Thermoelectricity of interacting particles: A numerical approach

A method for computing the thermopower in interacting systems is proposed. This approach, which relies on Monte Carlo simulations, is illustrated first for a diatomic chain of hard-point elastically colliding particles and then in the case of a one-dimensional gas with (screened) Coulomb interparticle interaction. Numerical simulations up to $N>10^4$ particles confirm the general theoretical arguments for momentum-conserving systems and show that the thermoelectric figure of merit increases linearly with the system size.Comment: 8 pages, 6 figure

Strongly Tunable Anisotropic Thermal Transport in MoS2 by Strain and Lithium Intercalation: First--Principles Calculations

The possibility of tuning the vibrational properties and the thermal conductivity of layered van der Waals materials either chemically or mechanically paves the way to significant advances in nanoscale heat management. Using first-principles calculations we investigate the modulation of heat transport in MoS2 by lithium intercalation and cross-plane strain. We find that both the in-plane and cross-plane thermal conductivity (kr, kz) of MoS2 are extremely sensitive to both strain and electrochemical intercalation. Combining lithium intercalation and strain, the in-plane and cross-plane thermal conductivity can be tuned over one and two orders of magnitude, respectively. Furthermore, since kr and kz respond in different ways to intercalation and strain, the thermal conductivity anisotropy can be modulated by two orders of magnitude. The underlying mechanisms for such large tunability of the anisotropic thermal conductivity of \Mos are explored by computing and analyzing the dispersion relations, group velocities, relaxation times and mean free paths of phonons. Since both intercalation and strain can be applied reversibly, their stark effect on thermal conductivity can be exploited to design novel phononic devices, as well as for thermal management in MoS2-based electronic and optoelectronic systems

Gender-based clinical study on the association of cognitive impairment with drinking and smoking

Purpose: To evaluate the relationship between alcohol consumption and cigarette smoking among the elderly population of a Chinese city with a risk of developing cognitive decline and dementia.Methods: In this study, 1687 participants from the suburban town of Yanliang in Xi'an Sub-province, Shanxi Province, China in the age group of 60 - 65 years and who have not develop cognitive decline were assessed over a 6-year period. The study involved the evaluation of gender-based effect on alcohol consumption and smoking cigarette and its impact on cognitive functions.Results: The study observed that smokers have a higher risk of cognitive decline than non-smokers (odds ratio = 1.51; 95 % CI = (1.07 – 2.11). Interestingly, the odds ratio of the smokers among the female subjects was 1.54; 95 % CI (1.02 - 2.49) compared to female non-smokers. Moreover, a dosedependent relationship was observed for those female smoker with higher pack-years compared to nonsmokers (p = 0.003). On the other hand, regular alcohol consumption also increased the possibility of dementia and cognitive decline (odds ratio = 1.69; CI at 95 % = (1.03 – 2.75), hence a dose-dependent relationship was observed between male users (p = 0.042).Conclusion: The results suggest that alcohol consumption and smoking are linked with cognitive decline among the female subjects in the age group of 60 – 65 years. Thus, the relationship between these factors is characterized by gender difference which may be due to female sex hormones.Keywords: Cognitive health, Alcohol consumptions, Smoking, Elderly populatio

Mn-Intercalated MoSe2_2 under pressure: electronic structure and vibrational characterization of a dilute magnetic semiconductor

Intercalation offers a promising way to alter the physical properties of two-dimensional (2D) layered materials. Here we investigate the electronic and vibrational properties of 2D layered MoSe$_2$ intercalated with atomic manganese at ambient and high pressure up to 7 GPa by Raman scattering and electronic structure calculations. The behavior of optical phonons is studied experimentally with a diamond anvil cell and computationally through density functional theory calculations. Experiment and theory show excellent agreement in optical phonon behavior. The previously Raman inactive A$_{2u}$ mode is activated and enhanced with intercalation and pressure, and a new Raman mode appears upon decompression, indicating a possible onset of a localized structural transition, involving the bonding or trapping of intercalant in 2D layered materials. Density functional theory calculations reveal a shift of Fermi level into the conduction band and spin polarization in Mn$_x$MoSe$_2$ that increases at low Mn concentration and low pressure. Our results suggest that intercalation and pressurization of van der Waals materials may allow one to obtain dilute magnetic semiconductors with controllable properties, providing a viable route for the development of new materials for spintronic applications.Comment: 8 pages, 5 figure

Diffusion of heat, energy, momentum, and mass in one-dimensional systems

We study diffusion processes of local fluctuations of heat, energy, momentum, and mass in three paradigmatic one-dimensional systems. For each system, diffusion processes of four physical quantities are simulated and the cross correlations between them are investigated. We find that, in all three systems, diffusion processes of energy and mass can be perfectly expressed as a linear combination of those of heat and momentum, suggesting that diffusion processes of heat and momentum may represent the heat mode and the sound mode in the hydrodynamic theory. In addition, the dynamic structure factor, which describes the diffusion behavior of local mass density fluctuations, is in general insufficient for probing diffusion processes of other quantities because in some cases there is no correlation between them. We also find that the diffusion behavior of heat can be qualitatively different from that of energy, and, as a result, previous studies trying to relate heat conduction to energy diffusion should be revisited.Comment: 7 pages, 4 figure