Power Laws from Linear Neuronal Cable Theory: Power Spectral Densities of the Soma Potential, Soma Membrane Current and Single-Neuron Contribution to the EEG

PubMed Central

Pettersen, Klas H.; Lindén, Henrik; Tetzlaff, Tom; Einevoll, Gaute T.

2014-01-01

Power laws, that is, power spectral densities (PSDs) exhibiting behavior for large frequencies f, have been observed both in microscopic (neural membrane potentials and currents) and macroscopic (electroencephalography; EEG) recordings. While complex network behavior has been suggested to be at the root of this phenomenon, we here demonstrate a possible origin of such power laws in the biophysical properties of single neurons described by the standard cable equation. Taking advantage of the analytical tractability of the so called ball and stick neuron model, we derive general expressions for the PSD transfer functions for a set of measures of neuronal activity: the soma membrane current, the current-dipole moment (corresponding to the single-neuron EEG contribution), and the soma membrane potential. These PSD transfer functions relate the PSDs of the respective measurements to the PSDs of the noisy input currents. With homogeneously distributed input currents across the neuronal membrane we find that all PSD transfer functions express asymptotic high-frequency power laws with power-law exponents analytically identified as for the soma membrane current, for the current-dipole moment, and for the soma membrane potential. Comparison with available data suggests that the apparent power laws observed in the high-frequency end of the PSD spectra may stem from uncorrelated current sources which are homogeneously distributed across the neural membranes and themselves exhibit pink () noise distributions. While the PSD noise spectra at low frequencies may be dominated by synaptic noise, our findings suggest that the high-frequency power laws may originate in noise from intrinsic ion channels. The significance of this finding goes beyond neuroscience as it demonstrates how power laws with a wide range of values for the power-law exponent α may arise from a simple, linear partial differential equation. PMID:25393030

Power laws from linear neuronal cable theory: power spectral densities of the soma potential, soma membrane current and single-neuron contribution to the EEG.

PubMed

Pettersen, Klas H; Lindén, Henrik; Tetzlaff, Tom; Einevoll, Gaute T

2014-11-01

Power laws, that is, power spectral densities (PSDs) exhibiting 1/f(α) behavior for large frequencies f, have been observed both in microscopic (neural membrane potentials and currents) and macroscopic (electroencephalography; EEG) recordings. While complex network behavior has been suggested to be at the root of this phenomenon, we here demonstrate a possible origin of such power laws in the biophysical properties of single neurons described by the standard cable equation. Taking advantage of the analytical tractability of the so called ball and stick neuron model, we derive general expressions for the PSD transfer functions for a set of measures of neuronal activity: the soma membrane current, the current-dipole moment (corresponding to the single-neuron EEG contribution), and the soma membrane potential. These PSD transfer functions relate the PSDs of the respective measurements to the PSDs of the noisy input currents. With homogeneously distributed input currents across the neuronal membrane we find that all PSD transfer functions express asymptotic high-frequency 1/f(α) power laws with power-law exponents analytically identified as α∞(I) = 1/2 for the soma membrane current, α∞(p) = 3/2 for the current-dipole moment, and α∞(V) = 2 for the soma membrane potential. Comparison with available data suggests that the apparent power laws observed in the high-frequency end of the PSD spectra may stem from uncorrelated current sources which are homogeneously distributed across the neural membranes and themselves exhibit pink (1/f) noise distributions. While the PSD noise spectra at low frequencies may be dominated by synaptic noise, our findings suggest that the high-frequency power laws may originate in noise from intrinsic ion channels. The significance of this finding goes beyond neuroscience as it demonstrates how 1/f(α) power laws with a wide range of values for the power-law exponent α may arise from a simple, linear partial differential equation.

Sponge-like nanoporous single crystals of gold

PubMed Central

Khristosov, Maria Koifman; Bloch, Leonid; Burghammer, Manfred; Kauffmann, Yaron; Katsman, Alex; Pokroy, Boaz

2015-01-01

Single crystals in nature often demonstrate fascinating intricate porous morphologies rather than classical faceted surfaces. We attempt to grow such crystals, drawing inspiration from biogenic porous single crystals. Here we show that nanoporous single crystals of gold can be grown with no need for any elaborate fabrication steps. These crystals are found to grow following solidification of a eutectic composition melt that forms as a result of the dewetting of nanometric thin films. We also present a kinetic model that shows how this nano-porous single-crystalline structure can be obtained, and which allows the potential size of the porous single crystal to be predicted. Retaining their single-crystalline nature is due to the fact that the full crystallization process is faster than the average period between two subsequent nucleation events. Our findings clearly demonstrate that it is possible to form single-crystalline nano porous metal crystals in a controlled manner. PMID:26554856

Anisotropic carrier mobility in single- and bi-layer C3N sheets

NASA Astrophysics Data System (ADS)

Wang, Xueyan; Li, Qingfang; Wang, Haifeng; Gao, Yan; Hou, Juan; Shao, Jianxin

2018-05-01

Based on the density functional theory combined with the Boltzmann transport equation with relaxation time approximation, we investigate the electronic structure and predict the carrier mobility of single- and bi-layer newly fabricated 2D carbon nitrides C3N. Although C3N sheets possess graphene-like planar hexagonal structure, the calculated carrier mobility is remarkably anisotropic, which is found mainly induced by the anisotropic effective masses and deformation potential constants. Importantly, we find that both the electron and hole mobilities are considerable high, for example, the hole mobility along the armchair direction of single-layer C3N sheets can arrive as high as 1.08 ×104 cm2 V-1 s-1, greatly larger than that of C2N-h2D and many other typical 2D materials. Owing to the high and anisotropic carrier mobility and appropriate band gap, single- and bi-layer semiconducting C3N sheets may have great potential applications in high performance electronic and optoelectronic devices.

Multiphase flow microfluidics for the production of single or multiple emulsions for drug delivery.

PubMed

Zhao, Chun-Xia

2013-11-01

Considerable effort has been directed towards developing novel drug delivery systems. Microfluidics, capable of generating monodisperse single and multiple emulsion droplets, executing precise control and operations on these droplets, is a powerful tool for fabricating complex systems (microparticles, microcapsules, microgels) with uniform size, narrow size distribution and desired properties, which have great potential in drug delivery applications. This review presents an overview of the state-of-the-art multiphase flow microfluidics for the production of single emulsions or multiple emulsions for drug delivery. The review starts with a brief introduction of the approaches for making single and multiple emulsions, followed by presentation of some potential drug delivery systems (microparticles, microcapsules and microgels) fabricated in microfluidic devices using single or multiple emulsions as templates. The design principles, manufacturing processes and properties of these drug delivery systems are also discussed and compared. Furthermore, drug encapsulation and drug release (including passive and active controlled release) are provided and compared highlighting some key findings and insights. Finally, site-targeting delivery using multiphase flow microfluidics is also briefly introduced. Copyright © 2013 Elsevier B.V. All rights reserved.

Quantifying the quantum gate fidelity of single-atom spin qubits in silicon by randomized benchmarking.

PubMed

Muhonen, J T; Laucht, A; Simmons, S; Dehollain, J P; Kalra, R; Hudson, F E; Freer, S; Itoh, K M; Jamieson, D N; McCallum, J C; Dzurak, A S; Morello, A

2015-04-22

Building upon the demonstration of coherent control and single-shot readout of the electron and nuclear spins of individual (31)P atoms in silicon, we present here a systematic experimental estimate of quantum gate fidelities using randomized benchmarking of 1-qubit gates in the Clifford group. We apply this analysis to the electron and the ionized (31)P nucleus of a single P donor in isotopically purified (28)Si. We find average gate fidelities of 99.95% for the electron and 99.99% for the nuclear spin. These values are above certain error correction thresholds and demonstrate the potential of donor-based quantum computing in silicon. By studying the influence of the shape and power of the control pulses, we find evidence that the present limitation to the gate fidelity is mostly related to the external hardware and not the intrinsic behaviour of the qubit.

Quantum Stirling heat engine and refrigerator with single and coupled spin systems

NASA Astrophysics Data System (ADS)

Huang, Xiao-Li; Niu, Xin-Ya; Xiu, Xiao-Ming; Yi, Xue-Xi

2014-02-01

We study the reversible quantum Stirling cycle with a single spin or two coupled spins as the working substance. With the single spin as the working substance, we find that under certain conditions the reversed cycle of a heat engine is NOT a refrigerator, this feature holds true for a Stirling heat engine with an ion trapped in a shallow potential as its working substance. The efficiency of quantum Stirling heat engine can be higher than the efficiency of the Carnot engine, but the performance coefficient of the quantum Stirling refrigerator is always lower than its classical counterpart. With two coupled spins as the working substance, we find that a heat engine can turn to a refrigerator due to the increasing of the coupling constant, this can be explained by the properties of the isothermal line in the magnetic field-entropy plane.

Dissociation between sustained single-neuron spiking and transient β-LFP oscillations in primate motor cortex

PubMed Central

Rule, Michael E.; Vargas-Irwin, Carlos E.; Donoghue, John P.

2017-01-01

Determining the relationship between single-neuron spiking and transient (20 Hz) β-local field potential (β-LFP) oscillations is an important step for understanding the role of these oscillations in motor cortex. We show that whereas motor cortex firing rates and beta spiking rhythmicity remain sustained during steady-state movement preparation periods, β-LFP oscillations emerge, in contrast, as short transient events. Single-neuron mean firing rates within and outside transient β-LFP events showed no differences, and no consistent correlation was found between the beta oscillation amplitude and firing rates, as was the case for movement- and visual cue-related β-LFP suppression. Importantly, well-isolated single units featuring beta-rhythmic spiking (43%, 125/292) showed no apparent or only weak phase coupling with the transient β-LFP oscillations. Similar results were obtained for the population spiking. These findings were common in triple microelectrode array recordings from primary motor (M1), ventral (PMv), and dorsal premotor (PMd) cortices in nonhuman primates during movement preparation. Although beta spiking rhythmicity indicates strong membrane potential fluctuations in the beta band, it does not imply strong phase coupling with β-LFP oscillations. The observed dissociation points to two different sources of variation in motor cortex β-LFPs: one that impacts single-neuron spiking dynamics and another related to the generation of mesoscopic β-LFP signals. Furthermore, our findings indicate that rhythmic spiking and diverse neuronal firing rates, which encode planned actions during movement preparation, may naturally limit the ability of different neuronal populations to strongly phase-couple to a single dominant oscillation frequency, leading to the observed spiking and β-LFP dissociation. NEW & NOTEWORTHY We show that whereas motor cortex spiking rates and beta (~20 Hz) spiking rhythmicity remain sustained during steady-state movement preparation periods, β-local field potential (β-LFP) oscillations emerge, in contrast, as transient events. Furthermore, the β-LFP phase at which neurons spike drifts: phase coupling is typically weak or absent. This dissociation points to two sources of variation in the level of motor cortex beta: one that impacts single-neuron spiking and another related to the generation of measured mesoscopic β-LFPs. PMID:28100654

Attention Influences Single Unit and Local Field Potential Response Latencies in Visual Cortical Area V4

PubMed Central

Sundberg, Kristy A.; Mitchell, Jude F.; Gawne, Timothy J.

2012-01-01

Many previous studies have demonstrated that changes in selective attention can alter the response magnitude of visual cortical neurons, but there has been little evidence for attention affecting response latency. Small latency differences, though hard to detect, can potentially be of functional importance, and may also give insight into the mechanisms of neuronal computation. We therefore reexamined the effect of attention on the response latency of both single units and the local field potential (LFP) in primate visual cortical area V4. We find that attention does produce small (1–2 ms) but significant reductions in the latency of both the spiking and LFP responses. Though attention, like contrast elevation, reduces response latencies, we find that the two have different effects on the magnitude of the LFP. Contrast elevations increase and attention decreases the magnitude of the initial deflection of the stimulus-evoked LFP. Both contrast elevation and attention increase the magnitude of the spiking response. We speculate that latencies may be reduced at higher contrast because stronger stimulus inputs drive neurons more rapidly to spiking threshold, while attention may reduce latencies by placing neurons in a more depolarized state closer to threshold before stimulus onset. PMID:23136440

ENHANCED TOXICITY OF CHARGED CARBON NANOTUBES AND ULTRAFINE CARBON BLACK PARTICLES

EPA Science Inventory

Man-made carbonaceous nano-particles such as single and multi-walled carbon nano-tubes (CNT) and ultra-fine carbon black (UFCB) particles are finding increasing applications in industry, but their potential toxic effects is of concern. In aqueous media, these particles cluster in...

Energy Efficiency Potential in the U.S. Single-Family Housing Stock

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, Eric J.; Christensen, Craig B.; Horowitz, Scott G.

Typical approaches for assessing energy efficiency potential in buildings use a limited number of prototypes, and therefore suffer from inadequate resolution when pass-fail cost-effectiveness tests are applied, which can significantly underestimate or overestimate the economic potential of energy efficiency technologies. This analysis applies a new approach to large-scale residential energy analysis, combining the use of large public and private data sources, statistical sampling, detailed building simulations, and high-performance computing to achieve unprecedented granularity - and therefore accuracy - in modeling the diversity of the single-family housing stock. The result is a comprehensive set of maps, tables, and figures showing themore » technical and economic potential of 50 plus residential energy efficiency upgrades and packages for each state. Policymakers, program designers, and manufacturers can use these results to identify upgrades with the highest potential for cost-effective savings in a particular state or region, as well as help identify customer segments for targeted marketing and deployment. The primary finding of this analysis is that there is significant technical and economic potential to save electricity and on-site fuel use in the single-family housing stock. However, the economic potential is very sensitive to the cost-effectiveness criteria used for analysis. Additionally, the savings of particular energy efficiency upgrades is situation-specific within the housing stock (depending on climate, building vintage, heating fuel type, building physical characteristics, etc.).« less

Simultaneous multi-patch-clamp and extracellular-array recordings: Single neuron reflects network activity

NASA Astrophysics Data System (ADS)

Vardi, Roni; Goldental, Amir; Sardi, Shira; Sheinin, Anton; Kanter, Ido

2016-11-01

The increasing number of recording electrodes enhances the capability of capturing the network’s cooperative activity, however, using too many monitors might alter the properties of the measured neural network and induce noise. Using a technique that merges simultaneous multi-patch-clamp and multi-electrode array recordings of neural networks in-vitro, we show that the membrane potential of a single neuron is a reliable and super-sensitive probe for monitoring such cooperative activities and their detailed rhythms. Specifically, the membrane potential and the spiking activity of a single neuron are either highly correlated or highly anti-correlated with the time-dependent macroscopic activity of the entire network. This surprising observation also sheds light on the cooperative origin of neuronal burst in cultured networks. Our findings present an alternative flexible approach to the technique based on a massive tiling of networks by large-scale arrays of electrodes to monitor their activity.

Simultaneous multi-patch-clamp and extracellular-array recordings: Single neuron reflects network activity.

PubMed

Vardi, Roni; Goldental, Amir; Sardi, Shira; Sheinin, Anton; Kanter, Ido

2016-11-08

The increasing number of recording electrodes enhances the capability of capturing the network's cooperative activity, however, using too many monitors might alter the properties of the measured neural network and induce noise. Using a technique that merges simultaneous multi-patch-clamp and multi-electrode array recordings of neural networks in-vitro, we show that the membrane potential of a single neuron is a reliable and super-sensitive probe for monitoring such cooperative activities and their detailed rhythms. Specifically, the membrane potential and the spiking activity of a single neuron are either highly correlated or highly anti-correlated with the time-dependent macroscopic activity of the entire network. This surprising observation also sheds light on the cooperative origin of neuronal burst in cultured networks. Our findings present an alternative flexible approach to the technique based on a massive tiling of networks by large-scale arrays of electrodes to monitor their activity.

Simultaneous multi-patch-clamp and extracellular-array recordings: Single neuron reflects network activity

PubMed Central

Vardi, Roni; Goldental, Amir; Sardi, Shira; Sheinin, Anton; Kanter, Ido

2016-01-01

The increasing number of recording electrodes enhances the capability of capturing the network’s cooperative activity, however, using too many monitors might alter the properties of the measured neural network and induce noise. Using a technique that merges simultaneous multi-patch-clamp and multi-electrode array recordings of neural networks in-vitro, we show that the membrane potential of a single neuron is a reliable and super-sensitive probe for monitoring such cooperative activities and their detailed rhythms. Specifically, the membrane potential and the spiking activity of a single neuron are either highly correlated or highly anti-correlated with the time-dependent macroscopic activity of the entire network. This surprising observation also sheds light on the cooperative origin of neuronal burst in cultured networks. Our findings present an alternative flexible approach to the technique based on a massive tiling of networks by large-scale arrays of electrodes to monitor their activity. PMID:27824075

Segmentation Fusion Techniques with Application to Plenoptic Images: A Survey.

NASA Astrophysics Data System (ADS)

Evin, D.; Hadad, A.; Solano, A.; Drozdowicz, B.

2016-04-01

The segmentation of anatomical and pathological structures plays a key role in the characterization of clinically relevant evidence from digital images. Recently, plenoptic imaging has emerged as a new promise to enrich the diagnostic potential of conventional photography. Since the plenoptic images comprises a set of slightly different versions of the target scene, we propose to make use of those images to improve the segmentation quality in relation to the scenario of a single image segmentation. The problem of finding a segmentation solution from multiple images of a single scene, is called segmentation fusion. This paper reviews the issue of segmentation fusion in order to find solutions that can be applied to plenoptic images, particularly images from the ophthalmological domain.

NASA’s Spitzer Reveals Largest Batch of Earth-Size, Habitable-Zone Planets Around a Single Star

NASA Image and Video Library

2017-02-22

NASA held a news conference Feb. 22 at the agency’s headquarters to discuss the finding by the Spitzer Space Telescope of seven Earth-sized planets around a tiny, nearby, ultra-cool dwarf star. Three of these planets are in the habitable zone, the region around the star in which liquid water is most likely to thrive on a rocky planet. This is the first time so many planets have been found in a single star's habitable zone, and the first time so many Earth-sized planets have been found around the same star. The finding of this planetary system, called TRAPPIST-1, is the best target yet for studying the atmospheres of potentially habitable, Earth-sized worlds

Chemical potential fluctuations in topological insulator (Bi0.5Sb0.5)2Te3-films visualized by photocurrent spectroscopy

NASA Astrophysics Data System (ADS)

Kastl, Christoph; Seifert, Paul; He, Xiaoyue; Wu, Kehui; Li, Yongqing; Holleitner, Alexander

2015-06-01

We investigate the photocurrent properties of the topological insulator (Bi0.5Sb0.5)2Te3 on SrTiO3-substrates. We find reproducible, submicron photocurrent patterns generated by long-range chemical potential fluctuations, occurring predominantly at the topological insulator/substrate interface. We fabricate nano-plowed constrictions which comprise single potential fluctuations. Hereby, we can quantify the magnitude of the disorder potential to be in the meV range. The results further suggest a dominating photo-thermoelectric current generated in the surface states in such nanoscale constrictions.

Optically probing the fine structure of a single Mn atom in an InAs quantum dot.

PubMed

Kudelski, A; Lemaître, A; Miard, A; Voisin, P; Graham, T C M; Warburton, R J; Krebs, O

2007-12-14

We report on the optical spectroscopy of a single InAs/GaAs quantum dot doped with a single Mn atom in a longitudinal magnetic field of a few Tesla. Our findings show that the Mn impurity is a neutral acceptor state A0 whose effective spin J=1 is significantly perturbed by the quantum dot potential and its associated strain field. The spin interaction with photocarriers injected in the quantum dot is shown to be ferromagnetic for holes, with an effective coupling constant of a few hundreds of mueV, but vanishingly small for electrons.

Matter-neutrino resonance in a multiangle neutrino bulb model

NASA Astrophysics Data System (ADS)

Vlasenko, Alexey; McLaughlin, G. C.

2018-04-01

Simulations of neutrino flavor evolution in compact merger environments have shown that neutrino flavor, and hence nucleosynthesis, can be strongly affected by the presence of matter-neutrino resonances (MNRs), where there is a cancelation between the matter and the neutrino potential. Simulations performed thus far follow flavor evolution along a single neutrino trajectory, but self-consistency requires all trajectories to be treated simultaneously, and it has not been known whether MNR phenomena would still occur in multiangle models. In this paper, we present the first fully multi-angle calculations of MNR. We find that familiar MNR phenomena, where neutrinos transform to a greater extent than anti-neutrinos and a feedback mechanism maintains the cancellation between the matter and neutrino potential, still occurs for a subset of angular bins, although the flavor transformation is not as efficient as in the single-angle case. In addition, we find other types of flavor transformation that are not seen in single-angle simulations. These flavor transformation phenomena appear to be robust and are present for a wide range of model parameters, as long as an MNR is present. Although computational constraints currently limit us to models with spherical symmetry, our results suggest that the presence of an MNR generally leads to large-scale neutrino flavor evolution in multiangle systems.

Single Versus Multiple Events Error Potential Detection in a BCI-Controlled Car Game With Continuous and Discrete Feedback.

PubMed

Kreilinger, Alex; Hiebel, Hannah; Müller-Putz, Gernot R

2016-03-01

This work aimed to find and evaluate a new method for detecting errors in continuous brain-computer interface (BCI) applications. Instead of classifying errors on a single-trial basis, the new method was based on multiple events (MEs) analysis to increase the accuracy of error detection. In a BCI-driven car game, based on motor imagery (MI), discrete events were triggered whenever subjects collided with coins and/or barriers. Coins counted as correct events, whereas barriers were errors. This new method, termed ME method, combined and averaged the classification results of single events (SEs) and determined the correctness of MI trials, which consisted of event sequences instead of SEs. The benefit of this method was evaluated in an offline simulation. In an online experiment, the new method was used to detect erroneous MI trials. Such MI trials were discarded and could be repeated by the users. We found that, even with low SE error potential (ErrP) detection rates, feasible accuracies can be achieved when combining MEs to distinguish erroneous from correct MI trials. Online, all subjects reached higher scores with error detection than without, at the cost of longer times needed for completing the game. Findings suggest that ErrP detection may become a reliable tool for monitoring continuous states in BCI applications when combining MEs. This paper demonstrates a novel technique for detecting errors in online continuous BCI applications, which yields promising results even with low single-trial detection rates.

Separating boys and girls and increasing weight? Assessing the impacts of single-sex schools through random assignment in Seoul

PubMed Central

Choi, Jaesung; Park, Hyunjoon; Behrman, Jere R.

2015-01-01

A growing body of research reports associations of school contexts with adolescents’ weight and weight-related behaviors. One interesting, but under-researched, dimension of school context that potentially matters for adolescents’ weight is the gender composition. If boys and girls are separated into single-sex schools, they might be less concerned about physical appearance, which may result in increased weight. Utilizing a unique setting in Seoul, Korea where students are randomly assigned to single-sex and coeducational schools within school districts, we estimate causal effects of single-sex schools on weight and weight-related behaviors. Our results show that students attending single-sex schools are more likely to be overweight, and that the effects are more pronounced for girls. We also find that girls in single-sex schools are less likely to engage in strenuous activities than their coeducational counterparts. PMID:25863424

Separating boys and girls and increasing weight? Assessing the impacts of single-sex schools through random assignment in Seoul.

PubMed

Choi, Jaesung; Park, Hyunjoon; Behrman, Jere R

2015-06-01

A growing body of research reports associations of school contexts with adolescents' weight and weight-related behaviors. One interesting, but under-researched, dimension of school context that potentially matters for adolescents' weight is the gender composition. If boys and girls are separated into single-sex schools, they might be less concerned about physical appearance, which may result in increased weight. Utilizing a unique setting in Seoul, Korea where students are randomly assigned to single-sex and coeducational schools within school districts, we estimate causal effects of single-sex schools on weight and weight-related behaviors. Our results show that students attending single-sex schools are more likely to be overweight, and that the effects are more pronounced for girls. We also find that girls in single-sex schools are less likely to engage in strenuous activities than their coeducational counterparts. Copyright © 2015 Elsevier Ltd. All rights reserved.

Explaining the Effect of Parent-Child Coresidence on Marriage Formation: The Case of Japan.

PubMed

Yu, Wei-Hsin; Kuo, Janet Chen-Lan

2016-10-01

Many single adult children in countries around the world live with their parents. Such coresidence has been thought to delay the transition to first marriage, although the exact reasons for the delay have not been sufficiently examined. Using panel data from Japan, we investigate whether changes in never-married adults' residential status lead to alterations in their marital aspirations, courtship behaviors, romantic opportunities, and perceived obstacles to marrying. Our estimation of fixed-effects models helps address potential bias caused by single individuals' selection into living in the parental home. The analysis indicates that living with parents is associated with a lower probability of forming romantic relationships, thereby decelerating the transition to first marriage. The never-married, however, do not desire marriage less, put less effort into finding romantic partners, or have fewer opportunities to meet potential partners when coresiding with parents. Overall, the findings suggest that living in the parental home increases never-married men's contentment with their immediate social environment, whereas it decreases women's psychological readiness to transition into adult roles, making both men and women less eager to settle into a romantic relationship.

Comment on 'Parametrization of Stillinger-Weber potential based on a valence force field model: application to single-layer MoS2 and black phosphorus'.

PubMed

Midtvedt, Daniel; Croy, Alexander

2016-06-10

We compare the simplified valence-force model for single-layer black phosphorus with the original model and recent ab initio results. Using an analytic approach and numerical calculations we find that the simplified model yields Young's moduli that are smaller compared to the original model and are almost a factor of two smaller than ab initio results. Moreover, the Poisson ratios are an order of magnitude smaller than values found in the literature.

Single photon emission tomography using 99mTc-HM-PAO in the investigation of dementia.

PubMed Central

Neary, D; Snowden, J S; Shields, R A; Burjan, A W; Northen, B; MacDermott, N; Prescott, M C; Testa, H J

1987-01-01

Single photon emission tomographic imaging of the brain using 99mTc HM-PAO was carried out in patients with a clinical diagnosis of Alzheimer's disease, non-Alzheimer frontal-lobe dementia, and progressive supranuclear palsy. Independent assessment of reductions in uptake revealed posterior hemisphere abnormalities in the majority of the Alzheimer group, and selective anterior hemisphere abnormalities in both other groups. The findings were consistent with observed patterns of mental impairment. The imaging technique has potential value in the differential diagnosis of primary cerebral atrophy. Images PMID:3499484

A systematic typology for negative Poisson's ratio materials and the prediction of complete auxeticity in pure silica zeolite JST.

PubMed

Siddorn, M; Coudert, F-X; Evans, K E; Marmier, A

2015-07-21

Single crystals can commonly have negative Poisson's ratio in a few directions; however more generalised auxeticity is rarer. We propose a typology to distinguish auxetic materials. We characterise numerous single crystals and demonstrate that partial auxeticity occurs for around 37%. We find average auxeticity to be limited to α-cristobalite and no example of complete auxeticity. We simulate two hundreds pure silica zeolites with empirical potentials and quantum chemistry methods, and for the first time identify complete auxeticity in a zeolite network, JST.

General Aviation Interior Noise. Part 3; Noise Control Measure Evaluation

NASA Technical Reports Server (NTRS)

Unruh, James F.; Till, Paul D.; Palumbo, Daniel L. (Technical Monitor)

2002-01-01

The work reported herein is an extension to the work accomplished under NASA Grant NAG1-2091 on the development of noise/source/path identification techniques for single engine propeller driven General Aviation aircraft. The previous work developed a Conditioned Response Analysis (CRA) technique to identify potential noise sources that contributed to the dominating tonal responses within the aircraft cabin. The objective of the present effort was to improve and verify the findings of the CRA and develop and demonstrate noise control measures for single engine propeller driven General Aviation aircraft.

A Novel MEMS Gyro North Finder Design Based on the Rotation Modulation Technique

PubMed Central

Zhang, Yongjian; Zhou, Bin; Song, Mingliang; Hou, Bo; Xing, Haifeng; Zhang, Rong

2017-01-01

Gyro north finders have been widely used in maneuvering weapon orientation, oil drilling and other areas. This paper proposes a novel Micro-Electro-Mechanical System (MEMS) gyroscope north finder based on the rotation modulation (RM) technique. Two rotation modulation modes (static and dynamic modulation) are applied. Compared to the traditional gyro north finders, only one single MEMS gyroscope and one MEMS accelerometer are needed, reducing the total cost since high-precision gyroscopes and accelerometers are the most expensive components in gyro north finders. To reduce the volume and enhance the reliability, wireless power and wireless data transmission technique are introduced into the rotation modulation system for the first time. To enhance the system robustness, the robust least square method (RLSM) and robust Kalman filter (RKF) are applied in the static and dynamic north finding methods, respectively. Experimental characterization resulted in a static accuracy of 0.66° and a dynamic repeatability accuracy of 1°, respectively, confirming the excellent potential of the novel north finding system. The proposed single gyro and single accelerometer north finding scheme is universal, and can be an important reference to both scientific research and industrial applications. PMID:28452936

Wakefield potentials of corrugated structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Novokhatski, A.

A corrugated structure, which is used in “dechirper” devices, is usually a pipe or two plates with small corrugations (bumps) on the walls. There is a good single-mode description of the wake potentials excited by a relativistic bunch if the wave length of the mode is much longer than the distance between the bumps in the pipe. However, ultrashort bunches, which are now used in free electron lasers, excite much higher frequency fields and the corresponding wake potentials will be very different from the single-mode description. We have made analyses of these wake potentials based on a numerical solution ofmore » Maxwell’s equations. It was confirmed that the behavior of the wakefields of ultrashort bunches in corrugated structures is not much different from the fields excited usually in accelerating structures where the wake potentials are described by the exponential function. For a practical application we present results for the SLAC “dechirper.” We also carried out calculations for a similar device, that was installed and measured at the Pohang Accelerator Laboratory, Korea. As a result, we find very good agreement with the experimental results.« less

Wakefield potentials of corrugated structures

DOE PAGES

Novokhatski, A.

2015-10-22

A corrugated structure, which is used in “dechirper” devices, is usually a pipe or two plates with small corrugations (bumps) on the walls. There is a good single-mode description of the wake potentials excited by a relativistic bunch if the wave length of the mode is much longer than the distance between the bumps in the pipe. However, ultrashort bunches, which are now used in free electron lasers, excite much higher frequency fields and the corresponding wake potentials will be very different from the single-mode description. We have made analyses of these wake potentials based on a numerical solution ofmore » Maxwell’s equations. It was confirmed that the behavior of the wakefields of ultrashort bunches in corrugated structures is not much different from the fields excited usually in accelerating structures where the wake potentials are described by the exponential function. For a practical application we present results for the SLAC “dechirper.” We also carried out calculations for a similar device, that was installed and measured at the Pohang Accelerator Laboratory, Korea. As a result, we find very good agreement with the experimental results.« less

Optimization Methods for Spiking Neurons and Networks

PubMed Central

Russell, Alexander; Orchard, Garrick; Dong, Yi; Mihalaş, Ştefan; Niebur, Ernst; Tapson, Jonathan; Etienne-Cummings, Ralph

2011-01-01

Spiking neurons and spiking neural circuits are finding uses in a multitude of tasks such as robotic locomotion control, neuroprosthetics, visual sensory processing, and audition. The desired neural output is achieved through the use of complex neuron models, or by combining multiple simple neurons into a network. In either case, a means for configuring the neuron or neural circuit is required. Manual manipulation of parameters is both time consuming and non-intuitive due to the nonlinear relationship between parameters and the neuron’s output. The complexity rises even further as the neurons are networked and the systems often become mathematically intractable. In large circuits, the desired behavior and timing of action potential trains may be known but the timing of the individual action potentials is unknown and unimportant, whereas in single neuron systems the timing of individual action potentials is critical. In this paper, we automate the process of finding parameters. To configure a single neuron we derive a maximum likelihood method for configuring a neuron model, specifically the Mihalas–Niebur Neuron. Similarly, to configure neural circuits, we show how we use genetic algorithms (GAs) to configure parameters for a network of simple integrate and fire with adaptation neurons. The GA approach is demonstrated both in software simulation and hardware implementation on a reconfigurable custom very large scale integration chip. PMID:20959265

Single-beam, dark toroidal optical traps for cold atoms

NASA Astrophysics Data System (ADS)

Fatemi, Fredrik K.; Olson, Spencer E.; Bashkansky, Mark; Dutton, Zachary; Terraciano, Matthew

2007-02-01

We demonstrate the generation of single-beam dark toroidal optical intensity distributions, which are of interest for neutral atom storage and atom interferometry. We demonstrate experimentally and numerically optical potentials that contain a ring-shaped intensity minimum, bounded in all directions by higher intensity. We use a spatial light modulator to alter the phase of an incident laser beam, and analyze the resulting optical propagation characteristics. For small toroidal traps (< 50 μm diameter), we find an optimal superposition of Laguerre-Gaussian modes that allows the formation of single-beam toroidal traps. We generate larger toroidal bottle traps by focusing hollow beams with toroidal lenses imprinted onto the spatial light modulator.

Scheme for generating distillation-favorable continuous-variable entanglement via three concurrent parametric down-conversions in a single χ⁽²⁾ nonlinear photonic crystal.

PubMed

Gong, Yan-Xiao; Zhang, ShengLi; Xu, P; Zhu, S N

2016-03-21

We propose to generate a single-mode-squeezing two-mode squeezed vacuum state via a single χ⁽²⁾ nonlinear photonic crystal. The state is favorable for existing Gaussian entanglement distillation schemes, since local squeezing operations can enhance the final entanglement and the success probability. The crystal is designed for enabling three concurrent quasi-phase-matching parametric-down conversions, and hence relieves the auxiliary on-line bi-side local squeezing operations. The compact source opens up a way for continuous-variable quantum technologies and could find more potential applications in future large-scale quantum networks.

Electrocardiographic Characteristics of Potential Organ Donors and Associations with Cardiac Allograft Utilization

PubMed Central

Khush, Kiran K.; Menza, Rebecca; Nguyen, John; Goldstein, Benjamin A.; Zaroff, Jonathan G.; Drew, Barbara J.

2012-01-01

Background Current regulations require that all cardiac allograft offers for transplantation must include an interpreted 12-lead electrocardiogram (ECG). However, little is known about the expected ECG findings in potential organ donors, or the clinical significance of any identified abnormalities in terms of cardiac allograft function and suitability for transplantation. Methods and Results A single experienced reviewer interpreted the first ECG obtained after brainstem herniation in 980 potential organ donors managed by the California Transplant Donor Network from 2002-2007. ECG abnormalities were summarized, and associations between specific ECG findings and cardiac allograft utilization for transplantation were studied. ECG abnormalities were present in 51% of all cases reviewed. The most common abnormalities included voltage criteria for left ventricular hypertrophy (LVH), prolongation of the corrected QT interval (QTc), and repolarization changes (ST/T wave abnormalities). Fifty seven percent of potential cardiac allografts in this cohort were accepted for transplantation. LVH on ECG was a strong predictor of allograft non-utilization. No significant associations were seen between QTc prolongation, repolarization changes and allograft utilization for transplantation, after adjusting for donor clinical variables and echocardiographic findings. Conclusions We have performed the first comprehensive study of ECG findings in potential donors for cardiac transplantation. Many of the common ECG abnormalities seen in organ donors may result from the heightened state of sympathetic activation that occurs after brainstem herniation, and are not associated with allograft utilization for transplantation. PMID:22615333

First-principles study of point defects at a semicoherent interface

DOE PAGES

Metsanurk, E.; Tamm, A.; Caro, A.; ...

2014-12-19

Most of the atomistic modeling of semicoherent metal-metal interfaces has so far been based on the use of semiempirical interatomic potentials. Here, we show that key conclusions drawn from previous studies are in contradiction with more precise ab-initio calculations. In particular we find that single point defects do not delocalize, but remain compact near the interfacial plane in Cu-Nb multilayers. Lastly, we give a simple qualitative explanation for this difference on the basis of the well known limited transferability of empirical potentials.

Classification of Hand Grasp Kinetics and Types Using Movement-Related Cortical Potentials and EEG Rhythms.

PubMed

Jochumsen, Mads; Rovsing, Cecilie; Rovsing, Helene; Niazi, Imran Khan; Dremstrup, Kim; Kamavuako, Ernest Nlandu

2017-01-01

Detection of single-trial movement intentions from EEG is paramount for brain-computer interfacing in neurorehabilitation. These movement intentions contain task-related information and if this is decoded, the neurorehabilitation could potentially be optimized. The aim of this study was to classify single-trial movement intentions associated with two levels of force and speed and three different grasp types using EEG rhythms and components of the movement-related cortical potential (MRCP) as features. The feature importance was used to estimate encoding of discriminative information. Two data sets were used. 29 healthy subjects executed and imagined different hand movements, while EEG was recorded over the contralateral sensorimotor cortex. The following features were extracted: delta, theta, mu/alpha, beta, and gamma rhythms, readiness potential, negative slope, and motor potential of the MRCP. Sequential forward selection was performed, and classification was performed using linear discriminant analysis and support vector machines. Limited classification accuracies were obtained from the EEG rhythms and MRCP-components: 0.48 ± 0.05 (grasp types), 0.41 ± 0.07 (kinetic profiles, motor execution), and 0.39 ± 0.08 (kinetic profiles, motor imagination). Delta activity contributed the most but all features provided discriminative information. These findings suggest that information from the entire EEG spectrum is needed to discriminate between task-related parameters from single-trial movement intentions.

Temporary hearing loss influences post-stimulus time histogram and single neuron action potential estimates from human compound action potentials

PubMed Central

Lichtenhan, Jeffery T.; Chertoff, Mark E.

2008-01-01

An analytic compound action potential (CAP) obtained by convolving functional representations of the post-stimulus time histogram summed across auditory nerve neurons [P(t)] and a single neuron action potential [U(t)] was fit to human CAPs. The analytic CAP fit to pre- and postnoise-induced temporary hearing threshold shift (TTS) estimated in vivoP(t) and U(t) and the number of neurons contributing to the CAPs (N). The width of P(t) decreased with increasing signal level and was wider at the lowest signal level following noise exposure. P(t) latency decreased with increasing signal level and was shorter at all signal levels following noise exposure. The damping and oscillatory frequency of U(t) increased with signal level. For subjects with large amounts of TTS, U(t) had greater damping than before noise exposure particularly at low signal levels. Additionally, U(t) oscillation was lower in frequency at all click intensities following noise exposure. N increased with signal level and was smaller after noise exposure at the lowest signal level. Collectively these findings indicate that neurons contributing to the CAP during TTS are fewer in number, shorter in latency, and poorer in synchrony than before noise exposure. Moreover, estimates of single neuron action potentials may decay more rapidly and have a lower oscillatory frequency during TTS. PMID:18397026

Family strengths, motivation, and resources as predictors of health promotion behavior in single-parent and two-parent families.

PubMed

Ford-Gilboe, M

1997-06-01

The extent to which selected aspects of family health potential (strengths, motivation, and resources) predicted health work (health-related problem-solving and goal attainment behaviors) was examined in a Canadian sample of 138 female-headed single-parent families and two-parent families. The mother and one child (age 10-14) each completed mailed self-report instruments to assess the independent variables of family cohesion, family pride, mother's non-traditional sex role orientation, general self-efficacy, internal health locus of control, network support, community support, and family income, as well as the dependent variable, health work. With the effects of mothers' education held constant, the independent variables predicted 22 to 27% of the variance in health work in the total sample and each family type. Family cohesion was the most consistent predictor of health work, accounting for 8 to 13% of the variance. The findings challenge existing problem-oriented views of single-parent families by focusing on their potential to engage in health promotion behavior.

Orientation-modulated attention effect on visual evoked potential: Application for PIN system using brain-computer interface.

PubMed

Wilaiprasitporn, Theerawit; Yagi, Tohru

2015-01-01

This research demonstrates the orientation-modulated attention effect on visual evoked potential. We combined this finding with our previous findings about the motion-modulated attention effect and used the result to develop novel visual stimuli for a personal identification number (PIN) application based on a brain-computer interface (BCI) framework. An electroencephalography amplifier with a single electrode channel was sufficient for our application. A computationally inexpensive algorithm and small datasets were used in processing. Seven healthy volunteers participated in experiments to measure offline performance. Mean accuracy was 83.3% at 13.9 bits/min. Encouraged by these results, we plan to continue developing the BCI-based personal identification application toward real-time systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simard, G.; et al.

We report constraints on cosmological parameters from the angular power spectrum of a cosmic microwave background (CMB) gravitational lensing potential map created using temperature data from 2500 degmore » $^2$ of South Pole Telescope (SPT) data supplemented with data from Planck in the same sky region, with the statistical power in the combined map primarily from the SPT data. We fit the corresponding lensing angular power spectrum to a model including cold dark matter and a cosmological constant ($$\\Lambda$$CDM), and to models with single-parameter extensions to $$\\Lambda$$CDM. We find constraints that are comparable to and consistent with constraints found using the full-sky Planck CMB lensing data. Specifically, we find $$\\sigma_8 \\Omega_{\\rm m}^{0.25}=0.598 \\pm 0.024$$ from the lensing data alone with relatively weak priors placed on the other $$\\Lambda$$CDM parameters. In combination with primary CMB data from Planck, we explore single-parameter extensions to the $$\\Lambda$$CDM model. We find $$\\Omega_k = -0.012^{+0.021}_{-0.023}$$ or $$M_{\

Characterization of normal feline renal vascular anatomy with dual-phase CT angiography.

PubMed

Cáceres, Ana V; Zwingenberger, Allison L; Aronson, Lillian R; Mai, Wilfried

2008-01-01

Helical computed tomography angiography was used to evaluate the renal vascular anatomy of potential feline renal donors. One hundred and fourteen computed tomography angiograms were reviewed. The vessels were characterized as single without bifurcation, single with bifurcation, double, or triple. Multiplicity was most commonly seen for the right renal vein (45/114 vs. 3/114 multiple left renal veins, 0/114 multiple right renal arteries, and 8/114 multiple left renal arteries). The right kidney was 13.3 times more likely than the left to have multiple renal veins. Additional vascular variants included double caudal vena cava and an accessory renal artery. For the left kidney, surgery and computed tomography angiography findings were in agreement in 92% of 74 cats. For the right kidney, surgery and computed tomography angiography findings were in agreement in 6/6 cats. Our findings of renal vascular anatomy variations in cats were similar to previous reports in humans. Identifying and recognizing the pattern of distribution of these vessels is important when performing renal transplantation.

Analysis of Potential Affect of The Green Pages Concept for Telephone Directories.

ERIC Educational Resources Information Center

Long, Jim

The project described addressed the feasibility of assessing the impact on low-income persons of the "Green Pages" concept, which seeks to improve the accessibility of public, non-profit, and survival human service agencies and other community information by centralizing them in a single, easy-to-find location in the phone book. This…

More than the "X" Factor! A Longitudinal Investigation of the Psychological Characteristics of Developing Excellence in Musical Development

ERIC Educational Resources Information Center

Macnamara, Aine; Collins, Dave

2009-01-01

Current findings in talent identification and development research have acknowledged that potential for future performance cannot be identified from single evaluations of performance or anthropometric factors (e.g. Abbott and Collins 2004). Recognising the role of psychological characteristics at elite levels, it is pertinent to consider the role…

Demonstration of a Single-Crystal Reflector-Filter for Enhancing Slow Neutron Beams

DOE PAGES

Muhrer, Guenter; Schönfeldt, Troels; Iverson, Erik B.; ...

2016-06-14

The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystalmore » reflector-filter and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains the long-wavelength benefit of the polycrystalline reflector-filter, without suffering the same loss of important intermediate wavelength neutrons. Ultimately, this finding extends the applicability of the reflector-filter concept to intermediate wavelengths, and furthermore indicates that the reflector-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering.« less

Area law from loop quantum gravity

NASA Astrophysics Data System (ADS)

Hamma, Alioscia; Hung, Ling-Yan; Marcianò, Antonino; Zhang, Mingyi

2018-03-01

We explore the constraints following from requiring the area law in the entanglement entropy in the context of loop quantum gravity. We find a unique solution to the single-link wave function in the large j limit, believed to be appropriate in the semiclassical limit. We then generalize our considerations to multilink coherent states, and find that the area law is preserved very generically using our single-link wave function as a building block. Finally, we develop the framework that generates families of multilink states that preserve the area law while avoiding macroscopic entanglement, the space-time analogue of "Schrödinger's cat." We note that these states, defined on a given set of graphs, are the ground states of some local Hamiltonian that can be constructed explicitly. This can potentially shed light on the construction of the appropriate Hamiltonian constraints in the LQG framework.

Study of the Mechanism of Irreversible Adsorption of Single-Walled Carbon Nanotubes to Sephacryl Hydrogel

NASA Astrophysics Data System (ADS)

Rolsma, Caleb

As a class of carbon-based nanomaterials, single-walled carbon nanotubes (SWNT) have many structural variations, called chiralities, each with different properties. Many potential applications of SWNT require the properties of a single chirality, but current synthesis methods can only produce single chiralities at prohibitive costs, or mixtures of chiralities at more affordable prices. Post-synthesis chirality separations provide a solution to this problem, and hydrogel separations are one such method. Despite much work in this field, the underlying interactions between SWNT and hydrogel are not fully understood. During separation, large quantities of SWNT are irretrievably lost due to irreversible adsorption to the hydrogel, posing a major problem to separation efficiency, while also offering an interesting scientific problem concerning the interaction of SWNT with hydrogels and surfactants. This thesis explores the problem of irreversible adsorption, offering an explanation for the process from a mechanistic viewpoint, opening new ways for improvement in separation. In brief, this work concludes adsorption follows three pathways, two of which lead to irreversible adsorption, both mediated by the presence of surfactants and limited by characteristics of the hydrogel surface. These findings stand to increase the general understanding of hydrogel SWNT separations, leading to improvements in separation, and bringing the research field closer to the many potential applications of single-chirality SWNT.

Improving the light-emitting properties of single-layered polyfluorene light-emitting devices by simple ionic liquid blending

NASA Astrophysics Data System (ADS)

Horike, Shohei; Nagaki, Hiroto; Misaki, Masahiro; Koshiba, Yasuko; Morimoto, Masahiro; Fukushima, Tatsuya; Ishida, Kenji

2018-03-01

This paper describes an evaluation of ionic liquids (ILs) as potential electrolytes for single-layered light-emitting devices with good emission performance. As optoelectronic devices continue to grow in abundance, high-performance light-emitting devices with a single emission layer are becoming increasingly important for low-cost production. We show that a simple technique of osmosing IL into the polymer layer can result in high luminous efficiency and good response times of single-layered light-emitting polymers, even without the additional stacking of charge carrier injection and transport layers. The IL contributions to the light-emission of the polymer are discussed from the perspectives of energy diagrams and of the electric double layers on the electrodes. Our findings enable a faster, cheaper, and lower-in-waste production of light-emitting devices.

Density functional theory study of bulk and single-layer magnetic semiconductor CrPS4

NASA Astrophysics Data System (ADS)

Zhuang, Houlong L.; Zhou, Jia

2016-11-01

Searching for two-dimensional (2D) materials with multifunctionality is one of the main goals of current research in 2D materials. Magnetism and semiconducting are certainly two desirable functional properties for a single 2D material. In line with this goal, here we report a density functional theory (DFT) study of bulk and single-layer magnetic semiconductor CrPS4. We find that the ground-state magnetic structure of bulk CrPS4 exhibits the A-type antiferromagnetic ordering, which transforms to ferromagnetic (FM) ordering in single-layer CrPS4. The calculated formation energy and phonon spectrum confirm the stability of single-layer CrPS4. The band gaps of FM single-layer CrPS4 calculated with a hybrid density functional are within the visible-light range. We also study the effects of FM ordering on the optical absorption spectra and band alignments for water splitting, indicating that single-layer CrPS4 could be a potential photocatalyst. Our work opens up ample opportunities of energy-related applications of single-layer CrPS4.

A multistep single-crystal-to-single-crystal bromodiacetylene dimerization

NASA Astrophysics Data System (ADS)

Hoheisel, Tobias N.; Schrettl, Stephen; Marty, Roman; Todorova, Tanya K.; Corminboeuf, Clémence; Sienkiewicz, Andrzej; Scopelliti, Rosario; Schweizer, W. Bernd; Frauenrath, Holger

2013-04-01

Packing constraints and precise placement of functional groups are the reason that organic molecules in the crystalline state often display unusual physical or chemical properties not observed in solution. Here we report a single-crystal-to-single-crystal dimerization of a bromodiacetylene that involves unusually large atom displacements as well as the cleavage and formation of several bonds. Density functional theory computations support a mechanism in which the dimerization is initiated by a [2 + 1] photocycloaddition favoured by the nature of carbon-carbon short contacts in the crystal structure. The reaction proceeded up to the theoretical degree of conversion without loss of crystallinity, and it was also performed on a preparative scale with good yield. Moreover, it represents the first synthetic pathway to (E)-1,2-dibromo-1,2-diethynylethenes, which could serve as synthetic intermediates for the preparation of molecular carbon scaffolds. Our findings both extend the scope of single-crystal-to-single-crystal reactions and highlight their potential as a synthetic tool for complex transformations.

On-Chip Waveguide Coupling of a Layered Semiconductor Single-Photon Source.

PubMed

Tonndorf, Philipp; Del Pozo-Zamudio, Osvaldo; Gruhler, Nico; Kern, Johannes; Schmidt, Robert; Dmitriev, Alexander I; Bakhtinov, Anatoly P; Tartakovskii, Alexander I; Pernice, Wolfram; Michaelis de Vasconcellos, Steffen; Bratschitsch, Rudolf

2017-09-13

Fully integrated quantum technology based on photons is in the focus of current research, because of its immense potential concerning performance and scalability. Ideally, the single-photon sources, the processing units, and the photon detectors are all combined on a single chip. Impressive progress has been made for on-chip quantum circuits and on-chip single-photon detection. In contrast, nonclassical light is commonly coupled onto the photonic chip from the outside, because presently only few integrated single-photon sources exist. Here, we present waveguide-coupled single-photon emitters in the layered semiconductor gallium selenide as promising on-chip sources. GaSe crystals with a thickness below 100 nm are placed on Si 3 N 4 rib or slot waveguides, resulting in a modified mode structure efficient for light coupling. Using optical excitation from within the Si 3 N 4 waveguide, we find nonclassicality of generated photons routed on the photonic chip. Thus, our work provides an easy-to-implement and robust light source for integrated quantum technology.

Task Allocation for Single Pilot Operations: A Role for the Ground

NASA Technical Reports Server (NTRS)

Johnson, Walter; Lachter, Joel; Feary, Mike; Comerford, Doreen; Battiste, Vernol; Mogford, Richard

2012-01-01

Researchers at NASA Ames Research Center and NASA Langley Research Center are jointly investigating issues associated with potential configurations for an environment in which a single pilot, or reduced crew, might operate. The research summarized in this document represents several of the efforts being put forth at NASA Ames Research Center. Specifically, researchers at NASA Ames Research Center coordinated and hosted a technical interchange meeting in order to gain insight from members of the aviation community. A description of this meeting and the findings are presented first. Thereafter, plans for ensuing research are presented.

Characterizing water-metal interfaces and machine learning potential energy surfaces

NASA Astrophysics Data System (ADS)

Ryczko, Kevin

In this thesis, we first discuss the fundamentals of ab initio electronic structure theory and density functional theory (DFT). We also discuss statistics related to computing thermodynamic averages of molecular dynamics (MD). We then use this theory to analyze and compare the structural, dynamical, and electronic properties of liquid water next to prototypical metals including platinum, graphite, and graphene. Our results are built on Born-Oppenheimer molecular dynamics (BOMD) generated using density functional theory (DFT) which explicitly include van der Waals (vdW) interactions within a first principles approach. All calculations reported use large simulation cells, allowing for an accurate treatment of the water-electrode interfaces. We have included vdW interactions through the use of the optB86b-vdW exchange correlation functional. Comparisons with the Perdew-Burke-Ernzerhof (PBE) exchange correlation functional are also shown. We find an initial peak, due to chemisorption, in the density profile of the liquid water-Pt interface not seen in the liquid water-graphite interface, liquid watergraphene interface, nor interfaces studied previously. To further investigate this chemisorption peak, we also report differences in the electronic structure of single water molecules on both Pt and graphite surfaces. We find that a covalent bond forms between the single water molecule and the platinum surface, but not between the single water molecule and the graphite surface. We also discuss the effects that defects and dopants in the graphite and graphene surfaces have on the structure and dynamics of liquid water. Lastly, we introduce artificial neural networks (ANNs), and demonstrate how they can be used to machine learn electronic structure calculations. As a proof of principle, we show the success of an ANN potential energy surfaces for a dimer molecule with a Lennard-Jones potential.

Syntactic and semantic processing of Chinese middle sentences: evidence from event-related potentials.

PubMed

Zeng, Tao; Mao, Wen; Lu, Qing

2016-05-25

Scalp-recorded event-related potentials are known to be sensitive to particular aspects of sentence processing. The N400 component is widely recognized as an effect closely related to lexical-semantic processing. The absence of an N400 effect in participants performing tasks in Indo-European languages has been considered evidence that failed syntactic category processing appears to block lexical-semantic integration and that syntactic structure building is a prerequisite of semantic analysis. An event-related potential experiment was designed to investigate whether such syntactic primacy can be considered to apply equally to Chinese sentence processing. Besides correct middles, sentences with either single semantic or single syntactic violation as well as double syntactic and semantic anomaly were used in the present research. Results showed that both purely semantic and combined violation induced a broad negativity in the time window 300-500 ms, indicating the independence of lexical-semantic integration. These findings provided solid evidence that lexical-semantic parsing plays a crucial role in Chinese sentence comprehension.

Effects of Shared Active Surface Technology on the Communication and Speech of Two Preschool Children with Disabilities

ERIC Educational Resources Information Center

Travers, Jason C.; Fefer, Sarah A.

2017-01-01

Shared active surface (SAS) technology can be described as a supersized tablet computer for multiple simultaneous users. SAS technology has the potential to resolve issues historically associated with learning via single-user computer technology. This study reports findings of a SAS on the social communication and nonsocial speech of two preschool…

Collective intelligence meets medical decision-making: the collective outperforms the best radiologist.

PubMed

Wolf, Max; Krause, Jens; Carney, Patricia A; Bogart, Andy; Kurvers, Ralf H J M

2015-01-01

While collective intelligence (CI) is a powerful approach to increase decision accuracy, few attempts have been made to unlock its potential in medical decision-making. Here we investigated the performance of three well-known collective intelligence rules ("majority", "quorum", and "weighted quorum") when applied to mammography screening. For any particular mammogram, these rules aggregate the independent assessments of multiple radiologists into a single decision (recall the patient for additional workup or not). We found that, compared to single radiologists, any of these CI-rules both increases true positives (i.e., recalls of patients with cancer) and decreases false positives (i.e., recalls of patients without cancer), thereby overcoming one of the fundamental limitations to decision accuracy that individual radiologists face. Importantly, we find that all CI-rules systematically outperform even the best-performing individual radiologist in the respective group. Our findings demonstrate that CI can be employed to improve mammography screening; similarly, CI may have the potential to improve medical decision-making in a much wider range of contexts, including many areas of diagnostic imaging and, more generally, diagnostic decisions that are based on the subjective interpretation of evidence.

Action potentials reliably invade axonal arbors of rat neocortical neurons

PubMed Central

Cox, Charles L.; Denk, Winfried; Tank, David W.; Svoboda, Karel

2000-01-01

Neocortical pyramidal neurons have extensive axonal arborizations that make thousands of synapses. Action potentials can invade these arbors and cause calcium influx that is required for neurotransmitter release and excitation of postsynaptic targets. Thus, the regulation of action potential invasion in axonal branches might shape the spread of excitation in cortical neural networks. To measure the reliability and extent of action potential invasion into axonal arbors, we have used two-photon excitation laser scanning microscopy to directly image action-potential-mediated calcium influx in single varicosities of layer 2/3 pyramidal neurons in acute brain slices. Our data show that single action potentials or bursts of action potentials reliably invade axonal arbors over a range of developmental ages (postnatal 10–24 days) and temperatures (24°C-30°C). Hyperpolarizing current steps preceding action potential initiation, protocols that had previously been observed to produce failures of action potential propagation in cultured preparations, were ineffective in modulating the spread of action potentials in acute slices. Our data show that action potentials reliably invade the axonal arbors of neocortical pyramidal neurons. Failures in synaptic transmission must therefore originate downstream of action potential invasion. We also explored the function of modulators that inhibit presynaptic calcium influx. Consistent with previous studies, we find that adenosine reduces action-potential-mediated calcium influx in presynaptic terminals. This reduction was observed in all terminals tested, suggesting that some modulatory systems are expressed homogeneously in most terminals of the same neuron. PMID:10931955

Label-free optical detection of single-base mismatches by the combination of nuclease and gold nanoparticles.

PubMed

Liu, Meiying; Yuan, Min; Lou, Xinhui; Mao, Hongju; Zheng, Dongmei; Zou, Ruxing; Zou, Nengli; Tang, Xiangrong; Zhao, Jianlong

2011-07-15

We report here an optical approach that enables highly selective and colorimetric single-base mismatch detection without the need of target modification, precise temperature control or stringent washes. The method is based on the finding that nucleoside monophosphates (dNMPs), which are digested elements of DNA, can better stabilize unmodified gold nanoparticles (AuNPs) than single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) with the same base-composition and concentration. The method combines the exceptional mismatch discrimination capability of the structure-selective nucleases with the attractive optical property of AuNPs. Taking S1 nuclease as one example, the perfectly matched 16-base synthetic DNA target was distinctively differentiated from those with single-base mutation located at any position of the 16-base synthetic target. Single-base mutations present in targets with varied length up to 80-base, located either in the middle or near to the end of the targets, were all effectively detected. In order to prove that the method can be potentially used for real clinic samples, the single-base mismatch detections with two HBV genomic DNA samples were conducted. To further prove the generality of this method and potentially overcome the limitation on the detectable lengths of the targets of the S1 nuclease-based method, we also demonstrated the use of a duplex-specific nuclease (DSN) for color reversed single-base mismatch detection. The main limitation of the demonstrated methods is that it is limited to detect mutations in purified ssDNA targets. However, the method coupled with various convenient ssDNA generation and purification techniques, has the potential to be used for the future development of detector-free testing kits in single nucleotide polymorphism screenings for disease diagnostics and treatments. Copyright © 2011 Elsevier B.V. All rights reserved.

Metabolic Imaging in Multiple Time Scales

PubMed Central

Ramanujan, V Krishnan

2013-01-01

We report here a novel combination of time-resolved imaging methods for probing mitochondrial metabolism multiple time scales at the level of single cells. By exploiting a mitochondrial membrane potential reporter fluorescence we demonstrate the single cell metabolic dynamics in time scales ranging from milliseconds to seconds to minutes in response to glucose metabolism and mitochondrial perturbations in real time. Our results show that in comparison with normal human mammary epithelial cells, the breast cancer cells display significant alterations in metabolic responses at all measured time scales by single cell kinetics, fluorescence recovery after photobleaching and by scaling analysis of time-series data obtained from mitochondrial fluorescence fluctuations. Furthermore scaling analysis of time-series data in living cells with distinct mitochondrial dysfunction also revealed significant metabolic differences thereby suggesting the broader applicability (e.g. in mitochondrial myopathies and other metabolic disorders) of the proposed strategies beyond the scope of cancer metabolism. We discuss the scope of these findings in the context of developing portable, real-time metabolic measurement systems that can find applications in preclinical and clinical diagnostics. PMID:24013043

Precise Synaptic Efficacy Alignment Suggests Potentiation Dominated Learning.

PubMed

Hartmann, Christoph; Miner, Daniel C; Triesch, Jochen

2015-01-01

Recent evidence suggests that parallel synapses from the same axonal branch onto the same dendritic branch have almost identical strength. It has been proposed that this alignment is only possible through learning rules that integrate activity over long time spans. However, learning mechanisms such as spike-timing-dependent plasticity (STDP) are commonly assumed to be temporally local. Here, we propose that the combination of temporally local STDP and a multiplicative synaptic normalization mechanism is sufficient to explain the alignment of parallel synapses. To address this issue, we introduce three increasingly complex models: First, we model the idealized interaction of STDP and synaptic normalization in a single neuron as a simple stochastic process and derive analytically that the alignment effect can be described by a so-called Kesten process. From this we can derive that synaptic efficacy alignment requires potentiation-dominated learning regimes. We verify these conditions in a single-neuron model with independent spiking activities but more realistic synapses. As expected, we only observe synaptic efficacy alignment for long-term potentiation-biased STDP. Finally, we explore how well the findings transfer to recurrent neural networks where the learning mechanisms interact with the correlated activity of the network. We find that due to the self-reinforcing correlations in recurrent circuits under STDP, alignment occurs for both long-term potentiation- and depression-biased STDP, because the learning will be potentiation dominated in both cases due to the potentiating events induced by correlated activity. This is in line with recent results demonstrating a dominance of potentiation over depression during waking and normalization during sleep. This leads us to predict that individual spine pairs will be more similar after sleep compared to after sleep deprivation. In conclusion, we show that synaptic normalization in conjunction with coordinated potentiation--in this case, from STDP in the presence of correlated pre- and post-synaptic activity--naturally leads to an alignment of parallel synapses.

Trends in Adsorption Energies of the Oxygenated Species on Single Platinum Atom Embedded in Carbon Nanotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siahrostami, Samira; Li, Guo-Ling; Nørskov, Jens K.

Herein we study the effect of strain on the catalytic activity of different Pt-doped single wall metallic carbon nanotubes (SWCNT) towards the oxygen reduction reaction (ORR). We consider the possibility of the Pt-doped at single vacancy inside the SWCNT to investigate the effect of confinement on the reaction mechanism. Density functional theory calculations indicate that for the SWCNTs with tube diameters below 7 Å, the strain energy varies significantly influencing the adsorption energies of the key intermediates of the ORR reaction. For the SWCNTs with tube diameters above 7 Å, on the other hand, both the calculated strain and themore » adsorption energies are almost constant. We furthermore find that the adsorption energies are strongly affected by confinement effects as shown for Pt-doped systems that are located inside the SWCNT. We show that the Pt-doped at single vacancy of the SWCNT strongly binds the oxygenated species under ORR potentials and therefore the active species is covered by oxo- or hydroxo group. Because the presence of Pt atoms doped at the single and double vacancies of the SWCNT is equivalently probable we also studied the Pt-doped at double vacancy. We find that the most active motif is the Pt-doped at double vacancy of SWCNT with 0.24V overpotenital.« less

Trends in Adsorption Energies of the Oxygenated Species on Single Platinum Atom Embedded in Carbon Nanotubes

DOE PAGES

Siahrostami, Samira; Li, Guo-Ling; Nørskov, Jens K.; ...

2017-09-30

Herein we study the effect of strain on the catalytic activity of different Pt-doped single wall metallic carbon nanotubes (SWCNT) towards the oxygen reduction reaction (ORR). We consider the possibility of the Pt-doped at single vacancy inside the SWCNT to investigate the effect of confinement on the reaction mechanism. Density functional theory calculations indicate that for the SWCNTs with tube diameters below 7 Å, the strain energy varies significantly influencing the adsorption energies of the key intermediates of the ORR reaction. For the SWCNTs with tube diameters above 7 Å, on the other hand, both the calculated strain and themore » adsorption energies are almost constant. We furthermore find that the adsorption energies are strongly affected by confinement effects as shown for Pt-doped systems that are located inside the SWCNT. We show that the Pt-doped at single vacancy of the SWCNT strongly binds the oxygenated species under ORR potentials and therefore the active species is covered by oxo- or hydroxo group. Because the presence of Pt atoms doped at the single and double vacancies of the SWCNT is equivalently probable we also studied the Pt-doped at double vacancy. We find that the most active motif is the Pt-doped at double vacancy of SWCNT with 0.24V overpotenital.« less

The stressors and vulnerabilities of young single childless women with breast cancer: a qualitative study.

PubMed

Corney, Roslyn; Puthussery, Shuby; Swinglehurst, Jane

2014-02-01

Marital or partnership status is seldom investigated as a primary contributing factor to women's wellbeing after a diagnosis of breast cancer. It has been suggested, however, that single childless women with breast cancer may face unique stressors. This paper explores the stressors and vulnerabilities of young single childless women with a first episode of breast cancer. A qualitative descriptive method was used. As part of a larger study examining fertility concerns of young childless women with first episode of breast cancer, in-depth semi-structured interviews were conducted with 10 single women. Recorded interviews were analysed using the framework approach. Findings cover three main themes: partnership worries; fertility concerns; and views about emotional and practical support received. Partnership worries included concerns about having to undergo treatment without a partner to support them; the fear of rejection by potential partners; and feelings about the precious time lost in diagnosis and treatment. Fertility concerns included dilemmas about having children and feelings about the options of pursuing Assisted Reproductive Techniques. Views about the emotional and practical support received included the overall support received as well as perceptions about the attitudes of health professionals towards fertility issues. Findings indicate that single childless women with breast cancer face additional vulnerabilities and may benefit from tailored support from health care professionals and interventions specifically targeted at them. Copyright © 2013 Elsevier Ltd. All rights reserved.

Triggered generation of single guided photons from a single atom in a nanofiber cavity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Kien, Fam; Hakuta, K.

2011-04-15

We study the deterministic generation of single guided-mode photons from an atom in the vicinity of a nanofiber with two fiber-Bragg-grating (FBG) mirrors. The technique is based on a cavity-enhanced Raman scattering process involving an adiabatic passage. We take into account the scattering of the pump field from the fiber, the multilevel structure of the atom, and the surface-induced van der Waals potential in describing the photon generation process. We find that, due to the confinement of the cavity field in the transverse plane of the fiber and in the space between the FBG mirrors, the probability of the generationmore » of a single guided-mode photon can be close to unity even when the finesse of the nanofiber cavity is moderate. We show the possibilities of saturation and power broadening in the behavior of the number of photons emitted into the nanofiber.« less

Dynamics of lineage commitment revealed by single-cell transcriptomics of differentiating embryonic stem cells.

PubMed

Semrau, Stefan; Goldmann, Johanna E; Soumillon, Magali; Mikkelsen, Tarjei S; Jaenisch, Rudolf; van Oudenaarden, Alexander

2017-10-23

Gene expression heterogeneity in the pluripotent state of mouse embryonic stem cells (mESCs) has been increasingly well-characterized. In contrast, exit from pluripotency and lineage commitment have not been studied systematically at the single-cell level. Here we measure the gene expression dynamics of retinoic acid driven mESC differentiation from pluripotency to lineage commitment, using an unbiased single-cell transcriptomics approach. We find that the exit from pluripotency marks the start of a lineage transition as well as a transient phase of increased susceptibility to lineage specifying signals. Our study reveals several transcriptional signatures of this phase, including a sharp increase of gene expression variability and sequential expression of two classes of transcriptional regulators. In summary, we provide a comprehensive analysis of the exit from pluripotency and lineage commitment at the single cell level, a potential stepping stone to improved lineage manipulation through timing of differentiation cues.

Bifurcation and stability of single and multiple vortex rings in three-dimensional Bose-Einstein condensates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bisset, R. N.; Wang, Wenlong; Ticknor, C.

Here, we investigate how single- and multi-vortex-ring states can emerge from a planar dark soliton in three-dimensional (3D) Bose-Einstein condensates (confined in isotropic or anisotropic traps) through bifurcations. We characterize such bifurcations quantitatively using a Galerkin-type approach and find good qualitative and quantitative agreement with our Bogoliubov–de Gennes (BdG) analysis. We also systematically characterize the BdG spectrum of the dark solitons, using perturbation theory, and obtain a quantitative match with our 3D BdG numerical calculations. We then turn our attention to the emergence of single- and multi-vortex-ring states. We systematically capture these as stationary states of the system and quantifymore » their BdG spectra numerically. We found that although the vortex ring may be unstable when bifurcating, its instabilities weaken and may even eventually disappear for sufficiently large chemical potentials and suitable trap settings. For instance, we demonstrate the stability of the vortex ring for an isotropic trap in the large-chemical-potential regime.« less

Bifurcation and stability of single and multiple vortex rings in three-dimensional Bose-Einstein condensates

DOE PAGES

Bisset, R. N.; Wang, Wenlong; Ticknor, C.; ...

2015-10-01

Here, we investigate how single- and multi-vortex-ring states can emerge from a planar dark soliton in three-dimensional (3D) Bose-Einstein condensates (confined in isotropic or anisotropic traps) through bifurcations. We characterize such bifurcations quantitatively using a Galerkin-type approach and find good qualitative and quantitative agreement with our Bogoliubov–de Gennes (BdG) analysis. We also systematically characterize the BdG spectrum of the dark solitons, using perturbation theory, and obtain a quantitative match with our 3D BdG numerical calculations. We then turn our attention to the emergence of single- and multi-vortex-ring states. We systematically capture these as stationary states of the system and quantifymore » their BdG spectra numerically. We found that although the vortex ring may be unstable when bifurcating, its instabilities weaken and may even eventually disappear for sufficiently large chemical potentials and suitable trap settings. For instance, we demonstrate the stability of the vortex ring for an isotropic trap in the large-chemical-potential regime.« less

Evidence of Magnetic Inversion in Single Ni Nanoparticles

DOE PAGES

Jiang, W.; Gartland, P.; Davidović, D.

2016-11-08

Superparamagnetism is an unwanted property of small magnetic particles where the magnetization of the particle flips randomly in time, due to thermal noise. There has been an increased attention in the properties of superparamagnetic particles recently, because of their potential applications in high density storage and medicine. In electron transport through single nanometer scale magnetic particles, the current can also cause the magnetization to flip randomly in time, even at low temperature. Here we show experimental evidence that when the current is then reduced towards zero in the applied magnetic field, the magnetization can reliably freeze about a higher anisotropy-energymore » minimum, where it tends to be inverted with respect to the magnetic field direction. Specifically, we use spin-unpolarized tunneling spectroscopy of discrete levels in single Ni particles 2–4 nm in diameter at mK-temperature, and find that the the magnetic excitation energy at the onset of current decreases when the magnetic field increases, reaching near degeneracy at nonzero magnetic field. We discuss the potential for spintronic applications such as current induced magnetization switching without any spin-polarized leads.« less

Evidence of Magnetic Inversion in Single Ni Nanoparticles

PubMed Central

Jiang, W.; Gartland, P.; Davidović, D.

2016-01-01

Superparamagnetism is an unwanted property of small magnetic particles where the magnetization of the particle flips randomly in time, due to thermal noise. There has been an increased attention in the properties of superparamagnetic particles recently, because of their potential applications in high density storage and medicine. In electron transport through single nanometer scale magnetic particles, the current can also cause the magnetization to flip randomly in time, even at low temperature. Here we show experimental evidence that when the current is then reduced towards zero in the applied magnetic field, the magnetization can reliably freeze about a higher anisotropy-energy minimum, where it tends to be inverted with respect to the magnetic field direction. Specifically, we use spin-unpolarized tunneling spectroscopy of discrete levels in single Ni particles 2–4 nm in diameter at mK-temperature, and find that the the magnetic excitation energy at the onset of current decreases when the magnetic field increases, reaching near degeneracy at nonzero magnetic field. We discuss the potential for spintronic applications such as current induced magnetization switching without any spin-polarized leads. PMID:27824076

Potential impact of single-risk-factor versus total risk management for the prevention of cardiovascular events in Seychelles

PubMed Central

Ndindjock, Roger; Gedeon, Jude; Mendis, Shanthi; Paccaud, Fred

2011-01-01

Abstract Objective To assess the prevalence of cardiovascular (CV) risk factors in Seychelles, a middle-income African country, and compare the cost-effectiveness of single-risk-factor management (treating individuals with arterial blood pressure ≥ 140/90 mmHg and/or total serum cholesterol ≥ 6.2 mmol/l) with that of management based on total CV risk (treating individuals with a total CV risk ≥ 10% or ≥ 20%). Methods CV risk factor prevalence and a CV risk prediction chart for Africa were used to estimate the 10-year risk of suffering a fatal or non-fatal CV event among individuals aged 40–64 years. These figures were used to compare single-risk-factor management with total risk management in terms of the number of people requiring treatment to avert one CV event and the number of events potentially averted over 10 years. Treatment for patients with high total CV risk (≥ 20%) was assumed to consist of a fixed-dose combination of several drugs (polypill). Cost analyses were limited to medication. Findings A total CV risk of ≥ 10% and ≥ 20% was found among 10.8% and 5.1% of individuals, respectively. With single-risk-factor management, 60% of adults would need to be treated and 157 cardiovascular events per 100 000 population would be averted per year, as opposed to 5% of adults and 92 events with total CV risk management. Management based on high total CV risk optimizes the balance between the number requiring treatment and the number of CV events averted. Conclusion Total CV risk management is much more cost-effective than single-risk-factor management. These findings are relevant for all countries, but especially for those economically and demographically similar to Seychelles. PMID:21479093

3-dimensional dark traps for low refractive index bio-cells using a single optical fiber Bessel beam.

PubMed

Zhang, Yu; Tang, Xiaoyun; Zhang, Yaxun; Su, Wenjie; Liu, Zhihai; Yang, Xinghua; Zhang, Jianzhong; Yang, Jun; Oh, Kyunghwan; Yuan, Libo

2018-06-15

We proposed and experimentally demonstrated 3-dimensional dark traps for low refractive index bio-cells using a single optical fiber Bessel beam. The Bessel beam was produced by concatenating single-mode fiber and a step index multimode fiber, which was then focused by a high refractive index glass microsphere integrated on the fiber end facet. The focused Bessel beam provided two dark fields along the axial direction, where stable trapping of low refractive index bio-cells was realized in a high refractive index liquid bath. The all-fiber and seamlessly integrated structure of the proposed scheme can find ample potential as a micro-optical probe in in situ characterization and manipulation of multiple bio-cells with refractive indices lower than that of the liquid bath.

Unsupported single-atom-thick copper oxide monolayers

NASA Astrophysics Data System (ADS)

Yin, Kuibo; Zhang, Yu-Yang; Zhou, Yilong; Sun, Litao; Chisholm, Matthew F.; Pantelides, Sokrates T.; Zhou, Wu

2017-03-01

Oxide monolayers may present unique opportunities because of the great diversity of properties of these materials in bulk form. However, reports on oxide monolayers are still limited. Here we report the formation of single-atom-thick copper oxide layers with a square lattice both in graphene pores and on graphene substrates using aberration-corrected scanning transmission electron microscopy. First-principles calculations find that CuO is energetically stable and its calculated lattice spacing matches well with the measured value. Furthermore, free-standing copper oxide monolayers are predicted to be semiconductors with band gaps ˜3 eV. The new wide-bandgap single-atom-thick copper oxide monolayers usher a new frontier to study the highly diverse family of two-dimensional oxides and explore their properties and their potential for new applications.

Gate tunable spin transport in graphene with Rashba spin-orbit coupling

NASA Astrophysics Data System (ADS)

Tan, Xiao-Dong; Liao, Xiao-Ping; Sun, Litao

2016-10-01

Recently, it attracts much attention to study spin-resolved transport properties in graphene with Rashba spin-orbit coupling (RSOC). One remarkable finding is that Klein tunneling in single layer graphene (SLG) with RSOC (SLG + R for short below) behaves as in bi-layer graphene (BLG). Based on the effective Dirac theory, we reconsider this tunneling problem and derive the analytical solution for the transmission coefficients. Our result shows that Klein tunneling in SLG + R and BLG exhibits completely different behaviors. More importantly, we find two new transmission selection rules in SLG + R, i.e., the single band to single band (S → S) and the single band to multiple bands (S → M) transmission regimes, which strongly depend on the relative height among Fermi level, RSOC, and potential barrier. Interestingly, in the S → S transmission regime, only normally incident electrons have capacity to pass through the barrier, while in the S → M transmission regime the angle-dependent tunneling becomes very prominent. Using the transmission coefficients, we also derive spin-resolved conductance analytically, and conductance oscillation with the increasing barrier height and zero conductance gap are found in SLG + R. The present study offers new insights and opportunities for developing graphene-based spin devices.

Integrated studies of uncultured microbes in the global ocean (Invited)

NASA Astrophysics Data System (ADS)

Dupont, C.; Rusch, D.; Martiny, A.; Lasken, R.

2010-12-01

The Global Ocean Sampling (GOS) initiative at the J. Craig Venter Institute represents the most extensive metagenomic study of a single environment. Early findings highlighted the potential of shotgun metagenomics to expand our knowledge of marine microbial biodiversity and physiology. However, it also became clear that many of the abundant marine microbes remain uncultured, hindering a direct connection between phylogeny and ecophysiology. In two recent studies, a combination of single cell genomics and aggressive assembly of binned metagenomic data have resulted in the acquisition of multiple genomes for two uncultured but globally relevant organisms. Metabolic reconstructions of the whole genomes revealed unique physiological adaptations in marine Prochlorococcus to high nutrient, low Fe regions of the global ocean and illuminated the potential ecological role of the gamma-proteobacterial 16S clade SAR86. The internal reference genomes also facilitate fragment recruitment based biogeographical studies, both at the whole genome level and the protein level.

Tracking individual action potentials throughout mammalian axonal arbors.

PubMed

Radivojevic, Milos; Franke, Felix; Altermatt, Michael; Müller, Jan; Hierlemann, Andreas; Bakkum, Douglas J

2017-10-09

Axons are neuronal processes specialized for conduction of action potentials (APs). The timing and temporal precision of APs when they reach each of the synapses are fundamentally important for information processing in the brain. Due to small diameters of axons, direct recording of single AP transmission is challenging. Consequently, most knowledge about axonal conductance derives from modeling studies or indirect measurements. We demonstrate a method to noninvasively and directly record individual APs propagating along millimeter-length axonal arbors in cortical cultures with hundreds of microelectrodes at microsecond temporal resolution. We find that cortical axons conduct single APs with high temporal precision (~100 µs arrival time jitter per mm length) and reliability: in more than 8,000,000 recorded APs, we did not observe any conduction or branch-point failures. Upon high-frequency stimulation at 100 Hz, successive became slower, and their arrival time precision decreased by 20% and 12% for the 100th AP, respectively.

Measuring the mechanical properties of molecular conformers

NASA Astrophysics Data System (ADS)

Jarvis, S. P.; Taylor, S.; Baran, J. D.; Champness, N. R.; Larsson, J. A.; Moriarty, P.

2015-09-01

Scanning probe-actuated single molecule manipulation has proven to be an exceptionally powerful tool for the systematic atomic-scale interrogation of molecular adsorbates. To date, however, the extent to which molecular conformation affects the force required to push or pull a single molecule has not been explored. Here we probe the mechanochemical response of two tetra(4-bromophenyl)porphyrin conformers using non-contact atomic force microscopy where we find a large difference between the lateral forces required for manipulation. Remarkably, despite sharing very similar adsorption characteristics, variations in the potential energy surface are capable of prohibiting probe-induced positioning of one conformer, while simultaneously permitting manipulation of the alternative conformational form. Our results are interpreted in the context of dispersion-corrected density functional theory calculations which reveal significant differences in the diffusion barriers for each conformer. These results demonstrate that conformational variation significantly modifies the mechanical response of even simple porpyhrins, potentially affecting many other flexible molecules.

Photoisomerization-induced manipulation of single-electron tunneling for novel Si-based optical memory.

PubMed

Hayakawa, Ryoma; Higashiguchi, Kenji; Matsuda, Kenji; Chikyow, Toyohiro; Wakayama, Yutaka

2013-11-13

We demonstrated optical manipulation of single-electron tunneling (SET) by photoisomerization of diarylethene molecules in a metal-insulator-semiconductor (MIS) structure. Stress is placed on the fact that device operation is realized in the practical device configuration of MIS structure and that it is not achieved in structures based on nanogap electrodes and scanning probe techniques. Namely, this is a basic memory device configuration that has the potential for large-scale integration. In our device, the threshold voltage of SET was clearly modulated as a reversible change in the molecular orbital induced by photoisomerization, indicating that diarylethene molecules worked as optically controllable quantum dots. These findings will allow the integration of photonic functionality into current Si-based memory devices, which is a unique feature of organic molecules that is unobtainable with inorganic materials. Our proposed device therefore has enormous potential for providing a breakthrough in Si technology.

Constraints on Cosmological Parameters from the Angular Power Spectrum of a Combined 2500 deg$^2$ SPT-SZ and Planck Gravitational Lensing Map

DOE PAGES

Simard, G.; et al.

2018-06-20

We report constraints on cosmological parameters from the angular power spectrum of a cosmic microwave background (CMB) gravitational lensing potential map created using temperature data from 2500 degmore » $^2$ of South Pole Telescope (SPT) data supplemented with data from Planck in the same sky region, with the statistical power in the combined map primarily from the SPT data. We fit the corresponding lensing angular power spectrum to a model including cold dark matter and a cosmological constant ($$\\Lambda$$CDM), and to models with single-parameter extensions to $$\\Lambda$$CDM. We find constraints that are comparable to and consistent with constraints found using the full-sky Planck CMB lensing data. Specifically, we find $$\\sigma_8 \\Omega_{\\rm m}^{0.25}=0.598 \\pm 0.024$$ from the lensing data alone with relatively weak priors placed on the other $$\\Lambda$$CDM parameters. In combination with primary CMB data from Planck, we explore single-parameter extensions to the $$\\Lambda$$CDM model. We find $$\\Omega_k = -0.012^{+0.021}_{-0.023}$$ or $$M_{\

Constraints on Cosmological Parameters from the Angular Power Spectrum of a Combined 2500 deg$^2$ SPT-SZ and Planck Gravitational Lensing Map

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simard, G.; et al.

We report constraints on cosmological parameters from the angular power spectrum of a cosmic microwave background (CMB) gravitational lensing potential map created using temperature data from 2500 degmore » $^2$ of South Pole Telescope (SPT) data supplemented with data from Planck in the same sky region, with the statistical power in the combined map primarily from the SPT data. We fit the corresponding lensing angular power spectrum to a model including cold dark matter and a cosmological constant ($$\\Lambda$$CDM), and to models with single-parameter extensions to $$\\Lambda$$CDM. We find constraints that are comparable to and consistent with constraints found using the full-sky Planck CMB lensing data. Specifically, we find $$\\sigma_8 \\Omega_{\\rm m}^{0.25}=0.598 \\pm 0.024$$ from the lensing data alone with relatively weak priors placed on the other $$\\Lambda$$CDM parameters. In combination with primary CMB data from Planck, we explore single-parameter extensions to the $$\\Lambda$$CDM model. We find $$\\Omega_k = -0.012^{+0.021}_{-0.023}$$ or $$M_{\

Single exposure EUV patterning of BEOL metal layers on the IMEC iN7 platform

NASA Astrophysics Data System (ADS)

Blanco Carballo, V. M.; Bekaert, J.; Mao, M.; Kutrzeba Kotowska, B.; Larivière, S.; Ciofi, I.; Baert, R.; Kim, R. H.; Gallagher, E.; Hendrickx, E.; Tan, L. E.; Gillijns, W.; Trivkovic, D.; Leray, P.; Halder, S.; Gallagher, M.; Lazzarino, F.; Paolillo, S.; Wan, D.; Mallik, A.; Sherazi, Y.; McIntyre, G.; Dusa, M.; Rusu, P.; Hollink, T.; Fliervoet, T.; Wittebrood, F.

2017-03-01

This paper summarizes findings on the iN7 platform (foundry N5 equivalent) for single exposure EUV (SE EUV) of M1 and M2 BEOL layers. Logic structures within these layers have been measured after litho and after etch, and variability was characterized both with conventional CD-SEM measurements as well as Hitachi contouring method. After analyzing the patterning of these layers, the impact of variability on potential interconnect reliability was studied by using MonteCarlo and process emulation simulations to determine if current litho/etch performance would meet success criteria for the given platform design rules.

Constant-roll (quasi-)linear inflation

NASA Astrophysics Data System (ADS)

Karam, A.; Marzola, L.; Pappas, T.; Racioppi, A.; Tamvakis, K.

2018-05-01

In constant-roll inflation, the scalar field that drives the accelerated expansion of the Universe is rolling down its potential at a constant rate. Within this framework, we highlight the relations between the Hubble slow-roll parameters and the potential ones, studying in detail the case of a single-field Coleman-Weinberg model characterised by a non-minimal coupling of the inflaton to gravity. With respect to the exact constant-roll predictions, we find that assuming an approximate slow-roll behaviour yields a difference of Δ r = 0.001 in the tensor-to-scalar ratio prediction. Such a discrepancy is in principle testable by future satellite missions. As for the scalar spectral index ns, we find that the existing 2-σ bound constrains the value of the non-minimal coupling to ξphi ~ 0.29–0.31 in the model under consideration.

Observational constraints on Tachyon and DBI inflation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Sheng; Liddle, Andrew R., E-mail: sl277@sussex.ac.uk, E-mail: arl@roe.ac.uk

2014-03-01

We present a systematic method for evaluation of perturbation observables in non-canonical single-field inflation models within the slow-roll approximation, which allied with field redefinitions enables predictions to be established for a wide range of models. We use this to investigate various non-canonical inflation models, including Tachyon inflation and DBI inflation. The Lambert W function will be used extensively in our method for the evaluation of observables. In the Tachyon case, in the slow-roll approximation the model can be approximated by a canonical field with a redefined potential, which yields predictions in better agreement with observations than the canonical equivalents. Formore » DBI inflation models we consider contributions from both the scalar potential and the warp geometry. In the case of a quartic potential, we find a formula for the observables under both non-relativistic (sound speed c{sub s}{sup 2} ∼ 1) and relativistic behaviour (c{sub s}{sup 2} || 1) of the scalar DBI inflaton. For a quadratic potential we find two branches in the non-relativistic c{sub s}{sup 2} ∼ 1 case, determined by the competition of model parameters, while for the relativistic case c{sub s}{sup 2} → 0, we find consistency with results already in the literature. We present a comparison to the latest Planck satellite observations. Most of the non-canonical models we investigate, including the Tachyon, are better fits to data than canonical models with the same potential, but we find that DBI models in the slow-roll regime have difficulty in matching the data.« less

Goldstone inflation

NASA Astrophysics Data System (ADS)

Croon, Djuna; Sanz, Verónica; Setford, Jack

2015-10-01

Identifying the inflaton with a pseudo-Goldstone boson explains the flatness of its potential. Successful Goldstone Inflation should also be robust against UV corrections, such as from quantum gravity: in the language of the effective field theory this implies that all scales are sub-Planckian. In this paper we present scenarios which realise both requirements by examining the structure of Goldstone potentials arising from Coleman-Weinberg contributions. We focus on single-field models, for which we notice that both bosonic and fermionic contributions are required and that spinorial fermion representations can generate the right potential shape. We then evaluate the constraints on non-Gaussianity from higher-derivative interactions, finding that axiomatic constraints on Goldstone boson scattering prevail over the current CMB measurements. The fit to CMB data can be connected to the UV completions for Goldstone Inflation, finding relations in the spectrum of new resonances. Finally, we show how hybrid inflation can be realised in the same context, where both the inflaton and the waterfall fields share a common origin as Goldstones.

The steady-state visual evoked potential in vision research: A review

PubMed Central

Norcia, Anthony M.; Appelbaum, L. Gregory; Ales, Justin M.; Cottereau, Benoit R.; Rossion, Bruno

2015-01-01

Periodic visual stimulation and analysis of the resulting steady-state visual evoked potentials were first introduced over 80 years ago as a means to study visual sensation and perception. From the first single-channel recording of responses to modulated light to the present use of sophisticated digital displays composed of complex visual stimuli and high-density recording arrays, steady-state methods have been applied in a broad range of scientific and applied settings.The purpose of this article is to describe the fundamental stimulation paradigms for steady-state visual evoked potentials and to illustrate these principles through research findings across a range of applications in vision science. PMID:26024451

Simultaneous fluorescence and quantitative phase microscopy with single-pixel detectors

NASA Astrophysics Data System (ADS)

Liu, Yang; Suo, Jinli; Zhang, Yuanlong; Dai, Qionghai

2018-02-01

Multimodal microscopy offers high flexibilities for biomedical observation and diagnosis. Conventional multimodal approaches either use multiple cameras or a single camera spatially multiplexing different modes. The former needs expertise demanding alignment and the latter suffers from limited spatial resolution. Here, we report an alignment-free full-resolution simultaneous fluorescence and quantitative phase imaging approach using single-pixel detectors. By combining reference-free interferometry with single-pixel detection, we encode the phase and fluorescence of the sample in two detection arms at the same time. Then we employ structured illumination and the correlated measurements between the sample and the illuminations for reconstruction. The recovered fluorescence and phase images are inherently aligned thanks to single-pixel detection. To validate the proposed method, we built a proof-of-concept setup for first imaging the phase of etched glass with the depth of a few hundred nanometers and then imaging the fluorescence and phase of the quantum dot drop. This method holds great potential for multispectral fluorescence microscopy with additional single-pixel detectors or a spectrometer. Besides, this cost-efficient multimodal system might find broad applications in biomedical science and neuroscience.

Technical aspects and recommendations for single-cell qPCR.

PubMed

Ståhlberg, Anders; Kubista, Mikael

2018-02-01

Single cells are basic physiological and biological units that can function individually as well as in groups in tissues and organs. It is central to identify, characterize and profile single cells at molecular level to be able to distinguish different kinds, to understand their functions and determine how they interact with each other. During the last decade several technologies for single-cell profiling have been developed and used in various applications, revealing many novel findings. Quantitative PCR (qPCR) is one of the most developed methods for single-cell profiling that can be used to interrogate several analytes, including DNA, RNA and protein. Single-cell qPCR has the potential to become routine methodology but the technique is still challenging, as it involves several experimental steps and few molecules are handled. Here, we discuss technical aspects and provide recommendation for single-cell qPCR analysis. The workflow includes experimental design, sample preparation, single-cell collection, direct lysis, reverse transcription, preamplification, qPCR and data analysis. Detailed reporting and sharing of experimental details and data will promote further development and make validation studies possible. Efforts aiming to standardize single-cell qPCR open up means to move single-cell analysis from specialized research settings to standard research laboratories. Copyright © 2017 Elsevier Ltd. All rights reserved.

The pattern of renal vessels in live related potential donors pool. A multislice computed tomography angiography review.

PubMed

Mishra, Anuj; Ehtuish, Ehtuish F

2006-06-01

To assess the renal vessel anatomy, compare the findings with the perioperative findings, to determine the sensitivity of multislice computed tomography (CT) angiography in the work-up of live potential donors and to discuss and compare the results of the present study with the reported results using single slice CT, magnetic resonance (MRI) and conventional angiography (CA). Retrospective analysis of the angiographic data of 118 of prospective live related kidney donors was carried out from October 2004 to August 2005 at the National Organ Transplant Centre, Tripoli Central Hospital, Libya. All donors underwent renal angiography on multislice (16-slice) CT scan using 80 cc intravenous contrast with 1.25 mm slice thickness followed by maximum intensity projection (MIP) and volume rendering techniques (VRT) post-processing algorithms. The number of vessels, vessel bifurcation, vessel morphology and venous anatomy were analyzed and the findings were compared with the surgical findings. Multislice spiral CT angiography (MSCTA) showed clear delineation of the main renal arteries in all donors with detailed vessel morphology. The study revealed 100% sensitivity in detection of accessory renal vessels, with an overall incidence of 26.7%, which is the most common distribution in the parahilar region. The present study showed 100% sensitivity in the visualization and detection of main and accessory renal vessels. These results were comparable with conventional angiography which has so far been considered as the gold standard and were found superior in specificity and accuracy to the use of single slice CT (SSCT) and MR in the angiographic work-up of live renal donors. Due to improved detection of accessory vessels less than 2 mm in diameter, a higher incidence of aberrant vessels was seen on the right side as has been suggested so far.

Lithium acts as a potentiator of AMPAR currents in hippocampal CA1 cells by selectively increasing channel open probability

PubMed Central

Gebhardt, Christine; Cull-Candy, Stuart G

2010-01-01

Recent evidence suggests that lithium, which is used in the treatment of bipolar disorders, may act by influencing AMPAR properties at central glutamatergic synapses. While it is clear that lithium potentiates recombinant AMPAR responses in a subunit specific way, the origin of this potentiation is not known. We examined the effects of lithium on native AMPAR channels in CA1 pyramidal cells in hippocampal slices where AMPARs are expected to be associated with auxiliary subunits. We found that lithium produced a selective increase in single-channel open probability (Popen), with little effect on single-channel conductance or burst length. From the present and previous finding it is likely that lithium causes a reduction in the time to recovery from desensitization, resulting in the observed increase in Popen. This would be consistent with the view that lithium acts like certain other allosteric AMPAR modulators to reduce the time spent in the desensitized state, but differs from those that act by slowing dissociation of glutamate. PMID:20807790

Articulation Artifacts During Overt Language Production in Event-Related Brain Potentials: Description and Correction.

PubMed

Ouyang, Guang; Sommer, Werner; Zhou, Changsong; Aristei, Sabrina; Pinkpank, Thomas; Abdel Rahman, Rasha

2016-11-01

Overt articulation produces strong artifacts in the electroencephalogram and in event-related potentials (ERPs), posing a serious problem for investigating language production with these variables. Here we describe the properties of articulation-related artifacts and propose a novel correction procedure. Experiment 1 co-recorded ERPs and trajectories of the articulators with an electromagnetic articulograph from a single participant. The generalization of the findings from the single participant to standard picture naming was investigated in Experiment 2. Both experiments provided evidence that articulation-induced artifacts may start up to 300 ms or more prior to voice onset or voice key onset-depending on the specific measure; they are highly similar in topography across many different phoneme patterns and differ mainly in their time course and amplitude. ERPs were separated from articulation-related artifacts with residue iteration decomposition (RIDE). After obtaining the artifact-free ERPs, their correlations with the articulatory trajectories dropped near to zero. Artifact removal with independent component analysis was less successful; while correlations with the articulatory movements remained substantial, early components prior to voice onset were attenuated in reconstructed ERPs. These findings offer new insights into the nature of articulation artifacts; together with RIDE as method for artifact removal the present report offers a fresh perspective for ERP studies requiring overt articulation.

How Oxytocin Receptor (OXTR) Single Nucleotide Polymorphisms Act on Prosociality: The Mediation Role of Moral Evaluation.

PubMed

Shang, Siyuan; Wu, Nan; Su, Yanjie

2017-01-01

Prosociality is related to numerous positive outcomes, and mechanisms underlying individual differences in prosociality have been widely discussed. Recently, research has found converging evidence on the influence of the oxytocin receptor ( OXTR ) gene on prosociality. Meanwhile, moral reasoning, a key precursor for social behavior, has also been associated with variability in OXTR gene, thus the relationship between OXTR and prosociality is assumed to be mediated by moral evaluation. The current study examines the relationship in question, and includes gender as a potential moderator. Self-reported prosociality on Prosocial Tendencies Measure and evaluation on the moral acceptability of behaviors in stories from 790 Chinese adolescents (32.4% boys) were analyzed for the influence of their OXTR single nucleotide polymorphisms (SNPs). Results showed that SNP at site rs2254298 was indirectly associated with prosocial behaviors via moral evaluation of behaviors, and this effect was moderated by gender. Our findings suggest an indirect association between genetic variations in OXTR and prosociality through moral evaluation, indicating the potential pathway from genetic variability to prosociality through level of moral development. We also provide some evidence that the role of oxytocin system may to some extent depend on gender. These findings may promote our understanding of the genetic and biological roots of prosociality and morality.

Single Motherhood, Alcohol Dependence, and Smoking During Pregnancy: A Propensity Score Analysis.

PubMed

Waldron, Mary; Bucholz, Kathleen K; Lian, Min; Lessov-Schlaggar, Christina N; Miller, Ruth Huang; Lynskey, Michael T; Knopik, Valerie S; Madden, Pamela A F; Heath, Andrew C

2017-09-01

Few studies linking single motherhood and maternal smoking during pregnancy consider correlated risk from problem substance use beyond history of smoking and concurrent use of alcohol. In the present study, we used propensity score methods to examine whether the risk of smoking during pregnancy associated with single motherhood is the result of potential confounders, including alcohol dependence. Data were drawn from mothers participating in a birth cohort study of their female like-sex twin offspring (n = 257 African ancestry; n = 1,711 European or other ancestry). We conducted standard logistic regression models predicting smoking during pregnancy from single motherhood at twins' birth, followed by propensity score analyses comparing single-mother and two-parent families stratified by predicted probability of single motherhood. In standard models, single motherhood predicted increased risk of smoking during pregnancy in European ancestry but not African ancestry families. In propensity score analyses, rates of smoking during pregnancy were elevated in single-mother relative to two-parent European ancestry families across much of the spectrum a priori risk of single motherhood. Among African ancestry families, within-strata comparisons of smoking during pregnancy by single-mother status were nonsignificant. These findings highlight single motherhood as a unique risk factor for smoking during pregnancy in European ancestry mothers, over and above alcohol dependence. Additional research is needed to identify risks, beyond single motherhood, associated with smoking during pregnancy in African ancestry mothers.

Living Arrangements and the Well-being of Single Mothers in Japan

PubMed Central

Raymo, James M.; Zhou, Yanfei

2012-01-01

The goal of this paper is to evaluate the extent to which the well-being of single mothers in Japan is related to coresidence with other adults. Using data from a representative survey of households headed by single mothers, we examine two measures of subjective well-being: perceived economic circumstances and self-rated health. One-fourth of the single mothers surveyed were coresiding with another adult(s) and it is clear that these women fare significantly better than their non-coresiding counterparts on both measures of well-being. Net of several theoretically relevant sociodemographic, family, and employment characteristics, single mothers living with others were significantly less likely to report somewhat difficult/difficult economic circumstances or fair/poor health. Efforts to account for potential endogeneity between well-being and living arrangements suggested that self-rated health, but not subjective economic well-being, is related to selection into coresidence. Single mothers in fair/poor health appear more likely to coreside with others and, accounting for this selection, intergenerational coresidence appears to be very beneficial for self-rated health. We discuss the implications of these findings for processes of stratification in Japan in light of the limited public income support available to single mothers. PMID:23144521

Watching Individual Enzymes at Work

NASA Astrophysics Data System (ADS)

Blank, Kerstin; Rocha, Susana; De Cremer, Gert; Roeffaers, Maarten B. J.; Uji-i, Hiroshi; Hofkens, Johan

Single-molecule fluorescence experiments are a powerful tool to analyze reaction mechanisms of enzymes. Because of their unique potential to detect heterogeneities in space and time, they have provided unprecedented insights into the nature and mechanisms of conformational changes related to the catalytic reaction. The most important finding from experiments with single enzymes is the generally observed phenomenon that the catalytic rate constants fluctuate over time (dynamic disorder). These fluctuations originate from conformational changes occurring on time scales, which are similar to or slower than that of the catalytic reaction. Here, we summarize experiments with enzymes that show dynamic disorder and introduce new experimental strategies showing how single-molecule fluorescence experiments can be applied to address other open questions in medical and industrial enzymology, such as enzyme inactivation processes, reactant transfer in cascade reactions, and the mechanisms of interfacial catalysis.

Understanding the psychosocial aspects of HIV / AIDS prevention for northern Thai single adolescent migratory women workers.

PubMed

Cash, K; Anansuchatkul, B; Busayawong, W

1999-04-01

This study describes formative research about sex, sexuality, and sexual relationships of northern Thai single female migratory laborers. Methodologies included focus group discussions, observation, and in-depth individual interviews. Findings revealed that these women were sexually active, although the actual number of girls who were or had been sexually active could not be determined. It was also found that serial partners were much common than multiple partner relationships. And that these young women did not practice safe sex which can be considered as a potential social consequences of negotiating safe sex often outweigh health consequences. Furthermore, respondents reported that condoms were "men's business" and that there are irreconcilable social costs if a single woman talks about condoms or AIDS. From these findings, it is suggested that these young women and girls, regardless of their occupation or marital status or age, need HIV/AIDS education. Condoms need to be brought out of the disease spectrum and into the family planning and contraceptive spectrum. Educational interventions and material should address young people's emotional and relational needs including their desire to be modern and acceptable to peers.

Fabrication of quantum dots in undoped Si/Si 0.8Ge 0.2 heterostructures using a single metal-gate layer

DOE PAGES

Lu, T. M.; Gamble, J. K.; Muller, R. P.; ...

2016-08-01

Enhancement-mode Si/SiGe electron quantum dots have been pursued extensively by many groups for their potential in quantum computing. Most of the reported dot designs utilize multiple metal-gate layers and use Si/SiGe heterostructures with Ge concentration close to 30%. Here, we report the fabrication and low-temperature characterization of quantum dots in the Si/Si 0.8Ge 0.2 heterostructures using only one metal-gate layer. We find that the threshold voltage of a channel narrower than 1 μm increases as the width decreases. The higher threshold can be attributed to the combination of quantum confinement and disorder. We also find that the lower Ge ratiomore » used here leads to a narrower operational gate bias range. The higher threshold combined with the limited gate bias range constrains the device design of lithographic quantum dots. We incorporate such considerations in our device design and demonstrate a quantum dot that can be tuned from a single dot to a double dot. Furthermore, the device uses only a single metal-gate layer, greatly simplifying device design and fabrication.« less

Application of stochastic multiattribute analysis to assessment of single walled carbon nanotube synthesis processes.

PubMed

Canis, Laure; Linkov, Igor; Seager, Thomas P

2010-11-15

The unprecedented uncertainty associated with engineered nanomaterials greatly expands the need for research regarding their potential environmental consequences. However, decision-makers such as regulatory agencies, product developers, or other nanotechnology stakeholders may not find the results of such research directly informative of decisions intended to mitigate environmental risks. To help interpret research findings and prioritize new research needs, there is an acute need for structured decision-analytic aids that are operable in a context of extraordinary uncertainty. Whereas existing stochastic decision-analytic techniques explore uncertainty only in decision-maker preference information, this paper extends model uncertainty to technology performance. As an illustrative example, the framework is applied to the case of single-wall carbon nanotubes. Four different synthesis processes (arc, high pressure carbon monoxide, chemical vapor deposition, and laser) are compared based on five salient performance criteria. A probabilistic rank ordering of preferred processes is determined using outranking normalization and a linear-weighted sum for different weighting scenarios including completely unknown weights and four fixed-weight sets representing hypothetical stakeholder views. No single process pathway dominates under all weight scenarios, but it is likely that some inferior process technologies could be identified as low priorities for further research.

Inflation with Whip-Shaped Suppressed Scalar Power Spectra

NASA Astrophysics Data System (ADS)

Hazra, Dhiraj Kumar; Shafieloo, Arman; Smoot, George F.; Starobinsky, Alexei A.

2014-08-01

Motivated by the idea that inflation occurs at the grand unified theory symmetry breaking scale, in this Letter we construct a new class of large field inflaton potentials where the inflaton starts with a power law potential; after an initial period of relatively fast roll that lasts until after a few e folds inside the horizon it transits to the attractor of the slow roll part of the potential with a lower power. Because of the initial fast roll stages of inflation, we find a suppression in scalar primordial power at large scales and at the same time the choice of the potential can provide us a tensor primordial spectrum with a high amplitude. This suppression in scalar power with a large tensor-to-scalar ratio helps us to reconcile the Planck and BICEP2 data in a single framework. We find that a transition from a cubic to quadratic form of inflaton potential generates an appropriate suppression in the power of the scalar primordial spectrum that provides a significant improvement in fit compared to the power law model when compared with Planck and BICEP2 data together. We calculate the extent of non-Gaussianity, specifically, the bispectrum for the best fit potential, and show that it is consistent with Planck bispectrum constraints.

Gender differences in the mental health of single parents: New Zealand evidence from a household panel survey.

PubMed

Collings, Sunny; Jenkin, Gabrielle; Carter, Kristie; Signal, Louise

2014-05-01

In many countries single parents report poorer mental health than partnered parents. This study investigates whether there are gender differences in the mental health of single parents in New Zealand (and whether any gender difference varies with that among partnered parents), and examines key social and demographic mediators that may account for this difference. We used data on 905 single parents and 4,860 partnered parents from a New Zealand household panel survey that included the Kessler-10 measure of psychological distress. Linear regression analyses were used to investigate both interactions of gender and parental status, and confounding or mediation by other covariates. High/very high levels of psychological distress were reported by 15.7 % of single mothers and 9.1 % of single fathers, and 6.1 % of partnered mothers and 4.1 % of partnered fathers. In an Ordinary Least Squares regression of continuous K10 scores on gender, parental status and the interaction of both (plus adjustment for ethnicity, number of children and age), female single parents had a 1.46 higher K10 score than male single parents (95 % CI 0.48-2.44; 1.46). This difference was 0.98 (95 % CI -0.04 to 1.99) points greater than the gender difference among partnered parents. After controlling for further confounding or mediating covariates (educational level, labour force status and socioeconomic deprivation) both the gender difference among single parents (0.38, -0.56 to 1.31) and the interaction of gender and parental status (0.28 greater gender difference among single parents, -0.69 to 1.65) greatly reduced in magnitude and became non-significant, mainly due to adjustment for individual socioeconomic deprivation. The poorer mental health of single parents remains an important epidemiological phenomenon. Although research has produced mixed findings of the nature of gender differences in the mental health of single parents, our research adds to the increasing evidence that it is single mothers who have worse mental health. Our findings on the potential explanations of the gender difference in sole parent mental health suggest that socioeconomic deprivation is a key contributor.

Self-consistent quasi-static parallel electric field associated with substorm growth phase

NASA Astrophysics Data System (ADS)

Le Contel, O.; Pellat, R.; Roux, A.

2000-06-01

A new approach is proposed to calculate the self-consistent parallel electric field associated with the response of a plasma to quasi-static electromagnetic perturbations (ωωd<ω and ωd>ω (ωd being the bounce averaged magnetic drift frequency equal to kyvd, where ky is the wave number in the y direction and vd the bounce averaged magnetic drift velocity). The first regime (ωd<ω) corresponds to small particle energy and/or small ky, while the second regime (ωd>ω) is adapted to large energies and/or large ky. In particular, in the limit ωd<ω and |vd|<|uy|, where uy is the diamagnetic velocity proportional to the pressure gradient, we find a parallel electric field proportional to the pressure gradient and directed toward the ionosphere in the dusk sector and toward the equator in the dawn sector. This parallel electric field corresponds to a potential drop of a few hundred volts that can accelerate electrons and produce a differential drift between electrons and ions.

Predominant Occupation of the Class I MHC Molecule H-2Kwm7 with a Single Self-peptide Suggests a Mechanism for its Diabetes-protective Effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brims, D.; Qian, J; Jarchum, I

2010-01-01

Type 1 diabetes (T1D) is an autoimmune disease characterized by T cell-mediated destruction of insulin-producing pancreatic {beta} cells. In both humans and the non-obese diabetic (NOD) mouse model of T1D, class II MHC alleles are the primary determinant of disease susceptibility. However, class I MHC genes also influence risk. These findings are consistent with the requirement for both CD{sup 4+} and CD{sup 8+} T cells in the pathogenesis of T1D. Although a large body of work has permitted the identification of multiple mechanisms to explain the diabetes-protective effect of particular class II MHC alleles, studies examining the protective influence ofmore » class I alleles are lacking. Here, we explored this question by performing biochemical and structural analyses of the murine class I MHC molecule H-2K{sup wm7}, which exerts a diabetes-protective effect in NOD mice. We have found that H-2K{sup wm7} molecules are predominantly occupied by the single self-peptide VNDIFERI, derived from the ubiquitous protein histone H2B. This unexpected finding suggests that the inability of H-2K{sup wm7} to support T1D development could be due, at least in part, to the failure of peptides from critical {beta}-cell antigens to adequately compete for binding and be presented to T cells. Predominant presentation of a single peptide would also be expected to influence T-cell selection, potentially leading to a reduced ability to select a diabetogenic CD{sup 8+} T-cell repertoire. The report that one of the predominant peptides bound by T1D-protective HLA-A*31 is histone derived suggests the potential translation of our findings to human diabetes-protective class I MHC molecules.« less

Single-Trial Analysis of V1 Responses Suggests Two Transmission States

NASA Technical Reports Server (NTRS)

Shah, A. S.; Knuth, K. H.; Truccolo, W. A.; Mehta, A. D.; McGinnis, T.; OConnell, N.; Ding, M.; Bressler, S. L.; Schroeder, C. E.

2002-01-01

Sensory processing in the visual, auditory, and somatosensory systems is often studied by recording electrical activity in response to a stimulus of interest. Typically, multiple trial responses to the stimulus are averaged to isolate the stereotypic response from noise. However, averaging ignores dynamic variability in the neuronal response, which is potentially critical to understanding stimulus-processing schemes. Thus, we developed the multiple component, Event-Related Potential (mcERP) model. This model asserts that multiple components, defined as stereotypic waveforms, comprise the stimulus-evoked response and that these components may vary in amplitude and latency from trial to trial. Application of this model to data recorded simultaneously from all six laminae of V1 in an awake, behaving monkey performing a visual discrimination yielded three components. The first component localized to granular V1, the second was located in supragranular V1, and the final component displayed a multi-laminar distribution. These modeling results, which take into account single-trial response dynamics, illustrated that the initial activation of VI occurs in the granular layer followed by activation in the supragranular layers. This finding is expected because the average response in those layers demonstrates the same progression and because anatomical evidence suggests that the feedforward input in V1 enters the granular layer and progresses to supragranular layers. In addition to these findings, the granular component of the model displayed several interesting trial-to-trial characteristics including (1) a bimodal latency distribution, (2) a latency-related variation in response amplitude, (3) a latency correlation with the supragranular component, and (4) an amplitude and latency association with the multi-laminar component. Direct analyses of the single-trial data were consistent with these model predictions. These findings suggest that V1 has at least 2 transmission states, which may be modulated by various effects such as attention, dynamics in local EEG rhythm, or variation in sensory inputs.

How meaningful are risk determinations in the absence of a complete dataset? Making the case for publishing standardized test guideline and 'no effect' studies for evaluating the safety of nanoparticulates versus spurious 'high effect' results from single investigative studies.

PubMed

Warheit, David B; Donner, E Maria

2015-06-01

A recent review article critically assessed the effectiveness of published research articles in nanotoxicology to meaningfully address health and safety issues for workers and consumers. The main conclusions were that, based on a number of flaws in study designs, the potential risk from exposures to nanomaterials is highly exaggerated, and that no 'nano-specific' adverse effects, different from exposures to bulk particles, have been convincingly demonstrated. In this brief editorial we focus on a related tangential issue which potentially compromises the integrity of basic risk science. We note that some single investigation studies report specious toxicity findings, which make the conclusions more alarming and attractive and publication worthy. In contrast, the standardized, carefully conducted, 'guideline study results' are often ignored because they can frequently report no adverse effects; and as a consequence are not considered as novel findings for publication purposes, and therefore they are never considered as newsworthy in the popular press. Yet it is the Organization for Economic Cooperation and Development (OECD) type test guideline studies that are the most reliable for conducting risk assessments. To contrast these styles and approaches, we present the results of a single study which reports high toxicological effects in rats following low-dose, short-term oral exposures to nanoscale titanium dioxide particles concomitant with selective investigative analyses. Alternatively, the findings of OECD test guideline 408, standardized guideline oral toxicity studies conducted for 90 days at much higher doses (1000 mg kg -1 ) in male and female rats demonstrated no adverse effects following a very thorough and complete clinical chemical, as well as histopathological evaluation of all of the relevant organs in the body. This discrepancy in study findings is not reconciled by the fact that several biokinetic studies in rats and humans demonstrate little or no uptake of nanoscale or pigment-grade TiO 2 particles following oral exposures. We conclude that to develop a competent risk assessment profile, results derived from standardized, guideline-type studies, and even 'no effect' study findings provide critically useful input for assessing safe levels of exposure; and should, in principle, be readily acceptable for publication in peer-reviewed toxicology journals. This is a necessary prerequisite for developing a complete dataset for risk assessment determinations.

Motor planning flexibly optimizes performance under uncertainty about task goals.

PubMed

Wong, Aaron L; Haith, Adrian M

2017-03-03

In an environment full of potential goals, how does the brain determine which movement to execute? Existing theories posit that the motor system prepares for all potential goals by generating several motor plans in parallel. One major line of evidence for such theories is that presenting two competing goals often results in a movement intermediate between them. These intermediate movements are thought to reflect an unintentional averaging of the competing plans. However, normative theories suggest instead that intermediate movements might actually be deliberate, generated because they improve task performance over a random guessing strategy. To test this hypothesis, we vary the benefit of making an intermediate movement by changing movement speed. We find that participants generate intermediate movements only at (slower) speeds where they measurably improve performance. Our findings support the normative view that the motor system selects only a single, flexible motor plan, optimized for uncertain goals.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lima, Jonas R. F., E-mail: jonas.iasd@gmail.com

We study the electronic and transport properties of a graphene-based superlattice theoretically by using an effective Dirac equation. The superlattice consists of a periodic potential applied on a single-layer graphene deposited on a substrate that opens an energy gap of 2Δ in its electronic structure. We find that extra Dirac points appear in the electronic band structure under certain conditions, so it is possible to close the gap between the conduction and valence minibands. We show that the energy gap E{sub g} can be tuned in the range 0 ≤ E{sub g} ≤ 2Δ by changing the periodic potential. We analyze the low energymore » electronic structure around the contact points and find that the effective Fermi velocity in very anisotropic and depends on the energy gap. We show that the extra Dirac points obtained here behave differently compared to previously studied systems.« less

Mean first passage time of active Brownian particle in one dimension

NASA Astrophysics Data System (ADS)

Scacchi, A.; Sharma, A.

2018-02-01

We investigate the mean first passage time of an active Brownian particle in one dimension using numerical simulations. The activity in one dimension is modelled as a two state model; the particle moves with a constant propulsion strength but its orientation switches from one state to other as in a random telegraphic process. We study the influence of a finite resetting rate r on the mean first passage time to a fixed target of a single free active Brownian particle and map this result using an effective diffusion process. As in the case of a passive Brownian particle, we can find an optimal resetting rate r* for an active Brownian particle for which the target is found with the minimum average time. In the case of the presence of an external potential, we find good agreement between the theory and numerical simulations using an effective potential approach.

Universal Expression of Efficiency at Maximum Power: A Quantum-Mechanical Brayton Engine Working with a Single Particle Confined in a Power-Law Trap

NASA Astrophysics Data System (ADS)

Ye, Zhuo-Lin; Li, Wei-Sheng; Lai, Yi-Ming; He, Ji-Zhou; Wang, Jian-Hui

2015-12-01

We propose a quantum-mechanical Brayton engine model that works between two superposed states, employing a single particle confined in an arbitrary power-law trap as the working substance. Applying the superposition principle, we obtain the explicit expressions of the power and efficiency, and find that the efficiency at maximum power is bounded from above by the function: η+ = θ/(θ + 1), with θ being a potential-dependent exponent. Supported by the National Natural Science Foundation of China under Grant Nos. 11505091, 11265010, and 11365015, and the Jiangxi Provincial Natural Science Foundation under Grant No. 20132BAB212009

Spin symmetry in the Dirac sea derived from the bare nucleon-nucleon interaction

NASA Astrophysics Data System (ADS)

Shen, Shihang; Liang, Haozhao; Meng, Jie; Ring, Peter; Zhang, Shuangquan

2018-06-01

The spin symmetry in the Dirac sea has been investigated with relativistic Brueckner-Hartree-Fock theory using the bare nucleon-nucleon interaction. Taking the nucleus 16O as an example and comparing the theoretical results with the data, the definition of the single-particle potential in the Dirac sea is studied in detail. It is found that if the single-particle states in the Dirac sea are treated as occupied states, the ground state properties are in better agreement with experimental data. Moreover, in this case, the spin symmetry in the Dirac sea is better conserved and it is more consistent with the findings using phenomenological relativistic density functionals.

Ultrafast carrier capture and Auger recombination in single GaN/InGaN multiple quantum well nanowires

DOE PAGES

Boubanga-Tombet, Stephane; Wright, Jeremy B.; Lu, Ping; ...

2016-11-04

Ultrafast optical microscopy is an important tool for examining fundamental phenomena in semiconductor nanowires with high temporal and spatial resolution. In this paper, we used this technique to study carrier dynamics in single GaN/InGaN core–shell nonpolar multiple quantum well nanowires. We find that intraband carrier–carrier scattering is the main channel governing carrier capture, while subsequent carrier relaxation is dominated by three-carrier Auger recombination at higher densities and bimolecular recombination at lower densities. Finally, the Auger constants in these nanowires are approximately 2 orders of magnitude lower than in planar InGaN multiple quantum wells, highlighting their potential for future light-emitting devices.

Infant Neurobehavioral Development

PubMed Central

Lester, Barry M.; Miller, Robin J.; Hawes, Katheleen; Salisbury, Amy; Bigsby, Rosemarie; Sullivan, Mary C.; Padbury, James F.

2011-01-01

The trend toward single-room neonatal intensive care units (NICUs) is increasing; however scientific evidence is, at this point, mostly anecdotal. This is a critical time to assess the impact of the single-room NICU on improving medical and neurobehavioral outcomes of the preterm infant. We have developed a theoretical model that may be useful in studying how the change from an open-bay NICU to a single-room NICU could affect infant medical and neurobehavioral outcome. The model identifies mediating factors that are likely to accompany the change to a single-room NICU. These mediating factors include family centered care, developmental care, parenting and family factors, staff behavior and attitudes, and medical practices. Medical outcomes that plan to be measured are sepsis, length of stay, gestational age at discharge, weight gain, illness severity, gestational age at enteral feeding, and necrotizing enterocolitis (NEC). Neurobehavioral outcomes include the NICU Network Neurobehavioral Scale (NNNS) scores, sleep state organization and sleep physiology, infant mother feeding interaction scores, and pain scores. Preliminary findings on the sample of 150 patients in the open-bay NICU showed a “baseline” of effects of family centered care, developmental care, parent satisfaction, maternal depression, and parenting stress on the neurobehavioral outcomes of the newborn. The single-room NICU has the potential to improve the neurobehavioral status of the infant at discharge. Neurobehavioral assessment can assist with early detection and therefore preventative intervention to maximize developmental outcome. We also present an epigenetic model of the potential effects of maternal care on improving infant neurobehavioral status. PMID:21255702

Relation between functional magnetic resonance imaging (fMRI) and single neuron, local field potential (LFP) and electrocorticography (ECoG) activity in human cortex.

PubMed

Ojemann, George A; Ojemann, Jeffrey; Ramsey, Nick F

2013-01-01

The relation between changes in the blood oxygen dependent metabolic changes imaged by functional magnetic resonance imaging (fMRI) and neural events directly recorded from human cortex from single neurons, local field potentials (LFPs) and electrocorticogram (ECoG) is critically reviewed, based on the published literature including findings from the authors' laboratories. All these data are from special populations, usually patients with medically refractory epilepsy, as this provides the major opportunity for direct cortical neuronal recording in humans. For LFP and ECoG changes are often sought in different frequency bands, for single neurons in frequency of action potentials. Most fMRI studies address issues of functional localization. The relation of those findings to localized changes in neuronal recordings in humans has been established in several ways. Only a few studies have directly compared changes in activity from the same sites in the same individual, using the same behavioral measure. More often the comparison has been between fMRI and electrophysiologic changes in populations recorded from the same functional anatomic system as defined by lesion effects; in a few studies those systems have been defined by fMRI changes such as the "default" network. The fMRI-electrophysiologic relationships have been evaluated empirically by colocalization of significant changes, and by quantitative analyses, often multiple linear regression. There is some evidence that the fMRI-electrophysiology relationships differ in different cortical areas, particularly primary motor and sensory cortices compared to association cortex, but also within areas of association cortex. Although crucial for interpretation of fMRI changes as reflecting neural activity in human cortex, controversy remains as to these relationships. Supported by: Dutch Technology Foundation and University of Utrecht Grant UGT7685, ERC-Advanced grant 320708 (NR) and NIH grant NS065186 (JO).

Metastatic pancreatic cancer: Is there a light at the end of the tunnel?

PubMed Central

Vaccaro, Vanja; Sperduti, Isabella; Vari, Sabrina; Bria, Emilio; Melisi, Davide; Garufi, Carlo; Nuzzo, Carmen; Scarpa, Aldo; Tortora, Giampaolo; Cognetti, Francesco; Reni, Michele; Milella, Michele

2015-01-01

Due to extremely poor prognosis, pancreatic cancer (PDAC) represents the fourth leading cause of cancer-related death in Western countries. For more than a decade, gemcitabine (Gem) has been the mainstay of first-line PDAC treatment. Many efforts aimed at improving single-agent Gem efficacy by either combining it with a second cytotoxic/molecularly targeted agent or pharmacokinetic modulation provided disappointing results. Recently, the field of systemic therapy of advanced PDAC is finally moving forward. Polychemotherapy has shown promise over single-agent Gem: regimens like PEFG-PEXG-PDXG and GTX provide significant potential advantages in terms of survival and/or disease control, although sometimes at the cost of poor tolerability. The PRODIGE 4/ACCORD 11 was the first phase III trial to provide unequivocal benefit using the polychemotherapy regimen FOLFIRINOX; however the less favorable safety profile and the characteristics of the enrolled population, restrict the use of FOLFIRINOX to young and fit PDAC patients. The nanoparticle albumin-bound paclitaxel (nab-Paclitaxel) formulation was developed to overcome resistance due to the desmoplastic stroma surrounding pancreatic cancer cells. Regardless of whether or not this is its main mechanisms of action, the combination of nab-Paclitaxel plus Gem showed a statistically and clinically significant survival advantage over single agent Gem and significantly improved all the secondary endpoints. Furthermore, recent findings on maintenance therapy are opening up potential new avenues in the treatment of advanced PDAC, particularly in a new era in which highly effective first-line regimens allow patients to experience prolonged disease control. Here, we provide an overview of recent advances in the systemic treatment of advanced PDAC, mostly focusing on recent findings that have set new standards in metastatic disease. Potential avenues for further development in the metastatic setting and current efforts to integrate new effective chemotherapy regimens in earlier stages of disease (neoadjuvant, adjuvant, and multimodal approaches in both resectable and unresectable patients) are also briefly discussed. PMID:25944992

Metastatic pancreatic cancer: Is there a light at the end of the tunnel?

PubMed

Vaccaro, Vanja; Sperduti, Isabella; Vari, Sabrina; Bria, Emilio; Melisi, Davide; Garufi, Carlo; Nuzzo, Carmen; Scarpa, Aldo; Tortora, Giampaolo; Cognetti, Francesco; Reni, Michele; Milella, Michele

2015-04-28

Due to extremely poor prognosis, pancreatic cancer (PDAC) represents the fourth leading cause of cancer-related death in Western countries. For more than a decade, gemcitabine (Gem) has been the mainstay of first-line PDAC treatment. Many efforts aimed at improving single-agent Gem efficacy by either combining it with a second cytotoxic/molecularly targeted agent or pharmacokinetic modulation provided disappointing results. Recently, the field of systemic therapy of advanced PDAC is finally moving forward. Polychemotherapy has shown promise over single-agent Gem: regimens like PEFG-PEXG-PDXG and GTX provide significant potential advantages in terms of survival and/or disease control, although sometimes at the cost of poor tolerability. The PRODIGE 4/ACCORD 11 was the first phase III trial to provide unequivocal benefit using the polychemotherapy regimen FOLFIRINOX; however the less favorable safety profile and the characteristics of the enrolled population, restrict the use of FOLFIRINOX to young and fit PDAC patients. The nanoparticle albumin-bound paclitaxel (nab-Paclitaxel) formulation was developed to overcome resistance due to the desmoplastic stroma surrounding pancreatic cancer cells. Regardless of whether or not this is its main mechanisms of action, the combination of nab-Paclitaxel plus Gem showed a statistically and clinically significant survival advantage over single agent Gem and significantly improved all the secondary endpoints. Furthermore, recent findings on maintenance therapy are opening up potential new avenues in the treatment of advanced PDAC, particularly in a new era in which highly effective first-line regimens allow patients to experience prolonged disease control. Here, we provide an overview of recent advances in the systemic treatment of advanced PDAC, mostly focusing on recent findings that have set new standards in metastatic disease. Potential avenues for further development in the metastatic setting and current efforts to integrate new effective chemotherapy regimens in earlier stages of disease (neoadjuvant, adjuvant, and multimodal approaches in both resectable and unresectable patients) are also briefly discussed.

SU (2) lattice gauge theory simulations on Fermi GPUs

NASA Astrophysics Data System (ADS)

Cardoso, Nuno; Bicudo, Pedro

2011-05-01

In this work we explore the performance of CUDA in quenched lattice SU (2) simulations. CUDA, NVIDIA Compute Unified Device Architecture, is a hardware and software architecture developed by NVIDIA for computing on the GPU. We present an analysis and performance comparison between the GPU and CPU in single and double precision. Analyses with multiple GPUs and two different architectures (G200 and Fermi architectures) are also presented. In order to obtain a high performance, the code must be optimized for the GPU architecture, i.e., an implementation that exploits the memory hierarchy of the CUDA programming model. We produce codes for the Monte Carlo generation of SU (2) lattice gauge configurations, for the mean plaquette, for the Polyakov Loop at finite T and for the Wilson loop. We also present results for the potential using many configurations (50,000) without smearing and almost 2000 configurations with APE smearing. With two Fermi GPUs we have achieved an excellent performance of 200× the speed over one CPU, in single precision, around 110 Gflops/s. We also find that, using the Fermi architecture, double precision computations for the static quark-antiquark potential are not much slower (less than 2× slower) than single precision computations.

Single field double inflation and primordial black holes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kannike, K.; Marzola, L.; Raidal, M.

Within the framework of scalar-tensor theories, we study the conditions that allow single field inflation dynamics on small cosmological scales to significantly differ from that of the large scales probed by the observations of cosmic microwave background. The resulting single field double inflation scenario is characterised by two consequent inflation eras, usually separated by a period where the slow-roll approximation fails. At large field values the dynamics of the inflaton is dominated by the interplay between its non-minimal coupling to gravity and the radiative corrections to the inflaton self-coupling. For small field values the potential is, instead, dominated by amore » polynomial that results in a hilltop inflation. Without relying on the slow-roll approximation, which is invalidated by the appearance of the intermediate stage, we propose a concrete model that matches the current measurements of inflationary observables and employs the freedom granted by the framework on small cosmological scales to give rise to a sizeable population of primordial black holes generated by large curvature fluctuations. We find that these features generally require a potential with a local minimum. We show that the associated primordial black hole mass function is only approximately lognormal.« less

Can isolated single black holes produce X-ray novae?

NASA Astrophysics Data System (ADS)

Matsumoto, Tatsuya; Teraki, Yuto; Ioka, Kunihito

2018-03-01

Almost all black holes (BHs) and BH candidates in our Galaxy have been discovered as soft X-ray transients, so-called X-ray novae. X-ray novae are usually considered to arise from binary systems. Here, we propose that X-ray novae are also caused by isolated single BHs. We calculate the distribution of the accretion rate from interstellar matter to isolated BHs, and find that BHs in molecular clouds satisfy the condition of the hydrogen-ionization disc instability, which results in X-ray novae. The estimated event rate is consistent with the observed one. We also check an X-ray novae catalogue (Corral-Santana et al.) and find that 16/59 ˜ 0.27 of the observed X-ray novae are potentially powered by isolated BHs. The possible candidates include IGR J17454-2919, XTE J1908-094, and SAX J1711.6-3808. Near-infrared photometric and spectroscopic follow-ups can exclude companion stars for a BH census in our Galaxy.

A Rout to Protect Quantum Gates constructed via quantum walks from Noises.

PubMed

Du, Yi-Mu; Lu, Li-Hua; Li, You-Quan

2018-05-08

The continuous-time quantum walk on a one-dimensional graph of odd number of sites with an on-site potential at the center is studied. We show that such a quantum-walk system can construct an X-gate of a single qubit as well as a control gate for two qubits, when the potential is much larger than the hopping strength. We investigate the decoherence effect and find that the coherence time can be enhanced by either increasing the number of sites on the graph or the ratio of the potential to the hopping strength, which is expected to motivate the design of the quantum gate with long coherence time. We also suggest several experimental proposals to realize such a system.

Integrable cosmological potentials

NASA Astrophysics Data System (ADS)

Sokolov, V. V.; Sorin, A. S.

2017-09-01

The problem of classification of the Einstein-Friedman cosmological Hamiltonians H with a single scalar inflaton field φ, which possess an additional integral of motion polynomial in momenta on the shell of the Friedman constraint H=0, is considered. Necessary and sufficient conditions for the existence of the first-, second- and third-degree integrals are derived. These conditions have the form of ODEs for the cosmological potential V(φ). In the case of linear and quadratic integrals we find general solutions of the ODEs and construct the corresponding integrals explicitly. A new wide class of Hamiltonians that possess a cubic integral is derived. The corresponding potentials are represented in parametric form in terms of the associated Legendre functions. Six families of special elementary solutions are described, and sporadic superintegrable cases are discussed.

High-energy electron emission from metallic nano-tips driven by intense single-cycle terahertz pulses

PubMed Central

Li, Sha; Jones, R. R.

2016-01-01

Electrons ejected from atoms and subsequently driven to high energies in strong laser fields enable techniques from attosecond pulse generation to imaging with rescattered electrons. Analogous processes govern strong-field electron emission from nanostructures, where long wavelength radiation and large local field enhancements hold the promise for producing electrons with substantially higher energies, allowing for higher resolution time-resolved imaging. Here we report on the use of single-cycle terahertz pulses to drive electron emission from unbiased nano-tips. Energies exceeding 5 keV are observed, substantially greater than previously attained at higher drive frequencies. Despite large differences in the magnitude of the respective local fields, we find that the maximum electron energies are only weakly dependent on the tip radius, for 10 nm

Single-row versus double-row rotator cuff repair: techniques and outcomes.

PubMed

Dines, Joshua S; Bedi, Asheesh; ElAttrache, Neal S; Dines, David M

2010-02-01

Double-row rotator cuff repair techniques incorporate a medial and lateral row of suture anchors in the repair configuration. Biomechanical studies of double-row repair have shown increased load to failure, improved contact areas and pressures, and decreased gap formation at the healing enthesis, findings that have provided impetus for clinical studies comparing single-row with double-row repair. Clinical studies, however, have not yet demonstrated a substantial improvement over single-row repair with regard to either the degree of structural healing or functional outcomes. Although double-row repair may provide an improved mechanical environment for the healing enthesis, several confounding variables have complicated attempts to establish a definitive relationship with improved rates of healing. Appropriately powered rigorous level I studies that directly compare single-row with double-row techniques in matched tear patterns are necessary to further address these questions. These studies are needed to justify the potentially increased implant costs and surgical times associated with double-row rotator cuff repair.

Klein tunneling phenomenon with pair creation process

NASA Astrophysics Data System (ADS)

Wu, G. Z.; Zhou, C. T.; Fu, L. B.

2018-01-01

In this paper, we study the Klein tunneling phenomenon with electron-positron pair creation process. Pairs can be created from the vacuum by a supercritical single-well potential (for electrons). In the time region, the time-dependent growth pattern of the created pairs can be characterized by four distinct regimes which can be considered as four different statuses of the single well. We find that if positrons penetrate the single well by Klein tunneling in different statuses, the total number of the tunneling positrons will be different. If Klein tunneling begins at the initial stage of the first status i.e. when the sing well is empty, the tunneling process and the total number of tunneling positrons are similar to the traditional Klein tunneling case without considering the pair creation process. As the tunneling begins later, the total tunneling positron number increases. The number will finally settle to an asymptotic value when the tunneling begins later than the settling-down time t s of the single well which has been defined in this paper.

Using Single Colors and Color Pairs to Communicate Basic Tastes II: Foreground-Background Color Combinations.

PubMed

Woods, Andy T; Marmolejo-Ramos, Fernando; Velasco, Carlos; Spence, Charles

2016-01-01

People associate basic tastes (e.g., sweet, sour, bitter, and salty) with specific colors (e.g., pink or red, green or yellow, black or purple, and white or blue). In the present study, we investigated whether a color bordered by another color (either the same or different) would give rise to stronger taste associations relative to a single patch of color. We replicate previous findings, highlighting the existence of a robust crossmodal correspondence between individual colors and basic tastes. On occasion, color pairs were found to communicate taste expectations more consistently than were single color patches. Furthermore, and in contrast to a recent study in which the color pairs were shown side-by-side, participants took no longer to match the color pairs with tastes than the single colors (they had taken twice as long to respond to the color pairs in the previous study). Possible reasons for these results are discussed, and potential applications for the results, and for the testing methodology developed, are outlined.

Using Single Colors and Color Pairs to Communicate Basic Tastes II: Foreground–Background Color Combinations

PubMed Central

Marmolejo-Ramos, Fernando; Velasco, Carlos; Spence, Charles

2016-01-01

People associate basic tastes (e.g., sweet, sour, bitter, and salty) with specific colors (e.g., pink or red, green or yellow, black or purple, and white or blue). In the present study, we investigated whether a color bordered by another color (either the same or different) would give rise to stronger taste associations relative to a single patch of color. We replicate previous findings, highlighting the existence of a robust crossmodal correspondence between individual colors and basic tastes. On occasion, color pairs were found to communicate taste expectations more consistently than were single color patches. Furthermore, and in contrast to a recent study in which the color pairs were shown side-by-side, participants took no longer to match the color pairs with tastes than the single colors (they had taken twice as long to respond to the color pairs in the previous study). Possible reasons for these results are discussed, and potential applications for the results, and for the testing methodology developed, are outlined. PMID:27708752

Two-step fabrication of single-layer rectangular SnSe flakes

NASA Astrophysics Data System (ADS)

Jiang, Jizhou; Wong, Calvin Pei Yu; Zou, Jing; Li, Shisheng; Wang, Qixing; Chen, Jianyi; Qi, Dianyu; Wang, Hongyu; Eda, Goki; Chua, Daniel H. C.; Shi, Yumeng; Zhang, Wenjing; Thye Shen Wee, Andrew

2017-06-01

Recent findings about ultrahigh thermoelectric performances in SnSe single crystals have stimulated research on this binary semiconductor material. Furthermore, single-layer SnSe is an interesting analogue of phosphorene, with potential applications in two-dimensional (2D) nanoelectronics. Although significant advances in the synthesis of SnSe nanocrystals have been made, fabrication of well-defined large-sized single-layer SnSe flakes in a facile way still remains a challenge. The growth of single-layer rectangular SnSe flakes with a thickness of ~6.8 Å and lateral dimensions of about 30 µm  ×  50 µm is demonstrated by a two-step synthesis method, where bulk rectangular SnSe flakes were synthesized first by a vapor transport deposition method followed by a nitrogen etching technique to fabricate single-layer rectangular SnSe flakes in an atmospheric pressure system. The as-obtained rectangular SnSe flakes exhibited a pure crystalline phase oriented along the a-axis direction. Field-effect transistor devices fabricated on individual single-layer rectangular SnSe flakes using gold electrodes exhibited p-doped ambipolar behavior and a hole mobility of about 0.16 cm2 V-1 s-1. This two-step fabrication method can be helpful for growing other similar 2D large-sized single-layer materials.

Diffusion in Single Supported Lipid Bilayers

NASA Astrophysics Data System (ADS)

Armstrong, C. L.; Trapp, M.; Rheinstädter, M. C.

2011-03-01

Despite their potential relevance for the development of functionalized surfaces and biosensors, the study of single supported membranes using neutron scattering has been limited by the challenge of obtaining relevant dynamic information from a sample with minimal material. Using state of the art neutron instrumentation we have, for the first time, modeled lipid diffusion in single supported lipid bilayers. While we find that the diffusion coefficient for the single bilayer system is comparable to a multi-lamellar lipid system, the molecular mechanism for lipid motion in the single bilayer is a continuous diffusion process with no sign of the flow-like ballistic motion reported in the stacked membrane system. In the future, these membranes will be used to hold and align proteins, mimicking physiological conditions enabling the study of protein structure, function and interactions in relevant and highly topical membrane/protein systems with minimal sample material. C.L. Armstrong, M.D. Kaye, M. Zamponi, E. Mamontov, M. Tyagi, T. Jenkins and M.C. Rheinstädter, Soft Matter Communication, 2010, Advance Article, DOI: 10.1039/C0SM00637H

Cell water potential, osmotic potential, and turgor in the epidermis and mesophyll of transpiring leaves : Combined measurements with the cell pressure probe and nanoliter osmometer.

PubMed

Nonami, H; Schulze, E D

1989-01-01

Water potential, osmotic potential and turgor measurements obtained by using a cell pressure probe together with a nanoliter osmometer were compared with measurements obtained with an isopiestic psychrometer. Both types of measurements were conducted in the mature region of Tradescantia virginiana L. leaves under non-transpiring conditions in the dark, and gave similar values of all potentials. This finding indicates that the pressure probe and the osmometer provide accurate measurements of turgor, osmotic potentials and water potentials. Because the pressure probe does not require long equilibration times and can measure turgor of single cells in intact plants, the pressure probe together with the osmometer was used to determine in-situ cell water potentials, osmotic potentials and turgor of epidermal and mesophyll cells of transpiring leaves as functions of stomatal aperture and xylem water potential. When the xylem water potential was-0.1 MPa, the stomatal aperture was at its maximum, but turgor of both epidermal and mesophyll cells was relatively low. As the xylem water potential decreased, the stomatal aperture became gradually smaller, whereas turgor of both epidermal and mesophyll cells first increased and afterward decreased. Water potentials of the mesophyll cells were always lower than those of the epidermal cells. These findings indicate that evaporation of water is mainly occurring from mesophyll cells and that peristomatal transpiration could be less important than it has been proposed previously, although peristomatal transpiration may be directly related to regulation of turgor in the guard cells.

ΛcN interaction from lattice QCD and its application to Λc hypernuclei

NASA Astrophysics Data System (ADS)

Miyamoto, Takaya; Aoki, Sinya; Doi, Takumi; Gongyo, Shinya; Hatsuda, Tetsuo; Ikeda, Yoichi; Inoue, Takashi; Iritani, Takumi; Ishii, Noriyoshi; Kawai, Daisuke; Murano, Keiko; Nemura, Hidekatsu; Sasaki, Kenji

2018-03-01

The interaction between Λc and a nucleon (N) is investigated by employing the HAL QCD method in the (2 + 1)-flavor lattice QCD on a (2.9fm) 3 volume at mπ ≃ 410 , 570 , 700 MeV. We study the central potential in S10 channel as well as central and tensor potentials in S31-3D1 channel, and find that the tensor potential for Λc N is negligibly weak and central potentials in both S10 and S31-3D1 channels are almost identical with each other except at short distances. Phase shifts and scattering lengths calculated with these potentials show that the interaction of Λc N system is attractive and has a similar strength in S10 and S31 channels at low energies (i.e. the kinetic energy less than about 40 MeV). While the attractions are not strong enough to form two-body bound states, our results lead to a possibility to form Λc hypernuclei for sufficiently large atomic numbers (A). To demonstrate this, we derive a single-folding potential for Λc hypernuclei from the Λc-nucleon potential obtained in lattice QCD, and find that Λc hypernuclei can exist for A ≥ 12 with the binding energies of a few MeV. We also estimate the Coulomb effect for the Λc hypernuclei.

Orbits in elementary, power-law galaxy bars - 1. Occurrence and role of single loops

NASA Astrophysics Data System (ADS)

Struck, Curtis

2018-05-01

Orbits in galaxy bars are generally complex, but simple closed loop orbits play an important role in our conceptual understanding of bars. Such orbits are found in some well-studied potentials, provide a simple model of the bar in themselves, and may generate complex orbit families. The precessing, power ellipse (p-ellipse) orbit approximation provides accurate analytic orbit fits in symmetric galaxy potentials. It remains useful for finding and fitting simple loop orbits in the frame of a rotating bar with bar-like and symmetric power-law potentials. Second-order perturbation theory yields two or fewer simple loop solutions in these potentials. Numerical integrations in the parameter space neighbourhood of perturbation solutions reveal zero or one actual loops in a range of such potentials with rising rotation curves. These loops are embedded in a small parameter region of similar, but librating orbits, which have a subharmonic frequency superimposed on the basic loop. These loops and their librating companions support annular bars. Solid bars can be produced in more complex potentials, as shown by an example with power-law indices varying with radius. The power-law potentials can be viewed as the elementary constituents of more complex potentials. Numerical integrations also reveal interesting classes of orbits with multiple loops. In two-dimensional, self-gravitating bars, with power-law potentials, single-loop orbits are very rare. This result suggests that gas bars or oval distortions are unlikely to be long-lived, and that complex orbits or three-dimensional structure must support self-gravitating stellar bars.

Study on mixis potential of rotifer resting eggs ( Brachionus plicatilis) with different collection times and different preservation periods

NASA Astrophysics Data System (ADS)

Zhou, Li; Zheng, Yan; Xiang, Jian-Hai

2001-09-01

The present study investigated the possible changes in the mixis potential of rotifer resting eggs produced by a single stock of Brachionus plicatilis and collected and preserved annually from 1985 1998. Several clones derived from each batch of resting eggs were cultured under the same conditions for 21 days. The percentage of clones appearing resting eggs and the average yield of resting eggs produced from each clone were recorded and statistically analyzed to find the differences between the mixis potential of those resting egg batches. Results showed that different batches of resting eggs had different mictic levels among their descendent clones; but no regular relationship was found between the mixis potential of resting eggs and their collection times/preservation periods. Several internal and external factors that might affect the mixis potential of resting eggs were discussed.

Hunting for brown dwarf binaries with X-Shooter

NASA Astrophysics Data System (ADS)

Manjavacas, E.; Goldman, B.; Alcalá, J. M.; Zapatero-Osorio, M. R.; Béjar, B. J. S.; Homeier, D.; Bonnefoy, M.; Smart, R. L.; Henning, T.; Allard, F.

2015-05-01

The refinement of the brown dwarf binary fraction may contribute to the understanding of the substellar formation mechanisms. Peculiar brown dwarf spectra or discrepancy between optical and near-infrared spectral type classification of brown dwarfs may indicate unresolved brown dwarf binary systems. We obtained medium-resolution spectra of 22 brown dwarfs of potential binary candidates using X-Shooter at the VLT. We aimed to select brown dwarf binary candidates. We also tested whether BT-Settl 2014 atmospheric models reproduce the physics in the atmospheres of these objects. To find different spectral type spectral binaries, we used spectral indices and we compared the selected candidates to single spectra and composition of two single spectra from libraries, to try to reproduce our X-Shooter spectra. We also created artificial binaries within the same spectral class, and we tried to find them using the same method as for brown dwarf binaries with different spectral types. We compared our spectra to the BT-Settl models 2014. We selected six possible candidates to be combination of L plus T brown dwarfs. All candidates, except one, are better reproduced by a combination of two single brown dwarf spectra than by a single spectrum. The one-sided F-test discarded this object as a binary candidate. We found that we are not able to find the artificial binaries with components of the same spectral type using the same method used for L plus T brown dwarfs. Best matches to models gave a range of effective temperatures between 950 K and 1900 K, a range of gravities between 4.0 and 5.5. Some best matches corresponded to supersolar metallicity.

Permeability of nanonet structures constructed on the basis of carbon tubes

NASA Astrophysics Data System (ADS)

Bubenchikov, M. A.; Nikipelova, T. I.; Tsyrenova, V. B.; Chelnokova, A. S.

2017-11-01

An approximate integration of a potential of paired molecular interactions over the circumferential coordinate is used to find the potential of the interaction between a molecule and an infinite carbon nanotube (CNT). Based on the obtained energy of interaction between the tube and the molecules, local effective radii of the investigated carbon structures with respect to the molecules of the separated gas mixture are found. This makes it possible to calculate permeability of a single-layer, along with a two-layer CNT packing. The conducted research allowed calculating permeability of a nanonet structure as permeability of a two-layer packing of carbon nanotubes for the first time.

Striking hematological abnormalities in patients with microcephalic osteodysplastic primordial dwarfism type II (MOPD II): a potential role of pericentrin in hematopoiesis.

PubMed

Unal, Sule; Alanay, Yasemin; Cetin, Mualla; Boduroglu, Koray; Utine, Eda; Cormier-Daire, Valerie; Huber, Celine; Ozsurekci, Yasemin; Kilic, Esra; Simsek Kiper, Ozlem Pelin; Gumruk, Fatma

2014-02-01

Microcephalic osteodysplastic primordial dwarfism type II (MOPD II) is a rare primordial dwarfism that is similar to Seckel syndrome. Seckel syndrome is known to be associated with various hematological abnormalities; however, hematological findings in MOPD II patients have not been previously reported. The present study aimed to describe the hematological findings in a series of eight patients with MOPD II from a single center. The study included eight patients with MOPD II that were analyzed via molecular testing, and physical and laboratory examinations. Molecular testing showed that seven of the eight patients had pericentrin (PCNT) gene mutations. Hematological evaluation showed that 7 (87.5%) patients had thrombocytosis, 6 (75%) had leukocytosis, 5 (62.5%) had both leukocytosis and thrombocytosis, and 2 (25%) had anemia. We report leukocytosis and thrombocytosis as a common hematologic abnormality in patients with MOPD II. The present findings may improve our understanding of the potential function of the PCNT gene in hematopoietic cell proliferation and differentiation. © 2013 Wiley Periodicals, Inc.

Eugenol prevents amyloid formation of proteins and inhibits amyloid-induced hemolysis

NASA Astrophysics Data System (ADS)

Dubey, Kriti; Anand, Bibin G.; Shekhawat, Dolat Singh; Kar, Karunakar

2017-02-01

Eugenol has attracted considerable attention because of its potential for many pharmaceutical applications including anti-inflammatory, anti-tumorigenic and anti-oxidant properties. Here, we have investigated the effect of eugenol on amyloid formation of selected globular proteins. We find that both spontaneous and seed-induced aggregation processes of insulin and serum albumin (BSA) are significantly suppressed in the presence of eugenol. Isothermal titration calorimetric data predict a single binding site for eugenol-insulin complex confirming the affinity of eugenol for native soluble insulin species. We also find that eugenol suppresses amyloid-induced hemolysis. Our findings reveal the inherent ability of eugenol to stabilize native proteins and to delay the conversion of protein species of native conformation into β-sheet assembled mature fibrils, which seems to be crucial for its inhibitory effect.

Real-time estimation and biofeedback of single-neuron firing rates using local field potentials

PubMed Central

Hall, Thomas M.; Nazarpour, Kianoush; Jackson, Andrew

2014-01-01

The long-term stability and low-frequency composition of local field potentials (LFPs) offer important advantages for robust and efficient neuroprostheses. However, cortical LFPs recorded by multi-electrode arrays are often assumed to contain only redundant information arising from the activity of large neuronal populations. Here we show that multichannel LFPs in monkey motor cortex each contain a slightly different mixture of distinctive slow potentials that accompany neuronal firing. As a result, the firing rates of individual neurons can be estimated with surprising accuracy. We implemented this method in a real-time biofeedback brain–machine interface, and found that monkeys could learn to modulate the activity of arbitrary neurons using feedback derived solely from LFPs. These findings provide a principled method for monitoring individual neurons without long-term recording of action potentials. PMID:25394574

Hierarchical nanostructured WO3-SnO2 for selective sensing of volatile organic compounds

NASA Astrophysics Data System (ADS)

Nayak, Arpan Kumar; Ghosh, Ruma; Santra, Sumita; Guha, Prasanta Kumar; Pradhan, Debabrata

2015-07-01

It remains a challenge to find a suitable gas sensing material that shows a high response and shows selectivity towards various gases simultaneously. Here, we report a mixed metal oxide WO3-SnO2 nanostructured material synthesized in situ by a simple, single-step, one-pot hydrothermal method at 200 °C in 12 h, and demonstrate its superior sensing behavior towards volatile organic compounds (VOCs) such as ammonia, ethanol and acetone. SnO2 nanoparticles with controlled size and density were uniformly grown on WO3 nanoplates by varying the tin precursor. The density of the SnO2 nanoparticles on the WO3 nanoplates plays a crucial role in the VOC selectivity. The responses of the present mixed metal oxides are found to be much higher than the previously reported results based on single/mixed oxides and noble metal-doped oxides. In addition, the VOC selectivity is found to be highly temperature-dependent, with optimum performance obtained at 200 °C, 300 °C and 350 °C for ammonia, ethanol and acetone, respectively. The present results on the cost-effective noble metal-free WO3-SnO2 sensor could find potential application in human breath analysis by non-invasive detection.It remains a challenge to find a suitable gas sensing material that shows a high response and shows selectivity towards various gases simultaneously. Here, we report a mixed metal oxide WO3-SnO2 nanostructured material synthesized in situ by a simple, single-step, one-pot hydrothermal method at 200 °C in 12 h, and demonstrate its superior sensing behavior towards volatile organic compounds (VOCs) such as ammonia, ethanol and acetone. SnO2 nanoparticles with controlled size and density were uniformly grown on WO3 nanoplates by varying the tin precursor. The density of the SnO2 nanoparticles on the WO3 nanoplates plays a crucial role in the VOC selectivity. The responses of the present mixed metal oxides are found to be much higher than the previously reported results based on single/mixed oxides and noble metal-doped oxides. In addition, the VOC selectivity is found to be highly temperature-dependent, with optimum performance obtained at 200 °C, 300 °C and 350 °C for ammonia, ethanol and acetone, respectively. The present results on the cost-effective noble metal-free WO3-SnO2 sensor could find potential application in human breath analysis by non-invasive detection. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02571k

On the limited recognition of inorganic surfaces by short peptides compared with antibodies.

PubMed

Artzy-Schnirman, Arbel; Abu-Shah, Enas; Dishon, Matan; Soifer, Hadas; Sivan, Yotam; Reiter, Yoram; Benhar, Itai; Sivan, Uri

2014-06-01

The vast potential applications of biomolecules that bind inorganic surfaces led mostly to the isolation of short peptides that target selectively specific materials. The demonstrated differential affinity toward certain surfaces created the impression that the recognition capacity of short peptides may match that of rigid biomolecules. In the following, we challenge this view by comparing the capacity of antibody molecules to discriminate between the (100) and (111A) facets of a gallium arsenide semiconductor crystal with the capacity of short peptides to do the same. Applying selection from several peptide and single chain phage display libraries, we find a number of antibody molecules that bind preferentially a given crystal facet but fail to isolate, in dozens of attempts, a single peptide capable of such recognition. The experiments underscore the importance of rigidity to the recognition of inorganic flat targets and therefore set limitations on potential applications of short peptides in biomimetics. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.

Parsing the genetic heterogeneity of chromosome 12q susceptibility genes for Alzheimer disease by family-based association analysis.

PubMed

Lin, Ping-I; Martin, Eden R; Browning-Large, Carrie A; Schmechel, Donald E; Welsh-Bohmer, Kathleen A; Doraiswamy, P Murali; Gilbert, John R; Haines, Jonathan L; Pericak-Vance, Margaret A

2006-07-01

Previous linkage studies have suggested that chromosome 12 may harbor susceptibility genes for late-onset Alzheimer disease (LOAD). No risk genes on chromosome 12 have been conclusively identified yet. We have reported that the linkage evidence for LOAD in a 12q region was significantly increased in autopsy-confirmed families particularly for those showing no linkage to alpha-T catenin gene, a LOAD candidate gene on chromosome 10 [LOD score increased from 0.1 in the autopsy-confirmed subset to 4.19 in the unlinked subset (optimal subset); p<0.0001 for the increase in LOD score], indicating a one-LOD support interval spanning 6 Mb. To further investigate this finding and to identify potential candidate LOAD risk genes for follow-up analysis, we analyzed 99 single nucleotide polymorphisms in this region, for the overall sample, the autopsy-confirmed subset, and the optimal subset, respectively, for comparison. We saw no significant association (p<0.01) in the overall sample. In the autopsy-confirmed subset, the best finding was obtained in the activation transcription factor 7 (ATF7) gene (single-locus association, p=0.002; haplotype association global, p=0.007). In the optimal subset, the best finding was obtained in the hypothetical protein FLJ20436 (FLJ20436) gene (single-locus association, p=0.0026). These results suggest that subset and covariate analyses may be one approach to help identify novel susceptibility genes on chromosome 12q for LOAD.

Gram-scale synthesis of single-crystalline graphene quantum dots with superior optical properties.

PubMed

Wang, Liang; Wang, Yanli; Xu, Tao; Liao, Haobo; Yao, Chenjie; Liu, Yuan; Li, Zhen; Chen, Zhiwen; Pan, Dengyu; Sun, Litao; Wu, Minghong

2014-10-28

Graphene quantum dots (GQDs) have various alluring properties and potential applications, but their large-scale applications are limited by current synthetic methods that commonly produce GQDs in small amounts. Moreover, GQDs usually exhibit polycrystalline or highly defective structures and thus poor optical properties. Here we report the gram-scale synthesis of single-crystalline GQDs by a facile molecular fusion route under mild and green hydrothermal conditions. The synthesis involves the nitration of pyrene followed by hydrothermal treatment in alkaline aqueous solutions, where alkaline species play a crucial role in tuning their size, functionalization and optical properties. The single-crystalline GQDs are bestowed with excellent optical properties such as bright excitonic fluorescence, strong excitonic absorption bands extending to the visible region, large molar extinction coefficients and long-term photostability. These high-quality GQDs can find a large array of novel applications in bioimaging, biosensing, light emitting diodes, solar cells, hydrogen production, fuel cells and supercapacitors.

NASA's Single-Pilot Operations Technical Interchange Meeting: Proceedings and Findings

NASA Technical Reports Server (NTRS)

Comerford, Doreen; Brandt, Summer L.; Lachter, Joel B.; Wu, Shu-Chieh; Mogford, Richard H.; Battiste, Vernol; Johnson, Walter W.

2013-01-01

Researchers at the National Aeronautics and Space Administration (NASA) Ames Research Center and Langley Research Center are jointly investigating issues associated with potential concepts, or configurations, in which a single pilot might operate under conditions that are currently reserved for a minimum of two pilots. As part of early efforts, NASA Ames Research Center hosted a technical interchange meeting in order to gain insight from members of the aviation community regarding single-pilot operations (SPO). The meeting was held on April 10-12, 2012 at NASA Ames Research Center. Professionals in the aviation domain were invited because their areas of expertise were deemed to be directly related to an exploration of SPO. NASA, in selecting prospective participants, attempted to represent various relevant sectors within the aviation domain. Approximately 70 people representing government, academia, and industry attended. A primary focus of this gathering was to consider how tasks and responsibilities might be re-allocated to allow for SPO.

Theoretical Investigation of Single-Molecule Sensing Using Nanotube-Enhanced Circular Dichroism.

PubMed

Silva, Jaime; Milne, Bruce F; Nogueira, Fernando

2018-06-19

First-principles calculations have been used to investigate the potential use of circular dichroism (CD) spectroscopy in single-molecule sensing. Using a real-space implementation of time-dependent density functional theory (TDDFT), several systems involving single-walled carbon nanotubes (SWCNT) and small molecules have been studied to evaluate their CD response. Large induced CD (ICD) effects, differing for each test molecule, were observed in all SWCNT-molecule complexes. As the SWCNT used in this study shows no intrinsic CD response, the ICD spectra are the result of interaction with the small molecules. This finding is general and independent of the (a)chiral nature of the adsorbed molecule. Our results indicate that it is possible to design a system that uses SWCNT for detection of molecules using the change in CD spectrum of the system induced by adsorption of the molecule onto the SWCNT surface.

Stiffness, working stroke, and force of single-myosin molecules in skeletal muscle: elucidation of these mechanical properties via nonlinear elasticity evaluation.

PubMed

Kaya, Motoshi; Higuchi, Hideo

2013-11-01

In muscles, the arrays of skeletal myosin molecules interact with actin filaments and continuously generate force at various contraction speeds. Therefore, it is crucial for myosin molecules to generate force collectively and minimize the interference between individual myosin molecules. Knowledge of the elasticity of myosin molecules is crucial for understanding the molecular mechanisms of muscle contractions because elasticity directly affects the working and drag (resistance) force generation when myosin molecules are positively or negatively strained. The working stroke distance is also an important mechanical property necessary for elucidation of the thermodynamic efficiency of muscle contractions at the molecular level. In this review, we focus on these mechanical properties obtained from single-fiber and single-molecule studies and discuss recent findings associated with these mechanical properties. We also discuss the potential molecular mechanisms associated with reduction of the drag effect caused by negatively strained myosin molecules.

Sub-micrometre accurate free-form optics by three-dimensional printing on single-mode fibres

PubMed Central

Gissibl, Timo; Thiele, Simon; Herkommer, Alois; Giessen, Harald

2016-01-01

Micro-optics are widely used in numerous applications, such as beam shaping, collimation, focusing and imaging. We use femtosecond 3D printing to manufacture free-form micro-optical elements. Our method gives sub-micrometre accuracy so that direct manufacturing even on single-mode fibres is possible. We demonstrate the potential of our method by writing different collimation optics, toric lenses, free-form surfaces with polynomials of up to 10th order for intensity beam shaping, as well as chiral photonic crystals for circular polarization filtering, all aligned onto the core of the single-mode fibres. We determine the accuracy of our optics by analysing the output patterns as well as interferometrically characterizing the surfaces. We find excellent agreement with numerical calculations. 3D printing of microoptics can achieve sufficient performance that will allow for rapid prototyping and production of beam-shaping and imaging devices. PMID:27339700

Sub-micrometre accurate free-form optics by three-dimensional printing on single-mode fibres.

PubMed

Gissibl, Timo; Thiele, Simon; Herkommer, Alois; Giessen, Harald

2016-06-24

Micro-optics are widely used in numerous applications, such as beam shaping, collimation, focusing and imaging. We use femtosecond 3D printing to manufacture free-form micro-optical elements. Our method gives sub-micrometre accuracy so that direct manufacturing even on single-mode fibres is possible. We demonstrate the potential of our method by writing different collimation optics, toric lenses, free-form surfaces with polynomials of up to 10th order for intensity beam shaping, as well as chiral photonic crystals for circular polarization filtering, all aligned onto the core of the single-mode fibres. We determine the accuracy of our optics by analysing the output patterns as well as interferometrically characterizing the surfaces. We find excellent agreement with numerical calculations. 3D printing of microoptics can achieve sufficient performance that will allow for rapid prototyping and production of beam-shaping and imaging devices.

Tuning and Switching Enantioselectivity of Asymmetric Carboligation in an Enzyme through Mutational Analysis of a Single Hot Spot.

PubMed

Wechsler, Cindy; Meyer, Danilo; Loschonsky, Sabrina; Funk, Lisa-Marie; Neumann, Piotr; Ficner, Ralf; Brodhun, Florian; Müller, Michael; Tittmann, Kai

2015-12-01

Enantioselective bond making and breaking is a hallmark of enzyme action, yet switching the enantioselectivity of the reaction is a difficult undertaking, and typically requires extensive screening of mutant libraries and multiple mutations. Here, we demonstrate that mutational diversification of a single catalytic hot spot in the enzyme pyruvate decarboxylase gives access to both enantiomers of acyloins acetoin and phenylacetylcarbinol, important pharmaceutical precursors, in the case of acetoin even starting from the unselective wild-type protein. Protein crystallography was used to rationalize these findings and to propose a mechanistic model of how enantioselectivity is controlled. In a broader context, our studies highlight the efficiency of mechanism-inspired and structure-guided rational protein design for enhancing and switching enantioselectivity of enzymatic reactions, by systematically exploring the biocatalytic potential of a single hot spot. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sub-micrometre accurate free-form optics by three-dimensional printing on single-mode fibres

NASA Astrophysics Data System (ADS)

Gissibl, Timo; Thiele, Simon; Herkommer, Alois; Giessen, Harald

2016-06-01

Micro-optics are widely used in numerous applications, such as beam shaping, collimation, focusing and imaging. We use femtosecond 3D printing to manufacture free-form micro-optical elements. Our method gives sub-micrometre accuracy so that direct manufacturing even on single-mode fibres is possible. We demonstrate the potential of our method by writing different collimation optics, toric lenses, free-form surfaces with polynomials of up to 10th order for intensity beam shaping, as well as chiral photonic crystals for circular polarization filtering, all aligned onto the core of the single-mode fibres. We determine the accuracy of our optics by analysing the output patterns as well as interferometrically characterizing the surfaces. We find excellent agreement with numerical calculations. 3D printing of microoptics can achieve sufficient performance that will allow for rapid prototyping and production of beam-shaping and imaging devices.

Temporal interference with frequency-controllable long photons from independent cold atomic sources

NASA Astrophysics Data System (ADS)

Qian, Peng; Gu, Zhenjie; Wen, Rong; Zhang, Weiping; Chen, J. F.

2018-01-01

The interference of single photons from independent sources is an essential tool in quantum information processing. However, the interfering of photons with long temporal states in a time-resolved manner has rarely been studied. This is because without transmitting spectral filters or coupling to a cavity mode single photons generated in traditional nonlinear crystals suffer from a short temporal profile below 1 ns. With spectral correlation maintained in the biphotons generated from spontaneous four-wave mixing process in cold atom clouds, here we demonstrate the temporal interference of two frequency-tunable long photons from two independent cold atomic sources. We observe and analyze the interference of frequency-mismatched photons, where the phenomenon of the quantum beat at megahertz separation is displayed. Our paper provides more details for the quantum beat of two independent narrow-band single photons, which may find potential application in frequency-encoded photonic qubits in quantum information processing.

Learning rules for spike timing-dependent plasticity depend on dendritic synapse location.

PubMed

Letzkus, Johannes J; Kampa, Björn M; Stuart, Greg J

2006-10-11

Previous studies focusing on the temporal rules governing changes in synaptic strength during spike timing-dependent synaptic plasticity (STDP) have paid little attention to the fact that synaptic inputs are distributed across complex dendritic trees. During STDP, propagation of action potentials (APs) back to the site of synaptic input is thought to trigger plasticity. However, in pyramidal neurons, backpropagation of single APs is decremental, whereas high-frequency bursts lead to generation of distal dendritic calcium spikes. This raises the question whether STDP learning rules depend on synapse location and firing mode. Here, we investigate this issue at synapses between layer 2/3 and layer 5 pyramidal neurons in somatosensory cortex. We find that low-frequency pairing of single APs at positive times leads to a distance-dependent shift to long-term depression (LTD) at distal inputs. At proximal sites, this LTD could be converted to long-term potentiation (LTP) by dendritic depolarizations suprathreshold for BAC-firing or by high-frequency AP bursts. During AP bursts, we observed a progressive, distance-dependent shift in the timing requirements for induction of LTP and LTD, such that distal synapses display novel timing rules: they potentiate when inputs are activated after burst onset (negative timing) but depress when activated before burst onset (positive timing). These findings could be explained by distance-dependent differences in the underlying dendritic voltage waveforms driving NMDA receptor activation during STDP induction. Our results suggest that synapse location within the dendritic tree is a crucial determinant of STDP, and that synapses undergo plasticity according to local rather than global learning rules.

Bulk viscous quintessential inflation

NASA Astrophysics Data System (ADS)

Haro, Jaume; Pan, Supriya

In a spatially-flat Friedmann-Lemaître-Robertson-Walker universe, the incorporation of bulk viscous process in general relativity leads to an appearance of a nonsingular background of the universe that both at early and late times depicts an accelerated universe. These early and late scenarios of the universe can be analytically calculated and mimicked, in the context of general relativity, by a single scalar field whose potential could also be obtained analytically where the early inflationary phase is described by a one-dimensional Higgs potential and the current acceleration is realized by an exponential potential. We show that the early inflationary universe leads to a power spectrum of the cosmological perturbations which match with current observational data, and after leaving the inflationary phase, the universe suffers a phase transition needed to explain the reheating of the universe via gravitational particle production. Furthermore, we find that at late times, the universe enters into the de Sitter phase that can explain the current cosmic acceleration. Finally, we also find that such bulk viscous-dominated universe attains the thermodynamical equilibrium, but in an asymptotic manner.

Carbon nanotubes buckypaper radiation studies for medical physics applications.

PubMed

Alanazi, Abdulaziz; Alkhorayef, Mohammed; Alzimami, Khalid; Jurewicz, Izabela; Abuhadi, Nouf; Dalton, Alan; Bradley, D A

2016-11-01

Graphite ion chambers and semiconductor diode detectors have been used to make measurements in phantoms but these active devices represent a clear disadvantage when considered for in vivo dosimetry. In such circumstance, dosimeters with atomic number similar to human tissue are needed. Carbon nanotubes have properties that potentially meet the demand, requiring low voltage in active devices and an atomic number similar to adipose tissue. In this study, single-wall carbon nanotubes (SWCNTs) buckypaper has been used to measure the beta particle dose deposited from a strontium-90 source, the medium displaying thermoluminescence at potentially useful sensitivity. As an example, the samples show a clear response for a dose of 2Gy. This finding suggests that carbon nanotubes can be used as a passive dosimeter specifically for the high levels of radiation exposures used in radiation therapy. Furthermore, the finding points towards further potential applications such as for space radiation measurements, not least because the medium satisfies a demand for light but strong materials of minimal capacitance. Copyright © 2016 Elsevier Ltd. All rights reserved.

Integration trumps selection in object recognition.

PubMed

Saarela, Toni P; Landy, Michael S

2015-03-30

Finding and recognizing objects is a fundamental task of vision. Objects can be defined by several "cues" (color, luminance, texture, etc.), and humans can integrate sensory cues to improve detection and recognition [1-3]. Cortical mechanisms fuse information from multiple cues [4], and shape-selective neural mechanisms can display cue invariance by responding to a given shape independent of the visual cue defining it [5-8]. Selective attention, in contrast, improves recognition by isolating a subset of the visual information [9]. Humans can select single features (red or vertical) within a perceptual dimension (color or orientation), giving faster and more accurate responses to items having the attended feature [10, 11]. Attention elevates neural responses and sharpens neural tuning to the attended feature, as shown by studies in psychophysics and modeling [11, 12], imaging [13-16], and single-cell and neural population recordings [17, 18]. Besides single features, attention can select whole objects [19-21]. Objects are among the suggested "units" of attention because attention to a single feature of an object causes the selection of all of its features [19-21]. Here, we pit integration against attentional selection in object recognition. We find, first, that humans can integrate information near optimally from several perceptual dimensions (color, texture, luminance) to improve recognition. They cannot, however, isolate a single dimension even when the other dimensions provide task-irrelevant, potentially conflicting information. For object recognition, it appears that there is mandatory integration of information from multiple dimensions of visual experience. The advantage afforded by this integration, however, comes at the expense of attentional selection. Copyright © 2015 Elsevier Ltd. All rights reserved.

Integration trumps selection in object recognition

PubMed Central

Saarela, Toni P.; Landy, Michael S.

2015-01-01

Summary Finding and recognizing objects is a fundamental task of vision. Objects can be defined by several “cues” (color, luminance, texture etc.), and humans can integrate sensory cues to improve detection and recognition [1–3]. Cortical mechanisms fuse information from multiple cues [4], and shape-selective neural mechanisms can display cue-invariance by responding to a given shape independent of the visual cue defining it [5–8]. Selective attention, in contrast, improves recognition by isolating a subset of the visual information [9]. Humans can select single features (red or vertical) within a perceptual dimension (color or orientation), giving faster and more accurate responses to items having the attended feature [10,11]. Attention elevates neural responses and sharpens neural tuning to the attended feature, as shown by studies in psychophysics and modeling [11,12], imaging [13–16], and single-cell and neural population recordings [17,18]. Besides single features, attention can select whole objects [19–21]. Objects are among the suggested “units” of attention because attention to a single feature of an object causes the selection of all of its features [19–21]. Here, we pit integration against attentional selection in object recognition. We find, first, that humans can integrate information near-optimally from several perceptual dimensions (color, texture, luminance) to improve recognition. They cannot, however, isolate a single dimension even when the other dimensions provide task-irrelevant, potentially conflicting information. For object recognition, it appears that there is mandatory integration of information from multiple dimensions of visual experience. The advantage afforded by this integration, however, comes at the expense of attentional selection. PMID:25802154

Causal Effects of Single-Sex Schools on College Entrance Exams and College Attendance: Random Assignment in Seoul High Schools

PubMed Central

Park, Hyunjoon; Behrman, Jere R.; Choi, Jaesung

2012-01-01

Despite the voluminous literature on the potentials of single-sex schools, there is no consensus on the effects of single-sex schools because of student selection of school types. We exploit a unique feature of schooling in Seoul—the random assignment of students into single-sex versus coeducational high schools—to assess causal effects of single-sex schools on college entrance exam scores and college attendance. Our validation of the random assignment shows comparable socioeconomic backgrounds and prior academic achievement of students attending single-sex schools and coeducational schools, which increases the credibility of our causal estimates of single-sex school effects. The three-level hierarchical model shows that attending all-boys schools or all-girls schools, rather than coeducational schools, is significantly associated with higher average scores on Korean and English test scores. Applying the school district fixed-effects models, we find that single-sex schools produce a higher percentage of graduates who attended four-year colleges and a lower percentage of graduates who attended two-year junior colleges than do coeducational schools. The positive effects of single-sex schools remain substantial, even after we take into account various school-level variables, such as teacher quality, the student-teacher ratio, the proportion of students receiving lunch support, and whether the schools are public or private. PMID:23073751

Causal effects of single-sex schools on college entrance exams and college attendance: random assignment in Seoul high schools.

PubMed

Park, Hyunjoon; Behrman, Jere R; Choi, Jaesung

2013-04-01

Despite the voluminous literature on the potentials of single-sex schools, there is no consensus on the effects of single-sex schools because of student selection of school types. We exploit a unique feature of schooling in Seoul-the random assignment of students into single-sex versus coeducational high schools-to assess causal effects of single-sex schools on college entrance exam scores and college attendance. Our validation of the random assignment shows comparable socioeconomic backgrounds and prior academic achievement of students attending single-sex schools and coeducational schools, which increases the credibility of our causal estimates of single-sex school effects. The three-level hierarchical model shows that attending all-boys schools or all-girls schools, rather than coeducational schools, is significantly associated with higher average scores on Korean and English test scores. Applying the school district fixed-effects models, we find that single-sex schools produce a higher percentage of graduates who attended four-year colleges and a lower percentage of graduates who attended two-year junior colleges than do coeducational schools. The positive effects of single-sex schools remain substantial, even after we take into account various school-level variables, such as teacher quality, the student-teacher ratio, the proportion of students receiving lunch support, and whether the schools are public or private.

Low-Dimensional Materials for Optoelectronic and Bioelectronic Applications

NASA Astrophysics Data System (ADS)

Hong, Tu

In this thesis, we first discuss the fundamentals of ab initio electronic structure theory and density functional theory (DFT). We also discuss statistics related to computing thermodynamic averages of molecular dynamics (MD). We then use this theory to analyze and compare the structural, dynamical, and electronic properties of liquid water next to prototypical metals including platinum, graphite, and graphene. Our results are built on Born-Oppenheimer molecular dynamics (BOMD) generated using density functional theory (DFT) which explicitly include van der Waals (vdW) interactions within a first principles approach. All calculations reported use large simulation cells, allowing for an accurate treatment of the water-electrode interfaces. We have included vdW interactions through the use of the optB86b-vdW exchange correlation functional. Comparisons with the Perdew-Burke-Ernzerhof (PBE) exchange correlation functional are also shown. We find an initial peak, due to chemisorption, in the density profile of the liquid water-Pt interface not seen in the liquid water-graphite interface, liquid watergraphene interface, nor interfaces studied previously. To further investigate this chemisorption peak, we also report differences in the electronic structure of single water molecules on both Pt and graphite surfaces. We find that a covalent bond forms between the single water molecule and the platinum surface, but not between the single water molecule and the graphite surface. We also discuss the effects that defects and dopants in the graphite and graphene surfaces have on the structure and dynamics of liquid water. Lastly, we introduce artificial neural networks (ANNs), and demonstrate how they can be used to machine learn electronic structure calculations. As a proof of principle, we show the success of an ANN potential energy surfaces for a dimer molecule with a Lennard-Jones potential.

Fabrication of a single sub-micron pore spanning a single crystal (100) diamond membrane and impact on particle translocation [Particle translocation through a single crystal diamond pore fabricated by electron beam induced chemical etching

DOE PAGES

Webb, Jennifer R.; Martin, Aiden A.; Johnson, Robert P.; ...

2017-06-21

The fabrication of sub-micron pores in single crystal diamond membranes, which span the entirety of the membrane, is described for the first time, and the translocation properties of polymeric particles through the pore investigated. The pores are produced using a combination of laser micromachining to form the membrane and electron beam induced etching to form the pore. Single crystal diamond as the membrane material, has the advantages of chemical stability and durability, does not hydrate and swell, has outstanding electrical properties that facilitate fast, low noise current-time measurements and is optically transparent for combined optical-conductance sensing. The resulting pores aremore » characterized individually using both conductance measurements, employing a microcapillary electrochemical setup, and electron microscopy. Proof-of-concept experiments to sense charged polystyrene particles as they are electrophoretically driven through a single diamond pore are performed, and the impact of this new pore material on particle translocation is explored. As a result, these findings reveal the potential of diamond as a platform for pore-based sensing technologies and pave the way for the fabrication of single nanopores which span the entirety of a diamond membrane.« less

Fabrication of a single sub-micron pore spanning a single crystal (100) diamond membrane and impact on particle translocation [Particle translocation through a single crystal diamond pore fabricated by electron beam induced chemical etching

DOE Office of Scientific and Technical Information (OSTI.GOV)

Webb, Jennifer R.; Martin, Aiden A.; Johnson, Robert P.

The fabrication of sub-micron pores in single crystal diamond membranes, which span the entirety of the membrane, is described for the first time, and the translocation properties of polymeric particles through the pore investigated. The pores are produced using a combination of laser micromachining to form the membrane and electron beam induced etching to form the pore. Single crystal diamond as the membrane material, has the advantages of chemical stability and durability, does not hydrate and swell, has outstanding electrical properties that facilitate fast, low noise current-time measurements and is optically transparent for combined optical-conductance sensing. The resulting pores aremore » characterized individually using both conductance measurements, employing a microcapillary electrochemical setup, and electron microscopy. Proof-of-concept experiments to sense charged polystyrene particles as they are electrophoretically driven through a single diamond pore are performed, and the impact of this new pore material on particle translocation is explored. As a result, these findings reveal the potential of diamond as a platform for pore-based sensing technologies and pave the way for the fabrication of single nanopores which span the entirety of a diamond membrane.« less

Toward FRP-Based Brain-Machine Interfaces—Single-Trial Classification of Fixation-Related Potentials

PubMed Central

Finke, Andrea; Essig, Kai; Marchioro, Giuseppe; Ritter, Helge

2016-01-01

The co-registration of eye tracking and electroencephalography provides a holistic measure of ongoing cognitive processes. Recently, fixation-related potentials have been introduced to quantify the neural activity in such bi-modal recordings. Fixation-related potentials are time-locked to fixation onsets, just like event-related potentials are locked to stimulus onsets. Compared to existing electroencephalography-based brain-machine interfaces that depend on visual stimuli, fixation-related potentials have the advantages that they can be used in free, unconstrained viewing conditions and can also be classified on a single-trial level. Thus, fixation-related potentials have the potential to allow for conceptually different brain-machine interfaces that directly interpret cortical activity related to the visual processing of specific objects. However, existing research has investigated fixation-related potentials only with very restricted and highly unnatural stimuli in simple search tasks while participant’s body movements were restricted. We present a study where we relieved many of these restrictions while retaining some control by using a gaze-contingent visual search task. In our study, participants had to find a target object out of 12 complex and everyday objects presented on a screen while the electrical activity of the brain and eye movements were recorded simultaneously. Our results show that our proposed method for the classification of fixation-related potentials can clearly discriminate between fixations on relevant, non-relevant and background areas. Furthermore, we show that our classification approach generalizes not only to different test sets from the same participant, but also across participants. These results promise to open novel avenues for exploiting fixation-related potentials in electroencephalography-based brain-machine interfaces and thus providing a novel means for intuitive human-machine interaction. PMID:26812487

The role of potential agents in making spatial perspective taking social

PubMed Central

Clements-Stephens, Amy M.; Vasiljevic, Katarina; Murray, Alexandra J.; Shelton, Amy L.

2013-01-01

A striking relationship between visual spatial perspective taking (VSPT) and social skills has been demonstrated for perspective-taking tasks in which the target of the imagined or inferred perspective is a potential agent, suggesting that the presence of a potential agent may create a social context for the seemingly spatial task of imagining a novel visual perspective. In a series of studies, we set out to investigate how and when a target might be viewed as sufficiently agent-like to incur a social influence on VSPT performance. By varying the perceptual and conceptual features that defined the targets as potential agents, we find that even something as simple as suggesting animacy for a simple wooden block may be sufficient. More critically, we found that experience with one potential agent influenced the performance with subsequent targets, either by inducing or eliminating the influence of social skills on VSPT performance. These carryover effects suggest that the relationship between social skills and VSPT performance is mediated by a complex relationship that includes the task, the target, and the context in which that target is perceived. These findings highlight potential problems that arise when identifying a task as belonging exclusively to a single cognitive domain and stress instead the highly interactive nature of cognitive domains and their susceptibility to cross-domain individual differences. PMID:24046735

Testing the economic independence hypothesis: the effect of an exogenous increase in child support on subsequent marriage and cohabitation.

PubMed

Cancian, Maria; Meyer, Daniel R

2014-06-01

We examine the effects of an increase in income on the cohabitation and marriage of single mothers. Using data from an experiment that resulted in randomly assigned differences in child support receipt for welfare-receiving single mothers, we find that exogenous income increases (as a result of receiving all child support that was paid) are associated with significantly lower cohabitation rates between mothers and men who are not the fathers of their child(ren). Overall, these results support the hypothesis that additional income increases disadvantaged women's economic independence by reducing the need to be in the least stable type of partnerships. Our results also show the potential importance of distinguishing between biological and social fathers.

The cumulative impact of sexual revictimization on emotion regulation difficulties: an examination of female inmates.

PubMed

Walsh, Kate; DiLillo, David; Scalora, Mario J

2011-08-01

The present study examined associations between child sexual abuse (CSA), adult sexual victimization, and emotion regulation difficulties in a sample of 168 incarcerated women. Approximately 50% of the participants reported CSA, 54% reported adult sexual victimization, and 38% reported sexual revictimization (i.e., CSA and adult victimization). Revictimized women reported significantly greater difficulties with several facets of emotion regulation when compared to singly victimized and nonvictimized women. Interestingly, singly victimized women did not demonstrate greater emotion regulation deficits when compared to nonvictims. Findings suggest that the negative impact of victimization experiences on adult emotion regulation abilities may be cumulative. Furthermore, they highlight the potential importance of assessing and targeting emotion regulation difficulties among child abuse and adult sexual victimization survivors.

Possibility designing half-wave and full-wave molecular rectifiers by using single benzene molecule

NASA Astrophysics Data System (ADS)

Abbas, Mohammed A.; Hanoon, Falah H.; Al-Badry, Lafy F.

2018-02-01

This work focused on possibility designing half-wave and full-wave molecular rectifiers by using single and two benzene rings, respectively. The benzene rings were threaded by a magnetic flux that changes over time. The quantum interference effect was considered as the basic idea in the rectification action, the para and meta configurations were investigated. All the calculations are performed by using steady-state theoretical model, which is based on the time-dependent Hamiltonian model. The electrical conductance and the electric current are considered as DC output signals of half-wave and full-wave molecular rectifiers. The finding in this work opens up the exciting potential to use these molecular rectifiers in molecular electronics.

Metamaterial split ring resonator as a sensitive mechanical vibration sensor

NASA Astrophysics Data System (ADS)

Sikha Simon, K.; Chakyar, Sreedevi P.; Andrews, Jolly; Joseph V., P.

2017-06-01

This paper introduces a sensitive vibration sensor based on microwave metamaterial Split Ring Resonator (SRR) capable of detecting any ground vibration. The experimental setup consists of single Broad-side Coupled SRR (BCSRR) unit fixed on a cantilever capable of sensitive vibrations. It is arranged between transmitting and receiving probes of a microwave measurement system. The absorption level variations at the resonant frequency due to the displacement from the reference plane of SRR, which is a function of the strength of external mechanical vibration, is analyzed. This portable and cost effective sensor working on a single frequency is observed to be capable of detecting even very weak vibrations. This may find potential applications in the field of tamper-proofing, mining, quarrying and earthquake sensing.

Single-cell transcriptomics using spliced leader PCR: Evidence for multiple losses of photosynthesis in polykrikoid dinoflagellates.

PubMed

Gavelis, Gregory S; White, Richard A; Suttle, Curtis A; Keeling, Patrick J; Leander, Brian S

2015-07-17

Most microbial eukaryotes are uncultivated and thus poorly suited to standard genomic techniques. This is the case for Polykrikos lebouriae, a dinoflagellate with ultrastructurally aberrant plastids. It has been suggested that these plastids stem from a novel symbiosis with either a diatom or haptophyte, but this hypothesis has been difficult to test as P. lebouriae dwells in marine sand rife with potential genetic contaminants. We applied spliced-leader targeted PCR (SLPCR) to obtain dinoflagellate-specific transcriptomes on single-cell isolates of P. lebouriae from marine sediments. Polykrikos lebouriae expressed nuclear-encoded photosynthetic genes that were characteristic of the peridinin-plastids of dinoflagellates, rather than those from a diatom of haptophyte. We confirmed these findings at the genomic level using multiple displacement amplification (MDA) to obtain a partial plastome of P. lebouriae. From these data, we infer that P. lebouriae has retained the peridinin plastids ancestral for dinoflagellates as a whole, while its closest relatives have lost photosynthesis multiple times independently. We discuss these losses with reference to mixotrophy in polykrikoid dinoflagellates. Our findings demonstrate new levels of variation associated with the peridinin plastids of dinoflagellates and the usefulness of SLPCR approaches on single cell isolates. Unlike other transcriptomic methods, SLPCR has taxonomic specificity, and can in principle be adapted to different splice-leader bearing groups.

Kinetics of MDR Transport in Tumor-Initiating Cells

PubMed Central

Koshkin, Vasilij; Yang, Burton B.; Krylov, Sergey N.

2013-01-01

Multidrug resistance (MDR) driven by ABC (ATP binding cassette) membrane transporters is one of the major causes of treatment failure in human malignancy. MDR capacity is thought to be unevenly distributed among tumor cells, with higher capacity residing in tumor-initiating cells (TIC) (though opposite finding are occasionally reported). Functional evidence for enhanced MDR of TICs was previously provided using a “side population” assay. This assay estimates MDR capacity by a single parameter - cell’s ability to retain fluorescent MDR substrate, so that cells with high MDR capacity (“side population”) demonstrate low substrate retention. In the present work MDR in TICs was investigated in greater detail using a kinetic approach, which monitors MDR efflux from single cells. Analysis of kinetic traces obtained allowed for the estimation of both the velocity (V max) and affinity (K M) of MDR transport in single cells. In this way it was shown that activation of MDR in TICs occurs in two ways: through the increase of V max in one fraction of cells, and through decrease of K M in another fraction. In addition, kinetic data showed that heterogeneity of MDR parameters in TICs significantly exceeds that of bulk cells. Potential consequences of these findings for chemotherapy are discussed. PMID:24223908

Lesion location and cognitive impact of cerebral small vessel disease.

PubMed

Biesbroek, J Matthijs; Weaver, Nick A; Biessels, Geert Jan

2017-04-25

Cerebral small vessel disease (SVD) is an important cause of cognitive impairment. Important MRI manifestations of SVD include white matter hyperintensities (WMH) and lacunes. This narrative review addresses the role of anatomical lesion location in the impact of SVD on cognition, integrating findings from early autopsy studies with emerging findings from recent studies with advanced image analysis techniques. Early autopsy and imaging studies of small case series indicate that single lacunar infarcts in, for example the thalamus, caudate nucleus or internal capsule can cause marked cognitive impairment. However, the findings of such case studies may not be generalizable. Emerging location-based image analysis approaches are now being applied to large cohorts. Recent studies show that WMH burden in strategic white matter tracts, such as the forceps minor or anterior thalamic radiation (ATR), is more relevant in explaining variance in cognitive functioning than global WMH volume. These findings suggest that the future diagnostic work-up of memory clinic patients could potentially be improved by shifting from a global assessment of WMH and lacune burden towards a quantitative assessment of lesion volumes within strategic brain regions. In this review, a summary of currently known strategic regions for SVD-related cognitive impairment is provided, highlighting recent technical developments in SVD research. The potential and challenges of location-based approaches for diagnostic purposes in clinical practice are discussed, along with their potential prognostic and therapeutic applications. © 2017 The Author(s). published by Portland Press Limited on behalf of the Biochemical Society.

The environmental effect on the radial breathing mode of carbon nanotubes in water

NASA Astrophysics Data System (ADS)

Longhurst, M. J.; Quirke, N.

2006-06-01

We investigate, using molecular dynamics, the effect on the radial breathing mode (RBM) frequency of immersion in water for a range of single-walled carbon nanotubes. We find that nanotube-water interactions are responsible for an upshift in the RBM frequency of the order of 4-10 wave numbers. The upshift is comprised of two components: increased hydrostatic pressure on the nanotube due to curvature effects, and the dynamic coupling of the RBM with its solvation shell. In contrast to much of the current literature, we find that the latter of the two effects is dominant. This could serve as an innovative tool for determining the interaction potential between nanotubes/graphitic surfaces and fluids.

Regulation of Gene Editing Activity Directed by Single-Stranded Oligonucleotides and CRISPR/Cas9 Systems

PubMed Central

Bialk, Pawel; Rivera-Torres, Natalia; Strouse, Bryan; Kmiec, Eric B.

2015-01-01

Single-stranded DNA oligonucleotides (ssODNs) can direct the repair of a single base mutation in human genes. While the regulation of this gene editing reaction has been partially elucidated, the low frequency with which repair occurs has hampered development toward clinical application. In this work a CRISPR/Cas9 complex is employed to induce double strand DNA breakage at specific sites surrounding the nucleotide designated for exchange. The result is a significant elevation in ssODN-directed gene repair, validated by a phenotypic readout. By analysing reaction parameters, we have uncovered restrictions on gene editing activity involving CRISPR/Cas9 complexes. First, ssODNs that hybridize to the non-transcribed strand direct a higher level of gene repair than those that hybridize to the transcribed strand. Second, cleavage must be proximal to the targeted mutant base to enable higher levels of gene editing. Third, DNA cleavage enables a higher level of gene editing activity as compared to single-stranded DNA nicks, created by modified Cas9 (Nickases). Fourth, we calculated the hybridization potential and free energy levels of ssODNs that are complementary to the guide RNA sequences of CRISPRs used in this study. We find a correlation between free energy potential and the capacity of single-stranded oligonucleotides to inhibit specific DNA cleavage activity, thereby indirectly reducing gene editing activity. Our data provide novel information that might be taken into consideration in the design and usage of CRISPR/Cas9 systems with ssODNs for gene editing. PMID:26053390

Regulation of Gene Editing Activity Directed by Single-Stranded Oligonucleotides and CRISPR/Cas9 Systems.

PubMed

Bialk, Pawel; Rivera-Torres, Natalia; Strouse, Bryan; Kmiec, Eric B

2015-01-01

Single-stranded DNA oligonucleotides (ssODNs) can direct the repair of a single base mutation in human genes. While the regulation of this gene editing reaction has been partially elucidated, the low frequency with which repair occurs has hampered development toward clinical application. In this work a CRISPR/Cas9 complex is employed to induce double strand DNA breakage at specific sites surrounding the nucleotide designated for exchange. The result is a significant elevation in ssODN-directed gene repair, validated by a phenotypic readout. By analysing reaction parameters, we have uncovered restrictions on gene editing activity involving CRISPR/Cas9 complexes. First, ssODNs that hybridize to the non-transcribed strand direct a higher level of gene repair than those that hybridize to the transcribed strand. Second, cleavage must be proximal to the targeted mutant base to enable higher levels of gene editing. Third, DNA cleavage enables a higher level of gene editing activity as compared to single-stranded DNA nicks, created by modified Cas9 (Nickases). Fourth, we calculated the hybridization potential and free energy levels of ssODNs that are complementary to the guide RNA sequences of CRISPRs used in this study. We find a correlation between free energy potential and the capacity of single-stranded oligonucleotides to inhibit specific DNA cleavage activity, thereby indirectly reducing gene editing activity. Our data provide novel information that might be taken into consideration in the design and usage of CRISPR/Cas9 systems with ssODNs for gene editing.

Random walk on a leash: a simple single-molecule diffusion model for surface-tethered redox molecules with flexible linkers.

PubMed

Huang, Kuan-Chun; White, Ryan J

2013-08-28

We develop a random walk model to simulate the Brownian motion and the electrochemical response of a single molecule confined to an electrode surface via a flexible molecular tether. We use our simple model, which requires no prior knowledge of the physics of the molecular tether, to predict and better understand the voltammetric response of surface-confined redox molecules when motion of the redox molecule becomes important. The single molecule is confined to a hemispherical volume with a maximum radius determined by the flexible molecular tether (5-20 nm) and is allowed to undergo true three-dimensional diffusion. Distance- and potential-dependent electron transfer probabilities are evaluated throughout the simulations to generate cyclic voltammograms of the model system. We find that at sufficiently slow cyclic voltammetric scan rates the electrochemical reaction behaves like an adsorbed redox molecule with no mass transfer limitation; thus, the peak current is proportional to the scan rate. Conversely, at faster scan rates the diffusional motion of the molecule limits the simulated peak current, which exhibits a linear dependence on the square root of the scan rate. The switch between these two limiting regimes occurs when the diffusion layer thickness, (2Dt)(1/2), is ~10 times the tether length. Finally, we find that our model predicts the voltammetric behavior of a redox-active methylene blue tethered to an electrode surface via short flexible single-stranded, polythymine DNAs, allowing the estimation of diffusion coefficients for the end-tethered molecule.

The Effect of Phonons in RbCl Quantum Pseudodot Qubits

NASA Astrophysics Data System (ADS)

Sun, Yong; Ding, Zhao-Hua; Xiao, Jing-Lin

2016-07-01

By employing the Pekar variational method, the eigenenergies and eigenfunctions of the ground and first-excited states are obtained in a strong electron-longitudinal optical (LO) phonon coupling RbCl quantum pseudodot (QPD). A single qubit can be realized in this two-level quantum system. The electron probability density (EPD) oscillates in the RbCl QPD with a certain period. The investigated results show that the EPD rises with raising the chemical potential of the two-dimensional electron gas and the zero point of the pseudoharmonic potential, whereas it decays with increasing the polaron radius. However, the oscillating period (OP) possesses precisely the opposite characteristics. Through the results and analysis above, we find three ways to adjust the EPD and the OP via changing the chemical potential of the two-dimensional electron gas, the zero point of the pseudoharmonic potential, and the polaron radius.

Clinical Interpretation and Implications of Whole-Genome Sequencing

PubMed Central

Dewey, Frederick E.; Grove, Megan E.; Pan, Cuiping; Goldstein, Benjamin A.; Bernstein, Jonathan A.; Chaib, Hassan; Merker, Jason D.; Goldfeder, Rachel L.; Enns, Gregory M.; David, Sean P.; Pakdaman, Neda; Ormond, Kelly E.; Caleshu, Colleen; Kingham, Kerry; Klein, Teri E.; Whirl-Carrillo, Michelle; Sakamoto, Kenneth; Wheeler, Matthew T.; Butte, Atul J.; Ford, James M.; Boxer, Linda; Ioannidis, John P. A.; Yeung, Alan C.; Altman, Russ B.; Assimes, Themistocles L.; Snyder, Michael; Ashley, Euan A.; Quertermous, Thomas

2014-01-01

IMPORTANCE Whole-genome sequencing (WGS) is increasingly applied in clinical medicine and is expected to uncover clinically significant findings regardless of sequencing indication. OBJECTIVES To examine coverage and concordance of clinically relevant genetic variation provided by WGS technologies; to quantitate inherited disease risk and pharmacogenomic findings in WGS data and resources required for their discovery and interpretation; and to evaluate clinical action prompted by WGS findings. DESIGN, SETTING, AND PARTICIPANTS An exploratory study of 12 adult participants recruited at Stanford University Medical Center who underwent WGS between November 2011 and March 2012. A multidisciplinary team reviewed all potentially reportable genetic findings. Five physicians proposed initial clinical follow-up based on the genetic findings. MAIN OUTCOMES AND MEASURES Genome coverage and sequencing platform concordance in different categories of genetic disease risk, person-hours spent curating candidate disease-risk variants, interpretation agreement between trained curators and disease genetics databases, burden of inherited disease risk and pharmacogenomic findings, and burden and interrater agreement of proposed clinical follow-up. RESULTS Depending on sequencing platform, 10% to 19% of inherited disease genes were not covered to accepted standards for single nucleotide variant discovery. Genotype concordance was high for previously described single nucleotide genetic variants (99%-100%) but low for small insertion/deletion variants (53%-59%). Curation of 90 to 127 genetic variants in each participant required a median of 54 minutes (range, 5-223 minutes) per genetic variant, resulted in moderate classification agreement between professionals (Gross κ, 0.52; 95%CI, 0.40-0.64), and reclassified 69%of genetic variants cataloged as disease causing in mutation databases to variants of uncertain or lesser significance. Two to 6 personal disease-risk findings were discovered in each participant, including 1 frameshift deletion in the BRCA1 gene implicated in hereditary breast and ovarian cancer. Physician review of sequencing findings prompted consideration of a median of 1 to 3 initial diagnostic tests and referrals per participant, with fair interrater agreement about the suitability of WGS findings for clinical follow-up (Fleiss κ, 0.24; P < 001). CONCLUSIONS AND RELEVANCE In this exploratory study of 12 volunteer adults, the use of WGS was associated with incomplete coverage of inherited disease genes, low reproducibility of detection of genetic variation with the highest potential clinical effects, and uncertainty about clinically reportable findings. In certain cases, WGS will identify clinically actionable genetic variants warranting early medical intervention. These issues should be considered when determining the role of WGS in clinical medicine. PMID:24618965

SU (2) lattice gauge theory simulations on Fermi GPUs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cardoso, Nuno, E-mail: nunocardoso@cftp.ist.utl.p; Bicudo, Pedro, E-mail: bicudo@ist.utl.p

2011-05-10

In this work we explore the performance of CUDA in quenched lattice SU (2) simulations. CUDA, NVIDIA Compute Unified Device Architecture, is a hardware and software architecture developed by NVIDIA for computing on the GPU. We present an analysis and performance comparison between the GPU and CPU in single and double precision. Analyses with multiple GPUs and two different architectures (G200 and Fermi architectures) are also presented. In order to obtain a high performance, the code must be optimized for the GPU architecture, i.e., an implementation that exploits the memory hierarchy of the CUDA programming model. We produce codes formore » the Monte Carlo generation of SU (2) lattice gauge configurations, for the mean plaquette, for the Polyakov Loop at finite T and for the Wilson loop. We also present results for the potential using many configurations (50,000) without smearing and almost 2000 configurations with APE smearing. With two Fermi GPUs we have achieved an excellent performance of 200x the speed over one CPU, in single precision, around 110 Gflops/s. We also find that, using the Fermi architecture, double precision computations for the static quark-antiquark potential are not much slower (less than 2x slower) than single precision computations.« less

Agreement Between Computed Tomography and Pathologic Nodule Counts in Colorectal Lung Metastases.

PubMed

Marron, M Carmen; Lora, David; Gamez, Pablo; Rivas, Juan J; Embun, Raul; Molins, Laureano; de la Cruz, Javier

2016-01-01

Computed tomography is the most common technique used to estimate the number of pulmonary metastases and their resectability. A lack of agreement between radiologic and surgical pathologic findings could potentially lead to incomplete resection or to rejection of patients for potentially curative treatments. The objective of this study was to estimate the disagreement between the number of radiologic lesions and the number of histologically confirmed malignant lesions excised from patients with pulmonary metastases from colorectal cancer. This was a multicenter longitudinal study using a national registry. All patients underwent open surgery for pulmonary metastasectomy. Radiologic unilateral involvement was documented in 345 of 404 patients (85%); 253 (73%) presented with single nodules. The radiologic and malignant pathologic findings were concordant in 316 (78%) patients. The two independent predictors of discordance between computed tomography and the number of pathologic metastases were the bilateral involvement and the number of radiologic nodules. This model explained 28% of the variability in the disagreement frequency and discriminated between agreement and disagreement in 85% of the patients. Discrepancies increased with the nodule count with an odds ratio of 6.17 (95% confidence interval, 4.08 to 9.33) per additional nodule. For similar nodule counts, a lower disagreement frequency was observed among bilateral cases (odds ratio, 0.2; 95% confidence interval, 0.07 to 0.55). Differences between the radiologic and pathologic findings were documented in 1 of every 5 patients. The correlation was very accurate in patients with single radiologic nodules. However, half of the patients with more nodules showed discrepancies. Copyright © 2016 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Constraints on Cosmological Parameters from the Angular Power Spectrum of a Combined 2500 deg2 SPT-SZ and Planck Gravitational Lensing Map

NASA Astrophysics Data System (ADS)

Simard, G.; Omori, Y.; Aylor, K.; Baxter, E. J.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Cho, H.-M.; Chown, R.; Crawford, T. M.; Crites, A. T.; de Haan, T.; Dobbs, M. A.; Everett, W. B.; George, E. M.; Halverson, N. W.; Harrington, N. L.; Henning, J. W.; Holder, G. P.; Hou, Z.; Holzapfel, W. L.; Hrubes, J. D.; Knox, L.; Lee, A. T.; Leitch, E. M.; Luong-Van, D.; Manzotti, A.; McMahon, J. J.; Meyer, S. S.; Mocanu, L. M.; Mohr, J. J.; Natoli, T.; Padin, S.; Pryke, C.; Reichardt, C. L.; Ruhl, J. E.; Sayre, J. T.; Schaffer, K. K.; Shirokoff, E.; Staniszewski, Z.; Stark, A. A.; Story, K. T.; Vanderlinde, K.; Vieira, J. D.; Williamson, R.; Wu, W. L. K.

2018-06-01

We report constraints on cosmological parameters from the angular power spectrum of a cosmic microwave background (CMB) gravitational lensing potential map created using temperature data from 2500 deg2 of South Pole Telescope (SPT) data supplemented with data from Planck in the same sky region, with the statistical power in the combined map primarily from the SPT data. We fit the lensing power spectrum to a model including cold dark matter and a cosmological constant ({{Λ }}{CDM}), and to models with single-parameter extensions to {{Λ }}{CDM}. We find constraints that are comparable to and consistent with those found using the full-sky Planck CMB lensing data, e.g., {σ }8{{{Ω }}}{{m}}0.25 = 0.598 ± 0.024 from the lensing data alone with weak priors placed on other parameters. Combining with primary CMB data, we explore single-parameter extensions to {{Λ }}{CDM}. We find {{{Ω }}}k =-{0.012}-0.023+0.021 or {M}ν < 0.70 eV at 95% confidence, in good agreement with results including the lensing potential as measured by Planck. We include two parameters that scale the effect of lensing on the CMB: {A}L, which scales the lensing power spectrum in both the lens reconstruction power and in the smearing of the acoustic peaks, and {A}φ φ , which scales only the amplitude of the lensing reconstruction power spectrum. We find {A}φ φ × {A}L = 1.01 ± 0.08 for the lensing map made from combined SPT and Planck data, indicating that the amount of lensing is in excellent agreement with expectations from the observed CMB angular power spectrum when not including the information from smearing of the acoustic peaks.

Asymmetric structured microfiber-based temperature sensor

NASA Astrophysics Data System (ADS)

Xian, Pei; Feng, Guoying; Dai, Shenyu; Zhou, Shouhuan

2017-04-01

A temperature sensor formed by a cascaded sphere and an abrupt taper, together in a standard single-mode fiber, was developed. The dip of the measured spectrum signal shifted obviously when the surrounding temperature changed. Measurement sensitivity to 18.36 pm/°C was shown with the surrounding temperature ranging from 35°C to 395°C. Due to its compact size and all-fiber configuration, the proposed sensor has the advantages of simplicity and low-cost fabrication, thus the device would find potential applications in sensing fields.

How meaningful are risk determinations in the absence of a complete dataset? Making the case for publishing standardized test guideline and ‘no effect’ studies for evaluating the safety of nanoparticulates versus spurious ‘high effect’ results from single investigative studies

NASA Astrophysics Data System (ADS)

Warheit, David B.; Donner, E. Maria

2015-06-01

A recent review article critically assessed the effectiveness of published research articles in nanotoxicology to meaningfully address health and safety issues for workers and consumers. The main conclusions were that, based on a number of flaws in study designs, the potential risk from exposures to nanomaterials is highly exaggerated, and that no ‘nano-specific’ adverse effects, different from exposures to bulk particles, have been convincingly demonstrated. In this brief editorial we focus on a related tangential issue which potentially compromises the integrity of basic risk science. We note that some single investigation studies report specious toxicity findings, which make the conclusions more alarming and attractive and publication worthy. In contrast, the standardized, carefully conducted, ‘guideline study results’ are often ignored because they can frequently report no adverse effects; and as a consequence are not considered as novel findings for publication purposes, and therefore they are never considered as newsworthy in the popular press. Yet it is the Organization for Economic Cooperation and Development (OECD) type test guideline studies that are the most reliable for conducting risk assessments. To contrast these styles and approaches, we present the results of a single study which reports high toxicological effects in rats following low-dose, short-term oral exposures to nanoscale titanium dioxide particles concomitant with selective investigative analyses. Alternatively, the findings of OECD test guideline 408, standardized guideline oral toxicity studies conducted for 90 days at much higher doses (1000 mg kg-1) in male and female rats demonstrated no adverse effects following a very thorough and complete clinical chemical, as well as histopathological evaluation of all of the relevant organs in the body. This discrepancy in study findings is not reconciled by the fact that several biokinetic studies in rats and humans demonstrate little or no uptake of nanoscale or pigment-grade TiO2 particles following oral exposures. We conclude that to develop a competent risk assessment profile, results derived from standardized, guideline-type studies, and even ‘no effect’ study findings provide critically useful input for assessing safe levels of exposure; and should, in principle, be readily acceptable for publication in peer-reviewed toxicology journals. This is a necessary prerequisite for developing a complete dataset for risk assessment determinations.

Single K ATP channel opening in response to action potential firing in mouse dentate granule neurons.

PubMed

Tanner, Geoffrey R; Lutas, Andrew; Martínez-François, Juan Ramón; Yellen, Gary

2011-06-08

ATP-sensitive potassium channels (K(ATP) channels) are important sensors of cellular metabolic state that link metabolism and excitability in neuroendocrine cells, but their role in nonglucosensing central neurons is less well understood. To examine a possible role for K(ATP) channels in modulating excitability in hippocampal circuits, we recorded the activity of single K(ATP) channels in cell-attached patches of granule cells in the mouse dentate gyrus during bursts of action potentials generated by antidromic stimulation of the mossy fibers. Ensemble averages of the open probability (p(open)) of single K(ATP) channels over repeated trials of stimulated spike activity showed a transient increase in p(open) in response to action potential firing. Channel currents were identified as K(ATP) channels through blockade with glibenclamide and by comparison with recordings from Kir6.2 knock-out mice. The transient elevation in K(ATP) p(open) may arise from submembrane ATP depletion by the Na(+)-K(+) ATPase, as the pump blocker strophanthidin reduced the magnitude of the elevation. Both the steady-state and stimulus-elevated p(open) of the recorded channels were higher in the presence of the ketone body R-β-hydroxybutyrate, consistent with earlier findings that ketone bodies can affect K(ATP) activity. Using perforated-patch recording, we also found that K(ATP) channels contribute to the slow afterhyperpolarization following an evoked burst of action potentials. We propose that activity-dependent opening of K(ATP) channels may help granule cells act as a seizure gate in the hippocampus and that ketone-body-mediated augmentation of the activity-dependent opening could in part explain the effect of the ketogenic diet in reducing epileptic seizures.

Socioeconomic status, parenting, and externalizing problems in African American single-mother homes: A person-oriented approach.

PubMed

Anton, Margaret T; Jones, Deborah J; Youngstrom, Eric A

2015-06-01

African American youth, particularly those from single-mother homes, are overrepresented in statistics on externalizing problems. The family is a central context in which to understand externalizing problems; however, reliance on variable-oriented approaches to the study of parenting, which originate from work with intact, middle-income, European American families, may obscure important information regarding variability in parenting styles among African American single mothers, and in turn, variability in youth outcomes as well. The current study demonstrated that within African American single-mother families: (a) a person-, rather than variable-, oriented approach to measuring parenting style may further elucidate variability; (b) socioeconomic status may provide 1 context within which to understanding variability in parenting style; and (c) 1 marker of socioeconomic status, income, and parenting style may each explain variability in youth externalizing problems; however, the interaction between income and parenting style was not significant. Findings have potential implications for better understanding the specific contexts in which externalizing problems may be most likely to occur within this at-risk and underserved group. (c) 2015 APA, all rights reserved).

More evidence for non-maternal inheritance of mitochondrial DNA?

PubMed

Bandelt, H-J; Kong, Q-P; Parson, W; Salas, A

2005-12-01

A single case of paternal co-transmission of mitochondrial DNA (mtDNA) in humans has been reported so far. To find potential instances of non-maternal inheritance of mtDNA. Published medical case studies (of single patients) were searched for irregular mtDNA patterns by comparing the given haplotype information for different clones or tissues with the worldwide mtDNA database as known to date-a method that has proved robust and reliable for the detection of flawed mtDNA sequence data. More than 20 studies were found reporting clear cut instances with mtDNAs of different ancestries in single individuals. As examples, cases are reviewed from recent published reports which, at face value, may be taken as evidence for paternal inheritance of mtDNA or recombination. Multiple types (or recombinant types) of quite dissimilar mitochondrial DNA from different parts of the known mtDNA phylogeny are often reported in single individuals. From re-analyses and corrigenda of forensic mtDNA data, it is apparent that the phenomenon of mixed or mosaic mtDNA can be ascribed solely to contamination and sample mix up.

Socioeconomic Status, Parenting, and Externalizing Problems in African American Single-Mother Homes: A Person-Oriented Approach

PubMed Central

Anton, Margaret T.; Jones, Deborah J.; Youngstrom, Eric A.

2016-01-01

African American youth, particularly those from single-mother homes, are overrepresented in statistics on externalizing problems. The family is a central context in which to understand externalizing problems; however, reliance on variable-oriented approaches to the study of parenting, which originate from work with intact, middle-income, European American families, may obscure important information regarding variability in parenting styles among African American single mothers, and in turn, variability in youth outcomes as well. The current study demonstrated that within African American single-mother families: (a) a person-, rather than variable-, oriented approach to measuring parenting style may further elucidate variability; (b) socioeconomic status may provide 1 context within which to understanding variability in parenting style; and (c) 1 marker of socioeconomic status, income, and parenting style may each explain variability in youth externalizing problems; however, the interaction between income and parenting style was not significant. Findings have potential implications for better understanding the specific contexts in which externalizing problems may be most likely to occur within this at-risk and underserved group. PMID:26053349

Many-Body Localization and Quantum Nonergodicity in a Model with a Single-Particle Mobility Edge.

PubMed

Li, Xiaopeng; Ganeshan, Sriram; Pixley, J H; Das Sarma, S

2015-10-30

We investigate many-body localization in the presence of a single-particle mobility edge. By considering an interacting deterministic model with an incommensurate potential in one dimension we find that the single-particle mobility edge in the noninteracting system leads to a many-body mobility edge in the corresponding interacting system for certain parameter regimes. Using exact diagonalization, we probe the mobility edge via energy resolved entanglement entropy (EE) and study the energy resolved applicability (or failure) of the eigenstate thermalization hypothesis (ETH). Our numerical results indicate that the transition separating area and volume law scaling of the EE does not coincide with the nonthermal to thermal transition. Consequently, there exists an extended nonergodic phase for an intermediate energy window where the many-body eigenstates violate the ETH while manifesting volume law EE scaling. We also establish that the model possesses an infinite temperature many-body localization transition despite the existence of a single-particle mobility edge. We propose a practical scheme to test our predictions in atomic optical lattice experiments which can directly probe the effects of the mobility edge.

A Cellular Automata-based Model for Simulating Restitution Property in a Single Heart Cell.

PubMed

Sabzpoushan, Seyed Hojjat; Pourhasanzade, Fateme

2011-01-01

Ventricular fibrillation is the cause of the most sudden mortalities. Restitution is one of the specific properties of ventricular cell. The recent findings have clearly proved the correlation between the slope of restitution curve with ventricular fibrillation. This; therefore, mandates the modeling of cellular restitution to gain high importance. A cellular automaton is a powerful tool for simulating complex phenomena in a simple language. A cellular automaton is a lattice of cells where the behavior of each cell is determined by the behavior of its neighboring cells as well as the automata rule. In this paper, a simple model is depicted for the simulation of the property of restitution in a single cardiac cell using cellular automata. At first, two state variables; action potential and recovery are introduced in the automata model. In second, automata rule is determined and then recovery variable is defined in such a way so that the restitution is developed. In order to evaluate the proposed model, the generated restitution curve in our study is compared with the restitution curves from the experimental findings of valid sources. Our findings indicate that the presented model is not only capable of simulating restitution in cardiac cell, but also possesses the capability of regulating the restitution curve.

Abdominal Emergencies in Patients with Stage IV Melanoma: The Role of Surgery: A Single-centre Experience.

PubMed

Mantas, Dimitrios; Damaskos, Christos; Garmpis, Nikolaos; Dimitroulis, Dimitrios; Garmpi, Anna; Gogas, Helen

2018-06-01

Metastatic melanoma is an aggressive disease with poor prognosis. Melanoma can potentially involve any organ. In this article, we report on a single-centre experience in emergency surgery for M1c melanoma. Twenty-eight consecutive patients with M1c melanoma underwent surgical exploration due to abdominal emergencies. Pre-operative computed tomography confirmed the diagnosis and the location of the affected site. Pre-operative lactate dehydrogenase serum levels and post-operative histopathology findings were recorded. Intestinal obstruction was the most frequent intraoperative finding (75%). The ileum was most frequently affected (28.6%). Multifocal disease and extra-gastrointestinal tract metastases were present in 25% of cases each. Lactate dehydrogenase serum level was increased in 75% of the patients. Most patients underwent an enterectomy. Curative surgery for stage IV melanoma remains debatable, but surgery for patients presenting with abdominal emergencies appears to improve both survival rate and prognosis. Combined novel therapies and surgical resection is currently being studied with promising results. Copyright© 2018, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.

Adsorbing H₂S onto a single graphene sheet: A possible gas sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reshak, A. H., E-mail: maalidph@yahoo.co.uk; Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis; Auluck, S.

2014-09-14

The electronic structure of pristine graphene sheet and the resulting structure of adsorbing a single molecule of H₂S on pristine graphene in three different sites (bridge, top, and hollow) are studied using the full potential linearized augmented plane wave method. Our calculations show that the adsorption of H₂S molecule on the bridge site opens up a small direct energy gap of about 0.1 eV at symmetry point M, while adsorption of H₂S on top site opens a gap of 0.3 eV around the symmetry point K. We find that adsorbed H₂S onto the hollow site of pristine graphene sheet causesmore » to push the conduction band minimum and the valence band maximum towards Fermi level resulting in a metallic behavior. Comparing the angular momentum decomposition of the atoms projected electronic density of states of pristine graphene sheet with that of H₂S–graphene for three different cases, we find a significant influence of the location of the H₂S molecule on the electronic properties especially the strong hybridization between H₂S molecule and graphene sheet.« less

Heterojunction oxide thin-film transistors with unprecedented electron mobility grown from solution.

PubMed

Faber, Hendrik; Das, Satyajit; Lin, Yen-Hung; Pliatsikas, Nikos; Zhao, Kui; Kehagias, Thomas; Dimitrakopulos, George; Amassian, Aram; Patsalas, Panos A; Anthopoulos, Thomas D

2017-03-01

Thin-film transistors made of solution-processed metal oxide semiconductors hold great promise for application in the emerging sector of large-area electronics. However, further advancement of the technology is hindered by limitations associated with the extrinsic electron transport properties of the often defect-prone oxides. We overcome this limitation by replacing the single-layer semiconductor channel with a low-dimensional, solution-grown In 2 O 3 /ZnO heterojunction. We find that In 2 O 3 /ZnO transistors exhibit band-like electron transport, with mobility values significantly higher than single-layer In 2 O 3 and ZnO devices by a factor of 2 to 100. This marked improvement is shown to originate from the presence of free electrons confined on the plane of the atomically sharp heterointerface induced by the large conduction band offset between In 2 O 3 and ZnO. Our finding underscores engineering of solution-grown metal oxide heterointerfaces as an alternative strategy to thin-film transistor development and has the potential for widespread technological applications.

Heterojunction oxide thin-film transistors with unprecedented electron mobility grown from solution

PubMed Central

Faber, Hendrik; Das, Satyajit; Lin, Yen-Hung; Pliatsikas, Nikos; Zhao, Kui; Kehagias, Thomas; Dimitrakopulos, George; Amassian, Aram; Patsalas, Panos A.; Anthopoulos, Thomas D.

2017-01-01

Thin-film transistors made of solution-processed metal oxide semiconductors hold great promise for application in the emerging sector of large-area electronics. However, further advancement of the technology is hindered by limitations associated with the extrinsic electron transport properties of the often defect-prone oxides. We overcome this limitation by replacing the single-layer semiconductor channel with a low-dimensional, solution-grown In2O3/ZnO heterojunction. We find that In2O3/ZnO transistors exhibit band-like electron transport, with mobility values significantly higher than single-layer In2O3 and ZnO devices by a factor of 2 to 100. This marked improvement is shown to originate from the presence of free electrons confined on the plane of the atomically sharp heterointerface induced by the large conduction band offset between In2O3 and ZnO. Our finding underscores engineering of solution-grown metal oxide heterointerfaces as an alternative strategy to thin-film transistor development and has the potential for widespread technological applications. PMID:28435867

Variability of acute extracellular action potential measurements with multisite silicon probes

PubMed Central

Scott, Kimberly M.; Du, Jiangang; Lester, Henry A.; Masmanidis, Sotiris C.

2012-01-01

Device miniaturization technologies have led to significant advances in sensors for extracellular measurements of electrical activity in the brain. Multisite, silicon-based probes containing implantable electrode arrays afford greater coverage of neuronal activity than single electrodes and therefore potentially offer a more complete view of how neuronal ensembles encode information. However, scaling up the number of sites is not sufficient to ensure capture of multiple neurons, as action potential signals from extracellular electrodes may vary due to numerous factors. In order to understand the large-scale recording capabilities and potential limitations of multisite probes, it is important to quantify this variability, and to determine whether certain key device parameters influence the recordings. Here we investigate the effect of four parameters, namely, electrode surface, width of the structural support shafts, shaft number, and position of the recording site relative to the shaft tip. This study employs acutely implanted silicon probes containing up to 64 recording sites, whose performance is evaluated by the metrics of noise, spike amplitude, and spike detection probability. On average, we find no significant effect of device geometry on spike amplitude and detection probability but we find significant differences among individual experiments, with the likelihood of detecting spikes varying by a factor of approximately three across trials. PMID:22971352

Potential Genetic Risk Factors for Chronic TMD: Genetic Associations from the OPPERA Case Control Study

PubMed Central

Smith, Shad B.; Maixner, Dylan; Greenspan, Joel; Dubner, Ron; Fillingim, Roger; Ohrbach, Richard; Knott, Charles; Slade, Gary; Bair, Eric; Gibson, Dustin G.; Zaykin, Dmitri V.; Weir, Bruce; Maixner, William; Diatchenko, Luda

2011-01-01

Genetic factors play a role in the etiology of persistent pain conditions, putatively by modulating underlying processes such as nociceptive sensitivity, psychological well-being, inflammation, and autonomic response. However, to date, only a few genes have been associated with temporomandibular disorders (TMD). This study evaluated 358 genes involved in pain processes, comparing allelic frequencies between 166 cases with chronic TMD and 1442 controls enrolled in the OPPERA (Orofacial Pain: Prospective Evaluation and Risk Assessment) study cooperative agreement. To enhance statistical power, 182 TMD cases and 170 controls from a similar study were included in the analysis. Genotyping was performed using the Pain Research Panel, an Affymetrix gene chip representing 3295 single nucleotide polymorphisms, including ancestry-informative markers that were used to adjust for population stratification. Adjusted associations between genetic markers and TMD case status were evaluated using logistic regression. The OPPERA findings provided evidence supporting previously-reported associations between TMD and two genes: HTR2A and COMT. Other genes were revealed as potential new genetic risk factors for TMD, including NR3C1, CAMK4, CHRM2, IFRD1, and GRK5. While these findings need to be replicated in independent cohorts, the genes potentially represent important markers of risk for TMD and they identify potential targets for therapeutic intervention. PMID:22074755

Evaluation of copper, aluminum, and nickel interatomic potentials on predicting the elastic properties

NASA Astrophysics Data System (ADS)

Rassoulinejad-Mousavi, Seyed Moein; Mao, Yijin; Zhang, Yuwen

2016-06-01

Choice of appropriate force field is one of the main concerns of any atomistic simulation that needs to be seriously considered in order to yield reliable results. Since investigations on the mechanical behavior of materials at micro/nanoscale have been becoming much more widespread, it is necessary to determine an adequate potential which accurately models the interaction of the atoms for desired applications. In this framework, reliability of multiple embedded atom method based interatomic potentials for predicting the elastic properties was investigated. Assessments were carried out for different copper, aluminum, and nickel interatomic potentials at room temperature which is considered as the most applicable case. Examined force fields for the three species were taken from online repositories of National Institute of Standards and Technology, as well as the Sandia National Laboratories, the LAMMPS database. Using molecular dynamic simulations, the three independent elastic constants, C11, C12, and C44, were found for Cu, Al, and Ni cubic single crystals. Voigt-Reuss-Hill approximation was then implemented to convert elastic constants of the single crystals into isotropic polycrystalline elastic moduli including bulk modulus, shear modulus, and Young's modulus as well as Poisson's ratio. Simulation results from massive molecular dynamic were compared with available experimental data in the literature to justify the robustness of each potential for each species. Eventually, accurate interatomic potentials have been recommended for finding each of the elastic properties of the pure species. Exactitude of the elastic properties was found to be sensitive to the choice of the force fields. Those potentials that were fitted for a specific compound may not necessarily work accurately for all the existing pure species. Tabulated results in this paper might be used as a benchmark to increase assurance of using the interatomic potential that was designated for a problem.

Biomarkers of PTSD: military applications and considerations.

PubMed

Lehrner, Amy; Yehuda, Rachel

2014-01-01

Although there are no established biomarkers for posttraumatic stress disorder (PTSD) as yet, biological investigations of PTSD have made progress identifying the pathophysiology of PTSD. Given the biological and clinical complexity of PTSD, it is increasingly unlikely that a single biomarker of disease will be identified. Rather, investigations will more likely identify different biomarkers that indicate the presence of clinically significant PTSD symptoms, associate with risk for PTSD following trauma exposure, and predict or identify recovery. While there has been much interest in PTSD biomarkers, there has been less discussion of their potential clinical applications, and of the social, legal, and ethical implications of such biomarkers. This article will discuss possible applications of PTSD biomarkers, including the social, legal, and ethical implications of such biomarkers, with an emphasis on military applications. Literature on applications of PTSD biomarkers and on potential ethical and legal implications will be reviewed. Biologically informed research findings hold promise for prevention, assessment, treatment planning, and the development of prophylactic and treatment interventions. As with any biological indicator of disorder, there are potentially positive and negative clinical, social, legal, and ethical consequences of using such biomarkers. Potential clinical applications of PTSD biomarkers hold promise for clinicians, patients, and employers. The search for biomarkers of PTSD should occur in tandem with an interdisciplinary discussion regarding the potential implications of applying biological findings in clinical and employment settings.

Theory of superconductivity with non-Hermitian and parity-time reversal symmetric Cooper pairing symmetry

NASA Astrophysics Data System (ADS)

Ghatak, Ananya; Das, Tanmoy

2018-01-01

Recently developed parity (P ) and time-reversal (T ) symmetric non-Hermitian systems govern a rich variety of new and characteristically distinct physical properties, which may or may not have a direct analog in their Hermitian counterparts. We study here a non-Hermitian, PT -symmetric superconducting Hamiltonian that possesses a real quasiparticle spectrum in the PT -unbroken region of the Brillouin zone. Within a single-band mean-field theory, we find that real quasiparticle energies are possible when the superconducting order parameter itself is either Hermitian or anti-Hermitian. Within the corresponding Bardeen-Cooper-Schrieffer (BCS) theory, we find that several properties are characteristically distinct and novel in the non-Hermitian pairing case than its Hermitian counterpart. One of our significant findings is that while a Hermitian superconductor gives a second-order phase transition, the non-Hermitian one produces a robust first-order phase transition. The corresponding thermodynamic properties and the Meissner effect are also modified accordingly. Finally, we discuss how such a PT -symmetric pairing can emerge from an antisymmetric potential, such as the Dzyloshinskii-Moriya interaction, but with an external bath, or complex potential, among others.

Frequency and distribution of incidental findings deemed appropriate for S modifier designation on low-dose CT in a lung cancer screening program.

PubMed

Reiter, Michael J; Nemesure, Allison; Madu, Ezemonye; Reagan, Lisa; Plank, April

2018-06-01

To describe the frequency, distribution and reporting patterns of incidental findings receiving the Lung-RADS S modifier on low-dose chest computed tomography (CT) among lung cancer screening participants. This retrospective investigation included 581 individuals who received baseline low-dose chest CT for lung cancer screening between October 2013 and June 2017 at a single center. Incidental findings resulting in assignment of Lung-RADS S modifier were recorded as were incidental abnormalities detailed within the body of the radiology report only. A subset of 60 randomly selected CTs was reviewed by a second (blinded) radiologist to evaluate inter-rater variability of Lung-RADS reporting. A total of 261 (45%) participants received the Lung-RADS S modifier on baseline CT with 369 incidental findings indicated as potentially clinically significant. Coronary artery calcification was most commonly reported, accounting for 182 of the 369 (49%) findings. An additional 141 incidentalomas of the same types as these 369 findings were described in reports but were not labelled with the S modifier. Therefore, as high as 69% (402 of 581) of participants could have received the S modifier if reporting was uniform. Inter-radiologist concordance of S modifier reporting in a subset of 60 participants was poor (42% agreement, kappa = 0.2). Incidental findings are commonly identified on chest CT for lung cancer screening, yet reporting of the S modifier within Lung-RADS is inconsistent. Specific guidelines are necessary to better define potentially clinically significant abnormalities and to improve reporting uniformity. Copyright © 2018 Elsevier B.V. All rights reserved.

Carbon nanotubes enhance CpG uptake and potentiate antiglioma immunity.

PubMed

Zhao, Dongchang; Alizadeh, Darya; Zhang, Leying; Liu, Wei; Farrukh, Omar; Manuel, Edwin; Diamond, Don J; Badie, Behnam

2011-02-15

Stimulation of toll-like receptor-9 (TLR9) by CpG oligodeoxynucleotides (CpG) has been shown to counteract the immunosuppressive microenvironment and to inhibit tumor growth in glioma models. Because TLR9 is located intracellularly, we hypothesized that methods that enhance its internalization may also potentiate its immunostimulatory response. The goal of this study was to evaluate carbon nanotubes (CNT) as a CpG delivery vehicle in brain tumor models. Functionalized single-walled CNTs were conjugated with CpG (CNT-CpG) and evaluated in vitro and in mice bearing intracranial GL261 gliomas. Flow cytometry was used to assess CNT-CpG uptake and antiglioma immune response. Tumor growth was measured by bioluminescent imaging, histology, and animal survival. CNT-CpG was nontoxic and enhanced CpG uptake both in vitro and intracranial gliomas. CNT-mediated CpG delivery also potentiated proinflammatory cytokine production by primary monocytes. Interestingly, a single intracranial injection of low-dose CNT-CpG (but not free CpG or blank CNT) eradicated intracranial GL261 gliomas in half of tumor-bearing mice. Moreover, surviving animals exhibited durable tumor-free remission (>3 months), and were protected from intracranial tumor rechallenge, demonstrating induction of long-term antitumor immunity. These findings suggest that CNTs can potentiate CpG immunopotency by enhancing its delivery into tumor-associated inflammatory cells. ©2010 AACR.

Carbon Nanotubes Enhance CpG Uptake and Potentiate Anti-Glioma Immunity

PubMed Central

Zhao, Dongchang; Alizadeh, Darya; Zhang, Leying; Liu, Wei; Farrukh, Omar; Manuel, Edwin; Diamond, Don J.; Badie, Behnam

2010-01-01

Purpose Stimulation of toll-like receptor-9 (TLR9) by CpG oligodeoxynucleotides (CpG) has been shown to counteract the immunosuppressive microenvironment and to inhibit tumor growth in glioma models. Since TLR9 is located intracellularly, we hypothesized that methods that enhance its internalization may also potentiate its immunostimulatory response. The goal of this study was to evaluate carbon nanotubes (CNTs) as a CpG delivery vehicle in brain tumor models. Experimental Design Functionalized single-walled CNTs were conjugated with CpG (CNT-CpG) and evaluated in vitro and in mice bearing intracranial GL261 gliomas. Flow cytometry was used to assess CNT-CpG uptake and anti-glioma immune response. Tumor growth was measured by bioluminescent imaging, histology, and animal survival. Results CNT-CpG was nontoxic and enhanced CpG uptake both in vitro and intracranial gliomas. CNT-mediated CpG delivery also potentiated pro-inflammatory cytokine production by primary monocytes. Interestingly, a single intracranial injection of low-dose CNT-CpG (but not free CpG or blank CNT) eradicated intracranial GL261 gliomas in half of tumor-bearing mice. Moreover, surviving animals exhibited durable tumor-free remission (> 3 months), and were protected from intracranial tumor rechallenge, demonstrating induction of long-term anti-tumor immunity. Conclusions These findings suggest that CNTs can potentiate CpG immunopotency by enhancing its delivery into tumor-associated inflammatory cells. PMID:21088258

A quantum perturbative pair distribution for determining interatomic potentials from extended x-ray absorption spectroscopy

NASA Astrophysics Data System (ADS)

Piazza, F.

2002-11-01

In this paper we develop a technique for determining interatomic potentials in materials in the quantum regime from single-shell extended x-ray absorption spectroscopy (EXAFS) spectra. We introduce a pair distribution function, based on ordinary quantum time-independent perturbation theory. In the proposed scheme, the model potential parameters enter the distribution through a fourth-order Taylor expansion of the potential, and are directly refined in the fit of the model signal to the experimental spectrum. We discuss in general the validity of our theoretical framework, namely the quantum regime and perturbative treatment, and work out a simple tool for monitoring the sensitivity of our theory in determining lattice anharmonicities based on the statistical F-test. As an example, we apply our formalism to an EXAFS spectrum at the Ag K edge of AgI at T = 77 K. We determine the Ag-I potential parameters and find good agreement with previous studies.

Decision making and action implementation: evidence for an early visually triggered motor activation specific to potential actions.

PubMed

Tandonnet, Christophe; Garry, Michael I; Summers, Jeffery J

2013-07-01

To make a decision may rely on accumulating evidence in favor of one alternative until a threshold is reached. Sequential-sampling models differ by the way of accumulating evidence and the link with action implementation. Here, we tested a model's prediction of an early action implementation specific to potential actions. We assessed the dynamics of action implementation in go/no-go and between-hand choice tasks by transcranial magnetic stimulation of the motor cortex (single- or paired-pulse TMS; 3-ms interstimulus interval). Prior to implementation of the selected action, the amplitude of the motor evoked potential first increased whatever the visual stimulus but only for the hand potentially involved in the to-be-produced action. These findings suggest that visual stimuli can trigger an early motor activation specific to potential actions, consistent with race-like models with continuous transmission between decision making and action implementation. Copyright © 2013 Society for Psychophysiological Research.

The Cumulative Impact of Sexual Revictimization on Emotion Regulation Difficulties: An Examination of Female Inmates

PubMed Central

Walsh, Kate; DiLillo, David; Scalora, Mario J.

2012-01-01

The present study examined associations between child sexual abuse (CSA), adult sexual victimization, and emotion regulation difficulties in a sample of 168 incarcerated women. Approximately 50 % of the sample reported CSA, 54% reported adult sexual victimization, and 38% reported sexual revictimization (i.e., CSA and adult victimization). Revictimized women reported significantly greater difficulties with several facets of emotion regulation when compared to singly victimized and non-victimized women. Interestingly, singly victimized women did not demonstrate greater emotion regulation deficits when compared to non-victims. Findings suggest that the negative impact of victimization experiences on adult emotion regulation abilities may be cumulative. Further, they highlight the potential importance of assessing and targeting emotion regulation difficulties among child abuse and adult sexual victimization survivors. PMID:21727155

Nonradiative Energy Transfer from Individual CdSe/ZnS Quantum Dots to Single-Layer and Few-Layer Tin Disulfide

DOE PAGES

Zang, Huidong; Routh, Prahlad K.; Huang, Yuan; ...

2016-03-31

We study the combination of zero-dimensional (0D) colloidal CdSe/ZnS quantum dots with tin disulfide (SnS 2), a two-dimensional (2D)-layered metal dichalcogenide, results in 0D–2D hybrids with enhanced light absorption properties. These 0D–2D hybrids, when exposed to light, exhibit intrahybrid nonradiative energy transfer from photoexcited CdSe/ZnS quantum dots to SnS 2. Using single nanocrystal spectroscopy, we find that the rate for energy transfer in 0D–2D hybrids increases with added number of SnS 2 layers, a positive manifestation toward the potential functionality of such 2D-based hybrids in applications such as photovoltaics and photon sensing.

Nonradiative Energy Transfer from Individual CdSe/ZnS Quantum Dots to Single-Layer and Few-Layer Tin Disulfide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zang, Huidong; Routh, Prahlad K.; Huang, Yuan

We study the combination of zero-dimensional (0D) colloidal CdSe/ZnS quantum dots with tin disulfide (SnS 2), a two-dimensional (2D)-layered metal dichalcogenide, results in 0D–2D hybrids with enhanced light absorption properties. These 0D–2D hybrids, when exposed to light, exhibit intrahybrid nonradiative energy transfer from photoexcited CdSe/ZnS quantum dots to SnS 2. Using single nanocrystal spectroscopy, we find that the rate for energy transfer in 0D–2D hybrids increases with added number of SnS 2 layers, a positive manifestation toward the potential functionality of such 2D-based hybrids in applications such as photovoltaics and photon sensing.

A facile one-step fluorescence method for the quantitation of low-content single base deamination impurity in synthetic oligonucleotides.

PubMed

Su, Xiaoye; Liang, Ruiting; Stolee, Jessica A

2018-06-05

Oligonucleotides are being researched and developed as potential drug candidates for the treatment of a broad spectrum of diseases. The characterization of antisense oligonucleotide (ASO) impurities caused by base mutations (e.g. deamination) which are closely related to the target ASO is a significant analytical challenge. Herein, we describe a novel one-step method, utilizing a strategy that combines fluorescence-ON detection with competitive hybridization, to achieve single base mutation quantitation in extensively modified synthetic ASOs. Given that this method is highly specific and sensitive (LoQ = 4 nM), we envision that it will find utility for screening other impurities as well as sequencing modified oligonucleotides. Copyright © 2018 Elsevier B.V. All rights reserved.

Cooperative single-photon subradiant states in a three-dimensional atomic array

NASA Astrophysics Data System (ADS)

Jen, H. H.

2016-11-01

We propose a complete superradiant and subradiant states that can be manipulated and prepared in a three-dimensional atomic array. These subradiant states can be realized by absorbing a single photon and imprinting the spatially-dependent phases on the atomic system. We find that the collective decay rates and associated cooperative Lamb shifts are highly dependent on the phases we manage to imprint, and the subradiant state of long lifetime can be found for various lattice spacings and atom numbers. We also investigate both optically thin and thick atomic arrays, which can serve for systematic studies of super- and sub-radiance. Our proposal offers an alternative scheme for quantum memory of light in a three-dimensional array of two-level atoms, which is applicable and potentially advantageous in quantum information processing.

Equilibrium properties of dense hydrogen isotope gases based on the theory of simple fluids.

PubMed

Kowalczyk, Piotr; MacElroy, J M D

2006-08-03

We present a new method for the prediction of the equilibrium properties of dense gases containing hydrogen isotopes. The proposed approach combines the Feynman-Hibbs effective potential method and a deconvolution scheme introduced by Weeks et al. The resulting equations of state and the chemical potentials as functions of pressure for each of the hydrogen isotope gases depend on a single set of Lennard-Jones parameters. In addition to its simplicity, the proposed method with optimized Lennard-Jones potential parameters accurately describes the equilibrium properties of hydrogen isotope fluids in the regime of moderate temperatures and pressures. The present approach should find applications in the nonlocal density functional theory of inhomogeneous quantum fluids and should also be of particular relevance to hydrogen (clean energy) storage and to the separation of quantum isotopes by novel nanomaterials.

Investigating and improving student understanding of quantum mechanics in the context of single photon interference

NASA Astrophysics Data System (ADS)

Marshman, Emily; Singh, Chandralekha

2017-06-01

Single photon experiments involving a Mach-Zehnder interferometer can illustrate the fundamental principles of quantum mechanics, e.g., the wave-particle duality of a single photon, single photon interference, and the probabilistic nature of quantum measurement involving single photons. These experiments explicitly make the connection between the abstract quantum theory and concrete laboratory settings and have the potential to help students develop a solid grasp of the foundational issues in quantum mechanics. Here we describe students' conceptual difficulties with these topics in the context of Mach-Zehnder interferometer experiments with single photons and how the difficulties found in written surveys and individual interviews were used as a guide in the development of a Quantum Interactive Learning Tutorial (QuILT). The QuILT uses an inquiry-based approach to learning and takes into account the conceptual difficulties found via research to help upper-level undergraduate and graduate students learn about foundational quantum mechanics concepts using the concrete quantum optics context. It strives to help students learn the basics of quantum mechanics in the context of single photon experiment, develop the ability to apply fundamental quantum principles to experimental situations in quantum optics, and explore the differences between classical and quantum ideas in a concrete context. We discuss the findings from in-class evaluations suggesting that the QuILT was effective in helping students learn these abstract concepts.

A Single-Level Tunnel Model to Account for Electrical Transport through Single Molecule- and Self-Assembled Monolayer-based Junctions

PubMed Central

Garrigues, Alvar R.; Yuan, Li; Wang, Lejia; Mucciolo, Eduardo R.; Thompon, Damien; del Barco, Enrique; Nijhuis, Christian A.

2016-01-01

We present a theoretical analysis aimed at understanding electrical conduction in molecular tunnel junctions. We focus on discussing the validity of coherent versus incoherent theoretical formulations for single-level tunneling to explain experimental results obtained under a wide range of experimental conditions, including measurements in individual molecules connecting the leads of electromigrated single-electron transistors and junctions of self-assembled monolayers (SAM) of molecules sandwiched between two macroscopic contacts. We show that the restriction of transport through a single level in solid state junctions (no solvent) makes coherent and incoherent tunneling formalisms indistinguishable when only one level participates in transport. Similar to Marcus relaxation processes in wet electrochemistry, the thermal broadening of the Fermi distribution describing the electronic occupation energies in the electrodes accounts for the exponential dependence of the tunneling current on temperature. We demonstrate that a single-level tunnel model satisfactorily explains experimental results obtained in three different molecular junctions (both single-molecule and SAM-based) formed by ferrocene-based molecules. Among other things, we use the model to map the electrostatic potential profile in EGaIn-based SAM junctions in which the ferrocene unit is placed at different positions within the molecule, and we find that electrical screening gives rise to a strongly non-linear profile across the junction. PMID:27216489

Anderson localization of partially incoherent light

DOE Office of Scientific and Technical Information (OSTI.GOV)

Capeta, D.; Radic, J.; Buljan, H.

We study Anderson localization and propagation of partially spatially incoherent wavepackets in linear disordered potentials, motivated by the insight that interference phenomena resulting from multiple scattering are affected by the coherence of the waves. We find that localization is delayed by incoherence: the more incoherent the waves are, the longer they diffusively spread while propagating in the medium. However, if all the eigenmodes of the system are exponentially localized (as in one- and two-dimensional disordered systems), any partially incoherent wavepacket eventually exhibits localization with exponentially decaying tails, after sufficiently long propagation distances. Interestingly, we find that the asymptotic behavior ofmore » the incoherent beam is similar to that of a single instantaneous coherent realization of the beam.« less

Theory of the development of alternans in the heart during controlled diastolic interval pacing

NASA Astrophysics Data System (ADS)

Otani, Niels F.

2017-09-01

The beat-to-beat alternation in action potential durations (APDs) in the heart, called APD alternans, has been linked to the development of serious cardiac rhythm disorders, including ventricular tachycardia and fibrillation. The length of the period between action potentials, called the diastolic interval (DI), is a key dynamical variable in the standard theory of alternans development. Thus, methods that control the DI may be useful in preventing dangerous cardiac rhythms. In this study, we examine the dynamics of alternans during controlled-DI pacing using a series of single-cell and one-dimensional (1D) fiber models of alternans dynamics. We find that a model that combines a so-called memory model with a calcium cycling model can reasonably explain two key experimental results: the possibility of alternans during constant-DI pacing and the phase lag of APDs behind DIs during sinusoidal-DI pacing. We also find that these results can be replicated by incorporating the memory model into an amplitude equation description of a 1D fiber. The 1D fiber result is potentially concerning because it seems to suggest that constant-DI control of alternans can only be effective over only a limited region in space.

Effect of electron irradiation on superconductivity in single crystals of Ba ( Fe 1 – x Ru x ) 2 As 2 ( x = 0.24 )

DOE PAGES

Prozorov, R.; Kończykowski, M.; Tanatar, M. A.; ...

2014-11-18

A single crystal of isovalently substituted Ba(Fe 1-xRu x) 2As 2 (x=0.24) is sequentially irradiated with 2.5 MeV electrons up to a maximum dose of 2.1×10 19 e -/cm 2. The electrical resistivity is measured in situ at T=22 K during the irradiation and ex situ as a function of temperature between subsequent irradiation runs. Upon irradiation, the superconducting transition temperature T c decreases and the residual resistivity ρ0 increases. We find that electron irradiation leads to the fastest suppression of T c compared to other types of artificially introduced disorder, probably due to the strong short-range potential of themore » pointlike irradiation defects. As a result, a more detailed analysis within a multiband scenario with variable scattering potential strength shows that the observed T c versus ρ 0 is fully compatible with s ± pairing, in contrast to earlier claims that this model leads to a too rapid suppression of T c with scattering.« less

A framework for a critical assessment of the quality of epidemiological studies of driver health and accident risk.

PubMed

Elvik, Rune

2011-11-01

A large number of studies have tried to assess how various aspects of driver health influence driver involvement in accidents. The objective of this paper is to provide a framework for a critical assessment of the quality these studies from a methodological point of view. Examples are given of how various sources of bias and confounding can produce study findings that are highly misleading. Ten potential sources of error and bias in epidemiological studies of the contribution of driver health impairments to road accidents are discussed: (1) Poor description of the medical conditions whose effects are studied (measurement error). (2) Inadequate control for the effects of exposure on accident rate. (3) Sampling endogeneity with respect to assessment for fitness to drive (outcome-based sampling; self-selection bias). (4) Combined exposure to several risk factors. (5) Poor control for potentially confounding factors. (6) Failure to specify potentially moderating factors (interaction effects). (7) Failure to consider a severity gradient with respect to the effect of health impairments. (8) Failure to specify the compliance of drivers with medical treatments or treatment effectiveness. (9) No data on the population prevalence of various health conditions. (10) The use of multiple study approaches and methods making the comparison and synthesis of findings difficult. Examples are given of how all these items may influence the findings of a single study or make synthesising findings from multiple studies difficult. A checklist for assessing study quality is provided. Copyright © 2011 Elsevier Ltd. All rights reserved.

Single-Cell Analysis of Human Pancreas Reveals Transcriptional Signatures of Aging and Somatic Mutation Patterns.

PubMed

Enge, Martin; Arda, H Efsun; Mignardi, Marco; Beausang, John; Bottino, Rita; Kim, Seung K; Quake, Stephen R

2017-10-05

As organisms age, cells accumulate genetic and epigenetic errors that eventually lead to impaired organ function or catastrophic transformation such as cancer. Because aging reflects a stochastic process of increasing disorder, cells in an organ will be individually affected in different ways, thus rendering bulk analyses of postmitotic adult cells difficult to interpret. Here, we directly measure the effects of aging in human tissue by performing single-cell transcriptome analysis of 2,544 human pancreas cells from eight donors spanning six decades of life. We find that islet endocrine cells from older donors display increased levels of transcriptional noise and potential fate drift. By determining the mutational history of individual cells, we uncover a novel mutational signature in healthy aging endocrine cells. Our results demonstrate the feasibility of using single-cell RNA sequencing (RNA-seq) data from primary cells to derive insights into genetic and transcriptional processes that operate on aging human tissue. Copyright © 2017 Elsevier Inc. All rights reserved.

High-harmonic and single attosecond pulse generation using plasmonic field enhancement in ordered arrays of gold nanoparticles with chirped laser pulses.

PubMed

Yang, Ying-Ying; Scrinzi, Armin; Husakou, Anton; Li, Qian-Guang; Stebbings, Sarah L; Süßmann, Frederik; Yu, Hai-Juan; Kim, Seungchul; Rühl, Eckart; Herrmann, Joachim; Lin, Xue-Chun; Kling, Matthias F

2013-01-28

Coherent XUV sources, which may operate at MHz repetition rate, could find applications in high-precision spectroscopy and for spatio-time-resolved measurements of collective electron dynamics on nanostructured surfaces. We theoretically investigate utilizing the enhanced plasmonic fields in an ordered array of gold nanoparticles for the generation of high-harmonic, extreme-ultraviolet (XUV) radiation. By optimization of the chirp of ultrashort laser pulses incident on the array, our simulations indicate a potential route towards the temporal shaping of the plasmonic near-field and, in turn, the generation of single attosecond pulses. The inherent effects of inhomogeneity of the local fields on the high-harmonic generation are analyzed and discussed. While taking the inhomogeneity into account does not affect the optimal chirp for the generation of a single attosecond pulse, the cut-off energy of the high-harmonic spectrum is enhanced by about a factor of two.

Filopodia Conduct Target Selection in Cortical Neurons Using Differences in Signal Kinetics of a Single Kinase.

PubMed

Mao, Yu-Ting; Zhu, Julia X; Hanamura, Kenji; Iurilli, Giuliano; Datta, Sandeep Robert; Dalva, Matthew B

2018-05-16

Dendritic filopodia select synaptic partner axons by interviewing the cell surface of potential targets, but how filopodia decipher the complex pattern of adhesive and repulsive molecular cues to find appropriate contacts is unknown. Here, we demonstrate in cortical neurons that a single cue is sufficient for dendritic filopodia to reject or select specific axonal contacts for elaboration as synaptic sites. Super-resolution and live-cell imaging reveals that EphB2 is located in the tips of filopodia and at nascent synaptic sites. Surprisingly, a genetically encoded indicator of EphB kinase activity, unbiased classification, and a photoactivatable EphB2 reveal that simple differences in the kinetics of EphB kinase signaling at the tips of filopodia mediate the choice between retraction and synaptogenesis. This may enable individual filopodia to choose targets based on differences in the activation rate of a single tyrosine kinase, greatly simplifying the process of partner selection and suggesting a general principle. Copyright © 2018 Elsevier Inc. All rights reserved.

Experimental Study of Direct Laser Deposition of Ti-6Al-4V and Inconel 718 by Using Pulsed Parameters

PubMed Central

Shah, Kamran; Haq, Izhar Ul; Shah, Shaukat Ali; Khan, Farid Ullah; Khan, Sikander

2014-01-01

Laser direct metal deposition (LDMD) has developed from a prototyping to a single metal manufacturing tool. Its potential for creating multimaterial and functionally graded structures is now beginning to be explored. This work is a first part of a study in which a single layer of Inconel 718 is deposited on Ti-6Al-4V substrate. Single layer tracks were built at a range of powder mass flow rates using a coaxial nozzle and 1.5 kW diode laser operating in both continuous and pulsed beam modes. This part of the study focused on the experimental findings during the deposition of Inconel 718 powder on Ti-6Al-4V substrate. Scanning electron microscopy (SEM) and X-ray diffraction analysis were performed for characterization and phase identification. Residual stress measurement had been carried out to ascertain the effects of laser pulse parameters on the crack development during the deposition process. PMID:24592190

Exercise improves behavioral, neurocognitive, and scholastic performance in children with attention-deficit/hyperactivity disorder.

PubMed

Pontifex, Matthew B; Saliba, Brian J; Raine, Lauren B; Picchietti, Daniel L; Hillman, Charles H

2013-03-01

To examine the effect of a single bout of moderate-intensity aerobic exercise on preadolescent children with attention-deficit/hyperactivity disorder (ADHD) using objective measures of attention, brain neurophysiology, and academic performance. Using a within-participants design, task performance and event-related brain potentials were assessed while participants performed an attentional-control task following a bout of exercise or seated reading during 2 separate, counterbalanced sessions. Following a single 20-minute bout of exercise, both children with ADHD and healthy match control children exhibited greater response accuracy and stimulus-related processing, with the children with ADHD also exhibiting selective enhancements in regulatory processes, compared with after a similar duration of seated reading. In addition, greater performance in the areas of reading and arithmetic were observed following exercise in both groups. These findings indicate that single bouts of moderately intense aerobic exercise may have positive implications for aspects of neurocognitive function and inhibitory control in children with ADHD. Copyright © 2013 Mosby, Inc. All rights reserved.

Low-Level Blast Exposure Increases Transient Receptor Potential Vanilloid 1 (TRPV1) Expression in the Rat Cornea

PubMed Central

Por, Elaine D.; Choi, Jae-Hyek; Lund, Brian J.

2016-01-01

ABSTRACT Background: Blast-related ocular injuries sustained by military personnel have led to rigorous efforts to elucidate the effects of blast exposure on neurosensory function. Recent studies have provided some insight into cognitive and visual deficits sustained following blast exposure; however, limited data are available on the effects of blast on pain and inflammatory processes. Investigation of these secondary effects of blast exposure is necessary to fully comprehend the complex pathophysiology of blast-related injuries. The overall purpose of this study is to determine the effects of single and repeated blast exposure on pain and inflammatory mediators in ocular tissues. Methods: A compressed air shock tube was used to deliver a single or repeated blast (68.0 ± 2.7 kPa) to anesthetized rats daily for 5 days. Immunohistochemistry was performed on ocular tissues to determine the expression of the transient receptor potential vanilloid 1 (TRPV1) channel, calcitonin gene-related peptide (CGRP), substance P (SP), and endothelin-1 (ET-1) following single and repeated blast exposure. Neutrophil infiltration and myeloperoxidase (MPO) expression were also assessed in blast tissues via immunohistochemistry and enzyme-linked immunosorbent assay (ELISA) analysis, respectively. Results: TRPV1 expression was increased in rat corneas exposed to both single and repeated blast. Increased secretion of CGRP, SP, and ET-1 was also detected in rat corneas as compared to control. Moreover, repeated blast exposure resulted in neutrophil infiltration in the cornea and stromal layer as compared to control animals. Conclusion: Single and repeated blast exposure resulted in increased expression of TRPV1, CGRP, SP, and ET-1 as well as neutrophil infiltration. Collectively, these findings provide novel insight into the activation of pain and inflammation signaling mediators following blast exposure. PMID:27049881

Potential impact of single-risk-factor versus total risk management for the prevention of cardiovascular events in Seychelles.

PubMed

Ndindjock, Roger; Gedeon, Jude; Mendis, Shanthi; Paccaud, Fred; Bovet, Pascal

2011-04-01

To assess the prevalence of cardiovascular (CV) risk factors in Seychelles, a middle-income African country, and compare the cost-effectiveness of single-risk-factor management (treating individuals with arterial blood pressure ≥ 140/90 mmHg and/or total serum cholesterol ≥ 6.2 mmol/l) with that of management based on total CV risk (treating individuals with a total CV risk ≥ 10% or ≥ 20%). CV risk factor prevalence and a CV risk prediction chart for Africa were used to estimate the 10-year risk of suffering a fatal or non-fatal CV event among individuals aged 40-64 years. These figures were used to compare single-risk-factor management with total risk management in terms of the number of people requiring treatment to avert one CV event and the number of events potentially averted over 10 years. Treatment for patients with high total CV risk (≥ 20%) was assumed to consist of a fixed-dose combination of several drugs (polypill). Cost analyses were limited to medication. A total CV risk of ≥ 10% and ≥ 20% was found among 10.8% and 5.1% of individuals, respectively. With single-risk-factor management, 60% of adults would need to be treated and 157 cardiovascular events per 100000 population would be averted per year, as opposed to 5% of adults and 92 events with total CV risk management. Management based on high total CV risk optimizes the balance between the number requiring treatment and the number of CV events averted. Total CV risk management is much more cost-effective than single-risk-factor management. These findings are relevant for all countries, but especially for those economically and demographically similar to Seychelles.

Finding a Single Molecule in a Haystack: Optical Detection and Spectroscopy of Single Absorbers in Solids

DTIC Science & Technology

1989-08-18

CODES 18 SUBJECT TERMS (Continue on reverse if necessary and identify by block number) FIELD GROUP SUB-GROUP Single Molecule Detection Pentacene in p...and 10 additional pentacene molecules. This may be accomplished by- a combination of laser FM spectroscopy and either Stark or ultrasonic double...6099 408-927-2426 ABSTRACT: Single-absorber optical spectroscopy in solids is described for the case of finding a single pentacene molecule in a

Evoked-potential changes following discrimination learning involving complex sounds

PubMed Central

Orduña, Itzel; Liu, Estella H.; Church, Barbara A.; Eddins, Ann C.; Mercado, Eduardo

2011-01-01

Objective Perceptual sensitivities are malleable via learning, even in adults. We trained adults to discriminate complex sounds (periodic, frequency-modulated sweep trains) using two different training procedures, and used psychoacoustic tests and evoked potential measures (the N1-P2 complex) to assess changes in both perceptual and neural sensitivities. Methods Training took place either on a single day, or daily across eight days, and involved discrimination of pairs of stimuli using a single-interval, forced-choice task. In some participants, training started with dissimilar pairs that became progressively more similar across sessions, whereas in others training was constant, involving only one, highly similar, stimulus pair. Results Participants were better able to discriminate the complex sounds after training, particularly after progressive training, and the evoked potentials elicited by some of the sounds increased in amplitude following training. Significant amplitude changes were restricted to the P2 peak. Conclusion Our findings indicate that changes in perceptual sensitivities parallel enhanced neural processing. Significance These results are consistent with the proposal that changes in perceptual abilities arise from the brain’s capacity to adaptively modify cortical representations of sensory stimuli, and that different training regimens can lead to differences in cortical sensitivities, even after relatively short periods of training. PMID:21958655

Myricetin and methyl eugenol combination enhances the anticancer activity, cell cycle arrest and apoptosis induction of cis-platin against HeLa cervical cancer cell lines

PubMed Central

Yi, Jin-Ling; Shi, Song; Shen, Yan-Li; Wang, Ling; Chen, Hai-Yan; Zhu, Jun; Ding, Yan

2015-01-01

Drug combination therapies are common practice in the treatment of cancer. In this study, we evaluated the anticancer effects of myricetin (MYR), methyl eugenol (MEG) and cisplatin (CP) both separately as well as in combination against cervical cancer (HeLa) cells. To demonstrate whether MYR and MEG enhance the anticancer activity of CP against cervical cancer cells, we treated HeLa cells with MYR and MEG alone or in combination with cisplatin and evaluated cell growth and apoptosis using MTT (3 (4, 5 dimethyl thiazol 2yl) 2, 5 diphenyltetrazolium bromide) assay, LDH release assay, flow cytometry and fluorescence microscopy. The results revealed that, as compared to single drug treatment, the combination of MYR or MEG with CP resulted in greater effect in inhibiting cancer cell growth and inducing apoptosis. Cell apoptosis induction, Caspase-3 activity, cell cycle arrest and mitochondrial membrane potential loss were systematically studied to reveal the mechanisms of synergy between MYR, MEG and CP. Combination of MYR or MEG with CP resulted in more potent apoptosis induction as revealed by fluorescence microscopy using Hoechst 33258 and AO-ETBR staining. The combination treatment also increased the number of cells in G0/G1 phase dramatically as compared to single drug treatment. Mitochondrial membrane potential loss (ΛΨm) as well as Caspase-3 activity was much higher in combination treatment as compared to single drug treatment. Findings of this investigation suggest that MYR and MEG combined with cisplatin is a potential clinical chemotherapeutic approach in human cervical cancer. PMID:25972998

Stable habitable zones of single Jovian planet systems

NASA Astrophysics Data System (ADS)

Agnew, Matthew T.; Maddison, Sarah T.; Thilliez, Elodie; Horner, Jonathan

2017-11-01

With continued improvement in telescope sensitivity and observational techniques, the search for rocky planets in stellar habitable zones is entering an exciting era. With so many exoplanetary systems available for follow-up observations to find potentially habitable planets, one needs to prioritize the ever-growing list of candidates. We aim to determine which of the known planetary systems are dynamically capable of hosting rocky planets in their habitable zones, with the goal of helping to focus future planet search programmes. We perform an extensive suite of numerical simulations to identify regions in the habitable zones of single Jovian planet systems where Earth-mass planets could maintain stable orbits, specifically focusing on the systems in the Catalog of Earth-like Exoplanet Survey Targets (CELESTA). We find that small, Earth-mass planets can maintain stable orbits in cases where the habitable zone is largely, or partially, unperturbed by a nearby Jovian, and that mutual gravitational interactions and resonant mechanisms are capable of producing stable orbits even in habitable zones that are significantly or completely disrupted by a Jovian. Our results yield a list of 13 single Jovian planet systems in CELESTA that are not only capable of supporting an Earth-mass planet on stable orbits in their habitable zone, but for which we are also able to constrain the orbits of the Earth-mass planet such that the induced radial velocity signals would be detectable with next generation instruments.

Protective effects of pulmonary epithelial lining fluid on oxidative stress and DNA single-strand breaks caused by ultrafine carbon black, ferrous sulphate and organic extract of diesel exhaust particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chuang, Hsiao-Chi; Division of Pulmonary Medicine, Department of Internal Medicine, Shuang Ho Hospital, Taipei Medical University, Taipei, Taiwan; Cheng, Yi-Ling

Pulmonary epithelial lining fluid (ELF) is the first substance to make contact with inhaled particulate matter (PM) and interacts chemically with PM components. The objective of this study was to determine the role of ELF in oxidative stress, DNA damage and the production of proinflammatory cytokines following physicochemical exposure to PM. Ultrafine carbon black (ufCB, 15 nm; a model carbonaceous core), ferrous sulphate (FeSO{sub 4}; a model transition metal) and a diesel exhaust particle (DEP) extract (a model organic compound) were used to examine the acellular oxidative potential of synthetic ELF and non-ELF systems. We compared the effects of exposuremore » to ufCB, FeSO{sub 4} and DEP extract on human alveolar epithelial Type II (A549) cells to determine the levels of oxidative stress, DNA single-strand breaks and interleukin-8 (IL-8) production in ELF and non-ELF systems. The effects of ufCB and FeSO{sub 4} on the acellular oxidative potential, cellular oxidative stress and DNA single-strand breakage were mitigated significantly by the addition of ELF, whereas there was no decrease following treatment with the DEP extract. There was no significant effect on IL-8 production following exposure to samples that were suspended in ELF/non-ELF systems. The results of the present study indicate that ELF plays an important role in the initial defence against PM in the pulmonary environment. Experimental components, such as ufCB and FeSO{sub 4}, induced the production of oxidative stress and led to DNA single-strand breaks, which were moderately prevented by the addition of ELF. These findings suggest that ELF plays a protective role against PM-driven oxidative stress and DNA damage. -- Highlights: ► To determine the role of ELF in ROS, DNA damage and IL-8 after exposure to PM. ► ufCB, FeSO{sub 4} and DEP extract were used to examine the protective effects of ELF. ► PM-driven oxidative stress and DNA single-strand breakage were mitigated by ELF. ► The findings suggest that ELF has a protective role against PM. ► The synthetic ELF system could reduce the use of animals in PM-driven ROS testing.« less

Robust determination of the chemical potential in the pole expansion and selected inversion method for solving Kohn-Sham density functional theory

NASA Astrophysics Data System (ADS)

Jia, Weile; Lin, Lin

2017-10-01

Fermi operator expansion (FOE) methods are powerful alternatives to diagonalization type methods for solving Kohn-Sham density functional theory (KSDFT). One example is the pole expansion and selected inversion (PEXSI) method, which approximates the Fermi operator by rational matrix functions and reduces the computational complexity to at most quadratic scaling for solving KSDFT. Unlike diagonalization type methods, the chemical potential often cannot be directly read off from the result of a single step of evaluation of the Fermi operator. Hence multiple evaluations are needed to be sequentially performed to compute the chemical potential to ensure the correct number of electrons within a given tolerance. This hinders the performance of FOE methods in practice. In this paper, we develop an efficient and robust strategy to determine the chemical potential in the context of the PEXSI method. The main idea of the new method is not to find the exact chemical potential at each self-consistent-field (SCF) iteration but to dynamically and rigorously update the upper and lower bounds for the true chemical potential, so that the chemical potential reaches its convergence along the SCF iteration. Instead of evaluating the Fermi operator for multiple times sequentially, our method uses a two-level strategy that evaluates the Fermi operators in parallel. In the regime of full parallelization, the wall clock time of each SCF iteration is always close to the time for one single evaluation of the Fermi operator, even when the initial guess is far away from the converged solution. We demonstrate the effectiveness of the new method using examples with metallic and insulating characters, as well as results from ab initio molecular dynamics.

Robust determination of the chemical potential in the pole expansion and selected inversion method for solving Kohn-Sham density functional theory.

PubMed

Jia, Weile; Lin, Lin

2017-10-14

Fermi operator expansion (FOE) methods are powerful alternatives to diagonalization type methods for solving Kohn-Sham density functional theory (KSDFT). One example is the pole expansion and selected inversion (PEXSI) method, which approximates the Fermi operator by rational matrix functions and reduces the computational complexity to at most quadratic scaling for solving KSDFT. Unlike diagonalization type methods, the chemical potential often cannot be directly read off from the result of a single step of evaluation of the Fermi operator. Hence multiple evaluations are needed to be sequentially performed to compute the chemical potential to ensure the correct number of electrons within a given tolerance. This hinders the performance of FOE methods in practice. In this paper, we develop an efficient and robust strategy to determine the chemical potential in the context of the PEXSI method. The main idea of the new method is not to find the exact chemical potential at each self-consistent-field (SCF) iteration but to dynamically and rigorously update the upper and lower bounds for the true chemical potential, so that the chemical potential reaches its convergence along the SCF iteration. Instead of evaluating the Fermi operator for multiple times sequentially, our method uses a two-level strategy that evaluates the Fermi operators in parallel. In the regime of full parallelization, the wall clock time of each SCF iteration is always close to the time for one single evaluation of the Fermi operator, even when the initial guess is far away from the converged solution. We demonstrate the effectiveness of the new method using examples with metallic and insulating characters, as well as results from ab initio molecular dynamics.

Increasing availability and consumption of single cigarettes: Trends and implications for smoking cessation from the ITC Mexico Survey

PubMed Central

Hall, Marissa G.; Fleischer, Nancy L.; Shigematsu, Luz Myriam Reynales; Arillo-Santillán, Edna; Thrasher, James F.

2015-01-01

Objective Determine (1) trends in single cigarette availability and purchasing in Mexico, and (2) the association between neighborhood access to singles and cessation behavior among adult Mexican smokers. Methods We analyzed data from Wave 4 (2010), Wave 5 (2011), and Wave 6 (2012) of the Mexican International Tobacco Control Policy Evaluation Survey. We used data from all three waves to examine time trends in singles availability and purchasing. To explore the association between neighborhood access to singles and cessation behavior, we used data from participants who were smokers at Wave 5 and followed up at Wave 6 (n=1272). Findings The percentage of participants who saw singles sold daily (45.2% in 2010; 51.4% in 2011; 64.9% in 2012), who bought singles at least once a week (22.3% in 2010; 29.1% in 2011; 29.1% in 2012), and whose last cigarette purchase was a single (16.6% in 2010; 20.7% in 2011; 25.8% in 2012) increased significantly from 2010 to 2012 (all p<.001). The average percentage of residents who reported seeing singles sold daily in their neighborhood in 2012 was 60% (SD=25%). In adjusted analyses, smokers living in neighborhoods with higher access to singles were less likely to make a quit attempt (risk ratio (RR)=0.72; 95% confidence interval (CI): 0.46–1.12), and more likely to relapse (RR=1.30; CI: 0.94–1.82), but these results were not statistically significant. Conclusions Single cigarettes appear widely accessible in Mexico and growing in availability. Future research should explore potential explanations, consequences, and effective methods for reducing the availability of single cigarettes. PMID:25192772

Scaling Law of Urban Ride Sharing.

PubMed

Tachet, R; Sagarra, O; Santi, P; Resta, G; Szell, M; Strogatz, S H; Ratti, C

2017-03-06

Sharing rides could drastically improve the efficiency of car and taxi transportation. Unleashing such potential, however, requires understanding how urban parameters affect the fraction of individual trips that can be shared, a quantity that we call shareability. Using data on millions of taxi trips in New York City, San Francisco, Singapore, and Vienna, we compute the shareability curves for each city, and find that a natural rescaling collapses them onto a single, universal curve. We explain this scaling law theoretically with a simple model that predicts the potential for ride sharing in any city, using a few basic urban quantities and no adjustable parameters. Accurate extrapolations of this type will help planners, transportation companies, and society at large to shape a sustainable path for urban growth.

Potential of mean force between two hydrophobic solutes in water.

PubMed

Southall, Noel T; Dill, Ken A

2002-12-10

We study the potential of mean force between two nonpolar solutes in the Mercedes Benz model of water. Using NPT Monte Carlo simulations, we find that the solute size determines the relative preference of two solute molecules to come into contact ('contact minimum') or to be separated by a single layer of water ('solvent-separated minimum'). Larger solutes more strongly prefer the contacting state, while smaller solutes have more tendency to become solvent-separated, particularly in cold water. The thermal driving forces oscillate with solute separation. Contacts are stabilized by entropy, whereas solvent-separated solute pairing is stabilized by enthalpy. The free energy of interaction for small solutes is well-approximated by scaled-particle theory. Copyright 2002 Elsevier Science B.V.

EEG gamma coherence and other correlates of subjective reports during ayahuasca experiences.

PubMed

Stuckey, David E; Lawson, Robert; Luna, Luis Eduardo

2005-06-01

The current study examined QEEG power and coherence of ayahuasca experiences with two experienced participants in a Brazilian jungle setting. An exploratory case series design was adopted for naturalistic field research. EEGs recorded during visual imagery was compared to eyes-closed baselines. The most important findings were increases in global EEG coherence in the 36-44 Hz and 50-64 Hz frequency bands for both subjects. Widely distributed cortical hyper-coherence seems reasonable given the intense synesthesia during ayahuasca experiences. Other findings include increased modal EEG alpha frequency and global power decreases across the cortex in most frequency bands, which concur with the EEG of psychedelics literature. Exploratory analysis revealed the usefulness of analyzing single Hz bins over the standard wide-band analysis. The discovery-oriented naturalistic approach developed for this study resulted in potentially important findings. We believe that finding increases in global gamma coherence during peak psychedelic experiences might contribute to the discussion of binding theory. Also, in light of recent research with gamma coherence during advanced meditative conditions, our findings might further the comparison of shamanic psychedelic practices with meditation.

Zika Risk and Pregnancy in Clinical Practice: Ongoing Experience as the Outbreak Evolves.

PubMed

Rao, Rashmi; Gaw, Stephanie L; Han, Christina S; Platt, Lawrence D; Silverman, Neil S

2017-06-01

To describe a single U.S. perinatal center's ongoing experience with evaluating pregnant patients with potential exposure to Zika virus infection. This is an institutional review board-approved longitudinal observational study from January to August 2016 from a single perinatal referral center. Patients who had traveled to or had sexual contact with a person who traveled to a region with documented local Zika virus transmission were included in the study. The aim of the study was to identify the rate of confirmed infection among pregnant women referred to our center with established risk factors for Zika virus acquisition. We also sought to characterize travel patterns that constituted risk, to identify rates of symptoms suggesting infection, and to potentially describe findings suggestive of congenital Zika virus infection in prenatal ultrasound evaluations. We evaluated 185 pregnant women with potential Zika virus exposure. Testing was offered in accordance with the version of the Centers for Disease Control and Prevention guidelines in place at the time of the consultation visit. Geographic exposure data showed Mexico (44%), the Caribbean (17%), North America (16%), South America (13%), and Central America (9%) to be the most common areas in which potential exposure occurred. One hundred twenty-three (67%) patients reported insect bites and 19 (10%) patients reported symptoms. Overall, five (3% of all) patients had prenatal ultrasound findings suggestive of possible fetal Zika virus infection; all their Zika virus test results returned negative. These findings included microcephaly, echogenic intracardiac foci, and ventricular calcifications. Of the 153 Zika virus screening tests ordered, eight (5%) immunoglobulin M results returned positive or equivocal with only one positive through confirmatory testing. Overall, 1 of 185 (0.5%) of all those consulted and 1 of 153 (0.7%) of those tested had a confirmed Zika virus infection with no confirmed fetal or neonatal infections. We identified low rates of confirmed maternal Zika virus infection in our cohort, but the number of patients described here demonstrates the magnitude of concern existing among both patients and physicians regarding possible perinatal Zika virus infection. It also underscores the need for health care providers to be prepared to answer questions, explain laboratory and ultrasound results, and describe testing options for concerned patients and their families.

Efficiency at Maximum Power Output of a Quantum-Mechanical Brayton Cycle

NASA Astrophysics Data System (ADS)

Yuan, Yuan; He, Ji-Zhou; Gao, Yong; Wang, Jian-Hui

2014-03-01

The performance in finite time of a quantum-mechanical Brayton engine cycle is discussed, without introduction of temperature. The engine model consists of two quantum isoenergetic and two quantum isobaric processes, and works with a single particle in a harmonic trap. Directly employing the finite-time thermodynamics, the efficiency at maximum power output is determined. Extending the harmonic trap to a power-law trap, we find that the efficiency at maximum power is independent of any parameter involved in the model, but depends on the confinement of the trapping potential.

Structure of novel rat major histocompatibility complex class II genes RT1.Ha and Hb

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arimura, Yutaka; Tang, Wei Ran; Koda, Toshiaki

1995-03-01

We have cloned the novel rat MHC class II genes, RT1.Ha and Hb, which are homologous to human HLA-DPA and DPB. RT1.Hb is a pseudogene, whereas RT1.Ha is apparently intact and may have transcriptional potential. In addition, with an RT1.Ha probe, we detecteda single Southern hybridization band in the genome of the mouse. This finding may aford an opportunity to analyze the HLA-DPA homologue in the mouse genome. 18 refs., 4 figs., 1 tab.

Reconsidering the "Good Divorce"

PubMed

Amato, Paul R; Kane, Jennifer B; James, Spencer

2011-12-01

This study attempted to assess the notion that a "good divorce" protects children from the potential negative consequences of marital dissolution. A cluster analysis of data on postdivorce parenting from 944 families resulted in three groups: cooperative coparenting, parallel parenting, and single parenting. Children in the cooperative coparenting (good divorce) cluster had the smallest number of behavior problems and the closest ties to their fathers. Nevertheless, children in this cluster did not score significantly better than other children on 10 additional outcomes. These findings provide only modest support for the good divorce hypothesis.

Reconsidering the “Good Divorce”

PubMed Central

Amato, Paul R.; Kane, Jennifer B.; James, Spencer

2011-01-01

This study attempted to assess the notion that a “good divorce” protects children from the potential negative consequences of marital dissolution. A cluster analysis of data on postdivorce parenting from 944 families resulted in three groups: cooperative coparenting, parallel parenting, and single parenting. Children in the cooperative coparenting (good divorce) cluster had the smallest number of behavior problems and the closest ties to their fathers. Nevertheless, children in this cluster did not score significantly better than other children on 10 additional outcomes. These findings provide only modest support for the good divorce hypothesis. PMID:22125355

Recombination of H(3+) and D(3+) ions with electrons

NASA Technical Reports Server (NTRS)

Johnsen, R.; Gougousi, T.; Golde, M. F.

1994-01-01

Flowing-afterglow measurements in decaying H3(+) or D3(+) plasmas suggest that de-ionization does not occur by simple binary recombination of a single ion species. We find that vibrational excitation of the ions fails to provide an explanation for the effect, contrary to an earlier suggestion. Instead, we suggest that collisional stabilization of H3** Rydberg molecules by ambient electrons introduces an additional dependence on electron density. The proposed mechanism would permit plasma de-ionization to occur without the need for dissociative recombination by the mechanism of potential-surface crossings.

Single Cobalt Atoms with Precise N-Coordination as Superior Oxygen Reduction Reaction Catalysts.

PubMed

Yin, Peiqun; Yao, Tao; Wu, Yuen; Zheng, Lirong; Lin, Yue; Liu, Wei; Ju, Huanxin; Zhu, Junfa; Hong, Xun; Deng, Zhaoxiang; Zhou, Gang; Wei, Shiqiang; Li, Yadong

2016-08-26

A new strategy for achieving stable Co single atoms (SAs) on nitrogen-doped porous carbon with high metal loading over 4 wt % is reported. The strategy is based on a pyrolysis process of predesigned bimetallic Zn/Co metal-organic frameworks, during which Co can be reduced by carbonization of the organic linker and Zn is selectively evaporated away at high temperatures above 800 °C. The spherical aberration correction electron microscopy and extended X-ray absorption fine structure measurements both confirm the atomic dispersion of Co atoms stabilized by as-generated N-doped porous carbon. Surprisingly, the obtained Co-Nx single sites exhibit superior ORR performance with a half-wave potential (0.881 V) that is more positive than commercial Pt/C (0.811 V) and most reported non-precious metal catalysts. Durability tests revealed that the Co single atoms exhibit outstanding chemical stability during electrocatalysis and thermal stability that resists sintering at 900 °C. Our findings open up a new routine for general and practical synthesis of a variety of materials bearing single atoms, which could facilitate new discoveries at the atomic scale in condensed materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tuneable complementary metamaterial structures based on graphene for single and multiple transparency windows

PubMed Central

Ding, Jun; Arigong, Bayaner; Ren, Han; Zhou, Mi; Shao, Jin; Lu, Meng; Chai, Yang; Lin, Yuankun; Zhang, Hualiang

2014-01-01

Novel graphene-based tunable plasmonic metamaterials featuring single and multiple transparency windows are numerically studied in this paper. The designed structures consist of a graphene layer perforated with quadrupole slot structures and dolmen-like slot structures printed on a substrate. Specifically, the graphene-based quadrupole slot structure can realize a single transparency window, which is achieved without breaking the structure symmetry. Further investigations have shown that the single transparency window in the proposed quadrupole slot structure is more likely originated from the quantum effect of Autler-Townes splitting. Then, by introducing a dipole slot to the quadrupole slot structure to form the dolmen-like slot structure, an additional transmission dip could occur in the transmission spectrum, thus, a multiple-transparency-window system can be achieved (for the first time for graphene-based devices). More importantly, the transparency windows for both the quadrupole slot and the dolmen-like slot structures can be dynamically controlled over a broad frequency range by varying the Fermi energy levels of the graphene layer (through electrostatic gating). The proposed slot metamaterial structures with tunable single and multiple transparency windows could find potential applications in many areas such as multiple-wavelength slow-light devices, active plasmonic switching, and optical sensing. PMID:25146672

Tuneable complementary metamaterial structures based on graphene for single and multiple transparency windows.

PubMed

Ding, Jun; Arigong, Bayaner; Ren, Han; Zhou, Mi; Shao, Jin; Lu, Meng; Chai, Yang; Lin, Yuankun; Zhang, Hualiang

2014-08-22

Novel graphene-based tunable plasmonic metamaterials featuring single and multiple transparency windows are numerically studied in this paper. The designed structures consist of a graphene layer perforated with quadrupole slot structures and dolmen-like slot structures printed on a substrate. Specifically, the graphene-based quadrupole slot structure can realize a single transparency window, which is achieved without breaking the structure symmetry. Further investigations have shown that the single transparency window in the proposed quadrupole slot structure is more likely originated from the quantum effect of Autler-Townes splitting. Then, by introducing a dipole slot to the quadrupole slot structure to form the dolmen-like slot structure, an additional transmission dip could occur in the transmission spectrum, thus, a multiple-transparency-window system can be achieved (for the first time for graphene-based devices). More importantly, the transparency windows for both the quadrupole slot and the dolmen-like slot structures can be dynamically controlled over a broad frequency range by varying the Fermi energy levels of the graphene layer (through electrostatic gating). The proposed slot metamaterial structures with tunable single and multiple transparency windows could find potential applications in many areas such as multiple-wavelength slow-light devices, active plasmonic switching, and optical sensing.

Mate-choice copying in single and coupled women: the influence of mate acceptance and mate rejection decisions of other women.

PubMed

Deng, Yan; Zheng, Yong

2015-01-26

Studies of humans and non-human animals indicate that females tend to change the likelihood of choosing a potential mate based on the decisions of other females; this is known as mate-choice copying. In a sample of both single and coupled women, we examined the influence of other women's (model) mate-choice decisions, including mate acceptance and mate rejection, on participants' attractiveness ratings of men (target) and willingness of mate selection. We also examined whether different types of relationships between the target men and the model women affected mate-choice copying. We found that both the single and coupled women showed mate-choice copying, but their response patterns differed. The significant effects for single women were dependent on a decrease in attractiveness ratings when they perceived the models' mate rejection. However, the significant findings for coupled women relied on an increase in attractiveness ratings when they observed the models' mate acceptance. Furthermore, the relationship status between the target men and the model women affected the magnitude of mate-choice copying effects for the single women. Specifically, they showed less mate-choice copying when the targets and models were in a committed romantic relationship than when in a temporary relationship.

Microscopic theory of cavity-enhanced single-photon emission from optical two-photon Raman processes

NASA Astrophysics Data System (ADS)

Breddermann, Dominik; Praschan, Tom; Heinze, Dirk; Binder, Rolf; Schumacher, Stefan

2018-03-01

We consider cavity-enhanced single-photon generation from stimulated two-photon Raman processes in three-level systems. We compare four fundamental system configurations, one Λ -, one V-, and two ladder (Ξ -) configurations. These can be realized as subsystems of a single quantum dot or of quantum-dot molecules. For a new microscopic understanding of the Raman process, we analyze the Heisenberg equation of motion applying the cluster-expansion scheme. Within this formalism an exact and rigorous definition of a cavity-enhanced Raman photon via its corresponding Raman correlation is possible. This definition for example enables us to systematically investigate the on-demand potential of Raman-transition-based single-photon sources. The four system arrangements can be divided into two subclasses, Λ -type and V-type, which exhibit strongly different Raman-emission characteristics and Raman-emission probabilities. Moreover, our approach reveals whether the Raman path generates a single photon or just induces destructive quantum interference with other excitation paths. Based on our findings and as a first application, we gain a more detailed understanding of experimental data from the literature. Our analysis and results are also transferable to the case of atomic three-level-resonator systems and can be extended to more complicated multilevel schemes.

One-Pot Solvothermal in Situ Growth of 1D Single-Crystalline NiSe on Ni Foil as Efficient and Stable Transparent Conductive Oxide Free Counter Electrodes for Dye-Sensitized Solar Cells.

PubMed

Bao, Chao; Li, Faxin; Wang, Jiali; Sun, Panpan; Huang, Niu; Sun, Yihua; Fang, Liang; Wang, Lei; Sun, Xiaohua

2016-12-07

One-dimensional single-crystal nanostructural nickel selenides were successfully in situ grown on metal nickel foils by two simple one-step solvothermal methods, which formed NiSe/Ni counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The nickel foil acted as the nickel source in the reaction process, a supporting substrate, and an electron transport "speedway". Electrochemical testing indicated that the top 1D single-crystal NiSe exhibited prominent electrocatalytic activity for I 3 - reduction. Due to the metallic conductivity of Ni substrate and the outstanding electrocatalytic activity of single-crystal NiSe, the DSSC based on a NiSe/Ni CE exhibited higher fill factor (FF) and larger short-circuit current density (J sc ) than the DSSC based on Pt/FTO CE. The corresponding power conversion efficiency (6.75%) outperformed that of the latter (6.18%). Moreover, the NiSe/Ni CEs also showed excellent electrochemical stability in the I - /I 3 - redox electrolyte. These findings indicated that single-crystal NiSe in situ grown on Ni substrate was a potential candidate to replace Pt/TCO as a cheap and highly efficient counter electrode of DSSC.

Combining features from ERP components in single-trial EEG for discriminating four-category visual objects.

PubMed

Wang, Changming; Xiong, Shi; Hu, Xiaoping; Yao, Li; Zhang, Jiacai

2012-10-01

Categorization of images containing visual objects can be successfully recognized using single-trial electroencephalograph (EEG) measured when subjects view images. Previous studies have shown that task-related information contained in event-related potential (ERP) components could discriminate two or three categories of object images. In this study, we investigated whether four categories of objects (human faces, buildings, cats and cars) could be mutually discriminated using single-trial EEG data. Here, the EEG waveforms acquired while subjects were viewing four categories of object images were segmented into several ERP components (P1, N1, P2a and P2b), and then Fisher linear discriminant analysis (Fisher-LDA) was used to classify EEG features extracted from ERP components. Firstly, we compared the classification results using features from single ERP components, and identified that the N1 component achieved the highest classification accuracies. Secondly, we discriminated four categories of objects using combining features from multiple ERP components, and showed that combination of ERP components improved four-category classification accuracies by utilizing the complementarity of discriminative information in ERP components. These findings confirmed that four categories of object images could be discriminated with single-trial EEG and could direct us to select effective EEG features for classifying visual objects.

Single-cell genomics-based analysis of virus–host interactions in marine surface bacterioplankton

DOE PAGES

Labonté, Jessica M.; Swan, Brandon K.; Poulos, Bonnie; ...

2015-04-07

Viral infections dynamically alter the composition and metabolic potential of marine microbial communities and the evolutionary trajectories of host populations with resulting feedback on biogeochemical cycles. It is quite possible that all microbial populations in the ocean are impacted by viral infections. Our knowledge of virus–host relationships, however, has been limited to a minute fraction of cultivated host groups. Here, we utilized single-cell sequencing to obtain genomic blueprints of viruses inside or attached to individual bacterial and archaeal cells captured in their native environment, circumventing the need for host and virus cultivation. Furthermore, a combination of comparative genomics, metagenomic fragmentmore » recruitment, sequence anomalies and irregularities in sequence coverage depth and genome recovery were utilized to detect viruses and to decipher modes of virus–host interactions. Members of all three tailed phage families were identified in 20 out of 58 phylogenetically and geographically diverse single amplified genomes (SAGs) of marine bacteria and archaea. At least four phage–host interactions had the characteristics of late lytic infections, all of which were found in metabolically active cells. One virus had genetic potential for lysogeny. Our findings include first known viruses of Thaumarchaeota, Marinimicrobia, Verrucomicrobia and Gammaproteobacteria clusters SAR86 and SAR92. Viruses were also found in SAGs of Alphaproteobacteria and Bacteroidetes. A high fragment recruitment of viral metagenomic reads confirmed that most of the SAG-associated viruses are abundant in the ocean. This study demonstrates that single-cell genomics, in conjunction with sequence-based computational tools, enable in situ, cultivation-independent insights into host–virus interactions in complex microbial communities.« less

Study of Fission Barrier Heights of Uranium Isotopes by the Macroscopic-Microscopic Method

NASA Astrophysics Data System (ADS)

Zhong, Chun-Lai; Fan, Tie-Shuan

2014-09-01

Potential energy surfaces of uranium nuclei in the range of mass numbers 229 through 244 are investigated in the framework of the macroscopic-microscopic model and the heights of static fission barriers are obtained in terms of a double-humped structure. The macroscopic part of the nuclear energy is calculated according to Lublin—Strasbourg-drop (LSD) model. Shell and pairing corrections as the microscopic part are calculated with a folded-Yukawa single-particle potential. The calculation is carried out in a five-dimensional parameter space of the generalized Lawrence shapes. In order to extract saddle points on the potential energy surface, a new algorithm which can effectively find an optimal fission path leading from the ground state to the scission point is developed. The comparison of our results with available experimental data and others' theoretical results confirms the reliability of our calculations.

Surface-peaked medium effects in the interaction of nucleons with finite nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aguayo, F. J.; Arellano, H. F.

We investigate the asymptotic separation of the optical model potential for nucleon-nucleus scattering in momentum space, where the potential is split into a medium-independent term and another depending exclusively on the gradient of the density-dependent g matrix. This decomposition confines the medium sensitivity of the nucleon-nucleus coupling to the surface of the nucleus. We examine this feature in the context of proton-nucleus scattering at beam energies between 30 and 100 MeV and find that the pn coupling accounts for most of this sensitivity. Additionally, based on this general structure of the optical potential we are able to treat both, themore » medium dependence of the effective interaction and the full mixed density as described by single-particle shell models. The calculated scattering observables agree within 10% with those obtained by Arellano, Brieva, and Love in their momentum-space g-folding approach.« less

Two-field axion-monodromy hybrid inflation model: Dante's Waterfall

NASA Astrophysics Data System (ADS)

Carone, Christopher D.; Erlich, Joshua; Sensharma, Anuraag; Wang, Zhen

2015-02-01

We describe a hybrid axion-monodromy inflation model motivated by the Dante's Inferno scenario. In Dante's Inferno, a two-field potential features a stable trench along which a linear combination of the two fields slowly rolls, rendering the dynamics essentially identical to that of single-field chaotic inflation. A shift symmetry allows for the Lyth bound to be effectively evaded as in other axion-monodromy models. In our proposal, the potential is concave downward near the origin and the inflaton trajectory is a gradual downward spiral, ending at a point where the trench becomes unstable. There, the fields begin falling rapidly towards the minimum of the potential and inflation terminates as in a hybrid model. We find parameter choices that reproduce observed features of the cosmic microwave background, and discuss our model in light of recent results from the BICEP2 and Planck experiments.

Detecting Friedel oscillations in ultracold Fermi gases

NASA Astrophysics Data System (ADS)

Riechers, Keno; Hueck, Klaus; Luick, Niclas; Lompe, Thomas; Moritz, Henning

2017-09-01

Investigating Friedel oscillations in ultracold gases would complement the studies performed on solid state samples with scanning-tunneling microscopes. In atomic quantum gases interactions and external potentials can be tuned freely and the inherently slower dynamics allow to access non-equilibrium dynamics following a potential or interaction quench. Here, we examine how Friedel oscillations can be observed in current ultracold gas experiments under realistic conditions. To this aim we numerically calculate the amplitude of the Friedel oscillations which are induced by a potential barrier in a 1D Fermi gas and compare it to the expected atomic and photonic shot noise in a density measurement. We find that to detect Friedel oscillations the signal from several thousand one-dimensional systems has to be averaged. However, as up to 100 parallel one-dimensional systems can be prepared in a single run with present experiments, averaging over about 100 images is sufficient.

Autonomic responses to correct outcomes and interaction errors during single-switch scanning among children with severe spastic quadriplegic cerebral palsy

PubMed Central

2014-01-01

Background The combination of single-switch access technology and scanning is the most promising means of augmentative and alternative communication for many children with severe physical disabilities. However, the physical impairment of the child and the technology’s limited ability to interpret the child’s intentions often lead to false positives and negatives (corresponding to accidental and missed selections, respectively) occurring at rates that frustrate the user and preclude functional communication. Multiple psychophysiological studies have associated cardiac deceleration and increased phasic electrodermal activity with self-realization of errors among able-bodied individuals. Thus, physiological measurements have potential utility at enhancing single-switch access, provided that such prototypical autonomic responses exist in persons with profound disabilities. Methods The present case series investigated the autonomic responses of three pediatric single-switch users with severe spastic quadriplegic cerebral palsy, in the context of a single-switch letter matching activity. Each participant exhibited distinct autonomic responses to activity engagement. Results Our analysis confirmed the presence of the autonomic response pattern of cardiac deceleration and increased phasic electrodermal activity following true positives, false positives and false negatives errors, but not subsequent to true negative outcomes. Conclusions These findings suggest that there may be merit in complementing single-switch input with autonomic measurements to improve augmentative and alternative communications for pediatric access technology users. PMID:24607065

The influence of single bursts vs. single spikes at excitatory dendrodendritic synapses

PubMed Central

Masurkar, Arjun V.; Chen, Wei R.

2015-01-01

The synchronization of neuronal activity is thought to enhance information processing. There is much evidence supporting rhythmically bursting external tufted cells (ETCs) of the rodent olfactory bulb glomeruli coordinating the activation of glomerular interneurons and mitral cells via dendrodendritic excitation. However, as bursting has variable significance at axodendritic cortical synapses, it is not clear if ETC bursting imparts a specific functional advantage over the preliminary spike in dendrodendritic synaptic networks. To answer this question, we investigated the influence of single ETC bursts and spikes with the in-vitro rat olfactory bulb preparation at different levels of processing, via calcium imaging of presynaptic ETC dendrites, dual electrical recording of ETC–interneuron synaptic pairs, and multicellular calcium imaging of ETC-induced population activity. Our findings supported single ETC bursts, vs. single spikes, driving robust presynaptic calcium signaling, which in turn was associated with profound extension of the initial monosynaptic spike-driven dendrodendritic excitatory postsynaptic potential. This extension could be driven by either the spike-dependent or spike-independent components of the burst. At the population level, burst-induced excitation was more widespread and reliable compared with single spikes. This further supports the ETC network, in part due to a functional advantage of bursting at excitatory dendrodendritic synapses, coordinating synchronous activity at behaviorally relevant frequencies related to odor processing in vivo. PMID:22277089

Autonomic responses to correct outcomes and interaction errors during single-switch scanning among children with severe spastic quadriplegic cerebral palsy.

PubMed

Leung, Brian; Chau, Tom

2014-03-08

The combination of single-switch access technology and scanning is the most promising means of augmentative and alternative communication for many children with severe physical disabilities. However, the physical impairment of the child and the technology's limited ability to interpret the child's intentions often lead to false positives and negatives (corresponding to accidental and missed selections, respectively) occurring at rates that frustrate the user and preclude functional communication. Multiple psychophysiological studies have associated cardiac deceleration and increased phasic electrodermal activity with self-realization of errors among able-bodied individuals. Thus, physiological measurements have potential utility at enhancing single-switch access, provided that such prototypical autonomic responses exist in persons with profound disabilities. The present case series investigated the autonomic responses of three pediatric single-switch users with severe spastic quadriplegic cerebral palsy, in the context of a single-switch letter matching activity. Each participant exhibited distinct autonomic responses to activity engagement. Our analysis confirmed the presence of the autonomic response pattern of cardiac deceleration and increased phasic electrodermal activity following true positives, false positives and false negatives errors, but not subsequent to true negative outcomes. These findings suggest that there may be merit in complementing single-switch input with autonomic measurements to improve augmentative and alternative communications for pediatric access technology users.

A finite-temperature Hartree-Fock code for shell-model Hamiltonians

NASA Astrophysics Data System (ADS)

Bertsch, G. F.; Mehlhaff, J. M.

2016-10-01

The codes HFgradZ.py and HFgradT.py find axially symmetric minima of a Hartree-Fock energy functional for a Hamiltonian supplied in a shell model basis. The functional to be minimized is the Hartree-Fock energy for zero-temperature properties or the Hartree-Fock grand potential for finite-temperature properties (thermal energy, entropy). The minimization may be subjected to additional constraints besides axial symmetry and nucleon numbers. A single-particle operator can be used to constrain the minimization by adding it to the single-particle Hamiltonian with a Lagrange multiplier. One can also constrain its expectation value in the zero-temperature code. Also the orbital filling can be constrained in the zero-temperature code, fixing the number of nucleons having given Kπ quantum numbers. This is particularly useful to resolve near-degeneracies among distinct minima.

The Association of DRD2 with Insight Problem Solving.

PubMed

Zhang, Shun; Zhang, Jinghuan

2016-01-01

Although the insight phenomenon has attracted great attention from psychologists, it is still largely unknown whether its variation in well-functioning human adults has a genetic basis. Several lines of evidence suggest that genes involved in dopamine (DA) transmission might be potential candidates. The present study explored for the first time the association of dopamine D2 receptor gene ( DRD2 ) with insight problem solving. Fifteen single-nucleotide polymorphisms (SNPs) covering DRD2 were genotyped in 425 unrelated healthy Chinese undergraduates, and were further tested for association with insight problem solving. Both single SNP and haplotype analysis revealed several associations of DRD2 SNPs and haplotypes with insight problem solving. In conclusion, the present study provides the first evidence for the involvement of DRD2 in insight problem solving, future studies are necessary to validate these findings.

The Association of DRD2 with Insight Problem Solving

PubMed Central

Zhang, Shun; Zhang, Jinghuan

2016-01-01

Although the insight phenomenon has attracted great attention from psychologists, it is still largely unknown whether its variation in well-functioning human adults has a genetic basis. Several lines of evidence suggest that genes involved in dopamine (DA) transmission might be potential candidates. The present study explored for the first time the association of dopamine D2 receptor gene (DRD2) with insight problem solving. Fifteen single-nucleotide polymorphisms (SNPs) covering DRD2 were genotyped in 425 unrelated healthy Chinese undergraduates, and were further tested for association with insight problem solving. Both single SNP and haplotype analysis revealed several associations of DRD2 SNPs and haplotypes with insight problem solving. In conclusion, the present study provides the first evidence for the involvement of DRD2 in insight problem solving, future studies are necessary to validate these findings. PMID:27933030

Dispersion relations for circular single and double dusty plasma chains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tkachenko, D. V.; Misko, V. R.; Sheridan, T. E.

2011-10-15

We derive dispersion relations for a system of identical particles confined in a two-dimensional annular harmonic well and which interact through a Yukawa potential, e.g., a dusty plasma ring. When the particles are in a single chain (i.e., a one-dimensional ring), we find a longitudinal acoustic mode and a transverse optical mode which show approximate agreement with the dispersion relation for a straight configuration for large radii of the ring. When the radius decreases, the dispersion relations modify: there appears an anticrossing of the modes near the crossing point resulting in a frequency gap between the lower and upper branchesmore » of the modified dispersion relations. For the double chain (i.e., a two-dimensional zigzag configuration), the dispersion relation has four branches: longitudinal acoustic and optical and transverse acoustic and optical.« less

Dispersion relations for circular single and double dusty plasma chains

NASA Astrophysics Data System (ADS)

Tkachenko, D. V.; Sheridan, T. E.; Misko, V. R.

2011-10-01

We derive dispersion relations for a system of identical particles confined in a two-dimensional annular harmonic well and which interact through a Yukawa potential, e.g., a dusty plasma ring. When the particles are in a single chain (i.e., a one-dimensional ring), we find a longitudinal acoustic mode and a transverse optical mode which show approximate agreement with the dispersion relation for a straight configuration for large radii of the ring. When the radius decreases, the dispersion relations modify: there appears an anticrossing of the modes near the crossing point resulting in a frequency gap between the lower and upper branches of the modified dispersion relations. For the double chain (i.e., a two-dimensional zigzag configuration), the dispersion relation has four branches: longitudinal acoustic and optical and transverse acoustic and optical.

The effectiveness of therapeutic assessment with an adult client: a single-case study using a time-series design.

PubMed

Aschieri, Filippo; Smith, Justin D

2012-01-01

This article presents the therapeutic assessment (TA; Finn, 2007) of a traumatized young woman named Claire. Claire reported feeling debilitated by academic demands and the expectations of her parents, and was finding it nearly impossible to progress in her studies. She was also finding it difficult to develop and sustain intimate relationships. The emotional aspects of close relationships were extremely difficult for her and she routinely blamed herself for her struggles in this arena. The assessor utilized the TA model for adults, with the exception of not including an optional intervention session. The steps of TA, particularly the extended inquiry and the discussion of test findings along the way, cultivated a supportive and empathic atmosphere with Claire. By employing the single-case time-series experimental design used in previous TA studies (e.g., Smith, Handler, & Nash, 2010; Smith, Wolf, Handler, & Nash, 2009), the authors demonstrated that Claire experienced statistically significant improvement correlated with the onset of TA. Results indicated that participation in TA coincided with a positive shift in the trajectory of her reported symptoms and with recognizing the affection she held for others in her life. This case illustrates the successful application of case-based time-series methodology in the evaluation of an adult TA. The potential implications for future study are discussed.

Epidemic spreading on dual-structure networks with mobile agents

NASA Astrophysics Data System (ADS)

Yao, Yiyang; Zhou, Yinzuo

2017-02-01

The rapid development of modern society continually transforms the social structure which leads to an increasingly distinct dual structure of higher population density in urban areas and lower density in rural areas. Such structure may induce distinctive spreading behavior of epidemics which does not happen in a single type structure. In this paper, we study the epidemic spreading of mobile agents on dual structure networks based on SIRS model. First, beyond the well known epidemic threshold for generic epidemic model that when the infection rate is below the threshold a pertinent infectious disease will die out, we find the other epidemic threshold which appears when the infection rate of a disease is relatively high. This feature of two thresholds for the SIRS model may lead to the elimination of infectious disease when social network has either high population density or low population density. Interestingly, however, we find that when a high density area is connected to a low density may cause persistent spreading of the infectious disease, even though the same disease will die out when it spreads in each single area. This phenomenon indicates the critical role of the connection between the two areas which could radically change the behavior of spreading dynamics. Our findings, therefore, provide new understanding of epidemiology pertinent to the characteristic modern social structure and have potential to develop controlling strategies accordingly.

The Role of Symbiont Genetic Distance and Potential Adaptability in Host Preference Towards Pseudonocardia Symbionts in Acromyrmex Leaf-Cutting Ants

PubMed Central

Poulsen, Michael; Maynard, Janielle; Roland, Damien L; Currie, Cameron R

2011-01-01

Fungus-growing ants display symbiont preference in behavioral assays, both towards the fungus they cultivate for food and Actinobacteria they maintain on their cuticle for antibiotic production against parasites. These Actinobacteria, genus Pseudonocardia Henssen (Pseudonocardiacea: Actinomycetales), help defend the ants' fungal mutualist from specialized parasites. In Acromyrmex Mayr (Hymenoptera: Formicidae) leaf-cutting ants, individual colonies maintain either a single or a few strains of Pseudonocardia, and the symbiont is primarily vertically transmitted between generations by colony-founding queens. A recent report found that Acromyrmex workers are able to differentiate between their native Pseudonocardia strain and non-native strains isolated from sympatric or allopatric Acromyrmex species, and show preference for their native strain. Here we explore worker preference when presented with two non-native strains, elucidating the role of genetic distance on preference between strains and Pseudonocardia origin. Our findings suggest that ants tend to prefer bacteria more closely related to their native bacterium and that genetic similarity is probably more important than whether symbionts are ant-associated or free-living. Preliminary findings suggest that when continued exposure to a novel Pseudonocardia strain occurs, ant symbiont preference is potentially adaptable, with colonies apparently being able to alter symbiont preference over time. These findings are discussed in relation to the role of adaptive recognition, potential ecological flexibility in symbiont preference, and more broadly, in relation to self versus non-self recognition. PMID:22225537

A SYSTEMATIC SEARCH FOR COROTATING INTERACTION REGIONS IN APPARENTLY SINGLE GALACTIC WOLF-RAYET STARS. II. A GLOBAL VIEW OF THE WIND VARIABILITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chene, A.-N.; St-Louis, N., E-mail: achene@astro-udec.cl, E-mail: stlouis@astro.umontreal.ca

This study is the second part of a survey searching for large-scale spectroscopic variability in apparently single Wolf-Rayet (WR) stars. In a previous paper (Paper I), we described and characterized the spectroscopic variability level of 25 WR stars observable from the northern hemisphere and found 3 new candidates presenting large-scale wind variability, potentially originating from large-scale structures named corotating interaction regions (CIRs). In this second paper, we discuss an additional 39 stars observable from the southern hemisphere. For each star in our sample, we obtained 4-5 high-resolution spectra with a signal-to-noise ratio of {approx}100 and determined its variability level usingmore » the approach described in Paper I. In total, 10 new stars are found to show large-scale spectral variability of which 7 present CIR-type changes (WR 8, WR 44, WR55, WR 58, WR 61, WR 63, WR 100). Of the remaining stars, 20 were found to show small-amplitude changes and 9 were found to show no spectral variability as far as can be concluded from the data on hand. Also, we discuss the spectroscopic variability level of all single galactic WR stars that are brighter than v {approx} 12.5, and some WR stars with 12.5 < v {<=} 13.5, i.e., all the stars presented in our two papers and four more stars for which spectra have already been published in the literature. We find that 23/68 stars (33.8%) present large-scale variability, but only 12/54 stars ({approx}22.1%) are potentially of CIR type. Also, we find that 31/68 stars (45.6%) only show small-scale variability, most likely due to clumping in the wind. Finally, no spectral variability is detected based on the data on hand for 14/68 (20.6%) stars. Interestingly, the variability with the highest amplitude also has the widest mean velocity dispersion.« less

Size-Dependent Biexciton Quantum Yields and Carrier Dynamics of Quasi-Two-Dimensional Core/Shell Nanoplatelets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Xuedan; Diroll, Benjamin T.; Cho, Wooje

Quasi-two-dimensional nanoplatelets (NPLs) possess fundamentally different excitonic properties from zero-dimensional quantum dots. We study lateral size-dependent photon emission statistics and carrier dynamics of individual NPLs using second-order photon correlation (g( 2)(τ)) spectroscopy and photoluminescence (PL) intensity-dependent lifetime analysis. Room-temperature radiative lifetimes of NPLs can be derived from maximum PL intensity periods in PL time traces. It first decreases with NPL lateral size and then stays constant, deviating from the electric dipole approximation. Analysis of the PL time traces further reveals that the single exciton quantum yield in NPLs decreases with NPL lateral size and increases with protecting shell thickness, indicatingmore » the importance of surface passivation on NPL emission quality. Second-order photon correlation (g( 2)(τ)) studies of single NPLs show that the biexciton quantum yield is strongly dependent on the lateral size and single exciton quantum yield of the NPLs. In large NPLs with unity single exciton quantum yield, the corresponding biexciton quantum yield can reach unity. In conclusion, these findings reveal that by careful growth control and core–shell material engineering, NPLs can be of great potential for light amplification and integrated quantum photonic applications.« less

Size-Dependent Biexciton Quantum Yields and Carrier Dynamics of Quasi-Two-Dimensional Core/Shell Nanoplatelets

DOE PAGES

Ma, Xuedan; Diroll, Benjamin T.; Cho, Wooje; ...

2017-08-08

Quasi-two-dimensional nanoplatelets (NPLs) possess fundamentally different excitonic properties from zero-dimensional quantum dots. We study lateral size-dependent photon emission statistics and carrier dynamics of individual NPLs using second-order photon correlation (g( 2)(τ)) spectroscopy and photoluminescence (PL) intensity-dependent lifetime analysis. Room-temperature radiative lifetimes of NPLs can be derived from maximum PL intensity periods in PL time traces. It first decreases with NPL lateral size and then stays constant, deviating from the electric dipole approximation. Analysis of the PL time traces further reveals that the single exciton quantum yield in NPLs decreases with NPL lateral size and increases with protecting shell thickness, indicatingmore » the importance of surface passivation on NPL emission quality. Second-order photon correlation (g( 2)(τ)) studies of single NPLs show that the biexciton quantum yield is strongly dependent on the lateral size and single exciton quantum yield of the NPLs. In large NPLs with unity single exciton quantum yield, the corresponding biexciton quantum yield can reach unity. In conclusion, these findings reveal that by careful growth control and core–shell material engineering, NPLs can be of great potential for light amplification and integrated quantum photonic applications.« less

Spontaneous Fluctuations in Sensory Processing Predict Within-Subject Reaction Time Variability.

PubMed

Ribeiro, Maria J; Paiva, Joana S; Castelo-Branco, Miguel

2016-01-01

When engaged in a repetitive task our performance fluctuates from trial-to-trial. In particular, inter-trial reaction time variability has been the subject of considerable research. It has been claimed to be a strong biomarker of attention deficits, increases with frontal dysfunction, and predicts age-related cognitive decline. Thus, rather than being just a consequence of noise in the system, it appears to be under the control of a mechanism that breaks down under certain pathological conditions. Although the underlying mechanism is still an open question, consensual hypotheses are emerging regarding the neural correlates of reaction time inter-trial intra-individual variability. Sensory processing, in particular, has been shown to covary with reaction time, yet the spatio-temporal profile of the moment-to-moment variability in sensory processing is still poorly characterized. The goal of this study was to characterize the intra-individual variability in the time course of single-trial visual evoked potentials and its relationship with inter-trial reaction time variability. For this, we chose to take advantage of the high temporal resolution of the electroencephalogram (EEG) acquired while participants were engaged in a 2-choice reaction time task. We studied the link between single trial event-related potentials (ERPs) and reaction time using two different analyses: (1) time point by time point correlation analyses thereby identifying time windows of interest; and (2) correlation analyses between single trial measures of peak latency and amplitude and reaction time. To improve extraction of single trial ERP measures related with activation of the visual cortex, we used an independent component analysis (ICA) procedure. Our ERP analysis revealed a relationship between the N1 visual evoked potential and reaction time. The earliest time point presenting a significant correlation of its respective amplitude with reaction time occurred 175 ms after stimulus onset, just after the onset of the N1 peak. Interestingly, single trial N1 latency correlated significantly with reaction time, while N1 amplitude did not. In conclusion, our findings suggest that inter-trial variability in the timing of extrastriate visual processing contributes to reaction time variability.

Spontaneous Fluctuations in Sensory Processing Predict Within-Subject Reaction Time Variability

PubMed Central

Ribeiro, Maria J.; Paiva, Joana S.; Castelo-Branco, Miguel

2016-01-01

When engaged in a repetitive task our performance fluctuates from trial-to-trial. In particular, inter-trial reaction time variability has been the subject of considerable research. It has been claimed to be a strong biomarker of attention deficits, increases with frontal dysfunction, and predicts age-related cognitive decline. Thus, rather than being just a consequence of noise in the system, it appears to be under the control of a mechanism that breaks down under certain pathological conditions. Although the underlying mechanism is still an open question, consensual hypotheses are emerging regarding the neural correlates of reaction time inter-trial intra-individual variability. Sensory processing, in particular, has been shown to covary with reaction time, yet the spatio-temporal profile of the moment-to-moment variability in sensory processing is still poorly characterized. The goal of this study was to characterize the intra-individual variability in the time course of single-trial visual evoked potentials and its relationship with inter-trial reaction time variability. For this, we chose to take advantage of the high temporal resolution of the electroencephalogram (EEG) acquired while participants were engaged in a 2-choice reaction time task. We studied the link between single trial event-related potentials (ERPs) and reaction time using two different analyses: (1) time point by time point correlation analyses thereby identifying time windows of interest; and (2) correlation analyses between single trial measures of peak latency and amplitude and reaction time. To improve extraction of single trial ERP measures related with activation of the visual cortex, we used an independent component analysis (ICA) procedure. Our ERP analysis revealed a relationship between the N1 visual evoked potential and reaction time. The earliest time point presenting a significant correlation of its respective amplitude with reaction time occurred 175 ms after stimulus onset, just after the onset of the N1 peak. Interestingly, single trial N1 latency correlated significantly with reaction time, while N1 amplitude did not. In conclusion, our findings suggest that inter-trial variability in the timing of extrastriate visual processing contributes to reaction time variability. PMID:27242470

A Quantitative Comparison of the Behavior of Human Ventricular Cardiac Electrophysiology Models in Tissue

PubMed Central

Elshrif, Mohamed M.; Cherry, Elizabeth M.

2014-01-01

Numerical integration of mathematical models of heart cell electrophysiology provides an important computational tool for studying cardiac arrhythmias, but the abundance of available models complicates selecting an appropriate model. We study the behavior of two recently published models of human ventricular action potentials, the Grandi-Pasqualini-Bers (GPB) and the O'Hara-Virág-Varró-Rudy (OVVR) models, and compare the results with four previously published models and with available experimental and clinical data. We find the shapes and durations of action potentials and calcium transients differ between the GPB and OVVR models, as do the magnitudes and rate-dependent properties of transmembrane currents and the calcium transient. Differences also occur in the steady-state and S1–S2 action potential duration and conduction velocity restitution curves, including a maximum conduction velocity for the OVVR model roughly half that of the GPB model and well below clinical values. Between single cells and tissue, both models exhibit differences in properties, including maximum upstroke velocity, action potential amplitude, and minimum diastolic interval. Compared to experimental data, action potential durations for the GPB and OVVR models agree fairly well (although OVVR epicardial action potentials are shorter), but maximum slopes of steady-state restitution curves are smaller. Although studies show alternans in normal hearts, it occurs only in the OVVR model, and only for a narrow range of cycle lengths. We find initiated spiral waves do not progress to sustained breakup for either model. The dominant spiral wave period of the GPB model falls within clinically relevant values for ventricular tachycardia (VT), but for the OVVR model, the dominant period is longer than periods associated with VT. Our results should facilitate choosing a model to match properties of interest in human cardiac tissue and to replicate arrhythmia behavior more closely. Furthermore, by indicating areas where existing models disagree, our findings suggest avenues for further experimental work. PMID:24416228

Bayesian view of single-qubit clocks, and an energy versus accuracy tradeoff

NASA Astrophysics Data System (ADS)

Gopalkrishnan, Manoj; Kandula, Varshith; Sriram, Praveen; Deshpande, Abhishek; Muralidharan, Bhaskaran

2017-09-01

We bring a Bayesian approach to the analysis of clocks. Using exponential distributions as priors for clocks, we analyze how well one can keep time with a single qubit freely precessing under a magnetic field. We find that, at least with a single qubit, quantum mechanics does not allow exact timekeeping, in contrast to classical mechanics, which does. We find the design of the single-qubit clock that leads to maximum accuracy. Further, we find an energy versus accuracy tradeoff—the energy cost is at least kBT times the improvement in accuracy as measured by the entropy reduction in going from the prior distribution to the posterior distribution. We propose a physical realization of the single-qubit clock using charge transport across a capacitively coupled quantum dot.

Low-frequency rTMS inhibitory effects in the primary motor cortex: Insights from TMS-evoked potentials.

PubMed

Casula, Elias P; Tarantino, Vincenza; Basso, Demis; Arcara, Giorgio; Marino, Giuliana; Toffolo, Gianna Maria; Rothwell, John C; Bisiacchi, Patrizia S

2014-09-01

The neuromodulatory effects of repetitive transcranial magnetic stimulation (rTMS) have been mostly investigated by peripheral motor-evoked potentials (MEPs). New TMS-compatible EEG systems allow a direct investigation of the stimulation effects through the analysis of TMS-evoked potentials (TEPs). We investigated the effects of 1-Hz rTMS over the primary motor cortex (M1) of 15 healthy volunteers on TEP evoked by single pulse TMS over the same area. A second experiment in which rTMS was delivered over the primary visual cortex (V1) of 15 healthy volunteers was conducted to examine the spatial specificity of the effects. Single-pulse TMS evoked four main components: P30, N45, P60 and N100. M1-rTMS resulted in a significant decrease of MEP amplitude and in a significant increase of P60 and N100 amplitude. There was no effect after V1-rTMS. 1-Hz rTMS appears to increase the amount of inhibition following a TMS pulse, as demonstrated by the higher N100 and P60, which are thought to originate from GABAb-mediated inhibitory post-synaptic potentials. Our results confirm the reliability of the TMS-evoked N100 as a marker of cortical inhibition and provide insight into the neuromodulatory effects of 1-Hz rTMS. The present finding could be of relevance for therapeutic and diagnostic purposes. Copyright © 2014 Elsevier Inc. All rights reserved.

Communicating Experimental Findings in Single Case Design Research: How to Use Celeration Values and Celeration Multipliers to Measure Direction, Magnitude, and Change of Slope

ERIC Educational Resources Information Center

Datchuk, Shawn M.; Kubina, Richard M., Jr.

2011-01-01

The accumulation of scientific knowledge greatly depends upon the critical review of experimental findings by ones peers. In single case design research, experimenters present findings with graphical displays of data and narrative description of a visual analysis. To aid in efficient and accurate description of experimental findings, the research…

Optical potential from first principles

DOE PAGES

Rotureau, J.; Danielewicz, P.; Hagen, G.; ...

2017-02-15

Here, we develop a method to construct a microscopic optical potential from chiral interactions for nucleon-nucleus scattering. The optical potential is constructed by combining the Green’s function approach with the coupled-cluster method. To deal with the poles of the Green’s function along the real energy axis we employ a Berggren basis in the complex energy plane combined with the Lanczos method. Using this approach, we perform a proof-of-principle calculation of the optical potential for the elastic neutron scattering on 16O. For the computation of the ground-state of 16O, we use the coupled-cluster method in the singles-and-doubles approximation, while for themore » A ±1 nuclei we use particle-attached/removed equation-of-motion method truncated at two-particle-one-hole and one-particle-two-hole excitations, respectively. We verify the convergence of the optical potential and scattering phase shifts with respect to the model-space size and the number of discretized complex continuum states. We also investigate the absorptive component of the optical potential (which reflects the opening of inelastic channels) by computing its imaginary volume integral and find an almost negligible absorptive component at low-energies. To shed light on this result, we computed excited states of 16O using equation-of-motion coupled-cluster method with singles-and- doubles excitations and we found no low-lying excited states below 10 MeV. Furthermore, most excited states have a dominant two-particle-two-hole component, making higher-order particle-hole excitations necessary to achieve a precise description of these core-excited states. We conclude that the reduced absorption at low-energies can be attributed to the lack of correlations coming from the low-order cluster truncation in the employed coupled-cluster method.« less

Enrichment and identification of polycyclic aromatic compound-degrading bacteria enriched from sediment samples.

PubMed

Long, Rachel M; Lappin-Scott, Hilary M; Stevens, Jamie R

2009-07-01

The degradation of polycyclic aromatic compounds (PACs) has been widely studied. Knowledge of the degradation of PACs by microbial populations can be utilized in the remediation of contaminated sites. To isolate and identify PAC-degrading bacteria for potential use in future bioremediation programmes, we established a series of PAC enrichments under the same experimental conditions from a single sediment sample taken from a highly polluted estuarine site. Enrichment cultures were established using the pollutants: anthracene, phenanthrene and dibenzothiophene as a sole carbon source. The shift in microbial community structure on each of these carbon sources was monitored by analysis of a time series of samples from each culture using 16S rRNA polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Significantly, our findings demonstrate that shifts in the constituent species within each degradative community are directly attributable to enrichment with different PACs. Subsequently, we characterized the microorganisms comprising the degradative communities within each enrichment using 16S rRNA sequence data. Our findings demonstrate that the ability to degrade PACs is present in five divisions of the Proteobacteria and Actinobacteria. By determining the precise identity of the PAC-degrading bacterial species isolated from a single sediment sample, and by comparing our findings with previously published research, we demonstrate how bacteria with similar PAC degrading capabilities and 16S rRNA signatures are found in similarly polluted environments in geographically very distant locations, e.g., China, Italy, Japan and Hawaii. Such a finding suggests that geographical barriers do not limit the distribution of key PAC-degrading bacteria; this finding is in accordance with the Baas-Becking hypothesis "everything is everywhere; the environment selects" and may have significant consequences for the global distribution of PAC-degrading bacteria and their use in bioremediation.

Crossovers are associated with mutation and biased gene conversion at recombination hotspots.

PubMed

Arbeithuber, Barbara; Betancourt, Andrea J; Ebner, Thomas; Tiemann-Boege, Irene

2015-02-17

Meiosis is a potentially important source of germline mutations, as sites of meiotic recombination experience recurrent double-strand breaks (DSBs). However, evidence for a local mutagenic effect of recombination from population sequence data has been equivocal, likely because mutation is only one of several forces shaping sequence variation. By sequencing large numbers of single crossover molecules obtained from human sperm for two recombination hotspots, we find direct evidence that recombination is mutagenic: Crossovers carry more de novo mutations than nonrecombinant DNA molecules analyzed for the same donors and hotspots. The observed mutations were primarily CG to TA transitions, with a higher frequency of transitions at CpG than non-CpGs sites. This enrichment of mutations at CpG sites at hotspots could predominate in methylated regions involving frequent single-stranded DNA processing as part of DSB repair. In addition, our data set provides evidence that GC alleles are preferentially transmitted during crossing over, opposing mutation, and shows that GC-biased gene conversion (gBGC) predominates over mutation in the sequence evolution of hotspots. These findings are consistent with the idea that gBGC could be an adaptation to counteract the mutational load of recombination.

Crossovers are associated with mutation and biased gene conversion at recombination hotspots

PubMed Central

Arbeithuber, Barbara; Betancourt, Andrea J.; Ebner, Thomas; Tiemann-Boege, Irene

2015-01-01

Meiosis is a potentially important source of germline mutations, as sites of meiotic recombination experience recurrent double-strand breaks (DSBs). However, evidence for a local mutagenic effect of recombination from population sequence data has been equivocal, likely because mutation is only one of several forces shaping sequence variation. By sequencing large numbers of single crossover molecules obtained from human sperm for two recombination hotspots, we find direct evidence that recombination is mutagenic: Crossovers carry more de novo mutations than nonrecombinant DNA molecules analyzed for the same donors and hotspots. The observed mutations were primarily CG to TA transitions, with a higher frequency of transitions at CpG than non-CpGs sites. This enrichment of mutations at CpG sites at hotspots could predominate in methylated regions involving frequent single-stranded DNA processing as part of DSB repair. In addition, our data set provides evidence that GC alleles are preferentially transmitted during crossing over, opposing mutation, and shows that GC-biased gene conversion (gBGC) predominates over mutation in the sequence evolution of hotspots. These findings are consistent with the idea that gBGC could be an adaptation to counteract the mutational load of recombination. PMID:25646453

Ensemble stacking mitigates biases in inference of synaptic connectivity.

PubMed

Chambers, Brendan; Levy, Maayan; Dechery, Joseph B; MacLean, Jason N

2018-01-01

A promising alternative to directly measuring the anatomical connections in a neuronal population is inferring the connections from the activity. We employ simulated spiking neuronal networks to compare and contrast commonly used inference methods that identify likely excitatory synaptic connections using statistical regularities in spike timing. We find that simple adjustments to standard algorithms improve inference accuracy: A signing procedure improves the power of unsigned mutual-information-based approaches and a correction that accounts for differences in mean and variance of background timing relationships, such as those expected to be induced by heterogeneous firing rates, increases the sensitivity of frequency-based methods. We also find that different inference methods reveal distinct subsets of the synaptic network and each method exhibits different biases in the accurate detection of reciprocity and local clustering. To correct for errors and biases specific to single inference algorithms, we combine methods into an ensemble. Ensemble predictions, generated as a linear combination of multiple inference algorithms, are more sensitive than the best individual measures alone, and are more faithful to ground-truth statistics of connectivity, mitigating biases specific to single inference methods. These weightings generalize across simulated datasets, emphasizing the potential for the broad utility of ensemble-based approaches.

Will-Nordtvedt PPN formalism applied to renormalization group extensions of general relativity

NASA Astrophysics Data System (ADS)

Toniato, Júnior D.; Rodrigues, Davi C.; de Almeida, Álefe O. F.; Bertini, Nicolas

2017-09-01

We apply the full Will-Nordtvedt version of the parametrized post-Newtonian (PPN) formalism to a class of general relativity extensions that are based on nontrivial renormalization group (RG) effects at large scales. We focus on a class of models in which the gravitational coupling constant G is correlated with the Newtonian potential. A previous PPN analysis considered a specific realization of the RG effects, and only within the Eddington-Robertson-Schiff version of the PPN formalism, which is a less complete and robust PPN formulation. Here we find stronger, more precise bounds, and with less assumptions. We also consider the external potential effect (EPE), which is an effect that is intrinsic to this framework and depends on the system environment (it has some qualitative similarities to the screening mechanisms of modified gravity theories). We find a single particular RG realization that is not affected by the EPE. Some physical systems have been pointed out as candidates for measuring the possible RG effects in gravity at large scales; for any of them the Solar System bounds need to be considered.

Non-provocative diagnostics of photosensitivity using visual evoked potentials.

PubMed

Vermeulen, Joost; Kalitzin, Stiliyan; Parra, Jaime; Dekker, Erwin; Vossepoel, Albert; da Silva, Fernando Lopes

2008-04-01

Photosensitive epilepsy (PSE) is the most common form of reflex epilepsy. Usually, to find out whether a patient is sensitive, he/she is stimulated visually with, e.g. a stroboscopic light stimulus at variable frequency and intensity until a photo paroxysmal response (PPR) occurs. The research described in this work aims to find whether photosensitivity can be detected without provoking a PPR. Twenty-two subjects, 15 with known photosensitivity, were stimulated with visual stimuli that did not provoke a PPR. Using an "evoked response representation", 18 features were analytically derived from EEG signals. Single- and multi-feature classification paradigms were applied to extract those features that separate best subjects with PSE from controls. Two variables in the "evoked response representation", a frequency term and a goodness of fit term to a particular template, appeared to be best suited to make a prediction about the photosensitivity of a subject. Evoked responses appear to carry information about potential PSE. This result can be useful for screening patients for photosensitivity and it may also help to assess in a quantitative way the effectiveness of medical therapy.

Virtual screening and pharmacophore design for a novel theoretical inhibitor of macrophage stimulating factor as a metastatic agent.

PubMed

Torktaz, Ibrahim; Mohamadhashem, Faezeh; Esmaeili, Abolghasem; Behjati, Mohaddeseh; Sharifzadeh, Sara

2013-01-01

Metastasis is a crucial aspect of cancer. Macrophage stimulating protein (MSP) is a single chain protein and can be cleaved by serum proteases. MSP has several roles in metastasis. In this in silico study, MSP as a metastatic agent was considered as a drug target. Crystallographic structure of MSP was retrieved from protein data bank. To find a chemical inhibitor of MSP, a library of KEGG compounds was screened and 1000 shape complemented ligands were retrieved with FindSite algorithm. Molegro Virtual Docker (MVD) software was used for docking simulation of shape complemented ligands against MSP. Moldock score was used as scoring function for virtual screening and potential inhibitors with more negative binding energy were obtained. PLANS scoring function was used for revaluation of virtual screening data. The top found chemical had binding affinity of -183.55 based on MolDock score and equal to -66.733 PLANTs score to MSP structure. Based on pharmacophore model of potential inhibitor, this study suggests that the chemical which was found in this research and its derivate can be used for subsequent laboratory studies.

Evaluating and interpreting cross-taxon congruence: Potential pitfalls and solutions

NASA Astrophysics Data System (ADS)

Gioria, Margherita; Bacaro, Giovanni; Feehan, John

2011-05-01

Characterizing the relationship between different taxonomic groups is critical to identify potential surrogates for biodiversity. Previous studies have shown that cross-taxa relationships are generally weak and/or inconsistent. The difficulties in finding predictive patterns have often been attributed to the spatial and temporal scales of these studies and on the differences in the measure used to evaluate such relationships (species richness versus composition). However, the choice of the analytical approach used to evaluate cross-taxon congruence inevitably represents a major source of variation. Here, we described the use of a range of methods that can be used to comprehensively assess cross-taxa relationships. To do so, we used data for two taxonomic groups, wetland plants and water beetles, collected from 54 farmland ponds in Ireland. Specifically, we used the Pearson correlation and rarefaction curves to analyse patterns in species richness, while Mantel tests, Procrustes analysis, and co-correspondence analysis were used to evaluate congruence in species composition. We compared the results of these analyses and we described some of the potential pitfalls associated with the use of each of these statistical approaches. Cross-taxon congruence was moderate to strong, depending on the choice of the analytical approach, on the nature of the response variable, and on local and environmental conditions. Our findings indicate that multiple approaches and measures of community structure are required for a comprehensive assessment of cross-taxa relationships. In particular, we showed that selection of surrogate taxa in conservation planning should not be based on a single statistic expressing the degree of correlation in species richness or composition. Potential solutions to the analytical issues associated with the assessment of cross-taxon congruence are provided and the implications of our findings in the selection of surrogates for biodiversity are discussed.

Electron spin relaxation in a transition-metal dichalcogenide quantum dot

NASA Astrophysics Data System (ADS)

Pearce, Alexander J.; Burkard, Guido

2017-06-01

We study the relaxation of a single electron spin in a circular quantum dot in a transition-metal dichalcogenide monolayer defined by electrostatic gating. Transition-metal dichalcogenides provide an interesting and promising arena for quantum dot nano-structures due to the combination of a band gap, spin-valley physics and strong spin-orbit coupling. First we will discuss which bound state solutions in different B-field regimes can be used as the basis for qubits states. We find that at low B-fields combined spin-valley Kramers qubits to be suitable, while at large magnetic fields pure spin or valley qubits can be envisioned. Then we present a discussion of the relaxation of a single electron spin mediated by electron-phonon interaction via various different relaxation channels. In the low B-field regime we consider the spin-valley Kramers qubits and include impurity mediated valley mixing which will arise in disordered quantum dots. Rashba spin-orbit admixture mechanisms allow for relaxation by in-plane phonons either via the deformation potential or by piezoelectric coupling, additionally direct spin-phonon mechanisms involving out-of-plane phonons give rise to relaxation. We find that the relaxation rates scale as \\propto B 6 for both in-plane phonons coupling via deformation potential and the piezoelectric effect, while relaxation due to the direct spin-phonon coupling scales independant to B-field to lowest order but depends strongly on device mechanical tension. We will also discuss the relaxation mechanisms for pure spin or valley qubits formed in the large B-field regime.

Repeated, but Not Acute, Stress Suppresses Inflammatory Plasma Extravasation

NASA Astrophysics Data System (ADS)

Strausbaugh, Holly J.; Dallman, Mary F.; Levine, Jon D.

1999-12-01

Clinical findings suggest that inflammatory disease symptoms are aggravated by ongoing, repeated stress, but not by acute stress. We hypothesized that, compared with single acute stressors, chronic repeated stress may engage different physiological mechanisms that exert qualitatively different effects on the inflammatory response. Because inhibition of plasma extravasation, a critical component of the inflammatory response, has been associated with increased disease severity in experimental arthritis, we tested for a potential repeated stress-induced inhibition of plasma extravasation. Repeated, but not single, exposures to restraint stress produced a profound inhibition of bradykinin-induced synovial plasma extravasation in the rat. Experiments examining the mechanism of inhibition showed that the effect of repeated stress was blocked by adrenalectomy, but not by adrenal medullae denervation, suggesting that the adrenal cortex mediates this effect. Consistent with known effects of stress and with mediation by the adrenal cortex, restraint stress evoked repeated transient elevations of plasma corticosterone levels. This elevated corticosterone was necessary and sufficient to produce inhibition of plasma extravasation because the stress-induced inhibition was blocked by preventing corticosterone synthesis and, conversely, induction of repeated transient elevations in plasma corticosterone levels mimicked the effects of repeated stress. These data suggest that repetition of a mild stressor can induce changes in the physiological state of the animal that enable a previously innocuous stressor to inhibit the inflammatory response. These findings provide a potential explanation for the clinical association between repeated stress and aggravation of inflammatory disease symptoms and provide a model for study of the biological mechanisms underlying the stress-induced aggravation of chronic inflammatory diseases.

Genome-wide detection of intervals of genetic heterogeneity associated with complex traits

PubMed Central

Llinares-López, Felipe; Grimm, Dominik G.; Bodenham, Dean A.; Gieraths, Udo; Sugiyama, Mahito; Rowan, Beth; Borgwardt, Karsten

2015-01-01

Motivation: Genetic heterogeneity, the fact that several sequence variants give rise to the same phenotype, is a phenomenon that is of the utmost interest in the analysis of complex phenotypes. Current approaches for finding regions in the genome that exhibit genetic heterogeneity suffer from at least one of two shortcomings: (i) they require the definition of an exact interval in the genome that is to be tested for genetic heterogeneity, potentially missing intervals of high relevance, or (ii) they suffer from an enormous multiple hypothesis testing problem due to the large number of potential candidate intervals being tested, which results in either many false positives or a lack of power to detect true intervals. Results: Here, we present an approach that overcomes both problems: it allows one to automatically find all contiguous sequences of single nucleotide polymorphisms in the genome that are jointly associated with the phenotype. It also solves both the inherent computational efficiency problem and the statistical problem of multiple hypothesis testing, which are both caused by the huge number of candidate intervals. We demonstrate on Arabidopsis thaliana genome-wide association study data that our approach can discover regions that exhibit genetic heterogeneity and would be missed by single-locus mapping. Conclusions: Our novel approach can contribute to the genome-wide discovery of intervals that are involved in the genetic heterogeneity underlying complex phenotypes. Availability and implementation: The code can be obtained at: http://www.bsse.ethz.ch/mlcb/research/bioinformatics-and-computational-biology/sis.html. Contact: felipe.llinares@bsse.ethz.ch Supplementary information: Supplementary data are available at Bioinformatics online. PMID:26072488

Role of mitogen activated protein kinases in skin tumorigenicity of Patulin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saxena, Neha; Ansari, Kausar M.; Kumar, Rahul

2011-12-15

WHO has highlighted the need to evaluate dermal toxicity of mycotoxins including Patulin (PAT), detected in several fruits. In this study the skin carcinogenic potential of topically applied PAT was investigated. Single topical application of PAT (400 nmol) showed enhanced cell proliferation ({approx} 2 fold), along with increased generation of ROS and activation of ERK, p38 and JNK MAPKs, in mouse skin. PAT exposure also showed activation of downstream target proteins, c-fos, c-Jun and NF-{kappa}B transcription factors. Further, single topical application of PAT (400 nmol) followed by twice weekly application of TPA resulted in tumor formation after 14 weeks, indicatingmore » the tumor initiating activity of PAT. However no tumors were observed when PAT was used either as a complete carcinogen (80 nmol) or as a tumor promoter (20 nmol and 40 nmol) for 25 weeks. Histopathological findings of tumors found in PAT/TPA treated mice showed that these tumors were of squamous cell carcinoma type and similar to those found in the positive control group (DMBA/TPA) along with significant increase of lipid peroxidation and decrease in free sulfydryls, catalase, superoxide dismutase and glutathione reductase activities. The results suggest the possible role of free radicals in PAT mediated dermal tumorigenicity involving MAPKs. -- Highlights: Black-Right-Pointing-Pointer Single topical application of Patulin showed enhanced cell proliferation. Black-Right-Pointing-Pointer Patulin activate MAPKs, c-fos, c-Jun and NF-{kappa}B transcription factors. Black-Right-Pointing-Pointer Patulin showed skin tumor initiating potential. Black-Right-Pointing-Pointer We could not detect skin tumor promoting potential of Patulin at the tested dose. Black-Right-Pointing-Pointer However prolonged exposure of Patulin at a higher dose may promote tumor.« less

Molecular Dynamics in Physiological Solutions: Force Fields, Alkali Metal Ions, and Ionic Strength.

PubMed

Zhang, Chao; Raugei, Simone; Eisenberg, Bob; Carloni, Paolo

2010-07-13

The monovalent ions Na(+) and K(+) and Cl(-) are present in any living organism. The fundamental thermodynamic properties of solutions containing such ions is given as the excess (electro-)chemical potential differences of single ions at finite ionic strength. This quantity is key for many biological processes, including ion permeation in membrane ion channels and DNA-protein interaction. It is given by a chemical contribution, related to the ion activity, and an electric contribution, related to the Galvani potential of the water/air interface. Here we investigate molecular dynamics based predictions of these quantities by using a variety of ion/water force fields commonly used in biological simulation, namely the AMBER (the newly developed), CHARMM, OPLS, Dang95 with TIP3P, and SPC/E water. Comparison with experiment is made with the corresponding values for salts, for which data are available. The calculations based on the newly developed AMBER force field with TIP3P water agrees well with experiment for both KCl and NaCl electrolytes in water solutions, as previously reported. The simulations based on the CHARMM-TIP3P and Dang95-SPC/E force fields agree well for the KCl and NaCl solutions, respectively. The other models are not as accurate. Single cations excess (electro-)chemical potential differences turn out to be similar for all the force fields considered here. In the case of KCl, the calculated electric contribution is consistent with higher level calculations. Instead, such agreement is not found with NaCl. Finally, we found that the calculated activities for single Cl(-) ions turn out to depend clearly on the type of counterion used, with all the force fields investigated. The implications of these findings for biomolecular systems are discussed.

Broken symmetry phase transition in solid p-H 2, o-D 2 and HD: crystal field effects

NASA Astrophysics Data System (ADS)

Freiman, Yu. A.; Hemley, R. J.; Jezowski, A.; Tretyak, S. M.

1999-04-01

We report the effect of the crystal field (CF) on the broken symmetry phase transition (BSP) in solid parahydrogen, orthodeuterium, and hydrogen deuteride. The CF was calculated taking into account a distortion from the ideal HCP structure. We find that, in addition to the molecular field generated by the coupling terms in the intermolecular potential, the Hamiltonian of the system contains a crystal-field term, originating from single-molecular terms in the intermolecular potential. Ignoring the CF is the main cause of the systematic underestimation of the transition pressure, characteristic of published theories of the BSP transition. The distortion of the lattice that gives rise to the negative CF in response to the applied pressure is in accord with the general Le Chatelier-Braun principle.

Safinamide (Newron Pharmaceuticals).

PubMed

Chazot, P L

2001-06-01

Safinamide (formerly PNU-151774E), a sodium and calcium channel modulator that also inhibits monoamine oxidase B (MAOB), is under development by Newron Pharmaceuticals for the potential treatment of epilepsy, Parkinson's disease (PD), pain and stroke [345222], [348351]. Phase I trials for epilepsy and PD have been completed, and dose-finding studies for both indications had commenced in March 2001 [401685]. The compound was previously developed by Pharmacia & Upjohn (P&U) for the potential treatment of epilepsy, an indication for which it initially reached phase I trials [294891], [345007]. Newron acquired the rights to safinamide from P&U at the end of 1998. Results from two phase I trials of the compound (single ascending dose and steady state at three doses), completed in March 2000, demonstrated that the drug is well tolerated with good bioavailability and linear pharmacokinetics [359652].

Applications of health information exchange information to public health practice.

PubMed

Kierkegaard, Patrick; Kaushal, Rainu; Vest, Joshua R

2014-01-01

Increased information availability, timeliness, and comprehensiveness through health information exchange (HIE) can support public health practice. The potential benefits to disease monitoring, disaster response, and other public health activities served as an important justification for the US' investments in HIE. After several years of HIE implementation and funding, we sought to determine if any of the anticipated benefits of exchange participation were accruing to state and local public health practitioners participating in five different exchanges. Using qualitative interviews and template analyses, we identified public health efforts and activities that were improved by participation in HIE. HIE supported public health activities consistent with expectations in the literature. However, no single department realized all the potential benefits of HIE identified. These findings suggest ways to improve HIE usage in public health.

Applications of Health Information Exchange Information to Public Health Practice

PubMed Central

Kierkegaard, Patrick; Kaushal, Rainu; Vest, Joshua R

2014-01-01

Increased information availability, timeliness, and comprehensiveness through health information exchange (HIE) can support public health practice. The potential benefits to disease monitoring, disaster response, and other public health activities served as an important justification for the US’ investments in HIE. After several years of HIE implementation and funding, we sought to determine if any of the anticipated benefits of exchange participation were accruing to state and local public health practitioners participating in five different exchanges. Using qualitative interviews and template analyses, we identified public health efforts and activities that were improved by participation in HIE. HIE supported public health activities consistent with expectations in the literature. However, no single department realized all the potential benefits of HIE identified. These findings suggest ways to improve HIE usage in public health. PMID:25954386

KCNE Regulation of K+ Channel Trafficking – a Sisyphean Task?

PubMed Central

Kanda, Vikram A.; Abbott, Geoffrey W.

2012-01-01

Voltage-gated potassium (Kv) channels shape the action potentials of excitable cells and regulate membrane potential and ion homeostasis in excitable and non-excitable cells. With 40 known members in the human genome and a variety of homomeric and heteromeric pore-forming α subunit interactions, post-translational modifications, cellular locations, and expression patterns, the functional repertoire of the Kv α subunit family is monumental. This versatility is amplified by a host of interacting proteins, including the single membrane-spanning KCNE ancillary subunits. Here, examining both the secretory and the endocytic pathways, we review recent findings illustrating the surprising virtuosity of the KCNE proteins in orchestrating not just the function, but also the composition, diaspora and retrieval of channels formed by their Kv α subunit partners. PMID:22754540

Many-body delocalization with random vector potentials

NASA Astrophysics Data System (ADS)

Cheng, Chen; Mondaini, Rubem

2016-11-01

We study the ergodic properties of excited states in a model of interacting fermions in quasi-one-dimensional chains subjected to a random vector potential. In the noninteracting limit, we show that arbitrarily small values of this complex off-diagonal disorder trigger localization for the whole spectrum; the divergence of the localization length in the single-particle basis is characterized by a critical exponent ν which depends on the energy density being investigated. When short-range interactions are included, the localization is lost, and the system is ergodic regardless of the magnitude of disorder in finite chains. Our numerical results suggest a delocalization scheme for arbitrary small values of interactions. This finding indicates that the standard scenario of the many-body localization cannot be obtained in a model with random gauge fields.

Molecular dynamics study of the melting of a supported 887-atom Pd decahedron.

PubMed

Schebarchov, D; Hendy, S C; Polak, W

2009-04-08

We employ classical molecular dynamics simulations to investigate the melting behaviour of a decahedral Pd(887) cluster on a single layer of graphite (graphene). The interaction between Pd atoms is modelled with an embedded-atom potential, while the adhesion of Pd atoms to the substrate is approximated with a Lennard-Jones potential. We find that the decahedral structure persists at temperatures close to the melting point, but that just below the melting transition, the cluster accommodates to the substrate by means of complete melting and then recrystallization into an fcc structure. These structural changes are in qualitative agreement with recently proposed models, and they verify the existence of an energy barrier preventing softly deposited clusters from 'wetting' the substrate at temperatures below the melting point.

Imaging Action Potential in Single Mammalian Neurons by Tracking the Accompanying Sub-Nanometer Mechanical Motion.

PubMed

Yang, Yunze; Liu, Xian-Wei; Wang, Hui; Yu, Hui; Guan, Yan; Wang, Shaopeng; Tao, Nongjian

2018-03-28

Action potentials in neurons have been studied traditionally by intracellular electrophysiological recordings and more recently by the fluorescence detection methods. Here we describe a label-free optical imaging method that can measure mechanical motion in single cells with a sub-nanometer detection limit. Using the method, we have observed sub-nanometer mechanical motion accompanying the action potential in single mammalian neurons by averaging the repeated action potential spikes. The shape and width of the transient displacement are similar to those of the electrically recorded action potential, but the amplitude varies from neuron to neuron, and from one region of a neuron to another, ranging from 0.2-0.4 nm. The work indicates that action potentials may be studied noninvasively in single mammalian neurons by label-free imaging of the accompanying sub-nanometer mechanical motion.

Changes in the potential multiple cropping system in response to climate change in China from 1960-2010.

PubMed

Liu, Luo; Xu, Xinliang; Zhuang, Dafang; Chen, Xi; Li, Shuang

2013-01-01

The multiple cropping practice is essential to agriculture because it has been shown to significantly increase the grain yield and promote agricultural economic development. In this study, potential multiple cropping systems in China are calculated based on meteorological observation data by using the Agricultural Ecology Zone (AEZ) model. Following this, the changes in the potential cropping systems in response to climate change between the 1960s and the 2010s were subsequently analyzed. The results indicate that the changes of potential multiple cropping systems show tremendous heterogeneity in respect to the spatial pattern in China. A key finding is that the magnitude of change of the potential cropping systems showed a pattern of increase both from northern China to southern China and from western China to eastern China. Furthermore, the area found to be suitable only for single cropping decreased, while the area suitable for triple cropping increased significantly from the 1960s to the 2000s. During the studied period, the potential multiple cropping index (PMCI) gap between rain-fed and irrigated scenarios increased from 18% to 24%, which indicated noticeable growth of water supply limitations under the rain-fed scenario. The most significant finding of this research was that from the 1960s to the 2000s climate change had led to a significant increase of PMCI by 13% under irrigated scenario and 7% under rain-fed scenario across the whole of China. Furthermore, the growth of the annual mean temperature is identified as the main reason underlying the increase of PMCI. It has also been noticed that across China the changes of potential multiple cropping systems under climate change were different from region to region.

Absence or presence? Complexities in the donor narratives of single mothers using sperm donation

PubMed Central

Zadeh, S.; Freeman, T.; Golombok, S.

2016-01-01

STUDY QUESTION How do single mothers who have conceived a child via anonymous or identity-release sperm donation represent the donor? SUMMARY ANSWER While the majority of mothers described their anonymous and identity-release donors as symbolically significant to their families, others were more likely to emphasize that their lack of information limited their thoughts about him. WHAT IS KNOWN ALREADY There is limited understanding of the factors that impact upon how single mothers represent the donor, and whether or not they are determined by specific donor programmes (anonymous or identity-release). STUDY DESIGN, SIZE, DURATION Qualitative interviews were conducted with 46 women who had treatment at a UK licensed fertility clinic during the years 2003–2009. Twenty mothers (43%) had used an anonymous donor, and 26 (57%) had used an identity-release donor. PARTICIPANTS/MATERIALS, SETTING, METHODS Among the 46 mothers interviewed, all had at least one child conceived via donor insemination who was between the ages of 4 and 9 years. Mothers were heterosexual and were currently without a live-in and/or long-term partner. Interview data were analysed qualitatively according to the principles of thematic analysis. MAIN RESULTS AND THE ROLE OF CHANCE Findings indicated marked diversity in single mothers' representations of the donor. Most (n = 27) mothers talked about the donor as symbolically significant to family life and were likely to describe the donor as (i) a gift-giver, (ii) a gene-giver and (iii) a potential partner. Others (n = 16) talked about the donor as (i) unknown, (ii) part of a process and (iii) out of sight and out of mind. There were mothers with anonymous and identity-release donors in each group. Several mothers explained that their feelings about the donor had changed over time. LIMITATIONS, REASONS FOR CAUTION All mothers conceived at a licensed fertility clinic in the UK. Findings are limited to individuals willing and able to take part in research on donor conception. WIDER IMPLICATIONS OF THE FINDINGS The study offers greater insight into the factors influencing the donor narratives produced in single-mother families. It has implications for the counselling and treatment of single women seeking fertility treatment with donor gametes in both anonymous and identity-release programmes. Given that the number of clinics offering identity-release programmes worldwide seems to be increasing, the finding that single women may have varying preferences with regard to donor type, and varying interest levels with regard to donor information, is important. It is recommended that clinicians and other fertility clinic staff guard against making assumptions about such preferences and any thoughts and feelings about the donor or donor information on the basis of marital status. STUDY FUNDING/COMPETING INTEREST(S) This study was funded by the Wellcome Trust [097857/Z/11/Z]. The authors have no conflicts of interest to declare. PMID:26545622

Test for Non-Synergistic Interactions in Phytomedicine, Just as You Do for Isolated Compounds

PubMed Central

Patel, Areeba; Mondal, Amit

2018-01-01

Phytomedicine has often been used as “alternative therapy,” which in our opinion is unfortunate as it prevents its main actions being systematically studied, side effects explored, and toxicity tested, like all single-compound-based medicine. Our group is interested in finding which traditional or modern phytomedicines actually work and which are simply “working” through placebo, standardizing phytomedicine preparations, studying their toxicity, and finding active molecules in plants for modification and chemical synthesis as single compounds. Although fluctuation in efficacy due to seasonal and geographical variations in phytomedicine remains a concern, if well regulated, even plant extracts without isolated compounds can serve medicinal needs where single-compound options are currently not great. A potential concern with such phytomedicine is frequent mixing of ingredients in commercial formulations without test of synergism. Our study on the use of 2 traditional plants for Parkinson disease shows a clear lack of synergism, and to study nonsynergism better, we developed a new visualization approach. In this commentary, using our study on Parkinson disease as an example, we make a case for better evaluation of phytomedicines, especially testing for synergistic interactions. We also critique our own exploration of oxidative stress and few behavioral parameters alone to lay grounds for what we and hopefully others can do in future to extract more information from their phytomedicine studies. We hope this commentary acts as a good warning for anyone mixing 2 phytomedicines without testing. PMID:29706766

Differences in conformational stability of the two alpha domains of the disease-associated and non-disease-associated subtypes of HLA-B27.

PubMed

Rana, Manish Kumar; Luthra-Guptasarma, Manni

2017-01-01

The MHC Class I molecule, HLA-B27, is strongly linked with development of the inflammatory arthritic disease, ankylosing spondylitis (AS); whereas the B*2705 subtype shows strong association, B*2709 is not associated with disease, even though the two subtypes differ in only a single residue at position 116. Currently, attention is focused on the misfolding propensities of these two subtypes, including studies of disulfide-linked dimers and non-covalently formed high molecular weight (HMW) aggregates. Using mutants retaining only a single cysteine at positions C67 or C164, and using a cysteine-reactive, environment-sensitive, fluorescence probe (acrylodan), we find that within the same overall population of identical single-cysteine HLA-B27 molecules, there exist sub-populations which (a) possess free cysteines which react with acrylodan, (b) form disulfide-linked dimers, and (c) form HMW aggregates. Further, using acrylodan fluorescence, we find (d) that the α1 and α2 domains unfold independently of each other in HMW aggregates, (e) that these two domains of B*2709 are less stable to chemical and thermal denaturation than the corresponding domains of B*2705, suggesting easier clearance of misfolded molecules in the former, and (f) C67 is much more exposed in B*2705 than in B*2709, which could potentially explain how B*2705 more easily forms C67-mediated disulfide-bonded dimers. Copyright © 2016. Published by Elsevier B.V.

Test for Non-Synergistic Interactions in Phytomedicine, Just as You Do for Isolated Compounds.

PubMed

Patel, Areeba; Khan, Farooq Ali; Sikdar, Arindam; Mondal, Amit; Shukla, Sunil Dutt; Khurana, Sukant

2018-01-01

Phytomedicine has often been used as "alternative therapy," which in our opinion is unfortunate as it prevents its main actions being systematically studied, side effects explored, and toxicity tested, like all single-compound-based medicine. Our group is interested in finding which traditional or modern phytomedicines actually work and which are simply "working" through placebo, standardizing phytomedicine preparations, studying their toxicity, and finding active molecules in plants for modification and chemical synthesis as single compounds. Although fluctuation in efficacy due to seasonal and geographical variations in phytomedicine remains a concern, if well regulated, even plant extracts without isolated compounds can serve medicinal needs where single-compound options are currently not great. A potential concern with such phytomedicine is frequent mixing of ingredients in commercial formulations without test of synergism. Our study on the use of 2 traditional plants for Parkinson disease shows a clear lack of synergism, and to study nonsynergism better, we developed a new visualization approach. In this commentary, using our study on Parkinson disease as an example, we make a case for better evaluation of phytomedicines, especially testing for synergistic interactions. We also critique our own exploration of oxidative stress and few behavioral parameters alone to lay grounds for what we and hopefully others can do in future to extract more information from their phytomedicine studies. We hope this commentary acts as a good warning for anyone mixing 2 phytomedicines without testing.

Investigating contactless high frequency ultrasound microbeam stimulation for determination of invasion potential of breast cancer cells.

PubMed

Hwang, Jae Youn; Lee, Nan Sook; Lee, Changyang; Lam, Kwok Ho; Kim, Hyung Ham; Woo, Jonghye; Lin, Ming-Yi; Kisler, Kassandra; Choi, Hojong; Zhou, Qifa; Chow, Robert H; Shung, K Kirk

2013-10-01

In this article, we investigate the application of contactless high frequency ultrasound microbeam stimulation (HFUMS) for determining the invasion potential of breast cancer cells. In breast cancer patients, the finding of tumor metastasis significantly worsens the clinical prognosis. Thus, early determination of the potential of a tumor for invasion and metastasis would significantly impact decisions about aggressiveness of cancer treatment. Recent work suggests that invasive breast cancer cells (MDA-MB-231), but not weakly invasive breast cancer cells (MCF-7, SKBR3, and BT-474), display a number of neuronal characteristics, including expression of voltage-gated sodium channels. Since sodium channels are often co-expressed with calcium channels, this prompted us to test whether single-cell stimulation by a highly focused ultrasound microbeam would trigger Ca(2+) elevation, especially in highly invasive breast cancer cells. To calibrate the diameter of the microbeam ultrasound produced by a 200-MHz single element LiNbO3 transducer, we focused the beam on a wire target and performed a pulse-echo test. The width of the beam was ∼17 µm, appropriate for single cell stimulation. Membrane-permeant fluorescent Ca(2+) indicators were utilized to monitor Ca(2+) changes in the cells due to HFUMS. The cell response index (CRI), which is a composite parameter reflecting both Ca(2+) elevation and the fraction of responding cells elicited by HFUMS, was much greater in highly invasive breast cancer cells than in the weakly invasive breast cancer cells. The CRI of MDA-MB-231 cells depended on peak-to-peak amplitude of the voltage driving the transducer. These results suggest that HFUMS may serve as a novel tool to determine the invasion potential of breast cancer cells, and with further refinement may offer a rapid test for invasiveness of tumor biopsies in situ. Copyright © 2013 Wiley Periodicals, Inc.

Determination of the ionization potentials of security-relevant substances with single photon ionization mass spectrometry using synchrotron radiation.

PubMed

Schramm, E; Mühlberger, F; Mitschke, S; Reichardt, G; Schulte-Ladbeck, R; Pütz, M; Zimmermann, R

2008-02-01

Several ionization potentials (IPs) of security relevant substances were determined with single photon ionization time of flight mass spectrometry (SPI-TOFMS) using monochromatized synchrotron radiation from the "Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung" (BESSY). In detail, the IPs of nine explosives and related compounds, seven narcotics and narcotics precursors, and one chemical warfare agent (CWA) precursor were determined, whereas six IPs already known from the literature were verified correctly. From seven other substances, including one CWA precursor, the IP could not be determined as the molecule ion peak could not be detected. For these substances the appearance energy (AE) of a main fragment was determined. The analyzed security-relevant substances showed IPs significantly below the IPs of common matrix compounds such as nitrogen and oxygen. Therefore, it is possible to find photon energies in between, whereby the molecules of interest can be detected with SPI in very low concentrations due to the shielding of the matrix. All determined IPs except the one of the explosive EGDN were below 10.5 eV. Hence, laser-generated 118 nm photons can be applied for detecting almost all security-relevant substances by, e.g., SPI-TOFMS.

Theranostic Nanoseeds for Efficacious Internal Radiation Therapy of Unresectable Solid Tumors

NASA Astrophysics Data System (ADS)

Moeendarbari, Sina; Tekade, Rakesh; Mulgaonkar, Aditi; Christensen, Preston; Ramezani, Saleh; Hassan, Gedaa; Jiang, Ruiqian; Öz, Orhan K.; Hao, Yaowu; Sun, Xiankai

2016-02-01

Malignant tumors are considered “unresectable” if they are adhere to vital structures or the surgery would cause irreversible damages to the patients. Though a variety of cytotoxic drugs and radiation therapies are currently available in clinical practice to treat such tumor masses, these therapeutic modalities are always associated with substantial side effects. Here, we report an injectable nanoparticle-based internal radiation source that potentially offers more efficacious treatment of unresectable solid tumors without significant adverse side effects. Using a highly efficient incorporation procedure, palladium-103, a brachytherapy radioisotope in clinical practice, was coated to monodispersed hollow gold nanoparticles with a diameter about 120 nm, to form 103Pd@Au nanoseeds. The therapeutic efficacy of 103Pd@Au nanoseeds were assessed when intratumorally injected into a prostate cancer xenograft model. Five weeks after a single-dose treatment, a significant tumor burden reduction (>80%) was observed without noticeable side effects on the liver, spleen and other organs. Impressively, >95% nanoseeds were retained inside the tumors as monitored by Single Photon Emission Computed Tomography (SPECT) with the gamma emissions of 103Pd. These findings show that this nanoseed-based brachytherapy has the potential to provide a theranostic solution to unresectable solid tumors.

Propensity of a single-walled carbon nanotube-peptide to mimic a KK10 peptide in an HLA-TCR complex

NASA Astrophysics Data System (ADS)

Feng, Mei; Bell, David R.; Zhou, Ruhong

2017-12-01

The application of nanotechnology to improve disease diagnosis, treatment, monitoring, and prevention is the goal of nanomedicine. We report here a theoretical study of a functionalized single-walled carbon nanotube (CNT) mimic binding to a human leukocyte antigen-T cell receptor (HLA-TCR) immune complex as a first attempt of a potential nanomedicine for human immunodeficiency virus (HIV) vaccine development. The carbon nanotube was coated with three arginine residues to imitate the HIV type 1 immunodominant viral peptide KK10 (gag 263-272: KRWIILGLNK), named CNT-peptide hereafter. Through molecular dynamics simulations, we explore the CNT-peptide and KK10 binding to an important HLA-TCR complex. Our results suggest that the CNT-peptide and KK10 bind comparably to the HLA-TCR complex, but the CNT-peptide forms stronger interactions with the TCR. Desorption simulations highlight the innate flexibility of KK10 over the CNT-peptide, resulting in a slightly higher desorption energy required for KK10 over the CNT-peptide. Our findings indicate that the designed CNT-peptide mimic has favorable propensity to activate TCR pathways and should be further explored to understand therapeutic potential.

Smart grid initialization reduces the computational complexity of multi-objective image registration based on a dual-dynamic transformation model to account for large anatomical differences

NASA Astrophysics Data System (ADS)

Bosman, Peter A. N.; Alderliesten, Tanja

2016-03-01

We recently demonstrated the strong potential of using dual-dynamic transformation models when tackling deformable image registration problems involving large anatomical differences. Dual-dynamic transformation models employ two moving grids instead of the common single moving grid for the target image (and single fixed grid for the source image). We previously employed powerful optimization algorithms to make use of the additional flexibility offered by a dual-dynamic transformation model with good results, directly obtaining insight into the trade-off between important registration objectives as a result of taking a multi-objective approach to optimization. However, optimization has so far been initialized using two regular grids, which still leaves a great potential of dual-dynamic transformation models untapped: a-priori grid alignment with image structures/areas that are expected to deform more. This allows (far) less grid points to be used, compared to using a sufficiently refined regular grid, leading to (far) more efficient optimization, or, equivalently, more accurate results using the same number of grid points. We study the implications of exploiting this potential by experimenting with two new smart grid initialization procedures: one manual expert-based and one automated image-feature-based. We consider a CT test case with large differences in bladder volume with and without a multi-resolution scheme and find a substantial benefit of using smart grid initialization.

Dissection of the IgNAR V domain: molecular scanning and orthologue database mining define novel IgNAR hallmarks and affinity maturation mechanisms.

PubMed

Fennell, B J; Darmanin-Sheehan, A; Hufton, S E; Calabro, V; Wu, L; Müller, M R; Cao, W; Gill, D; Cunningham, O; Finlay, W J J

2010-07-09

The shark antigen-binding V(NAR) domain has the potential to provide an attractive alternative to traditional biotherapeutics based on its small size, advantageous physiochemical properties, and unusual ability to target clefts in enzymes or cell surface molecules. The V(NAR) shares many of the properties of the well-characterised single-domain camelid V(H)H but is much less understood at the molecular level. We chose the hen-egg-lysozyme-specific archetypal Type I V(NAR) 5A7 and used ribosome display in combination with error-prone mutagenesis to interrogate the entire sequence space. We found a high level of mutational plasticity across the V(NAR) domain, particularly within the framework 2 and hypervariable region 2 regions. A number of residues important for affinity were identified, and a triple mutant combining A1D, S61R, and G62R resulted in a K(D) of 460 pM for hen egg lysozyme, a 20-fold improvement over wild-type 5A7, and the highest K(D) yet reported for V(NAR)-antigen interactions. These findings were rationalised using structural modelling and indicate the importance of residues outside the classical complementarity determining regions in making novel antigen contacts that modulate affinity. We also located two solvent-exposed residues (G15 and G42), distant from the V(NAR) paratope, which retain function upon mutation to cysteine and have the potential to be exploited as sites for targeted covalent modification. Our findings with 5A7 were extended to all known NAR structures using an in-depth bioinformatic analysis of sequence data available in the literature and a newly generated V(NAR) database. This study allowed us to identify, for the first time, both V(NAR)-specific and V(NAR)/Ig V(L)/TCR V(alpha) overlapping hallmark residues, which are critical for the structural and functional integrity of the single domain. Intriguingly, each of our designated V(NAR)-specific hallmarks align precisely with previously defined mutational 'cold spots' in natural nurse shark cDNA sequences. These findings will aid future V(NAR) engineering and optimisation studies towards the development of V(NAR) single-domain proteins as viable biotherapeutics. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Single-donor islet transplantation and long-term insulin independence in select patients with type 1 diabetes mellitus.

PubMed

Al-Adra, David P; Gill, Richdeep S; Imes, Sharleen; O'Gorman, Doug; Kin, Tatsuya; Axford, Sara J; Shi, Xinzhe; Senior, Peter A; Shapiro, A M James

2014-11-15

Islet transplantation is a recognized treatment option for select patients with type I diabetes mellitus. However, islet infusions from multiple donors are often required to achieve insulin independence. Ideally, insulin independence would be achieved routinely with only a single donor. Identification of factors associated with insulin independence after single-donor islet transplantation may help to select recipient-donor combinations with the highest probability of success. Subjects undergoing islet transplantation at a single center (Edmonton, Canada) between March 1999 and August 2013 were included. Recipient, donor, and transplant characteristics were collected and compared between recipients who became insulin independent after one islet transplantation and those who did not. Thirty-one patients achieved insulin independence after a single-donor islet transplantation, and 149 did not. Long-term insulin-free survival was not different between the groups. Factors significantly associated with single-donor success included recipient age, insulin requirement at baseline, donor weight, donor body mass index, islet transplant mass, and peritransplant heparin and insulin administration. On multivariate analysis, pretransplantation daily insulin requirements, the use of peritransplantation heparin and insulin infusions, and islet transplant mass remained significant. We have identified clinically relevant differences defining the achievement of insulin independence after single-donor transplantation. Based on these differences, a preoperative insulin requirement of less than 0.6 U/kg per day and receiving more than 5,646 islet equivalents (IEQ)/kg have a sensitivity of 84% and 71% and specificity of 50% and 50%, respectively, for insulin independence after single-donor islet transplantation. With ideal patient selection, this finding could potentially increase single-donor transplantation success and may be especially relevant for presensitized subjects or those who may subsequently require renal replacement.

Evaluation of copper, aluminum, and nickel interatomic potentials on predicting the elastic properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rassoulinejad-Mousavi, Seyed Moein; Mao, Yijin; Zhang, Yuwen, E-mail: zhangyu@missouri.edu

Choice of appropriate force field is one of the main concerns of any atomistic simulation that needs to be seriously considered in order to yield reliable results. Since investigations on the mechanical behavior of materials at micro/nanoscale have been becoming much more widespread, it is necessary to determine an adequate potential which accurately models the interaction of the atoms for desired applications. In this framework, reliability of multiple embedded atom method based interatomic potentials for predicting the elastic properties was investigated. Assessments were carried out for different copper, aluminum, and nickel interatomic potentials at room temperature which is considered asmore » the most applicable case. Examined force fields for the three species were taken from online repositories of National Institute of Standards and Technology, as well as the Sandia National Laboratories, the LAMMPS database. Using molecular dynamic simulations, the three independent elastic constants, C{sub 11}, C{sub 12}, and C{sub 44}, were found for Cu, Al, and Ni cubic single crystals. Voigt-Reuss-Hill approximation was then implemented to convert elastic constants of the single crystals into isotropic polycrystalline elastic moduli including bulk modulus, shear modulus, and Young's modulus as well as Poisson's ratio. Simulation results from massive molecular dynamic were compared with available experimental data in the literature to justify the robustness of each potential for each species. Eventually, accurate interatomic potentials have been recommended for finding each of the elastic properties of the pure species. Exactitude of the elastic properties was found to be sensitive to the choice of the force fields. Those potentials that were fitted for a specific compound may not necessarily work accurately for all the existing pure species. Tabulated results in this paper might be used as a benchmark to increase assurance of using the interatomic potential that was designated for a problem.« less

A mixed-methods approach to systematic reviews.

PubMed

Pearson, Alan; White, Heath; Bath-Hextall, Fiona; Salmond, Susan; Apostolo, Joao; Kirkpatrick, Pamela

2015-09-01

There are an increasing number of published single-method systematic reviews that focus on different types of evidence related to a particular topic. As policy makers and practitioners seek clear directions for decision-making from systematic reviews, it is likely that it will be increasingly difficult for them to identify 'what to do' if they are required to find and understand a plethora of syntheses related to a particular topic.Mixed-methods systematic reviews are designed to address this issue and have the potential to produce systematic reviews of direct relevance to policy makers and practitioners.On the basis of the recommendations of the Joanna Briggs Institute International Mixed Methods Reviews Methodology Group in 2012, the Institute adopted a segregated approach to mixed-methods synthesis as described by Sandelowski et al., which consists of separate syntheses of each component method of the review. Joanna Briggs Institute's mixed-methods synthesis of the findings of the separate syntheses uses a Bayesian approach to translate the findings of the initial quantitative synthesis into qualitative themes and pooling these with the findings of the initial qualitative synthesis.

Diffraction catastrophes and semiclassical quantum mechanics for Veselago lensing in graphene

NASA Astrophysics Data System (ADS)

Reijnders, K. J. A.; Katsnelson, M. I.

2017-07-01

We study the effect of trigonal warping on the focusing of electrons by n-p junctions in graphene. We find that perfect focusing, which was predicted for massless Dirac fermions, is only preserved for one specific lattice orientation. In the general case, trigonal warping leads to the formation of cusp caustics, with a different position of the focus for graphene's two valleys. We develop a semiclassical theory to compute these positions and find very good agreement with tight-binding simulations. Considering the transmission as a function of potential strength, we find that trigonal warping splits the single Dirac peak into two distinct peaks, leading to valley polarization. We obtain the transmission curves from tight-binding simulations and find that they are in very good agreement with the results of a billiard model that incorporates trigonal warping. Furthermore, the positions of the transmission maxima and the scaling of the peak width are accurately predicted by our semiclassical theory. Our semiclassical analysis can easily be carried over to other Dirac materials, which generally have different Fermi surface distortions.

Genetics of Oxidative Stress in Obesity

PubMed Central

Rupérez, Azahara I.; Gil, Angel; Aguilera, Concepción M.

2014-01-01

Obesity is a multifactorial disease characterized by the excessive accumulation of fat in adipose tissue and peripheral organs. Its derived metabolic complications are mediated by the associated oxidative stress, inflammation and hypoxia. Oxidative stress is due to the excessive production of reactive oxygen species or diminished antioxidant defenses. Genetic variants, such as single nucleotide polymorphisms in antioxidant defense system genes, could alter the efficacy of these enzymes and, ultimately, the risk of obesity; thus, studies investigating the role of genetic variations in genes related to oxidative stress could be useful for better understanding the etiology of obesity and its metabolic complications. The lack of existing literature reviews in this field encouraged us to gather the findings from studies focusing on the impact of single nucleotide polymorphisms in antioxidant enzymes, oxidative stress-producing systems and transcription factor genes concerning their association with obesity risk and its phenotypes. In the future, the characterization of these single nucleotide polymorphisms (SNPs) in obese patients could contribute to the development of controlled antioxidant therapies potentially beneficial for the treatment of obesity-derived metabolic complications. PMID:24562334

Genetics of oxidative stress in obesity.

PubMed

Rupérez, Azahara I; Gil, Angel; Aguilera, Concepción M

2014-02-20

Obesity is a multifactorial disease characterized by the excessive accumulation of fat in adipose tissue and peripheral organs. Its derived metabolic complications are mediated by the associated oxidative stress, inflammation and hypoxia. Oxidative stress is due to the excessive production of reactive oxygen species or diminished antioxidant defenses. Genetic variants, such as single nucleotide polymorphisms in antioxidant defense system genes, could alter the efficacy of these enzymes and, ultimately, the risk of obesity; thus, studies investigating the role of genetic variations in genes related to oxidative stress could be useful for better understanding the etiology of obesity and its metabolic complications. The lack of existing literature reviews in this field encouraged us to gather the findings from studies focusing on the impact of single nucleotide polymorphisms in antioxidant enzymes, oxidative stress-producing systems and transcription factor genes concerning their association with obesity risk and its phenotypes. In the future, the characterization of these single nucleotide polymorphisms (SNPs) in obese patients could contribute to the development of controlled antioxidant therapies potentially beneficial for the treatment of obesity-derived metabolic complications.

Cooperative single-photon subradiant states in a three-dimensional atomic array

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jen, H.H., E-mail: sappyjen@gmail.com

2016-11-15

We propose a complete superradiant and subradiant states that can be manipulated and prepared in a three-dimensional atomic array. These subradiant states can be realized by absorbing a single photon and imprinting the spatially-dependent phases on the atomic system. We find that the collective decay rates and associated cooperative Lamb shifts are highly dependent on the phases we manage to imprint, and the subradiant state of long lifetime can be found for various lattice spacings and atom numbers. We also investigate both optically thin and thick atomic arrays, which can serve for systematic studies of super- and sub-radiance. Our proposal offers an alternative schememore » for quantum memory of light in a three-dimensional array of two-level atoms, which is applicable and potentially advantageous in quantum information processing. - Highlights: • Cooperative single-photon subradiant states in a three-dimensional atomic array. • Subradiant state manipulation via spatially-increasing phase imprinting. • Quantum storage of light in the subradiant state in two-level atoms.« less

Efficient removal of nitrobenzene and concomitant electricity production by single-chamber microbial fuel cells with activated carbon air-cathode.

PubMed

Zhang, Enren; Wang, Feng; Zhai, Wenjing; Scott, Keith; Wang, Xu; Diao, Guowang

2017-04-01

Single-chamber microbial fuel cells (S-MFCs) with bio-anodes and activated carbon (AC) air-cathodes showed high nitrobenzene (NB) tolerance and NB removal with concomitant electricity production. The maximum power over 25Wm -3 could be obtained when S-MFCs were operated in the NB loading range of 1.2-6.2molm -3 d -1 , and stable electricity production over 13.7Wm -3 could be produced in a NB loading range of 1.2-14.7molm -3 d -1 . The present S-MFCs exhibited high NB removal performance with NB removal efficiency over 97% even when the NB loading rate was increased to 17.2molm -3 d -1 . The potential NB reduced product (i.e. aniline) could also be effectively removed from influents. The findings in this study means that single-chamber MFCs assembled with pre-enriched bio-anodes and AC air-cathodes could be developed as effective bio-electrochemical systems to remove NB from wastewaters and to harvest energy instead of consuming energy. Copyright © 2017 Elsevier Ltd. All rights reserved.

Measurement, modeling, and simulation of cryogenic SiGe HBT amplifier circuits for fast single spin readout

NASA Astrophysics Data System (ADS)

England, Troy; Curry, Matthew; Carr, Steve; Swartzentruber, Brian; Lilly, Michael; Bishop, Nathan; Carrol, Malcolm

2015-03-01

Fast, low-power quantum state readout is one of many challenges facing quantum information processing. Single electron transistors (SETs) are potentially fast, sensitive detectors for performing spin readout of electrons bound to Si:P donors. From a circuit perspective, however, their output impedance and nonlinear conductance are ill suited to drive the parasitic capacitance typical of coaxial conductors used in cryogenic environments, necessitating a cryogenic amplification stage. We will discuss calibration data, as well as modeling and simulation of cryogenic silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) circuits connected to a silicon SET and operating at 4 K. We find a continuum of solutions from simple, single-HBT amplifiers to more complex, multi-HBT circuits suitable for integration, with varying noise levels and power vs. bandwidth tradeoffs. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE Office of Basic Energy Sciences user facility. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000.

Observing Optical Plasmons on a Single Nanometer Scale

PubMed Central

Cohen, Moshik; Shavit, Reuven; Zalevsky, Zeev

2014-01-01

The exceptional capability of plasmonic structures to confine light into deep subwavelength volumes has fashioned rapid expansion of interest from both fundamental and applicative perspectives. Surface plasmon nanophotonics enables to investigate light - matter interaction in deep nanoscale and harness electromagnetic and quantum properties of materials, thus opening pathways for tremendous potential applications. However, imaging optical plasmonic waves on a single nanometer scale is yet a substantial challenge mainly due to size and energy considerations. Here, for the first time, we use Kelvin Probe Force Microscopy (KPFM) under optical illumination to image and characterize plasmonic modes. We experimentally demonstrate unprecedented spatial resolution and measurement sensitivity both on the order of a single nanometer. By comparing experimentally obtained images with theoretical calculation results, we show that KPFM maps may provide valuable information on the phase of the optical near field. Additionally, we propose a theoretical model for the relation between surface plasmons and the material workfunction measured by KPFM. Our findings provide the path for using KPFM for high resolution measurements of optical plasmons, prompting the scientific frontier towards quantum plasmonic imaging on submolecular scales. PMID:24556874

Functionalization of multi-walled carbon nanotubes with iron phthalocyanine via a liquid chemical reaction for oxygen reduction in alkaline media

NASA Astrophysics Data System (ADS)

Yan, Xiaomei; Xu, Xiao; Liu, Qin; Guo, Jia; Kang, Longtian; Yao, Jiannian

2018-06-01

Iron single-atom catalyst in form of iron-nitrogen-carbon structure possesses the excellent catalytic activity in various chemical reactions. However, exploring a sustainable and stable single-atom metal catalyst still faces a great challenge due to low yield and complicated synthesis. Here, we report a functional multi-wall carbon nanotubes modified with iron phthalocyanine molecules via a liquid chemical reaction and realize the performance of similar single-atom catalysis for oxygen reduction reaction. A serial of characterizations strongly imply the structure change of iron phthalocyanine molecule and its close recombination with multi-wall carbon nanotubes, which are in favor of ORR catalysis. Compared to commercial platinum-carbon catalyst, composites exhibit superior activity for oxygen reduction reaction with higher half-wave potential (0.86 V), lower Tafel slope (38 mV dec-1), higher limiting current density and excellent electrochemical stability. The corresponding Zinc-air battery also presents higher maximum power density and discharge stability. Therefore, these findings provide a facile route to synthesize a highly efficient non-precious metal carbon-based catalyst.

Yeast Srs2 Helicase Promotes Redistribution of Single-Stranded DNA-Bound RPA and Rad52 in Homologous Recombination Regulation.

PubMed

De Tullio, Luisina; Kaniecki, Kyle; Kwon, Youngho; Crickard, J Brooks; Sung, Patrick; Greene, Eric C

2017-10-17

Srs2 is a super-family 1 helicase that promotes genome stability by dismantling toxic DNA recombination intermediates. However, the mechanisms by which Srs2 remodels or resolves recombination intermediates remain poorly understood. Here, single-molecule imaging is used to visualize Srs2 in real time as it acts on single-stranded DNA (ssDNA) bound by protein factors that function in recombination. We demonstrate that Srs2 is highly processive and translocates rapidly (∼170 nt per second) in the 3'→5' direction along ssDNA saturated with replication protein A (RPA). We show that RPA is evicted from DNA during the passage of Srs2. Remarkably, Srs2 also readily removes the recombination mediator Rad52 from RPA-ssDNA and, in doing so, promotes rapid redistribution of both Rad52 and RPA. These findings have important mechanistic implications for understanding how Srs2 and related nucleic acid motor proteins resolve potentially pathogenic nucleoprotein intermediates. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Diversity-oriented synthesis yields novel multistage antimalarial inhibitors.

PubMed

Kato, Nobutaka; Comer, Eamon; Sakata-Kato, Tomoyo; Sharma, Arvind; Sharma, Manmohan; Maetani, Micah; Bastien, Jessica; Brancucci, Nicolas M; Bittker, Joshua A; Corey, Victoria; Clarke, David; Derbyshire, Emily R; Dornan, Gillian L; Duffy, Sandra; Eckley, Sean; Itoe, Maurice A; Koolen, Karin M J; Lewis, Timothy A; Lui, Ping S; Lukens, Amanda K; Lund, Emily; March, Sandra; Meibalan, Elamaran; Meier, Bennett C; McPhail, Jacob A; Mitasev, Branko; Moss, Eli L; Sayes, Morgane; Van Gessel, Yvonne; Wawer, Mathias J; Yoshinaga, Takashi; Zeeman, Anne-Marie; Avery, Vicky M; Bhatia, Sangeeta N; Burke, John E; Catteruccia, Flaminia; Clardy, Jon C; Clemons, Paul A; Dechering, Koen J; Duvall, Jeremy R; Foley, Michael A; Gusovsky, Fabian; Kocken, Clemens H M; Marti, Matthias; Morningstar, Marshall L; Munoz, Benito; Neafsey, Daniel E; Sharma, Amit; Winzeler, Elizabeth A; Wirth, Dyann F; Scherer, Christina A; Schreiber, Stuart L

2016-10-20

Antimalarial drugs have thus far been chiefly derived from two sources-natural products and synthetic drug-like compounds. Here we investigate whether antimalarial agents with novel mechanisms of action could be discovered using a diverse collection of synthetic compounds that have three-dimensional features reminiscent of natural products and are underrepresented in typical screening collections. We report the identification of such compounds with both previously reported and undescribed mechanisms of action, including a series of bicyclic azetidines that inhibit a new antimalarial target, phenylalanyl-tRNA synthetase. These molecules are curative in mice at a single, low dose and show activity against all parasite life stages in multiple in vivo efficacy models. Our findings identify bicyclic azetidines with the potential to both cure and prevent transmission of the disease as well as protect at-risk populations with a single oral dose, highlighting the strength of diversity-oriented synthesis in revealing promising therapeutic targets.

Catalytically active Au-O(OH) x- species stabilized by alkali ions on zeolites and mesoporous oxides

DOE PAGES

Yang, Ming; Li, Sha; Wang, Yuan; ...

2014-11-27

Here we report that the addition of alkali ions (sodium or potassium) to gold on KLTL-zeolite and mesoporous MCM-41 silica stabilizes mononuclear gold in Au-O(OH) x-(Na or K) ensembles. This single-site gold species is active for the low-temperature (<200°C) water-gas shift (WGS) reaction. Unexpectedly, gold is thus similar to platinum in creating –O linkages with more than eight alkali ions and establishing an active site on various supports. The intrinsic activity of the single-site gold species is the same on irreducible supports as on reducible ceria, iron oxide, and titania supports, apparently all sharing a common, similarly structured gold activemore » site. This finding paves the way for using earth-abundant supports to disperse and stabilize precious metal atoms with alkali additives for the WGS and potentially other fuel-processing reactions.« less

Theoretical analysis of polarization-coupled mode splitting in a single microfiber knot-ring resonator

NASA Astrophysics Data System (ADS)

Qiu, Weiqia; Zhou, Junjie; Yu, Jianhui; Xiao, Yi; Lu, Huihui; Guan, Heyuan; Zhong, Yongchun; Zhang, Jun; Chen, Zhe

2016-06-01

We established a theoretical model for a single knot-ring resonator and investigated the transmission spectrum by Jones matrix. The numerical results show that two orthogonal polarization modes of knot-ring, which are originally resonated at the same wavelength, will split into two resonant modes with different wavelengths. The mode splitting is due to the coupling between the two orthogonal polarization modes in the knot-ring when the twisted angle of the twist coupler is not exactly equal to 2mπ (m is an integer). It is also found that the separation of the mode splitting is linearly proportional to the deviation angle δθ with a high correlation coefficient of 99.6% and a slope of 3.17 nm/rad. Furthermore, a transparency phenomenon analogous to coupled-resonator-induced transparency was also predicted by the model. These findings may have potential applications in lasers and sensors.

Modeling of the gate-controlled Kondo effect at carbon point defects in graphene

NASA Astrophysics Data System (ADS)

May, Daniel; Lo, Po-Wei; Deltenre, Kira; Henke, Anika; Mao, Jinhai; Jiang, Yuhang; Li, Guohong; Andrei, Eva Y.; Guo, Guang-Yu; Anders, Frithjof B.

2018-04-01

We study the magnetic properties in the vicinity of a single carbon defect in a monolayer of graphene. We include the unbound σ orbital and the vacancy-induced bound π state in an effective two-orbital single-impurity model. The local magnetic moments are stabilized by the Coulomb interaction as well as a significant ferromagnetic Hund's rule coupling between the orbitals predicted by a density functional theory calculation. A hybridization between the orbitals and the Dirac fermions is generated by the curvature of the graphene sheet in the vicinity of the vacancy. We present results for the local spectral function calculated using Wilson's numerical renormalization group approach for a realistic graphene band structure and find three different regimes depending on the filling, the controlling chemical potential, and the hybridization strength. These different regions are characterized by different magnetic properties. The calculated spectral functions qualitatively agree with recent scanning tunneling spectra on graphene vacancies.

Influence of crystal orientation and ion bombardment on the nitrogen diffusivity in single-crystalline austenitic stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinavicius, A.; Abrasonis, G.; Moeller, W.

2011-10-01

The nitrogen diffusivity in single-crystalline AISI 316L austenitic stainless steel (ASS) during ion nitriding has been investigated at different crystal orientations ((001), (110), (111)) under variations of ion flux (0.3-0.7 mA cm{sup -2}), ion energy (0.5-1.2 keV), and temperature (370-430 deg. C). The nitrogen depth profiles obtained from nuclear reaction analysis are in excellent agreement with fits using the model of diffusion under the influence of traps, from which diffusion coefficients were extracted. At fixed ion energy and flux, the diffusivity varies by a factor up to 2.5 at different crystal orientations. At (100) orientation, it increases linearly with increasingmore » ion flux or energy. The findings are discussed on the basis of atomistic mechanisms of interstitial diffusion, potential lattice distortions, local decomposition, and ion-induced lattice vibrational excitations.« less

The Most Earth Size, Habitable Zone Planets around a Single Star on This Week @NASA – 02/24/2017

NASA Image and Video Library

2017-02-24

NASA held a news conference Feb. 22 at the agency’s headquarters to discuss the finding by the agency’s Spitzer Space Telescope of seven Earth-sized planets around a tiny, relatively nearby, ultra-cool dwarf star. Three of the planets in this system, known as TRAPPIST-1, are in the habitable zone – the region around the star in which liquid water is most likely to thrive on a rocky planet. This is the first time so many planets have been found in a single star's habitable zone outside our solar system, and is the best target yet for studying the atmospheres of potentially habitable, Earth-sized worlds. Also, Kennedy’s Pad 39A, Back in Business, Russian Cargo Ship Arrives at Space Station, RS-25 Engine Tests Resume at Stennis, Structural Testing Begins on SLS Hardware, and 55th Anniversary of Friendship 7 Flight!

Toy Control Program evaluation.

PubMed

Stewart, H A; Ormond, C; Seeger, B R

1991-08-01

The Toy Control Program for the Apple IIe microcomputer is a software and hardware package developed for the training of single-switch scanning skills. The specially designed scanning programs provide on screen visual feedback and activate a battery-powered toy to reinforce performance. This study examined whether the training of preschool subjects in single-switch scanning skills with the Toy Control Program would result in increased task completion scores and increased levels of attention to task, as compared with conditions of toy activation only and microcomputer programs with screen reinforcement only. The results showed that the subjects paid significantly more attention to the toys as reinforcers (p less than .01). No significant difference was found for the performance results of the three conditions. These findings support the use of a program like the Toy Control Program, which integrates the instructional capabilities of a computer with the reinforcement potential of a toy and the creativity of a therapist.

A single macrolichen constitutes hundreds of unrecognized species.

PubMed

Lücking, Robert; Dal-Forno, Manuela; Sikaroodi, Masoumeh; Gillevet, Patrick M; Bungartz, Frank; Moncada, Bibiana; Yánez-Ayabaca, Alba; Chaves, José Luis; Coca, Luis Fernando; Lawrey, James D

2014-07-29

The number of Fungi is estimated at between 1.5 and 3 million. Lichenized species are thought to make up a comparatively small portion of this figure, with unrecognized species richness hidden among little-studied, tropical microlichens. Recent findings, however, suggest that some macrolichens contain a large number of unrecognized taxa, increasing known species richness by an order of magnitude or more. Here we report the existence of at least 126 species in what until recently was believed to be a single taxon: the basidiolichen fungus Dictyonema glabratum, also known as Cora pavonia. Notably, these species are not cryptic but morphologically distinct. A predictive model suggests an even larger number, with more than 400 species. These results call into question species concepts in presumably well-known macrolichens and demonstrate the need for accurately documenting such species richness, given the importance of these lichens in endangered ecosystems such as paramos and the alarming potential for species losses throughout the tropics.

Enhanced Dopamine-Dependent Hippocampal Plasticity after Single MK-801 Application

PubMed Central

Bartsch, Julia C; Fidzinski, Pawel; Huck, Jojanneke HJ; Hörtnagl, Heide; Kovács, Richard; Liotta, Agustin; Priller, Josef; Wozny, Christian; Behr, Joachim

2015-01-01

Dopaminergic hyperfunction and N-methyl-D-aspartate receptor (NMDAR) hypofunction have both been implicated in psychosis. Dopamine-releasing drugs and NMDAR antagonists replicate symptoms associated with psychosis in healthy humans and exacerbate symptoms in patients with schizophrenia. Though hippocampal dysfunction contributes to psychosis, the impact of NMDAR hypofunction on hippocampal plasticity remains poorly understood. Here, we used an NMDAR antagonist rodent model of psychosis to investigate hippocampal long-term potentiation (LTP). We found that single systemic NMDAR antagonism results in a region-specific, presynaptic LTP at hippocampal CA1-subiculum synapses that is induced by activation of D1/D5 dopamine receptors and modulated by L-type voltage-gated Ca2+ channels. Thereby, our findings may provide a cellular mechanism how NMDAR antagonism can lead to an enhanced hippocampal output causing activation of the hippocampus-ventral tegmental area-loop and overdrive of the dopamine system. PMID:25315194

Bulk viscous cosmology with causal transport theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piattella, Oliver F.; Fabris, Júlio C.; Zimdahl, Winfried, E-mail: oliver.piattella@gmail.com, E-mail: fabris@pq.cnpq.br, E-mail: winfried.zimdahl@pq.cnpq.br

2011-05-01

We consider cosmological scenarios originating from a single imperfect fluid with bulk viscosity and apply Eckart's and both the full and the truncated Müller-Israel-Stewart's theories as descriptions of the non-equilibrium processes. Our principal objective is to investigate if the dynamical properties of Dark Matter and Dark Energy can be described by a single viscous fluid and how such description changes when a causal theory (Müller-Israel-Stewart's, both in its full and truncated forms) is taken into account instead of Eckart's non-causal one. To this purpose, we find numerical solutions for the gravitational potential and compare its behaviour with the corresponding ΛCDMmore » case. Eckart's and the full causal theory seem to be disfavoured, whereas the truncated theory leads to results similar to those of the ΛCDM model for a bulk viscous speed in the interval 10{sup −11} || cb{sup 2} ∼< 10{sup −8}.« less

A genomic history of Aboriginal Australia.

PubMed

Malaspinas, Anna-Sapfo; Westaway, Michael C; Muller, Craig; Sousa, Vitor C; Lao, Oscar; Alves, Isabel; Bergström, Anders; Athanasiadis, Georgios; Cheng, Jade Y; Crawford, Jacob E; Heupink, Tim H; Macholdt, Enrico; Peischl, Stephan; Rasmussen, Simon; Schiffels, Stephan; Subramanian, Sankar; Wright, Joanne L; Albrechtsen, Anders; Barbieri, Chiara; Dupanloup, Isabelle; Eriksson, Anders; Margaryan, Ashot; Moltke, Ida; Pugach, Irina; Korneliussen, Thorfinn S; Levkivskyi, Ivan P; Moreno-Mayar, J Víctor; Ni, Shengyu; Racimo, Fernando; Sikora, Martin; Xue, Yali; Aghakhanian, Farhang A; Brucato, Nicolas; Brunak, Søren; Campos, Paula F; Clark, Warren; Ellingvåg, Sturla; Fourmile, Gudjugudju; Gerbault, Pascale; Injie, Darren; Koki, George; Leavesley, Matthew; Logan, Betty; Lynch, Aubrey; Matisoo-Smith, Elizabeth A; McAllister, Peter J; Mentzer, Alexander J; Metspalu, Mait; Migliano, Andrea B; Murgha, Les; Phipps, Maude E; Pomat, William; Reynolds, Doc; Ricaut, Francois-Xavier; Siba, Peter; Thomas, Mark G; Wales, Thomas; Wall, Colleen Ma'run; Oppenheimer, Stephen J; Tyler-Smith, Chris; Durbin, Richard; Dortch, Joe; Manica, Andrea; Schierup, Mikkel H; Foley, Robert A; Lahr, Marta Mirazón; Bowern, Claire; Wall, Jeffrey D; Mailund, Thomas; Stoneking, Mark; Nielsen, Rasmus; Sandhu, Manjinder S; Excoffier, Laurent; Lambert, David M; Willerslev, Eske

2016-10-13

The population history of Aboriginal Australians remains largely uncharacterized. Here we generate high-coverage genomes for 83 Aboriginal Australians (speakers of Pama-Nyungan languages) and 25 Papuans from the New Guinea Highlands. We find that Papuan and Aboriginal Australian ancestors diversified 25-40 thousand years ago (kya), suggesting pre-Holocene population structure in the ancient continent of Sahul (Australia, New Guinea and Tasmania). However, all of the studied Aboriginal Australians descend from a single founding population that differentiated ~10-32 kya. We infer a population expansion in northeast Australia during the Holocene epoch (past 10,000 years) associated with limited gene flow from this region to the rest of Australia, consistent with the spread of the Pama-Nyungan languages. We estimate that Aboriginal Australians and Papuans diverged from Eurasians 51-72 kya, following a single out-of-Africa dispersal, and subsequently admixed with archaic populations. Finally, we report evidence of selection in Aboriginal Australians potentially associated with living in the desert.

Stability of the wobbling motion in the triaxially deformed odd-A nucleus

NASA Astrophysics Data System (ADS)

Tanabe, Kosai; Sugawara-Tanabe, Kazuko

2017-12-01

In order to analyze the content of the exact solutions for particle-rotor models with both the rigid and the hydrodynamical moments of inertia (MoI), as a theoretical probe we apply the Holstein-Primakoff (HP) boson expansion method to the total angular momentum I and the single-particle angular momentum j. We study the competition between Coriolis force and the single-particle potential by employing the different choices of the diagonal HP boson representations for the components of I and j along a common coordinate axis, and along perpendicular axes. We do not find any wobbling level sequence associated with the rotation around the principal axis with the medium MoI. The staggering in the alignments of I about the axis with the medium MoI is found in the limited range of I, while the vector R(=I-j) is confined about the axis with the largest MoI.

Protease activated receptor-2 (PAR2): possible target of phytochemicals.

PubMed

Kakarala, Kavita Kumari; Jamil, Kaiser

2015-09-01

The use of phytochemicals either singly or in combination with other anticancer drugs comes with an advantage of less toxicity and minimal side effects. Signaling pathways play central role in cell cycle, cell growth, metabolism, etc. Thus, the identification of phytochemicals with promising antagonistic effect on the receptor/s playing key role in single transduction may have better therapeutic application. With this background, phytochemicals were screened against protease-activated receptor 2 (PAR2). PAR2 belongs to the superfamily of GPCRs and is an important target for breast cancer. Using in silico methods, this study was able to identify the phytochemicals with promising binding affinity suggesting their therapeutic potential in the treatment of breast cancer. The findings from this study acquires importance as the information on the possible agonists and antagonists of PAR2 is limited due its unique mechanism of activation.

Poverty and union formation among never-married single mothers in the Netherlands, 1989-2005.

PubMed

Kalmijn, Matthijs; Monden, Christiaan

2010-11-01

Using panel data from Dutch tax records linked to the municipality registry, we investigate how the partner status of never-married single mothers changes in the years after the birth of their first child. To explore a possible accumulation of financial problems, we study the effects of income on the chances of entering a marital or cohabiting union. We also examine the effects of finding a partner on income for never-married single mothers. Finding a partner substantially improves income. We find that about half of the never-married single mothers marry or start cohabiting within 10 years of the first birth, but that these are usually mothers with average and higher incomes. Not only are never-married single mothers more likely to be poor at the time of first birth, the poor are also more likely to remain single. There seems to be an accumulation of disadvantage in this special group in Dutch society.

On the running of the spectral index to all orders: a new model-dependent approach to constrain inflationary models

NASA Astrophysics Data System (ADS)

Zarei, Moslem

2016-06-01

In conventional model-independent approaches, the power spectrum of primordial perturbations is characterized by such free parameters as the spectral index, its running, the running of running, and the tensor-to-scalar ratio. In this work we show that, at least for simple inflationary potentials, one can find the primordial scalar and tensor power spectra exactly by resumming over all the running terms. In this model-dependent method, we expand the power spectra about the pivot scale to find the series terms as functions of the e-folding number for some single field models of inflation. Interestingly, for the viable models studied here, one can sum over all the terms and evaluate the exact form of the power spectra. This in turn gives more accurate parametrization of the specific models studied in this work. We finally compare our results with recent cosmic microwave background data to find that our new power spectra are in good agreement with the data.

Motif finding in DNA sequences based on skipping nonconserved positions in background Markov chains.

PubMed

Zhao, Xiaoyan; Sze, Sing-Hoi

2011-05-01

One strategy to identify transcription factor binding sites is through motif finding in upstream DNA sequences of potentially co-regulated genes. Despite extensive efforts, none of the existing algorithms perform very well. We consider a string representation that allows arbitrary ignored positions within the nonconserved portion of single motifs, and use O(2(l)) Markov chains to model the background distributions of motifs of length l while skipping these positions within each Markov chain. By focusing initially on positions that have fixed nucleotides to define core occurrences, we develop an algorithm to identify motifs of moderate lengths. We compare the performance of our algorithm to other motif finding algorithms on a few benchmark data sets, and show that significant improvement in accuracy can be obtained when the sites are sufficiently conserved within a given sample, while comparable performance is obtained when the site conservation rate is low. A software program (PosMotif ) and detailed results are available online at http://faculty.cse.tamu.edu/shsze/posmotif.

The influence of single bursts versus single spikes at excitatory dendrodendritic synapses.

PubMed

Masurkar, Arjun V; Chen, Wei R

2012-02-01

The synchronization of neuronal activity is thought to enhance information processing. There is much evidence supporting rhythmically bursting external tufted cells (ETCs) of the rodent olfactory bulb glomeruli coordinating the activation of glomerular interneurons and mitral cells via dendrodendritic excitation. However, as bursting has variable significance at axodendritic cortical synapses, it is not clear if ETC bursting imparts a specific functional advantage over the preliminary spike in dendrodendritic synaptic networks. To answer this question, we investigated the influence of single ETC bursts and spikes with the in vitro rat olfactory bulb preparation at different levels of processing, via calcium imaging of presynaptic ETC dendrites, dual electrical recording of ETC -interneuron synaptic pairs, and multicellular calcium imaging of ETC-induced population activity. Our findings supported single ETC bursts, versus single spikes, driving robust presynaptic calcium signaling, which in turn was associated with profound extension of the initial monosynaptic spike-driven dendrodendritic excitatory postsynaptic potential. This extension could be driven by either the spike-dependent or spike-independent components of the burst. At the population level, burst-induced excitation was more widespread and reliable compared with single spikes. This further supports the ETC network, in part due to a functional advantage of bursting at excitatory dendrodendritic synapses, coordinating synchronous activity at behaviorally relevant frequencies related to odor processing in vivo. © 2012 The Authors. European Journal of Neuroscience © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

Energy Savings Potential of SSL in Horticultural Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stober, Kelsey; Lee, Kyung; Yamada, Mary

Report that presents the findings for horticultural lighting applications where light-emitting diode (LED) products are now competing with traditional light sources. The three main categories of indoor horticulture were investigated: supplemented greenhouses, which use electric lighting to extend the hours of daylight, supplement low levels of sunlight on cloudy days, or disrupt periods of darkness to alter plant growth; non-stacked indoor farms, where plants are grown in a single layer on the floor under ceiling-mounted lighting; and vertical farms, where plants are stacked along vertical shelving to maximize grow space, and the lighting is typically mounted within the shelving units.

Automatically augmenting lifelog events using pervasively generated content from millions of people.

PubMed

Doherty, Aiden R; Smeaton, Alan F

2010-01-01

In sensor research we take advantage of additional contextual sensor information to disambiguate potentially erroneous sensor readings or to make better informed decisions on a single sensor's output. This use of additional information reinforces, validates, semantically enriches, and augments sensed data. Lifelog data is challenging to augment, as it tracks one's life with many images including the places they go, making it non-trivial to find associated sources of information. We investigate realising the goal of pervasive user-generated content based on sensors, by augmenting passive visual lifelogs with "Web 2.0" content collected by millions of other individuals.

Energy Conversion Properties of ZnSiP2, a Lattice-Matched Material for Silicon-Based Tandem Photovoltaics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinez, Aaron D.; Warren, Emily L.; Gorai, Prashun

ZnSiP2 demonstrates promising potential as an optically active material on silicon. There has been a longstanding need for wide band gap materials that can be integrated with Si for tandem photovoltaics and other optoelectronic applications. ZnSiP2 is an inexpensive, earth abundant, wide band gap material that is stable and lattice matched with silicon. This conference proceeding summarizes our PV-relevant work on bulk single crystal ZnSiP2, highlighting the key findings and laying the ground work for integration into Si-based tandem devices.

Graphene-based materials: fabrication and application for adsorption in analytical chemistry.

PubMed

Wang, Xin; Liu, Bo; Lu, Qipeng; Qu, Qishu

2014-10-03

Graphene, a single layer of carbon atoms densely packed into a honeycomb crystal lattice with unique electronic, chemical, and mechanical properties, is the 2D allotrope of carbon. Owing to the remarkable properties, graphene and graphene-based materials are likely to find potential applications as a sorbent in analytical chemistry. The current review focuses predominantly on the recent development of graphene-based materials and demonstrates their enhanced performance in adsorption of organic compounds, metal ions, and solid phase extraction as well as in separation science since mostly 2012. Copyright © 2014 Elsevier B.V. All rights reserved.

On the predictiveness of single-field inflationary models

NASA Astrophysics Data System (ADS)

Burgess, C. P.; Patil, Subodh P.; Trott, Michael

2014-06-01

We re-examine the predictiveness of single-field inflationary models and discuss how an unknown UV completion can complicate determining inflationary model parameters from observations, even from precision measurements. Besides the usual naturalness issues associated with having a shallow inflationary potential, we describe another issue for inflation, namely, unknown UV physics modifies the running of Standard Model (SM) parameters and thereby introduces uncertainty into the potential inflationary predictions. We illustrate this point using the minimal Higgs Inflationary scenario, which is arguably the most predictive single-field model on the market, because its predictions for A S , r and n s are made using only one new free parameter beyond those measured in particle physics experiments, and run up to the inflationary regime. We find that this issue can already have observable effects. At the same time, this UV-parameter dependence in the Renormalization Group allows Higgs Inflation to occur (in principle) for a slightly larger range of Higgs masses. We comment on the origin of the various UV scales that arise at large field values for the SM Higgs, clarifying cut off scale arguments by further developing the formalism of a non-linear realization of SU L (2) × U(1) in curved space. We discuss the interesting fact that, outside of Higgs Inflation, the effect of a non-minimal coupling to gravity, even in the SM, results in a non-linear EFT for the Higgs sector. Finally, we briefly comment on post BICEP2 attempts to modify the Higgs Inflation scenario.

Single-parent family structure and sleep problems in black and white adolescents.

PubMed

Troxel, Wendy M; Lee, Laisze; Hall, Martica; Matthews, Karen A

2014-02-01

Sleep is critical for adolescent health and is influenced by the family environment. In our study, we examined if family structure defined as single- vs. two-parent households affected adolescent sleep. Participants were 242 (57% black; 47% boys) healthy adolescents (mean age, 15.7 years). Sleep was measured using self-report and wrist actigraphy over seven consecutive nights. Outcomes were actigraphy-assessed sleep duration and sleep efficiency (SE) for the full week and weekends and weekdays separately, as well as self-reported sleep-wake problems and variability in bedtimes. Linear regression examined the relationship between family structure and sleep, after adjusting for age, sex, race, body mass index, and depressive symptoms, parental education, family conflict, and financial strain. Race and sex were examined as potential moderators. After adjusting for covariates, adolescents from single-parent households had poorer SE across the week and shorter sleep duration on weekends. White adolescents from two-parent households had fewer sleep-wake problems and lower bedtime variability, whereas black adolescents from single-parent households had the lowest weekend SE. There were no significant differences in family structure-sex interactions. Our findings are the first to demonstrate that single-parent family structure is an independent correlate of sleep problems in adolescents and they highlight the moderating role of race. Copyright © 2013 Elsevier B.V. All rights reserved.

Selective distillation phenomenon in two-species Bose-Einstein condensates in open boundary optical lattices.

PubMed

Bai, Xiao-Dong; Zhang, Mei; Xiong, Jun; Yang, Guo-Jian; Deng, Fu-Guo

2015-11-24

We investigate the formation of discrete breathers (DBs) and the dynamics of the mixture of two-species Bose-Einstein condensates (BECs) in open boundary optical lattices using the discrete nonlinear Schrödinger equations. The results show that the coupling of intra- and interspecies interaction can lead to the existence of pure single-species DBs and symbiotic DBs (i.e., two-species DBs). Furthermore, we find that there is a selective distillation phenomenon in the dynamics of the mixture of two-species BECs. One can selectively distil one species from the mixture of two-species BECs and can even control dominant species fraction by adjusting the intra- and interspecies interaction in optical lattices. Our selective distillation mechanism may find potential application in quantum information storage and quantum information processing based on multi-species atoms.

Selective distillation phenomenon in two-species Bose-Einstein condensates in open boundary optical lattices

PubMed Central

Bai, Xiao-Dong; Zhang, Mei; Xiong, Jun; Yang, Guo-Jian; Deng, Fu-Guo

2015-01-01

We investigate the formation of discrete breathers (DBs) and the dynamics of the mixture of two-species Bose-Einstein condensates (BECs) in open boundary optical lattices using the discrete nonlinear Schrödinger equations. The results show that the coupling of intra- and interspecies interaction can lead to the existence of pure single-species DBs and symbiotic DBs (i.e., two-species DBs). Furthermore, we find that there is a selective distillation phenomenon in the dynamics of the mixture of two-species BECs. One can selectively distil one species from the mixture of two-species BECs and can even control dominant species fraction by adjusting the intra- and interspecies interaction in optical lattices. Our selective distillation mechanism may find potential application in quantum information storage and quantum information processing based on multi-species atoms. PMID:26597592

Coronal Element Abundances of the Post-Common Envelope Binary V471 Tauri with ASCA

NASA Technical Reports Server (NTRS)

Still, Martin; Hussain, Gaitee; White, Nicholas E. (Technical Monitor)

2002-01-01

We report on ASCA observations of the coronally active companion star in the post-common envelope binary V471 Tau. While it would be prudent to check the following results with grating spectroscopy, we find that a single-temperature plasma model does not fit the data. Two temperature models with variable abundances indicate that Fe is underabundant compared to the Hyades photospheric mean, whereas, the high first ionization potential element Ne is overabundant. This is indicative of the inverse first ionization effect, believed to result from the fractionation of ionized material by the magnetic field in the upper atmosphere of the star. Evolutionary calculations indicate that there should be no peculiar abundances on the companion star resulting from the common envelope epoch. Indeed, we find no evidence for peculiar abundances, although uncertainties are high.

Managing family life while studying: single mothers' lived experience of being students in a nursing program.

PubMed

Ogunsiji, Olayide; Wilkes, Lesley

Evidence suggests that single parent families are more likely to be affected by social problems associated with poor health and poverty. Single parent families are growing in number and are overwhelmingly headed by women. Despite their increasing number and their level of vulnerability, the lived experiences of single mothers have attracted little attention in the literature. Still little is known about many aspects of life as experienced by single mothers. Nursing is a profession that is dominated by women, and every year a number of single mothers enroll in undergraduate nurse education programs. Currently, there is little information about the experiences of women who are single mothers, undertaking a nursing degree in a university. This paper reports a study that explored the lived experiences of five single mother undergraduate nursing students. van Manen's phenomenological method informed the design and conduct of the study. Findings were grouped into the following themes: being exhausted all the time; being overwhelmed with worries; and being hopeful of the future. Findings of this study revealed that the single mothers' major health concerns were chronic tiredness and overwhelming worries. However, their being in the university was perceived as being health promoting and restoring to their self-esteem. Implications for educators, health providers and women's health services are drawn from the findings.

Gene expression profile of human lung epithelial cells chronically exposed to single-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Chen, Dongquan; Stueckle, Todd A.; Luanpitpong, Sudjit; Rojanasakul, Yon; Lu, Yongju; Wang, Liying

2015-01-01

A rapid increase in utility of engineered nanomaterials, including carbon nanotubes (CNTs), has raised a concern over their safety. Based on recent evidence from animal studies, pulmonary exposure of CNTs may lead to nanoparticle accumulation in the deep lung without effective clearance which could interact with local lung cells for a long period of time. Physicochemical similarities of CNTs to asbestos fibers may contribute to their asbestos-like carcinogenic potential after long-term exposure, which has not been well addressed. More studies are needed to identify and predict the carcinogenic potential and mechanisms for promoting their safe use. Our previous study reported a long-term in vitro exposure model for CNT carcinogenicity and showed that 6-month sub-chronic exposure of single-walled carbon nanotubes (SWCNT) causes malignant transformation of human lung epithelial cells. In addition, the transformed cells induced tumor formation in mice and exhibited an apoptosis resistant phenotype, a key characteristic of cancer cells. Although the potential role of p53 in the transformation process was identified, the underlying mechanisms of oncogenesis remain largely undefined. Here, we further examined the gene expression profile by using genome microarrays to profile molecular mechanisms of SWCNT oncogenesis. Based on differentially expressed genes, possible mechanisms of SWCNT-associated apoptosis resistance and oncogenesis were identified, which included activation of pAkt/p53/Bcl-2 signaling axis, increased gene expression of Ras family for cell cycle control, Dsh-mediated Notch 1, and downregulation of apoptotic genes BAX and Noxa. Activated immune responses were among the major changes of biological function. Our findings shed light on potential molecular mechanisms and signaling pathways involved in SWCNT oncogenic potential.

Increasing relative nonclassicality quantified by standard entanglement potentials by dissipation and unbalanced beam splitting

NASA Astrophysics Data System (ADS)

Miranowicz, Adam; Bartkiewicz, Karol; Lambert, Neill; Chen, Yueh-Nan; Nori, Franco

2015-12-01

If a single-mode nonclassical light is combined with the vacuum on a beam splitter, then the output state is entangled. As proposed in [Phys. Rev. Lett. 94, 173602 (2005), 10.1103/PhysRevLett.94.173602], by measuring this output-state entanglement for a balanced lossless beam splitter, one can quantify the input-state nonclassicality. These measures of nonclassicality (referred to as entanglement potentials) can be based, in principle, on various entanglement measures, leading to the negativity (NP) and concurrence (CP) potentials, and the potential for the relative entropy of entanglement (REEP). We search for the maximal relative nonclassicality, which can be achieved by comparing two entanglement measures for (i) arbitrary two-qubit states and (ii) those which can be generated from a photon-number qubit via a balanced lossless beam splitter, where the qubit basis states are the vacuum and single-photon states. Surprisingly, we find that the maximal relative nonclassicality, measured by the REEP for a given value of the NP, can be increased (if NP <0.527 ) by using either a tunable beam splitter or by amplitude damping of the output state of the balanced beam splitter. We also show that the maximal relative nonclassicality, measured by the NP for a given value of the REEP, can be increased by phase damping (dephasing). Note that the entanglement itself is not increased by these losses (since they act locally), but the possible ratios of different measures are affected. Moreover, we show that partially dephased states can be more nonclassical than both pure states and completely dephased states, by comparing the NP for a given value of the REEP. Thus, one can conclude that not all standard entanglement measures can be used as entanglement potentials. Alternatively, one can infer that a single balanced lossless beam splitter is not always transferring the whole nonclassicality of its input state into the entanglement of its output modes. The application of a lossy beam splitter can solve this problem, at least for the cases analyzed in this paper.

Welfare Reform and Labor Force Exit by Young, Low-Skilled Single Males.

PubMed

Groves, Lincoln H

2016-04-01

While the labor market woes of low-skilled male workers in the United States over the past several decades have been well documented, the academic literature identifying causal factors leading to declines in labor force participation (LFP) by young, low-skilled males remains scant. To address this gap, I use the timing and characteristics of welfare-reform policies implemented during the 1990s and fixed-effects, instrumental variable regression modeling to show that policies seeking to increase LFP rates for low-skilled single mothers inadvertently led to labor force exit by young, low-skilled single males. Using data from the Current Population Survey and a bundle of work inducements enacted by states throughout the 1990s as exogenous variation in a quasi-experimental design, I find that the roughly 10 percentage point increase in LFP for low-skilled single mothers facilitated by welfare reform resulted in a statistically significant 2.8 percentage point decline in LFP for young, low-skilled single males. After conducting a series of robustness checks, I conclude that this result is driven entirely by white males, who responded to welfare-reform policies with a 3.7 percentage point decline in labor supply. Young black males, as well as other groups of potentially affected workers, appear to be uninfluenced by the labor supply response of less-educated single mothers to welfare reform. Impacts on young, single white males are large and economically significant, suggesting that nearly 150,000 males departed the formal labor market in response to directed welfare-reform policies.

Single cell gene expression profiling of cortical osteoblast lineage cells.

PubMed

Flynn, James M; Spusta, Steven C; Rosen, Clifford J; Melov, Simon

2013-03-01

In tissues with complex architectures such as bone, it is often difficult to purify and characterize specific cell types via molecular profiling. Single cell gene expression profiling is an emerging technology useful for characterizing transcriptional profiles of individual cells isolated from heterogeneous populations. In this study we describe a novel procedure for the isolation and characterization of gene expression profiles of single osteoblast lineage cells derived from cortical bone. Mixed populations of different cell types were isolated from adult long bones of C57BL/6J mice by enzymatic digestion, and subsequently subjected to FACS to purify and characterize osteoblast lineage cells via a selection strategy using antibodies against CD31, CD45, and alkaline phosphatase (AP), specific for mature osteoblasts. The purified individual osteoblast lineage cells were then profiled at the single cell level via nanofluidic PCR. This method permits robust gene expression profiling on single osteoblast lineage cells derived from mature bone, potentially from anatomically distinct sites. In conjunction with this technique, we have also shown that it is possible to carry out single cell profiling on cells purified from fixed and frozen bone samples without compromising the gene expression signal. The latter finding means the technique can be extended to biopsies of bone from diseased individuals. Our approach for single cell expression profiling provides a new dimension to the transcriptional profile of the primary osteoblast lineage population in vivo, and has the capacity to greatly expand our understanding of how these cells may function in vivo under normal and diseased states. Copyright © 2012 Elsevier Inc. All rights reserved.

The efficacy of single-stage open intramedullary nailing of neglected femur fractures.

PubMed

Boopalan, P R J V C; Sait, Azad; Jepegnanam, Thilak Samuel; Matthai, Thomas; Varghese, Viju Daniel

2014-02-01

Neglected femur fractures are not rare in the developing world. Treatment options include single-stage open reduction and intramedullary nailing, or open release, skeletal traction, and then second-stage open intramedullary nailing, with bone grafting. Single-stage procedures have the potential advantage of avoiding neurovascular complications secondary to acute lengthening, but they require a second operation, with potentially increased resource use and infection risk. We sought to determine the (1) likelihood of union, (2) complications and reoperations, and (3) functional results with single-stage open intramedullary nailing without bone grafting in patients with neglected femur fractures. Between January 2003 and December 2007, 17 consecutive patients presented to our practice with neglected femoral shaft fractures. All were treated with single-stage nailing without bone grafting. There were 15 men and two women with a median age of 27 years. The average time from fracture to treatment was 13 weeks (range, 4-44 weeks). Eleven patients underwent open nailing with interlocked nails and six were treated with cloverleaf Kuntscher nails. Patients were followed for a minimum of 6 months (mean, 33 months; range, 6-72 months). The mean preoperative ROM of the knee was 28° (range, 10°-150°) and femoral length discrepancy was 3.1 cm (range, 1-5 cm). All fractures united and the mean time to union was 16 weeks (range, 7-32 weeks). There were no neurologic complications secondary to acute lengthening. The mean postoperative ROM of the knee was 130° (range, 60°-150°). All patients were able to return to preinjury work. Sixteen patients regained their original femoral length. One-stage open intramedullary nailing of neglected femoral diaphyseal fractures without bone grafting was safe and effective, and obviated the need for a two-stage approach. Although the findings need to be replicated in larger numbers of patients, we believe this technique may be useful in treating patients with this injury, and may offer advantages in resource-constrained environments.

Old and new results about single-photon sensitivity in human vision

NASA Astrophysics Data System (ADS)

Nelson, Philip C.

2016-04-01

It is sometimes said that ‘our eyes can see single photons’. This article begins by finding a more precise version of that claim and reviewing evidence gathered for it up to around 1985 in two distinct realms, those of human psychophysics and single-cell physiology. Finding a single framework that accommodates both kinds of result is then a nontrivial challenge, and one that sets severe quantitative constraints on any model of dim-light visual processing. This article presents one such model and compares it to a recent experiment.

Response of jammed packings to thermal fluctuations

NASA Astrophysics Data System (ADS)

Wu, Qikai; Bertrand, Thibault; Shattuck, Mark D.; O'Hern, Corey S.

2017-12-01

We focus on the response of mechanically stable (MS) packings of frictionless, bidisperse disks to thermal fluctuations, with the aim of quantifying how nonlinearities affect system properties at finite temperature. In contrast, numerous prior studies characterized the structural and mechanical properties of MS packings of frictionless spherical particles at zero temperature. Packings of disks with purely repulsive contact interactions possess two main types of nonlinearities, one from the form of the interaction potential (e.g., either linear or Hertzian spring interactions) and one from the breaking (or forming) of interparticle contacts. To identify the temperature regime at which the contact-breaking nonlinearities begin to contribute, we first calculated the minimum temperatures Tc b required to break a single contact in the MS packing for both single- and multiple-eigenmode perturbations of the T =0 MS packing. We find that the temperature required to break a single contact for equal velocity-amplitude perturbations involving all eigenmodes approaches the minimum value obtained for a perturbation in the direction connecting disk pairs with the smallest overlap. We then studied deviations in the constant volume specific heat C¯V and deviations of the average disk positions Δ r from their T =0 values in the temperature regime TC ¯V100 for linear spring interactions is independent of system size. This result emphasizes that contact-breaking nonlinearities are dominant over form nonlinearities in the low-temperature range Tc b

Integrative clinical sequencing in the management of children and young adults with refractory or relapsed cancer

PubMed Central

Mody, Rajen J.; Wu, Yi-Mi; Lonigro, Robert J.; Cao, Xuhong; Roychowdhury, Sameek; Vats, Pankaj; Frank, Kevin M.; Prensner, John R.; Asangani, Irfan; Palanisamy, Nallasivam; Dillman, Jonathan R.; Rabah, Raja M.; Kunju, Laxmi Priya; Everett, Jessica; Raymond, Victoria M.; Ning, Yu; Su, Fengyun; Wang, Rui; Stoffel, Elena M.; Innis, Jeffrey W.; Roberts, J. Scott; Robertson, Patricia L.; Yanik, Gregory; Chamdin, Aghiad; Connelly, James A.; Choi, Sung; Harris, Andrew C.; Kitko, Carrie; Rao, Rama Jasty; Levine, John E.; Castle, Valerie P.; Hutchinson, Raymond J.; Talpaz, Moshe; Robinson, Dan R.; Chinnaiyan, Arul M.

2016-01-01

Importance Cancer is caused by a diverse array of somatic and germline genomic aberrations. Advances in genomic sequencing technologies have improved the ability to detect these molecular aberrations with greater sensitivity. However, integrating them into clinical management in an individualized manner has proven challenging. Objective To evaluate the use of integrative clinical sequencing and genetic counseling in the assessment and treatment of children and young adults with cancer. Design, Settings and Participants An observational, consecutive case series (May 2012–October 2014) of 102 children and young adults (mean age, 10.6; median age, 11.5, range: 0–22 years) with relapsed, refractory, or rare cancer at a single major academic medical center. Exposures Each participant underwent integrative clinical exome (tumor and germline DNA) and transcriptome (tumor RNA) sequencing along with genetic counseling. Results were discussed in a multi-disciplinary Precision Medicine Tumor Board (PMTB) and recommendations were reported to treating physicians and families. Main Outcomes and Measures Proportion of patients with potentially actionable findings (PAF), results of clinical actions based on integrative clinical sequencing (ICS), and estimated proportion of patients or their families at risk for future cancer. PAF was defined as any genomic findings discovered during sequencing analysis that could lead to a 1) change in patient management by providing a targetable molecular aberration, 2) change in diagnosis or risk stratification or 3) provides cancer-related germline findings, which inform patients/families about a potential future risk of various cancers; Results We screened 104 patients and enrolled 102 patients of which 91 (89%) had adequate tumor tissue available to complete sequencing and only these patients were included in all subsequent calculations, including 28 (31%) with hematological malignancies and 63 (69%) with solid tumors. Overall, 42 (46%) patients had PAFs which changed patient management including, 54% (15/28) with hematological malignancies and 43% (27/63) with solid tumors. Overall, individualized actions were taken in 23 of the 91 (25%) patients and families based on actionable ICS findings, including change in treatment in 14 (15%) and genetic counseling for future cancer risk in 9 (10%) patients. 9/91 (10%) of these personalized clinical interventions resulted in ongoing partial clinical remission of 8–16 months duration or help sustain complete clinical remission of 6–21 months duration. All 9 (10%) patients and families with actionable incidental genetic findings agreed to formal genetic counseling and screening. Conclusions and Relevance In this single center case series of children and young adults with relapsed or refractory cancer, incorporation of data from integrative clinical sequencing into clinical management was feasible, revealed potentially actionable findings in 46% of patients, and was associated with change in treatment and family genetic counseling in a small proportion of patients. The lack of a control group limited our ability to judge whether better clinical outcomes were achieved compared to standard care. PMID:26325560

Relationship between single nucleotide polymorphism of glycogen synthase gene of Pacific oyster Crassostrea gigas and its glycogen content

NASA Astrophysics Data System (ADS)

Liu, Siwei; Li, Qi; Yu, Hong; Kong, Lingfeng

2017-02-01

Glycogen is important not only for the energy supplementary of oysters, but also for human consumption. High glycogen content can improve the stress survival of oyster. A key enzyme in glycogenesis is glycogen synthase that is encoded by glycogen synthase gene GYS. In this study, the relationship between single nucleotide polymorphisms (SNPs) in coding regions of Crassostrea gigas GYS (Cg-GYS) and individual glycogen content was investigated with 321 individuals from five full-sib families. Single-strand conformation polymorphism (SSCP) procedure was combined with sequencing to confirm individual SNP genotypes of Cg-GYS. Least-square analysis of variance was performed to assess the relationship of variation in glycogen content of C. gigas with single SNP genotype and SNP haplotype. As a consequence, six SNPs were found in coding regions to be significantly associated with glycogen content ( P < 0.01), from which we constructed four main haplotypes due to linkage disequilibrium. Furthermore, the most effective haplotype H2 (GAGGAT) had extremely significant relationship with high glycogen content ( P < 0.0001). These findings revealed the potential influence of Cg-GYS polymorphism on the glycogen content and provided molecular biological information for the selective breeding of good quality traits of C. gigas.

Genotype Reconstruction of Paternity in European Lobsters (Homarus gammarus).

PubMed

Ellis, Charlie D; Hodgson, David J; André, Carl; Sørdalen, Tonje K; Knutsen, Halvor; Griffiths, Amber G F

2015-01-01

Decapod crustaceans exhibit considerable variation in fertilisation strategies, ranging from pervasive single paternity to the near-ubiquitous presence of multiple paternity, and such knowledge of mating systems and behaviour are required for the informed management of commercially-exploited marine fisheries. We used genetic markers to assess the paternity of individual broods in the European lobster, Homarus gammarus, a species for which paternity structure is unknown. Using 13 multiplexed microsatellite loci, three of which are newly described in this study, we genotyped 10 eggs from each of 34 females collected from an Atlantic peninsula in the south-western United Kingdom. Single reconstructed paternal genotypes explained all observed progeny genotypes in each of the 34 egg clutches, and each clutch was fertilised by a different male. Simulations indicated that the probability of detecting multiple paternity was in excess of 95% if secondary sires account for at least a quarter of the brood, and in excess of 99% where additional sire success was approximately equal. Our results show that multiple paternal fertilisations are either absent, unusual, or highly skewed in favour of a single male among H. gammarus in this area. Potential mechanisms upholding single paternal fertilisation are discussed, along with the prospective utility of parentage assignments in evaluations of hatchery stocking and other fishery conservation approaches in light of this finding.

Reciprocal and Complementary Sibling Interactions: Relations with Socialization Outcomes in the Kindergarten Classroom

PubMed Central

Harrist, Amanda W.; Achacoso, Joseph A.; John, Aesha; Pettit, Gregory S.; Bates, John E.; Dodge, Kenneth A.

2013-01-01

Research Findings To examine associations between sibling interaction patterns and later social outcomes in single- and two-parent families, 113 kindergarteners took part in naturalistic observations at home with siblings, classmates participated in sociometric interviews, and teachers completed behavior ratings. Sibling interactions were coded using a newly-developed 39-item checklist, and proportions of complementary and reciprocal sibling interactions computed. Complementarity occurred more among dyads where kindergartners were with toddler or infant siblings than among kindergartners with older or near-age younger siblings. Higher levels of complementarity predicted lower levels of internalizing but were not related to externalizing problems. Kindergartners’ sociometric status in the classroom differed as a function of sibling interaction patterns, with neglected and controversial children experiencing less complementarity/more reciprocity than popular, average, and rejected children. Finally, there was some evidence for differential associations of sibling interaction patterns with social outcomes for children in single- versus two-parent families: regressions testing interaction effects show sibling reciprocity positively associated with kindergartners’ social skills only in single-parent families, and complementary sibling interactions positively related to internalizing problems only in two-parent families. Implications for Practice Those working with divorcing or other single-parent families might consider sibling interactions as a potential target for social skill building. PMID:26005311

Antioxidant and anticholinesterase potential of diterpenoid alkaloids from Aconitum heterophyllum.

PubMed

Ahmad, Hanif; Ahmad, Shujaat; Shah, Syed Adnan Ali; Latif, Abdul; Ali, Mumtaz; Khan, Farman Ali; Tahir, Muhammad Nawaz; Shaheen, Farzana; Wadood, Abdul; Ahmad, Manzoor

2017-07-01

Extensive chromatographic separations performed on the basic (pH=8-10) chloroform soluble fraction of Aconitum heterophyllum resulted in the isolation of three new diterpenoid alkaloids, 6β-Methoxy, 9β-dihydroxylheteratisine (1), 1α,11,13β-trihydroxylhetisine (2), 6,15β-dihydroxylhetisine (3), and the known compounds iso-atisine (4), heteratisine (5), hetisinone (6), 19-epi-isoatisine (7), and atidine (8). Structures of the isolated compounds were established by means of mass and NMR spectroscopy as well as single crystal X-ray crystallography. Compounds 1-8 were screened for their antioxidant and enzyme inhibition activities followed by in silico studies to find out the possible inhibitory mechanism of the tested compounds. This work is the first report demonstrating significant antioxidant and anticholinesterase potentials of diterpenoid alkaloids isolated from a natural source. Copyright © 2017 Elsevier Ltd. All rights reserved.

Pilot testing a couples-focused intervention for mild cognitive impairment.

PubMed

Lu, Yvonne Yueh-Feng; Haase, Joan E; Weaver, Michael

2013-05-01

The purpose of this pilot was to evaluate the acceptability, feasibility, and potential benefits of the multicomponent, Daily Enhancement of Meaningful Activity (DEMA) intervention, which was tailored to help couples facing mild cognitive impairment (MCI) work together to meet goals, remain engaged in meaningful activities, and adapt to changes over time. Using a single-group design, 10 individuals with MCI and their family caregivers were recruited to participate in the DEMA intervention over 6 biweekly sessions. Data were collected pre-and at 1 week and 3 months postintervention completion rates indicated the program and study procedures were well accepted. Qualitative and quantitative finding indicated positive trends in meaningful activity performance and maintenance of health-related outcomes, as well as high program satisfaction. The DEMA intervention is potentially promising but needs further testing in a randomized clinical trial.

Absence or presence? Complexities in the donor narratives of single mothers using sperm donation.

PubMed

Zadeh, S; Freeman, T; Golombok, S

2016-01-01

How do single mothers who have conceived a child via anonymous or identity-release sperm donation represent the donor? While the majority of mothers described their anonymous and identity-release donors as symbolically significant to their families, others were more likely to emphasize that their lack of information limited their thoughts about him. There is limited understanding of the factors that impact upon how single mothers represent the donor, and whether or not they are determined by specific donor programmes (anonymous or identity-release). Qualitative interviews were conducted with 46 women who had treatment at a UK licensed fertility clinic during the years 2003-2009. Twenty mothers (43%) had used an anonymous donor, and 26 (57%) had used an identity-release donor. Among the 46 mothers interviewed, all had at least one child conceived via donor insemination who was between the ages of 4 and 9 years. Mothers were heterosexual and were currently without a live-in and/or long-term partner. Interview data were analysed qualitatively according to the principles of thematic analysis. Findings indicated marked diversity in single mothers' representations of the donor. Most (n = 27) mothers talked about the donor as symbolically significant to family life and were likely to describe the donor as (i) a gift-giver, (ii) a gene-giver and (iii) a potential partner. Others (n = 16) talked about the donor as (i) unknown, (ii) part of a process and (iii) out of sight and out of mind. There were mothers with anonymous and identity-release donors in each group. Several mothers explained that their feelings about the donor had changed over time. All mothers conceived at a licensed fertility clinic in the UK. Findings are limited to individuals willing and able to take part in research on donor conception. The study offers greater insight into the factors influencing the donor narratives produced in single-mother families. It has implications for the counselling and treatment of single women seeking fertility treatment with donor gametes in both anonymous and identity-release programmes. Given that the number of clinics offering identity-release programmes worldwide seems to be increasing, the finding that single women may have varying preferences with regard to donor type, and varying interest levels with regard to donor information, is important. It is recommended that clinicians and other fertility clinic staff guard against making assumptions about such preferences and any thoughts and feelings about the donor or donor information on the basis of marital status. This study was funded by the Wellcome Trust [097857/Z/11/Z]. The authors have no conflicts of interest to declare. © The Author 2015. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology.

Adsorption of Ca2+ on single layer graphene oxide.

PubMed

Terracciano, Amalia; Zhang, Jianfeng; Christodoulatos, Christos; Wu, Fengchang; Meng, Xiaoguang

2017-07-01

Graphene oxide (GO) holds great promise for a broad array of applications in many fields, but also poses serious potential risks to human health and the environment. In this study, the adsorptive properties of GO toward Ca 2+ and Na + were investigated using batch adsorption experiments, zeta potential measurements, and spectroscopic analysis. When pH increased from 4 to 9, Ca 2+ adsorption by GO and the zeta potential of GO increased significantly. Raman spectra suggest that Ca 2+ was strongly adsorbed on the GO via -COOCa + formation. On the other hand, Na + was adsorbed into the electrical diffuse layer as an inert counterion to increase the diffuse layer zeta potential. While the GO suspension became unstable with increasing pH from 4 to 10 in the presence of Ca 2+ , it was more stable at higher pH in the NaCl solution. The findings of this research provide insights in the adsorption of Ca 2+ on GO and fundamental basis for prediction of its effect on the colloidal stability of GO in the environment. Copyright © 2017. Published by Elsevier B.V.

Primary central nervous system lymphoma in immunocompetent individuals: a single center experience.

PubMed

Aki, Hilal; Uzunaslan, Didem; Saygin, Caner; Batur, Sebnem; Tuzuner, Nukhet; Kafadar, Ali; Ongoren, Seniz; Oz, Buge

2013-01-01

Primary central nervous system lymphoma (PCNSL) is defined as the involvement of brain, leptomeninges, eyes or spinal cord by non-Hodgkin lymphoma. The role of various prognostic markers in predicting adverse outcome is debated. To investigate the clinical and immunohistochemical findings of immunocompetent PCNSL cases (39 cases) diagnosed at the study center, and evaluate the influence of potential prognostic factors on overall survival (OS) of patients. Data regarding patient characteristics, neuroimaging, pathological and immunohistochemical features and follow-up were obtained from patient records. The influence of potential prognostic parameters on OS was investigated by log-rank test and Cox regression analysis. Patients who received combined chemotherapy and radiotherapy had a significantly better OS when compared to chemotherapy alone. Other variables included in this study were not associated with a significant survival advantage. In this study, we failed to demonstrate a relationship between different clinicopathological variables and OS of patients. Prospective studies with large patient series are needed to investigate other potential prognostic factors.

Hawking-Moss instanton in nonlinear massive gravity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Ying-li; Saito, Ryo; Sasaki, Misao, E-mail: yingli@yukawa.kyoto-u.ac.jp, E-mail: rsaito@yukawa.kyoto-u.ac.jp, E-mail: misao@yukawa.kyoto-u.ac.jp

2013-02-01

As a first step toward understanding a lanscape of vacua in a theory of non-linear massive gravity, we consider a landscape of a single scalar field and study tunneling between a pair of adjacent vacua. We study the Hawking-Moss (HM) instanton that sits at a local maximum of the potential, and evaluate the dependence of the tunneling rate on the parameters of the theory. It is found that provided with the same physical HM Hubble parameter H{sub HM}, depending on the values of parameters α{sub 3} and α{sub 4} in the action (2.2), the corresponding tunneling rate can be eithermore » enhanced or suppressed when compared to the one in the context of General Relativity (GR). Furthermore, we find the constraint on the ratio of the physical Hubble parameter to the fiducial one, which constrains the form of potential. This result is in sharp contrast to GR where there is no bound on the minimum value of the potential.« less

Mouse model of chromosome mosaicism reveals lineage-specific depletion of aneuploid cells and normal developmental potential.

PubMed

Bolton, Helen; Graham, Sarah J L; Van der Aa, Niels; Kumar, Parveen; Theunis, Koen; Fernandez Gallardo, Elia; Voet, Thierry; Zernicka-Goetz, Magdalena

2016-03-29

Most human pre-implantation embryos are mosaics of euploid and aneuploid cells. To determine the fate of aneuploid cells and the developmental potential of mosaic embryos, here we generate a mouse model of chromosome mosaicism. By treating embryos with a spindle assembly checkpoint inhibitor during the four- to eight-cell division, we efficiently generate aneuploid cells, resulting in embryo death during peri-implantation development. Live-embryo imaging and single-cell tracking in chimeric embryos, containing aneuploid and euploid cells, reveal that the fate of aneuploid cells depends on lineage: aneuploid cells in the fetal lineage are eliminated by apoptosis, whereas those in the placental lineage show severe proliferative defects. Overall, the proportion of aneuploid cells is progressively depleted from the blastocyst stage onwards. Finally, we show that mosaic embryos have full developmental potential, provided they contain sufficient euploid cells, a finding of significance for the assessment of embryo vitality in the clinic.

Molecular Insights into Carbon Nanotube Supercapacitors: Capacitance Independent of Voltage and Temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Guang; Li, Song; Atchison, Jennifer S.

2013-04-12

Molecular dynamics (MD) simulations of supercapacitors with single-walled carbon nanotube (SWCNT) electrodes in room-temperature ionic liquids were performed to investigate the influences of the applied electrical potential, the radius/curvature of SWCNTs, and temperature on their capacitive behavior. It is found that (1) SWCNTs-based supercapacitors exhibit a near-flat capacitance–potential curve, (2) the capacitance increases as the tube radius decreases, and (3) the capacitance depends little on the temperature. We report the first MD study showing the influence of the electrode curvature on the capacitance–potential curve and negligible dependence of temperature on capacitance of tubular electrode. The latter is in good agreementmore » with recent experimental findings and is attributed to the similarity of the electrical double layer (EDL) microstructure with temperature varying from 260 to 400 K. The electrode curvature effect is explained by the dominance of charge overscreening and increased ion density per unit area of electrode surface.« less

Thermodynamic scaling of glassy dynamics and dynamic heterogeneities in metallic glass-forming liquid

NASA Astrophysics Data System (ADS)

Hu, Yuan-Chao; Shang, Bao-Shuang; Guan, Peng-Fei; Yang, Yong; Bai, Hai-Yang; Wang, Wei-Hua

2016-09-01

A ternary metallic glass-forming liquid is found to be not strongly correlating thermodynamically, but its average dynamics, dynamic heterogeneities including the high order dynamic correlation length, and static structure are still well described by thermodynamic scaling with the same scaling exponent γ. This may indicate that the metallic liquid could be treated as a single-parameter liquid. As an intrinsic material constant stemming from the fundamental interatomic interactions, γ is theoretically predicted from the thermodynamic fluctuations of the potential energy and the virial. Although γ is conventionally understood merely from the repulsive part of the inter-particle potentials, the strong correlation between γ and the Grüneisen parameter up to the accuracy of the Dulong-Petit approximation demonstrates the important roles of anharmonicity and attractive force of the interatomic potential in governing glass transition of metallic glassformers. These findings may shed light on how to understand metallic glass formation from the fundamental interatomic interactions.

Why is the correlation between gene importance and gene evolutionary rate so weak?

PubMed

Wang, Zhi; Zhang, Jianzhi

2009-01-01

One of the few commonly believed principles of molecular evolution is that functionally more important genes (or DNA sequences) evolve more slowly than less important ones. This principle is widely used by molecular biologists in daily practice. However, recent genomic analysis of a diverse array of organisms found only weak, negative correlations between the evolutionary rate of a gene and its functional importance, typically measured under a single benign lab condition. A frequently suggested cause of the above finding is that gene importance determined in the lab differs from that in an organism's natural environment. Here, we test this hypothesis in yeast using gene importance values experimentally determined in 418 lab conditions or computationally predicted for 10,000 nutritional conditions. In no single condition or combination of conditions did we find a much stronger negative correlation, which is explainable by our subsequent finding that always-essential (enzyme) genes do not evolve significantly more slowly than sometimes-essential or always-nonessential ones. Furthermore, we verified that functional density, approximated by the fraction of amino acid sites within protein domains, is uncorrelated with gene importance. Thus, neither the lab-nature mismatch nor a potentially biased among-gene distribution of functional density explains the observed weakness of the correlation between gene importance and evolutionary rate. We conclude that the weakness is factual, rather than artifactual. In addition to being weakened by population genetic reasons, the correlation is likely to have been further weakened by the presence of multiple nontrivial rate determinants that are independent from gene importance. These findings notwithstanding, we show that the principle of slower evolution of more important genes does have some predictive power when genes with vastly different evolutionary rates are compared, explaining why the principle can be practically useful despite the weakness of the correlation.

Method for Estimating Evaporative Potential (IM/CLO) from ASTM Standard Single Wind Velocity Measures

DTIC Science & Technology

2016-08-10

IM/CLO) FROM ASTM STANDARD SINGLE WIND VELOCITY MEASURES DISCLAIMER The opinions or assertions contained herein are the private views of the...USARIEM TECHNICAL REPORT T16-14 METHOD FOR ESTIMATING EVAPORATIVE POTENTIAL (IM/CLO) FROM ASTM STANDARD SINGLE WIND VELOCITY...ASTM STANDARD SINGLE WIND VELOCITY MEASURES Adam W. Potter Biophysics and Biomedical Modeling Division U.S. Army Research Institute of Environmental

Hemoglobin genetics: recent contributions of GWAS and gene editing

PubMed Central

Smith, Elenoe C.; Orkin, Stuart H.

2016-01-01

The β-hemoglobinopathies are inherited disorders resulting from altered coding potential or expression of the adult β-globin gene. Impaired expression of β-globin reduces adult hemoglobin (α2β2) production, the hallmark of β-thalassemia. A single-base mutation at codon 6 leads to formation of HbS (α2βS2) and sickle cell disease. While the basis of these diseases is known, therapy remains largely supportive. Bone marrow transplantation is the only curative therapy. Patients with elevated levels of fetal hemoglobin (HbF, α2γ2) as adults exhibit reduced symptoms and enhanced survival. The β-globin gene locus is a paradigm of cell- and developmental stage-specific regulation. Although the principal erythroid cell transcription factors are known, mechanisms responsible for silencing of the γ-globin gene were obscure until application of genome-wide association studies (GWAS). Here, we review findings in the field. GWAS identified BCL11A as a candidate negative regulator of γ-globin expression. Subsequent studies have established BCL11A as a quantitative repressor. GWAS-related single-nucleotide polymorphisms lie within an essential erythroid enhancer of the BCL11A gene. Disruption of a discrete region within the enhancer reduces BCL11A expression and induces HbF expression, providing the basis for gene therapy using gene editing tools. A recently identified, second silencing factor, leukemia/lymphoma-related factor/Pokemon, shares features with BCL11A, including interaction with the nucleosome remodeling deacetylase repressive complex. These findings suggest involvement of a common pathway for HbF silencing. In addition, we discuss other factors that may be involved in γ-globin gene silencing and their potential manipulation for therapeutic benefit in treating the β-hemoglobinopathies. PMID:27340226

Impact of acute administration of escitalopram on the processing of emotional and neutral images: a randomized crossover fMRI study of healthy women.

PubMed

Outhred, Tim; Das, Pritha; Felmingham, Kim L; Bryant, Richard A; Nathan, Pradeep J; Malhi, Gin S; Kemp, Andrew H

2014-07-01

Acute neural effects of antidepressant medication on emotion processing biases may provide the foundation on which clinical outcomes are based. Along with effects on positive and negative stimuli, acute effects on neutral stimuli may also relate to antidepressant efficacy, yet these effects are still to be investigated. The present study therefore examined the impact of a single dose of the selective serotonin reuptake inhibitor escitalopram (20 mg) on positive, negative and neutral stimuli using pharmaco-fMRI. Within a double-blind, randomized, placebo-controlled crossover design, healthy women completed 2 sessions of treatment administration and fMRI scanning separated by a 1-week washout period. We enrolled 36 women in our study. When participants were administered escitalopram relative to placebo, left amygdala activity was increased and right inferior frontal gyrus (IFG) activity was decreased during presentation of positive pictures (potentiation of positive emotion processing). In contrast, escitalopram was associated with decreased left amygdala and increased right IFG activity during presentation of negative pictures (attenuation of negative emotion processing). In addition, escitalopram decreased right IFG activity during the processing of neutral stimuli, akin to the effects on positive stimuli (decrease in negative appraisal). Although we used a women-only sample to reduce heterogeneity, our results may not generalize to men. Potential unblinding, which was related to the subjective occurrence of side effects, occurred in the study; however, manipulation check analyses demonstrated that results were not impacted. These novel findings demonstrate that a single dose of the commonly prescribed escitalopram facilitates a positive information processing bias. These findings provide an important lead for better understanding effects of antidepressant medication.

Fluorescent carbon nanoparticles derived from natural materials of mango fruit for bio-imaging probes

NASA Astrophysics Data System (ADS)

Jeong, Chan Jin; Roy, Arup Kumer; Kim, Sung Han; Lee, Jung-Eun; Jeong, Ji Hoon; Insik; Park, Sung Young

2014-11-01

Water soluble fluorescent carbon nanoparticles (FCP) obtained from a single natural source, mango fruit, were developed as unique materials for non-toxic bio-imaging with different colors and particle sizes. The prepared FCPs showed blue (FCP-B), green (FCP-G) and yellow (FCP-Y) fluorescence, derived by the controlled carbonization method. The FCPs demonstrated hydrodynamic diameters of 5-15 nm, holding great promise for clinical applications. The biocompatible FCPs demonstrated great potential in biological fields through the results of in vitro imaging and in vivo biodistribution. Using intravenously administered FCPs with different colored particles, we precisely defined the clearance and biodistribution, showing rapid and efficient urinary excretion for safe elimination from the body. These findings therefore suggest the promising possibility of using natural sources for producing fluorescent materials.Water soluble fluorescent carbon nanoparticles (FCP) obtained from a single natural source, mango fruit, were developed as unique materials for non-toxic bio-imaging with different colors and particle sizes. The prepared FCPs showed blue (FCP-B), green (FCP-G) and yellow (FCP-Y) fluorescence, derived by the controlled carbonization method. The FCPs demonstrated hydrodynamic diameters of 5-15 nm, holding great promise for clinical applications. The biocompatible FCPs demonstrated great potential in biological fields through the results of in vitro imaging and in vivo biodistribution. Using intravenously administered FCPs with different colored particles, we precisely defined the clearance and biodistribution, showing rapid and efficient urinary excretion for safe elimination from the body. These findings therefore suggest the promising possibility of using natural sources for producing fluorescent materials. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04805a

Effectiveness of native and exotic arbuscular mycorrhizal fungi on nutrient uptake and ion homeostasis in salt-stressed Cajanus cajan L. (Millsp.) genotypes.

PubMed

Garg, Neera; Pandey, Rekha

2015-04-01

Soil salinity is an increasing problem worldwide, restricting plant growth and production. Research findings show that arbuscular mycorrhizal (AM) fungi have the potential to reduce negative effects of salinity. However, plant growth responses to AM fungi vary as a result of genetic variation in mycorrhizal colonization and plant growth responsiveness. Thus, profitable use of AM requires selection of a suitable combination of host plant and fungal partner. A greenhouse experiment was conducted to compare effectiveness of a native AM fungal inoculum sourced from saline soil and two single exotic isolates, Funneliformis mossseae and Rhizophagus irregularis (single or dual mix), on Cajanus cajan (L.) Millsp. genotypes (Paras and Pusa 2002) under salt stress (0-100 mM NaCl). While salinity reduced plant biomass and disturbed ionic status in both genotypes, Pusa 2002 was more salt tolerant and ensured higher AM fungal colonization, plant biomass and nutrient content with favourable ion status under salinity. Although all AM fungi reduced negative effects of salt stress, R. irregularis (alone or in combination with F. mosseae) displayed highest efficiency under salinity, resulting in highest biomass, yield, nutrient uptake and improved membrane stability with favourable K(+)/Na(+) and Ca(2+)/Na(+) ratios in the host plant. Higher effectiveness of R. irregularis correlated with higher root colonization, indicating that the symbiosis formed by R. irregularis had more stable viability and efficiency under salt stress. These findings enhance understanding of the functional diversity of AM fungi in ameliorating plant salt stress tolerance and suggest the potential use of R. irregularis for increasing Cajanus cajan productivity in saline soils.

Clinical utility of MRI and SPECT in the diagnosis of cognitive impairment referred to memory clinic.

PubMed

Guinane, John; Ng, Boon Lung

2018-05-01

ABSTRACTBackground:Despite of their limited availability and potential for significant variation between and within each modality, this is the first study to prospectively measure the clinical utility of MRI and/or SPECT brain scanning in addition to the routine diagnostic workup of patients presenting to memory clinic. A single center study was conducted over a convenience of 12-month sampling period. For each patient referred for MRI and/or SPECT scanning, the primary geriatrician or psychogeriatrician was asked to assign an initial diagnosis. The initial diagnosis was then compared with the final consensus diagnosis after any scans or neuropsychology testing had been completed. During the 12-month study period, 66 patients (26%) were referred for scans out of a total of 253 patients included in the study. There were 16/44 (36%) positive MRI outcomes and 13/35 (37%) positive SPECT outcomes. The diagnosis changed consistent with the MRI scan findings in 11/44 (25%) and changed consistent with the SPECT scan findings in 9/35 (26%). Potentially reversible pathology was identified in a single patient, 1/50 (2%), via an MRI scan that suggested normal pressure hydrocephalus. The number needed to test for one positive outcome was 3.8 (95% CI 2.0-23.3), 6.0 (95% CI NA), and 1.7 (95% CI 1.3-2.5) for MRI only, SPECT only, and MRI and SPECT together, respectively. The clinical utility of MRI and/or SPECT scanning in this study may be broadly superior to the available international evidence, and further research is needed to identify predictors of positive scan outcomes.

Perspectives about family meals from single-headed and dual-headed households: a qualitative analysis.

PubMed

Berge, Jerica M; Hoppmann, Caroline; Hanson, Carrie; Neumark-Sztainer, Dianne

2013-12-01

Cross-sectional and longitudinal research has shown that family meals are protective for adolescent healthful eating behaviors. However, little is known about what parents think of these findings and whether parents from single- vs dual-headed households have differing perspectives about the findings. In addition, parents' perspectives regarding barriers to applying the findings on family meals in their own homes and suggestions for more widespread adoption of the findings are unknown. The current study aimed to identify single- and dual-headed household parents' perspectives regarding the research findings on family meals, barriers to applying the findings in their own homes, and suggestions for helping families have more family meals. The current qualitative study included 59 parents who participated in substudy of two linked multilevel studies-EAT 2010 (Eating and Activity in Teens) and Families and Eating and Activity in Teens (F-EAT). Parents (91.5% female) were racially/ethnically and socioeconomically diverse. Data were analyzed using a grounded theory approach. Results from the current study suggest that parents from both single- and dual-headed households have similar perspectives regarding why family meals are protective for healthful eating habits for adolescents (eg, provides structure/routine, opportunities for communication, connection), but provide similar and different reasons for barriers to family meals (eg, single-headed=cost vs dual-headed=lack of creativity) and ideas and suggestions for how to increase the frequency of family meals (eg, single-headed=give fewer options vs dual-headed=include children in the meal preparation). Findings can help inform public health intervention researchers and providers who work with adolescents and their families to understand how to approach discussions regarding reasons for having family meals, barriers to carrying out family meals, and ways to increase family meals depending on family structure. Copyright © 2013 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

Perspectives about Family Meals from Single-Headed and Dual-Headed Households: A Qualitative Analysis

PubMed Central

Berge, Jerica M.; Hoppmann, Caroline; Hanson, Carrie; Neumark-Sztainer, Dianne

2013-01-01

Cross-sectional and longitudinal research has shown that family meals are protective for adolescent healthful eating behaviors. However, little is known about what parents think of these findings and whether parents from single- versus dual-headed households have differing perspectives about the findings. Additionally, parents’ perspectives regarding barriers to applying the findings on family meals in their own homes and suggestions for more wide-spread adoption of the findings are unknown. The current study aimed to identify single- and dual-headed household parents’ perspectives regarding the research findings on family meals, barriers to applying the findings in their own homes and suggestions for helping families have more family meals. The current qualitative study included 59 parents who participated in sub-study of two linked multi-level studies—EAT 2010 (Eating and Activity in Teens) and Families and Eating and Activity in Teens (F-EAT). Parents (91.5% female) were racially/ethnically and socio-economically diverse. Data were analyzed using a grounded theory approach. Results from the current study suggest that parents from both single- and dual-headed households have similar perspectives regarding why family meals are protective for healthful eating habits for adolescents (e.g., provides structure/routine, opportunities for communication, connection), but provide similar and different reasons for barriers to family meals (e.g., single-headed=cost vs. dual-headed=lack of creativity) and ideas and suggestions for how to increase the frequency of family meals (e.g., single-headed=give fewer options vs. dual-headed=include children in the meal preparation). Findings may help inform public health intervention researchers and providers who work with adolescents and their families to understand how to approach discussions regarding reasons for having family meals, barriers to carrying out family meals and ways to increase family meals depending on family structure. PMID:24238144

Cortical actin networks induce spatio-temporal confinement of phospholipids in the plasma membrane - a minimally invasive investigation by STED-FCS

NASA Astrophysics Data System (ADS)

Andrade, Débora M.; Clausen, Mathias P.; Keller, Jan; Mueller, Veronika; Wu, Congying; Bear, James E.; Hell, Stefan W.; Lagerholm, B. Christoffer; Eggeling, Christian

2015-06-01

Important discoveries in the last decades have changed our view of the plasma membrane organisation. Specifically, the cortical cytoskeleton has emerged as a key modulator of the lateral diffusion of membrane proteins. Cytoskeleton-dependent compartmentalised lipid diffusion has been proposed, but this concept remains controversial because this phenomenon has thus far only been observed with artefact-prone probes in combination with a single technique: single particle tracking. In this paper, we report the first direct observation of compartmentalised phospholipid diffusion in the plasma membrane of living cells using a minimally invasive, fluorescent dye labelled lipid analogue. These observations were made using optical STED nanoscopy in combination with fluorescence correlation spectroscopy (STED-FCS), a technique which allows the study of membrane dynamics on a sub-millisecond time-scale and with a spatial resolution of down to 40 nm. Specifically, we find that compartmentalised phospholipid diffusion depends on the cortical actin cytoskeleton, and that this constrained diffusion is directly dependent on the F-actin branching nucleator Arp2/3. These findings provide solid evidence that the Arp2/3-dependent cortical actin cytoskeleton plays a pivotal role in the dynamic organisation of the plasma membrane, potentially regulating fundamental cellular processes.

Nanoparticle fouling and its combination with organic fouling during forward osmosis process for silver nanoparticles removal from simulated wastewater

NASA Astrophysics Data System (ADS)

Zhao, Yanxiao; Wang, Xinhua; Wang, Zhiwei; Li, Xiufen; Ren, Yueping

2016-05-01

The increasing and wide application of silver nanoparticles (Ag NPs) has resulted in their appearance in wastewater. In consideration of their potential toxicity and environmental impacts, it is necessary to find effective technology for their removal from wastewater. Here, forward osmosis (FO) membrane was applied for Ag NPs removal from wastewater, and single and combined fouling of nanoparticles and organic macromolecules were further investigated during the FO process. The findings demonstrated that FO membrane can effectively remove Ag NPs from wastewater due to its high rejection performance. Fouling tests indicated that water flux declined appreciably even at the beginning of the single Ag NPs fouling test, and more remarkable flux decline and larger amounts of deposited Ag NPs were observed with an increase of Ag NPs concentration. However, the addition of bovine serum albumin (BSA) could effectively alleviate the FO membrane fouling induced by Ag NPs. The interaction between Ag NPs and BSA was responsible for this phenomenon. BSA can easily form a nanoparticle-protein corona surrounded nanoparticles, which prevented nanoparticles from aggregation due to the steric stabilization mechanism. Furthermore, the interaction between BSA and Ag NPs occurred not only in wastewater but also on FO membrane surface.

Small is big: Interactive Trumps passive information in breaking information barriers and impacting behavioral antecedents

DOE PAGES

Beck, Ariane L.; Lakkaraju, Kiran; Rai, Varun; ...

2017-01-18

The wealth of information available on seemingly every topic creates a considerable challenge both for information providers trying to rise above the noise and discerning individuals trying to find relevant, trustworthy information. We approach this information problem by investigating how passive versus interactive information interventions can impact the antecedents of behavior change using the context of solar energy adoption, where persistent information gaps are known to reduce market potential. We use two experiments to investigate the impact of both passive and interactive approaches to information delivery on the antecedents (attitudes, subjective norms, and perceived behavioral control in the Theory ofmore » Planned Behavior) of intentions and behavior, as well as their effect on intentions and behavior directly. The passive information randomized control trial delivered via Amazon Mechanical Turk tests the effectiveness of delivering the same content in a single message versus multiple shorter messages. The interactive information delivery uses an online (mobile and PC) trivia-style gamification platform. Both experiments use the same content and are carried out over a two-week time period. Lastly, our findings suggest that interactive, gamified information has greater impact than passive information, and that shorter multiple messages of passive information are more effective than a single passive message.« less

Small is big: Interactive Trumps passive information in breaking information barriers and impacting behavioral antecedents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beck, Ariane L.; Lakkaraju, Kiran; Rai, Varun

The wealth of information available on seemingly every topic creates a considerable challenge both for information providers trying to rise above the noise and discerning individuals trying to find relevant, trustworthy information. We approach this information problem by investigating how passive versus interactive information interventions can impact the antecedents of behavior change using the context of solar energy adoption, where persistent information gaps are known to reduce market potential. We use two experiments to investigate the impact of both passive and interactive approaches to information delivery on the antecedents (attitudes, subjective norms, and perceived behavioral control in the Theory ofmore » Planned Behavior) of intentions and behavior, as well as their effect on intentions and behavior directly. The passive information randomized control trial delivered via Amazon Mechanical Turk tests the effectiveness of delivering the same content in a single message versus multiple shorter messages. The interactive information delivery uses an online (mobile and PC) trivia-style gamification platform. Both experiments use the same content and are carried out over a two-week time period. Lastly, our findings suggest that interactive, gamified information has greater impact than passive information, and that shorter multiple messages of passive information are more effective than a single passive message.« less

Functional neuroimaging of psychotherapeutic processes in anxiety and depression: from mechanisms to predictions.

PubMed

Lueken, Ulrike; Hahn, Tim

2016-01-01

The review provides an update of functional neuroimaging studies that identify neural processes underlying psychotherapy and predict outcomes following psychotherapeutic treatment in anxiety and depressive disorders. Following current developments in this field, studies were classified as 'mechanistic' or 'predictor' studies (i.e., informing neurobiological models about putative mechanisms versus aiming to provide predictive information). Mechanistic evidence points toward a dual-process model of psychotherapy in anxiety disorders with abnormally increased limbic activation being decreased, while prefrontal activity is increased. Partly overlapping findings are reported for depression, albeit with a stronger focus on prefrontal activation following treatment. No studies directly comparing neural pathways of psychotherapy between anxiety and depression were detected. Consensus is accumulating for an overarching role of the anterior cingulate cortex in modulating treatment response across disorders. When aiming to quantify clinical utility, the need for single-subject predictions is increasingly recognized and predictions based on machine learning approaches show high translational potential. Present findings encourage the search for predictors providing clinically meaningful information for single patients. However, independent validation as a crucial prerequisite for clinical use is still needed. Identifying nonresponders a priori creates the need for alternative treatment options that can be developed based on an improved understanding of those neural mechanisms underlying effective interventions.

Small Is Big: Interactive Trumps Passive Information in Breaking Information Barriers and Impacting Behavioral Antecedents.

PubMed

Beck, Ariane L; Lakkaraju, Kiran; Rai, Varun

2017-01-01

The wealth of information available on seemingly every topic creates a considerable challenge both for information providers trying to rise above the noise and discerning individuals trying to find relevant, trustworthy information. We approach this information problem by investigating how passive versus interactive information interventions can impact the antecedents of behavior change using the context of solar energy adoption, where persistent information gaps are known to reduce market potential. We use two experiments to investigate the impact of both passive and interactive approaches to information delivery on the antecedents (attitudes, subjective norms, and perceived behavioral control in the Theory of Planned Behavior) of intentions and behavior, as well as their effect on intentions and behavior directly. The passive information randomized control trial delivered via Amazon Mechanical Turk tests the effectiveness of delivering the same content in a single message versus multiple shorter messages. The interactive information delivery uses an online (mobile and PC) trivia-style gamification platform. Both experiments use the same content and are carried out over a two-week time period. Our findings suggest that interactive, gamified information has greater impact than passive information, and that shorter multiple messages of passive information are more effective than a single passive message.

A NEW METHOD FOR FINDING POINT SOURCES IN HIGH-ENERGY NEUTRINO DATA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Ke; Miller, M. Coleman

The IceCube collaboration has reported the first detection of high-energy astrophysical neutrinos, including ∼50 high-energy starting events, but no individual sources have been identified. It is therefore important to develop the most sensitive and efficient possible algorithms to identify the point sources of these neutrinos. The most popular current method works by exploring a dense grid of possible directions to individual sources, and identifying the single direction with the maximum probability of having produced multiple detected neutrinos. This method has numerous strengths, but it is computationally intensive and because it focuses on the single best location for a point source,more » additional point sources are not included in the evidence. We propose a new maximum likelihood method that uses the angular separations between all pairs of neutrinos in the data. Unlike existing autocorrelation methods for this type of analysis, which also use angular separations between neutrino pairs, our method incorporates information about the point-spread function and can identify individual point sources. We find that if the angular resolution is a few degrees or better, then this approach reduces both false positive and false negative errors compared to the current method, and is also more computationally efficient up to, potentially, hundreds of thousands of detected neutrinos.« less

Cortical actin networks induce spatio-temporal confinement of phospholipids in the plasma membrane--a minimally invasive investigation by STED-FCS.

PubMed

Andrade, Débora M; Clausen, Mathias P; Keller, Jan; Mueller, Veronika; Wu, Congying; Bear, James E; Hell, Stefan W; Lagerholm, B Christoffer; Eggeling, Christian

2015-06-29

Important discoveries in the last decades have changed our view of the plasma membrane organisation. Specifically, the cortical cytoskeleton has emerged as a key modulator of the lateral diffusion of membrane proteins. Cytoskeleton-dependent compartmentalised lipid diffusion has been proposed, but this concept remains controversial because this phenomenon has thus far only been observed with artefact-prone probes in combination with a single technique: single particle tracking. In this paper, we report the first direct observation of compartmentalised phospholipid diffusion in the plasma membrane of living cells using a minimally invasive, fluorescent dye labelled lipid analogue. These observations were made using optical STED nanoscopy in combination with fluorescence correlation spectroscopy (STED-FCS), a technique which allows the study of membrane dynamics on a sub-millisecond time-scale and with a spatial resolution of down to 40 nm. Specifically, we find that compartmentalised phospholipid diffusion depends on the cortical actin cytoskeleton, and that this constrained diffusion is directly dependent on the F-actin branching nucleator Arp2/3. These findings provide solid evidence that the Arp2/3-dependent cortical actin cytoskeleton plays a pivotal role in the dynamic organisation of the plasma membrane, potentially regulating fundamental cellular processes.

Cortical actin networks induce spatio-temporal confinement of phospholipids in the plasma membrane – a minimally invasive investigation by STED-FCS

PubMed Central

Andrade, Débora M.; Clausen, Mathias P.; Keller, Jan; Mueller, Veronika; Wu, Congying; Bear, James E.; Hell, Stefan W.; Lagerholm, B. Christoffer; Eggeling, Christian

2015-01-01

Important discoveries in the last decades have changed our view of the plasma membrane organisation. Specifically, the cortical cytoskeleton has emerged as a key modulator of the lateral diffusion of membrane proteins. Cytoskeleton-dependent compartmentalised lipid diffusion has been proposed, but this concept remains controversial because this phenomenon has thus far only been observed with artefact-prone probes in combination with a single technique: single particle tracking. In this paper, we report the first direct observation of compartmentalised phospholipid diffusion in the plasma membrane of living cells using a minimally invasive, fluorescent dye labelled lipid analogue. These observations were made using optical STED nanoscopy in combination with fluorescence correlation spectroscopy (STED-FCS), a technique which allows the study of membrane dynamics on a sub-millisecond time-scale and with a spatial resolution of down to 40 nm. Specifically, we find that compartmentalised phospholipid diffusion depends on the cortical actin cytoskeleton, and that this constrained diffusion is directly dependent on the F-actin branching nucleator Arp2/3. These findings provide solid evidence that the Arp2/3-dependent cortical actin cytoskeleton plays a pivotal role in the dynamic organisation of the plasma membrane, potentially regulating fundamental cellular processes. PMID:26118385

HABITABLE PLANETS ECLIPSING BROWN DWARFS: STRATEGIES FOR DETECTION AND CHARACTERIZATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belu, Adrian R.; Selsis, Franck; Raymond, Sean N.

2013-05-10

Given the very close proximity of their habitable zones, brown dwarfs (BDs) represent high-value targets in the search for nearby transiting habitable planets that may be suitable for follow-up occultation spectroscopy. In this paper, we develop search strategies to find habitable planets transiting BDs depending on their maximum habitable orbital period (P{sub HZ{sub out}}). Habitable planets with P{sub HZ{sub out}} shorter than the useful duration of a night (e.g., 8-10 hr) can be screened with 100% completeness from a single location and in a single night (near-IR). More luminous BDs require continuous monitoring for longer duration, e.g., from space ormore » from a longitude-distributed network (one test scheduling achieved three telescopes, 13.5 contiguous hours). Using a simulated survey of the 21 closest known BDs (within 7 pc) we find that the probability of detecting at least one transiting habitable planet is between 4.5{sup +5.6}{sub -1.4}% and 56{sup +31}{sub -13}%, depending on our assumptions. We calculate that BDs within 5-10 pc are characterizable for potential biosignatures with a 6.5 m space telescope using {approx}1% of a five-year mission's lifetime spread over a contiguous segment only one-fifth to one-tenth of this duration.« less

Small Is Big: Interactive Trumps Passive Information in Breaking Information Barriers and Impacting Behavioral Antecedents

PubMed Central

2017-01-01

The wealth of information available on seemingly every topic creates a considerable challenge both for information providers trying to rise above the noise and discerning individuals trying to find relevant, trustworthy information. We approach this information problem by investigating how passive versus interactive information interventions can impact the antecedents of behavior change using the context of solar energy adoption, where persistent information gaps are known to reduce market potential. We use two experiments to investigate the impact of both passive and interactive approaches to information delivery on the antecedents (attitudes, subjective norms, and perceived behavioral control in the Theory of Planned Behavior) of intentions and behavior, as well as their effect on intentions and behavior directly. The passive information randomized control trial delivered via Amazon Mechanical Turk tests the effectiveness of delivering the same content in a single message versus multiple shorter messages. The interactive information delivery uses an online (mobile and PC) trivia-style gamification platform. Both experiments use the same content and are carried out over a two-week time period. Our findings suggest that interactive, gamified information has greater impact than passive information, and that shorter multiple messages of passive information are more effective than a single passive message. PMID:28099478

Single Folding Optical Potential for Elastic Scattering of Protons from 14N and 16O in a Wide Range of Energies

NASA Astrophysics Data System (ADS)

Hamada, Sh.

2018-03-01

Available experimental data for protons elastically scattered from 14N and 16O target nuclei are reanalyzed within the framework of single folding optical potential (SFOP) model. In this model, the real part of the potential is derived on the basis of single folding potential. The renormalization factor N r is extracted for the two aforementioned nuclear systems. Theoretical calculations fairly reproduce the experimental data in the whole angular range. Energy dependence of real and imaginary volume integrals as well as reaction cross sections are discussed.

Single-cell epigenomics: powerful new methods for understanding gene regulation and cell identity.

PubMed

Clark, Stephen J; Lee, Heather J; Smallwood, Sébastien A; Kelsey, Gavin; Reik, Wolf

2016-04-18

Emerging single-cell epigenomic methods are being developed with the exciting potential to transform our knowledge of gene regulation. Here we review available techniques and future possibilities, arguing that the full potential of single-cell epigenetic studies will be realized through parallel profiling of genomic, transcriptional, and epigenetic information.

In silico predictions of LH2 ring sizes from the crystal structure of a single subunit using molecular dynamics simulations.

PubMed

Janosi, Lorant; Keer, Harindar; Cogdell, Richard J; Ritz, Thorsten; Kosztin, Ioan

2011-07-01

Most of the currently known light-harvesting complexes 2 (LH2) rings are formed by 8 or 9 subunits. As of now, questions like "what factors govern the LH2 ring size?" and "are there other ring sizes possible?" remain largely unanswered. Here, we investigate by means of molecular dynamics (MD) simulations and stochastic modeling the possibility of predicting the size of an LH2 ring from the sole knowledge of the high resolution crystal structure of a single subunit. Starting with single subunits of two LH2 rings with known size, that is, an 8-ring from Rs. moliscianum (MOLI) and a 9-ring from Rps. acidophila (ACI), and one with unknown size (referred to as X), we build atomic models of subunit dimers corresponding to assumed 8-, 9-, and 10-ring geometries. After inserting each of the dimers into a lipid-water environment, we determine the preferred angle between the corresponding subunits by three methods: (1) energy minimization, (2) free MD simulations, and (3) potential of mean force calculations. We find that the results from all three methods are consistent with each other, and when taken together, it allows one to predict with reasonable level of confidence the sizes of the corresponding ring structures. One finds that X and ACI very likely form a 9-ring, while MOLI is more likely to form an 8-ring than a 9-ring. Finally, we discuss both the merits and limitations of all three prediction methods. Copyright © 2011 Wiley-Liss, Inc.

Dynamics of Single Flux Rope in the Reconnection Scaling Experiment

NASA Astrophysics Data System (ADS)

Feng, Y.; Sears, J.; Intrator, T.; Weber, T.; Swan, H.; Dunn, J. P.; Gao, K.; Chapdelaine, L.

2013-12-01

A magnetic flux tube threaded by current is a flux rope with helically twisted field lines. In the Reconnection Scaling Experiment (RSX) we use a plasma gun to generate a single flux rope with a choice of axial boundary conditions. If this flux rope is driven hard enough, i.e., when J●B /B2 is larger than the kink instability threshold, we measure a helically distorted kinked structure. Rather than exploding in an Alfvén time, this kink appears to saturate to a steady amplitude, helical, gyrating flux rope, which persists as long as the plasma gun sources the current. To understand it, we have experimentally measured three-dimensional (3D) profiles of various quantities of this flux rope. These quantities include magnetic field B, plasma density n and potential φ, ion flow velocity vi, so that current density J, electron flow velocity ve and electron pressure Pe can also be derived. Consequently we can analyze the single flux rope dynamics systematically in 3D. Besides gyrating (writhe), we also find the flux rope has a spin (twist) center, around which the J×B - ▽Pe ≠ 0 suggesting that there should be other forces for the radial balance. We also find that there is a reverse current moving around with the flux rope at some locations, i.e. there are local induced currents that are not at all apparent from measurements outside the 3D volume. Work supported by LANL-DOE, DOE Fusion Energy Sciences DE-AC52-06NA25396, NASA Geospace NNHIOA044I Basic, CMSO, SULI, NUF.

Modeling the dynamics and kinetics of HIV-1 Gag during viral assembly.

PubMed

Tomasini, Michael D; Johnson, Daniel S; Mincer, Joshua S; Simon, Sanford M

2018-01-01

We report a computational model for the assembly of HIV-1 Gag into immature viral particles at the plasma membrane. To reproduce experimental structural and kinetic properties of assembly, a process occurring on the order of minutes, a coarse-grained representation consisting of a single particle per Gag molecule is developed. The model uses information relating the functional interfaces implicated in Gag assembly, results from cryo electron-tomography, and biophysical measurements from fluorescence microscopy, such as the dynamics of Gag assembly at single virions. These experimental constraints eliminated many classes of potential interactions, and narrowed the model to a single interaction scheme with two non-equivalent interfaces acting to form Gags into a hexamer, and a third interface acting to link hexamers together. This model was able to form into a hexameric structure with correct lattice spacing and reproduced biologically relevant growth rates. We explored the effect of genomic RNA seeding punctum growth, finding that RNA may be a factor in locally concentrating Gags to initiate assembly. The simulation results infer that completion of assembly cannot be governed simply by Gag binding kinetics. However the addition of membrane curvature suggests that budding of the virion from the plasma membrane could factor into slowing incorporation of Gag at an assembly site resulting in virions of the same size and number of Gag molecules independent of Gag concentration or the time taken to complete assembly. To corroborate the results of our simulation model, we developed an analytic model for Gag assembly finding good agreement with the simulation results.

The effect of single and multiple infections on atopy and wheezing in children

PubMed Central

Alcantara-Neves, Neuza Maria; Veiga, Rafael Valente; Dattoli, Vitor Camilo Cavalcante; Fiaccone, Rosimeire Leovigildo; Esquivel, Renata; Cruz, Álvaro Augusto; Cooper, Philip John; Rodrigues, Laura Cunha; Barreto, Maurício Lima

2016-01-01

Background The current epidemic of asthma and atopy has been explained by alterations in immune responses related to reduction in childhood infections. However, the findings of epidemiologic studies investigating the association between infection with atopy and asthma have been inconsistent. Objective We sought to investigate the effect of single or multiple infections (pathogen burden) on atopy and wheeze in urban children from Latin America. Methods Specific IgE against aeroallergens (sIgE) and skin prick test (SPT) reactivity for the most common local allergens were measured in 1128 children aged 4 to 11 years. Data on wheezing and potential confounders were collected by questionnaire. Infections by 8 pathogens were assessed by using serology and stool examination. Associations of wheeze and atopic outcomes with single and multiple infections were analyzed by means of logistic regression. Results Negative results for Toxoplasma gondii were associated with a higher prevalence of sIgE (≥0.70 kU/L), whereas negative results for Ascaris lumbricoides, T gondii, herpes simplex virus, and EBV were associated with a higher prevalence of SPT reactivity. Children with 3 or fewer infection markers had a higher prevalence of sIgE and SPT reactivity compared with those with 4 or more infection markers. However, isolated infections or pathogen burden were not associated with the prevalence of atopic or nonatopic wheeze. Conclusion The findings provide support for the idea that the hygiene hypothesis is operating in an urban Latin American context, but its expression is thus far restricted to the atopic status of patients and not the perceived asthma symptoms. PMID:22035877

Modeling the dynamics and kinetics of HIV-1 Gag during viral assembly

PubMed Central

Tomasini, Michael D.; Johnson, Daniel S.; Mincer, Joshua S.

2018-01-01

We report a computational model for the assembly of HIV-1 Gag into immature viral particles at the plasma membrane. To reproduce experimental structural and kinetic properties of assembly, a process occurring on the order of minutes, a coarse-grained representation consisting of a single particle per Gag molecule is developed. The model uses information relating the functional interfaces implicated in Gag assembly, results from cryo electron-tomography, and biophysical measurements from fluorescence microscopy, such as the dynamics of Gag assembly at single virions. These experimental constraints eliminated many classes of potential interactions, and narrowed the model to a single interaction scheme with two non-equivalent interfaces acting to form Gags into a hexamer, and a third interface acting to link hexamers together. This model was able to form into a hexameric structure with correct lattice spacing and reproduced biologically relevant growth rates. We explored the effect of genomic RNA seeding punctum growth, finding that RNA may be a factor in locally concentrating Gags to initiate assembly. The simulation results infer that completion of assembly cannot be governed simply by Gag binding kinetics. However the addition of membrane curvature suggests that budding of the virion from the plasma membrane could factor into slowing incorporation of Gag at an assembly site resulting in virions of the same size and number of Gag molecules independent of Gag concentration or the time taken to complete assembly. To corroborate the results of our simulation model, we developed an analytic model for Gag assembly finding good agreement with the simulation results. PMID:29677208

Lipid diffusion in the distal and proximal leaflets of supported lipid bilayer membranes studied by single particle tracking

NASA Astrophysics Data System (ADS)

Schoch, Rafael L.; Barel, Itay; Brown, Frank L. H.; Haran, Gilad

2018-03-01

Supported lipid bilayers (SLBs) have been studied extensively as simple but powerful models for cellular membranes. Yet, potential differences in the dynamics of the two leaflets of a SLB remain poorly understood. Here, using single particle tracking, we obtain a detailed picture of bilayer dynamics. We observe two clearly separate diffusing populations, fast and slow, that we associate with motion in the distal and proximal leaflets of the SLB, respectively, based on fluorescence quenching experiments. We estimate diffusion coefficients using standard techniques as well as a new method based on the blur of images due to motion. Fitting the observed diffusion coefficients to a two-leaflet membrane hydrodynamic model allows for the simultaneous determination of the intermonolayer friction coefficient and the substrate-membrane friction coefficient, without any prior assumptions on the strengths of the relevant interactions. Remarkably, our calculations suggest that the viscosity of the interfacial water confined between the membrane and the substrate is elevated by ˜104 as compared to bulk water. Using hidden Markov model analysis, we then obtain insight into the transbilayer movement of lipids. We find that lipid flip-flop dynamics are very fast, with half times in the range of seconds. Importantly, we find little evidence for membrane defect mediated lipid flip-flop for SLBs at temperatures well above the solid-to-liquid transition, though defects seem to be involved when the SLBs are cooled down. Our work thus shows that the combination of single particle tracking and advanced hydrodynamic modeling provides a powerful means to obtain insight into membrane dynamics.

Arterial Spin Labeling Magnetic Resonance Perfusion for Traumatic Brain Injury: Technical Challenges and Potentials.

PubMed

Andre, Jalal B

2015-10-01

Traumatic brain injury (TBI), including concussion, is a public health concern, as it affects over 1.7 million persons in the United States per year. Yet, the diagnosis of TBI, particularly mild TBI (mTBI), can be controversial, as neuroimaging findings can be sparse on conventional magnetic resonance and computed tomography examinations, and when present, often poorly correlate with clinical signs and symptoms. Furthermore, the discussion of TBI, concussion, and head impact exposure is immediately complicated by the many differing opinions of what constitutes each, their respective severities, and how the underlying biomechanics of the inciting head impact might alter the distribution, severity, and prognosis of the underlying brain injury. Advanced imaging methodologies hold promise in improving the sensitivity and detectability of associated imaging biomarkers that might better correlate with patient outcome and prognostication, allowing for improved triage and therapeutic guidance in the setting of TBI, particularly in mTBI. This work will examine the defining symptom complex associated with mTBI and explore changes in cerebral blood flow measured by arterial spin labeling, as a potential imaging biomarker for TBI, and briefly correlate these observations with findings identified by single photon emission computed tomography and positron emission tomography imaging.

Virtual Screening and Pharmacophore Design for a Novel Theoretical Inhibitor of Macrophage Stimulating Factor as a Metastatic Agent

PubMed Central

Torktaz, Ibrahim; Mohamadhashem, Faezeh; Esmaeili, Abolghasem; Behjati, Mohaddeseh; Sharifzadeh, Sara

2013-01-01

Introduction: Metastasis is a crucial aspect of cancer. Macrophage stimulating protein (MSP) is a single chain protein and can be cleaved by serum proteases. MSP has several roles in metastasis. In this in silico study, MSP as a metastatic agent was considered as a drug target. Methods: Crystallographic structure of MSP was retrieved from protein data bank. To find a chemical inhibitor of MSP, a library of KEGG compounds was screened and 1000 shape complemented ligands were retrieved with FindSite algorithm. Molegro Virtual Docker (MVD) software was used for docking simulation of shape complemented ligands against MSP. Moldock score was used as scoring function for virtual screening and potential inhibitors with more negative binding energy were obtained. PLANS scoring function was used for revaluation of virtual screening data. Results: The top found chemical had binding affinity of -183.55 based on MolDock score and equal to -66.733 PLANTs score to MSP structure. Conclusion: Based on pharmacophore model of potential inhibitor, this study suggests that the chemical which was found in this research and its derivate can be used for subsequent laboratory studies. PMID:24163807

The Role of Binding Site on the Mechanical Unfolding Mechanism of Ubiquitin

NASA Astrophysics Data System (ADS)

Cao, Penghui; Yoon, Gwonchan; Tao, Weiwei; Eom, Kilho; Park, Harold S.

2015-03-01

We apply novel atomistic simulations based on potential energy surface exploration to investigate the constant force-induced unfolding of ubiquitin. At the experimentally-studied force clamping level of 100 pN, we find a new unfolding mechanism starting with the detachment between β5 and β3 involving the binding site of ubiquitin, the Ile44 residue. This new unfolding pathway leads to the discovery of new intermediate configurations, which correspond to the end-to-end extensions previously seen experimentally. More importantly, it demonstrates the novel finding that the binding site of ubiquitin can be responsible not only for its biological functions, but also its unfolding dynamics. We also report in contrast to previous single molecule constant force experiments that when the clamping force becomes smaller than about 300 pN, the number of intermediate configurations increases dramatically, where almost all unfolding events at 100 pN involve an intermediate configuration. By directly calculating the life times of the intermediate configurations from the height of the barriers that were crossed on the potential energy surface, we demonstrate that these intermediate states were likely not observed experimentally due to their lifetimes typically being about two orders of magnitude smaller than the experimental temporal resolution.

Constraints on texture zero and cofactor zero models for neutrino mass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whisnant, K.; Liao, Jiajun; Marfatia, D.

2014-06-24

Imposing a texture or cofactor zero on the neutrino mass matrix reduces the number of independent parameters from nine to seven. Since five parameters have been measured, only two independent parameters would remain in such models. We find the allowed regions for single texture zero and single cofactor zero models. We also find strong similarities between single texture zero models with one mass hierarchy and single cofactor zero models with the opposite mass hierarchy. We show that this correspondence can be generalized to texture-zero and cofactor-zero models with the same homogeneous costraints on the elements and cofactors.

Microchip Screening Platform for Single Cell Assessment of NK Cell Cytotoxicity

PubMed Central

Guldevall, Karolin; Brandt, Ludwig; Forslund, Elin; Olofsson, Karl; Frisk, Thomas W.; Olofsson, Per E.; Gustafsson, Karin; Manneberg, Otto; Vanherberghen, Bruno; Brismar, Hjalmar; Kärre, Klas; Uhlin, Michael; Önfelt, Björn

2016-01-01

Here, we report a screening platform for assessment of the cytotoxic potential of individual natural killer (NK) cells within larger populations. Human primary NK cells were distributed across a silicon–glass microchip containing 32,400 individual microwells loaded with target cells. Through fluorescence screening and automated image analysis, the numbers of NK and live or dead target cells in each well could be assessed at different time points after initial mixing. Cytotoxicity was also studied by time-lapse live-cell imaging in microwells quantifying the killing potential of individual NK cells. Although most resting NK cells (≈75%) were non-cytotoxic against the leukemia cell line K562, some NK cells were able to kill several (≥3) target cells within the 12-h long experiment. In addition, the screening approach was adapted to increase the chance to find and evaluate serial killing NK cells. Even if the cytotoxic potential varied between donors, it was evident that a small fraction of highly cytotoxic NK cells were responsible for a substantial portion of the killing. We demonstrate multiple assays where our platform can be used to enumerate and characterize cytotoxic cells, such as NK or T cells. This approach could find use in clinical applications, e.g., in the selection of donors for stem cell transplantation or generation of highly specific and cytotoxic cells for adoptive immunotherapy. PMID:27092139

Strength of the interatomic potential derived from angular scans in LEIS

NASA Astrophysics Data System (ADS)

Primetzhofer, D.; Markin, S. N.; Draxler, M.; Beikler, R.; Taglauer, E.; Bauer, P.

2008-09-01

Angular scans were performed for a Cu(1 0 0) single crystal and He + ions. The results were compared to MARLOWE, KALYPSO and FAN simulations to obtain information on the interaction potential. The influence of the used evaluation procedure on the deduced scattering potential was investigated. The scattering potential is found to be weaker than what is predicted by an uncorrected TFM potential. It was found that the use of a single screening correction factor is applicable in a wide range of impact parameters. It is further shown that selection of single scattering trajectories and a limitation of information depth to the surface layers is possible for neutral and charge integrated spectra.

WEATHER ON OTHER WORLDS. II. SURVEY RESULTS: SPOTS ARE UBIQUITOUS ON L AND T DWARFS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metchev, Stanimir A.; Heinze, Aren; Apai, Dániel

2015-02-01

We present results from the Weather on Other Worlds Spitzer Exploration Science program to investigate photometric variability in L and T dwarfs, usually attributed to patchy clouds. We surveyed 44 L3-T8 dwarfs, spanning a range of J – K{sub s} colors and surface gravities. We find that 14/23 (61%{sub −20%}{sup +17%}, 95% confidence) of our single L3-L9.5 dwarfs are variable with peak-to-peak amplitudes between 0.2% and 1.5%, and 5/16 (31%{sub −17%}{sup +25%}) of our single T0-T8 dwarfs are variable with amplitudes between 0.8% and 4.6%. After correcting for sensitivity, we find that 80%{sub −27%}{sup +20%} of L dwarfs vary bymore » ≥0.2%, and 36%{sub −17%}{sup +26%} of T dwarfs vary by ≥0.4%. Given viewing geometry considerations, we conclude that photospheric heterogeneities causing >0.2% 3-5 μm flux variations are present on virtually all L dwarfs, and probably on most T dwarfs. A third of L dwarf variables show irregular light curves, indicating that L dwarfs may have multiple spots that evolve over a single rotation. Also, approximately a third of the periodicities are on timescales >10 hr, suggesting that slowly rotating brown dwarfs may be common. We observe an increase in the maximum amplitudes over the entire spectral type range, revealing a potential for greater temperature contrasts in T dwarfs than in L dwarfs. We find a tentative association (92% confidence) between low surface gravity and high-amplitude variability among L3-L5.5 dwarfs. Although we can not confirm whether lower gravity is also correlated with a higher incidence of variables, the result is promising for the characterization of directly imaged young extrasolar planets through variability.« less

Topology and weights in a protein domain interaction network--a novel way to predict protein interactions.

PubMed

Wuchty, Stefan

2006-05-23

While the analysis of unweighted biological webs as diverse as genetic, protein and metabolic networks allowed spectacular insights in the inner workings of a cell, biological networks are not only determined by their static grid of links. In fact, we expect that the heterogeneity in the utilization of connections has a major impact on the organization of cellular activities as well. We consider a web of interactions between protein domains of the Protein Family database (PFAM), which are weighted by a probability score. We apply metrics that combine the static layout and the weights of the underlying interactions. We observe that unweighted measures as well as their weighted counterparts largely share the same trends in the underlying domain interaction network. However, we only find weak signals that weights and the static grid of interactions are connected entities. Therefore assuming that a protein interaction is governed by a single domain interaction, we observe strong and significant correlations of the highest scoring domain interaction and the confidence of protein interactions in the underlying interactions of yeast and fly. Modeling an interaction between proteins if we find a high scoring protein domain interaction we obtain 1, 428 protein interactions among 361 proteins in the human malaria parasite Plasmodium falciparum. Assessing their quality by a logistic regression method we observe that increasing confidence of predicted interactions is accompanied by high scoring domain interactions and elevated levels of functional similarity and evolutionary conservation. Our results indicate that probability scores are randomly distributed, allowing to treat static grid and weights of domain interactions as separate entities. In particular, these finding confirms earlier observations that a protein interaction is a matter of a single interaction event on domain level. As an immediate application, we show a simple way to predict potential protein interactions by utilizing expectation scores of single domain interactions.

A likelihood-based approach to identifying contaminated food products using sales data: performance and challenges.

PubMed

Kaufman, James; Lessler, Justin; Harry, April; Edlund, Stefan; Hu, Kun; Douglas, Judith; Thoens, Christian; Appel, Bernd; Käsbohrer, Annemarie; Filter, Matthias

2014-07-01

Foodborne disease outbreaks of recent years demonstrate that due to increasingly interconnected supply chains these type of crisis situations have the potential to affect thousands of people, leading to significant healthcare costs, loss of revenue for food companies, and--in the worst cases--death. When a disease outbreak is detected, identifying the contaminated food quickly is vital to minimize suffering and limit economic losses. Here we present a likelihood-based approach that has the potential to accelerate the time needed to identify possibly contaminated food products, which is based on exploitation of food products sales data and the distribution of foodborne illness case reports. Using a real world food sales data set and artificially generated outbreak scenarios, we show that this method performs very well for contamination scenarios originating from a single "guilty" food product. As it is neither always possible nor necessary to identify the single offending product, the method has been extended such that it can be used as a binary classifier. With this extension it is possible to generate a set of potentially "guilty" products that contains the real outbreak source with very high accuracy. Furthermore we explore the patterns of food distributions that lead to "hard-to-identify" foods, the possibility of identifying these food groups a priori, and the extent to which the likelihood-based method can be used to quantify uncertainty. We find that high spatial correlation of sales data between products may be a useful indicator for "hard-to-identify" products.

Recognition of voice commands using adaptation of foreign language speech recognizer via selection of phonetic transcriptions

NASA Astrophysics Data System (ADS)

Maskeliunas, Rytis; Rudzionis, Vytautas

2011-06-01

In recent years various commercial speech recognizers have become available. These recognizers provide the possibility to develop applications incorporating various speech recognition techniques easily and quickly. All of these commercial recognizers are typically targeted to widely spoken languages having large market potential; however, it may be possible to adapt available commercial recognizers for use in environments where less widely spoken languages are used. Since most commercial recognition engines are closed systems the single avenue for the adaptation is to try set ways for the selection of proper phonetic transcription methods between the two languages. This paper deals with the methods to find the phonetic transcriptions for Lithuanian voice commands to be recognized using English speech engines. The experimental evaluation showed that it is possible to find phonetic transcriptions that will enable the recognition of Lithuanian voice commands with recognition accuracy of over 90%.

Psychological comorbidities and their relationship to self-reported handicap in samples of dizzy patients.

PubMed

Piker, Erin G; Jacobson, Gary P; McCaslin, Devin L; Grantham, Sarah L

2008-04-01

Factors such as anxiety, depression, somatic awareness, autonomic symptoms, and differences in coping strategies are known to affect dizziness handicap. We studied these factors in 63 consecutive "dizzy" patients. This sample was subgrouped into normals and patients with benign paroxysmal positional vertigo, compensated and uncompensated unilateral peripheral vestibular system impairment, or abnormal vestibular evoked myogenic potential as a single significant diagnostic finding. Results showed that (1) anxiety and depression occur with greater frequency in dizzy patients than in the normal population; (2) the magnitude of anxiety, depression, somatization, and autonomic symptoms does not differ significantly in subgroups of patients; (3) women tended to report greater handicap and somatic/autonomic symptoms; and (4) Dizziness Handicap Inventory total scores were correlated with patients' complaints of somatic/autonomic symptoms, anxiety, depression, and coping strategies. These findings suggest that self-reported measures represent unique pieces of information important for the management of dizzy patients.

Effects of Sulpiride on True and False Memories of Thematically Related Pictures and Associated Words in Healthy Volunteers

PubMed Central

Guarnieri, Regina V.; Ribeiro, Rafaela L.; de Souza, Altay A. Lino; Galduróz, José Carlos F.; Covolan, Luciene; Bueno, Orlando F. A.

2016-01-01

Episodic memory, working memory, emotional memory, and attention are subject to dopaminergic modulation. However, the potential role of dopamine on the generation of false memories is unknown. This study defined the role of the dopamine D2 receptor on true and false recognition memories. Twenty-four young, healthy volunteers ingested a single dose of placebo or 400 mg oral sulpiride, a dopamine D2-receptor antagonist, just before starting the recognition memory task in a randomized, double-blind, and placebo-controlled trial. The sulpiride group presented more false recognitions during visual and verbal processing than the placebo group, although both groups had the same indices of true memory. These findings demonstrate that dopamine D2 receptors blockade in healthy volunteers can specifically increase the rate of false recognitions. The findings fit well the two-process view of causes of false memories, the activation/monitoring failures model. PMID:27047394

Bilateral preictal signature of phase-amplitude coupling in canine epilepsy.

PubMed

Gagliano, Laura; Bou Assi, Elie; Nguyen, Dang K; Rihana, Sandy; Sawan, Mohamad

2018-01-01

Seizure forecasting would improve the quality of life of patients with refractory epilepsy. Although early findings were optimistic, no single feature has been found capable of individually characterizing brain dynamics during transition to seizure. Cross-frequency phase amplitude coupling has been recently proposed as a precursor of seizure activity. This work evaluates the existence of a statistically significant difference in mean phase amplitude coupling distribution between the preictal and interictal states of seizures in dogs with bilaterally implanted intracranial electrodes. Results show a statistically significant change (p<0.05) of phase amplitude coupling during the preictal phase. This change is correlated with the position of implanted electrodes and is more significant within high-gamma frequency bands. These findings highlight the potential benefit of bilateral iEEG analysis and the feasibility of seizure forecasting based on slow modulation of high frequency amplitude. Copyright © 2017 Elsevier B.V. All rights reserved.

Localization-delocalization transition in a system of quantum kicked rotors.

PubMed

Creffield, C E; Hur, G; Monteiro, T S

2006-01-20

The quantum dynamics of atoms subjected to pairs of closely spaced delta kicks from optical potentials are shown to be quite different from the well-known paradigm of quantum chaos, the single delta-kick system. We find the unitary matrix has a new oscillating band structure corresponding to a cellular structure of phase space and observe a spectral signature of a localization-delocalization transition from one cell to several. We find that the eigenstates have localization lengths which scale with a fractional power L approximately h(-0.75) and obtain a regime of near-linear spectral variances which approximate the "critical statistics" relation summation2(L) approximately or equal to chi(L) approximately 1/2 (1-nu)L, where nu approximately 0.75 is related to the fractal classical phase-space structure. The origin of the nu approximately 0.75 exponent is analyzed.

Extreme sensitivity of graphene photoconductivity to environmental gases.

PubMed

Docherty, Callum J; Lin, Cheng-Te; Joyce, Hannah J; Nicholas, Robin J; Herz, Laura M; Li, Lain-Jong; Johnston, Michael B

2012-01-01

Graphene is a single layer of covalently bonded carbon atoms, which was discovered only 8 years ago and yet has already attracted intense research and commercial interest. Initial research focused on its remarkable electronic properties, such as the observation of massless Dirac fermions and the half-integer quantum Hall effect. Now graphene is finding application in touch-screen displays, as channels in high-frequency transistors and in graphene-based integrated circuits. The potential for using the unique properties of graphene in terahertz-frequency electronics is particularly exciting; however, initial experiments probing the terahertz-frequency response of graphene are only just emerging. Here we show that the photoconductivity of graphene at terahertz frequencies is dramatically altered by the adsorption of atmospheric gases, such as nitrogen and oxygen. Furthermore, we observe the signature of terahertz stimulated emission from gas-adsorbed graphene. Our findings highlight the importance of environmental conditions on the design and fabrication of high-speed, graphene-based devices.

Is inflation from unwinding fluxes IIB?

NASA Astrophysics Data System (ADS)

Gautason, Fridrik Freyr; Schillo, Marjorie; Van Riet, Thomas

2017-03-01

In this paper we argue that the mechanism of unwinding inflation is naturally present in warped compactifications of type IIB string theory with local throats. The unwinding of flux is caused by its annihilation against branes. The resulting inflaton potential is linear with periodic modulations. We initiate an analysis of the inflationary dynamics and cosmological observables, which are highly constrained by moduli stabilization. For the simplified model of single-Kähler Calabi-Yau spaces we find that many, though not all of the consistency constraints can be satisfied. Particularly, in this simple model geometric constraints are in tension with obtaining the observed amplitude of the scalar power spectrum. However, we do find 60 efolds of inflation with a trans-Planckian field excursion which offers the hope that slightly more complicated models can lead to a fully consistent explicit construction of large field inflation of this kind.

Coupling the Leidenfrost effect and elastic deformations to power sustained bouncing

NASA Astrophysics Data System (ADS)

Waitukaitis, Scott R.; Zuiderwijk, Antal; Souslov, Anton; Coulais, Corentin; van Hecke, Martin

2017-11-01

The Leidenfrost effect occurs when an object near a hot surface vaporizes rapidly enough to lift itself up and hover. Although well understood for liquids and stiff sublimable solids, nothing is known about the effect with materials whose stiffness lies between these extremes. Here we introduce a new phenomenon that occurs with vaporizable soft solids--the elastic Leidenfrost effect. By dropping hydrogel spheres onto hot surfaces we find that, rather than hovering, they energetically bounce several times their diameter for minutes at a time. With high-speed video during a single impact, we uncover high-frequency microscopic gap dynamics at the sphere/substrate interface. We show how these otherwise-hidden agitations constitute work cycles that harvest mechanical energy from the vapour and sustain the bouncing. Our findings suggest a new strategy for injecting mechanical energy into a widely used class of soft materials, with potential relevance to fields such as active matter, soft robotics and microfluidics.

Transition from single to multiple axial potential structure in expanding helicon plasma

NASA Astrophysics Data System (ADS)

Ghosh, Soumen; Chattopadhyay, P. K.; Ghosh, J.; Pal, R.; Bora, D.

2017-02-01

Transition from single to multiple axial potential structure (MAPS) formation is reported in expanding helicon plasma. This transition is created by forming a cusp magnetic field at the downstream after the expansion throat. Two distinct potential drops are separated by a uniform axial potential zone. Non-uniform axial density distribution exists in expanding helicon systems. A cusp-like field nourishes both the axial density gradients sufficient enough for the formation of these two distinct potential drops. It is also shown that both single and multiple axial potential structures are observed only when both geometric and magnetic expansions closely coincide with each other. Coexistence of these two expansions at the same location enhances plasma expansion which facilitates deviation from Boltzmann distribution and violates quasi-neutrality locally.

A calibration of the stellar mass fundamental plane at z ∼ 0.5 using the micro-lensing-induced flux ratio anomalies of macro-lensed quasars {sup ,} {sup ,}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schechter, Paul L.; Pooley, David; Blackburne, Jeffrey A.

2014-10-01

We measure the stellar mass surface densities of early-type galaxies by observing the micro-lensing of macro-lensed quasars caused by individual stars, including stellar remnants, brown dwarfs, and red dwarfs too faint to produce photometric or spectroscopic signatures. Instead of observing multiple micro-lensing events in a single system, we combine single-epoch X-ray snapshots of 10 quadruple systems, and compare the measured relative magnifications for the images with those computed from macro-models. We use these to normalize a stellar mass fundamental plane constructed using a Salpeter initial mass function with a low-mass cutoff of 0.1 M {sub ☉} and treat the zeropointmore » of the surface mass density as a free parameter. Our method measures the graininess of the gravitational potential produced by individual stars, in contrast to methods that decompose a smooth total gravitational potential into two smooth components, one stellar and one dark. We find the median likelihood value for the normalization factor F by which the Salpeter stellar masses must be multiplied is 1.23, with a one sigma confidence range, dominated by small number statistics, of 0.77« less

A Review on the Traditional Chinese Medicinal Herbs and Formulae with Hypolipidemic Effect

PubMed Central

Sham, Tung-Ting; Chan, Chi-On; Wang, You-Hua; Yang, Jian-Mei; Mok, Daniel Kam-Wah; Chan, Shun-Wan

2014-01-01

Hyperlipidemia, characterized by the abnormal blood lipid profiles, is one of the dominant factors of many chronic diseases such as diabetes, obesity, and cardiovascular diseases (CVD). For the low cost, effectiveness, and fewer side effects, the popularity of using traditional Chinese medicine (TCM) to handle hyperlipidemia is increasing and its role in health care has been recognized by the public at large. Despite the importance of TCM herbs and formulations, there is no comprehensive review summarizing their scientific findings on handling hyperlipidemia. This review summarizes the recent experimental and clinical results of nine representative single Chinese herbs and seven classic TCM formulae that could improve lipid profiles so as to help understand and compare their underlying mechanisms. Most of single herbs and formulae demonstrated the improvement of hyperlipidemic conditions with multiple and diverse mechanisms of actions similar to conventional Western drugs in spite of their mild side effects. Due to increasing popularity of TCM, more extensive, well-designed preclinical and clinical trials on the potential synergistic and adverse side effects of herb-drug interactions as well as their mechanisms are warranted. Hyperlipidemic patients should be warned about the potential risks of herb-drug interactions, particularly those taking anticoagulants and antiplatelet drugs. PMID:25110708

Analysis of Multiplexed Nanosensor Arrays Based on Near-Infrared Fluorescent Single-Walled Carbon Nanotubes.

PubMed

Dong, Juyao; Salem, Daniel P; Sun, Jessica H; Strano, Michael S

2018-04-24

The high-throughput, label-free detection of biomolecules remains an important challenge in analytical chemistry with the potential of nanosensors to significantly increase the ability to multiplex such assays. In this work, we develop an optical sensor array, printable from a single-walled carbon nanotube/chitosan ink and functionalized to enable a divalent ion-based proximity quenching mechanism for transducing binding between a capture protein or an antibody with the target analyte. Arrays of 5 × 6, 200 μm near-infrared (nIR) spots at a density of ≈300 spots/cm 2 are conjugated with immunoglobulin-binding proteins (proteins A, G, and L) for the detection of human IgG, mouse IgM, rat IgG2a, and human IgD. Binding kinetics are measured in a parallel, multiplexed fashion from each sensor spot using a custom laser scanning imaging configuration with an nIR photomultiplier tube detector. These arrays are used to examine cross-reactivity, competitive and nonspecific binding of analyte mixtures. We find that protein G and protein L functionalized sensors report selective responses to mouse IgM on the latter, as anticipated. Optically addressable platforms such as the one examined in this work have potential to significantly advance the real-time, multiplexed biomolecular detection of complex mixtures.

Time-dependent density functional theory beyond Kohn-Sham Slater determinants.

PubMed

Fuks, Johanna I; Nielsen, Søren E B; Ruggenthaler, Michael; Maitra, Neepa T

2016-08-03

When running time-dependent density functional theory (TDDFT) calculations for real-time simulations of non-equilibrium dynamics, the user has a choice of initial Kohn-Sham state, and typically a Slater determinant is used. We explore the impact of this choice on the exchange-correlation potential when the physical system begins in a 50 : 50 superposition of the ground and first-excited state of the system. We investigate the possibility of judiciously choosing a Kohn-Sham initial state that minimizes errors when adiabatic functionals are used. We find that if the Kohn-Sham state is chosen to have a configuration matching the one that dominates the interacting state, this can be achieved for a finite time duration for some but not all such choices. When the Kohn-Sham system does not begin in a Slater determinant, we further argue that the conventional splitting of the exchange-correlation potential into exchange and correlation parts has limited value, and instead propose a decomposition into a "single-particle" contribution that we denote v, and a remainder. The single-particle contribution can be readily computed as an explicit orbital-functional, reduces to exchange in the Slater determinant case, and offers an alternative to the adiabatic approximation as a starting point for TDDFT approximations.

Adjustable vector Airy light-sheet single optical tweezers: negative radiation forces on a subwavelength spheroid and spin torque reversal

NASA Astrophysics Data System (ADS)

Mitri, Farid G.

2018-01-01

Generalized solutions of vector Airy light-sheets, adjustable per their derivative order m, are introduced stemming from the Lorenz gauge condition and Maxwell's equations using the angular spectrum decomposition method. The Cartesian components of the incident radiated electric, magnetic and time-averaged Poynting vector fields in free space (excluding evanescent waves) are determined and computed with particular emphasis on the derivative order of the Airy light-sheet and the polarization on the magnetic vector potential forming the beam. Negative transverse time-averaged Poynting vector components can arise, while the longitudinal counterparts are always positive. Moreover, the analysis is extended to compute the optical radiation force and spin torque vector components on a lossless dielectric prolate subwavelength spheroid in the framework of the electric dipole approximation. The results show that negative forces and spin torques sign reversal arise depending on the derivative order of the beam, the polarization of the magnetic vector potential, and the orientation of the subwavelength prolate spheroid in space. The spin torque sign reversal suggests that counter-clockwise or clockwise rotations around the center of mass of the subwavelength spheroid can occur. The results find useful applications in single Airy light-sheet tweezers, particle manipulation, handling, and rotation applications to name a few examples.

Single-Walled Carbon Nanotubes Modulate the B- to A-DNA Transition

PubMed Central

2015-01-01

We study the conformational equilibrium between B-to-A forms of ds-DNA adsorbed onto a single-walled carbon nanotube (SWNT) using free energy profile calculations based on all-atom molecular dynamics simulations. The potential of mean force (PMF) of the B-to-A transition of ds-DNA in the presence of an uncharged (10,0) carbon nanotube for two dodecamers with poly-AT or poly-GC sequences is calculated as a function of a root-mean-square-distance (ΔRMSD) difference metric for the B-to-A transition. The calculations reveal that in the presence of a SWNT DNA favors B-form DNA significantly in both poly-GC and poly-AT sequences. Furthermore, the poly-AT DNA:SWNT complex shows a higher energy penalty for adopting an A-like conformation than poly-GC DNA:SWNT by several kcal/mol. The presence of a SWNT on either poly-AT or poly-GC DNA affects the PMF of the transition such that the B form is favored by as much as 10 kcal/mol. In agreement with published data, we find a potential energy minimum between A and B-form DNA at ΔRMSD ≈ −1.5 Å and that the presence of the SWNT moves this minimum by as much as ΔRMSD = 3 Å. PMID:25553205

Single leg separation prevalence among explanted Björk-Shiley prosthetic heart valves.

PubMed

Blot, William J; Signorello, Lisa B; Cohen, Sarah S; Ibrahim, Michel A

2007-11-01

Björk-Shiley convexo-concave (BSCC) prosthetic heart valves are believed to have been implanted in over 86,000 patients worldwide. Limited data are available on the prevalence of single leg separations (SLS) of the valves' outlet struts, a potential precursor to complete valve fracture. Data maintained by the manufacturer, including results of examinations for SLS in explanted valves, were merged with available information on the characteristics of the valve. The prevalence of SLS in the examined valves was calculated according to valve angle, size, position, and study. Among 343 examined valves, the overall prevalence of SLS was 8.2%, but this varied significantly by valve size, being three-fold higher among 29+ mm valves than among smaller valves, with statistically non-significantly higher prevalences among mitral than aortic, and among 70 degrees than 60 degrees valves. By applying the size, position and angle-specific SLS prevalences to the worldwide valve distribution, it is estimated that SLS may be present in 6.8% (95% confidence limits 4.1-9.4%) of all BSCC valves. These findings suggest that SLS may affect between 820 and 1,880 of the almost 20,000 BSCC valves among surviving patients worldwide. Such estimates help frame the context for potential patient screenings, should imaging and acoustic techniques to detect SLS become available.

Spontaneous and evoked release are independently regulated at individual active zones.

PubMed

Melom, Jan E; Akbergenova, Yulia; Gavornik, Jeffrey P; Littleton, J Troy

2013-10-30

Neurotransmitter release from synaptic vesicle fusion is the fundamental mechanism for neuronal communication at synapses. Evoked release following an action potential has been well characterized for its function in activating the postsynaptic cell, but the significance of spontaneous release is less clear. Using transgenic tools to image single synaptic vesicle fusion events at individual release sites (active zones) in Drosophila, we characterized the spatial and temporal dynamics of exocytotic events that occur spontaneously or in response to an action potential. We also analyzed the relationship between these two modes of fusion at single release sites. A majority of active zones participate in both modes of fusion, although release probability is not correlated between the two modes of release and is highly variable across the population. A subset of active zones is specifically dedicated to spontaneous release, indicating a population of postsynaptic receptors is uniquely activated by this mode of vesicle fusion. Imaging synaptic transmission at individual release sites also revealed general rules for spontaneous and evoked release, and indicate that active zones with similar release probability can cluster spatially within individual synaptic boutons. These findings suggest neuronal connections contain two information channels that can be spatially segregated and independently regulated to transmit evoked or spontaneous fusion signals.

Attention Process Training-3 to improve reading comprehension in mild aphasia: A single-case experimental design study.

PubMed

Lee, Jaime B; Sohlberg, McKay Moore; Harn, Beth; Horner, Robert; Cherney, Leora R

2018-06-04

People with aphasia frequently present with nonlinguistic deficits, in addition to their compromised language abilities, which may contribute to their problems with reading comprehension. Treatment of attention, working memory and executive control may improve reading comprehension in individuals with aphasia, particularly those with mild reading problems. This single-case experimental design study evaluated the efficacy of Attention Process Training-3, an intervention combining direct attention training and metacognitive facilitation, for improving reading comprehension in individuals with mild aphasia. A multiple baseline design across six participants was used to evaluate treatment effects. The primary outcome measure was a maze reading task. Cognitive measures were administered pre- and post-treatment. Visual inspection of graphed maze reading performance data indicated a basic effect between APT-3 and improved maze reading for three of the six participants. Quantitative analyses, using Tau-U, corroborated findings identified through visual analysis. The overall effect size was significant (Tau = .48, p = .01). Results suggest that APT-3 has the potential to improve reading in individuals with aphasia, but that it may be more efficacious under certain conditions. Treatment and participant variables, including intensity of treatment and metacognitive strategy usage, are discussed as potential influences on participants' responsiveness to APT-3.

The acute potentiating effects of back squats on athlete performance.

PubMed

Crewther, Blair T; Kilduff, Liam P; Cook, Christian J; Middleton, Matt K; Bunce, Paul J; Yang, Guang-Zhong

2011-12-01

Crewther, BT, Kilduff, LP, Cook, CJ, Middleton, MK, Bunce, PJ, and Yang, G-Z. The acute potentiating effects of back squats on athlete performance. J Strength Cond Res 25(12): 3319-3325, 2011-This study examined the acute potentiating effects of back squats on athlete performance with a specific focus on movement specificity and the individual timing of potentiation. Nine subelite male rugby players performed 3 protocols on separate occasions using a randomized, crossover, and counterbalanced design. Each protocol consisted of performance testing before a single set of 3 repetition maximum (3RM) back squats, followed by retesting at ∼15 seconds, 4, 8, 12, and 16 minutes. The 3 tests were countermovement jumps (CMJs), sprint performance (5 and 10 m), and 3-m horizontal sled pushes with a 100-kg load. Relationships between the individual changes in salivary testosterone and cortisol concentrations and performance were also examined. The 3RM squats significantly (p < 0.001) improved CMJ height at 4 (3.9 ± 1.9%), 8 (3.5 ± 1.5%), and 12 (3.0 ± 1.4%) minutes compared with baseline values, but no temporal changes in sprinting and sled times were identified. On an individual level, the peak relative changes in CMJ height (6.4 ± 2.1%, p < 0.001) were greater than the 3-m sled (1.4 ± 0.6%), 5-m (2.6 ± 1.0%), and 10-m sprint tests (1.8 ± 1.0%). In conclusion, a single set of 3RM squats was found effective in acutely enhancing CMJ height in the study population, especially when the recovery period was individualized for each athlete. The study results also suggest that the potentiating effects of squats may exhibit some degree of movement specificity, being greater for those exercises with similar movement patterns. The current findings have practical implications for prescribing warm-up exercises, individualizing training programs, and for interpreting postactivation potentiation research.

Orientation sensors by defocused imaging of single gold nano-bipyramids

NASA Astrophysics Data System (ADS)

Zhang, Fanwei; Li, Qiang; Rao, Wenye; Hu, Hongjin; Gao, Ye; Wu, Lijun

2018-01-01

Optical probes for nanoscale orientation sensing have attracted much attention in the field of single-molecule detections. Noble metal especially Au nanoparticles (NPs) exhibit extraordinary plasmonic properties, great photostability, excellent biocompatibility and nontoxicity, and thereby could be alternative labels to conventional applied organic dyes or quantum dots. One type of the most interesting metallic NPs is Au nanorods (AuNRs). Its anisotropic emission accompanied with anisotropic shape is potentially applicable in orientation sensing. Recently, we resolved the 3D orientation of single AuNRs within one frame by deliberately introducing an aberration (slight shift of the dipole away from the focal plane) to the imaging system1 . This defocused imaging technique is based on the electron transition dipole approximation and the fact that the dipole radiation exhibits an angular anisotropy. Since the photoluminescence quantum yield (PLQY) can be enhanced by the "lightning rod effect" (at a sharp angled surface) and localized SPR modes, that of the single Au nano-bipyramid (AuNB) with more sharp tips or edges was found to be doubled comparing to AuNRs with a same effective size2. Here, with a 532 nm excitation, we find that the PL properties of individual AuNBs can be described by three perpendicularly-arranged dipoles (with different ratios). Their PL defocused images are bright, clear and exhibit obvious anisotropy. These properties suggest that AuNBs are excellent candidates for orientation sensing labels in single molecule detections.

The demand for a dengue vaccine: a contingent valuation survey in Metro Manila.

PubMed

Palanca-Tan, Rosalina

2008-02-13

Using data gathered from a contingent valuation survey, this study estimated the willingness to pay (WTP) for a single dengue fever vaccine and the household demand function for dengue vaccines. Mean WTP for the vaccine ranged from US$27 to US$32 and household demand averaged 2 per household. Our findings indicate sufficiently high WTP for dengue vaccines and hence a significant potential for selling the vaccine in private markets. For the lower income groups with lower capacity to pay, a mass vaccination campaign program in which part of the financial costs are covered by vaccine user charges is viable.

Towards a magnetoresistive platform for neural signal recording

NASA Astrophysics Data System (ADS)

Sharma, P. P.; Gervasoni, G.; Albisetti, E.; D'Ercoli, F.; Monticelli, M.; Moretti, D.; Forte, N.; Rocchi, A.; Ferrari, G.; Baldelli, P.; Sampietro, M.; Benfenati, F.; Bertacco, R.; Petti, D.

2017-05-01

A promising strategy to get deeper insight on brain functionalities relies on the investigation of neural activities at the cellular and sub-cellular level. In this framework, methods for recording neuron electrical activity have gained interest over the years. Main technological challenges are associated to finding highly sensitive detection schemes, providing considerable spatial and temporal resolution. Moreover, the possibility to perform non-invasive assays would constitute a noteworthy benefit. In this work, we present a magnetoresistive platform for the detection of the action potential propagation in neural cells. Such platform allows, in perspective, the in vitro recording of neural signals arising from single neurons, neural networks and brain slices.

Cascaded Brillouin lasing in monolithic barium fluoride whispering gallery mode resonators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Guoping, E-mail: guoping.lin@femto-st.fr; Diallo, Souleymane; Saleh, Khaldoun

2014-12-08

We report the observation of stimulated Brillouin scattering and lasing at 1550 nm in barium fluoride (BaF{sub 2}) crystal. Brillouin lasing was achieved with ultra-high quality (Q) factor monolithic whispering gallery mode mm-size disk resonators. Overmoded resonators were specifically used to provide cavity resonances for both the pump and all Brillouin Stokes waves. Single and multiple Brillouin Stokes radiations with frequency shift ranging from 8.2 GHz up to 49 GHz have been generated through cascaded Brillouin lasing. BaF{sub 2} resonator-based Brillouin lasing can find potential applications for high-coherence lasers and microwave photonics.

Lobar holoprosencephaly in a Miniature Schnauzer with hypodipsic hypernatremia.

PubMed

Sullivan, Stacey A; Harmon, Barry G; Purinton, P Thomas; Greene, Craig E; Glerum, Leigh E

2003-12-15

A 9-month-old male Miniature Schnauzer was examined because of a lifelong history of behavioral abnormalities, including hypodipsia. Diagnostic evaluation revealed marked hypernatremia and a single forebrain ventricle. The behavioral abnormalities did not resolve with correction of the hypernatremia, and the dog was euthanatized. At necropsy, midline forebrain structures were absent or reduced in size, and normally paired forebrain structures were incompletely separated. Findings were diagnostic for holoprosencephaly, a potentially genetic disorder and the likely cause of the hypodipsia. Similar evaluation of affected Miniature Schnauzer dogs may reveal whether holoprosencephaly routinely underlies the thirst deficiency that may be seen in dogs of this breed.

A space-efficient algorithm for local similarities.

PubMed

Huang, X Q; Hardison, R C; Miller, W

1990-10-01

Existing dynamic-programming algorithms for identifying similar regions of two sequences require time and space proportional to the product of the sequence lengths. Often this space requirement is more limiting than the time requirement. We describe a dynamic-programming local-similarity algorithm that needs only space proportional to the sum of the sequence lengths. The method can also find repeats within a single long sequence. To illustrate the algorithm's potential, we discuss comparison of a 73,360 nucleotide sequence containing the human beta-like globin gene cluster and a corresponding 44,594 nucleotide sequence for rabbit, a problem well beyond the capabilities of other dynamic-programming software.

Features from the non-attractor beginning of inflation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Yi-Fu; Wang, Dong-Gang; Wang, Ziwei

2016-10-01

We study the effects of the non-attractor initial conditions for the canonical single-field inflation. The non-attractor stage can last only several e -folding numbers, and should be followed by hilltop inflation. This two-stage evolution leads to large scale suppression in the primordial power spectrum, which is favored by recent observations. Moreover we give a detailed calculation of primordial non-Gaussianity due to the ''from non-attractor to slow-roll'' transition, and find step features in the local and equilateral shapes. We conclude that a plateau-like inflaton potential with an initial non-attractor phase yields interesting features in both power spectrum and bispectrum.

Lighting market alchemy: Will we find a pot of gold at the end of the III-V rainbow?

NASA Astrophysics Data System (ADS)

Conway, Kathryn M.

2004-12-01

With a focus on visible spectrum light emitting diodes (LEDs), three questions frame this update. First, what are the market and financial outlooks for light-producing compound semiconductor materials and devices? Second, which applications offer the greatest growth potential for the next five to ten years and with which technologies will they likely compete for market share? Third, how can photonics experts contribute to accelerated successes for LEDs and other solid-state lighting technologies such as quantum dots? Using the rainbow as a metaphor for the market, the author examines developments in single color, multiple color and "white light" products.

Water transfer and loss in hit-and-run collisions

NASA Astrophysics Data System (ADS)

Burger, C.; Maindl, T. I.; Schäfer, C.

2017-09-01

This work focuses on transfer and loss of volatiles, like water, in hit-and-run collisions, where especially the smaller one of the colliding pair is often stripped of considerable amounts of its initial volatile content, but still survives the encounter more or less intact. We find water losses up to 75 percent in a single collision, depending on various parameters, especially velocity, impact angle and mass ratio, but also on the total colliding mass. The physical state, especially vaporization of volatiles, is found to be particularly important in collisions of approximately Mars-sized bodies, with high impact energies, but still potentially easy volatile escape.

Decay and the double-decay properties of edge bands of phosphorene ribbons

NASA Astrophysics Data System (ADS)

Yang, M.; Duan, H.-J.; Wang, R.-Q.

2015-11-01

Phosphorene (a monolayer of black phosphorus) recently spurred much attention due to its potential for application. We notice there are two types of zigzag edge and two types of armchair edge for phosphorene lattice. We study the winding number of various types of edge of phosphorene ribbons and conclude that, besides on the typical zigzag edge, the flat zero-energy edge band can be found in the ribbon of another nontypical armchair edge. The localization of these edge bands is investigated analytically. We find every single edge state of the atypical armchair edge decays to the bulk at two different decay rates.

Spin filtering through ferromagnetic BiMn O3 tunnel barriers

NASA Astrophysics Data System (ADS)

Gajek, M.; Bibes, M.; Barthélémy, A.; Bouzehouane, K.; Fusil, S.; Varela, M.; Fontcuberta, J.; Fert, A.

2005-07-01

We report on experiments of spin filtering through ultrathin single-crystal layers of the insulating and ferromagnetic oxide BiMnO3 (BMO). The spin polarization of the electrons tunneling from a gold electrode through BMO is analyzed with a counterelectrode of the half-metallic oxide La2/3Sr1/3MnO3 (LSMO). At 3K we find a 50% change of the tunnel resistances according to whether the magnetizations of BMO and LSMO are parallel or opposite. This effect corresponds to a spin-filtering efficiency of up to 22%. Our results thus show the potential of complex ferromagnetic insulating oxides for spin filtering and injection.

Strain-induced negative differential resistance in ultrasmall carbon nanotube

NASA Astrophysics Data System (ADS)

Fang, Hui; Zhang, Fei-Peng; Ruan, Xing-Xiang; Huang, Can-Sheng; Jiang, Zhi-Nian; Peng, Jin-Yun; Wang, Ru-Zhi

2017-08-01

The transport properties in ultrasmall single-wall carbon nanotubes (SWCNTs) under tensile strain have been theoretically investigated. The regular negative differential resistance (NDR) induced by the strain undergoes a process from enhancement to weakening in the zigzag (3,0) SWCNT. The NDR achieves maximum with applying 4% tensile strain. Compared to the case of (3,0) SWCNT, that NDR cannot be manipulated by applying strain clearly in (4,0) and (5,0) ultrasmall SWCNTs with tensile strain lower than 10%. It proposes this strain-induced NDR effect to demonstrate the possibility of finding potential applications in SWCNT-based NDR nanodevices such as in memory devices, oscillators and fast switching devices.

Epoxide reduction with hydrazine on graphene: a first principles study.

PubMed

Kim, Min Chan; Hwang, Gyeong S; Ruoff, Rodney S

2009-08-14

Mechanisms for epoxide reduction with hydrazine on a single-layer graphene sheet are examined using quantum mechanical calculations within the framework of gradient-corrected spin-polarized density-functional theory. We find that the reduction reaction is mainly governed by epoxide ring opening which is initiated by H transfer from hydrazine or its derivatives. In addition, our calculations suggest that the epoxide reduction by hydrazine may predominantly follow a direct Eley-Rideal mechanism rather than a Langmuir-Hinshelwood mechanism. We also discuss the generation of various hydrazine derivatives during the reduction of graphene oxide with hydrazine and their potential contribution to lowering the barrier height of epoxide ring opening.

Equilibrium finite-frequency noise of an interacting mesoscopic capacitor studied in time-dependent density functional theory

NASA Astrophysics Data System (ADS)

Dittmann, Niklas; Splettstoesser, Janine; Helbig, Nicole

2018-03-01

We calculate the frequency-dependent equilibrium noise of a mesoscopic capacitor in time-dependent density functional theory (TDDFT). The capacitor is modeled as a single-level quantum dot with on-site Coulomb interaction and tunnel coupling to a nearby reservoir. The noise spectra are derived from linear-response conductances via the fluctuation-dissipation theorem. Thereby, we analyze the performance of a recently derived exchange-correlation potential with time-nonlocal density dependence in the finite-frequency linear-response regime. We compare our TDDFT noise spectra with real-time perturbation theory and find excellent agreement for noise frequencies below the reservoir temperature.

Snapshot 3D tracking of insulin granules in live cells

NASA Astrophysics Data System (ADS)

Wang, Xiaolei; Huang, Xiang; Gdor, Itay; Daddysman, Matthew; Yi, Hannah; Selewa, Alan; Haunold, Theresa; Hereld, Mark; Scherer, Norbert F.

2018-02-01

Rapid and accurate volumetric imaging remains a challenge, yet has the potential to enhance understanding of cell function. We developed and used a multifocal microscope (MFM) for 3D snapshot imaging to allow 3D tracking of insulin granules labeled with mCherry in MIN6 cells. MFM employs a special diffractive optical element (DOE) to simultaneously image multiple focal planes. This simultaneous acquisition of information determines the 3D location of single objects at a speed only limited by the array detector's frame rate. We validated the accuracy of MFM imaging/tracking with fluorescence beads; the 3D positions and trajectories of single fluorescence beads can be determined accurately over a wide range of spatial and temporal scales. The 3D positions and trajectories of single insulin granules in a 3.2um deep volume were determined with imaging processing that combines 3D decovolution, shift correction, and finally tracking using the Imaris software package. We find that the motion of the granules is superdiffusive, but less so in 3D than 2D for cells grown on coverslip surfaces, suggesting an anisotropy in the cytoskeleton (e.g. microtubules and action).

New Insights on Developmental Dyslexia Subtypes: Heterogeneity of Mixed Reading Profiles

PubMed Central

Zoubrinetzky, Rachel; Bielle, Frédérique; Valdois, Sylviane

2014-01-01

We examined whether classifications based on reading performance are relevant to identify cognitively homogeneous subgroups of dyslexic children. Each of the 71 dyslexic participants was selected to have a mixed reading profile, i.e. poor irregular word and pseudo-word reading performance (accuracy and speed). Despite their homogeneous reading profile, the participants were found to split into four distinct cognitive subgroups, characterized by a single phonological disorder, a single visual attention span disorder, a double deficit or none of these disorders. The two subgroups characterized by single and contrasted cognitive disorders were found to exhibit a very similar reading pattern but more contrasted spelling performance (quantitative analysis). A qualitative analysis of the error types produced in reading and spelling provided some cues about the participants' underlying cognitive deficit. The overall findings disqualify subtyping based on reading profiles as a classification method to identify cognitively homogeneous subgroups of dyslexic children. They rather show an opaque relationship between the cognitive underpinnings of developmental dyslexia and their behavioral manifestations in reading and spelling. Future neuroimaging and genetic studies should take this issue into account since synthesizing over cognitively heterogeneous children would entail potential pitfalls. PMID:24918441

Reflection and transmission coefficients of a single layer in poroelastic media.

PubMed

Corredor, Robiel Martinez; Santos, Juan E; Gauzellino, Patricia M; Carcione, José M

2014-06-01

Wave propagation in poroelastic media is a subject that finds applications in many fields of research, from geophysics of the solid Earth to material science. In geophysics, seismic methods are based on the reflection and transmission of waves at interfaces or layers. It is a relevant canonical problem, which has not been solved in explicit form, i.e., the wave response of a single layer, involving three dissimilar media, where the properties of the media are described by Biot's theory. The displacement fields are recast in terms of potentials and the boundary conditions at the two interfaces impose continuity of the solid and fluid displacements, normal and shear stresses, and fluid pressure. The existence of critical angles is discussed. The results are verified by taking proper limits-zero and 100% porosity-by comparison to the canonical solutions corresponding to single-phase solid (elastic) media and fluid media, respectively, and the case where the layer thickness is zero, representing an interface separating two poroelastic half-spaces. As examples, it was calculated the reflection and transmission coefficients for plane wave incident at a highly permeable and compliant fluid-saturated porous layer, and the case where the media are saturated with the same fluid.

Tuning electronic properties by oxidation-reduction reactions at graphene-ruthenium interface

DOE PAGES

Kandyba, Viktor; Al-Mahboob, Abdullah; Giampietri, Alessio; ...

2018-06-06

Mass production of graphene is associated with the growth on catalysts used also in other chemical reactions. In this study, we exploit the oxidation-reduction to tailor the properties of single layer graphene domains with incorporated bi-layer patches on ruthenium. Using photoelectron spectromicroscopy techniques, we find that oxygen, intercalating under single layer and making it p-doped by the formation of Ru-O x, does not intercalate under the bilayer patches with n-doped upper layer, but decorates them under single layer surrounding creating lateral p-n junctions with chemical potential difference of 1.2 eV. O-reduction by thermal treatment in vacuum results in C-vacancy defectsmore » enhancing electronic coupling of remained graphene to Ru, whereas in H 2, vacancy formation is suppressed. Also, for the domains below 15–25 μm size, after O-reduction in H 2, graphene/Ru coupling is restored, while wrinkle pattern produced by O-intercalation is irreversible and can trap reaction products between the wrinkles and Ru surface step edges. In fact, in certain regions of bigger domains, the products, containing H 2O and/or its fragments, remain at the interface, making graphene decoupled and undoped.« less

Graphene quantum dots with visible light absorption of the carbon core: insights from single-particle spectroscopy and first principles based theory

NASA Astrophysics Data System (ADS)

Ghosh, Siddharth; Awasthi, Manohar; Ghosh, Moumita; Seibt, Michael; Niehaus, Thomas A.

2016-12-01

Luminescent carbon nanodots (CND) are a recent addition to the family of carbon nanostructures. Interestingly, a large group of CNDs are fluorescent in the visible spectrum and possess single dipole emitters with potential applications in super-resolution microscopy, quantum information science, and optoelectronics. There is a large diversity of CND’s size as well as a strong variability of edge topology and functional groups in real samples. This hampers a direct comparison of experimental and theoretical findings that is necessary to understand the unusual photophysics of these systems. Here, we derive atomistic models of finite sized (<2.5 nm) CNDs from high resolution transmission electron microscopy (HRTEM) which are studied using approximate time-dependent density functional theory. The atomistic models are found to be primarily two-dimensional (2D) and can hence be categorised as graphene quantum dots (GQD). The GQD model structures that are presented here show excitation energies in the visible spectrum matching previous single GQD level photoluminescence studies. We also present the effect of edge hydroxyl and carboxyl functional groups on the absorption spectrum. Overall, the study reveals the atomistic origin of CNDs photoluminescence in the visible range.

Improved genome recovery and integrated cell-size analyses of individual uncultured microbial cells and viral particles.

PubMed

Stepanauskas, Ramunas; Fergusson, Elizabeth A; Brown, Joseph; Poulton, Nicole J; Tupper, Ben; Labonté, Jessica M; Becraft, Eric D; Brown, Julia M; Pachiadaki, Maria G; Povilaitis, Tadas; Thompson, Brian P; Mascena, Corianna J; Bellows, Wendy K; Lubys, Arvydas

2017-07-20

Microbial single-cell genomics can be used to provide insights into the metabolic potential, interactions, and evolution of uncultured microorganisms. Here we present WGA-X, a method based on multiple displacement amplification of DNA that utilizes a thermostable mutant of the phi29 polymerase. WGA-X enhances genome recovery from individual microbial cells and viral particles while maintaining ease of use and scalability. The greatest improvements are observed when amplifying high G+C content templates, such as those belonging to the predominant bacteria in agricultural soils. By integrating WGA-X with calibrated index-cell sorting and high-throughput genomic sequencing, we are able to analyze genomic sequences and cell sizes of hundreds of individual, uncultured bacteria, archaea, protists, and viral particles, obtained directly from marine and soil samples, in a single experiment. This approach may find diverse applications in microbiology and in biomedical and forensic studies of humans and other multicellular organisms.Single-cell genomics can be used to study uncultured microorganisms. Here, Stepanauskas et al. present a method combining improved multiple displacement amplification and FACS, to obtain genomic sequences and cell size information from uncultivated microbial cells and viral particles in environmental samples.

Understanding the scale of the single ion free energy: A critical test of the tetra-phenyl arsonium and tetra-phenyl borate assumption

NASA Astrophysics Data System (ADS)

Duignan, Timothy T.; Baer, Marcel D.; Mundy, Christopher J.

2018-06-01

The tetra-phenyl arsonium and tetra-phenyl borate (TATB) assumption is a commonly used extra-thermodynamic assumption that allows single ion free energies to be split into cationic and anionic contributions. The assumption is that the values for the TATB salt can be divided equally. This is justified by arguing that these large hydrophobic ions will cause a symmetric response in water. Experimental and classical simulation work has raised potential flaws with this assumption, indicating that hydrogen bonding with the phenyl ring may favor the solvation of the TB- anion. Here, we perform ab initio molecular dynamics simulations of these ions in bulk water demonstrating that there are significant structural differences. We quantify our findings by reproducing the experimentally observed vibrational shift for the TB- anion and confirm that this is associated with hydrogen bonding with the phenyl rings. Finally, we demonstrate that this results in a substantial energetic preference of the water to solvate the anion. Our results suggest that the validity of the TATB assumption, which is still widely used today, should be reconsidered experimentally in order to properly reference single ion solvation free energy, enthalpy, and entropy.

Ultrasensitive Detection of Single-Walled Carbon Nanotubes Using Surface Plasmon Resonance.

PubMed

Jang, Daeho; Na, Wonhwi; Kang, Minwook; Kim, Namjoon; Shin, Sehyun

2016-01-05

Because single-walled carbon nanotubes (SWNTs) are known to be a potentially dangerous material, inducing cancers and other diseases, any possible leakage of SWNTs through an aquatic medium such as drinking water will result in a major public threat. To solve this problem, for the present study, a highly sensitive, quantitative detection method of SWNTs in an aqueous solution was developed using surface plasmon resonance (SPR) spectroscopy. For a highly sensitive and specific detection, a strong affinity conjugation with biotin-streptavidin was adopted on an SPR sensing mechanism. During the pretreatment process, the SWNT surface was functionalized and hydrophilized using a thymine-chain based biotinylated single-strand DNA linker (B-ssDNA) and bovine serum albumin (BSA). The pretreated SWNTs were captured on a sensing film, the surface of which was immobilized with streptavidin on biotinylated gold film. The captured SWNTs were measured in real-time using SPR spectroscopy. Specific binding with SWNTs was verified through several validation experiments. The present method using an SPR sensor is capable of detecting SWNTs of as low as 100 fg/mL, which is the lowest level reported thus far for carbon-nanotube detection. In addition, the SPR sensor showed a linear characteristic within the range of 100 pg/mL to 200 ng/mL. These findings imply that the present SPR sensing method can detect an extremely low level of SWNTs in an aquatic environment with high sensitivity and high specificity, and thus any potential leakage of SWNTs into an aquatic environment can be precisely monitored within a couple of hours.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Labonté, Jessica M.; Swan, Brandon K.; Poulos, Bonnie

Viral infections dynamically alter the composition and metabolic potential of marine microbial communities and the evolutionary trajectories of host populations with resulting feedback on biogeochemical cycles. It is quite possible that all microbial populations in the ocean are impacted by viral infections. Our knowledge of virus–host relationships, however, has been limited to a minute fraction of cultivated host groups. Here, we utilized single-cell sequencing to obtain genomic blueprints of viruses inside or attached to individual bacterial and archaeal cells captured in their native environment, circumventing the need for host and virus cultivation. Furthermore, a combination of comparative genomics, metagenomic fragmentmore » recruitment, sequence anomalies and irregularities in sequence coverage depth and genome recovery were utilized to detect viruses and to decipher modes of virus–host interactions. Members of all three tailed phage families were identified in 20 out of 58 phylogenetically and geographically diverse single amplified genomes (SAGs) of marine bacteria and archaea. At least four phage–host interactions had the characteristics of late lytic infections, all of which were found in metabolically active cells. One virus had genetic potential for lysogeny. Our findings include first known viruses of Thaumarchaeota, Marinimicrobia, Verrucomicrobia and Gammaproteobacteria clusters SAR86 and SAR92. Viruses were also found in SAGs of Alphaproteobacteria and Bacteroidetes. A high fragment recruitment of viral metagenomic reads confirmed that most of the SAG-associated viruses are abundant in the ocean. This study demonstrates that single-cell genomics, in conjunction with sequence-based computational tools, enable in situ, cultivation-independent insights into host–virus interactions in complex microbial communities.« less

Therapeutic profile of single-fraction radiosurgery of vestibular schwannoma: unrelated malignancy predicts tumor control

PubMed Central

Wowra, Berndt; Muacevic, Alexander; Fürweger, Christoph; Schichor, Christian; Tonn, Jörg-Christian

2012-01-01

Radiosurgery has become an accepted treatment option for vestibular schwannomas. Nevertheless, predictors of tumor control and treatment toxicity in current radiosurgery of vestibular schwannomas are not well understood. To generate new information on predictors of tumor control and cranial nerve toxicity of single-fraction radiosurgery of vestibular schwannomas, we conducted a single-institution long-term observational study of radiosurgery for sporadic vestibular schwannomas. Minimum follow-up was 3 years. Investigated as potential predictors of tumor control and cranial nerve toxicity were treatment technology; tumor resection preceding radiosurgery; tumor size; gender; patient age; history of cancer, vascular disease, or metabolic disease; tumor volume; radiosurgical prescription dose; and isodose line. Three hundred eighty-six patients met inclusion criteria. Treatment failure was observed in 27 patients. History of unrelated cancer (strongest predictor) and prescription dose significantly predicted tumor control. The cumulative incidence of treatment failure was 30% after 6.5 years in patients with unrelated malignancy and 10% after ≥15 years in patients without such cancer (P < .02). Tumor volume was the only predictor of trigeminal neuropathy (observed in 6 patients). No predictor of facial nerve toxicity was found. On the House and Brackmann scale, 1 patient had a permanent one-level drop and 7 a transient drop of 1 to 3 levels. Serviceable hearing was preserved in 75.1%. Tumor hearing before radiosurgery, recurrence, and prescription isodose predicted ototoxicity. Unrelated malignancy is a strong predictor of tumor control. Tumor recurrence predominantly predicts ototoxicity. These findings potentially will aid future clinical decision making in ambiguous cases. PMID:22561798

Physiological stimuli evoke two forms of endocytosis in bovine chromaffin cells.

PubMed

Chan, S A; Smith, C

2001-12-15

1. Exocytosis and endocytosis were measured following single, or trains of, simulated action potentials (sAP) in bovine adrenal chromaffin cells. Catecholamine secretion was measured by oxidative amperometry and cell membrane turnover was measured by voltage clamp cell capacitance measurements. 2. The sAPs evoked inward Na(+) and Ca(2+) currents that were statistically identical to those evoked by native action potential waveforms. On average, a single secretory granule underwent fusion following sAP stimulation. An equivalent amount of membrane was then quickly internalised (tau = 560 ms). 3. Stimulation with sAP trains revealed a biphasic relationship between cell firing rate and endocytic activity. At basal stimulus frequencies (single to 0.5 Hz) cells exhibited a robust membrane internalisation that then diminished as firing increased to intermediate levels (1.9 and 6 Hz). However at the higher stimulation rates (10 and 16 Hz) endocytic activity rebounded and was again able to effectively maintain cell surface near pre-stimulus levels. 4. Treatment with cyclosporin A and FK506, inhibitors of the phosphatase calcineurin, left endocytosis characteristics unaltered at the lower basal stimulus levels, but blocked the resurgence in endocytosis seen in control cells at higher sAP frequencies. 5. Based on these findings we propose that, under physiological electrical stimulation, chromaffin cells internalise membrane via two distinct pathways that are separable. One is prevalent at basal stimulus frequencies, is lessened with increased firing, and is insensitive to cyclosporin A and FK506. A second endocytic form is activated by increased firing frequencies, and is selectively blocked by cyclosporin A and FK506.

Physiological stimuli evoke two forms of endocytosis in bovine chromaffin cells

PubMed Central

Chan, Shyue-An; Smith, Corey

2001-01-01

Exocytosis and endocytosis were measured following single, or trains of, simulated action potentials (sAP) in bovine adrenal chromaffin cells. Catecholamine secretion was measured by oxidative amperometry and cell membrane turnover was measured by voltage clamp cell capacitance measurements. The sAPs evoked inward Na+ and Ca2+ currents that were statistically identical to those evoked by native action potential waveforms. On average, a single secretory granule underwent fusion following sAP stimulation. An equivalent amount of membrane was then quickly internalised (τ = 560 ms). Stimulation with sAP trains revealed a biphasic relationship between cell firing rate and endocytic activity. At basal stimulus frequencies (single to 0.5 Hz) cells exhibited a robust membrane internalisation that then diminished as firing increased to intermediate levels (1.9 and 6 Hz). However at the higher stimulation rates (10 and 16 Hz) endocytic activity rebounded and was again able to effectively maintain cell surface near pre-stimulus levels. Treatment with cyclosporin A and FK506, inhibitors of the phosphatase calcineurin, left endocytosis characteristics unaltered at the lower basal stimulus levels, but blocked the resurgence in endocytosis seen in control cells at higher sAP frequencies. Based on these findings we propose that, under physiological electrical stimulation, chromaffin cells internalise membrane via two distinct pathways that are separable. One is prevalent at basal stimulus frequencies, is lessened with increased firing, and is insensitive to cyclosporin A and FK506. A second endocytic form is activated by increased firing frequencies, and is selectively blocked by cyclosporin A and FK506. PMID:11744761

Incidental finding of single coronary artery in a patient with alcoholic cardiomyopathy presenting as acute heart failure.

PubMed

McNair, Patrick; Jones, Erica; Truong, Quynh; Singh, Harsimran

Single coronary artery is a rare clinical finding. Diagnosis is typically made incidentally after the patient presents with symptoms and undergoes coronary angiography, coronary computed tomography angiography (CTA), or post-mortem during autopsy. Several high-risk features of anomalous coronary arteries have been described in the literature. Our paper describes a case of dilated alcoholic cardiomyopathy presenting as heart failure with diagnostic workup incidentally revealing single coronary artery. Copyright © 2017 Elsevier Inc. All rights reserved.

Spatially Resolved Sensitivity of Single-Particle Plasmon Sensors

PubMed Central

2018-01-01

The high sensitivity of localized surface plasmon resonance sensors to the local refractive index allows for the detection of single-molecule binding events. Though binding events of single objects can be detected by their induced plasmon shift, the broad distribution of observed shifts remains poorly understood. Here, we perform a single-particle study wherein single nanospheres bind to a gold nanorod, and relate the observed plasmon shift to the binding location using correlative microscopy. To achieve this we combine atomic force microscopy to determine the binding location, and single-particle spectroscopy to determine the corresponding plasmon shift. As expected, we find a larger plasmon shift for nanospheres binding at the tip of a rod compared to its sides, in good agreement with numerical calculations. However, we also find a broad distribution of shifts even for spheres that were bound at a similar location to the nanorod. Our correlative approach allows us to disentangle effects of nanoparticle dimensions and binding location, and by comparison to numerical calculations we find that the biggest contributor to this observed spread is the dispersion in nanosphere diameter. These experiments provide insight into the spatial sensitivity and signal-heterogeneity of single-particle plasmon sensors and provides a framework for signal interpretation in sensing applications. PMID:29520315

Resolving Evolutionary Relationships in Closely Related Species with Whole-Genome Sequencing Data

PubMed Central

Nater, Alexander; Burri, Reto; Kawakami, Takeshi; Smeds, Linnéa; Ellegren, Hans

2015-01-01

Using genetic data to resolve the evolutionary relationships of species is of major interest in evolutionary and systematic biology. However, reconstructing the sequence of speciation events, the so-called species tree, in closely related and potentially hybridizing species is very challenging. Processes such as incomplete lineage sorting and interspecific gene flow result in local gene genealogies that differ in their topology from the species tree, and analyses of few loci with a single sequence per species are likely to produce conflicting or even misleading results. To study these phenomena on a full phylogenomic scale, we use whole-genome sequence data from 200 individuals of four black-and-white flycatcher species with so far unresolved phylogenetic relationships to infer gene tree topologies and visualize genome-wide patterns of gene tree incongruence. Using phylogenetic analysis in nonoverlapping 10-kb windows, we show that gene tree topologies are extremely diverse and change on a very small physical scale. Moreover, we find strong evidence for gene flow among flycatcher species, with distinct patterns of reduced introgression on the Z chromosome. To resolve species relationships on the background of widespread gene tree incongruence, we used four complementary coalescent-based methods for species tree reconstruction, including complex modeling approaches that incorporate post-divergence gene flow among species. This allowed us to infer the most likely species tree with high confidence. Based on this finding, we show that regions of reduced effective population size, which have been suggested as particularly useful for species tree inference, can produce positively misleading species tree topologies. Our findings disclose the pitfalls of using loci potentially under selection as phylogenetic markers and highlight the potential of modeling approaches to disentangle species relationships in systems with large effective population sizes and post-divergence gene flow. PMID:26187295

Increasing N200 Potentials Via Visual Stimulus Depicting Humanoid Robot Behavior.

PubMed

Li, Mengfan; Li, Wei; Zhou, Huihui

2016-02-01

Achieving recognizable visual event-related potentials plays an important role in improving the success rate in telepresence control of a humanoid robot via N200 or P300 potentials. The aim of this research is to intensively investigate ways to induce N200 potentials with obvious features by flashing robot images (images with meaningful information) and by flashing pictures containing only solid color squares (pictures with incomprehensible information). Comparative studies have shown that robot images evoke N200 potentials with recognizable negative peaks at approximately 260 ms in the frontal and central areas. The negative peak amplitudes increase, on average, from 1.2 μV, induced by flashing the squares, to 6.7 μV, induced by flashing the robot images. The data analyses support that the N200 potentials induced by the robot image stimuli exhibit recognizable features. Compared with the square stimuli, the robot image stimuli increase the average accuracy rate by 9.92%, from 83.33% to 93.25%, and the average information transfer rate by 24.56 bits/min, from 72.18 bits/min to 96.74 bits/min, in a single repetition. This finding implies that the robot images might provide the subjects with more information to understand the visual stimuli meanings and help them more effectively concentrate on their mental activities.

Parents' Views on Mixed and Single-Sex Secondary Schools.

ERIC Educational Resources Information Center

West, Anne; Hunter, Jay

1993-01-01

Reports on two studies of British parental attitudes toward coeducational and single-sex secondary schools. Finds few differences between the parents of primary school girls and boys who will attend secondary schools in the future. Also finds a large majority of boys' parents believe that social advantages accrue for boys educated with girls. (CFR)

Accuracy of Protein Embedding Potentials: An Analysis in Terms of Electrostatic Potentials.

PubMed

Olsen, Jógvan Magnus Haugaard; List, Nanna Holmgaard; Kristensen, Kasper; Kongsted, Jacob

2015-04-14

Quantum-mechanical embedding methods have in recent years gained significant interest and may now be applied to predict a wide range of molecular properties calculated at different levels of theory. To reach a high level of accuracy in embedding methods, both the electronic structure model of the active region and the embedding potential need to be of sufficiently high quality. In fact, failures in quantum mechanics/molecular mechanics (QM/MM)-based embedding methods have often been associated with the QM/MM methodology itself; however, in many cases the reason for such failures is due to the use of an inaccurate embedding potential. In this paper, we investigate in detail the quality of the electronic component of embedding potentials designed for calculations on protein biostructures. We show that very accurate explicitly polarizable embedding potentials may be efficiently designed using fragmentation strategies combined with single-fragment ab initio calculations. In fact, due to the self-interaction error in Kohn-Sham density functional theory (KS-DFT), use of large full-structure quantum-mechanical calculations based on conventional (hybrid) functionals leads to less accurate embedding potentials than fragment-based approaches. We also find that standard protein force fields yield poor embedding potentials, and it is therefore not advisable to use such force fields in general QM/MM-type calculations of molecular properties other than energies and structures.

Finding Coefficients of the Full Array of Motion-Independent N-Body Potentials of Metric Gravity from Gravity's Exterior and Interior Effacement Algebra

NASA Astrophysics Data System (ADS)

Nordtvedt, Kenneth

2018-01-01

In the author's previous publications, a recursive linear algebraic method was introduced for obtaining (without gravitational radiation) the full potential expansions for the gravitational metric field components and the Lagrangian for a general N-body system. Two apparent properties of gravity— Exterior Effacement and Interior Effacement—were defined and fully enforced to obtain the recursive algebra, especially for the motion-independent potential expansions of the general N-body situation. The linear algebraic equations of this method determine the potential coefficients at any order n of the expansions in terms of the lower-order coefficients. Then, enforcing Exterior and Interior Effacement on a selecedt few potential series of the full motion-independent potential expansions, the complete exterior metric field for a single, spherically-symmetric mass source was obtained, producing the Schwarzschild metric field of general relativity. In this fourth paper of this series, the complete spatial metric's motion-independent potentials for N bodies are obtained using enforcement of Interior Effacement and knowledge of the Schwarzschild potentials. From the full spatial metric, the complete set of temporal metric potentials and Lagrangian potentials in the motion-independent case can then be found by transfer equations among the coefficients κ( n, α) → λ( n, ɛ) → ξ( n, α) with κ( n, α), λ( n, ɛ), ξ( n, α) being the numerical coefficients in the spatial metric, the Lagrangian, and the temporal metric potential expansions, respectively.

Creating Geologically Based Radon Potential Maps for Kentucky

NASA Astrophysics Data System (ADS)

Overfield, B.; Hahn, E.; Wiggins, A.; Andrews, W. M., Jr.

2017-12-01

Radon potential in the United States, Kentucky in particular, has historically been communicated using a single hazard level for each county; however, physical phenomena are not controlled by administrative boundaries, so single-value county maps do not reflect the significant variations in radon potential in each county. A more accurate approach uses bedrock geology as a predictive tool. A team of nurses, health educators, statisticians, and geologists partnered to create 120 county maps showing spatial variations in radon potential by intersecting residential radon test kit results (N = 60,000) with a statewide 1:24,000-scale bedrock geology coverage to determine statistically valid radon-potential estimates for each geologic unit. Maps using geology as a predictive tool for radon potential are inherently more detailed than single-value county maps. This mapping project revealed that areas in central and south-central Kentucky with the highest radon potential are underlain by shales and karstic limestones.

Single-Particle Mobility Edge in a One-Dimensional Quasiperiodic Optical Lattice

NASA Astrophysics Data System (ADS)

Lüschen, Henrik P.; Scherg, Sebastian; Kohlert, Thomas; Schreiber, Michael; Bordia, Pranjal; Li, Xiao; Das Sarma, S.; Bloch, Immanuel

2018-04-01

A single-particle mobility edge (SPME) marks a critical energy separating extended from localized states in a quantum system. In one-dimensional systems with uncorrelated disorder, a SPME cannot exist, since all single-particle states localize for arbitrarily weak disorder strengths. However, in a quasiperiodic system, the localization transition can occur at a finite detuning strength and SPMEs become possible. In this Letter, we find experimental evidence for the existence of such a SPME in a one-dimensional quasiperiodic optical lattice. Specifically, we find a regime where extended and localized single-particle states coexist, in good agreement with theoretical simulations, which predict a SPME in this regime.

Structural and molecular remodeling of dendritic spine substructures during long-term potentiation

PubMed Central

Bosch, Miquel; Castro, Jorge; Saneyoshi, Takeo; Matsuno, Hitomi; Sur, Mriganka; Hayashi, Yasunori

2014-01-01

SUMMARY Synapses store information by long-lasting modifications of their structure and molecular composition, but the precise chronology of these changes has not been studied at single synapse resolution in real time. Here we describe the spatiotemporal reorganization of postsynaptic substructures during long-term potentiation (LTP) at individual dendritic spines. Proteins translocated to the spine in four distinct patterns through three sequential phases. In the initial phase, the actin cytoskeleton was rapidly remodeled while active cofilin was massively transported to the spine. In the stabilization phase, cofilin formed a stable complex with F-actin, was persistently retained at the spine, and consolidated spine expansion. In contrast, the postsynaptic density (PSD) was independently remodeled, as PSD scaffolding proteins did not change their amount and localization until a late protein synthesis-dependent third phase. Our findings show how and when spine substructures are remodeled during LTP and explain why synaptic plasticity rules change over time. PMID:24742465

[Visual perception of Kanji characters and complicated figures. Part 3. Visual P300 event-related potentials in patients with attention deficit/hyperactivity disorders].

PubMed

Shirane, Seiko; Inagaki, Masumi; Sata, Yoshimi; Kaga, Makiko

2004-07-01

In order to evaluate visual perception, the P300 event-related potentials (ERPs) for visual oddball tasks were recorded in 11 patients with attention deficit/hyperactivity disorders (AD/HD), 12 with mental retardation (MR) and 14 age-matched healthy controls. With the aim of revealing trial-to-trial variabilities which are neglected by investigating averaged ERPs, single sweep P300s (ss-P300s) were assessed in addition to averaged P300. There were no significant differences of averaged P300 latency and amplitude between controls and AD/HD patients. AD/HD patients showed an increased variability in the amplitude of ss-P300s, while MR patient showed an increased variability in latency. These findings suggest that in AD/HD patients general attention is impaired to a larger extent than selective attention and visual perception.

Pilot Testing a Couples-focused Intervention for Mild Cognitive Impairment

PubMed Central

Lu, Yvonne Yueh-Feng; Haase, Joan E.; Weaver, Michael

2014-01-01

The purpose of this pilot study was to evaluate the acceptability, feasibility, and potential benefits of the multi-component Daily Enhancement of Meaningful Activity (DEMA) intervention, which was tailored to help couples facing mild cognitive impairment (MCI) work together to meet goals, remain engaged in meaningful activities, and adapt to changes over time. Using a single-group design, 10 persons with MCI and their family caregivers were recruited to receive DEMA over six bi-weekly sessions. Data were collected pre- and at one week and three months post-intervention. Consent, session, and questionnaire completion rates indicated the program and study procedures were well accepted. Qualitative and quantitative findings indicated positive trends in meaningful activity performance and maintenance of health-related outcomes, as well as high program satisfaction. The DEMA is a potentially promising intervention that will need further testing in a randomized clinical trial. PMID:23767062

The effects of speech controls on performance in advanced helicopters in a double stimulation paradigm

NASA Technical Reports Server (NTRS)

Bortolussi, Michael R.; Vidulich, Michael A.

1991-01-01

The potential benefit of speech as a control modality has been investigated with mixed results. Earlier studies suggests that speech controls can reduce the potential of manual control overloads and improve time-sharing performance. However, these benefits were not without costs. Pilots reported higher workload levels associated with the use of speech controls. To further investigate these previous findings, an experiment was conducted in a simulation of an advanced single-pilot, scout/attack helicopter at NASA-Ames' ICAB (interchangeable cab) facility. Objective performance data suggested that speech control modality was effective in reducing interference of discrete, time-shared responses during continuous flight control activity. Subjective ratings, however, indicated that the speech control modality increased workload. Post-flight debriefing indicated that these results were mainly due to the increased effort to speak precisely to a less than perfect voice recognition system.

Emergent dynamics of laboratory insect swarms

NASA Astrophysics Data System (ADS)

Kelley, Douglas H.; Ouellette, Nicholas T.

2013-01-01

Collective animal behaviour occurs at nearly every biological size scale, from single-celled organisms to the largest animals on earth. It has long been known that models with simple interaction rules can reproduce qualitative features of this complex behaviour. But determining whether these models accurately capture the biology requires data from real animals, which has historically been difficult to obtain. Here, we report three-dimensional, time-resolved measurements of the positions, velocities, and accelerations of individual insects in laboratory swarms of the midge Chironomus riparius. Even though the swarms do not show an overall polarisation, we find statistical evidence for local clusters of correlated motion. We also show that the swarms display an effective large-scale potential that keeps individuals bound together, and we characterize the shape of this potential. Our results provide quantitative data against which the emergent characteristics of animal aggregation models can be benchmarked.

A global synthesis of plant extinction rates in urban areas.

PubMed

Hahs, Amy K; McDonnell, Mark J; McCarthy, Michael A; Vesk, Peter A; Corlett, Richard T; Norton, Briony A; Clemants, Steven E; Duncan, Richard P; Thompson, Ken; Schwartz, Mark W; Williams, Nicholas S G

2009-11-01

Plant extinctions from urban areas are a growing threat to biodiversity worldwide. To minimize this threat, it is critical to understand what factors are influencing plant extinction rates. We compiled plant extinction rate data for 22 cities around the world. Two-thirds of the variation in plant extinction rates was explained by a combination of the city's historical development and the current proportion of native vegetation, with the former explaining the greatest variability. As a single variable, the amount of native vegetation remaining also influenced extinction rates, particularly in cities > 200 years old. Our study demonstrates that the legacies of landscape transformations by agrarian and urban development last for hundreds of years, and modern cities potentially carry a large extinction debt. This finding highlights the importance of preserving native vegetation in urban areas and the need for mitigation to minimize potential plant extinctions in the future.

Controlling the layer localization of gapless states in bilayer graphene with a gate voltage

NASA Astrophysics Data System (ADS)

Jaskólski, W.; Pelc, M.; Bryant, Garnett W.; Chico, Leonor; Ayuela, A.

2018-04-01

Experiments in gated bilayer graphene with stacking domain walls present topological gapless states protected by no-valley mixing. Here we research these states under gate voltages using atomistic models, which allow us to elucidate their origin. We find that the gate potential controls the layer localization of the two states, which switches non-trivially between layers depending on the applied gate voltage magnitude. We also show how these bilayer gapless states arise from bands of single-layer graphene by analyzing the formation of carbon bonds between layers. Based on this analysis we provide a model Hamiltonian with analytical solutions, which explains the layer localization as a function of the ratio between the applied potential and interlayer hopping. Our results open a route for the manipulation of gapless states in electronic devices, analogous to the proposed writing and reading memories in topological insulators.

Partial breaking of the Coulombic ordering of ionic liquids confined in carbon nanopores

PubMed Central

Futamura, Ryusuke; Iiyama, Taku; Takasaki, Yuma; Gogotsi, Yury; Biggs, Mark J.; Salanne, Mathieu; Ségalini, Julie; Simon, Patrice; Kaneko, Katsumi

2017-01-01

Ionic liquids are composed of equal quantities of positive and negative ions. In the bulk, electrical neutrality occurs in these liquids due to Coulombic ordering, in which ion shells of alternating charge form around a central ion. Their structure under confinement is far less well understood. This hinders the widespread application of ionic liquids in technological applications. Here we use scattering experiments to resolve the structure of the widely used ionic liquid (EMI-TFSI) when it is confined inside nanoporous carbons. We show that Coulombic ordering reduces when the pores can only accommodate a single layer of ions. Instead, equally-charged ion pairs are formed due to the induction of an electric potential of opposite sign in the carbon pore walls. This non-Coulombic ordering is further enhanced in the presence of an applied external electric potential. This finding opens the door for the design of better materials for electrochemical applications. PMID:28920938

Brane-world motion in compact dimensions

NASA Astrophysics Data System (ADS)

Greene, Brian; Levin, Janna; Parikh, Maulik

2011-08-01

The topology of extra dimensions can break global Lorentz invariance, singling out a globally preferred frame even in flat spacetime. Through experiments that probe global topology, an observer can determine her state of motion with respect to the preferred frame. This scenario is realized if we live on a brane universe moving through a flat space with compact extra dimensions. We identify three experimental effects due to the motion of our universe that one could potentially detect using gravitational probes. One of these relates to the peculiar properties of the twin paradox in multiply-connected spacetimes. Another relies on the fact that the Kaluza-Klein modes of any bulk field are sensitive to boundary conditions. A third concerns the modification to the Newtonian potential on a moving brane. Remarkably, we find that even small extra dimensions are detectable by brane observers if the brane is moving sufficiently fast. Communicated by P R L V Moniz

Of Men and Mice: Modeling the Fragile X Syndrome

PubMed Central

Dahlhaus, Regina

2018-01-01

The Fragile X Syndrome (FXS) is one of the most common forms of inherited intellectual disability in all human societies. Caused by the transcriptional silencing of a single gene, the fragile x mental retardation gene FMR1, FXS is characterized by a variety of symptoms, which range from mental disabilities to autism and epilepsy. More than 20 years ago, a first animal model was described, the Fmr1 knock-out mouse. Several other models have been developed since then, including conditional knock-out mice, knock-out rats, a zebrafish and a drosophila model. Using these model systems, various targets for potential pharmaceutical treatments have been identified and many treatments have been shown to be efficient in preclinical studies. However, all attempts to turn these findings into a therapy for patients have failed thus far. In this review, I will discuss underlying difficulties and address potential alternatives for our future research. PMID:29599705

Translocation and gross deletion breakpoints in human inherited disease and cancer II: Potential involvement of repetitive sequence elements in secondary structure formation between DNA ends.

PubMed

Chuzhanova, Nadia; Abeysinghe, Shaun S; Krawczak, Michael; Cooper, David N

2003-09-01

Translocations and gross deletions are responsible for a significant proportion of both cancer and inherited disease. Although such gene rearrangements are nonuniformly distributed in the human genome, the underlying mutational mechanisms remain unclear. We have studied the potential involvement of various types of repetitive sequence elements in the formation of secondary structure intermediates between the single-stranded DNA ends that recombine during rearrangements. Complexity analysis was used to assess the potential of these ends to form secondary structures, the maximum decrease in complexity consequent to a gross rearrangement being used as an indicator of the type of repeat and the specific DNA ends involved. A total of 175 pairs of deletion/translocation breakpoint junction sequences available from the Gross Rearrangement Breakpoint Database [GRaBD; www.uwcm.ac.uk/uwcm/mg/grabd/grabd.html] were analyzed. Potential secondary structure was noted between the 5' flanking sequence of the first breakpoint and the 3' flanking sequence of the second breakpoint in 49% of rearrangements and between the 5' flanking sequence of the second breakpoint and the 3' flanking sequence of the first breakpoint in 36% of rearrangements. Inverted repeats, inversions of inverted repeats, and symmetric elements were found in association with gross rearrangements at approximately the same frequency. However, inverted repeats and inversions of inverted repeats accounted for the vast majority (83%) of deletions plus small insertions, symmetric elements for one-half of all antigen receptor-mediated translocations, while direct repeats appear only to be involved in mediating simple deletions. These findings extend our understanding of illegitimate recombination by highlighting the importance of secondary structure formation between single-stranded DNA ends at breakpoint junctions. Copyright 2003 Wiley-Liss, Inc.

Men's Preferences for Physical Activity Interventions: An Exploratory Study Using a Factorial Survey Design Created With R Software.

PubMed

Chatfield, Sheryl L; Gamble, Abigail; Hallam, Jeffrey S

2018-03-01

Effective exercise interventions are needed to improve quality of life and decrease the impact of chronic disease. Researchers suggest males have been underrepresented in exercise intervention studies, resulting in less understanding of their exercise practices. Findings from preference survey methods suggest reasonable association between preference and behavior. The purpose of the research described in this article was to use factorial survey, a preference method, to identify the characteristics of exercise interventions most likely to appeal to male participants, so preferences might be incorporated into future intervention research. The research was guided by the framework of Bandura's social cognitive theory, such that variations in individual, environmental, and behavioral factors were incorporated into vignettes. Participants included 53 adult male nonadministrative staff and contract employees at a public university in the Southeastern United States, who each scored 8 vignettes resulting in 423 observations. Multilevel models were used to assess the influence of the factors. Participants scored vignettes that included exercising with a single partner, playing basketball, and exercising in the evening higher than vignettes with other options. Qualitative analysis of an open response item identified additional alternatives in group size, participant desire for coaching support, and interest in programs that incorporate a range of activity alternatives. Findings from this research were consistent with elements of social cognitive theory as applied to health promotion. Factorial surveys potentially provide a resource effective means of identifying participants' preferences for use when planning interventions. The addition of a single qualitative item helped clarify and expand findings from statistical analysis.

Identification by whole-genome resequencing of gene defect responsible for severe hypercholesterolemia

PubMed Central

Rios, Jonathan; Stein, Evan; Shendure, Jay; Hobbs, Helen H.; Cohen, Jonathan C.

2010-01-01

Whole-genome sequencing is a potentially powerful tool for the diagnosis of genetic diseases. Here, we used sequencing-by-ligation to sequence the genome of an 11-month-old breast-fed girl with xanthomas and very high plasma cholesterol levels (1023 mg/dl). Her parents had normal plasma cholesterol levels and reported no family history of hypercholesterolemia, suggesting either an autosomal recessive disorder or a de novo mutation. Known genetic causes of severe hypercholesterolemia were ruled out by sequencing the responsible genes (LDLRAP, LDLR, PCSK9, APOE and APOB), and sitosterolemia was ruled out by documenting a normal plasma sitosterol:cholesterol ratio. Sequencing revealed 3 797 207 deviations from the reference sequence, of which 9726 were nonsynonymous single-nucleotide substitutions. A total of 9027 of the nonsynonymous substitutions were present in dbSNP or in 21 additional individuals from whom complete exonic sequences were available. The 699 novel nonsynonymous substitutions were distributed among 604 genes, 23 of which were single-copy genes that each contained 2 nonsynonymous substitutions consistent with an autosomal recessive model. One gene, ABCG5, had two nonsense mutations (Q16X and R446X). This finding indicated that the infant has sitosterolemia. Thus, whole-genome sequencing led to the diagnosis of a known disease with an atypical presentation. Diagnosis was confirmed by the finding of severe sitosterolemia in a blood sample obtained after the infant had been weaned. These findings demonstrate that whole-genome (or exome) sequencing can be a valuable aid to diagnose genetic diseases, even in individual patients. PMID:20719861

High-Performance Single-Photon Sources via Spatial Multiplexing

DTIC Science & Technology

2014-01-01

ingredient for tasks such as quantum cryptography , quantum repeater, quantum teleportation, quantum computing, and truly-random number generation. Recently...SECURITY CLASSIFICATION OF: Single photons sources are desired for many potential quantum information applications. One common method to produce...photons sources are desired for many potential quantum information applications. One common method to produce single photons is based on a “heralding

The intergenerational transfer of psychosocial risk: mediators of vulnerability and resilience.

PubMed

Serbin, Lisa A; Karp, Jennifer

2004-01-01

The recurrence of social, behavioral, and health problems in successive generations of families is a prevalent theme in both the scientific and popular literatures. This review discusses recent conceptual models and findings from longitudinal studies concerning the intergenerational transfer of psychosocial risk, including intergenerational continuity, and the processes whereby a generation of parents may place their offspring at elevated risk for social, behavioral, and health problems. Key findings include the mediational effects of parenting and environmental factors in the transfer of risk. In both girls and boys, childhood aggression and antisocial behavior appear to predict long-term trajectories that place offspring at risk. Sequelae of childhood aggression that may threaten the well-being of offspring include school failure, adolescent risk-taking behavior, early and single parenthood, and family poverty. These childhood and adolescent behavioral styles also predict harsh, aggressive, neglectful, and unstimulating parenting behavior toward offspring. Buffering factors within at-risk families include maternal educational attainment and constructive parenting practices (e.g., emotional warmth, consistent disciplinary practices, and cognitive scaffolding). These findings highlight the potential application and relevance of intergenerational studies for social, educational, and health policy.

Trapping behavior of Shockley-Read-Hall recombination centers in silicon solar cells

NASA Astrophysics Data System (ADS)

Gogolin, R.; Harder, N. P.

2013-08-01

We investigate the correlation between increased apparent carrier lifetime in photoconductance-based lifetime measurements and actually reduced recombination lifetime as measured by photoluminescence measurements. These findings are further reconfirmed by I-V curve measurements of solar cells. In particular, we show experimental results for lifetime samples and solar cells with and without hydrogen passivation. In the samples and solar cells without hydrogen passivation, we find both a stronger trapping behavior and a lower recombination lifetime. Our model provides a consistent description of the observation of both, the increased apparent lifetime from carrier trapping and the decreasing recombination lifetime. In our model, both are caused by a single physical mechanism; i.e., by Recombination-Active-Trap (RAT) states. Upon fitting the experimental lifetime data, we find that the RAT-defect parameters for the hydrogen-passivated and non-hydrogen-passivated lifetime samples and solar cells are identical except for the defect concentration: hydrogen-passivation reduced the defect density by 50% in both, the lifetime samples and solar cells. We conclude that trapping should be considered as an indication for hidden, yet potentially strongly increased, low injection recombination activity.

Beam wander of coherent and partially coherent Airy beam arrays in a turbulent atmosphere

NASA Astrophysics Data System (ADS)

Wen, Wei; Jin, Ying; Hu, Mingjun; Liu, Xianlong; Cai, Yangjian; Zou, Chenjuan; Luo, Mi; Zhou, Liwang; Chu, Xiuxiang

2018-05-01

The beam wander properties of coherent and partially coherent Airy beam arrays in a turbulent atmosphere are investigated. Based on the analytical results, we find that the beam wander of partially coherent Airy beam arrays is significantly reduced compared with the wander of a partially coherent Airy beam by numerical simulation. Moreover, the beam wander of a 2 × 2 partially coherent Airy beam arrays is significantly reduced compared with the wander of a 2 × 2 partially coherent Gaussian beam arrays. By using the definition of beam wander arrays factor which is used to characterize the capability of beam arrays for reducing the beam wander effect compared with a single beam, we find that the arrays factor of partially coherent Airy beam arrays is significantly less than that of partially coherent Gaussian beam arrays with the same arrays order. We also find that an artificial reduction of the initial coherence of laser arrays can be used to decrease the beam wander effect. These results indicate that the partially coherent Airy beam arrays have potential applications in long-distance free-space optical communications.

Local classifiers for evoked potentials recorded from behaving rats.

PubMed

Jakuczun, Wit; Kublik, Ewa; Wójcik, Daniel K; Wróbel, Andrzej

2005-01-01

Dynamic states of the brain determine the way information is processed in local neural networks. We have applied classical conditioning paradigm in order to study whether habituated and aroused states can be differentiated in single barrel column of rat's somatosensory cortex by means of analysis of field potentials evoked by stimulation of a single vibrissa. A new method using local classifiers is presented which allows for reliable and meaningful classification of single evoked potentials which might be consequently attributed to different functional states of the cortical column.

Molecular allergy diagnostics using IgE singleplex determinations: methodological and practical considerations for use in clinical routine: Part 18 of the Series Molecular Allergology.

PubMed

Kleine-Tebbe, Jörg; Jakob, Thilo

Allergen molecules (synonyms: single allergens, allergen components) open up new horizons for the targeted allergen-specific diagnostics of immunoglobulin E (IgE) in singleplex determination. The following rationales support the targeted use of allergen molecules and, more importantly, improve test properties: (1) increased test sensitivity ("analytical sensitivity"), particularly when important allergens are under-represented or lacking in the extract; (2) improved test selectivity (analytical specificity), particularly when the selected IgE repertoire against an allergen yields additional information on: (a) potential risk, (b) possible cross-reactivity, or (c) primary (species-specific) sensitization. However, the appropriate indication for the use of single allergens can only be established on a case-by-case basis (depending on the clinical context and previous history) and in an allergen-specific manner (depending on the allergen source and the single allergens available), rather than in a standardized way. Numerous investigations on suspected food allergy, insect venom allergy, or sensitization to respiratory allergens have meanwhile demonstrated the successful use of defined molecules for allergen-specific singleplex IgE diagnosis. Specific IgE to single allergens is limited in its suitability to predict the clinical relevance of sensitivity on an individual basis. In food allergies, one can at best identify the relative risk of a clinical reaction on the basis of an IgE profile, but no absolutely reliable prediction on (future) tolerance can be made. Ultimately, the clinical relevance of all IgE findings depends on the presence of corresponding symptoms and can only be assessed on an individual basis (previous history, symptom log, and provocation testing with the relevant allergen source where appropriate). Thus, also in molecular allergology, the treating physician and not the test result should determine the clinical relevance of diagnostic findings. Supplementary material is available for this article at 10.1007/s40629-015-0067-z and is accessible for authorized users.

Multiple-input multiple-output causal strategies for gene selection.

PubMed

Bontempi, Gianluca; Haibe-Kains, Benjamin; Desmedt, Christine; Sotiriou, Christos; Quackenbush, John

2011-11-25

Traditional strategies for selecting variables in high dimensional classification problems aim to find sets of maximally relevant variables able to explain the target variations. If these techniques may be effective in generalization accuracy they often do not reveal direct causes. The latter is essentially related to the fact that high correlation (or relevance) does not imply causation. In this study, we show how to efficiently incorporate causal information into gene selection by moving from a single-input single-output to a multiple-input multiple-output setting. We show in synthetic case study that a better prioritization of causal variables can be obtained by considering a relevance score which incorporates a causal term. In addition we show, in a meta-analysis study of six publicly available breast cancer microarray datasets, that the improvement occurs also in terms of accuracy. The biological interpretation of the results confirms the potential of a causal approach to gene selection. Integrating causal information into gene selection algorithms is effective both in terms of prediction accuracy and biological interpretation.

Quantum proofs can be verified using only single-qubit measurements

NASA Astrophysics Data System (ADS)

Morimae, Tomoyuki; Nagaj, Daniel; Schuch, Norbert

2016-02-01

Quantum Merlin Arthur (QMA) is the class of problems which, though potentially hard to solve, have a quantum solution that can be verified efficiently using a quantum computer. It thus forms a natural quantum version of the classical complexity class NP (and its probabilistic variant MA, Merlin-Arthur games), where the verifier has only classical computational resources. In this paper, we study what happens when we restrict the quantum resources of the verifier to the bare minimum: individual measurements on single qubits received as they come, one by one. We find that despite this grave restriction, it is still possible to soundly verify any problem in QMA for the verifier with the minimum quantum resources possible, without using any quantum memory or multiqubit operations. We provide two independent proofs of this fact, based on measurement-based quantum computation and the local Hamiltonian problem. The former construction also applies to QMA1, i.e., QMA with one-sided error.

Using shape to turn off blinking for two-colour multiexciton emission in CdSe/CdS tetrapods

NASA Astrophysics Data System (ADS)

Mishra, Nimai; Orfield, Noah J.; Wang, Feng; Hu, Zhongjian; Krishnamurthy, Sachidananda; Malko, Anton V.; Casson, Joanna L.; Htoon, Han; Sykora, Milan; Hollingsworth, Jennifer A.

2017-05-01

Semiconductor nanostructures capable of emitting from two excited states and thereby of producing two photoluminescence colours are of fundamental and potential technological significance. In this limited class of nanocrystals, CdSe/CdS core/arm tetrapods exhibit the unusual trait of two-colour (red and green) multiexcitonic emission, with green emission from the CdS arms emerging only at high excitation fluences. Here we show that by synthetic shape-tuning, both this multi-colour emission process, and blinking and photobleaching behaviours of single tetrapods can be controlled. Specifically, we find that the properties of dual emission and single-nanostructure photostability depend on different structural parameters--arm length and arm diameter, respectively--but that both properties can be realized in the same nanostructure. Furthermore, based on results of correlated photoluminescence and transient absorption measurements, we conclude that hole-trap filling in the arms and partial state-filling in the core are necessary preconditions for the observation of multiexciton multi-colour emission.

Social information signaling by neurons in primate striatum.

PubMed

Klein, Jeffrey T; Platt, Michael L

2013-04-22

Social decisions depend on reliable information about others. Consequently, social primates are motivated to acquire information about the identity, social status, and reproductive quality of others. Neurophysiological and neuroimaging studies implicate the striatum in the motivational control of behavior. Neuroimaging studies specifically implicate the ventromedial striatum in signaling motivational aspects of social interaction. Despite this evidence, precisely how striatal neurons encode social information remains unknown. Therefore, we probed the activity of single striatal neurons in monkeys choosing between visual social information at the potential expense of fluid reward. We show for the first time that a population of neurons located primarily in medial striatum selectively signals social information. Surprisingly, representation of social information was unrelated to simultaneously expressed social preferences. A largely nonoverlapping population of neurons that was not restricted to the medial striatum signaled information about fluid reward. Our findings demonstrate that information about social context and nutritive reward are maintained largely independently in striatum, even when both influence decisions to execute a single action. Copyright © 2013 Elsevier Ltd. All rights reserved.

RNA-dependent RNA targeting by CRISPR-Cas9

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strutt, Steven C.; Torrez, Rachel M.; Kaya, Emine

Double-stranded DNA (dsDNA) binding and cleavage by Cas9 is a hallmark of type II CRISPR-Cas bacterial adaptive immunity. All known Cas9 enzymes are thought to recognize DNA exclusively as a natural substrate, providing protection against DNA phage and plasmids. Here, we show that Cas9 enzymes from both subtypes II-A and II-C can recognize and cleave single-stranded RNA (ssRNA) by an RNA-guided mechanism that is independent of a protospacer-adjacent motif (PAM) sequence in the target RNA. RNA-guided RNA cleavage is programmable and site-specific, and we find that this activity can be exploited to reduce infection by single-stranded RNA phage in vivo.more » We also demonstrate that Cas9 can direct PAM-independent repression of gene expression in bacteria. In conclusion, these results indicate that a subset of Cas9 enzymes have the ability to act on both DNA and RNA target sequences, and suggest the potential for use in programmable RNA targeting applications.« less

RNA-dependent RNA targeting by CRISPR-Cas9

DOE PAGES

Strutt, Steven C.; Torrez, Rachel M.; Kaya, Emine; ...

2018-01-05

Double-stranded DNA (dsDNA) binding and cleavage by Cas9 is a hallmark of type II CRISPR-Cas bacterial adaptive immunity. All known Cas9 enzymes are thought to recognize DNA exclusively as a natural substrate, providing protection against DNA phage and plasmids. Here, we show that Cas9 enzymes from both subtypes II-A and II-C can recognize and cleave single-stranded RNA (ssRNA) by an RNA-guided mechanism that is independent of a protospacer-adjacent motif (PAM) sequence in the target RNA. RNA-guided RNA cleavage is programmable and site-specific, and we find that this activity can be exploited to reduce infection by single-stranded RNA phage in vivo.more » We also demonstrate that Cas9 can direct PAM-independent repression of gene expression in bacteria. In conclusion, these results indicate that a subset of Cas9 enzymes have the ability to act on both DNA and RNA target sequences, and suggest the potential for use in programmable RNA targeting applications.« less

Using shape to turn off blinking for two-colour multiexciton emission in CdSe/CdS tetrapods

PubMed Central

Mishra, Nimai; Orfield, Noah J.; Wang, Feng; Hu, Zhongjian; Krishnamurthy, Sachidananda; Malko, Anton V.; Casson, Joanna L.; Htoon, Han; Sykora, Milan; Hollingsworth, Jennifer A.

2017-01-01

Semiconductor nanostructures capable of emitting from two excited states and thereby of producing two photoluminescence colours are of fundamental and potential technological significance. In this limited class of nanocrystals, CdSe/CdS core/arm tetrapods exhibit the unusual trait of two-colour (red and green) multiexcitonic emission, with green emission from the CdS arms emerging only at high excitation fluences. Here we show that by synthetic shape-tuning, both this multi-colour emission process, and blinking and photobleaching behaviours of single tetrapods can be controlled. Specifically, we find that the properties of dual emission and single-nanostructure photostability depend on different structural parameters—arm length and arm diameter, respectively—but that both properties can be realized in the same nanostructure. Furthermore, based on results of correlated photoluminescence and transient absorption measurements, we conclude that hole-trap filling in the arms and partial state-filling in the core are necessary preconditions for the observation of multiexciton multi-colour emission. PMID:28497776

Towards a web-based decision support tool for selecting appropriate statistical test in medical and biological sciences.

PubMed

Suner, Aslı; Karakülah, Gökhan; Dicle, Oğuz

2014-01-01

Statistical hypothesis testing is an essential component of biological and medical studies for making inferences and estimations from the collected data in the study; however, the misuse of statistical tests is widely common. In order to prevent possible errors in convenient statistical test selection, it is currently possible to consult available test selection algorithms developed for various purposes. However, the lack of an algorithm presenting the most common statistical tests used in biomedical research in a single flowchart causes several problems such as shifting users among the algorithms, poor decision support in test selection and lack of satisfaction of potential users. Herein, we demonstrated a unified flowchart; covers mostly used statistical tests in biomedical domain, to provide decision aid to non-statistician users while choosing the appropriate statistical test for testing their hypothesis. We also discuss some of the findings while we are integrating the flowcharts into each other to develop a single but more comprehensive decision algorithm.

Loading direction-dependent shear behavior at different temperatures of single-layer chiral graphene sheets

NASA Astrophysics Data System (ADS)

Zhao, Yang; Dong, Shuhong; Yu, Peishi; Zhao, Junhua

2018-06-01

The loading direction-dependent shear behavior of single-layer chiral graphene sheets at different temperatures is studied by molecular dynamics (MD) simulations. Our results show that the shear properties (such as shear stress-strain curves, buckling strains, and failure strains) of chiral graphene sheets strongly depend on the loading direction due to the structural asymmetry. The maximum values of both the critical buckling shear strain and the failure strain under positive shear deformation can be around 1.4 times higher than those under negative shear deformation. For a given chiral graphene sheet, both its failure strain and failure stress decrease with increasing temperature. In particular, the amplitude to wavelength ratio of wrinkles for different chiral graphene sheets under shear deformation using present MD simulations agrees well with that from the existing theory. These findings provide physical insights into the origins of the loading direction-dependent shear behavior of chiral graphene sheets and their potential applications in nanodevices.

Frequency modulation atomic force microscopy: a dynamic measurement technique for biological systems

NASA Astrophysics Data System (ADS)

Higgins, Michael J.; Riener, Christian K.; Uchihashi, Takayuki; Sader, John E.; McKendry, Rachel; Jarvis, Suzanne P.

2005-03-01

Frequency modulation atomic force microscopy (FM-AFM) has been modified to operate in a liquid environment within an atomic force microscope specifically designed for investigating biological samples. We demonstrate the applicability of FM-AFM to biological samples using the spectroscopy mode to measure the unbinding forces of a single receptor-ligand (biotin-avidin) interaction. We show that quantitative adhesion force measurements can only be obtained provided certain modifications are made to the existing theory, which is used to convert the detected frequency shifts to an interaction force. Quantitative force measurements revealed that the unbinding forces for the biotin-avidin interaction were greater than those reported in previous studies. This finding was due to the use of high average tip velocities, which were calculated to be two orders of magnitude greater than those typically used in unbinding receptor-ligand experiments. This study therefore highlights the potential use of FM-AFM to study a range of biological systems, including living cells and/or single biomolecule interactions.

Generalized speed and cost rate in transitionless quantum driving

NASA Astrophysics Data System (ADS)

Xu, Zhen-Yu; You, Wen-Long; Dong, Yu-Li; Zhang, Chengjie; Yang, W. L.

2018-03-01

Transitionless quantum driving, also known as counterdiabatic driving, is a unique shortcut technique to adiabaticity, enabling a fast-forward evolution to the same target quantum states as those in the adiabatic case. However, as nothing is free, the fast evolution is obtained at the cost of stronger driving fields. Here, given the system initially gets prepared in equilibrium states, we construct relations between the dynamical evolution speed and the cost rate of transitionless quantum driving in two scenarios: one that preserves the transitionless evolution for a single energy eigenstate (individual driving), and the other that maintains all energy eigenstates evolving transitionlessly (collective driving). Remarkably, we find that individual driving may cost as much as collective driving, in contrast to the common belief that individual driving is more economical than collective driving in multilevel systems. We then present a potentially practical proposal to demonstrate the above phenomena in a three-level Landau-Zener model using the electronic spin system of a single nitrogen-vacancy center in diamond.

Magnetoresistance devices based on single-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Hod, Oded; Rabani, Eran; Baer, Roi

2005-08-01

We demonstrate the physical principles for the construction of a nanometer-sized magnetoresistance device based on the Aharonov-Bohm effect [Phys. Rev. 115, 485 (1959)]. The proposed device is made of a short single-walled carbon nanotube (SWCNT) placed on a substrate and coupled to a tip/contacts. We consider conductance due to the motion of electrons along the circumference of the tube (as opposed to the motion parallel to its axis). We find that the circumference conductance is sensitive to magnetic fields threading the SWCNT due to the Aharonov-Bohm effect, and show that by retracting the tip/contacts, so that the coupling to the SWCNT is reduced, very high sensitivity to the threading magnetic field develops. This is due to the formation of a narrow resonance through which the tunneling current flows. Using a bias potential the resonance can be shifted to low magnetic fields, allowing the control of conductance with magnetic fields of the order of 1 T.

Walking in Two French Neighborhoods: A Study of How Park Numbers and Locations Relate to Everyday Walking

PubMed Central

Rioux, Liliane; Werner, Carol M.; Mokounkolo, Rene; Brown, Barbara B.

2017-01-01

Research indicates that people are drawn to green spaces with attractive amenities. This study extends that finding by comparing walking patterns in two neighborhoods with different numbers of parks; parks did not differ in rated attractiveness nor did neighborhoods differ substantially in rated walkability. Adults, aged 32–86 years (n = 90), drew their 3 most recent walking routes on maps of their neighborhood. Analyses showed that participants’ round trips were longer by 265.5 meters (.16 mile) in the neighborhood with a single, large, centrally located park (p < .02). However, participants in the neighborhood with multiple, small, more distributed parks, visited more streets, p < .001, more streets with green spaces, p < .038, and used more varied routes, p < .012. Results suggest there are potential benefits to both layouts. Large centralized parks may invite longer walks; smaller, well-distributed parks may invite more varied routes suggestive of appropriation and motivation processes. Both layouts might be combined in a single neighborhood to attract more walkers. PMID:28579664

A single macrolichen constitutes hundreds of unrecognized species

PubMed Central

Lücking, Robert; Dal-Forno, Manuela; Sikaroodi, Masoumeh; Gillevet, Patrick M.; Bungartz, Frank; Moncada, Bibiana; Yánez-Ayabaca, Alba; Chaves, José Luis; Coca, Luis Fernando; Lawrey, James D.

2014-01-01

The number of Fungi is estimated at between 1.5 and 3 million. Lichenized species are thought to make up a comparatively small portion of this figure, with unrecognized species richness hidden among little-studied, tropical microlichens. Recent findings, however, suggest that some macrolichens contain a large number of unrecognized taxa, increasing known species richness by an order of magnitude or more. Here we report the existence of at least 126 species in what until recently was believed to be a single taxon: the basidiolichen fungus Dictyonema glabratum, also known as Cora pavonia. Notably, these species are not cryptic but morphologically distinct. A predictive model suggests an even larger number, with more than 400 species. These results call into question species concepts in presumably well-known macrolichens and demonstrate the need for accurately documenting such species richness, given the importance of these lichens in endangered ecosystems such as paramos and the alarming potential for species losses throughout the tropics. PMID:24982168

RNA-dependent RNA targeting by CRISPR-Cas9

PubMed Central

Strutt, Steven C; Torrez, Rachel M; Kaya, Emine; Negrete, Oscar A

2018-01-01

Double-stranded DNA (dsDNA) binding and cleavage by Cas9 is a hallmark of type II CRISPR-Cas bacterial adaptive immunity. All known Cas9 enzymes are thought to recognize DNA exclusively as a natural substrate, providing protection against DNA phage and plasmids. Here, we show that Cas9 enzymes from both subtypes II-A and II-C can recognize and cleave single-stranded RNA (ssRNA) by an RNA-guided mechanism that is independent of a protospacer-adjacent motif (PAM) sequence in the target RNA. RNA-guided RNA cleavage is programmable and site-specific, and we find that this activity can be exploited to reduce infection by single-stranded RNA phage in vivo. We also demonstrate that Cas9 can direct PAM-independent repression of gene expression in bacteria. These results indicate that a subset of Cas9 enzymes have the ability to act on both DNA and RNA target sequences, and suggest the potential for use in programmable RNA targeting applications. PMID:29303478

Mass mortality events and the role of necrophagous invertebrates.

PubMed

Tomberlin, Jeffery K; Barton, Brandon T; Lashley, Marcus A; Jordan, Heather R

2017-10-01

Scale is important in understanding and applying concepts in ecology. Historically, the mechanisms regulating necrophagous arthropod community structure have been well explored on a single vertebrate carcass. However, practically nothing is known of whether such findings can be extrapolated to cases where large numbers of carcasses have been introduced into an ecosystem at a single time point. With the increasing incidences of mass mortality events (MMEs), understanding how scale effects community assembly of necrophagous insects and the resulting bottom-up or top-down effects on the impacted ecosystem are of utmost importance. Unfortunately, MMEs are unpredictable, making their study nearly impossible within a robust experimental framework. The objectives of this paper are to provide a brief overview of what is known with regards to ecological responses to carrion, opine on the ramifications of MMEs on local communities, and provide a brief overview of knowledge gaps, avenues for future research, and a potential study systems for rigorous MME experiments. Copyright © 2017 Elsevier Inc. All rights reserved.