Thinking outside the curve, part I: modeling birthweight distribution

<p>Abstract</p> <p>Background</p> <p>Greater epidemiologic understanding of the relationships among fetal-infant mortality and its prognostic factors, including birthweight, could have vast public health implications. A key step toward that understanding is a realistic and tractable framework for analyzing birthweight distributions and fetal-infant mortality. The present paper is the first of a two-part series that introduces such a framework.</p> <p>Methods</p> <p>We propose describing a birthweight distribution via a normal mixture model in which the number of components is determined from the data using a model selection criterion rather than fixed <it>a priori</it>.</p> <p>Results</p> <p>We address a number of methodological issues, including how the number of components selected depends on the sample size, how the choice of model selection criterion influences the results, and how estimates of mixture model parameters based on multiple samples from the same population can be combined to produce confidence intervals. As an illustration, we find that a 4-component normal mixture model reasonably describes the birthweight distribution for a population of white singleton infants born to heavily smoking mothers. We also compare this 4-component normal mixture model to two competitors from the existing literature: a contaminated normal model and a 2-component normal mixture model. In a second illustration, we discover that a 6-component normal mixture model may be more appropriate than a 4-component normal mixture model for a general population of black singletons.</p> <p>Conclusions</p> <p>The framework developed in this paper avoids assuming the existence of an interval of birthweights over which there are no compromised pregnancies and does not constrain birthweights within compromised pregnancies to be normally distributed. Thus, the present framework can reveal heterogeneity in birthweight that is undetectable via a contaminated normal model or a 2-component normal mixture model.</p

New insights on structure and stratigraphic interpretation for assessing the hydrocarbon potentiality of the offshore Nile Delta basin, Egypt

The study area lies around the petroleum provinces of the Egyptian Offshore Nile Delta basin. The existing exploration data are sparse, and any effort made on the strati-structural interpretation is challenging for exploratory drilling campaigns, even with meager well control. Keeping in view the issues and major challenges, the authors propose new methodologies, tools and new insights into the interpretation of the existing data and information, to make the study area more attractive for investors and detailed exploration studies. The published geological work existing within the vicinity of the study area is an added value to the new insights of current interpretation and knowledge acquisition. Pliocene–Pleistocene section is the main target in the study area, since it has quality reservoirs, holding commercial hydrocarbons. Pre-salt source rocks may have charged the reservoirs in the study area. Structural complexities and heterogeneities at target levels are likely to impact the seismic wavelet property intricacies and thus the data processing qualities. Post- and pre-salt tectonics in the northern part of Sinai, the Nile Cone, and how they affect the structural framework and the seismic interpretation work in the study area are described. For the purpose of understanding the combinational trapping mechanism, stratigraphic features and the structural geology are integrated using new tools and technologies. Several strati-structural plays are interpreted in the study area that support the detailed exploration campaigns, and the existing major hydrocarbon plays associated within shelf, slope and deep-marine geological events in nearby offshore regions. Diapir salt, rotated fault blocks and growth faults within syn-sediment systems are other plays to be investigated. The study is an effort of compiled work from many published sources, putting all ideas into a positive perspective and has better understanding of new opportunities, leads and prospects for investment purposes in the Nile Delta offshore basin

First- and second-order contributions to depth perception in anti-correlated random dot stereograms.

The binocular energy model of neural responses predicts that depth from binocular disparity might be perceived in the reversed direction when the contrast of dots presented to one eye is reversed. While reversed-depth has been found using anti-correlated random-dot stereograms (ACRDS) the findings are inconsistent across studies. The mixed findings may be accounted for by the presence of a gap between the target and surround, or as a result of overlap of dots around the vertical edges of the stimuli. To test this, we assessed whether (1) the gap size (0, 19.2 or 38.4 arc min) (2) the correlation of dots or (3) the border orientation (circular target, or horizontal or vertical edge) affected the perception of depth. Reversed-depth from ACRDS (circular no-gap condition) was seen by a minority of participants, but this effect reduced as the gap size increased. Depth was mostly perceived in the correct direction for ACRDS edge stimuli, with the effect increasing with the gap size. The inconsistency across conditions can be accounted for by the relative reliability of first- and second-order depth detection mechanisms, and the coarse spatial resolution of the latter

Investigation of whisker growth from alkaline non-cyanide zinc electrodeposits

Electroplated zinc finishes have been widely used in the packaging of electronic products for many years as a result of their excellent corrosion resistance and relatively low cost. However, the spontaneous formation of whiskers on zinc electroplated components, which are capable of resulting in electrical shorting or other damaging effects, can be highly problematic for the reliability of long-life electrical and electronic equipment. This work investigated the mechanism for whisker growth from zinc electrodeposited mild steel substrates. The incubation time for whisker growth from the surface of nodules on the surface of the electrodeposit was considerably reduced compared with that from the planar deposit surface. Recrystallisation of the as-deposited columnar structure was observed at the whisker root. This result is consistent with some recent whisker growth models based on recrystallisation. There was no evidence of iron-zinc (Fe-Zn) intermetallic formation at the iron/zinc (Fe/Zn) interface or within the zinc coating beneath the whiskers

Kidins220/ARMS Is a Novel Modulator of Short-Term Synaptic Plasticity in Hippocampal GABAergic Neurons

Kidins220 (Kinase D interacting substrate of 220 kDa)/ARMS (Ankyrin Repeat-rich Membrane Spanning) is a scaffold protein highly expressed in the nervous system. Previous work on neurons with altered Kidins220/ARMS expression suggested that this protein plays multiple roles in synaptic function. In this study, we analyzed the effects of Kidins220/ARMS ablation on basal synaptic transmission and on a variety of short-term plasticity paradigms in both excitatory and inhibitory synapses using a recently described Kidins220 full knockout mouse. Hippocampal neuronal cultures prepared from embryonic Kidins220−/− (KO) and wild type (WT) littermates were used for whole-cell patch-clamp recordings of spontaneous and evoked synaptic activity. Whereas glutamatergic AMPA receptor-mediated responses were not significantly affected in KO neurons, specific differences were detected in evoked GABAergic transmission. The recovery from synaptic depression of inhibitory post-synaptic currents in WT cells showed biphasic kinetics, both in response to paired-pulse and long-lasting train stimulation, while in KO cells the respective slow components were strongly reduced. We demonstrate that the slow recovery from synaptic depression in WT cells is caused by a transient reduction of the vesicle release probability, which is absent in KO neurons. These results suggest that Kidins220/ARMS is not essential for basal synaptic transmission and various forms of short-term plasticity, but instead plays a novel role in the mechanisms regulating the recovery of synaptic strength in GABAergic synapses

Supracervical hysterectomy versus total abdominal hysterectomy: perceived effects on sexual function

BACKGROUND: Our investigation sought to compare changes in sexual function following supracervical hysterectomy (SCH) and total abdominal hysterectomy (TAH). METHODS: A retrospective chart review was performed to identify all patients who underwent supracervical hysterectomy or total abdominal hysterectomy at a tertiary care center. Patients who met criteria for participation were sent a one page confidential, anonymous questionnaire to assess sexual function experienced both pre- and postoperatively. A total of 69 patients in each group were eligible for participation. A multiple logistic regression model was used to analyze measured variables. RESULTS: Forty-eight percent (n = 33) of women undergoing a SCH returned the questionnaire, while 39% (n = 27) of those undergoing a TAH chose to participate. There were no significant demographic differences between the two groups. Patients who underwent TAH reported worse postoperative sexual outcome than SCH patients with respect to intercourse frequency, orgasm frequency and overall sexual satisfaction (P = 0.01, 0.03, and 0.03, respectively). Irrespective of type of hysterectomy, 35% of patients who underwent bilateral salpingoophorectomy (BSO) with hysterectomy experienced worse overall sexual satisfaction compared to 3% of patients who underwent hysterectomy alone (P = 0.02). CONCLUSIONS: Our data suggest that TAH patients experienced worse postoperative sexual function than SCH patients with respect to intercourse frequency and overall sexual satisfaction. Irrespective of type of hysterectomy, patients who underwent bilateral salpingoophorectomy experienced worse overall sexual satisfaction

Cyanobacterial Cell Lineage Analysis of the Spatiotemporal hetR Expression Profile during Heterocyst Pattern Formation in Anabaena sp. PCC 7120

Diazotrophic heterocyst formation in the filamentous cyanobacterium, Anabaena sp. PCC 7120, is one of the simplest pattern formations known to occur in cell differentiation. Most previous studies on heterocyst patterning were based on statistical analysis using cells collected or observed at different times from a liquid culture, which would mask stochastic fluctuations affecting the process of pattern formation dynamics in a single bacterial filament. In order to analyze the spatiotemporal dynamics of heterocyst formation at the single filament level, here we developed a culture system to monitor simultaneously bacterial development, gene expression, and phycobilisome fluorescence. We also developed micro-liquid chamber arrays to analyze multiple Anabaena filaments at the same time. Cell lineage analyses demonstrated that the initial distributions of hetR::gfp and phycobilisome fluorescence signals at nitrogen step-down were not correlated with the resulting distribution of developed heterocysts. Time-lapse observations also revealed a dynamic hetR expression profile at the single-filament level, including transient upregulation accompanying cell division, which did not always lead to heterocyst development. In addition, some cells differentiated into heterocysts without cell division after nitrogen step-down, suggesting that cell division in the mother cells is not an essential requirement for heterocyst differentiation

Moderation in management research: What, why, when and how.

Many theories in management, psychology, and other disciplines rely on moderating variables: those which affect the strength or nature of the relationship between two other variables. Despite the near-ubiquitous nature of such effects, the methods for testing and interpreting them are not always well understood. This article introduces the concept of moderation and describes how moderator effects are tested and interpreted for a series of model types, beginning with straightforward two-way interactions with Normal outcomes, moving to three-way and curvilinear interactions, and then to models with non-Normal outcomes including binary logistic regression and Poisson regression. In particular, methods of interpreting and probing these latter model types, such as simple slope analysis and slope difference tests, are described. It then gives answers to twelve frequently asked questions about testing and interpreting moderator effects