Estimating the entropy and quantifying the impurity of a swarm of surface-hopping trajectories: A new perspective on decoherence

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

Ouyang, Wenjun; Subotnik, Joseph E., E-mail: subotnik@sas.upenn.edu

2014-05-28

In this article, we consider the intrinsic entropy of Tully's fewest switches surface hopping (FSSH) algorithm (as estimated by the impurity of the density matrix) [J. Chem. Phys. 93, 1061 (1990)]. We show that, even for a closed system, the total impurity of a FSSH calculation increases in time (rather than stays constant). This apparent failure of the FSSH algorithm can be traced back to an incorrect, approximate treatment of the electronic coherence between wavepackets moving along different potential energy surfaces. This incorrect treatment of electronic coherence also prevents the FSSH algorithm from correctly describing wavepacket recoherences (which is amore » well established limitation of the FSSH method). Nevertheless, despite these limitations, the FSSH algorithm often predicts accurate observables because the electronic coherence density is modulated by a phase factor which varies rapidly in phase space and which often integrates to almost zero. Adding “decoherence” events on top of a FSSH calculation completely destroys the incorrect FSSH electronic coherence and effectively sets the Poincaré recurrence time for wavepacket recoherence to infinity; this modification usually increases FSSH accuracy (assuming there are no recoherences) while also offering long-time stability for trajectories. In practice, we show that introducing “decoherence” events does not change the total FSSH impurity significantly, but does lead to more accurate evaluations of the impurity of the electronic subsystem.« less

Surface hopping investigation of the relaxation dynamics in radical cations

DOE PAGES

Assmann, Mariana; Weinacht, Thomas; Matsika, Spiridoula

2016-01-19

Ionization processes can lead to the formation of radical cations with population in several ionic states. In this study, we examine the dynamics of three radical cations starting from an excited ionic state using trajectory surface hopping dynamics in combination with multiconfigurational electronic structure methods. The efficiency of relaxation to the ground state is examined in an effort to understand better whether fragmentation of cations is likely to occur directly on excited states or after relaxation to the ground state. The results on cyclohexadiene, hexatriene, and uracil indicate that relaxation to the ground ionic state is very fast in thesemore » systems, while fragmentation before relaxation is rare. Ultrafast relaxation is facilitated by the close proximity of electronic states and the presence of two- and three-state conical intersections. Furthermore, examining the properties of the systems in the Franck-Condon region can give some insight into the subsequent dynamics.« less

Mixed quantum/classical investigation of the photodissociation of NH3(Ã) and a practical method for maintaining zero-point energy in classical trajectories

NASA Astrophysics Data System (ADS)

Bonhommeau, David; Truhlar, Donald G.

2008-07-01

The photodissociation dynamics of ammonia upon excitation of the out-of-plane bending mode (mode ν2 with n2=0,…,6 quanta of vibration) in the à electronic state is investigated by means of several mixed quantum/classical methods, and the calculated final-state properties are compared to experiments. Five mixed quantum/classical methods are tested: one mean-field approach (the coherent switching with decay of mixing method), two surface-hopping methods [the fewest switches with time uncertainty (FSTU) and FSTU with stochastic decay (FSTU/SD) methods], and two surface-hopping methods with zero-point energy (ZPE) maintenance [the FSTU /SD+trajectory projection onto ZPE orbit (TRAPZ) and FSTU /SD+minimal TRAPZ (mTRAPZ) methods]. We found a qualitative difference between final NH2 internal energy distributions obtained for n2=0 and n2>1, as observed in experiments. Distributions obtained for n2=1 present an intermediate behavior between distributions obtained for smaller and larger n2 values. The dynamics is found to be highly electronically nonadiabatic with all these methods. NH2 internal energy distributions may have a negative energy tail when the ZPE is not maintained throughout the dynamics. The original TRAPZ method was designed to maintain ZPE in classical trajectories, but we find that it leads to unphysically high internal vibrational energies. The mTRAPZ method, which is new in this work and provides a general method for maintaining ZPE in either single-surface or multisurface trajectories, does not lead to unphysical results and is much less time consuming. The effect of maintaining ZPE in mixed quantum/classical dynamics is discussed in terms of agreement with experimental findings. The dynamics for n2=0 and n2=6 are also analyzed to reveal details not available from experiment, in particular, the time required for quenching of electronic excitation and the adiabatic energy gap and geometry at the time of quenching.

Mixed quantum/classical investigation of the photodissociation of NH3(A) and a practical method for maintaining zero-point energy in classical trajectories.

PubMed

Bonhommeau, David; Truhlar, Donald G

2008-07-07

The photodissociation dynamics of ammonia upon excitation of the out-of-plane bending mode (mode nu(2) with n(2)=0,[ellipsis (horizontal)],6 quanta of vibration) in the A electronic state is investigated by means of several mixed quantum/classical methods, and the calculated final-state properties are compared to experiments. Five mixed quantum/classical methods are tested: one mean-field approach (the coherent switching with decay of mixing method), two surface-hopping methods [the fewest switches with time uncertainty (FSTU) and FSTU with stochastic decay (FSTU/SD) methods], and two surface-hopping methods with zero-point energy (ZPE) maintenance [the FSTUSD+trajectory projection onto ZPE orbit (TRAPZ) and FSTUSD+minimal TRAPZ (mTRAPZ) methods]. We found a qualitative difference between final NH(2) internal energy distributions obtained for n(2)=0 and n(2)>1, as observed in experiments. Distributions obtained for n(2)=1 present an intermediate behavior between distributions obtained for smaller and larger n(2) values. The dynamics is found to be highly electronically nonadiabatic with all these methods. NH(2) internal energy distributions may have a negative energy tail when the ZPE is not maintained throughout the dynamics. The original TRAPZ method was designed to maintain ZPE in classical trajectories, but we find that it leads to unphysically high internal vibrational energies. The mTRAPZ method, which is new in this work and provides a general method for maintaining ZPE in either single-surface or multisurface trajectories, does not lead to unphysical results and is much less time consuming. The effect of maintaining ZPE in mixed quantum/classical dynamics is discussed in terms of agreement with experimental findings. The dynamics for n(2)=0 and n(2)=6 are also analyzed to reveal details not available from experiment, in particular, the time required for quenching of electronic excitation and the adiabatic energy gap and geometry at the time of quenching.

Parallel Monotonic Basin Hopping for Low Thrust Trajectory Optimization

NASA Technical Reports Server (NTRS)

McCarty, Steven L.; McGuire, Melissa L.

2018-01-01

Monotonic Basin Hopping has been shown to be an effective method of solving low thrust trajectory optimization problems. This paper outlines an extension to the common serial implementation by parallelizing it over any number of available compute cores. The Parallel Monotonic Basin Hopping algorithm described herein is shown to be an effective way to more quickly locate feasible solutions, and improve locally optimal solutions in an automated way without requiring a feasible initial guess. The increased speed achieved through parallelization enables the algorithm to be applied to more complex problems that would otherwise be impractical for a serial implementation. Low thrust cislunar transfers and a hybrid Mars example case demonstrate the effectiveness of the algorithm. Finally, a preliminary scaling study quantifies the expected decrease in solve time compared to a serial implementation.,

Multi-state nonadiabatic deactivation mechanism of coumarin revealed by ab initio on-the-fly trajectory surface hopping dynamic simulation.

PubMed

Gan, Yanzhen; Yue, Ling; Guo, Xugeng; Zhu, Chaoyuan; Cao, Zexing

2017-05-17

An on-the-fly trajectory surface hopping dynamic simulation has been performed for revealing the multi-state nonadiabatic deactivation mechanism of coumarin. The mechanism involves three adiabatic excited states, S 3 (ππ*L b ), S 2 (nπ*, ππ*L a ) and S 1 (ππ*L a , nπ*), and the ground state S 0 at the four state-averaged complete active space self-consistent field, SA4-CASSCF(12,10)/6-31G* level of theory. Upon photoexcitation to the third excited state S 3 (ππ*L b ) in the Franck-Condon region, 80% sampling trajectories decay to the dark S 2 (nπ*) state within an average of 5 fs via the conical intersection S 3 (ππ*L b )/S 2 (nπ*), while 20% decay to the S 2 (ππ*L a ) state within an average of 11 fs via the conical intersection S 3 (ππ*L b )/S 2 (ππ*L a ). Then, sampling trajectories via S 2 (nπ*)/S 1 (ππ*L a ) continue with ultrafast decay processes to give a final distribution of quantum yields as follows: 42% stay on the dark S 1 (nπ*) state, 43.3% go back to the ground S 0 state, 12% undergo a ring-opening reaction to the Z-form S 0 (Z) state, and 2.7% go to the E-form S 0 (E) state. The lifetimes of the excited states are estimated as follows: the S 3 state is about 12 fs on average, the S 2 state is about 80 fs, and the S 1 state has a fast component of about 160 fs and a slow component of 15 ps. The simulated ultrafast radiationless deactivation pathways of photoexcited coumarin immediately interpret the experimentally observed weak fluorescence emission.

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

Agostini, Federica; Abedi, Ali; Suzuki, Yasumitsu

The decomposition of electronic and nuclear motion presented in Abedi et al. [Phys. Rev. Lett. 105, 123002 (2010)] yields a time-dependent potential that drives the nuclear motion and fully accounts for the coupling to the electronic subsystem. Here, we show that propagation of an ensemble of independent classical nuclear trajectories on this exact potential yields dynamics that are essentially indistinguishable from the exact quantum dynamics for a model non-adiabatic charge transfer problem. We point out the importance of step and bump features in the exact potential that are critical in obtaining the correct splitting of the quasiclassical nuclear wave packetmore » in space after it passes through an avoided crossing between two Born-Oppenheimer surfaces and analyze their structure. Finally, an analysis of the exact potentials in the context of trajectory surface hopping is presented, including preliminary investigations of velocity-adjustment and the force-induced decoherence effect.« less

The Effect of the Spin-Forbidden Co((sup 1) Sigma plus) plus O((sup 3) P) Yields CO2 (1 Sigma (sub G) plus) Recombination Reaction on Afterbody Heating of Mars Entry Vehicles

NASA Technical Reports Server (NTRS)

Xu, Lu T.; Jaffe, Richard L.; Schwenke, David W.; Panesi, Marco

2017-01-01

Vibrationally excited CO2, formed by two-body recombination from CO((sup 1) sigma plus) and O((sup 3) P) in the wake behind spacecraft entering the Martian atmosphere reaction, is potentially responsible for the higher than anticipated radiative heating of the backshell, compared to pre-flight predictions. This process involves a spin-forbidden transition of the transient triplet CO2 molecule to the longer-lived singlet. To accurately predict the singlet-triplet transition probability and estimate the thermal rate coefficient of the recombination reaction, ab initio methods were used to compute the first singlet and three lowest triplet CO2 potential energy surfaces and the spin-orbit coupling matrix elements between these states. Analytical fits to these four potential energy surfaces were generated for surface hopping trajectory calculations, using Tully's fewest switches surface hopping algorithm. Preliminary results for the trajectory calculations are presented. The calculated probability of a CO((sup 1) sigma plus) and O((sup 3) P) collision leading to singlet CO2 formation is on the order of 10 (sup -4). The predicted flowfield conditions for various Mars entry scenarios predict temperatures in the range of 1000 degrees Kelvin - 4000 degrees Kelvin and pressures in the range of 300-2500 pascals at the shoulder and in the wake, which is consistent with a heavy-particle collision frequency of 10 (sup 6) to 10 (sup 7) per second. Owing to this low collision frequency, it is likely that CO((sup 1) sigma plus) molecules formed by this mechanism will mostly be frozen in a highly nonequilibrium rovibrational energy state until they relax by photoemission.

Comparison of a laboratory grade force platform with a Nintendo Wii Balance Board on measurement of postural control in single-leg stance balance tasks.

PubMed

Huurnink, Arnold; Fransz, Duncan P; Kingma, Idsart; van Dieën, Jaap H

2013-04-26

Training and testing of balance have potential applications in sports and medicine. Laboratory grade force plates (FP) are considered the gold standard for the measurement of balance performance. Measurements in these systems are based on the parameterization of center of pressure (CoP) trajectories. Previous research validated the inexpensive, widely available and portable Nintendo Wii Balance Board (WBB). The novelty of the present study is that FP and WBB are compared on CoP data that was collected simultaneously, by placing the WBB on the FP. Fourteen healthy participants performed ten sequences of single-leg stance tasks with eyes open (EO), eyes closed (EC) and after a sideways hop (HOP). Within trial comparison of the two systems showed small root-mean-square differences for the CoP trajectories in the x and y direction during the three tasks (mean±SD; EO: 0.33±0.10 and 0.31±0.16 mm; EC: 0.58±0.17 and 0.63±0.19 mm; HOP: 0.74±0.34 and 0.74±0.27 mm, respectively). Additionally, during all 420 trials, comparison of FP and WBB revealed very high Pearson's correlation coefficients (r) of the CoP trajectories (x: 0.999±0.002; y: 0.998±0.003). A general overestimation was found on the WBB compared to the FP for 'CoP path velocity' (EO: 5.3±1.9%; EC: 4.0±1.4%; HOP: 4.6±1.6%) and 'mean absolute CoP sway' (EO: 3.5±0.7%; EC: 3.7±0.5%; HOP: 3.6±1.0%). This overestimation was highly consistent over the 140 trials per task (r>0.996). The present findings demonstrate that WBB is sufficiently accurate in quantifying CoP trajectory, and overall amplitude and velocity during single-leg stance balance tasks. Copyright © 2013 Elsevier Ltd. All rights reserved.

Hip-Hop to Prevent Substance Use and HIV among African-American Youth: A Preliminary Investigation

ERIC Educational Resources Information Center

Turner-Musa, Jocelyn O.; Rhodes, Warren A.; Harper, P. Thandi Hicks; Quinton, Sylvia L.

2008-01-01

Substance use and HIV risk behaviors are increasing among African-American youth. Interventions that incorporate youth values and beliefs are needed to reduce this trajectory. Hip-hop plays an important role in the lives of many African-American youth and provides a context within which to prevent risky behaviors. The current study examines the…

Trajectory-based nonadiabatic dynamics with time-dependent density functional theory.

PubMed

Curchod, Basile F E; Rothlisberger, Ursula; Tavernelli, Ivano

2013-05-10

Understanding the fate of an electronically excited molecule constitutes an important task for theoretical chemistry, and practical implications range from the interpretation of atto- and femtosecond spectroscopy to the development of light-driven molecular machines, the control of photochemical reactions, and the possibility of capturing sunlight energy. However, many challenging conceptual and technical problems are involved in the description of these phenomena such as 1) the failure of the well-known Born-Oppenheimer approximation; 2) the need for accurate electronic properties such as potential energy surfaces, excited nuclear forces, or nonadiabatic coupling terms; and 3) the necessity of describing the dynamics of the photoexcited nuclear wavepacket. This review provides an overview of the current methods to address points 1) and 3) and shows how time-dependent density functional theory (TDDFT) and its linear-response extension can be used for point 2). First, the derivation of Ehrenfest dynamics and nonadiabatic Bohmian dynamics is discussed and linked to Tully's trajectory surface hopping. Second, the coupling of these trajectory-based nonadiabatic schemes with TDDFT is described in detail with special emphasis on the derivation of the required electronic structure properties. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Two-dimensional description of surface-bounded exospheres with application to the migration of water molecules on the Moon

NASA Astrophysics Data System (ADS)

Schorghofer, Norbert

2015-05-01

On the Moon, water molecules and other volatiles are thought to migrate along ballistic trajectories. Here, this migration process is described in terms of a two-dimensional partial differential equation for the surface concentration, based on the probability distribution of thermal ballistic hops. A random-walk model, a corresponding diffusion coefficient, and a continuum description are provided. In other words, a surface-bounded exosphere is described purely in terms of quantities on the surface, which can provide computational and conceptual advantages. The derived continuum equation can be used to calculate the steady-state distribution of the surface concentration of volatile water molecules. An analytic steady-state solution is obtained for an equatorial ring; it reveals the width and mass of the pileup of molecules at the morning terminator.

Nonadiabatic Molecular Dynamics and Orthogonality Constrained Density Functional Theory

NASA Astrophysics Data System (ADS)

Shushkov, Philip Georgiev

The exact quantum dynamics of realistic, multidimensional systems remains a formidable computational challenge. In many chemical processes, however, quantum effects such as tunneling, zero-point energy quantization, and nonadiabatic transitions play an important role. Therefore, approximate approaches that improve on the classical mechanical framework are of special practical interest. We propose a novel ring polymer surface hopping method for the calculation of chemical rate constants. The method blends two approaches, namely ring polymer molecular dynamics that accounts for tunneling and zero-point energy quantization, and surface hopping that incorporates nonadiabatic transitions. We test the method against exact quantum mechanical calculations for a one-dimensional, two-state model system. The method reproduces quite accurately the tunneling contribution to the rate and the distribution of reactants between the electronic states for this model system. Semiclassical instanton theory, an approach related to ring polymer molecular dynamics, accounts for tunneling by the use of periodic classical trajectories on the inverted potential energy surface. We study a model of electron transfer in solution, a chemical process where nonadiabatic events are prominent. By representing the tunneling electron with a ring polymer, we derive Marcus theory of electron transfer from semiclassical instanton theory after a careful analysis of the tunneling mode. We demonstrate that semiclassical instanton theory can recover the limit of Fermi's Golden Rule rate in a low-temperature, deep-tunneling regime. Mixed quantum-classical dynamics treats a few important degrees of freedom quantum mechanically, while classical mechanics describes affordably the rest of the system. But the interface of quantum and classical description is a challenging theoretical problem, especially for low-energy chemical processes. We therefore focus on the semiclassical limit of the coupled nuclear-electronic dynamics. We show that the time-dependent Schrodinger equation for the electrons employed in the widely used fewest switches surface hopping method is applicable only in the limit of nearly identical classical trajectories on the different potential energy surfaces. We propose a short-time decoupling algorithm that restricts the use of the Schrodinger equation only to the interaction regions. We test the short-time approximation on three model systems against exact quantum-mechanical calculations. The approximation improves the performance of the surface hopping approach. Nonadiabatic molecular dynamics simulations require the efficient and accurate computation of ground and excited state potential energy surfaces. Unlike the ground state calculations where standard methods exist, the computation of excited state properties is a challenging task. We employ time-independent density functional theory, in which the excited state energy is represented as a functional of the total density. We suggest an adiabatic-like approximation that simplifies the excited state exchange-correlation functional. We also derive a set of minimal conditions to impose exactly the orthogonality of the excited state Kohn-Sham determinant to the ground state determinant. This leads to an efficient, variational algorithm for the self-consistent optimization of the excited state energy. Finally, we assess the quality of the excitation energies obtained by the new method on a set of 28 organic molecules. The new approach provides results of similar accuracy to time-dependent density functional theory.

Decoherence and surface hopping: When can averaging over initial conditions help capture the effects of wave packet separation?

NASA Astrophysics Data System (ADS)

Subotnik, Joseph E.; Shenvi, Neil

2011-06-01

Fewest-switches surface hopping (FSSH) is a popular nonadiabatic dynamics method which treats nuclei with classical mechanics and electrons with quantum mechanics. In order to simulate the motion of a wave packet as accurately as possible, standard FSSH requires a stochastic sampling of the trajectories over a distribution of initial conditions corresponding, e.g., to the Wigner distribution of the initial quantum wave packet. Although it is well-known that FSSH does not properly account for decoherence effects, there is some confusion in the literature about whether or not this averaging over a distribution of initial conditions can approximate some of the effects of decoherence. In this paper, we not only show that averaging over initial conditions does not generally account for decoherence, but also why it fails to do so. We also show how an apparent improvement in accuracy can be obtained for a fortuitous choice of model problems, even though this improvement is not possible, in general. For a basic set of one-dimensional and two-dimensional examples, we find significantly improved results using our recently introduced augmented FSSH algorithm.

Multi-state trajectory approach to non-adiabatic dynamics: General formalism and the active state trajectory approximation

NASA Astrophysics Data System (ADS)

Tao, Guohua

2017-07-01

A general theoretical framework is derived for the recently developed multi-state trajectory (MST) approach from the time dependent Schrödinger equation, resulting in equations of motion for coupled nuclear-electronic dynamics equivalent to Hamilton dynamics or Heisenberg equation based on a new multistate Meyer-Miller (MM) model. The derived MST formalism incorporates both diabatic and adiabatic representations as limiting cases and reduces to Ehrenfest or Born-Oppenheimer dynamics in the mean-field or the single-state limits, respectively. In the general multistate formalism, nuclear dynamics is represented in terms of a set of individual state-specific trajectories, while in the active state trajectory (AST) approximation, only one single nuclear trajectory on the active state is propagated with its augmented images running on all other states. The AST approximation combines the advantages of consistent nuclear-coupled electronic dynamics in the MM model and the single nuclear trajectory in the trajectory surface hopping (TSH) treatment and therefore may provide a potential alternative to both Ehrenfest and TSH methods. The resulting algorithm features in a consistent description of coupled electronic-nuclear dynamics and excellent numerical stability. The implementation of the MST approach to several benchmark systems involving multiple nonadiabatic transitions and conical intersection shows reasonably good agreement with exact quantum calculations, and the results in both representations are similar in accuracy. The AST treatment also reproduces the exact results reasonably, sometimes even quantitatively well, with a better performance in the adiabatic representation.

A study on a wheel-based stair-climbing robot with a hopping mechanism

NASA Astrophysics Data System (ADS)

Kikuchi, Koki; Sakaguchi, Keisuke; Sudo, Takayuki; Bushida, Naoki; Chiba, Yasuhiro; Asai, Yuji

2008-08-01

In this study, we propose a simple hopping mechanism using the vibration of a two-degree-of-freedom system for a wheel-based stair-climbing robot. The robot, consisting of two bodies connected by springs and a wire, hops by releasing energy stored in the springs and quickly travels using wheels mounted in its lower body. The trajectories of the bodies during hopping change in accordance with the design parameters, such as the reduced mass of the two bodies, the mass ratio between the upper and lower bodies, the spring constant, the control parameters such as the initial contraction of the spring and the wire tension. This property allows the robot to quickly and economically climb up and down stairs, leap over obstacles, and landing softly without complex control. In this paper, the characteristics of hopping motion for the design and control parameters are clarified by both numerical simulations and experiments. Furthermore, using the robot design based on the results the abilities to hop up and down a step, leap over a cable, and land softly are demonstrated.

Communication: Standard surface hopping predicts incorrect scaling for Marcus' golden-rule rate: The decoherence problem cannot be ignored

NASA Astrophysics Data System (ADS)

Landry, Brian R.; Subotnik, Joseph E.

2011-11-01

We evaluate the accuracy of Tully's surface hopping algorithm for the spin-boson model for the case of a small diabatic coupling parameter (V). We calculate the transition rates between diabatic surfaces, and we compare our results to the expected Marcus rates. We show that standard surface hopping yields an incorrect scaling with diabatic coupling (linear in V), which we demonstrate is due to an incorrect treatment of decoherence. By modifying standard surface hopping to include decoherence events, we recover the correct scaling (˜V2).

Wind-invariant saltation heights imply linear scaling of aeolian saltation flux with shear stress.

PubMed

Martin, Raleigh L; Kok, Jasper F

2017-06-01

Wind-driven sand transport generates atmospheric dust, forms dunes, and sculpts landscapes. However, it remains unclear how the flux of particles in aeolian saltation-the wind-driven transport of sand in hopping trajectories-scales with wind speed, largely because models do not agree on how particle speeds and trajectories change with wind shear velocity. We present comprehensive measurements, from three new field sites and three published studies, showing that characteristic saltation layer heights remain approximately constant with shear velocity, in agreement with recent wind tunnel studies. These results support the assumption of constant particle speeds in recent models predicting linear scaling of saltation flux with shear stress. In contrast, our results refute widely used older models that assume that particle speed increases with shear velocity, thereby predicting nonlinear 3/2 stress-flux scaling. This conclusion is further supported by direct field measurements of saltation flux versus shear stress. Our results thus argue for adoption of linear saltation flux laws and constant saltation trajectories for modeling saltation-driven aeolian processes on Earth, Mars, and other planetary surfaces.

Hip-hop to prevent substance use and HIV among African-American youth: a preliminary investigation.

PubMed

Turner-Musa, Jocelyn O; Rhodes, Warren A; Harper, P Thandi Hicks; Quinton, Sylvia L

2008-01-01

Substance use and HIV risk behaviors are increasing among African-American youth. Interventions that incorporate youth values and beliefs are needed to reduce this trajectory. Hip-hop plays an important role in the lives of many African-American youth and provides a context within which to prevent risky behaviors. The current study examines the efficacy of a hip-hop based substance use and HIV preventive intervention that targets African-American middle-school youth. The sample consists of 68 middle-school students who completed baseline and 6-month follow-up assessments. Findings suggest that students in the intervention group were significantly more likely to have higher knowledge of perception of drug risk and more knowledge about HIV/AIDS compared to students in the comparison group at the 6-month post-intervention assessment. Discussion is centered on implications of hip-hop as a viable approach for preventing substance use and HIV within a high-risk group.

Three-Dimensional Tracking of Interfacial Hopping Diffusion

NASA Astrophysics Data System (ADS)

Wang, Dapeng; Wu, Haichao; Schwartz, Daniel K.

2017-12-01

Theoretical predictions have suggested that molecular motion at interfaces—which influences processes including heterogeneous catalysis, (bio)chemical sensing, lubrication and adhesion, and nanomaterial self-assembly—may be dominated by hypothetical "hops" through the adjacent liquid phase, where a diffusing molecule readsorbs after a given hop according to a probabilistic "sticking coefficient." Here, we use three-dimensional (3D) single-molecule tracking to explicitly visualize this process for human serum albumin at solid-liquid interfaces that exert varying electrostatic interactions on the biomacromolecule. Following desorption from the interface, a molecule experiences multiple unproductive surface encounters before readsorption. An average of approximately seven surface collisions is required for the repulsive surfaces, decreasing to approximately two and a half for surfaces that are more attractive. The hops themselves are also influenced by long-range interactions, with increased electrostatic repulsion causing hops of longer duration and distance. These findings explicitly demonstrate that interfacial diffusion is dominated by biased 3D Brownian motion involving bulk-surface coupling and that it can be controlled by influencing short- and long-range adsorbate-surface interactions.

Molecular Dynamics Simulation of Salt Diffusion in Polyelectrolyte Assemblies.

PubMed

Zhang, Ran; Duan, Xiaozheng; Ding, Mingming; Shi, Tongfei

2018-06-05

The diffusion of salt ions and charged probe molecules in polyelectrolyte assemblies is often assumed to follow a theoretical hopping model, in which the diffusing ion is hopping between charged sites of chains based on electroneutrality. However, experimental verification of diffusing pathway at such microscales is difficult, and the corresponding molecular mechanisms remain elusive. In this study, we perform all-atom molecular dynamics (MD) simulations of salt diffusion in polyelectrolyte (PE) assembly of poly (sodium 4-styrenesulfonate) (PSS) and poly (diallyldimethylammonium chloride) (PDAC). Besides the ion hopping mode, the diffusing trajectories are found presenting common features of a jump process, i.e., subjecting to PE relaxation, water pockets in the structure open and close, thus the ion can move from one pocket to another. Anomalous subdiffusion of ions and water is observed due to the trapping scenarios in these water pockets. The jump events are much rarer compared with ion hopping but significantly increases salt diffusion with increasing temperature. Our result strongly indicates that salt diffusion in hydrated PDAC/PSS is a combined process of ion hopping and jump motion. This provides new molecular explanation for the coupling of salt motion with chain motion and the nonlinear increase of salt diffusion at glass transition temperature.

Quasi-periodic continuation along a continuous symmetry

NASA Astrophysics Data System (ADS)

Salomone, Matthew David

Given a system of differential equations which admits a continuous group of symmetries and possesses a periodic solution, we show that under certain nondegeneracy assumptions there always exists a continuous family containing infinitely many periodic and quasi-periodic trajectories. This generalizes the continuation method of Poincaré to orbits which are not necessarily periodic. We apply these results in the setting of the Lagrangian N -body problem of homogeneous potential to characterize an infinite family of rotating nonplanar "hip-hop" orbits in the four-body problem of equal masses, and show how some other trajectories in the N -body theory may be extended to infinite families of periodic and quasi-periodic trajectories.

The energy landscape of glassy dynamics on the amorphous hafnium diboride surface

NASA Astrophysics Data System (ADS)

Nguyen, Duc; Mallek, Justin; Cloud, Andrew N.; Abelson, John R.; Girolami, Gregory S.; Lyding, Joseph; Gruebele, Martin

2014-11-01

Direct visualization of the dynamics of structural glasses and amorphous solids on the sub-nanometer scale provides rich information unavailable from bulk or conventional single molecule techniques. We study the surface of hafnium diboride, a conductive ultrahigh temperature ceramic material that can be grown in amorphous films. Our scanning tunneling movies have a second-to-hour dynamic range and single-point current measurements extend that to the millisecond-to-minute time scale. On the a-HfB2 glass surface, two-state hopping of 1-2 nm diameter cooperatively rearranging regions or "clusters" occurs from sub-milliseconds to hours. We characterize individual clusters in detail through high-resolution (<0.5 nm) imaging, scanning tunneling spectroscopy and voltage modulation, ruling out individual atoms, diffusing adsorbates, or pinned charges as the origin of the observed two-state hopping. Smaller clusters are more likely to hop, larger ones are more likely to be immobile. HfB2 has a very high bulk glass transition temperature Tg, and we observe no three-state hopping or sequential two-state hopping previously seen on lower Tg glass surfaces. The electronic density of states of clusters does not change when they hop up or down, allowing us to calibrate an accurate relative z-axis scale. By directly measuring and histogramming single cluster vertical displacements, we can reconstruct the local free energy landscape of individual clusters, complete with activation barrier height, a reaction coordinate in nanometers, and the shape of the free energy landscape basins between which hopping occurs. The experimental images are consistent with the compact shape of α-relaxors predicted by random first order transition theory, whereas the rapid hopping rate, even taking less confined motion at the surface into account, is consistent with β-relaxations. We make a proposal of how "mixed" features can show up in surface dynamics of glasses.

Mixed quantum-classical simulations of the vibrational relaxation of photolyzed carbon monoxide in a hemoprotein

NASA Astrophysics Data System (ADS)

Schubert, Alexander; Falvo, Cyril; Meier, Christoph

2016-08-01

We present mixed quantum-classical simulations on relaxation and dephasing of vibrationally excited carbon monoxide within a protein environment. The methodology is based on a vibrational surface hopping approach treating the vibrational states of CO quantum mechanically, while all remaining degrees of freedom are described by means of classical molecular dynamics. The CO vibrational states form the "surfaces" for the classical trajectories of protein and solvent atoms. In return, environmentally induced non-adiabatic couplings between these states cause transitions describing the vibrational relaxation from first principles. The molecular dynamics simulation yields a detailed atomistic picture of the energy relaxation pathways, taking the molecular structure and dynamics of the protein and its solvent fully into account. Using the ultrafast photolysis of CO in the hemoprotein FixL as an example, we study the relaxation of vibrationally excited CO and evaluate the role of each of the FixL residues forming the heme pocket.

Atomistic non-adiabatic dynamics of the LH2 complex with a GPU-accelerated ab initio exciton model.

PubMed

Sisto, Aaron; Stross, Clem; van der Kamp, Marc W; O'Connor, Michael; McIntosh-Smith, Simon; Johnson, Graham T; Hohenstein, Edward G; Manby, Fred R; Glowacki, David R; Martinez, Todd J

2017-06-14

We recently outlined an efficient multi-tiered parallel ab initio excitonic framework that utilizes time dependent density functional theory (TDDFT) to calculate ground and excited state energies and gradients of large supramolecular complexes in atomistic detail - enabling us to undertake non-adiabatic simulations which explicitly account for the coupled anharmonic vibrational motion of all the constituent atoms in a supramolecular system. Here we apply that framework to the 27 coupled bacterio-chlorophyll-a chromophores which make up the LH2 complex, using it to compute an on-the-fly nonadiabatic surface-hopping (SH) trajectory of electronically excited LH2. Part one of this article is focussed on calibrating our ab initio exciton Hamiltonian using two key parameters: a shift δ, which corrects for the error in TDDFT vertical excitation energies; and an effective dielectric constant ε, which describes the average screening of the transition-dipole coupling between chromophores. Using snapshots obtained from equilibrium molecular dynamics simulations (MD) of LH2, we tune the values of both δ and ε through fitting to the thermally broadened experimental absorption spectrum, giving a linear absorption spectrum that agrees reasonably well with experiment. In part two of this article, we construct a time-resolved picture of the coupled vibrational and excitation energy transfer (EET) dynamics in the sub-picosecond regime following photo-excitation. Assuming Franck-Condon excitation of a narrow eigenstate band centred at 800 nm, we use surface hopping to follow a single nonadiabatic dynamics trajectory within the full eigenstate manifold. Consistent with experimental data, this trajectory gives timescales for B800→B850 population transfer (τ B800→B850 ) between 650-1050 fs, and B800 population decay (τ 800→ ) between 10-50 fs. The dynamical picture that emerges is one of rapidly fluctuating LH2 eigenstates that are delocalized over multiple chromophores and undergo frequent crossing on a femtosecond timescale as a result of the atomic vibrations of the constituent chromophores. The eigenstate fluctuations arise from disorder that is driven by vibrational dynamics with multiple characteristic timescales. The scalability of our ab initio excitonic computational framework across massively parallel architectures opens up the possibility of addressing a wide range of questions, including how specific dynamical motions impact both the pathways and efficiency of electronic energy-transfer within large supramolecular systems.

Tuning Monotonic Basin Hopping: Improving the Efficiency of Stochastic Search as Applied to Low-Thrust Trajectory Optimization

NASA Technical Reports Server (NTRS)

Englander, Jacob A.; Englander, Arnold C.

2014-01-01

Trajectory optimization methods using monotonic basin hopping (MBH) have become well developed during the past decade [1, 2, 3, 4, 5, 6]. An essential component of MBH is a controlled random search through the multi-dimensional space of possible solutions. Historically, the randomness has been generated by drawing random variable (RV)s from a uniform probability distribution. Here, we investigate the generating the randomness by drawing the RVs from Cauchy and Pareto distributions, chosen because of their characteristic long tails. We demonstrate that using Cauchy distributions (as first suggested by J. Englander [3, 6]) significantly improves monotonic basin hopping (MBH) performance, and that Pareto distributions provide even greater improvements. Improved performance is defined in terms of efficiency and robustness. Efficiency is finding better solutions in less time. Robustness is efficiency that is undiminished by (a) the boundary conditions and internal constraints of the optimization problem being solved, and (b) by variations in the parameters of the probability distribution. Robustness is important for achieving performance improvements that are not problem specific. In this work we show that the performance improvements are the result of how these long-tailed distributions enable MBH to search the solution space faster and more thoroughly. In developing this explanation, we use the concepts of sub-diffusive, normally-diffusive, and super-diffusive random walks (RWs) originally developed in the field of statistical physics.

Excited state dynamics of thiophene and bithiophene: new insights into theoretically challenging systems.

PubMed

Prlj, Antonio; Curchod, Basile F E; Corminboeuf, Clémence

2015-06-14

The computational elucidation and proper description of the ultrafast deactivation mechanisms of simple organic electronic units, such as thiophene and its oligomers, is as challenging as it is contentious. A comprehensive excited state dynamics analysis of these systems utilizing reliable electronic structure approaches is currently lacking, with earlier pictures of the photochemistry of these systems being conceived based upon high-level static computations or lower level dynamic trajectories. Here a detailed surface hopping molecular dynamics of thiophene and bithiophene using the algebraic diagrammatic construction to second order (ADC(2)) method is presented. Our findings illustrate that ring puckering plays an important role in thiophene photochemistry and that the photostability increases when going upon dimerization into bithiophene.

Complex trajectories in a classical periodic potential

NASA Astrophysics Data System (ADS)

Anderson, Alexander G.; Bender, Carl M.

2012-11-01

This paper examines the complex trajectories of a classical particle in the potential V(x) = -cos (x). Almost all the trajectories describe a particle that hops from one well to another in an erratic fashion. However, it is shown analytically that there are two special classes of trajectories x(t) determined only by the energy of the particle and not by the initial position of the particle. The first class consists of periodic trajectories; that is, trajectories that return to their initial position x(0) after some real time T. The second class consists of trajectories for which there exists a real time T such that x(t + T) = x(t) ± 2π. These two classes of classical trajectories are analogous to valence and conduction bands in quantum mechanics, where the quantum particle either remains localized or else tunnels resonantly (conducts) through a crystal lattice. These two special types of trajectories are associated with sets of energies of measure 0. For other energies, it is shown that for long times the average velocity of the particle becomes a fractal-like function of energy.

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

Nguyen, Duc; Girolami, Gregory S.; Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801

Direct visualization of the dynamics of structural glasses and amorphous solids on the sub-nanometer scale provides rich information unavailable from bulk or conventional single molecule techniques. We study the surface of hafnium diboride, a conductive ultrahigh temperature ceramic material that can be grown in amorphous films. Our scanning tunneling movies have a second-to-hour dynamic range and single-point current measurements extend that to the millisecond-to-minute time scale. On the a-HfB{sub 2} glass surface, two-state hopping of 1–2 nm diameter cooperatively rearranging regions or “clusters” occurs from sub-milliseconds to hours. We characterize individual clusters in detail through high-resolution (<0.5 nm) imaging, scanning tunnelingmore » spectroscopy and voltage modulation, ruling out individual atoms, diffusing adsorbates, or pinned charges as the origin of the observed two-state hopping. Smaller clusters are more likely to hop, larger ones are more likely to be immobile. HfB{sub 2} has a very high bulk glass transition temperature T{sub g}, and we observe no three-state hopping or sequential two-state hopping previously seen on lower T{sub g} glass surfaces. The electronic density of states of clusters does not change when they hop up or down, allowing us to calibrate an accurate relative z-axis scale. By directly measuring and histogramming single cluster vertical displacements, we can reconstruct the local free energy landscape of individual clusters, complete with activation barrier height, a reaction coordinate in nanometers, and the shape of the free energy landscape basins between which hopping occurs. The experimental images are consistent with the compact shape of α-relaxors predicted by random first order transition theory, whereas the rapid hopping rate, even taking less confined motion at the surface into account, is consistent with β-relaxations. We make a proposal of how “mixed” features can show up in surface dynamics of glasses.« less

Wind-invariant saltation heights imply linear scaling of aeolian saltation flux with shear stress

PubMed Central

Martin, Raleigh L.; Kok, Jasper F.

2017-01-01

Wind-driven sand transport generates atmospheric dust, forms dunes, and sculpts landscapes. However, it remains unclear how the flux of particles in aeolian saltation—the wind-driven transport of sand in hopping trajectories—scales with wind speed, largely because models do not agree on how particle speeds and trajectories change with wind shear velocity. We present comprehensive measurements, from three new field sites and three published studies, showing that characteristic saltation layer heights remain approximately constant with shear velocity, in agreement with recent wind tunnel studies. These results support the assumption of constant particle speeds in recent models predicting linear scaling of saltation flux with shear stress. In contrast, our results refute widely used older models that assume that particle speed increases with shear velocity, thereby predicting nonlinear 3/2 stress-flux scaling. This conclusion is further supported by direct field measurements of saltation flux versus shear stress. Our results thus argue for adoption of linear saltation flux laws and constant saltation trajectories for modeling saltation-driven aeolian processes on Earth, Mars, and other planetary surfaces. PMID:28630907

An efficient solution to the decoherence enhanced trivial crossing problem in surface hopping

NASA Astrophysics Data System (ADS)

Bai, Xin; Qiu, Jing; Wang, Linjun

2018-03-01

We provide an in-depth investigation of the time interval convergence when both trivial crossing and decoherence corrections are applied to Tully's fewest switches surface hopping (FSSH) algorithm. Using one force-based and one energy-based decoherence strategies as examples, we show decoherence corrections intrinsically enhance the trivial crossing problem. We propose a restricted decoherence (RD) strategy and incorporate it into the self-consistent (SC) fewest switches surface hopping algorithm [L. Wang and O. V. Prezhdo, J. Phys. Chem. Lett. 5, 713 (2014)]. The resulting SC-FSSH-RD approach is applied to general Hamiltonians with different electronic couplings and electron-phonon couplings to mimic charge transport in tens to hundreds of molecules. In all cases, SC-FSSH-RD allows us to use a large time interval of 0.1 fs for convergence and the simulation time is reduced by over one order of magnitude. Both the band and hopping mechanisms of charge transport have been captured perfectly. SC-FSSH-RD makes surface hops in the adiabatic representation and can be implemented in both diabatic and locally diabatic representations for wave function propagation. SC-FSSH-RD can potentially describe general nonadiabatic dynamics of electrons and excitons in organics and other materials.

Adsorbate hopping via vibrational-mode coupling induced by femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Ueba, H.; Hayashi, M.; Paulsson, M.; Persson, B. N. J.

2008-09-01

We study the heat transfer from femtosecond laser-heated hot electrons in a metal to adsorbates in the presence of vibrational-mode coupling. The theory is successfully applied to the experimental result of atomic oxygen hopping on a vicinal Pt(111) surface. The effective friction coupling between hot electrons and the vibrational mode relevant to the hopping motion depends on the transient temperature of the partner mode excited by hot electrons. The calculated two-pulse correlation and fluence dependence of the hopping probability reproduce the experimental results, which were previously analyzed using the hot-electron temperature (Te) -dependent friction ηa(Te) in a conventional heat transfer equation. A possible elementary process behind such a hypothetic modeling using ηa(Te) is discussed in terms of an indirect heating of the vibrational mode for hopping at the surface.

Accelerated sampling by infinite swapping of path integral molecular dynamics with surface hopping

NASA Astrophysics Data System (ADS)

Lu, Jianfeng; Zhou, Zhennan

2018-02-01

To accelerate the thermal equilibrium sampling of multi-level quantum systems, the infinite swapping limit of a recently proposed multi-level ring polymer representation is investigated. In the infinite swapping limit, the ring polymer evolves according to an averaged Hamiltonian with respect to all possible surface index configurations of the ring polymer and thus connects the surface hopping approach to the mean-field path-integral molecular dynamics. A multiscale integrator for the infinite swapping limit is also proposed to enable efficient sampling based on the limiting dynamics. Numerical results demonstrate the huge improvement of sampling efficiency of the infinite swapping compared with the direct simulation of path-integral molecular dynamics with surface hopping.

Data mining of molecular dynamics data reveals Li diffusion characteristics in garnet Li7La3Zr2O12

PubMed Central

Chen, Chi; Lu, Ziheng; Ciucci, Francesco

2017-01-01

Understanding Li diffusion in solid conductors is essential for the next generation Li batteries. Here we show that density-based clustering of the trajectories computed using molecular dynamics simulations helps elucidate the Li diffusion mechanism within the Li7La3Zr2O12 (LLZO) crystal lattice. This unsupervised learning method recognizes lattice sites, is able to give the site type, and can identify Li hopping events. Results show that, while the cubic LLZO has a much higher hopping rate compared to its tetragonal counterpart, most of the Li hops in the cubic LLZO do not contribute to the diffusivity due to the dominance of back-and-forth type jumps. The hopping analysis and local Li configuration statistics give evidence that Li diffusivity in cubic LLZO is limited by the low vacancy concentration. The hopping statistics also shows uncorrelated Poisson-like diffusion for Li in the cubic LLZO, and correlated diffusion for Li in the tetragonal LLZO in the temporal scale. Further analysis of the spatio-temporal correlation using site-to-site mutual information confirms the weak site dependence of Li diffusion in the cubic LLZO as the origin for the uncorrelated diffusion. This work puts forward a perspective on combining machine learning and information theory to interpret results of molecular dynamics simulations. PMID:28094317

Data mining of molecular dynamics data reveals Li diffusion characteristics in garnet Li7La3Zr2O12

NASA Astrophysics Data System (ADS)

Chen, Chi; Lu, Ziheng; Ciucci, Francesco

2017-01-01

Understanding Li diffusion in solid conductors is essential for the next generation Li batteries. Here we show that density-based clustering of the trajectories computed using molecular dynamics simulations helps elucidate the Li diffusion mechanism within the Li7La3Zr2O12 (LLZO) crystal lattice. This unsupervised learning method recognizes lattice sites, is able to give the site type, and can identify Li hopping events. Results show that, while the cubic LLZO has a much higher hopping rate compared to its tetragonal counterpart, most of the Li hops in the cubic LLZO do not contribute to the diffusivity due to the dominance of back-and-forth type jumps. The hopping analysis and local Li configuration statistics give evidence that Li diffusivity in cubic LLZO is limited by the low vacancy concentration. The hopping statistics also shows uncorrelated Poisson-like diffusion for Li in the cubic LLZO, and correlated diffusion for Li in the tetragonal LLZO in the temporal scale. Further analysis of the spatio-temporal correlation using site-to-site mutual information confirms the weak site dependence of Li diffusion in the cubic LLZO as the origin for the uncorrelated diffusion. This work puts forward a perspective on combining machine learning and information theory to interpret results of molecular dynamics simulations.

Water-induced polaron formation at the pentacene surface: Quantum mechanical molecular mechanics simulations

NASA Astrophysics Data System (ADS)

Cramer, Tobias; Steinbrecher, Thomas; Koslowski, Thorsten; Case, David A.; Biscarini, Fabio; Zerbetto, Francesco

2009-04-01

Water is an omnipresent polar impurity that is expected to be the origin of many electric degradation phenomena observed in organic semiconductors. Here, we describe a microscopic model for polaron formation in the outermost layer of a pentacene crystal due to the polarization of a nearby water layer. The efficient coupling of a classical force field that describes the liquid with a tight-binding model that represents the π system of the organic layer permits the calculation of nanosecond length trajectories. The model predicts that the reorientation of water dipoles stabilizes positive charge carriers on average by 0.6 eV and thus leads to a polaron trap state at the liquid interface. Thermal fluctuations of the water molecules provoke two-dimensional diffusive hopping of the charge carrier parallel to the interface with mobilities of up to 0.6cm2s-1V-1 and lead to an amorphous broadening of the valence-band tail. As a consequence, water-filled nanocavities act as trapping sites in pentacene transistors. Instead, a complete wetting of the organic film is expected to result in fast thermally activated hopping transport. Polaron trapping is thus not expected to be a limiting factor for transistor-based sensors that operate under water.

Lateral hopping of CO molecules on Pt(111) surface by femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Hayashi, M.; Ootsuka, Y.; Paulsson, M.; Persson, B. N. J.; Ueba, H.

2009-12-01

Theory of heat transfer between adsorbate vibrational degrees of freedom and ultrafast laser heated hot electrons including vibrational intermode coupling is applied to calculate two-pulse correlation, laser fluence dependence and time dependence of lateral hopping of CO molecules from a step to terrace site on a stepped Pt (111) surface. The intermode coupling is a key ingredient to describe vibrational heating of the frustrated translation mode responsible for the CO hopping. The calculated results are in good agreement with the experimental results, especially if we scale down the experimentally determined absorbed fluence. It is found that CO hopping is induced by indirect heating of the FT mode by the FR mode with a strong frictional coupling to hot electrons.

Attractor hopping between polarization dynamical states in a vertical-cavity surface-emitting laser subject to parallel optical injection

NASA Astrophysics Data System (ADS)

Denis-le Coarer, Florian; Quirce, Ana; Valle, Angel; Pesquera, Luis; Rodríguez, Miguel A.; Panajotov, Krassimir; Sciamanna, Marc

2018-03-01

We present experimental and theoretical results of noise-induced attractor hopping between dynamical states found in a single transverse mode vertical-cavity surface-emitting laser (VCSEL) subject to parallel optical injection. These transitions involve dynamical states with different polarizations of the light emitted by the VCSEL. We report an experimental map identifying, in the injected power-frequency detuning plane, regions where attractor hopping between two, or even three, different states occur. The transition between these behaviors is characterized by using residence time distributions. We find multistability regions that are characterized by heavy-tailed residence time distributions. These distributions are characterized by a -1.83 ±0.17 power law. Between these regions we find coherence enhancement of noise-induced attractor hopping in which transitions between states occur regularly. Simulation results show that frequency detuning variations and spontaneous emission noise play a role in causing switching between attractors. We also find attractor hopping between chaotic states with different polarization properties. In this case, simulation results show that spontaneous emission noise inherent to the VCSEL is enough to induce this hopping.

Atomistic non-adiabatic dynamics of the LH2 complex with a GPU-accelerated ab initio exciton model

DOE PAGES

Sisto, Aaron; Stross, Clem; van der Kamp, Marc W.; ...

2017-03-28

We recently outlined an efficient multi-tiered parallel ab initio excitonic framework that utilizes time dependent density functional theory (TDDFT) to calculate ground and excited state energies and gradients of large supramolecular complexes in atomistic detail – enabling us to undertake non-adiabatic simulations which explicitly account for the coupled anharmonic vibrational motion of all the constituent atoms in a supramolecular system. Here we apply that framework to the 27 coupled bacterio-chlorophyll-a chromophores which make up the LH2 complex, using it to compute an on-the-fly nonadiabatic surface-hopping (SH) trajectory of electronically excited LH2. Part one of this article is focussed on calibratingmore » our ab initio exciton Hamiltonian using two key parameters: a shift δ, which corrects for the error in TDDFT vertical excitation energies; and an effective dielectric constant ε, which describes the average screening of the transition-dipole coupling between chromophores. Using snapshots obtained from equilibrium molecular dynamics simulations (MD) of LH2, we tune the values of both δ and ε through fitting to the thermally broadened experimental absorption spectrum, giving a linear absorption spectrum that agrees reasonably well with experiment. In part two of this article, we construct a time-resolved picture of the coupled vibrational and excitation energy transfer (EET) dynamics in the sub-picosecond regime following photo-excitation. Assuming Franck–Condon excitation of a narrow eigenstate band centred at 800 nm, we use surface hopping to follow a single nonadiabatic dynamics trajectory within the full eigenstate manifold. Consistent with experimental data, this trajectory gives timescales for B800→B850 population transfer (τ B800→B850) between 650–1050 fs, and B800 population decay (τ 800→) between 10–50 fs. The dynamical picture that emerges is one of rapidly fluctuating LH2 eigenstates that are delocalized over multiple chromophores and undergo frequent crossing on a femtosecond timescale as a result of the atomic vibrations of the constituent chromophores. The eigenstate fluctuations arise from disorder that is driven by vibrational dynamics with multiple characteristic timescales. The scalability of our ab initio excitonic computational framework across massively parallel architectures opens up the possibility of addressing a wide range of questions, including how specific dynamical motions impact both the pathways and efficiency of electronic energy-transfer within large supramolecular systems.« less

Ab initio implementation of quantum trajectory mean-field approach and dynamical simulation of the N{sub 2}CO photodissociation

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

Xie, Binbin; Liu, Lihong; Cui, Ganglong

2015-11-21

In this work, the recently introduced quantum trajectory mean-field (QTMF) approach is implemented and employed to explore photodissociation dynamics of diazirinone (N{sub 2}CO), which are based on the high-level ab initio calculation. For comparison, the photodissociation process has been simulated as well with the fewest-switches surface hopping (FSSH) and the ab initio multiple spawning (AIMS) methods. Overall, the dynamical behavior predicted by the three methods is consistent. The N{sub 2}CO photodissociation at λ > 335 nm is an ultrafast process and the two C—N bonds are broken in a stepwise way, giving birth to CO and N{sub 2} as themore » final products in the ground state. Meanwhile, some noticeable differences were found in the QTMF, FSSH, and AIMS simulated time constants for fission of the C—N bonds, excited-state lifetime, and nonadiabatic transition ratios in different intersection regions. These have been discussed in detail. The present study provides a clear evidence that direct ab initio QTMF approach is one of the reliable tools for simulating nonadiabatic dynamics processes.« less

Toward rational nanoparticle synthesis: predicting surface intermixing in bimetallic alloy nanocatalysts

DOE PAGES

Roling, Luke T.; Mavrikakis, Manos

2017-09-19

In this paper, we present a database of first-principles calculated activation energy barriers for two competitive processes involving bimetallic adatom-surface permutations of ten transition metals: (i) adatom “hopping” diffusion and (ii) adatom substitution into the surface. We consider the surface structure sensitivity of these events as well as coverage effects. We find that surface hopping mechanisms are facile and always preferred to substitution events on close-packed fcc(111) and hcp(0001) surfaces. However, surface atom substitution is more facile on the more open fcc(100) surfaces and is competitive with adatom surface hopping, which is more difficult than on the close-packed surfaces. Finally,more » by comparing the absolute and relative magnitudes of the energetics of hopping and substitution, our calculations can offer qualitative predictions of intermixing and other phenomena relevant to nanocrystal growth, such as the tendency to form intermixed alloys or core–shell structures during layer-by-layer nanoparticle synthesis involving a given bimetallic pair, and thereby inform the rational design and synthesis of novel bimetallic nanomaterials.« less

Molecular dynamics simulation of the cooperative adsorption of barley lipid transfer protein and cis-isocohumulone at the vacuum-water interface.

PubMed

Euston, S R; Hughes, P; Naser, Md A; Westacott, R E

2008-11-01

Molecular dynamic simulations have been carried out on systems containing a mixture of barley lipid transfer protein (LTP) and cis-isocohumulone (a hop derived iso-alpha-acid) in one of its enol forms, in bulk water and at the vacuum-water interface. In solution, the cis-isocohumulone molecules bind to the surface of the LTP molecule. The mechanism of binding appears to be purely hydrophobic in nature via desolvation of the protein surface. Binding of hop acids to the LTP leads to a small change in the 3-D conformation of the protein, but no change in the proportion of secondary structure present in helices, even though there is a significant degree of hop acid binding to the helical regions. At the vacuum-water interface, cis-isocohumulone shows a high surface activity and adsorbs rapidly at the interface. LTP then shows a preference to bind to the preadsorbed hop acid layer at the interface rather than to the bare water-vacuum interface. The free energy of adsorption of LTP at the hop-vacuum-water interface is more favorable than for adsorption at the vacuum-water interface. Our results support the view that hop iso-alpha-acids promote beer foam stability by forming bridges between separate adsorbed protein molecules, thus strengthening the adsorbed protein layer and reducing foam breakdown by lamellar phase drainage. The results also suggest a second mechanism may also occur, whereby the concentration of protein at the interface is increased via enhanced protein adsorption to adsorbed hop acid layers. This too would increase foam stability through its effect on the stabilizing protein layer around the foam bubbles.

Dynamically biased statistical model for the ortho/para conversion in the H2 + H3+ → H3+ + H2 reaction.

PubMed

Gómez-Carrasco, Susana; González-Sánchez, Lola; Aguado, Alfredo; Sanz-Sanz, Cristina; Zanchet, Alexandre; Roncero, Octavio

2012-09-07

In this work we present a dynamically biased statistical model to describe the evolution of the title reaction from statistical to a more direct mechanism, using quasi-classical trajectories (QCT). The method is based on the one previously proposed by Park and Light [J. Chem. Phys. 126, 044305 (2007)]. A recent global potential energy surface is used here to calculate the capture probabilities, instead of the long-range ion-induced dipole interactions. The dynamical constraints are introduced by considering a scrambling matrix which depends on energy and determine the probability of the identity/hop/exchange mechanisms. These probabilities are calculated using QCT. It is found that the high zero-point energy of the fragments is transferred to the rest of the degrees of freedom, what shortens the lifetime of H(5)(+) complexes and, as a consequence, the exchange mechanism is produced with lower proportion. The zero-point energy (ZPE) is not properly described in quasi-classical trajectory calculations and an approximation is done in which the initial ZPE of the reactants is reduced in QCT calculations to obtain a new ZPE-biased scrambling matrix. This reduction of the ZPE is explained by the need of correcting the pure classical level number of the H(5)(+) complex, as done in classical simulations of unimolecular processes and to get equivalent quantum and classical rate constants using Rice-Ramsperger-Kassel-Marcus theory. This matrix allows to obtain a ratio of hop/exchange mechanisms, α(T), in rather good agreement with recent experimental results by Crabtree et al. [J. Chem. Phys. 134, 194311 (2011)] at room temperature. At lower temperatures, however, the present simulations predict too high ratios because the biased scrambling matrix is not statistical enough. This demonstrates the importance of applying quantum methods to simulate this reaction at the low temperatures of astrophysical interest.

Dynamically biased statistical model for the ortho/para conversion in the H2+H3+ --> H3++ H2 reaction

NASA Astrophysics Data System (ADS)

Gómez-Carrasco, Susana; González-Sánchez, Lola; Aguado, Alfredo; Sanz-Sanz, Cristina; Zanchet, Alexandre; Roncero, Octavio

2012-09-01

In this work we present a dynamically biased statistical model to describe the evolution of the title reaction from statistical to a more direct mechanism, using quasi-classical trajectories (QCT). The method is based on the one previously proposed by Park and Light [J. Chem. Phys. 126, 044305 (2007), 10.1063/1.2430711]. A recent global potential energy surface is used here to calculate the capture probabilities, instead of the long-range ion-induced dipole interactions. The dynamical constraints are introduced by considering a scrambling matrix which depends on energy and determine the probability of the identity/hop/exchange mechanisms. These probabilities are calculated using QCT. It is found that the high zero-point energy of the fragments is transferred to the rest of the degrees of freedom, what shortens the lifetime of H_5^+ complexes and, as a consequence, the exchange mechanism is produced with lower proportion. The zero-point energy (ZPE) is not properly described in quasi-classical trajectory calculations and an approximation is done in which the initial ZPE of the reactants is reduced in QCT calculations to obtain a new ZPE-biased scrambling matrix. This reduction of the ZPE is explained by the need of correcting the pure classical level number of the H_5^+ complex, as done in classical simulations of unimolecular processes and to get equivalent quantum and classical rate constants using Rice-Ramsperger-Kassel-Marcus theory. This matrix allows to obtain a ratio of hop/exchange mechanisms, α(T), in rather good agreement with recent experimental results by Crabtree et al. [J. Chem. Phys. 134, 194311 (2011), 10.1063/1.3587246] at room temperature. At lower temperatures, however, the present simulations predict too high ratios because the biased scrambling matrix is not statistical enough. This demonstrates the importance of applying quantum methods to simulate this reaction at the low temperatures of astrophysical interest.

Ab initio calculation of diffusion barriers for Cu adatom hopping on Cu(1 0 0) surface and evolution of atomic configurations

NASA Astrophysics Data System (ADS)

Zhang, Wei; Gan, Jie; Li, Qian; Gao, Kun; Sun, Jian; Xu, Ning; Ying, Zhifeng; Wu, Jiada

2011-06-01

The self-diffusion dynamics of Cu adatoms on Cu(1 0 0) surface has been studied based on the calculation of the energy barriers for various hopping events using lattice-gas based approach and a modified model. To simplify the description of the interactions and the calculation of the energy barrier, a three-tier hierarchy of description of atomic configurations was conceived in which the active adatom and its nearest atoms were chosen to constitute basic configuration and taken as a whole to study many-body interactions of the atoms in various atomic configurations, whereas the impacts of the next nearest atoms on the diffusion of the active adatom were considered as multi-site interactions. Besides the simple hopping of single adatoms, the movements of dimers and trimers as the results of multiple hopping events have also been examined. Taking into account the hopping events of all adatoms, the stability of atomic configurations has been examined and the evolution of atomic configurations has also been analyzed.

Sub-nanometer glass surface dynamics induced by illumination

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

Nguyen, Duc; Nienhaus, Lea; Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801

2015-06-21

Illumination is known to induce stress and morphology changes in opaque glasses. Amorphous silicon carbide (a-SiC) has a smaller bandgap than the crystal. Thus, we were able to excite with 532 nm light a 1 μm amorphous surface layer on a SiC crystal while recording time-lapse movies of glass surface dynamics by scanning tunneling microscopy (STM). Photoexcitation of the a-SiC surface layer through the transparent crystal avoids heating the STM tip. Up to 6 × 10{sup 4} s, long movies of surface dynamics with 40 s time resolution and sub-nanometer spatial resolution were obtained. Clusters of ca. 3-5 glass formingmore » units diameter are seen to cooperatively hop between two states at the surface. Photoexcitation with green laser light recruits immobile clusters to hop, rather than increasing the rate at which already mobile clusters hop. No significant laser heating was observed. Thus, we favor an athermal mechanism whereby electronic excitation of a-SiC directly controls glassy surface dynamics. This mechanism is supported by an exciton migration-relaxation-thermal diffusion model. Individual clusters take ∼1 h to populate states differently after the light intensity has changed. We believe the surrounding matrix rearranges slowly when it is stressed by a change in laser intensity, and clusters serve as a diagnostic. Such cluster hopping and matrix rearrangement could underlie the microscopic mechanism of photoinduced aging of opaque glasses.« less

Simulations of optically switchable molecular machines for particle transport.

PubMed

Raeker, Tim; Jansen, Björn; Behrens, Dominik; Hartke, Bernd

2018-03-24

A promising application for design and deployment of molecular machines is nanoscale transport, driven by artificial cilia. In this contribution, we present several further steps toward this goal, beyond our first-generation artificial cilium (Raeker et al., J. Phys. Chem. A 2012, 116, 11241). Promising new azobenzene-derivatives were tested for use as cilium motors. Using a QM/MM partitioning in on-the-fly photodynamics, excited-state surface-hopping trajectories were calculated for each isomerization direction and each motor version. The methods used were reparametrized semiempirical quantum chemistry together with floating-occupation configuration interaction as the QM part and the OPLSAA-L forcefield as MM part. In addition, we simulated actual particle transport by a single cilium attached to a model surface, with varying attachment strengths and modes, and with transport targets ranging from single atoms to multi-molecule arrangements. Our results provide valuable design guidelines for cilia-driven nanoscale transport and emphasize the need to carefully select the whole setup (not just the cilium itself, but also its surface attachment and the dynamic cilium-target interaction) to achieve true transport. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

Design, testing, and performance of a hybrid micro vehicle---The Hopping Rotochute

NASA Astrophysics Data System (ADS)

Beyer, Eric W.

The Hopping Rotochute is a new hybrid micro vehicle that has been developed to robustly explore environments with rough terrain while minimizing energy consumption over long periods of time. The device consists of a small coaxial rotor system housed inside a lightweight cage. The vehicle traverses an area by intermittently powering a small electric motor which drives the rotor system, allowing the vehicle to hop over obstacles of various shapes and sizes. A movable internal mass controls the direction of travel while the egg-like exterior shape and low mass center allows the vehicle to passively reorient itself to an upright attitude when in contact with the ground. This dissertation presents the design, fabrication, and testing of a radio-controlled Hopping Rotochute prototype as well as an analytical study of the flight performance of the device. The conceptual design iterations are first outlined which were driven by the mission and system requirements assigned to the vehicle. The aerodynamic, mechanical, and electrical design of a prototype is then described, based on the final conceptual design, with particular emphasis on the fundamental trades that must be negotiated for this type of hopping vehicle. The fabrication and testing of this prototype is detailed as well as experimental results obtained from a motion capture system. Basic flight performance of the prototype are reported which demonstrates that the Hopping Rotochute satisfies all appointed system requirements. A dynamic model of the Hopping Rotochute is also developed in this thesis and employed to predict the flight performance of the vehicle. The dynamic model includes aerodynamic loads from the body and rotor system as well as a soft contact model to estimate the forces and moments during ground contact. The experimental methods used to estimate the dynamic model parameters are described while comparisons between measured and simulated motion are presented. Good correlation between these motions is shown to validate the dynamic model. Using the validated dynamic model, simulations were performed to better understand the dynamics of the device. In addition, key parameters such as system weight, rotor speed, internal mass weight and location, as well as battery capacity are varied to explore and optimize flight performance characteristics such as single hop height and range, number of hops, and total achievable range. The sensitivity of the Hopping Rotochute to atmospheric winds is also investigated as is the ability of the device to perform trajectory shaping.

Low-coverage surface diffusion in complex periodic energy landscapes: Analytical solution for systems with symmetric hops and application to intercalation in topological insulators

NASA Astrophysics Data System (ADS)

Gosálvez, Miguel A.; Otrokov, Mikhail M.; Ferrando, Nestor; Ryabishchenkova, Anastasia G.; Ayuela, Andres; Echenique, Pedro M.; Chulkov, Evgueni V.

2016-02-01

This is the first of two papers that introduce a general expression for the tracer diffusivity in complex, periodic energy landscapes with M distinct hop rates in one-, two-, and three-dimensional diluted systems (low-coverage, single-tracer limit). The present report focuses on the analysis of diffusion in systems where the end sites of the hops are located symmetrically with respect to the hop origins (symmetric hops), as encountered in many ideal surfaces and bulk materials. For diffusion in two dimensions, a number of formulas are presented for complex combinations of the different hops in systems with triangular, rectangular, and square symmetry. The formulas provide values in excellent agreement with kinetic Monte Carlo simulations, concluding that the diffusion coefficient can be directly determined from the proposed expressions without performing the simulations. Based on the diffusion barriers obtained from first-principles calculations and a physically meaningful estimate of the attempt frequencies, the proposed formulas are used to analyze the diffusion of Cu, Ag, and Rb adatoms on the surface and within the van der Waals (vdW) gap of a model topological insulator, Bi2Se3 . Considering the possibility of adsorbate intercalation from the terraces to the vdW gaps at morphological steps, we infer that, at low coverage and room temperature, (i) a majority of the Rb atoms bounce back at the steps and remain on the terraces, (ii) Cu atoms mostly intercalate into the vdW gap, the remaining fraction staying at the steps, and (iii) Ag atoms essentially accumulate at the steps and gradually intercalate into the vdW gap. These conclusions are in good qualitative agreement with previous experiments. The companion report (M. A. Gosálvez et al., Phys. Rev. B, submitted] extends the present study to the description of systems that contain asymmetric hops.

The lunar hopping transporter

NASA Technical Reports Server (NTRS)

Degner, R.; Kaplan, M. H.; Manning, J.; Meetin, R.; Pasternack, S.; Peterson, S.; Seifert, H.

1971-01-01

Research on several aspects of lunar transport using the hopping mode is reported. Hopping exploits the weak lunar gravity, permits fuel economy because of partial recompression of propellant gas on landing, and does not require a continuous smooth surface for operation. Three questions critical to the design of a lunar hopping vehicle are addressed directly in this report: (1) the tolerance of a human pilot for repeated accelerations; (2) means for controlling vehicle attitude during ballistic flight; and (3) means of propulsion. In addition, a small scale terrestrial demonstrator built to confirm feasibility of the proposed operational mode is described, along with results of preliminary study of unmanned hoppers for moon exploration.

Surface hopping with a manifold of electronic states. II. Application to the many-body Anderson-Holstein model

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

Dou, Wenjie; Subotnik, Joseph E.; Nitzan, Abraham

We investigate a simple surface hopping (SH) approach for modeling a single impurity level coupled to a single phonon and an electronic (metal) bath (i.e., the Anderson-Holstein model). The phonon degree of freedom is treated classically with motion along–and hops between–diabatic potential energy surfaces. The hopping rate is determined by the dynamics of the electronic bath (which are treated implicitly). For the case of one electronic bath, in the limit of small coupling to the bath, SH recovers phonon relaxation to thermal equilibrium and yields the correct impurity electron population (as compared with numerical renormalization group). For the case ofmore » out of equilibrium dynamics, SH current-voltage (I-V) curve is compared with the quantum master equation (QME) over a range of parameters, spanning the quantum region to the classical region. In the limit of large temperature, SH and QME agree. Furthermore, we can show that, in the limit of low temperature, the QME agrees with real-time path integral calculations. As such, the simple procedure described here should be useful in many other contexts.« less

Nanoscale live cell imaging using hopping probe ion conductance microscopy

PubMed Central

Novak, Pavel; Li, Chao; Shevchuk, Andrew I.; Stepanyan, Ruben; Caldwell, Matthew; Hughes, Simon; Smart, Trevor G.; Gorelik, Julia; Ostanin, Victor P.; Lab, Max J.; Moss, Guy W. J.; Frolenkov, Gregory I.; Klenerman, David; Korchev, Yuri E.

2009-01-01

We describe a major advance in scanning ion conductance microscopy: a new hopping mode that allows non-contact imaging of the complex surfaces of live cells with resolution better than 20 nm. The effectiveness of this novel technique was demonstrated by imaging networks of cultured rat hippocampal neurons and mechanosensory stereocilia of mouse cochlear hair cells. The technique allows studying nanoscale phenomena on the surface of live cells under physiological conditions. PMID:19252505

Signaling induced by hop/STI-1 depends on endocytosis

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

Americo, Tatiana A.; Chiarini, Luciana B.; Linden, Rafael

The co-chaperone hop/STI-1 is a ligand of the cell surface prion protein (PrP{sup C}), and their interaction leads to signaling and biological effects. Among these, hop/STI-1 induces proliferation of A172 glioblastoma cells, dependent on both PrP{sup C} and activation of the Erk pathway. We tested whether clathrin-mediated endocytosis affects signaling induced by hop/STI-1. Both hyperosmolarity induced by sucrose and monodansyl-cadaverine blocked Erk activity induced by hop/STI-1, without affecting the high basal Akt activity typical of A172. The endocytosis inhibitors also affected the sub-cellular distribution of phosphorylated Erk, consistent with blockade of the latter's activity. The data indicate that signaling inducedmore » by hop/STI-1 depends on endocytosis. These findings are consistent with a role of sub-cellular trafficking in signal transduction following engagement by PrP{sup C} by ligands such as hop/STI-1, and may help help unravel both the functions of the prion protein, as well as possible loss-of-function components of prion diseases.« less

A open loop guidance architecture for navigationally robust on-orbit docking

NASA Technical Reports Server (NTRS)

Chern, Hung-Sheng

1995-01-01

The development of an open-hop guidance architecture is outlined for autonomous rendezvous and docking (AR&D) missions to determine whether the Global Positioning System (GPS) can be used in place of optical sensors for relative initial position determination of the chase vehicle. Feasible command trajectories for one, two, and three impulse AR&D maneuvers are determined using constrained trajectory optimization. Early AR&D command trajectory results suggest that docking accuracies are most sensitive to vertical position errors at the initial conduction of the chase vehicle. Thus, a feasible command trajectory is based on maximizing the size of the locus of initial vertical positions for which a fixed sequence of impulses will translate the chase vehicle into the target while satisfying docking accuracy requirements. Documented accuracies are used to determine whether relative GPS can achieve the vertical position error requirements of the impulsive command trajectories. Preliminary development of a thruster management system for the Cargo Transfer Vehicle (CTV) based on optimal throttle settings is presented to complete the guidance architecture. Results show that a guidance architecture based on a two impulse maneuvers generated the best performance in terms of initial position error and total velocity change for the chase vehicle.

Gravity-Assist Trajectories to the Ice Giants: An Automated Method to Catalog Mass- Or Time-Optimal Solutions

NASA Technical Reports Server (NTRS)

Hughes, Kyle M.; Knittel, Jeremy M.; Englander, Jacob A.

2017-01-01

This work presents an automated method of calculating mass (or time) optimal gravity-assist trajectories without a priori knowledge of the flyby-body combination. Since gravity assists are particularly crucial for reaching the outer Solar System, we use the Ice Giants, Uranus and Neptune, as example destinations for this work. Catalogs are also provided that list the most attractive trajectories found over launch dates ranging from 2024 to 2038. The tool developed to implement this method, called the Python EMTG Automated Trade Study Application (PEATSA), iteratively runs the Evolutionary Mission Trajectory Generator (EMTG), a NASA Goddard Space Flight Center in-house trajectory optimization tool. EMTG finds gravity-assist trajectories with impulsive maneuvers using a multiple-shooting structure along with stochastic methods (such as monotonic basin hopping) and may be run with or without an initial guess provided. PEATSA runs instances of EMTG in parallel over a grid of launch dates. After each set of runs completes, the best results within a neighborhood of launch dates are used to seed all other cases in that neighborhood-allowing the solutions across the range of launch dates to improve over each iteration. The results here are compared against trajectories found using a grid-search technique, and PEATSA is found to outperform the grid-search results for most launch years considered.

Gravity-Assist Trajectories to the Ice Giants: An Automated Method to Catalog Mass-or Time-Optimal Solutions

NASA Technical Reports Server (NTRS)

Hughes, Kyle M.; Knittel, Jeremy M.; Englander, Jacob A.

2017-01-01

This work presents an automated method of calculating mass (or time) optimal gravity-assist trajectories without a priori knowledge of the flyby-body combination. Since gravity assists are particularly crucial for reaching the outer Solar System, we use the Ice Giants, Uranus and Neptune, as example destinations for this work. Catalogs are also provided that list the most attractive trajectories found over launch dates ranging from 2024 to 2038. The tool developed to implement this method, called the Python EMTG Automated Trade Study Application (PEATSA), iteratively runs the Evolutionary Mission Trajectory Generator (EMTG), a NASA Goddard Space Flight Center in-house trajectory optimization tool. EMTG finds gravity-assist trajectories with impulsive maneuvers using a multiple-shooting structure along with stochastic methods (such as monotonic basin hopping) and may be run with or without an initial guess provided. PEATSA runs instances of EMTG in parallel over a grid of launch dates. After each set of runs completes, the best results within a neighborhood of launch dates are used to seed all other cases in that neighborhood---allowing the solutions across the range of launch dates to improve over each iteration. The results here are compared against trajectories found using a grid-search technique, and PEATSA is found to outperform the grid-search results for most launch years considered.

Superdiffusive motion of membrane-targeting C2 domains

NASA Astrophysics Data System (ADS)

Campagnola, Grace; Nepal, Kanti; Schroder, Bryce W.; Peersen, Olve B.; Krapf, Diego

2015-12-01

Membrane-targeting domains play crucial roles in the recruitment of signalling molecules to the plasma membrane. For most peripheral proteins, the protein-to-membrane interaction is transient. After proteins dissociate from the membrane they have been observed to rebind following brief excursions in the bulk solution. Such membrane hops can have broad implications for the efficiency of reactions on membranes. We study the diffusion of membrane-targeting C2 domains using single-molecule tracking in supported lipid bilayers. The ensemble-averaged mean square displacement (MSD) exhibits superdiffusive behaviour. However, traditional time-averaged MSD analysis of individual trajectories remains linear and does not reveal superdiffusion. Our observations are explained in terms of bulk excursions that introduce jumps with a heavy-tail distribution. These hopping events allow proteins to explore large areas in a short time. The experimental results are shown to be consistent with analytical models of bulk-mediated diffusion and numerical simulations.

Monte Carlo sampling of Wigner functions and surface hopping quantum dynamics

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

Kube, Susanna; Lasser, Caroline; Weber, Marcus

2009-04-01

The article addresses the achievable accuracy for a Monte Carlo sampling of Wigner functions in combination with a surface hopping algorithm for non-adiabatic quantum dynamics. The approximation of Wigner functions is realized by an adaption of the Metropolis algorithm for real-valued functions with disconnected support. The integration, which is necessary for computing values of the Wigner function, uses importance sampling with a Gaussian weight function. The numerical experiments agree with theoretical considerations and show an error of 2-3%.

Mixed quantum-classical simulations of the vibrational relaxation of photolyzed carbon monoxide in a hemoprotein

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

Schubert, Alexander, E-mail: schubert@irsamc.ups-tlse.fr; Meier, Christoph; Falvo, Cyril

2016-08-07

We present mixed quantum-classical simulations on relaxation and dephasing of vibrationally excited carbon monoxide within a protein environment. The methodology is based on a vibrational surface hopping approach treating the vibrational states of CO quantum mechanically, while all remaining degrees of freedom are described by means of classical molecular dynamics. The CO vibrational states form the “surfaces” for the classical trajectories of protein and solvent atoms. In return, environmentally induced non-adiabatic couplings between these states cause transitions describing the vibrational relaxation from first principles. The molecular dynamics simulation yields a detailed atomistic picture of the energy relaxation pathways, taking themore » molecular structure and dynamics of the protein and its solvent fully into account. Using the ultrafast photolysis of CO in the hemoprotein FixL as an example, we study the relaxation of vibrationally excited CO and evaluate the role of each of the FixL residues forming the heme pocket.« less

Nonadiabatic ab initio molecular dynamics with PME-ONIOM scheme of photoisomerization reaction between 1,3-cyclohexadiene and 1,3,5-cis-hexatriene in solution phase

NASA Astrophysics Data System (ADS)

Ohta, Ayumi; Kobayashi, Osamu; Danielache, Sebastian O.; Nanbu, Shinkoh

2017-03-01

The ultra-fast photoisomerization reactions between 1,3-cyclohexadiene (CHD) and 1,3,5-cis-hexatriene (HT) in both hexane and ethanol solvents were revealed by nonadiabatic ab initio molecular dynamics (AI-MD) with a particle-mesh Ewald summation method and our Own N-layered Integrated molecular Orbital and molecular Mechanics model (PME-ONIOM) scheme. Zhu-Nakamura version trajectory surface hopping method (ZN-TSH) was employed to treat the ultra-fast nonadiabatic decaying process. The results for hexane and ethanol simulations reasonably agree with experimental data. The high nonpolar-nonpolar affinity between CHD and the solvent was observed in hexane solvent, which definitely affected the excited state lifetimes, the product branching ratio of CHD:HT, and solute (CHD) dynamics. In ethanol solvent, however, the CHD solute was isomerized in the solvent cage caused by the first solvation shell. The photochemical dynamics in ethanol solvent results in the similar property to the process appeared in vacuo (isolated CHD dynamics).

Scaling relationships for nonadiabatic energy relaxation times in warm dense matter: toward understanding the equation of state.

PubMed

Pradhan, Ekadashi; Magyar, Rudolph J; Akimov, Alexey V

2016-11-30

Understanding the dynamics of electron-ion energy transfer in warm dense (WD) matter is important to the measurement of equation of state (EOS) properties and for understanding the energy balance in dynamic simulations. In this work, we present a comprehensive investigation of nonadiabatic electron relaxation and thermal excitation dynamics in aluminum under high pressure and temperature. Using quantum-classical trajectory surface hopping approaches, we examine the role of nonadiabatic couplings and electronic decoherence in electron-nuclear energy transfer in WD aluminum. The computed timescales range from 400 fs to 4.0 ps and are consistent with existing experimental studies. We have derived general scaling relationships between macroscopic parameters of WD systems such as temperature or mass density and the timescales of energy redistribution between quantum and classical degrees of freedom. The scaling laws are supported by computational results. We show that electronic decoherence plays essential role and can change the functional dependencies qualitatively. The established scaling relationships can be of use in modelling of WD matter.

Recent Advances and Perspectives on Nonadiabatic Mixed Quantum-Classical Dynamics.

PubMed

Crespo-Otero, Rachel; Barbatti, Mario

2018-05-16

Nonadiabatic mixed quantum-classical (NA-MQC) dynamics methods form a class of computational theoretical approaches in quantum chemistry tailored to investigate the time evolution of nonadiabatic phenomena in molecules and supramolecular assemblies. NA-MQC is characterized by a partition of the molecular system into two subsystems: one to be treated quantum mechanically (usually but not restricted to electrons) and another to be dealt with classically (nuclei). The two subsystems are connected through nonadiabatic couplings terms to enforce self-consistency. A local approximation underlies the classical subsystem, implying that direct dynamics can be simulated, without needing precomputed potential energy surfaces. The NA-MQC split allows reducing computational costs, enabling the treatment of realistic molecular systems in diverse fields. Starting from the three most well-established methods-mean-field Ehrenfest, trajectory surface hopping, and multiple spawning-this review focuses on the NA-MQC dynamics methods and programs developed in the last 10 years. It stresses the relations between approaches and their domains of application. The electronic structure methods most commonly used together with NA-MQC dynamics are reviewed as well. The accuracy and precision of NA-MQC simulations are critically discussed, and general guidelines to choose an adequate method for each application are delivered.

Stimulated Raman signals at conical intersections: Ab initio surface hopping simulation protocol with direct propagation of the nuclear wave function

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

Kowalewski, Markus, E-mail: mkowalew@uci.edu; Mukamel, Shaul, E-mail: smukamel@uci.edu

2015-07-28

Femtosecond Stimulated Raman Spectroscopy (FSRS) signals that monitor the excited state conical intersections dynamics of acrolein are simulated. An effective time dependent Hamiltonian for two C—H vibrational marker bands is constructed on the fly using a local mode expansion combined with a semi-classical surface hopping simulation protocol. The signals are obtained by a direct forward and backward propagation of the vibrational wave function on a numerical grid. Earlier work is extended to fully incorporate the anharmonicities and intermode couplings.

Dispersive Sachdev-Ye-Kitaev model: Band structure and quantum chaos

NASA Astrophysics Data System (ADS)

Zhang, Pengfei

2017-11-01

The Sachdev-Ye-Kitaev (SYK) model is a concrete model for a non-Fermi liquid with maximally chaotic behavior in (0 +1 ) dimensions. In order to gain some insights into real materials in higher dimensions where fermions could hop between different sites, here we consider coupling a SYK lattice by constant hopping. We call this the dispersive SYK model. Focusing on (1 +1 ) -dimensional homogeneous hopping, by either tuning the temperature or the relative strength of the random interaction (hopping) and constant hopping, we find a crossover between a dispersive metal to an incoherent metal, where the dynamic exponent z changes from 1 to ∞ . We study the crossover by calculating the spectral function, charge density correlator, and the Lyapunov exponent. We further find the Lyapunov exponent becomes larger when the chemical potential is tuned to approach a van Hove singularity because of the large density of states near the Fermi surface. The effect of the topological nontrivial bands is also discussed.

Nonadiabatic molecular dynamics simulations: synergies between theory and experiments.

PubMed

Tavernelli, Ivano

2015-03-17

Recent developments in nonadiabatic dynamics enabled ab inito simulations of complex ultrafast processes in the condensed phase. These advances have opened new avenues in the study of many photophysical and photochemical reactions triggered by the absorption of electromagnetic radiation. In particular, theoretical investigations can be combined with the most sophisticated femtosecond experimental techniques to guide the interpretation of measured time-resolved observables. At the same time, the availability of experimental data at high (spatial and time) resolution offers a unique opportunity for the benchmarking and the improvement of those theoretical models used to describe complex molecular systems in their natural environment. The established synergy between theory and experiments can produce a better understanding of new ultrafast physical and chemical processes at atomistic scale resolution. Furthermore, reliable ab inito molecular dynamics simulations can already be successfully employed as predictive tools to guide new experiments as well as the design of novel and better performing materials. In this paper, I will give a concise account on the state of the art of molecular dynamics simulations of complex molecular systems in their excited states. The principal aim of this approach is the description of a given system of interest under the most realistic ambient conditions including all environmental effects that influence experiments, for instance, the interaction with the solvent and with external time-dependent electric fields, temperature, and pressure. To this end, time-dependent density functional theory (TDDFT) is among the most efficient and accurate methods for the representation of the electronic dynamics, while trajectory surface hopping gives a valuable representation of the nuclear quantum dynamics in the excited states (including nonadiabatic effects). Concerning the environment and its effects on the dynamics, the quantum mechanics/molecular mechanics (QM/MM) approach has the advantage of providing an atomistic (even though approximated) description of the solvent molecules, which is crucial for the characterization of all ultrafast relaxation phenomena that depend on the geometrical arrangement at the interface between a molecule and the solvent, for example, the hydrogen bond network. After a short description of the TDDFT-based implementation of Ehrenfest and trajectory surface hopping dynamics, I will present applications in different domains of molecular chemistry and physics: the analysis and the understanding of (time-resolved) X-ray absorption spectra, the interpretation of the ultrafast relaxation dynamics of photoexcited dyes in solution, and the design of specific laser pulses (capable of inducing desired chemical reactions) using local control theory.

Non-adiabatic effects in thermochemistry, spectroscopy and kinetics: the general importance of all three Born-Oppenheimer breakdown corrections.

PubMed

Reimers, Jeffrey R; McKemmish, Laura K; McKenzie, Ross H; Hush, Noel S

2015-10-14

Using a simple model Hamiltonian, the three correction terms for Born-Oppenheimer (BO) breakdown, the adiabatic diagonal correction (DC), the first-derivative momentum non-adiabatic correction (FD), and the second-derivative kinetic-energy non-adiabatic correction (SD), are shown to all contribute to thermodynamic and spectroscopic properties as well as to thermal non-diabatic chemical reaction rates. While DC often accounts for >80% of thermodynamic and spectroscopic property changes, the commonly used practice of including only the FD correction in kinetics calculations is rarely found to be adequate. For electron-transfer reactions not in the inverted region, the common physical picture that diabatic processes occur because of surface hopping at the transition state is proven inadequate as the DC acts first to block access, increasing the transition state energy by (ℏω)(2)λ/16J(2) (where λ is the reorganization energy, J the electronic coupling and ω the vibration frequency). However, the rate constant in the weakly-coupled Golden-Rule limit is identified as being only inversely proportional to this change rather than exponentially damped, owing to the effects of tunneling and surface hopping. Such weakly-coupled long-range electron-transfer processes should therefore not be described as "non-adiabatic" processes as they are easily described by Born-Huang ground-state adiabatic surfaces made by adding the DC to the BO surfaces; instead, they should be called just "non-Born-Oppenheimer" processes. The model system studied consists of two diabatic harmonic potential-energy surfaces coupled linearly through a single vibration, the "two-site Holstein model". Analytical expressions are derived for the BO breakdown terms, and the model is solved over a large parameter space focusing on both the lowest-energy spectroscopic transitions and the quantum dynamics of coherent-state wavepackets. BO breakdown is investigated pertinent to: ammonia inversion, aromaticity in benzene, the Creutz-Taube ion, the bacterial photosynthetic reaction centre, BNB, the molecular conductor Alq3, and inverted-region charge recombination in a ferrocene-porphyrin-fullerene triad photosynthetic model compound. Throughout, the fundamental nature of BO breakdown is linked to the properties of the cusp catastrophe: the cusp diameter is shown to determine the magnitudes of all couplings, numerical basis-set and trajectory-integration requirements, and to determine the transmission coefficient κ used to understand deviations from transition-state theory.

Hopping and trapping mechanisms in organic field-effect transistors

NASA Astrophysics Data System (ADS)

Konezny, S. J.; Bussac, M. N.; Zuppiroli, L.

2010-01-01

A charge carrier in the channel of an organic field-effect transistor (OFET) is coupled to the electric polarization of the gate in the form of a surface Fröhlich polaron [N. Kirova and M. N. Bussac, Phys. Rev. B 68, 235312 (2003)]. We study the effects of the dynamical field of polarization on both small-polaron hopping and trap-limited transport mechanisms. We present numerical calculations of polarization energies, band-narrowing effects due to polarization, hopping barriers, and interface trap depths in pentacene and rubrene transistors as functions of the dielectric constant of the gate insulator and demonstrate that a trap-and-release mechanism more appropriately describes transport in high-mobility OFETs. For mobilities on the order 0.1cm2/Vs and below, all states are highly localized and hopping becomes the predominant mechanism.

Nonadiabatic dynamics of photo-induced proton-coupled electron transfer reactions via ring-polymer surface hopping

NASA Astrophysics Data System (ADS)

Shakib, Farnaz; Huo, Pengfei

Photo-induced proton-coupled electron transfer reactions (PCET) are at the heart of energy conversion reactions in photocatalysis. Here, we apply the recently developed ring-polymer surface-hopping (RPSH) approach to simulate the nonadiabatic dynamics of photo-induced PCET. The RPSH method incorporates ring-polymer (RP) quantization of the proton into the fewest-switches surface-hopping (FSSH) approach. Using two diabatic electronic states, corresponding to the electron donor and acceptor states, we model photo-induced PCET with the proton described by a classical isomorphism RP. From the RPSH method, we obtain numerical results that are comparable to those obtained when the proton is treated quantum mechanically. This accuracy stems from incorporating exact quantum statistics, such as proton tunnelling, into approximate quantum dynamics. Additionally, RPSH offers the numerical accuracy along with the computational efficiency. Namely, compared to the FSSH approach in vibronic representation, there is no need to calculate a massive number of vibronic states explicitly. This approach opens up the possibility to accurately and efficiently simulate photo-induced PCET with multiple transferring protons or electrons.

Hybrid Differential Dynamic Programming with Stochastic Search

NASA Technical Reports Server (NTRS)

Aziz, Jonathan; Parker, Jeffrey; Englander, Jacob

2016-01-01

Differential dynamic programming (DDP) has been demonstrated as a viable approach to low-thrust trajectory optimization, namely with the recent success of NASAs Dawn mission. The Dawn trajectory was designed with the DDP-based Static Dynamic Optimal Control algorithm used in the Mystic software. Another recently developed method, Hybrid Differential Dynamic Programming (HDDP) is a variant of the standard DDP formulation that leverages both first-order and second-order state transition matrices in addition to nonlinear programming (NLP) techniques. Areas of improvement over standard DDP include constraint handling, convergence properties, continuous dynamics, and multi-phase capability. DDP is a gradient based method and will converge to a solution nearby an initial guess. In this study, monotonic basin hopping (MBH) is employed as a stochastic search method to overcome this limitation, by augmenting the HDDP algorithm for a wider search of the solution space.

Bridge-mediated hopping or superexchange electron-transfer processes in bis(triarylamine) systems

NASA Astrophysics Data System (ADS)

Lambert, Christoph; Nöll, Gilbert; Schelter, Jürgen

2002-09-01

Hopping and superexchange are generally considered to be alternative electron-transfer mechanisms in molecular systems. In this work we used mixed-valence radical cations as model systems for the investigation of electron-transfer pathways. We show that substituents attached to a conjugated bridge connecting two triarylamine redox centres have a marked influence on the near-infrared absorption spectra of the corresponding cations. Spectral analysis, followed by evaluation of the electron-transfer parameters using the Generalized Mulliken-Hush theory and simulation of the potential energy surfaces, indicate that hopping and superexchange are not alternatives, but are both present in the radical cation with a dimethoxybenzene bridge. We found that the type of electron-transfer mechanism depends on the bridge-reorganization energy as well as on the bridge-state energy. Because superexchange and hopping follow different distance laws, our findings have implications for the design of new molecular and polymeric electron-transfer materials.

Steerable Hopping Six-Legged Robot

NASA Technical Reports Server (NTRS)

Younse, Paulo; Aghazarian, Hrand

2010-01-01

The figure depicts selected aspects of a six-legged robot that moves by hopping and that can be steered in the sense that it can be launched into a hop in a controllable direction. This is a prototype of hopping robots being developed for use in scientific exploration of rough terrain on remote planets that have surface gravitation less than that of Earth. Hopping robots could also be used on Earth, albeit at diminished hopping distances associated with the greater Earth gravitation. The upper end of each leg is connected through two universal joints to an upper and a lower hexagonal frame, such that the tilt of the leg depends on the relative position of the two frames. Two non-back-driveable worm-gear motor drives are used to control the relative position of the two frames along two axes 120 apart, thereby controlling the common tilt of all six legs and thereby, further, controlling the direction of hopping. Each leg includes an upper and a lower aluminum frame segment with a joint between them. A fiberglass spring, connected via hinges to both segments, is used to store hopping energy prior to launch into a hop and to cushion the landing at the end of the hop. A cable for loading the spring is run into each leg through the center of the universal joints and then down along the center lines of the segments to the lower end of the leg. A central spool actuated by a motor with a harmonic drive and an electromagnetic clutch winds in all six cables to compress all six springs (thereby also flexing all six legs) simultaneously. To ensure that all the legs push off and land in the same direction, timing- belt pulley drives are attached to the leg segments, restricting the flexing and extension of all six legs to a common linear motion. In preparation for a hop, the spool can be driven to load the spring legs by an amount corresponding to a desired hop distance within range. The amount of compression can be computed from the reading of a shaft-angle encoder that indicates the amount by which the spool has been turned. When the robot is ready to hop, the electromagnetic clutch disengages the motor from the spool, thus releasing the cable restraints on the springs and allowing the springs to extend all six legs simultaneously.

Composition-dependent metallic glass alloys correlate atomic mobility with collective glass surface dynamics.

PubMed

Nguyen, Duc; Zhu, Zhi-Guang; Pringle, Brian; Lyding, Joseph; Wang, Wei-Hua; Gruebele, Martin

2016-06-22

Glassy metallic alloys are richly tunable model systems for surface glassy dynamics. Here we study the correlation between atomic mobility, and the hopping rate of surface regions (clusters) that rearrange collectively on a minute to hour time scale. Increasing the proportion of low-mobility copper atoms in La-Ni-Al-Cu alloys reduces the cluster hopping rate, thus establishing a microscopic connection between atomic mobility and dynamics of collective rearrangements at a glass surface made from freshly exposed bulk glass. One composition, La60Ni15Al15Cu10, has a surface resistant to re-crystallization after three heating cycles. When thermally cycled, surface clusters grow in size from about 5 glass-forming units to about 8 glass-forming units, evidence of surface aging without crystal formation, although its bulk clearly forms larger crystalline domains. Such kinetically stable glass surfaces may be of use in applications where glassy coatings stable against heating are needed.

Knee joint kinematics and kinetics during the hop and cut after soft tissue artifact suppression: Time to reconsider ACL injury mechanisms?

PubMed

Smale, Kenneth B; Potvin, Brigitte M; Shourijeh, Mohammad S; Benoit, Daniel L

2017-09-06

The recent development of a soft tissue artifact (STA) suppression method allows us to re-evaluate the tibiofemoral kinematics currently linked to non-contact knee injuries. The purpose of this study was therefore to evaluate knee joint kinematics and kinetics in six degrees of freedom (DoF) during the loading phases of a jump lunge and side cut using this in silico method. Thirty-five healthy adults completed these movements and their surface marker trajectories were then scaled and processed with OpenSim's inverse kinematics (IK) and inverse dynamics tools. Knee flexion angle-dependent kinematic constraints defined based on previous bone pin (BP) marker trajectories were then applied to the OpenSim model during IK and these constrained results were then processed with the standard inverse dynamics tool. Significant differences for all hip, knee, and ankle DoF were observed after STA suppression for both the jump lunge and side cut. Using clinically relevant effect size estimates, we conclude that STA contamination had led to misclassifications in hip transverse plane angles, knee frontal and transverse plane angles, medial/lateral and distractive/compressive knee translations, and knee frontal plane moments between the NoBP and the BP IK solutions. Our results have substantial clinical implications since past research has used joint kinematics and kinetics contaminated by STA to identify risk factors for musculoskeletal injuries. Copyright © 2017 Elsevier Ltd. All rights reserved.

A stable high-order perturbation of surfaces method for numerical simulation of diffraction problems in triply layered media

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

Hong, Youngjoon, E-mail: hongy@uic.edu; Nicholls, David P., E-mail: davidn@uic.edu

The accurate numerical simulation of linear waves interacting with periodic layered media is a crucial capability in engineering applications. In this contribution we study the stable and high-order accurate numerical simulation of the interaction of linear, time-harmonic waves with a periodic, triply layered medium with irregular interfaces. In contrast with volumetric approaches, High-Order Perturbation of Surfaces (HOPS) algorithms are inexpensive interfacial methods which rapidly and recursively estimate scattering returns by perturbation of the interface shape. In comparison with Boundary Integral/Element Methods, the stable HOPS algorithm we describe here does not require specialized quadrature rules, periodization strategies, or the solution ofmore » dense non-symmetric positive definite linear systems. In addition, the algorithm is provably stable as opposed to other classical HOPS approaches. With numerical experiments we show the remarkable efficiency, fidelity, and accuracy one can achieve with an implementation of this algorithm.« less

Hybrid Differential Dynamic Programming with Stochastic Search

NASA Technical Reports Server (NTRS)

Aziz, Jonathan; Parker, Jeffrey; Englander, Jacob A.

2016-01-01

Differential dynamic programming (DDP) has been demonstrated as a viable approach to low-thrust trajectory optimization, namely with the recent success of NASA's Dawn mission. The Dawn trajectory was designed with the DDP-based Static/Dynamic Optimal Control algorithm used in the Mystic software.1 Another recently developed method, Hybrid Differential Dynamic Programming (HDDP),2, 3 is a variant of the standard DDP formulation that leverages both first-order and second-order state transition matrices in addition to nonlinear programming (NLP) techniques. Areas of improvement over standard DDP include constraint handling, convergence properties, continuous dynamics, and multi-phase capability. DDP is a gradient based method and will converge to a solution nearby an initial guess. In this study, monotonic basin hopping (MBH) is employed as a stochastic search method to overcome this limitation, by augmenting the HDDP algorithm for a wider search of the solution space.

The initial stage of uranium oxidation: mechanism of UO(2) scale formation in the presence of a native lateral stress field.

PubMed

Chernia, Z; Ben-Eliyahu, Y; Kimmel, G; Braun, G; Sariel, J

2006-11-23

In this work, an oxidation model for alpha-uranium is presented. It describes the internally lateral stress field built in the oxide scale during the reaction. The thickness of the elastic, stress-preserving oxide (UO(2+x)) scale is less than 0.5 microm. A lateral, 6.5 GPa stress field has been calculated from strains derived from line shifts (delta(2theta)) as measured by the X-ray diffraction of UO(2). It is shown that in the elastic growth domain, (110) is the main UO(2) growth plane for gas-solid oxidation. The diffusion-limited oxidation mechanism discussed here is based on the known "2:2:2" cluster theory which describes the mechanism of fluorite-based hyperstoichiometric oxides. In this study, it is adapted to describe oxygen-anion hopping. Anion hopping toward the oxide-metal interface proceeds at high rates in the [110] direction, hence making this pipeline route the principal growth direction in UO(2) formation. It is further argued that growth in the pure elastic domain of the oxide scale should be attributed entirely to anion hopping in 110. Anions, diffusing isotropically via grain boundaries and cracks, are shown to have a significant impact on the overall oxidation rate in relatively thick (>0.35 microm) oxide scales if followed by an avalanche break off in the postelastic regime. Stress affects oxidation in the elastic domain by controlling the hopping rate directly. In the postelastic regime, stress weakens hopping, indirectly, by enhancing isotropic diffusion. Surface roughness presents an additional hindering factor for the anion hopping. In comparison to anisotropic hopping, diffusion of isotropic hopping has a lower activation energy barrier. Therefore, a relatively stronger impact at lower temperatures due to isotropic diffusion is displayed.

Correlated electron-nuclear dissociation dynamics: classical versus quantum motion

NASA Astrophysics Data System (ADS)

Schaupp, Thomas; Albert, Julian; Engel, Volker

2017-01-01

We investigate the coupled electron-nuclear dynamics in a model system which undergoes dissociation. In choosing different initial conditions, the cases of adiabatic and non-adiabatic dissociation are realized. We treat the coupled electronic and nuclear motion in the complete configuration space so that classically, no surface hopping procedures have to be incorporated in the case that more than a single adiabatic electronic state is populated during the fragmentation. Due to the anharmonic interaction potential, it is expected that classical mechanics substantially deviate from quantum mechanics. However, we provide examples where the densities and fragmentation yields obtained from the two treatments are in astonishingly strong agreement in the case that one starts in the electronic ground state initially. As expected, larger deviations are found if one starts in electronically excited states where trajectories are sampled from the more spatially extended electronic wave function. In that case, higher initial energies are accessed, and the motion proceeds in regions with increasing degree of anharmonicity. Contribution to the Topical Issue "Dynamics of Molecular Systems (MOLEC 2016)", edited by Alberto Garcia-Vela, Luis Banares and Maria Luisa Senent.

Ultrafast Electronic Relaxation through a Conical Intersection: Nonadiabatic Dynamics Disentangled through an Oscillator Strength-Based Diabatization Framework

DOE PAGES

Medders, Gregory R.; Alguire, Ethan C.; Jain, Amber; ...

2017-01-18

Here, we employ surface hopping trajectories to model the short-time dynamics of gas-phase and partially solvated 4-(N,N-dimethylamino)benzonitrile (DMABN), a dual fluorescent molecule that is known to undergo a nonadiabatic transition through a conical intersection. To compare theory vs time-resolved fluorescence measurements, we calculate the mixed quantum–classical density matrix and the ensemble averaged transition dipole moment. We introduce a diabatization scheme based on the oscillator strength to convert the TDDFT adiabatic states into diabatic states of L a and L b character. Somewhat surprisingly, we find that the rate of relaxation reported by emission to the ground state is almost 50%more » slower than the adiabatic population relaxation. Although our calculated adiabatic rates are largely consistent with previous theoretical calculations and no obvious effects of decoherence are seen, the diabatization procedure introduced here enables an explicit picture of dynamics in the branching plane, raising tantalizing questions about geometric phase effects in systems with dozens of atoms.« less

Low temperature resistivity studies of SmB6: Observation of two-dimensional variable-range hopping conductivity

NASA Astrophysics Data System (ADS)

Batkova, Marianna; Batko, Ivan; Gabáni, Slavomír; Gažo, Emil; Konovalova, Elena; Filippov, Vladimir

2018-05-01

We studied electrical resistance of a single-crystalline SmB6 sample with a focus on the region of the "low-temperature resistivity plateau". Our observations did not show any true saturation of the electrical resistance at temperatures below 3 K down to 70 mK. According to our findings, temperature dependence of the electrical conduction in a certain temperature interval above 70 mK can be decomposed into a temperature-independent term and a temperature-activated term that can be described by variable-range hopping formula for two-dimensional systems, exp [ -(T0 / T) 1 / 3 ]. Thus, our results indicate importance of hopping type of electrical transport in the near-surface region of SmB6.

Augmented Ehrenfest dynamics yields a rate for surface hopping

NASA Astrophysics Data System (ADS)

Subotnik, Joseph E.

2010-04-01

We present a new algorithm for mixed quantum-classical dynamics that helps bridge the gap between mean-field (Ehrenfest) and surface-hopping dynamics by defining a natural rate of decoherence. In order to derive this decoherence result, we have expanded the number of independent variables in the usual Ehrenfest routine so that mixed quantum-classical derivatives are now propagated in time alongside the usual Ehrenfest variables. Having done so, we compute a unique rate of decoherence using two independent approaches: (i) by comparing the equations of motion for the joint nuclear-electronic probability density in phase space according to Ehrenfest dynamics versus partial Wigner transform dynamics and (ii) by introducing a frozen Gaussian interpretation of Ehrenfest dynamics which allows nuclear wave packets to separate. The first consequence of this work is a means to rigorously check the accuracy of standard Ehrenfest dynamics. Second, this paper suggests a nonadiabatic dynamics algorithm, whereby the nuclei are propagated on the mean-field (Ehrenfest) potential energy surface and undergo stochastic decoherence events. Our work resembles the surface-hopping algorithm of Schwartz and co-workers [J. Chem. Phys. 123, 234106 (2005)]—only now without any adjustable parameters. For the case of two electronic states, we present numerical results on the so-called "Tully problems" and emphasize that future numerical benchmarking is still needed. Future work will also treat the problem of three or more electronic states.

WOBBLE: A Proposed Mission to Characterize Past and Present Water on Mars

NASA Technical Reports Server (NTRS)

Udrea, Bogdan; Delory, Greg; Landis, Geoffrey; Duvet, Ludovic; Choudhuri, Ahsan; Prina, Mauro; Moreels, Pierre; Bedard, Donald; Furano, Gianluca

2002-01-01

WOBBLE ("Water Observations from a Balloon Borne Light Explorer") is a mission concept study for a small robotic probe to explore Mars and to accomplish a scientific mission compatible with the goals of the NASA Code S enterprise. The detection of past or present water is a crucial goal for Mars exploration, representing a cross-cutting science theme relevant to past or extant life, climate history, sample return missions and eventual human exploration. The WOBBLE mission concept was developed to study evidence of water using in-situ detection methods. The features on Mars most suited to this investigation are the gullies identified by Malin and Edgett as evidence for recent, near-surface runoff of liquid water. These features are typically located on the inside face of crater rims, where the local slope angle is at or near the angle of repose. This makes the terrain difficult or impossible to access with conventional wheeled rover technology. Combined with the small size of the gullies in relation to a standard landing error ellipse, scientific investigation of these features requires a new approach to surface mobility. WOBBLE uses a low-altitude balloon-borne platform to traverse the surface from the landing site, to the investigation site, and then rise up the slope to investigate the regions of interest at close range. Of the mobility technologies available for near-term Mars exploration, only a balloon platform is capable of a well targeted, detailed sampling of the gully regions over periods of days or more. The science approach embodied in WOBBLE is two-pronged, designed to investigate both the historical evidence of liquid water utilizing high-resolution geomorphology and the characterization of mineral deposits, and present subsurface liquid water using radar sounding techniques. The WOBBLE balloon is a high-pressure hydrogen gas design, 24 meters in diameter and lifting a total payload of 130 kg, including a high-resolution camera/IR imager, Raman spectrometer, and a ground penetrating radar (GPR) sounder. The stowed balloon and payload are designed to fit within the current airbag delivery system being built for the Mars Exploration Rovers. Characterization of local meteorological conditions and wind is made over the initial sols following landing and before balloon inflation. Following balloon inflation and launch, a controlled, targeted approach toward the identified regions of interest is made in a series of several low-altitude "hops," with the balloon tethered to the ground between the hop intervals. A "snake" system is used to control the altitude to a few tens of meters above the local ground level. Enroute to the target gully, GPR soundings and Raman spectroscopy measurements study past or present water, while continued camera bearings and meteorological measurements refine the next "hop" trajectory. Once at the gully/outflow region, GPR and Raman soundings continue while the camera obtains detailed, approx. 0.5 cm images for geomorphology studies. The WOBBLE concept is applicable to Mars Scout, Mars Surveyor, or Discovery class missions.

Plasmodium falciparum Hop (PfHop) Interacts with the Hsp70 Chaperone in a Nucleotide-Dependent Fashion and Exhibits Ligand Selectivity.

PubMed

Zininga, Tawanda; Makumire, Stanely; Gitau, Grace Wairimu; Njunge, James M; Pooe, Ofentse Jacob; Klimek, Hanna; Scheurr, Robina; Raifer, Hartmann; Prinsloo, Earl; Przyborski, Jude M; Hoppe, Heinrich; Shonhai, Addmore

2015-01-01

Heat shock proteins (Hsps) play an important role in the development and pathogenicity of malaria parasites. One of the most prominent functions of Hsps is to facilitate the folding of other proteins. Hsps are thought to play a crucial role when malaria parasites invade their host cells and during their subsequent development in hepatocytes and red blood cells. It is thought that Hsps maintain proteostasis under the unfavourable conditions that malaria parasites encounter in the host environment. Although heat shock protein 70 (Hsp70) is capable of independent folding of some proteins, its functional cooperation with heat shock protein 90 (Hsp90) facilitates folding of some proteins such as kinases and steroid hormone receptors into their fully functional forms. The cooperation of Hsp70 and Hsp90 occurs through an adaptor protein called Hsp70-Hsp90 organising protein (Hop). We previously characterised the Hop protein from Plasmodium falciparum (PfHop). We observed that the protein co-localised with the cytosol-localised chaperones, PfHsp70-1 and PfHsp90 at the blood stages of the malaria parasite. In the current study, we demonstrated that PfHop is a stress-inducible protein. We further explored the direct interaction between PfHop and PfHsp70-1 using far Western and surface plasmon resonance (SPR) analyses. The interaction of the two proteins was further validated by co-immunoprecipitation studies. We observed that PfHop and PfHsp70-1 associate in the absence and presence of either ATP or ADP. However, ADP appears to promote the association of the two proteins better than ATP. In addition, we investigated the specific interaction between PfHop TPR subdomains and PfHsp70-1/ PfHsp90, using a split-GFP approach. This method allowed us to observe that TPR1 and TPR2B subdomains of PfHop bind preferentially to the C-terminus of PfHsp70-1 compared to PfHsp90. Conversely, the TPR2A motif preferentially interacted with the C-terminus of PfHsp90. Finally, we observed that recombinant PfHop occasionally eluted as a protein species of twice its predicted size, suggesting that it may occur as a dimer. We conducted SPR analysis which suggested that PfHop is capable of self-association in presence or absence of ATP/ADP. Overall, our findings suggest that PfHop is a stress-inducible protein that directly associates with PfHsp70-1 and PfHsp90. In addition, the protein is capable of self-association. The findings suggest that PfHop serves as a module that brings these two prominent chaperones (PfHsp70-1 and PfHsp90) into a functional complex. Since PfHsp70-1 and PfHsp90 are essential for parasite growth, findings from this study are important towards the development of possible antimalarial inhibitors targeting the cooperation of these two chaperones.

Non-adiabatic dynamics close to conical intersections and the surface hopping perspective

PubMed Central

Malhado, João Pedro; Bearpark, Michael J.; Hynes, James T.

2014-01-01

Conical intersections play a major role in the current understanding of electronic de-excitation in polyatomic molecules, and thus in the description of photochemistry and photophysics of molecular systems. This article reviews aspects of the basic theory underlying the description of non-adiabatic transitions at conical intersections, with particular emphasis on the important case when the dynamics of the nuclei are treated classically. Within this classical nuclear motion framework, the main aspects of the surface hopping methodology in the conical intersection context are presented. The emerging picture from this treatment is that of electronic transitions around conical intersections dominated by the interplay of the nuclear velocity and the derivative non-adiabatic coupling vector field. PMID:25485263

Detrending with Empirical Mode Decomposition (DEMD): Theory, Evaluation, and Application

NASA Astrophysics Data System (ADS)

Bolch, Michael Adam

Land-surface heterogeneity (LSH) at different scales has significant influence on atmospheric boundary layer (ABL) buoyant and shear turbulence generation and transfers of water, carbon and heat. The extent of proliferation of this influence into larger-scale circulations and atmospheric structures is a topic continually investigated in experimental and numerical studies, in many cases with the hopes of improving land-atmosphere parameterizations for modeling purposes. The blending height is a potential metric for the vertical propagation of LSH effects into the ABL, and has been the subject of study for several decades. Proper assessment of the efficacy of blending height theory invites the combination of observations throughout ABLs above different LSH scales with model simulations of the observed ABL and LSH conditions. The central goal of this project is to develop an apt and thoroughly scrutinized method for procuring ABL observations that are accurately detrended and justifiably relevant for such a study, referred to here as Detrending with Empirical Mode Decomposition (DEMD). The Duke University helicopter observation platform (HOP) provides ABL data [wind (u, v, and w), temperature ( T), moisture (q), and carbon dioxide (CO 2)] at a wide range of altitudes, especially in the lower ABL, where LSH effects are most prominent, and where other aircraft-based platforms cannot fly. Also, lower airspeeds translate to higher resolution of the scalars and fluxes needed to evaluate blending height theory. To confirm noninterference of the main rotor downwash with the HOP sensors, and also to identify optimal airspeeds, analytical, numerical, and observational studies are presented. Analytical analysis clears the main rotor downwash from the HOP nose at airspeeds above 10 m s-1. Numerical models find an acceptable range from 20-40 m s-1, due to a growing compressed air preceding the HOP nose. The first observational study finds no impact of different HOP airspeeds on measurements from ˜18 m s -1 to ˜55 m s-1 over a stable marine boundary layer (MBL). Another set of observations studies HOP and tower data, using the Duke University Mobile Micrometeorological Station (MMS) over an MBL, and concludes that HOP sensible heat (SH), latent heat (LE), and carbon dioxide (F CO2) fluxes align well with MMS findings. The HOP sensors provide ABL data at 40 Hz, as well as a real-time display of theta for in-flight ABL height estimation. Sensor calibration and alignment procedures indicate usable ABL measurements. HOP data are especially susceptible to the spurious influence of platform motion on ABL data, largely due to the low-altitude and low-airspeed capabilities of the HOP. For example, HOP altitude motion in the presence of a lapse rate can cause spurious T fluctuations. Empirical mode decomposition (EMD) can separate HOP data into a set of adaptive and unique intrinsic mode functions (IMFs), often with physical meaning. DEMD aims to correct for spurious contributions to HOP data, while merging EMD with a correlation analysis to adjust data without eliminating relevant ABL dynamics. To evaluate DEMD efficacy, two-dimensional synthetic T fields with simulated turbulence over a prescribed lapse rate are sampled with altitude fluctuations similar to HOP flights, and with a wide range of T perturbation and sampling path parameter variations. DEMD recovers the prescribed lapse rate within 1% on average for the 552 test cases passing the filtering criteria. The method is further evaluated via application to vertical cross sections taken from the Ocean-Land-Atmosphere Model (OLAM) large-eddy simulation (LES) results, where DEMD shows improved accuracy of SH recovery. DEMD is applied to three low-altitude HOP flight legs flown on 19 June 2007 during the Cloud and Land Surface Interaction Campaign (CLASIC), both as an example of practical application and to compare DEMD to the initially proposed method (Holder et al. 2011, hereafter H11). H11 dictates the elimination of correlated IMFs, along with other subtle differences from DEMD, which also eliminates any ABL motions embedded in those IMFs. As suspected, the H11 method produces marked reductions of variances and turbulence kinetic energy (TKE) and substantial deviations in SH, LE, and FCO2 compared to DEMD. DEMD detrends without unnecessary elimination. DEMD is vital for ensuring accurate scalars and fluxes from HOP data, and a strategy for future research is presented that integrates properly detrended observations from the CLASIC HOP dataset with OLAM simulations to explore LSH effects on ABL processes and evaluate blending height theory.

Harvesting electricity from human hair.

PubMed

Tulachan, Brindan; Singh, Sushil K; Philip, Deepu; Das, Mainak

2016-01-01

Electrical conductivity of human hair is a debatable issue among hair experts and scientists. There are unsubstantiated claims that hair conducts electricity. However, hair experts provided ample evidence that hair is an insulator. Although wet hair exhibited drastic reduction in resistivity; scientists regarded hair as a proton semiconductor at the best. Here, we demonstrate that hair filaments generate electricity on absorbing water vapor between 50 degrees and 80 degrees C. This electricity can operate low power electronic systems. Essentially, we are exposing the hydrated hair polymer to a high temperature (50 degrees-80 degrees C). It has long been speculated that when certain biopolymers are simultaneously hydrated and exposed to high temperature, they exhibit significant proton hopping at a specific temperature regime. This happens due to rapid movement of water molecules on the polymer surface. This lead us to speculate that the observed flow of current is partly ionic and partly due to "proton hopping" in the hydrated nano spaces of hair filament. Such proton hopping is exceptionally high when the hydrated hair polymer is exposed to a temperature between 50 degrees and 80 degrees C. Differential scanning calorimetry data further corroborated the results and indicated that indeed at this temperature range, there is an enormous movement of water molecules on the hair polymer surface. This enormously rapid movement of water molecules lead to the "making and breaking" of innumerable hydrogen bonds and thus resulting in hopping of the protons. What is challenging is "how to tap these hopping protons to obtain useful electricity?" We achieved this by placing a bundle of hair between two different electrodes having different electro negativities, and exposing it to water vapor (water + heat). The two different electrodes offered directionality to the hopping protons and the existing ions and thus resulting in the generation of useful current. Further, by continuously hydrating the polymer with water vapor, we prolonged the process. If this interesting aspect of polymer is exploited further and fine tuned, then it will open new avenues for development of sophisticated polymer-based systems, which could be used to harvest electricity from waste heat.

Observation of Landau levels on nitrogen-doped flat graphite surfaces without external magnetic fields

PubMed Central

Kondo, Takahiro; Guo, Donghui; Shikano, Taishi; Suzuki, Tetsuya; Sakurai, Masataka; Okada, Susumu; Nakamura, Junji

2015-01-01

Under perpendicular external magnetic fields, two-dimensional carriers exhibit Landau levels (LLs). However, it has recently been reported that LLs have been observed on graphene and graphite surfaces without external magnetic fields being applied. These anomalous LLs have been ascribed primarily to a strain of graphene sheets, leading to in-plane hopping modulation of electrons. Here, we report the observation of the LLs of massive Dirac fermions on atomically flat areas of a nitrogen-doped graphite surface in the absence of external magnetic fields. The corresponding magnetic fields were estimated to be as much as approximately 100 T. The generation of the LLs at the area with negligible strain can be explained by inequivalent hopping of π electrons that takes place at the perimeter of high-potential domains surrounded by positively charged substituted graphitic-nitrogen atoms. PMID:26549618

Surface hopping with a manifold of electronic states. I. Incorporating surface-leaking to capture lifetimes

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

Ouyang, Wenjun; Dou, Wenjie; Subotnik, Joseph E., E-mail: subotnik@sas.upenn.edu

2015-02-28

We investigate the incorporation of the surface-leaking (SL) algorithm into Tully’s fewest-switches surface hopping (FSSH) algorithm to simulate some electronic relaxation induced by an electronic bath in conjunction with some electronic transitions between discrete states. The resulting SL-FSSH algorithm is benchmarked against exact quantum scattering calculations for three one-dimensional model problems. The results show excellent agreement between SL-FSSH and exact quantum dynamics in the wide band limit, suggesting the potential for a SL-FSSH algorithm. Discrepancies and failures are investigated in detail to understand the factors that will limit the reliability of SL-FSSH, especially the wide band approximation. Considering the easinessmore » of implementation and the low computational cost, we expect this method to be useful in studying processes involving both a continuum of electronic states (where electronic dynamics are probabilistic) and processes involving only a few electronic states (where non-adiabatic processes cannot ignore short-time coherence)« less

An On-the-Fly Surface-Hopping Program JADE for Nonadiabatic Molecular Dynamics of Polyatomic Systems: Implementation and Applications.

PubMed

Du, Likai; Lan, Zhenggang

2015-04-14

Nonadiabatic dynamics simulations have rapidly become an indispensable tool for understanding ultrafast photochemical processes in complex systems. Here, we present our recently developed on-the-fly nonadiabatic dynamics package, JADE, which allows researchers to perform nonadiabatic excited-state dynamics simulations of polyatomic systems at an all-atomic level. The nonadiabatic dynamics is based on Tully's surface-hopping approach. Currently, several electronic structure methods (CIS, TDHF, TDDFT(RPA/TDA), and ADC(2)) are supported, especially TDDFT, aiming at performing nonadiabatic dynamics on medium- to large-sized molecules. The JADE package has been interfaced with several quantum chemistry codes, including Turbomole, Gaussian, and Gamess (US). To consider environmental effects, the Langevin dynamics was introduced as an easy-to-use scheme into the standard surface-hopping dynamics. The JADE package is mainly written in Fortran for greater numerical performance and Python for flexible interface construction, with the intent of providing open-source, easy-to-use, well-modularized, and intuitive software in the field of simulations of photochemical and photophysical processes. To illustrate the possible applications of the JADE package, we present a few applications of excited-state dynamics for various polyatomic systems, such as the methaniminium cation, fullerene (C20), p-dimethylaminobenzonitrile (DMABN) and its primary amino derivative aminobenzonitrile (ABN), and 10-hydroxybenzo[h]quinoline (10-HBQ).

Surface modifications with Lissajous trajectories using atomic force microscopy

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

Cai, Wei; Yao, Nan, E-mail: nyao@princeton.edu

2015-09-14

In this paper, we report a method for atomic force microscopy surface modifications with single-tone and multiple-resolution Lissajous trajectories. The tip mechanical scratching experiments with two series of Lissajous trajectories were carried out on monolayer films. The scratching processes with two scan methods have been illustrated. As an application, the tip-based triboelectrification phenomenon on the silicon dioxide surface with Lissajous trajectories was investigated. The triboelectric charges generated within the tip rubbed area on the surface were characterized in-situ by scanning Kelvin force microscopy. This method would provide a promising and cost-effective approach for surface modifications and nanofabrication.

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

McDaniel, Jesse G.; Yethiraj, Arun, E-mail: yethiraj@chem.wisc.edu

The diffusion of protons in self-assembled systems is potentially important for the design of efficient proton exchange membranes. In this work, we study proton dynamics in a low-water content, lamellar phase of a sodium-carboxylate gemini surfactant/water system using computer simulations. The hopping of protons via the Grotthuss mechanism is explicitly allowed through the multi-state empirical valence bond method. We find that the hydronium ion is trapped on the hydrophobic side of the surfactant-water interface, and proton diffusion then proceeds by hopping between surface sites. The importance of hydrophobic traps is surprising because one would expect the hydronium ions to bemore » trapped at the charged headgroups. The physics illustrated in this system should be relevant to the proton dynamics in other amphiphilic membrane systems, whenever there exist exposed hydrophobic surface regions.« less

Photo-induced changes of the surface band bending in GaN: Influence of growth technique, doping and polarity

NASA Astrophysics Data System (ADS)

Winnerl, Andrea; Pereira, Rui N.; Stutzmann, Martin

2017-05-01

In this work, we use conductance and contact potential difference photo-transient data to study the influence of the growth technique, doping, and crystal polarity on the kinetics of photo-generated charges in GaN. We found that the processes, and corresponding time scales, involved in the decay of charge carriers generated at and close to the GaN surface via photo-excitation are notably independent of the growth technique, doping (n- and p-types), and also crystal polarity. Hence, the transfer of photo-generated charges from band states back to surface states proceeds always by hopping via shallow defect states in the space-charge region (SCR) close to the surface. Concerning the charge carrier photo-generation kinetics, we observe considerable differences between samples grown with different techniques. While for GaN grown by metal-organic chemical vapor deposition, the accumulation of photo-conduction electrons results mainly from a combined trapping-hopping process (slow), where photo-generated electrons hop via shallow defect states to the conduction band (CB), in hydride vapor phase epitaxy and molecular beam epitaxy materials, a faster direct process involving electron transfer via CB states is also present. The time scales of both processes are quite insensitive to the doping level and crystal polarity. However, these processes become irrelevant for very high doping levels (both n- and p-types), where the width of the SCR is much smaller than the photon penetration depth, and therefore, most charge carriers are generated outside the SCR.

Effects of CO2 adsorption on proton migration on a hydrated ZrO2 surface: an ab initio molecular dynamics study.

PubMed

Sato, Ryuhei; Shibuta, Yasushi; Shimojo, Fuyuki; Yamaguchi, Shu

2017-08-02

Hydration reactions on a carbonate-terminated cubic ZrO 2 (110) surface were analyzed using ab initio molecular dynamics (AIMD) simulations. After hydration reactions, carbonates were still present on the surface at 500 K. However, these carbonates are very weak conjugate bases and only act as steric hindrance in proton hopping processes between acidic chemisorbed H 2 O molecules (Zr-OH 2 ) and monodentate hydroxyl groups (Zr-OH - ). Similar to a carbonate-free hydrated surface, Zr-OH 2 , Zr-OH - , and polydentate hydroxyl groups ([double bond splayed left]OH + ) were observed, while the ratio of acidic Zr-OH 2 was significantly larger than that on the carbonate-free hydrated surface. A thermodynamic discussion and bond property analysis reveal that CO 2 adsorption significantly decreases the basicity of surface oxide ions ([double bond splayed left]O), whereas the acidity of Zr-OH 2 is not affected. As a result, protons released from [double bond splayed left]OH + react with Zr-OH - to form Zr-OH 2 , leading to a deficiency of proton acceptor sites, which decreases the proton conductivity by the hopping mechanism.

A new bioenergetic and thermodynamic approach to batch photoautotrophic growth of Arthrospira (Spirulina) platensis in different photobioreactors and under different light conditions.

PubMed

da Silva, Milena Fernandes; Casazza, Alessandro Alberto; Ferrari, Pier Francesco; Perego, Patrizia; Bezerra, Raquel Pedrosa; Converti, Attilio; Porto, Ana Lucia Figueiredo

2016-05-01

Photobioreactor configuration, mode of operation and light intensity are known to strongly impact on cyanobacteria growth. To shed light on these issues, kinetic, bioenergetic and thermodynamic parameters of batch Arthrospira platensis cultures were estimated along the time at photosynthetic photon flux density (PPFD) of 70μmolm(-2)s(-1) in different photobioreactors with different surface/volume ratio (S/V), namely open pond (0.25cm(-1)), shaken flask (0.48cm(-1)), horizontal photobioreactor (HoP) (1.94cm(-1)) and helicoidal photobioreactor (HeP) (3.88cm(-1)). Maximum biomass concentration and productivity remarkably increased with S/V up to 1.94cm(-1). HoP was shown to be the best-performing system throughout the whole runs, while HeP behaved better only at the start. Runs carried out in HoP increasing PPFD from 40 to 100μmolm(-2)s(-1) revealed a progressive enhancement of bioenergetics and thermodynamics likely because of favorable light distribution. HoP appeared to be a promising configuration to perform high-yield indoor cyanobacterial cultures. Copyright © 2016 Elsevier Ltd. All rights reserved.

Study of Exciton Hopping Transport in PbS Colloidal Quantum Dot Thin Films Using Frequency- and Temperature-Scanned Photocarrier Radiometry

NASA Astrophysics Data System (ADS)

Hu, Lilei; Mandelis, Andreas; Melnikov, Alexander; Lan, Xinzheng; Hoogland, Sjoerd; Sargent, Edward H.

2017-01-01

Solution-processed colloidal quantum dots (CQDs) are promising materials for realizing low-cost, large-area, and flexible photovoltaic devices. The study of charge carrier transport in quantum dot solids is essential for understanding energy conversion mechanisms. Recently, solution-processed two-layer oleic-acid-capped PbS CQD solar cells with one layer treated with tetrabutylammonium iodide (TBAI) serving as the main light-absorbing layer and the other treated with 1,2-ethanedithiol (EDT) acting as an electron-blocking/hole-extraction layer were reported. These solar cells demonstrated a significant improvement in power conversion efficiency of 8.55% and long-term air stability. Coupled with photocarrier radiometry measurements, this work used a new trap-state mediated exciton hopping transport model, specifically for CQD thin films, to unveil and quantify exciton transport mechanisms through the extraction of hopping transport parameters including exciton lifetimes, hopping diffusivity, exciton detrapping time, and trap-state density. It is shown that PbS-TBAI has higher trap-state density than PbS-EDT that results in higher PbS-EDT exciton lifetimes. Hopping diffusivities of both CQD thin film types show similar temperature dependence, particularly higher temperatures yield higher hopping diffusivity. The higher diffusivity of PbS-TBAI compared with PbS-EDT indicates that PbS-TBAI is a much better photovoltaic material than PbS-EDT. Furthermore, PCR temperature spectra and deep-level photothermal spectroscopy provided additional insights to CQD surface trap states: PbS-TBAI thin films exhibit a single dominant trap level, while PbS-EDT films with lower trap-state densities show multiple trap levels.

Bluetongue Virus Serotype 1 Outbreak in the Basque Country (Northern Spain) 2007–2008. Data Support a Primary Vector Windborne Transport

PubMed Central

García-Lastra, Rodrigo; Leginagoikoa, Iratxe; Plazaola, Jose M.; Ocabo, Blanca; Aduriz, Gorka; Nunes, Telmo; Juste, Ramón A.

2012-01-01

Background Bluetongue (BT) is a vector-borne disease of ruminants that has expanded its traditional global distribution in the last decade. Recently, BTV-1 emerged in Southern Spain and caused several outbreaks in livestock reaching the north of the country. The aim of this paper was to review the emergence of BTV-1 in the Basque Country (Northern Spain) during 2007 and 2008 analyzing the possibility that infected Culicoides were introduced into Basque Country by winds from the infected areas of Southern Spain. Methodology/Principal Findings We use a complex HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model to draw wind roses and backward wind trajectories. The analysis of winds showed September 28 to October 2 as the only period for the introduction of infected midges in the Basque Country. These wind trajectories crossed through the areas affected by serotype 1 on those dates in the South of the Iberian Peninsula. Additionally meteorological data, including wind speed and humidity, and altitude along the trajectories showed suitable conditions for Culicoides survival and dispersion. Conclusions/Significance An active infection in medium-long distance regions, wind with suitable speed, altitude and trajectory, and appropriate weather can lead to outbreaks of BTV-1 by transport of Culicoides imicola, not only over the sea (as reported previously) but also over the land. This shows that an additional factor has to be taken into account for the control of the disease which is currently essentially based on the assumption that midges will only spread the virus in a series of short hops. Moreover, the epidemiological and serological data cannot rule out the involvement of other Culicoides species in the spread of the infection, especially at a local level. PMID:22479628

45 MPH 6,000-Pound and 10,000-Pound Rough Terrain Fork Lift Truck Feasibility Study.

DTIC Science & Technology

1986-06-24

Airport Post Office Box 66911 Chicago, IL 60666 NPN Security Classification of This Page REPORT DOCUMENTATION PAGE la . Report Security Classification...HOP Unausended Duadin., 20 - I: - 1 1.8 Inch RMS Road 14 la -3 * Clam C (0.93 Inch RMS) Rod w 12 10 10 Per~cent 9 P 7 U. 3 Percent 3 2 0 20 40 SPM...elm 10 67- * * 3 o *" - .2 0 20 40 W (mph) 4/2/ SOJA Figure 75. Rear Wheel Hop on Four Road Surfaces (10K RTFLT Unsuspended Baseline) " Page 93 Adding

A path planning method for robot end effector motion using the curvature theory of the ruled surfaces

NASA Astrophysics Data System (ADS)

Güler, Fatma; Kasap, Emin

Using the curvature theory for the ruled surfaces a technique for robot trajectory planning is presented. This technique ensures the calculation of robot’s next path. The positional variation of the Tool Center Point (TCP), linear velocity, angular velocity are required in the work area of the robot. In some circumstances, it may not be physically achievable and a re-computation of the robot trajectory might be necessary. This technique is suitable for re-computation of the robot trajectory. We obtain different robot trajectories which change depending on the darboux angle function and define trajectory ruled surface family with a common trajectory curve with the rotation trihedron. Also, the motion of robot end effector is illustrated with examples.

Surface hopping with a manifold of electronic states. III. Transients, broadening, and the Marcus picture

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

Dou, Wenjie; Subotnik, Joseph E.; Nitzan, Abraham

2015-06-21

In a previous paper [Dou et al., J. Chem. Phys. 142, 084110 (2015)], we have introduced a surface hopping (SH) approach to deal with the Anderson-Holstein model. Here, we address some interesting aspects that have not been discussed previously, including transient phenomena and extensions to arbitrary impurity-bath couplings. In particular, in this paper we show that the SH approach captures phonon coherence beyond the secular approximation, and that SH rates agree with Marcus theory at steady state. Finally, we show that, in cases where the electronic tunneling rate depends on nuclear position, a straightforward use of Marcus theory rates yieldsmore » a useful starting point for capturing level broadening. For a simple such model, we find I-V curves that exhibit negative differential resistance.« less

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

McDaniel, Jesse G.; Yethiraj, Arun

The diffusion of protons in self-assembled systems is potentially important for the design of efficient proton exchange membranes. In this work, we study proton dynamics in a low-water content, lamellar phase of an sodium-carboxylate gemini surfactant/water system using computer simulations. The hopping of protons via the Grotthuss mechanism is explicity allowed through the multi-state empirical valence bond (MS-EVB) method. We find that the hydronium ion is trapped on the hydrophobic side of the surfactant-water interface, and proton diffusion then proceeds by hopping between surface sites. The importance of hydrophobic traps is surprising, because one would expect the hydronium ions tomore » be trapped at the charged head-groups. Finally, the physics illustrated in this system should be relevant to the proton dynamics in other amphiphilic membrane systems, whenever there exists exposed hydrophobic surface regions.« less

Frequency hopping due to acousto-electric interaction in ZnO based surface acoustic wave oscillator

NASA Astrophysics Data System (ADS)

Dasgupta, Daipayan; Sreenivas, K.

2011-08-01

A 36 MHz surface acoustic wave delay line based oscillator has been used to study the effect of acousto-electric interaction due to photo generated charge carriers in rf sputtered ZnO film under UV illumination (λ = 365 nm, 20-100 μW/cm2). Design aspects for developing a delay line based SAW oscillator are specified. The observed linear downshift in frequency (2.2 to 19.0 kHz) with varying UV intensity (20-100 μW/cm2) is related to the fractional velocity change due to acousto-electric interaction. UV illumination level of 100 μW/cm2 leads to a characteristic frequency hopping behavior arising due to a change in the oscillation criteria, and is attributed to the complex interplay between the increased attenuation and velocity shift.

THE RELATIONSHIP BETWEEN VARIOUS MODES OF SINGLE LEG POSTURAL CONTROL ASSESSMENT

PubMed Central

Schmitz, Randy

2012-01-01

Purpose/Background: While various techniques have been developed to assess the postural control system, little is known about the relationship between single leg static and functional balance. The purpose of the current study was to determine the relationship between the performance measures of several single leg postural stability tests. Methods: Forty six recreationally active college students (17 males, 29 females, 21±3 yrs, 173±10 cm) performed six single leg tests in a counterbalanced order: 1) Firm Surface-Eyes Open, 2) Firm Surface-Eyes Closed, 3) Multiaxial Surface-Eyes Open, 4) Multiaxial Surface-Eyes Closed, 5) Star Excursion Balance Test (posterior medial reach), 6) Single leg Hop-Stabilization Test. Bivariate correlations were conducted between the six outcome variables. Results: Mild to moderate correlations existed between the static tests. No significant correlations existed involving either of the functional tests. Conclusions: The results indicate that while performance of static balance tasks are mildly to moderately related, they appear to be unrelated to functional reaching or hopping movements, supporting the utilization of a battery of tests to determine overall postural control performance. Level of Evidence: 3b PMID:22666640

Scanning ion conductance microscopy for visualizing the three-dimensional surface topography of cells and tissues.

PubMed

Nakajima, Masato; Mizutani, Yusuke; Iwata, Futoshi; Ushiki, Tatsuo

2018-01-01

Scanning ion conductance microscopy (SICM), which belongs to the family of scanning probe microscopy, regulates the tip-sample distance by monitoring the ion current through the use of an electrolyte-filled nanopipette as the probing tip. Thus, SICM enables "contact-free" imaging of cell surface topography in liquid conditions. In this paper, we applied hopping mode SICM for obtaining topographical images of convoluted tissue samples such as trachea and kidney in phosphate buffered saline. Some of the SICM images were compared with the images obtained by scanning electron microscopy (SEM) after drying the same samples. We showed that the imaging quality of hopping mode SICM was excellent enough for investigating the three-dimensional surface structure of the soft tissue samples. Thus, SICM is expected to be used for imaging a wide variety of cells and tissues - either fixed or alive- at high resolution under physiologically relevant liquid conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Correlated matrix-fluctuation-mediated activated transport of dilute penetrants in glass-forming liquids and suspensions

NASA Astrophysics Data System (ADS)

Zhang, Rui; Schweizer, Kenneth S.

2017-05-01

We formulate a microscopic, force-level statistical mechanical theory for the activated diffusion of dilute penetrants in dense liquids, colloidal suspensions, and glasses. The approach explicitly and self-consistently accounts for coupling between penetrant hopping and matrix dynamic displacements that actively facilitate the hopping event. The key new ideas involve two mechanistically (at a stochastic trajectory level) coupled dynamic free energy functions for the matrix and spherical penetrant particles. A single dynamic coupling parameter quantifies how much the matrix displaces relative to the penetrant when the latter reaches its transition state which is determined via the enforcement of a temporal causality or coincidence condition. The theory is implemented for dilute penetrants smaller than the matrix particles, with or without penetrant-matrix attractive forces. Model calculations reveal a rich dependence of the penetrant diffusion constant and degree of dynamic coupling on size ratio, volume fraction, and attraction strength. In the absence of attractions, a near exponential decrease of penetrant diffusivity with size ratio over an intermediate range is predicted, in contrast to the much steeper, non-exponential variation if one assumes local matrix dynamical fluctuations are not correlated with penetrant motion. For sticky penetrants, the relative and absolute influence of caging versus physical bond formation is studied. The conditions for a dynamic crossover from the case where a time scale separation between penetrant and matrix activated hopping exists to a "slaved" or "constraint release" fully coupled regime are determined. The particle mixture model is mapped to treat experimental thermal systems and applied to make predictions for the diffusivity of water, toluene, methanol, and oxygen in polyvinylacetate liquids and glasses. The theory agrees well with experiment with values of the penetrant-matrix size ratio close to their chemically intuitive values.

Correlated matrix-fluctuation-mediated activated transport of dilute penetrants in glass-forming liquids and suspensions

PubMed Central

Schweizer, Kenneth S.

2017-01-01

We formulate a microscopic, force-level statistical mechanical theory for the activated diffusion of dilute penetrants in dense liquids, colloidal suspensions, and glasses. The approach explicitly and self-consistently accounts for coupling between penetrant hopping and matrix dynamic displacements that actively facilitate the hopping event. The key new ideas involve two mechanistically (at a stochastic trajectory level) coupled dynamic free energy functions for the matrix and spherical penetrant particles. A single dynamic coupling parameter quantifies how much the matrix displaces relative to the penetrant when the latter reaches its transition state which is determined via the enforcement of a temporal causality or coincidence condition. The theory is implemented for dilute penetrants smaller than the matrix particles, with or without penetrant-matrix attractive forces. Model calculations reveal a rich dependence of the penetrant diffusion constant and degree of dynamic coupling on size ratio, volume fraction, and attraction strength. In the absence of attractions, a near exponential decrease of penetrant diffusivity with size ratio over an intermediate range is predicted, in contrast to the much steeper, non-exponential variation if one assumes local matrix dynamical fluctuations are not correlated with penetrant motion. For sticky penetrants, the relative and absolute influence of caging versus physical bond formation is studied. The conditions for a dynamic crossover from the case where a time scale separation between penetrant and matrix activated hopping exists to a “slaved” or “constraint release” fully coupled regime are determined. The particle mixture model is mapped to treat experimental thermal systems and applied to make predictions for the diffusivity of water, toluene, methanol, and oxygen in polyvinylacetate liquids and glasses. The theory agrees well with experiment with values of the penetrant-matrix size ratio close to their chemically intuitive values. PMID:28527449

Symmetric Trajectories for the 2N-Body Problem with Equal Masses

NASA Astrophysics Data System (ADS)

Terracini, Susanna; Venturelli, Andrea

2007-06-01

We consider the problem of 2 N bodies of equal masses in mathbb{R}^3 for the Newtonian-like weak-force potential r -σ, and we prove the existence of a family of collision-free nonplanar and nonhomographic symmetric solutions that are periodic modulo rotations. In addition, the rotation number with respect to the vertical axis ranges in a suitable interval. These solutions have the hip-hop symmetry, a generalization of that introduced in [19], for the case of many bodies and taking account of a topological constraint. The argument exploits the variational structure of the problem, and is based on the minimization of Lagrangian action on a given class of paths.

Surface Modeling of Workpiece and Tool Trajectory Planning for Spray Painting Robot

PubMed Central

Tang, Yang; Chen, Wei

2015-01-01

Automated tool trajectory planning for spray-painting robots is still a challenging problem, especially for a large free-form surface. A grid approximation of a free-form surface is adopted in CAD modeling in this paper. A free-form surface model is approximated by a set of flat patches. We describe here an efficient and flexible tool trajectory optimization scheme using T-Bézier curves calculated in a new way from trigonometrical bases. The distance between the spray gun and the free-form surface along the normal vector is varied. Automotive body parts, which are large free-form surfaces, are used to test the scheme. The experimental results show that the trajectory planning algorithm achieves satisfactory performance. This algorithm can also be extended to other applications. PMID:25993663

Surface modeling of workpiece and tool trajectory planning for spray painting robot.

PubMed

Tang, Yang; Chen, Wei

2015-01-01

Automated tool trajectory planning for spray-painting robots is still a challenging problem, especially for a large free-form surface. A grid approximation of a free-form surface is adopted in CAD modeling in this paper. A free-form surface model is approximated by a set of flat patches. We describe here an efficient and flexible tool trajectory optimization scheme using T-Bézier curves calculated in a new way from trigonometrical bases. The distance between the spray gun and the free-form surface along the normal vector is varied. Automotive body parts, which are large free-form surfaces, are used to test the scheme. The experimental results show that the trajectory planning algorithm achieves satisfactory performance. This algorithm can also be extended to other applications.

Multiple coupled landscapes and non-adiabatic dynamics with applications to self-activating genes.

PubMed

Chen, Cong; Zhang, Kun; Feng, Haidong; Sasai, Masaki; Wang, Jin

2015-11-21

Many physical, chemical and biochemical systems (e.g. electronic dynamics and gene regulatory networks) are governed by continuous stochastic processes (e.g. electron dynamics on a particular electronic energy surface and protein (gene product) synthesis) coupled with discrete processes (e.g. hopping among different electronic energy surfaces and on and off switching of genes). One can also think of the underlying dynamics as the continuous motion on a particular landscape and discrete hoppings among different landscapes. The main difference of such systems from the intra-landscape dynamics alone is the emergence of the timescale involved in transitions among different landscapes in addition to the timescale involved in a particular landscape. The adiabatic limit when inter-landscape hoppings are fast compared to continuous intra-landscape dynamics has been studied both analytically and numerically, but the analytical treatment of the non-adiabatic regime where the inter-landscape hoppings are slow or comparable to continuous intra-landscape dynamics remains challenging. In this study, we show that there exists mathematical mapping of the dynamics on 2(N) discretely coupled N continuous dimensional landscapes onto one single landscape in 2N dimensional extended continuous space. On this 2N dimensional landscape, eddy current emerges as a sign of non-equilibrium non-adiabatic dynamics and plays an important role in system evolution. Many interesting physical effects such as the enhancement of fluctuations, irreversibility, dissipation and optimal kinetics emerge due to non-adiabaticity manifested by the eddy current illustrated for an N = 1 self-activator. We further generalize our theory to the N-gene network with multiple binding sites and multiple synthesis rates for discretely coupled non-equilibrium stochastic physical and biological systems.

Adsorption and dynamics of Si atoms at the monolayer Pb/Si(111) surface

NASA Astrophysics Data System (ADS)

Kumar, Rakesh; Fang, Chuang-Kai; Lee, Chih-Hao; Hwang, Ing-Shouh

2017-06-01

In this work, we studied the adsorption behavior of deposited Si atoms along with their diffusion and other dynamic processes on a Pb monolayer-covered Si(111) surface from 125 to 230 K using a variable-temperature scanning tunneling microscope. The Pb-covered Si(111) surface forms a low-symmetry rowlike (√{7 }×√{3 } ) structure in this temperature range and the Si atoms bind favorably to two specific on-top sites (T1 A and T1 B) on the trimer row after deposition at the sample temperature of ˜125 K . The Si atoms were immobile at low temperatures and started to switch between the two neighboring T1 A and T1 B sites within the same trimer when the temperature was raised to ˜150 K . When the temperature was raised above ˜160 K , the adsorbed Si atoms could hop to other trimers along the same trimer row. Below ˜170 K , short hops to adjacent trimers dominated, but long hops dominated at temperatures above ˜170 K . The activation energy and prefactor for the Si atoms diffusion were derived through analysis of continuous-time imaging at temperatures from 160 to 174 K. In addition, irreversible aggregation of single Si atoms into Si clusters started to occur at the phase boundaries or defective sites at temperatures above ˜170 K . At temperature above ˜180 K , nearly all Si atoms aggregated into clusters, which may have important implications for the atomic mechanism of epitaxial growth of Si on the Pb-covered Si(111) surface. In addition, our study provides strong evidence for breaking in the mirror symmetry in the (√{7 }×√{3 } )-Pb structure, which has implications for the atomic model of this controversial structure.

Heterogeneous activation in 2D colloidal glass-forming liquids classified by machine learning

NASA Astrophysics Data System (ADS)

Ma, Xiaoguang; Davidson, Zoey; Still, Tim; Ivancic, Robert; Schoenholz, Sam S.; Sussman, Daniel M.; Liu, A. J.; Yodh, A. G.

The trajectories of particles in colloidal glass-forming liquids are often characterized by long periods of ``in-cage'' fluctuations and rapid ``cage-breaking'' rearrangements. We study the rate of such rearrangements and its connection with local cage structures in a 2D binary mixture of poly(N-isopropyl acrylamide) spheres. We use the hopping function, Phop (t) , to identify rearrangements within particle trajectories. Then we obtain distributions of the residence time tR between consecutive rearrangements. The mean residence time tR (S) is found to correlate with the local configurations for the rearranging particles, characterized by 70 radial structural features and softness S, which ranks the structural similarities with respect to rearranging particles. Furthermore, tR (S) for particles with similar softness decays monotonically with increasing softness, indicating correlation between rearrangement rates and softness S. Finally we find that the conditional and full probability distribution functions, P (tR | S) and P (tR) , are well explained by a thermal activation model. We acknowledge financial supports from NSF-MRSEC DMR11-20901, NSF DMR16-07378, and NASA NNX08AO0G.

Robust passive dynamics of the musculoskeletal system compensate for unexpected surface changes during human hopping

PubMed Central

van der Krogt, Marjolein M.; de Graaf, Wendy W.; Farley, Claire T.; Moritz, Chet T.; Richard Casius, L. J.; Bobbert, Maarten F.

2009-01-01

When human hoppers are surprised by a change in surface stiffness, they adapt almost instantly by changing leg stiffness, implying that neural feedback is not necessary. The goal of this simulation study was first to investigate whether leg stiffness can change without neural control adjustment when landing on an unexpected hard or unexpected compliant (soft) surface, and second to determine what underlying mechanisms are responsible for this change in leg stiffness. The muscle stimulation pattern of a forward dynamic musculoskeletal model was optimized to make the model match experimental hopping kinematics on hard and soft surfaces. Next, only surface stiffness was changed to determine how the mechanical interaction of the musculoskeletal model with the unexpected surface affected leg stiffness. It was found that leg stiffness adapted passively to both unexpected surfaces. On the unexpected hard surface, leg stiffness was lower than on the soft surface, resulting in close-to-normal center of mass displacement. This reduction in leg stiffness was a result of reduced joint stiffness caused by lower effective muscle stiffness. Faster flexion of the joints due to the interaction with the hard surface led to larger changes in muscle length, while the prescribed increase in active state and resulting muscle force remained nearly constant in time. Opposite effects were found on the unexpected soft surface, demonstrating the bidirectional stabilizing properties of passive dynamics. These passive adaptations to unexpected surfaces may be critical when negotiating disturbances during locomotion across variable terrain. PMID:19589956

Photodissociation dynamics of CH{sub 3}C(O)SH in argon matrix: A QM/MM nonadiabatic dynamics simulation

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

Xia, Shu-Hua; Liu, Xiang-Yang; Fang, Qiu

2015-11-21

In this work, we have first employed the combined quantum mechanics/molecular mechanics (QM/MM) method to study the photodissociation mechanism of thioacetic acid CH{sub 3}C(O)SH in the S{sub 1}, T{sub 1}, and S{sub 0} states in argon matrix. CH{sub 3}C(O)SH is treated quantum mechanically using the complete active space self-consistent field and complete active space second-order perturbation theory methods; argon matrix is described classically using Lennard-Jones potentials. We find that the C-S bond fission is predominant due to its small barriers of ca. 3.0 and 1.0 kcal/mol in the S{sub 1} and T{sub 1} states. It completely suppresses the nearby C—Cmore » bond fission. After the bond fission, the S{sub 1} radical pair of CH{sub 3}CO and SH can decay to the S{sub 0} and T{sub 1} states via internal conversion and intersystem crossing, respectively. In the S{sub 0} state, the radical pair can either recombine to form CH{sub 3}C(O)SH or proceed to form molecular products of CH{sub 2}CO and H{sub 2}S. We have further employed our recently developed QM/MM generalized trajectory-based surface-hopping method to simulate the photodissociation dynamics of CH{sub 3}C(O)SH. In 1 ps dynamics simulation, 56% trajectories stay at the Franck-Condon region; the S{sub 1} C—S bond fission takes place in the remaining 44% trajectories. Among all nonadiabatic transitions, the S{sub 1} → S{sub 0} internal conversion is major (55%) but the S{sub 1} → T{sub 1} intersystem crossing is still comparable and cannot be ignored, which accounts for 28%. Finally, we have found a radical channel generating the molecular products of CH{sub 2}CO and H{sub 2}S, which is complementary to the concerted molecular channel. The present work sets the stage for simulating photodissociation dynamics of similar thio-carbonyl systems in matrix.« less

A comparative study of different methods for calculating electronic transition rates

NASA Astrophysics Data System (ADS)

Kananenka, Alexei A.; Sun, Xiang; Schubert, Alexander; Dunietz, Barry D.; Geva, Eitan

2018-03-01

We present a comprehensive comparison of the following mixed quantum-classical methods for calculating electronic transition rates: (1) nonequilibrium Fermi's golden rule, (2) mixed quantum-classical Liouville method, (3) mean-field (Ehrenfest) mixed quantum-classical method, and (4) fewest switches surface-hopping method (in diabatic and adiabatic representations). The comparison is performed on the Garg-Onuchic-Ambegaokar benchmark charge-transfer model, over a broad range of temperatures and electronic coupling strengths, with different nonequilibrium initial states, in the normal and inverted regimes. Under weak to moderate electronic coupling, the nonequilibrium Fermi's golden rule rates are found to be in good agreement with the rates obtained via the mixed quantum-classical Liouville method that coincides with the fully quantum-mechanically exact results for the model system under study. Our results suggest that the nonequilibrium Fermi's golden rule can serve as an inexpensive yet accurate alternative to Ehrenfest and the fewest switches surface-hopping methods.

Importance of hydrophobic traps for proton diffusion in lyotropic liquid crystals

DOE PAGES

McDaniel, Jesse G.; Yethiraj, Arun

2016-03-04

The diffusion of protons in self-assembled systems is potentially important for the design of efficient proton exchange membranes. In this work, we study proton dynamics in a low-water content, lamellar phase of an sodium-carboxylate gemini surfactant/water system using computer simulations. The hopping of protons via the Grotthuss mechanism is explicity allowed through the multi-state empirical valence bond (MS-EVB) method. We find that the hydronium ion is trapped on the hydrophobic side of the surfactant-water interface, and proton diffusion then proceeds by hopping between surface sites. The importance of hydrophobic traps is surprising, because one would expect the hydronium ions tomore » be trapped at the charged head-groups. Finally, the physics illustrated in this system should be relevant to the proton dynamics in other amphiphilic membrane systems, whenever there exists exposed hydrophobic surface regions.« less

Single-Step Electrophoretic Deposition of Non-noble Metal Catalyst Layer with Low Onset Voltage for Ethanol Electro-oxidation.

PubMed

Ahmadi Daryakenari, Ahmad; Hosseini, Davood; Ho, Ya-Lun; Saito, Takumi; Apostoluk, Aleksandra; Müller, Christoph R; Delaunay, Jean-Jacques

2016-06-29

A single-step electrophoretic deposition (EPD) process is used to fabricate catalyst layers which consist of nickel oxide nanoparticles attached on the surface of nanographitic flakes. Magnesium ions present in the colloid charge positively the flake's surface as they attach on it and are also used to bind nanographitic flakes together. The fabricated catalyst layers showed a very low onset voltage (-0.2 V vs Ag/AgCl) in the electro-oxidation of ethanol. To clarify the occurring catalytic mechanism, we performed annealing treatment to produce samples having a different electrochemical behavior with a large onset voltage. Temperature dependence measurements of the layer conductivity pointed toward a charge transport mechanism based on hopping for the nonannealed layers, while the drift transport is observed in the annealed layers. The hopping charge transport is responsible for the appearance of the low onset voltage in ethanol electro-oxidation.

Kinetic barriers for Cd and Te adatoms on Cd and Te terminated CdTe (111) surface using ab initio simulations

NASA Astrophysics Data System (ADS)

Naderi, Ebadollah; Nanavati, Sachin P.; Majumder, Chiranjib; Ghaisas, S. V.

2014-03-01

In the present work we have calculated using density functional theory (DFT), diffusion barrier potentials on both the CdTe (111) surfaces, Cd terminated (A-type) & Te terminated (B-type). We employ nudge elastic band method (NEB) for obtaining the barrier potentials. The barrier is computed for Cd and for Te adatoms on both A-type and B-type surfaces. We report two energetically favourable positions along the normal to the surface, one above and other below the surface. The one above the surface has binding energy slightly more the one below. According to the results of this work, binding energy (in all cases) for adatoms are reasonable and close to experimental data. The barrier potential for hopping adatoms (Cd and Te) on both the surfaces is less than 0.35 eV. Apart from these most probable sites, there are other at least two sites on both the types of surfaces which are meta stable. We have also computed barriers for hopping to and from these meta stable positions. The present results can shade light on the defect formation mechanism in CdTe thin films during growth. The authors would like to thank C-DAC for the computing time on its PARAM series of supercomputers and DST Govt. of India, for partial funding.

Confined diffusion of transmembrane proteins and lipids induced by the same actin meshwork lining the plasma membrane

PubMed Central

Fujiwara, Takahiro K.; Iwasawa, Kokoro; Kalay, Ziya; Tsunoyama, Taka A.; Watanabe, Yusuke; Umemura, Yasuhiro M.; Murakoshi, Hideji; Suzuki, Kenichi G. N.; Nemoto, Yuri L.; Morone, Nobuhiro; Kusumi, Akihiro

2016-01-01

The mechanisms by which the diffusion rate in the plasma membrane (PM) is regulated remain unresolved, despite their importance in spatially regulating the reaction rates in the PM. Proposed models include entrapment in nanoscale noncontiguous domains found in PtK2 cells, slow diffusion due to crowding, and actin-induced compartmentalization. Here, by applying single-particle tracking at high time resolutions, mainly to the PtK2-cell PM, we found confined diffusion plus hop movements (termed “hop diffusion”) for both a nonraft phospholipid and a transmembrane protein, transferrin receptor, and equal compartment sizes for these two molecules in all five of the cell lines used here (actual sizes were cell dependent), even after treatment with actin-modulating drugs. The cross-section size and the cytoplasmic domain size both affected the hop frequency. Electron tomography identified the actin-based membrane skeleton (MSK) located within 8.8 nm from the PM cytoplasmic surface of PtK2 cells and demonstrated that the MSK mesh size was the same as the compartment size for PM molecular diffusion. The extracellular matrix and extracellular domains of membrane proteins were not involved in hop diffusion. These results support a model of anchored TM-protein pickets lining actin-based MSK as a major mechanism for regulating diffusion. PMID:26864625

HOP family plays a major role in long-term acquired thermotolerance in Arabidopsis.

PubMed

Fernández-Bautista, Nuria; Fernández-Calvino, Lourdes; Muñoz, Alfonso; Toribio, René; Mock, Hans P; Castellano, M Mar

2018-05-08

HSP70-HSP90 organizing protein (HOP) is a family of cytosolic cochaperones whose molecular role in thermotolerance is quite unknown in eukaryotes and unexplored in plants. In this article, we describe that the three members of the AtHOP family display a different induction pattern under heat, being HOP3 highly regulated during the challenge and the attenuation period. Despite HOP3 is the most heat-regulated member, the analysis of the hop1 hop2 hop3 triple mutant demonstrates that the three HOP proteins act redundantly to promote long-term acquired thermotolerance in Arabidopsis. HOPs interact strongly with HSP90 and part of the bulk of HOPs shuttles from the cytoplasm to the nuclei and to cytoplasmic foci during the challenge. RNAseq analyses demonstrate that, although the expression of the Hsf targets is not generally affected, the transcriptional response to heat is drastically altered during the acclimation period in the hop1 hop2 hop3 triple mutant. This mutant also displays an unusual high accumulation of insoluble and ubiquitinated proteins under heat, which highlights the additional role of HOP in protein quality control. These data reveal that HOP family is involved in different aspects of the response to heat, affecting the plant capacity to acclimate to high temperatures for long periods. © 2018 John Wiley & Sons Ltd.

Longitudinal hopping in intervehicle communication: Theory and simulations on modeled and empirical trajectory data

NASA Astrophysics Data System (ADS)

Thiemann, Christian; Treiber, Martin; Kesting, Arne

2008-09-01

Intervehicle communication enables vehicles to exchange messages within a limited broadcast range and thus self-organize into dynamical and geographically embedded wireless ad hoc networks. We study the longitudinal hopping mode in which messages are transported using equipped vehicles driving in the same direction as a relay. Given a finite communication range, we investigate the conditions where messages can percolate through the network, i.e., a linked chain of relay vehicles exists between the sender and receiver. We simulate message propagation in different traffic scenarios and for different fractions of equipped vehicles. Simulations are done with both, modeled and empirical traffic data. These results are used to test the limits of applicability of an analytical model assuming a Poissonian distance distribution between the relays. We found a good agreement for homogeneous traffic scenarios and sufficiently low percentages of equipped vehicles. For higher percentages, the observed connectivity was higher than that of the model while in stop-and-go traffic situations it was lower. We explain these results in terms of correlations of the distances between the relay vehicles. Finally, we introduce variable transmission ranges and found that this additional stochastic component generally increased connectivity compared to a deterministic transmission with the same mean.

Microscopic origins of charge transport in triphenylene systems

NASA Astrophysics Data System (ADS)

Thompson, Ian R.; Coe, Mary K.; Walker, Alison B.; Ricci, Matteo; Roscioni, Otello M.; Zannoni, Claudio

2018-06-01

We study the effects of molecular ordering on charge transport at the mesoscale level in a layer of ≈9000 hexa-octyl-thio-triphenylene discotic mesogens with dimensions of ≈20 ×20 ×60 nm3 . Ordered (columnar) and disordered isotropic morphologies are obtained from a combination of atomistic and coarse-grained molecular-dynamics simulations. Electronic structure codes are used to find charge hopping rates at the microscopic level. Energetic disorder is included through the Thole model. Kinetic Monte Carlo simulations then predict charge mobilities. We reproduce the large increase in mobility in going from an isotropic to a columnar morphology. To understand how these mobilities depend on the morphology and hopping rates, we employ graph theory to analyze charge trajectories by representing the film as a charge-transport network. This approach allows us to identify spatial correlations of molecule pairs with high transfer rates. These pairs must be linked to ensure good transport characteristics or may otherwise act as traps. Our analysis is straightforward to implement and will be a useful tool in linking materials to device performance, for example, to investigate the influence of local inhomogeneities in the current density. Our mobility-field curves show an increasing mobility with field, as would be expected for an organic semiconductor.

QTAIM and Stress Tensor Characterization of Intramolecular Interactions Along Dynamics Trajectories of a Light-Driven Rotary Molecular Motor.

PubMed

Wang, Lingling; Huan, Guo; Momen, Roya; Azizi, Alireza; Xu, Tianlv; Kirk, Steven R; Filatov, Michael; Jenkins, Samantha

2017-06-29

A quantum theory of atoms in molecules (QTAIM) and stress tensor analysis was applied to analyze intramolecular interactions influencing the photoisomerization dynamics of a light-driven rotary molecular motor. For selected nonadiabatic molecular dynamics trajectories characterized by markedly different S 1 state lifetimes, the electron densities were obtained using the ensemble density functional theory method. The analysis revealed that torsional motion of the molecular motor blades from the Franck-Condon point to the S 1 energy minimum and the S 1 /S 0 conical intersection is controlled by two factors: greater numbers of intramolecular bonds before the hop-time and unusually strongly coupled bonds between the atoms of the rotor and the stator blades. This results in the effective stalling of the progress along the torsional path for an extended period of time. This finding suggests a possibility of chemical tuning of the speed of photoisomerization of molecular motors and related molecular switches by reshaping their molecular backbones to decrease or increase the degree of coupling and numbers of intramolecular bond critical points as revealed by the QTAIM/stress tensor analysis of the electron density. Additionally, the stress tensor scalar and vector analysis was found to provide new methods to follow the trajectories, and from this, new insight was gained into the behavior of the S 1 state in the vicinity of the conical intersection.

Multi-Hop Teleportation of an Unknown Qubit State Based on W States

NASA Astrophysics Data System (ADS)

Zhou, Xiang-Zhen; Yu, Xu-Tao; Zhang, Zai-Chen

2018-04-01

Quantum teleportation is important in quantum communication networks. Considering that quantum state information is also transmitted between two distant nodes, intermediated nodes are employed and two multi-hop teleportation protocols based on W state are proposed. One is hop-by-hop teleportation protocol and the other is the improved multi-hop teleportation protocol with centralized unitary transformation. In hop-by-hop protocol, the transmitted quantum state needs to be recovered at every node on the route. In improved multi-hop teleportation protocol with centralized unitary transformation, intermediate nodes need not to recover the transmitted quantum state. Compared to the hop-by-hop protocol, the improved protocol can reduce the transmission delay and improve the transmission efficiency.

A Survey of Ballistic Transfers to the Lunar Surface

NASA Technical Reports Server (NTRS)

Anderson, Rodney L.; Parker, Jeffrey S.

2011-01-01

In this study techniques are developed which allow an analysis of a range of different types of transfer trajectories from the Earth to the lunar surface. Trajectories ranging from those obtained using the invariant manifolds of unstable orbits to those derived from collision orbits are analyzed. These techniques allow the computation of trajectories encompassing low-energy trajectories as well as more direct transfers. The range of possible trajectory options is summarized, and a broad range of trajectories that exist as a result of the Sun's influence are computed and analyzed. The results are then classified by type, and trades between different measures of cost are discussed.

Perceived bitterness character of beer in relation to hop variety and the impact of hop aroma.

PubMed

Oladokun, Olayide; James, Sue; Cowley, Trevor; Dehrmann, Frieda; Smart, Katherine; Hort, Joanne; Cook, David

2017-09-01

The impact of hop variety and hop aroma on perceived beer bitterness intensity and character was investigated using analytical and sensory methods. Beers made from malt extract were hopped with 3 distinctive hop varieties (Hersbrucker, East Kent Goldings, Zeus) to achieve equi-bitter levels. A trained sensory panel determined the bitterness character profile of each singly-hopped beer using a novel lexicon. Results showed different bitterness character profiles for each beer, with hop aroma also found to change the hop variety-derived bitterness character profiles of the beer. Rank-rating evaluations further showed the significant effect of hop aroma on selected key bitterness character attributes, by increasing perceived harsh and lingering bitterness, astringency, and bitterness intensity via cross-modal flavour interactions. This study advances understanding of the complexity of beer bitterness perception by demonstrating that hop variety selection and hop aroma both impact significantly on the perceived intensity and character of this key sensory attribute. Copyright © 2017 Elsevier Ltd. All rights reserved.

From "They" Science to "Our" Science: Hip Hop Epistemology in STEAM Education

NASA Astrophysics Data System (ADS)

Dolberry, Maurice E.

Hip hop has moved from being considered a type of music into being understood as a culture in which a prominent type of music originates. Hip hop culture has a philosophy and epistemological constructs as well. This study analyzed those constructs to determine how conceptions of science factor in hip hop worldviews. Pedagogical models in culturally responsive teaching and Science, Technology, Engineering, Arts, and Mathematics (STEAM) education were also examined to discern their philosophical connections with hip hop culture. These connections were used to create two theoretical models. The first one, Hip Hop Science, described how scientific thought functions in hip hop culture. The second model, Hip Hop STEAM Pedagogy, proposes how hip hop culture can inform STEAM teaching practices. The study began by using Critical Race Theory to create a theoretical framework proposing how the two theoretical models could be derived from the philosophical and pedagogical concepts. Content analysis and narrative inquiry were used to analyze data collected from scholarly texts, hip hop songs, and interviews with hip hop-responsive educators. The data from these sources were used initially to assess the adequacy of the proposed theoretical framework, and subsequently to improve its viability. Four overlapping themes emerged from the data analyses, including hip hop-resistance to formal education; how hip hop culture informs pedagogical practice in hip hop-responsive classrooms; conceptions of knowledge and reality that shape how hip hoppers conduct scientific inquiry; and hip hop-based philosophies of effective teaching for hip hoppers as a marginalized cultural group. The findings indicate that there are unique connections between hip hop epistemology, sciencemindedness, and pedagogical practices in STEAM education. The revised theoretical framework clarified the nature of these connections, and supported claims from prior research that hip hop culture provides viable sites of engagement for STEAM educators. It concluded with suggestions for future research that further explicates hip hop epistemology and Hip Hop STEAM Pedagogy.

Rapid sampling of local minima in protein energy surface and effective reduction through a multi-objective filter

PubMed Central

2013-01-01

Background Many problems in protein modeling require obtaining a discrete representation of the protein conformational space as an ensemble of conformations. In ab-initio structure prediction, in particular, where the goal is to predict the native structure of a protein chain given its amino-acid sequence, the ensemble needs to satisfy energetic constraints. Given the thermodynamic hypothesis, an effective ensemble contains low-energy conformations which are similar to the native structure. The high-dimensionality of the conformational space and the ruggedness of the underlying energy surface currently make it very difficult to obtain such an ensemble. Recent studies have proposed that Basin Hopping is a promising probabilistic search framework to obtain a discrete representation of the protein energy surface in terms of local minima. Basin Hopping performs a series of structural perturbations followed by energy minimizations with the goal of hopping between nearby energy minima. This approach has been shown to be effective in obtaining conformations near the native structure for small systems. Recent work by us has extended this framework to larger systems through employment of the molecular fragment replacement technique, resulting in rapid sampling of large ensembles. Methods This paper investigates the algorithmic components in Basin Hopping to both understand and control their effect on the sampling of near-native minima. Realizing that such an ensemble is reduced before further refinement in full ab-initio protocols, we take an additional step and analyze the quality of the ensemble retained by ensemble reduction techniques. We propose a novel multi-objective technique based on the Pareto front to filter the ensemble of sampled local minima. Results and conclusions We show that controlling the magnitude of the perturbation allows directly controlling the distance between consecutively-sampled local minima and, in turn, steering the exploration towards conformations near the native structure. For the minimization step, we show that the addition of Metropolis Monte Carlo-based minimization is no more effective than a simple greedy search. Finally, we show that the size of the ensemble of sampled local minima can be effectively and efficiently reduced by a multi-objective filter to obtain a simpler representation of the probed energy surface. PMID:24564970

Chemical desorption and diffusive dust chemistry

NASA Astrophysics Data System (ADS)

Dulieu, Francois; Pirronello, Valerio; Minissale, Marco; Congiu, Emanuele; Baouche, Saoud; Chaabouni, Henda; Moudens, Audrey; Accolla, Mario; Cazaux, Stephanie; Manicò, Giulio

In molecular clouds, gaseous species can accrete efficiently on the cold surfaces of dust grains. As for radical-radical reactions, the surface of the grains acts as a third body, and changes dramatically the efficiency of the reactions (i.e., H2 formation), or lowers considerably the barrier to formation (i.e., H2O synthesis) in comparison with gas phase reaction processes. These properties make dust grains efficient catalytic templates. However, the chemical role of dust grains depends on the diffusive properties of the reactive partners. Over the last years, we have developed experimental tools and methods to explore the chemistry occurring on cold (6-50K) surfaces. We have obtained some hints about the diffusivity of H on amorphous ice, and studied in detail the diffusion of O atoms. The latter species appears to have a hopping rate in the range 0.01-100 hops/sec. The diffusion rate of O atoms is dependent on the surface morphology and on the surface temperature. The diffusion law is compatible with a diffusion dominated by quantum tunnelling rather than classical thermal hopping. Using H, O, N atoms and, indirectly, OH and HCO radicals, we have begun to explore many chemical reactive networks. In this presentation, I will focus on the formation of H2O and CO2, and will propose many possible formation routes to obtain these chemical traps. The molecules formed on surfaces have a certain probability of desorbing upon their formation. This non-thermal desorption mechanism, or chemical desorption, has been proposed to explain why some molecules can be detected in the gas phase of those region where they were believed to be part of the icy mantles covering dust grains. We have shown that this process can be very efficient, but is very sensitive to the substrate and the surroundings of the reaction site, is dependent on the kind of molecule formed and its chemical pathway. In my presentation I will present how the surface coverage and the type of reaction can play a major role in the chemical desorption process. I will discuss of possible key parameters that rule this process.

Winding trajectories of noncircular composite shells

NASA Astrophysics Data System (ADS)

Nikityuk, V. A.; Fedorov, V. V.

1995-07-01

An approach has been proposed for determination of the trajectory parameters of a layer formed by winding of continuous ribbons on a complicated surface. An algorithm has been developed for determining the geodesic trajectories of the reinforcement fiber arrangement, reinforcement angles, and geodesic deviation angles. Conditions have been formulated for positional stability of the ribbons on the surface and avoidance of gaps and overlapping between the ribbons along with restrictions to the surface form. Results are given for a calculation of the geodesic turn parameters on a fuselage surface, which is not a surface of revolution, of a light airplane.

Metastability in plyometric training on unstable surfaces: a pilot study

PubMed Central

2014-01-01

Background In the past, plyometric training (PT) has been predominantly performed on stable surfaces. The purpose of this pilot study was to examine effects of a 7-week lower body PT on stable vs. unstable surfaces. This type of exercise condition may be denoted as metastable equilibrium. Methods Thirty-three physically active male sport science students (age: 24.1 ± 3.8 years) were randomly assigned to a PT group (n = 13) exercising on stable (STAB) and a PT group (n = 20) on unstable surfaces (INST). Both groups trained countermovement jumps, drop jumps, and practiced a hurdle jump course. In addition, high bar squats were performed. Physical fitness tests on stable surfaces (hexagonal obstacle test, countermovement jump, hurdle drop jump, left-right hop, dynamic and static balance tests, and leg extension strength) were used to examine the training effects. Results Significant main effects of time (ANOVA) were found for the countermovement jump, hurdle drop jump, hexagonal test, dynamic balance, and leg extension strength. A significant interaction of time and training mode was detected for the countermovement jump in favor of the INST group. No significant improvements were evident for either group in the left-right hop and in the static balance test. Conclusions These results show that lower body PT on unstable surfaces is a safe and efficient way to improve physical performance on stable surfaces. PMID:25089202

Trajectory fitting in function space with application to analytic modeling of surfaces

NASA Technical Reports Server (NTRS)

Barger, Raymond L.

1992-01-01

A theory for representing a parameter-dependent function as a function trajectory is described. Additionally, a theory for determining a piecewise analytic fit to the trajectory is described. An example is given that illustrates the application of the theory to generating a smooth surface through a discrete set of input cross-section shapes. A simple procedure for smoothing in the parameter direction is discussed, and a computed example is given. Application of the theory to aerodynamic surface modeling is demonstrated by applying it to a blended wing-fuselage surface.

Mean-trajectory approximation for electronic and vibrational-electronic nonlinear spectroscopy

NASA Astrophysics Data System (ADS)

Loring, Roger F.

2017-04-01

Mean-trajectory approximations permit the calculation of nonlinear vibrational spectra from semiclassically quantized trajectories on a single electronically adiabatic potential surface. By describing electronic degrees of freedom with classical phase-space variables and subjecting these to semiclassical quantization, mean-trajectory approximations may be extended to compute both nonlinear electronic spectra and vibrational-electronic spectra. A general mean-trajectory approximation for both electronic and nuclear degrees of freedom is presented, and the results for purely electronic and for vibrational-electronic four-wave mixing experiments are quantitatively assessed for harmonic surfaces with linear electronic-nuclear coupling.

Spray Cooling Trajectory Angle Impact Upon Heat Flux Using a Straight Finned Enhanced Surface

NASA Technical Reports Server (NTRS)

Silk, Eric A.; Kim, Jungho; Kiger, Ken

2005-01-01

Experiments were conducted to study the effects of spray trajectory angles upon heat flux for flat and enhanced surface spray cooling. The surface enhancement consisted of straight fins machined on the top surface of a copper heater block. Spray cooling curves were obtained with the straight fin surface aligned both parallel (axial) and perpendicular (transverse) to the spray axis. Measurements were also obtained on a flat surface heater block for comparison purposes. Each copper block had a cross-sectional area of 2.0 sq cm. A 2x2 nozzle array was used with PF-5060 as the working fluid. Thermal performance data was obtained under nominally degassed (chamber pressure of 41.4 kPa) conditions. Results show that the maximum CHF in all cases was attained for a trajectory angle of 30' from the surface normal. Furthermore, trajectory angles applied to straight finned surfaces can have a critical heat flux (CHF) enhancement as much as 75% (heat flux value of 140 W/sq cm) relative to the vertical spray orientation for the analogous flat surface case under nominally degassed conditions.

Characterization of a highly hop-resistant Lactobacillus brevis strain lacking hop transport.

PubMed

Behr, Jürgen; Gänzle, Michael G; Vogel, Rudi F

2006-10-01

Resistance to hops is a prerequisite for lactic acid bacteria to spoil beer. In this study we analyzed mechanisms of hop resistance of Lactobacillus brevis at the metabolism, membrane physiology, and cell wall composition levels. The beer-spoiling organism L. brevis TMW 1.465 was adapted to high concentrations of hop compounds and compared to a nonadapted strain. Upon adaptation to hops the metabolism changed to minimize ethanol stress. Fructose was used predominantly as a carbon source by the nonadapted strain but served as an electron acceptor upon adaptation to hops, with concomitant formation of acetate instead of ethanol. Furthermore, hop adaptation resulted in higher levels of lipoteichoic acids (LTA) incorporated into the cell wall and altered composition and fluidity of the cytoplasmic membrane. The putative transport protein HitA and enzymes of the arginine deiminase pathway were overexpressed upon hop adaptation. HorA was not expressed, and the transport of hop compounds from the membrane to the extracellular space did not account for increased resistance to hops upon adaptation. Accordingly, hop resistance is a multifactorial dynamic property, which can develop during adaptation. During hop adaptation, arginine catabolism contributes to energy and generation of the proton motive force until a small fraction of the population has established structural improvements. This acquired hop resistance is energy independent and involves an altered cell wall composition. LTA shields the organism from accompanying stresses and provides a reservoir of divalent cations, which are otherwise scarce as a result of their complexation by hop acids. Some of the mechanisms involved in hop resistance overlap with mechanisms of pH resistance and ethanol tolerance and as a result enable beer spoilage by L. brevis.

Helicobacter pylori HopE and HopV porins present scarce expression among clinical isolates

PubMed Central

Lienlaf, Maritza; Morales, Juan Pablo; Díaz, María Inés; Díaz, Rodrigo; Bruce, Elsa; Siegel, Freddy; León, Gloria; Harris, Paul R; Venegas, Alejandro

2010-01-01

AIM: To evaluate how widely Helicobacter pylori (H. pylori) HopE and HopV porins are expressed among Chilean isolates and how seroprevalent they are among infected patients in Chile. METHODS: H. pylori hopE and hopV genes derived from strain CHCTX-1 were cloned by polymerase chain reaction (PCR), sequenced and expressed in Escherichia coli AD494 (DE3). Gel-purified porins were used to prepare polyclonal antibodies. The presence of both genes was tested by PCR in a collection of H. pylori clinical isolates and their expression was detected in lysates by immunoblotting. Immune responses against HopE, HopV and other H. pylori antigens in sera from infected and non-infected patients were tested by Western blotting using these sera as first antibody on recombinant H. pylori antigens. RESULTS: PCR and Western blotting assays revealed that 60 and 82 out of 130 Chilean isolates carried hopE and hopV genes, respectively, but only 16 and 9, respectively, expressed these porins. IgG serum immunoreactivity evaluation of 69 H. pylori-infected patients revealed that HopE and HopV were infrequently recognized (8.7% and 10.1% respectively) compared to H. pylori VacA (68.1%) and CagA (59.5%) antigens. Similar values were detected for IgA serum immunoreactivity against HopE (11.6%) and HopV (10.5%) although lower values for VacA (42%) and CagA (17.4%) were obtained when compared to the IgG response. CONCLUSION: A scarce expression of HopE and HopV among Chilean isolates was found, in agreement with the infrequent seroconversion against these antigens when tested in infected Chilean patients. PMID:20082477

Energy management that generates terrain following versus apex-preserving hopping in man and machine.

PubMed

Kalveram, Karl Theodor; Haeufle, Daniel F B; Seyfarth, André; Grimmer, Sten

2012-01-01

While hopping, 12 subjects experienced a sudden step down of 5 or 10 cm. Results revealed that the hopping style was "terrain following". It means that the subjects pursued to keep the distance between maximum hopping height (apex) and ground profile constant. The spring-loaded inverse pendulum (SLIP) model, however, which is currently considered as template for stable legged locomotion would predict apex-preserving hopping, by which the absolute maximal hopping height is kept constant regardless of changes of the ground level. To get more insight into the physics of hopping, we outlined two concepts of energy management: "constant energy supply", by which in each bounce--regardless of perturbations--the same amount of mechanical energy is injected, and "lost energy supply", by which the mechanical energy that is going to be dissipated in the current cycle is assessed and replenished. When tested by simulations and on a robot testbed capable of hopping, constant energy supply generated stable and robust terrain following hopping, whereas lost energy supply led to something like apex-preserving hopping, which, however, lacks stability as well as robustness. Comparing simulated and machine hopping with human hopping suggests that constant energy supply has a good chance to be used by humans to generate hopping.

Multi-hop teleportation based on W state and EPR pairs

NASA Astrophysics Data System (ADS)

Hai-Tao, Zhan; Xu-Tao, Yu; Pei-Ying, Xiong; Zai-Chen, Zhang

2016-05-01

Multi-hop teleportation has significant value due to long-distance delivery of quantum information. Many studies about multi-hop teleportation are based on Bell pairs, partially entangled pairs or W state. The possibility of multi-hop teleportation constituted by partially entangled pairs relates to the number of nodes. The possibility of multi-hop teleportation constituted by double W states is after n-hop teleportation. In this paper, a multi-hop teleportation scheme based on W state and EPR pairs is presented and proved. The successful possibility of quantum information transmitted hop by hop through intermediate nodes is deduced. The possibility of successful transmission is after n-hop teleportation. Project supported by the National Natural Science Foundation of China (Grant No. 61571105), the Prospective Future Network Project of Jiangsu Province, China (Grant No. BY2013095-1-18), and the Independent Project of State Key Laboratory of Millimeter Waves, China (Grant No. Z201504).

Rethinking Pedagogy in Urban Spaces: Implementing Hip-Hop Pedagogy in the Urban Science Classroom

ERIC Educational Resources Information Center

Adjapong, Edmund S.; Emdin, Christopher

2015-01-01

A significant amount of research regarding Hip-Hop Based Education (HHBE) fails to provide insight on how to incorporate elements of Hip-Hop into daily teaching practices; rather Hip-Hop based educators focus mainly on incorporating Hip-Hop culture into curricula. This study explores the benefits of using two specific Hip-Hop pedagogical practices…

Structural, optical and morphological studies of Cd2+ doping in CH3NH3PbI3 perovskite semiconductor at Pb2+ site for photovoltaic applications

NASA Astrophysics Data System (ADS)

Parrey, Khursheed; Warish, Mohd.; Devi, Nisha; Niazi, A.; Aziz, A.; Ansari, S. G.

2018-05-01

Doping of semiconductors in a controlled mannner have paramount technological importance as far as the optical and electronic properties of the devices are concerned. Hybrid organic-inorganic perovskites (HOPs) as intrinsic semiconductors have sensational properties required for both the solar photovoltaics and perovskite light emitting diodes. However, undoped and complexity in the dpoing process of HOPs have limited their exploitation in the field of elcronics. In this papper we present the synthesis of HOP semiconductor (CH3NH3PbI3) doped in Pb2+ position by Cd2+. We studied the effect of the incorporation of Cd2+ into the crystalline structure and analysed the changes in the properties like crystal structure, optical absorption and the surface morphology. The structure of HOPs confirmed by X-ray diffraction analysis is tetragonal perovskite type. It can be found that the crystallinity of the samples was enhanced with the doping concentration as the intensity of diffraction peaks were observed to increase with doping. The absorption spectra as obtained from UV-Visible spectrophotometry and Tauc plot analysis indicated that the band gap observed (1.73 eV) is direct type and gets reduced to 1.67 eV with the doping concentration. The red shift may be due to the increase in the size of nanocrystalline material with doping.

Evidence of a Cell Surface Role for Hsp90 Complex Proteins Mediating Neuroblast Migration in the Subventricular Zone.

PubMed

Miyakoshi, Leo M; Marques-Coelho, Diego; De Souza, Luiz E R; Lima, Flavia R S; Martins, Vilma R; Zanata, Silvio M; Hedin-Pereira, Cecilia

2017-01-01

In most mammalian brains, the subventricular zone (SVZ) is a germinative layer that maintains neurogenic activity throughout adulthood. Neuronal precursors arising from this region migrate through the rostral migratory stream (RMS) and reach the olfactory bulbs where they differentiate and integrate into the local circuitry. Recently, studies have shown that heat shock proteins have an important role in cancer cell migration and blocking Hsp90 function was shown to hinder cell migration in the developing cerebellum. In this work, we hypothesize that chaperone complexes may have an important function regulating migration of neuronal precursors from the subventricular zone. Proteins from the Hsp90 complex are present in the postnatal SVZ as well as in the RMS. Using an in vitro SVZ explant model, we have demonstrated the expression of Hsp90 and Hop/STI1 by migrating neuroblasts. Treatment with antibodies against Hsp90 and co-chaperone Hop/STI1, as well as Hsp90 and Hsp70 inhibitors hinder neuroblast chain migration. Time-lapse videomicroscopy analysis revealed that cell motility and average migratory speed was decreased after exposure to both antibodies and inhibitors. Antibodies recognizing Hsp90, Hsp70, and Hop/STI1 were found bound to the membranes of cells from primary SVZ cultures and biotinylation assays demonstrated that Hsp70 and Hop/STI1 could be found on the external leaflet of neuroblast membranes. The latter could also be detected in conditioned medium samples obtained from cultivated SVZ cells. Our results suggest that chaperones Hsp90, Hsp70, and co-chaperone Hop/STI1, components of the Hsp90 complex, regulate SVZ neuroblast migration in a concerted manner through an extracellular mechanism.

Particle-Surface Interaction Model and Method of Determining Particle-Surface Interactions

NASA Technical Reports Server (NTRS)

Hughes, David W. (Inventor)

2012-01-01

A method and model of predicting particle-surface interactions with a surface, such as the surface of a spacecraft. The method includes the steps of: determining a trajectory path of a plurality of moving particles; predicting whether any of the moving particles will intersect a surface; predicting whether any of the particles will be captured by the surface and/or; predicting a reflected trajectory and velocity of particles reflected from the surface.

Suppression of Plant Immune Responses by the Pseudomonas savastanoi pv. savastanoi NCPPB 3335 Type III Effector Tyrosine Phosphatases HopAO1 and HopAO2

PubMed Central

Castañeda-Ojeda, María Pilar; Moreno-Pérez, Alba; Ramos, Cayo; López-Solanilla, Emilia

2017-01-01

The effector repertoire of the olive pathogen P. savastanoi pv. savastanoi NCPPB 3335 includes two members of the HopAO effector family, one of the most diverse T3E families of the P. syringae complex. The study described here explores the phylogeny of these dissimilar members, HopAO1 and HopAO2, among the complex and reveals their activities as immune defense suppressors. Although HopAO1 is predominantly encoded by phylogroup 3 strains isolated from woody organs of woody hosts, both HopAO1 and HopAO2 are phylogenetically clustered according to the woody/herbaceous nature of their host of isolation, suggesting host specialization of the HopAO family across the P. syringae complex. HopAO1 and HopAO2 translocate into plant cells and show hrpL-dependent expression, which allows their classification as actively deployed type III effectors. Our data also show that HopAO1 and HopAO2 possess phosphatase activity, a hallmark of the members of this family. Both of them exert an inhibitory effect on early plant defense responses, such as ROS production and callose deposition, and are able to suppress ETI responses induced by the effectorless polymutant of P. syringae pv. tomato DC3000 (DC3000D28E) in Nicotiana. Moreover, we demonstrate that a ΔhopAO1 mutant of P. savastanoi NCPBB 3335 exhibits a reduced fitness and virulence in olive plants, which supports the relevance of this effector during the interaction of this strain with its host plants. This work contributes to the field with the first report regarding functional analysis of HopAO homologs encoded by P. syringae or P. savastanoi strains isolated from woody hosts. PMID:28529516

Respiratory disease associated with occupational inhalation to hop (Humulus lupulus) during harvest and processing.

PubMed

Reeb-Whitaker, Carolyn K; Bonauto, David K

2014-11-01

There is little published evidence for occupational respiratory disease caused by hop dust inhalation. In the United States, hops are commercially produced in the Pacific Northwest region. To describe occupational respiratory disease in hop workers. Washington State workers' compensation claims filed by hop workers for respiratory disease were systematically identified and reviewed. Incidence rates of respiratory disease in hop workers were compared with rates in field vegetable crop farm workers. Fifty-seven cases of respiratory disease associated with hop dust inhalation were reported from 1995 to 2011. Most cases (61%) were diagnosed by the attending health care practitioner as having work-related asthma. Seven percent of cases were diagnosed as chronic obstructive pulmonary disease, and the remaining cases were diagnosed as allergic respiratory disorders (eg, allergic rhinitis) or asthma-associated symptoms (eg, dyspnea). Cases were associated with hop harvesting, secondary hop processing, and indirect exposure. The incidence rate of respiratory disease in hop workers was 15 cases per 10,000 full-time workers, which was 30 times greater than the incidence rate for field vegetable crop workers. A strong temporal association between hop dust exposure and respiratory symptoms and a clear association between an increase in hop dust concentrations and the clinical onset of symptoms were apparent in 3 cases. Occupational exposure to hop dust is associated with respiratory disease. Respiratory disease rates were higher in hop workers than in a comparison group of agricultural workers. Additional research is needed before hop dust can be confirmed as a causative agent for occupational asthma. Copyright © 2014 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

Semiclassical modelling of finite-pulse effects on non-adiabatic photodynamics via initial condition filtering: The predissociation of NaI as a test case

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

Martínez-Mesa, Aliezer; Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, D-14476 Potsdam-Golm; Saalfrank, Peter

2015-05-21

Femtosecond-laser pulse driven non-adiabatic spectroscopy and dynamics in molecular and condensed phase systems continue to be a challenge for theoretical modelling. One of the main obstacles is the “curse of dimensionality” encountered in non-adiabatic, exact wavepacket propagation. A possible route towards treating complex molecular systems is via semiclassical surface-hopping schemes, in particular if they account not only for non-adiabatic post-excitation dynamics but also for the initial optical excitation. One such approach, based on initial condition filtering, will be put forward in what follows. As a simple test case which can be compared with exact wavepacket dynamics, we investigate the influencemore » of the different parameters determining the shape of a laser pulse (e.g., its finite width and a possible chirp) on the predissociation dynamics of a NaI molecule, upon photoexcitation of the A(0{sup +}) state. The finite-pulse effects are mapped into the initial conditions for semiclassical surface-hopping simulations. The simulated surface-hopping diabatic populations are in qualitative agreement with the quantum mechanical results, especially concerning the subpicosend photoinduced dynamics, the main deviations being the relative delay of the non-adiabatic transitions in the semiclassical picture. Likewise, these differences in the time-dependent electronic populations calculated via the semiclassical and the quantum methods are found to have a mild influence on the overall probability density distribution. As a result, the branching ratios between the bound and the dissociative reaction channels and the time-evolution of the molecular wavepacket predicted by the semiclassical method agree with those computed using quantum wavepacket propagation. Implications for more challenging molecular systems are given.« less

FOB-SH: Fragment orbital-based surface hopping for charge carrier transport in organic and biological molecules and materials

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

Spencer, J.; Gajdos, F.; Blumberger, J., E-mail: j.blumberger@ucl.ac.uk

2016-08-14

We introduce a fragment orbital-based fewest switches surface hopping method, FOB-SH, designed to efficiently simulate charge carrier transport in strongly fluctuating condensed phase systems such as organic semiconductors and biomolecules. The charge carrier wavefunction is expanded and the electronic Hamiltonian constructed in a set of singly occupied molecular orbitals of the molecular sites that mediate the charge transfer. Diagonal elements of the electronic Hamiltonian (site energies) are obtained from a force field, whereas the off-diagonal or electronic coupling matrix elements are obtained using our recently developed analytic overlap method. We derive a general expression for the exact forces on themore » adiabatic ground and excited electronic state surfaces from the nuclear gradients of the charge localized electronic states. Applications to electron hole transfer in a model ethylene dimer and through a chain of ten model ethylenes validate our implementation and demonstrate its computational efficiency. On the larger system, we calculate the qualitative behaviour of charge mobility with change in temperature T for different regimes of the intermolecular electronic coupling. For small couplings, FOB-SH predicts a crossover from a thermally activated regime at low temperatures to a band-like transport regime at higher temperatures. For higher electronic couplings, the thermally activated regime disappears and the mobility decreases according to a power law. This is interpreted by a gradual loss in probability for resonance between the sites as the temperature increases. The polaron hopping model solved for the same system gives a qualitatively different result and underestimates the mobility decay at higher temperatures. Taken together, the FOB-SH methodology introduced here shows promise for a realistic investigation of charge carrier transport in complex organic, aqueous, and biological systems.« less

FOB-SH: Fragment orbital-based surface hopping for charge carrier transport in organic and biological molecules and materials

NASA Astrophysics Data System (ADS)

Spencer, J.; Gajdos, F.; Blumberger, J.

2016-08-01

We introduce a fragment orbital-based fewest switches surface hopping method, FOB-SH, designed to efficiently simulate charge carrier transport in strongly fluctuating condensed phase systems such as organic semiconductors and biomolecules. The charge carrier wavefunction is expanded and the electronic Hamiltonian constructed in a set of singly occupied molecular orbitals of the molecular sites that mediate the charge transfer. Diagonal elements of the electronic Hamiltonian (site energies) are obtained from a force field, whereas the off-diagonal or electronic coupling matrix elements are obtained using our recently developed analytic overlap method. We derive a general expression for the exact forces on the adiabatic ground and excited electronic state surfaces from the nuclear gradients of the charge localized electronic states. Applications to electron hole transfer in a model ethylene dimer and through a chain of ten model ethylenes validate our implementation and demonstrate its computational efficiency. On the larger system, we calculate the qualitative behaviour of charge mobility with change in temperature T for different regimes of the intermolecular electronic coupling. For small couplings, FOB-SH predicts a crossover from a thermally activated regime at low temperatures to a band-like transport regime at higher temperatures. For higher electronic couplings, the thermally activated regime disappears and the mobility decreases according to a power law. This is interpreted by a gradual loss in probability for resonance between the sites as the temperature increases. The polaron hopping model solved for the same system gives a qualitatively different result and underestimates the mobility decay at higher temperatures. Taken together, the FOB-SH methodology introduced here shows promise for a realistic investigation of charge carrier transport in complex organic, aqueous, and biological systems.

Evaluation of altimetry-derived surface current products using Lagrangian drifter trajectories in the eastern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Liu, Yonggang; Weisberg, Robert H.; Vignudelli, Stefano; Mitchum, Gary T.

2014-05-01

Lagrangian particle trajectory models based on several altimetry-derived surface current products are used to hindcast the drifter trajectories observed in the eastern Gulf of Mexico during May to August 2010 (the Deepwater Horizon oil spill incident). The performances of the trajectory models are gauged in terms of Lagrangian separation distances (d) and a nondimensional skill score (s), respectively. A series of numerical experiments show that these altimetry-based trajectory models have about the same performance, with a certain improvement by adding surface wind Ekman components, especially over the shelf region. However, their hindcast skills are slightly better than those of the data assimilative numerical model output. After 3 days' simulation the altimetry-based trajectory models have mean d values of 75-83 and 34-42 km (s values of 0.49-0.51 and 0.35-0.43) in the Gulf of Mexico deep water area and on the West Florida Continental Shelf, respectively. These satellite altimetry data products are useful for providing essential information on ocean surface currents of use in water property transports, offshore oil and gas operations, hazardous spill mitigation, search and rescue, etc.

Path-integral isomorphic Hamiltonian for including nuclear quantum effects in non-adiabatic dynamics

NASA Astrophysics Data System (ADS)

Tao, Xuecheng; Shushkov, Philip; Miller, Thomas F.

2018-03-01

We describe a path-integral approach for including nuclear quantum effects in non-adiabatic chemical dynamics simulations. For a general physical system with multiple electronic energy levels, a corresponding isomorphic Hamiltonian is introduced such that Boltzmann sampling of the isomorphic Hamiltonian with classical nuclear degrees of freedom yields the exact quantum Boltzmann distribution for the original physical system. In the limit of a single electronic energy level, the isomorphic Hamiltonian reduces to the familiar cases of either ring polymer molecular dynamics (RPMD) or centroid molecular dynamics Hamiltonians, depending on the implementation. An advantage of the isomorphic Hamiltonian is that it can easily be combined with existing mixed quantum-classical dynamics methods, such as surface hopping or Ehrenfest dynamics, to enable the simulation of electronically non-adiabatic processes with nuclear quantum effects. We present numerical applications of the isomorphic Hamiltonian to model two- and three-level systems, with encouraging results that include improvement upon a previously reported combination of RPMD with surface hopping in the deep-tunneling regime.

Mechanisms and dynamics of protonation and lithiation of ferrocene.

PubMed

Sharma, Nishant; Ajay, Jayanth K; Venkatasubbaiah, Krishnan; Lourderaj, Upakarasamy

2015-09-14

By elucidating the mechanism of the simplest electrophilic substitution reaction of ferrocene, it was found that the verification of the protonation reaction has been a difficulty. In the work reported here, ab initio chemical dynamics simulations were performed at B3LYP/DZVP level of theory to understand the atomic level mechanisms of protonation and lithiation of ferrocene. Protonation of ferrocene resulted in the agostic and metal-protonated forms. Trajectory calculations revealed that protonation of ferrocene occurs by exo and endo mechanisms, with exo being the major path. H(+) was found to be mobile and hopped from the Cp ring to the metal center and vice versa after the initial attack on ferrocene, with the metal-complex having a shorter lifetime. These results remove the ambiguity surrounding the mechanism, as proposed in earlier experimental and computational studies. Lithiation of ferrocene resulted in the formation of cation-π and metal-lithiated complexes. Similar to protonation, trajectory results revealed that both exo and endo paths were followed, with the exo path being the major one. In addition, lithiated-ferrocene exhibited planetary motion. The major path (exo) followed in the protonation and lithiation of ferrocene is consistent with the observations in earlier experimental studies for other hard electrophiles.

A first principles kinetic Monte Carlo investigation of the adsorption and mobility of gadolinium on the (100) surface of tungsten

NASA Astrophysics Data System (ADS)

Samin, Adib J.; Zhang, Jinsuo

2017-05-01

An accurate characterization of lanthanide adsorption and mobility on tungsten surfaces is important for pyroprocessing. In the present study, the adsorption and diffusion of gadolinium on the (100) surface of tungsten was investigated. It was found that the hollow sites were the most energetically favorable for the adsorption. It was further observed that a magnetic moment was induced following the adsorption of gadolinium on the tungsten surface and that the system with adsorbed hollow sites had the largest magnetization. A pathway for the surface diffusion of gadolinium was determined to occur by hopping between the nearest neighbor hollow sites via the bridge site and the activation energy for the hop was calculated to be 0.75 eV. The surface diffusion process was further assessed using two distinct kinetic Monte Carlo models; one that accounted for lateral adsorbate interactions up to the second nearest neighbor and one that did not account for such interatomic interactions in the adlayer. When the lateral interactions were included in the simulations, the diffusivity was observed to have a strong dependence on coverage (for the coverage values being studied). The effects of lateral interactions were further observed in a one-dimensional simulation of the diffusion equation where the asymmetry in the surface coverage profile upon its approach to a steady state distribution was clear in comparison with the simulations which did not account for those interactions.

A Hybrid DV-Hop Algorithm Using RSSI for Localization in Large-Scale Wireless Sensor Networks.

PubMed

Cheikhrouhou, Omar; M Bhatti, Ghulam; Alroobaea, Roobaea

2018-05-08

With the increasing realization of the Internet-of-Things (IoT) and rapid proliferation of wireless sensor networks (WSN), estimating the location of wireless sensor nodes is emerging as an important issue. Traditional ranging based localization algorithms use triangulation for estimating the physical location of only those wireless nodes that are within one-hop distance from the anchor nodes. Multi-hop localization algorithms, on the other hand, aim at localizing the wireless nodes that can physically be residing at multiple hops away from anchor nodes. These latter algorithms have attracted a growing interest from research community due to the smaller number of required anchor nodes. One such algorithm, known as DV-Hop (Distance Vector Hop), has gained popularity due to its simplicity and lower cost. However, DV-Hop suffers from reduced accuracy due to the fact that it exploits only the network topology (i.e., number of hops to anchors) rather than the distances between pairs of nodes. In this paper, we propose an enhanced DV-Hop localization algorithm that also uses the RSSI values associated with links between one-hop neighbors. Moreover, we exploit already localized nodes by promoting them to become additional anchor nodes. Our simulations have shown that the proposed algorithm significantly outperforms the original DV-Hop localization algorithm and two of its recently published variants, namely RSSI Auxiliary Ranging and the Selective 3-Anchor DV-hop algorithm. More precisely, in some scenarios, the proposed algorithm improves the localization accuracy by almost 95%, 90% and 70% as compared to the basic DV-Hop, Selective 3-Anchor, and RSSI DV-Hop algorithms, respectively.

Quantitative Improvements in Hop Test Scores After a 6-Week Neuromuscular Training Program.

PubMed

Meierbachtol, Adam; Rohman, Eric; Paur, Eric; Bottoms, John; Tompkins, Marc

2016-09-12

In patients who have undergone anterior cruciate ligament reconstruction (ACLR), the effect of neuromuscular re-education (NMR) programs on standard hop tests outcomes, including limb symmetry indices (LSIs), is unknown. Both legs will show improvement in hop test-measured units after neuromuscular training, but the involved leg will show relatively greater improvement leading to improved limb symmetry. Patients younger than 18 years will show more improvement than patients who are older. Retrospective cohort study. Level 3. Patients self-selected their participation in this NMR program, which was completed after traditional outpatient physical therapy. Pre- and post-hop test scores were recorded as the primary outcome measure. Seventy-one patients met the inclusion criteria and completed hop testing. Overall, the involved leg showed significant improvements (pretest/posttest) for single-leg hop (138.30 cm/156.89 cm), triple crossover hop (370.05 cm/423.11 cm), and timed hop (2.21 s/1.99 s). Similarly, on the uninvolved leg, improvements were seen for the single-leg hop (159.30 cm/171.87 cm) and triple crossover hop (427.50 cm/471.27 cm). Overall mean limb symmetry improved across all 4 hop tests, but there was significant improvement only on the single-leg hop (87% pretest to 92% posttest). Patients younger than 18 years showed mean significant LSI improvement on the triple crossover hop. Utilizing an intensive 6-week NMR program after ACLR prior to return to sport can improve quantitative hop test measurements. Patients younger than 18 years had greater improvement than those 18 years and older. Advanced NMR programs can be successfully utilized in the postoperative ACLR setting to improve quantitative limb symmetry. © 2016 The Author(s).

Quantitative Improvements in Hop Test Scores After a 6-Week Neuromuscular Training Program

PubMed Central

Meierbachtol, Adam; Rohman, Eric; Paur, Eric; Bottoms, John; Tompkins, Marc

2016-01-01

Background: In patients who have undergone anterior cruciate ligament reconstruction (ACLR), the effect of neuromuscular re-education (NMR) programs on standard hop tests outcomes, including limb symmetry indices (LSIs), is unknown. Hypothesis: Both legs will show improvement in hop test–measured units after neuromuscular training, but the involved leg will show relatively greater improvement leading to improved limb symmetry. Patients younger than 18 years will show more improvement than patients who are older. Study Design: Retrospective cohort study. Level of Evidence: Level 3. Methods: Patients self-selected their participation in this NMR program, which was completed after traditional outpatient physical therapy. Pre– and post–hop test scores were recorded as the primary outcome measure. Results: Seventy-one patients met the inclusion criteria and completed hop testing. Overall, the involved leg showed significant improvements (pretest/posttest) for single-leg hop (138.30 cm/156.89 cm), triple crossover hop (370.05 cm/423.11 cm), and timed hop (2.21 s/1.99 s). Similarly, on the uninvolved leg, improvements were seen for the single-leg hop (159.30 cm/171.87 cm) and triple crossover hop (427.50 cm/471.27 cm). Overall mean limb symmetry improved across all 4 hop tests, but there was significant improvement only on the single-leg hop (87% pretest to 92% posttest). Patients younger than 18 years showed mean significant LSI improvement on the triple crossover hop. Conclusion: Utilizing an intensive 6-week NMR program after ACLR prior to return to sport can improve quantitative hop test measurements. Patients younger than 18 years had greater improvement than those 18 years and older. Clinical Relevance: Advanced NMR programs can be successfully utilized in the postoperative ACLR setting to improve quantitative limb symmetry. PMID:27620968

Analysis of several Boolean operation based trajectory generation strategies for automotive spray applications

NASA Astrophysics Data System (ADS)

Gao, Guoyou; Jiang, Chunsheng; Chen, Tao; Hui, Chun

2018-05-01

Industrial robots are widely used in various processes of surface manufacturing, such as thermal spraying. The established robot programming methods are highly time-consuming and not accurate enough to fulfil the demands of the actual market. There are many off-line programming methods developed to reduce the robot programming effort. This work introduces the principle of several based robot trajectory generation strategy on planar surface and curved surface. Since the off-line programming software is widely used and thus facilitates the robot programming efforts and improves the accuracy of robot trajectory, the analysis of this work is based on the second development of off-line programming software Robot studio™. To meet the requirements of automotive paint industry, this kind of software extension helps provide special functions according to the users defined operation parameters. The presented planning strategy generates the robot trajectory by moving an orthogonal surface according to the information of coating surface, a series of intersection curves are then employed to generate the trajectory points. The simulation results show that the path curve created with this method is successive and smooth, which corresponds to the requirements of automotive spray industrial applications.

A Glider-Assisted Link Disruption Restoration Mechanism in Underwater Acoustic Sensor Networks.

PubMed

Jin, Zhigang; Wang, Ning; Su, Yishan; Yang, Qiuling

2018-02-07

Underwater acoustic sensor networks (UASNs) have become a hot research topic. In UASNs, nodes can be affected by ocean currents and external forces, which could result in sudden link disruption. Therefore, designing a flexible and efficient link disruption restoration mechanism to ensure the network connectivity is a challenge. In the paper, we propose a glider-assisted restoration mechanism which includes link disruption recognition and related link restoring mechanism. In the link disruption recognition mechanism, the cluster heads collect the link disruption information and then schedule gliders acting as relay nodes to restore the disrupted link. Considering the glider's sawtooth motion, we design a relay location optimization algorithm with a consideration of both the glider's trajectory and acoustic channel attenuation model. The utility function is established by minimizing the channel attenuation and the optimal location of glider is solved by a multiplier method. The glider-assisted restoration mechanism can greatly improve the packet delivery rate and reduce the communication energy consumption and it is more general for the restoration of different link disruption scenarios. The simulation results show that glider-assisted restoration mechanism can improve the delivery rate of data packets by 15-33% compared with cooperative opportunistic routing (OVAR), the hop-by-hop vector-based forwarding (HH-VBF) and the vector based forward (VBF) methods, and reduce communication energy consumption by 20-58% for a typical network's setting.

A Glider-Assisted Link Disruption Restoration Mechanism in Underwater Acoustic Sensor Networks

PubMed Central

Wang, Ning; Su, Yishan; Yang, Qiuling

2018-01-01

Underwater acoustic sensor networks (UASNs) have become a hot research topic. In UASNs, nodes can be affected by ocean currents and external forces, which could result in sudden link disruption. Therefore, designing a flexible and efficient link disruption restoration mechanism to ensure the network connectivity is a challenge. In the paper, we propose a glider-assisted restoration mechanism which includes link disruption recognition and related link restoring mechanism. In the link disruption recognition mechanism, the cluster heads collect the link disruption information and then schedule gliders acting as relay nodes to restore the disrupted link. Considering the glider’s sawtooth motion, we design a relay location optimization algorithm with a consideration of both the glider’s trajectory and acoustic channel attenuation model. The utility function is established by minimizing the channel attenuation and the optimal location of glider is solved by a multiplier method. The glider-assisted restoration mechanism can greatly improve the packet delivery rate and reduce the communication energy consumption and it is more general for the restoration of different link disruption scenarios. The simulation results show that glider-assisted restoration mechanism can improve the delivery rate of data packets by 15–33% compared with cooperative opportunistic routing (OVAR), the hop-by-hop vector-based forwarding (HH-VBF) and the vector based forward (VBF) methods, and reduce communication energy consumption by 20–58% for a typical network’s setting. PMID:29414898

Hip-Hop to Health Jr. Obesity Prevention Effectiveness Trial: Post-Intervention Results

PubMed Central

Fitzgibbon, M. L.; Stolley, M. R.; Schiffer, L.; Braunschweig, C. L.; Gomez, S. L.; Van Horn, L.; Dyer, A.

2013-01-01

The preschool years offer an opportunity to interrupt the trajectory toward obesity in black children. The Hip-Hop to Health Jr. Obesity Prevention Effectiveness Trial was a group-randomized controlled trial assessing the feasibility and effectiveness of a teacher-delivered weight control intervention for black preschool children. The 618 participating children were enrolled in 18 schools administered by the Chicago Public Schools. Children enrolled in the 9 schools randomized to the intervention group received a 14-week weight control intervention delivered by their classroom teachers. Children in the 9 control schools received a general health intervention. Height and weight, physical activity, screen time, and diet data were collected at baseline and post-intervention. At post-intervention, children in the intervention schools engaged in more moderate-to vigorous physical activity than children in the control schools (difference between adjusted group means=7.46 min/day, p=.02). Also, children in the intervention group had less total screen time (−27.8 min/day, p=.05). There were no significant differences in BMI, BMI Z score, or dietary intake. It is feasible to adapt an obesity prevention program to be taught by classroom teachers. The intervention showed positive influences on physical activity and screen time, but not diet. Measuring diet and physical activity in preschool children remains a challenge, and interventions delivered by classroom teachers require both intensive initial training and ongoing individualized supervision. PMID:21193852

Hip-Hop to Health Jr. Obesity Prevention Effectiveness Trial: postintervention results.

PubMed

Fitzgibbon, Marian L; Stolley, Melinda R; Schiffer, Linda A; Braunschweig, Carol L; Gomez, Sandra L; Van Horn, Linda; Dyer, Alan R

2011-05-01

The preschool years offer an opportunity to interrupt the trajectory toward obesity in black children. The Hip-Hop to Health Jr. Obesity Prevention Effectiveness Trial was a group-randomized controlled trial assessing the feasibility and effectiveness of a teacher-delivered weight control intervention for black preschool children. The 618 participating children were enrolled in 18 schools administered by the Chicago Public Schools. Children enrolled in the nine schools randomized to the intervention group received a 14-week weight control intervention delivered by their classroom teachers. Children in the nine control schools received a general health intervention. Height and weight, physical activity, screen time, and diet data were collected at baseline and postintervention. At postintervention, children in the intervention schools engaged in more moderate-to-vigorous physical activity (MVPA) than children in the control schools (difference between adjusted group means = 7.46 min/day, P = 0.02). Also, children in the intervention group had less total screen time (-27.8 min/day, P = 0.05). There were no significant differences in BMI, BMI Z score, or dietary intake. It is feasible to adapt an obesity prevention program to be taught by classroom teachers. The intervention showed positive influences on physical activity and screen time, but not on diet. Measuring diet and physical activity in preschool children remains a challenge, and interventions delivered by classroom teachers require both intensive initial training and ongoing individualized supervision.

HopBase: a unified resource for Humulus genomics

PubMed Central

Hill, Steven T.; Sudarsanam, Ramcharan

2017-01-01

Abstract Hop (Humulus lupulus L. var lupulus) is a dioecious plant of worldwide significance, used primarily for bittering and flavoring in brewing beer. Studies on the medicinal properties of several unique compounds produced by hop have led to additional interest from pharmacy and healthcare industries as well as livestock production as a natural antibiotic. Genomic research in hop has resulted a published draft genome and transcriptome assemblies. As research into the genomics of hop has gained interest, there is a critical need for centralized online genomic resources. To support the growing research community, we report the development of an online resource "HopBase.org." In addition to providing a gene annotation to the existing Shinsuwase draft genome, HopBase makes available genome assemblies and annotations for both the cultivar “Teamaker” and male hop accession number USDA 21422M. These genome assemblies, gene annotations, along with other common data, coupled with a genome browser and BLAST database enable the hop community to enter the genomic age. The HopBase genomic resource is accessible at http://hopbase.org and http://hopbase.cgrb.oregonstate.edu. PMID:28415075

Surface adsorption and hopping cause probe-size-dependent microrheology of actin networks

NASA Astrophysics Data System (ADS)

He, Jun; Tang, Jay X.

2011-04-01

A network of filaments formed primarily by the abundant cytoskeletal protein actin gives animal cells their shape and elasticity. The rheological properties of reconstituted actin networks have been studied by tracking micron-sized probe beads embedded within the networks. We investigate how microrheology depends on surface properties of probe particles by varying the stickiness of their surface. For this purpose, we chose carboxylate polystyrene (PS) beads, silica beads, bovine serum albumin (BSA) -coated PS beads, and polyethylene glycol (PEG) -grafted PS beads, which show descending stickiness to actin filaments, characterized by confocal imaging and microrheology. Probe size dependence of microrheology is observed for all four types of beads. For the slippery PEG beads, particle-tracking microrheology detects weaker networks using smaller beads, which tend to diffuse through the network by hopping from one confinement “cage” to another. This trend is reversed for the other three types of beads, for which microrheology measures stiffer networks for smaller beads due to physisorption of nearby filaments to the bead surface. We explain the probe size dependence with two simple models. We also evaluate depletion effect near nonadsorption bead surface using quantitative image analysis and discuss the possible impact of depletion on microrheology. Analysis of these effects is necessary in order to accurately define the actin network rheology both in vitro and in vivo.

Field Trip 5: HYDROGEOLOGY OF BEER AND WINE IN THE YAKIMA VALLEY

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

Last, George V.; Bachmann, Matthew P.; Bjornstad, Bruce N.

The climate and geology of eastern Washington are ideally suited to the production of hops and wine grapes. Nearly all of Washington’s hop and wine-grape production is located in the lower Yakima River Basin , which is one of the most intensively irrigated areas in the United States. Most of this irrigation water has been supplied by surface water reservoirs and canal systems drawing from the Yakima River. However, increasing demands for water has spurred the increased use of groundwater resources. This field trip guide explores many aspects of the geology and hydrogeology in the lower Yakima River Basin, particularlymore » as they relate to water resources that support the local beer and wine industries.« less

Let Me Blow Your Mind: Hip Hop Feminist Futures in Theory and Praxis

ERIC Educational Resources Information Center

Lindsey, Treva B.

2015-01-01

This essay brings together key theoretical interventions in hip-hop feminism to explore the continued, but undervalued, significance of hip-hop feminism in urban education. More specifically, the essay challenges narrow conceptualizations of the "hip hop subject" as Black and male by using hip-hop feminist theory to incorporate the lived…

Variable range hopping in ZnO films

NASA Astrophysics Data System (ADS)

Ali, Nasir; Ghosh, Subhasis

2018-04-01

We report the variable range hopping in ZnO films grown by RF magnetron sputtering in different argon and oxygen partial pressure. It has been found that Mott variable range hopping dominant over Efros variable range hopping in all ZnO films. It also has been found that hopping distance and energy increases with increasing oxygen partial pressure.

Crustal Rock: Recorder of Oblique Impactor Meteoroid Trajectories

NASA Astrophysics Data System (ADS)

Ahrens, Thomas J.

2005-07-01

Oblique impact experiments in which 2g lead bullets strike samples of San Marcos granite and Bedford limestone at 1.2 km/s induce zones of increased crack density (termed shocked damage) which result in local decreases in bulk and shear moduli that results in maximum decreases of 30-40% in compressional and shear wave velocity (Budianski and O'Connell). Initial computer simulation of oblique impacts of meteorites (Pierazzo and Melosh) demonstrate the congruence of peak shock stress trajectory with the pre-impact meteoroid trajectory. We measure (Ai and Ahrens) via multi-beam (˜ 300) tomographic inversion, the sub-impact surface distribution of damage from the decreases in compressional wave velocity in the 20 x 20 x 15 cm rock target. The damage profiles for oblique impacts are markedly asymmetric (in plane of pre-impact meteoroid pre-impact trajectory) beneath the nearly round excavated craters. Thus, meteorite trajectory information can be recorded in planetary surfaces. Asymmetric sub-surface seismic velocity profiles beneath the Manson (Iowa) and Ries (Germany) impact craters demonstrate that pre-impact meteoroid trajectories records remain accessible for at least ˜ 10 ^ 8 years.

New insights into the nonadiabatic state population dynamics of model proton-coupled electron transfer reactions from the mixed quantum-classical Liouville approach

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

Shakib, Farnaz A.; Hanna, Gabriel, E-mail: gabriel.hanna@ualberta.ca

In a previous study [F. A. Shakib and G. Hanna, J. Chem. Phys. 141, 044122 (2014)], we investigated a model proton-coupled electron transfer (PCET) reaction via the mixed quantum-classical Liouville (MQCL) approach and found that the trajectories spend the majority of their time on the mean of two coherently coupled adiabatic potential energy surfaces. This suggested a need for mean surface evolution to accurately simulate observables related to ultrafast PCET processes. In this study, we simulate the time-dependent populations of the three lowest adiabatic states in the ET-PT (i.e., electron transfer preceding proton transfer) version of the same PCET modelmore » via the MQCL approach and compare them to the exact quantum results and those obtained via the fewest switches surface hopping (FSSH) approach. We find that the MQCL population profiles are in good agreement with the exact quantum results and show a significant improvement over the FSSH results. All of the mean surfaces are shown to play a direct role in the dynamics of the state populations. Interestingly, our results indicate that the population transfer to the second-excited state can be mediated by dynamics on the mean of the ground and second-excited state surfaces, as part of a sequence of nonadiabatic transitions that bypasses the first-excited state surface altogether. This is made possible through nonadiabatic transitions between different mean surfaces, which is the manifestation of coherence transfer in MQCL dynamics. We also investigate the effect of the strength of the coupling between the proton/electron and the solvent coordinate on the state population dynamics. Drastic changes in the population dynamics are observed, which can be understood in terms of the changes in the potential energy surfaces and the nonadiabatic couplings. Finally, we investigate the state population dynamics in the PT-ET (i.e., proton transfer preceding electron transfer) and concerted versions of the model. The PT-ET results confirm the participation of all of the mean surfaces, albeit in different proportions compared to the ET-PT case, while the concerted results indicate that the mean of the ground- and first-excited state surfaces only plays a role, due to the large energy gaps between the ground- and second-excited state surfaces.« less

Featherless Dinosaurs and the Hip-Hop Simulacrum: Reconsidering Hip-Hop's Appropriateness for the Music Classroom

ERIC Educational Resources Information Center

Kruse, Adam J.

2016-01-01

This article offers considerations for music teachers interested in including hip-hop music in their classrooms but who might feel concerned with or overwhelmed by issues of appropriateness. Two concerns related to hip-hop music are examined: language and negative social themes. Commercial interests in hip-hop music have created a simulacrum (or…

The Formation of "Hip-Hop Academicus"--How American Scholars Talk about the Academisation of Hip-Hop

ERIC Educational Resources Information Center

Soderman, Johan

2013-01-01

Social activism and education have been associated with hip-hop since it emerged in New York City 38 years ago. Therefore, it might not be surprising that universities have become interested in hip-hop. This article aims to highlight this "hip-hop academisation" and analyse the discursive mechanisms that manifest in these academisation…

Hip-hop as a resource for understanding the urban context

NASA Astrophysics Data System (ADS)

Brown, Bryan

2010-06-01

This review explores Edmin's "Science education for the hip-hop generation" by documenting how he frames hip-hop as a means to access urban student culture. He argues that hip-hop is more than a mere music genre, but rather a culture that provides young people with ways of connecting to the world. Two primary ideas emerged as central to his work. First, he contends that students develop communal relationships and collective identities based on the common experiences expressed in hip-hop. Second, he identifies how the conscious recognition of institutional oppression serves a central feature in urban schools. Emdin's rich, and personal call for a greater understanding of hip-hop culture provides the text with an unmatched strength. He skillfully uses personal narratives from his own experience as well as quotes and references from hip-hop songs to make the nuances of hip hop transparent to science educators. Conversely, the limitation of this text is found in its unfulfilled promise to provide pragmatic examples of how to engage in a hip-hop based science education. Emdin's work is ultimately valuable as it extends our current knowledge about urban students and hip-hop in meaningful ways.

Mechanisms of Hop Inhibition Include the Transmembrane Redox Reaction▿

PubMed Central

Behr, Jürgen; Vogel, Rudi F.

2010-01-01

In this work, a novel mechanistic model of hop inhibition beyond the proton ionophore action toward (beer spoiling) bacteria was developed. Investigations were performed with model systems using cyclic voltammetry for the determination of redox processes/conditions in connection with growth challenges with hop-sensitive and -resistant Lactobacillus brevis strains in the presence of oxidants. Cyclic voltammetry identified a transmembrane redox reaction of hop compounds at low pH (common in beer) and in the presence of manganese (present in millimolar levels in lactic acid bacteria). The antibacterial action of hop compounds could be extended from the described proton ionophore activity, lowering the intracellular pH, to pronounced redox reactivity, causing cellular oxidative damage. Accordingly, a correlation between the resistance of L. brevis strains to a sole oxidant to their resistance to hop could not be expected and was not detected. However, in connection with our recent study concerning hop ionophore properties and the resistance of hop-sensitive and -tolerant L. brevis strains toward proton ionophores (J. Behr and R. F. Vogel, J. Agric. Food Chem. 57:6074-6081, 2009), we suggest that both ionophore and oxidant resistance are required for survival under hop stress conditions and confirmed this correlation according to the novel mechanistic model. In consequence, the expression of several published hop resistance mechanisms involved in manganese binding/transport and intracellular redox balance, as well as that of proteins involved in oxidative stress under “highly reducing” conditions (cf. anaerobic cultivation and “antioxidative” hop compounds in the growth medium), is now comprehensible. Accordingly, hop resistance as a multifactorial dynamic property at least implies distinct resistance levels against two different mechanisms of hop inhibition, namely, proton ionophore-induced and oxidative stress-induced mechanisms. Beyond this specific model of hop inhibition, these investigations provide general insight on the role of electrophysiology and ion homeostasis in bacterial stress responses to membrane-active drugs. PMID:19880646

Starting with Style: Toward a Second Wave of Hip-Hop Education Research and Practice

ERIC Educational Resources Information Center

Petchauer, Emery

2015-01-01

One fundamental breakthrough in the field of hip-hop education in recent years is the shift from understanding hip-hop solely as content to understanding hip-hop also as aesthetic form. In this article, I chart the roots of this shift across disciplines and focus on what it might mean for the future of hip-hop education, pedagogy, and research in…

Landing Mechanics During Side Hopping and Crossover Hopping Maneuvers in Noninjured Women and Women With Anterior Cruciate Ligament Reconstruction

PubMed Central

Ortiz, Alexis; Olson, Sharon; Trudelle-Jackson, Elaine; Rosario, Martin; Venegas, Heidi L.

2011-01-01

Objective To compare, landing mechanics and electromyographic activity of the lower extremities during side hopping and crossover hopping maneuvers, in noninjured women and women with anterior cruciate ligament (ACL) reconstruction. Design A case-control study. Setting A 3-dimensional motion analysis laboratory. Participants Twenty-eight young women (range, 21–35 years) (15 control subjects and 13 subjects with ACL reconstruction). Patients and Methods All participants performed a side-to-side hopping task that consisted of hopping single-legged 10 times consecutively from side to side across 2 lines marked 30 cm apart on 2 individual force plates. The task was designated as a side hopping when the hop was to the opposite side of the stance leg and as crossover hopping when the hop was toward the side of the stance leg. Main Outcome Measurements Peak hip-/knee-joint angles; peak knee extension/abduction joint moments; electromyographic studies of the gluteus maximus, gluteus medius, rectus femoris, and hamstring muscles; and quadriceps/hamstring co-contraction ratio were compared between the groups by means of 2 × 2 multivariate analysis of variance tests (group × maneuver). Results Noninjured women and women with ACL reconstruction exhibited similar hip-and knee-joint angles during both types of hopping. Hip-joint angles were greater during the crossover hopping in both groups, and knee-joint angles did not differ between the groups or hops. Knee-joint moments demonstrated a significant group × maneuver interaction. Greater knee extension and valgus moments were noted in the control group during crossover hopping, and greater knee abduction moments were noted in the ACL group during side hopping. Electromyographic data revealed no statistically significantly differences between the groups. Conclusions Women with ACL reconstruction exhibited the restoration of functional biomechanical movements such as hip-/knee-joint angles and lower extremity neuromuscular activation during side-to-side athletic tasks. However, not all biomechanical strategies are restored years after surgery, and women who have undergone a procedure such as ACL reconstruction may continue to exhibit knee-joint abduction moments that increase the risk of additional knee injury. PMID:21257128

Explicit Two-Phase Modeling of the Initiation of Saltation over Heterogeneous Sand Beds

NASA Astrophysics Data System (ADS)

Turney, F. A.; Kok, J. F.; Martin, R. L.; Burr, D. M.; Bridges, N.; Ortiz, C. P.; Smith, J. K.; Emery, J. P.; Van Lew, J. T.

2016-12-01

The initiation of aeolian sediment transport is key in understanding the geomorphology of arid landscapes and emission of mineral dust into the atmosphere. Despite its importance, the process of saltation initiation remains poorly understood, and current models are highly simplified. Previous models of the initiation of aeolian saltation have assumed the particle bed to be monodisperse and homogeneous in arrangement, ignoring the distribution of particle thresholds created by different bed geometries and particle sizes. In addition, mean wind speeds are often used in place of a turbulent wind field, ignoring the distribution of wind velocities at the particle level. Furthermore, the transition from static bed to steady state saltation is often modeled as resulting directly from fluid lifting, while in reality particles need to hop and roll along the surface before attaining enough height and momentum to initiate the cascade of particle splashes that characterizes saltation. We simulate the initiation of saltation with a coupled two-phase CFD-DEM model that overcomes the shortcomings of previous models by explicitly modeling particle-particle and particle-fluid interactions at the particle scale. We constrain our model against particle trajectories taken from high speed video of initiation at the Titan Wind Tunnel at NASA Ames. Results give us insight into the probability that saltation will be initiated, given stochastic variations in bed properties and wind velocity.

High-Speed On-Board Data Processing for Science Instruments: HOPS

NASA Technical Reports Server (NTRS)

Beyon, Jeffrey

2015-01-01

The project called High-Speed On-Board Data Processing for Science Instruments (HOPS) has been funded by NASA Earth Science Technology Office (ESTO) Advanced Information Systems Technology (AIST) program during April, 2012 â€" April, 2015. HOPS is an enabler for science missions with extremely high data processing rates. In this three-year effort of HOPS, Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) and 3-D Winds were of interest in particular. As for ASCENDS, HOPS replaces time domain data processing with frequency domain processing while making the real-time on-board data processing possible. As for 3-D Winds, HOPS offers real-time high-resolution wind profiling with 4,096-point fast Fourier transform (FFT). HOPS is adaptable with quick turn-around time. Since HOPS offers reusable user-friendly computational elements, its FPGA IP Core can be modified for a shorter development period if the algorithm changes. The FPGA and memory bandwidth of HOPS is 20 GB/sec while the typical maximum processor-to-SDRAM bandwidth of the commercial radiation tolerant high-end processors is about 130-150 MB/sec. The inter-board communication bandwidth of HOPS is 4 GB/sec while the effective processor-to-cPCI bandwidth of commercial radiation tolerant high-end boards is about 50-75 MB/sec. Also, HOPS offers VHDL cores for the easy and efficient implementation of ASCENDS and 3-D Winds, and other similar algorithms. A general overview of the 3-year development of HOPS is the goal of this presentation.

Sufficient Amounts of Functional HOP2/MND1 Complex Promote Interhomolog DNA Repair but Are Dispensable for Intersister DNA Repair during Meiosis in Arabidopsis[W

PubMed Central

Uanschou, Clemens; Ronceret, Arnaud; Von Harder, Mona; De Muyt, Arnaud; Vezon, Daniel; Pereira, Lucie; Chelysheva, Liudmila; Kobayashi, Wataru; Kurumizaka, Hitoshi; Schlögelhofer, Peter; Grelon, Mathilde

2013-01-01

During meiosis, homologous recombination (HR) is essential to repair programmed DNA double-strand breaks (DSBs), and a dedicated protein machinery ensures that the homologous chromosome is favored over the nearby sister chromatid as a repair template. The HOMOLOGOUS-PAIRING PROTEIN2/MEIOTIC NUCLEAR DIVISION PROTEIN1 (HOP2/MND1) protein complex has been identified as a crucial factor of meiotic HR in Arabidopsis thaliana, since loss of either MND1 or HOP2 results in failure of DNA repair. We isolated two mutant alleles of HOP2 (hop2-2 and hop2-3) that retained the capacity to repair meiotic DSBs via the sister chromatid but failed to use the homologous chromosome. We show that in these alleles, the recombinases RADIATION SENSITIVE51 (RAD51) and DISRUPTED MEIOTIC cDNA1 (DMC1) are loaded, but only the intersister DNA repair pathway is activated. The hop2-2 phenotype is correlated with a decrease in HOP2/MND1 complex abundance. In hop2-3, a truncated HOP2 protein is produced that retains its ability to bind to DMC1 and DNA but forms less stable complexes with MND1 and fails to efficiently stimulate DMC1-driven D-loop formation. Genetic analyses demonstrated that in the absence of DMC1, HOP2/MND1 is dispensable for RAD51-mediated intersister DNA repair, while in the presence of DMC1, a minimal amount of functional HOP2/MND1 is essential to drive intersister DNA repair. PMID:24363313

Triton Hopper: Exploring Neptune's Captured Kuiper Belt Object

NASA Technical Reports Server (NTRS)

Oleson, Steve; Landis, Geoffrey

2018-01-01

Neptune's moon Triton is a fascinating object, a dynamic moon with an atmosphere, and geysers. Triton is unique in the outer solar system in that it is most likely a captured Kuiper belt object (KBO), a leftover building block of the solar system. When Voyager flew by it was the coldest body yet found in our solar system (33 degrees Kelvin) and had volcanic activity, geysers, and a thin atmosphere. It is covered in ices made from nitrogen, water, and carbon-dioxide, and shows surface deposits of tholins, organic compounds that may be precursor chemicals to the origin of life. Exploring Triton will be a challenge well beyond anything done in previous missions; but the unique environment of Triton also allows some new possibilities for mobility. We developed a conceptual design of a Triton Hopping probe that both analyzes the surface and collects it for use to propel its hops. The Hopper would land near the South Pole in 2040 where geysers have been detected. Depending the details of propulsion chosen the Hopper should be able to jump over 300 kilometers in 60 hops or less, exploring the surface and thin atmosphere on its way. This craft will autonomously carry out detailed scientific investigations on the surface, below the surface (drilling) and in the upper atmosphere to provide unprecedented knowledge of a KBO-turned moon and expanding NASA's existing capabilities in deep space planetary exploration to include Hoppers using different ices for propellant. Triton is roughly 2700 kilometers in diameter with a surface of mostly frozen nitrogen, mostly water ice crust and core of metal and rock. Its gravity is half that of Earth's Moon and its atmosphere is 170,000th of Earth's or 0.3 of Mars.The mission concept studied investigated the full surface and atmospheric phenomenon: chemical composition of surface and near subsurface materials, the thin atmosphere, volcanic and geyser activity. Measurements of all these aspects of Triton's unique environment can only be made through focused in-situ exploration with a well-instrumented craft. And this craft will be provided revolutionary mobility, nearly global, using in-situ ices as propellants. While other concepts have looked at gathering gases at Mars to propel a hopper, long periods of time are needed to gather the thin CO2 atmosphere. Several gases, mainly nitrogen are on the surface in a readily dense ice form and just need to be picked up, vaporized and used for propellant.

Hopping Robot with Wheels

NASA Technical Reports Server (NTRS)

Barlow, Edward; Marzwell, Nevellie; Fuller, Sawyer; Fionni, Paolo; Tretton, Andy; Burdick, Joel; Schell, Steve

2003-01-01

A small prototype mobile robot is capable of (1) hopping to move rapidly or avoid obstacles and then (2) moving relatively slowly and precisely on the ground by use of wheels in the manner of previously reported exploratory robots of the "rover" type. This robot is a descendant of a more primitive hopping robot described in "Minimally Actuated Hopping Robot" (NPO- 20911), NASA Tech Briefs, Vol. 26, No. 11 (November 2002), page 50. There are many potential applications for robots with hopping and wheeled-locomotion (roving) capabilities in diverse fields of endeavor, including agriculture, search-and-rescue operations, general military operations, removal or safe detonation of land mines, inspection, law enforcement, and scientific exploration on Earth and remote planets. The combination of hopping and roving enables this robot to move rapidly over very rugged terrain, to overcome obstacles several times its height, and then to position itself precisely next to a desired target. Before a long hop, the robot aims itself in the desired hopping azimuth and at a desired takeoff angle above horizontal. The robot approaches the target through a series of hops and short driving operations utilizing the steering wheels for precise positioning.

Disruption of prion protein-HOP engagement impairs glioblastoma growth and cognitive decline and improves overall survival.

PubMed

Lopes, M H; Santos, T G; Rodrigues, B R; Queiroz-Hazarbassanov, N; Cunha, I W; Wasilewska-Sampaio, A P; Costa-Silva, B; Marchi, F A; Bleggi-Torres, L F; Sanematsu, P I; Suzuki, S H; Oba-Shinjo, S M; Marie, S K N; Toulmin, E; Hill, A F; Martins, V R

2015-06-01

Glioblastomas (GBMs) are resistant to current therapy protocols and identification of molecules that target these tumors is crucial. Interaction of secreted heat-shock protein 70 (Hsp70)-Hsp90-organizing protein (HOP) with cellular prion protein (PrP(C)) triggers a large number of trophic effects in the nervous system. We found that both PrP(C) and HOP are highly expressed in human GBM samples relative to non-tumoral tissue or astrocytoma grades I-III. High levels of PrP(C) and HOP were associated with greater GBM proliferation and lower patient survival. HOP-PrP(C) binding increased GBM proliferation in vitro via phosphatidylinositide 3-kinase and extracellular-signal-regulated kinase pathways, and a HOP peptide mimicking the PrP(C) binding site (HOP230-245) abrogates this effect. PrP(C) knockdown impaired tumor growth and increased survival of mice with tumors. In mice, intratumor delivery of HOP230-245 peptide impaired proliferation and promoted apoptosis of GBM cells. In addition, treatment with HOP230-245 peptide inhibited tumor growth, maintained cognitive performance and improved survival. Thus, together, the present results indicate that interfering with PrP(C)-HOP engagement is a promising approach for GBM therapy.

Association of Quadriceps Strength and Psychosocial Factors With Single-Leg Hop Performance in Patients With Meniscectomy.

PubMed

Hsu, Chao-Jung; George, Steven Z; Chmielewski, Terese L

2016-12-01

Clinicians use the single-leg hop test to assess readiness for return to sports after knee injury. Few studies have reported the results of single-leg hop testing after meniscectomy. Additionally, the contributions of impairments in quadriceps strength and psychosocial factors to single-leg hop performance are unknown. To compare single-leg hop performance (distance and landing mechanics) between limbs and to examine the association of single-leg hop performance with quadriceps strength and psychosocial factors in patients with meniscectomy. Descriptive laboratory study. A total of 22 subjects who underwent meniscectomy for traumatic meniscal tears received either standard rehabilitation alone or with additional quadriceps strengthening. Testing was conducted immediately postrehabilitation and at 1 year postsurgery. A single-leg hop test was performed bilaterally, and hop distance was used to create a hop symmetry index. Landing mechanics (peak knee flexion angle, knee extension moment, and peak vertical ground-reaction force) were analyzed with a motion-capture system and a force plate. An isokinetic dynamometer (60 deg/s) assessed knee extensor peak torque and rate of torque development (RTD 0-200ms and RTD 0-peak torque ). Questionnaires assessed fear of reinjury (Tampa Scale for Kinesiophobia [TSK-11]) and self-efficacy (Knee Activity Self-Efficacy [KASE]). Rehabilitation groups did not significantly differ in single-leg hop performance; therefore, groups were combined for further analyses. The mean hop symmetry index was 88.6% and 98.9% at postrehabilitation and 1 year postsurgery, respectively. Compared with the nonsurgical limb, the surgical limb showed decreased peak knee flexion angle at postrehabilitation and decreased knee extension moment at 1 year postsurgery. The hop symmetry index was positively associated with peak torque, RTD 0-200ms , and the KASE score at postrehabilitation. Moreover, at postrehabilitation, the peak knee flexion angle was positively associated with peak torque and RTD 0-200ms , and the knee extension moment was positively associated with RTD 0-200ms . At 1 year postsurgery, peak knee flexion angle and knee extension moment were both positively associated with peak torque, RTD 0-200ms , and RTD 0-peak torque . Although the hop symmetry index could be considered satisfactory for returning to sports, asymmetries in landing mechanics still exist in the first year postmeniscectomy. Greater quadriceps strength was associated with greater single-leg hop distance and better landing mechanics at both postrehabilitation and 1 year postsurgery. Knee activity self-efficacy was the only psychosocial factor associated with single-leg hop performance and isolated to a positive association with single-leg hop distance at postrehabilitation. Rate of development is not typically measured in the clinic but can be an additional quadriceps measure to monitor for single-leg hop performance. Quadriceps strength and psychosocial factors appear to have separate influence on single-leg hop performance after meniscectomy, which has implications for developing appropriate interventions for optimal single-leg hop performance.

Association of Quadriceps Strength and Psychosocial Factors With Single-Leg Hop Performance in Patients With Meniscectomy

PubMed Central

Hsu, Chao-Jung; George, Steven Z.; Chmielewski, Terese L.

2016-01-01

Background: Clinicians use the single-leg hop test to assess readiness for return to sports after knee injury. Few studies have reported the results of single-leg hop testing after meniscectomy. Additionally, the contributions of impairments in quadriceps strength and psychosocial factors to single-leg hop performance are unknown. Purpose: To compare single-leg hop performance (distance and landing mechanics) between limbs and to examine the association of single-leg hop performance with quadriceps strength and psychosocial factors in patients with meniscectomy. Study Design: Descriptive laboratory study. Methods: A total of 22 subjects who underwent meniscectomy for traumatic meniscal tears received either standard rehabilitation alone or with additional quadriceps strengthening. Testing was conducted immediately postrehabilitation and at 1 year postsurgery. A single-leg hop test was performed bilaterally, and hop distance was used to create a hop symmetry index. Landing mechanics (peak knee flexion angle, knee extension moment, and peak vertical ground-reaction force) were analyzed with a motion-capture system and a force plate. An isokinetic dynamometer (60 deg/s) assessed knee extensor peak torque and rate of torque development (RTD0-200ms and RTD0–peak torque). Questionnaires assessed fear of reinjury (Tampa Scale for Kinesiophobia [TSK-11]) and self-efficacy (Knee Activity Self-Efficacy [KASE]). Results: Rehabilitation groups did not significantly differ in single-leg hop performance; therefore, groups were combined for further analyses. The mean hop symmetry index was 88.6% and 98.9% at postrehabilitation and 1 year postsurgery, respectively. Compared with the nonsurgical limb, the surgical limb showed decreased peak knee flexion angle at postrehabilitation and decreased knee extension moment at 1 year postsurgery. The hop symmetry index was positively associated with peak torque, RTD0-200ms, and the KASE score at postrehabilitation. Moreover, at postrehabilitation, the peak knee flexion angle was positively associated with peak torque and RTD0-200ms, and the knee extension moment was positively associated with RTD0-200ms. At 1 year postsurgery, peak knee flexion angle and knee extension moment were both positively associated with peak torque, RTD0-200ms, and RTD0–peak torque. Conclusion: Although the hop symmetry index could be considered satisfactory for returning to sports, asymmetries in landing mechanics still exist in the first year postmeniscectomy. Greater quadriceps strength was associated with greater single-leg hop distance and better landing mechanics at both postrehabilitation and 1 year postsurgery. Knee activity self-efficacy was the only psychosocial factor associated with single-leg hop performance and isolated to a positive association with single-leg hop distance at postrehabilitation. Clinical Relevance: Rate of development is not typically measured in the clinic but can be an additional quadriceps measure to monitor for single-leg hop performance. Quadriceps strength and psychosocial factors appear to have separate influence on single-leg hop performance after meniscectomy, which has implications for developing appropriate interventions for optimal single-leg hop performance. PMID:28210647

Routing protocol for wireless quantum multi-hop mesh backbone network based on partially entangled GHZ state

NASA Astrophysics Data System (ADS)

Xiong, Pei-Ying; Yu, Xu-Tao; Zhang, Zai-Chen; Zhan, Hai-Tao; Hua, Jing-Yu

2017-08-01

Quantum multi-hop teleportation is important in the field of quantum communication. In this study, we propose a quantum multi-hop communication model and a quantum routing protocol with multihop teleportation for wireless mesh backbone networks. Based on an analysis of quantum multi-hop protocols, a partially entangled Greenberger-Horne-Zeilinger (GHZ) state is selected as the quantum channel for the proposed protocol. Both quantum and classical wireless channels exist between two neighboring nodes along the route. With the proposed routing protocol, quantum information can be transmitted hop by hop from the source node to the destination node. Based on multi-hop teleportation based on the partially entangled GHZ state, a quantum route established with the minimum number of hops. The difference between our routing protocol and the classical one is that in the former, the processes used to find a quantum route and establish quantum channel entanglement occur simultaneously. The Bell state measurement results of each hop are piggybacked to quantum route finding information. This method reduces the total number of packets and the magnitude of air interface delay. The deduction of the establishment of a quantum channel between source and destination is also presented here. The final success probability of quantum multi-hop teleportation in wireless mesh backbone networks was simulated and analyzed. Our research shows that quantum multi-hop teleportation in wireless mesh backbone networks through a partially entangled GHZ state is feasible.

Scheduling with hop-by-hop priority increasing in meshed optical burst-switched network

NASA Astrophysics Data System (ADS)

Chang, Hao; Luo, Jiangtao; Zhang, Zhizhong; Xia, Da; Gong, Jue

2006-09-01

In OBS, JET (Just-Enough-Time) is the classical wavelength reservation scheme. But there is a phenomenon that the burst priority decreasing hop-by-hop in multi-hop networks that will waste the bandwidth that was used in the upstream. Based on the HPI (Hop-by-hop Priority Increasing) proposed in the former research, this paper will do an unprecedented simulation in 4×4 meshed topology, which is closer to the real network environment with the help of a NS2-based OBSN simulation platform constructed by ourselves. By contrasting, the drop probability and throughput on one of the longest end-to-end path lengths in the whole networks, it shows that the HPI scheme can improve the utilance of bandwidth better.

Is scaffold hopping a reliable indicator for the ability of computational methods to identify structurally diverse active compounds?

NASA Astrophysics Data System (ADS)

Dimova, Dilyana; Bajorath, Jürgen

2017-07-01

Computational scaffold hopping aims to identify core structure replacements in active compounds. To evaluate scaffold hopping potential from a principal point of view, regardless of the computational methods that are applied, a global analysis of conventional scaffolds in analog series from compound activity classes was carried out. The majority of analog series was found to contain multiple scaffolds, thus enabling the detection of intra-series scaffold hops among closely related compounds. More than 1000 activity classes were found to contain increasing proportions of multi-scaffold analog series. Thus, using such activity classes for scaffold hopping analysis is likely to overestimate the scaffold hopping (core structure replacement) potential of computational methods, due to an abundance of artificial scaffold hops that are possible within analog series.

Different surface sensing of the cell body and nucleus in healthy primary cells and in a cancerous cell line on nanogrooves.

PubMed

Davidson, Patricia M; Bigerelle, Maxence; Reiter, Günter; Anselme, Karine

2015-10-01

Cancer cells are known to have alterations compared to healthy cells, but can these differences extend to the way cells interact with their environment? Here, the authors focused on the alignment on an array of grooves of nanometer depth using two cell types: healthy osteoprogenitor primary cells (HOP) and a cancerous osteosarcoma (SaOs-2) cell line. Another concern was how this alignment affects the cell's interior, namely, the nucleus. Based on the results, it is proposed that these two cell types respond to different size regimes: SaOs-2 cells are more sensitive to shallow grooves while HOP cells are strongly aligned with deep grooves. As a measure of the impact of cell alignment on the nucleus the orientation and elongation of the nucleus were determined. Compared to HOP cells, the cell nucleus of SaOs-2 cells is more aligned and elongated in response to grooves, suggesting a softer nucleus and/or increased force transmission. These results support the hypothesis that cancer cells have reduced nucleus rigidity compared to healthy ones and further indicate differences in sensing, which may be important during metastasis.

Hop crop wild relatives

USDA-ARS?s Scientific Manuscript database

The versatile hop plant, Humulus L., is a climbing, vine with a perennial root. The genus includes three species, H. japonicus, H. lupulus, and H. yunnanensis. The European hops (H. lupulus) is the species of primary economic importance from which most hop cultivars have been selected. This species ...

Quantifying exciton hopping in disordered media with quenching sites: Application to arrays of quantum dots

NASA Astrophysics Data System (ADS)

Miyazaki, Jun

2013-10-01

We present an analytical method for quantifying exciton hopping in an energetically disordered system with quenching sites. The method is subsequently used to provide a quantitative understanding of exciton hopping in a quantum dot (QD) array. Several statistical quantities that characterize the dynamics (survival probability, average number of distinct sites visited, average hopping distance, and average hopping rate in the initial stage) are obtained experimentally by measuring time-resolved fluorescence intensities at various temperatures. The time evolution of these quantities suggests in a quantitative way that at low temperature an exciton tends to be trapped at a local low-energy site, while at room temperature, exciton hopping occurs repeatedly, leading to a large hopping distance. This method will serve to facilitate highly efficient optoelectronic devices using QDs such as photovoltaic cells and light-emitting diodes, since exciton hopping is considered to strongly influence their operational parameters. The presence of a dark QD (quenching site) that exhibits fast decay is also quantified.

The impact of hop bitter acid and polyphenol profiles on the perceived bitterness of beer.

PubMed

Oladokun, Olayide; Tarrega, Amparo; James, Sue; Smart, Katherine; Hort, Joanne; Cook, David

2016-08-15

Thirty-four commercial lager beers were analysed for their hop bitter acid, phenolic acid and polyphenol contents. Based on analytical data, it was evident that the beers had been produced using a range of different raw materials and hopping practices. Principal Components Analysis was used to select a sub-set of 10 beers that contained diverse concentrations of the analysed bitter compounds. These beers were appraised sensorially to determine the impacts of varying hop acid and polyphenolic profiles on perceived bitterness character. Beers high in polyphenol and hop acid contents were perceived as having 'harsh' and 'progressive' bitterness, whilst beers that had evidently been conventionally hopped were 'sharp' and 'instant' in their bitterness. Beers containing light-stable hop products (tetrahydro-iso-α-acids) were perceived as 'diminishing', 'rounded' and 'acidic' in bitterness. The hopping strategy adopted by brewers impacts on the nature, temporal profile and intensity of bitterness perception in beer. Copyright © 2016 Elsevier Ltd. All rights reserved.

DOW-PR DOlphin and Whale Pods Routing Protocol for Underwater Wireless Sensor Networks (UWSNs).

PubMed

Wadud, Zahid; Ullah, Khadem; Hussain, Sajjad; Yang, Xiaodong; Qazi, Abdul Baseer

2018-05-12

Underwater Wireless Sensor Networks (UWSNs) have intrinsic challenges that include long propagation delays, high mobility of sensor nodes due to water currents, Doppler spread, delay variance, multipath, attenuation and geometric spreading. The existing Weighting Depth and Forwarding Area Division Depth Based Routing (WDFAD-DBR) protocol considers the weighting depth of the two hops in order to select the next Potential Forwarding Node (PFN). To improve the performance of WDFAD-DBR, we propose DOlphin and Whale Pod Routing protocol (DOW-PR). In this scheme, we divide the transmission range into a number of transmission power levels and at the same time select the next PFNs from forwarding and suppressed zones. In contrast to WDFAD-DBR, our scheme not only considers the packet upward advancement, but also takes into account the number of suppressed nodes and number of PFNs at the first and second hops. Consequently, reasonable energy reduction is observed while receiving and transmitting packets. Moreover, our scheme also considers the hops count of the PFNs from the sink. In the absence of PFNs, the proposed scheme will select the node from the suppressed region for broadcasting and thus ensures minimum loss of data. Besides this, we also propose another routing scheme (whale pod) in which multiple sinks are placed at water surface, but one sink is embedded inside the water and is physically connected with the surface sink through high bandwidth connection. Simulation results show that the proposed scheme has high Packet Delivery Ratio (PDR), low energy tax, reduced Accumulated Propagation Distance (APD) and increased the network lifetime.

DOW-PR DOlphin and Whale Pods Routing Protocol for Underwater Wireless Sensor Networks (UWSNs)

PubMed Central

Wadud, Zahid; Ullah, Khadem; Hussain, Sajjad; Yang, Xiaodong; Qazi, Abdul Baseer

2018-01-01

Underwater Wireless Sensor Networks (UWSNs) have intrinsic challenges that include long propagation delays, high mobility of sensor nodes due to water currents, Doppler spread, delay variance, multipath, attenuation and geometric spreading. The existing Weighting Depth and Forwarding Area Division Depth Based Routing (WDFAD-DBR) protocol considers the weighting depth of the two hops in order to select the next Potential Forwarding Node (PFN). To improve the performance of WDFAD-DBR, we propose DOlphin and Whale Pod Routing protocol (DOW-PR). In this scheme, we divide the transmission range into a number of transmission power levels and at the same time select the next PFNs from forwarding and suppressed zones. In contrast to WDFAD-DBR, our scheme not only considers the packet upward advancement, but also takes into account the number of suppressed nodes and number of PFNs at the first and second hops. Consequently, reasonable energy reduction is observed while receiving and transmitting packets. Moreover, our scheme also considers the hops count of the PFNs from the sink. In the absence of PFNs, the proposed scheme will select the node from the suppressed region for broadcasting and thus ensures minimum loss of data. Besides this, we also propose another routing scheme (whale pod) in which multiple sinks are placed at water surface, but one sink is embedded inside the water and is physically connected with the surface sink through high bandwidth connection. Simulation results show that the proposed scheme has high Packet Delivery Ratio (PDR), low energy tax, reduced Accumulated Propagation Distance (APD) and increased the network lifetime. PMID:29757208

DIFFERENTIAL DIAGNOSTIC PROCESS AND CLINICAL DECISION MAKING IN A YOUNG ADULT FEMALE WITH LATERAL HIP PAIN: A CASE REPORT.

PubMed

Livingston, Jennifer I; Deprey, Sara M; Hensley, Craig P

2015-10-01

differential diagnosis and clinical decision making. Young adults with lateral hip pain are often referred to physical therapy (PT). A thorough examination is required to obtain a diagnosis and guide management. The purpose of this case report is to describe the physical therapist's differential diagnostic process and clinical decision making for a subject with the referring diagnosis of trochanteric bursitis. A 29-year-old female presented to PT with limited sitting and running tolerance secondary to right lateral hip pain. Her symptoms began three months prior when she abruptly changed her running intensity and frequency of weight bearing activities, including running and low impact plyometrics for the lower extremity. Physical examination revealed a positive Trendelenburg sign, manual muscle test that was weak and painless of the right hip abductors, and pain elicited when performing a vertical hop on a concrete surface (+single leg hop test), but pain-free when performing the same single leg hop on a foam surface. Examination findings warranted discussion with the referring physician for further diagnostic imaging. Magnetic resonance imaging revealed a focus of edema in the posterior acetabulum, suspicious for an acetabular stress fracture. The subject was subsequently diagnosed with an acetabular stress fracture and restricted from running and plyometrics for four weeks. Thorough examination and appropriate clinical decision making by the physical therapist at the initial examination led to the diagnosis of an acetabular stress fracture in this subject. Clinicians must be aware of symptoms and signs which place the subject at risk for stress fracture for timely referral and management. 4.

Quantum trajectories in elastic atom-surface scattering: threshold and selective adsorption resonances.

PubMed

Sanz, A S; Miret-Artés, S

2005-01-01

The elastic resonant scattering of He atoms off the Cu(117) surface is fully described with the formalism of quantum trajectories provided by Bohmian mechanics. Within this theory of quantum motion, the concept of trapping is widely studied and discussed. Classically, atoms undergo impulsive collisions with the surface, and then the trapped motion takes place covering at least two consecutive unit cells. However, from a Bohmian viewpoint, atom trajectories can smoothly adjust to the equipotential energy surface profile in a sort of sliding motion; thus the trapping process could eventually occur within one single unit cell. In particular, both threshold and selective adsorption resonances are explained by means of this quantum trapping considering different space and time scales. Furthermore, a mapping between each region of the (initial) incoming plane wave and the different parts of the diffraction and resonance patterns can be easily established, an important issue only provided by a quantum trajectory formalism. (c) 2005 American Institute of Physics.

Time synchronization of a frequency-hopped MFSK communication system

NASA Technical Reports Server (NTRS)

Simon, M. K.; Polydoros, A.; Huth, G. K.

1981-01-01

In a frequency-hopped (FH) multiple-frequency-shift-keyed (MFSK) communication system, frequency hopping causes the necessary frequency transitions for time synchronization estimation rather than the data sequence as in the conventional (nonfrequency-hopped) system. Making use of this observation, this paper presents a fine synchronization (i.e., time errors of less than a hop duration) technique for estimation of FH timing. The performance degradation due to imperfect FH time synchronization is found in terms of the effect on bit error probability as a function of full-band or partial-band noise jamming levels and of the number of hops used in the FH timing estimate.

Hop/STI1 modulates retinal proliferation and cell death independent of PrP{sup C}

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

Arruda-Carvalho, Maithe; Njaine, Brian; Silveira, Mariana S.

Hop/STI1 is a co-chaperone adaptor protein for Hsp70/Hsp90 complexes. Hop/STI1 is found extracellularly and modulates cell death and differentiation through interaction with the prion protein (PrP{sup C}). Here, we investigated the expression of hop/STI1 and its role upon cell proliferation and cell death in the developing retina. Hop/STI1 is more expressed in developing rat retina than in the mature tissue. Hop/STI1 blocks retinal cell death in the neuroblastic layer (NBL) in a PrP{sup C} dependent manner, but failed to protect ganglion cells against axotomy-induced cell death. An antibody raised against hop/STI1 ({alpha}-STI1) blocked both ganglion cell and NBL cell deathmore » independent of PrP{sup C}. cAMP/PKA, ERK, PI3K and PKC signaling pathways were not involved in these effects. Hop/STI1 treatment reduced proliferation, while {alpha}-STI1 increased proliferation in the developing retina, both independent of PrP{sup C}. We conclude that hop/STI1 can modulate both proliferation and cell death in the developing retina independent of PrP{sup C}.« less

Varietal discrimination of hop pellets by near and mid infrared spectroscopy.

PubMed

Machado, Julio C; Faria, Miguel A; Ferreira, Isabel M P L V O; Páscoa, Ricardo N M J; Lopes, João A

2018-04-01

Hop is one of the most important ingredients of beer production and several varieties are commercialized. Therefore, it is important to find an eco-real-time-friendly-low-cost technique to distinguish and discriminate hop varieties. This paper describes the development of a method based on vibrational spectroscopy techniques, namely near- and mid-infrared spectroscopy, for the discrimination of 33 commercial hop varieties. A total of 165 samples (five for each hop variety) were analysed by both techniques. Principal component analysis, hierarchical cluster analysis and partial least squares discrimination analysis were the chemometric tools used to discriminate positively the hop varieties. After optimizing the spectral regions and pre-processing methods a total of 94.2% and 96.6% correct hop varieties discrimination were obtained for near- and mid-infrared spectroscopy, respectively. The results obtained demonstrate the suitability of these vibrational spectroscopy techniques to discriminate different hop varieties and consequently their potential to be used as an authenticity tool. Compared with the reference procedures normally used for hops variety discrimination these techniques are quicker, cost-effective, non-destructive and eco-friendly. Copyright © 2017 Elsevier B.V. All rights reserved.

The 1963 Hip-Hop Machine: Hip-Hop Pedagogy as Composition.

ERIC Educational Resources Information Center

Rice, Jeff

2003-01-01

Proposes an alternative invention strategy for research-based argumentative writing. Investigates the coincidental usage of the term "whatever" in hip-hop, theory, and composition studies. Presents a "whatever-pedagogy" identified as "hip-hop pedagogy," a writing practice that models itself after digital sampling's…

Research on synchronization technology of frequency hopping communication system

NASA Astrophysics Data System (ADS)

Zhao, Xiangwu; Quan, Houde; Cui, Peizhang

2018-05-01

Frequency Hopping (FH) communication is a technology of spread spectrum communication. It has strong anti-interference, anti-interception and security capabilities, and has been widely applied in the field of communications. Synchronization technology is one of the most crucial technologies in frequency hopping communication. The speed of synchronization establishment and the reliability of synchronous system directly affect the performance of frequency hopping communication system. Therefore, the research of synchronization technology in frequency hopping communication has important value.

Hip-Hop as a Resource for Understanding the Urban Context: A Review of Christopher Edmin's--Science Education for the Hip-Hop Generation, Sense Publishers, Rotterdam, 2010

ERIC Educational Resources Information Center

Brown, Bryan

2010-01-01

This review explores Edmin's "Science education for the hip-hop generation" by documenting how he frames hip-hop as a means to access urban student culture. He argues that hip-hop is more than a mere music genre, but rather a culture that provides young people with ways of connecting to the world. Two primary ideas emerged as central to…

Formation and electrical transport properties of pentacene nanorod crystal.

PubMed

Akai-Kasaya, M; Ohmori, C; Kawanishi, T; Nashiki, M; Saito, A; Aono, M; Kuwahara, Y

2010-09-10

The monophasic formation of an uncharted pentacene crystal, the pentacene nanorod, has been investigated. The restricted formation of the pentacene nanorod on a bare mica surface reveals a peculiar surface catalytic crystal growth mode of the pentacene. We demonstrated the charge transport measurements through a single pentacene nanorod and analyzed the data using a periodic hopping conduction model. The results revealed that the pentacene nanorod has a periodic conductive node within their one-dimensional crystal.

A new method of hybrid frequency hopping signals selection and blind parameter estimation

NASA Astrophysics Data System (ADS)

Zeng, Xiaoyu; Jiao, Wencheng; Sun, Huixian

2018-04-01

Frequency hopping communication is widely used in military communications at home and abroad. In the case of single-channel reception, it is scarce to process multiple frequency hopping signals both effectively and simultaneously. A method of hybrid FH signals selection and blind parameter estimation is proposed. The method makes use of spectral transformation, spectral entropy calculation and PRI transformation basic theory to realize the sorting and parameter estimation of the components in the hybrid frequency hopping signal. The simulation results show that this method can correctly classify the frequency hopping component signal, and the estimated error of the frequency hopping period is about 5% and the estimated error of the frequency hopping frequency is less than 1% when the SNR is 10dB. However, the performance of this method deteriorates seriously at low SNR.

Chemical transformations of characteristic hop secondary metabolites in relation to beer properties and the brewing process: a review.

PubMed

Steenackers, Bart; De Cooman, Luc; De Vos, Dirk

2015-04-01

The annual production of hops (Humulus lupulus L.) exceeds 100,000 mt and is almost exclusively consumed by the brewing industry. The value of hops is attributed to their characteristic secondary metabolites; these metabolites are precursors which are transformed during the brewing process into important bittering, aromatising and preservative components with rather low efficiency. By selectively transforming these components off-line, both their utilisation efficiency and functionality can be significantly improved. Therefore, the chemical transformations of these secondary metabolites will be considered with special attention to recent advances in the field. The considered components are the hop alpha-acids, hop beta-acids and xanthohumol, which are components unique to hops, and alpha-humulene and beta-caryophyllene, sesquiterpenes which are highly characteristic of hops. Copyright © 2014 Elsevier Ltd. All rights reserved.

High-Speed On-Board Data Processing Platform for LIDAR Projects at NASA Langley Research Center

NASA Astrophysics Data System (ADS)

Beyon, J.; Ng, T. K.; Davis, M. J.; Adams, J. K.; Lin, B.

2015-12-01

The project called High-Speed On-Board Data Processing for Science Instruments (HOPS) has been funded by NASA Earth Science Technology Office (ESTO) Advanced Information Systems Technology (AIST) program during April, 2012 - April, 2015. HOPS is an enabler for science missions with extremely high data processing rates. In this three-year effort of HOPS, Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) and 3-D Winds were of interest in particular. As for ASCENDS, HOPS replaces time domain data processing with frequency domain processing while making the real-time on-board data processing possible. As for 3-D Winds, HOPS offers real-time high-resolution wind profiling with 4,096-point fast Fourier transform (FFT). HOPS is adaptable with quick turn-around time. Since HOPS offers reusable user-friendly computational elements, its FPGA IP Core can be modified for a shorter development period if the algorithm changes. The FPGA and memory bandwidth of HOPS is 20 GB/sec while the typical maximum processor-to-SDRAM bandwidth of the commercial radiation tolerant high-end processors is about 130-150 MB/sec. The inter-board communication bandwidth of HOPS is 4 GB/sec while the effective processor-to-cPCI bandwidth of commercial radiation tolerant high-end boards is about 50-75 MB/sec. Also, HOPS offers VHDL cores for the easy and efficient implementation of ASCENDS and 3-D Winds, and other similar algorithms. A general overview of the 3-year development of HOPS is the goal of this presentation.

Hip-Hopping across China: Intercultural Formulations of Local Identities

ERIC Educational Resources Information Center

Barrett, Catrice

2012-01-01

The linguistic dimensions of globalized hip-hop cannot be understood simply as a byproduct of English as an American export. As hip-hop mobilizes, it is common (and arguably necessary) for global hip-hop communities to struggle through purposeful, semiotically rooted dialectics over what constitutes "authentic" and respectable forms of…

Revolutionizing Environmental Education through Indigenous Hip Hop Culture

ERIC Educational Resources Information Center

Gorlewski, Julie; Porfilio, Brad J.

2012-01-01

Based upon the life histories of six Indigenous hip hop artists of the Beat Nation artist collective, this essay captures how Indigenous hip hop has the potential to revolutionize environmental education. Hip hop provides Indigenous youth an emancipatory space to raise their opposition to neocolonial controls of Indigenous territories that…

Back-tracking of primary particle trajectories for muons detected at the Earth surface

NASA Astrophysics Data System (ADS)

Shutenko, V. V.

2017-01-01

Investigations of cosmic rays on the surface of the Earth allow to derive information of applied character on the conditions of the interplanetary magnetic field and of the geomagnetic field. For this purpose, it is necessary to collate trajectories of particles detected in the ground-based detector to trajectories of primary cosmic rays in the heliosphere. This problem is solved by means of various back-tracking methods. In this work, one of such methods is presented.

Leucine-rich-repeat-containing variable lymphocyte receptors as modules to target plant-expressed proteins

DOE PAGES

Velásquez, André C.; Nomura, Kinya; Cooper, Max D.; ...

2017-04-19

The ability to target and manipulate protein-based cellular processes would accelerate plant research; yet, the technology to specifically and selectively target plant-expressed proteins is still in its infancy. Leucine-rich repeats (LRRs) are ubiquitously present protein domains involved in mediating protein–protein interactions. LRRs confer the binding specificity to the highly diverse variable lymphocyte receptor (VLR) antibodies (including VLRA, VLRB and VLRC types) that jawless vertebrates make as the functional equivalents of jawed vertebrate immunoglobulin-based antibodies. Here, VLRBs targeting an effector protein from a plant pathogen, HopM1, were developed by immunizing lampreys and using yeast surface display to select for high-affinity VLRBs.more » HopM1-specific VLRBs (VLRM1) were expressed in planta in the cytosol, the trans-Golgi network, and the apoplast. Expression of VLRM1 was higher when the protein localized to an oxidizing environment that would favor disulfide bridge formation (when VLRM1 was not localized to the cytoplasm), as disulfide bonds are necessary for proper VLR folding. VLRM1 specifically interacted in planta with HopM1 but not with an unrelated bacterial effector protein while HopM1 failed to interact with a non-specific VLRB. Later, VLRs may be used as flexible modules to bind proteins or carbohydrates of interest in planta, with broad possibilities for their use by binding directly to their targets and inhibiting their action, or by creating chimeric proteins with new specificities in which endogenous LRR domains are replaced by those present in VLRs.« less

Leucine-rich-repeat-containing variable lymphocyte receptors as modules to target plant-expressed proteins

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

Velásquez, André C.; Nomura, Kinya; Cooper, Max D.

The ability to target and manipulate protein-based cellular processes would accelerate plant research; yet, the technology to specifically and selectively target plant-expressed proteins is still in its infancy. Leucine-rich repeats (LRRs) are ubiquitously present protein domains involved in mediating protein–protein interactions. LRRs confer the binding specificity to the highly diverse variable lymphocyte receptor (VLR) antibodies (including VLRA, VLRB and VLRC types) that jawless vertebrates make as the functional equivalents of jawed vertebrate immunoglobulin-based antibodies. Here, VLRBs targeting an effector protein from a plant pathogen, HopM1, were developed by immunizing lampreys and using yeast surface display to select for high-affinity VLRBs.more » HopM1-specific VLRBs (VLRM1) were expressed in planta in the cytosol, the trans-Golgi network, and the apoplast. Expression of VLRM1 was higher when the protein localized to an oxidizing environment that would favor disulfide bridge formation (when VLRM1 was not localized to the cytoplasm), as disulfide bonds are necessary for proper VLR folding. VLRM1 specifically interacted in planta with HopM1 but not with an unrelated bacterial effector protein while HopM1 failed to interact with a non-specific VLRB. Later, VLRs may be used as flexible modules to bind proteins or carbohydrates of interest in planta, with broad possibilities for their use by binding directly to their targets and inhibiting their action, or by creating chimeric proteins with new specificities in which endogenous LRR domains are replaced by those present in VLRs.« less

Classification of Scaffold Hopping Approaches

PubMed Central

Sun, Hongmao; Tawa, Gregory; Wallqvist, Anders

2012-01-01

The general goal of drug discovery is to identify novel compounds that are active against a preselected biological target with acceptable pharmacological properties defined by marketed drugs. Scaffold hopping has been widely applied by medicinal chemists to discover equipotent compounds with novel backbones that have improved properties. In this review, scaffold hopping is classified into four major categories, namely heterocycle replacements, ring opening or closure, peptidomimetics, and topology-based hopping. The structural diversity of original and final scaffolds with respect to each category will be reviewed. The advantages and limitations of small, medium, and large-step scaffold hopping will also be discussed. Software that is frequently used to facilitate different kinds of scaffold hopping methods will be summarized. PMID:22056715

A dynamical mean-field study of orbital-selective Mott phase enhanced by next-nearest neighbor hopping

NASA Astrophysics Data System (ADS)

Niu, Yuekun; Sun, Jian; Ni, Yu; Song, Yun

2018-06-01

The dynamical mean-field theory is employed to study the orbital-selective Mott transition (OSMT) of the two-orbital Hubbard model with nearest neighbor hopping and next-nearest neighbor (NNN) hopping. The NNN hopping breaks the particle-hole symmetry at half filling and gives rise to an asymmetric density of states (DOS). Our calculations show that the broken symmetry of DOS benefits the OSMT, where the region of the orbital-selective Mott phase significantly extends with the increasing NNN hopping integral. We also find that Hund's rule coupling promotes OSMT by blocking the orbital fluctuations, but the influence of NNN hopping is more remarkable.

The Helicopter Observation Platform for Marine and Continental Boundary Layer Studies

NASA Astrophysics Data System (ADS)

Avissar, R.; Broad, K.; Walko, R. L.; Drennan, W. M.; Williams, N. J.

2016-02-01

The University of Miami has acquired a commercial helicopter (Airbus H125) that was transformed into a one-of-a-kind Helicopter Observation Platform (HOP) that fills critical gaps in physical, chemical and biological observations of the environment. This new research facility is designed to carry sensors and instrument inlets in the undisturbed air in front of the helicopter nose at low airspeed and at various altitudes, from a few feet above the Earth's surface (where much of the climate and weather "action" takes place, and where we live) and up through the atmospheric boundary layer and the mid troposphere. The HOP, with its hovering capability, is also ideal for conducting various types of remote-sensing observations. It provides a unique and essential component of airborne measurement whose purpose, among others, is to quantify the exchanges of gases and energy at the Earth surface, as well as aerosol properties that affect the environment, the climate system, and human health. For its first scientific mission, an eddy-correlation system is being mounted in front of its nose to conduct high-frequency measurements of turbulence variables relevant to atmospheric boundary layer studies.Fully fueled and with both pilot and co-pilot on board, the HOP can carry a scientific payload of up to about 1,000 lbs internally (about 3,000 lbs externally) and fly for nearly 4 hours without refueling at an airspeed of 65 knots ( 30 m/s) that is ideal for in-situ observations. Its fast cruising speed is about 140 knots andits range, at that speed, is about 350 nautical miles. This specific helicopter was chosen because of its flat floor design, which is particularly convenient for installing scientific payload and also because of its high-altitude capability (it is the only commercial helicopter that ever landed at the top of Mt Everest).The HOP is available to the entire scientific community for any project that is feasible from a flight safety point of view and that fulfills the flight regulations of the country that it is flown in. It can be easily transported anywhere in the world and can also be operated from a properly equipped ship at sea foroceanographic research.

A community-based obesity prevention program for minority children: rationale and study design for Hip-Hop to Health Jr.

PubMed

Fitzgibbon, Marian L; Stolley, Melinda R; Dyer, Alan R; VanHorn, Linda; KauferChristoffel, Katherine

2002-02-01

BACKGROUND; The increasing prevalence of overweight among children in the United States presents a national health priority. Higher rates of overweight/obesity among minority women place their children at increased risk. Although increased rates of overweight are observed in 4- to 5-year-old children, they are not observed in 2- to 3-year-old children. Therefore, early prevention efforts incorporating families are critical. The primary aim of Hip-Hop to Health Jr. is to alter the trajectory toward overweight/obesity among preschool African-American and Latino children. This 5-year randomized intervention is conducted in 24 Head Start programs, where each site is randomized to either a 14-week dietary/physical activity intervention or a general health intervention. This paper presents the rationale and design of the study. Efficacy of the intervention will be determined by weight change for the children and parent/caretaker. Secondary measures include reductions in dietary fat and increases in fiber, fruit/vegetable intake, and physical activity. Baseline data will be presented in future papers. The problem of overweight/obesity is epidemic in the United States. Behaviors related to diet and physical activity are established early in life and modeled by family members. Early intervention efforts addressing the child and family are needed to prevent obesity later in life. This paper describes a comprehensive, family-oriented obesity prevention program for minority preschool children. Copyright 2002 American Health Foundation and Elsevier Science (USA).

Effects of 2 ankle destabilization devices on electromyography measures during functional exercises in individuals with chronic ankle instability.

PubMed

Donovan, Luke; Hart, Joseph M; Hertel, Jay

2015-03-01

Randomized crossover laboratory study. To determine the effects of ankle destabilization devices on surface electromyography (sEMG) measures of selected lower extremity muscles during functional exercises in participants with chronic ankle instability. Ankle destabilization devices are rehabilitation tools that can be worn as a boot or sandal to increase lower extremity muscle activation during walking in healthy individuals. However, they have not been tested in a population with pathology. Fifteen adults with chronic ankle instability participated. Surface electromyography electrodes were located over the anterior tibialis, fibularis longus, lateral gastrocnemius, rectus femoris, biceps femoris, and gluteus medius. The activity level of these muscles was recorded in a single testing session during unipedal stance with eyes closed, the Star Excursion Balance Test, lateral hops, and treadmill walking. Each task was performed under 3 conditions: shod, ankle destabilization boot, and ankle destabilization sandal. Surface electromyography signal amplitudes were measured for each muscle during each exercise for all 3 conditions. Participants demonstrated a significant increase, with moderate to large effect sizes, in sEMG signal amplitude of the fibularis longus in the ankle destabilization boot and ankle destabilization sandal conditions during the unipedal eyes-closed balance test, the Star Excursion Balance Test in the anterior and posteromedial directions, lateral hops, and walking, when compared to the shod condition. Both devices also resulted in an increase in sEMG signal amplitudes, with large effect sizes of the lateral gastrocnemius, rectus femoris, biceps femoris, and gluteus medius during the unipedal-stance-with-eyes-closed test, compared to the shod condition. Wearing ankle destabilization devices caused greater muscle activation during functional exercises in individuals with chronic ankle instability. Based on the magnitude of the effect, there were consistent increases in fibularis longus sEMG amplitudes during the unipedal eyes-closed balance test, the Star Excursion Balance Test in the anterior and posteromedial directions, and pre-initial contact and post-initial contact during lateral hops and walking.

A Mobile Asteroid Surface Scout (MASCOT) for the Hayabusa 2 Mission to 1999 JU3: The Scientific Approach

NASA Astrophysics Data System (ADS)

Jaumann, Ralf; Bibring, Jean-Pierre; Glassmeier, Karl-Heinz; Grott, Matthias; Ho, Tra-Mi; Ulamec, Stepahn; Schmitz, Nicole; Auster, Ulrich; Biele, Jens; Kuninaka, Hitoshi; Okada, Tatsuaki; Yoshikawa, Makoto; Watanabe, Sei-ichhiro; Fujimoto, Masaki; Spohn, Tilman; Koncz, Alexander; Michaelis, Harald

2014-05-01

MASCOT, a Mobile Asteroid Surface Scout, will support JAXA's Hayabusa 2 mission to investigate the C-type asteroid 1999 JU3 (1). The German Aer-ospace Center (DLR) develops MASCOT with contributions from CNES (France) (2,3). Main objective is to in-situ map the asteroid's geomorpholo-gy, the intimate structure, texture and composition of the regolith (dust, soil and rocks), and the thermal, mechanical, and magnetic properties of the sur-face in order to provide ground truth for the orbiter remote measurements, support the selection of sampling sites, and provide context information for the returned samples. MASCOT comprises a payload of four scientific in-struments: camera, radiometer, magnetometer and hyperspectral microscope. C- and D-type asteroids hold clues to the origin of the solar system, the for-mation of planets, the origins of water and life on Earth, the protection of Earth from impacts, and resources for future human exploration. C- and D-types are dark and difficult to study from Earth, and have only been glimpsed by spacecraft. While results from recent missions (e.g., Hayabusa, NEAR (4, 5, 6)) have dramatically increased our understanding of asteroids, important questions remain. For example, characterizing the properties of asteroid regolith in-situ would deliver important ground truth for further understanding telescopic and orbital observations and samples of such aster-oids. MASCOT will descend and land on the asteroid and will change its position two times by hopping. This enables measurements during descent, at the landing and hopping positions #1-3, and during hopping. References: (1) Vilas, F., Astronomical J. 1101-1105, 2008; (2) Ulamec, S., et al., Acta Astronautica, Vol. 93, pp. 460-466; (3) Jaumann et al., 45th LPSC, Houston; (4) Special Issue, Science, Vol. 312 no. 5778, 2006; (5) Special Issue Science, Vol. 333 no. 6046, 2011. (6) Bell, L., Mitton, J-., Cambridge Univ. Press, 2002.

A Mobile Asteroid Surface Scout (MASCOT) for the Hayabusa 2 Mission to 1999 JU3: The Scientific Approach

NASA Astrophysics Data System (ADS)

Jaumann, Ralf; Bibring, Jean-Pierre; Glassmeier, Karl-Heinz; Grott, Matthias; Ho, Tra-Mie; Ulamec, Stephan; Schmitz, Nicole; Auster, Hans-Ulrich; Biele, Jens; Kuninaka, Hitoshi; Okada, Tatsuaki; Yoshikawa, Makoto; Watanabe, Sei-ichhiro; Fujimoto, Masaki; Spohn, Tilman

2013-04-01

Mascot, a Mobile Asteroid Surface Scout, will support JAXA's Hayabusa 2 mission to investigate the C-type asteroid 1999 JU3 (1). The German Aero-space Center (DLR) develops Mascot with contributions from CNES (France) (2). Main objective is to in-situ map the asteroid's geomorphology, the intimate structure, texture and composition of the regolith (dust, soil and rocks), and the thermal, mechanical, and magnetic properties of the surface in order to provide ground truth for the orbiter remote measurements, sup-port the selection of sampling sites, and provide context information for the returned samples. Mascot comprises a payload of four scientific instruments: camera, radiometer, magnetometer and hyperspectral microscope. C- and D-type asteroids hold clues to the origin of the solar system, the formation of planets, the origins of water and life on Earth, the protection of Earth from impacts, and resources for future human exploration. C- and D-types are dark and difficult to study from Earth, and have only been glimpsed by spacecraft. While results from recent missions (e.g., Hayabusa, NEAR (3, 4, 5)) have dramatically increased our understanding of asteroids, important questions remain. For example, characterizing the properties of asteroid reg-olith in-situ would deliver important ground truth for further understanding telescopic and orbital observations and samples of such asteroids. Mascot will descend and land on the asteroid and will change its position two times by hopping. This enables measurements during descent, at the landing and hopping positions #1-3, and during hopping. References: (1) Vilas, F., Astronomical J. 1101-1105, 2008; (2) Ulamec, S., et al., COSPAR, General Assembly, Mysore/India, 2012; (3) Special Issue, Science, Vol. 312 no. 5778, 2006; (4) Special Issue Science, Vol. 333 no. 6046, 2011; (5) Bell, L., Mitton, J-., Cambridge Univ. Press, 2002.

Hydrogen bond strengthening induces fluorescence quenching of PRODAN derivative by turning on twisted intramolecular charge transfer

NASA Astrophysics Data System (ADS)

Yang, Yonggang; Li, Donglin; Li, Chaozheng; Liu, YuFang; Jiang, Kai

2017-12-01

Researchers have proposed different effective mechanisms of hydrogen bonding (HB) on the fluorescence of 6-propionyl-2-dimethylaminonaphthalene (PRODAN) and its derivatives. Herein, excited state transition and dynamics analysis confirm that the fluorescence of PD (a derivative of PRODAN with ethyl replaced by 3-hydroxy-2,2-dimethylpropan) emits from the planar intramolecular charge transfer (PICT) state rather than twist ICT (TICT) state, because the fluorescence emission and surface hopping from the TICT state to the twist ground (T-S0) state is energy forbidden. Nevertheless, the strengthening of intramolecular-HB (intra-HB) and intermolecular-HB (inter-HB) of PD-(methanol)2 smooth the pathway of surface hopping from TICT to T-S0 state and the external conversion going to planar ground state by decreasing the energy difference of the two states. This smoothing changes the fluorescence state of PD-(methanol)2 to the TICT state in which fluorescence emission does not occur but surface hopping, leading to the partial fluorescence quenching of PD in methanol solvent. This conclusion is different from previous related reports. Moreover, the inter-HB strengthening of PD-methanol in PICT state induces the cleavage of intra-HB and a fluorescence red-shift of 54 nm compared to PD. This red-shift increases to 66 nm for PD-(methanol)2 for the strengthening of the one intra-HB and two inter-HBs. The dipole moments of PD-methanol and PD-(methanol)2 respectively increase about 10.3D and 8.1D in PICT state compared to PD. The synergistic effect of intra-HB and inter-HB induces partial quenching of PD in methanol solvent by turning on the TICT state and fluorescence red-shift. This work gives a reasonable description on the fluorescence red-shift and partial quenching of PD in methanol solvent, which will bring insight into the study of spectroscopic properties of molecules owning better spectral characteristics.

Hydrogen bond strengthening induces fluorescence quenching of PRODAN derivative by turning on twisted intramolecular charge transfer.

PubMed

Yang, Yonggang; Li, Donglin; Li, Chaozheng; Liu, YuFang; Jiang, Kai

2017-12-05

Researchers have proposed different effective mechanisms of hydrogen bonding (HB) on the fluorescence of 6-propionyl-2-dimethylaminonaphthalene (PRODAN) and its derivatives. Herein, excited state transition and dynamics analysis confirm that the fluorescence of PD (a derivative of PRODAN with ethyl replaced by 3-hydroxy-2,2-dimethylpropan) emits from the planar intramolecular charge transfer (PICT) state rather than twist ICT (TICT) state, because the fluorescence emission and surface hopping from the TICT state to the twist ground (T-S 0 ) state is energy forbidden. Nevertheless, the strengthening of intramolecular-HB (intra-HB) and intermolecular-HB (inter-HB) of PD-(methanol) 2 smooth the pathway of surface hopping from TICT to T-S 0 state and the external conversion going to planar ground state by decreasing the energy difference of the two states. This smoothing changes the fluorescence state of PD-(methanol) 2 to the TICT state in which fluorescence emission does not occur but surface hopping, leading to the partial fluorescence quenching of PD in methanol solvent. This conclusion is different from previous related reports. Moreover, the inter-HB strengthening of PD-methanol in PICT state induces the cleavage of intra-HB and a fluorescence red-shift of 54nm compared to PD. This red-shift increases to 66nm for PD-(methanol) 2 for the strengthening of the one intra-HB and two inter-HBs. The dipole moments of PD-methanol and PD-(methanol) 2 respectively increase about 10.3D and 8.1D in PICT state compared to PD. The synergistic effect of intra-HB and inter-HB induces partial quenching of PD in methanol solvent by turning on the TICT state and fluorescence red-shift. This work gives a reasonable description on the fluorescence red-shift and partial quenching of PD in methanol solvent, which will bring insight into the study of spectroscopic properties of molecules owning better spectral characteristics. Copyright © 2017 Elsevier B.V. All rights reserved.

Deterministic Multi-hop Controlled Teleportation of Arbitrary Single-Qubit State

NASA Astrophysics Data System (ADS)

Peng, Jia-yin; Bai, Ming-qiang; Mo, Zhi-wen

2017-10-01

Multi-hop teleportation is of great significance due to long-distance delivery of quantum information and wireless quantum communication networks. In existing protocols of multi-hop teleportation, the more nodes, the smaller the success probability. In this paper, fusing the ideas of multi-hop teleportation and controlled teleportation, we put forward a scheme for implementing multi-hop controlled teleportation of single-qubit state. A set of ingenious three-qubit non-maximally entangled states are constructed to serve as the quantum channels. The information is perfectly transmitted hop by hop through teleportation under the control of the supervisors. Unit success probability can be achieved independent of channel's entanglement degree and the number of intermediate nodes. Only Pauli operations, single-qubit rotation, Hadamard gate, controlled-NOT gate, Bell-state measurement and single-qubit measurement are used in our scheme, so this scheme is easily realized in physical experiment.

Ferrocene-decorated nanocrystalline cellulose with charge carrier mobility.

PubMed

Eyley, Samuel; Shariki, Sara; Dale, Sara E C; Bending, Simon; Marken, Frank; Thielemans, Wim

2012-04-24

Ferrocene-decorated cellulose nanowhiskers were prepared by the grafting of ethynylferrocene onto azide functionalized cotton-derived cellulose nanowhiskers using azide-alkyne cycloaddition. Successful surface modification and retention of the crystalline morphology of the nanocrystals was confirmed by elemental analysis, inductively coupled plasma-atomic emission spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The coverage with ferrocenyl is high (approximately 1.14 × 10(-3) mol g(-1) or 4.6 × 10(13) mol cm(-2) corresponding to a specific area of 61 Å(2) per ferrocene). Cyclic voltammetry measurements of films formed by deposition of ferrocene-decorated nanowhiskers showed that this small spacing of redox centers along the nanowhisker surface allowed conduction hopping of electrons. The apparent diffusion coefficient for electron (or hole) hopping via Fe(III/II) surface sites is estimated as Dapp = 10(-19) m(2)s(-1) via impedance methods, a value significantly less than nonsolvated ferrocene polymers, which would be expected as the 1,2,3-triazole ring forms a rigid linker tethering the ferrocene to the nanowhisker surface. In part, this is believed to be also due to "bottleneck" diffusion of charges across contact points where individual cellulose nanowhiskers contact each other. However, the charge-communication across the nanocrystal surface opens up the potential for use of cellulose nanocrystals as a charge percolation template for the preparation of conducting films via covalent surface modification (with applications similar to those using adsorbed conducting polymers), for use in bioelectrochemical devices to gently transfer and remove electrons without the need for a solution-soluble redox mediator, or for the fabrication of three-dimensional self-assembled conducting networks.

Tuning Monotonic Basin Hopping: Improving the Efficiency of Stochastic Search as Applied to Low-Thrust Trajectory Optimization

NASA Technical Reports Server (NTRS)

Englander, Jacob; Englander, Arnold

2014-01-01

Trajectory optimization methods using MBH have become well developed during the past decade. An essential component of MBH is a controlled random search through the multi-dimensional space of possible solutions. Historically, the randomness has been generated by drawing RVs from a uniform probability distribution. Here, we investigate the generating the randomness by drawing the RVs from Cauchy and Pareto distributions, chosen because of their characteristic long tails. We demonstrate that using Cauchy distributions (as first suggested by Englander significantly improves MBH performance, and that Pareto distributions provide even greater improvements. Improved performance is defined in terms of efficiency and robustness, where efficiency is finding better solutions in less time, and robustness is efficiency that is undiminished by (a) the boundary conditions and internal constraints of the optimization problem being solved, and (b) by variations in the parameters of the probability distribution. Robustness is important for achieving performance improvements that are not problem specific. In this work we show that the performance improvements are the result of how these long-tailed distributions enable MBH to search the solution space faster and more thoroughly. In developing this explanation, we use the concepts of sub-diffusive, normally-diffusive, and super-diffusive RWs originally developed in the field of statistical physics.

Wish to Live: The Hip-Hop Feminism Pedagogy Reader. Educational Psychology. Volume 3

ERIC Educational Resources Information Center

Brown, Ruth Nicole, Ed.; Kwakye, Chamara Jewel, Ed.

2012-01-01

"Wish To Live: The Hip-hop Feminism Pedagogy Reader" moves beyond the traditional understanding of the four elements of hip-hop culture--rapping, breakdancing, graffiti art, and deejaying--to articulate how hip-hop feminist scholarship can inform educational practices and spark, transform, encourage, and sustain local and global youth…

Precision QTL mapping of downy mildew resistance in Hop (Humulus lupulus L.)

USDA-ARS?s Scientific Manuscript database

Hop Downy mildew (DM) is an obligate parasite causing severe losses in hop if not controlled. Resistance to this pathogen is a primary goal for hop breeding programs. The objective of this study was to identify QTLs linked to DM resistance. Next-generation-sequencing was performed on a mapping po...

Genomics of the hop psuedo-autosomal regions

USDA-ARS?s Scientific Manuscript database

Hop is one of the few crop species with female and male plants with sex being determined by either XX or XY chromosomes. Hop cones are only produced in female hops with or without fertilization. This has lead to most genomic research being directed toward female plants. Very little work has been don...

Behind Beats and Rhymes: Working Class from a Hampton Roads Hip Hop Homeplace

ERIC Educational Resources Information Center

Durham, Aisha S.

2009-01-01

The film documentary titled "Hip Hop: beyond beats and rhymes" captures ongoing conversations among scholars, cultural critics, and hip hop insiders about the state of African Americans by interrogating distinct expressive forms associated with hip hop culture. Durham draws from two scenes to describe her memories as the researched…

Flipping the Misogynist Script: Gender, Agency, Hip Hop and Music Education

ERIC Educational Resources Information Center

Tobias, Evan S.

2014-01-01

Excluding Hip Hop culture and rap music from music education misses opportunities for addressing key aspects of popular culture, society, and students' lives. This article addresses intersections of Hip Hop, gender, and music education to forward potential Hip Hop praxis. After tracing related scholarship, I discuss and problematize…

Studies of aircraft differential maneuvering. Report 75-27: Calculating of differential-turning barrier surfaces. Report 75-26: A user's guide to the aircraft energy-turn and tandem-motion computer programs. Report 75-7: A user's guide to the aircraft energy-turn hodograph program. [numerical analysis of tactics and aircraft maneuvers of supersonic attack aircraft

NASA Technical Reports Server (NTRS)

Kelley, H. J.; Lefton, L.

1976-01-01

The numerical analysis of composite differential-turn trajectory pairs was studied for 'fast-evader' and 'neutral-evader' attitude dynamics idealization for attack aircraft. Transversality and generalized corner conditions are examined and the joining of trajectory segments discussed. A criterion is given for the screening of 'tandem-motion' trajectory segments. Main focus is upon the computation of barrier surfaces. Fortunately, from a computational viewpoint, the trajectory pairs defining these surfaces need not be calculated completely, the final subarc of multiple-subarc pairs not being required. Some calculations for pairs of example aircraft are presented. A computer program used to perform the calculations is included.

Simulation of clustering and anisotropy due to Co step-edge segregation in vapor-deposited CoPt3

NASA Astrophysics Data System (ADS)

Maranville, B. B.; Schuerman, M.; Hellman, F.

2006-03-01

An atomistic mechanism is proposed for the creation of structural anisotropy and consequent large perpendicular magnetic anisotropy in vapor-deposited films of CoPt3 . Energetic considerations of bonding in Co-Pt suggest that Co segregates to step edges due to their low coordination, for all film orientations, while Pt segregates to the two low index surfaces. Coalescence of islands during growth cause these Co-rich step edges to become flat thin Co platelets in a Pt rich matrix, giving rise to the experimentally observed magnetic anisotropy. This proposed model is tested with kinetic Monte Carlo simulation of the vapor deposition growth. A tight-binding, second-moment approximation to the interatomic potential is used to calculate the probability of an atom hopping from one surface site to another, assuming an Arrhenius-like activation model of surface motion. Growth is simulated by allowing many hopping events per adatom. The simulated as-grown films show an asymmetry in Co-Co bonding between the in-plane and out-of-plane directions, in good agreement with experimental data. The growth temperature dependence found in the simulations is strong and similar to that seen in experiments, and an increase in Co edge segregation with increasing temperature is also observed.

Routing the asteroid surface vehicle with detailed mechanics

NASA Astrophysics Data System (ADS)

Yu, Yang; Baoyin, He-Xi

2014-06-01

The motion of a surface vehicle on/above an irregular object is investigated for a potential interest in the insitu explorations to asteroids of the solar system. A global valid numeric method, including detailed gravity and geomorphology, is developed to mimic the behaviors of the test particles governed by the orbital equations and surface coupling effects. A general discussion on the surface mechanical environment of a specified asteroid, 1620 Geographos, is presented to make a global evaluation of the surface vehicle's working conditions. We show the connections between the natural trajectories near the ground and differential features of the asteroid surface, which describes both the good and bad of typical terrains from the viewpoint of vehicles' dynamic performances. Monte Carlo simulations are performed to take a further look at the trajectories of particles initializing near the surface. The simulations reveal consistent conclusions with the analysis, i.e., the open-field flat ground and slightly concave basins/valleys are the best choices for the vehicles' dynamical security. The dependence of decending trajectories on the releasing height is studied as an application; the results show that the pole direction (where the centrifugal force is zero) is the most stable direction in which the shift of a natural trajectory will be well limited after landing. We present this work as an example for pre-analysis that provides guidance to engineering design of the exploration site and routing the surface vehicles.

3-Sulfanyl-4-methylpentan-1-ol in Dry-Hopped Beers: First Evidence of Glutathione S-Conjugates in Hop (Humulus lupulus L.).

PubMed

Kankolongo Cibaka, Marie-Lucie; Decourrière, Laura; Lorenzo-Alonso, Celso-José; Bodart, Etienne; Robiette, Raphaël; Collin, Sonia

2016-11-16

Monovarietal dry-hopped beers were produced with the dual-purpose hop cultivars Amarillo, Hallertau Blanc, and Mosaic. The grapefruit-like 3-sulfanyl-4-methylpentan-1-ol was found in all three beers at concentrations much higher than expected on the basis of the free thiol content in hop. Even cysteinylated precursors proved unable to explain our results. As observed in wine, the occurrence of S-glutathione precursors was therefore suspected in hop. The analytical standards of S-3-(4-methyl-1-hydroxypentyl)glutathione, never described before, and of S-3-(1-hydroxyhexyl)glutathione, previously evidenced in grapes, were chemically synthesized. An optimized extraction of glutathionylated precursors was then applied to Amarillo, Hallertau Blanc, and Mosaic hop samples. HPLC-ESI(+)MS/MS revealed, for the first time, the occurrence of S-3-(1-hydroxyhexyl)glutathione and S-3-(4-methyl-1-hydroxypentyl)glutathione in hop, at levels well above those reported for their cysteinylated counterparts. S-3-(1-Hydroxyhexyl)glutathione emerged in all cases as the major adduct in hop. Yet, although 3-sulfanylhexan-1-ol seems relatively ubiquitous in free, cysteinylated, and glutathionylated forms, the glutathione adduct of 3-sulfanyl-4-methylpentan-1-ol, never evidenced in other plants up to now, was found only in the Hallertau Blanc variety.

Involvement of Vacuolar Sequestration and Active Transport in Tolerance of Saccharomyces cerevisiae to Hop Iso-α-Acids▿ † ¶

PubMed Central

Hazelwood, Lucie A.; Walsh, Michael C.; Pronk, Jack T.; Daran, Jean-Marc

2010-01-01

The hop plant, Humulus lupulus L., has an exceptionally high content of secondary metabolites, the hop α-acids, which possess a range of beneficial properties, including antiseptic action. Studies performed on the mode of action of hop iso-α-acids have hitherto been restricted to lactic acid bacteria. The present study investigated molecular mechanisms of hop iso-α-acid resistance in the model eukaryote Saccharomyces cerevisiae. Growth inhibition occurred at concentrations of hop iso-α-acids that were an order of magnitude higher than those found with hop-tolerant prokaryotes. Chemostat-based transcriptome analysis and phenotype screening of the S. cerevisiae haploid gene deletion collection were used as complementary methods to screen for genes involved in hop iso-α-acid detoxification and tolerance. This screening and further analysis of deletion mutants confirmed that yeast tolerance to hop iso-α-acids involves three major processes, active proton pumping into the vacuole by the vacuolar-type ATPase to enable vacuolar sequestration of iso-α-acids and alteration of cell wall structure and, to a lesser extent, active export of iso-α-acids across the plasma membrane. Furthermore, iso-α-acids were shown to affect cellular metal homeostasis by acting as strong zinc and iron chelators. PMID:19915041

A Review of Hip Hop-Based Interventions for Health Literacy, Health Behaviors, and Mental Health.

PubMed

Robinson, Cendrine; Seaman, Elizabeth L; Montgomery, LaTrice; Winfrey, Adia

2018-06-01

African-American children and adolescents experience an undue burden of disease for many health outcomes compared to their White peers. More research needs to be completed for this priority population to improve their health outcomes and ameliorate health disparities. Integrating hip hop music or hip hop dance into interventions may help engage African-American youth in health interventions and improve their health outcomes. We conducted a review of the literature to characterize hip hop interventions and determine their potential to improve health. We searched Web of Science, Scopus, PsycINFO, and EMBASE to identify studies that assessed hip hop interventions. To be included, studies had to (1) be focused on a psychosocial or physical health intervention that included hip hop and (2) present quantitative data assessing intervention outcomes. Twenty-three articles were identified as meeting all inclusion criteria and were coded by two reviewers. Articles were assessed with regards to sample characteristics, study design, analysis, intervention components, and results. Hip hop interventions have been developed to improve health literacy, health behavior, and mental health. The interventions were primarily targeted to African-American and Latino children and adolescents. Many of the health literacy and mental health studies used non-experimental study designs. Among the 12 (of 14) health behavior studies that used experimental designs, the association between hip hop interventions and positive health outcomes was inconsistent. The number of experimental hip hop intervention studies is limited. Future research is required to determine if hip hop interventions can promote health.

The Pseudomonas syringae type III effector HopG1 targets mitochondria, alters plant development, and suppresses plant innate immunity

PubMed Central

Block, Anna; Guo, Ming; Li, Guangyong; Elowsky, Christian; Clemente, Thomas E.; Alfano, James R.

2009-01-01

Summary The bacterial plant pathogen Pseudomonas syringae uses a type III protein secretion system to inject type III effectors into plant cells. Primary targets of these effectors appear to be effector-triggered immunity (ETI) and pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI). The type III effector HopG1 is a suppressor of ETI that is broadly conserved in bacterial plant pathogens. Here we show that HopG1 from P. syringae pv. tomato DC3000 also suppresses PTI. Interestingly, HopG1 localizes to plant mitochondria, suggesting that its suppression of innate immunity may be linked to a perturbation of mitochondrial function. While HopG1 possesses no obvious mitochondrial signal peptide, its N-terminal two-thirds was sufficient for mitochondrial localization. A HopG1-GFP fusion lacking HopG1’s N-terminal 13 amino acids was not localized to the mitochondria reflecting the importance of the N-terminus for targeting. Constitutive expression of HopG1 in Arabidopsis thaliana, Nicotiana tabacum (tobacco) and Lycopersicon esculentum (tomato) dramatically alters plant development resulting in dwarfism, increased branching and infertility. Constitutive expression of HopG1 in planta leads to reduced respiration rates and an increased basal level of reactive oxygen species. These findings suggest that HopG1’s target is mitochondrial and that effector/target interaction promotes disease by disrupting mitochondrial functions. PMID:19863557

Differential regulation of detoxification enzymes in hepatic and mammary tissue by hops (Humulus lupulus) in vitro and in vivo

PubMed Central

Dietz, Birgit M.; Hagos, Ghenet K.; Eskra, Jillian N.; Wijewickrama, Gihani T.; Anderson, Jeffrey R.; Nikolic, Dejan; Guo, Jian; Wright, Brian; Chen, Shao-Nong; Pauli, Guido F.; van Breemen, Richard B.; Bolton, Judy L.

2013-01-01

Scope Hops contain the phytoestrogen, 8-prenylnaringenin, and the cytoprotective compound, xanthohumol (XH). XH induces the detoxification enzyme, NAD(P)H-quinone oxidoreductase (NQO1) in vitro; however, the tissue distribution of XH and 8-prenylnaringenin and their tissue specific activity have not been analyzed. Methods and results A standardized hop extract (p.o.) and XH (s.c.) were administered to Sprague-Dawley rats over four days. LC-MS-MS analysis of plasma, liver and mammary gland revealed that XH accumulated in liver and mammary glands. Compared with the low level in the original extract, 8-prenylnaringenin was enriched in the tissues. Hops and XH induced NQO1 in the liver, while only hops reduced NQO1 activity in the mammary gland. Mechanistic studies revealed that hops modulated NQO1 through three mechanisms. In liver cells, 1) XH modified Keap1 leading to Nrf2 translocation and antioxidant response element (ARE) activation; 2) hop-mediated ARE induction was partially mediated through phosphorylation of Nrf2 by PKC; 3) in breast cells, 8-prenylnaringenin reduced NQO1 likely through binding to ERα, recruiting Nrf2, and downregulating ARE-regulated genes. Conclusions XH and 8-prenylnaringenin in dietary hops are bioavailable to the target tissues. While hops and XH might be cytoprotective in the liver, 8-prenylnaringenin seems responsible for hop-mediated NQO1 reduction in the mammary gland. PMID:23512484

The Effect of Rap/Hip-Hop Music on Young Adult Smoking: An Experimental Study.

PubMed

Harakeh, Zeena; Bogt, Tom F M Ter

2018-02-16

Music may influence young people's behavior through its lyrics. Substance use references occur more frequently in rap/hip-hop than in other music genres. The aim was to examine whether the exposure to rap/hip-hop lyrics referring to substance use affected cigarette smoking. An experiment with a 3-group between subject design was conducted among 74 daily-smoking young adults ranging in age from 17 to 25 years old. Three conditions were tested in a mobile lab (camper vehicle) from May to December 2011, i.e., regular chart pop music (N = 28), rap/hip-hop with non-frequent references to substance use (N = 24), and rap/hip-hop with frequent references to substance use (N = 22). One-way ANOVA showed that participants listening to substance use infused rap/hip-hop songs felt significantly less pleasant, liked the songs less, and comprehended the songs less compared to participants listening to pop songs. Poisson loglinear analyses revealed that compared to the pop music condition, none of the two rap/hip-hop music conditions had a significant effect on acute smoking. Thus, contrary to expectations, the two different rap/hip-hop conditions did not have a significantly different effect on acute smoking. Listening to rap/hip-hop, even rap hip/hop with frequent referrals to substance use (primarily alcohol and drug use, and general smoking referrals), does not seem to encourage cigarette smoking among Dutch daily-smoking young adults, at least short term.

Development of a Mars Airplane Entry, Descent, and Flight Trajectory

NASA Technical Reports Server (NTRS)

Murray, James E.; Tartabini, Paul V.

2001-01-01

An entry, descent, and flight (EDF) trajectory profile for a Mars airplane mission is defined as consisting of the following elements: ballistic entry of an aeroshell; supersonic deployment of a decelerator parachute; subsonic release of a heat shield; release, unfolding, and orientation of an airplane to flight attitude; and execution of a pull up maneuver to achieve trimmed, horizontal flight. Using the Program to Optimize Simulated Trajectories (POST) a trajectory optimization problem was formulated. Model data representative of a specific Mars airplane configuration, current models of the Mars surface topography and atmosphere, and current estimates of the interplanetary trajectory, were incorporated into the analysis. The goal is to develop an EDF trajectory to maximize the surface-relative altitude of the airplane at the end of a pull up maneuver, while subject to the mission design constraints. The trajectory performance was evaluated for three potential mission sites and was found to be site-sensitive. The trajectory performance, examined for sensitivity to a number of design and constraint variables, was found to be most sensitive to airplane mass, aerodynamic performance characteristics, and the pull up Mach constraint. Based on the results of this sensitivity study, an airplane-drag optimized trajectory was developed that showed a significant performance improvement.

Hip external rotation strength predicts hop performance after anterior cruciate ligament reconstruction.

PubMed

Kline, Paul W; Burnham, Jeremy; Yonz, Michael; Johnson, Darren; Ireland, Mary Lloyd; Noehren, Brian

2018-04-01

Quadriceps strength and single-leg hop performance are commonly evaluated prior to return to sport after anterior cruciate ligament reconstruction (ACLR). However, few studies have documented potential hip strength deficits after ACLR, or ascertained the relative contribution of quadriceps and hip strength to hop performance. Patients cleared for return to sports drills after ACLR were compared to a control group. Participants' peak isometric knee extension, hip abduction, hip extension, and hip external rotation (HER) strength were measured. Participants also performed single-leg hops, timed hops, triple hops, and crossover hops. Between-limb comparisons for the ACLR to control limb and the non-operative limb were made using independent two-sample and paired sample t tests. Pearson's correlations and stepwise multiple linear regression were used to determine the relationships and predictive ability of limb strength, graft type, sex, and limb dominance to hop performance. Sixty-five subjects, 20 ACLR [11F, age 22.8 (15-45) years, 8.3 ± 2 months post-op, mass 70.47 ± 12.95 kg, height 1.71 ± 0.08 m, Tegner 5.5 (3-9)] and 45 controls [22F, age 25.8 (15-45) years, mass 74.0 ± 15.2 kg, height 1.74 ± 0.1 m, Tegner 6 (3-7)], were tested. Knee extension (4.4 ± 1.5 vs 5.4 ± 1.8 N/kg, p = 0.02), HER (1.4 ± 0.4 vs 1.7 ± 0.5 N/kg, p = 0.04), single-leg hop (146 ± 37 vs 182 ± 38% limb length, p < 0.01), triple hop (417 ± 106 vs 519 ± 102% limb length, p < 0.01), timed hop (3.3 ± 2.0 vs 2.3 ± 0.6 s, p < 0.01), and crossover hop (364 ± 107 vs 446 ± 123% limb length, p = 0.01) were significantly impaired in the operative versus control subject limbs. Similar deficits existed between the operative and non-operative limbs. Knee extension and HER strength were significantly correlated with each of the hop tests, but only HER significantly predicted hop performance. After ACLR, patients have persistent HER strength, knee extension strength, and hop test deficits in the operative limb compared to the control and non-operative limbs, even after starting sport-specific drills. Importantly, HER strength independently predicted hop performance. Based on these findings, to resolve between-limb deficits in strength and hop performance clinicians should include HER strengthening exercises in post-operative rehabilitation. Prognostic Study, Level II.

Electronic excitation and quenching of atoms at insulator surfaces

NASA Technical Reports Server (NTRS)

Swaminathan, P. K.; Garrett, Bruce C.; Murthy, C. S.

1988-01-01

A trajectory-based semiclassical method is used to study electronically inelastic collisions of gas atoms with insulator surfaces. The method provides for quantum-mechanical treatment of the internal electronic dynamics of a localized region involving the gas/surface collision, and a classical treatment of all the nuclear degrees of freedom (self-consistently and in terms of stochastic trajectories), and includes accurate simulation of the bath-temperature effects. The method is easy to implement and has a generality that holds promise for many practical applications. The problem of electronically inelastic dynamics is solved by computing a set of stochastic trajectories that on thermal averaging directly provide electronic transition probabilities at a given temperature. The theory is illustrated by a simple model of a two-state gas/surface interaction.

Analysis of the Free-Energy Surface of Proteins from Reversible Folding Simulations

PubMed Central

Allen, Lucy R.; Krivov, Sergei V.; Paci, Emanuele

2009-01-01

Computer generated trajectories can, in principle, reveal the folding pathways of a protein at atomic resolution and possibly suggest general and simple rules for predicting the folded structure of a given sequence. While such reversible folding trajectories can only be determined ab initio using all-atom transferable force-fields for a few small proteins, they can be determined for a large number of proteins using coarse-grained and structure-based force-fields, in which a known folded structure is by construction the absolute energy and free-energy minimum. Here we use a model of the fast folding helical λ-repressor protein to generate trajectories in which native and non-native states are in equilibrium and transitions are accurately sampled. Yet, representation of the free-energy surface, which underlies the thermodynamic and dynamic properties of the protein model, from such a trajectory remains a challenge. Projections over one or a small number of arbitrarily chosen progress variables often hide the most important features of such surfaces. The results unequivocally show that an unprojected representation of the free-energy surface provides important and unbiased information and allows a simple and meaningful description of many-dimensional, heterogeneous trajectories, providing new insight into the possible mechanisms of fast-folding proteins. PMID:19593364

Analysis of the free-energy surface of proteins from reversible folding simulations.

PubMed

Allen, Lucy R; Krivov, Sergei V; Paci, Emanuele

2009-07-01

Computer generated trajectories can, in principle, reveal the folding pathways of a protein at atomic resolution and possibly suggest general and simple rules for predicting the folded structure of a given sequence. While such reversible folding trajectories can only be determined ab initio using all-atom transferable force-fields for a few small proteins, they can be determined for a large number of proteins using coarse-grained and structure-based force-fields, in which a known folded structure is by construction the absolute energy and free-energy minimum. Here we use a model of the fast folding helical lambda-repressor protein to generate trajectories in which native and non-native states are in equilibrium and transitions are accurately sampled. Yet, representation of the free-energy surface, which underlies the thermodynamic and dynamic properties of the protein model, from such a trajectory remains a challenge. Projections over one or a small number of arbitrarily chosen progress variables often hide the most important features of such surfaces. The results unequivocally show that an unprojected representation of the free-energy surface provides important and unbiased information and allows a simple and meaningful description of many-dimensional, heterogeneous trajectories, providing new insight into the possible mechanisms of fast-folding proteins.

QTL examination of a bi-parental mapping population segregating for “short-stature” in hop (Humulus lupulus L.)

USDA-ARS?s Scientific Manuscript database

Increasing labor costs and reduced labor pools for hop production have resulted in the necessity to develop strategies to improve efficiency and automate hop production and harvest. One solution for reducing labor inputs is the use and production of “low-trellis” hop varieties optimized for mechani...

First report of hop stunt viroid from sweet cherry with dapple apple fruit symptoms in China

USDA-ARS?s Scientific Manuscript database

Hop stunt viroid (HSVd), the type member of the genus Hostuviroid, family Pospiviroidae, was first described from hops with stunt disease in Japan. HSVd has a wide host range that includes hop, cucumber, citrus, grapevine, plum, pear, peach, apricot and almond and is the causal agent of serious dis...

Hip-Hop(e): The Cultural Practice and Critical Pedagogy of International Hip-Hop. Adolescent Cultures, School, and Society. Volume 56

ERIC Educational Resources Information Center

Porfilio, Brad J., Ed.; Viola, Michael J., Ed.

2012-01-01

Illuminating hip-hop as an important cultural practice and a global social movement, this collaborative project highlights the emancipatory messages and cultural work generated by the organic intellectuals of global hip-hop. Contributors describe the social realities--globalization, migration, poverty, criminalization, and racism--youth are…

Hip-Hop and the Academic Canon

ERIC Educational Resources Information Center

Abe, Daudi

2009-01-01

Over the last 30 years, the hip-hop movement has risen from the margins to become the preeminent force in US popular culture. In more recent times academics have begun to harness the power of hip-hop culture and use it as a means of infusing transformative knowledge into the mainstream academic discourse. On many college campuses, hip-hop's…

21 CFR 173.270 - Hexane.

Code of Federal Regulations, 2010 CFR

2010-04-01

..., at a level not to exceed 25 parts per million. (b) In hops extract as a residue from the extraction of hops, at a level not to exceed 2.2 percent by weight; Provided, That: (1) The hops extract is added to the wort before or during cooking in the manufacture of beer. (2) The label of the hops extract...

21 CFR 173.270 - Hexane.

Code of Federal Regulations, 2011 CFR

2011-04-01

..., at a level not to exceed 25 parts per million. (b) In hops extract as a residue from the extraction of hops, at a level not to exceed 2.2 percent by weight; Provided, That: (1) The hops extract is added to the wort before or during cooking in the manufacture of beer. (2) The label of the hops extract...

Human Exploration of Mars

NASA Astrophysics Data System (ADS)

Gwynne, Owen; McKay, Chris; Zubrin, Robert

1991-06-01

Novel approaches to the human exploration of Mars are considered with emphasis on a space suit design, extraterrestrial surface mobility, and water supply. A possible way of transporting personnel on the surface of Mars uses a suborbital rocket that will hop from one site to the next, refuelling each time it lands and giving the Martian explorers effective global mobility. Telepresence could be used to avoid limiting the people on Mars to a small exploration area as a result of a lack of transportation infrastructure. Drawings and photographs are included.

Dynamics of charges and solitons

NASA Astrophysics Data System (ADS)

Barros, Manuel; Ferrández, Ángel; Garay, Óscar J.

2018-02-01

We first show that trajectories traced by charges moving in rotational magnetic fields are, basically, the non-parallel geodesics of surfaces of revolution with coincident axis. Thus, people living in a surface of revolution are not able to sense the magnetic Hall effect induced by the surrounding magnetic field and perceive charges as influenced, exclusively, by the gravity action on the surface of revolution. Secondly, the extended Hasimoto transformations are introduced and then used to identify trajectories of charges moving through a Killing rotational magnetic field in terms of non-circular elastic curves. As a consequence, we see that in this case charges evolve along trajectories which are obtained as extended Hasimoto transforms of solitons of the filament equation.

Scaffold hopping in drug discovery using inductive logic programming.

PubMed

Tsunoyama, Kazuhisa; Amini, Ata; Sternberg, Michael J E; Muggleton, Stephen H

2008-05-01

In chemoinformatics, searching for compounds which are structurally diverse and share a biological activity is called scaffold hopping. Scaffold hopping is important since it can be used to obtain alternative structures when the compound under development has unexpected side-effects. Pharmaceutical companies use scaffold hopping when they wish to circumvent prior patents for targets of interest. We propose a new method for scaffold hopping using inductive logic programming (ILP). ILP uses the observed spatial relationships between pharmacophore types in pretested active and inactive compounds and learns human-readable rules describing the diverse structures of active compounds. The ILP-based scaffold hopping method is compared to two previous algorithms (chemically advanced template search, CATS, and CATS3D) on 10 data sets with diverse scaffolds. The comparison shows that the ILP-based method is significantly better than random selection while the other two algorithms are not. In addition, the ILP-based method retrieves new active scaffolds which were not found by CATS and CATS3D. The results show that the ILP-based method is at least as good as the other methods in this study. ILP produces human-readable rules, which makes it possible to identify the three-dimensional features that lead to scaffold hopping. A minor variant of a rule learnt by ILP for scaffold hopping was subsequently found to cover an inhibitor identified by an independent study. This provides a successful result in a blind trial of the effectiveness of ILP to generate rules for scaffold hopping. We conclude that ILP provides a valuable new approach for scaffold hopping.

Aspirin increases susceptibility of Helicobacter pylori to metronidazole by augmenting endocellular concentrations of antimicrobials.

PubMed

Zhang, Xiao-Ping; Wang, Wei-Hong; Tian, Yu; Gao, Wen; Li, Jiang

2009-02-28

To investigate the mechanisms of aspirin increasing the susceptibility of Helicobacter pylori (H pylori) to metronidazole. H pylori reference strain 26695 and two metronidazole-resistant isolates of H pylori were included in this study. Strains were incubated in Brucella broth with or without aspirin (1 mmol/L). The rdxA gene of H pylori was amplified by PCR and sequenced. The permeability of H pylori to antimicrobials was determined by analyzing the endocellular radioactivity of the cells after incubated with [7-(3)H]-tetracycline. The outer membrane proteins (OMPs) of H pylori 26695 were depurated and analyzed by SDS-PAGE. The expression of 5 porins (hopA, hopB, hopC, hopD and hopE) and the putative RND efflux system (hefABC) of H pylori were analyzed using real-time quantitative PCR. The mutations in rdxA gene did not change in metronidazole resistant isolates treated with aspirin. The radioactivity of H pylori increased when treated with aspirin, indicating that aspirin improved the permeability of the outer membrane of H pylori. However, the expression of two OMP bands between 55 kDa and 72 kDa altered in the presence of aspirin. The expression of the mRNA of hopA, hopB, hopC, hopD, hopE and hefA, hefB, hefC of H pylori did not change when treated with aspirin. Although aspirin increases the susceptibility of H pylori to metronidazole, it has no effect on the mutations of rdxA gene of H pylori. Aspirin increases endocellular concentrations of antimicrobials probably by altering the OMP expression.

Standardization of Weed Pollen Extracts, Japanese Hop and Mugwort, in Korea

PubMed Central

Jeong, Kyoung Yong; Son, Mina; Choi, Soo-Young; Park, Kyung Hee; Park, Hye Jung; Hong, Chein-Soo; Lee, Jae-Hyun

2016-01-01

Purpose Japanese hop (Humulus spp.) and mugwort (Artemisia spp.) are notable causes of autumn pollinosis in East Asia. However, Japanese hop and mugwort pollen extracts, which are widely used for the diagnosis, have not been standardized. This study was performed to standardize Japanese hop and mugwort pollen extracts. Materials and Methods Allergen extracts were prepared in a standardized way using locally collected Humulus japonicus and purchased Artemisia vulgaris pollens. The immunoglobulin E (IgE) reactivities of prepared extracts were compared with commercial extracts via IgE immunoblotting and inhibition analyses. Intradermal skin tests were performed to determine the bioequivalent allergy unit (BAU). Results The IgE reactive components of the extracts via IgE immunoblotting were similar to those of commercial extracts. A 11-kDa allergen showed the strongest IgE reactivity in Japanese hop, as did a 28-kDa allergen in mugwort pollen extracts. Allergenic potencies of the investigatory Japanese hop and mugwort extracts were essentially indistinguishable from the commercial ones. Sums of erythema of 50 mm by the intradermal skin test (ΣED50) were calculated to be 14.4th and 13.6th three-fold dilutions for Japanese hop and mugwort extracts, respectively. Therefore, the allergenic activity of the prepared extracts was 90827.4 BAU/mg for Japanese hop and 34412 BAU/mg for mugwort. Conclusion We produced Japanese hop and mugwort pollen extracts using a standardized method. Standardized Japanese hop and mugwort pollen extracts will facilitate the production of improved diagnostic and immunotherapeutic reagents. PMID:26847293

Implementation of a School Nurse-led Intervention for Children With Severe Obesity in New York City Schools.

PubMed

Schroeder, Krista; Jia, Haomiao; Wang, Y Claire; Smaldone, Arlene

The Healthy Options and Physical Activity Program (HOP) is a school nurse-led intervention for children with severe obesity. HOP was developed by experts at the New York City Department of Health and Mental Hygiene and implemented in New York City schools beginning in 2012. The purpose of this study was to evaluate HOP implementation with the goal of informing HOP refinement and potential future HOP dissemination. This study entailed a retrospective analysis of secondary data. Analytic methods included descriptive statistics, Wilcoxon rank sum and Chi square tests, and multivariate logistic regression. During the 2012-2013 school year, 20,518 children were eligible for HOP. Of these, 1054 (5.1%) were enrolled in the program. On average, enrolled children attended one HOP session during the school year. Parent participation was low (3.2% of HOP sessions). Low nurse workload, low school poverty, higher grade level, higher BMI percentile, and chronic illness diagnosis were associated with student enrollment in HOP. As currently delivered, HOP is not likely to be efficacious. Lessons learned from this evaluation are applicable to future nurse-led obesity interventions. Prior to implementing a school nurse-led obesity intervention, nursing workload and available support must be carefully considered. Interventions should be designed to facilitate (and possibly require) parent involvement. Nurses who deliver obesity interventions may require additional training in obesity treatment. With attention to these lessons learned, evidence-based school nurse-led obesity interventions can be developed. Copyright © 2017 Elsevier Inc. All rights reserved.

Genetic interactions between the chromosome axis-associated protein Hop1 and homologous recombination determinants in Schizosaccharomyces pombe.

PubMed

Brown, Simon David; Jarosinska, Olga Dorota; Lorenz, Alexander

2018-03-17

Hop1 is a component of the meiosis-specific chromosome axis and belongs to the evolutionarily conserved family of HORMA domain proteins. Hop1 and its orthologs in higher eukaryotes are a major factor in promoting double-strand DNA break formation and inter-homolog recombination. In budding yeast and mammals, they are also involved in a meiotic checkpoint kinase cascade monitoring the completion of double-strand DNA break repair. We used the fission yeast, Schizosaccharomyces pombe, which lacks a canonical synaptonemal complex to test whether Hop1 has a role beyond supporting the generation of double-strand DNA breaks and facilitating inter-homolog recombination events. We determined how mutants of homologous recombination factors genetically interact with hop1, studied the role(s) of the HORMA domain of Hop1, and characterized a bio-informatically predicted interactor of Hop1, Aho1 (SPAC688.03c). Our observations indicate that in fission yeast, Hop1 does require its HORMA domain to support wild-type levels of meiotic recombination and localization to meiotic chromatin. Furthermore, we show that hop1∆ only weakly interacts genetically with mutants of homologous recombination factors, and in fission yeast likely has no major role beyond break formation and promoting inter-homolog events. We speculate that after the evolutionary loss of the synaptonemal complex, Hop1 likely has become less important for modulating recombination outcome during meiosis in fission yeast, and that this led to a concurrent rewiring of genetic pathways controlling meiotic recombination.

Two Hop Adaptive Vector Based Quality Forwarding for Void Hole Avoidance in Underwater WSNs

PubMed Central

Javaid, Nadeem; Ahmed, Farwa; Wadud, Zahid; Alrajeh, Nabil; Alabed, Mohamad Souheil; Ilahi, Manzoor

2017-01-01

Underwater wireless sensor networks (UWSNs) facilitate a wide range of aquatic applications in various domains. However, the harsh underwater environment poses challenges like low bandwidth, long propagation delay, high bit error rate, high deployment cost, irregular topological structure, etc. Node mobility and the uneven distribution of sensor nodes create void holes in UWSNs. Void hole creation has become a critical issue in UWSNs, as it severely affects the network performance. Avoiding void hole creation benefits better coverage over an area, less energy consumption in the network and high throughput. For this purpose, minimization of void hole probability particularly in local sparse regions is focused on in this paper. The two-hop adaptive hop by hop vector-based forwarding (2hop-AHH-VBF) protocol aims to avoid the void hole with the help of two-hop neighbor node information. The other protocol, quality forwarding adaptive hop by hop vector-based forwarding (QF-AHH-VBF), selects an optimal forwarder based on the composite priority function. QF-AHH-VBF improves network good-put because of optimal forwarder selection. QF-AHH-VBF aims to reduce void hole probability by optimally selecting next hop forwarders. To attain better network performance, mathematical problem formulation based on linear programming is performed. Simulation results show that by opting these mechanisms, significant reduction in end-to-end delay and better throughput are achieved in the network. PMID:28763014

Two Hop Adaptive Vector Based Quality Forwarding for Void Hole Avoidance in Underwater WSNs.

PubMed

Javaid, Nadeem; Ahmed, Farwa; Wadud, Zahid; Alrajeh, Nabil; Alabed, Mohamad Souheil; Ilahi, Manzoor

2017-08-01

Underwater wireless sensor networks (UWSNs) facilitate a wide range of aquatic applications in various domains. However, the harsh underwater environment poses challenges like low bandwidth, long propagation delay, high bit error rate, high deployment cost, irregular topological structure, etc. Node mobility and the uneven distribution of sensor nodes create void holes in UWSNs. Void hole creation has become a critical issue in UWSNs, as it severely affects the network performance. Avoiding void hole creation benefits better coverage over an area, less energy consumption in the network and high throughput. For this purpose, minimization of void hole probability particularly in local sparse regions is focused on in this paper. The two-hop adaptive hop by hop vector-based forwarding (2hop-AHH-VBF) protocol aims to avoid the void hole with the help of two-hop neighbor node information. The other protocol, quality forwarding adaptive hop by hop vector-based forwarding (QF-AHH-VBF), selects an optimal forwarder based on the composite priority function. QF-AHH-VBF improves network good-put because of optimal forwarder selection. QF-AHH-VBF aims to reduce void hole probability by optimally selecting next hop forwarders. To attain better network performance, mathematical problem formulation based on linear programming is performed. Simulation results show that by opting these mechanisms, significant reduction in end-to-end delay and better throughput are achieved in the network.

The Habc Domain of the SNARE Vam3 Interacts with the HOPS Tethering Complex to Facilitate Vacuole Fusion*

PubMed Central

Lürick, Anna; Kuhlee, Anne; Bröcker, Cornelia; Kümmel, Daniel; Raunser, Stefan; Ungermann, Christian

2015-01-01

Membrane fusion at vacuoles requires a consecutive action of the HOPS tethering complex, which is recruited by the Rab GTPase Ypt7, and vacuolar SNAREs to drive membrane fusion. It is assumed that the Sec1/Munc18-like Vps33 within the HOPS complex is largely responsible for SNARE chaperoning. Here, we present direct evidence for HOPS binding to SNAREs and the Habc domain of the Vam3 SNARE protein, which may explain its function during fusion. We show that HOPS interacts strongly with the Vam3 Habc domain, assembled Q-SNAREs, and the R-SNARE Ykt6, but not the Q-SNARE Vti1 or the Vam3 SNARE domain. Electron microscopy combined with Nanogold labeling reveals that the binding sites for vacuolar SNAREs and the Habc domain are located in the large head of the HOPS complex, where Vps16 and Vps33 have been identified before. Competition experiments suggest that HOPS bound to the Habc domain can still interact with assembled Q-SNAREs, whereas Q-SNARE binding prevents recognition of the Habc domain. In agreement, membranes carrying Vam3ΔHabc fuse poorly unless an excess of HOPS is provided. These data suggest that the Habc domain of Vam3 facilitates the assembly of the HOPS/SNARE machinery at fusion sites and thus supports efficient membrane fusion. PMID:25564619

Hip-Hop Is My Passport! Using Hip-Hop and Digital Literacies to Understand Global Citizenship Education

ERIC Educational Resources Information Center

Horton, Akesha Monique

2013-01-01

Hip-hop has exploded around the world among youth. It is not simply an American source of entertainment; it is a global cultural movement that provides a voice for youth worldwide who have not been able to express their "cultural world" through mainstream media. The emerging field of critical hip-hop pedagogy has produced little…

"Deeper than Rap": Gifted Males and Their Relationship with Hip Hop Culture

ERIC Educational Resources Information Center

Callahan, J. Sean; Grantham, Tarek C.

2012-01-01

One would be hard-pressed to deny the impact that hip hop is having on gifted students. More specifically, because hip hop is a creative and exciting male-dominated culture, gifted males gravitate to hip hop culture. From the perspective of two Black men from two different generations, this article was inspired by discussions about the role of hip…

HPLC Analysis of [Alpha]- and [Beta]-Acids in Hops

ERIC Educational Resources Information Center

Danenhower, Travis M.; Force, Leyna J.; Petersen, Kenneth J.; Betts, Thomas A.; Baker, Gary A.

2008-01-01

Hops have been used for centuries to impart aroma and bitterness to beer. The cones of the female hop plant contain both essential oils, which include many of the fragrant components of hops, and a collection of compounds known as [alpha]- and [beta]-acids that are the precursors to bittering agents. In order for brewers to predict the ultimate…

Complex Personhood of Hip Hop & the Sensibilities of the Culture That Fosters Knowledge of Self & Self-Determination

ERIC Educational Resources Information Center

Love, Bettina L.

2016-01-01

Hip hop music and culture have a complex identity in that hip hop is based in self-determination, resistance, and the long enduring fight for Black freedom, but was also created alongside the seductiveness of the material and psychological conditions of capitalism, sexism, and patriarchy. Hip hop pedagogy (HHP) as a pedagogical framework is…

HIP HOP for HIV Awareness: Using Hip Hop Culture to Promote Community-Level HIV Prevention

ERIC Educational Resources Information Center

Hill, Mandy J.; Hallmark, Camden J.; McNeese, Marlene; Blue, Nike; Ross, Michael W.

2014-01-01

The goal of this paper was to determine the effectiveness of the HIP HOP for HIV Awareness intervention, an innovative model utilising an exchange of an HIV test for a hip hop concert ticket, in a metropolitan city among African American youth and young adults. A subset of intervention participants participated in standardised testing, sex…

Advances and Promises of Layered Halide Hybrid Perovskite Semiconductors.

PubMed

Pedesseau, Laurent; Sapori, Daniel; Traore, Boubacar; Robles, Roberto; Fang, Hong-Hua; Loi, Maria Antonietta; Tsai, Hsinhan; Nie, Wanyi; Blancon, Jean-Christophe; Neukirch, Amanda; Tretiak, Sergei; Mohite, Aditya D; Katan, Claudine; Even, Jacky; Kepenekian, Mikaël

2016-11-22

Layered halide hybrid organic-inorganic perovskites (HOP) have been the subject of intense investigation before the rise of three-dimensional (3D) HOP and their impressive performance in solar cells. Recently, layered HOP have also been proposed as attractive alternatives for photostable solar cells and revisited for light-emitting devices. In this review, we combine classical solid-state physics concepts with simulation tools based on density functional theory to overview the main features of the optoelectronic properties of layered HOP. A detailed comparison between layered and 3D HOP is performed to highlight differences and similarities. In the same way as the cubic phase was established for 3D HOP, here we introduce the tetragonal phase with D 4h symmetry as the reference phase for 2D monolayered HOP. It allows for detailed analysis of the spin-orbit coupling effects and structural transitions with corresponding electronic band folding. We further investigate the effects of octahedral tilting on the band gap, loss of inversion symmetry and possible Rashba effect, quantum confinement, and dielectric confinement related to the organic barrier, up to excitonic properties. Altogether, this paper aims to provide an interpretive and predictive framework for 3D and 2D layered HOP optoelectronic properties.

A rapid isothermal assay for the detection of Hop stunt viroid in hop plants (Humulus lupulus), and its application in disease surveys.

PubMed

Kappagantu, Madhu; Villamor, Dan Edward V; Bullock, Jeff M; Eastwell, Kenneth C

2017-07-01

Hop stunt disease caused by Hop stunt viroid (HSVd) is a growing threat to hop cultivation globally. HSVd spreads mainly by use of contaminated planting material and by mechanical means. Thorough testing of hop yards and removal of infected bines are critical components of efforts to control the spread of the disease. Reverse transcription-polymerase chain reaction (RT-PCR) has become the primary technique used for HSVd detection; however, sample handling and analysis are technically challenging. In this study, a robust reverse transcription-recombinase polymerase amplification (RT-RPA) assay was developed to facilitate analysis of multiple samples. The assay was optimized with all major variants of HSVd from other host species in addition to hop variants. Used in conjunction with sample collection cards, RT-RPA accommodates large sample numbers. Greenhouse and farm samples tested with RT-RPA were also tested with RT-PCR and a 100% correlation between the two techniques was found. Copyright © 2017. Published by Elsevier B.V.

Extreme trajectory approach to the problem of determining the degree of stability of a laser surface scanning system

NASA Astrophysics Data System (ADS)

Nikitin, V. N.; Chemodanov, V. B.

2018-02-01

The degree of stability of a laser system for surface scanning with nonlinear multiplicative crosstalks is discussed. To determine its stability, the action functional is introduced, which is defined on the set of virtual (achievable) trajectories. The action functional is a measure of external action, which should be applied to a system to move it along a predetermined trial trajectory in the state space.The degree of stability of the system depends on the minimum value of the action functional which is reached on the extreme trajectory transferring the laser scanning system from equilibrium to the limit of the normal operation range. Numerical methods are proposed for calculating the degree of stability.

Antifeedant activity of xanthohumol and supercritical carbon dioxide extract of spent hops against stored product pests.

PubMed

Jackowski, J; Hurej, M; Rój, E; Popłoński, J; Kośny, L; Huszcza, E

2015-08-01

Xanthohumol, a prenylated flavonoid from hops, and a supercritical carbon dioxide extract of spent hops were studied for their antifeedant activity against stored product insect pests: Sitophilus granarius L., Tribolium confusum Duv. and Trogoderma granarium Everts. Xanthohumol exhibited medium deterrent activity against the adults of S. granarius L. and larvae of T. confusum Duv. The spent hops extract was more active than xanthohumol towards the adults of T. confusum Duv. The potential application of the crude spent hops extract as a feeding deterrent against the stored product pests is proposed.

Single-Leg Hop Test Performance and Isokinetic Knee Strength After Anterior Cruciate Ligament Reconstruction in Athletes

PubMed Central

Sueyoshi, Ted; Nakahata, Akihiro; Emoto, Gen; Yuasa, Tomoki

2017-01-01

Background: Isokinetic strength and hop tests are commonly used to assess athletes’ readiness to return to sport after knee surgery. Purpose/Hypothesis: The purpose of this study was to investigate the results of single-leg hop and isokinetic knee strength testing in athletes who underwent anterior cruciate ligament reconstruction (ACLR) upon returning to sport participation as well as to study the correlation between these 2 test batteries. The secondary purpose was to compare the test results by graft type (patellar tendon or hamstring). It was hypothesized that there would be no statistically significant limb difference in either isokinetic knee strength or single-leg hop tests, that there would be a moderate to strong correlation between the 2 test batteries, and that there would be no significant difference between graft types. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Twenty-nine high school and collegiate athletes who underwent ACLR participated in this study. At the time of return to full sport participation, a series of hop tests and knee extension/flexion isokinetic strength measurements were conducted. The results were analyzed using analysis of variance and Pearson correlation (r). Results: The timed 6-m hop test was the only hop test that showed a significant difference between the involved and uninvolved limbs (2.3 and 2.2 seconds, respectively; P = .02). A significant difference between limbs in knee strength was found for flexion peak torque/body weight at 180 deg/s (P = .03), flexion total work/body weight at 180 deg/s (P = .04), and flexion peak torque/body weight at 300 deg/s (P = .03). The strongest correlation between the hop tests and knee strength was found between the total distance of the hop tests and flexion total work/body weight at 300 deg/s (r = 0.69) and between the timed 6-m hop test and flexion peak torque/body weight at 300 deg/s (r = –0.54). There was no statistically significant difference in hop test performance or isokinetic knee strength between graft types. Conclusion: The single-leg hop tests and isokinetic strength measurements were both useful for a bilateral comparison of knee functional performance and strength. Knee flexion strength deficits and flexion-to-extension ratios seemed to be correlated with single-leg hop test performance. There was no difference in postoperative hop test performance or knee strength according to graft type. PMID:29164167

Fermiology and Superconductivity of Topological Surface States in PdTe2

NASA Astrophysics Data System (ADS)

Clark, O. J.; Neat, M. J.; Okawa, K.; Bawden, L.; Marković, I.; Mazzola, F.; Feng, J.; Sunko, V.; Riley, J. M.; Meevasana, W.; Fujii, J.; Vobornik, I.; Kim, T. K.; Hoesch, M.; Sasagawa, T.; Wahl, P.; Bahramy, M. S.; King, P. D. C.

2018-04-01

We study the low-energy surface electronic structure of the transition-metal dichalcogenide superconductor PdTe2 by spin- and angle-resolved photoemission, scanning tunneling microscopy, and density-functional theory-based supercell calculations. Comparing PdTe2 with its sister compound PtSe2 , we demonstrate how enhanced interlayer hopping in the Te-based material drives a band inversion within the antibonding p -orbital manifold well above the Fermi level. We show how this mediates spin-polarized topological surface states which form rich multivalley Fermi surfaces with complex spin textures. Scanning tunneling spectroscopy reveals type-II superconductivity at the surface, and moreover shows no evidence for an unconventional component of its superconducting order parameter, despite the presence of topological surface states.

Single-leg hop testing following fatiguing exercise: reliability and biomechanical analysis.

PubMed

Augustsson, J; Thomeé, R; Lindén, C; Folkesson, M; Tranberg, R; Karlsson, J

2006-04-01

A fatiguing exercise protocol was combined with single-leg hop testing to improve the possibilities of evaluating the effects of training or rehabilitation interventions. In the first test-retest experiment, 11 healthy male subjects performed two trials of single-leg hops under three different test conditions: non-fatigued and following fatiguing exercise, which consisted of unilateral weight machine knee extensions at 80% and 50%, respectively, of 1 repetition maximum (1 RM) strength. Intraclass correlation coefficients ranged from 0.75 to 0.98 for different hop test conditions, indicating that all tests were reliable. For the second experiment, eight healthy male subjects performed the fatiguing exercise protocol to investigate how fatigue influences lower-extremity joint kinematics and kinetics during single-leg hops. Hip, knee and ankle joint angles, moments and powers, as well as ground-reaction forces were recorded with a six-camera, motion-capture system and a force platform. Recovery of hop performance following the fatiguing exercise was also measured. During the take-off for the single-leg hops, hip and knee flexion angles, generated powers for the knee and ankle joints, and ground-reaction forces decreased for the fatigued hop conditions compared with the non-fatigued condition (P<0.05). Compared with landing during the non-fatigued condition, hip moments and ground-reaction forces were lower for the fatigued hop conditions (P<0.05). The negative joint power was two to three times greater for the knee than for the hip and five to 10 times greater for the knee than for the ankle during landing for all test conditions (P<0.05). Most measured variables had recovered three minutes post-exercise. It is concluded that the fatiguing exercise protocol combined with single-leg hop testing was a reliable method for investigating functional performance under fatigued test conditions. Further, subjects utilized an adapted hop strategy, which employed less hip and knee flexion and generated powers for the knee and ankle joints during take-off, and less hip joint moments during landing under fatigued conditions. The large negative power values observed at the knee joint during the landing phase of the single-leg hop, during which the quadriceps muscle activates eccentrically, indicate that not only hop distance but also the ability to perform successful landings should be investigated when assessing dynamic knee function.

Balancing the competing requirements of saltatorial and fossorial specialisation: burrowing costs in the spinifex hopping mouse, Notomys alexis.

PubMed

White, Craig R; Matthews, Philip G D; Seymour, Roger S

2006-06-01

Semi-fossorial animals (burrowing surface foragers) need to balance the competing morphological requirements of terrestrial and burrowing locomotion. These species rarely show the same degree of claw, forelimb and pectoral girdle structural development that fully fossorial forms (burrowing subterranean foragers) do, but nevertheless invest considerable amounts of energy in burrow systems. The compromise between terrestrial and burrowing locomotion was investigated by measuring net costs of burrowing and pedestrian transport in the spinifex hopping mouse, Notomys alexis, a species that forages in open areas in arid environments and is adapted for saltatorial locomotion. The net cost of transport by burrowing of hopping mice was found to be more expensive than for specialised fossorial species, and burrows were estimated to represent an energy investment equivalent to the terrestrial locomotion expected to be incurred in 17-100 days. A phylogenetically independent-contrasts approach revealed that morphological specialisation for burrowing was associated with low maximum running speeds in fossorial mammals and, for non-fossorial rodents and marsupials, maximum running speed was positively correlated with an index of habitat structure that ranged from arboreal to open desert. The high terrestrial speeds attainable by this semi-fossorial species by saltatory locomotion apparently outweigh the energetic savings that would be associated with burrowing specialisation.

Hip Hop Culture's OGs: A Narrative Inquiry into the Intersection of Hip Hop Culture, Black Males and Their Schooling Experiences

ERIC Educational Resources Information Center

Buchanan, Ian P.

2013-01-01

Using a critical race lens, this narrative study employs a focus group design to explore the intersections between black males, hip hop culture and schooling experiences. To provide a sociocultural grounding, this study first reviews the research literature around hip hop culture.s sociocultural development and its impact as a culture force that…

Beats, Rhymes, and Classroom Life: Hip-Hop Pedagogy and the Politics of Identity

ERIC Educational Resources Information Center

Hill, Marc Lamont

2009-01-01

For over a decade, educators have looked to capitalize on the appeal of hip-hop culture, sampling its language, techniques, and styles as a way of reaching out to students. But beyond a fashionable hipness, what does hip-hop have to offer our schools? In this revelatory new book, Marc Lamont Hill shows how a serious engagement with hip-hop culture…

Engaging Black Males on Their Own Terms: What Schools Can Learn from Black Males Who Produce Hip-Hop

ERIC Educational Resources Information Center

Irby, Decoteau J.; Petchauer, Emery; Kirkland, David

2013-01-01

Education scholars and practitioners have much to learn about engagement and motivation of Black males by directing their inquiries to more organic sites of hip-hop cultural production outside of schools. One such site is the hip-hop's informal labor economy where Black males engage in earning money through hip-hop cultural production. Labor…

Bringing Back Sweet (and Not so Sweet) Memories: The Cultural Politics of Memory, Hip-Hop, and Generational Identities

ERIC Educational Resources Information Center

Hill, Marc Lamont

2009-01-01

This article examines the salience of collective "memory" and "remembering" among a group of students in Hip-Hop Lit, a hip-hop centered English literature course that I co-taught at "Howard High School," an urban high school in the Northeastern United States. Specifically, this article examines the memory work that occurred within Hip-Hop Lit in…

Interpolating moving least-squares methods for fitting potential energy surfaces: using classical trajectories to explore configuration space.

PubMed

Dawes, Richard; Passalacqua, Alessio; Wagner, Albert F; Sewell, Thomas D; Minkoff, Michael; Thompson, Donald L

2009-04-14

We develop two approaches for growing a fitted potential energy surface (PES) by the interpolating moving least-squares (IMLS) technique using classical trajectories. We illustrate both approaches by calculating nitrous acid (HONO) cis-->trans isomerization trajectories under the control of ab initio forces from low-level HF/cc-pVDZ electronic structure calculations. In this illustrative example, as few as 300 ab initio energy/gradient calculations are required to converge the isomerization rate constant at a fixed energy to approximately 10%. Neither approach requires any preliminary electronic structure calculations or initial approximate representation of the PES (beyond information required for trajectory initial conditions). Hessians are not required. Both approaches rely on the fitting error estimation properties of IMLS fits. The first approach, called IMLS-accelerated direct dynamics, propagates individual trajectories directly with no preliminary exploratory trajectories. The PES is grown "on the fly" with the computation of new ab initio data only when a fitting error estimate exceeds a prescribed tight tolerance. The second approach, called dynamics-driven IMLS fitting, uses relatively inexpensive exploratory trajectories to both determine and fit the dynamically accessible configuration space. Once exploratory trajectories no longer find configurations with fitting error estimates higher than the designated accuracy, the IMLS fit is considered to be complete and usable in classical trajectory calculations or other applications.

Hop/Sti1 – A Two-Faced Cochaperone Involved in Pattern Recognition Receptor Maturation and Viral Infection

PubMed Central

Lamm, Christian E.; Kraner, Max. E.; Hofmann, Jörg; Börnke, Frederik; Mock, Hans-Peter; Sonnewald, Uwe

2017-01-01

Perception of pathogens by host pattern recognition receptors (PRRs) or R proteins is a prerequisite to promote successful immune responses. The Hsp70/Hsp90 organizing protein Hop/Sti1, a multifunctional cochaperone, has been implicated in the maturation of a receptor-like kinase (RLK) necessary for chitin sensing. However, it remains unknown whether Hop/Sti1 is generally participating in PRR genesis. Using RNA-interference (RNAi), we silenced Hop/Sti1 expression in Nicotiana tabacum to gain further insight into the role of the cochaperone in plant defense responses. As expected, transgenic plants do not respond to chitin treatment anymore. In contrast to this, trafficking and functionality of the flagellin PRR FLS2 were unaltered, suggesting a selective involvement of Hop/Sti1 during PRR maturation. Furthermore, Hop/Sti1 was identified as a cellular determinant of Potato virus Y (PVY) symptom development in tobacco, since PVY was able to accumulate to near wild-type level without provoking the usual veinal necrosis phenotype. In addition, typical antiviral host defense responses were suppressed in the transgenic plants. These data suggest that perception of PVY is dependent on Hop/Sti1-mediated receptor maturation, while viral symptoms represent a failing attempt to restrict PVY spread. In addition, Hop/Sti1 colocalized with virus-induced membrane aggregates in wild-type plants. The retention of Hop/Sti1 in potential viral replication complexes suggests a role during viral translation/replication, explaining why RNAi-lines do not exhibit increased susceptibility to PVY. This study provides evidence for a dual role of Hop/Sti1 in PRR maturation and pathogen perception as well as in promoting viral proliferation. PMID:29075278

Hop Distance Symmetry Does Not Indicate Normal Landing Biomechanics in Adolescent Athletes With Recent Anterior Cruciate Ligament Reconstruction.

PubMed

Wren, Tishya A L; Mueske, Nicole M; Brophy, Christopher H; Pace, J Lee; Katzel, Mia J; Edison, Bianca R; VandenBerg, Curtis D; Zaslow, Tracy L

2018-03-30

Study Design Retrospective cohort. Background Return to sport (RTS) protocols after anterior cruciate ligament reconstruction (ACLR) often include assessment of hop distance symmetry. However, it is unclear if movement deficits are present regardless of hop symmetry. Objectives To assess biomechanics and symmetry of adolescent athletes following ACLR during a single leg hop for distance. Methods Forty-six patients with ACLR (5-12 months post-surgery; 27 female; age 15.6, SD 1.7 years) were classified as asymmetric (operative limb hop distance <90% of non-operative limb; n=17) or symmetric (n=29). Lower extremity biomechanics were compared among operative and contralateral limbs and 24 symmetric controls (12 female; age 14.7, SD 1.5 years) using ANOVA. Results Compared to controls, asymmetric patients hopped a shorter distance on their operative limb (P<0.001), while symmetric patients hopped an intermediate distance on both sides (P≥0.12). During landing, operative limbs, regardless of hop distance, exhibited lower knee flexion moments compared to controls and the contralateral side (P≤0.04) with lower knee energy absorption than the contralateral side (P≤0.006). During take-off, both symmetric and asymmetric patients had less hip extension and smaller ankle range of motion on the operative side compared with controls (P≤0.05). Asymmetric patients also had lower hip range of motion on the operative, compared with the contralateral, side (P=0.001). Conclusion Both symmetric and asymmetric patients offloaded the operative knee; symmetric patients achieved symmetry in part by hopping a shorter distance on the contralateral side. Therefore, hop distance symmetry may not be an adequate test of single limb function and RTS readiness. Level of Evidence 2b. J Orthop Sports Phys Ther, Epub 30 Mar 2018. doi:10.2519/jospt.2018.7817.

Aspirin increases susceptibility of Helicobacter pylori to metronidazole by augmenting endocellular concentrations of antimicrobials

PubMed Central

Zhang, Xiao-Ping; Wang, Wei-Hong; Tian, Yu; Gao, Wen; Li, Jiang

2009-01-01

AIM: To investigate the mechanisms of aspirin increasing the susceptibility of Helicobacter pylori (H pylori) to metronidazole. METHODS: H pylori reference strain 26 695 and two metronidazole-resistant isolates of H pylori were included in this study. Strains were incubated in Brucella broth with or without aspirin (1 mmol/L). The rdxA gene of H pylori was amplified by PCR and sequenced. The permeability of H pylori to antimicrobials was determined by analyzing the endocellular radioactivity of the cells after incubated with [7-3H]-tetracycline. The outer membrane proteins (OMPs) of H pylori 26 695 were depurated and analyzed by SDS-PAGE. The expression of 5 porins (hopA, hopB, hopC, hopD and hopE) and the putative RND efflux system (hefABC) of H pylori were analyzed using real-time quantitative PCR. RESULTS: The mutations in rdxA gene did not change in metronidazole resistant isolates treated with aspirin. The radioactivity of H pylori increased when treated with aspirin, indicating that aspirin improved the permeability of the outer membrane of H pylori. However, the expression of two OMP bands between 55 kDa and 72 kDa altered in the presence of aspirin. The expression of the mRNA of hopA, hopB, hopC, hopD, hopE and hefA, hefB, hefC of H pylori did not change when treated with aspirin. CONCLUSION: Although aspirin increases the susceptibility of H pylori to metronidazole, it has no effect on the mutations of rdxA gene of H pylori. Aspirin increases endocellular concentrations of antimicrobials probably by altering the OMP expression. PMID:19248190

Comparison of the carboxy-terminal DP-repeat region in the co-chaperones Hop and Hip

PubMed Central

Nelson, Gregory M.; Huffman, Holly; Smith, David F.

2003-01-01

Functional steroid receptor complexes are assembled and maintained by an ordered pathway of interactions involving multiple components of the cellular chaperone machinery. Two of these components, Hop and Hip, serve as co-chaperones to the major heat shock proteins (Hsps), Hsp70 and Hsp90, and participate in intermediate stages of receptor assembly. In an effort to better understand the functions of Hop and Hip in the assembly process, we focused on a region of similarity located near the C-terminus of each co-chaperone. Contained within this region is a repeated sequence motif we have termed the DP repeat. Earlier mutagenesis studies implicated the DP repeat of either Hop or Hip in Hsp70 binding and in normal assembly of the co-chaperones with progesterone receptor (PR) complexes. We report here that the DP repeat lies within a protease-resistant domain that extends to or is near the C-terminus of both co-chaperones. Point mutations in the DP repeats render the C-terminal regions hypersensitive to proteolysis. In addition, a Hop DP mutant displays altered proteolytic digestion patterns, which suggest that the DP-repeat region influences the folding of other Hop domains. Although the respective DP regions of Hop and Hip share sequence and structural similarities, they are not functionally interchangeable. Moreover, a double-point mutation within the second DP-repeat unit of Hop that converts this to the sequence found in Hip disrupts Hop function; however, the corresponding mutation in Hip does not alter its function. We conclude that the DP repeats are important structural elements within a C-terminal domain, which is important for Hop and Hip function. PMID:14627198

Comparison of the carboxy-terminal DP-repeat region in the co-chaperones Hop and Hip.

PubMed

Nelson, Gregory M; Huffman, Holly; Smith, David F

2003-01-01

Functional steroid receptor complexes are assembled and maintained by an ordered pathway of interactions involving multiple components of the cellular chaperone machinery. Two of these components, Hop and Hip, serve as co-chaperones to the major heat shock proteins (Hsps), Hsp70 and Hsp90, and participate in intermediate stages of receptor assembly. In an effort to better understand the functions of Hop and Hip in the assembly process, we focused on a region of similarity located near the C-terminus of each co-chaperone. Contained within this region is a repeated sequence motif we have termed the DP repeat. Earlier mutagenesis studies implicated the DP repeat of either Hop or Hip in Hsp70 binding and in normal assembly of the co-chaperones with progesterone receptor (PR) complexes. We report here that the DP repeat lies within a protease-resistant domain that extends to or is near the C-terminus of both co-chaperones. Point mutations in the DP repeats render the C-terminal regions hypersensitive to proteolysis. In addition, a Hop DP mutant displays altered proteolytic digestion patterns, which suggest that the DP-repeat region influences the folding of other Hop domains. Although the respective DP regions of Hop and Hip share sequence and structural similarities, they are not functionally interchangeable. Moreover, a double-point mutation within the second DP-repeat unit of Hop that converts this to the sequence found in Hip disrupts Hop function; however, the corresponding mutation in Hip does not alter its function. We conclude that the DP repeats are important structural elements within a C-terminal domain, which is important for Hop and Hip function.

Characterization of host-dependent mutations of apple fruit crinkle viroid replicating in newly identified experimental hosts suggests maintenance of stem-loop structures in the left-hand half of the molecule is important for replication.

PubMed

Suzuki, Takahiro; Fujibayashi, Misato; Hataya, Tatsuji; Taneda, Akito; He, Ying-Hong; Tsushima, Taro; Duraisamy, Ganesh Selvaraj; Siglová, Kristyna; Matoušek, Jaroslav; Sano, Teruo

2017-03-01

Apple fruit crinkle viroid (AFCVd) is a tentative member of the genus Apscaviroid, family Pospiviroidae. AFCVd has a narrow host range and is known to infect apple, hop and persimmon as natural hosts. In this study, tomato, cucumber and wild hop have been identified as new experimental herbaceous hosts. Foliar symptoms were very mild or virtually undetectable, but fruits of infected tomato were small, cracked and distorted. These symptoms resemble those observed on some AFCVd-sensitive apple cultivars. After transfer to tomato, cucumber and wild hop, sequence changes were detected in a natural AFCVd isolate from hop, and major variants in tomato, cucumber and wild hop differed in 10, 8 or 2 nucleotides, respectively, from the predominant one in the inoculum. The major variants in tomato and cucumber were almost identical, and the one in wild hop was very similar to the one in cultivated hop. Detailed analyses of the host-dependent sequence changes that appear in a naturally occurring AFCVd isolate from hop after transfer to tomato using small RNA deep sequence data and infectivity studies with dimeric RNA transcripts followed by progeny analysis indicate that the major AFCVd variant in tomato emerged by selection of a minor variant present in the inoculum (i.e. hop) followed by one to two host-dependent de novo mutations. Comparison of the secondary structures of major variants in hop, tomato and persimmon after transfer to tomato suggested that maintenance of stem-loop structures in the left-hand half of the molecule is critical for infection.

Confined diffusion of transmembrane proteins and lipids induced by the same actin meshwork lining the plasma membrane.

PubMed

Fujiwara, Takahiro K; Iwasawa, Kokoro; Kalay, Ziya; Tsunoyama, Taka A; Watanabe, Yusuke; Umemura, Yasuhiro M; Murakoshi, Hideji; Suzuki, Kenichi G N; Nemoto, Yuri L; Morone, Nobuhiro; Kusumi, Akihiro

2016-04-01

The mechanisms by which the diffusion rate in the plasma membrane (PM) is regulated remain unresolved, despite their importance in spatially regulating the reaction rates in the PM. Proposed models include entrapment in nanoscale noncontiguous domains found in PtK2 cells, slow diffusion due to crowding, and actin-induced compartmentalization. Here, by applying single-particle tracking at high time resolutions, mainly to the PtK2-cell PM, we found confined diffusion plus hop movements (termed "hop diffusion") for both a nonraft phospholipid and a transmembrane protein, transferrin receptor, and equal compartment sizes for these two molecules in all five of the cell lines used here (actual sizes were cell dependent), even after treatment with actin-modulating drugs. The cross-section size and the cytoplasmic domain size both affected the hop frequency. Electron tomography identified the actin-based membrane skeleton (MSK) located within 8.8 nm from the PM cytoplasmic surface of PtK2 cells and demonstrated that the MSK mesh size was the same as the compartment size for PM molecular diffusion. The extracellular matrix and extracellular domains of membrane proteins were not involved in hop diffusion. These results support a model of anchored TM-protein pickets lining actin-based MSK as a major mechanism for regulating diffusion. © 2016 Fujiwara et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

The Influence of Projectile Trajectory Angle on the Simulated Impact Response of a Shuttle Leading Edge Wing Panel

NASA Technical Reports Server (NTRS)

Spellman, Regina L.; Jones, Lisa E.; Lyle, Karen H.; Jackson, Karen E.; Fasanella, Edwin L.

2005-01-01

In support of recommendations by the Columbia Accident Investigation Board, a team has been studying the effect of debris impacting the reinforced carbon-carbon panels of the shuttle leading edge. The objective of this study was to examine the effect of varying parameters of the debris trajectory on the damage tolerance. Impacts at the upper and lower surface and the apex of the leading edge were examined. For each location, trajectory variances included both the alpha and beta directions. The results of the analysis indicated in all cases the beta sweep decreased the amount of damage to the panel. The increases in alpha resulted in a significant increase in damage to the RCC panel. In particular, for the lower surface, where the alpha can increase by 10 degrees, there was a nearly 40% increase in the impulse. As a result, it is recommended that for future analyses, a 10 degree offset in alpha from the nominal trajectory is included for impacts on the lower surface. It is also recommended to assume a straight aft, or zero beta, trajectory for a more conservative analysis.

Hopper on wheels: evolving the hopping robot concept

NASA Technical Reports Server (NTRS)

Schell, S.; Tretten, A.; Burdick, J.; Fuller, S. B.; Fiorini, P.

2001-01-01

This paper describes the evolution of our concept of hopping robot for planetary exploration, that combines coarse long range mobility achieved by hopping, with short range wheeled mobility for precision target acquisition.

Performance Analysis of Millimeter-Wave Multi-hop Machine-to-Machine Networks Based on Hop Distance Statistics

PubMed Central

2018-01-01

As an intrinsic part of the Internet of Things (IoT) ecosystem, machine-to-machine (M2M) communications are expected to provide ubiquitous connectivity between machines. Millimeter-wave (mmWave) communication is another promising technology for the future communication systems to alleviate the pressure of scarce spectrum resources. For this reason, in this paper, we consider multi-hop M2M communications, where a machine-type communication (MTC) device with the limited transmit power relays to help other devices using mmWave. To be specific, we focus on hop distance statistics and their impacts on system performances in multi-hop wireless networks (MWNs) with directional antenna arrays in mmWave for M2M communications. Different from microwave systems, in mmWave communications, wireless channel suffers from blockage by obstacles that heavily attenuate line-of-sight signals, which may result in limited per-hop progress in MWNs. We consider two routing strategies aiming at different types of applications and derive the probability distributions of their hop distances. Moreover, we provide their baseline statistics assuming the blockage-free scenario to quantify the impact of blockages. Based on the hop distance analysis, we propose a method to estimate the end-to-end performances (e.g., outage probability, hop count, and transmit energy) of the mmWave MWNs, which provides important insights into mmWave MWN design without time-consuming and repetitive end-to-end simulation. PMID:29329248

Characterization of the Mammalian CORVET and HOPS Complexes and Their Modular Restructuring for Endosome Specificity*

PubMed Central

van der Kant, Rik; Jonker, Caspar T. H.; Wijdeven, Ruud H.; Bakker, Jeroen; Janssen, Lennert; Klumperman, Judith; Neefjes, Jacques

2015-01-01

Trafficking of cargo through the endosomal system depends on endosomal fusion events mediated by SNARE proteins, Rab-GTPases, and multisubunit tethering complexes. The CORVET and HOPS tethering complexes, respectively, regulate early and late endosomal tethering and have been characterized in detail in yeast where their sequential membrane targeting and assembly is well understood. Mammalian CORVET and HOPS subunits significantly differ from their yeast homologues, and novel proteins with high homology to CORVET/HOPS subunits have evolved. However, an analysis of the molecular interactions between these subunits in mammals is lacking. Here, we provide a detailed analysis of interactions within the mammalian CORVET and HOPS as well as an additional endosomal-targeting complex (VIPAS39-VPS33B) that does not exist in yeast. We show that core interactions within CORVET and HOPS are largely conserved but that the membrane-targeting module in HOPS has significantly changed to accommodate binding to mammalian-specific RAB7 interacting lysosomal protein (RILP). Arthrogryposis-renal dysfunction-cholestasis (ARC) syndrome-associated mutations in VPS33B selectively disrupt recruitment to late endosomes by RILP or binding to its partner VIPAS39. Within the shared core of CORVET/HOPS, we find that VPS11 acts as a molecular switch that binds either CORVET-specific TGFBRAP1 or HOPS-specific VPS39/RILP thereby allowing selective targeting of these tethering complexes to early or late endosomes to time fusion events in the endo/lysosomal pathway. PMID:26463206

Performance Analysis of Millimeter-Wave Multi-hop Machine-to-Machine Networks Based on Hop Distance Statistics.

PubMed

Jung, Haejoon; Lee, In-Ho

2018-01-12

As an intrinsic part of the Internet of Things (IoT) ecosystem, machine-to-machine (M2M) communications are expected to provide ubiquitous connectivity between machines. Millimeter-wave (mmWave) communication is another promising technology for the future communication systems to alleviate the pressure of scarce spectrum resources. For this reason, in this paper, we consider multi-hop M2M communications, where a machine-type communication (MTC) device with the limited transmit power relays to help other devices using mmWave. To be specific, we focus on hop distance statistics and their impacts on system performances in multi-hop wireless networks (MWNs) with directional antenna arrays in mmWave for M2M communications. Different from microwave systems, in mmWave communications, wireless channel suffers from blockage by obstacles that heavily attenuate line-of-sight signals, which may result in limited per-hop progress in MWNs. We consider two routing strategies aiming at different types of applications and derive the probability distributions of their hop distances. Moreover, we provide their baseline statistics assuming the blockage-free scenario to quantify the impact of blockages. Based on the hop distance analysis, we propose a method to estimate the end-to-end performances (e.g., outage probability, hop count, and transmit energy) of the mmWave MWNs, which provides important insights into mmWave MWN design without time-consuming and repetitive end-to-end simulation.

Interaction of alcoholic extracts of hops with cocaine and paracetamol in mice.

PubMed

Horvat, Olga; Raskovic, Aleksandar; Jakovljevic, Vida; Sabo, Jan; Berenji, Janos

2007-01-01

This work describes a study of the interaction in the mouse model of alcoholic extracts of hops of Magnum, Aroma and wild genotypes with drugs that have excitatory effect on the cerebral cortex (cocaine) and analgesic action (paracetamol). Hop drying and preparation of the extracts were carried out according to standard pharmacological procedures for preparing total alcoholic extracts of dry herbs, consisting of one part of dry drug and two parts of 70% alcohol. The mice received four doses i.p. of 0.5% aqueous solutions of the above-mentioned extracts (10 ml/kg) 24, 16, 4 and 0.5 h prior to receiving cocaine (25 mg/kg) or paracetamol (80 mg/kg). The parameter investigated was the change in spontaneous motility of mice after combined treatment with the extracts and cocaine/paracetamol compared to control animals that received the same dose of the drug after treatment with physiological solution. Only the ethanolic extract of Magnum hops increased the spontaneous motility of mice, while none of the extracts showed analgesic action as measured by the hot-plate method. In the interaction with cocaine, the extract of Magnum hops suppressed almost completely the action of cocaine compared to controls. Extracts of the other hops also decreased the cocaine-induced locomotor activity of mice, but to a lesser extent. Hop extracts exhibited a significant pharmacological interaction with paracetamol, with the most pronounced increase in analgesic action being found for the ethanolic extract of Aroma hops and the tert-butanolic extract of wild hops.

Modelling the long-term evolution of worst-case Arctic oil spills.

PubMed

Blanken, Hauke; Tremblay, Louis Bruno; Gaskin, Susan; Slavin, Alexander

2017-03-15

We present worst-case assessments of contamination in sea ice and surface waters resulting from hypothetical well blowout oil spills at ten sites in the Arctic Ocean basin. Spill extents are estimated by considering Eulerian passive tracers in the surface ocean of the MITgcm (a hydrostatic, coupled ice-ocean model). Oil in sea ice, and contamination resulting from melting of oiled ice, is tracked using an offline Lagrangian scheme. Spills are initialized on November 1st 1980-2010 and tracked for one year. An average spill was transported 1100km and potentially affected 1.1 million km 2 . The direction and magnitude of simulated oil trajectories are consistent with known large-scale current and sea ice circulation patterns, and trajectories frequently cross international boundaries. The simulated trajectories of oil in sea ice match observed ice drift trajectories well. During the winter oil transport by drifting sea ice is more significant than transport with surface currents. Copyright © 2017 Elsevier Ltd. All rights reserved.

Hip-Hop--What's in It for the Academy? Self-Understanding, Pedagogy and Aesthetical Learning Processes in Everyday Cultural Praxis

ERIC Educational Resources Information Center

Söderman, Johan; Sernhede, Ove

2016-01-01

Since hip-hop first appeared in New York over 35 years ago, it has been associated with social activism and education. Accordingly, it is not surprising that academic institutions in universities and K-12 schools are interested in hip-hop. In this article, we will highlight the "hip-hop academisation" and map out a new direction in a…

Wheeled hopping robot

DOEpatents

Fischer, Gary J [Albuquerque, NM

2010-08-17

The present invention provides robotic vehicles having wheeled and hopping mobilities that are capable of traversing (e.g. by hopping over) obstacles that are large in size relative to the robot and, are capable of operation in unpredictable terrain over long range. The present invention further provides combustion powered linear actuators, which can include latching mechanisms to facilitate pressurized fueling of the actuators, as can be used to provide wheeled vehicles with a hopping mobility.

Rapid differentiation of Chinese hop varieties (Humulus lupulus) using volatile fingerprinting by HS-SPME-GC-MS combined with multivariate statistical analysis.

PubMed

Liu, Zechang; Wang, Liping; Liu, Yumei

2018-01-18

Hops impart flavor to beer, with the volatile components characterizing the various hop varieties and qualities. Fingerprinting, especially flavor fingerprinting, is often used to identify 'flavor products' because inconsistencies in the description of flavor may lead to an incorrect definition of beer quality. Compared to flavor fingerprinting, volatile fingerprinting is simpler and easier. We performed volatile fingerprinting using head space-solid phase micro-extraction gas chromatography-mass spectrometry combined with similarity analysis and principal component analysis (PCA) for evaluating and distinguishing between three major Chinese hops. Eighty-four volatiles were identified, which were classified into seven categories. Volatile fingerprinting based on similarity analysis did not yield any obvious result. By contrast, hop varieties and qualities were identified using volatile fingerprinting based on PCA. The potential variables explained the variance in the three hop varieties. In addition, the dendrogram and principal component score plot described the differences and classifications of hops. Volatile fingerprinting plus multivariate statistical analysis can rapidly differentiate between the different varieties and qualities of the three major Chinese hops. Furthermore, this method can be used as a reference in other fields. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industry.

Real-Time On-Board Airborne Demonstration of High-Speed On-Board Data Processing for Science Instruments (HOPS)

NASA Technical Reports Server (NTRS)

Beyon, Jeffrey Y.; Ng, Tak-Kwong; Davis, Mitchell J.; Adams, James K.; Bowen, Stephen C.; Fay, James J.; Hutchinson, Mark A.

2015-01-01

The project called High-Speed On-Board Data Processing for Science Instruments (HOPS) has been funded by NASA Earth Science Technology Office (ESTO) Advanced Information Systems Technology (AIST) program since April, 2012. The HOPS team recently completed two flight campaigns during the summer of 2014 on two different aircrafts with two different science instruments. The first flight campaign was in July, 2014 based at NASA Langley Research Center (LaRC) in Hampton, VA on the NASA's HU-25 aircraft. The science instrument that flew with HOPS was Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) CarbonHawk Experiment Simulator (ACES) funded by NASA's Instrument Incubator Program (IIP). The second campaign was in August, 2014 based at NASA Armstrong Flight Research Center (AFRC) in Palmdale, CA on the NASA's DC-8 aircraft. HOPS flew with the Multifunctional Fiber Laser Lidar (MFLL) instrument developed by Excelis Inc. The goal of the campaigns was to perform an end-to-end demonstration of the capabilities of the HOPS prototype system (HOPS COTS) while running the most computationally intensive part of the ASCENDS algorithm real-time on-board. The comparison of the two flight campaigns and the results of the functionality tests of the HOPS COTS are presented in this paper.

Co-chaperone Hsp70/Hsp90-organizing protein (Hop) is required for transposon silencing and Piwi-interacting RNA (piRNA) biogenesis.

PubMed

Karam, Joseph A; Parikh, Rasesh Y; Nayak, Dhananjaya; Rosenkranz, David; Gangaraju, Vamsi K

2017-04-14

Piwi-interacting RNAs (piRNAs) are 26-30-nucleotide germ line-specific small non-coding RNAs that have evolutionarily conserved function in mobile genetic element (transposons) silencing and maintenance of genome integrity. Drosophila Hsp70/90-organizing protein homolog (Hop), a co-chaperone, interacts with piRNA-binding protein Piwi and mediates silencing of phenotypic variations. However, it is not known whether Hop has a direct role in piRNA biogenesis and transposon silencing. Here, we show that knockdown of Hop in the germ line nurse cells (GLKD) of Drosophila ovaries leads to activation of transposons. Hop GLKD females can lay eggs at the same rate as wild-type counterparts, but the eggs do not hatch into larvae. Hop GLKD leads to the accumulation of γ-H2Av foci in the germ line, indicating increased DNA damage in the ovary. We also show that Hop GLKD-induced transposon up-regulation is due to inefficient piRNA biogenesis. Based on these results, we conclude that Hop is a critical component of the piRNA pathway and that it maintains genome integrity by silencing transposons. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Selective binding of meiosis-specific yeast Hop1 protein to the holliday junctions distorts the DNA structure and its implications for junction migration and resolution.

PubMed

Tripathi, Pankaj; Anuradha, S; Ghosal, Gargi; Muniyappa, K

2006-12-08

Saccharomyces cerevisiae HOP1, which encodes a component of synaptonemal complex (SC), plays an important role in both gene conversion and crossing over between homologs, as well as enforces meiotic recombination checkpoint control over the progression of recombination intermediates. In hop1Delta mutants, meiosis-specific double-strand breaks (DSBs) are reduced to 10% of the wild-type level, and at aberrantly late times, these DSBs are processed into inter-sister recombination intermediates. However, the underlying mechanism by which Hop1 protein regulates these nuclear events remains obscure. Here we show that Hop1 protein interacts selectively with the Holliday junction, changes its global conformation and blocks the dissolution of the junction by a RecQ helicase. The Holliday junction-Hop1 protein complexes are significantly more stable at higher ionic strengths and molar excess of unlabeled competitor DNA than complexes containing other recombination intermediates. Structural analysis of the Holliday junction using 2-aminopurine fluorescence emission, DNase I footprinting and KMnO4 probing provide compelling evidence that Hop1 protein binding induces significant distortion at the center of the Holliday junction. We propose that Hop1 protein might coordinate the physical monitoring of meiotic recombination intermediates with the process of branch migration of Holliday junction.

Optimization of conditions for supercritical fluid extraction of flavonoids from hops (Humulus lupulus L.)*

PubMed Central

He, Guo-qing; Xiong, Hao-ping; Chen, Qi-he; Ruan, Hui; Wang, Zhao-yue; Traoré, Lonseny

2005-01-01

Waste hops are good sources of flavonoids. Extraction of flavonoids from waste hops (SC-CO2 extracted hops) using supercritical fluids technology was investigated. Various temperatures, pressures and concentrations of ethanol (modifier) and the ratio (w/w) of solvent to material were tested in this study. The results of single factor and orthogonal experiments showed that at 50 °C, 25 MPa, the ratio of solvent to material (50%), ethanol concentration (80%) resulted in maximum extraction yield flavonoids (7.8 mg/g). HPLC-MS analysis of the extracts indicated that flavonoids obtained were xanthohumol, the principal prenylflavonoid in hops. PMID:16187413

Urban hopper.

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

Xavier, Patrick Gordon; Feddema, John Todd; Little, Charles Quentin

2010-03-01

Hopping robots provide the possibility of breaking the link between the size of a ground vehicle and the largest obstacle that it can overcome. For more than a decade, DARPA and Sandia National Laboratories have been developing small-scale hopping robot technology, first as part of purely hopping platforms and, more recently, as part of platforms that are capable of both wheeled and hopping locomotion. In this paper we introduce the Urban Hopper robot and summarize its capabilities. The advantages of hopping for overcoming certain obstacles are discussed. Several configurations of the Urban Hopper are described, as are intelligent capabilities ofmore » the system. Key challenges are discussed.« less

An Efficient Next Hop Selection Algorithm for Multi-Hop Body Area Networks

PubMed Central

Ayatollahitafti, Vahid; Ngadi, Md Asri; Mohamad Sharif, Johan bin; Abdullahi, Mohammed

2016-01-01

Body Area Networks (BANs) consist of various sensors which gather patient’s vital signs and deliver them to doctors. One of the most significant challenges faced, is the design of an energy-efficient next hop selection algorithm to satisfy Quality of Service (QoS) requirements for different healthcare applications. In this paper, a novel efficient next hop selection algorithm is proposed in multi-hop BANs. This algorithm uses the minimum hop count and a link cost function jointly in each node to choose the best next hop node. The link cost function includes the residual energy, free buffer size, and the link reliability of the neighboring nodes, which is used to balance the energy consumption and to satisfy QoS requirements in terms of end to end delay and reliability. Extensive simulation experiments were performed to evaluate the efficiency of the proposed algorithm using the NS-2 simulator. Simulation results show that our proposed algorithm provides significant improvement in terms of energy consumption, number of packets forwarded, end to end delay and packet delivery ratio compared to the existing routing protocol. PMID:26771586

A study of numerical methods for computing reentry trajectories for shuttle-type space vehicles

NASA Technical Reports Server (NTRS)

1972-01-01

The reuseable exterior insulation system (REI) is studied to determine the optimal reentry trajectory for a space shuttle, which minimizes the heat input to the fuselage. The REI is composed of titanium, covered by a surface insulation material. The method of perturbation functions was used to generate the trajectories, and proved to be an effective technique for generating families of solutions, once an initial trajectory has been obtained.

Azobenzene as a photoregulator covalently attached to RNA: a quantum mechanics/molecular mechanics-surface hopping dynamics study.

PubMed

Mondal, Padmabati; Granucci, Giovanni; Rastädter, Dominique; Persico, Maurizio; Burghardt, Irene

2018-05-28

The photoregulation of nucleic acids by azobenzene photoswitches has recently attracted considerable interest in the context of emerging biotechnological applications. To understand the mechanism of photoinduced isomerisation and conformational control in these complex biological environments, we employ a Quantum Mechanics/Molecular Mechanics (QM/MM) approach in conjunction with nonadiabatic Surface Hopping (SH) dynamics. Two representative RNA-azobenzene complexes are investigated, both of which contain the azobenzene chromophore covalently attached to an RNA double strand via a β-deoxyribose linker. Due to the pronounced constraints of the local RNA environment, it is found that trans -to- cis isomerization is slowed down to a time scale of ∼10-15 picoseconds, in contrast to 500 femtoseconds in vacuo , with a quantum yield reduced by a factor of two. By contrast, cis -to- trans isomerization remains in a sub-picosecond regime. A volume-conserving isomerization mechanism is found, similarly to the pedal-like mechanism previously identified for azobenzene in solution phase. Strikingly, the chiral RNA environment induces opposite right-handed and left-handed helicities of the ground-state cis -azobenzene chromophore in the two RNA-azobenzene complexes, along with an almost completely chirality conserving photochemical pathway for these helical enantiomers.

Systematic characterization of a 1550 nm microelectromechanical (MEMS)-tunable vertical-cavity surface-emitting laser (VCSEL) with 7.92 THz tuning range for terahertz photomixing systems

NASA Astrophysics Data System (ADS)

Haidar, M. T.; Preu, S.; Cesar, J.; Paul, S.; Hajo, A. S.; Neumeyr, C.; Maune, H.; Küppers, F.

2018-01-01

Continuous-wave (CW) terahertz (THz) photomixing requires compact, widely tunable, mode-hop-free driving lasers. We present a single-mode microelectromechanical system (MEMS)-tunable vertical-cavity surface-emitting laser (VCSEL) featuring an electrothermal tuning range of 64 nm (7.92 THz) that exceeds the tuning range of commercially available distributed-feedback laser (DFB) diodes (˜4.8 nm) by a factor of about 13. We first review the underlying theory and perform a systematic characterization of the MEMS-VCSEL, with particular focus on the parameters relevant for THz photomixing. These parameters include mode-hop-free CW tuning with a side-mode-suppression-ratio >50 dB, a linewidth as narrow as 46.1 MHz, and wavelength and polarization stability. We conclude with a demonstration of a CW THz photomixing setup by subjecting the MEMS-VCSEL to optical beating with a DFB diode driving commercial photomixers. The achievable THz bandwidth is limited only by the employed photomixers. Once improved photomixers become available, electrothermally actuated MEMS-VCSELs should allow for a tuning range covering almost the whole THz domain with a single system.

Non-adiabatic molecular dynamics by accelerated semiclassical Monte Carlo

DOE PAGES

White, Alexander J.; Gorshkov, Vyacheslav N.; Tretiak, Sergei; ...

2015-07-07

Non-adiabatic dynamics, where systems non-radiatively transition between electronic states, plays a crucial role in many photo-physical processes, such as fluorescence, phosphorescence, and photoisomerization. Methods for the simulation of non-adiabatic dynamics are typically either numerically impractical, highly complex, or based on approximations which can result in failure for even simple systems. Recently, the Semiclassical Monte Carlo (SCMC) approach was developed in an attempt to combine the accuracy of rigorous semiclassical methods with the efficiency and simplicity of widely used surface hopping methods. However, while SCMC was found to be more efficient than other semiclassical methods, it is not yet as efficientmore » as is needed to be used for large molecular systems. Here, we have developed two new methods: the accelerated-SCMC and the accelerated-SCMC with re-Gaussianization, which reduce the cost of the SCMC algorithm up to two orders of magnitude for certain systems. In many cases shown here, the new procedures are nearly as efficient as the commonly used surface hopping schemes, with little to no loss of accuracy. This implies that these modified SCMC algorithms will be of practical numerical solutions for simulating non-adiabatic dynamics in realistic molecular systems.« less

Single-legged Hop Tests as Predictors of Self-reported Knee Function After Anterior Cruciate Ligament Reconstruction

PubMed Central

Logerstedt, David; Grindem, Hege; Lynch, Andrew; Eitzen, Ingrid; Engebretsen, Lars; Risberg, May Arna; Axe, Michael J.; Snyder-Mackler, Lynn

2012-01-01

Background Single-legged hop tests are commonly used functional performance measures that can capture limb asymmetries in patients after anterior cruciate ligament (ACL) reconstruction. Hop tests hold potential as predictive factors of self-reported knee function in individuals after ACL reconstruction. Hypothesis Single-legged hop tests conducted preoperatively would not and 6 months after ACL reconstruction would predict self-reported knee function (International Knee Documentation Committee [IKDC] 2000) 1 year after ACL reconstruction. Study Design Cohort study (prognosis); Level of evidence, 2. Methods One hundred twenty patients who were treated with ACL reconstruction performed 4 single-legged hop tests preoperatively and 6 months after ACL reconstruction. Self-reported knee function within normal ranges was defined as IKDC 2000 scores greater than or equal to the age- and sex-specific normative 15th percentile score 1 year after surgery. Logistic regression analyses were performed to identify predictors of self-reported knee function within normal ranges. The area under the curve (AUC) from receiver operating characteristic curves was used as a measure of discriminative accuracy. Results Eighty-five patients completed single-legged hop tests 6 months after surgery and the 1-year follow-up with 68 patients classified as having self-reported knee function within normal ranges 1 year after reconstruction. The crossover hop and 6-m timed hop limb symmetry index (LSI) 6 months after ACL reconstruction were the strongest individual predictors of self-reported knee function (odds ratio, 1.09 and 1.10) and the only 2 tests in which the confidence intervals of the discriminatory accuracy (AUC) were above 0.5 (AUC = 0.68). Patients with knee function below normal ranges were over 5 times more likely of having a 6-m timed hop LSI lower than the 88% cutoff than those with knee function within normal ranges. Patients with knee function within normal ranges were 4 times more likely to have a crossover hop LSI greater than the 95% cutoff than those with knee function below normal ranges. No preoperative single-legged hop test predicted self-reported knee function within normal ranges 1 year after ACL reconstruction (all P > .353). Conclusion Single-legged hop tests conducted 6 months after ACL reconstruction can predict the likelihood of successful and unsuccessful outcome 1 year after ACL reconstruction. Patients demonstrating less than the 88% cutoff score on the 6-m timed hop test at 6 months may benefit from targeted training to improve limb symmetry in an attempt to normalize function. Patients with minimal side-to-side differences on the crossover hop test at 6 months possibly will have good knee function at 1 year if they continue with their current training regimen. Preoperative single-legged hop tests are not able to predict postoperative outcomes. PMID:22926749

Full-dimensional quantum calculations of the vibrational states of H5(+).

PubMed

Song, Hongwei; Lee, Soo-Ying; Yang, Minghui; Lu, Yunpeng

2013-03-28

Full-dimensional quantum calculations of the vibrational states of H5(+) have been performed on the accurate potential energy surface developed by Xie et al. [J. Chem. Phys. 122, 224307 (2005)]. The zero point energies of H5(+), H4D(+), D4H(+), and D5(+) and their ground-state geometries are presented and compared with earlier theoretical results. The first 10 low-lying excited states of H5(+) are assigned to the fundamental, overtone, and combination of the H2-H3(+) stretch, the shared proton hopping and the out-of-plane torsion. The ground-state torsional tunneling splitting, the fundamental of the photon hopping mode and the first overtone of the torsion mode are 87.3 cm(-1), 354.4 cm(-1), and 444.0 cm(-1), respectively. All of these values agree well with the diffusion Monte Carlo and multi-configuration time-dependent Hartree results where available.

Formation of novel rare-gas-containing molecules by molecular photodissociation in clusters.

PubMed

Cohen, A; Niv, M Y; Gerber, R B

2001-01-01

Recent work by Räsänen and coworkers showed that photolysis of hydrides in rare-gas matrices results in part in formation of novel, rare-gas-containing molecules. Thus, photolysis of HCl in Xe and of H2O in Xe result respectively in formation of HXeCl and HXeOH in the Xe matrices. Ab initio calculations show that the compounds HRgY so formed are stable in isolation, and that by the strength and nature of the bonding these are molecules, very different from the corresponding weakly bound clusters Rg...HY. This paper presents a study of the formation mechanism of HRgY following the photolysis of HY in clusters Rgn(HY). Calculations are described for HXeCl, as a representative example. Potential energy surfaces that govern the formation of HXeCl in the photolysis of HCl in xenon clusters are obtained, and the dynamics on these surfaces is analyzed, partly with insight from trajectories of molecular dynamics simulations. The potential surfaces are obtained by a new variant of the DIM (diatomics in molecules) and DIIS (diatomics in ionic systems) models. Non-adiabatic couplings are also obtained. The main results are: (1) Properties of HXeCl predicted by the DIM-DIIS model are in reasonable accord with results of ab initio calculations. (2) The potential along the isomerization path HXeCl-->Xe...HCl predicted by DIM is in semiquantitative accord with the ab initio results. (3) Surface-hopping molecular dynamics simulations of the process in clusters, with "on the fly" calculations of the DIM-DIIS potentials and non-adiabatic couplings are computationally feasible. (4) Formation of HXeCl, following photolysis of HCl in Xe54(HCl), requires cage-exit of the H atom as a precondition. The H atom and the Cl can then attack the same Xe atom on opposite sides, leading to charge transfer and production of the ionic HXeCl. (5) Non-adiabatic processes play an important role, both in the reagent configurations, and at the charge-transfer stage. The results open the way to predictions of the formation of new HRgY species.

An oilspill trajectory analysis model with a variable wind deflection angle

USGS Publications Warehouse

Samuels, W.B.; Huang, N.E.; Amstutz, D.E.

1982-01-01

The oilspill trajectory movement algorithm consists of a vector sum of the surface drift component due to wind and the surface current component. In the U.S. Geological Survey oilspill trajectory analysis model, the surface drift component is assumed to be 3.5% of the wind speed and is rotated 20 degrees clockwise to account for Coriolis effects in the Northern Hemisphere. Field and laboratory data suggest, however, that the deflection angle of the surface drift current can be highly variable. An empirical formula, based on field observations and theoretical arguments relating wind speed to deflection angle, was used to calculate a new deflection angle at each time step in the model. Comparisons of oilspill contact probabilities to coastal areas calculated for constant and variable deflection angles showed that the model is insensitive to this changing angle at low wind speeds. At high wind speeds, some statistically significant differences in contact probabilities did appear. ?? 1982.

Homothallism in Pseudoperonospora humuli

USDA-ARS?s Scientific Manuscript database

The hop downy mildew pathogen, Pseudoperonospora humuli, forms oospores abundantly in diseased hop tissue. Diverse monosporangial isolates of P. humuli collected from Japan, Germany, and five states in the USA readily formed oospores within hop leaves when inoculated singly, suggesting homothallism....

"Makin' Somethin' Outta Little-to-Nufin'': Racism, Revision and Rotating Records--The Hip-Hop DJ in Composition Praxis

ERIC Educational Resources Information Center

Craig, Todd

2015-01-01

Prompted by a moment in the classroom in which the DJ becomes integral for the writing instructor, this article looks at how the hip-hop DJ and hip-hop DJ/Producer become the intrinsic examples for first-year college writing students to think about how they conduct revision in their writing. After a review of two seminal hip-hop books and other…

"Words of Wisdom": An Expectancy-Value Examination of Relationships among Hip-Hop Racial Socialization and Racial Identity of African-American College Students

ERIC Educational Resources Information Center

Gangloff-Bailey, Felicia

2017-01-01

The influence of hip hop culture and music on African-American youth is profound and can be used as a tool to shape positive outcomes in education. Hip hop has been used effectively in the classroom to engage students and enhance their critical thinking (Gangloff-Bailey & Freeman, 2014). In addition, hip hop has been described as a socializer…

Evaluation of 1-hydroxypyrene as a biological marker of industrial exposure to polycyclic aromatic hydrocarbons

NASA Astrophysics Data System (ADS)

Calderon, Francisco M.

1993-03-01

One hundred twenty-two workers (sixteen from a coke production plant and 106 from a graphite electrode manufacturing plant) agreed to participate in this study evaluating the relationship between exposure to polycyclic aromatic hydrocarbons (PAHs) and urinary excretion of 1-hydroxypyrene (1-HOP), the main metabolite of pyrene. The results show that the concentration of pyrene in air is highly correlated with total PAHs (r equals 0.83, P < 0.0001). The correlation coefficient between pyrene in air and 1-HOP is (r equals 0.69, P < 0.0001) and between 1-HOP and total PAHs is (r equals 0.77, P < 0.0001). The biological half life of the 1-HOP was determined (18 hrs) and the noninterference of smoking habits in relation to 1-HOP urinary excretion was established, concluding that 1-HOP is a suitable bioindicator of the occupational exposure to PAHs.

Vortex variable range hopping in a conventional superconducting film

NASA Astrophysics Data System (ADS)

Percher, Ilana M.; Volotsenko, Irina; Frydman, Aviad; Shklovskii, Boris I.; Goldman, Allen M.

2017-12-01

The behavior of a disordered amorphous thin film of superconducting indium oxide has been studied as a function of temperature and magnetic field applied perpendicular to its plane. A superconductor-insulator transition has been observed, though the isotherms do not cross at a single point. The curves of resistance versus temperature on the putative superconducting side of this transition, where the resistance decreases with decreasing temperature, obey two-dimensional Mott variable-range hopping of vortices over wide ranges of temperature and resistance. To estimate the parameters of hopping, the film is modeled as a granular system and the hopping of vortices is treated in a manner analogous to hopping of charges. The reason the long-range interaction between vortices over the range of magnetic fields investigated does not lead to a stronger variation of resistance with temperature than that of two-dimensional Mott variable-range hopping remains unresolved.

Structural studies on the co-chaperone Hop and its complexes with Hsp90.

PubMed

Onuoha, S C; Coulstock, E T; Grossmann, J G; Jackson, S E

2008-06-13

The tetratricopeptide repeat domain (TPR)-containing co-chaperone Hsp-organising protein (Hop) plays a critical role in mediating interactions between Heat Shock Protein (Hsp)70 and Hsp90 as part of the cellular assembly machine. It also modulates the ATPase activity of both Hsp70 and Hsp90, thus facilitating client protein transfer between the two. Despite structural work on the individual domains of Hop, no structure for the full-length protein exists, nor is it clear exactly how Hop interacts with Hsp90, although it is known that its primary binding site is the C-terminal MEEVD motif. Here, we have undertaken a biophysical analysis of the structure and binding of Hop to Hsp90 using a variety of truncation mutants of both Hop and Hsp90, in addition to mutants of Hsp90 that are thought to modulate the conformation, in particular the N-terminal dimerisation of the chaperone. The results establish that whilst the primary binding site of Hop is the C-terminal MEEVD peptide of Hsp90, binding also occurs at additional sites in the C-terminal and middle domain. In contrast, we show that another TPR-containing co-chaperone, CyP40, binds solely to the C-terminus of Hsp90. Truncation mutants of Hop were generated and used to investigate the dimerisation interface of the protein. In good agreement with recently published data, we find that the TPR2a domain that contains the Hsp90-binding site is also the primary site for dimerisation. However, our results suggest that residues within the TPR2b may play a role. Together, these data along with shape reconstruction analysis from small-angle X-ray scattering measurements are used to generate a solution structure for full-length Hop, which we show has an overall butterfly-like quaternary structure. Studies on the nucleotide dependence of Hop binding to Hsp90 establish that Hop binds to the nucleotide-free, 'open' state of Hsp90. However, the Hsp90-Hop complex is weakened by the conformational changes that occur in Hsp90 upon ATP binding. Together, the data are used to propose a detailed model of how Hop may help present the client protein to Hsp90 by aligning the bound client on Hsp70 with the middle domain of Hsp90. It is likely that Hop binds to both monomers of Hsp90 in the form of a clamp, interacting with residues in the middle domain of Hsp90, thus preventing ATP hydrolysis, possibly by the prevention of association of N-terminal and middle domains in individual Hsp90 monomers.

A basin-hopping Monte Carlo investigation of the structural and energetic properties of 55- and 561-atom bimetallic nanoclusters: the examples of the ZrCu, ZrAl, and CuAl systems.

PubMed

De Souza, Douglas G; Cezar, Henrique M; Rondina, Gustavo G; de Oliveira, Marcelo F; Da Silva, Juarez L F

2016-05-05

We report a basin-hopping Monte Carlo investigation within the embedded-atom method of the structural and energetic properties of bimetallic ZrCu, ZrAl, and CuAl nanoclusters with 55 and 561 atoms. We found that unary Zr55, Zr561, Cu55, Cu561, Al55, and Al561 systems adopt the well known compact icosahedron (ICO) structure. The excess energy is negative for all systems and compositions, which indicates an energetic preference for the mixing of both chemical species. The ICO structure is preserved if a few atoms of the host system are replaced by different species, however, the composition limit in which the ICO structure is preserved depends on both the host and new chemical species. Using several structural analyses, three classes of structures, namely ideal ICO, nearly ICO, and distorted ICO structures, were identified. As the amounts of both chemical species change towards a more balanced composition, configurations far from the ICO structure arise and the dominant structures are nearly spherical, which indicates a strong minimization of the surface energy by decreasing the number of atoms with lower coordination on the surface. The average bond lengths follow Vegard's law almost exactly for ZrCu and ZrAl, however, this is not the case for CuAl. Furthermore, the radial distribution allowed us to identify the presence of an onion-like behavior in the surface of the 561-atom CuAl nanocluster with the Al atoms located in the outermost surface shell, which can be explained by the lower surface energies of the Al surfaces compared with the Cu surfaces. In ZrCu and ZrAl the radial distribution indicates a nearly homogeneous distribution for the chemical species, however, with a slightly higher concentration of Al atoms on the ZrAl surface, which can also be explained by the lower surface energy.

Persistence length measurements from stochastic single-microtubule trajectories.

PubMed

van den Heuvel, M G L; Bolhuis, S; Dekker, C

2007-10-01

We present a simple method to determine the persistence length of short submicrometer microtubule ends from their stochastic trajectories on kinesin-coated surfaces. The tangent angle of a microtubule trajectory is similar to a random walk, which is solely determined by the stiffness of the leading tip and the velocity of the microtubule. We demonstrate that even a single-microtubule trajectory suffices to obtain a reliable value of the persistence length. We do this by calculating the variance in the tangent trajectory angle of an individual microtubule. By averaging over many individual microtubule trajectories, we find that the persistence length of microtubule tips is 0.24 +/- 0.03 mm.

The HOPS/Class C Vps Complex Tethers High-Curvature Membranes via a Direct Protein-Membrane Interaction.

PubMed

Ho, Ruoya; Stroupe, Christopher

2016-10-01

Membrane tethering is a physical association of two membranes before their fusion. Many membrane tethering factors have been identified, but the interactions that mediate inter-membrane associations remain largely a matter of conjecture. Previously, we reported that the homotypic fusion and protein sorting/Class C vacuolar protein sorting (HOPS/Class C Vps) complex, which has two binding sites for the yeast vacuolar Rab GTPase Ypt7p, can tether two low-curvature liposomes when both membranes bear Ypt7p. Here, we show that HOPS tethers highly curved liposomes to Ypt7p-bearing low-curvature liposomes even when the high-curvature liposomes are protein-free. Phosphorylation of the curvature-sensing amphipathic lipid-packing sensor (ALPS) motif from the Vps41p HOPS subunit abrogates tethering of high-curvature liposomes. A HOPS complex without its Vps39p subunit, which contains one of the Ypt7p binding sites in HOPS, lacks tethering activity, though it binds high-curvature liposomes and Ypt7p-bearing low-curvature liposomes. Thus, HOPS tethers highly curved membranes via a direct protein-membrane interaction. Such high-curvature membranes are found at the sites of vacuole tethering and fusion. There, vacuole membranes bend sharply, generating large areas of vacuole-vacuole contact. We propose that HOPS localizes via the Vps41p ALPS motif to these high-curvature regions. There, HOPS binds via Vps39p to Ypt7p in an apposed vacuole membrane. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Leg exoskeleton reduces the metabolic cost of human hopping.

PubMed

Grabowski, Alena M; Herr, Hugh M

2009-09-01

During bouncing gaits such as hopping and running, leg muscles generate force to enable elastic energy storage and return primarily from tendons and, thus, demand metabolic energy. In an effort to reduce metabolic demand, we designed two elastic leg exoskeletons that act in parallel with the wearer's legs; one exoskeleton consisted of a multiple leaf (MLE) and the other of a single leaf (SLE) set of fiberglass springs. We hypothesized that hoppers, hopping on both legs, would adjust their leg stiffness while wearing an exoskeleton so that the combination of the hopper and exoskeleton would behave as a linear spring-mass system with the same total stiffness as during normal hopping. We also hypothesized that decreased leg force generation while wearing an exoskeleton would reduce the metabolic power required for hopping. Nine subjects hopped in place at 2.0, 2.2, 2.4, and 2.6 Hz with and without an exoskeleton while we measured ground reaction forces, exoskeletal compression, and metabolic rates. While wearing an exoskeleton, hoppers adjusted their leg stiffness to maintain linear spring-mass mechanics and a total stiffness similar to normal hopping. Without accounting for the added weight of each exoskeleton, wearing the MLE reduced net metabolic power by an average of 6% and wearing the SLE reduced net metabolic power by an average of 24% compared with hopping normally at frequencies between 2.0 and 2.6 Hz. Thus, when hoppers used external parallel springs, they likely decreased the mechanical work performed by the legs and substantially reduced metabolic demand compared with hopping without wearing an exoskeleton.

Knee Joint Loading during Single-Leg Forward Hopping.

PubMed

Krupenevich, Rebecca L; Pruziner, Alison L; Miller, Ross H

2017-02-01

Increased or abnormal loading on the intact limb is thought to contribute to the relatively high risk of knee osteoarthritis in this limb for individuals with unilateral lower limb loss. This theory has been assessed previously by studying walking, but knee joint loading during walking is often similar between individuals with and without limb loss, prompting assessment of other movements that may place unusual loads on the knee. One such movement, hopping, is a form of locomotion that individuals with unilateral lower limb loss may situationally use instead of walking, but the mechanical effects of hopping on the intact limb are unknown. Compare knee joint kinetics of healthy adults during single-leg forward hopping compared to walking, a more traditional form of locomotion. Twenty-four healthy adults walked and hopped at self-selected speeds of 1.5 and 2.3 m·s, respectively. Joint moments were calculated using inverse dynamics. A paired Student's t-test was utilized to compare peak, impulse, and loading rate (LR) of knee adduction moment (KAM), and peak knee flexion moment (KFM) between walking and hopping. Peak KFM and KAM LR were greater during hopping compared to walking (peak KFM: 20.73% vs 5.51% body weight (BW) × height (Ht), P < 0.001; KAM LR: 0.47 vs. 0.33 BW·Ht·s, P = 0.01). Kinetic measures affecting knee joint loading are greater in hopping compared to walking. It may be advisable to limit single-leg forward hopping in the limb loss population until it is known if these loads increase knee osteoarthritis risk.

Localization in one-dimensional lattices with non-nearest-neighbor hopping: Generalized Anderson and Aubry-Andre models

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

Biddle, J.; Priour, D. J. Jr.; Wang, B.

We study the quantum localization phenomena of noninteracting particles in one-dimensional lattices based on tight-binding models with various forms of hopping terms beyond the nearest neighbor, which are generalizations of the famous Aubry-Andre and noninteracting Anderson models. For the case with deterministic disordered potential induced by a secondary incommensurate lattice (i.e., the Aubry-Andre model), we identify a class of self-dual models, for which the boundary between localized and extended eigenstates are determined analytically by employing a generalized Aubry-Andre transformation. We also numerically investigate the localization properties of nondual models with next-nearest-neighbor hopping, Gaussian, and power-law decay hopping terms. We findmore » that even for these nondual models, the numerically obtained mobility edges can be well approximated by the analytically obtained condition for localization transition in the self-dual models, as long as the decay of the hopping rate with respect to distance is sufficiently fast. For the disordered potential with genuinely random character, we examine scenarios with next-nearest-neighbor hopping, exponential, Gaussian, and power-law decay hopping terms numerically. We find that the higher-order hopping terms can remove the symmetry in the localization length about the energy band center compared to the Anderson model. Furthermore, our results demonstrate that for the power-law decay case, there exists a critical exponent below which mobility edges can be found. Our theoretical results could, in principle, be directly tested in shallow atomic optical lattice systems enabling non-nearest-neighbor hopping.« less

Beer spoilage bacteria and hop resistance.

PubMed

Sakamoto, Kanta; Konings, Wil N

2003-12-31

For brewing industry, beer spoilage bacteria have been problematic for centuries. They include some lactic acid bacteria such as Lactobacillus brevis, Lactobacillus lindneri and Pediococcus damnosus, and some Gram-negative bacteria such as Pectinatus cerevisiiphilus, Pectinatus frisingensis and Megasphaera cerevisiae. They can spoil beer by turbidity, acidity and the production of unfavorable smell such as diacetyl or hydrogen sulfide. For the microbiological control, many advanced biotechnological techniques such as immunoassay and polymerase chain reaction (PCR) have been applied in place of the conventional and time-consuming method of incubation on culture media. Subsequently, a method is needed to determine whether the detected bacterium is capable of growing in beer or not. In lactic acid bacteria, hop resistance is crucial for their ability to grow in beer. Hop compounds, mainly iso-alpha-acids in beer, have antibacterial activity against Gram-positive bacteria. They act as ionophores which dissipate the pH gradient across the cytoplasmic membrane and reduce the proton motive force (pmf). Consequently, the pmf-dependent nutrient uptake is hampered, resulting in cell death. The hop-resistance mechanisms in lactic acid bacteria have been investigated. HorA was found to excrete hop compounds in an ATP-dependent manner from the cell membrane to outer medium. Additionally, increased proton pumping by the membrane bound H(+)-ATPase contributes to hop resistance. To energize such ATP-dependent transporters hop-resistant cells contain larger ATP pools than hop-sensitive cells. Furthermore, a pmf-dependent hop transporter was recently presented. Understanding the hop-resistance mechanisms has enabled the development of rapid methods to discriminate beer spoilage strains from nonspoilers. The horA-PCR method has been applied for bacterial control in breweries. Also, a discrimination method was developed based on ATP pool measurement in lactobacillus cells. However, some potential hop-resistant strains cannot grow in beer unless they have first been exposed to subinhibitory concentration of hop compounds. The beer spoilage ability of Pectinatus spp. and M. cerevisiae has been poorly studied. Since all the strains have been reported to be capable of beer spoiling, species identification is sufficient for the breweries. However, with the current trend of beer flavor (lower alcohol and bitterness), there is the potential risk that not yet reported bacteria will contribute to beer spoilage. Investigation of the beer spoilage ability of especially Gram-negative bacteria may be useful to reduce this risk.

Molecular dynamics simulation of three plastic additives' diffusion in polyethylene terephthalate.

PubMed

Li, Bo; Wang, Zhi-Wei; Lin, Qin-Bao; Hu, Chang-Ying

2017-06-01

Accurate diffusion coefficient data of additives in a polymer are of paramount importance for estimating the migration of the additives over time. This paper shows how this diffusion coefficient can be estimated for three plastic additives [2-(2'-hydroxy-5'-methylphenyl) (UV-P), 2,6-di-tert-butyl-4-methylphenol (BHT) and di-(2-ethylhexyl) phthalate (DEHP)] in polyethylene terephthalate (PET) using the molecular dynamics (MD) simulation method. MD simulations were performed at temperatures of 293-433 K. The diffusion coefficient was calculated through the Einstein relationship connecting the data of mean-square displacement at different times. Comparison of the diffusion coefficients simulated by the MD simulation technique, predicted by the Piringer model and experiments, showed that, except for a few samples, the MD-simulated values were in agreement with the experimental values within one order of magnitude. Furthermore, the diffusion process for additives is discussed in detail, and four factors - the interaction energy between additive molecules and PET, fractional free volume, molecular shape and size, and self-diffusion of the polymer - are proposed to illustrate the microscopic diffusion mechanism. The movement trajectories of additives in PET cell models suggested that the additive molecules oscillate slowly rather than hopping for a long time. Occasionally, when a sufficiently large hole was created adjacently, the molecule could undergo spatial motion by jumping into the free-volume hole and consequently start a continuous oscillation and hop. The results indicate that MD simulation is a useful approach for predicting the microstructure and diffusion coefficient of plastic additives, and help to estimate the migration level of additives from PET packaging.

Hop limited epidemic-like information spreading in mobile social networks with selfish nodes

NASA Astrophysics Data System (ADS)

Wu, Yahui; Deng, Su; Huang, Hongbin

2013-07-01

Similar to epidemics, information can be transmitted directly among users in mobile social networks. Different from epidemics, we can control the spreading process by adjusting the corresponding parameters (e.g., hop count) directly. This paper proposes a theoretical model to evaluate the performance of an epidemic-like spreading algorithm, in which the maximal hop count of the information is limited. In addition, our model can be used to evaluate the impact of users’ selfish behavior. Simulations show the accuracy of our theoretical model. Numerical results show that the information hop count can have an important impact. In addition, the impact of selfish behavior is related to the information hop count.

Decoding Hip-Hop's Cultural Impact: Scholars Are Poised to Take a Close Look at the Influence of Hip-Hop on the Social Identity, Values of Today's Youth

ERIC Educational Resources Information Center

Roach, Ronald

2004-01-01

As a cultural movement, hip-hop manages to get billed as both a positive and negative influence on young people, especially on Black and Latino youth. On one hand, there are African American activists, artists and entrepreneurs, such as Russell Simmons, who seek to build a progressive political movement among young hip-hop fans and who have had…

A Global Approach to the Optimal Trajectory Based on an Improved Ant Colony Algorithm for Cold Spray

NASA Astrophysics Data System (ADS)

Cai, Zhenhua; Chen, Tingyang; Zeng, Chunnian; Guo, Xueping; Lian, Huijuan; Zheng, You; Wei, Xiaoxu

2016-12-01

This paper is concerned with finding a global approach to obtain the shortest complete coverage trajectory on complex surfaces for cold spray applications. A slicing algorithm is employed to decompose the free-form complex surface into several small pieces of simple topological type. The problem of finding the optimal arrangement of the pieces is translated into a generalized traveling salesman problem (GTSP). Owing to its high searching capability and convergence performance, an improved ant colony algorithm is then used to solve the GTSP. Through off-line simulation, a robot trajectory is generated based on the optimized result. The approach is applied to coat real components with a complex surface by using the cold spray system with copper as the spraying material.

Semi-analytical model for a static sheath including a weakly collisional presheath

NASA Astrophysics Data System (ADS)

Shirafuji, Tatsuru; Denpoh, Kazuki

2018-06-01

A semi-analytical static sheath (SASS) model can provide a spatial potential profile on a biased surface with microstructures, which can be used for predicting ion trajectories on the surface. However, two- or three-dimensional SASS models require a search procedure for a sheath edge equipotential profile, at which ions have the Bohm velocity, as the starting positions for calculating ion trajectories. This procedure can be troublesome when surface microstructures have complex structures. This difficulty is due to the fact that the SASS model cannot handle a presheath region. In this work, we propose a modified SASS model that can handle a presheath region. By using the modified SASS model, ion trajectories can be calculated from edges with arbitrary geometry without searching for the equipotential profile corresponding to sheath edges.

Nerve Conduction Through Dendrites via Proton Hopping.

PubMed

Kier, Lemont B

2017-01-01

In our previous studies of nerve conduction conducted by proton hopping, we have considered the axon, soma, synapse and the nodes of Ranvier. The role of proton hopping described the passage of information through each of these units of a typical nerve system. The synapse projects information from the axon to the dendrite and their associated spines. We have invoked the passage of protons via a hopping mechanism to illustrate the continuum of the impulse through the system, via the soma following the dendrites. This is proposed to be a continuum invoked by the proton hopping method. With the proposal of the activity through the dendrites, via proton hopping, a complete model of the nerve function is invoked. At each step to the way, a water pathway is present and is invoked in the proposed model as the carrier of the message via proton hopping. The importance of the dendrites is evident by the presence of a vast number of spines, each possessing the possibility to carry unique messages through the nervous system. With this model of the role of dendrites, functioning with the presence of proton hopping, a complete model of the nerve system is presented. The validity of this model will be available for further studies and models to assess it's validity. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Antimicrobial activity of hop extracts against foodborne pathogens for meat applications.

PubMed

Kramer, B; Thielmann, J; Hickisch, A; Muranyi, P; Wunderlich, J; Hauser, C

2015-03-01

The objective of this study was the fundamental investigation of the antimicrobial efficiency of various hop extracts against selected foodborne pathogens in vitro, as well as their activity against Listeria monocytogenes in a model meat marinade and on marinated pork tenderloins. In a first step, the minimum inhibitory concentrations (MIC) of three hop extracts containing either α- or β-acids or xanthohumol were determined against test bacteria including L. monocytogenes, Staphylococcus aureus, Salmonella enterica and Escherichia coli by a colorimetric method based on the measurement of bacterial metabolic activity. Moreover, the influence of either lactic or citric acid on the antimicrobial activity of the hop extracts was evaluated. The efficiency of hop extracts as a natural food preservative was then tested in a model meat marinade at 2 and 8°C, respectively, and finally on marinated pork. The experiments showed that Gram-positive bacteria were strongly inhibited by hop extracts containing β-acids and xanthohumol (MIC values of 6.3 and 12.5 ppm, respectively), whereas the antimicrobial activity of the investigated α-acid extract was significantly lower (MIC values of 200 ppm). Gram-negative bacteria were highly resistant against all tested hop extracts. Acidification of the test media led to a decrease of the MIC values. The inhibitory activity of the hop extracts against L. monocytogenes was strongly reduced in a fat-containing model meat marinade, but the efficiency of β-acids in this matrix could be increased by lowering pH and storage temperatures. By applying 0.5 % β-acids at pH = 5 in a model marinade, the total aerobic count of pork tenderloins was reduced up to 0.9 log10 compared with marinated pork without hop extract after 2 weeks of storage at 5°C. β-acid containing hop extracts have proven to possess a high antimicrobial activity against Gram-positive bacteria in vitro and in a practice-related application for food preservation. Antimicrobial hop extracts could be used as natural preservatives in food applications to extend the shelf life and to increase the safety of fresh products. © 2014 The Society for Applied Microbiology.

Type III Effector Diversification via Both Pathoadaptation and Horizontal Transfer in Response to a Coevolutionary Arms Race

PubMed Central

Ma, Wenbo; Dong, Frederick F. T; Stavrinides, John; Guttman, David S

2006-01-01

The concept of the coevolutionary arms race holds a central position in our understanding of pathogen–host interactions. Here we identify the molecular mechanisms and follow the stepwise progression of an arms race in a natural system. We show how the evolution and function of the HopZ family of type III secreted effector proteins carried by the plant pathogen Pseudomonas syringae are influenced by a coevolutionary arms race between pathogen and host. We surveyed 96 isolates of P. syringae and identified three homologs (HopZ1, HopZ2, and HopZ3) distributed among ∼45% of the strains. All alleles were sequenced and their expression was confirmed. Evolutionary analyses determined that the diverse HopZ1 homologs are ancestral to P. syringae, and have diverged via pathoadaptive mutational changes into three functional and two degenerate forms, while HopZ2 and HopZ3 have been brought into P. syringae via horizontal transfer from other ecologically similar bacteria. A PAML selection analysis revealed that the C terminus of HopZ1 is under strong positive selection. Despite the extensive genetic variation observed in this family, all three homologs have cysteine–protease activity, although their substrate specificity may vary. The introduction of the ancestral hopZ1 allele into strains harboring alternate alleles results in a resistance protein-mediated defense response in their respective hosts, which is not observed with the endogenous allele. These data indicate that the P. syringae HopZ family has undergone allelic diversification via both pathoadaptive mutational changes and horizontal transfer in response to selection imposed by the host defense system. This genetic diversity permits the pathogen to avoid host defenses while still maintaining a virulence-associated protease, thereby allowing it to thrive on its current host, while simultaneously impacting its host range. PMID:17194219

Energetics and biomechanics of locomotion by red kangaroos (Macropus rufus).

PubMed

Kram, R; Dawson, T J

1998-05-01

As red kangaroos hop faster over level ground, their rate of oxygen consumption (indicating metabolic energy consumption) remains nearly the same. This phenomenon has been attributed to exceptional elastic energy storage and recovery via long compliant tendons in the legs. Alternatively, red kangaroos may have exceptionally efficient muscles. To estimate efficiency, we measured the metabolic cost of uphill hopping, where muscle fibers must perform mechanical work against gravity. We found that uphill hopping was much more expensive than level hopping. The maximal rate of oxygen consumption measured (3 ml O2 kg-1 s-1) exceeds all but a few vertebrate species. However, efficiency values were normal, approximately 30%. At faster level hopping speeds the effective mechanical advantage of the extensor muscles of the ankle joint remained the same. Thus, kangaroos generate the same muscular force at all speeds but do so more rapidly at faster hopping speeds. This contradicts a recent hypothesis for what sets the cost of locomotion. The cost of transport (J kg-1 m-1) decreases at faster hopping speeds, yet red kangaroos prefer to use relatively slow speeds that avoid high levels of tendon stress.

Low Power Multi-Hop Networking Analysis in Intelligent Environments.

PubMed

Etxaniz, Josu; Aranguren, Gerardo

2017-05-19

Intelligent systems are driven by the latest technological advances in many different areas such as sensing, embedded systems, wireless communications or context recognition. This paper focuses on some of those areas. Concretely, the paper deals with wireless communications issues in embedded systems. More precisely, the paper combines the multi-hop networking with Bluetooth technology and a quality of service (QoS) metric, the latency. Bluetooth is a radio license-free worldwide communication standard that makes low power multi-hop wireless networking available. It establishes piconets (point-to-point and point-to-multipoint links) and scatternets (multi-hop networks). As a result, many Bluetooth nodes can be interconnected to set up ambient intelligent networks. Then, this paper presents the results of the investigation on multi-hop latency with park and sniff Bluetooth low power modes conducted over the hardware test bench previously implemented. In addition, the empirical models to estimate the latency of multi-hop communications over Bluetooth Asynchronous Connectionless Links (ACL) in park and sniff mode are given. The designers of devices and networks for intelligent systems will benefit from the estimation of the latency in Bluetooth multi-hop communications that the models provide.

Low Power Multi-Hop Networking Analysis in Intelligent Environments

PubMed Central

Etxaniz, Josu; Aranguren, Gerardo

2017-01-01

Intelligent systems are driven by the latest technological advances in many different areas such as sensing, embedded systems, wireless communications or context recognition. This paper focuses on some of those areas. Concretely, the paper deals with wireless communications issues in embedded systems. More precisely, the paper combines the multi-hop networking with Bluetooth technology and a quality of service (QoS) metric, the latency. Bluetooth is a radio license-free worldwide communication standard that makes low power multi-hop wireless networking available. It establishes piconets (point-to-point and point-to-multipoint links) and scatternets (multi-hop networks). As a result, many Bluetooth nodes can be interconnected to set up ambient intelligent networks. Then, this paper presents the results of the investigation on multi-hop latency with park and sniff Bluetooth low power modes conducted over the hardware test bench previously implemented. In addition, the empirical models to estimate the latency of multi-hop communications over Bluetooth Asynchronous Connectionless Links (ACL) in park and sniff mode are given. The designers of devices and networks for intelligent systems will benefit from the estimation of the latency in Bluetooth multi-hop communications that the models provide. PMID:28534847

Gold Binding by Native and Chemically Modified Hops Biomasses

PubMed Central

López, M. Laura; Peralta-Videa, J. R.; de la Rosa, G.; Armendáriz, V.; Herrera, I.; Troiani, H.; Henning, J.

2005-01-01

Heavy metals from mining, smelting operations and other industrial processing facilities pollute wastewaters worldwide. Extraction of metals from industrial effluents has been widely studied due to the economic advantages and the relative ease of technical implementation. Consequently, the search for new and improved methodologies for the recovery of gold has increased. In this particular research, the use of cone hops biomass (Humulus lupulus) was investigated as a new option for gold recovery. The results showed that the gold binding to native hops biomass was pH dependent from pH 2 to pH 6, with a maximum percentage binding at pH 3. Time dependency studies demonstrated that Au(III) binding to native and modified cone hops biomasses was found to be time independent at pH 2 while at pH 5, it was time dependent. Capacity experiments demonstrated that at pH 2, esterified hops biomass bound 33.4 mg Au/g of biomass, while native and hydrolyzed hops biomasses bound 28.2 and 12.0 mg Au/g of biomass, respectively. However, at pH 5 the binding capacities were 38.9, 37.8 and 11.4 mg of Au per gram of native, esterified and hydrolyzed hops biomasses, respectively. PMID:18365087

Rice Protein Matrix Enhances Circulating Levels of Xanthohumol Following Acute Oral Intake of Spent Hops in Humans.

PubMed

O'Connor, Annalouise; Konda, Veera; Reed, Ralph L; Christensen, J Mark; Stevens, Jan F; Contractor, Nikhat

2018-03-01

Xanthohumol (XN), a prenylated flavonoid found in hops, exhibits anti-inflammatory and antioxidant properties. However, poor bioavailability may limit therapeutic applications. As food components are known to modulate polyphenol absorption, the objective is to determine whether a protein matrix could enhance the bioavailability of XN post oral consumption in humans. This is a randomized, double-blind, crossover study in healthy participants (n = 6) evaluating XN and its major metabolites (isoxanthohumol [IX], 6- and 8-prenylnaringenin [6-PN, 8-PN]) for 6 h following consumption of 12.4 mg of XN delivered via a spent hops-rice protein matrix preparation or a control spent hops preparation. Plasma XN and metabolites are measured by LC-MS/MS. C max , T max , and area-under-the-curve (AUC) values were determined. Circulating XN and metabolite response to each treatment was not bioequivalent. Plasma concentrations of XN and XN + metabolites (AUC) are greater with consumption of the spent hops-rice protein matrix preparation. Compared to a standard spent hops powder, a protein-rich spent hops matrix demonstrates enhanced plasma levels of XN and metabolites following acute oral intake. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sequence analyses reveal that a TPR-DP module, surrounded by recombinable flanking introns, could be at the origin of eukaryotic Hop and Hip TPR-DP domains and prokaryotic GerD proteins.

PubMed

Hernández Torres, Jorge; Papandreou, Nikolaos; Chomilier, Jacques

2009-05-01

The co-chaperone Hop [heat shock protein (HSP) organising protein] is known to bind both Hsp70 and Hsp90. Hop comprises three repeats of a tetratricopeptide repeat (TPR) domain, each consisting of three TPR motifs. The first and last TPR domains are followed by a domain containing several dipeptide (DP) repeats called the DP domain. These analyses suggest that the hop genes result from successive recombination events of an ancestral TPR-DP module. From a hydrophobic cluster analysis of homologous Hop protein sequences derived from gene families, we can postulate that shifts in the open reading frames are at the origin of the present sequences. Moreover, these shifts can be related to the presence or absence of biological function. We propose to extend the family of Hop co-chaperons into the kingdom of bacteria, as several structurally related genes have been identified by hydrophobic cluster analysis. We also provide evidence of common structural characteristics between hop and hip genes, suggesting a shared precursor of ancestral TPR-DP domains.

Condom use and hip hop culture: the case of urban young men in New York City.

PubMed

Muñoz-Laboy, Miguel A; Castellanos, Daniel H; Haliburton, Chanel S; del Aguila, Ernesto Vasquez; Weinstein, Hannah J; Parker, Richard G

2008-06-01

We explored how young men's perceptions of and participation in hip hop culture--urban social and artistic expressions, such as clothing style, breakdancing, graffiti, and rap music--and how contextual factors of the hip hop scene may be associated with their condom use, condom-use self-efficacy, and sense of community. We conducted a cross-sectional survey of 95 African American and Latino men aged 15 to 25 years as part of a 4-year ethnographic study in New York City. Differences in young men's perceptions of and levels of affiliation with hip hop culture were not statistically associated with differences in their sense of community or condom-use self-efficacy. Frequency of participation in the hip hop nightclub scene was the strongest factor negatively associated with condom use. Popular discourses on young men's health risks often blame youths' cultures such as the hip hop culture for increased risk practices but do not critically examine how risk emerges in urban young men's lives and what aspects of youths' culture can be protective. Further research needs to focus on contextual factors of risk such as the role of hip hop nightlife on increased HIV risk.

Calculation of water drop trajectories to and about arbitrary three-dimensional lifting and nonlifting bodies in potential airflow

NASA Technical Reports Server (NTRS)

Norment, H. G.

1985-01-01

Subsonic, external flow about nonlifting bodies, lifting bodies or combinations of lifting and nonlifting bodies is calculated by a modified version of the Hess lifting code. Trajectory calculations can be performed for any atmospheric conditions and for all water drop sizes, from the smallest cloud droplet to large raindrops. Experimental water drop drag relations are used in the water drop equations of motion and effects of gravity settling are included. Inlet flow can be accommodated, and high Mach number compressibility effects are corrected for approximately. Seven codes are described: (1) a code used to debug and plot body surface description data; (2) a code that processes the body surface data to yield the potential flow field; (3) a code that computes flow velocities at arrays of points in space; (4) a code that computes water drop trajectories from an array of points in space; (5) a code that computes water drop trajectories and fluxes to arbitrary target points; (6) a code that computes water drop trajectories tangent to the body; and (7) a code that produces stereo pair plots which include both the body and trajectories. Accuracy of the calculations is discussed, and trajectory calculation results are compared with prior calculations and with experimental data.

Hybrid spread spectrum radio system

DOEpatents

Smith, Stephen F.; Dress, William B.

2010-02-02

Systems and methods are described for hybrid spread spectrum radio systems. A method includes modulating a signal by utilizing a subset of bits from a pseudo-random code generator to control an amplification circuit that provides a gain to the signal. Another method includes: modulating a signal by utilizing a subset of bits from a pseudo-random code generator to control a fast hopping frequency synthesizer; and fast frequency hopping the signal with the fast hopping frequency synthesizer, wherein multiple frequency hops occur within a single data-bit time.

Energy landscape in frustrated systems: Cation hopping in pyrochlores

NASA Astrophysics Data System (ADS)

Brooks Hinojosa, Beverly; Asthagiri, Aravind; Nino, Juan C.

2013-07-01

We investigate the dynamics of the local environment and electronic structure in inherently dipolar frustrated pyrochlore compounds to help identify the fundamental nature of dipolar disorder in pyrochlore systems and determine the necessary and sufficient conditions for dielectric relaxation. We map out the energy landscape associated with cation hopping events in three compounds and correlate the hopping pathway with experimental dielectric response. Comprehensive analysis of the calculations allows us to postulate rules to predict the occurrence of relaxation and cation hopping pathways.

Hopping robot

DOEpatents

Spletzer, Barry L.; Fischer, Gary J.; Marron, Lisa C.; Martinez, Michael A.; Kuehl, Michael A.; Feddema, John T.

2001-01-01

The present invention provides a hopping robot that includes a misfire tolerant linear actuator suitable for long trips, low energy steering and control, reliable low energy righting, miniature low energy fuel control. The present invention provides a robot with hopping mobility, capable of traversing obstacles significant in size relative to the robot and capable of operation on unpredictable terrain over long range. The present invention further provides a hopping robot with misfire-tolerant combustion actuation, and with combustion actuation suitable for use in oxygen-poor environments.

Electron Transfer Pathways Facilitating U(VI) Reduction by Fe(II) on Al- vs Fe-Oxides

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

Taylor, S. D.; Becker, U.; Rosso, K. M.

This study continues mechanistic development of heterogeneous electron transfer (ET) pathways at mineral surfaces in aquatic environments that enable the reduction U(VI) by surface-associated Fe(II). Using computational molecular simulation within the framework of Marcus Theory, our findings highlight the importance of the configurations and interaction of the electron donor and acceptor species with the substrate, with respect to influencing its electronic structure and thereby the ability of semiconducting minerals to facilitate ET. U(VI) reduction by surface-associated Fe(II) (adsorbed or structurally incorporated into the lattice) on an insulating, corundum (001) surface (α-Al2O3) occurs when proximal inner-sphere (IS) surface complexes are formed,more » such that ET occurs through a combination of direct exchange (i.e., Fe d- and U f-orbitals overlap through space) and superexchange via intervening surface oxygen atoms. U(VI) reduction by coadsorbed Fe(II) on the isostructural semiconducting hematite (α-Fe2O3) basal surface requires either their direct electronic interaction (e.g., IS complexation) or mediation of this interaction indirectly through the surface via an intrasurface pathway. Conceptually possible longer-range ET by charge-hopping through surface Fe atoms was investigated to determine whether this indirect pathway is competitive with direct ET. The calculations show that energy barriers are large for this conduction-based pathway; interfacial ET into the hematite surface is endothermic (+80.1 kJ/mol) and comprises the rate-limiting step (10–6 s–1). The presence of the IS adsorbates appears to weaken the electronic coupling between underlying Fe ions within the surface, resulting in slower intra-surface ET (10–5 s–1) than expected in the bulk basal plane. Our findings lay out first insights into donor-acceptor communication via a charge-hopping pathway through the surface for heterogeneous reduction of U(VI) by Fe(II) and help provide a basis for experimental interrogation of this important process at mineral-water interfaces.« less

Seabird drift as a proxy to estimate surface currents in the western Mediterranean?

NASA Astrophysics Data System (ADS)

Gomez-Navarro, Laura; Sánchez-Román, Antonio; Pascual, Ananda; Fablet, Ronan; Hernandez-Carrasco, Ismael; Mason, Evan; Arcos, José Manuel; Oro, Daniel

2017-04-01

Seabird trajectories can be used as proxies to investigate the dynamics of marine systems and their spatiotemporal evolution. Previous studies have mainly been based on analyses of long range flights, where birds are travelling at high velocities over long time periods. Such data have been used to study wind patterns, and areas of avian feeding and foraging have also been used to study oceanic fronts. Here we focus on "slow moving" periods (which we associate to when birds appear to be drifting on the sea surface), in order to investigate bird drift as a proxy for sea surface currents in the western Mediterranean Sea. We analyse trajectories corresponding to "slow moving" periods recorded by GPSs attached to individuals of the species Calonectris diomedea ( Scopoli's shearwater) from mid August to mid September 2012. The trajectories are compared with sea level anomaly (SLA), sea surface temperature (SST), Finite Size Lyapunov Exponents (FSLE), wind fields, and the outputs from an automated sea-surface-height based eddy tracker. The SLA and SST datasets were obtained from the Copernicus Marine Environment Monitoring Service (CMEMS) with a spatial resolution of 1/8 ̊ and 1/100 ̊ respectively while the FSLEs were computed from the SLA dataset. Finally, the wind data comes from the outputs of the CCMPv2 numerical model. This model has a global coverage with a spatial resolution of 1/4 ̊. Interesting relationships between the trajectories and SLA fields are found. According to the angle between the SLA gradient and the trajectories of birds, we classify drifts into three scenarios: perpendicular, parallel and other, which are associated with different driving forces. The first scenario implies that bird drift is driven by geostrophic sea surface currents. The second we associate with wind drag as the main driving force. This is validated through the wind dataset. Moreover, from the SST, FSLEs and the eddy tracker, we obtain supplementary information on the presence of oceanic structures (such as eddies or fronts), not observed in the SLA field due to its limited spatial and temporal resolutions. Therefore, this data helps to explain some of the third case scenario trajectories.

[Abnormal growth of spine in patients with adolescent idiopathic thoracic scoliosis].

PubMed

Bao, Hongda; Liu, Zhen; Qiu, Yong; Zhu, Feng; Zhu, Zezhang; Zhang, Wen

2014-05-01

To investigate if the growth patterns of the spine and pelvis are consistent in adolescent idiopathic scoliosis (AIS) patients with single thoracic curves. Forty-eight thoracic adolescent idiopathic scoliosis (T-AIS) female patients and 48 healthy age-matched adolescents were recruited consecutively between December 2011 and October 2012. Radiographic parameters including height of spine (HOS), length of spine (LOS), height of thoracic spine (HOT), length of thoracic spine (LOT), height of pelvis (HOP), width of pelvis (WOP) and width of thorax (WOT) were measured on the long-cassette posteroanterior standing radiographs. In addition, ratios including HOS/HOP, LOS/HOP, HOT/HOP, LOT/HOP, LOS/LOT, WOT/WOP were also calculated. Independent t-test was performed to compare the radiographic parameters and ratios between the two groups. Compared to the age-matched healthy adolescents, T-AIS patients had a significantly higher LOS and LOT (t = -2.364 and -1.495, P = 0.020 and 0.043) and smaller HOS and HOT (t = 2.060 and 3.359, P = 0.042 and 0.001). Yet, all of HOP, WOP and WOT showed no significant difference between T-AIS patients and healthy adolescents. Similarly, LOS/HOP and LOT/HOP were significantly higher in T-AIS patients as may be expected with an average LOS/HOP of 2.26 ± 0.14 in normal controls.In addition, LOS/LOT in normal controls had a trend of increase with age which was different from the stable LOS/LOT in T-AIS patients, indicating an increased growth of thoracic vertebra compared to lumbar vertebra. Compared to the age-matched healthy adolescents, T-AIS patients have an abnormal growth characteristics with longer spine. The growth of pelvis and thorax show no significant differences between T-AIS patients and healthy adolescents.

Nuclear magnetic resonance and high-performance liquid chromatography techniques for the characterization of bioactive compounds from Humulus lupulus L. (hop).

PubMed

Bertelli, Davide; Brighenti, Virginia; Marchetti, Lucia; Reik, Anna; Pellati, Federica

2018-06-01

Humulus lupulus L. (hop) represents one of the most cultivated crops, it being a key ingredient in the brewing process. Many health-related properties have been described for hop extracts, making this plant gain more interest in the field of pharmaceutical and nutraceutical research. Among the analytical tools available for the phytochemical characterization of plant extracts, quantitative nuclear magnetic resonance (qNMR) represents a new and powerful technique. In this ambit, the present study was aimed at the development of a new, simple, and efficient qNMR method for the metabolite fingerprinting of bioactive compounds in hop cones, taking advantage of the novel ERETIC 2 tool. To the best of our knowledge, this is the first attempt to apply this method to complex matrices of natural origin, such as hop extracts. The qNMR method set up in this study was applied to the quantification of both prenylflavonoids and bitter acids in eight hop cultivars. The performance of this analytical method was compared with that of HPLC-UV/DAD, which represents the most frequently used technique in the field of natural product analysis. The quantitative data obtained for hop samples by means of the two aforementioned techniques highlighted that the amount of bioactive compounds was slightly higher when qNMR was applied, although the order of magnitude of the values was the same. The accuracy of qNMR was comparable to that of the chromatographic method, thus proving to be a reliable tool for the analysis of these secondary metabolites in hop extracts. Graphical abstract Graphical abstract related to the extraction and analytical methods applied in this work for the analysis of bioactive compounds in Humulus lupulus L. (hop) cones.

Gender differences in active musculoskeletal stiffness. Part II. Quantification of leg stiffness during functional hopping tasks.

PubMed

Granata, K P; Padua, D A; Wilson, S E

2002-04-01

Leg stiffness was compared between age-matched males and females during hopping at preferred and controlled frequencies. Stiffness was defined as the linear regression slope between the vertical center of mass (COM) displacement and ground-reaction forces recorded from a force plate during the stance phase of the hopping task. Results demonstrate that subjects modulated the vertical displacement of the COM during ground contact in relation to the square of hopping frequency. This supports the accuracy of the spring-mass oscillator as a representative model of hopping. It also maintained peak vertical ground-reaction load at approximately three times body weight. Leg stiffness values in males (33.9+/-8.7 kN/m) were significantly (p<0.01) greater than in females (26.3+/-6.5 kN/m) at each of three hopping frequencies, 3.0, 2.5 Hz, and a preferred hopping rate. In the spring-mass oscillator model leg stiffness and body mass are related to the frequency of motion. Thus male subjects necessarily recruited greater leg stiffness to drive their heavier body mass at the same frequency as the lighter female subjects during the controlled frequency trials. However, in the preferred hopping condition the stiffness was not constrained by the task because frequency was self-selected. Nonetheless, both male and female subjects hopped at statistically similar preferred frequencies (2.34+/-0.22 Hz), therefore, the females continued to demonstrate less leg stiffness. Recognizing the active muscle stiffness contributes to biomechanical stability as well as leg stiffness, these results may provide insight into the gender bias in risk of musculoskeletal knee injury.

Performance on the Functional Movement Screen™ is related to hop performance, but not to hip and knee strength in collegiate football players

PubMed Central

Willigenburg, Nienke; Hewett, Timothy E.

2016-01-01

Objective To define the relationship between FMS™ scores and hop performance, hip strength, and knee strength in collegiate football players. Design Cross-sectional cohort. Participants Freshmen of a division I collegiate American football team (n=59). Main Outcome Measures The athletes performed the FMS™, as well as a variety of hop tests, isokinetic knee strength and isometric hip strength tasks. We recorded total FMS™ score, peak strength and hop performance, and we calculated asymmetries between legs on the different tasks. Spearman’s correlation coefficients quantified the relationships these measures, and chi-square analyses compared the number of athletes with asymmetries on the different tasks. Results We observed significant correlations (r=0.38–0.56, p≤0.02) between FMS™ scores and hop distance, but not between FMS™ scores and hip or knee strength (all p≥0.21). The amount of asymmetry on the FMS™ test was significantly correlated to the amount of asymmetry on the timed 6m hop (r=0.44, p<0.01), but not to hip or knee strength asymmetries between limbs (all p≥0.34). Conclusions FMS™ score was positively correlated to hop distance, and limb asymmetry in FMS™ tasks was correlated to limb asymmetry in 6m hop time in football players. No significant correlations were observed between FMS™ score and hip and knee strength, or between FMS™ asymmetry and asymmetries in hip and knee strength between limbs. These results indicate that a simple hop for distance test may be a time and cost efficient alternative to FMS™ testing in athletes and that functional asymmetries between limbs do not coincide with strength asymmetries. PMID:26886801

Performance on the Functional Movement Screen Is Related to Hop Performance But Not to Hip and Knee Strength in Collegiate Football Players.

PubMed

Willigenburg, Nienke; Hewett, Timothy E

2017-03-01

To define the relationship between Functional Movement Screen (FMS) scores and hop performance, hip strength, and knee strength in collegiate football players. Cross-sectional cohort. Freshmen of a Division I collegiate American football team (n = 59). The athletes performed the FMS, and also a variety of hop tests, isokinetic knee strength, and isometric hip strength tasks. We recorded total FMS score, peak strength, and hop performance, and we calculated asymmetries between legs on the different tasks. Spearman correlation coefficients quantified the relationships between these measures, and χ analyses compared the number of athletes with asymmetries on the different tasks. We observed significant correlations (r = 0.38-0.56, P ≤ 0.02) between FMS scores and hop distance but not between FMS scores and hip or knee strength (all P ≥ 0.21). The amount of asymmetry on the FMS test was significantly correlated to the amount of asymmetry on the timed 6-m hop (r = 0.44, P < 0.01) but not to hip or knee strength asymmetries between limbs (all P ≥ 0.34). Functional Movement Screen score was positively correlated to hop distance, and limb asymmetry in FMS tasks was correlated to limb asymmetry in 6-m hop time in football players. No significant correlations were observed between FMS score and hip and knee strength or between FMS asymmetry and asymmetries in hip and knee strength between limbs. These results indicate that a simple hop for distance test may be a time-efficient and cost-efficient alternative to FMS testing in athletes and that functional asymmetries between limbs do not coincide with strength asymmetries.

No difference between mechanical perturbation training with compliant surface and manual perturbation training on knee functional performance after ACL rupture.

PubMed

Nawasreh, Zakariya; Logerstedt, David; Failla, Mathew; Snyder-Mackler, Lynn

2017-10-27

Manual perturbation training improves dynamic knee stability and functional performance after anterior cruciate ligament rupture (ACL-rupture). However, it is limited to static standing position and does not allow time-specific perturbations at different phase of functional activities. The purpose of this study was to investigate whether administering mechanical perturbation training including compliant surface provides effects similar to manual perturbation training on knee functional measures after an acute ACL-rupture. Sixteen level I/II athletes with ACL-ruptures participated in this preliminary study. Eight patients received mechanical (Mechanical) and eight subjects received manual perturbation training (Manual). All patients completed a functional testing (isometric quadriceps strength, single-legged hop tests) and patient-reported measures (Knee Outcome Survey-Activities of Daily Living Scale (KOS-ADLS), Global Rating Score (GRS), International Knee Documentation Committee 2000 (IKDC 2000) at pre- and post-training. 2 × 2 ANOVA was used for data analysis. No significant group-by-time interactions were found for all measures (p > 0.18). Main effects of time were found for single hop (Pre-testing: 85.14% ± 21.07; Post-testing: 92.49% ± 17.55), triple hop (Pre-testing: 84.64% ± 14.17; Post-testing: 96.64% ± 11.14), KOS-ADLS (Pre-testing: 81.13% ± 11.12; Post-testing: 88.63% ± 12.63), GRS (Pre-testing: 68.63% ± 15.73; Post-testing: 78.81% ± 13.85), and IKDC 2000 (Pre-testing: 66.66% ± 9.85; Post-testing: 76.05% ± 14.62) (p < 0.032). Administering mechanical perturbation training using compliant surfaces induce effects similar to manual perturbation training on knee functional performance after acute ACL-rupture. The clinical significance is both modes of training improve patients' functional-performance and limb-to-limb movement symmetry, and enhancing the patients' self-reported of knee functional measures after ACL rupture. Mechanical perturbation that provides a compliant surface might be utilized as part of the ACL rehabilitation training. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Mode Hopping in Semiconductor Lasers

NASA Astrophysics Data System (ADS)

Heumier, Timothy Alan

Semiconductor lasers have found widespread use in fiberoptic communications, merchandising (bar-code scanners), entertainment (videodisc and compact disc players), and in scientific inquiry (spectroscopy, laser cooling). Some uses require a minimum degree of stability of wavelength which is not met by these lasers: Under some conditions, semiconductor lasers can discontinuously switch wavelengths in a back-and-forth manner. This is called mode hopping. We show that mode hopping is directly correlated to noise in the total intensity, and that this noise is easily detected by a photodiode. We also show that there are combinations of laser case temperature and injection current which lead to mode hopping. Conversely, there are other combinations for which the laser is stable. These results are shown to have implications for controlling mode hopping.

Statistical Field Estimation for Complex Coastal Regions and Archipelagos (PREPRINT)

DTIC Science & Technology

2011-04-09

and study the computational properties of these schemes. Specifically, we extend a multiscale Objective Analysis (OA) approach to complex coastal...computational properties of these schemes. Specifically, we extend a multiscale Objective Analysis (OA) approach to complex coastal regions and... multiscale free-surface code builds on the primitive-equation model of the Harvard Ocean Predic- tion System (HOPS, Haley et al. (2009)). Additionally

A Mobile Asteroid Surface Scout (MASCOT) for the Hayabusa 2 Mission to 1999 JU3: The Scientific Approach

NASA Astrophysics Data System (ADS)

Jaumann, Ralf; Bibring, Jean-Piere; Glassmeier, Karl-Heiz; Grott, Mathias; Ho, Tra-Mi; Ulamec, Stefan; Schmitz, Nicole; Auster, Ulrich; Biele, Jens; Kuninaka, Hitoshi; Okada, Tatsuaki; Yoshikawa, Makoto; Watanabe, Sei-ichiro; Fujimoto, Masaki; Spohn, Tilman; Koncz, Aalexander; Hercik, Davis; Michaelis, Harald

2015-04-01

MASCOT, a Mobile Asteroid Surface Scout, will support JAXA's Hayabusa 2 mission to investigate the C-type asteroid 1999 JU3 (1). The German Aer-ospace Center (DLR) develops MASCOT with contributions from CNES (France) (2,3,4). Main objective is to in-situ map the asteroid's geomorphol-ogy, the intimate mixture, texture and composition of the regolith (dust, soil and rocks), and the thermal, mechanical, and magnetic properties of the sur-face in order to provide ground truth for the orbiter remote measurements, support the selection of sampling sites, and provide context information for the returned samples. MASCOT comprises a payload of four scientific in-struments: camera, radiometer, magnetometer and hyperspectral microscope. C- and D-type asteroids hold clues to the origin of the solar system, the for-mation of planets, the origins of water and life on Earth, the protection of Earth from impacts, and resources for future human exploration. C- and D-types are dark and difficult to study from Earth, and have only been glimpsed by spacecraft. While results from recent missions (e.g., Hayabusa, NEAR (5, 6, 7)) have dramatically increased our understanding of asteroids, important questions remain open. For example, characterizing the properties of asteroid regolith in-situ would deliver important ground truth for further understanding telescopic and orbital observations and samples of such asteroids. MASCOT will descend and land on the asteroid and will change its own position up to two times by hopping. This enables measurements during descent, at the landing and hopping positions #1-3, and during hopping. Hayabusa 2 together with MASCOT launched December 3rd 2014, will arrive at 1999JU3 in 2018 and return samples back to Earth in 2020. References: (1) Vilas, F., Astronomical J. 1101-1105, 2008; (2) Ulamec, S., et al., Acta Astronautica, Vol. 93, pp. 460-466; (3) Jaumann et al., 45th LPSC, #1812, Houston; (4) Ho et al., 45th LPSC, #2535, Houston; (5) Spe-cial Issue, Science, Vol. 312 no. 5778, 2006; (6) Special Issue Science, Vol. 333 no. 6046, 2011. (7) Bell, L., Mitton, J-., Cambridge Univ. Press, 2002.

Hop powdery mildew control through alteration of spring pruning practices

USDA-ARS?s Scientific Manuscript database

Since 1997, Podosphaera macularis, the causal agent of hop powdery mildew, has become a recurrent threat to hops in the Pacific Northwest because of the potential to reduce cone yield and quality. Disease management practices often involve preventative fungicide applications, but alternative approac...

Relationships between Xanthohumol and Polyphenol Content in Hop Leaves and Hop Cones with Regard to Water Supply and Cultivar

PubMed Central

Čeh, Barbara; Kač, Milica; Košir, Iztok J.; Abram, Veronika

2007-01-01

The effect of water supply – especially of drought stress – on the content of some secondary metabolites in hops (Humulus lupulus L.) was studied. The experiment took place in 2006. Some relevant data from 2005 were included for comparison. Leaves and cones of nine hop cultivars grown under field conditions as well as in a pot experiment under three water regimes were analyzed. The cultivars ranged from those most grown in Slovenia to promising crossbreed being tested. Leaves were sampled from July 18, 2006 to August 18, 2006, while cones were picked in the time of technological maturity. Standard analytical methods were applied to determine the contents of xanthohumol, polyphenols and α-acids in hop leaves and hop cones. The contents of the secondary metabolites in question depended more on the cultivar under investigation than on the water supply, at least as far the growing conditions for a relatively normal development of the plant were met.

Pseudomonas HopU1 modulates plant immune receptor levels by blocking the interaction of their mRNAs with GRP7.

PubMed

Nicaise, Valerie; Joe, Anna; Jeong, Byeong-ryool; Korneli, Christin; Boutrot, Freddy; Westedt, Isa; Staiger, Dorothee; Alfano, James R; Zipfel, Cyril

2013-03-06

Pathogens target important components of host immunity to cause disease. The Pseudomonas syringae type III-secreted effector HopU1 is a mono-ADP-ribosyltransferase required for full virulence on Arabidopsis thaliana. HopU1 targets several RNA-binding proteins including GRP7, whose role in immunity is still unclear. Here, we show that GRP7 associates with translational components, as well as with the pattern recognition receptors FLS2 and EFR. Moreover, GRP7 binds specifically FLS2 and EFR transcripts in vivo through its RNA recognition motif. HopU1 does not affect the protein-protein associations between GRP7, FLS2 and translational components. Instead, HopU1 blocks the interaction between GRP7 and FLS2 and EFR transcripts in vivo. This inhibition correlates with reduced FLS2 protein levels upon Pseudomonas infection in a HopU1-dependent manner. Our results reveal a novel virulence strategy used by a microbial effector to interfere with host immunity.

HopW1 from Pseudomonas syringae disrupts the actin cytoskeleton to promote virulence in Arabidopsis.

PubMed

Kang, Yongsung; Jelenska, Joanna; Cecchini, Nicolas M; Li, Yujie; Lee, Min Woo; Kovar, David R; Greenberg, Jean T

2014-06-01

A central mechanism of virulence of extracellular bacterial pathogens is the injection into host cells of effector proteins that modify host cellular functions. HopW1 is an effector injected by the type III secretion system that increases the growth of the plant pathogen Pseudomonas syringae on the Columbia accession of Arabidopsis. When delivered by P. syringae into plant cells, HopW1 causes a reduction in the filamentous actin (F-actin) network and the inhibition of endocytosis, a known actin-dependent process. When directly produced in plants, HopW1 forms complexes with actin, disrupts the actin cytoskeleton and inhibits endocytosis as well as the trafficking of certain proteins to vacuoles. The C-terminal region of HopW1 can reduce the length of actin filaments and therefore solubilize F-actin in vitro. Thus, HopW1 acts by disrupting the actin cytoskeleton and the cell biological processes that depend on actin, which in turn are needed for restricting P. syringae growth in Arabidopsis.

Hop Optimization and Relay Node Selection in Multi-hop Wireless Ad-Hoc Networks

NASA Astrophysics Data System (ADS)

Li, Xiaohua(Edward)

In this paper we propose an efficient approach to determine the optimal hops for multi-hop ad hoc wireless networks. Based on the assumption that nodes use successive interference cancellation (SIC) and maximal ratio combining (MRC) to deal with mutual interference and to utilize all the received signal energy, we show that the signal-to-interference-plus-noise ratio (SINR) of a node is determined only by the nodes before it, not the nodes after it, along a packet forwarding path. Based on this observation, we propose an iterative procedure to select the relay nodes and to calculate the path SINR as well as capacity of an arbitrary multi-hop packet forwarding path. The complexity of the algorithm is extremely low, and scaling well with network size. The algorithm is applicable in arbitrarily large networks. Its performance is demonstrated as desirable by simulations. The algorithm can be helpful in analyzing the performance of multi-hop wireless networks.

Odor-Active Compounds in the Special Flavor Hops Huell Melon and Polaris.

PubMed

Neiens, Silva D; Steinhaus, Martin

2018-02-14

The volatiles isolated from samples of the special flavor hop varieties, Huell Melon and Polaris, and from the aroma hop variety, Hallertau Tradition, by solvent extraction and solvent-assisted flavor evaporation (SAFE) were subjected to a comparative aroma extract dilution analysis (cAEDA), which resulted in 46 odor-active compounds in the flavor dilution (FD) factor range of 16 to 2048. On the basis of high FD factors, myrcene, (3R)-linalool, and 2- and 3-methylbutanoic acid were confirmed as important variety-independent hop odorants. (1R,4S)-Calamenene was identified for the first time as an odor-active compound in hops. Clear differences in the FD factors and their subsequent objectification by stable isotope dilution quantitation suggested that high concentrations of the esters ethyl 2-methylbutanoate, ethyl 2-methylpropanoate, and propyl 2-methylbutanoate cause the characteristic fruity, cantaloupe-like odor note in Huell Melon hops, whereas the fruity and minty odor notes in Polaris are associated with high amounts of 3-methylbutyl acetate and 1,8-cineole.

Female PFP patients present alterations in eccentric muscle activity but not the temporal order of activation of the vastus lateralis muscle during the single leg triple hop test.

PubMed

Kalytczak, Marcelo Martins; Lucareli, Paulo Roberto Garcia; Dos Reis, Amir Curcio; Bley, André Serra; Biasotto-Gonzalez, Daniela Aparecida; Correa, João Carlos Ferrari; Politti, Fabiano

2018-04-07

This study aimed to compare the concentric and eccentric activity and the temporal order of peak activity of the hip and knee muscles between women with patellofemoral pain (PFP) and healthy women during the single leg triple hop test (SLTHT). Electromyographic (EMG) and Kinematic data were collected from 14 healthy women (CG) and 14 women diagnosed with PFP (PFG) during a single session of the single leg triple hop test. Integral surface electromyography (iEMG) data of the hip and knee muscles in eccentric and concentric phases and the length of time that each muscle needed to reach the maximal peak of muscle activity were calculated. The iEMG in the eccentric phase was significantly higher (p < 0.05) than the concentric phase, for the gluteus maximus and gluteus medius muscles (CG and PFG) and for the vastus lateralis muscle (PFG). The vastus lateralis muscle was the first muscle to reach the highest peak of activity in the PFG, and the third to reach this peak in the CG. In the present study, the activity of the vastus lateralis muscle during the eccentric phase of the jump was greater than concentric phase, as a temporal anticipation of its peak in activity among women with PFP. Copyright © 2018 Elsevier B.V. All rights reserved.

High-throughput genotyping of hop (Humulus lupulus L.) utilising diversity arrays technology (DArT).

PubMed

Howard, E L; Whittock, S P; Jakše, J; Carling, J; Matthews, P D; Probasco, G; Henning, J A; Darby, P; Cerenak, A; Javornik, B; Kilian, A; Koutoulis, A

2011-05-01

Implementation of molecular methods in hop (Humulus lupulus L.) breeding is dependent on the availability of sizeable numbers of polymorphic markers and a comprehensive understanding of genetic variation. However, use of molecular marker technology is limited due to expense, time inefficiency, laborious methodology and dependence on DNA sequence information. Diversity arrays technology (DArT) is a high-throughput cost-effective method for the discovery of large numbers of quality polymorphic markers without reliance on DNA sequence information. This study is the first to utilise DArT for hop genotyping, identifying 730 polymorphic markers from 92 hop accessions. The marker quality was high and similar to the quality of DArT markers previously generated for other species; although percentage polymorphism and polymorphism information content (PIC) were lower than in previous studies deploying other marker systems in hop. Genetic relationships in hop illustrated by DArT in this study coincide with knowledge generated using alternate methods. Several statistical analyses separated the hop accessions into genetically differentiated North American and European groupings, with hybrids between the two groups clearly distinguishable. Levels of genetic diversity were similar in the North American and European groups, but higher in the hybrid group. The markers produced from this time and cost-efficient genotyping tool will be a valuable resource for numerous applications in hop breeding and genetics studies, such as mapping, marker-assisted selection, genetic identity testing, guidance in the maintenance of genetic diversity and the directed breeding of superior cultivars.

Systematic assessment of scaffold hopping versus activity cliff formation across bioactive compound classes following a molecular hierarchy.

PubMed

Stumpfe, Dagmar; Dimova, Dilyana; Bajorath, Jürgen

2015-07-01

Scaffold hopping and activity cliff formation define opposite ends of the activity landscape feature spectrum. To rationalize these events at the level of scaffolds, active compounds involved in scaffold hopping were required to contain topologically distinct scaffolds but have only limited differences in potency, whereas compounds involved in activity cliffs were required to share the same scaffold but have large differences in potency. A systematic search was carried out for compounds involved in scaffold hopping and/or activity cliff formation. Results obtained for compound data sets covering more than 300 human targets revealed clear trends. If scaffolds represented multiple but fewer than 10 active compounds, nearly 90% of all scaffolds were exclusively involved in hopping events. With increasing compound coverage, the fraction of scaffolds involved in both scaffold hopping and activity cliff formation significantly increased to more than 50%. However, ∼40% of the scaffolds representing large numbers of active compounds continued to be exclusively involved in scaffold hopping. More than 200 scaffolds with broad target coverage were identified that consistently represented potent compounds and yielded an abundance of scaffold hops in the low-nanomolar range. These and other subsets of scaffolds we characterized are of prime interest for structure-activity relationship (SAR) exploration and compound design. Therefore, the complete scaffold classification generated in the course of our analysis is made freely available. Copyright © 2015 Elsevier Ltd. All rights reserved.

Calculation of Water Drop Trajectories to and About Arbitrary Three-Dimensional Bodies in Potential Airflow

NASA Technical Reports Server (NTRS)

Norment, H. G.

1980-01-01

Calculations can be performed for any atmospheric conditions and for all water drop sizes, from the smallest cloud droplet to large raindrops. Any subsonic, external, non-lifting flow can be accommodated; flow into, but not through, inlets also can be simulated. Experimental water drop drag relations are used in the water drop equations of motion and effects of gravity settling are included. Seven codes are described: (1) a code used to debug and plot body surface description data; (2) a code that processes the body surface data to yield the potential flow field; (3) a code that computes flow velocities at arrays of points in space; (4) a code that computes water drop trajectories from an array of points in space; (5) a code that computes water drop trajectories and fluxes to arbitrary target points; (6) a code that computes water drop trajectories tangent to the body; and (7) a code that produces stereo pair plots which include both the body and trajectories. Code descriptions include operating instructions, card inputs and printouts for example problems, and listing of the FORTRAN codes. Accuracy of the calculations is discussed, and trajectory calculation results are compared with prior calculations and with experimental data.

Hop acid-rich spent craft brewer's yeast modulates gut bacterial growth

USDA-ARS?s Scientific Manuscript database

Alpha and beta hop acids (humulones and lupulones) from Humulus lupulus are inhibitors of Gram-positive organisms and important natural antibiotics for beer fermentation and carbohydrate feed stocks for biofuel production. Recent observations (Bryant and Cohen) of high levels of hop acids in spent ...

HopBase: A unified resource for Humulus genomics

USDA-ARS?s Scientific Manuscript database

Hop (Humulus lupulus L. var lupulus) is a plant of worldwide significance, used primarily for its’ bittering and flavoring in brewing beer. Studies on the medicinal properties of several unique compounds produced by hop has led to additional interest from pharmacy and healthcare industries as well a...

Investigating Cultural Collision: Educators' Perceptions of Hip-Hop Culture

ERIC Educational Resources Information Center

Beachum, Floyd D.

2013-01-01

Hip-hop music has been embraced worldwide by youth, pummeled in the media for supposedly increasing social misery and hailed as a significant musical breakthrough. Hip-hop culture has transcended musical boundaries and now impacts speech, clothing, mannerisms, movies, websites, television programming, magazines, and energy drinks (Dyson, 2007;…

Optimum Detection Of Slow-Frequency-Hopping Signals

NASA Technical Reports Server (NTRS)

Levitt, Barry K.; Cheng, Unjeng

1994-01-01

Two papers present theoretical analyses of various schemes for coherent and noncoherent detection of M-ary-frequency-shift-keyed (MFSK) signals with slow frequency hopping. Special attention focused on continuous-phase-modulation (CPM) subset of SFH/MFSK signals, for which frequency modulation such carrier phase remains continuous (albeit unknown) during each hop.

Toward Hip-Hop Pedagogies for Music Education

ERIC Educational Resources Information Center

Kruse, Adam J.

2016-01-01

Music education scholarship in the areas of popular, vernacular, and participatory musicianship has grown in the past decades; however, music education research concerned specifically with hip-hop has been relatively scarce. Because hip-hop music can differ tremendously from the traditional western genres with which many music educators are most…

21 CFR 172.560 - Modified hop extract.

Code of Federal Regulations, 2010 CFR

2010-04-01

... manufactured by one of the following processes: (1) The additive is manufactured from a hexane extract of hops... solids is made up in approximately 0.012 n alkaline methyl alcohol (6 milliliters of 1 n sodium hydroxide... hops by a sequence of extractions and fractionations, using methylene chloride, hexane, and methyl...

21 CFR 172.560 - Modified hop extract.

Code of Federal Regulations, 2013 CFR

2013-04-01

... manufactured by one of the following processes: (1) The additive is manufactured from a hexane extract of hops... solids is made up in approximately 0.012 n alkaline methyl alcohol (6 milliliters of 1 n sodium hydroxide... hops by a sequence of extractions and fractionations, using methylene chloride, hexane, and methyl...

21 CFR 172.560 - Modified hop extract.

Code of Federal Regulations, 2012 CFR

2012-04-01

... manufactured by one of the following processes: (1) The additive is manufactured from a hexane extract of hops... solids is made up in approximately 0.012 n alkaline methyl alcohol (6 milliliters of 1 n sodium hydroxide... hops by a sequence of extractions and fractionations, using methylene chloride, hexane, and methyl...

21 CFR 172.560 - Modified hop extract.

Code of Federal Regulations, 2011 CFR

2011-04-01

... manufactured by one of the following processes: (1) The additive is manufactured from a hexane extract of hops... solids is made up in approximately 0.012 n alkaline methyl alcohol (6 milliliters of 1 n sodium hydroxide... hops by a sequence of extractions and fractionations, using methylene chloride, hexane, and methyl...

Framing and Reviewing Hip-Hop Educational Research

ERIC Educational Resources Information Center

Petchauer, Emery

2009-01-01

Hip-hop has become relevant to the field of education because of its implications for understanding language, learning, identity, curriculum, and other areas. This integrative review provides historical context and cohesion for the burgeoning and discursive body of hip-hop scholarship by framing it according to three heuristic categories and…

Hip-Hop Education Resources

ERIC Educational Resources Information Center

Hall, Marcella Runell

2009-01-01

Hip-hop music and culture are often cited as being public pedagogy, meaning the music itself has intrinsic educational value. Non-profit organizations and individual educators have graciously taken the lead in utilizing hip-hop to educate. As the academy continues to debate its effectiveness, teachers and community organizers are moving forward.…

The frequency hopping pattern design for random hopping frequency signal based on stationary phase principle

NASA Astrophysics Data System (ADS)

Liao, Zhikun; Lu, Dawei; Hu, Jiemin; Zhang, Jun

2018-04-01

For the random hopping frequency signal, the modulated frequencies are randomly distributed over given bandwidth. The randomness of modulated frequency not only improves the electronic counter countermeasure capability for radar systems, but also determines its performance of range compression. In this paper, the range ambiguity function of RHF signal is firstly derived. Then, a design method of frequency hopping pattern based on stationary phase principle to improve the peak to side-lobe ratio is proposed. Finally, the simulated experiments show a good effectiveness of the presented design method.

Crossing the dividing surface of transition state theory. IV. Dynamical regularity and dimensionality reduction as key features of reactive trajectories

NASA Astrophysics Data System (ADS)

Lorquet, J. C.

2017-04-01

The atom-diatom interaction is studied by classical mechanics using Jacobi coordinates (R, r, θ). Reactivity criteria that go beyond the simple requirement of transition state theory (i.e., PR* > 0) are derived in terms of specific initial conditions. Trajectories that exactly fulfill these conditions cross the conventional dividing surface used in transition state theory (i.e., the plane in configuration space passing through a saddle point of the potential energy surface and perpendicular to the reaction coordinate) only once. Furthermore, they are observed to be strikingly similar and to form a tightly packed bundle of perfectly collimated trajectories in the two-dimensional (R, r) configuration space, although their angular motion is highly specific for each one. Particular attention is paid to symmetrical transition states (i.e., either collinear or T-shaped with C2v symmetry) for which decoupling between angular and radial coordinates is observed, as a result of selection rules that reduce to zero Coriolis couplings between modes that belong to different irreducible representations. Liapunov exponents are equal to zero and Hamilton's characteristic function is planar in that part of configuration space that is visited by reactive trajectories. Detailed consideration is given to the concept of average reactive trajectory, which starts right from the saddle point and which is shown to be free of curvature-induced Coriolis coupling. The reaction path Hamiltonian model, together with a symmetry-based separation of the angular degree of freedom, provides an appropriate framework that leads to the formulation of an effective two-dimensional Hamiltonian. The success of the adiabatic approximation in this model is due to the symmetry of the transition state, not to a separation of time scales. Adjacent trajectories, i.e., those that do not exactly fulfill the reactivity conditions have similar characteristics, but the quality of the approximation is lower. At higher energies, these characteristics persist, but to a lesser degree. Recrossings of the dividing surface then become much more frequent and the phase space volumes of initial conditions that generate recrossing-free trajectories decrease. Altogether, one ends up with an additional illustration of the concept of reactive cylinder (or conduit) in phase space that reactive trajectories must follow. Reactivity is associated with dynamical regularity and dimensionality reduction, whatever the shape of the potential energy surface, no matter how strong its anharmonicity, and whatever the curvature of its reaction path. Both simplifying features persist during the entire reactive process, up to complete separation of fragments. The ergodicity assumption commonly assumed in statistical theories is inappropriate for reactive trajectories.

Gold Binding by Native and Chemically Modified Hops Biomasses

DOE PAGES

López, M. Laura; Gardea-Torresdey, J. L.; Peralta-Videa, J. R.; ...

2005-01-01

Heavy metals from mining, smelting operations and other industrial processing facilities pollute wastewaters worldwide. Extraction of metals from industrial effluents has been widely studied due to the economic advantages and the relative ease of technical implementation. Consequently, the search for new and improved methodologies for the recovery of gold has increased. In this particular research, the use of cone hops biomass ( Humulus lupulus ) was investigated as a new option for gold recovery. The results showed that the gold binding to native hops biomass was pH dependent from pH 2 to pH 6, with a maximum percentage binding atmore » pH 3. Time dependency studies demonstrated that Au(III) binding to native and modified cone hops biomasses was found to be time independent at pH 2 while at pH 5, it was time dependent. Capacity experiments demonstrated that at pH 2, esterified hops biomass bound 33.4 mg Au/g of biomass, while native and hydrolyzed hops biomasses bound 28.2 and 12.0 mg Au/g of biomass, respectively. However, at pH 5 the binding capacities were 38.9, 37.8 and 11.4 mg of Au per gram of native, esterified and hydrolyzed hops biomasses, respectively.« less

Sequence analyses reveal that a TPR–DP module, surrounded by recombinable flanking introns, could be at the origin of eukaryotic Hop and Hip TPR–DP domains and prokaryotic GerD proteins

PubMed Central

Papandreou, Nikolaos; Chomilier, Jacques

2008-01-01

The co-chaperone Hop [heat shock protein (HSP) organising protein] is known to bind both Hsp70 and Hsp90. Hop comprises three repeats of a tetratricopeptide repeat (TPR) domain, each consisting of three TPR motifs. The first and last TPR domains are followed by a domain containing several dipeptide (DP) repeats called the DP domain. These analyses suggest that the hop genes result from successive recombination events of an ancestral TPR–DP module. From a hydrophobic cluster analysis of homologous Hop protein sequences derived from gene families, we can postulate that shifts in the open reading frames are at the origin of the present sequences. Moreover, these shifts can be related to the presence or absence of biological function. We propose to extend the family of Hop co-chaperons into the kingdom of bacteria, as several structurally related genes have been identified by hydrophobic cluster analysis. We also provide evidence of common structural characteristics between hop and hip genes, suggesting a shared precursor of ancestral TPR–DP domains. Electronic supplementary material The online version of this article (doi:10.1007/s12192-008-0083-8) contains supplementary material, which is available to authorized users. PMID:18987995

Extreme Kinematics in Selected Hip Hop Dance Sequences.

PubMed

Bronner, Shaw; Ojofeitimi, Sheyi; Woo, Helen

2015-09-01

Hip hop dance has many styles including breakdance (breaking), house, popping and locking, funk, streetdance, krumping, Memphis jookin', and voguing. These movements combine the complexity of dance choreography with the challenges of gymnastics and acrobatic movements. Despite high injury rates in hip hop dance, particularly in breakdance, to date there are no published biomechanical studies in this population. The purpose of this study was to compare representative hip hop steps found in breakdance (toprock and breaking) and house and provide descriptive statistics of the angular displacements that occurred in these sequences. Six expert female hip hop dancers performed three choreographed dance sequences, top rock, breaking, and house, to standardized music-based tempos. Hip, knee, and ankle kinematics were collected during sequences that were 18 to 30 sec long. Hip, knee, and ankle three-dimensional peak joint angles were compared in repeated measures ANOVAs with post hoc tests where appropriate (p<0.01). Peak angles of the breaking sequence, which included floorwork, exceeded the other two sequences in the majority of planes and joints. Hip hop maximal joint angles exceeded reported activities of daily living and high injury sports such as gymnastics. Hip hop dancers work at weight-bearing joint end ranges where muscles are at a functional disadvantage. These results may explain why lower extremity injury rates are high in this population.

Technical strategy of triple jump: differences of inverted pendulum model between hop-dominated and balance techniques.

PubMed

Fujibayashi, Nobuaki; Otsuka, Mitsuo; Yoshioka, Shinsuke; Isaka, Tadao

2017-10-24

The present study aims to cross-sectionally clarify the characteristics of the motions of an inverted pendulum model, a stance leg, a swing leg and arms in different triple-jumping techniques to understand whether or not hop displacement is relatively longer rather than step and jump displacements. Eighteen male athletes performed the triple jump with a full run-up. Based on the technique of the jumpers, they were classified as hop-dominated (n = 10) or balance (n = 8) jumpers. The kinematic data were calculated using motion capture and compared between the two techniques using the inverted pendulum model. The hop-dominated jumpers had a significantly longer hop displacement and faster vertical centre-of-mass (COM) velocity of their whole body at hop take-off, which was generated by faster rotation behaviours of inverted pendulum model and faster swinging behaviours of arms. Conversely, balance jumpers had a significantly longer jump displacement and faster horizontal COM velocity of their whole body at take-off, which was generated by a stiffer inverted pendulum model and stance leg. The results demonstrate that hop-dominated and balance jumpers enhanced each dominated-jump displacement using different swing- and stance-leg motions. This information may help to enhance the actual displacement of triple jumpers using different jumping techniques.

Effects of dietary hop (Humulus lupulus L.) β-acids on quality attributes, composition and oxidative stability of pork meat.

PubMed

Sbardella, Maicon; Racanicci, Aline Mc; Gois, Franz D; de Lima, Cristiane B; Migotto, Dannielle L; Costa, Leandro B; Miyada, Valdomiro S

2018-04-01

The effects of dietary levels of hop β-acids on physical attributes, lipid oxidation and chemical composition of pork meat were evaluated. Thirty-two castrated male pigs obtained from a complete block design feeding experiment (6.23 ± 0.42 kg initial body weight (BW) to 20.45 ± 0.95 kg final BW) and fed diets supplemented with 0, 120, 240 or 360 mg kg -1 hop β-acids during 35 days were slaughtered to sample longissimus dorsi muscle for meat analysis. No effects (P > 0.05) of dietary hop β-acids were observed on meat physical attributes. Quadratic effects (P < 0.05) of hop β-acids were observed on lipid and protein contents and on thiobarbituric acid-reactive substance (TBARS) values of meatballs, whose equations allowed the estimation of dietary hop β-acid levels of 176, 169 and 181 mg kg -1 to provide up to 16.20% lipid reduction, 1.95% protein accretion and 23.31% TBARS reduction respectively. Dietary hop β-acids fed to pigs might reduce lipid, increase protein and reduce lipid oxidation without affecting physical attributes of the pork meat. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Condom Use and Hip Hop Culture: The Case of Urban Young Men in New York City

PubMed Central

Muñoz-Laboy, Miguel A.; Castellanos, Daniel H.; Haliburton, Chanel S.; del Aguila, Ernesto Vasquez; Weinstein, Hannah J.; Parker, Richard G.

2008-01-01

Objectives. We explored how young men’s perceptions of and participation in hip hop culture—urban social and artistic expressions, such as clothing style, breakdancing, graffiti, and rap music—and how contextual factors of the hip hop scene may be associated with their condom use, condom-use self-efficacy, and sense of community. Methods. We conducted a cross-sectional survey of 95 African American and Latino men aged 15 to 25 years as part of a 4-year ethnographic study in New York City. Results. Differences in young men’s perceptions of and levels of affiliation with hip hop culture were not statistically associated with differences in their sense of community or condom-use self-efficacy. Frequency of participation in the hip hop nightclub scene was the strongest factor negatively associated with condom use. Conclusions. Popular discourses on young men’s health risks often blame youths’ cultures such as the hip hop culture for increased risk practices but do not critically examine how risk emerges in urban young men’s lives and what aspects of youths’ culture can be protective. Further research needs to focus on contextual factors of risk such as the role of hip hop nightlife on increased HIV risk. PMID:18445799

The Hip-Hop club scene: Gender, grinding and sex.

PubMed

Muñoz-Laboy, Miguel; Weinstein, Hannah; Parker, Richard

2007-01-01

Hip-Hop culture is a key social medium through which many young men and women from communities of colour in the USA construct their gender. In this study, we focused on the Hip-Hop club scene in New York City with the intention of unpacking narratives of gender dynamics from the perspective of young men and women, and how these relate to their sexual experiences. We conducted a three-year ethnographic study that included ethnographic observations of Hip-Hop clubs and their social scene, and in-depth interviews with young men and young women aged 15-21. This paper describes how young people negotiate gender relations on the dance floor of Hip-Hop clubs. The Hip-Hop club scene represents a context or setting where young men's masculinities are contested by the social environment, where women challenge hypermasculine privilege and where young people can set the stage for what happens next in their sexual and emotional interactions. Hip-Hop culture therefore provides a window into the gender and sexual scripts of many urban minority youth. A fuller understanding of these patterns can offer key insights into the social construction of sexual risk, as well as the possibilities for sexual health promotion, among young people in urban minority populations.

Crossing the dividing surface of transition state theory. III. Once and only once. Selecting reactive trajectories

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

Lorquet, J. C., E-mail: jc.lorquet@ulg.ac.be

2015-09-14

The purpose of the present work is to determine initial conditions that generate reacting, recrossing-free trajectories that cross the conventional dividing surface of transition state theory (i.e., the plane in configuration space passing through a saddle point of the potential energy surface and perpendicular to the reaction coordinate) without ever returning to it. Local analytical equations of motion valid in the neighborhood of this planar surface have been derived as an expansion in Poisson brackets. We show that the mere presence of a saddle point implies that reactivity criteria can be quite simply formulated in terms of elements of thismore » series, irrespective of the shape of the potential energy function. Some of these elements are demonstrated to be equal to a sum of squares and thus to be necessarily positive, which has a profound impact on the dynamics. The method is then applied to a three-dimensional model describing an atom-diatom interaction. A particular relation between initial conditions is shown to generate a bundle of reactive trajectories that form reactive cylinders (or conduits) in phase space. This relation considerably reduces the phase space volume of initial conditions that generate recrossing-free trajectories. Loci in phase space of reactive initial conditions are presented. Reactivity is influenced by symmetry, as shown by a comparative study of collinear and bent transition states. Finally, it is argued that the rules that have been derived to generate reactive trajectories in classical mechanics are also useful to build up a reactive wave packet.« less

Rapidly accelerating Mathieu and Weber surface plasmon beams.

PubMed

Libster-Hershko, Ana; Epstein, Itai; Arie, Ady

2014-09-19

We report the generation of two types of self-accelerating surface plasmon beams which are solutions of the nonparaxial Helmholtz equation in two dimensions. These beams preserve their shape while propagating along either elliptic (Mathieu beam) or parabolic (Weber beam) trajectories. We show that owing to the nonparaxial nature of the Weber beam, it maintains its shape over a much larger distance along the parabolic trajectory, with respect to the corresponding solution of the paraxial equation-the Airy beam. Dynamic control of the trajectory is realized by translating the position of the illuminating free-space beam. Finally, the ability of these beams to self-heal after blocking obstacles is demonstrated as well.

A Multicomponent UV Analysis of ["alpha"]- and ["beta"]-Acids in Hops

ERIC Educational Resources Information Center

Egts, Haley; Durben, Dan J.; Dixson, John A.; Zehfus, Micheal H.

2012-01-01

A method is presented for the determination of ["alpha"]- and ["beta"]-acids (humulones and lupulones) in a hops sample using a multicomponent UV spectroscopic analysis of a methanolic hop extract. When compared with standard methods, this lab can be considered "greener" because it uses smaller volumes of safer solvents (methanol instead of…

Development of biological control of Tetranychus urticae (Acari:Tetranychidae) and Phorodon humuli (Hemiptera: Aphididae) in Oregon Hop yards

USDA-ARS?s Scientific Manuscript database

The temporal development of biological control of arthropod pests in perennial cropping systems is largely unreported. In this study, the development of biological control of twospotted spider mite, Tetranychus urticae Koch and hop aphid, Phorodon humuli (Schrank) in a new planting of hop in Oregon...

Hip-Hop and a Hybrid Text in a Postsecondary English Class

ERIC Educational Resources Information Center

Sanchez, Deborah M.

2010-01-01

This study explores the epistemology present in hip-hop music and its reflection in the writing of one African American student in a postsecondary transitional English class. An integration of hip-hop and academic literacy practices in the student's essay challenges the supremacy of a "standard" academic English and deficit perspectives about…

QTL analysis of resistance to powdery mildew in Hop (Humulus lupulus L.)

USDA-ARS?s Scientific Manuscript database

Powdery mildew infection of hop results in significant production losses on an annual basis by reducing yields as well as cone quality. One of the best means to increase yield and quality is the production of resistant hop lines. Breeding for resistance can be significantly improved and accelerate...

Hip-Hop, Social Justice, and Environmental Education: Toward a Critical Ecological Literacy

ERIC Educational Resources Information Center

Cermak, Michael J.

2012-01-01

This essay describes an educational initiative that used environmentally themed (green) hip-hop to stimulate learning in an environmental science classroom. Students were then challenged to compose their own green hip-hop and their lyrics demonstrated skills that have thematic consistency around what is called a Critical Ecological Literacy (CEL).…

Teaching Controversal Topics in Contemporary German Culture through Hip-Hop

ERIC Educational Resources Information Center

Putnam, Michael

2006-01-01

This article discusses the rich cultural resources embedded with German hip-hop music and its potential impact on the foreign language classroom. In particular, this article suggests methods and materials for integrating German hip-hop music in the discussion of recent controversial cultural events and attitudes in German after the "Wende."

Being Hipped to Their Hop: Tapping into Young Minds through Hip Hop Play

ERIC Educational Resources Information Center

Broughton, Anthony

2017-01-01

Adults gain a wealth of knowledge from listening to the voices of children through intentional observations and interactions [Owocki, G., and Y. M. Goodman. 2002. "Kidwatching: Documenting Children's Literacy Development." Portsmouth: Heinemann]. Hip Hop play may provide optimal opportunities for teachers to tap into the young minds of…

75 FR 59260 - HOP Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-27

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER10-2658-000] HOP Energy, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for Blanket Section... of HOP Energy, LLC's application for market-based rate authority, with an accompanying rate tariff...

Framing Hip Hop: New Methodologies for New Times

ERIC Educational Resources Information Center

Dimitriadis, Greg

2015-01-01

This article revisits the central impulse behind early advocacy for ethnographic approaches to hip hop--that critics should try as much as possible to limit their own certainties around what hip hop can and might mean. While ethnographic approaches can engender the kinds of personal dislocations that allow for this negotiation, they do not…

Student Perceptions of the Hip Hop Culture's Influence on the Undergraduate Experience

ERIC Educational Resources Information Center

Wessel, Roger D.; Wallaert, Kerry A.

2011-01-01

This study sought to determine how identification and engagement with the hip hop culture influenced the educational experiences of undergraduate students at a Midwestern, predominately White university by interviewing 11 students who self-identified as being immersed in the hip hop culture. Through a qualitative, phenomenological investigation,…

Hip Hop Is Now: An Evolving Youth Culture

ERIC Educational Resources Information Center

Taylor, Carl; Taylor, Virgil

2007-01-01

Emerging from Rap music, Hip Hop has become a lifestyle to many modern youth around the world. Embodying both creativity and controversy, Hip Hop mirrors the values, violence, and hypocrisy of modern culture. The authors dispel some of the simplistic views that surround this evolving youth movement embraced by millions of young people who are…

Affiliation and Alienation: Hip-Hop, Rap, and Urban Science Education

ERIC Educational Resources Information Center

Emdin, Christopher

2010-01-01

The critiques of rap artists and other participants in hip-hop culture provide data for teachers and researchers to investigate the attitudes of US urban youth towards schooling. This study explores the complex relationships between hip-hop and science education by examining how rap lyrics project beliefs about schooling, the relevance of existing…

Factors of Intensification in the Hops Cluster of Chuvashia

ERIC Educational Resources Information Center

Zakharov, Anatoly I.; Evgrafov, Oleg V.; Zakharov, Dmitry A.; Ivanova, Elena V.; Tolstova, Marija L.; Tsaregorodtsev, Evgeny I.

2016-01-01

The complex analysis of development of hop-growing for 1971-2015 is carried out. In the conditions of the field experiment made in the Chuvash Republic hop-growing intensification elements--technology of its cultivation, mechanization are fulfilled. Based on researches it is established that the main internal allowance of increase in efficiency of…

Exact Open Quantum System Dynamics Using the Hierarchy of Pure States (HOPS).

PubMed

Hartmann, Richard; Strunz, Walter T

2017-12-12

We show that the general and numerically exact Hierarchy of Pure States method (HOPS) is very well applicable to calculate the reduced dynamics of an open quantum system. In particular, we focus on environments with a sub-Ohmic spectral density (SD) resulting in an algebraic decay of the bath correlation function (BCF). The universal applicability of HOPS, reaching from weak to strong coupling for zero and nonzero temperature, is demonstrated by solving the spin-boson model for which we find perfect agreement with other methods, each one suitable for a special regime of parameters. The challenges arising in the strong coupling regime are not only reflected in the computational effort needed for the HOPS method to converge but also in the necessity for an importance sampling mechanism, accounted for by the nonlinear variant of HOPS. In order to include nonzero-temperature effects in the strong coupling regime we found that it is highly favorable for the HOPS method to use the zero-temperature BCF and include temperature via a stochastic Hermitian contribution to the system Hamiltonian.

Results of Computing Amplitude and Phase of the VLF Wave Using Wave Hop Theory

NASA Astrophysics Data System (ADS)

Pal, Sujay; Basak, Tamal; Chakrabarti, Sandip K.

2011-07-01

We present the basics of the wave hop theory to compute the amplitude and phase of the VLF signals. We use the Indian Navy VTX transmitter at 18.2 kHz as an example of the source and compute the VLF propagation characteristics for several propagation paths using the wave-hop theory. We find the signal amplitudes as a function of distance from the transmitter using wave hop theory in different bearing angles and compare with the same obtained from the Long Wave Propagation Capability (LWPC) code which uses the mode theory. We repeat a similar exercise for the diurnal and seasonal behavior. We note that the signal variation by wave hop theory gives more detailed information in the day time. We further present the spatial variation of the signal amplitude over whole of India at a given time including the effect of sunrise and sunset terminator and also compare the same with that from the mode theory. We point out that the terminator effect is clearly understood in wave hop results than that from the mode theory.

Not letting the left leg know what the right leg is doing: limb-specific locomotor adaptation to sensory-cue conflict.

PubMed

Durgin, Frank H; Fox, Laura F; Hoon Kim, Dong

2003-11-01

We investigated the phenomenon of limb-specific locomotor adaptation in order to adjudicate between sensory-cue-conflict theory and motor-adaptation theory. The results were consistent with cue-conflict theory in demonstrating that two different leg-specific hopping aftereffects are modulated by the presence of conflicting estimates of self-motion from visual and nonvisual sources. Experiment 1 shows that leg-specific increases in forward drift during attempts to hop in place on one leg while blindfolded vary according to the relationship between visual information and motor activity during an adaptation to outdoor forward hopping. Experiment 2 shows that leg-specific changes in performance on a blindfolded hopping-to-target task are similarly modulated by the presence of cue conflict during adaptation to hopping on a treadmill. Experiment 3 shows that leg-specific aftereffects from hopping additionally produce inadvertent turning during running in place while blindfolded. The results of these experiments suggest that these leg-specific locomotor aftereffects are produced by sensory-cue conflict rather than simple motor adaptation.

Why do mammals hop? Understanding the ecology, biomechanics and evolution of bipedal hopping.

PubMed

McGowan, Craig P; Collins, Clint E

2018-06-15

Bipedal hopping is a specialized mode of locomotion that has arisen independently in at least five groups of mammals. We review the evolutionary origins of these groups, examine three of the most prominent hypotheses for why bipedal hopping may have arisen, and discuss how this unique mode of locomotion influences the behavior and ecology of modern species. While all bipedal hoppers share generally similar body plans, differences in underlying musculoskeletal anatomy influence what performance benefits each group may derive from this mode of locomotion. Based on a review of the literature, we conclude that the most likely reason that bipedal hopping evolved is associated with predator avoidance by relatively small species in forested environments. Yet, the morphological specializations associated with this mode of locomotion have facilitated the secondary acquisition of performance characteristics that enable these species to be highly successful in ecologically demanding environments such as deserts. We refute many long-held misunderstandings about the origins of bipedal hopping and identify potential areas of research that would advance the understanding of this mode of locomotion. © 2018. Published by The Company of Biologists Ltd.

Landing mechanics during single hop for distance in females following anterior cruciate ligament reconstruction compared to healthy controls.

PubMed

Trigsted, Stephanie M; Post, Eric G; Bell, David R

2017-05-01

To determine possible differences in single-hop kinematics and kinetics in females with anterior cruciate ligament reconstruction compared to healthy controls. A second purpose was to make comparisons between the healthy and reconstructed limbs. Subjects were grouped based on surgical status (33 ACLR patients and 31 healthy controls). 3D motion capture synchronized with force plates was used to capture the landing phase of three successful trials of single hop for distance during a single data collection session. Peak values during the loading phase were analysed. Subjects additionally completed three successful trials of the triple hop for distance Tegner activity scale and International Knee Document Committee 2000 (IKDC). Controls demonstrated greater peak knee flexion and greater internal knee extension moment and hip extension moment than ACLR subjects. Within the ACLR group, the healthy limb exhibited greater peak knee flexion, hip flexion, hip extension moment, single hop and triple hops for distance and normalized quadriceps strength. Patients who undergo anterior cruciate ligament reconstruction land in a more extended posture when compared to healthy controls and compared to their healthy limb. III.

Automated trajectory planning for multiple-flyby interplanetary missions

NASA Astrophysics Data System (ADS)

Englander, Jacob

Many space mission planning problems may be formulated as hybrid optimal control problems (HOCP), i.e. problems that include both real-valued variables and categorical variables. In interplanetary trajectory design problems the categorical variables will typically specify the sequence of planets at which to perform flybys, and the real-valued variables will represent the launch date, ight times between planets, magnitudes and directions of thrust, flyby altitudes, etc. The contribution of this work is a framework for the autonomous optimization of multiple-flyby interplanetary trajectories. The trajectory design problem is converted into a HOCP with two nested loops: an "outer-loop" that finds the sequence of flybys and an "inner-loop" that optimizes the trajectory for each candidate yby sequence. The problem of choosing a sequence of flybys is posed as an integer programming problem and solved using a genetic algorithm (GA). This is an especially difficult problem to solve because GAs normally operate on a fixed-length set of decision variables. Since in interplanetary trajectory design the number of flyby maneuvers is not known a priori, it was necessary to devise a method of parameterizing the problem such that the GA can evolve a variable-length sequence of flybys. A novel "null gene" transcription was developed to meet this need. Then, for each candidate sequence of flybys, a trajectory must be found that visits each of the flyby targets and arrives at the final destination while optimizing some cost metric, such as minimizing ▵v or maximizing the final mass of the spacecraft. Three different classes of trajectory are described in this work, each of which requireda different physical model and optimization method. The choice of a trajectory model and optimization method is especially challenging because of the nature of the hybrid optimal control problem. Because the trajectory optimization problem is generated in real time by the outer-loop, the inner-loop optimization algorithm cannot require any a priori information and must always return a solution. In addition, the upper and lower bounds on each decision variable cannot be chosen a priori by the user because the user has no way to know what problem will be solved. Instead a method of choosing upper and lower bounds via a set of simple rules was developed and used for all three types of trajectory optimization problem. Many optimization algorithms were tested and discarded until suitable algorithms were found for each type of trajectory. The first class of trajectories use chemical propulsion and may only apply a ▵v at the periapse of each flyby. These Multiple Gravity Assist (MGA) trajectories are optimized using a cooperative algorithm of Differential Evolution (DE) and Particle Swarm Optimization (PSO). The second class of trajectories, known as Multiple Gravity Assist with one Deep Space Maneuver (MGA-DSM), also use chemical propulsion but instead of maneuvering at the periapse of each flyby as in the MGA case a maneuver is applied at a free point along each planet-to-planet arc, i.e. there is one maneuver for each pair of flybys. MGA-DSM trajectories are parameterized by more variables than MGA trajectories, and so the cooperative algorithm of DE and PSO that was used to optimize MGA trajectories was found to be less effective when applied to MGA-DSM. Instead, either PSO or DE alone were found to be more effective. The third class of trajectories addressed in this work are those using continuousthrust propulsion. Continuous-thrust trajectory optimization problems are more challenging than impulsive-thrust problems because the control variables are a continuous time series rather than a small set of parameters and because the spacecraft does not follow a conic section trajectory, leading to a large number of nonlinear constraints that must be satisfied to ensure that the spacecraft obeys the equations of motion. Many models and optimization algorithms were applied including direct transcription with nonlinear programming (DTNLP), the inverse-polynomial shapebased method, and feasible region analysis. However the only physical model and optimization method that proved reliable enough were the Sims-Flanagan transcription coupled with a nonlinear programming solver and the monotonic basin hopping (MBH) global search heuristic. The methods developed here are demonstrated to optimize a set of example trajectories, including a recreation of the Cassini mission, a Galileo-like mission, and conceptual continuous-thrust missions to Jupiter, Mercury, and Uranus.

A multicolour graph as a complete topological invariant for \\Omega-stable flows without periodic trajectories on surfaces

NASA Astrophysics Data System (ADS)

Kruglov, V. E.; Malyshev, D. S.; Pochinka, O. V.

2018-01-01

Studying the dynamics of a flow on surfaces by partitioning the phase space into cells with the same limit behaviour of trajectories within a cell goes back to the classical papers of Andronov, Pontryagin, Leontovich and Maier. The types of cells (the number of which is finite) and how the cells adjoin one another completely determine the topological equivalence class of a flow with finitely many special trajectories. If one trajectory is chosen in every cell of a rough flow without periodic orbits, then the cells are partitioned into so-called triangular regions of the same type. A combinatorial description of such a partition gives rise to the three-colour Oshemkov-Sharko graph, the vertices of which correspond to the triangular regions, and the edges to separatrices connecting them. Oshemkov and Sharko proved that such flows are topologically equivalent if and only if the three-colour graphs of the flows are isomorphic, and described an algorithm of distinguishing three-colour graphs. But their algorithm is not efficient with respect to graph theory. In the present paper, we describe the dynamics of Ω-stable flows without periodic trajectories on surfaces in the language of four-colour graphs, present an efficient algorithm for distinguishing such graphs, and develop a realization of a flow from some abstract graph. Bibliography: 17 titles.

The Huygens Descent Trajectory Working Group and the Reconstruction of the Huygens Probe Entry and Descent Trajectory at Titan

NASA Astrophysics Data System (ADS)

Atkinson, David H.; Kazeminejad, Bobby; Lebreton, Jean-Pierre

2015-04-01

Cassini/Huygens, a flagship mission to explore the rings, atmosphere, magnetic field, and moons that make up the Saturn system, is a joint endeavor of NASA, the European Space Agency, and Agenzia Spaziale Italiana. Comprising two spacecraft - a Saturn orbiter built by NASA and a Titan entry/descent probe built by the European Space Agency - Cassini/Huygens was launched in October 1997 and arrived at Saturn in 2004. The Huygens probe parachuted to the surface of Titan in January 2005. During the descent, six science instruments provided measurements of Titan's atmosphere, clouds, and winds, and photographed Titan's surface. It was recognized early in the Huygens program that to correctly interpret and correlate results from the probe science experiments and to provide a reference set of data for ground truth calibration of the Cassini orbiter remote sensing observations, an accurate reconstruction of the probe entry and descent trajectory and surface landing location would be necessary. The Huygens Descent Trajectory Working Group (DTWG) was chartered in 1996 as a subgroup of the Huygens Science Working Team. With membership comprising representatives from all the probe engineering and instrument teams as well as representatives of industry and the Cassini and Huygens Project Scientists, the DTWG presented an organizational framework within which instrument data was shared, the entry and descent trajectory reconstruction implemented, and the trajectory reconstruction efficiently disseminated. The primary goal of the Descent Trajectory Working Group was to develop retrieval methodologies for the probe descent trajectory reconstruction from the entry interface altitude of 1270 km to the surface using navigation data, and engineering and science data acquired by the instruments on the Huygens Probe, and to provide a reconstruction of the Huygens probe trajectory from entry to the surface of Titan that is maximally consistent with all available engineering and science data sets. The official project entry and descent trajectory reconstruction effort was published by the DTWG in 2007. A revised descent trajectory was released in 2010 that accounts for updated measurements of Titan's pole coordinates derived from radar images of Titan taken during Cassini flybys after 2007. The effect of the updated pole positions on Huygens is a southward shift of the trajectory by about 0.3 degrees with a much smaller effect of less than 0.01 degree in the zonal (west to east) direction. The revised Huygens landing coordinates of 192.335 degrees West and 10.573 degrees South with longitude and latitude residuals of respectively 0.035 degrees and 0.007 degrees, respectively, are in excellent agreement with results of recent landing site investigations using visual and radar images from the Cassini VIMS instrument. Acknowledgements *J.-P.L's work was performed while at ESA/ESTEC. DA and BK would like to express appreciation to the European Space Agency's Research and Scientific Support Department for funding the Descent Trajectory Working Group. The work of the Descent Trajectory Working Group would not have been possible without the dedicated efforts of all the Huygens principal investigators and their teams, and the science and engineering data provided from each experiment team, including M. Fulchignoni and the HASI Team, H. Niemann and the GCMS Team, J. Zarnecki and the SSP Team, M. Tomasko and the DISR Team, M. Bird and the DWE Team, and G. Israel and the ACP Team. Additionally, special thanks for many years of support to D.L. Matson, R.T. Mitchell, M. Pérez-Ayúcar, O. Witasse; J. Jones, D. Roth, N. Strange on the Cassini Navigation Team at JPL; A.-M. Schipper and P. Couzin at Thales Alenia; C. Sollazzo, D. Salt, J. Wheadon and S. Standley from the Huygens Ops Team; and R. Trautner and H. Svedhem on the Radar Team at ESTEC.

Evaluation of Ocean Models Using Observed and Simulated Drifter Trajectories: Impact of Sea Surface Height on Synthetic Profiles for Data Assimilation

DTIC Science & Technology

2007-07-17

in the study of Lumpkin and North Atlantic 0°-80’N 100*-0°W 29 Pazos [2007]. North Brazil Current 00-20ON 70°-40OW 36 [IS] Simulated trajectories are...ShelfRes., 21, 47-67. field. The observed drifter is a sample among many possible Lumpkin, R., and M. Pazos (2007), Measuring surface currents with Sur

Spinal pedicle screw planning using deformable atlas registration

NASA Astrophysics Data System (ADS)

Goerres, J.; Uneri, A.; De Silva, T.; Ketcha, M.; Reaungamornrat, S.; Jacobson, M.; Vogt, S.; Kleinszig, G.; Osgood, G.; Wolinsky, J.-P.; Siewerdsen, J. H.

2017-04-01

Spinal screw placement is a challenging task due to small bone corridors and high risk of neurological or vascular complications, benefiting from precision guidance/navigation and quality assurance (QA). Implicit to both guidance and QA is the definition of a surgical plan—i.e. the desired trajectories and device selection for target vertebrae—conventionally requiring time-consuming manual annotations by a skilled surgeon. We propose automation of such planning by deriving the pedicle trajectory and device selection from a patient’s preoperative CT or MRI. An atlas of vertebrae surfaces was created to provide the underlying basis for automatic planning—in this work, comprising 40 exemplary vertebrae at three levels of the spine (T7, T8, and L3). The atlas was enriched with ideal trajectory annotations for 60 pedicles in total. To define trajectories for a given patient, sparse deformation fields from the atlas surfaces to the input (CT or MR image) are applied on the annotated trajectories. Mean value coordinates are used to interpolate dense deformation fields. The pose of a straight trajectory is optimized by image-based registration to an accumulated volume of the deformed annotations. For evaluation, input deformation fields were created using coherent point drift (CPD) to perform a leave-one-out analysis over the atlas surfaces. CPD registration demonstrated surface error of 0.89  ±  0.10 mm (median  ±  interquartile range) for T7/T8 and 1.29  ±  0.15 mm for L3. At the pedicle center, registered trajectories deviated from the expert reference by 0.56  ±  0.63 mm (T7/T8) and 1.12  ±  0.67 mm (L3). The predicted maximum screw diameter differed by 0.45  ±  0.62 mm (T7/T8), and 1.26  ±  1.19 mm (L3). The automated planning method avoided screw collisions in all cases and demonstrated close agreement overall with expert reference plans, offering a potentially valuable tool in support of surgical guidance and QA.

Spinal pedicle screw planning using deformable atlas registration.

PubMed

Goerres, J; Uneri, A; De Silva, T; Ketcha, M; Reaungamornrat, S; Jacobson, M; Vogt, S; Kleinszig, G; Osgood, G; Wolinsky, J-P; Siewerdsen, J H

2017-04-07

Spinal screw placement is a challenging task due to small bone corridors and high risk of neurological or vascular complications, benefiting from precision guidance/navigation and quality assurance (QA). Implicit to both guidance and QA is the definition of a surgical plan-i.e. the desired trajectories and device selection for target vertebrae-conventionally requiring time-consuming manual annotations by a skilled surgeon. We propose automation of such planning by deriving the pedicle trajectory and device selection from a patient's preoperative CT or MRI. An atlas of vertebrae surfaces was created to provide the underlying basis for automatic planning-in this work, comprising 40 exemplary vertebrae at three levels of the spine (T7, T8, and L3). The atlas was enriched with ideal trajectory annotations for 60 pedicles in total. To define trajectories for a given patient, sparse deformation fields from the atlas surfaces to the input (CT or MR image) are applied on the annotated trajectories. Mean value coordinates are used to interpolate dense deformation fields. The pose of a straight trajectory is optimized by image-based registration to an accumulated volume of the deformed annotations. For evaluation, input deformation fields were created using coherent point drift (CPD) to perform a leave-one-out analysis over the atlas surfaces. CPD registration demonstrated surface error of 0.89  ±  0.10 mm (median  ±  interquartile range) for T7/T8 and 1.29  ±  0.15 mm for L3. At the pedicle center, registered trajectories deviated from the expert reference by 0.56  ±  0.63 mm (T7/T8) and 1.12  ±  0.67 mm (L3). The predicted maximum screw diameter differed by 0.45  ±  0.62 mm (T7/T8), and 1.26  ±  1.19 mm (L3). The automated planning method avoided screw collisions in all cases and demonstrated close agreement overall with expert reference plans, offering a potentially valuable tool in support of surgical guidance and QA.

Hip abduction-adduction strength and one-leg hop tests: test-retest reliability and relationship to function in elite ice hockey players.

PubMed

Kea, J; Kramer, J; Forwell, L; Birmingham, T

2001-08-01

Single group, test-retest. To determine: (1) hip abduction and adduction torques during concentric and eccentric muscle actions, (2) medial and lateral one-leg hop distances, (3) the test-retest reliability of these measurements, and (4) the relationship between isokinetic measures of hip muscle strength and hop distances in elite ice hockey players. The skating motion used in ice hockey requires strong contractions of the hip and knee musculature. However, baseline scores for hip strength and hop distances, their test-retest reliability, and measures of the extent to which these tests are related for this population are not available. The dominant leg of 27 men (mean age 20 +/- 3 yrs) was tested on 2 occasions. Hip abduction and adduction movements were completed at 60 degrees.s(-1) angular velocity, with the subject lying on the non-test side and the test leg moving vertically in the subject's coronal plane. One-leg hops requiring jumping from and landing on the same leg without losing balance were completed in the medial and lateral directions. Hip adduction torques were significantly greater than abduction torques during both concentric and eccentric muscle actions, while no significant difference was observed between medial and lateral hop distances. Although hop test scores produced excellent ICCs (> 0.75) when determined using scores on 1 occasion, torques needed to be averaged over 2 test occasions to reach this level. Correlations between the strength and hop tests ranged from slight to low (r = -0.26 to 0.27) and were characterized by wide 95% confidence intervals (-0.54 to 0.61). Isokinetic tests of hip abduction and adduction did not provide a strong indication of performance during sideways hop tests. Although isokinetic tests can provide a measure of muscular strength under specific test conditions, they should not be relied upon as a primary indicator of functional abilities or readiness to return to activity.

Associations Among Quadriceps Strength and Rate of Torque Development 6 Weeks Post Anterior Cruciate Ligament Reconstruction and Future Hop and Vertical Jump Performance: A Prospective Cohort Study.

PubMed

Pua, Yong-Hao; Mentiplay, Benjamin F; Clark, Ross A; Ho, Jia-Ying

2017-11-01

Study Design Prospective cohort. Background Quadriceps strength is associated with hop distance and jump height in persons who have undergone anterior cruciate ligament (ACL) reconstruction. However, it is unknown whether the ability to rapidly generate quadriceps torque in the early phase of recovery is associated with future hopping and jumping performance in this population. Objective To evaluate the prospective associations among quadriceps strength and rate of torque development (RTD) and single-leg hop for distance, vertical jump height, vertical ground reaction force (vGRF), and vertical force loading rate during a landing task in persons who have undergone ACL reconstruction. Methods Seventy patients with unilateral ACL reconstruction participated. At 6 weeks post ACL reconstruction, isometric quadriceps strength and RTD were measured using a dynamometer. At 6 months following ACL reconstruction, patients performed the single-leg hop for distance test. Patients also performed the single-leg vertical jump test on a force plate that measured maximum jump height, vGRF, and average loading rate during landing. Results Both quadriceps strength and RTD at 6 weeks post ACL reconstruction were associated with all hopping and jumping measures at 6 months post ACL reconstruction (P≤.04). Single-leg hop distance was associated more closely with quadriceps strength than with quadriceps RTD (P = .05), and vertical jump height and vGRF measures were associated more closely with quadriceps RTD than with quadriceps strength (P = .05 and P<.01, respectively). Both quadriceps measures were associated with loading rate. Conclusion Quadriceps strength and RTD are complementary but distinct predictors of future hopping and jumping performance in persons who have undergone ACL reconstruction. These findings may contribute to improved rehabilitation of patients who are at risk for poor jumping/hopping performance and abnormal knee loading. J Orthop Sports Phys Ther 2017;47(11):845-852. Epub 13 Oct 2017. doi:10.2519/jospt.2017.7133.

Transport mechanism of reverse surface leakage current in AlGaN/GaN high-electron mobility transistor with SiN passivation

NASA Astrophysics Data System (ADS)

Zheng, Xue-Feng; Fan, Shuang; Chen, Yong-He; Kang, Di; Zhang, Jian-Kun; Wang, Chong; Mo, Jiang-Hui; Li, Liang; Ma, Xiao-Hua; Zhang, Jin-Cheng; Hao, Yue

2015-02-01

The transport mechanism of reverse surface leakage current in the AlGaN/GaN high-electron mobility transistor (HEMT) becomes one of the most important reliability issues with the downscaling of feature size. In this paper, the research results show that the reverse surface leakage current in AlGaN/GaN HEMT with SiN passivation increases with the enhancement of temperature in the range from 298 K to 423 K. Three possible transport mechanisms are proposed and examined to explain the generation of reverse surface leakage current. By comparing the experimental data with the numerical transport models, it is found that neither Fowler-Nordheim tunneling nor Frenkel-Poole emission can describe the transport of reverse surface leakage current. However, good agreement is found between the experimental data and the two-dimensional variable range hopping (2D-VRH) model. Therefore, it is concluded that the reverse surface leakage current is dominated by the electron hopping through the surface states at the barrier layer. Moreover, the activation energy of surface leakage current is extracted, which is around 0.083 eV. Finally, the SiN passivated HEMT with a high Al composition and a thin AlGaN barrier layer is also studied. It is observed that 2D-VRH still dominates the reverse surface leakage current and the activation energy is around 0.10 eV, which demonstrates that the alteration of the AlGaN barrier layer does not affect the transport mechanism of reverse surface leakage current in this paper. Project supported by the National Natural Science Foundation of China (Grant Nos. 61334002, 61106106, and 61474091), the Opening Project of Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory, China (Grant No. ZHD201206), the New Experiment Development Funds for Xidian University, China (Grant No. SY1213), the 111 Project, China (Grant No. B12026), the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, China, and the Fundamental Research Funds for the Central Universities, China (Grant No. K5051325002).

Spectral properties near the Mott transition in the two-dimensional t-J model with next-nearest-neighbor hopping

NASA Astrophysics Data System (ADS)

Kohno, Masanori

2018-05-01

The single-particle spectral properties of the two-dimensional t-J model with next-nearest-neighbor hopping are investigated near the Mott transition by using cluster perturbation theory. The spectral features are interpreted by considering the effects of the next-nearest-neighbor hopping on the shift of the spectral-weight distribution of the two-dimensional t-J model. Various anomalous features observed in hole-doped and electron-doped high-temperature cuprate superconductors are collectively explained in the two-dimensional t-J model with next-nearest-neighbor hopping near the Mott transition.

Ultrafast hopping dynamics of 5f electrons in the Mott insulator UO₂ studied by femtosecond pump-probe spectroscopy.

PubMed

An, Yong Q; Taylor, Antoinette J; Conradson, Steven D; Trugman, Stuart A; Durakiewicz, Tomasz; Rodriguez, George

2011-05-20

We describe a femtosecond pump-probe study of ultrafast hopping dynamics of 5f electrons in the Mott insulator UO₂ following Mott-gap excitation at temperatures of 5-300 K. Hopping-induced response of the lattice and electrons is probed by transient reflectivity at mid- and above-gap photon energies, respectively. These measurements show an instantaneous hop, subsequent picosecond lattice deformation, followed by acoustic phonon emission and microsecond relaxation. Temperature-dependent studies indicate that the slow relaxation results from Hubbard excitons formed by U³⁺-U⁵⁺ pairs.

No evidence hip joint angle modulates intrinsically produced stretch reflex in human hopping.

PubMed

Gibson, W; Campbell, A; Allison, G

2013-09-01

Motor output in activities such as walking and hopping is suggested to be mediated neurally by purported stretch reflex augmentation of muscle output. Reflex EMG activity during these tasks has been frequently investigated in the soleus muscle; with alterations in reflex amplitude being associated with changes in hip joint angle/phase of the gait cycle. Previous work has focussed on reflex activity induced by an artificial perturbation or by induction of H-reflexes. As such, it is currently unknown if stretch reflex activity induced intrinsically (as part of the task) is modulated by changes in hip joint angle. This study investigated whether hip joint angle modulated reflex EMG 'burst' activity during a hopping task performed on a custom-built partially reclined sleigh. Ten subjects participated; EMG and kinematic data (VICON motor capture system) was collected for each hop cycle. Participants completed 5 sets of 30s of self-paced hopping in (1) hip neutral and (2) hip 60° flexion conditions. There was no difference in EMG 'burst' activity or in sagittal plane kinematics (knee/ankle) in the hopping task between the two conditions. The results indicate that during a functional task such as hopping, changes in hip angle do not alter the stretch reflex-like activity associated with landing. Copyright © 2013 Elsevier B.V. All rights reserved.

Musculoskeletal modelling deconstructs the paradoxical effects of elastic ankle exoskeletons on plantar-flexor mechanics and energetics during hopping

PubMed Central

Farris, Dominic James; Hicks, Jennifer L.; Delp, Scott L.; Sawicki, Gregory S.

2014-01-01

Experiments have shown that elastic ankle exoskeletons can be used to reduce ankle joint and plantar-flexor muscle loading when hopping in place and, in turn, reduce metabolic energy consumption. However, recent experimental work has shown that such exoskeletons cause less favourable soleus (SO) muscle–tendon mechanics than is observed during normal hopping, which might limit the capacity of the exoskeleton to reduce energy consumption. To directly link plantar-flexor mechanics and energy consumption when hopping in exoskeletons, we used a musculoskeletal model of the human leg and a model of muscle energetics in simulations of muscle–tendon dynamics during hopping with and without elastic ankle exoskeletons. Simulations were driven by experimental electromyograms, joint kinematics and exoskeleton torque taken from previously published data. The data were from seven males who hopped at 2.5 Hz with and without elastic ankle exoskeletons. The energetics model showed that the total rate of metabolic energy consumption by ankle muscles was not significantly reduced by an ankle exoskeleton. This was despite large reductions in plantar-flexor force production (40–50%). The lack of larger metabolic reductions with exoskeletons was attributed to increases in plantar-flexor muscle fibre velocities and a shift to less favourable muscle fibre lengths during active force production. This limited the capacity for plantar-flexors to reduce activation and energy consumption when hopping with exoskeleton assistance. PMID:25278469

Photodynamics of oxybenzone sunscreen: Nonadiabatic dynamics simulations.

PubMed

Li, Chun-Xiang; Guo, Wei-Wei; Xie, Bin-Bin; Cui, Ganglong

2016-08-21

Herein we have used combined static electronic structure calculations and "on-the-fly" global-switching trajectory surface-hopping dynamics simulations to explore the photochemical mechanism of oxybenzone sunscreen. We have first employed the multi-configurational CASSCF method to optimize minima, conical intersections, and minimum-energy reaction paths related to excited-state intramolecular proton transfer (ESIPT) and excited-state decays in the (1)ππ(∗), (1)nπ(∗), and S0 states (energies are refined at the higher MS-CASPT2 level). According to the mapped potential energy profiles, we have identified two ultrafast excited-state deactivation pathways for the initially populated (1)ππ(∗) system. The first is the diabatic ESIPT process along the (1)ππ(∗) potential energy profile. The generated (1)ππ(∗) keto species then decays to the S0 state via the keto (1)ππ(∗)/gs conical intersection. The second is internal conversion to the dark (1)nπ(∗) state near the (1)ππ(∗) /(1)nπ(∗) crossing point in the course of the diabatic (1)ππ(∗) ESIPT process. Our following dynamics simulations have shown that the ESIPT and (1)ππ(∗) → S0 internal conversion times are 104 and 286 fs, respectively. Finally, our present work demonstrates that in addition to the ESIPT process and the (1)ππ(∗) → S0 internal conversion in the keto region, the (1)ππ(∗) → (1)nπ(∗) internal conversion in the enol region plays as well an important role for the excited-state relaxation dynamics of oxybenzone.

Photodynamics of oxybenzone sunscreen: Nonadiabatic dynamics simulations

NASA Astrophysics Data System (ADS)

Li, Chun-Xiang; Guo, Wei-Wei; Xie, Bin-Bin; Cui, Ganglong

2016-08-01

Herein we have used combined static electronic structure calculations and "on-the-fly" global-switching trajectory surface-hopping dynamics simulations to explore the photochemical mechanism of oxybenzone sunscreen. We have first employed the multi-configurational CASSCF method to optimize minima, conical intersections, and minimum-energy reaction paths related to excited-state intramolecular proton transfer (ESIPT) and excited-state decays in the 1ππ∗, 1nπ∗, and S0 states (energies are refined at the higher MS-CASPT2 level). According to the mapped potential energy profiles, we have identified two ultrafast excited-state deactivation pathways for the initially populated 1ππ∗ system. The first is the diabatic ESIPT process along the 1ππ∗ potential energy profile. The generated 1ππ∗ keto species then decays to the S0 state via the keto 1ππ∗/gs conical intersection. The second is internal conversion to the dark 1nπ∗ state near the 1ππ∗ /1nπ∗ crossing point in the course of the diabatic 1ππ∗ ESIPT process. Our following dynamics simulations have shown that the ESIPT and 1ππ∗ → S0 internal conversion times are 104 and 286 fs, respectively. Finally, our present work demonstrates that in addition to the ESIPT process and the 1ππ∗ → S0 internal conversion in the keto region, the 1ππ∗ → 1nπ∗ internal conversion in the enol region plays as well an important role for the excited-state relaxation dynamics of oxybenzone.

Computing the Viscosity of Supercooled Liquids: Markov Network Model

PubMed Central

Li, Ju; Kushima, Akihiro; Eapen, Jacob; Lin, Xi; Qian, Xiaofeng; Mauro, John C.; Diep, Phong; Yip, Sidney

2011-01-01

The microscopic origin of glass transition, when liquid viscosity changes continuously by more than ten orders of magnitude, is challenging to explain from first principles. Here we describe the detailed derivation and implementation of a Markovian Network model to calculate the shear viscosity of deeply supercooled liquids based on numerical sampling of an atomistic energy landscape, which sheds some light on this transition. Shear stress relaxation is calculated from a master-equation description in which the system follows a transition-state pathway trajectory of hopping among local energy minima separated by activation barriers, which is in turn sampled by a metadynamics-based algorithm. Quantitative connection is established between the temperature variation of the calculated viscosity and the underlying potential energy and inherent stress landscape, showing a different landscape topography or “terrain” is needed for low-temperature viscosity (of order 107 Pa·s) from that associated with high-temperature viscosity (10−5 Pa·s). Within this range our results clearly indicate the crossover from an essentially Arrhenius scaling behavior at high temperatures to a low-temperature behavior that is clearly super-Arrhenius (fragile) for a Kob-Andersen model of binary liquid. Experimentally the manifestation of this crossover in atomic dynamics continues to raise questions concerning its fundamental origin. In this context this work explicitly demonstrates that a temperature-dependent “terrain” characterizing different parts of the same potential energy surface is sufficient to explain the signature behavior of vitrification, at the same time the notion of a temperature-dependent effective activation barrier is quantified. PMID:21464988

How Does a Hopping Kangaroo Breathe?

ERIC Educational Resources Information Center

Giuliodori, Mauricio J.; Lujan, Heidi L.; Janbaih, Hussein; DiCarlo, Stephen E.

2010-01-01

We developed a model to demonstrate how a hopping kangaroo breathes. Interestingly, a kangaroo uses less energy to breathe while hopping than while standing still. This occurs, in part, because rather than using muscle power to move air into and out of the lungs, air is pulled into (inspiration) and pushed out of (expiration) the lungs as the…

Christian Hip Hop as Pedagogy: A South African Case Study

ERIC Educational Resources Information Center

Abraham, Ibrahim

2015-01-01

Drawing on interviews with creators of Christian hip hop music in South Africa, this article demonstrates that this genre of popular music and youth culture is utilised as a form of pedagogy to transmit religious beliefs and values to contemporary youth. The pedagogical aspects of hip hop have been recognised in research on the topic, but the…

Hip Hop as Empowerment: Voices in El Alto, Bolivia

ERIC Educational Resources Information Center

Tarifa, Ariana

2012-01-01

In response to neoliberal policies that have been in place since 1985, Bolivian young people have increasingly used hip hop music as a means of protest and to reclaim social and political participation. Hip hop in Latin America tells the story of the struggles that marginalized people have suffered, and speaks to the effects of international…

Hegemony, Hope, and the Harlem Renaissance: Taking Hip Hop Culture Seriously

ERIC Educational Resources Information Center

Price, Robert J., Jr.

2005-01-01

Adult education instructors and administrators, who typically are not members of the hip hop generation, often have little knowledge and understanding of rap music (also known as gangsta rap) and hip hop culture, and consequently do not take the black popular cultural phenomenon seriously as it relates to adult education. Adult educators,…

Towards a Pedagogy of Hip Hop in Urban Teacher Education

ERIC Educational Resources Information Center

Bridges, Thurman

2011-01-01

This article draws from a qualitative study often Black male K-12 teachers from the Hip Hop Generation who are closely connected to Hip Hop culture and have been effective in addressing the academic and social needs of Black boys. Through an analysis of their social, educational and cultural experiences, this article highlights three organizing…

We Got Next: Hip-Hop Pedagogy and the Next Generation of Democratic Education

ERIC Educational Resources Information Center

Dando, Michael

2017-01-01

Using daily experiences and existing identities as the subject matter, a hip-hop-centered class encourages students to develop a critical lens so that they can "envision a social order which supports their full humanity" (Shor, 1987, p. 48) and embraces the idea that hip-hop culture provides context for students to develop critical…

Don't Believe the Hype: Hip-Hop Literacies and English Education

ERIC Educational Resources Information Center

Belle, Crystal

2016-01-01

Current scholarship suggests that many youths identify with hip-hop, especially youths of color. Study of this artistic form has been suggested as a means of helping youths acquire and become fluent in literacy practices. This article explores how the use of a hip-hop literacies curriculum addressed the literacy skills of urban ninth-grade English…

Polish Hip Hop as a Form of Multiliteracies and Situated Learning

ERIC Educational Resources Information Center

Torrence, Michael L.

2009-01-01

The purpose of this ethnographic study was to examine Hip Hop in Poland through the lens of multiliteracies and situated learning. This analysis is concerned with the transmission of Hip Hop to and within Wroclaw, Poland, and its acculturation and assimilation in Wroclaw, Poland. Further, this study seeks to illustrate how professional Polish Hip…

78 FR 13346 - Medicare Program; Changes to the Semi-Annual Meeting of the Advisory Panel on Hospital Outpatient...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-27

... (HOP Panel)--March 11 and March 12, 2013 AGENCY: Centers for Medicare & Medicaid Services (CMS), HHS... Program; Semi-Annual Meeting of the Advisory Panel on Hospital Outpatient Payment (HOP Panel)--March 11...-annual meeting of the Advisory Panel on Hospital Outpatient Payment (HOP, the Panel) for 2013. We note...

78 FR 7434 - Medicare Program: Notice of Two Membership Appointments to the Advisory Panel on Hospital...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-01

... Panel on Hospital Outpatient Payment (HOP, the Panel). The two new appointments to the Panel will each... Classification groups and weights. The Advisory Panel on Hospital Outpatient Payment (HOP, the Panel) is governed... members to the Advisory Panel on Hospital Outpatient Payment (HOP, the Panel) to fill two vacancies on the...

Hip-Hop Is the Healer: Sense of Belonging and Diversity among Hip-Hop Collegians

ERIC Educational Resources Information Center

Sulé, V. Thandi

2016-01-01

Sense of belonging is recognized as a factor contributing to persistence to graduation. Furthermore, interactional diversity is associated with learning and civic outcomes--touted higher education goals. Hip-hop culture, one of the most influential cultural creations of the mid-20th century, has succeeded in attracting devotees from diverse…

Hip-Hop Culture in College Students' Lives: Elements, Embodiment, and Higher Edutainment

ERIC Educational Resources Information Center

Petchauer, Emery

2011-01-01

College campuses have become rich sites of hip-hop culture and knowledge production. Despite the attention that campus personnel and researchers have paid to student life, the field of higher education has often misunderstood the ways that hip-hop culture exists in college students' lives. Based upon in-depth interviews, observations of…

Trends in German Hip Hop Music and Its Usefulness for the Classroom

ERIC Educational Resources Information Center

Schmidt, Johannes

2008-01-01

German hip hop music has proved productive, especially since 2000 when rap in Germany experienced something like a first crisis. As a response, German hip hop artists and record labels have ventured off in several different directions including other musical genres, different topics, and new approaches to German rap. This article discusses the…

Representin': Drawing from Hip-Hop and Urban Youth Culture to Inform Teacher Education

ERIC Educational Resources Information Center

Irizarry, Jason G.

2009-01-01

The potential of drawing from urban youth culture, and hip-hop more specifically, to serve as a bridge to the standard curriculum has been well documented. However, the richness and potential benefits of hip-hop are more far-reaching and present significant implications for teacher education and professional development efforts as well. This…

Empowerment in Context: Lessons from Hip-Hop Culture for Social Work Practice

ERIC Educational Resources Information Center

Travis, Raphael, Jr.; Deepak, Anne

2011-01-01

Hip-hop culture can be used as a conduit to enhanced cultural competence and practice skills through the individual and community empowerment framework. This framework is introduced as a tool for direct practice that allows social workers to understand the competing messages within hip-hop culture and how they may impact youths by promoting or…

A shared-care model of obesity treatment for 3-10 year old children: protocol for the HopSCOTCH randomised controlled trial.

PubMed

Wake, Melissa; Lycett, Kate; Sabin, Matthew A; Gunn, Jane; Gibbons, Kay; Hutton, Cathy; McCallum, Zoe; York, Elissa; Stringer, Michael; Wittert, Gary

2012-03-28

Despite record rates of childhood obesity, effective evidence-based treatments remain elusive. While prolonged tertiary specialist clinical input has some individual impact, these services are only available to very few children. Effective treatments that are easily accessible for all overweight and obese children in the community are urgently required. General practitioners are logical care providers for obese children but high-quality trials indicate that, even with substantial training and support, general practitioner care alone will not suffice to improve body mass index (BMI) trajectories. HopSCOTCH (the Shared Care Obesity Trial in Children) will determine whether a shared-care model, in which paediatric obesity specialists co-manage obesity with general practitioners, can improve adiposity in obese children. Randomised controlled trial nested within a cross-sectional BMI survey conducted across 22 general practices in Melbourne, Australia. Children aged 3-10 years identified as obese by Centers for Disease Control criteria at their family practice, and randomised to either a shared-care intervention or usual care. A single multidisciplinary obesity clinic appointment at Melbourne's Royal Children's Hospital, followed by regular appointments with the child's general practitioner over a 12 month period. To support both specialist and general practice consultations, web-based shared-care software was developed to record assessment, set goals and actions, provide information to caregivers, facilitate communication between the two professional groups, and jointly track progress. Primary - change in BMI z-score. Secondary - change in percentage fat and waist circumference; health status, body satisfaction and global self-worth. This will be the first efficacy trial of a general-practitioner based, shared-care model of childhood obesity management. If effective, it could greatly improve access to care for obese children. Australian New Zealand Clinical Trials Registry ACTRN12608000055303.

Investigation of electronic noise in selected mesoscopic devices

NASA Astrophysics Data System (ADS)

Camino, Fernando Enrique

In the last few years, several experiments and theoretical works have confirmed the importance of shot-noise measurements as a source of information about the charge transport in electronic devices, information that is not in all cases accessible from conductance measurements. The use of shot-noise for the direct confirmation of the fractional charge in the fractional quantum Hall effect or the identification of the transport mechanism in negative differential resistance devices are a few examples of its importance. In this thesis, we have performed shot-noise measurements on two semiconductor-based systems in which shot noise is different from the Poissonian value 2eI The first one is a superconductor/semiconductor/superconductor (sp/sm/sp) junction where the superconducting electrodes are 0.5 um apart and the semiconductor bridge between them is composed of a two-dimensional electron gas (2-DEG). The second system is a 2-DEG in the hopping conduction regime. The fabrication of sp/sm/sp junctions is explained in detail in this work as so are the noise measurements of two devices that show enhancement from the Poissonian value. These devices present the signatures of the phenomenon of Andreev reflections and supercurrent at 1.2K; therefore, we tentatively attribute the enhancement to this phenomenon, which has been predicted to give giant noise enhancement for superconducting quantum point contacts (SQPC). On the other hand, in the hoping conduction device, we have observed shot-noise suppression from its classical value, confirming in a different material system a previous experimental result that was explained by percolation theory. In addition, we have driven the system to a region where percolation theory seems to fail, signaling a reconstruction of the hopping trajectories.

Theoretical rate constants of super-exchange hole transfer and thermally induced hopping in DNA.

PubMed

Shimazaki, Tomomi; Asai, Yoshihiro; Yamashita, Koichi

2005-01-27

Recently, the electronic properties of DNA have been extensively studied, because its conductivity is important not only to the study of fundamental biological problems, but also in the development of molecular-sized electronics and biosensors. We have studied theoretically the reorganization energies, the activation energies, the electronic coupling matrix elements, and the rate constants of hole transfer in B-form double-helix DNA in water. To accommodate the effects of DNA nuclear motions, a subset of reaction coordinates for hole transfer was extracted from classical molecular dynamics (MD) trajectories of DNA in water and then used for ab initio quantum chemical calculations of electron coupling constants based on the generalized Mulliken-Hush model. A molecular mechanics (MM) method was used to determine the nuclear Franck-Condon factor. The rate constants for two types of mechanisms of hole transfer-the thermally induced hopping (TIH) and the super-exchange mechanisms-were determined based on Marcus theory. We found that the calculated matrix elements are strongly dependent on the conformations of the nucleobase pairs of hole-transferable DNA and extend over a wide range of values for the "rise" base-step parameter but cluster around a particular value for the "twist" parameter. The calculated activation energies are in good agreement with experimental results. Whereas the rate constant for the TIH mechanism is not dependent on the number of A-T nucleobase pairs that act as a bridge, the rate constant for the super-exchange process rapidly decreases when the length of the bridge increases. These characteristic trends in the calculated rate constants effectively reproduce those in the experimental data of Giese et al. [Nature 2001, 412, 318]. The calculated rate constants were also compared with the experimental results of Lewis et al. [Nature 2000, 406, 51].

Analysis of muscle activity and ankle joint movement during the side-hop test.

PubMed

Yoshida, Masahiro; Taniguchi, Keigo; Katayose, Masaki

2011-08-01

Functional performance tests (FPTs) that consist of movements, such as hopping, landing, and cutting, provide useful measurements. Although some tests have been established for kinematic studies of the knee joint, very few tests have been established for the ankle joint. To use the FPT as a test battery for patients with an ankle sprain, it is necessary to document typical patterns of muscle activation and range of motion (ROM) of the ankle joint during FPTs. Therefore, the purpose of this study was to investigate the pattern of the ROM of the ankle inversion/eversion and the muscle activity of the peroneus longus muscle (PL) and the tibial anterior muscle (TA) in normal subjects during the side-hop test. To emphasize the characteristics of ROM and electromyography (EMG) at each phase, the side-hop tests were divided into 4 phases: lateral-hop contact phase (LC), lateral-hop flight phase (LF), medial hop contact phase (MC), and medial hop flight phase (MF), and the ROM of ankle inversion/eversion, a peak angle of ankle inversion, and Integral EMG (IEMG) of PL and TA compared among 4 phases. Fifteen male subjects with no symptoms of ankle joint problems participated in this research. The ROM of ankle inversion/eversion during the side-hop test was 27 ± 3.8° (mean ± SD), and there was a significant difference in the ROM of ankle inversion/eversion among 4 phases (p < 0.05). The phase in which the widest ROM was presented was the MF. A peak angle of the ankle inversion at MC was significantly greater than at LC and MF (p <0.05). A peak angle of the ankle inversion at LF was significantly greater than at LC and MF. The PL remained contracting with 50-160% of maximal voluntary contraction (MVC). The IEMGs of PL in both the contact phases were significantly greater than in both the flight phases (p < 0.05). In addition, the PL activity at LC was significantly greater than at MC. The TA remained contracting at 50-80% of MVC through the side-hop test. The IEMG of TA at both the contact phases was significantly greater than at 2 flight phases. However, there was no significant difference between LC and MF. Results of this study could be useful as basic data when evaluating the validity of the side-hop test for patients with ankle sprain.

Reliability and validity of functional performance tests in dancers with hip dysfunction.

PubMed

Kivlan, Benjamin R; Carcia, Christopher R; Clemente, F Richard; Phelps, Amy L; Martin, Robroy L

2013-08-01

Quasi-experimental, repeated measures. Functional performance tests that identify hip joint impairments and assess the effect of intervention have not been adequately described for dancers. The purpose of this study was to examine the reliability and validity of hop and balance tests among a group of dancers with musculoskeletal pain in the hip region. NINETEEN FEMALE DANCERS (AGE: 18.90±1.11 years; height: 164.85±6.95 cm; weight: 60.37±8.29 kg) with unilateral hip pain were assessed utilizing the cross-over reach, medial triple hop, lateral triple hop, and cross-over hop tests on two occasions, 2 days apart. Test-retest reliability and comparisons between the involved and uninvolved side for each respective test were determined. Intra-class correlation coefficients for the functional performance tests ranged from 0.89-0.96. The cross-over reach test had a SEM of 2.79 cm and a MDC of 7.73 cm. The medial and lateral triple hop tests had SEM values of 7.51 cm and 8.17 cm, and MDC values of 20.81 cm and 22.62 cm, respectively. The SEM was 0.15 seconds and the MDC was 0.42 seconds for the cross-over hop test. Performance on the medial triple hop test was significantly less on the involved side (370.21±38.26 cm) compared to the uninvolved side (388.05±41.49 cm); t(18) = -4.33, p<0.01. The side-to-side comparisons of the cross-over reach test (involved mean=61.68±10.9 cm; uninvolved mean=61.69±8.63 cm); t(18) = -0.004, p=0.99, lateral triple hop test (involved mean=306.92±35.79 cm; uninvolved mean=310.68±24.49 cm); t(18) = -0.55, p=0.59, and cross-over hop test (involved mean=2.49±0.34 seconds; uninvolved mean= 2.61±0.42 seconds; t(18) = -1.84, p=0.08) were not statistically different between sides. The functional performance tests used in this study can be reliably performed on dancers with unilateral hip pain. The medial triple hop test was the only functional performance test with evidence of validity in side-to-side comparisons. These results suggest that the medial triple hop test may be a reliable and valid functional performance test to assess impairments related to hip pain among dancers. 3b. Non-consecutive cohort study.

RELIABILITY AND VALIDITY OF FUNCTIONAL PERFORMANCE TESTS IN DANCERS WITH HIP DYSFUNCTION

PubMed Central

Carcia, Christopher R.; Clemente, F. Richard; Phelps, Amy L.; Martin, RobRoy L.

2013-01-01

Study Design: Quasi-experimental, repeated measures. Purpose/Background: Functional performance tests that identify hip joint impairments and assess the effect of intervention have not been adequately described for dancers. The purpose of this study was to examine the reliability and validity of hop and balance tests among a group of dancers with musculoskeletal pain in the hip region. Methods: Nineteen female dancers (age: 18.90±1.11 years; height: 164.85±6.95 cm; weight: 60.37±8.29 kg) with unilateral hip pain were assessed utilizing the cross-over reach, medial triple hop, lateral triple hop, and cross-over hop tests on two occasions, 2 days apart. Test-retest reliability and comparisons between the involved and uninvolved side for each respective test were determined. Results: Intra-class correlation coefficients for the functional performance tests ranged from 0.89-0.96. The cross-over reach test had a SEM of 2.79 cm and a MDC of 7.73 cm. The medial and lateral triple hop tests had SEM values of 7.51 cm and 8.17 cm, and MDC values of 20.81 cm and 22.62 cm, respectively. The SEM was 0.15 seconds and the MDC was 0.42 seconds for the cross-over hop test. Performance on the medial triple hop test was significantly less on the involved side (370.21±38.26 cm) compared to the uninvolved side (388.05±41.49 cm); t(18) = −4.33, p<0.01. The side-to-side comparisons of the cross-over reach test (involved mean=61.68±10.9 cm; uninvolved mean=61.69±8.63 cm); t(18) = −0.004, p=0.99, lateral triple hop test (involved mean=306.92±35.79 cm; uninvolved mean=310.68±24.49 cm); t(18) = −0.55, p=0.59, and cross-over hop test (involved mean=2.49±0.34 seconds; uninvolved mean= 2.61±0.42 seconds; t(18) = −1.84, p=0.08) were not statistically different between sides. Conclusion: The functional performance tests used in this study can be reliably performed on dancers with unilateral hip pain. The medial triple hop test was the only functional performance test with evidence of validity in side-to-side comparisons. These results suggest that the medial triple hop test may be a reliable and valid functional performance test to assess impairments related to hip pain among dancers. Level of Evidence: 3b. Non-consecutive cohort study PMID:24175123

Optimal solar sail planetocentric trajectories

NASA Technical Reports Server (NTRS)

Sackett, L. L.

1977-01-01

The analysis of solar sail planetocentric optimal trajectory problem is described. A computer program was produced to calculate optimal trajectories for a limited performance analysis. A square sail model is included and some consideration is given to a heliogyro sail model. Orbit to a subescape point and orbit to orbit transfer are considered. Trajectories about the four inner planets can be calculated and shadowing, oblateness, and solar motion may be included. Equinoctial orbital elements are used to avoid the classical singularities, and the method of averaging is applied to increase computational speed. Solution of the two-point boundary value problem which arises from the application of optimization theory is accomplished with a Newton procedure. Time optimal trajectories are emphasized, but a penalty function has been considered to prevent trajectories which intersect a planet's surface.

Postactivation potentiation can counteract declines in force and power that occur after stretching.

PubMed

Kümmel, J; Kramer, A; Cronin, N J; Gruber, M

2017-12-01

Stretching can decrease a muscle's maximal force, whereas short but intense muscle contractions can increase it. We hypothesized that when combined, postactivation potentiation induced by reactive jumps would counteract stretch-induced decrements in drop jump (DJ) performance. Moreover, we measured changes in muscle twitch forces and ankle joint stiffness (K A nkle ) to examine underlying mechanisms. Twenty subjects completed three DJs and 10 electrically evoked muscle twitches of the triceps surae subsequent to four different conditioning activities and control. The conditioning activities were 10 hops, 20s of static stretching of the triceps surae muscle, 20s of stretching followed by 10 hops, and vice versa. After 10 hops, twitch peak torque (TPT) was 20% and jump height 5% higher compared with control with no differences in K A nkle . After stretching, TPT and jump height were both 9% and K A nkle 6% lower. When hops and stretching were combined as conditioning activities, jump height was not different compared with control but significantly higher (11% and 8%) compared with stretching. TPTs were 16% higher compared with control when the hops were performed after stretching and 9% higher compared with the reverse order. K A nkle was significantly lower when stretching was performed after the hops (6%) compared with control, but no significant difference was observed when hops were performed after stretching. These results demonstrate that conditioning hops can counteract stretch-related declines in DJ performance. Furthermore, the differences in TPTs and K A nkle between combined conditioning protocols indicate that the order of conditioning tasks might play an important role at the muscle-tendon level. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Star Formation Under the Outflow: The Discovery of a Non-thermal Jet from OMC-2 FIR 3 and Its Relationship to the Deeply Embedded FIR 4 Protostar

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

Osorio, Mayra; Díaz-Rodríguez, Ana K.; Anglada, Guillem

We carried out multiwavelength (0.7–5 cm), multi-epoch (1994–2015) Very Large Array (VLA) observations toward the region enclosing the bright far-IR sources FIR 3 (HOPS 370) and FIR 4 (HOPS 108) in OMC-2. We report the detection of 10 radio sources, 7 of them identified as young stellar objects. We image a well-collimated radio jet with a thermal free–free core (VLA 11) associated with the Class I intermediate-mass protostar HOPS 370. The jet features several knots (VLA 12N, 12C, 12S) of non-thermal radio emission (likely synchrotron from shock-accelerated relativistic electrons) at distances of ∼7500–12,500 au from the protostar, in a regionmore » where other shock tracers have been previously identified. These knots are moving away from the HOPS 370 protostar at ∼100 km s{sup −1}. The Class 0 protostar HOPS 108, which itself is detected as an independent, kinematically decoupled radio source, falls in the path of these non-thermal radio knots. These results favor the previously proposed scenario in which the formation of HOPS 108 is triggered by the impact of the HOPS 370 outflow with a dense clump. However, HOPS 108 has a large proper motion velocity of ∼30 km s{sup −1}, similar to that of other runaway stars in Orion, whose origin would be puzzling within this scenario. Alternatively, an apparent proper motion could result because of changes in the position of the centroid of the source due to blending with nearby extended emission, variations in the source shape, and/or opacity effects.« less

Fitting coupled potential energy surfaces for large systems: Method and construction of a 3-state representation for phenol photodissociation in the full 33 internal degrees of freedom using multireference configuration interaction determined data

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

Zhu, Xiaolei, E-mail: virtualzx@gmail.com; Yarkony, David R., E-mail: yarkony@jhu.edu

2014-01-14

A recently reported algorithm for representing adiabatic states coupled by conical intersections using a quasi-diabatic state Hamiltonian in four and five atom systems is extended to treat nonadiabatic processes in considerably larger molecules. The method treats all internal degrees of freedom and uses electronic structure data from ab initio multireference configuration interaction wave functions with nuclear configuration selection based on quasi-classical surface hopping trajectories. The method is shown here to be able to treat ∼30 internal degrees of freedom including dissociative and large amplitude internal motion. Two procedures are introduced which are essential to the algorithm, a null space projectormore » which removes basis functions from the fitting process until they are needed and a partial diagonalization technique which allows for automated, but accurate, treatment of the vicinity of extended seams of conical intersections of two or more states. These procedures are described in detail. The method is illustrated using the photodissociaton of phenol, C{sub 6}H{sub 5}OH(X{sup ~1}A{sup ′}) + hv → C{sub 6}H{sub 5}OH(A{sup ~1}A{sup ′}, B{sup ~1}A{sup ′′}) → C{sub 6}H{sub 5}O(X{sup ~2}B{sub 1}, A{sup ~2}B{sub 2}) + H as a test case. Ab initio electronic structure data for the 1,2,3{sup 1}A states of phenol, which are coupled by conical intersections, are obtained from multireference first order configuration interaction wave functions. The design of bases to simultaneously treat large amplitude motion and dissociation is described, as is the ability of the fitting procedure to smooth the irregularities in the electronic energies attributable to the orbital changes that are inherent to nonadiabatic processes.« less

Avoided crossings: A study of the nonadiabatic transition probabilities

NASA Astrophysics Data System (ADS)

Desouter-Lecomte, M.; Leyh-Nihant, B.; Praet, M. T.; Lorquet, J. C.

1987-06-01

An approximate solution to the problem of constructing a pair of diabatic states exists only if certain requirements are fulfilled, for example, when the nonadiabatic coupling results from an interaction between two electronic configurations which are doubly excited with respect to one another. It is then possible to build up a model in which the series expansion of the elements of the Hamiltonian matrix is truncated after the first nonzero term. This leads to several conclusions concerning the nonadiabatic transition probability which differentiate conical intersections from avoided crossings. For the latter, the nonadiabatic coupling matrix elements (which are Lorentzians with an area equal to π/2) reach their maximum at the nuclear geometry for which ΔE (the energy gap between adiabatic surfaces) is a minimum. The loci along which the angle θ of the orthogonal transformation which relates adiabatic and diabatic wave functions keeps a constant value are a set of parallel straight lines which coincides with the loci along which ΔE remains constant. This reference direction in the configuration space corresponds to nuclear trajectories which are unable to bring about a nonadiabatic transition. In the case of avoided crossings, there exists only one nuclear degree of freedom which gives rise to surface hopping. Conical intersections, on the other hand, have two such active degrees of freedom. This creates a qualitative difference between the two cases which makes conical intersections more efficient as funnels than avoided crossings. A two-dimensional extension of the Landau-Zener formula is derived for avoided crossings. It contains a factor of anisotropy. It is possible, at least in favorable cases, to extract approximate diabatic quantities from ab initio calculations and to compare them with the predictions of these models. This has been done for two 2A1 electronic states of the CH+2 ion. The results are found to agree with the predictions of the model, at least in a restricted range of internuclear distances.

Treating primary insomnia - the efficacy of valerian and hops.

PubMed

Salter, Shanah; Brownie, Sonya

2010-06-01

To evaluate the efficacy of valerian and hops in the treatment of primary insomnia. The AMED and MEDLINE databases were searched for primary sources of literature published between 1950 and 2009, using keywords: herbal medicine, medicinal plants, herbal, Valeriana officinalis, valerian, Humulus lupulus, hops, sleep, insomnia. Studies were included if they evaluated the efficacy of valerian or hops in improving primary insomnia in adults: sixteen studies met the inclusion criteria. Twelve of these found that the use of valerian, on its own, or in combination with hops, is associated with improvements in some sleep parameters (eg. sleep latency and quality of sleep). However, these results need to be interpreted cautiously as there were significant differences in design between the studies. Further randomised, double blind, placebo controlled trials are needed before such herbal treatments can be confidently recommended for the treatment of primary insomnia.

Flexible scheme to truncate the hierarchy of pure states.

PubMed

Zhang, P-P; Bentley, C D B; Eisfeld, A

2018-04-07

The hierarchy of pure states (HOPS) is a wavefunction-based method that can be used for numerically modeling open quantum systems. Formally, HOPS recovers the exact system dynamics for an infinite depth of the hierarchy. However, truncation of the hierarchy is required to numerically implement HOPS. We want to choose a "good" truncation method, where by "good" we mean that it is numerically feasible to check convergence of the results. For the truncation approximation used in previous applications of HOPS, convergence checks are numerically challenging. In this work, we demonstrate the application of the "n-particle approximation" to HOPS. We also introduce a new approximation, which we call the "n-mode approximation." We then explore the convergence of these truncation approximations with respect to the number of equations required in the hierarchy in two exemplary problems: absorption and energy transfer of molecular aggregates.

Flexible scheme to truncate the hierarchy of pure states

NASA Astrophysics Data System (ADS)

Zhang, P.-P.; Bentley, C. D. B.; Eisfeld, A.

2018-04-01

The hierarchy of pure states (HOPS) is a wavefunction-based method that can be used for numerically modeling open quantum systems. Formally, HOPS recovers the exact system dynamics for an infinite depth of the hierarchy. However, truncation of the hierarchy is required to numerically implement HOPS. We want to choose a "good" truncation method, where by "good" we mean that it is numerically feasible to check convergence of the results. For the truncation approximation used in previous applications of HOPS, convergence checks are numerically challenging. In this work, we demonstrate the application of the "n-particle approximation" to HOPS. We also introduce a new approximation, which we call the "n-mode approximation." We then explore the convergence of these truncation approximations with respect to the number of equations required in the hierarchy in two exemplary problems: absorption and energy transfer of molecular aggregates.

Ca + HF - The anatomy of a chemical insertion reaction

NASA Technical Reports Server (NTRS)

Jaffe, R. L.; Pattengill, M. D.; Mascarello, F. G.; Zare, R. N.

1987-01-01

A comprehensive first-principles theoretical investigation of the gas phase reaction Ca + HF - CaF + H is reported. Ab initio potential energy calculations are first discussed, along with characteristics of the computed potential energy surface. Next, the fitting of the computed potential energy points to a suitable analytical functional form is described, and maps of the fitted potential surface are displayed. The methodology and results of a classical trajectory calculation utilizing the fitted potential surface are presented. Finally, the significance of the trajectory study results is discussed, and generalizations concerning dynamical aspects of Ca + HF scattering are drawn.

Entry trajectory and atmosphere reconstruction methodologies for the Mars Exploration Rover mission

NASA Astrophysics Data System (ADS)

Desai, Prasun N.; Blanchard, Robert C.; Powell, Richard W.

2004-02-01

The Mars Exploration Rover (MER) mission will land two landers on the surface of Mars, arriving in January 2004. Both landers will deliver the rovers to the surface by decelerating with the aid of an aeroshell, a supersonic parachute, retro-rockets, and air bags for safely landing on the surface. The reconstruction of the MER descent trajectory and atmosphere profile will be performed for all the phases from hypersonic flight through landing. A description of multiple methodologies for the flight reconstruction is presented from simple parameter identification methods through a statistical Kalman filter approach.

The effect of dust lifting process on the electrical properties of the atmosphere

NASA Astrophysics Data System (ADS)

Esposito, Francesca; Molinaro, Roberto; Ionut Popa, Ciprian; Molfese, Cesare; Cozzolino, Fabio; Marty, Laurent; Taj-Eddine, Kamal; Di Achille, Gaetano; Silvestro, Simone; Ori, Gian Gabriele

2015-04-01

Airborne dust and aerosol particles affect climate by absorbing and scattering thermal and solar radiation and acting as condensation nuclei for the formation of clouds. So, they strongly influence the atmospheric thermal structure, balance and circulation. On Earth and Mars, this 'climate forcing' is one of the most uncertain processes in climate change predictions. Wind-driven blowing of sand and dust is also responsible for shaping planetary surfaces through the formation of sand dunes and ripples, the erosion of rocks, and the creation and transport of soil particles. These processes are not confined to Earth, but occur also on Mars, Venus and Titan. It is clear that the knowledge of the atmospheric dust properties and the mechanisms of dust settling and raising into the atmosphere are important to understand planetary climate and surface evolution. On Mars the physical processes responsible for dust injection into the atmosphere are still poorly understood, but they likely involve saltation as on Earth. Saltation is a process where large sand grains are forced by the wind to move in ballistic trajectories on the soil surface. During these hops they hit dust particles, that are well bound to the soil due to interparticle cohesive forces, thus transferring to them the momentum necessary to be entrained into the atmosphere. Recently, it has been shown that this process is also responsible to generate strong electric fields in the atmosphere up to 100-150 kV/m. This enhanced electric force acts as a feedback in the dust lifting process, lowering the threshold of the wind friction velocity u* necessary to initiate sand saltation. It is an important aspect of dust lifting process that need to be well characterized and modeled. Even if literature reports several measurements of E-fields in dust devils events, very few reports deal with atmospheric electric properties during dust storms or isolated gusts. We present here preliminary results of an intense field test campaign we performed in the West Sahara during the 2013 and 2014 dust storm seasons. We collected a statistical meaningful set of data characterizing relationship between dust lifting and atmospheric E-field that had never been achieved so far.

NEAR-SURFACE AIR PARCEL TRAJECTORIES - ST. LOUIS, 1975

EPA Science Inventory

The utility of air parcel trajectories is described for the diagnosis of mesometeorological and urban air pollution problems. A technique is described that uses the St. Louis Regional Air Monitoring System (RAMS) to provide wind measurements for the local urban scale. A computeri...

Flight Deck Surface Trajectory-Based Operations

NASA Technical Reports Server (NTRS)

Foyle, David C.; Hooey, Becky L.; Bakowski, Deborah L.

2017-01-01

Surface Trajectory-Based Operations (STBO) is a future concept for surface operations where time requirements are incorporated into taxi operations to support surface planning and coordination. Pilot-in-the-loop flight deck simulations have been conducted to study flight deck displays algorithms to aid pilots in complying with the time requirements of time-based taxi operations (i.e., at discrete locations in 3 12 D operations or at all points along the route in 4DT operations). The results of these studies (conformance, time-of-arrival error, eye-tracking data, and safety ratings) are presented. Flight deck simulation work done in collaboration with DLR is described. Flight deck research issues in future auto-taxi operations are also introduced.

Predicting muscle forces during the propulsion phase of single leg triple hop test.

PubMed

Alvim, Felipe Costa; Lucareli, Paulo Roberto Garcia; Menegaldo, Luciano Luporini

2018-01-01

Functional biomechanical tests allow the assessment of musculoskeletal system impairments in a simple way. Muscle force synergies associated with movement can provide additional information for diagnosis. However, such forces cannot be directly measured noninvasively. This study aims to estimate muscle activations and forces exerted during the preparation phase of the single leg triple hop test. Two different approaches were tested: static optimization (SO) and computed muscle control (CMC). As an indirect validation, model-estimated muscle activations were compared with surface electromyography (EMG) of selected hip and thigh muscles. Ten physically healthy active women performed a series of jumps, and ground reaction forces, kinematics and EMG data were recorded. An existing OpenSim model with 92 musculotendon actuators was used to estimate muscle forces. Reflective markers data were processed using the OpenSim Inverse Kinematics tool. Residual Reduction Algorithm (RRA) was applied recursively before running the SO and CMC. For both, the same adjusted kinematics were used as inputs. Both approaches presented similar residuals amplitudes. SO showed a closer agreement between the estimated activations and the EMGs of some muscles. Due to inherent EMG methodological limitations, the superiority of SO in relation to CMC can be only hypothesized. It should be confirmed by conducting further studies comparing joint contact forces. The workflow presented in this study can be used to estimate muscle forces during the preparation phase of the single leg triple hop test and allows investigating muscle activation and coordination. Copyright © 2017 Elsevier B.V. All rights reserved.

Redirected charge transport arising from diazonium grafting of carbon coated LiFePO4.

PubMed

Madec, L; Seid, K A; Badot, J-C; Humbert, B; Moreau, P; Dubrunfaut, O; Lestriez, B; Guyomard, D; Gaubicher, J

2014-11-07

The morphological and the electrical properties of carbon coated LiFePO4 (LFPC) active material functionalized by 4-ethynylbenzene tetrafluoroboratediazonium salt were investigated. For this purpose, FTIR, Raman, XPS, High Resolution Transmission Electron Microscopy (HRTEM) and Broadband Dielectric Spectroscopy (BDS) were considered. Electronic conductivities of LFPC samples at room temperature were found to decrease in a large frequency range upon simple immersion in polar solvents and to decrease further upon functionalization. Due to their high dipole moment, strongly physisorbed molecules detected by XPS likely add barriers to electron hopping. Significant alteration of the carbon coating conductivity was only observed, however, upon functionalization. This effect is most presumably associated with an increase in the sp(3) content determined by Raman spectroscopy, which is a strong indication of the formation of a covalent bond between the organic layer and the carbon coating. In this case, the electron flux appears to be redirected and relayed by short-range (intra chain) and long-range (inter chain) electron transport through molecular oligomers anchored at the LFPC surface. The latter are controlled by tunnelling and slightly activated hopping, which enable higher conductivity at low temperature (T < 250 K). Alteration of the electron transport within the carbon coating also allows detection of a relaxation phenomenon that corresponds to small polaron hopping in bulk LiFePO4. XPS and HRTEM images allow a clear correlation of these findings with the island type oligomeric structure of grafted molecules.

Sista Girl Rock: Women of Colour and Hip-Hop Deejaying as Raced/Gendered Knowledge and Language

ERIC Educational Resources Information Center

Craig, Todd; Kynard, Carmen

2017-01-01

This article seeks to introduce and situate a seldom-explored subject: the role and contribution of women hip-hop deejays in the testosterone-filled genre called hip-hop. Grounding the analysis in the interviews of six women deejays--Spinderella, Kuttin Kandi, Pam the Funkstress, Reborn, Shorty Wop and Natasha Diggs--"Sista Girl Rock"…

Hip-Hop Feminism: A Standpoint to Enhance the Positive Self-Identity of Black College Women

ERIC Educational Resources Information Center

Henry, Wilma J.

2010-01-01

The popularity of hip-hop among young Black college women, coupled with the deluge of negative and positive messages in this culture regarding these women's identity, signals an opportunity for the arrival of a contemporary, culturally relevant epistemology--hip-hop feminism. Through the lens of Black feminist theory, this article explores hip-hop…

I Feel What He Was Doin': Responding to Justice-Oriented Teaching through Hip-Hop Aesthetics

ERIC Educational Resources Information Center

Petchauer, Emery

2011-01-01

This study illustrates a set of learning activities designed from two hip-hop aesthetics and explores their use among a classroom of African American preservice teachers who graduated from urban school districts. Based on the two hip-hop aesthetics of kinetic consumption and autonomy/distance, the specific goal of these learning activities is to…

75 FR 70236 - Hop Beta Acids; Receipt of Application for Emergency Exemption, Solicitation of Public Comment

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-17

... of Agriculture to use hop beta acids (CAS Reg. No. none specified) to treat up to 181,000 honey bee... exemption regional request for use of hop beta acids in honey bee hives to control varroa mites. Information... effect on honey bee populations. The parasitic mite is considered the primary pest of honeybees and its...

"They Wasn't Makin' My Kinda Music": A Hip-Hop Musician's Perspective on School, Schooling, and School Music

ERIC Educational Resources Information Center

Kruse, Adam J.

2016-01-01

This article focuses on a hip-hop perspective of school, schooling, and school music. The study involves applications of ethnographic (including autoethnographic) techniques within the framework of a holistic multiple case study. One case is an adult amateur hip-hop musician named Terrence (pseudonym), and the other is myself (a traditionally…

Hip-Hop, the "Obama Effect," and Urban Science Education

ERIC Educational Resources Information Center

Emdin, Christopher; Lee, Okhee

2012-01-01

Background/Context: With the ever increasing diversity of schools, and the persistent need to develop teaching strategies for the students who attend today's urban schools, hip-hop culture has been proposed to be a means through which urban youth can find success in school. As a result, studies of the role of hip-hop in urban education have grown…

Supporting Communication and Argumentation in Urban Science Education: Hip-Hop, the Battle, and the Cypher

ERIC Educational Resources Information Center

Emdin, Christopher

2011-01-01

This paper is based on an exploration of communication and argumentation in urban science classrooms, and provides a description of the role that Hip-hop based education plays in supporting these major components of science education. The paper is intended to both support, and critique conventional uses of hip-hop based education, and provide…

Sampling Practices and Social Spaces: Exploring a Hip-Hop Approach to Higher Education

ERIC Educational Resources Information Center

Petchauer, Emery

2010-01-01

Much more than a musical genre, hip-hop culture exists as an animating force in the lives of many young adults. This article looks beyond the moral concerns often associated with rap music to explore how hip-hop as a larger set of expressions and practices implicates the educational experiences, activities, and approaches for students. The article…

Hip-Hop's Influence on the Identity Development of Black Female College Students: A Literature Review

ERIC Educational Resources Information Center

Henry, Wilma J.; West, Nicole M.; Jackson, Andrea

2010-01-01

This article explores unique issues regarding the effects of hip-hop culture on the identity development of young Black female college students. Through the lenses of womanist and Black feminist perspectives, the intersecting impact of race and gender are reviewed within the context of the competing influences of hip-hop on Black female identity.…

Being Hip-Hop: Beyond Skills and Songs

ERIC Educational Resources Information Center

Kruse, Adam J.

2016-01-01

In this article, I offer four principles relevant to hip-hop cultures (keep it real, flip the script, make some noise, and stay fresh) and explore how these principles might affect music classrooms. I argue that a music classroom that works to keep it real, flip the script, make some noise, and stay fresh might go beyond teaching hip-hop skills…

Fresh Faces, New Places: Moving beyond Teacher-Researcher Perspectives in Hip-Hop-Based Education Research

ERIC Educational Resources Information Center

Irby, Decoteau J.; Hall, H. Bernard

2011-01-01

Grounded in critical and culturally relevant theory, hip-hop-based education (HHBE) research documents the use of hip-hop in educational settings. Despite the richness of the emerging field, overreliance on teacher-researcher perspectives leaves much to be desired. Little is known of the extent and ways HHBE is used by nonresearching K-12…

"You Don't Have to Claim Her": Reconstructing Black Femininity through Critical Hip-Hop Literacy

ERIC Educational Resources Information Center

Kelly, Lauren Leigh

2016-01-01

This article explores the ways in which females who identify with hip-hop often develop and construct their identities in relation to media representations of blackness and femininity in hip-hop music and culture. In order for educators to support female students in constructing identities of empowerment and agency, they should be willing and able…

Culturally Relevant Teaching: Hip-Hop Pedagogy in Urban Schools. Counterpoints: Studies in the Postmodern Theory of Education. Volume 396

ERIC Educational Resources Information Center

Prier, Darius D.

2012-01-01

"Culturally Relevant Teaching" centers hip-hop culture as a culturally relevant form of critical pedagogy in urban pre-service teacher education programs. In this important book, Darius D. Prier explores how hip-hop artists construct a sense of democratic education and pedagogy with transformative possibilities in their schools and communities. In…

White Privilege? The Intersection of Hip-Hop and Whiteness as a Catalyst for Cross-Racial Interaction among White Males

ERIC Educational Resources Information Center

Sulé, Venice Thandi

2015-01-01

Given the prevalence of racial segregation in the U.S., college is an opportunity to prepare students for diversity through cross-racial interaction. Hip-hop, a culture steeped in black and Latino experiences, has significant white supporters. Through diversity and critical whiteness frameworks, this research considers how white hip-hop collegians…

Design of Compressed Sensing Algorithm for Coal Mine IoT Moving Measurement Data Based on a Multi-Hop Network and Total Variation.

PubMed

Wang, Gang; Zhao, Zhikai; Ning, Yongjie

2018-05-28

As the application of a coal mine Internet of Things (IoT), mobile measurement devices, such as intelligent mine lamps, cause moving measurement data to be increased. How to transmit these large amounts of mobile measurement data effectively has become an urgent problem. This paper presents a compressed sensing algorithm for the large amount of coal mine IoT moving measurement data based on a multi-hop network and total variation. By taking gas data in mobile measurement data as an example, two network models for the transmission of gas data flow, namely single-hop and multi-hop transmission modes, are investigated in depth, and a gas data compressed sensing collection model is built based on a multi-hop network. To utilize the sparse characteristics of gas data, the concept of total variation is introduced and a high-efficiency gas data compression and reconstruction method based on Total Variation Sparsity based on Multi-Hop (TVS-MH) is proposed. According to the simulation results, by using the proposed method, the moving measurement data flow from an underground distributed mobile network can be acquired and transmitted efficiently.

Electrical transport via variable range hopping in an individual multi-wall carbon nanotube

NASA Astrophysics Data System (ADS)

Husain Khan, Zishan; Husain, M.; Perng, T. P.; Salah, Numan; Habib, Sami

2008-11-01

E-beam lithography is used to make four leads on an individual multi-wall carbon nanotube for carrying out electrical transport measurements. Temperature dependence of conductance of an individual multi-wall carbon nanotube (MWNT) is studied over a temperature range of (297 4.8 K). The results indicate that the conduction is governed by variable range hopping (VRH) for the entire temperature range (297 4.8 K). This VRH mechanism changes from three dimensions (3D) to two dimensions (2D) as we go down to 70 K. Three-dimensional variable range hopping (3D VRH) is responsible for conduction in the temperature range (297 70 K), which changes to two-dimensional VRH for much lower temperatures (70 4.8 K). For 3D VRH, various Mott parameters such as density of states, hopping distance and hopping energy have been calculated. The 2D VRH mechanism has been applied for the temperature range (70 4.8 K) and, with the help of this model, the parameters such as localization length and hopping distance are calculated. All these parameters give interesting information about this complex structure, which may be useful for many applications.

Quantitation of 4-Methyl-4-sulfanylpentan-2-one (4MSP) in Hops by a Stable Isotope Dilution Assay in Combination with GC×GC-TOFMS: Method Development and Application To Study the Influence of Variety, Provenance, Harvest Year, and Processing on 4MSP Concentrations.

PubMed

Reglitz, Klaas; Steinhaus, Martin

2017-03-22

A stable isotope dilution assay was developed for quantitation of 4-methyl-4-sulfanylpentan-2-one (4MSP) in hops. The approach included the use of 4-( 13 C)methyl-4-sulfanyl(1,3,5- 13 C 3 )pentan-2-one as internal standard, selective isolation of hop thiols by mercurated agarose, and GC×GC-TOFMS analysis. Application of the method to 53 different hop samples revealed 4MSP concentrations between <1 and 114 μg/kg. Notably high concentrations were associated with United States varieties such as Citra, Eureka, Simcoe, and Apollo, whereas 4MSP was absent from traditional German and English varieties. Further experiments showed that besides the variety, also harvest year and storage vitally influenced 4MSP concentrations, whereas the impact of provenance was less pronounced. Hop processing such as drying and pelletizing had only a minor impact on 4MSP concentrations. Like the majority of other hop volatiles, 4MSP is predominantly located in the lupulin glands.

Studying the hopping parameters of half-Heusler NaAuS using maximally localized Wannier function

NASA Astrophysics Data System (ADS)

Sihi, Antik; Lal, Sohan; Pandey, Sudhir K.

2018-04-01

Here, the electronic behavior of half-Heusler NaAuS is studied using PBEsol exchange correlation functional by plotting the band structure curve. These bands are reproduced using maximally localized Wannier function using WANNIER90. Tight-binding bands are nicely matched with density functional theory bands. By fitting the tight-binding model, hopping parameter for NaAuS is obtained by including Na 2s, 2p, Au 6s, 5p, 5d and S 3s, 3p orbitals within the energy interval of -5 to 16 eV around the Fermi level. In present study, hopping integrals for NaAuS are computed for the first primitive unit cell atoms as well as the first nearest neighbor primitive unit cell. The most dominating hopping integrals are found for Na (3s) - S (3s), Na (2px) - S (2px), Au (6s) - S (3px), Au (6s) - S (3py) and Au (6s) - S (3pz) orbitals. The hopping integrals for the first nearest neighbor primitive unit cell are also discussed in this manuscript. In future, these hopping integrals are very important to find the topological invariant for NaAuS compound.

Collision-based energetic comparison of rolling and hopping over obstacles

PubMed Central

Iida, Fumiya

2018-01-01

Locomotion of machines and robots operating in rough terrain is strongly influenced by the mechanics of the ground-machine interactions. A rolling wheel in terrain with obstacles is subject to collisional energy losses, which is governed by mechanics comparable to hopping or walking locomotion. Here we investigate the energetic cost associated with overcoming an obstacle for rolling and hopping locomotion, using a simple mechanics model. The model considers collision-based interactions with the ground and the obstacle, without frictional losses, and we quantify, analyse, and compare the sources of energetic costs for three locomotion strategies. Our results show that the energetic advantages of the locomotion strategies are uniquely defined given the moment of inertia and the Froude number associated with the system. We find that hopping outperforms rolling at larger Froude numbers and vice versa. The analysis is further extended for a comparative study with animals. By applying size and inertial properties through an allometric scaling law of hopping and trotting animals to our models, we found that the conditions at which hopping becomes energetically advantageous to rolling roughly corresponds to animals’ preferred gait transition speeds. The energetic collision losses as predicted by the model are largely verified experimentally. PMID:29538459

Trajectories and traversal times in quantum tunneling

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

Huang, Zhi Hong.

1989-01-01

The classical concepts of trajectories and traversal times applied to quantum tunneling are discussed. By using the Wentzel-Kramers-Brillouin approximation, it is found that in a forbidden region of a multidimensional space the wave function can be described by two sets of trajectories, or equivalently by two sets of wave fronts. The trajectories belonging to different sets are mutually orthogonal. An extended Huygens construction is proposed to determine these wave fronts and trajectories. In contrast to the classical results in the allowed region, these trajectories couple to each other. However, if the incident wave is normal to the turning surface, themore » trajectories are found to be independent and can be determined by Newton's equations of motion with inverted potential and energy. The multidimensional tunneling theory is then applied to the scanning tunneling microscope to calculate the current density distribution and to derive the expressions for the lateral resolution and the surface corrugation amplitude. The traversal time in quantum tunneling, i.e. tunneling time, is found to depend on model calculations and simulations. Computer simulation of a wave packet tunneling through a square barrier is performed. Several approaches, including the phase method, Larmor clock, and time-dependent barrier model, are investigated. For a square barrier, two characteristic times are found: One is equal to the barrier width divided by the magnitude of the imaginary velocity; the other is equal to the decay length divided by the incident velocity. It is believed that the tunneling time can only be defined operationally.« less

Symplectic approach to calculation of magnetic field line trajectories in physical space with realistic magnetic geometry in divertor tokamaks

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

Punjabi, Alkesh; Ali, Halima

A new approach to integration of magnetic field lines in divertor tokamaks is proposed. In this approach, an analytic equilibrium generating function (EGF) is constructed in natural canonical coordinates ({psi},{theta}) from experimental data from a Grad-Shafranov equilibrium solver for a tokamak. {psi} is the toroidal magnetic flux and {theta} is the poloidal angle. Natural canonical coordinates ({psi},{theta},{phi}) can be transformed to physical position (R,Z,{phi}) using a canonical transformation. (R,Z,{phi}) are cylindrical coordinates. Another canonical transformation is used to construct a symplectic map for integration of magnetic field lines. Trajectories of field lines calculated from this symplectic map in natural canonicalmore » coordinates can be transformed to trajectories in real physical space. Unlike in magnetic coordinates [O. Kerwin, A. Punjabi, and H. Ali, Phys. Plasmas 15, 072504 (2008)], the symplectic map in natural canonical coordinates can integrate trajectories across the separatrix surface, and at the same time, give trajectories in physical space. Unlike symplectic maps in physical coordinates (x,y) or (R,Z), the continuous analog of a symplectic map in natural canonical coordinates does not distort trajectories in toroidal planes intervening the discrete map. This approach is applied to the DIII-D tokamak [J. L. Luxon and L. E. Davis, Fusion Technol. 8, 441 (1985)]. The EGF for the DIII-D gives quite an accurate representation of equilibrium magnetic surfaces close to the separatrix surface. This new approach is applied to demonstrate the sensitivity of stochastic broadening using a set of perturbations that generically approximate the size of the field errors and statistical topological noise expected in a poloidally diverted tokamak. Plans for future application of this approach are discussed.« less

Symplectic approach to calculation of magnetic field line trajectories in physical space with realistic magnetic geometry in divertor tokamaks

NASA Astrophysics Data System (ADS)

Punjabi, Alkesh; Ali, Halima

2008-12-01

A new approach to integration of magnetic field lines in divertor tokamaks is proposed. In this approach, an analytic equilibrium generating function (EGF) is constructed in natural canonical coordinates (ψ,θ) from experimental data from a Grad-Shafranov equilibrium solver for a tokamak. ψ is the toroidal magnetic flux and θ is the poloidal angle. Natural canonical coordinates (ψ,θ,φ) can be transformed to physical position (R,Z,φ) using a canonical transformation. (R,Z,φ) are cylindrical coordinates. Another canonical transformation is used to construct a symplectic map for integration of magnetic field lines. Trajectories of field lines calculated from this symplectic map in natural canonical coordinates can be transformed to trajectories in real physical space. Unlike in magnetic coordinates [O. Kerwin, A. Punjabi, and H. Ali, Phys. Plasmas 15, 072504 (2008)], the symplectic map in natural canonical coordinates can integrate trajectories across the separatrix surface, and at the same time, give trajectories in physical space. Unlike symplectic maps in physical coordinates (x,y) or (R,Z), the continuous analog of a symplectic map in natural canonical coordinates does not distort trajectories in toroidal planes intervening the discrete map. This approach is applied to the DIII-D tokamak [J. L. Luxon and L. E. Davis, Fusion Technol. 8, 441 (1985)]. The EGF for the DIII-D gives quite an accurate representation of equilibrium magnetic surfaces close to the separatrix surface. This new approach is applied to demonstrate the sensitivity of stochastic broadening using a set of perturbations that generically approximate the size of the field errors and statistical topological noise expected in a poloidally diverted tokamak. Plans for future application of this approach are discussed.

The small GTPase Arl8b regulates assembly of the mammalian HOPS complex on lysosomes

PubMed Central

Khatter, Divya; Raina, Vivek B.; Dwivedi, Devashish; Sindhwani, Aastha; Bahl, Surbhi; Sharma, Mahak

2015-01-01

The homotypic fusion and protein sorting (HOPS) complex is a multi-subunit complex conserved from yeast to mammals that regulates late endosome and lysosome fusion. However, little is known about how the HOPS complex is recruited to lysosomes in mammalian cells. Here, we report that the small GTPase Arl8b, but not Rab7 (also known as RAB7A), is essential for membrane localization of the human (h)Vps41 subunit of the HOPS complex. Assembly of the core HOPS subunits to Arl8b- and hVps41-positive lysosomes is guided by their subunit–subunit interactions. RNA interference (RNAi)-mediated depletion of hVps41 resulted in the impaired degradation of EGFR that was rescued upon expression of wild-type but not an Arl8b-binding-defective mutant of hVps41, suggesting that Arl8b-dependent lysosomal localization of hVps41 is required for its endocytic function. Furthermore, we have also identified that the Arl8b effector SKIP (also known as PLEKHM2) interacts with and recruits HOPS subunits to Arl8b and kinesin-positive peripheral lysosomes. Accordingly, RNAi-mediated depletion of SKIP impaired lysosomal trafficking and degradation of EGFR. These findings reveal that Arl8b regulates the association of the human HOPS complex with lysosomal membranes, which is crucial for the function of this tethering complex in endocytic degradation. PMID:25908847

Performance analysis of decode-and-forward dual-hop optical spatial modulation with diversity combiner over atmospheric turbulence

NASA Astrophysics Data System (ADS)

Odeyemi, Kehinde O.; Owolawi, Pius A.; Srivastava, Viranjay M.

2017-11-01

Dual-hops transmission is a growing interest technique that can be used to mitigate against atmospheric turbulence along the Free Space Optical (FSO) communication links. This paper analyzes the performance of Decode-and-Forward (DF) dual-hops FSO systems in-conjunction with spatial modulation and diversity combiners over a Gamma-Gamma atmospheric turbulence channel using heterodyne detection. Maximum Ratio Combiner (MRC), Equal Gain Combiner (EGC) and Selection Combiner (SC) are considered at the relay and destination as mitigation tools to improve the system error performance. Power series expansion of modified Bessel function is used to derive the closed form expression for the end-to-end Average Pairwise Error Probability (APEP) expressions for each of the combiners under study and a tight upper bound on the Average Bit Error Rate (ABER) per hop is given. Thus, the overall end-to-end ABER for the dual-hops FSO system is then evaluated. The numerical results depicted that dual-hops transmission systems outperformed the direct link systems. Moreover, the impact of having the same and different combiners at the relay and destination are also presented. The results also confirm that the combination of dual hops transmission with spatial modulation and diversity combiner significantly improves the systems error rate with the MRC combiner offering an optimal performance with respect to variation in atmospheric turbulence, change in links average received SNR and link range of the system.

A Robot Trajectory Optimization Approach for Thermal Barrier Coatings Used for Free-Form Components

NASA Astrophysics Data System (ADS)

Cai, Zhenhua; Qi, Beichun; Tao, Chongyuan; Luo, Jie; Chen, Yuepeng; Xie, Changjun

2017-10-01

This paper is concerned with a robot trajectory optimization approach for thermal barrier coatings. As the requirements of high reproducibility of complex workpieces increase, an optimal thermal spraying trajectory should not only guarantee an accurate control of spray parameters defined by users (e.g., scanning speed, spray distance, scanning step, etc.) to achieve coating thickness homogeneity but also help to homogenize the heat transfer distribution on the coating surface. A mesh-based trajectory generation approach is introduced in this work to generate path curves on a free-form component. Then, two types of meander trajectories are generated by performing a different connection method. Additionally, this paper presents a research approach for introducing the heat transfer analysis into the trajectory planning process. Combining heat transfer analysis with trajectory planning overcomes the defects of traditional trajectory planning methods (e.g., local over-heating), which helps form the uniform temperature field by optimizing the time sequence of path curves. The influence of two different robot trajectories on the process of heat transfer is estimated by coupled FEM models which demonstrates the effectiveness of the presented optimization approach.

Thermal re-design of the Galileo spacecraft for a Venus-earth-earth-gravity assist (VEEGA) trajectory

NASA Technical Reports Server (NTRS)

Reeve, R.

1989-01-01

The cancellation of the Centaur upper stage program in the aftermath of the Challenger tragedy forced a redesign of the flight trajectory of the Galileo spacecraft to Jupiter, i.e., from a direct trajectory to the Venus-earth-earth-gravity-assist (VEEGA) trajectory on the lower energy two-stage inertial upper stage (IUS), with the result that the spacecraft would be exposed to more than twofold increase in peak solar irradiance. This paper describes the general system-level thermal redesign effort for the Galileo spacecraft, from the start of feasibility studies to its final implementation. Results indicate that the addition of sunshades and the generous utilization of second-surface aluminized Kapton surface material for reflecting high percentages of incident solar irradiation would 'harden' the spacecraft's existing thermal protection system adequately, provided that sun-pointing at the relatively higher solar irradiance levels could be maintained. The final miximum flight temperature predictions for the spacecraft's subsystem thermal designs are given.

Leidenfrost vapour layer moderation of the drag crisis and trajectories of superhydrophobic and hydrophilic spheres falling in water.

PubMed

Vakarelski, Ivan U; Chan, Derek Y C; Thoroddsen, Sigurdur T

2014-08-21

We investigate the dynamic effects of a Leidenfrost vapour layer sustained on the surface of heated steel spheres during free fall in water. We find that a stable vapour layer sustained on the textured superhydrophobic surface of spheres falling through 95 °C water can reduce the hydrodynamic drag by up to 75% and stabilize the sphere trajectory for the Reynolds number between 10(4) and 10(6), spanning the drag crisis in the absence of the vapour layer. For hydrophilic spheres under the same conditions, the transition to drag reduction and trajectory stability occurs abruptly at a temperature different from the static Leidenfrost point. The observed drag reduction effects are attributed to the disruption of the viscous boundary layer by the vapour layer whose thickness depends on the water temperature. Both the drag reduction and the trajectory stabilization effects are expected to have significant implications for development of sustainable vapour layer based technologies.

Mesoscale Numerical Investigations of Air Traffic Emissions over the North Atlantic during SONEX Flight 8: A Case Study

NASA Technical Reports Server (NTRS)

Bieberbach, George, Jr.; Fuelberg, Henry E.; Thompson, Anne M.; Schmitt, Alf; Hannan, John R.; Gregory, G. L.; Kondo, Yutaka; Knabb, Richard D.; Sachse, G. W.; Talbot, R. W.

1999-01-01

Chemical data from flight 8 of NASA's Subsonic Assessment (SASS) Ozone and Nitrogen Oxide Experiment (SONEX) exhibited signatures consistent with aircraft emissions, stratospheric air, and surface-based pollution. These signatures are examined in detail, focussing on the broad aircraft emission signatures that are several hundred kilometers in length. A mesoscale meteorological model provides high resolution wind data that are used to calculate backward trajectories arriving at locations along the flight track. These trajectories are compared to aircraft locations in the North Atlantic Flight Corridor over a 27-33 hour period. Time series of flight level NO and the number of trajectory/aircraft encounters within the NAFC show excellent agreement. Trajectories arriving within the stratospheric and surface-based pollution regions are found to experience very few aircraft encounters. Conversely, there are many trajectory/aircraft encounters within the two chemical signatures corresponding to aircraft emissions. Even many detailed fluctuations of NO within the two aircraft signature regions correspond to similar fluctuations in aircraft encountered during the previous 27-33 hours. Results indicate that high resolution meteorological modeling, when coupled with detailed aircraft location data, is useful for understanding chemical signatures from aircraft emissions at scales of several hundred kilometers.

Simulation of Downlink Synchronization for a Frequency-Hopped Satellite Communication System

DTIC Science & Technology

1992-04-01

naflonie SIMULATION OF DOWNLINK SYNCHRONIZATION FOR A FREQUENCY-HOPPED SATELLITE COMMUNICATION SYSTEM (U) by Lyle Waper_Communicadion and Xa elo Elkaoftron...is offset by an increase in complexity while establishing the communication link, termed synchronization . This document describes a downlink... synchronization process that involves the transmission of synchronization hops by the satellite and a two-step ground terminal synchonization procedure. In

Schooling Teachers, Schooling Ourselves: Insights and Reflections from Teaching K-12 Teachers How to Use Hip-Hop to Educate Students

ERIC Educational Resources Information Center

Irby, Decoteau J.; Hall, H. Bernard; Hill, Marc L.

2013-01-01

Hip-hop-based education (HHBE) research analyzes how hip-hop culture is used to produce favorable educational outcomes. Despite its richness, the work reveals little about how to prepare practicing K-12 teachers to use HHBE toward the critical ends reflected in extant HHBE literature. In this article, we challenge many tacit assumptions of HHBE…

Bridging Theory and Practice: Using Hip-Hop Pedagogy as a Culturally Relevant Approach in the Urban Science Classroom

ERIC Educational Resources Information Center

Adjapong, Edmund S.

2017-01-01

This dissertation explores the context of urban science education as it relates to the achievement and engagement of urban youth. This study provides a framework for Hip-Hop Pedagogy, an approach to teaching and learning anchored in the creative elements of Hip-Hop culture, in STEM as an innovative approach to teaching and learning demonstrates…

Hip-Hop High School: A Study of the Attitudes, Beliefs and Perceptions of Suburban High School Faculty towards Representation of the Hip-Hop Culture

ERIC Educational Resources Information Center

Rowland, Ronald K.

2011-01-01

Research historically has demonstrated that a generational disconnect between the popular cultures from which students and teachers define normative behavior can impact classroom management and student learning. The purpose of this study was to examine attitudes, beliefs and perceptions of high school faculty toward the hip-hop culture and its…

"Dear Tupac, You Speak to Me": Recruiting Hip Hop as Curriculum at a School for Pregnant and Parenting Teens

ERIC Educational Resources Information Center

Hallman, Heidi L.

2009-01-01

This article provides a rich representation of how in-school practices that recruit students' "out-of-school" literacies, such as hip hop, can be used as critical bridges in students' learning. Hip hop, conceptualized in this article as an "out-of-school" literacy, works as a vehicle for curricular change at Eastview School for Pregnant and…

Deal with It We Must: Education, Social Justice, and the Curriculum of Hip Hop Culture

ERIC Educational Resources Information Center

Baszile, Denise Taliaferro

2009-01-01

Although hip hop culture has been one of the most significant urban youth movements over the last three decades, it has only recently gained attention within the educational literature as a force to be reckoned with. And even then, much of the literature seeks to understand how hip hop can be used to engage students in the official school…

Dialoguing, Cultural Capital, and Student Engagement: Toward a Hip Hop Pedagogy in the High School and University Classroom

ERIC Educational Resources Information Center

Rodriguez, Louie F.

2009-01-01

Hip hop culture is typically excluded from conventional educational spaces within the U.S. Drawing on the experiences of an educator who works with urban high school students and university level pre- and in-service educators, this article examines the role of hip hop culture for student engagement in two settings--an alternative high school…