Low Cardiorespiratory Fitness is an Independent Predictor of Metabolic Syndrome in Young Korean Adults

Objective: To investigate the relationship between cardio/respiratory fitness (CRF) and metabolic syndrome (MS) in young Korean men. Design: In a cross-sectional study, we examined 909 young Korean men (mean±SD age, 24.0±2 years) who were healthy and not taking any medications affecting blood pressure, glucose, or lipids concentrations. Body fatness, resting blood pressures, and fasting blood levels of lipids, glucose, and insulin were measured with our standardized laboratory protocols. CRF was quantified as the maximum volume of minute oxygen consumption measured during a graded treadmill test. Metabolic syndrome was defined with the National Cholesterol Education Program Adult Treatment Panel III criteria and a modified cut-off value of waist circumference from the Asia-Pacific Perspective: Redefining Obesity and its Treatment. Results: Group analyses showed significant and inverse dose-response trends between the metabolic syndrome markers and CRF levels such that men with high and moderate CRF levels had more favorable profiles in body fatness, resting blood pressures, mean values in fasting lipids, glucose, and insulin, and homeostasis model of assessment-insulin resistance than men with low CRF level. After adjusting for several potential confounders such as age, smoking, and body fatness variables, the low and moderate CRF groups had odds of 4.64 (95% CI, 2.00 to 10.79) and 2.57 (95% CI, 1.04 to 6.34) for having metabolic syndrome than the high CRF group. Conclusion: These findings suggest that low CRF is a significant and independent risk factor for metabolic syndrome in young Korean men

On the correspondence between CAL and lagged cohort life expectancy

It has been established that under certain mortality assumptions, the current value of the Cross-sectional Average length of Life (CAL) is equal to the life expectancy for the cohort currently reaching its life expectancy. This correspondence is important, because the life expectancy for the cohort currently reaching its life expectancy, or lagged cohort life expectancy (LCLE), has been discussed in the tempo literature as a summary mortality measure of substantive interest. In this paper, we build on previous work by evaluating the extent to which the correspondence holds in actual populations. We also discuss the implications of the CAL-LCLE correspondence (or lack thereof) for using CAL as a measure of cohort life expectancy, and for understanding the connection between CAL, LCLE, and underlying period mortality conditions.cohort mortality, life expectancy, mortality measures, tempo effects

A variational perturbation scheme for many-particle systems in the functional integral approach

A variational Perturbation theory based on the functional integral approach is formulated for many-particle systems. Using the variational action obtained through Jensen-Peierls' inequality, a perturbative expansion scheme for the thermodynamic potential is established. A modified Wick's theorem is obtained for the variational perturbation expansions. This theorem allows one to carry out systematic calculations of higher order terms without worrying about the double counting problem. A model numerical calculation was carried out on a nucleon gas system interacting through the Yukawa-type potential to test the efficiency of the present method.Comment: accepted for publication in Phys. Rev.

Suppressed Superconductivity of the Surface Conduction Layer in Bi2_2Sr2_2CaCu2_2O8+x_{8+x} Single Crystals Probed by {\it c}-Axis Tunneling Measurements

We fabricated small-size stacks on the surface of Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ (BSCCO-2212) single crystals with the bulk transition temperature $T_c$$\simeq$90 K, each containing a few intrinsic Josephson junctions. Below a critical temperature $T_c'$ ($\ll$ $T_c$), we have observed a weakened Josephson coupling between the CuO$_2$ superconducting double layer at the crystal surface and the adjacent one located deeper inside a stack. The quasiparticle branch in the $IV$ data of the weakened Josephson junction (WJJ) fits well to the tunneling characteristics of a d-wave superconductor($'$)/insulator/d-wave superconductor (D$'$ID) junction. Also, the tunneling resistance in the range $T_c'$$<$$T$$<$$T_c$ agrees well with the tunneling in a normal metal/insulator/d-wave superconductor (NID) junction. In spite of the suppressed superconductivity at the surface layer the symmetry of the order parameter appears to remain unaffected.Comment: 13 pages, 6 figure

Thermoelectric Properties of Bismuth Antimony Telluride Alloys

Commonly used ozone-depleting refrigerants in refrigerators will be completely phased out in less than 15 years according to the Montreal Protocol. This imminent challenge can be tackled effectively by replacing the current vapor-compression cooling with environmentally sustainable thermoelectric cooling. P-type (Bi0.25Sb0.75)2Te3 alloys have been intensively studied over the past 50 years for cooling applications because of their high thermoelectric performance near room temperature. However, the electronic origin of the high thermoelectric efficiency of (Bi0.25Sb0.75)2Te3 alloys is often understated or ignored completely. In this thesis, the underlying physics of high electronic performance observed in the particular alloy composition, (Bi2Te3).25–(Sb2Te3).75, is investigated. It was demonstrated with two-band transport calculation that the convergence of bands occurred at (Bi2Te3).25–(Sb2Te3).75. A zT improvement of 17 % was also achieved in zone-levelled (Bi0.25Sb.75)2Te3 crystals by controlling their carrier concentration while using the two-band model as a guide. With the optimum electronic efficiency theoretically calculated and achieved experimentally, the thesis moves on to minimize lattice thermal conductivity of (Bi0.25Sb.75)2Te3 for the maximum zT. A new liquid compaction method was devised to produce dense arrays of dislocations in grain boundaries of nanostructured (Bi0.25Sb.75)2Te3. The grain boundary dislocations were found to be highly effective in scattering phonons and a substantial improvement in zT was possible (zT = 1.86 at 320 K). The understanding of phonon scattering by dislocations was in turn applied to phonon scattering at grain boundaries of polycrystalline materials. By demonstrating that the frequency-dependent dislocation scattering can replace the commonly used frequency-independent boundary scattering by Casimir, this thesis suggests that the grain boundary dislocation scattering may be responsible for the mechanism of phonon scattering at grain boundaries

A Daily Activity Monitoring System for Internet of Things-Assisted Living in Home Area Networks

In this paper, a daily activity monitoring system for Internet of Things (IoT)- assisted living in home area networks is proposed in order to provide care for elderly people who live alone. The proposed system consists of two main parts: an IoT-assisted living space with contactless activity sensors, a help trigger, and an emergency gateway and a daily activity monitoring server with a range of components including data collection, event and user management, activity analysis and reporting, and so on. The contactless activity sensors can be placed anywhere in the home, and the emergency gateway collects data from them, detects emergency situations reported through the help trigger, and communicates with the daily activity monitoring server. The server analyzes and reports the daily activities and activity patterns of elderly users using a predefined activity index. In addition, unexpected emergency situations can be estimated and prevented through analysis of the activity information

Positivity Bounds on Higgs-Portal Dark Matter

We consider the positivity bounds for WIMP scalar dark matter with effective Higgs-portal couplings up to dimension-8 operators. Taking the superposed states for Standard Model Higgs and scalar dark matter, we show that the part of the parameter space for the effective couplings, otherwise unconstrained by phenomenological bounds, is ruled out by the positivity bounds on the dimension-8 derivative operators. We find that dark matter relic density, direct and indirect detection and LHC constraints are complementary to the positivity bounds in constraining the effective Higgs-portal couplings. In the effective theory obtained from massive graviton or radion, there appears a correlation between dimension-8 operators and other effective Higgs-portal couplings for which the strong constraint from direct detection can be evaded. Nailing down the parameter space mainly by relic density, direct detection and positivity bounds, we find that there are observable cosmic ray signals coming from the dark matter annihilations into a pair of Higgs bosons, $WW$ or $ZZ$.Comment: 31 pages, 6 figures, v2: one-loop corrections to the positivity bounds added, version to be published in JHE