804 research outputs found
Electrical thermo-optic tuning of ultrahigh-Q microtoroid resonators
The ability to tune resonant frequency in optical microcavities is an essential feature for many applications. Integration of electrical-based tuning as part of the fabrication process has been a key advantage of planar microresonant devices. Until recently, the combination of these features has not been available in devices that operate in the ultrahigh-Q regime where device quality factors (Q) can exceed 100 million. In this letter, we demonstrate an electrically tunable resonator on a chip with ultrahigh-quality factors. Futhermore, the devices have demonstrated tuning rates in excess of 85 GHz/V2 and are capable of tuning more than 300 GHz
Friendship Quality in Youth Disability Sport: Perceptions of a Best Friend
The purpose of the current investigation was to examine friendship quality with a best friend in youth disability sport with an international sample of moderately experienced athletes with disabilities ages 9 to 18 years. Participants were 85 males and 65 females from four countries who competed in track and field and swimming. Data were collected with the Sport Friendship Quality Scale (Weiss & Smith, 1999). An exploratory factor analyses indicated that participants viewed their friendship quality with a best friend in disability sport as having both positive and negative dimensions. The latter focused exclusively on conflict experiences. Females reported stronger perceptions of the benefits of their friendships than males did; whereas no gender differences occurred in perceptions of the negative aspects to friendships. Item analyses indicated that females scored higher than males on questions reflecting loyalty, providing intimacy, self-esteem, supportiveness, having things in common, and playing together
Kiwi forego vison in the guidance of their nocturnal activities
We propose that the Kiwi visual system has undergone adaptive regression evolution driven by the trade-off between the relatively low rate of gain of visual information that is possible at low light levels, and the metabolic costs of extracting that information
Statistical modelling of transcript profiles of differentially regulated genes
Background: The vast quantities of gene expression profiling data produced in microarray studies, and
the more precise quantitative PCR, are often not statistically analysed to their full potential. Previous
studies have summarised gene expression profiles using simple descriptive statistics, basic analysis of
variance (ANOVA) and the clustering of genes based on simple models fitted to their expression profiles
over time. We report the novel application of statistical non-linear regression modelling techniques to
describe the shapes of expression profiles for the fungus Agaricus bisporus, quantified by PCR, and for E.
coli and Rattus norvegicus, using microarray technology. The use of parametric non-linear regression models
provides a more precise description of expression profiles, reducing the "noise" of the raw data to
produce a clear "signal" given by the fitted curve, and describing each profile with a small number of
biologically interpretable parameters. This approach then allows the direct comparison and clustering of
the shapes of response patterns between genes and potentially enables a greater exploration and
interpretation of the biological processes driving gene expression.
Results: Quantitative reverse transcriptase PCR-derived time-course data of genes were modelled. "Splitline"
or "broken-stick" regression identified the initial time of gene up-regulation, enabling the classification
of genes into those with primary and secondary responses. Five-day profiles were modelled using the
biologically-oriented, critical exponential curve, y(t) = A + (B + Ct)Rt + ε. This non-linear regression
approach allowed the expression patterns for different genes to be compared in terms of curve shape,
time of maximal transcript level and the decline and asymptotic response levels. Three distinct regulatory
patterns were identified for the five genes studied. Applying the regression modelling approach to
microarray-derived time course data allowed 11% of the Escherichia coli features to be fitted by an
exponential function, and 25% of the Rattus norvegicus features could be described by the critical
exponential model, all with statistical significance of p < 0.05.
Conclusion: The statistical non-linear regression approaches presented in this study provide detailed
biologically oriented descriptions of individual gene expression profiles, using biologically variable data to
generate a set of defining parameters. These approaches have application to the modelling and greater
interpretation of profiles obtained across a wide range of platforms, such as microarrays. Through careful
choice of appropriate model forms, such statistical regression approaches allow an improved comparison
of gene expression profiles, and may provide an approach for the greater understanding of common
regulatory mechanisms between genes
Cluster randomised trials in the medical literature: two bibliometric surveys
Background: Several reviews of published cluster randomised trials have reported that about half did not take clustering into account in the analysis, which was thus incorrect and potentially misleading. In this paper I ask whether cluster randomised trials are increasing in both number and quality of reporting. Methods: Computer search for papers on cluster randomised trials since 1980, hand search of trial reports published in selected volumes of the British Medical Journal over 20 years. Results: There has been a large increase in the numbers of methodological papers and of trial reports using the term 'cluster random' in recent years, with about equal numbers of each type of paper. The British Medical Journal contained more such reports than any other journal. In this journal there was a corresponding increase over time in the number of trials where subjects were randomised in clusters. In 2003 all reports showed awareness of the need to allow for clustering in the analysis. In 1993 and before clustering was ignored in most such trials. Conclusion: Cluster trials are becoming more frequent and reporting is of higher quality. Perhaps statistician pressure works
OncoLog Volume 47, Number 09, September 2002
Is Hormone Replacement Therapy an Option for Women with a History of Breast Cancer?
Breast Cancer Survivor Devotes Life to Helping Those at High Risk for Hereditary Cancers
I Have Something to Tell You. Counselors Support Family Communication about Genetic Susceptibility to Cancer
DiaLog: Bigger than a Blood Test: Ethical Cautions about Genetic Testing, by Martin L. Smith, STD, and Anne J. Flamm, JD
House Call: Just a Phase: Understanding Clinical Trials
Discovery Sheds Light on How Breast Cancer Cells Progress to More Aggressive Formshttps://openworks.mdanderson.org/oncolog/1109/thumbnail.jp
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