3,847 research outputs found
Randomization Technique, Allocation Concealment, Masking, And Susceptibility Of Trials To Selection Bias
It is widely believed that baseline imbalances in randomized clinical trials must necessarily be random. Yet even among masked randomized trials conducted with allocation concealment, there are mechanisms by which patients with specific covariates may be selected for inclusion into a particular treatment group. This selection bias would force imbalance in those covariates, measured or unmeasured, that are used for the patient selection. Unfortunately, few trials provide adequate information to determine even if there was allocation concealment, how the randomization was conducted, and how successful the masking may have been, let alone if selection bias was adequately controlle d. In this article we reinforce the message that allocation details should be presented in full. We also facilitate such reporting by identifying and clarifying the role of specific reportable design features. Because the designs that eliminate all selection bias are rarely feasible in practice, our development has important implications for not only the implementation, but also the reporting and interpretation, of randomized clinical trials
Laboratory procedures manual for the firefly luciferase assay for adenosine triphosphate (ATP)
A manual on the procedures and instruments developed for the adenosine triphosphate (ATP) luciferase assay is presented. Data cover, laboratory maintenance, maintenance of bacterial cultures, bacteria measurement, reagents, luciferase procedures, and determination of microbal susceptibility to antibiotics
Effect of row spacing, nitrogen and weed control on crop and weed in low rainfall zones of western Australia
Wide rows essentially ensure some temporal and spatial water availability in water-limiting crop environments, thus minimising the risk of water deficits at critical crop growth stages to ensure profitable yields (Whish et al., 2005). Presence of weeds will have a major impact on water availability to crops irrespective of planting geometries. Decreasing crop plant population and increasing row spacing decreases crop competitive ability against weeds, and generally wider row spacing will reduce crop competition for homogeneously distributed production factors, as postulated mathematically by Fischer and Miles, (1973). Hence good weed management becomes critical to the success of wide row systems, as failure to control water-using weeds defeats the purpose of wide row cropping where water conservation is the focus. With a perceived decline in rainfall in central and eastern wheat belt of Western Australia (WA), wide row cropping practices may prove more productive if weeds can be managed by appropriate herbicides and depriving weeds from applied nitrogen (N). We examined the effect of nitrogen and herbicide on the crop performance and weed control under normal and wide row spacing in a wheat – lupin– canola rotation at Cunderdin and wheat – chickpea rotation at Merredin, WA
Correspondence between geometrical and differential definitions of the sine and cosine functions and connection with kinematics
In classical physics, the familiar sine and cosine functions appear in two
forms: (1) geometrical, in the treatment of vectors such as forces and
velocities, and (2) differential, as solutions of oscillation and wave
equations. These two forms correspond to two different definitions of
trigonometric functions, one geometrical using right triangles and unit
circles, and the other employing differential equations. Although the two
definitions must be equivalent, this equivalence is not demonstrated in
textbooks. In this manuscript, the equivalence between the geometrical and the
differential definition is presented assuming no a priori knowledge of the
properties of sine and cosine functions. We start with the usual length
projections on the unit circle and use elementary geometry and elementary
calculus to arrive to harmonic differential equations. This more general and
abstract treatment not only reveals the equivalence of the two definitions but
also provides an instructive perspective on circular and harmonic motion as
studied in kinematics. This exercise can help develop an appreciation of
abstract thinking in physics.Comment: 6 pages including 1 figur
Immobilisation of Higher Activity Wastes from Nuclear Reactor Production of 99
A variety of intermediate- and low-level liquid and solid wastes are produced from reactor production of 99Mo using UAl alloy or UO2 targets and in principle can be collectively or individually converted into waste forms. At ANSTO, we have legacy acidic uranyl-nitrate-rich intermediate level waste (ILW) from the latter, and an alkaline liquid ILW, a U-rich filter cake, plus a shorter lived liquid stream that rapidly decays to low-level waste (LLW) standards, from the former. The options considered consist of cementitious products, glasses, glass-ceramics, or ceramics produced by vitrification or hot isostatic pressing for intermediate-level wastes. This paper discusses the progress in waste form development and processing to treat ANSTO’s ILW streams arising from 99Mo. The various waste forms and the reason for the process option chosen will be reviewed. We also address the concerns over adapting our chosen process for use in a hot-cell environment
A hierarchical model of transcriptional dynamics allows robust estimation of transcription rates in populations of single cells with variable gene copy number
Motivation: cis-regulatory DNA sequence elements, such as enhancers and silencers, function to control the spatial and temporal expression of their target genes. Although the overall levels of gene expression in large cell populations seem to be precisely controlled, transcription of individual genes in single cells is extremely variable in real time. It is, therefore, important to understand how these cis-regulatory elements function to dynamically control transcription at single-cell resolution. Recently, statistical methods have been proposed to back calculate the rates involved in mRNA transcription using parameter estimation of a mathematical model of transcription and translation. However, a major complication in these approaches is that some of the parameters, particularly those corresponding to the gene copy number and transcription rate, cannot be distinguished; therefore, these methods cannot be used when the copy number is unknown.
Results: Here, we develop a hierarchical Bayesian model to estimate biokinetic parameters from live cell enhancer–promoter reporter measurements performed on a population of single cells. This allows us to investigate transcriptional dynamics when the copy number is variable across the population. We validate our method using synthetic data and then apply it to quantify the function of two known developmental enhancers in real time and in single cells
Molecular Electroporation and the Transduction of Oligoarginines
Certain short polycations, such as TAT and polyarginine, rapidly pass through
the plasma membranes of mammalian cells by an unknown mechanism called
transduction as well as by endocytosis and macropinocytosis. These
cell-penetrating peptides (CPPs) promise to be medically useful when fused to
biologically active peptides. I offer a simple model in which one or more CPPs
and the phosphatidylserines of the inner leaflet form a kind of capacitor with
a voltage in excess of 180 mV, high enough to create a molecular electropore.
The model is consistent with an empirical upper limit on the cargo peptide of
40--60 amino acids and with experimental data on how the transduction of a
polyarginine-fluorophore into mouse C2C12 myoblasts depends on the number of
arginines in the CPP and on the CPP concentration. The model makes three
testable predictions.Comment: 15 pages, 5 figure
Bose-Einstein correlations for Levy stable source distributions
The peak of the two-particle Bose-Einstein correlation functions has a very
interesting structure. It is often believed to have a multivariate Gaussian
form. We show here that for the class of stable distributions, characterized by
the index of stability , the peak has a stretched exponential
shape. The Gaussian form corresponds then to the special case of .
We give examples for the Bose-Einstein correlation functions for univariate as
well as multivariate stable distributions, and check the model against
two-particle correlation data.Comment: 30 pages, 1 figure, an important misprint in former eqs. (37-38) and
other minor misprints are corrected, citations update
- …