Semi-Empirical Modeling of SLD Physics

NASA Technical Reports Server (NTRS)

Wright, William B.; Potapczuk, Mark G.

2004-01-01

The effects of supercooled large droplets (SLD) in icing have been an area of much interest in recent years. As part of this effort, the assumptions used for ice accretion software have been reviewed. A literature search was performed to determine advances from other areas of research that could be readily incorporated. Experimental data in the SLD regime was also analyzed. A semi-empirical computational model is presented which incorporates first order physical effects of large droplet phenomena into icing software. This model has been added to the LEWICE software. Comparisons are then made to SLD experimental data that has been collected to date. Results will be presented for the comparison of water collection efficiency, ice shape and ice mass.

Volume-Of-Fluid Simulation for Predicting Two-Phase Cooling in a Microchannel

NASA Astrophysics Data System (ADS)

Gorle, Catherine; Parida, Pritish; Houshmand, Farzad; Asheghi, Mehdi; Goodson, Kenneth

2014-11-01

Two-phase flow in microfluidic geometries has applications of increasing interest for next generation electronic and optoelectronic systems, telecommunications devices, and vehicle electronics. While there has been progress on comprehensive simulation of two-phase flows in compact geometries, validation of the results in different flow regimes should be considered to determine the predictive capabilities. In the present study we use the volume-of-fluid method to model the flow through a single micro channel with cross section 100 × 100 μm and length 10 mm. The channel inlet mass flux and the heat flux at the lower wall result in a subcooled boiling regime in the first 2.5 mm of the channel and a saturated flow regime further downstream. A conservation equation for the vapor volume fraction, and a single set of momentum and energy equations with volume-averaged fluid properties are solved. A reduced-physics phase change model represents the evaporation of the liquid and the corresponding heat loss, and the surface tension is accounted for by a source term in the momentum equation. The phase change model used requires the definition of a time relaxation parameter, which can significantly affect the solution since it determines the rate of evaporation. The results are compared to experimental data available from literature, focusing on the capability of the reduced-physics phase change model to predict the correct flow pattern, temperature profile and pressure drop.

A universal order underlying the pseudogap regime of the underdoped high Tc cuprates

NASA Astrophysics Data System (ADS)

Harrison, Neil

2014-03-01

A major achievement in condensed matter physics in the last quarter century has been a step towards the understanding of the unconventional d-wave superconducting state in the copper-oxide materials. Surprisingly, the normal state out of which the superconducting state emerges remains a mystery at low charge carrier densities, i.e., in the underdoped regime. This regime is of particular interest because it is characterised by an unusual momentum dependent energy pseudogap in the excitation spectrum that has defied explanation and is key to a full understanding of the unconventional d-wave superconducting state. I will present new quantum oscillation experimental results within the pseudogap regime of the high Tc superconductors YBa2Cu3O6+x and YBa2Cu4O8 which now extend up to the optimally-doped regime. These data reveal the evolution of the Fermi surface approaching the putative quantum critical point under the superconducting dome. A comprehensive angle-resolved study of the Fermi surface enables us to unambiguously identify a specific form of order that accounts for the observed quantum oscillations as well as other spectroscopic, transport and thermodynamic probes within the pseudogap regime. The author would like to thank B. Ramshaw, S. Sebastian, F. Balakirev, C. Mielke, M. Altarawneh, P. Goddard, S. Sabok, B. Babrowski, D. Bonn, W. Hardy, R. Liang and G. Lonzarich. This work was supported by the DOE BES ``Science of 100 tesla'' project and by the NSF and Florida State.

Toward a Physical Characterization of Raindrop Collision Outcome Regimes

NASA Technical Reports Server (NTRS)

Testik, F. Y.; Barros, Ana P.; Bilven, Francis L.

2011-01-01

A comprehensive raindrop collision outcome regime diagram that delineates the physical conditions associated with the outcome regimes (i.e., bounce, coalescence, and different breakup types) of binary raindrop collisions is proposed. The proposed diagram builds on a theoretical regime diagram defined in the phase space of collision Weber numbers We and the drop diameter ratio p by including critical angle of impact considerations. In this study, the theoretical regime diagram is first evaluated against a comprehensive dataset for drop collision experiments representative of raindrop collisions in nature. Subsequently, the theoretical regime diagram is modified to explicitly describe the dominant regimes of raindrop interactions in (We, p) by delineating the physical conditions necessary for the occurrence of distinct types of collision-induced breakup (neck/filament, sheet, disk, and crown breakups) based on critical angle of impact consideration. Crown breakup is a subtype of disk breakup for lower collision kinetic energy that presents distinctive morphology. Finally, the experimental results are analyzed in the context of the comprehensive collision regime diagram, and conditional probabilities that can be used in the parameterization of breakup kernels in stochastic models of raindrop dynamics are provided.

Linking meteorological drivers of spring-summer drought regimes to agricultural drought risk in China

NASA Astrophysics Data System (ADS)

Dai, L.; Wright, J. S.; Yu, C.; Huang, W. Y.

2017-12-01

As a drought prone country, China has experienced frequent severe droughts in recent decades. Drought frequency and severity are projected to increase in China under climate change. An understanding of the physical processes that contribute to extreme droughts is essential for seasonal forecasting, but the dominant physical mechanisms responsible for droughts in most parts of China are still unclear. Moreover, despite numerous studies on droughts in China, there are few clear connections between the meteorological and climatological drivers of extreme droughts and the associated agricultural consequences. This knowledge gap limits the capacity for decision-making support in drought management. The objectives of this study are (1) to identify robust spring-summer drought regimes over China, (2) to investigate the physical mechanisms associated with each regime, and (3) to better clarify connections between meteorological drought regimes and agricultural drought risk. First, we identify six drought regimes over China by applying an area-weighted k-means clustering technique to spatial patterns of spring-summer Standardized Precipitation Index (SPI) obtained from the ten-member ERA-20CM ensemble for 1900-2010. Second, we project these drought regimes onto agricultural drought risk maps for the three major cereal crops (rice, maize, and wheat) in China. Taking into account historical harvest areas for these crops, we then evaluate the potential impact of each drought regime on agricultural production. Third, the physical mechanisms and meteorological context behind each drought regimes are investigated based on monthly outputs from ERA20CM. We analyze the preceding and concurrent atmospheric circulation anomalies associated with each regime, and propose mechanistic explanations for drought development. This work provides a new perspective on diagnosing the physical mechanisms behind seasonal droughts, and lays a foundation for improving seasonal drought prediction and water management practices in China.

Handbook of the Radiation Regime of the Arctic Basin: Results from the Drift Stations

NASA Technical Reports Server (NTRS)

Mishin, A. A.; Marshunova, M. S.; Radionov, V. F. (Editor); Colony, R. (Editor)

1994-01-01

This Handbook summarizes the radiation data from the Soviet 'North Pole' drifting research stations operated in the Arctic from 1950 to 1991. The Handbook contains reduced mean monthly values of the fluxes of solar radiation for solar elevations up to 35 deg at 5 deg intervals, monthly totals of the net radiation and its constituents, and mean monthly values of the albedo of the sea-ice surfaces. The Handbook presents information of interest to specialists studying the physics of the atmosphere, climatology, geography, and related disciplines.

Minimal Intensity Physical Activity (Standing and Walking) of Longer Duration Improves Insulin Action and Plasma Lipids More than Shorter Periods of Moderate to Vigorous Exercise (Cycling) in Sedentary Subjects When Energy Expenditure Is Comparable

PubMed Central

Duvivier, Bernard M. F. M.; Schaper, Nicolaas C.; Bremers, Michelle A.; van Crombrugge, Glenn; Menheere, Paul P. C. A.; Kars, Marleen; Savelberg, Hans H. C. M.

2013-01-01

Background Epidemiological studies suggest that excessive sitting time is associated with increased health risk, independent of the performance of exercise. We hypothesized that a daily bout of exercise cannot compensate the negative effects of inactivity during the rest of the day on insulin sensitivity and plasma lipids. Methodology/Principal Findings Eighteen healthy subjects, age 21±2 year, BMI 22.6±2.6 kgm−2 followed randomly three physical activity regimes for four days. Participants were instructed to sit 14 hr/day (sitting regime); to sit 13 hr/day and to substitute 1 hr of sitting with vigorous exercise 1 hr (exercise regime); to substitute 6 hrs sitting with 4 hr walking and 2 hr standing (minimal intensity physical activity (PA) regime). The sitting and exercise regime had comparable numbers of sitting hours; the exercise and minimal intensity PA regime had the same daily energy expenditure. PA was assessed continuously by an activity monitor (ActivPAL) and a diary. Measurements of insulin sensitivity (oral glucose tolerance test, OGTT) and plasma lipids were performed in the fasting state, the morning after the 4 days of each regime. In the sitting regime, daily energy expenditure was about 500 kcal lower than in both other regimes. Area under the curve for insulin during OGTT was significantly lower after the minimal intensity PA regime compared to both sitting and exercise regimes 6727.3±4329.4 vs 7752.0±3014.4 and 8320.4±5383.7 mU•min/ml, respectively. Triglycerides, non-HDL cholesterol and apolipoprotein B plasma levels improved significantly in the minimal intensity PA regime compared to sitting and showed non-significant trends for improvement compared to exercise. Conclusions One hour of daily physical exercise cannot compensate the negative effects of inactivity on insulin level and plasma lipids if the rest of the day is spent sitting. Reducing inactivity by increasing the time spent walking/standing is more effective than one hour of physical exercise, when energy expenditure is kept constant. PMID:23418444

Ultra-low current beams in UMER to model space-charge effects in high-energy proton and ion machines

NASA Astrophysics Data System (ADS)

Bernal, S.; Beaudoin, B.; Baumgartner, H.; Ehrenstein, S.; Haber, I.; Koeth, T.; Montgomery, E.; Ruisard, K.; Sutter, D.; Yun, D.; Kishek, R. A.

2017-03-01

The University of Maryland Electron Ring (UMER) has operated traditionally in the regime of strong space-charge dominated beam transport, but small-current beams are desirable to significantly reduce the direct (incoherent) space-charge tune shift as well as the tune depression. This regime is of interest to model space-charge effects in large proton and ion rings similar to those used in nuclear physics and spallation neutron sources, and also for nonlinear dynamics studies of lattices inspired on the Integrable Optics Test Accelerator (IOTA). We review the definitions of beam vs. space-charge intensities and discuss three methods for producing very small beam currents in UMER. We aim at generating 60µA - 1.0mA, 100 ns, 10 keV beams with normalized rms emittances of the order of 0.1 - 1.0µm.

Field-induced superconducting phase of FeSe in the BCS-BEC cross-over

PubMed Central

Kasahara, Shigeru; Watashige, Tatsuya; Hanaguri, Tetsuo; Kohsaka, Yuhki; Yamashita, Takuya; Shimoyama, Yusuke; Mizukami, Yuta; Endo, Ryota; Ikeda, Hiroaki; Aoyama, Kazushi; Terashima, Taichi; Uji, Shinya; Wolf, Thomas; von Löhneysen, Hilbert; Shibauchi, Takasada; Matsuda, Yuji

2014-01-01

Fermi systems in the cross-over regime between weakly coupled Bardeen–Cooper–Schrieffer (BCS) and strongly coupled Bose–Einstein-condensate (BEC) limits are among the most fascinating objects to study the behavior of an assembly of strongly interacting particles. The physics of this cross-over has been of considerable interest both in the fields of condensed matter and ultracold atoms. One of the most challenging issues in this regime is the effect of large spin imbalance on a Fermi system under magnetic fields. Although several exotic physical properties have been predicted theoretically, the experimental realization of such an unusual superconducting state has not been achieved so far. Here we show that pure single crystals of superconducting FeSe offer the possibility to enter the previously unexplored realm where the three energies, Fermi energy εF, superconducting gap Δ, and Zeeman energy, become comparable. Through the superfluid response, transport, thermoelectric response, and spectroscopic-imaging scanning tunneling microscopy, we demonstrate that εF of FeSe is extremely small, with the ratio Δ/εF∼1(∼0.3) in the electron (hole) band. Moreover, thermal-conductivity measurements give evidence of a distinct phase line below the upper critical field, where the Zeeman energy becomes comparable to εF and Δ. The observation of this field-induced phase provides insights into previously poorly understood aspects of the highly spin-polarized Fermi liquid in the BCS-BEC cross-over regime. PMID:25378706

Interface structure in nanoscale multilayers near continuous-to-discontinuous regime

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

Pradhan, P. C.; Majhi, A.; Nayak, M., E-mail: mnayak@rrcat.gov.in

2016-07-28

Interfacial atomic diffusion, reaction, and formation of microstructure in nanoscale level are investigated in W/B{sub 4}C multilayer (ML) system as functions of thickness in ultrathin limit. Hard x-ray reflectivity (XRR) and x-ray diffuse scattering in conjunction with x-ray absorption near edge spectroscopy (XANES) in soft x-ray and hard x-ray regimes and depth profiling x-ray photoelectron spectroscopy (XPS) have been used to precisely evaluate detailed interfacial structure by systematically varying the individual layer thickness from continuous-to-discontinuous regime. It is observed that the interfacial morphology undergoes an unexpected significant modification as the layer thickness varies from continuous-to-discontinuous regime. The interfacial atomic diffusionmore » increases, the physical density of W layer decreases and that of B{sub 4}C layer increases, and further more interestingly the in-plane correlation length decreases substantially as the layer thickness varies from continuous-to-discontinuous regime. This is corroborated using combined XRR and x-ray diffused scattering analysis. XANES and XPS results show formation of more and more tungsten compounds at the interfaces as the layer thickness decreases below the percolation threshold due to increase in the contact area between the elements. The formation of compound enhances to minimize certain degree of disorder at the interfaces in the discontinuous region that enables to maintain the periodic structure in ML. The degree of interfacial atomic diffusion, interlayer interaction, and microstructure is correlated as a function of layer thickness during early stage of film growth.« less

Prediction of gas-liquid two-phase flow regime in microgravity

NASA Technical Reports Server (NTRS)

Lee, Jinho; Platt, Jonathan A.

1993-01-01

An attempt is made to predict gas-liquid two-phase flow regime in a pipe in a microgravity environment through scaling analysis based on dominant physical mechanisms. Simple inlet geometry is adopted in the analysis to see the effect of inlet configuration on flow regime transitions. Comparison of the prediction with the existing experimental data shows good agreement, though more work is required to better define some physical parameters. The analysis clarifies much of the physics involved in this problem and can be applied to other configurations.

Physical and mechanical properties of the B2 compound NiAl

NASA Technical Reports Server (NTRS)

Noebe, R. D.; Bowman, R. R.; Nathal, M. V.

1993-01-01

Considerable work has been performed on NiAl over the last three decades, with an extremely rapid growth in research on this intermetallic occurring in the last few years due to recent interest in this material for electronic and high temperature structural applications. However, many physical properties and the controlling fracture and deformation mechanisms over certain temperature regimes are still in question. Part of this problem lies in the incomplete characterization of many of the alloys previously investigated. Fragmentary data on processing conditions, chemistry, microstructure and the apparent difficulty in accurately measuring composition has made direct comparison between individual studies sometimes tenuous. Therefore, the purpose of this review is to summarize all available mechanical and pertinent physical properties on NiAl, stressing the most recent investigations, in an attempt to understand the behavior of NiAl and its alloys over a broad temperature range.

Static and Dynamic Magnetic Response in Ferrofluids

DTIC Science & Technology

2007-10-30

much below (dodecane) the carrier fluid freezing temperatures providing interesting regimes to study the relaxation mechanisms associated with the...blocking temperature was just above (hexane) and much below (dodecane) the carrier fluid freezing temperatures providing interesting regimes to study...focused mainly on the following tasks: 1. Chemical synthesis of iron oxide and soft ferrite nanoparticles using co- precipitation, structural and

Propulsion System for Very High Altitude Subsonic Unmanned Aircraft

NASA Technical Reports Server (NTRS)

Bents, David J.; Mockler, Ted; Maldonado, Jaime; Harp, James L., Jr.; King, Joseph F.; Schmitz, Paul C.

1998-01-01

This paper explains why a spark ignited gasoline engine, intake pressurized with three cascaded stages of turbocharging, was selected to power NASA's contemplated next generation of high altitude atmospheric science aircraft. Beginning with the most urgent science needs (the atmospheric sampling mission) and tracing through the mission requirements which dictate the unique flight regime in which this aircraft has to operate (subsonic flight at greater then 80 kft) we briefly explore the physical problems and constraints, the available technology options and the cost drivers associated with developing a viable propulsion system for this highly specialized aircraft. The paper presents the two available options (the turbojet and the turbocharged spark ignited engine) which are discussed and compared in the context of the flight regime. We then show how the unique nature of the sampling mission, coupled with the economic considerations pursuant to aero engine development, point to the spark ignited engine as the only cost effective solution available. Surprisingly, this solution compares favorably with the turbojet in the flight regime of interest. Finally, some remarks are made about NASA's present state of development, and future plans to flight demonstrate the three stage turbocharged powerplant.

Reactor monitoring using antineutrino detectors

NASA Astrophysics Data System (ADS)

Bowden, N. S.

2011-08-01

Nuclear reactors have served as the antineutrino source for many fundamental physics experiments. The techniques developed by these experiments make it possible to use these weakly interacting particles for a practical purpose. The large flux of antineutrinos that leaves a reactor carries information about two quantities of interest for safeguards: the reactor power and fissile inventory. Measurements made with antineutrino detectors could therefore offer an alternative means for verifying the power history and fissile inventory of a reactor as part of International Atomic Energy Agency (IAEA) and/or other reactor safeguards regimes. Several efforts to develop this monitoring technique are underway worldwide.

Study of the Warm Dense Matter with XANES spectroscopy - Applications to planetary interiors

NASA Astrophysics Data System (ADS)

Denoeud, Adrien

With the recent discovery of many exoplanets, modelling the interior of these celestial bodies is becoming a fascinating scientific challenge. In this context, it is crucial to accurately know the equations of state and the macroscopic and microscopic physical properties of their constituent materials in the Warm Dense Matter regime (WDM). Moreover, planetary models rely almost exclusively on physical properties obtained using first principles simulations based on density functional theory (DFT) predictions. It is thus of paramount importance to validate the basic underlying mechanisms occurring for key planetary constituents (metallization, dissociation, structural modifications, phase transitions, etc....) as pressure and temperature both increase. In this work, we were interested in two materials that can be mainly found in the Earth-like planets: silica, or SiO2, as a model compound of the silicates that constitute the major part of their mantles, and iron, which is found in abundance in their cores. These two materials were compressed and brought to the WDM regime by using strong shock created by laser pulses during various experiments performed on the LULI2000 (Palaiseau, France) and the JLF (Livermore, US) laser facilities and on the LCLS XFEL (Stanford, US). In order to penetrate this dense matter and to have access to its both ionic and electronic structures, we have probed silica and iron with time-resolved X-ray Absorption Near Edge Structure (XANES). In parallel with these experiments, we performed quantum molecular dynamics simulations based on DFT at conditions representative of the region investigated experimentally so as to extract the interesting physical processes and comprehend the limits of the implemented models. In particular, these works allowed us to highlight the metallization processes of silica in temperature and the structural changes of its liquid in density, as well as to more constrain the melting curve of iron at very high pressures.

Physics Without Physics. The Power of Information-theoretical Principles

NASA Astrophysics Data System (ADS)

D'Ariano, Giacomo Mauro

2017-01-01

David Finkelstein was very fond of the new information-theoretic paradigm of physics advocated by John Archibald Wheeler and Richard Feynman. Only recently, however, the paradigm has concretely shown its full power, with the derivation of quantum theory (Chiribella et al., Phys. Rev. A 84:012311, 2011; D'Ariano et al., 2017) and of free quantum field theory (D'Ariano and Perinotti, Phys. Rev. A 90:062106, 2014; Bisio et al., Phys. Rev. A 88:032301, 2013; Bisio et al., Ann. Phys. 354:244, 2015; Bisio et al., Ann. Phys. 368:177, 2016) from informational principles. The paradigm has opened for the first time the possibility of avoiding physical primitives in the axioms of the physical theory, allowing a re-foundation of the whole physics over logically solid grounds. In addition to such methodological value, the new information-theoretic derivation of quantum field theory is particularly interesting for establishing a theoretical framework for quantum gravity, with the idea of obtaining gravity itself as emergent from the quantum information processing, as also suggested by the role played by information in the holographic principle (Susskind, J. Math. Phys. 36:6377, 1995; Bousso, Rev. Mod. Phys. 74:825, 2002). In this paper I review how free quantum field theory is derived without using mechanical primitives, including space-time, special relativity, Hamiltonians, and quantization rules. The theory is simply provided by the simplest quantum algorithm encompassing a countable set of quantum systems whose network of interactions satisfies the three following simple principles: homogeneity, locality, and isotropy. The inherent discrete nature of the informational derivation leads to an extension of quantum field theory in terms of a quantum cellular automata and quantum walks. A simple heuristic argument sets the scale to the Planck one, and the currently observed regime where discreteness is not visible is the so-called "relativistic regime" of small wavevectors, which holds for all energies ever tested (and even much larger), where the usual free quantum field theory is perfectly recovered. In the present quantum discrete theory Einstein relativity principle can be restated without using space-time in terms of invariance of the eigenvalue equation of the automaton/walk under change of representations. Distortions of the Poincaré group emerge at the Planck scale, whereas special relativity is perfectly recovered in the relativistic regime. Discreteness, on the other hand, has some plus compared to the continuum theory: 1) it contains it as a special regime; 2) it leads to some additional features with GR flavor: the existence of an upper bound for the particle mass (with physical interpretation as the Planck mass), and a global De Sitter invariance; 3) it provides its own physical standards for space, time, and mass within a purely mathematical adimensional context. The paper ends with the future perspectives of this project, and with an Appendix containing biographic notes about my friendship with David Finkelstein, to whom this paper is dedicated.

Low-Temperature Synthesis of New Ternary Chalcogenide Compounds of Copper, Gold, and Mercury Using Alkali Metal Polychalcogenide Fluxes

NASA Astrophysics Data System (ADS)

Park, Younbong

In last two decades great efforts have been exerted to find new materials with interesting optical, electrical, and catalytic properties. Metal chalcogenides have been studied extensively because of their interesting physical properties and rich structural chemistry, among the potential materials. Prior to this work, most known metal chalcogenides had been synthesized at high temperature (T > 500^circC). Intermediate temperature synthesis in solid state chemistry was seldom pursued because of the extremely slow diffusion rates between reactants. This intermediate temperature regime could be a new synthesis condition if one looks for new materials with unusual structural features and properties. Metastable or kinetically stable compounds can be stabilized in this intermediate temperature regime, in contrast to the thermodynamically stable high temperature compounds. Molten salts, especially alkali metal polychalcogenide fluxes, can provide a route for exploring new chalcogenide materials at intermediate temperatures. These fluxes are very reactive and melt as low as 145^circC (mp of K_2S_4). Using these fluxes as reaction media, we have encountered many novel chalcogenide compounds with unusual structures and interesting electrical properties (semiconductors to metallic conductors). Low-dimensional polychalcogenide compounds of alpha-ACuQ_4 (A = K, Cs; Q = S, Se), beta -KCuS_4, KAuQ_5 (Q = S, Se), K_3AuSe_ {13}, Na_3AuSe _8, and CsAuSe_3 exhibit the beautiful structural diversity and bonding flexibility of the polychalcogenide ligands. In addition, many novel chalcogenide compounds of Cu, Hg, and Au with low-dimensional structures. The preparation of novel mixed -valence Cu compounds, K_2Cu _5Te_5, Cs _3Cu_8Te_ {10}, Na_3Cu _4Se_4, K _3Cu_8S_4 Te_2, and KCu_4 S_2Te, which show interesting metallic properties, especially underscores the enormous potential of the molten salt method for the synthesis of new chalcogenide materials with interesting physical properties. The materials prepared in this study can be classified as a new class of chalcogenide compounds due to their unique structures. In this dissertation the synthesis, characterization with emphasis on structures, charge transport properties, and magnetic susceptibilities of the materials will be illustrated.

The ideas behind self-consistent expansion

NASA Astrophysics Data System (ADS)

Schwartz, Moshe; Katzav, Eytan

2008-04-01

In recent years we have witnessed a growing interest in various non-equilibrium systems described in terms of stochastic nonlinear field theories. In some of those systems, like KPZ and related models, the interesting behavior is in the strong coupling regime, which is inaccessible by traditional perturbative treatments such as dynamical renormalization group (DRG). A useful tool in the study of such systems is the self-consistent expansion (SCE), which might be said to generate its own 'small parameter'. The self-consistent expansion (SCE) has the advantage that its structure is just that of a regular expansion, the only difference is that the simple system around which the expansion is performed is adjustable. The purpose of this paper is to present the method in a simple and understandable way that hopefully will make it accessible to a wider public working on non-equilibrium statistical physics.

The German Physical Society in the Third Reich: Local Conservatism between Co-optation and Autonomy.

NASA Astrophysics Data System (ADS)

Beyler, Richard

2006-05-01

During the National Socialism regime the German Physical Society (GPS), like many other German professional organizations, faced difficult choices along the spectrum of co-optation into the Nazi power structure and autonomy from the regime. This paper examines several examples of the Society's actions which shown an seeking to maintain traditional disciplinary standards while at the same time selectively cooperating with some of the regime's expectations. The successful riposte to ardent Nazi Johannes Stark's effort to become GPS chair in 1933 showed that the GPS was able to assert its traditional disciplinary authority structure even in the face of efforts to subsume the Society under the leadership principle favored by the Nazis. The Society's later election of industrial physicist Carl Ramsauer showed the GPS emphsizing the strategic (also military) importance of physics--and also willing to accommodate the regime's demand for the exclusion of non-Aryans. Finally, the choices behind the GPS's awarding of its presitigious Max Planck Medal in the late 1930's and early 40's show that both achievement in physics and political considerations--favoring scientists sympathetic to the regime, avoiding those antagonistic to it--were taken into account. Taken together, these examples demonstrate a kind of ``local conservativism'' that was at some times at odds with Nazi ideology but which nevertheless avoided open confrontation and indeed selectively cooperated with the regime's agenda.

Low-order modelling of a drop on a highly-hydrophobic substrate: statics and dynamics

NASA Astrophysics Data System (ADS)

Wray, Alexander W.; Matar, Omar K.; Davis, Stephen H.

2017-11-01

We analyse the behaviour of droplets resting on highly-hydrophobic substrates. This problem is of practical interest due to its appearance in many physical contexts involving the spreading, wetting, and dewetting of fluids on solid substrates. In mathematical terms, it exhibits an interesting challenge as the interface is multi-valued as a function of the natural Cartesian co-ordinates, presenting a stumbling block to typical low-order modelling techniques. Nonetheless, we show that in the static case, the interfacial shape is governed by the Young-Laplace equation, which may be solved explicitly in terms of elliptic functions. We present simple low-order expressions that faithfully reproduce the shapes. We then consider the dynamic case, showing that the predictions of our low-order model compare favourably with those obtained from direct numerical simulations. We also examine the characteristic flow regimes of interest. EPSRC, UK, MEMPHIS program Grant (EP/K003976/1), RAEng Research Chair (OKM).

Negative refraction and sub-wavelength focusing in the visible range using transparent metallo-dielectric stacks.

PubMed

Scalora, Michael; D'Aguanno, Giuseppe; Mattiucci, Nadia; Bloemer, Mark J; de Ceglia, Domenico; Centini, Marco; Mandatori, Antonio; Sibilia, Concita; Akozbek, Neset; Cappeddu, Mirko G; Fowler, Mark; Haus, Joseph W

2007-01-22

We numerically demonstrate negative refraction of the Poynting vector and sub-wavelength focusing in the visible part of the spectrum using a transparent multilayer, metallo-dielectric photonic band gap structure. Our results reveal that in the wavelength regime of interest evanescent waves are not transmitted by the structure, and that the main underlying physical mechanisms for sub-wavelength focusing are resonance tunneling, field localization, and propagation effects. These structures offer several advantages: tunability and high transmittance (50% or better) across the visible and near IR ranges; large object-image distances, with image planes located beyond the range where the evanescent waves have decayed. From a practical point of view, our findings point to a simpler way to fabricate a material that exhibits negative refraction and maintains high transparency across a broad wavelength range. Transparent metallo-dielectric stacks also provide an opportunity to expand the exploration of wave propagation phenomena in metals, both in the linear and nonlinear regimes.

[Eugenics and Falange through the journal Ser (1942-1957)].

PubMed

Rendon, Sara Navarro

2016-01-01

Biopolitics has played an important role in fascist totalitarianism and the-Francoist regime was no exception. From the and with ultimate goal or regulating the population, measures were implemented to increase, care for and indoctrinate the population. This present study analyses the selection and promotion measures of some populations and the marginalisation of others proposed the Spanish Falangist Movement's official publication in the field of medicine, the journal Ser, Revista Medico-Social by the National Delegation of Health of the Traditionalist Spanish Phalanx of the Committees of the National Syndicalist Offensivie (F.E.T y de las J. O. N. S. 1942-1957). In this respect, the analysis of eugenic ideas and practice defended therein become especially interesting, claiming that, through indoctrination and health development, the race would be improved both physically and mentally. From the systematic analysis of the journals's contenets it has been demonstrated that this was one of the instruments used by the dictatorial regime to reconfigure eugenics in accordance with Catholic morals and national syndicalist politics.

Patterns of variability in supercritical hadronic systems

NASA Astrophysics Data System (ADS)

Petropoulou, M.; Mastichiadis, A.

2018-07-01

A unique and often overlooked property of a source loaded with relativistic protons is that it can become supercritical, i.e. it can undergo an abrupt transition from a radiatively inefficient to a radiatively efficient state once its proton energy density exceeds a certain threshold. In this paper, we investigate the temporal variability of hadronic systems in this hardly explored regime. We show that there exists a range of proton densities that prevent the system from reaching a steady state, but drive it instead in a quasi-periodic mode. The escaping radiation then exhibits limit cycles, even if all physical parameters are held constant in time. We extend our analysis to cases where the proton injection rate varies with time and explore the variability patterns of escaping radiation as the system moves in and out from the supercritical regime. We examine the relevance of our results to the variability of the prompt gamma-ray burst emission and show that, at least on a phenomenological level, some interesting analogies exist.

Observation of symmetry-protected topological band with ultracold fermions

PubMed Central

Song, Bo; Zhang, Long; He, Chengdong; Poon, Ting Fung Jeffrey; Hajiyev, Elnur; Zhang, Shanchao; Liu, Xiong-Jun; Jo, Gyu-Boong

2018-01-01

Symmetry plays a fundamental role in understanding complex quantum matter, particularly in classifying topological quantum phases, which have attracted great interests in the recent decade. An outstanding example is the time-reversal invariant topological insulator, a symmetry-protected topological (SPT) phase in the symplectic class of the Altland-Zirnbauer classification. We report the observation for ultracold atoms of a noninteracting SPT band in a one-dimensional optical lattice and study quench dynamics between topologically distinct regimes. The observed SPT band can be protected by a magnetic group and a nonlocal chiral symmetry, with the band topology being measured via Bloch states at symmetric momenta. The topology also resides in far-from-equilibrium spin dynamics, which are predicted and observed in experiment to exhibit qualitatively distinct behaviors in quenching to trivial and nontrivial regimes, revealing two fundamental types of spin-relaxation dynamics related to bulk topology. This work opens the way to expanding the scope of SPT physics with ultracold atoms and studying nonequilibrium quantum dynamics in these exotic systems. PMID:29492457

Environmental controls on food web regimes: A fluvial perspective

NASA Astrophysics Data System (ADS)

Power, Mary E.

2006-02-01

Because food web regimes control the biomass of primary producers (e.g., plants or algae), intermediate consumers (e.g., invertebrates), and large top predators (tuna, killer whales), they are of societal as well as academic interest. Some controls over food web regimes may be internal, but many are mediated by conditions or fluxes over large spatial scales. To understand locally observed changes in food webs, we must learn more about how environmental gradients and boundaries affect the fluxes of energy, materials, or organisms through landscapes or seascapes that influence local species interactions. Marine biologists and oceanographers have overcome formidable challenges of fieldwork on the high seas to make remarkable progress towards this goal. In river drainage networks, we have opportunities to address similar questions at smaller spatial scales, in ecosystems with clear physical structure and organization. Despite these advantages, we still have much to learn about linkages between fluxes from watershed landscapes and local food webs in river networks. Longitudinal (downstream) gradients in productivity, disturbance regimes, and habitat structure exert strong effects on the organisms and energy sources of river food webs, but their effects on species interactions are just beginning to be explored. In fluid ecosystems with less obvious physical structure, like the open ocean, discerning features that control the movement of organisms and affect food web dynamics is even more challenging. In both habitats, new sensing, tracing and mapping technologies have revealed how landscape or seascape features (e.g., watershed divides, ocean fronts or circulation cells) channel, contain or concentrate organisms, energy and materials. Field experiments and direct in situ observations of basic natural history, however, remain as vital as ever in interpreting the responses of biota to these features. We need field data that quantify the many spatial and temporal scales of functional relationships that link environments, fluxes and food web interactions to understand how they will respond to intensifying anthropogenic forcing over the coming decades.

Discrete multi-physics simulations of diffusive and convective mass transfer in boundary layers containing motile cilia in lungs.

PubMed

Ariane, Mostapha; Kassinos, Stavros; Velaga, Sitaram; Alexiadis, Alessio

2018-04-01

In this paper, the mass transfer coefficient (permeability) of boundary layers containing motile cilia is investigated by means of discrete multi-physics. The idea is to understand the main mechanisms of mass transport occurring in a ciliated-layer; one specific application being inhaled drugs in the respiratory epithelium. The effect of drug diffusivity, cilia beat frequency and cilia flexibility is studied. Our results show the existence of three mass transfer regimes. A low frequency regime, which we called shielding regime, where the presence of the cilia hinders mass transport; an intermediate frequency regime, which we have called diffusive regime, where diffusion is the controlling mechanism; and a high frequency regime, which we have called convective regime, where the degree of bending of the cilia seems to be the most important factor controlling mass transfer in the ciliated-layer. Since the flexibility of the cilia and the frequency of the beat changes with age and health conditions, the knowledge of these three regimes allows prediction of how mass transfer varies with these factors. Copyright © 2018 Elsevier Ltd. All rights reserved.

Bubbles, shocks and elementary technical trading strategies

NASA Astrophysics Data System (ADS)

Fry, John

2014-01-01

In this paper we provide a unifying framework for a set of seemingly disparate models for bubbles, shocks and elementary technical trading strategies in financial markets. Markets operate by balancing intrinsic levels of risk and return. This seemingly simple observation is commonly over-looked by academics and practitioners alike. Our model shares its origins in statistical physics with others. However, under our approach, changes in market regime can be explicitly shown to represent a phase transition from random to deterministic behaviour in prices. This structure leads to an improved physical and econometric model. We develop models for bubbles, shocks and elementary technical trading strategies. The list of empirical applications is both interesting and topical and includes real-estate bubbles and the on-going Eurozone crisis. We close by comparing the results of our model with purely qualitative findings from the finance literature.

Analytical pricing formulas for hybrid variance swaps with regime-switching

NASA Astrophysics Data System (ADS)

Roslan, Teh Raihana Nazirah; Cao, Jiling; Zhang, Wenjun

2017-11-01

The problem of pricing discretely-sampled variance swaps under stochastic volatility, stochastic interest rate and regime-switching is being considered in this paper. An extension of the Heston stochastic volatility model structure is done by adding the Cox-Ingersoll-Ross (CIR) stochastic interest rate model. In addition, the parameters of the model are permitted to have transitions following a Markov chain process which is continuous and discoverable. This hybrid model can be used to illustrate certain macroeconomic conditions, for example the changing phases of business stages. The outcome of our regime-switching hybrid model is presented in terms of analytical pricing formulas for variance swaps.

Outcome regimes of binary raindrop collisions

NASA Astrophysics Data System (ADS)

Testik, Firat Y.

2009-11-01

This study delineates the physical conditions that are responsible for the occurrence of main outcome regimes (i.e., bounce, coalescence, and breakup) for binary drop collisions with a precipitation microphysics perspective. Physical considerations based on the collision kinetic energy and the surface energies of the colliding drops lead to the development of a theoretical regime diagram for the drop/raindrop collision outcomes in the We- p plane ( We — Weber number, p — raindrop diameter ratio). This theoretical regime diagram is supported by laboratory experimental observations of drop collisions using high-speed imaging. Results of this fundamental study bring in new insights into the quantitative understanding of drop dynamics, applications of which extend beyond precipitation microphysics. In particular, results of this drop collision study are expected to give impetus to the physics-based dynamic modeling of the drop size distributions that is essential for various typical modern engineering applications, including numerical modeling of evolution of raindrop size distribution in rain shaft.

Spiral-like multi-beam emission via transformation electromagnetics

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

Tichit, Paul-Henri, E-mail: paul-henri.tichit@u-psud.fr; Burokur, Shah Nawaz, E-mail: shah-nawaz.burokur@u-psud.fr; Lustrac, André de, E-mail: andre.de-lustrac@u-psud.fr

Transformation electromagnetics offers an unconventional approach for the design of novel radiating devices. Here, we propose an electromagnetic metamaterial able to split an isotropic radiation into multiple directive beams. By applying transformations that modify distance and angles, we show how the multiple directive beams can be steered at will. We describe transformation of the metric space and the calculation of the material parameters. Different transformations are proposed for a possible physical realization through the use of engineered artificial metamaterials. Full wave simulations are performed to validate the proposed approach. The idea paves the way to interesting applications in various domainsmore » in microwave and optical regimes.« less

Applied Impact Physics Research

NASA Astrophysics Data System (ADS)

Wickert, Matthias

2013-06-01

Applied impact physics research is based on the capability to examine impact processes for a wide range of impact conditions with respect to velocity as well as mass and shape of the projectile. For this reason, Fraunhofer EMI operates a large variety of launchers that address velocities up to ordnance velocities as single stage powder gun but which can also be operated as two-stage light gas guns achieving the regime of low earth orbital velocity. Thereby for projectile masses of up to 100 g hypervelocity impact phenomena up to 7.8 km/s can be addressed. Advanced optical diagnostic techniques like microsecond video are used as commercial systems but - since impact phenomena are mostly related with debris or dust - specialized diagnostics are developed in-house like x-ray cinematography and x-ray tomography. Selected topics of the field of applied impact physics will be presented like the interesting behavior of long rods penetrating low-density materials or experimental findings at hypervelocity for this class of materials as well as new x-ray diagnositic techniques.

Review of the physical and mechanical properties and potential applications of the B2 compound NiAl: Unabridged version of a paper published in International materials review

NASA Technical Reports Server (NTRS)

Noebe, Ronald D.; Bowman, Randy R.; Nathal, Michael V.

1992-01-01

Considerable work has been performed on NiAl over the last three decades, with an extremely rapid growth in research on this intermetallic occurring in the last few years due to recent interest in this material for electronic and high temperature structural applications. However, many physical properties and the controlling fracture and deformation mechanisms over certain temperature regimes are still in question. Part of this problem lies in the incomplete characterization of many of the alloys previously investigated. Fragmentary data on processing conditions, chemistry, microstructure and the apparent difficulty in accurately measuring composition has made direct comparison between individual studies sometimes tenuous. Therefore, the purpose of this review is to summarize all available mechanical and pertinent physical properties on NiAl, stressing the most recent investigations, in an attempt to understand the behavior of NiAl and its alloys over a broad temperature range.

Study of thermal annealing effect on Bragg gratings photo-inscribed in step-index polymer optical fibers

NASA Astrophysics Data System (ADS)

Hu, X.; Kinet, D.; Mégret, P.; Caucheteur, C.

2016-04-01

In this paper, both non-annealed and annealed trans-4-stilbenemethanol-doped step-index polymer optical fibers were photo-inscribed using a 325 nm HeCd laser with two different beam power densities reaching the fiber core. In the high density regime where 637 mW/mm2 are used, the grating reflectivity is stable over time after the photo-writing process but the reflected spectrum is of limited quality, as the grating physical length is limited to 1.2 mm. To produce longer gratings exhibiting more interesting spectral features, the beam is enlarged to 6 mm, decreasing the power density to 127 mW/mm2. In this second regime, the grating reflectivity is not stable after the inscription process but tends to decay for both kinds of fibers. A fortunate property in this case results from the possibility to fully recover the initial reflectivity using a post-inscription thermal annealing, where the gratings are annealed at 80 °C during 2 days. The observed evolutions for both regimes are attributed to the behavior of the excited intermediate states between the excited singlet and the ground singlet state of trans- and cis-isomers as well as the temperature-dependent glassy polymer matrix.

Nonlocal correlations in a macroscopic measurement scenario

NASA Astrophysics Data System (ADS)

Kunkri, Samir; Banik, Manik; Ghosh, Sibasish

2017-02-01

Nonlocality is one of the main characteristic features of quantum systems involving more than one spatially separated subsystem. It is manifested theoretically as well as experimentally through violation of some local realistic inequality. On the other hand, classical behavior of all physical phenomena in the macroscopic limit gives a general intuition that any physical theory for describing microscopic phenomena should resemble classical physics in the macroscopic regime, the so-called macrorealism. In the 2-2-2 scenario (two parties, with each performing two measurements and each measurement having two outcomes), contemplating all the no-signaling correlations, we characterize which of them would exhibit classical (local realistic) behavior in the macroscopic limit. Interestingly, we find correlations which at the single-copy level violate the Bell-Clauser-Horne-Shimony-Holt inequality by an amount less than the optimal quantum violation (i.e., Cirel'son bound 2 √{2 } ), but in the macroscopic limit gives rise to a value which is higher than 2 √{2 } . Such correlations are therefore not considered physical. Our study thus provides a sufficient criterion to identify some of unphysical correlations.

Ultracold neutral plasmas

NASA Astrophysics Data System (ADS)

Lyon, M.; Rolston, S. L.

2017-01-01

By photoionizing samples of laser-cooled atoms with laser light tuned just above the ionization limit, plasmas can be created with electron and ion temperatures below 10 K. These ultracold neutral plasmas have extended the temperature bounds of plasma physics by two orders of magnitude. Table-top experiments, using many of the tools from atomic physics, allow for the study of plasma phenomena in this new regime with independent control over the density and temperature of the plasma through the excitation process. Characteristic of these systems is an inhomogeneous density profile, inherited from the density distribution of the laser-cooled neutral atom sample. Most work has dealt with unconfined plasmas in vacuum, which expand outward at velocities of order 100 m/s, governed by electron pressure, and with lifetimes of order 100 μs, limited by stray electric fields. Using detection of charged particles and optical detection techniques, a wide variety of properties and phenomena have been observed, including expansion dynamics, collective excitations in both the electrons and ions, and collisional properties. Through three-body recombination collisions, the plasmas rapidly form Rydberg atoms, and clouds of cold Rydberg atoms have been observed to spontaneously avalanche ionize to form plasmas. Of particular interest is the possibility of the formation of strongly coupled plasmas, where Coulomb forces dominate thermal motion and correlations become important. The strongest impediment to strong coupling is disorder-induced heating, a process in which Coulomb energy from an initially disordered sample is converted into thermal energy. This restricts electrons to a weakly coupled regime and leaves the ions barely within the strongly coupled regime. This review will give an overview of the field of ultracold neutral plasmas, from its inception in 1999 to current work, including efforts to increase strong coupling and effects on plasma properties due to strong coupling.

Hard matching for boosted tops at two loops

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

Hoang, Andre H.; Pathak, Aditya; Pietrulewicz, Piotr

2015-12-10

Here, cross sections for top quarks provide very interesting physics opportunities, being both sensitive to new physics and also perturbatively tractable due to the large top quark mass. Rigorous factorization theorems for top cross sections can be derived in several kinematic scenarios, including the boosted regime in the peak region that we consider here. In the context of the corresponding factorization theorem for e +e – collisions we extract the last missing ingredient that is needed to evaluate the cross section differential in the jet-mass at two-loop order, namely the matching coefficient at the scale μ≃m t. Our extraction alsomore » yields the final ingredients needed to carry out logarithmic re-summation at next-to-next-to-leading logarithmic order (or N 3LL if we ignore the missing 4-loop cusp anomalous dimension). This coefficient exhibits an amplitude level rapidity logarithm starting at O(α 2 s) due to virtual top quark loops, which we treat using rapidity renormalization group (RG) evolution. Interestingly, this rapidity RG evolution appears in the matching coefficient between two effective theories around the heavy quark mass scale μ ≃ m t.« less

Analysis of plasma particle and energy fluxes to material surfaces from tokamak edge turbulence simulations

NASA Astrophysics Data System (ADS)

Umansky, M. V.; Cohen, B. I.; Rognlien, T. D.; Boedo, J. A.; Rudakov, D. L.

2012-10-01

Recent BOUT simulations of edge plasma turbulence in L-mode regime in the boundary region of DIII-D tokamak have demonstrated reasonable match with key edge diagnostics [1]. Order-of-magnitude level agreement has been found in the characteristic amplitude, wavenumber, and frequency of turbulent fluctuations, as compared with experimental data from reciprocating edge Langmuir probe and Beam Emission Spectroscopy systems. Owing to this encouraging agreement, output data from these simulations are analyzed to get insights on physical mechanisms and properties of plasma particle and energy fluxes to material surfaces. Of particular interest is plasma turbulence propagating into, or generated in, the far scrape-off layer region where plasma interacts with material walls. Results of statistical analyses of simulated turbulence plasma transport will be presented and physical implications will be discussed. [4pt] [1] B.I. Cohen et al., APS-DPP 2012

Ultra-high strain in epitaxial silicon carbide nanostructures utilizing residual stress amplification

NASA Astrophysics Data System (ADS)

Phan, Hoang-Phuong; Nguyen, Tuan-Khoa; Dinh, Toan; Ina, Ginnosuke; Kermany, Atieh Ranjbar; Qamar, Afzaal; Han, Jisheng; Namazu, Takahiro; Maeda, Ryutaro; Dao, Dzung Viet; Nguyen, Nam-Trung

2017-04-01

Strain engineering has attracted great attention, particularly for epitaxial films grown on a different substrate. Residual strains of SiC have been widely employed to form ultra-high frequency and high Q factor resonators. However, to date, the highest residual strain of SiC was reported to be limited to approximately 0.6%. Large strains induced into SiC could lead to several interesting physical phenomena, as well as significant improvement of resonant frequencies. We report an unprecedented nanostrain-amplifier structure with an ultra-high residual strain up to 8% utilizing the natural residual stress between epitaxial 3C-SiC and Si. In addition, the applied strain can be tuned by changing the dimensions of the amplifier structure. The possibility of introducing such a controllable and ultra-high strain will open the door to investigating the physics of SiC in large strain regimes and the development of ultra sensitive mechanical sensors.

Vector rogue waves and baseband modulation instability in the defocusing regime.

PubMed

Baronio, Fabio; Conforti, Matteo; Degasperis, Antonio; Lombardo, Sara; Onorato, Miguel; Wabnitz, Stefan

2014-07-18

We report and discuss analytical solutions of the vector nonlinear Schrödinger equation that describe rogue waves in the defocusing regime. This family of solutions includes bright-dark and dark-dark rogue waves. The link between modulational instability (MI) and rogue waves is displayed by showing that only a peculiar kind of MI, namely baseband MI, can sustain rogue-wave formation. The existence of vector rogue waves in the defocusing regime is expected to be a crucial progress in explaining extreme waves in a variety of physical scenarios described by multicomponent systems, from oceanography to optics and plasma physics.

Backward bifurcations, turning points and rich dynamics in simple disease models.

PubMed

Zhang, Wenjing; Wahl, Lindi M; Yu, Pei

2016-10-01

In this paper, dynamical systems theory and bifurcation theory are applied to investigate the rich dynamical behaviours observed in three simple disease models. The 2- and 3-dimensional models we investigate have arisen in previous investigations of epidemiology, in-host disease, and autoimmunity. These closely related models display interesting dynamical behaviors including bistability, recurrence, and regular oscillations, each of which has possible clinical or public health implications. In this contribution we elucidate the key role of backward bifurcations in the parameter regimes leading to the behaviors of interest. We demonstrate that backward bifurcations with varied positions of turning points facilitate the appearance of Hopf bifurcations, and the varied dynamical behaviors are then determined by the properties of the Hopf bifurcation(s), including their location and direction. A Maple program developed earlier is implemented to determine the stability of limit cycles bifurcating from the Hopf bifurcation. Numerical simulations are presented to illustrate phenomena of interest such as bistability, recurrence and oscillation. We also discuss the physical motivations for the models and the clinical implications of the resulting dynamics.

Quantifying alteration of river flow regime by large reservoirs in France

NASA Astrophysics Data System (ADS)

Cipriani, Thomas; Sauquet, Eric

2017-04-01

Reservoirs may highly modify river flow regime. Knowing the alterations is of importance to better understand the biological and physical patterns along the river network. However data are not necessary available to carry out an analysis of modifications at a national scale, e.g. due to industrial interests or to lack of measurements. The objective of this study is to quantify the changes in a set of hydrological indices due to large reservoirs in France combining different data sources. The analysis is based on a comparison between influenced discharges (observed discharges) and natural discharges available from: (i) gauging stations available upstream the dam, (ii) regionalization procedures (Sauquet et al., 2008; Sauquet et Catalogne, 2011; Cipriani et al., 2012), or (iii) historical data free from human influence close to the dam location. The impact of large reservoirs is assessed considering different facets of the river flow regime, including flood quantiles, low flow characteristics, quantiles from the flow duration curve and the twelve mean monthly discharges. The departures from the indice representative of natural conditions quantify the effect of the reservoir management on the river flow regime. The analysis is based on 62 study cases. Results show large spread in terms of impact depending on the purposes of the reservoirs and the season of interest. Results also point out inconsistencies in data (water balance between outflow and inflow, downstream of the dam is not warranted) due to uncertainties in mean monthly discharges and to the imperfect knowledge of inflows and outflows. Lastly, we suggest a typology of hydrological alterations based on the purposes of the reservoirs. Cipriani T., Toilliez T., Sauquet E. (2012). Estimating 10 year return period peak flows and flood durations at ungauged locations in France. La Houille Blanche, 4-5: 5-13, doi : 10.1051/lhb/2012024. Sauquet E., Catalogne C. (2011). Comparison of catchment grouping methods for flow duration curve estimation at ungauged sites in France. Hydrology and Earth System Sciences, 15: 2421-2435, doi:10.5194/hess-15-2421-2011. Sauquet E., Gottschalk L., Krasovskaïa I. (2008). Estimating mean monthly runoff at ungauged locations: an application to France. Hydrology Research, 39(5-6): 403-423.

Hydrodynamic equations for electrons in graphene obtained from the maximum entropy principle

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

Barletti, Luigi, E-mail: luigi.barletti@unifi.it

2014-08-15

The maximum entropy principle is applied to the formal derivation of isothermal, Euler-like equations for semiclassical fermions (electrons and holes) in graphene. After proving general mathematical properties of the equations so obtained, their asymptotic form corresponding to significant physical regimes is investigated. In particular, the diffusive regime, the Maxwell-Boltzmann regime (high temperature), the collimation regime and the degenerate gas limit (vanishing temperature) are considered.

Stationary bubble formation and cavity collapse in wedge-shaped hoppers

PubMed Central

Yagisawa, Yui; Then, Hui Zee; Okumura, Ko

2016-01-01

The hourglass is one of the apparatuses familiar to everyone, but reveals intriguing behaviors peculiar to granular materials, and many issues are remained to be explored. In this study, we examined the dynamics of falling sand in a special form of hourglass, i.e., a wedge-shaped hopper, when a suspended granular layer is stabilized to a certain degree. As a result, we found remarkably different dynamic regimes of bubbling and cavity. In the bubbling regime, bubbles of nearly equal size are created in the sand at a regular time interval. In the cavity regime, a cavity grows as sand beads fall before a sudden collapse of the cavity. Bubbling found here is quite visible to a level never discussed in the physics literature and the cavity regime is a novel phase, which is neither continuous, intermittent nor completely blocked phase. We elucidate the physical conditions necessary for the bubbling and cavity regimes and develop simple theories for the regimes to successfully explain the observed phenomena by considering the stability of a suspended granular layer and clogging of granular flow at the outlet of the hopper. The bubbling and cavity regimes could be useful for mixing a fluid with granular materials. PMID:27138747

Photothermoelectric and photovoltaic effects both present in MoS2

PubMed Central

Zhang, Youwei; Li, Hui; Wang, Lu; Wang, Haomin; Xie, Xiaomin; Zhang, Shi-Li; Liu, Ran; Qiu, Zhi-Jun

2015-01-01

As a finite-energy-bandgap alternative to graphene, semiconducting molybdenum disulfide (MoS2) has recently attracted extensive interest for energy and sensor applications. In particular for broad-spectral photodetectors, multilayer MoS2 is more appealing than its monolayer counterpart. However, little is understood regarding the physics underlying the photoresponse of multilayer MoS2. Here, we employ scanning photocurrent microscopy to identify the nature of photocurrent generated in multilayer MoS2 transistors. The generation and transport of photocurrent in multilayer MoS2 are found to differ from those in other low-dimensional materials that only contribute with either photovoltaic effect (PVE) or photothermoelectric effect (PTE). In multilayer MoS2, the PVE at the MoS2-metal interface dominates in the accumulation regime whereas the hot-carrier-assisted PTE prevails in the depletion regime. Besides, the anomalously large Seebeck coefficient observed in multilayer MoS2, which has also been reported by others, is caused by hot photo-excited carriers that are not in thermal equilibrium with the MoS2 lattice. PMID:25605348

Phonon Effects on Charge Transport Through a Two State Molecule

NASA Astrophysics Data System (ADS)

Ulloa, Sergio E.; Yudiarsah, Efta

2008-03-01

We study the effect of local and non-local phonon on the transport properties of a molecule model described by two- electronic states. The local phonon interaction is tackled by means of a Lang Firsov transformation [1,2]. The interaction with non-local phonons (phonon-assisted hopping) is considered perturbatively up to the first nonzero order in the self energy. The presence of different kinds of electron-phonon interaction open new transmission channels. In addition to the polaron shift and replicas due to local phonons, non-local phonons cause the appearance of new satellite states around the initial states. In the weak coupling regime of non-local phonon and electrons, states are shifted an amount proportional to square of the interaction. However, in the strong coupling regime, the non-linear effects emerge and display more interesting features on transport properties. Additional features on transport properties due to new transmission channel are shown to appear at finite temperatures. [1] G. D. Mahan, Many-particle physics, 3rd ed. (Plenum Publishers, New York, 2000). [2] R. Gutierrez et al., Phys. Rev. B. 74, 235105 (2006).

Single electron relativistic clock interferometer

NASA Astrophysics Data System (ADS)

Bushev, P. A.; Cole, J. H.; Sholokhov, D.; Kukharchyk, N.; Zych, M.

2016-09-01

Although time is one of the fundamental notions in physics, it does not have a unique description. In quantum theory time is a parameter ordering the succession of the probability amplitudes of a quantum system, while according to relativity theory each system experiences in general a different proper time, depending on the system's world line, due to time dilation. It is therefore of fundamental interest to test the notion of time in the regime where both quantum and relativistic effects play a role, for example, when different amplitudes of a single quantum clock experience different magnitudes of time dilation. Here we propose a realization of such an experiment with a single electron in a Penning trap. The clock can be implemented in the electronic spin precession and its time dilation then depends on the radial (cyclotron) state of the electron. We show that coherent manipulation and detection of the electron can be achieved already with present day technology. A single electron in a Penning trap is a technologically ready platform where the notion of time can be probed in a hitherto untested regime, where it requires a relativistic as well as quantum description.

Born-Infeld inspired modifications of gravity

NASA Astrophysics Data System (ADS)

Beltrán Jiménez, Jose; Heisenberg, Lavinia; Olmo, Gonzalo J.; Rubiera-Garcia, Diego

2018-01-01

General Relativity has shown an outstanding observational success in the scales where it has been directly tested. However, modifications have been intensively explored in the regimes where it seems either incomplete or signals its own limit of validity. In particular, the breakdown of unitarity near the Planck scale strongly suggests that General Relativity needs to be modified at high energies and quantum gravity effects are expected to be important. This is related to the existence of spacetime singularities when the solutions of General Relativity are extrapolated to regimes where curvatures are large. In this sense, Born-Infeld inspired modifications of gravity have shown an extraordinary ability to regularise the gravitational dynamics, leading to non-singular cosmologies and regular black hole spacetimes in a very robust manner and without resorting to quantum gravity effects. This has boosted the interest in these theories in applications to stellar structure, compact objects, inflationary scenarios, cosmological singularities, and black hole and wormhole physics, among others. We review the motivations, various formulations, and main results achieved within these theories, including their observational viability, and provide an overview of current open problems and future research opportunities.

Weak measurements beyond the Aharonov-Albert-Vaidman formalism

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

Wu Shengjun; Li Yang

2011-05-15

We extend the idea of weak measurements to the general case, provide a complete treatment, and obtain results for both the regime when the preselected and postselected states (PPS) are almost orthogonal and the regime when they are exactly orthogonal. We surprisingly find that for a fixed interaction strength, there may exist a maximum signal amplification and a corresponding optimum overlap of PPS to achieve it. For weak measurements in the orthogonal regime, we find interesting quantities that play the same role that weak values play in the nonorthogonal regime.

The interaction of intense subpicosecond laser pulses with underdense plasmas

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

Coverdale, Christine Ann

1995-05-11

Laser-plasma interactions have been of interest for many years not only from a basic physics standpoint, but also for their relevance to numerous applications. Advances in laser technology in recent years have resulted in compact laser systems capable of generating (psec), 10 16 W/cm 2 laser pulses. These lasers have provided a new regime in which to study laser-plasma interactions, a regime characterized by L plasma ≥ 2L Rayleigh > cτ. The goal of this dissertation is to experimentally characterize the interaction of a short pulse, high intensity laser with an underdense plasma (n o ≤ 0.05n cr). Specifically, themore » parametric instability known as stimulated Raman scatter (SRS) is investigated to determine its behavior when driven by a short, intense laser pulse. Both the forward Raman scatter instability and backscattered Raman instability are studied. The coupled partial differential equations which describe the growth of SRS are reviewed and solved for typical experimental laser and plasma parameters. This solution shows the growth of the waves (electron plasma and scattered light) generated via stimulated Raman scatter. The dispersion relation is also derived and solved for experimentally accessible parameters. The solution of the dispersion relation is used to predict where (in k-space) and at what frequency (in ω-space) the instability will grow. Both the nonrelativistic and relativistic regimes of the instability are considered.« less

Experimental Observations on a Low Strain Counter-Flow Diffusion Flame: Flow and Bouyancy Effects

NASA Technical Reports Server (NTRS)

Sutula, J. A.; Torero, J. L.; Ezekoye, O. A.

1999-01-01

Diffusion flames are of great interest in fire safety and many industrial processes. The counter-flow configuration provides a constant strain flow, and therefore is ideal to study the structure of diffusion flames. Most studies have concentrated on the high velocity, high strain limit, since buoyantly induced instabilities will disintegrate the planar flame as the velocity decreases. Only recently, experimental studies in microgravity conditions have begun to explore the low strain regimes. Numerical work has shown the coupling between gas phase reaction rates, soot reaction rates, and radiation. For these programs, size, geometry and experimental conditions have been chosen to keep the flame unaffected by the physical boundaries. When the physical boundaries can not be considered infinitely far from the reaction zone discrepancies arise. A computational study that includes boundary effects and accounts for the deviations occurring when the major potential flow assumptions are relaxed was presented by Borlik et al. This development properly incorporates all heat loss terms and shows the possibility of extinction in the low strain regime. A major constraint of studying the low strain regime is buoyancy. Buoyant instabilities have been shown to have a significant effect on the nature of reactants and heat transport, and can introduce instabilities on the flow that result in phenomena such as flickering or fingering. The counter-flow configuration has been shown to provide a flame with no symmetry disrupting instabilities for inlet velocities greater than 50 mm/s. As the velocity approaches this limit, the characteristic length of the experiment has to be reduced to a few millimetres so as to keep the Rayleigh number (Ra(sub L) = (Beta)(g(sub 0))(L(exp 3) del T)/(alpha(v))) below 2000. In this work, a rectangular counter-flow burner was used to study a two-dimensional counter-flow diffusion flame. Flow visualisation and Particle Image Velocimetry served to describe the nature of the stagnation plane for strain rates smaller than 100 (1/s). These experiments were conducted with a non-reacting flow. Video images of a propane air diffusion flame were used to describe the behaviour of a diffusion flame in this regime. Flame geometry and pulsation frequency are described.

Understanding Femtosecond-Pulse Laser Damage through Fundamental Physics Simulations

NASA Astrophysics Data System (ADS)

Mitchell, Robert A., III

It did not take long after the invention of the laser for the field of laser damage to appear. For several decades researchers have been studying how lasers damage materials, both for the basic scientific understanding of highly nonequilibrium processes as well as for industrial applications. Femtosecond pulse lasers create little collateral damage and a readily reproducible damage pattern. They are easily tailored to desired specifications and are particularly powerful and versatile tools, contributing even more industrial interest in the field. As with most long-standing fields of research, many theoretical tools have been developed to model the laser damage process, covering a wide range of complexities and regimes of applicability. However, most of the modeling methods developed are either too limited in spatial extent to model the full morphology of the damage crater, or incorporate only a small subset of the important physics and require numerous fitting parameters and assumptions in order to match values interpolated from experimental data. Demonstrated in this work is the first simulation method capable of fundamentally modeling the full laser damage process, from the laser interaction all the way through to the resolidification of the target, on a large enough scale that can capture the full morphology of the laser damage crater so as to be compared directly to experimental measurements instead of extrapolated values, and all without any fitting parameters. The design, implementation, and testing of this simulation technique, based on a modified version of the particle-in-cell (PIC) method, is presented. For a 60 fs, 1 mum wavelength laser pulse with fluences of 0.5 J/cm 2, 1.0 J/cm2, and 2.0 J/cm2 the resulting laser damage craters in copper are shown and, using the same technique applied to experimental crater morphologies, a laser damage fluence threshold is calculated of 0.15 J/cm2, consistent with current experiments performed under conditions similar to those in the simulation. Lastly, this method is applied to the phenomenon known as LIPSS, or Laser-Induced Periodic Surface Structures; a problem of fundamental importance that is also of great interest for industrial applications. While LIPSS have been observed for decades in laser damage experiments, the exact physical mechanisms leading to the periodic corrugation on the surface of a target have been highly debated, with no general consensus. Applying this technique to a situation known to create LIPSS in a single shot, the generation of this periodicity is observed, the wavelength of the damage is consistent with experimental measures and, due to the fundamental nature of the simulation method, the physical mechanisms behind LIPSS are examined. The mechanism behind LIPSS formation in the studied regime is shown to be the formation of and interference with an evanescent surface electromagnetic wave known as a surface plasmon-polariton. This shows that not only can this simulation technique model a basic laser damage situation, but it is also flexible and powerful enough to be applied to complex areas of research, allowing for new physical insight in regimes that are difficult to probe experimentally.

MOND as a regime of quantum gravity

NASA Astrophysics Data System (ADS)

Smolin, Lee

2017-10-01

We propose that there is a regime of quantum gravity phenomena, for the case that the cosmological constant is small and positive, which concerns physics at temperatures below the de Sitter temperature, or length scales larger than the horizon. We observe that the standard form of the equivalence principle does not apply in this regime; we consider instead that a weakened form of the equivalence principle might hold in which the ratio of gravitational to inertial mass is a function of environmental parameters. We consider possible principles to determine that function. These lead to behavior that, in the limit of ℏ→0 and c →∞ , reproduces the modifications of Newtonian dynamics first proposed by Milgrom. Thus modified newtonian dynamics is elucidated as coding the physics of a novel regime of quantum gravity phenomena. We propose also an effective description of this regime in terms of a bimetric theory, valid in the approximation where the metric is static. This predicts a new effect, which modifies gravity for radial motions.

Fundamental and functional aspects of mesoscopic architectures with examples in physics, cell biology, and chemistry.

PubMed

Kalay, Ziya

2011-08-01

How small can a macroscopic object be made without losing its intended function? Obviously, the smallest possible size is determined by the size of an atom, but it is not so obvious how many atoms are required to assemble an object so small, and yet that performs the same function as its macroscopic counterpart. In this review, we are concerned with objects of intermediate nature, lying between the microscopic and the macroscopic world. In physics and chemistry literature, this regime in-between is often called mesoscopic, and is known to bear interesting and counterintuitive features. After a brief introduction to the concept of mesoscopic systems from the perspective of physics, we discuss the functional aspects of mesoscopic architectures in cell biology, and supramolecular chemistry through many examples from the literature. We argue that the biochemistry of the cell is largely regulated by mesoscopic functional architectures; however, the significance of mesoscopic phenomena seems to be quite underappreciated in biological sciences. With this motivation, one of our main purposes here is to emphasize the critical role that mesoscopic structures play in cell biology and biochemistry.

Semiparametric Estimation of the Impacts of Longitudinal Interventions on Adolescent Obesity using Targeted Maximum-Likelihood: Accessible Estimation with the ltmle Package

PubMed Central

Decker, Anna L.; Hubbard, Alan; Crespi, Catherine M.; Seto, Edmund Y.W.; Wang, May C.

2015-01-01

While child and adolescent obesity is a serious public health concern, few studies have utilized parameters based on the causal inference literature to examine the potential impacts of early intervention. The purpose of this analysis was to estimate the causal effects of early interventions to improve physical activity and diet during adolescence on body mass index (BMI), a measure of adiposity, using improved techniques. The most widespread statistical method in studies of child and adolescent obesity is multi-variable regression, with the parameter of interest being the coefficient on the variable of interest. This approach does not appropriately adjust for time-dependent confounding, and the modeling assumptions may not always be met. An alternative parameter to estimate is one motivated by the causal inference literature, which can be interpreted as the mean change in the outcome under interventions to set the exposure of interest. The underlying data-generating distribution, upon which the estimator is based, can be estimated via a parametric or semi-parametric approach. Using data from the National Heart, Lung, and Blood Institute Growth and Health Study, a 10-year prospective cohort study of adolescent girls, we estimated the longitudinal impact of physical activity and diet interventions on 10-year BMI z-scores via a parameter motivated by the causal inference literature, using both parametric and semi-parametric estimation approaches. The parameters of interest were estimated with a recently released R package, ltmle, for estimating means based upon general longitudinal treatment regimes. We found that early, sustained intervention on total calories had a greater impact than a physical activity intervention or non-sustained interventions. Multivariable linear regression yielded inflated effect estimates compared to estimates based on targeted maximum-likelihood estimation and data-adaptive super learning. Our analysis demonstrates that sophisticated, optimal semiparametric estimation of longitudinal treatment-specific means via ltmle provides an incredibly powerful, yet easy-to-use tool, removing impediments for putting theory into practice. PMID:26046009

The spinning Kerr-black-hole-mirror bomb: A lower bound on the radius of the reflecting mirror

NASA Astrophysics Data System (ADS)

Hod, Shahar

2016-10-01

The intriguing superradiant amplification phenomenon allows an orbiting scalar field to extract rotational energy from a spinning Kerr black hole. Interestingly, the energy extraction rate can grow exponentially in time if the black-hole-field system is placed inside a reflecting mirror which prevents the field from radiating its energy to infinity. This composed Kerr-black-hole-scalar-field-mirror system, first designed by Press and Teukolsky, has attracted the attention of physicists over the last four decades. Previous numerical studies of this spinning black-hole bomb have revealed the interesting fact that the superradiant instability shuts down if the reflecting mirror is placed too close to the black-hole horizon. In the present study we use analytical techniques to explore the superradiant instability regime of this composed Kerr-black-hole-linearized-scalar-field-mirror system. In particular, it is proved that the lower bound rm/r+ >1/2 (√{ 1 +8M/r- } - 1) provides a necessary condition for the development of the exponentially growing superradiant instabilities in this composed physical system, where rm is the radius of the confining mirror and r± are the horizon radii of the spinning Kerr black hole. We further show that, in the linearized regime, this analytically derived lower bound on the radius of the confining mirror agrees with direct numerical computations of the superradiant instability spectrum which characterizes the spinning black-hole-mirror bomb.

Multi-regime transport model for leaching behavior of heterogeneous porous materials.

PubMed

Sanchez, F; Massry, I W; Eighmy, T; Kosson, D S

2003-01-01

Utilization of secondary materials in civil engineering applications (e.g. as substitutes for natural aggregates or binder constituents) requires assessment of the physical and environment properties of the product. Environmental assessment often necessitates evaluation of the potential for constituent release through leaching. Currently most leaching models used to estimate long-term field performance assume that the species of concern is uniformly dispersed in a homogeneous porous material. However, waste materials are often comprised of distinct components such as coarse or fine aggregates in a cement concrete or waste encapsulated in a stabilized matrix. The specific objectives of the research presented here were to (1) develop a one-dimensional, multi-regime transport model (i.e. MRT model) to describe the release of species from heterogeneous porous materials and, (2) evaluate simple limit cases using the model for species when release is not dependent on pH. Two different idealized model systems were considered: (1) a porous material contaminated with the species of interest and containing inert aggregates and, (2) a porous material containing the contaminant of interest only in the aggregates. The effect of three factors on constituent release were examined: (1) volume fraction of material occupied by the aggregates compared to a homogeneous porous material, (2) aggregate size and, (3) differences in mass transfer rates between the binder and the aggregates. Simulation results confirmed that assuming homogeneous materials to evaluate the release of contaminants from porous waste materials may result in erroneous long-term field performance assessment.

Stability and dynamics of the edge pedestal in the low collisionality regime: physics mechanisms for steady-state ELM-free operation

NASA Astrophysics Data System (ADS)

Snyder, P. B.; Burrell, K. H.; Wilson, H. R.; Chu, M. S.; Fenstermacher, M. E.; Leonard, A. W.; Moyer, R. A.; Osborne, T. H.; Umansky, M.; West, W. P.; Xu, X. Q.

2007-08-01

Understanding the physics of the edge pedestal and edge localized modes (ELMs) is of great importance for ITER and the optimization of the tokamak concept. The peeling-ballooning model has quantitatively explained many observations, including ELM onset and pedestal constraints, in the standard H-mode regime. The ELITE code has been developed to efficiently evaluate peeling-ballooning stability for comparison with observation and predictions for future devices. We briefly review recent progress in the peeling-ballooning model, including experimental validation of ELM onset and pedestal height predictions, and nonlinear 3D simulations of ELM dynamics, which together lead to an emerging understanding of the physics of the onset and dynamics of ELMs in the standard intermediate to high collisionality regime. We also discuss new studies of the apparent power dependence of the pedestal, and studies of the impact of sheared toroidal flow. Recently, highly promising low collisionality regimes without ELMs have been discovered, including the quiescent H-mode (QH) and resonant magnetic perturbation (RMP) regimes. We present recent observations from the DIII-D tokamak of the density, shape and rotation dependence of QH discharges, and studies of the peeling-ballooning stability in this regime. We propose a model of the QH-mode in which the observed edge harmonic oscillation (EHO) is a saturated kink/peeling mode which is destabilized by current and rotation, and drives significant transport, allowing a near steady-state edge plasma. The model quantitatively predicts the observed density dependence and qualitatively predicts observed mode structure, rotation dependence and outer gap dependence. Low density RMP discharges are found to operate in a similar regime, but with the EHO replaced by an applied magnetic perturbation.

Magnetorotational dynamo chimeras. The missing link to turbulent accretion disk dynamo models?

NASA Astrophysics Data System (ADS)

Riols, A.; Rincon, F.; Cossu, C.; Lesur, G.; Ogilvie, G. I.; Longaretti, P.-Y.

2017-02-01

In Keplerian accretion disks, turbulence and magnetic fields may be jointly excited through a subcritical dynamo mechanisminvolving magnetorotational instability (MRI). This dynamo may notably contribute to explaining the time-variability of various accreting systems, as high-resolution simulations of MRI dynamo turbulence exhibit statistical self-organization into large-scale cyclic dynamics. However, understanding the physics underlying these statistical states and assessing their exact astrophysical relevance is theoretically challenging. The study of simple periodic nonlinear MRI dynamo solutions has recently proven useful in this respect, and has highlighted the role of turbulent magnetic diffusion in the seeming impossibility of a dynamo at low magnetic Prandtl number (Pm), a common regime in disks. Arguably though, these simple laminar structures may not be fully representative of the complex, statistically self-organized states expected in astrophysical regimes. Here, we aim at closing this seeming discrepancy by reporting the numerical discovery of exactly periodic, yet semi-statistical "chimeral MRI dynamo states" which are the organized outcome of a succession of MRI-unstable, non-axisymmetric dynamical stages of different forms and amplitudes. Interestingly, these states, while reminiscent of the statistical complexity of turbulent simulations, involve the same physical principles as simpler laminar cycles, and their analysis further confirms the theory that subcritical turbulent magnetic diffusion impedes the sustainment of an MRI dynamo at low Pm. Overall, chimera dynamo cycles therefore offer an unprecedented dual physical and statistical perspective on dynamos in rotating shear flows, which may prove useful in devising more accurate, yet intuitive mean-field models of time-dependent turbulent disk dynamos. Movies associated to Fig. 1 are available at http://www.aanda.org

The effect of allometric scaling in coral thermal microenvironments

PubMed Central

Ong, Robert H.; Kaandorp, Jaap A.; Mullins, Benjamin J.; Caley, M. Julian

2017-01-01

A long-standing interest in marine science is in the degree to which environmental conditions of flow and irradiance, combined with optical, thermal and morphological characteristics of individual coral colonies, affects their sensitivity of thermal microenvironments and susceptibility to stress-induced bleaching within and/or among colonies. The physiological processes in Scleractinian corals tend to scale allometrically as a result of physical and geometric constraints on body size and shape. There is a direct relationship between scaling to thermal stress, thus, the relationship between allometric scaling and rates of heating and cooling in coral microenvironments is a subject of great interest. The primary aim of this study was to develop an approximation that predicts coral thermal microenvironments as a function of colony morphology (shape and size), light or irradiance, and flow velocity or regime. To do so, we provided intuitive interpretation of their energy budgets for both massive and branching colonies, and then quantified the heat-size exponent (b*) and allometric constant (m) using logarithmic linear regression. The data demonstrated a positive relationship between thermal rates and changes in irradiance, A/V ratio, and flow, with an interaction where turbulent regime had less influence on overall stress which may serve to ameliorate the effects of temperature rise compared to the laminar regime. These findings indicated that smaller corals have disproportionately higher stress, however they can reach thermal equilibrium quicker. Moreover, excellent agreements between the predicted and simulated microscale temperature values with no significant bias were observed for both the massive and branching colonies, indicating that the numerical approximation should be within the accuracy with which they could be measured. This study may assist in estimating the coral microscale temperature under known conditions of water flow and irradiance, in particular when examining the intra- and inter-colony variability found during periods of bleaching conditions. PMID:29023468

Enhanced Verification Test Suite for Physics Simulation Codes

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

Kamm, J R; Brock, J S; Brandon, S T

2008-10-10

This document discusses problems with which to augment, in quantity and in quality, the existing tri-laboratory suite of verification problems used by Los Alamos National Laboratory (LANL), Lawrence Livermore National Laboratory (LLNL), and Sandia National Laboratories (SNL). The purpose of verification analysis is demonstrate whether the numerical results of the discretization algorithms in physics and engineering simulation codes provide correct solutions of the corresponding continuum equations. The key points of this document are: (1) Verification deals with mathematical correctness of the numerical algorithms in a code, while validation deals with physical correctness of a simulation in a regime of interest.more » This document is about verification. (2) The current seven-problem Tri-Laboratory Verification Test Suite, which has been used for approximately five years at the DOE WP laboratories, is limited. (3) Both the methodology for and technology used in verification analysis have evolved and been improved since the original test suite was proposed. (4) The proposed test problems are in three basic areas: (a) Hydrodynamics; (b) Transport processes; and (c) Dynamic strength-of-materials. (5) For several of the proposed problems we provide a 'strong sense verification benchmark', consisting of (i) a clear mathematical statement of the problem with sufficient information to run a computer simulation, (ii) an explanation of how the code result and benchmark solution are to be evaluated, and (iii) a description of the acceptance criterion for simulation code results. (6) It is proposed that the set of verification test problems with which any particular code be evaluated include some of the problems described in this document. Analysis of the proposed verification test problems constitutes part of a necessary--but not sufficient--step that builds confidence in physics and engineering simulation codes. More complicated test cases, including physics models of greater sophistication or other physics regimes (e.g., energetic material response, magneto-hydrodynamics), would represent a scientifically desirable complement to the fundamental test cases discussed in this report. The authors believe that this document can be used to enhance the verification analyses undertaken at the DOE WP Laboratories and, thus, to improve the quality, credibility, and usefulness of the simulation codes that are analyzed with these problems.« less

Physical aspects of computing the flow of a viscous fluid

NASA Technical Reports Server (NTRS)

Mehta, U. B.

1984-01-01

One of the main themes in fluid dynamics at present and in the future is going to be computational fluid dynamics with the primary focus on the determination of drag, flow separation, vortex flows, and unsteady flows. A computation of the flow of a viscous fluid requires an understanding and consideration of the physical aspects of the flow. This is done by identifying the flow regimes and the scales of fluid motion, and the sources of vorticity. Discussions of flow regimes deal with conditions of incompressibility, transitional and turbulent flows, Navier-Stokes and non-Navier-Stokes regimes, shock waves, and strain fields. Discussions of the scales of fluid motion consider transitional and turbulent flows, thin- and slender-shear layers, triple- and four-deck regions, viscous-inviscid interactions, shock waves, strain rates, and temporal scales. In addition, the significance and generation of vorticity are discussed. These physical aspects mainly guide computations of the flow of a viscous fluid.

Status of a minimal composite Higgs theory

NASA Astrophysics Data System (ADS)

Fodor, Zoltan; Holland, Kieran; Kuti, Julius; Mondal, Santanu; Nogradi, Daniel; Wong, Chik Him

2017-12-01

We analyze three sets of gauge ensembles in our extended physics program of a particularly important BSM gauge theory with a fermion doublet in the two-index symmetric (sextet) representation of the SU(3) BSM color gauge group. Our investigations include chiral symmetry breaking (χSB) in the p-regime and 𝜖-regime, the mass of the composite 0++ scalar, resonance spectroscopy, new physics from gauge anomaly constraints, and the role of stable sextet BSM baryons with Electroweak interactions in dark matter searches. Important new goals include studies of the 0++ scalar entangled with Goldstone dynamics in the p-regime and the 𝜖-regime, the resonance spectrum with particular attention to emerging LHC signals, like recent hints for diphoton excess at 750 GeV or diboson anomalies in the 2 TeV range. All results reported here are preliminary before journal publication including some post-conference material for the discussion.

Systematic study of the physical origin of ferromagnetism in CeO2 -δ nanoparticles

NASA Astrophysics Data System (ADS)

Ribeiro, A. N.; Ferreira, N. S.

2017-04-01

We have carried out a Schrieffer-Wolff transformation on a general tight-binding Hamiltonian and obtained a 4 f -one-band effective Hubbard Hamiltonian to study the physical origin of ferromagnetism in CeO2 -δ nanoparticle systems. For a low temperature regime and low concentrations of oxygen vacancies, isolated vacancies have previously been showed to form on the {100 } and {110 } surfaces and our studies indicate these will be in singlet and triplet states, respectively. This is sustained by a superexchange interaction between the 4 f electrons of the two cerium atoms, which are the nearest neighbors of the vacancy, and ferromagnetism and antiferromagnetism can coexist. Moreover, increasing the vacancy concentration we found that pairs of vacancies, which have been previously shown to form on the {111 } surfaces, produce Nagaoka ferromagnetism and isolated vacancies in the bulk produce an antiferromagnetic sign. Furthermore, further oxygen vacancy increases are previously known to favor the formation of oxygen vacancy clusters. In this case, our results showed a weakening of the magnetic correlations with respect to temperature. Thus, at a fixed temperature, the magnetic moment is reduced when the concentration of vacancies is increased, which is in agreement with experimental results reported in the literature. Interestingly, at a room-temperature regime, the antiferromagnetic order is destroyed and only the ferromagnetic couplings, produced mainly by isolated vacancies on the {110 } surfaces, survive. Finally, as temperature is increased further, the paramagnetic behavior of 4 f electrons dominates.

Study and modeling of finite rate chemistry effects in turbulent non-premixed flames

NASA Technical Reports Server (NTRS)

Vervisch, Luc

1993-01-01

The development of numerical models that reflect some of the most important features of turbulent reacting flows requires information about the behavior of key quantities in well defined combustion regimes. In turbulent flames, the coupling between turbulent and chemical processes is so strong that it is extremely difficult to isolate the role played by one individual physical phenomenon. Direct numerical simulation (hereafter DNS) allows us to study in detail the turbulence-chemistry interaction in some restricted but completely defined situations. Globally, non-premixed flames are controlled by two limiting regimes: the fast chemistry case, where the turbulent flame can be pictured as a random distribution of local chemical equilibrium problems; and the slow chemistry case, where the chemistry integrates in time the turbulent fluctuations. The Damkoehler number, ratio of a mechanical time scale to chemical time scale, is used to distinguish between these regimes. Today most of the industrial computer codes are able to perform predictions in the hypothesis of local equilibrium chemistry using a presumed shape for the probability density function (pdt) of the conserved scalar. However, the finite rate chemistry situation is of great interest because industrial burners usually generate regimes in which, at some points, the flame is undergoing local extinction or at least non-equilibrium situations. Moreover, this variety of situations strongly influences the production of pollutants. To quantify finite rate chemistry effect, the interaction between a non-premixed flame and a free decaying turbulence is studied using DNS. The attention is focused on the dynamic of extinction, and an attempt is made to quantify the effect of the reaction on the small scale mixing process. The unequal diffusivity effect is also addressed. Finally, a simple turbulent combustion model based on the DNS observations and tractable in real flow configurations is proposed.

Radiation effects on ETFE polymer exposed to glow discharge

NASA Astrophysics Data System (ADS)

Minamisawa, Renato Amaral; Abidzina, Volha; de Almeida, Adelaide; Budak, Satilmis; Tereshko, I.; Elkin, I.; Ila, Daryush

2007-08-01

The polymer ethylenetetrafluoroethylene (ETFE) is composed of alternating ethylene and tetrafluoroethylene segments. Because it has applications in areas such as medical physics and industrial coatings, there is a great interest in surface modification studies of ETFE polymer. When this material is exposed to ionizing radiation it suffers damage that depends on the type, energy and intensity of the irradiation. In order to determine the radiation damage mechanism from exposure to low voltage plasma, ETFE films were exposed to residual gas plasma in glow discharge regime to a fluence of 2 × 1017 ions/cm2. Irradiated films were analyzed with optical absorption photospectrometry, Fourier transform infrared (FTIR) and Raman spectroscopy to determine the chemical nature of the structural changes caused by low energy glow discharge.

MODELING PHYSICAL HABITAT PARAMETERS

EPA Science Inventory

Salmonid populations can be affected by alterations in stream physical habitat. Fish productivity is determined by the stream's physical habitat structure ( channel form, substrate distribution, riparian vegetation), water quality, flow regime and inputs from the watershed (sedim...

Real-time full-field characterization of transient dissipative soliton dynamics in a mode-locked laser

NASA Astrophysics Data System (ADS)

Ryczkowski, P.; Närhi, M.; Billet, C.; Merolla, J.-M.; Genty, G.; Dudley, J. M.

2018-04-01

Dissipative solitons are remarkably localized states of a physical system that arise from the dynamical balance between nonlinearity, dispersion and environmental energy exchange. They are the most universal form of soliton that can exist, and are seen in far-from-equilibrium systems in many fields, including chemistry, biology and physics. There has been particular interest in studying their properties in mode-locked lasers, but experiments have been limited by the inability to track the dynamical soliton evolution in real time. Here, we use simultaneous dispersive Fourier transform and time-lens measurements to completely characterize the spectral and temporal evolution of ultrashort dissipative solitons as their dynamics pass through a transient unstable regime with complex break-up and collisions before stabilization. Further insight is obtained from reconstruction of the soliton amplitude and phase and calculation of the corresponding complex-valued eigenvalue spectrum. These findings show how real-time measurements provide new insights into ultrafast transient dynamics in optics.

Relativistic frequency upshift to the extreme ultraviolet regime using self-induced oscillatory flying mirrors

PubMed Central

Kim, I Jong; Pae, Ki Hong; Kim, Chul Min; Kim, Hyung Taek; Yun, Hyeok; Yun, Sang Jae; Sung, Jae Hee; Lee, Seong Ku; Yoon, Jin Woo; Yu, Tae Jun; Jeong, Tae Moon; Nam, Chang Hee; Lee, Jongmin

2012-01-01

Coherent short-wavelength radiation from laser–plasma interactions is of increasing interest in disciplines including ultrafast biomolecular imaging and attosecond physics. Using solid targets instead of atomic gases could enable the generation of coherent extreme ultraviolet radiation with higher energy and more energetic photons. Here we present the generation of extreme ultraviolet radiation through coherent high-harmonic generation from self-induced oscillatory flying mirrors—a new-generation mechanism established in a long underdense plasma on a solid target. Using a 30-fs, 100-TW Ti:sapphire laser, we obtain wavelengths as short as 4.9 nm for an optimized level of amplified spontaneous emission. Particle-in-cell simulations show that oscillatory flying electron nanosheets form in a long underdense plasma, and suggest that the high-harmonic generation is caused by reflection of the laser pulse from electron nanosheets. We expect this extreme ultraviolet radiation to be valuable in realizing a compact X-ray instrument for research in biomolecular imaging and attosecond physics. PMID:23187631

Recent theoretical advances on superradiant phase transitions

NASA Astrophysics Data System (ADS)

Baksic, Alexandre; Nataf, Pierre; Ciuti, Cristiano

2013-03-01

The Dicke model describing a single-mode boson field coupled to two-level systems is an important paradigm in quantum optics. In particular, the physics of ``superradiant phase transitions'' in the ultrastrong coupling regime is the subject of a vigorous research activity in both cavity and circuit QED. Recently, we explored the rich physics of two interesting generalizations of the Dicke model: (i) A model describing the coupling of a boson mode to two independent chains A and B of two-level systems, where chain A is coupled to one quadrature of the boson field and chain B to the orthogonal quadrature. This original model leads to a quantum phase transition with a double symmetry breaking and a fourfold ground state degeneracy. (ii) A generalized Dicke model with three-level systems including the diamagnetic term. In contrast to the case of two-level atoms for which no-go theorems exist, in the case of three-level system we prove that the Thomas-Reich-Kuhn sum rule does not always prevent a superradiant phase transition.

Deciphering Equatorial Pacific Deep Sea Sediment Transport Regimes by Core-Log-Seismic Integration

NASA Astrophysics Data System (ADS)

Ortiz, E.; Tominaga, M.; Marcantonio, F.

2017-12-01

Investigating deep-sea sediment transportation and deposition regimes is a key to accurately understand implications from geological information recorded by pelagic sediments, e.g. climate signals. However, except for physical oceanographic particle trap experiments, geochemical analyses of in situsediments, and theoretical modeling of the relation between the bottom currents and sediment particle flux, it has remained a challenging task to document the movement of deep sea sediments, that takes place over time. We utilized high-resolution, multichannel reflection seismic data from the eastern equatorial Pacific region with drilling and logging results from two Integrated Ocean Drilling Program (IODP) sites, the Pacific Equatorial Age Transect (PEAT) 7 (Site U1337) and 8 (Site U1338), to characterize sediment transportation regimes on 18-24 Ma oceanic crust. Site U1337, constructed by a series of distinct abyssal hills and abyssal basins; Site U1338, located 570 km SE from Site U1337 site and constructed by a series of ridges, seamounts, and abyssal hills. These sites are of particular interest due to their proximity to the equatorial productivity zone, areas with high sedimentation rates and preservation of carbonate-bearing sediment that provide invaluable insights on equatorial Pacific ecosystems and carbon cycle. We integrate downhole geophysical logging data as well as geochemistry and physical properties measurements on recovered cores from IODP Sites U1337 and U1338 to comprehensively examine the mobility of deep-sea sediments and sediment diagenesis over times in a quasi-3D manner. We also examine 1100 km of high resolution underway seismic surveys from site survey lines in between PEAT 7 and 8 in order to investigate changes in sediment transportation between both sites. Integrating detailed seismic interpretations, high resolution core data, and 230Th flux measurements we aim to create a detailed chronological sedimentation and sediment diagenesis history of this area.

Regimes of turbulence without an energy cascade

PubMed Central

Barenghi, C. F.; Sergeev, Y. A.; Baggaley, A. W.

2016-01-01

Experiments and numerical simulations of turbulent 4He and 3He-B have established that, at hydrodynamic length scales larger than the average distance between quantum vortices, the energy spectrum obeys the same 5/3 Kolmogorov law which is observed in the homogeneous isotropic turbulence of ordinary fluids. The importance of the 5/3 law is that it points to the existence of a Richardson energy cascade from large eddies to small eddies. However, there is also evidence of quantum turbulent regimes without Kolmogorov scaling. This raises the important questions of why, in such regimes, the Kolmogorov spectrum fails to form, what is the physical nature of turbulence without energy cascade, and whether hydrodynamical models can account for the unusual behaviour of turbulent superfluid helium. In this work we describe simple physical mechanisms which prevent the formation of Kolmogorov scaling in the thermal counterflow, and analyze the conditions necessary for emergence of quasiclassical regime in quantum turbulence generated by injection of vortex rings at low temperatures. Our models justify the hydrodynamical description of quantum turbulence and shed light into an unexpected regime of vortex dynamics. PMID:27761005

Foucault and the Architecture of Surveillance: Creating Regimes of Power in Schools, Shrines, and Society

ERIC Educational Resources Information Center

Piro, Joseph M.

2008-01-01

Michel Foucault's critical studies concerning regimes of power are of special interest when applied to architecture. In particular, he warned of the hazards of building surveillance into architectural structures for the purpose of monitoring people and took as his historical exemplar English philosopher Jeremy Bentham's "Panopticon," a structure…

Forest Conservation, Value Conflict, and Interest Formation in a Honduran National Park

ERIC Educational Resources Information Center

Pfeffer, Max J.; Schelhas, John W.; Day, Leyla Ann

2001-01-01

We argue that attempts to superimpose park regulatory regimes on existing land uses in the tropics represent conflicts between alternative cultural models of natural resource management. The results of such conflicts are unique regulatory regimes emerging from distinctive processes that redefine the terms and limits of natural resource use. In…

Identifying optimal dosage regimes under safety constraints: An application to long term opioid treatment of chronic pain.

PubMed

Laber, Eric B; Wu, Fan; Munera, Catherine; Lipkovich, Ilya; Colucci, Salvatore; Ripa, Steve

2018-04-30

There is growing interest and investment in precision medicine as a means to provide the best possible health care. A treatment regime formalizes precision medicine as a sequence of decision rules, one per clinical intervention period, that specify if, when and how current treatment should be adjusted in response to a patient's evolving health status. It is standard to define a regime as optimal if, when applied to a population of interest, it maximizes the mean of some desirable clinical outcome, such as efficacy. However, in many clinical settings, a high-quality treatment regime must balance multiple competing outcomes; eg, when a high dose is associated with substantial symptom reduction but a greater risk of an adverse event. We consider the problem of estimating the most efficacious treatment regime subject to constraints on the risk of adverse events. We combine nonparametric Q-learning with policy-search to estimate a high-quality yet parsimonious treatment regime. This estimator applies to both observational and randomized data, as well as settings with variable, outcome-dependent follow-up, mixed treatment types, and multiple time points. This work is motivated by and framed in the context of dosing for chronic pain; however, the proposed framework can be applied generally to estimate a treatment regime which maximizes the mean of one primary outcome subject to constraints on one or more secondary outcomes. We illustrate the proposed method using data pooled from 5 open-label flexible dosing clinical trials for chronic pain. © 2018 The Authors. Statistics in Medicine Published by John Wiley & Sons, Ltd.

Coronal loop seismology using damping of standing kink oscillations by mode coupling. II. additional physical effects and Bayesian analysis

NASA Astrophysics Data System (ADS)

Pascoe, D. J.; Anfinogentov, S.; Nisticò, G.; Goddard, C. R.; Nakariakov, V. M.

2017-04-01

Context. The strong damping of kink oscillations of coronal loops can be explained by mode coupling. The damping envelope depends on the transverse density profile of the loop. Observational measurements of the damping envelope have been used to determine the transverse loop structure which is important for understanding other physical processes such as heating. Aims: The general damping envelope describing the mode coupling of kink waves consists of a Gaussian damping regime followed by an exponential damping regime. Recent observational detection of these damping regimes has been employed as a seismological tool. We extend the description of the damping behaviour to account for additional physical effects, namely a time-dependent period of oscillation, the presence of additional longitudinal harmonics, and the decayless regime of standing kink oscillations. Methods: We examine four examples of standing kink oscillations observed by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). We use forward modelling of the loop position and investigate the dependence on the model parameters using Bayesian inference and Markov chain Monte Carlo (MCMC) sampling. Results: Our improvements to the physical model combined with the use of Bayesian inference and MCMC produce improved estimates of model parameters and their uncertainties. Calculation of the Bayes factor also allows us to compare the suitability of different physical models. We also use a new method based on spline interpolation of the zeroes of the oscillation to accurately describe the background trend of the oscillating loop. Conclusions: This powerful and robust method allows for accurate seismology of coronal loops, in particular the transverse density profile, and potentially reveals additional physical effects.

Linear tearing mode stability equations for a low collisionality toroidal plasma

NASA Astrophysics Data System (ADS)

Connor, J. W.; Hastie, R. J.; Helander, P.

2009-01-01

Tearing mode stability is normally analysed using MHD or two-fluid Braginskii plasma models. However for present, or future, large hot tokamaks like JET or ITER the collisionality is such as to place them in the banana regime. Here we develop a linear stability theory for the resonant layer physics appropriate to such a regime. The outcome is a set of 'fluid' equations whose coefficients encapsulate all neoclassical physics: the neoclassical Ohm's law, enhanced ion inertia, cross-field transport of particles, heat and momentum all play a role. While earlier treatments have also addressed this type of neoclassical physics we differ in incorporating the more physically relevant 'semi-collisional fluid' regime previously considered in cylindrical geometry; semi-collisional effects tend to screen the resonant surface from the perturbed magnetic field, preventing reconnection. Furthermore we also include thermal physics, which may modify the results. While this electron description is of wide relevance and validity, the fluid treatment of the ions requires the ion banana orbit width to be less than the semi-collisional electron layer. This limits the application of the present theory to low magnetic shear—however, this is highly relevant to the sawtooth instability—or to colder ions. The outcome of the calculation is a set of one-dimensional radial differential equations of rather high order. However, various simplifications that reduce the computational task of solving these are discussed. In the collisional regime, when the set reduces to a single second-order differential equation, the theory extends previous work by Hahm et al (1988 Phys. Fluids 31 3709) to include diamagnetic-type effects arising from plasma gradients, both in Ohm's law and the ion inertia term of the vorticity equation. The more relevant semi-collisional regime pertaining to JET or ITER, is described by a pair of second-order differential equations, extending the cylindrical equations of Drake et al (1983 Phys. Fluids 26 2509) to toroidal geometry.

Deep Strong Coupling Regime of the Jaynes-Cummings Model

NASA Astrophysics Data System (ADS)

Casanova, J.; Romero, G.; Lizuain, I.; García-Ripoll, J. J.; Solano, E.

2010-12-01

We study the quantum dynamics of a two-level system interacting with a quantized harmonic oscillator in the deep strong coupling regime (DSC) of the Jaynes-Cummings model, that is, when the coupling strength g is comparable or larger than the oscillator frequency ω (g/ω≳1). In this case, the rotating-wave approximation cannot be applied or treated perturbatively in general. We propose an intuitive and predictive physical frame to describe the DSC regime where photon number wave packets bounce back and forth along parity chains of the Hilbert space, while producing collapse and revivals of the initial population. We exemplify our physical frame with numerical and analytical considerations in the qubit population, photon statistics, and Wigner phase space.

Provision of wear resistance and fatigue strength of surfaces during electroerosive processing

NASA Astrophysics Data System (ADS)

Fedonin, O. N.; Syanov, S. Yu; Papikyan, A. M.

2018-03-01

This article is a generalization of the results of theoretical studies of the effect of erosion control regimes on the operational properties of mold-forming parts of molds. The main problem is the provision of wear resistance and fatigue strength in the electroerosion processing of these types of products. The analysis showed that the fatigue strength is affected by the processing regimes and the coefficient after the erosion treatment. The index of wear resistance is determined both by the treatment modes and by the physical-mechanical properties of the billet materials. To ensure the operational performance of products, it is necessary to establish the physical picture of the processing of complex profile parts by finding the optimum eroding regime.

Statistics of vacuum breakdown in the high-gradient and low-rate regime

NASA Astrophysics Data System (ADS)

Wuensch, Walter; Degiovanni, Alberto; Calatroni, Sergio; Korsbäck, Anders; Djurabekova, Flyura; Rajamäki, Robin; Giner-Navarro, Jorge

2017-01-01

In an increasing number of high-gradient linear accelerator applications, accelerating structures must operate with both high surface electric fields and low breakdown rates. Understanding the statistical properties of breakdown occurrence in such a regime is of practical importance for optimizing accelerator conditioning and operation algorithms, as well as of interest for efforts to understand the physical processes which underlie the breakdown phenomenon. Experimental data of breakdown has been collected in two distinct high-gradient experimental set-ups: A prototype linear accelerating structure operated in the Compact Linear Collider Xbox 12 GHz test stands, and a parallel plate electrode system operated with pulsed DC in the kV range. Collected data is presented, analyzed and compared. The two systems show similar, distinctive, two-part distributions of number of pulses between breakdowns, with each part corresponding to a specific, constant event rate. The correlation between distance and number of pulses between breakdown indicates that the two parts of the distribution, and their corresponding event rates, represent independent primary and induced follow-up breakdowns. The similarity of results from pulsed DC to 12 GHz rf indicates a similar vacuum arc triggering mechanism over the range of conditions covered by the experiments.

Simple scaling laws for the evaporation of droplets pinned on pillars: Transfer-rate- and diffusion-limited regimes.

PubMed

Hernandez-Perez, Ruth; García-Cordero, José L; Escobar, Juan V

2017-12-01

The evaporation of droplets can give rise to a wide range of interesting phenomena in which the dynamics of the evaporation are crucial. In this work, we find simple scaling laws for the evaporation dynamics of axisymmetric droplets pinned on millimeter-sized pillars. Different laws are found depending on whether evaporation is limited by the diffusion of vapor molecules or by the transfer rate across the liquid-vapor interface. For the diffusion-limited regime, we find that a mass-loss rate equal to 3/7 of that of a free-standing evaporating droplet brings a good balance between simplicity and physical correctness. We also find a scaling law for the evaporation of multicomponent solutions. The scaling laws found are validated against experiments of the evaporation of droplets of (1) water, (2) blood plasma, and (3) a mixture of water and polyethylene glycol, pinned on acrylic pillars of different diameters. These results shed light on the macroscopic dynamics of evaporation on pillars as a first step towards the understanding of other complex phenomena that may be taking place during the evaporation process, such as particle transport and chemical reactions.

Simple scaling laws for the evaporation of droplets pinned on pillars: Transfer-rate- and diffusion-limited regimes

NASA Astrophysics Data System (ADS)

Hernandez-Perez, Ruth; García-Cordero, José L.; Escobar, Juan V.

2017-12-01

The evaporation of droplets can give rise to a wide range of interesting phenomena in which the dynamics of the evaporation are crucial. In this work, we find simple scaling laws for the evaporation dynamics of axisymmetric droplets pinned on millimeter-sized pillars. Different laws are found depending on whether evaporation is limited by the diffusion of vapor molecules or by the transfer rate across the liquid-vapor interface. For the diffusion-limited regime, we find that a mass-loss rate equal to 3/7 of that of a free-standing evaporating droplet brings a good balance between simplicity and physical correctness. We also find a scaling law for the evaporation of multicomponent solutions. The scaling laws found are validated against experiments of the evaporation of droplets of (1) water, (2) blood plasma, and (3) a mixture of water and polyethylene glycol, pinned on acrylic pillars of different diameters. These results shed light on the macroscopic dynamics of evaporation on pillars as a first step towards the understanding of other complex phenomena that may be taking place during the evaporation process, such as particle transport and chemical reactions.

Using an effective dimensionality to map the force-extension relation for a semi-flexible polymer in a nanoslit

NASA Astrophysics Data System (ADS)

de Haan, Hendrick

2015-03-01

The force-extension relation for a semi-flexible polymer is well described by the Marko-Siggia equation in both two and three dimensions. However, while of interest for experimental systems such as DNA in nanopits, the behaviour between these limiting dimensionalities is less understood. I will present results from simulations of a polymer subject to a stretching force F confined in nanoslits of varying heights h. Going from the 3D case to the 2D case, both the coefficients of the equation and the relevant persistence length are shown to change. This observation leads to the definition of an effective dimensionality, deff, to characterize the system. At low F, using deff in a generalized form of the Marko-Siggia relation provides good agreement with the simulation curves. However, at high F, deff drifts back towards d = 3 . 0 . The reason behind this F dependence is discussed. Semi-empirical forms for strong and weak confinement regimes will be presented and shown to give good agreement across all slit heights and stretching forces. deff is thus dependent on h and F and provides a cohesive physical picture for all regimes.

Aperture Array Photonic Metamaterials: Theoretical approaches, numerical techniques and a novel application

NASA Astrophysics Data System (ADS)

Lansey, Eli

Optical or photonic metamaterials that operate in the infrared and visible frequency regimes show tremendous promise for solving problems in renewable energy, infrared imaging, and telecommunications. However, many of the theoretical and simulation techniques used at lower frequencies are not applicable to this higher-frequency regime. Furthermore, technological and financial limitations of photonic metamaterial fabrication increases the importance of reliable theoretical models and computational techniques for predicting the optical response of photonic metamaterials. This thesis focuses on aperture array metamaterials. That is, a rectangular, circular, or other shaped cavity or hole embedded in, or penetrating through a metal film. The research in the first portion of this dissertation reflects our interest in developing a fundamental, theoretical understanding of the behavior of light's interaction with these aperture arrays, specifically regarding enhanced optical transmission. We develop an approximate boundary condition for metals at optical frequencies, and a comprehensive, analytical explanation of the physics underlying this effect. These theoretical analyses are augmented by computational techniques in the second portion of this thesis, used both for verification of the theoretical work, and solving more complicated structures. Finally, the last portion of this thesis discusses the results from designing, fabricating and characterizing a light-splitting metamaterial.

The CAPTAIN liquid argon neutrino experiment

DOE PAGES

Liu, Qiuguang

2015-01-01

The CAPTAIN liquid argon experiment is designed to make measurements of scientific importance to long-baseline neutrino physics and physics topics that will be explored by large underground detectors. The experiment employs two detectors – a primary detector with approximately 10-ton of liquid argon that will be deployed at different facilities for physics measurements and a prototype detector with 2-ton of liquid argon for configuration testing. The physics programs for CAPTAIN include measuring neutron interactions at Los Alamos Neutron Science Center, measuring neutrino interactions in medium energy regime (1.5–5 GeV) at Fermilab's NuMI beam, and measuring neutrino interactions in low energymore » regime (< 50 MeV) at stopped pion sources for supernova neutrino studies.« less

Quantum Regime of a Two-Dimensional Phonon Cavity

NASA Astrophysics Data System (ADS)

Bolgar, Aleksey N.; Zotova, Julia I.; Kirichenko, Daniil D.; Besedin, Ilia S.; Semenov, Aleksander V.; Shaikhaidarov, Rais S.; Astafiev, Oleg V.

2018-06-01

We realize the quantum regime of a surface acoustic wave (SAW) resonator by demonstrating vacuum Rabi mode splitting due to interaction with a superconducting artificial atom. Reaching the quantum regime is physically difficult and technologically challenging since SAW devices consist of large arrays of narrow metal strips. This work paves the way for realizing analogues of quantum optical phenomena with phonons and can be useful in on-chip quantum electronics.

Physical models of polarization mode dispersion

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

Menyuk, C.R.; Wai, P.K.A.

The effect of randomly varying birefringence on light propagation in optical fibers is studied theoretically in the parameter regime that will be used for long-distance communications. In this regime, the birefringence is large and varies very rapidly in comparison to the nonlinear and dispersive scale lengths. We determine the polarization mode dispersion, and we show that physically realistic models yield the same result for polarization mode dispersion as earlier heuristic models that were introduced by Poole. We also prove an ergodic theorem.

What can we learn from noise? — Mesoscopic nonequilibrium statistical physics —

PubMed Central

KOBAYASHI, Kensuke

2016-01-01

Mesoscopic systems — small electric circuits working in quantum regime — offer us a unique experimental stage to explorer quantum transport in a tunable and precise way. The purpose of this Review is to show how they can contribute to statistical physics. We introduce the significance of fluctuation, or equivalently noise, as noise measurement enables us to address the fundamental aspects of a physical system. The significance of the fluctuation theorem (FT) in statistical physics is noted. We explain what information can be deduced from the current noise measurement in mesoscopic systems. As an important application of the noise measurement to statistical physics, we describe our experimental work on the current and current noise in an electron interferometer, which is the first experimental test of FT in quantum regime. Our attempt will shed new light in the research field of mesoscopic quantum statistical physics. PMID:27477456

What can we learn from noise? - Mesoscopic nonequilibrium statistical physics.

PubMed

Kobayashi, Kensuke

2016-01-01

Mesoscopic systems - small electric circuits working in quantum regime - offer us a unique experimental stage to explorer quantum transport in a tunable and precise way. The purpose of this Review is to show how they can contribute to statistical physics. We introduce the significance of fluctuation, or equivalently noise, as noise measurement enables us to address the fundamental aspects of a physical system. The significance of the fluctuation theorem (FT) in statistical physics is noted. We explain what information can be deduced from the current noise measurement in mesoscopic systems. As an important application of the noise measurement to statistical physics, we describe our experimental work on the current and current noise in an electron interferometer, which is the first experimental test of FT in quantum regime. Our attempt will shed new light in the research field of mesoscopic quantum statistical physics.

Definition of two-phase flow behaviors for spacecraft design

NASA Technical Reports Server (NTRS)

Reinarts, Thomas R.; Best, Frederick R.; Miller, Katherine M.; Hill, Wayne S.

1991-01-01

Data for complete models of two-phase flow in microgravity are taken from in-flight experiments and applied to an adiabatic flow-regime analysis to study the feasibility of two-phase systems for spacecraft. The data are taken from five in-flight experiments by Hill et al. (1990) in which a two-phase pump circulates a freon mixture and vapor and liquid flow streams are measured. Adiabatic flow regimes are analyzed based on the experimental superficial velocities of liquid and vapor, and comparisons are made with the results of two-phase flow regimes at 1 g. A motion analyzer records the flow characteristics at a rate of 1000 frames/sec, and stratified flow regimes are reported at 1 g. The flow regimes observed under microgravitational conditions are primarily annular and include slug and bubbly-slug regimes. The present data are of interest to the design and analysis of two-phase thermal-management systems for use in space missions.

Dirac mass generation from crystal symmetry breaking on the surfaces of topological crystalline insulators

DOE PAGES

Zeljkovic, Ilija; Okada, Yoshinori; Serbyn, Maksym; ...

2015-02-16

The tunability of topological surface states and controllable opening of the Dirac gap are of fundamental and practical interest in the field of topological materials. In the newly discovered topological crystalline insulators (TCIs), theory predicts that the Dirac node is protected by a crystalline symmetry and that the surface state electrons can acquire a mass if this symmetry is broken. Recent studies have detected signatures of a spontaneously generated Dirac gap in TCIs; however, the mechanism of mass formation remains elusive. In this work, we present scanning tunnelling microscopy (STM) measurements of the TCI Pb 1-xSn xSe for a widemore » range of alloy compositions spanning the topological and non-topological regimes. The STM topographies reveal a symmetry-breaking distortion on the surface, which imparts mass to the otherwise massless Dirac electrons—a mechanism analogous to the long sought-after Higgs mechanism in particle physics. Interestingly, the measured Dirac gap decreases on approaching the trivial phase, whereas the magnitude of the distortion remains nearly constant. Our data and calculations reveal that the penetration depth of Dirac surface states controls the magnitude of the Dirac mass. At the limit of the critical composition, the penetration depth is predicted to go to infinity, resulting in zero mass, consistent with our measurements. Lastly, we discover the existence of surface states in the non-topological regime, which have the characteristics of gapped, double-branched Dirac fermions and could be exploited in realizing superconductivity in these materials.« less

Physical mechanisms leading to two-dimensional gas content evolution within a volcanic conduit

NASA Astrophysics Data System (ADS)

Collombet, M.; Burgisser, A.; Chevalier, L. A. C.

2017-12-01

The eruption of viscous magma at the Earth's surface often gives rise to abrupt regime changes. The transition from the gentle effusion of a lava dome to brief but powerful explosions is a common regime change. This transition is often preceded by the sealing of the shallow part of the volcanic conduit and the accumulation of volatile-rich magma underneath, a situation that collects the energy to be brutally released during the subsequent explosion. While conduit sealing is well-documented, volatile accumulation has proven harder to characterize. In this study, we use a 2D conduit flow numerical model including gas loss within the magma and into the wallrock to follow the evolution of gas content during a regime transition. Using various initial porosity distributions, permeability laws and boundary conditions, we track the physical parameters that prevent or enhance gas escape from the magma. Our approach aims to identify the physical processes controlling eruptive transitions and to highlight the importance of using field data observations to constrain numerical models.

Vegetation dynamics

Treesearch

Sammy L. King; Terry J. Antrobus; Sarah Billups

2000-01-01

A disturbance can be defined as "any relatively discrete event in time that disrupts ecosystem, community, or population structure and changes resources, substrate availability, or the physical environment" (Pickett and White 1985). Vegetation dynamics are a function of the temporal and spatial patterns of the disturbance regime. Natural disturbance regimes...

Atomistic and molecular effects in electric double layers at high surface charges

DOE PAGES

Templeton, Jeremy Alan; Lee, Jonathan; Mani, Ali

2015-06-16

Here, the Poisson–Boltzmann theory for electrolytes near a charged surface is known to be invalid due to unaccounted physics associated with high ion concentration regimes. In order to investigate this regime, fluids density functional theory (f-DFT) and molecular dynamics (MD) simulations were used to determine electric surface potential as a function of surface charge. Based on these detailed computations, for electrolytes with nonpolar solvent, the surface potential is shown to depend quadratically on the surface charge in the high charge limit. We demonstrate that modified Poisson–Boltzmann theories can model this limit if they are augmented with atomic packing densities providedmore » by MD. However, when the solvent is a highly polar molecule water an intermediate regime is identified in which a constant capacitance is realized. Simulation results demonstrate the mechanism underlying this regime, and for the salt water system studied here, it persists throughout the range of physically realistic surface charge densities so the potential’s quadratic surface charge dependence is not obtained.« less

Plasma physics and related challenges of millimeter-wave-to-terahertz and high power microwave generationa)

NASA Astrophysics Data System (ADS)

Booske, John H.

2008-05-01

Homeland security and military defense technology considerations have stimulated intense interest in mobile, high power sources of millimeter-wave (mmw) to terahertz (THz) regime electromagnetic radiation, from 0.1 to 10THz. While vacuum electronic sources are a natural choice for high power, the challenges have yet to be completely met for applications including noninvasive sensing of concealed weapons and dangerous agents, high-data-rate communications, high resolution radar, next generation acceleration drivers, and analysis of fluids and condensed matter. The compact size requirements for many of these high frequency sources require miniscule, microfabricated slow wave circuits. This necessitates electron beams with tiny transverse dimensions and potentially very high current densities for adequate gain. Thus, an emerging family of microfabricated, vacuum electronic devices share many of the same plasma physics challenges that are currently confronting "classic" high power microwave (HPM) generators including long-life bright electron beam sources, intense beam transport, parasitic mode excitation, energetic electron interaction with surfaces, and rf air breakdown at output windows. The contemporary plasma physics and other related issues of compact, high power mmw-to-THz sources are compared and contrasted to those of HPM generation, and future research challenges and opportunities are discussed.

On small beams with large topological charge: II. Photons, electrons and gravitational waves

NASA Astrophysics Data System (ADS)

Krenn, Mario; Zeilinger, Anton

2018-06-01

Beams of light with a large topological charge significantly change their spatial structure when they are focused strongly. Physically, it can be explained by an emerging electromagnetic field component in the direction of propagation, which is neglected in the simplified scalar wave picture in optics. Here we ask: is this a specific photonic behavior, or can similar phenomena also be predicted for other species of particles? We show that the same modification of the spatial structure exists for relativistic electrons as well as for focused gravitational waves. However, this is for different physical reasons: for electrons, which are described by the Dirac equation, the spatial structure changes due to a spin–orbit coupling in the relativistic regime. In gravitational waves described with linearized general relativity, the curvature of space–time between the transverse and propagation direction leads to the modification of the spatial structure. Thus, this universal phenomenon exists for both massive and massless elementary particles with spin 1/2, 1 and 2. It would be very interesting whether other types of particles such as composite systems (neutrons or C60) or neutrinos show a similar behavior and how this phenomenon can be explained in a unified physical way.

Computational Study of Collisions Between O(3P) and NO(2Pi) at Temperatures Relevant to the Hypersonic Flight Regime

DTIC Science & Technology

2014-10-29

hypersonic flight regime. For this reason, the thermal rate coefficients for reactive processes involving O(3P) and NO(2_) are relevant over a wide...hypersonic flight regime. For this reason, the thermal rate coefficients for reactive processes involving O(3P) and NO(2) are relevant over a wide...N) is of particular interest since the thermal dissociation threshold for O2 is lower than that for N2 in air. A central question is how

Nonequilibrium Quantum Simulation in Circuit QED

NASA Astrophysics Data System (ADS)

Raftery, James John

Superconducting circuits have become a leading architecture for quantum computing and quantum simulation. In particular, the circuit QED framework leverages high coherence qubits and microwave resonators to construct systems realizing quantum optics models with exquisite precision. For example, the Jaynes-Cummings model has been the focus of significant theoretical interest as a means of generating photon-photon interactions. Lattices of such strongly correlated photons are an exciting new test bed for exploring non-equilibrium condensed matter physics such as dissipative phase transitions of light. This thesis covers a series of experiments which establish circuit QED as a powerful tool for exploring condensed matter physics with photons. The first experiment explores the use of ultra high speed arbitrary waveform generators for the direct digital synthesis of complex microwave waveforms. This new technique dramatically simplifies the classical control chain for quantum experiments and enables high bandwidth driving schemes expected to be essential for generating interesting steady-states and dynamical behavior. The last two experiments explore the rich physics of interacting photons, with an emphasis on small systems where a high degree of control is possible. The first experiment realizes a two-site system called the Jaynes-Cummings dimer, which undergoes a self-trapping transition where the strong photon-photon interactions block photon hopping between sites. The observation of this dynamical phase transition and the related dissipation-induced transition are key results of this thesis. The final experiment augments the Jaynes-Cummings dimer by redesigning the circuit to include in-situ control over photon hopping between sites using a tunable coupler. This enables the study of the dimer's localization transition in the steady-state regime.

Experimental triple-slit interference in a strongly driven V-type artificial atom

NASA Astrophysics Data System (ADS)

Dada, Adetunmise C.; Santana, Ted S.; Koutroumanis, Antonios; Ma, Yong; Park, Suk-In; Song, Jindong; Gerardot, Brian D.

2017-08-01

Rabi oscillations of a two-level atom appear as a quantum interference effect between the amplitudes associated with atomic superpositions, in analogy with the classic double-slit experiment which manifests a sinusoidal interference pattern. By extension, through direct detection of time-resolved resonance fluorescence from a quantum-dot neutral exciton driven in the Rabi regime, we experimentally demonstrate triple-slit-type quantum interference via quantum erasure in a V-type three-level artificial atom. This result is of fundamental interest in the experimental studies of the properties of V-type three-level systems and may pave the way for further insight into their coherence properties as well as applications for quantum information schemes. It also suggests quantum dots as candidates for multipath-interference experiments for probing foundational concepts in quantum physics.

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

Liu, Chang; Fox, William; Bhattacharjee, Amitava

Recent theory has demonstrated a novel physics regime for magnetic reconnection in high-energy-density plasmas where the magnetic field is advected by heat flux via the Nernst effect. In this paper, we elucidate the physics of the electron dissipation layer in this regime. Through fully kinetic simulation and a generalized Ohm's law derived from first principles, we show that momentum transport due to a nonlocal effect, the heat-flux-viscosity, provides the dissipation mechanism for magnetic reconnection. Scaling analysis, and simulations show that the reconnection process comprises a magnetic field compression stage and quasisteady reconnection stage, and the characteristic width of the currentmore » sheet in this regime is several electron mean-free paths. Finally, these results show the important interplay between nonlocal transport effects and generation of anisotropic components to the distribution function.« less

Dogs lap using acceleration-driven open pumping

PubMed Central

Gart, Sean; Socha, John J.; Vlachos, Pavlos P.; Jung, Sunghwan

2015-01-01

Dogs lap because they have incomplete cheeks and cannot suck. When lapping, a dog’s tongue pulls a liquid column from the bath, suggesting that the hydrodynamics of column formation are critical to understanding how dogs drink. We measured lapping in 19 dogs and used the results to generate a physical model of the tongue’s interaction with the air–fluid interface. These experiments help to explain how dogs exploit the fluid dynamics of the generated column. The results demonstrate that effects of acceleration govern lapping frequency, which suggests that dogs curl the tongue to create a larger liquid column. Comparing lapping in dogs and cats reveals that, despite similar morphology, these carnivores lap in different physical regimes: an unsteady inertial regime for dogs and steady inertial regime for cats. PMID:26668382

Admissible perturbations and false instabilities in PT -symmetric quantum systems

NASA Astrophysics Data System (ADS)

Znojil, Miloslav

2018-03-01

One of the most characteristic mathematical features of the PT -symmetric quantum mechanics is the explicit Hamiltonian dependence of its physical Hilbert space of states H =H (H ) . Some of the most important physical consequences are discussed, with emphasis on the dynamical regime in which the system is close to phase transition. Consistent perturbation treatment of such a regime is proposed. An illustrative application of the innovated perturbation theory to a non-Hermitian but PT -symmetric user-friendly family of J -parametric "discrete anharmonic" quantum Hamiltonians H =H (λ ⃗) is provided. The models are shown to admit the standard probabilistic interpretation if and only if the parameters remain compatible with the reality of the spectrum, λ ⃗∈D(physical ) . In contradiction to conventional wisdom, the systems are then shown to be stable with respect to admissible perturbations, inside the domain D(physical ), even in the immediate vicinity of the phase-transition boundaries ∂ D(physical ) .

31 CFR 593.304 - Interest.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 31 Money and Finance:Treasury 3 2012-07-01 2012-07-01 false Interest. 593.304 Section 593.304 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY FORMER LIBERIAN REGIME OF CHARLES TAYLOR SANCTIONS REGULATIONS...

31 CFR 593.304 - Interest.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 31 Money and Finance:Treasury 3 2013-07-01 2013-07-01 false Interest. 593.304 Section 593.304 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY FORMER LIBERIAN REGIME OF CHARLES TAYLOR SANCTIONS REGULATIONS...

31 CFR 593.304 - Interest.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 31 Money and Finance:Treasury 3 2014-07-01 2014-07-01 false Interest. 593.304 Section 593.304 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY FORMER LIBERIAN REGIME OF CHARLES TAYLOR SANCTIONS REGULATIONS...

31 CFR 593.304 - Interest.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 31 Money and Finance:Treasury 3 2011-07-01 2011-07-01 false Interest. 593.304 Section 593.304 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY FORMER LIBERIAN REGIME OF CHARLES TAYLOR SANCTIONS REGULATIONS...

31 CFR 593.304 - Interest.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 31 Money and Finance: Treasury 3 2010-07-01 2010-07-01 false Interest. 593.304 Section 593.304 Money and Finance: Treasury Regulations Relating to Money and Finance (Continued) OFFICE OF FOREIGN ASSETS CONTROL, DEPARTMENT OF THE TREASURY FORMER LIBERIAN REGIME OF CHARLES TAYLOR SANCTIONS REGULATIONS...

Tunable Kondo physics in a carbon nanotube double quantum dot.

PubMed

Chorley, S J; Galpin, M R; Jayatilaka, F W; Smith, C G; Logan, D E; Buitelaar, M R

2012-10-12

We investigate a tunable two-impurity Kondo system in a strongly correlated carbon nanotube double quantum dot, accessing the full range of charge regimes. In the regime where both dots contain an unpaired electron, the system approaches the two-impurity Kondo model. At zero magnetic field the interdot coupling disrupts the Kondo physics and a local singlet state arises, but we are able to tune the crossover to a Kondo screened phase by application of a magnetic field. All results show good agreement with a numerical renormalization group study of the device.

ECOLOGICAL ANALYSIS OF HYDROLOGIC DISTURBANCE REGIMES IN STREAMS OF NORTH AND SOUTH DAKOTA

EPA Science Inventory

Streamflow variability is an important component of physical disturbance in streams, and is likely to be a major organizing feature of habitat for stream fishes. The disturbance regime in streams is frequently described by the variability in streamflow from both floods and prolo...

Stochastic Parametrisations and Regime Behaviour of Atmospheric Models

NASA Astrophysics Data System (ADS)

Arnold, Hannah; Moroz, Irene; Palmer, Tim

2013-04-01

The presence of regimes is a characteristic of non-linear, chaotic systems (Lorenz, 2006). In the atmosphere, regimes emerge as familiar circulation patterns such as the El-Nino Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO) and Scandinavian Blocking events. In recent years there has been much interest in the problem of identifying and studying atmospheric regimes (Solomon et al, 2007). In particular, how do these regimes respond to an external forcing such as anthropogenic greenhouse gas emissions? The importance of regimes in observed trends over the past 50-100 years indicates that in order to predict anthropogenic climate change, our climate models must be able to represent accurately natural circulation regimes, their statistics and variability. It is well established that representing model uncertainty as well as initial condition uncertainty is important for reliable weather forecasts (Palmer, 2001). In particular, stochastic parametrisation schemes have been shown to improve the skill of weather forecast models (e.g. Berner et al., 2009; Frenkel et al., 2012; Palmer et al., 2009). It is possible that including stochastic physics as a representation of model uncertainty could also be beneficial in climate modelling, enabling the simulator to explore larger regions of the climate attractor including other flow regimes. An alternative representation of model uncertainty is a perturbed parameter scheme, whereby physical parameters in subgrid parametrisation schemes are perturbed about their optimal value. Perturbing parameters gives a greater control over the ensemble than multi-model or multiparametrisation ensembles, and has been used as a representation of model uncertainty in climate prediction (Stainforth et al., 2005; Rougier et al., 2009). We investigate the effect of including representations of model uncertainty on the regime behaviour of a simulator. A simple chaotic model of the atmosphere, the Lorenz '96 system, is used to study the predictability of regime changes (Lorenz 1996, 2006). Three types of models are considered: a deterministic parametrisation scheme, stochastic parametrisation schemes with additive or multiplicative noise, and a perturbed parameter ensemble. Each forecasting scheme was tested on its ability to reproduce the attractor of the full system, defined in a reduced space based on EOF decomposition. None of the forecast models accurately capture the less common regime, though a significant improvement is observed over the deterministic parametrisation when a temporally correlated stochastic parametrisation is used. The attractor for the perturbed parameter ensemble improves on that forecast by the deterministic or white additive schemes, showing a distinct peak in the attractor corresponding to the less common regime. However, the 40 constituent members of the perturbed parameter ensemble each differ greatly from the true attractor, with many only showing one dominant regime with very rare transitions. These results indicate that perturbed parameter ensembles must be carefully analysed as individual members may have very different characteristics to the ensemble mean and to the true system being modelled. On the other hand, the stochastic parametrisation schemes tested performed well, improving the simulated climate, and motivating the development of a stochastic earth-system simulator for use in climate prediction. J. Berner, G. J. Shutts, M. Leutbecher, and T. N. Palmer. A spectral stochastic kinetic energy backscatter scheme and its impact on flow dependent predictability in the ECMWF ensemble prediction system. J. Atmos. Sci., 66(3):603-626, 2009. Y. Frenkel, A. J. Majda, and B. Khouider. Using the stochastic multicloud model to improve tropical convective parametrisation: A paradigm example. J. Atmos. Sci., 69(3):1080-1105, 2012. E. N. Lorenz. Predictability: a problem partly solved. In Proceedings, Seminar on Predictability, 4-8 September 1995, volume 1, pages 1-18, Shinfield Park, Reading, 1996. ECMWF. E. N. Lorenz. Regimes in simple systems. J. Atmos. Sci., 63(8):2056-2073, 2006. T. N Palmer. A nonlinear dynamical perspective on model error: A proposal for non-local stochastic-dynamic parametrisation in weather and climate prediction models. Q. J. Roy. Meteor. Soc., 127(572):279-304, 2001. T. N. Palmer, R. Buizza, F. Doblas-Reyes, T. Jung, M. Leutbecher, G. J. Shutts, M. Steinheimer, and A. Weisheimer. Stochastic parametrization and model uncertainty. Technical Report 598, European Centre for Medium-Range Weather Forecasts, 2009. J. Rougier, D. M. H. Sexton, J. M. Murphy, and D. Stainforth. Analyzing the climate sensitivity of the HadSM3 climate model using ensembles from different but related experiments. J. Climate, 22:3540-3557, 2009. S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K. B. Averyt, Tignor M., and H. L. Miller. Climate models and their evaluation. In Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge, United Kingdom and New York, NY, USA, 2007. Cambridge University Press. D. A Stainforth, T. Aina, C. Christensen, M. Collins, N. Faull, D. J. Frame, J. A. Kettleborough, S. Knight, A. Martin, J. M. Murphy, C. Piani, D. Sexton, L. A. Smith, R. A Spicer, A. J. Thorpe, and M. R Allen. Uncertainty in predictions of the climate response to rising levels of greenhouse gases. Nature, 433(7024):403-406, 2005.

STM Studies of Spin-­Orbit Coupled Phases in Real-­ and Momentum-­Space

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

Madhavan, Vidya

The recently discovered class of spin-orbit coupled materials with interesting topological character are fascinating both from fundamental as well as application point of view. Two striking examples are 3D topological insulators (TIs) and topological crystalline insulators (TCIs). These materials host linearly dispersing (Dirac like) surface states with an odd number of Dirac nodes and are predicted to carry a quantized half-integer value of the axion field. The non-trivial topological properties of TIs and TCIs arise from strong spin-orbit coupling leading to an inverted band structure; which also leads to the chiral spin texture in momentum space. In this project wemore » used low temperature scanning tunneling microscopy (STM) and spectroscopy (STS) to study materials with topological phases in real- and momentum-space. We studied both single crystals and thin films of topological materials which are susceptible to being tuned by doping, strain or gating, allowing us to explore their physical properties in the most interesting regimes and set the stage for future technological applications. .« less

Topologically nontrivial Fermi regions and their novel electromagnetic response properties

NASA Astrophysics Data System (ADS)

Lee, Ching Hua; Zhang, Xiao

In the last decade, there has been a surge of interest in the application of topology to condensed matter physics. So far, most studies have been concerned with the novel properties that arise due to nontrivial band topology, i.e Quantum Anomalous Hall and Z2 topological insulators (TIs). In this talk, I shall describe another context where nontrivial topology also leads to interesting, measurable effects. Within the semi-classical Boltzmann approach, it can be shown that a topologically nontrivial Fermi sea region generically exhibits a non-monotonic nonlinear electromagnetic response in the limit of low chemical potential. Such topologically nontrivial regions of filled states can arise in experimentally realized TI heterostructures or materials with large Rashba splitting, i.e. BiTeI, where the Fermi sea is not simply connected. A non-monotonic electromagnetic response implies regimes of negative differential resistance, which have important applications in technologies involving microwave generation, like motion sensing and radio astronomy. We hope that nontrivial Fermi sea topology will hence provide another route for the realization of such technologies.

A full-angle Monte-Carlo scattering technique including cumulative and single-event Rutherford scattering in plasmas

NASA Astrophysics Data System (ADS)

Higginson, Drew P.

2017-11-01

We describe and justify a full-angle scattering (FAS) method to faithfully reproduce the accumulated differential angular Rutherford scattering probability distribution function (pdf) of particles in a plasma. The FAS method splits the scattering events into two regions. At small angles it is described by cumulative scattering events resulting, via the central limit theorem, in a Gaussian-like pdf; at larger angles it is described by single-event scatters and retains a pdf that follows the form of the Rutherford differential cross-section. The FAS method is verified using discrete Monte-Carlo scattering simulations run at small timesteps to include each individual scattering event. We identify the FAS regime of interest as where the ratio of temporal/spatial scale-of-interest to slowing-down time/length is from 10-3 to 0.3-0.7; the upper limit corresponds to Coulomb logarithm of 20-2, respectively. Two test problems, high-velocity interpenetrating plasma flows and keV-temperature ion equilibration, are used to highlight systems where including FAS is important to capture relevant physics.

Transient dynamics of a quantum-dot: From Kondo regime to mixed valence and to empty orbital regimes

NASA Astrophysics Data System (ADS)

Cheng, YongXi; Li, ZhenHua; Wei, JianHua; Nie, YiHang; Yan, YiJing

2018-04-01

Based on the hierarchical equations of motion approach, we study the time-dependent transport properties of a strongly correlated quantum dot system in the Kondo regime (KR), mixed valence regime (MVR), and empty orbital regime (EOR). We find that the transient current in KR shows the strongest nonlinear response and the most distinct oscillation behaviors. Both behaviors become weaker in MVR and diminish in EOR. To understand the physical insight, we examine also the corresponding dot occupancies and the spectral functions, with their dependence on the Coulomb interaction, temperature, and applied step bias voltage. The above nonlinear and oscillation behaviors could be understood as the interplay between dynamical Kondo resonance and single electron resonant-tunneling.

Dynamic regime marginal structural mean models for estimation of optimal dynamic treatment regimes, Part I: main content.

PubMed

Orellana, Liliana; Rotnitzky, Andrea; Robins, James M

2010-01-01

Dynamic treatment regimes are set rules for sequential decision making based on patient covariate history. Observational studies are well suited for the investigation of the effects of dynamic treatment regimes because of the variability in treatment decisions found in them. This variability exists because different physicians make different decisions in the face of similar patient histories. In this article we describe an approach to estimate the optimal dynamic treatment regime among a set of enforceable regimes. This set is comprised by regimes defined by simple rules based on a subset of past information. The regimes in the set are indexed by a Euclidean vector. The optimal regime is the one that maximizes the expected counterfactual utility over all regimes in the set. We discuss assumptions under which it is possible to identify the optimal regime from observational longitudinal data. Murphy et al. (2001) developed efficient augmented inverse probability weighted estimators of the expected utility of one fixed regime. Our methods are based on an extension of the marginal structural mean model of Robins (1998, 1999) which incorporate the estimation ideas of Murphy et al. (2001). Our models, which we call dynamic regime marginal structural mean models, are specially suitable for estimating the optimal treatment regime in a moderately small class of enforceable regimes of interest. We consider both parametric and semiparametric dynamic regime marginal structural models. We discuss locally efficient, double-robust estimation of the model parameters and of the index of the optimal treatment regime in the set. In a companion paper in this issue of the journal we provide proofs of the main results.

Dimension-dependent stimulated radiative interaction of a single electron quantum wavepacket

NASA Astrophysics Data System (ADS)

Gover, Avraham; Pan, Yiming

2018-06-01

In the foundation of quantum mechanics, the spatial dimensions of electron wavepacket are understood only in terms of an expectation value - the probability distribution of the particle location. One can still inquire how the quantum electron wavepacket size affects a physical process. Here we address the fundamental physics problem of particle-wave duality and the measurability of a free electron quantum wavepacket. Our analysis of stimulated radiative interaction of an electron wavepacket, accompanied by numerical computations, reveals two limits. In the quantum regime of long wavepacket size relative to radiation wavelength, one obtains only quantum-recoil multiphoton sidebands in the electron energy spectrum. In the opposite regime, the wavepacket interaction approaches the limit of classical point-particle acceleration. The wavepacket features can be revealed in experiments carried out in the intermediate regime of wavepacket size commensurate with the radiation wavelength.

Momentum transport and nonlocality in heat-flux-driven magnetic reconnection in high-energy-density plasmas.

PubMed

Liu, Chang; Fox, William; Bhattacharjee, Amitava; Thomas, Alexander G R; Joglekar, Archis S

2017-10-01

Recent theory has demonstrated a novel physics regime for magnetic reconnection in high-energy-density plasmas where the magnetic field is advected by heat flux via the Nernst effect. Here we elucidate the physics of the electron dissipation layer in this regime. Through fully kinetic simulation and a generalized Ohm's law derived from first principles, we show that momentum transport due to a nonlocal effect, the heat-flux-viscosity, provides the dissipation mechanism for magnetic reconnection. Scaling analysis, and simulations show that the reconnection process comprises a magnetic field compression stage and quasisteady reconnection stage, and the characteristic width of the current sheet in this regime is several electron mean-free paths. These results show the important interplay between nonlocal transport effects and generation of anisotropic components to the distribution function.

Electron spin relaxation in a transition-metal dichalcogenide quantum dot

NASA Astrophysics Data System (ADS)

Pearce, Alexander J.; Burkard, Guido

2017-06-01

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

Effects of cylinder Reynolds number on the turbulent horseshoe vortex system and near wake of a surface-mounted circular cylinder

NASA Astrophysics Data System (ADS)

Kirkil, Gokhan; Constantinescu, George

2014-11-01

The turbulent horseshoe vortex (HV) system and the near-wake flow past a circular cylinder mounted on a flat bed in an open channel are investigated based on results of eddy-resolving simulations and supporting flow visualizations. Of particular interest are the changes in the mean flow and turbulence statistics within the HV region as the necklace vortices wrap around the cylinder's base and the variation of the mean flow and turbulence statistics in the near wake, in between the channel bed and the free surface. While it is well known that the drag crisis induces important changes in the flow past infinitely-long circular cylinders, the changes are less understood and more complex for the case of flow past a surface-mounted cylinder. A detailed discussion of the changes in the flow physics between cylinder Reynolds numbers at which the flow in the upstream part of the separated shear layers (SSLs) is laminar (Re = 16,000, subcritical flow regime) and Reynolds numbers at which transition occurs inside the attached boundary layers away from the bed and the flow within the SSLs is turbulent (Re = 500,000, supercritical flow regime). The changes between the two regimes in the dynamics and level of coherence of the large-scale coherent structures (necklace vortices, vortex tubes shed in the SSLs and roller vortices shed in the wake) and their capacity to induce high-magnitude bed friction velocities in the mean and instantaneous flow fields and to amplify the near-bed turbulence are analyzed.

Binomial tree method for pricing a regime-switching volatility stock loans

NASA Astrophysics Data System (ADS)

Putri, Endah R. M.; Zamani, Muhammad S.; Utomo, Daryono B.

2018-03-01

Binomial model with regime switching may represents the price of stock loan which follows the stochastic process. Stock loan is one of alternative that appeal investors to get the liquidity without selling the stock. The stock loan mechanism resembles that of American call option when someone can exercise any time during the contract period. From the resembles both of mechanism, determination price of stock loan can be interpreted from the model of American call option. The simulation result shows the behavior of the price of stock loan under a regime-switching with respect to various interest rate and maturity.

Nanosecond-pulse-controlled higher-order sideband comb in a GaAs optomechanical disk resonator in the non-perturbative regime

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

Xiong, Hao, E-mail: haoxiong1217@gmail.com; Si, Liu-Gang, E-mail: siliugang@gmail.com; Lü, Xin-You

2014-10-15

We propose an interesting scheme for tunable high-order sideband comb generation by utilizing ultrastrong optomechanical interaction in a GaAs optomechanical disk resonator beyond the perturbative approximation. We analyze the nonlinear nature of the optomechanical interaction, and give a full description of the non-perturbative effects. It is shown, within the non-perturbative regime, that high-order sideband comb with large intensities can be realized and controlled in a GaAs optomechanical disk resonator with experimentally achievable system parameters, and the non-perturbative regime leads to rich and nontrivial behavior.

Kramers turnover: From energy diffusion to spatial diffusion using metadynamics

PubMed Central

Tiwary, Pratyush; Berne, B. J.

2016-01-01

We consider the rate of transition for a particle between two metastable states coupled to a thermal environment for various magnitudes of the coupling strength using the recently proposed infrequent metadynamics approach [P. Tiwary and M. Parrinello, Phys. Rev. Lett. 111, 230602 (2013)]. We are interested in understanding how this approach for obtaining rate constants performs as the dynamics regime changes from energy diffusion to spatial diffusion. Reassuringly, we find that the approach works remarkably well for various coupling strengths in the strong coupling regime, and to some extent even in the weak coupling regime. PMID:27059558

Modified unified kinetic scheme for all flow regimes.

PubMed

Liu, Sha; Zhong, Chengwen

2012-06-01

A modified unified kinetic scheme for the prediction of fluid flow behaviors in all flow regimes is described. The time evolution of macrovariables at the cell interface is calculated with the idea that both free transport and collision mechanisms should be considered. The time evolution of macrovariables is obtained through the conservation constraints. The time evolution of local Maxwellian distribution is obtained directly through the one-to-one mapping from the evolution of macrovariables. These improvements provide more physical realities in flow behaviors and more accurate numerical results in all flow regimes especially in the complex transition flow regime. In addition, the improvement steps introduce no extra computational complexity.

The OMZ and nutrient features as a signature of interannual and low-frequency variability in the Peruvian upwelling system

NASA Astrophysics Data System (ADS)

Graco, Michelle I.; Purca, Sara; Dewitte, Boris; Castro, Carmen G.; Morón, Octavio; Ledesma, Jesús; Flores, Georgina; Gutiérrez, Dimitri

2017-10-01

Over the last decades, the Humboldt Current upwelling ecosystem, particularly the northern component off the coast of Peru, has drawn the interest of the scientific community because of its unique characteristics: it is the upwelling system with the biggest catch productivity despite the fact it is embedded in a shallow and intense oxygen minimum zone (OMZ). It is also an area of intense nitrogen loss and anammox activity and experiences large interannual variability associated with the equatorial remote forcing. In this context, we examined the oceanographic and biogeochemical variability associated with the OMZ off central Peru from a monthly time series (1996-2011) recorded off the coast of Callao (12° 02' S, 77° 29' W). The data reveal a rich spectrum of variability in the OMZ that includes frequencies ranging from seasonal to interannual scales. Due to the efficient oceanic teleconnection off Peru, the observed variability is interpreted in the light of an estimate of the equatorial Kelvin wave contribution to sea level anomalies considering the peculiarities of its vertical structure (i.e., the first two baroclinic modes). The span of the data set allows us to contrast two OMZ regimes. The strong regime is associated with the strong 1997-1998 equatorial Pacific El Niño, during which the OMZ adjusted to Kelvin-wave-induced downwelling conditions that switched off the upwelling and drastically reduced nutrient availability. The weak regime corresponds to the post-2000 period associated with the occurrence of moderate central Pacific El Niño events and enhanced equatorial Kelvin wave activity, in which mean upwelling conditions are maintained. It is shown that the characteristics of the coupling between physics and biogeochemistry is distinct between the two regimes with the weak regime being associated with a larger explained variance in biogeochemical properties not linearly related to the ENSO oceanic teleconnection. The data also reveal a long-term trend from 1999 corresponding to a deepening of the oxygen-deficient waters and warming. The implications of our results for understanding the OMZ dynamics off Peru are discussed.

Surface Rupture Effects on Earthquake Moment-Area Scaling Relations

NASA Astrophysics Data System (ADS)

Luo, Yingdi; Ampuero, Jean-Paul; Miyakoshi, Ken; Irikura, Kojiro

2017-09-01

Empirical earthquake scaling relations play a central role in fundamental studies of earthquake physics and in current practice of earthquake hazard assessment, and are being refined by advances in earthquake source analysis. A scaling relation between seismic moment ( M 0) and rupture area ( A) currently in use for ground motion prediction in Japan features a transition regime of the form M 0- A 2, between the well-recognized small (self-similar) and very large (W-model) earthquake regimes, which has counter-intuitive attributes and uncertain theoretical underpinnings. Here, we investigate the mechanical origin of this transition regime via earthquake cycle simulations, analytical dislocation models and numerical crack models on strike-slip faults. We find that, even if stress drop is assumed constant, the properties of the transition regime are controlled by surface rupture effects, comprising an effective rupture elongation along-dip due to a mirror effect and systematic changes of the shape factor relating slip to stress drop. Based on this physical insight, we propose a simplified formula to account for these effects in M 0- A scaling relations for strike-slip earthquakes.

Composite Fermions: Motivation, Successes, and Application to Fractional Quantum Hall Effect in Graphene

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

Jain, Jainendra

2011-07-15

The fractional quantum Hall effect (FQHE) is one of the most amazing collective states discovered in modern times. A remarkably detailed and accurate understanding of its nonperturbative physics has been achieved in terms of a new class of exotic particles called composite fermions. I will begin with a brief review of the composite fermion theory and its outstanding successes. The rest of the talk will be concerned with fractional quantum Hall effect in graphene, observed recently. I will present results of theoretical studies that demonstrate that composite fermions are formed in graphene as well, but the spin and valley degeneraciesmore » and the linear dispersion of electrons produce interesting new physics relative to that in the usual two-dimensional GaAs systems. Composite fermion theory allows detailed predictions about FQHE in graphene in regimes when either or both of the spin and valley degeneracies are broken. I will discuss the relevance of our theory to recent experiments. This work on FQHE in graphene has been performed in collaboration with Csaba Toke.« less

The influence of human physical activity and contaminated clothing type on particle resuspension.

PubMed

McDonagh, A; Byrne, M A

2014-01-01

A study was conducted to experimentally quantify the influence of three variables on the level of resuspension of hazardous aerosol particles from clothing. Variables investigated include physical activity level (two levels, low and high), surface type (four different clothing material types), and time i.e. the rate at which particles resuspend. A mixture of three monodisperse tracer-labelled powders, with median diameters of 3, 5, and 10 microns, was used to "contaminate" the samples, and the resuspended particles were analysed in real-time using an Aerodynamic Particle Sizer (APS), and also by Neutron Activation Analysis (NAA). The overall finding was that physical activity resulted in up to 67% of the contamination deposited on clothing being resuspended back into the air. A detailed examination of the influence of physical activity level on resuspension, from NAA, revealed that the average resuspended fraction (RF) of particles at low physical activity was 28 ± 8%, and at high physical activity was 30 ± 7%, while the APS data revealed a tenfold increase in the cumulative mass of airborne particles during high physical activity in comparison to that during low physical activity. The results also suggest that it is not the contaminated clothing's fibre type which influences particle resuspension, but the material's weave pattern (and hence the material's surface texture). Investigation of the time variation in resuspended particle concentrations indicated that the data were separable into two distinct regimes: the first (occurring within the first 1.5 min) having a high, positive rate of change of airborne particle concentration relative to the second regime. The second regime revealed a slower rate of change of particle concentration and remained relatively unchanged for the remainder of each resuspension event. Copyright © 2013 Elsevier Ltd. All rights reserved.

The natural sediment regime in rivers: broadening the foundation for ecosystem management

USGS Publications Warehouse

Wohl, Ellen E.; Bledsoe, Brian P.; Jacobson, Robert B.; Poff, N. LeRoy; Rathburn, Sara L.; Walters, David M.; Wilcox, Andrew C.

2015-01-01

Water and sediment inputs are fundamental drivers of river ecosystems, but river management tends to emphasize flow regime at the expense of sediment regime. In an effort to frame a more inclusive paradigm for river management, we discuss sediment inputs, transport, and storage within river systems; interactions among water, sediment, and valley context; and the need to broaden the natural flow regime concept. Explicitly incorporating sediment is challenging, because sediment is supplied, transported, and stored by nonlinear and episodic processes operating at different temporal and spatial scales than water and because sediment regimes have been highly altered by humans. Nevertheless, managing for a desired balance between sediment supply and transport capacity is not only tractable, given current geomorphic process knowledge, but also essential because of the importance of sediment regimes to aquatic and riparian ecosystems, the physical template of which depends on sediment-driven river structure and function.

Correlation between piezoresponse nonlinearity and hysteresis in ferroelectric crystals at nanoscale

DOE PAGES

Kalinin, Sergei V.; Jesse, Stephen; Yang, Yaodong; ...

2016-04-27

Here, the nonlinear response of a ferroic to external fields has been studied for decades, garnering interest for both understanding fundamental physics, as well as technological applications such as memory devices. Yet, the behavior of ferroelectrics at mesoscopic regimes remains poorly understood, and the scale limits of theories developed for macroscopic regimes are not well tested experimentally. Here, we test the link between piezo-nonlinearity and local piezoelectric strain hysteresis, via AC-field dependent measurements in conjunction with first order reversal curve (FORC) measurements on (K,Na)NbO 3 crystals with band-excitation piezoelectric force microscopy. The correlation coefficient between nonlinearity amplitude and the FORCmore » of the polarization switching shows a clear decrease in correlation with increasing AC bias, suggesting the impact of domain wall clamping on the DC measurement case. Further, correlation of polynomial fitting terms from the nonlinear measurements with the hysteresis loop area reveals that the largest correlations are reserved for the quadratic terms, which is expected for irreversible domain wall motion contributions that impact both piezoelectric behavior as well as minor loop formation. These confirm the link between local piezoelectric nonlinearity, domain wall motion and minor loop formation, and suggest that existing theories (such as Preisach) are applicable at these length scales, with associated implications for future nanoscale devices.« less

Bursting of a bubble confined in between two plates

NASA Astrophysics Data System (ADS)

Murano, Mayuko; Kimono, Natsuki; Okumura, Ko

2015-11-01

Rupture of liquid thin films, driven by surface tension, has attracted interests of scientists for many years. It is also a daily phenomenon familiar to everyone in the form of the bursting of soap films. In recent years, many studies in confined geometries (e.g. in a Hele-Shaw cell) have revealed physical mechanisms of the dynamics of bubbles and drops. As for a liquid film sandwiched in between another liquid immiscible to the film liquid in the Hele-Shaw cell, it is reported that the thin film bursts at a constant speed and the speed depends on the viscosity of the surrounding liquid when the film is less viscous, although a rim is not formed at the bursting tip; this is because the circular symmetry of the hole in the bursting film is lost. Here, we study the bursting speed of a thin film sandwiched between air instead of the surrounding liquid in the Hele-Shaw cell to seek different scaling regimes. By measuring the bursting velocity and the film thickness of an air bubble with a high speed camera, we have found a new scaling law in viscous regime. This research was partly supported by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).

Electrotunable artificial molecules based on van der Waals heterostructures

PubMed Central

Zhang, Zhuo-Zhi; Song, Xiang-Xiang; Luo, Gang; Deng, Guang-Wei; Mosallanejad, Vahid; Taniguchi, Takashi; Watanabe, Kenji; Li, Hai-Ou; Cao, Gang; Guo, Guang-Can; Nori, Franco; Guo, Guo-Ping

2017-01-01

Quantum confinement has made it possible to detect and manipulate single-electron charge and spin states. The recent focus on two-dimensional (2D) materials has attracted significant interests on possible applications to quantum devices, including detecting and manipulating either single-electron charging behavior or spin and valley degrees of freedom. However, the most popular model systems, consisting of tunable double-quantum-dot molecules, are still extremely difficult to realize in these materials. We show that an artificial molecule can be reversibly formed in atomically thin MoS2 sandwiched in hexagonal boron nitride, with each artificial atom controlled separately by electrostatic gating. The extracted values for coupling energies at different regimes indicate a single-electron transport behavior, with the coupling strength between the quantum dots tuned monotonically. Moreover, in the low-density regime, we observe a decrease of the conductance with magnetic field, suggesting the observation of Coulomb blockade weak anti-localization. Our experiments demonstrate for the first time the realization of an artificial quantum-dot molecule in a gated MoS2 van der Waals heterostructure, which could be used to investigate spin-valley physics. The compatibility with large-scale production, gate controllability, electron-hole bipolarity, and new quantum degrees of freedom in the family of 2D materials opens new possibilities for quantum electronics and its applications. PMID:29062893

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

Kalinin, Sergei V.; Jesse, Stephen; Yang, Yaodong

Here, the nonlinear response of a ferroic to external fields has been studied for decades, garnering interest for both understanding fundamental physics, as well as technological applications such as memory devices. Yet, the behavior of ferroelectrics at mesoscopic regimes remains poorly understood, and the scale limits of theories developed for macroscopic regimes are not well tested experimentally. Here, we test the link between piezo-nonlinearity and local piezoelectric strain hysteresis, via AC-field dependent measurements in conjunction with first order reversal curve (FORC) measurements on (K,Na)NbO 3 crystals with band-excitation piezoelectric force microscopy. The correlation coefficient between nonlinearity amplitude and the FORCmore » of the polarization switching shows a clear decrease in correlation with increasing AC bias, suggesting the impact of domain wall clamping on the DC measurement case. Further, correlation of polynomial fitting terms from the nonlinear measurements with the hysteresis loop area reveals that the largest correlations are reserved for the quadratic terms, which is expected for irreversible domain wall motion contributions that impact both piezoelectric behavior as well as minor loop formation. These confirm the link between local piezoelectric nonlinearity, domain wall motion and minor loop formation, and suggest that existing theories (such as Preisach) are applicable at these length scales, with associated implications for future nanoscale devices.« less

The Paradox of Restoring Native River Landscapes and Restoring Native Ecosystems in the Colorado River System

NASA Astrophysics Data System (ADS)

Schmidt, J. C.

2014-12-01

Throughout the Colorado River basin (CRb), scientists and river managers collaborate to improve native ecosystems. Native ecosystems have deteriorated due to construction of dams and diversions that alter natural flow, sediment supply, and temperature regimes, trans-basin diversions that extract large amounts of water from some segments of the channel network, and invasion of non-native animals and plants. These scientist/manager collaborations occur in large, multi-stakeholder, adaptive management programs that include the Lower Colorado River Multi-Species Conservation Program, the Glen Canyon Dam Adaptive Management Program, and the Upper Colorado River Endangered Species Recovery Program. Although a fundamental premise of native species recovery is that restoration of predam flow regimes inevitably leads to native species recovery, such is not the case in many parts of the CRb. For example, populations of the endangered humpback chub (Gila cypha) are largest in the sediment deficit, thermally altered conditions of the Colorado River downstream from Glen Canyon Dam, but these species occur in much smaller numbers in the upper CRb even though the flow regime, sediment supply, and sediment mass balance are less perturbed. Similar contrasts in the physical and biological response of restoration of predam flow regimes occurs in floodplains dominated by nonnative tamarisk (Tamarix spp.) where reestablishment of floods has the potential to exacerbate vertical accretion processes that disconnect the floodplain from the modern flow regime. A significant challenge in restoring segments of the CRb is to describe this paradox of physical and biological response to reestablishment of pre-dam flow regimes, and to clearly identify objectives of environmentally oriented river management. In many cases, understanding the nature of the perturbation to sediment mass balance caused by dams and diversions and understanding the constraints imposed by societal commitments to provide assured water supplies and hydroelectricity constrains the opportunities for rehabilitation and limits the management objectives to focus either on restoring predam physical processes or recovering native fish fauna and/or recovering native plant communities.

The Mediterranean Sea regime shift at the end of the 1980s, and intriguing parallelisms with other European basins.

PubMed

Conversi, Alessandra; Fonda Umani, Serena; Peluso, Tiziana; Molinero, Juan Carlos; Santojanni, Alberto; Edwards, Martin

2010-05-19

Regime shifts are abrupt changes encompassing a multitude of physical properties and ecosystem variables, which lead to new regime conditions. Recent investigations focus on the changes in ecosystem diversity and functioning associated to such shifts. Of particular interest, because of the implication on climate drivers, are shifts that occur synchronously in separated basins. In this work we analyze and review long-term records of Mediterranean ecological and hydro-climate variables and find that all point to a synchronous change in the late 1980s. A quantitative synthesis of the literature (including observed oceanic data, models and satellite analyses) shows that these years mark a major change in Mediterranean hydrographic properties, surface circulation, and deep water convection (the Eastern Mediterranean Transient). We provide novel analyses that link local, regional and basin scale hydrological properties with two major indicators of large scale climate, the North Atlantic Oscillation index and the Northern Hemisphere Temperature index, suggesting that the Mediterranean shift is part of a large scale change in the Northern Hemisphere. We provide a simplified scheme of the different effects of climate vs. temperature on pelagic ecosystems. Our results show that the Mediterranean Sea underwent a major change at the end of the 1980s that encompassed atmospheric, hydrological, and ecological systems, for which it can be considered a regime shift. We further provide evidence that the local hydrography is linked to the larger scale, northern hemisphere climate. These results suggest that the shifts that affected the North, Baltic, Black and Mediterranean (this work) Seas at the end of the 1980s, that have been so far only partly associated, are likely linked as part a northern hemisphere change. These findings bear wide implications for the development of climate change scenarios, as synchronous shifts may provide the key for distinguishing local (i.e., basin) anthropogenic drivers, such as eutrophication or fishing, from larger scale (hemispheric) climate drivers.

Optical scheme for simulating post-quantum nonlocality distillation.

PubMed

Chu, Wen-Jing; Yang, Ming; Pan, Guo-Zhu; Yang, Qing; Cao, Zhuo-Liang

2016-11-28

An optical scheme for simulating nonlocality distillation is proposed in post-quantum regime. The nonlocal boxes are simulated by measurements on appropriately pre- and post-selected polarization entangled photon pairs, i.e. post-quantum nonlocality is simulated by exploiting fair-sampling loophole in a Bell test. Mod 2 addition on the outputs of two nonlocal boxes combined with pre- and post-selection operations constitutes the key operation of simulating nonlocality distillation. This scheme provides a possible tool for the experimental study on the nonlocality in post-quantum regime and the exact physical principle precisely distinguishing physically realizable correlations from nonphysical ones.

Towards an analytical framework for tailoring supercontinuum generation.

PubMed

Castelló-Lurbe, David; Vermeulen, Nathalie; Silvestre, Enrique

2016-11-14

A fully analytical toolbox for supercontinuum generation relying on scenarios without pulse splitting is presented. Furthermore, starting from the new insights provided by this formalism about the physical nature of direct and cascaded dispersive wave emission, a unified description of this radiation in both normal and anomalous dispersion regimes is derived. Previously unidentified physics of broadband spectra reported in earlier works is successfully explained on this basis. Finally, a foundry-compatible few-millimeters-long silicon waveguide allowing octave-spanning supercontinuum generation pumped at telecom wavelengths in the normal dispersion regime is designed, hence showcasing the potential of this new analytical approach.

The locking and unlocking thresholds for tearing modes in a cylindrical tokamak

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

Huang, Wenlong; Zhu, Ping, E-mail: pzhu@ustc.edu.cn; Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706

2016-03-15

The locking and unlocking thresholds for tearing modes are in general different. In this work, the physics origin for this difference is illustrated from theory analysis, and a numerical procedure is developed to find both locking and unlocking thresholds. In particular, a new scaling law for the unlocking threshold that is valid in both weak and strong rotation regimes has been derived from the lowest amplitude of the RMP (resonant magnetic perturbation) allowed for the locked-mode solution. Above the unlocking threshold, the criterion for the phase-flip instability is extended to identify the entire locked-mode states. Two different regimes of themore » RMP amplitude in terms of the accessibility of the locked-mode states have been found. In the first regime, the locked-mode state may or may not be accessible depending on the initial conditions of an evolving island. In the second regime, the locked-mode state can always be reached regardless of the initial conditions of the tearing mode. The lowest RMP amplitude for the second regime is determined to be the mode-locking threshold. The different characteristics of the two regimes above the unlocking threshold reveal the underlying physics for the gap between the locking and unlocking thresholds and provide an explanation for the closely related and widely observed hysteresis phenomena in island evolution during the sweeping process of the RMP amplitude up and down across that threshold gap.« less

Nonlinear saturation of the slab ITG instability and zonal flow generation with fully kinetic ions

NASA Astrophysics Data System (ADS)

Miecnikowski, Matthew T.; Sturdevant, Benjamin J.; Chen, Yang; Parker, Scott E.

2018-05-01

Fully kinetic turbulence models are of interest for their potential to validate or replace gyrokinetic models in plasma regimes where the gyrokinetic expansion parameters are marginal. Here, we demonstrate fully kinetic ion capability by simulating the growth and nonlinear saturation of the ion-temperature-gradient instability in shearless slab geometry assuming adiabatic electrons and including zonal flow dynamics. The ion trajectories are integrated using the Lorentz force, and the cyclotron motion is fully resolved. Linear growth and nonlinear saturation characteristics show excellent agreement with analogous gyrokinetic simulations across a wide range of parameters. The fully kinetic simulation accurately reproduces the nonlinearly generated zonal flow. This work demonstrates nonlinear capability, resolution of weak gradient drive, and zonal flow physics, which are critical aspects of modeling plasma turbulence with full ion dynamics.

Vibrational dynamics of vocal folds using nonlinear normal modes.

PubMed

Pinheiro, Alan P; Kerschen, Gaëtan

2013-08-01

Many previous works involving physical models, excised and in vivo larynges have pointed out nonlinear vibration in vocal folds during voice production. Moreover, theoretical studies involving mechanical modeling of these folds have tried to gain a profound understanding of the observed nonlinear phenomena. In this context, the present work uses the nonlinear normal mode theory to investigate the nonlinear modal behavior of 16 subjects using a two-mass mechanical modeling of the vocal folds. The free response of the conservative system at different energy levels is considered to assess the impact of the structural nonlinearity of the vocal fold tissues. The results show very interesting and complex nonlinear phenomena including frequency-energy dependence, subharmonic regimes and, in some cases, modal interactions, entrainment and bifurcations. Copyright © 2012 IPEM. Published by Elsevier Ltd. All rights reserved.

Surface Spectroscopy Center Of Excellence Project

NASA Technical Reports Server (NTRS)

Wooden, Diane

2014-01-01

We propose to develop a national center of excellence in Regolith Radiative Transfer (RRT), i.e., in modeling spectral reflectivity and emissivity of grainy or structured surfaces. The focus is the regime where the structural elements of grainy surfaces have grain sizes and separations of tens of microns, comparable to the wavelengths carrying diagnostic compositional information. This regime is of fundamental interest to remote sensing of planetary and terrestrial surfaces.

Optimizing management regimes for carbon storage and other benefits in uneven-aged stands dominated by Norway spruce, with a derivation of the economic supply of carbon storage

Treesearch

Joseph Buongiorno; Espen Andreas Halvorsen; Ole Martin Bollandsas; Terje Gobakken; Ole Hofstad

2012-01-01

This study sought optimal sustainable management regimes of uneven-aged Norway spruce-dominated stands with multiple objectives. The criteria were financial returns, CO2 sequestration and diversity of tree size and species. At prevailing timber prices, harvest and transport costs, and interest rates, uneven-aged management for timber alone was...

Solar neutrino spectroscopy

NASA Astrophysics Data System (ADS)

Wurm, Michael

2017-04-01

More than forty years after the first detection of neutrinos from the Sun, the spectroscopy of solar neutrinos has proven to be an on-going success story. The long-standing puzzle about the observed solar neutrino deficit has been resolved by the discovery of neutrino flavor oscillations. Today's experiments have been able to solidify the standard MSW-LMA oscillation scenario by performing precise measurements over the whole energy range of the solar neutrino spectrum. This article reviews the enabling experimental technologies: On the one hand multi-kiloton-scale water Cherenkov detectors performing measurements in the high-energy regime of the spectrum, on the other end ultrapure liquid-scintillator detectors that allow for a low-threshold analysis. The current experimental results on the fluxes, spectra and time variation of the different components of the solar neutrino spectrum will be presented, setting them in the context of both neutrino oscillation physics and the hydrogen fusion processes embedded in the Standard Solar Model. Finally, the physics potential of state-of-the-art detectors and a next generation of experiments based on novel techniques will be assessed in the context of the most interesting open questions in solar neutrino physics: a precise measurement of the vacuum-matter transition curve of electron-neutrino oscillation probability that offers a definitive test of the basic MSW-LMA scenario or the appearance of new physics; and a first detection of neutrinos from the CNO cycle that will provide new information on solar metallicity and stellar physics.

Quantum metabolism explains the allometric scaling of metabolic rates.

PubMed

Demetrius, Lloyd; Tuszynski, J A

2010-03-06

A general model explaining the origin of allometric laws of physiology is proposed based on coupled energy-transducing oscillator networks embedded in a physical d-dimensional space (d = 1, 2, 3). This approach integrates Mitchell's theory of chemi-osmosis with the Debye model of the thermal properties of solids. We derive a scaling rule that relates the energy generated by redox reactions in cells, the dimensionality of the physical space and the mean cycle time. Two major regimes are found corresponding to classical and quantum behaviour. The classical behaviour leads to allometric isometry while the quantum regime leads to scaling laws relating metabolic rate and body size that cover a broad range of exponents that depend on dimensionality and specific parameter values. The regimes are consistent with a range of behaviours encountered in micelles, plants and animals and provide a conceptual framework for a theory of the metabolic function of living systems.

Momentum transport and nonlocality in heat-flux-driven magnetic reconnection in high-energy-density plasmas

DOE PAGES

Liu, Chang; Fox, William; Bhattacharjee, Amitava; ...

2017-10-06

Recent theory has demonstrated a novel physics regime for magnetic reconnection in high-energy-density plasmas where the magnetic field is advected by heat flux via the Nernst effect. In this paper, we elucidate the physics of the electron dissipation layer in this regime. Through fully kinetic simulation and a generalized Ohm's law derived from first principles, we show that momentum transport due to a nonlocal effect, the heat-flux-viscosity, provides the dissipation mechanism for magnetic reconnection. Scaling analysis, and simulations show that the reconnection process comprises a magnetic field compression stage and quasisteady reconnection stage, and the characteristic width of the currentmore » sheet in this regime is several electron mean-free paths. Finally, these results show the important interplay between nonlocal transport effects and generation of anisotropic components to the distribution function.« less

Exploring Ultrahigh-Intensity Laser-Plasma Interaction Physics with QED Particle-in-Cell Simulations

NASA Astrophysics Data System (ADS)

Luedtke, S. V.; Yin, L.; Labun, L. A.; Albright, B. J.; Stark, D. J.; Bird, R. F.; Nystrom, W. D.; Hegelich, B. M.

2017-10-01

Next generation high-intensity lasers are reaching intensity regimes where new physics-quantum electrodynamics (QED) corrections to otherwise classical plasma dynamics-becomes important. Modeling laser-plasma interactions in these extreme settings presents a challenge to traditional particle-in-cell (PIC) codes, which either do not have radiation reaction or include only classical radiation reaction. We discuss a semi-classical approach to adding quantum radiation reaction and photon production to the PIC code VPIC. We explore these intensity regimes with VPIC, compare with results from the PIC code PSC, and report on ongoing work to expand the capability of VPIC in these regimes. This work was supported by the U.S. DOE, Los Alamos National Laboratory Science program, LDRD program, NNSA (DE-NA0002008), and AFOSR (FA9550-14-1-0045). HPC resources provided by TACC, XSEDE, and LANL Institutional Computing.

Use of physically-based models and Soil Taxonomy to identify soil moisture classes: Problems and proposals

NASA Astrophysics Data System (ADS)

Bonfante, A.; Basile, A.; de Mascellis, R.; Manna, P.; Terribile, F.

2009-04-01

Soil classification according to Soil Taxonomy include, as fundamental feature, the estimation of soil moisture regime. The term soil moisture regime refers to the "presence or absence either of ground water or of water held at a tension of less than 1500 kPa in the soil or in specific horizons during periods of the year". In the classification procedure, defining of the soil moisture control section is the primary step in order to obtain the soil moisture regimes classification. Currently, the estimation of soil moisture regimes is carried out through simple calculation schemes, such as Newhall and Billaux models, and only in few cases some authors suggest the use of different more complex models (i.e., EPIC) In fact, in the Soil Taxonomy, the definition of the soil moisture control section is based on the wetting front position in two different conditions: the upper boundary is the depth to which a dry soil will be moistened by 2.5 cm of water within 24 hours and the lower boundary is the depth to which a dry soil will be moistened by 7.5 cm of water within 48 hours. Newhall, Billaux and EPIC models don't use physical laws to describe soil water flows, but they use a simple bucket-like scheme where the soil is divided into several compartments and water moves, instantly, only downward when the field capacity is achieved. On the other side, a large number of one-dimensional hydrological simulation models (SWAP, Cropsyst, Hydrus, MACRO, etc..) are available, tested and successfully used. The flow is simulated according to pressure head gradients through the numerical solution of the Richard's equation. These simulation models can be fruitful used to improve the study of soil moisture regimes. The aims of this work are: (i) analysis of the soil moisture control section concept by a physically based model (SWAP); (ii) comparison of the classification obtained in five different Italian pedoclimatic conditions (Mantova and Lodi in northern Italy; Salerno, Benevento and Caserta in southern Italy) applying the classical models (Newhall e Billaux) and the physically-based models (CropSyst e SWAP), The results have shown that the Soil Taxonomy scheme for the definition of the soil moisture regime is unrealistic for the considered Mediterranean soil hydrological conditions. In fact, the same classifications arise irrespective of the soil type. In this respect some suggestions on how modified the section control boundaries were formulated. Keywords: Soil moisture regimes, Newhall, Swap, Soil Taxonomy

Physical Applications of a Simple Approximation of Bessel Functions of Integer Order

ERIC Educational Resources Information Center

Barsan, V.; Cojocaru, S.

2007-01-01

Applications of a simple approximation of Bessel functions of integer order, in terms of trigonometric functions, are discussed for several examples from electromagnetism and optics. The method may be applied in the intermediate regime, bridging the "small values regime" and the "asymptotic" one, and covering, in this way, an area of great…

Producing Homogeneity as a Historical Tradition. Neo-Conservatism, Precarity and Citizenship Education in Poland

ERIC Educational Resources Information Center

Cervinkova, Hana

2016-01-01

In this paper, I am interested in exploring citizenship regimes as they emerge from the interplay of neoliberal and neoconservative developments in contemporary Europe. I am particularly interested in the connections between different types of contemporary precarity and citizenship imaginaries as they transpire at the historical nexus of a…

Interest Groups, the Courts, and Educational Equality: A Policy Regimes Approach to "Vergara v. California"

ERIC Educational Resources Information Center

Superfine, Benjamin Michael; Thompson, Alea R.

2016-01-01

In "Vergara v. California" (2014), a trial-level court ruled that California laws governing teacher tenure and dismissal were unconstitutional. This study analyzes "Vergara" in light of the shifting use of the courts to promote equal educational opportunities and the changing power bases of educational interest groups,…

Collective Poisson process with periodic rates: applications in physics from micro-to nanodevices.

PubMed

da Silva, Roberto; Lamb, Luis C; Wirth, Gilson Inacio

2011-01-28

Continuous reductions in the dimensions of semiconductor devices have led to an increasing number of noise sources, including random telegraph signals (RTS) due to the capture and emission of electrons by traps at random positions between oxide and semiconductor. The models traditionally used for microscopic devices become of limited validity in nano- and mesoscale systems since, in such systems, distributed quantities such as electron and trap densities, and concepts like electron mobility, become inadequate to model electrical behaviour. In addition, current experimental works have shown that RTS in semiconductor devices based on carbon nanotubes lead to giant current fluctuations. Therefore, the physics of this phenomenon and techniques to decrease the amplitudes of RTS need to be better understood. This problem can be described as a collective Poisson process under different, but time-independent, rates, τ(c) and τ(e), that control the capture and emission of electrons by traps distributed over the oxide. Thus, models that consider calculations performed under time-dependent periodic capture and emission rates should be of interest in order to model more efficient devices. We show a complete theoretical description of a model that is capable of showing a noise reduction of current fluctuations in the time domain, and a reduction of the power spectral density in the frequency domain, in semiconductor devices as predicted by previous experimental work. We do so through numerical integrations and a novel Monte Carlo Markov chain (MCMC) algorithm based on microscopic discrete values. The proposed model also handles the ballistic regime, relevant in nano- and mesoscale devices. Finally, we show that the ballistic regime leads to nonlinearity in the electrical behaviour.

Implicit unified gas-kinetic scheme for steady state solutions in all flow regimes

NASA Astrophysics Data System (ADS)

Zhu, Yajun; Zhong, Chengwen; Xu, Kun

2016-06-01

This paper presents an implicit unified gas-kinetic scheme (UGKS) for non-equilibrium steady state flow computation. The UGKS is a direct modeling method for flow simulation in all regimes with the updates of both macroscopic flow variables and microscopic gas distribution function. By solving the macroscopic equations implicitly, a predicted equilibrium state can be obtained first through iterations. With the newly predicted equilibrium state, the evolution equation of the gas distribution function and the corresponding collision term can be discretized in a fully implicit way for fast convergence through iterations as well. The lower-upper symmetric Gauss-Seidel (LU-SGS) factorization method is implemented to solve both macroscopic and microscopic equations, which improves the efficiency of the scheme. Since the UGKS is a direct modeling method and its physical solution depends on the mesh resolution and the local time step, a physical time step needs to be fixed before using an implicit iterative technique with a pseudo-time marching step. Therefore, the physical time step in the current implicit scheme is determined by the same way as that in the explicit UGKS for capturing the physical solution in all flow regimes, but the convergence to a steady state speeds up through the adoption of a numerical time step with large CFL number. Many numerical test cases in different flow regimes from low speed to hypersonic ones, such as the Couette flow, cavity flow, and the flow passing over a cylinder, are computed to validate the current implicit method. The overall efficiency of the implicit UGKS can be improved by one or two orders of magnitude in comparison with the explicit one.

Diffraction of electrons at intermediate energies: The role of phonons

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

Ascolani, H.; Zampieri, G.

1996-07-01

The intensity of electrons reflected {open_quote}{open_quote}elastically{close_quote}{close_quote} from crystalline surfaces presents two regimes: the low-energy or LEED regime ({lt}500 eV), in which the electrons are reflected along the Bragg directions, and the intermediate-energy or XPD/AED regime ({gt}500 eV), in which the maxima of intensity are along the main crystallographic axes. We present a model which explains this transition in terms of the excitation/absorption of phonons during the scattering. {copyright} {ital 1996 American Institute of Physics.}

Elasticity of entangled polymer loops: Olympic gels

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

Vilgis, T.A.; Otto, M.

1997-08-01

In this Rapid Communication we present a scaling theory for the elasticity of olympic gels, i.e., gels where the elasticity is a consequence of topology only. It is shown that two deformation regimes exist. The first is the nonaffine deformation regime where the free energy scales linear with the deformation. In the large (affine) deformation regime the free energy is shown to scale as F{proportional_to}{lambda}{sup 5/2} where {lambda} is the deformation ratio. Thus a highly non-Hookian stress-strain relation is predicted. {copyright} {ital 1997} {ital The American Physical Society}

A review of at rest droplet growth equations for condensing nitrogen in transonic cryogenic wind tunnels

NASA Technical Reports Server (NTRS)

Hall, R. M.; Kramer, S. A.

1979-01-01

Droplet growth equations are reviewed in the free-molecular, transition, and continuum flow regimes with the assumption that the droplets are at rest with respect to the vapor. As comparison calculations showed, it was important to use a growth equation designed for the flow regime of interest. Otherwise, a serious over-prediction of droplet growth may result. The growth equation by Gyarmathy appeared to be applicable throughout the flow regimes and involved no iteration. His expression also avoided the uncertainty associated with selecting a mass accommodation coefficient and consequently involved less uncertainty in specifying adjustable parameters than many of the other growth equations.

Comparative climatology of four marine stratocumulus regimes

NASA Technical Reports Server (NTRS)

Hanson, Howard P.

1990-01-01

The climatology of marine stratocumulus (MSc) cloud regimes off the west coasts of California, Peru, Morocco, and Angola are examined. Long-term, annual averages are presented for several quantities of interest in the four MSc regimes. The climatologies were constructed using the Comprehensive Ocean-Atmosphere Data Set (COADS). A 40 year time series of observations was extracted for 32 x 32 deg analysis domains. The data were taken from the monthly-averaged, 2 deg product. The resolution of the analysis is therefore limited to scales of greater than 200 km with submonthly variability not resolved. The averages of total cloud cover, sea surface temperature, and surface pressure are presented.

Labour Universities: Physical Education and the Indoctrination of the Working Class

ERIC Educational Resources Information Center

Delgado-Granados, Patricia; Ramírez-Macías, Gonzalo

2014-01-01

This paper explores the role of physical education in Labour Universities (1955-1978) during Franco's regime as an instrument of indoctrination and declassing of the working class. The conclusions obtained after the study and the analysis of various primary sources indicate that, initially, physical education was used as an instrument of…

How can prescribed burning and harvesting restore shortleaf pine-oak woodland at the landscape scale in central United States? Modeling joint effects of harvest and fire regimes

Treesearch

Wenchi Jin; Hong S. He; Stephen R. Shifley; Wen J. Wang; John M. Kabrick; Brian K. Davidson

2018-01-01

Historical fire regimes in the central United States maintained open-canopy shortleaf pine-oak woodlands on xeric sites. Following large-scale harvest and fire suppression, those woodlands grew denser with more continuous canopy cover, and they gained mesic species at the expense of shortleaf pine. There is high interest in restoring shortleaf pine-oak woodlands; most...

Optimal two-stage dynamic treatment regimes from a classification perspective with censored survival data.

PubMed

Hager, Rebecca; Tsiatis, Anastasios A; Davidian, Marie

2018-05-18

Clinicians often make multiple treatment decisions at key points over the course of a patient's disease. A dynamic treatment regime is a sequence of decision rules, each mapping a patient's observed history to the set of available, feasible treatment options at each decision point, and thus formalizes this process. An optimal regime is one leading to the most beneficial outcome on average if used to select treatment for the patient population. We propose a method for estimation of an optimal regime involving two decision points when the outcome of interest is a censored survival time, which is based on maximizing a locally efficient, doubly robust, augmented inverse probability weighted estimator for average outcome over a class of regimes. By casting this optimization as a classification problem, we exploit well-studied classification techniques such as support vector machines to characterize the class of regimes and facilitate implementation via a backward iterative algorithm. Simulation studies of performance and application of the method to data from a sequential, multiple assignment randomized clinical trial in acute leukemia are presented. © 2018, The International Biometric Society.

A quantum diffusion law

NASA Astrophysics Data System (ADS)

Satpathi, Urbashi; Sinha, Supurna; Sorkin, Rafael D.

2017-12-01

We analyse diffusion at low temperature by bringing the fluctuation-dissipation theorem (FDT) to bear on a physically natural, viscous response-function R(t) . The resulting diffusion-law exhibits several distinct regimes of time and temperature, each with its own characteristic rate of spreading. As with earlier analyses, we find logarithmic spreading in the quantum regime, indicating that this behavior is robust. A consistent R(t) must satisfy the key physical requirements of Wightman positivity and passivity, and we prove that ours does so. We also prove in general that these two conditions are equivalent when the FDT holds. Given current technology, our diffusion law can be tested in a laboratory with ultra cold atoms.

An integrated model for the natural flow regime in the Cerro Prieto hydrothermal system based upon petrological and isotope geochemical criteria

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

Elders, W.A.; Williams, A.E.; Hoagland, J..

1981-01-01

Studies of cuttings and cores at Cerro Prieto have now been extended to more than 50 boreholes. The aims of this petrological and isotopic work are to determine the shape of the reservoir, its physical properties, and its temperature distribution and flow regime before the steam field was produced.

Evolution from successive phase transitions to "morphotropic phase boundary" in BaTiO3-based ferroelectrics

NASA Astrophysics Data System (ADS)

Zhou, Chao; Ke, Xiaoqin; Yao, Yonggang; Yang, Sen; Ji, Yuanchao; Liu, Wenfeng; Yang, Yaodong; Zhang, Lixue; Hao, Yanshuang; Ren, Shuai; Zhang, Le; Ren, Xiaobing

2018-04-01

Obtaining superior physical properties for ferroic materials by manipulating the phase transitions is a key concern in solid state physics. Here, we investigated the dielectric permittivity, piezoelectric coefficient d33, storage modulus, and crystal symmetry of (1-x)Ba(Ti0.8Zr0.2)O3-x(Ba1-yCay)TiO3 (BZT-xBCyT) systems to demonstrate the gradual evolution process from successive phase transitions in BaTiO3 to the morphotropic phase boundary (MPB) regime in BZT-xBC0.3T. Furthermore, we analysed with a Landau-type theoretical model to show that the high field-sensitive response (dielectric permittivity) originates from a small polarization anisotropy and low energy barrier at the quadruple point. Together, the intermediate orthorhombic phase regime and the tetragonal-orthorhombic and orthorhombic-rhombohedral phase boundaries constitute the MPB. Our work not only reconciles the arguments regarding whether the structural state around the MPB corresponds to a single-phase regime or a multiple-phase-coexistence regime but also suggests an effective method to design high-performance functional ferroic materials by tailoring the successive phase transitions.

The Effects of Instruction of Creative Invention on Students' Situational Interest in Physics Lesson

NASA Astrophysics Data System (ADS)

Leung, Tim

There are a few empirical studies (Palmer, 2008; Dohn, 2010) or intervention programs (Hidi & Harackiewicz, 2000) about students' situational interest in physics lessons, although the declining interest in physics among students has been well documented in the research literature (Gardner, 1998 ; International Bureau for Education, 2001; European Commission, 2007; Oon & Subramaniam, 2011). Even in the research area of science education, yet little is known about how to trigger students' catching and holding situational interest in a physics lesson. In this study, five intervention lessons of creative invention were developed. Each lesson consists of three parts including Eberle's (1971, 1972) SCAMPER technique on the creative thinking, knowledge and concepts of physics curriculum, hands-on activities related to both SCAMPER technique and physics concepts. Two surveys were developed and used to measure the situational interest and individual interest of students in physics lessons. Qualitative conversational interviews were used to interpret the sources of situational interest of students in physics lessons. Results in this study indicate that new inventive products and television programs or films related to SCAMPER can trigger the catching interest in physics lessons. Meaningful hands-on activities related to both SCAMPER technique and physics concepts can trigger the holding interest in physics lessons. There is no significant difference in situational interest among students with different academic abilities except in the topic related to electronic components. The students with lower academic ability have greater situational interest than the students with higher academic ability in learning the topic related to electronic components. There is no significant difference in situational interest between boys and girls except in the topic related to revolving paper lantern. Girls have higher situational interest than boys in learning the topic related to revolving paper lantern. The findings in this study suggest that educators can use instruction of creative invention to trigger students' situational interest and enhance students' individual interest in physics lessons.

Phytoplankton response to the contrasting physical regimes in the eastern Arabian Sea during north east monsoon

NASA Astrophysics Data System (ADS)

Chndrasekhararao, A. V.; Kurian, Siby; Vidya, P. J.; Gauns, Mangesh; Shenoy, Damodar M.; Mulla, Amara; Naik, Hema; Reddy, T. Venugopal; Naqvi, S. W. A.

2018-06-01

Phytoplankton abundance and composition in two contrasting physical regimes - convective mixing in the northeastern Arabian Sea (NEAS) and Arabian Sea mini warm pool (ASMWP) in the southeastern Arabian Sea (SEAS) - were investigated during the northeast monsoon (NEM) of 2015 and 2017. Observations in 2015 were carried out late during the season, and only one station in the north (at 21°N latitude) fell within the zone of convective mixing where microplankton was dominated by diatoms. In 2017, convective mixing occurred even at 16°N latitude, but the microplankton contribution was low, presumably due to low Si/N ratios. Within the convective mixing regime of the NEAS, chlorophyll (Chl) a concentrations were higher in 2015 (maximum 1080 ng L-1; average 493 ng L-1) than in 2017 (maximum 673 ng L-1; average 263 ng L-1). In contrast, picophytoplankton were dominant in the ASMWP of the SEAS with peak abundance associated with the subsurface chlorophyll maximum. A warm core eddy was present in 2015 in the SEAS where four times higher Prochlorococcus counts were found within the core of the eddy than at its periphery. This study provides the first description of the phytoplankton community in the ASMWP. Our results clearly demonstrate phytoplankton response to the contrasting physical conditions, highlighting the role of bio-physical coupling in the productivity of the Arabian Sea.

Untangling outcomes of de jure and de facto community-based management of natural resources.

PubMed

Agarwala, Meghna; Ginsberg, Joshua R

2017-12-01

We systematically reviewed the literature on the tragedy of the commons and common-property resources. We segregated studies by legal management regimes (de jure regimes) and management that develops in practice (de facto regimes) to understand how the structure of regime formation affects the outcome of community management on sustainability of resource use. De facto regimes, developed within the community, are more likely to have positive impacts on the resource. However, de facto regimes are fragile and not resilient in the face of increased population pressure and unregulated markets, and de facto management regimes are less successful where physical exclusion of external agents from resources is more difficult. Yet, formalization or imposition of de jure management regimes can have complicated impacts on sustainability. The imposition of de jure regimes usually has a negative outcome when existing de facto regimes operate at larger scales than the imposed de jure regime. In contrast, de jure regimes have largely positive impacts when the de facto regimes operate at scales smaller than the overlying de jure regimes. Formalization may also be counterproductive because of elite capture and the resulting de facto privatization (that allows elites to effectively exclude others) or de facto open access (where the disenfranchised may resort to theft and elites cannot effectively exclude them). This underscores that although the global movement to formalize community-management regimes may address some forms of inequity and may produce better outcomes, it does not ensure resource sustainability and may lead to greater marginalization of users. Comparison of governance systems that differentiate between initiatives that legitimize existing de facto regimes and systems that create new de facto regimes, investigations of new top-down de jure regimes, and studies that further examine different approaches to changing de jure regimes to de facto regimes are avenues for further inquiry. © 2017 Society for Conservation Biology.

Bridging the Conceptual Gap between Free Fall and Drag-Dominated Regimes

ERIC Educational Resources Information Center

de Obaldia, Elida; Miller, Norma; Wittel, Fred; Jaimison, George; Wallis, Kendra

2016-01-01

Some misconceptions about physics are hard to change. For example, students continue to believe that heavier objects fall faster than light ones, even after a year of physics instruction. Physics misconceptions are persistent. Light objects do fall more slowly if their size-to-weight ratio is sufficient for drag to be appreciable. Motion through a…

Design of a Data Catalogue for Perdigão-2017 Field Experiment: Establishing the Relevant Parameters, Post-Processing Techniques and Users Access

NASA Astrophysics Data System (ADS)

Palma, J. L.; Belo-Pereira, M.; Leo, L. S.; Fernando, J.; Wildmann, N.; Gerz, T.; Rodrigues, C. V.; Lopes, A. S.; Lopes, J. C.

2017-12-01

Perdigão is the largest of a series of wind-mapping studies embedded in the on-going NEWA (New European Wind Atlas) Project. The intensive observational period of the Perdigão field experiment resulted in an unprecedented volume of data, covering several wind conditions through 46 consecutive days between May and June 2017. For researchers looking into specific events, it is time consuming to scrutinise the datasets looking for appropriate conditions. Such task becomes harder if the parameters of interest were not measured directly, instead requiring their computation from the raw datasets. This work will present the e-Science platform developed by University of Porto for the Perdigao dataset. The platform will assist scientists of Perdigao and the larger scientific community in extrapolating the datasets associated to specific flow regimes of interest as well as automatically performing post-processing/filtering operations internally in the platform. We will illustrate the flow regime categories identified in Perdigao based on several parameters such as weather type classification, cloud characteristics, as well as stability regime indicators (Brunt-Väisälä frequency, Scorer parameter, potential temperature inversion heights, dimensionless Richardson and Froude numbers) and wind regime indicators. Examples of some of the post-processing techniques available in the e-Science platform, such as the Savitzky-Golay low-pass filtering technique, will be also presented.

A full-angle Monte-Carlo scattering technique including cumulative and single-event Rutherford scattering in plasmas [Theory of cumulative large-angle collisions in plasmas

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

Higginson, Drew P.

Here, we describe and justify a full-angle scattering (FAS) method to faithfully reproduce the accumulated differential angular Rutherford scattering probability distribution function (pdf) of particles in a plasma. The FAS method splits the scattering events into two regions. At small angles it is described by cumulative scattering events resulting, via the central limit theorem, in a Gaussian-like pdf; at larger angles it is described by single-event scatters and retains a pdf that follows the form of the Rutherford differential cross-section. The FAS method is verified using discrete Monte-Carlo scattering simulations run at small timesteps to include each individual scattering event.more » We identify the FAS regime of interest as where the ratio of temporal/spatial scale-of-interest to slowing-down time/length is from 10 -3 to 0.3–0.7; the upper limit corresponds to Coulomb logarithm of 20–2, respectively. Two test problems, high-velocity interpenetrating plasma flows and keV-temperature ion equilibration, are used to highlight systems where including FAS is important to capture relevant physics.« less

Significant enhancement of magnetoresistance with the reduction of particle size in nanometer scale

PubMed Central

Das, Kalipada; Dasgupta, P.; Poddar, A.; Das, I.

2016-01-01

The Physics of materials with large magnetoresistance (MR), defined as the percentage change of electrical resistance with the application of external magnetic field, has been an active field of research for quite some times. In addition to the fundamental interest, large MR has widespread application that includes the field of magnetic field sensor technology. New materials with large MR is interesting. However it is more appealing to vast scientific community if a method describe to achieve many fold enhancement of MR of already known materials. Our study on several manganite samples [La1−xCaxMnO3 (x = 0.52, 0.54, 0.55)] illustrates the method of significant enhancement of MR with the reduction of the particle size in nanometer scale. Our experimentally observed results are explained by considering model consisted of a charge ordered antiferromagnetic core and a shell having short range ferromagnetic correlation between the uncompensated surface spins in nanoscale regime. The ferromagnetic fractions obtained theoretically in the nanoparticles has been shown to be in the good agreement with the experimental results. The method of several orders of magnitude improvement of the magnetoresistive property will have enormous potential for magnetic field sensor technology. PMID:26837285

A full-angle Monte-Carlo scattering technique including cumulative and single-event Rutherford scattering in plasmas [Theory of cumulative large-angle collisions in plasmas

DOE PAGES

Higginson, Drew P.

2017-08-12

Here, we describe and justify a full-angle scattering (FAS) method to faithfully reproduce the accumulated differential angular Rutherford scattering probability distribution function (pdf) of particles in a plasma. The FAS method splits the scattering events into two regions. At small angles it is described by cumulative scattering events resulting, via the central limit theorem, in a Gaussian-like pdf; at larger angles it is described by single-event scatters and retains a pdf that follows the form of the Rutherford differential cross-section. The FAS method is verified using discrete Monte-Carlo scattering simulations run at small timesteps to include each individual scattering event.more » We identify the FAS regime of interest as where the ratio of temporal/spatial scale-of-interest to slowing-down time/length is from 10 -3 to 0.3–0.7; the upper limit corresponds to Coulomb logarithm of 20–2, respectively. Two test problems, high-velocity interpenetrating plasma flows and keV-temperature ion equilibration, are used to highlight systems where including FAS is important to capture relevant physics.« less

Existence and numerical simulation of periodic traveling wave solutions to the Casimir equation for the Ito system

NASA Astrophysics Data System (ADS)

Abbasbandy, S.; Van Gorder, R. A.; Hajiketabi, M.; Mesrizadeh, M.

2015-10-01

We consider traveling wave solutions to the Casimir equation for the Ito system (a two-field extension of the KdV equation). These traveling waves are governed by a nonlinear initial value problem with an interesting nonlinearity (which actually amplifies in magnitude as the size of the solution becomes small). The nonlinear problem is parameterized by two initial constant values, and we demonstrate that the existence of solutions is strongly tied to these parameter values. For our interests, we are concerned with positive, bounded, periodic wave solutions. We are able to classify parameter regimes which admit such solutions in full generality, thereby obtaining a nice existence result. Using the existence result, we are then able to numerically simulate the positive, bounded, periodic solutions. We elect to employ a group preserving scheme in order to numerically study these solutions, and an outline of this approach is provided. The numerical simulations serve to illustrate the properties of these solutions predicted analytically through the existence result. Physically, these results demonstrate the existence of a type of space-periodic structure in the Casimir equation for the Ito model, which propagates as a traveling wave.

Organic Power Electronics: Transistor Operation in the kA/cm2 Regime

PubMed Central

Klinger, Markus P.; Fischer, Axel; Kaschura, Felix; Widmer, Johannes; Kheradmand-Boroujeni, Bahman; Ellinger, Frank; Leo, Karl

2017-01-01

In spite of interesting features as flexibility, organic thin-film transistors have commercially lagged behind due to the low mobilities of organic semiconductors associated with hopping transport. Furthermore, organic transistors usually have much larger channel lengths than their inorganic counterparts since high-resolution structuring is not available in low-cost production schemes. Here, we present an organic permeable-base transistor (OPBT) which, despite extremely simple processing without any high-resolution structuring, achieve a performance beyond what has so far been possible using organic semiconductors. With current densities above 1 kA cm−2 and switching speeds towards 100 MHz, they open the field of organic power electronics. Finding the physical limits and an effective mobility of only 0.06 cm2 V−1 s−1, this OPBT device architecture has much more potential if new materials optimized for its geometry will be developed. PMID:28303924

Relativistic-microwave theory of ball lightning.

PubMed

Wu, H-C

2016-06-22

Ball lightning, a fireball sometimes observed during lightnings, has remained unexplained. Here we present a comprehensive theory for the phenomenon: At the tip of a lightning stroke reaching the ground, a relativistic electron bunch can be produced, which in turn excites intense microwave radiation. The latter ionizes the local air and the radiation pressure evacuates the resulting plasma, forming a spherical plasma bubble that stably traps the radiation. This mechanism is verified by particle simulations. The many known properties of ball lightning, such as the occurrence site, relation to the lightning channels, appearance in aircraft, its shape, size, sound, spark, spectrum, motion, as well as the resulting injuries and damages, are also explained. Our theory suggests that ball lighting can be created in the laboratory or triggered during thunderstorms. Our results should be useful for lightning protection and aviation safety, as well as stimulate research interest in the relativistic regime of microwave physics.

Mantle dynamics and seismic tomography

PubMed Central

Tanimoto, Toshiro; Lay, Thorne

2000-01-01

Three-dimensional imaging of the Earth's interior, called seismic tomography, has achieved breakthrough advances in the last two decades, revealing fundamental geodynamical processes throughout the Earth's mantle and core. Convective circulation of the entire mantle is taking place, with subducted oceanic lithosphere sinking into the lower mantle, overcoming the resistance to penetration provided by the phase boundary near 650-km depth that separates the upper and lower mantle. The boundary layer at the base of the mantle has been revealed to have complex structure, involving local stratification, extensive structural anisotropy, and massive regions of partial melt. The Earth's high Rayleigh number convective regime now is recognized to be much more interesting and complex than suggested by textbook cartoons, and continued advances in seismic tomography, geodynamical modeling, and high-pressure–high-temperature mineral physics will be needed to fully quantify the complex dynamics of our planet's interior. PMID:11035784

Supramolecular ferroelectrics.

PubMed

Tayi, Alok S; Kaeser, Adrien; Matsumoto, Michio; Aida, Takuzo; Stupp, Samuel I

2015-04-01

Supramolecular chemistry uses non-covalent interactions to coax molecules into forming ordered assemblies. The construction of ordered materials with these reversible bonds has led to dramatic innovations in organic electronics, polymer science and biomaterials. Here, we review how supramolecular strategies can advance the burgeoning field of organic ferroelectricity. Ferroelectrics - materials with a spontaneous and electrically reversible polarization - are touted for use in non-volatile computer memories, sensors and optics. Historically, this physical phenomenon has been studied in inorganic materials, although some organic examples are known and strong interest exists to extend the search for ferroelectric molecular systems. Other undiscovered applications outside this regime could also emerge. We describe the key features necessary for molecular and supramolecular dipoles in organic ferroelectrics and their incorporation into ordered systems, such as porous frameworks and liquid crystals. The goal of this Review is to motivate the development of innovative supramolecular ferroelectrics that exceed the performance and usefulness of known systems.

Supermassive blackholes without super Eddington accretion

NASA Astrophysics Data System (ADS)

Christian, Damian Joseph; Kim, Matt I.; Garofalo, David; D'Avanzo, Jaclyn; Torres, John

2017-08-01

We explore the X-ray luminosity function at high redshift for active galactic nuclei using an albeit simplified model for mass build-up using a combination of mergers and mass accretion in the gap paradigm (Garofalo et al. 2010). Using a retrograde-dominated configuration we find an interesting low probability channel for the growth of one billion solar mass black holes within hundreds of millions of years of the big bang without appealing to super Eddington accretion (Kim et al. 2016). This result is made more compelling by the connection between this channel and an end product involving active galaxies with FRI radio morphology but weaker jet powers in mildly sub-Eddington accretion regimes. We will discuss our connection between the unexplained paucity of a given family of AGNs and the rapid growth of supermassive black holes, two heretofore seemingly unrelated aspects of the physics of AGNs that will help further understand their properties and evolution.

On the conditions for the onset of nonlinear chirping structures in NSTX

NASA Astrophysics Data System (ADS)

Duarte, Vinicius; Podesta, Mario; Berk, Herbert; Gorelenkov, Nikolai

2015-11-01

The nonlinear dynamics of phase space structures is a topic of interest in tokamak physics in connection with fast ion loss mechanisms. The onset of phase-space holes and clumps has been theoretically shown to be associated with an explosive solution of an integro-differential, nonlocal cubic equation that governs the early mode amplitude evolution in the weakly nonlinear regime. The existence and stability of the solutions of the cubic equation have been theoretically studied as a function of Fokker-Planck coefficients for the idealized case of a single resonant point of a localized mode. From realistic computations of NSTX mode structures and resonant surfaces, we calculate effective pitch angle scattering and slowing-down (drag) collisional coefficients and analyze NSTX discharges for different cases with respect to chirping experimental observation. Those results are confronted to the theory that predicts the parameters region that allow for chirping to take place.

Improved Spectral Calculations for Discrete Schrődinger Operators

NASA Astrophysics Data System (ADS)

Puelz, Charles

This work details an O(n2) algorithm for computing spectra of discrete Schrődinger operators with periodic potentials. Spectra of these objects enhance our understanding of fundamental aperiodic physical systems and contain rich theoretical structure of interest to the mathematical community. Previous work on the Harper model led to an O(n2) algorithm relying on properties not satisfied by other aperiodic operators. Physicists working with the Fibonacci Hamiltonian, a popular quasicrystal model, have instead used a problematic dynamical map approach or a sluggish O(n3) procedure for their calculations. The algorithm presented in this work, a blend of well-established eigenvalue/vector algorithms, provides researchers with a more robust computational tool of general utility. Application to the Fibonacci Hamiltonian in the sparsely studied intermediate coupling regime reveals structure in canonical coverings of the spectrum that will prove useful in motivating conjectures regarding band combinatorics and fractal dimensions.

Relativistic-microwave theory of ball lightning

NASA Astrophysics Data System (ADS)

Wu, H.-C.

2016-06-01

Ball lightning, a fireball sometimes observed during lightnings, has remained unexplained. Here we present a comprehensive theory for the phenomenon: At the tip of a lightning stroke reaching the ground, a relativistic electron bunch can be produced, which in turn excites intense microwave radiation. The latter ionizes the local air and the radiation pressure evacuates the resulting plasma, forming a spherical plasma bubble that stably traps the radiation. This mechanism is verified by particle simulations. The many known properties of ball lightning, such as the occurrence site, relation to the lightning channels, appearance in aircraft, its shape, size, sound, spark, spectrum, motion, as well as the resulting injuries and damages, are also explained. Our theory suggests that ball lighting can be created in the laboratory or triggered during thunderstorms. Our results should be useful for lightning protection and aviation safety, as well as stimulate research interest in the relativistic regime of microwave physics.

Relativistic-microwave theory of ball lightning

PubMed Central

Wu, H.-C.

2016-01-01

Ball lightning, a fireball sometimes observed during lightnings, has remained unexplained. Here we present a comprehensive theory for the phenomenon: At the tip of a lightning stroke reaching the ground, a relativistic electron bunch can be produced, which in turn excites intense microwave radiation. The latter ionizes the local air and the radiation pressure evacuates the resulting plasma, forming a spherical plasma bubble that stably traps the radiation. This mechanism is verified by particle simulations. The many known properties of ball lightning, such as the occurrence site, relation to the lightning channels, appearance in aircraft, its shape, size, sound, spark, spectrum, motion, as well as the resulting injuries and damages, are also explained. Our theory suggests that ball lighting can be created in the laboratory or triggered during thunderstorms. Our results should be useful for lightning protection and aviation safety, as well as stimulate research interest in the relativistic regime of microwave physics. PMID:27328835

Transversal stability of the bouncing ball on a concave surface.

PubMed

Chastaing, J-Y; Pillet, G; Taberlet, N; Géminard, J-C

2015-05-01

A ball bouncing repeatedly on a vertically vibrating surface constitutes the famous "bouncing ball" problem, a nonlinear system used in the 1980s, and still in use nowadays, to illustrate the route to chaos by period doubling. In experiments, in order to avoid the ball escape that would be inevitable with a flat surface, a concave lens is often used to limit the horizontal motion. However, we observe experimentally that the system is not stable. The ball departs from the system axis and exhibits a pendular motion in the permanent regime. We propose theoretical arguments to account for the decrease of the growth rate and of the asymptotic-size of the trajectory when the frequency of the vibration is increased. The instability is very sensitive to the physics of the contacts, which makes it a potentially interesting way to study the collisions rules, or to test the laws used in numerical studies of granular matter.

Many-body Tunneling and Nonequilibrium Dynamics of Doublons in Strongly Correlated Quantum Dots.

PubMed

Hou, WenJie; Wang, YuanDong; Wei, JianHua; Zhu, ZhenGang; Yan, YiJing

2017-05-30

Quantum tunneling dominates coherent transport at low temperatures in many systems of great interest. In this work we report a many-body tunneling (MBT), by nonperturbatively solving the Anderson multi-impurity model, and identify it a fundamental tunneling process on top of the well-acknowledged sequential tunneling and cotunneling. We show that the MBT involves the dynamics of doublons in strongly correlated systems. Proportional to the numbers of dynamical doublons, the MBT can dominate the off-resonant transport in the strongly correlated regime. A T 3/2 -dependence of the MBT current on temperature is uncovered and can be identified as a fingerprint of the MBT in experiments. We also prove that the MBT can support the coherent long-range tunneling of doublons, which is well consistent with recent experiments on ultracold atoms. As a fundamental physical process, the MBT is expected to play important roles in general quantum systems.

Identification techniques for highly boosted W bosons that decay into hadrons

DOE PAGES

Khachatryan, Vardan

2014-12-02

In searches for new physics in the energy regime of the LHC, it is becoming increasingly important to distinguish single-jet objects that originate from the merging of the decay products of W bosons produced with high transverse momenta from jets initiated by single partons. Algorithms are defined to identify such W jets for different signals of interest, using techniques that are also applicable to other decays of bosons to hadrons that result in a single jet, such as those from highly boosted Z and Higgs bosons. The efficiency for tagging W jets is measured in data collected with the CMSmore » detector at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.7 fb -1. The performance of W tagging in data is compared with predictions from several Monte Carlo simulators.« less

Fundamental Interactions for Atom Interferometry with Ultracold Quantum Gases in a Microgravity Environment

NASA Astrophysics Data System (ADS)

D'Incao, Jose P.; Willians, Jason R.

2015-05-01

Precision atom interferometers (AI) in space are a key element for several applications of interest to NASA. Our proposal for participating in the Cold Atom Laboratory (CAL) onboard the International Space Station is dedicated to mitigating the leading-order systematics expected to corrupt future high-precision AI-based measurements of fundamental physics in microgravity. One important focus of our proposal is to enhance initial state preparation for dual-species AIs. Our proposed filtering scheme uses Feshbach molecular states to create highly correlated mixtures of heteronuclear atomic gases in both their position and momentum distributions. We will detail our filtering scheme along with the main factors that determine its efficiency. We also show that the atomic and molecular heating and loss rates can be mitigated at the unique temperature and density regimes accessible on CAL. This research is supported by the National Aeronautics and Space Administration.

The neutrino mass hierarchy measurement with a neutrino telescope in the Mediterranean Sea: A feasibility study

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

Tsirigotis, A. G.; Collaboration: KM3NeT Collaboration

With the measurement of a non zero value of the θ{sub 13} neutrino mixing parameter, interest in neutrinos as source of the baryon asymmetry of the universe has increased. Among the measurements of a rich and varied program in near future neutrino physics is the determination of the mass hierarchy. We present the status of a study of the feasibility of using a densely instrumented undersea neutrino detector to determine the mass hierarchy, utilizing the Mikheyev-Smirnov-Wolfenstein (MSW) effect on atmospheric neutrino oscillations. The detector will use technology developed for KM3NeT. We present the systematic studies of the optimization of amore » detector in the required 5–10 GeV energy regime. These studies include new tracking and interaction identification algorithms as well as geometrical optimizations of the detector.« less

The Advanced Gamma-Ray Imaging System (AGIS)

NASA Astrophysics Data System (ADS)

Williams, David A.; AGIS Collaboration

2009-01-01

The spectacular astrophysical discoveries made by the present generation of ground-based gamma-ray observatories have opened a new era in the exploration of the highest energy Universe and have conclusively established the field of very-high-energy (VHE) astronomy, covering the energy regime above about 50 GeV. The detection of nearly 100 galactic and extragalactic sources has generated considerable interest in the astronomy, astrophysics and particle physics communities and has stimulated ambitious ideas and plans for future gamma-ray observatories. AGIS is a concept for a next generation VHE observatory with a collecting area on the scale of a square kilometer being developed by an international collaboration. It would have significantly improved angular and energy resolution, increased field of view, and an order of magnitude increase in sensitivity over existing space or ground-based instruments in the energy range 40 GeV to 100 TeV. The scientific motivations and R&D roadmap for AGIS will be discussed.

The Study of Interpenetration Length between dPS Films and PS-grafted Layers

NASA Astrophysics Data System (ADS)

Lee, Hoyeon; Jo, Seongjun; Hirata, Toyoaki; Yamada, Norifumi L.; Tanaka, Keiji; Ryu, Du Yeol

In polymer thin film system, the type of interfacial interaction is a critical parameter to determining the thermal and physical properties of polymer films. Interestingly, the interfacial energy of grafted substrates with polymer chains is remarkably altered by simply controlling grafting density, which has been referred to as autophobicity. In this study, we investigated the interpenetrating interfaces between deuterated polystyrene (dPS) and grafted substrates with the same chemical identity. PS-grafted substrates were prepared using a grafting-to approach with hydroxyl end-functionalized polystyrene (PSOH) in a dry brush regime, where the brush thickness and grafting density were determined based on the chain length (or molecular weight, Mn) of PSOHs. The interpenetration lengths (ξ) at interfaces between dPS and PS-grafted layers were characterized using neutron reflectivity (NR) measurements (performed at the SOFIA beam-line at J-PARC, Japan). Academic adviser.

Thermodynamic studies of different black holes with modifications of entropy

NASA Astrophysics Data System (ADS)

Haldar, Amritendu; Biswas, Ritabrata

2018-02-01

In recent years, the thermodynamic properties of black holes are topics of interests. We investigate the thermodynamic properties like surface gravity and Hawking temperature on event horizon of regular black holes viz. Hayward Class and asymptotically AdS (Anti-de Sitter) black holes. We also analyze the thermodynamic volume and naive geometric volume of asymptotically AdS black holes and show that the entropy of these black holes is simply the ratio of the naive geometric volume to thermodynamic volume. We plot the different graphs and interpret them physically. We derive the `cosmic-Censorship-Inequality' for both type of black holes. Moreover, we calculate the thermal heat capacity of aforesaid black holes and study their stabilities in different regimes. Finally, we compute the logarithmic correction to the entropy for both the black holes considering the quantum fluctuations around the thermal equilibrium and study the corresponding thermodynamics.

Organic Power Electronics: Transistor Operation in the kA/cm2 Regime.

PubMed

Klinger, Markus P; Fischer, Axel; Kaschura, Felix; Widmer, Johannes; Kheradmand-Boroujeni, Bahman; Ellinger, Frank; Leo, Karl

2017-03-17

In spite of interesting features as flexibility, organic thin-film transistors have commercially lagged behind due to the low mobilities of organic semiconductors associated with hopping transport. Furthermore, organic transistors usually have much larger channel lengths than their inorganic counterparts since high-resolution structuring is not available in low-cost production schemes. Here, we present an organic permeable-base transistor (OPBT) which, despite extremely simple processing without any high-resolution structuring, achieve a performance beyond what has so far been possible using organic semiconductors. With current densities above 1 kA cm -2 and switching speeds towards 100 MHz, they open the field of organic power electronics. Finding the physical limits and an effective mobility of only 0.06 cm 2  V -1  s -1 , this OPBT device architecture has much more potential if new materials optimized for its geometry will be developed.

Towards a comprehensive model for the electronic and vibrational structure of the Creutz-Taube ion.

PubMed

Reimers, Jeffrey R; Wallace, Brett B; Hush, Noel S

2008-01-13

Since the synthesis of the Creutz-Taube ion, the nature of its charge localization has been of immense scientific interest, this molecule providing a model system for the understanding of the operation of biological photosynthetic and electron-transfer processes. However, recent work has shown that its nature remains an open question. Many systems of this type, including photosynthetic reaction centres, are of current research interest, and thereby the Creutz-Taube ion provides an important chemical paradigm: the key point of interest is the details of how such molecules behave. We lay the groundwork for the construction of a comprehensive model for its chemical and spectroscopic properties. Advances are described in some of the required areas including: simulation of electronic absorption spectra; quantitative depiction of the large interaction of the ion's electronic description with solvent motions; and the physics of Ru-NH3 spectator-mode vibrations. We show that details of the solvent electron-phonon coupling are critical in the interpretation of the spectator-mode vibrations, as these strongly mix with solvent motions when 0.75<2J/lambda<1. In this regime, a double-well potential exists which does not support localized zero-point vibration, and many observed properties of the Creutz-Taube ion are shown to be consistent with the hypothesis that the ion has this character.

The unlikely high efficiency of a molecular motor based on active motion

NASA Astrophysics Data System (ADS)

Ebeling, W.

2015-07-01

The efficiency of a simple model of a motor converting chemical into mechanical energy is studied analytically. The model motor shows interesting properties corresponding qualitatively to motors investigated in experiments. The efficiency increases with the load and may for low loss reach high values near to 100 percent in a narrow regime of optimal load. It is shown that the optimal load and the maximal efficiency depend by universal power laws on the dimensionless loss parameter. Stochastic effects decrease the stability of motor regimes with high efficiency and make them unlikely. Numerical studies show efficiencies below the theoretical optimum and demonstrate that special ratchet profiles my stabilize efficient regimes.

Microstructured optical fiber photonic wires with subwavelength core diameter.

PubMed

Lizé, Yannick; Mägi, Eric; Ta'eed, Vahid; Bolger, Jeremy; Steinvurzel, Paul; Eggleton, Benjamin

2004-07-12

We demonstrate fabrication of robust, low-loss silica photonic wires using tapered microstructured silica optical fiber. The fiber is tapered by a factor of fifty while retaining the internal structure and leaving the air holes completely open. The air holes isolate the core mode from the surrounding environment, making it insensitive to surface contamination and contact leakage, suggesting applications as nanowires for photonic circuits . We describe a transition between two different operation regimes of our photonic wire from the embedded regime, where the mode is isolated from the environment, to the evanescent regime, where more than 70% of the mode intensity can propagate outside of the fiber. Interesting dispersion and nonlinear properties are identified.

Center for Hypersonic Combined Cycle Flow Physics

DTIC Science & Technology

2015-03-24

team of expert experimentalists and numerical and chemical kinetic modelers. Flowfields were examined in the turbine /ramjet dual inlet mode transition...using data from the NASA Glenn IMX facility and RANS calculations. In the ramjet/scramjet mode regime a dual-mode combustion wind tunnel was developed...SUBJECT TERMS Hypersonic combined cycle propulsion, turbine /ram dual-inlet transition, ram/scram dual-mode transition, hypervelocity regime, RANS, Hybrid

Trends in Physical Activity Interest in the College and University Setting

ERIC Educational Resources Information Center

Melton, Bridget; Hansen, Andrew; Gross, Jonathon

2010-01-01

High levels of interest in physical activity courses correlate positively with student participation. Awareness of students' physical activity interests allows college and university program coordinators to match student interests with appropriate course offerings. Purpose: The purpose of this research is to track students' physical activity…

Transient chaos - a resolution of breakdown of quantum-classical correspondence in optomechanics.

PubMed

Wang, Guanglei; Lai, Ying-Cheng; Grebogi, Celso

2016-10-17

Recently, the phenomenon of quantum-classical correspondence breakdown was uncovered in optomechanics, where in the classical regime the system exhibits chaos but in the corresponding quantum regime the motion is regular - there appears to be no signature of classical chaos whatsoever in the corresponding quantum system, generating a paradox. We find that transient chaos, besides being a physically meaningful phenomenon by itself, provides a resolution. Using the method of quantum state diffusion to simulate the system dynamics subject to continuous homodyne detection, we uncover transient chaos associated with quantum trajectories. The transient behavior is consistent with chaos in the classical limit, while the long term evolution of the quantum system is regular. Transient chaos thus serves as a bridge for the quantum-classical transition (QCT). Strikingly, as the system transitions from the quantum to the classical regime, the average chaotic transient lifetime increases dramatically (faster than the Ehrenfest time characterizing the QCT for isolated quantum systems). We develop a physical theory to explain the scaling law.

Transient chaos - a resolution of breakdown of quantum-classical correspondence in optomechanics

PubMed Central

Wang, Guanglei; Lai, Ying-Cheng; Grebogi, Celso

2016-01-01

Recently, the phenomenon of quantum-classical correspondence breakdown was uncovered in optomechanics, where in the classical regime the system exhibits chaos but in the corresponding quantum regime the motion is regular - there appears to be no signature of classical chaos whatsoever in the corresponding quantum system, generating a paradox. We find that transient chaos, besides being a physically meaningful phenomenon by itself, provides a resolution. Using the method of quantum state diffusion to simulate the system dynamics subject to continuous homodyne detection, we uncover transient chaos associated with quantum trajectories. The transient behavior is consistent with chaos in the classical limit, while the long term evolution of the quantum system is regular. Transient chaos thus serves as a bridge for the quantum-classical transition (QCT). Strikingly, as the system transitions from the quantum to the classical regime, the average chaotic transient lifetime increases dramatically (faster than the Ehrenfest time characterizing the QCT for isolated quantum systems). We develop a physical theory to explain the scaling law. PMID:27748418

Chaos and wave propagation regimes

NASA Astrophysics Data System (ADS)

Colosi, John

2003-04-01

Ray chaos theory and parabolic equation numerical modeling were two thrusts of Fred Tappert's research that were perpetually in tension. Fred was interested in the problem of identifying wave propagation regimes, most notably the strong focusing caustic regime and its evolution into the saturation regime. On the one hand, chaos theory held the seed of the complexity Fred believed existed in ocean acoustic wavefields; on the other hand ocean acoustic ray chaos theory (which Fred helped to pioneer) was a disdainful approximation to the full wave treatments offered by parabolic equation calculations. Fred was convinced that the saturation limit could not be obtained using ray theory and therefore he examined a new field of inquiry: a blend of chaotic ray insight and full wave dynamics called wave chaos. This talk will discuss some of Fred's insights on this topic and how they relate to observations from basin scale acoustic transmissions.

Tunable nonequilibrium dynamics of field quenches in spin ice

PubMed Central

Mostame, Sarah; Castelnovo, Claudio; Moessner, Roderich; Sondhi, Shivaji L.

2014-01-01

We present nonequilibrium physics in spin ice as a unique setting that combines kinematic constraints, emergent topological defects, and magnetic long-range Coulomb interactions. In spin ice, magnetic frustration leads to highly degenerate yet locally constrained ground states. Together, they form a highly unusual magnetic state—a “Coulomb phase”—whose excitations are point-like defects—magnetic monopoles—in the absence of which effectively no dynamics is possible. Hence, when they are sparse at low temperature, dynamics becomes very sluggish. When quenching the system from a monopole-rich to a monopole-poor state, a wealth of dynamical phenomena occur, the exposition of which is the subject of this article. Most notably, we find reaction diffusion behavior, slow dynamics owing to kinematic constraints, as well as a regime corresponding to the deposition of interacting dimers on a honeycomb lattice. We also identify potential avenues for detecting the magnetic monopoles in a regime of slow-moving monopoles. The interest in this model system is further enhanced by its large degree of tunability and the ease of probing it in experiment: With varying magnetic fields at different temperatures, geometric properties—including even the effective dimensionality of the system—can be varied. By monitoring magnetization, spin correlations or zero-field NMR, the dynamical properties of the system can be extracted in considerable detail. This establishes spin ice as a laboratory of choice for the study of tunable, slow dynamics. PMID:24379372

Superfluid drag in the two-component Bose-Hubbard model

NASA Astrophysics Data System (ADS)

Sellin, Karl; Babaev, Egor

2018-03-01

In multicomponent superfluids and superconductors, co- and counterflows of components have, in general, different properties. A. F. Andreev and E. P. Bashkin [Sov. Phys. JETP 42, 164 (1975)] discussed, in the context of He3/He4 superfluid mixtures, that interparticle interactions produce a dissipationless drag. The drag can be understood as a superflow of one component induced by phase gradients of the other component. Importantly, the drag can be both positive (entrainment) and negative (counterflow). The effect is known to have crucial importance for many properties of diverse physical systems ranging from the dynamics of neutron stars and rotational responses of Bose mixtures of ultracold atoms to magnetic responses of multicomponent superconductors. Although substantial literature exists that includes the drag interaction phenomenologically, only a few regimes are covered by quantitative studies of the microscopic origin of the drag and its dependence on microscopic parameters. Here we study the microscopic origin and strength of the drag interaction in a quantum system of two-component bosons on a lattice with short-range interaction. By performing quantum Monte Carlo simulations of a two-component Bose-Hubbard model we obtain dependencies of the drag strength on the boson-boson interactions and properties of the optical lattice. Of particular interest are the strongly correlated regimes where the ratio of coflow and counterflow superfluid stiffnesses can diverge, corresponding to the case of saturated drag.

Coupled modes locally interacting with qubits: Critical assessment of the rotating-wave approximation

NASA Astrophysics Data System (ADS)

Cárdenas, P. C.; Teixeira, W. S.; Semião, F. L.

2017-04-01

The interaction of qubits with quantized modes of electromagnetic fields has been largely addressed in the quantum optics literature under the rotating wave approximation (RWA), where rapid oscillating terms in the qubit-mode interaction picture Hamiltonian can be neglected. At the same time, it is generally accepted that, provided the interaction is sufficiently strong or for long times, the RWA tends to describe physical phenomena incorrectly. In this work, we extend the investigation of the validity of the RWA to a more involved setup where two qubit-mode subsystems are brought to interaction through their harmonic coordinates. Our treatment is all analytic thanks to a sequence of carefully chosen unitary transformations, which allows us to diagonalize the Hamiltonian within and without the RWA. By also considering qubit dephasing, we find that the purity of the two-qubit state presents non-Markovian features which become more pronounced as the coupling between the modes gets stronger and the RWA loses its validity. In the same regime, there occurs fast generation of entanglement between the qubits, which is also not correctly described under the RWA. The setup and results presented here clearly show the limitations of the RWA in a scenario amenable to exact description and free from numerical uncertainties. Consequently, it may be of interest for the community working with cavity or circuit quantum electrodynamic systems in the strong coupling regime.

Comparison of different cooling regimes within a shortened liquid cooling/warming garment on physiological and psychological comfort during exercise

NASA Technical Reports Server (NTRS)

Leon, Gloria R.; Koscheyev, Victor S.; Coca, Aitor; List, Nathan

2004-01-01

The aim of this study was to compare the effectiveness of different cooling regime intensities to maintain physiological and subjective comfort during physical exertion levels comparable to that engaged in during extravehicular activities (EVA) in space. We studied eight subjects (six males, two females) donned in our newly developed physiologically based shortened liquid cooling/warming garment (SLCWG). Rigorous (condition 1) and mild (condition 2) water temperature cooling regimes were compared at physical exertion levels comparable to that performed during EVA to ascertain the effectiveness of a lesser intensity of cooling in maintaining thermal comfort, thus reducing energy consumption in the portable life support system. Exercise intensity was varied across stages of the session. Finger temperature, rectal temperature, and subjective perception of overall body and hand comfort were assessed. Finger temperature was significantly higher in the rigorous cooling condition and showed a consistent increase across exercise stages, likely due to the restriction of heat extraction because of the intensive cold. In the mild cooling condition, finger temperature exhibited an overall decline with cooling, indicating greater heat extraction from the body. Rectal temperature was not significantly different between conditions, and showed a steady increase over exercise stages in both rigorous and mild cooling conditions. Ratings of overall comfort were 30% higher (more positive) and more stable in mild cooling (p<0.001). The mild cooling regime was more effective than rigorous cooling in allowing the process of heat exchange to occur, thus maintaining thermal homeostasis and subjective comfort during physical exertion.

A large-scale magnetic shield with 10{sup 6} damping at millihertz frequencies

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

Altarev, I.; Bales, M.; Fierlinger, K.

We present a magnetically shielded environment with a damping factor larger than 1 × 10{sup 6} at the mHz frequency regime and an extremely low field and gradient over an extended volume. This extraordinary shielding performance represents an improvement of the state-of-the-art in the difficult regime of damping very low-frequency distortions by more than an order of magnitude. This technology enables a new generation of high-precision measurements in fundamental physics and metrology, including searches for new physics far beyond the reach of accelerator-based experiments. We discuss the technical realization of the shield with its improvements in design.

Femtosecond pulses propagation through pure water

NASA Astrophysics Data System (ADS)

Naveira, Lucas; Sokolov, Alexei; Byeon, Joong-Hyeok; Kattawar, George

2007-10-01

Recently, considerable attention has been dedicated to the field of optical precursors, which can possibly be applied to long-distance underwater communications. Input beam intensities have been carefully adjusted to keep experiments in the linear regime, and some experiments have shown violation of the Beer-Lambert law. We are presently carrying out experiments using femtosecond laser pulses propagating through pure water strictly in the linear regime to study this interesting and important behavior. We are also employing several new and innovative schemes to more clearly define the phenomena.

The continuum limit of aN-1(2) spin chains

NASA Astrophysics Data System (ADS)

Vernier, Eric; Jacobsen, Jesper Lykke; Saleur, Hubert

2016-10-01

Building on our previous work for a2(2) and a3(2) we explore systematically the continuum limit of gapless aN-1(2) vertex models and spin chains. We find the existence of three possible regimes. Regimes I and II for a2n-1(2) are related with a2n-1(2) Toda, and described by n compact bosons. Regime I for a2n(2) is related with a2n(2) Toda and involves n compact bosons, while regime II is related instead with B(1) (0 , n) super Toda, and involves in addition a single Majorana fermion. The most interesting is regime III, where non-compact degrees of freedom appear, generalising the emergence of the Euclidean black hole CFT in the a2(2) case. For a2n(2) we find a continuum limit made of n compact and n non-compact bosons, while for a2n-1(2) we find n compact and n - 1 non-compact bosons. We also find deep relations between aN-1(2) in regime III and the gauged WZW models SO (N) / SO (N - 1).

Ultra-powerful compact amplifiers for short laser pulses

NASA Astrophysics Data System (ADS)

Malkin, Vladimir

1999-11-01

Laser compressors-amplifiers more powerful and compact than ones based on the currently most advanced chirped pulse amplification technique must handle ultrahigh laser intensities. The medium capable of bearing those is plasma. An interesting kinetic regime of short laser pulse amplification by Compton backscattering of counterpropagating laser pump in plasma, akin to superradiant amplification in free-electron lasers, has been proposed recently (Shvets G., Fisch N. J., Pukhov A., and Meyer-ter-Vehn J., Phys. Rev. Lett., v.81, 4879 (1998)). However, the conversion efficiency of pump energy into a short pulse appears to be higher in a transient Raman backscattering regime (Malkin V. M., Shvets G. and Fisch N. J., Phys. Rev. Lett., v.82, 4448 (1999)), where the integrity of the three-wave interaction is maintained. In this regime the pump is completely depleted through the full nonlinear stage of the interaction, so that unwanted Raman and modulational instabilities limit just the amplification time, while the efficiency is kept about 100%. For instance, a 2*10^14 W/cm^2, 1 μm-wavelength laser pump can be compressed within 5 mm length, which is less than the length for filamentation instabilities to develop, to a 30--40 fsec pulse with fluence 6 kJ/cm^2. Such an output pulse is a thousand times shorter and a million time more intensive than outputs of conventional Raman amplifiers operating in a stationary regime. Yet larger amplification distances and output energies can be achieved by suppressing filamentation instabilities. It appears (Malkin V. M., Shvets G. and Fisch N. J., Submitted to Phys. Rev. Lett.) that appropriate detuning of the resonance (by plasma density gradient or/and chirping the pump laser) suppresses the Raman near-forward scattering instability of the pumped pulse, as well as the pump Raman backscattering instability to noise, while the high efficiency of the amplification still persists. The respective new class of transient amplification regimes, generalizing the classical pi-pulse regime of exactly resonant amplification, is described quantitatively. These regimes are of broad interest, being applicable also to other processes such as Brillouin scattering.

Numerical Simulation of Ultra-Fast Pulse Propagation in Two-Photon Absorbing Medium

DTIC Science & Technology

2011-08-01

physical problems including coherent- and incoherent regimes of optical power limiting, saturation, CEP effects, soliton formation etc. It can be also...coherent- and incoherent regimes of optical power limiting, saturation, CEP effects, electromagnetically induced transparency, soliton formation etc...experimental data ( dark blue); Upper panel - 1PA spectrum; Lower panel - 2PA cross section spectrum. The parameter values used are shown in Table 1. 10

Scaling analysis of gas-liquid two-phase flow pattern in microgravity

NASA Technical Reports Server (NTRS)

Lee, Jinho

1993-01-01

A scaling analysis of gas-liquid two-phase flow pattern in microgravity, based on the dominant physical mechanism, was carried out with the goal of predicting the gas-liquid two-phase flow regime in a pipe under conditions of microgravity. The results demonstrated the effect of inlet geometry on the flow regime transition. A comparison of the predictions with existing experimental data showed good agreement.

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

Shaing, K.C.; Hazeltine, R.D.

Electron transport fluxes in the potato plateau regime are calculated from the solutions of the drift kinetic equation and fluid equations. It is found that the bootstrap current density remains finite in the region close to the magnetic axis, although it decreases with increasing collision frequency. This finite amount of the bootstrap current in the relatively collisional regime is important in modeling tokamak startup with 100{percent} bootstrap current. {copyright} {ital 1997 American Institute of Physics.}

Strong Interaction Studies with PANDA at FAIR

NASA Astrophysics Data System (ADS)

Schönning, Karin

2016-10-01

The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of nuclear-, hadron- and atomic physics experiments. The future PANDA experiment at FAIR will offer a broad physics programme with emphasis on different aspects of hadron physics. Understanding the strong interaction in the perturbative regime remains one of the greatest challenges in contemporary physics and hadrons provide several important keys. In these proceedings, PANDA will be presented along with some high-lights of the planned physics programme.

Ecological studies of a regulated stream: Huntington River, Emery County, Utah

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

Winget, R.N.

1984-04-30

A 36.9 x 10/sup 6/ m/sup 3/ reservoir constructed on Huntington River, Emery County, Utah, resulted in changes in physical habitat, water quality, temperature, and flow regime. The greatest changes in physical habitat resulted from: (1) sediment additions from dam and road construction plus erosion of reservoir basin during filling; and (2) changing stream flow from a spring high runoff regime to a moderated flow regime. Elimination of spring nutrient concentration peaks and overall reduction of total dissolved nutrient availability in the river plus moderate reductions in pH were the most apparent water quality changes below the reservoir. Water temperaturemore » changes were an increased diurnal and seasonal constancy, summer depression, and winter elevation, generally limited to a 10-12 km reach below the dam. Physical and chemical changes altered macroinvertebrate community structure, with changes greatest near the dam and progressively less as distance downstream increased. Below the dam: (1) more environmentally tolerant taxa increased their dominance; (2) relative numbers of smaller sized individuals increased in relation to larger individuals; and (3) filter feeding, collector/gatherers, and scapers gained an advantage over shredders. Macroinvertebrate taxa with small instar larvae present from late summer to early fall were negatively impacted by the unnaturally high July and August flows. The reservoir became a physical barrier to downstream larval drift and upcanyon and downcanyon immigration of adults, resulting in reduced numbers of several species above and below the reservoir. 50 references, 12 figures, 3 tables.« less

Studies of L-T Separated Kaon Electroproduction

NASA Astrophysics Data System (ADS)

Trotta, Richard; Horn, Tanja; Vargas, Andres

2017-09-01

QCD is characterized by two emergent phenomena: confinement and dynamical chiral symmetry breaking (DCSB). Pion and kaon form factors are of particular interest as they are connected to the Goldstone modes of DCSB. The flavor degrees of freedom of the produced meson selectively probe aspects of the reaction mechanism and the transition from hadronic to partonic degrees of freedom. There has been significant progress in the theoretical description of the nucleon structure in terms of QCD degrees of freedom, in particular through Generalized Parton Distributions (GPDs).The last decade saw a dramatic improvement in precision of charged pion form factor data and new results have become available on the pion transition form factor. The kaon provides an interesting way to expand these studies, opening the possibility to access the production mechanism involving strangeness. Kaon data at larger virtual photon mass allow one to search for the onset of the partonic picture. In this regime, hard and soft physics have been shown to factorize and GPDs provide the most complete description of the non-perturbative physics. The lack of necessary experimental facilities has left a gap in L-T separated data for exclusive K + production from the proton above the resonance region.The newly upgraded 12 GeV beam energy at Jlab, in addition to the recently built SHMS spectrometer for Hall C, has provided an opportunity to expand the kaon data. Recent kaon form factor and cross section results will be discussed showing the impact of E12-09-011, the running Jlab 12 GeV kaon experiment. NSF Grants PHY1306227, PHY1306418 and PHY1530874.

Shear thickening in concentrated suspensions: phenomenology, mechanisms and relations to jamming

NASA Astrophysics Data System (ADS)

Brown, Eric; Jaeger, Heinrich M.

2014-04-01

Shear thickening is a type of non-Newtonian behavior in which the stress required to shear a fluid increases faster than linearly with shear rate. Many concentrated suspensions of particles exhibit an especially dramatic version, known as Discontinuous Shear Thickening (DST), in which the stress suddenly jumps with increasing shear rate and produces solid-like behavior. The best known example of such counter-intuitive response to applied stresses occurs in mixtures of cornstarch in water. Over the last several years, this shear-induced solid-like behavior together with a variety of other unusual fluid phenomena has generated considerable interest in the physics of densely packed suspensions. In this review, we discuss the common physical properties of systems exhibiting shear thickening, and different mechanisms and models proposed to describe it. We then suggest how these mechanisms may be related and generalized, and propose a general phase diagram for shear thickening systems. We also discuss how recent work has related the physics of shear thickening to that of granular materials and jammed systems. Since DST is described by models that require only simple generic interactions between particles, we outline the broader context of other concentrated many-particle systems such as foams and emulsions, and explain why DST is restricted to the parameter regime of hard-particle suspensions. Finally, we discuss some of the outstanding problems and emerging opportunities.

Multi-Physics Modelling of Fault Mechanics Using REDBACK: A Parallel Open-Source Simulator for Tightly Coupled Problems

NASA Astrophysics Data System (ADS)

Poulet, Thomas; Paesold, Martin; Veveakis, Manolis

2017-03-01

Faults play a major role in many economically and environmentally important geological systems, ranging from impermeable seals in petroleum reservoirs to fluid pathways in ore-forming hydrothermal systems. Their behavior is therefore widely studied and fault mechanics is particularly focused on the mechanisms explaining their transient evolution. Single faults can change in time from seals to open channels as they become seismically active and various models have recently been presented to explain the driving forces responsible for such transitions. A model of particular interest is the multi-physics oscillator of Alevizos et al. (J Geophys Res Solid Earth 119(6), 4558-4582, 2014) which extends the traditional rate and state friction approach to rate and temperature-dependent ductile rocks, and has been successfully applied to explain spatial features of exposed thrusts as well as temporal evolutions of current subduction zones. In this contribution we implement that model in REDBACK, a parallel open-source multi-physics simulator developed to solve such geological instabilities in three dimensions. The resolution of the underlying system of equations in a tightly coupled manner allows REDBACK to capture appropriately the various theoretical regimes of the system, including the periodic and non-periodic instabilities. REDBACK can then be used to simulate the drastic permeability evolution in time of such systems, where nominally impermeable faults can sporadically become fluid pathways, with permeability increases of several orders of magnitude.

Collective behaviour of dislocations in a finite medium

NASA Astrophysics Data System (ADS)

Kooiman, M.; Hütter, M.; Geers, M. G. D.

2014-04-01

We derive the grand-canonical partition function of straight and parallel dislocation lines without making a priori assumptions on the temperature regime. Such a systematic derivation for dislocations has, to the best of our knowledge, not been carried out before, and several conflicting assumptions on the free energy of dislocations have been made in the literature. Dislocations have gained interest as they are the carriers of plastic deformation in crystalline materials and solid polymers, and they constitute a prototype system for two-dimensional Coulomb particles. Our microscopic starting level is the description of dislocations as used in the discrete dislocation dynamics (DDD) framework. The macroscopic level of interest is characterized by the temperature, the boundary deformation and the dislocation density profile. By integrating over state space, we obtain a field theoretic partition function, which is a functional integral of the Boltzmann weight over an auxiliary field. The Hamiltonian consists of a term quadratic in the field and an exponential of this field. The partition function is strongly non-local, and reduces in special cases to the sine-Gordon model. Moreover, we determine implicit expressions for the response functions and the dominant scaling regime for metals, namely the low-temperature regime.

Kinetic nanofriction: a mechanism transition from quasi-continuous to ballistic-like Brownian regime

PubMed Central

2012-01-01

Surface diffusion of mobile adsorbates is not only the key to control the rate of dynamical processes on solid surfaces, e.g. epitaxial growth, but also of fundamental importance for recent technological applications, such as nanoscale electro-mechanical, tribological, and surface probing devices. Though several possible regimes of surface diffusion have been suggested, the nanoscale surface Brownian motion, especially in the technologically important low friction regimes, remains largely unexplored. Using molecular dynamics simulations, we show for the first time, that a C60 admolecule on a graphene substrate exhibits two distinct regimes of nanoscale Brownian motion: a quasi-continuous and a ballistic-like. A crossover between these two regimes is realized by changing the temperature of the system. We reveal that the underlying physical origin for this crossover is a mechanism transition of kinetic nanofriction arising from distinctive ways of interaction between the admolecule and the graphene substrate in these two regimes due to the temperature change. Our findings provide insight into surface mass transport and kinetic friction control at the nanoscale. PMID:22353343

Control of Synchronization Regimes in Networks of Mobile Interacting Agents

NASA Astrophysics Data System (ADS)

Perez-Diaz, Fernando; Zillmer, Ruediger; Groß, Roderich

2017-05-01

We investigate synchronization in a population of mobile pulse-coupled agents with a view towards implementations in swarm-robotics systems and mobile sensor networks. Previous theoretical approaches dealt with range and nearest-neighbor interactions. In the latter case, a synchronization-hindering regime for intermediate agent mobility is found. We investigate the robustness of this intermediate regime under practical scenarios. We show that synchronization in the intermediate regime can be predicted by means of a suitable metric of the phase response curve. Furthermore, we study more-realistic K -nearest-neighbor and cone-of-vision interactions, showing that it is possible to control the extent of the synchronization-hindering region by appropriately tuning the size of the neighborhood. To assess the effect of noise, we analyze the propagation of perturbations over the network and draw an analogy between the response in the hindering regime and stable chaos. Our findings reveal the conditions for the control of clock or activity synchronization of agents with intermediate mobility. In addition, the emergence of the intermediate regime is validated experimentally using a swarm of physical robots interacting with cone-of-vision interactions.

MODIS Microphysical Regimes for Examining Apparent Aerosol Effects on Clouds and Precipitation

NASA Astrophysics Data System (ADS)

Oreopoulos, L.; Cho, N.; Lee, D.; Kato, S.; Lebsock, M. D.; Yuan, T.; Huffman, G. J.

2014-12-01

We use a 10-year record of MODIS Terra and Aqua Level-3 joint histograms of cloud optical thickness (COT) and cloud effective radius (CER) to derive so-called cloud microphysical regimes by means of clustering analysis. The regimes reveal the dominant modes of COT and CER co-variations around the globe for both liquid and ice phases. The clustering analysis is capable of separating regimes so that each is dominated by one of the two water phases and can be associated with previously derived "dynamical" regimes. The microphysical regimes serve as an appropriate basis to study possible effects of aerosols on cloud microphysical changes and precipitation. To this end, we employ MODIS aerosol loading measurements either in terms of aerosol index or aerosol optical depth and spatiotemporally matched precipitation (from either GPCP, TRMM or CloudSat) to examine intra-regime variability, regime transitions from morning (Terra) to afternoon (Aqua), and regime precipitation characteristics for locally low, average, and high aerosol loadings. Breakdowns by ocean/land and geographical zone (e.g., tropics vs. midlatitudes) are essential for physical interpretation of the results. The analysis conducted so far reveals notable differences in apparent characteristics of low- and high-cloud dominated microphysical regimes when in different aerosol environments. The presentation will attempt to examine whether the picture painted by our work is consistent with prevailing expectations, rooted to either modeling or prior observational studies, on how clouds and precipitation respond to distinct aerosol environments.

Evaluation of Efficacy of Preventive Measures under Hypokinesia.

ERIC Educational Resources Information Center

Zorbas, Yan G.; Matveyev, Ivan O.

1987-01-01

The study evaluated the efficacy of physical exercise alone and in combination with other preventive measures with 24 adult male subjects kept under a bed rest regime. It was concluded that physical exercise was the most reliable measure in counteracting neuromuscular system disorders under diminished muscular activity conditions. (Author/DB)

Oscillations and Rolling for Duffing's Equation

NASA Astrophysics Data System (ADS)

Aref'eva, I. Ya.; Piskovskiy, E. V.; Volovich, I. V.

2013-01-01

The Duffing equation has been used to model nonlinear dynamics not only in mechanics and electronics but also in biology and in neurology for the brain process modeling. Van der Pol's method is often used in nonlinear dynamics to improve perturbation theory results when describing small oscillations. However, in some other problems of nonlinear dynamics particularly in case of Duffing-Higgs equation in field theory, for the Einsten-Friedmann equations in cosmology and for relaxation processes in neurology not only small oscillations regime is of interest but also the regime of slow rolling. In the present work a method for approximate solution to nonlinear dynamics equations in the rolling regime is developed. It is shown that in order to improve perturbation theory in the rolling regime it turns out to be effective to use an expansion in hyperbolic functions instead of trigonometric functions as it is done in van der Pol's method in case of small oscillations. In particular the Duffing equation in the rolling regime is investigated using solution expressed in terms of elliptic functions. Accuracy of obtained approximation is estimated. The Duffing equation with dissipation is also considered.

Optimal exploration systems

NASA Astrophysics Data System (ADS)

Klesh, Andrew T.

This dissertation studies optimal exploration, defined as the collection of information about given objects of interest by a mobile agent (the explorer) using imperfect sensors. The key aspects of exploration are kinematics (which determine how the explorer moves in response to steering commands), energetics (which determine how much energy is consumed by motion and maneuvers), informatics (which determine the rate at which information is collected) and estimation (which determines the states of the objects). These aspects are coupled by the steering decisions of the explorer. We seek to improve exploration by finding trade-offs amongst these couplings and the components of exploration: the Mission, the Path and the Agent. A comprehensive model of exploration is presented that, on one hand, accounts for these couplings and on the other hand is simple enough to allow analysis. This model is utilized to pose and solve several exploration problems where an objective function is to be minimized. Specific functions to be considered are the mission duration and the total energy. These exploration problems are formulated as optimal control problems and necessary conditions for optimality are obtained in the form of two-point boundary value problems. An analysis of these problems reveals characteristics of optimal exploration paths. Several regimes are identified for the optimal paths including the Watchtower, Solar and Drag regime, and several non-dimensional parameters are derived that determine the appropriate regime of travel. The so-called Power Ratio is shown to predict the qualitative features of the optimal paths, provide a metric to evaluate an aircrafts design and determine an aircrafts capability for flying perpetually. Optimal exploration system drivers are identified that provide perspective as to the importance of these various regimes of flight. A bank-to-turn solar-powered aircraft flying at constant altitude on Mars is used as a specific platform for analysis using the coupled model. Flight-paths found with this platform are presented that display the optimal exploration problem characteristics. These characteristics are used to form heuristics, such as a Generalized Traveling Salesman Problem solver, to simplify the exploration problem. These heuristics are used to empirically show the successful completion of an exploration mission by a physical explorer.

Effects of cylinder Reynolds number on the turbulent horseshoe vortex system and near wake of a surface-mounted circular cylinder

NASA Astrophysics Data System (ADS)

Kirkil, Gokhan; Constantinescu, George

2015-07-01

The turbulent horseshoe vortex (HV) system and the near-wake flow past a circular cylinder mounted on a flat bed in an open channel are investigated based on the results of eddy-resolving simulations and supporting flow visualizations. Of particular interest are the changes in the mean flow and turbulence statistics within the HV region as the necklace vortices wrap around the cylinder's base and the variation of the mean flow and turbulence statistics in the near wake, in between the channel bed and the free surface. While it is well known that the drag crisis induces important changes in the flow past infinitely long circular cylinders, the changes are less understood and more complex for the case of flow past a surface-mounted cylinder. This is because even at very high cylinder Reynolds numbers, ReD, the flow regime remains subcritical in the vicinity of the bed surface due to the reduction of the incoming flow velocity within the bottom boundary layer. The paper provides a detailed discussion of the changes in the flow physics between cylinder Reynolds numbers at which the flow in the upstream part of the separated shear layers (SSLs) is laminar (ReD = 16 000, subcritical flow regime) and Reynolds numbers at which the transition occurs inside the attached boundary layers away from the bed and the flow within the SSLs is turbulent (ReD = 5 ∗ 105, supercritical flow regime). The changes between the two regimes in the dynamics and level of coherence of the large-scale coherent structures (necklace vortices, vortex tubes shed in the SSLs and roller vortices shed in the wake) and their capacity to induce high-magnitude bed friction velocities in the mean and instantaneous flow fields and to amplify the near-bed turbulence are analyzed. Being able to quantitatively and qualitatively describe these changes is critical to understand Reynolds-number-induced scale effects on sediment erosion mechanisms around cylinders mounted on a loose bed, which is a problem of great practical relevance (e.g., for pier scour studies).

Multiphase Flow: The Gravity of the Situation

NASA Technical Reports Server (NTRS)

Hewitt, Geoffrey F.

1996-01-01

A brief survey is presented of flow patterns in two-phase, gas-liquid flows at normal and microgravity, the differences between them being explored. It seems that the flow patterns in zero gravity are in general much simpler than those in normal gravity with only three main regimes (namely bubbly, slug and annular flows) being observed. Each of these three regimes is then reviewed, with particular reference to identification of areas of study where investigation of flows at microgravity might not only be interesting in themselves, but also throw light on mechanisms at normal earth gravity. In bubbly flow, the main area of interest seems to be that of bubble coalescence. In slug flow, the extension of simple displacement experiments to the zero gravity case would appear to be a useful option, supplemented by computational fluid dynamics (CFD) studies. For annular flow, the most interesting area appears to be the study of the mechanisms of disturbance waves; it should be possible to extend the region of investigation of the onset and behavior of these waves to much low gas velocities where measurements are clearly much easier.

Proton imaging of stochastic magnetic fields

NASA Astrophysics Data System (ADS)

Bott, A. F. A.; Graziani, C.; Tzeferacos, P.; White, T. G.; Lamb, D. Q.; Gregori, G.; Schekochihin, A. A.

2017-12-01

Recent laser-plasma experiments (Fox et al., Phys. Rev. Lett., vol. 111, 2013, 225002; Huntington et al., Nat. Phys., vol. 11(2), 2015, 173-176 Tzeferacos et al., Phys. Plasmas, vol. 24(4), 2017a, 041404; Tzeferacos et al., 2017b, arXiv:1702.03016 [physics.plasm-ph]) report the existence of dynamically significant magnetic fields, whose statistical characterisation is essential for a complete understanding of the physical processes these experiments are attempting to investigate. In this paper, we show how a proton-imaging diagnostic can be used to determine a range of relevant magnetic-field statistics, including the magnetic-energy spectrum. To achieve this goal, we explore the properties of an analytic relation between a stochastic magnetic field and the image-flux distribution created upon imaging that field. This `Kugland image-flux relation' was previously derived (Kugland et al., Rev. Sci. Instrum. vol. 83(10), 2012, 101301) under simplifying assumptions typically valid in actual proton-imaging set-ups. We conclude that, as with regular electromagnetic fields, features of the beam's final image-flux distribution often display a universal character determined by a single, field-scale dependent parameter - the contrast parameter s/{\\mathcal{M}}lB$ - which quantifies the relative size of the correlation length B$ of the stochastic field, proton displacements s$ due to magnetic deflections and the image magnification . For stochastic magnetic fields, we establish the existence of four contrast regimes, under which proton-flux images relate to their parent fields in a qualitatively distinct manner. These are linear, nonlinear injective, caustic and diffusive. The diffusive regime is newly identified and characterised. The nonlinear injective regime is distinguished from the caustic regime in manifesting nonlinear behaviour, but as in the linear regime, the path-integrated magnetic field experienced by the beam can be extracted uniquely. Thus, in the linear and nonlinear injective regimes we show that the magnetic-energy spectrum can be obtained under a further statistical assumption of isotropy. This is not the case in the caustic or diffusive regimes. We discuss complications to the contrast-regime characterisation arising for inhomogeneous, multi-scale stochastic fields, which can encompass many contrast regimes, as well as limitations currently placed by experimental capabilities on one's ability to extract magnetic-field statistics. The results presented in this paper are of consequence in providing a comprehensive description of proton images of stochastic magnetic fields, with applications for improved analysis of proton-flux images.

Rotating-fluid experiments with an atmospheric general circulation model

NASA Technical Reports Server (NTRS)

Geisler, J. E.; Pitcher, E. J.; Malone, R. C.

1983-01-01

In order to determine features of rotating fluid flow that are dependent on the geometry, rotating annulus-type experiments are carried out with a numerical model in spherical coordinates. Rather than constructing and testing a model expressly for this purpose, it is found expedient to modify an existing general circulation model of the atmosphere by removing the model physics and replacing the lower boundary with a uniform surface. A regime diagram derived from these model experiments is presented; its major features are interpreted and contrasted with the major features of rotating annulus regime diagrams. Within the wave regime, a narrow region is found where one or two zonal wave numbers are dominant. The results reveal no upper symmetric regime; wave activity at low rotation rates is thought to be maintained by barotropic rather than baroclinic processes.

Interaction between two polyelectrolyte brushes.

PubMed

Kumar, N Arun; Seidel, Christian

2007-08-01

We report molecular dynamics simulations on completely charged polyelectrolyte brushes grafted to two parallel surfaces. The pressure Pi is evaluated as a function of separation D between the two grafting planes. For decreasing separation, Pi shows several regimes distinguished by their scaling with D which reflects the different physical nature of the various regimes. At weak compression the pressure obeys the 1D power law predicted by scaling theory of an ideal gas of counterions in the osmotic brush regime. In addition we find that the brushes shrink as they approach each other trying to avoid interpenetration. At higher compressions where excluded volume interactions become important, we obtain scaling exponents between -2 at small grafting density rho(a) and -3 at large rho(a). This behavior indicates a transition from a brush under good solvent condition to the melt regime with increasing grafting density.

Weight-reducing diets.

PubMed

Balabanski, L

1985-01-01

No single diet exists for the treatment of obesity. On the contrary, a variety of diet regimes should be taken in consideration in this disease. Even a normoenergic diet can produce the desired reduction of overweight if it is combined with physical exercise. A moderately reducing diet has a number of advantages over the very low-energic ones, as it leads to the preservation of the lean body mass, especially when the diet is accompanied by a regime of high physical activity. In obesity and other metabolic disorders, it is convenient to include in the diet low-energy foods rich in fiber with a possibly specific hypolipidemic effect, such as soy dishes, pectin-enriched dishes, fruit purees and juices, skimmed milk yogurt, wheat bran bisquits, and others.

Understanding and Predicting Profile Structure and Parametric Scaling of Intrinsic Rotation

NASA Astrophysics Data System (ADS)

Wang, Weixing

2016-10-01

It is shown for the first time that turbulence-driven residual Reynolds stress can account for both the shape and magnitude of the observed intrinsic toroidal rotation profile. Nonlinear, global gyrokinetic simulations using GTS of DIII-D ECH plasmas indicate a substantial ITG fluctuation-induced non-diffusive momentum flux generated around a mid-radius-peaked intrinsic toroidal rotation profile. The non-diffusive momentum flux is dominated by the residual stress with a negligible contribution from the momentum pinch. The residual stress profile shows a robust anti-gradient, dipole structure in a set of ECH discharges with varying ECH power. Such interesting features of non-diffusive momentum fluxes, in connection with edge momentum sources and sinks, are found to be critical to drive the non-monotonic core rotation profiles in the experiments. Both turbulence intensity gradient and zonal flow ExB shear are identified as major contributors to the generation of the k∥-asymmetry needed for the residual stress generation. By balancing the residual stress and the momentum diffusion, a self-organized, steady-state rotation profile is calculated. The predicted core rotation profiles agree well with the experimentally measured main-ion toroidal rotation. The validated model is further used to investigate the characteristic dependence of global rotation profile structure in the multi-dimensional parametric space covering turbulence type, q-profile structure and collisionality with the goal of developing physics understanding needed for rotation profile control and optimization. Interesting results obtained include intrinsic rotation reversal induced by ITG-TEM transition in flat-q profile regime and by change in q-profile from weak to normal shear.. Fluctuation-generated poloidal Reynolds stress is also shown to significantly modify the neoclassical poloidal rotation in a way consistent with experimental observations. Finally, the first-principles-based model is applied to studying the ρ * -scaling and predicting rotations in ITER regime. Work supported by U.S. DOE Contract DE-AC02-09-CH11466.

Lack of interest in physical activity - individual and environmental attributes in adults across Europe: The SPOTLIGHT project.

PubMed

Carraça, Eliana V; Mackenbach, Joreintje D; Lakerveld, Jeroen; Rutter, Harry; Oppert, Jean-Michel; De Bourdeaudhuij, Ilse; Compernolle, Sofie; Roda, Célina; Bardos, Helga; Teixeira, Pedro J

2018-06-01

A considerable proportion of European adults report little or no interest in physical activity. Identifying individual-level and environmental-level characteristics of these individuals can help designing effective interventions and policies to promote physical activity. This cross-sectional study additionally explored associations between level of interest and physical activity, after controlling for other individual and environmental variables. Measures of objective and perceived features of the physical environment of residence, self-reported physical activity and other lifestyle behaviors, barriers towards physical activity, general health, and demographics were obtained from 5205 European adults participating in the 2014 online SPOTLIGHT survey. t-Tests, chi-square tests, and generalized estimating equations with negative binomial log-link function were conducted. Adults not interested in physical activity reported a higher BMI and a lower self-rated health, were less educated, and to a smaller extent female and less frequently employed. They were more prone to have less healthy eating habits, and to perceive more barriers towards physical activity. Only minor differences were observed in environmental attributes: the non-interested were slightly more likely to live in neighborhoods objectively characterized as less aesthetic and containing more destinations, and perceived as less functional, safe, and aesthetic. Even after controlling for other individual and environmental factors, interest in physical activity remained a significant correlate of physical activity, supporting the importance of this association. This study is among the first to describe characteristics of individuals with reduced interest in physical activity, suggesting that (lack of) interest is a robust correlate of physical activity in several personal and environmental conditions. Copyright © 2018 Elsevier Inc. All rights reserved.

A curricular frame for physics education: Development, comparison with students' interests, and impact on students' achievement and self-concept

NASA Astrophysics Data System (ADS)

Häussler, Peter; Hoffmann, Lore

2000-11-01

This article presents three interlinked studies aimed at: (1) developing a curricular frame for physics education; (2) assessing the students' interest in the contents, contexts, and activities that are suggested by that curricular frame; and (3) developing a curriculum that is in line with that frame and measuring its cognitive and emotional effects on students. The curricular frame was developed by adopting the Delphi technique and drawing on the expertise of 73 persons selected according to specified selection criteria. Interest data of some 8000 students and information of the presently taught physics curriculum were sampled longitudinally as well as cross-sectionally in various German Länder (states) by questionnaire. The third study comprised 23 experimental and 7 control classes. As a result of the comparison between the features of the curricular frame, the interest structure of students, and the current physics curriculum, there is a remarkable congruency between students' interest in physics and the kind of physics education identified in the Delphi study as being relevant. However, there is a considerable discrepancy between students' interest and the kind of physics instruction practiced in the physics classroom. Regression analysis revealed that students' interest in physics as a school subject is hardly related to their interest in physics, but mainly to the students' self-esteem of being good achievers. The data strongly suggest physics be taught so that students have a chance to develop a positive physics-related self-concept and to link physics with situations they encounter outside the classroom. A curriculum based on these principles proved superior compared to a traditional curriculum.

Moving into the 21st Century: Curriculum Strategies for Children's Physical Education. PACE VI Presentation Handouts.

ERIC Educational Resources Information Center

Belka, David E., Ed.

The handouts from the Ohio conference PACE (Positive Approaches to Children's Education) VI are presented. Among them are: (1) "Hugs" (submitted by A. Braselton); (2) "Rhythmic Activities for 2001" (L. Hardman); (3) "A Strategy for Cognitive Development in Physical Education" (C. Regimal); (4) "It's the Kids That…

Volume versus value maximization illustrated for Douglas-fir with thinning

Treesearch

Kurt H. Riitters; J. Douglas Brodie; Chiang Kao

1982-01-01

Economic and physical criteria for selecting even-aged rotation lengths are reviewed with examples of their optimizations. To demonstrate the trade-off between physical volume, economic return, and stand diameter, examples of thinning regimes for maximizing volume, forest rent, and soil expectation are compared with an example of maximizing volume without thinning. The...

Fermilab Today

Science.gov Websites

Fundamental Physics in the Non-Linear Regime 3:30 p.m. Director's Coffee Break - 2nd Flr X-Over 4:00 p.m. All Week archive Fermilab Safety Tip of the Week archive Linear Collider News archive Fermilab Today Committee ECFA Study of Physics and Detectors for a Linear Collider" and GDE member, explained the

Identifying microturbulence regimes in a TCV discharge making use of physical constraints on particle and heat fluxes

DOE PAGES

Mariani, Alberto; Brunner, S.; Dominski, J.; ...

2018-01-17

Reducing the uncertainty on physical input parameters derived from experimental measurements is essential towards improving the reliability of gyrokinetic turbulence simulations. This can be achieved by introducing physical constraints. Amongst them, the zero particle flux condition is considered here. A first attempt is also made to match as well the experimental ion/electron heat flux ratio. This procedure is applied to the analysis of a particular Tokamak à Configuration Variable discharge. A detailed reconstruction of the zero particle flux hyper-surface in the multi-dimensional physical parameter space at fixed time of the discharge is presented, including the effect of carbon as themore » main impurity. Both collisionless and collisional regimes are considered. Hyper-surface points within the experimental error bars are found. In conclusion, the analysis is done performing gyrokinetic simulations with the local version of the GENE code, computing the fluxes with a Quasi-Linear (QL) model and validating the QL results with non-linear simulations in a subset of cases.« less

Identifying microturbulence regimes in a TCV discharge making use of physical constraints on particle and heat fluxes

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

Mariani, Alberto; Brunner, S.; Dominski, J.

Reducing the uncertainty on physical input parameters derived from experimental measurements is essential towards improving the reliability of gyrokinetic turbulence simulations. This can be achieved by introducing physical constraints. Amongst them, the zero particle flux condition is considered here. A first attempt is also made to match as well the experimental ion/electron heat flux ratio. This procedure is applied to the analysis of a particular Tokamak à Configuration Variable discharge. A detailed reconstruction of the zero particle flux hyper-surface in the multi-dimensional physical parameter space at fixed time of the discharge is presented, including the effect of carbon as themore » main impurity. Both collisionless and collisional regimes are considered. Hyper-surface points within the experimental error bars are found. In conclusion, the analysis is done performing gyrokinetic simulations with the local version of the GENE code, computing the fluxes with a Quasi-Linear (QL) model and validating the QL results with non-linear simulations in a subset of cases.« less

Nicholas Metropolis Award for Outstanding Doctoral Thesis Work in Computational Physics Talk: Equation of State of the Dilute Fermi Gases

NASA Astrophysics Data System (ADS)

Chang, Soon Yong

2008-04-01

In the recent years, dilute Fermi gases have played the center stage role in the many-body physics. The gas of neutral alkali atoms such as Lithium-6 and Potassium-40 can be trapped at temperatures below the Fermi degeneracy. The most relevant feature of these gases is that the interaction is tunable and strongly interacting superfluid can be artificially created. I will discuss the recent progress in understanding the ground state properties of the dilute Fermi gases at different interaction regimes. First, I will present the case of the spin symmetric systems where the Fermi gas can smoothly crossover from the BCS regime to the BEC regime. Then, I will discuss the case of the spin polarized systems, where different quantum phases can occur as a function of the polarization. In the laboratory, the trapped Fermi gas shows spatial dependence of the different quantum phases. This can be understood in the context of the local variation of the chemical potential. I will present the most accurate quantum ab initio results and the relevant experiments.

Momentum transport and non-local transport in heat-flux-driven magnetic reconnection in HEDP

NASA Astrophysics Data System (ADS)

Liu, Chang; Fox, Will; Bhattacharjee, Amitava

2016-10-01

Strong magnetic fields are readily generated in high-energy-density plasmas and can affect the heat confinement properties of the plasma. Magnetic reconnection can in turn be important as an inverse process, which destroys or reconfigures the magnetic field. Recent theory has demonstrated a novel physics regime for reconnection in high-energy-density plasmas where the magnetic field is advected into the reconnection layer by plasma heat flux via the Nernst effect. In this work we elucidate the physics of the electron dissipation layer in this heat-flux-driven regime. Through fully kinetic simulation and a new generalized Ohm's law, we show that momentum transport due to the heat-flux-viscosity effect provides the dissipation mechanism to allow magnetic field line reconnection. Scaling analysis and simulations show that the characteristic width of the current sheet in this regime is several electron mean-free-paths. These results additionally show a coupling between non-local transport and momentum transport, which in turn affects the dynamics of the magnetic field. This work was supported by the U.S. Department of Energy under Contract No. DE-SC0008655.

The Saturnian Environment as a Unique Laboratory for Collisionless Shock Waves

NASA Astrophysics Data System (ADS)

Sulaiman, Ali; Masters, Adam; Dougherty, Michele; Burgess, David; Fujimoto, Masaki; Hospodarsky, George

2016-04-01

Collisionless shock waves are ubiquitous in the universe and fundamental to understanding the nature of collisionless plasmas. The interplay between particles (ions and electrons) and fields (electromagnetic) introduces a variety of both physical and geometrical parameters such as Mach numbers (e.g. MA, Mf), β, and θBn. These vary drastically from terrestrial to astrophysical regimes resulting in radically different characteristics of shocks. This poses two complexities. Firstly, separating the influences of these parameters on physical mechanisms such as energy dissipation. Secondly, correlating observations of shock waves over a wide range of each parameter, enough to span across different regimes. Investigating the latter has been restricted since the majority of studies on shocks at exotic regimes (such as supernova remnants) have been achieved either remotely or via simulations, but rarely by means of in-situ observations. It is not clear what happens in the higher MA regime. Here we show the parameter space of MA for all bow shock crossings from 2004-2012 as measured by the Cassini spacecraft. We found that the Saturnian bow shock exhibits characteristics akin to both terrestrial and astrophysical regimes (MA of order 100), which is principally controlled by the upstream magnetic field strength. Moreover, we estimated the θbn of each crossing and were able to further constrain the sample into categories of similar features. Our results demonstrate how MA plays a central role in controlling the onset of physical mechanisms in collisionless shocks, particularly reformation. While ongoing studies have investigated this process extensively both theoretically and via simulations, their observations remain few and far between. We show conclusive evidence for cyclic reformation controlled by specular ion reflection occurring at the predicted timescale of ˜0.3 τc, where τc is the ion gyroperiod. In addition, we experimentally underpin the relationship between reformation and MA and focus on the magnetic structure of such shocks to further show that for the same MA, a reforming shock exhibits stronger magnetic field amplification than a shock that is not reforming. We anticipate our comprehensive assessment to give deeper insight to high MA collisionless shocks and provide a broader scope for understanding the structures and mechanisms of collisionless shocks. This can potentially bridge the gap between more modest MA observed in near-Earth space and more exotic astrophysical regimes where shock processes play central roles.

Life science students' attitudes, interest, and performance in introductory physics for life sciences: An exploratory study

NASA Astrophysics Data System (ADS)

Crouch, Catherine H.; Wisittanawat, Panchompoo; Cai, Ming; Renninger, K. Ann

2018-06-01

In response to national calls for improved physical sciences education for students pursuing careers in the life sciences and medicine, reformed introductory physics for life sciences (IPLS) courses are being developed. This exploratory study is among the first to assess the effect of an IPLS course on students' attitudes, interest, and performance. The IPLS course studied was the second semester of introductory physics, following a standard first semester course, allowing the outcomes of the same students in a standard course and in an IPLS course to be compared. In the IPLS course, each physics topic was introduced and elaborated in the context of a life science example, and developing students' skills in applying physics to life science situations was an explicitly stated course goal. Items from the Colorado Learning about Science Survey were used to assess change in students' attitudes toward and their interest in physics. Whereas the same students' attitudes declined during the standard first semester course, we found that students' attitudes toward physics hold steady or improve in the IPLS course. In particular, students with low initial interest in physics displayed greater increases in both attitudes and interest during the IPLS course than in the preceding standard course. We also find that in the IPLS course, students' interest in the life science examples is a better predictor of their performance than their pre-IPLS interest in physics. Our work suggests that the life science examples in the IPLS course can support the development of student interest in physics and positively influence their performance.

Folding time dependence of the motions of a molecular motor in an amorphous medium

NASA Astrophysics Data System (ADS)

Ciobotarescu, Simona; Bechelli, Solene; Rajonson, Gabriel; Migirditch, Samuel; Hester, Brooke; Hurduc, Nicolae; Teboul, Victor

2017-12-01

We investigate the dependence of the displacements of a molecular motor embedded inside a glassy material on its folding characteristic time τf. We observe two different time regimes. For slow foldings (regime I) the diffusion evolves very slowly with τf, while for rapid foldings (regime II) the diffusion increases strongly with τf(D ≈τf-2 ), suggesting two different physical mechanisms. We find that in regime I the motor's displacement during the folding process is counteracted by a reverse displacement during the unfolding, while in regime II this counteraction is much weaker. We notice that regime I behavior is reminiscent of the scallop theorem that holds for larger motors in a continuous medium. We find that the difference in the efficiency of the motor's motion explains most of the observed difference between the two regimes. For fast foldings the motor trajectories differ significantly from the opposite trajectories induced by the following unfolding process, resulting in a more efficient global motion than for slow foldings. This result agrees with the fluctuation theorems expectation for time reversal mechanisms. In agreement with the fluctuation theorems we find that the motors are unexpectedly more efficient when they are generating more entropy, a result that can be used to increase dramatically the motor's motion.

Health inequalities according to educational level in different welfare regimes: a comparison of 23 European countries.

PubMed

Eikemo, Terje A; Huisman, Martijn; Bambra, Clare; Kunst, Anton E

2008-05-01

The object of this study was to determine whether the magnitude of educational health inequalities varies between European countries with different welfare regimes. The data source is based on the first and second wave of the European Social Survey. The first health indicator describes people's mental and physical health in general, while the second reports cases of any limiting longstanding illness. Educational inequalities in health were measured as the difference in health between people with an average number of years of education and people whose educational years lay one standard deviation below the national average. Moreover, South European welfare regimes had the largest health inequalities, while countries with Bismarckian welfare regimes tended to demonstrate the smallest. Although the other welfare regimes ranked relatively close to each other, the Scandinavian welfare regimes were placed less favourably than the Anglo-Saxon and East European. Thus, this study shows an evident patterning of magnitudes of health inequalities according to features of European welfare regimes. Although the greater distribution of welfare benefits within the Scandinavian countries are likely to have a protective effect for disadvantaged cities in these countries, other factors such as relative deprivation and class-patterned health behaviours might be acting to widen health inequalities.

O-regime dynamics and modeling in Tore Supra

NASA Astrophysics Data System (ADS)

Turco, F.; Giruzzi, G.; Imbeaux, F.; Udintsev, V. S.; Artaud, J. F.; Barana, O.; Dumont, R.; Mazon, D.; Ségui, J.-L.

2009-06-01

The regime of nonlinear temperature oscillations (O-regime), characteristic of noninductive discharges on Tore Supra [Équipe Tore Supra, Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, France, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 1, p. 9], is investigated in its triggering and suppressing mechanism. This regime can be described by two nonlinearly coupled equations for the current density j(r ) and the electron temperature Te(r) where the equation coefficients are functions of j and Te themselves. Both the integrated modeling code CRONOS [V. Basiuk et al., Nucl. Fusion 43, 822 (2003)] and a two-patch predator-prey system with diffusion and noise have been used and results have been compared to the experimental observations of the O-regime. A database of discharges is analyzed which features monotonic, flat, and reversed safety factor (q) profiles in order to characterize the action of external actuators on the regime dynamics with the widest generality. Electron cyclotron current drive and neutral beam injections have been used in order to induce localized perturbations in the total current profile j(r ) as well as to change the plasma confinement conditions in the central region. Magnetic shear perturbations and modifications of the heat transport turn out to be the central parameters governing the dynamics of the O-regime.

Computational study of hot electron generation and energy transport in intense laser produced hot dense matter

NASA Astrophysics Data System (ADS)

Mishra, Rohini

Present ultra high power lasers are capable of producing high energy density (HED) plasmas, in controlled way, with a density greater than solid density and at a high temperature of keV (1 keV ˜ 11,000,000° K). Matter in such extreme states is particularly interesting for (HED) physics such as laboratory studies of planetary and stellar astrophysics, laser fusion research, pulsed neutron source etc. To date however, the physics in HED plasma, especially, the energy transport, which is crucial to realize applications, has not been understood well. Intense laser produced plasmas are complex systems involving two widely distinct temperature distributions and are difficult to model by a single approach. Both kinetic and collisional process are equally important to understand an entire process of laser-solid interaction. By implementing atomic physics models, such as collision, ionization, and radiation damping, self consistently, in state-of-the-art particle-in-cell code (PICLS) has enabled to explore the physics involved in the HED plasmas. Laser absorption, hot electron transport, and isochoric heating physics in laser produced hot dense plasmas are studied with a help of PICLS simulations. In particular, a novel mode of electron acceleration, namely DC-ponderomotive acceleration, is identified in the super intense laser regime which plays an important role in the coupling of laser energy to a dense plasma. Geometric effects on hot electron transport and target heating processes are examined in the reduced mass target experiments. Further, pertinent to fast ignition, laser accelerated fast electron divergence and transport in the experiments using warm dense matter (low temperature plasma) is characterized and explained.

Critical regimes driven by recurrent mobility patterns of reaction-diffusion processes in networks

NASA Astrophysics Data System (ADS)

Gómez-Gardeñes, J.; Soriano-Paños, D.; Arenas, A.

2018-04-01

Reaction-diffusion processes1 have been widely used to study dynamical processes in epidemics2-4 and ecology5 in networked metapopulations. In the context of epidemics6, reaction processes are understood as contagions within each subpopulation (patch), while diffusion represents the mobility of individuals between patches. Recently, the characteristics of human mobility7, such as its recurrent nature, have been proven crucial to understand the phase transition to endemic epidemic states8,9. Here, by developing a framework able to cope with the elementary epidemic processes, the spatial distribution of populations and the commuting mobility patterns, we discover three different critical regimes of the epidemic incidence as a function of these parameters. Interestingly, we reveal a regime of the reaction-diffussion process in which, counter-intuitively, mobility is detrimental to the spread of disease. We analytically determine the precise conditions for the emergence of any of the three possible critical regimes in real and synthetic networks.

Tunable liquid microlens arrays in electrode-less configuration and their accurate characterization by interference microscopy.

PubMed

Miccio, L; Finizio, A; Grilli, S; Vespini, V; Paturzo, M; De Nicola, S; Ferraro, Pietro

2009-02-16

A special class of tunable liquid microlenses is presented here. The microlenses are generated by an electrowetting effect under an electrode-less configuration and they exhibit two different regimes that are named here as separated lens regime (SLR) and wave-like lens regime (WLR). The lens effect is induced by the pyroelectricity of polar dielectric crystals, as was proved in principle in a previous work by the same authors (S. Grilli et al., Opt. Express 16, 8084, 2008). Compared to that work, the improvements to the experimental set-up and procedure allow to reveal the two lens regimes which exhibit different optical properties. A digital holography technique is used to reconstruct the transmitted wavefront during focusing and a focal length variation in the millimetre range is observed. The tunability of such microlenses could be of great interest to the field of micro-optics thanks to the possibility to achieve focus tuning without moving parts and thus favouring the miniaturization of the optical systems.

Ecological forecasting in the presence of abrupt regime shifts

NASA Astrophysics Data System (ADS)

Dippner, Joachim W.; Kröncke, Ingrid

2015-10-01

Regime shifts may cause an intrinsic decrease in the potential predictability of marine ecosystems. In such cases, forecasts of biological variables fail. To improve prediction of long-term variability in environmental variables, we constructed a multivariate climate index and applied it to forecast ecological time series. The concept is demonstrated herein using climate and macrozoobenthos data from the southern North Sea. Special emphasis is given to the influence of selection of length of fitting period to the quality of forecast skill especially in the presence of regime shifts. Our results indicate that the performance of multivariate predictors in biological forecasts is much better than that of single large-scale climate indices, especially in the presence of regime shifts. The approach used to develop the index is generally applicable to all geographical regions in the world and to all areas of marine biology, from the species level up to biodiversity. Such forecasts are of vital interest for practical aspects of the sustainable management of marine ecosystems and the conservation of ecosystem goods and services.

Effectiveness of international environmental regimes: Existing knowledge, cutting-edge themes, and research strategies

PubMed Central

Young, Oran R.

2011-01-01

International environmental regimes—especially those regimes articulated in multilateral environmental agreements—have been a subject of intense interest within the scientific community over the last three decades. However, there are substantial differences of opinion regarding the effectiveness of these governance systems or the degree to which they are successful in solving the problems leading to their creation. This article provides a critical review of the literature on this topic. It extracts and summarizes what is known about the effectiveness of environmental regimes in the form of a series of general and specific propositions. It identifies promising topics for consideration in the next phase of research in this field. Additionally, it comments on the research strategies available to pursue this line of analysis. The general conclusions are that international environmental regimes can and do make a difference, although often in conjunction with a number of other factors, and that a strategy of using a number of tools combined can help to improve understanding of the determinants of success. PMID:22143795

Unifying quantum heat transfer in a nonequilibrium spin-boson model with full counting statistics

NASA Astrophysics Data System (ADS)

Wang, Chen; Ren, Jie; Cao, Jianshu

2017-02-01

To study the full counting statistics of quantum heat transfer in a driven nonequilibrium spin-boson model, we develop a generalized nonequilibrium polaron-transformed Redfield equation with an auxiliary counting field. This enables us to study the impact of qubit-bath coupling ranging from weak to strong regimes. Without external modulations, we observe maximal values of both steady-state heat flux and noise power in moderate coupling regimes, below which we find that these two transport quantities are enhanced by the finite-qubit-energy bias. With external modulations, the geometric-phase-induced heat flux shows a monotonic decrease upon increasing the qubit-bath coupling at zero qubit energy bias (without bias). While under the finite-qubit-energy bias (with bias), the geometric-phase-induced heat flux exhibits an interesting reversal behavior in the strong coupling regime. Our results unify the seemingly contradictory results in weak and strong qubit-bath coupling regimes and provide detailed dissections for the quantum fluctuation of nonequilibrium heat transfer.

The Impact of Explicit Teaching of Methodological Aspects of Physics on Scientistic Beliefs and Interest

NASA Astrophysics Data System (ADS)

Korte, Stefan; Berger, Roland; Hänze, Martin

2017-05-01

We assessed the impact of teaching methodological aspects of physics on students' scientistic beliefs and subject interest in physics in a repeated-measurement design with a total of 142 students of upper secondary physics classes. Students gained knowledge of methodological aspects from the pre-test to the post-test and reported reduced scientistic beliefs, both from their own views and from their presumed prototypical physicists' views. We found no direct impact of teaching on students' subject interest in physics. As path analysis indicates, this result can be traced back to opposing paths: Lower scientistic beliefs of students attenuate subject interest while lower presumed scientistic beliefs that they hold of physicists foster subject interest. This finding is in accordance with the self-to-prototype matching theory that predicts an impact of the overlap between students' self-image and their prototypical image on subject interest in physics.

Welfare regimes, labour policies and unhealthy psychosocial working conditions: a comparative study with 9917 older employees from 12 European countries.

PubMed

Dragano, Nico; Siegrist, Johannes; Wahrendorf, Morten

2011-09-01

Recent analyses explored associations of welfare state regimes with population health, with particular interest in differences between social protection-oriented versus more liberal regimes. Little is known about such associations with work-related health. The aims of this contribution are (1) to study variations of quality of work according to type of welfare regime and (2) to analyse differences in the size of effects of quality of work on workers' health according to type of welfare regime. The authors use cross-sectional and longitudinal data from two studies ('Survey of Health, Ageing and Retirement in Europe' and the 'English Longitudinal Study on Ageing') with 9917 employed men and women (aged 50 to 64) in 12 European countries. Psychosocial quality of work is measured by low control and effort-reward imbalance at work. Depressive symptoms are introduced as a health indicator. Linear multilevel models and logistic regression analyses are performed to test the hypotheses. In addition to the welfare regime typology, the authors introduce labour policy and economy-related macro indicators. Between-country variations in quality of work are largely explained by macro indicators and welfare regimes, with poorer quality of work in countries with less emphasis on older workers' protection. Moreover, in the Liberal and Southern welfare regime, effects of quality of work on depressive symptoms are relatively strongest (adjusted ORs varying from 1.45 to 2.64). Active labour policies and reliable social protection measures (eg, Scandinavian welfare regime) exert beneficial effects on the health and well-being of older workers. More emphasis on improving quality of work among this group is warranted.

Liability risk sharing regime for U.S. commercial space transportation : study and analysis

DOT National Transportation Integrated Search

2002-04-01

The Federal Aviation Administration of the Department of Transportation (DOT), in cooperation with interested federal agencies, has performed a study and analysis of seven issues specifically identified in the Space Competitiveness Act, and provides ...

Understanding Molecular Conduction: Old Wine in a New Bottle?

NASA Astrophysics Data System (ADS)

Ghosh, Avik

2007-03-01

Molecules provide an opportunity to test our understanding of fundamental non-equilibrium transport processes, as well as explore new device possibilities. We have developed a unified approach to nanoscale conduction, coupling bandstructure and electrostatics of the channel and contacts with a quantum kinetic theory of current flow. This allows us to describe molecular conduction at various levels of detail, -- from quantum corrected compact models, to semi-empirical models for quick physical insights, and `first-principles' calculations of current-voltage (I-V) characteristics with no adjustable parameters. Using this suite of tools, we can quantitatively explain various experimental I-Vs, including complex reconstructed silicon substrates. We find that conduction in most molecules is contact dominated, and limited by fundamental electrostatic and thermodynamic restrictions quite analogous to those faced by the silicon industry, barring a few interesting exceptions. The distinction between molecular and silicon electronics must therefore be probed at a more fundamental level. Ultra-short molecules are unique in that they possess large Coulomb energies as well as anomalous vibronic couplings with current flow -- in other words, strong non-equilibrium electron-electron and electron-phonon correlations. These effects yield prominent experimental signatures, but require a completely different modeling approach -- in fact, popular approaches to include correlation typically do not work for non-equilibrium. Molecules exhibit rich physics, including the ability to function both as weakly interacting current conduits (quantum wires) as well as strongly correlated charge storage centers (quantum dots). Theoretical treatment of the intermediate coupling regime is particularly challenging, with a large `fine structure constant' for transport that negates orthodox theories of Coulomb Blockade and phonon-assisted tunneling. It is in this regime that the scientific and technological merits of molecular conductors may need to be explored. For instance, the tunable quantum coupling of current flow in silicon transistors with engineered molecular scatterers could lead to devices that operate on completely novel principles.

Synthesis and Explosive Consolidation of Titanium, Aluminium, Boron and Carbon Containing Powders

NASA Astrophysics Data System (ADS)

Chikhradze, Mikheil; Oniashvili, George; Chikhradze, Nikoloz; D. S Marquis, Fernand

2016-10-01

The development of modern technologies in the field of materials science has increased the interest towards the bulk materials with improved physical, chemical and mechanical properties. Composites, fabricated in Ti-Al-B-C systems are characterized by unique physical and mechanical properties. They are attractive for aerospace, power engineering, machine and chemical applications. The technologies to fabricate ultrafine grained powder and bulk materials in Ti-Al-B-C system are described in the paper. It includes results of theoretical and experimental investigation for selection of powders composition and determination of thermodynamic conditions for bland preparation, as well as optimal technological parameters for mechanical alloying and adiabatic compaction. The crystalline coarse Ti, Al, C powders and amorphous B were used as precursors and blends with different compositions of Ti-Al, Ti-Al-C, Ti-B-C and Ti-Al-B were prepared. Preliminary determination/selection of blend compositions was made on the basis of phase diagrams. The powders were mixed according to the selected ratios of components to produce the blend. Blends were processed in “Fritsch” Planetary premium line ball mill for mechanical alloying, syntheses of new phases, amorphization and ultrafine powder production. The blends processing time was variable: 1 to 20 hours. The optimal technological regimes of nano blend preparation were determined experimentally. Ball milled nano blends were placed in metallic tube and loaded by shock waves for realization of consolidation in adiabatic regime. The structure and properties of the obtained ultrafine grained materials depending on the processing parameters are investigated and discussed. For consolidation of the mixture, explosive compaction technology is applied at room temperatures. The prepared mixtures were located in low carbon steel tube and blast energies were used for explosive consolidation compositions. The relationship of ball milling technological parameters and explosive consolidation conditions on the structure/properties of the obtained samples are described in the paper.

Topological quantum error correction in the Kitaev honeycomb model

NASA Astrophysics Data System (ADS)

Lee, Yi-Chan; Brell, Courtney G.; Flammia, Steven T.

2017-08-01

The Kitaev honeycomb model is an approximate topological quantum error correcting code in the same phase as the toric code, but requiring only a 2-body Hamiltonian. As a frustrated spin model, it is well outside the commuting models of topological quantum codes that are typically studied, but its exact solubility makes it more amenable to analysis of effects arising in this noncommutative setting than a generic topologically ordered Hamiltonian. Here we study quantum error correction in the honeycomb model using both analytic and numerical techniques. We first prove explicit exponential bounds on the approximate degeneracy, local indistinguishability, and correctability of the code space. These bounds are tighter than can be achieved using known general properties of topological phases. Our proofs are specialized to the honeycomb model, but some of the methods may nonetheless be of broader interest. Following this, we numerically study noise caused by thermalization processes in the perturbative regime close to the toric code renormalization group fixed point. The appearance of non-topological excitations in this setting has no significant effect on the error correction properties of the honeycomb model in the regimes we study. Although the behavior of this model is found to be qualitatively similar to that of the standard toric code in most regimes, we find numerical evidence of an interesting effect in the low-temperature, finite-size regime where a preferred lattice direction emerges and anyon diffusion is geometrically constrained. We expect this effect to yield an improvement in the scaling of the lifetime with system size as compared to the standard toric code.

Factors that affect the physical science career interest of female students: Testing five common hypotheses

NASA Astrophysics Data System (ADS)

Hazari, Zahra; Potvin, Geoff; Lock, Robynne M.; Lung, Florin; Sonnert, Gerhard; Sadler, Philip M.

2013-12-01

There are many hypotheses regarding factors that may encourage female students to pursue careers in the physical sciences. Using multivariate matching methods on national data drawn from the Persistence Research in Science and Engineering (PRiSE) project (n=7505), we test the following five commonly held beliefs regarding what factors might impact females’ physical science career interest: (i) having a single-sex physics class, (ii) having a female physics teacher, (iii) having female scientist guest speakers in physics class, (iv) discussing the work of female scientists in physics class, and (v) discussing the underrepresentation of women in physics class. The effect of these experiences on physical science career interest is compared for female students who are matched on several factors, including prior science interests, prior mathematics interests, grades in science, grades in mathematics, and years of enrollment in high school physics. No significant effects are found for single-sex classes, female teachers, female scientist guest speakers, and discussing the work of female scientists. However, discussions about women’s underrepresentation have a significant positive effect.

A glittering icon of Fascist femininity: Trebisonda "Ondina" Valla.

PubMed

Gori, G

2001-01-01

This essay focuses on the second decade of the Italian Fascist regime through its emblematic symbol, Trebisonda 'Ondina' Valla. Valla gained first place in the 80 metre hurdles at the Berlin Olympics of 1936, and became the first world-class female athlete in Italian history, in spite of the generally backward condition of Italian women. In those years, a paternalistic and conservative society deeply discriminated against female participation in not only sport but also other cultural activities. The Catholic Church, medical expertise, eugenics theories and the fascist regime were all opposed to female competitive sport. The Church demanded female morality, modesty and domesticity while, the medical profession recommend only basic physical exercise for female health and motherhood. While promoting the myth of the New Italy as a modern nation, Fascism wished it to be inhabited by a traditional womanhood. Paradoxically, however, Mussolini supported Valla because she epitomized a dynamic fascism and brought Italian Fascism international visibility. The serendipitous value of Valla was that she encouraged young women to attempt to force open the bars of their political cage, and at the same time forced the fascist ideology to reconsider and reconstruct fascist principles in the interest of international propaganda. Thus while Valla was a political instrument of fascist purpose, she was also an agent of female emancipation. She was a political icon that also became a gender icon. In both roles she became a symbol of congratulation but also of confrontation, contradiction and paradox.

Physical mechanisms of timing jitter in photon detection by current-carrying superconducting nanowires

NASA Astrophysics Data System (ADS)

Sidorova, Mariia; Semenov, Alexej; Hübers, Heinz-Wilhelm; Charaev, Ilya; Kuzmin, Artem; Doerner, Steffen; Siegel, Michael

2017-11-01

We studied timing jitter in the appearance of photon counts in meandering nanowires with different fractional amount of bends. Intrinsic timing jitter, which is the probability density function of the random time delay between photon absorption in current-carrying superconducting nanowire and appearance of the normal domain, reveals two different underlying physical mechanisms. In the deterministic regime, which is realized at large photon energies and large currents, jitter is controlled by position-dependent detection threshold in straight parts of meanders. It decreases with the increase in the current. At small photon energies, jitter increases and its current dependence disappears. In this probabilistic regime jitter is controlled by Poisson process in that magnetic vortices jump randomly across the wire in areas adjacent to the bends.

Pressure gradient induced generation of microbubbles

NASA Astrophysics Data System (ADS)

Evangelio, Alvaro; Campo-Cortes, Francisco; Gordillo, Jose Manuel

2015-11-01

It is well known that the controlled production of monodisperse bubbles possesses uncountable applications in medicine, pharmacy and industry. Here we provide with a detailed physical description of the bubble formation processes taking place in a type of flow where the liquid pressure gradient can be straightforwardly controlled. In our experiments, a gas flow rate discharges through a cylindrical needle into a pressurized chamber. The pressure gradient created from the exit of the injection needle towards the entrance of a extraction duct promotes the stretching of the gas ligament downstream. In our analysis, which is supported by an exhaustive experimental study in which the liquid viscosity is varied by three orders of magnitude, different regimes can be distinguished depending mainly on the Reynolds number. Through our physical modeling, we provide closed expressions for both the bubbling frequencies and for the bubble diameters as well as the conditions under which a monodisperse generation is obtained in all regimes found. The excellent agreement between our expressions and the experimental data fully validates our physical modeling.

Mercantilist Development in Russia: The Legitimacy of State Power, State Identity, and the Energy Charter Regime (1990--2010)

NASA Astrophysics Data System (ADS)

Bruynooghe, Daniel; Wynn, Henry P.

This dissertation investigates the creation, adaptation, and demise of international regimes. Specifically, I ask why international regimes sometimes fail to fulfill their original purpose. Empirically, I examine the evolution and eventual failure of the Energy Charter (ECH), a multilateral regime that governs the Eurasian energy economy. Modeled after the European Steel and Coal Community, the original goal of the regime was to capitalize on economic complementarities in energy to integrate Gorbachev's reforming USSR (later Russia) with Europe and promote pan-European cooperation and peace. By 2010, integration had failed, and the regime itself had become a source of conflict. To understand this outcome, I focus on the foreign energy policy of Russia, a central state within the ECH, which actively participated in designing the regime in the 1990s but two decades later decided that it was no longer in its interest. Using data collected from interviews and archival searches during field research in Russia, Brussels, and Paris, I find that under President Yeltsin, low domestic sovereignty meant the state could not integrate key domestic players into ECH policy-making. This led Russia to conclude a bargain that it could not implement domestically. Under President Putin, high domestic sovereignty meant the state had sufficient capacity to corral these recalcitrant actors. However, the new policy that emerged compelled Russia to attempt to modify the ECH in ways that violated previously accepted norms, thereby alienating its European partners and undermining the regime. This study supports Hegemonic Stability theory which suggests that we can expect regime failure after major shifts in the distribution of power produce changes in the interests and policies of key states. I extend this finding by showing that Russian state power increased due to changes in elite conceptions about the legitimacy of state power. I demonstrate this by using over time comparisons between most similar cases, tracing the process through which ECH policy evolved, and examining intervening variables---state building strategies and elite identities vis-a-vis the state---that changed over time in unexpected ways. The shift in elite beliefs had a transformative effect on the structure of domestic politics, generating new patterns of authority, a higher level of state domestic sovereignty, and enhanced state power. Finally, state domestic sovereignty was associated with state capacity to organize domestic groups, behave as a unitary actor, and follow through on international commitments. To capture these developments, I use the concept of state identity which combines the level of domestic sovereignty (high or low) with elite beliefs about the state's role in the international system (regime maker or regime taker). This generates a typology of four state identities---master, pretender, disciple, and apprentice---that can be used to understand regime outcomes more generally. In political economy, I use the term mercantilist instead of master to connect my research with realist insights about the role of power in international political economy. I propose the term "mercantilist development" which refers to a state that attempts to fundamentally change the structure of the international economy in order to accumulate capital. Thus, mercantilist development helps us understand the micro-mechanisms through which the structure of the international system changes. Finally, I explore the factors associated with successful regime adaptation to accommodate rising powers, an especially pressing contemporary concern given that the balance of power is expected to shift considerably in the twenty-first century.

Architectures of Practice: Constraining or Enabling PE in Primary Schools

ERIC Educational Resources Information Center

Petrie, Kirsten

2016-01-01

To the outside observer, physical education in many primary schools, both in Aotearoa New Zealand and internationally, continues be practised in ways that students of the 1970s would recognise. The only significant change would arguably be the introduction of an increased regime of testing, and a narrower focus on physical health agendas. This is…

Competitive agents in a market: Statistical physics of the minority game

NASA Astrophysics Data System (ADS)

Sherrington, David

2007-10-01

A brief review is presented of the minority game, a simple frustrated many-body system stimulated by considerations of a market of competitive speculative agents. Its cooperative behaviour exhibits phase transitions and both ergodic and non-ergodic regimes. It provides novel challenges to statistical physics, reminiscent of those of mean-field spin glasses.

The Role of Interest in Physical Education: A Review of Research Evidence

ERIC Educational Resources Information Center

Chen, Ang; Wang, Yubing

2017-01-01

This article focuses on the research on interest, especially situational interest, in physical education. Interest has been considered a powerful motivator for children and adolescents. Based on a conceptualization of individual and situational interest, a reasonable size of evidence has been accumulated showing that situational interest motivates…

Effect of perforation on flow past a conic cylinder at \\varvec{Re} = 100 : wavy vortex and sign laws

NASA Astrophysics Data System (ADS)

Lin, L. M.; Zhong, X. F.; Wu, Y. X.

2018-04-01

In order to find the intrinsic physical mechanism of the original Kármán vortex wavily distorted across the span due to the introduction of three-dimensional (3-D) geometric disturbances, a flow past a peak-perforated conic shroud is numerically simulated at a Reynolds number of 100. Based on previous work by Meiburg and Lasheras (1988), the streamwise and vertical interactions with spanwise vortices are introduced and analyzed. Then vortex-shedding patterns in the near wake for different flow regimes are reinspected and illustrated from the view of these two interactions. Generally, in regime I, spanwise vortices are a little distorted due to the weak interaction. Then in regime II, spanwise vortices, even though curved obviously, are still shed synchronously with moderate streamwise and vertical interactions. But in regime III, violently wavy spanwise vortices in some vortex-shedding patterns, typically an Ω -type vortex, are mainly attributed to the strong vertical interactions, while other cases, such as multiple vortex-shedding patterns in sub-regime III-D, are resulted from complex streamwise and vertical interactions. A special phenomenon, spacial distribution of streamwise and vertical components of vorticity with specific signs in the near wake, is analyzed based on two models of streamwise and vertical vortices in explaining physical reasons of top and bottom shear layers wavily varied across the span. Then these two models and above two interactions are unified. Finally two sign laws are summarized: the first sign law for streamwise and vertical components of vorticity is positive in the upper shear layer, but negative in the lower shear layer, while the second sign law for three vorticity components is always negative in the wake.

Defining And Employing Reference Conditions For Ecological Restoration Of The Lower Missouri River, USA

NASA Astrophysics Data System (ADS)

Jacobson, R. B.; Elliott, C. M.; Reuter, J. M.

2008-12-01

Ecological reference conditions are especially challenging for large, intensively managed rivers like the Lower Missouri. Historical information provides broad understanding of how the river has changed, but translating historical information into quantitative reference conditions remains a challenge. Historical information is less available for biological and chemical conditions than for physical conditions. For physical conditions, much of the early historical condition is documented in date-specific measurements or maps, and it is difficult to determine how representative these conditions are for a river system that was characterized historically by large floods and high channel migration rates. As an alternative to a historically defined least- disturbed condition, spatial variation within the Missouri River basin provides potential for defining a best- attainable reference condition. A possibility for the best-attainable condition for channel morphology is an unchannelized segment downstream of the lowermost dam (rkm 1298 - 1203). This segment retains multiple channels and abundant sandbars although it has a highly altered flow regime and a greatly diminished sediment supply. Conversely, downstream river segments have more natural flow regimes, but have been narrowed and simplified for navigation and bank stability. We use two computational tools to compensate for the lack of ideal reference conditions. The first is a hydrologic model that synthesizes natural and altered flow regimes based on 100 years of daily inputs to the river (daily routing model, DRM, US Army Corps of Engineers, 1998); the second tool is hydrodynamic modeling of habitat availability. The flow-regime and hydrodynamic outputs are integrated to define habitat-duration curves as the basis for reference conditions (least-disturbed flow regime and least-disturbed channel morphology). Lacking robust biological response models, we use mean residence time of water and a habitat diversity index as generic ecosystem indicators.

Bandgap oscillation in quasiperiodic (BN)xCy nanotubes

NASA Astrophysics Data System (ADS)

Freitas, A.; Bezerra, C. G.; Azevedo, S.; Machado, L. D.; Pedreira, D. O.

2016-12-01

In the present contribution, we apply first-principles calculations to study the effects of quasiperiodic disorder on the physical properties of BN and C nanotubes. We take BN nanotubes (BNNTs) and C nanotubes (CNTs) as building blocks and construct quasiperiodic BNxCy nanotubes according to the Fibonacci sequence. We studied armchair and zigzag nanotubes of varying diameters. Our results demonstrate that the energy gap oscillates as a function of the n-generation index of the Fibonacci sequence. Moreover, we show that the choice of the BNNTs and CNTs may lead to a quasiperiodic BNxCy nanotube presenting an adjustable energy gap. We obtained a variety of quasiperiodic nanotubes with energy gaps ranging from 0.29 eV to 1.06 eV, which may be of interest for specific technological applications. Finally, it is also demonstrated that the specific heat of the quasiperiodic zigzag and armchair nanotubes presents an oscillatory behavior in the low temperature regime, and that this behavior depends on the curvature of the nanotube.

In situ magnetic resonance measurement of conversion, hydrodynamics and mass transfer during single- and two-phase flow in fixed-bed reactors.

PubMed

Gladden, L F; Alexander, P; Britton, M M; Mantle, M D; Sederman, A J; Yuen, E H L

2003-01-01

In recent years there has been increasing interest in applying magnetic resonance (MR) techniques in areas of engineering and chemical technology. The science that underpins many of these applications is the physics and chemistry of transport and reaction processes in porous materials. Key to the exploitation of MR methods will be our ability to demonstrate that MR yields information that cannot be obtained using conventional measurement techniques in engineering research. This article describes two case studies that highlight the power of MR to give new insights to chemical engineers. First, we demonstrate the application of MR techniques to explore both mass transfer and chemical conversion in situ within a fixed bed of catalyst, and we then use these data to identify the rate-controlling step of the chemical conversion. Second, we implement a rapid imaging technique to study the stability of the gas-liquid distribution in the low- and high-interaction two-phase flow regimes in a trickle-bed reactor.

Electrical and Optical Characteristics of Undoped and Se-Doped Bi2S3 Transistors

NASA Astrophysics Data System (ADS)

Kilcoyne, Colin; Alsaqqa, Ali; Rahman, Ajara A.; Whittaker-Brooks, Luisa; Sambandamurthy, G.

Semiconducting chalcogenides have been drawing increased attention due to their interesting physical properties, especially in low dimensional structures. Bi2S3 has demonstrated a high optical absorption coefficient, a large bulk mobility, small bandgap, high Seebeck coefficient, and low thermal conductivity. These properties make it a good candidate for optical, electric and thermoelectric applications. However, control over the electrical properties for enhanced thermoelectric performance and optical applications is desired. We present electrical transport and optical properties from individual nanowire and few-layer transistors of single crystalline undoped and Se-doped Bi2S3-xSex. All devices exhibit n-type semiconducting behavior and the ON/OFF ratio, mobility, and conductivity noise behavior are studied as functions of dopant concentration, temperature, and charge carrier density in different conduction regimes. The roles of dopant driven scattering mechanisms and mobility/carrier density fluctuations will be discussed. The potential for this series of materials as optical and electrical switches will be presented. NSF DMR.

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

Ozaki, N.; Nellis, W. J.; Mashimo, T.

Materials at high pressures and temperatures are of great current interest for warm dense matter physics, planetary sciences, and inertial fusion energy research. Shock-compression equation-of-state data and optical reflectivities of the fluid dense oxide, Gd 3Ga 5O 12 (GGG), were measured at extremely high pressures up to 2.6 TPa (26 Mbar) generated by high-power laser irradiation and magnetically-driven hypervelocity impacts. Above 0.75 TPa, the GGG Hugoniot data approach/reach a universal linear line of fluid metals, and the optical reflectivity most likely reaches a constant value indicating that GGG undergoes a crossover from fluid semiconductor to poor metal with minimum metallicmore » conductivity (MMC). These results suggest that most fluid compounds, e.g., strong planetary oxides, reach a common state on the universal Hugoniot of fluid metals (UHFM) with MMC at sufficiently extreme pressures and temperatures. Lastly, the systematic behaviors of warm dense fluid would be useful benchmarks for developing theoretical equation-of-state and transport models in the warm dense matter regime in determining computational predictions.« less

The topological susceptibility from grand canonical simulations in the interacting instanton liquid model: Chiral phase transition and axion mass

NASA Astrophysics Data System (ADS)

Wantz, Olivier; Shellard, E. P. S.

2010-04-01

This is the last in a series of papers on the topological susceptibility in the interacting instanton liquid model (IILM). We will derive improved finite temperature interactions to study the thermodynamic limit of grand canonical Monte Carlo simulations in the quenched and unquenched case with light, physical quark masses. In particular, we will be interested in chiral symmetry breaking. The paper culminates by giving, for the first time, a well-motivated temperature-dependent axion mass. Especially, this work finally provides a computation of the axion mass in the low temperature regime, ma2fa2=1.46×10-3Λ41+0.50 T/Λ1+(3.53 . It connects smoothly to the high temperature dilute gas approximation; the latter is improved by including quark threshold effects. To compare with earlier studies, we also provide the usual power-law ma2=αΛ4fa2(T, where Λ=400 MeV, n=6.68 and α=1.68×10-7.

Assessment of Wind Turbine Component Loads Under Yaw-Offset Conditions

DOE PAGES

Damiani, Rick R.; Dana, Scott; Annoni, Jennifer; ...

2018-04-13

Renewed interest in yaw control for wind turbine and power plants for wake redirection and load mitigation demands a clear understanding of the effects of running with skewed inflow. In this paper, we investigate the physics of yawed operations, building up the complexity from a simplified analytical treatment to more complex aeroelastic simulations. Results in terms of damage equivalent loads (DELs) and extreme loads under operating, misaligned conditions are compared to data collected from an instrumented, utility-scale wind turbine. The analysis shows that multiple factors are responsible for the DELs of the various components, and that airfoil aerodynamics, elastic characteristicsmore » of the rotor, and turbulence intensities are the primary drivers. Both fatigue and extreme loads are observed to have relatively complex trends with yaw offsets, which can change depending on the wind-speed regime. As a result, good agreement is found between predicted and measured trends for both fatigue and ultimate loads.« less

Assessment of Wind Turbine Component Loads Under Yaw-Offset Conditions

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

Damiani, Rick R.; Dana, Scott; Annoni, Jennifer

Renewed interest in yaw control for wind turbine and power plants for wake redirection and load mitigation demands a clear understanding of the effects of running with skewed inflow. In this paper, we investigate the physics of yawed operations, building up the complexity from a simplified analytical treatment to more complex aeroelastic simulations. Results in terms of damage equivalent loads (DELs) and extreme loads under operating, misaligned conditions are compared to data collected from an instrumented, utility-scale wind turbine. The analysis shows that multiple factors are responsible for the DELs of the various components, and that airfoil aerodynamics, elastic characteristicsmore » of the rotor, and turbulence intensities are the primary drivers. Both fatigue and extreme loads are observed to have relatively complex trends with yaw offsets, which can change depending on the wind-speed regime. As a result, good agreement is found between predicted and measured trends for both fatigue and ultimate loads.« less

Comparison of cryogenic low-pass filters.

PubMed

Thalmann, M; Pernau, H-F; Strunk, C; Scheer, E; Pietsch, T

2017-11-01

Low-temperature electronic transport measurements with high energy resolution require both effective low-pass filtering of high-frequency input noise and an optimized thermalization of the electronic system of the experiment. In recent years, elaborate filter designs have been developed for cryogenic low-level measurements, driven by the growing interest in fundamental quantum-physical phenomena at energy scales corresponding to temperatures in the few millikelvin regime. However, a single filter concept is often insufficient to thermalize the electronic system to the cryogenic bath and eliminate spurious high frequency noise. Moreover, the available concepts often provide inadequate filtering to operate at temperatures below 10 mK, which are routinely available now in dilution cryogenic systems. Herein we provide a comprehensive analysis of commonly used filter types, introduce a novel compact filter type based on ferrite compounds optimized for the frequency range above 20 GHz, and develop an improved filtering scheme providing adaptable broad-band low-pass characteristic for cryogenic low-level and quantum measurement applications at temperatures down to few millikelvin.

Comparison of cryogenic low-pass filters

NASA Astrophysics Data System (ADS)

Thalmann, M.; Pernau, H.-F.; Strunk, C.; Scheer, E.; Pietsch, T.

2017-11-01

Low-temperature electronic transport measurements with high energy resolution require both effective low-pass filtering of high-frequency input noise and an optimized thermalization of the electronic system of the experiment. In recent years, elaborate filter designs have been developed for cryogenic low-level measurements, driven by the growing interest in fundamental quantum-physical phenomena at energy scales corresponding to temperatures in the few millikelvin regime. However, a single filter concept is often insufficient to thermalize the electronic system to the cryogenic bath and eliminate spurious high frequency noise. Moreover, the available concepts often provide inadequate filtering to operate at temperatures below 10 mK, which are routinely available now in dilution cryogenic systems. Herein we provide a comprehensive analysis of commonly used filter types, introduce a novel compact filter type based on ferrite compounds optimized for the frequency range above 20 GHz, and develop an improved filtering scheme providing adaptable broad-band low-pass characteristic for cryogenic low-level and quantum measurement applications at temperatures down to few millikelvin.

Transient regime in second harmonic generation

NASA Astrophysics Data System (ADS)

Szeftel, Jacob; Sandeau, Laure; Sandeau, Nicolas; Delezoide, Camille; Khater, Antoine

2013-09-01

The time growth of the electromagnetic field at the fundamental and double frequencies is studied from the very onset of the second harmonic generation (SHG) process for a set of dipoles lacking a symmetry centre and exhibiting a nonresonant coupling with a classical electromagnetic field. This approach consists first of solving the Schrödinger equation by applying a generalised Rabi rotation to the Hamiltonian describing the light-dipole interaction. This rotation has been devised for the resulting Hamiltonian to show up time-independent for both components of the electromagnetic field at the fundamental frequency and the second harmonic one. Then an energy conservation argument, derived from the Poynting theorem, is introduced to work out an additional relationship between the electromagnetic field and its associated electric polarisation. Finally this analysis yields the full time behaviour of all physical quantities of interest. The calculated results reproduce accurately both the observed spatial oscillations of the SHG intensity (Maker's fringes) and its power law dependence on the intensity of the incoming light at the fundamental frequency.

Nonlinear optical properties and excited state dynamics of sandwich-type mixed (phthalocyaninato)(Schiff-base) triple-decker complexes: Effect of rare earth atom

NASA Astrophysics Data System (ADS)

Li, Zhongguo; Gao, Feng; Xiao, Zhengguo; Wu, Xingzhi; Zuo, Jinglin; Song, Yinglin

2018-07-01

The third-order nonlinear optical properties of two di-lanthanide (Ln = Tb and Dy) sandwich complexes with mixed phthalocyanine and Schiff-base ligands were studied using Z-scan technique at 532 nm with 20 ps and 4 ns pulses. Both complexes exhibit reverse saturable absorption and self-focusing effect in ps regime, while the second-order hyperpolarizability decreases from Dy to Tb. Interestingly, the Tb triple-decker complexes show larger nonlinear absorption than Dy complexes on ns timescale. The time-resolved pump-probe measurements demonstrate that the nonlinear optical response was caused by excited-state mechanism related to the five-level model, while the singlet state lifetime of Dy complexes is 3 times shorter than that of Tb complexes. Our results indicate the lanthanide ions play a critical role in the photo-physical properties of triple-decker phthalocyanine complexes for their application as optical limiting materials.

Quantifying the Pathway and Predicting Spontaneous Emulsification during Material Exchange in a Two Phase Liquid System.

PubMed

Spooner, Stephen; Rahnama, Alireza; Warnett, Jason M; Williams, Mark A; Li, Zushu; Sridhar, Seetharaman

2017-10-30

Kinetic restriction of a thermodynamically favourable equilibrium is a common theme in materials processing. The interfacial instability in systems where rate of material exchange is far greater than the mass transfer through respective bulk phases is of specific interest when tracking the transient interfacial area, a parameter integral to short processing times for productivity streamlining in all manufacturing where interfacial reaction occurs. This is even more pertinent in high-temperature systems for energy and cost savings. Here the quantified physical pathway of interfacial area change due to material exchange in liquid metal-molten oxide systems is presented. In addition the predicted growth regime and emulsification behaviour in relation to interfacial tension as modelled using phase-field methodology is shown. The observed in-situ emulsification behaviour links quantitatively the geometry of perturbations as a validation method for the development of simulating the phenomena. Thus a method is presented to both predict and engineer the formation of micro emulsions to a desired specification.

Physics in Context--A Means to Encourage Student Interest in Physics

ERIC Educational Resources Information Center

Waltner, Christine; Wiesner, Hartmut; Rachel, Alexander

2007-01-01

Physics instruction that is student oriented will generate a long-term individual interest and therefore a lifelong openness to science. Phenomena of nature are part of the fields of interest which provide context leading to greater student interest. In this paper we present the locomotion of fish and sperm in a way which can be used to teach in…

Exploration of quantum-memory-assisted entropic uncertainty relations in a noninertial frame

NASA Astrophysics Data System (ADS)

Wang, Dong; Ming, Fei; Huang, Ai-Jun; Sun, Wen-Yang; Shi, Jia-Dong; Ye, Liu

2017-05-01

The uncertainty principle offers a bound to show accuracy of the simultaneous measurement outcome for two incompatible observables. In this letter, we investigate quantum-memory-assisted entropic uncertainty relation (QMA-EUR) when the particle to be measured stays at an open system, and another particle is treated as quantum memory under a noninertial frame. In such a scenario, the collective influence of the unital and nonunital noise environment, and of the relativistic motion of the system, on the QMA-EUR is examined. By numerical analysis, we conclude that, firstly, the noises and the Unruh effect can both increase the uncertainty, due to the decoherence of the bipartite system induced by the noise or Unruh effect; secondly, the uncertainty is more affected by the noises than by the Unruh effect from the acceleration; thirdly, unital noises can reduce the uncertainty in long-time regime. We give a possible physical interpretation for those results: that the information of interest is redistributed among the bipartite, the noisy environment and the physically inaccessible region in the noninertial frame. Therefore, we claim that our observations provide an insight into dynamics of the entropic uncertainty in a noninertial frame, and might be important to quantum precision measurement under relativistic motion.

Tunneling spectra for electrons in the lowest Landau level

NASA Astrophysics Data System (ADS)

Burnell, F. J.; Simon, Steven H.

2010-03-01

The recently developed experimental technique of time dependent capacitance spectroscopy [1] allows for measurements of high-resolution tunneling spectra of 2DEGs in the quantum Hall regime, giving a detailed probe of the single particle spectral function (electron addition and subtraction spectra). These experiments show a number of interesting features including Landau level structure, exchange enhanced Zeeman energy, Coulomb gap physics, effects of fractional quantization, as well as several key features that remain to be explained. While there has been some prior theoretical work[2] towards explaining low energy Coulomb gap features of tunneling spectra found in much earlier tunneling experiments [3], the new experiments[1] have uncovered physics outside of the prior theoretical explanations. Building on a number of these prior theoretical works, we investigate theoretically the expected tunneling spectra for electrons in low Landau levels, including the effects of electron spin and coupling to collective modes. [1] O. E. Dial, R.C. Ashoori, L.N. Pfeiffer, and K.W. West, Nature 448, 176-179 (2007) ; O. E. Dial et al, unpublished. [2] I. Aleiner et al, Phys. Rev. Lett 74 3435; (1994) S. R. E. Yang and A. MacDonald PRL 70 4110 (1993); S. He, P.M. Platzman, and B. I. Halperin, PRL 71 777 (1993). [3] J. P. Eisenstein et al, Phy. Rev. Lett. 69, 3804 (1992).

Using White Dwarf Companions of Blue Stragglers to Constrain Mass Transfer Physics

NASA Astrophysics Data System (ADS)

Gosnell, Natalie M.; Leiner, Emily; Geller, Aaron M.; Knigge, Christian; Mathieu, Robert D.; Sills, Alison; Leigh, Nathan

2018-06-01

Complete membership studies of old open clusters reveal that 25% of the evolved stars follow pathways in stellar evolution that are impacted by binary evolution. Recent studies show that the majority of blue straggler stars, traditionally defined to be stars brighter and bluer than the corresponding main sequence turnoff, are formed through mass transfer from a giant star onto a main sequence companion, resulting in a white dwarf in a binary system with a blue straggler. We will present constraints on the histories and mass transfer efficiencies for two blue straggler-white dwarf binaries in open cluster NGC 188. The constraints are a result of measuring white dwarf cooling temperatures and surface gravities with HST COS far-ultraviolet spectroscopy. This information sets both the timeline for mass transfer and the stellar masses in the pre-mass transfer binary, allowing us to constrain aspects of the mass transfer physics. One system is formed through Case C mass transfer, leaving a CO-core white dwarf, and provides an interesting test case for mass transfer from an asymptotic giant branch star in an eccentric system. The other system formed through Case B mass transfer, leaving a He-core white dwarf, and challenges our current understanding of the expected regimes for stable mass transfer from red giant branch stars.

Transport processes in magnetically confined plasmas in the nonlinear regime.

PubMed

Sonnino, Giorgio

2006-06-01

A field theory approach to transport phenomena in magnetically confined plasmas is presented. The thermodynamic field theory (TFT), previously developed for treating the generic thermodynamic system out of equilibrium, is applied to plasmas physics. Transport phenomena are treated here as the effect of the field linking the thermodynamic forces with their conjugate flows combined with statistical mechanics. In particular, the Classical and the Pfirsch-Schluter regimes are analyzed by solving the thermodynamic field equations of the TFT in the weak-field approximation. We found that, the TFT does not correct the expressions of the ionic heat fluxes evaluated by the neoclassical theory in these two regimes. On the other hand, the fluxes of matter and electronic energy (heat flow) is further enhanced in the nonlinear Classical and Pfirsch-Schluter regimes. These results seem to be in line with the experimental observations. The complete set of the electronic and ionic transport equations in the nonlinear Banana regime, is also reported. A paper showing the comparison between our theoretic results and the experimental observations in the JET machine is currently in preparation.

An intervention study to enhance girls' interest, self-concept, and achievement in physics classes

NASA Astrophysics Data System (ADS)

Häussler, Peter; Hoffmann, Lore

2002-11-01

Many interest studies have shown the decline of students' interest in physics during secondary education, particularly among girls. Research into physics-related interests of students suggests applying different measures to reduce or reverse that trend such as: (a) suggesting curricular changes that do justice to the specific interests and experiences of girls, (b) improving the ability of teachers to support girls in the development of a positive physics related self-concept, and (c) changing to an organizational setting that gives girls a better chance to improve their self-concept about physics. The purpose of this study was to examine whether these hypothetically effective measures lead to an improvement of the situation for girls when implemented in the physics classroom. The intervention took a whole school year of some 60 one-hour lessons and comprised 12 experimental and 7 control classes of seventh graders (age about 13). Their immediate and long-term achievements, as well as their change of interest in physics, their subjectively experienced competence, and their physics-related self-concept were assessed by written tests at various stages of the intervention. The intervention proved successful and significantly improved most of these indicators for girls (and boys) in the experimental group.

Plasma Physics Challenges of MM-to-THz and High Power Microwave Generation

NASA Astrophysics Data System (ADS)

Booske, John

2007-11-01

Homeland security and military defense technology considerations have stimulated intense interest in mobile, high power sources of millimeter-wave to terahertz regime electromagnetic radiation, from 0.1 to 10 THz. While sources at the low frequency end, i.e., the gyrotron, have been deployed or are being tested for diverse applications such as WARLOC radar and active denial systems, the challenges for higher frequency sources have yet to be completely met for applications including noninvasive sensing of concealed weapons and dangerous agents, high-data-rate communications, and high resolution spectroscopy and atmospheric sensing. The compact size requirements for many of these high frequency sources requires miniscule, micro-fabricated slow wave circuits with high rf ohmic losses. This necessitates electron beams with not only very small transverse dimensions but also very high current density for adequate gain. Thus, the emerging family of mm-to-THz e-beam-driven vacuum electronics devices share many of the same plasma physics challenges that currently confront ``classic'' high power microwave (HPM) generators [1] including bright electron sources, intense beam transport, energetic electron interaction with surfaces and rf air breakdown at output windows. Multidimensional theoretical and computational models are especially important for understanding and addressing these challenges. The contemporary plasma physics issues, recent achievements, as well as the opportunities and outlook on THz and HPM will be addressed. [1] R.J. Barker, J.H. Booske, N.C. Luhmann, and G.S. Nusinovich, Modern Microwave and Millimeter-Wave Power Electronics (IEEE/Wiley, 2005).

From Finite Time to Finite Physical Dimensions Thermodynamics: The Carnot Engine and Onsager's Relations Revisited

NASA Astrophysics Data System (ADS)

Feidt, Michel; Costea, Monica

2018-04-01

Many works have been devoted to finite time thermodynamics since the Curzon and Ahlborn [1] contribution, which is generally considered as its origin. Nevertheless, previous works in this domain have been revealed [2], [3], and recently, results of the attempt to correlate Finite Time Thermodynamics with Linear Irreversible Thermodynamics according to Onsager's theory were reported [4]. The aim of the present paper is to extend and improve the approach relative to thermodynamic optimization of generic objective functions of a Carnot engine with linear response regime presented in [4]. The case study of the Carnot engine is revisited within the steady state hypothesis, when non-adiabaticity of the system is considered, and heat loss is accounted for by an overall heat leak between the engine heat reservoirs. The optimization is focused on the main objective functions connected to engineering conditions, namely maximum efficiency or power output, except the one relative to entropy that is more fundamental. Results given in reference [4] relative to the maximum power output and minimum entropy production as objective function are reconsidered and clarified, and the change from finite time to finite physical dimension was shown to be done by the heat flow rate at the source. Our modeling has led to new results of the Carnot engine optimization and proved that the primary interest for an engineer is mainly connected to what we called Finite Physical Dimensions Optimal Thermodynamics.

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

Oliveira, Gilson F. de, E-mail: gilson@otica.ufpb.br; Lorenzo, Orlando di; Chevrollier, Martine

We study the statistics of the amplitude of the synchronization error in chaotic electronic circuits coupled through linear feedback. Depending on the coupling strength, our system exhibits three qualitatively different regimes of synchronization: weak coupling yields independent oscillations; moderate to strong coupling produces a regime of intermittent synchronization known as attractor bubbling; and stronger coupling produces complete synchronization. In the regime of moderate coupling, the probability distribution for the sizes of desynchronization events follows a power law, with an exponent that can be adjusted by changing the coupling strength. Such power-law distributions are interesting, as they appear in many complexmore » systems. However, most of the systems with such a behavior have a fixed value for the exponent of the power law, while here we present an example of a system where the exponent of the power law is easily tuned in real time.« less

Unjamming a granular hopper by vibration

NASA Astrophysics Data System (ADS)

Janda, A.; Maza, D.; Garcimartín, A.; Kolb, E.; Lanuza, J.; Clément, E.

2009-07-01

We present an experimental study of the outflow of a hopper continuously vibrated by a piezoelectric device. Outpouring of grains can be achieved for apertures much below the usual jamming limit observed for non-vibrated hoppers. Granular flow persists down to the physical limit of one grain diameter, a limit reached for a finite vibration amplitude. For the smaller orifices, we observe an intermittent regime characterized by alternated periods of flow and blockage. Vibrations do not significantly modify the flow rates both in the continuous and the intermittent regime. The analysis of the statistical features of the flowing regime shows that the flow time significantly increases with the vibration amplitude. However, at low vibration amplitude and small orifice sizes, the jamming time distribution displays an anomalous statistics.

Effect of Finite Computational Domain on Turbulence Scaling Law in Both Physical and Spectral Spaces

NASA Technical Reports Server (NTRS)

Hou, Thomas Y.; Wu, Xiao-Hui; Chen, Shiyi; Zhou, Ye

1998-01-01

The well-known translation between the power law of energy spectrum and that of the correlation function or the second order structure function has been widely used in analyzing random data. Here, we show that the translation is valid only in proper scaling regimes. The regimes of valid translation are different for the correlation function and the structure function. Indeed, they do not overlap. Furthermore, in practice, the power laws exist only for a finite range of scales. We show that this finite range makes the translation inexact even in the proper scaling regime. The error depends on the scaling exponent. The current findings are applicable to data analysis in fluid turbulence and other stochastic systems.

Resolving boosted jets with XCone

DOE PAGES

Thaler, Jesse; Wilkason, Thomas F.

2015-12-01

We show how the recently proposed XCone jet algorithm smoothly interpolates between resolved and boosted kinematics. When using standard jet algorithms to reconstruct the decays of hadronic resonances like top quarks and Higgs bosons, one typically needs separate analysis strategies to handle the resolved regime of well-separated jets and the boosted regime of fat jets with substructure. XCone, by contrast, is an exclusive cone jet algorithm that always returns a fixed number of jets, so jet regions remain resolved even when (sub)jets are overlapping in the boosted regime. In this paper, we perform three LHC case studies $-$ dijet resonances,more » Higgs decays to bottom quarks, and all-hadronic top pairs$-$ that demonstrate the physics applications of XCone over a wide kinematic range.« less

Physics in France Circa 1850-1914; its National Organisation, Characteristics and Content.

NASA Astrophysics Data System (ADS)

Davis, John L.

1990-01-01

Available from UMI in association with The British Library. The thesis begins with an examination of what was understood by the term 'physics' in France circa. 1850. The development of the centralised state educational system and the physics research which was produced within this system in Paris and the provinces, is then considered. Although all the relevant institutions, where some form of physics or physical science was taught, have been examined, the Ecole Polytechnique, and the Ecole Normale Superieure have a particular importance in the early period of this study. As time passed and as a result of reforms put in hand by the republican regime which came out of the defeat of the Franco -Prussian war of 1870-71, the universite system grew in importance, while the role of the Polytechnique declined. The Ecole Normale, the Paris Faculty and the provincial faculties form part of the universite system and participated in its growth. A knowledge of the objectives of the physics courses in these institutions helps in the understanding of the characteristics of physics in France in this period. The central objective was, largely, to produce either science teachers, or (in the case of the Polytechnique), a type of elite 'technocrat', for the state, i.e. men who could communicate clearly, or technically utilise knowledge, which was already established on a firm theoretical basis. This is not to say that research had no place in the institutions of higher education, on the contrary, and this research, carried out by both teachers and students, is examined here to try to relate its form and content to the particular institution in which it was carried out. The role of national organisations like the Societe de physique and the Association Francaise pour l'avancement des sciences in the development of physics in France is also considered, as is the role of the Academie des sciences. The predominantly experimental nature of physics research in France is related to the interests of these organisations, to the requirements of the licence programme, and to the increasingly fierce competition for membership of the physics section of the Academie.

Physical activity, psychiatric distress, and interest in exercise group participation among individuals seeking methadone maintenance treatment with and without chronic pain.

PubMed

Beitel, Mark; Stults-Kolehmainen, Matthew; Cutter, Christopher J; Schottenfeld, Richard S; Eggert, Kathy; Madden, Lynn M; Kerns, Robert D; Liong, Christopher; Ginn, Joel; Barry, Declan T

2016-03-01

Physical activity may improve chronic pain, anxiety, and depression, which are prevalent among patients in methadone maintenance treatment (MMT), but relatively little is known about the physical activity levels or interest in exercise of patients in MMT. We used a brief self-report instrument to assess physical activity levels, chronic pain, psychiatric distress, and interest in exercise group participation among 303 adults seeking MMT. Most (73%) reported no moderate or vigorous intensity physical activity in the past week; 27% met recommended physical activity levels, and 24% reported interest in exercise group participation. Participants with (compared to those without) chronic pain had higher levels of psychiatric distress and were less likely to meet recommended levels of physical activity (p < .05), but did not differ significantly in their interest in participating in an exercise group. Participants who met recommended levels of physical activity in the past week were more likely to be men and had lower levels of depression than others (p < .05). Low levels of physical activity and low interest in exercise group participation among patients entering MMT point to the need for and likely challenges of implementing exercise interventions in MMT. © American Academy of Addiction Psychiatry.

ZnO thin film as MSG for sensitive biosensor

NASA Astrophysics Data System (ADS)

Iftimie, N.; Savin, A.; Steigmann, R.; Faktorova, D.; Salaoru, I.

2016-08-01

In this paper, we investigate the cholesterol sensors consisting of a mixture of cholesterol oxidase (ChOx) and zinc oxide (ZnO) nanoparticles were grown on ITO/glass substrates by vacuum thermal evaporation method and their sensing characteristics are examined in air. Also, the interest in surface waves appeared due to evanescent waves in the metallic strip grating in sub-wavelength regime. Before testing the transducer with metamaterials lens in the sub-wavelength regime, a simulation of the evanescent wave's formation has been performed at the edge of Ag strips, with thicknesses in the range of micrometers.

Electrostatic bending response of a charged helix

NASA Astrophysics Data System (ADS)

Zampetaki, A. V.; Stockhofe, J.; Schmelcher, P.

2018-04-01

We explore the electrostatic bending response of a chain of charged particles confined on a finite helical filament. We analyze how the energy difference Δ E between the bent and the unbent helical chain scales with the length of the helical segment and the radius of curvature and identify features that are not captured by the standard notion of the bending rigidity, normally used as a measure of bending tendency in the linear response regime. Using Δ E to characterize the bending response of the helical chain we identify two regimes with qualitatively different bending behaviors for the ground state configuration: the regime of small and the regime of large radius-to-pitch ratio, respectively. Within the former regime, Δ E changes smoothly with the variation of the system parameters. Of particular interest are its oscillations with the number of charged particles encountered for commensurate fillings which yield length-dependent oscillations in the preferred bending direction of the helical chain. We show that the origin of these oscillations is the nonuniformity of the charge distribution caused by the long-range character of the Coulomb interactions and the finite length of the helix. In the second regime of large values of the radius-to-pitch ratio, sudden changes in the ground state structure of the charges occur as the system parameters vary, leading to complex and discontinuous variations in the ground state bending response Δ E .

Microbial ecology in a future climate: effects of temperature and moisture on microbial communities of two boreal fens.

PubMed

Peltoniemi, Krista; Laiho, Raija; Juottonen, Heli; Kiikkilä, Oili; Mäkiranta, Päivi; Minkkinen, Kari; Pennanen, Taina; Penttilä, Timo; Sarjala, Tytti; Tuittila, Eeva-Stiina; Tuomivirta, Tero; Fritze, Hannu

2015-07-01

Impacts of warming with open-top chambers on microbial communities in wet conditions and in conditions resulting from moderate water-level drawdown (WLD) were studied across 0-50 cm depth in northern and southern boreal sedge fens. Warming alone decreased microbial biomass especially in the northern fen. Impact of warming on microbial PLFA and fungal ITS composition was more obvious in the northern fen and linked to moisture regime and sample depth. Fungal-specific PLFA increased in the surface peat in the drier regime and decreased in layers below 10 cm in the wet regime after warming. OTUs representing Tomentella and Lactarius were observed in drier regime and Mortierella in wet regime after warming in the northern fen. The ectomycorrhizal fungi responded only to WLD. Interestingly, warming together with WLD decreased archaeal 16S rRNA copy numbers in general, and fungal ITS copy numbers in the northern fen. Expectedly, many results indicated that microbial response on warming may be linked to the moisture regime. Results indicated that microbial community in the northern fen representing Arctic soils would be more sensitive to environmental changes. The response to future climate change clearly may vary even within a habitat type, exemplified here by boreal sedge fen. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

The Relationship of Freshmen's Physics Achievement and Their Related Affective Characteristics

ERIC Educational Resources Information Center

Gungor, Almer (Abak); Eryilmaz, Ali; Fakioglu, Turgut

2007-01-01

The purpose of this study was to determine the best-fitting structural equation model between the freshmen's physics achievement and selected affective characteristics related to physics. These characteristics are students' situational interest in physics, personal interest in physics, aspiring extra activities related to physics, importance of…

Approximate solutions to Mathieu's equation

NASA Astrophysics Data System (ADS)

Wilkinson, Samuel A.; Vogt, Nicolas; Golubev, Dmitry S.; Cole, Jared H.

2018-06-01

Mathieu's equation has many applications throughout theoretical physics. It is especially important to the theory of Josephson junctions, where it is equivalent to Schrödinger's equation. Mathieu's equation can be easily solved numerically, however there exists no closed-form analytic solution. Here we collect various approximations which appear throughout the physics and mathematics literature and examine their accuracy and regimes of applicability. Particular attention is paid to quantities relevant to the physics of Josephson junctions, but the arguments and notation are kept general so as to be of use to the broader physics community.

Ocean Carbon States: Data Mining in Observations and Numerical Simulations Results

NASA Astrophysics Data System (ADS)

Latto, R.; Romanou, A.

2017-12-01

Advanced data mining techniques are rapidly becoming widely used in Climate and Earth Sciences with the purpose of extracting new meaningful information from increasingly larger and more complex datasets. This is particularly important in studies of the global carbon cycle, where any lack of understanding of its combined physical and biogeochemical drivers is detrimental to our ability to accurately describe, understand, and predict CO2 concentrations and their changes in the major carbon reservoirs. The analysis presented here evaluates the use of cluster analysis as a means of identifying and comparing spatial and temporal patterns extracted from observational and model datasets. As the observational data is organized into various regimes, which we will call "ocean carbon states", we gain insight into the physical and/or biogeochemical processes controlling the ocean carbon cycle as well as how well these processes are simulated by a state-of-the-art climate model. We find that cluster analysis effectively produces realistic, dynamic regimes that can be associated with specific processes at different temporal scales for both observations and the model. In addition, we show how these regimes can be used to illustrate and characterize the model biases in the model air-sea flux of CO2. These biases are attributed to biases in salinity, sea surface temperature, wind speed, and nitrate, which are then used to identify the physical processes that are inaccurately reproduced by the model. In this presentation, we provide a proof-of-concept application using simple datasets, and we expand to more complex ones, using several physical and biogeochemical variable pairs, thus providing considerable insight into the mechanisms and phases of the ocean carbon cycle over different temporal and spatial scales.

Characterizing the physical-basis of orographic rainfall retrieval errors due to terrain artifacts on GPM-DPR reflectivity profiles

NASA Astrophysics Data System (ADS)

Arulraj, M.; Barros, A. P.

2017-12-01

GPM-DPR reflectivity profiles in mountainous regions are severely handicapped by low level ground-clutter artifacts which have different error characteristics depending on landform (upwind slopes of high mountains versus complex topography in middle-mountains) and precipitation regime. These artifacts result in high detection and estimation errors especially in mid-latitude and tropical mountain regions where low-level light precipitation and complex multi-layer clouds interact with incoming storms. Here, we present results assessment studies in the Southern Appalachian Mountains (SAM) and preliminary results over the eastern slopes of the Andes using ground-based observations from the long-term hydrometeorological networks and model studies toward developing a physically-based framework to systematically identify and attribute measurement errors. Specifically, the focus is on events when GPM-DPR Ka- and Ku- Band precipitation radar misses low-level precipitation with vertical altitude less than 2 km AGL (above ground level). For this purpose, ground-based MRR and Parsivel disdrometer observations near the surface are compared with the reflectivity profiles observed by the GPM-DPR overpasses, the raindrop-size spectra are used to classify the precipitation regime associated with different classes of detection and estimation errors. This information will be used along with a coupled rainfall dynamics and radar simulator model to 1) merge the low-level GPM-DPR measured reflectivity with the MRR reflectivities optimally under strict physically-based constraints and 2) build a library of reflectivity profile corrections. Finally, preliminary 4D analysis of the organization of reflectivity correction modes, microphysical regimes, topography and storm environment will be presented toward developing a general physically-based error model.

A paradigm for modeling and computation of gas dynamics

NASA Astrophysics Data System (ADS)

Xu, Kun; Liu, Chang

2017-02-01

In the continuum flow regime, the Navier-Stokes (NS) equations are usually used for the description of gas dynamics. On the other hand, the Boltzmann equation is applied for the rarefied flow. These two equations are based on distinguishable modeling scales for flow physics. Fortunately, due to the scale separation, i.e., the hydrodynamic and kinetic ones, both the Navier-Stokes equations and the Boltzmann equation are applicable in their respective domains. However, in real science and engineering applications, they may not have such a distinctive scale separation. For example, around a hypersonic flying vehicle, the flow physics at different regions may correspond to different regimes, where the local Knudsen number can be changed significantly in several orders of magnitude. With a variation of flow physics, theoretically a continuous governing equation from the kinetic Boltzmann modeling to the hydrodynamic Navier-Stokes dynamics should be used for its efficient description. However, due to the difficulties of a direct modeling of flow physics in the scale between the kinetic and hydrodynamic ones, there is basically no reliable theory or valid governing equations to cover the whole transition regime, except resolving flow physics always down to the mean free path scale, such as the direct Boltzmann solver and the Direct Simulation Monte Carlo (DSMC) method. In fact, it is an unresolved problem about the exact scale for the validity of the NS equations, especially in the small Reynolds number cases. The computational fluid dynamics (CFD) is usually based on the numerical solution of partial differential equations (PDEs), and it targets on the recovering of the exact solution of the PDEs as mesh size and time step converging to zero. This methodology can be hardly applied to solve the multiple scale problem efficiently because there is no such a complete PDE for flow physics through a continuous variation of scales. For the non-equilibrium flow study, the direct modeling methods, such as DSMC, particle in cell, and smooth particle hydrodynamics, play a dominant role to incorporate the flow physics into the algorithm construction directly. It is fully legitimate to combine the modeling and computation together without going through the process of constructing PDEs. In other words, the CFD research is not only to obtain the numerical solution of governing equations but to model flow dynamics as well. This methodology leads to the unified gas-kinetic scheme (UGKS) for flow simulation in all flow regimes. Based on UGKS, the boundary for the validation of the Navier-Stokes equations can be quantitatively evaluated. The combination of modeling and computation provides a paradigm for the description of multiscale transport process.

Interest of Grade Ten Students toward Physics among Other Science Subjects, Case of Wolaita Soddo Town Governmental Secondary Schools, Ethiopia

ERIC Educational Resources Information Center

Hamelo, Shewangzaw

2016-01-01

This paper has proposed to investigate the interest in students towards physics among other science subjects. The investigation was carried out with 490 samples of grade ten students in Wolaita Soddo town governmental schools. Thus, overall result indicates that the interest in students towards physics is low and students hate to learn physics in…

Basis set study of classical rotor lattice dynamics.

PubMed

Witkoskie, James B; Wu, Jianlan; Cao, Jianshu

2004-03-22

The reorientational relaxation of molecular systems is important in many phenomenon and applications. In this paper, we explore the reorientational relaxation of a model Brownian rotor lattice system with short range interactions in both the high and low temperature regimes. In this study, we use a basis set expansion to capture collective motions of the system. The single particle basis set is used in the high temperature regime, while the spin wave basis is used in the low temperature regime. The equations of motion derived in this approach are analogous to the generalized Langevin equation, but the equations render flexibility by allowing nonequilibrium initial conditions. This calculation shows that the choice of projection operators in the generalized Langevin equation (GLE) approach corresponds to defining a specific inner-product space, and this inner-product space should be chosen to reveal the important physics of the problem. The basis set approach corresponds to an inner-product and projection operator that maintain the orthogonality of the spherical harmonics and provide a convenient platform for analyzing GLE expansions. The results compare favorably with numerical simulations, and the formalism is easily extended to more complex systems. (c) 2004 American Institute of Physics

Regimes of Diurnal Variation of Summer Rainfall over Subtropical East Asia

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

Yuan W.; Lin W.; Yu, R.

2012-05-01

Using hourly rain gauge records and Tropical Rainfall Measuring Mission 3B42 from 1998 to 2006, the authors present an analysis of the diurnal characteristics of summer rainfall over subtropical East Asia. The study shows that there are four different regimes of distinct diurnal variation of rainfall in both the rain gauge and the satellite data. They are located over the Tibetan Plateau with late-afternoon and midnight peaks, in the western China plain with midnight to early-morning peaks, in the eastern China plain with double peaks in late afternoon and early morning, and over the East China Sea with an early-morningmore » peak. No propagation of diurnal phases is found from the land to the ocean across the coastlines. The different diurnal regimes are highly correlated with the inhomogeneous underlying surface, such as the plateau, plain, and ocean, with physical mechanisms consistent with the large-scale 'mountain-valley' and 'land-sea' breezes and convective instability. These diurnal characteristics over subtropical East Asia can be used as diagnostic metrics to evaluate the physical parameterization and hydrological cycle of climate models over East Asia.« less

Foundational Principles for Large-Scale Inference: Illustrations Through Correlation Mining.

PubMed

Hero, Alfred O; Rajaratnam, Bala

2016-01-01

When can reliable inference be drawn in fue "Big Data" context? This paper presents a framework for answering this fundamental question in the context of correlation mining, wifu implications for general large scale inference. In large scale data applications like genomics, connectomics, and eco-informatics fue dataset is often variable-rich but sample-starved: a regime where the number n of acquired samples (statistical replicates) is far fewer than fue number p of observed variables (genes, neurons, voxels, or chemical constituents). Much of recent work has focused on understanding the computational complexity of proposed methods for "Big Data". Sample complexity however has received relatively less attention, especially in the setting when the sample size n is fixed, and the dimension p grows without bound. To address fuis gap, we develop a unified statistical framework that explicitly quantifies the sample complexity of various inferential tasks. Sampling regimes can be divided into several categories: 1) the classical asymptotic regime where fue variable dimension is fixed and fue sample size goes to infinity; 2) the mixed asymptotic regime where both variable dimension and sample size go to infinity at comparable rates; 3) the purely high dimensional asymptotic regime where the variable dimension goes to infinity and the sample size is fixed. Each regime has its niche but only the latter regime applies to exa cale data dimension. We illustrate this high dimensional framework for the problem of correlation mining, where it is the matrix of pairwise and partial correlations among the variables fua t are of interest. Correlation mining arises in numerous applications and subsumes the regression context as a special case. we demonstrate various regimes of correlation mining based on the unifying perspective of high dimensional learning rates and sample complexity for different structured covariance models and different inference tasks.

A Stand-Alone Interactive Physics Showcase

ERIC Educational Resources Information Center

Pfaff, Daniel; Hagelgans, Anja; Weidemuller, Matthias; Bretzer, Klaus

2012-01-01

We present a showcase with interactive exhibits of basic physical experiments that constitutes a complementary method for teaching physics and interesting students in physical phenomena. Our interactive physics showcase, shown in Fig. 1, stimulates interest for science by letting the students experience, firsthand, surprising phenomena and…

Generalized scaling of seasonal thermal stratification in lakes

NASA Astrophysics Data System (ADS)

Shatwell, T.; Kirillin, G.

2016-12-01

The mixing regime is fundamental to the biogeochemisty and ecology of lakes because it determines the vertical transport of matter such as gases, nutrients, and organic material. Whereas shallow lakes are usually polymictic and regularly mix to the bottom, deep lakes tend to stratify seasonally, separating surface water from deep sediments and deep water from the atmosphere. Although empirical relationships exist to predict the mixing regime, a physically based, quantitative criterion is lacking. Here we review our recent research on thermal stratification in lakes at the transition between polymictic and stratified regimes. Using the mechanistic balance between potential and kinetic energy in terms of the Richardson number, we derive a generalized physical scaling for seasonal stratification in a closed lake basin. The scaling parameter is the critical mean basin depth that delineates polymictic and seasonally stratified lakes based on lake water transparency (Secchi depth), lake length, and an annual mean estimate for the Monin-Obukhov length. We validated the scaling on available data of 374 global lakes using logistic regression and found it to perform better than other criteria including a conventional open basin scaling or a simple depth threshold. The scaling has potential applications in estimating large scale greenhouse gas fluxes from lakes because the required inputs, like water transparency and basin morphology, can be acquired using the latest remote sensing technologies. The generalized scaling is universal for freshwater lakes and allows the seasonal mixing regime to be estimated without numerically solving the heat transport equations.

Interpreting the spatio-temporal patterns of sea turtle strandings: Going with the flow

USGS Publications Warehouse

Hart, K.M.; Mooreside, P.; Crowder, L.B.

2006-01-01

Knowledge of the spatial and temporal distribution of specific mortality sources is crucial for management of species that are vulnerable to human interactions. Beachcast carcasses represent an unknown fraction of at-sea mortalities. While a variety of physical (e.g., water temperature) and biological (e.g., decomposition) factors as well as the distribution of animals and their mortality sources likely affect the probability of carcass stranding, physical oceanography plays a major role in where and when carcasses strand. Here, we evaluate the influence of nearshore physical oceanographic and wind regimes on sea turtle strandings to decipher seasonal trends and make qualitative predictions about stranding patterns along oceanfront beaches. We use results from oceanic drift-bottle experiments to check our predictions and provide an upper limit on stranding proportions. We compare predicted current regimes from a 3D physical oceanographic model to spatial and temporal locations of both sea turtle carcass strandings and drift bottle landfalls. Drift bottle return rates suggest an upper limit for the proportion of sea turtle carcasses that strand (about 20%). In the South Atlantic Bight, seasonal development of along-shelf flow coincides with increased numbers of strandings of both turtles and drift bottles in late spring and early summer. The model also predicts net offshore flow of surface waters during winter - the season with the fewest relative strandings. The drift bottle data provide a reasonable upper bound on how likely carcasses are to reach land from points offshore and bound the general timeframe for stranding post-mortem (< two weeks). Our findings suggest that marine turtle strandings follow a seasonal regime predictable from physical oceanography and mimicked by drift bottle experiments. Managers can use these findings to reevaluate incidental strandings limits and fishery takes for both nearshore and offshore mortality sources. ?? 2005 Elsevier Ltd. All rights reserved.

High Harmonic Fast Wave Damping on an Ion Beam: NSTX and DIII-D Regimes Compared

NASA Astrophysics Data System (ADS)

Pinsker, R. I.; Choi, C. C.; Petty, C. C.; Porkolab, M.; Wilson, J. R.; Murakami, M.; Harvey, R. W.

2004-11-01

Both NSTX and DIII-D use the combination of fast Alfven waves (FW) and neutral beam injection (NBI) for central electron heating and current drive. Damping of the fast wave on the beam ions at moderate to high harmonics (4th--20th) of the beam ion cyclotron frequency represents a loss process. In DIII-D current drive experiments at low density in which 4th and 8th harmonics were compared, damping at the 8th harmonic damping was much weaker than at the 4th [1]. However, recent simulations have predicted that in higher density and higher beam power regimes (of interest to the Advanced Tokamak program) the beam ion absorption will transition to the unmagnetized ion regime, where the damping is significant and essentially independent of harmonic number. In the present work, the transition from magnetized to unmagnetized ion regimes for the NSTX and DIII-D HHFW experiments is studied theoretically, with a combination of simple semi-analytic models and numerical models. \\vspace0.25 em [1] C.C. Petty, et al., Plasma Phys. and Contr. Fusion 43, 1747 (2001).

Large Amplitude Oscillatory Shear (LAOS) of Acrylic Emulsion-Based Pressure Sensitive Adhesives (PSAs)

NASA Astrophysics Data System (ADS)

Zhang, Sipei; Nakatani, Alan; Griffith, William

Large Amplitude Oscillatory Shear (LAOS) testing has recently taken on renewed interest in the rheological community. It is a very useful tool to probe the viscoelastic response of materials in the non-linear regime. Much of the discussion on polymers in the LAOS field has focused on melts in or near the terminal flow regime. Here we present a LAOS study conducted on a commercial rheometer for acrylic emulsion-based pressure sensitive adhesive (PSA) films in the plateau regime. The films behaved qualitatively similar over an oscillation frequency range of 0.5-5 rad/s. From Fourier transform analysis, the fifth or even the seventh order harmonic could be observed at large applied strains. From stress decomposition analysis or Lissajous curves, inter-cycle elastic softening, or type I behavior, was observed for all films as the strain increases, while intra-cycle strain hardening occurred at strains in the LAOS regime. Overall, as acid content increases, it was found that the trend in elasticity under large applied strains agreed very well with the trend in cohesive strength of the films.

Direct numerical simulation of vacillation in convection induced by centrifugal buoyancy

NASA Astrophysics Data System (ADS)

Pitz, Diogo B.; Marxen, Olaf; Chew, John W.

2017-11-01

Flows induced by centrifugal buoyancy occur in industrial systems, such as in the compressor cavities of gas turbines, as well as in flows of geophysical interest. In this numerical study we use direct numerical simulation (DNS) to investigate the transition between the steady waves regime, which is characterized by great regularity, to the vacillation regime, which is critical to understand transition to the fully turbulent regime. From previous work it is known that the onset of convection occurs in the form of pairs of nearly-circular rolls which span the entire axial length of the cavity, with small deviations near the parallel, no-slip end walls. When non-linearity sets in triadic interactions occur and, depending on the value of the centrifugal Rayleigh number, the flow is dominated by either a single mode and its harmonics or by broadband effects if turbulence develops. In this study we increase the centrifugal Rayleigh number progressively and investigate mode interactions during the vacillation regime which eventually lead to chaotic motion. Diogo B. Pitz acknowledges the financial support from the Capes foundation through the Science without Borders program.

Drop coalescence and liquid flow in a single Plateau border

NASA Astrophysics Data System (ADS)

Cohen, Alexandre; Fraysse, Nathalie; Raufaste, Christophe

2015-05-01

We report a comprehensive study of the flow of liquid triggered by injecting a droplet into a liquid foam microchannel, also called a Plateau border. This drop-injected experiment reveals an intricate dynamics for the liquid redistribution, with two contrasting regimes observed, ruled either by inertia or viscosity. We devoted a previous study [A. Cohen et al., Phys. Rev. Lett. 112, 218303 (2014), 10.1103/PhysRevLett.112.218303] to the inertial imbibition regime, unexpected at such small length scales. Here we report other features of interest of the drop-injected experiment, related to the coalescence of the droplet with the liquid microchannel, to both the inertial and viscous regimes, and to the occurrence of liquid flow through the soap films as well as effects of the interfacial rheology. The transition between the two regimes is investigated and qualitatively accounted for. The relevance of our results to liquid foam drainage is tackled by considering the flow of liquid at the nodes of the network of interconnected microchannels. Extensions of our study to liquid foams are discussed.

Ensemble average theory of gravity

NASA Astrophysics Data System (ADS)

Khosravi, Nima

2016-12-01

We put forward the idea that all the theoretically consistent models of gravity have contributions to the observed gravity interaction. In this formulation, each model comes with its own Euclidean path-integral weight where general relativity (GR) has automatically the maximum weight in high-curvature regions. We employ this idea in the framework of Lovelock models and show that in four dimensions the result is a specific form of the f (R ,G ) model. This specific f (R ,G ) satisfies the stability conditions and possesses self-accelerating solutions. Our model is consistent with the local tests of gravity since its behavior is the same as in GR for the high-curvature regime. In the low-curvature regime the gravitational force is weaker than in GR, which can be interpreted as the existence of a repulsive fifth force for very large scales. Interestingly, there is an intermediate-curvature regime where the gravitational force is stronger in our model compared to GR. The different behavior of our model in comparison with GR in both low- and intermediate-curvature regimes makes it observationally distinguishable from Λ CDM .

Physical habitat simulation system reference manual: version II

USGS Publications Warehouse

Milhous, Robert T.; Updike, Marlys A.; Schneider, Diane M.

1989-01-01

There are four major components of a stream system that determine the productivity of the fishery (Karr and Dudley 1978). These are: (1) flow regime, (2) physical habitat structure (channel form, substrate distribution, and riparian vegetation), (3) water quality (including temperature), and (4) energy inputs from the watershed (sediments, nutrients, and organic matter). The complex interaction of these components determines the primary production, secondary production, and fish population of the stream reach. The basic components and interactions needed to simulate fish populations as a function of management alternatives are illustrated in Figure I.1. The assessment process utilizes a hierarchical and modular approach combined with computer simulation techniques. The modular components represent the "building blocks" for the simulation. The quality of the physical habitat is a function of flow and, therefore, varies in quality and quantity over the range of the flow regime. The conceptual framework of the Incremental Methodology and guidelines for its application are described in "A Guide to Stream Habitat Analysis Using the Instream Flow Incremental Methodology" (Bovee 1982). Simulation of physical habitat is accomplished using the physical structure of the stream and streamflow. The modification of physical habitat by temperature and water quality is analyzed separately from physical habitat simulation. Temperature in a stream varies with the seasons, local meteorological conditions, stream network configuration, and the flow regime; thus, the temperature influences on habitat must be analysed on a stream system basis. Water quality under natural conditions is strongly influenced by climate and the geological materials, with the result that there is considerable natural variation in water quality. When we add the activities of man, the possible range of water quality possibilities becomes rather large. Consequently, water quality must also be analysed on a stream system basis. Such analysis is outside the scope of this manual, which concentrates on simulation of physical habitat based on depth, velocity, and a channel index. The results form PHABSIM can be used alone or by using a series of habitat time series programs that have been developed to generate monthly or daily habitat time series from the Weighted Usable Area versus streamflow table resulting from the habitat simulation programs and streamflow time series data. Monthly and daily streamflow time series may be obtained from USGS gages near the study site or as the output of river system management models.

Predicting streamflow regime metrics for ungauged streamsin Colorado, Washington, and Oregon

NASA Astrophysics Data System (ADS)

Sanborn, Stephen C.; Bledsoe, Brian P.

2006-06-01

Streamflow prediction in ungauged basins provides essential information for water resources planning and management and ecohydrological studies yet remains a fundamental challenge to the hydrological sciences. A methodology is presented for stratifying streamflow regimes of gauged locations, classifying the regimes of ungauged streams, and developing models for predicting a suite of ecologically pertinent streamflow metrics for these streams. Eighty-four streamflow metrics characterizing various flow regime attributes were computed along with physical and climatic drainage basin characteristics for 150 streams with little or no streamflow modification in Colorado, Washington, and Oregon. The diverse hydroclimatology of the study area necessitates flow regime stratification and geographically independent clusters were identified and used to develop separate predictive models for each flow regime type. Multiple regression models for flow magnitude, timing, and rate of change metrics were quite accurate with many adjusted R2 values exceeding 0.80, while models describing streamflow variability did not perform as well. Separate stratification schemes for high, low, and average flows did not considerably improve models for metrics describing those particular aspects of the regime over a scheme based on the entire flow regime. Models for streams identified as 'snowmelt' type were improved if sites in Colorado and the Pacific Northwest were separated to better stratify the processes driving streamflow in these regions thus revealing limitations of geographically independent streamflow clusters. This study demonstrates that a broad suite of ecologically relevant streamflow characteristics can be accurately modeled across large heterogeneous regions using this framework. Applications of the resulting models include stratifying biomonitoring sites and quantifying linkages between specific aspects of flow regimes and aquatic community structure. In particular, the results bode well for modeling ecological processes related to high-flow magnitude, timing, and rate of change such as the recruitment of fish and riparian vegetation across large regions.

DEVELOPMENT OF FIELD-BASED EMPIRICAL MODELS OF SUITABLE TEMPERATURE REGIMES FOR INTERIOR SALMONIDS

EPA Science Inventory

Interior salmonids are species of growing interest and concern in the Pacific Northwest. Evidence of population declines associated with habitat loss and fragmentation have culminate in every species being listed, or proposed or petitioned for listing under he Endangered Species...

CTBT on-site inspections

NASA Astrophysics Data System (ADS)

Zucca, J. J.

2014-05-01

On-site inspection (OSI) is a critical part of the verification regime for the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The OSI verification regime provides for international inspectors to make a suite of measurements and observations on site at the location of an event of interest. The other critical component of the verification regime is the International Monitoring System (IMS), which is a globally distributed network of monitoring stations. The IMS along with technical monitoring data from CTBT member countries, as appropriate, will be used to trigger an OSI. After the decision is made to carry out an OSI, it is important for the inspectors to deploy to the field site rapidly to be able to detect short-lived phenomena such as the aftershocks that may be observable after an underground nuclear explosion. The inspectors will be on site from weeks to months and will be working with many tens of tons of equipment. Parts of the OSI regime will be tested in a field exercise in the country of Jordan late in 2014. The build-up of the OSI regime has been proceeding steadily since the CTBT was signed in 1996 and is on track to becoming a deterrent to someone considering conducting a nuclear explosion in violation of the Treaty.

Experimental investigation on flow past nine cylinders in a square configuration

NASA Astrophysics Data System (ADS)

Ma, Lili; Gao, Yangyang; Guo, Zhen; Wang, Lizhong

2018-04-01

An experimental investigation on flow past nine cylinders in a square configuration was carried out using the particle image velocimetry technique and load cell in a water channel. The center-to-center spacing ratio L/D was in the range of 1.5-3.0 and the Reynolds number Re was varied from 1500 to 5000. The effects of spacing ratio and Reynolds number on the instantaneous time-averaged flow fields and force coefficients are investigated. The results show that three distinct flow regimes are categorized with variation of the spacing ratios and Reynolds numbers, namely, shielding flow regime, transition flow regime and vortex shedding flow regime. Depending on the interferences of shear layers around the nine cylinders, each flow regime is further divided into two types of flow patterns. An interesting feature of bistable flow pattern with different flow modes is observed at small spacing ratio L/D = 1.5. The non-dimensional vortex shedding frequencies appear to be more associated with the individual shear layers rather than the multiple cylinders. Moreover, force analysis, streamline topologies and Reynolds stress contours are presented to elucidate the effects of spacing ratio and Reynolds number on the complex wake interference among the nine cylinders. The flow characteristics and force coefficients are found to be more sensitive to L/D rather than Re.

Non-Fermi-liquid behavior in nonequilibrium transport through Co-doped Au chains connected to fourfold symmetric leads

NASA Astrophysics Data System (ADS)

Di Napoli, S.; Roura-Bas, P.; Weichselbaum, Andreas; Aligia, A. A.

2014-09-01

We calculate the differential conductance as a function of temperature and bias voltage, G (T,V), through Au monatomic chains with a substitutional Co atom as a magnetic impurity, connected to a fourfold symmetric lead. The system was recently proposed as a possible scenario for observation of the overscreened Kondo physics. Stretching the chain, the system could be tuned through a quantum critical point (QCP) with three different regimes: overscreened, underscreened, and non-Kondo phases. We present calculations of the impurity spectral function by using the numerical renormalization group for the three different regimes characterizing the QCP. Nontrivial behavior of the spectral function is reported near the QCP. Comparison with results using the noncrossing approximation (NCA) shows that the latter is reliable in the overscreened regime, when the anisotropy is larger than the Kondo temperature. For these parameters, which correspond to realistic previous estimates, G (T,V) calculated within NCA exhibits clear signatures of the non-Fermi-liquid behavior within the overscreened regime.

Effects of flow regime and pesticides on periphytic communities: evolution and role of biodiversity.

PubMed

Villeneuve, Aurélie; Montuelle, Bernard; Bouchez, Agnès

2011-04-01

The effects of chemical and physical factors on periphyton structure, diversity and functioning were investigated in an outdoor mesocosm experiment. Stream biofilms were subjected to a pesticide mix (diuron and azoxystrobin) under two different hydraulic regimes. The hydraulic regimes differed by spatial variations of flow conditions (turbulent with high variations vs. laminar with low variations). The effects of the hydraulic regime and pesticides were assessed at the level of the periphytic communities. We focused on the change in the biodiversity of these communities under the two hydraulic regimes, and on the role of these biodiversity changes in case of pesticide contamination. Changes in structural (biomass, cell density), diversity (community composition assessed by PCR-DGGE and microscopic analysis) and functional (bacterial and algal production, sensitivity to the herbicide) parameters were monitored throughout a 2-month experiment. The results showed that exposure to pesticides affected the phytobenthic community targeted by the herbicide, impacting on both its growth dynamics and its primary production. Conversely, the impact of the flow regime was greater than that of pesticides on the non-target bacterial community with higher bacterial density and production in laminar mesocosms (uniform regime). An interaction between flow and pollution effects was also observed. Communities that developed in turbulent mesocosms (heterogeneous regime) were more diversified, as a result of increased microhabitat heterogeneity due to high spatial variations. However, this higher biodiversity did not increase the ability of these biofilms to tolerate pesticides, as expected. On the contrary, the sensitivity of these communities to pesticide contamination was, in fact, increased. Copyright © 2011 Elsevier B.V. All rights reserved.

A holistic view of marine regime shifts

PubMed Central

Conversi, Alessandra; Dakos, Vasilis; Gårdmark, Anna; Ling, Scott; Folke, Carl; Mumby, Peter J.; Greene, Charles; Edwards, Martin; Blenckner, Thorsten; Casini, Michele; Pershing, Andrew; Möllmann, Christian

2015-01-01

Understanding marine regime shifts is important not only for ecology but also for developing marine management that assures the provision of ecosystem services to humanity. While regime shift theory is well developed, there is still no common understanding on drivers, mechanisms and characteristic of abrupt changes in real marine ecosystems. Based on contributions to the present theme issue, we highlight some general issues that need to be overcome for developing a more comprehensive understanding of marine ecosystem regime shifts. We find a great divide between benthic reef and pelagic ocean systems in how regime shift theory is linked to observed abrupt changes. Furthermore, we suggest that the long-lasting discussion on the prevalence of top-down trophic or bottom-up physical drivers in inducing regime shifts may be overcome by taking into consideration the synergistic interactions of multiple stressors, and the special characteristics of different ecosystem types. We present a framework for the holistic investigation of marine regime shifts that considers multiple exogenous drivers that interact with endogenous mechanisms to cause abrupt, catastrophic change. This framework takes into account the time-delayed synergies of these stressors, which erode the resilience of the ecosystem and eventually enable the crossing of ecological thresholds. Finally, considering that increased pressures in the marine environment are predicted by the current climate change assessments, in order to avoid major losses of ecosystem services, we suggest that marine management approaches should incorporate knowledge on environmental thresholds and develop tools that consider regime shift dynamics and characteristics. This grand challenge can only be achieved through a holistic view of marine ecosystem dynamics as evidenced by this theme issue.

StreamThermal: A software package for calculating thermal metrics from stream temperature data

USGS Publications Warehouse

Tsang, Yin-Phan; Infante, Dana M.; Stewart, Jana S.; Wang, Lizhu; Tingly, Ralph; Thornbrugh, Darren; Cooper, Arthur; Wesley, Daniel

2016-01-01

Improving quality and better availability of continuous stream temperature data allows natural resource managers, particularly in fisheries, to understand associations between different characteristics of stream thermal regimes and stream fishes. However, there is no convenient tool to efficiently characterize multiple metrics reflecting stream thermal regimes with the increasing amount of data. This article describes a software program packaged as a library in R to facilitate this process. With this freely-available package, users will be able to quickly summarize metrics that describe five categories of stream thermal regimes: magnitude, variability, frequency, timing, and rate of change. The installation and usage instruction of this package, the definition of calculated thermal metrics, as well as the output format from the package are described, along with an application showing the utility for multiple metrics. We believe this package can be widely utilized by interested stakeholders and greatly assist more studies in fisheries.

Influence of phonon-assisted tunneling on the linear thermoelectric transport through molecular quantum dots

NASA Astrophysics Data System (ADS)

Khedri, A.; Meden, V.; Costi, T. A.

2017-11-01

We investigate the effect of vibrational degrees of freedom on the linear thermoelectric transport through a single-level quantum dot described by the spinless Anderson-Holstein impurity model. To study the effects of strong electron-phonon coupling, we use the nonperturbative numerical renormalization group approach. We also compare our results, at weak to intermediate coupling, with those obtained by employing the functional renormalization group method, finding good agreement in this parameter regime. When applying a gate voltage at finite temperatures, the inelastic scattering processes, induced by phonon-assisted tunneling, result in an interesting interplay between electrical and thermal transport. We explore different parameter regimes and identify situations for which the thermoelectric power as well as the dimensionless figure of merit are significantly enhanced via a Mahan-Sofo type of mechanism. We show, in particular, that this occurs at strong electron-phonon coupling and in the antiadiabatic regime.

Behaviour of a ZnO thin film as MSG for biosensing material in sub-wavelength regime

NASA Astrophysics Data System (ADS)

Iftimie, N.; Steigmann, R.; Danila, N. A.; Iacomi, F.; Faktorova, D.; Savin, A.

2016-11-01

Zinc oxide nanostructured materials, such as films and nanoparticles, could provide a suitable platform for development of high performance biosensing material due to their unique fundamental material properties. In this study, the enzyme biosensing consisting of a zinc oxide (ZnO) nanoparticles were grown on SiO2/Si substrates by vacuum thermal evaporation method and their sensing characteristics are examined in air and investigated. The film morphology is characterized by X-ray diffraction (XRD) the film crystalline quality and by scanning electron microscopy (SEM). Also, the interest in surface waves appeared due to evanescent waves in the metallic strip grating structure (MSG-Ag/ZnO/SiO2/Si) in sub-wavelength regime. Before testing the sensor with metamaterials (MMs) lens in the sub-wavelength regime, a simulation of the evanescent wave's formation has been performed at the edge of Ag strips, with thicknesses in the range of micrometers.

A comparative study of noisy signal evolution in 2R all-optical regenerators with normal and anomalous average dispersions using an accelerated Multicanonical Monte Carlo method.

PubMed

Lakoba, Taras I; Vasilyev, Michael

2008-10-27

In [Opt. Express 15, 10061 (2007)] we proposed a new regime of multichannel all-optical regeneration that required anomalous average dispersion. This regime is superior to the previously studied normal-dispersion regime when signal distortions are deterministic in their temporal shape. However, there was a concern that the regenerator with anomalous average dispersion may be prone to noise amplification via modulational instability. Here, we show that this, in general, is not the case. Moreover, in the range of input powers that is of interest for multichannel regeneration, the device with anomalous average dispersion may even provide less noise amplification than the one with normal dispersion. These results are obtained with an improved version of the parallelized modification of the Multicanonical Monte Carlo method proposed in [IEEE J. Sel. Topics Quantum Electron. 14, 599 (2008)].

Large and local-scale influences on physical and chemical characteristics of coastal waters of Western Europe during winter

NASA Astrophysics Data System (ADS)

Tréguer, Paul; Goberville, Eric; Barrier, Nicolas; L'Helguen, Stéphane; Morin, Pascal; Bozec, Yann; Rimmelin-Maury, Peggy; Czamanski, Marie; Grossteffan, Emilie; Cariou, Thierry; Répécaud, Michel; Quéméner, Loic

2014-11-01

There is now a strong scientific consensus that coastal marine systems of Western Europe are highly sensitive to the combined effects of natural climate variability and anthropogenic climate change. However, it still remains challenging to assess the spatial and temporal scales at which climate influence operates. While large-scale hydro-climatic indices, such as the North Atlantic Oscillation (NAO) or the East Atlantic Pattern (EAP) and the weather regimes such as the Atlantic Ridge (AR), are known to be relevant predictors of physical processes, changes in coastal waters can also be related to local hydro-meteorological and geochemical forcing. Here, we study the temporal variability of physical and chemical characteristics of coastal waters located at about 48°N over the period 1998-2013 using (1) sea surface temperature, (2) sea surface salinity and (3) nutrient concentration observations for two coastal sites located at the outlet of the Bay of Brest and off Roscoff, (4) river discharges of the major tributaries close to these two sites and (5) regional and local precipitation data over the region of interest. Focusing on the winter months, we characterize the physical and chemical variability of these coastal waters and document changes in both precipitation and river runoffs. Our study reveals that variability in coastal waters is connected to the large-scale North Atlantic atmospheric circulation but is also partly explained by local river influences. Indeed, while the NAO is strongly related to changes in sea surface temperature at the Brest and Roscoff sites, the EAP and the AR have a major influence on precipitations, which in turn modulate river discharges that impact sea surface salinity at the scale of the two coastal stations.

Impact on Comets and Asteroids

NASA Technical Reports Server (NTRS)

OKeefe, John D.; Stewart, Sarah T.; Ahrens, Thomas J.

2001-01-01

We characterized the impact physics in collisions on porous bodies by various density projectiles and defined different penetration modes (compression, spreading, or breakup) based on transitions between instability regimes. Additional information is contained in the original extended abstract.

Weak- versus strong-disorder superfluid—Bose glass transition in one dimension

NASA Astrophysics Data System (ADS)

Doggen, Elmer V. H.; Lemarié, Gabriel; Capponi, Sylvain; Laflorencie, Nicolas

2017-11-01

Using large-scale simulations based on matrix product state and quantum Monte Carlo techniques, we study the superfluid to Bose glass transition for one-dimensional attractive hard-core bosons at zero temperature, across the full regime from weak to strong disorder. As a function of interaction and disorder strength, we identify a Berezinskii-Kosterlitz-Thouless critical line with two different regimes. At small attraction where critical disorder is weak compared to the bandwidth, the critical Luttinger parameter Kc takes its universal Giamarchi-Schulz value Kc=3 /2 . Conversely, a nonuniversal Kc>3 /2 emerges for stronger attraction where weak-link physics is relevant. In this strong-disorder regime, the transition is characterized by self-similar power-law-distributed weak links with a continuously varying characteristic exponent α .

QCD thermodynamics with two flavors at Nt=6

NASA Astrophysics Data System (ADS)

Bernard, Claude; Ogilvie, Michael C.; Degrand, Thomas A.; Detar, Carleton; Gottlieb, Steven; Krasnitz, Alex; Sugar, R. L.; Toussaint, D.

1992-05-01

The first results of numerical simulations of quantum chromodynamics on the Intel iPSC/860 parallel processor are presented. We performed calculations with two flavors of Kogut-Susskind quarks at Nt=6 with masses of 0.15T and 0.075T (0.025 and 0.0125 in lattice units) in order to locate the crossover from the low-temperature regime of ordinary hadronic matter to the high-temperature chirally symmetric regime. As with other recent two-flavor simulations, these calculations are insufficient to distinguish between a rapid crossover and a true phase transition. The phase transition is either absent or feeble at this quark mass. An improved estimate of the crossover temperature in physical units is given and results are presented for the hadronic screening lengths in both the high- and low-temperature regimes.

Hyperextended Cosmological Perturbation Theory: Predicting Nonlinear Clustering Amplitudes

NASA Astrophysics Data System (ADS)

Scoccimarro, Román; Frieman, Joshua A.

1999-07-01

We consider the long-standing problem of predicting the hierarchical clustering amplitudes Sp in the strongly nonlinear regime of gravitational evolution. N-body results for the nonlinear evolution of the bispectrum (the Fourier transform of the three-point density correlation function) suggest a physically motivated Ansatz that yields the strongly nonlinear behavior of the skewness, S3, starting from leading-order perturbation theory. When generalized to higher order (p>3) polyspectra or correlation functions, this Ansatz leads to a good description of nonlinear amplitudes in the strongly nonlinear regime for both scale-free and cold dark matter models. Furthermore, these results allow us to provide a general fitting formula for the nonlinear evolution of the bispectrum that interpolates between the weakly and strongly nonlinear regimes, analogous to previous expressions for the power spectrum.

Advanced-Retarded Differential Equations in Quantum Photonic Systems

NASA Astrophysics Data System (ADS)

Alvarez-Rodriguez, Unai; Perez-Leija, Armando; Egusquiza, Iñigo L.; Gräfe, Markus; Sanz, Mikel; Lamata, Lucas; Szameit, Alexander; Solano, Enrique

2017-02-01

We propose the realization of photonic circuits whose dynamics is governed by advanced-retarded differential equations. Beyond their mathematical interest, these photonic configurations enable the implementation of quantum feedback and feedforward without requiring any intermediate measurement. We show how this protocol can be applied to implement interesting delay effects in the quantum regime, as well as in the classical limit. Our results elucidate the potential of the protocol as a promising route towards integrated quantum control systems on a chip.

Cold War Agency: The United States and the Failure of the DIEM Experiment

DTIC Science & Technology

2017-03-01

2000s to establish democratic regimes in Afghanistan and Iraq reflect an American foreign policy tradition that began at the end of World War II. The...Afghanistan and Iraq reflect an American foreign policy tradition that began at the end of World War II. The pairing of national security interests...Afghanistan and Iraq reflect an American foreign policy tradition that began at the end of World War II. The pairing of national security interests with the

Advanced-Retarded Differential Equations in Quantum Photonic Systems

PubMed Central

Alvarez-Rodriguez, Unai; Perez-Leija, Armando; Egusquiza, Iñigo L.; Gräfe, Markus; Sanz, Mikel; Lamata, Lucas; Szameit, Alexander; Solano, Enrique

2017-01-01

We propose the realization of photonic circuits whose dynamics is governed by advanced-retarded differential equations. Beyond their mathematical interest, these photonic configurations enable the implementation of quantum feedback and feedforward without requiring any intermediate measurement. We show how this protocol can be applied to implement interesting delay effects in the quantum regime, as well as in the classical limit. Our results elucidate the potential of the protocol as a promising route towards integrated quantum control systems on a chip. PMID:28230090

Diurnal Temperature Regime in the Regolith Surface Layer of the Lagado Planitia Region on Phobos: Model Predictions for Different Seasons

NASA Astrophysics Data System (ADS)

Kuzmin, R. O.; Zabalueva, E. V.

2018-03-01

The paper contains the data on the thermal and physical characteristic of the surface regolith of the Martian satellite Phobos obtained from the spaceborne remote sensing (with the Mariner 9, Viking, and Mars Global Surveyor orbiters and the Phobos-2 spacecraft) and the results of the numerical modeling of the thermal regime in the surface regolith (on diurnal and seasonal scales) performed for the prospective landing site in the Lagado Planitia region located in the anti-Martian hemisphere of Phobos.

Four-junction superconducting circuit

PubMed Central

Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J. Q.

2016-01-01

We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit. PMID:27356619

Strong-field plasmonic photoemission in the mid-IR at <1 GW/cm² intensity.

PubMed

Teichmann, S M; Rácz, P; Ciappina, M F; Pérez-Hernández, J A; Thai, A; Fekete, J; Elezzabi, A Y; Veisz, L; Biegert, J; Dombi, P

2015-01-12

We investigated nonlinear photoemission from plasmonic films with femtosecond, mid-infrared pulses at 3.1 μm wavelength. Transition between regimes of multi-photon-induced and tunneling emission is demonstrated at an unprecedentedly low intensity of <1 GW/cm(2). Thereby, strong-field nanophysics can be accessed at extremely low intensities by exploiting nanoscale plasmonic field confinement, enhancement and ponderomotive wavelength scaling at the same time. Results agree well with quantum mechanical modelling. Our scheme demonstrates an alternative paradigm and regime in strong-field physics.

OSA Proceedings of the Topical Meeting on Optical Amplifiers and Their Applications, Held in Snowmass Village, Colorado on 24 - 26 July 1991. Volume 13

DTIC Science & Technology

1992-05-22

signal gain saturation and nearly degenerate four-wave mixing, are reviewed from the view- 11.00 am points of physical mechanis-n and use. (p. 126...regimes. J. F. Marcerou. H. Fevrier, J. Hervo. J. Auge, Alcate! A hsthorn Recherche, France. Noise properties of EDFA ere studied in various signal regimes...FRIDAY, JULY 26, 1991 FRIDAY, JULY 26, 1991-Continued CABARET LOBBY 9:15 am FAS Signal statistical effects from stimulated Brillouin 7:00 am-5:00

Dynamics in terahertz semiconductor microcavity: quantum noise spectra

NASA Astrophysics Data System (ADS)

Jabri, H.; Eleuch, H.

2018-05-01

We investigate the physics of an optical semiconductor microcavity containing a coupled double quantum well interacting with cavity photons. The photon statistics of the transmitted light by the cavity is explored. We show that the nonlinear interactions in the direct and indirect excitonic modes generate an important squeezing despite the weak nonlinearities. When the strong coupling regime is achieved, the noise spectra of the system is dominated by the indirect exciton distribution. At the opposite, in the weak regime, direct excitons contribute much larger in the noise spectra.

Assessment of nonequilibrium radiation computation methods for hypersonic flows

NASA Technical Reports Server (NTRS)

Sharma, Surendra

1993-01-01

The present understanding of shock-layer radiation in the low density regime, as appropriate to hypersonic vehicles, is surveyed. Based on the relative importance of electron excitation and radiation transport, the hypersonic flows are divided into three groups: weakly ionized, moderately ionized, and highly ionized flows. In the light of this division, the existing laboratory and flight data are scrutinized. Finally, an assessment of the nonequilibrium radiation computation methods for the three regimes in hypersonic flows is presented. The assessment is conducted by comparing experimental data against the values predicted by the physical model.

[Rehabilitative medical technology for the correction of microcirculatory disorders in patients with arterial hypertension].

PubMed

Kul'chitskaia, D B

2009-01-01

The study with the use of laser Doppler flowmetry has revealed pathological changes in the microcirculatory system of patients with arterial hypertension. Their treatment with a low-frequency magnetic field showed that its effect on microcirculation depends on the regime and site of application of magnetotherapy as well as its combination with other physical factors. Frontal application of the magnetic field had the most pronounced beneficial effect on dynamic characteristics of microcirculation. Pulsed regime of magnetotherapy was more efficacious than conventional one. Amplipulse magnetotherapy produced better results than monotherapy.

Who Becomes a Physics Major? A Long-term Longitudinal Study Examining the Roles of Pre-college Beliefs about Physics and Learning Physics, Interest, and Academic Achievement

NASA Astrophysics Data System (ADS)

Perkins, Katherine K.; Gratny, Mindy

2010-10-01

In this paper, we examine the correlation between students' beliefs upon entering college and their likelihood of continuing on to become a physics major. Since 2004, we have collected CLASS survey and self-reported level-of-interest responses from students in the first-term, introductory calculus-based physics course (N>2500). Here, we conduct a retrospective analysis of students' incoming CLASS scores and level of interest, comparing those students who go on to become physics majors with those who do not. We find the incoming CLASS scores and reported interest of these future physics majors to be substantially higher than the class average, indicating that these students enter their first college course already having quite expert-like beliefs. The comparative differences are much smaller for grades, SAT score, and university predicted-GPA.

Effects of climate change on ecological disturbance in the northern Rockies

USGS Publications Warehouse

Loehman, Rachel A.; Bentz, Barbara J.; DeNitto, Gregg A.; Keane, Robert E.; Manning, Mary E.; Duncan, Jacob P.; Egan, Joel M.; Jackson, Marcus B.; Kegley, Sandra; Lockman, I. Blakey; Pearson, Dean E.; Powell, James A.; Shelly, Steve; Steed, Brytten E.; Zambino, Paul J.; Halofsky, Jessica E.; Peterson, David L.

2018-01-01

Disturbances alter ecosystem, community, or population structure and change elements of the biological and/or physical environment. Climate changes can alter the timing, magnitude, frequency, and duration of disturbance events, as well as the interactions of disturbances on a landscape, and climate change may already be affecting disturbance events and regimes. Interactions among disturbance regimes, such as the cooccurrence in space and time of bark beetle outbreaks and wildfires, can result in highly visible, rapidly occurring, and persistent changes in landscape composition and structure. Understanding how altered disturbance patterns and multiple disturbance interactions might result in novel and emergent landscape behaviors is critical for addressing climate change impacts and for designing land management strategies that are appropriate for future climates This chapter describes the ecology of important disturbance regimes in the Northern Rockies region, and potential shifts in these regimes as a consequence of observed and projected climate change. We summarize five disturbance types present in the Northern Rockies that are sensitive to a changing climate--wildfires, bark beetles, white pine blister rust (Cronartium ribicola), other forest diseases, and nonnative plant invasions—and provide information that can help managers anticipate how, when, where, and why climate changes may alter the characteristics of disturbance regimes.

X-Ray generation by the laser-plasma interaction in the regime of relativistic electronic spring

NASA Astrophysics Data System (ADS)

Gonoskov, Arkady; Blackburn, Thomas; Blanco, Manuel; Flores-Arias, M. T.; Wettervik, Benjamin; Marklund, Mattias

2017-10-01

Inducing and controlling relativistic motion of surface electrons in overdense plasmas with high-intensity lasers is a promising way to produce X-rays with unique properties, including high brightness, ultra-short duration and tunable polarization. Although the well-studied relativistic oscillating mirror (ROM) regime provides robust generation of high harmonics, the amplitude of the outgoing light in this regime is always equal to that of the incident radiation because the conversion takes place continuously without energy accumulation. This restriction can be overcome by increasing the laser intensity and/or decreasing the plasma density such that n / a < 10 . In this case the plasma acts as a spring, first accumulating up to 60% of the energy of one laser cycle, then re-emitting it in the form of a burst of high harmonics. Under optimal conditions this burst can be both 100 times shorter in duration and 100 times higher in intensity. The theory of relativistic electronic spring (RES) describes a wide variety of interaction scenarios in this regime and provides insight into the underlying physics. The talk will concern the prospects of creating and controlling XUV bursts of exceptional brightness in the RES regime.

Underwater Light Regimes in Rivers from Multiple Measurement Approaches

NASA Astrophysics Data System (ADS)

Gardner, J.; Ensign, S.; Houser, J.; Doyle, M.

2017-12-01

Underwater light regimes are complex over space and time. Light in rivers is less understood compared to other aquatic systems, yet light is often the limiting resource and a fundamental control of many biological and physical processes in riverine systems. We combined multiple measurement approaches (fixed-site and flowpath) to understand underwater light regimes. We measured vertical light profiles over time (fixed-site) with stationary buoys and over space and time (flowpath) with Lagrangian neutrally buoyant sensors in two different large US rivers; the Upper Mississippi River in Wisconsin, USA and the Neuse River in North Carolina, USA. Fixed site data showed light extinction coefficients, and therefore the depth of the euphotic zone, varied up to three-fold within a day. Flowpath data revealed the stochastic nature of light regimes from the perspective of a neutrally buoyant particle as it moves throughout the water column. On average, particles were in the euphotic zone between 15-50% of the time. Combining flowpath and fixed-site data allowed spatial disaggregation of a river reach to determine if changes in the light regime were due to space or time as well as development of a conceptual model of the dynamic euphotic zone of rivers.

Constitutive model development for flows of granular materials

NASA Astrophysics Data System (ADS)

Chialvo, Sebastian

Granular flows are ubiquitous in both natural and industrial processes. When com- posed of dry, noncohesive particles, they manifest three different flow regimes---commonly referred to as the quasistatic, inertial, and intermediate regimes---each of which exhibits its own dependences on solids volume fraction, shear rate, and particle-level properties. The differences in these regimes can be attributed to microscale phenomena, with quasistatic flows being dominated by enduring, frictional contacts between grains, inertial flows by grain collisions, and intermediate flows by a combination of the two. Existing constitutive models for the solids-phase stress tend to focus on one or two regimes at a time, with a limited degree of success; the same is true of models for wall-boundary conditions for granular flows. Moreover, these models tend not to be based on detailed particle-level flow data, either from experiment or simulation. Clearly, a comprehensive modeling framework is lacking. The work in this thesis aims to address these issues by proposing continuum models constructed on the basis of discrete element method (DEM) simulations of granular shear flows. Specifically, we propose (a) a constitutive stress model that bridges the three dense flow regimes, (b) an modified kinetic-theory model that covers both the dense and dilute ends of the inertial regime, and (c) a boundary-condition model for dense, wall-bounded flows. These models facilitate the modeling of a wide range of flow systems of practical interest and provide ideas for further model development and refinement.

Nonlinear Dynamics of Complex Coevolutionary Systems in Historical Times

NASA Astrophysics Data System (ADS)

Perdigão, Rui A. P.

2016-04-01

A new theoretical paradigm for statistical-dynamical modeling of complex coevolutionary systems is introduced, with the aim to provide historical geoscientists with a practical tool to analyse historical data and its underlying phenomenology. Historical data is assumed to represent the history of dynamical processes of physical and socio-economic nature. If processes and their governing laws are well understood, they are often treated with traditional dynamical equations: deterministic approach. If the governing laws are unknown or impracticable, the process is often treated as if being random (even if it is not): statistical approach. Although single eventful details - such as the exact spatiotemporal structure of a particular hydro-meteorological incident - may often be elusive to a detailed analysis, the overall dynamics exhibit group properties summarized by a simple set of categories or dynamical regimes at multiple scales - from local short-lived convection patterns to large-scale hydro-climatic regimes. The overwhelming microscale complexity is thus conveniently wrapped into a manageable group entity, such as a statistical distribution. In a stationary setting whereby the distribution is assumed to be invariant, alternating regimes are approachable as dynamical intermittence. For instance, in the context of bimodal climatic oscillations such as NAO and ENSO, each mode corresponds to a dynamical regime or phase. However, given external forcings or longer-term internal variability and multiscale coevolution, the structural properties of the system may change. These changes in the dynamical structure bring about a new distribution and associated regimes. The modes of yesteryear may no longer exist as such in the new structural order of the system. In this context, aside from regime intermittence, the system exhibits structural regime change. New oscillations may emerge whilst others fade into the annals of history, e.g. particular climate fluctuations during the Little Ice Age. Traditional theories of stochastic processes and dynamical systems are grounded on the existence of so-called dynamical invariants; properties that remain unchanged as the dynamics unfold, assuming structural invariance and ergodicity of the underlying system. However, such theories are no longer optimal when trying to understand and model long-term historical records of coevolutionary systems. A new paradigm is thus needed. Therefore, we introduce a new class of dynamical systems that reinvent themselves as the dynamics unfold. Rather than only changing variables and parameters under a rigid framework, the governing laws are malleable themselves. The novel formulation captures and explains the coevolutionary dynamics of multiscale hydroclimatic systems, bringing along a physically sound understanding of their regimes, transitions and extremes over a long-term history.

An Examination of the Multidimensionality of Situational Interest in Elementary School Physical Education

PubMed Central

Sun, Haichun; Chen, Ang; Ennis, Catherine; Martin, Robert; Shen, Bo

2015-01-01

It has been demonstrated that situational interest in physical activity may derive from five dimensional sources, Novelty, Optimal Challenge, Attention Demand, Exploration Intent, and Instant Enjoyment. The purpose of this study was to examine the multidimensional sources in elementary school physical education. The five dimensions were measured in 5,717 students in third, fourth, and fifth grades from a random sample of 30 elementary schools. Students’ responses were randomly divided into two samples for a two-step confirmatory factor analysis. The results confirmed that the five dimensions are primary sources of situational interest for elementary school physical education. The findings implied that situational interest should be taken into account as a necessary curricular component in elementary physical education. PMID:18431952

An evaluation of collision models in the Method of Moments for rarefied gas problems

NASA Astrophysics Data System (ADS)

Emerson, David; Gu, Xiao-Jun

2014-11-01

The Method of Moments offers an attractive approach for solving gaseous transport problems that are beyond the limit of validity of the Navier-Stokes-Fourier equations. Recent work has demonstrated the capability of the regularized 13 and 26 moment equations for solving problems when the Knudsen number, Kn (where Kn is the ratio of the mean free path of a gas to a typical length scale of interest), is in the range 0.1 and 1.0-the so-called transition regime. In comparison to numerical solutions of the Boltzmann equation, the Method of Moments has captured both qualitatively, and quantitatively, results of classical test problems in kinetic theory, e.g. velocity slip in Kramers' problem, temperature jump in Knudsen layers, the Knudsen minimum etc. However, most of these results have been obtained for Maxwell molecules, where molecules repel each other according to an inverse fifth-power rule. Recent work has incorporated more traditional collision models such as BGK, S-model, and ES-BGK, the latter being important for thermal problems where the Prandtl number can vary. We are currently investigating the impact of these collision models on fundamental low-speed problems of particular interest to micro-scale flows that will be discussed and evaluated in the presentation. Engineering and Physical Sciences Research Council under Grant EP/I011927/1 and CCP12.

Teaching the Delightful Laws of Physics in a Survey Course

NASA Astrophysics Data System (ADS)

Hewitt, Paul G.

2015-10-01

How physics can be made interesting is a question that needs no answer. That's because physics is interesting! It's a field of study jam-packed with fascination and wonder. The general public has an enormous thirst for physics knowledge, as indicated by the great numbers who purchase science magazines and books and watch NOVA and other science specials. A related question, how to make a physics course interesting, is something that we can answer. All we have to do is present physics at a proper pace in the language of the learner. My adage has always been that if the first course in physics is delightful, the rigor of a follow-up course will be welcomed.

Exploring Situational Interest Sources in the French Physical Education Context

ERIC Educational Resources Information Center

Roure, Cédric; Pasco, Denis

2018-01-01

Based on the framework of interest, studies have shown that situational interest possesses strong motivation potential for students in physical education. Understanding how teachers can use situational interest in a classroom context is critical to motivate students. However, such investigations have been exclusively conducted in the United States…

Influence of physical exercise on traumatic brain injury deficits: scaffolding effect.

PubMed

Archer, Trevor

2012-05-01

Traumatic brain injury (TBI) may be due to a bump, blow, or jolt to the head or a penetrating head injury that disrupts normal brain function; it presents an ever-growing, serious public health problem that causes a considerable number of fatalities and cases of permanent disability annually. Physical exercise restores the healthy homeostatic regulation of stress, affect and the regulation of hypothalamic-pituitary-adrenal axis. Physical activity attenuates or reverses the performance deficits observed in neurocognitive tasks. It induces anti-apoptotic effects and buttresses blood-brain barrier intactness. Exercise offers a unique non-pharmacologic, non-invasive intervention that incorporates different regimes, whether dynamic or static, endurance, or resistance. Exercise intervention protects against vascular risk factors that include hypertension, diabetes, cellular inflammation, and aortic rigidity. It induces direct changes in cerebrovasculature that produce beneficial changes in cerebral blood flow, angiogenesis and vascular disease improvement. The improvements induced by physical exercise regimes in brain plasticity and neurocognitive performance are evident both in healthy individuals and in those afflicted by TBI. The overlap and inter-relations between TBI effects on brain and cognition as related to physical exercise and cognition may provide lasting therapeutic benefits for recovery from TBI. It seems likely that some modification of the notion of scaffolding would postulate that physical exercise reinforces the adaptive processes of the brain that has undergone TBI thereby facilitating the development of existing networks, albeit possibly less efficient, that compensate for those lost through damage. © Springer Science+Business Media, LLC 2011

100 years of the physics of diodes

NASA Astrophysics Data System (ADS)

Zhang, Peng; Valfells, Ágúst; Ang, L. K.; Luginsland, J. W.; Lau, Y. Y.

2017-03-01

The Child-Langmuir Law (CL), discovered a century ago, gives the maximum current that can be transported across a planar diode in the steady state. As a quintessential example of the impact of space charge shielding near a charged surface, it is central to the studies of high current diodes, such as high power microwave sources, vacuum microelectronics, electron and ion sources, and high current drivers used in high energy density physics experiments. CL remains a touchstone of fundamental sheath physics, including contemporary studies of nanoscale quantum diodes and nano gap based plasmonic devices. Its solid state analog is the Mott-Gurney law, governing the maximum charge injection in solids, such as organic materials and other dielectrics, which is important to energy devices, such as solar cells and light emitting diodes. This paper reviews the important advances in the physics of diodes since the discovery of CL, including virtual cathode formation and extension of CL to multiple dimensions, to the quantum regime, and to ultrafast processes. We review the influence of magnetic fields, multiple species in bipolar flow, electromagnetic and time dependent effects in both short pulse and high frequency THz limits, and single electron regimes. Transitions from various emission mechanisms (thermionic-, field-, and photoemission) to the space charge limited state (CL) will be addressed, especially highlighting the important simulation and experimental developments in selected contemporary areas of study. We stress the fundamental physical links between the physics of beams to limiting currents in other areas, such as low temperature plasmas, laser plasmas, and space propulsion.

Misura di g con pendolo non in regime caotico

NASA Astrophysics Data System (ADS)

Sigismondi, Costantino

2017-02-01

The measurement of the gravity acceleration with pendulum is a basic experiment in Newtonian physics, but the correct choice of wire and weight to suspend can avoid to have a cahotic instead of simple pendulum.

Interpreting the Weibull fitting parameters for diffusion-controlled release data

NASA Astrophysics Data System (ADS)

Ignacio, Maxime; Chubynsky, Mykyta V.; Slater, Gary W.

2017-11-01

We examine the diffusion-controlled release of molecules from passive delivery systems using both analytical solutions of the diffusion equation and numerically exact Lattice Monte Carlo data. For very short times, the release process follows a √{ t } power law, typical of diffusion processes, while the long-time asymptotic behavior is exponential. The crossover time between these two regimes is determined by the boundary conditions and initial loading of the system. We show that while the widely used Weibull function provides a reasonable fit (in terms of statistical error), it has two major drawbacks: (i) it does not capture the correct limits and (ii) there is no direct connection between the fitting parameters and the properties of the system. Using a physically motivated interpolating fitting function that correctly includes both time regimes, we are able to predict the values of the Weibull parameters which allows us to propose a physical interpretation.

A three-dimensional simulation of transition and early turbulence in a time-developing mixing layer

NASA Technical Reports Server (NTRS)

Cain, A. B.; Reynolds, W. C.; Ferziger, J. H.

1981-01-01

The physics of the transition and early turbulence regimes in the time developing mixing layer was investigated. The sensitivity of the mixing layer to the disturbance field of the initial condition is considered. The growth of the momentum thickness, the mean velocity profile, the turbulence kinetic energy, the Reynolds stresses, the anisotropy tensor, and particle track pictures of computations are all examined in an effort to better understand the physics of these regimes. The amplitude, spectrum shape, and random phases of the initial disturbance field were varied. A scheme of generating discrete orthogonal function expansions on some nonuniform grids was developed. All cases address the early or near field of the mixing layer. The most significant result shows that the secondary instability of the mixing layer is produced by spanwise variations in the straining field of the primary vortex structures.

Interplay between writhe and knotting for swollen and compact polymers.

PubMed

Baiesi, Marco; Orlandini, Enzo; Whittington, Stuart G

2009-10-21

The role of the topology and its relation with the geometry of biopolymers under different physical conditions is a nontrivial and interesting problem. Aiming at understanding this issue for a related simpler system, we use Monte Carlo methods to investigate the interplay between writhe and knotting of ring polymers in good and poor solvents. The model that we consider is interacting self-avoiding polygons on the simple cubic lattice. For polygons with fixed knot type, we find a writhe distribution whose average depends on the knot type but is insensitive to the length N of the polygon and to solvent conditions. This "topological contribution" to the writhe distribution has a value that is consistent with that of ideal knots. The standard deviation of the writhe increases approximately as square root(N) in both regimes, and this constitutes a geometrical contribution to the writhe. If the sum over all knot types is considered, the scaling of the standard deviation changes, for compact polygons, to approximately N(0.6). We argue that this difference between the two regimes can be ascribed to the topological contribution to the writhe that, for compact chains, overwhelms the geometrical one, thanks to the presence of a large population of complex knots at relatively small values of N. For polygons with fixed writhe, we find that the knot distribution depends on the chosen writhe, with the occurrence of achiral knots being considerably suppressed for large writhe. In general, the occurrence of a given knot thus depends on a nontrivial interplay between writhe, chain length, and solvent conditions.

Observations of decay-less low-amplitude kink oscillations of EUV coronal loops

NASA Astrophysics Data System (ADS)

Nisticò, Giuseppe; Nakariakov, Valery; Anfinogentov, Sergey

The high spatial and temporal resolution observations at Extreme Ultra-Violet (EUV) wavelengths from the Atmospheric Imaging Assembly (AIA) of the Solar Dynamics Observatory (SDO) reveal new features in kink oscillations of coronal loops. We show that, in addition to the well-known rapidly decaying oscillations, a new type of kink waves is present, characterized by low-amplitude and undamped oscillations, that we define as decay-less. Typical periods range from 2.5 to 12 min in both regimes and are different for different loops, increasing with the loop length. Estimates of the loop lengths are supported by three dimensional reconstruction of the loop geometry. The amplitude for the decay-less regime is about 1 Mm, close to the spatial resolution of the AIA instruments. The oscillation phase, measured by the cross-correlation method, is found to be constant along each analysed loop, and the spatial structure of the phase of the oscillations corresponds to the fundamental standing kink mode. We show that the observed behaviours are consistent with the empirical model of a damped linear oscillator excited by a continuous low-amplitude harmonic driver, in addition to an eventual impulsive high-amplitude driver. The observed life-time of the oscillations is likely to be determined by the observational conditions rather than any physical damping. However, the balance between the driving and damping is a necessary ingredient of this model. The properties of this type of transverse oscillations make them interesting object of study in the framework of resonant absorption theory and coronal heating process.

Negligible Electronic Interaction between Photoexcited Electron–Hole Pairs and Free Electrons in Phosphorus–Boron Co-Doped Silicon Nanocrystals

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

Limpens, Rens; Fujii, Minoru; Neale, Nathan R.

Phosphorus (P) and boron (B) co-doped Si nanocrystals (NCs) have raised interest in the optoelectronic industry due to their electronic tunability, optimal carrier multiplication properties, and straightforward dispersibility in polar solvents. Yet a basic understanding of the interaction of photoexcited electron-hole (e-h) pairs with new physical features that are introduced by the co-doping process (free carriers, defect states, and surface chemistry) is missing. Here, we present the first study of the ultrafast carrier dynamics in SiO2-embedded P-B co-doped Si NC ensembles using induced absorption spectroscopy through a two-step approach. First, the induced absorption data show that the large fraction ofmore » the dopants residing on the NC surface slows down carrier relaxation dynamics within the first 20 ps relative to intrinsic (undoped) Si NCs, which we interpret as enhanced surface passivation. On longer time-scales (picosecond to nanosecond regime), we observe a speeding up of the carrier relaxation dynamics and ascribe it to doping-induced trap states. This argument is deduced from the second part of the study, where we investigate multiexciton interactions. From a stochastic modeling approach we show that localized carriers, which are introduced by the P or B dopants, have minor electronic interactions with the photoexcited e-h pairs. This is understood in light of the strong localization of the introduced carriers on their original P- or B-dopant atoms, due to the strong quantum confinement regime in these relatively small NCs (<6 nm).« less

Detection of different reconnection regions from kinetic simulations during island coalescence after asymmetric magnetic reconnection

NASA Astrophysics Data System (ADS)

Cazzola, Emanuele; Berchem, Jean; Innocenti, Maria Elena; Goldman, Martin V.; Newman, David L.; Zhou, Meng; Lapenta, Giovanni

2017-04-01

In this work we present new results from fully kinetic simulations of the magnetic islands coalescence dynamics after asymmetric magnetic reconnection. In a previous work, we have shown that three different reconnection regions can be identified when a new frame of reference based on the local magnetic field is set. These regions were marked as X, D and M whether they describe, respectively, a traditional X-line event, an event between two diverging islands or an event between two merging islands [1, 2]. The results shown here extend the previous analysis to a more realistic regime, including a remarkable temperature transition across the current sheet. In particular, regions X, D, and M are also observed within this new regime, featuring yet new interesting characteristics. Special attention is given to the particles agyrotropic and anisotropic behavior as fundamental signatures for the detection of these regions with satellites. These results are timely for the ongoing MMS mission, whose data from the magnetopause crossing are presently being analyzed. In fact, data revealed that an intense flux-ropes activity takes place in this region of the magnetosphere, which makes the presence of this set of reconnection regions highly expected. [1] Cazzola, E., et al. "On the electron dynamics during island coalescence in asymmetric magnetic reconnection." Physics of Plasmas (1994-present) 22.9 (2015): 092901. [2] Cazzola, E., et al. "On the electron agyrotropy during rapid asymmetric magnetic island coalescence in presence of a guide field." Geophysical Research Letters 43.15 (2016): 7840-7849.

Negligible Electronic Interaction between Photoexcited Electron-Hole Pairs and Free Electrons in Phosphorus-Boron Co-Doped Silicon Nanocrystals

DOE PAGES

Limpens, Rens; Neale, Nathan R; Fujii, Minoru; ...

2018-03-05

Phosphorus (P) and boron (B) co-doped Si nanocrystals (NCs) have raised interest in the optoelectronic industry due to their electronic tunability, optimal carrier multiplication properties, and straightforward dispersibility in polar solvents. Yet a basic understanding of the interaction of photoexcited electron-hole (e-h) pairs with new physical features that are introduced by the co-doping process (free carriers, defect states, and surface chemistry) is missing. Here, we present the first study of the ultrafast carrier dynamics in SiO2-embedded P-B co-doped Si NC ensembles using induced absorption spectroscopy through a two-step approach. First, the induced absorption data show that the large fraction ofmore » the dopants residing on the NC surface slows down carrier relaxation dynamics within the first 20 ps relative to intrinsic (undoped) Si NCs, which we interpret as enhanced surface passivation. On longer time-scales (picosecond to nanosecond regime), we observe a speeding up of the carrier relaxation dynamics and ascribe it to doping-induced trap states. This argument is deduced from the second part of the study, where we investigate multiexciton interactions. From a stochastic modeling approach we show that localized carriers, which are introduced by the P or B dopants, have minor electronic interactions with the photoexcited e-h pairs. This is understood in light of the strong localization of the introduced carriers on their original P- or B-dopant atoms, due to the strong quantum confinement regime in these relatively small NCs (<6 nm).« less

Negligible Electronic Interaction between Photoexcited Electron–Hole Pairs and Free Electrons in Phosphorus–Boron Co-Doped Silicon Nanocrystals

DOE PAGES

Limpens, Rens; Fujii, Minoru; Neale, Nathan R.; ...

2018-02-28

Phosphorus (P) and boron (B) co-doped Si nanocrystals (NCs) have raised interest in the optoelectronic industry due to their electronic tunability, optimal carrier multiplication properties, and straightforward dispersibility in polar solvents. Yet a basic understanding of the interaction of photoexcited electron-hole (e-h) pairs with new physical features that are introduced by the co-doping process (free carriers, defect states, and surface chemistry) is missing. Here, we present the first study of the ultrafast carrier dynamics in SiO2-embedded P-B co-doped Si NC ensembles using induced absorption spectroscopy through a two-step approach. First, the induced absorption data show that the large fraction ofmore » the dopants residing on the NC surface slows down carrier relaxation dynamics within the first 20 ps relative to intrinsic (undoped) Si NCs, which we interpret as enhanced surface passivation. On longer time-scales (picosecond to nanosecond regime), we observe a speeding up of the carrier relaxation dynamics and ascribe it to doping-induced trap states. This argument is deduced from the second part of the study, where we investigate multiexciton interactions. From a stochastic modeling approach we show that localized carriers, which are introduced by the P or B dopants, have minor electronic interactions with the photoexcited e-h pairs. This is understood in light of the strong localization of the introduced carriers on their original P- or B-dopant atoms, due to the strong quantum confinement regime in these relatively small NCs (<6 nm).« less

Advanced Ultrafast Spectroscopy for Chemical Detection of Nuclear Fuel Cycle Materials

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

Villa-Aleman, E.; Houk, A.; Spencer, W.

The development of new signatures and observables from processes related to proliferation activities are often related to the development of technologies. In our physical world, the intensity of observables is linearly related to the input drivers (light, current, voltage, etc.). Ultrafast lasers with high peak energies, opens the door to a new regime where the intensity of the observables is not necessarily linear with the laser energy. Potential nonlinear spectroscopic applications include chemical detection via remote sensing through filament generation, material characterization and processing, chemical reaction specificity, surface phenomena modifications, X-ray production, nuclear fusion, etc. The National Security Directorate lasermore » laboratory is currently working to develop new tools for nonproliferation research with femtosecond and picosecond lasers. Prior to this project, we could only achieve laser energies in the 5 nano-Joule range, preventing the study of nonlinear phenomena. To advance our nonproliferation research into the nonlinear regime we require laser pulses in the milli-Joule (mJ) energy range. We have procured and installed a 35 fs-7 mJ laser, operating at one-kilohertz repetition rate, to investigate elemental and molecular detection of materials in the laboratory with potential applications in remote sensing. Advanced, nonlinear Raman techniques will be used to study materials of interest that are in a matrix of many materials and currently with these nonlinear techniques we can achieve greater than three orders of magnitude signal enhancement. This work studying nuclear fuel cycle materials with nonlinear spectroscopies will advance SRNL research capabilities and grow a core capability within the DOE complex.« less

Thermal bleaching in single fluorescent molecules under two-photon excitation regime

NASA Astrophysics Data System (ADS)

Chirico, Giuseppe; Cannone, Fabio; Baldini, Giancarlo; Diaspro, Alberto

2003-07-01

Single molecule spectroscopy often requires the immobilization of the molecules onto solid or quasi-solid substrates and the use of relatively high excitation intensity We have studied the fluorescence emission of four common dyes used for bio-imaging studies, rhodamine 6G, fluorescein, pyrene and indo-1 at the single molecule level under two-photon excitation regime. We focus on two-photon excitation thermal effects on the stability of the single molecules, influencing the internal photo-dynamics and the total duration of the fluorescent emission. Single dye molecules, spread on a glass substrate by spin coating, show a constant fluorescence output till a sudden transition to a dark state very close to the background. The bleaching time that is found to vary in the series pyrene, Indo-1, fluorescein and rhodamine 6G from the fastest to the slowest one respectively, has a Gaussian distribution suggesting that bleaching is not due to photo-bleaching. Moreover it shows a correlation to the amount of absorbed power not re-irradiated as fluorescence and to the complexity of the molecule. These observations are interpreted as thermal bleaching where the temperature increase is induced by the two-photon excitation process. This study should be extended to different trapping media of interest in single molecule basic research and applications, such as silica and polyacrylamide gels or nanosctructured polyelectrolyte matrices. We think that the observed behavior and the correlations found to the molecular chemical and physical parameters, may be of some help for the design of molecules with switching on-off behavior of longer duration.

On the effects of adaptive reservoir operating rules in hydrological physically-based models

NASA Astrophysics Data System (ADS)

Giudici, Federico; Anghileri, Daniela; Castelletti, Andrea; Burlando, Paolo

2017-04-01

Recent years have seen a significant increase of the human influence on the natural systems both at the global and local scale. Accurately modeling the human component and its interaction with the natural environment is key to characterize the real system dynamics and anticipate future potential changes to the hydrological regimes. Modern distributed, physically-based hydrological models are able to describe hydrological processes with high level of detail and high spatiotemporal resolution. Yet, they lack in sophistication for the behavior component and human decisions are usually described by very simplistic rules, which might underperform in reproducing the catchment dynamics. In the case of water reservoir operators, these simplistic rules usually consist of target-level rule curves, which represent the average historical level trajectory. Whilst these rules can reasonably reproduce the average seasonal water volume shifts due to the reservoirs' operation, they cannot properly represent peculiar conditions, which influence the actual reservoirs' operation, e.g., variations in energy price or water demand, dry or wet meteorological conditions. Moreover, target-level rule curves are not suitable to explore the water system response to climate and socio economic changing contexts, because they assume a business-as-usual operation. In this work, we quantitatively assess how the inclusion of adaptive reservoirs' operating rules into physically-based hydrological models contribute to the proper representation of the hydrological regime at the catchment scale. In particular, we contrast target-level rule curves and detailed optimization-based behavioral models. We, first, perform the comparison on past observational records, showing that target-level rule curves underperform in representing the hydrological regime over multiple time scales (e.g., weekly, seasonal, inter-annual). Then, we compare how future hydrological changes are affected by the two modeling approaches by considering different future scenarios comprising climate change projections of precipitation and temperature and projections of electricity prices. We perform this comparative assessment on the real-world water system of Lake Como catchment in the Italian Alps, which is characterized by the massive presence of artificial hydropower reservoirs heavily altering the natural hydrological regime. The results show how different behavioral model approaches affect the system representation in terms of hydropower performance, reservoirs dynamics and hydrological regime under different future scenarios.

Building Maritime Security in Southeast Asia: Outsiders Not Welcome?

DTIC Science & Technology

2008-01-01

Perspective/ RSIS0182007.pdf. 4. See Catherine Zara Raymond, “The Malacca Straits and the Threat of Maritime Terror- ism,” Power and Interest News...Catherine Zara Raymond (Singapore: World Scientific, 2005), p. 263. 39. Arthur Stein, “Coordination and Collabora- tion: Regimes in an Anarchic World

Monitoring adaptive genetic responses to environmental change

Treesearch

Michael M. Hansen; Isabelle Olivieri; Donald M. Waller; Einar E. Nielsen; F. W. Allendorf; M. K. Schwartz; C. S. Baker; D. P. Gregovich; J. A. Jackson; K. C. Kendall; L. Laikre; K. McKelvey; M. C. Neel; N. Ryman; R. Short Bull; J. B. Stetz; D. A. Tallmon; C. D. Vojta; R. S. Waples

2012-01-01

Widespread environmental changes including climate change, selective harvesting and landscape alterations now greatly affect selection regimes for most organisms. How animals and plants can adapt to these altered environments via contemporary evolution is thus of strong interest. We discuss how to use genetic monitoring to study adaptive responses via repeated analysis...

From Kondo to local singlet state in graphene nanoribbons with magnetic impurities

NASA Astrophysics Data System (ADS)

Diniz, G. S.; Luiz, G. I.; Latgé, A.; Vernek, E.

2018-03-01

A detailed analysis of the Kondo effect of a magnetic impurity in a zigzag graphene nanoribbon is addressed. An adatom is coupled to the graphene nanoribbon via a hybridization amplitude Γimp in a hollow- or top-site configuration. In addition, the adatom is also weakly coupled to a metallic scanning tunnel microscope (STM) tip by a hybridization function Γtip that provides a Kondo screening of its magnetic moment. The entire system is described by an Anderson-like Hamiltonian whose low-temperature physics is accessed by employing the numerical renormalization-group approach, which allows us to obtain the thermodynamic properties used to compute the Kondo temperature of the system. We find two screening regimes when the adatom is close to the edge of the zigzag graphene nanoribbon: (1) a weak-coupling regime (Γimp≪Γtip ), in which the edge states produce an enhancement of the Kondo temperature TK, and (2) a strong-coupling regime (Γimp≫Γtip ), in which a local singlet is formed, to the detriment of the Kondo screening by the STM tip. These two regimes can be clearly distinguished by the dependence of their characteristic temperature T* on the coupling between the adatom and the carbon sites of the graphene nanoribbon Vimp. We observe that in the weak-coupling regime T* increases exponentially with Vimp2. Differently, in the strong-coupling regime, T* increases linearly with Vimp2.

Teleconnection, Regime Shift, and Predictability of Climate Extremes: A Case Study for the Russian Heat Wave and Pakistan Flood in Summer 2010

NASA Technical Reports Server (NTRS)

Lau, W. K.; Reale, O.; Kim, K.

2011-01-01

In this talk, we present observational evidence showing that the two major extremes events of the summer of 2010, i.e., the Russian heat wave and the Pakistan flood were physically connected. We find that the Pakistan flood was contributed by a series of unusually heavy rain events over the upper Indus River Basin in July-August. The rainfall regimes shifted from an episodic heavy rain regime in mid-to-late July to a steady heavy rain regime in August. An atmospheric Rossby wave associated with the development of the Russian heat wave was instrumental in spurring the episodic rain events , drawing moisture from the Bay of Bengal and the northern Arabian Sea. The steady rain regime was maintained primarily by monsoon moisture surges from the deep tropics. From experiments with the GEOS-5 forecast system, we assess the predictability of the heavy rain events associated with the Pakistan flood. Preliminary results indicate that there are significantly higher skills in the rainfall forecasts during the episodic heavy rain events in July, compared to the steady rain period in early to mid-August. The change in rainfall predictability may be related to scale interactions between the extratropics and the tropics resulting in a modulation of rainfall predictability by the circulation regimes.

Space-Time Variability in River Flow Regimes of Northeast Turkey

NASA Astrophysics Data System (ADS)

Saris, F.; Hannah, D. M.; Eastwood, W. J.

2011-12-01

The northeast region of Turkey is characterised by relatively high annual precipitation totals and river flow. It is a mountainous region with high ecological status and also it is of prime interest to the energy sector. These characteristics make this region an important area for a hydroclimatology research in terms of future availability and management of water resources. However, there is not any previous research identifying hydroclimatological variability across the region. This study provides first comprehensive and detailed information on river flow regimes of northeast Turkey which is delimited by two major river basins namely East Black Sea (EBS) and Çoruh River (ÇRB) basins. A novel river flow classification is used that yields a large-scale perspective on hydroclimatology patterns of the region and allows interpretations regarding the controlling factors on river flow variability. River flow regimes are classified (with respect to timing and magnitude of flow) to examine spatial variability based on long-term average regimes, and also by grouping annual regimes for each station-year to identify temporal (between-year) variability. Results indicate that rivers in northeast Turkey are characterised by marked seasonal flow variation with an April-May-June maximum flow period. Spatial variability in flow regime seasonality is dependent largely on the topography of the study area. The EBS Basin, for which the North Anatolian Mountains cover the eastern part, is characterised by a May-June peak; whereas the ÇRB is defined by an April-May flow peak. The timing of river flows indicates that snowmelt is an important process and contributor of river flow maxima for both basins. The low flow season is January and February. Intermediate and low regime magnitude classes dominate in ÇRB and EBS basins, respectively, while high flow magnitude class is observed for one station only across the region. Result of regime stability analysis (year-to-year variation) shows that April-May and May-June peak shape classes together with low and intermediate magnitude classes are the most frequent and persistent flow regimes. This research has advanced understanding of hydroclimatological processes in northeast Turkey by identifying river flow regimes and together with explanations regarding the controlling factors on river flow variability.

Analysis of Future Streamflow Regimes under Global Change Scenarios in Central Chile for Ecosystem Sustainability

NASA Astrophysics Data System (ADS)

Henriquez Dole, L. E.; Gironas, J. A.; Vicuna, S.

2015-12-01

Given the critical role of the streamflow regime for ecosystem sustainability, modeling long term effects of climate change and land use change on streamflow is important to predict possible impacts in stream ecosystems. Because flow duration curves are largely used to characterize the streamflow regime and define indices of ecosystem health, they were used to represent and analyze in this study the stream regime in the Maipo River Basin in Central Chile. Water and Environmental Assessment and Planning (WEAP) model and the Plant Growth Model (PGM) were used to simulate water distribution, consumption in rural areas and stream flows on a weekly basis. Historical data (1990-2014), future land use scenarios (2030/2050) and climate change scenarios were included in the process. Historical data show a declining trend in flows mainly by unprecedented climatic conditions, increasing interest among users on future streamflow scenarios. In the future, under an expected decline in water availability coupled with changes in crop water demand, water users will be forced to adapt by changing water allocation rules. Such adaptation actions would in turns affect the streamflow regime. Future scenarios for streamflow regime show dramatic changes in water availability and temporal distribution. Annual weekly mean flows can reduce in 19% in the worst scenario and increase in 3.3% in the best of them, and variability in streamflow increases nearly 90% in all scenarios under evaluation. The occurrence of maximum and minimum monthly flows changes, as June instead of July becomes the driest month, and December instead of January becomes the month with maximum flows. Overall, results show that under future scenarios streamflow is affected and altered by water allocation rules to satisfy water demands, and thus decisions will need to consider the streamflow regime (and habitat) in order to be sustainable.

Threshold-Switchable Particles (TSP) to Control Internal Hemorrhage

DTIC Science & Technology

2013-12-01

and morphology and divided into three regimes: a 3-D gel, 2-D mat, and a 1-D thin film. They determined that the critical parameters determining...of critical physical parameters / dimensionless groups (through both simulation and experiment) such as pre-shear/mixing rate, the Weber and Ohnesorge...Capillary Pinch-Off Phase Diagram. This plot was constructed to aid in the identification of important physical parameters in blood plasma pinch-off

Integrated Modeling and Analysis of Physical Oceanographic and Acoustic Processes

DTIC Science & Technology

2015-09-30

goal is to improve ocean physical state and acoustic state predictive capabilities. The goal fitting the scope of this project is the creation of... Project -scale objectives are to complete targeted studies of oceanographic processes in a few regimes, accompanied by studies of acoustic propagation...by the basic research efforts of this project . An additional objective is to develop improved computational tools for acoustics and for the

Physics of self-aligned assembly at room temperature

NASA Astrophysics Data System (ADS)

Dubey, V.; Beyne, E.; Derakhshandeh, J.; De Wolf, I.

2018-01-01

Self-aligned assembly, making use of capillary forces, is considered as an alternative to active alignment during thermo-compression bonding of Si chips in the 3D heterogeneous integration process. Various process parameters affect the alignment accuracy of the chip over the patterned binding site on a substrate/carrier wafer. This paper discusses the chip motion due to wetting and capillary force using a transient coupled physics model for the two regimes (that is, wetting regime and damped oscillatory regime) in the temporal domain. Using the transient model, the effect of the volume of the liquid and the placement accuracy of the chip on the alignment force is studied. The capillary time (that is, the time it takes for the chip to reach its mean position) for the chip is directly proportional to the placement offset and inversely proportional to the viscosity. The time constant of the harmonic oscillations is directly proportional to the gap between the chips due to the volume of the fluid. The predicted behavior from transient simulations is next experimentally validated and it is confirmed that the liquid volume and the initial placement affect the final alignment accuracy of the top chip on the bottom substrate. With statistical experimental data, we demonstrate an alignment accuracy reaching <1 μm.

Can We Use Single-Column Models for Understanding the Boundary Layer Cloud-Climate Feedback?

NASA Astrophysics Data System (ADS)

Dal Gesso, S.; Neggers, R. A. J.

2018-02-01

This study explores how to drive Single-Column Models (SCMs) with existing data sets of General Circulation Model (GCM) outputs, with the aim of studying the boundary layer cloud response to climate change in the marine subtropical trade wind regime. The EC-EARTH SCM is driven with the large-scale tendencies and boundary conditions as derived from two different data sets, consisting of high-frequency outputs of GCM simulations. SCM simulations are performed near Barbados Cloud Observatory in the dry season (January-April), when fair-weather cumulus is the dominant low-cloud regime. This climate regime is characterized by a near equilibrium in the free troposphere between the long-wave radiative cooling and the large-scale advection of warm air. In the SCM, this equilibrium is ensured by scaling the monthly mean dynamical tendency of temperature and humidity such that it balances that of the model physics in the free troposphere. In this setup, the high-frequency variability in the forcing is maintained, and the boundary layer physics acts freely. This technique yields representative cloud amount and structure in the SCM for the current climate. Furthermore, the cloud response to a sea surface warming of 4 K as produced by the SCM is consistent with that of the forcing GCM.

On transition from diffuse mode to the constricted one with high-current cathode spot in overvoltage open discharge in D2

NASA Astrophysics Data System (ADS)

Akishev, Yu S.; Karalnik, V. B.; Medvedev, M. A.; Petryakov, A. V.; Trushkin, N. I.; Shafikov, A. G.

2017-11-01

So called “open discharges” in a narrow gap between the solid cathode and grid anode are widely used for generation of the pulsed high-current electron beams with energy up to 100 keV. The need to get high-energy e-beams leads to the necessity in using of strong overvoltage of the short gas gap with the reduced electric field of the order of 105 Td or higher. The discharge under strong overvoltage is unstable and tends to transit into high-current regime with low voltage. In the case of the open discharge in D2 at low pressure (about 0.5-2 Torr) and powered by stepwise voltage with amplitude up to 25 kV we revealed that this discharge exhibits two diffuse regimes which follow one by one and finally transits into the constricted mode with formation of high-current spots on the cathode. The physical properties of these gas discharge regimes have been explored in detail with the usage of the fast multi-frame camera synchronized with the current and voltage of discharge. Our findings promote more insight into physics of the overvoltage open discharge generating the e-beams with energy up to 25 keV.

A collective phase in resource competition in a highly diverse ecosystem

NASA Astrophysics Data System (ADS)

Tikhonov, Mikhail; Monasson, Remi

Recent technological advances uncovered that most habitats, including the human body, harbor hundreds of coexisting microbial ``species''. The problem of understanding such complex communities is currently at the forefront of medical and environmental sciences. A particularly intriguing question is whether the high-diversity regime (large number of species N) gives rise to qualitatively novel phenomena that could not be intuited from analysis of low-dimensional models (with few species). However, few existing approaches allow studying this regime, except in simulations. Here, we use methods of statistical physics to show that the large- N limit of a classic ecological model of resource competition introduced by MacArthur in 1969 can be solved analytically. Our results provide a tractable model where the implications of large dimensionality of eco-evolutionary problems can be investigated. In particular, we show that at high diversity, the MacArthur model exhibits a phase transition into a curious regime where the environment constructed by the community becomes a collective property, insensitive to the external conditions such as the total resource influx supplied to the community. Supported by Harvard Center of Mathematical Sciences and Applications, and the Simons Foundation. This work was completed at the Aspen Center for Physics, supported by National Science Foundation Grant PHY-1066293.

Maximizing the thermoelectric performance of topological insulator Bi2Te3 films in the few-quintuple layer regime

NASA Astrophysics Data System (ADS)

Liang, Jinghua; Cheng, Long; Zhang, Jie; Liu, Huijun; Zhang, Zhenyu

2016-04-01

Using first-principles calculations and the Boltzmann theory, we explore the feasibility to maximize the thermoelectric figure of merit (ZT) of topological insulator Bi2Te3 films in the few-quintuple layer regime. We discover that the delicate competitions between the surface and bulk contributions, coupled with the overall quantum size effects, lead to a novel and generic non-monotonous dependence of ZT on the film thickness. In particular, when the system crosses into the topologically non-trivial regime upon increasing the film thickness, the much longer surface relaxation time associated with the robust nature of the topological surface states results in a maximal ZT value, which can be further optimized to ~2.0 under physically realistic conditions. We also reveal the appealing potential of bridging the long-standing ZT asymmetry of p- and n-type Bi2Te3 systems.Using first-principles calculations and the Boltzmann theory, we explore the feasibility to maximize the thermoelectric figure of merit (ZT) of topological insulator Bi2Te3 films in the few-quintuple layer regime. We discover that the delicate competitions between the surface and bulk contributions, coupled with the overall quantum size effects, lead to a novel and generic non-monotonous dependence of ZT on the film thickness. In particular, when the system crosses into the topologically non-trivial regime upon increasing the film thickness, the much longer surface relaxation time associated with the robust nature of the topological surface states results in a maximal ZT value, which can be further optimized to ~2.0 under physically realistic conditions. We also reveal the appealing potential of bridging the long-standing ZT asymmetry of p- and n-type Bi2Te3 systems. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00724d

Herschel survey and modelling of externally-illuminated photoevaporating protoplanetary disks.

PubMed

Champion, J; Berné, O; Vicente, S; Kamp, I; Le Petit, F; Gusdorf, A; Joblin, C; Goicoechea, J R

2017-08-01

Protoplanetary disks undergo substantial mass-loss by photoevaporation, a mechanism which is crucial to their dynamical evolution. However, the processes regulating the gas energetics have not been well constrained by observations so far. We aim at studying the processes involved in disk photoevaporation when it is driven by far-UV photons (i.e. 6 < E < 13.6 eV). We present a unique Herschel survey and new ALMA observations of four externally-illuminated photoevaporating disks (a.k.a. proplyds). For the analysis of these data, we developed a 1D model of the photodissociation region (PDR) of a proplyd, based on the Meudon PDR code and we computed the far infrared line emission. With this model, we successfully reproduce most of the observations and derive key physical parameters, i.e. densities at the disk surface of about 10 6 cm -3 and local gas temperatures of about 1000 K. Our modelling suggests that all studied disks are found in a transitional regime resulting from the interplay between several heating and cooling processes that we identify. These differ from those dominating in classical PDRs i.e. grain photo-electric effect and cooling by [OI] and [CII] FIR lines. This specific energetic regime is associated to an equilibrium dynamical point of the photoevaporation flow: the mass-loss rate is self-regulated to keep the envelope column density at a value that maintains the temperature at the disk surface around 1000 K. From the physical parameters derived from our best-fit models, we estimate mass-loss rates - of the order of 10 -7 M ⊙ /yr - that are in agreement with earlier spectroscopic observation of ionised gas tracers. This holds only if we assume photoevaporation in the supercritical regime where the evaporation flow is launched from the disk surface at sound speed. We have identified the energetic regime regulating FUV-photoevaporation in proplyds. This regime could be implemented into models of the dynamical evolution of protoplanetary disks.

Photoelectron circular dichroism in different ionization regimes

NASA Astrophysics Data System (ADS)

Wollenhaupt, Matthias

2016-12-01

Photoelectron circular dichroism (PECD) describes an asymmetry in the photoelectron angular distribution (PAD) from photoionization of randomly oriented enantiomers with circularly polarized light. Beaulieu et al present a comprehensive set of measured PADs from multiphoton ionization of limonene and fenchone in different ionization regimes (multiphoton and tunneling) and analyze the resulting PECD (Beaulieu et al 2016 New J. Phys. 18 102002). From their observations the authors conclude that the PECD is universal in the sense that the molecular chirality is encoded in the PAD independent of the ionization regime. The analysis is supplemented by a classical model based on electron scattering in a chiral potential. The paper presents beautiful data and is an important step towards a more complete physical picture of PECD. The results and their interpretation stimulate the ongoing vivid debate on the role of resonances in multiphoton PECD.

Nondiffusive transport regimes for suprathermal ions in turbulent plasmas

NASA Astrophysics Data System (ADS)

Bovet, A.; Fasoli, A.; Ricci, P.; Furno, I.; Gustafson, K.

2015-04-01

The understanding of the transport of suprathermal ions in the presence of turbulence is important for fusion plasmas in the burning regime that will characterize reactors, and for space plasmas to understand the physics of particle acceleration. Here, three-dimensional measurements of a suprathermal ion beam in the toroidal plasma device TORPEX are presented. These measurements demonstrate, in a turbulent plasma, the existence of subdiffusive and superdiffusive transport of suprathermal ions, depending on their energy. This result stems from the unprecedented combination of uniquely resolved measurements and first-principles numerical simulations that reveal the mechanisms responsible for the nondiffusive transport. The transport regime is determined by the interaction of the suprathermal ion orbits with the turbulent plasma dynamics, and is strongly affected by the ratio of the suprathermal ion energy to the background plasma temperature.

Amplification through chaotic synchronization in spatially extended beam-plasma systems

NASA Astrophysics Data System (ADS)

Moskalenko, Olga I.; Frolov, Nikita S.; Koronovskii, Alexey A.; Hramov, Alexander E.

2017-12-01

In this paper, we have studied the relationship between chaotic synchronization and microwave signal amplification in coupled beam-plasma systems. We have considered a 1D particle-in-cell numerical model of unidirectionally coupled beam-plasma oscillatory media being in the regime of electron pattern formation. We have shown the significant gain of microwave oscillation power in coupled beam-plasma media being in the different regimes of generation. The discovered effect has a close connection with the chaotic synchronization phenomenon, so we have observed that amplification appears after the onset of the complete time scale synchronization regime in the analyzed coupled spatially extended systems. We have also provided the numerical study of physical processes in the chain of beam-plasma systems leading to the chaotic synchronization and the amplification of microwave oscillations power, respectively.

Physical habitat predictors of Manayunkia speciosa distribution in the Klamath River and implications for management of Ceratomyxa shasta, a parasite with a complex life cycle

NASA Astrophysics Data System (ADS)

Jordan, M. S.; Alexander, J. D.; Grant, G. E.; Bartholomew, J. L.

2011-12-01

Management strategies for parasites with complex life cycles may target not the parasite itself, but one of the alternate hosts. One approach is to decrease habitat for the alternate host, and in river systems flow manipulations may be employed. Two-dimensional hydraulic models can be powerful tools for predicting the relationship between flow alterations and changes in physical habit, however they require a rigorous definition of physical habitat for the organism of interest. We present habitat characterization data for the case of the alternate host of a salmonid parasite and introduce how it will be used in conjunction with a 2-dimensional hydraulic model. Ceratomyxa shasta is a myxozoan parasite of salmonids that requires a freshwater polychaete Manayunkia speciosa to complete its life cycle. Manayunkia speciosa is a small (3mm) benthic filter-feeding worm that attaches itself perpendicularly to substrate through construction of a flexible tube. In the Klamath River, CA/OR, C. shasta causes significant juvenile salmon mortality, imposing social and economic losses on commercial, sport and tribal fisheries. An interest in manipulating habitat for the polychaete host to decrease the abundance of C. shasta has therefore developed. Unfortunately, there are limited data on the habitat requirements of M. speciosa or the influence of streamflow regime and hydraulics on population dynamics and infection prevalence. This work aims to address these data needs by identifying physical habitat variables that influence the distribution of M. speciosa and determining the relationship between those variables, M. speciosa population density, and C. shasta infection prevalence. Biological samples were collected from nine sites representing three river features (runs, pools, and eddies) within the Klamath River during the summer and fall of 2010 and 2011. Environmental data including depth, velocity, and substrate, were collected at each polychaete sampling location. We tested for differences in environmental variables and polychaete densities among months and river features. Preliminary data suggest differences in density among months and river features as well as relationships among density and water velocity and substrate type. Polychaetes are currently being assayed for C. shasta infection, which will ultimately be included in our analyses. The data will subsequently be used in conjunction with a 2-dimensional hydraulic model to evaluate habitat stability and the influence of varied streamflow senarios.

Minimal string theories and integrable hierarchies

NASA Astrophysics Data System (ADS)

Iyer, Ramakrishnan

Well-defined, non-perturbative formulations of the physics of string theories in specific minimal or superminimal model backgrounds can be obtained by solving matrix models in the double scaling limit. They provide us with the first examples of completely solvable string theories. Despite being relatively simple compared to higher dimensional critical string theories, they furnish non-perturbative descriptions of interesting physical phenomena such as geometrical transitions between D-branes and fluxes, tachyon condensation and holography. The physics of these theories in the minimal model backgrounds is succinctly encoded in a non-linear differential equation known as the string equation, along with an associated hierarchy of integrable partial differential equations (PDEs). The bosonic string in (2,2m-1) conformal minimal model backgrounds and the type 0A string in (2,4 m) superconformal minimal model backgrounds have the Korteweg-de Vries system, while type 0B in (2,4m) backgrounds has the Zakharov-Shabat system. The integrable PDE hierarchy governs flows between backgrounds with different m. In this thesis, we explore this interesting connection between minimal string theories and integrable hierarchies further. We uncover the remarkable role that an infinite hierarchy of non-linear differential equations plays in organizing and connecting certain minimal string theories non-perturbatively. We are able to embed the type 0A and 0B (A,A) minimal string theories into this single framework. The string theories arise as special limits of a rich system of equations underpinned by an integrable system known as the dispersive water wave hierarchy. We find that there are several other string-like limits of the system, and conjecture that some of them are type IIA and IIB (A,D) minimal string backgrounds. We explain how these and several other string-like special points arise and are connected. In some cases, the framework endows the theories with a non-perturbative definition for the first time. Notably, we discover that the Painleve IV equation plays a key role in organizing the string theory physics, joining its siblings, Painleve I and II, whose roles have previously been identified in this minimal string context. We then present evidence that the conjectured type II theories have smooth non-perturbative solutions, connecting two perturbative asymptotic regimes, in a 't Hooft limit. Our technique also demonstrates evidence for new minimal string theories that are not apparent in a perturbative analysis.

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

Zieb, Kristofer James Ekhart; Hughes, Henry Grady III; Xu, X. George

The release of version 6.2 of the MCNP6 radiation transport code is imminent. To complement the newest release, a summary of the heavy charged particle physics models used in the 1 MeV to 1 GeV energy regime is presented. Several changes have been introduced into the charged particle physics models since the merger of the MCNP5 and MCNPX codes into MCNP6. Here, this article discusses the default models used in MCNP6 for continuous energy loss, energy straggling, and angular scattering of heavy charged particles. Explanations of the physics models’ theories are included as well.

Development of students' interest in particle physics as effect of participating in a Masterclass

NASA Astrophysics Data System (ADS)

Gedigk, Kerstin; Pospiech, Gesche

2016-05-01

The International Hands On Particle Physics Masterclasses are enjoying increasing popularity worldwide every year. In Germany a national program was brought to live in 2010, which offers these appreciated events to whole classes or courses of high school students all over the year. These events were evaluated concerning the issues of students' interest in particle physics and their perception of the events. How several interest variables interact with each other and the perception of the events is answered by structural equation modelling (sect. 5.2). The results give information about the events' effects on the students' interest development in particle physics, show which event features are important ( e.g. the authenticity) and give information about practical approaches to improve the effects of the Masterclasses. Section 5.3 deals with a group of participants which have a high interest in particle physics 6-8 weeks after the participation. The number of these students is remarkable large, with 26% of all participants. The investigation of this group shows that the Masterclass participation has the same positive effect on both sexes and all levels of physics education.

The diagnostics of ultra-short pulse laser-produced plasma

NASA Astrophysics Data System (ADS)

Roth, Markus

2011-09-01

Since the invention of the laser, coherent light has been used to break down solid or gaseous material and transform it into a plasma. Over the last three decades two things have changed. Due to multiple advancements and design of high power lasers it is now possible to increase the electric and magnetic field strength that pushed the electron motion towards the regime of relativistic plasma physics. Moreover, due to the short pulse duration of the driving laser the underlying physics has become so transient that concepts like thermal equilibrium (even a local one) or spatial isotropy start to fail. Consequently short pulse laser-driven plasmas have become a rich source of new phenomena that we are just about beginning to explore. Such phenomena, like particle acceleration, nuclear laser-induced reactions, the generation of coherent secondary radiation ranging from THz to high harmonics and the production of attosecond pulses have excited an enormous interest in the study of short pulse laser plasmas. The diagnostics of such ultra-short pulse laser plasmas is a challenging task that involves many and different techniques compared to conventional laser-produced plasmas. While this review cannot cover the entire field of diagnostics that has been developed over the last years, we will try to give a summarizing description of the most important techniques that are currently being used.

Orbital angular momentum light frequency conversion and interference with quasi-phase matching crystals.

PubMed

Zhou, Zhi-Yuan; Ding, Dong-Sheng; Jiang, Yun-Kun; Li, Yan; Shi, Shuai; Wang, Xi-Shi; Shi, Bao-Sen

2014-08-25

Light with helical phase structures, carrying quantized orbital angular momentum (OAM), has many applications in both classical and quantum optics, such as high-capacity optical communications and quantum information processing. Frequency conversion is a basic technique to expand the frequency range of the fundamental light. The frequency conversion of OAM-carrying light gives rise to new physics and applications such as up-conversion detection of images and generation of high dimensional OAM entanglements. Quasi-phase matching (QPM) nonlinear crystals are good candidates for frequency conversion, particularly due to their high-valued effective nonlinear coefficients and no walk-off effect. Here we report the first experimental second-harmonic generation (SHG) of an OAM-carried light with a QPM crystal, where a UV light with OAM of 100 ℏ is generated. OAM conservation is verified using a specially designed interferometer. With a pump beam carrying an OAM superposition of opposite sign, we observe interesting interference phenomena in the SHG light; specifically, a photonics gear-like structure is obtained that gives direct evidence of OAM conservation, which will be very useful for ultra-sensitive angular measurements. Besides, we also develop a theory to reveal the underlying physics of the phenomena. The methods and theoretical analysis shown here are also applicable to other frequency conversion processes, such as sum frequency generation and difference-frequency generation, and may also be generalized to the quantum regime for single photons.

An internet survey of the characteristics and physical activity of community-dwelling Australian adults with acquired brain injury: Exploring interest in an internet-delivered self-management program focused on physical activity.

PubMed

Jones, Taryn M; Dean, Catherine M; Dear, Blake F; Hush, Julia M; Titov, Nickolai

2016-01-01

Individuals with acquired brain injury (ABI) are more likely to be physically inactive and experience barriers to accessing services to address inactivity. This study was designed to guide the development of an internet-delivered self-management program to increase physical activity after ABI. The aims of this study were to examine the current physical activity status of community-dwelling Australian adults with ABI, the barriers to physical activity they experience and to explore interest an internet-delivered self-management program aimed at increasing physical activity. An online survey of Australian adults with ABI was used to collect information about demographic characteristics; general health; emotional well-being; mobility and physical activity status, and satisfaction; barriers to physical activity; confidence in overcoming barriers, and; interest in an internet self-management program. Data were analyzed descriptively and correlational analyses examined relationships between variables. Data were analyzed from 59 respondents. Over half were not satisfied with their current physical activity status. The most frequently reported barriers were pain/discomfort, fatigue and fear, and confidence to overcome these barriers was very low. Interest in an internet-delivered self-management program was high (74%) and not related to the amount of physical activity, satisfaction with physical activity and mobility status or total number of barriers. Australian adults with ABI are not satisfied with their activity levels and experience barriers in maintaining their physical activity levels. Participants were interested in accessing an internet-delivered self-management program aimed at improving physical activity levels. Therefore such a program warrants development and evaluation. Copyright © 2016 Elsevier Inc. All rights reserved.

Competitive Modes for the Detection of Chaotic Parameter Regimes in the General Chaotic Bilinear System of Lorenz Type

NASA Astrophysics Data System (ADS)

Mallory, Kristina; van Gorder, Robert A.

We study chaotic behavior of solutions to the bilinear system of Lorenz type developed by Celikovsky and Vanecek [1994] through an application of competitive modes. This bilinear system of Lorenz type is one possible canonical form holding the Lorenz equation as a special case. Using a competitive modes analysis, which is a completely analytical method allowing one to identify parameter regimes for which chaos may occur, we are able to demonstrate a number of parameter regimes which admit a variety of distinct chaotic behaviors. Indeed, we are able to draw some interesting conclusions which relate the behavior of the mode frequencies arising from writing the state variables for the Celikovsky-Vanecek model as coupled oscillators, and the types of emergent chaotic behaviors observed. The competitive modes analysis is particularly useful if all but one of the model parameters are fixed, and the remaining free parameter is used to modify the chaos observed, in a manner analogous to a bifurcation parameter. Through a thorough application of the method, we are able to identify several parameter regimes which give new dynamics (such as specific forms of chaos) which were not observed or studied previously in the Celikovsky-Vanecek model. Therefore, the results demonstrate the advantage of the competitive modes approach for detecting new parameter regimes leading to chaos in third-order dynamical systems.

Phenological Versus Meteorological Controls on Land-atmosphere Water and Carbon Fluxes

NASA Technical Reports Server (NTRS)

Puma, Michael J.; Koster, Randal D.; Cook, Benjamin I.

2013-01-01

Phenological dynamics and their related processes strongly constrain land-atmosphere interactions, but their relative importance vis-à-vis meteorological forcing within general circulation models (GCMs) is still uncertain. Using an off-line land surface model, we evaluate leaf area and meteorological controls on gross primary productivity, evapotranspiration, transpiration, and runoff at four North American sites, representing different vegetation types and background climates. Our results demonstrate that compared to meteorological controls, variation in leaf area has a dominant control on gross primary productivity, a comparable but smaller influence on transpiration, a weak influence on total evapotranspiration, and a negligible impact on runoff. Climate regime and characteristic variations in leaf area have important modulating effects on these relative controls, which vary depending on the fluxes and timescales of interest. We find that leaf area in energylimited evaporative regimes tends to exhibit greater control on annual gross primary productivity than in moisture-limited regimes, except when vegetation exhibits little interannual variation in leaf area. For transpiration, leaf area control is somewhat less in energylimited regimes and greater in moisture-limited regimes for maximum pentad and annual fluxes. These modulating effects of climate and leaf area were less clear for other fluxes and at other timescales. Our findings are relevant to land-atmosphere coupling in GCMs, especially considering that leaf area variations are a fundamental element of land use and land cover change simulations.

Deep Time Ecosystem Engineers: The Correlation between Palaeozoic Vegetation, Evolution of Physical Riverine Habitats, and Plant and Animal Terrestrialization

NASA Astrophysics Data System (ADS)

Davies, N. S.; Gibling, M. R.

2012-04-01

Evidence from the deep time geological record attests to the fundamental importance of plant life to the construction of physical habitats within fluvial environments. Data from an extensive literature review and original fieldwork has demonstrated that many landforms and geomorphic features present in modern river systems do not appear in the deep time stratigraphic record until terrestrial vegetation had adopted certain evolutionary advances that enabled them: for example, stable point bars are associated with the development of deep rooting in the Siluro-Devonian and avulsive anabranching fluvial systems appear at the same time as extensive arborescent vegetation in the Carboniferous. In this presentation, we demonstrate a correlation between the diversification of physical fluvial sedimentary environments and the expansion of terrestrial fauna and flora throughout the Cambrian to Carboniferous, and offer an explanation for this observation that considers plants as ecosystem engineers on an evolutionary timescale. Many extrinsic factors have been considered when attempting to identify controls on the evolutionary timelines of terrestrialization for various different organisms. Factors such as O2 and CO2 levels in the atmosphere, climatic events, global tectonic organisation, sea-level changes, extinction events, weathering rates and nutrient supply are all known to have played a role. However, another factor is likely to have been a fundamental prerequisite for achieving terrestrial biodiversity: the variety of physical habitats available for newly evolved organisms. In fluvial environments, this is a function of the diversity of hydrodynamic regimes (both temporal and spatial) within the world's river systems. In a world where only sheet-like ephemeral braided rivers existed, such as appears to be the case in pre-vegetation settings, both the geographic extent of riparian margins and the diversity of hydrodynamic regimes would be minimal. However, as fluvial corridors narrowed throughout the Ordovician and Silurian, the potential importance of riparian zones as a global biome would have increased as they became more extensive in continental environments. Furthermore, the move towards climatic controls on the ephemeral or perennial nature of streams would have boosted the diversity of temporally diverse hydrodynamic regimes. As single-thread meandering channels and extensive muddy floodplains, stabilised by vegetation, became significant components of the global suite of alluvial geomorphic components throughout the Siluro-Devonian, further diversification of the extent and diversity of physical habitats within the global riparian biome occurred. Into the Carboniferous, the evolution of the anabranching habit within alluvial systems created further new physical landforms for colonization and would have promoted increasingly complex hyporheic flow regimes. Furthermore the associated advent of arborescent vegetation and, specifically, the large woody debris supplied by this, would have created a wealth of new microhabitats for continental organisms. The expanding extent and diversity of physical alluvial niches during the Palaeozoic can be argued to be an underappreciated driver of the terrestrialization of early continental life. The study of the deep time fossil and stratigraphic record also illustrates that vegetation is a fundamental prerequisite for the creation of biogeomorphic alluvial landforms and physical habitats and microhabitats.

Heat dissipation in the quasiballistic regime studied using the Boltzmann equation in the spatial frequency domain

DOE PAGES

Hua, Chengyun; Minnich, Austin J.

2018-01-10

Quasiballistic heat conduction, in which some phonons propagate ballistically over a thermal gradient, has recently become of intense interest. Most works report that the thermal resistance associated with nanoscale heat sources is far larger than predicted by Fourier's law; however, recent experiments show that in certain cases the difference is negligible despite the heaters being far smaller than phonon mean-free paths. In this work, we examine how thermal resistance depends on the heater geometry using analytical solutions of the Boltzmann equation. We show that the spatial frequencies of the heater pattern play the key role in setting the thermal resistancemore » rather than any single geometric parameter, and that for many geometries the thermal resistance in the quasiballistic regime is no different than the Fourier prediction. We further demonstrate that the spectral distribution of the heat source also plays a major role in the resulting transport, unlike in the diffusion regime. Our work provides an intuitive link between the heater geometry, spectral heating distribution, and the effective thermal resistance in the quasiballistic regime, a finding that could impact strategies for thermal management in electronics and other applications.« less

Thermodynamics of the mesoscopic thermoelectric heat engine beyond the linear-response regime.

PubMed

Yamamoto, Kaoru; Hatano, Naomichi

2015-10-01

Mesoscopic thermoelectric heat engine is much anticipated as a device that allows us to utilize with high efficiency wasted heat inaccessible by conventional heat engines. However, the derivation of the heat current in this engine seems to be either not general or described too briefly, even inappropriately in some cases. In this paper, we give a clear-cut derivation of the heat current of the engine with suitable assumptions beyond the linear-response regime. It resolves the confusion in the definition of the heat current in the linear-response regime. After verifying that we can construct the same formalism as that of the cyclic engine, we find the following two interesting results within the Landauer-Büttiker formalism: the efficiency of the mesoscopic thermoelectric engine reaches the Carnot efficiency if and only if the transmission probability is finite at a specific energy and zero otherwise; the unitarity of the transmission probability guarantees the second law of thermodynamics, invalidating Benenti et al.'s argument in the linear-response regime that one could obtain a finite power with the Carnot efficiency under a broken time-reversal symmetry [Phys. Rev. Lett. 106, 230602 (2011)]. These results demonstrate how quantum mechanics constrains thermodynamics.

Heat dissipation in the quasiballistic regime studied using the Boltzmann equation in the spatial frequency domain

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

Hua, Chengyun; Minnich, Austin J.

Quasiballistic heat conduction, in which some phonons propagate ballistically over a thermal gradient, has recently become of intense interest. Most works report that the thermal resistance associated with nanoscale heat sources is far larger than predicted by Fourier's law; however, recent experiments show that in certain cases the difference is negligible despite the heaters being far smaller than phonon mean-free paths. In this work, we examine how thermal resistance depends on the heater geometry using analytical solutions of the Boltzmann equation. We show that the spatial frequencies of the heater pattern play the key role in setting the thermal resistancemore » rather than any single geometric parameter, and that for many geometries the thermal resistance in the quasiballistic regime is no different than the Fourier prediction. We further demonstrate that the spectral distribution of the heat source also plays a major role in the resulting transport, unlike in the diffusion regime. Our work provides an intuitive link between the heater geometry, spectral heating distribution, and the effective thermal resistance in the quasiballistic regime, a finding that could impact strategies for thermal management in electronics and other applications.« less

Micro/Nano-pore Network Analysis of Gas Flow in Shale Matrix

PubMed Central

Zhang, Pengwei; Hu, Liming; Meegoda, Jay N.; Gao, Shengyan

2015-01-01

The gas flow in shale matrix is of great research interests for optimized shale gas extraction. The gas flow in the nano-scale pore may fall in flow regimes such as viscous flow, slip flow and Knudsen diffusion. A 3-dimensional nano-scale pore network model was developed to simulate dynamic gas flow, and to describe the transient properties of flow regimes. The proposed pore network model accounts for the various size distributions and low connectivity of shale pores. The pore size, pore throat size and coordination number obey normal distribution, and the average values can be obtained from shale reservoir data. The gas flow regimes were simulated using an extracted pore network backbone. The numerical results show that apparent permeability is strongly dependent on pore pressure in the reservoir and pore throat size, which is overestimated by low-pressure laboratory tests. With the decrease of reservoir pressure, viscous flow is weakening, then slip flow and Knudsen diffusion are gradually becoming dominant flow regimes. The fingering phenomenon can be predicted by micro/nano-pore network for gas flow, which provides an effective way to capture heterogeneity of shale gas reservoir. PMID:26310236

Micro/Nano-pore Network Analysis of Gas Flow in Shale Matrix.

PubMed

Zhang, Pengwei; Hu, Liming; Meegoda, Jay N; Gao, Shengyan

2015-08-27

The gas flow in shale matrix is of great research interests for optimized shale gas extraction. The gas flow in the nano-scale pore may fall in flow regimes such as viscous flow, slip flow and Knudsen diffusion. A 3-dimensional nano-scale pore network model was developed to simulate dynamic gas flow, and to describe the transient properties of flow regimes. The proposed pore network model accounts for the various size distributions and low connectivity of shale pores. The pore size, pore throat size and coordination number obey normal distribution, and the average values can be obtained from shale reservoir data. The gas flow regimes were simulated using an extracted pore network backbone. The numerical results show that apparent permeability is strongly dependent on pore pressure in the reservoir and pore throat size, which is overestimated by low-pressure laboratory tests. With the decrease of reservoir pressure, viscous flow is weakening, then slip flow and Knudsen diffusion are gradually becoming dominant flow regimes. The fingering phenomenon can be predicted by micro/nano-pore network for gas flow, which provides an effective way to capture heterogeneity of shale gas reservoir.

Amazing Physics: Learning about Work, Energy and Projectile Motion in a Historical Context

ERIC Educational Resources Information Center

Tural, Guner

2013-01-01

Teaching physics through a historical context provides effective learning and increases students' motivation for and interest in physics. For example, trebuchets and mangonels may be interesting historical contexts for learning about energy, work, and projectile motion. In this study, the implementation of physics lessons related to these subjects…

The fluid mechanics of thrombus formation

NASA Technical Reports Server (NTRS)

1972-01-01

Experimental data are presented for the growth of thrombi (blood clots) in a stagnation point flow of fresh blood. Thrombus shape, size and structure are shown to depend on local flow conditions. The evolution of a thrombus is described in terms of a physical model that includes platelet diffusion, a platelet aggregation mechanism, and diffusion and convection of the chemical species responsible for aggregation. Diffusion-controlled and convection-controlled regimes are defined by flow parameters and thrombus location, and the characteristic growth pattern in each regime is explained. Quantitative comparisons with an approximate theoretical model are presented, and a more general model is formulated.

Core plasma design of the compact helical reactor with a consideration of the equipartition effect

NASA Astrophysics Data System (ADS)

Goto, T.; Miyazawa, J.; Yanagi, N.; Tamura, H.; Tanaka, T.; Sakamoto, R.; Suzuki, C.; Seki, R.; Satake, S.; Nunami, M.; Yokoyama, M.; Sagara, A.; the FFHR Design Group

2018-07-01

Integrated physics analysis of plasma operation scenario of the compact helical reactor FFHR-c1 has been conducted. The DPE method, which predicts radial profiles in a reactor by direct extrapolation from the reference experimental data, has been extended to implement the equipartition effect. Close investigation of the plasma operation regime has been conducted and a candidate plasma operation point of FFHR-c1 has been identified within the parameter regime that has already been confirmed in LHD experiment in view of MHD equilibrium, MHD stability and neoclassical transport.

Atomic physics effects on tokamak edge drift-tearing modes

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

Hahm, T.S.

1993-03-01

The effects of ionization and charge exchange on the linear stability of drift-tearing modes are analytically investigated. In particular, the linear instability threshold {Delta}{sup Th}, produced by ion sound wave coupling is modified. In the strongly collisional regime, the ionization breaks up the near cancellation of the perturbed electric field and the pressure gradient along the magnetic field, and increases the threshold. In the semi-collisional regime, both ionization and charge exchange act as drag on the ion parallel velocity, and consequently decrease the threshold by reducing the effectiveness of ion sound wave propagation.

Atomic physics effects on tokamak edge drift-tearing modes

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

Hahm, T.S.

1993-03-01

The effects of ionization and charge exchange on the linear stability of drift-tearing modes are analytically investigated. In particular, the linear instability threshold [Delta][sup Th], produced by ion sound wave coupling is modified. In the strongly collisional regime, the ionization breaks up the near cancellation of the perturbed electric field and the pressure gradient along the magnetic field, and increases the threshold. In the semi-collisional regime, both ionization and charge exchange act as drag on the ion parallel velocity, and consequently decrease the threshold by reducing the effectiveness of ion sound wave propagation.

Foundational Principles for Large-Scale Inference: Illustrations Through Correlation Mining

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

Hero, Alfred O.; Rajaratnam, Bala

When can reliable inference be drawn in the ‘‘Big Data’’ context? This article presents a framework for answering this fundamental question in the context of correlation mining, with implications for general large-scale inference. In large-scale data applications like genomics, connectomics, and eco-informatics, the data set is often variable rich but sample starved: a regime where the number n of acquired samples (statistical replicates) is far fewer than the number p of observed variables (genes, neurons, voxels, or chemical constituents). Much of recent work has focused on understanding the computational complexity of proposed methods for ‘‘Big Data.’’ Sample complexity, however, hasmore » received relatively less attention, especially in the setting when the sample size n is fixed, and the dimension p grows without bound. To address this gap, we develop a unified statistical framework that explicitly quantifies the sample complexity of various inferential tasks. Sampling regimes can be divided into several categories: 1) the classical asymptotic regime where the variable dimension is fixed and the sample size goes to infinity; 2) the mixed asymptotic regime where both variable dimension and sample size go to infinity at comparable rates; and 3) the purely high-dimensional asymptotic regime where the variable dimension goes to infinity and the sample size is fixed. Each regime has its niche but only the latter regime applies to exa-scale data dimension. We illustrate this high-dimensional framework for the problem of correlation mining, where it is the matrix of pairwise and partial correlations among the variables that are of interest. Correlation mining arises in numerous applications and subsumes the regression context as a special case. We demonstrate various regimes of correlation mining based on the unifying perspective of high-dimensional learning rates and sample complexity for different structured covariance models and different inference tasks.« less

Foundational Principles for Large-Scale Inference: Illustrations Through Correlation Mining

PubMed Central

Hero, Alfred O.; Rajaratnam, Bala

2015-01-01

When can reliable inference be drawn in fue “Big Data” context? This paper presents a framework for answering this fundamental question in the context of correlation mining, wifu implications for general large scale inference. In large scale data applications like genomics, connectomics, and eco-informatics fue dataset is often variable-rich but sample-starved: a regime where the number n of acquired samples (statistical replicates) is far fewer than fue number p of observed variables (genes, neurons, voxels, or chemical constituents). Much of recent work has focused on understanding the computational complexity of proposed methods for “Big Data”. Sample complexity however has received relatively less attention, especially in the setting when the sample size n is fixed, and the dimension p grows without bound. To address fuis gap, we develop a unified statistical framework that explicitly quantifies the sample complexity of various inferential tasks. Sampling regimes can be divided into several categories: 1) the classical asymptotic regime where fue variable dimension is fixed and fue sample size goes to infinity; 2) the mixed asymptotic regime where both variable dimension and sample size go to infinity at comparable rates; 3) the purely high dimensional asymptotic regime where the variable dimension goes to infinity and the sample size is fixed. Each regime has its niche but only the latter regime applies to exa cale data dimension. We illustrate this high dimensional framework for the problem of correlation mining, where it is the matrix of pairwise and partial correlations among the variables fua t are of interest. Correlation mining arises in numerous applications and subsumes the regression context as a special case. we demonstrate various regimes of correlation mining based on the unifying perspective of high dimensional learning rates and sample complexity for different structured covariance models and different inference tasks. PMID:27087700

Foundational Principles for Large-Scale Inference: Illustrations Through Correlation Mining

DOE PAGES

Hero, Alfred O.; Rajaratnam, Bala

2015-12-09

When can reliable inference be drawn in the ‘‘Big Data’’ context? This article presents a framework for answering this fundamental question in the context of correlation mining, with implications for general large-scale inference. In large-scale data applications like genomics, connectomics, and eco-informatics, the data set is often variable rich but sample starved: a regime where the number n of acquired samples (statistical replicates) is far fewer than the number p of observed variables (genes, neurons, voxels, or chemical constituents). Much of recent work has focused on understanding the computational complexity of proposed methods for ‘‘Big Data.’’ Sample complexity, however, hasmore » received relatively less attention, especially in the setting when the sample size n is fixed, and the dimension p grows without bound. To address this gap, we develop a unified statistical framework that explicitly quantifies the sample complexity of various inferential tasks. Sampling regimes can be divided into several categories: 1) the classical asymptotic regime where the variable dimension is fixed and the sample size goes to infinity; 2) the mixed asymptotic regime where both variable dimension and sample size go to infinity at comparable rates; and 3) the purely high-dimensional asymptotic regime where the variable dimension goes to infinity and the sample size is fixed. Each regime has its niche but only the latter regime applies to exa-scale data dimension. We illustrate this high-dimensional framework for the problem of correlation mining, where it is the matrix of pairwise and partial correlations among the variables that are of interest. Correlation mining arises in numerous applications and subsumes the regression context as a special case. We demonstrate various regimes of correlation mining based on the unifying perspective of high-dimensional learning rates and sample complexity for different structured covariance models and different inference tasks.« less

Hydrogen technology survey: Thermophysical properties

NASA Technical Reports Server (NTRS)

Mccarty, R. D.

1975-01-01

The thermodynamic functions, transport properties, and physical properties of both liquid and gaseous hydrogen are presented. The low temperature regime is emphasized. The tabulation of the properties of normal hydrogen in both Si and engineering units is given along with the tabulation of parahydrogen.

At the Very Root of the Development of Interest: Using Human Body Contexts to Improve Women's Emotional Engagement in Introductory Physics

ERIC Educational Resources Information Center

Allaire-Duquette, Geneviève; Charland, Patrick; Riopel, Martin

2014-01-01

In physics, women find contexts concerning human biology, medical applications, or natural phenomena highly relevant (Hoffmann, 2002), and the rareness or absence of these in physics curricula may make it more difficult for women to develop and maintain their interest in physics. To date, research in physics education addressing student's…

Discussion of production logging as an integral part of horizontal-well transient-pressure test

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

Babu, D.K.; Odeh, A.S.

1994-09-01

Ahmed and Badry discussed the identification of flow regimes for a horizontal well. The well produces from an infinitely extending slab-like reservoir of finite thickness. The system allows a top and bottom boundary. Reference 1 indicates the possible existence of two early radial-flow periods and illustrates them in Figures. Kuchuk et al., and Daviau give the theoretical basis for the existence of such flow regimes. The flow is essentially 2D and in vertical planes. The authors agree that a second early radial-flow period could exist from a strictly theoretical viewpoint. However, certain important physical constraints, which were not explicitly mentionedmore » in the above works, must be met before it can occur and for a reliable and valid analysis of the pressure data. The authors will show that the second early radial-flow regime could exist only if the well were extremely close to a no-flow boundary and they quantify extremely close. Hence, an engineer must use extreme caution in conducting pressure analysis on the basis of a second early radial-flow regime.« less

Collisional effects on the numerical recurrence in Vlasov-Poisson simulations

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

Pezzi, Oreste; Valentini, Francesco; Camporeale, Enrico

The initial state recurrence in numerical simulations of the Vlasov-Poisson system is a well-known phenomenon. Here, we study the effect on recurrence of artificial collisions modeled through the Lenard-Bernstein operator [A. Lenard and I. B. Bernstein, Phys. Rev. 112, 1456–1459 (1958)]. By decomposing the linear Vlasov-Poisson system in the Fourier-Hermite space, the recurrence problem is investigated in the linear regime of the damping of a Langmuir wave and of the onset of the bump-on-tail instability. The analysis is then confirmed and extended to the nonlinear regime through an Eulerian collisional Vlasov-Poisson code. It is found that, despite being routinely used,more » an artificial collisionality is not a viable way of preventing recurrence in numerical simulations without compromising the kinetic nature of the solution. Moreover, it is shown how numerical effects associated to the generation of fine velocity scales can modify the physical features of the system evolution even in nonlinear regime. This means that filamentation-like phenomena, usually associated with low amplitude fluctuations contexts, can play a role even in nonlinear regime.« less

The study of pinch regimes based on radiation-enhanced compression and anomalous resistivity phenomena and their effects on hard x-ray emission in a Mather type dense plasma focus device (SABALAN2)

NASA Astrophysics Data System (ADS)

Piriaei, D.; Mahabadi, T. D.; Javadi, S.; Ghoranneviss, M.; Saw, S. H.; Lee, S.

2015-12-01

In this study, by using argon and nitrogen as the filling gases in a Mather type dense plasma focus device at different values of pressure and charging voltage, two different kinds of pinch regimes were observed for each of the gases. The physics of the pinch regimes could be explained by using the two versions of the Lee's computational model which predicted each of the scenarios and clarified their differences between the two gases according to the radiation-enhanced compression and, additionally, predicted the pinch regimes through the anomalous resistivity effect during the pinch time. This was accomplished through the fitting process (simulation) on the current signal. Moreover, the characteristic amplitude and time scales of the anomalous resistances were obtained. The correlations between the features of the plasma current dip and the emitted hard x-ray pulses were observed. The starting time, intensity, duration, and the multiple or single feature of the emitted hard x-ray strongly correlated to the same respective features of the current dip.

Ultrastrong coupling of a single artificial atom to an electromagnetic continuum in the nonperturbative regime

NASA Astrophysics Data System (ADS)

Forn-Díaz, P.; García-Ripoll, J. J.; Peropadre, B.; Orgiazzi, J.-L.; Yurtalan, M. A.; Belyansky, R.; Wilson, C. M.; Lupascu, A.

2017-01-01

The study of light-matter interaction has led to important advances in quantum optics and enabled numerous technologies. Over recent decades, progress has been made in increasing the strength of this interaction at the single-photon level. More recently, a major achievement has been the demonstration of the so-called strong coupling regime, a key advancement enabling progress in quantum information science. Here, we demonstrate light-matter interaction over an order of magnitude stronger than previously reported, reaching the nonperturbative regime of ultrastrong coupling (USC). We achieve this using a superconducting artificial atom tunably coupled to the electromagnetic continuum of a one-dimensional waveguide. For the largest coupling, the spontaneous emission rate of the atom exceeds its transition frequency. In this USC regime, the description of atom and light as distinct entities breaks down, and a new description in terms of hybrid states is required. Beyond light-matter interaction itself, the tunability of our system makes it a promising tool to study a number of important physical systems, such as the well-known spin-boson and Kondo models.

Airbreathing combined cycle engine systems

NASA Technical Reports Server (NTRS)

Rohde, John

1992-01-01

The Air Force and NASA share a common interest in developing advanced propulsion systems for commercial and military aerospace vehicles which require efficient acceleration and cruise operation in the Mach 4 to 6 flight regime. The principle engine of interest is the turboramjet; however, other combined cycles such as the turboscramjet, air turborocket, supercharged ejector ramjet, ejector ramjet, and air liquefaction based propulsion are also of interest. Over the past months careful planning and program implementation have resulted in a number of development efforts that will lead to a broad technology base for those combined cycle propulsion systems. Individual development programs are underway in thermal management, controls materials, endothermic hydrocarbon fuels, air intake systems, nozzle exhaust systems, gas turbines and ramjet ramburners.

Analytical solutions by squeezing to the anisotropic Rabi model in the nonperturbative deep-strong-coupling regime

NASA Astrophysics Data System (ADS)

Zhang, Yu-Yu; Chen, Xiang-You

2017-12-01

An unexplored nonperturbative deep strong coupling (npDSC) achieved in superconducting circuits has been studied in the anisotropic Rabi model by the generalized squeezing rotating-wave approximation. Energy levels are evaluated analytically from the reformulated Hamiltonian and agree well with numerical ones in a wide range of coupling strength. Such improvement ascribes to deformation effects in the displaced-squeezed state presented by the squeezed momentum variance, which are omitted in previous displaced states. The atom population dynamics confirms the validity of our approach for the npDSC strength. Our approach offers the possibility to explore interesting phenomena analytically in the npDSC regime in qubit-oscillator experiments.

Droplet states in quantum XXZ spin systems on general graphs

NASA Astrophysics Data System (ADS)

Fischbacher, C.; Stolz, G.

2018-05-01

We study XXZ spin systems on general graphs. In particular, we describe the formation of droplet states near the bottom of the spectrum in the Ising phase of the model, where the Z-term dominates the XX-term. As key tools, we use particle number conservation of XXZ systems and symmetric products of graphs with their associated adjacency matrices and Laplacians. Of particular interest to us are strips and multi-dimensional Euclidean lattices, for which we discuss the existence of spectral gaps above the droplet regime. We also prove a Combes-Thomas bound which shows that the eigenstates in the droplet regime are exponentially small perturbations of strict (classical) droplets.

Damping of coupled harmonic oscillators

NASA Astrophysics Data System (ADS)

Dolfo, Gilles; Vigué, Jacques

2018-03-01

When two harmonic oscillators are coupled in the presence of damping, their dynamics exhibit two very different regimes depending on the relative magnitude of the coupling and damping terms At resonance, when the coupling has its largest effect, if the coupling dominates the damping, there is a periodic exchange of energy between the two oscillators while, in the opposite case, the energy transfer from one oscillator to the other one is irreversible. We prove that the border between these two regimes goes through an exceptional point and we briefly explain what is an exceptional point. The present paper is written for undergraduate students, with some knowledge in classical mechanics, but it may also be of interest for graduate students.

Decoherence-induced conductivity in the one-dimensional Anderson model

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

Stegmann, Thomas; Wolf, Dietrich E.; Ujsághy, Orsolya

We study the effect of decoherence on the electron transport in the one-dimensional Anderson model by means of a statistical model [1, 2, 3, 4, 5]. In this model decoherence bonds are randomly distributed within the system, at which the electron phase is randomized completely. Afterwards, the transport quantity of interest (e.g. resistance or conductance) is ensemble averaged over the decoherence configurations. Averaging the resistance of the sample, the calculation can be performed analytically. In the thermodynamic limit, we find a decoherence-driven transition from the quantum-coherent localized regime to the Ohmic regime at a critical decoherence density, which is determinedmore » by the second-order generalized Lyapunov exponent (GLE) [4].« less

Quantum Behavior of an Autonomous Maxwell Demon

NASA Astrophysics Data System (ADS)

Chapman, Adrian; Miyake, Akimasa

2015-03-01

A Maxwell Demon is an agent that can exploit knowledge of a system's microstate to perform useful work. The second law of thermodynamics is only recovered upon taking into account the work required to irreversibly update the demon's memory, bringing information theoretic concepts into a thermodynamic framework. Recently, there has been interest in modeling a classical Maxwell demon as an autonomous physical system to study this information-work tradeoff explicitly. Motivated by the idea that states with non-local entanglement structure can be used as a computational resource, we ask whether these states have thermodynamic resource quality as well by generalizing a particular classical autonomous Maxwell demon to the quantum regime. We treat the full quantum description using a matrix product operator formalism, which allows us to handle quantum and classical correlations in a unified framework. Applying this, together with techniques from statistical mechanics, we are able to approximate nonlocal quantities such as the erasure performed on the demon's memory register when correlations are present. Finally, we examine how the demon may use these correlations as a resource to outperform its classical counterpart.

Density matrix renormalization group study of a three-orbital Hubbard model with spin-orbit coupling in one dimension

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

Kaushal, Nitin; Herbrych, Jacek W.; Nocera, Alberto

Using the density matrix renormalization group technique we study the effect of spin-orbit coupling on a three-orbital Hubbard model in the (t 2g) 4 sector and in one dimension. Fixing the Hund coupling to a robust value compatible with some multiorbital materials, we present the phase diagram varying the Hubbard U and spin-orbit coupling λ, at zero temperature. Our results are shown to be qualitatively similar to those recently reported using the dynamical mean-field theory in higher dimensions, providing a robust basis to approximate many-body techniques. Among many results, we observe an interesting transition from an orbital-selective Mott phase tomore » an excitonic insulator with increasing λ at intermediate U. In the strong U coupling limit, we find a nonmagnetic insulator with an effective angular momentum <(J eff) 2>≠0 near the excitonic phase, smoothly connected to the <(J eff) 2>=0 regime. In conclusion, we also provide a list of quasi-one-dimensional materials where the physics discussed in this paper could be realized.« less

Density matrix renormalization group study of a three-orbital Hubbard model with spin-orbit coupling in one dimension

NASA Astrophysics Data System (ADS)

Kaushal, Nitin; Herbrych, Jacek; Nocera, Alberto; Alvarez, Gonzalo; Moreo, Adriana; Reboredo, F. A.; Dagotto, Elbio

2017-10-01

Using the density matrix renormalization group technique we study the effect of spin-orbit coupling on a three-orbital Hubbard model in the (t2g) 4 sector and in one dimension. Fixing the Hund coupling to a robust value compatible with some multiorbital materials, we present the phase diagram varying the Hubbard U and spin-orbit coupling λ , at zero temperature. Our results are shown to be qualitatively similar to those recently reported using the dynamical mean-field theory in higher dimensions, providing a robust basis to approximate many-body techniques. Among many results, we observe an interesting transition from an orbital-selective Mott phase to an excitonic insulator with increasing λ at intermediate U . In the strong U coupling limit, we find a nonmagnetic insulator with an effective angular momentum 〈(Jeff)2〉≠0 near the excitonic phase, smoothly connected to the 〈(Jeff)2〉=0 regime. We also provide a list of quasi-one-dimensional materials where the physics discussed in this paper could be realized.

Environmental chemistry at vapor/water interfaces: insights from vibrational sum frequency generation spectroscopy.

PubMed

Jubb, Aaron M; Hua, Wei; Allen, Heather C

2012-01-01

The chemistry that occurs at surfaces has been an intense area of study for many years owing to its complexity and importance in describing a wide range of physical phenomena. The vapor/water interface is particularly interesting from an environmental chemistry perspective as this surface plays host to a wide range of chemistries that influence atmospheric and geochemical interactions. The application of vibrational sum frequency generation (VSFG), an inherently surface-specific, even-order nonlinear optical spectroscopy, enables the direct interrogation of various vapor/aqueous interfaces to elucidate the behavior and reaction of chemical species within the surface regime. In this review we discuss the application of VSFG to the study of a variety of atmospherically important systems at the vapor/aqueous interface. Chemical systems presented include inorganic ionic solutions prevalent in aqueous marine aerosols, small molecular solutes, and long-chain fatty acids relevant to fat-coated aerosols. The ability of VSFG to probe both the organization and reactions that may occur for these systems is highlighted. A future perspective toward the application of VSFG to the study of environmental interfaces is also provided.

Density matrix renormalization group study of a three-orbital Hubbard model with spin-orbit coupling in one dimension

DOE PAGES

Kaushal, Nitin; Herbrych, Jacek W.; Nocera, Alberto; ...

2017-10-09

Using the density matrix renormalization group technique we study the effect of spin-orbit coupling on a three-orbital Hubbard model in the (t 2g) 4 sector and in one dimension. Fixing the Hund coupling to a robust value compatible with some multiorbital materials, we present the phase diagram varying the Hubbard U and spin-orbit coupling λ, at zero temperature. Our results are shown to be qualitatively similar to those recently reported using the dynamical mean-field theory in higher dimensions, providing a robust basis to approximate many-body techniques. Among many results, we observe an interesting transition from an orbital-selective Mott phase tomore » an excitonic insulator with increasing λ at intermediate U. In the strong U coupling limit, we find a nonmagnetic insulator with an effective angular momentum <(J eff) 2>≠0 near the excitonic phase, smoothly connected to the <(J eff) 2>=0 regime. In conclusion, we also provide a list of quasi-one-dimensional materials where the physics discussed in this paper could be realized.« less

ClassLess: A Comprehensive Database of Young Stellar Objects

NASA Astrophysics Data System (ADS)

Hillenbrand, Lynne A.; baliber, nairn

2015-08-01

We have designed and constructed a database intended to house catalog and literature-published measurements of Young Stellar Objects (YSOs) within ~1 kpc of the Sun. ClassLess, so called because it includes YSOs in all stages of evolution, is a relational database in which user interaction is conducted via HTML web browsers, queries are performed in scientific language, and all data are linked to the sources of publication. Each star is associated with a cluster (or clusters), and both spatially resolved and unresolved measurements are stored, allowing proper use of data from multiple star systems. With this fully searchable tool, myriad ground- and space-based instruments and surveys across wavelength regimes can be exploited. In addition to primary measurements, the database self consistently calculates and serves higher level data products such as extinction, luminosity, and mass. As a result, searches for young stars with specific physical characteristics can be completed with just a few mouse clicks. We are in the database population phase now, and are eager to engage with interested experts worldwide on local galactic star formation and young stellar populations.

Beller Lecture: The Roots of Leo Szilard and his Interdisciplinarity

NASA Astrophysics Data System (ADS)

Marx, George

1998-04-01

A Central European among the whites was said about Leo Szilard who originated from a polycultural family. In the early 20th century he grew up in Hungary, at the crossroads of history, where political regimes, national borders, ideological doctrines, ``final truths'' changed in a dizzying cavalcade. Instead of conservative dogmatism this social environment required critical thinking in order to survive. World War I was the school of Theodore von Kármán, John von Neumann, Eugene P. Wigner and Leo Szilard; each of them learned trespassing political and disciplinary boundaries without inhibition. Their sensitivity for trends had been utilized by the United States when war efforts and high tech required orientation under new horizons. Szilard's interest ranged from statistical physics through information theory to biological evolution, from life phenomena through hot atoms to nuclear strategy. His intellectual adventures might look crazy jumps for specialists. But now, looking back to the political and technological history of the 20th century one can see than it was a consequent progress of a future-sensitive mind.

Role of nuclear charge change and nuclear recoil on shaking processes and their possible implication on physical processes

NASA Astrophysics Data System (ADS)

Sharma, Prashant

2017-12-01

The probable role of the sudden nuclear charge change and nuclear recoil in the shaking processes during the neutron- or heavy-ion-induced nuclear reactions and weakly interacting massive particle-nucleus scattering has been investigated in the present work. Using hydrogenic wavefunctions, general analytical expressions of survival, shakeup/shakedown, and shakeoff probability have been derived for various subshells of hydrogen-like atomic systems. These expressions are employed to calculate the shaking, shakeup/shakedown, and shakeoff probabilities in some important cases of interest in the nuclear astrophysics and the dark matter search experiments. The results underline that the shaking processes are one of the probable channels of electronic transitions during the weakly interacting massive particle-nucleus scattering, which can be used to probe the dark matter in the sub-GeV regime. Further, it is found that the shaking processes initiating due to nuclear charge change and nuclear recoil during the nuclear reactions may influence the electronic configuration of the participating atomic systems and thus may affect the nuclear reaction measurements at astrophysically relevant energies.

Relativistically strong electromagnetic radiation in a plasma

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

Bulanov, S. V., E-mail: svbulanov@gmail.com, E-mail: bulanov.sergei@jaea.go.jp; Esirkepov, T. Zh.; Kando, M.

Physical processes in a plasma under the action of relativistically strong electromagnetic waves generated by high-power lasers have been briefly reviewed. These processes are of interest in view of the development of new methods for acceleration of charged particles, creation of sources of bright hard electromagnetic radiation, and investigation of macroscopic quantum-electrodynamical processes. Attention is focused on nonlinear waves in a laser plasma for the creation of compact electron accelerators. The acceleration of plasma bunches by the radiation pressure of light is the most efficient regime of ion acceleration. Coherent hard electromagnetic radiation in the relativistic plasma is generated inmore » the form of higher harmonics and/or electromagnetic pulses, which are compressed and intensified after reflection from relativistic mirrors created by nonlinear waves. In the limit of extremely strong electromagnetic waves, radiation friction, which accompanies the conversion of radiation from the optical range to the gamma range, fundamentally changes the behavior of the plasma. This process is accompanied by the production of electron–positron pairs, which is described within quantum electrodynamics theory.« less

Study of radiative heat transfer in Ångström- and nanometre-sized gaps

DOE PAGES

Cui, Longji; Jeong, Wonho; Fernández-Hurtado, Víctor; ...

2017-02-15

Radiative heat transfer in Ångström- and nanometre-sized gaps is of great interest because of both its technological importance and open questions regarding the physics of energy transfer in this regime. Here in this paper we report studies of radiative heat transfer in few Å to 5nm gap sizes, performed under ultrahigh vacuum conditions between a Au-coated probe featuring embedded nanoscale thermocouples and a heated planar Au substrate that were both subjected to various surface-cleaning procedures. By drawing on the apparent tunnelling barrier height as a signature of cleanliness, we found that upon systematically cleaning via a plasma or locally pushingmore » the tip into the substrate by a few nanometres, the observed radiative conductances decreased from unexpectedly large values to extremely small ones—below the detection limit of our probe—as expected from our computational results. Our results show that it is possible to avoid the confounding effects of surface contamination and systematically study thermal radiation in Ångström- and nanometre-sized gaps.« less

Connection between Fermi contours of zero-field electrons and ν =1/2 composite fermions in two-dimensional systems

NASA Astrophysics Data System (ADS)

Ippoliti, Matteo; Geraedts, Scott D.; Bhatt, R. N.

2017-07-01

We investigate the relation between the Fermi sea (FS) of zero-field carriers in two-dimensional systems and the FS of the corresponding composite fermions which emerge in a high magnetic field at filling ν =1/2 , as the kinetic energy dispersion is varied. We study cases both with and without rotational symmetry and find that there is generally no straightforward relation between the geometric shapes and topologies of the two FSs. In particular, we show analytically that the composite Fermi liquid (CFL) is completely insensitive to a wide range of changes to the zero-field dispersion which preserve rotational symmetry, including ones that break the zero-field FS into multiple disconnected pieces. In the absence of rotational symmetry, we show that the notion of "valley pseudospin" in many-valley systems is generically not transferred to the CFL, in agreement with experimental observations. We also discuss how a rotationally symmetric band structure can induce a reordering of the Landau levels, opening interesting possibilities of observing higher-Landau-level physics in the high-field regime.

Simulation of the AC corona phenomenon with experimental validation

NASA Astrophysics Data System (ADS)

Villa, Andrea; Barbieri, Luca; Marco, Gondola; Malgesini, Roberto; Leon-Garzon, Andres R.

2017-11-01

The corona effect, and in particular the Trichel phenomenon, is an important aspect of plasma physics with many technical applications, such as pollution reduction, surface and medical treatments. This phenomenon is also associated with components used in the power industry where it is, in many cases, the source of electro-magnetic disturbance, noise and production of undesired chemically active species. Despite the power industry to date using mainly alternating current (AC) transmission, most of the studies related to the corona effect have been carried out with direct current (DC) sources. Therefore, there is technical interest in validating numerical codes capable of simulating the AC phenomenon. In this work we describe a set of partial differential equations that are comprehensive enough to reproduce the distinctive features of the corona in an AC regime. The model embeds some selectable chemical databases, comprising tens of chemical species and hundreds of reactions, the thermal dynamics of neutral species and photoionization. A large set of parameters—deduced from experiments and numerical estimations—are compared, to assess the effectiveness of the proposed approach.

Measurement Matrix Design for Phase Retrieval Based on Mutual Information

NASA Astrophysics Data System (ADS)

Shlezinger, Nir; Dabora, Ron; Eldar, Yonina C.

2018-01-01

In phase retrieval problems, a signal of interest (SOI) is reconstructed based on the magnitude of a linear transformation of the SOI observed with additive noise. The linear transform is typically referred to as a measurement matrix. Many works on phase retrieval assume that the measurement matrix is a random Gaussian matrix, which, in the noiseless scenario with sufficiently many measurements, guarantees invertability of the transformation between the SOI and the observations, up to an inherent phase ambiguity. However, in many practical applications, the measurement matrix corresponds to an underlying physical setup, and is therefore deterministic, possibly with structural constraints. In this work we study the design of deterministic measurement matrices, based on maximizing the mutual information between the SOI and the observations. We characterize necessary conditions for the optimality of a measurement matrix, and analytically obtain the optimal matrix in the low signal-to-noise ratio regime. Practical methods for designing general measurement matrices and masked Fourier measurements are proposed. Simulation tests demonstrate the performance gain achieved by the proposed techniques compared to random Gaussian measurements for various phase recovery algorithms.

Testing universality of Efimov Physics based on a mass-imbalanced Li-Cs mixture

NASA Astrophysics Data System (ADS)

Johansen, Jacob; Desalvo, Brian; Patel, Krutik; Chin, Cheng

2017-04-01

Efimov states are notable for their universal geometric scaling and are observable in ultracold atomic systems employing magnetic Feshbach resonances. In addition to geometric scaling, which we observed previously by taking advantage of a reduced Efimov scaling constant in our mass imbalanced 6Li-133Cs system, an interesting pattern has emerged in Efimov measurements: while expected to be non-universal, the absolute positions of Efimov resonances appear to scale simply with van der Waals length. Theories attempting to explain this observation have predicted a dependence on the strength of the Feshbach resonance for narrow resonances, yet experiments attempting to probe this regime have so far been inconsistent with the predicted dependence. In this talk, we focus primarily on our recent measurements showing dependence on Feshbach resonance strength. We directly compare two Feshbach resonances, one broad and one very narrow, which are nearly identical with the exception of the resonance strength, and find a striking difference in the first Efimov resonance position. Our measurement makes significant strides toward resolving the discrepancy between experiment and theory which exists in the field today.

Quantum information processing by weaving quantum Talbot carpets

NASA Astrophysics Data System (ADS)

Farías, Osvaldo Jiménez; de Melo, Fernando; Milman, Pérola; Walborn, Stephen P.

2015-06-01

Single-photon interference due to passage through a periodic grating is considered in a novel proposal for processing D -dimensional quantum systems (quDits) encoded in the spatial degrees of freedom of light. We show that free-space propagation naturally implements basic single-quDit gates by means of the Talbot effect: an intricate time-space carpet of light in the near-field diffraction regime. By adding a diagonal phase gate, we show that a complete set of single-quDit gates can be implemented. We then introduce a spatially dependent beam splitter that allows for projective measurements in the computational basis and can be used for the implementation of controlled operations between two quDits. Universal quantum information processing can then be implemented with linear optics and ancilla photons via postselection and feed-forward following the original proposal of Knill-Laflamme and Milburn. Although we consider photons, our scheme should be directly applicable to a number of other physical systems. Interpretation of the Talbot effect as a quantum logic operation provides a beautiful and interesting way to visualize quantum computation through wave propagation and interference.

Modeling drain current of indium zinc oxide thin film transistors prepared by solution deposition technique

NASA Astrophysics Data System (ADS)

Qiang, Lei; Liang, Xiaoci; Cai, Guangshuo; Pei, Yanli; Yao, Ruohe; Wang, Gang

2018-06-01

Indium zinc oxide (IZO) thin film transistor (TFT) deposited by solution method is of considerable technological interest as it is a key component for the fabrication of flexible and cheap transparent electronic devices. To obtain a principal understanding of physical properties of solution-processed IZO TFT, a new drain current model that account for the charge transport is proposed. The formulation is developed by incorporating the effect of gate voltage on mobility and threshold voltage with the carrier charges. It is demonstrated that in IZO TFTs the below threshold regime should be divided into two sections: EC - EF > 3kT and EC - EF ≤ 3kT, where kT is the thermal energy, EF and EC represent the Fermi level and the conduction band edge, respectively. Additionally, in order to describe conduction mechanisms more accurately, the extended mobility edge model is conjoined, which can also get rid of the complicated and lengthy computations. The good agreement between measured and calculated results confirms the efficiency of this model for the design of integrated large-area thin film circuits.

NUMERICAL SIMULATIONS OF KELVIN–HELMHOLTZ INSTABILITY: A TWO-DIMENSIONAL PARAMETRIC STUDY

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

Tian, Chunlin; Chen, Yao, E-mail: chunlin.tian@sdu.edu.cn

2016-06-10

Using two-dimensional simulations, we numerically explore the dependences of Kelvin–Helmholtz (KH) instability upon various physical parameters, including viscosity, the width of the sheared layer, flow speed, and magnetic field strength. In most cases, a multi-vortex phase exists between the initial growth phase and the final single-vortex phase. The parametric study shows that the evolutionary properties, such as phase duration and vortex dynamics, are generally sensitive to these parameters, except in certain regimes. An interesting result is that for supersonic flows, the phase durations and saturation of velocity growth approach constant values asymptotically as the sonic Mach number increases. We confirmmore » that the linear coupling between magnetic field and KH modes is negligible if the magnetic field is weak enough. The morphological behavior suggests that the multi-vortex coalescence might be driven by the underlying wave–wave interaction. Based on these results, we present a preliminary discussion of several events observed in the solar corona. The numerical models need to be further improved to perform a practical diagnostic of the coronal plasma properties.« less

Training, Muscle Fatigue, and Stress Fractures

DTIC Science & Technology

1988-07-15

fractures in the lower appendicular skeleton of new recruits. During peacetime, stress fractures are by far the most co~m~n physical injury in the...research program is to study the etiology of the stress fracture lesion, and isolate any aspects of a physical regime which may exacerbate this...34 of remodelLig, to use the model to identify those areas of the cortex at greatest risk of failure, and the activities which accelerate the deleterious

Numerical modeling of flow focusing: Quantitative characterization of the flow regimes

NASA Astrophysics Data System (ADS)

Mamet, V.; Namy, P.; Dedulle, J.-M.

2017-09-01

Among droplet generation technologies, the flow focusing technique is a major process due to its control, stability, and reproducibility. In this process, one fluid (the continuous phase) interacts with another one (the dispersed phase) to create small droplets. Experimental assays in the literature on gas-liquid flow focusing have shown that different jet regimes can be obtained depending on the operating conditions. However, the underlying physical phenomena remain unclear, especially mechanical interactions between the fluids and the oscillation phenomenon of the liquid. In this paper, based on published studies, a numerical diphasic model has been developed to take into consideration the mechanical interaction between phases, using the Cahn-Hilliard method to monitor the interface. Depending on the liquid/gas inputs and the geometrical parameters, various regimes can be obtained, from a steady state regime to an unsteady one with liquid oscillation. In the dispersed phase, the model enables us to compute the evolution of fluid flow, both in space (size of the recirculation zone) and in time (period of oscillation). The transition between unsteady and stationary regimes is assessed in relation to liquid and gas dimensionless numbers, showing the existence of critical thresholds. This model successfully highlights, qualitatively and quantitatively, the influence of the geometry of the nozzle, in particular, its inner diameter.

General slip regime permeability model for gas flow through porous media

NASA Astrophysics Data System (ADS)

Zhou, Bo; Jiang, Peixue; Xu, Ruina; Ouyang, Xiaolong

2016-07-01

A theoretical effective gas permeability model was developed for rarefied gas flow in porous media, which holds over the entire slip regime with the permeability derived as a function of the Knudsen number. This general slip regime model (GSR model) is derived from the pore-scale Navier-Stokes equations subject to the first-order wall slip boundary condition using the volume-averaging method. The local closure problem for the volume-averaged equations is studied analytically and numerically using a periodic sphere array geometry. The GSR model includes a rational fraction function of the Knudsen number which leads to a limit effective permeability as the Knudsen number increases. The mechanism for this behavior is the viscous fluid inner friction caused by converging-diverging flow channels in porous media. A linearization of the GSR model leads to the Klinkenberg equation for slightly rarefied gas flows. Finite element simulations show that the Klinkenberg model overestimates the effective permeability by as much as 33% when a flow approaches the transition regime. The GSR model reduces to the unified permeability model [F. Civan, "Effective correlation of apparent gas permeability in tight porous media," Transp. Porous Media 82, 375 (2010)] for the flow in the slip regime and clarifies the physical significance of the empirical parameter b in the unified model.

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

Greenly, John B.; Seyler, Charles

Experimental and computational studies of high energy density plasma streams ablated from fine wires. Laboratory of Plasma Studies, School of Electrical and Computer Engineering, Cornell University. Principal Investigators: Dr. John B. Greenly and Dr. Charles E. Seyler. This report summarizes progress during the final year of this project to study the physics of high energy density (HED) plasma streams of 10^17-10^20/cm3 density and high velocity (~100-500 km/s). Such streams are produced from 5-250 micrometer diameter wires heated and ionized by a 1 MA, 250 ns current pulse on the COBRA pulsed power facility at Cornell University. Plasma is ablated frommore » the wires and is driven away to high velocity by unbalanced JxB force. A wire, or an array of wires, can persist as an essentially stationary, continuous source of this streaming plasma for >200 ns, even with driving magnetic fields of many Tesla and peak current densities in the plasma of many MA/cm2. At the heart of the ablation stream generation is the continuous transport of mass from the relatively cold, near-solid-density wire "core" into current-carrying plasma within 1 mm of the wire, followed by the magnetic acceleration of that plasma and its trapped flux to form a directed stream. In the first two years of this program, an advancing understanding of ablation physics led to the discovery of several novel wire ablation experimental regimes. In the final year, one of these new HED plasma regimes has been studied in quantitative detail. This regime studies highly reproducible magnetic reconnection in strongly radiating plasma with supersonic and superalfvenic flow, and shock structures in the outflow. The key discovery is that very heavy wires, e.g. 250 micrometer diameter Al or 150 micrometer Cu, behave in a qualitatively different way than the lighter wires typically used in wire-array Z-pinches. Such wires can be configured to produce a static magnetic X-point null geometry that stores magnetic and thermal energy; reconnection and outflow are triggered when the current begins to decrease and the electric field reverses. The reconnecting flow is driven by both magnetic and thermal pressure forces, and it has been found to be possible to vary the configuration so that one or the other dominates. The magnetic null extends into a current sheet that is heated and radiates strongly, with supersonic outflows. This is the first study of reconnection in this HED plasma regime. This compressible, radiative regime, and the triggering mechanism, may be relevant to solar and astrophysical processes. The PERSEUS extended MHD code has been developed for simulation of these phenomena, and will continue to be used and further developed to help interpret and understand experimental results, as well as to guide experimental design. The code is well-suited to simulations of shocks, and includes Hall and electron inertia physics that appear to be of importance in a number of ablation flow regimes, and definitely in the reconnection regime when gradient scales are comparable to the ion inertial scale. During the final year, our graduate student supported by this grant completed a new version of PERSEUS with the finite volume computational scheme replaced by a discontinuous Galerkin method that gives much less diffusive behavior and allows faster run time and higher spatial resolution. Thecode is now being used to study shock structures produced in the outflow region of the reconnection regime.« less

Electronic transport in graphene: p-n junctions, shot noise, and nanoribbons

NASA Astrophysics Data System (ADS)

Williams, James Ryan

2009-12-01

Novel, two-dimensional materials have allowed for the inception and elucidation of a plethora of physical phenomena. On such material, a hexagonal lattice of carbon atoms called graphene, is a unique, truly two-dimensional molecular conductor. This thesis describes six experiments that elucidate some interesting physical properties and technological applications of graphene, with an emphasis on graphene-based p-n junctions. A technique for the creation of high-quality p-n junctions of graphene is described. Transport measurements at zero magnetic field demonstrate local control of the carrier type and density bipolar graphene-based junctions. In the quantum Hall regime, new plateaus in the conductance are observed and explained in terms of mode mixing at the p-n interface. Shot noise in unipolar and bipolar graphene devices is measured. A density-independent Fano factor is observed, contrary to theoretical expectations. Further, an independence on device geometry is also observed. The role of disorder on the measured Fano factor is discussed, and comparison to recent theory for disordered graphene is made. The effect of a two-terminal geometry, where the device aspect ratio is different from unity, is measured experimentally and analyzed theoretically. A method for extracting layer number from the conductance extrema is proposed. A method for a conformal mapping of a device with asymmetric contacts to a rectangle is demonstrated. Finally, possible origins of discrepancies between theory and experiment are discussed. Transport along p-n junctions in graphene is reported. Enhanced transport along the junction is observed and attributed to states that exist at the p-n interface. A correspondence between the observed phenomena at low-field and in the quantum Hall regime is observed. An electric field perpendicular to the junction is found to reduce the enhanced conductance at the p-n junction. A corollary between the p-n interface states and "snake states" in an inhomogeneous magnetic field is proposed and its relationship to the minimum conductivity in graphene is discussed. A final pair of experiments demonstrate how a helium ion microscope can be used to reduce the dimensionality of graphene one further, producing graphene nanoribbons. The effect of etching on transport and doping level of the graphene nanoribbons is discussed.

Deep search for companions to probable young brown dwarfs. VLT/NACO adaptive optics imaging using IR wavefront sensing

NASA Astrophysics Data System (ADS)

Chauvin, G.; Faherty, J.; Boccaletti, A.; Cruz, K.; Lagrange, A.-M.; Zuckerman, B.; Bessell, M. S.; Beuzit, J.-L.; Bonnefoy, M.; Dumas, C.; Lowrance, P.; Mouillet, D.; Song, I.

2012-12-01

Aims: We have obtained high contrast images of four nearby, faint, and very low mass objects 2MASS J04351455-1414468, SDSS J044337.61+000205.1, 2MASS J06085283-2753583 and 2MASS J06524851-5741376 (hereafter 2MASS0435-14, SDSS0443+00, 2MASS0608-27 and 2MASS0652-57), identified in the field as probable isolated young brown dwarfs. Our goal was to search for binary companions down to the planetary mass regime. Methods: We used the NAOS-CONICA adaptive optics instrument (NACO) and its unique capability to sense the wavefront in the near-infrared to acquire sharp images of the four systems in Ks, with a field of view of 28'' × 28''. Additional J and L' imaging and follow-up observations at a second epoch were obtained for 2MASS0652-57. Results: With a typical contrast ΔKs = 4.0-7.0 mag, our observations are sensitive down to the planetary mass regime considering a minimum age of 10 to 120 Myr for these systems. No additional point sources are detected in the environment of 2MASS0435-14, SDSS0443+00 and 2MASS0608-27 between 0.1-12'' (i.e. about 2 to 250 AU at 20 pc). 2MASS0652-57 is resolved as a ~230 mas binary. Follow-up observations reject a background contaminate, resolve the orbital motion of the pair, and confirm with high confidence that the system is physically bound. The J, Ks and L' photometry suggest a q ~ 0.7-0.8 mass ratio binary with a probable semi-major axis of 5-6 AU. Among the four systems, 2MASS0652-57 is probably the less constrained in terms of age determination. Further analysis would be necessary to confirm its youth. It would then be interesting to determine its orbital and physical properties to derive the system's dynamical mass and to test evolutionary model predictions. Based on observations collected at the European Southern Observatory, Chile (ESO programmes 076.C-0554(A), 076.C-0554(B) and 085.C-0257(A).

Insights into big sagebrush seedling storage practices

Treesearch

Emily C. Overton; Jeremiah R. Pinto; Anthony S. Davis

2013-01-01

Big sagebrush (Artemisia tridentata Nutt. [Asteraceae]) is an essential component of shrub-steppe ecosystems in the Great Basin of the US, where degradation due to altered fire regimes, invasive species, and land use changes have led to increased interest in the production of high-quality big sagebrush seedlings for conservation and restoration projects. Seedling...

EFFECTS OF FLOOD PULSES ON NITRIFICATION RATES IN UPPER MISSISSIPPI RIVER FORESTED FLOODPLAINS, 2ND PRESENTATION IN 2007

EPA Science Inventory

Presentation is designed to enlighten the interested masses about potentials in nutrient trading and ecosystem services in our great river floodplain ecosystems. It is not intended for policy, rather to stimulate thought on the importance of natural flooding regimes and how to b...

Overview of U.S. Legislation and Regulations Affecting Offshore Natural Gas and Oil Activity

EIA Publications

2005-01-01

This article presents a summary of the legislative and regulatory regime that affects natural gas and oil exploration and production in offshore regions of the United States. It discusses the role and importance of these areas as well as the competing interests surrounding ownership, production, exploration and conservation.

Nonlinear optics in organic cavity polaritons (Conference Presentation)

NASA Astrophysics Data System (ADS)

Singer, Kenneth D.; Liu, Bin; Crescimanno, Michael; Twieg, Robert J.

2017-02-01

Coupling between excitons belonging to organic dyes and photons in a microcavities forming cavity polaritons have been receiving attention for their fundamental interest as well as potential applications in coherent light sources. Organic materials are of particular interest as the coupling is particularly strong due to the large oscillator strength of conjugated organic molecules. The resulting coupling in organic materials is routinely in the strong regime. Ultrastrong coupling between photons and excitons in microcavities containing organic dyes and semiconductors has been recently observed in room temperature. We have studied the coupling between cavity pairs in the ultrastrong regime and found that the high order terms in the modified Jaynes-Cummings model result in broken degeneracy between the symmetric and antisymmetric modes. The unusually strong coupling between cavity photons and organic excitons dovetail with the robust nonlinear optical responses of the same materials. This provides a new and promising hybrid material for photonics. We report on measurements of photorefraction in organic cavities containing a derivative of the photorefractive organic glass based on 2-dicyanomethylene-3-cyano-2,5-dihydrofuran (DCDHF).

The Impact of Explicit Teaching of Methodological Aspects of Physics on Scientistic Beliefs and Interest

ERIC Educational Resources Information Center

Korte, Stefan; Berger, Roland; Hänze, Martin

2017-01-01

We assessed the impact of teaching methodological aspects of physics on students' scientistic beliefs and subject interest in physics in a repeated-measurement design with a total of 142 students of upper secondary physics classes. Students gained knowledge of methodological aspects from the pre-test to the post-test and reported reduced…

Teaching the Delightful Laws of Physics in a Survey Course

ERIC Educational Resources Information Center

Hewitt, Paul G.

2015-01-01

How physics can be made interesting is a question that needs no answer. That's because physics is interesting! It's a field of study jam-packed with fascination and wonder. The general public has an enormous thirst for physics knowledge, as indicated by the great numbers who purchase science magazines and books and watch "NOVA" and other…

International Law: How It Affects Rules of Engagement and Responses in Information Warfare

DTIC Science & Technology

1997-03-01

with the least expenditure of life, time, and physical resources. Humanity. Prohibits the employment of any kind or degree of force not necessary...the beginning of warfare, the intent has been to physically and psychologically destroy an adversary. Little consideration was given to the amount of...threat to US security interests. For example, core interests are those interests dealing with the physical survival of a country or directly threatening

Understanding first-year students’ curiosity and interest about physics—lessons learned from the HOPE project

NASA Astrophysics Data System (ADS)

Levrini, Olivia; De Ambrosis, Anna; Hemmer, Sabine; Laherto, Antti; Malgieri, Massimiliano; Pantano, Ornella; Tasquier, Giulia

2017-03-01

This paper focuses on results of an interview based survey of first-year university physics students, carried out within the EU Horizons in Physics Education (HOPE) project (http://hopenetwork.eu/). 94 interviews conducted in 13 universities have been analyzed to investigate the factors that inspire young people to study physics. In particular, the main motivational factor, which was proven to consist of personal interest and curiosity, was unfolded into different categories and detailed interest profiles were produced. The results are arguably useful to help academic curriculum developers and teaching personnel in physics departments to provide guidance to students in developing and focusing their interest towards specific sub-fields and/or to design targeted recruitment and outreach initiatives.

Climate-driven regime shifts in Arctic marine benthos

PubMed Central

Kortsch, Susanne; Primicerio, Raul; Beuchel, Frank; Renaud, Paul E.; Rodrigues, João; Lønne, Ole Jørgen; Gulliksen, Bjørn

2012-01-01

Climate warming can trigger abrupt ecosystem changes in the Arctic. Despite the considerable interest in characterizing and understanding the ecological impact of rapid climate warming in the Arctic, few long time series exist that allow addressing these research goals. During a 30-y period (1980–2010) of gradually increasing seawater temperature and decreasing sea ice cover in Svalbard, we document rapid and extensive structural changes in the rocky-bottom communities of two Arctic fjords. The most striking component of the benthic reorganization was an abrupt fivefold increase in macroalgal cover in 1995 in Kongsfjord and an eightfold increase in 2000 in Smeerenburgfjord. Simultaneous changes in the abundance of benthic invertebrates suggest that the macroalgae played a key structuring role in these communities. The abrupt, substantial, and persistent nature of the changes observed is indicative of a climate-driven ecological regime shift. The ecological processes thought to drive the observed regime shifts are likely to promote the borealization of these Arctic marine communities in the coming years. PMID:22891319

Experimental and Theoretical Investigations on the Nanoscale Kinetic Friction in Ambient Environmental Conditions.

PubMed

Gueye, Birahima; Zhang, Yan; Wang, Yujuan; Chen, Yunfei

2015-07-08

The liquid lubrication, thermolubricity and dynamic lubricity due to mechanical oscillations are investigated with an atomic force microscope in ambient environmental conditions with different relative humidity (RH) levels. Experimental results demonstrate that high humidity at low-temperature regime enhances the liquid lubricity while at high-temperature regime it hinders the effect of the thermolubricity due to the formation of liquid bridges. Friction response to the dynamic lubricity in both high- and low-temperature regimes keeps the same trends, namely the friction force decreases with increasing the amplitude of the applied vibration on the tip regardless of the RH levels. An interesting finding is that for the dynamic lubricity at high temperature, high-humidity condition leads to the friction forces higher than that at low-humidity condition while at low temperature the opposite trend is observed. An extended two-dimensional dynamic model accounting for the RH is proposed to interpret the frictional mechanism in ambient conditions.

Towards biobank privacy regimes in responsible innovation societies: ESBB conference in Granada 2012.

PubMed

Lauss, Georg; Schröder, Christina; Dabrock, Peter; Eder, Johann; Hamacher, Kay; Kuhn, Klaus A; Gottweis, Herbert

2013-10-01

The creation of socially and technically robust biobank privacy regimes presupposes knowledge of and compliance with legal rules, professional standards of the biomedical community, and state-of-the-art data safety and security measures. The strategies in privacy management and data protection presented in this review show a trend that goes beyond searching for compromises or efforts of balancing scientific demands for efficiency and societal demands for effective privacy regimes. They focus on developing synergies that facilitate cooperative use of biomaterials and data and enhance sample search efficiency for researchers on the one hand, and protect rights and interests of donors and citizens on the other hand. Among the issues covered are: a) ethical sensitivities and public perceptions on privacy in biobanking b) tools and procedures that allow maintenance of the rights and dignity of donors, without jeopardizing legitimate information needs of researchers and autonomy of biobanks, and c) a privacy sensitive framework for sharing of data and biomaterials in the research context.

Topical review: spins and mechanics in diamond

NASA Astrophysics Data System (ADS)

Lee, Donghun; Lee, Kenneth W.; Cady, Jeffrey V.; Ovartchaiyapong, Preeti; Bleszynski Jayich, Ania C.

2017-03-01

There has been rapidly growing interest in hybrid quantum devices involving a solid-state spin and a macroscopic mechanical oscillator. Such hybrid devices create exciting opportunities to mediate interactions between disparate quantum bits (qubits) and to explore the quantum regime of macroscopic mechanical objects. In particular, a system consisting of the nitrogen-vacancy defect center (NV center) in diamond coupled to a high-quality-factor mechanical oscillator is an appealing candidate for such a hybrid quantum device, as it utilizes the highly coherent and versatile spin properties of the defect center. In this paper, we will review recent experimental progress on diamond-based hybrid quantum devices in which the spin and orbital dynamics of single defects are driven by the motion of a mechanical oscillator. In addition, we discuss prospective applications for this device, including long-range, phonon-mediated spin-spin interactions, and phonon cooling in the quantum regime. We conclude the review by evaluating the experimental limitations of current devices and identifying alternative device architectures that may reach the strong coupling regime.

Leakage of Microwave Ovens

ERIC Educational Resources Information Center

Abdul-Razzaq, W.; Bushey, R.; Winn, G.

2011-01-01

Physics is essential for students who want to succeed in science and engineering. Excitement and interest in the content matter contribute to enhancing this success. We have developed a laboratory experiment that takes advantage of microwave ovens to demonstrate important physical concepts and increase interest in physics. This experiment…

Exploring load, velocity, and surface disorder dependence of friction with one-dimensional and two-dimensional models.

PubMed

Dagdeviren, Omur E

2018-08-03

The effect of surface disorder, load, and velocity on friction between a single asperity contact and a model surface is explored with one-dimensional and two-dimensional Prandtl-Tomlinson (PT) models. We show that there are fundamental physical differences between the predictions of one-dimensional and two-dimensional models. The one-dimensional model estimates a monotonic increase in friction and energy dissipation with load, velocity, and surface disorder. However, a two-dimensional PT model, which is expected to approximate a tip-sample system more realistically, reveals a non-monotonic trend, i.e. friction is inert to surface disorder and roughness in wearless friction regime. The two-dimensional model discloses that the surface disorder starts to dominate the friction and energy dissipation when the tip and the sample interact predominantly deep into the repulsive regime. Our numerical calculations address that tracking the minimum energy path and the slip-stick motion are two competing effects that determine the load, velocity, and surface disorder dependence of friction. In the two-dimensional model, the single asperity can follow the minimum energy path in wearless regime; however, with increasing load and sliding velocity, the slip-stick movement dominates the dynamic motion and results in an increase in friction by impeding tracing the minimum energy path. Contrary to the two-dimensional model, when the one-dimensional PT model is employed, the single asperity cannot escape to the minimum energy minimum due to constraint motion and reveals only a trivial dependence of friction on load, velocity, and surface disorder. Our computational analyses clarify the physical differences between the predictions of the one-dimensional and two-dimensional models and open new avenues for disordered surfaces for low energy dissipation applications in wearless friction regime.

Dynamics of a spherical particle in an acoustic field: A multiscale approach

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

Xie, Jin-Han, E-mail: J.H.Xie@ed.ac.uk; Vanneste, Jacques

2014-10-15

A rigid spherical particle in an acoustic wave field oscillates at the wave period but has also a mean motion on a longer time scale. The dynamics of this mean motion is crucial for numerous applications of acoustic microfluidics, including particle manipulation and flow visualisation. It is controlled by four physical effects: acoustic (radiation) pressure, streaming, inertia, and viscous drag. In this paper, we carry out a systematic multiscale analysis of the problem in order to assess the relative importance of these effects depending on the parameters of the system that include wave amplitude, wavelength, sound speed, sphere radius, andmore » viscosity. We identify two distinguished regimes characterised by a balance among three of the four effects, and we derive the equations that govern the mean particle motion in each regime. This recovers and organises classical results by King [“On the acoustic radiation pressure on spheres,” Proc. R. Soc. A 147, 212–240 (1934)], Gor'kov [“On the forces acting on a small particle in an acoustical field in an ideal fluid,” Sov. Phys. 6, 773–775 (1962)], and Doinikov [“Acoustic radiation pressure on a rigid sphere in a viscous fluid,” Proc. R. Soc. London A 447, 447–466 (1994)], clarifies the range of validity of these results, and reveals a new nonlinear dynamical regime. In this regime, the mean motion of the particle remains intimately coupled to that of the surrounding fluid, and while viscosity affects the fluid motion, it plays no part in the acoustic pressure. Simplified equations, valid when only two physical effects control the particle motion, are also derived. They are used to obtain sufficient conditions for the particle to behave as a passive tracer of the Lagrangian-mean fluid motion.« less

Wind-driving protostellar accretion discs - I. Formulation and parameter constraints

NASA Astrophysics Data System (ADS)

Königl, Arieh; Salmeron, Raquel; Wardle, Mark

2010-01-01

We study a model of weakly ionized, protostellar accretion discs that are threaded by a large-scale, ordered magnetic field and power a centrifugally driven wind. We consider the limiting case where the wind is the main repository of the excess disc angular momentum and generalize the radially localized disc model of Wardle & Königl, which focused on the ambipolar diffusion regime, to other field diffusivity regimes, notably Hall and Ohm. We present a general formulation of the problem for nearly Keplerian, vertically isothermal discs using both the conductivity-tensor and the multifluid approaches and simplify it to a normalized system of ordinary differential equations in the vertical space coordinate. We determine the relevant parameters of the problem and investigate, using the vertical-hydrostatic-equilibrium approximation and other simplifications, the parameter constraints on physically viable solutions for discs in which the neutral particles are dynamically well coupled to the field already at the mid-plane. When the charged particles constitute a two-component ion-electron plasma, one can identify four distinct sub-regimes in the parameter domain where the Hall diffusivity dominates and three sub-regimes in the Ohm-dominated domain. Two of the Hall sub-regimes can be characterized as being ambipolar diffusion-like and two as being Ohm-like: the properties of one member of the first pair of sub-regimes are identical to those of the ambipolar diffusion regime, whereas one member of the second pair has the same characteristics as one of the Ohm sub-regimes. All the Hall sub-regimes have Brb/|Bφb| (ratio of radial-to-azimuthal magnetic field amplitudes at the disc surface) >1, whereas in two Ohm sub-regimes this ratio is <1. When the two-component plasma consists, instead, of positively and negatively charged grains of equal mass, the entire Hall domain and one of the Ohm sub-regimes with Brb/|Bφb| < 1 disappear. All viable solutions require the mid-plane neutral-ion momentum exchange time to be shorter than the local orbital time. We also infer that vertical magnetic squeezing always dominates over gravitational tidal compression in this model. In a follow-up paper we will present exact solutions that test the results of this analysis in the Hall regime.

Hemodynamic transition driven by stent porosity in sidewall aneurysms.

PubMed

Bouillot, Pierre; Brina, Olivier; Ouared, Rafik; Lovblad, Karl-Olof; Farhat, Mohamed; Pereira, Vitor Mendes

2015-05-01

The healing process of intracranial aneurysms (IAs) treated with flow diverter stents (FDSs) depends on the IA flow modifications and on the epithelization process over the neck. In sidewall IA models with straight parent artery, two main hemodynamic regimes with different flow patterns and IA flow magnitude were broadly observed for unstented and high porosity stented IA on one side, and low porosity stented IA on the other side. The hemodynamic transition between these two regimes is potentially involved in thrombosis formation. In the present study, CFD simulations and multi-time lag (MTL) particle imaging velocimetry (PIV) measurements were combined to investigate the physical nature of this transition. Measurable velocity fields and non-measurable shear stress and pressure fields were assessed experimentally and numerically in the aneurysm volume in the presence of stents with various porosities. The two main regimes observed in both PIV and CFD showed typical flow features of shear and pressure driven regimes. In particular, the waveform of the averaged IA velocities was matching both the shear stress waveform at IA neck or the pressure gradient waveform in parent artery. Moreover, the transition between the two regimes was controlled by stent porosity: a decrease of stent porosity leads to an increase (decrease) of pressure differential (shear stress) through IA neck. Finally, a good PIV-CFD agreement was found except in transitional regimes and low motion eddies due to small mismatch of PIV-CFD running conditions. Copyright © 2015 Elsevier Ltd. All rights reserved.

Transport properties of an asymmetric mixture in the dense plasma regime

DOE PAGES

Ticknor, Christopher; Kress, Joel David; Collins, Lee A.; ...

2016-06-23

Here, we study how concentration changes ionic transport properties along isobars-isotherms for a mixture of hydrogen and silver, representative of turbulent layers relevant to inertial confinement fusion and astrophysics. Hydrogen will typically be fully ionized while silver will be only partially ionized but can have a large effective charge. This will lead to very different physical conditions for the H and Ag. Large first principles orbital free molecular dynamics simulations are performed and the resulting transport properties are analyzed. Comparisons are made with transport theory in the kinetic regime and in the coupled regime. The addition of a small amountmore » of heavy element in a light material has a dramatic effect on viscosity and diffusion of the mixture. This effect is explained through kinetic theory as a manifestation of a crossover between classical diffusion and Lorentz diffusion.« less

Kinetics and thermodynamics of living copolymerization processes.

PubMed

Gaspard, Pierre

2016-11-13

Theoretical advances are reported on the kinetics and thermodynamics of free and template-directed living copolymerizations. Until recently, the kinetic theory of these processes had only been established in the fully irreversible regime, in which the attachment rates are only considered. However, the entropy production is infinite in this regime and the approach to thermodynamic equilibrium cannot be investigated. For this purpose, the detachment rates should also be included. Inspite of this complication, the kinetics can be exactly solved in the regimes of steady growth and depolymerization. In this way, analytical expressions are obtained for the mean growth velocity, the statistical properties of the copolymer sequences, as well as the thermodynamic entropy production. The results apply to DNA replication, transcription and translation, allowing us to understand important aspects of molecular evolution.This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'. © 2016 The Author(s).

Neoclassical quasilinear theory in the superbanana plateau regime and banana kinetics in tokamaks

NASA Astrophysics Data System (ADS)

Shaing, K. C.

2017-12-01

Neoclassical quasilinear transport theory, which is part of a more general theory that unifies neoclassical and quasilinear theories, is extended to the superbanana plateau regime for low frequency (of the order of the drift frequency) electrostatic fluctuations. The physics mechanism that is responsible for the transport losses in this regime is the superbanana plateau resonance. Besides the usual magnetic drifts, Doppler shifted mode frequency also contributes to the resonance condition. Because the characteristic frequency involved in the resonance is of the order of the drift frequency, which is lower than either the bounce or the transit frequency of the particles, the transport losses are higher than the losses calculated in the conventional quasilinear theory. The important effects of the finite banana width, i.e., banana kinetics, are included and are found to reduce the transport losses for short wavelength modes. The implications on the energetic alpha particle energy loss are discussed.

Use of observational and model-derived fields and regime model output statistics in mesoscale forecasting

NASA Technical Reports Server (NTRS)

Forbes, G. S.; Pielke, R. A.

1985-01-01

Various empirical and statistical weather-forecasting studies which utilize stratification by weather regime are described. Objective classification was used to determine weather regime in some studies. In other cases the weather pattern was determined on the basis of a parameter representing the physical and dynamical processes relevant to the anticipated mesoscale phenomena, such as low level moisture convergence and convective precipitation, or the Froude number and the occurrence of cold-air damming. For mesoscale phenomena already in existence, new forecasting techniques were developed. The use of cloud models in operational forecasting is discussed. Models to calculate the spatial scales of forcings and resultant response for mesoscale systems are presented. The use of these models to represent the climatologically most prevalent systems, and to perform case-by-case simulations is reviewed. Operational implementation of mesoscale data into weather forecasts, using both actual simulation output and method-output statistics is discussed.

Kinetics and thermodynamics of living copolymerization processes

NASA Astrophysics Data System (ADS)

Gaspard, Pierre

2016-11-01

Theoretical advances are reported on the kinetics and thermodynamics of free and template-directed living copolymerizations. Until recently, the kinetic theory of these processes had only been established in the fully irreversible regime, in which the attachment rates are only considered. However, the entropy production is infinite in this regime and the approach to thermodynamic equilibrium cannot be investigated. For this purpose, the detachment rates should also be included. Inspite of this complication, the kinetics can be exactly solved in the regimes of steady growth and depolymerization. In this way, analytical expressions are obtained for the mean growth velocity, the statistical properties of the copolymer sequences, as well as the thermodynamic entropy production. The results apply to DNA replication, transcription and translation, allowing us to understand important aspects of molecular evolution. This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'.

Concepts and application of dynamic separation for agility and super-maneuverability of aircraft: An assessment

NASA Technical Reports Server (NTRS)

Freymuth, Peter

1992-01-01

Aims for improvement of fighter aircraft pursued by the unsteady flow community are high agility (the ability of the aircraft to make close turns in a low-speed regime) and super maneuverability (the ability of the aircraft to operate at high angles of attack in a post stall regime during quick maneuvers in a more extended speed range). High agility requires high lift coefficients at low speeds in a dynamic situation and this requirement can be met by dynamically forced separation or by quasistatic stall control. The competing methods will be assessed based on the known physics. Maneuvering into the post stall regime also involves dynamic separation but because even fast maneuvers involving the entire aircraft are 'aerodynamically slow' the resulting dynamic vortex structures should be considered 'elicited' rather than 'forced.' More work seems to be needed in this area of elicited dynamic separation.

Validation and Error Characterization for the Global Precipitation Measurement

NASA Technical Reports Server (NTRS)

Bidwell, Steven W.; Adams, W. J.; Everett, D. F.; Smith, E. A.; Yuter, S. E.

2003-01-01

The Global Precipitation Measurement (GPM) is an international effort to increase scientific knowledge on the global water cycle with specific goals of improving the understanding and the predictions of climate, weather, and hydrology. These goals will be achieved through several satellites specifically dedicated to GPM along with the integration of numerous meteorological satellite data streams from international and domestic partners. The GPM effort is led by the National Aeronautics and Space Administration (NASA) of the United States and the National Space Development Agency (NASDA) of Japan. In addition to the spaceborne assets, international and domestic partners will provide ground-based resources for validating the satellite observations and retrievals. This paper describes the validation effort of Global Precipitation Measurement to provide quantitative estimates on the errors of the GPM satellite retrievals. The GPM validation approach will build upon the research experience of the Tropical Rainfall Measuring Mission (TRMM) retrieval comparisons and its validation program. The GPM ground validation program will employ instrumentation, physical infrastructure, and research capabilities at Supersites located in important meteorological regimes of the globe. NASA will provide two Supersites, one in a tropical oceanic and the other in a mid-latitude continental regime. GPM international partners will provide Supersites for other important regimes. Those objectives or regimes not addressed by Supersites will be covered through focused field experiments. This paper describes the specific errors that GPM ground validation will address, quantify, and relate to the GPM satellite physical retrievals. GPM will attempt to identify the source of errors within retrievals including those of instrument calibration, retrieval physical assumptions, and algorithm applicability. With the identification of error sources, improvements will be made to the respective calibration, assumption, or algorithm. The instrumentation and techniques of the Supersites will be discussed. The GPM core satellite, with its dual-frequency radar and conically scanning radiometer, will provide insight into precipitation drop-size distributions and potentially increased measurement capabilities of light rain and snowfall. The ground validation program will include instrumentation and techniques commensurate with these new measurement capabilities.

Expectancy beliefs and perceived values of Chinese college students in physical education and physical activity.

PubMed

Chen, Ang; Liu, Xinlan

2008-03-01

The expectancy-value theory postulates that motivation relies on individuals' beliefs of success, perceived Attainment, Intrinsic Interest, and Utility values and Cost. This study examined Chinese college students' expectancy-value motivation in relation to physical education and self-initiated physical activity. A random sample of 368 Chinese university students responded to questionnaires on perceived expectancy beliefs, perceived values, and cost in terms of their experiences in mandatory physical education programs and in self-initiated after-school physical activity. They reported their choice decisions for continuing physical education. Data were analyzed using descriptive statistics, X2, logistic and linear regressions. The physical education curriculum was perceived as a major cost to motivation. Motivated by the Intrinsic Interest and Utility value, most students chose to continue to take physical education. Self-initiated after-school physical activity was motivated by the Attainment value only. No association was found between self-initiated physical activity and Liking or Disliking of physical education. Motivation for physical education and for self-initiated physical activity derived from different perceived values. The Attainment value motivates the students for self-initiated physical activity, whereas Intrinsic Interest and Utility values motivate them to choose to continue physical education.

Matter under extreme conditions experiments at the Linac Coherent Light Source

DOE PAGES

Glenzer, S. H.; Fletcher, L. B.; Galtier, E.; ...

2015-12-10

The Matter in Extreme Conditions end station at the Linac Coherent Light Source (LCLS) is a new tool enabling accurate pump-probe measurements for studying the physical properties of matter in the high-energy density physics regime. This instrument combines the world’s brightest x-ray source, the LCLS x-ray beam, with high-power lasers consisting of two nanosecond Nd:glass laser beams and one short-pulse Ti:sapphire laser. These lasers produce short-lived states of matter with high pressures, high temperatures or high densities with properties that are important for applications in nuclear fusion research, laboratory astrophysics and the development of intense radiation sources. In the firstmore » experiments, we have performed highly accurate x-ray diffraction and x-ray Thomson scattering techniques on shock-compressed matter resolving the transition from compressed solid matter to a co-existence regime and into the warm dense matter state. Furthermore, these complex charged-particle systems are dominated by strong correlations and quantum effects. They exist in planetary interiors and laboratory experiments, e.g., during high-power laser interactions with solids or the compression phase of inertial confinement fusion implosions. Applying record peak brightness X rays resolves the ionic interactions at atomic (Ångstrom) scale lengths and measure the static structure factor, which is a key quantity for determining equation of state data and important transport coefficients. Simultaneously, spectrally resolved measurements of plasmon features provide dynamic structure factor information that yield temperature and density with unprecedented precision at micron-scale resolution in dynamic compression experiments. This set of studies demonstrates our ability to measure fundamental thermodynamic properties that determine the state of matter in the high-energy density physics regime.« less

Physics of thermal transport and increased electron temperature turbulence in the edge pedestal of ELM-free, H-mode regimes on DIII-D

NASA Astrophysics Data System (ADS)

Sung, Choongki

2017-10-01

It has been observed, for the first time, that suppression of Edge Localized Modes (ELMs) in tokamak plasmas is accompanied by an increase in electron temperature turbulence. A correlation electron cyclotron emission technique has been utilized to quantify the observed increase: 40% increase in Quiescent H-mode (QH-mode) and 70% increase in 3D field ELM suppressed H-mode. Since reliable ELM-free H-mode operation is essential for future burning plasma experiments, it is crucial to develop a validated predictive capability for these plasmas. Linear stability analysis using TGLF has provided an explanation for the observations and has indicated that the underlying physical mechanisms are different in the two regimes. In QH-mode, profile gradients and the associated linear growth rate are decreased compared to ELMing H-mode. However, the ExB shearing rate is reduced by an even greater factor such that turbulent transport is no longer suppressed by flow shear. In contrast, during 3D field ELM suppressed H-mode, gradients are increased and TGLF predicts that a large increase in linear growth rate is primarily responsible for the increased turbulence. Power balance analysis using ONETWO is also consistent with the changes in electron thermal transport being due to the increased turbulence. These new findings are significant since they i) provide a physics explanation of these changes via TGLF analysis and enable validation of the model in the key pedestal region, and ii) support the hypothesis that turbulent transport partially replaces ELM-dominated transport during ELM-free operation. These results form a basis to develop a predictive understanding of pedestal regulation in ELM suppressed regimes. Supported by the US DOE under DE-FG02-08ER54984, DE-FC02-04ER54698.

A School-Based Study on Situational Interest of Investigative Study in Senior Physics

ERIC Educational Resources Information Center

Leung, Yat-yin

2015-01-01

This paper reports the findings from the interview data of a research aiming at studying how to trigger students' situational interest in physics and its implications on learning and teaching in the New Senior Secondary (NSS) physics curriculum. 49 students from a boys' school were invited to write one to three learning experiences in physics that…

On the Declining Interest in Physics among Students--From the Perspective of Teachers

ERIC Educational Resources Information Center

Oon, Pey-Tee; Subramaniam, R.

2011-01-01

This study examines physics teachers' views on factors that contribute to the declining interest in physics among school students. A total of 190 physics teachers from 91 secondary schools and nine junior colleges in Singapore participated in this study, which used a survey instrument to seek their views. Rasch analysis was used to analyze the…

Policy for Physical Education and School Sport in England, 2003-2010: Vested Interests and Dominant Discourses

ERIC Educational Resources Information Center

Jung, Hyunwoo; Pope, Stacey; Kirk, David

2016-01-01

Background: The salience of physical education and school sport (PESS) in England changed dramatically in the 2000s in terms of central government investment and political interests. The government put in place the physical education, school sport and club links strategy and the physical education and sport strategy for young people for a…

13 CFR 123.203 - What interest rate will my business pay on a physical disaster business loan and what are the...

Code of Federal Regulations, 2012 CFR

2012-01-01

... business pay on a physical disaster business loan and what are the repayment terms? 123.203 Section 123.203 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION DISASTER LOAN PROGRAM Physical Disaster Business Loans § 123.203 What interest rate will my business pay on a physical disaster business loan and...

13 CFR 123.203 - What interest rate will my business pay on a physical disaster business loan and what are the...

Code of Federal Regulations, 2013 CFR

2013-01-01

... business pay on a physical disaster business loan and what are the repayment terms? 123.203 Section 123.203 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION DISASTER LOAN PROGRAM Physical Disaster Business Loans § 123.203 What interest rate will my business pay on a physical disaster business loan and...

13 CFR 123.203 - What interest rate will my business pay on a physical disaster business loan and what are the...

Code of Federal Regulations, 2014 CFR

2014-01-01

... business pay on a physical disaster business loan and what are the repayment terms? 123.203 Section 123.203 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION DISASTER LOAN PROGRAM Physical Disaster Business Loans § 123.203 What interest rate will my business pay on a physical disaster business loan and...

13 CFR 123.203 - What interest rate will my business pay on a physical disaster business loan and what are the...

Code of Federal Regulations, 2011 CFR

2011-01-01

... business pay on a physical disaster business loan and what are the repayment terms? 123.203 Section 123.203 Business Credit and Assistance SMALL BUSINESS ADMINISTRATION DISASTER LOAN PROGRAM Physical Disaster Business Loans § 123.203 What interest rate will my business pay on a physical disaster business loan and...

The influence of open fracture anisotropy on CO2 movement within geological storage complexes

NASA Astrophysics Data System (ADS)

Bond, C. E.; Wightman, R.; Ringrose, P. S.

2012-12-01

Carbon mitigation through the geological storage of carbon dioxide is dependent on the ability of geological formations to store CO2 trapping it within a geological storage complex. Secure long-term containment needs to be demonstrated, due to both political and social drivers, meaning that this containment must be verifiable over periods of 100-105 years. The effectiveness of sub-surface geological storage systems is dependent on trapping CO2 within a volume of rock and is reliant on the integrity of the surrounding rocks, including their chemical and physical properties, to inhibit migration to the surface. Oil and gas reservoir production data, and field evidence show that fracture networks have the potential to act as focused pathways for fluid movement. Fracture networks can allow large volumes of fluid to migrate to the surface within the time scales of interest. In this paper we demonstrate the importance of predicting the effects of fracture networks in storage, using a case study from the In Salah CO2 storage site, and show how the fracture permeability is closely controlled by the stress regime that determines the open fracture network. Our workflow combines well data of imaged fractures, with a discrete fracture network (DFN) model of tectonically induced fractures, within the horizon of interest. The modelled and observed fractures have been compared and combined with present day stress data to predict the open fracture network and its implications for anisotropic movement of CO2 in the sub-surface. The created fracture network model has been used to calculate the 2D permeability tensor for the reservoir for two scenarios: 1) a model in which all fractures are permeable, based on the whole DFN model and 2) those fractures determined to be in dilatational failure under the present day stress regime, a sub-set of the DFN. The resulting permeability anisotropy tensors show distinct anisotropies for the predicted CO2 movement within the reservoir. These predictions have been compared with InSAR imagery of surface uplift, used as an indicator of fluid pressure and movement in the sub-surface, around the CO2 injection wells. The analysis shows that the permeability tensor with the greatest anisotropy, that for the DFN sub-set of open fractures, matches well with the anisotropy in surface uplift imaged by InSAR. We demonstrate that predicting fracture networks alone does not predict fluid movement in the sub-surface, and that fracture permeability is closely controlled by the stress regime that determines the open fracture network. Our results show that a workflow of fracture network prediction combined with present day stress analysis can be used to successfully predict CO2 movement in the sub-surface at an active injection site.

13 CFR 123.203 - What interest rate will my business pay on a physical disaster business loan and what are the...

Code of Federal Regulations, 2010 CFR

2010-01-01

... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false What interest rate will my... Business Loans § 123.203 What interest rate will my business pay on a physical disaster business loan and what are the repayment terms? (a) SBA will announce interest rates with each disaster declaration. If...

Influence of Out-of-School Experiences and Learning Styles on Interest in Biology, Chemistry and Physics among Higher Secondary Boys and Girls in Kerala

ERIC Educational Resources Information Center

Gafoor, K. Abdul

2017-01-01

Adopting an experiential learning explanation for varying student interest in the three sciences, out-of-school experience questionnaire, scale of interest in science and Kolb's learning style inventory were administered on 775 higher secondary students in Kerala. Despite their similar achievement levels, boys had higher interest in physics, and…

Using Achievement Goals and Interest to Predict Learning in Physical Education

ERIC Educational Resources Information Center

Shen, Bo; Chen, Ang; Guan, Jianmin

2007-01-01

On the basis of an integrated theoretical approach to achievement motivation, the authors designed this study to investigate the potential influence of mastery goal, performance-approach and avoidance-approach goals, individual interest, and situational interest on students' learning in a physical education softball unit. The authors collected and…

Body contouring surgery for military personnel following massive weight loss.

PubMed

Chong, S J; Kok, Y O; Foo, C L

2011-12-01

The burgeoning global obesity epidemic extends to the military service, where 6-53% of military personnel are overweight. Obese military personnel who adhere to a strict training and diet regime may potentially achieve and maintain significant weight loss. They may however face physical problems such as excess skin folds causing discomfort, difficulty in uniform fitting, personal hygiene, interference with full physical activities and psychological issues such as body image dissatisfaction, low self esteem and difficulty in social acceptance. We present a case report of a highly motivated military conscript who achieved and maintained significant weight loss but had physical defects following Massive Weight Loss. Body contouring surgery was successfully utilised to correct his physical defects and allowed him to return to full physical duties.

A Treasure Trove of Physics from a Common Source-Automobile Acceleration Data

NASA Astrophysics Data System (ADS)

Graney, Christopher M.

2005-11-01

What is better than interesting, challenging physics with good data free for the taking to which everyone can relate? That's what is available to anyone who digs into the reams of automobile performance tests that have been available in popular magazines since the 1950s. Opportunities to do and teach interesting physics abound, as evidenced by the frequent appearance of "physics of cars" articles in The Physics Teacher.1-6

Factors Influencing Labeling Nonconsensual Sex as Sexual Assault.

PubMed

Yndo, Monica C; Zawacki, Tina

2017-03-01

The current study examined the effects of physical attractiveness and sexual interest cues on men's sexual perceptions of women and whether increases in sexual perceptions of a woman would lead to decreases in labeling of subsequent nonconsensual sex as sexual assault. Two hundred thirty-three male college students ( M age = 19.17, SD = 1.22) read a vignette describing a hypothetical social interaction between a man and a woman; within the vignette, the female character's physical attractiveness (attractive vs. less attractive) and the degree to which the female character behaved interested in the male character (uninterested vs. ambiguous) were manipulated. The vignette ends with the male character physically forcing sexual intercourse with the female character. After reading the vignette, participants' labeling of the nonconsensual sex as sexual assault was addressed. Participants' perceptions of the female character's sexual interest in the male character prior to the nonconsensual sex was assessed as a dependent variable during stopping points in the vignette, prior to sexual assault. Both physical attractiveness and interest cues had a significant positive influence on men's perception of the female character as sexually interested. In addition, perceptions of sexual interest had a direct negative effect on sexual assault labeling. These results indicate that increases in physical attractiveness and interest cues increase perceptions of sexual interest, in turn decreasing the labeling of nonconsensual sex as sexual assault. This experimental research contributes to the literature on misperception of sexual interest and sexual assault labeling. These findings provide implications for intervention programs and for forensic issues related to sexual assault.

Non-Traditional Security Threats in the Border Areas: Terrorism, Piracy, Environmental Degradation in Southeast Asian Maritime Domain

NASA Astrophysics Data System (ADS)

Dabova, E. L.

2013-11-01

In addition to facilitating peaceful trade and economic development, sovereign territory, territorial waters and international waters are being used by various criminal groups that pose threats to governments, businesses and civilian population in Southeast Asia. Nonstate criminal maritime activities were not receiving appropriate attention as they were overshadowed by traditional military security challenges. Yet more and more frequently, the non-traditional actors challenge lines of communication, jeopardize access to strategic resources, complicate traditional defence tasks, and harm the environment. Understanding the nature of non-traditional threats, and the ways to combat them, requires international legal, historical and political science analysis within a united problem-oriented approach. A fair critique to pure interest, power and knowledge -based theories of regime formation was developed by E.K. Leonard's1, who explained the evolution of the international system from the global governance perspective. The present study is based on the premise that pure nation-state approaches are incapable of providing a theoretical ground for addressing the growing influence of international criminal networks in South East Asia. From an international relations theory perspective, the author of this study agrees with D.Snidal2 that the hegemonic stability theory has "limits" and is insufficient in describing modern challenges to sustainable international security regime, including non-traditional threats, where collective action is more efficient from an interest and capability standpoint. At the same time the author of this study does not share the viewpoint on "marginalization"3 of international law in current international order due to its fragmentation and regionalization4 and "global power shifts"5 . The United Nations, as a global institution at the top of the vertical hierarchy of international legal order, and the EU as an example of "self-contained" regime along with other subsystems like South East Asia may have different approaches to global governance, international constitutional order, or particular cases such as the measure of infringement of human rights when targeting individuals suspected of terrorist links. Yet international law remains the key part of the Asian and global security regime. The hypothesis of this study is that the "void of governance" regime in territorial and international waters provides lucrative environment for developing terrorism, piracy, environmental degradation, and other criminal activities that pose untraditional threats to the regional security. This "void of governance" regime can be caused by either, or both, de jure or de facto insufficient control over particular marine territories.

Boris Novozhilov: Life and contribution to the physics of combustion

NASA Astrophysics Data System (ADS)

Novozhilov, Vasily

2018-04-01

Professor Boris Novozhilov (1930-2017) passed away on February 19th, 2017 in Moscow. The present paper provides brief account of his life and contributions to the physics of combustion. From extensive scientific legacy left by Boris, several major achievements are discussed here: Zeldovich-Novozhilov (ZN) theory of unsteady solid propellant combustion, contributions to thermal explosion theory, the theory of spin combustion, discovery of propellant combustion transition to chaotic regimes through Feigenbaum period bifurcation scenario.

The Physics of Imaging with Remote Sensors : Photon State Space & Radiative Transfer

NASA Technical Reports Server (NTRS)

Davis, Anthony B.

2012-01-01

Standard (mono-pixel/steady-source) retrieval methodology is reaching its fundamental limit with access to multi-angle/multi-spectral photo- polarimetry. Next... Two emerging new classes of retrieval algorithm worth nurturing: multi-pixel time-domain Wave-radiometry transition regimes, and more... Cross-fertilization with bio-medical imaging. Physics-based remote sensing: - What is "photon state space?" - What is "radiative transfer?" - Is "the end" in sight? Two wide-open frontiers! center dot Examples (with variations.

A comparison of socioeconomic differences in physical functioning and perceived health among male and female employees in Britain, Finland and Japan.

PubMed

Martikainen, Pekka; Lahelma, Eero; Marmot, Michael; Sekine, Michikazu; Nishi, Nobuo; Kagamimori, Sadanobu

2004-09-01

We compared the pattern of socioeconomic inequalities in physical functioning and perceived health among male and female employees in Britain, Finland and Japan. Participants were male and female public sector employees in Britain, Finland and Japan, who were economically active and 40-60 year-olds at the time of data collection. We measured perceived health and physical functioning (SF-36 physical component summary) with standardized health questionnaires. The results obtained here reconfirm the similarity of the patterns of ill-health of those with lower socioeconomic status among non-manual men and women in Britain and Finland. These data also provide good evidence for a socioeconomic gradient in ill-health among Japanese non-manual men, although this gradient was less systematic. For Japanese men poorer health of manual workers as compared to non-manual workers was well demonstrated. However, among Japanese women socioeconomic differences in health were small and inconsistent. In conclusion, Britain, Finland and Japan--representing 'liberal', 'Nordic' and 'conservative' welfare state regimes--produce broadly similar patterns of socioeconomic differences in health among men. However, different patterns of labour force participation and welfare provision in different welfare regimes may bring about different patterns of socioeconomic differences in health for working women. This is exemplified by the lack of health inequalities among employed Japanese women. Copyright 2004 Elseiver Ltd.

The efficiency of driving chemical reactions by a physical non-equilibrium is kinetically controlled.

PubMed

Göppel, Tobias; Palyulin, Vladimir V; Gerland, Ulrich

2016-07-27

An out-of-equilibrium physical environment can drive chemical reactions into thermodynamically unfavorable regimes. Under prebiotic conditions such a coupling between physical and chemical non-equilibria may have enabled the spontaneous emergence of primitive evolutionary processes. Here, we study the coupling efficiency within a theoretical model that is inspired by recent laboratory experiments, but focuses on generic effects arising whenever reactant and product molecules have different transport coefficients in a flow-through system. In our model, the physical non-equilibrium is represented by a drift-diffusion process, which is a valid coarse-grained description for the interplay between thermophoresis and convection, as well as for many other molecular transport processes. As a simple chemical reaction, we consider a reversible dimerization process, which is coupled to the transport process by different drift velocities for monomers and dimers. Within this minimal model, the coupling efficiency between the non-equilibrium transport process and the chemical reaction can be analyzed in all parameter regimes. The analysis shows that the efficiency depends strongly on the Damköhler number, a parameter that measures the relative timescales associated with the transport and reaction kinetics. Our model and results will be useful for a better understanding of the conditions for which non-equilibrium environments can provide a significant driving force for chemical reactions in a prebiotic setting.

A process-based hierarchical framework for monitoring glaciated alpine headwaters

USGS Publications Warehouse

Weekes, Anne A.; Torgersen, Christian E.; Montgomery, David R.; Woodward, Andrea; Bolton, Susan M.

2012-01-01

Recent studies have demonstrated the geomorphic complexity and wide range of hydrologic regimes found in alpine headwater channels that provide complex habitats for aquatic taxa. These geohydrologic elements are fundamental to better understand patterns in species assemblages and indicator taxa and are necessary to aquatic monitoring protocols that aim to track changes in physical conditions. Complex physical variables shape many biological and ecological traits, including life history strategies, but these mechanisms can only be understood if critical physical variables are adequately represented within the sampling framework. To better align sampling design protocols with current geohydrologic knowledge, we present a conceptual framework that incorporates regional-scale conditions, basin-scale longitudinal profiles, valley-scale glacial macroform structure, valley segment-scale (i.e., colluvial, alluvial, and bedrock), and reach-scale channel types. At the valley segment- and reach-scales, these hierarchical levels are associated with differences in streamflow and sediment regime, water source contribution and water temperature. Examples of linked physical-ecological hypotheses placed in a landscape context and a case study using the proposed framework are presented to demonstrate the usefulness of this approach for monitoring complex temporal and spatial patterns and processes in glaciated basins. This approach is meant to aid in comparisons between mountain regions on a global scale and to improve management of potentially endangered alpine species affected by climate change and other stressors.