55 research outputs found
Doubly robust estimation and sensitivity analysis for marginal structural quantile models
The marginal structure quantile model (MSQM) is a useful tool to characterize
the causal effect of a time-varying treatment on the full distribution of
potential outcomes. However, to date, only the inverse probability weighting
(IPW) approach has been developed to identify the structural causal parameters
in MSQM, which requires correct specification of the propensity score models
for the treatment assignment mechanism. We propose a doubly robust approach for
the MSQM under the semiparametric framework. We derive the efficient influence
function associated with a MSQM and estimate causal parameters in the MSQM by
combining IPW and a new iterative conditional regression approach that models
the full potential outcome distribution. The proposed approach is consistent if
either of the models associated with treatment assignment or the potential
outcome distributions is correctly specified, and is locally efficient if both
models are correct. To implement the doubly robust MSQM estimator, we propose
to solve a smoothed estimating equation to facilitate efficient computation of
the point and variance estimates. In addition, we develop a new confounding
function and sensitivity analysis strategy to investigate the robustness of
several MSQM estimators when the no unmeasured confounding assumption is
violated. We apply the proposed methods to the Yale New Haven Health System
Electronic Health Record data to study the causal effect of antihypertensive
medications to inpatients with severe hypertension, and assess the robustness
of findings to unmeasured time-varying confounding
Performance Analysis of the Unary Coding Aided SWIPT in a Single-User Z-Channel
Radio frequency (RF) signal based simultaneous wireless information and power transfer (SWIPT) has emerged as a promising technique for satisfying both the communication and charging requests of the massively deployed IoT devices. Different from the physical layer and the medium-access-control layer design for coordinating the SWIPT in the RF band, we study its coding-level control from the information theoretical perspective. Due to its practical implementation of the decoder and its flexibility on the codeword structure, the unary code is chosen as a potential joint information and energy encoder. By conceiving the classic Z-channel, the mutual information and the energy harvesting performance of the unary coding aided SWIPT transceiver is analysed. Furthermore, the optimal codeword distribution is obtained for maximising the mutual information, while satisfying the minimum energy harvesting requirement. Our theoretical analysis and the optimal coding design are demonstrated by the numerical results
Influence of turbid flood water release on sediment deposition and phosphorus distribution in the bed sediment of the Three Gorges Reservoir, China
Excessive phosphorus (P) loading was identified as an urgent problem during the post-Three Gorges Reservoir (TGR) period. Turbid water with high suspended sediment loads has been periodically released during the flood season to mitigate sediment deposition in the TGR, but limited attention has been paid to its effect on the distribution of P in bed sediment within the reservoir. In this study, field surveys, historical monitoring data related to sediment deposition, and physiochemical properties and the fractional P content in the mainstream surface sediment and representative column sediment, were used to investigate the effect of turbid flood water release on P distribution in bed sediment. The results revealed that turbid flood water release could discharge approximately 20% of the suspended sediment inflow entering the TGR. Additionally, both the particle size of the inflow sediment and suspended sediment flux tended to decline, and the deposited sediment volume tended to constantly increase in the TGR at a rate of 0.117 billion tonnes per year between 2004 and 2016. The median particle size (MPS) was larger for surface sediment obtained in the flood season than for that obtained in the dry season, and the MPS tended to increase with an increase in the sediment depth from 0 to 20 cm. The total phosphorus (TP) content in sediment ranged from 2.6% to 17.5% lower in the flood water releasing period than in the non-flood water storing period. However, no consistent variation was detected for the vertical distribution of P fraction in the top 20 cm of bed sediment. Compared with lakes with slow deposition rates, the TGR showed a rapid sedimentation rate of >1.0 m/y, which mostly resulted in the uniform distribution of the surface sediment P fraction
Effect of symbiotic fungi-Armillaria gallica on the yield of Gastrodia elata Bl. and insight into the response of soil microbial community
Armillaria members play important roles in the nutrient supply and growth modulation of Gastrodia elata Bl., and they will undergo severe competition with native soil organisms before colonization and become symbiotic with G. elata. Unraveling the response of soil microbial organisms to symbiotic fungi will open up new avenues to illustrate the biological mechanisms driving G. elata’s benefit from Armillaria. For this purpose, Armillaria strains from four main G. elata production areas in China were collected, identified, and co-planted with G. elata in Guizhou Province. The result of the phylogenetic tree indicated that the four Armillaria strains shared the shortest clade with Armillaria gallica. The yields of G. elata were compared to uncover the potential role of these A. gallica strains. Soil microbial DNA was extracted and sequenced using Illumina sequencing of 16S and ITS rRNA gene amplicons to decipher the changes of soil bacterial and fungal communities arising from A. gallica strains. The yield of G. elata symbiosis with the YN strain (A. gallica collected from Yunnan) was four times higher than that of the GZ strain (A. gallica collected from Guizhou) and nearly two times higher than that of the AH and SX strains (A. gallica collected from Shanxi and Anhui). We found that the GZ strain induced changes in the bacterial community, while the YN strain mainly caused changes in the fungal community. Similar patterns were identified in non-metric multidimensional scaling analysis, in which the GZ strain greatly separated from others in bacterial structure, while the YN strain caused significant separation from other strains in fungal structure. This current study revealed the assembly and response of the soil microbial community to A. gallica strains and suggested that exotic strains of A. gallica might be helpful in improving the yield of G. elata by inducing changes in the soil fungal community
Reticulation is a Risk Factor of Progressive Subpleural non-Fibrotic Interstitial Lung Abnormalities
Rationale: Interstitial lung abnormalities (ILAs) are being increasingly identified in clinical
practice. In particular for subpleural non-fibrotic ILAs, the risk of progression over time and
the risk factors for progressive behavior are still largely unknown.
Objectives: To determine the age band prevalence of ILAs and the risk of radiological
progression of subpleural non-fibrotic ILAs over time in a large health check-up population,
and to identify how reticulation contributes to the risk of radiological progression.
Methods: Based on ILAs definition by the Fleischner Society, low-dose chest CT images from
community-dwelling population undergone health check-up were evaluated for ILAs.
Multivariable logistic regression was used to assess the risk of radiological progression.
Measurements and Main Results: Among 155,539 individuals, 3,300 (2.1%) were confirmed
to have ILAs: the vast majority (81.7%) were defined as subpleural non-fibrotic ILAs. The
prevalence of ILAs increased linearly with age (P for trend<0.0001). Of 454 individuals with
subpleural non-fibrotic ILAs, 198 (43.6%) had radiological progression over 4 years. The
presence of reticulation on initial imaging was an independent predictor of radiological
progression (OR 1.9; 95%CI 1.2-3.0, P=0.0040). No difference in radiological progression was
identified between subpleural non-fibrotic ILAs with extensive reticulation and subpleural
fibrotic ILAs (73.0% vs. 68.8%, P=0.7626).
Conclusions: The prevalence of ILAs increases linearly with age. Nearly half of subpleural
non-fibrotic ILAs progress radiologically over 4 years. The presence of reticulation is a risk
factor for radiological progression. Subpleural non-fibrotic ILAs with extensive reticulation
are likely to be a feature of subpleural fibrotic ILAs
Overexpression of the FBA and TPI genes promotes high production of HDMF in Zygosaccharomyces rouxii
4-Hydroxy-2,5-dimethyl-3 (2H)-furanone (HDMF) is widely used in the food industry as a spice and flavoring agent with high market demand. In this study, fructose-1,6-bisphosphate aldolase (FBA) and triose phosphate isomerase (TPI) were overexpressed in Zygosaccharomyces rouxii in the form of single and double genes, respectively, via electroporation. High-yield HDMF-engineered yeast strains were constructed by combining the analysis of gene expression levels obtained by real-time fluorescence quantitative PCR technology and HDMF production measured by HPLC. The results showed that there was a significant positive correlation between the production of HDMF and the expression levels of the FBA and TPI genes in yeast; the expression levels of the FBA and TPI genes were also positively correlated (p < 0.05). Compared with the wild type (WT), the engineered strains F10-D, T17-D, and TF15-A showed marked increases in HDMF production and FBA and TPI gene expression (p < 0.05) and exhibited great genetic stability with no obvious differences in biomass or colony morphology. In addition, the exogenous addition of d-fructose promoted the growth of Z. rouxii. Among the engineered strains, when fermented in YPD media supplemented with d-fructose for 5 days, TF15-A (overexpressing the FBA and TPI genes) generated the highest HDMF production of 13.39 mg/L, which is 1.91 times greater than that of the wild-type strain. The results above indicated that FBA and TPI, which are key enzymes involved in the process of HDMF biosynthesis by Z. rouxii, positively regulate the synthesis of HDMF at the transcriptional level. d-fructose can be used as a precursor for the biosynthesis of HDMF by engineered yeast in industrial production
Nanocomposite ZnO–SnO2 Nanofibers Synthesized by Electrospinning Method
We report the characterization of mixed oxides nanocomposite nanofibers of (1 − x) ZnO-(x)SnO2 (x ≤ 0.45) synthesized by electrospinning technique. The diameter of calcined nanofibers depends on Sn content. Other phases like SnO, ZnSnO3, and Zn2SnO4 were absent. Photoluminescence studies show that there is a change in the blue/violet luminescence confirming the presence of Sn in Zn-rich composition. Present study shows that the crystalline nanocomposite nanofibers with stoichiometry of (1 − x)ZnO-(x)SnO2 (x ≤ 0.45) stabilize after the calcination and possess some morphological and optical properties that strongly depend on Sn content
Genetic Epidemiology of Glioblastoma Multiforme: Confirmatory and New Findings from Analyses of Human Leukocyte Antigen Alleles and Motifs
Human leukocyte antigen (HLA) class I genes mediate cytotoxic T-lymphocyte responses and natural killer cell function. In a previous study, several HLA-B and HLA-C alleles and haplotypes were positively or negatively associated with the occurrence and prognosis of glioblastoma multiforme (GBM).As an extension of the Upper Midwest Health Study, we have performed HLA genotyping for 149 GBM patients and 149 healthy control subjects from a non-metropolitan population consisting almost exclusively of European Americans. Conditional logistic regression models did not reproduce the association of HLA-B*07 or the B*07-Cw*07 haplotype with GBM. Nonetheless, HLA-A*32, which has previously been shown to predispose GBM patients to a favorable prognosis, was negatively associated with occurrence of GBM (odds ratio=0.41, p=0.04 by univariate analysis). Other alleles (A*29, A*30, A*31 and A*33) within the A19 serology group to which A*32 belongs showed inconsistent trends. Sequencing-based HLA-A genotyping established that A*3201 was the single A*32 allele underlying the observed association. Additional evaluation of HLA-A promoter and exon 1 sequences did not detect any unexpected single nucleotide polymorphisms that could suggest differential allelic expression. Further analyses restricted to female GBM cases and controls revealed a second association with a specific HLA-B sequence motif corresponding to Bw4-80Ile (odds ratio=2.71, p=0.02).HLA-A allelic product encoded by A*3201 is likely to be functionally important to GBM. The novel, sex-specific association will require further confirmation in other representative study populations
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