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Search Results: 1 - 10 of 465729 matches for " Jennifer A Tate "
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On the road to diploidization? Homoeolog loss in independently formed populations of the allopolyploid Tragopogon miscellus (Asteraceae)
Jennifer A Tate, Prashant Joshi, Kerry A Soltis, Pamela S Soltis, Douglas E Soltis
BMC Plant Biology , 2009, DOI: 10.1186/1471-2229-9-80
Abstract: Of the 13 loci analyzed in 84 T. miscellus individuals, 11 showed loss of at least one parental homoeolog in the young allopolyploids. Two loci were retained in duplicate for all polyploid individuals included in this study. Nearly half (48%) of the individuals examined lost a homoeolog of at least one locus, with several individuals showing loss at more than one locus. Patterns of loss were stochastic among individuals from the independently formed populations, except that the T. dubius copy was lost twice as often as T. pratensis.This study represents the most extensive survey of the fate of genes duplicated by allopolyploidy in individuals from natural populations. Our results indicate that the road to genome downsizing and ultimate genetic diploidization may occur quickly through homoeolog loss, but with some genes consistently maintained as duplicates. Other genes consistently show evidence of homoeolog loss, suggesting repetitive aspects to polyploid genome evolution.Allopolyploidy combines the processes of hybridization with genome doubling, and together, these provide a potential avenue for instantaneous speciation [1-3]. Whole-genome sequencing efforts have revolutionized our thinking about the significance of polyploidy, as it is clear that paleopolyploidy is a common phenomenon. Ancient whole-genome duplications have been detected in many eukaryotic lineages, including angiosperms, vertebrates, and yeast [4-12]. Polyploidy has been particularly prevalent in flowering plants, where previous estimates indicated that 30–70% of angiosperm species had polyploidy in their ancestry [reviewed in [13]]. In the last decade, the view of polyploidy in angiosperms has changed, and it is now appreciated that perhaps all angiosperm lineages have experienced at least one round of polyploidy, with many lineages undergoing two or more such episodes [14-18]. On more recent timescales, molecular data have also revealed that most extant polyploid plant species have formed rec
Similar patterns of rDNA evolution in synthetic and recently formed natural populations of Tragopogon (Asteraceae) allotetraploids
Hana Malinska, Jennifer A Tate, Roman Matyasek, Andrew R Leitch, Douglas E Soltis, Pamela S Soltis, Ales Kovarik
BMC Evolutionary Biology , 2010, DOI: 10.1186/1471-2148-10-291
Abstract: Using Southern blot hybridization and fluorescent in situ hybridization (FISH), we analyzed copy numbers and distribution of these highly reiterated genes in seven lines of synthetic T. mirus (110 individuals) and four lines of synthetic T. miscellus (71 individuals). Variation among diploid parents accounted for most of the observed gene imbalances detected in F1 hybrids but cannot explain frequent deviations from repeat additivity seen in the allotetraploid lines. Polyploid lineages involving the same diploid parents differed in rDNA genotype, indicating that conditions immediately following genome doubling are crucial for rDNA changes. About 19% of the resynthesized allotetraploid individuals had equal rDNA contributions from the diploid parents, 74% were skewed towards either T. porrifolius or T. pratensis-type units, and only 7% had more rDNA copies of T. dubius-origin compared to the other two parents. Similar genotype frequencies were observed among natural populations. Despite directional reduction of units, the additivity of 35S rDNA locus number is maintained in 82% of the synthetic lines and in all natural allotetraploids.Uniparental reductions of homeologous rRNA gene copies occurred in both synthetic and natural populations of Tragopogon allopolyploids. The extent of these rDNA changes was generally higher in natural populations than in the synthetic lines. We hypothesize that locus-specific and chromosomal changes in early generations of allopolyploids may influence patterns of rDNA evolution in later generations.Chromosome counts suggest that between 30 and 100% of angiosperm species are polyploids [1], and Wood et al. [2] propose that 15% of angiosperm speciation events are associated with polyploidy whereas recent genomic studies of selected model and crop species have revealed that all plant genomes sequenced to date have signatures of one or more whole-genome duplications in their evolutionary history [3,4]. The success of newly formed angiosperm
Fostering Scholarship Capacity: The Experience of Nurse Educators
Penelope A. Cash,Betty Tate
Canadian Journal for the Scholarship of Teaching and Learning , 2012,
Abstract: In a milieu where traditional views of scholarship are embedded in the culture of educational institutions, and nursing programs in particular, this paper reports on a research project designed to support nurse educators’ capacity to engage in scholarly activities. Rogers’ (2003, 2004) “Diffusion of Innovation” model provided a theoretical vantage point from which to consider the ways scholarly inquiry in and across the nursing programs could be promoted. The project was evaluated between 2004 and 2007 using both quantitative and qualitative methods. In this paper we highlight some of the meanings emerging from the qualitative information collected because this data best illustrates Rogers’ (2003) model. Although significant progress was made towards building scholarship capacity with nursing faculty there remains ongoing work to be undertaken. Continuing to support a broader view of scholarship and intentional scholarship capacity building, particularly the scholarship of teaching and learning is becoming increasingly difficult given existing cultural and structural contradictions such as traditional ideologies associated with research; the competitiveness associated with the valuing of individual research; lack of infrastructure supports; and time for research in contexts where there are decreasing numbers of faculty. The authors think it is important to pay attention to this feedback as advances in scholarship of teaching and learning may be at risk.Le présent article traite d’un projet de recherche visant à soutenir la capacité des enseignants en sciences infirmières à entreprendre des activités scientifiques dans un milieu où la vision traditionnelle de l’avancement des connaissances en enseignement et en apprentissage est enchassée dans la culture des institutions d’enseignement, et en particulier, dans les programmes de sciences infirmières. Le modèle de diffusion de l’innovation de Rogers (2003, 2004) a fourni un point de vue théorique à partir duquel il est possible de réfléchir à la fa on de promouvoir la recherche en pédagogie de l’enseignement supérieur dans les programmes de sciences infirmières. Le projet a fait l’objet d’une évaluation qualitative et quantitative entre 2004 et 2007. Dans cet article, nous soulignons certaines interprétations qui émergent des données qualitatives recueillies parce qu’elles illustrent le mieux le modèle de Rogers (2003). Même si d’importants progrès ont été effectués en matière de renforcement des capacités relatives à l’avancement des connaissances en pédagogie chez les enseignants en sciences infirmiè
An algebraic extension of Dirac quantization: Examples
A. Ashtekar,Ranjeet S. Tate
Physics , 1994, DOI: 10.1063/1.530684
Abstract: An extension of the Dirac procedure for the quantization of constrained systems is necessary to address certain issues that are left open in Dirac's original proposal. These issues play an important role especially in the context of non-linear, diffeomorphism invariant theories such as general relativity. Recently, an extension of the required type was proposed by one of us using algebraic quantization methods. In this paper, the key conceptual and technical aspects of the algebraic program are illustrated through a number of finite dimensional examples. The choice of examples and some of the analysis is motivated by certain peculiar problems endemic to quantum gravity. However, prior knowledge of general relativity is not assumed in the main discussion. Indeed, the methods introduced and conclusions arrived at are applicable to any system with first class constraints. In particular, they resolve certain technical issues which are present also in the reduced phase space approach to quantization of these systems.
Drought and Associated Impacts in the Great Plains of the United States—A Review  [PDF]
Jeffrey B. Basara, Joanna N. Maybourn, Casey M. Peirano, Jennifer E. Tate, Parker J. Brown, Jake D. Hoey, Brandon R. Smith
International Journal of Geosciences (IJG) , 2013, DOI: 10.4236/ijg.2013.46A2009
Abstract:

The Great Plains region of the United States is susceptible to drought of all kinds including meteorological/climatological, agricultural, hydrological, and socioeconomic. Drought conditions in the region span varying spatial and temporal scales and the causes include: 1) certain synoptic conditions that favor drought such as mid-tropospheric ridging over the drought-affected area and a weak low-level jet; 2) sea surface temperature anomalies and associated teleconnections; 3) land-atmosphere coupling; and 4) anthropogenic effects. While drought can span as few as a couple of months, the most severe droughts can occur at the decadal scale such as the 1930s Dust Bowl, the worst drought in recent history from a societal standpoint. Such droughts in the Great Plains have widespread impacts on agriculture, water resources, human health, and the economy.

Defect physics of BaCuChF (Ch=S, Se, Te) p-type transparent conductors
A. Zakutayev,J. Tate,G. Schneider
Physics , 2010, DOI: 10.1103/PhysRevB.82.195204
Abstract: Native point defects, defect complexes, and oxygen impurities in BaCuChF were studied using density functional theory calculations, self-consistent thermodynamic simulations, and various experimental techniques. Unintentional p-type conductivity in BaCuChF is explained by the presence of copper vacancies with transition levels in the valence band. These acceptor-like defects are partially compensated by donor-like chalcogen vacancies with transition levels deep in the gap. Chalcogen vacancies also cause the experimentally observed sub-gap photoluminescence, optical absorption, and persistent photoconductivity in BaCuSF and BaCuSeF. In thermodynamic equilibrium, both copper and chalcogen vacancies have low formation enthalpies and are likely to form defect complexes among themselves and with fluorine interstitials. The calculated Fermi level pinning range in BaCuChF is narrow and located close to the valence band maximum. It makes BaCuChF a suitable transparent p-type contact layer for optoelectronic applications, but hinders attempts to fabricate transparent thin film transistors using this material. Oxygen-related defects do not affect bulk BaCuChF properties, but surface oxidation decreases the mean free path of free holes by almost an order of magnitude.
Transient absorption and reshaping of ultrafast XUV light by laser-dressed helium
Mette B. Gaarde,Christian Buth,Jennifer L. Tate,Kenneth J. Schafer
Physics , 2010, DOI: 10.1103/PhysRevA.83.013419
Abstract: We present a theoretical study of transient absorption and reshaping of extreme ultraviolet (XUV) pulses by helium atoms dressed with a moderately strong infrared (IR) laser field. We formulate the atomic response using both the frequency-dependent absorption cross section and a time-frequency approach based on the time-dependent dipole induced by the light fields. The latter approach can be used in cases when an ultrafast dressing pulse induces transient effects, and/or when the atom exchanges energy with multiple frequency components of the XUV field. We first characterize the dressed atom response by calculating the frequency-dependent absorption cross section for XUV energies between 20 and 24 eV for several dressing wavelengths between 400 and 2000 nm and intensities up to 10^12 W/cm^2. We find that for dressing wavelengths near 1600 nm, there is an Autler-Townes splitting of the 1s ---> 2p transition that can potentially lead to transparency for absorption of XUV light tuned to this transition. We study the effect of this XUV transparency in a macroscopic helium gas by incorporating the time-frequency approach into a solution of the coupled Maxwell-Schr\"odinger equations. We find rich temporal reshaping dynamics when a 61 fs XUV pulse resonant with the 1s ---> 2p transition propagates through a helium gas dressed by an 11 fs, 1600 nm laser pulse.
Optimal Design of a Multibody Self-Referencing Attenuator  [PDF]
Dongmei Zhou, Jennifer A. Eden
Journal of Power and Energy Engineering (JPEE) , 2015, DOI: 10.4236/jpee.2015.39005
Abstract: The purpose of this paper is to determine the optimal size and number of tubes for a generic attenuator that is similar to Pelamis P2, the wave energy converter. Simulations using ANSYS Workbench, Design Modeler, and AQWA are performed to study the energy absorption at the nodes between the tubes. The analysis is limited to linearized hydrodynamic fluid waves loading on floating bodies by employing three-dimensional radiation/diffraction theory in regular waves in the frequency domain. Three sets of tests are conducted by varying total tube number, each tube length and the order of tubes with different lengths. After a systematic study in the frequency domain, the optimal size and number of the genetic attenuator is recommended.
Ionization of Rydberg atoms embedded in an ultracold plasma
Nicolas Vanhaecke,Daniel Comparat,Duncan A. Tate,Pierre Pillet
Physics , 2004, DOI: 10.1103/PhysRevA.71.013416
Abstract: We have studied the behavior of cold Rydberg atoms embedded in an ultracold plasma. We demonstrate that even deeply bound Rydberg atoms are completely ionized in such an environment, due to electron collisions. Using a fast pulse extraction of the electrons from the plasma we found that the number of excess positive charges, which is directly related to the electron temperature Te, is not strongly affected by the ionization of the Rydberg atoms. Assuming a Michie-King equilibrium distribution, in analogy with globular star cluster dynamics, we estimate Te. Without concluding on heating or cooling of the plasma by the Rydberg atoms, we discuss the range for changing the plasma temperature by adding Rydberg atoms.
The Development of LISTEN: A Novel Intervention for Loneliness  [PDF]
Laurie A. Theeke, Jennifer A. Mallow
Open Journal of Nursing (OJN) , 2015, DOI: 10.4236/ojn.2015.52016
Abstract: Purpose: The purpose of this paper is to present the development of LISTEN (Loneliness Intervention using Story Theory to Enhance Nursing-sensitive outcomes), a new intervention for loneliness. Methods: LISTEN was developed using the Medical Research Council (MRC) framework for intervention development. Extensive literature review revealed that belonging, relating, placing in community, challenges, and meanings of coping were concepts significant to loneliness. Past interventions were limited but it was determined from a recent meta-analysis that enhanced effectiveness might result from interventions that targeted the poorly adapted cognitive processes of loneliness. These processes include social undesirability, stigma, and negative thoughts about self in relation to others. LISTEN is designed to be delivered in a determined logical sequence of 5 sessions, each focusing on the concepts relevant to loneliness as derived from the literature. For each session, intervention delivery is guided by the concepts from story theory (including intentional dialogue, nurse as listener, examination of self in relation to others and community, synthesizing concerns and patterns, and identifying messages) and the principles of cognitive restructuring (self-assessment of maladaptive cognitions, emotions, and behaviors, identifying challenges of changing, reconceptualization of self, new skill acquisition through group interaction, and identifying patterns of meaning in loneliness). Results: LISTEN is developed and the first randomized trial is complete with a sample of 27 lonely, chronically ill, community dwelling, and older adults. LISTEN was evaluated as feasible to deliver by the study team and acceptable for significantly diminishing loneliness by participants of the LISTEN groups who were compared to attention control groups (p < 0.5). Conclusions: LISTEN has the potential to enhance health by diminishing loneliness which could result in improving the long-term negative known sequelae of loneliness. Future longitudinal randomized trials are needed in varied populations to assess long term health and healthcare system benefit of using LISTEN to treat loneliness.
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