Search results for "Null"
showing 10 items of 396 documents
Disruption of TCBA1 associated with a de novo t(1;6)(q32.2;q22.3) presenting in a child with developmental delay and recurrent infections
2005
A boy with developmental delay, particularly of speech, a distinct face, antineutrophil cytoplasmic antibodies, and recurrent infections was found to have an apparently balanced de novo t(1;6)(q32.3;q22.3) translocation. Fluorescent in situ hybridisation with BAC/PAC clones and long range polymerase chain reaction products assessed in the human genome sequence localised the chromosome 1 breakpoint to a 9.8 kb segment within a hypothetical gene, LOC388735, and the chromosome 6 breakpoint to a 12.8 kb segment in intron 4 of the T-cell lymphoma breakpoint-associated target 1 (TCBA1) gene. Disruption and/or formation of TCBA1 fusion genes in T cell lymphoma and leukaemia cell lines suggests a r…
The Export-Productivity Link in Brazilian Manufacturing Firms
2015
This paper explores the link between exports and total factor productivity in Brazilian manufacturing firms over the period 2000–08. The Brazilian experience is instructive, as it is a case of an economy that expanded aggregate exports significantly, but with stagnant aggregate growth in total factor productivity. The paper first estimates firm-level total factor productivity under alternative assumptions (exogenous and endogenous law of motion for productivity) following a GMM procedure. In turn, the analysis uses stochastic dominance techniques to assess whether the ex ante most productive firms are those that start exporting (self-selection hypothesis). Finally, the paper tests whether e…
Multiple mating by females is a natural outcome of a null model of mate encounters
2012
Why do females of so many species mate multiply? The question makes use of an implicit null model that females by default should be monandrous and that polyandry requires an explanation. Here, we make thesimplepoint that females encountermates overtheir lifetimeina stochasticmanner,andas theyshouldacceptatleastonemale,acceptanceofallmales maybea betternullmodelthanthemore advanced strategy of accepting thefirst satisfactory one and rejecting all others. The advantage of this view is that it makes it explicit that females must accept and reject mates without precise knowledge of future mate encounters. In insects, for example, limitations of cognitive and sensory capabilities make it hard fo…
On the coupling dynamics between thermally stressed beams and granular chains
2015
The in-situ measurement of thermal stress in slender beams, or long continuous welded rails, may prevent structural anomalies. With this aim, we investigated the coupling dynamics between a beam and the highly nonlinear solitary waves propagating along a straight granular chain in contact with the beam. We hypothesized that these waves can be used to measure the stress of thermally loaded structures, or to infer the neutral temperature, i.e., the temperature at which this stress is null. We studied numerically and experimentally the mechanical interaction of one and two straight chains of spherical particles in contact with a prismatic beam that is subjected to heat. The results show that c…
On the Use of L-shaped Granular Chains for the Assessment of Thermal Stress in Slender Structures
2014
Slender beams subjected to compressive load are common in civil engineering. The rapid in-situ measurement of this stress may help preventing structural anomalies. In this article, we describe the coupling mechanism between highly nonlinear solitary waves (HNSWs) propagating along an L- shaped granular system and a beam in contact with the gran- ular medium. We evaluate the use of these waves to measure stress in thermally loaded structures and to estimate the neutral temperature, i.e. the temperature at which the stress is null. We investigate numerically and experimentally one and two L- shaped chains of spherical particles in contact with a prismatic beam subjected to heat. We find that …
Statistical validation of rival models for observable stochastic process and its identification
2011
In this paper, for statistical validation of rival (analytical or simulation) models collected for modeling observable process in stochastic system (say, transportation or service system), a uniformly most powerful invariant (UMPI) test is developed from the generalized maximum likelihood ratio (GMLR). This test can be considered as a result of a new approach to solving the Behrens-Fisher problem when covariance matrices of multivariate normal populations (compared with respect to their means) are different and unknown. The test makes use of an invariant statistic whose distribution, under the null hypothesis, does not depend on the unknown (nuisance) parameters. The sample size and thresho…
X-ray transforms in pseudo-Riemannian geometry
2016
We study the problem of recovering a function on a pseudo-Riemannian manifold from its integrals over all null geodesics in three geometries: pseudo-Riemannian products of Riemannian manifolds, Minkowski spaces and tori. We give proofs of uniqueness anc characterize non-uniqueness in different settings. Reconstruction is sometimes possible if the signature $(n_1,n_2)$ satisfies $n_1\geq1$ and $n_2\geq2$ or vice versa and always when $n_1,n_2\geq2$. The proofs are based on a Pestov identity adapted to null geodesics (product manifolds) and Fourier analysis (other geometries). The problem in a Minkowski space of any signature is a special case of recovering a function in a Euclidean space fro…
Fire disturbance disrupts co-occurrence patterns of terrestrial vertebrates in Mediterranean woodlands
2006
Aim This paper uses null model analysis to explore the pattern of species co-occurrence of terrestrial vertebrate fauna in fire-prone, mixed evergreen oak woodlands. Location The Erico–Quercion ilicis of the Mediterranean belt (50–800 m a.s.l.) in the Madonie mountain range, a regional park in northern Sicily (37°50′ N, 14°05′ E), Italy. Methods The stratified sampling of vertebrates in a secondary succession of recent burned areas (BA, 1–2 years old), intermediate burned areas (INT, 4–10 years old) and ancient burned areas (CNB, > 50 years old), plus forest fragments left within burned areas (FF, 1–2 years old) permitted the comparison of patterns of species co-occurrence using a set of…
Self-regulation Training and Job Search Behavior: A Natural Field Experiment Within an Active Labor Market Program
2019
Recent evidence suggests that self-regulation abilities play an important role for the job finding success of unemployed persons. We conduct a randomized controlled trial embedded in an established labor market reactivation program to examine the effect of a self-regulation training on job search effort of long-term unemployed participants. Our treatment involves teaching a self-regulation strategy based on mental contrasting with implementation intentions. We find that the treatment has a positive effect on the quality of application documents as well as on the probability of participants submitting their documents on time. However, we do not find a significant positive effect on labor mar…
A complete system of Engel curves in the Spanish economy
2003
The main goal of this article is the estimation of the consumption–income relationship along with socio–economic factors using cross section data from the Spanish Household Expenditure Survey 1991. The data has been grouped according to exogenous criteria to avoid the problem of null expenditure. First, a non–linear system of equation is estimated, from which the linear form that best fits the used data is tested. Finally, income elasticities are calculated considering three alternative formulations depending on how an initial income increment is distributed among consumers. Income elasticities are shown for the whole income distribution