Generating a dynamical M2 brane from super-gravitons in a pp-wave background

We present a detail study of dynamically generating a M2 brane from super-gravitons (or D0 branes) in a pp-wave background possessing maximal spacetime SUSY. We have three kinds of dynamical solutions depending on the excess energy which appears as an order parameter signalling a critical phenomenon about the solutions. As the excess energy is below a critical value, we have two branches of the solution, one can have its size zero while the other cannot for each given excess energy. However there can be an instanton tunnelling between the two. Once the excess energy is above the critical value, we have a single solution whose dynamical behavior is basically independent of the background chosen and whose size can be zero at some instant. A by product of this study is that the size of particles or extended objects can grow once there is a non-zero excess energy even without the presence of a background flux, therefore lending support to the spacetime uncertainty principle.

Pareto-based Dynamic Difficulty Adjustment of a Competitive Exergame for Arm Rehabilitation (Preprint)

BACKGROUND Lack of motivation is a major hindrance to frequent and intense exercise which is critical to rehabilitating people with arm disabilities due to old age, neurological disorders or stroke. Recently, the use of interpersonal exergames has been associated with increased motivation and exercise intensity in arm rehabilitation and is becoming a common trend. However, the Dynamic Difficulty Adjustment (DDA) of such games is still an open issue because unlike the traditional DDA frameworks where game intensity is simply adapted to suit the players' performance, the aim of DDA for exergames is to optimize the conflicting objectives namely of intensity and performance. Objective: To design a dedicated DDA for rehabilitation exergames that optimize the conflicting objectives of intensity and performance by generating a set of feasible trade-off solutions. Based on the rehabilitative needs, the tradeoff worth information of each solution is to be used to select a unique solution. OBJECTIVE To design a dedicated DDA for rehabilitation exergames that optimizes the conflicting objectives of intensity and performance by generating a set of feasible trade-off solutions. Based on the rehabilitative needs, the tradeoff worth information of each solution is to be used to select a unique solution. METHODS We designed a Pareto-based DDA for a competitive exergame that optimizes the two conflicting objectives. Using a set of feasible solutions generated during the first episode of the game, the proposed Pareto-based DDA is used to modify the parameters of the game. Optimizing conflicting objectives generally results in a set of trade-off solutions called Pareto optimal set instead of a single solution. Therefore, the DDA is capable of selecting a single solution from the optimal Pareto based on the trade-off worth information of each solution in the optimal Pareto set. RESULTS Results: Experimental results with 12 unimpaired participants show the capability of the proposed Pareto-based DDA to online adjust the game parameters effectively based on a trade-off between the intensity and motivation. CONCLUSIONS Since rehabilitation outcomes rely on both intensity and motivation, unlike traditional DDA approaches, the capability of Pareto-based DDA to provide trade-off solutions between conflicting objectives of intensity and motivation is very promising to rehabilitation outcomes. However, multi-session investigation over a period of time needs to be carried out to examine if they influence rehabilitation outcomes positively. CLINICALTRIAL This work is not a clinical trial. Although humans participated in this study, they participate in the evaluation of a single-session of a rehabilitation exergame rather than a comprehensive rehabilitation intervention with no health outcomes investigated.

Copyright Regulation of Relations with regard to Software: Current State and Perspectives

— The legal regulation of relations about software (computer programs) is conducted mainly in two directions: copyright and patent law. But despite lengthy discussions in scientific circles in almost all countries, there is no final and single solution to this issue. Historically, the model of copyright protection of the object under study offers a cheaper and faster procedure than the model of protection of software by patent law. Patent protection requires a rather expensive and lengthy examination of software for world (absolute) novelty, during which the object itself may become obsolete and become unpopular with potential users. Therefore, the copyright regime for the protection of software has received preferential recognition. Accordingly, the article attempts to investigate the problems of the existing in the world copyright model of software protection and the possibility of patenting them. Keywords— software, copyright, patent law, object of protection

Steel Slag and Autoclaved Aerated Concrete Grains as Low-Cost Adsorbents to Remove Cd2+ and Pb2+ in Wastewater: Effects of Mixing Proportions of Grains and Liquid-to-Solid Ratio

This study investigated the applicability of industrial by-products such as steel slag (SS) and autoclaved aerated concrete (AAC) grains (<0.105, 0.105–2, 2–4.75 mm) as low-cost adsorbents for simultaneous removal of Cd2+ and Pb2+ in wastewater. A series of batch adsorption experiments was carried out in single and binary-metal solutions of Cd2+ and Pb2+ by changing the mixing proportions of SS and AAC grains. In addition, the effect of the liquid-to-solid ratio (L/S) on the removal of Cd2+ and Pb2+ in multi-metal solution was examined. Results showed that SS grains had a high affinity with Cd2+ in the single solution, while AAC grains had an affinity with Pb2+. In the binary solution, the mixtures of SS and AAC grains removed both Cd2+ and Pb2+ well; especially, the tested adsorbents of SS+AAC [1:1] and SS+AAC [1:4] mixtures achieved approximately 100% removal of both metals. Based on the results in the multi-metal solutions, the metal removal % and selectivity sequence varied depending on the mixed proportions of SS and AAC grains and L/S values. It was found that the SS+AAC [1:1] mixture of SS and AAC grains showed 100% removals of Cd2+, Pb2+, Cu2+, Ni2+, and Zn2+ simultaneously at L/S = 10 and 60.

The Initial Algebraic Knowledge of Preservice Teachers

Early algebra proposes to incorporate algebra in primary school from the first years of schooling. The success of this incorporation depends, to a large extent, on the training of teachers, so the objective of this article is to study whether the degree of algebraic knowledge of student teachers at the beginning of their training. To conduct this, 106 preservice teachers were given a questionnaire. This survey is based on two daily life situations. They had to propose tasks to develop algebraic reasoning in primary school students. Most of the participants designed tasks in which they assigned specific values to the indeterminate ones and solved them arithmetically. In this way, they transformed open situations and numerous opportunities to promote algebraic thinking in students through the generalization and representation of relationships and functions into closed single-solution problems that do not promote algebraic thinking. We can see from the results that the participants’ algebraic knowledge is insufficient. Therefore, it is necessary to include in their training process the programs and experiences that will allow them to design tasks in order to detect and promote algebraic thinking in their future students. Sequences of tasks are presented to develop both situations by generalizing and representing relationships and functions, which can serve as a starting point for future training programs and experiences.

A Closure for the Virtual Origin of Turbulent Plumes

An isolated source of surface buoyancy, be it a campfire or burning city, gives rise to a turbulent plume. Well above the surface, the plume properties asymptote to the well-known solutions of Morton, Taylor, and Turner (MTT), but a closure is still lacking for the virtual origin. A closure for the virtual origin is sought here in the case of a turbulent plume sustained by a circular source of surface buoyancy in an unstratified and unsheared fluid. In the high Reynolds number limit, it is argued that all such plumes asymptote to a single solution. Direct numerical simulation (DNS) of this solution exhibits a virtual origin located a distance below the surface equal to 1.1 times the radius of the buoyancy source. This solution is compared to the previously used assumption that the MTT plume is fully spun-up at the surface, and that assumption is found to give buoyancies that are off by an order of magnitude. With regards to the citywide firestorm triggered by the nuclear attack on Hiroshima, it is found that the spun-up-at-surface MTT solution would have trapped radioactive soot within about a hundred meters of the surface, whereas the DNS solution presented here corroborates observations of the plume reaching well into the troposphere.

Biosorbents from Plant Fibers of Hemp and Flax for Metal Removal: Comparison of Their Biosorption Properties

Lignocellulosic fibers extracted from plants are considered an interesting raw material for environmentally friendly products with multiple applications. This work investigated the feasibility of using hemp- and flax-based materials in the form of felts as biosorbents for the removal of metals present in aqueous solutions. Biosorption of Al, Cd, Co, Cu, Mn, Ni and Zn from a single solution by the two lignocellulosic-based felts was examined using a batch mode. The parameters studied were initial metal concentration, adsorbent dosage, contact time, and pH. In controlled conditions, the results showed that: (i) the flax-based felt had higher biosorption capacities with respect to the metals studied than the hemp-based felt; (ii) the highest removal efficiency was always obtained for Cu ions, and the following order of Cu > Cd > Zn > Ni > Co > Al > Mn was found for both examined biosorbents; (iii) the process was rapid and 10 min were sufficient to attain the equilibrium; (iv) the efficiency improved with the increase of the adsorbent dosage; and (v) the biosorption capacities were independent of pH between 4 and 6. Based on the obtained results, it can be considered that plant-based felts are new, efficient materials for metal removal.