Simulation of electron transport in quantum well devices

Double barrier resonant tunneling diodes (DBRTD) have received much attention as possible terahertz devices. Despite impressive experimental results, the specifics of the device physics (i.e., how the electrons propagate through the structure) are only qualitatively understood. Therefore, better transport models are warranted if this technology is to mature. In this paper, the Lattice Wigner function is used to explain the important transport issues associated with DBRTD device behavior

The Stability of Strange Star Crusts and Strangelets

We construct strangelets, taking into account electrostatic effects, including Debye screening, and arbitrary surface tension sigma of the interface between vacuum and quark matter. We find that there is a critical surface tension sigma_crit below which large strangelets are unstable to fragmentation and below which quark star surfaces will fragment into a crystalline crust made of charged strangelets immersed in an electron gas. We derive a model-independent relationship between sigma_crit and two parameters that characterize any quark matter equation of state. For reasonable model equations of state, we find sigma_crit typically of order a few MeV/fm^2. If sigma <= sigma_crit, the size-distribution of strangelets in cosmic rays could feature a peak corresponding to the stable strangelets that we construct.Comment: 11 pages, LaTe

Meissner screening mass in two-flavor quark matter at nonzero temperature

We calculate the Meissner screening mass of gluons 4--7 in two-flavor quark matter at nonzero temperature. To this end, we study the effective potential of the 2SC/g2SC phases including a vector condensate $$and calculate the Meissner mass from the potential curvature with respect to$$. We find that the Meissner mass becomes real at the critical temperature which is about the half of the chemical potential mismatch. The phase diagram of the neutral two-flavor color superconductor is presented in the plane of temperature and coupling strength. We indicate the unstable region for gluons 4--7 on the phase diagram.Comment: 4 pages, 3 figures, minor revisions to text, version to appear in PR

Green Tea Consumption Reduces Oxidative Stress in Parkinson’s Disease Patients

Oxidative stress is one of the underlying causes of Parkinson’s disease (PD). Because of its antioxidant effect, we hypothesize that green tea consumption (3 cups daily for 3 months) would improve antioxidant status and reduces oxidative damage in Parkinson’s disease. Fifteen subjects who were within the first five years of PD, on stable PD medication, and not regular green tea consumers were recruited. Iron status, oxidative stress and PD status were evaluated before and after 3 months of green tea consumption. Hemoglobin, serum iron, iron saturation and ferritin concentrations were used to assess iron status. Antioxidant enzymes including catalase, superoxide dismutase (SOD), and glutathione peroxidase (GPx) were measured to determine antioxidant status. Lipid peroxidation and protein carbonyls were measured as oxidative damage markers. There were no changes in total motor scores of the Unified Parkinson’s Disease Rating Scale (UPDRS), PDQ-39 total scores and various iron status markers after 3 months. Catalase (p \u3c 0.05) and SOD activities (p \u3c 0.005) were increased significantly indicating an improvement of antioxidant status. Both lipid peroxidation and protein carbonyls decreased by ~52% (p \u3c 0.01) with green tea consumption, indicating less oxidative stress. In conclusion, 3 cups of green tea consumption for 3 months can improve antioxidant status and reduce oxidative damage in PD patients. Further studies are needed to determine if these changes result in slowing the disease progression

Imbedded Optical Fiber Sensor of Differential Strain in Composites

Fiber sensors have specifically been applied to the quantitative nondestructive characterization of materials for several years [1–3]. Due to the inherent similarity of unjacketed glass-on-glass optical fibers and individual graphite fibers in graphite/epoxy composites in particular, a number of investigators have considered the use of optical fibers as sensors which may be imbedded directly within composite laminae. The effects of temperature and strain integrated along the length of the sensor fiber in a composite specimen can be determined using a variety of simple methods. Spatial resolution of such quantities along the imbedded fiber in length may be obtained using several more complicated distributed fiber sensing techniques. Strain tensor quantities may be determined by both presuming accurate models of the applied stress and knowing the photoelastic and mechanical properties of the imbedded fiber

Chromomagnetic instability in two-flavor quark matter at nonzero temperature

We calculate the effective potential of the 2SC/g2SC phases including vector condensates ($$and$$) and study the gluonic phase and the single plane-wave Larkin-Ovchinnikov-Fulde-Ferrell state at nonzero temperature. Our analysis is performed within the framework of the gauged Nambu--Jona-Lasinio model. We compute potential curvatures with respect to the vector condensates and investigate the temperature dependence of the Meissner masses squared of gluons of color 4--7 and 8 in the neutral 2SC/g2SC phases. The phase diagram is presented in the plane of temperature and coupling strength. The unstable regions for gluons 4--7 and 8 are mapped out on the phase diagram. We find that, apart from the case of strong coupling, the 2SC/g2SC phases at low temperatures are unstable against the vector condensation until the temperature reaches tens of MeV.Comment: 10 pages, 10 figures, revisions to text, published in Phys. Rev.