Seeking for reliable double-hybrid density functionals without fitting parameters: The PBE0-2 functional

Without the use of any empirical fitting to experimental or high-level ab initio data, we present a double-hybrid density functional approximation for the exchange-correlation energy, combining the exact Hartree-Fock exchange and second-order Moller-Plesset (MP2) correlation with the Perdew-Burke-Ernzerhof (PBE) functional. This functional, denoted as PBE0-2, is shown to be accurate for a wide range of applications, when compared with other functionals and the ab initio MP2 method. The qualitative failures of conventional density functional approximations, such as self-interaction error and noncovalent interaction error, are significantly reduced by PBE0-2.Comment: accepted for publication in Chem. Phys. Lett., 5 pages, 5 figures, 1 table, supplementary material not include

Social Bots: Human-Like by Means of Human Control?

Social bots are currently regarded an influential but also somewhat mysterious factor in public discourse and opinion making. They are considered to be capable of massively distributing propaganda in social and online media and their application is even suspected to be partly responsible for recent election results. Astonishingly, the term `Social Bot' is not well defined and different scientific disciplines use divergent definitions. This work starts with a balanced definition attempt, before providing an overview of how social bots actually work (taking the example of Twitter) and what their current technical limitations are. Despite recent research progress in Deep Learning and Big Data, there are many activities bots cannot handle well. We then discuss how bot capabilities can be extended and controlled by integrating humans into the process and reason that this is currently the most promising way to go in order to realize effective interactions with other humans.Comment: 36 pages, 13 figure

Inflation uncertainty revisited: A proposal for robust measurement

Any measure of unobserved inflation uncertainty relies on specific assumptions which are most likely not fulfilled completely. This calls into question whether an individual measure delivers a reliable signal. To reduce idiosyncratic measurement error, we propose using common information contained in different measures derived from survey data, a variety of forecast models, and volatility models. We show that all measures are driven by a common component which constitutes an indicator for inflation uncertainty. Moreover, the idiosyncratic component of survey disagreement contains systematic measurement error during economic downturns. Finally, we study the Friedman-Ball hypothesis. Using the indicator, it turns out that higher inflation is followed by higher uncertainty. By contrast, we obtain contradictory results for the individual measures. We also document that, after an inflationary shock, uncertainty decreases in the first two months which is traceable to the energy component in CPI inflation.Inflation uncertainty, inflation, survey data, stochastic volatility, GARCH, principal component analysis

Physical Fitness in College Students

Obesity is a major problem facing the United States today. Physical inactivity can lead to obesity resulting in a variety of health problems, including premature death. Therefore the objective of the study was to identify physical fitness differences between gender, age, and physical activity level in college students. A fitness assessment test consisting of cardiorespiratory endurance, flexibility, muscular strength, and muscular endurance was performed in seventy-nine (43 male, 36 female) subjects ranging in age from 18 to 22 years old. Results indicate greater physical fitness in upper classmen when compared to lower classmen. Also, our data indicate that students that exercise 150 or more minutes per week are more physically fit when compared to students that exercise less than 150 minutes per week. In conclusion, physical activity interventions should be offered to college students and especially underclassmen to decrease the incidence of inactivity and obesity

On the Applicability of OGSA-BES to D-Grid Community Scheduling Systems

In this paper, we exemplary review the requirements of two Grid communities in the D-Grid project and identify similarities in the addressed scientific applications respectively. To facilitate Grid scheduler interoperability on the underlying heterogeneous middleware systems we extend the standardized OGSA-BES interface and propose a basic concept for the exploitation of collaboration potential in the D-Grid community in general. Compared with existing meta-scheduling architectures there will be no need for a central scheduler instance

On Single-Objective Sub-Graph-Based Mutation for Solving the Bi-Objective Minimum Spanning Tree Problem

We contribute to the efficient approximation of the Pareto-set for the classical $\mathcal{NP}$-hard multi-objective minimum spanning tree problem (moMST) adopting evolutionary computation. More precisely, by building upon preliminary work, we analyse the neighborhood structure of Pareto-optimal spanning trees and design several highly biased sub-graph-based mutation operators founded on the gained insights. In a nutshell, these operators replace (un)connected sub-trees of candidate solutions with locally optimal sub-trees. The latter (biased) step is realized by applying Kruskal's single-objective MST algorithm to a weighted sum scalarization of a sub-graph. We prove runtime complexity results for the introduced operators and investigate the desirable Pareto-beneficial property. This property states that mutants cannot be dominated by their parent. Moreover, we perform an extensive experimental benchmark study to showcase the operator's practical suitability. Our results confirm that the sub-graph based operators beat baseline algorithms from the literature even with severely restricted computational budget in terms of function evaluations on four different classes of complete graphs with different shapes of the Pareto-front

Catalytic difunctionalization of unactivated alkenes with unreactive hexamethyldisilane through regeneration of silylium ions

A metal‐free, intermolecular syn‐addition of hexamethyldisilane across simple alkenes is reported. The catalytic cycle is initiated and propagated by the transfer of a methyl group from the disilane to a silylium‐ion‐like intermediate, corresponding to the (re)generation of the silylium‐ion catalyst. The key feature of the reaction sequence is the cleavage of the Si−Si bond in a 1,3‐silyl shift from silicon to carbon. A central intermediate of the catalysis was structurally characterized by X‐ray diffraction, and the computed reaction mechanism is fully consistent with the experimental findings.TU Berlin, Open-Access-Mittel - 201