental implementation, as well as a MURI grant from the Air Force Office of Scientific Research under Award No. FA9550-16-1-0121 for the theory. J. E. and C. M. acknowledge support from National Science Foundation Graduate Research Fellowships (Grant No. DGE-1144083). C. H.-G. acknowl- edges support from the Marie Curie International Outgoing Fellowship within the EU Seventh Framework Programme for Research and Technological Development (2007-2013), under REA Grant No. 328334, from Junta de Castilla y LeoĢn (Project No. SA046U16) and Spanish Ministerio de EconomiĢa y Competitividad, MINECO (Projects No. FIS2013-44174-P and No. FIS2016-75652-P). Part of this work utilized the Janus supercomputer, which is sup- ported by the U.S. National Science Foundation (Grant No. CNS-0821794) and the University of Colorado Boulder
Factors affecting the early establishment of neonatal intestinal flora and its intervention measures
In recent years, it has become evident that early-life intestinal flora plays a pivotal role in determining human health. Consequently, it is imperative to explore the establishment of neonatal intestinal flora and its influencing factors. Early neonatal intestinal flora is influenced by a multitude of factors, including maternal and infant-related factors, as well as external environment. This review summarizes the colonization mechanism of intestinal flora in the early life of newborns and discussed their influence on the establishment of neonatal intestinal flora, taking into account factors such as delivery mode, gestational age and feeding mode. Additionally, this review delves into the natural or artificial reconstruction of intestinal flora colonization defects in infants born via cesarean section and premature infants, with the goal of establishing a theoretical foundation for preventing and treating issues related to neonatal intestinal flora colonization and associated diseases
Effects of bisphenol A exposure at different circadian time on hepatic lipid metabolism in mice
BackgroundLipid metabolism in liver shows circadian-dependent profiles. The hepatotoxicity of environmental chemicals is dependent on circadian time. ObjectiveTo observe the effects of bisphenol A (BPA) exposure at different zeitgeber time (ZT) on hepatic and blood lipid metabolism and decipher the underlying mechanisms related to circadian rhythm in mice. MethodsThirty-five female C57BL/6J mice were sacrificed every 4 h in a light-dark cycle (12 h/12 h). The liver tissues were collected to describe the circadian profiles of hepatic Rev-erba, Bmal1, Clock, Srebp1c, and Chrebp mRNA expression levels within 24 h. Thirty female mice were divided into 6 groups by the timing (ZT3 represents the 3 h after light on, ZT15 represents the 3 h after light off) and dose (50 or 500 Ī¼gĀ·kgā1Ā·dā1) of BPA exposure to observe hepatotoxicity. Mice were gavaged with designed doses of BPA once per day for 4 weeks. Mice were maintained with ad libitum access to food and water and measured body weight weekly. After the experiment, mice were euthanatized and liver tissues were separated to determine the biochemical indicators of lipid metabolism and lipid metabolism- and circadian-related gene mRNA expressions. ResultsHepatic Rev-erba, Bmal1, Clock, Srebp1c, and Chrebp mRNA expression levels were rhythmic during a 24 h period in mice. At ZT3 and ZT15, BPA did not alter body weight, plasma glucose, plasma total cholesterol, plasma low density lipoprotein cholesterol, and plasma triglycerides (P>0.05). The plasma high density lipoprotein cholesterol decreased in the 50 Ī¼gĀ·kgā1Ā·dā1 BPA group at ZT3 by 14.56% compared with the control group (P<0.05). The liver triglycerides increased in the 50 Ī¼gĀ·kgā1Ā·dā1 BPA group at ZT15 by 115.20% compared with the control group (P<0.05). BPA decreased Srebp1c mRNA expression level when dosing at ZT3 and increased Chrebp, Srebp1c, and Acc1 mRNA expression levels when dosing at ZT15 compared with the control group (P<0.05). BPA increased Bmal1 mRNA expression level and decreased Rev-erbĪ± mRNA expression level at ZT3 exposure and decreased Bmal1 and increased Rev-erbĪ± mRNA expression level at ZT15 exposure (P<0.05). ConclusionBPA exposure at light or dark period has different effects on hepatic lipid metabolism in mice. Hepatic lipid deposit appears when BPA is dosed at dark period. Rev-erbĪ±-Bmal1 regulation circuits and the subsequent upregulation of Srebp1c and Chrebp and the target gene Acc1 may be involved
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