55 research outputs found
War Fighting in Cyberspace: Evolving Force Presentation and Command and Control
The Department of Defense (DOD) is endeavoring to define war fighting in the global cyberspace domain. Creation of US Cyber Command (USCYBERCOM), a subunified functional combatant command (FCC) under US Strategic Command (USSTRATCOM), is a huge step in integrating and coordinating the defense, protection, and operation of DOD networks; however, this step does not mean that USCYBERCOM will perform or manage all cyberspace functions. In fact the vast majority of cyberspace functions conducted by the services and combatant commands (COCOM), although vital for maintaining access to the domain in support of their operations, are not of an active war-fighting nature. We apply the concepts of war fighting, offense, and active defense to the domain of cyber space and propose several recommendations to aid USCYBERCOM as it works with the services and geographic combatant commands (GCC) to fight in cyberspace
Functional Movement Screentm Scores in Collegiate Track and Field Athletes in Relation to Injury Risk and Performance
Purpose: The purpose of this study was to examine the relationship between Functional Movement Screentm (FMS) scores, injury rate, and performance in collegiate track and field athletes. Methods: Forty seven male (n=17) and female (n=30) competitive track and field athletes at an NCAA Division I university volunteered for this study. As part of their regular team assessment, the athletes were evaluated on three separate occasions using the FMS tool: in August, one week prior to the start of university organized practice for the fall (T1); in December, one week prior to the end of the fall academic semester (T2); and in March, the week following the conclusion of the indoor competition season (T3). The FMS consists of the performance of seven fundamental movement patterns that are evaluated and scored by a trained professional. For each time point, athletes were divided into two categories based on total FMS score (≤14 and ≥15). Throughout the competitive season, injuries were tracked and categorized as either mild (no loss of practice or competition time) or moderate/severe (loss of practice or competition time). As part of an ongoing injury prevention program, athletes performed generalized corrective exercises for 15 min 2-3 times per week. The performance in the last event of the season (conference meet) was also recorded. Results: Average FMS scores significantly (p\u3c0.05) decreased across the three time points (Mean ± SD, T1: 15.5 ± 2.2, T2: 14.9 ± 1.8, T3: 14.7 ± 1.6) despite that generalized corrective exercises were performed. Analyses of results found no association between FMS scores and likelihood to sustain a moderate/severe injury. Athletes with a score of ≤14 on the FMS at T1 were 3.1 times more likely not to place in the top 8 at the conference meet. 53% of the athletes who had a score of ≥15 at T1 placed in the top 8 at the meet while only 27% of athletes with a score of ≤14 at T1 placed in the top 8 at the meet. Conclusion: FMS scores ≤14 indicate reduced performance ability but not increased likelihood of injury in track and field athletes
Broadband optical properties of large-area monolayer CVD molybdenum disulfide
Recently emerging large-area single-layer MoS[subscript 2] grown by chemical vapor deposition has triggered great interest due to its exciting potential for applications in advanced electronic and optoelectronic devices. Unlike gapless graphene, MoS[subscript 2] has an intrinsic band gap in the visible which crosses over from an indirect to a direct gap when reduced to a single atomic layer. In this paper, we report a comprehensive study of fundamental optical properties of MoS[subscript 2] revealed by optical spectroscopy of Raman, photoluminescence, and vacuum ultraviolet spectroscopic ellipsometry. A band gap of 1.42 eV is determined by the absorption threshold of bulk MoS[subscript 2] that shifts to 1.83 eV in monolayer MoS[subscript 2]. We extracted the high precision dielectric function up to 9.0 eV, which leads to the identification of many unique interband transitions at high symmetry points in the MoS[subscript 2] momentum space. The positions of the so-called A and B excitons in single layers are found to shift upwards in energy compared with those of the bulk form and have smaller separation because of the decreased interactions between the layers. A very strong optical critical point predicted to correspond to a quasiparticle gap is observed at 2.86 eV, which is attributed to optical transitions along the parallel bands between the M and Γ points in the reduced Brillouin zone. The absence of the bulk MoS[subscript 2] spin-orbit interaction peak at ~3.0 eV in monolayer MoS[subscript 2] is, as predicted, the consequence of the coalescence of nearby excitons. A higher energy optical transition at 3.98 eV, commonly occurring in bulk semiconductors, is associated with a combination of several critical points. Additionally, extending into the vacuum ultraviolet energy spectrum are a series of newly observed oscillations representing optical transitions from valence bands to higher conduction bands of the monolayer MoS[subscript 2] complex band structure. These optical transitions herein reported enhance our understanding of monolayer MoS[subscript 2] as well as of two-dimensional systems in general and thus provide informative guidelines for MoS[subscript 2] optical device designs and theoretical considerations.China. Ministry of Science and Technology (Grant 2011CB921904)China. Ministry of Education (Grant 113003A)National Natural Science Foundation (China) (Grant 61321001)Municipal Science & Technology Commission. Beijing Natural Science Foundation (grant Z141100003814006)National Science Foundation (U.S.) (STC Center for Integrated Quantum Materials Grant DMR-1231319
Phase Stability of Hexagonal/cubic Boron Nitride Nanocomposites
Boron nitride (BN) is an exceptional material and among its polymorphs,
two-dimensional (2D) hexagonal and three-dimensional (3D) cubic BN (h-BN and
c-BN) phases are most common. The phase stability regimes of these BN phases
are still under debate and phase transformations of h-BN/c-BN remain a topic of
interest. Here, we investigate the phase stability of 2D/3D h-BN/c-BN
nanocomposites and show that the co-existence of two phases can lead to strong
non-linear optical properties and low thermal conductivity at room temperature.
Furthermore, spark-plasma sintering of the nanocomposite shows complete phase
transformation to 2D h-BN with improved crystalline quality, where 3D c-BN
grain sizes governs the nucleation and growth kinetics. Our demonstration might
be insightful in phase engineering of BN polymorphs based nanocomposites with
desirable properties for optoelectronics and thermal energy management
applications.Comment: 29 pages, 5 figure
Desorption kinetics of hydrophobic organic chemicals from sediment to water: A review of data and models
Resuspension of contaminated sediment can lead to the release of toxic compounds to surface waters where they are more bioavailable and mobile. Because the timeframe of particle resettling during such events is shorter than that needed to reach equilibrium, a kinetic approach is required for modeling the release process. Due to the current inability of common theoretical approaches to predict site-specific release rates, empirical algorithms incorporating the phenomenological assumption of biphasic, or fast and slow, release dominate the descriptions of nonpolar organic chemical release in the literature. Two first-order rate constants and one fraction are sufficient to characterize practically all of the data sets studied. These rate constants were compared to theoretical model parameters and functionalities, including chemical properties of the contaminants and physical properties of the sorbents, to determine if the trends incorporated into the hindered diffusion model are consistent with the parameters used in curve fitting. The results did not correspond to the parameter dependence of the hindered diffusion model. No trend in desorption rate constants, for either fast or slow release, was observed to be dependent on KOC or aqueous solubility for six and seven orders of magnitude, respectively. The same was observed for aqueous diffusivity and sediment fraction organic carbon. The distribution of kinetic rate constant values was approximately log-normal, ranging from 0.1 to 50 d-1 for the fast release (average ∼5 d-1) and 0.0001 to 0.1 d-1 for the slow release (average ∼0.03 d-1). The implications of these findings with regard to laboratory studies, theoretical desorption process mechanisms, and water quality modeling needs are presented and discussed. © 2007 SETAC
A multi-method comparison of Atchafalaya Basin surface water organic matter samples
Surface water organic matter (OM) was isolated from two distinct sites within the Atchafalaya Basin using a combination of XAD-8 and XAD-4 non-ionic macroporous resins and characterized by a suite of analytical methods, including elemental analysis, 13C cross polarization magic angle spinning nuclear magnetic resonance, attenuated total reflectance Fourier transform infrared, luminescence spectroscopy including parallel factor analysis, and ultraviolet-visible spectroscopy. The major findings of the study are (i) despite the large differences in hydrology, optical properties, iron content, dissolved oxygen, and degree of human exploitation, the spectral and elemental signatures of the hydrophobic acids and transphilic acids fractions of the isolated OM for the different sites were remarkably similar; (ii) the luminescence characteristics of the four studied fractions provided information on the relative contributions from terrestrial and microbial input sources, as well as the degree of humification; and (iii) a detailed analysis of the total luminescence data led to a new dual excitation model based on quinone exciplexes for long wavelength emissions. Copyright © 2009 by the American Society of Agronomy, Corp Science Society of America, and soil Science of America. All right reserved
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