Low-bias Negative Differential Resistance effect in armchair graphene nanoribbon junctions

Graphene nanoribbons with armchair edges (AGNRs) have bandgaps that can be flexibly tuned via the ribbon width. A junction made of a narrower AGNR sandwiched between two wider AGNR leads was recently reported to possess two perfect transmission channels close to the Fermi level. Here, we report that by using a bias voltage to drive these transmission channels into the gap of the wider AGNR lead, we can obtain a negative differential resistance (NDR) effect. Owing to the intrinsic properties of the AGNR junctions, the on-set bias reaches as low as ~ 0.2 V and the valley current almost vanishes. We further show that such NDR effect is robust against details of the atomic structure of the junction, substrate and whether the junction is made by etching or by hydrogenation.Comment: The following article has been submitted to Applied Physics Letters (http://scitation.aip.org/content/aip/journal/apl). Copyright (2014) Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported Licens

Analysis of air and airborne particles movements in a hospital operating theater

In this study a computational fluid dynamics (CFD) method was used to develop a validated model of a hospital operating theater. The model was employed to perform simulation to predict the distribution of airflow and movement of the airborne particles inside the operating theater at a steady-state condition. The airborne particles were modeled as discrete particles which were released from the exposed body surface of the surgical staffs at a rate of 10 CFU/s. The effect of laminar inlet air flow velocity on the airborne particles concentration around the operating table was examined. It was found that the air flows straight downward from the air-conditioning diffuser towards the middle of the operating table. However, the existence of the medical lamp causes a vortex air flow condition below it. Air also penetrates the ultra-clean area on the opposite side of the operating table. The airborne particles are washed away from the vicinity of the operating table by the air flow. This is more effective when the supply air flow velocity is high. At low air flow velocity, some particles appear to penetrate into the ultra-clean area near the edges of the operating table. At higher air flow velocity, the airborne particles seem to be more effectively washed away from this region. High concentration of airborne particles occurs underneath the medical lamp due to vortices created by the air flow. Higher air flow velocity increases the level of particles concentration in this area

Fundamental Structure of General Stochastic Dynamical Systems: High-Dimension Case

No one has proved that mathematically general stochastic dynamical systems have a special structure. Thus, we introduce a structure of a general stochastic dynamical system. According to scientific understanding, we assert that its deterministic part can be decomposed into three significant parts: the gradient of the potential function, friction matrix and Lorenz matrix. Our previous work proved this structure for the low-dimension case. In this paper, we prove this structure for the high-dimension case. Hence, this structure of general stochastic dynamical systems is fundamental

The Classification and Surgical Strategy of Intracardiac Leiomyomatosis

BackgroundThere is a great deal of heterogeneity in the surgical strategy to treat intracardiac leiomyomatosis (ICL), leading to a need to create a theoretical tool to clarify this situation.MethodsThe data of 14 cases of ICL surgically treated in Anzhen Hospital from February 1995 to February 2009 were retrospectively reviewed. A system for classifying ICL was proposed based on four features of the lesion: size of intracardiac component; extent of inferior vena cava (IVC) involvement; venous pathway from uterus to IVC; and laterality of the lesion in the pelvis. The 14 cases of ICL were treated through multiple surgical strategies.ResultsThere were no operative deaths. The follow-up was 73.1 ± 59.2 months and one patient died from recurrence due to incomplete excision 5 months after the primary procedure. The 5-year survival rate calculated through Kaplan-Meier survival curve was 93.16 ± 4.98%. Of the surviving patients, 13 had ICL, 10 were in the New York Heart Association (NYHA) class I, and three were in NYHA class II.ConclusionThe surgical treatment of ICL can obtain a good mid- to long-term survival rate and satisfactory heart function, and the proposed classification system for ICL may be helpful to guide the selection of the surgical strategy for ICL, and may serve as the future basis for standardising the reporting of ICL management