2,679 research outputs found
Randomization, Endogeneity and Laboratory Experiments
In conducting experiments with multiple trials, outcomes from previous trials can impact on current behavior. One of the most obvious cases in which this can happen, and the case considered in this paper, is in an auction market experiment, where earnings from previous auction trials alter cash balances which, in turn, can affect bidding behavior. (The most obvious mechanism for such a result, within standard theory, is if bidders are risk averse and do not have constant absolute risk aversion. One can imagine a number of non-standard reasons for such effects as well.) Use of OLS regressions with cash balances included as a right hand side variable are likely to lead to a biased estimate of the cash balance effect since the variation in cash balances is largely related to differences in bidding strategies across individuals. Fixed effect regressions can commonly control for these endogeniety problems at the potential cost of obtaining inefficient estimates, since this estimator does not exploit between-individual variation. This paper addresses this problem in two ways. First we consider an experimental design that reduces the potential bias of OLS estimates while increasing the precision of fixed effect estimates. Second, we consider instrumental variables estimation of the cash balance effect where the instruments are produced by the experimental design. To the best of our knowledge, neither of these approaches has been explored in the experimental literature.
Psychological interventions in asthma
Asthma is a multifactorial chronic respiratory disease characterised by recurrent episodes of airway obstruction. The current management of asthma focuses principally on pharmacological treatments, which have a strong evidence base underlying their use. However, in clinical practice, poor symptom control remains a common problem for patients with asthma. Living with asthma has been linked with psychological co-morbidity including anxiety, depression, panic attacks and behavioural factors such as poor adherence and suboptimal self-management. Psychological disorders have a higher-than-expected prevalence in patients with difficult-to-control asthma. As psychological considerations play an important role in the management of people with asthma, it is not surprising that many psychological therapies have been applied in the management of asthma. There are case reports which support their use as an adjunct to pharmacological therapy in selected individuals, and in some clinical trials, benefit is demonstrated, but the evidence is not consistent. When findings are quantitatively synthesised in meta-analyses, no firm conclusions are able to be drawn and no guidelines recommend psychological interventions. These inconsistencies in findings may in part be due to poor study design, the combining of results of studies using different interventions and the diversity of ways patient benefit is assessed. Despite this weak evidence base, the rationale for psychological therapies is plausible, and this therapeutic modality is appealing to both patients and their clinicians as an adjunct to conventional pharmacological treatments. What are urgently required are rigorous evaluations of psychological therapies in asthma, on a par to the quality of pharmaceutical trials. From this evidence base, we can then determine which interventions are beneficial for our patients with asthma management and more specifically which psychological therapy is best suited for each patient
How to make experimental economics research more reproducible: lessons from other disciplines and a new proposal
Efforts in the spirit of this special issue aim at improving the reproducibility of experimental economics, in response to the recent discussions regarding the “research reproducibility crisis.” We put this endeavour in perspective by summarizing the main ways (to our knowledge) that have been proposed – by researchers from several disciplines – to alleviate the problem. We discuss the scope for economic theory to contribute to evaluating the proposals. We argue that a potential key impediment to replication is the expectation of negative reactions by the authors of the individual study, and suggest that incentives for having one’s work replicated should increase
Pregnant women with bronchial asthma benefit from progressive muscle relaxation: A randomized, prospective, controlled trial
Background: Asthma is a serious medical problem in pregnancy and is often associated with stress, anger and poor quality of life. The aim of this study was to determine the efficacy of progressive muscle relaxation (PMR) on change in blood pressure, lung parameters, heart rate, anger and health-related quality of life in pregnant women with bronchial asthma. Methods: We treated a sample of 64 pregnant women with bronchial asthma from the local population in an 8-week randomized, prospective, controlled trial. Thirty-two were selected for PMR, and 32 received a placebo intervention. The systolic blood pressure, forced expiratory volume in the first second, peak expiratory flow and heart rate were tested, and the State-Trait Anger Expression Inventory and Health Survey (SF-36) were employed. Results: According to the intend-to-treat principle, a significant reduction in systolic blood pressure and a significant increase in both forced expiratory volume in the first second and peak expiratory flow were observed after PMR. The heart rate showed a significant increase in the coefficient of variation, root mean square of successive differences and high frequency ranges, in addition to a significant reduction in low and middle frequency ranges. A significant reduction on three of five State-Trait Anger Expression Inventory scales, and a significant increase on seven of eight SF-36 scales were observed. Conclusions: PMR appears to be an effective method to improve blood pressure, lung parameters and heart rate, and to decrease anger levels, thus enhancing health-related quality of life in pregnant women with bronchial asthma. Copyright (c) 2006 S. Karger AG, Basel
Lyashko-Looijenga morphisms and submaximal factorisations of a Coxeter element
When W is a finite reflection group, the noncrossing partition lattice NCP_W
of type W is a rich combinatorial object, extending the notion of noncrossing
partitions of an n-gon. A formula (for which the only known proofs are
case-by-case) expresses the number of multichains of a given length in NCP_W as
a generalised Fuss-Catalan number, depending on the invariant degrees of W. We
describe how to understand some specifications of this formula in a case-free
way, using an interpretation of the chains of NCP_W as fibers of a
Lyashko-Looijenga covering (LL), constructed from the geometry of the
discriminant hypersurface of W. We study algebraically the map LL, describing
the factorisations of its discriminant and its Jacobian. As byproducts, we
generalise a formula stated by K. Saito for real reflection groups, and we
deduce new enumeration formulas for certain factorisations of a Coxeter element
of W.Comment: 18 pages. Version 2 : corrected typos and improved presentation.
Version 3 : corrected typos, added illustrated example. To appear in Journal
of Algebraic Combinatoric
Threshold Dose for Shrimp: A Risk Characterization Based on Objective Reactions in Clinical Studies
A DBPCFC [double-blind, placebo-controlled food challenge] of shrimp-allergic adults was conducted to obtain individual threshold doses. Results of this study and published research were combined and a population threshold for shrimp was determined from dose-distribution modeling. The shrimp-allergic population seems to have a higher threshold compared to other populations for other food allergens. Additional shrimp challenges should be done to confirm these initial results
Breakdown of the Mott insulator: Exact solution of an asymmetric Hubbard model
The breakdown of the Mott insulator is studied when the dissipative tunneling
into the environment is introduced to the system. By exactly solving the
one-dimensional asymmetric Hubbard model, we show how such a breakdown of the
Mott insulator occurs. As the effect of the tunneling is increased, the Hubbard
gap is monotonically decreased and finally disappears, resulting in the
insulator-metal transition. We discuss the origin of this quantum phase
transition in comparison with other non-Hermitian systems recently studied.Comment: 7 pages, revte
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