606 research outputs found
CSO superpotentials
Motivated by their application to holographic RG flows and hairy black holes
in Einstein-scalar systems, we present a collection of superpotentials driving
the dynamics of and four-dimensional
supergravities. These theories arise as consistent truncations of the
electric/magnetic families of maximal supergravities,
with , discovered by Dall'Agata et al. The and
truncations describe and invariant sectors, respectively, and contain AdS
solutions preserving supersymmetry within the full
theories, as well as various gauge symmetries. Realisations in terms of
non-geometric type IIB as well as geometric massive type IIA backgrounds are
also discussed. The aim of this note is to provide easy to handle
superpotentials that facilitate the study of gravitational and gauge aspects of
the maximal supergravities avoiding the
technicalities required in their construction.Comment: 10 pages, 1 table. v2: Published versio
Optimal Power Allocation for A Massive MIMO Relay Aided Secure Communication
In this paper, we address the problem of optimal power allocation at the
relay in two-hop secure communications under practical conditions. To guarantee
secure communication during the long-distance transmission, the massive MIMO
(M-MIMO) relaying techniques are explored to significantly enhance wireless
security. The focus of this paper is on the analysis and design of optimal
power assignment for a decode-and-forward (DF) M-MIMO relay, so as to maximize
the secrecy outage capacity and minimize the interception probability,
respectively. Our study reveals the condition for a nonnegative the secrecy
outage capacity, obtains closed-form expressions for optimal power, and
presents the asymptotic characteristics of secrecy performance. Finally,
simulation results validate the effectiveness of the proposed schemes
Development of a fully coupled biogeochemical reactive transport model to simulate microbial oxidation of organic carbon and pyrite under nitrate‐reducing conditions
©2018. American Geophysical UnionIn regions with intensive agriculture nitrate is one of the most relevant contaminants in groundwater. Denitrification reduces elevated nitrate concentrations in many aquifers, yet the denitrification potential is limited by the concentration of available electron donors. The aim of this work was to study the denitrification potential and its limitation in natural sediments. A column experiment was conducted using sediments with elevated concentrations of organic carbon (total organic carbon 3,247 mg C/kg) and pyrite (chromium reducible sulfur 150 mg/kg). Groundwater with high nitrate concentration (100 mg/L) was injected. Measurements were taken over 160 days at five different depths including N‐ and S‐isotope analysis for selected samples. A reactive transport model was developed, which couples nitrate reduction with the oxidation of organic carbon (heterotrophic denitrification) and pyrite (autolithotrophic denitrification), and considers also transport and growth of denitrifying microbes. The denitrification pathway showed a temporal sequence from initially heterotrophic to autolithotrophic. However, maximum rates were lower for heterotrophic (11 mmol N/(L*a)) than for autolithotrophic denitrification (48 mmol N/(L*a)). The modeling showed that denitrifying microbes initially preferred highly reactive organic carbon as the electron donor for denitrification but were also able to utilize pyrite. The results show that after 160 days nitrate increased again to 50 mg/L. At this time only 0.5% of the total organic carbon and 46% of the available pyrite was oxidized. This indicates that denitrification rates strongly decrease before the electron donors are depleted either by a low reactivity (total organic carbon) or a diminishing reactive surface possibly due to the presence of coatings (pyrite)
Annotated directory of US Government information system projects of potential interest to NASA/SSPO
The purpose of this research activity was to develop a list for NASA of major U.S. government information systems contacts who are able to cooperate with NASA on technical interchange. The list contains the names of appropriate managers involved in major information system projects, U.S. government office officials, and their hierarchy up to the highest officials whose major responsibilities include government information systems development
The Bell Has Rung: Answering the Door for Student-Athlete Concussion Issues in the National Collegiate Athletic Association
This Note examines the NCAA\u27s unwillingness to enforce the requirement that all NCAA institutions must implement a concussion management plan; the NCAA\u27s refusal to apply its appropriate enforcement mechanism when member institutions violate their concussion management plans, which are instituted in order to protect student-athletes from concussions; how both of these failures result in more concussions and a higher probability of debilitating long-term effects; and solutions to remedy this grave injustice. Part II describes what a concussion is, the long-term effects of concussions, the NCAA\u27s management of concussions, and lawsuits challenging the NCAA in relation to concussions. Part III analyzes the inefficiencies of the NCAA in its management of concussions, the previous and current lawsuits\u27 failure to stimulate change within the NCAA, and the proposed solutions that will help create a safe environment for student-athletes
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