Amalgamated products and properly 3-realizable groups

In this paper, we show that the class of all properly 3-realizable groups is closed under amalgamated free products (and HNN-extensions) over finite groups. We recall that $G$ is said to be properly 3-realizable if there exists a compact 2-polyhedron $K$ with $\pi_1(K) \cong G$ and whose universal cover $\tilde{K}$ has the proper homotopy type of a 3-manifold (with boundary).Comment: J. Pure Appl. Alg., to appea

Phase Diagram of a Classical Fluid in a Quenched Random Potential

We consider the phase diagram of a classical fluid in the presence of a random pinning potential of arbitrary strength. Introducing replicas for averaging over the quenched disorder, we use the hypernetted chain approximation to calculate the correlations in the replicated liquid. The freezing transition of the liquid into a nearly crystalline state is studied using a density functional approach, and the liquid-to-glass transition is studied using a phenomenological replica symmetry breaking approach introduced by Mezard and Parisi. The first-order liquid-to-crystal transition is found to change to a continuous liquid-to-glass transition as the strength of the disorder is increased above a threshold value.Comment: 7 pages, 4 figures, to appear in EuroPhysics Letter

Conceptual Model for Serious Games Design: Case Study of Children with Attention Deficit Hyperactivity Disorder

The field of Serious Games (SGs) is relatively new; however, so far, these have focused more on assessing impacts on results rather than identifying the most appropriate implementation phases to obtain a successful SG. The present work proposes a conceptual model for the design of SGs, which is based on four stages: Analysis, Design, Development, and Evaluation, under the life cycle of the software. For the validation of the model, an SG called ATHYNOS was developed, which was applied in a case study comparing it with the traditional therapy. The results obtained allowed to demonstrate that the SGs is a complementary tool for the treatment of children diagnosed with Attention Deficit Hyperactivity Disorder (ADHD).     Keywords: ATHYNOS, conceptual model, serious games design, attention deficit disorde

Quinstant Dark Energy Predictions for Structure Formation

We explore the predictions of a class of dark energy models, quinstant dark energy, concerning the structure formation in the Universe, both in the linear and non-linear regimes. Quinstant dark energy is considered to be formed by quintessence and a negative cosmological constant. We conclude that these models give good predictions for structure formation in the linear regime, but fail to do so in the non-linear one, for redshifts larger than one.Comment: 9 pages, 14 figures, "Accepted for publication in Astrophysics & Space Science

Effects of Gamma Ray Bursts in Earth Biosphere

We continue former work on the modeling of potential effects of Gamma Ray Bursts on Phanerozoic Earth. We focus on global biospheric effects of ozone depletion and show a first modeling of the spectral reduction of light by NO2 formed in the stratosphere. We also illustrate the current complexities involved in the prediction of how terrestrial ecosystems would respond to this kind of burst. We conclude that more biological field and laboratory data are needed to reach even moderate accuracy in this modelingComment: Accepted for publication in Astrophysics & Space Scienc

Ten systemic steps for sustainable energy savings in small and medium enterprises

Energy savings are a priority in the different industrial sectors including Small and Medium Enterprises (SMEs). They have a conceptual perception of energy savings by replacing their service and production technologies with more efficient one. However, this technological change requires large-scale investment. There is another approach that can be used to reduce energy costs that has less impact on company production costs and does not require investments in technology. This approach considers planning and control procedures, which are considered in the present study. This study proposes a new method consisting of 10 systematic steps to achieve energy savings in SMEs. This method initially evaluates when, how, and where the energy is used, then identifies opportunities to achieve sustainable energy savings. The method involves various activities including an assessment of energy efficiency based on final energy consumption, adjusting production plans with low energy consumption and costs, and monitoring the energy budget. Application of this methodology in SMEs can save energy around 5 − 20% over a period of 1 to 3 y with some very low payback periods of less than a year. Operational controls implementation in Significant Energy Uses (SEU) can save energy around 2 − 5% of the consumption, without requiring investment in technology

Identification of energy saving potential in steam boiler through an ISO 50001 standard

The energy performance of steam boilers, such as the efficiency and the evaporation ratio can decrease along time because of the poor combustion, heat transfer fouling, poor operation, and low maintenance rate. The energy indicators assessment allows to observe the abnormal operational deviations to implement corrective action, so it is necessary to find out the level of efficiency in real time to evaluate the thermal performance, which is an obligatory requirement to implement the energy management program in the industry. As a contribution in the area of energy efficiency in steam boilers, the results of an applied research are presented, where the behavior of steam production and gas consumption as input variables were considered to apply the methodology and obtain the energy saving results on a boiler from 125.000lb/h steam capacity. The consumption and energy production control charts, the base and goal line, and base 100 indicators were calculated to facilitate the energy monitoring of the steam boiler for a period six month. Letting the application of the methodology to recognize saving opportunities starting from the analysis of variables that impact the energy consumption affected by different ways energy consumption of the company. The study showed a linear base with the form EB = 0.0595x + 0.988, with a linear correlation equal to R2 = 0.973 and a goal line EG = 0.0586x + 1.3814, with a linear correlation of R² = 0.97, which means statistical validity in the data collection. Additionally, the base 100 index was calculated to identify satisfactory the peaks of energy efficiency, showing efficiency and inefficiency in the process. The study shows that data reflected below the efficiency rate (100) are considered peaks of energy inefficiency, which means energy saving opportunities for operational control, maintenance management, production planning, besides the typical ones due to technological changes

Magnon valley Hall effect in CrI3-based vdW heterostructures

Magnonic excitations in the two-dimensional (2D) van der Waals (vdW) ferromagnet CrI3 are studied. We find that bulk magnons exhibit a non-trivial topological band structure without the need for Dzyaloshinskii-Moriya (DM) interaction. This is shown in vdW heterostructures, consisting of single-layer CrI3 on top of different 2D materials as MoTe2, HfS2 and WSe2. We find numerically that the proposed substrates modify substantially the out-of-plane magnetic anisotropy on each sublattice of the CrI3 subsystem. The induced staggered anisotropy, combined with a proper band inversion, leads to the opening of a topological gap of the magnon spectrum. Since the gap is opened non-symmetrically at the K+ and K- points of the Brillouin zone, an imbalance in the magnon population between these two valleys can be created under a driving force. This phenomenon is in close analogy to the so-called valley Hall effect (VHE), and thus termed as magnon valley Hall effect (MVHE). In linear response to a temperature gradient we quantify this effect by the evaluation of the temperature-dependence of the magnon thermal Hall effect. These findings open a different avenue by adding the valley degrees of freedom besides the spin, in the study of magnons