Critical points for finite Fibonacci chains of point delta-interactions and orthogonal polynomials

International Nuclear Information System (INIS)

De Prunele, E

2011-01-01

For a one-dimensional Schroedinger operator with a finite number n of point delta-interactions with a common intensity, the parameters are the intensity, the n - 1 intercenter distances and the mass. Critical points are points in the parameters space of the Hamiltonian where one bound state appears or disappears. The study of critical points for Hamiltonians with point delta-interactions arranged along a Fibonacci chain is shown to be closely related to the study of the so-called Fibonacci operator, a discrete one-dimensional Schroedinger-type operator, which occurs in the context of tight binding Hamiltonians. These critical points are the zeros of orthogonal polynomials previously studied in the context of special diatomic linear chains with elastic nearest-neighbor interaction. Properties of the zeros (location, asymptotic behavior, gaps, ...) are investigated. The perturbation series from the solvable periodic case is determined. The measure which yields orthogonality is investigated numerically from the zeros. It is shown that the transmission coefficient at zero energy can be expressed in terms of the orthogonal polynomials and their associated polynomials. In particular, it is shown that when the number of point delta-interactions is equal to a Fibonacci number minus 1, i.e. when the intervals between point delta-interactions form a palindrome, all the Fibonacci chains at critical points are completely transparent at zero energy. (paper)

Critical Dynamics : The Expansion of the Master Equation Including a Critical Point

NARCIS (Netherlands)

Dekker, H.

1980-01-01

In this thesis it is shown how to solve the master equation for a Markov process including a critical point by means of successive approximations in terms of a small parameter. A critical point occurs if, by adjusting an externally controlled quantity, the system shows a transition from normal

Euler Strut: A Mechanical Analogy for Dynamics in the Vicinity of a Critical Point

Science.gov (United States)

Bobnar, Jaka; Susman, Katarina; Parsegian, V. Adrian; Rand, Peter R.; Cepic, Mojca; Podgornik, Rudolf

2011-01-01

An anchored elastic filament (Euler strut) under an external point load applied to its free end is a simple model for a second-order phase transition. In the static case, a load greater than the critical load causes a Euler buckling instability, leading to a change in the filament's shape. The analysis of filament dynamics with an external point…

Universal Postquench Prethermalization at a Quantum Critical Point

Science.gov (United States)

Gagel, Pia; Orth, Peter P.; Schmalian, Jörg

2014-11-01

We consider an open system near a quantum critical point that is suddenly moved towards the critical point. The bath-dominated diffusive nonequilibrium dynamics after the quench is shown to follow scaling behavior, governed by a critical exponent that emerges in addition to the known equilibrium critical exponents. We determine this exponent and show that it describes universal prethermalized coarsening dynamics of the order parameter in an intermediate time regime. Implications of this quantum critical prethermalization are: (i) a power law rise of order and correlations after an initial collapse of the equilibrium state and (ii) a crossover to thermalization that occurs arbitrarily late for sufficiently shallow quenches.

Critical point dewetting: competition between the gravity and the dispersion force

International Nuclear Information System (INIS)

Ohmasa, Y; Takahashi, S; Fujii, K; Yao, M

2008-01-01

Near the critical temperature of an immiscible binary liquid system, a solid substrate is usually covered completely by one of the liquid phases. This phenomenon is called the 'critical point wetting , which is predicted by Cahn in 1977, and have been confirmed for many fluid systems experimentally. However, we found that liquid Se-Tl system on a quartz substrate does not show the critical point wetting near the liquid-liquid critical point. On a contrary, when the temperature goes down from the critical point, a Se-rich wetting film intrudes between the Tl-rich bulk liquid and the quartz wall. This result is a clear evidence of the 'critical point dewetting' phenomenon. It is suggested from a theoretical consideration that the critical point dewetting takes place as a result of the competition between the long-range dispersion force and the gravity

Critical Point in Self-Organized Tissue Growth

Science.gov (United States)

Aguilar-Hidalgo, Daniel; Werner, Steffen; Wartlick, Ortrud; González-Gaitán, Marcos; Friedrich, Benjamin M.; Jülicher, Frank

2018-05-01

We present a theory of pattern formation in growing domains inspired by biological examples of tissue development. Gradients of signaling molecules regulate growth, while growth changes these graded chemical patterns by dilution and advection. We identify a critical point of this feedback dynamics, which is characterized by spatially homogeneous growth and proportional scaling of patterns with tissue length. We apply this theory to the biological model system of the developing wing of the fruit fly Drosophila melanogaster and quantitatively identify signatures of the critical point.

Critical point phenomena: universal physics at large length scales

International Nuclear Information System (INIS)

Bruce, A.; Wallace, D.

1993-01-01

This article is concerned with the behaviour of a physical system at, or close to, a critical point (ebullition, ferromagnetism..): study of the phenomena displayed in the critical region (Ising model, order parameter, correlation length); description of the configurations (patterns) formed by the microscopic degrees of freedom near a critical point, essential concepts of the renormalization group (coarse-graining, system flow, fixed-point and scale-invariance); how these concepts knit together to form the renormalization group method; and what kind of problems may be resolved by the renormalization group method. 12 figs., 1 ref

Universal signatures of fractionalized quantum critical points.

Science.gov (United States)

Isakov, Sergei V; Melko, Roger G; Hastings, Matthew B

2012-01-13

Ground states of certain materials can support exotic excitations with a charge equal to a fraction of the fundamental electron charge. The condensation of these fractionalized particles has been predicted to drive unusual quantum phase transitions. Through numerical and theoretical analysis of a physical model of interacting lattice bosons, we establish the existence of such an exotic critical point, called XY*. We measure a highly nonclassical critical exponent η = 1.493 and construct a universal scaling function of winding number distributions that directly demonstrates the distinct topological sectors of an emergent Z(2) gauge field. The universal quantities used to establish this exotic transition can be used to detect other fractionalized quantum critical points in future model and material systems.

The location of the second critical point of water

Science.gov (United States)

Kanno, Hitoshi; Miyata, Kuniharu

2006-05-01

Based on the DTA data for homogeneous ice nucleation of emulsified liquid water at low temperatures and high pressures, the location of the second critical point (SCP) of water, which is expected to exist in addition to the normal liquid-vapor critical point, is estimated to be at 145 K pressure). It is shown that SCP is closely associated with the break point of the curve for the homogeneous ice nucleation temperature ( TH) of liquid water and with the transition between low density and high density amorphous solid water (LDA and HDA). Although the existence of SCP has become more realistic, the location seems to be less favorable to the water model of the second-critical-point interpretation.

Two critical tests for the Critical Point earthquake

Science.gov (United States)

Tzanis, A.; Vallianatos, F.

2003-04-01

It has been credibly argued that the earthquake generation process is a critical phenomenon culminating with a large event that corresponds to some critical point. In this view, a great earthquake represents the end of a cycle on its associated fault network and the beginning of a new one. The dynamic organization of the fault network evolves as the cycle progresses and a great earthquake becomes more probable, thereby rendering possible the prediction of the cycle’s end by monitoring the approach of the fault network toward a critical state. This process may be described by a power-law time-to-failure scaling of the cumulative seismic release rate. Observational evidence has confirmed the power-law scaling in many cases and has empirically determined that the critical exponent in the power law is typically of the order n=0.3. There are also two theoretical predictions for the value of the critical exponent. Ben-Zion and Lyakhovsky (Pure appl. geophys., 159, 2385-2412, 2002) give n=1/3. Rundle et al. (Pure appl. geophys., 157, 2165-2182, 2000) show that the power-law activation associated with a spinodal instability is essentially identical to the power-law acceleration of Benioff strain observed prior to earthquakes; in this case n=0.25. More recently, the CP model has gained support from the development of more dependable models of regional seismicity with realistic fault geometry that show accelerating seismicity before large events. Essentially, these models involve stress transfer to the fault network during the cycle such, that the region of accelerating seismicity will scale with the size of the culminating event, as for instance in Bowman and King (Geophys. Res. Let., 38, 4039-4042, 2001). It is thus possible to understand the observed characteristics of distributed accelerating seismicity in terms of a simple process of increasing tectonic stress in a region already subjected to stress inhomogeneities at all scale lengths. Then, the region of

Washing and chilling as critical control points in pork slaughter hazard analysis and critical control point (HACCP) systems.

Science.gov (United States)

Bolton, D J; Pearce, R A; Sheridan, J J; Blair, I S; McDowell, D A; Harrington, D

2002-01-01

The aim of this research was to examine the effects of preslaughter washing, pre-evisceration washing, final carcass washing and chilling on final carcass quality and to evaluate these operations as possible critical control points (CCPs) within a pork slaughter hazard analysis and critical control point (HACCP) system. This study estimated bacterial numbers (total viable counts) and the incidence of Salmonella at three surface locations (ham, belly and neck) on 60 animals/carcasses processed through a small commercial pork abattoir (80 pigs d(-1)). Significant reductions (P HACCP in pork slaughter plants. This research will provide a sound scientific basis on which to develop and implement effective HACCP in pork abattoirs.

Unbounded critical points for a class of lower semicontinuous functionals

OpenAIRE

Pellacci, Benedetta; Squassina, Marco

2003-01-01

In this paper we prove existence and multiplicity results of unbounded critical points for a general class of weakly lower semicontinuous functionals. We will apply a suitable nonsmooth critical point theory.

Interplay of quantum and classical fluctuations near quantum critical points

International Nuclear Information System (INIS)

Continentino, Mucio Amado

2011-01-01

For a system near a quantum critical point (QCP), above its lower critical dimension d L , there is in general a critical line of second-order phase transitions that separates the broken symmetry phase at finite temperatures from the disordered phase. The phase transitions along this line are governed by thermal critical exponents that are different from those associated with the quantum critical point. We point out that, if the effective dimension of the QCP, d eff = d + z (d is the Euclidean dimension of the system and z the dynamic quantum critical exponent) is above its upper critical dimension d c there is an intermingle of classical (thermal) and quantum critical fluctuations near the QCP. This is due to the breakdown of the generalized scaling relation ψ = νz between the shift exponent ψ of the critical line and the crossover exponent νz, for d + z > d c by a dangerous irrelevant interaction. This phenomenon has clear experimental consequences, like the suppression of the amplitude of classical critical fluctuations near the line of finite temperature phase transitions as the critical temperature is reduced approaching the QCP. (author)

Microbial profile and critical control points during processing of 'robo ...

African Journals Online (AJOL)

Microbial profile and critical control points during processing of 'robo' snack from ... the relevant critical control points especially in relation to raw materials and ... to the quality of the various raw ingredients used were the roasting using earthen

Universal post-quench prethermalization at a quantum critical point

Science.gov (United States)

Orth, Peter P.; Gagel, Pia; Schmalian, Joerg

2015-03-01

We consider an open system near a quantum critical point that is suddenly moved towards the critical point. The bath-dominated diffusive non-equilibrium dynamics after the quench is shown to follow scaling behavior, governed by a critical exponent that emerges in addition to the known equilibrium critical exponents. We determine this exponent and show that it describes universal prethermalized coarsening dynamics of the order parameter in an intermediate time regime. Implications of this quantum critical prethermalization are a powerlaw rise of order and correlations after an initial collapse of the equilibrium state and a crossover to thermalization that occurs arbitrarily late for sufficiently shallow quenches. [1] P. Gagel, P. P. Orth, J. Schmalian, Phys.Rev. Lett. (in press) arXiv:1406.6387

Precise Determination of Quantum Critical Points by the Violation of the Entropic Area Law

OpenAIRE

Xavier, J. C.; Alcaraz, F. C.

2011-01-01

Finite-size scaling analysis turns out to be a powerful tool to calculate the phase diagram as well as the critical properties of two dimensional classical statistical mechanics models and quantum Hamiltonians in one dimension. The most used method to locate quantum critical points is the so called crossing method, where the estimates are obtained by comparing the mass gaps of two distinct lattice sizes. The success of this method is due to its simplicity and the ability to provide accurate r...

Anomalous properties and coexistence of antiferromagnetism and superconductivity near a quantum critical point in rare-earth intermetallides

International Nuclear Information System (INIS)

Val’kov, V. V.; Zlotnikov, A. O.

2013-01-01

Mechanisms of the appearance of anomalous properties experimentally observed at the transition through the quantum critical point in rare-earth intermetallides have been studied. Quantum phase transitions are induced by the external pressure and are manifested as the destruction of the long-range antiferromagnetic order at zero temperature. The suppression of the long-range order is accompanied by an increase in the area of the Fermi surface, and the effective electron mass is strongly renormalized near the quantum critical point. It has been shown that such a renormalization is due to the reconstruction of the quasiparticle band, which is responsible for the formation of heavy fermions. It has been established that these features hold when the coexistence phase of antiferromagnetism and superconductivity is implemented near the quantum critical point.

Exact renormalization group equation for the Lifshitz critical point

Science.gov (United States)

Bervillier, C.

2004-10-01

An exact renormalization equation (ERGE) accounting for an anisotropic scaling is derived. The critical and tricritical Lifshitz points are then studied at leading order of the derivative expansion which is shown to involve two differential equations. The resulting estimates of the Lifshitz critical exponents compare well with the O(ε) calculations. In the case of the Lifshitz tricritical point, it is shown that a marginally relevant coupling defies the perturbative approach since it actually makes the fixed point referred to in the previous perturbative calculations O(ε) finally unstable.

Search for the QCD critical point at SPS energies

CERN Document Server

Anticic, T.; Barna, D.; Bartke, J.; Betev, L.; Bialkowska, H.; Blume, C.; Boimska, B.; Botje, M.; Bracinik, J.; Buncic, P.; Cerny, V.; Christakoglou, P.; Chung, P.; Chvala, O.; Cramer, J.G.; Csato, P.; Dinkelaker, P.; Eckardt, V.; Fodor, Z.; Foka, P.; Friese, V.; Gal, J.; Gazdzicki, M.; Genchev, V.; Gladysz, E.; Grebieszkow, K.; Hegyi, S.; Hohne, C.; Kadija, K.; Karev, A.; Kikola, D.; Kolesnikov, V.I.; Kornas, E.; Korus, R.; Kowalski, M.; Kreps, M.; Laszlo, A.; Lacey, R.; van Leeuwen, M.; Levai, P.; Litov, L.; Lungwitz, B.; Makariev, M.; Malakhov, A.I.; Mateev, M.; Melkumov, G.L.; Mischke, A.; Mitrovski, M.; Mrowczynski, St.; Palla, G.; Panagiotou, A.D.; Petridis, A.; Peryt, W.; Pikna, M.; Pluta, J.; Prindle, D.; Puhlhofer, F.; Renfordt, R.; Roland, C.; Roland, G.; Rybczynski, M.; Rybicki, A.; Sandoval, A.; Schmitz, N.; Schuster, T.; Seyboth, P.; Sikler, F.; Sitar, B.; Skrzypczak, E.; Slodkowski, M.; Stefanek, G.; Stock, R.; Strabel, C.; Strobele, H.; Susa, T.; Szentpetery, I.; Sziklai, J.; Szuba, M.; Szymanski, P.; Trubnikov, V.; Utvic, M.; Varga, D.; Vassiliou, M.; Veres, G.I.; Vesztergombi, G.; Vranic, D.; Wlodarczyk, Z.; Wojtaszek-Szwarc, A.; Yoo, I.K.; Abgrall, N.; Aduszkiewicz, A.; Andrieu, B.; Anticic, T.; Antoniou, N.; Argyriades, J.; Asryan, A.G.; Blondel, A.; Blumer, J.; Boldizsar, L.; Bravar, A.; Brzychczyk, J.; Bubak, A.; Bunyatov, S.A.; Choi, K.-U.; Chung, P.; Cleymans, J.; Derkach, D.A.; Diakonos, F.; Dominik, W.; Dumarchez, J.; Engel, R.; Ereditato, A.; Feofilov, G.A.; Ferrero, A.; Gazdzicki, M.; Golubeva, M.; Grzeszczuk, A.; Guber, F.; Hasegawa, T.; Haungs, A.; Igolkin, S.; Ivanov, A.S.; Ivashkin, A.; Katrynska, N.; Kielczewska, D.; Kisiel, J.; Kobayashi, T.; Kolev, D.; Kolevatov, R.S.; Kondratiev, V.P.; Kowalski, S.; Kurepin, A.; Lacey, R.; Lyubushkin, V.V.; Majka, Z.; Marchionni, A.; Marcinek, A.; Maris, I.; Matveev, V.; Meregaglia, A.; Messina, M.; Mijakowski, P.; Montaruli, T.; Murphy, S.; Nakadaira, T.; Naumenko, P.A.; Nikolic, V.; Nishikawa, K.; Palczewski, T.; Planeta, R.; Popov, B.A.; Posiadala, M.; Przewlocki, P.; Rauch, W.; Ravonel, M.; Rohrich, D.; Rondio, E.; Rossi, B.; Roth, M.; Rubbia, A.; Sadovsky, A.; Sakashita, K.; Sekiguchi, T.; Seyboth, P.; Shibata, M.; Sissakian, A.N.; Sorin, A.S.; Staszel, P.; Stepaniak, J.; Strabel, C.; Stroebele, H.; Tada, M.; Taranenko, A.; Tsenov, R.; Ulrich, R.; Unger, M.; Vechernin, V.V.; Zipper, W.

2009-01-01

Lattice QCD calculations locate the QCD critical point at energies accessible at the CERN Super Proton Synchrotron (SPS). We present average transverse momentum and multiplicity fluctuations, as well as baryon and anti-baryon transverse mass spectra which are expected to be sensitive to effects of the critical point. The future CP search strategy of the NA61/SHINE experiment at the SPS is also discussed.

Identification of critical points of thermal environment in broiler production

Directory of Open Access Journals (Sweden)

AG Menezes

2010-03-01

Full Text Available This paper describes an exploratory study carried out to determine critical control points and possible risks in hatcheries and broiler farms. The study was based in the identification of the potential hazards existing in broiler production, from the hatchery to the broiler farm, identifying critical control points and defining critical limits. The following rooms were analyzed in the hatchery: egg cold storage, pre-heating, incubator, and hatcher rooms. Two broiler houses were studied in two different farms. The following data were collected in the hatchery and broiler houses: temperature (ºC and relative humidity (%, air velocity (m s-1, ammonia levels, and light intensity (lx. In the broiler house study, a questionnaire using information of the Broiler Production Good Practices (BPGP manual was applied, and workers were interviewed. Risk analysis matrices were build to determine Critical Control Points (CCP. After data collection, Statistical Process Control (SPC was applied through the analysis of the Process Capacity Index, using the software program Minitab15®. Environmental temperature and relative humidity were the critical points identified in the hatchery and in both farms. The classes determined as critical control points in the broiler houses were poultry litter, feeding, drinking water, workers' hygiene and health, management and biosecurity, norms and legislation, facilities, and activity planning. It was concluded that CCP analysis, associated with SPC control tools and guidelines of good production practices, may contribute to improve quality control in poultry production.

21 CFR 120.8 - Hazard Analysis and Critical Control Point (HACCP) plan.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 2 2010-04-01 2010-04-01 false Hazard Analysis and Critical Control Point (HACCP... SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION HAZARD ANALYSIS AND CRITICAL CONTROL POINT (HACCP) SYSTEMS General Provisions § 120.8 Hazard Analysis and Critical Control Point (HACCP) plan. (a) HACCP plan. Each...

Theory of finite-entanglement scaling at one-dimensional quantum critical points.

Science.gov (United States)

Pollmann, Frank; Mukerjee, Subroto; Turner, Ari M; Moore, Joel E

2009-06-26

Studies of entanglement in many-particle systems suggest that most quantum critical ground states have infinitely more entanglement than noncritical states. Standard algorithms for one-dimensional systems construct model states with limited entanglement, which are a worse approximation to quantum critical states than to others. We give a quantitative theory of previously observed scaling behavior resulting from finite entanglement at quantum criticality. Finite-entanglement scaling in one-dimensional systems is governed not by the scaling dimension of an operator but by the "central charge" of the critical point. An important ingredient is the universal distribution of density-matrix eigenvalues at a critical point [P. Calabrese and A. Lefevre, Phys. Rev. A 78, 032329 (2008)10.1103/PhysRevA.78.032329]. The parameter-free theory is checked against numerical scaling at several quantum critical points.

Fermion-induced quantum critical points

OpenAIRE

Li, Zi-Xiang; Jiang, Yi-Fan; Jian, Shao-Kai; Yao, Hong

2017-01-01

A unified theory of quantum critical points beyond the conventional Landau?Ginzburg?Wilson paradigm remains unknown. According to Landau cubic criterion, phase transitions should be first-order when cubic terms of order parameters are allowed by symmetry in the Landau?Ginzburg free energy. Here, from renormalization group analysis, we show that second-order quantum phase transitions can occur at such putatively first-order transitions in interacting two-dimensional Dirac semimetals. As such t...

Deconfined Quantum Critical Points: Symmetries and Dualities

Directory of Open Access Journals (Sweden)

Chong Wang

2017-09-01

Full Text Available The deconfined quantum critical point (QCP, separating the Néel and valence bond solid phases in a 2D antiferromagnet, was proposed as an example of (2+1D criticality fundamentally different from standard Landau-Ginzburg-Wilson-Fisher criticality. In this work, we present multiple equivalent descriptions of deconfined QCPs, and use these to address the possibility of enlarged emergent symmetries in the low-energy limit. The easy-plane deconfined QCP, besides its previously discussed self-duality, is dual to N_{f}=2 fermionic quantum electrodynamics, which has its own self-duality and hence may have an O(4×Z_{2}^{T} symmetry. We propose several dualities for the deconfined QCP with SU(2 spin symmetry which together make natural the emergence of a previously suggested SO(5 symmetry rotating the Néel and valence bond solid orders. These emergent symmetries are implemented anomalously. The associated infrared theories can also be viewed as surface descriptions of (3+1D topological paramagnets, giving further insight into the dualities. We describe a number of numerical tests of these dualities. We also discuss the possibility of “pseudocritical” behavior for deconfined critical points, and the meaning of the dualities and emergent symmetries in such a scenario.

Thermal conductivity at a disordered quantum critical point

International Nuclear Information System (INIS)

Hartnoll, Sean A.; Ramirez, David M.; Santos, Jorge E.

2016-01-01

Strongly disordered and strongly interacting quantum critical points are difficult to access with conventional field theoretic methods. They are, however, both experimentally important and theoretically interesting. In particular, they are expected to realize universal incoherent transport. Such disordered quantum critical theories have recently been constructed holographically by deforming a CFT by marginally relevant disorder. In this paper we find additional disordered fixed points via relevant disordered deformations of a holographic CFT. Using recently developed methods in holographic transport, we characterize the thermal conductivity in both sets of theories in 1+1 dimensions. The thermal conductivity is found to tend to a constant at low temperatures in one class of fixed points, and to scale as T"0"."3 in the other. Furthermore, in all cases the thermal conductivity exhibits discrete scale invariance, with logarithmic in temperature oscillations superimposed on the low temperature scaling behavior. At no point do we use the replica trick.

The existence of trajectories joining critical points

International Nuclear Information System (INIS)

Yu Shuxiang.

1985-01-01

In this paper, using the notion of an isolating block and the concept of canonical regions, three existence criteria of trajectories connecting a pair of critical points of planar differential equations are given. (author)

Susceptibilities from a black hole engineered EoS with a critical point

International Nuclear Information System (INIS)

Portillo, Israel

2017-01-01

Currently at the Beam Energy Scan at RHIC experimental efforts are being made to find the QCD critical point. On the theoretical side, the behavior of higher-order susceptibilities of the net-baryon charge from Lattice QCD at µ B = 0 may allow us to estimate the position of the critical point in the QCD phase diagram. However, even if the series expansion continues to higher-orders, there is always the possibility to miss the critical point behavior due to truncation errors. An alternative approach is to use a black hole engineered holographic model, which displays a critical point at large densities and matches lattice susceptibilities at µB = 0. Using the thermodynamic data from this black hole model, we obtain the freeze-out points extracted from the net-protons distribution measured at STAR and explore higher order fluctuations at the lowest energies at the beam energy scan to investigate signatures of the critical point. (paper)

Spotlighting quantum critical points via quantum correlations at finite temperatures

International Nuclear Information System (INIS)

Werlang, T.; Ribeiro, G. A. P.; Rigolin, Gustavo

2011-01-01

We extend the program initiated by T. Werlang et al. [Phys. Rev. Lett. 105, 095702 (2010)] in several directions. Firstly, we investigate how useful quantum correlations, such as entanglement and quantum discord, are in the detection of critical points of quantum phase transitions when the system is at finite temperatures. For that purpose we study several thermalized spin models in the thermodynamic limit, namely, the XXZ model, the XY model, and the Ising model, all of which with an external magnetic field. We compare the ability of quantum discord, entanglement, and some thermodynamic quantities to spotlight the quantum critical points for several different temperatures. Secondly, for some models we go beyond nearest neighbors and also study the behavior of entanglement and quantum discord for second nearest neighbors around the critical point at finite temperature. Finally, we furnish a more quantitative description of how good all these quantities are in spotlighting critical points of quantum phase transitions at finite T, bridging the gap between experimental data and those theoretical descriptions solely based on the unattainable absolute zero assumption.

Visualizing Robustness of Critical Points for 2D Time-Varying Vector Fields

KAUST Repository

Wang, B.

2013-06-01

Analyzing critical points and their temporal evolutions plays a crucial role in understanding the behavior of vector fields. A key challenge is to quantify the stability of critical points: more stable points may represent more important phenomena or vice versa. The topological notion of robustness is a tool which allows us to quantify rigorously the stability of each critical point. Intuitively, the robustness of a critical point is the minimum amount of perturbation necessary to cancel it within a local neighborhood, measured under an appropriate metric. In this paper, we introduce a new analysis and visualization framework which enables interactive exploration of robustness of critical points for both stationary and time-varying 2D vector fields. This framework allows the end-users, for the first time, to investigate how the stability of a critical point evolves over time. We show that this depends heavily on the global properties of the vector field and that structural changes can correspond to interesting behavior. We demonstrate the practicality of our theories and techniques on several datasets involving combustion and oceanic eddy simulations and obtain some key insights regarding their stable and unstable features. © 2013 The Author(s) Computer Graphics Forum © 2013 The Eurographics Association and Blackwell Publishing Ltd.

Visualizing Robustness of Critical Points for 2D Time-Varying Vector Fields

KAUST Repository

Wang, B.; Rosen, P.; Skraba, P.; Bhatia, H.; Pascucci, V.

2013-01-01

Analyzing critical points and their temporal evolutions plays a crucial role in understanding the behavior of vector fields. A key challenge is to quantify the stability of critical points: more stable points may represent more important phenomena or vice versa. The topological notion of robustness is a tool which allows us to quantify rigorously the stability of each critical point. Intuitively, the robustness of a critical point is the minimum amount of perturbation necessary to cancel it within a local neighborhood, measured under an appropriate metric. In this paper, we introduce a new analysis and visualization framework which enables interactive exploration of robustness of critical points for both stationary and time-varying 2D vector fields. This framework allows the end-users, for the first time, to investigate how the stability of a critical point evolves over time. We show that this depends heavily on the global properties of the vector field and that structural changes can correspond to interesting behavior. We demonstrate the practicality of our theories and techniques on several datasets involving combustion and oceanic eddy simulations and obtain some key insights regarding their stable and unstable features. © 2013 The Author(s) Computer Graphics Forum © 2013 The Eurographics Association and Blackwell Publishing Ltd.

Quantum Triple Point and Quantum Critical End Points in Metallic Magnets.

Science.gov (United States)

Belitz, D; Kirkpatrick, T R

2017-12-29

In low-temperature metallic magnets, ferromagnetic (FM) and antiferromagnetic (AFM) orders can exist, adjacent to one another or concurrently, in the phase diagram of a single system. We show that universal quantum effects qualitatively alter the known phase diagrams for classical magnets. They shrink the region of concurrent FM and AFM order, change various transitions from second to first order, and, in the presence of a magnetic field, lead to either a quantum triple point where the FM, AFM, and paramagnetic phases all coexist or a quantum critical end point.

Critical Point Cancellation in 3D Vector Fields: Robustness and Discussion.

Science.gov (United States)

Skraba, Primoz; Rosen, Paul; Wang, Bei; Chen, Guoning; Bhatia, Harsh; Pascucci, Valerio

2016-02-29

Vector field topology has been successfully applied to represent the structure of steady vector fields. Critical points, one of the essential components of vector field topology, play an important role in describing the complexity of the extracted structure. Simplifying vector fields via critical point cancellation has practical merit for interpreting the behaviors of complex vector fields such as turbulence. However, there is no effective technique that allows direct cancellation of critical points in 3D. This work fills this gap and introduces the first framework to directly cancel pairs or groups of 3D critical points in a hierarchical manner with a guaranteed minimum amount of perturbation based on their robustness, a quantitative measure of their stability. In addition, our framework does not require the extraction of the entire 3D topology, which contains non-trivial separation structures, and thus is computationally effective. Furthermore, our algorithm can remove critical points in any subregion of the domain whose degree is zero and handle complex boundary configurations, making it capable of addressing challenging scenarios that may not be resolved otherwise. We apply our method to synthetic and simulation datasets to demonstrate its effectiveness.

Critical point anomalies include expansion shock waves

Energy Technology Data Exchange (ETDEWEB)

Nannan, N. R., E-mail: ryan.nannan@uvs.edu [Mechanical Engineering Discipline, Anton de Kom University of Suriname, Leysweg 86, PO Box 9212, Paramaribo, Suriname and Process and Energy Department, Delft University of Technology, Leeghwaterstraat 44, 2628 CA Delft (Netherlands); Guardone, A., E-mail: alberto.guardone@polimi.it [Department of Aerospace Science and Technology, Politecnico di Milano, Via La Masa 34, 20156 Milano (Italy); Colonna, P., E-mail: p.colonna@tudelft.nl [Propulsion and Power, Delft University of Technology, Kluyverweg 1, 2629 HS Delft (Netherlands)

2014-02-15

From first-principle fluid dynamics, complemented by a rigorous state equation accounting for critical anomalies, we discovered that expansion shock waves may occur in the vicinity of the liquid-vapor critical point in the two-phase region. Due to universality of near-critical thermodynamics, the result is valid for any common pure fluid in which molecular interactions are only short-range, namely, for so-called 3-dimensional Ising-like systems, and under the assumption of thermodynamic equilibrium. In addition to rarefaction shock waves, diverse non-classical effects are admissible, including composite compressive shock-fan-shock waves, due to the change of sign of the fundamental derivative of gasdynamics.

Defect production in nonlinear quench across a quantum critical point.

Science.gov (United States)

Sen, Diptiman; Sengupta, K; Mondal, Shreyoshi

2008-07-04

We show that the defect density n, for a slow nonlinear power-law quench with a rate tau(-1) and an exponent alpha>0, which takes the system through a critical point characterized by correlation length and dynamical critical exponents nu and z, scales as n approximately tau(-alphanud/(alphaznu+1)) [n approximately (alphag((alpha-1)/alpha)/tau)(nud/(znu+1))] if the quench takes the system across the critical point at time t=0 [t=t(0) not = 0], where g is a nonuniversal constant and d is the system dimension. These scaling laws constitute the first theoretical results for defect production in nonlinear quenches across quantum critical points and reproduce their well-known counterpart for a linear quench (alpha=1) as a special case. We supplement our results with numerical studies of well-known models and suggest experiments to test our theory.

Fermionic quantum critical point of spinless fermions on a honeycomb lattice

International Nuclear Information System (INIS)

Wang, Lei; Corboz, Philippe; Troyer, Matthias

2014-01-01

Spinless fermions on a honeycomb lattice provide a minimal realization of lattice Dirac fermions. Repulsive interactions between nearest neighbors drive a quantum phase transition from a Dirac semimetal to a charge-density-wave state through a fermionic quantum critical point, where the coupling of the Ising order parameter to the Dirac fermions at low energy drastically affects the quantum critical behavior. Encouraged by a recent discovery (Huffman and Chandrasekharan 2014 Phys. Rev. B 89 111101) of the absence of the fermion sign problem in this model, we study the fermionic quantum critical point using the continuous-time quantum Monte Carlo method with a worm-sampling technique. We estimate the transition point V/t=1.356(1) with the critical exponents ν=0.80(3) and η=0.302(7). Compatible results for the transition point are also obtained with infinite projected entangled-pair states. (paper)

Pasteurised milk and implementation of HACCP (Hazard Analysis Critical Control Point

Directory of Open Access Journals (Sweden)

T.B Murdiati

2004-10-01

Full Text Available The purpose of pasteurisation is to destroy pathogen bacteria without affecting the taste, flavor, and nutritional value. A study on the implementation of HACCP (Hazard Analysis Critical Control Point in producing pasteurized milk was carried out in four processing unit of pasteurised milk, one in Jakarta, two in Bandung and one in Bogor. The critical control points in the production line were identified. Milk samples were collected from the critical points and were analysed for the total number of microbes. Antibiotic residues were detected on raw milks. The study indicated that one unit in Bandung dan one unit in Jakarta produced pasteurized milk with lower number of microbes than the other units, due to better management and control applied along the chain of production. Penisilin residues was detected in raw milk used by unit in Bogor. Six critical points and the hazard might arise in those points were identified, as well as how to prevent the hazards. Quality assurance system such as HACCP would be able to produce high quality and safety of pasteurised milk, and should be implemented gradually.

Critical Point Dryer: Tousimis 916B Series C

Data.gov (United States)

Federal Laboratory Consortium — Description:CORAL Name: Critical Point DryerThis system utilizes CO 2to dry fragile suspended and floating structures Specifications / Capabilities:Wafer size up to...

Entropy excess in strongly correlated Fermi systems near a quantum critical point

Energy Technology Data Exchange (ETDEWEB)

Clark, J.W., E-mail: jwc@wuphys.wustl.edu [McDonnell Center for the Space Sciences and Department of Physics, Washington University, St. Louis, MO 63130 (United States); Zverev, M.V. [Russian Research Centre Kurchatov Institute, Moscow, 123182 (Russian Federation); Moscow Institute of Physics and Technology, Moscow, 123098 (Russian Federation); Khodel, V.A. [Russian Research Centre Kurchatov Institute, Moscow, 123182 (Russian Federation); McDonnell Center for the Space Sciences and Department of Physics, Washington University, St. Louis, MO 63130 (United States)

2012-12-15

A system of interacting, identical fermions described by standard Landau Fermi-liquid (FL) theory can experience a rearrangement of its Fermi surface if the correlations grow sufficiently strong, as occurs at a quantum critical point where the effective mass diverges. As yet, this phenomenon defies full understanding, but salient aspects of the non-Fermi-liquid (NFL) behavior observed beyond the quantum critical point are still accessible within the general framework of the Landau quasiparticle picture. Self-consistent solutions of the coupled Landau equations for the quasiparticle momentum distribution n(p) and quasiparticle energy spectrum {epsilon}(p) are shown to exist in two distinct classes, depending on coupling strength and on whether the quasiparticle interaction is regular or singular at zero momentum transfer. One class of solutions maintains the idempotency condition n{sup 2}(p)=n(p) of standard FL theory at zero temperature T while adding pockets to the Fermi surface. The other solutions are characterized by a swelling of the Fermi surface and a flattening of the spectrum {epsilon}(p) over a range of momenta in which the quasiparticle occupancies lie between 0 and 1 even at T=0. The latter, non-idempotent solution is revealed by analysis of a Poincare mapping associated with the fundamental Landau equation connecting n(p) and {epsilon}(p) and validated by solution of a variational condition that yields the symmetry-preserving ground state. Significantly, this extraordinary solution carries the burden of a large temperature-dependent excess entropy down to very low temperatures, threatening violation of the Nernst Theorem. It is argued that certain low-temperature phase transitions, notably those involving Cooper-pair formation, offer effective mechanisms for shedding the entropy excess. Available measurements in heavy-fermion compounds provide concrete support for such a scenario. - Highlights: Black-Right-Pointing-Pointer Extension of Landau

Critical Control Points in the Processing of Cassava Tuber for Ighu ...

African Journals Online (AJOL)

Determination of the critical control points in the processing of cassava tuber into Ighu was carried out. The critical control points were determined according to the Codex guidelines for the application of the HACCP system by conducting hazard analysis. Hazard analysis involved proper examination of each processing step ...

Critical point of view: a Wikipedia reader

NARCIS (Netherlands)

Lovink, G.; Tkacz, N.

2011-01-01

For millions of internet users around the globe, the search for new knowledge begins with Wikipedia. The encyclopedia’s rapid rise, novel organization, and freely offered content have been marveled at and denounced by a host of commentators. Critical Point of View moves beyond unflagging praise,

Solving the Richardson equations close to the critical points

Energy Technology Data Exchange (ETDEWEB)

DomInguez, F [Departamento de Matematicas, Universidad de Alcala, 28871 Alcala de Henares (Spain); Esebbag, C [Departamento de Matematicas, Universidad de Alcala, 28871 Alcala de Henares (Spain); Dukelsky, J [Instituto de Estructura de la Materia, CSIC, Serrano 123, 28006 Madrid (Spain)

2006-09-15

We study the Richardson equations close to the critical values of the pairing strength g{sub c}, where the occurrence of divergences precludes numerical solutions. We derive a set of equations for determining the critical g values and the non-collapsing pair energies. Studying the behaviour of the solutions close to the critical points, we develop a procedure to solve numerically the Richardson equations for arbitrary coupling strength.

Robustness of critical points in a complex adaptive system: Effects of hedge behavior

Science.gov (United States)

Liang, Yuan; Huang, Ji-Ping

2013-08-01

In our recent papers, we have identified a class of phase transitions in the market-directed resource-allocation game, and found that there exists a critical point at which the phase transitions occur. The critical point is given by a certain resource ratio. Here, by performing computer simulations and theoretical analysis, we report that the critical point is robust against various kinds of human hedge behavior where the numbers of herds and contrarians can be varied widely. This means that the critical point can be independent of the total number of participants composed of normal agents, herds and contrarians, under some conditions. This finding means that the critical points we identified in this complex adaptive system (with adaptive agents) may also be an intensive quantity, similar to those revealed in traditional physical systems (with non-adaptive units).

Dynamical Response near Quantum Critical Points.

Science.gov (United States)

Lucas, Andrew; Gazit, Snir; Podolsky, Daniel; Witczak-Krempa, William

2017-02-03

We study high-frequency response functions, notably the optical conductivity, in the vicinity of quantum critical points (QCPs) by allowing for both detuning from the critical coupling and finite temperature. We consider general dimensions and dynamical exponents. This leads to a unified understanding of sum rules. In systems with emergent Lorentz invariance, powerful methods from quantum field theory allow us to fix the high-frequency response in terms of universal coefficients. We test our predictions analytically in the large-N O(N) model and using the gauge-gravity duality and numerically via quantum Monte Carlo simulations on a lattice model hosting the interacting superfluid-insulator QCP. In superfluid phases, interacting Goldstone bosons qualitatively change the high-frequency optical conductivity and the corresponding sum rule.

Higgs inflation at the critical point

CERN Document Server

Bezrukov, Fedor

2014-01-01

Higgs inflation can occur if the Standard Model (SM) is a self-consistent effective field theory up to inflationary scale. This leads to a lower bound on the Higgs boson mass, $M_h \\geq M_{\\text{crit}}$. If $M_h$ is more than a few hundreds of MeV above the critical value, the Higgs inflation predicts the universal values of inflationary indexes, $r\\simeq 0.003$ and $n_s\\simeq 0.97$, independently on the Standard Model parameters. We show that in the vicinity of the critical point $M_{\\text{crit}}$ the inflationary indexes acquire an essential dependence on the mass of the top quark $m_t$ and $M_h$. In particular, the amplitude of the gravitational waves can exceed considerably the universal value.

Liquid-Vapor Argon Isotope Fractionation from the Triple Point to the Critical Point

DEFF Research Database (Denmark)

Phillips, J. T.; Linderstrøm-Lang, C. U.; Bigeleisen, J.

1972-01-01

are compared at the same molar volume. The isotope fractionation factor α for 36Ar∕40Ar between liquid and vapor has been measured from the triple point to the critical temperature. The results are compared with previous vapor pressure data, which cover the range 84–102°K. Although the agreement is within....... The fractionation factor approaches zero at the critical temperature with a nonclassical critical index equal to 0.42±0.02.〈∇2Uc〉/ρc in liquid argon is derived from the experimental fractionation data and calculations of 〈∇2Ug〉/ρg for a number of potential functions for gaseous argon....

Pseudo-critical point in anomalous phase diagrams of simple plasma models

International Nuclear Information System (INIS)

Chigvintsev, A Yu; Iosilevskiy, I L; Noginova, L Yu

2016-01-01

Anomalous phase diagrams in subclass of simplified (“non-associative”) Coulomb models is under discussion. The common feature of this subclass is absence on definition of individual correlations for charges of opposite sign. It is e.g. modified OCP of ions on uniformly compressible background of ideal Fermi-gas of electrons OCP(∼), or a superposition of two non-ideal OCP(∼) models of ions and electrons etc. In contrast to the ordinary OCP model on non-compressible (“rigid”) background OCP(#) two new phase transitions with upper critical point, boiling and sublimation, appear in OCP(∼) phase diagram in addition to the well-known Wigner crystallization. The point is that the topology of phase diagram in OCP(∼) becomes anomalous at high enough value of ionic charge number Z . Namely, the only one unified crystal- fluid phase transition without critical point exists as continuous superposition of melting and sublimation in OCP(∼) at the interval ( Z 1 < Z < Z 2 ). The most remarkable is appearance of pseudo-critical points at both boundary values Z = Z 1 ≈ 35.5 and Z = Z 2 ≈ 40.0. It should be stressed that critical isotherm is exactly cubic in both these pseudo-critical points. In this study we have improved our previous calculations and utilized more complicated model components equation of state provided by Chabrier and Potekhin (1998 Phys. Rev. E 58 4941). (paper)

Program computes single-point failures in critical system designs

Science.gov (United States)

Brown, W. R.

1967-01-01

Computer program analyzes the designs of critical systems that will either prove the design is free of single-point failures or detect each member of the population of single-point failures inherent in a system design. This program should find application in the checkout of redundant circuits and digital systems.

Hazard analysis and critical control point (HACCP) history and conceptual overview.

Science.gov (United States)

Hulebak, Karen L; Schlosser, Wayne

2002-06-01

The concept of Hazard Analysis and Critical Control Point (HACCP) is a system that enables the production of safe meat and poultry products through the thorough analysis of production processes, identification of all hazards that are likely to occur in the production establishment, the identification of critical points in the process at which these hazards may be introduced into product and therefore should be controlled, the establishment of critical limits for control at those points, the verification of these prescribed steps, and the methods by which the processing establishment and the regulatory authority can monitor how well process control through the HACCP plan is working. The history of the development of HACCP is reviewed, and examples of practical applications of HACCP are described.

Engineering Surface Critical Behavior of (2 +1 )-Dimensional O(3) Quantum Critical Points

Science.gov (United States)

Ding, Chengxiang; Zhang, Long; Guo, Wenan

2018-06-01

Surface critical behavior (SCB) refers to the singularities of physical quantities on the surface at the bulk phase transition. It is closely related to and even richer than the bulk critical behavior. In this work, we show that three types of SCB universality are realized in the dimerized Heisenberg models at the (2 +1 )-dimensional O(3) quantum critical points by engineering the surface configurations. The ordinary transition happens if the surface is gapped in the bulk disordered phase, while the gapless surface state generally leads to the multicritical special transition, even though the latter is precluded in classical phase transitions because the surface is in the lower critical dimension. An extraordinary transition is induced by the ferrimagnetic order on the surface of the staggered Heisenberg model, in which the surface critical exponents violate the results of the scaling theory and thus seriously challenge our current understanding of extraordinary transitions.

Pseudo-critical point in anomalous phase diagrams of simple plasma models

Science.gov (United States)

Chigvintsev, A. Yu; Iosilevskiy, I. L.; Noginova, L. Yu

2016-11-01

Anomalous phase diagrams in subclass of simplified (“non-associative”) Coulomb models is under discussion. The common feature of this subclass is absence on definition of individual correlations for charges of opposite sign. It is e.g. modified OCP of ions on uniformly compressible background of ideal Fermi-gas of electrons OCP(∼), or a superposition of two non-ideal OCP(∼) models of ions and electrons etc. In contrast to the ordinary OCP model on non-compressible (“rigid”) background OCP(#) two new phase transitions with upper critical point, boiling and sublimation, appear in OCP(∼) phase diagram in addition to the well-known Wigner crystallization. The point is that the topology of phase diagram in OCP(∼) becomes anomalous at high enough value of ionic charge number Z. Namely, the only one unified crystal- fluid phase transition without critical point exists as continuous superposition of melting and sublimation in OCP(∼) at the interval (Z 1 points at both boundary values Z = Z 1 ≈ 35.5 and Z = Z 2 ≈ 40.0. It should be stressed that critical isotherm is exactly cubic in both these pseudo-critical points. In this study we have improved our previous calculations and utilized more complicated model components equation of state provided by Chabrier and Potekhin (1998 Phys. Rev. E 58 4941).

Big Bang as a Critical Point

Directory of Open Access Journals (Sweden)

Jakub Mielczarek

2017-01-01

Full Text Available This article addresses the issue of possible gravitational phase transitions in the early universe. We suggest that a second-order phase transition observed in the Causal Dynamical Triangulations approach to quantum gravity may have a cosmological relevance. The phase transition interpolates between a nongeometric crumpled phase of gravity and an extended phase with classical properties. Transition of this kind has been postulated earlier in the context of geometrogenesis in the Quantum Graphity approach to quantum gravity. We show that critical behavior may also be associated with a signature change in Loop Quantum Cosmology, which occurs as a result of quantum deformation of the hypersurface deformation algebra. In the considered cases, classical space-time originates at the critical point associated with a second-order phase transition. Relation between the gravitational phase transitions and the corresponding change of symmetry is underlined.

Flow topology of rare back flow events and critical points in turbulent channels and toroidal pipes

Science.gov (United States)

Chin, C.; Vinuesa, R.; Örlü, R.; Cardesa, J. I.; Noorani, A.; Schlatter, P.; Chong, M. S.

2018-04-01

A study of the back flow events and critical points in the flow through a toroidal pipe at friction Reynolds number Re τ ≈ 650 is performed and compared with the results in a turbulent channel flow at Re τ ≈ 934. The statistics and topological properties of the back flow events are analysed and discussed. Conditionally-averaged flow fields in the vicinity of the back flow event are obtained, and the results for the torus show a similar streamwise wall-shear stress topology which varies considerably for the spanwise wall-shear stress when compared to the channel flow. The comparison between the toroidal pipe and channel flows also shows fewer back flow events and critical points in the torus. This cannot be solely attributed to differences in Reynolds number, but is a clear effect of the secondary flow present in the toroidal pipe. A possible mechanism is the effect of the secondary flow present in the torus, which convects momentum from the inner to the outer bend through the core of the pipe, and back from the outer to the inner bend through the pipe walls. In the region around the critical points, the skin-friction streamlines and vorticity lines exhibit similar flow characteristics with a node and saddle pair for both flows. These results indicate that back flow events and critical points are genuine features of wall-bounded turbulence, and are not artifacts of specific boundary or inflow conditions in simulations and/or measurement uncertainties in experiments.

Critical point relascope sampling for unbiased volume estimation of downed coarse woody debris

Science.gov (United States)

Jeffrey H. Gove; Michael S. Williams; Mark J. Ducey; Mark J. Ducey

2005-01-01

Critical point relascope sampling is developed and shown to be design-unbiased for the estimation of log volume when used with point relascope sampling for downed coarse woody debris. The method is closely related to critical height sampling for standing trees when trees are first sampled with a wedge prism. Three alternative protocols for determining the critical...

Slow dynamics at critical points: the field-theoretical perspective

International Nuclear Information System (INIS)

Gambassi, Andrea

2006-01-01

The dynamics at a critical point provides a simple instance of slow collective evolution, characterised by aging phenomena and by a violation of the fluctuation-dissipation relation even for long times. By virtue of the universality in critical phenomena it is possible to provide quantitative predictions for some aspects of these behaviours by field-theoretical methods. We review some of the theoretical results that have been obtained in recent years for the relevant (universal) quantities, such as the fluctuation-dissipation ratio, associated with the non-equilibrium critical dynamics

Detecting quantum critical points using bipartite fluctuations.

Science.gov (United States)

Rachel, Stephan; Laflorencie, Nicolas; Song, H Francis; Le Hur, Karyn

2012-03-16

We show that the concept of bipartite fluctuations F provides a very efficient tool to detect quantum phase transitions in strongly correlated systems. Using state-of-the-art numerical techniques complemented with analytical arguments, we investigate paradigmatic examples for both quantum spins and bosons. As compared to the von Neumann entanglement entropy, we observe that F allows us to find quantum critical points with much better accuracy in one dimension. We further demonstrate that F can be successfully applied to the detection of quantum criticality in higher dimensions with no prior knowledge of the universality class of the transition. Promising approaches to experimentally access fluctuations are discussed for quantum antiferromagnets and cold gases.

Hysteresis critical point of nitrogen in porous glass: occurrence of sample spanning transition in capillary condensation.

Science.gov (United States)

Morishige, Kunimitsu

2009-06-02

To examine the mechanisms for capillary condensation and for capillary evaporation in porous glass, we measured the hysteresis critical points and desorption scanning curves of nitrogen in four kinds of porous glasses with different pore sizes (Vycor, CPG75A, CPG120A, and CPG170A). The shapes of the hysteresis loop in the adsorption isotherm of nitrogen for the Vycor and the CPG75A changed with temperature, whereas those for the CPG120A and the CPG170A remained almost unchanged with temperature. The hysteresis critical points for the Vycor and the CPG75A fell on the common line observed previously for ordered mesoporous silicas. On the other hand, the hysteresis critical points for the CPG120A and the CPG170A deviated appreciably from the common line. This strongly suggests that capillary evaporation of nitrogen in the interconnected and disordered pores of both the Vycor and the CPG75A follows a cavitation process at least in the vicinity of their hysteresis critical temperatures in the same way as that in the cagelike pores of the ordered silicas, whereas the hysteresis critical points in the CPG120A and the CPG170A have origin different from that in the cagelike pores. The desorption scanning curves for the CPG75A indicated the nonindependence of the porous domains. On the other hand, for both the CPG120A and the CPG170A, we obtained the scanning curves that are expected from the independent domain theory. All these results suggest that sample spanning transitions in capillary condensation and evaporation take place inside the interconnected pores of both the CPG120A and the CPG170A.

Critical Points of Contact

DEFF Research Database (Denmark)

Jensen, Ole B.; Wind, Simon; Lanng, Ditte Bendix

2012-01-01

In this brief article, we shall illustrate the application of the analytical and interventionist concept of ‘Critical Points of Contact’ (CPC) through a number of urban design studios. The notion of CPC has been developed over a span of the last three to four years and is reported in more detail...... elsewhere (Jensen & Morelli 2011). In this article, we will only discuss the conceptual and theoretical framing superficially, since our real interest is to show and discuss the concept's application value to spatial design in a number of urban design studios. The 'data' or the projects presented are seven...... in urban design at Aalborg University, where urban design consists of both an analytical and an interventionist field of operation. Furthermore, the content of the CPC concept links to research in mobilities, the network city, and urban design. These are among the core pillars of both the masters programme...

An assessment of the melting, boiling, and critical point data of the alkali metals

International Nuclear Information System (INIS)

Ohse, R.W.; Babelot, J.F.; Magill, J.

1985-01-01

The measured melting, boiling and critical point data of the alkali metals are reviewed. Emphasis has been given to the assessment of the critical point data. The main experimental techniques for measurements in the critical region are described. The selected data are given. Best estimates of the critical constants of lithium are given. (author)

Matter fields near quantum critical point in (2+1)-dimensional U(1) gauge theory

International Nuclear Information System (INIS)

Liu Guozhu; Li Wei; Cheng Geng

2010-01-01

We study chiral phase transition and confinement of matter fields in (2+1)-dimensional U(1) gauge theory of massless Dirac fermions and scalar bosons. The vanishing scalar boson mass, r=0, defines a quantum critical point between the Higgs phase and the Coulomb phase. We consider only the critical point r=0 and the Coulomb phase with r>0. The Dirac fermion acquires a dynamical mass when its flavor is less than certain critical value N f c , which depends quantitatively on the flavor N b and the scalar boson mass r. When N f f c , the matter fields carrying internal gauge charge are all confined if r≠0 but are deconfined at the quantum critical point r=0. The system has distinct low-energy elementary excitations at the critical point r=0 and in the Coulomb phase with r≠0. We calculate the specific heat and susceptibility of the system at r=0 and r≠0, which can help to detect the quantum critical point and to judge whether dynamical fermion mass generation takes place.

A critical analysis of the tender points in fibromyalgia.

Science.gov (United States)

Harden, R Norman; Revivo, Gadi; Song, Sharon; Nampiaparampil, Devi; Golden, Gary; Kirincic, Marie; Houle, Timothy T

2007-03-01

To pilot methodologies designed to critically assess the American College of Rheumatology's (ACR) diagnostic criteria for fibromyalgia. Prospective, psychophysical testing. An urban teaching hospital. Twenty-five patients with fibromyalgia and 31 healthy controls (convenience sample). Pressure pain threshold was determined at the 18 ACR tender points and five sham points using an algometer (dolorimeter). The patients "algometric total scores" (sums of the patients' average pain thresholds at the 18 tender points) were derived, as well as pain thresholds across sham points. The "algometric total score" could differentiate patients with fibromyalgia from normals with an accuracy of 85.7% (P pain across sham points than across ACR tender points, sham points also could be used for diagnosis (85.7%; Ps tested vs other painful conditions. The points specified by the ACR were only modestly superior to sham points in making the diagnosis. Most importantly, this pilot suggests single points, smaller groups of points, or sham points may be as effective in diagnosing fibromyalgia as the use of all 18 points, and suggests methodologies to definitively test that hypothesis.

Universal conductance and conductivity at critical points in integer quantum Hall systems.

Science.gov (United States)

Schweitzer, L; Markos, P

2005-12-16

The sample averaged longitudinal two-terminal conductance and the respective Kubo conductivity are calculated at quantum critical points in the integer quantum Hall regime. In the limit of large system size, both transport quantities are found to be the same within numerical uncertainty in the lowest Landau band, and , respectively. In the second-lowest Landau band, a critical conductance is obtained which indeed supports the notion of universality. However, these numbers are significantly at variance with the hitherto commonly believed value . We argue that this difference is due to the multifractal structure of critical wave functions, a property that should generically show up in the conductance at quantum critical points.

A magnetically induced quantum critical point in holography

NARCIS (Netherlands)

Gursoy, U.; Gnecchi, A.; Toldo, C.; Papadoulaki, O.

We investigate quantum critical points in a 2+1 dimensional gauge theory at finite chemical potential χ and magnetic field B. The gravity dual is based on 4D NN = 2 Fayet-Iliopoulos gauged supergravity and the solutions we consider — that are constructed analytically — are extremal, dyonic,

Optical Studies of Pure Fluids about Their Critical Points

Science.gov (United States)

Pang, Kian Tiong

Three optical experiments were performed on pure fluids near their critical points. In the first two setups, CH_3F and H_2C:CF _2 were each tested in a temperature -controlled, prism-shaped cell and a thin parallel-windows cell. In the prism cell, a laser beam was additionally deflected by the fluid present. From the deflection data, the refractive index was related to the density to find the Lorentz-Lorenz function. Critical temperature (T _{c}), density, refractive index and electronic polarizability were found. In the second experiment, a critically-filled, thin parallel-windows cell was placed in one arm of a Mach-Zehnder interoferometer. Fluid density was monitored by changes in the fringe pattern with changing cell temperature. The aim was to improve on the precision of T_{c}: T_{c}{rm (CH}_3 F) = (44cdot9087 +/- 0cdot0002)C; T _{c}{rm(H}_2C:CF _2) = (29cdot7419 +/- 0cdot0001)C; and, to study the coexistence curve and diameter as close to T_{c} as possible. The critical behaviour was compared to the theoretical renormalization group calculations. The derived coefficients were tested against a proposed three-body interaction to explain the field-mixing term in the diameter near the critical point. It was found that H_2C:CF_2 behaved as predicted by such an interaction; CH _3F (and CHF_3) did not. The third experiment was a feasibility study to find out if (critical) isotherms could be measured optically in a setup which combined the prism and parallel-windows cells. The aim was to map isotherms in as wide a range of pressure and density as possible and to probe the critical region directly. Pressure was monitored by a precise digital pressure gauge. CH_3F and CHF _3 were tested in this system. It was found that at low densities, the calculated second and third virial coefficients agreed with reference values. However, the data around the critical point were not accurate enough for use to calculate the critical exponent, delta . The calculated value was

Quantum critical point revisited by dynamical mean-field theory

Science.gov (United States)

Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei M.

2017-03-01

Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. The QCP is characterized by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. We use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. By comparing with the calculations based on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.

Completely mixed state is a critical point for three-qubit entanglement

International Nuclear Information System (INIS)

Tamaryan, Sayatnova

2011-01-01

Pure three-qubit states have five algebraically independent and one algebraically dependent polynomial invariants under local unitary transformations and an arbitrary entanglement measure is a function of these six invariants. It is shown that if the reduced density operator of a some qubit is a multiple of the unit operator, than the geometric entanglement measure of the pure three-qubit state is absolutely independent of the polynomial invariants and is a constant for such tripartite states. Hence a one-particle completely mixed state is a critical point for the geometric measure of entanglement. -- Highlights: → Geometric measure of pure three-qubits is expressed in terms of polynomial invariants. → When one Bloch vector is zero the measure is independent of the remaining invariants. → Hence a one-particle completely mixed state is a critical point for the geometric measure. → The existence of the critical points is an inherent feature of the entanglement.

Completely mixed state is a critical point for three-qubit entanglement

Energy Technology Data Exchange (ETDEWEB)

Tamaryan, Sayatnova, E-mail: sayat@mail.yerphi.am [Department of Theoretical Physics, A. Alikhanyan National Laboratory, Yerevan (Armenia)

2011-06-06

Pure three-qubit states have five algebraically independent and one algebraically dependent polynomial invariants under local unitary transformations and an arbitrary entanglement measure is a function of these six invariants. It is shown that if the reduced density operator of a some qubit is a multiple of the unit operator, than the geometric entanglement measure of the pure three-qubit state is absolutely independent of the polynomial invariants and is a constant for such tripartite states. Hence a one-particle completely mixed state is a critical point for the geometric measure of entanglement. -- Highlights: → Geometric measure of pure three-qubits is expressed in terms of polynomial invariants. → When one Bloch vector is zero the measure is independent of the remaining invariants. → Hence a one-particle completely mixed state is a critical point for the geometric measure. → The existence of the critical points is an inherent feature of the entanglement.

Elliptic Euler–Poisson–Darboux equation, critical points and integrable systems

International Nuclear Information System (INIS)

Konopelchenko, B G; Ortenzi, G

2013-01-01

The structure and properties of families of critical points for classes of functions W(z, z-bar ) obeying the elliptic Euler–Poisson–Darboux equation E(1/2, 1/2) are studied. General variational and differential equations governing the dependence of critical points in variational (deformation) parameters are found. Explicit examples of the corresponding integrable quasi-linear differential systems and hierarchies are presented. There are the extended dispersionless Toda/nonlinear Schrödinger hierarchies, the ‘inverse’ hierarchy and equations associated with the real-analytic Eisenstein series E(β, β-bar ;1/2) among them. The specific bi-Hamiltonian structure of these equations is also discussed. (paper)

Singularity of the London penetration depth at quantum critical points in superconductors.

Science.gov (United States)

Chowdhury, Debanjan; Swingle, Brian; Berg, Erez; Sachdev, Subir

2013-10-11

We present a general theory of the singularity in the London penetration depth at symmetry-breaking and topological quantum critical points within a superconducting phase. While the critical exponents and ratios of amplitudes on the two sides of the transition are universal, an overall sign depends upon the interplay between the critical theory and the underlying Fermi surface. We determine these features for critical points to spin density wave and nematic ordering, and for a topological transition between a superconductor with Z2 fractionalization and a conventional superconductor. We note implications for recent measurements of the London penetration depth in BaFe2(As(1-x)P(x))2 [K. Hashimoto et al., Science 336, 1554 (2012)].

Development of a High Temperature Antenna Pointing Mechanism for BepiColombo Planetary Orbiter

Science.gov (United States)

Campo, Pablo; Barrio, Aingeru; Puente, Nicolas; Kyle, Robert

2013-09-01

BepiColombo is an ESA mission to Mercury its planetary orbiter (MPO) has two antenna pointing mechanism, High gain antenna pointing mechanism steers and points a large reflector which is integrated at system level by TAS-I Rome. Medium gain antenna (MGA) APM points a 1.5 m boom with a horn antenna. Both radiating elements exposed to sun fluxes as high as 10 solar constants without protections.The pointing mechanism is a major challenge as high performances are required in a harsh environment. It has required the development of new technologies, and components specially dedicated for the mission needs. Some of the state of the art required for the mission was achieved during the preparatory technology development activities [1]. However the number of critical elements involved, and the difficulties of some areas have required the continuation of the developments, and new research activities had to be launched in CD phase. Some of the major concerns and related areas of development are:- High temperature and long life requirements for the gearhead motors (up to 15500 equivalent APM revolutions, 19 million motor revolution)- Low thermal distortion of the mechanical chain, being at the same time insulating from external environment and interfaces (55 arcsec pointing error)- Low heat leak to the spacecraft (in the order of 50W per APM)- High precision position control, low microvibration noise and error stability in motion (16 arcsec/s)- High power radio frequency (18W in band Ka, 30 in X band) with phase stability for use in radio-science (3mm in Ka band, 5o in X band).- Wide range of motion (full 360o with end-stops)Currently HGA APM EQM azimuth and elevation stages are assembled and ready for test at actuator level.

Quantum critical point revisited by dynamical mean-field theory

International Nuclear Information System (INIS)

Xu, Wenhu; Kotliar, Gabriel; Rutgers University, Piscataway, NJ; Tsvelik, Alexei M.

2017-01-01

Dynamical mean-field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. We characterize the QCP by a universal scaling form of the self-energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low-energy kink and the high-energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high-energy antiferromagnetic paramagnons. Here, we use the frequency-dependent four-point correlation function of spin operators to calculate the momentum-dependent correction to the electron self-energy. Furthermore, by comparing with the calculations based on the spin-fermion model, our results indicate the frequency dependence of the quasiparticle-paramagnon vertices is an important factor to capture the momentum dependence in quasiparticle scattering.

The critical point of quantum chromodynamics through lattice and ...

Indian Academy of Sciences (India)

The Padé approximants are the rational functions. PL. M (z) = .... Deviations from a smooth behaviour near the critical point are visible in these extrap- ... see that there is evidence, albeit statistically not very significant, that the kurtosis changes.

Conductivity of Weakly Disordered Metals Close to a "Ferromagnetic" Quantum Critical Point

Science.gov (United States)

Kastrinakis, George

2018-05-01

We calculate analytically the conductivity of weakly disordered metals close to a "ferromagnetic" quantum critical point in the low-temperature regime. Ferromagnetic in the sense that the effective carrier potential V(q,ω ), due to critical fluctuations, is peaked at zero momentum q=0. Vertex corrections, due to both critical fluctuations and impurity scattering, are explicitly considered. We find that only the vertex corrections due to impurity scattering, combined with the self-energy, generate appreciable effects as a function of the temperature T and the control parameter a, which measures the proximity to the critical point. Our results are consistent with resistivity experiments in several materials displaying typical Fermi liquid behaviour, but with a diverging prefactor of the T^2 term for small a.

Vector boson excitations near deconfined quantum critical points.

Science.gov (United States)

Huh, Yejin; Strack, Philipp; Sachdev, Subir

2013-10-18

We show that the Néel states of two-dimensional antiferromagnets have low energy vector boson excitations in the vicinity of deconfined quantum critical points. We compute the universal damping of these excitations arising from spin-wave emission. Detection of such a vector boson will demonstrate the existence of emergent topological gauge excitations in a quantum spin system.

Electron self-trapping at quantum and classical critical points

NARCIS (Netherlands)

Auslender, M.I.; Katsnelson, M.I.

2006-01-01

Using Feynman path integral technique estimations of the ground state energy have been found for a conduction electron interacting with order parameter fluctuations near quantum critical points. In some cases only singular perturbation theory in the coupling constant emerges for the electron ground

Zero-field quantum critical point in CeCoIn5.

Science.gov (United States)

Tokiwa, Y; Bauer, E D; Gegenwart, P

2013-09-06

Quantum criticality in the normal and superconducting states of the heavy-fermion metal CeCoIn5 is studied by measurements of the magnetic Grüneisen ratio ΓH and specific heat in different field orientations and temperatures down to 50 mK. A universal temperature over magnetic field scaling of ΓH in the normal state indicates a hidden quantum critical point at zero field. Within the superconducting state, the quasiparticle entropy at constant temperature increases upon reducing the field towards zero, providing additional evidence for zero-field quantum criticality.

Metallic magnets without inversion symmetry and antiferromagnetic quantum critical points

Energy Technology Data Exchange (ETDEWEB)

Fischer, I.A.

2006-07-01

This thesis focusses on two classes of systems that exhibit non-Fermi liquid behaviour in experiments: we investigated aspects of chiral ferromagnets and of antiferromagnetic metals close to a quantum critical point. In chiral ferromagnets, the absence of inversion symmetry makes spin-orbit coupling possible, which leads to a helical modulation of the ferromagnetically ordered state. We studied the motion of electrons in the magnetically ordered state of a metal without inversion symmetry by calculating their generic band-structure. We found that spin-orbit coupling, although weak, has a profound effect on the shape of the Fermi surface: On a large portion of the Fermi surface the electron motion parallel to the helix practically stops. Signatures of this effect can be expected to show up in measurements of the anomalous Hall effect. Recent neutron scattering experiments uncovered the existence of a peculiar kind of partial order in a region of the phase diagram adjacent to the ordered state of the chiral ferromagnet MnSi. Starting from the premise that this partially ordered state is a thermodynamically distinct phase, we investigated an extended Ginzburg-Landau theory for chiral ferromagnets. In a certain parameter regime of the Ginzburg-Landau theory we identified crystalline phases that are reminiscent of the so-called blue phases in liquid crystals. Many antiferromagnetic heavy-fermion systems can be tuned into a regime where they exhibit non-Fermi liquid exponents in the temperature dependence of thermodynamic quantities such as the specific heat capacity; this behaviour could be due to a quantum critical point. If the quantum critical behaviour is field-induced, the external field does not only suppress antiferromagnetism but also induces spin precession and thereby influences the dynamics of the order parameter. We investigated the quantum critical behavior of clean antiferromagnetic metals subject to a static, spatially uniform external magnetic field. We

Molecular dynamics simulation of a binary mixture near the lower critical point

Energy Technology Data Exchange (ETDEWEB)

Pousaneh, Faezeh; Edholm, Olle, E-mail: oed@kth.se [Theoretical Biological Physics, Department of Theoretical Physics, Royal Institute of Technology (KTH), AlbaNova University Center, SE-106 91 Stockholm (Sweden); Maciołek, Anna [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Max-Planck-Institut für Intelligente Systeme, Heisenbergstrasse 3, D-70569 Stuttgart (Germany)

2016-07-07

2,6-lutidine molecules mix with water at high and low temperatures but in a wide intermediate temperature range a 2,6-lutidine/water mixture exhibits a miscibility gap. We constructed and validated an atomistic model for 2,6-lutidine and performed molecular dynamics simulations of 2,6-lutidine/water mixture at different temperatures. We determined the part of demixing curve with the lower critical point. The lower critical point extracted from our data is located close to the experimental one. The estimates for critical exponents obtained from our simulations are in a good agreement with the values corresponding to the 3D Ising universality class.

Understanding and Modeling the Evolution of Critical Points under Gaussian Blurring

NARCIS (Netherlands)

Kuijper, A.; Florack, L.M.J.; Heyden, A.; Sparr, G.; Nielsen, M.; Johansen, P.

2002-01-01

In order to investigate the deep structure of Gaussian scale space images, one needs to understand the behaviour of critical points under the influence of parameter-driven blurring. During this evolution two different types of special points are encountered, the so-called scale space saddles and the

IMAGE-PLANE ANALYSIS OF n-POINT-MASS LENS CRITICAL CURVES AND CAUSTICS

Energy Technology Data Exchange (ETDEWEB)

Danek, Kamil; Heyrovský, David, E-mail: kamil.danek@utf.mff.cuni.cz, E-mail: heyrovsky@utf.mff.cuni.cz [Institute of Theoretical Physics, Faculty of Mathematics and Physics, Charles University in Prague (Czech Republic)

2015-06-10

The interpretation of gravitational microlensing events caused by planetary systems or multiple stars is based on the n-point-mass lens model. The first planets detected by microlensing were well described by the two-point-mass model of a star with one planet. By the end of 2014, four events involving three-point-mass lenses had been announced. Two of the lenses were stars with two planetary companions each; two were binary stars with a planet orbiting one component. While the two-point-mass model is well understood, the same cannot be said for lenses with three or more components. Even the range of possible critical-curve topologies and caustic geometries of the three-point-mass lens remains unknown. In this paper we provide new tools for mapping the critical-curve topology and caustic cusp number in the parameter space of n-point-mass lenses. We perform our analysis in the image plane of the lens. We show that all contours of the Jacobian are critical curves of re-scaled versions of the lens configuration. Utilizing this property further, we introduce the cusp curve to identify cusp-image positions on all contours simultaneously. In order to track cusp-number changes in caustic metamorphoses, we define the morph curve, which pinpoints the positions of metamorphosis-point images along the cusp curve. We demonstrate the usage of both curves on simple two- and three-point-mass lens examples. For the three simplest caustic metamorphoses we illustrate the local structure of the image and source planes.

Detection of quantum critical points by a probe qubit.

Science.gov (United States)

Zhang, Jingfu; Peng, Xinhua; Rajendran, Nageswaran; Suter, Dieter

2008-03-14

Quantum phase transitions occur when the ground state of a quantum system undergoes a qualitative change when an external control parameter reaches a critical value. Here, we demonstrate a technique for studying quantum systems undergoing a phase transition by coupling the system to a probe qubit. It uses directly the increased sensibility of the quantum system to perturbations when it is close to a critical point. Using an NMR quantum simulator, we demonstrate this measurement technique for two different types of quantum phase transitions in an Ising spin chain.

An Improved Computational Method for the Calculation of Mixture Liquid-Vapor Critical Points

Science.gov (United States)

Dimitrakopoulos, Panagiotis; Jia, Wenlong; Li, Changjun

2014-05-01

Knowledge of critical points is important to determine the phase behavior of a mixture. This work proposes a reliable and accurate method in order to locate the liquid-vapor critical point of a given mixture. The theoretical model is developed from the rigorous definition of critical points, based on the SRK equation of state (SRK EoS) or alternatively, on the PR EoS. In order to solve the resulting system of nonlinear equations, an improved method is introduced into an existing Newton-Raphson algorithm, which can calculate all the variables simultaneously in each iteration step. The improvements mainly focus on the derivatives of the Jacobian matrix, on the convergence criteria, and on the damping coefficient. As a result, all equations and related conditions required for the computation of the scheme are illustrated in this paper. Finally, experimental data for the critical points of 44 mixtures are adopted in order to validate the method. For the SRK EoS, average absolute errors of the predicted critical-pressure and critical-temperature values are 123.82 kPa and 3.11 K, respectively, whereas the commercial software package Calsep PVTSIM's prediction errors are 131.02 kPa and 3.24 K. For the PR EoS, the two above mentioned average absolute errors are 129.32 kPa and 2.45 K, while the PVTSIM's errors are 137.24 kPa and 2.55 K, respectively.

Scaling, crossover, and classical behavior in the order parameter equation for coexisting phases of benzene from triple point to critical point

International Nuclear Information System (INIS)

Shimansky, Yu.I.; Shimanskaya, E.T.

1996-01-01

The temperature dependence of the density along the coexistence curve of benzene in the vicinity of the critical point and in a wide temperature range down to the triple point was investigated. The original results as well as literature data were statistically treated. A regression analysis of data on the critical exponents and critical amplitudes used as fitting parameters in a model equations was carried out. An adequate description of the order parameter by the three-term scaling equation in the entire two-phase (liquid-gas) region of benzene was obtained with experimental values of Β O -0.352 ±0.003 and δ = 1.3 ± 0.2, which are inconsistent with the Ising model (Β O = 0.325) and the Wegner exponent (δ = 0.5), respectively. It is shown that the equation with fixed classical exponents does not adequately describe the experimental data even far from the critical point

Scaling functions for the Inverse Compressibility near the QCD critical point

Science.gov (United States)

Lacey, Roy

2017-09-01

The QCD phase diagram can be mapped out by studying fluctuations and their response to changes in the temperature and baryon chemical potential. Theoretical studies indicate that the cumulant ratios Cn /Cm used to characterize the fluctuation of conserved charges, provide a valuable probe of deconfinement and chiral dynamics, as well as for identifying the position of the critical endpoint (CEP) in the QCD phase diagram. The ratio C1 /C2 , which is linked to the inverse compressibility, vanishes at the CEP due to the divergence of the net quark number fluctuations at the critical point belonging to the Z(2) universality class. Therefore, it's associated scaling function can give insight on the location of the critical end point, as well as the critical exponents required to assign its static universality class. Scaling functions for the ratio C1 /C2 , obtained from net-proton multiplicity distributions for a broad range of collision centralities in Au+Au (√{sNN} = 7.7 - 200 GeV) collisions will be presented and discussed.

The Critical Point Entanglement and Chaos in the Dicke Model

Directory of Open Access Journals (Sweden)

Lina Bao

2015-07-01

Full Text Available Ground state properties and level statistics of the Dicke model for a finite number of atoms are investigated based on a progressive diagonalization scheme (PDS. Particle number statistics, the entanglement measure and the Shannon information entropy at the resonance point in cases with a finite number of atoms as functions of the coupling parameter are calculated. It is shown that the entanglement measure defined in terms of the normalized von Neumann entropy of the reduced density matrix of the atoms reaches its maximum value at the critical point of the quantum phase transition where the system is most chaotic. Noticeable change in the Shannon information entropy near or at the critical point of the quantum phase transition is also observed. In addition, the quantum phase transition may be observed not only in the ground state mean photon number and the ground state atomic inversion as shown previously, but also in fluctuations of these two quantities in the ground state, especially in the atomic inversion fluctuation.

Model for a Ferromagnetic Quantum Critical Point in a 1D Kondo Lattice

Science.gov (United States)

Komijani, Yashar; Coleman, Piers

2018-04-01

Motivated by recent experiments, we study a quasi-one-dimensional model of a Kondo lattice with ferromagnetic coupling between the spins. Using bosonization and dynamical large-N techniques, we establish the presence of a Fermi liquid and a magnetic phase separated by a local quantum critical point, governed by the Kondo breakdown picture. Thermodynamic properties are studied and a gapless charged mode at the quantum critical point is highlighted.

One-norm geometric quantum discord and critical point estimation in the XY spin chain

Energy Technology Data Exchange (ETDEWEB)

Cheng, Chang-Cheng; Wang, Yao; Guo, Jin-Liang, E-mail: guojinliang80@163.com

2016-11-15

In contrast with entanglement and quantum discord (QD), we investigate the thermal quantum correlation in terms of Schatten one-norm geometric quantum discord (GQD) in the XY spin chain, and analyze their capabilities in detecting the critical point of quantum phase transition. We show that the one-norm GQD can reveal more properties about quantum correlation between two spins, especially for the long-range quantum correlation at finite temperature. Under the influences of site distance, anisotropy and temperature, one-norm GQD and its first derivative make it possible to detect the critical point efficiently for a general XY spin chain. - Highlights: • Comparing with entanglement and QD, one-norm GQD is more robust versus the temperature. • One-norm GQD is more efficient in characterization of long-range quantum correlation between two distant qubits. • One-norm GQD performs well in highlighting the critical point of QPT at zero or low finite temperature. • One-norm GQD has a number of advantages over QD in detecting the critical point of the spin chain.

Theory of First Order Chemical Kinetics at the Critical Point of Solution.

Science.gov (United States)

Baird, James K; Lang, Joshua R

2017-10-26

Liquid mixtures, which have a phase diagram exhibiting a miscibility gap ending in a critical point of solution, have been used as solvents for chemical reactions. The reaction rate in the forward direction has often been observed to slow down as a function of temperature in the critical region. Theories based upon the Gibbs free energy of reaction as the driving force for chemical change have been invoked to explain this behavior. With the assumption that the reaction is proceeding under relaxation conditions, these theories expand the free energy in a Taylor series about the position of equilibrium. Since the free energy is zero at equilibrium, the leading term in the Taylor series is proportional to the first derivative of the free energy with respect to the extent of reaction. To analyze the critical behavior of this derivative, the theories exploit the principle of critical point isomorphism, which is thought to govern all critical phenomena. They find that the derivative goes to zero in the critical region, which accounts for the slowing down observed in the reaction rate. As has been pointed out, however, most experimental rate investigations have been carried out under irreversible conditions as opposed to relaxation conditions [Shen et al. J. Phys. Chem. A 2015, 119, 8784-8791]. Below, we consider a reaction governed by first order kinetics and invoke transition state theory to take into account the irreversible conditions. We express the apparent activation energy in terms of thermodynamic derivatives evaluated under standard conditions as well as the pseudoequilibrium conditions associated with the reactant and the activated complex. We show that these derivatives approach infinity in the critical region. The apparent activation energy follows this behavior, and its divergence accounts for the slowing down of the reaction rate.

Noise and time delay induce critical point in a bistable system

Science.gov (United States)

Zhang, Jianqiang; Nie, Linru; Yu, Lilong; Zhang, Xinyu

2014-07-01

We study relaxation time Tc of time-delayed bistable system driven by two cross-correlated Gaussian white noises that one is multiplicative and the other is additive. By means of numerical calculations, the results indicate that: (i) Combination of noise and time delay can induce two critical points about the relaxation time at some certain noise cross-correlation strength λ under the condition that the multiplicative intensity D equals to the additive noise intensity α. (ii) For each fixed D or α, there are two symmetrical critical points which locates in the regions of positive and negative correlations, respectively. Namely, as λ equals to the critical value λc, Tc is independent of the delay time and the result of Tc versus τ is a horizontal line, but as |λ|>|λc| (or |λ|decreases) with the delay time increasing. (iii) In the presence of D = α, the change of λc with D is two symmetrical curves about the axis of λc = 0, and the critical value λc is close to zero for a smaller D, which approaches to +1 or -1 for a greater D.

Duality between the Deconfined Quantum-Critical Point and the Bosonic Topological Transition

Directory of Open Access Journals (Sweden)

Yan Qi Qin

2017-09-01

Full Text Available Recently, significant progress has been made in (2+1-dimensional conformal field theories without supersymmetry. In particular, it was realized that different Lagrangians may be related by hidden dualities; i.e., seemingly different field theories may actually be identical in the infrared limit. Among all the proposed dualities, one has attracted particular interest in the field of strongly correlated quantum-matter systems: the one relating the easy-plane noncompact CP^{1} model (NCCP^{1} and noncompact quantum electrodynamics (QED with two flavors (N=2 of massless two-component Dirac fermions. The easy-plane NCCP^{1} model is the field theory of the putative deconfined quantum-critical point separating a planar (XY antiferromagnet and a dimerized (valence-bond solid ground state, while N=2 noncompact QED is the theory for the transition between a bosonic symmetry-protected topological phase and a trivial Mott insulator. In this work, we present strong numerical support for the proposed duality. We realize the N=2 noncompact QED at a critical point of an interacting fermion model on the bilayer honeycomb lattice and study it using determinant quantum Monte Carlo (QMC simulations. Using stochastic series expansion QMC simulations, we study a planar version of the S=1/2 J-Q spin Hamiltonian (a quantum XY model with additional multispin couplings and show that it hosts a continuous transition between the XY magnet and the valence-bond solid. The duality between the two systems, following from a mapping of their phase diagrams extending from their respective critical points, is supported by the good agreement between the critical exponents according to the proposed duality relationships. In the J-Q model, we find both continuous and first-order transitions, depending on the degree of planar anisotropy, with deconfined quantum criticality surviving only up to moderate strengths of the anisotropy. This explains previous claims of no deconfined

Transcriptomic responses to darkness stress point to common coral bleaching mechanisms

Science.gov (United States)

Desalvo, M. K.; Estrada, A.; Sunagawa, S.; Medina, Mónica

2012-03-01

Coral bleaching occurs in response to numerous abiotic stressors, the ecologically most relevant of which is hyperthermic stress due to increasing seawater temperatures. Bleaching events can span large geographic areas and are currently a salient threat to coral reefs worldwide. Much effort has been focused on understanding the molecular and cellular events underlying bleaching, and these studies have mainly utilized heat and light stress regimes. In an effort to determine whether different stressors share common bleaching mechanisms, we used complementary DNA (cDNA) microarrays for the corals Acropora palmata and Montastraea faveolata (containing >10,000 features) to measure differential gene expression during darkness stress. Our results reveal a striking transcriptomic response to darkness in A. palmata involving chaperone and antioxidant up-regulation, growth arrest, and metabolic modifications. As these responses were previously measured during thermal stress, our results suggest that different stressors may share common bleaching mechanisms. Furthermore, our results point to hypoxia and endoplasmic reticulum stress as critical cellular events involved in molecular bleaching mechanisms. On the other hand, we identified a meager transcriptomic response to darkness in M. faveolata where gene expression differences between host colonies and sampling locations were greater than differences between control and stressed fragments. This and previous coral microarray studies reveal the immense range of transcriptomic responses that are possible when studying two coral species that differ greatly in their ecophysiology, thus pointing to the importance of comparative approaches in forecasting how corals will respond to future environmental change.

Impact of resonance decays on critical point signals in net-proton fluctuations

Energy Technology Data Exchange (ETDEWEB)

Bluhm, Marcus; Schaefer, Thomas [North Carolina State University, Department of Physics, Raleigh, NC (United States); Nahrgang, Marlene [SUBATECH, UMR 6457, Universite de Nantes, Ecole des Mines de Nantes, IN2P3/CNRS, Nantes (France); Duke University, Department of Physics, Durham, NC (United States); Bass, Steffen A. [Duke University, Department of Physics, Durham, NC (United States)

2017-04-15

The non-monotonic beam energy dependence of the higher cumulants of net-proton fluctuations is a widely studied signature of the conjectured presence of a critical point in the QCD phase diagram. In this work we study the effect of resonance decays on critical fluctuations. We show that resonance effects reduce the signatures of critical fluctuations, but that for reasonable parameter choices critical effects in the net-proton cumulants survive. The relative role of resonance decays has a weak dependence on the order of the cumulants studied with a slightly stronger suppression of critical effects for higher-order cumulants. (orig.)

Criticality benchmarks for COG: A new point-wise Monte Carlo code

International Nuclear Information System (INIS)

Alesso, H.P.; Pearson, J.; Choi, J.S.

1989-01-01

COG is a new point-wise Monte Carlo code being developed and tested at LLNL for the Cray computer. It solves the Boltzmann equation for the transport of neutrons, photons, and (in future versions) charged particles. Techniques included in the code for modifying the random walk of particles make COG most suitable for solving deep-penetration (shielding) problems. However, its point-wise cross-sections also make it effective for a wide variety of criticality problems. COG has some similarities to a number of other computer codes used in the shielding and criticality community. These include the Lawrence Livermore National Laboratory (LLNL) codes TART and ALICE, the Los Alamos National Laboratory code MCNP, the Oak Ridge National Laboratory codes 05R, 06R, KENO, and MORSE, the SACLAY code TRIPOLI, and the MAGI code SAM. Each code is a little different in its geometry input and its random-walk modification options. Validating COG consists in part of running benchmark calculations against critical experiments as well as other codes. The objective of this paper is to present calculational results of a variety of critical benchmark experiments using COG, and to present the resulting code bias. Numerous benchmark calculations have been completed for a wide variety of critical experiments which generally involve both simple and complex physical problems. The COG results, which they report in this paper, have been excellent

Testing of the BipiColombo Antenna Pointing Mechanism

Science.gov (United States)

Campo, Pablo; Barrio, Aingeru; Martin, Fernando

2015-09-01

BepiColombo is an ESA mission to Mercury, its planetary orbiter (MPO) has two antenna pointing mechanism, High gain antenna (HGA) pointing mechanism steers and points a large reflector which is integrated at system level by TAS-I Rome. Medium gain antenna (MGA) APM points a 1.5 m boom with a horn antenna. Both radiating elements are exposed to sun fluxes as high as 10 solar constants without protections.A previous paper [1] described the design and development process to solve the challenges of performing in harsh environment.. Current paper is focused on the testing process of the qualification units. Testing performance of antenna pointing mechanism in its specific environmental conditions has required special set-up and techniques. The process has provided valuable feedback on the design and the testing methods which have been included in the PFM design and tests.Some of the technologies and components were developed on dedicated items priort to EQM, but once integrated, test behaviour had relevant differences.Some of the major concerns for the APM testing are:- Create during the thermal vacuum testing the qualification temperature map with gradients along the APM. From of 200oC to 70oC.- Test in that conditions the radio frequency and pointing performances adding also high RF power to check the power handling and self-heating of the rotary joint.- Test in life up to 12000 equivalent APM revolutions, that is 14.3 million motor revolutions in different thermal conditions.- Measure low thermal distortion of the mechanical chain, being at the same time insulated from external environment and interfaces (55 arcsec pointing error)- Perform deployment of large items guaranteeing during the process low humidity, below 5% to protect dry lubrication- Verify stability with representative inertia of large boom or reflector 20 Kgm2.

An assessment of the melting, boiling, and critical point data of the alkali metals

International Nuclear Information System (INIS)

Ohse, R.W.; Babelot, J.-F.; Magill, J.

1985-01-01

The paper reviews the measured melting, boiling and critical point data of alkali metals. A survey of the static heat generation methods for density and pressure-volume-temperature measurements is given. Measured data on the melting and boiling temperatures of lithium, sodium, potassium, rubidium and caesium are summarised. Also measured critical point data for the same five alkali metals are presented, and discussed. (U.K.)

Quantum Critical Point revisited by the Dynamical Mean Field Theory

Science.gov (United States)

Xu, Wenhu; Kotliar, Gabriel; Tsvelik, Alexei

Dynamical mean field theory is used to study the quantum critical point (QCP) in the doped Hubbard model on a square lattice. The QCP is characterized by a universal scaling form of the self energy and a spin density wave instability at an incommensurate wave vector. The scaling form unifies the low energy kink and the high energy waterfall feature in the spectral function, while the spin dynamics includes both the critical incommensurate and high energy antiferromagnetic paramagnons. We use the frequency dependent four-point correlation function of spin operators to calculate the momentum dependent correction to the electron self energy. Our results reveal a substantial difference with the calculations based on the Spin-Fermion model which indicates that the frequency dependence of the the quasiparitcle-paramagnon vertices is an important factor. The authors are supported by Center for Computational Design of Functional Strongly Correlated Materials and Theoretical Spectroscopy under DOE Grant DE-FOA-0001276.

Microbial profile and critical control points during processing of 'robo ...

African Journals Online (AJOL)

STORAGESEVER

2009-05-18

May 18, 2009 ... frying, surface fat draining, open-air cooling, and holding/packaging in polyethylene films during sales and distribution. The product was, however, classified under category III with respect to risk and the significance of monitoring and evaluation of quality using the hazard analysis critical control point.

Temperature dependence of the interband critical points of bulk Ge and strained Ge on Si

Science.gov (United States)

Fernando, Nalin S.; Nunley, T. Nathan; Ghosh, Ayana; Nelson, Cayla M.; Cooke, Jacqueline A.; Medina, Amber A.; Zollner, Stefan; Xu, Chi; Menendez, Jose; Kouvetakis, John

2017-11-01

Epitaxial Ge layers on a Si substrate experience a tensile biaxial stress due to the difference between the thermal expansion coefficients of the Ge epilayer and the Si substrate, which can be measured using asymmetric X-ray diffraction reciprocal space maps. This stress depends on temperature and affects the band structure, interband critical points, and optical spectra. This manuscripts reports careful measurements of the temperature dependence of the dielectric function and the interband critical point parameters of bulk Ge and Ge epilayers on Si using spectroscopic ellipsometry from 80 to 780 K and from 0.8 to 6.5 eV. The authors find a temperature-dependent redshift of the E1 and E1 + Δ1 critical points in Ge on Si (relative to bulk Ge). This redshift can be described well with a model based on thermal expansion coefficients, continuum elasticity theory, and the deformation potential theory for interband transitions. The interband transitions leading to E0‧ and E2 critical points have lower symmetry and therefore are not affected by the stress.

Hazard analysis and critical control point (HACCP) for an ultrasound food processing operation.

Science.gov (United States)

Chemat, Farid; Hoarau, Nicolas

2004-05-01

Emerging technologies, such as ultrasound (US), used for food and drink production often cause hazards for product safety. Classical quality control methods are inadequate to control these hazards. Hazard analysis of critical control points (HACCP) is the most secure and cost-effective method for controlling possible product contamination or cross-contamination, due to physical or chemical hazard during production. The following case study on the application of HACCP to an US food-processing operation demonstrates how the hazards at the critical control points of the process are effectively controlled through the implementation of HACCP.

Supersymmetric quantum mechanics under point singularities

International Nuclear Information System (INIS)

Uchino, Takashi; Tsutsui, Izumi

2003-01-01

We provide a systematic study on the possibility of supersymmetry (SUSY) for one-dimensional quantum mechanical systems consisting of a pair of lines R or intervals [-l, l] each having a point singularity. We consider the most general singularities and walls (boundaries) at x = ±l admitted quantum mechanically, using a U(2) family of parameters to specify one singularity and similarly a U(1) family of parameters to specify one wall. With these parameter freedoms, we find that for a certain subfamily the line systems acquire an N = 1 SUSY which can be enhanced to N = 4 if the parameters are further tuned, and that these SUSY are generically broken except for a special case. The interval systems, on the other hand, can accommodate N = 2 or N = 4 SUSY, broken or unbroken, and exhibit a rich variety of (degenerate) spectra. Our SUSY systems include the familiar SUSY systems with the Dirac δ(x)-potential, and hence are extensions of the known SUSY quantum mechanics to those with general point singularities and walls. The self-adjointness of the supercharge in relation to the self-adjointness of the Hamiltonian is also discussed

Root and critical point behaviors of certain sums of polynomials

Indian Academy of Sciences (India)

Seon-Hong Kim

2018-04-24

Apr 24, 2018 ... Root and critical point behaviors of certain sums of polynomials. SEON-HONG KIM1,∗. , SUNG YOON KIM2, TAE HYUNG KIM2 and SANGHEON LEE2. 1Department of Mathematics, Sookmyung Women's University, Seoul 140-742, Korea. 2Gyeonggi Science High School, Suwon 440-800, Korea.

Infrared conformality and bulk critical points: SU(2) with heavy adjoint quarks

CERN Document Server

Lucini, Biagio; Rago, Antonio; Rinaldi, Enrico

2013-01-01

The lattice phase structure of a gauge theory can be a serious obstruction to Monte Carlo studies of its continuum behaviour. This issue is particularly delicate when numerical studies are performed to determine whether a theory is in a (near-)conformal phase. In this work we investigate the heavy mass limit of the SU(2) gauge theory with Nf=2 adjoint fermions and its lattice phase diagram, showing the presence of a critical point ending a line of first order bulk phase transition. The relevant gauge observables and the low-lying spectrum are monitored in the vicinity of the critical point with very good control over different systematic effects. The scaling properties of masses and susceptibilities open the possibility that the effective theory at criticality is a scalar theory in the universality class of the four-dimensional Gaussian model. This behaviour is clearly different from what is observed for SU(2) gauge theory with two dynamical adjoint fermions, whose (near-)conformal numerical signature is henc...

Evolving towards a critical point: A possible electromagnetic way in which the critical regime is reached as the rupture approaches

Directory of Open Access Journals (Sweden)

P. G. Kapiris

2003-01-01

Full Text Available In analogy to the study of critical phase transitions in statistical physics, it has been argued recently that the fracture of heterogeneous materials could be viewed as a critical phenomenon, either at laboratory or at geophysical scales. If the picture of the development of the fracture is correct one may guess that the precursors may reveal the critical approach of the main-shock. When a heterogeneous material is stretched, its evolution towards breaking is characterized by the appearance of microcracks before the final  break-up. Microcracks produce both acoustic and electromagnetic(EM emission in the frequency range from VLF to VHF. The microcracks and the associated acoustic and EM activities constitute the so-called precursors of general fracture. These precursors are detectable not only at laboratory but also at geophysical scales. VLF and VHF acoustic and EM emissions have been reported resulting from volcanic and seismic activities in various geologically distinct regions of the world. In the present work we attempt to establish the hypothesis that the evolution of the Earth's crust towards the critical point takes place not only in a mechanical but also in an electromagnetic sense. In other words, we focus on the possible electromagnetic criticality, which is reached while the catastrophic rupture in the Earth's crust approaches. Our main tool is the monitoring of micro-fractures that occur before the final breakup, by recording their radio-electromagnetic emissions. We show that the spectral power law analysis of the electromagnetic precursors reveals distinguishing signatures of underlying critical dynamics, such as: (i the emergence of memory effects; (ii the decrease with time of the anti-persistence behaviour; (iii the presence of persistence properties in the tail of the sequence of the precursors; and (iv the acceleration of the precursory electro-magnetic energy release. Moreover, the statistical analysis of the amplitudes of

Finite Blaschke products with prescribed critical points, Stieltjes polynomials, and moment problems

Science.gov (United States)

Semmler, Gunter; Wegert, Elias

2017-09-01

The determination of a finite Blaschke product from its critical points is a well-known problem with interrelations to several other topics. Though existence and uniqueness of solutions are established for long, we present new aspects which have not yet been explored to their full extent. In particular, we show that the following three problems are equivalent: (i) determining a finite Blaschke product from its critical points, (ii) finding the equilibrium position of moveable point charges interacting with a special configuration of fixed charges, and (iii) solving a moment problem for the canonical representation of power moments on the real axis. These equivalences are not only of theoretical interest, but also open up new perspectives for the design of algorithms. For instance, the second problem is closely linked to the determination of certain Stieltjes and Van Vleck polynomials for a second order ODE and characterizes solutions as global minimizers of an energy functional.

Black holes as critical point of quantum phase transition.

Science.gov (United States)

Dvali, Gia; Gomez, Cesar

We reformulate the quantum black hole portrait in the language of modern condensed matter physics. We show that black holes can be understood as a graviton Bose-Einstein condensate at the critical point of a quantum phase transition, identical to what has been observed in systems of cold atoms. The Bogoliubov modes that become degenerate and nearly gapless at this point are the holographic quantum degrees of freedom responsible for the black hole entropy and the information storage. They have no (semi)classical counterparts and become inaccessible in this limit. These findings indicate a deep connection between the seemingly remote systems and suggest a new quantum foundation of holography. They also open an intriguing possibility of simulating black hole information processing in table-top labs.

The critical current of point symmetric Josephson tunnel junctions

International Nuclear Information System (INIS)

Monaco, Roberto

2016-01-01

Highlights: • We disclose some geometrical properties of the critical current field dependence that apply to a large class of Josephson junctions characterized by a point symmetric shape. • The developed theory is valid for any orientation of the applied magnetic field, therefore it allows the determine the consequences of field misalignment in the experimental setups. • We also address that the threshold curves of Josephson tunnel junctions with complex shapes can be expressed as a linear combination of the threshold curves of junctions with simpler point symmetric shapes. - Abstract: The physics of Josephson tunnel junctions drastically depends on their geometrical configurations. The shape of the junction determines the specific form of the magnetic-field dependence of its Josephson current. Here we address the magnetic diffraction patterns of specially shaped planar Josephson tunnel junctions in the presence of an in-plane magnetic field of arbitrary orientations. We focus on a wide ensemble of junctions whose shape is invariant under point reflection. We analyze the implications of this type of isometry and derive the threshold curves of junctions whose shape is the union or the relative complement of two point symmetric plane figures.

Seafood safety: economics of hazard analysis and Critical Control Point (HACCP) programmes

National Research Council Canada - National Science Library

Cato, James C

1998-01-01

.... This document on economic issues associated with seafood safety was prepared to complement the work of the Service in seafood technology, plant sanitation and Hazard Analysis Critical Control Point (HACCP) implementation...

Searching for the QCD Critical Point with the Energy Dependence of pt Fluctuations

Science.gov (United States)

Novak, John; STAR Collaboration

2013-10-01

If systems produced in relativistic heavy-ion collisions pass near the QCD critical point while cooling, the correlation length of the system may diverge due to the phenomena of critical opalescence. The transverse momentum distribution, being related to the state variable temperature, might be sensitive to this change in correlation length. Non-monotonic behavior with changing incident energy or centrality of any transverse momentum observable that is sensitive to the correlation length could thus be indicative of the QCD critical point. Accordingly, we report measurements related to transverse momentum fluctuations such as as a function of event centrality and incident energy for Au+Au collisions at √{sNN} = 7.7, 11.5, 19.6, 27, 39, 62.4, and 200 GeV using the STAR detector at RHIC. The results are compared to UrQMD model predictions and previous experimental measurements.

Intrinsic low pass filtering improves signal-to-noise ratio in critical-point flexure biosensors

International Nuclear Information System (INIS)

Jain, Ankit; Alam, Muhammad Ashraful

2014-01-01

A flexure biosensor consists of a suspended beam and a fixed bottom electrode. The adsorption of the target biomolecules on the beam changes its stiffness and results in change of beam's deflection. It is now well established that the sensitivity of sensor is maximized close to the pull-in instability point, where effective stiffness of the beam vanishes. The question: “Do the signal-to-noise ratio (SNR) and the limit-of-detection (LOD) also improve close to the instability point?”, however remains unanswered. In this article, we systematically analyze the noise response to evaluate SNR and establish LOD of critical-point flexure sensors. We find that a flexure sensor acts like an effective low pass filter close to the instability point due to its relatively small resonance frequency, and rejects high frequency noise, leading to improved SNR and LOD. We believe that our conclusions should establish the uniqueness and the technological relevance of critical-point biosensors.

Generalized correlation of latent heats of vaporization of coal liquid model compounds between their freezing points and critical points

Energy Technology Data Exchange (ETDEWEB)

Sivaraman, A.; Kobuyashi, R.; Mayee, J.W.

1984-02-01

Based on Pitzer's three-parameter corresponding states principle, the authors have developed a correlation of the latent heat of vaporization of aromatic coal liquid model compounds for a temperature range from the freezing point to the critical point. An expansion of the form L = L/sub 0/ + ..omega..L /sub 1/ is used for the dimensionless latent heat of vaporization. This model utilizes a nonanalytic functional form based on results derived from renormalization group theory of fluids in the vicinity of the critical point. A simple expression for the latent heat of vaporization L = D/sub 1/epsilon /SUP 0.3333/ + D/sub 2/epsilon /SUP 0.8333/ + D/sub 4/epsilon /SUP 1.2083/ + E/sub 1/epsilon + E/sub 2/epsilon/sup 2/ + E/sub 3/epsilon/sup 3/ is cast in a corresponding states principle correlation for coal liquid compounds. Benzene, the basic constituent of the functional groups of the multi-ring coal liquid compounds, is used as the reference compound in the present correlation. This model works very well at both low and high reduced temperatures approaching the critical point (0.02 < epsilon = (T /SUB c/ - T)/(T /SUB c/- 0.69)). About 16 compounds, including single, two, and three-ring compounds, have been tested and the percent root-mean-square deviations in latent heat of vaporization reported and estimated through the model are 0.42 to 5.27%. Tables of the coefficients of L/sub 0/ and L/sub 1/ are presented. The contributing terms of the latent heat of vaporization function are also presented in a table for small increments of epsilon.

Hygienic-sanitary working practices and implementation of a Hazard Analysis and Critical Control Point (HACCP plan in lobster processing industries

Directory of Open Access Journals (Sweden)

Cristina Farias da Fonseca

2013-03-01

Full Text Available This study aimed to verify the hygienic-sanitary working practices and to create and implement a Hazard Analysis Critical Control Point (HACCP in two lobster processing industries in Pernambuco State, Brazil. The industries studied process frozen whole lobsters, frozen whole cooked lobsters, and frozen lobster tails for exportation. The application of the hygienic-sanitary checklist in the industries analyzed achieved conformity rates over 96% to the aspects evaluated. The use of the Hazard Analysis Critical Control Point (HACCP plan resulted in the detection of two critical control points (CCPs including the receiving and classification steps in the processing of frozen lobster and frozen lobster tails, and an additional critical control point (CCP was detected during the cooking step of processing of the whole frozen cooked lobster. The proper implementation of the Hazard Analysis Critical Control Point (HACCP plan in the lobster processing industries studied proved to be the safest and most cost-effective method to monitor each critical control point (CCP hazards.

Mechanisms of chain adsorption on porous substrates and critical conditions of polymer chromatography.

Science.gov (United States)

Cimino, Richard T; Rasmussen, Christopher J; Brun, Yefim; Neimark, Alexander V

2016-11-01

Polymer adsorption is a ubiquitous phenomenon with numerous technological and healthcare applications. The mechanisms of polymer adsorption on surfaces and in pores are complex owing to a competition between various entropic and enthalpic factors. Due to adsorption of monomers to the surface, the chain gains in enthalpy yet loses in entropy because of confining effects. This competition leads to the existence of critical conditions of adsorption when enthalpy gain and entropy loss are in balance. The critical conditions are controlled by the confining geometry and effective adsorption energy, which depends on the solvent composition and temperature. This phenomenon has important implications in polymer chromatography, since the retention at the critical point of adsorption (CPA) is chain length independent. However, the mechanisms of polymer adsorption in pores are poorly understood and there is an ongoing discussion in the theoretical literature about the very existence of CPA for polymer adsorption on porous substrates. In this work, we examine the mechanisms of chain adsorption on a model porous substrate using Monte Carlo (MC) simulations. We distinguish three adsorption mechanisms depending on the chain location: on external surface, completely confined in pores, and also partially confined in pores in so-called "flower" conformations. The free energies of different conformations of adsorbed chains are calculated by the incremental gauge cell MC method that allows one to determine the partition coefficient as a function of the adsorption potential, pore size, and chain length. We confirm the existence of the CPA for chain length independent separation on porous substrates, which is explained by the dominant contributions of the chain adsorption at the external surface, in particular in flower conformations. Moreover, we show that the critical conditions for porous and nonporous substrates are identical and depend only on the surface chemistry. The theoretical

The application of hazard analysis and critical control points and risk management in the preparation of anti-cancer drugs.

Science.gov (United States)

Bonan, Brigitte; Martelli, Nicolas; Berhoune, Malik; Maestroni, Marie-Laure; Havard, Laurent; Prognon, Patrice

2009-02-01

To apply the Hazard analysis and Critical Control Points method to the preparation of anti-cancer drugs. To identify critical control points in our cancer chemotherapy process and to propose control measures and corrective actions to manage these processes. The Hazard Analysis and Critical Control Points application began in January 2004 in our centralized chemotherapy compounding unit. From October 2004 to August 2005, monitoring of the process nonconformities was performed to assess the method. According to the Hazard Analysis and Critical Control Points method, a multidisciplinary team was formed to describe and assess the cancer chemotherapy process. This team listed all of the critical points and calculated their risk indexes according to their frequency of occurrence, their severity and their detectability. The team defined monitoring, control measures and corrective actions for each identified risk. Finally, over a 10-month period, pharmacists reported each non-conformity of the process in a follow-up document. Our team described 11 steps in the cancer chemotherapy process. The team identified 39 critical control points, including 11 of higher importance with a high-risk index. Over 10 months, 16,647 preparations were performed; 1225 nonconformities were reported during this same period. The Hazard Analysis and Critical Control Points method is relevant when it is used to target a specific process such as the preparation of anti-cancer drugs. This method helped us to focus on the production steps, which can have a critical influence on product quality, and led us to improve our process.

Determining the Critical Point of a Sigmoidal Curve via its Fourier Transform

International Nuclear Information System (INIS)

Bilge, Ayse Humeyra; Ozdemir, Yunus

2016-01-01

A sigmoidal curve y(t) is a monotone increasing curve such that all derivatives vanish at infinity. Let t_n be the point where the nth derivative of y(t) reaches its global extremum. In the previous work on sol-gel transition modelled by the Susceptible-Infected- Recovered (SIR) system, we observed that the sequence { t_n } seemed to converge to a point that agrees qualitatively with the location of the gel point [2]. In the present work we outline a proof that for sigmoidal curves satisfying fairly general assumptions on their Fourier transform, the sequence { t_n } is convergent and we call it “the critical point of the sigmoidal curve”. In the context of phase transitions, the limit point is interpreted as a junction point of two different regimes where all derivatives undergo their highest rate of change. (paper)

Origin of chaos near critical points of quantum flow.

Science.gov (United States)

Efthymiopoulos, C; Kalapotharakos, C; Contopoulos, G

2009-03-01

The general theory of motion in the vicinity of a moving quantum nodal point (vortex) is studied in the framework of the de Broglie-Bohm trajectory method of quantum mechanics. Using an adiabatic approximation, we find that near any nodal point of an arbitrary wave function psi there is an unstable point (called the X point) in a frame of reference moving with the nodal point. The local phase portrait forms always a characteristic pattern called the "nodal-point- X -point complex." We find general formulas for this complex as well as necessary and sufficient conditions of validity of the adiabatic approximation. We demonstrate that chaos emerges from the consecutive scattering events of the orbits with nodal-point- X -point complexes. The scattering events are of two types (called type I and type II). A theoretical model is constructed yielding the local value of the Lyapunov characteristic numbers in scattering events of both types. The local Lyapunov characteristic number scales as an inverse power of the speed of the nodal point in the rest frame, implying that it scales proportionally to the size of the nodal-point- X -point complex. It is also an inverse power of the distance of a trajectory from the X point's stable manifold far from the complex. This distance plays the role of an effective "impact parameter." The results of detailed numerical experiments with different wave functions, possessing one, two, or three moving nodal points, are reported. Examples are given of regular and chaotic trajectories, and the statistics of the Lyapunov characteristic numbers of the orbits are found and compared to the number of encounter events of each orbit with the nodal-point- X -point complexes. The numerical results are in agreement with the theory, and various phenomena appearing at first as counterintuitive find a straightforward explanation.

Universal postquench coarsening and aging at a quantum critical point

Science.gov (United States)

Gagel, Pia; Orth, Peter P.; Schmalian, Jörg

2015-09-01

The nonequilibrium dynamics of a system that is located in the vicinity of a quantum critical point is affected by the critical slowing down of order-parameter correlations with the potential for novel out-of-equilibrium universality. After a quantum quench, i.e., a sudden change of a parameter in the Hamiltonian, such a system is expected to almost instantly fall out of equilibrium and undergo aging dynamics, i.e., dynamics that depends on the time passed since the quench. Investigating the quantum dynamics of an N -component φ4 model coupled to an external bath, we determine this universal aging and demonstrate that the system undergoes a coarsening, governed by a critical exponent that is unrelated to the equilibrium exponents of the system. We analyze this behavior in the large-N limit, which is complementary to our earlier renormalization-group analysis, allowing in particular the direct investigation of the order-parameter dynamics in the symmetry-broken phase and at the upper critical dimension. By connecting the long-time limit of fluctuations and response, we introduce a distribution function that shows that the system remains nonthermal and exhibits quantum coherence even on long time scales.

CRITICAL CONTROL POINT IDENTIFICATION THROUGH TROPHOLOGICAL MEAT PRODUCTION CHAINFROM FIELD TO FORK

Directory of Open Access Journals (Sweden)

A. V. Borodin

2017-01-01

Full Text Available  Competitive production management is impossible without comprehensive hazard monitoring and critical parameters control at every stage of food production from raw material and auxiliary materials delivery to ready product realization, which is difficult without modern IT-support. The HACCP (Hazard Analysis and Critical Control Points approach to product safety differs from ready product testing for compliance with NaTD requirements (Normative and Technical Documentation and emphasizes the importance of the process approach to monitoring at every stage of food production. Critical control points (CCP identification is a stage, where the presence of a risk of manufacturing products that are unsafe for human health is recognized and it is possible to take action to its elimination, prevention or reduction to an acceptable level. The use of soſtware package significantly increases the enterprise HACCP system efficiency. The article describes methodological bases for IT-approach to the CCP identification in the trophological meat production chain from field to fork. The algorithmic support and soſtware for the «Decision tree», which allows detecting existing hazards, identifying risks, determining CCPs and describing them, has been developed.

Analytical solution of point kinetic equations for sub-critical systems

International Nuclear Information System (INIS)

Henrice Junior, Edson; Goncalves, Alessandro C.

2013-01-01

This article presents an analytical solution for the set of point kinetic equations for sub-critical reactors. This solution stems from the ordinary, non-homogeneous differential equation that rules the neutron density and that presents the incomplete Gamma function in its functional form. The method used proved advantageous and allowed practical applications such as the linear insertion of reactivity, considering an external constant source or with both varying linearly. (author)

CRITICAL CONTROL POINTS ON THE TECHNOLOGICAL FLOW OF PANIFICATION

Directory of Open Access Journals (Sweden)

Gigel PARASCHIV

2013-05-01

Full Text Available Bread and panification products are intended for direct human consumption and underlying nutritional pyramid, it can affect the consumers health in case of biological, chemical or physical contamination, immediate or delayed, by noxious accumulation in the human organism. Only by rigorous compliance of the production rules throughout the technological process can ensure the quality and food safety of these products. If the risk can be prevented, eliminated or reduce to an acceptable level, as a result of a control actions made at that stage, it is considered a Critical Control Point (CCP. There can be checkpoints where it can exert a control action. Thus, the checkpoint is represented by any stage in which the risk factors, biological, chemical or physical, can be controlled in order to prevent, disrupt or reduce them to an acceptable level. This paper is referring to the control points on the technological flow of the bread fabrication, in all phases of this technological flow, laying stress on that points (or phases which can affect security and food safety, through the influence of parameters of any kind on the quality of finished products.

Theoretical, experimental and numerical diagnose of critical power point of thermoelectric generators

DEFF Research Database (Denmark)

Chen, Min; Gao, Xin

2014-01-01

of the critical power point in the series and parallel TEM arrays. Secondly, experiments of a series-parallel hybrid interconnected TEG are presented to clearly quantify the theoretical analyses. Finally, the hierarchical simulation, based on the SPICE (simulation program with integrated circuit emphasis...

Tool for identifying critical control points in embedded purchasing activities in SMEs

NARCIS (Netherlands)

Hagelaar, Geoffrey; Staal, Anne; Holman, Richard; Walhof, Gert

2015-01-01

This paper discusses risk and uncertainty aspects and proposes an assessment tool leading to identification of critical control points (CCPs) within purchasing-oriented activities of small and medium enterprises (SMEs). Identifying such CCPs is the basis for developing SME purchasing instruments to

Critical control points for the management of microbial growth in HVAC systems

NARCIS (Netherlands)

Gommers, S; Franchimon, F.; Bronswijk, van J.E.M.H.; Strøm-Tejsen, P; Olesen, BW; Wargocki, P; Zukowska, D; Toftum, J

2008-01-01

Office buildings with HVAC systems consistently report Sick Building Symptoms that are derived from microbial growth. We used the HACCP methodology to find the main critical control points (CCPs) for microbial management of HVAC systems in temperate climates. Desk research revealed relative humidity

Mechanics of occurrence of critical flow in compressible two-phase flow

International Nuclear Information System (INIS)

Katto, Yoshiro; Sudo, Yukio

1976-01-01

Fundamental framework of mechanics for the occurrence of critical flow is investigated, following the principle that the critical flow appears as a limit in a continuous change of state of flow along a nozzle (or a pipe) and should be derived only from simultaneous mechanical equations concerned with the flow. Mathematical procedures with which the critical flow: (i) the single phase flow of an arbitrary fluid, unrestricted by the equation of state of ideal gas, where the number of simultaneous equations is equal to the number of independent variables, and (ii) the one-component, separated two-phase flow under saturated condition, where the number of equations exceeds that of variables. In each case, interesting mechanism of leading to the occurrence of a limiting state of flow at a definite cross-section in a nozzle (incl. a pipe) is clarified, and a definite state of flow at the critical cross-section is also determined. Then, the analysis is extended to the critical flow which should appear in the completely isolated and the homogeneously dispersed, two-component, two-phase flow (composed of a compressible and an incompressible substance). It is found that the analyses of these special flow patterns provide several supplementary information to the mechanics of critical flow. (auth.)

21 CFR 123.6 - Hazard analysis and Hazard Analysis Critical Control Point (HACCP) plan.

Science.gov (United States)

2010-04-01

... Control Point (HACCP) plan. 123.6 Section 123.6 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF... Provisions § 123.6 Hazard analysis and Hazard Analysis Critical Control Point (HACCP) plan. (a) Hazard... fish or fishery product being processed in the absence of those controls. (b) The HACCP plan. Every...

Electric conductivity of alkali metal vapors in the region of critical point

International Nuclear Information System (INIS)

Likal'ter, A.A.

1982-01-01

A behaviour of alkali metal conductivity in the vicinity of a critical point has been analyzed on the base of deVeloped representations on a vapor state. A phenomenological conductivity theory has been developed, which is in a good agreement with experimental data obtained

Performance of supercritical Brayton cycle using CO2-based binary mixture at varying critical points for SFR applications

International Nuclear Information System (INIS)

Jeong, Woo Seok; Jeong, Yong Hoon

2013-01-01

Highlights: • Supercritical CO 2 -based gas mixture Brayton cycles were investigated for a SFR. • The critical point of CO 2 is the lowest cycle operating limit of the S-CO 2 cycles. • Mixing additives with CO 2 changes the CO 2 critical point. • CO 2 –Xe and CO 2 –Kr cycles achieve higher cycle efficiencies than the S-CO 2 cycles. • CO 2 –H 2 S and CO 2 –cyclohexane cycles perform better at higher heat sink temperatures. -- Abstract: The supercritical carbon dioxide Brayton cycle (S-CO 2 cycle) has attracted much attention as an alternative to the Rankine cycle for sodium-cooled fast reactors (SFRs). The higher cycle efficiency of the S-CO 2 cycle results from the considerably decreased compressor work because the compressor behaves as a pump in the proximity of the CO 2 vapor–liquid critical point. In order to fully utilize this feature, the main compressor inlet condition should be controlled to be close to the critical point of CO 2 . This indicates that the critical point of CO 2 is a constraint on the minimum cycle condition for S-CO 2 cycles. Modifying the CO 2 critical point by mixing additive gases could be considered as a method of enhancing the performance and broadening the applicability of the S-CO 2 cycle. Due to the drastic fluctuations of the thermo-physical properties of fluids near the critical point, an in-house cycle analysis code using the NIST REFPROP database was implemented. Several gases were selected as potential additives considering their thermal stability and chemical interaction with sodium in the temperature range of interest and the availability of the mixture property database: xenon, krypton, hydrogen sulfide, and cyclohexane. The performances of the optimized CO 2 -containing binary mixture cycles with simple recuperated and recompression layouts were compared with the reference S-CO 2 , CO 2 –Ar, CO 2 –N 2 , and CO 2 –O 2 cycles. For the decreased critical temperatures, the CO 2 –Xe and CO 2 �

Search for signatures of phase transition and critical point in heavy ion collisions

International Nuclear Information System (INIS)

Tokarev, M.V.; Kechechyan, A.; Alakhverdyants, A.; Zborovsky, I.

2011-01-01

The general concepts in the critical phenomena related with the notions of 'scaling' and 'universality' are considered. Behavior of various systems near a phase transition is displayed. Search for clear signatures of the phase transition of the nuclear matter and location of the critical point in heavy ion collisions (HIC) is discussed. The experimental data on inclusive spectra measured in HIC at RHIC and SPS over a wide range of energies s NN 1/2 = 9-200 GeV are analyzed in the framework of z-scaling. A microscopic scenario of the constituent interactions is presented. Dependence of the energy loss on the momentum of the produced hadron, energy and centrality of the collision is studied. Self-similarity of the constituent interactions described in terms of momentum fractions is used to characterize the nuclear medium by 'specific heat' and colliding nuclei by fractal dimensions. Preferable kinematical regions to search for signatures of the phase transition of the nuclear matter produced in HIC are discussed. Discontinuity of the 'specific heat' is assumed to be a signature of the phase transition and the critical point

System implementation of hazard analysis and critical control points (HACCP) in a nitrogen production plant

International Nuclear Information System (INIS)

Barrantes Salazar, Alexandra

2014-01-01

System of hazard analysis and critical control points are deployed in a production plant of liquid nitrogen. The fact that the nitrogen has become a complement to food packaging to increase shelf life, or provide a surface that protect it from manipulation, has been the main objective. Analysis of critical control points for the nitrogen production plant has been the adapted methodology. The knowledge of both the standard and the production process, as well as the on site verification process, have been necessary. In addition, all materials and/or processing units that are found in contact with the raw material or the product under study were evaluated. Such a way that the intrinsic risks of each were detected, from the physical, chemical and biological points of view according to the origin or pollution source. For each found risk was evaluated the probability of occurrence according to the frequency and gravity of it, with these variables determined was achieved the definition of the type of risk detected. In the cases that was presented a greater risk or critical, these were subjected decision tree; with which is concluded the non determination of critical control points. However, for each one of them were established the maximum permitted limits. To generate each of the results it has literature or scientific reference of reliable provenance, where is indicated properly the support of the evaluated matter. In a general way, the material matrix and the process matrix are found without critical control points; so that the project is concluded in the analysis, and it has to generate without the monitoring system and verification. To increase this project is suggested in order to cover the packaging system of gaseous nitrogen, due to it was delimited to liquid nitrogen. Furthermore, the liquid nitrogen is a 100% automated and closed process so the introduction of contaminants is very reduced, unlike the gaseous nitrogen process. (author) [es

Energy scales and magnetoresistance at a quantum critical point

Energy Technology Data Exchange (ETDEWEB)

Shaginyan, V.R. [Petersburg Nuclear Physics Institute, RAS, Gatchina, 188300 (Russian Federation); Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); CTSPS, Clark Atlanta University, Atlanta, GA 30314 (United States)], E-mail: vrshag@thd.pnpi.spb.ru; Amusia, M.Ya. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Msezane, A.Z. [CTSPS, Clark Atlanta University, Atlanta, GA 30314 (United States); Popov, K.G. [Komi Science Center, Ural Division, RAS, 3a Chernova street, Syktyvkar, 167982 (Russian Federation); Stephanovich, V.A. [Opole University, Institute of Mathematics and Informatics, Opole, 45-052 (Poland)

2009-03-02

The magnetoresistance (MR) of CeCoIn{sub 5} is notably different from that in many conventional metals. We show that a pronounced crossover from negative to positive MR at elevated temperatures and fixed magnetic fields is determined by the scaling behavior of quasiparticle effective mass. At a quantum critical point (QCP) this dependence generates kinks (crossover points from fast to slow growth) in thermodynamic characteristics (like specific heat, magnetization, etc.) at some temperatures when a strongly correlated electron system transits from the magnetic field induced Landau-Fermi liquid (LFL) regime to the non-Fermi liquid (NFL) one taking place at rising temperatures. We show that the above kink-like peculiarity separates two distinct energy scales in QCP vicinity - low temperature LFL scale and high temperature one related to NFL regime. Our comprehensive theoretical analysis of experimental data permits to reveal for the first time new MR and kinks scaling behavior as well as to identify the physical reasons for above energy scales.

Diagnosis as the First Critical Point in the Treatment Trajectory

DEFF Research Database (Denmark)

Missel, Malene; Pedersen, Jesper H; Hendriksen, Carsten

2015-01-01

sociology. RESULTS: The findings are presented as themes that summarize and express the ways in which a diagnosis affects patients' daily lives: the cancer diagnosis comes as a shock, it changes everyday awareness; it presents the patient with an unfamiliar body, disturbs social relationships, forces......BACKGROUND: Significant advances have been made in the surgical treatment of lung cancer while patient experiences with diagnosis, treatment, and rehabilitation remain only sparsely researched. OBJECTIVE: The objective of this study was to investigate how the diagnosis affects the daily lives...... of patients with operable lung cancer in order to identify their needs for care interventions from the point of diagnosis to hospitalization. METHODS: We investigated patients' lived experiences from a longitudinal perspective at 4 critical time points during the treatment trajectory; we present here...

Some critical considerations on the present epistemological and scientific debate on quantum mechanics

International Nuclear Information System (INIS)

Ghirardi, G.C.

1985-09-01

Some general methodological considerations aimed to guarantee the necessary logical rigor to the present debate on quantum mechanics are presented. In particular some misunderstandings about the implications of the critical analysis put forward by Einstein, Podolsky and Rosen (EPR) which can be found in the literature, are discussed. These misunderstandings are shown to arise from possible underestimates, overestimates and misinterpretations of the EPR argument. It is argued that the difficulties pointed out by EPR are, in a sense that will be defined precisely, unavoidable. A model which tries to solve the difficulties arising from quantum non separability effects when macroscopic systems are involved, is briefly sketched. (author)

LIFE CYCLE ASSESSMENT AND HAZARD ANALYSIS AND CRITICAL CONTROL POINTS TO THE PASTA PRODUCT

Directory of Open Access Journals (Sweden)

Yulexis Meneses Linares

2016-10-01

Full Text Available The objective of this work is to combine the Life Cycle Assessment (LCA and Hazard Analysis and Critical Control Points (HACCP methodologies for the determination of risks that the food production represents to the human health and the ecosystem. The environmental performance of the production of pastas in the “Marta Abreu” Pasta Factory of Cienfuegos is assessed, where the critical control points determined by the biological dangers (mushrooms and plagues and the physical dangers (wood, paper, thread and ferromagnetic particles were the raw materials: flour, semolina and its mixtures, and the disposition and extraction of them. Resources are the most affected damage category due to the consumption of fossil fuels.

Critical behaviors of gravity under quantum perturbations

Directory of Open Access Journals (Sweden)

ZHANG Hongsheng

2014-02-01

Full Text Available Phase transition and critical phenomenon is a very interesting topic in thermodynamics and statistical mechanics. Gravity is believed to have deep and inherent relation to thermodynamics. Near the critical point,the perturbation becomes significant. Thus for ordinary matter (governed by interactions besides gravity the critical behavior will become very different if we ignore the perturbations around the critical point,such as mean field theory. We find that the critical exponents for RN-AdS spacetime keep the same values even when we consider the full quantum perturbations. This indicates a key difference between gravity and ordinary thermodynamic system.

Towards an approach to assess critical quality points (CQPs) in food production systems : a case study on French fries production

NARCIS (Netherlands)

Ali, M.

2012-01-01

This thesis investigated how to develop an approach for the systematic and science based assessment of those points in food production systems that have a critical effect on quality; such points could be designated as critical quality points (CQPs). One of the fundamental objectives of quality

A simple method for determining the critical point of the soil water retention curve

DEFF Research Database (Denmark)

Chen, Chong; Hu, Kelin; Ren, Tusheng

2017-01-01

he transition point between capillary water and adsorbed water, which is the critical point Pc [defined by the critical matric potential (ψc) and the critical water content (θc)] of the soil water retention curve (SWRC), demarcates the energy and water content region where flow is dominated......, a fixed tangent line method was developed to estimate Pc as an alternative to the commonly used flexible tangent line method. The relationships between Pc, and particle-size distribution and specific surface area (SSA) were analyzed. For 27 soils with various textures, the mean RMSE of water content from...... the fixed tangent line method was 0.007 g g–1, which was slightly better than that of the flexible tangent line method. With increasing clay content or SSA, ψc was more negative initially but became less negative at clay contents above ∼30%. Increasing the silt contents resulted in more negative ψc values...

Order parameter fluctuations at a critical point - an exact result about percolation -

International Nuclear Information System (INIS)

Botet, Robert

2011-01-01

The order parameter of the system in the critical state, is expected to undergo large non-Gaussian fluctuations. However, almost nothing is known about the mathematical forms of the possible probability distributions of the order parameter. A remarkable exception is the site-percolation on the Bethe lattice, for which the complete order-parameter distribution has been recently derived at the critical point. Surprisingly, it appears to be the Kolmogorov-Smirnov distribution, well known in very different areas of mathematical statistics. In the present paper, we explain first how this special distribution could appear naturally in the context of the critical systems, under the assumption (still virtually unstudied) of the exponential distribution of the number of domains of a given size. In a second part, we present for the first time the complete derivation of the order-parameter distribution for the critical percolation model on the Bethe lattice, thus completing a recent publication announcing this result.

Transition from the mechanics of material points to the mechanics of structured particles

Science.gov (United States)

Somsikov, V. M.

2016-01-01

In this paper, necessity of creation of mechanics of structured particles is discussed. The way to create this mechanics within the laws of classical mechanics with the use of energy equation is shown. The occurrence of breaking of time symmetry within the mechanics of structured particles is shown, as well as the introduction of concept of entropy in the framework of classical mechanics. The way to create the mechanics of non-equilibrium systems in the thermodynamic approach is shown. It is also shown that the use of hypothesis of holonomic constraints while deriving the canonical Lagrange equation made it impossible to describe irreversible dynamics. The difference between the mechanics of structured particles and the mechanics of material points is discussed. It is also shown that the matter is infinitely divisible according to the laws of classical mechanics.

Critical current scaling and the pivot-point in Nb3Sn strands

International Nuclear Information System (INIS)

Tsui, Y; Hampshire, D P

2012-01-01

Detailed measurements are provided of the engineering critical current density (J c ) and the index of transition (n-value) of two different types of advanced ITER Nb 3 Sn superconducting strand for fusion applications. The samples consist of one internal-tin strand (OST) and two bronze-route strands (BEAS I and BEAS II—reacted using different heat treatments). Tests on different sections of these wires show that prior to applying strain, J c is homogeneous to better than 2% along the length of each strand. J c data have been characterized as a function of magnetic field (B ≤ 14.5 T), temperature (4.2 K ≤ T ≤ 12 K) and applied axial strain ( − 1% ≤ ε A ≤ 0.8%). Strain-cycling tests demonstrate that the variable strain J c data are reversible to better than 2% when the applied axial strain is in the range of − 1% ≤ ε A ≤ 0.5%. The wires are damaged when the intrinsic strain (ε I ) is ε I ≥ 0.55% and ε I ≥ 0.23% for the OST and BEAS strands, respectively. The strain dependences of the normalized J c for each type of strand are similar to those of prototype strands of similar design measured in 2005 and 2008 to about 2% which makes them candidate strands for a round-robin interlaboratory comparison. The J c data are described by Durham, ITER and Josephson-junction parameterizations to an accuracy of about 4%. For all of these scaling laws, the percentage difference between the data and the parameterization is larger when J c is small, caused by high B, T or |ε I |. The n-values can be described by a modified power law of the form n=1+rI c s , where r and s are approximately constant and I c is the critical current. It has long been known that pivot-points (or cross-overs) in J c occur at high magnetic field and temperature. Changing the magnetic field or temperature from one side of the pivot-point to the other changes the highest J c sample to the lowest J c sample and vice versa. The pivot-point follows the B–T phase boundary

Neuromuscular control of the point to point and oscillatory movements of a sagittal arm with the actor-critic reinforcement learning method.

Science.gov (United States)

Golkhou, Vahid; Parnianpour, Mohamad; Lucas, Caro

2005-04-01

In this study, we have used a single link system with a pair of muscles that are excited with alpha and gamma signals to achieve both point to point and oscillatory movements with variable amplitude and frequency.The system is highly nonlinear in all its physical and physiological attributes. The major physiological characteristics of this system are simultaneous activation of a pair of nonlinear muscle-like-actuators for control purposes, existence of nonlinear spindle-like sensors and Golgi tendon organ-like sensor, actions of gravity and external loading. Transmission delays are included in the afferent and efferent neural paths to account for a more accurate representation of the reflex loops.A reinforcement learning method with an actor-critic (AC) architecture instead of middle and low level of central nervous system (CNS), is used to track a desired trajectory. The actor in this structure is a two layer feedforward neural network and the critic is a model of the cerebellum. The critic is trained by state-action-reward-state-action (SARSA) method. The critic will train the actor by supervisory learning based on the prior experiences. Simulation studies of oscillatory movements based on the proposed algorithm demonstrate excellent tracking capability and after 280 epochs the RMS error for position and velocity profiles were 0.02, 0.04 rad and rad/s, respectively.

Turbidity very near the critical point of methanol-cyclohexane mixtures

Science.gov (United States)

Kopelman, R. B.; Gammon, R. W.; Moldover, M. R.

1984-04-01

The turbidity of a critical mixture of methanol and cyclohexane has been measured extremely close to the consolute point. The data span the reduced-temperature range between 10 to the -7th and 10 to the -3d, which is two decades closer to Tc than previous measurements. In this temperature range, the turbidity varies approximately as 1nt, as expected from the integrated form for Ornstein-Zernike scattering. A thin cell (200-micron optical path) with a very small volume (0.08 ml) was used to avoid multiple scattering. A carefully controlled temperature history was used to mix the sample and to minimize the effects of critical wetting layers. The data are consistent with a correlation-length amplitude of 3.9 plus or minus 1.0 A, in agreement with the value 3.5 A calculated from two-scale-factor universality and heat-capacity data from the literature.

Turbidity very near the critical point of methanol-cyclohexane mixtures

Science.gov (United States)

Kopelman, R. B.; Gammon, R. W.; Moldover, M. R.

1984-01-01

The turbidity of a critical mixture of methanol and cyclohexane has been measured extremely close to the consolute point. The data span the reduced-temperature range between 10 to the -7th and 10 to the -3d, which is two decades closer to Tc than previous measurements. In this temperature range, the turbidity varies approximately as 1nt, as expected from the integrated form for Ornstein-Zernike scattering. A thin cell (200-micron optical path) with a very small volume (0.08 ml) was used to avoid multiple scattering. A carefully controlled temperature history was used to mix the sample and to minimize the effects of critical wetting layers. The data are consistent with a correlation-length amplitude of 3.9 plus or minus 1.0 A, in agreement with the value 3.5 A calculated from two-scale-factor universality and heat-capacity data from the literature.

Thermal properties of ionic systems near the liquid-liquid critical point.

Science.gov (United States)

Méndez-Castro, Pablo; Troncoso, Jacobo; Pérez-Sánchez, Germán; Peleteiro, José; Romaní, Luis

2011-12-07

Isobaric heat capacity per unit volume, C(p), and excess molar enthalpy, h(E), were determined in the vicinity of the critical point for a set of binary systems formed by an ionic liquid and a molecular solvent. Moreover, and, since critical composition had to be accurately determined, liquid-liquid equilibrium curves were also obtained using a calorimetric method. The systems were selected with a view on representing, near room temperature, examples from clearly solvophobic to clearly coulombic behavior, which traditionally was related with the electric permittivity of the solvent. The chosen molecular compounds are: ethanol, 1-butanol, 1-hexanol, 1,3-dichloropropane, and diethylcarbonate, whereas ionic liquids are formed by imidazolium-based cations and tetrafluoroborate or bis-(trifluromethylsulfonyl)amide anions. The results reveal that solvophobic critical behavior-systems with molecular solvents of high dielectric permittivity-is very similar to that found for molecular binary systems. However, coulombic systems-those with low permittivity molecular solvents-show strong deviations from the results usually found for these magnitudes near the liquid-liquid phase transition. They present an extremely small critical anomaly in C(p)-several orders of magnitude lower than those typically obtained for binary mixtures-and extremely low h(E)-for one system even negative, fact not observed, up to date, for any liquid-liquid transition in the nearness of an upper critical solution temperature. © 2011 American Institute of Physics

Electron-density critical points analysis and catastrophe theory to forecast structure instability in periodic solids.

Science.gov (United States)

Merli, Marcello; Pavese, Alessandro

2018-03-01

The critical points analysis of electron density, i.e. ρ(x), from ab initio calculations is used in combination with the catastrophe theory to show a correlation between ρ(x) topology and the appearance of instability that may lead to transformations of crystal structures, as a function of pressure/temperature. In particular, this study focuses on the evolution of coalescing non-degenerate critical points, i.e. such that ∇ρ(x c ) = 0 and λ 1 , λ 2 , λ 3 ≠ 0 [λ being the eigenvalues of the Hessian of ρ(x) at x c ], towards degenerate critical points, i.e. ∇ρ(x c ) = 0 and at least one λ equal to zero. The catastrophe theory formalism provides a mathematical tool to model ρ(x) in the neighbourhood of x c and allows one to rationalize the occurrence of instability in terms of electron-density topology and Gibbs energy. The phase/state transitions that TiO 2 (rutile structure), MgO (periclase structure) and Al 2 O 3 (corundum structure) undergo because of pressure and/or temperature are here discussed. An agreement of 3-5% is observed between the theoretical model and experimental pressure/temperature of transformation.

Entanglement entropy of 2D conformal quantum critical points: hearing the shape of a quantum drum.

Science.gov (United States)

Fradkin, Eduardo; Moore, Joel E

2006-08-04

The entanglement entropy of a pure quantum state of a bipartite system A union or logical sumB is defined as the von Neumann entropy of the reduced density matrix obtained by tracing over one of the two parts. In one dimension, the entanglement of critical ground states diverges logarithmically in the subsystem size, with a universal coefficient that for conformally invariant critical points is related to the central charge of the conformal field theory. We find that the entanglement entropy of a standard class of z=2 conformal quantum critical points in two spatial dimensions, in addition to a nonuniversal "area law" contribution linear in the size of the AB boundary, generically has a universal logarithmically divergent correction, which is completely determined by the geometry of the partition and by the central charge of the field theory that describes the critical wave function.

Critical point of Nf=3 QCD from lattice simulations in the canonical ensemble

International Nuclear Information System (INIS)

Li Anyi; Alexandru, Andrei; Liu, Keh-Fei

2011-01-01

A canonical ensemble algorithm is employed to study the phase diagram of N f =3 QCD using lattice simulations. We lock in the desired quark number sector using an exact Fourier transform of the fermion determinant. We scan the phase space below T c and look for an S-shape structure in the chemical potential, which signals the coexistence phase of a first order phase transition in finite volume. Applying Maxwell construction, we determine the boundaries of the coexistence phase at three temperatures and extrapolate them to locate the critical point. Using an improved gauge action and improved Wilson fermions on lattices with a spatial extent of 1.8 fm and quark masses close to that of the strange, we find the critical point at T E =0.925(5)T c and baryon chemical potential μ B E =2.60(8)T c .

Fluid mechanics a geometrical point of view

CERN Document Server

Rajeev, S G

2018-01-01

Fluid Mechanics: A Geometrical Point of View emphasizes general principles of physics illustrated by simple examples in fluid mechanics. Advanced mathematics (e.g., Riemannian geometry and Lie groups) commonly used in other parts of theoretical physics (e.g. General Relativity or High Energy Physics) are explained and applied to fluid mechanics. This follows on from the author's book Advanced Mechanics (Oxford University Press, 2013). After introducing the fundamental equations (Euler and Navier-Stokes), the book provides particular cases: ideal and viscous flows, shocks, boundary layers, instabilities, and transients. A restrained look at integrable systems (KdV) leads into a formulation of an ideal fluid as a hamiltonian system. Arnold's deep idea, that the instability of a fluid can be understood using the curvature of the diffeomorphism group, will be explained. Leray's work on regularity of Navier-Stokes solutions, and the modern developments arising from it, will be explained in language for physicists...

Critical points and magnitude of impacts on the packing line: effect on ripening and quality of 'Packham's Triumph' pears

Directory of Open Access Journals (Sweden)

Josiane Pasini

2017-06-01

Full Text Available Pears have a very sensitive epidermis and are prone to signal mechanical blemishes, which result in reduced visual quality and low consumer acceptance. The objective of this work was to identify critical points and the magnitude of impact forces on a packing line at a commercial packinghouse. The effect of injuries on ripening and quality of ´Packham´s Triumph´ pears was also evaluated after cold storage. The packing line was scrutinized on its transfer points, fruit drop heights and cushioning overlays, which allowed to acquire the maximum accelerations on each spot. The maximum acceleration forces were reproduced in the lab with ‘Packham’s Triumph’ pears to evaluate the effects on fruit quality after cold storage. Four critical points were noticed on the packing line: at the transfer from the conveyor belt to the lifting rollers, at the transfer from the lifting rollers to the washing ramp with rotatory brushes, at the entrance to the singulator at the end of the conveyor belt and at the drop from the sizer to the packing stalls. Ripening of ‘Packham’s Triumph’ pears invariably came about during cold storage, and independently of the imposed impacts. The impacts under the circumstances of the test did not affect the quality of ´Packham´s Triumph´ pears kept for up to 120 days at cold storage followed by five days at room temperature.

Potential Improvements of Supercritical Recompression CO2 Brayton Cycle Coupled with KALIMER-600 by Modifying Critical Point of CO2

International Nuclear Information System (INIS)

Jeong, Woo Seok; Lee, Jeong Ik; Jeong, Yong Hoon; No, Hee Cheon

2010-01-01

Most of the existing designs of a Sodium cooled Fast Reactor (SFR) have a Rankine cycle as an electric power generation cycle. This has the risk of a sodium water reaction. To prevent any hazards from a sodium water reaction, an indirect Brayton cycle using Supercritical Carbon dioxide (S-CO 2 ) as the working fluids for a SFR is an alternative approach to improve the current SFR design. The supercritical Brayton cycle is defined as a cycle with operating conditions above the critical point and the main compressor inlet condition located slightly above the critical point of working fluid. This is because the main advantage of the cycle comes from significantly decreased compressor work just above the critical point due to high density near boundary between supercritical state and subcritical state. For this reason, the minimum temperature and pressure of cycle are just above the CO 2 critical point. In other words, the critical point acts as a limitation of the lowest operating condition of the cycle. In general, lowering the minimum temperature of a thermodynamic cycle can increase the efficiency and the minimum temperature can be decreased by shifting the critical point of CO 2 as mixed with other gases. In this paper, potential enhancement of S-CO 2 cycle coupled with KALIMER-600, which has been developed at KAERI, was investigated using a developed cycle code with a gas mixture property program

Effective intermolecular potential and critical point for C60 molecule

Science.gov (United States)

Ramos, J. Eloy

2017-07-01

The approximate nonconformal (ANC) theory is applied to the C60 molecule. A new binary potential function is developed for C60, which has three parameters only and is obtained by averaging the site-site carbon interactions on the surface of two C60 molecules. It is shown that the C60 molecule follows, to a good approximation, the corresponding states principle with n-C8H18, n-C4F10 and n-C5F12. The critical point of C60 is estimated in two ways: first by applying the corresponding states principle under the framework of the ANC theory, and then by using previous computer simulations. The critical parameters obtained by applying the corresponding states principle, although very different from those reported in the literature, are consistent with the previous results of the ANC theory. It is shown that the Girifalco potential does not correspond to an average of the site-site carbon-carbon interaction.

Eigenstrain as a mechanical set-point of cells.

Science.gov (United States)

Lin, Shengmao; Lampi, Marsha C; Reinhart-King, Cynthia A; Tsui, Gary; Wang, Jian; Nelson, Carl A; Gu, Linxia

2018-02-05

Cell contraction regulates how cells sense their mechanical environment. We sought to identify the set-point of cell contraction, also referred to as tensional homeostasis. In this work, bovine aortic endothelial cells (BAECs), cultured on substrates with different stiffness, were characterized using traction force microscopy (TFM). Numerical models were developed to provide insights into the mechanics of cell-substrate interactions. Cell contraction was modeled as eigenstrain which could induce isometric cell contraction without external forces. The predicted traction stresses matched well with TFM measurements. Furthermore, our numerical model provided cell stress and displacement maps for inspecting the fundamental regulating mechanism of cell mechanosensing. We showed that cell spread area, traction force on a substrate, as well as the average stress of a cell were increased in response to a stiffer substrate. However, the cell average strain, which is cell type-specific, was kept at the same level regardless of the substrate stiffness. This indicated that the cell average strain is the tensional homeostasis that each type of cell tries to maintain. Furthermore, cell contraction in terms of eigenstrain was found to be the same for both BAECs and fibroblast cells in different mechanical environments. This implied a potential mechanical set-point across different cell types. Our results suggest that additional measurements of contractility might be useful for monitoring cell mechanosensing as well as dynamic remodeling of the extracellular matrix (ECM). This work could help to advance the understanding of the cell-ECM relationship, leading to better regenerative strategies.

Classical dynamics of the Abelian Higgs model from the critical point and beyond

Directory of Open Access Journals (Sweden)

G.C. Katsimiga

2015-09-01

Full Text Available We present two different families of solutions of the U(1-Higgs model in a (1+1 dimensional setting leading to a localization of the gauge field. First we consider a uniform background (the usual vacuum, which corresponds to the fully higgsed-superconducting phase. Then we study the case of a non-uniform background in the form of a domain wall which could be relevantly close to the critical point of the associated spontaneous symmetry breaking. For both cases we obtain approximate analytical nodeless and nodal solutions for the gauge field resulting as bound states of an effective Pöschl–Teller potential created by the scalar field. The two scenaria differ only in the scale of the characteristic localization length. Numerical simulations confirm the validity of the obtained analytical solutions. Additionally we demonstrate how a kink may be used as a mediator driving the dynamics from the critical point and beyond.

Acute enhancement of the upper critical field for superconductivity approaching a quantum critical point in URhGe

Energy Technology Data Exchange (ETDEWEB)

Levy, F; Huxley, A [CEA, SPSMS, DRFMC, F-38054 Grenoble, (France); Levy, F; Sheikin, I [CNRS, GHMFL, F-38042 Grenoble, (France); Huxley, A [Univ Edinburgh, Scottish Univ Phys Alliance, Sch Phys, Edinburgh EH9 3JZ, Midlothian, (United Kingdom)

2007-07-01

When a pure material is tuned to the point where a continuous phase-transition line is crossed at zero temperature, known as a quantum critical point (QCP), completely new correlated quantum ordered states can form. These phases include exotic forms of superconductivity. However, as superconductivity is generally suppressed by a magnetic field, the formation of superconductivity ought not to be possible at extremely high field. Here, we report that as we tune the ferromagnet, URhGe, towards a QCP by applying a component of magnetic field in the material's easy magnetic plane, superconductivity survives in progressively higher fields applied simultaneously along the material's magnetic hard axis. Thus, although superconductivity never occurs above a temperature of 0.5 K, we find that it can survive in extremely high magnetic fields, exceeding 28 T. (authors)

Soft modes at the critical end point in the chiral effective models

International Nuclear Information System (INIS)

Fujii, Hirotsugu; Ohtani, Munehisa

2004-01-01

At the critical end point in QCD phase diagram, the scalar, vector and entropy susceptibilities are known to diverge. The dynamic origin of this divergence is identified within the chiral effective models as softening of a hydrodynamic mode of the particle-hole-type motion, which is a consequence of the conservation law of the baryon number and the energy. (author)

Liberation From Mechanical Ventilation in Critically Ill Adults

DEFF Research Database (Denmark)

Schmidt, Gregory A; Girard, Timothy D; Kress, John P

2017-01-01

BACKGROUND: This clinical practice guideline addresses six questions related to liberation from mechanical ventilation in critically ill adults. It is the result of a collaborative effort between the American Thoracic Society (ATS) and the American College of Chest Physicians (CHEST). METHODS: A ...

Interactions and ``puff clustering'' close to the critical point in pipe flow

Science.gov (United States)

Vasudevan, Mukund; Hof, Björn

2017-11-01

The first turbulent structures to arise in pipe flow are puffs. Albeit transient in nature, their spreading determines if eventually turbulence becomes sustained. Due to the extremely long time scales involved in these processes it is virtually impossible to directly observe the transition and the flow patterns that are eventually assumed in the long time limit. We present a new experimental approach where, based on the memoryless nature of turbulent puffs, we continuously recreate the flow pattern exiting the pipe. These periodic boundary conditions enable us to show that the flow pattern eventually settles to a statistically steady state. While our study confirms the value of the critical point of Rec 2040 , the flow fields show that puffs interact over longer ranges than previously suspected. As a consequence puffs tend to cluster and these regions of large puff densities travel across the puff pattern in a wave like fashion. While transition in Couette flow has been shown to fall into the ``directed percolation'', pipe flow may be more complicated since long range interactions are prohibited for the percolation transition type. Extensive measurements at the critical point will be presented to clarify the nature of the transition.

Implementation of a direct procedure for critical point computations using preconditioned iterative solvers

Czech Academy of Sciences Publication Activity Database

Kouhia, R.; Tůma, Miroslav; Mäkinen, J.; Fedoroff, A.; Marjamäki, H.

108-109, October (2012), s. 110-117 ISSN 0045-7949 R&D Projects: GA ČR(CZ) GAP108/11/0853 Institutional research plan: CEZ:AV0Z10300504 Keywords : non-linear eigenvalue problem * equilibrium equations * critical points * preconditioned iterations Subject RIV: BA - General Mathematics Impact factor: 1.509, year: 2012

Communication: Analytic continuation of the virial series through the critical point using parametric approximants

Energy Technology Data Exchange (ETDEWEB)

Barlow, Nathaniel S., E-mail: nsbsma@rit.edu [School of Mathematical Sciences, Rochester Institute of Technology, Rochester, New York 14623 (United States); Schultz, Andrew J., E-mail: ajs42@buffalo.edu; Kofke, David A., E-mail: kofke@buffalo.edu [Department of Chemical and Biological Engineering, University at Buffalo, State University of New York, Buffalo, New York 14260 (United States); Weinstein, Steven J., E-mail: sjweme@rit.edu [Department of Chemical Engineering, Rochester Institute of Technology, Rochester, New York 14623 (United States)

2015-08-21

The mathematical structure imposed by the thermodynamic critical point motivates an approximant that synthesizes two theoretically sound equations of state: the parametric and the virial. The former is constructed to describe the critical region, incorporating all scaling laws; the latter is an expansion about zero density, developed from molecular considerations. The approximant is shown to yield an equation of state capable of accurately describing properties over a large portion of the thermodynamic parameter space, far greater than that covered by each treatment alone.

Communication: Analytic continuation of the virial series through the critical point using parametric approximants.

Science.gov (United States)

Barlow, Nathaniel S; Schultz, Andrew J; Weinstein, Steven J; Kofke, David A

2015-08-21

The mathematical structure imposed by the thermodynamic critical point motivates an approximant that synthesizes two theoretically sound equations of state: the parametric and the virial. The former is constructed to describe the critical region, incorporating all scaling laws; the latter is an expansion about zero density, developed from molecular considerations. The approximant is shown to yield an equation of state capable of accurately describing properties over a large portion of the thermodynamic parameter space, far greater than that covered by each treatment alone.

Coherent inflationary dynamics for Bose-Einstein condensates crossing a quantum critical point

Science.gov (United States)

Feng, Lei; Clark, Logan W.; Gaj, Anita; Chin, Cheng

2018-03-01

Quantum phase transitions, transitions between many-body ground states, are of extensive interest in research ranging from condensed-matter physics to cosmology1-4. Key features of the phase transitions include a stage with rapidly growing new order, called inflation in cosmology5, followed by the formation of topological defects6-8. How inflation is initiated and evolves into topological defects remains a hot topic of debate. Ultracold atomic gas offers a pristine and tunable platform to investigate quantum critical dynamics9-21. We report the observation of coherent inflationary dynamics across a quantum critical point in driven Bose-Einstein condensates. The inflation manifests in the exponential growth of density waves and populations in well-resolved momentum states. After the inflation stage, extended coherent dynamics is evident in both real and momentum space. We present an intuitive description of the quantum critical dynamics in our system and demonstrate the essential role of phase fluctuations in the formation of topological defects.

Simple description of odd-A nuclei around the critical point of the spherical to axially deformed shape phase transition

International Nuclear Information System (INIS)

Zhang Yu; Pan Feng; Liu Yuxin; Luo Yanan; Draayer, J. P.

2011-01-01

An analytically solvable model, X(3/2j+1), is proposed to describe odd-A nuclei near the X(3) critical point. The model is constructed based on a collective core described by the X(3) critical point symmetry coupled to a spin-j particle. A detailed analysis of the spectral patterns for cases j=1/2 and j=3/2 is provided to illustrate dynamical features of the model. By comparing theory with experimental data and results of other models, it is found that the X(3/2j+1) model can be taken as a simple yet very effective scheme to describe those odd-A nuclei with an even-even core at the critical point of the spherical to axially deformed shape phase transition.

Phase holonomy, zero-point energy cancellation and supersymmetric quantum mechanics

International Nuclear Information System (INIS)

Iida, Shinji; Kuratsuji, Hiroshi

1987-01-01

We show that the zero-point energy of bosons is cancelled out by the phase holonomy which is induced by the adiabatic deformation of a boson system coupled with a fermion. This mechanism results in a supersymmetric quantum mechanics as a special case and presents a possible dynamical origin of supersymmetry. (orig.)

Biogeochemical control points in a water-limited critical zone

Science.gov (United States)

Chorover, J.; Brooks, P. D.; Gallery, R. E.; McIntosh, J. C.; Olshansky, Y.; Rasmussen, C.

2017-12-01

The routing of water and carbon through complex terrain is postulated to control structure evolution in the sub-humid critical zone of the southwestern US. By combining measurements of land-atmosphere exchange, ecohydrologic partitioning, and subsurface biogeochemistry, we seek to quantify how a heterogeneous (in time and space) distribution of "reactants" impacts both short-term (sub-)catchment response (e.g., pore and surface water chemical dynamics) and long-term landscape evolution (e.g., soil geochemistry/morphology and regolith weathering depth) in watersheds underlain by rhyolite and schist. Instrumented pedons in convergent, planar, and divergent landscape positions show distinct depth-dependent responses to precipitation events. Wetting front propagation, dissolved carbon flux and associated biogeochemical responses (e.g., pulses of CO2 production, O2 depletion, solute release) vary with topography, revealing the influence of lateral subsidies of water and carbon. The impacts of these episodes on the evolution of porous media heterogeneity is being investigated by statistical analysis of pore water chemistry, chemical/spectroscopic studies of solid phase organo-mineral products, sensor-derived water characteristic curves, and quantification of co-located microbial community activity/composition. Our results highlight the interacting effects of critical zone structure and convergent hydrologic flows in the evolution of biogeochemical control points.

Critical point in the QCD phase diagram for extremely strong background magnetic fields

International Nuclear Information System (INIS)

Endrödi, Gergely

2015-01-01

Lattice simulations have demonstrated that a background (electro)magnetic field reduces the chiral/deconfinement transition temperature of quantum chromodynamics for eB<1 GeV 2 . On the level of observables, this reduction manifests itself in an enhancement of the Polyakov loop and in a suppression of the light quark condensates (inverse magnetic catalysis) in the transition region. In this paper, we report on lattice simulations of 1+1+1-flavor QCD at an unprecedentedly high value of the magnetic field eB=3.25 GeV 2 . Based on the behavior of various observables, it is shown that even at this extremely strong field, inverse magnetic catalysis prevails and the transition, albeit becoming sharper, remains an analytic crossover. In addition, we develop an algorithm to directly simulate the asymptotically strong magnetic field limit of QCD. We find strong evidence for a first-order deconfinement phase transition in this limiting theory, implying the presence of a critical point in the QCD phase diagram. Based on the available lattice data, we estimate the location of the critical point.

Critical point in the phase diagram of primordial quark-gluon matter from black hole physics

Science.gov (United States)

Critelli, Renato; Noronha, Jorge; Noronha-Hostler, Jacquelyn; Portillo, Israel; Ratti, Claudia; Rougemont, Romulo

2017-11-01

Strongly interacting matter undergoes a crossover phase transition at high temperatures T ˜1012 K and zero net-baryon density. A fundamental question in the theory of strong interactions, QCD, is whether a hot and dense system of quarks and gluons displays critical phenomena when doped with more quarks than antiquarks, where net-baryon number fluctuations diverge. Recent lattice QCD work indicates that such a critical point can only occur in the baryon dense regime of the theory, which defies a description from first principles calculations. Here we use the holographic gauge/gravity correspondence to map the fluctuations of baryon charge in the dense quark-gluon liquid onto a numerically tractable gravitational problem involving the charge fluctuations of holographic black holes. This approach quantitatively reproduces ab initio results for the lowest order moments of the baryon fluctuations and makes predictions for the higher-order baryon susceptibilities and also for the location of the critical point, which is found to be within the reach of heavy-ion collision experiments.

Equilibration of matter near the QCD critical point

International Nuclear Information System (INIS)

Bravina, L V; Arsene, I; Nilsson, M S; Tywoniuk, K; Zabrodin, E E

2006-01-01

The relaxation of hot and dense nuclear matter to local equilibrium in the central zone of heavy-ion collisions at energies around 40 A GeV is studied within the microscopic transport model. Dynamical calculations performed for the central cell in the reaction are compared to the predictions of the thermal statistical model. It is found that kinetic, thermal and chemical equilibrations of the expanding hadronic matter are nearly approached for the period of 10-18 fm/c. Within this time, the matter in the cell expands almost isentropically. It is quite interesting that in the T-μ B plane the system crosses the critical point predicted by lattice QCD calculations. Similar to the cells studied at lower (AGS) and higher (SPS, RHIC) energies, the central cell at 40 A GeV possesses negative (though small) net strangeness. Several peculiarities are observed as well. These features can be attributed to the transition from baryon-dominated to meson-dominated matter, discussed recently

Shift of critical points in the parametrically modulated Henon map with coexisting attractors

International Nuclear Information System (INIS)

Saucedo-Solorio, J.M.; Pisarchik, A.N.; Aboites, V.

2002-01-01

We study how the critical point positions change in the parametrically modulated Henon map with coexisting period-1 and period-3 attractors. In particular, a new type of scaling law is found coinciding with that evidenced by laser experiments. We show that resonance phenomena play a crucial role in deformation of attractors and their basins of attraction

Macro-mechanics controls quantum mechanics: mechanically controllable quantum conductance switching of an electrochemically fabricated atomic-scale point contact.

Science.gov (United States)

Staiger, Torben; Wertz, Florian; Xie, Fangqing; Heinze, Marcel; Schmieder, Philipp; Lutzweiler, Christian; Schimmel, Thomas

2018-01-12

Here, we present a silver atomic-scale device fabricated and operated by a combined technique of electrochemical control (EC) and mechanically controllable break junction (MCBJ). With this EC-MCBJ technique, we can perform mechanically controllable bistable quantum conductance switching of a silver quantum point contact (QPC) in an electrochemical environment at room temperature. Furthermore, the silver QPC of the device can be controlled both mechanically and electrochemically, and the operating mode can be changed from 'electrochemical' to 'mechanical', which expands the operating mode for controlling QPCs. These experimental results offer the perspective that a silver QPC may be used as a contact for a nanoelectromechanical relay.

Hierarchy of exactly solvable spin-1/2 chains with so (N)_I critical points

NARCIS (Netherlands)

Lahtinen, V.; Mansson, T.; Ardonne, E.

2014-01-01

We construct a hierarchy of exactly solvable spin-1/2 chains with so(N)1 critical points. Our construction is based on the framework of condensate-induced transitions between topological phases. We employ this framework to construct a Hamiltonian term that couples N transverse field Ising chains

[Powdered infant formulae preparation guide for hospitals based on Hazard Analysis and Critical Control Points (HACCP) principles].

Science.gov (United States)

Vargas-Leguás, H; Rodríguez Garrido, V; Lorite Cuenca, R; Pérez-Portabella, C; Redecillas Ferreiro, S; Campins Martí, M

2009-06-01

This guide for the preparation of powdered infant formulae in hospital environments is a collaborative work between several hospital services and is based on national and European regulations, international experts meetings and the recommendations of scientific societies. This guide also uses the Hazard Analysis and Critical Control Point principles proposed by Codex Alimentarius and emphasises effective verifying measures, microbiological controls of the process and the corrective actions when monitoring indicates that a critical control point is not under control. It is a dynamic guide and specifies the evaluation procedures that allow it to be constantly adapted.

CETF Space Station payload pointing system design and analysis feasibility study. [Critical Evaluation Task Force

Science.gov (United States)

Smagala, Tom; Mcglew, Dave

1988-01-01

The expected pointing performance of an attached payload coupled to the Critical Evaluation Task Force Space Station via a payload pointing system (PPS) is determined. The PPS is a 3-axis gimbal which provides the capability for maintaining inertial pointing of a payload in the presence of disturbances associated with the Space Station environment. A system where the axes of rotation were offset from the payload center of mass (CM) by 10 in. in the Z axis was studied as well as a system having the payload CM offset by only 1 inch. There is a significant improvement in pointing performance when going from the 10 in. to the 1 in. gimbal offset.

Higher moments of net kaon multiplicity distributions at RHIC energies for the search of QCD Critical Point at STAR

Directory of Open Access Journals (Sweden)

Sarkar Amal

2013-11-01

Full Text Available In this paper we report the measurements of the various moments mean (M, standard deviation (σ skewness (S and kurtosis (κ of the net-Kaon multiplicity distribution at midrapidity from Au+Au collisions at √sNN = 7.7 to 200 GeV in the STAR experiment at RHIC in an effort to locate the critical point in the QCD phase diagram. These moments and their products are related to the thermodynamic susceptibilities of conserved quantities such as net baryon number, net charge, and net strangeness as also to the correlation length of the system. A non-monotonic behavior of these variable indicate the presence of the critical point. In this work we also present the moments products Sσ, κσ2 of net-Kaon multiplicity distribution as a function of collision centrality and energies. The energy and the centrality dependence of higher moments of net-Kaons and their products have been compared with it0s Poisson expectation and with simulations from AMPT which does not include the critical point. From the measurement at all seven available beam energies, we find no evidence for a critical point in the QCD phase diagram for √sNN below 200 GeV.

An application of liquid sublayer dryout mechanism to the prediction of critical heat flux under low pressure and low velocity conditions in round tubes

International Nuclear Information System (INIS)

Lee, Kwang-Won; Yang, Jae-Young; Baik, Se-Jin

1997-01-01

Based on several experimental evidences for nucleate boiling in annular film and the existence of residual liquid film flow rate at the critical heat flux (CHF) location, the liquid sublayer dryout (LSD) mechanism under annular film is firstly introduced to evaluate the CHF data at low pressure and low velocity (LPLV) conditions, which would not be predicted by a normal annular film dryout (AFD) model. In this study, the CHF occurrence due to annular film separation or breaking down is phenomenologically modelled by applying the LSD mechanism to this situation. In this LSD mechanism, the liquid sublayer thickness, the incoming liquid velocity to the liquid sublayer, and the axial distance from the onset of annular flow to the CHF location are used as the phenomena-controlling parameters. From the model validation on the 1406 CHF data points ranging over P = 0.1 - 2 MPa, G = 4 - 499 kg/m 2 s, L/D = 4 - 402, most of CHF data (more than 1000 points) are predicted within ±30% error bounds by the LSD mechanism. However, some calculation results that critical qualities are less than 0.4 are considerably overestimated by this mechanism. These overpredictions seem to be caused by inadequate CHF mechanism classification criteria and an insufficient consideration of the flow instability effect on CHF. Further studies for a new classification criterion screening the CHF data affected by flow instabilities and a new bubble detachment model for LPLV conditions are needed to improve the model accuracy. (author)

Pathophysiological Mechanisms of Laser Correction in Critical Conditions

Directory of Open Access Journals (Sweden)

V. L. Kozhura

2006-01-01

Full Text Available The paper provides the generalized results of studies dealing with the use of low-intensive laser irradiation in blood loss-induced critical conditions in an experiment and in patients with severe mechanical injury. In the light of recent data and the data available in the literature, the authors consider some pathophysiological mechanisms of action of laser radiation at all living matter organization levels: molecular, cellular, organ, and systemic. The feasibilities of laser correction of hemostastic disorders are defined in relation to the volume of blood loss and the functional state of compensatory systems. 

Testing to fulfill HACCP (Hazard Analysis Critical Control Points) requirements: principles and examples.

Science.gov (United States)

Gardner, I A

1997-12-01

On-farm HACCP (hazard analysis critical control points) monitoring requires cost-effective, yet accurate and reproducible tests that can determine the status of cows, milk, and the dairy environment. Tests need to be field-validated, and their limitations need to be established so that appropriate screening strategies can be initiated and test results can be rationally interpreted. For infections and residues of low prevalence, tests or testing strategies that are highly specific help to minimize false-positive results and excessive costs to the dairy industry. The determination of the numbers of samples to be tested in HACCP monitoring programs depends on the specific purpose of the test and the likely prevalence of the agent or residue at the critical control point. The absence of positive samples from a herd test should not be interpreted as freedom from a particular agent or residue unless the entire herd has been tested with a test that is 100% sensitive. The current lack of field-validated tests for most of the chemical and infectious agents of concern makes it difficult to ensure that the stated goals of HACCP programs are consistently achieved.

Prediction of the critical point and the dew- and bubble-point curves fo natural gases. Tennen gas no rinkaiten oyobi roten futten kyokusen no suisan

Energy Technology Data Exchange (ETDEWEB)

Endo, T. (Hitachi, Ltd., Tokyo (Japan)); Arai, D.; Uematsu, M. (Keio University, Tokyo (Japan). Faculty of Science and Technology)

1993-02-25

Related to the natural gas transport by pipeline, etc., the critical point, dew point and bubble point of natural gas were presumed by calculation through equation of state for determining the exact thermophysical values. The natural gas is multi-component mixed fluid which is represented by methane as a representative component. It considerably differs in composition by its place of origin. Because the conventional method was complicated in process for thermodynamically determining the most stable composition of phases, algorithm of phasic equilibrium was applied by the equation of state which used the discrimination method by Nitta, et al. for the therodynamic stability of phases. The method by Michelsen was applied to the flash calculation, and figuration of both dew point and bubble point curves, while that by Heidemann, et al. was done to the critical point calculation. Peng-Robinson's was applied to an equation of state. To start the calculation, the constant of seven two-component systems the main component of which was methane was determined as a function of temperature based on the actually measured gas/liquid equilibrium value. Then, possibility of calculatively presuming the thermophysical values was shown through comparison of the actually measured values with those obtained by applying the present method to the above systems. Finally, the presumption was made for the natural gas which differed in place of origin. 17 refs., 15 figs., 2 tabs.

Thermodynamics of diffusion under pressure and stress: Relation to point defect mechanisms

International Nuclear Information System (INIS)

Aziz, M.J.

1997-01-01

A thermodynamic formalism is developed for illuminating the predominant point defect mechanism of self- and impurity diffusion in silicon and is used to provide a rigorous basis for point defect-based interpretation of diffusion experiments in biaxially strained epitaxial layers in the Si endash Ge system. A specific combination of the hydrostatic and biaxial stress dependences of the diffusivity is ±1 times the atomic volume, depending upon whether the predominant mechanism involves vacancies or interstitials. Experimental results for Sb diffusion in biaxially strained Si endash Ge films and ab initio calculations of the activation volume for Sb diffusion by a vacancy mechanism are in quantitative agreement with no free parameters. Key parameters are identified that must be measured or calculated for a quantitative test of interstitial-based mechanisms. copyright 1997 American Institute of Physics

Dynamical simulation of a linear sigma model near the critical point

Energy Technology Data Exchange (ETDEWEB)

Wesp, Christian; Meistrenko, Alex; Greiner, Carsten [Institut fuer Theoretische Physik, Goethe-Universitaet Frankfurt, Max-von-Laue-Strasse 1, D-60438 Frankfurt (Germany); Hees, Hendrik van [Frankfurt Institute for Advanced Studies, Ruth-Moufang-Strasse 1, D-60438 Frankfurt (Germany)

2014-07-01

The intention of this study is the search for signatures of the chiral phase transition. To investigate the impact of fluctuations, e.g. of the baryon number, on the transition or a critical point, the linear sigma model is treated in a dynamical 3+1D numerical simulation. Chiral fields are approximated as classical fields, quarks are described by quasi particles in a Vlasov equation. Additional dynamic is implemented by quark-quark and quark-sigma-field interaction. For a consistent description of field-particle interactions, a new Monte-Carlo-Langevin-like formalism has been developed and is discussed.

Study on a New Steering Mechanism for Point-the-Bit Rotary Steerable System

Directory of Open Access Journals (Sweden)

Yuanzhi Li

2014-02-01

Full Text Available This paper presents a novel steering mechanism embedded in a point-the-bit rotary steerable system (RSS for oilfield exploitation. The new steering mechanism adopts a set of universal joints to alleviate the high alternative strain on drilling mandrel and employs a specially designed planetary gear small tooth number difference (PGSTD to achieve directional steering. Its principle and characteristics are explained and examined through a series of analyses. First, the eccentric displacement vector of the offset point on the drilling mandrel is formulated and kinematic solutions are established. Next, structural design for the new steering mechanism is addressed. Then, procedures and program architectures for simulating offset state of the drilling mandrel and motion trajectory of the whole steering mechanism are presented. After that, steering motion simulations of the new steering mechanism for both 2D and 3D well trajectories are then performed by combining LabVIEW and SolidWorks. Finally, experiments on the steering motion control of the new steering mechanism prototype are carried out. The simulations and experiments reveal that the steering performance of the new steering mechanism is satisfied. The research can provide good guidance for further research and engineering application of the point-the-bit RSS.

Structure and applications of point form relativistic quantum mechanics

International Nuclear Information System (INIS)

Klink, W.H.

2003-01-01

The framework of point form relativistic quantum mechanics is used to construct mass and current operators for hadronic systems with finite degree of freedom. For the point form all of the interactions are in the four-momentum operator and, since Lorentz transformations are kinematic, the theory is manifestly covariant. In the Bakamjian-Thomas version of the point form the four-momentum operator is written as a product of the four-velocity operator and mass operator, where the mass operator is the sum of free and interacting mass operators. Interacting mass operators can be constructed from vertices, matrix elements of local field operators evaluated at the space-time point zero, where the states are eigenstates of the four-velocity. Applications include the study of the spectra and widths of vector mesons, viewed as bound states of quark-antiquark pairs. Besides mass operators, current operators are needed to compute form factors. Form factors are matrix elements of current operators on mass operator eigenstates and are often calculated with one-body current operators (in the point form this is called the point form spectator approximation); but in a properly relativistic theory there must also be many-body current operators. Minimal currents needed to satisfy current conservation in the presence of hadronic interactions (called dynamically determined currents) are shown to be easily calculated in the point form. (author)

Critical point measurement of some polycyclic aromatic hydrocarbons

International Nuclear Information System (INIS)

Nikitin, Eugene D.; Popov, Alexander P.

2015-01-01

Highlights: • Critical properties of five polycyclic aromatic hydrocarbons were measured. • These hydrocarbons decompose at near-critical temperatures. • Pulse-heating method with short residence times was used. - Abstract: The critical temperatures and the critical pressures of five polycyclic aromatic compounds, namely, acenaphthene, fluorene, anthracene, phenanthrene, and pyrene have been measured. All the compounds studied decompose at near-critical temperatures. A pulse-heating technique applicable to measuring the critical properties of thermally unstable compounds has been used. The times from the beginning of a heating pulse to the moment of reaching the critical temperature were from (0.06 to 0.85) ms. The short residence times provide little degradation of the substances in the course of the experiments. The experimental critical parameters of the polycyclic aromatic compounds have been compared with those estimated by five predictive methods. The acentric factors of polycyclic aromatic compounds studied have been calculated

Macro-mechanics controls quantum mechanics: mechanically controllable quantum conductance switching of an electrochemically fabricated atomic-scale point contact

Science.gov (United States)

Staiger, Torben; Wertz, Florian; Xie, Fangqing; Heinze, Marcel; Schmieder, Philipp; Lutzweiler, Christian; Schimmel, Thomas

2018-01-01

Here, we present a silver atomic-scale device fabricated and operated by a combined technique of electrochemical control (EC) and mechanically controllable break junction (MCBJ). With this EC-MCBJ technique, we can perform mechanically controllable bistable quantum conductance switching of a silver quantum point contact (QPC) in an electrochemical environment at room temperature. Furthermore, the silver QPC of the device can be controlled both mechanically and electrochemically, and the operating mode can be changed from ‘electrochemical’ to ‘mechanical’, which expands the operating mode for controlling QPCs. These experimental results offer the perspective that a silver QPC may be used as a contact for a nanoelectromechanical relay.

Recommendations for dealing with waste contaminated with Ebola virus: a Hazard Analysis of Critical Control Points approach.

Science.gov (United States)

Edmunds, Kelly L; Elrahman, Samira Abd; Bell, Diana J; Brainard, Julii; Dervisevic, Samir; Fedha, Tsimbiri P; Few, Roger; Howard, Guy; Lake, Iain; Maes, Peter; Matofari, Joseph; Minnigh, Harvey; Mohamedani, Ahmed A; Montgomery, Maggie; Morter, Sarah; Muchiri, Edward; Mudau, Lutendo S; Mutua, Benedict M; Ndambuki, Julius M; Pond, Katherine; Sobsey, Mark D; van der Es, Mike; Zeitoun, Mark; Hunter, Paul R

2016-06-01

To assess, within communities experiencing Ebola virus outbreaks, the risks associated with the disposal of human waste and to generate recommendations for mitigating such risks. A team with expertise in the Hazard Analysis of Critical Control Points framework identified waste products from the care of individuals with Ebola virus disease and constructed, tested and confirmed flow diagrams showing the creation of such products. After listing potential hazards associated with each step in each flow diagram, the team conducted a hazard analysis, determined critical control points and made recommendations to mitigate the transmission risks at each control point. The collection, transportation, cleaning and shared use of blood-soiled fomites and the shared use of latrines contaminated with blood or bloodied faeces appeared to be associated with particularly high levels of risk of Ebola virus transmission. More moderate levels of risk were associated with the collection and transportation of material contaminated with bodily fluids other than blood, shared use of latrines soiled with such fluids, the cleaning and shared use of fomites soiled with such fluids, and the contamination of the environment during the collection and transportation of blood-contaminated waste. The risk of the waste-related transmission of Ebola virus could be reduced by the use of full personal protective equipment, appropriate hand hygiene and an appropriate disinfectant after careful cleaning. Use of the Hazard Analysis of Critical Control Points framework could facilitate rapid responses to outbreaks of emerging infectious disease.

Supercritical CO2 Brayton cycle compression and control near the critical point

International Nuclear Information System (INIS)

Wright, S. A.; Fuller, R.; Noall, J.; Radel, R.; Vernon, M. E.; Pickard, P. S.

2008-01-01

This report describes the supercritical compression and control issues, the analysis, and the measured test results of a small-scale supercritical CO 2 (S-CO 2 ) compression test-loop. The test loop was developed by Sandia and is described in a companion paper in this conference. The results of these experiments will for the first time evaluate and experimentally demonstrate supercritical compression and the required compressor inlet control approaches on an appropriate scale in a series of test loops at Sandia National Laboratories. The Sandia effort is focused on the main compressor of a supercritical Brayton loop while a separate DOE Gen lV program focus is on studying similar behavior in re-compression Brayton cycles that have dual compressors. One of the main goals of this program is to develop and demonstrate the ability to design, operate, and control the supercritical compression process near the critical point due to highly non-linear behavior near this point. This Sandia supercritical test-loop uses a 50 kW radial compressor to pump supercritical CO 2 (S-CO 2 ) through an orifice and through a water-cooled gas-chiller. At the design point the compressor flow rate is 3.5 kg/s, the inlet pressure is 7, 690 kPa, the pressure ratio is 1.8, the inlet temperature is 305 K, and the shaft speed is 75, 000 rpm. The purpose of the loop is to study the compression and control issues near the critical point. To study compression we intend to compare the design code predictions for efficiency and change in enthalpy (or pressure ratio / head) of the radial compressor with the measured results from actual tests. In the tests the inlet flow, temperature, and pressure, will be varied around the critical point of CO 2 (Tc=304.2 K, and Pc=7.377 MPa). To study control, the test loop will use a variety of methods including inventory control, shaft speed control, and cooling water flow rate, and cooling water temperature control methods to set the compressor inlet temperature

Generalized Attractor Points in Gauged Supergravity

Energy Technology Data Exchange (ETDEWEB)

Kachru, Shamit; /Stanford U., Phys. Dept. /SLAC; Kallosh, Renata; /Stanford U., Phys. Dept.; Shmakova, Marina; /KIPAC, Menlo Park /SLAC /Stanford U., Phys. Dept.

2011-08-15

The attractor mechanism governs the near-horizon geometry of extremal black holes in ungauged 4D N=2 supergravity theories and in Calabi-Yau compactifications of string theory. In this paper, we study a natural generalization of this mechanism to solutions of arbitrary 4D N=2 gauged supergravities. We define generalized attractor points as solutions of an ansatz which reduces the Einstein, gauge field, and scalar equations of motion to algebraic equations. The simplest generalized attractor geometries are characterized by non-vanishing constant anholonomy coefficients in an orthonormal frame. Basic examples include Lifshitz and Schroedinger solutions, as well as AdS and dS vacua. There is a generalized attractor potential whose critical points are the attractor points, and its extremization explains the algebraic nature of the equations governing both supersymmetric and non-supersymmetric attractors.

Sub-critical cohesive crack propagation with hydro-mechanical coupling and friction

Directory of Open Access Journals (Sweden)

S. Valente

2016-01-01

Full Text Available Looking at the long-time behaviour of a dam, it is necessary to assume that the water can penetrate a possible crack washing away some components of the concrete. This type of corrosion reduces the tensile strength and fracture energy of the concrete compared to the same parameters measured during a short-time laboratory test. This phenomenon causes the so called sub-critical crack propagation. That is the reason why the International Commission of Large Dams recommends to neglect the tensile strength of the joint between the dam and the foundation, which is the weakest point of a gravity dam. In these conditions a shear displacement discontinuity starts growing in a point, called Fictitious Crack Tip (shortened FCT, which is still subjected to a compression stress. In order to manage this problem, in this paper the cohesive crack model is re-formulated with the focus on the shear stress component. In this context, the classical Newton-Raphson method fails to converge to an equilibrium state. Therefore the approach used is based on two stages: (a a global one in which the FCT is moved ahead of one increment; (b a local one in which the non-linear conditions occurring in the Fracture Process Zone are taken into account. This two-stage approach, which is known in the literature as a Large Time Increment method, is able to model three different mechanical regimes occurring during the crack propagation between a dam and the foundation rock.

Evaluation of the i-STAT point-of-care analyzer in critically ill adult patients.

Science.gov (United States)

Steinfelder-Visscher, Jacoline; Teerenstra, Steven; Gunnewiek, Jacqueline M T Klein; Weerwind, Patrick W

2008-03-01

Point-of-care analyzers may benefit therapeutic decision making by reducing turn-around-time for samples. This is especially true when biochemical parameters exceed the clinical reference range, in which acute and effective treatment is essential. We therefore evaluated the analytical performance of the i-STAT point-of-care analyzer in two critically ill adult patient populations. During a 3-month period, 48 blood samples from patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) and 42 blood samples from non-cardiac patients who needed intensive care treatment were analyzed on both the i-STAT analyzer (CPB and non-CPB mode, respectively) and our laboratory analyzers (RapidLab 865/Sysmex XE-2100 instrument). The agreement analysis for quantitative data was used to compare i-STAT to RapidLab for blood gas/electrolytes and for hematocrit with the Sysmex instrument. Point-of-care electrolytes and blood gases had constant deviation, except for pH, pO2, and hematocrit. A clear linear trend in deviation of i-STAT from RapidLab was noticed for pH during CPB (r = 0.32, p = .03) and for pO2 > 10 kPa during CPB (r = -0.59, p pO2 pO2 pO2 range (10.6 pO2 range below 25% (n = 11) using the i-STAT. The i-STAT analyzer is suitable for point-of-care testing of electrolytes and blood gases in critically ill patients, except for high pO2. However, the discrepancy in hematocrit bias shows that accuracy established in one patient population cannot be automatically extrapolated to other patient populations, thus stressing the need for separate evaluation.

Hodograph solutions of the dispersionless coupled KdV hierarchies, critical points and the Euler-Poisson-Darboux equation

International Nuclear Information System (INIS)

Konopelchenko, B; Alonso, L MartInez; Medina, E

2010-01-01

It is shown that the hodograph solutions of the dispersionless coupled KdV (dcKdV) hierarchies describe critical and degenerate critical points of a scalar function which obeys the Euler-Poisson-Darboux equation. Singular sectors of each dcKdV hierarchy are found to be described by solutions of higher genus dcKdV hierarchies. Concrete solutions exhibiting shock-type singularities are presented.

Self-organized critical pinball machine

DEFF Research Database (Denmark)

Flyvbjerg, H.

2004-01-01

The nature of self-organized criticality (SOC) is pin-pointed with a simple mechanical model: a pinball machine. Its phase space is fully parameterized by two integer variables, one describing the state of an on-going game, the other describing the state of the machine. This is the simplest...

Silver (Ag) Transport Mechanisms in TRISO coated particles: A Critical Review

Energy Technology Data Exchange (ETDEWEB)

I J van Rooyen; J H Neethling; J A A Engelbrecht; P M van Rooyen; G Strydom

2012-10-01

Transport of 110mAg in the intact SiC layer of TRISO coated particles has been studied for approximately 30 years without arriving at a satisfactory explanation of the transport mechanism. In this paper the possible mechanisms postulated in previous experimental studies, both in-reactor and out-of reactor research environment studies are critically reviewed and of particular interest are relevance to very high temperature gas reactor operating and accident conditions. Among the factors thought to influence Ag transport are grain boundary stoichiometry, SiC grain size and shape, the presence of free silicon, nano-cracks, thermal decomposition, palladium attack, transmutation products, layer thinning and coated particle shape. Additionally new insight to nature and location of fission products has been gained via recent post irradiation electron microscopy examination of TRISO coated particles from the DOE’s fuel development program. The combined effect of critical review and new analyses indicates a direction for investigating possible the Ag transport mechanism including the confidence level with which these mechanisms may be experimentally verified.

Silver (Ag) transport mechanisms in TRISO coated particles: A critical review

Energy Technology Data Exchange (ETDEWEB)

Rooyen, I.J. van, E-mail: isabella.vanrooyen@inl.gov [Idaho National Laboratory, Idaho Falls, ID 83415-6188 (United States); Dunzik-Gougar, M.L. [Department of Nuclear Engineering, Idaho State University, ID (United States); Rooyen, P.M. van [Philip M. van Rooyen Network Consultants, Midlands Estates (South Africa)

2014-05-01

Transport of {sup 110m}Ag in the intact SiC layer of TRISO coated particles has been studied for approximately 30 years without arriving at a satisfactory explanation of the transport mechanism. In this paper the possible mechanisms postulated in previous experimental studies, both in-reactor and out-of reactor research environment studies are critically reviewed and of particular interest are relevance to very high temperature gas reactor operating and accident conditions. Among the factors thought to influence Ag transport are grain boundary stoichiometry, SiC grain size and shape, the presence of free silicon, nano-cracks, thermal decomposition, palladium attack, transmutation products, layer thinning and coated particle shape. Additionally new insight to nature and location of fission products has been gained via recent post irradiation electron microscopy examination of TRISO coated particles from the DOE's fuel development program. The combined effect of critical review and new analyses indicates a direction for investigating possible the Ag transport mechanism including the confidence level with which these mechanisms may be experimentally verified.

The chiral critical point of $N_f$=3 QCD at finite density to the order $(\\mu/T)^4$

CERN Document Server

De Forcrand, Philippe

2008-01-01

QCD with three degenerate quark flavours at zero baryon density exhibits a first order thermal phase transition for small quark masses, which changes to a smooth crossover for some critical quark mass m^c_0, i.e. the chiral critical point. It is generally believed that as an (even) function of quark chemical potential, m_c(mu), the critical point moves to larger quark masses, constituting the critical endpoint of a first order phase transition in theories with m\\geq m^c_0. To test this, we consider a Taylor expansion of m_c(mu) around mu=0 and determine the first two coefficients from lattice simulations with staggered fermions on N_t=4 lattices. We employ two different techniques: a) calculating the coefficients directly from a mu=0 ensemble using a novel finite difference method, and b) fitting them to simulation data obtained for imaginary chemical potentials. The mu^2 and mu^4 coefficients are found to be negative by both methods, with consistent absolute values. Combining both methods gives evidence that...

Assessment of hygiene standards and Hazard Analysis Critical Control Points implementation on passenger ships.

Science.gov (United States)

Mouchtouri, Varavara; Malissiova, Eleni; Zisis, Panagiotis; Paparizou, Evina; Hadjichristodoulou, Christos

2013-01-01

The level of hygiene on ferries can have impact on travellers' health. The aim of this study was to assess the hygiene standards of ferries in Greece and to investigate whether Hazard Analysis Critical Control Points (HACCP) implementation contributes to the hygiene status and particularly food safety aboard passenger ships. Hygiene inspections on 17 ferries in Greece were performed using a standardized inspection form, with a 135-point scale. Thirty-four water and 17 food samples were collected and analysed. About 65% (11/17) of ferries were scored with >100 points. Ferries with HACCP received higher scores during inspection compared to those without HACCP (p value food samples, only one was found positive for Salmonella spp. Implementation of management systems including HACCP principles can help to raise the level of hygiene aboard passenger ships.

CePdAl. A frustrated Kondo lattice at a quantum critical point

Energy Technology Data Exchange (ETDEWEB)

Fritsch, Veronika [EP 6, Electronic Correlations and Magnetism, University of Augsburg (Germany); Karlsruhe Institute of Technology (Germany); Sakai, Akito; Gegenwart, Philipp [EP 6, Electronic Correlations and Magnetism, University of Augsburg (Germany); Huesges, Zita; Lucas, Stefan; Stockert, Oliver [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Kittler, Wolfram; Taubenheim, Christian; Grube, Kai; Loehneysen, Hilbert von [Karlsruhe Institute of Technology (Germany); Huang, Chien-Lung [Karlsruhe Institute of Technology (Germany); Max Planck Institute for Chemical Physics of Solids, Dresden (Germany)

2016-07-01

CePdAl is one of the rare frustrated Kondo lattice systems that can be tuned across a quantum critical point (QCP) by means of chemical pressure, i. e., the substitution of Pd by Ni. Magnetic frustration and Kondo effect are antithetic phenomena: The Kondo effect with the incipient delocalization of the magnetic moments, is not beneficial for the formation of a frustrated state. On the other hand, magnetic frustrated exchange interactions between the local moments can result in a breakdown of Kondo screening. Furthermore, the fate of frustration is unclear when approaching the QCP, since there is no simple observable to quantify the degree of frustration. We present thermodynamic and neutron scattering experiments on CePd{sub 1-x}Ni{sub x}Al close to the critical concentration x ∼0.14. Our experiments indicate that even at the QCP magnetic frustration is still present, opening the perspective to find new universality classes at such a quantum phase transition.

Neural avalanches at the critical point between replay and non-replay of spatiotemporal patterns.

Directory of Open Access Journals (Sweden)

Silvia Scarpetta

Full Text Available We model spontaneous cortical activity with a network of coupled spiking units, in which multiple spatio-temporal patterns are stored as dynamical attractors. We introduce an order parameter, which measures the overlap (similarity between the activity of the network and the stored patterns. We find that, depending on the excitability of the network, different working regimes are possible. For high excitability, the dynamical attractors are stable, and a collective activity that replays one of the stored patterns emerges spontaneously, while for low excitability, no replay is induced. Between these two regimes, there is a critical region in which the dynamical attractors are unstable, and intermittent short replays are induced by noise. At the critical spiking threshold, the order parameter goes from zero to one, and its fluctuations are maximized, as expected for a phase transition (and as observed in recent experimental results in the brain. Notably, in this critical region, the avalanche size and duration distributions follow power laws. Critical exponents are consistent with a scaling relationship observed recently in neural avalanches measurements. In conclusion, our simple model suggests that avalanche power laws in cortical spontaneous activity may be the effect of a network at the critical point between the replay and non-replay of spatio-temporal patterns.

Recommendations for mechanical ventilation of critically ill children from the Paediatric Mechanical Ventilation Consensus Conference (PEMVECC).

Science.gov (United States)

Kneyber, Martin C J; de Luca, Daniele; Calderini, Edoardo; Jarreau, Pierre-Henri; Javouhey, Etienne; Lopez-Herce, Jesus; Hammer, Jürg; Macrae, Duncan; Markhorst, Dick G; Medina, Alberto; Pons-Odena, Marti; Racca, Fabrizio; Wolf, Gerhard; Biban, Paolo; Brierley, Joe; Rimensberger, Peter C

2017-12-01

Much of the common practice in paediatric mechanical ventilation is based on personal experiences and what paediatric critical care practitioners have adopted from adult and neonatal experience. This presents a barrier to planning and interpretation of clinical trials on the use of specific and targeted interventions. We aim to establish a European consensus guideline on mechanical ventilation of critically children. The European Society for Paediatric and Neonatal Intensive Care initiated a consensus conference of international European experts in paediatric mechanical ventilation to provide recommendations using the Research and Development/University of California, Los Angeles, appropriateness method. An electronic literature search in PubMed and EMBASE was performed using a combination of medical subject heading terms and text words related to mechanical ventilation and disease-specific terms. The Paediatric Mechanical Ventilation Consensus Conference (PEMVECC) consisted of a panel of 15 experts who developed and voted on 152 recommendations related to the following topics: (1) general recommendations, (2) monitoring, (3) targets of oxygenation and ventilation, (4) supportive measures, (5) weaning and extubation readiness, (6) normal lungs, (7) obstructive diseases, (8) restrictive diseases, (9) mixed diseases, (10) chronically ventilated patients, (11) cardiac patients and (12) lung hypoplasia syndromes. There were 142 (93.4%) recommendations with "strong agreement". The final iteration of the recommendations had none with equipoise or disagreement. These recommendations should help to harmonise the approach to paediatric mechanical ventilation and can be proposed as a standard-of-care applicable in daily clinical practice and clinical research.

On the critical temperature, normal boiling point, and vapor pressure of ionic liquids.

Science.gov (United States)

Rebelo, Luis P N; Canongia Lopes, José N; Esperança, José M S S; Filipe, Eduardo

2005-04-07

One-stage, reduced-pressure distillations at moderate temperature of 1-decyl- and 1-dodecyl-3-methylimidazolium bistriflilamide ([Ntf(2)](-)) ionic liquids (ILs) have been performed. These liquid-vapor equilibria can be understood in light of predictions for normal boiling points of ILs. The predictions are based on experimental surface tension and density data, which are used to estimate the critical points of several ILs and their corresponding normal boiling temperatures. In contrast to the situation found for relatively unstable ILs at high-temperature such as those containing [BF(4)](-) or [PF(6)](-) anions, [Ntf(2)](-)-based ILs constitute a promising class in which reliable, accurate vapor pressure measurements can in principle be performed. This property is paramount for assisting in the development and testing of accurate molecular models.

Implementation of the critical points model in a SFM-FDTD code working in oblique incidence

Energy Technology Data Exchange (ETDEWEB)

Hamidi, M; Belkhir, A; Lamrous, O [Laboratoire de Physique et Chimie Quantique, Universite Mouloud Mammeri, Tizi-Ouzou (Algeria); Baida, F I, E-mail: omarlamrous@mail.ummto.dz [Departement d' Optique P.M. Duffieux, Institut FEMTO-ST UMR 6174 CNRS Universite de Franche-Comte, 25030 Besancon Cedex (France)

2011-06-22

We describe the implementation of the critical points model in a finite-difference-time-domain code working in oblique incidence and dealing with dispersive media through the split field method. Some tests are presented to validate our code in addition to an application devoted to plasmon resonance of a gold nanoparticles grating.

Vegetation community change points suggest that critical loads of nutrient nitrogen may be too high

Science.gov (United States)

Wilkins, Kayla; Aherne, Julian; Bleasdale, Andy

2016-12-01

It is widely accepted that elevated nitrogen deposition can have detrimental effects on semi-natural ecosystems, including changes to plant diversity. Empirical critical loads of nutrient nitrogen have been recommended to protect many sensitive European habitats from significant harmful effects. In this study, we used Threshold Indicator Taxa Analysis (TITAN) to investigate shifts in vegetation communities along an atmospheric nitrogen deposition gradient for twenty-two semi-natural habitat types (as described under Annex I of the European Union Habitats Directive) in Ireland. Significant changes in vegetation community, i.e., change points, were determined for twelve habitats, with seven habitats showing a decrease in the number of positive indicator species. Community-level change points indicated a decrease in species abundance along a nitrogen deposition gradient ranging from 3.9 to 15.3 kg N ha-1 yr-1, which were significantly lower than recommended critical loads (Wilcoxon signed-rank test; V = 6, p < 0.05). These results suggest that lower critical loads of empirical nutrient nitrogen deposition may be required to protect many European habitats. Changes to vegetation communities may mean a loss of sensitive indicator species and potentially rare species in these habitats, highlighting how emission reductions policies set under the National Emissions Ceilings Directive may be directly linked to meeting the goal set out under the European Union's Biodiversity Strategy of "halting the loss of biodiversity" across Europe by 2020.

Quasiparticle mass enhancement close to the quantum critical point in BaFe2(As(1-x)P(x))2.

Science.gov (United States)

Walmsley, P; Putzke, C; Malone, L; Guillamón, I; Vignolles, D; Proust, C; Badoux, S; Coldea, A I; Watson, M D; Kasahara, S; Mizukami, Y; Shibauchi, T; Matsuda, Y; Carrington, A

2013-06-21

We report a combined study of the specific heat and de Haas-van Alphen effect in the iron-pnictide superconductor BaFe2(As(1-x)P(x))2. Our data when combined with results for the magnetic penetration depth give compelling evidence for the existence of a quantum critical point close to x=0.30 which affects the majority of the Fermi surface by enhancing the quasiparticle mass. The results show that the sharp peak in the inverse superfluid density seen in this system results from a strong increase in the quasiparticle mass at the quantum critical point.

Core-softened fluids, water-like anomalies, and the liquid-liquid critical points.

Science.gov (United States)

Salcedo, Evy; de Oliveira, Alan Barros; Barraz, Ney M; Chakravarty, Charusita; Barbosa, Marcia C

2011-07-28

Molecular dynamics simulations are used to examine the relationship between water-like anomalies and the liquid-liquid critical point in a family of model fluids with multi-Gaussian, core-softened pair interactions. The core-softened pair interactions have two length scales, such that the longer length scale associated with a shallow, attractive well is kept constant while the shorter length scale associated with the repulsive shoulder is varied from an inflection point to a minimum of progressively increasing depth. The maximum depth of the shoulder well is chosen so that the resulting potential reproduces the oxygen-oxygen radial distribution function of the ST4 model of water. As the shoulder well depth increases, the pressure required to form the high density liquid decreases and the temperature up to which the high-density liquid is stable increases, resulting in the shift of the liquid-liquid critical point to much lower pressures and higher temperatures. To understand the entropic effects associated with the changes in the interaction potential, the pair correlation entropy is computed to show that the excess entropy anomaly diminishes when the shoulder well depth increases. Excess entropy scaling of diffusivity in this class of fluids is demonstrated, showing that decreasing strength of the excess entropy anomaly with increasing shoulder depth results in the progressive loss of water-like thermodynamic, structural and transport anomalies. Instantaneous normal mode analysis was used to index the overall curvature distribution of the fluid and the fraction of imaginary frequency modes was shown to correlate well with the anomalous behavior of the diffusivity and the pair correlation entropy. The results suggest in the case of core-softened potentials, in addition to the presence of two length scales, energetic, and entropic effects associated with local minima and curvatures of the pair interaction play an important role in determining the presence of water

[Introduction of hazard analysis and critical control points (HACCP) principles at the flight catering food production plant].

Science.gov (United States)

Popova, A Yu; Trukhina, G M; Mikailova, O M

In the article there is considered the quality control and safety system implemented in the one of the largest flight catering food production plant for airline passengers and flying squad. The system for the control was based on the Hazard Analysis And Critical Control Points (HACCP) principles and developed hygienic and antiepidemic measures. There is considered the identification of hazard factors at stages of the technical process. There are presented results of the analysis data of monitoring for 6 critical control points over the five-year period. The quality control and safety system permit to decline food contamination risk during acceptance, preparation and supplying of in-flight meal. There was proved the efficiency of the implemented system. There are determined further ways of harmonization and implementation for HACCP principles in the plant.

Quantum mechanical cluster calculations of critical scintillation processes

International Nuclear Information System (INIS)

Derenzo, Stephen E.; Klintenberg, Mattias K.; Weber, Marvin J.

2000-01-01

This paper describes the use of commercial quantum chemistry codes to simulate several critical scintillation processes. The crystal is modeled as a cluster of typically 50 atoms embedded in an array of typically 5,000 point charges designed to reproduce the electrostatic field of the infinite crystal. The Schrodinger equation is solved for the ground, ionized, and excited states of the system to determine the energy and electron wave function. Computational methods for the following critical processes are described: (1) the formation and diffusion of relaxed holes, (2) the formation of excitons, (3) the trapping of electrons and holes by activator atoms, (4) the excitation of activator atoms, and (5) thermal quenching. Examples include hole diffusion in CsI, the exciton in CsI, the excited state of CsI:Tl, the energy barrier for the diffusion of relaxed holes in CaF2 and PbF2, and prompt hole trapping by activator atoms in CaF2:Eu and CdS:Te leading to an ultra-fast (<50ps) scintillation rise time.

Critical Opalescence around the QCD Critical Point and Second-order Relativistic Hydrodynamic Equations Compatible with Boltzmann Equation

International Nuclear Information System (INIS)

Kunihiro, Teiji; Minami, Yuki; Tsumura, Kyosuke

2009-01-01

The dynamical density fluctuations around the QCD critical point (CP) are analyzed using relativistic dissipative fluid dynamics, and we show that the sound mode around the QCD CP is strongly attenuated whereas the thermal fluctuation stands out there. We speculate that if possible suppression or disappearance of a Mach cone, which seems to be created by the partonic jets at RHIC, is observed as the incident energy of the heavy-ion collisions is decreased, it can be a signal of the existence of the QCD CP. We have presented the Israel-Stewart type fluid dynamic equations that are derived rigorously on the basis of the (dynamical) renormalization group method in the second part of the talk, which we omit here because of a lack of space.

Critical Opalescence around the QCD Critical Point and Second-order Relativistic Hydrodynamic Equations Compatible with Boltzmann Equation

Science.gov (United States)

Kunihiro, Teiji; Minami, Yuki; Tsumura, Kyosuke

2009-11-01

The dynamical density fluctuations around the QCD critical point (CP) are analyzed using relativistic dissipative fluid dynamics, and we show that the sound mode around the QCD CP is strongly attenuated whereas the thermal fluctuation stands out there. We speculate that if possible suppression or disappearance of a Mach cone, which seems to be created by the partonic jets at RHIC, is observed as the incident energy of the heavy-ion collisions is decreased, it can be a signal of the existence of the QCD CP. We have presented the Israel-Stewart type fluid dynamic equations that are derived rigorously on the basis of the (dynamical) renormalization group method in the second part of the talk, which we omit here because of a lack of space.

Atmospheric Convective Organization: Self-Organized Criticality or Homeostasis?

Science.gov (United States)

Yano, Jun-Ichi

2015-04-01

Atmospheric convection has a tendency organized on a hierarchy of scales ranging from the mesoscale to the planetary scales, with the latter especially manifested by the Madden-Julian oscillation. The present talk examines two major possible mechanisms of self-organization identified in wider literature from a phenomenological thermodynamic point of view by analysing a planetary-scale cloud-resolving model simulation. The first mechanism is self-organized criticality. A saturation tendency of precipitation rate with the increasing column-integrated water, reminiscence of critical phenomena, indicates self-organized criticality. The second is a self-regulation mechanism that is known as homeostasis in biology. A thermodynamic argument suggests that such self-regulation maintains the column-integrated water below a threshold by increasing the precipitation rate. Previous analyses of both observational data as well as cloud-resolving model (CRM) experiments give mixed results. A satellite data analysis suggests self-organized criticality. Some observational data as well as CRM experiments support homeostasis. Other analyses point to a combination of these two interpretations. In this study, a CRM experiment over a planetary-scale domain with a constant sea-surface temperature is analyzed. This analysis shows that the relation between the column-integrated total water and precipitation suggests self-organized criticality, whereas the one between the column-integrated water vapor and precipitation suggests homeostasis. The concurrent presence of these two mechanisms are further elaborated by detailed statistical and budget analyses. These statistics are scale invariant, reflecting a spatial scaling of precipitation processes. These self-organization mechanisms are most likely be best theoretically understood by the energy cycle of the convective systems consisting of the kinetic energy and the cloud-work function. The author has already investigated the behavior of this

Stability theory of critical cases and the bifurcation points of the stationary solutions of the Lorenz model

International Nuclear Information System (INIS)

Bakasov, A.A.; Govorkov, B.B. Jr.

1990-08-01

The critical case in stability theory is the case when it is impossible to study the stability of solutions over the linear part of ordinary differential equations. This situation is usual at the bifurcation points. There exists a powerful and constructive approach to investigate the stability - the theory of critical cases created by Lyapunov. The famous Lorenz model is used in this article as an illustration of the power of the method (new results). (author). 27 refs

Accurate Determination of the Quasiparticle and Scaling Properties Surrounding the Quantum Critical Point of Disordered Three-Dimensional Dirac Semimetals.

Science.gov (United States)

Fu, Bo; Zhu, Wei; Shi, Qinwei; Li, Qunxiang; Yang, Jinlong; Zhang, Zhenyu

2017-04-07

Exploiting the enabling power of the Lanczos method in momentum space, we determine accurately the quasiparticle and scaling properties of disordered three-dimensional Dirac semimetals surrounding the quantum critical point separating the semimetal and diffusive metal regimes. We unveil that the imaginary part of the quasiparticle self-energy obeys a common power law before, at, and after the quantum phase transition, but the power law is nonuniversal, whose exponent is dependent on the disorder strength. More intriguingly, whereas a common power law is also found for the real part of the self-energy before and after the phase transition, a distinctly different behavior is identified at the critical point, characterized by the existence of a nonanalytic logarithmic singularity. This nonanalytical correction serves as the very basis for the unusual power-law behaviors of the quasiparticles and many other physical properties surrounding the quantum critical point. Our approach also allows the ready and reliable determination of the scaling properties of the correlation length and dynamical exponents. We further show that the central findings are valid for both uncorrelated and correlated disorder distributions and should be directly comparable with future experimental observations.

HACCP (Hazard Analysis and Critical Control Points) to guarantee safe water reuse and drinking water production--a case study.

Science.gov (United States)

Dewettinck, T; Van Houtte, E; Geenens, D; Van Hege, K; Verstraete, W

2001-01-01

To obtain a sustainable water catchment in the dune area of the Flemish west coast, the integration of treated domestic wastewater in the existing potable water production process is planned. The hygienic hazards associated with the introduction of treated domestic wastewater into the water cycle are well recognised. Therefore, the concept of HACCP (Hazard Analysis and Critical Control Points) was used to guarantee hygienically safe drinking water production. Taking into account the literature data on the removal efficiencies of the proposed advanced treatment steps with regard to enteric viruses and protozoa and after setting high quality limits based on the recent progress in quantitative risk assessment, the critical control points (CCPs) and points of attention (POAs) were identified. Based on the HACCP analysis a specific monitoring strategy was developed which focused on the control of these CCPs and POAs.

HACCP (Hazard Analysis Critical Control Points): is it coming to the dairy?

Science.gov (United States)

Cullor, J S

1997-12-01

The risks and consequences of foodborne and waterborne pathogens are coming to the forefront of public health concerns, and strong pressure is being applied on agriculture for immediate implementation of on-farm controls. The FDA is considering HACCP (Hazard Analysis Critical Control Points) as the new foundation for revision of the US Food Safety Assurance Program because HACCP is considered to be a science-based, systematic approach to the prevention of food safety problems. In addition, the implementation of HACCP principles permits more government oversight through requirements for standard operating procedures and additional systems for keeping records, places primary responsibility for ensuring food safety on the food manufacturer or distributor, and may assist US food companies in competing more effectively in the world market. With the HACCP-based program in place, a government investigator should be able to determine and evaluate both current and past conditions that are critical to ensuring the safety of the food produced by the facility. When this policy is brought to the production unit, the impact for producers and veterinarians will be substantial.

The implementation of a Hazard Analysis and Critical Control Point management system in a peanut butter ice cream plant

Directory of Open Access Journals (Sweden)

Yu-Ting Hung

2015-09-01

Full Text Available To ensure the safety of the peanut butter ice cream manufacture, a Hazard Analysis and Critical Control Point (HACCP plan has been designed and applied to the production process. Potential biological, chemical, and physical hazards in each manufacturing procedure were identified. Critical control points for the peanut butter ice cream were then determined as the pasteurization and freezing process. The establishment of a monitoring system, corrective actions, verification procedures, and documentation and record keeping were followed to complete the HACCP program. The results of this study indicate that implementing the HACCP system in food industries can effectively enhance food safety and quality while improving the production management.

Increased Dicarbonyl Stress as a Novel Mechanism of Multi-Organ Failure in Critical Illness

Directory of Open Access Journals (Sweden)

Bas C. T. van Bussel

2017-02-01

Full Text Available Molecular pathological pathways leading to multi-organ failure in critical illness are progressively being unravelled. However, attempts to modulate these pathways have not yet improved the clinical outcome. Therefore, new targetable mechanisms should be investigated. We hypothesize that increased dicarbonyl stress is such a mechanism. Dicarbonyl stress is the accumulation of dicarbonyl metabolites (i.e., methylglyoxal, glyoxal, and 3-deoxyglucosone that damages intracellular proteins, modifies extracellular matrix proteins, and alters plasma proteins. Increased dicarbonyl stress has been shown to impair the renal, cardiovascular, and central nervous system function, and possibly also the hepatic and respiratory function. In addition to hyperglycaemia, hypoxia and inflammation can cause increased dicarbonyl stress, and these conditions are prevalent in critical illness. Hypoxia and inflammation have been shown to drive the rapid intracellular accumulation of reactive dicarbonyls, i.e., through reduced glyoxalase-1 activity, which is the key enzyme in the dicarbonyl detoxification enzyme system. In critical illness, hypoxia and inflammation, with or without hyperglycaemia, could thus increase dicarbonyl stress in a way that might contribute to multi-organ failure. Thus, we hypothesize that increased dicarbonyl stress in critical illness, such as sepsis and major trauma, contributes to the development of multi-organ failure. This mechanism has the potential for new therapeutic intervention in critical care.

Relativity, Symmetry, and the Structure of Quantum Theory, Volume 2; Point form relativistic quantum mechanics

Science.gov (United States)

Klink, William H.; Schweiger, Wolfgang

2018-03-01

This book covers relativistic quantum theory from the point of view of a particle theory, based on the irreducible representations of the Poincaré group, the group that expresses the symmetry of Einstein relativity. There are several ways of formulating such a theory; this book develops what is called relativistic point form quantum mechanics, which, unlike quantum field theory, deals with a fixed number of particles in a relativistically invariant way. A chapter is devoted to applications of point form quantum mechanics to nuclear physics.

Recommendations for mechanical ventilation of critically ill children from the Paediatric Mechanical Ventilation Consensus Conference (PEMVECC)

NARCIS (Netherlands)

Kneyber, Martin C. J.; de Luca, Daniele; Calderini, Edoardo; Jarreau, Pierre-Henri; Javouhey, Etienne; Lopez-Herce, Jesus; Hammer, Jurg; Macrae, Duncan; Markhorst, Dick G.; Medina, Alberto; Pons-Odena, Marti; Racca, Fabrizio; Wolf, Gerhard; Biban, Paolo; Brierley, Joe; Rimensberger, Peter C.

2017-01-01

Purpose: Much of the common practice in paediatric mechanical ventilation is based on personal experiences and what paediatric critical care practitioners have adopted from adult and neonatal experience. This presents a barrier to planning and interpretation of clinical trials on the use of specific

Compressibility and specific heats of heavier condensed rare gases near the liquid-vapour critical point

International Nuclear Information System (INIS)

March, N.H.

2003-08-01

Sarkisov (J. Chem. Phys. 119, 373, 2003) has recently discussed the structural behaviour of a simple fluid near the liquid-vapour critical point. His work, already compared with computer simulation studies, is here brought into direct contact for the heavier condensed rare gases Ar, Kr and Xe with (a) experiment and (b) earlier theoretical investigations. Directions for future studies then emerge. (author)

Nuclear criticality safety: general. 3. Tokaimura Criticality Accident: Point Model Stochastic Neutronic Interpretation

International Nuclear Information System (INIS)

Mechitoua, Boukhmes

2001-01-01

step is based on the knowledge of the reactivity insertion. 2. Initiation probability for one neutron P(t). 3. Initiation probability with the neutron source P S (t). Japanese specialists told us that the accident happened during the seventh batch pouring. They estimated the k eff before and at the end of this operation: After the sixth batch, K=0.981, and at the end of the seventh batch, K=1.030. When the accident happened (neutron burst), 3 $ was inserted in 15 s, so if we suppose a linear insertion, we have a slope equal to 20 c/s. We may write K(t) = 1 + wt with w = 0.2 β = 0.00160/s. During the accident, there was between 14 and 16 kg of uranium with an enrichment of 18.8%. We have calculated P S (t) and we have taken into account six internal source levels: 1. spontaneous fission: 150 to 170 to 200 n/s; 2. (α, n) reactions and others of this type, and amplification of the internal source during the delayed critical phase: 500 to 1000 to 2000 n/s. In Fig. 2, we can see that the initiation occurred almost surely before 7 s and with a probability close to 0.46 before 2 s with a source of 200 n/s. With a source of 2000 n/s, we have higher initiation probabilities; for example, the initiation occurred almost surely before 2 s and with a probability close to 0.77 before 1 s after the critical time. These results are interesting because they show that a supercritical system does not lead immediately to initiation. One may have short supercritical excursion with no neutron production. The point model approach is useful for gaining a good understanding of what can be the stochastic neutronic contribution for the interpretation of criticality accidents. The results described in this paper may be useful for the interpretation of the time delay between the critical state time and the neutron burst. The thought process we have described may be used in the 'real world', that is, with multigroup or continuous-energy simulations

Degradation mechanism and thermal stability of urea nitrate below the melting point

International Nuclear Information System (INIS)

Desilets, Sylvain; Brousseau, Patrick; Chamberland, Daniel; Singh, Shanti; Feng, Hongtu; Turcotte, Richard; Anderson, John

2011-01-01

Highlights: → Decomposition mechanism of urea nitrate. → Spectral characterization of the decomposition mechanism. → Thermal stability of urea nitrate at 50, 70 and 100 o C. → Chemical balance of decomposed products released. - Abstract: Aging and degradation of urea nitrate below the melting point, at 100 o C, was studied by using thermal analysis and spectroscopic methods including IR, Raman, 1 H and 13 C NMR techniques. It was found that urea nitrate was completely degraded after 72 h at 100 o C into a mixture of solids (69%) and released gaseous species (31%). The degradation mechanism below the melting point was clearly identified. The remaining solid mixture was composed of ammonium nitrate, urea and biuret while unreacted residual nitric and isocyanic acids as well as traces of ammonia were released as gaseous species at 100 o C. The thermal stability of urea nitrate, under extreme storage conditions (50 o C), was also examined by isothermal nano-calorimetry.

Critical parameters of hard-core Yukawa fluids within the structural theory

Science.gov (United States)

Bahaa Khedr, M.; Osman, S. M.

2012-10-01

A purely statistical mechanical approach is proposed to account for the liquid-vapor critical point based on the mean density approximation (MDA) of the direct correlation function. The application to hard-core Yukawa (HCY) fluids facilitates the use of the series mean spherical approximation (SMSA). The location of the critical parameters for HCY fluid with variable intermolecular range is accurately calculated. Good agreement is observed with computer simulation results and with the inverse temperature expansion (ITE) predictions. The influence of the potential range on the critical parameters is demonstrated and the universality of the critical compressibility ratio is discussed. The behavior of the isochoric and isobaric heat capacities along the equilibrium line and the near vicinity of the critical point is discussed in details.

Critical endline of the finite temperature phase transition for 2+1 flavor QCD away from the SU(3-flavor symmetric point

Directory of Open Access Journals (Sweden)

Nakamura Yoshifumi

2018-01-01

Full Text Available We investigate the critical end line of the finite temperature phase transition of QCD away from the SU(3-flavor symmetric point at zero chemical potential. We employ the renormalization-group improved Iwasaki gauge action and non-perturbatively O(a- improved Wilson-clover fermion action. The critical end line is determined by using the intersection point of kurtosis, employing the multi-parameter, multi-ensemble reweighting method at the temporal size NT = 6 and lattice spacing as low as a ≈0.19 fm.

The implementation of a Hazard Analysis and Critical Control Point management system in a peanut butter ice cream plant.

Science.gov (United States)

Hung, Yu-Ting; Liu, Chi-Te; Peng, I-Chen; Hsu, Chin; Yu, Roch-Chui; Cheng, Kuan-Chen

2015-09-01

To ensure the safety of the peanut butter ice cream manufacture, a Hazard Analysis and Critical Control Point (HACCP) plan has been designed and applied to the production process. Potential biological, chemical, and physical hazards in each manufacturing procedure were identified. Critical control points for the peanut butter ice cream were then determined as the pasteurization and freezing process. The establishment of a monitoring system, corrective actions, verification procedures, and documentation and record keeping were followed to complete the HACCP program. The results of this study indicate that implementing the HACCP system in food industries can effectively enhance food safety and quality while improving the production management. Copyright © 2015. Published by Elsevier B.V.

Development of safe mechanism for surgical robots using equilibrium point control method.

Science.gov (United States)

Park, Shinsuk; Lim, Hokjin; Kim, Byeong-sang; Song, Jae-bok

2006-01-01

This paper introduces a novel mechanism for surgical robotic systems to generate human arm-like compliant motion. The mechanism is based on the idea of the equilibrium point control hypothesis which claims that multi-joint limb movements are achieved by shifting the limbs' equilibrium positions defined by neuromuscular activity. The equilibrium point control can be implemented on a robot manipulator by installing two actuators at each joint of the manipulator, one to control the joint position, and the other to control the joint stiffness. This double-actuator mechanism allows us to arbitrarily manipulate the stiffness (or impedance) of a robotic manipulator as well as its position. Also, the force at the end-effector can be estimated based on joint stiffness and joint angle changes without using force transducers. A two-link manipulator and a three-link manipulator with the double-actuator units have been developed, and experiments and simulation results show the potential of the proposed approach. By creating the human arm-like behavior, this mechanism can improve the performance of robot manipulators to execute stable and safe movement in surgical environments by using a simple control scheme.

Effect of gravity on density distributions and orthopositronium annihilation rates in ethane and methane near the critical point

International Nuclear Information System (INIS)

Sharma, S.C.; Kafle, S.R.S.

1983-01-01

The effect of gravity on density distributions has been studied in ethane and methane near their critical points using the linear-model parametric equation of state. The results obtained from this study are used to further understand the sensitivity of orthopositronium annihilation rates to density fluctuations in molecular gases. It is shown that the influence of gravity is too small to account for the recently observed dependence of orthopositronium annihilation rates on the density of ethane gas at 306.4 K. However, a significant variation in local density vs height is calculated at temperatures closer to the gas--liquid critical point. The density and temperature dependencies of the annihilation rates of orthopositronium atoms, recently observed in ethane and methane gases, are discussed in terms of the findings of this study

Quantum criticality in Einstein-Maxwell-dilaton gravity

International Nuclear Information System (INIS)

Wen, Wen-Yu

2012-01-01

We investigate the quantum Lifshitz criticality in a general background of Einstein-Maxwell-dilaton gravity. In particular, we demonstrate the existence of critical point with dynamic critical exponent z by tuning a nonminimal coupling to its critical value. We also study the effect of nonminimal coupling and exponent z to the Efimov states and holographic RG flow in the overcritical region. We have found that the nonminimal coupling increases the instability for a probe scalar to condensate and its back reaction is discussed. At last, we give a quantum mechanics treatment to a solvable system with z=2, and comment for generic z>2.

Mechanism of West Nile Virus Neuroinvasion: A Critical Appraisal

Directory of Open Access Journals (Sweden)

Willy W. Suen

2014-07-01

Full Text Available West Nile virus (WNV is an important emerging neurotropic virus, responsible for increasingly severe encephalitis outbreaks in humans and horses worldwide. However, the mechanism by which the virus gains entry to the brain (neuroinvasion remains poorly understood. Hypotheses of hematogenous and transneural entry have been proposed for WNV neuroinvasion, which revolve mainly around the concepts of blood-brain barrier (BBB disruption and retrograde axonal transport, respectively. However, an over‑representation of in vitro studies without adequate in vivo validation continues to obscure our understanding of the mechanism(s. Furthermore, WNV infection in the current rodent models does not generate a similar viremia and character of CNS infection, as seen in the common target hosts, humans and horses. These differences ultimately question the applicability of rodent models for pathogenesis investigations. Finally, the role of several barriers against CNS insults, such as the blood-cerebrospinal fluid (CSF, the CSF-brain and the blood-spinal cord barriers, remain largely unexplored, highlighting the infancy of this field. In this review, a systematic and critical appraisal of the current evidence relevant to the possible mechanism(s of WNV neuroinvasion is conducted.

75 FR 8239 - School Food Safety Program Based on Hazard Analysis and Critical Control Point Principles (HACCP...

Science.gov (United States)

2010-02-24

... (HACCP); Approval of Information Collection Request AGENCY: Food and Nutrition Service, USDA. ACTION... Safety Program Based on Hazard Analysis and Critical Control Point Principles (HACCP) was published on... must be based on the (HACCP) system established by the Secretary of Agriculture. The food safety...

Identification of gram-negative bacteria from critical control points of raw and pasteurized cow milk consumed at Gondar town and its suburbs, Ethiopia.

Science.gov (United States)

Garedew, Legesse; Berhanu, Ayalew; Mengesha, Desalegne; Tsegay, Getachew

2012-11-06

Milk is highly prone to contamination and can serve as an efficient vehicle for human transmission of foodborne pathogens, especially gram-negative bacteria, as these are widely distributed in the environment. This cross-sectional study of gram-negative staining bacterial contamination of milk meant for human consumption was carried out from October 2010 to May 2011 in Gondar town, Ethiopia. Milk samples were collected from critical control points, from production to consumption, that were hypothesized to be a source of potential contamination. Milk sampling points included smallholder's milk producers, dairy co-operatives, a milk processing plant, and supermarkets. The hygienic procedures applied during milking, milk collection, transportation, pasteurization, and postpasteurization storage conditions at these specified critical control points were evaluated. Standard bacteriological cultivation and biochemical assays were used to isolate and identify bacterial pathogens in the milk samples. The results of the current study showed that conditions for contamination of raw milk at different critical points were due to less hygienic practices in pre-milking udder preparation, sub-optimal hygiene of milk handlers, and poor sanitation practices associated with milking and storage equipments. Among all critical control points considered, transportation containers at milk collection centers and at processing plants were found to be the most heavily contaminated with gram-negative staining bacterial species. Overall, 54 different bacterial species were indentified, and Escherichia coli (29.6%), Pseudomonas aeruginosa (18.5%), and Klebsiella pneumoniae (16.7%), were the most commonly identified gram-negative staining bacterial pathogens. Of particular interest was that no gram-negative staining bacteria were isolated from pasteurized milk samples with varying shelf life. This study showed the presence of diverse pathogenic gram-negative staining bacterial species in raw

Identification of gram-negative bacteria from critical control points of raw and pasteurized cow milk consumed at Gondar town and its suburbs, Ethiopia

Directory of Open Access Journals (Sweden)

Garedew Legesse

2012-11-01

Full Text Available Abstract Background Milk is highly prone to contamination and can serve as an efficient vehicle for human transmission of foodborne pathogens, especially gram-negative bacteria, as these are widely distributed in the environment. Methods This cross-sectional study of gram-negative staining bacterial contamination of milk meant for human consumption was carried out from October 2010 to May 2011 in Gondar town, Ethiopia. Milk samples were collected from critical control points, from production to consumption, that were hypothesized to be a source of potential contamination. Milk sampling points included smallholder’s milk producers, dairy co-operatives, a milk processing plant, and supermarkets. The hygienic procedures applied during milking, milk collection, transportation, pasteurization, and postpasteurization storage conditions at these specified critical control points were evaluated. Standard bacteriological cultivation and biochemical assays were used to isolate and identify bacterial pathogens in the milk samples. Results The results of the current study showed that conditions for contamination of raw milk at different critical points were due to less hygienic practices in pre-milking udder preparation, sub-optimal hygiene of milk handlers, and poor sanitation practices associated with milking and storage equipments. Among all critical control points considered, transportation containers at milk collection centers and at processing plants were found to be the most heavily contaminated with gram-negative staining bacterial species. Overall, 54 different bacterial species were indentified, and Escherichia coli (29.6%, Pseudomonas aeruginosa (18.5%, and Klebsiella pneumoniae (16.7%, were the most commonly identified gram-negative staining bacterial pathogens. Of particular interest was that no gram-negative staining bacteria were isolated from pasteurized milk samples with varying shelf life. Conclusion This study showed the presence of

An utilization of liquid sublayer dryout mechanism in predicting critical heat flux under low pressure and low velocity conditions in round tubes

International Nuclear Information System (INIS)

Lee, Kwang-Won; Baik, Se-Jin; Ro, Tae-Sun

2000-01-01

From a theoretical assessment of extensive critical heat flux (CHF) data under low pressure and low velocity (LPLV) conditions, it was found out that lots of CHF data would not be well predicted by a normal annular film dryout (AFD) mechanism, although their flow patterns were identified as annular-mist flow. To predict these CHF data, a liquid sublayer dryout (LSD) mechanism has been newly utilized in developing the mechanistic CHF model based on each identified CHF mechanism. This mechanism postulates that the CHF occurrence is caused by dryout of the thin liquid sublayer resulting from the annular film separation or breaking down due to nucleate boiling in annular film or hydrodynamic fluctuation. In principle, this mechanism well supports the experimental evidence of residual film flow rate at the CHF location, which can not be explained by the AFD mechanism. For a comparative assessment of each mechanism, the CHF model based on the LSD mechanism is developed together with that based on the AFD mechanism. The validation of these models is performed on the 1406 CHF data points ranging over P=0.1-2 MPa, G=4-499 kg m -2 s -1 , L/D=4-402. This model validation shows that 1055 and 231 CHF data are predicted within ±30 error bound by the LSD mechanism and the AFD mechanism, respectively. However, some CHF data whose critical qualities are <0.4 or whose tube length-to-diameter ratios are <70 are considerably overestimated by the CHF model based on the LSD mechanism. These overestimations seem to be caused by an inadequate CHF mechanism classification and an insufficient consideration of the flow instability effect on CHF. Further studies for a new classification criterion screening the CHF data affected by flow instabilities as well as a new bubble detachment model for LPLV conditions, are needed to improve the model accuracy.

Brain-lung crosstalk in critical care: how protective mechanical ventilation can affect the brain homeostasis.

Science.gov (United States)

Mazzeo, A T; Fanelli, V; Mascia, L

2013-03-01

The maintenance of brain homeostasis against multiple internal and external challenges occurring during the acute phase of acute brain injury may be influenced by critical care management, especially in its respiratory, hemodynamic and metabolic components. The occurrence of acute lung injury represents the most frequent extracranial complication after brain injury and deserves special attention in daily practice as optimal ventilatory strategy for patients with acute brain and lung injury are potentially in conflict. Protecting the lung while protecting the brain is thus a new target in the modern neurointensive care. This article discusses the essentials of brain-lung crosstalk and focuses on how mechanical ventilation may exert an active role in the process of maintaining or treatening brain homeostasis after acute brain injury, highlighting the following points: 1) the role of inflammation as common pathomechanism of both acute lung and brain injury; 2) the recognition of ventilatory induced lung injury as determinant of systemic inflammation affecting distal organs, included the brain; 3) the possible implication of protective mechanical ventilation strategy on the patient with an acute brain injury as an undiscovered area of research in both experimental and clinical settings.

Test of phi(sup 2) model predictions near the (sup 3)He liquid-gas critical point

Science.gov (United States)

Barmatz, M.; Zhong, F.; Hahn, I.

2000-01-01

NASA is supporting the development of an experiment called MISTE (Microgravity Scaling Theory Experiment) for future International Space Station mission. The main objective of this flight experiment is to perform in-situ PVT, heat capacity at constant volume, C(sub v) and chi(sub tau), measurements in the asymptotic region near the (sup 3)He liquid-gas critical point.

Brake lock mechanism for the two axis pointing system

Science.gov (United States)

Posey, Alan; Clark, Mike; Mignosa, Larry

1991-01-01

Six months prior to shipment of the Broadband X-ray Telescope to the Kennedy Space Center for flight aboard the Space Shuttle Columbia, a major system failure occurred. During modal survey testing of the telescope's gimbal pointing system, the roll axis brake unexpectedly released. Low level vibration and static preloads present during the modal survey were within the expected flight environment. Brake release during shuttle liftoff or ascent was an unacceptable risk to mission success; thus, a Brake Lock Mechanism (BLM) was developed.

Critical two-point functions and the lace expansion for spread-out high-dimensional percolation and related models

NARCIS (Netherlands)

Hara, T.; Hofstad, van der R.W.; Slade, G.

2003-01-01

We consider spread-out models of self-avoiding walk, bond percolation, lattice trees and bond lattice animals on ${\\mathbb{Z}^d}$, having long finite-range connections, above their upper critical dimensions $d=4$ (self-avoiding walk), $d=6$ (percolation) and $d=8$ (trees and animals). The two-point

Existence of a critical point in the phase diagram of the ideal relativistic neutral Bose gas

International Nuclear Information System (INIS)

Park, Jeong-Hyuck; Kim, Sang-Woo

2011-01-01

We explore the phase transitions of the ideal relativistic neutral Bose gas confined in a cubic box, without assuming the thermodynamic limit nor continuous approximation. While the corresponding non-relativistic canonical partition function is essentially a one-variable function depending on a particular combination of temperature and volume, the relativistic canonical partition function is genuinely a two-variable function of them. Based on an exact expression for the canonical partition function, we performed numerical computations for up to 10 5 particles. We report that if the number of particles is equal to or greater than a critical value, which amounts to 7616, the ideal relativistic neutral Bose gas features a spinodal curve with a critical point. This enables us to depict the phase diagram of the ideal Bose gas. The consequent phase transition is first order below the critical pressure or second order at the critical pressure. The exponents corresponding to the singularities are 1/2 and 2/3, respectively. We also verify the recently observed 'Widom line' in the supercritical region.

[Preliminary studies on critical control point of traceability system in wolfberry].

Science.gov (United States)

Liu, Sai; Xu, Chang-Qing; Li, Jian-Ling; Lin, Chen; Xu, Rong; Qiao, Hai-Li; Guo, Kun; Chen, Jun

2016-07-01

As a traditional Chinese medicine, wolfberry (Lycium barbarum) has a long cultivation history and a good industrial development foundation. With the development of wolfberry production, the expansion of cultivation area and the increased attention of governments and consumers on food safety, the quality and safety requirement of wolfberry is higher demanded. The quality tracing and traceability system of production entire processes is the important technology tools to protect the wolfberry safety, and to maintain sustained and healthy development of the wolfberry industry. Thus, this article analyzed the wolfberry quality management from the actual situation, the safety hazard sources were discussed according to the HACCP (hazard analysis and critical control point) and GAP (good agricultural practice for Chinese crude drugs), and to provide a reference for the traceability system of wolfberry. Copyright© by the Chinese Pharmaceutical Association.

Cooperation, competition and the emergence of criticality in communities of adaptive systems

International Nuclear Information System (INIS)

Hidalgo, Jorge; Muñoz, Miguel A; Grilli, Jacopo; Suweis, Samir; Maritan, Amos

2016-01-01

The hypothesis that living systems can benefit from operating at the vicinity of critical points has gained momentum in recent years. Criticality may confer an optimal balance between too ordered and exceedingly noisy states. Here we present a model, based on information theory and statistical mechanics, illustrating how and why a community of agents aimed at understanding and communicating with each other converges to a globally coherent state in which all individuals are close to an internal critical state, i.e. at the borderline between order and disorder. We study—both analytically and computationally—the circumstances under which criticality is the best possible outcome of the dynamical process, confirming the convergence to critical points under very generic conditions. Finally, we analyze the effect of cooperation (agents trying to enhance not only their fitness, but also that of other individuals) and competition (agents trying to improve their own fitness and to diminish those of competitors) within our setting. The conclusion is that, while competition fosters criticality, cooperation hinders it and can lead to more ordered or more disordered consensual outcomes. (paper: classical statistical mechanics, equilibrium and non-equilibrium)

Healthcare disparities in critical illness.

Science.gov (United States)

Soto, Graciela J; Martin, Greg S; Gong, Michelle Ng

2013-12-01

To summarize the current literature on racial and gender disparities in critical care and the mechanisms underlying these disparities in the course of acute critical illness. MEDLINE search on the published literature addressing racial, ethnic, or gender disparities in acute critical illness, such as sepsis, acute lung injury, pneumonia, venous thromboembolism, and cardiac arrest. Clinical studies that evaluated general critically ill patient populations in the United States as well as specific critical care conditions were reviewed with a focus on studies evaluating factors and contributors to health disparities. Study findings are presented according to their association with the prevalence, clinical presentation, management, and outcomes in acute critical illness. This review presents potential contributors for racial and gender disparities related to genetic susceptibility, comorbidities, preventive health services, socioeconomic factors, cultural differences, and access to care. The data are organized along the course of acute critical illness. The literature to date shows that disparities in critical care are most likely multifactorial involving individual, community, and hospital-level factors at several points in the continuum of acute critical illness. The data presented identify potential targets as interventions to reduce disparities in critical care and future avenues for research.

Search for the critical point of strongly interacting matter at the CERN SPS NA61/SHINE experiment

CERN Document Server

Turko, L

2015-01-01

The NA61/SHINE experiment performs a detailed study of the onset of deconfinement and search for critical point of hadronic matter by colliding nuclei of different sizes at various beam momenta from 13A to 158A GeV/c. Experimental setup and results on the theoretically expected signatures are discussed.

Critical phenomena of liquid 4He in the vicinity of the upper lambda point

International Nuclear Information System (INIS)

Takada, T.; Watanabe, T.

1982-01-01

We determined C/sub p/ along six isobars near T/sub lambda/ in the vicinity of the upper superfluid transition point (upper lambda point) from measurements of C/sub v/ and (partialP/partialT)/sub v/ along six isochores. C/sub p/ was analyzed with the function C/sub p/ = (A/α)epsilon/sup -alpha/(1+Depsilon/sup -Delta/)+B for T>T/sub lambda/, and the same function with primed coefficients for T 4 He near T/sub lambda/, that is, the correction term due to the irrelevant variable increases with pressure even in the small range epsilon - 3 . This indicates that the pressure depresses the true critical region. The universality of the amplitude ratio A/A' was confirmed even in the vicinity of the upper lambda point by specific heat measurements. With constraints α = α' = -0.02, δ = δ' = -0.5, and B = B' the pressure-independent amplitude ratios A/A' = 1.088 +- 0.007 and D/D' = 0.85 +- 0.2 were obtained. AD/A'D' = 0.93 +- 0.2 implies that the pressure has a similar effect on C/sub p/ in the normal fluid and superfluid regions, within experimental errors

The Hausdorff dimension of random walks and the correlation length critical exponent in Euclidean field theory

International Nuclear Information System (INIS)

Kiskis, J.; Narayanan, R.; Vranas, P.

1993-01-01

The authors study the random walk representation of the two-point function in statistical mechanics models near the critical point. Using standard scaling arguments, the authors show that the critical exponent v describing the vanishing of the physical mass at the critical point is equal to v θ /d w , where d w is the Hausdorff dimension of the walk, and v θ = var-phi, where var-phi is the crossover exponent known in the context of field theory. This implies that the Hausdorff dimension of the walk is var-phi/v for O(N) models. 3 refs

The effective QCD phase diagram and the critical end point

Directory of Open Access Journals (Sweden)

Alejandro Ayala

2015-08-01

Full Text Available We study the QCD phase diagram on the temperature T and quark chemical potential μ plane, modeling the strong interactions with the linear sigma model coupled to quarks. The phase transition line is found from the effective potential at finite T and μ taking into account the plasma screening effects. We find the location of the critical end point (CEP to be (μCEP/Tc,TCEP/Tc∼(1.2,0.8, where Tc is the (pseudocritical temperature for the crossover phase transition at vanishing μ. This location lies within the region found by lattice inspired calculations. The results show that in the linear sigma model, the CEP's location in the phase diagram is expectedly determined solely through chiral symmetry breaking. The same is likely to be true for all other models which do not exhibit confinement, provided the proper treatment of the plasma infrared properties for the description of chiral symmetry restoration is implemented. Similarly, we also expect these corrections to be substantially relevant in the QCD phase diagram.

Transition from columnar to point pinning in coated conductors: critical currents that are independent of magnetic field direction

International Nuclear Information System (INIS)

Zuev, Yuri L; Hun Wee, Sung; Christen, David K

2012-01-01

We identify a sharp crossover in the vortex pinning of a high-temperature superconductor with nanocolumnar stacks of precipitates as strong vortex pinning centers. Above a particular, temperature-dependent field B X (T) the vortex response is no longer determined by the nanocolumns, and is instead determined by point-like pinning. This crossover is evident as a change in the dependence of the critical current density on the angle between the applied magnetic field and the nanocolumns. It also leads to the field-orientation-independent power law index n of the E–J curves. Below the transition, there is a strong maximum in J C when the field is aligned parallel to the columns and n depends on field direction. Above the transition, n is independent of the field direction and there is a J C minimum for H parallel to the columns. We discuss a possible mechanism for such behavior change, as well as testing and confirming a prediction that the crossover must become very broad at high temperatures and low fields. (paper)

Singularities of classical and quantum correlations at critical points of the Lipkin–Meshkov–Glick model in bipartitions and tripartitions of spins

International Nuclear Information System (INIS)

Zhang, Xiu-xing; Li, Fu-li

2013-01-01

By using the lowest order expansion in the number of spins, we study the classical correlation (CC) and quantum correlations (QCs) between two spin subgroups of the Lipkin–Meshkov–Glick (LMG) model in both binary and trinary decompositions of spins. In the case of bipartitions, we find that the CC and all the QCs are divergent in the same singular behavior at the critical point of the LMG model. In the case of tripartitions, however, the CC is still divergent but the QCs remain finite at the critical point. The present result shows that the CC is very robust but the QCs are much frangible to the environment disturbance.

Blow-up Mechanism of Classical Solutions to Quasilinear Hyperbolic Systems in the Critical Case

Institute of Scientific and Technical Information of China (English)

无

2006-01-01

This paper deals with the blow-up phenomenon, particularly, the geometric blow-up mechanism, of classical solutions to the Cauchy problem for quasilinear hyperbolic systems in the critical case. We prove that it is still the envelope of the same family of characteristics which yields the blowup of classical solutions to the Cauchy problem in the critical case.

Brit Crit: Turning Points in British Rock Criticism 1960-1990

DEFF Research Database (Denmark)

Gudmundsson, Gestur; Lindberg, U.; Michelsen, M.

2002-01-01

had national specific traits and there have been more profound paradigm shifts than in American rock criticism. This is primarily explained by the fact that American rock criticism is more strongly connected to general cultural history, while the UK rock criticism has been more alienated from dominant......The article examines the development of rock criticism in the United Kingdom from the perspective of a Bourdieuan field-analysis. Early British rock critics, like Nik Cohn, were international pioneers, a few years later there was a strong American influence, but British rock criticism has always...... culture and more linked to youth culture. However, also in the UK rock criticism has been part and parcel of the legitimation of rock culture and has moved closer to dominant fields and positions in the cultural hierarchy....

Critical Performance of Turbopump Mechanical Elements for Rocket Engine

Science.gov (United States)

Takada, Satoshi; Kikuchi, Masataka; Sudou, Takayuki; Iwasaki, Fumiya; Watanabe, Yoshiaki; Yoshida, Makoto

It is generally acknowledged that bearings and axial seals have a tendency to go wrong compared with other rocket engine elements. And when those components have malfunction, missions scarcely succeed. However, fundamental performance (maximum rotational speed, minimum flow rate, power loss, durability, etc.) of those components has not been grasped yet. Purpose of this study is to grasp a critical performance of mechanical seal and hybrid ball bearing of turbopump. In this result, it was found that bearing outer race temperature and bearing coolant outlet temperature changed along saturation line of liquid hydrogen when flow rate was decreased under critical pressure. And normal operation of bearing was possible under conditions of more than 70,000 rpm of rotational speed and more than 0.2 liter/s of coolant flow rate. Though friction coefficient of seal surface increased several times of original value after testing, the seal showed a good performance same as before.

Analysis of risk factors from salmonella infections and determination of critical control points in poultry industry production chain

Directory of Open Access Journals (Sweden)

Velhner Maja

2005-01-01

Full Text Available This paper encompasses problems related to infection caused by Salmonella spp in poultry. The need to carry out adequate control measures and to provide safe food is emphasized. Using experiences from other countries, critical control points are presented in flocks during rearing and in hatcheries. In attempt to diagnose disease as early as possible and to advise proper therapy, the significance of serology monitoring is underlined. In order to produce safe food there is a need to control disease applying our Regulations concerning eradication of Salmonella spp in poultry flocks that is given in Official paper of Republic of Serbia No 6&88 and also to include serology monitoring in poultry flocks. Veterinary practitioners are expected to perform analysis of critical control points in poultry industry as well as to determine specificity and differences in production for single farms, which would enable more effective struggle with diseases in general.

The effect of point mutations on structure and mechanical properties of collagen-like fibril: A molecular dynamics study

Energy Technology Data Exchange (ETDEWEB)

Marlowe, Ashley E.; Singh, Abhishek; Yingling, Yaroslava G., E-mail: yara_yingling@ncsu.edu

2012-12-01

Understanding sequence dependent mechanical and structural properties of collagen fibrils is important for the development of artificial biomaterials for medical and nanotechnological applications. Moreover, point mutations are behind many collagen associated diseases, including Osteogenesis Imperfecta (OI). We conducted a combination of classical and steered atomistic molecular dynamics simulations to examine the effect of point mutations on structure and mechanical properties of short collagen fibrils which include mutations of glycine to alanine, aspartic acid, cysteine, and serine or mutations of hydroxyproline to arginine, asparagine, glutamine, and lysine. We found that all mutations disrupt structure and reduce strength of the collagen fibrils, which may affect the hierarchical packing of the fibrils. The glycine mutations were more detrimental to mechanical strength of the fibrils (WT > Ala > Ser > Cys > Asp) than that of hydroxyproline (WT > Arg > Gln > Asn > Lys). The clinical outcome for glycine mutations agrees well with the trend in reduction of fibril's tensile strength predicted by our simulations. Overall, our results suggest that the reduction in mechanical properties of collagen fibrils may be used to predict the clinical outcome of mutations. Highlights: Black-Right-Pointing-Pointer All mutations disrupt structure and bonding pattern and reduce strength of the collagen fibrils. Black-Right-Pointing-Pointer Gly based mutations are worst to mechanical integrity of fibrils than that of Hyp. Black-Right-Pointing-Pointer Lys and Arg mutations most dramatically destabilize collagen fibril properties. Black-Right-Pointing-Pointer Clinical outcome of mutations may be related to the reduced mechanical properties of fibrils.

Relative criterion for validity of a semiclassical approach to the dynamics near quantum critical points.

Science.gov (United States)

Wang, Qian; Qin, Pinquan; Wang, Wen-ge

2015-10-01

Based on an analysis of Feynman's path integral formulation of the propagator, a relative criterion is proposed for validity of a semiclassical approach to the dynamics near critical points in a class of systems undergoing quantum phase transitions. It is given by an effective Planck constant, in the relative sense that a smaller effective Planck constant implies better performance of the semiclassical approach. Numerical tests of this relative criterion are given in the XY model and in the Dicke model.

Percolation systems away from the critical point

Indian Academy of Sciences (India)

DEEPAK DHAR. Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India ... There is more to percolation theory than the critical exponents. Of course, an experi- .... simple qualitative arguments. In the summation ...

Fluctuations and correlations of conserved charges near the QCD critical point

International Nuclear Information System (INIS)

Fu Weijie; Wu Yueliang

2010-01-01

We study the fluctuations and correlations of conserved charges, such as the baryon number, the electric charge and the strangeness, at the finite temperature and the nonzero baryon chemical potential in an effective model. The fluctuations are calculated up to the fourth-order and the correlations to the third-order. We find that the second-order fluctuations and correlations have a peak or valley structure when the chiral phase transition takes place with the increase of the baryon chemical potential; the third-order fluctuations and correlations change their signs during the chiral phase transition; and the fourth-order fluctuations have two maxima and one minimum. We also depict contour plots of various fluctuations and correlations of conserved charges in the plane of temperature and the baryon chemical potential. It is found that higher-order fluctuations and correlations of conserved charges are superior to the second-order ones to be used to search for the critical point in heavy ion collision experiments.

Thermal-neutron multiple scattering: critical double scattering

International Nuclear Information System (INIS)

Holm, W.A.

1976-01-01

A quantum mechanical formulation for multiple scattering of thermal-neutrons from macroscopic targets is presented and applied to single and double scattering. Critical nuclear scattering from liquids and critical magnetic scattering from ferromagnets are treated in detail in the quasielastic approximation for target systems slightly above their critical points. Numerical estimates are made of the double scattering contribution to the critical magnetic cross section using relevant parameters from actual experiments performed on various ferromagnets. The effect is to alter the usual Lorentzian line shape dependence on neutron wave vector transfer. Comparison with corresponding deviations in line shape resulting from the use of Fisher's modified form of the Ornstein-Zernike spin correlations within the framework of single scattering theory leads to values for the critical exponent eta of the modified correlations which reproduce the effect of double scattering. In addition, it is shown that by restricting the range of applicability of the multiple scattering theory from the outset to critical scattering, Glauber's high energy approximation can be used to provide a much simpler and more powerful description of multiple scattering effects. When sufficiently close to the critical point, it provides a closed form expression for the differential cross section which includes all orders of scattering and has the same form as the single scattering cross section with a modified exponent for the wave vector transfer

Low skeletal muscle area is a risk factor for mortality in mechanically ventilated critically ill patients

OpenAIRE

Weijs, Peter JM; Looijaard, Wilhelmus GPM; Dekker, Ingeborg M; Stapel, Sandra N; Girbes, Armand R; Straaten, Heleen M Oudemans-van; Beishuizen, Albertus

2014-01-01

Introduction Higher body mass index (BMI) is associated with lower mortality in mechanically ventilated critically ill patients. However, it is yet unclear which body component is responsible for this relationship. Methods This retrospective analysis in 240 mechanically ventilated critically ill patients included adult patients in whom a computed tomography (CT) scan of the abdomen was made on clinical indication between 1 day before and 4 days after admission to the intensive care unit. CT s...

Failure mode, effect and criticality analysis (FMECA) on mechanical subsystems of diesel generator at NPP

International Nuclear Information System (INIS)

Kim, Tae Woon; Singh, Brijendra; Sung, Tae Yong; Park, Jin Hee; Lee, Yoon Hwan

1996-06-01

Largely, the RCM approach can be divided in three phases; (1) Functional failure analysis (FFA) on the selected system or subsystem, (2) Failure mode, effect and criticality analysis (FMECA) to identify the impact of failure to plant safety or economics, (3) Logical tree analysis (LTA) to select appropriate preventive maintenance and surveillance tasks. This report presents FMECA results for six mechanical subsystems of the diesel generators of nuclear power plants. The six mechanical subsystems are Starting air, Lub oil, Governor, Jacket water cooling, Fuel, and Engine subsystems. Generic and plant-specific failure and maintenance records are reviewed to identify critical components/failure modes. FMECA was performed for these critical component/failure modes. After reviewing current preventive maintenance activities of Wolsung unit 1, draft RCM recommendations are developed. 6 tabs., 16 refs. (Author)

Failure mode, effect and criticality analysis (FMECA) on mechanical subsystems of diesel generator at NPP

Energy Technology Data Exchange (ETDEWEB)

Kim, Tae Woon; Singh, Brijendra; Sung, Tae Yong; Park, Jin Hee; Lee, Yoon Hwan [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1996-06-01

Largely, the RCM approach can be divided in three phases; (1) Functional failure analysis (FFA) on the selected system or subsystem, (2) Failure mode, effect and criticality analysis (FMECA) to identify the impact of failure to plant safety or economics, (3) Logical tree analysis (LTA) to select appropriate preventive maintenance and surveillance tasks. This report presents FMECA results for six mechanical subsystems of the diesel generators of nuclear power plants. The six mechanical subsystems are Starting air, Lub oil, Governor, Jacket water cooling, Fuel, and Engine subsystems. Generic and plant-specific failure and maintenance records are reviewed to identify critical components/failure modes. FMECA was performed for these critical component/failure modes. After reviewing current preventive maintenance activities of Wolsung unit 1, draft RCM recommendations are developed. 6 tabs., 16 refs. (Author).

Probing Critical Point Energies of Transition Metal Dichalcogenides: Surprising Indirect Gap of Single Layer WSe 2

KAUST Repository

Zhang, Chendong; Chen, Yuxuan; Johnson, Amber; Li, Ming-yang; Li, Lain-Jong; Mende, Patrick C.; Feenstra, Randall M.; Shih, Chih Kang

2015-01-01

By using a comprehensive form of scanning tunneling spectroscopy, we have revealed detailed quasi-particle electronic structures in transition metal dichalcogenides, including the quasi-particle gaps, critical point energy locations, and their origins in the Brillouin zones. We show that single layer WSe surprisingly has an indirect quasi-particle gap with the conduction band minimum located at the Q-point (instead of K), albeit the two states are nearly degenerate. We have further observed rich quasi-particle electronic structures of transition metal dichalcogenides as a function of atomic structures and spin-orbit couplings. Such a local probe for detailed electronic structures in conduction and valence bands will be ideal to investigate how electronic structures of transition metal dichalcogenides are influenced by variations of local environment.

Probing Critical Point Energies of Transition Metal Dichalcogenides: Surprising Indirect Gap of Single Layer WSe 2

KAUST Repository

Zhang, Chendong

2015-09-21

By using a comprehensive form of scanning tunneling spectroscopy, we have revealed detailed quasi-particle electronic structures in transition metal dichalcogenides, including the quasi-particle gaps, critical point energy locations, and their origins in the Brillouin zones. We show that single layer WSe surprisingly has an indirect quasi-particle gap with the conduction band minimum located at the Q-point (instead of K), albeit the two states are nearly degenerate. We have further observed rich quasi-particle electronic structures of transition metal dichalcogenides as a function of atomic structures and spin-orbit couplings. Such a local probe for detailed electronic structures in conduction and valence bands will be ideal to investigate how electronic structures of transition metal dichalcogenides are influenced by variations of local environment.

Phase space barriers and dividing surfaces in the absence of critical points of the potential energy: Application to roaming in ozone

Energy Technology Data Exchange (ETDEWEB)

Mauguière, Frédéric A. L., E-mail: frederic.mauguiere@bristol.ac.uk; Collins, Peter, E-mail: peter.collins@bristol.ac.uk; Wiggins, Stephen, E-mail: stephen.wiggins@mac.com [School of Mathematics, University of Bristol, Bristol BS8 1TW (United Kingdom); Kramer, Zeb C., E-mail: zebcolterkramer@gmail.com; Ezra, Gregory S., E-mail: gse1@cornell.edu [Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853 (United States); Carpenter, Barry K., E-mail: carpenterb1@cardiff.ac.uk [School of Chemistry, Cardiff University, Cardiff CF10 3AT (United Kingdom); Farantos, Stavros C., E-mail: farantos@iesl.forth.gr [Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, and Department of Chemistry, University of Crete, Iraklion 711 10, Crete (Greece)

2016-02-07

We examine the phase space structures that govern reaction dynamics in the absence of critical points on the potential energy surface. We show that in the vicinity of hyperbolic invariant tori, it is possible to define phase space dividing surfaces that are analogous to the dividing surfaces governing transition from reactants to products near a critical point of the potential energy surface. We investigate the problem of capture of an atom by a diatomic molecule and show that a normally hyperbolic invariant manifold exists at large atom-diatom distances, away from any critical points on the potential. This normally hyperbolic invariant manifold is the anchor for the construction of a dividing surface in phase space, which defines the outer or loose transition state governing capture dynamics. We present an algorithm for sampling an approximate capture dividing surface, and apply our methods to the recombination of the ozone molecule. We treat both 2 and 3 degrees of freedom models with zero total angular momentum. We have located the normally hyperbolic invariant manifold from which the orbiting (outer) transition state is constructed. This forms the basis for our analysis of trajectories for ozone in general, but with particular emphasis on the roaming trajectories.

An application of the 'end-point' method to the minimum critical mass problem in two group transport theory

International Nuclear Information System (INIS)

Williams, M.M.R.

2003-01-01

A two group integral equation derived using transport theory, which describes the fuel distribution necessary for a flat thermal flux and minimum critical mass, is solved by the classical end-point method. This method has a number of advantages and in particular highlights the changing behaviour of the fissile mass distribution function in the neighbourhood of the core-reflector interface. We also show how the reflector thermal flux behaves and explain the origin of the maximum which arises when the critical size is less than that corresponding to minimum critical mass. A comparison is made with diffusion theory and the necessary and somewhat artificial presence of surface delta functions in the fuel distribution is shown to be analogous to the edge transients that arise naturally in transport theory

Scanning electron microscope autoradiography of critical point dried biological samples

International Nuclear Information System (INIS)

Weiss, R.L.

1980-01-01

A technique has been developed for the localization of isotopes in the scanning electron microscope. Autoradiographic studies have been performed using a model system and a unicellular biflagellate alga. One requirement of this technique is that all manipulations be carried out on samples that are maintained in a liquid state. Observations of a source of radiation ( 125 I-ferritin) show that the nuclear emulsion used to detect radiation is active under these conditions. Efficiency measurement performed using 125 I-ferritin indicate that 125 I-SEM autoradiography is an efficient process that exhibits a 'dose dependent' response. Two types of labeling methods were used with cells, surface labeling with 125 I and internal labeling with 3 H. Silver grains appeared on labeled cells after autoradiography, removal of residual gelatin and critical point drying. The location of grains was examined on a flagellated green alga (Chlamydomonas reinhardi) capable of undergoing cell fusion. Fusion experiments using labeled and unlabeled cells indicate that 1. Labeling is specific for incorporated radioactivity; 2. Cell surface structure is preserved in SEM autoradiographs and 3. The technique appears to produce reliable autoradiographs. Thus scanning electron microscope autoradiography should provide a new and useful experimental approach

Dynamic scaling near the lambda point of liquid helium and at bicritical points

International Nuclear Information System (INIS)

Dohm, V.

1979-02-01

The critical dynamics of liquid helium and of uniaxial antiferromagnets at bicritical points are studied by means of renormalized field theory. The problem of dynamic scaling is analyzed in detail. Explicit calculations are performed using the epsilon-expansion in d = 4 - epsilon dimensions. Results in one- and two-loop order, i.e. first and second order in epsilon, are obtained for dynamic critical exponents, dynamic transient exponents, amplitude ratios and scaling functions at and above the critical points. (orig.)

Food safety and nutritional quality for the prevention of non communicable diseases: the Nutrient, hazard Analysis and Critical Control Point process (NACCP).

Science.gov (United States)

Di Renzo, Laura; Colica, Carmen; Carraro, Alberto; Cenci Goga, Beniamino; Marsella, Luigi Tonino; Botta, Roberto; Colombo, Maria Laura; Gratteri, Santo; Chang, Ting Fa Margherita; Droli, Maurizio; Sarlo, Francesca; De Lorenzo, Antonino

2015-04-23

The important role of food and nutrition in public health is being increasingly recognized as crucial for its potential impact on health-related quality of life and the economy, both at the societal and individual levels. The prevalence of non-communicable diseases calls for a reformulation of our view of food. The Hazard Analysis and Critical Control Point (HACCP) system, first implemented in the EU with the Directive 43/93/CEE, later replaced by Regulation CE 178/2002 and Regulation CE 852/2004, is the internationally agreed approach for food safety control. Our aim is to develop a new procedure for the assessment of the Nutrient, hazard Analysis and Critical Control Point (NACCP) process, for total quality management (TMQ), and optimize nutritional levels. NACCP was based on four general principles: i) guarantee of health maintenance; ii) evaluate and assure the nutritional quality of food and TMQ; iii) give correct information to the consumers; iv) ensure an ethical profit. There are three stages for the application of the NACCP process: 1) application of NACCP for quality principles; 2) application of NACCP for health principals; 3) implementation of the NACCP process. The actions are: 1) identification of nutritional markers, which must remain intact throughout the food supply chain; 2) identification of critical control points which must monitored in order to minimize the likelihood of a reduction in quality; 3) establishment of critical limits to maintain adequate levels of nutrient; 4) establishment, and implementation of effective monitoring procedures of critical control points; 5) establishment of corrective actions; 6) identification of metabolic biomarkers; 7) evaluation of the effects of food intake, through the application of specific clinical trials; 8) establishment of procedures for consumer information; 9) implementation of the Health claim Regulation EU 1924/2006; 10) starting a training program. We calculate the risk assessment as follows

A QCD chiral critical point at small chemical potential: is it there or not?

CERN Document Server

de Forcrand, Philippe; Philipsen, Owe

2007-01-01

For a QCD chiral critical point to exist, the parameter region of small quark masses for which the finite temperature transition is first-order must expand when the chemical potential is turned on. This can be tested by a Taylor expansion of the critical surface (m_{u,d},m_s)_c(mu). We present a new method to perform this Taylor expansion numerically, which we first test on an effective model of QCD with static, dense quarks. We then present the results for QCD with 3 degenerate flavors. For a lattice with N_t=4 time-slices, the first-order region shrinks as the chemical potential is turned on. This implies that, for physical quark masses, the analytic crossover which occurs at mu=0 between the hadronic and the plasma regimes remains crossover in the mu-region where a Taylor expansion is reliable, i.e. mu less than or similar to T. We present preliminary results from finer lattices indicating that this situation persists, as does the discrepancy between the curvature of T_c(mu) and the experimentally observed...

Splitting of the zero-energy Landau level and universal dissipative conductivity at critical points in disordered graphene.

Science.gov (United States)

Ortmann, Frank; Roche, Stephan

2013-02-22

We report on robust features of the longitudinal conductivity (σ(xx)) of the graphene zero-energy Landau level in the presence of disorder and varying magnetic fields. By mixing an Anderson disorder potential with a low density of sublattice impurities, the transition from metallic to insulating states is theoretically explored as a function of Landau-level splitting, using highly efficient real-space methods to compute the Kubo conductivities (both σ(xx) and Hall σ(xy)). As long as valley degeneracy is maintained, the obtained critical conductivity σ(xx) =/~ 1.4e(2)/h is robust upon an increase in disorder (by almost 1 order of magnitude) and magnetic fields ranging from about 2 to 200 T. When the sublattice symmetry is broken, σ(xx) eventually vanishes at the Dirac point owing to localization effects, whereas the critical conductivities of pseudospin-split states (dictating the width of a σ(xy) = 0 plateau) change to σ(xx) =/~ e(2)/h, regardless of the splitting strength, superimposed disorder, or magnetic strength. These findings point towards the nondissipative nature of the quantum Hall effect in disordered graphene in the presence of Landau level splitting.

Bulk and boundary critical behavior at Lifshitz points

Indian Academy of Sciences (India)

Lifshitz points are multicritical points at which a disordered phase, a homogeneous ordered phase, and a modulated ordered phase meet. Their bulk universality classes are described by natural generalizations of the standard 4 model. Analyzing these models systematically via modern field-theoretic renormalization ...

Point form relativistic quantum mechanics and relativistic SU(6)

Science.gov (United States)

Klink, W. H.

1993-01-01

The point form is used as a framework for formulating a relativistic quantum mechanics, with the mass operator carrying the interactions of underlying constituents. A symplectic Lie algebra of mass operators is introduced from which a relativistic harmonic oscillator mass operator is formed. Mass splittings within the degenerate harmonic oscillator levels arise from relativistically invariant spin-spin, spin-orbit, and tensor mass operators. Internal flavor (and color) symmetries are introduced which make it possible to formulate a relativistic SU(6) model of baryons (and mesons). Careful attention is paid to the permutation symmetry properties of the hadronic wave functions, which are written as polynomials in Bargmann spaces.

The critical catastrophe revisited

International Nuclear Information System (INIS)

De Mulatier, Clélia; Rosso, Alberto; Dumonteil, Eric; Zoia, Andrea

2015-01-01

The neutron population in a prototype model of nuclear reactor can be described in terms of a collection of particles confined in a box and undergoing three key random mechanisms: diffusion, reproduction due to fissions, and death due to absorption events. When the reactor is operated at the critical point, and fissions are exactly compensated by absorptions, the whole neutron population might in principle go to extinction because of the wild fluctuations induced by births and deaths. This phenomenon, which has been named critical catastrophe, is nonetheless never observed in practice: feedback mechanisms acting on the total population, such as human intervention, have a stabilizing effect. In this work, we revisit the critical catastrophe by investigating the spatial behaviour of the fluctuations in a confined geometry. When the system is free to evolve, the neutrons may display a wild patchiness (clustering). On the contrary, imposing a population control on the total population acts also against the local fluctuations, and may thus inhibit the spatial clustering. The effectiveness of population control in quenching spatial fluctuations will be shown to depend on the competition between the mixing time of the neutrons (i.e. the average time taken for a particle to explore the finite viable space) and the extinction time

Thermodynamic and real-space structural evidence of a 2D critical point in phospholipid monolayers

DEFF Research Database (Denmark)

Nielsen, Lars K.; Bjørnholm, Thomas; Mouritsen, Ole G.

2007-01-01

The two-dimensional phase diagram of phospholipid monolayers at air-water interfaces has been constructed from Langmuir compression isotherms. The coexistence region between the solid and fluid phases of the monolayer ends at the critical temperature of the transition. The small-scale lateral...... structure of the monolayers has been imaged by atomic force microscopy in the nm to mu m range at distinct points in the phase diagram. The lateral structure is immobilized by transferring the monolayer from an air-water interface to a solid mica support using Langmuir-Blodgett techniques. A transfer...

Non-Fermi Liquid Behavior Close to a Quantum Critical Point in a Ferromagnetic State without Local Moments

Directory of Open Access Journals (Sweden)

E. Svanidze

2015-03-01

Full Text Available A quantum critical point (QCP occurs upon chemical doping of the weak itinerant ferromagnet Sc_{3.1}In. Remarkable for a system with no local moments, the QCP is accompanied by non-Fermi liquid behavior, manifested in the logarithmic divergence of the specific heat both in the ferro-and the paramagnetic states, as well as linear temperature dependence of the low-temperature resistivity. With doping, critical scaling is observed close to the QCP, as the critical exponents δ, γ, and β have weak composition dependence, with δ nearly twice and β almost half of their respective mean-field values. The unusually large paramagnetic moment μ_{PM}∼1.3μ_{B}/F.U. is nearly composition independent. Evidence for strong spin fluctuations, accompanying the QCP at x_{c}=0.035±0.005, may be ascribed to the reduced dimensionality of Sc_{3.1}In, associated with the nearly one-dimensional Sc-In chains.

Picture change error in quasirelativistic electron/spin density, Laplacian and bond critical points

KAUST Repository

Bučinský , Luká š; Kucková , Lenka; Malček, Michal; Koží šek, Jozef; Biskupič, Stanislav; Jayatilaka, Dylan; Bü chel, Gabriel E.; Arion, Vladimir B.

2014-01-01

The change of picture of the quasirelativistic Hartree-Fock wave functions is considered for electron/spin densities, the negative Laplacian of electron density and the appropriate bond critical point characteristics from the Quantum Theory of Atoms In Molecules (QTAIM). [OsCl5(Hpz)]- and [RuCl5(NO)]2- transition metal complexes are considered. Both, scalar relativistic and spin-orbit effects have been accounted for using the Infinite Order Two Component (IOTC) Hamiltonian. Picture change error (PCE) correction in the electron and spin densities and the Laplacian of electron density are treated analytically. Generally, PCE is found significant only in the core region of the atoms for the electron/spin density as well as Laplacian.©2014 Elsevier B.V. All rights reserved.

Picture change error in quasirelativistic electron/spin density, Laplacian and bond critical points

KAUST Repository

Bučinský, Lukáš

2014-06-01

The change of picture of the quasirelativistic Hartree-Fock wave functions is considered for electron/spin densities, the negative Laplacian of electron density and the appropriate bond critical point characteristics from the Quantum Theory of Atoms In Molecules (QTAIM). [OsCl5(Hpz)]- and [RuCl5(NO)]2- transition metal complexes are considered. Both, scalar relativistic and spin-orbit effects have been accounted for using the Infinite Order Two Component (IOTC) Hamiltonian. Picture change error (PCE) correction in the electron and spin densities and the Laplacian of electron density are treated analytically. Generally, PCE is found significant only in the core region of the atoms for the electron/spin density as well as Laplacian.©2014 Elsevier B.V. All rights reserved.

Thermo-mechanical constitutive modeling of unsaturated clays based on the critical state concepts

OpenAIRE

Tourchi, Saeed; Hamidi, Amir

2015-01-01

A thermo-mechanical constitutive model for unsaturated clays is constructed based on the existing model for saturated clays originally proposed by the authors. The saturated clays model was formulated in the framework of critical state soil mechanics and modified Cam-clay model. The existing model has been generalized to simulate the experimentally observed behavior of unsaturated clays by introducing Bishop's stress and suction as independent stress parameters and modifying the hardening rul...

LaCu6-xAgx : A promising host of an elastic quantum critical point

Science.gov (United States)

Poudel, L.; Cruz, C. de la; Koehler, M. R.; McGuire, M. A.; Keppens, V.; Mandrus, D.; Christianson, A. D.

2018-05-01

Structural properties of LaCu6-xAgx have been investigated using neutron and x-ray diffraction, and resonant ultrasound spectroscopy (RUS) measurements. Diffraction measurements indicate a continuous structural transition from orthorhombic (Pnma) to monoclinic (P21 / c) structure. RUS measurements show softening of natural frequencies at the structural transition, consistent with the elastic nature of the structural ground state. The structural transition temperatures in LaCu6-xAgx decrease with Ag composition until the monoclinic phase is completely suppressed at xc = 0.225 . All of the evidence is consistent with the presence of an elastic quantum critical point in LaCu6-xAgx .

[Incorporation of the Hazard Analysis and Critical Control Point system (HACCP) in food legislation].

Science.gov (United States)

Castellanos Rey, Liliana C; Villamil Jiménez, Luis C; Romero Prada, Jaime R

2004-01-01

The Hazard Analysis and Critical Control Point system (HACCP), recommended by different international organizations as the Codex Alimentarius Commission, the World Trade Organization (WTO), the International Office of Epizootics (OIE) and the International Convention for Vegetables Protection (ICPV) amongst others, contributes to ensuring the innocuity of food along the agro-alimentary chain and requires of Good Manufacturing Practices (GMP) for its implementation, GMP's which are legislated in most countries. Since 1997, Colombia has set rules and legislation for application of HACCP system in agreement with international standards. This paper discusses the potential and difficulties of the legislation enforcement and suggests some policy implications towards food safety.

Multiple critical points and liquid-liquid equilibria from the van der Waals like equations of state

International Nuclear Information System (INIS)

Artemenko, Sergey; Lozovsky, Taras; Mazur, Victor

2008-01-01

The principal aim of this work is a comprehensive analysis of the phase diagram of water via the van der Waals like equations of state (EoSs) which are considered as superpositions of repulsive and attractive forces. We test more extensively the modified van der Waals EoS (MVDW) proposed by Skibinski et al (2004 Phys. Rev. E 69 061206) and refine this model by introducing instead of the classical van der Waals repulsive term a very accurate hard sphere EoS over the entire stable and metastable regions (Liu 2006 Preprint cond-mat/0605392). It was detected that the simplest form of MVDW EoS displays a complex phase behavior, including three critical points, and identifies four fluid phases (gas, low density liquid (LDL), high density liquid (HDL), and very high density liquid (VHDL)). Moreover the experimentally observed (Mallamace et al 2007 Proc. Natl Acad. Sci. USA 104 18387) anomalous behavior of the density of water in the deeply supercooled region (a density minimum) is reproduced by the MWDW EoS. An improvement of the repulsive part does not change the topological picture of the phase behavior of water in the wide range of thermodynamic variables. The new parameters set for second and third critical points are recognized by thorough analysis of experimental data for the loci of thermodynamic response function extrema

A critical view of the mechanism(s) of toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin. Implications for human safety assessment.

Science.gov (United States)

Rozman, K

1989-01-01

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been an important issue in occupational and environmental health for nearly two decades. During this period scientists have studied its possible impacts on exposed human populations. At the same time enormous efforts were made to elucidate the mechanism of TCDD action in various biological models. This paper provides a critical view of the advances made towards understanding the mechanism of TCDD action. Major topics discussed include the Ah-receptor hypothesis, TCDD as a thyroid hormone agonist, TCDD and vitamin A deficiency, TCDD's effect on receptor regulation, and its effect on intermediary metabolism including related hormonal responses. Although the exact mechanism of TCDD action is not yet known, more information is available on the toxicity of this compound than perhaps on that of any other substance. This wealth of information allows important conclusions regarding the assessment of acute, as well as of chronic, toxicities of TCDD for humans. There is no documented case of human death as a result of exposure to TCDD. It appears that humans are acutely less sensitive to TCDD than some animal species. The cause of TCDD-induced lethality in rats is a progressive lethal hypoglycemia due to inhibition of gluconeogenesis. Regulation of this metabolic pathway is quite different amongst species, although primates share great similarities. The assumption that the cause of TCDD-induced death in primates, in analogy to rats, is inhibition of gluconeogenesis would suggest that the acute toxicity of TCDD in humans would be in the range seen in rhesus monkeys (70-300 micrograms/kg). These values are about midway between the most (guinea pig) and least (hamster) sensitive species. TCDD is not a genotoxic agent and not an initiator, but promoter of tumor formation. There is considerable evidence that promotion of cancer, like any other chronic end point of toxicity, is a threshold-type biological process. Therefore, a linear

Extending a real-time operating system with a mechanism for criticality-level changes

NARCIS (Netherlands)

Gupta, T.

2015-01-01

Systems robustness, cost reduction and certification play an important role in the automotive domain. If there is a fault, e.g. task overshooting its allocated execution time, sufficient mechanisms should be available to safeguard the system against those. Applications of different criticalities

Quantum criticality around metal-insulator transitions of strongly correlated electron systems

Science.gov (United States)

Misawa, Takahiro; Imada, Masatoshi

2007-03-01

Quantum criticality of metal-insulator transitions in correlated electron systems is shown to belong to an unconventional universality class with violation of the Ginzburg-Landau-Wilson (GLW) scheme formulated for symmetry breaking transitions. This unconventionality arises from an emergent character of the quantum critical point, which appears at the marginal point between the Ising-type symmetry breaking at nonzero temperatures and the topological transition of the Fermi surface at zero temperature. We show that Hartree-Fock approximations of an extended Hubbard model on square lattices are capable of such metal-insulator transitions with unusual criticality under a preexisting symmetry breaking. The obtained universality is consistent with the scaling theory formulated for Mott transitions and with a number of numerical results beyond the mean-field level, implying that preexisting symmetry breaking is not necessarily required for the emergence of this unconventional universality. Examinations of fluctuation effects indicate that the obtained critical exponents remain essentially exact beyond the mean-field level. It further clarifies the whole structure of singularities by a unified treatment of the bandwidth-control and filling-control transitions. Detailed analyses of the criticality, containing diverging carrier density fluctuations around the marginal quantum critical point, are presented from microscopic calculations and reveal the nature as quantum critical “opalescence.” The mechanism of emerging marginal quantum critical point is ascribed to a positive feedback and interplay between the preexisting gap formation present even in metals and kinetic energy gain (loss) of the metallic carrier. Analyses of crossovers between GLW type at nonzero temperature and topological type at zero temperature show that the critical exponents observed in (V,Cr)2O3 and κ-ET -type organic conductors provide us with evidence for the existence of the present marginal

Part I: Hazard, sensorial and economic implications of applying the hazard analysis and critical control points to irradiated ready-to-eat meals

International Nuclear Information System (INIS)

Haruvy, Y.F.

2009-01-01

The classical methodology of hazard analysis and critical control points focuses on hazards and related implications. A new methodology is suggested here, one that attempts at a systematic simultaneous assessment of safety hazards, sensorial failures and economic risks, and the critical control points necessary for their early detection and/or prevention of their potential outcomes. The new methodology also attempts to combine the three parameters to form a qualitative prioritization of the numerous control points and to screen those that can be cost effective for implementation. This is demonstrated in this paper for a complex product, i.e. radiation sterilized ready-to-eat meals. Hence, a fourth parameter specific to this product - the radiation specific pitfall - is also assessed. The advantages and drawbacks of the combined assessment methodology are described and their overall possible impact is discussed. Finally, the suggested combined assessment and control system for ensuring the safety and quality of food can provide a more structured and critical approach to control identified hazards, compared with that achievable by traditional inspection and quality control procedures. It has the potential to identify areas of concern where failure has not yet been experienced, making it particularly useful for new operations and products thereafter. (author)

Hazard analysis of critical control points assessment as a tool to respond to emerging infectious disease outbreaks.

Directory of Open Access Journals (Sweden)

Kelly L Edmunds

Full Text Available Highly pathogenic avian influenza virus (HPAI strain H5N1 has had direct and indirect economic impacts arising from direct mortality and control programmes in over 50 countries reporting poultry outbreaks. HPAI H5N1 is now reported as the most widespread and expensive zoonotic disease recorded and continues to pose a global health threat. The aim of this research was to assess the potential of utilising Hazard Analysis of Critical Control Points (HACCP assessments in providing a framework for a rapid response to emerging infectious disease outbreaks. This novel approach applies a scientific process, widely used in food production systems, to assess risks related to a specific emerging health threat within a known zoonotic disease hotspot. We conducted a HACCP assessment for HPAI viruses within Vietnam's domestic poultry trade and relate our findings to the existing literature. Our HACCP assessment identified poultry flock isolation, transportation, slaughter, preparation and consumption as critical control points for Vietnam's domestic poultry trade. Introduction of the preventative measures highlighted through this HACCP evaluation would reduce the risks posed by HPAI viruses and pressure on the national economy. We conclude that this HACCP assessment provides compelling evidence for the future potential that HACCP analyses could play in initiating a rapid response to emerging infectious diseases.

The Subtle Balance between Lipolysis and Lipogenesis: A Critical Point in Metabolic Homeostasis.

Science.gov (United States)

Saponaro, Chiara; Gaggini, Melania; Carli, Fabrizia; Gastaldelli, Amalia

2015-11-13

Excessive accumulation of lipids can lead to lipotoxicity, cell dysfunction and alteration in metabolic pathways, both in adipose tissue and peripheral organs, like liver, heart, pancreas and muscle. This is now a recognized risk factor for the development of metabolic disorders, such as obesity, diabetes, fatty liver disease (NAFLD), cardiovascular diseases (CVD) and hepatocellular carcinoma (HCC). The causes for lipotoxicity are not only a high fat diet but also excessive lipolysis, adipogenesis and adipose tissue insulin resistance. The aims of this review are to investigate the subtle balances that underlie lipolytic, lipogenic and oxidative pathways, to evaluate critical points and the complexities of these processes and to better understand which are the metabolic derangements resulting from their imbalance, such as type 2 diabetes and non alcoholic fatty liver disease.

Introduction of the system of hazard analysis critical control point to ensure the safety of irradiated food

International Nuclear Information System (INIS)

Sajet, A.S.

2014-01-01

Hazard Analysis Critical Control Point (HACCP) is a preventive system for food safety. It identifies safety risks faced by food. Identified points are controlled ensuring product safety. Because of presence of many of the pathogenic microorganisms and parasites in food which caused cases of food poisoning and many diseases transmitted through food, the current methods of food production could not prevent food contamination or prevent the growth of these pathogens completely because of being a part of the normal flora in the environment. Irradiation technology helped to control diseases transmitted through food, caused by pathological microorganisms and parasites present in food. The application of a system based on risk analysis as a means of risk management in food chain, demonstrated the importance of food irradiation. (author)

Hazard analysis and critical control point to irradiated food in Brazil

International Nuclear Information System (INIS)

Boaratti, Maria de Fatima Guerra

2004-01-01

Food borne diseases, in particular gastro-intestinal infections, represent a very large group of pathologies with a strong negative impact on the health of the population because of their widespread nature. Little consideration is given to such conditions due to the fact that their symptoms are often moderate and self-limiting. This has led to a general underestimation of their importance, and consequently to incorrect practices during the preparation and preservation of food, resulting in the frequent occurrence of outbreaks involving groups of varying numbers of consumers. Despite substantial efforts in the avoidance of contamination, an upward trend in the number of outbreaks of food borne illnesses caused by non-spore forming pathogenic bacteria are reported in many countries. Good hygienic practices can reduce the level of contamination but the most important pathogens cannot presently be eliminated from most farms, nor is it possible to eliminate them by primary processing, particularly from those foods which are sold raw. Several decontamination methods exist but the most versatile treatment among them is the ionizing radiation procedure. HACCP (Hazard Analysis and Critical Control Point) is a management system in which food safety is addressed through the analysis and control of biological, chemical, and physical hazards from raw material production, procurement and handling, to manufacturing, distribution and consumption of the finished product. For successful implementation of a HACCP plan, management must be strongly committed to the HACCP concept. A firm commitment to HACCP by top management provides company employees with a sense of the importance of producing safe food. At the same time, it has to be always emphasized that, like other intervention strategies, irradiation must be applied as part of a total sanitation program. The benefits of irradiation should never be considered as an excuse for poor quality or for poor handling and storage conditions

Mechanism research on coupling effect between dew point corrosion and ash deposition

International Nuclear Information System (INIS)

Wang, Yun-Gang; Zhao, Qin-Xin; Zhang, Zhi-Xiang; Zhang, Zhi-Chao; Tao, Wen-Quan

2013-01-01

In order to study the coupling mechanism between ash deposition and dew point corrosion, five kinds of tube materials frequently used as anti-dew point corrosion materials were selected as research objects. Dew point corrosion and ash deposition experiments were performed with a new type experimental device in a Chinese thermal power plant. The microstructures of the materials and the composition of ash deposition were analyzed by X-ray diffraction (XRD) and Energy Dispersive Spectrometer (EDS). The results showed that the ash deposition layer could be divided into non-condensation zone, the main condensation zone and the secondary condensation zone. The acid vapor condensed in the main condensation zone rather than directly on the tube wall surface. The dew point corrosion mainly is oxygen corrosion under the condition of the viscosity ash deposition, and the corrosion products are composed of the ash and acid reaction products in the outer layer, iron sulfate in the middle layer, and iron oxide in the inner layer. The innermost layer is the main corrosion layer. With the increase of the tube wall temperature, the ash deposition changes from the viscosity ash deposition to the dry loose ash deposition, the ash deposition rate decreases dramatically and dew point corrosion is alleviated efficiently. The sulfuric dew point corrosion resistance of the five test materials is as follows: 316L > ND > Corten>20G > 20 steel. -- Highlights: ► Dew point corrosion and ash deposition tests of five materials were performed. ► Acid vapor condensed in the ash deposit rather than directly on the tube surface. ► Dew point corrosion resistance is as follow: 316L > ND > Corten>20G > 20 steel. ► Dew point corrosion mainly is oxygen corrosion under viscosity ash deposition

Quantum Critical Higgs

Science.gov (United States)

Bellazzini, Brando; Csáki, Csaba; Hubisz, Jay; Lee, Seung J.; Serra, Javi; Terning, John

2016-10-01

The appearance of the light Higgs boson at the LHC is difficult to explain, particularly in light of naturalness arguments in quantum field theory. However, light scalars can appear in condensed matter systems when parameters (like the amount of doping) are tuned to a critical point. At zero temperature these quantum critical points are directly analogous to the finely tuned standard model. In this paper, we explore a class of models with a Higgs near a quantum critical point that exhibits non-mean-field behavior. We discuss the parametrization of the effects of a Higgs emerging from such a critical point in terms of form factors, and present two simple realistic scenarios based on either generalized free fields or a 5D dual in anti-de Sitter space. For both of these models, we consider the processes g g →Z Z and g g →h h , which can be used to gain information about the Higgs scaling dimension and IR transition scale from the experimental data.

CRITICAL MECHANICAL PROPERTIES OF STRUCTURAL LIGHT-WEIGHT CONCRETE AND THE EFFECTS OF THESE PROPERTIES ON THE DESIGN OF THE PAVEMENT STRUCTURE.

Science.gov (United States)

1965-01-01

In this study, critical mechanical properties of structural lightweight concrete were determined and utilized in the evaluation of a design of concrete pavements. Also presented are the critical mechanical properties resulting from unrestrained and r...

Universal Signatures of Quantum Critical Points from Finite-Size Torus Spectra: A Window into the Operator Content of Higher-Dimensional Conformal Field Theories.

Science.gov (United States)

Schuler, Michael; Whitsitt, Seth; Henry, Louis-Paul; Sachdev, Subir; Läuchli, Andreas M

2016-11-18

The low-energy spectra of many body systems on a torus, of finite size L, are well understood in magnetically ordered and gapped topological phases. However, the spectra at quantum critical points separating such phases are largely unexplored for (2+1)D systems. Using a combination of analytical and numerical techniques, we accurately calculate and analyze the low-energy torus spectrum at an Ising critical point which provides a universal fingerprint of the underlying quantum field theory, with the energy levels given by universal numbers times 1/L. We highlight the implications of a neighboring topological phase on the spectrum by studying the Ising* transition (i.e. the transition between a Z_{2} topological phase and a trivial paramagnet), in the example of the toric code in a longitudinal field, and advocate a phenomenological picture that provides qualitative insight into the operator content of the critical field theory.

Itinerant density instability at classical and quantum critical points

Science.gov (United States)

Feng, Yejun; van Wezel, Jasper; Flicker, Felix; Wang, Jiyang; Silevitch, D. M.; Littlewood, P. B.; Rosenbaum, T. F.

2015-03-01

Itinerant density waves are model systems for studying quantum critical behavior. In both the model spin- and charge-density-wave systems Cr and NbSe2, it is possible to drive a continuous quantum phase transition with critical pressures below 10 GPa. Using x-ray diffraction techniques, we are able to directly track the evolution of the ordering wave vector Q across the pressure-temperature phase diagram. We find a non-monotonic dependence of Q on pressure. Using a Landau-Ginsburg theoretical framework developed by McMillan for CDWs, we evaluate the importance of the physical terms in driving the formation of ordered states at both the thermal and quantum phase transitions. We find that the itinerant instability is the deciding factor for the emergent order, which is further influenced by the critical fluctuations in both the thermal and quantum limits.

CRITICAL INDICATORS IN MECHANIZED HARVEST GRAINS AND FIBER

Directory of Open Access Journals (Sweden)

E. Boeing

2017-10-01

Full Text Available Due to the growth in grain production and intensification of production systems losses are inevitable. The harvest as the last operation performed in the field requires better attention. Although the origins are varied and losses occur both before and during harvesting, approximately 80% of them occur by mechanisms of action of the harvester cutting platform. It is necessary to know the causes of losses, whether physical or physiological operational. Thus, the objective was to conduct a survey of potential losses and / or environmental factors that affect machinery and effectively and should be prioritized in a management program in order to raise the efficiency of harvesting. From the collected data determined if the potential of critical failures through the method of analysis and failure mode effects, using a questionnaire listed with the selected quality indicators. It was concluded that in the mechanical harvesting of cotton harvested product loss and impurity had insusceptible rates be prioritized goals in the management of the production process. While the grain crop (soybean / corn moisture grain and grain breaks are still the main causes in the loss of quality of the product, stressing the importance of harvesters in improving the characteristics at harvest in order to minimize qualitative grain losses.

Statistical theory of dislocation configurations in a random array of point obstacles

International Nuclear Information System (INIS)

Labusch, R.

1977-01-01

The stable configurations of a dislocation in an infinite random array of point obstacles are analyzed using the mathematical methods of statistical mechanics. The theory provides exact distribution functions of the forces on pinning points and of the link lengths between points on the line. The expected number of stable configurations is a function of the applied stress. This number drops to zero at the critical stress. Due to a degeneracy problem in the line count, the value of the flow stress cannot be determined rigorously, but we can give a good approximation that is very close to the empirical value

Application of hazard analysis critical control points (HACCP) to organic chemical contaminants in food.

Science.gov (United States)

Ropkins, K; Beck, A J

2002-03-01

Hazard Analysis Critical Control Points (HACCP) is a systematic approach to the identification, assessment, and control of hazards that was developed as an effective alternative to conventional end-point analysis to control food safety. It has been described as the most effective means of controlling foodborne diseases, and its application to the control of microbiological hazards has been accepted internationally. By contrast, relatively little has been reported relating to the potential use of HACCP, or HACCP-like procedures, to control chemical contaminants of food. This article presents an overview of the implementation of HACCP and discusses its application to the control of organic chemical contaminants in the food chain. Although this is likely to result in many of the advantages previously identified for microbiological HACCP, that is, more effective, efficient, and economical hazard management, a number of areas are identified that require further research and development. These include: (1) a need to refine the methods of chemical contaminant identification and risk assessment employed, (2) develop more cost-effective monitoring and control methods for routine chemical contaminant surveillance of food, and (3) improve the effectiveness of process optimization for the control of chemical contaminants in food.

Application of Hazard Analysis and Critical Control Points (HACCP) to the Cultivation Line of Mushroom and Other Cultivated Edible Fungi.

Science.gov (United States)

Pardo, José E; de Figueirêdo, Vinícius Reis; Alvarez-Ortí, Manuel; Zied, Diego C; Peñaranda, Jesús A; Dias, Eustáquio Souza; Pardo-Giménez, Arturo

2013-09-01

The Hazard analysis and critical control points (HACCP) is a preventive system which seeks to ensure food safety and security. It allows product protection and correction of errors, improves the costs derived from quality defects and reduces the final overcontrol. In this paper, the system is applied to the line of cultivation of mushrooms and other edible cultivated fungi. From all stages of the process, only the reception of covering materials (stage 1) and compost (stage 3), the pre-fruiting and induction (step 6) and the harvest (stage 7) have been considered as critical control point (CCP). The main hazards found were the presence of unauthorized phytosanitary products or above the permitted dose (stages 6 and 7), and the presence of pathogenic bacteria (stages 1 and 3) and/or heavy metals (stage 3). The implementation of this knowledge will allow the self-control of their productions based on the system HACCP to any plant dedicated to mushroom or other edible fungi cultivation.

The Hazard Analysis and Critical Control Points (HACCP) generic model for the production of Thai fermented pork sausage (Nham).

Science.gov (United States)

Paukatong, K V; Kunawasen, S

2001-01-01

Nham is a traditional Thai fermented pork sausage. The major ingredients of Nham are ground pork meat and shredded pork rind. Nham has been reported to be contaminated with Salmonella spp., Staphylococcus aureus, and Listeria monocytogenes. Therefore, it is a potential cause of foodborne diseases for consumers. A Hazard Analysis and Critical Control Points (HACCP) generic model has been developed for the Nham process. Nham processing plants were observed and a generic flow diagram of Nham processes was constructed. Hazard analysis was then conducted. Other than microbial hazards, the pathogens previously found in Nham, sodium nitrite and metal were identified as chemical and physical hazards in this product, respectively. Four steps in the Nham process have been identified as critical control points. These steps are the weighing of the nitrite compound, stuffing, fermentation, and labeling. The chemical hazard of nitrite must be controlled during the weighing step. The critical limit of nitrite levels in the Nham mixture has been set at 100-200 ppm. This level is high enough to control Clostridium botulinum but does not cause chemical hazards to the consumer. The physical hazard from metal clips could be prevented by visual inspection of every Nham product during stuffing. The microbiological hazard in Nham could be reduced in the fermentation process. The critical limit of the pH of Nham was set at lower than 4.6. Since this product is not cooked during processing, finally, educating the consumer, by providing information on the label such as "safe if cooked before consumption", could be an alternative way to prevent the microbiological hazards of this product.

Thermodynamic properties of water in the critical region

International Nuclear Information System (INIS)

Veloso, Marcelo A.

2009-01-01

The supercritical-water-cooled reactor (SCWR) is one of the nuclear reactor technologies selected for research and development under the Generation IV program. SCWRs offer the potential for high thermal efficiencies and considerable plant simplifications for improved economics. One of the main characteristics of critical water is the strong variations of its thermal-physical properties in the vicinity of the critical point. These large variations may result in an unusual heat transfer behavior. The 1967 IFC Formulation for Industrial Use, which until 1998 formed the basis of steam tables used in many areas of steam power industry throughout the world since the late 1960's, has been now replaced with the IAPWS IF-97 Formulation for the Thermodynamic Properties of Water and Steam for Industrial Use, adopted by the International Association for the Properties of Water and Steam (IAPWS) in 1997. An IAPWS release points out that this new formulation has some unsatisfactory features in the immediate vicinity of the critical point. In order to investigate this singular aspect, which is crucial to better understand the heat transfer mechanism in a SCWR system, predictions by the IAPWS-IF97 formulation will be compared with thermodynamic properties values predicted by an alternative crossover equation of state as well as with experimental data found in literature. (author)

Complex Interaction Mechanisms between Dislocations and Point Defects Studied in Pure Aluminium by a Two-Wave Acoustic Coupling Technique

Science.gov (United States)

Bremnes, O.; Progin, O.; Gremaud, G.; Benoit, W.

1997-04-01

Ultrasonic experiments using a two-wave coupling technique were performed on 99.999% pure Al in order to study the interaction mechanisms occurring between dislocations and point defects. The coupling technique consists in measuring the attenuation of ultrasonic waves during low-frequency stress cycles (t). One obtains closed curves () called signatures whose shape and evolution are characteristic of the interaction mechanism controlling the low-frequency dislocation motion. The signatures observed were attributed to the interaction of the dislocations with extrinsic point defects. A new interpretation of the evolution of the signatures measured below 200 K with respect to temperature and stress frequency had to be established: they are linked to depinning of immobile point defects, whereas a thermally activated depinning mechanism does not fit the observations. The signatures measured between 200 and 370 K were interpreted as dragging and depinning of extrinsic point defects which are increasingly mobile with temperature.

Liquid-liquid critical point in a simple analytical model of water

Science.gov (United States)

Urbic, Tomaz

2016-10-01

A statistical model for a simple three-dimensional Mercedes-Benz model of water was used to study phase diagrams. This model on a simple level describes the thermal and volumetric properties of waterlike molecules. A molecule is presented as a soft sphere with four directions in which hydrogen bonds can be formed. Two neighboring waters can interact through a van der Waals interaction or an orientation-dependent hydrogen-bonding interaction. For pure water, we explored properties such as molar volume, density, heat capacity, thermal expansion coefficient, and isothermal compressibility and found that the volumetric and thermal properties follow the same trends with temperature as in real water and are in good general agreement with Monte Carlo simulations. The model exhibits also two critical points for liquid-gas transition and transition between low-density and high-density fluid. Coexistence curves and a Widom line for the maximum and minimum in thermal expansion coefficient divides the phase space of the model into three parts: in one part we have gas region, in the second a high-density liquid, and the third region contains low-density liquid.

[Optimal energy supply in different age groups of critically ill children on mechanical ventilation].

Science.gov (United States)

Li, X H; Ji, J; Qian, S Y

2018-01-02

Objective: To analyze the resting energy expenditure and optimal energy supply in different age groups of critically ill children on mechanical ventilation in pediatric intensive care unit (PICU). Methods: Patients on mechanical ventilation hospitalized in PICU of Beijing Children's Hospital from March 2015 to March 2016 were enrolled prospectively. Resting energy expenditure of patients was calculated by US Med Graphic company critical care management (CCM) energy metabolism test system after mechanical ventilation. Patients were divided into three groups:10 years. The relationship between the measured and predictive resting energy expenditure was analyzed with correlation analysis; while the metabolism status and the optimal energy supply in different age groups were analyzed with chi square test and variance analysis. Results: A total of 102 patients were enrolled, the measured resting energy expenditure all correlated with predictive resting energy expenditure in different age groups (10 years ( r= 0.5, P= 0.0) ) . A total of 40 cases in group, including: 14 cases of low metabolism (35%), 14 cases of normal metabolism (35%), and 12 cases of high metabolism (30%); 45 cases in 3-10 years group, including: 22 cases of low metabolism (49%), 19 cases of normal metabolism (42%), 4 cases of high metabolism (9%); 17 cases in > 10 years group, including: 12 cases of low metabolism (71%), 4 cases of normal metabolism (23%), 1 case of high metabolism (6%). Metabolism status showed significant differences between different age groups ( χ (2)=11.30, P age groups ( F= 46.57, Pgroup, (184±53) kJ/ (kg⋅d) in 3-10 years group, and (120±30) kJ/ (kg⋅d) in > 10 years group. Conclusion: The resting energy metabolism of the critically ill children on mechanical ventilation is negatively related to the age. The actual energy requirement should be calculated according to different ages.

APS Quantum Critical Higgs

CERN Document Server

Bellazzini, Brando; Hubisz, Jay; Lee, Seung J.; Serra, Javi; Terning, John

2016-01-01

The appearance of the light Higgs boson at the LHC is difficult to explain, particularly in light of naturalness arguments in quantum field theory. However light scalars can appear in condensed matter systems when parameters (like the amount of doping) are tuned to a critical point. At zero temperature these quantum critical points are directly analogous to the finely tuned standard model. In this paper we explore a class of models with a Higgs near a quantum critical point that exhibits non-mean-field behavior. We discuss the parametrization of the effects of a Higgs emerging from such a critical point in terms of form factors, and present two simple realistic scenarios based on either generalized free fields or a 5D dual in AdS space. For both of these models we consider the processes $gg\\to ZZ$ and $gg\\to hh$, which can be used to gain information about the Higgs scaling dimension and IR transition scale from the experimental data.

Predicting critical temperatures of ionic and non-ionic fluids from thermophysical data obtained near the melting point

Science.gov (United States)

Weiss, Volker C.

2015-10-01

In the correlation and prediction of thermophysical data of fluids based on a corresponding-states approach, the critical temperature Tc plays a central role. For some fluids, in particular ionic ones, however, the critical region is difficult or even impossible to access experimentally. For molten salts, Tc is on the order of 3000 K, which makes accurate measurements a challenging task. Room temperature ionic liquids (RTILs) decompose thermally between 400 K and 600 K due to their organic constituents; this range of temperatures is hundreds of degrees below recent estimates of their Tc. In both cases, reliable methods to deduce Tc based on extrapolations of experimental data recorded at much lower temperatures near the triple or melting points are needed and useful because the critical point influences the fluid's behavior in the entire liquid region. Here, we propose to employ the scaling approach leading to universal fluid behavior [Román et al., J. Chem. Phys. 123, 124512 (2005)] to derive a very simple expression that allows one to estimate Tc from the density of the liquid, the surface tension, or the enthalpy of vaporization measured in a very narrow range of low temperatures. We demonstrate the validity of the approach for simple and polar neutral fluids, for which Tc is known, and then use the methodology to obtain estimates of Tc for ionic fluids. When comparing these estimates to those reported in the literature, good agreement is found for RTILs, whereas the ones for the molten salts NaCl and KCl are lower than previous estimates by 10%. The coexistence curve for ionic fluids is found to be more adequately described by an effective exponent of βeff = 0.5 than by βeff = 0.33.

Controlling organic chemical hazards in food manufacturing: a hazard analysis critical control points (HACCP) approach.

Science.gov (United States)

Ropkins, K; Beck, A J

2002-08-01

Hazard analysis by critical control points (HACCP) is a systematic approach to the identification, assessment and control of hazards. Effective HACCP requires the consideration of all hazards, i.e., chemical, microbiological and physical. However, to-date most 'in-place' HACCP procedures have tended to focus on the control of microbiological and physical food hazards. In general, the chemical component of HACCP procedures is either ignored or limited to applied chemicals, e.g., food additives and pesticides. In this paper we discuss the application of HACCP to a broader range of chemical hazards, using organic chemical contaminants as examples, and the problems that are likely to arise in the food manufacturing sector. Chemical HACCP procedures are likely to result in many of the advantages previously identified for microbiological HACCP procedures: more effective, efficient and economical than conventional end-point-testing methods. However, the high costs of analytical monitoring of chemical contaminants and a limited understanding of formulation and process optimisation as means of controlling chemical contamination of foods are likely to prevent chemical HACCP becoming as effective as microbiological HACCP.

The critical oxide thickness for Pb-free reflow soldering on Cu substrate

Energy Technology Data Exchange (ETDEWEB)

Chung, C. Key [Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan (China); Assembly Test Global Materials, Intel Microelectronics Asia Ltd, B1, No. 205, Tun-Hwa North Road, 10595 Taipei, Taiwan (China); Chen, Y.J.; Li, C.C. [Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan (China); Kao, C.R., E-mail: crkao@ntu.edu.tw [Department of Materials Science and Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617, Taiwan (China)

2012-06-01

Oxidation is an undesirable effect of reflow soldering. Non-wetting occurs when the oxide layer grows above the critical thickness. Characterizing the critical oxide thickness for soldering is challenging due to oxide's nano-scale thickness and irregular topographic surface. In this paper, the critical copper oxide thickness was characterized by Time-of-Flight Secondary Ion Mass Spectrometry, Scanning Electron Microscopy, Energy-Dispersive X-ray spectroscopy, and Transmission Electron Microscopy. Copper substrates were coated with an Organic-Solderable-Preservative (OSP) layer and baked at 150 Degree-Sign C and 85% Relative Humidity for different amounts of time. The onset of the non-wetting phenomenon occurred when the oxide thickness reached 18 {+-} 5 nm. As the oxide grew beyond this critical thickness, the percentage of non-wetting solder joint increased exponentially. The growth of the oxide thickness followed a parabolic rate law. The rate constant of oxidation was 0.6 Multiplication-Sign 10{sup -15} cm{sup 2} min{sup -1}. Oxidation resulted from interdiffusion of copper and oxygen atoms through the OSP and oxide layers. The oxidation mechanism will be presented and discussed. - Highlights: Black-Right-Pointing-Pointer Critical oxide thickness for Pb free solder on Cu substrate is 18 {+-} 5 nm. Black-Right-Pointing-Pointer Above the critical oxide, non-wet solder joint increases exponentially. Black-Right-Pointing-Pointer A maximum 13-nm oxide thickness is suggested for good solder joint. Black-Right-Pointing-Pointer Initial growth of oxide thickness is logarithmic and then parabolic after 12 nm. Black-Right-Pointing-Pointer Thick oxide (360-560 nm) is formed as pores shorten the oxidation path.

The pathogenetic mechanisms of lesion and reconstruction of hematosis at critical radiation sickness

International Nuclear Information System (INIS)

Tukhtaev, T.M.

1978-01-01

In this chapter author made conclusion that for understanding pathogenetic mechanisms lead to critical radiation sickness after influence ionizing radiation it is necessary to take into account the consecution of all reactions beginning from physical and chemical processes of interaction radiation with matter till displaying final radiation effect on cell level and organism

Anderson transition on the Cayley tree as a traveling wave critical point for various probability distributions

International Nuclear Information System (INIS)

Monthus, Cecile; Garel, Thomas

2009-01-01

For Anderson localization on the Cayley tree, we study the statistics of various observables as a function of the disorder strength W and the number N of generations. We first consider the Landauer transmission T N . In the localized phase, its logarithm follows the traveling wave form T N ≅(ln T N )-bar + ln t* where (i) the disorder-averaged value moves linearly (ln(T N ))-bar≅-N/ξ loc and the localization length diverges as ξ loc ∼(W-W c ) -ν loc with ν loc = 1 and (ii) the variable t* is a fixed random variable with a power-law tail P*(t*) ∼ 1/(t*) 1+β(W) for large t* with 0 N are governed by rare events. In the delocalized phase, the transmission T N remains a finite random variable as N → ∞, and we measure near criticality the essential singularity (ln(T ∞ ))-bar∼-|W c -W| -κ T with κ T ∼ 0.25. We then consider the statistical properties of normalized eigenstates Σ x |ψ(x)| 2 = 1, in particular the entropy S = -Σ x |ψ(x)| 2 ln |ψ(x)| 2 and the inverse participation ratios (IPR) I q = Σ x |ψ(x)| 2q . In the localized phase, the typical entropy diverges as S typ ∼( W-W c ) -ν S with ν S ∼ 1.5, whereas it grows linearly as S typ (N) ∼ N in the delocalized phase. Finally for the IPR, we explain how closely related variables propagate as traveling waves in the delocalized phase. In conclusion, both the localized phase and the delocalized phase are characterized by the traveling wave propagation of some probability distributions, and the Anderson localization/delocalization transition then corresponds to a traveling/non-traveling critical point. Moreover, our results point toward the existence of several length scales that diverge with different exponents ν at criticality

Critical incidents and critical incident stress management (CISM) - an employee assistance programme (EAP) perspective

OpenAIRE

Terblanche, Lourie; van Wyk, André

2014-01-01

Employees are increasingly becoming victims of critical incidents. From a systems theory point of view, it is necessary to acknowledge the impact of critical incidents not only on the personal life of the employee, but on the workplace itself. Employees respond differently to critical incidents, which makes it even more complicated when this reaches the point of requiring therapeutic intervention. The most common response to critical incidents may be the risk of developing post-traumatic s...

Critical and post-critical behaviour of two-degree-of-freedom flutter-based generators

Science.gov (United States)

Pigolotti, Luca; Mannini, Claudio; Bartoli, Gianni; Thiele, Klaus

2017-09-01

Energy harvesting from flow-induced vibrations is a recent research field, which considers a diverse range of systems, among which two-degree-of-freedom flutter-based solutions were individuated as good candidates to obtain high energy performance. In the present work, numerical linear analyses and wind-tunnel tests were conducted on a flat-plate sectional model. The aim is to identify some design guidelines for generators exploiting the classical-flutter instability, through the investigation of the critical condition and the response during the post-critical regime. Many sets of governing parameters of interest from the energy-harvesting point of view were considered, including high levels of heaving damping to simulate the operation of a conversion apparatus. In particular, eccentricity of the elastic centre and small downstream mass unbalance can be introduced as solutions aiming at optimal operative ranges. The collected results suggest the high potentiality of flutter-based generators, and a significant enhancement of performance can be envisaged. Moreover, they contribute to improve the knowledge of the flutter excitation mechanism and to widen the dataset of measurements in the post-critical regime.

Universal fine structure of the specific heat at the critical λ-point for an ideal Bose gas in an arbitrary trap

International Nuclear Information System (INIS)

Tarasov, S V; Kocharovsky, Vl V; Kocharovsky, V V

2014-01-01

We analytically find the universal fine structure of the noted discontinuity in the value and/or derivative of the specific heat of an ideal Bose gas in an arbitrary trap in the whole critical region around the λ-point of the Bose–Einstein condensation. The result reveals a remarkable dependence of the λ-point structure on the trap's form and boundary conditions, even for a macroscopically large system. We suggest measuring this strong effect in the experiments with a controllable trap potential. (paper)

A case of hypoglycemiainduced QT prolongation leading to torsade de pointes and a review of pathophysiological mechanisms

Directory of Open Access Journals (Sweden)

Faris Hannoodi

2017-06-01

Full Text Available Torsades de pointes is a life-threatening cardiac arrhythmia. Occurrence of this arrhythmia as a result of hypoglycemia has not been reported in the literature. We describe an interesting case of an insulindependent diabetic patient presenting with torsades de pointes resulting from hypoglycemia. A 62-year-old male was admitted to the hospital following an episode of severe insulin-induced hypoglycemia and a cardiac arrest. He was found to unresponsive at home after taking insulin. His serum glucose was found to be 18. He was given juice initially to normalize his glucose and was then transferred by EMS to ER where he was given 5% dextrose infusion. Analysis of the LifeVest rhythm recording showed torsades de pointes that was terminated by defibrillation of the LifeVest. Several mechanisms are responsible for torsade, including QT interval prolongation, adrenalin secretion and calcium overload leading to intracellular calcium oscillations. These mechanisms are a trigger to torsade de pointes. Predisposing factors were present leading torsade to occur.

First-Order Interfacial Transformations with a Critical Point: Breaking the Symmetry at a Symmetric Tilt Grain Boundary

Science.gov (United States)

Yang, Shengfeng; Zhou, Naixie; Zheng, Hui; Ong, Shyue Ping; Luo, Jian

2018-02-01

First-order interfacial phaselike transformations that break the mirror symmetry of the symmetric ∑5 (210 ) tilt grain boundary (GB) are discovered by combining a modified genetic algorithm with hybrid Monte Carlo and molecular dynamics simulations. Density functional theory calculations confirm this prediction. This first-order coupled structural and adsorption transformation, which produces two variants of asymmetric bilayers, vanishes at an interfacial critical point. A GB complexion (phase) diagram is constructed via semigrand canonical ensemble atomistic simulations for the first time.

Percolation Systems away from the Critical Point

OpenAIRE

Dhar, Deepak

2001-01-01

This article reviews some effects of disorder in percolation systems even away from the critical density p_c. For densities below p_c, the statistics of large clusters defines the animals problem. Its relation to the directed animals problem and the Lee-Yang edge singularity problem is described. Rare compact clusters give rise to Griffiths singuraties in the free energy of diluted ferromagnets, and lead to a very slow relaxation of magnetization. In biassed diffusion on percolation clusters,...

Microbiological performance of Hazard Analysis Critical Control Point (HACCP)-based food safety management systems: A case of Nile perch processing company

NARCIS (Netherlands)

Kussaga, J.B.; Luning, P.A.; Tiisekwa, B.P.M.; Jacxsens, L.

2017-01-01

This study aimed at giving insight into microbiological safety output of a Hazard Analysis Critical Control Point (HACCP)-based Food Safety Management System (FSMS) of a Nile perch exporting company by using a combined assessment, This study aimed at giving insight into microbiological safety output

Scaling of the distribution function and the critical exponents near the point of a marginal stability under the Vlasov-Poisson equations

International Nuclear Information System (INIS)

Ivanov, Alexei

2000-08-01

A model system, described by the consistent Vlasov-Poisson equations under periodical boundary conditions, has been studied numerically near the point of a marginal stability. The power laws, typical for a system, undergoing a second-order phase transition, hold in a vicinity of the critical point: (i) A ∝ -θ β , β=1.907±0.006 for θ ≤ 0, where A is the saturated amplitude of the marginally-stable mode; (ii) χ ∝ θ -γ as θ → 0, γ=γ - =1.020±0.008 for θ + =0.995±0.020 for θ > 0, where χ=∂A/∂F 1 at F 1 → 0 is the susceptibility to external drive of the strain F 1 ; (iii) at θ=0 the system responds to external drive as A ∝ F 1 1/δ , and δ=1.544±0.002. θ=( 2 >- cr 2 >)/ cr 2 > is the dimensionless reduced velocity dispersion. Within the error of computation these critical exponents satisfy to equality γ=β(δ-1), known in thermodynamics as the Widom equality, which is direct consequence of scaling invariance of the Fourier components f m of the distribution function f at |θ| m (λ at t, λ av v, λ aθ θ, λ aA0 A 0 , λ aF F 1 )=λf m (t, v, θ, A 0 , F 1 ) at θ approx. = 0. On the contrary to thermodynamics these critical indices indicate to a very wide critical area. In turn, it means that critical phenomena may determine macroscopic dynamics of a large fraction of systems. (author)

Pain Measurement in Mechanically Ventilated Patients After Cardiac Surgery: Comparison of the Behavioral Pain Scale (BPS) and the Critical-Care Pain Observation Tool (CPOT).

Science.gov (United States)

Rijkenberg, Saskia; Stilma, Willemke; Bosman, Robert J; van der Meer, Nardo J; van der Voort, Peter H J

2017-08-01

The Behavioral Pain Scale (BPS) and Critical-Care Pain Observation Tool (CPOT) are behavioral pain assessment tools for sedated and unconscious critically ill patients. The aim of this study was to compare the reliability, internal consistency, and discriminant validation of the BPS and the CPOT simultaneously in mechanically ventilated patients after cardiac surgery. A prospective, observational cohort study. A 20-bed closed-format intensive care unit with mixed medical, surgical, and cardiac surgery patients in a teaching hospital in Amsterdam, The Netherlands. The study comprised 72 consecutive intubated and mechanically ventilated patients after cardiac surgery who were not able to self-report pain. Two nurses assessed the BPS and CPOT simultaneously and independently at the following 4 moments: rest, a nonpainful procedure (oral care), rest, and a painful procedure (turning). Both scores showed a significant increase of 2 points between rest and turning. The median BPS score of nurse 1 showed a significant increase of 1 point between rest and the nonpainful procedure (oral care), whereas both median CPOT scores did not change. The interrater reliability of the BPS and CPOT showed fair-to-good agreement of 0.74 overall. During the periods of rest 1 and rest 2, values ranged from 0.24 to 0.46. Cronbach's alpha values for the BPS were 0.62 (nurse 1) and 0.59 (nurse 2) compared with 0.65 and 0.58, respectively, for the CPOT. The BPS and CPOT are reliable and valid pain assessment tools in a daily clinical setting. However, the discriminant validation of both scores seems less satisfactory in sedated or agitated patients and this topic requires further investigation. Copyright © 2017 Elsevier Inc. All rights reserved.

The critical behaviour of self-dual Z(N) spin systems - Finite size scaling and conformal invariance

International Nuclear Information System (INIS)

Alcaraz, F.C.

1986-01-01

Critical properties of a family of self-dual two dimensional Z(N) models whose bulk free energy is exacly known at the self-dual point are studied. The analysis is performed by studing the finite size behaviour of the corresponding one dimensional quantum Hamiltonians which also possess an exact solution at their self-dual point. By exploring finite size scaling ideas and the conformal invariance of the critical infinite system the critical temperature and critical exponents as well as the central charge associated with the underlying conformal algebra are calculated for N up to 8. The results strongly suggest that the recently constructed Z(N) quantum field theory of Zamolodchikov and Fateev (1985) is the underlying field theory associated with these statistical mechanical systems. It is also tested, for the Z(5) case, the conjecture that these models correspond to the bifurcation points, in the phase diagram of the general Z(N) spin model, where a massless phase originates. (Author) [pt

Liquid behavior at critical and supercritical conditions

Science.gov (United States)

Chiu, Huei-Huang; Gross, Klaus W.

1989-10-01

At a JANNAF workshop, the issue of fluids at and above the critical point was discussed to obtain a better understanding of similar conditions in combustion chambers of rocket engines. Invited experts from academic, industrial, and government institutions presented the most recent physical, numerical, and experimental advances. During the final discussion period, it was agreed that: (1) no analytical capability exists to simulate subject conditions; (2) mechanisms reflected by opalescence, the solubility of gases, other interfacial phenomena listed, and fluorescence diagnostics are new and important; (3) multicomponent mixtures, radiation, critical fluctuation, and other recorded ones pose unknown effects; and (4) various identified analytical and experimental actions must be initiated in a mutually supporting sequence.

Lung protective mechanical ventilation strategies in cardiothoracic critical care: a retrospective study

Directory of Open Access Journals (Sweden)

Zochios V

2016-11-01

Full Text Available Vasileios Zochios,1–3 Matthew Hague,3,4 Kimberly Giraud,5 Nicola Jones3 1Department of Intensive Care Medicine, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, 2Institute of Inflammation and Ageing, College of Medical and Dental Sciences, University of Birmingham, 3Department of Anesthesia and Intensive Care Medicine, Papworth Hospital NHS Foundation Trust, Papworth Everard, Cambridge, 4Department of Medicine, Colchester Hospital University NHS Foundation Trust, Colchester General Hospital, Colchester, 5Research and Development Department, Papworth Hospital NHS Foundation Trust, Papworth Everard, Cambridge, UK Abstract: A body of evidence supports the use of low tidal volumes in ventilated patients without lung pathology to slow progress to acute respiratory distress syndrome (ARDS due to ventilator associated lung injury. We undertook a retrospective chart review and tested the hypothesis that tidal volume is a predictor of mortality in cardiothoracic (medical and surgical critical care patients receiving invasive mechanical ventilation. Independent predictors of mortality in our study included: type of surgery, albumin, H+, bilirubin, and fluid balance. In particular, it is important to note that cardiac, thoracic, and transplant surgical patients were associated with lower mortality. However, our study did not sample equally from The Berlin Definition of ARDS severity categories (mild, moderate, and severe hypoxemia. Although our study was not adequately powered to detect a difference in mortality between these groups, it will inform the development of a large prospective cohort study exploring the role of low tidal volume ventilation in cardiothoracic critically ill patients. Keywords: lung protective ventilation, cardiothoracic critical care, acute respiratory distress syndrome, invasive mechanical ventilation

Comparison study of hybrid VS critical systems in point kinetics

International Nuclear Information System (INIS)

Ritter, G.; Tommasi, J.; Slessarev, L.; Salvatores, M.; Mouney, H.; Vergnes, J.

1999-01-01

An essential motivation for hybrid systems is a potentially high level of intrinsic safety against reactivity accidents. In this respect, it is necessary to assess the behaviour of an Accelerator Driven System during a TOP, LOF or TOC accident. A comparison between a critical and sub-critical reactor shows a larger sensitivity for the critical system. The ADS has an unquestionable advantage in case of TOP but a less favourable behaviour as for LOFWS type of accidents. However in the ADS cases, the beam could be easily shut off during the transient. Therefore, a part of the R and D effort should be focused on the monitoring and control of power. (author)

Constraints on Stress Components at the Internal Singular Point of an Elastic Compound Structure

Science.gov (United States)

Pestrenin, V. M.; Pestrenina, I. V.

2017-03-01

The classical analytical and numerical methods for investigating the stress-strain state (SSS) in the vicinity of a singular point consider the point as a mathematical one (having no linear dimensions). The reliability of the solution obtained by such methods is valid only outside a small vicinity of the singular point, because the macroscopic equations become incorrect and microscopic ones have to be used to describe the SSS in this vicinity. Also, it is impossible to set constraint or to formulate solutions in stress-strain terms for a mathematical point. These problems do not arise if the singular point is identified with the representative volume of material of the structure studied. In authors' opinion, this approach is consistent with the postulates of continuum mechanics. In this case, the formulation of constraints at a singular point and their investigation becomes an independent problem of mechanics for bodies with singularities. This method was used to explore constraints at an internal singular point (representative volume) of a compound wedge and a compound rib. It is shown that, in addition to the constraints given in the classical approach, there are also constraints depending on the macroscopic parameters of constituent materials. These constraints turn the problems of deformable bodies with an internal singular point into nonclassical ones. Combinations of material parameters determine the number of additional constraints and the critical stress state at the singular point. Results of this research can be used in the mechanics of composite materials and fracture mechanics and in studying stress concentrations in composite structural elements.

Zero-point oscillations, zero-point fluctuations, and fluctuations of zero-point oscillations

International Nuclear Information System (INIS)

Khalili, Farit Ya

2003-01-01

Several physical effects and methodological issues relating to the ground state of an oscillator are considered. Even in the simplest case of an ideal lossless harmonic oscillator, its ground state exhibits properties that are unusual from the classical point of view. In particular, the mean value of the product of two non-negative observables, kinetic and potential energies, is negative in the ground state. It is shown that semiclassical and rigorous quantum approaches yield substantially different results for the ground state energy fluctuations of an oscillator with finite losses. The dependence of zero-point fluctuations on the boundary conditions is considered. Using this dependence, it is possible to transmit information without emitting electromagnetic quanta. Fluctuations of electromagnetic pressure of zero-point oscillations are analyzed, and the corresponding mechanical friction is considered. This friction can be viewed as the most fundamental mechanism limiting the quality factor of mechanical oscillators. Observation of these effects exceeds the possibilities of contemporary experimental physics but almost undoubtedly will be possible in the near future. (methodological notes)

PENERAPAN SISTEM HAZARD ANALYSIS CRITICAL CONTROL POINT (HACCP PADA PROSES PEMBUATAN KERIPIK TEMPE

Directory of Open Access Journals (Sweden)

Rahmi Yuniarti

2015-06-01

Full Text Available Malang is one of the industrial centers of tempe chips. To maintain the quality and food safety, analysis is required to identify the hazards during the production process. This study was conducted to identify the hazards during the production process of tempe chips and provide recommendations for developing a HACCP system. The phases of production process of tempe chips are started from slice the tempe, move it to the kitchen, coat it with flour dough, fry it in the pan, drain it, package it, and then storage it. There are 3 types of potential hazards in terms of biological, physical, and chemical during the production process. With the CCP identification, there are three processes that have Critical Control Point. There are the process of slicing tempe, immersion of tempe into the flour mixture and draining. Recommendations for the development of HACCP systems include recommendations related to employee hygiene, supporting equipment, 5-S analysis, and the production layout.

Effective and fundamental quantum fields at criticality

Energy Technology Data Exchange (ETDEWEB)

Scherer, Michael

2010-10-28

We employ Wetterich's approach to functional renormalization as a suitable method to investigate universal phenomena in non-perturbative quantum field theories both qualitatively and quantitatively. Therefore we derive and investigate flow equations for a class of chiral Yukawa models with and without gauge bosons and reveal fixed-point mechanisms. In four dimensions chiral Yukawa systems serve as toy models for the standard model Higgs sector and show signatures of asymptotically safe fixed points by a balancing of bosonic and fermionic contributions. In the approximations investigated this renders the theory fundamental and solves the triviality problem. Further, we obtain predictions for the Higgs mass and even for the top mass of our toy model. In three dimensions we compute the critical exponents which define new universality classes and provide benchmark values for systems of strongly correlated chiral fermions. In a Yukawa system of non-relativistic two-component fermions a fixed point dominates the renormalization flow giving rise to universality in the BCS-BEC crossover. We push the functional renormalization method to a quantitative level and we compute the critical temperature and the single-particle gap with a considerable precision for the whole crossover. Finally, we provide further evidence for the asymptotic safety scenario in quantum gravity by confirming the existence of an ultraviolet fixed point under inclusion of a curvature-ghost coupling. (orig.)

Effective and fundamental quantum fields at criticality

International Nuclear Information System (INIS)

Scherer, Michael

2010-01-01

We employ Wetterich's approach to functional renormalization as a suitable method to investigate universal phenomena in non-perturbative quantum field theories both qualitatively and quantitatively. Therefore we derive and investigate flow equations for a class of chiral Yukawa models with and without gauge bosons and reveal fixed-point mechanisms. In four dimensions chiral Yukawa systems serve as toy models for the standard model Higgs sector and show signatures of asymptotically safe fixed points by a balancing of bosonic and fermionic contributions. In the approximations investigated this renders the theory fundamental and solves the triviality problem. Further, we obtain predictions for the Higgs mass and even for the top mass of our toy model. In three dimensions we compute the critical exponents which define new universality classes and provide benchmark values for systems of strongly correlated chiral fermions. In a Yukawa system of non-relativistic two-component fermions a fixed point dominates the renormalization flow giving rise to universality in the BCS-BEC crossover. We push the functional renormalization method to a quantitative level and we compute the critical temperature and the single-particle gap with a considerable precision for the whole crossover. Finally, we provide further evidence for the asymptotic safety scenario in quantum gravity by confirming the existence of an ultraviolet fixed point under inclusion of a curvature-ghost coupling. (orig.)

Scaling of the distribution function and the critical exponents near the point of a marginal stability under the Vlasov-Poisson equations

Energy Technology Data Exchange (ETDEWEB)

Lvanov, Alexei [Theory and Computer Simulation Center, National Inst. for Fusion Science, Toki, Gifu (Japan)

2000-08-01

A model system, described by the consistent Vlasov-Poisson equations under periodical boundary conditions, has been studied numerically near the point of a marginal stability. The power laws, typical for a system, undergoing a second-order phase transition, hold in a vicinity of the critical point: (i) A {proportional_to} -{theta}{sup {beta}}, {beta}=1.907{+-}0.006 for {theta} {<=} 0, where A is the saturated amplitude of the marginally-stable mode; (ii) {chi} {proportional_to} {theta}{sup -{gamma}} as {theta} {yields} 0, {gamma}={gamma}{sub -}=1.020{+-}0.008 for {theta} < 0, and {gamma}={gamma}{sub +}=0.995{+-}0.020 for {theta} > 0, where {chi}={partial_derivative}A/{partial_derivative}F{sub 1} at F{sub 1} {yields} 0 is the susceptibility to external drive of the strain F{sub 1}; (iii) at {theta}=0 the system responds to external drive as A {proportional_to} F{sub 1}{sup 1/{delta}}, and {delta}=1.544{+-}0.002. {theta}=(-)/ is the dimensionless reduced velocity dispersion. Within the error of computation these critical exponents satisfy to equality {gamma}={beta}({delta}-1), known in thermodynamics as the Widom equality, which is direct consequence of scaling invariance of the Fourier components f{sub m} of the distribution function f at |{theta}| << 1, i.e. f{sub m}({lambda}{sup at}t, {lambda}{sup av}v, {lambda}{sup a{theta}}{theta}, {lambda}{sup aA0}A{sub 0}, {lambda}{sup aF}F{sub 1})={lambda}f{sub m}(t, v, {theta}, A{sub 0}, F{sub 1}) at {theta} approx. = 0. On the contrary to thermodynamics these critical indices indicate to a very wide critical area. In turn, it means that critical phenomena may determine macroscopic dynamics of a large fraction of systems. (author)

Introduction to critical and multicritical phenomena

International Nuclear Information System (INIS)

Salinas, S.R.A.

1984-01-01

The behavior of matter in the neighborhood of simple critical points is treated. The concepts of critical exponents and universality are introduced, and the classical theories of the critical behavior and the phenomenological scaling theories of the thermodynamic functions and the critical correlations are described. Finally the first part is ended with a discription of the theory of the renormalization group, which gives the microscopic bases of the scaling laws. In the second part of these notes four types of multicritical points which have already been detected in solid crystals; tricritical, bicritical, tetracritical, and Lifshitz points are studied. Landau's theory and the formulation of the scaling laws in the neighborhood of these points is described. The main features of some theoretical models which produce multicritical points - the Ising metamagnet and the BEG model which exhibit tricritical points, and the ANNNI model, which exhibits a Lifshitz point are also described. The renormalization group approach in the Fourier space to the Ising metamagnet, and the new techniques of partial differential approximants to analyze the scaling behavior in the neighborhood of the multicritical points is presented. (Author) [pt

[Experience with knowledge development in food handlers with te implementation of Hazard Analysis Critical control points (HACCP) in a hospital food service].

Science.gov (United States)

de Sousa, A A; de Salles, R K; Felipe, M R; Tosin, I

1999-03-01

The present article has as objective to describe the methodology of an experience of implantation of Hazard Analyses Critical Control Points (HACCP) with food handlers in a hospital food service establishment, inside of a conception of relationship and construction of knowledge. Meetings with the food handlers and nutritionists, with the objective of raising the difficulties poined for the sector and the work to be developed. The HACCP consisted of the evaluation of the operations, following the sequential steps recommended, looking itself to instruct the food handlers on the methods of the operations and its interpretations. The detected critical points, the measures of control, the criteria of correction and the monitoring have widely been argued, serving as didactic elements for the reconstruction of quality of the preparations. The discussions generated actions that were developed in short term, revealing the need of a more effective and continuous partnership for the new proposals.

Quantum Multicriticality near the Dirac-Semimetal to Band-Insulator Critical Point in Two Dimensions: A Controlled Ascent from One Dimension

Science.gov (United States)

Roy, Bitan; Foster, Matthew S.

2018-01-01

We compute the effects of generic short-range interactions on gapless electrons residing at the quantum critical point separating a two-dimensional Dirac semimetal and a symmetry-preserving band insulator. The electronic dispersion at this critical point is anisotropic (Ek=±√{v2kx2+b2ky2 n } with n =2 ), which results in unconventional scaling of thermodynamic and transport quantities. Because of the vanishing density of states [ϱ (E )˜|E |1 /n ], this anisotropic semimetal (ASM) is stable against weak short-range interactions. However, for stronger interactions, the direct Dirac-semimetal to band-insulator transition can either (i) become a fluctuation-driven first-order transition (although unlikely in a particular microscopic model considered here, the anisotropic honeycomb lattice extended Hubbard model) or (ii) get avoided by an intervening broken-symmetry phase. We perform a controlled renormalization group analysis with the small parameter ɛ =1 /n , augmented with a 1 /n expansion (parametrically suppressing quantum fluctuations in the higher dimension) by perturbing away from the one-dimensional limit, realized by setting ɛ =0 and n →∞ . We identify charge density wave (CDW), antiferromagnet (AFM), and singlet s -wave superconductivity as the three dominant candidates for broken symmetry. The onset of any such order at strong coupling (˜ɛ ) takes place through a continuous quantum phase transition across an interacting multicritical point, where the ordered phase, band insulator, Dirac, and anisotropic semimetals meet. We also present the phase diagram of an extended Hubbard model for the ASM, obtained via the controlled deformation of its counterpart in one dimension. The latter displays spin-charge separation and instabilities to CDW, spin density wave, and Luther-Emery liquid phases at arbitrarily weak coupling. The spin density wave and Luther-Emery liquid phases deform into pseudospin SU(2)-symmetric quantum critical points separating the

Quantum Multicriticality near the Dirac-Semimetal to Band-Insulator Critical Point in Two Dimensions: A Controlled Ascent from One Dimension

Directory of Open Access Journals (Sweden)

Bitan Roy

2018-03-01

Full Text Available We compute the effects of generic short-range interactions on gapless electrons residing at the quantum critical point separating a two-dimensional Dirac semimetal and a symmetry-preserving band insulator. The electronic dispersion at this critical point is anisotropic (E_{k}=±sqrt[v^{2}k_{x}^{2}+b^{2}k_{y}^{2n}] with n=2, which results in unconventional scaling of thermodynamic and transport quantities. Because of the vanishing density of states [ϱ(E∼|E|^{1/n}], this anisotropic semimetal (ASM is stable against weak short-range interactions. However, for stronger interactions, the direct Dirac-semimetal to band-insulator transition can either (i become a fluctuation-driven first-order transition (although unlikely in a particular microscopic model considered here, the anisotropic honeycomb lattice extended Hubbard model or (ii get avoided by an intervening broken-symmetry phase. We perform a controlled renormalization group analysis with the small parameter ε=1/n, augmented with a 1/n expansion (parametrically suppressing quantum fluctuations in the higher dimension by perturbing away from the one-dimensional limit, realized by setting ε=0 and n→∞. We identify charge density wave (CDW, antiferromagnet (AFM, and singlet s-wave superconductivity as the three dominant candidates for broken symmetry. The onset of any such order at strong coupling (∼ε takes place through a continuous quantum phase transition across an interacting multicritical point, where the ordered phase, band insulator, Dirac, and anisotropic semimetals meet. We also present the phase diagram of an extended Hubbard model for the ASM, obtained via the controlled deformation of its counterpart in one dimension. The latter displays spin-charge separation and instabilities to CDW, spin density wave, and Luther-Emery liquid phases at arbitrarily weak coupling. The spin density wave and Luther-Emery liquid phases deform into pseudospin SU(2-symmetric quantum critical

Comparing Face-To-Face and Asynchronous Online Communication as Mechanisms for Critical Reflective Dialogue

Science.gov (United States)

Salter, Susan; Douglas, Tracy; Kember, David

2017-01-01

Two mechanisms for engaging in critical reflective dialogue are discussed and compared: face-to-face meetings and asynchronous online discussion. The context is an umbrella action research project, with over 20 participants, which aimed to improve practices in online teaching and contribute to the development of graduate attributes. The article…

Tuning critical failure with viscoelasticity: How aftershocks inhibit criticality in an analytical mean field model of fracture.

Science.gov (United States)

Baro Urbea, J.; Davidsen, J.

2017-12-01

The hypothesis of critical failure relates the presence of an ultimate stability point in the structural constitutive equation of materials to a divergence of characteristic scales in the microscopic dynamics responsible of deformation. Avalanche models involving critical failure have determined universality classes in different systems: from slip events in crystalline and amorphous materials to the jamming of granular media or the fracture of brittle materials. However, not all empirical failure processes exhibit the trademarks of critical failure. As an example, the statistical properties of ultrasonic acoustic events recorded during the failure of porous brittle materials are stationary, except for variations in the activity rate that can be interpreted in terms of aftershock and foreshock activity (J. Baró et al., PRL 2013).The rheological properties of materials introduce dissipation, usually reproduced in atomistic models as a hardening of the coarse-grained elements of the system. If the hardening is associated to a relaxation process the same mechanism is able to generate temporal correlations. We report the analytic solution of a mean field fracture model exemplifying how criticality and temporal correlations are tuned by transient hardening. We provide a physical meaning to the conceptual model by deriving the constitutive equation from the explicit representation of the transient hardening in terms of a generalized viscoelasticity model. The rate of 'aftershocks' is controlled by the temporal evolution of the viscoelastic creep. At the quasistatic limit, the moment release is invariant to rheology. Therefore, the lack of criticality is explained by the increase of the activity rate close to failure, i.e. 'foreshocks'. Finally, the avalanche propagation can be reinterpreted as a pure mathematical problem in terms of a stochastic counting process. The statistical properties depend only on the distance to a critical point, which is universal for any

Bohr model description of the critical point for the first order shape phase transition

Science.gov (United States)

Budaca, R.; Buganu, P.; Budaca, A. I.

2018-01-01

The critical point of the shape phase transition between spherical and axially deformed nuclei is described by a collective Bohr Hamiltonian with a sextic potential having simultaneous spherical and deformed minima of the same depth. The particular choice of the potential as well as the scaled and decoupled nature of the total Hamiltonian leads to a model with a single free parameter connected to the height of the barrier which separates the two minima. The solutions are found through the diagonalization in a basis of Bessel functions. The basis is optimized for each value of the free parameter by means of a boundary deformation which assures the convergence of the solutions for a fixed basis dimension. Analyzing the spectral properties of the model, as a function of the barrier height, revealed instances with shape coexisting features which are considered for detailed numerical applications.

Angular and magnetic field dependences of critical current in irradiated YBaCuO single crystals

International Nuclear Information System (INIS)

Petrusenko, Yu.

2010-01-01

The investigation of mechanisms responsible for the current-carrying capability of irradiated high-temperature superconductors (HTSC) was realized. For the purpose, experiments were made to investigate the effect of point defects generated by high-energy electron irradiation on the critical temperature and the critical current in high-Tc superconducting single crystals YBa 2 Cu 3 O 7-x . The transport current density measured in HTSC single crystals YBa 2 Cu 3 O 7-x by the dc-method was found to exceed 80000 A/cm 2 . The experiments have demonstrated a more than 30-fold increase in the critical current density in single crystals irradiated with 2.5 MeV electrons to a dose of 3·10 18 el/cm 2 . Detailed studies were made into the anisotropy of critical current and the dependence of critical current on the external magnetic field strength in irradiated single crystals. A high efficiency of point defects as centers of magnetic vortex pinning in HTSC single crystals was first demonstrated.

Data collapse and critical dynamics in neuronal avalanche data

Science.gov (United States)

Butler, Thomas; Friedman, Nir; Dahmen, Karin; Beggs, John; Deville, Lee; Ito, Shinya

2012-02-01

The tasks of information processing, computation, and response to stimuli require neural computation to be remarkably flexible and diverse. To optimally satisfy the demands of neural computation, neuronal networks have been hypothesized to operate near a non-equilibrium critical point. In spite of their importance for neural dynamics, experimental evidence for critical dynamics has been primarily limited to power law statistics that can also emerge from non-critical mechanisms. By tracking the firing of large numbers of synaptically connected cortical neurons and comparing the resulting data to the predictions of critical phenomena, we show that cortical tissues in vitro can function near criticality. Among the most striking predictions of critical dynamics is that the mean temporal profiles of avalanches of widely varying durations are quantitatively described by a single universal scaling function (data collapse). We show for the first time that this prediction is confirmed in neuronal networks. We also show that the data have three additional features predicted by critical phenomena: approximate power law distributions of avalanche sizes and durations, samples in subcritical and supercritical phases, and scaling laws between anomalous exponents.

Early warning of climate tipping points from critical slowing down: comparing methods to improve robustness

Science.gov (United States)

Lenton, T. M.; Livina, V. N.; Dakos, V.; Van Nes, E. H.; Scheffer, M.

2012-01-01

We address whether robust early warning signals can, in principle, be provided before a climate tipping point is reached, focusing on methods that seek to detect critical slowing down as a precursor of bifurcation. As a test bed, six previously analysed datasets are reconsidered, three palaeoclimate records approaching abrupt transitions at the end of the last ice age and three models of varying complexity forced through a collapse of the Atlantic thermohaline circulation. Approaches based on examining the lag-1 autocorrelation function or on detrended fluctuation analysis are applied together and compared. The effects of aggregating the data, detrending method, sliding window length and filtering bandwidth are examined. Robust indicators of critical slowing down are found prior to the abrupt warming event at the end of the Younger Dryas, but the indicators are less clear prior to the Bølling-Allerød warming, or glacial termination in Antarctica. Early warnings of thermohaline circulation collapse can be masked by inter-annual variability driven by atmospheric dynamics. However, rapidly decaying modes can be successfully filtered out by using a long bandwidth or by aggregating data. The two methods have complementary strengths and weaknesses and we recommend applying them together to improve the robustness of early warnings. PMID:22291229

In-vitro diagnostic devices introduction to current point-of-care diagnostic devices

CERN Document Server

Cheng, Chao-Min; Chen, Chien-Fu

2016-01-01

Addressing the origin, current status, and future development of point-of-care diagnostics, and serving to integrate knowledge and tools from Analytical Chemistry, Bioengineering, Biomaterials, and Nanotechnology, this book focusses on addressing the collective and combined needs of industry and academia (including medical schools) to effectively conduct interdisciplinary research. In addition to summarizing and detailing developed diagnostic devices, this book will attempt to point out the possible future trends of development for point-of-care diagnostics using both scientifically based research and practical engineering needs with the aim to help novices comprehensively understand the development of point-of-care diagnostics. This includes demonstrating several common but critical principles and mechanisms used in point-of-care diagnostics that address practical needs (e.g., disease or healthcare monitoring) using two well-developed examples so far: 1) blood glucose meters (via electrochemistry); and, 2) p...

Improved experimental determination of critical-point data for tungsten

International Nuclear Information System (INIS)

Fucke, W.; Seydel, U.

1980-01-01

It is shown that under certain conditions in resistive pulse-heating experiments, refractory liquid metals can be heated up to the limit of thermodynamic stability (spinodal) of the superheated liquid. Here, an explosion-like decomposition takes place which is directly monitored by measurements of expansion, surface radiation, and electric resistivity, thus allowing the determination of the temperature-pressure dependence of the spinodal transition. A comparison of the spinodal equation obtained this way with theoretical models yields the critical temperature Tsub(c), pressure psub(c), and volume vsub(c). A completely experimentally-determined set of the critical parameters for tungsten is presented: Tsub(c) = (13400 +- 1400) K, psub(c) = (3370 +- 850) bar, vsub(c) = (43 +- 4) cm 3 mol -1 . (author)

The Point Is to Change It! Introduction to Critical Political Interventions in Media and Communication Studies

Directory of Open Access Journals (Sweden)

Sašo Slaček Brlek

2017-03-01

Full Text Available The intention of this paper is to provide a historical overview and an introduction to the interviews with Bodgan Osolnik, Breda Pavlič, Cees Hamelink, Daya K. Thussu, Peter Golding and Dan Hind presented in this special section. Following Marx, we entitled the section The Point Is to Change It! Critical Political Interventions in Media and Communication Studies. We discuss the need for critical theory to bridge the divide between theory and practice because this notion is central to all of the interviews in one way or another. We also provide a historical contextualization of important theoretical as well as political developments in the 1970s and 1980s. This period may be seen as a watershed era for the critical political economy of communication and for the political articulation of demands for a widespread transformation and democratization in the form of the New World Information and Communication Order initiative. We believe that many contemporary issues have a long history, with their roots firmly based in this era. The historical perspective therefore cannot be seen as nostalgia, but as an attempt to understand the historical relations of power and how they have changed and shifted. In our view, the historical perspective is crucial not only for understanding long-lasting historical trends, but also to remind ourselves that the world is malleable, and to keep alive the promises of the progressive struggles of the past.

Introduction to the critical and multicritical phenomena

International Nuclear Information System (INIS)

Salinas, S.R.A.

1982-09-01

The behavior of matter in the neighborhood of simple critical points is treated. The concepts of critical exponents and universality is introduced and the classical theories of the critical behavior and the phenomenological scaling theories of the thermodynamic functions and the critical correlations are described. Finally, a description of the theory of the renormalization group, which gives the microscopic bases of the scaling laws is ended . Four types of multicritical points which have already been detected in solid crystals tricritical, bicritical, tetracritical, and Lifshitz points are studied. Landa's theory and the formulation of the scaling laws in the neighborhood of these points is described. Also, the main features of some theoretical models which produce multicritical points-the Ising metamagnet and BEG model, which exhibit tricritical points, and the ANNNI model, which exhibits a Lifshitz point are described. The renormalization group approach in the Fourier space to the Ising metamagnet, and the new techniques of partial differential aproximants to analyze the scaling behavior in the neighborhood of the multicritical points are presented. (Author) [pt

Critical composition fluctuations in artificial and cell-derived lipid membranes

Science.gov (United States)

Honerkamp-Smith, Aurelia

2014-03-01

Cell plasma membranes contain a mixture of lipid types which can segregate into coexisting liquids, a thermodynamic phenomenon which may contribute to biological functions. Simplified, artificial three-component lipid vesicles can be prepared which display a critical miscibility transition near room temperature. We found that such vesicles exhibit concentration fluctuations whose size, composition, and timescales vary consistently with critical exponents for two-dimensional conserved order parameter systems. However, the critical miscibility transition is also observed in vesicles formed directly from the membranes of living cells, despite their more complex composition and the presence of membrane proteins. I will describe our critical fluctuation measurements and also review a variety of more recent work by other researchers. Proximity to a critical point alters the spatial distribution and aggregation tendencies of proteins, and makes lipid mixtures more susceptible to domain formation by protein-mediated interactions, such as adhesion zones. Recent work suggests that critical temperature depression may also be relevant to the mechanism of anaesthetic action.

Mechanical Stimulation of the HT7 Acupuncture Point to Reduce Ethanol Self-Administration in Rats

Directory of Open Access Journals (Sweden)

Suk-Yun Kang

2017-01-01

Full Text Available Background. Alcoholism, which is a disabling addiction disorder, is a major public health problem worldwide. The present study was designed to determine whether the application of acupuncture at the Shenmen (HT7 point suppresses voluntary alcohol consumption in addicted rats and whether this suppressive effect is potentiated by the administration of naltrexone. Methods. Rats were initially trained to self-administer a sucrose solution by operating a lever. A mechanical acupuncture instrument (MAI for objective mechanical stimulation was used on rats whose baseline response had been determined. In addition, the effect of HT7 acupuncture on beta-endorphin concentration and ethanol intake via naltrexone were investigated in different groups. Results. We found that ethanol intake and beta-endorphin level in rats being treated with the MAI at the HT7 point reduced significantly. The treatment of naltrexone at high doses reduced the ethanol intake and low-dose injection of naltrexone in conjunction with the MAI also suppressed ethanol intake. Conclusions. The results of the current study indicate that using the MAI at the HT7 point effectively reduces ethanol consumption in rats. Furthermore, the coadministration of the MAI and a low dose of naltrexone can produce some more potent reducing effect of ethanol intake than can acupuncture alone.

CRITICAL INCIDENTS AND CRITICAL INCIDENT STRESS MANAGEMENT (CISM – AN EMPLOYEE ASSISTANCE PROGRAMME (EAP PERSPECTIVE

Directory of Open Access Journals (Sweden)

Terblanche, Lourie

2014-04-01

Full Text Available Employees are increasingly becoming victims of critical incidents. From a systems theory point of view, it is necessary to acknowledge the impact of critical incidents not only on the personal life of the employee, but on the workplace itself. Employees respond differently to critical incidents, which makes it even more complicated when this reaches the point of requiring therapeutic intervention. The most common response to critical incidents may be the risk of developing post-traumatic stress disorder (PTSD and/or depression. This reality requires management – through the Employee Assistance Programme (EAP – to be able to effectively deal with such critical incidents.

Critical N = (1, 1) general massive supergravity

Science.gov (United States)

Deger, Nihat Sadik; Moutsopoulos, George; Rosseel, Jan

2018-04-01

In this paper we study the supermultiplet structure of N = (1, 1) General Massive Supergravity at non-critical and critical points of its parameter space. To do this, we first linearize the theory around its maximally supersymmetric AdS3 vacuum and obtain the full linearized Lagrangian including fermionic terms. At generic values, linearized modes can be organized as two massless and 2 massive multiplets where supersymmetry relates them in the standard way. At critical points logarithmic modes appear and we find that in three of such points some of the supersymmetry transformations are non-invertible in logarithmic multiplets. However, in the fourth critical point, there is a massive logarithmic multiplet with invertible supersymmetry transformations.

CANDU pressure tube leak detection by annulus gas dew point measurement. A critical review

International Nuclear Information System (INIS)

Greening, F.R.

2017-01-01

In the event of a pressure tube leak from a small through-wall crack during CANDU reactor operations, there is a regulatory requirement - referred to as Leak Before Break (LBB) - for the licensee to demonstrate that there will be sufficient time for the leak to be detected and the reactor shut down before the crack grows to the critical size for fast-uncontrolled rupture. In all currently operating CANDU reactors, worldwide, this LBB requirement is met via continuous dew point measurements of the CO_2 gas circulating in the reactor's Annulus Gas System (AGS). In this paper the historical development and current status of this leak detection capability is reviewed and the use of moisture injection tests as a verification procedure is critiqued. It is concluded that these tests do not represent AGS conditions that are to be expected in the event of a real pressure tube leak.

Bohr model description of the critical point for the first order shape phase transition

Directory of Open Access Journals (Sweden)

R. Budaca

2018-01-01

Full Text Available The critical point of the shape phase transition between spherical and axially deformed nuclei is described by a collective Bohr Hamiltonian with a sextic potential having simultaneous spherical and deformed minima of the same depth. The particular choice of the potential as well as the scaled and decoupled nature of the total Hamiltonian leads to a model with a single free parameter connected to the height of the barrier which separates the two minima. The solutions are found through the diagonalization in a basis of Bessel functions. The basis is optimized for each value of the free parameter by means of a boundary deformation which assures the convergence of the solutions for a fixed basis dimension. Analyzing the spectral properties of the model, as a function of the barrier height, revealed instances with shape coexisting features which are considered for detailed numerical applications.

CANDU pressure tube leak detection by annulus gas dew point measurement. A critical review

Energy Technology Data Exchange (ETDEWEB)

Greening, F.R. [CTS-NA, Tiverton, ON (Canada)

2017-03-15

In the event of a pressure tube leak from a small through-wall crack during CANDU reactor operations, there is a regulatory requirement - referred to as Leak Before Break (LBB) - for the licensee to demonstrate that there will be sufficient time for the leak to be detected and the reactor shut down before the crack grows to the critical size for fast-uncontrolled rupture. In all currently operating CANDU reactors, worldwide, this LBB requirement is met via continuous dew point measurements of the CO{sub 2} gas circulating in the reactor's Annulus Gas System (AGS). In this paper the historical development and current status of this leak detection capability is reviewed and the use of moisture injection tests as a verification procedure is critiqued. It is concluded that these tests do not represent AGS conditions that are to be expected in the event of a real pressure tube leak.

Signals for the QCD phase transition and critical point in a Langevin dynamical model

International Nuclear Information System (INIS)

Herold, Christoph; Bleicher, Marcus; Yan, Yu-Peng

2013-01-01

The search for the critical point is one of the central issues that will be investigated in the upcoming FAIR project. For a profound theoretical understanding of the expected signals we go beyond thermodynamic studies and present a fully dynamical model for the chiral and deconfinement phase transition in heavy ion collisions. The corresponding order parameters are propagated by Langevin equations of motions on a thermal background provided by a fluid dynamically expanding plasma of quarks. By that we are able to describe nonequilibrium effects occurring during the rapid expansion of a hot fireball. For an evolution through the phase transition the formation of a supercooled phase and its subsequent decay crucially influence the trajectories in the phase diagram and lead to a significant reheating of the quark medium at highest baryon densities. Furthermore, we find inhomogeneous structures with high density domains along the first order transition line within single events.

The asymptotic behaviour of a critical point reactor in the absence of a controller

International Nuclear Information System (INIS)

Bansal, N.K.; Borgwaldt, H.

1976-11-01

A method is presented to calculate the first and second moments of neutron and precursor populations for a critical reactor system described by point kinetic equations and possessing inherent reactivity fluctuations. The equations have been linearised on the assumption that the system has a large average neutron population and that the amplitude of reactivity fluctuations is sufficiently small. The reactivity noise is assumed to be band limited white with a corner frequency higher than all the time constants of the system. Explicit expressions for the exact time development of the moments have been obtained for the case of a reactor without reactivity feedback and with one group of delayed neutrons. It is found that the expected values of the neutron and delayed neutron precursor numbers tend asymptotically to stationary values, whereas the mean square deviations increase linearly with time at an extremely low rate. (orig.) [de

Focal and Reentrant Mechanisms of Torsades de Pointes: EAD, Reentry, or Chimera?

Directory of Open Access Journals (Sweden)

Yuji Murakawa, MD

2011-01-01

Full Text Available Torsades de pointes (TdP. is characterized not only by its electrocardiographic morphology but also by a tendency to spontaneously terminate. Although clinical and experimental studies suggested that TdP is triggered exclusively by early afterdepolarization, the reentrant mechanism seems to play a certain role in its maintenance. In this article, I review the studies that investigated the origin and activation sequences of the twisting QRS complexes of TdP, and discuss whether it is fortunate or unfortunate for us if TdP has something to do with reentry.

Nematic quantum critical point without magnetism in FeSe1-xSx superconductors.

Science.gov (United States)

Hosoi, Suguru; Matsuura, Kohei; Ishida, Kousuke; Wang, Hao; Mizukami, Yuta; Watashige, Tatsuya; Kasahara, Shigeru; Matsuda, Yuji; Shibauchi, Takasada

2016-07-19

In most unconventional superconductors, the importance of antiferromagnetic fluctuations is widely acknowledged. In addition, cuprate and iron-pnictide high-temperature superconductors often exhibit unidirectional (nematic) electronic correlations, including stripe and orbital orders, whose fluctuations may also play a key role for electron pairing. In these materials, however, such nematic correlations are intertwined with antiferromagnetic or charge orders, preventing the identification of the essential role of nematic fluctuations. This calls for new materials having only nematicity without competing or coexisting orders. Here we report systematic elastoresistance measurements in FeSe1-xSx superconductors, which, unlike other iron-based families, exhibit an electronic nematic order without accompanying antiferromagnetic order. We find that the nematic transition temperature decreases with sulfur content x; whereas, the nematic fluctuations are strongly enhanced. Near [Formula: see text], the nematic susceptibility diverges toward absolute zero, revealing a nematic quantum critical point. The obtained phase diagram for the nematic and superconducting states highlights FeSe1-xSx as a unique nonmagnetic system suitable for studying the impact of nematicity on superconductivity.

Criticality in third order lovelock gravity and butterfly effect

International Nuclear Information System (INIS)

Qaemmaqami, Mohammad M.

2018-01-01

We study third order Lovelock Gravity in D = 7 at the critical point which three (A)dS vacua degenerate into one. We see there is not propagating graviton at the critical point. And also we compute the butterfly velocity for this theory at the critical point by considering the shock wave solutions near horizon, this is important to note that although there is no propagating graviton at the critical point, due to boundary gravitons the butterfly velocity is non-zero. Finally we observe that the butterfly velocity for third order Lovelock Gravity at the critical point in D = 7 is less than the butterfly velocity for Einstein-Gauss-Bonnet Gravity at the critical point in D = 7 which is less than the butterfly velocity in D = 7 for Einstein Gravity, v B E.H > v B E.G.B > v B 3rdLovelock . Maybe we can conclude that by adding higher order curvature corrections to Einstein Gravity the butterfly velocity decreases. (orig.)

Criticality in third order lovelock gravity and butterfly effect

Science.gov (United States)

Qaemmaqami, Mohammad M.

2018-01-01

We study third order Lovelock Gravity in D=7 at the critical point which three (A)dS vacua degenerate into one. We see there is not propagating graviton at the critical point. And also we compute the butterfly velocity for this theory at the critical point by considering the shock wave solutions near horizon, this is important to note that although there is no propagating graviton at the critical point, due to boundary gravitons the butterfly velocity is non-zero. Finally we observe that the butterfly velocity for third order Lovelock Gravity at the critical point in D=7 is less than the butterfly velocity for Einstein-Gauss-Bonnet Gravity at the critical point in D=7 which is less than the butterfly velocity in D = 7 for Einstein Gravity, vB^{E.H}>vB^{E.G.B}>vB^{3rd Lovelock} . Maybe we can conclude that by adding higher order curvature corrections to Einstein Gravity the butterfly velocity decreases.

Development and Qualification of an Antenna Pointing Mechanism for the ExoMars High-Gain Antenna

Science.gov (United States)

St-Andre, Stephane; Dumais, Marie-Christine; Lebel, Louis-Philippe; Langevin, Jean-Paul; Horth, Richard; Winton, Alistair; Lebleu, Denis

2015-09-01

The European Space Agency ExoMars 2016 mission required a gimbaled High Gain Antenna (HGA) for orbiter-to-earth communications. The ExoMars Program is a cooperative program between ESA and ROSCOSMOS with participation of NASA. The ExoMars Program industrial consortium is led by THALES ALENIA SPACE.This paper presents the design and qualification test results of the Antenna Pointing Mechanism (APM) used to point the HGA towards Earth. This electrically redundant APM includes motors, drive trains, optical encoders, cable cassette and RF Rotary Joints.Furthermore, the paper describes the design, development and the qualification approach applied to this APM. The design challenges include a wide pointing domain necessary to maximise the communication duty cycle during the early operation phase, the interplanetary cruise phase and during the mission’s orbital science phase. Other design drivers are an extended rotation cycle life with very low backlash yielding little wear and accurate position feedback on both axes. Major challenges and related areas of development include:• Large moments are induced on the APM due to aerobraking forces when the Mars atmosphere is used to slow the orbiter into its science mission orbit,• Thermal control of the critical components of the APM due to the different environments of the various phases of the mission. Also, the large travel range of the actuators complicated the radiator design in order to maintain clearances and to avoid overheating.• The APM, with a mass less than 17.5 kg, is exposed to a demanding dynamic environment due to its mounting on the spacecraft thrust tube and aggravated by its elevated location on the payload.• Power and Data transmission between elevation and azimuth axes through a compact large rotation range spiral type cable cassette.• Integration of a 16 bit redundant encoder on both axes for position feedback: Each encoder is installed on the back of a rotary actuator and is coupled using the

Lung protective mechanical ventilation strategies in cardiothoracic critical care: a retrospective study.

Science.gov (United States)

Zochios, Vasileios; Hague, Matthew; Giraud, Kimberly; Jones, Nicola

2016-01-01

A body of evidence supports the use of low tidal volumes in ventilated patients without lung pathology to slow progress to acute respiratory distress syndrome (ARDS) due to ventilator associated lung injury. We undertook a retrospective chart review and tested the hypothesis that tidal volume is a predictor of mortality in cardiothoracic (medical and surgical) critical care patients receiving invasive mechanical ventilation. Independent predictors of mortality in our study included: type of surgery, albumin, H + , bilirubin, and fluid balance. In particular, it is important to note that cardiac, thoracic, and transplant surgical patients were associated with lower mortality. However, our study did not sample equally from The Berlin Definition of ARDS severity categories (mild, moderate, and severe hypoxemia). Although our study was not adequately powered to detect a difference in mortality between these groups, it will inform the development of a large prospective cohort study exploring the role of low tidal volume ventilation in cardiothoracic critically ill patients.

Prevention of criticality accidents

International Nuclear Information System (INIS)

Canavese, S.I.

1982-01-01

These notes used in the postgraduate course on Radiological Protection and Nuclear Safety discuss macro-and microscopic nuclear constants for fissile materials systems. Critical systems: their definition; criteria to analyze the critical state; determination of the critical size; analysis of practical problems about prevention of criticality. Safety of isolated units and of sets of units. Application of standards. Conception of facilities from the criticality control view point. (author) [es

Critical sizes and critical characteristics of nanoclusters, nanostructures and nanomaterials

International Nuclear Information System (INIS)

Suzdalev, I.P.

2005-01-01

Full text: Critical sizes and characteristics of nanoclusters and nanostructures are introduced as the parameters of nanosystems and nanomaterials. The next critical characteristics are considered: atomic and electronic 'magic number', critical size of cluster nucleation, critical size of melting-freezing of cluster, critical size of quantum (laser) radiation, critical sizes for the single electron conductivity, critical energy and magnetic field for the magnetic tunneling, critical cluster sizes for the giant magnetic resistance, critical size of the first order magnetic phase transition. The critical characteristics are estimated by thermodynamic approaches, by Moessbauer spectroscopy, AFM, heat capacity, SQUID magnetometry and other technique, The influence of cluster-cluster interactions, cluster-matrix interactions and cluster defects on cluster atomic dynamics, cluster melting, cluster critical sizes, Curie or Neel points and the character of magnetic phase transitions were investigated. The applications of critical size and critical characteristic parameters for the nanomaterial characterization are considered

Field-Induced Quantum Critical Point and Nodal Superconductivity in the Heavy-Fermion Superconductor Ce_{2}PdIn_{8}

Directory of Open Access Journals (Sweden)

J. K. Dong

2011-09-01

Full Text Available The in-plane resistivity ρ and thermal conductivity κ of the heavy-fermion superconductor Ce_{2}PdIn_{8} single crystals were measured down to 50 mK. A field-induced quantum critical point, occurring at the upper critical field H_{c2}, is demonstrated from the ρ(T∼T near H_{c2} and ρ(T∼T^{2} when further increasing the field. The large residual linear term κ_{0}/T at zero field and the rapid increase of κ(H/T at low field give evidence for nodal superconductivity in Ce_{2}PdIn_{8}. The jump of κ(H/T near H_{c2} suggests a first-order-like phase transition at low temperature. These results mimic the features of the famous CeCoIn_{5} superconductor, implying that Ce_{2}PdIn_{8} may be another interesting compound to investigate for the interplay between magnetism and superconductivity.

On the critical frontiers of Potts ferromagnets

International Nuclear Information System (INIS)

Magalhaes, A.C.N. de; Tsallis, C.

1981-01-01

A conjecture concerning the critical frontiers of q- state Potts ferromagnets on d- dimensional lattices (d > 1) which generalize a recent one stated for planar lattices is formulated. The present conjecture is verified within satisfactory accuracy (exactly in some cases) for all the lattices or arrays whose critical points are known. Its use leads to the prediction of: a) a considerable amount of new approximate critical points (26 on non-planar regular lattices, some others on Husimi trees and cacti); b) approximate critical frontiers for some 3- dimensional lattices; c) the possibly asymptotically exact critical point on regular lattices in the limit d→infinite for all q>=1; d) the possibly exact critical frontier for the pure Potts model on fully anisotropic Bethe lattices; e) the possibly exact critical frontier for the general quenched random-bond Potts ferromagnet (any P(J)) on isotropic Bethe lattices. (Author) [pt

Reliability assessment of shut-off rod drive mechanism for TAPP - 3 and 4 and critical facility through life cycle testing

International Nuclear Information System (INIS)

Singh, Manjit; Badodkar, D.N.; Singh, N.K.; Dalal, N.S.; Mishra, M.K.; Veda Vyas, G.; Kothari, C.B.; Rao, V.V.S.S.; Saraf, R.K.

2006-01-01

Shut-off rod drive mechanism forms a safety critical system of a nuclear reactor. It is the space constraints for the given reactor layout, which makes design of shut-off rod drive mechanism (SRDM) a custom built design. Design of SRDM adopts fail-safe, replaceability and the simplicity criterion ensuring very high reliability of its operation. Shut-off rod drive mechanism for TAPP-3 and 4 and 'Critical Facility' have been recently designed and developed at Division of Remote Handling and Robotics (DRHR), BARC. These are designed with a number of advanced features and these are significantly different than those used in Dhruva and 220 MWe PHWRs. Design of SRDM is qualified through proto typing and life cycle testing on a full-scale test set-up. This paper gives details of qualification and life cycle test data for prototype SRDM for TAPP-3 and 4 and 'Critical Facility' and reliability assessment. (author)

Quantum mechanics interpretation: scalled debate

International Nuclear Information System (INIS)

Sanchez Gomez, J. L.

2000-01-01

This paper discusses the two main issues of the so called quantum debate, that started in 1927 with the famous Bohr-Einstein controversy; namely non-separability and the projection postulate. Relevant interpretations and formulations of quantum mechanics are critically analyzed in the light of the said issues. The treatment is focused chiefly on fundamental points, so that technical ones are practically not dealt with here. (Author) 20 refs

Revision of nucleated boiling mechanisms

International Nuclear Information System (INIS)

Converti, J.; Balino, J.L.

1987-01-01

The boiling occurrence plays an important role in the power reactors energy transfer. But still, there is not a final theory on the boiling mechanisms. This paper presents a critical analysis of the most important nucleated boiling models that appear in literature. The conflicting points are identified and experiments are proposed to clear them up. Some of these experiments have been performed at the Thermohydraulics laboratory (Bariloche Atomic Center). (Author)

Critical Point Facility (CPE) Group in the Spacelab Payload Operations Control Center (SL POCC)

Science.gov (United States)

1992-01-01

The primary payload for Space Shuttle Mission STS-42, launched January 22, 1992, was the International Microgravity Laboratory-1 (IML-1), a pressurized manned Spacelab module. The goal of IML-1 was to explore in depth the complex effects of weightlessness of living organisms and materials processing. Around-the-clock research was performed on the human nervous system's adaptation to low gravity and effects of microgravity on other life forms such as shrimp eggs, lentil seedlings, fruit fly eggs, and bacteria. Materials processing experiments were also conducted, including crystal growth from a variety of substances such as enzymes, mercury iodide, and a virus. The Huntsville Operations Support Center (HOSC) Spacelab Payload Operations Control Center (SL POCC) at the Marshall Space Flight Center (MSFC) was the air/ground communication channel used between the astronauts and ground control teams during the Spacelab missions. Featured is the Critical Point Facility (CPE) group in the SL POCC during STS-42, IML-1 mission.

Trigger mechanisms of secondary sclerosing cholangitis in critically ill patients.

Science.gov (United States)

Leonhardt, Silke; Veltzke-Schlieker, Wilfried; Adler, Andreas; Schott, Eckart; Hetzer, Roland; Schaffartzik, Walter; Tryba, Michael; Neuhaus, Peter; Seehofer, Daniel

2015-03-31

In recent years the development of secondary sclerosing cholangitis in critically ill patients (SSC-CIP) has increasingly been perceived as a separate disease entity. About possible trigger mechanisms of SSC-CIP has been speculated, systematic investigations on this issue are still lacking. The purpose of this study was to evaluate the prevalence and influence of promoting factors. Temporality, consistency and biological plausibility are essential prerequisites for causality. In this study, we investigated the temporality and consistency of possible triggers of SSC-CIP in a large case series. Biological plausibility of the individual triggers is discussed in a scientific context. SSC-CIP cases were recruited retrospectively from 2633 patients who underwent or were scheduled for liver transplantation at the University Hospital Charité, Berlin. All patients who developed secondary sclerosing cholangitis in association with intensive care treatment were included. Possible trigger factors during the course of the initial intensive care treatment were recorded. Sixteen patients (68% males, mean age 45.87 ± 14.64 years) with a confirmed diagnosis of SSC-CIP were identified. Of the 19 risk factors investigated, particularly severe hypotension with a prolonged decrease in mean arterial blood pressure (MAP) to <65 mmHg and systemic inflammatory response syndrome (SIRS) were established as possible triggers of SSC-CIP. The occurrence of severe hypotension appears to be the first and most significant step in the pathogenesis. It seems that severe hypotension has a critical effect on the blood supply of bile ducts when it occurs together with additional microcirculatory disturbances. In critically ill patients with newly acquired cholestasis the differential diagnosis of SSC-CIP should be considered when they have had an episode of haemodynamic instability with a prolonged decrease in MAP, initial need for large amounts of blood transfusions or colloids, and early

Risk analysis of hematopoietic stem cell transplant process: failure mode, effect, and criticality analysis and hazard analysis critical control point methods integration based on guidelines to good manufacturing practice for medicinal product ANNEX 20 (February 2008).

Science.gov (United States)

Gianassi, S; Bisin, S; Bindi, B; Spitaleri, I; Bambi, F

2010-01-01

The collection and handling of hematopoietic stem cells (HSCs) must meet high quality requirements. An integrated Quality Risk Management can help to identify and contain potential risks related to HSC production. Risk analysis techniques allow one to "weigh" identified hazards, considering the seriousness of their effects, frequency, and detectability, seeking to prevent the most harmful hazards. The Hazard Analysis Critical Point, recognized as the most appropriate technique to identify risks associated with physical, chemical, and biological hazards for cellular products, consists of classifying finished product specifications and limits of acceptability, identifying all off-specifications, defining activities that can cause them, and finally establishing both a monitoring system for each Critical Control Point and corrective actions for deviations. The severity of possible effects on patients, as well as the occurrence and detectability of critical parameters, are measured on quantitative scales (Risk Priority Number [RPN]). Risk analysis was performed with this technique on manipulation process of HPC performed at our blood center. The data analysis showed that hazards with higher values of RPN with greater impact on the process are loss of dose and tracking; technical skills of operators and manual transcription of data were the most critical parameters. Problems related to operator skills are handled by defining targeted training programs, while other critical parameters can be mitigated with the use of continuous control systems. The blood center management software was completed by a labeling system with forms designed to be in compliance with standards in force and by starting implementation of a cryopreservation management module. Copyright 2010 Elsevier Inc. All rights reserved.

Topological fluid mechanics of Axisymmetric Flow

DEFF Research Database (Denmark)

Brøns, Morten

1998-01-01

Topological fluid mechanics in the sense of the present paper is the study and classification of flow patterns close to a critical point. Here we discuss the topology of steady viscous incompressible axisymmetric flows in the vicinity of the axis. Following previous studies the velocity field v...... to the authors knowledge has not been used systematically to high orders in topological fluid mechanics. We compare the general results with experimental and computational results on the Vogel-Ronneberg flow. We show that the topology changes observed when recirculating bubbles on the vortex axis are created...

Chemical Dynamics and Critical Phenomena: Electrical Conductivity and Reactivity of Benzyl Bromide in Triethylamine+Water Near its Consolute Point

Science.gov (United States)

Specker, Christopher D.; Ellis, Joel M.; Baird, James K.

2007-06-01

The binary liquid mixture of triethylamine+water has a lower consolute point at a critical composition of 32.27mass% triethylamine. Starting at a temperature within the one-phase region, the electrical conductivity of a sample of this mixture was measured and found to increase smoothly with increasing temperature before falling sharply at 291.24K (18.09°C). Since opalescence was visible at this temperature, it was identified with the critical solution temperature of the binary mixture. A solution of 90 μL of benzyl bromide dissolved in 90mL of 32.27mass% triethylamine+water was prepared, and the resulting Menschutkin reaction between benzyl bromide and triethylamine was allowed to come to equilibrium. The electrical conductivity of this equilibrium mixture was measured in the one-phase region and was found to increase smoothly with increasing temperature before rising sharply at 291.55K (18.40°C). This temperature was identified as the critical temperature of the ternary. The rate of approach of the ternary mixture to chemical equilibrium was also measured and shown to be governed by a first-order rate law. The temperature dependence of the rate coefficient followed the Arrhenius equation up to a temperature of about 290.74K (17.59°C). Above this temperature, the rate coefficient fell by as much as 22% below the value predicted by extrapolation of the Arrhenius equation. This suppression in the rate reaction in the vicinity of the critical temperature can be interpreted as evidence for the existence of critical slowing down.

Use of the hazard analysis and critical control points (HACCP) risk assessment on a medical device for parenteral application.

Science.gov (United States)

Jahnke, Michael; Kühn, Klaus-Dieter

2003-01-01

In order to guarantee the consistently high quality of medical products for human use, it is absolutely necessary that flawless hygiene conditions are maintained by the strict observance of hygiene rules. With the growing understanding of the impact of process conditions on the quality of the resulting product, process controls (surveillance) have gained increasing importance to complete the quality profile traditionally defined by post-process product testing. Today, process controls have become an important GMP requirement for the pharmaceutical industry. However, before quality process controls can be introduced, the manufacturing process has to be analyzed, with the focus on its critical quality-influencing steps. The HACCP (Hazard Analysis and Critical Control Points) method is well recognized as a useful tool in the pharmaceutical industry. This risk analysis, following the guidelines of the HACCP method and the monitoring of critical steps during the manufacturing process was applied to the manufacture of methyl methacrylate solution used for bone cement and led to the establishment of a preventative monitoring system and constitutes an effective concept for quality assurance of hygiene and all other parameters influencing the quality of the product.

Pressure-induced unconventional superconductivity near a quantum critical point in CaFe2As2

International Nuclear Information System (INIS)

Kawasaki, S; Tabuchi, T; Zheng Guoqing; Wang, X F; Chen, X H

2010-01-01

75 As-zero-field nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements are performed on CaFe 2 As 2 under pressure. At P = 4.7 and 10.8 kbar, the temperature dependencies of nuclear-spin-lattice relaxation rate (1/T 1 ) measured in the tetragonal phase show no coherence peak just below T c (P) and decrease with decreasing temperature. The superconductivity is gapless at P = 4.7 kbar but evolves to that with multiple gaps at P = 10.8 kbar. We find that the superconductivity appears near a quantum critical point under pressures in the range 4.7 kbar ≤ P ≤ 10.8 kbar. Both electron correlation and superconductivity disappear in the collapsed tetragonal phase. A systematic study under pressure indicates that electron correlations play a vital role in forming Cooper pairs in this compound.

Criticality in third order lovelock gravity and butterfly effect

Energy Technology Data Exchange (ETDEWEB)

Qaemmaqami, Mohammad M. [Institute for Research in Fundamental Sciences (IPM), School of Particles and Accelerators, Tehran (Iran, Islamic Republic of)

2018-01-15

We study third order Lovelock Gravity in D = 7 at the critical point which three (A)dS vacua degenerate into one. We see there is not propagating graviton at the critical point. And also we compute the butterfly velocity for this theory at the critical point by considering the shock wave solutions near horizon, this is important to note that although there is no propagating graviton at the critical point, due to boundary gravitons the butterfly velocity is non-zero. Finally we observe that the butterfly velocity for third order Lovelock Gravity at the critical point in D = 7 is less than the butterfly velocity for Einstein-Gauss-Bonnet Gravity at the critical point in D = 7 which is less than the butterfly velocity in D = 7 for Einstein Gravity, v{sub B}{sup E.H} > v{sub B}{sup E.G.B} > v{sub B}{sup 3rdLovelock}. Maybe we can conclude that by adding higher order curvature corrections to Einstein Gravity the butterfly velocity decreases. (orig.)

A sensorless method for measuring the point mobility of mechanical structures

Science.gov (United States)

Boulandet, R.; Michau, M.; Herzog, P.; Micheau, P.; Berry, A.

2016-09-01

This paper presents a convenient and cost-effective experimental tool for measuring the mobility characteristics of a mechanical structure. The objective is to demonstrate that the point mobility measurement can be performed using only an electrodynamic inertial exciter. Unlike previous work based on voice coil actuators, no load cell or accelerometer is needed. Instead, it is theoretically shown that the mobility characteristics of the structure can be estimated from variations in the electrical input impedance of the actuator fixed onto it, provided that the electromechanical parameters of the actuator are known. The proof of concept is made experimentally using a cheap commercially available actuator on a simply supported plate, leading to a good dynamic range from 100 Hz to 1 kHz. The methodology to assess the basic parameters of the actuator is also given. Measured data are compared to a standard shaker testing and the strengths and weaknesses of the sensorless mobility measuring device are discussed. It is believed that this sensorless mobility measuring device can be a convenient experimental tool to determine the dynamic characteristics of a wide range of mechanical structures.

Management of critically ill patients receiving noninvasive and invasive mechanical ventilation in the emergency department

Directory of Open Access Journals (Sweden)

Rose L

2012-03-01

Full Text Available Louise RoseLawrence S Bloomberg Faculty of Nursing, University of Toronto, Toronto, Ontario, CanadaAbstract: Patients requiring noninvasive and invasive ventilation frequently present to emergency departments, and may remain for prolonged periods due to constrained critical care services. Emergency clinicians often do not receive the same education on management of mechanical ventilation or have similar exposure to these patients as do their critical care colleagues. The aim of this review was to synthesize the evidence on management of patients requiring noninvasive and invasive ventilation in the emergency department including indications, clinical applications, monitoring priorities, and potential complications. Noninvasive ventilation is recommended for patients with acute exacerbation of chronic obstructive pulmonary disease or cardiogenic pulmonary edema. Less evidence supports its use in asthma and other causes of acute respiratory failure. Use of noninvasive ventilation in the prehospital setting is relatively new, and some evidence suggests benefit. Monitoring priorities for noninvasive ventilation include response to treatment, respiratory and hemodynamic stability, noninvasive ventilation tolerance, detection of noninvasive ventilation failure, and identification of air leaks around the interface. Application of injurious ventilation increases patient morbidity and mortality. Lung-protective ventilation with low tidal volumes based on determination of predicted body weight and control of plateau pressure has been shown to reduce mortality in patients with acute respiratory distress syndrome, and some evidence exists to suggest this strategy should be used in patients without lung injury. Monitoring of the invasively ventilated patient should focus on assessing response to mechanical ventilation and other interventions, and avoiding complications, such as ventilator-associated pneumonia. Several key aspects of management of noninvasive

Some remarks concerning the equation of state near a critical point

International Nuclear Information System (INIS)

Lebrun, J.P.

1977-01-01

The thermodynamical scaling hypothesis is referred to in terms of SLsub(2,R) representations. The Josephson-Schofield proposal to avoid non-analyticity on the critical isotherm is shown to conflict with the Lebowitz-Penrose theorem in the one-phase region. One proposes to uniformize the critical region using e.g. Beltrami's equations and derives from the implicit function theorem a simple relation between the exponents (β, delta)

Demerit points systems.

NARCIS (Netherlands)

2006-01-01

In 2012, 21 of the 27 EU Member States had some form of demerit points system. In theory, demerit points systems contribute to road safety through three mechanisms: 1) prevention of unsafe behaviour through the risk of receiving penalty points, 2) selection and suspension of the most frequent

Dofetilide induced torsade de pointes: Mechanism, risk factors and management strategies

Directory of Open Access Journals (Sweden)

Abhishek Jaiswal

2014-11-01

Full Text Available Dofetilide is an effective antiarrhythmic agent for conversion of atrial fibrillation and atrial flutter as well as maintenance of sinus rhythm in appropriately selected patients. However, as with other antiarrhythmic agents, proarrhythmia is a known adverse effect. The risk of dofetilide induced torsade de pointes (Tdp is low when used with strict dosing criteria guided by renal function, QT interval and concomitant drug therapy. Benefit from dofetilide use must be individualized and weighed against the side effects and the role of other available treatment options. In this review, we discuss the underlying mechanism, risk factors and precautionary measures to avoid dofetilide induced QT prolongation and ventricular tachycardia/Tdp. We suggest a scheme for the management of QT prolongation, ventricular arrhythmia and Tdp as well.

Wave-particle duality and Bohr's complementarity principle in quantum mechanics

International Nuclear Information System (INIS)

Sen, D.; Basu, A.N.; Sengupta, S.

1995-01-01

Interest on Bohr's complementarity principle has recently been revived particularly because of several thought experiments and some actually performed experiments to test the validity of mutual exclusiveness of wave and particle properties. A critical review of the situation is undertaken and it is pointed out that the problem with mutual exclusiveness arises because of some vagueness in the conventional formulation. An attempt is made to remove this vagueness by connecting the origin of mutual exclusiveness to some principles of quantum mechanics. Accordingly, it becomes obvious that to contradict complementarity principle without contradicting quantum mechanics would be impossible. Some of the recent experiments are critically analysed. (author). 31 refs., 3 ills

Readiness to implement Hazard Analysis and Critical Control Point (HACCP) systems in Iowa schools.

Science.gov (United States)

Henroid, Daniel; Sneed, Jeannie

2004-02-01

To evaluate current food-handling practices, food safety prerequisite programs, and employee knowledge and food safety attitudes and provide baseline data for implementing Hazard Analysis and Critical Control Point (HACCP) systems in school foodservice. One member of the research team visited each school to observe food-handling practices and assess prerequisite programs using a structured observation form. A questionnaire was used to determine employees' attitudes, knowledge, and demographic information. A convenience sample of 40 Iowa schools was recruited with input from the Iowa Department of Education. Descriptive statistics were used to summarize data. One-way analysis of variance was used to assess differences in attitudes and food safety knowledge among managers, cooks, and other foodservice employees. Multiple linear regression assessed the relationship between manager and school district demographics and the food safety practice score. Proper food-handling practices were not being followed in many schools and prerequisite food safety programs for HACCP were found to be inadequate for many school foodservice operations. School foodservice employees were found to have a significant amount of food safety knowledge (15.9+/-2.4 out of 20 possible points). School districts with managers (P=.019) and employees (P=.030) who had a food handler certificate were found to have higher food safety practice scores. Emphasis on implementing prerequisite programs in preparation for HACCP is needed in school foodservice. Training programs, both basic food safety such as ServSafe and HACCP, will support improvement of food-handling practices and implementation of prerequisite programs and HACCP.

Intensively exploited Mediterranean aquifers: resilience and proximity to critical points of seawater intrusion

Science.gov (United States)

Mazi, K.; Koussis, A. D.; Destouni, G.

2013-11-01

We investigate here seawater intrusion in three prominent Mediterranean aquifers that are subject to intensive exploitation and modified hydrologic regimes by human activities: the Nile Delta Aquifer, the Israel Coastal Aquifer and the Cyprus Akrotiri Aquifer. Using a generalized analytical sharp-interface model, we review the salinization history and current status of these aquifers, and quantify their resilience/vulnerability to current and future sea intrusion forcings. We identify two different critical limits of sea intrusion under groundwater exploitation and/or climatic stress: a limit of well intrusion, at which intruded seawater reaches key locations of groundwater pumping, and a tipping point of complete sea intrusion upto the prevailing groundwater divide of a coastal aquifer. Either limit can be reached, and ultimately crossed, under intensive aquifer exploitation and/or climate-driven change. We show that sea intrusion vulnerability for different aquifer cases can be directly compared in terms of normalized intrusion performance curves. The site-specific assessments show that the advance of seawater currently seriously threatens the Nile Delta Aquifer and the Israel Coastal Aquifer. The Cyprus Akrotiri Aquifer is currently somewhat less threatened by increased seawater intrusion.

Wall shear stress fixed points in cardiovascular fluid mechanics.

Science.gov (United States)

Arzani, Amirhossein; Shadden, Shawn C

2018-05-17

Complex blood flow in large arteries creates rich wall shear stress (WSS) vectorial features. WSS acts as a link between blood flow dynamics and the biology of various cardiovascular diseases. WSS has been of great interest in a wide range of studies and has been the most popular measure to correlate blood flow to cardiovascular disease. Recent studies have emphasized different vectorial features of WSS. However, fixed points in the WSS vector field have not received much attention. A WSS fixed point is a point on the vessel wall where the WSS vector vanishes. In this article, WSS fixed points are classified and the aspects by which they could influence cardiovascular disease are reviewed. First, the connection between WSS fixed points and the flow topology away from the vessel wall is discussed. Second, the potential role of time-averaged WSS fixed points in biochemical mass transport is demonstrated using the recent concept of Lagrangian WSS structures. Finally, simple measures are proposed to quantify the exposure of the endothelial cells to WSS fixed points. Examples from various arterial flow applications are demonstrated. Copyright © 2018 Elsevier Ltd. All rights reserved.

Ablation threshold and ablation mechanism transition of polyoxymethylene irradiated by CO2 laser.

Science.gov (United States)

Li, Gan; Cheng, Mousen; Li, Xiaokang

2016-09-01

Polyoxymethylene (POM) decomposes gradually as it is heated up by the irradiation of CO2 laser; the long-chain molecules of POM are broken into short chains, which leads to the lowering of the melting point and the critical temperature of the ablation products. When the product temperature is above the melting point, ablation comes up in the way of vaporization; when the product temperature is higher than the critical temperature, all liquid products are transformed into gas instantly and the ablation mechanism is changed. The laser fluence at which significant ablation is observed is defined as the ablation threshold, and the fluence corresponding to the ablation mechanism changing is denoted as the flyover threshold. In this paper, random pyrolysis is adopted to describe the pyrolytic decomposition of POM, and consequently, the components of the pyrolysis products under different pyrolysis rates are acquired. The Group Contribution method is used to count the thermodynamic properties of the pyrolysis products, and the melting point and the critical temperature of the product mixture are obtained by the Mixing Law. The Knudsen layer relationship is employed to evaluate the ablation mass removal when the product temperature is below the critical temperature. The gas dynamics conservation laws associated with the Jouguet condition are used to calculate the mass removal when the product temperature is higher than the critical temperature. Based on the model, a set of simulations for various laser intensities and lengths are carried out to generalize the relationships between the thresholds and the laser parameters. Besides the ablated mass areal density, which fits the experimental data quite well, the ablation temperature, pyrolysis rate, and product components are also discussed for a better understanding of the ablation mechanism of POM.

Faraday instability in a near-critical fluid under weightlessness.

Science.gov (United States)

Gandikota, G; Chatain, D; Amiroudine, S; Lyubimova, T; Beysens, D

2014-01-01

Experiments on near-critical hydrogen have been conducted under magnetic compensation of gravity to investigate the Faraday instability that arises at the liquid-vapor interface under zero-gravity conditions. We investigated such instability in the absence of stabilizing gravity. Under such conditions, vibration orients the interface and can destabilize it. The experiments confirm the existence of Faraday waves and demonstrate a transition from a square to a line pattern close to the critical point. They also show a transition very close to the critical point from Faraday to periodic layering of the vapor-liquid interface perpendicular to vibration. It was seen that the Faraday wave instability is favored when the liquid-vapor density difference is large enough (fluid far from the critical point), whereas periodic layering predominates for small difference in the liquid and vapor densities (close to the critical point). It was observed for the Faraday wave instability that the wavelength of the instability decreases as one approaches the critical point. The experimental results demonstrate good agreement to the dispersion relation for zero gravity except for temperatures very close to the critical point where a transition from a square pattern to a line pattern is detected, similarly to what is observed under 1g conditions.

Critical dynamics

International Nuclear Information System (INIS)

Dekker, H.

1980-01-01

It is shown how to solve the master equation for a Markov process including a critical point by means of successive approximations in terms of a small parameter. A critical point occurs if, by adjusting an externally controlled quantity, the system shows a transition from normal monostable to bistable behaviour. The fundamental idea of the theory is to separate the master equation into its proper irreducible part and a corrective remainder. The irreducible or zeroth order stochastic approximation will be a relatively simple Fokker-Planck equation that contains the essential features of the process. Once the solution of this irreducible equation is known, the higher order corrections in the original master equation can be incorporated in a systematic manner. (Auth.)

Dynamics of quantum discord in a quantum critical environment

International Nuclear Information System (INIS)

Xi Zhengjun; Li Yongming; Lu Xiaoming; Sun Zhe

2011-01-01

We study the dynamics of quantum discord (QD) of two qubits independently coupled to an Ising spin chain in a transverse field, which exhibits a quantum phase transition. For this model, we drive the corresponding Kraus operators, obtain the analytic results of QD and compare the dynamics of QD with the dynamics of relative entropy of entanglement nearby the critical point. It is shown that the impact of the quantum criticality environment on QD can be concentrated in a very narrow region nearby the critical point, so it supplies an efficient way to detect the critical points. In the vicinity of the critical point, the evolution of QD is shown to be more complicated than that of entanglement. Furthermore, we find that separable states can also be used to reflect the quantum criticality of the environment.

Highly precise (liquid + liquid) equilibrium and heat capacity measurements near the critical point for [Bmim][BF4] + 1H, 1H, 2H, 2H perfluoroctanol

International Nuclear Information System (INIS)

Pérez-Sánchez, G.; Troncoso, J.; Losada-Pérez, P.; Méndez-Castro, P.; Romaní, L.

2013-01-01

Highlights: • Highly precise liquid–liquid curves for [Bmim][BF 4 ] + perfluoroctanol are reported. • Critical behavior of heat capacity for the same system was also characterized. • In contrast to previous results, no coulombic/solvophobic crossover for coexistence curve diameter was found. • The system criticality shows characteristics both solvophobic and coulombic. -- Abstract: Liquid + liquid equilibrium of the system [Bmim][BF 4 ] + 1H, 1H, 2H, 2H perfluoroctanol using a highly precise methodology based on refractive index measurements was experimentally determined. In addition, isobaric heat capacity near the critical point was obtained. The performance of the new refractive index set-up was successfully checked against the coexistence curve of the system dimethyl carbonate + decane, since highly accurate data are available in the literature. The choice of [Bmim][BF 4 ] + 1H, 1H, 2H, 2H perfluoroctanol was motivated by a previous experimental work, whose results suggest that this system could present characteristics of both solvophobic and coulombic behavior, which are the two categories to which an ionic system can belong. Although this was previously observed for other ionic systems, this mixture presented a very striking feature: the diameter of the coexistence curve seemed to change its criticality in the studied temperature range, from solvophobic far away to coulombic close to the critical point. The results of this work reveal that, in fact, [Bmim][BF 4 ] + 1H, 1H, 2H, 2H perfluoroctanol presents characteristics of both solvophobic and coulombic criticality, but no evidence of the observed crossover over the experimental temperature range has been found

Hazard analysis and critical control points among Chinese food business operators

OpenAIRE

Stefano Saccares; Paolo Amadei; Gianfranco Masotti; Roberto Condoleo; Alessandra Guidi

2014-01-01

The purpose of the present paper is to highlight some critical situations emerged during the implementation of long-term projects locally managed by Prevention Services, to control some manufacturing companies in Rome and Prato, Central Italy. In particular, some critical issues on the application of self-control in marketing and catering held by Chinese operators are underlined. The study showed serious flaws in preparing and controlling of manuals for good hygiene practice, participating of...

Bulk and interfacial molecular structure near liquid-liquid critical points

Energy Technology Data Exchange (ETDEWEB)

Manzanares-Papayanopoulos, Emilio

2000-09-01

Critical behaviour occurs when two coexisting phases merge identity without abrupt change in physical properties. The detail of this behaviour is nowadays considered universal, being dominated by the divergence of the correlation length {xi}. Following this universality, the detailed behaviour can be studied experimentally using any convenient system. For that reason, the study of fluids, and in particular fluid mixtures, offers a useful platform since critical behaviour in such systems can often be studied at convenient temperatures and pressures. Although criticality is a consequence of the divergence of {xi}, and so in a sense is a large-scale phenomenon, nevertheless it has an influence on events at molecular level. This aspect of criticality has received relatively little study compared to the enormous effort expended over the past thirty years in elucidating the macroscopic or phenomenological aspects of criticality. The signature of criticality at molecular level is the central theme running through this research.The aim of the work described in this thesis was to investigate the surface and transport properties of near-critical binary liquid mixtures. The surface properties mainly concerned the adsorption and wetting behaviour at the vapour-liquid and liquid-solid interfaces. The transport property studied was the shear viscosity at bulk or macroscopic level and the corresponding property at molecular or microscopic level, the micro viscosity. The work presented in this thesis comprises the experimental measurements and the theoretical interpretations drawn from the results. The experimental work was varied, using both classical and modern techniques. The theoretical interpretation was used as directed towards validating and comparing the results of the experimental programme with the predictions of the current classical critical-state theories. The systems investigated have been mostly alkane + perfluoroalkane mixtures or mixtures with very similar

Onset of deconfinement and search for the critical point of strongly interacting matter at CERN SPS energies

CERN Document Server

Rybczyński, Maciej

2014-01-01

The exploration of the QCD phase diagram particularly the search for a phase transition from hadronic to partonic degrees of freedom and possibly a critical endpoint, is one of the most challenging tasks in present heavy-ion physics. As observed by the NA49 experiment, several hadronic observables in central Pb+Pb collisions at the CERN SPS show qualitative changes in their energy dependence. These features are not observed in elementary interactions and indi- cate the onset of a phase transition in the SPS energy range. The existence of a critical point is expected to result in the increase of event-by-event fluctuations of various hadronic observables provided that the freeze-out of the measured hadrons occurs close to its location in the phase di- agram and the evolution of the final hadron phase does not erase the fluctuations signals. Further information about the existence and nature of a phase transition in the SPS energy range can be gained from the studies of event-by-event fluctuations of final stat...

Hematopoietic transcriptional mechanisms: from locus-specific to genome-wide vantage points.

Science.gov (United States)

DeVilbiss, Andrew W; Sanalkumar, Rajendran; Johnson, Kirby D; Keles, Sunduz; Bresnick, Emery H

2014-08-01

Hematopoiesis is an exquisitely regulated process in which stem cells in the developing embryo and the adult generate progenitor cells that give rise to all blood lineages. Master regulatory transcription factors control hematopoiesis by integrating signals from the microenvironment and dynamically establishing and maintaining genetic networks. One of the most rudimentary aspects of cell type-specific transcription factor function, how they occupy a highly restricted cohort of cis-elements in chromatin, remains poorly understood. Transformative technologic advances involving the coupling of next-generation DNA sequencing technology with the chromatin immunoprecipitation assay (ChIP-seq) have enabled genome-wide mapping of factor occupancy patterns. However, formidable problems remain; notably, ChIP-seq analysis yields hundreds to thousands of chromatin sites occupied by a given transcription factor, and only a fraction of the sites appear to be endowed with critical, non-redundant function. It has become en vogue to map transcription factor occupancy patterns genome-wide, while using powerful statistical tools to establish correlations to inform biology and mechanisms. With the advent of revolutionary genome editing technologies, one can now reach beyond correlations to conduct definitive hypothesis testing. This review focuses on key discoveries that have emerged during the path from single loci to genome-wide analyses, specifically in the context of hematopoietic transcriptional mechanisms. Copyright © 2014 ISEH - International Society for Experimental Hematology. Published by Elsevier Inc. All rights reserved.

Exceptional points near first- and second-order quantum phase transitions.

Science.gov (United States)

Stránský, Pavel; Dvořák, Martin; Cejnar, Pavel

2018-01-01

We study the impact of quantum phase transitions (QPTs) on the distribution of exceptional points (EPs) of the Hamiltonian in the complex-extended parameter domain. Analyzing first- and second-order QPTs in the Lipkin-Meshkov-Glick model we find an exponentially and polynomially close approach of EPs to the respective critical point with increasing size of the system. If the critical Hamiltonian is subject to random perturbations of various kinds, the averaged distribution of EPs close to the critical point still carries decisive information on the QPT type. We therefore claim that properties of the EP distribution represent a parametrization-independent signature of criticality in quantum systems.

Correlation of dew- and bubble-point curves for binary refrigerant mixtures. [Correlation between dew-point pressure(saturated vapor state) and bubble-point pressure(saturated liquid state)]. Niseibunkei kongo reibai no roten oyobi futten kyokusen no sokan

Energy Technology Data Exchange (ETDEWEB)

Yada, N. (Kanagawa Institute of Technology, Kanagawa (Japan)); Watanabe, K. (Keio University, Tokyo (Japan). Faculty of Science and Technology)

1991-12-25

The paper makes a correlation expressing dew- and bubble-point curves using measured values for seven binary refrigerant freon-mixtures. In most binary systems at the same temperature, the pressure shows a different value between in a saturated vapor state (dew-point pressure) and in a saturated liquid state (bubble-point pressure). The target is such correlation as has as simple a function form as possible and is able to estimate even near the critical point where it used to be difficult to estimate. The pressure difference between measured values of the dew- and bubble-point pressure and values calculated from Raoult's law showing an ideal mixture of fluid is expressed by a simple function form of reduced temperature Tr and molar fraction. Tr is thermodynamic temperature/critical temperature. Reproducibility of this correlation is less than {plus minus}3% of the pressure deviation. Concerning also the arbitary composition range and near the critical point, the dew- and bubble-point pressure can be calculated accurately. 24 refs., 4 figs., 5 tabs.

Surface Damage Mechanism of Monocrystalline Si Under Mechanical Loading

Science.gov (United States)

Zhao, Qingliang; Zhang, Quanli; To, Suet; Guo, Bing

2017-03-01

Single-point diamond scratching and nanoindentation on monocrystalline silicon wafer were performed to investigate the surface damage mechanism of Si under the contact loading. The results showed that three typical stages of material removal appeared during dynamic scratching, and a chemical reaction of Si with the diamond indenter and oxygen occurred under the high temperature. In addition, the Raman spectra of the various points in the scratching groove indicated that the Si-I to β-Sn structure (Si-II) and the following β-Sn structure (Si-II) to amorphous Si transformation appeared under the rapid loading/unloading condition of the diamond grit, and the volume change induced by the phase transformation resulted in a critical depth (ductile-brittle transition) of cut (˜60 nm ± 15 nm) much lower than the theoretical calculated results (˜387 nm). Moreover, it also led to abnormal load-displacement curves in the nanoindentation tests, resulting in the appearance of elbow and pop-out effects (˜270 nm at 20 s, 50 mN), which were highly dependent on the loading/unloading conditions. In summary, phase transformation of Si promoted surface deformation and fracture under both static and dynamic mechanical loading.

HYGIENE PRACTICES IN URBAN RESTAURANTS AND CHALLENGES TO IMPLEMENTING FOOD SAFETY AND HAZARD ANALYSIS CRITICAL CONTROL POINTS (HACCP) PROGRAMMES IN THIKA TOWN, KENYA.

Science.gov (United States)

Muinde, R K; Kiinyukia, C; Rombo, G O; Muoki, M A

2012-12-01

To determine the microbial load in food, examination of safety measures and possibility of implementing an Hazard Analysis Critical Control Points (HACCP) system. The target population for this study consisted of restaurants owners in Thika. Municipality (n = 30). Simple randomsamples of restaurantswere selected on a systematic sampling method of microbial analysis in cooked, non-cooked, raw food and water sanitation in the selected restaurants. Two hundred and ninety eight restaurants within Thika Municipality were selected. Of these, 30 were sampled for microbiological testing. From the study, 221 (74%) of the restaurants were ready to eat establishments where food was prepared early enough to hold and only 77(26%) of the total restaurants, customers made an order of food they wanted. 118(63%) of the restaurant operators/staff had knowledge on quality control on food safety measures, 24 (8%) of the restaurants applied these knowledge while 256 (86%) of the restaurants staff showed that food contains ingredients that were hazard if poorly handled. 238 (80%) of the resultants used weighing and sorting of food materials, 45 (15%) used preservation methods and the rest used dry foods as critical control points on food safety measures. The study showed that there was need for implementation of Hazard Analysis Critical Control Points (HACCP) system to enhance food safety. Knowledge of HACCP was very low with 89 (30%) of the restaurants applying some of quality measures to the food production process systems. There was contamination with Coliforms, Escherichia coli and Staphylococcus aureus microbial though at very low level. The means of Coliforms, Escherichia coli and Staphylococcus aureas microbial in sampled food were 9.7 x 103CFU/gm, 8.2 x 103 CFU/gm and 5.4 x 103 CFU/gm respectively with Coliforms taking the highest mean.

Critical behavior and duality in extended Sine-Gordon theories

International Nuclear Information System (INIS)

Boyanovsky, D.; Holman, R.

1991-01-01

We study the critical properties of vectorial sine-Gordon theories based on the root system of simply-laced Lie algebras. We introduce the dual operators and study the renormalization aspects of these theories. These models are identified with vectorial Coulomb gas models of electric and magnetic charges and generalized Toda field theories. We prove that these theories are consistently renormalizable for simply-laced Lie algebras, but non-renormalizable in general in the non-simply-laced case. These models provide a description for the statistical mechanics of melting in the SU(3) case. They also provide a simplified model for strings compactified on root lattices. We compute the RG beta functions to quadratic order for general simply-laced algebras and find that in general there is a Weyl singlet, self-dual fixed point. This fixed point describes a critical theory with condensates of electric and magnetic charges corresponding to tachyonic and winding modes in string language. The different phases are related by Weyl and duality symmetry. The phase structure is conjectured in the general case, and analyzed in detail for SU(3) and SO(6). We compute Zamolodchikov's c-function to cubic order in the couplings in the general case and the conformal anomaly at the self-dual fixed point for SU(N). (orig.)

Two-dimensional critical phenomena

International Nuclear Information System (INIS)

Saleur, H.

1987-09-01

Two dimensional critical systems are studied using transformation to free fields and conformal invariance methods. The relations between the two approaches are also studied. The analytical results obtained generally depend on universality hypotheses or on renormalization group trajectories which are not established rigorously, so numerical verifications, mainly using the transfer matrix approach, are presented. The exact determination of critical exponents; the partition functions of critical models on toruses; and results as the critical point is approached are discussed [fr

The mechanism of uranium adsorption on Resin 508 and isoelectric point of the resin

International Nuclear Information System (INIS)

Han Qingping; Lu Weichang; Su Huijuan; Hu Jinbo; Zhang Liqin; Chen Banglin

1990-01-01

The adsorption process of uranium by Resin 508 at the solid-liquid interface was investigated and the mechanism of uranium adsorption including adsorption dynamics, adsorption thermodynamics and isoelectric point of resin was studied. The results are as follows: The maximum of uranium adsorption is attained at pH5-7; Uranium adsorption isotherm by Resin 508 in experimental conditions agrees with Langmuir's adsorption isotherm, the maximum of uranium adsorbed (Vm) is 716 mg U/g-dried resin; The adsorption of uranium by Resin 508 is an endothermic reaction and ΔH = 16.87 kJ/mol; The exchange-adsorption rate is mainly controlled by liquid film diffusion; The isoelectric points of Resin 508 before and after uranium adsorption are found to be pH7.5 and pH5.7 respectively. It is a specific adsorption for uranium

Osmotic actuation for microfluidic components in point-of-care applications

KAUST Repository

Chen, Yu-Chih

2013-01-01

We present a novel design of micropumps and valves driven by osmotic force for point-of-care applications. Although there have been significant progresses in microfluidic components and control devices such as fluidic diodes, switches, resonators and digital-to-analog converters, the ultimate power source still depends on bulky off-chip components, which are expensive and cannot be easily miniaturized. For point-of-care applications, it is critical to integrate all the components in a compact size at low cost. In this work, we report two key active components actuated by osmotic mechanism for total integrated microfluidic system. For the proof of concept, we have demonstrated valve actuation, which can maintain stable ON/OFF switching operations under 125 kPa back pressure. We have also implemented an osmotic pump, which can pump a high flow rate over 30 μL/min for longer than 30 minutes. The experimental data demonstrates the possibility and potential of applying osmotic actuation in point-of-care disposable microfluidics. © 2013 IEEE.

The effect of point mutations on structure and mechanical properties of collagen-like fibril: A molecular dynamics study

International Nuclear Information System (INIS)

Marlowe, Ashley E.; Singh, Abhishek; Yingling, Yaroslava G.

2012-01-01

Understanding sequence dependent mechanical and structural properties of collagen fibrils is important for the development of artificial biomaterials for medical and nanotechnological applications. Moreover, point mutations are behind many collagen associated diseases, including Osteogenesis Imperfecta (OI). We conducted a combination of classical and steered atomistic molecular dynamics simulations to examine the effect of point mutations on structure and mechanical properties of short collagen fibrils which include mutations of glycine to alanine, aspartic acid, cysteine, and serine or mutations of hydroxyproline to arginine, asparagine, glutamine, and lysine. We found that all mutations disrupt structure and reduce strength of the collagen fibrils, which may affect the hierarchical packing of the fibrils. The glycine mutations were more detrimental to mechanical strength of the fibrils (WT > Ala > Ser > Cys > Asp) than that of hydroxyproline (WT > Arg > Gln > Asn > Lys). The clinical outcome for glycine mutations agrees well with the trend in reduction of fibril's tensile strength predicted by our simulations. Overall, our results suggest that the reduction in mechanical properties of collagen fibrils may be used to predict the clinical outcome of mutations. Highlights: ► All mutations disrupt structure and bonding pattern and reduce strength of the collagen fibrils. ► Gly based mutations are worst to mechanical integrity of fibrils than that of Hyp. ► Lys and Arg mutations most dramatically destabilize collagen fibril properties. ► Clinical outcome of mutations may be related to the reduced mechanical properties of fibrils.

Critical dynamics in population vaccinating behavior.

Science.gov (United States)

Pananos, A Demetri; Bury, Thomas M; Wang, Clara; Schonfeld, Justin; Mohanty, Sharada P; Nyhan, Brendan; Salathé, Marcel; Bauch, Chris T

2017-12-26

Vaccine refusal can lead to renewed outbreaks of previously eliminated diseases and even delay global eradication. Vaccinating decisions exemplify a complex, coupled system where vaccinating behavior and disease dynamics influence one another. Such systems often exhibit critical phenomena-special dynamics close to a tipping point leading to a new dynamical regime. For instance, critical slowing down (declining rate of recovery from small perturbations) may emerge as a tipping point is approached. Here, we collected and geocoded tweets about measles-mumps-rubella vaccine and classified their sentiment using machine-learning algorithms. We also extracted data on measles-related Google searches. We find critical slowing down in the data at the level of California and the United States in the years before and after the 2014-2015 Disneyland, California measles outbreak. Critical slowing down starts growing appreciably several years before the Disneyland outbreak as vaccine uptake declines and the population approaches the tipping point. However, due to the adaptive nature of coupled behavior-disease systems, the population responds to the outbreak by moving away from the tipping point, causing "critical speeding up" whereby resilience to perturbations increases. A mathematical model of measles transmission and vaccine sentiment predicts the same qualitative patterns in the neighborhood of a tipping point to greatly reduced vaccine uptake and large epidemics. These results support the hypothesis that population vaccinating behavior near the disease elimination threshold is a critical phenomenon. Developing new analytical tools to detect these patterns in digital social data might help us identify populations at heightened risk of widespread vaccine refusal. Copyright © 2017 the Author(s). Published by PNAS.

Criticality meets learning: Criticality signatures in a self-organizing recurrent neural network.

Science.gov (United States)

Del Papa, Bruno; Priesemann, Viola; Triesch, Jochen

2017-01-01

Many experiments have suggested that the brain operates close to a critical state, based on signatures of criticality such as power-law distributed neuronal avalanches. In neural network models, criticality is a dynamical state that maximizes information processing capacities, e.g. sensitivity to input, dynamical range and storage capacity, which makes it a favorable candidate state for brain function. Although models that self-organize towards a critical state have been proposed, the relation between criticality signatures and learning is still unclear. Here, we investigate signatures of criticality in a self-organizing recurrent neural network (SORN). Investigating criticality in the SORN is of particular interest because it has not been developed to show criticality. Instead, the SORN has been shown to exhibit spatio-temporal pattern learning through a combination of neural plasticity mechanisms and it reproduces a number of biological findings on neural variability and the statistics and fluctuations of synaptic efficacies. We show that, after a transient, the SORN spontaneously self-organizes into a dynamical state that shows criticality signatures comparable to those found in experiments. The plasticity mechanisms are necessary to attain that dynamical state, but not to maintain it. Furthermore, onset of external input transiently changes the slope of the avalanche distributions - matching recent experimental findings. Interestingly, the membrane noise level necessary for the occurrence of the criticality signatures reduces the model's performance in simple learning tasks. Overall, our work shows that the biologically inspired plasticity and homeostasis mechanisms responsible for the SORN's spatio-temporal learning abilities can give rise to criticality signatures in its activity when driven by random input, but these break down under the structured input of short repeating sequences.

Photoacoustic Point Source

International Nuclear Information System (INIS)

Calasso, Irio G.; Craig, Walter; Diebold, Gerald J.

2001-01-01

We investigate the photoacoustic effect generated by heat deposition at a point in space in an inviscid fluid. Delta-function and long Gaussian optical pulses are used as sources in the wave equation for the displacement potential to determine the fluid motion. The linear sound-generation mechanism gives bipolar photoacoustic waves, whereas the nonlinear mechanism produces asymmetric tripolar waves. The salient features of the photoacoustic point source are that rapid heat deposition and nonlinear thermal expansion dominate the production of ultrasound

Changing the Culture of Academic Medicine: Critical Mass or Critical Actors?

Science.gov (United States)

Helitzer, Deborah L; Newbill, Sharon L; Cardinali, Gina; Morahan, Page S; Chang, Shine; Magrane, Diane

2017-05-01

By 2006, women constituted 34% of academic medical faculty, reaching a critical mass. Theoretically, with critical mass, culture and policy supportive of gender equity should be evident. We explore whether having a critical mass of women transforms institutional culture and organizational change. Career development program participants were interviewed to elucidate their experiences in academic health centers (AHCs). Focus group discussions were held with institutional leaders to explore their perceptions about contemporary challenges related to gender and leadership. Content analysis of both data sources revealed points of convergence. Findings were interpreted using the theory of critical mass. Two nested domains emerged: the individual domain included the rewards and personal satisfaction of meaningful work, personal agency, tensions between cultural expectations of family and academic roles, and women's efforts to work for gender equity. The institutional domain depicted the sociocultural environment of AHCs that shaped women's experience, both personally and professionally, lack of institutional strategies to engage women in organizational initiatives, and the influence of one leader on women's ascent to leadership. The predominant evidence from this research demonstrates that the institutional barriers and sociocultural environment continue to be formidable obstacles confronting women, stalling the transformational effects expected from achieving a critical mass of women faculty. We conclude that the promise of critical mass as a turning point for women should be abandoned in favor of "critical actor" leaders, both women and men, who individually and collectively have the commitment and power to create gender-equitable cultures in AHCs.

Photoinduced second harmonic generation of LaFe4Sb12near spin fluctuated critical points

International Nuclear Information System (INIS)

Nouneh, K.; Viennois, R.; Kityk, I.V.; Terki, F.; Charar, S.; Benet, S.; Paschen, S.

2004-01-01

The temperature dependence of the resistivity, the Seebeck coefficient and photoinduced second harmonic generation (PISHG) are studied near the quantum critical point in the skutterudite compound LaFe 4 Sb 12 , possessing increased spin fluctuations. We observed a large maximum of the PISHG at a temperature of about 15 K. The PISHG signal increases substantially below 35 K. We found a correlation between the temperature dependences of PISHG, resistivity and Seebeck coefficient. We proposed a phenomenological explanation for the occurrence of the PISHG signal in LaFe 4 Sb 12 implying strong spin fluctuations exist in this system, which may present some interest for the study of other spin fluctuation systems. Physical insight into the phenomenon observed is grounded in the participation of anharmonic electron-phonon and electron-paramagnon interactions stimulated by inducing light in the interactions with the photoexcited dipole moments. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Condensation of Methane in the Metal-Organic Framework IRMOF-1: Evidence for Two Critical Points.

Science.gov (United States)

Höft, Nicolas; Horbach, Jürgen

2015-08-19

Extensive grand canonical Monte Carlo simulations in combination with successive umbrella sampling are used to investigate the condensation of methane in the nanoporous crystalline material IRMOF-1. Two different types of novel condensation transitions are found, each of them ending in a critical point: (i) a fluid-fluid transition at higher densities (the analog of the liquid-gas transition in the bulk) and (ii) a phase transition at low densities on the surface of the IRMOF-1 structure. The nature of these transitions is different from the usual capillary condensation in thin films and cylindrical pores where the coexisting phases are confined in one or two of the three spatial dimensions. In contrast to that, in IRMOF-1 the different phases can be described as bulk phases that are inhomogeneous due to the presence of the metal-organic framework. As a consequence, the condensation transitions in IRMOF-1 belong to the three-dimensional (3D) Ising universality class.

New Type of Quantum Criticality in the Pyrochlore Iridates

Directory of Open Access Journals (Sweden)

Lucile Savary

2014-11-01

Full Text Available Magnetic fluctuations and electrons couple in intriguing ways in the vicinity of zero-temperature phase transitions—quantum critical points—in conducting materials. Quantum criticality is implicated in non-Fermi liquid behavior of diverse materials and in the formation of unconventional superconductors. Here, we uncover an entirely new type of quantum critical point describing the onset of antiferromagnetism in a nodal semimetal engendered by the combination of strong spin-orbit coupling and electron correlations, and which is predicted to occur in the iridium oxide pyrochlores. We formulate and solve a field theory for this quantum critical point by renormalization group techniques and show that electrons and antiferromagnetic fluctuations are strongly coupled and that both these excitations are modified in an essential way. This quantum critical point has many novel features, including strong emergent spatial anisotropy, a vital role for Coulomb interactions, and highly unconventional critical exponents. Our theory motivates and informs experiments on pyrochlore iridates and constitutes a singular realistic example of a nontrivial quantum critical point with gapless fermions in three dimensions.

The Point Mass Concept

Directory of Open Access Journals (Sweden)

Lehnert B.

2011-04-01

Full Text Available A point-mass concept has been elaborated from the equations of the gravitational field. One application of these deductions results in a black hole configuration of the Schwarzschild type, having no electric charge and no angular momentum. The critical mass of a gravitational collapse with respect to the nuclear binding energy is found to be in the range of 0.4 to 90 solar masses. A second application is connected with the spec- ulation about an extended symmetric law of gravitation, based on the options of positive and negative mass for a particle at given positive energy. This would make masses of equal polarity attract each other, while masses of opposite polarity repel each other. Matter and antimatter are further proposed to be associated with the states of positive and negative mass. Under fully symmetric conditions this could provide a mechanism for the separation of antimatter from matter at an early stage of the universe.

The Point Mass Concept

Directory of Open Access Journals (Sweden)

Lehnert B.

2011-04-01

Full Text Available A point-mass concept has been elaborated from the equations of the gravitational field. One application of these deductions results in a black hole configuration of the Schwarzschild type, having no electric charge and no angular momentum. The critical mass of a gravitational collapse with respect to the nuclear binding energy is found to be in the range of 0.4 to 90 solar masses. A second application is connected with the speculation about an extended symmetric law of gravitation, based on the options of positive and negative mass for a particle at given positive energy. This would make masses of equal polarity attract each other, while masses of opposite polarity repel each other. Matter and antimatter are further proposed to be associated with the states of positive and negative mass. Under fully symmetric conditions this could provide a mechanism for the separation of antimatter from matter at an early stage of the universe.

The application of quality risk management to the bacterial endotoxins test: use of hazard analysis and critical control points.

Science.gov (United States)

Annalaura, Carducci; Giulia, Davini; Stefano, Ceccanti

2013-01-01

Risk analysis is widely used in the pharmaceutical industry to manage production processes, validation activities, training, and other activities. Several methods of risk analysis are available (for example, failure mode and effects analysis, fault tree analysis), and one or more should be chosen and adapted to the specific field where they will be applied. Among the methods available, hazard analysis and critical control points (HACCP) is a methodology that has been applied since the 1960s, and whose areas of application have expanded over time from food to the pharmaceutical industry. It can be easily and successfully applied to several processes because its main feature is the identification, assessment, and control of hazards. It can be also integrated with other tools, such as fishbone diagram and flowcharting. The aim of this article is to show how HACCP can be used to manage an analytical process, propose how to conduct the necessary steps, and provide data templates necessary to document and useful to follow current good manufacturing practices. In the quality control process, risk analysis is a useful tool for enhancing the uniformity of technical choices and their documented rationale. Accordingly, it allows for more effective and economical laboratory management, is capable of increasing the reliability of analytical results, and enables auditors and authorities to better understand choices that have been made. The aim of this article is to show how hazard analysis and critical control points can be used to manage bacterial endotoxins testing and other analytical processes in a formal, clear, and detailed manner.

Numerical Analysis of S-CO{sub 2} Test Loop Transient Conditions near the Critical Point of CO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Bae, Seong Jun; Oh, Bongseong; Ahn, Yoonhan; Baik, Seongjoon; Lee, Jekyoung; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2016-05-15

It was identified that controlling CO{sub 2} compressor operation near the critical point is one of the most important issues to operate a S-CO{sub 2} Brayton cycle with a high efficiency. Despite the growing interest in the S-CO{sub 2} Brayton cycle, a few previous research on the transient analysis of the S-CO{sub 2} system has been conducted previously. Moreover, previous studies have some limitation in the modelled test facility, and the experiment was not performed to observe specific scenario. The KAIST research team has conducted S-CO{sub 2} system transient experiments with the CO{sub 2} compressing test facility called SCO{sub 2}PE (Supercritical CO{sub 2} Pressurizing Experiment) at KAIST In this study, authors use the transient analysis code GAMMA (Gas Multidimensional Multicomponent mixture Analysis) code for analyzing the experiment. Two transient scenarios were selected in this study; over cooling and under cooling situations. The selected transient situation is of particular interest since the compressor inlet conditions start to drift away from the critical point of CO{sub 2}. The results represent that the GAMMA code can simulate the S-CO{sub 2} test facility, SCO{sub 2}PE. However, as shown in the cooling water flow rate increasing scenario, the GAMMA code shows calculation error when the phase change occurs. Furthermore, although the results of the cooling water flow rate decrease case shows reasonable agreement with the experimental data, there are still some unexplained differences between the experimental data and the GAMMA code prediction.

Migraine strikes as neuronal excitability reaches a tipping point.

Directory of Open Access Journals (Sweden)

Marten Scheffer

Full Text Available Self-propagating waves of cerebral neuronal firing, known as spreading depolarisations, are believed to be at the roots of migraine attacks. We propose that the start of spreading depolarisations corresponds to a critical transition that occurs when dynamic brain networks approach a tipping point. We show that this hypothesis is consistent with current pathogenetic insights and observed dynamics. Our view implies that migraine strikes when modulating factors further raise the neuronal excitability in genetically predisposed subjects to a level where even minor perturbations can trigger spreading depolarisations. A corollary is that recently discovered generic early warning indicators for critical transitions may be used to predict the onset of migraine attacks even before patients are clinically aware. This opens up new avenues for dissecting the mechanisms for the onset of migraine attacks and for identifying novel prophylactic treatment targets for the prevention of attacks.

Quench dynamics near a quantum critical point: Application to the sine-Gordon model

International Nuclear Information System (INIS)

De Grandi, C.; Polkovnikov, A.; Gritsev, V.

2010-01-01

We discuss the quench dynamics near a quantum critical point focusing on the sine-Gordon model as a primary example. We suggest a unified approach to sudden and slow quenches, where the tuning parameter λ(t) changes in time as λ(t)∼υt r , based on the adiabatic expansion of the excitation probability in powers of υ. We show that the universal scaling of the excitation probability can be understood through the singularity of the generalized adiabatic susceptibility χ 2r+2 (λ), which for sudden quenches (r=0) reduces to the fidelity susceptibility. In turn this class of susceptibilities is expressed through the moments of the connected correlation function of the quench operator. We analyze the excitations created after a sudden quench of the cosine potential using a combined approach of form-factors expansion and conformal perturbation theory for the low-energy and high-energy sector, respectively. We find the general scaling laws for the probability of exciting the system, the density of excited quasiparticles, the entropy and the heat generated after the quench. In the two limits where the sine-Gordon model maps to hard-core bosons and free massive fermions we provide the exact solutions for the quench dynamics and discuss the finite temperature generalizations.

Weightless experiments to probe universality of fluid critical behavior

Science.gov (United States)

Lecoutre, C.; Guillaument, R.; Marre, S.; Garrabos, Y.; Beysens, D.; Hahn, I.

2015-06-01

Near the critical point of fluids, critical opalescence results in light attenuation, or turbidity increase, that can be used to probe the universality of critical behavior. Turbidity measurements in SF6 under weightlessness conditions on board the International Space Station are performed to appraise such behavior in terms of both temperature and density distances from the critical point. Data are obtained in a temperature range, far (1 K) from and extremely close (a few μ K ) to the phase transition, unattainable from previous experiments on Earth. Data are analyzed with renormalization-group matching classical-to-critical crossover models of the universal equation of state. It results that the data in the unexplored region, which is a minute deviant from the critical density value, still show adverse effects for testing the true asymptotic nature of the critical point phenomena.

A comprehensive review of the implementation of hazard analysis critical control point (HACCP) to the production of flour and flour-based products.

Science.gov (United States)

Arvanitoyannis, Ioannis S; Traikou, Athina

2005-01-01

The production of flour and semolina and their ensuing products, such as bread, cake, spaghetti, noodles, and corn flakes, is of major importance, because these products constitute some of the main ingredients of the human diet. The Hazard Analysis Critical Control Point (HACCP) system aims at ensuring the safety of these products. HACCP has been implemented within the frame of this study on various products of both Asian and European origin; the hazards, critical control limits (CCLs), observation practices, and corrective actions have been summarized in comprehensive tables. Furthermore, the various production steps, packaging included, were thoroughly analyzed, and reference was made to both the traditional and new methodologies in an attempt to pinpoint the occurring differences (advantages and disadvantages) per process.

Low skeletal muscle area is a risk factor for mortality in mechanically ventilated critically ill patients.

Science.gov (United States)

Weijs, Peter J M; Looijaard, Wilhelmus G P M; Dekker, Ingeborg M; Stapel, Sandra N; Girbes, Armand R; Oudemans-van Straaten, H M; Beishuizen, Albertus

2014-01-13

Higher body mass index (BMI) is associated with lower mortality in mechanically ventilated critically ill patients. However, it is yet unclear which body component is responsible for this relationship. This retrospective analysis in 240 mechanically ventilated critically ill patients included adult patients in whom a computed tomography (CT) scan of the abdomen was made on clinical indication between 1 day before and 4 days after admission to the intensive care unit. CT scans were analyzed at the L3 level for skeletal muscle area, expressed as square centimeters. Cutoff values were defined by receiver operating characteristic (ROC) curve analysis: 110 cm2 for females and 170 cm2 for males. Backward stepwise regression analysis was used to evaluate low-muscle area in relation to hospital mortality, with low-muscle area, sex, BMI, Acute Physiologic and Chronic Health Evaluation (APACHE) II score, and diagnosis category as independent variables. This study included 240 patients, 94 female and 146 male patients. Mean age was 57 years; mean BMI, 25.6 kg/m2. Muscle area for females was significantly lower than that for males (102 ± 23 cm2 versus 158 ± 33 cm2; P muscle area was observed in 63% of patients for both females and males. Mortality was 29%, significantly higher in females than in males (37% versus 23%; P = 0.028). Low-muscle area was associated with higher mortality compared with normal-muscle area in females (47.5% versus 20%; P = 0.008) and in males (32.3% versus 7.5%; P muscle area, sex, and APACHE II score, whereas BMI and admission diagnosis were not. Odds ratio for low-muscle area was 4.3 (95% confidence interval, 2.0 to 9.0, P muscle mass appeared as primary predictor, not sex. Low skeletal muscle area, as assessed by CT scan during the early stage of critical illness, is a risk factor for mortality in mechanically ventilated critically ill patients, independent of sex and APACHE II score. Further analysis suggests muscle mass as primary predictor, not

Psychotropic Drug Use in Physically Restrained, Critically Ill Adults Receiving Mechanical Ventilation.

Science.gov (United States)

Guenette, Melanie; Burry, Lisa; Cheung, Alexandra; Farquharson, Tara; Traille, Marlene; Mantas, Ioanna; Mehta, Sangeeta; Rose, Louise

2017-09-01

Restraining therapies (physical or pharmacological) are used to promote the safety of both patients and health care workers. Some guidelines recommend nonpharmacological or pharmacological interventions be used before physical restraints in critically ill patients. To characterize psychotropic drug interventions before and after use of physical restraints in critically ill adults receiving mechanical ventilation. A single-center, prospective, observational study documenting psychotropic drug use and Sedation-Agitation Scale (SAS) scores in the 2 hours before and the 6 hours after application of physical restraints. Ninety-three patients were restrained for a median of 21 hours (interquartile range, 9-70 hours). Thirty percent of patients did not receive a psychotropic drug or had a drug stopped or decreased before physical restraints were applied. More patients received a psychotropic drug intervention after use of physical restraints than before (86% vs 56%, P = .001). Administration of opioids was more common after the use of physical restraints (54% vs 20% of patients, P = .001) and accounted for more drug interventions (45% vs 29%, P = .001). Fifty patients had SAS scores from both time periods; 16% remained oversedated, 24% were appropriately sedated, and 16% remained agitated in both time periods. Patients became oversedated (20%), more agitated (10%), less agitated (8%), and less sedated (6%) after restraint use. Psychotropic drug interventions (mostly using opioids) were more common after use of physical restraints. Some patients may be physically restrained for anticipated treatment interference without consideration of pharmacological options and without documented agitation. ©2017 American Association of Critical-Care Nurses.

We did well but we definitely have to do better: four critical points about fluxnet

Science.gov (United States)

Kutsch, W. L.

2014-12-01

Fluxnet is a real success story of data integration. The scientific outcome is overwhelming. Nevertheless: in a time of methodological consolidation and transfer of the networks to technically more integrated infrastructures, a critical view on its weak points may strengthen the future success and our position within biogeochemical science. Four points should be discussed: We have to select our sites more thoroughly. We need better data curation. We should think about 'forgetting' some of the older datasets. We have responsibility for the results of integration studies. ad 1: We had to learn during the past years that the EC is not applicable in all terrains. Slope and footprint problems are widespread and sites have to be critically scrutinized before being sure that we submit valuable ecological information. This is time consuming and may be frustrating since we have to accept that we had sometimes invested lots of work and money for building a flux tower at a site that is not suitable for the method. Nevertheless, a clear site quality policy should be developed among infrastructures and integrating activities. ad 2: In some cases it has turned out that the information about different steps leading from the raw data to a number in integrated scientific papers has been lost. This is a big challenge to research infrastructures that should develop common rules for data curation to increase trust in integration activities. ad 3: In the first approach Fluxnet left the responsibility for site and data quality to the site PI and accepted more or less all data submitted. Further approaches and in particular long-term infrastructures have to develop strategies to reject (or at least flag) data from sites that are prone by terrain problems. This includes that in future integration studies we should stop using some of the datasets from the 'wild old times' when we did not know better. ad4: We need a strategy to communicate with data users that are far away from practical

Critical point of gas-liquid type phase transition and phase equilibrium functions in developed two-component plasma model.

Science.gov (United States)

Butlitsky, M A; Zelener, B B; Zelener, B V

2014-07-14

A two-component plasma model, which we called a "shelf Coulomb" model has been developed in this work. A Monte Carlo study has been undertaken to calculate equations of state, pair distribution functions, internal energies, and other thermodynamics properties. A canonical NVT ensemble with periodic boundary conditions was used. The motivation behind the model is also discussed in this work. The "shelf Coulomb" model can be compared to classical two-component (electron-proton) model where charges with zero size interact via a classical Coulomb law. With important difference for interaction of opposite charges: electrons and protons interact via the Coulomb law for large distances between particles, while interaction potential is cut off on small distances. The cut off distance is defined by an arbitrary ɛ parameter, which depends on system temperature. All the thermodynamics properties of the model depend on dimensionless parameters ɛ and γ = βe(2)n(1/3) (where β = 1/kBT, n is the particle's density, kB is the Boltzmann constant, and T is the temperature) only. In addition, it has been shown that the virial theorem works in this model. All the calculations were carried over a wide range of dimensionless ɛ and γ parameters in order to find the phase transition region, critical point, spinodal, and binodal lines of a model system. The system is observed to undergo a first order gas-liquid type phase transition with the critical point being in the vicinity of ɛ(crit) ≈ 13(T(*)(crit) ≈ 0.076), γ(crit) ≈ 1.8(v(*)(crit) ≈ 0.17), P(*)(crit) ≈ 0.39, where specific volume v* = 1/γ(3) and reduced temperature T(*) = ɛ(-1).

Mechanisms of Photo-Induced Deformations of Liquid Crystal Elastomers

Science.gov (United States)

Dawson, Nathan; Kuzyk, Mark; Neal, Jeremy; Luchette, Paul; Palffy-Muhoray, Peter

2010-03-01

Over a century ago, Alexander Graham Bell invented the photophone, which he used to transmit mechanical information on a beam of light. We report on the use of an active Fabry-Perot interferometer to encode and detect mechanical information using the photomechanical effect of a liquid crystal elastomer (LCE) that is placed at a critical point between the reflectors. These are the first steps in the creation of ultra smart materials which require a large photomechanical response. Thus, understanding the underlying mechanisms is critical. Only limited studies of the mechanisms of the photomechanical effect, such as photo-isomerization, photo-reorientation and thermal effects have been studied in azo-dye-doped LCEs and in azo-dye-doped polymer fibers have been reported. The focus of our present work is to use the Fabry-Perot transducer geometry to study the underlying mechanisms and to determine the relevant material parameters that are used to develop theoretical models of the response. We use various intensity-modulated optical wave forms to determine the frequency response of the material, which are used to predict the material response.

Criticality and entanglement in random quantum systems

International Nuclear Information System (INIS)

Refael, G; Moore, J E

2009-01-01

We review studies of entanglement entropy in systems with quenched randomness, concentrating on universal behavior at strongly random quantum critical points. The disorder-averaged entanglement entropy provides insight into the quantum criticality of these systems and an understanding of their relationship to non-random ('pure') quantum criticality. The entanglement near many such critical points in one dimension shows a logarithmic divergence in subsystem size, similar to that in the pure case but with a different universal coefficient. Such universal coefficients are examples of universal critical amplitudes in a random system. Possible measurements are reviewed along with the one-particle entanglement scaling at certain Anderson localization transitions. We also comment briefly on higher dimensions and challenges for the future.

Introductory lectures on critical phenomena

International Nuclear Information System (INIS)

Khajehpour, M.R.H.

1988-09-01

After a presentation of classical models for phase transitions and critical phenomena (Van der Waals theory, Weiss theory of ferromagnetism) and theoretical models (Ising model, XY model, Heisenberg model, spherical model) the Landau theory of critical and multicritical points and some single applications of renormalization group method in static critical phenomena are presented. 115 refs, figs and tabs

Phantom black holes and critical phenomena

Energy Technology Data Exchange (ETDEWEB)

Azreg-Aïnou, Mustapha [Engineering Faculty, Başkent University, Bağlıca Campus, Ankara (Turkey); Marques, Glauber T. [Universidade Federal Rural da Amazônia ICIBE-LASIC, Av. Presidente Tancredo Neves 2501, CEP 66077-901—Belém/PA (Brazil); Rodrigues, Manuel E., E-mail: azreg@baskent.edu.tr, E-mail: gtadaiesky@hotmail.com, E-mail: esialg@gmail.com [Faculdade de Ciências Exatas e Tecnologia, Universidade Federal do Pará, Campus Universitário de Abaetetuba, CEP 68440-000, Abaetetuba, Pará (Brazil)

2014-07-01

We consider the two classes cosh and sinh of normal and phantom black holes of Einstein-Maxwell-dilaton theory. The thermodynamics of these holes is characterized by heat capacities that may have both signs depending on the parameters of the theory. Leaving aside the normal Reissner-Nordström black hole, it is shown that only some phantom black holes of both classes exhibit critical phenomena. The two classes share a nonextremality, but special, critical point where the transition is continuous and the heat capacity, at constant charge, changes sign with an infinite discontinuity. This point yields a classification scheme for critical points. It is concluded that the two unstable and stable phases coexist on one side of the criticality state and disappear on the other side, that is, there is no configuration where only one phase exists. The sinh class has an extremality critical point where the entropy diverges. The transition from extremality to nonextremality with the charge held constant is accompanied by a loss of mass and an increase in the temperature. A special case of this transition is when the hole is isolated (microcanonical ensemble), it will evolve by emission of energy, which results in a decrease of its mass, to the final state of minimum mass and vanishing heat capacity. The Ehrenfest scheme of classification is inaccurate in this case but the generalized one due to Hilfer leads to conclude that the transition is of order less than unity. Fluctuations near criticality are also investigated.

Full On-Device Stay Points Detection in Smartphones for Location-Based Mobile Applications