Mojave Applied Ecology Notes Summer 2010

Survey of monitoring and management for conservation of rare plants, Roadside restoration techniques in Joshua Tree NP, and an update on renewable energy developments in the Southwestern desert

Uniparental Disomy and Genome Imprinting: an Overview

The following paper is concerned with potential changes in the normal epigenetic process in a diploid individual, when a chromosome pair or segment is inherited from one parent only, instead of the expected biparental contribution. This aberrant mode of transmission arises from the high rate of gamete aneuploidy in humans. It has received the name uniparental disomy (UPD), and has emerged as an important factor in the new field of nontraditional inheritance, depicted in Table 1. The following definitions may foster a better understanding of this discussion. UPD is the inheritance of both copies of a chromosome [or chromosomal segment(s)] from a single parent, instead of the normal biparental transmission of the pair. In isodisomy, the two uniparental copies are identical, being derived from the same parental chromosome. In heterodisomy, the two uniparental chromosomes are different, being derived from the homologues of a pai

Quasielastic neutrino scattering from oxygen and the atmospheric neutrino problem

We examine several phenomena beyond the scope of Fermi-gas models that affect the quasielastic scattering (from oxygen) of neutrinos in the 0.1 -- 3.0 GeV range. These include Coulomb interactions of outgoing protons and leptons, a realistic finite-volume mean field, and the residual nucleon-nucleon interaction. None of these effects are accurately represented in the Monte Carlo simulations used to predict event rates due to $\mu$ and $e$ neutrinos from cosmic-ray collisions in the atmosphere. We nevertheless conclude that the neglected physics cannot account for the anomalous $\mu$ to $e$ ratio observed at Kamiokande and IMB, and is unlikely to change absolute event rates by more than 10--15\%. We briefly mention other phenomena, still to be investigated in detail, that may produce larger changes.Comment: In Revtex version 2. 14 pages, 3 figures (available on request from J. Engel, tel. 302-831-4354, [email protected]

Model-independent assessment of current direct searches for spin-dependent dark matter

I evaluate the current results of spin-dependent weakly interacting massive particle (WIMP) searches within a model-independent framework, showing the most restrictive limits to date derive from the combination of xenon and sodium iodide experiments. The extension of this analysis to the case of positive signal experiments is elaborated.Comment: 4 pages, 4 figures, revised and accepted for publication on Phys. Rev. Let

Local correlation functional for electrons in two dimensions

We derive a local approximation for the correlation energy in two-dimensional electronic systems. In the derivation we follow the scheme originally developed by Colle and Salvetti for three dimensions, and consider a Gaussian approximation for the pair density. Then, we introduce an ad-hoc modification which better accounts for both the long-range correlation, and the kinetic-energy contribution to the correlation energy. The resulting functional is local, and depends parametrically on the number of electrons in the system. We apply this functional to the homogeneous electron gas and to a set of two-dimensional quantum dots covering a wide range of electron densities and thus various amounts of correlation. In all test cases we find an excellent agreement between our results and the exact correlation energies. Our correlation functional has a form that is simple and straightforward to implement, but broadly outperforms the commonly used local-density approximation

Intrinsic-Density Functionals

The Hohenberg-Kohn theorem and Kohn-Sham procedure are extended to functionals of the localized intrinsic density of a self-bound system such as a nucleus. After defining the intrinsic-density functional, we modify the usual Kohn-Sham procedure slightly to evaluate the mean-field approximation to the functional, and carefully describe the construction of the leading corrections for a system of fermions in one dimension with a spin-degeneracy equal to the number of particles N. Despite the fact that the corrections are complicated and nonlocal, we are able to construct a local Skyrme-like intrinsic-density functional that, while different from the exact functional, shares with it a minimum value equal to the exact ground-state energy at the exact ground-state intrinsic density, to next-to-leading order in 1/N. We briefly discuss implications for real Skyrme functionals.Comment: 15 page

Correlations between hidden units in multilayer neural networks and replica symmetry breaking

We consider feed-forward neural networks with one hidden layer, tree architecture and a fixed hidden-to-output Boolean function. Focusing on the saturation limit of the storage problem the influence of replica symmetry breaking on the distribution of local fields at the hidden units is investigated. These field distributions determine the probability for finding a specific activation pattern of the hidden units as well as the corresponding correlation coefficients and therefore quantify the division of labor among the hidden units. We find that although modifying the storage capacity and the distribution of local fields markedly replica symmetry breaking has only a minor effect on the correlation coefficients. Detailed numerical results are provided for the PARITY, COMMITTEE and AND machines with K=3 hidden units and nonoverlapping receptive fields.Comment: 9 pages, 3 figures, RevTex, accepted for publication in Phys. Rev.

Interpersonal suicide risk for Latino/a Americans: Investigating thwarted belongingness, perceived burdensomeness, and cultural factors of relevance

There is evidence that different racial groups not only complete suicide at different rates, but conceptualize suicidal behavior differently (American Association of Suicidology [AAS], 2016; Brownson, Becker, Shadick, Jaggers, & Nitkin-Kaner, 2014; Maris, Berma, & Silverman, 2000; Shadick, Backus, & Babot, 2015). Evidence also exists indicating that key culture-based variables such as acculturation, enculturation, and acculturative stress are important variables to explore in research using Latino/a samples (Bernal, 1990; Del Pilar, 2009; Padilla & Lindholm, 1984), and may be related to the suicidal behavior of Latino/as (Fortuna, Perez, Canino, Sribney, & Alegria, 2007; Perez-Rodriguez, Baca-Garcia, Oquendo, Wang, Wall, et al., 2014), especially Latino/a college students (Gomez, Miranda, & Polanco, 2011; Hovey & King, 1996; Saldana, 1994; Walker, Wingate, Obasi, & Joiner, 2008). The Interpersonal-Psychological Theory of Suicide (IPTS; Joiner, 2005; Van Orden, Cukrowicz, Witte, & Joiner, 2012; Van Orden, Witte, Gordon, Bender, & Joiner, 2008; Van Orden, Witte, Cukrowicz, Braithwaite, Selby, & Joiner, 2010), a recent theory in suicidology that has generated a significant amount of research, does not include culture-based factors within its model, and has not been shown to fit well when used to explain the suicidal behavior of racially diverse people (Davidson, Wingate, Slish, & Rasmussen, 2010; O’Keefe, Wingate, Tucker, Thoades-Kerswill, Slish, & Davidson, 2014; Wong, Koo, Tran, Chiu, & Mok, 2011; Garza & Pettit, 2010). In my study, I tested and expanded upon IPTS, by applying Joiner’s construct of suicidal desire (as measured by the sub-constructs of thwarted belongingness and perceived burdensomeness) to Latino/a American college students, to examine the ways in which the IPTS theory can predict their past, current, and future suicidal behavior. In addition, I gave consideration to Latino/a cultural factors by examining the moderating effects of acculturation and enculturation, as well as the potential mediation effects of acculturative stress, on the relation between primary IPTS constructs and past, present, and future suicidal risk. In a sample of 147 Latino/a American college students, results indicate that the IPTS, and perceived burdensomeness in particular, is useful in predicting suicidal risk. Acculturation, enculturation, and acculturative stress were not found to significantly moderate or mediate the relations of the IPTS model. However, enculturation was found to be a particularly salient cultural variable in the explanation of Latino/a American college student’s experience of perceived burdensomeness and its relation to their suicidal risk. Implications for continued examination of the role that relevant cultural factors play in the context of thwarted belongingness, perceived burdensomeness, and Latino/a American college student suicidal risk, as well as implications for utilizing the IPTS in future research and clinical work, are discussed

A study of determinants and prevalence of Rheumatic Heart Disease in Cape Town

Includes abstract.Includes bibliographical references.Rheumatic Heart Disease (RHD) is a post-infectious immune disease ascribed to an interaction between a rheumatogenic strain of group A streptococcus, a susceptible host who lives in poor social conditions with limited access to medical facilities. The disease process begins with repeated group A streptococcal (GAS) infections, which, subsequently result in acute rheumatic fever (ARF). In the absence of intervention, repeated bouts of ARF in turn, may result in progression to RHD, particularly in those ARF patients with cardiac involvement. The prevalence of ARF and RHD in developed countries has shown considerable decline during the last century, largely attributed to improved living conditions and access to healthcare. Epidemiological data from developing countries, while scant, indicate a continued high prevalence of GAS-positive pharyngitis and RHD. Furthermore, while much is known about the social factors and the microbial agent that predispose individuals to ARF, little progress has been made in elucidating genetic susceptibility factors that are reproducible in different populations. This thesis aimed to establish determinants of RHD as well as to document the prevalence of RHD in South African school children. The specific objectives of each study component were as follows: To derive quantitative estimates of the size of the genetic contribution to the risk of developing ARF/RHD. To determine the prevalence of GAS carriage and emm strains of GAS isolates among asymptomatic children enrolled in primary and secondary school. To describe the epidemiology of GAS among 3- to 15-year old children with pharyngitis attending primary health care facilities. To develop a clinical prediction rule for diagnosis of GAS throat infection that is valid for children aged 5-15 years in the primary care setting within the South African context. To determine the prevalence of echocardiographically-proven rheumatic heart disease in school children