Competition processes, a tool to model pathogen adaptation time

In many biological contexts, humans try to control harmful populations by introducing resistance into their habitat. However, this strategy is rarely durable because of swift pathogen adaptation to a new hostile environment. Multi-resistance is thought to be a way to delay pathogen adaptation. To understand the population adaptation to multi-resistance environment on the waiting time before emergence of a multi-virulent mutant. We formulated a stochastic population model based on the competition processes with mutation, migration and recombination. We included a fitness cost for mutants overcoming resistance. To estimate the emergence time, we permormed numerical simulations in which we vary pathogens life history traits and the environment structure. The numerical simulation showed the strong dependence of the emergence time on the environment structure. In the case of diversified environment including mono-resistant and susceptible areas, emergence time is a parabolic function of the fraction of resistant area. The emergence time was longer for low and high resistant area fractions, because of induced low migration and mutation probabilities. For multi-resistant environment, emergence time increases with the increase of number of resistances and with the decrease of the transition environments proportion. The results of the model provide insight into our understanding the interplay between used disease control strategy and the pathogen evolution rate to overcome the resistance. The model can be used for designing control strategies preventing rapid adaptation of harmful populations

Relationships Among Expectations of Reentry Problems of International Students Living in On-Campus Apartments and Off-Campus Housing at Andrews University and Selected Student Characteristics

Problem. Andrews University has maintained a large international student population throughout the years, but no previous study exists that examines expectations of reentry problems among international students. Consequently, neither has there been data collected on important demographic variables influencing the sojourn experience of this group, nor does there exist information about relationships among demographic variables and specific reentry areas that shape the students\u27 expectations about the return home. Method. The Expectations of Problems Upon Return to the Home Country Among International Students at Andrews University survey instrument was developed. Descriptive statistics were used to discover demographic characteristics and frequency of responses. t-tests were done to identify the presence of significant differences between selected dichotomous student characteristics and seven areas of reentry concern. One-way ANOVAs were done to explore main effects among non-dichotomous variables and two-way ANOVAs were done to explore possible interactions. Results. Unmarried students had significantly higher expectations of problems in the return experience in regard to three reentry areas: national and political conditions (p =.001), educational aspects (p =.049) and professional aspects (p =.006). Students who socialized little, or not at all, with other students from the same country had significantly lower expectations of problems in regard to professional aspects in the return experience than those who socialized more (p =.0248). Seven significant main effects and ten significant interactive effects were obtained for variables unrelated to hypotheses in the study. Conclusions. Marital status, age, level of degree program, location of Andrews University, use of English language and socialization with students from the home country represent significant student characteristics that shape expectations of reentry problems in regard to cultural adjustment, national and political conditions, professional aspects and church work adjustment. Professional integration is an issue of primary concern

Localization for Random Unitary Operators

We consider unitary analogs of $1-$dimensional Anderson models on $l^2(\Z)$ defined by the product $U_\omega=D_\omega S$ where $S$ is a deterministic unitary and $D_\omega$ is a diagonal matrix of i.i.d. random phases. The operator $S$ is an absolutely continuous band matrix which depends on a parameter controlling the size of its off-diagonal elements. We prove that the spectrum of $U_\omega$ is pure point almost surely for all values of the parameter of $S$. We provide similar results for unitary operators defined on $l^2(\N)$ together with an application to orthogonal polynomials on the unit circle. We get almost sure localization for polynomials characterized by Verblunski coefficients of constant modulus and correlated random phases

Linking the High-Resolution Architecture of Modern and Ancient Wave-Dominated Deltas : Processes, Products and Forcing Factors

Many thoughts and concepts used in this paper were initially developed as a result of work conducted with funding provided to the WAVE Consortium at the Australian School of Petroleum, University of Adelaide (RBA, BKV and JB). The consortium sponsors (Apache, BAPETCO, BHPBP, BG, BP, Chevron, ConocoPhillips, Nexen, OMV, Shell, Statoil, Todd Energy, and Woodside Energy) are thus thanked for making this work possible. We are indebted to journal reviewers Cornel Olariu and Howard Feldman, and to Associate Editor Janok Bhattacharya for numerous comments and suggestions that improved the clarity of the manuscript.Peer reviewedPostprin

Eigenvalue distributions from a star product approach

We use the well-known isomorphism between operator algebras and function spaces equipped with a star product to study the asymptotic properties of certain matrix sequences in which the matrix dimension $D$ tends to infinity. Our approach is based on the $su(2)$ coherent states which allow for a systematic 1/D expansion of the star product. This produces a trace formula for functions of the matrix sequence elements in the large-$D$ limit which includes higher order (finite-$D$) corrections. From this a variety of analytic results pertaining to the asymptotic properties of the density of states, eigenstates and expectation values associated with the matrix sequence follows. It is shown how new and existing results in the settings of collective spin systems and orthogonal polynomial sequences can be readily obtained as special cases. In particular, this approach allows for the calculation of higher order corrections to the zero distributions of a large class of orthogonal polynomials.Comment: 25 pages, 8 figure

Applications of Human Tissue-Engineered Blood Vessel Models to Study the Effects of Shed Membrane Microparticles from T-Lymphocytes on Vascular Function

Microparticles (MPs) are membrane vesicles harboring cell surface proteins and containing cytoplasmic components of the original cell. High levels of circulating MPs have been detected in pathological states associated with vascular dysfunction. We took advantage of the self-assembly method of tissue engineering to produce in vitro three vascular constructs from human vascular smooth muscle cells and fibroblasts to investigate the role of the adventitia in the modulation of vascular tone by MPs, comparing the contractile response of each of these constructs to histamine. The first two were composed of an adventitia (tissue-engineered vascular adventitia (TEVA)) or a media (tissue-engineered vascular media (TEVM)) solely, and the third one contained a media and an adventitia (tissue-engineered vascular media and adventitia (TEVMA)). In the three constructs, the results show that histamine induces contraction insensitive to blockade of inducible nitric oxide (NO) synthase (iNOS) and cyclooxygenase-2 (COX-2) and not affected by MP treatment. MPs decreased NO production and nuclear factor (NF)-κB expression but did not affect superoxide anion (O2−) release in TEVA. MPs enhanced NF-κB expression but did not affect iNOS and COX-2 expression or NO or O2− release in TEVM. In TEVMA, MPs did not enhance NF-κB expression, but COX-2 expression was higher, and O2− release was lower. Thus, MPs affected NO, O2−, NF-κB, and COX-2 in a subtle fashion to maintain the contractile response to histamine. The use of tissue-engineered vascular constructs results in a better understanding of the effect of MPs on human adventitia and media