Two-color QCD at high density

QCD at high chemical potential has interesting properties such as deconfinement of quarks. Two-color QCD, which enables numerical simulations on the lattice, constitutes a laboratory to study QCD at high chemical potential. Among the interesting properties of two-color QCD at high density is the diquark condensation, for which we present recent results obtained on a finer lattice compared to previous studies. The quark propagator in two-color QCD at non-zero chemical potential is referred to as the Gor'kov propagator. We express the Gor'kov propagator in terms of form factors and present recent lattice simulation results.Comment: Talk given at the conference Confinement XI, September 8-12, 2014, St. Petersburg, Russia. 8 pages, 15 figure

On frontal and ventilated models of the main thermocline

A new similarity approach is applied to the thermocline equations in order to examine contrasting frontal and ventilated models of the main thermocline. The method of solution involves reducing the number of independent variables of the controlling partial differential equation, leading to a particular form for the solutions which satisfy appropriate boundary conditions. A frontal model of the thermocline is obtained following the study of Salmon and Hollerbach (1991). When the vertical diffusivity becomes vanishingly small, an interior front in the subtropical gyre appears at the depth where the vertical velocity changes sign. The front separates downwelling warm water in the subtropical gyre from the underlying upwelling of cold, deep water. These solutions appear to be robust to changes in the vertical diffusivity profile, as long as there is a small, nonzero value in the interior. However, when there is uniform diffusivity, there is no implied surface heat flux and surface isotherms are coincident with streamlines. As the diffusivity increases toward the surface, the surface heat input increases in magnitude and the temperature field becomes more plausible. A ventilated model of the thermocline is formed using the similarity approach with a diffusive surface boundary-layer overlying an adiabatic interior. In this case, the temperature and velocity fields are solved for in the limit of uniform potential vorticity. There is now a more plausible cross-isothermal flow in the surface layer with a polewards decrease in temperature, and the implied surface heat input increases equatorwards. Fluid is subducted from the surface boundary layer into the adiabatic interior and forms a continuous thermocline. In conclusion, the contrasting frontal and ventilated solutions arise from modeling different aspects of the circulation, rather than depending on the type of model employed. The ventilated solutions form a thermocline by advecting the surface temperature field into the interior of a subtropical gyre, whereas the frontal solutions create a thermocline from the interaction of the wind-driven gyre and the underlying thermohaline circulation. These thermocline solutions might occur separately or together in the real ocean, although both solutions might be modified by higher-order processes or more complicated forcing

PROVE Endurance Car Front Suspension

This document details the collaborative Mechanical Engineering Senior Project with Cal Poly PROVE Lab on PROVE Lab’s Project 2; an electric vehicle designed to travel 1000 miles on a single charge. Logan Simon, Justine Kwan, and Lauren Williams are given the challenge of designing an innovative proof of concept front suspension suspension for this vehicle. After detailed research of new suspension systems, it was determined that the innovative nature could be in the form of unique manufacturing methods, materials use, or mechanical design. At this point in time, this vehicle is a purely conceptual design with no concrete requirements. Therefore engineering specifications were generated based on vehicles of similar size and function, such as PROVE Lab Project 1, Tesla’s Roadster, and the BMW z4. These specification included vehicle weight, speed, vertical travel, system weight, travel speed, and track width. Since this car is aimed to travel 1000 miles on one charge, efficiency is a big concern for the design. From ideation, the three suspension configurations of interest were MacPherson, double wishbone, and multi-link. A decision matrix was created to evaluate these designs based on design requirements, resulting in the selection of the multi-link configuration. However, after further investigation it was decided that a double wishbone configuration would provide nearly equal performance and be much more manageable of a task on the senior project time frame, compared to multi-link. The focus of the project then shifted to innovative manufacturing methods. Carbon fiber was chosen as the material to be used due to its lightweight nature, its accessibility through PROVE lab, and its lack of usage in a suspension system thus far. The upright would provide the most weight savings, so it was designed as a carbon fiber sandwich panel. Computer analysis of the system included SolidWorks FEA, Tsai Wu Failure Analysis, and ANSYS composite analysis to verify Tsai Wu. Four destructive tests were performed to validate the analysis and to determine the number of plies to be used for the final part. With all four tests passing the minimum load requirements with a factor of safety above 1, 16 plies per laminate was chosen and with an additional 8 plies around the edges. The final system proves that a carbon fiber suspension that is structurally sound for maximum loading cases and that cuts weight down to 4.3 pounds is possible. The full non-destructive test will be performed by the PROVE Project 2 team in the future, unassociated with this senior project

Antiretroviral therapy initiated soon after HIV diagnosis as standard care: potential to save lives?

In 2008, an estimated 33.4 million people were infected with human immunodeficiency virus (HIV) and ~4 million people were receiving antiretroviral therapy (ART). However, in 2007, an estimated 6.7 million people were in need of ART under the current World Health Organization guidelines, and 2.7 million more people became infected with HIV. Most of those not currently eligible for ART will become eligible within the next decade, making the current treatment strategy unsustainable. The development of cheaper, less toxic, and more potent antiretrovirals over the past decade has made it possible to consider novel strategies of arresting the HIV/AIDS epidemic. Evidence is growing that ART can be used to prevent HIV transmission and that earlier initiation of treatment is beneficial for those infected with HIV. A mathematical model predicts that by testing whole communities annually and treating all who are infected immediately, up to 7.2 million AIDS-related deaths could be prevented in the next 40 years, long-term funding required to fight the HIV epidemic could be reduced, and, most importantly, control of the HIV/ AIDS epidemic could be regained within 1–2 years of full-scale implementation of the strategy. We discuss the development of the concept of ART for the prevention of HIV transmission and the modeled impact that a test-and-treat strategy could have on the HIV epidemic, and consequently argue that a field trial should be carried out to confirm model parameters, highlight any practical problems, and test the model’s predictions

Playing Kant at the Court of King Arthur

This article contrasts the sense in which those whom Bernard Williams called ‘political realists’ and John Rawls are committed to the idea that political philosophy has to be distinctively political. Distinguishing the realist critique of political moralism from debates over ideal and non-ideal theory, it is argued that Rawls is more realist than many realists realise, and that realists can learn more about how to make a distinctively political vision of how our life together should be organised from his theorising, although it also points to a worrying tendency among Rawlsians to reach for inappropriately moralised arguments. G. A. Cohen’s advocacy of socialism and the second season of HBO’s The Wire are used as examples to illustrate these points

A Global Plate Model Including Lithospheric Deformation Along Major Rifts and Orogens Since the Triassic

Global deep‐time plate motion models have traditionally followed a classical rigid plate approach, even though plate deformation is known to be significant. Here we present a global Mesozoic–Cenozoic deforming plate motion model that captures the progressive extension of all continental margins since the initiation of rifting within Pangea at ~240 Ma. The model also includes major failed continental rifts and compressional deformation along collision zones. The outlines and timing of regional deformation episodes are reconstructed from a wealth of published regional tectonic models and associated geological and geophysical data. We reconstruct absolute plate motions in a mantle reference frame with a joint global inversion using hot spot tracks for the last 80 million years and minimizing global trench migration velocities and net lithospheric rotation. In our optimized model, net rotation is consistently below 0.2°/Myr, and trench migration scatter is substantially reduced. Distributed plate deformation reaches a Mesozoic peak of 30 × 106 km2 in the Late Jurassic (~160–155 Ma), driven by a vast network of rift systems. After a mid‐Cretaceous drop in deformation, it reaches a high of 48 x 106 km2 in the Late Eocene (~35 Ma), driven by the progressive growth of plate collisions and the formation of new rift systems. About a third of the continental crustal area has been deformed since 240 Ma, partitioned roughly into 65% extension and 35% compression. This community plate model provides a framework for building detailed regional deforming plate networks and form a constraint for models of basin evolution and the plate‐mantle system

Crystallization, X-ray diffraction analysis and preliminary structure determination of the TIR domain from the flax resistance protein L6

The Toll/interleukin-1 receptor (TIR) domain is a protein-protein interaction domain that is found in both animal and plant immune receptors. In animal Toll-like receptor signalling, both homotypic TIR-domain interactions between two receptor molecules and heterotypic interactions between receptors and TIR-domain-containing adaptors are required for initiation of an innate immune response. The TIR domains in cytoplasmic nucleotide-binding/leucine-rich repeat (NB-LRR) plant disease-resistance proteins are not as well characterized, but recent studies have suggested a role in defence signalling. In this study, the crystallization, X-ray diffraction analysis and preliminary structure determination of the TIR domain from the flax resistance protein L6 (L6TIR) are reported. Plate-like crystals of L6TIR were obtained using PEG 200 as a precipitant and diffracted X-rays to 2.3 angstrom resolution. Pseudo-translation complicated the initial assignment of the crystal symmetry, which was ultimately found to correspond to space group P2(1)2(1)2 with two molecules per asymmetric unit. The structure of L6TIR was solved by molecular replacement using the structure of the TIR-domain-containing protein AT1G72930 from Arabidopsis as a template

Decoding Earth’s plate tectonic history using sparse geochemical data

Accurately mapping plate boundary types and locations through time is essential for understanding the evolution of the plate-mantle system and the exchange of material between the solid Earth and surface environments. However, the complexity of the Earth system and the cryptic nature of the geological record make it difficult to discriminate tectonic environments through deep time. Here we present a new method for identifying tectonic paleo-environments on Earth through a data mining approach using global geochemical data. We first fingerprint a variety of present-day tectonic environments utilising up to 136 geochemical data attributes in any available combination. A total of 38301 geochemical analyses from basalts aged from 5–0 Ma together with a well-established plate reconstruction model are used to construct a suite of discriminatory models for the first order tectonic environments of subduction and mid-ocean ridge as distinct from intraplate hotspot oceanic environments, identifying 41, 35, and 39 key discriminatory geochemical attributes, respectively. After training and validation, our model is applied to a global geochemical database of 1547 basalt samples of unknown tectonic origin aged between 1000–410 Ma, a relatively ill-constrained period of Earth's evolution following the breakup of the Rodinia supercontinent, producing 56 unique global tectonic environment predictions throughout the Neoproterozoic and Early Paleozoic. Predictions are used to discriminate between three alternative published Rodinia configuration models, identifying the model demonstrating the closest spatio-temporal consistency with the basalt record, and emphasizing the importance of integrating geochemical data into plate reconstructions. Our approach offers an extensible framework for constructing full-plate, deep-time reconstructions capable of assimilating a broad range of geochemical and geological observations, enabling next generation Earth system models