Rapid dissipation in a current sheet driven by footpoints motions

Context.Wave energy dissipation by viscous and resistive damping in magnetic coronal plasmas is addressed. A two and one half dimensional, line-tied magnetic channel is considered whose footpoints are disturbed by buffeting motions of the photosphere. Aims.The aim of the analysis is to determine how effectively shear Alfvén waves, driven by footpoint motions and resonating in the channel, can be damped by visco-resistive friction. Methods.The problem is analyzed using a mixture of numerical and analytic techniques. Dynamic simulations, based on a cyclic footpoint driver, show that phase mixing resulting from variations in the magnetic field of the channel is instrumental in setting up a permanent "resonance regime" for the system. Analytic methods are used to analyze the resonance regime and to develop scaling laws for the rate of energy dissipation. Results.We show that in the general case where the Alfvén velocity profile may be linearized around the resonance, the dissipation rate is "fast" in that it is not limited by small damping coefficients. Although large energies can accumulate within the channel in the limit of very small damping, we show that by tuning the driver to low frequencies, both the energy level and the dissipation rate can be made insensitive to the level of the damping

Visco-resistive shear wave dissipation in magnetic X-points

We consider the viscous and resistive dissipation of perpendicularly polarized shear waves propagating within a planar magnetic X-point. To highlight the role played by the two-dimensional geometry, the damping of travelling Alfvèn waves that propagate within an unbounded, but non-orthogonal X-point topology is analyzed. It is shown that the separatrix geometry affects both the dissipation time and the visco-resistive scaling of the energy decay. Our main focus, however, is on developing a theoretical description of standing wave dissipation for orthogonal, line-tied X-points. A combination of numerical and analytic treatments confirms that phase mixing provides a very effective mechanism for dissipating the wave energy. We show that wave decay comprises two main phases, an initial rapid decay followed by slower eigenmode evolution, both of which are only weakly dependent on the visco-resistive damping coefficients

Near Optimal Exploration-Exploitation in Non-Communicating Markov Decision Processes

While designing the state space of an MDP, it is common to include states that are transient or not reachable by any policy (e.g., in mountain car, the product space of speed and position contains configurations that are not physically reachable). This leads to defining weakly-communicating or multi-chain MDPs. In this paper, we introduce \tucrl, the first algorithm able to perform efficient exploration-exploitation in any finite Markov Decision Process (MDP) without requiring any form of prior knowledge. In particular, for any MDP with $S^{\texttt{C}}$ communicating states, $A$ actions and $\Gamma^{\texttt{C}} \leq S^{\texttt{C}}$ possible communicating next states, we derive a $\widetilde{O}(D^{\texttt{C}} \sqrt{\Gamma^{\texttt{C}} S^{\texttt{C}} AT})$ regret bound, where $D^{\texttt{C}}$ is the diameter (i.e., the longest shortest path) of the communicating part of the MDP. This is in contrast with optimistic algorithms (e.g., UCRL, Optimistic PSRL) that suffer linear regret in weakly-communicating MDPs, as well as posterior sampling or regularised algorithms (e.g., REGAL), which require prior knowledge on the bias span of the optimal policy to bias the exploration to achieve sub-linear regret. We also prove that in weakly-communicating MDPs, no algorithm can ever achieve a logarithmic growth of the regret without first suffering a linear regret for a number of steps that is exponential in the parameters of the MDP. Finally, we report numerical simulations supporting our theoretical findings and showing how TUCRL overcomes the limitations of the state-of-the-art

Sorteerwater gereinigd met ozon

Energie uit de lucht wordt het tegenwoordig ook wel genoemd. Futuroloog Wim de Ridder weet het zeker : uit zonne-energie gehaalde elektriciteit wordt steeds goedkoper. Over zo'n tien jaar komt er een omslag en wordt het mogelijk stroom voor een habbekrats te producere

Evolution of Occupational Therapy Practice: Life History of Charlie Baumer, COTA

Charlie Baumer is a Certified Occupational Therapy Assistant (COTA) who was interviewed by two year II occupational therapy students at the University of North Dakota at Casper College as part of a life history qualitative study. The interview was a semi-structured interview that lasted two hours with questions that were geared toward the history and evolution of occupational therapy in Wyoming. This single interview is a part of a larger life history qualitative study to gather information in regards to the history and evolution of occupational therapy practice in North Dakota and Wyoming through the life histories of occupational therapy in both states. The students designed a series of questions regarding Charlie\u27s perspective on the profession, his experiences, and how the profession has changed in Wyoming overtime. This study is intended to contribute to current and future generations of occupational therapy practice has evolved over time in North Dakota and Wyoming. Upon data analysis, the students identified three categories, Legality, OT Practice, and Characteristics. Charlie demonstrated his passion for occupational therapy by sharing his experiences within the profession. His contribution to the profession indicated how occupational therapy has evolved in the state of Wyoming and how it will continue to evolve.https://commons.und.edu/ot-oral-histories-posters/1006/thumbnail.jp

From Here to There: An Occupational Screening Tool for Transitioning Soldiers

Time has shown that it can be difficult for military personnel to resume their typical life roles within civilian life. The wars in Iraq and Afghanistan were the longest wars in United States history and involved some of the most intense ground engagements since Vietnam (Cogan, 2014). This left many soldiers to deal with the traumatic experiences they went through. This study aimed at developing a screening tool to address the difficulties experienced by veterans during their transition into civilian life. The researchers began with a thorough review of literature to identify the occupational challenges the project would address. Following completion of the literature review, the researchers identified an occupational therapy model to guide the development of the screening tool and accompanying manual. Once the tool and the manual was created the researchers presented the documents to a local veterans club and finally presented the project at oral comprehensive exams at the university. The researchers created the Military Community Reintegration Screen (MCRS), which addresses three domains related to the person, occupation, and environment. Each domain is further broken down into subdomains and tasks that are specific to a veteran’s transition to civilian life. The manual addresses how to use and score the screening tool, as well as when to make a referral to occupational therapy services. This tool has not been clinically tested or used. Further research on the development, usefulness, and effectiveness of the screening tool is still desired by the researchers. Screening tools and assessments are available to military personnel for reintegration into the community; however, they are generally used from research purposes or are not part of the separation requirements, therefore, are not being completed by the soldiers. There are still individuals who are not receiving the treatment they need and due to the stigma around mental illness, many soldiers who are vulnerable to mental illness are denying their need for mental health treatment

RECENT ADVANCES IN METAL-CATALYZED C-H FUNCTIONALIZATION OF PYRIMIDINONES, QUINAZOLINONES AND FUSED QUINAZOLINONES

International audienceThis review emphasises the recent developments in metal-catalyzed functionalization using direct C-H bond activation of pyrimidinones (uracils), quinazolinones and quinazolinone-based fused poly-N-heterocycles as well as metal-catalyzed C-H functionalization of high valuable 2-arylquinazolinones

Evolution of Occupational Therapy Practice: Life History of Charlie Baumer, COTA

Charlie Baumer is a Certified Occupational Therapy Assistant (COTA) who was interviewed by two year II occupational therapy students at the University of North Dakota at Casper College as part of a life history qualitative study. The interview was a semi-structured interview that lasted two hours with questions that were geared toward the history and evolution of occupational therapy in Wyoming. This single interview is a part of a larger life history qualitative study to gather information in regards to the history and evolution of occupational therapy practice in North Dakota and Wyoming through the life histories of occupational therapy in both states. The students designed a series of questions regarding Charlie\u27s perspective on the profession, his experiences, and how the profession has changed in Wyoming overtime. This study is intended to contribute to current and future generations of occupational therapy practice has evolved over time in North Dakota and Wyoming. Upon data analysis, the students identified three categories, Legality, OT Practice, and Characteristics. Charlie demonstrated his passion for occupational therapy by sharing his experiences within the profession. His contribution to the profession indicated how occupational therapy has evolved in the state of Wyoming and how it will continue to evolve

Uniform system of dried fruit cost accounting

There is every reason for believing that the California dried fruit industry can be materially benefited by the adoption of a uniform cost determining system. These benefits will inure not only to the factors engaged in packing and distributing, but also to the thousands of growers engaged in producing dried fruits. The Dried Fruit Association of California, dedicated as it is to promoting the welfare of this basic State industry, earnestly urges its members not only to study, but to install the uniform system proposed in this pamphlet. A full knowledge of costs is just as important to a packer as is a knowledge of products and trade practices

Annual report of the Fruit Growers' Association of Ontario, 1921

The reports are also published in the Annual report of the Department of Agriculture of the province of Ontario, and in the Sessional papers of the province of Ontario "Printed by order of the Legislative Assembly" [-1923] "Printed by order of ... Minister of Agriculture" [1924-] 25th, 1893- pub. by the Ontario Department of Agriculture, Toronto 1890 -1908 reports are bound with the corresponding annual reports of the Entomological Society of Ontario 1894 -1905 reports are bound with the corresponding annual reports of the Fruit Experiment Stations of Ontario 1906 -1910 reports are bound with the corresponding Report of the Fruit Branch, Dept. of Agriculture, Ontari