Confidence-interval construction for rate ratio in matched-pair studies with incomplete data

Matched-pair design is often used in clinical trials to increase the efficiency of establishing equivalence between two treatments with binary outcomes. In this article, we consider such a design based on rate ratio in the presence of incomplete data. The rate ratio is one of the most frequently used indices in comparing efficiency of two treatments in clinical trials. In this article, we propose 10 confidence-interval estimators for the rate ratio in incomplete matched-pair designs. A hybrid method that recovers variance estimates required for the rate ratio from the confidence limits for single proportions is proposed. It is noteworthy that confidence intervals based on this hybrid method have closed-form solution. The performance of the proposed confidence intervals is evaluated with respect to their exact coverage probability, expected confidence interval width, and distal and mesial noncoverage probability. The results show that the hybrid Agresti–Coull confidence interval based on Fieller’s theorem performs satisfactorily for small to moderate sample sizes. Two real examples from clinical trials are used to illustrate the proposed confidence intervals.postprin

Management and outcome of antenatally diagnosed congenital cystic adenomatoid malformation of the lung

Objective: To review the management and outcome of babies with antenatally diagnosed congenital cystic adenomatoid malformation. Design: Retrospective cohort review. Setting: Tertiary neonatal care unit at Queen Mary Hospital and antenatal diagnostic centre at Tsan Yuk Hospital. Patients: Consecutive patients with antenatally suspected congenital cystic adenomatoid malformation in their concepti among antenatal patients attending Tsan Yuk Hospital from 1994 to 2002. Twenty-four of 33 cases were referred to Queen Mary Hospital for postnatal management and for whom comprehensive records were available for analysis in 23. Interventions: Postnatal interventions in their babies included investigational imaging for congenital cystic adenomatoid malformation and surgery. Main outcome measures: Antenatal and postnatal outcome, as well as pathology of the excised lesions. Results: Antenatal outcome: termination of pregnancy in two cases and spontaneous abortion in one; in-utero regression was documented in nine cases and in one hydropic change was apparent. Postnatal outcome: only eight of 20 babies born alive had symptoms in neonatal period. Two developed serious infective complications in infancy, one with documented in-utero regression. Pulmonary parenchymal abnormalities were detected on computed tomography of the thorax in six of seven cases with normal or non-specific chest radiograph findings. Among nine cases with in-utero regression, congenital cystic adenomatoid malformation was confirmed by operative histology in five and abnormal computed tomography findings in three. Fifteen babies underwent surgical excision, one of whom died because of severe pre-existing pulmonary hypoplasia and nine endured minor postoperative complications. A favourable outcome was documented at a mean follow-up of 22 months (range, 2 months-7 years). Conclusions: In-utero regression of congenital cystic adenomatoid malformation on antenatal ultrasound may not represent genuine resolution. Computed tomographic thorax should be considered in all newborns with antenatally diagnosed congenital cystic adenomatoid malformation, and if confirmed early operation before first hospital discharge is recommended.published_or_final_versio

From chaos to order: Chain-length dependence of the free energy of formation of meso-tetraalkylporphyrin self-assembled monolayer polymorphs

© 2016 American Chemical Society. We demonstrate that systematic errors can be reduced and physical insight gained through investigation of the dependence of free energies for meso-tetraalkylporphyrin self-assembled monolayers (SAMs) polymorphism on the alkyl chain length m. These SAMs form on highly ordered pyrolytic graphite (HOPG) from organic solution, displaying manifold densities and atomic structures. SAMs with m = 11-19 are investigated experimentally while those with m = 6-28 are simulated using density-functional theory (DFT). It is shown that, for m = 15 or more, the alkyl chains crystallize to dominate SAM structure. Meso-tetraalkylporphyrin SAMs of length less than 11 have never been observed, a presumed effect of inadequate surface attraction. Instead, we show that free energies of SAM formation actually enhance as the chain length decreases. The inability to image regular SAMs stems from the appearance of many polymorphic forms of similar free energy, preventing SAM ordering. We also demonstrate a significant odd/even effect in SAM structure arising from packing anomalies. Comparison of the chain-length dependence of formation free energies allows the critical dispersion interactions between molecules, solvent, and substrate to be directly examined. Interpretation of the STM data combined with measured enthalpies indicates that Grimme's D3 explicit-dispersion correction and the implicit solvent correction of Floris, Tomasi and Pascual Ahuir are both quantitatively accurate and very well balanced to each other

Genetic study of congenital bile-duct dilatation identifies de novo and inherited variants in functionally related genes

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Genetic evidence for multiple invasions of subterranean termites into Canada

Modern quantum chemical electronic structure methods typically applied to localized chemical bonding are developed to predict atomic structures and free energies for meso-Tetraalkylporphyrin self-Assembled monolayer (SAM) polymorph formation from organic solution on highly ordered pyrolytic graphite surfaces. Large polymorphdependent dispersion-induced substrate-molecule interactions (e.g., -100 kcal mol-1 to -150 kcal mol-1 for tetratrisdecylporphyrin) are found to drive SAM formation, opposed nearly completely by large polymorph-dependent dispersion-induced solvent interactions (70- 110 kcal mol-1) and entropy effects (25-40 kcal mol-1 at 298 K) favoring dissolution. Dielectric continuum models of the solvent are used, facilitating consideration of many possible SAM polymorphs, along with quantum mechanical/molecular mechanical and dispersion- corrected density functional theory calculations. These predict and interpret newly measured and existing high-resolution scanning tunnelling microscopy images of SAM structure, rationalizing polymorph formation conditions. A wide range of molecular condensed matter properties at room temperature now appear suitable for prediction and analysis using electronic structure calculations

Effect of ZnCdTe-Alloyed Nanocrystals on Polymer–Fullerene Bulk Heterojunction Solar Cells

The photovoltaic properties of solar cell based on the blends of poly[2-methoxy-5-(2-ethylhexoxy-1,4-phenylenevinylene) (MEH-PPV), fullerene (C60), and ZnCdTe-alloyed nanocrystals were investigated. Comparing the spectral response of photocurrent of the MEH-PPV:C60(+ZnCdTe) nanocomposite device with that of the devices based on MEH-PPV:C60and pristine MEH-PPV, one can find that the nanocomposite device exhibits an enhanced photocurrent. In comparing the composite devices with different ZnCdTe:[MEH-PPV + C60] weight ratios of 10 wt% (D1–1), 20 wt% (D1–2), 40 wt% (D1–3), and 70 wt% (D1–4), it was found that the device D1–3exhibits the best performance. The power conversion efficiency (η) is improved doubly compared with that of the MEH-PPV:C60device

From sparse to dense and from assortative to disassortative in online social networks

Inspired by the analysis of several empirical online social networks, we propose a simple reaction-diffusion-like coevolving model, in which individuals are activated to create links based on their states, influenced by local dynamics and their own intention. It is shown that the model can reproduce the remarkable properties observed in empirical online social networks; in particular, the assortative coefficients are neutral or negative, and the power law exponents are smaller than 2. Moreover, we demonstrate that, under appropriate conditions, the model network naturally makes transition(s) from assortative to disassortative, and from sparse to dense in their characteristics. The model is useful in understanding the formation and evolution of online social networks.Comment: 10 pages, 7 figures and 2 table

Comparing factors affecting commencement and cessation of betel quid chewing behavior in Taiwanese adults

<p>Abstract</p> <p>Background</p> <p>Betel quid is the fourth most common used substance in the world after tobacco, alcohol and caffeine. Although factors related to betel quid chewing or cessation of behaviors were reported previously, few studies simultaneously compared both behaviors in the same population. In addition, it is essential to consider time-to-event concept, since the chance of developing or stopping habit may vary over time. The purpose of this study was to compare the risk factors for commencement and cessation of betel quid chewing behaviors in a time-to-event setting.</p> <p>Methods</p> <p>A stratified multi-stage cluster sampling with selection probabilities proportional to size (PPS) was designed for Taiwanese adults with aged 18 years old and above. Kaplan-Meier estimates and Cox proportional hazard regression models were used to compare and calculate the hazard rate ratios for related factors to commencement or cessation of chewing habits.</p> <p>Results</p> <p>In Taiwan, men had a higher betel quid chewing rate (M: 20.9%, W: 1.2%), but woman chewers had a lower cessation rate (M: 27.5%, W: 12.7%). The hazard rate ratio (HRR) of having chewing habit changed from 4.22 (men vs women) univariately to 1.38 multivariablely, which indicated gender differences were confounded by other factors. In multivariable analysis, the risk factors of gender, education and ethnicity were significantly associated with both starting and cessation of betel quid chewing behavior. The factors of occupation, cigarette smoking and alcohol drinking were only associated with starting habit.</p> <p>Conclusion</p> <p>Commencement or cessation of chewing behavior involves a scenario of time, hence it is preferable to use a time-to-event approach for the comparison. The cessation rates of betel quid chewing were decreasingly associated with the daily consumption of betel quid. Hence, reducing of daily amount in betel quid cessation program may be associated with future stopping habit.</p

Stimulus-dependent maximum entropy models of neural population codes

Neural populations encode information about their stimulus in a collective fashion, by joint activity patterns of spiking and silence. A full account of this mapping from stimulus to neural activity is given by the conditional probability distribution over neural codewords given the sensory input. To be able to infer a model for this distribution from large-scale neural recordings, we introduce a stimulus-dependent maximum entropy (SDME) model---a minimal extension of the canonical linear-nonlinear model of a single neuron, to a pairwise-coupled neural population. The model is able to capture the single-cell response properties as well as the correlations in neural spiking due to shared stimulus and due to effective neuron-to-neuron connections. Here we show that in a population of 100 retinal ganglion cells in the salamander retina responding to temporal white-noise stimuli, dependencies between cells play an important encoding role. As a result, the SDME model gives a more accurate account of single cell responses and in particular outperforms uncoupled models in reproducing the distributions of codewords emitted in response to a stimulus. We show how the SDME model, in conjunction with static maximum entropy models of population vocabulary, can be used to estimate information-theoretic quantities like surprise and information transmission in a neural population.Comment: 11 pages, 7 figure