Cox model with interval‐censored covariate in cohort studies

In cohort studies the outcome is often time to a particular event, and subjects are followed at regular intervals. Periodic visits may also monitor a secondary irreversible event influencing the event of primary interest, and a significant proportion of subjects develop the secondary event over the period of follow‐up. The status of the secondary event serves as a time‐varying covariate, but is recorded only at the times of the scheduled visits, generating incomplete time‐varying covariates. While information on a typical time‐varying covariate is missing for entire follow‐up period except the visiting times, the status of the secondary event are unavailable only between visits where the status has changed, thus interval‐censored. One may view interval‐censored covariate of the secondary event status as missing time‐varying covariates, yet missingness is partial since partial information is provided throughout the follow‐up period. Current practice of using the latest observed status produces biased estimators, and the existing missing covariate techniques cannot accommodate the special feature of missingness due to interval censoring. To handle interval‐censored covariates in the Cox proportional hazards model, we propose an available‐data estimator, a doubly robust‐type estimator as well as the maximum likelihood estimator via EM algorithm and present their asymptotic properties. We also present practical approaches that are valid. We demonstrate the proposed methods using our motivating example from the Northern Manhattan Study.     

Twins are more different than commonly believed,but made less different by compensating behaviors

Twin studies are popular, because twins are believed to be the same/similar in genes and environmental exposures. It is well documented, however, that the firstborns are healthier at birth. We use the entire U.S. record of twin births during 1995–2000 to show that the survival duration parameters differ between twins depending on the birth order. We also find that wiser (i.e., older or educated) or married (i.e., resource-richer) mothers take more care of the weaker, which is a “compensating” behavior reducing the twin difference, as opposed to “reinforcing (the twin difference)” behavior. The systematic survival pattern difference and the mother's intervention against nature send cautions to twin studies that regard twins homogeneous to interpret their findings accordingly. Since the survival duration in our data is 97% right-censored in one year, we devise a quantile-based ‘fixed-effect’ semiparametric estimator that can handle heavy censoring, which is our methodological contribution.     

Dance education in Singapore: Policy,discourse, and practice

This article provides an overview of dance education in schools in Singapore with regard to physical education, co-curricular activity, initiatives by the National Arts Council's Arts Education unit, and pre-tertiary and tertiary dance programs. In an effort to gain a better understanding of how well the official discourse and the reality of schooling in dance interconnect, a meta-analysis of published articles, conference papers, committee reports, and curricula was conducted. Situated within the larger sociocultural, political, and historical contexts, Singapore presents a curious case for probing the merits and limitations of research, policy initiatives, and policy implementation. In the conclusion, the author argues that the development of a coherent dance education in Singapore requires “fixing” three dilemmas—meritocratic schooling in dance, the ill-defined and exhaustive use of the term “talent,” and the uneven research that has not kept pace with the policy initiatives.     

Biology and comparative predation efficacy of three heteropteran species recorded as predators ofBemisia tabaci in Maharashtra

Two mirids,Deraeocoris sp. andCampylomma nicolasi Reuter and one lygaeid,Geocoris ochropterus Fieber were found preying onB. tabaci (Gennadius) for the first time in Maharashtra State of India during 1987–88. Their biology and predation capacity onB. tabaci were studied in detail under laboratory conditions. The nymphal stage ofDeraeocoris sp. passed through 6 instars, whereas 5 instars in case of the remaining species.G. ochropterus, Deraeocoris sp. andC. nicolasi consumed on an average 482.5, 275.3 and 128.8 nymphs of 57.3, 25.5 and 20.6 days, respectively. On the basis of consumption rate per day,Deraeocoris sp. proved to be a superior predator. Part of Ph. D. Thesis submitted to Marathwada Agricultural University, Parbhani 431402, India.     

The Genetic Basis of Morphological Diversity in Domesticated Goldfish

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The ecological and evolutionary significance of frost in the context of climate change

The effects that below-freezing temperature (frost) can have at times of year when it is unusual are an interesting ecological phenomenon that has received little attention. The physiological consequence of formation of ice crystals in plant tissue is often death of the plants, or at least of sensitive parts that can include flower buds, ovaries, and leaves. The loss of potential for sexual reproduction can have long-lasting effects on the demography of annuals and long-lived perennials, because the short-term negative effects of frosts can result in longer-term benefits through lowered populations of seed predators. The loss of host plants can have dramatic consequences for herbivores, even causing local extinctions, and the loss of just flowers can also affect populations of seed predators and their parasitoids. Frosts can cause local extinctions and influence the geographical distribution of some species. The potential for global climate change to influence the frequency and distribution of frost events is uncertain, but it seems likely that they may become more frequent in some areas and less frequent in others.     

The lateral cervical nucleus in the cat

Summary Profiles of 14 neurons all sectioned through the nucleolar plane and 87 isolated dendritic profiles have been analyzed with respect to the surface area covered by boutons and astroglial processes. This analysis has revealed two different types of neurons within the lateral cervical nucleus (LCN) of the cat. The cell types also differ in other ultrastructural respects. One type, which probably consists of projection neurons, is characterized by a rather large size, a relatively small nucleus, numerous mitochondria, well developed granular and agranular endoplasmic reticulum. The cell membrane of these cells shows somatic spines and the perikaryon is covered with boutons to a mean extent of 42%. The other cell type, which probably is internuncial, is smaller, has a proportionally larger nucleus, few mitochondria and a poorly developed granular and agranular endoplasmic reticulum. These cells show no somatic spines and the perikaryal membrane is covered with boutons to an extent of about 10%. Also the bouton populations contacting the two cell types differ from one another. The proportion of internuncial neurons within the LCN has been estimated to about 8%. The internuncial neurons seem to have no preferential localization.The primary dendrites of the projection neurons have a bouton covering of about 48%. No proportional differences in covering could be revealed between different sizes of dendrites.The results are discussed in relation to what is known about the anatomical and physiological organization of the LCN, and also compared with the results obtained in other similar investigations on other parts of the central nervous system.The author is grateful to fil.kand. Göran Engholm for his help with the statistical considerations.This work was supported by grants from Anders Otto Swärds Stiftelse, Stiftelsen Lars Hiertas minne, Åhlén och Holms stiftelse, Åke Wibergs stiftelse and the Swedish Medical Research Council (Project No B70-12X-2710).     

Xanthenone-based hydrazones as potent α-glucosidase inhibitors: Synthesis,solid state self-assembly and in silico studies

Xanthenone based hydrazone derivatives (5a–n) have been synthesized as potential α-glucosidase inhibitors. All synthesized compounds (5a–n) are characterized by their FTIR, ¹H NMR, ¹³C NMR and HRMS, and in case of 5g also by X-ray crystallographic technique. The compounds unveiled a varying degree of α-glucosidase inhibitory activity when compared with standard acarbose (IC₅₀ = 375.38 ± 0.12 µM). Amongst the series, compound 5l (IC₅₀ = 62.25 ± 0.11 µM) bearing a trifluoromethyl phenyl group is found to be the most active compound. Molecular modelling is performed to establish the binding pattern of the more active compound 5l, which revealed the significance of substitution pattern. The pharmacological properties of molecules are also calculated by MedChem Designer which determines the ADME (absorption, distribution, metabolism, excretion) properties of molecules. The solid state self-assembly of compound 5g is discussed to show the conformation and role of iminoamide moiety in the molecular packing.     

Low-Fat Diets May Prevent Weight Gain in Sedentary Women: Prospective Observations From the Population Study of Women in Gothenburg,Sweden

The Population Study of Women in Gothenburg, Sweden is an ongoing prospective study of female residents who were recruited from the local registry in 1968–1969 when they were 38–60 years old. The data presented here were collected from 361 healthy women who underwent a baseline physical examination including a supplementary dietary history interview and returned for a second general health examination 6 years later. This report identifies a subgroup of 57 women who were sedentary during their leisure time and appear to have been particularly susceptible to gaining weight as a function of the fat content of their diets. Specifically, longitudinal analysis of body weights in the whole sample revealed a statistical interaction between leisure-time physical activity and habitual dietary fat intake (energy-%), as reported at the baseline examination, in the prediction of subsequent weight change. Further stratified analysis suggested that weight changes were significantly dependent on dietary fat intake among the sedentary women only. High energy intake also predicted weight gain in the sedentary group, although the predictive value for a high-fat diet was of marginal significance after adjusting for total energy consumption. These results suggest that sedentary recreational activity plus a low-fat diet may have a combined contribution to weight change that is not equivalent to the sum of the separate effects. Such a synergy between two modifiable lifestyle factors seems highly relevant for prevention of obesity.