Electric Power Grids Under High-Absenteeism Pandemics: History, Context, Response, and Opportunities.

Widespread outbreaks of infectious disease, i.e., the so-called pandemics that may travel quickly and silently beyond boundaries, can significantly upsurge the morbidity and mortality over large-scale geographical areas. They commonly result in enormous economic losses, political disruptions, social unrest, and quickly evolve to a national security concern. Societies have been shaped by pandemics and outbreaks for as long as we have had societies. While differing in nature and in realizations, they all place the normal life of modern societies on hold. Common interruptions include job loss, infrastructure failure, and political ramifications. The electric power systems, upon which our modern society relies, is driving a myriad of interdependent services, such as water systems, communication networks, transportation systems, health services, etc. With the sudden shifts in electric power generation and demand portfolios and the need to sustain quality electricity supply to end customers (particularly mission-critical services) during pandemics, safeguarding the nation's electric power grid in the face of such rapidly evolving outbreaks is among the top priorities. This paper explores the various mechanisms through which the electric power grids around the globe are influenced by pandemics in general and COVID-19 in particular, shares the lessons learned and best practices taken in different sectors of the electric industry in responding to the dramatic shifts enforced by such threats, and provides visions for a pandemic-resilient electric grid of the future. [Abstract copyright: This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/.

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

An Exact Solution Approach for Portfolio Optimization Problems under Stochastic and Integer Constraints

In this paper, we study extensions of the classical Markowitz’ mean-variance portfolio optimization model. First, we consider that the expected asset returns are stochastic by introducing aprobabilistic constraint imposing that the expected return of the constructed portfolio must exceeda prescribed return level with a high confidence level. We study the deterministic equivalents ofthese models. In particular, we define under which types of probability distributions the deterministic equivalents are second-order cone programs, and give exact or approximate closed-form formulations. Second, we account for real-world trading constraints, such as the need to diversify theinvestments in a number of industrial sectors, the non-profitability of holding small positions and theconstraint of buying stocks by lots, modeled with integer variables. To solve the resulting problems,we propose an exact solution approach in which the uncertainty in the estimate of the expected returns and the integer trading restrictions are simultaneously considered. The proposed algorithmicapproach rests on a non-linear branch-and-bound algorithm which features two new branching rules.The first one is a static rule, called idiosyncratic risk branching, while the second one is dynamic andcalled portfolio risk branching. The proposed branching rules are implemented and tested using theopen-source framework of the solver Bonmin. The comparison of the computational results obtainedwith standard MINLP solvers and with the proposed approach shows the effectiveness of this latterwhich permits to solve to optimality problems with up to 200 assets in a reasonable amount of time

Effects of dietary restraint vs exercise during weight maintenance in obese men

Effects of dietary restraint vs exercise during weight maintenance in obese men. Lejeune MP, Van Aggel-Leijssen DP, Van Baak MA, Westerterp-Plantenga MS. Department of Human Biology, University of Maastricht, Maastricht, The Netherlands. [email protected] OBJECTIVE: To investigate the effect of dietary restraint with or without exercise during weight maintenance after energy restriction. SUBJECTS AND METHODS: In total, 40 obese male subjects (mean BMI 32.3 kg/m(2); mean age 39 y) were recruited and randomly divided into a diet (D; n=20) and a diet plus exercise (DE; n=20) group. Both groups participated in an energy restriction programme (ER), which was followed by a weight maintenance phase (WM). Subjects in the DE also participated in an exercise programme. Body mass (BM) and the scores on the three factor eating questionnaire (TFEQ) were measured before and after the ER and after WM. RESULTS: No significant differences between both groups were found. All data taken together showed that BM loss during ER was explained by initial BM (r(2)=0.3, P<0.0005) and inversely by initial cognitive restraint (F1) (r(2)=0.4, P<0.0005) in a stepwise regression. BM regain during WM was explained by BM loss (r(2)=0.5, P<0.001) and by increase in F1 during ER (r(2)=0.6, P<0.001), while the exercise intervention did not contribute further to the explained variation. Subjects with a relatively high diet frequency prior to the study had relatively significant higher initial F1 scores (P<0.05). During ER, increase in F1 was associated with decrease in general hunger (F3). CONCLUSION: Successful BM loss was associated with higher initial BM and lower initial F1. Successful WM was explained by BM loss and increase in F1 during ER, irrespective of possible exercise training effects. Successful WM was reduced when F1 scores reach their limit, due to diet-frequenc

One-step chemically vapor deposited hybrid 1T-MoS2/2H-MoS2 heterostructures towards methylene blue photodegradation

International audienceThe photocatalytic degradation of methylene blue is a straightforward and cost-effective solution for water decontamination. Although many materials have been reported so far for this purpose, the proposed solutions inflicted high fabrication costs and low efficiencies. Here, we report on the synthesis of tetragonal (1T) and hexagonal (2H) mixed molybdenum disulfide (MoS2) heterostructures for an improved photocatalytic degradation efficiency by means of a single-step chemical vapor deposition (CVD) technique. We demonstrate that the 1T-MoS2/2H-MoS2 heterostructures exhibited a narrow bandgap ∼ 1.7 eV, and a very low reflectance (<5%) under visible-light, owing to their particular vertical micro-flower-like structure. We exfoliated the CVD-synthesised 1T-MoS2/2H-MoS2 films to assess their photodegradation properties towards the standard methylene blue dye. Our results showed that the photo-degradation rate-constant of the 1T-MoS2/2H-MoS2 heterostructures is much greater under UV excitation (i.e., 12.5 × 10-3 min-1) than under visible light illumination (i.e., 9.2 × 10-3 min-1). Our findings suggested that the intermixing of the conductive 1T-MoS2 with the semi-conducting 2H-MoS2 phases favors the photogeneration of electron-hole pairs. More importantly, it promotes a higher efficient charge transfer, which accelerates the methylene blue photodegradation process