The goal of this study was to revise the development length equation of ACI 318- 05 and to better reflect test results for high-strength concrete. The revision of the equation was accomplished using test results tabulated in the Database 10-2001maintained by ACI committee 408. Equations for development length in ACI 318-05 and ACI 408.3 examined to understand the issues to be considered for revision on the variability of test data. The development length equation in ACI 318-05 was very conservative for [compressive strength of concrete][less than or equal to]14,000 psi based on the experimental data in Database 10-2001 of ACI Committee 408. On the contrary, the ACI 318-05 may be less conservative for high-strength concrete, [compressive strength of concrete] [greater than or equal to]14,000 psi . Thus, modified design equations were proposed to provide realistic values for normal strength concrete and conservatively for high-strength concrete. The ACI 318-05 equation was modified for 1) compressive strength of concrete and 2) confinement as expressed by the term [minimum side cover, cover over the bar or wire, or one-half the center-to-center spacing of the bars or wires] + [contribution of confining reinforcement across potential splitting planes] / [normal diameter of bar] in ACI 318-05. The basic assumption is that bar stress is a linear function of development length, and development length is the length required for bar stresses to reach the yield. / text

In this thesis, we study a Bäcklund transformation for minimal surfaces - surfaces with vanishing mean curvature - transforming a given minimal surface into a possible infinity of new ones. The transformation, also carrying with it mappings between solutions to the elliptic Liouville equation, is first derived by using geometrical concepts, and then by using algebraic methods alone - the latter we have not been able to find elsewhere. We end by exploiting the transformation in an example, transforming the catenoid into a family of new minimal surfaces.

Not available / text

Not available / text

Some semiconductor devices such as lasers have long had critical dimensions on the nanoscale where quantum effects are critical. Others such as MOSFETs are now being scaled to within this regime. Quantum effects neglected in semiclassical models become increasing important at the nanoscale. Meanwhile, scattering remains important even in MOSFETs of 10 nm and below. Therefore, accurate quantum transport simulators with scattering are needed to explore the essential device physics at the nanoscale. The work of this dissertation is aimed at developing accurate quantum transport simulation tools for deep submicron device modeling, as well as utilizing these simulation tools to study the quantum transport and scattering effects in the nano-scale semiconductor devices. The basic quantum transport method "Schrödinger Equation Monte Carlo" (SEMC) provides a physically rigorous treatment of quantum transport and phasebreaking inelastic scattering (in 3D) via real (actual) scattering processes such as optical and acoustic phonon scattering. The SEMC method has been used previously to simulate carrier transport in nano-scaled devices in order to gauge the potential reliability of semiclassical models, phase-coherent quantum transport, and other limiting models as the transition from classical to quantum transport is approached. In this work, SEMC-1D and SEMC-2D versions with long range polar optical scattering processes have been developed and used to simulate quantum transport in tunnel injection lasers and nanoscaled III-V MOSFETs. Simulation results serve not only to demonstrate the capabilities of the developed quantum transport simulators, but also to illuminate the importance of physically accurate simulation of scattering for the predictive modeling of transport in nano-scaled devices.

The concept of metamemory proposes that supplementary to typically measured memory abilities, memory monitoring and control processes are used to optimise learning. Accurate memory monitoring appears to be underpinned by a range of cognitive, and possibly affective, contributions. In populations with these deficits, metamemory has been shown to be impaired. In Multiple Sclerosis (MS), only a limited metamemory literature exists, surprising given that MS is a leading cause of disability among people of working age, and cognitive and mood disorder is common. Using structural equation modelling, this study of 100 people with MS explored factors contributing to performance on episodic Judgment of Learning, Retrospective Confidence and Feeling of Knowing. Given its negative influence on cognitive domains in MS, the impact of information processing deficits on metamemory was also investigated. Finally, memory self-report, a frequently used clinical indicator of memory functioning, was assessed. Findings suggest that memory complaint is associated with mood, and is unrelated to tested memory. Second, Retrospective Confidence Judgments were predictive of memory performance, even in the presence of memory impairment. Third, an unusual finding of maintained underconfidence at delay was observed in the Judgment of Learning task. Finally, Feeling of Knowing judgments related to executive, but not to memory ability. A novel finding in respect of this judgment was of processing speed relating negatively to accuracy, in the context of executive dysfunction. This suggests that some top-down direction of processing resources may be a factor in supporting accuracy, rather than the speed at which information is processed. Of all the task-based judgments, accuracy in this judgment was the only one with a reliable association with mood. Faster processing speed, executive dysfunction and least depression symptomatology related to low accuracy, perhaps typifying a profile of disinhibition seen in MS, characterised by poorly constrained processing and apparently elevated mood.

The history of planet formation and evolution is strongly tied to understanding the outcomes of a wide range of impact events, from slow accretionary events to hypervelocity events that melt and vaporize large fractions of the colliding bodies. To better understand impact processes, their effects on planetary evolution, and how to interpret geochemical data, we need to improve our knowledge of the behavior of materials over the entire range of conditions accessed by collisions. Here I present experimental results from gas gun, laser driven, and pulsed power facilities. Together these facilities can access the tremendously wide range of pressure and temperature conditions achieved in natural impact events. This work focuses on the thermodynamics of impacts to better understand the phase transitions that most strongly affect the dynamics and chemical consequences of a collision. I show that the entropy generation during collisions is the most natural means of interpreting the thermodynamic processes that occur during an impact event. For materials with sufficient thermodynamic data at high pressures and temperatures, I present a method for obtaining the entropy generation during an impact. With the knowledge of the entropy, I present new shock-and-release techniques to investigate the liquid-vapor region of the phase diagram. I also show that for materials without sufficient data to calculate the entropy generation during an impact, one can use the shock-and-release techniques described here to determine the entropy in the high pressure shock state. With better equation of state models that are constrained by our experimental data, our confidence in impact models improves dramatically. Using a high fidelity equation of state for \(H_2O\). ice, I derive scaling laws for how much \(H_2O\) ice melts and vaporizes for impacts onto icy bodies. Recognizing that icy bodies are not pure ice, I have performed experiments to show how the impact energy partitions between the disparate phases. Finally, I discuss some of the uncertainties in using the laboratory experiments to directly interpret the effects of impacts in nature. / Earth and Planetary Sciences

<p>Cells express a variety of proteins on their surface that allows them to sample the world. These proteins are embedded in the plasma membrane, a bilayer of lipids that surrounds the cell. Since the lipid and protein dimensions are in the nanometer range, they are subject to thermal agitation by water molecules and show characteristic diffusive motion. The diffusive movement of these proteins plays a critical role in the cell's ability to react to external signals and regulate its internal environment. </p><p>One prominent application of protein diffusion is in the synaptic connection, where is the highly localized concentration of receptors. The receptive dendrite membrane contains many types of receptors that are accumulated to form functional microdomains opposite the presynaptic terminal buttons that release neurotransmitters. Experiments reveal that receptors move from extrasynaptic locations to synaptic locations by lateral diffusion, thereby concentrating receptors at synapses. Two key processes that control synaptic AMPAR numbers are receptor diffusion within the synaptic and extrasynaptic space and interactions between receptors and PSD scaffold proteins. Electron microscopy images suggest that the PSD is highly crowded potentially limiting the ability of receptors to diffuse and interact with scaffold proteins. However, the contribution of macromolecular crowding to receptor retention remains to be tested systematically. </p><p>Here, we combine experimental and computational approaches to test the effect of synaptic steric hindrance on receptor mobility and enrichment. We first investigate how the diffusion is influenced by membrane geometry. The membrane itself can have three-dimensional structure, which means that the actual path length of diffusion can be different from a projected path length. Here, we use a position Langevin equation for diffusion, which incorporates curvature and gradient effects of surfaces. Numeric simulation of the equation allows for the prediction of effective diffusion coefficients over corrugated surfaces.</p><p>In order to examine the distinct contributions of crowding and receptor-scaffold binding, we developed a computational model for AMPA-receptor diffusion in the synaptic and extrasynaptic space, which contains immobile obstacles, representing scaffolding, receptor and adhesion molecules in the PSD. The spatial distribution of scaffold proteins was determined directly from photo-activated localization microscopy measurements that mapped molecular positions with a resolution of ~20 nm. The AMPAR/scaffold association and dissociation rates were adjusted by computer simulations to fit single-particle tracking and fluorescence recovery after photobleaching measurements. The model predicts the recovery curves are influenced mostly by size changes while variation of kinetic rates did not significantly alter receptor residence time or mobility. We also examined the effect of binding, by adding a single synaptic binding motif to a small transmembrane protein, which slows its diffusion within the synapse. These results suggest that both protein size and binding play important roles in retaining surface-diffusing TM proteins within the excitatory synapse and shed light on the biophysical mechanisms that lead to high density of AMPARs at synapses.</p> / Dissertation

In order to fully explicate the role of news media in individuals’ political participation, this dissertation aims at establishing an integrative structural model that specifies relationships among news media use, its antecedents and mediators of its influence on political participation. The proposed model is comprised of key factors of political participation that previous research has identified. The relational structure is based on models and theories relevant to prediction of political behaviors. Specifically, the model integrates (a) communication mediation model, which posits that communication behaviors (i.e., news media use and interpersonal discussion) mediate the effects of socio-demographic variables (i.e., income, education, age, gender, and race) and political dispositions (i.e., political interest, partisanship and ideology) on political outcomes; (b) agenda-setting theory, which posits that frequent exposure to news media increases the salience of news objects in audiences’ minds; (c) cognitive mediation model, which posits that elaborative and collective thinking is a prerequisite to produce political outcomes of news exposure; (d) theory of planned behavior, which posits that human behavior can be best predicted by three proximal variables (i.e., attitudes, subjective norms, and perceived behavioral control); (e) O-S-R-O-R (orientations-stimulus-reasoning-orientations-response) model of communication effects, which provides a parsimonious framework of effect process. Using the structural equation modeling (SEM) method, this dissertation analyzes the 2008 American National Election Studies data set to test the validity of the proposed structural model. Results indicate that frequent exposure to news media stimulates attentive news use as well as intra- and interpersonal reasoning, which produce a wide range of political outcomes. Two reasoning behaviors (i.e., self-reflection and interpersonal political discussion) are critical mechanisms that linked news media use to various political outcomes including political participation. Personal-psychological mediators, such as strength in affects, personal traits, opinions about political issues, campaign interest, political knowledge, attitude strength, perceived ability of political parties and political efficacy all significantly mediate the influence of news media use on political participation. News media use mediates significant portion of effects that a set of preexisting variables have on political participation as well as various types of political orientations. / text

We study the initial value problem for the defocusing nonlinear wave equation with cubic nonlinearity F(u)=|u|^2u in the energy-supercritical regime, that is dimensions d\geq 5. We prove that solutions to this equation satisfying an a priori bound in the critical homogeneous Sobolev space exist globally in time and scatter in the case of spatial dimensions d\geq 6 with general (possibly non-radial) initial data, and in the case of spatial dimension d=5 with radial initial data. / text