Dissociative recombination of cold H3+ and its interstellar implications

H3+ plays a key role in interstellar chemistry as the initiator of ion-molecule chemistry. The amount of H3+ observed in dense interstellar clouds is consistent with expectations, but the large abundance of H3+ seen in diffuse clouds is not easily explained by simple chemical models. A crucial parameter in predicting the abundance of H3+ in diffuse clouds is the rate constant for dissociative recombination (DR) with electrons. The value of this constant has been very controversial, because different experimental techniques have yielded very different results, perhaps owing to varying degrees of rotational and vibrational excitation of the H3+ ions. If the value of this rate constant under interstellar conditions were much lower than usually assumed, the large H3+ abundance could be easily explained. In an attempt to pin down this crucial rate constant, we have performed DR measurements at the CRYRING ion storage ring in Stockholm, using a supersonic expansion ion source to produce rotationally cold H3+ ions. These measurements suggest that the DR rate constant in diffuse clouds is not much lower than usually assumed and that the abundant H3+ must be due to either a low electron fraction or a high ionization rate.     

Quenching of electrogenerated chemiluminescence by phenols, hydroquinones, catechols, and benzoquinones

Efficient quenching of Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridine) electrogenerated chemiluminescence has been observed in the presence of phenols, catechols, hydroquinones, and benzoquinones. In most instances, quenching is observed with 100-fold excess of quencher over Ru(bpy)(3)(2+), with complete quenching observed between 1000- and 2000-fold excess. The mechanism of quenching is believed to involve energy transfer from the excited-state luminophore to benzoquinone. In the case of phenols, catechols, and hydroquinones, quenching is believed to occur via a benzoquinone derivative formed at the electrode surface. Photoluminescence and UV-visible experiments coupled with bulk electrolysis support the formation of benzoquinone products upon electrochemical oxidation.     

Laser-activated membrane introduction mass spectrometry for high-throughput evaluation of bulk heterogeneous catalysts

Laser-activated membrane introduction mass spectrometry (LAMIMS), a high-throughput screening method, evaluates heterogeneous catalysts under realistic reactor conditions. It is a precise, versatile system requiring no moving parts. The catalyst array is supported on carbon paper overlaid upon a silicone rubber membrane configured in a variation of membrane introduction mass spectrometry as introduced by Cooks. The carbon paper serves as a heat-dissipating gas diffusion layer that permits laser heating of catalyst samples far above the decomposition temperature of the polymer membrane that separates the array from the mass spectrometer vacuum chamber. A computer-controlled CO2 bar code writing laser is used for fine-tune heating of the catalyst spots above the base temperature of the LAMIMS reactor. The detailed design and performance of LAMIMS is demonstrated on arrays of "real world" bulk water-gas shift catalysts using natural and isotopically labeled reactor feed streams. A bulk catalyst array spot can be evaluated for activity and selectivity in as little as 1.5 min. All array screening results were confirmed by industrial microreactor evaluations.     

Bus transfer systems: requirements, implementation, and experiences

A bus transfer system is designed to provide process continuity to the loads attached to a motor bus while transferring the bus from one source to another. A successful bus transfer under contingent conditions provides immense value and benefits to continuous process operations that cannot afford an interruption of power supply to plant auxiliaries. This paper describes some real-world bus transfer requirements, implementations, and experiences in thermal power plants and continuous process industry plants. The fast, in-phase, residual voltage, and momentary paralleling transfer methods are described, compared, and evaluated. The spin-down characteristics for different motor buses are analyzed, and the feasibility of the different transfer modes is deduced. Auto-initiation criterion for bus transfer is explored, using a combination of bus undervoltage, underfrequency, and (df/dt) characteristics. Different integrated system requirements, such as monitoring of readiness conditions, breaker failure detection and corrective action logic, and online testing measures, are discussed. The results of the resultant "hot" load trials and their benefits to the system are explained and interpreted. The concept of islanded transfer for grid-free operations of captive generation-load systems is discussed and elaborated.     

Optimization by estimation of distribution with DEUM framework based on Markov random fields

This paper presents a Markov random field (MRF) approach to estimating and sampling the probability distribution in populations of solutions.The approach is used to define a class of algorithms under the general heading distribution estimation using Markov random fields (DEUM).DEUM is a subclass of estimation of distribution algorithms (EDAs) where interaction between solution variables is represented as an undirected graph and the joint probability of a solution is factorized as a Gibbs distribution derived from the structure of the graph.The focus of this paper will be on describing the three main characteristics of DEUM framework,which distinguishes it from the traditional EDA.They are:1) use of MRF models,2) fitness modeling approach to estimating the parameter of the model and 3) Monte Carlo approach to sampling from the model.     

Kinematics and Wear of Tool Blades for Scrap Tire Shredding

The wear of tool blades for cost-effective scrap tire shredding is investigated. Rotary disk cutters are widely used for cutting scrap tires into small pieces. The hard, wear-resistant tool blades mounted on the periphery of disk cutters maintain a narrow gap between blades and generate the cutting action. The kinematics of the relative motion of two adjacent disk cutters is derived to model the overlap region on blades during cutting. The model predictions match well with the actual shapes of the worn regions on used tool blades. The wear of tool blades made of AISI D2 and CRU-WEAR (CW) tool steels for scrap tire shredding is evaluated. A coordinate measurement machine was used to measure the tool wear. The wear on the blade surface is not uniform. Regions with high wear rate are explained using the kinematics analysis. The CW blades show a lower wear rate, about half of that of D2 blades, and a potential choice for cost savings.     

A summary of the Colorado Clinical Psychology/Expanded Mental Health Benefits Experiment.

Conducted an experiment to test 2 alterations in the Medicare program: (1) increasing the proportion of allowable charges for outpatient mental health services that Medicare will reimburse and raising the annual limit of reimbursement, and (2) reimbursing psychologists directly, rather than through a supervising physician, for providing mental health services. The experiment was conducted by Blue Cross/Blue Shield of Colorado from October 1976 to December 1978. All Medicare beneficiaries in that state were randomly assigned to 4 groups, each having a different combination of the 2 variables: coverage and practitioner status. The evaluation consisted of 2 primary components: assessing how successfully the operational aspects of the experiment functioned and determining the impact of the experimental changes on the use, cost, and delivery of mental health and medical services reimbursed by Medicare. There appeared to be no administrative barriers to implementing the changes necessary to select eligible psychologists to participate, select the services to be covered, or implement reimbursement procedures for clinical psychologists. However, the case-by-case peer review system developed for the experiment experienced administrative problems and was costly. There were no significant effects on the utilization of Medicare services, overall program costs, or the delivery of care. (4 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Software Support for Computerized Electromyography in Clinical Dentistry

This paper describes the software system for a minicomputer-based real-time data-acquisition system that is currently being used by clinical dental personnel of the University of Michigan Dental Research Institute. Because this system is utilized by operators who are unfamiliar with computers it is highly interactive. Also described are the software design considerations engendered by such a research environment.