Showing papers by "Wright-Patterson Air Force Base published in 2014"
TL;DR: A simple method to fabricate wrinkled graphene with high stretchability and transparency was reported, which showed a high transparency and can be stretched up to 40% strain without obvious performance change over hundreds of stretching cycles.
Abstract: Transparent and/or stretchable energy storage devices have attracted intense attention due to their unique optical and/or mechanical properties as well as their intrinsic energy storage function However, it remains a great challenge to integrate transparent and stretchable properties into an energy storage device because the currently developed electrodes are either transparent or stretchable, but not both Herein, we report a simple method to fabricate wrinkled graphene with high stretchability and transparency The resultant wrinkled graphene sheets were used as both current collector and electrode materials to develop transparent and stretchable supercapacitors, which showed a high transparency (57% at 550 nm) and can be stretched up to 40% strain without obvious performance change over hundreds of stretching cycles
390 citations
TL;DR: In this article, a review of advances in the design and exploration of hard coatings with high temperature adaptive behavior in tribological contacts is reviewed, where advances with ab initio modeling of intrinsically layered solids point to new compositions for thermally stable, easy to shear ceramic coatings, load and temperature-adaptive surfaces with arrays of compliant carbon and boron nitride nanotubes as well as low friction two-dimensional structures.
Abstract: Progress in the design and exploration of hard coatings with high temperature adaptive behavior in tribological contacts is reviewed. When coupled with most recent surface engineering strategies for high temperature contact thermal management, this progress opens a huge opportunity for adaptive coating applications on machine parts, where oils and coolants are commonly used. The adaptive mechanisms discussed here include metal diffusion and formation of lubricant phases at worn surfaces, thermally- and mechanically-induced phase transitions in hexagonal solids, contact surface tribo-chemical evolutions to form phases with low melting point, formation of easy to shear solid oxides, and others. All of these adaptive mechanisms are combined in nanocomposite coatings with synergistic self-adaptation of surface structure and chemistry to lubricate from ambient temperatures to 1000 °C and provide surface chemical and structural reversibility during temperature cycling to maintain low friction coefficients. The review also highlights emerging surface adaptive concepts, where advances with ab initio modeling of intrinsically layered solids point to new compositions for thermally stable, easy to shear ceramic coatings, load- and temperature-adaptive surfaces with arrays of compliant carbon and boron nitride nanotubes as well as low friction two-dimensional structures. Approaches for self-regulation of coating thermal conductivity, heat flow, and thermal spike mitigations are discussed in the context of surface structure evolution and phase transitions. Future progress is linked to the development of in situ exploration techniques, capable of identifying adaptive surface chemistry and structural evolutions in broad temperature regimes. When combined with predictive modeling, such approaches drastically accelerate adaptive coating developments. The review identifies opportunities, strategies, and challenges for designs and applications of hard coatings with high temperature adaptive lubrication and contact thermal management.
185 citations
TL;DR: In this article, the authors summarize recent progress in this emerging research field and present some rational concepts for the design and development of the GO-based hole- or electron-extraction layers for high-performance PSCs, along with challenges and perspectives.
Abstract: Owing to their solution processability, unique two-dimensional structure, and functionalization-induced tunable electronic structures, graphene oxide (GO) and its derivatives have been used as a new class of efficient hole- and electron-extraction materials in polymer solar cells (PSCs). Highly efficient and stable PSCs have been fabricated with GO and its derivatives as hole- and/or electron-extraction layers. In this review, we summarize recent progress in this emerging research field. We also present some rational concepts for the design and development of the GO-based hole- or electron-extraction layers for high-performance PSCs, along with challenges and perspectives.
176 citations
TL;DR: Suggestions about ethical challenges in caring for the critically ill or injured during pandemics or disasters are provided, focusing on five essential domains: triage and allocation, ethical concerns of patients and families, ethical responsibilities to providers, conduct of research, and international concerns.
147 citations
TL;DR: In this article, a state-space formulation for the aerodynamics of flapping flight is presented, where the Duhamel's principle, applied in linear unsteady flows, is extended to non-conventional lift curves to capture the LEV contribution.
142 citations
TL;DR: In this article, the variability and control of peptide adsorption on silica nanoparticle surfaces are explained as a function of pH, particle diameter, and peptide electrostatic charge using molecular dynamics simulations with the CHARMM-INTERFACE force field.
Abstract: Silica nanostructures are biologically available and find wide applications for drug delivery, catalysts, separation processes, and composites. However, specific adsorption of biomolecules on silica surfaces and control in biomimetic synthesis remain largely unpredictable. In this contribution, the variability and control of peptide adsorption on silica nanoparticle surfaces are explained as a function of pH, particle diameter, and peptide electrostatic charge using molecular dynamics simulations with the CHARMM-INTERFACE force field. Adsorption free energies and specific binding residues are analyzed in molecular detail, providing experimentally elusive, atomic-level information on the complex dynamics of aqueous electric double layers in contact with biological molecules. Tunable contributions to adsorption are described in the context of specific silica surface chemistry, including ion pairing, hydrogen bonds, hydrophobic interactions, and conformation effects. Remarkable agreement is found for compute...
119 citations
TL;DR: Glass in not a panacea as some supporters claim, but it does point the way to design interventions that effect reduced load in multitasking, and discussions of these identified benefits are framed within the potential of new in-vehicle systems that bring both novel forms of distraction and tools for mitigation into the driver’s seat.
Abstract: OBJECTIVE: We assess the driving distraction potential of texting with Google Glass (Glass), a mobile wearable platform capable of receiving and sending short-message-service and other messaging formats. BACKGROUND: A known roadway danger, texting while driving has been targeted by legislation and widely banned. Supporters of Glass claim the head-mounted wearable computer is designed to deliver information without concurrent distraction. Existing literature supports the supposition that design decisions incorporated in Glass might facilitate messaging for drivers. METHOD: We asked drivers in a simulator to drive and use either Glass or a smartphone-based messaging interface, then interrupted them with an emergency brake event. Both the response event and subsequent recovery were analyzed. RESULTS: Glass-delivered messages served to moderate but did not eliminate distracting cognitive demands. A potential passive cost to drivers merely wearing Glass was also observed. Messaging using either device impaired driving as compared to driving without multitasking. CONCLUSION: Glass in not a panacea as some supporters claim, but it does point the way to design interventions that effect reduced load in multitasking. APPLICATION: Discussions of these identified benefits are framed within the potential of new in-vehicle systems that bring both novel forms of distraction and tools for mitigation into the driver's seat. Keywords: Driver distraction; Keywords: Driver distraction; Language: en
118 citations
TL;DR: Increased community level air pollution is associated with reduced leisure-time physical activity particularly among the normal weight, providing additional evidence that air pollution should be investigated as an environmental determinant of inactivity.
Abstract: Background
Physical inactivity, ambient air pollution and obesity are modifiable risk factors for non-communicable diseases, with the first accounting for 10% of premature deaths worldwide. Although community level interventions may target each simultaneously, research on the relationship between these risk factors is lacking.
113 citations
TL;DR: This work addresses the problem of target detection in passive multiple-input multiple-output (MIMO) radar networks without utilization of direct-path reference signals, and a generalized likelihood ratio test is derived.
Abstract: This work addresses the problem of target detection in passive multiple-input multiple-output (MIMO) radar networks without utilization of direct-path reference signals. A generalized likelihood ratio test for this problem is derived, and the distribution of the test statistic is identified under both hypotheses. Equivalence is established between passive MIMO radar networks without references and passive source localization networks. Numerical examples demonstrate important characteristics of the detector, namely, the asymmetric contributions to detection performance from transmitters and receivers, and non-coherent integration gain as a function of signal length. The ambiguity properties of this detector are also investigated, and it is shown that the salient ambiguities can be explained in terms of the time-difference of arrival, frequency-difference of arrival, and angle-of-arrival of the target signals.
103 citations
TL;DR: With controllable bandgap, good solubility and film forming property, graphene oxide nanoribbons serve as a new class of excellent hole extraction materials for efficient and stable polymer solar cells outperforming their counterparts based on conventional hole extraction material, including PEDOT:PSS.
Abstract: : Owing to its unique 2-dimensional carbon nanostructure with unique electrical, optical, thermal, and mechanical properties, graphene has attracted a great deal of interest. [ 1,2 ] While the pristine graphene is a zero-bandgap material with metal-like conductivity, graphene nanoribbon (GNR) is semiconducting with an opened bandgap induced by the quasi-one-dimensional confinement of charge carriers. [ 3 8 ] However, graphene and its nanoribbons without functionalization are insoluble and infusible. The poor processability has precluded the pristine graphene materials, including GNR, for various potential applications. This limitation has been circumvented by oxidizing graphene with acids (e.g., H 2 SO 4 /KMnO 4 ) to produce graphene oxide (GO) with oxygen-containing groups (e.g., COOH, OH) around and on the carbon basal plane, [ 2 ] leading to low-cost mass production of soluble graphene derivatives for potential applications. By introducing the oxygen-rich groups around a graphene nanoribbon, the resultant graphene oxide nanoribbon (GOR) should show a synergistic effect to have the bandgap of GNR and solution processability of GO. Therefore, GORs could be a new class of solution-processable semiconducting materials attractive for optoelectronic applications. In this study, we demonstrate, for the first time, that GOR can be used as an excellent hole-extraction material to significantly improve the performance of polymer solar cells (PSCs). PSCs using polymeric materials to convert solar energy to electricity is an emerging photovoltaic technology to compete with the widely used photovoltaic technologies based on inorganic materials. [ 9 ] In spite of many advantages (e.g., low cost, flexibility, and semi-transparency), the efficiency and lifetime of PSCs are still largely limited by, among other factors, the poor charge extraction from the active layer to electrodes.
100 citations
TL;DR: It is demonstrated that metal oxide materials decorated with noble metal nanoparticles advance visible light photocatalytic activity toward new reactions not typically driven by light, including H2 generation through H2O reduction at the Cu2O surface.
Abstract: Transitioning energy-intensive and environmentally intensive processes toward sustainable conditions is necessary in light of the current global condition. To this end, photocatalytic processes represent new approaches for H2 generation; however, their application toward tandem catalytic reactivity remains challenging. Here, we demonstrate that metal oxide materials decorated with noble metal nanoparticles advance visible light photocatalytic activity toward new reactions not typically driven by light. For this, Pd nanoparticles were deposited onto Cu2O cubes to generate a composite structure. Once characterized, their hydrodehalogenation activity was studied via the reductive dechlorination of polychlorinated biphenyls. To this end, tandem catalytic reactivity was observed with H2 generation via H2O reduction at the Cu2O surface, followed by dehalogenation at the Pd using the in situ generated H2. Such results present methods to achieve sustainable catalytic technologies by advancing photocatalytic appro...
TL;DR: In this article, the authors report on the preparation of color-tunable mirrors based on electrically regulated bandwidth broadening of the circularly polarized reflection of polymer-stabilized cholesteric liquid crystals (PSCLCs).
Abstract: We report on the preparation of color-tunable mirrors based on electrically regulated bandwidth broadening of the circularly polarized reflection of polymer-stabilized cholesteric liquid crystals (PSCLCs). A number of improvements relating to the practical implementation of these materials are detailed including color and bandwidth stability, baseline optical properties, and response times. Experimentation reported herein focuses on the contribution of structural chirality, viscoelastic properties of the polymer network architecture, and electro-optic drive schemes. Through the examination of samples prepared in different conditions and compositions, we further elucidate the dominant role of structural chirality as well as the impact of cross-linking of the polymer stabilizing network on the threshold voltage and relative change in bandwidth per voltage (Δ(Δλ)/V). Furthermore, the appearance of nonideal optical properties (scatter and haze) in some samples is shown to be correlated with the polymer/LC com...
TL;DR: An overview of the model-based measures of SFT is provided, together with a tutorial on designing a DFP experiment to take advantage of all SFT measures in a single experiment and a new package for performing SFT analyses using R for statistical computing is introduced.
Abstract: Systems factorial technology (SFT) comprises a set of powerful nonparametric models and measures, together with a theory-driven experiment methodology termed the double factorial paradigm (DFP), for assessing the cognitive information-processing mechanisms supporting the processing of multiple sources of information in a given task (Townsend and Nozawa, Journal of Mathematical Psychology 39:321–360, 1995). We provide an overview of the model-based measures of SFT, together with a tutorial on designing a DFP experiment to take advantage of all SFT measures in a single experiment. Illustrative examples are given to highlight the breadth of applicability of these techniques across psychology. We further introduce and demonstrate a new package for performing SFT analyses using R for statistical computing.
TL;DR: Artificial hair sensors consisting of a piezoresistive carbon-nanotube-coated glass fiber embedded in a microcapillary that resemble a hair plug that may be integrated in a wide range of host materials are assembled and characterized.
Abstract: Artificial hair sensors consisting of a piezoresistive carbon-nanotube-coated glass fiber embedded in a microcapillary are assembled and characterized. Individual sensors resemble a hair plug that may be integrated in a wide range of host materials. The sensors demonstrate an air-flow detection threshold of less than 1 m/s with a piezoresistive sensitivity of 1.3% per m/s air-flow change.
TL;DR: Overall, these findings on low dielectric contrast PNCs clearly point to the performance benefits of functionalizing the nanoparticle surface with high-molecular-weight polymers for polymer nanostructured dielectrics.
Abstract: Demands to increase the stored energy density of electrostatic capacitors have spurred the development of materials with enhanced dielectric breakdown, improved permittivity, and reduced dielectric loss. Polymer nanocomposites (PNCs), consisting of a blend of amorphous polymer and dielectric nanofillers, have been studied intensely to satisfy these goals; however, nanoparticle aggregates, field localization due to dielectric mismatch between particle and matrix, and the poorly understood role of interface compatibilization have challenged progress. To expand the understanding of the inter-relation between these factors and, thus, enable rational optimization of low and high contrast PNC dielectrics, we compare the dielectric performance of matrix-free hairy nanoparticle assemblies (aHNPs) to blended PNCs in the regime of low dielectric contrast to establish how morphology and interface impact energy storage and breakdown across different polymer matrices (polystyrene, PS, and poly(methyl methacrylate), PM...
TL;DR: In this paper, the authors present a methodology and tool developed for multi-tier SC risk modeling and analysis using a Bayesian theory-based approach that is capable of analyzing the conditional relationships between events.
Abstract: Purpose
– Globally expanding supply chains (SCs) have grown in complexity increasing the nature and magnitude of risks companies are exposed to. Effective methods to identify, model and analyze these risks are needed. Risk events often influence each other and rarely act independently. The SC risk management practices currently used are mostly qualitative in nature and are unable to fully capture this interdependent influence of risks. The purpose of this paper is to present a methodology and tool developed for multi-tier SC risk modeling and analysis.
Design/methodology/approach
– SC risk taxonomy is developed to identify and document all potential risks in SCs and a risk network map that captures the interdependencies between risks is presented. A Bayesian Theory-based approach, that is capable of analyzing the conditional relationships between events, is used to develop the methodology to assess the influence of risks on SC performance
Findings
– Application of the methodology to an industry case study for validation reveals the usefulness of the Bayesian Theory-based approach and the tool developed. Back propagation to identify root causes and sensitivity of risk events in multi-tier SCs is discussed.
Practical implications
– SC risk management has grown in significance over the past decade. However, the methods used to model and analyze these risks by practitioners is still limited to basic qualitative approaches that cannot account for the interdependent effect of risk events. The method presented in this paper and the tool developed demonstrates the potential of using Bayesian Belief Networks to comprehensively model and study the effects or SC risks. The taxonomy presented will also be very useful for managers as a reference guide to begin risk identification.
Originality/value
– The taxonomy developed presents a comprehensive compilation of SC risks at organizational, industry, and external levels. A generic, customizable software tool developed to apply the Bayesian approach permits capturing risks and the influence of their interdependence to quantitatively model and analyze SC risks, which is lacking.
TL;DR: This work shows that extending the selection with higher stringency conditions leads to lower amounts eluted by the target but higher copy numbers of a sequence with enhanced binding, and serves as proof-of-principle work toward development of point of care diagnostics for medical, combat, or bioterrorism targets.
Abstract: The first-known aptamer for the stress biomarker cortisol was selected using a tunable stringency magnetic bead selection strategy. The capture DNA probe immobilized on the beads was systematically lengthened to increase the number of bases bound to the complementary pool primer regions following selection enrichment. This resulted in a single sequence (15–1) dominating the final round 15 pool, where the same sequence was the second-highest copy number candidate in the enriched pool with the shorter capture DNA probe (round 13). A thorough analysis of the next-generation sequencing results showed that a high copy number may only correlate with enhanced affinity under certain stringency and enrichment conditions, in contrast with prior published reports. Aptamer 15–1 demonstrated enhanced binding to cortisol (K
d = 6.9 ± 2.8 μM by equilibrium dialysis; 16.1 ± 0.6 μM by microscale thermophoresis) when compared with the top sequence from round 13 and the negative control progesterone. Whereas most aptamer selections terminate at the selection round demonstrating the highest enrichment, this work shows that extending the selection with higher stringency conditions leads to lower amounts eluted by the target but higher copy numbers of a sequence with enhanced binding. The structure-switching aptamer was applied to a gold nanoparticle assay in buffer and was shown to discriminate between cortisol and two other stress biomarkers, norepinephrine and epinephrine, and a structurally analogous biomarker of liver dysfunction, cholic acid. We believe this approach enhances aptamer selection and serves as proof-of-principle work toward development of point-of-care diagnostics for medical, combat, or bioterrorism targets.
TL;DR: In this paper, the impact of polymer backbone rigidity on the photomechanical response in a series of linear, azobenzene-functionalized polymers was examined, and it was shown that increasing the rigidity of the polymer backbone increases the magnitude of stress that is generated but decreases the angle of cantilever deflection.
Abstract: Azobenzene-functionalized polyimide materials can directly transduce light into mechanical force. Here, we examine the impact of polymer backbone rigidity on the photomechanical response in a series of linear, azobenzene-functionalized polymers. The rigidity of the backbone was varied by the polymerization of five dianhydride monomers with a newly synthesized diamine (azoBPA-diamine). The azobenzene-functionalized linear polymers exhibit glass transition temperatures (Tg) ranging from 276 to 307 °C and maintain excellent thermal stability. The photomechanical response of these materials was characterized by photoinduced cantilever bending as well as direct measurement of photogenerated stress upon exposure to linearly polarized, 445 nm light. Increasing the rigidity of the polymer backbone increases the magnitude of stress that is generated but decreases the angle of cantilever deflection.
TL;DR: In this paper, the authors developed a computational model of α precipitation in Ti alloys, via the phase-field method, in order to investigate the fundamental cause of the observed microstructural changes.
TL;DR: In this paper, HfO2 films were characterized by studying their growth behavior, microstructure, and optical properties, and a correlation between growth conditions, micro-structure and optical constants is established.
TL;DR: A set of 12 polyimides with one or three polar CN dipoles directly attached to the aromatic diamine part were synthesized and their electric energy storage properties were studied using broadband dielectric spectroscopy (BDS) and electric displacement electric field (D-E) loop measurements to determine their potential for high temperature film capacitors for aerospace applications.
Abstract: A set of 12 new polyimides (PIs) with one or three polar CN dipoles directly attached to the aromatic diamine part were synthesized and their electric energy storage properties were studied using broadband dielectric spectroscopy (BDS) and electric displacement–electric field (D–E) loop measurements to determine their potential for high temperature film capacitors for aerospace applications. It was found that adding highly polar nitrile groups to the PI structure increased permittivity and thus electrical energy storage, especially at high temperatures, and 3 CN dipoles were better than 1 CN dipole. Below the glass transition temperature (Tg), a weak γ transition was observed around −100 °C and a broad β transition was observed between 100 and 150 °C. It was the β (i.e., precursor dipolar motion before long-range segmental motion, or glass transition), rather than the γ sub-Tg transition that substantially increased the permittivity of PIs. From the BDS results on PIs having 3 nitrile groups, the enhancement in permittivity from permanent dipoles decreased with dianhydride in the order of pyromellitic dianhydride (PMDA) > 4,4′-oxydiphthalic dianhydride (OPDA) > 1,1,1,3,3,3-hexafluoropropane dianhydride (6FDA) > 4,4′-benzophenonetetracarboxylic dianhydride (BTDA). Meanwhile, the increase in permittivity also decreased in the order of para–para, meta–para, and meta–meta linkage in the diamine, suggesting that the para–para linkage favored easier dipole rotation than the meta–meta linkage. From the D–E loop study, the PIs with a combination of PMDA dianhydride and a para–para linkage exhibited the highest discharged energy density and a reasonably low loss.
TL;DR: This work grows thin MoS2 films uniformly over large areas with strong basal plane (002) or edge plane (100) orientations to characterize thermal anisotropy and demonstrates the importance of thermal boundary scattering in limiting thermal conductivity in nano-crystallineMoS2 thin films.
Abstract: In this work, we grow thin MoS2 films (50–150 nm) uniformly over large areas (>1 cm2) with strong basal plane (002) or edge plane (100) orientations to characterize thermal anisotropy. Measurement results are correlated with molecular dynamics simulations of thermal transport for perfect and defective MoS2 crystals. The correlation between predicted (simulations) and measured (experimental) thermal conductivity are attributed to factors such as crystalline domain orientation and size, thereby demonstrating the importance of thermal boundary scattering in limiting thermal conductivity in nano-crystalline MoS2 thin films. Furthermore, we demonstrate that the cross-plane thermal conductivity of the films is strongly impacted by exposure to ambient humidity.
TL;DR: The reversible capacity of graphene foam when used as anode in lithium ion battery is improved by the presence of graphene "eggshells", as compared to the unfilled foam, attributed to the higher rate of lithium diffusion, better buffering of strain associated with lithiation/delithiation and higher volumetric energy density.
Abstract: Highly porous, N-doped graphene foam is synthesized by chemical vapor deposition process on nickel foam. The voids of the graphene foam can be filled with curved graphene sheets by impregnating the nickel foam template with micrometer-sized nickel powder. Subsequent etching of nickel produces a graphene “eggshells”-in-graphene foam structure. The reversible capacity of such graphene foam when used as anode in lithium ion battery is improved by the presence of graphene “eggshells”, as compared to the unfilled foam. The improvement is attributed to the higher rate of lithium diffusion, better buffering of strain associated with lithiation/delithiation and higher volumetric energy density of the unique eggshell-in-graphene foam structure.
TL;DR: This work uses gold-doped carbon dots from controlled synthesis as water-soluble catalysts for a closer examination of the visible-light photoconversion of CO2 into small organic acids, including acetic acid and demonstrates the nanoscale semiconductor-equivalent nature of carbon dots.
Abstract: Carbon “quantum” dots (or carbon dots) have emerged as a new class of optical nanomaterials. Beyond the widely reported bright fluorescence emissions in carbon dots, their excellent photoinduced redox properties that resemble those found in conventional semiconductor nanostructures are equally valuable, with photon–electron conversion applications from photovoltaics to CO2 photocatalytic reduction. In this work we used gold-doped carbon dots from controlled synthesis as water-soluble catalysts for a closer examination of the visible-light photoconversion of CO2 into small organic acids, including acetic acid (for which the reduction requires many more electrons than that for formic acid) and, more interestingly, for the significantly enhanced photoconversion with higher CO2 pressures over an aqueous solution of the photocatalysts. The results demonstrate the nanoscale semiconductor-equivalent nature of carbon dots, with excellent potential in energy conversion applications.
TL;DR: At higher transition energy corresponding to S0 → Sn transition region, the NLT method yields effective multiphoton absorption stronger than the 2PEF measurement in the same systems, and this effect is tentatively attributed to nearly saturated excited-state absorption (ESA).
Abstract: We study instantaneous two-photon absorption (2PA) in a series of nominally quasi-centrosymmetric trans-bis(tributylphosphine)-bis-(4-((9,9-diethyl-7-ethynyl-9H-fluoren-2-yl) ethynyl)-R)-platinum complexes, where 11 different substituents, R = N(phenyl)2(NPh2), NH2, OCH3, t-butyl, CH3, H, F, CF3, CN, benzothiazole, and NO2, represent a range of electron-donating (ED) and electron-withdrawing (EW) strengths, while the Pt core acts as a weak ED group. We measure the 2PA cross section in the 540–810 nm excitation wavelength range by complementary femtosecond two-photon excited fluorescence (2PEF) and nonlinear transmission (NLT) methods and compare the obtained values to those of the Pt-core chromophore and the corresponding noncentrosymmetric side group (ligand) chromophores. Peak 2PA cross sections of neutral and ED-substituted Pt complexes occur at S0 → Sn transitions to higher energy states, above the lowest-energy S0 → S1 transition, and the corresponding values increase systematically with increasing E...
TL;DR: This work established that Apt-AuNPs can be used to design robust assays to be used in the field, and the rapid identification of cocaine in mixtures mimicking street samples was demonstrated.
TL;DR: The evidence supports the view that tDCS can accelerate learning and enhance performance in a range of complex cognitive tasks and may provide an alternative or addition to other training methods.
Abstract: Objective: The authors evaluate the effectiveness of noninvasive brain stimulation, in particular, transcranial direct current stimulation (tDCS), for accelerating learning and enhancing human performance on complex tasks. Background: Developing expertise in complex tasks typically requires extended training and practice. Neuroergonomics research has suggested new methods that can accelerate learning and boost human performance. TDCS is one such method. It involves the application of a weak DC current to the scalp and has the potential to modulate brain networks underlying the performance of a perceptual, cognitive, or motor task. Method: Examples of tDCS studies of declarative and procedural learning are discussed. This mini-review focuses on studies employing complex simulations representative of surveillance and security operations, intelligence analysis, and procedural learning in complex monitoring. Results: The evidence supports the view that tDCS can accelerate learning and enhance performance in a range of complex cognitive tasks. Initial findings also suggest that such benefits can be retained over time, but additional research is needed on training schedules and transfer of training. Conclusion: Noninvasive brain stimulation can accelerate skill acquisition in complex tasks and may provide an alternative or addition to other training methods.
TL;DR: Previous published work that used oxytocin immunoassays without sample extraction should be reexamined and future research exploring links between endogenous human Oxytocin and trust or social behavior should proceed with careful consideration of methods and appropriate biofluids for analysis.
Abstract: Expanding interest in oxytocin, particularly the role of endogenous oxytocin in human social behavior, has created a pressing need for replication of results and verification of assay methods. In this study, we sought to replicate and extend previous results correlating plasma oxytocin with trust and trustworthy behavior. As a necessary first step, the two most commonly used commercial assays were compared in human plasma via the addition of a known quantity of exogenous oxytocin, with and without sample extraction. Plasma sample extraction was found to be critical in obtaining repeatable concentrations of oxytocin. In the subsequent trust experiment, twelve samples in duplicate, from each of 82 participants, were collected over approximately six hours during the performance of a Prisoner’s Dilemma task paradigm that stressed human interpersonal trust. We found no significant relationship between plasma oxytocin concentrations and trusting or trustworthy behavior. In light of these findings, previous published work that used oxytocin immunoassays without sample extraction should be reexamined and future research exploring links between endogenous human oxytocin and trust or social behavior should proceed with careful consideration of methods and appropriate biofluids for analysis.
TL;DR: In this paper, the underlying mechanism of the electrically-controllable bandwidth broadening in polymer-stabilized cholesteric liquid crystals (PSCLCs) is isolated by employing a variety of electro-optic experiments.
Abstract: Cholesteric liquid crystals (CLCs) are selectively reflective materials that can exhibit a number of dynamic optical responses. We recently reported on electrically-induced, seven-fold increase in bandwidth in polymer stabilized CLCs (PSCLCs) subjected to DC electric fields. Here, the underlying mechanism of the electrically-controllable bandwidth broadening in PSCLCs is isolated by employing a variety of electro-optic experiments. We conclude that the mechanism is ionic charge trapping by the polymer network which subjects the material system to pitch expansion near the positive electrode and pitch compression near the negative electrode resulting in approximately linear pitch variation throughout the cell thickness.
TL;DR: High altitude residence predicts lower rates of new obesity diagnoses among overweight service members in the U.S. Army and Air Force, and the net balance of harms and benefits of high altitude on obesity prevention is assessed.
Abstract: We sought to evaluate whether residence at high altitude is associated with the development of obesity among those at increased risk of becoming obese. Obesity, a leading global health priority, is often refractory to care. A potentially novel intervention is hypoxia, which has demonstrated positive long-term metabolic effects in rats. Whether or not high altitude residence confers benefit in humans, however, remains unknown. Using a quasi-experimental, retrospective study design, we observed all outpatient medical encounters for overweight active component enlisted service members in the U.S. Army or Air Force from January 2006 to December 2012 who were stationed in the United States. We compared high altitude (>1.96 kilometers above sea level) duty assignment with low altitude (<0.98 kilometers). The outcome of interest was obesity related ICD-9 codes (278.00-01, V85.3x-V85.54) by Cox regression. We found service members had a lower hazard ratio (HR) of incident obesity diagnosis if stationed at high altitude as compared to low altitude (HR 0.59, 95% confidence interval [CI] 0.54–0.65; p<0.001). Using geographic distribution of obesity prevalence among civilians throughout the U.S. as a covariate (as measured by the Centers for Disease Control and Prevention and the REGARDS study) also predicted obesity onset among service members. In conclusion, high altitude residence predicts lower rates of new obesity diagnoses among overweight service members in the U.S. Army and Air Force. Future studies should assign exposure using randomization, clarify the mechanism(s) of this relationship, and assess the net balance of harms and benefits of high altitude on obesity prevention.