Probing the phonon surface interaction by wave packet simulation: effect of roughness and morphology

One way to reduce the lattice thermal conductivity of solids is to induce additional phonon surface scattering through nanostructures. However, how phonons interact with boundaries, especially at the atomic level, is not well understood. In this work, we performed two-dimensional atomistic wave packet simulations to investigate the phonon surface interaction. Emphasis has been given to the angular-resolved phonon reflection at smooth, periodically rough, and amorphous surfaces. We found that the acoustic phonon reflection at a smooth surface is not simply specular. Mode conversion can occur after reflection, and the detailed energy distribution after reflection will dependent on surface condition and polarization of incident phonon. At periodically rough surfaces, the reflected wave packet distribution does not follow the well-known Ziman's model, but shows a nonmonotonic dependence on the depth of surface roughness. When an amorphous layer is attached to the surface, the incident wave packet will be absorbed by the amorphous region, and results in quite diffusive reflection. Our results clearly show that the commonly used specular-diffusive model is not enough to describe the phonon reflection at a periodically rough surface, while an amorphous layer can induce strong diffusive reflection. This work provides a careful analysis of phonon reflection at a surface with different morphology, which is important to a better understanding of thermal transport in various nanostructures.Comment: 15pages, 9 figure

Epigenetics involvement in Parkinson’s disease and manganese-induced neurotoxicity

Parkinson's disease (PD) is a progressive neurological disorder of CNS and one of the most common neurodegenerative diseases. The exact mechanisms underlying PD has been unclear but it is believed that multiple factors are involved. Excessive exposure to manganese (Mn) can causes its accumulation in the human brain and subsequent neural damage and even development of PD-like movement disorder, referred to as manganism. Although recent studies indicated the pathologic and clinical distinction between PD and Mn-induced neurotoxicity, genetically they have been shown some common features and associations. In recent years, the role of epigenetic changes has been well studied in brain development as well as different brain diseases including PD. Meanwhile, environmental agents including Mn have been found to damage the developing and mature nervous system through altering epigenetic regulatory pathways such as DNA methylation. The aim of this contribution was to review the epigenetic involvement in the etiology of PD and Mn-induced neurotoxicity. Other aspects of these syndromes were also discussed. Several lines of evidence have indicated that epigenetic modulation of gene plays more important roles in PD processes. On the other hand, Maternal Mn exposure has been found to be able to cause epigenetic changes in genes associated with neurodegeneration. The current data is very limited to show the association of MN-induced epigenetic changes and PD etiology. Although conclusion about the relationship between PD and Mn exposure need more consolidated studies, studying the molecular mechanisms of the effect of Mn, genetically and epigenetically will be helpful to understand the etiology of PD which is essential for therapeutic strategies of this disease

Malathion-induced testicular toxicity is associated with spermatogenic apoptosis and alterations in testicular enzymes and hormone levels in male Wistar rats

Malathion has a broad range of toxicities while its reproductive effects have not been fully elucidated. In this study, we treated animals with malathion by gavage at doses of 0, 33.75, 54, and 108 mg/kg for 60 days and evaluated the alterations in histology, biochemistry and serology. Malathion caused the reduction in the sperm counts and motility. The reduced body and testis weights were coupled with mild to severe degenerative changes in seminiferous tubules. We found malathion at 54 mg/kg increased spermatogenic apoptosis rate which was confirmed by changes in protein expression of Bax and Bcl-2. The activities of testicular enzymes including ACP, LDH and γ-GT were significantly altered with the reduced level of reproductive hormones such as LH, FSH and T. These results indicate that malathion can elicit deleterious effects on reproductive system of rats. The abnormal levels of hormones and apoptotic proteins induced by malathion may play important roles

Electromagnetic Performance Comparison between 12-Phase Switched Flux and Surface-Mounted PM Machines for Direct-Drive Wind Power Generation

In this article, the 12-phase switched flux permanent magnet (PM) (SFPM) machine and three surface-mounted PM (SPM) machines designed for direct-drive wind power generation are comparatively analyzed. First, feasible stator-slot/rotor-pole combinations for symmetrical 12-phase winding layout are investigated for both machine topologies. Second, the key design parameters of the PM generators including the split ratio and stator teeth width ratio are optimized by finite element analysis to achieve a high phase fundamental EMF per turn and a low cogging torque, both of which are desired by the direct-drive wind power generator. Third, electromagnetic performances including air-gap field, cogging torque, static torque, inductance, output voltage and its regulation factor, output power, and efficiency of the generators are compared. A 10-kW 24-slot/22-pole SFPM prototype is built and tested to validate the FE predicted results.</p

Enhancing the quantum entanglement and EPR steering of a coupled optomechanical system with a squeezed vacuum field

Quantum entanglement and Einstein-Podolsky-Rosen (EPR) steering are valuable resources in quantum information processing. How to enhance the quantum entanglement and EPR steering of coupled optomechanical systems with a weak squeezed vacuum field are studied when the displacement of detuning induced by the mechanical mode is considered. Compared with the condition that the system interacts with a vacuum environment, the quantum entanglement and EPR steering are stronger when the squeezed vacuum field is applied. A squeezed vacuum field with a large degree is not beneficial to enhance the quantum entanglement and EPR steering. Rather than the squeezing parameter of the squeezed vacuum field, the reference phase plays a vital role in this model

Evaluation of Fermentation Dynamics and Structural Carbohydrate Degradation of Napiergrass Ensiled with Additives of Urea and Molasses

This study examined the effects of urea and molasses on fermentation dynamics and structural carbohydrate degradation of Napiergrass (Pennisetum purpureum Schumach), which was ensiled in laboratory silos for 3, 7, 14, and 30 days at the ambient temperature. The treatments were additions (fresh weight basis) of: no molasses or urea (control), no molasses and 0.4% urea (U), 4% molasses and 0% urea (M), 4% molasses and 0.4% urea (MU). The results showed that the control group produced an unstable fermentation. U silage always had smallest amount of lactic acid and highest levels of pH, acetic acid, butyric acid and ammonia nitrogen. Compared with control, both M and MU increased water soluble carbohydrate contents which promoted lactic acid fermentation domination, but MU did not restrain clostridial fermentation. After 30 days of ensiling, compared with the control, both M and MU lowered structural carbohydrate contents, and U lowered crude protein content but MU increased this parameter. It was concluded that the combination of 4% molasses with 0.4% urea could improve the fermentation and nutritive qualities of Napiergrass but was not sufficient to inhibit clostridial fermentation

Acute and contained rupture of the descending thoracic aorta: Treatment with endovascular stent grafts

AbstractPurpose: The purpose of this study was to evaluate feasibility and safety of endovascular stent grafting for the treatment of patients with rupture of the descending thoracic aorta. Methods: Thirteen patients with rupture of the descending thoracic aorta were treated with endovascular stent grafting. Six patients were treated on the day of diagnosis because their vital signs were unstable, and the other seven patients were treated electively. Five patients had infection or potential infection, and the other eight patients did not. Expanded polytetrafluoroethylene-covered or polyester-covered Z stents were used in all patients. Results: Stent grafts were successfully placed in all patients. No endoleaks were observed at the end of the procedure. However, rebleeding was observed within 2 weeks of the procedure in two patients with infection. Six patients (46%) died within 5 months of the procedure (mean survival period, 61 ± 60 days). All five patients with infection (100%) died, and only one of eight patients without infection (13%) died (P <.01). The remaining seven patients are alive during the mean follow-up period of 21 months (overall survival rate, 54%), although additional surgical interventions, including surgical conversion in one case and upper extremity extraanatomic bypass in the other, were necessary in two of these patients. Conclusion: Endovascular stent grafting may be a safe and feasible method for the treatment of rupture of the descending thoracic aorta in selected patients without infection. However, its usefulness in terms of long-term prognosis appears to be extremely limited, especially in patients with infection. (J Vasc Surg 2003;37:100-5.

Photon blockade with a trapped Λ\Lambda-type three-level atom in asymmetrical cavity

We propose a scheme to manipulate strong and nonreciprocal photon blockades in asymmetrical Fabry-Perot cavity with a $\Lambda$-type three-level atom. Utilizing the mechanisms of both conventional and unconventional blockade, the strong photon blockade is achieved by the anharmonic eigenenergy spectrum brought by $\Lambda$-type atom and the destructive quantum interference effect induced by a microwave field. By optimizing the system parameters, the manipulation of strong photon blockade over a wide range of cavity detuning can be realized. Using spatial symmetry breaking introduced by the asymmetry of cavity, the direction-dependent nonreciprocal photon blockade can be achieved, and the nonreciprocity can reach the maximum at optimal cavity detuning. In particular, manipulating the occurring position of nonreciprocal photon blockade can be implemented by simply adjusting the cavity detuning. Our scheme provides feasible access for generating high-quality nonreciprocal single-photon sources