Quantum-mechanical reaction rate constants from centroid molecular dynamics simulations: Barrier crossing in an asymmetrical double-well

Quantum-mechanical reaction rate constants were calculated from centroid molecular dynamics (CMD) simulations, for the case of barrier crossing in an asymmetrical double-well potential bilinearly coupled to a harmonic bath. The calculation is based on a recently proposed formulation of the reaction rate constant in terms of the position—flux correlation function, which can be approximated via CMD in a well-defined manner. The predictions of CMD and various simplified versions of it are compared to exact results, which were obtained via the quasi-adiabatic propagator path integral (QUAPI) method, and/or path integral quantum transition state theory (PI-QTST). The predictions based on CMD are found to be in good agreement with both.     

Effective deadlock resolution with self-interested partially-rational agents

This paper pertains to distributed deadlock resolution in settings populated with self-interested bounded-rational autonomous agents. In particular it reports the results of extensive experimentation with 66 agents, each using a deadlock resolution strategy developed and maintained throughout the experiment by a different human decision maker. While from the game-theoretic perspective a simple equilibrium-based solution can be engineered for the problem, it is shown that such a solution fails to hold with bounded-rational agents, even when its principles are thoroughly explained to the individuals that maintain the agents’ strategies. Instead, we show that the system converges to a steady-state, in which the agents use a rich set of different strategies, varying in their performance, as each of them has a different belief regarding its ability to improve, based on the behaviors of the others. To improve system performance, we develop and implement a restructuring heuristic that changes the input each agent receives, as a means of affecting the agents’ decisions to better align with the desired solution. The restructured deadlock presented to each agent is based on former deadlocks it had experienced. Our experiments demonstrate the effectiveness of the restructuring heuristic in facilitating a new steady-state in which the system as a whole substantially improves its performance. The efficiency of the method, in terms of the size of the set of former experiences required for effectively restructuring the agents’ input, is demonstrated through a comparison with a neural network implementation of input restructuring, showing a substantial advantage to the restructuring heuristic.     

The effectiveness of Light Rail transit in achieving regional CO<Subscript>2</Subscript> emissions targets is linked to building energy use: insights from system dynamics modeling

Cities worldwide face the challenges of accommodating a growing population, while reducing emissions to meet climate mitigation targets. Public transit investments are often proposed as a way to curb emissions while maintaining healthy urban economies. However, cities face a system-level challenge in that transportation systems have cascading effects on land use and economic development. Understanding how an improved public transit system could affect urban growth and emissions requires a system-level view of a city, to anticipate side effects that could run counter to policy goals. To address this knowledge gap, we conducted a case study on the rapidly growing Research Triangle, North Carolina (USA) region, which has proposed to build a Light Railway by 2026 along a heavily used transportation corridor between the cities of Durham and Chapel Hill. At the same time, Durham County has set a goal of lowering greenhouse gas emissions by 30% from a 2005 baseline by 2030. In collaboration with local stakeholders, we developed a system dynamics model to simulate how Light Rail transit and concurrent policies could help or hinder these sustainable growth goals. The Durham–Orange Light Rail Project (D–O LRP) model simulates urban–regional dynamics between 2000 and 2040, including feedbacks from energy spending on economic growth and from land scarcity on development. Counter to expectations, model scenarios that included Light Rail had as much as 5% higher regional energy use and CO₂ emissions than business-as-usual (BAU) by 2040 despite many residents choosing to use public transit instead of private vehicles. This was largely due to an assumption that Light Rail increases demand for commercial development in the station areas, creating new jobs and attracting new residents. If regional solar capacity grew to 640 MW, this would offset the emissions growth, mostly from new buildings, that is indirectly due to Light Rail. National trends in building and automobile energy efficiency, as well as federal emissions regulation under the Clean Power Plan, would also allow significant progress toward the 2030 Durham emissions reduction goal. By simulating the magnitude of technology and policy effects, the D–O LRP model can enable policy makers to make strategic choices about regional growth.     

冶炼烟气净化：所有步骤在一台设备内完成

介绍Kimre公司的SXF^TM半错流洗涤器的结构、优点和应用。该洗涤器采用卧式并流气液接触方式,可根据需要分隔成不同操作段,在由交织单丝构成的纤维介质上完成气体的冷却、净化和除沫。与传统立式逆流填料塔相比,该洗涤器的优点为：高度低,泵、阀门、控制器等可在地面安装,容易操作和维修;液气比范围宽;可进行多级操作,包括在一台设备内完成多个化学过程。如用于冶炼烟气净化,所有步骤可在一台设备内完成。列举了化肥厂造粒塔气体净化、磷酸厂气体除氟和硫酸厂干燥塔除沫等应用实例。     

How do clinicians reconcile conditions and medications? The cognitive context of medication reconciliation

Medication omissions and dosing failures are frequent during transitions in patient care. Medication reconciliation (MR) requires bridging discrepancies in a patient’s medical history as a setting for care changes. MR has been identified as vulnerable to failure, and a clinician’s cognition during MR remains poorly described in the literature. We sought to explore cognition in MR tasks. Specifically, we sought to explore how clinicians make sense of conditions and medications. We observed 24 anesthesia providers performing a card-sorting task to sort conditions and medications for a fictional patient. We analyzed the spatial properties of the data using statistical methods. Most of the participants (58%) arranged the medications along a straight line (p < 0.001). They sorted medications by organ systems (Friedman’s χ ²(54) = 325.7, p < 0.001). These arrangements described the clinical correspondence between each two medications (Wilcoxon W = 192.0, p < 0.001). A cluster analysis showed that the subjects matched conditions and medications related to the same organ system together (Wilcoxon W = 1917.0, p < 0.001). We conclude that the clinicians commonly arranged the information into two groups (conditions and medications) and assigned an internal order within these groups, according to organ systems. They also matched between conditions and medications according to similar criteria. These findings were also supported by verbal protocol analysis. The findings strengthen the argument that organ-based information is pivotal to a clinician’s cognition during MR. Understanding the strategies and heuristics, clinicians employ through the MR process may help to develop practices to promote patient safety.     

On controllability and trajectory tracking of a kinematic vehicle model

This paper presents some further results concerning the issues of controllability and trajectory tracking regarding a front-wheel drive vehicle kinematic model. A simple procedure for computing an open-loop control strategy that transfers the system between given initial and final states, is presented. In particular, the input function is computed by means of a set of linear algebraic equations. The resulting motion planning procedure allows us to present a control scheme for solving the trajectory (a time-parameterized reference signal) tracking problem. Various applications of the approach in forward and backward motions are considered, and simulation results are presented.     

Quantitative characterization of extruded film texture

Quantitative characterization of the texture of extruded low density polyethylene films was attempted with the aid of concepts such as the scale and intensity of segregation. The scale of segregation defined along a line and the profile of the scale of segregation were found to be useful modifications of the originally defined scale of segregation. The former, which is obtained by taking concentration points along a line, was needed because the film texture is non-isotropic, while the latter, which is obtained by repeated calculations of the scale of segregation over a varying size sample was needed, for a more accurate representation of this texture. The profile of the scale of segregation leads to a few typical values, which perhaps, can be related to particular features of the mixing mechanisms in the extruder.     

Fast computation of limit cycles in an industrial application

A model problem is described that requires the study of a system of the form v(t) = F _P (v(t), t) which depends on a set of parameters P, and where 1. The problem comes from an industrial application where it is a kernel of an optimization procedure. The optimization depends on computing the limit cycle, and the problem needs to be solved repeatedly. Short computation time is therefore essential. The naive approach is to integrate the equation forward in time, starting from an arbitrary initial condition, until the transients disappear and the limit cycle is approximated within a given tolerance. This approach is too slow and thus impractical in the context of the optimization procedure. The problem involves two types of asymptotic considerations: long-time asymptotics and small-parameter asymptotics. Here a simple approach is demonstrated, based on implementing the averaging method. This reduces the solution time to the point that the optimization procedure becomes feasible.     

Stereoselective recognition of monolayers of cholesterol, ent-cholesterol, and epicholesterol by an antibody

The interaction between a monoclonal antibody and four distinct monolayers with varying degrees of structural, chemical, and stereochemical similarity were studied and quantified. The antibody, raised and selected against cholesterol monohydrate crystals, interacts with cholesterol monolayers stereospecifically, but not enantiospecifically. Monolayers of ent-cholesterol molecules, which are chemically identical to cholesterol and whose structure is the exact mirror image of the cholesterol monolayer, interact with the antibody to the same extent as the cholesterol monolayers. The affinity of the antibody for both enantiomeric monolayers is extremely high. However, the antibody does not interact with monolayers of epicholesterol, which is an epimer of cholesterol: The hydroxy group in epicholesterol is in the 3alpha position rather than in the 3beta position, imposing a different angle between the hydroxy group and the rigid steroid backbone, and a different packing of the molecules. Monolayers of triacontanol, a long-chain primary aliphatic alcohol, interact with the antibody to a lesser extent than the cholesterol and ent-cholesterol monolayers, presumably due to the structural flexibility of the triacontanol molecule. The lack of chiral discrimination by the antibody is thus correlated to the level at which the chirality is exposed at the surface of the monolayers.     

On a periodic training sequence in DFE to reduce the steady-stateerror probability

A periodic transmission of a short resetting sequence used to “fill up” the decision-feedback equalizer feedback filter memory with correct symbols is proposed to reduce the propagation error. Two strategies are considered: full and partial reset, where the entire memory and some part of it is reset, respectively. For any given steady-state bit-error rate, the period of the resetting sequence is found by use of the Markov chain limit theorem. It is shown, via an illustrative example, that for low signal-to-noise ratio (SNR), the resetting strategy outperforms Bose-Chaudhuri-Hocquenghen (BCH) code with the same code rate. Moreover, a joint resetting and error correction coding strategy is considered, which is better than BCH code for low and medium SNR