Cosmological Constant and Gravitational Repulsion Effect: 1. Homogeneous models with radiation

Within the framework of the minimum quadratic Poincare gauge theory of gravity in the Riemann-Cartan spacetime we study the influence of gravitational vacuum energy density (a cosmological constant) on the dynamics of various gravitating systems. It is shown that the inclusion of the cosmological term can lead to gravitational repulsion. For some simple cases of spatially homogeneous cosmological models with radiation we obtain non-singular solutions in form of elementary functions and elliptic integrals.Comment: REVTEX, 11 pages, Syracuse University preprint SU-GP-93/5-

Individual Resilience, Social Support, and Health Risk Behaviors in Adolescents and Young Adults: Study on Cross-sectional and Longitudinal Samples

Resilience is considered the ability that a person gains positive achievements despite exposure to significantly adverse life conditions. However, a majority of previous research has focused on human developmental tasks or academic achievements. Evidence of resilience on health risk behaviors has not been comprehensively established yet. The purposes of this dissertation were to extend the existing literature about the stability of resilience through time, to examine how the resilience scale concurrently and prospectively predict resilience statuses, and to explore effects of Social support over a long period of lifetime. The dissertation used a secondary database from the public-use version of the National Longitudinal Study of Adolescent Health (Add Health). Resilience status was defined as a lack of health risk behaviors of suicide, violence and substance use. Resilience scale was constructed by using 35 items from the Add Health data. Data were analyzed data were analyzed using logistic regression and Generalized Estimating Equations (GEE) models. The results showed that resilience status in general and adversity populations varied over time. However, when viewed over a long period of lifetime, individual resiliency on health risk behaviors appears to be rather stable. The resilience scale and its subscales strongly predicted resilience status at a given point in time or over time. Parental support had little or no effect on resilience status, having more number of close friends increased the risk of some health behaviors, and religious services led participants to become more resilient on some health risk behaviors. This research will provide policy makers better knowledge about the role of resilience on health risk behaviors during the transition from adolescence to adulthood. The findings may contribute to the existing literature by extending the knowledge of how resilience on the domain of health risk behaviors changes over time and which factors influence on the resilience process

Inverse design of metamaterials via topology optimization

Metamaterials are artificial composites with micro-structures that are systematically designed such that the macroscopic behavior can accommodate particular functionalities or exhibit extraordinary properties, which are not commonly found in natural materials. Topology and geometry of micro-structures play an important role in characterizing the properties of the metamaterials. Inverse design of metamaterials via topology optimization methods offer new topological features and helps in achieving novel physical mechanism or high-performance functionalities. Inverse design is an iterative process, that involves numerical analysis and requires much computational resources. This dissertation proposes the methodology for designing metamaterials using topology optimization with level set functions and model order reduction methods. Level set method enables design with smooth boundaries, while the computational effort required in solving large linear system of equations is eliminated with reduced basis approximations. An example of the inverse design method from the dissertation is to find a unit cell structure that results in macroscopic properties with intended elastic modulus for instance, with negative Poisson's ratio. The other example is to enhance hydrophone performance in 1-3 piezoelectric composites. Numerical examples demonstrate that the methodology is computationally efficient and robust for designing metamaterials. Taking advantage of inverse design as a powerful tool in designing metamaterials, it is adopted in this dissertation for the waveguides design. The second part of this thesis aims to design phononic crystals that offer robust transport of mechanical waves on the interfaces. The propagating wave modes in plate-like structures are topologically protected edge states and are analogous to quantum valley hall effect and quantum spin hall effect in the electronic systems. The computational inverse design methodology adopted is through topology optimization using genetic algorithm to find optimized unit cell geometries resulting from objective functions based on band structures and wave modes. The optimized phononic crystals support wave propagation against backscattering inspite of the presence of defects.Metamaterialien sind künstliche Verbundwerkstoffe mit Mikrostrukturen, die systematisch so gestaltet sind, dass das makroskopische Verhalten besondere Funktionen oder außergewöhnliche Eigenschaften aufweist, die in natürlichen Materialien nicht üblich sind. Topologie und Geometrie der Mikrostrukturen spielen eine wichtige Rolle bei der Charakterisierung der Eigenschaften der Metamaterialien. Das inverse Design von Metamaterialien mittels Topologie-Optimierungsmethoden bietet neue topologische Eigenschaften und hilft bei der Erreichung neuartiger physikalischer Mechanismen oder Hochleistungsfunktionen. Inverses Design ist ein iterativer Prozess, der numerische Analysen beinhaltet und viel Rechenleistung erfordert. In dieser Dissertation wird eine Methodik für den Entwurf von Metamaterialien unter Verwendung von Topologieoptimierung mit Level-Set-Funktionen und Methoden zur Reduzierung der Modellordnung vorgeschlagen. Die Level-Set-Methode ermöglicht ein Design mit glatten Grenzen, während der Rechenaufwand, der für die Lösung großer linearer Gleichungssysteme erforderlich ist, durch reduzierte Basisapproximationen entfällt. Ein Beispiel für die inverse Entwurfsmethode aus der Dissertation ist die Suche nach einer Einheitszellenstruktur, die zu makroskopischen Eigenschaften mit beabsichtigtem Elastizitätsmodul führt, beispielsweise mit negativer Poissonzahl. Ein anderes Beispiel ist die Verbesserung der Leistung von Hydrophonen in 1-3 piezoelektrischen Verbundwerkstoffen. Numerische Beispiele zeigen, dass die Methodik für die Entwicklung von Metamaterialien rechnerisch effizient und robust ist. Die Vorteile des inversen Designs als leistungsfähiges Werkzeug bei der Entwicklung von Metamaterialien werden in dieser Dissertation für die Entwicklung von Wellenleitern genutzt. Der zweite Teil dieser Arbeit zielt darauf ab, phononische Kristalle zu entwerfen, die einen robusten Transport von mechanischen Wellen an den Grenzflächen ermöglichen. Die sich ausbreitenden Wellenmoden in plattenförmigen Strukturen sind topologisch geschützte Randzustände und entsprechen dem Quanten-Tal-Hall-Effekt und dem Quanten-Spin-Hall-Effekt in elektronischen Systemen. Die angewandte rechnerische inverse Entwurfsmethodik besteht in der Topologieoptimierung mit Hilfe eines genetischen Algorithmus, um optimierte Einheitszellengeometrien zu finden, die sich aus Zielfunktionen auf der Grundlage von Bandstrukturen und Wellenmoden ergeben. Die optimierten phononischen Kristalle unterstützen die Wellenausbreitung trotz des Vorhandenseins von Defekten gegen Rückstreuung

Probabilistic models for protein conformational changes

Proteins are macromolecules that perform multiple functions. They are not rigid molecules, but instead proteins can change their conformation to perform critical tasks driven by binding small ligands, by assembling into large macromolecular complexes or by physiological factors. Characterization of protein conformational change and analyzing transitional pathways along protein conformational states are essentially tasks for computational biology. Here we propose probabilistic models to characterize protein conformational change. The first model disentangles protein structure into rigid bodies, whereas the second model proposes the probabilistic network model for the transitions between conformational states. Our first model is a generative process using Gaussian mixture models to represent rigid domains, which generated the input structures through spatial transformation. To estimate our model parameters, we use two approaches: using deterministic Expectation- Maximization algorithm and stochastic Gibbs sampler. The second model is an elastic way to expand the application spectrum of our model. The model uses anharmonic springs that involve the molecular distances that are allowed to break in a stochastic fashion. The function of the spring potential is inferred from a statistical analysis of a database of large-scale conformational changes in proteins. In addition we deploy our model in a webservice, as well as we deposit a precomputed dataset of rigid domains and a selective dataset of conformational pathway between conformational states. Finally, we employ graph-based algorithms to solve the problem of a model-free base solution. This work is not limited to biological applications, but can also be applied to robotics and computer vision. This thesis is based on the following publications and manuscripts, respectively: • Thach Nguyen, Michael Habeck, A probabilistic model for detecting rigid domains in protein structures, Bioinformatics, Volume 32, Issue 17, 1 September 2016, Pages i710–i717, https://doi.org/10.1093/bioinformatics/btw442 • Habeck M, Nguyen T. A probabilistic network model for structural transitions in biomolecules.Proteins. 2018;86:634–643.https://doi.org/10.1002/prot.25490 • Linh Dang, Thach Nguyen, Michael Habeck, and StephanWaack. A graph-based algorithm for detecting rigid domains in protein structures. Submitted • Thach Nguyen, Christian Böhm, Michael Habeck, A computational web server for segmenting protein structure into rigid bodies, in preparation

Influences Of Lime And Coconut Fiber To Arsenic Uptake On Peanuts In An Phu District, An Giang Province

Arsenic (As) contamination in deep-well water has presently been warned in some areas of An Giang province. The previous studies in An Phu district showed that the level of As in soils was also many folds higher than international standards that need to be studied; particularly in land use and water supply in agricultural production. The objectives of this research were to: (i) evaluate the situation of As contain in soil and well water from cultivated lands in An Phu district, An Giang province; (ii) evaluate the impact of coconut fiber and liming methods on the uptake and accumulation of As in peanuts. The survey studies indicated that all of deep-well water samples were contaminated with As from 97,5 μg/l to 469 μg/l in An Phu district. These levels exceed Vietnamese and WHO standards (<10 μg/L), and all studied communes used deep-well water for watering their crops (69,6%). The As averages of soil samples inside dikes were higher than outside dikes from 1,5 to 2 times. As concentration of all soil samples for planting peanuts inside the dike are always higher than outside the dike from 1,5 to 2 times. The averages of As levels of arable land samples inside dikes of An Phu district were from 40,1 to 47,8 mg/kg. When applied 5 tons of lime and coconut fiber per ha reduced As levels at 55,3% compared with treatment without lime and coconut fiber. The results also showed that, when applied lime 5 tons of lime and coconut fiber per ha had a significant effect on the growth and yield of peanuts. Productivity of the peanut that increased from 9,10% to 30,4%, compared without liming and coconut fiber. When applied lime, coconut fiber had a significant effect on amount of As in grains and bodies of peanuts was lower than without lime and coconut fiber treatments.The yield components indicated, peanuts were planted with coconut fiber and l liming, that had the best result and the the lowest was without liming and coconut fiber. When applied 5 tons of liming combined with coconut fiber per ha had the highest results, both level of As reduction in peanut grains and productivity. Necessary to study many levels of liming and coconut fiber and residual lime in the soil for the next crops. It recommend that people have safe farming methods and effects on soils of as contamination