Analysis of constant tension-induced rupture of lipid membranes using activation energy.

PubMed

Karal, Mohammad Abu Sayem; Levadnyy, Victor; Yamazaki, Masahito

2016-05-11

The stretching of biomembranes and lipid membranes plays important roles in various physiological and physicochemical phenomena. Here we analyzed the rate constant kp of constant tension-induced rupture of giant unilamellar vesicles (GUVs) as a function of tension σ using their activation energy Ua. To determine the values of kp, we applied constant tension to a GUV membrane using the micropipette aspiration method and observed the rupture of GUVs, and then analyzed these data statistically. First, we investigated the temperature dependence of kp for GUVs of charged lipid membranes composed of negatively charged dioleoylphosphatidylglycerol (DOPG) and electrically neutral dioleoylphosphatidylcholine (DOPC). By analyzing this result, the values of Ua of tension-induced rupture of DOPG/DOPC-GUVs were obtained. Ua decreased with an increase in σ, supporting the classical theory of tension-induced pore formation. The analysis of the relationship between Ua and σ using the theory on the electrostatic interaction effects on the tension-induced rupture of GUVs provided the equation of Ua including electrostatic interaction effects, which well fits the experimental data of the tension dependence of Ua. A constant which does not depend on tension, U0, was also found to contribute significantly to Ua. The Arrhenius equations for kp using the equation of Ua and the parameters determined by the above analysis fit well to the experimental data of the tension dependence of kp for DOPG/DOPC-GUVs as well as for DOPC-GUVs. On the basis of these results, we discussed the possible elementary processes underlying the tension-induced rupture of GUVs of lipid membranes. These results indicate that the Arrhenius equation using the experimentally determined Ua is useful in the analysis of tension-induced rupture of GUVs.

A simple cosmology with a varying fine structure constant.

PubMed

Sandvik, Håvard Bunes; Barrow, John D; Magueijo, João

2002-01-21

We investigate the cosmological consequences of a theory in which the electric charge e can vary. In this theory the fine structure "constant," alpha, remains almost constant in the radiation era, undergoes a small increase in the matter era, but approaches a constant value when the universe starts accelerating because of a positive cosmological constant. This model satisfies geonuclear, nucleosynthesis, and cosmic microwave background constraints on time variation in alpha, while fitting the observed accelerating Universe and evidence for small alpha variations in quasar spectra. It also places specific restrictions on the nature of the dark matter. Further tests, involving stellar spectra and Eötvös experiments, are proposed.

A procedure to find thermodynamic equilibrium constants for CO2 and CH4 adsorption on activated carbon.

PubMed

Trinh, T T; van Erp, T S; Bedeaux, D; Kjelstrup, S; Grande, C A

2015-03-28

Thermodynamic equilibrium for adsorption means that the chemical potential of gas and adsorbed phase are equal. A precise knowledge of the chemical potential is, however, often lacking, because the activity coefficient of the adsorbate is not known. Adsorption isotherms are therefore commonly fitted to ideal models such as the Langmuir, Sips or Henry models. We propose here a new procedure to find the activity coefficient and the equilibrium constant for adsorption which uses the thermodynamic factor. Instead of fitting the data to a model, we calculate the thermodynamic factor and use this to find first the activity coefficient. We show, using published molecular simulation data, how this procedure gives the thermodynamic equilibrium constant and enthalpies of adsorption for CO2(g) on graphite. We also use published experimental data to find similar thermodynamic properties of CO2(g) and of CH4(g) adsorbed on activated carbon. The procedure gives a higher accuracy in the determination of enthalpies of adsorption than ideal models do.

Bottom-up driven involuntary auditory evoked field change: constant sound sequencing amplifies but does not sharpen neural activity.

PubMed

Okamoto, Hidehiko; Stracke, Henning; Lagemann, Lothar; Pantev, Christo

2010-01-01

The capability of involuntarily tracking certain sound signals during the simultaneous presence of noise is essential in human daily life. Previous studies have demonstrated that top-down auditory focused attention can enhance excitatory and inhibitory neural activity, resulting in sharpening of frequency tuning of auditory neurons. In the present study, we investigated bottom-up driven involuntary neural processing of sound signals in noisy environments by means of magnetoencephalography. We contrasted two sound signal sequencing conditions: "constant sequencing" versus "random sequencing." Based on a pool of 16 different frequencies, either identical (constant sequencing) or pseudorandomly chosen (random sequencing) test frequencies were presented blockwise together with band-eliminated noises to nonattending subjects. The results demonstrated that the auditory evoked fields elicited in the constant sequencing condition were significantly enhanced compared with the random sequencing condition. However, the enhancement was not significantly different between different band-eliminated noise conditions. Thus the present study confirms that by constant sound signal sequencing under nonattentive listening the neural activity in human auditory cortex can be enhanced, but not sharpened. Our results indicate that bottom-up driven involuntary neural processing may mainly amplify excitatory neural networks, but may not effectively enhance inhibitory neural circuits.

Change in fibrinolytic activity under the influence of a constant magnetic field. [blood coagulation normilization in heart patients

NASA Technical Reports Server (NTRS)

Yepishina, S. G.

1974-01-01

The fibrinolytic activity of plasma changes under the influence of a constant magnetic field (CMF) with a strength of 250 or 2500 oersteds. CMF shows a tendency toward normalization of fibrinolytic processes in the presence of pathological disturbances in fibrinolysis activation.

Elongational flow of polymer melts at constant strain rate, constant stress and constant force

NASA Astrophysics Data System (ADS)

Wagner, Manfred H.; Rolón-Garrido, Víctor H.

2013-04-01

Characterization of polymer melts in elongational flow is typically performed at constant elongational rate or rarely at constant tensile stress conditions. One of the disadvantages of these deformation modes is that they are hampered by the onset of "necking" instabilities according to the Considère criterion. Experiments at constant tensile force have been performed even more rarely, in spite of the fact that this deformation mode is free from necking instabilities and is of considerable industrial relevance as it is the correct analogue of steady fiber spinning. It is the objective of the present contribution to present for the first time a full experimental characterization of a long-chain branched polyethylene melt in elongational flow. Experiments were performed at constant elongation rate, constant tensile stress and constant tensile force by use of a Sentmanat Extensional Rheometer (SER) in combination with an Anton Paar MCR301 rotational rheometer. The accessible experimental window and experimental limitations are discussed. The experimental data are modelled by using the Wagner I model. Predictions of the steady-start elongational viscosity in constant strain rate and creep experiments are found to be identical, albeit only by extrapolation of the experimental data to Hencky strains of the order of 6. For constant stress experiments, a minimum in the strain rate and a corresponding maximum in the elongational viscosity is found at a Hencky strain of the order of 3, which, although larger than the steady-state value, follows roughly the general trend of the steady-state elongational viscosity. The constitutive analysis also reveals that constant tensile force experiments indicate a larger strain hardening potential than seen in constant elongation rate or constant tensile stress experiments. This may be indicative of the effect of necking under constant elongation rate or constant tensile stress conditions according to the Considère criterion.

The Henry's constant of monochloramine.

PubMed

Garcia, Miguel A; Anderson, Michael A

2018-02-01

Monochloramine is a secondary disinfectant used in drinking water and is also formed in chlorinated wastewater. While known to hydrolyze over time and react with dissolved organic matter, its partitioning between the aqueous and gas phase has not been extensively studied. Preliminary experiments demonstrated that monochloramine concentrations in solutions open to the atmosphere or actively aerated decreased more rapidly than in sealed solutions, indicating significant losses to the atmosphere. For example, a monochloramine solution open to the atmosphere yielded a loss rate constant of 0.08 d -1 , a value twice that for sealed samples without headspace (0.04 d -1 ) where loss occurs exclusively as a result of hydrolysis. A solution aerated at 10 mL s -1 had a loss rate constant nearly 10× greater than that for hydrolysis alone (0.35 d -1 ). To better understand partitioning of monochloramine to the gas phase and potential for volatilization, the dimensionless Henry's law constants of monochloramine (K H ) were determined using an equilibrium headspace technique at five different temperatures (11, 16, 21, 27, and 32 °C). The resulting values ranged from 8 × 10 -3 to 4 × 10 -2 , indicating a semi-volatile compound, and were found to be consistent with quantitative structure activity relationship predictions. At 20 °C, monochloramine exhibits a dimensionless Henry's constant of about 1.7 × 10 -2 which is 35 times greater than ammonia but comparable to the Henry's constant of inorganic semi-volatile compounds such sulfur dioxide. The Henry's constant values for monochloramine suggests that volatilization could be a relevant loss process in open systems such as rivers receiving chlorinated wastewater effluent, swimming pools and cooling towers. Copyright © 2017 Elsevier Ltd. All rights reserved.

Remaining useful life prediction of degrading systems subjected to imperfect maintenance: Application to draught fans

NASA Astrophysics Data System (ADS)

Wang, Zhao-Qiang; Hu, Chang-Hua; Si, Xiao-Sheng; Zio, Enrico

2018-02-01

Current degradation modeling and remaining useful life prediction studies share a common assumption that the degrading systems are not maintained or maintained perfectly (i.e., to an as-good-as new state). This paper concerns the issues of how to model the degradation process and predict the remaining useful life of degrading systems subjected to imperfect maintenance activities, which can restore the health condition of a degrading system to any degradation level between as-good-as new and as-bad-as old. Toward this end, a nonlinear model driven by Wiener process is first proposed to characterize the degradation trajectory of the degrading system subjected to imperfect maintenance, where negative jumps are incorporated to quantify the influence of imperfect maintenance activities on the system's degradation. Then, the probability density function of the remaining useful life is derived analytically by a space-scale transformation, i.e., transforming the constructed degradation model with negative jumps crossing a constant threshold level to a Wiener process model crossing a random threshold level. To implement the proposed method, unknown parameters in the degradation model are estimated by the maximum likelihood estimation method. Finally, the proposed degradation modeling and remaining useful life prediction method are applied to a practical case of draught fans belonging to a kind of mechanical systems from steel mills. The results reveal that, for a degrading system subjected to imperfect maintenance, our proposed method can obtain more accurate remaining useful life predictions than those of the benchmark model in literature.

A model for solar constant secular changes

NASA Technical Reports Server (NTRS)

Schatten, Kenneth H.

1988-01-01

In this paper, contrast models for solar active region and global photospheric features are used to reproduce the observed Active Cavity Radiometer and Earth Radiation Budget secular trends in reasonably good fashion. A prediction for the next decade of solar constant variations is made using the model. Secular trends in the solar constant obtained from the present model support the view that the Maunder Minimum may be related to the Little Ice Age of the 17th century.

Theory of diffusion of active particles that move at constant speed in two dimensions.

PubMed

Sevilla, Francisco J; Gómez Nava, Luis A

2014-08-01

Starting from a Langevin description of active particles that move with constant speed in infinite two-dimensional space and its corresponding Fokker-Planck equation, we develop a systematic method that allows us to obtain the coarse-grained probability density of finding a particle at a given location and at a given time in arbitrary short-time regimes. By going beyond the diffusive limit, we derive a generalization of the telegrapher equation. Such generalization preserves the hyperbolic structure of the equation and incorporates memory effects in the diffusive term. While no difference is observed for the mean-square displacement computed from the two-dimensional telegrapher equation and from our generalization, the kurtosis results in a sensible parameter that discriminates between both approximations. We carry out a comparative analysis in Fourier space that sheds light on why the standard telegrapher equation is not an appropriate model to describe the propagation of particles with constant speed in dispersive media.

Effects of Constant Flow vs. Constant Pressure Perfusion on Fluid Filtration in Severe Hypothermic Isolated Blood-Perfused Rat Lungs.

PubMed

Halsøy, Kathrine; Kondratiev, Timofey; Tveita, Torkjel; Bjertnaes, Lars J

2016-01-01

Victims of severe accidental hypothermia are prone to fluid extravasation but rarely develop lung edema. We hypothesize that combined hypothermia-induced increase in pulmonary vascular resistance (PVR) and a concomitant fall in cardiac output protect the lungs against edema development. Our aim was to explore in hypothermic-isolated blood-perfused rat lungs whether perfusion at constant pressure influences fluid filtration differently from perfusion at constant flow. Isolated blood-perfused rat lungs were hanging freely in a weight transducer for measuring weight changes (ΔW). Fluid filtration coefficient (Kfc), was determined by transiently elevating left atrial pressure (Pla) by 5.8 mmHg two times each during normothermia (37°C) and during hypothermia (15°C). The lung preparations were randomized to two groups. One group was perfused with constant flow (Constant flow group) and the other group with constant pulmonary artery pressure (Constant PPA group). Microvascular pressure (Pmv) was determined before and during elevation of Pla (ΔPmv) by means of the double occlusion technique. Kfc was calculated with the formula Kfc = ΔW/ΔPmv/min. All Kfc values were normalized to predicted lung weight (P LW ), which was based on body weight (BW) according to the formula: P LW  = 0.0053 BW - 0.48 and presented as Kfc PLW in mg/min/mmHg/g. At cessation, bronchoalveolar lavage (BAL) fluid/perfusate protein concentration (B/P) ratio was determined photometrically. Data were analyzed with parametric or non-parametric tests as appropriate. p  < 0.05 considered as significant. Perfusate flow remained constant in the Constant flow group, but was more than halved during hypothermia in the Constant PPA group concomitant with a more fold increase in PVR. In the Constant flow group, Kfc PLW and B/P ratio increased significantly by more than 10-fold during hypothermia concerted by visible signs of edema in the trachea. Hemoglobin and hematocrit increased within

The effect of concentration- and temperature-dependent dielectric constant on the activity coefficient of NaCl electrolyte solutions

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

Valiskó, Mónika; Boda, Dezső, E-mail: boda@almos.vein.hu

2014-06-21

Our implicit-solvent model for the estimation of the excess chemical potential (or, equivalently, the activity coefficient) of electrolytes is based on using a dielectric constant that depends on the thermodynamic state, namely, the temperature and concentration of the electrolyte, ε(c, T). As a consequence, the excess chemical potential is split into two terms corresponding to ion-ion (II) and ion-water (IW) interactions. The II term is obtained from computer simulation using the Primitive Model of electrolytes, while the IW term is estimated from the Born treatment. In our previous work [J. Vincze, M. Valiskó, and D. Boda, “The nonmonotonic concentration dependencemore » of the mean activity coefficient of electrolytes is a result of a balance between solvation and ion-ion correlations,” J. Chem. Phys. 133, 154507 (2010)], we showed that the nonmonotonic concentration dependence of the activity coefficient can be reproduced qualitatively with this II+IW model without using any adjustable parameter. The Pauling radii were used in the calculation of the II term, while experimental solvation free energies were used in the calculation of the IW term. In this work, we analyze the effect of the parameters (dielectric constant, ionic radii, solvation free energy) on the concentration and temperature dependence of the mean activity coefficient of NaCl. We conclude that the II+IW model can explain the experimental behavior using a concentration-dependent dielectric constant and that we do not need the artificial concept of “solvated ionic radius” assumed by earlier studies.« less

Evolution of circadian rhythms in Drosophila melanogaster populations reared in constant light and dark regimes for over 330 generations.

PubMed

Shindey, Radhika; Varma, Vishwanath; Nikhil, K L; Sharma, Vijay Kumar

2017-01-01

Organisms are believed to have evolved circadian clocks as adaptations to deal with cyclic environmental changes, and therefore it has been hypothesized that evolution in constant environments would lead to regression of such clocks. However, previous studies have yielded mixed results, and evolution of circadian clocks under constant conditions has remained an unsettled topic of debate in circadian biology. In continuation of our previous studies, which reported persistence of circadian rhythms in Drosophila melanogaster populations evolving under constant light, here we intended to examine whether circadian clocks and the associated properties evolve differently under constant light and constant darkness. In this regard, we assayed activity-rest, adult emergence and oviposition rhythms of D. melanogaster populations which have been maintained for over 19 years (~330 generations) under three different light regimes - constant light (LL), light-dark cycles of 12:12 h (LD) and constant darkness (DD). We observed that while circadian rhythms in all the three behaviors persist in both LL and DD stocks with no differences in circadian period, they differed in certain aspects of the entrained rhythms when compared to controls reared in rhythmic environment (LD). Interestingly, we also observed that DD stocks have evolved significantly higher robustness or power of free-running activity-rest and adult emergence rhythms compared to LL stocks. Thus, our study, in addition to corroborating previous results of circadian clock evolution in constant light, also highlights that, contrary to the expected regression of circadian clocks, rearing in constant darkness leads to the evolution of more robust circadian clocks which may be attributed to an intrinsic adaptive advantage of circadian clocks and/or pleiotropic functions of clock genes in other traits.

Bubble mass center and fluid feedback force fluctuations activated by constant lateral impulse with variable thrust

NASA Technical Reports Server (NTRS)

Hung, R. J.; Long, Y. T.

1995-01-01

Sloshing dynamics within a partially filled rotating dewar of superfluid helium 2 are investigated in response to constant lateral impulse with variable thrust. The study, including how the rotating bubble of superfluid helium 2 reacts to the constant impulse with variable time period of thrust action in microgravity, how amplitudes of bubble mass center fluctuates with growth and decay of disturbances, and how fluid feedback forces fluctuates in activating on the rotating dewar through the dynamics of sloshing waves are investigated. The numerical computation of sloshing dynamics is based on the non-inertial frame spacecraft bound coordinate with lateral impulses actuating on the rotating dewar in both inertial and non-inertial frames of thrust. Results of the simulations are illustrated.

Where do those remains come from?

PubMed

Nociarová, Dominika; Adserias, M Jose; Malgosa, Assumpció; Galtés, Ignasi

2014-12-01

Part of the study of skeletal remains or corpses in advance decay located in the field involves determining their origin. They may be the result of criminal activity, accident, unearthed because of erosion, or they may also have originated from a cemetery. The discovery site, condition of the remains, and the associated artifacts, are factors that could be helpful for the forensic anthropologist to identify the origin of the remains. In order to contribute to this recognition, an analysis was made of the exhumations of 168 unclaimed human remains from the cemetery of Terrassa (Catalonia, Spain). This investigation presents a description of artifacts and conditions of remains that could indicate that the human remains may have originated from a cemetery. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Constants and pseudo-constants of the Kadomtsev-Petviashvili equation.

PubMed

Case, K M

1985-08-01

Elucidating earlier work, it is shown that the Kadomtsev-Petviashvili equation has n + 2 constants for all n >/= 0. It also has a pseudo-constant from which the constants can be obtained by differentiation with respect to time. The pseudo-constant can be obtained from a basis functional J(n) ((n+2)) = -1/18 [unk] y(n+2)q by taking repeated Poisson brackets with the Hamiltonian.

Constants and pseudo-constants of the Kadomtsev-Petviashvili equation

PubMed Central

Case, K. M.

1985-01-01

Elucidating earlier work, it is shown that the Kadomtsev-Petviashvili equation has n + 2 constants for all n ≥ 0. It also has a pseudo-constant from which the constants can be obtained by differentiation with respect to time. The pseudo-constant can be obtained from a basis functional Jn(n+2) = -1/18 [unk] yn+2q by taking repeated Poisson brackets with the Hamiltonian. PMID:16593588

Constants and pseudo-constants of the Kadomtsev-Petviashvili equation

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

Case, K.M.

1985-08-01

Elucidating earlier work, it is shown that the Kadomtsev-Petviashvili equation has n + 2 constants for all n greater than or equal to 0. It also has a pseudo-constant from which the constants can be obtained by differentiation with respect to time. The pseudo-constant can be obtained from a basis functional J/sub n/sup (n+2)/ = -1/18 integral y/sup n+2/ q by taking repeated Poisson brackets with the Hamiltonian.

Abiotic and Biotic Factors Regulating Inter-Kingdom Engagement between Insects and Microbe Activity on Vertebrate Remains

PubMed Central

Jordan, Heather R.; Tomberlin, Jeffery K.

2017-01-01

A number of abiotic and biotic factors are known to regulate arthropod attraction, colonization, and utilization of decomposing vertebrate remains. Such information is critical when assessing arthropod evidence associated with said remains in terms of forensic relevance. Interactions are not limited to just between the resource and arthropods. There is another biotic factor that has been historically overlooked; however, with the advent of high-throughput sequencing, and other molecular techniques, the curtain has been pulled back to reveal a microscopic world that is playing a major role with regards to carrion decomposition patterns in association with arthropods. The objective of this publication is to review many of these factors and draw attention to their impact on microbial, specifically bacteria, activity associated with these remains as it is our contention that microbes serve as a primary mechanism regulating associated arthropod behavior. PMID:28538664

Recommended Values of the Fundamental Physical Constants: A Status Report

PubMed Central

Taylor, Barry N.; Cohen, E. Richard

1990-01-01

We summarize the principal advances made in the fundamental physical constants field since the completion of the 1986 CODATA least-squares adjustment of the constants and discuss their implications for both the 1986 set of recommended values and the next least-squares adjustment. In general, the new results lead to values of the constants with uncertainties 5 to 7 times smaller than the uncertainties assigned the 1986 values. However, the changes in the values themselves are less than twice the 1986 assigned one-standard-deviation uncertainties and thus are not highly significant. Although much new data has become available since 1986, three new results dominate the analysis: a value of the Planck constant obtained from a realization of the watt; a value of the fine-structure constant obtained from the magnetic moment anomaly of the electron; and a value of the molar gas constant obtained from the speed of sound in argon. Because of their dominant role in determining the values and uncertainties of many of the constants, it is highly desirable that additional results of comparable uncertainty that corroborate these three data items be obtained before the next adjustment is carried out. Until then, the 1986 CODATA set of recommended values will remain the set of choice. PMID:28179787

Quantum-gravity predictions for the fine-structure constant

NASA Astrophysics Data System (ADS)

Eichhorn, Astrid; Held, Aaron; Wetterich, Christof

2018-07-01

Asymptotically safe quantum fluctuations of gravity can uniquely determine the value of the gauge coupling for a large class of grand unified models. In turn, this makes the electromagnetic fine-structure constant calculable. The balance of gravity and matter fluctuations results in a fixed point for the running of the gauge coupling. It is approached as the momentum scale is lowered in the transplanckian regime, leading to a uniquely predicted value of the gauge coupling at the Planck scale. The precise value of the predicted fine-structure constant depends on the matter content of the grand unified model. It is proportional to the gravitational fluctuation effects for which computational uncertainties remain to be settled.

New Quasar Studies Keep Fundamental Physical Constant Constant

NASA Astrophysics Data System (ADS)

2004-03-01

atoms together and the way light interacts with atoms. But are these fundamental physical constants really constant? Are those numbers always the same, everywhere in the Universe and at all times? This is not as naive a question as it may seem. Contemporary theories of fundamental interactions, such as the Grand Unification Theory or super-string theories that treat gravity and quantum mechanics in a consistent way, not only predict a dependence of fundamental physical constants with energy - particle physics experiments have shown the fine structure constant to grow to a value of about 1/128 at high collision energies - but allow for their cosmological time and space variations. A time dependence of the fundamental constants could also easily arise if, besides the three space dimensions, there exist more hidden dimensions. Already in 1955, the Russian physicist Lev Landau considered the possibility of a time dependence of alpha. In the late 1960s, George Gamow in the United States suggested that the charge of the electron, and therefore also alpha, may vary. It is clear however that such changes, if any, cannot be large or they would already have been detected in comparatively simple experiments. Tracking these possible changes thus requires the most sophisticated and precise techniques. Looking back in time In fact, quite strong constraints are already known to exist for the possible variation of the fine structure constant alpha. One such constraint is of geological nature. It is based on measures taken in the ancient natural fission reactor located near Oklo (Gabon, West Africa) and which was active roughly 2,000 million years ago. By studying the distribution of a given set of elements - isotopes of the rare earths, for example of samarium - which were produced by the fission of uranium, one can estimate whether the physical process happened at a faster or slower pace than we would expect it nowadays. Thus we can measure a possible change of the value of the

Strong resetting of the mammalian clock by constant light followed by constant darkness

PubMed Central

Chen, Rongmin; Seo, Dong-oh; Bell, Elijah; von Gall, Charlotte; Lee, Choogon

2008-01-01

The mammalian molecular circadian clock in the suprachiasmatic nuclei (SCN) regulates locomotor activity rhythms as well as clocks in peripheral tissues (Reppert and Weaver, 2002; Ko and Takahashi, 2006). Constant light (LL) can induce behavioral and physiological arrhythmicity, by desynchronizing clock cells in the SCN (Ohta et al., 2005). We examined how the disordered clock cells resynchronize by probing the molecular clock and measuring behavior in mice transferred from LL to constant darkness (DD). The circadian locomotor activity rhythms disrupted in LL become robustly rhythmic again from the beginning of DD, and the starting phase of the rhythm in DD is specific, not random, suggesting that the desynchronized clock cells are quickly reset in an unconventional manner by the L:D transition. By measuring mPERIOD protein rhythms, we showed that the SCN and peripheral tissue clocks quickly become rhythmic again in phase with the behavioral rhythms. We propose that this resetting mechanism may be different from conventional phase shifting, which involves light-induction of Period genes (Albrecht et al., 1997; Shearman et al., 1997; Shigeyoshi et al., 1997). Using our functional insights, we could shift the circadian phase of locomotor activity rhythms by 12 hours using a 15-hour LL treatment: essentially producing phase reversal by a single light pulse, a feat that has not been reported previously in wild-type mice and that has potential clinical utility. PMID:19005049

The Drosophila Receptor Protein Tyrosine Phosphatase LAR Is Required for Development of Circadian Pacemaker Neuron Processes That Support Rhythmic Activity in Constant Darkness But Not during Light/Dark Cycles

PubMed Central

Agrawal, Parul

2016-01-01

In Drosophila, a transcriptional feedback loop that is activated by CLOCK-CYCLE (CLK-CYC) complexes and repressed by PERIOD-TIMELESS (PER-TIM) complexes keeps circadian time. The timing of CLK-CYC activation and PER-TIM repression is regulated post-translationally, in part through rhythmic phosphorylation of CLK, PER, and TIM. Although kinases that control PER, TIM, and CLK levels, activity, and/or subcellular localization have been identified, less is known about phosphatases that control clock protein dephosphorylation. To identify clock-relevant phosphatases, clock-cell-specific RNAi knockdowns of Drosophila phosphatases were screened for altered activity rhythms. One phosphatase that was identified, the receptor protein tyrosine phosphatase leukocyte-antigen-related (LAR), abolished activity rhythms in constant darkness (DD) without disrupting the timekeeping mechanism in brain pacemaker neurons. However, expression of the neuropeptide pigment-dispersing factor (PDF), which mediates pacemaker neuron synchrony and output, is eliminated in the dorsal projections from small ventral lateral (sLNv) pacemaker neurons when Lar expression is knocked down during development, but not in adults. Loss of Lar function eliminates sLNv dorsal projections, but PDF expression persists in sLNv and large ventral lateral neuron cell bodies and their remaining projections. In contrast to the defects in lights-on and lights-off anticipatory activity seen in flies that lack PDF, Lar RNAi knockdown flies anticipate the lights-on and lights-off transition normally. Our results demonstrate that Lar is required for sLNv dorsal projection development and suggest that PDF expression in LNv cell bodies and their remaining projections mediate anticipation of the lights-on and lights-off transitions during a light/dark cycle. SIGNIFICANCE STATEMENT In animals, circadian clocks drive daily rhythms in physiology, metabolism, and behavior via transcriptional feedback loops. Because key circadian

EHealth: self-management in inflammatory bowel disease and in irritable bowel syndrome using novel constant-care web applications. EHealth by constant-care in IBD and IBS.

PubMed

Pedersen, Natalia

2015-12-01

Inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) are chronic gastrointestinal disorders of unknown aetiology of increasing incidence and changing disease activity or severity. Approximately 60-80% of IBD patients suffer from IBS. Monitoring and treatment goals of IBD are to optimise the disease course by prolonging remission periods and preventing or shortening periods of active disease. Constant-care web-monitoring and treatment approaches with active patient involvement have been proven effective in UC, increasing patients' adherence and improving the disease outcomes.   To assess the feasibility and efficacy of the novel constant-care eHealth applications in: i) CD patients treated with infliximab (IFX), ii) UC patients with active disease on mesalazine, iii) IBS patients and iv) IBD patients with IBS on a low FODMAP diet (LFD).   New constant-care web applications www.cd.constant-care.dk, www.meza.constant-care.dk and www.ibs.constant-care.dk in IBD patients were developed and assessed in this thesis. An integrated inflammatory burden measure of disease activity, consisting of a subjective (clinical indices) and of an objective (faecal calprotectin) part and a treatment guide to drug doses and intervals, was incorporated into the web applications and used by patients. Web-guided IFX treatment in CD demonstrated patients' inter- and intra-individual variability in infusion intervals and provided patients with individualised treatment according to their needs. Web-guided treatment with multimatrix mesalazine was efficacious in a majority of UC patients with mild-to-moderate disease activity. Web-guided IBS-monitoring in IBD and in IBS patients on LFD was shown to be a feasible method that actively involved patients in their disease management and had a positive short-term impact on the disease. Moreover, the new constant-care concepts were demonstrated to be safe and to have a positive impact on quality of life and adherence to treatment and

Orientation of pigeons exposed to constant light and released from familiar sites.

PubMed

Dall'Antonia, P; Luschi, P

1993-12-01

It has been proposed that homing pigeons may use pilotage to orient home when released from familiar sites. To test this possibility, a group of pigeons was released from familiar locations after being exposed to a constant bright light. This treatment produced the loss of the circadian rhythmicity of general activity of the birds and thus presumably impaired their time-compensating sun compass mechanism. Experimental birds, both anosmic and olfactorily unimpaired, did not show any tendency to orient home, their bearing distributions being generally not different from random. Their homing performances were also affected. These results show that initial orientation of pigeons released from familiar sites entails the use of the sun compass even when the birds are released after a treatment that makes them arrhythmic in their activity. The possibility that pilotage may play a role in the first part of the homing flight of pigeons remains to be demonstrated.

Revisiting the natural history of tuberculosis. The inclusion of constant reinfection, host tolerance, and damage-response frameworks leads to a better understanding of latent infection and its evolution towards active disease.

PubMed

Cardona, Pere-Joan

2010-02-01

Once Mycobacterium tuberculosis infects a person it can persist for a long time in a process called latent tuberculosis infection (LTBI). LTBI has traditionally been considered to involve the bacilli remaining in a non-replicating state (dormant) in old lesions but still retaining their ability to induce reactivation and cause active tuberculosis (TB) once a disruption of the immune response takes place. The present review aims to challenge these concepts by including recent experimental data supporting LTBI as a constant endogenous reinfection process as well as the recently introduced concepts of damage-response and tolerance frameworks to explain TB induction. These frameworks highlight the key role of an exaggerated and intolerant host response against M. tuberculosis bacilli which induces the classical TB cavity in immunocompetent adults once the constant endogenous reinfection process has resulted in the presence of bacilli in the upper lobes, where they can grow faster and the immune response is delayed. This essay intends to provide new clues to understanding the induction of TB in non-immunosuppressed patients.

Constant fields and constant gradients in open ionic channels.

PubMed Central

Chen, D P; Barcilon, V; Eisenberg, R S

1992-01-01

Ions enter cells through pores in proteins that are holes in dielectrics. The energy of interaction between ion and charge induced on the dielectric is many kT, and so the dielectric properties of channel and pore are important. We describe ionic movement by (three-dimensional) Nemst-Planck equations (including flux and net charge). Potential is described by Poisson's equation in the pore and Laplace's equation in the channel wall, allowing induced but not permanent charge. Asymptotic expansions are constructed exploiting the long narrow shape of the pore and the relatively high dielectric constant of the pore's contents. The resulting one-dimensional equations can be integrated numerically; they can be analyzed when channels are short or long (compared with the Debye length). Traditional constant field equations are derived if the induced charge is small, e.g., if the channel is short or if the total concentration gradient is zero. A constant gradient of concentration is derived if the channel is long. Plots directly comparable to experiments are given of current vs voltage, reversal potential vs. concentration, and slope conductance vs. concentration. This dielectric theory can easily be tested: its parameters can be determined by traditional constant field measurements. The dielectric theory then predicts current-voltage relations quite different from constant field, usually more linear, when gradients of total concentration are imposed. Numerical analysis shows that the interaction of ion and channel can be described by a mean potential if, but only if, the induced charge is negligible, that is to say, the electric field is spatially constant. Images FIGURE 1 PMID:1376159

Henry's law constants of polyols

NASA Astrophysics Data System (ADS)

Compernolle, S.; Müller, J.-F.

2014-12-01

Henry's law constants (HLC) are derived for several polyols bearing between 2 and 6 hydroxyl groups, based on literature data for water activity, vapour pressure and/or solubility. While deriving HLC and depending on the case, also infinite dilution activity coefficients (IDACs), solid state vapour pressures or activity coefficient ratios are obtained as intermediate results. An error analysis on the intermediate quantities and the obtained HLC is included. For most compounds, these are the first values reported, while others compare favourably with literature data in most cases. Using these values and those from a previous work (Compernolle and Müller, 2014), an assessment is made on the partitioning of polyols, diacids and hydroxy acids to droplet and aqueous aerosol.

Calculation of individual isotope equilibrium constants for geochemical reactions

USGS Publications Warehouse

Thorstenson, D.C.; Parkhurst, D.L.

2004-01-01

Theory is derived from the work of Urey (Urey H. C. [1947] The thermodynamic properties of isotopic substances. J. Chem. Soc. 562-581) to calculate equilibrium constants commonly used in geochemical equilibrium and reaction-transport models for reactions of individual isotopic species. Urey showed that equilibrium constants of isotope exchange reactions for molecules that contain two or more atoms of the same element in equivalent positions are related to isotope fractionation factors by ?? = (Kex)1/n, where n is the number of atoms exchanged. This relation is extended to include species containing multiple isotopes, for example 13C16O18O and 1H2H18O. The equilibrium constants of the isotope exchange reactions can be expressed as ratios of individual isotope equilibrium constants for geochemical reactions. Knowledge of the equilibrium constant for the dominant isotopic species can then be used to calculate the individual isotope equilibrium constants. Individual isotope equilibrium constants are calculated for the reaction CO2g = CO2aq for all species that can be formed from 12C, 13C, 16O, and 18O; for the reaction between 12C18 O2aq and 1H218Ol; and among the various 1H, 2H, 16O, and 18O species of H2O. This is a subset of a larger number of equilibrium constants calculated elsewhere (Thorstenson D. C. and Parkhurst D. L. [2002] Calculation of individual isotope equilibrium constants for implementation in geochemical models. Water-Resources Investigation Report 02-4172. U.S. Geological Survey). Activity coefficients, activity-concentration conventions for the isotopic variants of H2O in the solvent 1H216Ol, and salt effects on isotope fractionation have been included in the derivations. The effects of nonideality are small because of the chemical similarity of different isotopic species of the same molecule or ion. The temperature dependence of the individual isotope equilibrium constants can be calculated from the temperature dependence of the fractionation

Inflation with a smooth constant-roll to constant-roll era transition

NASA Astrophysics Data System (ADS)

Odintsov, S. D.; Oikonomou, V. K.

2017-07-01

In this paper, we study canonical scalar field models, with a varying second slow-roll parameter, that allow transitions between constant-roll eras. In the models with two constant-roll eras, it is possible to avoid fine-tunings in the initial conditions of the scalar field. We mainly focus on the stability of the resulting solutions, and we also investigate if these solutions are attractors of the cosmological system. We shall calculate the resulting scalar potential and, by using a numerical approach, we examine the stability and attractor properties of the solutions. As we show, the first constant-roll era is dynamically unstable towards linear perturbations, and the cosmological system is driven by the attractor solution to the final constant-roll era. As we demonstrate, it is possible to have a nearly scale-invariant power spectrum of primordial curvature perturbations in some cases; however, this is strongly model dependent and depends on the rate of the final constant-roll era. Finally, we present, in brief, the essential features of a model that allows oscillations between constant-roll eras.

Control of Dielectric Constant and Anti-Bacterial Activity of PVA-PEG/x-SnO2 Nanofiber

NASA Astrophysics Data System (ADS)

Diantoro, M.; Sari, L. A.; Istirohah, T.; Kusumawati, A. D.; Nasikhudin; Sunaryono

2018-05-01

Research in the utilization of organic natural materials for electronic devices and for the biological application becoming extensively studied. We report a comprehensive review of the role of SnO2 nanoparticle and the effect of light intensity on toxicity properties, antibacterial activity, microstructure and electrical properties of PVA-PEG nanofiber films. The PVA-PEG/SnO2 nanofiber structure has been successfully fabricated on the ITO-glass substrate. Characterization was performed on samples using FTIR, XRD, SEM, toxicity and antibacterial tests, as well as LCR measurement. The presence of various light intensities has also measured the dielectric constant. The addition of SnO2 nanoparticle influenced the structure of the PVA-PEG/SnO2 nanofiber bonding functional group indicated by the appearance of Sn-O-Sn peaks at 648.08 cm-1 and 958 cm-1 wavenumbers. The addition of SnO2 nanoparticles affects the grain size of SnO2. Addition of SnO2 nanoparticles increases the detected toxicity voltage but is still below the threshold. It means the compound is not toxic, or safe to use in the body. The film lacks the antibacterial power of S. Aurelius. The addition of nanoparticles SnO2 increases the dielectric constant but decreases with increasing frequency of input voltage and the intensity of light employed to PVA-PEG/SnO2 nanofiber. The application of the light intensity reduces the dielectric constant of the PVA-PEG/SnO2 nanofiber in all nanoparticle doping ranges.

Constant covariance in local vertical coordinates for near-circular orbits

NASA Technical Reports Server (NTRS)

Shepperd, Stanley W.

1991-01-01

A method is presented for devising a covariance matrix that either remains constant or grows in keeping with the presence of a period error in a rotating local-vertical coordinate system. The solution presented may prove useful in the initialization of simulation covariance matrices for near-circular-orbit problems. Use is made of the Clohessy-Wiltshire equations and the travelling-ellipse formulation.

A new estimate of the Hubble constant using the Virgo cluster distance

NASA Astrophysics Data System (ADS)

Visvanathan, N.

The Hubble constant, which defines the size and age of the universe, remains substantially uncertain. Attention is presently given to an improved distance to the Virgo Cluster obtained by means of the 1.05-micron luminosity-H I width relation of spirals. In order to improve the absolute calibration of the relation, accurate distances to the nearby SMC, LMC, N6822, SEX A and N300 galaxies have also been obtained, on the basis of the near-IR P-L relation of the Cepheids. A value for the global Hubble constant of 67 + or 4 km/sec per Mpc is obtained.

Guidelines for the recognition of cemetery remains in Greece.

PubMed

Eliopoulos, Constantine; Moraitis, Konstantinos; Reyes, Federico; Spiliopoulou, Chara; Manolis, Sotiris

2011-06-01

Forensic pathologists frequently consult anthropologists for the identification of skeletonized human remains. These remains may be the result of criminal activity or remains that were unearthed because of erosion, or during construction projects. In some cases, human remains that had been previously buried in a cemetery may be the subject of a forensic investigation. Early recognition of cemetery remains prevents unnecessary efforts and conserves precious resources. One of the key characteristics of cemetery remains is the presence of embalmed tissue. However, there are countries where embalming is not a common practice, and other clues must be sought for identifying previously buried remains. Current funerary customs in Greece and, in particular, the tradition of exhumations result in a large number of misplaced human remains. The present study presents examples of cemetery remains from Greece and offers guidelines for recognizing changes on skeletal remains that may be indicative of a cemetery origin. Location of discovery, condition of the remains, and the types of associated artifacts are all factors that aid forensic anthropologists in identifying cemetery remains.

Constant mortality and fertility over age in Hydra

PubMed Central

Schaible, Ralf; Scheuerlein, Alexander; Dańko, Maciej J.; Gampe, Jutta; Martínez, Daniel E.; Vaupel, James W.

2015-01-01

Senescence, the increase in mortality and decline in fertility with age after maturity, was thought to be inevitable for all multicellular species capable of repeated breeding. Recent theoretical advances and compilations of data suggest that mortality and fertility trajectories can go up or down, or remain constant with age, but the data are scanty and problematic. Here, we present compelling evidence for constant age-specific death and reproduction rates in Hydra, a basal metazoan, in a set of experiments comprising more than 3.9 million days of observations of individual Hydra. Our data show that 2,256 Hydra from two closely related species in two laboratories in 12 cohorts, with cohort age ranging from 0 to more than 41 y, have extremely low, constant rates of mortality. Fertility rates for Hydra did not systematically decline with advancing age. This falsifies the universality of the theories of the evolution of aging that posit that all species deteriorate with age after maturity. The nonsenescent life history of Hydra implies levels of maintenance and repair that are sufficient to prevent the accumulation of damage for at least decades after maturity, far longer than the short life expectancy of Hydra in the wild. A high proportion of stem cells, constant and rapid cell turnover, few cell types, a simple body plan, and the fact that the germ line is not segregated from the soma are characteristics of Hydra that may make nonsenescence feasible. Nonsenescence may be optimal because lifetime reproduction may be enhanced more by extending adult life spans than by increasing daily fertility. PMID:26644561

Constant mortality and fertility over age in Hydra.

PubMed

Schaible, Ralf; Scheuerlein, Alexander; Dańko, Maciej J; Gampe, Jutta; Martínez, Daniel E; Vaupel, James W

2015-12-22

Senescence, the increase in mortality and decline in fertility with age after maturity, was thought to be inevitable for all multicellular species capable of repeated breeding. Recent theoretical advances and compilations of data suggest that mortality and fertility trajectories can go up or down, or remain constant with age, but the data are scanty and problematic. Here, we present compelling evidence for constant age-specific death and reproduction rates in Hydra, a basal metazoan, in a set of experiments comprising more than 3.9 million days of observations of individual Hydra. Our data show that 2,256 Hydra from two closely related species in two laboratories in 12 cohorts, with cohort age ranging from 0 to more than 41 y, have extremely low, constant rates of mortality. Fertility rates for Hydra did not systematically decline with advancing age. This falsifies the universality of the theories of the evolution of aging that posit that all species deteriorate with age after maturity. The nonsenescent life history of Hydra implies levels of maintenance and repair that are sufficient to prevent the accumulation of damage for at least decades after maturity, far longer than the short life expectancy of Hydra in the wild. A high proportion of stem cells, constant and rapid cell turnover, few cell types, a simple body plan, and the fact that the germ line is not segregated from the soma are characteristics of Hydra that may make nonsenescence feasible. Nonsenescence may be optimal because lifetime reproduction may be enhanced more by extending adult life spans than by increasing daily fertility.

Constant curvature black holes in Einstein AdS gravity: Euclidean action and thermodynamics

NASA Astrophysics Data System (ADS)

Guilleminot, Pablo; Olea, Rodrigo; Petrov, Alexander N.

2018-03-01

We compute the Euclidean action for constant curvature black holes (CCBHs), as an attempt to associate thermodynamic quantities to these solutions of Einstein anti-de Sitter (AdS) gravity. CCBHs are gravitational configurations obtained by identifications along isometries of a D -dimensional globally AdS space, such that the Riemann tensor remains constant. Here, these solutions are interpreted as extended objects, which contain a (D -2 )-dimensional de-Sitter brane as a subspace. Nevertheless, the computation of the free energy for these solutions shows that they do not obey standard thermodynamic relations.

FOREWORD: International determination of the Avogadro constant International determination of the Avogadro constant

NASA Astrophysics Data System (ADS)

Massa, Enrico; Nicolaus, Arnold

2011-04-01

the mass-energy-frequency equivalence. Another effort is to monitor the stability of the Pt-Ir prototype: the technologies described in the present issue can be refined and finalized to calculate the mass variation of 1 kg 28Si spheres by monitoring the surface evolution without weighing them on a balance. The last activity is the determination of the mass of a 28Si sphere by electrical measurements using a watt balance and without any reference to the Pt-Ir prototype. In this framework, it will be necessary to demonstrate the mutual consistency and the stability of both the electrical and crystal mise en pratique of a kilogram definition based on a conventional value of the Planck constant. A related issue is to develop suitable procedures and protocols to disseminate the unit of mass from the new realizations. Since the molar Planck constant is well known via the measurement of the Rydberg constant, the accurate measurement of NA also provides an accurate and independent determination of the Planck constant, h. A comparison of the values of the Planck constant obtained via the watt-balance experiment and the NA determination tests quantum mechanics. In fact, the watt-balance value of h depends on solid state physics through the theories of Josephson and quantum Hall effects, whereas the value of h derived from NA depends on atomic physics through the energy level differences in hydrogen and deuterium, whose associated transition frequencies yield information on the Rydberg constant. Grateful thanks are addressed to H-J Pohl for his outstanding project management in Russia, to A K Kaliteevski and his colleagues of the Central Design Bureau of Machine Building and the Institute of Chemistry of High-Purity Substances for their dedication and the punctual delivery of the enriched material, to H Riemann and his staff of the Institut für Kristallzüchtung for the crystal growth, to our directors for their advice and financial support, and to our colleagues for their

Hydrolysis rate constants and activation parameters for phosphate- and phosphonate-bridged phthalonitrile monomers under acid, neutral and alkali conditions.

PubMed

Belsky, Kirill S; Sulimov, Artem V; Bulgakov, Boris A; Babkin, Alexandr V; Kepman, Alexey V

2017-08-01

Hydrolysis data for Bis(3-(3,4-dicyanophenoxy)phenyl) phenyl phosphate and Bis(3-(3,4-dicyanophenoxy)phenyl) phenylphosphonate under pH 4, 7 and 10 are presented. Conversion/time plots collected by HPLC analysis, typical chromatograms and NMR spectra of the reactions products are given. Pseudo-first order rate constants are determined for both substrates at 25, 50 and 80 °C. Activation parameters were calculated from Arrhenius equation.

Derivation of the midinfrared (5.0-25.0 micron) optical constants of hydrous carbonate and sulfate

NASA Technical Reports Server (NTRS)

Roush, Ted L.; Orenberg, James B.; Pollack, James B.

1993-01-01

There is ample theoretical and observational evidence suggesting liquid water was once stable at the surface of Mars. Because water is essential to the evolution of life, it is important to understand the types of environments in which the liquid water was present. For example, if water were present early in Mars' history, then this raises the possibility that biological activity may have evolved only to eventually become extinct as liquid water became scarce. Alternatively, if liquid water were stable only later in Mars' history, then it becomes problematic to envision mechanisms by which biological activity evolved and remained viable without water until more favorable conditions existed. Even without biological activity, atmospheric carbon dioxide dissolved in water can assist the chemical weathering of primary igneous minerals producing common secondary phases such as hydartes, carbonates, and sulfates. While the identification of hydrates, carbonates, and sulfates on Mars cannot provide direct evidence of biological activity, it can provide significant information regarding the presence and duration of an environment that would support the presence of liquid water at the surface. The specific mineralogy of these secondary phases can provide insight into the environments of their formation. For example, the slow precipitation that occurs in large standing bodies of water, e.g. oceans or lakes, commonly results in the formation of calcite, magnesite, dolomite, siderite, and rhodochrosite. Rapid precipitation that occurs in ephemeral bodies of water, e.g. hypersaline lakes or playas, can result in the formation of all of the above phases as well as aragonite, vaterite, hydrated carbonates, alkali carbonates, bicarbonates, and other poorly ordered phases. Absorption features identified in recent near-infrared spectra of Mars have been interpreted as being due to bicarbonate and bisulfate located in the mineral scaplite. Spectral data returned by the Mariner 6 and

A code of ethics for evidence-based research with ancient human remains.

PubMed

Kreissl Lonfat, Bettina M; Kaufmann, Ina Maria; Rühli, Frank

2015-06-01

As clinical research constantly advances and the concept of evolution becomes a strong and influential part of basic medical research, the absence of a discourse that deals with the use of ancient human remains in evidence-based research is becoming unbearable. While topics such as exhibition and excavation of human remains are established ethical fields of discourse, when faced with instrumentalization of ancient human remains for research (i.e., ancient DNA extractions for disease marker analyses) the answers from traditional ethics or even more practical fields of bio-ethics or more specific biomedical ethics are rare to non-existent. The Centre for Evolutionary Medicine at the University of Zurich solved their needs for discursive action through the writing of a self-given code of ethics which was written in dialogue with the researchers at the Institute and was published online in Sept. 2011: http://evolutionäremedizin.ch/coe/. The philosophico-ethical basis for this a code of conduct and ethics and the methods are published in this article. © 2015 Wiley Periodicals, Inc.

Effective rate constants for nanostructured heterogeneous catalysts

NASA Astrophysics Data System (ADS)

Hendy, Shaun; Gaston, Nicola; Zhang, Philip; Lund, Nat

2012-02-01

There is currently a high level of interest in the use of nanostructured materials for catalysis. For instance, gold, which is largely inert in the bulk, can exhibit strong catalytic activity when in nanoparticle form. With precious metal catalysts such as Pt and Pd in high demand, the use of these materials in nanoparticle form can also substantially reduce costs by exposure of more surface area for the same volume of material. When reactants are plentiful, the effective activity of a nanoparticulate catalyst will increase roughly with its surface area. However, under diffusion-limited conditions, the reactant must diffuse to active sites on the catalyst, so a high surface area and a high density of active sites may bring diminishing returns if reactant is consumed faster than it arrives. Here we apply a mathematical homogenisation approach to derive simple expressions for the effective reactivity of a nanostructured catalyst under diffusion limited conditions that relate the intrinsic rate constants of the surfaces presented by the catalyst to an effective rate constant. When highly active catalytic sites, such as step edges or other defects are present, we show that distinct limiting cases emerge depending on the degree of overlap of the reactant depletion zone about each site. In gases, the size of this depletion zone is approximately the mean free path, so the effective reactivity will depend on the structure of the catalyst on that scale. We discuss implications for the optimal design of nanoparticle catalysts.

Hypoglycemic drugs induce antioxidant aldehyde dehydrogenase activity and remain high in patients with glycemic control in type 2 diabetes.

PubMed

Picazo, Alejandra; Jiménez-Osorio, Angélica S; Zúñiga-Mejía, Porfirio; Pedraza-Chaverri, José; Monroy, Adriana; Rodríguez-Arellano, M Eunice; Barrera-Oviedo, Diana

2017-04-05

The antioxidant system results essential to control and prevent lipid peroxidation due to stress damage in type 2 diabetes. An example is aldehyde dehydrogenase (ALDH), an enzyme that is involved in the detoxification of aldehydes formed during lipid peroxidation. This study was conducted to evaluate ALDH activity and to determine their association with hypoglycemic treatment in type 2 diabetes patients. The study population consisted of 422 Mexican subjects: a control group and type 2 diabetes patients. Type 2 diabetes patients were re-classified as those with or without hypoglycemic treatment and those with or without glycemic control (according to glycated hemoglobin (HbA1c)). Clinical parameters, antioxidant enzyme activities (ALDH, superoxide dismutase (SOD), catalase and glutathione peroxidase) and oxidative markers (reactive oxygen species and thiobarbituric acid reactive substances (TBARS)) were evaluated. The activity of antioxidant enzymes and oxidative stress markers were higher in type 2 diabetes patients with hypoglycemic treatment and without glycemic control than control group. The activity of ALDH and SOD remained high in type 2 diabetes patients with moderate glycemic control while only ALDH's remained high in type 2 diabetes patients with tight glycemic control. Increased ALDH and SOD activities were associated with hypoglycemic therapy. TBARS levels were associated with glycemic control. The persistence of high ALDH and SOD activities in type 2 diabetes patients with glycemic control may be to avoid a significant damage due to the increase in reactive oxygen species and TBARS. It is possible that this new oxidative status prevented the development the classical complications of diabetes. Copyright © 2017 Elsevier B.V. All rights reserved.

Constant load and constant volume response of municipal solid waste in simple shear.

PubMed

Zekkos, Dimitrios; Fei, Xunchang

2017-05-01

Constant load and constant volume simple shear testing was conducted on relatively fresh municipal solid waste (MSW) from two landfills in the United States, one in Michigan and a second in Texas, at respective natural moisture content below field capacity. The results were assessed in terms of two failure strain criteria, at 10% and 30% shear strain, and two interpretations of effective friction angle. Overall, friction angle obtained assuming that the failure plane is horizontal and at 10% shear strain resulted in a conservative estimation of shear strength of MSW. Comparisons between constant volume and constant load simple shear testing results indicated significant differences in the shear response of MSW with the shear resistance in constant volume being lower than the shear resistance in constant load. The majority of specimens were nearly uncompacted during specimen preparation to reproduce the state of MSW in bioreactor landfills or in uncontrolled waste dumps. The specimens had identical percentage of <20mm material but the type of <20mm material was different. The <20mm fraction from Texas was finer and of high plasticity. MSW from Texas was overall weaker in both constant load and constant volume conditions compared to Michigan waste. The results of these tests suggest the possibility of significantly lower shear strength of MSW in bioreactor landfills where waste is placed with low compaction effort and constant volume, i.e., "undrained", conditions may occur. Compacted MSW specimens resulted in shear strength parameters that are higher than uncompacted specimens and closer to values reported in the literature. However, the normalized undrained shear strength in simple shear for uncompacted and compacted MSW was still higher than the normalized undrained shear strength reported in the literature for clayey and silty soils. Copyright © 2016 Elsevier Ltd. All rights reserved.

(In)validity of the constant field and constant currents assumptions in theories of ion transport.

PubMed Central

Syganow, A; von Kitzing, E

1999-01-01

Constant electric fields and constant ion currents are often considered in theories of ion transport. Therefore, it is important to understand the validity of these helpful concepts. The constant field assumption requires that the charge density of permeant ions and flexible polar groups is virtually voltage independent. We present analytic relations that indicate the conditions under which the constant field approximation applies. Barrier models are frequently fitted to experimental current-voltage curves to describe ion transport. These models are based on three fundamental characteristics: a constant electric field, negligible concerted motions of ions inside the channel (an ion can enter only an empty site), and concentration-independent energy profiles. An analysis of those fundamental assumptions of barrier models shows that those approximations require large barriers because the electrostatic interaction is strong and has a long range. In the constant currents assumption, the current of each permeating ion species is considered to be constant throughout the channel; thus ion pairing is explicitly ignored. In inhomogeneous steady-state systems, the association rate constant determines the strength of ion pairing. Among permeable ions, however, the ion association rate constants are not small, according to modern diffusion-limited reaction rate theories. A mathematical formulation of a constant currents condition indicates that ion pairing very likely has an effect but does not dominate ion transport. PMID:9929480

A novel remaining tendon preserving repair technique leads to improved outcomes in special rotator cuff tear patterns.

PubMed

Jeon, Yoon Sang; Kim, Rag Gyu; Shin, Sang-Jin

2018-05-16

The purpose of this study was to identify the tear pattern that could be anatomically repaired by preserving the remaining tendon on footprint and evaluate clinical outcomes of patients who underwent remaining tendon preserving cuff repair. Of 523 patients with full-thickness rotator cuff tears who underwent arthroscopic repair, 41 (7.8%) patients had repairable rotator cuff tear while preserving the remaining tendon. Among them, 31 patients were followed-up for more than 2 years, including 26 patients with posterior L-shaped tear and 5 patients with transtendinous tear patterns. Clinical outcomes were evaluated using ASES and Constant score, SANE score for patient satisfaction, and VAS for pain. MRI was taken for tendon integrity 6 months postoperatively. Of the 31 patients, 11 (35.5%) had previous injury history before rotator cuff tear, including 7 (26.9%) of the 26 patients with posterior L-shaped tear and 4 (80%) of the 5 patients with transtendinous tear. The average size of preoperative cuff tear was 17.8 ± 6.8 mm in anterior-to-posterior direction and 15.2 ± 5.1 mm in medial-to-lateral direction. ASES and Constant score, SANE score, and VAS for pain were significantly (p < 0.001) improved after remaining tendon preserving rotator cuff repair. Rotator cuff tendons of 22(84.6%) patients with posterior L-shaped tear and 4(80%) patients with transtendinous tear patterns were healed. Patients who underwent rotator cuff repair with preservation of the remaining tendon on the footprint obtained satisfactory functional outcomes. Rotator cuff tears in patients who had posterior L-shaped tear extending between supraspinatus and infraspinatus tendons or transtendinous tear pattern with substantial remaining tendon could be repaired using remaining tendon preserving repair technique. Anatomic reduction of torn cuff tendon without undue tension could be achieved using the remaining tendon preserving repair technique.

Cosmological constant and quantum gravitational corrections to the running fine structure constant.

PubMed

Toms, David J

2008-09-26

The quantum gravitational contribution to the renormalization group behavior of the electric charge in Einstein-Maxwell theory with a cosmological constant is considered. Quantum gravity is shown to lead to a contribution to the running charge not present when the cosmological constant vanishes. This reopens the possibility, suggested by Robinson and Wilczek, of altering the scaling behavior of gauge theories at high energies although our result differs. We show the possibility of an ultraviolet fixed point that is linked directly to the cosmological constant.

Oscillating PDF in termini of circadian pacemaker neurons and synchronous molecular clocks in downstream neurons are not sufficient for sustenance of activity rhythms in constant darkness.

PubMed

Prakash, Pavitra; Nambiar, Aishwarya; Sheeba, Vasu

2017-01-01

In Drosophila, neuropeptide Pigment Dispersing Factor (PDF) is expressed in small and large ventral Lateral Neurons (sLNv and lLNv), among which sLNv are critical for activity rhythms in constant darkness. Studies show that this is mediated by rhythmic accumulation and likely secretion of PDF from sLNv dorsal projections, which in turn synchronises molecular oscillations in downstream circadian neurons. Using targeted expression of a neurodegenerative protein Huntingtin in LNv, we evoke a selective loss of neuropeptide PDF and clock protein PERIOD from sLNv soma. However, PDF is not lost from sLNv dorsal projections and lLNv. These flies are behaviourally arrhythmic in constant darkness despite persistence of PDF oscillations in sLNv dorsal projections and synchronous PERIOD oscillations in downstream circadian neurons. We find that PDF oscillations in sLNv dorsal projections are not sufficient for sustenance of activity rhythms in constant darkness and this is suggestive of an additional component that is possibly dependent on sLNv molecular clock and PDF in sLNv soma. Additionally, despite loss of PERIOD in sLNv, their activity rhythms entrain to light/dark cycles indicating that sLNv molecular clocks are not necessary for entrainment. Under constant light, these flies lack PDF from both soma and dorsal projections of sLNv, and when subjected to light/dark cycles, show morning and evening anticipation and accurately phased morning and evening peaks. Thus, under light/dark cycles, PDF in sLNv is not necessary for morning anticipation.

Oscillating PDF in termini of circadian pacemaker neurons and synchronous molecular clocks in downstream neurons are not sufficient for sustenance of activity rhythms in constant darkness

PubMed Central

Prakash, Pavitra; Nambiar, Aishwarya; Sheeba, Vasu

2017-01-01

In Drosophila, neuropeptide Pigment Dispersing Factor (PDF) is expressed in small and large ventral Lateral Neurons (sLNv and lLNv), among which sLNv are critical for activity rhythms in constant darkness. Studies show that this is mediated by rhythmic accumulation and likely secretion of PDF from sLNv dorsal projections, which in turn synchronises molecular oscillations in downstream circadian neurons. Using targeted expression of a neurodegenerative protein Huntingtin in LNv, we evoke a selective loss of neuropeptide PDF and clock protein PERIOD from sLNv soma. However, PDF is not lost from sLNv dorsal projections and lLNv. These flies are behaviourally arrhythmic in constant darkness despite persistence of PDF oscillations in sLNv dorsal projections and synchronous PERIOD oscillations in downstream circadian neurons. We find that PDF oscillations in sLNv dorsal projections are not sufficient for sustenance of activity rhythms in constant darkness and this is suggestive of an additional component that is possibly dependent on sLNv molecular clock and PDF in sLNv soma. Additionally, despite loss of PERIOD in sLNv, their activity rhythms entrain to light/dark cycles indicating that sLNv molecular clocks are not necessary for entrainment. Under constant light, these flies lack PDF from both soma and dorsal projections of sLNv, and when subjected to light/dark cycles, show morning and evening anticipation and accurately phased morning and evening peaks. Thus, under light/dark cycles, PDF in sLNv is not necessary for morning anticipation. PMID:28558035

The Hippocampus Remains Activated over the Long Term for the Retrieval of Truly Episodic Memories

PubMed Central

Harand, Caroline; Bertran, Françoise; La Joie, Renaud; Landeau, Brigitte; Mézenge, Florence; Desgranges, Béatrice; Peigneux, Philippe; Eustache, Francis; Rauchs, Géraldine

2012-01-01

The role of the hippocampus in declarative memory consolidation is a matter of intense debate. We investigated the neural substrates of memory retrieval for recent and remote information using functional magnetic resonance imaging (fMRI). 18 young, healthy participants learned a series of pictures. Then, during two fMRI recognition sessions, 3 days and 3 months later, they had to determine whether they recognized or not each picture using the “Remember/Know” procedure. Presentation of the same learned images at both delays allowed us to track the evolution of memories and distinguish consistently episodic memories from those that were initially episodic and then became familiar or semantic over time and were retrieved without any contextual detail. Hippocampal activation decreased over time for initially episodic, later semantic memories, but remained stable for consistently episodic ones, at least in its posterior part. For both types of memories, neocortical activations were observed at both delays, notably in the ventromedial prefrontal and anterior cingulate cortices. These activations may reflect a gradual reorganization of memory traces within neural networks. Our data indicate maintenance and strengthening of hippocampal and cortico-cortical connections in the consolidation and retrieval of episodic memories over time, in line with the Multiple Trace theory (Nadel and Moscovitch, 1997). At variance, memories becoming semantic over time consolidate through strengthening of cortico-cortical connections and progressive disengagement of the hippocampus. PMID:22937055

Estimating Energy Conversion Efficiency of Thermoelectric Materials: Constant Property Versus Average Property Models

NASA Astrophysics Data System (ADS)

Armstrong, Hannah; Boese, Matthew; Carmichael, Cody; Dimich, Hannah; Seay, Dylan; Sheppard, Nathan; Beekman, Matt

2017-01-01

Maximum thermoelectric energy conversion efficiencies are calculated using the conventional "constant property" model and the recently proposed "cumulative/average property" model (Kim et al. in Proc Natl Acad Sci USA 112:8205, 2015) for 18 high-performance thermoelectric materials. We find that the constant property model generally predicts higher energy conversion efficiency for nearly all materials and temperature differences studied. Although significant deviations are observed in some cases, on average the constant property model predicts an efficiency that is a factor of 1.16 larger than that predicted by the average property model, with even lower deviations for temperature differences typical of energy harvesting applications. Based on our analysis, we conclude that the conventional dimensionless figure of merit ZT obtained from the constant property model, while not applicable for some materials with strongly temperature-dependent thermoelectric properties, remains a simple yet useful metric for initial evaluation and/or comparison of thermoelectric materials, provided the ZT at the average temperature of projected operation, not the peak ZT, is used.

Constant DI pacing suppresses cardiac alternans formation in numerical cable models

NASA Astrophysics Data System (ADS)

Zlochiver, S.; Johnson, C.; Tolkacheva, E. G.

2017-09-01

Cardiac repolarization alternans describe the sequential alternation of the action potential duration (APD) and can develop during rapid pacing. In the ventricles, such alternans may rapidly turn into life risking arrhythmias under conditions of spatial heterogeneity. Thus, suppression of alternans by artificial pacing protocols, or alternans control, has been the subject of numerous theoretical, numerical, and experimental studies. Yet, previous attempts that were inspired by chaos control theories were successful only for a short spatial extent (<2 cm) from the pacing electrode. Previously, we demonstrated in a single cell model that pacing with a constant diastolic interval (DI) can suppress the formation of alternans at high rates of activation. We attributed this effect to the elimination of feedback between the pacing cycle length and the last APD, effectively preventing restitution-dependent alternans from developing. Here, we extend this idea into cable models to study the extent by which constant DI pacing can control alternans during wave propagation conditions. Constant DI pacing was applied to ventricular cable models of up to 5 cm, using human kinetics. Our results show that constant DI pacing significantly shifts the onset of both cardiac alternans and conduction blocks to higher pacing rates in comparison to pacing with constant cycle length. We also demonstrate that constant DI pacing reduces the propensity of spatially discordant alternans, a precursor of wavebreaks. We finally found that the protective effect of constant DI pacing is stronger for increased electrotonic coupling along the fiber in the sense that the onset of alternans is further shifted to higher activation rates. Overall, these results support the potential clinical applicability of such type of pacing in improving protocols of implanted pacemakers, in order to reduce the risk of life-threatening arrhythmias. Future research should be conducted in order to experimentally validate

The Effects of Constant Time Delay Embedded into Teaching Activities for Teaching the Names of Clothes for Preschool Children with Developmental Disabilities

ERIC Educational Resources Information Center

Odluyurt, Serhat

2011-01-01

The general purpose of this study was to examine the effectiveness of constant time delay embedded in activities for teaching clothes name for preschool children with developmental disabilities. This study included four participants having Down syndrome with an age range of 43-46 months. All experimental sessions were conducted in one to one…

Constant symplectic 2-groupoids

NASA Astrophysics Data System (ADS)

Mehta, Rajan Amit; Tang, Xiang

2018-05-01

We propose a definition of symplectic 2-groupoid which includes integrations of Courant algebroids that have been recently constructed. We study in detail the simple but illustrative case of constant symplectic 2-groupoids. We show that the constant symplectic 2-groupoids are, up to equivalence, in one-to-one correspondence with a simple class of Courant algebroids that we call constant Courant algebroids. Furthermore, we find a correspondence between certain Dirac structures and Lagrangian sub-2-groupoids.

Electromyographic Comparison of Squats Using Constant or Variable Resistance.

PubMed

Andersen, Vidar; Steiro Fimland, Marius; Knutson Kolnes, Maria; Jensen, Susanne; Laume, Martine; Hole Saeterbakken, Atle

2016-12-01

Andersen, V, Fimland, MS, Kolnes, MK, Jensen, S, Laume, M and Saeterbakken, AH. Electromyographic comparison of squats using constant or variable resistance. J Strength Cond Res 30(12): 3456-3463, 2016-The aim of the study was to compare the electromyographic (EMG) activity of vastus lateralis, vastus medialis, rectus femoris, and biceps femoris when performing the squat with constant resistance or variable resistance with 2 or 4 elastic bands, respectively, contributing with a mean of 39 and 73% of the total loads. Nineteen resistance-trained women performed 6 repetition maximum using 3 different experimental conditions: free weights (FW), free weights + 2 elastic bands (FW + 2EB), and free weights + 4 elastic bands (FW + 4EB). During analyses, each repetition was divided into 6 phases: upper (more extended knee), middle, and lower phase of the descending and ascending movements. Increased activation in the upper parts of the movement was observed for both variable resistance conditions compared with constant resistance (9-51%, p < 0.001-0.050). Further, a dose-response effect of variable resistance was observed in the upper ascending movement, with 4 elastic bands increasing muscle activation more than 2 elastic bands (7-28%, p = 0.003-0.007). For the whole movement, a 12% higher activation of the biceps femoris was observed for FW + 4EB compared with FW (p = 0.005). There were no differences between the other conditions in any of the muscles (p = 0.077-1.000). In conclusion, performing the squat using free weights in combination with elastic bands seems to be preferable compared with free weights alone and more so with a high contribution from variable resistance to the total load.

Effects of constant pH and unsteady pH at different free ammonia concentrations on shortcut nitrification for landfill leachate treatment.

PubMed

Zhang, Chaosheng; Zhang, Shaoqing; Zhang, Liqiu; Rong, Hongwei; Zhang, Kefang

2015-04-01

On the basis of achieving shortcut nitrification in a lab-scale SBR, the effects of constant pH and unsteady pH at different free ammonia concentrations on shortcut nitrification for landfill leachate treatment was investigated. The results indicate that under the condition of DO of 0.5 ± 0.2 mg/L and temperature of 30 ± 2 °C, the absolute value of nitrite accumulation increased significantly with the increase in free ammonia (FA) concentration from 5.30 to 48.67 mg/L; however, the nitrite accumulation rate remained almost constant at a constant pH of 8.0 ± 0.1. Ammonia oxidation and the nitrite accumulation become slow with the pH decreased from 8.0 ± 0.1 to 7.5 ± 0.2, and the activities of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were severely inhibited when the pH further decreased to 6.5. More importantly, this study confirmed that the pH decrease from 8.0 to 6.5 within a short time exhibited significant negative effect on the ammonia oxidation rather than the FA concentration.

Authenticated DNA from Ancient Wood Remains

PubMed Central

LIEPELT, SASCHA; SPERISEN, CHRISTOPH; DEGUILLOUX, MARIE-FRANCE; PETIT, REMY J.; KISSLING, ROY; SPENCER, MATTHEW; DE BEAULIEU, JACQUES-LOUIS; TABERLET, PIERRE; GIELLY, LUDOVIC; ZIEGENHAGEN, BIRGIT

2006-01-01

• Background The reconstruction of biological processes and human activities during the last glacial cycle relies mainly on data from biological remains. Highly abundant tissues, such as wood, are candidates for a genetic analysis of past populations. While well-authenticated DNA has now been recovered from various fossil remains, the final ‘proof’ is still missing for wood, despite some promising studies. • Scope The goal of this study was to determine if ancient wood can be analysed routinely in studies of archaeology and palaeogenetics. An experiment was designed which included blind testing, independent replicates, extensive contamination controls and rigorous statistical tests. Ten samples of ancient wood from major European forest tree genera were analysed with plastid DNA markers. • Conclusions Authentic DNA was retrieved from wood samples up to 1000 years of age. A new tool for real-time vegetation history and archaeology is ready to use. PMID:16987920

20th century U.S. mineral prices decline in constant dollars

USGS Publications Warehouse

Sullivan, Daniel E.; Sznopek, John L.; Wagner, Lorie A.

2000-01-01

Price indexes developed by the U.S. Geological Survey (USGS) indicate that the long-term constant dollar price of key U.S. mineral raw materials declined over the last century, even though the need for mineral raw materials increased during the same period. Technologies and reduced production costs have allowed mineral production to remain profitable, while lower priced mineral products from domestic and foreign sources helped fuel growth in other sectors of the economy.

Examination of Effective Dielectric Constants Derived from Non-Spherical Melting Hydrometeor

NASA Astrophysics Data System (ADS)

Liao, L.; Meneghini, R.

2009-04-01

The bright band, a layer of enhanced radar echo associated with melting hydrometeors, is often observed in stratiform rain. Understanding the microphysical properties of melting hydrometeors and their scattering and propagation effects is of great importance in accurately estimating parameters of the precipitation from spaceborne radar and radiometers. However, one of the impediments in the study of the radar signature of the melting layer is the determination of effective dielectric constants of melting hydrometeors. Although a number of mixing formulas are available to compute the effective dielectric constants, their results vary to a great extent when water is a component of the mixture, such as in the case of melting snow. It is also physically unclear as to how to select among these various formulas. Furthermore, the question remains as to whether these mixing formulas can be applied to computations of radar polarimetric parameters from non-spherical melting particles. Recently, several approaches using numerical methods have been developed to derive the effective dielectric constants of melting hydrometeors, i.e., mixtures consisting of air, ice and water, based on more realistic melting models of particles, in which the composition of the melting hydrometeor is divided into a number of identical cells. Each of these cells is then assigned in a probabilistic way to be water, ice or air according to the distribution of fractional water contents for a particular particle. While the derived effective dielectric constants have been extensively tested at various wavelengths over a range of particle sizes, these numerical experiments have been restricted to the co-polarized scattering parameters from spherical particles. As polarimetric radar has been increasingly used in the study of microphysical properties of hydrometeors, an extension of the theory to polarimetric variables should provide additional information on melting processes. To account for polarimetric

Unraveling HIV protease flaps dynamics by Constant pH Molecular Dynamics simulations.

PubMed

Soares, Rosemberg O; Torres, Pedro H M; da Silva, Manuela L; Pascutti, Pedro G

2016-08-01

The active site of HIV protease (HIV-PR) is covered by two flaps. These flaps are known to be essential for the catalytic activity of the HIV-PR, but their exact conformations at the different stages of the enzymatic pathway remain subject to debate. Understanding the correct functional dynamics of the flaps might aid the development of new HIV-PR inhibitors. It is known that, the HIV-PR catalytic efficiency is pH-dependent, likely due to the influence of processes such as charge transfer and protonation/deprotonation of ionizable residues. Several Molecular Dynamics (MD) simulations have reported information about the HIV-PR flaps. However, in MD simulations the protonation of a residue is fixed and thus it is not possible to study the correlation between conformation and protonation state. To address this shortcoming, this work attempts to capture, through Constant pH Molecular Dynamics (CpHMD), the conformations of the apo, substrate-bound and inhibitor-bound HIV-PR, which differ drastically in their flap arrangements. The results show that the HIV-PR flaps conformations are defined by the protonation of the catalytic residues Asp25/Asp25' and that these residues are sensitive to pH changes. This study suggests that the catalytic aspartates can modulate the opening of the active site and substrate binding. Copyright © 2016 Elsevier Inc. All rights reserved.

Evolution of robust circadian clocks in Drosophila melanogaster populations reared in constant dark for over 330 generations

NASA Astrophysics Data System (ADS)

Shindey, Radhika; Varma, Vishwanath; Nikhil, K. L.; Sharma, Vijay Kumar

2016-10-01

Robustness is considered to be an important feature of biological systems which may evolve when the functionality of a trait is associated with higher fitness across multiple environmental conditions. Thus, the ability to maintain stable biological phenotypes across environments is thought to be of adaptive value. Previously, we have reported higher intrinsic activity levels (activity levels of free-running rhythm in constant darkness) and power of rhythm (as assessed by amplitude of the periodogram) in Drosophila melanogaster populations (stocks) reared in constant darkness (DD stocks) as compared to those reared in constant light (LL stocks) and 12:12-h light-dark cycles (LD stocks) for over 19 years (˜330 generations). In the current study, we intended to examine whether the enhanced levels of activity observed in DD stocks persist under various environments such as photoperiods, ambient temperatures, non-24-h light-dark (LD) cycles, and semi-natural conditions (SN). We found that DD stocks largely retain their phenotype of enhanced activity levels across most of the above-mentioned environments suggesting the evolution of robust circadian clocks in DD stocks. Furthermore, we compared the peak activity levels of the three stocks across different environmental conditions relative to their peaks in constant darkness and found that the change in peak activity levels upon entrainment was not significantly different across the three stocks for any of the examined environmental conditions. This suggests that the enhancement of activity levels in DD stocks is not due to differential sensitivity to environment. Thus, these results suggest that rearing in constant darkness (DD) leads to evolution of robust circadian clocks suggesting a possible adaptive value of possessing such rhythms under constant dark environments.

Evolution of robust circadian clocks in Drosophila melanogaster populations reared in constant dark for over 330 generations.

PubMed

Shindey, Radhika; Varma, Vishwanath; Nikhil, K L; Sharma, Vijay Kumar

2016-10-01

Robustness is considered to be an important feature of biological systems which may evolve when the functionality of a trait is associated with higher fitness across multiple environmental conditions. Thus, the ability to maintain stable biological phenotypes across environments is thought to be of adaptive value. Previously, we have reported higher intrinsic activity levels (activity levels of free-running rhythm in constant darkness) and power of rhythm (as assessed by amplitude of the periodogram) in Drosophila melanogaster populations (stocks) reared in constant darkness (DD stocks) as compared to those reared in constant light (LL stocks) and 12:12-h light-dark cycles (LD stocks) for over 19 years (∼330 generations). In the current study, we intended to examine whether the enhanced levels of activity observed in DD stocks persist under various environments such as photoperiods, ambient temperatures, non-24-h light-dark (LD) cycles, and semi-natural conditions (SN). We found that DD stocks largely retain their phenotype of enhanced activity levels across most of the above-mentioned environments suggesting the evolution of robust circadian clocks in DD stocks. Furthermore, we compared the peak activity levels of the three stocks across different environmental conditions relative to their peaks in constant darkness and found that the change in peak activity levels upon entrainment was not significantly different across the three stocks for any of the examined environmental conditions. This suggests that the enhancement of activity levels in DD stocks is not due to differential sensitivity to environment. Thus, these results suggest that rearing in constant darkness (DD) leads to evolution of robust circadian clocks suggesting a possible adaptive value of possessing such rhythms under constant dark environments.

CODATA Fundamental Physical Constants

National Institute of Standards and Technology Data Gateway

SRD 121 NIST CODATA Fundamental Physical Constants (Web, free access)   This site, developed in the Physics Laboratory at NIST, addresses three topics: fundamental physical constants, the International System of Units (SI), which is the modern metric system, and expressing the uncertainty of measurement results.

Estimation of hydrolysis rate constants for carbamates ...

EPA Pesticide Factsheets

Cheminformatics based tools, such as the Chemical Transformation Simulator under development in EPA’s Office of Research and Development, are being increasingly used to evaluate chemicals for their potential to degrade in the environment or be transformed through metabolism. Hydrolysis represents a major environmental degradation pathway; unfortunately, only a small fraction of hydrolysis rates for about 85,000 chemicals on the Toxic Substances Control Act (TSCA) inventory are in public domain, making it critical to develop in silico approaches to estimate hydrolysis rate constants. In this presentation, we compare three complementary approaches to estimate hydrolysis rates for carbamates, an important chemical class widely used in agriculture as pesticides, herbicides and fungicides. Fragment-based Quantitative Structure Activity Relationships (QSARs) using Hammett-Taft sigma constants are widely published and implemented for relatively simple functional groups such as carboxylic acid esters, phthalate esters, and organophosphate esters, and we extend these to carbamates. We also develop a pKa based model and a quantitative structure property relationship (QSPR) model, and evaluate them against measured rate constants using R square and root mean square (RMS) error. Our work shows that for our relatively small sample size of carbamates, a Hammett-Taft based fragment model performs best, followed by a pKa and a QSPR model. This presentation compares three comp

Rate Constants and Activation Energies for Gas-Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical.

PubMed

Safron, Andreas; Strandell, Michael; Kierkegaard, Amelie; Macleod, Matthew

2015-07-01

Reaction with hydroxyl radicals (OH) is the major pathway for removal of cyclic volatile methyl siloxanes (cVMS) from air. We present new measurements of second-order rate constants for reactions of the cVMS octamethylcyclotetrasiloxane (D 4 ), decamethylcyclopentasiloxane (D 5 ), and dodecamethylcyclohexasiloxane (D 6 ) with OH determined at temperatures between 313 and 353 K. Our measurements were made using the method of relative rates with cyclohexane as a reference substance and were conducted in a 140-mL gas-phase reaction chamber with online mass spectrometry analysis. When extrapolated to 298 K, our measured reaction rate constants of D 4 and D 5 with the OH radical are 1.9 × 10 -12 (95% confidence interval (CI): (1.7-2.2) × 10 -12 ) and 2.6 × 10 -12 (CI: (2.3-2.9) × 10 -12 ) cm 3 molecule -1 s -1 , respectively, which are 1.9× and 1.7× faster than previous measurements. Our measured rate constant for D 6 is 2.8 × 10 -12 (CI: (2.5-3.2) × 10 -12 ) cm 3 molecule -1 s -1 and to our knowledge there are no comparable laboratory measurements in the literature. Reaction rates for D 5 were 33% higher than for D 4 (CI: 30-37%), whereas the rates for D 6 were only 8% higher than for D 5 (CI: 5-10%). The activation energies of the reactions of D 4 , D 5 , and D 6 with OH were not statistically different and had a value of 4300 ± 2800 J/mol.

BOREAS RSS-17 Dielectric Constant Profile Measurements

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Nickeson, Jaime (Editor); McDonald, Kyle C.; Zimmerman, Reiner; Way, JoBea

2000-01-01

The BOREAS RSS-17 team acquired and analyzed imaging radar data from the ESA's ERS-1 over a complete annual cycle at the BOREAS sites in Canada in 1994 to detect shifts in radar backscatter related to varying environmental conditions. This data set consists of dielectric constant profile measurements from selected trees at various BOREAS flux tower sites. The relative dielectric constant was measured at C-band (frequency = 5 GHz) as a function of depth into the trunk of three trees at each site, Measurements were made during April 1994 with an Applied Microwave Corporation field PDP fitted with a 0.358-cm (0.141-inch) diameter coaxial probe tip. The data are available in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

A direct comparison of U.S. Environmental Protection Agency's method 304B and batch tests for determining activated-sludge biodegradation rate constants for volatile organic compounds

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

Cano, M.L.; Wilcox, M.E.; Compernolle, R. van

Biodegradation rate constants for volatile organic compounds (VOCs) in activated-sludge systems are needed to quantify emissions. One current US environmental Protection Agency method for determining a biodegradation rate constant is Method 304B. In this approach, a specific activated-sludge unit is simulated by a continuous biological treatment system with a sealed headspace. Batch experiments, however, can be alternatives to Method 304B. Two of these batch methods are the batch test that uses oxygen addition (BOX) and the serum bottle test (SBT). In this study, Method 304B was directly compared to BOX and SBT experiments. A pilot-scale laboratory reactor was constructed tomore » serve as the Method 304B unit. Biomass from the unit was also used to conduct BOX and modified SBT experiments (modification involved use of a sealed draft-tube reactor with a headspace recirculation pump instead of a serum bottle) for 1,2-dichloroethane, diisopropyl ether, methyl tertiary butyl ether, and toluene. Three experimental runs--each consisting of one Method 304B experiment, one BOX experiment, and one modified SBT experiment--were completed. The BOX and SBT data for each run were analyzed using a Monod model, and best-fit biodegradation kinetic parameters were determined for each experiment, including a first-order biodegradation rate constant (K{sub 1}). Experimental results suggest that for readily biodegradable VOCs the two batch techniques can provide improved means of determining biodegradation rate constants compared with Method 304B. In particular, these batch techniques avoid the Method 304B problem associated with steady-state effluent concentrations below analytical detection limits. However, experimental results also suggest that the two batch techniques should not be used to determine biodegradation rate constants for slowly degraded VOCs (i.e., K{sub 1} {lt} 0.1 L/g VSS-h).« less

Stability of colloidal gold and determination of the Hamaker constant

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

Demirci, S.; Enuestuen, B.V.; Turkevich, J.

1978-12-14

Previous computation of stability factors of colloidal gold from coagulation data was found to be in systematic error due to an underestimation of the particle concentration by electron microscopy. A new experimental technique was developed for determination of this concentration. Stability factors were recalculated from the previous data using the correct concentration. While most of the previously reported conclusions remain unchanged, the absolute rate of fast coagulation is found to agree with that predicted by the theory. A value of the Hamaker constant was determined from the corrected data.

Tachyon constant-roll inflation

NASA Astrophysics Data System (ADS)

Mohammadi, A.; Saaidi, Kh.; Golanbari, T.

2018-04-01

The constant-roll inflation is studied where the inflaton is taken as a tachyon field. Based on this approach, the second slow-roll parameter is taken as a constant which leads to a differential equation for the Hubble parameter. Finding an exact solution for the Hubble parameter is difficult and leads us to a numerical solution for the Hubble parameter. On the other hand, since in this formalism the slow-roll parameter η is constant and could not be assumed to be necessarily small, the perturbation parameters should be reconsidered again which, in turn, results in new terms appearing in the amplitude of scalar perturbations and the scalar spectral index. Utilizing the numerical solution for the Hubble parameter, we estimate the perturbation parameter at the horizon exit time and compare it with observational data. The results show that, for specific values of the constant parameter η , we could have an almost scale-invariant amplitude of scalar perturbations. Finally, the attractor behavior for the solution of the model is presented, and we determine that the feature could be properly satisfied.

Melatonin administration modifies circadian motor activity under constant light depending on the lighting conditions during suckling.

PubMed

Carpentieri, Agata R; Oliva, Clara; Díez-Noguera, Antoni; Cambras, Trinitat

2015-01-01

Early lighting conditions have been described to produce long-term effects on circadian behavior, which may also influence the response to agents acting on the circadian system. It has been suggested that melatonin (MEL) may act on the circadian pacemaker and as a scavenger of reactive oxygen and nitrogen species. Here, we studied the oxidative and behavioral changes caused by prolonged exposure to constant light (LL) in groups of rats that differed in MEL administration and in lighting conditions during suckling. The rats were exposed to either a light-dark cycle (LD) or LL. At 40 days old, rats were treated for 2 weeks with a daily subcutaneous injection of MEL (10 mg/kg body weight) or a vehicle at activity onset. Blood samples were taken before and after treatment, to determine catalase (CAT) activity and nitrite level in plasma. As expected, LL-reared rats showed a more stable motor activity circadian rhythm than LD rats. MEL treatment produced more reactivity in LD- than in LL rats, and was also able to alter the phase of the rhythm in LD rats. There were no significant differences in nitrite levels or CAT activity between the groups, although both variables increased with time. Finally, we also tested depressive signs by means of sucrose consumption, and anhedonia was found in LD males treated with MEL. The results suggest that the lighting conditions in early infancy are important for the long-term functionality of the circadian system, including rhythm manifestation, responses to MEL and mood alterations.

Vicinal fluorine-fluorine coupling constants: Fourier analysis

NASA Astrophysics Data System (ADS)

San Fabián, J.; Westra Hoekzema, A. J. A.

2004-10-01

Stereochemical dependences of vicinal fluorine-fluorine nuclear magnetic resonance coupling constants (3JFF) have been studied with the multiconfigurational self-consistent field in the restricted active space approach, with the second-order polarization propagator approximation (SOPPA), and with density functional theory. The SOPPA results show the best overall agreement with experimental couplings. The relationship with the dihedral angle between the coupled fluorines has been studied by Fourier analysis, the result is very different from that of proton-proton couplings. The Fourier coefficients do not resemble those of a typical Karplus equation. The four nonrelativistic contributions to the coupling constants of 1,2-difluoroethane configurations have been studied separately showing that up to six Fourier coefficients are required to reproduce the calculated values satisfactorily. Comparison with Fourier coefficients for matching hydrogen fluoride dimer configurations suggests that the higher order Fourier coefficients (Cn⩾3) originate mainly from through-space Fermi contact interaction. The through-space interaction is the main reason 3JFF do not follow the Karplus equation.

Numerical results on the transcendence of constants involving pi, e, and Euler's constant

NASA Technical Reports Server (NTRS)

Bailey, David H.

1988-01-01

The existence of simple polynomial equations (integer relations) for the constants e/pi, e + pi, log pi, gamma (Euler's constant), e exp gamma, gamma/e, gamma/pi, and log gamma is investigated by means of numerical computations. The recursive form of the Ferguson-Fourcade algorithm (Ferguson and Fourcade, 1979; Ferguson, 1986 and 1987) is implemented on the Cray-2 supercomputer at NASA Ames, applying multiprecision techniques similar to those described by Bailey (1988) except that FFTs are used instead of dual-prime-modulus transforms for multiplication. It is shown that none of the constants has an integer relation of degree eight or less with coefficients of Euclidean norm 10 to the 9th or less.

Rate Constants and Activation Energies for Gas‐Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical

PubMed Central

Safron, Andreas; Strandell, Michael; Kierkegaard, Amelie

2015-01-01

ABSTRACT Reaction with hydroxyl radicals (OH) is the major pathway for removal of cyclic volatile methyl siloxanes (cVMS) from air. We present new measurements of second‐order rate constants for reactions of the cVMS octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) with OH determined at temperatures between 313 and 353 K. Our measurements were made using the method of relative rates with cyclohexane as a reference substance and were conducted in a 140‐mL gas‐phase reaction chamber with online mass spectrometry analysis. When extrapolated to 298 K, our measured reaction rate constants of D4 and D5 with the OH radical are 1.9 × 10−12 (95% confidence interval (CI): (1.7–2.2) × 10−12) and 2.6 × 10−12 (CI: (2.3–2.9) × 10−12) cm3 molecule−1 s−1, respectively, which are 1.9× and 1.7× faster than previous measurements. Our measured rate constant for D6 is 2.8 × 10−12 (CI: (2.5–3.2) × 10−12) cm3 molecule−1 s−1 and to our knowledge there are no comparable laboratory measurements in the literature. Reaction rates for D5 were 33% higher than for D4 (CI: 30–37%), whereas the rates for D6 were only 8% higher than for D5 (CI: 5–10%). The activation energies of the reactions of D4, D5, and D6 with OH were not statistically different and had a value of 4300 ± 2800 J/mol. PMID:27708500

Let's Measure the Dielectric Constant of a Piece of Paper!

ERIC Educational Resources Information Center

Karlow, Edwin A.

1991-01-01

Described is a simple circuit with which students can observe the effect of common dielectric materials in a capacitor and measure the dielectric constant of a piece of paper. Discussed are the theory, apparatus construction, and experimental procedures for this activity. (CW)

Construction of exact constants of motion and effective models for many-body localized systems

NASA Astrophysics Data System (ADS)

Goihl, M.; Gluza, M.; Krumnow, C.; Eisert, J.

2018-04-01

One of the defining features of many-body localization is the presence of many quasilocal conserved quantities. These constants of motion constitute a cornerstone to an intuitive understanding of much of the phenomenology of many-body localized systems arising from effective Hamiltonians. They may be seen as local magnetization operators smeared out by a quasilocal unitary. However, accurately identifying such constants of motion remains a challenging problem. Current numerical constructions often capture the conserved operators only approximately, thus restricting a conclusive understanding of many-body localization. In this work, we use methods from the theory of quantum many-body systems out of equilibrium to establish an alternative approach for finding a complete set of exact constants of motion which are in addition guaranteed to represent Pauli-z operators. By this we are able to construct and investigate the proposed effective Hamiltonian using exact diagonalization. Hence, our work provides an important tool expected to further boost inquiries into the breakdown of transport due to quenched disorder.

Quantification aspects of constant pressure (ultra) high pressure liquid chromatography using mass-sensitive detectors with a nebulizing interface.

PubMed

Verstraeten, M; Broeckhoven, K; Lynen, F; Choikhet, K; Landt, K; Dittmann, M; Witt, K; Sandra, P; Desmet, G

2013-01-25

The present contribution investigates the quantitation aspects of mass-sensitive detectors with nebulizing interface (ESI-MSD, ELSD, CAD) in the constant pressure gradient elution mode. In this operation mode, the pressure is controlled and maintained at a set value and the liquid flow rate will vary according to the inverse mobile phase viscosity. As the pressure is continuously kept at the allowable maximum during the entire gradient run, the average liquid flow rate is higher compared to that in the conventional constant flow rate operation mode, thus shortening the analysis time. The following three mass-sensitive detectors were investigated: mass spectrometry detector (MS), evaporative light scattering detector (ELSD) and charged aerosol detector (CAD) and a wide variety of samples (phenones, polyaromatic hydrocarbons, wine, cocoa butter) has been considered. It was found that the nebulizing efficiency of the LC-interfaces of the three detectors under consideration changes with the increasing liquid flow rate. For the MS, the increasing flow rate leads to a lower peak area whereas for the ELSD the peak area increases compared to the constant flow rate mode. The peak area obtained with a CAD is rather insensitive to the liquid flow rate. The reproducibility of the peak area remains similar in both modes, although variation in system permeability compromises the 'long-term' reproducibility. This problem can however be overcome by running a flow rate program with an optimized flow rate and composition profile obtained from the constant pressure mode. In this case, the quantification remains reproducibile, despite any occuring variations of the system permeability. Furthermore, the same fragmentation pattern (MS) has been found in the constant pressure mode compared to the customary constant flow rate mode. Copyright © 2012 Elsevier B.V. All rights reserved.

REAR DETAIL OF RIGHT ENGINE AND WING. FLAPS REMAIN DOWN ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

REAR DETAIL OF RIGHT ENGINE AND WING. FLAPS REMAIN DOWN AND SPOILERS UP. THIS CONFIGURATION IS AUTOMATICALLY ACTIVATED ON ROLLOUT. - Greater Buffalo International Airport, Maintenance Hangar, Buffalo, Erie County, NY

Construction of Lines of Constant Density and Constant Refractive Index for Ternary Liquid Mixtures.

ERIC Educational Resources Information Center

Tasic, Aleksandar Z.; Djordjevic, Bojan D.

1983-01-01

Demonstrates construction of density constant and refractive index constant lines in triangular coordinate system on basis of systematic experimental determinations of density and refractive index for both homogeneous (single-phase) ternary liquid mixtures (of known composition) and the corresponding binary compositions. Background information,…

Effect of a physical activity programme in the aquatic environment on haemodynamic constants in pregnant women.

PubMed

Vázquez-Lara, Juana María; Ruiz-Frutos, Carlos; Rodríguez-Díaz, Luciano; Ramírez-Rodrigo, Jesús; Villaverde-Gutiérrez, Carmen; Torres-Luque, Gema

2017-09-20

To evaluate the effect of a physical activity programme in the aquatic environment with immersion up to the neck, of six weeks duration, on haemodynamic constants in pregnant women. A six-week physical activity programme in the aquatic environment was carried out with a total of 46 pregnant women, who were distributed into an experimental group (n = 18), which participated in the programme, and a control group (n = 28), which followed routine care. In both groups different haemodynamic measurements were evaluated before and after the program. At the beginning of the programme the mean systolic blood pressure was similar between groups, but diastolic blood pressure was slightly higher in the experimental group. When the measurements at the last session were compared, arterial pressures (systolic, diastolic and mean) were significantly higher in the control group (p <.050). Similarly, the initial plasma volume values did not differ between groups, but after the intervention, the control group women showed a higher mean (p <.010). The fraction of sodium excretion (FENa) increased significantly in the experimental group, after the programme, with a mean three times higher (p <.050). Aldosterone plasma levels did not show significant differences between the groups in the different measurements. A programme of swimming and immersion exercises in pregnant women contributes to hydrosaline balance, preventing an excessive increase in usual plasma volume during pregnancy and in the activity of the renin-aldosterone axis. Copyright © 2017 Elsevier España, S.L.U. All rights reserved.

The observational constraint on constant-roll inflation

NASA Astrophysics Data System (ADS)

Gao, Qing

2018-07-01

We discuss the constant-roll inflation with constant ɛ2 and constant \\bar η . By using the method of Bessel function approximation, the analytical expressions for the scalar and tensor power spectra, the scalar and tensor spectral tilts, and the tensor to scalar ratio are derived up to the first order of ɛ1. The model with constant ɛ2 is ruled out by the observations at the 3σ confidence level, and the model with constant \\bar η is consistent with the observations at the 1σ confidence level. The potential for the model with constant \\bar η is also obtained from the Hamilton-Jacobi equation. Although the observations constrain the constant-roll inflation to be the slow-roll inflation, the n s- r results from the constant-roll inflation are not the same as those from the slow-roll inflation even when \\bar η 0.01.

Elastic constants of calcite

USGS Publications Warehouse

Peselnick, L.; Robie, R.A.

1962-01-01

The recent measurements of the elastic constants of calcite by Reddy and Subrahmanyam (1960) disagree with the values obtained independently by Voigt (1910) and Bhimasenachar (1945). The present authors, using an ultrasonic pulse technique at 3 Mc and 25??C, determined the elastic constants of calcite using the exact equations governing the wave velocities in the single crystal. The results are C11=13.7, C33=8.11, C44=3.50, C12=4.82, C13=5.68, and C14=-2.00, in units of 1011 dyncm2. Independent checks of several of the elastic constants were made employing other directions and polarizations of the wave velocities. With the exception of C13, these values substantially agree with the data of Voigt and Bhimasenachar. ?? 1962 The American Institute of Physics.

Connecting Fundamental Constants

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

Di Mario, D.

2008-05-29

A model for a black hole electron is built from three basic constants only: h, c and G. The result is a description of the electron with its mass and charge. The nature of this black hole seems to fit the properties of the Planck particle and new relationships among basic constants are possible. The time dilation factor in a black hole associated with a variable gravitational field would appear to us as a charge; on the other hand the Planck time is acting as a time gap drastically limiting what we are able to measure and its dimension willmore » appear in some quantities. This is why the Planck time is numerically very close to the gravitational/electric force ratio in an electron: its difference, disregarding a {pi}{radical}(2) factor, is only 0.2%. This is not a coincidence, it is always the same particle and the small difference is between a rotating and a non-rotating particle. The determination of its rotational speed yields accurate numbers for many quantities, including the fine structure constant and the electron magnetic moment.« less

Estimation of thermodynamic acidity constants of some penicillinase-resistant penicillins.

PubMed

Demiralay, Ebru Çubuk; Üstün, Zehra; Daldal, Y Doğan

2014-03-01

In this work, thermodynamic acidity constants (pssKa) of methicillin, oxacillin, nafcillin, cloxacilin, dicloxacillin were determined with reverse phase liquid chromatographic method (RPLC) by taking into account the effect of the activity coefficients in hydro-organic water-acetonitrile binary mixtures. From these values, thermodynamic aqueous acidity constants of these drugs were calculated by different approaches. The linear relationships established between retention factors of the species and the polarity parameter of the mobile phase (ET(N)) was proved to predict accurately retention in LC as a function of the acetonitrile content (38%, 40% and 42%, v/v). Copyright © 2013 Elsevier B.V. All rights reserved.

How fundamental are fundamental constants?

NASA Astrophysics Data System (ADS)

Duff, M. J.

2015-01-01

I argue that the laws of physics should be independent of one's choice of units or measuring apparatus. This is the case if they are framed in terms of dimensionless numbers such as the fine structure constant, ?. For example, the standard model of particle physics has 19 such dimensionless parameters whose values all observers can agree on, irrespective of what clock, rulers or scales? they use to measure them. Dimensional constants, on the other hand, such as ?, c, G, e and k ?, are merely human constructs whose number and values differ from one choice of units to the next. In this sense, only dimensionless constants are 'fundamental'. Similarly, the possible time variation of dimensionless fundamental 'constants' of nature is operationally well defined and a legitimate subject of physical enquiry. By contrast, the time variation of dimensional constants such as ? or ? on which a good many (in my opinion, confusing) papers have been written, is a unit-dependent phenomenon on which different observers might disagree depending on their apparatus. All these confusions disappear if one asks only unit-independent questions. We provide a selection of opposing opinions in the literature and respond accordingly.

Effective optical constants of anisotropic materials

NASA Technical Reports Server (NTRS)

Aronson, J. R.; Emslie, A. G.

1980-01-01

The applicability of a technique for determining the optical constants of soil or aerosol components on the basis of measurements of the reflectance or transmittance of inhomogeneous samples of component material is investigated. Optical constants for a sample of very pure quartzite were obtained by a specular reflection technique and line parameters were calculated by classical dispersion theory. Predictions of the reflectance of powdered quartz were then derived from optical constants measured for the anisotropic quartz and for pure quartz crystals, and compared with experimental measurements. The calculated spectra are found to resemble each other moderately well in shape, however the reflectance level calculated from the psuedo-optical constants (quartzite) is consistently below that calculated from quartz values. The spectrum calculated from the quartz optical constants is also shown to represent the experimental nonrestrahlen features more accurately. It is thus concluded that although optical constants derived from inhomogeneous materials may represent the spectral features of a powdered sample qualitatively a quantitative fit to observed data is not likely.

Constant Communities in Complex Networks

NASA Astrophysics Data System (ADS)

Chakraborty, Tanmoy; Srinivasan, Sriram; Ganguly, Niloy; Bhowmick, Sanjukta; Mukherjee, Animesh

2013-05-01

Identifying community structure is a fundamental problem in network analysis. Most community detection algorithms are based on optimizing a combinatorial parameter, for example modularity. This optimization is generally NP-hard, thus merely changing the vertex order can alter their assignments to the community. However, there has been less study on how vertex ordering influences the results of the community detection algorithms. Here we identify and study the properties of invariant groups of vertices (constant communities) whose assignment to communities are, quite remarkably, not affected by vertex ordering. The percentage of constant communities can vary across different applications and based on empirical results we propose metrics to evaluate these communities. Using constant communities as a pre-processing step, one can significantly reduce the variation of the results. Finally, we present a case study on phoneme network and illustrate that constant communities, quite strikingly, form the core functional units of the larger communities.

The Arrow of Time In a Universe with a Positive Cosmological Constant Λ

NASA Astrophysics Data System (ADS)

Mersini-Houghton, Laura

There is a mounting evidence that our universe is propelled into an accelerated expansion driven by Dark Energy. The simplest form of Dark Energy is a cosmological constant Λ, which is woven into the fabric of spacetime. For this reason it is often referred to as vacuum energy. It has the "strange" property of maintaining a constant energy density despite the expanding volume of the universe. Universes whose energy ismade of Λ posses an event horizon with and eternally finite constant temperature and entropy, and are known as DeSitter geometries. Since the entropy of DeSitter spaces remains a finite constant, then the meaning of a thermodynamic arrow of time becomes unclear. Here we explore the consequences of a fundamental cosmological constant Λ for our universe. We show that when the gravitational entropy of a pure DeSitter state ultimately dominates over the matter entropy, then the thermodynamic arrow of time in our universe may reverse in scales of order a Hubble time. We find that due to the dynamics of gravity and entanglement with other domain, a finite size system such as a DeSitter patch with horizon size H 0 -1 has a finite lifetime ∆t. This phenomenon arises from the dynamic gravitational instabilities that develop during a DeSitter epoch and turn catastrophic. A reversed arrow of time is in disagreementwith observations. Thus we explore the possibilities that: Nature may not favor a fundamental Λ, or else general relativity may be modified in the infrared regime when Λ dominates the expansion of the Universe.

UAS stealth: target pursuit at constant distance using a bio-inspired motion camouflage guidance law.

PubMed

Strydom, Reuben; Srinivasan, Mandyam V

2017-09-21

The aim of this study is to derive a guidance law by which an unmanned aerial system(s) (UAS) can pursue a moving target at a constant distance, while concealing its own motion. We derive a closed-form solution for the trajectory of the UAS by imposing two key constraints: (1) the shadower moves in such a way as to be perceived as a stationary object by the shadowee, and (2) the distance between the shadower and shadowee is kept constant. Additionally, the theory presented in this paper considers constraints on the maximum achievable speed and acceleration of the shadower. Our theory is tested through Matlab simulations, which validate the camouflage strategy for both 2D and 3D conditions. Furthermore, experiments using a realistic vision-based implementation are conducted in a virtual environment, where the results demonstrate that even with noisy state information it is possible to remain well camouflaged using the constant distance motion camouflage technique.

The impact of constant light on the estrous cycle of the rat.

PubMed

Campbell, C S; Schwartz, N B

1980-04-01

The initial effects of constant bright light on the events of the rat estrous cycle were monitored in order to examine the interdependence of the hormonal and behavioral rhythms which comprise the cycle. Females exposed to constant bright light for only one cycle either failed to ovulate or showed a delay in the hormonal and behavioral events of the cycle as well as in ovulation. Females exposed to constant light for two cycles 1) failed to ovulate, 2) showed an advancement, or 3) showed a delay in the hormonal events of the estrous cycle and ovulation. Vaginal cytology and the onset of locomotor activity did not maintain their normal temporal relationships with the other events of the estrous cycle in constant light. In spite of the absence of an external timing signal, the majority of hormonal rhythms maintained their normal phase relationships and showed little sign of internal desynchrony. Ovaries in many animals showed high rates of follicular atresia early in the cycle, suggesting that the effects of bright constant light are far more complex than can be attributed to a simple absence of an external timing signal.

Universe of constant

NASA Astrophysics Data System (ADS)

Yongquan, Han

2016-10-01

The ideal gas state equation is not applicable to ordinary gas, it should be applied to the Electromagnetic ``gas'' that is applied to the radiation, the radiation should be the ultimate state of matter changes or initial state, the universe is filled with radiation. That is, the ideal gas equation of state is suitable for the Singular point and the universe. Maybe someone consider that, there is no vessel can accommodate radiation, it is because the Ordinary container is too small to accommodate, if the radius of your container is the distance that Light through an hour, would you still think it can't accommodates radiation? Modern scientific determinate that the radius of the universe now is about 1027 m, assuming that the universe is a sphere whose volume is approximately: V = 4.19 × 1081 cubic meters, the temperature radiation of the universe (cosmic microwave background radiation temperature of the universe, should be the closest the average temperature of the universe) T = 3.15k, radiation pressure P = 5 × 10-6 N / m 2, according to the law of ideal gas state equation, PV / T = constant = 6 × 1075, the value of this constant is the universe, The singular point should also equal to the constant Author: hanyongquan

Vicinal fluorine-fluorine coupling constants: Fourier analysis.

PubMed

San Fabián, J; Westra Hoekzema, A J A

2004-10-01

Stereochemical dependences of vicinal fluorine-fluorine nuclear magnetic resonance coupling constants (3JFF) have been studied with the multiconfigurational self-consistent field in the restricted active space approach, with the second-order polarization propagator approximation (SOPPA), and with density functional theory. The SOPPA results show the best overall agreement with experimental couplings. The relationship with the dihedral angle between the coupled fluorines has been studied by Fourier analysis, the result is very different from that of proton-proton couplings. The Fourier coefficients do not resemble those of a typical Karplus equation. The four nonrelativistic contributions to the coupling constants of 1,2-difluoroethane configurations have been studied separately showing that up to six Fourier coefficients are required to reproduce the calculated values satisfactorily. Comparison with Fourier coefficients for matching hydrogen fluoride dimer configurations suggests that the higher order Fourier coefficients (Cn> or =3) originate mainly from through-space Fermi contact interaction. The through-space interaction is the main reason 3JFF do not follow the Karplus equation. (c) 2004 American Institute of Physics

Theoretical rate constants of super-exchange hole transfer and thermally induced hopping in DNA.

PubMed

Shimazaki, Tomomi; Asai, Yoshihiro; Yamashita, Koichi

2005-01-27

Recently, the electronic properties of DNA have been extensively studied, because its conductivity is important not only to the study of fundamental biological problems, but also in the development of molecular-sized electronics and biosensors. We have studied theoretically the reorganization energies, the activation energies, the electronic coupling matrix elements, and the rate constants of hole transfer in B-form double-helix DNA in water. To accommodate the effects of DNA nuclear motions, a subset of reaction coordinates for hole transfer was extracted from classical molecular dynamics (MD) trajectories of DNA in water and then used for ab initio quantum chemical calculations of electron coupling constants based on the generalized Mulliken-Hush model. A molecular mechanics (MM) method was used to determine the nuclear Franck-Condon factor. The rate constants for two types of mechanisms of hole transfer-the thermally induced hopping (TIH) and the super-exchange mechanisms-were determined based on Marcus theory. We found that the calculated matrix elements are strongly dependent on the conformations of the nucleobase pairs of hole-transferable DNA and extend over a wide range of values for the "rise" base-step parameter but cluster around a particular value for the "twist" parameter. The calculated activation energies are in good agreement with experimental results. Whereas the rate constant for the TIH mechanism is not dependent on the number of A-T nucleobase pairs that act as a bridge, the rate constant for the super-exchange process rapidly decreases when the length of the bridge increases. These characteristic trends in the calculated rate constants effectively reproduce those in the experimental data of Giese et al. [Nature 2001, 412, 318]. The calculated rate constants were also compared with the experimental results of Lewis et al. [Nature 2000, 406, 51].

Application of the compensated Arrhenius formalism to explain the dielectric constant dependence of rates for Menschutkin reactions.

PubMed

Petrowsky, Matt; Glatzhofer, Daniel T; Frech, Roger

2013-11-21

The dependence of the reaction rate on solvent dielectric constant is examined for the reaction of trihexylamine with 1-bromohexane in a series of 2-ketones over the temperature range 25-80 °C. The rate constant data are analyzed using the compensated Arrhenius formalism (CAF), where the rate constant assumes an Arrhenius-like equation that also contains a dielectric constant dependence in the exponential prefactor. The CAF activation energies are substantially higher than those obtained using the simple Arrhenius equation. A master curve of the data is observed by plotting the prefactors against the solvent dielectric constant. The master curve shows that the reaction rate has a weak dependence on dielectric constant for values approximately less than 10 and increases more rapidly for dielectric constant values greater than 10.

Constant potential pulse polarography

USGS Publications Warehouse

Christie, J.H.; Jackson, L.L.; Osteryoung, R.A.

1976-01-01

The new technique of constant potential pulse polarography, In which all pulses are to be the same potential, is presented theoretically and evaluated experimentally. The response obtained is in the form of a faradaic current wave superimposed on a constant capacitative component. Results obtained with a computer-controlled system exhibit a capillary response current similar to that observed In normal pulse polarography. Calibration curves for Pb obtained using a modified commercial pulse polarographic instrument are in good accord with theoretical predictions.

Constant-roll tachyon inflation and observational constraints

NASA Astrophysics Data System (ADS)

Gao, Qing; Gong, Yungui; Fei, Qin

2018-05-01

For the constant-roll tachyon inflation, we derive the analytical expressions for the scalar and tensor power spectra, the scalar and tensor spectral tilts and the tensor to scalar ratio to the first order of epsilon1 by using the method of Bessel function approximation. The derived ns-r results are compared with the observations, we find that only the constant-roll inflation with ηH being a constant is consistent with the observations and observations constrain the constant-roll inflation to be slow-roll inflation. The tachyon potential is also reconstructed for the constant-roll inflation which is consistent with the observations.

Elastic constants and pressure derivative of elastic constants of Si1-xGex solid solution

NASA Astrophysics Data System (ADS)

Jivani, A. R.; Baria, J. K.; Vyas, P. S.; Jani, A. R.

2013-02-01

Elastic properties of Si1-xGex solid solution with arbitrary (atomic) concentration (x) are studied using the pseudo-alloy atom model based on the pseudopotential theory and on the higher-order perturbation scheme with the application of our own proposed model potential. We have used local-field correction function proposed by Sarkar et al to study Si-Ge system. The Elastic constants and pressure derivatives of elastic constants of the solid solution is investigated with different concentration x of Ge. It is found in the present study that the calculated numerical values of the aforesaid physical properties of Si-Ge system are function of x. The elastic constants (C11, C12 and C44) decrease linearly with increase in concentration x and pressure derivative of elastic constants (C11, C12 and C44) increase with the concentration x of Ge. This study provides better set of theoretical results for such solid solution for further comparison either with theoretical or experimental results.

Present status of astronomical constants

NASA Astrophysics Data System (ADS)

Fukushima, T.

Given was the additional information to the previous report on the recent progress in the determinations of astronomical constants (Fukushima 2000). First noted was the revision of LG as 6.969290134×10-10 based on the proposal to shift its status from a primary to a defining constant (Petit 2000). Next focused was the significant update of the correction to the current precession constant, Δp, based on the recent LLR-based determination (Chapront et al. 2000) as -0.3164+/-0.0030"/cy. By combining this and the equal weighted average of VLBI determinations (Mathews et al. 2000; Petrov 2000; Shirai and Fukushima 2000; Vondrak and Ron 2000) as -0.2968+/-0.0043"/cy, we derived the best estimate of precession constant as p = 5028.790+/-0.005"/cy. Also redetermined were some other quantities related to the precession formula; namely the offsets of Celestial Ephemeris Pole of the International Celestial Reference System as &Deltaψ0sinɛ0 = (-17.0+/-0.3) mas and Δɛ0 = (-5.1+/-0.3) mas. As a result, the obliquity of the ecliptic at the epoch J2000.0 was estimated as ɛ0 = 23°26'21."4059+/-0."0003. As a summary, presented was the (revised) IAU 2000 File of Current Best Estimates of astronomical constants, which is to replace the former 1994 version (Standish 1995).

Graviton fluctuations erase the cosmological constant

NASA Astrophysics Data System (ADS)

Wetterich, C.

2017-10-01

Graviton fluctuations induce strong non-perturbative infrared renormalization effects for the cosmological constant. The functional renormalization flow drives a positive cosmological constant towards zero, solving the cosmological constant problem without the need to tune parameters. We propose a simple computation of the graviton contribution to the flow of the effective potential for scalar fields. Within variable gravity, with effective Planck mass proportional to the scalar field, we find that the potential increases asymptotically at most quadratically with the scalar field. The solutions of the derived cosmological equations lead to an asymptotically vanishing cosmological "constant" in the infinite future, providing for dynamical dark energy in the present cosmological epoch. Beyond a solution of the cosmological constant problem, our simplified computation also entails a sizeable positive graviton-induced anomalous dimension for the quartic Higgs coupling in the ultraviolet regime, substantiating the successful prediction of the Higgs boson mass within the asymptotic safety scenario for quantum gravity.

Rate constants for chemical reactions in high-temperature nonequilibrium air

NASA Technical Reports Server (NTRS)

Jaffe, R. L.

1986-01-01

In the nonequilibrium atmospheric chemistry regime that will be encountered by the proposed Aeroassisted Orbital Transfer Vehicle in the upper atmosphere, where air density is too low for thermal and chemical equilibrium to be maintained, the detailed high temperature air chemistry plays a critical role in defining radiative and convective heating loads. Although vibrational and electronic temperatures remain low (less than 15,000 K), rotational and translational temperatures may reach 50,000 K. Attention is presently given to the effects of multiple temperatures on the magnitudes of various chemical reaction rate constants, for the cases of both bimolecular exchange reactions and collisional excitation and dissociation reactions.

CODATA recommended values of the fundamental constants

NASA Astrophysics Data System (ADS)

Mohr, Peter J.; Taylor, Barry N.

2000-11-01

A review is given of the latest Committee on Data for Science and Technology (CODATA) adjustment of the values of the fundamental constants. The new set of constants, referred to as the 1998 values, replaces the values recommended for international use by CODATA in 1986. The values of the constants, and particularly the Rydberg constant, are of relevance to the calculation of precise atomic spectra. The standard uncertainty (estimated standard deviation) of the new recommended value of the Rydberg constant, which is based on precision frequency metrology and a detailed analysis of the theory, is approximately 1/160 times the uncertainty of the 1986 value. The new set of recommended values as well as a searchable bibliographic database that gives citations to the relevant literature is available on the World Wide Web at physics.nist.gov/constants and physics.nist.gov/constantsbib, respectively. .

Binding Rate Constants Reveal Distinct Features of Disordered Protein Domains.

PubMed

Dogan, Jakob; Jonasson, Josefin; Andersson, Eva; Jemth, Per

2015-08-04

Intrinsically disordered proteins (IDPs) are abundant in the proteome and involved in key cellular functions. However, experimental data about the binding kinetics of IDPs as a function of different environmental conditions are scarce. We have performed an extensive characterization of the ionic strength dependence of the interaction between the molten globular nuclear co-activator binding domain (NCBD) of CREB binding protein and five different protein ligands, including the intrinsically disordered activation domain of p160 transcriptional co-activators (SRC1, TIF2, ACTR), the p53 transactivation domain, and the folded pointed domain (PNT) of transcription factor ETS-2. Direct comparisons of the binding rate constants under identical conditions show that the association rate constant, kon, for interactions between NCBD and disordered protein domains is high at low salt concentrations (90-350 × 10(6) M(-1) s(-1) at 4 °C) but is reduced significantly (10-30-fold) with an increasing ionic strength and reaches a plateau around physiological ionic strength. In contrast, the kon for the interaction between NCBD and the folded PNT domain is only 7 × 10(6) M(-1) s(-1) (4 °C and low salt) and displays weak ionic strength dependence, which could reflect a distinctly different association that relies less on electrostatic interactions. Furthermore, the basal rate constant (in the absence of electrostatic interactions) is high for the NCBD interactions, exceeding those typically observed for folded proteins. One likely interpretation is that disordered proteins have a large number of possible collisions leading to a productive on-pathway encounter complex, while folded proteins are more restricted in terms of orientation. Our results highlight the importance of electrostatic interactions in binding involving IDPs and emphasize the significance of including ionic strength as a factor in studies that compare the binding properties of IDPs to those of ordered proteins.

A Simple Method to Calculate the Temperature Dependence of the Gibbs Energy and Chemical Equilibrium Constants

ERIC Educational Resources Information Center

Vargas, Francisco M.

2014-01-01

The temperature dependence of the Gibbs energy and important quantities such as Henry's law constants, activity coefficients, and chemical equilibrium constants is usually calculated by using the Gibbs-Helmholtz equation. Although, this is a well-known approach and traditionally covered as part of any physical chemistry course, the required…

New perspectives on constant-roll inflation

NASA Astrophysics Data System (ADS)

Cicciarella, Francesco; Mabillard, Joel; Pieroni, Mauro

2018-01-01

We study constant-roll inflation using the β-function formalism. We show that the constant rate of the inflaton roll is translated into a first order differential equation for the β-function which can be solved easily. The solutions to this equation correspond to the usual constant-roll models. We then construct, by perturbing these exact solutions, more general classes of models that satisfy the constant-roll equation asymptotically. In the case of an asymptotic power law solution, these corrections naturally provide an end to the inflationary phase. Interestingly, while from a theoretical point of view (in particular in terms of the holographic interpretation) these models are intrinsically different from standard slow-roll inflation, they may have phenomenological predictions in good agreement with present cosmological data.

Total individual ion activity coefficients of calcium and carbonate in seawater at 25°C and 35%. salinity, and implications to the agreement between apparent and thermodynamic constants of calcite and aragonite

USGS Publications Warehouse

Plummer, Niel; Sundquist, Eric T.

1982-01-01

We have calculated the total individual ion activity coefficients of carbonate and calcium,  and , in seawater. Using the ratios of stoichiometric and thermodynamic constants of carbonic acid dissociation and total mean activity coefficient data measured in seawater, we have obtained values which differ significantly from those widely accepted in the literature. In seawater at 25°C and 35%. salinity the (molal) values of  and  are 0.038 ± 0.002 and 0.173 ± 0.010, respectively. These values of  and  are independent of liquid junction errors and internally consistent with the value . By defining  and  on a common scale (), the product  is independent of the assigned value of  and may be determined directly from thermodynamic measurements in seawater. Using the value  and new thermodynamic equilibrium constants for calcite and aragonite, we show that the apparent constants of calcite and aragonite are consistent with the thermodynamic equilibrium constants at 25°C and 35%. salinity. The demonstrated consistency between thermodynamic and apparent constants of calcite and aragonite does not support a hypothesis of stable Mg-calcite coatings on calcite or aragonite surfaces in seawater, and suggests that the calcite critical carbonate ion curve of Broecker and Takahashi (1978,Deep-Sea Research25, 65–95) defines the calcite equilibrium boundary in the oceans, within the uncertainty of the data.

Properties and effects of remaining carbon from waste plastics gasifying on iron scale reduction.

PubMed

Zhang, Chongmin; Chen, Shuwen; Miao, Xincheng; Yuan, Hao

2011-06-01

The carbonous activities of three kinds of carbon-bearing materials gasified from plastics were tested with coal coke as reference. The results showed that the carbonous activities of these remaining carbon-bearing materials were higher than that of coal-coke. Besides, the fractal analyses showed that the porosities of remaining carbon-bearing materials were higher than that of coal-coke. It revealed that these kinds of remaining carbon-bearing materials are conducive to improve the kinetics conditions of gas-solid phase reaction in iron scale reduction. Copyright © 2011 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

In situ generation of a hydroxyl radical by nanoporous activated carbon derived from rice husk for environmental applications: kinetic and thermodynamic constants.

PubMed

Karthikeyan, S; Sekaran, G

2014-03-07

The objective of this investigation is to evaluate the hydroxyl radical (˙OH) generation using nanoporous activated carbon (NPAC), derived from rice husk, and dissolved oxygen in water. The in situ production of the ˙OH radical was confirmed through the DMPO spin trapping method in EPR spectroscopy and quantitative determination by a deoxyribose assay procedure. NPAC served as a heterogeneous catalyst to degrade 2-deoxy-d-ribose (a reference compound) using hydroxyl radical generated from dissolved oxygen in water at temperatures in the range 313-373 K and pH 6, with first order rate constants (k = 9.2 × 10(-2) min(-1), k = 1.2 × 10(-1) min(-1), k = 1.3 × 10(-1) min(-1) and k = 1.68 × 10(-1) min(-1)). The thermodynamic constants for the generation of hydroxyl radicals by NPAC and dissolved oxygen in water were ΔG -1.36 kJ mol(-1) at 313 K, ΔH 17.73 kJ mol(-1) and ΔS 61.01 J mol(-1) K(-1).

Quintessential inflation from a variable cosmological constant in a 5D vacuum

NASA Astrophysics Data System (ADS)

Membiela, Agustin; Bellini, Mauricio

2006-10-01

We explore an effective 4D cosmological model for the universe where the variable cosmological constant governs its evolution and the pressure remains negative along all the expansion. This model is introduced from a 5D vacuum state where the (space-like) extra coordinate is considered as noncompact. The expansion is produced by the inflaton field, which is considered as nonminimally coupled to gravity. We conclude from experimental data that the coupling of the inflaton with gravity should be weak, but variable in different epochs of the evolution of the universe.

Capacitive Cells for Dielectric Constant Measurement

ERIC Educational Resources Information Center

Aguilar, Horacio Munguía; Maldonado, Rigoberto Franco

2015-01-01

A simple capacitive cell for dielectric constant measurement in liquids is presented. As an illustrative application, the cell is used for measuring the degradation of overheated edible oil through the evaluation of their dielectric constant.

Aerosol pH buffering in the southeastern US: Fine particles remain highly acidic despite large reductions in sulfate

NASA Astrophysics Data System (ADS)

Weber, R. J.; Guo, H.; Russell, A. G.; Nenes, A.

2015-12-01

pH is a critical aerosol property that impacts many atmospheric processes, including biogenic secondary organic aerosol formation, gas-particle phase partitioning, and mineral dust or redox metal mobilization. Particle pH has also been linked to adverse health effects. Using a comprehensive data set from the Southern Oxidant and Aerosol Study (SOAS) as the basis for thermodynamic modeling, we have shown that particles are currently highly acidic in the southeastern US, with pH between 0 and 2. Sulfate and ammonium are the main acid-base components that determine particle pH in this region, however they have different sources and their concentrations are changing. Over 15 years of network data show that sulfur dioxide emission reductions have resulted in a roughly 70 percent decrease in sulfate, whereas ammonia emissions, mainly link to agricultural activities, have been largely steady, as have gas phase ammonia concentrations. This has led to the view that particles are becoming more neutralized. However, sensitivity analysis, based on thermodynamic modeling, to changing sulfate concentrations indicates that particles have remained highly acidic over the past decade, despite the large reductions in sulfate. Furthermore, anticipated continued reductions of sulfate and relatively constant ammonia emissions into the future will not significantly change particle pH until sulfate drops to clean continental background levels. The result reshapes our expectation of future particle pH and implies that atmospheric processes and adverse health effects linked to particle acidity will remain unchanged for some time into the future.

Relativistic problems on astronomical constants.

NASA Astrophysics Data System (ADS)

Tao, Jinhe; Huang, Tianyi

1999-06-01

The fact that modern astronomical observational technique has made rapid progress and the 1PN approximation of general relativity has been extensively applied in celestial mechanics and astrometry, makes it is necessary to investigate and examine the system of astronomical constants carefully and rigorously in the relativistic framework. The mass of a celestial body in the solar system should be defined as its BD mass that changes relatively in an amount less than 10-19 and could be considered as a constant. The equations satisfied by the gravitational potentials are not Poisson equations anymore but depend on the choice of the coordinate gauge. Therefore the gravitational potentials cannot be expanded in the traditional harmonics. It is neccessary to choose the coordinate gauge and take BD multipole moments as astronomical constants. The obliquity of the ecliptic has been determined in high precision and it would be neccessary to give a conventional definition of the 1PN ecliptic. A relativistic definition of the geoid is important and left to be discussed. The astronomical constants that relate the units of time and length have been clearly defined but need to be clarified to avoid their misuse.

MILITARY PAY: Processes for Retaining Injured Army National Guard and Reserve Soldiers on Active Duty Have Been Improved, but Some Challenges Remain

DTIC Science & Technology

2007-05-01

Active Duty Have Been Improved, but Some Challenges Remain The Army’s MRP program has largely resolved the widespread delays in order processing that...interviewed confirmed that they did not experience gaps in pay and associated benefits because of order processing delays. However, some of the...and injured reserve component soldiers we interviewed, these improvements have virtually eliminated the widespread delays in order processing that

MATHEMATICAL CONSTANTS.

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

Robinson, H.P.; Potter, Elinor

1971-03-01

This collection of mathematical data consists of two tables of decimal constants arranged according to size rather than function, a third table of integers from 1 to 1000, giving some of their properties, and a fourth table listing some infinite series arranged according to increasing size of the coefficients of the terms. The decimal values of Tables I and II are given to 20 D.

Sequential Metabolic Phases as a Means to Optimize Cellular Output in a Constant Environment

PubMed Central

Bockmayr, Alexander; Holzhütter, Hermann-Georg

2015-01-01

Temporal changes of gene expression are a well-known regulatory feature of all cells, which is commonly perceived as a strategy to adapt the proteome to varying external conditions. However, temporal (rhythmic and non-rhythmic) changes of gene expression are also observed under virtually constant external conditions. Here we hypothesize that such changes are a means to render the synthesis of the metabolic output more efficient than under conditions of constant gene activities. In order to substantiate this hypothesis, we used a flux-balance model of the cellular metabolism. The total time span spent on the production of a given set of target metabolites was split into a series of shorter time intervals (metabolic phases) during which only selected groups of metabolic genes are active. The related flux distributions were calculated under the constraint that genes can be either active or inactive whereby the amount of protein related to an active gene is only controlled by the number of active genes: the lower the number of active genes the more protein can be allocated to the enzymes carrying non-zero fluxes. This concept of a predominantly protein-limited efficiency of gene expression clearly differs from other concepts resting on the assumption of an optimal gene regulation capable of allocating to all enzymes and transporters just that fraction of protein necessary to prevent rate limitation. Applying this concept to a simplified metabolic network of the central carbon metabolism with glucose or lactate as alternative substrates, we demonstrate that switching between optimally chosen stationary flux modes comprising different sets of active genes allows producing a demanded amount of target metabolites in a significantly shorter time than by a single optimal flux mode at fixed gene activities. Our model-based findings suggest that temporal expression of metabolic genes can be advantageous even under conditions of constant external substrate supply. PMID:25786979

The 1% concordance Hubble constant

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

Bennett, C. L.; Larson, D.; Weiland, J. L.

2014-10-20

The determination of the Hubble constant has been a central goal in observational astrophysics for nearly a hundred years. Extraordinary progress has occurred in recent years on two fronts: the cosmic distance ladder measurements at low redshift and cosmic microwave background (CMB) measurements at high redshift. The CMB is used to predict the current expansion rate through a best-fit cosmological model. Complementary progress has been made with baryon acoustic oscillation (BAO) measurements at relatively low redshifts. While BAO data do not independently determine a Hubble constant, they are important for constraints on possible solutions and checks on cosmic consistency. Amore » precise determination of the Hubble constant is of great value, but it is more important to compare the high and low redshift measurements to test our cosmological model. Significant tension would suggest either uncertainties not accounted for in the experimental estimates or the discovery of new physics beyond the standard model of cosmology. In this paper we examine in detail the tension between the CMB, BAO, and cosmic distance ladder data sets. We find that these measurements are consistent within reasonable statistical expectations and we combine them to determine a best-fit Hubble constant of 69.6 ± 0.7 km s{sup –1} Mpc{sup –1}. This value is based upon WMAP9+SPT+ACT+6dFGS+BOSS/DR11+H {sub 0}/Riess; we explore alternate data combinations in the text. The combined data constrain the Hubble constant to 1%, with no compelling evidence for new physics.« less

Carter constant and angular momentum

NASA Astrophysics Data System (ADS)

Mukherjee, Sajal; Nayak, K. Rajesh

We investigate the Carter-like constant in the case of a particle moving in a nonrelativistic dipolar potential. This special case is a missing link between the Carter constant in stationary and axially symmetric spacetimes (SASS) such as Kerr solution and its possible Newtonian counterpart. We use this system to carry over the definition of angular momentum from the Newtonian mechanics to the relativistic SASS.

High-Temperature Slow Crack Growth of Silicon Carbide Determined by Constant-Stress-Rate and Constant-Stress Testing

NASA Technical Reports Server (NTRS)

Choi, Sung H.; Salem, J. A.; Nemeth, N. N.

1998-01-01

High-temperature slow-crack-growth behaviour of hot-pressed silicon carbide was determined using both constant-stress-rate ("dynamic fatigue") and constant-stress ("static fatigue") testing in flexure at 1300 C in air. Slow crack growth was found to be a governing mechanism associated with failure of the material. Four estimation methods such as the individual data, the Weibull median, the arithmetic mean and the median deviation methods were used to determine the slow crack growth parameters. The four estimation methods were in good agreement for the constant-stress-rate testing with a small variation in the slow-crack-growth parameter, n, ranging from 28 to 36. By contrast, the variation in n between the four estimation methods was significant in the constant-stress testing with a somewhat wide range of n= 16 to 32.

REACTOR PHYSICS CONSTANTS

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

None

1963-07-01

This second edition is based on data available on March 15, 1961. Sections on constants necessary for the interpretation of experimental data and on digital computer programs for reactor design and reactor physics have been added. 1344 references. (D.C.W.)

Adjoint-based constant-mass partial derivatives

DOE PAGES

Favorite, Jeffrey A.

2017-09-01

In transport theory, adjoint-based partial derivatives with respect to mass density are constant-volume derivatives. Likewise, adjoint-based partial derivatives with respect to surface locations (i.e., internal interface locations and the outer system boundary) are constant-density derivatives. This study derives the constant-mass partial derivative of a response with respect to an internal interface location or the outer system boundary and the constant-mass partial derivative of a response with respect to the mass density of a region. Numerical results are given for a multiregion two-dimensional (r-z) cylinder for three very different responses: the uncollided gamma-ray flux at an external detector point, k effmore » of the system, and the total neutron leakage. Finally, results from the derived formulas compare extremely well with direct perturbation calculations.« less

Systematics of constant roll inflation

NASA Astrophysics Data System (ADS)

Anguelova, Lilia; Suranyi, Peter; Wijewardhana, L. C. R.

2018-02-01

We study constant roll inflation systematically. This is a regime, in which the slow roll approximation can be violated. It has long been thought that this approximation is necessary for agreement with observations. However, recently it was understood that there can be inflationary models with a constant, and not necessarily small, rate of roll that are both stable and compatible with the observational constraint ns ≈ 1. We investigate systematically the condition for such a constant-roll regime. In the process, we find a whole new class of inflationary models, in addition to the known solutions. We show that the new models are stable under scalar perturbations. Finally, we find a part of their parameter space, in which they produce a nearly scale-invariant scalar power spectrum, as needed for observational viability.

Theoretical Evaluation of the Transient Response of Constant Head and Constant Flow-Rate Permeability Tests

USGS Publications Warehouse

Zhang, M.; Takahashi, M.; Morin, R.H.; Esaki, T.

1998-01-01

A theoretical analysis is presented that compares the response characteristics of the constant head and the constant flowrate (flow pump) laboratory techniques for quantifying the hydraulic properties of geologic materials having permeabilities less than 10-10 m/s. Rigorous analytical solutions that describe the transient distributions of hydraulic gradient within a specimen are developed, and equations are derived for each method. Expressions simulating the inflow and outflow rates across the specimen boundaries during a constant-head permeability test are also presented. These solutions illustrate the advantages and disadvantages of each method, including insights into measurement accuracy and the validity of using Darcy's law under certain conditions. The resulting observations offer practical considerations in the selection of an appropriate laboratory test method for the reliable measurement of permeability in low-permeability geologic materials.

A full set of langatate high-temperature acoustic wave constants: elastic, piezoelectric, dielectric constants up to 900°C.

PubMed

Davulis, Peter M; da Cunha, Mauricio Pereira

2013-04-01

A full set of langatate (LGT) elastic, dielectric, and piezoelectric constants with their respective temperature coefficients up to 900°C is presented, and the relevance of the dielectric and piezoelectric constants and temperature coefficients are discussed with respect to predicted and measured high-temperature SAW propagation properties. The set of constants allows for high-temperature acoustic wave (AW) propagation studies and device design. The dielectric constants and polarization and conductive losses were extracted by impedance spectroscopy of parallel-plate capacitors. The measured dielectric constants at high temperatures were combined with previously measured LGT expansion coefficients and used to determine the elastic and piezoelectric constants using resonant ultrasound spectroscopy (RUS) measurements at temperatures up to 900°C. The extracted LGT piezoelectric constants and temperature coefficients show that e11 and e14 change by up to 62% and 77%, respectively, for the entire 25°C to 900°C range when compared with room-temperature values. The LGT high-temperature constants and temperature coefficients were verified by comparing measured and predicted phase velocities (vp) and temperature coefficients of delay (TCD) of SAW delay lines fabricated along 6 orientations in the LGT plane (90°, 23°, Ψ) up to 900°C. For the 6 tested orientations, the predicted SAW vp agree within 0.2% of the measured vp on average and the calculated TCD is within 9.6 ppm/°C of the measured value on average over the temperature range of 25°C to 900°C. By including the temperature dependence of both dielectric and piezoelectric constants, the average discrepancies between predicted and measured SAW properties were reduced, on average: 77% for vp, 13% for TCD, and 63% for the turn-over temperatures analyzed.

Sociodemographic inequalities in leisure-time physical activity and active commuting to school in Brazilian adolescents: National School Health Survey (PeNSE 2009, 2012, and 2015).

PubMed

Ferreira, Rodrigo Wiltgen; Varela, Andrea Ramirez; Monteiro, Luciana Zaranza; Häfele, César Augusto; Santos, Simone José Dos; Wendt, Andrea; Silva, Inácio Crochemore Mohnsam

2018-01-01

The objective of this study was to identify inequalities in leisure-time physical activity and active commuting to school in Brazilian adolescents, as well as trends according to gender, type of school, maternal schooling, and geographic region, from 2009 to 2015. This was a descriptive study based on data from the Brazilian National School Health Survey (PeNSE) in 2009, 2012, and 2015. Students were defined as active in their leisure time when they practiced at least 60 minutes of physical activity a day on five or more of the seven days prior to the interview. Active commuting to school was defined as walking or biking to school on the week prior to the interview. The outcomes were stratified by gender, type of school, maternal schooling, and geographic region. Inequalities were assessed by differences and ratios between the estimates, as well as summary inequality indices. The 2009, 2012, and 2015 surveys included 61,301, 61,145, and 51,192 schoolchildren, respectively. Prevalence of leisure-time physical activity was 13.8% in 2009, 15.9% in 2012, and 14.7% in 2015; the rates for active commuting to school were 70.6%, 61.7%, and 66.7%, respectively. Boys showed 10 percentage points higher prevalence of leisure-time physical activity and 5 points higher active commuting to school than girls. Children of mothers with more schooling showed a mean of 10 percentage points higher prevalence of leisure-time physical activity than children of mothers with the lowest schooling and some 30 percentage points lower in relation to active commuting to school. The observed inequalities remained constant over the course of the period. The study identified socioeconomic and gender inequalities that remained constant throughout the period and which were specific to each domain of physical activity.

Wormholes and the cosmological constant problem.

NASA Astrophysics Data System (ADS)

Klebanov, I.

The author reviews the cosmological constant problem and the recently proposed wormhole mechanism for its solution. Summation over wormholes in the Euclidean path integral for gravity turns all the coupling parameters into dynamical variables, sampled from a probability distribution. A formal saddle point analysis results in a distribution with a sharp peak at the cosmological constant equal to zero, which appears to solve the cosmological constant problem. He discusses the instabilities of the gravitational Euclidean path integral and the difficulties with its interpretation. He presents an alternate formalism for baby universes, based on the "third quantization" of the Wheeler-De Witt equation. This approach is analyzed in a minisuperspace model for quantum gravity, where it reduces to simple quantum mechanics. Once again, the coupling parameters become dynamical. Unfortunately, the a priori probability distribution for the cosmological constant and other parameters is typically a smooth function, with no sharp peaks.

Calculation of kinetic rate constants from thermodynamic data

NASA Technical Reports Server (NTRS)

Marek, C. John

1995-01-01

A new scheme for relating the absolute value for the kinetic rate constant k to the thermodynamic constant Kp is developed for gases. In this report the forward and reverse rate constants are individually related to the thermodynamic data. The kinetic rate constants computed from thermodynamics compare well with the current kinetic rate constants. This method is self consistent and does not have extensive rules. It is first demonstrated and calibrated by computing the HBr reaction from H2 and Br2. This method then is used on other reactions.

Walking at non-constant speeds: mechanical work, pendular transduction, and energy congruity.

PubMed

Balbinot, G

2017-05-01

Although almost half of all walking bouts in urban environments consist of less than 12 consecutive steps and several day-to-day gait activities contain transient gait responses, in most studies gait analysis is performed at steady-state. This study aimed to analyze external (W ext ) and internal mechanical work (W int ), pendulum-like mechanics, and elastic energy usage during constant and non-constant speeds. The mechanical work, pendular transduction, and energy congruity (an estimate of storage and release of elastic energy) during walking were computed using two force platforms. We found that during accelerating gait (+NCS) energy recovery is maintained, besides extra W + ext , for decelerating gait (-NCS) poor energy recovery was counterbalanced by W - ext and C% predominance. We report an increase in elastic energy usage with speed (4-11%). Both W - ext and %C suggests that elastic energy usage is higher at faster speeds and related to -NCS (≈20% of elastic energy usage). This study was the first to show evidences of elastic energy usage during constant and non-constant speeds. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Constant-roll (quasi-)linear inflation

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

Equivalent refractive-index structure constant of non-Kolmogorov turbulence.

PubMed

Li, Yujie; Zhu, Wenyue; Wu, Xiaoqing; Rao, Ruizhong

2015-09-07

The relationship between the non-Kolmogorov refractive-index structure constant and the Kolmogorov refractive-index structure constant is derived by using the refractive-index structure function and the variance of refractive-index fluctuations. It shows that the non-Kolmogorov structure constant is proportional to the Kolmogorov structure constant and the scaling factor depends on the outer scale and the spectral power law. For a fixed Kolmogorov structure constant, the non-Kolmogorov structure constant increases with a increasing outer scale for the power law less than 11/3, the trend is opposite for the power law greater than 11/3. This equivalent relation provides a way of obtaining the non-Kolmogorov structure constant by using the Kolmogorov structure constant.

Trends in participation rates for wildlife-associated outdoor recreation activities by age and race/ethnicity: implications for cohort-component projection models

Treesearch

John F. Dwyer; Allan Marsinko

1998-01-01

Cohort-component projection models have been used to explore the implications of increased aging and growth of racial/ethnic minority groups on number of participants in outdoor recreation activities in the years ahead. Projections usually assume that participation rates by age and race/ethnicity remain constant over time. This study looks at trends in activity...

Systematic harmonic power laws inter-relating multiple fundamental constants

NASA Astrophysics Data System (ADS)

Chakeres, Donald; Buckhanan, Wayne; Andrianarijaona, Vola

2017-01-01

Power laws and harmonic systems are ubiquitous in physics. We hypothesize that 2, π, the electron, Bohr radius, Rydberg constant, neutron, fine structure constant, Higgs boson, top quark, kaons, pions, muon, Tau, W, and Z when scaled in a common single unit are all inter-related by systematic harmonic powers laws. This implies that if the power law is known it is possible to derive a fundamental constant's scale in the absence of any direct experimental data of that constant. This is true for the case of the hydrogen constants. We created a power law search engine computer program that randomly generated possible positive or negative powers searching when the product of logical groups of constants equals 1, confirming they are physically valid. For 2, π, and the hydrogen constants the search engine found Planck's constant, Coulomb's energy law, and the kinetic energy law. The product of ratios defined by two constants each was the standard general format. The search engine found systematic resonant power laws based on partial harmonic fraction powers of the neutron for all of the constants with products near 1, within their known experimental precision, when utilized with appropriate hydrogen constants. We conclude that multiple fundamental constants are inter-related within a harmonic power law system.

Measuring Solar Radiation Incident on Earth: Solar Constant-3 (SOLCON-3)

NASA Technical Reports Server (NTRS)

Crommelynck, Dominique; Joukoff, Alexandre; Dewitte, Steven

2002-01-01

Life on Earth is possible because the climate conditions on Earth are relatively mild. One element of the climate on Earth, the temperature, is determined by the heat exchanges between the Earth and its surroundings, outer space. The heat exchanges take place in the form of electromagnetic radiation. The Earth gains energy because it absorbs solar radiation, and it loses energy because it emits thermal infrared radiation to cold space. The heat exchanges are in balance: the heat gained by the Earth through solar radiation equals the heat lost through thermal radiation. When the balance is perturbed, a temperature change and hence a climate change of the Earth will occur. One possible perturbation of the balance is the CO2 greenhouse effect: when the amount of CO2 in the atmosphere increases, this will reduce the loss of thermal infrared radiation to cold space. Earth will gain more heat and hence the temperature will rise. Another perturbation of the balance can occur through variation of the amount of energy emitted by the sun. When the sun emits more energy, this will directly cause a rise of temperature on Earth. For a long time scientists believed that the energy emitted by the sun was constant. The 'solar constant' is defined as the amount of solar energy received per unit surface at a distance of one astronomical unit (the average distance of Earth's orbit) from the sun. Accurate measurements of the variations of the solar constant have been made since 1978. From these we know that the solar constant varies approximately with the 11-year solar cycle observed in other solar phenomena, such as the occurrence of sunspots, dark spots that are sometimes visible on the solar surface. When a sunspot occurs on the sun, since the spot is dark, the radiation (light) emitted by the sun drops instantaneously. Oddly, periods of high solar activity, when a lot of sunspot numbers increase, correspond to periods when the average solar constant is high. This indicates that

A hundred years with the cosmological constant

NASA Astrophysics Data System (ADS)

Grøn, Øyvind G.

2018-07-01

The main points in the history of the cosmological constant are briefly discussed. As a conceptual background, useful for teaching of physics at an elementary college and university level, Newton’s theory formulated locally in terms of the Poisson equation is presented, and it is shown how it is modified by the introduction of the cosmological constant. The different physical interpretations of the cosmological constant, as introduced by Einstein in 1917 and interpreted by Lemaître in 1934, are presented. Energy conservation in an expanding universe dominated by vacuum energy is discussed. The connection between the cosmological constant and the quantum mechanical vacuum energy is mentioned, together with the problem that a quantum mechanical calculation of the density of the vacuum energy gives a vastly too large value of the cosmological constant. The article is concluded by reviewing a solution of this problem that was presented on May 11, 2017.

Global Kinetic Constants for Thermal Oxidative Degradation of a Cellulosic Paper

NASA Technical Reports Server (NTRS)

Kashiwagi, Takashi; Nambu, Hidesaburo

1992-01-01

Values of global kinetic constants for pyrolysis, thermal oxidative degradation, and char oxidation of a cellulosic paper were determined by a derivative thermal gravimetric study. The study was conducted at heating rates of 0.5, 1, 1.5, 3, and 5 C/min in ambient atmospheres of nitrogen, 0.28, 1.08, 5.2 percent oxygen concentrations, and air. Sample weight loss rate, concentrations of CO, CO2, and H2O in the degradation products, and oxygen consumption were continuously measured during the experiment. Values of activation energy, preexponential factor, orders of reaction, and yields of CO, CO2, H2O, total hydrocarbons, and char for each degradation reaction were derived from the results. Heat of reaction for each reaction was determined by differential scanning calorimetry. A comparison of the calculated CO, CO2, H2O, total hydrocarbons, sample weight loss rate, and oxygen consumption was made with the measured results using the derived kinetic constants, and the accuracy of the values of kinetic constants was discussed.

Information dissemination model for social media with constant updates

NASA Astrophysics Data System (ADS)

Zhu, Hui; Wu, Heng; Cao, Jin; Fu, Gang; Li, Hui

2018-07-01

With the development of social media tools and the pervasiveness of smart terminals, social media has become a significant source of information for many individuals. However, false information can spread rapidly, which may result in negative social impacts and serious economic losses. Thus, reducing the unfavorable effects of false information has become an urgent challenge. In this paper, a new competitive model called DMCU is proposed to describe the dissemination of information with constant updates in social media. In the model, we focus on the competitive relationship between the original false information and updated information, and then propose the priority of related information. To more effectively evaluate the effectiveness of the proposed model, data sets containing actual social media activity are utilized in experiments. Simulation results demonstrate that the DMCU model can precisely describe the process of information dissemination with constant updates, and that it can be used to forecast information dissemination trends on social media.

Effect on head-wind profiles and mean head-wind velocity on landing capacity flying constant-airspeed and constant-groundspeed approaches

NASA Technical Reports Server (NTRS)

Hastings, E. C., Jr.; Kelley, W. W.

1979-01-01

A study was conducted to determine the effect of head-wind profiles and mean head-wind velocities on runway landing capacity for airplanes flying constant-airspeed and constant-groundspeed approaches. It was determined that when the wind profiles were encountered with the currently used constant airspeed approach method, the landing capacity was reduced. The severity of these reductions increased as the mean head-wind value of the profile increased. When constant-groundspeed approaches were made in the same wind profiles, there were no losses in landing capacity. In an analysis of mean head winds, it was determined that in a mean head wind of 35 knots, the landing capacity using constant-airspeed approaches was 13% less than for the no wind condition. There were no reductions in landing capacity with constant-groundspeed approaches for mean head winds less than 35 knots. This same result was observed when the separation intervals between airplanes was reduced.

Automated Microwave Dielectric Constant Measurement

DTIC Science & Technology

1987-03-01

IJSWC TR 86-46 AD.-A 184 182 AUTOMATED MICROWAVE DIELECTRIC CONSTANT MEASUREMENT SYTIEM BY B. C. GLANCY A. KRALL PESEARCH AND TECHNOLOGY DEPARTMENT...NO0. NO. ACCESSION NO. Silver Spring, Maryland 20903-500061152N ZROO1 ZRO131 R1AA29 11. TITLE (Include Security Classification) AUTOMATED MICROWAVE ...constants as a funct on of microwave frequency has been simplified using an automated testing apparatus. This automated procedure is based on the use of a

Reports on Astronomical Constants

NASA Astrophysics Data System (ADS)

Fukushima, Toshio

Recent progress in the determination of astronomical constants is reviewed. By using the latest numerical integration of LC (Irwin and Fukushima, 1999) and the latest value of the geoidal potential W0 (Groten, 1999), we reestimated the general relativistic scale constants as LC = 1.480~826~867~4 × 10-8 ± 1.4 × 10-17, LG = 6.969~290~13 × 10-10 ± 6 × 10-18, and LB = 1.550~519~767~5 × 10-8 ± 2.0 × 10-17. Presented is a proposal to fix the numerical value of LG as the above in order to remove the geophysical ambiguity in its evaluation in the future. Next focused upon is the correction to the IAU 1976 Precession (Lieske et al., 1977). By simply averaging the latest VLBI-based determinations (Mathews et al., 2000; Petrov, 2000; Shirai and Fukushima, 2000; Vondrak and Ron, 2000) and the latest LLR-based determinations (Chapront et al., 1999), we obtained the best estimates of precession-related quantities at J2000.0: the general precession in longitude, p = 5~028.78 ± 0.03 ''/cy; obliquity of the ecliptic, ɛ0 = 23o26'21.''405~6 ± 0.''0005; and the pole offsets of the CEP of ICRS, Δ ψ0 sin ɛ0 = (-17.5 ± 0.8) mas, and Δ ɛ0 = (-5.2 ± 0.4) mas. After quoting the latest determination of mass of Pluto-Charon system (Tholen and Buie, 1997) and the recent change of G (Mohr and Taylor, 1999), proposed is a draft IAU 2000 File of Current Best Estimates of Astronomical Constants to replace the former 1994 version (Standish, 1995). It may even supplant the IAU 1976 System of Astronomical Constants (Duncombe et al., 1977), subject to discussion at this General Assembly.

Is There a Cosmological Constant?

NASA Technical Reports Server (NTRS)

Kochanek, Christopher; Oliversen, Ronald J. (Technical Monitor)

2002-01-01

The grant contributed to the publication of 18 refereed papers and 5 conference proceedings. The primary uses of the funding have been for page charges, travel for invited talks related to the grant research, and the support of a graduate student, Charles Keeton. The refereed papers address four of the primary goals of the proposal: (1) the statistics of radio lenses as a probe of the cosmological model (#1), (2) the role of spiral galaxies as lenses (#3), (3) the effects of dust on statistics of lenses (#7, #8), and (4) the role of groups and clusters as lenses (#2, #6, #10, #13, #15, #16). Four papers (#4, #5, #11, #12) address general issues of lens models, calibrations, and the relationship between lens galaxies and nearby galaxies. One considered cosmological effects in lensing X-ray sources (#9), and two addressed issues related to the overall power spectrum and theories of gravity (#17, #18). Our theoretical studies combined with the explosion in the number of lenses and the quality of the data obtained for them is greatly increasing our ability to characterize and understand the lens population. We can now firmly conclude both from our study of the statistics of radio lenses and our survey of extinctions in individual lenses that the statistics of optically selected quasars were significantly affected by extinction. However, the limits on the cosmological constant remain at lambda < 0.65 at a 2-sigma confidence level, which is in mild conflict with the results of the Type la supernova surveys. We continue to find that neither spiral galaxies nor groups and clusters contribute significantly to the production of gravitational lenses. The lack of group and cluster lenses is strong evidence for the role of baryonic cooling in increasing the efficiency of galaxies as lenses compared to groups and clusters of higher mass but lower central density. Unfortunately for the ultimate objective of the proposal, improved constraints on the cosmological constant, the next

Weak Acid Ionization Constants and the Determination of Weak Acid-Weak Base Reaction Equilibrium Constants in the General Chemistry Laboratory

ERIC Educational Resources Information Center

Nyasulu, Frazier; McMills, Lauren; Barlag, Rebecca

2013-01-01

A laboratory to determine the equilibrium constants of weak acid negative weak base reactions is described. The equilibrium constants of component reactions when multiplied together equal the numerical value of the equilibrium constant of the summative reaction. The component reactions are weak acid ionization reactions, weak base hydrolysis…

Interior of control house showing remains of controller. Moving the ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Interior of control house showing remains of controller. Moving the handle rotated the vertical shaft and porcelain cams to engage various electrical switches and activate the lift mechanism. All electrical components have been removed. - Potomac Edison Company, Chesapeake & Ohio Canal Bridge, Spanning C & O Canal South of U.S. 11, Williamsport, Washington County, MD

Internal Astigmatism in Myopes and Non-myopes: Compensation or Constant?

PubMed Central

Manny, Ruth E.; Deng, Li; Gwiazda, Jane; Hyman, Leslie; Weissberg, Erik; Scheiman, Mitchell; Fern, Karen D.

2016-01-01

Purpose To examine internal astigmatism (IA) in myopes and non-myopes using a new method to assess compensation of corneal astigmatism (CA) by IA, to look for predictors of high IA in young adult myopes and determine if as CA changes IA changes to reduce refractive astigmatism (RA) in an active compensatory process in myopes. Methods Right eye keratometry and cycloplegic autorefraction were measured annually over 14 years in 367 myopes and once in 204 non-myopes age- (mean 21.91 years ± 1.47), gender-, and ethnicity-matched to myopes at year 12. CA and RA at the corneal plane were expressed as J0, J45. IA = RA - CA. Inverse power transformation provided cylinder power and axis of IA for the compensation factor (IA/CA). Analyses included: 1) paired and unpaired t-tests (refractive data), 2) chi-square tests (distributions of compensation factor), 3) logistic regression analysis (predictors of high IA), and 4) linear mixed models (time effect on RA, CA and IA). Results The magnitude of IAJ0 varied by refractive error (myopes −0.25 ±0.24 vs non-myopes −0.32 ± 0.21, p<0.001). Compensation of CA by IA was poorer in myopes than non-myopes (χ2 p<0.001). When matched by CA, compensation remained poorer in myopes than non-myopes (χ2 all p≤ 0.04). Within each refractive group compensation was better when CA was low than high (χ2 p<0.001). When CA was low in myopes, high IA (≥1.00D) was less likely (p=0.01). Longitudinal follow-up of myopes found no evidence for an active compensatory role for IA as CA increased over time. There were differences in IAJ0 by ethnicity over time (p<0.0001). Conclusions In myopic and non-myopic eyes with low amounts of CA, IA may reduce CA’s contribution to RA, but IA is not a constant. However, there is no evidence for an active compensatory role for IA reducing CA in myopes. PMID:27564515

Daily fluctuation of hepatic P450 monooxygenase activities in male rats is controlled by the suprachiasmatic nucleus but remains unaffected by adrenal hormones.

PubMed

Furukawa, T; Manabe, S; Watanabe, T; Sehata, S; Sharyo, S; Okada, T; Mori, Y

1999-09-01

Hepatic P450 monooxygenase activities, which strongly influence the efficacy and/or toxicity of drugs, are known to fluctuate daily. We also know that the P450 activities assessed by measurement of 7-alkoxycoumarin O-dealkylase (ACD) activities fluctuate daily, with apparently high values during the dark period in male rats. However, there is little knowledge about the factors that regulate daily fluctuation of P450 monooxygenase activities. In the present study using rats, we induced lesions in the suprachiasmatic nucleus (SCN) of the brain, the known site of the body's internal clock, and examined the effects on the daily fluctuation of the ACD activities to clarify the relationship between the SCN and the daily fluctuation of P450 monooxygenase activities. In addition, adrenalectomy was performed to re-evaluate the influence of adrenal hormones on the P450 activities. Our results indicated that daily fluctuations of the hepatic ACD activities were completely eliminated in the SCN-lesioned rats. However, the ACD activities in the adrenalectomized rats showed apparent daily fluctuations with high values during the dark period and low values during the light period. Therefore, this study demonstrated that the daily fluctuation of the hepatic P450 monooxygenase activities in male rats is controlled by the SCN but remains unaffected by the adrenal hormones.

A constant threat for HIV: Fc-engineering to enhance broadly neutralizing antibody activity for immunotherapy of the acquired immunodeficiency syndrome.

PubMed

Nimmerjahn, Falk

2015-08-01

Passive immunotherapy with polyclonal or hyperimmune serum immunoglobulin G (IgG) preparations provides an efficient means of protecting immunocompromised patients from microbial infections. More recently, the use of passive immunotherapy to prevent or to treat established infections with the human immunodeficiency virus (HIV) has gained much attention, due to promising preclinical data obtained in monkey and humanized mouse in vivo model systems, demonstrating that the transfer of HIV-specific antibodies can not only prevent HIV infection, but also diminish virus load during chronic infection. Furthermore, an array of broadly neutralizing HIV-specific antibodies has become available and the importance of the IgG constant region as a critical modulator of broadly neutralizing activity has been demonstrated. The aim of this review is to summarize the most recent findings with regard to the molecular and cellular mechanisms responsible for antibody-mediated clearance of HIV infection, and to discuss how this may help to improve HIV therapy via optimizing Fcγ-receptor-dependent activities of HIV-specific antibodies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Soil-moisture constants and their variation

Treesearch

Walter M. Broadfoot; Hubert D. Burke

1958-01-01

"Constants" like field capacity, liquid limit, moisture equivalent, and wilting point are used by most students and workers in soil moisture. These constants may be equilibrium points or other values that describe soil moisture. Their values under specific soil and cover conditions have been discussed at length in the literature, but few general analyses and...

Age characteristics of changes in invertase activity of the mucous membrane of the small intestine

NASA Technical Reports Server (NTRS)

Rakhimov, K. R.; Aleksandrova, N. V.

1980-01-01

Rats of varying ages were subjected to stress from heat, cold, and hydrocortisone injection. Invertase activity in homogenates of small intestine mucous membranes was studied following sacrifice. Invertase activity was low in young animals, but increased sharply in 30 day old ones, remaining at a relatively constant level until old age. The study concludes that the stress hormone (corticosteroids, etc.) levels in the blood, which affects the formation of enteric enzyme levels and activities, and that age related peculiarities in invertase activity are a consequence of altered hormone status and epitheliocyte sensitivity.

Determination of the hydrolysis rate constants and activation energy of aesculin with capillary electrophoresis end-column amperometric detection.

PubMed

Zhang, Lan; Tong, Ping; Chen, Guonan

2005-12-09

Aesculetin is the product of the hydrolysis reaction of aesculin. A high sensitivity and good repeatability method based on capillary electrophoresis with amperometric detection (CE-AD) was developed for simultaneous determination of aesculin and aesculetin in the hydrolysate of aesculin. Under the optimum condition: 10mmol/L KH(2)PO(4)-5mmol/L Na(2)B(4)O(7) (pH 6.0) buffer, separation at 18kV and +900mV (versus Ag/AgCl) as the detection potential, the hydrolysis rate constants of aesculin hydrolysis at 25, 30, 35, 40 and 45 degrees C in 0.1mol/L KOH were obtained as 1.45x10(-2)min(-1), 2.01x10(-2)min(-1), 2.93x10(-2)min(-1), 3.76x10(-2)min(-1) and 5.05x10(-2)min(-1), respectively. It was calculated that the activation energy for aesculin hydrolysis was 49.4kJ/mol.

Degravitation, inflation and the cosmological constant as an afterglow

NASA Astrophysics Data System (ADS)

Patil, Subodh P.

2009-01-01

In this report, we adopt the phenomenological approach of taking the degravitation paradigm seriously as a consistent modification of gravity in the IR, and investigate its consequences for various cosmological situations. We motivate degravitation — where Netwon's constant is promoted to a scale dependent filter function — as arising from either a small (resonant) mass for the graviton, or as an effect in semi-classical gravity. After addressing how the Bianchi identities are to be satisfied in such a set up, we turn our attention towards the cosmological consequences of degravitation. By considering the example filter function corresponding to a resonantly massive graviton (with a filter scale larger than the present horizon scale), we show that slow roll inflation, hybrid inflation and old inflation remain quantitatively unchanged. We also find that the degravitation mechanism inherits a memory of past energy densities in the present epoch in such a way that is likely significant for present cosmological evolution. For example, if the universe underwent inflation in the past due to it having tunneled out of some false vacuum, we find that degravitation implies a remnant `afterglow' cosmological constant, whose scale immediately afterwards is parametrically suppressed by the filter scale (L) in Planck units Λ ~ l2pl/L2. We discuss circumstances through which this scenario reasonably yields the presently observed value for Λ ~ O(10-120). We also find that in a universe still currently trapped in some false vacuum state, resonance graviton models of degravitation only degravitate initially Planck or GUT scale energy densities down to the presently observed value over timescales comparable to the filter scale. We argue that different functional forms for the filter function will yield similar conclusions. In this way, we argue that although the degravitation models we study have the potential to explain why the cosmological constant is not large in addition to

Diurnal rhythm of the pituitary-adrenocortical response to stress: effect of constant light and constant darkness

NASA Technical Reports Server (NTRS)

Vernikos-Danellis, J.; Winget, C. M.; Hetherington, N. W.

1970-01-01

The existence of a biological rhythm in the response of animals to noxious stimuli and drugs is well known. However, the mechanism of this response is not well understood. This study was undertaken to describe the existence of a diurnal rhythm in the hypothalamic-pituitary-adrenocortical system before and after stress in female rats kept in controlled environmental conditions in 12L:12D, 24L:OD, or OL:24D. Plasma ACTH and plasma corticosterone concentrations were compared in unstressed animals. The time pattern in the response to stress was determined at four hourly intervals during a 24 hr period in which plasma ACTH and plasma corticosterone were measured at different time intervals. The stress response varied considerably with time of day in both magnitude and duration. The adrenals of rats exposed to constant light for 45 days atrophied, whereas the adrenals of animals kept in constant dark for the same period did not differ significantly from those of controls kept in 12L:12D. The increase in plasma ACTH in response to stress was greater both in the animals maintained in constant light and in constant dark than in the 12L:12D controls. Homeostatic mechanisms involved in these changes are discussed.

Averaging of elastic constants for polycrystals

DOE PAGES

Blaschke, Daniel N.

2017-10-13

Many materials of interest are polycrystals, i.e., aggregates of single crystals. Randomly distributed orientations of single crystals lead to macroscopically isotropic properties. Here in this paper, we briefly review strategies of calculating effective isotropic second and third order elastic constants from the single crystal ones. Our main emphasis is on single crystals of cubic symmetry. Specifically, the averaging of third order elastic constants has not been particularly successful in the past, and discrepancies have often been attributed to texturing of polycrystals as well as to uncertainties in the measurement of elastic constants of both poly and single crystals. While thismore » may well be true, we also point out here shortcomings in the theoretical averaging framework.« less

Role of endothelium sensitivity to shear stress in noradrenaline-induced constriction of feline femoral arterial bed under constant flow and constant pressure perfusions.

PubMed

Kartamyshev, Sergey P; Balashov, Sergey A; Melkumyants, Arthur M

2007-01-01

The effect of shear stress at the endothelium in the attenuation of the noradrenaline-induced constriction of the femoral vascular bed perfused at a constant blood flow was investigated in 16 anesthetized cats. It is known that the adrenergic vasoconstriction of the femoral vascular bed is considerably greater at a constant pressure perfusion than at a constant blood flow. This difference may depend on the ability of the endothelium to relax smooth muscle in response to an increase in wall shear stress. Since the shear stress is directly related to the blood flow and inversely related to the third power of vessel diameter, vasoconstriction at a constant blood flow increases the wall shear stress that is the stimulus for smooth muscle relaxation opposing constriction. On the other hand, at a constant perfusion pressure, vasoconstriction is accompanied by a decrease in flow rate, which prevents a wall shear stress increase. To reveal the effect of endothelial sensitivity to shear stress, we compared noradrenaline-induced changes in total and proximal arterial resistances during perfusion of the hind limb at a constant blood flow and at a constant pressure in vessels with intact and injured endothelium. We found that in the endothelium-intact bed the same concentration of noradrenaline at a constant flow caused an increase in overall vascular peripheral resistance that was half as large as at a constant perfusion pressure. This difference is mainly confined to the proximal arterial vessels (arteries and large arterioles) whose resistance at a constant flow increased only 0.19 +/- 0.03 times compared to that at a constant pressure. The removal of the endothelium only slightly increased constrictor responses at the perfusion under a constant pressure (noradrenaline-induced increases of both overall and proximal arterial resistance augmented by 12%), while the responses of the proximal vessels at a constant flow became 4.7 +/- 0.4 times greater than in the endothelium

Cosmological Constant: A Lesson from Bose-Einstein Condensates

NASA Astrophysics Data System (ADS)

Finazzi, Stefano; Liberati, Stefano; Sindoni, Lorenzo

2012-02-01

The cosmological constant is one of the most pressing problems in modern physics. We address this issue from an emergent gravity standpoint, by using an analogue gravity model. Indeed, the dynamics of the emergent metric in a Bose-Einstein condensate can be described by a Poisson-like equation with a vacuum source term reminiscent of a cosmological constant. The direct computation of this term shows that in emergent gravity scenarios this constant may be naturally much smaller than the naive ground-state energy of the emergent effective field theory. This suggests that a proper computation of the cosmological constant would require a detailed understanding about how Einstein equations emerge from the full microscopic quantum theory. In this light, the cosmological constant appears as a decisive test bench for any quantum or emergent gravity scenario.

Cosmological constant: a lesson from Bose-Einstein condensates.

PubMed

Finazzi, Stefano; Liberati, Stefano; Sindoni, Lorenzo

2012-02-17

The cosmological constant is one of the most pressing problems in modern physics. We address this issue from an emergent gravity standpoint, by using an analogue gravity model. Indeed, the dynamics of the emergent metric in a Bose-Einstein condensate can be described by a Poisson-like equation with a vacuum source term reminiscent of a cosmological constant. The direct computation of this term shows that in emergent gravity scenarios this constant may be naturally much smaller than the naive ground-state energy of the emergent effective field theory. This suggests that a proper computation of the cosmological constant would require a detailed understanding about how Einstein equations emerge from the full microscopic quantum theory. In this light, the cosmological constant appears as a decisive test bench for any quantum or emergent gravity scenario.

Dynamic Characteristics of The DSI-Type Constant-Flow Valves

NASA Astrophysics Data System (ADS)

Kang, Yuan; Hu, Sheng-Yan; Chou, Hsien-Chin; Lee, Hsing-Han

Constant flow valves have been presented in industrial applications or academic studies, which compensate recess pressures of a hydrostatic bearing to resist load fluctuating. The flow rate of constant-flow valves can be constant in spite of the pressure changes in recesses, however the design parameters must be specified. This paper analyzes the dynamic responses of DSI-type constant-flow valves that is designed as double pistons on both ends of a spool with single feedback of working pressure and regulating restriction at inlet. In this study the static analysis presents the specific relationships among design parameters for constant flow rate and the dynamic analyses give the variations around the constant flow rate as the working pressure fluctuates.

Brownian motion with adaptive drift for remaining useful life prediction: Revisited

NASA Astrophysics Data System (ADS)

Wang, Dong; Tsui, Kwok-Leung

2018-01-01

Linear Brownian motion with constant drift is widely used in remaining useful life predictions because its first hitting time follows the inverse Gaussian distribution. State space modelling of linear Brownian motion was proposed to make the drift coefficient adaptive and incorporate on-line measurements into the first hitting time distribution. Here, the drift coefficient followed the Gaussian distribution, and it was iteratively estimated by using Kalman filtering once a new measurement was available. Then, to model nonlinear degradation, linear Brownian motion with adaptive drift was extended to nonlinear Brownian motion with adaptive drift. However, in previous studies, an underlying assumption used in the state space modelling was that in the update phase of Kalman filtering, the predicted drift coefficient at the current time exactly equalled the posterior drift coefficient estimated at the previous time, which caused a contradiction with the predicted drift coefficient evolution driven by an additive Gaussian process noise. In this paper, to alleviate such an underlying assumption, a new state space model is constructed. As a result, in the update phase of Kalman filtering, the predicted drift coefficient at the current time evolves from the posterior drift coefficient at the previous time. Moreover, the optimal Kalman filtering gain for iteratively estimating the posterior drift coefficient at any time is mathematically derived. A discussion that theoretically explains the main reasons why the constructed state space model can result in high remaining useful life prediction accuracies is provided. Finally, the proposed state space model and its associated Kalman filtering gain are applied to battery prognostics.

Quantification of photoinduced bending of dynamic molecular crystals: from macroscopic strain to kinetic constants and activation energies.

PubMed

Chizhik, Stanislav; Sidelnikov, Anatoly; Zakharov, Boris; Naumov, Panče; Boldyreva, Elena

2018-02-28

Photomechanically reconfigurable elastic single crystals are the key elements for contactless, timely controllable and spatially resolved transduction of light into work from the nanoscale to the macroscale. The deformation in such single-crystal actuators is observed and usually attributed to anisotropy in their structure induced by the external stimulus. Yet, the actual intrinsic and external factors that affect the mechanical response remain poorly understood, and the lack of rigorous models stands as the main impediment towards benchmarking of these materials against each other and with much better developed soft actuators based on polymers, liquid crystals and elastomers. Here, experimental approaches for precise measurement of macroscopic strain in a single crystal bent by means of a solid-state transformation induced by light are developed and used to extract the related temperature-dependent kinetic parameters. The experimental results are compared against an overarching mathematical model based on the combined consideration of light transport, chemical transformation and elastic deformation that does not require fitting of any empirical information. It is demonstrated that for a thermally reversible photoreactive bending crystal, the kinetic constants of the forward (photochemical) reaction and the reverse (thermal) reaction, as well as their temperature dependence, can be extracted with high accuracy. The improved kinematic model of crystal bending takes into account the feedback effect, which is often neglected but becomes increasingly important at the late stages of the photochemical reaction in a single crystal. The results provide the most rigorous and exact mathematical description of photoinduced bending of a single crystal to date.

Unfolding of chondroitinase ABC Ι is dependent on thermodynamic driving force by kinetically rate constant-amplitude compensation: A stopped-flow fluorescence study.

PubMed

Shirdel, S Akram; Khalifeh, Khosrow; Ranjbar, Bijan; Golestani, Abolfazl; Khajeh, Khosro

2016-11-01

We had previously investigated the role of a loop on the activity and conformational stability of chondroitinase ABC Ι (cABC Ι) by constructing some representative mutants in which a network interaction around Asp 689 was manipulated. Here we extended our study by measuring the proteolytic resistance, long term and thermal stability as well as unfolding kinetics of these variants. Long term stability data at 4 and 25°C for 3 weeks indicates that all mutants remain considerably active at 4°C. Thermoinactivation rates for all variants shows that the wild type (WT) enzyme retained 50% of its activity after 2min keeping at 40°C, while L701T, H700N and H700N/L701T as conformationally stabilized variants, have slower inactivation rate. It was also found that compact and thermodynamically stabilized variants are more resistant to tryptolytic digestion. Also, kinetic curves of chemical unfolding of the enzyme variants from stopped-flow fluorescence measurements were best fitted into a three-exponential function with three rate constants and corresponding amplitudes. We found that the energy barrier of the fast unfolding phase is lower in stabilized variants; while the amplitude of this phase to the whole amplitude of the unfolding reaction is lower than that of destabilized variants, indicating more population of stabilized mutants unfold via slower unfolding phase. We concluded that the rate of local conformational change alone is not the same that is expected from global thermodynamic stability; however the corresponding amplitude can compensate the rate constant toward thermodynamic stability. Copyright © 2016 Elsevier Inc. All rights reserved.

Simple constant-current-regulated power supply

NASA Technical Reports Server (NTRS)

Priebe, D. H. E.; Sturman, J. C.

1977-01-01

Supply incorporates soft-start circuit that slowly ramps current up to set point at turn-on. Supply consists of full-wave rectifier, regulating pass transistor, current feedback circuit, and quad single-supply operational-amplifier circuit providing control. Technique is applicable to any system requiring constant dc current, such as vacuum tube equipment, heaters, or battery charges; it has been used to supply constant current for instrument calibration.

To compute lightness, illumination is not estimated, it is held constant.

PubMed

Gilchrist, Alan L

2018-05-03

The light reaching the eye from a surface does not indicate the black-gray-white shade of a surface (called lightness) because the effects of illumination level are confounded with the reflectance of the surface. Rotating a gray paper relative to a light source alters its luminance (intensity of light reaching the eye) but the lightness of the paper remains relatively constant. Recent publications have argued, as had Helmholtz (1866/1924), that the visual system unconsciously estimates the direction and intensity of the light source. We report experiments in which this theory was pitted against an alternative theory according to which illumination level and surface reflectance are disentangled by comparing only those surfaces that are equally illuminated, in other words, by holding illumination level constant. A 3-dimensional scene was created within which the rotation of a target surface would be expected to become darker gray according to the lighting estimation theory, but lighter gray according to the equi-illumination comparison theory, with results clearly favoring the latter. In a further experiment cues held to indicate light source direction (cast shadows, attached shadows, and glossy highlights) were completely eliminated and yet this had no effect on the results. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Growth rate and trapping efficacy of nematode-trapping fungi under constant and fluctuating temperatures.

PubMed

Fernández, A S; Larsen, M; Wolstrup, J; Grønvold, J; Nansen, P; Bjørn, H

1999-08-01

The effect of temperature on radial growth and predatory activity of different isolates of nematode-trapping fungi was assessed. Four isolates of Duddingtonia flagrans and one isolate of Arthrobotrys oligospora were inoculated on petri dishes containing either cornmeal agar (CMA) or faecal agar and then incubated for 14 days under three different constant and fluctuating temperature regimes. The radial growth was similar on the two substrates at each temperature regime. All fungal isolates showed a higher growth rate at a constant 20 degrees C. At 10 degrees and 15 degrees C, all D. flagrans isolates showed very similar patterns of radial growth at both constant and fluctuating temperatures. At 20 degrees C, they grew significantly faster at constant than at fluctuating temperatures. A. oligospora grew significantly faster than all D. flagrans isolates except when incubated at a fluctuating 20 degrees C. Spores of each fungal isolate were added to faecal cultures containing eggs of Cooperia oncophora at a concentration of 6250 spores/g faeces. The cultures were incubated for 14 days at the same temperature regimes described above. Control faeces (without fungal material) were also cultured. More larvae were recovered from the fungus-treated cultures incubated at a constant 10 degrees or 15 degrees C than from those incubated at the respective fluctuating temperatures, except for one D. flagrans isolate. Incubation at 20 degrees C showed the opposite effect. The general reduction observed in the number of nematode larvae due to fungal trapping was 18-25% and 48-80% for a constant and fluctuating 10 degrees C, 70-96% and 93-95% for a constant and fluctuating 15 degrees C, and 63-98% and 0-25% for a constant and fluctuating 20 degrees C, respectively.

Definition and Measurement of Selection Bias: From Constant Ratio to Constant Difference

ERIC Educational Resources Information Center

Cahan, Sorel; Gamliel, Eyal

2006-01-01

Despite its intuitive appeal and popularity, Thorndike's constant ratio (CR) model for unbiased selection is inherently inconsistent in "n"-free selection. Satisfaction of the condition for unbiased selection, when formulated in terms of success/acceptance probabilities, usually precludes satisfaction by the converse probabilities of…

Constant-pressure Blowers

NASA Technical Reports Server (NTRS)

Sorensen, E

1940-01-01

The conventional axial blowers operate on the high-pressure principle. One drawback of this type of blower is the relatively low pressure head, which one attempts to overcome with axial blowers producing very high pressure at a given circumferential speed. The Schicht constant-pressure blower affords pressure ratios considerably higher than those of axial blowers of conventional design with approximately the same efficiency.

Cosmological constant is a conserved charge

NASA Astrophysics Data System (ADS)

Chernyavsky, Dmitry; Hajian, Kamal

2018-06-01

Cosmological constant can always be considered as the on-shell value of a top form in gravitational theories. The top form is the field strength of a gauge field, and the theory enjoys a gauge symmetry. We show that cosmological constant is the charge of the global part of the gauge symmetry, and is conserved irrespective of the dynamics of the metric and other fields. In addition, we introduce its conjugate chemical potential, and prove the generalized first law of thermodynamics which includes variation of cosmological constant as a conserved charge. We discuss how our new term in the first law is related to the volume–pressure term. In parallel with the seminal Wald entropy, this analysis suggests that pressure can also be considered as a conserved charge.

Influences of brain tissue poroelastic constants on intracranial pressure (ICP) during constant-rate infusion.

PubMed

Li, Xiaogai; von Holst, Hans; Kleiven, Svein

2013-01-01

A 3D finite element (FE) model has been developed to study the mean intracranial pressure (ICP) response during constant-rate infusion using linear poroelasticity. Due to the uncertainties in the poroelastic constants for brain tissue, the influence of each of the main parameters on the transient ICP infusion curve was studied. As a prerequisite for transient analysis, steady-state simulations were performed first. The simulated steady-state pressure distribution in the brain tissue for a normal cerebrospinal fluid (CSF) circulation system showed good correlation with experiments from the literature. Furthermore, steady-state ICP closely followed the infusion experiments at different infusion rates. The verified steady-state models then served as a baseline for the subsequent transient models. For transient analysis, the simulated ICP shows a similar tendency to that found in the experiments, however, different values of the poroelastic constants have a significant effect on the infusion curve. The influence of the main poroelastic parameters including the Biot coefficient α, Skempton coefficient B, drained Young's modulus E, Poisson's ratio ν, permeability κ, CSF absorption conductance C(b) and external venous pressure p(b) was studied to investigate the influence on the pressure response. It was found that the value of the specific storage term S(ε) is the dominant factor that influences the infusion curve, and the drained Young's modulus E was identified as the dominant parameter second to S(ε). Based on the simulated infusion curves from the FE model, artificial neural network (ANN) was used to find an optimised parameter set that best fit the experimental curve. The infusion curves from both the FE simulation and using ANN confirmed the limitation of linear poroelasticity in modelling the transient constant-rate infusion.

Space Shuttle astrodynamical constants

NASA Technical Reports Server (NTRS)

Cockrell, B. F.; Williamson, B.

1978-01-01

Basic space shuttle astrodynamic constants are reported for use in mission planning and construction of ground and onboard software input loads. The data included here are provided to facilitate the use of consistent numerical values throughout the project.

The Conformal Factor and the Cosmological Constant

NASA Astrophysics Data System (ADS)

Giddings, Steven B.

The issue of the conformal factor in quantum gravity is examined for Lorentzian signature spacetimes. In Euclidean signature, the “wrong” sign of the conformal action makes the path integral undefined, but in Lorentzian signature this sign is tied to the instability of gravity and once this is accounted for the path integral should be well-defined. In this approach it is not obvious that the Baum-Hawking-Coleman mechanism for suppression of the cosmological constant functions. It is conceivable that since the multiuniverse system exhibits an instability for positive cosmological constant, the dynamics should force the system to zero cosmological constant.

Dynamical approach to the cosmological constant.

PubMed

Mukohyama, Shinji; Randall, Lisa

2004-05-28

We consider a dynamical approach to the cosmological constant. There is a scalar field with a potential whose minimum occurs at a generic, but negative, value for the vacuum energy, and it has a nonstandard kinetic term whose coefficient diverges at zero curvature as well as the standard kinetic term. Because of the divergent coefficient of the kinetic term, the lowest energy state is never achieved. Instead, the cosmological constant automatically stalls at or near zero. The merit of this model is that it is stable under radiative corrections and leads to stable dynamics, despite the singular kinetic term. The model is not complete, however, in that some reheating is required. Nonetheless, our approach can at the very least reduce fine-tuning by 60 orders of magnitude or provide a new mechanism for sampling possible cosmological constants and implementing the anthropic principle.

Hospital union election activity, 1974-85

PubMed Central

Becker, Edmund R.; Rakich, Jonathon S.

1988-01-01

This study, using National Labor Relations Board data and American Hospital Association data, reports on the status of union election activity in the hospital industry for a 65-month period, January 1980-May 1985, and contrasts it with earlier data for a similar 65-month time period (1974-79). Together these data provide a comprehensive overview of union election activity in non-Federal, nongovernment hospitals since the passage of the 1974 Nonprofit Hospital Amendments to the Taft-Hartley Act. The study analyzes union, election, hospital, and environmental characteristics. Comparisons over the two time periods show that, while union victory rates in hospital elections have remained constant, the total number of elections has declined dramatically in the hospital industry. PMID:10312518

Pavement Remaining Service Interval [Tech Brief

DOT National Transportation Integrated Search

2013-05-01

This document is a technical summary of the Federal Highway Administration reports, "Reformulated Pavement Remaining Service Life Framework" (FHWA-HRT-13-038) and "Pavement Remaining Service Interval Implementation Guidelines" (FHWA-HRT-13-050). At t...

Constant voltage and constant current control implementation for electric vehicles (evs) wireless charger

NASA Astrophysics Data System (ADS)

Tampubolon, Marojahan; Pamungkas, Laskar; Hsieh, Yao Ching; Chiu, Huang Jen

2018-04-01

This paper presents the implementation of Constant Voltage (CV) and Constant Current (CC) control for a wireless charger system. A battery charging system needs these control modes to ensure the safety of the battery and the effectiveness of the charging system. Here, the wireless charger system does not employ any post-regulator stage to control the output voltage and output current of the charger. But, it uses a variable frequency control incorporated with a conventional PI control. As a result, the size and the weight of the system are reduced. This paper discusses the brief review of the SS-WPT, control strategy and implementation of the CV and CC control. Experimental hardware with 2kW output power has been performed and tested. The results show that the proposed CV and CC control method works well with the system.

Asymptotically Vanishing Cosmological Constant in the Multiverse

NASA Astrophysics Data System (ADS)

Kawai, Hikaru; Okada, Takashi

We study the problem of the cosmological constant in the context of the multiverse in Lorentzian space-time, and show that the cosmological constant will vanish in the future. This sort of argument was started by Sidney Coleman in 1989, and he argued that the Euclidean wormholes make the multiverse partition function a superposition of various values of the cosmological constant Λ, which has a sharp peak at Λ = 0. However, the implication of the Euclidean analysis to our Lorentzian space-time is unclear. With this motivation, we analyze the quantum state of the multiverse in Lorentzian space-time by the WKB method, and calculate the density matrix of our universe by tracing out the other universes. Our result predicts vanishing cosmological constant. While Coleman obtained the enhancement at Λ = 0 through the action itself, in our Lorentzian analysis the similar enhancement arises from the front factor of eiS in the universe wave function, which is in the next leading order in the WKB approximation.

Prevalence of remaining horizontal instability in high-grade acromioclavicular joint injuries surgically managed.

PubMed

Cisneros, Luis Natera; Reiriz, Juan Sarasquete

2017-04-01

To determine the prevalence of remaining horizontal instability in high-grade acromioclavicular joint (ACJ) injuries surgically managed by means of four different surgical strategies and to assess its relation to the clinical outcomes and the quality of life. In this multicentric non-randomized retrospective study, 53 patients with high-grade ACJ injuries surgically managed (by means of open or arthroscopic surgery) were clinically and radiographically assessed at 24 months or more after shoulder surgery. The presence of post-surgical remaining horizontal instability was evaluated by means of Alexander or axillary X-ray views. The study population was divided into two groups: patients with evidence of post-surgical remaining horizontal instability and patients without evidence of post-surgical remaining horizontal instability at the last follow-up visit. The relationship between remaining horizontal instability and the quality-of-life questionnaires was analyzed. 18.87% (10/53) of the Alexander or axillary X-rays views showed post-surgical remaining horizontal instability at the last follow-up visit (INSTAB-group). Results of the questionnaires were: (1) physical SF36 score (INSTAB-group 57.02 ± 3.17  and NO-INSTAB-group 57.66 ± 3.30, p = 0.583); (2) mental SF36 score (INSTAB-group 53.95 ± 3.98  and NO-INSTAB-group 55.71 ± 3.30, p = 0.150); (3) NRS for pain (INSTAB-group 1.30 ± 1.49 and NO-INSTAB-group 0.83  ± 1.08, p = 0.260); (4) DASH questionnaire (INSTAB-group 5.27 ± 5.42 and NO-INSTAB-group 3.06 ± 2.30, p = 0.049); (5) Constant score (INSTAB-group 93.4 ± 3.5 and NO-INSTAB-group 94.83  ± 4.3, p = 0.333); and Global satisfaction (INSTAB-group 8.7  ± 0.95 and NO-INSTAB-group 8.64 ± 1.03, p = 0.874). Independently of the type of procedure, post-surgical remaining horizontal instability was present in almost one-fifth of the patients, and this group of patients showed a significantly worse DASH score. The

High Arctic lemmings remain reproductively active under predator-induced elevated stress.

PubMed

Fauteux, Dominique; Gauthier, Gilles; Berteaux, Dominique; Palme, Rupert; Boonstra, Rudy

2018-04-12

Non-consumptive effects of predation have rarely been assessed in wildlife populations even though their impact could be as important as lethal effects. Reproduction of individuals is one of the most important demographic parameters that could be affected by predator-induced stress, which in turn can have important consequences on population dynamics. We studied non-consumptive effects of predation on the reproductive activity (i.e., mating and fertilization) of a cyclic population of brown lemmings exposed to intense summer predation in the Canadian High Arctic. Lemmings were live-trapped, their reproductive activity (i.e., testes visible in males, pregnancy/lactation in females) assessed, and predators were monitored during the summers of 2014 and 2015 within a 9 ha predator-reduction exclosure delimited by a fence and covered by a net, and on an 11 ha control area. Stress levels were quantified non-invasively with fecal corticosterone metabolites (FCM). We found that FCM levels of lemmings captured outside the predator exclosure (n = 50) were 1.6 times higher than inside (n = 51). The proportion of pregnant/lactating adult females did not differ between the two areas, nor did the proportion of adult scrotal males. We found that lemmings showed physiological stress reactions due to high predation risk, but had no sign of reduced mating activity or fertility. Thus, our results do not support the hypothesis of reproductive suppression by predator-induced stress.

Constant phycobilisome size in chromatically adapted cells of the cyanobacterium Tolypothrix tenuis, and variation in Nostoc sp

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

Ohki, K.; Gantt, E.; Lipschultz, C.A.

1985-12-01

Phycobilisomes of Tolypothrix tenuis, a cyanobacterium capable of complete chromatic adaptation, were studied from cells grown in red and green light, and in darkness. The phycobilisome size remained constant irrespective of the light quality. The hemidiscoidal phycobilisomes had an average diameter of about 52 nanometers and height of about 33 nanometers, by negative staining. The thickness was equivalent to a physocyanin molecule (about 10 nanometers). The molar ratio of allophycocyanin, relative to other phycobiliproteins always remained at about 1:3. Phycobilisomes from red light grown cells and cells grown heterotrophically in darkness were indistinguishable in their pigment composition, polypeptide pattern, andmore » size. Eight polypeptides were resolved in the phycobilin region (17.5 to 23.5 kilodaltons) by isoelectric focusing followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Half of these were invariable, while others were variable in green and red light. It is inferred that phycoerythrin synthesis in green light resulted in a one for one substitution of phycocyanin, thus retaining a constant phycobilisome size. Tolypothrix appears to be one of the best examples of phycobiliprotein regulation with wavelength. By contrast, in Nostoc sp., the decrease in phycoerythrin in red light cells was accompanied by a decrease in phycobilisome size but not a regulated substitution.« less

Comparing otoacoustic emissions evoked by chirp transients with constant absorbed sound power and constant incident pressure magnitude.

PubMed

Keefe, Douglas H; Feeney, M Patrick; Hunter, Lisa L; Fitzpatrick, Denis F

2017-01-01

Human ear-canal properties of transient acoustic stimuli are contrasted that utilize measured ear-canal pressures in conjunction with measured acoustic pressure reflectance and admittance. These data are referenced to the tip of a probe snugly inserted into the ear canal. Promising procedures to calibrate across frequency include stimuli with controlled levels of incident pressure magnitude, absorbed sound power, and forward pressure magnitude. An equivalent pressure at the eardrum is calculated from these measured data using a transmission-line model of ear-canal acoustics parameterized by acoustically estimated ear-canal area at the probe tip and length between the probe tip and eardrum. Chirp stimuli with constant incident pressure magnitude and constant absorbed sound power across frequency were generated to elicit transient-evoked otoacoustic emissions (TEOAEs), which were measured in normal-hearing adult ears from 0.7 to 8 kHz. TEOAE stimuli had similar peak-to-peak equivalent sound pressure levels across calibration conditions. Frequency-domain TEOAEs were compared using signal level, signal-to-noise ratio (SNR), coherence synchrony modulus (CSM), group delay, and group spread. Time-domain TEOAEs were compared using SNR, CSM, instantaneous frequency and instantaneous bandwidth. Stimuli with constant incident pressure magnitude or constant absorbed sound power across frequency produce generally similar TEOAEs up to 8 kHz.

Dielectric-constant gas thermometry

NASA Astrophysics Data System (ADS)

Gaiser, Christof; Zandt, Thorsten; Fellmuth, Bernd

2015-10-01

The principles, techniques and results from dielectric-constant gas thermometry (DCGT) are reviewed. Primary DCGT with helium has been used for measuring T-T90 below the triple point of water (TPW), where T is the thermodynamic temperature and T90 is the temperature on the international temperature scale of 1990 (ITS-90), and, in an inverse regime with T as input quantity, for determining the Boltzmann constant at the TPW. Furthermore, DCGT allows the determination of several important material properties including the polarizability of neon and argon as well as the virial coefficients of helium, neon, and argon. With interpolating DCGT (IDCGT), the ITS-90 has been approximated in the temperature range from 4 K to 25 K. An overview and uncertainty budget for each of these applications of DCGT is provided, accompanied by corroborating evidence from the literature or, for IDCGT, a CIPM key comparison.

Effects of constant immigration on the dynamics and persistence of stable and unstable Drosophila populations

PubMed Central

Dey, Snigdhadip; Joshi, Amitabh

2013-01-01

Constant immigration can stabilize population size fluctuations but its effects on extinction remain unexplored. We show that constant immigration significantly reduced extinction in fruitfly populations with relatively stable or unstable dynamics. In unstable populations with oscillations of amplitude around 1.5 times the mean population size, persistence and constancy were unrelated. Low immigration enhanced persistence without affecting constancy whereas high immigration increased constancy without enhancing persistence. In relatively stable populations with erratic fluctuations of amplitude close to the mean population size, both low and high immigration enhanced persistence. In these populations, the amplitude of fluctuations relative to mean population size went down due to immigration, and their dynamics were altered to low-period cycles. The effects of immigration on the population size distribution and intrinsic dynamics of stable versus unstable populations differed considerably, suggesting that the mechanisms by which immigration reduced extinction risk depended on underlying dynamics in complex ways. PMID:23470546

Crayfish neuromuscular facilitation activated by constant presynaptic action potentials and depolarizing pulses

PubMed Central

Zucker, Robert S.

1974-01-01

1. Experiments were conducted to test the hypothesis that facilitation of transmitter release in response to repetitive stimulation of the exciter motor axon to the crayfish claw opener muscle is due to an increase in the amplitude or duration of the action potential in presynaptic terminals. No consistent changes were found in the nerve terminal potential (n.t.p.) recorded extracellularly at synaptic sites on the surface of muscle fibres. 2. Apparent changes in n.t.p. are attributed to three causes. (i) Some recordings are shown to be contaminated by non-specific muscle responses which grow during facilitation. (ii) Some averaged n.t.p.s exhibit opposite changes in amplitude and duration which suggest a change in the synchrony of presynaptic nerve impulses at different frequencies. (iii) Some changes in n.t.p. are blocked by γ-methyl glutamate, an antagonist of the post-synaptic receptor, which suggests that these changes are caused by small muscle movements. 3. The only change in n.t.p. believed to represent an actual change in the intracellular signal is a reduction in n.t.p. amplitude to the second of two stimuli separated by a brief interval. 4. Tetra-ethyl ammonium ions increase synaptic transmission about 20% and prolong the n.t.p. about 15%. This result suggests that an increase in n.t.p. large enough to increase transmission by the several hundred per cent occurring during facilitation would be detected. 5. The nerve terminals are electrically excitable, and most synaptic sites have a diphasic or triphasic n.t.p., which suggests that the motor neurone terminals are actively invaded by nerve impulses. 6. When nerve impulses are blocked in tetrodotoxin, depolarization of nerve terminals increases the frequency of miniature excitatory junctional potentials (e.j.p.s), and a phasic e.j.p. can be evoked by large, brief depolarizing pulses. Responses to repetitive or paired depolarizations of constant amplitude and duration exhibit a facilitation similar to that

Crayfish neuromuscular facilitation activated by constant presynaptic action potentials and depolarizing pulses.

PubMed

Zucker, R S

1974-08-01

1. Experiments were conducted to test the hypothesis that facilitation of transmitter release in response to repetitive stimulation of the exciter motor axon to the crayfish claw opener muscle is due to an increase in the amplitude or duration of the action potential in presynaptic terminals. No consistent changes were found in the nerve terminal potential (n.t.p.) recorded extracellularly at synaptic sites on the surface of muscle fibres.2. Apparent changes in n.t.p. are attributed to three causes.(i) Some recordings are shown to be contaminated by non-specific muscle responses which grow during facilitation.(ii) Some averaged n.t.p.s exhibit opposite changes in amplitude and duration which suggest a change in the synchrony of presynaptic nerve impulses at different frequencies.(iii) Some changes in n.t.p. are blocked by gamma-methyl glutamate, an antagonist of the post-synaptic receptor, which suggests that these changes are caused by small muscle movements.3. The only change in n.t.p. believed to represent an actual change in the intracellular signal is a reduction in n.t.p. amplitude to the second of two stimuli separated by a brief interval.4. Tetra-ethyl ammonium ions increase synaptic transmission about 20% and prolong the n.t.p. about 15%. This result suggests that an increase in n.t.p. large enough to increase transmission by the several hundred per cent occurring during facilitation would be detected.5. The nerve terminals are electrically excitable, and most synaptic sites have a diphasic or triphasic n.t.p., which suggests that the motor neurone terminals are actively invaded by nerve impulses.6. When nerve impulses are blocked in tetrodotoxin, depolarization of nerve terminals increases the frequency of miniature excitatory junctional potentials (e.j.p.s), and a phasic e.j.p. can be evoked by large, brief depolarizing pulses. Responses to repetitive or paired depolarizations of constant amplitude and duration exhibit a facilitation similar to that of e

Higher success rate with transcranial electrical stimulation of motor-evoked potentials using constant-voltage stimulation compared with constant-current stimulation in patients undergoing spinal surgery.

PubMed

Shigematsu, Hideki; Kawaguchi, Masahiko; Hayashi, Hironobu; Takatani, Tsunenori; Iwata, Eiichiro; Tanaka, Masato; Okuda, Akinori; Morimoto, Yasuhiko; Masuda, Keisuke; Tanaka, Yuu; Tanaka, Yasuhito

2017-10-01

During spine surgery, the spinal cord is electrophysiologically monitored via transcranial electrical stimulation of motor-evoked potentials (TES-MEPs) to prevent injury. Transcranial electrical stimulation of motor-evoked potential involves the use of either constant-current or constant-voltage stimulation; however, there are few comparative data available regarding their ability to adequately elicit compound motor action potentials. We hypothesized that the success rates of TES-MEP recordings would be similar between constant-current and constant-voltage stimulations in patients undergoing spine surgery. The objective of this study was to compare the success rates of TES-MEP recordings between constant-current and constant-voltage stimulation. This is a prospective, within-subject study. Data from 100 patients undergoing spinal surgery at the cervical, thoracic, or lumbar level were analyzed. The success rates of the TES-MEP recordings from each muscle were examined. Transcranial electrical stimulation with constant-current and constant-voltage stimulations at the C3 and C4 electrode positions (international "10-20" system) was applied to each patient. Compound muscle action potentials were bilaterally recorded from the abductor pollicis brevis (APB), deltoid (Del), abductor hallucis (AH), tibialis anterior (TA), gastrocnemius (GC), and quadriceps (Quad) muscles. The success rates of the TES-MEP recordings from the right Del, right APB, bilateral Quad, right TA, right GC, and bilateral AH muscles were significantly higher using constant-voltage stimulation than those using constant-current stimulation. The overall success rates with constant-voltage and constant-current stimulations were 86.3% and 68.8%, respectively (risk ratio 1.25 [95% confidence interval: 1.20-1.31]). The success rates of TES-MEP recordings were higher using constant-voltage stimulation compared with constant-current stimulation in patients undergoing spinal surgery. Copyright © 2017

Constant Chinese Loess Plateau dust source since the Late Miocene

NASA Astrophysics Data System (ADS)

Bird, Anna; Millar, Ian; Stevens, Thomas; Rodenburg, Tanja; Rittner, Martin; Vermeesch, Pieter; Lu, Huayu

2017-04-01

The dramatic deepening of northern hemisphere glaciation at the Pliocene-Pleistocene boundary is accompanied by major changes in global climate. The role of the global atmospheric dust cycle in this event is not clear; in particular, whether, changes in the dust cycle influenced climates change, or resulted from it. Miocene and Quaternary wind-blown Chinese loess records past dust-cycle history, influences of aridification and monsoon circulation. Previous work on the vast Chinese Loess Plateau is in conflict over whether changes in dust source occur at the Pliocene-Pleistocene boundary (2.59 Ma), or at 1.2 Ma, despite these intervals marking major shifts in monsoon dynamics (Sun 2005; Nie et al. 2014a). Here we present Sr, Nd and Hf isotopic data from multiple sites and show that the dust source remains the same across these boundaries. The use of isotope tracers from multiple sites allows us to demonstrate that shifts in sediment geochemistry can be explained by grain-size and weathering changes. Nd and Hf isotopes show that the dust was dominantly sourced from the Tibetan Plateau, with some input from bedrock underlying the Badain Jaran/Tengger deserts. This shows that a major established and constant dust source on the northern Tibetan Plateau has been active and unchanged since the late Miocene, despite dramatically changing climate conditions. Changes in loess accumulation are therefore a function of climate change in the Tibetan Plateau source regions rather than due to expanding source areas controlled by aridification over a widening area over the Pliocene and Quaternary.

A review of sex estimation techniques during examination of skeletal remains in forensic anthropology casework.

PubMed

Krishan, Kewal; Chatterjee, Preetika M; Kanchan, Tanuj; Kaur, Sandeep; Baryah, Neha; Singh, R K

2016-04-01

Sex estimation is considered as one of the essential parameters in forensic anthropology casework, and requires foremost consideration in the examination of skeletal remains. Forensic anthropologists frequently employ morphologic and metric methods for sex estimation of human remains. These methods are still very imperative in identification process in spite of the advent and accomplishment of molecular techniques. A constant boost in the use of imaging techniques in forensic anthropology research has facilitated to derive as well as revise the available population data. These methods however, are less reliable owing to high variance and indistinct landmark details. The present review discusses the reliability and reproducibility of various analytical approaches; morphological, metric, molecular and radiographic methods in sex estimation of skeletal remains. Numerous studies have shown a higher reliability and reproducibility of measurements taken directly on the bones and hence, such direct methods of sex estimation are considered to be more reliable than the other methods. Geometric morphometric (GM) method and Diagnose Sexuelle Probabiliste (DSP) method are emerging as valid methods and widely used techniques in forensic anthropology in terms of accuracy and reliability. Besides, the newer 3D methods are shown to exhibit specific sexual dimorphism patterns not readily revealed by traditional methods. Development of newer and better methodologies for sex estimation as well as re-evaluation of the existing ones will continue in the endeavour of forensic researchers for more accurate results. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

[PALEOPATHOLOGY OF HUMAN REMAINS].

PubMed

Minozzi, Simona; Fornaciari, Gino

2015-01-01

Many diseases induce alterations in the human skeleton, leaving traces of their presence in ancient remains. Paleopathological examination of human remains not only allows the study of the history and evolution of the disease, but also the reconstruction of health conditions in the past populations. This paper describes the most interesting diseases observed in skeletal samples from the Roman Imperial Age necropoles found in urban and suburban areas of Rome during archaeological excavations in the last decades. The diseases observed were grouped into the following categories: articular diseases, traumas, infections, metabolic or nutritional diseases, congenital diseases and tumours, and some examples are reported for each group. Although extensive epidemiological investigation in ancient skeletal records is impossible, the palaeopathological study allowed to highlight the spread of numerous illnesses, many of which can be related to the life and health conditions of the Roman population.

When is the growth index constant?

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

Polarski, David; Starobinsky, Alexei A.; Giacomini, Hector, E-mail: david.polarski@umontpellier.fr, E-mail: alstar@landau.ac.ru, E-mail: hector.giacomini@lmpt.univ-tours.fr

The growth index γ is an interesting tool to assess the phenomenology of dark energy (DE) models, in particular of those beyond general relativity (GR). We investigate the possibility for DE models to allow for a constant γ during the entire matter and DE dominated stages. It is shown that if DE is described by quintessence (a scalar field minimally coupled to gravity), this behaviour of γ is excluded either because it would require a transition to a phantom behaviour at some finite moment of time, or, in the case of tracking DE at the matter dominated stage, because themore » relative matter density Ω {sub m} appears to be too small. An infinite number of solutions, with Ω {sub m} and γ both constant, are found with w {sub DE} = 0 corresponding to Einstein-de Sitter universes. For all modified gravity DE models satisfying G {sub eff} ≥ G , among them the f ( R ) DE models suggested in the literature, the condition to have a constant w {sub DE} is strongly violated at the present epoch. In contrast, DE tracking dust-like matter deep in the matter era, but with Ω {sub m} <1, requires G {sub eff} > G and an example is given using scalar-tensor gravity for a range of admissible values of γ. For constant w {sub DE} inside GR, departure from a quasi-constant value is limited until today. Even a large variation of w {sub DE} may not result in a clear signature in the change of γ. The change however is substantial in the future and the asymptotic value of γ is found while its slope with respect to Ω {sub m} (and with respect to z ) diverges and tends to −∞.« less

A New Physical Constant And Its Importance To Energy Production

NASA Astrophysics Data System (ADS)

Angus, Andrew

2003-03-01

The purpose of this paper is to introduce a new physical constant symbolized by the Greek letter lambda. This paper explains how the new physical constant was derived. This paper also explains the significance of the new physical constant as an alternative explanation to Einstein's Law of Photoelectric Effect. The new physical constant leads to a deeper understanding of the nature of the photon. Furthermore, this new physical constant leads us to the existence of two types of photon, the Planck photon and the Angus photon. Finally, the author also explains the importance of this new physical constant in energy production.

On multisoliton solutions of the constant astigmatism equation

NASA Astrophysics Data System (ADS)

Hlaváč, Adam

2015-09-01

We introduce an algebraic formula producing infinitely many exact solutions of the constant astigmatism equation {z}{yy}+{(1/z)}{xx}+2=0 from a given seed. A construction of corresponding surfaces of constant astigmatism is then a matter of routine. As a special case, we consider multisoliton solutions of the constant astigmatism equation defined as counterparts of famous multisoliton solutions of the sine-Gordon equation. A few particular examples are surveyed as well.

Sustaining Community Participation: What Remains After the Money Ends?

NASA Astrophysics Data System (ADS)

Nkansa, Grace Akukwe; Chapman, David W.

2006-12-01

SUSTAINING COMMUNITY PARTICIPATION: WHAT REMAINS AFTER THE MONEY ENDS? - A major concern confronting development specialists in the education sector is the sustainability of project activities and outcomes, that is, their ability to persist once external funding ends. The increased attention of international development-assistance organizations to sustainability reflects the greater recent focus on outcome-based funding. The present study investigates differences between six communities in Ghana that varied in their ability to sustain externally initiated community-participation activities beyond the life of the external development-assistance project that promoted those activities. It was hypothesized that high- and low-sustaining communities differ in eight managerial and socio-cultural dimensions suggested by earlier research to be important for sustainability of community-level activities: planning, transparency, leadership, and participation, on one hand, and, on the other, social cohesion, resources, community skills, and valuing of education. Findings indicate that leadership and social cohesion are the two most vital elements in the sustainability of organizational structures intended to promote community participation in the oversight of local schools. Other factors suggested by the model are largely subsumed under leadership, so that the model can be simplified.

40 CFR 86.519-90 - Constant volume sampler calibration.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 19 2013-07-01 2013-07-01 false Constant volume sampler calibration... Regulations for 1978 and Later New Motorcycles; Test Procedures § 86.519-90 Constant volume sampler calibration. (a) The CVS (Constant Volume Sampler) is calibrated using an accurate flowmeter and restrictor...

40 CFR 86.519-90 - Constant volume sampler calibration.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 19 2012-07-01 2012-07-01 false Constant volume sampler calibration... Regulations for 1978 and Later New Motorcycles; Test Procedures § 86.519-90 Constant volume sampler calibration. (a) The CVS (Constant Volume Sampler) is calibrated using an accurate flowmeter and restrictor...

40 CFR 86.519-90 - Constant volume sampler calibration.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 18 2011-07-01 2011-07-01 false Constant volume sampler calibration... Regulations for 1978 and Later New Motorcycles; Test Procedures § 86.519-90 Constant volume sampler calibration. (a) The CVS (Constant Volume Sampler) is calibrated using an accurate flowmeter and restrictor...

40 CFR 86.519-90 - Constant volume sampler calibration.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 19 2014-07-01 2014-07-01 false Constant volume sampler calibration... Regulations for 1978 and Later New Motorcycles; Test Procedures § 86.519-90 Constant volume sampler calibration. (a) The CVS (Constant Volume Sampler) is calibrated using an accurate flowmeter and restrictor...

40 CFR 86.519-90 - Constant volume sampler calibration.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 18 2010-07-01 2010-07-01 false Constant volume sampler calibration... Regulations for 1978 and Later New Motorcycles; Test Procedures § 86.519-90 Constant volume sampler calibration. (a) The CVS (Constant Volume Sampler) is calibrated using an accurate flowmeter and restrictor...

Influence of a constant magnetic field on thrombocytes. [delay of blood coagulation time

NASA Technical Reports Server (NTRS)

Meyerova, Y. A.

1974-01-01

In an experiment on white mice it was found that a constant electromagnetic field with strength of 250-275 oersteds is biologically active at an exposure of 55 minutes. Qualitative and morphological changes in thrombocytes 1-3 days following exposure reduced their numbers, prolonged blood coagulation time and increased the number of leucocytes.

Leprosy: ancient disease remains a public health problem nowadays.

PubMed

Noriega, Leandro Fonseca; Chiacchio, Nilton Di; Noriega, Angélica Fonseca; Pereira, Gilmayara Alves Abreu Maciel; Vieira, Marina Lino

2016-01-01

Despite being an ancient disease, leprosy remains a public health problem in several countries -particularly in India, Brazil and Indonesia. The current operational guidelines emphasize the evaluation of disability from the time of diagnosis and stipulate as fundamental principles for disease control: early detection and proper treatment. Continued efforts are needed to establish and improve quality leprosy services. A qualified primary care network that is integrated into specialized service and the development of educational activities are part of the arsenal in the fight against the disease, considered neglected and stigmatizing.

A reservoir of time constants for memory traces in cortical neurons

PubMed Central

Bernacchia, Alberto; Seo, Hyojung; Lee, Daeyeol; Wang, Xiao-Jing

2011-01-01

According to reinforcement learning theory of decision making, reward expectation is computed by integrating past rewards with a fixed timescale. By contrast, we found that a wide range of time constants is available across cortical neurons recorded from monkeys performing a competitive game task. By recognizing that reward modulates neural activity multiplicatively, we found that one or two time constants of reward memory can be extracted for each neuron in prefrontal, cingulate, and parietal cortex. These timescales ranged from hundreds of milliseconds to tens of seconds, according to a power-law distribution, which is consistent across areas and reproduced by a “reservoir” neural network model. These neuronal memory timescales were weakly but significantly correlated with those of monkey's decisions. Our findings suggest a flexible memory system, where neural subpopulations with distinct sets of long or short memory timescales may be selectively deployed according to the task demands. PMID:21317906

Compensation of Verdet Constant Temperature Dependence by Crystal Core Temperature Measurement

PubMed Central

Petricevic, Slobodan J.; Mihailovic, Pedja M.

2016-01-01

Compensation of the temperature dependence of the Verdet constant in a polarimetric extrinsic Faraday sensor is of major importance for applying the magneto-optical effect to AC current measurements and magnetic field sensing. This paper presents a method for compensating the temperature effect on the Faraday rotation in a Bi12GeO20 crystal by sensing its optical activity effect on the polarization of a light beam. The method measures the temperature of the same volume of crystal that effects the beam polarization in a magnetic field or current sensing process. This eliminates the effect of temperature difference found in other indirect temperature compensation methods, thus allowing more accurate temperature compensation for the temperature dependence of the Verdet constant. The method does not require additional changes to an existing Δ/Σ configuration and is thus applicable for improving the performance of existing sensing devices. PMID:27706043

Rate Constants and Mechanisms of Protein–Ligand Binding

PubMed Central

Pang, Xiaodong; Zhou, Huan-Xiang

2017-01-01

Whereas protein–ligand binding affinities have long-established prominence, binding rate constants and binding mechanisms have gained increasing attention in recent years. Both new computational methods and new experimental techniques have been developed to characterize the latter properties. It is now realized that binding mechanisms, like binding rate constants, can and should be quantitatively determined. In this review, we summarize studies and synthesize ideas on several topics in the hope of providing a coherent picture of and physical insight into binding kinetics. The topics include microscopic formulation of the kinetic problem and its reduction to simple rate equations; computation of binding rate constants; quantitative determination of binding mechanisms; and elucidation of physical factors that control binding rate constants and mechanisms. PMID:28375732

Constant light suppresses production of Met-enkephalin-containing peptides in cultured splenic macrophages and impairs primary immune response in rats.

PubMed

Valdés-Tovar, Marcela; Escobar, Carolina; Solís-Chagoyán, Héctor; Asai, Miguel; Benítez-King, Gloria

2015-03-01

The light-dark cycle is an environmental factor that influences immune physiology, and so, variations of the photoperiod length result in altered immune responsivity. Macrophage physiology comprises a spectrum of functions that goes from host defense to immune down-regulation, in addition to their homeostatic activities. Macrophages also play a key role in the transition from innate to adaptive immune responses. Met-enkephalin (MEnk) has been recognized as a modulator of macrophage physiology acting in an autocrine or paracrine fashion to influence macrophage activation, phenotype polarization and production of cytokines that would enhance lymphocyte activation at early stages of an immune response. Previously it was shown that splenic MEnk tissue content is reduced in rats exposed to constant light. In this work, we explored whether production of Met-enkephalin-containing peptides (MECPs) in cultured splenic macrophages is affected by exposure of rats to a constant light regime. In addition, we explored whether primary immune response was impaired under this condition. We found that in rats, 15 days in constant light was sufficient to disrupt their general activity rhythm. Splenic MEnk content oscillations and levels were also blunted throughout a 24-h period in animals subjected to constant light. In agreement, de novo synthesis of MECPs evaluated through incorporation of (35)S-methionine was reduced in splenic macrophages from rats exposed to constant light. Moreover, MECPs immunocytochemistry showed a decrease in the intracellular content and lack of granule-like deposits in this condition. Furthermore, we found that primary T-dependent antibody response was compromised in rats exposed to constant light. In those animals, pharmacologic treatment with MEnk increased IFN-γ-secreting cells. Also, IL-2 secretion from antigen-stimulated splenocytes was reduced after incubation with naloxone, suggesting that immune-derived opioid peptides and stimulation of opioid

Fatty Acid Synthesis and Pyruvate Metabolism Pathways Remain Active in Dihydroartemisinin-Induced Dormant Ring Stages of Plasmodium falciparum

PubMed Central

Chen, Nanhua; LaCrue, Alexis N.; Teuscher, Franka; Waters, Norman C.; Gatton, Michelle L.; Kyle, Dennis E.

2014-01-01

Artemisinin (ART)-based combination therapy (ACT) is used as the first-line treatment of uncomplicated falciparum malaria worldwide. However, despite high potency and rapid action, there is a high rate of recrudescence associated with ART monotherapy or ACT long before the recent emergence of ART resistance. ART-induced ring-stage dormancy and recovery have been implicated as possible causes of recrudescence; however, little is known about the characteristics of dormant parasites, including whether dormant parasites are metabolically active. We investigated the transcription of 12 genes encoding key enzymes in various metabolic pathways in P. falciparum during dihydroartemisinin (DHA)-induced dormancy and recovery. Transcription analysis showed an immediate downregulation for 10 genes following exposure to DHA but continued transcription of 2 genes encoding apicoplast and mitochondrial proteins. Transcription of several additional genes encoding apicoplast and mitochondrial proteins, particularly of genes encoding enzymes in pyruvate metabolism and fatty acid synthesis pathways, was also maintained. Additions of inhibitors for biotin acetyl-coenzyme A (CoA) carboxylase and enoyl-acyl carrier reductase of the fatty acid synthesis pathways delayed the recovery of dormant parasites by 6 and 4 days, respectively, following DHA treatment. Our results demonstrate that most metabolic pathways are downregulated in DHA-induced dormant parasites. In contrast, fatty acid and pyruvate metabolic pathways remain active. These findings highlight new targets to interrupt recovery of parasites from ART-induced dormancy and to reduce the rate of recrudescence following ART treatment. PMID:24913167

Fatty acid synthesis and pyruvate metabolism pathways remain active in dihydroartemisinin-induced dormant ring stages of Plasmodium falciparum.

PubMed

Chen, Nanhua; LaCrue, Alexis N; Teuscher, Franka; Waters, Norman C; Gatton, Michelle L; Kyle, Dennis E; Cheng, Qin

2014-08-01

Artemisinin (ART)-based combination therapy (ACT) is used as the first-line treatment of uncomplicated falciparum malaria worldwide. However, despite high potency and rapid action, there is a high rate of recrudescence associated with ART monotherapy or ACT long before the recent emergence of ART resistance. ART-induced ring-stage dormancy and recovery have been implicated as possible causes of recrudescence; however, little is known about the characteristics of dormant parasites, including whether dormant parasites are metabolically active. We investigated the transcription of 12 genes encoding key enzymes in various metabolic pathways in P. falciparum during dihydroartemisinin (DHA)-induced dormancy and recovery. Transcription analysis showed an immediate downregulation for 10 genes following exposure to DHA but continued transcription of 2 genes encoding apicoplast and mitochondrial proteins. Transcription of several additional genes encoding apicoplast and mitochondrial proteins, particularly of genes encoding enzymes in pyruvate metabolism and fatty acid synthesis pathways, was also maintained. Additions of inhibitors for biotin acetyl-coenzyme A (CoA) carboxylase and enoyl-acyl carrier reductase of the fatty acid synthesis pathways delayed the recovery of dormant parasites by 6 and 4 days, respectively, following DHA treatment. Our results demonstrate that most metabolic pathways are downregulated in DHA-induced dormant parasites. In contrast, fatty acid and pyruvate metabolic pathways remain active. These findings highlight new targets to interrupt recovery of parasites from ART-induced dormancy and to reduce the rate of recrudescence following ART treatment. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Wall of fundamental constants

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

Olive, Keith A.; School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota, 55455; Peloso, Marco

2011-02-15

We consider the signatures of a domain wall produced in the spontaneous symmetry breaking involving a dilatonlike scalar field coupled to electromagnetism. Domains on either side of the wall exhibit slight differences in their respective values of the fine-structure constant, {alpha}. If such a wall is present within our Hubble volume, absorption spectra at large redshifts may or may not provide a variation in {alpha} relative to the terrestrial value, depending on our relative position with respect to the wall. This wall could resolve the contradiction between claims of a variation of {alpha} based on Keck/Hires data and of themore » constancy of {alpha} based on Very Large Telescope data. We derive the properties of the wall and the parameters of the underlying microscopic model required to reproduce the possible spatial variation of {alpha}. We discuss the constraints on the existence of the low-energy domain wall and describe its observational implications concerning the variation of the fundamental constants.« less

Diffusion constant of slowly rotating black three-brane

NASA Astrophysics Data System (ADS)

Amoozad, Z.; Sadeghi, J.

2018-01-01

In this paper, we take the slowly rotating black three-brane background and perturb it by introducing a vector gauge field. We find the components of the gauge field through Maxwell equations and Bianchi identities. Using currents and some ansatz we find Fick's first law at long wavelength regime. An interesting result for this non-trivial supergravity background is that the diffusion constant on the stretched horizon which emerges from Fick's first law is a complex constant. The pure imaginary part of the diffusion constant appears because the black three-brane has angular momentum. By taking the static limit of the corresponding black brane the well known diffusion constant will be recovered. On the other hand, from the point of view of the Fick's second law, we have the dispersion relation ω = - iDq2 and we found a damping of hydrodynamical flow in the holographically dual theory. Existence of imaginary term in the diffusion constant introduces an oscillating propagation of the gauge field in the dual field theory.

Hamaker constants of iron oxide nanoparticles.

PubMed

Faure, Bertrand; Salazar-Alvarez, German; Bergström, Lennart

2011-07-19

The Hamaker constants for iron oxide nanoparticles in various media have been calculated using Lifshitz theory. Expressions for the dielectric responses of three iron oxide phases (magnetite, maghemite, and hematite) were derived from recently published optical data. The nonretarded Hamaker constants for the iron oxide nanoparticles interacting across water, A(1w1) = 33 - 39 zJ, correlate relatively well with previous reports, whereas the calculated values in nonpolar solvents (hexane and toluene), A(131) = 9 - 29 zJ, are much lower than the previous estimates, particularly for magnetite. The magnitude of van der Waals interactions varies significantly between the studied phases (magnetite < maghemite < hematite), which highlights the importance of a thorough characterization of the particles. The contribution of magnetic dispersion interactions for particle sizes in the superparamagnetic regime was found to be negligible. Previous conjectures related to colloidal stability and self-assembly have been revisited on the basis of the new Lifshitz values of the Hamaker constants.

Strategies for obtaining long constant-pressure test times in shock tubes

DOE PAGES

Campbell, Matthew Frederick; Parise, T.; Tulgestke, A. M.; ...

2015-09-22

Several techniques have been developed for obtaining long, constant-pressure test times in reflected shock wave experiments in a shock tube, including the use of driver inserts, driver gas tailoring, helium gas diaphragm interfaces, driver extensions, and staged driver gas filling. Here, we detail these techniques, including discussion on the most recent strategy, staged driver gas filling. Experiments indicate that this staged filling strategy increases available test time by roughly 20 % relative to single-stage filling of tailored driver gas mixtures, while simultaneously reducing the helium required per shock by up to 85 %. This filling scheme involves firstly mixing amore » tailored helium–nitrogen mixture in the driver section as in conventional driver filling and, secondly, backfilling a low-speed-of-sound gas such as nitrogen or carbon dioxide from a port close to the end cap of the driver section. Using this staged driver gas filling, in addition to the other techniques listed above, post-reflected shock test times of up to 0.102 s (102 ms) at 524 K and 1.6 atm have been obtained. Spectroscopically based temperature measurements in non-reactive mixtures have confirmed that temperature and pressure conditions remain constant throughout the length of these long test duration trials. Finally, these strategies have been used to measure low-temperature n-heptane ignition delay times.« less

Dielectric constant of liquid alkanes and hydrocarbon mixtures

NASA Technical Reports Server (NTRS)

Sen, A. D.; Anicich, V. G.; Arakelian, T.

1992-01-01

The complex dielectric constants of n-alkanes with two to seven carbon atoms have been measured. The measurements were conducted using a slotted-line technique at 1.2 GHz and at atmospheric pressure. The temperature was varied from the melting point to the boiling point of the respective alkanes. The real part of the dielectric constant was found to decrease with increasing temperature and correlate with the change in the molar volume. An upper limit to all the loss tangents was established at 0.001. The complex dielectric constants of a few mixtures of liquid alkanes were also measured at room temperature. For a pentane-octane mixture the real part of the dielectric constant could be explained by the Clausius-Mosotti theory. For the mixtures of n-hexane-ethylacetate and n-hexane-acetone the real part of the dielectric constants could be explained by the Onsager theory extended to mixtures. The dielectric constant of the n-hexane-acetone mixture displayed deviations from the Onsager theory at the highest fractions of acetone. The dipole moments of ethylacetate and acetone were determined for dilute mixtures using the Onsager theory and were found to be in agreement with their accepted gas-phase values. The loss tangents of the mixtures exhibited a linear relationship with the volume fraction for low concentrations of the polar liquids.

Biodegradation testing of chemicals with high Henry's constants - Separating mass and effective concentration reveals higher rate constants.

PubMed

Birch, Heidi; Andersen, Henrik R; Comber, Mike; Mayer, Philipp

2017-05-01

During simulation-type biodegradation tests, volatile chemicals will continuously partition between water phase and headspace. This study addressed how (1) this partitioning affects test results and (2) can be accounted for by combining equilibrium partition and dynamic biodegradation models. An aqueous mixture of 9 (semi)volatile chemicals was first generated using passive dosing and then diluted with environmental surface water producing concentrations in the ng/L to μg/L range. After incubation for 2 h to 4 weeks, automated Headspace Solid Phase Microextraction (HS-SPME) was applied directly on the test systems to measure substrate depletion by biodegradation relatively to abiotic controls. HS-SPME was also applied to determine air to water partitioning ratios. Biodegradation rate constants relating to the chemical in the water phase, k water , were generally a factor 1 to 11 times higher than biodegradation rate constants relating to the total mass of chemical in the test system, k system , with one exceptional factor of 72 times for a long chain alkane. True water phase degradation rate constants were found (i) more appropriate for risk assessment than test system rate constants, (ii) to facilitate extrapolation to other air-water systems and (iii) to be better defined input parameters for aquatic exposure and fate models. Copyright © 2017 Elsevier Ltd. All rights reserved.

Comparing otoacoustic emissions evoked by chirp transients with constant absorbed sound power and constant incident pressure magnitude

PubMed Central

Keefe, Douglas H.; Feeney, M. Patrick; Hunter, Lisa L.; Fitzpatrick, Denis F.

2017-01-01

Human ear-canal properties of transient acoustic stimuli are contrasted that utilize measured ear-canal pressures in conjunction with measured acoustic pressure reflectance and admittance. These data are referenced to the tip of a probe snugly inserted into the ear canal. Promising procedures to calibrate across frequency include stimuli with controlled levels of incident pressure magnitude, absorbed sound power, and forward pressure magnitude. An equivalent pressure at the eardrum is calculated from these measured data using a transmission-line model of ear-canal acoustics parameterized by acoustically estimated ear-canal area at the probe tip and length between the probe tip and eardrum. Chirp stimuli with constant incident pressure magnitude and constant absorbed sound power across frequency were generated to elicit transient-evoked otoacoustic emissions (TEOAEs), which were measured in normal-hearing adult ears from 0.7 to 8 kHz. TEOAE stimuli had similar peak-to-peak equivalent sound pressure levels across calibration conditions. Frequency-domain TEOAEs were compared using signal level, signal-to-noise ratio (SNR), coherence synchrony modulus (CSM), group delay, and group spread. Time-domain TEOAEs were compared using SNR, CSM, instantaneous frequency and instantaneous bandwidth. Stimuli with constant incident pressure magnitude or constant absorbed sound power across frequency produce generally similar TEOAEs up to 8 kHz. PMID:28147608

Temperature Dependence Of Elastic Constants Of Polymers

NASA Technical Reports Server (NTRS)

Simha, Robert; Papazoglou, Elisabeth

1989-01-01

Two papers extend theory of elastic constants of disordered solids to finite temperatures below glass-transition temperatures. First paper, entitled "Elastic Constants of Disordered Solids II: Temperature Dependence," applies to cryogenic temperatures. Second paper, entitled "Theory of Thermoelastic Properties for Polymer Glasses," develops unified treatment for static compressional and elongational properties at temperatures up to glass-transition temperatures.

Experimental determination of the effective strong coupling constant

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

Alexandre Deur; Volker Burkert; Jian-Ping Chen

2007-07-01

We extract an effective strong coupling constant from low Q{sup 2} data on the Bjorken sum. Using sum rules, we establish its Q{sup 2}-behavior over the complete Q{sup 2}-range. The result is compared to effective coupling constants extracted from different processes and to calculations based on Schwinger-Dyson equations, hadron spectroscopy or lattice QCD. Although the connection between the experimentally extracted effective coupling constant and the calculations is not clear, the results agree surprisingly well.

Laser Measurements of the H Atom + Ozone Rate Constant at Atmospheric Temperatures

NASA Astrophysics Data System (ADS)

Liu, Y.; Smith, G. P.; Peng, J.; Reppert, K. J.; Callahan, S. L.

2015-12-01

The exothermic H + O3 reaction produces OH(v) Meinel band emissions, used to derive mesospheric H concentrations and chemical heating rates. We have remeasured its rate constant to reduce resulting uncertainties and the measurement extend to lower mesospheric temperatures using modern laser techniques. H atoms are produced by pulsed ultraviolet laser trace photolysis of O3, followed by reaction of O(D) with added H2. A second, delayed, frequency-mixed dye laser measures the reaction decay rate with the remaining ozone by laser induced fluorescence. We monitor either the H atom decay by 2 photon excitation at 205 nm and detection of red fluorescence, or the OH(v=9) product time evolution with excitation of the B-X (0,9) band at 237 nm and emission in blue B-A bands. By cooling the enclosed low pressure flow cell we obtained measurements from 146-305 K. Small kinetic modeling corrections are made for secondary regeneration of H atoms. The results fully confirm the current NASA JPL recommendation for this rate constant, and establish its extrapolation down to the lower temperatures of the mesosphere. This work was supported by the NSF Aeronomy Program and an NSF Physics summer REU student grant.

Cosmological constant in scale-invariant theories

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

Foot, Robert; Kobakhidze, Archil; Volkas, Raymond R.

2011-10-01

The incorporation of a small cosmological constant within radiatively broken scale-invariant models is discussed. We show that phenomenologically consistent scale-invariant models can be constructed which allow a small positive cosmological constant, providing certain relation between the particle masses is satisfied. As a result, the mass of the dilaton is generated at two-loop level. Another interesting consequence is that the electroweak symmetry-breaking vacuum in such models is necessarily a metastable ''false'' vacuum which, fortunately, is not expected to decay on cosmological time scales.

Temperature-dependent inotropic and lusitropic indices based on half-logistic time constants for four segmental phases in isovolumic left ventricular pressure-time curve in excised, cross-circulated canine heart.

PubMed

Mizuno, Ju; Mohri, Satoshi; Yokoyama, Takeshi; Otsuji, Mikiya; Arita, Hideko; Hanaoka, Kazuo

2017-02-01

Varying temperature affects cardiac systolic and diastolic function and the left ventricular (LV) pressure-time curve (PTC) waveform that includes information about LV inotropism and lusitropism. Our proposed half-logistic (h-L) time constants obtained by fitting using h-L functions for four segmental phases (Phases I-IV) in the isovolumic LV PTC are more useful indices for estimating LV inotropism and lusitropism during contraction and relaxation periods than the mono-exponential (m-E) time constants at normal temperature. In this study, we investigated whether the superiority of the goodness of h-L fits remained even at hypothermia and hyperthermia. Phases I-IV in the isovolumic LV PTCs in eight excised, cross-circulated canine hearts at 33, 36, and 38 °C were analyzed using h-L and m-E functions and the least-squares method. The h-L and m-E time constants for Phases I-IV significantly shortened with increasing temperature. Curve fitting using h-L functions was significantly better than that using m-E functions for Phases I-IV at all temperatures. Therefore, the superiority of the goodness of h-L fit vs. m-E fit remained at all temperatures. As LV inotropic and lusitropic indices, temperature-dependent h-L time constants could be more useful than m-E time constants for Phases I-IV.

A Graphical Procedure for the Simultaneous Determination of the Distribution Constant of Iodine and the Stability Constants of Trihalide Anions.

ERIC Educational Resources Information Center

Kahwa, I. A.

1984-01-01

Discusses a graphical procedure which allows the distribution constant of iodine to be determined simultaneously with the trihalide anion stability constant. In addition, the procedure extends the experimental chemistry from distribution equilibria to important thermodynamic and bonding features. Advantages of using the procedure are also…

Binding constant of cell adhesion receptors and substrate-immobilized ligands depends on the distribution of ligands

NASA Astrophysics Data System (ADS)

Li, Long; Hu, Jinglei; Xu, Guangkui; Song, Fan

2018-01-01

Cell-cell adhesion and the adhesion of cells to tissues and extracellular matrix, which are pivotal for immune response, tissue development, and cell locomotion, depend sensitively on the binding constant of receptor and ligand molecules anchored on the apposing surfaces. An important question remains of whether the immobilization of ligands affects the affinity of binding with cell adhesion receptors. We have investigated the adhesion of multicomponent membranes to a flat substrate coated with immobile ligands using Monte Carlo simulations of a statistical mesoscopic model with biologically relevant parameters. We find that the binding of the adhesion receptors to ligands immobilized on the substrate is strongly affected by the ligand distribution. In the case of ligand clusters, the receptor-ligand binding constant can be significantly enhanced due to the less translational entropy loss of lipid-raft domains in the model cell membranes upon the formation of additional complexes. For ligands randomly or uniformly immobilized on the substrate, the binding constant is rather decreased since the receptors localized in lipid-raft domains have to pay an energetic penalty in order to bind ligands. Our findings help to understand why cell-substrate adhesion experiments for measuring the impact of lipid rafts on the receptor-ligand interactions led to contradictory results.

Effects of high CO2 on growth and metabolism of Arabidopsis seedlings during growth with a constantly limited supply of nitrogen.

PubMed

Takatani, Nobuyuki; Ito, Takuro; Kiba, Takatoshi; Mori, Marie; Miyamoto, Tetsuro; Maeda, Shin-Ichi; Omata, Tatsuo

2014-02-01

Elevated CO2 has been reported to stimulate plant growth under nitrogen-sufficient conditions, but the effects of CO2 on growth in a constantly nitrogen-limited state, which is relevant to most natural habitats of plants, remain unclear. Here, we maintained Arabidopsis seedlings under such conditions by growing a mutant with reduced nitrate uptake activity on a medium containing nitrate as the sole nitrogen source. Under nitrogen-sufficient conditions (i.e. in the presence of ammonium), growth of shoots and roots of both the wild type (WT) and the mutant was increased approximately 2-fold by elevated CO2. Growth stimulation of shoots and roots by elevated CO2 was observed in the WT growing with nitrate as the sole nitrogen source, but in the mutant grown with nitrate, the high-CO2 conditions stimulated only the growth of roots. In the mutant, elevated CO2 caused well-known symptoms of nitrogen-starved plants, including decreased shoot/root ratio, reduced nitrate content and accumulation of anthocyanin, but also had an increased Chl content in the shoot, which was contradictory to the known effect of nitrogen depletion. A high-CO2-responsive change specific to the mutant was not observed in the levels of the major metabolites, although CO2 responses were observed in the WT and the mutant. These results indicated that elevated CO2 causes nitrogen limitation in the seedlings grown with a constantly limited supply of nitrogen, but the Chl content and the root biomass of the plant increase to enhance the activities of both photosynthesis and nitrogen uptake, while maintaining normal metabolism and response to high CO2.

Charged structure constants from modularity

NASA Astrophysics Data System (ADS)

Das, Diptarka; Datta, Shouvik; Pal, Sridip

2017-11-01

We derive a universal formula for the average heavy-heavy-light structure constants for 2 d CFTs with non-vanishing u(1) charge. The derivation utilizes the modular properties of one-point functions on the torus. Refinements in N=2 SCFTs, show that the resulting Cardy-like formula for the structure constants has precisely the same shifts in the central charge as that of the thermodynamic entropy found earlier. This analysis generalizes the recent results by Kraus and Maloney for CFTs with an additional global u(1) symmetry [1]. Our results at large central charge are also shown to match with computations from the holographic dual, which suggest that the averaged CFT three-point coefficient also serves as a useful probe of detecting black hole hair.

Regularizing cosmological singularities by varying physical constants

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

Dąbrowski, Mariusz P.; Marosek, Konrad, E-mail: mpdabfz@wmf.univ.szczecin.pl, E-mail: k.marosek@wmf.univ.szczecin.pl

2013-02-01

Varying physical constant cosmologies were claimed to solve standard cosmological problems such as the horizon, the flatness and the Λ-problem. In this paper, we suggest yet another possible application of these theories: solving the singularity problem. By specifying some examples we show that various cosmological singularities may be regularized provided the physical constants evolve in time in an appropriate way.

The method of constant stimuli is inefficient

NASA Technical Reports Server (NTRS)

Watson, Andrew B.; Fitzhugh, Andrew

1990-01-01

Simpson (1988) has argued that the method of constant stimuli is as efficient as adaptive methods of threshold estimation and has supported this claim with simulations. It is shown that Simpson's simulations are not a reasonable model of the experimental process and that more plausible simulations confirm that adaptive methods are much more efficient that the method of constant stimuli.

More exact solutions of the constant astigmatism equation

NASA Astrophysics Data System (ADS)

Hlaváč, Adam

2018-01-01

By using Bäcklund transformation for the sine-Gordon equation, new periodic exact solutions of the constant astigmatism equation zyy +(1 / z) xx + 2 = 0 are generated from a seed which corresponds to Lipschitz surfaces of constant astigmatism.

Accurate Determination of the Values of Fundamental Physical Constants: The Basis of the New "Quantum" SI Units

NASA Astrophysics Data System (ADS)

Karshenboim, S. G.

2018-03-01

The metric system appeared as the system of units designed for macroscopic (laboratory scale) measurements. The progress in accurate determination of the values of quantum constants (such as the Planck constant) in SI units shows that the capabilities in high-precision measurement of microscopic and macroscopic quantities in terms of the same units have increased substantially recently. At the same time, relative microscopic measurements (for example, the comparison of atomic transition frequencies or atomic masses) are often much more accurate than relative measurements of macroscopic quantities. This is the basis for the strategy to define units in microscopic phenomena and then use them on the laboratory scale, which plays a crucial role in practical methodological applications determined by everyday life and technologies. The international CODATA task group on fundamental constants regularly performs an overall analysis of the precision world data (the so-called Adjustment of the Fundamental Constants) and publishes their recommended values. The most recent evaluation was based on the data published by the end of 2014; here, we review the corresponding data and results. The accuracy in determination of the Boltzmann constant has increased, the consistency of the data on determination of the Planck constant has improved; it is these two dimensional constants that will be used in near future as the basis for the new definition of the kelvin and kilogram, respectively. The contradictions in determination of the Rydberg constant and the proton charge radius remain. The accuracy of determination of the fine structure constant and relative atomic weight of the electron has improved. Overall, we give a detailed review of the state of the art in precision determination of the values of fundamental constants. The mathematical procedure of the Adjustment, the new data and results are considered in detail. The limitations due to macroscopic properties of material

Report: EPA Prepared to Implement Strategic Human Capital Management Activities But Challenges Remain

EPA Pesticide Factsheets

Report #2004-P-00024, September 20, 2004. EPA’s headquarters and regional offices are prepared to implement strategic human capital management activities, but an alignment of office-level activities to the Agency’s Strategy for Human Capital is lacking.

Scalar-tensor theory of gravitation with negative coupling constant

NASA Technical Reports Server (NTRS)

Smalley, L. L.; Eby, P. B.

1976-01-01

The possibility of a Brans-Dicke scalar-tensor gravitation theory with a negative coupling constant is considered. The admissibility of a negative-coupling theory is investigated, and a simplified cosmological solution is obtained which allows a negative derivative of the gravitation constant. It is concluded that a Brans-Dicke theory with a negative coupling constant can be a viable alternative to general relativity and that a large negative value for the coupling constant seems to bring the original scalar-tensor theory into close agreement with perihelion-precession results in view of recent observations of small solar oblateness.

The Throw-and-Catch Model of Human Gait: Evidence from Coupling of Pre-Step Postural Activity and Step Location

PubMed Central

Bancroft, Matthew J.; Day, Brian L.

2016-01-01

Postural activity normally precedes the lift of a foot from the ground when taking a step, but its function is unclear. The throw-and-catch hypothesis of human gait proposes that the pre-step activity is organized to generate momentum for the body to fall ballistically along a specific trajectory during the step. The trajectory is appropriate for the stepping foot to land at its intended location while at the same time being optimally placed to catch the body and regain balance. The hypothesis therefore predicts a strong coupling between the pre-step activity and step location. Here we examine this coupling when stepping to visually-presented targets at different locations. Ten healthy, young subjects were instructed to step as accurately as possible onto targets placed in five locations that required either different step directions or different step lengths. In 75% of trials, the target location remained constant throughout the step. In the remaining 25% of trials, the intended step location was changed by making the target jump to a new location 96 ms ± 43 ms after initiation of the pre-step activity, long before foot lift. As predicted by the throw-and-catch hypothesis, when the target location remained constant, the pre-step activity led to body momentum at foot lift that was coupled to the intended step location. When the target location jumped, the pre-step activity was adjusted (median latency 223 ms) and prolonged (on average by 69 ms), which altered the body’s momentum at foot lift according to where the target had moved. We conclude that whenever possible the coupling between the pre-step activity and the step location is maintained. This provides further support for the throw-and-catch hypothesis of human gait. PMID:28066208

The Throw-and-Catch Model of Human Gait: Evidence from Coupling of Pre-Step Postural Activity and Step Location.

PubMed

Bancroft, Matthew J; Day, Brian L

2016-01-01

Postural activity normally precedes the lift of a foot from the ground when taking a step, but its function is unclear. The throw-and-catch hypothesis of human gait proposes that the pre-step activity is organized to generate momentum for the body to fall ballistically along a specific trajectory during the step. The trajectory is appropriate for the stepping foot to land at its intended location while at the same time being optimally placed to catch the body and regain balance. The hypothesis therefore predicts a strong coupling between the pre-step activity and step location. Here we examine this coupling when stepping to visually-presented targets at different locations. Ten healthy, young subjects were instructed to step as accurately as possible onto targets placed in five locations that required either different step directions or different step lengths. In 75% of trials, the target location remained constant throughout the step. In the remaining 25% of trials, the intended step location was changed by making the target jump to a new location 96 ms ± 43 ms after initiation of the pre-step activity, long before foot lift. As predicted by the throw-and-catch hypothesis, when the target location remained constant, the pre-step activity led to body momentum at foot lift that was coupled to the intended step location. When the target location jumped, the pre-step activity was adjusted (median latency 223 ms) and prolonged (on average by 69 ms), which altered the body's momentum at foot lift according to where the target had moved. We conclude that whenever possible the coupling between the pre-step activity and the step location is maintained. This provides further support for the throw-and-catch hypothesis of human gait.

Profiles of equilibrium constants for self-association of aromatic molecules

NASA Astrophysics Data System (ADS)

Beshnova, Daria A.; Lantushenko, Anastasia O.; Davies, David B.; Evstigneev, Maxim P.

2009-04-01

Analysis of the noncovalent, noncooperative self-association of identical aromatic molecules assumes that the equilibrium self-association constants are either independent of the number of molecules (the EK-model) or change progressively with increasing aggregation (the AK-model). The dependence of the self-association constant on the number of molecules in the aggregate (i.e., the profile of the equilibrium constant) was empirically derived in the AK-model but, in order to provide some physical understanding of the profile, it is proposed that the sources for attenuation of the equilibrium constant are the loss of translational and rotational degrees of freedom, the ordering of molecules in the aggregates and the electrostatic contribution (for charged units). Expressions are derived for the profiles of the equilibrium constants for both neutral and charged molecules. Although the EK-model has been widely used in the analysis of experimental data, it is shown in this work that the derived equilibrium constant, KEK, depends on the concentration range used and hence, on the experimental method employed. The relationship has also been demonstrated between the equilibrium constant KEK and the real dimerization constant, KD, which shows that the value of KEK is always lower than KD.

On determining dose rate constants spectroscopically.

PubMed

Rodriguez, M; Rogers, D W O

2013-01-01

To investigate several aspects of the Chen and Nath spectroscopic method of determining the dose rate constants of (125)I and (103)Pd seeds [Z. Chen and R. Nath, Phys. Med. Biol. 55, 6089-6104 (2010)] including the accuracy of using a line or dual-point source approximation as done in their method, and the accuracy of ignoring the effects of the scattered photons in the spectra. Additionally, the authors investigate the accuracy of the literature's many different spectra for bare, i.e., unencapsulated (125)I and (103)Pd sources. Spectra generated by 14 (125)I and 6 (103)Pd seeds were calculated in vacuo at 10 cm from the source in a 2.7 × 2.7 × 0.05 cm(3) voxel using the EGSnrc BrachyDose Monte Carlo code. Calculated spectra used the initial photon spectra recommended by AAPM's TG-43U1 and NCRP (National Council of Radiation Protection and Measurements) Report 58 for the (125)I seeds, or TG-43U1 and NNDC(2000) (National Nuclear Data Center, 2000) for (103)Pd seeds. The emitted spectra were treated as coming from a line or dual-point source in a Monte Carlo simulation to calculate the dose rate constant. The TG-43U1 definition of the dose rate constant was used. These calculations were performed using the full spectrum including scattered photons or using only the main peaks in the spectrum as done experimentally. Statistical uncertainties on the air kerma/history and the dose rate/history were ≤0.2%. The dose rate constants were also calculated using Monte Carlo simulations of the full seed model. The ratio of the intensity of the 31 keV line relative to that of the main peak in (125)I spectra is, on average, 6.8% higher when calculated with the NCRP Report 58 initial spectrum vs that calculated with TG-43U1 initial spectrum. The (103)Pd spectra exhibit an average 6.2% decrease in the 22.9 keV line relative to the main peak when calculated with the TG-43U1 rather than the NNDC(2000) initial spectrum. The measured values from three different investigations are

Beauty vector meson decay constants from QCD sum rules

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

Lucha, Wolfgang; Melikhov, Dmitri; D. V. Skobeltsyn Institute of Nuclear Physics, M. V. Lomonosov Moscow State University, 119991, Moscow

We present the outcomes of a very recent investigation of the decay constants of nonstrange and strange heavy-light beauty vector mesons, with special emphasis on the ratio of any such decay constant to the decay constant of the corresponding pseudoscalar meson, by means of Borel-transformed QCD sum rules. Our results suggest that both these ratios are below unity.

Optimal trace inequality constants for interior penalty discontinuous Galerkin discretisations of elliptic operators using arbitrary elements with non-constant Jacobians

NASA Astrophysics Data System (ADS)

Owens, A. R.; Kópházi, J.; Eaton, M. D.

2017-12-01

In this paper, a new method to numerically calculate the trace inequality constants, which arise in the calculation of penalty parameters for interior penalty discretisations of elliptic operators, is presented. These constants are provably optimal for the inequality of interest. As their calculation is based on the solution of a generalised eigenvalue problem involving the volumetric and face stiffness matrices, the method is applicable to any element type for which these matrices can be calculated, including standard finite elements and the non-uniform rational B-splines of isogeometric analysis. In particular, the presented method does not require the Jacobian of the element to be constant, and so can be applied to a much wider variety of element shapes than are currently available in the literature. Numerical results are presented for a variety of finite element and isogeometric cases. When the Jacobian is constant, it is demonstrated that the new method produces lower penalty parameters than existing methods in the literature in all cases, which translates directly into savings in the solution time of the resulting linear system. When the Jacobian is not constant, it is shown that the naive application of existing approaches can result in penalty parameters that do not guarantee coercivity of the bilinear form, and by extension, the stability of the solution. The method of manufactured solutions is applied to a model reaction-diffusion equation with a range of parameters, and it is found that using penalty parameters based on the new trace inequality constants result in better conditioned linear systems, which can be solved approximately 11% faster than those produced by the methods from the literature.

Optical constants of concentrated aqueous ammonium sulfate.

NASA Technical Reports Server (NTRS)

Remsberg, E. E.

1973-01-01

Using experimental data obtained from applying spectroscopy to a 39-wt-% aqueous ammonium sulfate solution, it is shown that, even though specific aerosol optical constants appear quite accurate, spectral variations may exist as functions of material composition or concentration or both. Prudent users of optical constant data must then include liberal data error estimates when performing calculations or in interpreting spectroscopic surveys of collected aerosol material.

Elastic constants from microscopic strain fluctuations

PubMed

Sengupta; Nielaba; Rao; Binder

2000-02-01

Fluctuations of the instantaneous local Lagrangian strain epsilon(ij)(r,t), measured with respect to a static "reference" lattice, are used to obtain accurate estimates of the elastic constants of model solids from atomistic computer simulations. The measured strains are systematically coarse-grained by averaging them within subsystems (of size L(b)) of a system (of total size L) in the canonical ensemble. Using a simple finite size scaling theory we predict the behavior of the fluctuations as a function of L(b)/L and extract elastic constants of the system in the thermodynamic limit at nonzero temperature. Our method is simple to implement, efficient, and general enough to be able to handle a wide class of model systems, including those with singular potentials without any essential modification. We illustrate the technique by computing isothermal elastic constants of "hard" and "soft" disk triangular solids in two dimensions from Monte Carlo and molecular dynamics simulations. We compare our results with those from earlier simulations and theory.

Using solid phase micro extraction to determine salting-out (Setschenow) constants for hydrophobic organic chemicals.

PubMed

Jonker, Michiel T O; Muijs, Barry

2010-06-01

With increasing ionic strength, the aqueous solubility and activity of organic chemicals are altered. This so-called salting-out effect causes the hydrophobicity of the chemicals to be increased and sorption in the marine environment to be more pronounced than in freshwater systems. The process can be described with empirical salting-out or Setschenow constants, which traditionally are determined by comparing aqueous solubilities in freshwater and saline water. Aqueous solubilities of hydrophobic organic chemicals (HOCs) however are difficult to determine, which might partly explain the limited size of the existing data base on Setschenow constants for these chemicals. In this paper, we propose an alternative approach for determining the constants, which is based on the use of solid phase micro extraction (SPME) fibers. Partitioning of polycyclic aromatic hydrocarbons (PAHs) to SPME fibers increased about 1.7 times when going from de-ionized water to seawater. From the log-linear relationship between SPME fiber-water partition coefficients and ionic strength, Setschenow constants were derived, which measured on average 0.35 L mol(-1). These values agreed with literature values existing for some of the investigated PAHs and were independent of solute hydrophobicity or molar volume. Based on the present data, SPME seems to be a convenient and suitable alternative technique to determine Setschenow constants for HOCs. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Direct Measurement of Equilibrium Constants for High-Affinity Hemoglobins

PubMed Central

Kundu, Suman; Premer, Scott A.; Hoy, Julie A.; Trent, James T.; Hargrove, Mark S.

2003-01-01

The biological functions of heme proteins are linked to their rate and affinity constants for ligand binding. Kinetic experiments are commonly used to measure equilibrium constants for traditional hemoglobins comprised of pentacoordinate ligand binding sites and simple bimolecular reaction schemes. However, kinetic methods do not always yield reliable equilibrium constants with more complex hemoglobins for which reaction mechanisms are not clearly understood. Furthermore, even where reaction mechanisms are clearly understood, it is very difficult to directly measure equilibrium constants for oxygen and carbon monoxide binding to high-affinity (KD ≪ 1 μM) hemoglobins. This work presents a method for direct measurement of equilibrium constants for high-affinity hemoglobins that utilizes a competition for ligands between the "target" protein and an array of "scavenger" hemoglobins with known affinities. This method is described for oxygen and carbon monoxide binding to two hexacoordinate hemoglobins: rice nonsymbiotic hemoglobin and Synechocystis hemoglobin. Our results demonstrate that although these proteins have different mechanisms for ligand binding, their affinities for oxygen and carbon monoxide are similar. Their large affinity constants for oxygen, 285 and ∼100 μM−1 respectively, indicate that they are not capable of facilitating oxygen transport. PMID:12770899

Size-dependent Hamaker constants for silver and gold nanoparticles

NASA Astrophysics Data System (ADS)

Pinchuk, Pavlo; Jiang, Ke

2015-08-01

Hamaker-Lifshitz constants are material specific constants that are used to calculate van der Waals interaction forces between small particles in solution. Typically, these constants are size-independent and material specific. According to the Lifshitz theory, the Hamaker-Lifshitz constants can be calculated by taking integrals that include the dielectric permittivity, as a function of frequency, of the interacting particles and the medium around particles. The dielectric permittivity of interacting metal nanoparticles can be calculated using the Drude model, which is based on the assumption of motion of free conducting electrons. For bulk metals, the Drude model does not predict any sizedependence of the dielectric permittivity. However, the conducting electrons in small noble metal nanoparticles (R ~ 10nm) exhibit surface scattering, which changes the complex permittivity function. In this work, we show theoretically that scattering of the free conducting electrons inside silver and gold nanoparticles with the size of 1 - 50 nm leads to size-dependent dielectric permittivity and Hamaker-Lifshitz constants. We calculate numerically the Hamaker-Lifshitz constants for silver and gold nanoparticles with different diameters. The results of the study might be of interests for understanding colloidal stability of metal nanoparticles.

Non-minimally coupled varying constants quantum cosmologies

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

Balcerzak, Adam, E-mail: abalcerz@wmf.univ.szczecin.pl

We consider gravity theory with varying speed of light and varying gravitational constant. Both constants are represented by non-minimally coupled scalar fields. We examine the cosmological evolution in the near curvature singularity regime. We find that at the curvature singularity the speed of light goes to infinity while the gravitational constant vanishes. This corresponds to the Newton's Mechanics limit represented by one of the vertex of the Bronshtein-Zelmanov-Okun cube [1,2]. The cosmological evolution includes both the pre-big-bang and post-big-bang phases separated by the curvature singularity. We also investigate the quantum counterpart of the considered theory and find the probability ofmore » transition of the universe from the collapsing pre-big-bang phase to the expanding post-big-bang phase.« less

Comparative activation states of tumor-associated and peritoneal macrophages from mice bearing an induced fibrosarcoma.

PubMed

Valdez, J C; de Alderete, N; Meson, O E; Sirena, A; Perdigon, G

1990-11-01

Balb/c mice bearing a methylcholanthrene-induced fibrosarcoma were used to compare the activation levels of tumor-associated and peritoneal macrophages. Two stages of tumor growth were examined, namely "small" and "large" tumors, with average diameters of 10 and 30 mm, respectively. The activation state, determined by measurement of both phagocytic index and beta-glucuronidase content, was found to be markedly higher in tumor-associated macrophages than in their peritoneal counterparts and it was, in addition, independent of tumor progression. The percentage of tumor-associated macrophages, which were detected on the basis of Fc receptor expression, remained constant in the growing neoplasm, at approximately 23% of total cell population. None of these parameters were affected by inoculation with an immunopotentiating dose of heat-killed Candida albicans which, on the other hand, seemed not to alter the course of the tumor. These data suggest that within the tumor microenvironment macrophages would somehow be maintained at a constant proportion and at a highly activated state, while outside the tumor they would be at a lower activation level. Our results also suggest that TAM would not possess antitumor activity in vivo, although we have found this activity in vitro.

Negative Dielectric Constant Material Based on Ion Conducting Materials

NASA Technical Reports Server (NTRS)

Gordon, Keith L. (Inventor); Kang, Jin Ho (Inventor); Park, Cheol (Inventor); Lillehei, Peter T. (Inventor); Harrison, Joycelyn S. (Inventor)

2017-01-01

Metamaterials or artificial negative index materials (NIMs) have generated great attention due to their unique and exotic electromagnetic properties. One exemplary negative dielectric constant material, which is an essential key for creating the NIMs, was developed by doping ions into a polymer, a protonated poly (benzimidazole) (PBI). The doped PBI showed a negative dielectric constant at megahertz (MHz) frequencies due to its reduced plasma frequency and an induction effect. The magnitude of the negative dielectric constant and the resonance frequency were tunable by doping concentration. The highly doped PBI showed larger absolute magnitude of negative dielectric constant at just above its resonance frequency than the less doped PBI.

Negative Dielectric Constant Material Based on Ion Conducting Materials

NASA Technical Reports Server (NTRS)

Gordon, Keith L. (Inventor); Kang, Jin Ho (Inventor); Harrison, Joycelyn S. (Inventor); Park, Cheol (Inventor); Lillehei, Peter T. (Inventor)

2014-01-01

Metamaterials or artificial negative index materials (NIMs) have generated great attention due to their unique and exotic electromagnetic properties. One exemplary negative dielectric constant material, which is an essential key for creating the NIMs, was developed by doping ions into a polymer, a protonated poly(benzimidazole) (PBI). The doped PBI showed a negative dielectric constant at megahertz (MHz) frequencies due to its reduced plasma frequency and an induction effect. The magnitude of the negative dielectric constant and the resonance frequency were tunable by doping concentration. The highly doped PBI showed larger absolute magnitude of negative dielectric constant at just above its resonance frequency than the less doped PBI.

Microbial metabolic activity in soil as measured by dehydrogenase determinations

NASA Technical Reports Server (NTRS)

Casida, L. E., Jr.

1977-01-01

The dehydrogenase technique for measuring the metabolic activity of microorganisms in soil was modified to use a 6-h, 37 C incubation with either glucose or yeast extract as the electron-donating substrate. The rate of formazan production remained constant during this time interval, and cellular multiplication apparently did not occur. The technique was used to follow changes in the overall metabolic activities of microorganisms in soil undergoing incubation with a limiting concentration of added nutrient. The sequence of events was similar to that obtained by using the Warburg respirometer to measure O2 consumption. However, the major peaks of activity occurred earlier with the respirometer. This possibly is due to the lack of atmospheric CO2 during the O2 consumption measurements.

Enhanced microbial coalbed methane generation: A review of research, commercial activity, and remaining challenges

USGS Publications Warehouse

Ritter, Daniel J.; Vinson, David S.; Barnhart, Elliott P.; Akob, Denise M.; Fields, Matthew W.; Cunningham, Al B.; Orem, William H.; McIntosh, Jennifer C.

2015-01-01

Coalbed methane (CBM) makes up a significant portion of the world’s natural gas resources. The discovery that approximately 20% of natural gas is microbial in origin has led to interest in microbially enhanced CBM (MECoM), which involves stimulating microorganisms to produce additional CBM from existing production wells. This paper reviews current laboratory and field research on understanding processes and reservoir conditions which are essential for microbial CBM generation, the progress of efforts to stimulate microbial methane generation in coal beds, and key remaining knowledge gaps. Research has been primarily focused on identifying microbial communities present in areas of CBM generation and attempting to determine their function, in-situ reservoir conditions that are most favorable for microbial CBM generation, and geochemical indicators of metabolic pathways of methanogenesis (i.e., acetoclastic or hydrogenotrophic methanogenesis). Meanwhile, researchers at universities, government agencies, and companies have focused on four primary MECoM strategies: 1) microbial stimulation (i.e., addition of nutrients to stimulate native microbes); 2) microbial augmentation (i.e., addition of microbes not native to or abundant in the reservoir of interest); 3) physically increasing microbial access to coal and distribution of amendments; and 4) chemically increasing the bioavailability of coal organics. Most companies interested in MECoM have pursued microbial stimulation: Luca Technologies, Inc., successfully completed a pilot scale field test of their stimulation strategy, while two others, Ciris Energy and Next Fuel, Inc., have undertaken smaller scale field tests. Several key knowledge gaps remain that need to be addressed before MECoM strategies can be implemented commercially. Little is known about the bacterial community responsible for coal biodegradation and how these microorganisms may be stimulated to enhance microbial methanogenesis. In addition, research

Estimation of Henry's Law Constant for a Diverse Set of Organic Compounds from Molecular Structure

EPA Science Inventory

The SPARC (SPARC Performs Automated Reasoning in Chemistry) vapor pressure and activity coefficient models were coupled to estimate Henry’s Law Constant (HLC) in water and in hexadecane for a wide range of non-polar and polar organic compounds without modification or additional p...

Determination of the Boltzmann constant by dielectric-constant gas thermometry

NASA Astrophysics Data System (ADS)

Fellmuth, Bernd; Fischer, Joachim; Gaiser, Christof; Jusko, Otto; Priruenrom, Tasanee; Sabuga, Wladimir; Zandt, Thorsten

2011-10-01

Within an international project directed to the new definition of the base unit kelvin, the Boltzmann constant k has been determined by dielectric-constant gas thermometry at PTB. In the pressure range from about 1 MPa to 7 MPa, 11 helium isotherms have been measured at the triple point of water (TPW) by applying a new special experimental setup consisting of a large-volume thermostat, a vacuum-isolated measuring system, stainless-steel 10 pF cylindrical capacitors, an autotransformer ratio capacitance bridge, a high-purity gas-handling system including a mass spectrometer, and traceably calibrated special pressure balances with piston-cylinder assemblies having effective areas of 2 cm2. The value of k has been deduced from the linear, ideal-gas term of an appropriate virial expansion fitted to the combined isotherms. A detailed uncertainty budget has been established by performing Monte Carlo simulations. The main uncertainty components result from the measurement of pressure and capacitance as well as the influence of the effective compressibility of the measuring capacitor and impurities contained in the helium gas. The combination of the results obtained at the TPW (kTPW = 1.380 654 × 10-23 J K-1, relative standard uncertainty 9.2 parts per million) with data measured earlier at low temperatures (21 K to 27 K, kLT = 1.380 657 × 10-23 J K-1, 15.9 parts per million) has yielded a value of k = 1.380 655 × 10-23 J K-1 with uncertainty of 7.9 parts per million.

Chandra Independently Determines Hubble Constant

NASA Astrophysics Data System (ADS)

2006-08-01

A critically important number that specifies the expansion rate of the Universe, the so-called Hubble constant, has been independently determined using NASA's Chandra X-ray Observatory. This new value matches recent measurements using other methods and extends their validity to greater distances, thus allowing astronomers to probe earlier epochs in the evolution of the Universe. "The reason this result is so significant is that we need the Hubble constant to tell us the size of the Universe, its age, and how much matter it contains," said Max Bonamente from the University of Alabama in Huntsville and NASA's Marshall Space Flight Center (MSFC) in Huntsville, Ala., lead author on the paper describing the results. "Astronomers absolutely need to trust this number because we use it for countless calculations." Illustration of Sunyaev-Zeldovich Effect Illustration of Sunyaev-Zeldovich Effect The Hubble constant is calculated by measuring the speed at which objects are moving away from us and dividing by their distance. Most of the previous attempts to determine the Hubble constant have involved using a multi-step, or distance ladder, approach in which the distance to nearby galaxies is used as the basis for determining greater distances. The most common approach has been to use a well-studied type of pulsating star known as a Cepheid variable, in conjunction with more distant supernovae to trace distances across the Universe. Scientists using this method and observations from the Hubble Space Telescope were able to measure the Hubble constant to within 10%. However, only independent checks would give them the confidence they desired, considering that much of our understanding of the Universe hangs in the balance. Chandra X-ray Image of MACS J1149.5+223 Chandra X-ray Image of MACS J1149.5+223 By combining X-ray data from Chandra with radio observations of galaxy clusters, the team determined the distances to 38 galaxy clusters ranging from 1.4 billion to 9.3 billion

On the Kolmogorov constant in stochastic turbulence models

NASA Astrophysics Data System (ADS)

Heinz, Stefan

2002-11-01

The Kolmogorov constant is fundamental in stochastic models of turbulence. To explain the reasons for observed variations of this quantity, it is calculated for two flows by various methods and data. Velocity fluctuations are considered as the sum of contributions due to anisotropy, acceleration fluctuations and stochastic forcing that is controlled by the Kolmogorov constant. It is shown that the effects of anisotropy and acceleration fluctuations are responsible for significant variations of the Kolmogorov constant. It is found near 2 for flows where anisotropy and acceleration fluctuations contribute to the energy budget, and near 6 if such contributions disappear.

Procedures for determining MATMOD-4V material constants

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

Lowe, T.C.

1993-11-01

The MATMOD-4V constitutive relations were developed from the original MATMOD model to extend the range of nonelastic deformation behaviors represented to include transient phenomena such as strain softening. Improvements in MATMOD-4V increased the number of independent material constants and the difficulty in determining their values. Though the constitutive relations are conceptually simple, their form and procedures for obtaining their constants can be complex. This paper reviews in detail the experiments, numerical procedures, and assumptions that have been used to determine a complete set of MATMOD-4V constants for high purity aluminum.

Methodology for extracting local constants from petroleum cracking flows

DOEpatents

Chang, Shen-Lin; Lottes, Steven A.; Zhou, Chenn Q.

2000-01-01

A methodology provides for the extraction of local chemical kinetic model constants for use in a reacting flow computational fluid dynamics (CFD) computer code with chemical kinetic computations to optimize the operating conditions or design of the system, including retrofit design improvements to existing systems. The coupled CFD and kinetic computer code are used in combination with data obtained from a matrix of experimental tests to extract the kinetic constants. Local fluid dynamic effects are implicitly included in the extracted local kinetic constants for each particular application system to which the methodology is applied. The extracted local kinetic model constants work well over a fairly broad range of operating conditions for specific and complex reaction sets in specific and complex reactor systems. While disclosed in terms of use in a Fluid Catalytic Cracking (FCC) riser, the inventive methodology has application in virtually any reaction set to extract constants for any particular application and reaction set formulation. The methodology includes the step of: (1) selecting the test data sets for various conditions; (2) establishing the general trend of the parametric effect on the measured product yields; (3) calculating product yields for the selected test conditions using coupled computational fluid dynamics and chemical kinetics; (4) adjusting the local kinetic constants to match calculated product yields with experimental data; and (5) validating the determined set of local kinetic constants by comparing the calculated results with experimental data from additional test runs at different operating conditions.

Scene-based nonuniformity correction using local constant statistics.

PubMed

Zhang, Chao; Zhao, Wenyi

2008-06-01

In scene-based nonuniformity correction, the statistical approach assumes all possible values of the true-scene pixel are seen at each pixel location. This global-constant-statistics assumption does not distinguish fixed pattern noise from spatial variations in the average image. This often causes the "ghosting" artifacts in the corrected images since the existing spatial variations are treated as noises. We introduce a new statistical method to reduce the ghosting artifacts. Our method proposes a local-constant statistics that assumes that the temporal signal distribution is not constant at each pixel but is locally true. This considers statistically a constant distribution in a local region around each pixel but uneven distribution in a larger scale. Under the assumption that the fixed pattern noise concentrates in a higher spatial-frequency domain than the distribution variation, we apply a wavelet method to the gain and offset image of the noise and separate out the pattern noise from the spatial variations in the temporal distribution of the scene. We compare the results to the global-constant-statistics method using a clean sequence with large artificial pattern noises. We also apply the method to a challenging CCD video sequence and a LWIR sequence to show how effective it is in reducing noise and the ghosting artifacts.

Guanidinium Group Remains Protonated in a Strongly Basic Arginine Solution

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

Xu, Bo; Jacobs, Michael I.; Kostko, Oleg

Knowledge of the acid dissociation constant of an amino acid has very important ramifications in the biochemistry of proteins and lipid bilayers in aqueous environments because charge and proton transfer depend on its value. The acid dissociation constant for the guanidinium group in arginine has historically been posited as 12.5, but there is substantial variation in published values over the years. Recent experiments suggest that the dissociation constant for arginine is much higher than 12.5, which explains why the arginine guanidinium group retains its positive charge under all physiological conditions. Here, we use X-ray photoelectron spectroscopy to study unsupported, aqueousmore » arginine nanoparticles. By varying the pH of the constituent solution, we provide evidence that the guanidinium group is protonated even in a very basic solution. By analyzing the energy shifts in the C and N X-ray photoelectron spectra, we establish a molecular level picture of how charge and proton transport in aqueous solutions of arginine occur.« less

Guanidinium Group Remains Protonated in a Strongly Basic Arginine Solution

DOE PAGES

Xu, Bo; Jacobs, Michael I.; Kostko, Oleg; ...

2017-05-16

Knowledge of the acid dissociation constant of an amino acid has very important ramifications in the biochemistry of proteins and lipid bilayers in aqueous environments because charge and proton transfer depend on its value. The acid dissociation constant for the guanidinium group in arginine has historically been posited as 12.5, but there is substantial variation in published values over the years. Recent experiments suggest that the dissociation constant for arginine is much higher than 12.5, which explains why the arginine guanidinium group retains its positive charge under all physiological conditions. Here, we use X-ray photoelectron spectroscopy to study unsupported, aqueousmore » arginine nanoparticles. By varying the pH of the constituent solution, we provide evidence that the guanidinium group is protonated even in a very basic solution. By analyzing the energy shifts in the C and N X-ray photoelectron spectra, we establish a molecular level picture of how charge and proton transport in aqueous solutions of arginine occur.« less

Arrhenius Rate: constant volume burn

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

Menikoff, Ralph

A constant volume burn occurs for an idealized initial state in which a large volume of reactants at rest is suddenly raised to a high temperature and begins to burn. Due to the uniform spatial state, there is no fluid motion and no heat conduction. This reduces the time evolu tion to an ODE for the reaction progress variable. With an Arrhenius reaction rate, two characteristics of thermal ignition are illustrated: induction time and thermal runaway. The Frank-Kamenetskii approximation then leads to a simple expression for the adiabatic induction time. For a first order reaction, the analytic solution is derivedmore » and used to illustrate the effect of varying the activation temperature; in particular, on the induction time. In general, the ODE can be solved numerically. This is used to illustrate the effect of varying the reaction order. We note that for a first order reaction, the time evolution of the reaction progress variable has an exponential tail. In contrast, for a reaction order less than one, the reaction completes in a nite time. The reaction order also affects the induction time.« less

Superintegrability on N-dimensional spaces of constant curvature from so( N + 1) and its contractions

NASA Astrophysics Data System (ADS)

Herranz, F. J.; Ballesteros, Á.

2008-05-01

The Lie—Poisson algebra so( N + 1) and some of its contractions are used to construct a family of superintegrable Hamiltonians on the N-dimensional spherical, Euclidean, hyperbolic, Minkowskian, and (anti-)de Sitter spaces. We firstly present a Hamiltonian which is a superposition of an arbitrary central potential with N arbitrary centrifugal terms. Such a system is quasi-maximally superintegrable since this is endowed with 2 N — 3 functionally independent constants of motion (plus the Hamiltonian). Secondly, we identify two maximally superintegrable Hamiltonians by choosing a specific central potential and finding at the same time the remaining integral. The former is the generalization of the Smorodinsky—Winternitz system to the above six spaces, while the latter is a generalization of the Kepler—Coulomb potential, for which the Laplace—Runge—Lenz N vector is also given. All the systems and constants of motion are explicitly expressed in a unified form in terms of ambient and polar coordinates as they are parametrized by two contraction parameters (curvature and signature of the metric).

Projection rule for complex-valued associative memory with large constant terms

NASA Astrophysics Data System (ADS)

Kitahara, Michimasa; Kobayashi, Masaki

Complex-valued Associative Memory (CAM) has an inherent property of rotation invariance. Rotation invariance produces many undesirable stable states and reduces the noise robustness of CAM. Constant terms may remove rotation invariance, but if the constant terms are too small, rotation invariance does not vanish. In this paper, we eliminate rotation invariance by introducing large constant terms to complex-valued neurons. We have to make constant terms sufficiently large to improve the noise robustness. We introduce a parameter to control the amplitudes of constant terms into projection rule. The large constant terms are proved to be effective by our computer simulations.

Role of dielectric constant in electrohydrodynamics of conducting fluids

NASA Technical Reports Server (NTRS)

Rhodes, Percy H.; Snyder, Robert S.; Roberts, Glyn O.

1992-01-01

Electrohydrodynamic (EHD) flows are driven by the interaction of an electric field with variations in electric conductivity or dielectric constant. In reported EHD experiments on the deformation of drops of immiscible dielectric fluids, the role of conductivity has tended to overshadow the role of dielectric constant. Often, large conductivity contrasts were convenient because the conductivities of the dielectric fluid were relatively uncertain. As a result, the observed effects were always qualitatively the same as if there had been no contrast in dielectric constant. Our early experiments studying the EHC deformations of cylindrical streams readily showed the conductivity effect but the dielectric constant effect was not discernible. We have modified our flow chamber and improved our method of observation and can now see an unequivocal dielectric constant effect which is in agreement with the prior theory. In this paper we first give a brief description of the physics of charge buildup at the interface of an immersed spherical drop or flowing cylindrical sample stream and then show how these charge distributions lead to interface distortions and accompanying viscous flows which constitute EHD. We next review theory and experiment describing the deformation of spherical drops. We show that in the reported drop deformation experiments, the contrast in dielectric constant was never sufficient to reverse the deformation due to the conductivity contrast. We review our work describing the deformation of a cylindrical stream of one fluid flowing in a parallel flow of another, and we compare the deformation equations with those for spherical drops. Finally, we show a definite experimental dielectric constant effect for cylindrical stream of aqueous polystyrene latex suspension. The dielectric constant varies with the frequency of the imposed electric field, and the associated EHD flow change is very apparent.

Getting through to circadian oscillators: why use constant routines?

NASA Technical Reports Server (NTRS)

Duffy, Jeanne F.; Dijk, Derk-Jan

2002-01-01

Overt 24-h rhythmicity is composed of both exogenous and endogenous components, reflecting the product of multiple (periodic) feedback loops with a core pacemaker at their center. Researchers attempting to reveal the endogenous circadian (near 24-h) component of rhythms commonly conduct their experiments under constant environmental conditions. However, even under constant environmental conditions, rhythmic changes in behavior, such as food intake or the sleep-wake cycle, can contribute to observed rhythmicity in many physiological and endocrine variables. Assessment of characteristics of the core circadian pacemaker and its direct contribution to rhythmicity in different variables, including rhythmicity in gene expression, may be more reliable when such periodic behaviors are eliminated or kept constant across all circadian phases. This is relevant for the assessment of the status of the circadian pacemaker in situations in which the sleep-wake cycle or food intake regimes are altered because of external conditions, such as in shift work or jet lag. It is also relevant for situations in which differences in overt rhythmicity could be due to changes in either sleep oscillatory processes or circadian rhythmicity, such as advanced or delayed sleep phase syndromes, in aging, or in particular clinical conditions. Researchers studying human circadian rhythms have developed constant routine protocols to assess the status of the circadian pacemaker in constant behavioral and environmental conditions, whereas this technique is often thought to be unnecessary in the study of animal rhythms. In this short review, the authors summarize constant routine methodology and what has been learned from constant routines and argue that animal and human circadian rhythm researchers should (continue to) use constant routines as a step on the road to getting through to central and peripheral circadian oscillators in the intact organism.

Variación temporal de las constantes fundamentales

NASA Astrophysics Data System (ADS)

Landau, S. J.; Vucetich, H.

La variación temporal de las constantes fundamentales es un problema que ha motivado numerosos trabajos teóricos y experimentales desde la hipótesis de los grandes números de Dirac en 1937. Entre los métodos experimentales y observacionales para establecer restricciones sobre la variación de las constantes fundamentes es importante mencionar: comparación entre relojes atómicos[1], métodos geofísicos[2][3], análisis de sistemas de absorción en quasares[4][5][6] y cotas provenientes de la nucleosíntesis primordial[7]. En un trabajo reciente[5], se reportó una significativa variación en la constante de estructura fina. Intentos de unificar las cuatro interacciones fundamentales dieron como resultado teorías con múltiples dimensiones como las teorías de Kaluza-Klein y teorías de supercuerdas. Estas teorías proporcionan un marco teórico natural para el estudio de la variación temporal de las constantes fundamentales. A su vez, un modelo sencillo para estudiar la variación de la constante de estructura fina, fue propuesto en [8], a partir de premisas muy generales como ser covarianza, invarianza de gauge, causalidad y invarianza ante reversiones temporales en el electromagnetismo. Diferentes versiones de las teorías antes mencionadas coinciden en predecir variaciones temporales de las constantes fundamentales pero difieren en la forma de esta variación[9][10]. De esta manera, las restricciones establecidas experimentalmente sobre la variación de las constantes fundamentales pueden ser una herramienta importante para testear estas diferentes teorías. En este trabajo, utilizamos las cotas provenientes de diversas técnicas experimentales, para testear si las mismas son consistentes con alguna de las teorías antes mencionadas. En particular, establecemos cotas sobre la variación de los parámentros libres de las diferentes teorías como por ejemplo el radio de las dimensiones extras en las teorías tipo Kaluza-Klein.

Fast optimization algorithms and the cosmological constant

NASA Astrophysics Data System (ADS)

Bao, Ning; Bousso, Raphael; Jordan, Stephen; Lackey, Brad

2017-11-01

Denef and Douglas have observed that in certain landscape models the problem of finding small values of the cosmological constant is a large instance of a problem that is hard for the complexity class NP (Nondeterministic Polynomial-time). The number of elementary operations (quantum gates) needed to solve this problem by brute force search exceeds the estimated computational capacity of the observable Universe. Here we describe a way out of this puzzling circumstance: despite being NP-hard, the problem of finding a small cosmological constant can be attacked by more sophisticated algorithms whose performance vastly exceeds brute force search. In fact, in some parameter regimes the average-case complexity is polynomial. We demonstrate this by explicitly finding a cosmological constant of order 10-120 in a randomly generated 1 09-dimensional Arkani-Hamed-Dimopoulos-Kachru landscape.

Convexity and concavity constants in Lorentz and Marcinkiewicz spaces

NASA Astrophysics Data System (ADS)

Kaminska, Anna; Parrish, Anca M.

2008-07-01

We provide here the formulas for the q-convexity and q-concavity constants for function and sequence Lorentz spaces associated to either decreasing or increasing weights. It yields also the formula for the q-convexity constants in function and sequence Marcinkiewicz spaces. In this paper we extent and enhance the results from [G.J.O. Jameson, The q-concavity constants of Lorentz sequence spaces and related inequalities, Math. Z. 227 (1998) 129-142] and [A. Kaminska, A.M. Parrish, The q-concavity and q-convexity constants in Lorentz spaces, in: Banach Spaces and Their Applications in Analysis, Conference in Honor of Nigel Kalton, May 2006, Walter de Gruyter, Berlin, 2007, pp. 357-373].

The constant displacement scheme for tracking particles in heterogeneous aquifers

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

Wen, X.H.; Gomez-Hernandez, J.J.

1996-01-01

Simulation of mass transport by particle tracking or random walk in highly heterogeneous media may be inefficient from a computational point of view if the traditional constant time step scheme is used. A new scheme which adjusts automatically the time step for each particle according to the local pore velocity, so that each particle always travels a constant distance, is shown to be computationally faster for the same degree of accuracy than the constant time step method. Using the constant displacement scheme, transport calculations in a 2-D aquifer model, with nature log-transmissivity variance of 4, can be 8.6 times fastermore » than using the constant time step scheme.« less

Constant-concentration boundary condition: Lessons from the HYDROCOIN variable-density groundwater benchmark problem

USGS Publications Warehouse

Konikow, Leonard F.; Sanford, W.E.; Campbell, P.J.

1997-01-01

In a solute-transport model, if a constant-concentration boundary condition is applied at a node in an active flow field, a solute flux can occur by both advective and dispersive processes. The potential for advective release is demonstrated by reexamining the Hydrologic Code Intercomparison (HYDROCOIN) project case 5 problem, which represents a salt dome overlain by a shallow groundwater system. The resulting flow field includes significant salinity and fluid density variations. Several independent teams simulated this problem using finite difference or finite element numerical models. We applied a method-of-characteristics model (MOCDENSE). The previous numerical implementations by HYDROCOIN teams of a constant-concentration boundary to represent salt release by lateral dispersion only (as stipulated in the original problem definition) was flawed because this boundary condition allows the release of salt into the flow field by both dispersion and advection. When the constant-concentration boundary is modified to allow salt release by dispersion only, significantly less salt is released into the flow field. The calculated brine distribution for case 5 depends very little on which numerical model is used, as long as the selected model is solving the proper equations. Instead, the accuracy of the solution depends strongly on the proper conceptualization of the problem, including the detailed design of the constant-concentration boundary condition. The importance and sensitivity to the manner of specification of this boundary does not appear to have been recognized previously in the analysis of this problem.

Constant-current control method of multi-function electromagnetic transmitter.

PubMed

Xue, Kaichang; Zhou, Fengdao; Wang, Shuang; Lin, Jun

2015-02-01

Based on the requirements of controlled source audio-frequency magnetotelluric, DC resistivity, and induced polarization, a constant-current control method is proposed. Using the required current waveforms in prospecting as a standard, the causes of current waveform distortion and current waveform distortion's effects on prospecting are analyzed. A cascaded topology is adopted to achieve 40 kW constant-current transmitter. The responsive speed and precision are analyzed. According to the power circuit of the transmitting system, the circuit structure of the pulse width modulation (PWM) constant-current controller is designed. After establishing the power circuit model of the transmitting system and the PWM constant-current controller model, analyzing the influence of ripple current, and designing an open-loop transfer function according to the amplitude-frequency characteristic curves, the parameters of the PWM constant-current controller are determined. The open-loop transfer function indicates that the loop gain is no less than 28 dB below 160 Hz, which assures the responsive speed of the transmitting system; the phase margin is 45°, which assures the stabilization of the transmitting system. Experimental results verify that the proposed constant-current control method can keep the control error below 4% and can effectively suppress load change caused by the capacitance of earth load.

Constant-current control method of multi-function electromagnetic transmitter

NASA Astrophysics Data System (ADS)

Xue, Kaichang; Zhou, Fengdao; Wang, Shuang; Lin, Jun

2015-02-01

Based on the requirements of controlled source audio-frequency magnetotelluric, DC resistivity, and induced polarization, a constant-current control method is proposed. Using the required current waveforms in prospecting as a standard, the causes of current waveform distortion and current waveform distortion's effects on prospecting are analyzed. A cascaded topology is adopted to achieve 40 kW constant-current transmitter. The responsive speed and precision are analyzed. According to the power circuit of the transmitting system, the circuit structure of the pulse width modulation (PWM) constant-current controller is designed. After establishing the power circuit model of the transmitting system and the PWM constant-current controller model, analyzing the influence of ripple current, and designing an open-loop transfer function according to the amplitude-frequency characteristic curves, the parameters of the PWM constant-current controller are determined. The open-loop transfer function indicates that the loop gain is no less than 28 dB below 160 Hz, which assures the responsive speed of the transmitting system; the phase margin is 45°, which assures the stabilization of the transmitting system. Experimental results verify that the proposed constant-current control method can keep the control error below 4% and can effectively suppress load change caused by the capacitance of earth load.

Factorial scopes of cardio-metabolic variables remain constant with changes in body temperature in the varanid lizard, Varanus rosenbergi.

PubMed

Clark, T D; Wang, T; Butler, P J; Frappell, P B

2005-04-01

The majority of information concerning the cardio-metabolic performance of varanids during exercise is limited to a few species at their preferred body temperature (T(b)) even though, being ectotherms, varanids naturally experience rather large changes in T(b). Although it is well established that absolute aerobic scope declines with decreasing T(b), it is not known whether changes in cardiac output (V(b)) and/or tissue oxygen extraction, (Ca(O2) - Cv(O2)), are in proportion to the rate of oxygen consumption (Vo(2)). To test this, we studied six Rosenberg's goannas (Varanus rosenbergi) while at rest and while maximally exercising on a treadmill both at 25 and 36 degrees C. During maximum exercise both at 25 and 36 degrees C, mass-specific rate of oxygen consumption (Vo(2kg)) increased with an absolute scope of 8.5 ml min(-1) kg(-1) and 15.7 ml min(-1) kg(-1), respectively. Interestingly, the factorial aerobic scope was temperature-independent and remained at 7.0 which, at each T(b), was primarily the result of an increase in V(bkg), governed by approximate twofold increases both in heart rate (f(H)) and cardiac stroke volume (V(Skg)). Both at 25 degrees C and 36 degrees C, the increase in V(bkg) alone was not sufficient to provide all of the additional oxygen required to attain maximal Vo(2kg), as indicated by a decrease in the blood convection requirement V(bkg)/Vo(2kg); hence, there was a compensatory twofold increase in (Ca(O2) - Cv(O2)). Although associated with an increase in hemoglobin-oxygen affinity, a decrease in T(b) did not impair unloading of oxygen at the tissues and act to reduce (Ca(O2) - Cv(O2)); both Ca(O2)) and Cv(O2)) were maintained across T(b). The change in Vo(2kg) with T(b), therefore, is solely reliant on the thermal dependence of V(bkg). Maintaining a high factorial aerobic scope across a range of T(b) confers an advantage in that cooler animals can achieve higher absolute aerobic scopes and presumably improved aerobic performance than

PCNA appears in two populations of slow and fast diffusion with a constant ratio throughout S-phase in replicating mammalian cells.

PubMed

Zessin, Patrick J M; Sporbert, Anje; Heilemann, Mike

2016-01-13

DNA replication is a fundamental cellular process that precedes cell division. Proliferating cell nuclear antigen (PCNA) is a central scaffold protein that orchestrates DNA replication by recruiting many factors essential for the replication machinery. We studied the mobility of PCNA in live mammalian cells using single-particle tracking in combination with photoactivated-localization microscopy (sptPALM) and found two populations. The first population which is only present in cells with active DNA replication, showed slow diffusion and was found to be located in replication foci. The second population showed fast diffusion, and represents the nucleoplasmic pool of unbound PCNA not involved in DNA replication. The ratio of these two populations remained constant throughout different stages of S-phase. A fraction of molecules in both populations showed spatially constrained mobility. We determined an exploration radius of ~100 nm for 13% of the slow-diffusing PCNA molecules, and of ~600 nm for 46% of the fast-diffusing PCNA molecules.

Microfabricated microengine with constant rotation rate

DOEpatents

Romero, Louis A.; Dickey, Fred M.

1999-01-01

A microengine uses two synchronized linear actuators as a power source and converts oscillatory motion from the actuators into constant rotational motion via direct linkage connection to an output gear or wheel. The microengine provides output in the form of a continuously rotating output gear that is capable of delivering drive torque at a constant rotation to a micromechanism. The output gear can have gear teeth on its outer perimeter for directly contacting a micromechanism requiring mechanical power. The gear is retained by a retaining means which allows said gear to rotate freely. The microengine is microfabricated of polysilicon on one wafer using surface micromachining batch fabrication.

Cosmological constant implementing Mach principle in general relativity

NASA Astrophysics Data System (ADS)

Namavarian, Nadereh; Farhoudi, Mehrdad

2016-10-01

We consider the fact that noticing on the operational meaning of the physical concepts played an impetus role in the appearance of general relativity (GR). Thus, we have paid more attention to the operational definition of the gravitational coupling constant in this theory as a dimensional constant which is gained through an experiment. However, as all available experiments just provide the value of this constant locally, this coupling constant can operationally be meaningful only in a local area. Regarding this point, to obtain an extension of GR for the large scale, we replace it by a conformal invariant model and then, reduce this model to a theory for the cosmological scale via breaking down the conformal symmetry through singling out a specific conformal frame which is characterized by the large scale characteristics of the universe. Finally, we come to the same field equations that historically were proposed by Einstein for the cosmological scale (GR plus the cosmological constant) as the result of his endeavor for making GR consistent with the Mach principle. However, we declare that the obtained field equations in this alternative approach do not carry the problem of the field equations proposed by Einstein for being consistent with Mach's principle (i.e., the existence of de Sitter solution), and can also be considered compatible with this principle in the Sciama view.

Semiconductor photoelastic constants measured by light scattering in superlattices

NASA Astrophysics Data System (ADS)

He, J.; Sapriel, J.; Brugger, H.

1989-03-01

The technique for the measurement of the photoelastic constants that is based on light scattering (Raman and Brillouin) by superlattice acoustic phonons is refined and applied to Ga1-xAlxAs and Si1-xGex materials. The photoelastic constants of Ga1-xAlxAs with respect to GaAs and those of Si0.5Ge0.5 with respect to Si are measured as a function of the wavelength of the laser excitation. One finds that the photoelastic constant of Ga1-xAlxAs undergoes a nonlinear variation with the aluminum concentration x and that the ratio of the photoelastic constants of Si0.5Ge0.5 and Si varies strongly as a function of laser wavelength.

Anharmonic Potential Constants and Their Dependence Upon Bond Length

DOE R&D Accomplishments Database

Herschbach, D. R.; Laurie, V. W.

1961-01-01

Empirical study of cubic and quartic vibrational force constants for diatomic molecules shows them to be approximately exponential functions of internuclear distance. A family of curves is obtained, determined by the location of the bonded atoms in rows of the periodic table. Displacements between successive curves correspond closely to those in Badger's rule for quadratic force constants (for which the parameters are redetermined to accord with all data now available). Constants for excited electronic and ionic states appear on practically the same curves as those for the ground states. Predictions based on the diatomic correlations agree with the available cubic constants for bond stretching in polyatomic molecules, regardless of the type of bonding involved. Implications of these regularities are discussed. (auth)

Smart Point Cloud: Definition and Remaining Challenges

NASA Astrophysics Data System (ADS)

Poux, F.; Hallot, P.; Neuville, R.; Billen, R.

2016-10-01

Dealing with coloured point cloud acquired from terrestrial laser scanner, this paper identifies remaining challenges for a new data structure: the smart point cloud. This concept arises with the statement that massive and discretized spatial information from active remote sensing technology is often underused due to data mining limitations. The generalisation of point cloud data associated with the heterogeneity and temporality of such datasets is the main issue regarding structure, segmentation, classification, and interaction for an immediate understanding. We propose to use both point cloud properties and human knowledge through machine learning to rapidly extract pertinent information, using user-centered information (smart data) rather than raw data. A review of feature detection, machine learning frameworks and database systems indexed both for mining queries and data visualisation is studied. Based on existing approaches, we propose a new 3-block flexible framework around device expertise, analytic expertise and domain base reflexion. This contribution serves as the first step for the realisation of a comprehensive smart point cloud data structure.

On determining dose rate constants spectroscopically

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

Rodriguez, M.; Rogers, D. W. O.

2013-01-15

Purpose: To investigate several aspects of the Chen and Nath spectroscopic method of determining the dose rate constants of {sup 125}I and {sup 103}Pd seeds [Z. Chen and R. Nath, Phys. Med. Biol. 55, 6089-6104 (2010)] including the accuracy of using a line or dual-point source approximation as done in their method, and the accuracy of ignoring the effects of the scattered photons in the spectra. Additionally, the authors investigate the accuracy of the literature's many different spectra for bare, i.e., unencapsulated {sup 125}I and {sup 103}Pd sources. Methods: Spectra generated by 14 {sup 125}I and 6 {sup 103}Pd seedsmore » were calculated in vacuo at 10 cm from the source in a 2.7 Multiplication-Sign 2.7 Multiplication-Sign 0.05 cm{sup 3} voxel using the EGSnrc BrachyDose Monte Carlo code. Calculated spectra used the initial photon spectra recommended by AAPM's TG-43U1 and NCRP (National Council of Radiation Protection and Measurements) Report 58 for the {sup 125}I seeds, or TG-43U1 and NNDC(2000) (National Nuclear Data Center, 2000) for {sup 103}Pd seeds. The emitted spectra were treated as coming from a line or dual-point source in a Monte Carlo simulation to calculate the dose rate constant. The TG-43U1 definition of the dose rate constant was used. These calculations were performed using the full spectrum including scattered photons or using only the main peaks in the spectrum as done experimentally. Statistical uncertainties on the air kerma/history and the dose rate/history were Less-Than-Or-Slanted-Equal-To 0.2%. The dose rate constants were also calculated using Monte Carlo simulations of the full seed model. Results: The ratio of the intensity of the 31 keV line relative to that of the main peak in {sup 125}I spectra is, on average, 6.8% higher when calculated with the NCRP Report 58 initial spectrum vs that calculated with TG-43U1 initial spectrum. The {sup 103}Pd spectra exhibit an average 6.2% decrease in the 22.9 keV line relative to the main peak

The contrasting roles of Planck's constant in classical and quantum theories

NASA Astrophysics Data System (ADS)

Boyer, Timothy H.

2018-04-01

We trace the historical appearance of Planck's constant in physics, and we note that initially the constant did not appear in connection with quanta. Furthermore, we emphasize that Planck's constant can appear in both classical and quantum theories. In both theories, Planck's constant sets the scale of atomic phenomena. However, the roles played in the foundations of the theories are sharply different. In quantum theory, Planck's constant is crucial to the structure of the theory. On the other hand, in classical electrodynamics, Planck's constant is optional, since it appears only as the scale factor for the (homogeneous) source-free contribution to the general solution of Maxwell's equations. Since classical electrodynamics can be solved while taking the homogenous source-free contribution in the solution as zero or non-zero, there are naturally two different theories of classical electrodynamics, one in which Planck's constant is taken as zero and one where it is taken as non-zero. The textbooks of classical electromagnetism present only the version in which Planck's constant is taken to vanish.

Cohesive Energy-Lattice Constant and Bulk Modulus-Lattice Constant Relationships: Alkali Halides, Ag Halides, Tl Halides

NASA Technical Reports Server (NTRS)

Schlosser, Herbert

1992-01-01

In this note we present two expressions relating the cohesive energy, E(sub coh), and the zero pressure isothermal bulk modulus, B(sub 0), of the alkali halides. Ag halides and TI halides, with the nearest neighbor distances, d(sub nn). First, we show that the product E(sub coh)d(sub 0) within families of halide crystals with common crystal structure is to a good approximation constant, with maximum rms deviation of plus or minus 2%. Secondly, we demonstrate that within families of halide crystals with a common cation and common crystal structure the product B(sub 0)d(sup 3.5)(sub nn) is a good approximation constant, with maximum rms deviation of plus or minus 1.36%.

Measuring Boltzmann's Constant with Carbon Dioxide

ERIC Educational Resources Information Center

Ivanov, Dragia; Nikolov, Stefan

2013-01-01

In this paper we present two experiments to measure Boltzmann's constant--one of the fundamental constants of modern-day physics, which lies at the base of statistical mechanics and thermodynamics. The experiments use very basic theory, simple equipment and cheap and safe materials yet provide very precise results. They are very easy and…

Skeletal Indicators of Shark Feeding on Human Remains: Evidence from Florida Forensic Anthropology Cases.

PubMed

Stock, Michala K; Winburn, Allysha P; Burgess, George H

2017-11-01

This research examines a series of six Florida forensic anthropology cases that exhibit taphonomic evidence of marine deposition and shark-feeding activities. In each case, we analyzed patterns of trauma/damage on the skeletal remains (e.g., sharp-force bone gouges and punctures) and possible mechanisms by which they were inflicted during shark predation/scavenging. In some cases, shark teeth were embedded in the remains; in the absence of this evidence, we measured interdental distance from defects in the bone to estimate shark body length, as well as to draw inferences about the potential species responsible. We discuss similarities and differences among the cases and make comparisons to literature documenting diagnostic shark-inflicted damage to human remains from nearby regions. We find that the majority of cases potentially involve bull or tiger sharks scavenging the remains of previously deceased, adult male individuals. This scavenging results in a distinctive taphonomic signature including incised gouges in cortical bone. © 2017 American Academy of Forensic Sciences.

MSG-Evoked c-Fos Activity in the Nucleus of the Solitary Tract Is Dependent upon Fluid Delivery and Stimulation Parameters

PubMed Central

Thompson, John A.

2016-01-01

The marker of neuronal activation, c-Fos, can be used to visualize spatial patterns of neural activity in response to taste stimulation. Because animals will not voluntarily consume aversive tastes, these stimuli are infused directly into the oral cavity via intraoral cannulae, whereas appetitive stimuli are given in drinking bottles. Differences in these 2 methods make comparison of taste-evoked brain activity between results that utilize these methods problematic. Surprisingly, the intraoral cannulae experimental conditions that produce a similar pattern of c-Fos activity in response to taste stimulation remain unexplored. Stimulation pattern (e.g., constant/intermittent) and hydration state (e.g., water-restricted/hydrated) are the 2 primary differences between delivering tastes via bottles versus intraoral cannulae. Thus, we quantified monosodium glutamate (MSG)-evoked brain activity, as measured by c-Fos, in the nucleus of the solitary tract (nTS; primary taste nucleus) across several conditions. The number and pattern of c-Fos neurons in the nTS of animals that were water-restricted and received a constant infusion of MSG via intraoral cannula most closely mimicked animals that consumed MSG from a bottle. Therefore, in order to compare c-Fos activity between cannulae-stimulated and bottle-stimulated animals, cannulated animals should be water restricted prior to stimulation, and receive taste stimuli at a constant flow. PMID:26762887

Optimal Server Scheduling to Maintain Constant Customer Waiting Times

DTIC Science & Technology

1988-12-01

I I• I I I I I LCn CN OPTIMAL SERVER SCHEDUUNG TO MAINTAIN CONSTANT CUSTOMER WAITING TIMES THESIS Thomas J. Frey Captain UISAF AFIT/GOR/ENS/88D-7...hw bees appsewlf in ple rtan. cd = , ’ S 087 AFIT/GORMENS/8D-7 OPTIMAL SERVER SCHEDUUNG TO MAINTAIN~ CONSTANT CUSTOMER WAITING TIMES THESIS Thomas j...CONSTANT CUSTOMER WAITING TIMES THESIS Presented to the Faculty of the School of Engineering of the Air Force Institute of Technology Air University In

Optimal plane change during constant altitude hypersonic flight

NASA Technical Reports Server (NTRS)

Mease, K. D.; Vinh, N. X.; Kuo, S. H.

1988-01-01

Future spacecraft operating in the vicinity of the earth may have resort to the atmosphere as an aid in effecting orbital change. While a previous treatment of this technique chose constant altitude, speed, and angle-of-attack values in order to maximize the plane change for a fixed amount of propellant consumption during hypersonic flight, the former two parameters are presently released from the constraint of constancy. The general characteristics of the optimal controls are described on the basis of the domain of maneuverability, and numerical solutions are obtained for several specific cases. Under the condition of constant-altitude flight, it is generally not optimal to fly at constant angle-of-attack.

Compilation of Henry's law constants, version 3.99

NASA Astrophysics Data System (ADS)

Sander, R.

2014-11-01

Many atmospheric chemicals occur in the gas phase as well as in liquid cloud droplets and aerosol particles. Therefore, it is necessary to understand the distribution between the phases. According to Henry's law, the equilibrium ratio between the abundances in the gas phase and in the aqueous phase is constant for a dilute solution. Henry's law constants of trace gases of potential importance in environmental chemistry have been collected and converted into a uniform format. The compilation contains 14775 values of Henry's law constants for 3214 species, collected from 639 references. It is also available on the internet at http://www.henrys-law.org.

Influence of different fertilizer supplements on decomposition of cereal stubble remains in chernozem soil

NASA Astrophysics Data System (ADS)

Nikolaev, I. V.; Klein, O. I.; Kulikova, N. A.; Stepanova, E. V.; Koroleva, O. V.

2009-04-01

Introduction Recently, many farmers have converted to low-disturbance tillage land cultivation as disk or plow fields can result in water and wind erosion of soil. So, crop residue and plant crowns and roots are left to hold the soil. However, low-disturbance tillage can be a challenge to manage since the key to crop production still requires good seed-to-soil contact. Therefore, decomposition of stubble in agricultural soils in situ is an issue of the day of modern agriculture. The aim of the present study was to compare different organic and inorganic fertilizer supplements on decomposition of cereal stubble remains in chernozem soil. Materials and methods Field trials were conducted in Krasnodar region, Russia. To promote stubble decomposition, a biopreparation that was cultural liquid obtained during cultivation of white-rot fungi Coriolus hirsutus 075 (Wulf Ex. Fr.) Quel. was used at the dosage of 150 ml/ha. The other tested supplements included ammonium nitrate (34 kg/ha), commercially available humate LignohumateTM (0.2 kg/ha) and combination of Lignohumate and biopreparation. Test plots were treated once after wheat harvesting. Non-treated ploughed plot was used as a blank. Soil samples were collected within 2 and 14 weeks after soil treatment. To control soil potential for stubble remains decomposition enzymatic activity is soil was determined. To perform soil analysis, stubble remains were carefully separated from soils followed by soil extraction with 0.14 M phosphate buffer pH 7.1 and analysis of the extracts for laccase and peroxidase activities [1,2]. Estimation of stubble decomposition in soil was performed by cellulose contents determination [3]. Results and discussion The obtained results demonstrated after 14 weeks of treatment increase of soil enzymatic activity due to soil supplementation was observed. Introduction of ammonium nitrate resulted in 108% of peroxidise activity as compared to blank. That value for Lignohumate variant was estimated

A Prodomain Fragment from the Proteolytic Activation of Growth Differentiation Factor 11 Remains Associated with the Mature Growth Factor and Keeps It Soluble.

PubMed

Pepinsky, Blake; Gong, Bang-Jian; Gao, Yan; Lehmann, Andreas; Ferrant, Janine; Amatucci, Joseph; Sun, Yaping; Bush, Martin; Walz, Thomas; Pederson, Nels; Cameron, Thomas; Wen, Dingyi

2017-08-22

Growth differentiation factor 11 (GDF11), a member of the transforming growth factor β (TGF-β) family, plays diverse roles in mammalian development. It is synthesized as a large, inactive precursor protein containing a prodomain, pro-GDF11, and exists as a homodimer. Activation requires two proteolytic processing steps that release the prodomains and transform latent pro-GDF11 into active mature GDF11. In studying proteolytic activation in vitro, we discovered that a 6-kDa prodomain peptide containing residues 60-114, PDP 60-114 , remained associated with the mature growth factor. Whereas the full-length prodomain of GDF11 is a functional antagonist, PDP 60-114 had no impact on activity. The specific activity of the GDF11/PDP 60-114 complex (EC 50 = 1 nM) in a SMAD2/3 reporter assay was identical to that of mature GDF11 alone. PDP 60-114 improved the solubility of mature GDF11 at neutral pH. As the growth factor normally aggregates/precipitates at neutral pH, PDP 60-114 can be used as a solubility-enhancing formulation. Expression of two engineered constructs with PDP 60-114 genetically fused to the mature domain of GDF11 through a 2x or 3x G4S linker produced soluble monomeric products that could be dimerized through redox reactions. The construct with a 3x G4S linker retained 10% activity (EC 50 = 10 nM), whereas the construct connected with a 2x G4S linker could only be activated (EC 50 = 2 nM) by protease treatment. Complex formation with PDP 60-114 represents a new strategy for stabilizing GDF11 in an active state that may translate to other members of the TGF-β family that form latent pro/mature domain complexes.

Our Universe from the cosmological constant

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

Barrau, Aurélien; Linsefors, Linda, E-mail: Aurelien.Barrau@cern.ch, E-mail: linda.linsefors@lpsc.in2p3.fr

The issue of the origin of the Universe and of its contents is addressed in the framework of bouncing cosmologies, as described for example by loop quantum gravity. If the current acceleration is due to a true cosmological constant, this constant is naturally conserved through the bounce and the Universe should also be in a (contracting) de Sitter phase in the remote past. We investigate here the possibility that the de Sitter temperature in the contracting branch fills the Universe with radiation that causes the bounce and the subsequent inflation and reheating. We also consider the possibility that this givesmore » rise to a cyclic model of the Universe and suggest some possible tests.« less

Revealing a circadian clock in captive arctic-breeding songbirds, lapland longspurs (Calcarius lapponicus), under constant illumination.

PubMed

Ashley, Noah T; Ubuka, Takayoshi; Schwabl, Ingrid; Goymann, Wolfgang; Salli, Brady M; Bentley, George E; Buck, C Loren

2014-12-01

Most organisms in temperate or tropic regions employ the light-dark (LD) cycle as the primary Zeitgeber to synchronize circadian rhythms. At higher latitudes (>66°33'), continuous illumination during the summer presents a significant time-keeping dilemma for polar-adapted species. Lapland longspurs (Calcarius lapponicus), arctic-breeding migratory songbirds, are one of the few recorded species maintaining an intact diel rhythm in activity and plasma melatonin titers during polar summer. However, it is unknown whether rhythms are endogenous and entrain to low-amplitude polar Zeitgeber signals, such as daily variations in light intensity and the spectral composition of the sun (as measured by color temperature). Wild-caught male and female longspurs were brought into captivity, and locomotor activity was assessed using infrared detection. To examine if rhythms were endogenous, birds were exposed to constant bright light (LL; 1300 lux) or constant darkness (DD; 0.1 lux). All birds exhibited free-running activity rhythms in LL and DD, suggesting the presence of a functional circadian clock. Mean periods in LL (22.86 h) were significantly shorter than those in DD (23.5 h), in accordance with Aschoff's rule. No birds entrained to diel changes in light intensity, color temperature, or both. To examine endogenous molecular clock function, the Per2 gene was partially cloned in longspurs (llPer2) and transcripts were measured in hypothalamic tissue punches, eye, and liver using competitive polymerase chain reaction. Ocular llPer2 gene expression was periodic in LL and elevated at ZT24 (CT24) for LD or constant conditions (LL and DD), but llPer2 rhythmicity was not detected in hypothalamus or liver. Plasma melatonin was significantly lower in LL compared with LD or DD. In conclusion, rhythmic ocular Per2 expression and melatonin secretion may maintain the circadian activity rhythm across the polar day. © 2014 The Author(s).

Planck's Constant as a Natural Unit of Measurement

ERIC Educational Resources Information Center

Quincey, Paul

2013-01-01

The proposed revision of SI units would embed Planck's constant into the definition of the kilogram, as a fixed constant of nature. Traditionally, Planck's constant is not readily interpreted as the size of something physical, and it is generally only encountered by students in the mathematics of quantum physics. Richard Feynman's…

On the ambiguity of the reaction rate constants in multivariate curve resolution for reversible first-order reaction systems.

PubMed

Schröder, Henning; Sawall, Mathias; Kubis, Christoph; Selent, Detlef; Hess, Dieter; Franke, Robert; Börner, Armin; Neymeyr, Klaus

2016-07-13

If for a chemical reaction with a known reaction mechanism the concentration profiles are accessible only for certain species, e.g. only for the main product, then often the reaction rate constants cannot uniquely be determined from the concentration data. This is a well-known fact which includes the so-called slow-fast ambiguity. This work combines the question of unique or non-unique reaction rate constants with factor analytic methods of chemometrics. The idea is to reduce the rotational ambiguity of pure component factorizations by considering only those concentration factors which are possible solutions of the kinetic equations for a properly adapted set of reaction rate constants. The resulting set of reaction rate constants corresponds to those solutions of the rate equations which appear as feasible factors in a pure component factorization. The new analysis of the ambiguity of reaction rate constants extends recent research activities on the Area of Feasible Solutions (AFS). The consistency with a given chemical reaction scheme is shown to be a valuable tool in order to reduce the AFS. The new methods are applied to model and experimental data. Copyright © 2016 Elsevier B.V. All rights reserved.

Temperature-Dependent Rate Constants and Substituent Effects for the Reactions of Hydroxyl Radicals With Three Partially Fluorinated Ethers

NASA Technical Reports Server (NTRS)

Hsu, K.-J.; DeMore, W. B.

1995-01-01

Rate constants and temperature dependencies for the reactions of OH with CF3OCH3 (HFOC-143a), CF2HOCF2H (HFOC-134), and CF3OCF2H (HFOC-125) were studied using a relative rate technique in the temperature range 298-393 K. The following absolute rate constants were derived: HFOC-143a, 1.9E-12 exp(-1555/T); HFOC-134, 1.9E-12 exp(-2006/T); HFOC-125, 4.7E-13 exp(-2095/T). Units are cm(exp 3)molecule(exp -1) s(exp -1). Substituent effects on OH abstraction rate constants are discussed, and it is shown that the CF3O group has an effect on the OH rate constants similar to that of a fluorine atom. The effects are related to changes in the C-H bond energies of the reactants (and thereby the activation energies) rather than changes in the preexponential factors. On the basis of a correlation of rate constants with bond energies, the respective D(C-H) bond strengths in the three ethers are found to be 102, 104, and 106 kcal/mol, with an uncertainty of about 1 kcal/mol.

Comparative efficacy of photo-activated disinfection and calcium hydroxide for disinfection of remaining carious dentin in deep cavities: a clinical study

PubMed Central

Sharma, Sidhartha; Shah, Naseem

2014-01-01

Objectives To comparatively evaluate the efficacy of photo-activated disinfection (PAD), calcium hydroxide (CH) and their combination on the treatment outcome of indirect pulp treatment (IPT). Materials and Methods Institutional ethical clearance and informed consent of the patients were taken. The study was also registered with clinical registry of India. Sixty permanent molars exhibiting deep occlusal carious lesion in patients with the age range of 18 - 22 yr were included. Clinical and radiographic evaluation and set inclusion and exclusion criteria's were followed. Gross caries excavation was accomplished. In group I (n = 20) PAD was applied for sixty seconds. In group II (n = 20), CH was applied to the remaining carious dentin, while in group III (n = 20), PAD application was followed by CH placement. The teeth were permanently restored. They were clinically and radiographically followed-up at 45 day, 6 mon and 12 mon. Relative density of the remaining affected dentin was measured by 'Radiovisiography (RVG) densitometric' analysis. Results Successful outcome with an increase in radiographic grey values were observed in all three groups. However, on inter-group comparison, this change was not significant (p > 0.05). Conclusions PAD and CH both have equal disinfection efficacy in the treatment of deep carious dentin. PAD alone is as effective for treatment of deep carious lesion as calcium hydroxide and hence can be used as an alternative to CH. They can be used independently in IPT, since combining both does not offer any additional therapeutic benefits. PMID:25110643

Atomic weights: no longer constants of nature

USGS Publications Warehouse

Coplen, Tyler B.; Holden, Norman E.

2011-01-01

Many of us were taught that the standard atomic weights we found in the back of our chemistry textbooks or on the Periodic Table of the Chemical Elements hanging on the wall of our chemistry classroom are constants of nature. This was common knowledge for more than a century and a half, but not anymore. The following text explains how advances in chemical instrumentation and isotopic analysis have changed the way we view atomic weights and why they are no longer constants of nature

Concentration dependence of molal conductivity and dielectric constant of 1-alcohol electrolytes using the compensated arrhenius formalism.

PubMed

Fleshman, Allison M; Petrowsky, Matt; Frech, Roger

2013-05-02

The molal conductivity of liquid electrolytes with low static dielectric constants (ε(s) < 10) decreases to a minimum at low concentrations (region I) and increases to a maximum at higher concentrations (region II) when plotted against the square root of the concentration. This behavior is investigated by applying the compensated Arrhenius formalism (CAF) to the molal conductivity, Λ, of a family of 1-alcohol electrolytes over a broad concentration range. A scaling procedure is applied that results in an energy of activation (E(a)) and an exponential prefactor (Λ0) that are both concentration dependent. It is shown that the increasing molal conductivity in region II results from the combined effect of (1) a decrease in the energy of activation calculated from the CAF, and (2) an inherent concentration dependence in the exponential prefactor that is partly due to the dielectric constant.

Circadian rhythms of locomotor activity in the subterranean Mashona mole rat, Cryptomys darlingi.

PubMed

Vasicek, Caroline A; Oosthuizen, Maria K; Cooper, Howard M; Bennett, Nigel C

2005-02-15

The Mashona mole rat, Cryptomys darlingi, is a social, subterranean African rodent that is rarely, if ever, exposed to light, and that exhibits a regressed visual system. This study investigated locomotor activity patterns of Mashona mole rats (n=12) under different light cycles. Activity was measured using either infrared captors (n=8) or running wheels (n=4). The mole rats entrained their activity to a standard (LD 12:12) photoperiod. They displayed either a nocturnal or diurnal activity preference with one bout of activity and one bout of rest. Therefore, as a species, the Mashona mole rat did not show a clear nocturnal or diurnal activity preference. When the LD (12:12) light cycle was inversed, the animals switched their activity, too. Under constant dark (DD), most mole rats (73%) showed a free-running circadian activity rhythm, but under constant light (LL), only some (36%) did. The free-run period of the rhythm (tau) ranged from 23.83 to 24.10 h. The remaining animals were arrhythmic. There was large interindividual and intraindividual variations in the rate and extent of entrainment, time of activity preference, and activity patterns. Possible reasons for the observed variations are discussed. It is concluded that the Mashona mole rat has an endogenous activity rhythm which approximates 24 h, that the mole rat can distinguish between light and dark, and that the endogenous clock utilises this photic information as a zeitgeber.

Vacuum-Assisted, Constant-Force Exercise Device

NASA Technical Reports Server (NTRS)

Hansen, Christopher P.; Jensen, Scott

2006-01-01

The vacuum-assisted, constant-force exercise device (VAC-FED) has been proposed to fill a need for a safe, reliable exercise machine that would provide constant loads that could range from 20 to 250 lb (0.09 to 1.12 kN) with strokes that could range from 6 to 36 in. (0.15 to 0.91 m). The VAC-FED was originally intended to enable astronauts in microgravity to simulate the lifting of free weights, but it could just as well be used on Earth for simulated weight lifting and other constant-force exercises. Because the VAC-FED would utilize atmospheric/vacuum differential pressure instead of weights to generate force, it could weigh considerably less than either a set of free weights or a typical conventional exercise machine based on weights. Also, the use of atmospheric/ vacuum differential pressure to generate force would render the VAC-FED inherently safer, relative to free weights and to conventional exercise machines that utilize springs to generate forces. The overall function of the VAC-FED would be to generate a constant tensile force in an output cable, which would be attached to a bar, handle, or other exercise interface. The primary force generator in the VAC-FED would be a piston in a cylinder. The piston would separate a volume vented to atmosphere at one end of the cylinder from an evacuated volume at the other end of the cylinder (see figure). Hence, neglecting friction at the piston seals, the force generated would be nearly constant equal to the area of the piston multiplied by the atmospheric/vacuum differential pressure. In the vented volume in the cylinder, a direct-force cable would be looped around a pulley on the piston, doubling the stroke and halving the tension. One end of the direct-force cable would be anchored to a cylinder cap; the other end of the direct-force cable would be wrapped around a variable-ratio pulley that would couple tension to the output cable. As its name suggests, the variable-ratio pulley would contain a mechanism that

Stress-stress fluctuation formula for elastic constants in the NPT ensemble

NASA Astrophysics Data System (ADS)

Lips, Dominik; Maass, Philipp

2018-05-01

Several fluctuation formulas are available for calculating elastic constants from equilibrium correlation functions in computer simulations, but the ones available for simulations at constant pressure exhibit slow convergence properties and cannot be used for the determination of local elastic constants. To overcome these drawbacks, we derive a stress-stress fluctuation formula in the NPT ensemble based on known expressions in the NVT ensemble. We validate the formula in the NPT ensemble by calculating elastic constants for the simple nearest-neighbor Lennard-Jones crystal and by comparing the results with those obtained in the NVT ensemble. For both local and bulk elastic constants we find an excellent agreement between the simulated data in the two ensembles. To demonstrate the usefulness of the formula, we apply it to determine the elastic constants of a simulated lipid bilayer.

Temperature and size-dependent Hamaker constants for metal nanoparticles

NASA Astrophysics Data System (ADS)

Jiang, K.; Pinchuk, P.

2016-08-01

Theoretical values of the Hamaker constant have been calculated for metal nanoparticles using Lifshitz theory. The theory describes the Hamaker constant in terms of the permittivity of the interacting bodies. Metal nanoparticles exhibit an internal size effect that alters the dielectric permittivity of the particle when its size falls below the mean free path of the conducting electrons. This size dependence of the permittivity leads to size-dependence of the Hamaker constant for metal nanoparticles. Additionally, the electron damping and the plasma frequency used to model the permittivity of the particle exhibit temperature-dependence, which lead to temperature dependence of the Hamaker constant. In this work, both the size and temperature dependence for gold, silver, copper, and aluminum nanoparticles is demonstrated. The results of this study might be of interest for studying the colloidal stability of nanoparticles in solution.

Temperature and size-dependent Hamaker constants for metal nanoparticles.

PubMed

Jiang, K; Pinchuk, P

2016-08-26

Theoretical values of the Hamaker constant have been calculated for metal nanoparticles using Lifshitz theory. The theory describes the Hamaker constant in terms of the permittivity of the interacting bodies. Metal nanoparticles exhibit an internal size effect that alters the dielectric permittivity of the particle when its size falls below the mean free path of the conducting electrons. This size dependence of the permittivity leads to size-dependence of the Hamaker constant for metal nanoparticles. Additionally, the electron damping and the plasma frequency used to model the permittivity of the particle exhibit temperature-dependence, which lead to temperature dependence of the Hamaker constant. In this work, both the size and temperature dependence for gold, silver, copper, and aluminum nanoparticles is demonstrated. The results of this study might be of interest for studying the colloidal stability of nanoparticles in solution.

Fundamental Insight on Developing Low Dielectric Constant Polyimides

NASA Technical Reports Server (NTRS)

Simpson, J. O.; SaintClair, A. K.

1997-01-01

Thermally stable, durable, insulative polyimides are in great demand for the fabrication of microelectronic devices. In this investigation dielectric and optical properties have been studied for several series of aromatic polyimides. The effect of polarizability, fluorine content, and free volume on dielectric constant was examined. In general, minimizing polarizability, maximizing free volume and fluorination all lowered dielectric constants in the polyimides studied.

Do migratory flight paths of raptors follow constant geographical or geomagnetic courses?

USGS Publications Warehouse

Thorup, K.; Fuller, M.; Alerstam, T.; Hake, M.; Kjellen, N.; Strandberg, R.

2006-01-01

We tested whether routes of raptors migrating over areas with homogeneous topography follow constant geomagnetic courses more or less closely than constant geographical courses. We analysed the routes taken over land of 45 individual raptors tracked by satellite-based radiotelemetry: 25 peregrine falcons, Falco peregrinus, on autumn migration between North and South America, and seven honey buzzards, Pernis apivorus, and 13 ospreys, Pandion haliaetus, on autumn migration between Europe and Africa. Overall, migration directions showed a better agreement with constant geographical than constant geomagnetic courses. Tracks deviated significantly from constant geomagnetic courses, but were not significantly different from geographical courses. After we removed movements directed far from the mean direction, which may not be migratory movements, migration directions still showed a better agreement with constant geographical than constant geomagnetic courses, but the directions of honey buzzards and ospreys were not significantly different from constant geomagnetic courses either. That migration routes of raptors followed by satellite telemetry are in closer accordance with constant geographical compass courses than with constant geomagnetic compass courses may indicate that geographical (e.g. based on celestial cues) rather than magnetic compass mechanisms are of dominating importance for the birds' long-distance orientation.

Presynaptic Active Zone Density during Development and Synaptic Plasticity.

PubMed

Clarke, Gwenaëlle L; Chen, Jie; Nishimune, Hiroshi

2012-01-01

Neural circuits transmit information through synapses, and the efficiency of synaptic transmission is closely related to the density of presynaptic active zones, where synaptic vesicles are released. The goal of this review is to highlight recent insights into the molecular mechanisms that control the number of active zones per presynaptic terminal (active zone density) during developmental and stimulus-dependent changes in synaptic efficacy. At the neuromuscular junctions (NMJs), the active zone density is preserved across species, remains constant during development, and is the same between synapses with different activities. However, the NMJ active zones are not always stable, as exemplified by the change in active zone density during acute experimental manipulation or as a result of aging. Therefore, a mechanism must exist to maintain its density. In the central nervous system (CNS), active zones have restricted maximal size, exist in multiple numbers in larger presynaptic terminals, and maintain a constant density during development. These findings suggest that active zone density in the CNS is also controlled. However, in contrast to the NMJ, active zone density in the CNS can also be increased, as observed in hippocampal synapses in response to synaptic plasticity. Although the numbers of known active zone proteins and protein interactions have increased, less is known about the mechanism that controls the number or spacing of active zones. The following molecules are known to control active zone density and will be discussed herein: extracellular matrix laminins and voltage-dependent calcium channels, amyloid precursor proteins, the small GTPase Rab3, an endocytosis mechanism including synaptojanin, cytoskeleton protein spectrins and β-adducin, and a presynaptic web including spectrins. The molecular mechanisms that organize the active zone density are just beginning to be elucidated.

Presynaptic Active Zone Density during Development and Synaptic Plasticity

PubMed Central

Clarke, Gwenaëlle L.; Chen, Jie; Nishimune, Hiroshi

2012-01-01

Neural circuits transmit information through synapses, and the efficiency of synaptic transmission is closely related to the density of presynaptic active zones, where synaptic vesicles are released. The goal of this review is to highlight recent insights into the molecular mechanisms that control the number of active zones per presynaptic terminal (active zone density) during developmental and stimulus-dependent changes in synaptic efficacy. At the neuromuscular junctions (NMJs), the active zone density is preserved across species, remains constant during development, and is the same between synapses with different activities. However, the NMJ active zones are not always stable, as exemplified by the change in active zone density during acute experimental manipulation or as a result of aging. Therefore, a mechanism must exist to maintain its density. In the central nervous system (CNS), active zones have restricted maximal size, exist in multiple numbers in larger presynaptic terminals, and maintain a constant density during development. These findings suggest that active zone density in the CNS is also controlled. However, in contrast to the NMJ, active zone density in the CNS can also be increased, as observed in hippocampal synapses in response to synaptic plasticity. Although the numbers of known active zone proteins and protein interactions have increased, less is known about the mechanism that controls the number or spacing of active zones. The following molecules are known to control active zone density and will be discussed herein: extracellular matrix laminins and voltage-dependent calcium channels, amyloid precursor proteins, the small GTPase Rab3, an endocytosis mechanism including synaptojanin, cytoskeleton protein spectrins and β-adducin, and a presynaptic web including spectrins. The molecular mechanisms that organize the active zone density are just beginning to be elucidated. PMID:22438837

Micro-milling of spent granular activated carbon for its possible reuse as an adsorbent: Remaining capacity and characteristics.

PubMed

Pan, Long; Takagi, Yuichi; Matsui, Yoshihiko; Matsushita, Taku; Shirasaki, Nobutaka

2017-05-01

We milled granular activated carbons (GACs) that had been used for 0-9 years in water treatment plants and produced carbon particles with different sizes and ages: powdered activated carbons (PAC, median diameter 12-42 μm), superfine PAC (SPAC, 0.9-3.5 μm), and submicron-sized SPAC (SSPAC, 220-290 nm). The fact that SPAC produced from 1-year-old GAC and SSPAC from 2-year-old GAC removed 2-methylisoborneol (MIB) from water with an efficiency similar to that of virgin PAC after a carbon contact time of 30 min suggests that spent GAC could be reused for water treatment after being milled. This potential for reuse was created by increasing the equilibrium adsorption capacity via reduction of the carbon particle size and improving the adsorption kinetics. During long-term (>1 year) use in GAC beds, the volume of pores in the carbon, particularly pores with widths of 0.6-0.9 nm, was greatly reduced. The equilibrium adsorption capacities of the carbon for compounds with molecular sizes in this range could therefore decrease with increasing carbon age. Among these compounds, the decreases of capacities were prominent for hydrophobic compounds, including MIB. For hydrophobic compounds, however, the equilibrium adsorption capacities could be increased with decreasing carbon particle size. The iodine number, among other indices, was best correlated with the equilibrium adsorption capacity of the MIB and would be a good index to assess the remaining MIB adsorption capacity of spent carbon. Spent GAC can possibly be reused as SPAC or SSPAC if its iodine number is ≥ 600 mg/g. Copyright © 2017 Elsevier Ltd. All rights reserved.

Can compactifications solve the cosmological constant problem?

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

Hertzberg, Mark P.; Center for Theoretical Physics, Department of Physics,Massachusetts Institute of Technology,77 Massachusetts Ave, Cambridge, MA 02139; Masoumi, Ali

2016-06-30

Recently, there have been claims in the literature that the cosmological constant problem can be dynamically solved by specific compactifications of gravity from higher-dimensional toy models. These models have the novel feature that in the four-dimensional theory, the cosmological constant Λ is much smaller than the Planck density and in fact accumulates at Λ=0. Here we show that while these are very interesting models, they do not properly address the real cosmological constant problem. As we explain, the real problem is not simply to obtain Λ that is small in Planck units in a toy model, but to explain whymore » Λ is much smaller than other mass scales (and combinations of scales) in the theory. Instead, in these toy models, all other particle mass scales have been either removed or sent to zero, thus ignoring the real problem. To this end, we provide a general argument that the included moduli masses are generically of order Hubble, so sending them to zero trivially sends the cosmological constant to zero. We also show that the fundamental Planck mass is being sent to zero, and so the central problem is trivially avoided by removing high energy physics altogether. On the other hand, by including various large mass scales from particle physics with a high fundamental Planck mass, one is faced with a real problem, whose only known solution involves accidental cancellations in a landscape.« less

Degravitation of the cosmological constant in bigravity

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

Platscher, Moritz; Smirnov, Juri, E-mail: moritz.platscher@mpi-hd.mpg.de, E-mail: juri.smirnov@mpi-hd.mpg.de

2017-03-01

In this article the phenomenon of degravitation of the cosmological constant is studied in the framework of bigravity. It is demonstrated that despite a sizable value of the cosmological constant its gravitational effect can be only mild. The bigravity framework is chosen for this demonstration as it leads to a consistent, ghost-free theory of massive gravity. We show that degravitation takes place in the limit where the physical graviton is dominantly a gauge invariant metric combination. We present and discuss several phenomenological consequences expected in this regime.

Identification of elastic, dielectric, and piezoelectric constants in piezoceramic disks.

PubMed

Perez, Nicolas; Andrade, Marco A B; Buiochi, Flavio; Adamowski, Julio C

2010-12-01

Three-dimensional modeling of piezoelectric devices requires a precise knowledge of piezoelectric material parameters. The commonly used piezoelectric materials belong to the 6mm symmetry class, which have ten independent constants. In this work, a methodology to obtain precise material constants over a wide frequency band through finite element analysis of a piezoceramic disk is presented. Given an experimental electrical impedance curve and a first estimate for the piezoelectric material properties, the objective is to find the material properties that minimize the difference between the electrical impedance calculated by the finite element method and that obtained experimentally by an electrical impedance analyzer. The methodology consists of four basic steps: experimental measurement, identification of vibration modes and their sensitivity to material constants, a preliminary identification algorithm, and final refinement of the material constants using an optimization algorithm. The application of the methodology is exemplified using a hard lead zirconate titanate piezoceramic. The same methodology is applied to a soft piezoceramic. The errors in the identification of each parameter are statistically estimated in both cases, and are less than 0.6% for elastic constants, and less than 6.3% for dielectric and piezoelectric constants.

Elastic Constants of Ni-Mn-Ga Magnetic Shape Memory Alloys

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

Stipcich, M.; Manosa, L.; Planes, A.

2004-01-01

We have measured the adiabatic second order elastic constants of two Ni-Mn-Ga magnetic shape memory crystals with different martensitic transition temperatures, using ultrasonic methods. The temperature dependence of the elastic constants has been followed across the ferromagnetic transition and down to the martensitic transition temperature. Within experimental errors no noticeable change in any of the elastic constants has been observed at the Curie point. The temperature dependence of the shear elastic constant C' has been found to be very different for the two alloys. Such a different behavior is in agreement with recent theoretical predictions for systems undergoing multi-stage structuralmore » transitions.« less

Fluctuations, ghosts, and the cosmological constant

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

Hirayama, T.; Holdom, B.

2004-12-15

For a large region of parameter space involving the cosmological constant and mass parameters, we discuss fluctuating spacetime solutions that are effectively Minkowskian on large time and distance scales. Rapid, small amplitude oscillations in the scale factor have a frequency determined by the size of a negative cosmological constant. A field with modes of negative energy is required. If it is gravity that induces a coupling between the ghostlike and normal fields, we find that this results in stochastic rather than unstable behavior. The negative energy modes may also permit the existence of Lorentz invariant fluctuating solutions of finite energymore » density. Finally we consider higher derivative gravity theories and find oscillating metric solutions in these theories without the addition of other fields.« less

LAMMPS Implementation of Constant Energy Dissipative Particle Dynamics (DPD-E)

DTIC Science & Technology

2014-03-01

LAMMPS Implementation of Constant Energy Dissipative Particle Dynamics (DPD-E) by James P. Larentzos, John K. Brennan, Joshua D. Moore, and...MD 21005-5069 ARL-TR-6863 March 2014 LAMMPS Implementation of Constant Energy Dissipative Particle Dynamics (DPD-E) James P...13 September 2013 4. TITLE AND SUBTITLE LAMMPS Implementation of Constant Energy Dissipative Particle Dynamics (DPD-E) 5a. CONTRACT NUMBER 5b

Flight Tests of a Remaining Flying Time Prediction System for Small Electric Aircraft in the Presence of Faults

NASA Technical Reports Server (NTRS)

Hogge, Edward F.; Kulkarni, Chetan S.; Vazquez, Sixto L.; Smalling, Kyle M.; Strom, Thomas H.; Hill, Boyd L.; Quach, Cuong C.

2017-01-01

This paper addresses the problem of building trust in the online prediction of a battery powered aircraft's remaining flying time. A series of flight tests is described that make use of a small electric powered unmanned aerial vehicle (eUAV) to verify the performance of the remaining flying time prediction algorithm. The estimate of remaining flying time is used to activate an alarm when the predicted remaining time is two minutes. This notifies the pilot to transition to the landing phase of the flight. A second alarm is activated when the battery charge falls below a specified limit threshold. This threshold is the point at which the battery energy reserve would no longer safely support two repeated aborted landing attempts. During the test series, the motor system is operated with the same predefined timed airspeed profile for each test. To test the robustness of the prediction, half of the tests were performed with, and half were performed without, a simulated powertrain fault. The pilot remotely engages a resistor bank at a specified time during the test flight to simulate a partial powertrain fault. The flying time prediction system is agnostic of the pilot's activation of the fault and must adapt to the vehicle's state. The time at which the limit threshold on battery charge is reached is then used to measure the accuracy of the remaining flying time predictions. Accuracy requirements for the alarms are considered and the results discussed.

Simple Model with Time-Varying Fine-Structure ``Constant''

NASA Astrophysics Data System (ADS)

Berman, M. S.

2009-10-01

Extending the original version written in colaboration with L.A. Trevisan, we study the generalisation of Dirac's LNH, so that time-variation of the fine-structure constant, due to varying electrical and magnetic permittivities is included along with other variations (cosmological and gravitational ``constants''), etc. We consider the present Universe, and also an inflationary scenario. Rotation of the Universe is a given possibility in this model.

Neuromuscular fatigue following constant versus variable-intensity endurance cycling in triathletes.

PubMed

Lepers, R; Theurel, J; Hausswirth, C; Bernard, T

2008-07-01

The aim of this study was to determine whether or not variable power cycling produced greater neuromuscular fatigue of knee extensor muscles than constant power cycling at the same mean power output. Eight male triathletes (age: 33+/-5 years, mass: 74+/-4 kg, VO2max: 62+/-5 mL kg(-1) min(-1), maximal aerobic power: 392+/-17 W) performed two 30 min trials on a cycle ergometer in a random order. Cycling exercise was performed either at a constant power output (CP) corresponding to 75% of the maximal aerobic power (MAP) or a variable power output (VP) with alternating +/-15%, +/-5%, and +/-10% of 75% MAP approximately every 5 min. Maximal voluntary contraction (MVC) torque, maximal voluntary activation level and excitation-contraction coupling process of knee extensor muscles were evaluated before and immediately after the exercise using the technique of electrically evoked contractions (single and paired stimulations). Oxygen uptake, ventilation and heart rate were also measured at regular intervals during the exercise. Averaged metabolic variables were not significantly different between the two conditions. Similarly, reductions in MVC torque (approximately -11%, P<0.05) after cycling were not different (P>0.05) between CP and VP trials. The magnitude of central and peripheral fatigue was also similar at the end of the two cycling exercises. It is concluded that, following 30 min of endurance cycling, semi-elite triathletes experienced no additional neuromuscular fatigue by varying power (from +/-5% to 15%) compared with a protocol that involved a constant power.

Energy consumption analysis of constant voltage and constant current operations in capacitive deionization

DOE PAGES

Qu, Yatian; Campbell, Patrick G.; Gu, Lei; ...

2016-09-21

Here we report our studies to compare energy consumption of a CDI cell in constant voltage (CV) and constant current (CC) operations, with a focus on understanding the underlying physics of consumption patterns. The comparison is conducted under conditions that the CV and CC operations result in the same amounts of input charge and within identical charging phase durations. We present two electrical circuit models to simulate energy consumption in charging phase: one is a simple RC circuit model, and the other a transmission line circuit model. We built and tested a CDI cell to validate the transmission line model,more » and performed a series of experiments to compare CV versus CC operation under the condition of equal applied charge and charging duration. The experiments show that CC mode consumes energy at 33.8 kJ per mole of ions removed, which is only 28% of CV mode energy consumption (120.6 kJ/mol), but achieves similar level of salt removals. Lastly, together, the models and experiment support our major conclusion that CC is more energy efficient than CV for equal charge and charging duration. The models also suggest that the lower energy consumption of CC in charging is due to its lower resistive dissipation.« less

Energy consumption analysis of constant voltage and constant current operations in capacitive deionization

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

Qu, Yatian; Campbell, Patrick G.; Gu, Lei

Here we report our studies to compare energy consumption of a CDI cell in constant voltage (CV) and constant current (CC) operations, with a focus on understanding the underlying physics of consumption patterns. The comparison is conducted under conditions that the CV and CC operations result in the same amounts of input charge and within identical charging phase durations. We present two electrical circuit models to simulate energy consumption in charging phase: one is a simple RC circuit model, and the other a transmission line circuit model. We built and tested a CDI cell to validate the transmission line model,more » and performed a series of experiments to compare CV versus CC operation under the condition of equal applied charge and charging duration. The experiments show that CC mode consumes energy at 33.8 kJ per mole of ions removed, which is only 28% of CV mode energy consumption (120.6 kJ/mol), but achieves similar level of salt removals. Lastly, together, the models and experiment support our major conclusion that CC is more energy efficient than CV for equal charge and charging duration. The models also suggest that the lower energy consumption of CC in charging is due to its lower resistive dissipation.« less

Base units of the SI, fundamental constants and modern quantum physics.

PubMed

Bordé, Christian J

2005-09-15

Over the past 40 years, a number of discoveries in quantum physics have completely transformed our vision of fundamental metrology. This revolution starts with the frequency stabilization of lasers using saturation spectroscopy and the redefinition of the metre by fixing the velocity of light c. Today, the trend is to redefine all SI base units from fundamental constants and we discuss strategies to achieve this goal. We first consider a kinematical frame, in which fundamental constants with a dimension, such as the speed of light c, the Planck constant h, the Boltzmann constant k(B) or the electron mass m(e) can be used to connect and redefine base units. The various interaction forces of nature are then introduced in a dynamical frame, where they are completely characterized by dimensionless coupling constants such as the fine structure constant alpha or its gravitational analogue alpha(G). This point is discussed by rewriting the Maxwell and Dirac equations with new force fields and these coupling constants. We describe and stress the importance of various quantum effects leading to the advent of this new quantum metrology. In the second part of the paper, we present the status of the seven base units and the prospects of their possible redefinitions from fundamental constants in an experimental perspective. The two parts can be read independently and they point to these same conclusions concerning the redefinitions of base units. The concept of rest mass is directly related to the Compton frequency of a body, which is precisely what is measured by the watt balance. The conversion factor between mass and frequency is the Planck constant, which could therefore be fixed in a realistic and consistent new definition of the kilogram based on its Compton frequency. We discuss also how the Boltzmann constant could be better determined and fixed to replace the present definition of the kelvin.

Time variation of fundamental constants in nonstandard cosmological models

NASA Astrophysics Data System (ADS)

Mosquera, M. E.; Civitarese, O.

2017-10-01

In this work we have studied the lithium problem in nonstandard cosmological models. In particular, by using the public code alterbbn, we have included in the computation of the primordial light nuclei abundances, the effects of the inclusion of dark energy and dark entropy, along with the variation of the fine structure constant and the Higgs vacuum expectation value. In order to set constrains on the variation of the fundamental constants we have compared our theoretical results with the available observational data. We have found that the lithium abundance is reduced for not-null variation at the 3 σ -level of both constants.

Structure and activation of pro-activin A

PubMed Central

Wang, Xuelu; Fischer, Gerhard; Hyvönen, Marko

2016-01-01

Activins are growth factors with multiple roles in the development and homeostasis. Like all TGF-β family of growth factors, activins are synthesized as large precursors from which mature dimeric growth factors are released proteolytically. Here we have studied the activation of activin A and determined crystal structures of the unprocessed precursor and of the cleaved pro-mature complex. Replacing the natural furin cleavage site with a HRV 3C protease site, we show how the protein gains its bioactivity after proteolysis and is as active as the isolated mature domain. The complex remains associated in conditions used for biochemical analysis with a dissociation constant of 5 nM, but the pro-domain can be actively displaced from the complex by follistatin. Our high-resolution structures of pro-activin A share features seen in the pro-TGF-β1 and pro-BMP-9 structures, but reveal a new oligomeric arrangement, with a domain-swapped, cross-armed conformation for the protomers in the dimeric protein. PMID:27373274

Automated real time constant-specificity surveillance for disease outbreaks.

PubMed

Wieland, Shannon C; Brownstein, John S; Berger, Bonnie; Mandl, Kenneth D

2007-06-13

For real time surveillance, detection of abnormal disease patterns is based on a difference between patterns observed, and those predicted by models of historical data. The usefulness of outbreak detection strategies depends on their specificity; the false alarm rate affects the interpretation of alarms. We evaluate the specificity of five traditional models: autoregressive, Serfling, trimmed seasonal, wavelet-based, and generalized linear. We apply each to 12 years of emergency department visits for respiratory infection syndromes at a pediatric hospital, finding that the specificity of the five models was almost always a non-constant function of the day of the week, month, and year of the study (p < 0.05). We develop an outbreak detection method, called the expectation-variance model, based on generalized additive modeling to achieve a constant specificity by accounting for not only the expected number of visits, but also the variance of the number of visits. The expectation-variance model achieves constant specificity on all three time scales, as well as earlier detection and improved sensitivity compared to traditional methods in most circumstances. Modeling the variance of visit patterns enables real-time detection with known, constant specificity at all times. With constant specificity, public health practitioners can better interpret the alarms and better evaluate the cost-effectiveness of surveillance systems.

Titration ELISA as a Method to Determine the Dissociation Constant of Receptor Ligand Interaction.

PubMed

Eble, Johannes A

2018-02-15

The dissociation constant describes the interaction between two partners in the binding equilibrium and is a measure of their affinity. It is a crucial parameter to compare different ligands, e.g., competitive inhibitors, protein isoforms and mutants, for their binding strength to a binding partner. Dissociation constants are determined by plotting concentrations of bound versus free ligand as binding curves. In contrast, titration curves, in which a signal that is proportional to the concentration of bound ligand is plotted against the total concentration of added ligand, are much easier to record. The signal can be detected spectroscopically and by enzyme-linked immunosorbent assay (ELISA). This is exemplified in a protocol for a titration ELISA that measures the binding of the snake venom-derived rhodocetin to its immobilized target domain of α2β1 integrin. Titration ELISAs are versatile and widely used. Any pair of interacting proteins can be used as immobilized receptor and soluble ligand, provided that both proteins are pure, and their concentrations are known. The difficulty so far has been to determine the dissociation constant from a titration curve. In this study, a mathematical function underlying titration curves is introduced. Without any error-prone graphical estimation of a saturation yield, this algorithm allows processing of the raw data (signal intensities at different concentrations of added ligand) directly by mathematical evaluation via non-linear regression. Thus, several titration curves can be recorded simultaneously and transformed into a set of characteristic parameters, among them the dissociation constant and the concentration of binding-active receptor, and they can be evaluated statistically. When combined with this algorithm, titration ELISAs gain the advantage of directly presenting the dissociation constant. Therefore, they may be used more efficiently in the future.

Planck Constant Determination from Power Equivalence

NASA Astrophysics Data System (ADS)

Newell, David B.

2000-04-01

Equating mechanical to electrical power links the kilogram, the meter, and the second to the practical realizations of the ohm and the volt derived from the quantum Hall and the Josephson effects, yielding an SI determination of the Planck constant. The NIST watt balance uses this power equivalence principle, and in 1998 measured the Planck constant with a combined relative standard uncertainty of 8.7 x 10-8, the most accurate determination to date. The next generation of the NIST watt balance is now being assembled. Modification to the experimental facilities have been made to reduce the uncertainty components from vibrations and electromagnetic interference. A vacuum chamber has been installed to reduce the uncertainty components associated with performing the experiment in air. Most of the apparatus is in place and diagnostic testing of the balance should begin this year. Once a combined relative standard uncertainty of one part in 10-8 has been reached, the power equivalence principle can be used to monitor the possible drift in the artifact mass standard, the kilogram, and provide an accurate alternative definition of mass in terms of fundamental constants. *Electricity Division, Electronics and Electrical Engineering Laboratory, Technology Administration, U.S. Department of Commerce. Contribution of the National Institute of Standards and Technology, not subject to copyright in the U.S.

Calculation of individual isotope equilibrium constants for implementation in geochemical models

USGS Publications Warehouse

Thorstenson, Donald C.; Parkhurst, David L.

2002-01-01

Theory is derived from the work of Urey to calculate equilibrium constants commonly used in geochemical equilibrium and reaction-transport models for reactions of individual isotopic species. Urey showed that equilibrium constants of isotope exchange reactions for molecules that contain two or more atoms of the same element in equivalent positions are related to isotope fractionation factors by , where is n the number of atoms exchanged. This relation is extended to include species containing multiple isotopes, for example and , and to include the effects of nonideality. The equilibrium constants of the isotope exchange reactions provide a basis for calculating the individual isotope equilibrium constants for the geochemical modeling reactions. The temperature dependence of the individual isotope equilibrium constants can be calculated from the temperature dependence of the fractionation factors. Equilibrium constants are calculated for all species that can be formed from and selected species containing , in the molecules and the ion pairs with where the subscripts g, aq, l, and s refer to gas, aqueous, liquid, and solid, respectively. These equilibrium constants are used in the geochemical model PHREEQC to produce an equilibrium and reaction-transport model that includes these isotopic species. Methods are presented for calculation of the individual isotope equilibrium constants for the asymmetric bicarbonate ion. An example calculates the equilibrium of multiple isotopes among multiple species and phases.

The Rate Constant for Fluorescence Quenching

ERIC Educational Resources Information Center

Legenza, Michael W.; Marzzacco, Charles J.

1977-01-01

Describes an experiment that utilizes fluorescence intensity measurements from a Spectronic 20 to determine the rate constant for the fluorescence quenching of various aromatic hydrocarbons by carbon tetrachloride in an ethanol solvent. (MLH)

Long persistence of rigor mortis at constant low temperature.

PubMed

Varetto, Lorenzo; Curto, Ombretta

2005-01-06

We studied the persistence of rigor mortis by using physical manipulation. We tested the mobility of the knee on 146 corpses kept under refrigeration at Torino's city mortuary at a constant temperature of +4 degrees C. We found a persistence of complete rigor lasting for 10 days in all the cadavers we kept under observation; and in one case, rigor lasted for 16 days. Between the 11th and the 17th days, a progressively increasing number of corpses showed a change from complete into partial rigor (characterized by partial bending of the articulation). After the 17th day, all the remaining corpses showed partial rigor and in the two cadavers that were kept under observation "à outrance" we found the absolute resolution of rigor mortis occurred on the 28th day. Our results prove that it is possible to find a persistence of rigor mortis that is much longer than the expected when environmental conditions resemble average outdoor winter temperatures in temperate zones. Therefore, this datum must be considered when a corpse is found in those environmental conditions so that when estimating the time of death, we are not misled by the long persistence of rigor mortis.

[Alcohol and work: remaining sober and return to work].

PubMed

Vittadini, G; Bandirali, M

2007-01-01

One of the most complex alcohol-driven problems is the job loss and the subsequent attempts to return to a professional activity. In order to better understand the issue, an epidemiologic investigation was carried out on a group of 162 alcoholics whilst hospitalised in a specialised clinic. The outcome shows the importance of remaining sober to keep or to be returned to one's own job. Unfortunately, local resources at hand, first of all joining an auto-mutual-help group, re still too little known and thus clearly underemployed. Therefore, an informative action within companies is highly desirable. Those alcoholics suffering from serious illnesses, especially mental ones represent a different issue. For these people a higher involvement of public authorities is desirable in creating protected job openings.

Identification of the remains of King Richard III.

PubMed

King, Turi E; Fortes, Gloria Gonzalez; Balaresque, Patricia; Thomas, Mark G; Balding, David; Maisano Delser, Pierpaolo; Neumann, Rita; Parson, Walther; Knapp, Michael; Walsh, Susan; Tonasso, Laure; Holt, John; Kayser, Manfred; Appleby, Jo; Forster, Peter; Ekserdjian, David; Hofreiter, Michael; Schürer, Kevin

2014-12-02

In 2012, a skeleton was excavated at the presumed site of the Grey Friars friary in Leicester, the last-known resting place of King Richard III. Archaeological, osteological and radiocarbon dating data were consistent with these being his remains. Here we report DNA analyses of both the skeletal remains and living relatives of Richard III. We find a perfect mitochondrial DNA match between the sequence obtained from the remains and one living relative, and a single-base substitution when compared with a second relative. Y-chromosome haplotypes from male-line relatives and the remains do not match, which could be attributed to a false-paternity event occurring in any of the intervening generations. DNA-predicted hair and eye colour are consistent with Richard's appearance in an early portrait. We calculate likelihood ratios for the non-genetic and genetic data separately, and combined, and conclude that the evidence for the remains being those of Richard III is overwhelming.

Identification of the remains of King Richard III

PubMed Central

King, Turi E.; Fortes, Gloria Gonzalez; Balaresque, Patricia; Thomas, Mark G.; Balding, David; Delser, Pierpaolo Maisano; Neumann, Rita; Parson, Walther; Knapp, Michael; Walsh, Susan; Tonasso, Laure; Holt, John; Kayser, Manfred; Appleby, Jo; Forster, Peter; Ekserdjian, David; Hofreiter, Michael; Schürer, Kevin

2014-01-01

In 2012, a skeleton was excavated at the presumed site of the Grey Friars friary in Leicester, the last-known resting place of King Richard III. Archaeological, osteological and radiocarbon dating data were consistent with these being his remains. Here we report DNA analyses of both the skeletal remains and living relatives of Richard III. We find a perfect mitochondrial DNA match between the sequence obtained from the remains and one living relative, and a single-base substitution when compared with a second relative. Y-chromosome haplotypes from male-line relatives and the remains do not match, which could be attributed to a false-paternity event occurring in any of the intervening generations. DNA-predicted hair and eye colour are consistent with Richard’s appearance in an early portrait. We calculate likelihood ratios for the non-genetic and genetic data separately, and combined, and conclude that the evidence for the remains being those of Richard III is overwhelming. PMID:25463651

The surface geometry of inherited joint and fracture trace patterns resulting from active and passive deformation

NASA Technical Reports Server (NTRS)

Podwysocki, M. H.; Gold, D. P.

1974-01-01

Hypothetical models are considered for detecting subsurface structure from the fracture or joint pattern, which may be influenced by the structure and propagated to the surface. Various patterns of an initially orthogonal fracture grid are modeled according to active and passive deformation mechanisms. In the active periclinal structure with a vertical axis, fracture frequency increased both over the dome and basin, and remained constant with decreasing depth to the structure. For passive periclinal features such as a reef or sand body, fracture frequency is determined by the arc of curvature and showed a reduction over the reefmound and increased over the basin.

Comparison of entrainment in constant volume and constant flux dense currents over sloping bottoms

NASA Astrophysics Data System (ADS)

Bhaganagar, K.; Nayamatullah, M.; Cenedese, C.

2014-12-01

Three dimensional high resolution large eddy simulations (LES) are employed to simulate lock-exchange and constant flux dense flows over inclined surface with the aim of investigating, visualizing and describing the turbulent structure and the evolution of bottom-propagating compositional density current at the channel bottom. The understanding of dynamics of density current is largely determined by the amount of interfacial mixing or entrainment between the ambient and dense fluids. No previous experimental or numerical studies have been done to estimate entrainment in classical lock-exchange system. The differences in entrainment between the lock-exchange and constant flux are explored. Comparing the results of flat bed with inclined surface results, flow exhibits significant differences near the leading edge or nose of the front of the density currents due to inclination of surface. Further, the instabilities are remarkably enhanced resulting Kelvin-Helmholtz and lobe-cleft type of instabilities arises much earlier in time. In this study, a brief analysis of entrainment on lock-exchange density current is presented using different bed slopes and a set of reduced gravity values (g'). We relate the entrainment value with different flow parameters such as Froude number (Fr) and Reynolds number (Re).

A non-destructive method for dating human remains

USGS Publications Warehouse

Lail, Warren K.; Sammeth, David; Mahan, Shannon; Nevins, Jason

2013-01-01

The skeletal remains of several Native Americans were recovered in an eroded state from a creek bank in northeastern New Mexico. Subsequently stored in a nearby museum, the remains became lost for almost 36 years. In a recent effort to repatriate the remains, it was necessary to fit them into a cultural chronology in order to determine the appropriate tribe(s) for consultation pursuant to the Native American Grave Protection and Repatriation Act (NAGPRA). Because the remains were found in an eroded context with no artifacts or funerary objects, their age was unknown. Having been asked to avoid destructive dating methods such as radiocarbon dating, the authors used Optically Stimulated Luminescence (OSL) to date the sediments embedded in the cranium. The OSL analyses yielded reliable dates between A.D. 1415 and A.D. 1495. Accordingly, we conclude that the remains were interred somewhat earlier than A.D. 1415, but no later than A.D. 1495. We believe the remains are from individuals ancestral to the Ute Mouache Band, which is now being contacted for repatriation efforts. Not only do our methods contribute to the immediate repatriation efforts, they provide archaeologists with a versatile, non-destructive, numerical dating method that can be used in many burial contexts.

Using Constant Time Delay to Teach Braille Word Recognition

ERIC Educational Resources Information Center

Hooper, Jonathan; Ivy, Sarah; Hatton, Deborah

2014-01-01

Introduction: Constant time delay has been identified as an evidence-based practice to teach print sight words and picture recognition (Browder, Ahlbrim-Delzell, Spooner, Mims, & Baker, 2009). For the study presented here, we tested the effectiveness of constant time delay to teach new braille words. Methods: A single-subject multiple baseline…

Constant pH Accelerated Molecular Dynamics Investigation of the pH Regulation Mechanism of Dinoflagellate Luciferase.

PubMed

Donnan, Patrick H; Ngo, Phong D; Mansoorabadi, Steven O

2018-01-23

The bioluminescence reaction in dinoflagellates involves the oxidation of an open-chain tetrapyrrole by the enzyme dinoflagellate luciferase (LCF). The activity of LCF is tightly regulated by pH, where the enzyme is essentially inactive at pH ∼8 and optimally active at pH ∼6. Little is known about the mechanism of LCF or the structure of the active form of the enzyme, although it has been proposed that several intramolecularly conserved histidine residues in the N-terminal region are important for the pH regulation mechanism. Here, constant pH accelerated molecular dynamics was employed to gain insight into the conformational activation of LCF induced by acidification.

Odor analysis of decomposing buried human remains

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

Vass, Arpad Alexander; Smith, Rob R; Thompson, Cyril V

2008-01-01

This study, conducted at the University of Tennessee's Anthropological Research Facility (ARF), lists and ranks the primary chemical constituents which define the odor of decomposition of human remains as detected at the soil surface of shallow burial sites. Triple sorbent traps were used to collect air samples in the field and revealed eight major classes of chemicals which now contain 478 specific volatile compounds associated with burial decomposition. Samples were analyzed using gas chromatography-mass spectrometry (GC-MS) and were collected below and above the body, and at the soil surface of 1.5-3.5 ft. (0.46-1.07 m) deep burial sites of four individualsmore » over a 4-year time span. New data were incorporated into the previously established Decompositional Odor Analysis (DOA) Database providing identification, chemical trends, and semi-quantitation of chemicals for evaluation. This research identifies the 'odor signatures' unique to the decomposition of buried human remains with projected ramifications on human remains detection canine training procedures and in the development of field portable analytical instruments which can be used to locate human remains in shallow burial sites.« less

MSG-Evoked c-Fos Activity in the Nucleus of the Solitary Tract Is Dependent upon Fluid Delivery and Stimulation Parameters.

PubMed

Stratford, Jennifer M; Thompson, John A

2016-03-01

The marker of neuronal activation, c-Fos, can be used to visualize spatial patterns of neural activity in response to taste stimulation. Because animals will not voluntarily consume aversive tastes, these stimuli are infused directly into the oral cavity via intraoral cannulae, whereas appetitive stimuli are given in drinking bottles. Differences in these 2 methods make comparison of taste-evoked brain activity between results that utilize these methods problematic. Surprisingly, the intraoral cannulae experimental conditions that produce a similar pattern of c-Fos activity in response to taste stimulation remain unexplored. Stimulation pattern (e.g., constant/intermittent) and hydration state (e.g., water-restricted/hydrated) are the 2 primary differences between delivering tastes via bottles versus intraoral cannulae. Thus, we quantified monosodium glutamate (MSG)-evoked brain activity, as measured by c-Fos, in the nucleus of the solitary tract (nTS; primary taste nucleus) across several conditions. The number and pattern of c-Fos neurons in the nTS of animals that were water-restricted and received a constant infusion of MSG via intraoral cannula most closely mimicked animals that consumed MSG from a bottle. Therefore, in order to compare c-Fos activity between cannulae-stimulated and bottle-stimulated animals, cannulated animals should be water restricted prior to stimulation, and receive taste stimuli at a constant flow. © The Author 2016. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Catalytic properties of thermophilic lactate dehydrogenase and halophilic malate dehydrogenase at high temperature and low water activity.

PubMed

Hecht, K; Wrba, A; Jaenicke, R

1989-07-15

Thermophilic lactate dehydrogenases from Thermotoga maritima and Bacillus stearothermophilus are stable up to temperature limits close to the optimum growth temperature of their parent organisms. Their catalytic properties are anomalous in that Km shows a drastic increase with increasing temperature. At low temperatures, the effect levels off. Extreme halophilic malate dehydrogenase from Halobacterium marismortui exhibits a similar anomaly. Increasing salt concentration (NaCl) leads to an optimum curve for Km, oxaloacctate while Km, NADH remains constant. Previous claims that the activity of halophilic malate dehydrogenase shows a maximum at 1.25 M NaCl are caused by limiting substrate concentration; at substrate saturation, specific activity of halophilic malate dehydrogenase reaches a constant value at ionic strengths I greater than or equal to 1 M. Non-halophilic (mitochondrial) malate dehydrogenase shows Km characteristics similar to those observed for the halophilic enzyme. The drastic decrease in specific activity of the mitochondrial enzyme at elevated salt concentrations is caused by the salt-induced increase in rigidity of the enzyme, rather than gross structural changes.

Wave propagation in and around negative-dielectric-constant discharge plasma

NASA Astrophysics Data System (ADS)

Sakai, Osamu; Iwai, Akinori; Omura, Yoshiharu; Iio, Satoshi; Naito, Teruki

2018-03-01

The modes of wave propagation in media with a negative dielectric constant are not simple, unlike those for electromagnetic waves in media with a positive dielectric constant (where modes propagate inside the media with positive phase velocity since the refractive index is usually positive). Instead, they depend on the permeability sign, either positive or negative, and exhibit completely different features. In this report, we investigated a wave confined on the surface of a negative-dielectric-constant and a positive-permeability plasma medium for which the refractive index is imaginary. The propagation mode is similar to surface plasmon polaritons on the metal containing free electrons, but its frequency band is different due to the significant spatial gradient of the dielectric constant and a different pressure term. We also studied a wave with a negative dielectric constant and negative permeability, where the refractive index is negative. This wave can propagate inside the media, but its phase velocity is negative. It also shares similar qualities with waves in plasmonic devices with negative permeability in the photon range.

The Solar Constant, Climate, and Some Tests of the Storage Hypothesis

NASA Technical Reports Server (NTRS)

Eddy, J. A.

1984-01-01

Activity related modulation of the solar constant can have practical consequences for climate only if storage is involved, as opposed to a detailed balance between sunspot blocking and facular reemission. Four empirical tests are considered that might distinguish between these opposing interpretations: monochromatic measurements of positive and negative flux; comparison of modelled and measured irradiance variations; the interpretation of secular trends in irradiance data; and the direct test of an anticipated signal in climate records of surface air temperature. The yet unanswered question of the role of faculae as possible reemitters of blocked radiation precludes a definitive answer, although other tests suggest their role to be minor, and that storage and an 11 year modulation is implicated. A crucial test is the behavior of the secular trend in irradiance in the declining years of the present activity cycle.

Remaining lifetime modeling using State-of-Health estimation

NASA Astrophysics Data System (ADS)

Beganovic, Nejra; Söffker, Dirk

2017-08-01

has lower degrees of freedom. Both approaches rely on previously developed lifetime models each of them corresponding to predefined SoH. Concerning first approach, model selection is aided by state-machine-based algorithm. In the second approach, model selection conditioned by tracking an exceedance of predefined thresholds is concerned. The approach is applied to data generated from tribological systems. By calculating Root Squared Error (RSE), Mean Squared Error (MSE), and Absolute Error (ABE) the accuracy of proposed models/approaches is discussed along with related advantages and disadvantages. Verification of the approach is done using cross-fold validation, exchanging training and test data. It can be stated that the newly introduced approach based on data (denoted as data-based or data-driven) parametric models can be easily established providing detailed information about remaining useful/consumed lifetime valid for systems with constant load but stochastically occurred damage.

Competition kinetics using the UV/H2O2 process: a structure reactivity correlation for the rate constants of hydroxyl radicals toward nitroaromatic compounds.

PubMed

García Einschlag, Fernando S; Carlos, Luciano; Capparelli, Alberto L

2003-10-01

The rate constants for hydroxyl radical reaction toward a set of nitroaromatic substrates kS, have been measured at 25 degrees C using competition experiments in the UV/H2O2 process. For a given pair of substrates S1 and S2, the relative reactivity beta (defined as kS1/kS2) was calculated from the slope of the corresponding double logarithmic plot, i.e., of ln[S1] vs. ln[S2]. This method is more accurate and remained linear for larger conversions in comparison with the plots of ln[S1] and ln[S2] against time. The rate constants measured ranged from 0.33 to 8.6 x 10(9) M(-1)s(-1). A quantitative structure-reactivity relationship was found using the Hammett equation. Assuming sigma values to be additive, a value of -0.60 was obtained for the reaction constant rho. This value agrees with the high reactivity and the electrophilic nature of HO* radical.

Determination of association constants between steroid compounds and albumins by partial-filling ACE.

PubMed

Amundsen, Lotta K; Sirén, Heli

2007-10-01

ACE is a popular technique for evaluating association constants between drugs and proteins. However, ACE has not previously been applied to study the association between electrically neutral biomolecules and plasma proteins. We studied the affinity between human and bovine serum albumins (HSA and BSA, respectively) and three neutral endogenous steroid hormones (testosterone, epitestosterone and androstenedione) and two synthetic analogues (methyltestosterone and fluoxymesterone) by applying the partial-filling technique in ACE (PF-ACE). From the endocrinological point of view, the distribution of endogenous steroids among plasma components is of great interest. Strong interactions with albumins suppress the biological activity of steroids. Notable differences in the association constants were observed. In the case of the endogenous steroids, the interactions between testosterone and the albumins were strongest, and those between androstenedione and the albumins were substantially weaker. The association constants, K(b), for testosterone, epitestosterone and androstenedione and HSA at 37 degrees C were 32 100 +/- 3600, 21 600 +/- 1500 and 13 300 +/- 1300 M(-1), respectively, while the corresponding values for the steroids and BSA were 18 800 +/- 1500, 14 000 +/- 400 and 7800 +/- 900 M(-1). Methyltestosterone was bound even more strongly than testosterone, while fluoxymesterone was only weakly bound by the albumins. Finally, the steroids were separated by PF-ACE with HSA and BSA used as resolving components.

Hydroxynonenal-stimulated activity of the uncoupling protein in Acanthamoeba castellanii mitochondria under phosphorylating conditions.

PubMed

Woyda-Ploszczyca, Andrzej; Jarmuszkiewicz, Wieslawa

2013-05-01

The influence of 4-hydroxy-2-nonenal (HNE), a lipid peroxidation end product, on the activity of the amoeba Acanthamoeba castellanii uncoupling protein (AcUCP) in isolated phosphorylating mitochondria was studied. Under phosphorylating conditions, exogenously added HNE induced GTP-sensitive AcUCP-mediated mitochondrial uncoupling. The HNE-induced proton leak decreased the yield of oxidative phosphorylation in an HNE concentration-dependent manner. The present study describes how the contributions of ATP synthase and HNE-induced AcUCP in phosphorylating respiration vary when the rate of succinate oxidation is decreased by limiting succinate uptake or inhibiting complex III activity within the range of a constant membrane potential. In phosphorylating mitochondria, at a given HNE concentration (100 μM), the efficiency of AcUCP in mitochondrial uncoupling increased as the respiratory rate decreased because the AcUCP contribution remained constant while the ATP synthase contribution decreased with the respiratory rate. HNE-induced uncoupling can be inhibited by GTP only when ubiquinone is sufficiently oxidized, indicating that in phosphorylating A. castellanii mitochondria, the sensitivity of AcUCP activity to GTP depends on the redox state of the membranous ubiquinone.

Cantilever spring constant calibration using laser Doppler vibrometry

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

Ohler, Benjamin

2007-06-15

Uncertainty in cantilever spring constants is a critical issue in atomic force microscopy (AFM) force measurements. Though numerous methods exist for calibrating cantilever spring constants, the accuracy of these methods can be limited by both the physical models themselves as well as uncertainties in their experimental implementation. Here we report the results from two of the most common calibration methods, the thermal tune method and the Sader method. These were implemented on a standard AFM system as well as using laser Doppler vibrometry (LDV). Using LDV eliminates some uncertainties associated with optical lever detection on an AFM. It also offersmore » considerably higher signal to noise deflection measurements. We find that AFM and LDV result in similar uncertainty in the calibrated spring constants, about 5%, using either the thermal tune or Sader methods provided that certain limitations of the methods and instrumentation are observed.« less

Instanton rate constant calculations close to and above the crossover temperature.

PubMed

McConnell, Sean; Kästner, Johannes

2017-11-15

Canonical instanton theory is known to overestimate the rate constant close to a system-dependent crossover temperature and is inapplicable above that temperature. We compare the accuracy of the reaction rate constants calculated using recent semi-classical rate expressions to those from canonical instanton theory. We show that rate constants calculated purely from solving the stability matrix for the action in degrees of freedom orthogonal to the instanton path is not applicable at arbitrarily low temperatures and use two methods to overcome this. Furthermore, as a by-product of the developed methods, we derive a simple correction to canonical instanton theory that can alleviate this known overestimation of rate constants close to the crossover temperature. The combined methods accurately reproduce the rate constants of the canonical theory along the whole temperature range without the spurious overestimation near the crossover temperature. We calculate and compare rate constants on three different reactions: H in the Müller-Brown potential, methylhydroxycarbene → acetaldehyde and H 2  + OH → H + H 2 O. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Imaging nanoclusters in the constant height mode of the dynamic SFM.

PubMed

Barth, Clemens; Pakarinen, Olli H; Foster, Adam S; Henry, Claude R

2006-04-14

For the first time, high quality images of metal nanoclusters which were recorded in the constant height mode of a dynamic scanning force microscope (dynamic SFM) are shown. Surfaces of highly ordered pyrolytic graphite (HOPG) were used as a test substrate since metal nanoclusters with well defined and symmetric shapes can be created by epitaxial growth. We performed imaging of gold clusters with sizes between 5 and 15 nm in both scanning modes, constant Δf mode and constant height mode, and compared the image contrast. We notice that clusters in constant height images appear much sharper, and exhibit more reasonable lateral shapes and sizes in comparison to images recorded in the constant Δf mode. With the help of numerical simulations we show that only a microscopically small part of the tip apex (nanotip) is probably the main contributor for the image contrast formation. In principle, the constant height mode can be used for imaging surfaces of any material, e.g. ionic crystals, as shown for the system Au/NaCl(001).

The Effects of Soil Texture on the Ability of Human Remains Detection Dogs to Detect Buried Human Remains.

PubMed

Alexander, Michael B; Hodges, Theresa K; Wescott, Daniel J; Aitkenhead-Peterson, Jacqueline A

2016-05-01

Despite technological advances, human remains detection (HRD) dogs still remain one of the best tools for locating clandestine graves. However, soil texture may affect the escape of decomposition gases and therefore the effectiveness of HDR dogs. Six nationally credentialed HRD dogs (three HRD only and three cross-trained) were evaluated on novel buried human remains in contrasting soils, a clayey and a sandy soil. Search time and accuracy were compared for the clayey soil and sandy soil to assess odor location difficulty. Sandy soil (p < 0.001) yielded significantly faster trained response times, but no significant differences were found in performance accuracy between soil textures or training method. Results indicate soil texture may be significant factor in odor detection difficulty. Prior knowledge of soil texture and moisture may be useful for search management and planning. Appropriate adjustments to search segment sizes, sweep widths and search time allotment depending on soil texture may optimize successful detection. © 2016 American Academy of Forensic Sciences.

Variable energy constant current accelerator structure

DOEpatents

Anderson, O.A.

1988-07-13

A variable energy, constant current ion beam accelerator structure is disclosed comprising an ion source capable of providing the desired ions, a pre-accelerator for establishing an initial energy level, a matching/pumping module having means for focusing means for maintaining the beam current, and at least one main accelerator module for continuing beam focus, with means capable of variably imparting acceleration to the beam so that a constant beam output current is maintained independent of the variable output energy. In a preferred embodiment, quadrupole electrodes are provided in both the matching/pumping module and the one or more accelerator modules, and are formed using four opposing cylinder electrodes which extend parallel to the beam axis and are spaced around the beam at 90/degree/ intervals with opposing electrodes maintained at the same potential. 12 figs., 3 tabs.

Dielectric constants of soils at microwave frequencies

NASA Technical Reports Server (NTRS)

Geiger, F. E.; Williams, D.

1972-01-01

A knowledge of the complex dielectric constant of soils is essential in the interpretation of microwave airborne radiometer data of the earth's surface. Measurements were made at 37 GHz on various soils from the Phoenix, Ariz., area. Extensive data have been obtained for dry soil and soil with water content in the range from 0.6 to 35 percent by dry weight. Measurements were made in a two arm microwave bridge and results were corrected for reflections at the sample interfaces by solution of the parallel dielectric plate problem. The maximum dielectric constants are about a factor of 3 lower than those reported for similar soils at X-band frequencies.

Further thoughts on the solar constant

NASA Astrophysics Data System (ADS)

Thompson, Frank

2018-05-01

I read with interest the recent paper (Brizova and Slegr 2017 Phys. Educ. 52 013008) regarding an experiment to measure the solar constant using a bolometer. The authors admitted that their measurements gave a value much lower than expected.

Rate constants measured for hydrated electron reactions with peptides and proteins

NASA Technical Reports Server (NTRS)

Braams, R.

1968-01-01

Effects of ionizing radiation on the amino acids of proteins and the reactivity of the protonated amino group depends upon the pK subscript a of the group. Estimates of the rate constants for reactions involving the amino acid side chains are presented. These rate constants gave an approximate rate constant for three different protein molecules.

Relaxing the cosmological constant: a proof of concept

NASA Astrophysics Data System (ADS)

Alberte, Lasma; Creminelli, Paolo; Khmelnitsky, Andrei; Pirtskhalava, David; Trincherini, Enrico

2016-12-01

We propose a technically natural scenario whereby an initially large cosmological constant (c.c.) is relaxed down to the observed value due to the dynamics of a scalar evolving on a very shallow potential. The model crucially relies on a sector that violates the null energy condition (NEC) and gets activated only when the Hubble rate becomes sufficiently small — of the order of the present one. As a result of NEC violation, this low-energy universe evolves into inflation, followed by reheating and the standard Big Bang cosmology. The symmetries of the theory force the c.c. to be the same before and after the NEC-violating phase, so that a late-time observer sees an effective c.c. of the correct magnitude. Importantly, our model allows neither for eternal inflation nor for a set of possible values of dark energy, the latter fixed by the parameters of the theory.

An adaptive-binning method for generating constant-uncertainty/constant-significance light curves with Fermi -LAT data

DOE PAGES

Lott, B.; Escande, L.; Larsson, S.; ...

2012-07-19

Here, we present a method enabling the creation of constant-uncertainty/constant-significance light curves with the data of the Fermi-Large Area Telescope (LAT). The adaptive-binning method enables more information to be encapsulated within the light curve than with the fixed-binning method. Although primarily developed for blazar studies, it can be applied to any sources. Furthermore, this method allows the starting and ending times of each interval to be calculated in a simple and quick way during a first step. The reported mean flux and spectral index (assuming the spectrum is a power-law distribution) in the interval are calculated via the standard LATmore » analysis during a second step. In the absence of major caveats associated with this method Monte-Carlo simulations have been established. We present the performance of this method in determining duty cycles as well as power-density spectra relative to the traditional fixed-binning method.« less

Optical constants of electroplated gold from spectroscopic ellipsometry

NASA Astrophysics Data System (ADS)

Synowicki, R. A.; Herzinger, Craig M.; Hall, James T.; Malingowski, Andrew

2017-11-01

The optical constants of an opaque electroplated gold film (Laser Gold from Epner Technology Inc.), were determined by spectroscopic ellipsometry at room temperature over the spectral range from 0.142 μm in the vacuum ultraviolet to 36 μm in the infrared (photon energy range 0.034-8.75 eV). Data from two separate ellipsometer instruments covering different spectral ranges were analyzed simultaneously. The optical constants n&k or ε1&ε2 were determined by fitting an oscillator dispersion model combining Drude, Gaussian, and Sellmeier dispersion functions to the experimental Ψ and Δ data. The data were analyzed using both an ideal bulk substrate model and a simple overlayer model to account for surface roughness. Including the optical surface roughness layer improved ellipsometric data fits in the UV, and using a separate Drude function for the surface layer improved fits in the infrared. The surface roughness was also characterized using an Atomic Force Microscope. Using an oscillator dispersion model for the optical constants determined in this work allows for more realistic extrapolation to longer infrared wavelengths. Extending optical constants out to 50 μm and beyond is important for calibrating far-infrared reflectance measurements. Applications include understanding the thermal performance of cryogenic space-based instruments, such as the James Webb Space Telescope (JWST).

Sulfated modification and anticoagulant activity of pumpkin (Cucurbita pepo, Lady Godiva) polysaccharide.

PubMed

Liang, Li; Ao, Le; Ma, Tao; Ni, Yuanying; Liao, Xiaojun; Hu, Xiaosong; Song, Yi

2018-01-01

Sulfated modification of pumpkin polysaccharide using CAS with pyridines as catalysts under different conditions was conducted to obtain different degrees of sulfation on a laboratory scale. Anticoagulant activities of pumpkin polysaccharide and its sulfated derivatives were also investigated employing various established in vitro systems. Results showed that addition of high ratio of CAS/pyridine under constant conditions could increase the degree of substitution. Sulfate substitution was further confirmed by the FT-IR and 13 C NMR analysis. The d f values between 2.11-2.73 indicated the relatively expanded conformation of the sulfated derivatives. The sulfated polysaccharides showed higher anticoagulant activities through activated partial thrombosis time (aPTT), thrombin time (TT), prothrombin time (PT) and anti-Xa activity assay, which revealed that better anticoagulant activities could be obtained when DS remained higher and M w maintained in a moderate range. Copyright © 2017 Elsevier B.V. All rights reserved.

Solubility-product constant and thermodynamic properties for synthetic otavite, CdCO3(s), and aqueous association constants for the Cd(II)-CO2-H2O system

USGS Publications Warehouse

Stipp, S.L.S.; Parks, George A.; Nordstrom, D. Kirk; Leckie, J.O.

1993-01-01

Considerable disparity exists in the published thermodynamic data for selected species in the Cd(II)-CO2-H2O system near 25??C and 1 atm pressure. Evaluation of published experimental and estimated data for aqueous cadmium-carbonate species suggests an association constant, pK, of -3.0 ?? 0.4 for CdCO30, about -1.5 for CdHCO3+, and -6.4 ?? 0.1 for Cd(CO3)22- (T = 298.15 K; P = 1 atm; I = 0). Examination of all available data for cadmium-hydrolysis species and ??-Cd(OH)2(s)) confirms that the consistent set of constants presented by Baes and Mesmer (Hydrolysis of Cations, 1976) is the best available. The solubility of synthetic otavite, CdCO3(s), has been measured in KClO4 solutions where I ??? 0.1 M. We calculated pKsp = 12.1 ?? 0.1 (T = 25.0??C; P = 1 atm; I = 0) from measured concentrations of Cd2+, measured PC02 and pH, our selected set of equilibrium constants, and activity corrections estimated using the Davies equation. Values at 5 and 50??C were 12.4 ?? 0.1 and 12.2 ?? 0.1, respectively. Based on the new solubility data and the CODATA key values for Cd2+ and CO32-, a new set of thermodynamic properties is recommended for otavite: ??Gf0 = -674.7 ?? 0.6 kJ/mol; ??Hf0 = -751.9 ?? 10 kJ/mol; S0 = 106 ?? 30 J/mol K; and ??Gr0 for the reaction Cd2+ + CO32- ??? CdCO3(s) is -69.08 ?? 0.57 kJ/m. ?? 1993.

Conjugate Acid-Base Pairs, Free Energy, and the Equilibrium Constant

ERIC Educational Resources Information Center

Beach, Darrell H.

1969-01-01

Describes a method of calculating the equilibrium constant from free energy data. Values of the equilibrium constants of six Bronsted-Lowry reactions calculated by the author's method and by a conventional textbook method are compared. (LC)

Wavelength dependence of Verdet constant of Tb{sup 3+}:Y{sub 2}O{sub 3} ceramics

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

Snetkov, I. L., E-mail: snetkov@appl.sci-nnov.ru; Palashov, O. V.; Permin, D. A.

2016-04-18

Samples of the magneto-active material—Tb{sup 3+}:Y{sub 2}O{sub 3} ceramics with Tb{sup 3+} ion concentrations of 10%, 20%, 30%, and 100% (Tb{sub 2}O{sub 3})—were prepared and studied. The wavelength dependence of Verdet constant in the 380 nm–1750 nm range was approximated for all investigated ceramic samples and was predicted for a pure Tb{sub 2}O{sub 3} material. Tb{sub 2}O{sub 3} ceramics demonstrates a more than three times higher Verdet constant in comparison with terbium gallium garnet crystal or ceramics. The linear dependence of the Verdet constant on Tb{sup 3+} ion concentration in the Tb{sup 3+}:Y{sub 2}O{sub 3} ceramics was demonstrated. The obtained data willmore » be useful for fabricating magneto-optical elements of Faraday devices based on Tb{sup 3+}:Y{sub 2}O{sub 3} with arbitrary Tb{sup 3+} ion concentration operating at room temperature in the wavelength range of 380 nm–1750 nm.« less

Free energy perturbation method for measuring elastic constants of liquid crystals

NASA Astrophysics Data System (ADS)

Joshi, Abhijeet

There is considerable interest in designing liquid crystals capable of yielding specific morphological responses in confined environments, including capillaries and droplets. The morphology of a liquid crystal is largely dictated by the elastic constants, which are difficult to measure and are only available for a handful of substances. In this work, a first-principles based method is proposed to calculate the Frank elastic constants of nematic liquid crystals directly from atomistic models. These include the standard splay, twist and bend deformations, and the often-ignored but important saddle-splay constant. The proposed method is validated using a well-studied Gay-Berne(3,5,2,1) model; we examine the effects of temperature and system size on the elastic constants in the nematic and smectic phases. We find that our measurements of splay, twist, and bend elastic constants are consistent with previous estimates for the nematic phase. We further outline the implementation of our approach for the saddle-splay elastic constant, and find it to have a value at the limits of the Ericksen inequalities. We then proceed to report results for the elastic constants commonly known liquid crystals namely 4-pentyl-4'-cynobiphenyl (5CB) using atomistic model, and show that the values predicted by our approach are consistent with a subset of the available but limited experimental literature.

Decomposition patterns of buried remains at different intervals in the Central Highveld region of South Africa.

PubMed

Marais-Werner, A; Myburgh, J; Meyer, A; Nienaber, W C; Steyn, M

2017-07-01

Burial of remains is an important factor when one attempts to establish the post-mortem interval as it reduces, and in extreme cases, excludes oviposition by Diptera species. This in turn leads to modification of the decomposition process. The aim of this study was to record decomposition patterns of buried remains using a pig model. The pattern of decomposition was evaluated at different intervals and recorded according to existing guidelines. In order to contribute to our knowledge on decomposition in different settings, a quantifiable approach was followed. Results indicated that early stages of decomposition occurred rapidly for buried remains within 7-33 days. Between 14 and 33 days, buried pigs displayed common features associated with the early to middle stages of decomposition, such as discoloration and bloating. From 33 to 90 days advanced decomposition manifested on the remains, and pigs then reached a stage of advanced decomposition where little change was observed in the next ±90-183 days after interment. Throughout this study, total body scores remained higher for surface remains. Overall, buried pigs followed a similar pattern of decomposition to those of surface remains, although at a much slower rate when compared with similar post-mortem intervals in surface remains. In this study, the decomposition patterns and rates of buried remains were mostly influenced by limited insect activity and adipocere formation which reduces the rate of decay in a conducive environment (i.e. burial in soil).

Cardiac activation heat remains inversely dependent on temperature over the range 27-37°C.

PubMed

Johnston, Callum M; Han, June-Chiew; Loiselle, Denis S; Nielsen, Poul M F; Taberner, Andrew J

2016-06-01

The relation between heat output and stress production (force per cross-sectional area) of isolated cardiac tissue is a key metric that provides insight into muscle energetic performance. The heat intercept of the relation, termed "activation heat," reflects the metabolic cost of restoring transmembrane gradients of Na(+) and K(+) following electrical excitation, and myoplasmic Ca(2+) concentration following its release from the sarcoplasmic reticulum. At subphysiological temperatures, activation heat is inversely dependent on temperature. Thus one may presume that activation heat would decrease even further at body temperature. However, this assumption is prima facie inconsistent with a study, using intact hearts, which revealed no apparent change in the combination of activation and basal metabolism between 27 and 37°C. It is thus desired to directly determine the change in activation heat between 27 and 37°C. In this study, we use our recently constructed high-thermal resolution muscle calorimeter to determine the first heat-stress relation of isolated cardiac muscle at 37°C. We compare the relation at 37°C to that at 27°C to examine whether the inverse temperature dependence of activation heat, observed under hypothermic conditions, prevails at body temperature. Our results show that activation heat was reduced (from 3.5 ± 0.3 to 2.3 ± 0.3 kJ/m(3)) at the higher temperature. This leads us to conclude that activation metabolism continues to decline as temperature is increased from hypothermia to normothermia and allows us to comment on results obtained from the intact heart by previous investigators. Copyright © 2016 the American Physiological Society.

Mittag-Leffler stability of fractional-order neural networks in the presence of generalized piecewise constant arguments.

PubMed

Wu, Ailong; Liu, Ling; Huang, Tingwen; Zeng, Zhigang

2017-01-01

Neurodynamic system is an emerging research field. To understand the essential motivational representations of neural activity, neurodynamics is an important question in cognitive system research. This paper is to investigate Mittag-Leffler stability of a class of fractional-order neural networks in the presence of generalized piecewise constant arguments. To identify neural types of computational principles in mathematical and computational analysis, the existence and uniqueness of the solution of neurodynamic system is the first prerequisite. We prove that the existence and uniqueness of the solution of the network holds when some conditions are satisfied. In addition, self-active neurodynamic system demands stable internal dynamical states (equilibria). The main emphasis will be then on several sufficient conditions to guarantee a unique equilibrium point. Furthermore, to provide deeper explanations of neurodynamic process, Mittag-Leffler stability is studied in detail. The established results are based on the theories of fractional differential equation and differential equation with generalized piecewise constant arguments. The derived criteria improve and extend the existing related results. Copyright © 2016 Elsevier Ltd. All rights reserved.

Caregivers as Teachers: Using Constant Time Delay To Teach Adults How To Use Constant Time Delay.

ERIC Educational Resources Information Center

Wall, Maureen E.; Gast, David L.

1997-01-01

A study involving four caregivers evaluated the effectiveness of a systematic instructional procedure known as constant time delay (CTD) in teaching caregivers how to use CTD to teach their adolescent or adult children, siblings, or clients with disabilities, response chain skills. Results found the procedure to be effective. (CR)

Sex determination of human remains from peptides in tooth enamel.

PubMed

Stewart, Nicolas Andre; Gerlach, Raquel Fernanda; Gowland, Rebecca L; Gron, Kurt J; Montgomery, Janet

2017-12-26

The assignment of biological sex to archaeological human skeletons is a fundamental requirement for the reconstruction of the human past. It is conventionally and routinely performed on adults using metric analysis and morphological traits arising from postpubertal sexual dimorphism. A maximum accuracy of ∼95% is possible if both the cranium and os coxae are present and intact, but this is seldom achievable for all skeletons. Furthermore, for infants and juveniles, there are no reliable morphological methods for sex determination without resorting to DNA analysis, which requires good DNA survival and is time-consuming. Consequently, sex determination of juvenile remains is rarely undertaken, and a dependable and expedient method that can correctly assign biological sex to human remains of any age is highly desirable. Here we present a method for sex determination of human remains by means of a minimally destructive surface acid etching of tooth enamel and subsequent identification of sex chromosome-linked isoforms of amelogenin, an enamel-forming protein, by nanoflow liquid chromatography mass spectrometry. Tooth enamel is the hardest tissue in the human body and survives burial exceptionally well, even when the rest of the skeleton or DNA in the organic fraction has decayed. Our method can reliably determine the biological sex of humans of any age using a body tissue that is difficult to cross-contaminate and is most likely to survive. The application of this method will make sex determination of adults and, for the first time, juveniles a reliable and routine activity in future bioarcheological and medico-legal science contexts. Copyright © 2017 the Author(s). Published by PNAS.

Fine structure constant defines visual transparency of graphene.

PubMed

Nair, R R; Blake, P; Grigorenko, A N; Novoselov, K S; Booth, T J; Stauber, T; Peres, N M R; Geim, A K

2008-06-06

There are few phenomena in condensed matter physics that are defined only by the fundamental constants and do not depend on material parameters. Examples are the resistivity quantum, h/e2 (h is Planck's constant and e the electron charge), that appears in a variety of transport experiments and the magnetic flux quantum, h/e, playing an important role in the physics of superconductivity. By and large, sophisticated facilities and special measurement conditions are required to observe any of these phenomena. We show that the opacity of suspended graphene is defined solely by the fine structure constant, a = e2/hc feminine 1/137 (where c is the speed of light), the parameter that describes coupling between light and relativistic electrons and that is traditionally associated with quantum electrodynamics rather than materials science. Despite being only one atom thick, graphene is found to absorb a significant (pa = 2.3%) fraction of incident white light, a consequence of graphene's unique electronic structure.

An Inverse Square Law Variation for Hubble's Constant

NASA Astrophysics Data System (ADS)

Day, Orville W., Jr.

1999-11-01

The solution to Einstein's gravitational field equations is examined, using a Robertson-Walker metric with positive curvature, when Hubble's parameter, H_0, is taken to be a constant divided by R^2. R is the cosmic scale factor for the universe treated as a three-dimensional hypersphere in a four-dimensional Euclidean space. This solution produces a self-energy of the universe, W^(0)_self, proportional to the square of the total mass, times the universal gravitational constant divided by the cosmic scale factor, R. This result is totally analogous to the self-energy of the electromagnetic field of a charged particle, W^(0)_self = ke^2/2r, where the total charge e is squared, k is the universal electric constant and r is the scale factor, usually identified as the radius of the particle. It is shown that this choice for H0 leads to physically meaningful results for the average mass density and pressure, and a deacceleration parameter q_0=1.

Median statistics estimates of Hubble and Newton's constants

NASA Astrophysics Data System (ADS)

Bethapudi, Suryarao; Desai, Shantanu

2017-02-01

Robustness of any statistics depends upon the number of assumptions it makes about the measured data. We point out the advantages of median statistics using toy numerical experiments and demonstrate its robustness, when the number of assumptions we can make about the data are limited. We then apply the median statistics technique to obtain estimates of two constants of nature, Hubble constant (H0) and Newton's gravitational constant ( G , both of which show significant differences between different measurements. For H0, we update the analyses done by Chen and Ratra (2011) and Gott et al. (2001) using 576 measurements. We find after grouping the different results according to their primary type of measurement, the median estimates are given by H0 = 72.5^{+2.5}_{-8} km/sec/Mpc with errors corresponding to 95% c.l. (2 σ) and G=6.674702^{+0.0014}_{-0.0009} × 10^{-11} Nm2kg-2 corresponding to 68% c.l. (1σ).

Design verification of large time constant thermal shields for optical reference cavities.

PubMed

Zhang, J; Wu, W; Shi, X H; Zeng, X Y; Deng, K; Lu, Z H

2016-02-01

In order to achieve high frequency stability in ultra-stable lasers, the Fabry-Pérot reference cavities shall be put inside vacuum chambers with large thermal time constants to reduce the sensitivity to external temperature fluctuations. Currently, the determination of thermal time constants of vacuum chambers is based either on theoretical calculation or time-consuming experiments. The first method can only apply to simple system, while the second method will take a lot of time to try out different designs. To overcome these limitations, we present thermal time constant simulation using finite element analysis (FEA) based on complete vacuum chamber models and verify the results with measured time constants. We measure the thermal time constants using ultrastable laser systems and a frequency comb. The thermal expansion coefficients of optical reference cavities are precisely measured to reduce the measurement error of time constants. The simulation results and the experimental results agree very well. With this knowledge, we simulate several simplified design models using FEA to obtain larger vacuum thermal time constants at room temperature, taking into account vacuum pressure, shielding layers, and support structure. We adopt the Taguchi method for shielding layer optimization and demonstrate that layer material and layer number dominate the contributions to the thermal time constant, compared with layer thickness and layer spacing.

Variations of the Solar Constant. [conference

NASA Technical Reports Server (NTRS)

Sofia, S. (Editor)

1981-01-01

The variations in data received from rocket-borne and balloon-borne instruments are discussed. Indirect techniques to measure and monitor the solar constant are presented. Emphasis is placed on the correlation of data from the Solar Maximum Mission and the Nimbus 7 satellites.

Benchmark of four popular virtual screening programs: construction of the active/decoy dataset remains a major determinant of measured performance.

PubMed

Chaput, Ludovic; Martinez-Sanz, Juan; Saettel, Nicolas; Mouawad, Liliane

2016-01-01

In a structure-based virtual screening, the choice of the docking program is essential for the success of a hit identification. Benchmarks are meant to help in guiding this choice, especially when undertaken on a large variety of protein targets. Here, the performance of four popular virtual screening programs, Gold, Glide, Surflex and FlexX, is compared using the Directory of Useful Decoys-Enhanced database (DUD-E), which includes 102 targets with an average of 224 ligands per target and 50 decoys per ligand, generated to avoid biases in the benchmarking. Then, a relationship between these program performances and the properties of the targets or the small molecules was investigated. The comparison was based on two metrics, with three different parameters each. The BEDROC scores with α = 80.5, indicated that, on the overall database, Glide succeeded (score > 0.5) for 30 targets, Gold for 27, FlexX for 14 and Surflex for 11. The performance did not depend on the hydrophobicity nor the openness of the protein cavities, neither on the families to which the proteins belong. However, despite the care in the construction of the DUD-E database, the small differences that remain between the actives and the decoys likely explain the successes of Gold, Surflex and FlexX. Moreover, the similarity between the actives of a target and its crystal structure ligand seems to be at the basis of the good performance of Glide. When all targets with significant biases are removed from the benchmarking, a subset of 47 targets remains, for which Glide succeeded for only 5 targets, Gold for 4 and FlexX and Surflex for 2. The performance dramatic drop of all four programs when the biases are removed shows that we should beware of virtual screening benchmarks, because good performances may be due to wrong reasons. Therefore, benchmarking would hardly provide guidelines for virtual screening experiments, despite the tendency that is maintained, i.e., Glide and Gold display better

Boson mapping techniques applied to constant gauge fields in QCD

NASA Technical Reports Server (NTRS)

Hess, Peter Otto; Lopez, J. C.

1995-01-01

Pairs of coordinates and derivatives of the constant gluon modes are mapped to new gluon-pair fields and their derivatives. Applying this mapping to the Hamiltonian of constant gluon fields results for large coupling constants into an effective Hamiltonian which separates into one describing a scalar field and another one for a field with spin two. The ground state is dominated by pairs of gluons coupled to color and spin zero with slight admixtures of color zero and spin two pairs. As color group we used SU(2).

The kinetics of inactivation of the rod phototransduction cascade with constant Ca2+i

PubMed Central

1996-01-01

A rich variety of mechanisms govern the inactivation of the rod phototransduction cascade. These include rhodopsin phosphorylation and subsequent binding of arrestin; modulation of rhodopsin kinase by S- modulin (recoverin); regulation of G-protein and phosphodiesterase inactivation by GTPase-activating factors; and modulation of guanylyl cyclase by a high-affinity Ca(2+)-binding protein. The dependence of several of the inactivation mechanisms on Ca2+i makes it difficult to assess the contributions of these mechanisms to the recovery kinetics in situ, where Ca2+i is dynamically modulated during the photoresponse. We recorded the circulating currents of salamander rods, the inner segments of which are held in suction electrodes in Ringer's solution. We characterized the response kinetics to flashes under two conditions: when the outer segments are in Ringer's solution, and when they are in low-Ca2+ choline solutions, which we show clamp Ca2+i very near its resting level. At T = 20-22 degrees C, the recovery phases of responses to saturating flashes producing 10(2.5)-10(4.5) photoisomerizations under both conditions are characterized by a dominant time constant, tau c = 2.4 +/- 0.4 s, the value of which is not dependent on the solution bathing the outer segment and therefore not dependent on Ca2+i. We extended a successful model of activation by incorporating into it a first-order inactivation of R*, and a first-order, simultaneous inactivation of G-protein (G*) and phosphodiesterase (PDE*). We demonstrated that the inactivation kinetics of families of responses obtained with Ca2+i clamped to rest are well characterized by this model, having one of the two inactivation time constants (tau r* or tau PDE*) equal to tau c, and the other time constant equal to 0.4 +/- 0.06 s. PMID:8741728

The Hubble Constant.

PubMed

Jackson, Neal

2007-01-01

I review the current state of determinations of the Hubble constant, which gives the length scale of the Universe by relating the expansion velocity of objects to their distance. In the last 20 years, much progress has been made and estimates now range between 60 and 75 km s -1 Mpc -1 , with most now between 70 and 75 km s -1 Mpc -1 , a huge improvement over the factor-of-2 uncertainty which used to prevail. Further improvements which gave a generally agreed margin of error of a few percent rather than the current 10% would be vital input to much other interesting cosmology. There are several programmes which are likely to lead us to this point in the next 10 years.

[Grades evaluation of Phellodendri chinensis cortex pieces based on quality constant].

PubMed

Deng, Zhe; Jiao, Meng-Jiao; Zhang, Jun; Zhang, Qing; Cui, Wen-Jin; Shen, Li; Cheng, Jin-Tang; Liu, An

2017-09-01

Quality constant is a comprehensive grades evaluation method for traditional Chinese medicine decoction pieces, which is better but based on traditional way. In this paper, a new grading mode for Phellodendri chinensis pieces was established based on quality constant evaluation method. The results showed that the range of relative quality constant for 15 batches of different samples was from 0.41 to 0.96. As customary, if these samples were divided into three grades: the relative quality constant shall be ≥0.77 for first grade; <0.77 but ≥0.48 for the second grade; and ＜0.48 for the third grade. This research indicated that the quality constant mode can be used to effectively grade the P. chinensis pieces in a scientific, reasonable, objective and specific way. Simultaneously, it provided a beneficial reference for grading cortex herbal pieces or medicines. Copyright© by the Chinese Pharmaceutical Association.

Determination of Henry’s Law Constants Using Internal Standards with Benchmark Values

EPA Science Inventory

It is shown that Henry’s law constants can be experimentally determined by comparing headspace content of compounds with known constants to interpolate the constants of other compounds. Studies were conducted over a range of water temperatures to identify temperature dependence....

Constant mean curvature slicings of Kantowski-Sachs spacetimes

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

Heinzle, J. Mark

2011-04-15

We investigate existence, uniqueness, and the asymptotic properties of constant mean curvature (CMC) slicings in vacuum Kantowski-Sachs spacetimes with positive cosmological constant. Since these spacetimes violate the strong energy condition, most of the general theorems on CMC slicings do not apply. Although there are in fact Kantowski-Sachs spacetimes with a unique CMC foliation or CMC time function, we prove that there also exist Kantowski-Sachs spacetimes with an arbitrary number of (families of) CMC slicings. The properties of these slicings are analyzed in some detail.

Optical constants of liquid and solid methane

NASA Technical Reports Server (NTRS)

Martonchik, John V.; Orton, Glenn S.

1994-01-01

The optical constants n(sub r) + in(sub i) of liquid methane and phase 1 solid methane were determined over the entire spectral range by the use of various data sources published in the literature. Kramers-Kronig analyses were performed on the absorption spectra of liquid methane at the boiling point (111 K) and the melting point (90 K) and on the absorption spectra of phase 1 solid methane at the melting point and at 30 K. Measurements of the static dielectric constant at these temperatures and refractive indices determined over limited spectral ranges were used as constraints in the analyses. Applications of methane optical properties to studies of outer solar system bodies are described.

Water Relations, Gas Exchange, and Nutrient Response to a Long Term Constant Water Deficit

NASA Technical Reports Server (NTRS)

Berry, Wade L.; Goldstein, Guillermo; Dreschel, Thomas W.; Wheeler, Raymond M.; Sager, John C.; Knott, William M.

1992-01-01

Wheat plants (Triticum aestivum) were grown for 43 days in a micro-porous tube nutrient delivery system. Roots were unable to penetrate the microporous tube, but grew on the surface and maintained capillary contact with the nutrient solution on the inside of the tube through the 5-microns pores of the porous tube. Water potential in the system was controlled at -0.4, -0.8, and -3.0 kPa by adjusting the applied pressure (hydrostatic head) to the nutrient solution flowing through the microporous tubes. A relatively small decrease in applied water potential from -0.4 to -3.0 kPa resulted in a 34% reduction of shoot growth but only a moderate reduction in the mid-day leaf water potential from - 1.3 to - 1.7 MPa. Carbon dioxide assimilation decreased and water use efficiency increased with the more negative applied water Potentials, while intercellular C02 concentration remained constant. The physiological responses observed in this study in response to small constant differences in applied water potentials were much greater than expected from either the applied water potential or the observed plant water potential. Even though the micro-porous tube may not represent natural conditions and could possibly introduce morphological and physiological artifacts , it enables a high degree of control of water potential that facilitates the investigation of many aspects of water relations not practical with other experimental systems.

In vitro and in vivo comparisons of constant resistance AC iontophoresis and DC iontophoresis.

PubMed

Li, S Kevin; Higuchi, William I; Zhu, Honggang; Kern, Steven E; Miller, David J; Hastings, Matthew S

2003-09-04

A previous in vitro constant electrical resistance alternating current (AC) iontophoresis study with human epidermal membrane (HEM) and a model neutral permeant has shown less inter- and intra-sample variability in iontophoretic transport relative to conventional constant direct current (DC) iontophoresis. The objectives of the present study were to address the following questions. (1) Can the skin electrical resistance be maintained at a constant level by AC in humans in vivo? (2) Are the in vitro data with HEM representative of those in vivo? (3) Does constant skin resistance AC iontophoresis have less inter- and intra-sample variability than conventional constant current DC iontophoresis in vivo? (4) What are the electrical and the barrier properties of skin during iontophoresis in vivo? In the present study, in vitro HEM experiments were carried out with the constant resistance AC and the conventional constant current DC methods using mannitol and glucose as the neutral model permeants. In vivo human experiments were performed using glucose as the permeant with a constant skin resistance AC only protocol and two conventional constant current DC methods (continuous constant current DC and constant current DC with its polarity alternated every 10 min with a 3:7 on:off duty cycle). Constant current DC iontophoresis was conducted with commercial constant current DC devices, and constant resistance AC iontophoresis was carried out by reducing and maintaining the skin resistance at a constant target value with AC supplied from a function generator. This study shows that (1) skin electrical resistance can be maintained at a constant level during AC iontophoresis in vivo; (2) HEM in vitro and human skin in vivo demonstrate similar electrical and barrier properties, and these properties are consistent with our previous findings; (3) there is general qualitative and semi-quantitative agreement between the HEM data in vitro and human skin data in vivo; and (4) constant

Preload-Based Starling-Like Control for Rotary Blood Pumps: Numerical Comparison with Pulsatility Control and Constant Speed Operation

PubMed Central

Mansouri, Mahdi; Salamonsen, Robert F.; Lim, Einly; Akmeliawati, Rini; Lovell, Nigel H.

2015-01-01

In this study, we evaluate a preload-based Starling-like controller for implantable rotary blood pumps (IRBPs) using left ventricular end-diastolic pressure (PLVED) as the feedback variable. Simulations are conducted using a validated mathematical model. The controller emulates the response of the natural left ventricle (LV) to changes in PLVED. We report the performance of the preload-based Starling-like controller in comparison with our recently designed pulsatility controller and constant speed operation. In handling the transition from a baseline state to test states, which include vigorous exercise, blood loss and a major reduction in the LV contractility (LVC), the preload controller outperformed pulsatility control and constant speed operation in all three test scenarios. In exercise, preload-control achieved an increase of 54% in mean pump flow (QP-) with minimum loading on the LV, while pulsatility control achieved only a 5% increase in flow and a decrease in mean pump speed. In a hemorrhage scenario, the preload control maintained the greatest safety margin against LV suction. PLVED for the preload controller was 4.9 mmHg, compared with 0.4 mmHg for the pulsatility controller and 0.2 mmHg for the constant speed mode. This was associated with an adequate mean arterial pressure (MAP) of 84 mmHg. In transition to low LVC, QP- for preload control remained constant at 5.22 L/min with a PLVED of 8.0 mmHg. With regards to pulsatility control, QP- fell to the nonviable level of 2.4 L/min with an associated PLVED of 16 mmHg and a MAP of 55 mmHg. Consequently, pulsatility control was deemed inferior to constant speed mode with a PLVED of 11 mmHg and a QP- of 5.13 L/min in low LVC scenario. We conclude that pulsatility control imposes a danger to the patient in the severely reduced LVC scenario, which can be overcome by using a preload-based Starling-like control approach. PMID:25849979

Diffusional falsification of kinetic constants on Lineweaver-Burk plots.

PubMed

Ghim, Y S; Chang, H N

1983-11-07

The effect of mass transfer resistances on the Lineweaver-Burk plots in immobilized enzyme systems has been investigated numerically and with analytical approximate solutions. While Hamilton, Gardner & Colton (1974) studied the effect of internal diffusion resistances in planar geometry, our study was extended to the combined effect of internal and external diffusion in cylindrical and spherical geometries as well. The variation of Lineweaver-Burk plots with respect to the geometries was minimized by modifying the Thiele modulus and the Biot number with the shape factor. Especially for a small Biot number all the three Lineweaver-Burk plots fell on a single line. As was discussed by Hamilton et al. (1974), the curvature of the line for large external diffusion resistances was small enough to be assumed linear, which was confirmed from the two approximate solutions for large and small substrate concentrations. Two methods for obtaining intrinsic kinetic constants were proposed: First, we obtained both maximum reaction rate and Michaelis constant by fitting experimental data to a straight line where external diffusion resistance was relatively large, and second, we obtained Michaelis constant from apparent Michaelis constant from the figure in case we knew maximum reaction rate a priori.

Josephson Metamaterial with a Widely Tunable Positive or Negative Kerr Constant

NASA Astrophysics Data System (ADS)

Zhang, Wenyuan; Huang, W.; Gershenson, M. E.; Bell, M. T.

2017-11-01

We report on the microwave characterization of a novel one-dimensional Josephson metamaterial composed of a chain of asymmetric superconducting quantum interference devices with nearest-neighbor coupling through common Josephson junctions. This metamaterial demonstrates a strong Kerr nonlinearity, with a Kerr constant tunable over a wide range, from positive to negative values, by a magnetic flux threading the superconducting quantum interference devices. The experimental results are in good agreement with the theory of nonlinear effects in Josephson chains. The metamaterial is very promising as an active medium for Josephson traveling-wave parametric amplifiers; its use facilitates phase matching in a four-wave-mixing process for efficient parametric gain.

Acoustic emission of rock mass under the constant-rate fluid injection

NASA Astrophysics Data System (ADS)

Shadrin Klishin, AV, VI

2018-03-01

The authors study acoustic emission in coal bed and difficult-to-cave roof under injection of fluid by pumps at a constant rate. The functional connection between the roof hydrofracture length and the total number of AE pulses is validated, it is also found that the coal bed hydroloosening time, injection rate and time behavior of acoustic emission activity depend on the fluid injection volume required until the fluid breakout in a roadway through growing fractures. In the formulas offered for the practical application, integral parameters that characterize permeability and porosity of rock mass and process parameters of the technology are found during test injection.

Discharge behavior of motor units in knee extensors during the initial stage of constant-force isometric contraction at low force level.

PubMed

Kamo, Mifuyu

2002-03-01

To elucidate the strategy of the activity of motor units (MUs) to maintain a constant-force isometric contraction, I examined the behavior of MUs in knee extensor muscles [(vastus medialis (VM), vastus lateralis (VL) and rectus femoris (RF)] during a sustained contraction at 5% of maximal voluntary contraction for 5 min. In all cases, the spike interval exhibited an elongating trend, and two discharge patterns were observed, continuous discharge and decruitment. In continuous-discharge MUs, the trend slope was steep immediately after the onset of constant force (steep phase), and then became gentle (gentle phase). Decruitments were observed frequently during each phase, and additional MU recruitment was observed throughout the contraction. The mean value of recruitment threshold force did not differ among the extensors. The mean spike interval at the onset of constant-force isometric contractions was shorter in RF than in VL. However, there were no differences in the duration and extent of the elongating trend, decruitment time and recruitment time among the extensors. The electromyogram of the antagonist biceps femoris muscle revealed no compensatory change for extensor activity. These results indicated that at a low force level, the strategy employed by the central nervous system to maintain constant force appears to involve cooperation among elongating trends in the spike interval, decruitment following elongation, and additional MU recruitment in synergistic muscles.

A comparison of constant-load and constant-deflection stress-corrosion tests on precracked DCB specimens. [Double Cantilever Beam

NASA Technical Reports Server (NTRS)

Dorward, R. C.; Hasse, K. R.

1978-01-01

A comparison is made between measurements of stress-corrosion crack propagation made by a constant-load procedure and by a constant-deflection procedure. Precracked double cantilever beam specimens from 7075 aluminum alloy plate were used. The specimens were oriented in such a way that cracking would begin in the short-transverse plane and would propagate in the rolling direction. The specimens were subjected to a buffered salt-chromate solution and a 3.6% synthetic sea salt solution. The measurements were made optically with a binocular microscope. Stress intensities and crack lengths were calculated and crack velocities were obtained. Velocity was plotted against the average calculated stress intensity. Good agreement between the two methods was found for the salt-chromate solution, although some descrepancies were noted for the artificial sea salt solution.

The Dependence of the Spring Constant in the Linear Range on Spring Parameters

ERIC Educational Resources Information Center

Khotimah, Siti Nurul; Viridi, Sparisoma; Widayani; Khairurrijal

2011-01-01

In basic physics laboratories, springs are normally used to determine both spring constants and the Earth's gravitational acceleration. Students generally do not notice that the spring constant is not a universal constant, but depends on the spring parameters. This paper shows and verifies that the spring constant in the linear range is inversely…

Path integration of head direction: updating a packet of neural activity at the correct speed using neuronal time constants.

PubMed

Walters, D M; Stringer, S M

2010-07-01

A key question in understanding the neural basis of path integration is how individual, spatially responsive, neurons may self-organize into networks that can, through learning, integrate velocity signals to update a continuous representation of location within an environment. It is of vital importance that this internal representation of position is updated at the correct speed, and in real time, to accurately reflect the motion of the animal. In this article, we present a biologically plausible model of velocity path integration of head direction that can solve this problem using neuronal time constants to effect natural time delays, over which associations can be learned through associative Hebbian learning rules. The model comprises a linked continuous attractor network and competitive network. In simulation, we show that the same model is able to learn two different speeds of rotation when implemented with two different values for the time constant, and without the need to alter any other model parameters. The proposed model could be extended to path integration of place in the environment, and path integration of spatial view.

Constant strain accumulation rate between major earthquakes on the North Anatolian Fault.

PubMed

Hussain, Ekbal; Wright, Tim J; Walters, Richard J; Bekaert, David P S; Lloyd, Ryan; Hooper, Andrew

2018-04-11

Earthquakes are caused by the release of tectonic strain accumulated between events. Recent advances in satellite geodesy mean we can now measure this interseismic strain accumulation with a high degree of accuracy. But it remains unclear how to interpret short-term geodetic observations, measured over decades, when estimating the seismic hazard of faults accumulating strain over centuries. Here, we show that strain accumulation rates calculated from geodetic measurements around a major transform fault are constant for its entire 250-year interseismic period, except in the ~10 years following an earthquake. The shear strain rate history requires a weak fault zone embedded within a strong lower crust with viscosity greater than ~10 20  Pa s. The results support the notion that short-term geodetic observations can directly contribute to long-term seismic hazard assessment and suggest that lower-crustal viscosities derived from postseismic studies are not representative of the lower crust at all spatial and temporal scales.

Spray Gun With Constant Mixing Ratio

NASA Technical Reports Server (NTRS)

Simpson, William G.

1987-01-01

Conceptual mechanism mounted in handle of spray gun maintains constant ratio between volumetric flow rates in two channels leading to spray head. With mechanism, possible to keep flow ratio near 1:1 (or another desired ratio) over range of temperatures, orifice or channel sizes, or clogging conditions.

Large numbers hypothesis. IV - The cosmological constant and quantum physics

NASA Technical Reports Server (NTRS)

Adams, P. J.

1983-01-01

In standard physics quantum field theory is based on a flat vacuum space-time. This quantum field theory predicts a nonzero cosmological constant. Hence the gravitational field equations do not admit a flat vacuum space-time. This dilemma is resolved using the units covariant gravitational field equations. This paper shows that the field equations admit a flat vacuum space-time with nonzero cosmological constant if and only if the canonical LNH is valid. This allows an interpretation of the LNH phenomena in terms of a time-dependent vacuum state. If this is correct then the cosmological constant must be positive.

Kny Coupling Constants and Form Factors from the Chiral Bag Model

NASA Astrophysics Data System (ADS)

Jeong, M. T.; Cheon, Il-T.

2000-09-01

The form factors and coupling constants for KNΛ and KNΣ interactions have been calculated in the framework of the Chiral Bag Model with vector mesons. Taking into account vector meson (ρ, ω, K*) field effects, we find -3.88 ≤ gKNΛ ≤ -3.67 and 1.15 ≤ gKNΣ ≤ 1.24, where the quark-meson coupling constants are determined by fitting the renormalized, πNN coupling constant, [gπNN(0)]2/4π = 14.3. It is shown that vector mesons make significant contributions to the coupling constants gKNΛ and gKNΣ. Our values are existing within the experimental limits compared to the phenomenological values extracted from the kaon photo production experiments.

Determination of magneto-optical constant of Fe films with weak measurements

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

Qiu, Xiaodong; Hu, Dejiao; Du, Jinglei

2014-09-29

In this letter, a detecting method for the magneto-optical constant is presented by using weak measurements. The photonic spin Hall effect (PSHE), which manifests itself as spin-dependent splitting, is introduced to characterize the magneto-optical constant, and a propagation model to describe the quantitative relation between the magneto-optical constant and the PSHE is established. According to the amplified shift of the PSHE detected by weak measurements, we determinate the magneto-optical constant of the Fe film sample. The Kerr rotation is measured via the standard polarimetry method to verify the rationality and feasibility of our method. These findings may provide possible applicationsmore » in magnetic physics research.« less

All That Remains of Exploded Star

NASA Image and Video Library

2011-10-24

Infrared images from NASA Spitzer Space Telescope and Wide-field Infrared Survey Explorer are combined in this image of RCW 86, the dusty remains of the oldest documented example of an exploding star, or supernova.

A two force-constant model for complexes B⋯M-X (B is a Lewis base and MX is any diatomic molecule): Intermolecular stretching force constants from centrifugal distortion constants D(J) or Δ(J).

PubMed

Bittner, Dror M; Walker, Nicholas R; Legon, Anthony C

2016-02-21

A two force-constant model is proposed for complexes of the type B⋯MX, in which B is a simple Lewis base of at least C2v symmetry and MX is any diatomic molecule lying along a Cn axis (n ≥ 2) of B. The model assumes a rigid subunit B and that force constants beyond quadratic are negligible. It leads to expressions that allow, in principle, the determination of three quadratic force constants F11, F12, and F22 associated with the r(B⋯M) = r2 and r(M-X) = r1 internal coordinates from the equilibrium centrifugal distortion constants DJ (e) or ΔJ (e), the equilibrium principal axis coordinates a1 and a2, and equilibrium principal moments of inertia. The model can be applied generally to complexes containing different types of intermolecular bond. For example, the intermolecular bond of B⋯MX can be a hydrogen bond if MX is a hydrogen halide, a halogen-bond if MX is a dihalogen molecule, or a stronger, coinage-metal bond if MX is a coinage metal halide. The equations were tested for BrCN, for which accurate equilibrium spectroscopic constants and a complete force field are available. In practice, equilibrium values of DJ (e) or ΔJ (e) for B⋯MX are not available and zero-point quantities must be used instead. The effect of doing so has been tested for BrCN. The zero-point centrifugal distortion constants DJ (0) or ΔJ (0) for all B⋯MX investigated so far are of insufficient accuracy to allow F11 and F22 to be determined simultaneously, even under the assumption F12 = 0 which is shown to be reasonable for BrCN. The calculation of F22 at a series of fixed values of F11 reveals, however, that in cases for which F11 is sufficiently larger than F22, a good approximation to F22 is obtained. Plots of F22 versus F11 have been provided for Kr⋯CuCl, Xe⋯CuCl, OC⋯CuCl, and C2H2⋯AgCl as examples. Even in cases where F22 ∼ F11 (e.g., OC⋯CuCl), such plots will yield either F22 or F11 if the other becomes available.

A two force-constant model for complexes B⋯M-X (B is a Lewis base and MX is any diatomic molecule): Intermolecular stretching force constants from centrifugal distortion constants DJ or ΔJ

NASA Astrophysics Data System (ADS)

Bittner, Dror M.; Walker, Nicholas R.; Legon, Anthony C.

2016-02-01

A two force-constant model is proposed for complexes of the type B⋯MX, in which B is a simple Lewis base of at least C2v symmetry and MX is any diatomic molecule lying along a Cn axis (n ≥ 2) of B. The model assumes a rigid subunit B and that force constants beyond quadratic are negligible. It leads to expressions that allow, in principle, the determination of three quadratic force constants F11, F12, and F22 associated with the r(B⋯M) = r2 and r(M-X) = r1 internal coordinates from the equilibrium centrifugal distortion constants DJ e or ΔJ e , the equilibrium principal axis coordinates a1 and a2, and equilibrium principal moments of inertia. The model can be applied generally to complexes containing different types of intermolecular bond. For example, the intermolecular bond of B⋯MX can be a hydrogen bond if MX is a hydrogen halide, a halogen-bond if MX is a dihalogen molecule, or a stronger, coinage-metal bond if MX is a coinage metal halide. The equations were tested for BrCN, for which accurate equilibrium spectroscopic constants and a complete force field are available. In practice, equilibrium values of DJ e or ΔJ e for B⋯MX are not available and zero-point quantities must be used instead. The effect of doing so has been tested for BrCN. The zero-point centrifugal distortion constants DJ 0 or ΔJ 0 for all B⋯MX investigated so far are of insufficient accuracy to allow F11 and F22 to be determined simultaneously, even under the assumption F12 = 0 which is shown to be reasonable for BrCN. The calculation of F22 at a series of fixed values of F11 reveals, however, that in cases for which F11 is sufficiently larger than F22, a good approximation to F22 is obtained. Plots of F22 versus F11 have been provided for Kr⋯CuCl, Xe⋯CuCl, OC⋯CuCl, and C2H2⋯AgCl as examples. Even in cases where F22 ˜ F11 (e.g., OC⋯CuCl), such plots will yield either F22 or F11 if the other becomes available.

Scanning mass spectrometry with integrated constant distance positioning

NASA Astrophysics Data System (ADS)

Li, Nan; Eckhard, Kathrin; Aßmann, Jens; Hagen, Volker; Otto, Horst; Chen, Xingxing; Schuhmann, Wolfgang; Muhler, Martin

2006-08-01

Scanning mass spectrometry is of growing importance for the characterization of catalytically active surfaces. The instrument presented here is capable of measuring catalytic activity spatially resolved by means of two concentric capillaries. The outer one is used for cofeeding reactants such as ethene and hydrogen to the sample surface, whereas the inner one is pumping off the product mixture as inlet to a quadrupole mass spectrometer. Three-dimensional measurements under stagnant-point flow conditions become possible based on a home-built capillary positioning unit. Step-motor driven positioning stages exhibiting a minimum step width of 2.5μm̸half step are used for the x, y positioning, and the step motor in z direction has a resolution of 1μm̸half step. The system is additionally equipped with a feedback loop for following the topography of the sample throughout scanning. Hence, the obtained catalytic data are unimpaired by signal changes caused by the morphology of the investigated structure. For distance control the argon ion current is used originating from externally fed argon diffusing into the confined space between the accurately positioned capillaries and the sample surface. A well-defined microchannel flow field with 400μm wide channels and 200μm wide mounds was chosen to evaluate the developed method. The catalytic activity of a Pt catalyst deposited on glassy carbon was successfully visualized in constant probe to sample distance. Simultaneously, the topography of the sample was recorded derived from the z positioning of the capillaries.

Determination of mass density, dielectric, elastic, and piezoelectric constants of bulk GaN crystal.

PubMed

Soluch, Waldemar; Brzozowski, Ernest; Lysakowska, Magdalena; Sadura, Jolanta

2011-11-01

Mass density, dielectric, elastic, and piezoelectric constants of bulk GaN crystal were determined. Mass density was obtained from the measured ratio of mass to volume of a cuboid. The dielectric constants were determined from the measured capacitances of an interdigital transducer (IDT) deposited on a Z-cut plate and from a parallel plate capacitor fabricated from this plate. The elastic and piezoelectric constants were determined by comparing the measured and calculated SAW velocities and electromechanical coupling coefficients on the Z- and X-cut plates. The following new constants were obtained: mass density p = 5986 kg/m(3); relative dielectric constants (at constant strain S) ε(S)(11)/ε(0) = 8.6 and ε(S)(11)/ε(0) = 10.5, where ε(0) is a dielectric constant of free space; elastic constants (at constant electric field E) C(E)(11) = 349.7, C(E)(12) = 128.1, C(E)(13) = 129.4, C(E)(33) = 430.3, and C(E)(44) = 96.5 GPa; and piezoelectric constants e(33) = 0.84, e(31) = -0.47, and e(15) = -0.41 C/m(2).

Simulating Supercapacitors: Can We Model Electrodes As Constant Charge Surfaces?

PubMed

Merlet, Céline; Péan, Clarisse; Rotenberg, Benjamin; Madden, Paul A; Simon, Patrice; Salanne, Mathieu

2013-01-17

Supercapacitors based on an ionic liquid electrolyte and graphite or nanoporous carbon electrodes are simulated using molecular dynamics. We compare a simplified electrode model in which a constant, uniform charge is assigned to each carbon atom with a realistic model in which a constant potential is applied between the electrodes (the carbon charges are allowed to fluctuate). We show that the simulations performed with the simplified model do not provide a correct description of the properties of the system. First, the structure of the adsorbed electrolyte is partly modified. Second, dramatic differences are observed for the dynamics of the system during transient regimes. In particular, upon application of a constant applied potential difference, the increase in the temperature, due to the Joule effect, associated with the creation of an electric current across the cell follows Ohm's law, while unphysically high temperatures are rapidly observed when constant charges are assigned to each carbon atom.

Predicting the remaining service life of concrete

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

Clifton, J.F.

1991-11-01

Nuclear power plants are providing, currently, about 17 percent of the U.S. electricity and many of these plants are approaching their licensed life of 40 years. The U.S. Nuclear Regulatory Commission and the Department of Energy`s Oak Ridge National Laboratory are carrying out a program to develop a methodology for assessing the remaining safe-life of the concrete components and structures in nuclear power plants. This program has the overall objective of identifying potential structural safety issues, as well as acceptance criteria, for use in evaluations of nuclear power plants for continued service. The National Institute of Standards and Technology (NIST)more » is contributing to this program by identifying and analyzing methods for predicting the remaining life of in-service concrete materials. This report examines the basis for predicting the remaining service lives of concrete materials of nuclear power facilities. Methods for predicting the service life of new and in-service concrete materials are analyzed. These methods include (1) estimates based on experience, (2) comparison of performance, (3) accelerated testing, (4) stochastic methods, and (5) mathematical modeling. New approaches for predicting the remaining service lives of concrete materials are proposed and recommendations for their further development given. Degradation processes are discussed based on considerations of their mechanisms, likelihood of occurrence, manifestations, and detection. They include corrosion, sulfate attack, alkali-aggregate reactions, frost attack, leaching, radiation, salt crystallization, and microbiological attack.« less

Expiratory Time Constant and Sleep Apnea Severity in the Overlap Syndrome.

PubMed

Wiriyaporn, Darunee; Wang, Lu; Aboussouan, Loutfi S

2016-03-01

Lung mechanics in the overlap of COPD and sleep apnea impact the severity of sleep apnea. Specifically, increased lung compliance with hyperinflation protects against sleep apnea, whereas increased airway resistance worsens sleep apnea. We sought to assess whether the expiratory time constant, which reflects lung mechanics, is associated with sleep apnea severity in such patients. Polysomnographies in 34 subjects with the overlap syndrome were reviewed. Three time constants were measured for each of up to 5 stages (wake, NREM stages, and REM). The time constants were derived by fitting time and pressure coordinates on the expiratory portion of a nasal pressure signal along an exponentially decaying equation, and solving for the time constant. Demographics, morphometrics, wake end-tidal CO2, right diaphragmatic arc on a chest radiograph, and the apnea-hypopnea index (AHI) were recorded. The time constant was not associated with age, gender, body mass index, right diaphragmatic arc, or wake end-tidal CO2, and was not significantly different between sleep stages. A mean time constant (TC) was therefore obtained. Subjects with a TC > 0.5 seconds had a greater AHI than those with a TC ≤ 0.5 seconds (median AHI 58 vs. 18, respectively, p = 0.003; Odds ratio of severe sleep apnea 10.6, 95% CI 3.9-51.1, p = 0.005). A larger time constant in the overlap syndrome is associated with increased odds of severe sleep apnea, suggesting a greater importance of airway resistance relative to lung compliance in sleep apnea causation in these subjects. © 2016 American Academy of Sleep Medicine.

Skin blood flow with elastic compressive extravehicular activity space suit.

PubMed

Tanaka, Kunihiko; Gotoh, Taro M; Morita, Hironobu; Hargens, Alan R

2003-10-01

During extravehicular activity (EVA), current space suits are pressurized with 100% oxygen at approximately 222 mmHg. A tight elastic garment, or mechanical counter pressure (MCP) suit that generates pressure by compression, may have several advantages over current space suit technology. In this study, we investigated local microcirculatory effects produced with negative ambient pressure with an MCP sleeve. The MCP glove and sleeve generated pressures similar to the current space suit. MCP remained constant during negative pressure due to unchanged elasticity of the material. Decreased skin capillary blood flow and temperature during MCP compression was counteracted by greater negative pressure or a smaller pressure differential.

Estimation of Anaerobic Debromination Rate Constants of PBDE Pathways Using an Anaerobic Dehalogenation Model.

PubMed

Karakas, Filiz; Imamoglu, Ipek

2017-04-01

This study aims to estimate anaerobic debromination rate constants (k m ) of PBDE pathways using previously reported laboratory soil data. k m values of pathways are estimated by modifying a previously developed model as Anaerobic Dehalogenation Model. Debromination activities published in the literature in terms of bromine substitutions as well as specific microorganisms and their combinations are used for identification of pathways. The range of estimated k m values is between 0.0003 and 0.0241 d -1 . The median and maximum of k m values are found to be comparable to the few available biologically confirmed rate constants published in the literature. The estimated k m values can be used as input to numerical fate and transport models for a better and more detailed investigation of the fate of individual PBDEs in contaminated sediments. Various remediation scenarios such as monitored natural attenuation or bioremediation with bioaugmentation can be handled in a more quantitative manner with the help of k m estimated in this study.

Silver (Ag)-Graphene oxide (GO) - Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanostructured composites with high dielectric constant and low dielectric loss

NASA Astrophysics Data System (ADS)

Moharana, Srikanta; Mahaling, Ram Naresh

2017-07-01

The Silver (Ag)-Graphene oxide (GO)-Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) composites were prepared by solution casting techniques and their dielectric properties were measured. Field emission scanning electron microscopy (FESEM) and X-ray analysis (XRD) confirmed that Ag layers were formed on the surface of the Graphene oxide sheets and homogeneously dispersed into the PVDF-HFP matrix. The result showed that the incorporation of Ag-GO nanoparticles greatly improved the dielectric constant value nearly about 65 at 100 Hz, which is comparatively much higher than that of pure PVDF-HFP. Furthermore, the dielectric loss of the composite remained at a low level (<0.1 at 100 Hz). A percolation threshold of 1.5 vol% of Ag-GO was calculated and explained accordingly. The composite having high dielectric constant and low dielectric loss might be used as dielectric materials for electronic capacitors.

The vibrational dependence of dissociative recombination: Rate constants for N{sub 2}{sup +}

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

Guberman, Steven L., E-mail: slg@sci.org

Dissociative recombination rate constants are reported with electron temperature dependent uncertainties for the lowest 5 vibrational levels of the N{sub 2}{sup +} ground state. The rate constants are determined from ab initio calculations of potential curves, electronic widths, quantum defects, and cross sections. At 100 K electron temperature, the rate constants overlap with the exception of the third vibrational level. At and above 300 K, the rate constants for excited vibrational levels are significantly smaller than that for the ground level. It is shown that any experimentally determined total rate constant at 300 K electron temperature that is smaller thanmore » 2.0 × 10{sup −7} cm{sup 3}/s is likely to be for ions that have a substantially excited vibrational population. Using the vibrational level specific rate constants, the total rate constant is in very good agreement with that for an excited vibrational distribution found in a storage ring experiment. It is also shown that a prior analysis of a laser induced fluorescence experiment is quantitatively flawed due to the need to account for reactions with unknown rate constants. Two prior calculations of the dissociative recombination rate constant are shown to be inconsistent with the cross sections upon which they are based. The rate constants calculated here contribute to the resolution of a 30 year old disagreement between modeled and observed N{sub 2}{sup +} ionospheric densities.« less

Clinical Course of Homozygous Hemoglobin Constant Spring in Pediatric Patients.

PubMed

Komvilaisak, Patcharee; Jetsrisuparb, Arunee; Fucharoen, Goonnapa; Komwilaisak, Ratana; Jirapradittha, Junya; Kiatchoosakun, Pakaphan

2018-04-17

Hemoglobin (Hb) Constant Spring is an alpha-globin gene variant due to a mutation of the stop codon resulting in the elongation of the encoded polypeptide from 141 to 172 amino acid residues. Patients with homozygous Hb Constant Spring are usually mildly anemic. We retrospectively describe clinical manifestations, diagnosis, laboratory investigations, treatment, and associated findings in pediatric patients with homozygous Hb Constant Spring followed-up at Srinagarind Hospital. Sixteen pediatric cases (5 males and 11 females) were diagnosed in utero (N=6) or postnatal (n=10). Eleven cases were diagnosed with homozygous Hb Constant Spring, 4 with homozygous Hb Constant Spring with heterozygous Hb E, and 1 with homozygous Hb Constant Spring with homozygous Hb E. Three cases were delivered preterm. Six patients had low birth weights. Clinical manifestations included fetal anemia in 6 cases, hepatomegaly in 1 case, hepatosplenomegaly in 2 cases, splenomegaly in 1 case. Twelve cases exhibited early neonatal jaundice, 9 of which required phototherapy. Six cases received red cell transfusions; 1 (3), >1 (3). After the first few months of life, almost all patients had mild microcytic hypochromic anemia and an increased reticulocyte count with a wide red cell distribution (RDW), but no longer required red cell transfusion. At 1 to 2 years of age, some patients still had mild microcytic hypochromic anemia and some had normocytic hypochromic anemia with Hb around 10 g/dL, increased reticulocyte count and wide RDW. Associated findings included hypothyroidism (2), congenital heart diseases (4), genitourinary abnormalities (3), gastrointestinal abnormalities (2), and developmental delay (1). Pediatric patients with homozygous Hb Constant Spring developed severe anemia in utero and up to the age of 2 to 3 months postnatal, requiring blood transfusions. Subsequently, their anemia was mild with no evidence of hepatosplenomegaly. Their Hb level was above 9 g/dL with hypochromic

Dielectric Anistropy and Elastic Constants Near the Nematic-Smectic A Transition

NASA Astrophysics Data System (ADS)

Visco, Angelo; Mahmood, Rizwan; Zapien, Donald

The present work examines the behavior of dielectric anisotropy and the elastic constants associated with the deformation of liquid crystal molecules under the influence of an AC electric field and measured by an Automatic Liquid Crystal Tester (ALCT). The systems investigated are of various concentrations of 5CB (4-Cyano-4'-pentylbiphenyl) and 8CB (4-octyl-4'-cyanobiphenyl) liquid crystal as a function of temperature. These studies are important due to the complexity of the coupling between the orientational (nematic) and positional (smectic A) order parameters that can drive this transition to be either continuous or discontinuous. Theoretically, NA transition is weakly first order due to nematic director fluctuations in semctic A phase. This is similar to the transition from normal to superconductor. Thus, there exists a triple point similar to He3/He4 mixtures. Moreover, despite more than four decades of intense work, our understanding of this complex and interesting problem remains unclear. The funding for the project was provided by Slippery Rock University (2015-2016).

21 CFR 1250.85 - Drinking fountains and coolers; ice; constant temperature bottles.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Drinking fountains and coolers; ice; constant... Drinking fountains and coolers; ice; constant temperature bottles. (a) Drinking fountains and coolers shall... prevent backflow. (b) Ice shall not be permitted to come in contact with water in coolers or constant...

21 CFR 1250.85 - Drinking fountains and coolers; ice; constant temperature bottles.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Drinking fountains and coolers; ice; constant... Drinking fountains and coolers; ice; constant temperature bottles. (a) Drinking fountains and coolers shall... prevent backflow. (b) Ice shall not be permitted to come in contact with water in coolers or constant...

21 CFR 1250.85 - Drinking fountains and coolers; ice; constant temperature bottles.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Drinking fountains and coolers; ice; constant... Drinking fountains and coolers; ice; constant temperature bottles. (a) Drinking fountains and coolers shall... prevent backflow. (b) Ice shall not be permitted to come in contact with water in coolers or constant...

21 CFR 1250.85 - Drinking fountains and coolers; ice; constant temperature bottles.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Drinking fountains and coolers; ice; constant... Drinking fountains and coolers; ice; constant temperature bottles. (a) Drinking fountains and coolers shall... prevent backflow. (b) Ice shall not be permitted to come in contact with water in coolers or constant...

21 CFR 1250.85 - Drinking fountains and coolers; ice; constant temperature bottles.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Drinking fountains and coolers; ice; constant... Drinking fountains and coolers; ice; constant temperature bottles. (a) Drinking fountains and coolers shall... prevent backflow. (b) Ice shall not be permitted to come in contact with water in coolers or constant...

A design study for a simple-to-fly, constant attitude light aircraft

NASA Technical Reports Server (NTRS)

Smetana, F. O.; Humphreys, D. E.; Montoya, R. J.; Rickard, W. W.; Wilkinson, I. E.

1973-01-01

The activities during a four-year study by doctoral students to evolve in detail a design for a simple-to-fly, constant attitude light airplane are described. The study indicated that such aircraft could materially reduce the hazards to light airplane occupants which arise from the high pilot work load and poor visibility that occur during landing. Preliminary cost studies indicate that in volume production this system would increase the cost of the aircraft in roughly the same fashion that automatic transmission, power steering, power brakes, and cruise control increase the cost of a compact car.

49 CFR 845.51 - Investigation to remain open.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 7 2010-10-01 2010-10-01 false Investigation to remain open. 845.51 Section 845... § 845.51 Investigation to remain open. Accident investigations are never officially closed but are kept open for the submission of new and pertinent evidence by any interested person. If the Board finds that...

49 CFR 845.51 - Investigation to remain open.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 7 2011-10-01 2011-10-01 false Investigation to remain open. 845.51 Section 845... § 845.51 Investigation to remain open. Accident investigations are never officially closed but are kept open for the submission of new and pertinent evidence by any interested person. If the Board finds that...

49 CFR 845.51 - Investigation to remain open.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 7 2013-10-01 2013-10-01 false Investigation to remain open. 845.51 Section 845... § 845.51 Investigation to remain open. Accident investigations are never officially closed but are kept open for the submission of new and pertinent evidence by any interested person. If the Board finds that...

49 CFR 845.51 - Investigation to remain open.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 7 2012-10-01 2012-10-01 false Investigation to remain open. 845.51 Section 845... § 845.51 Investigation to remain open. Accident investigations are never officially closed but are kept open for the submission of new and pertinent evidence by any interested person. If the Board finds that...

49 CFR 845.51 - Investigation to remain open.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 7 2014-10-01 2014-10-01 false Investigation to remain open. 845.51 Section 845... § 845.51 Investigation to remain open. Accident investigations are never officially closed but are kept open for the submission of new and pertinent evidence by any interested person. If the Board finds that...

The impact of inter-fraction dose variations on biological equivalent dose (BED): the concept of equivalent constant dose.

PubMed

Zavgorodni, S

2004-12-07

Inter-fraction dose fluctuations, which appear as a result of setup errors, organ motion and treatment machine output variations, may influence the radiobiological effect of the treatment even when the total delivered physical dose remains constant. The effect of these inter-fraction dose fluctuations on the biological effective dose (BED) has been investigated. Analytical expressions for the BED accounting for the dose fluctuations have been derived. The concept of biological effective constant dose (BECD) has been introduced. The equivalent constant dose (ECD), representing the constant physical dose that provides the same cell survival fraction as the fluctuating dose, has also been introduced. The dose fluctuations with Gaussian as well as exponential probability density functions were investigated. The values of BECD and ECD calculated analytically were compared with those derived from Monte Carlo modelling. The agreement between Monte Carlo modelled and analytical values was excellent (within 1%) for a range of dose standard deviations (0-100% of the dose) and the number of fractions (2 to 37) used in the comparison. The ECDs have also been calculated for conventional radiotherapy fields. The analytical expression for the BECD shows that BECD increases linearly with the variance of the dose. The effect is relatively small, and in the flat regions of the field it results in less than 1% increase of ECD. In the penumbra region of the 6 MV single radiotherapy beam the ECD exceeded the physical dose by up to 35%, when the standard deviation of combined patient setup/organ motion uncertainty was 5 mm. Equivalently, the ECD field was approximately 2 mm wider than the physical dose field. The difference between ECD and the physical dose is greater for normal tissues than for tumours.

Determination of stability constants of aminoglycoside antibiotics with their metal complexes

NASA Astrophysics Data System (ADS)

Tiwow, Vanny M. A.

2014-03-01

One group of aminoglycoside antibiotics contains aminosugars. The aminosugar neomycin B with its derivate product neamine (2-Deoxy-4-0-(2,6-diamino-2,6-dideoxy-α-D-glucopyranosyl)-D-Streptamine) was identified as a free ligands and metal complexes. In particular, the stability constants of metal complexes by potentiometric titration techniques were investigated. Our previous study had determined the acid dissociation constants of these aminosugars with few metal complexes in fair depth. In this work, the complexation of two pyridine-containing amino alcohols and an amino sugar (neamine) have been measured potentiometrically. For instance, the stability constant of copper(II) complexation were determine and the model system generated an excellent fit. Stability constants with several metals have been determined and will be reported.

Paramecia Swim with a constant propulsion in Solutions of Varying Viscosity

NASA Astrophysics Data System (ADS)

Valles, James M., Jr.; Jung, Ilyong; Mickalide, Harry; Park, Hojin; Powers, Thomas

2012-02-01

Paramecia swim through the coordinated beating of the 1000's of cilia covering their body. We have measured the swimming speed of populations of Paramecium Caudatam in solutions of different viscosity, η, to see how their propulsion changes with increased drag. We have found the average instantaneous speed, V to decrease monotonically with increasing η. The product ηv is roughly constant over a factor of 7 change in viscosity suggesting that paramecia swim at constant propulsion force. The distribution of swimming speeds is Gaussian. The width appears proportional to the average speed implying that both fast and slow swimmers exert a constant propulsion. We discuss the possibility that this behavior implies that the body cilia beat at constant force with varying viscosity.

Sub-Micrometer Zeolite Films on Gold-Coated Silicon Wafers with Single-Crystal-Like Dielectric Constant and Elastic Modulus

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

Tiriolo, Raffaele; Rangnekar, Neel; Zhang, Han

A low-temperature synthesis coupled with mild activation produces zeolite films exhibiting low dielectric constant (low-k) matching the theoretically predicted and experimentally measured values for single crystals. This synthesis and activation method allows for the fabrication of a device consisting of a b-oriented film of the pure-silica zeolite MFI (silicalite-1) supported on a gold-coated silicon wafer. The zeolite seeds are assembled by a manual assembly process and subjected to optimized secondary growth conditions that do not cause corrosion of the gold underlayer, while strongly promoting in-plane growth. The traditional calcination process is replaced with a non-thermal photochemical activation to ensure preservationmore » of an intact gold layer. The dielectric constant (k), obtained through measurement of electrical capacitance in a metal-insulator-metal configuration, highlights the ultralow k approximate to 1.7 of the synthetized films, which is among the lowest values reported for an MFI film. There is large improvement in elastic modulus of the film (E approximate to 54 GPa) over previous reports, potentially allowing for integration into silicon wafer processing technology.« less

Solution Strategies for Constant Acceleration Problems

ERIC Educational Resources Information Center

Wheaton, S. M.; Binder, P.-M.

2017-01-01

We discuss strategies for the general solution of single-step 1D constant acceleration problems. In a slightly restricted form, these problems have five variables (?"x," "v[subscript 0]," "v," "a" and "t") and two independent equations, so three variables must be given to solve for the other two,…

Tunneling Rate Constants for H2CO+H on Amorphous Solid Water Surfaces

NASA Astrophysics Data System (ADS)

Song, Lei; Kästner, Johannes

2017-12-01

Formaldehyde (H2CO) is one of the most abundant molecules observed in the icy mantle covering interstellar grains. Studying its evolution can contribute to our understanding of the formation of complex organic molecules in various interstellar environments. In this work, we investigated the hydrogenation reactions of H2CO yielding CH3O, CH2OH, and the hydrogen abstraction resulting in H2+HCO on an amorphous solid water (ASW) surface using a quantum mechanics/molecular mechanics (QM/MM) model. The binding energies of H2CO on the ASW surface vary broadly, from 1000 to 9370 K. No correlation was found between binding energies and activation energies of hydrogenation reactions. Combining instanton theory with QM/MM modeling, we calculated rate constants for the Langmuir-Hinshelwood and the Eley-Rideal mechanisms for the three product channels of H+H2CO surface reactions down to 59 K. We found that the channel producing CH2OH can be ignored, owing to its high activation barrier leading to significantly lower rates than the other two channels. The ASW surface influences the reactivity in favor of formation of CH3O (branching ratio ˜80%) and hinders the H2CO dissociation into H2+HCO. In addition, kinetic isotope effects are strong in all reaction channels and vary strongly between the channels. Finally, we provide fits of the rate constants to be used in astrochemical models.

Gravity with free initial conditions: A solution to the cosmological constant problem testable by CMB B -mode polarization

NASA Astrophysics Data System (ADS)

Totani, Tomonori

2017-10-01

In standard general relativity the universe cannot be started with arbitrary initial conditions, because four of the ten components of the Einstein's field equations (EFE) are constraints on initial conditions. In the previous work it was proposed to extend the gravity theory to allow free initial conditions, with a motivation to solve the cosmological constant problem. This was done by setting four constraints on metric variations in the action principle, which is reasonable because the gravity's physical degrees of freedom are at most six. However, there are two problems about this theory; the three constraints in addition to the unimodular condition were introduced without clear physical meanings, and the flat Minkowski spacetime is unstable against perturbations. Here a new set of gravitational field equations is derived by replacing the three constraints with new ones requiring that geodesic paths remain geodesic against metric variations. The instability problem is then naturally solved. Implications for the cosmological constant Λ are unchanged; the theory converges into EFE with nonzero Λ by inflation, but Λ varies on scales much larger than the present Hubble horizon. Then galaxies are formed only in small Λ regions, and the cosmological constant problem is solved by the anthropic argument. Because of the increased degrees of freedom in metric dynamics, the theory predicts new non-oscillatory modes of metric anisotropy generated by quantum fluctuation during inflation, and CMB B -mode polarization would be observed differently from the standard predictions by general relativity.

Polarographic determination of lead hydroxide formation constants at low ionic strength

USGS Publications Warehouse

Lind, Carol J.

1978-01-01

Values of formation constants for lead hydroxide at 25 ??C were calculated from normal pulse polarographic measurements of 10-6 M lead in 0.01 M sodium perchlorate. The low concentrations simulate those found in many freshwaters, permitting direct application of the values when considering distributions of lead species. The precise evaluation of species distribution in waters at other ionic strengths requires activity coefficient corrections. As opposed to much of the previously published work done at high ionic strength, the values reported here were obtained at low ionic strength, permitting use of smaller and better defined activity coefficient corrections. These values were further confirmed by differential-pulse polarography and differential-pulse anodic stripping voltammetry data. The logs of the values for ??1??? ??2???, and ??3??? were calculated to be 6.59, 10.80, and 13.63, respectively. When corrected to zero ionic strength these values were calculated to be 6.77, 11.07, and 13.89, respectively.

Receptor trafficking via the perinuclear recycling compartment accompanied by cell division is necessary for permanent neurotensin cell sensitization and leads to chronic mitogen-activated protein kinase activation.

PubMed

Toy-Miou-Leong, Mireille; Cortes, Catherine Llorens; Beaudet, Alain; Rostène, William; Forgez, Patricia

2004-03-26

Most G protein-coupled receptors are internalized after interaction with their respective ligand, a process that subsequently contributes to cell desensitization, receptor endocytosis, trafficking, and finally cell resensitization. Although cellular mechanisms leading to cell desensitization have been widely studied, those responsible for cell resensitization are still poorly understood. We examined here the traffic of the high affinity neurotensin receptor (NT1 receptor) following prolonged exposure to high agonist concentration. Fluorescence and confocal microscopy of Chinese hamster ovary, human neuroblastoma (CHP 212), and murine neuroblastoma (N1E-115) cells expressing green fluorescent protein-tagged NT1 receptor revealed that under prolonged treatment with saturating concentrations of neurotensin (NT) agonist, NT1 receptor and NT transiently accumulated in the perinuclear recycling compartment (PNRC). During this cellular event, cell surface receptors remained markedly depleted as detected by both confocal microscopy and (125)I-NT binding assays. In dividing cells, we observed that following prolonged NT agonist stimulation, NT1 receptors were removed from the PNRC, accumulated in dispersed vesicles inside the cytoplasm, and subsequently reappeared at the cell surface. This NT binding recovery allowed for constant cell sensitization and led to a chronic activation of mitogen-activated protein kinases p42 and p44. Under these conditions, the constant activation of NT1 receptor generates an oncogenic regulation. These observations support the potent role for neuropeptides, such as NT, in cancer progression.

Sizzling Remains of a Dead Star

NASA Image and Video Library

2013-01-07

This new view of the historical supernova remnant Cassiopeia A, located 11,000 light-years away, was taken by NASA Nuclear Spectroscopic Telescope Array, or NuSTAR. While the star is long dead, its remains are still bursting with action.

Oxidation of CO by N/sub 2/O between 1076 and 1228 K: determination of the rate constant of the exchange reaction

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

Loirat, H.; Caralp, F.; Destriau, M.

New measurements of the rate constant of the direct reaction of CO with N/sub 2/O are reported with the principal purpose of removing some of the remaining discrepancies on its value. Experiments were performed at lower temperatures (1076-1228 K) and lower pressure (approx. 15 Torr) than those prevailing in most of previous works, by using a static reactor. It is shown that, under these experimental conditions, the reaction proceeds essentially according to the direct reaction CO + N/sub 2/O ..-->.. CO/sub 2/ + N/sub 2/ (1). The previously proposed wet mechanism is not significant under our experimental conditions. It hasmore » to be taken into account, however, to describe the observed production and consumption of molecular oxygen. The Arrhenius expression derived from these experiments is k/sub 1/ = 10/sup 14.4 +/- 0.3 exp(-(46 +- 2) kcal mol/sup -1/RT) cm/sup 3/ mol/sup -1/ s/sup -1/. A detailed analysis of the results shows that the uncertainties in side reactions do not greatly influence the value of k/sub 1/. A critical discussion of the data reported in the literature is presented. In spite of remaining uncertainties in the reaction mechanism, the present results, obtained in a low-temperature range, show that the low activation energy values of reaction 1, reported in several works performed at higher temperatures, are highly unlikely« less

Dielectric constants of soils at microwave frequencies-2

NASA Technical Reports Server (NTRS)

Wang, J.; Schmugge, T.; Williams, D.

1978-01-01

The dielectric constants of several soil samples were measured at frequencies of 5 and 19 GHz using the infinite transmission line method. The results of these measurements are presented and discussed with respect to soil types and texture structures. A comparison is made with other measurements at 1.4 GHz. At all three frequencies, the dependence of dielectric constant on soil moisture can be approximated by two straight lines. At low moisture, the slope is less than at high moisture level. The intersection of the two lines is believed to be a function of soil texture.

Newman-Penrose constants of the Kerr-Newman metric

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

Gong Xuefei; Shang Yu; Bai Shan

The Newman-Unti formalism of the Kerr-Newman metric near future null infinity is developed, with which the Newman-Penrose constants for both the gravitational and electromagnetic fields of the Kerr-Newman metric are computed and shown to be zero. The multipole structure near future null infinity in the sense of Janis-Newman of the Kerr-Newman metric is then further studied. It is found that up to the 2{sup 4}-pole, modulo a constant dependent upon the order of the pole, these multipole moments agree with those of Geroch-Hansen multipole moments defined at spatial infinity.

Living Clusters and Crystals from Low-Density Suspensions of Active Colloids

NASA Astrophysics Data System (ADS)

Mognetti, B. M.; Šarić, A.; Angioletti-Uberti, S.; Cacciuto, A.; Valeriani, C.; Frenkel, D.

2013-12-01

Recent studies aimed at investigating artificial analogs of bacterial colonies have shown that low-density suspensions of self-propelled particles confined in two dimensions can assemble into finite aggregates that merge and split, but have a typical size that remains constant (living clusters). In this Letter, we address the problem of the formation of living clusters and crystals of active particles in three dimensions. We study two systems: self-propelled particles interacting via a generic attractive potential and colloids that can move toward each other as a result of active agents (e.g., by molecular motors). In both cases, fluidlike “living” clusters form. We explain this general feature in terms of the balance between active forces and regression to thermodynamic equilibrium. This balance can be quantified in terms of a dimensionless number that allows us to collapse the observed clustering behavior onto a universal curve. We also discuss how active motion affects the kinetics of crystal formation.

Imaging performance of an isotropic negative dielectric constant slab.

PubMed

Shivanand; Liu, Huikan; Webb, Kevin J

2008-11-01

The influence of material and thickness on the subwavelength imaging performance of a negative dielectric constant slab is studied. Resonance in the plane-wave transfer function produces a high spatial frequency ripple that could be useful in fabricating periodic structures. A cost function based on the plane-wave transfer function provides a useful metric to evaluate the planar slab lens performance, and using this, the optimal slab dielectric constant can be determined.

PEGylated nanomedicines: recent progress and remaining concerns.

PubMed

Vllasaliu, Driton; Fowler, Robyn; Stolnik, Snow

2014-01-01

Recent biopharma deals related to nanocarrier drug delivery technologies highlight the emergence of nanomedicine. This is perhaps an expected culmination of many years of research demonstrating the potential of nanomedicine as the next generation of therapeutics with improved performance. PEGylated nanocarriers play a key role within this field. The drug delivery advantages of nanomedicines in general are discussed, focusing on nanocarriers and PEGylated nanomedicines, including products under current development/clinical evaluation. Well-established drug delivery benefits of PEGylation (e.g., prolonged circulation) are only briefly covered. Instead, attention is deliberately made to less commonly reported advantages of PEGylation, including mucosal delivery of nanomedicines. Finally, some of the issues related to the safety of PEGylated nanomedicines in clinical application are discussed. The advent of nanomedicine providing therapeutic options of refined performance continues. Although PEGylation as a tool to improve the pharmacokinetics of nanomedicines is well established and is used clinically, other benefits of 'PEGnology', including enhancement of physicochemical properties and/or biocompatibility of actives and/or drug carriers, as well as mucosal delivery, have attracted less attention. While concerns regarding the clinical use of PEGylated nanomedicines remain, evidence suggests that at least some safety issues may be controlled by adequate designs of nanosystems.

Repatriation of human remains following death in international travellers.

PubMed

Connolly, Ruairi; Prendiville, Richard; Cusack, Denis; Flaherty, Gerard

2017-03-01

Death during international travel and the repatriation of human remains to one's home country is a distressing and expensive process. Much organization is required involving close liaison between various agencies. A review of the literature was conducted using the PubMed database. Search terms included: 'repatriation of remains', 'death', 'abroad', 'tourism', 'travel', 'travellers', 'travelling' and 'repatriation'. Additional articles were obtained from grey literature sources and reference lists. The local national embassy, travel insurance broker and tour operator are important sources of information to facilitate the repatriation of the deceased traveller. Formal identification of the deceased's remains is required and a funeral director must be appointed. Following this, the coroner in the country or jurisdiction receiving the repatriated remains will require a number of documents prior to providing clearance for burial. Costs involved in repatriating remains must be borne by the family of the deceased although travel insurance may help defray some of the costs. If the death is secondary to an infectious disease, cremation at the site of death is preferred. No standardized procedure is in place to deal with the remains of a migrant's body at present and these remains are often not repatriated to their country of origin. Repatriation of human remains is a difficult task which is emotionally challenging for the bereaving family and friends. As a travel medicine practitioner, it is prudent to discuss all eventualities, including the risk of death, during the pre-travel consultation. Awareness of the procedures involved in this process may ease the burden on the grieving family at a difficult time. © International Society of Travel Medicine, 2017. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

Teaching Nanochemistry: Madelung Constants of Nanocrystals

ERIC Educational Resources Information Center

Baker, Mark D.; Baker, A. David

2010-01-01

The Madelung constants for binary ionic nanoparticles are determined. The computational method described here sums the Coulombic interactions of each ion in the particle without the use of partial charges commonly used for bulk materials. The results show size-dependent lattice energies. This is a useful concept in teaching how properties such as…

Unruh thermal hadronization and the cosmological constant

NASA Astrophysics Data System (ADS)

Frassino, Antonia M.; Bleicher, Marcus; Mann, Robert B.

2018-05-01

We use black holes with a negative cosmological constant to investigate aspects of the freeze-out temperature for hadron production in high energy heavy-ion collisions. The two black hole solutions present in the anti-de Sitter geometry have different mass and are compared to the data showing that the small black hole solution is in good agreement. This is a new feature in the literature since the small black hole in general relativity has different thermodynamic behavior from that of the large black hole solution. We find that the inclusion of the cosmological constant (which can be interpreted as the plasma pressure) leads to a lowering of the temperature of the freeze-out curve as a function of the baryochemical potential, improving the description previously suggested by Castorina, Kharzeev, and Satz.

Remaining questions about clinical variola major.

PubMed

Lane, J Michael

2011-04-01

After the recent summary of World Health Organization-authorized research on smallpox, several clinical issues remain. This policy review addresses whether early hemorrhagic smallpox is disseminated intravascular coagulation and speculates about the cause of the high mortality rate among pregnant women and whether ocular smallpox is partly the result of trachoma or vitamin A deficiency. The joint destruction common in children with smallpox might be prevented by antiviral drugs, but intraarticular infusion of antiviral drugs is unprecedented. Development of highly effective antiviral drugs against smallpox raises the issue of whether postexposure vaccination can be performed without interference by an antiviral drug. Clinicians should consider whether patients with smallpox should be admitted to general hospitals. Although an adequate supply of second-generation smallpox vaccine exists in the United States, its use is unclear. Finally, political and ethical forces suggest that destruction of the remaining stocks of live smallpox virus is now appropriate.

A New Contribution for WYP 2005: The Golden Ratio, Bohr Radius, Planck's Constant, Fine-Structure Constant and g-Factors

NASA Astrophysics Data System (ADS)

Heyrovska, R.; Narayan, S.

2005-10-01

Recently, the ground state Bohr radius (aB) of hydrogen was shown to be divided into two Golden sections, aB,p = aB/ø2 and aB,e = aB/ø at the point of electrical neutrality, where ø = 1.618 is the Golden ratio (R. Heyrovska, Molecular Physics 103: 877-882, and the literature cited therein). The origin of the difference of two energy terms in the Rydberg equation was thus shown to be in the ground state energy itself, as shown below: EH = (1/2)e2/(κaB) = (1/2)(e2/κ) [(1/aB,p - (1/aB,e)] (1). This work brings some new results that 1) a unit charge in vacuum has a magnetic moment, 2) (e2/2κ) in eq. (1) is an electromagnetic condenser constant, 3) the de Broglie wavelengths of the proton and electron correspond to the Golden arcs of a circle with the Bohr radius, 4) the fine structure constant (α) is the ratio of the Planck's constants without and with the interaction of light with matter, 5) the g-factors of the electron and proton, ge/2 and gp/2 divide the Bohr radius at the magnetic center and 6) the ``mysterious'' value (137.036) of α -1 = (360/ø2) - (2/ø3), where (2/ø3) arises from the difference, (gp - ge).

The effects of capillary forces on the axisymmetric propagation of two-phase, constant-flux gravity currents in porous media

NASA Astrophysics Data System (ADS)

Golding, Madeleine J.; Huppert, Herbert E.; Neufeld, Jerome A.

2013-03-01

The effects of capillary forces on the propagation of two-phase, constant-flux gravity currents in a porous medium are studied analytically and numerically in an axisymmetric geometry. The fluid within a two-phase current generally only partially saturates the pore space it invades. For long, thin currents, the saturation distribution is set by the vertical balance between gravitational and capillary forces. The capillary pressure and relative permeability of the fluid in the current depend on this saturation. The action of capillary forces reduces the average saturation, thereby decreasing the relative permeability throughout the current. This results in a thicker current, which provides a steeper gradient to drive flow, and a more blunt-nose profile. The relative strength of gravity and capillary forces remains constant within a two-phase gravity current fed by a constant flux and spreading radially, due to mass conservation. For this reason, we use an axisymmetric representation of the framework developed by Golding et al. ["Two-phase gravity currents in porous media," J. Fluid Mech. 678, 248-270 (2011)], 10.1017/jfm.2011.110, to investigate the effect on propagation of varying the magnitude of capillary forces and the pore-size distribution. Scaling analysis indicates that axisymmetric two-phase gravity currents fed by a constant flux propagate like t1/2, similar to their single-phase counterparts [S. Lyle, H. E. Huppert, M. Hallworth, M. Bickle, and A. Chadwick, "Axisymmetric gravity currents in a porous medium," J. Fluid Mech. 543, 293-302 (2005)], 10.1017/S0022112005006713, with the effects of capillary forces encapsulated in the constant of proportionality. As a practical application of our new concepts and quantitative evaluations, we discuss the implications of our results for the process of carbon dioxide (CO2) sequestration, during which gravity currents consisting of supercritical CO2 propagate in rock saturated with aqueous brine. We apply our two

Remaining Useful Life Estimation in Prognosis: An Uncertainty Propagation Problem

NASA Technical Reports Server (NTRS)

Sankararaman, Shankar; Goebel, Kai

2013-01-01

The estimation of remaining useful life is significant in the context of prognostics and health monitoring, and the prediction of remaining useful life is essential for online operations and decision-making. However, it is challenging to accurately predict the remaining useful life in practical aerospace applications due to the presence of various uncertainties that affect prognostic calculations, and in turn, render the remaining useful life prediction uncertain. It is challenging to identify and characterize the various sources of uncertainty in prognosis, understand how each of these sources of uncertainty affect the uncertainty in the remaining useful life prediction, and thereby compute the overall uncertainty in the remaining useful life prediction. In order to achieve these goals, this paper proposes that the task of estimating the remaining useful life must be approached as an uncertainty propagation problem. In this context, uncertainty propagation methods which are available in the literature are reviewed, and their applicability to prognostics and health monitoring are discussed.

Constant light disrupts the circadian rhythm of steroidogenic proteins in the rat adrenal gland.

PubMed

Park, Shin Y; Walker, Jamie J; Johnson, Nicholas W; Zhao, Zidong; Lightman, Stafford L; Spiga, Francesca

2013-05-22

The circadian rhythm of corticosterone (CORT) secretion from the adrenal cortex is regulated by the suprachiasmatic nucleus (SCN), which is entrained to the light-dark cycle. Since the circadian CORT rhythm is associated with circadian expression of the steroidogenic acute regulatory (StAR) protein, we investigated the 24h pattern of hormonal secretion (ACTH and CORT), steroidogenic gene expression (StAR, SF-1, DAX1 and Nurr77) and the expression of genes involved in ACTH signalling (MC2R and MRAP) in rats entrained to a normal light-dark cycle. We found that circadian changes in ACTH and CORT were associated with the circadian expression of all gene targets; with SF-1, Nurr77 and MRAP peaking in the evening, and DAX1 and MC2R peaking in the morning. Since disruption of normal SCN activity by exposure to constant light abolishes the circadian rhythm of CORT in the rat, we also investigated whether the AM-PM variation of our target genes was also disrupted in rats exposed to constant light conditions for 5weeks. We found that the disruption of the AM-PM variation of ACTH and CORT secretion in rats exposed to constant light was accompanied by a loss of AM-PM variation in StAR, SF-1 and DAX1, and a reversed AM-PM variation in Nurr77, MC2R and MRAP. Our data suggest that circadian expression of StAR is regulated by the circadian expression of nuclear receptors and proteins involved in both ACTH signalling and StAR transcription. We propose that ACTH regulates the secretion of CORT via the circadian control of steroidogenic gene pathways that become dysregulated under the influence of constant light. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Large-scale patterns formed by solar active regions during the ascending phase of cycle 21

NASA Astrophysics Data System (ADS)

Gaizauskas, V.; Harvey, K. L.; Harvey, J. W.; Zwaan, C.

1983-02-01

Synoptic maps of photospheric magnetic fields prepared at the Kitt Peak National Observatory are used in investigating large-scale patterns in the spatial and temporal distribution of solar active regions for 27 solar rotations between 1977 and 1979. The active regions are found to be distributed in 'complexes of activity' (Bumba and Howard, 1965). With the working definition of a complex of activity based on continuity and proximity of the constituent active regions, the phenomenology of complexes is explored. It is found that complexes of activity form within one month and that they are typically maintained for 3 to 6 solar rotations by fresh injections of magnetic flux. During the active lifetime of a complex of activity, the total magnetic flux in the complex remains steady to within a factor of 2. The magnetic polarities are closely balanced, and each complex rotates about the sun at its own special, constant rate. In certain cases, the complexes form two diverging branches.

Air-Liquid Partition Coefficient for a Diverse Set of Organic Compounds: Henry’s Law Constant in Water and Hexadecane

EPA Science Inventory

The SPARC vapor pressure and activity coefficient models were coupled to estimate Henry’s Law Constant (HLC) in water and in hexadecane for a wide range of non-polar and polar solute organic compounds without modification to/or additional parameterization of the vapor pressure or...

Measurement of Setschenow constants for six hydrophobic compounds in simulated brines and use in predictive modeling for oil and gas systems.

PubMed

Burant, Aniela; Lowry, Gregory V; Karamalidis, Athanasios K

2016-02-01

Treatment and reuse of brines, produced from energy extraction activities, requires aqueous solubility data for organic compounds in saline solutions. The presence of salts decreases the aqueous solubility of organic compounds (i.e. salting-out effect) and can be modeled using the Setschenow Equation, the validity of which has not been assessed in high salt concentrations. In this study, we used solid-phase microextraction to determine Setschenow constants for selected organic compounds in aqueous solutions up to 2-5 M NaCl, 1.5-2 M CaCl2, and in Na-Ca binary electrolyte solutions to assess additivity of the constants. These compounds exhibited log-linear behavior up to these high NaCl concentrations. Log-linear decreases in solubility with increasing salt concentration were observed up to 1.5-2 M CaCl2 for all compounds, and added to a sparse database of CaCl2 Setschenow constants. Setschenow constants were additive in binary electrolyte mixtures. New models to predict CaCl2 and KCl Setschenow constants from NaCl Setschenow constants were developed, which successfully predicted the solubility of the compounds measured in this study. Overall, data show that the Setschenow Equation is valid for a wide range of salinity conditions typically found in energy-related technologies. Copyright © 2015 Elsevier Ltd. All rights reserved.

[Grades evaluation of Scutellariae Radix slices based on quality constant].

PubMed

Deng, Zhe; Zhang, Jun; Jiao, Meng-Jiao; Zhong, Wen; Cui, Wen-Jin; Cheng, Jin-Tang; Chen, Sha; Wang, Yue-Sheng; Liu, An

2017-05-01

By measuring the morphological indexes and the marker components content of 22 batches of Scutellariae Radix slices as well as calculating the quality constant, this research was aimed to establish a new method of evaluating the specifications and grades of Scutellariae Radix slices. The quality constants of these samples were in the range of 0.04-0.49, which can be divided into several grades based on the real requirement. If they were divided into three grades, the quality constant was ≥0.39 for the first grade, <0.39 but ≥0.24 for the second grade, and <0.24 for the third grade. This work indicated that the quality constants characterizing both apparent parameters and intrinsic quality can be used as a comprehensive evaluation index to classify the grades of traditional Chinese medicine quantitatively, clearly and objectively. The research results in this paper would provide new ideas and references for evaluating the specifications and grades of traditional Chinese medicines. Copyright© by the Chinese Pharmaceutical Association.

Constant-pH Molecular Dynamics Simulations for Large Biomolecular Systems

DOE PAGES

Radak, Brian K.; Chipot, Christophe; Suh, Donghyuk; ...

2017-11-07

We report that an increasingly important endeavor is to develop computational strategies that enable molecular dynamics (MD) simulations of biomolecular systems with spontaneous changes in protonation states under conditions of constant pH. The present work describes our efforts to implement the powerful constant-pH MD simulation method, based on a hybrid nonequilibrium MD/Monte Carlo (neMD/MC) technique within the highly scalable program NAMD. The constant-pH hybrid neMD/MC method has several appealing features; it samples the correct semigrand canonical ensemble rigorously, the computational cost increases linearly with the number of titratable sites, and it is applicable to explicit solvent simulations. The present implementationmore » of the constant-pH hybrid neMD/MC in NAMD is designed to handle a wide range of biomolecular systems with no constraints on the choice of force field. Furthermore, the sampling efficiency can be adaptively improved on-the-fly by adjusting algorithmic parameters during the simulation. Finally, illustrative examples emphasizing medium- and large-scale applications on next-generation supercomputing architectures are provided.« less

Constant-pH Molecular Dynamics Simulations for Large Biomolecular Systems

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

Radak, Brian K.; Chipot, Christophe; Suh, Donghyuk

We report that an increasingly important endeavor is to develop computational strategies that enable molecular dynamics (MD) simulations of biomolecular systems with spontaneous changes in protonation states under conditions of constant pH. The present work describes our efforts to implement the powerful constant-pH MD simulation method, based on a hybrid nonequilibrium MD/Monte Carlo (neMD/MC) technique within the highly scalable program NAMD. The constant-pH hybrid neMD/MC method has several appealing features; it samples the correct semigrand canonical ensemble rigorously, the computational cost increases linearly with the number of titratable sites, and it is applicable to explicit solvent simulations. The present implementationmore » of the constant-pH hybrid neMD/MC in NAMD is designed to handle a wide range of biomolecular systems with no constraints on the choice of force field. Furthermore, the sampling efficiency can be adaptively improved on-the-fly by adjusting algorithmic parameters during the simulation. Finally, illustrative examples emphasizing medium- and large-scale applications on next-generation supercomputing architectures are provided.« less

Frequency-constant Q, unity and disorder

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

Hargreaves, N.D.

1995-12-31

In exploration geophysics we obtain information about the earth by observing its response to different types of applied force. The response can cover the full range of possible Q values (where Q, the quality factor, is a measure of energy dissipation), from close to infinity in the case of deep crustal seismic to close to 0 in the case of many electromagnetic methods. When Q is frequency-constant, however, the various types of response have a common scaling behavior and can be described as being self-affine. The wave-equation then takes on a generalised form, changing from the standard wave-equation at Qmore » = {infinity} to the diffusion equation at Q = 0, via lossy, diffusive, propagation at intermediate Q values. Solutions of this wave-diffusion equation at any particular Q value can be converted to an equivalent set of results for any other Q value. In particular it is possible to convert from diffusive to wave propagation by a mapping from Q < {infinity} to Q = {infinity}. In the context of seismic sounding this is equivalent to applying inverse Q-filtering; in a more general context the mapping integrates different geophysical observations by referencing them to the common result at Q = {infinity}. The self-affinity of the observations for frequency-constant Q is an expression of scale invariance in the fundamental physical properties of the medium of propagation, this being the case whether the mechanism of diffusive propagation is scattering of intrinsic attenuation. Scale invariance, or fractal scaling, is a general property of disordered systems; the assumption of frequency-constant Q not only implies a unity between different geophysical observations, but also suggests that it is the disordered nature of the earth`s sub-surface that is the unifying factor.« less

A Constant-Force Resistive Exercise Unit

NASA Technical Reports Server (NTRS)

Colosky, Paul; Ruttley, Tara

2010-01-01

A constant-force resistive exercise unit (CFREU) has been invented for use in both normal gravitational and microgravitational environments. In comparison with a typical conventional exercise machine, this CFREU weighs less and is less bulky: Whereas weight plates and associated bulky supporting structures are used to generate resistive forces in typical conventional exercise machines, they are not used in this CFREU. Instead, resistive forces are generated in this CFREU by relatively compact, lightweight mechanisms based on constant-torque springs wound on drums. Each such mechanism is contained in a module, denoted a resistive pack, that includes a shaft for making a torque connection to a cable drum. During a stroke of resistive exercise, the cable is withdrawn from the cable drum against the torque exerted by the resistance pack. The CFREU includes a housing, within which can be mounted one or more resistive pack(s). The CFREU also includes mechanisms for engaging any combination of (1) one or more resistive pack(s) and (2) one or more spring(s) within each resistive pack to obtain a desired level of resistance.

Change is a Constant.

PubMed

Lubowitz, James H; Provencher, Matthew T; Brand, Jefferson C; Rossi, Michael J; Poehling, Gary G

2015-06-01

In 2015, Henry P. Hackett, Managing Editor, Arthroscopy, retires, and Edward A. Goss, Executive Director, Arthroscopy Association of North America (AANA), retires. Association is a positive constant, in a time of change. With change comes a need for continuing education, research, and sharing of ideas. While the quality of education at AANA and ISAKOS is superior and most relevant, the unique reason to travel and meet is the opportunity to interact with innovative colleagues. Personal interaction best stimulates new ideas to improve patient care, research, and teaching. Through our network, we best create innovation. Copyright © 2015 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Determination of acidity constants of curcumin in aqueous solution and apparent rate constant of its decomposition

NASA Astrophysics Data System (ADS)

Bernabé-Pineda, Margarita; Ramírez-Silva, María. Teresa; Romero-Romo, Mario; González-Vergara, Enrique; Rojas-Hernández, Alberto

2004-04-01

The stability of curcumin (H 3Cur) in aqueous media is improved when the systems in which it is present are at high pH values (higher than 11.7), fitting a model describable by a pseudo-zero order with a rate constant k' for the disappearance of the Cur 3- species of 1.39 (10 -9) M min -1. There were three acidity constants measured for the curcumin as follows: p KA3=10.51±0.01 corresponding to the equilibrium HCur 2-=Cur 3-+H +, a p KA2=9.88±0.02 corresponding to the equilibrium H 2Cur -=HCur -2+H +. These p KA values were attributed to the hydrogen of the phenol part of the curcumin, while the p KA1=8.38±0.04 corresponds to the equilibrium H 3Cur=H 2Cur -+H + and is attributed the acetylacetone type group. Formation of quinoid structures play an important role in the tautomeric forms of the curcumin in aqueous media, which makes the experimental values differ from the theoretically calculated ones, depending on the conditions adopted in the study.

Precisely and Accurately Inferring Single-Molecule Rate Constants

PubMed Central

Kinz-Thompson, Colin D.; Bailey, Nevette A.; Gonzalez, Ruben L.

2017-01-01

The kinetics of biomolecular systems can be quantified by calculating the stochastic rate constants that govern the biomolecular state versus time trajectories (i.e., state trajectories) of individual biomolecules. To do so, the experimental signal versus time trajectories (i.e., signal trajectories) obtained from observing individual biomolecules are often idealized to generate state trajectories by methods such as thresholding or hidden Markov modeling. Here, we discuss approaches for idealizing signal trajectories and calculating stochastic rate constants from the resulting state trajectories. Importantly, we provide an analysis of how the finite length of signal trajectories restrict the precision of these approaches, and demonstrate how Bayesian inference-based versions of these approaches allow rigorous determination of this precision. Similarly, we provide an analysis of how the finite lengths and limited time resolutions of signal trajectories restrict the accuracy of these approaches, and describe methods that, by accounting for the effects of the finite length and limited time resolution of signal trajectories, substantially improve this accuracy. Collectively, therefore, the methods we consider here enable a rigorous assessment of the precision, and a significant enhancement of the accuracy, with which stochastic rate constants can be calculated from single-molecule signal trajectories. PMID:27793280

On anthropic solutions of the cosmological constant problem

NASA Astrophysics Data System (ADS)

Banks, Tom; Dine, Michael; Motl, Lubos

2001-01-01

Motivated by recent work of Bousso and Polchinski (BP), we study theories which explain the small value of the cosmological constant using the anthropic principle. We argue that simultaneous solution of the gauge hierarchy problem is a strong constraint on any such theory. We exhibit three classes of models which satisfy these constraints. The first is a version of the BP model with precisely two large dimensions. The second involves 6-branes and antibranes wrapped on supersymmetric 3-cycles of Calabi-Yau manifolds, and the third is a version of the irrational axion model. All of them have possible problems in explaining the size of microwave background fluctuations. We also find that most models of this type predict that all constants in the low energy lagrangian, as well as the gauge groups and representation content, are chosen from an ensemble and cannot be uniquely determined from the fundamental theory. In our opinion, this significantly reduces the appeal of this kind of solution of the cosmological constant problem. On the other hand, we argue that the vacuum selection problem of string theory might plausibly have an anthropic, cosmological solution.

Constant-pH molecular dynamics using stochastic titration

NASA Astrophysics Data System (ADS)

Baptista, António M.; Teixeira, Vitor H.; Soares, Cláudio M.

2002-09-01

A new method is proposed for performing constant-pH molecular dynamics (MD) simulations, that is, MD simulations where pH is one of the external thermodynamic parameters, like the temperature or the pressure. The protonation state of each titrable site in the solute is allowed to change during a molecular mechanics (MM) MD simulation, the new states being obtained from a combination of continuum electrostatics (CE) calculations and Monte Carlo (MC) simulation of protonation equilibrium. The coupling between the MM/MD and CE/MC algorithms is done in a way that ensures a proper Markov chain, sampling from the intended semigrand canonical distribution. This stochastic titration method is applied to succinic acid, aimed at illustrating the method and examining the choice of its adjustable parameters. The complete titration of succinic acid, using constant-pH MD simulations at different pH values, gives a clear picture of the coupling between the trans/gauche isomerization and the protonation process, making it possible to reconcile some apparently contradictory results of previous studies. The present constant-pH MD method is shown to require a moderate increase of computational cost when compared to the usual MD method.

Infant motivation in dental health: attitude without constant reinforcement.

PubMed

Teixeira Alves, Fabiana Bucholdz; Kuhn, Eunice; Bordin, Danielle; Kozlowski, Vitoldo Antonio; Raggio, Daniela Procida; Fadel, Cristina Berger

2014-01-01

Social factors determine the child's behavior and motivation is an important task in the teaching-learning process. This longitudinal and cross-sectional study aimed to analyze the effectiveness of a motivational activity program for oral hygiene habits formation after motivation and without constant reinforcement. The sample was constituted of 26 children (mean 6 years old) from a Public Kindergarten School in Ponta Grossa, PR, Brazil. Data were collected applying a test-chart, with figures reporting the process of dental health/illness. Some figures were considered positive to dental health (dentist/Cod 1, toothbrush/Cod 3, dentifrice/dental floss/Cod 6, fruits/vegetables/Cod 7 and tooth without caries lesion/Cod 8) and negative on dental health (sweets/Cod 2, bacteria/Cod 4, tooth with caries lesion/Cod 5). The figures presentation occurred in three different stages: First stage - figures were presented to children without previous knowledge; second stage - following the motivational presentation, and third stage - 30 days after the first contact. On the first stage, most children select good for the figures considered harmful to their teeth (Cod 2-88%; Cod 4-77% and Cod 5-65%). On the second stage, there was a lower percentage: 23% (P < 0.0001), 8% (P < 0.0001), and 23% (P = 0.0068) related to the Cod 2, 4, and 5. On the third stage, the results showed again an association with the good choice to these figures considered harmful (Cod 2-85%, Cod 4-65% and Cod 5-54%) similar the results obtained on the first stage. The motivational programs performed without constant reinforcement does not have a positive influence in changing the child's behavior related to a better dental care.

Cosmological Constant as a Manifestation of the Hierarchy

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

Chen, Pisin; Gu, Je-An

2007-12-21

There has been the suggestion that the cosmological constant as implied by the dark energy is related to the well-known hierarchy between the Planck scale, M{sub PI}, and the Standard Model scale, M{sub SM}. Here we further propose that the same framework that addresses this hierarchy problem must also address the smallness problem of the cosmological constant. Specifically, we investigate the minimal supersymmetric (SUSY) extension of the Randall-Sundrum model where SUSY-breaking is induced on the TeV brane and transmitted into the bulk. We show that the Casimir energy density of the system indeed conforms with the observed dark energy scale.

Equilibrium constant for calcium ion and ascorbate ion.

PubMed

Tsao, C S

1984-02-15

The combination of calcium and ascorbic acid in water at 25 degrees C has been examined by measuring the change of free calcium ion concentration as ascorbate was added in small increment to a solution of calcium. The data show clearly that complex formation between calcium ion and ascorbate ion occurred. At ionic strength mu = 0.1-0.2, the equilibrium constant of Ca++ and the singly-charged ascorbate ion has been measured to be 2.1 M-1. The precision of the result is better than 5% and the accuracy is estimated to be better than 20%. The application of the equilibrium constants is discussed.

Gladstone-Dale constant for CF4. [experimental design

NASA Technical Reports Server (NTRS)

Burner, A. W., Jr.; Goad, W. K.

1980-01-01

The Gladstone-Dale constant, which relates the refractive index to density, was measured for CF4 by counting fringes of a two-beam interferometer, one beam of which passes through a cell containing the test gas. The experimental approach and sources of systematic and imprecision errors are discussed. The constant for CF4 was measured at several wavelengths in the visible region of the spectrum. A value of 0.122 cu cm/g with an uncertainty of plus or minus 0.001 cu cm/g was determined for use in the visible region. A procedure for noting the departure of the gas density from the ideal-gas law is discussed.

Search for time modulations in the decay constant of 40K and 226Ra at the underground Gran Sasso Laboratory

NASA Astrophysics Data System (ADS)

Bellotti, E.; Broggini, C.; Di Carlo, G.; Laubenstein, M.; Menegazzo, R.

2018-05-01

Time modulations at per mil level have been reported to take place in the decay constant of several nuclei with period of one year (most cases) but also of about one month or one day. On the other hand, experiments with similar or better sensitivity have been unable to detect any modulation. In this letter we give the results of the activity study of two different sources: 40K and 226Ra. The two gamma spectrometry experiments have been performed underground at the Gran Sasso Laboratory, this way suppressing the time dependent cosmic ray background. Briefly, our measurements reached the sensitivity of 3.4 and 3.5 parts over 106 for 40K and 226Ra, respectively (1 sigma) and they do not show any statistically significant evidence of time dependence in the decay constant. We also give the results of the activity measurement at the time of the two strong X-class solar flares which took place in September 2017. Our data do not show any unexpected time dependence in the decay rate of 40K in correspondence with the two flares. To the best of our knowledge, these are the most precise and accurate results on the stability of the decay constant as function of time.

Comparison between variable and constant rotor speed operation on WINDMEL-II

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

Sasamoto, Akira; Matsumiya, Hikaru; Kawamura, Shunji

1996-10-01

On a wind turbine control system for rotor revolution speed, it is believed that variable speed operation has the advantages over constant speed from a view point of both aerodynamics and mechanics. However, there is no experimental study which shows the differences. In this report, the authors intend to clarify the differences about shaft torque by using experimental data, from a new wind turbine system which has both variable and constant operation. The result in observation of the experimental data shows that variable speed operational shaft torque is lower than constant speed operational one.

Note: Spring constant calibration of nanosurface-engineered atomic force microscopy cantilevers

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

Ergincan, O., E-mail: orcunergincan@gmail.com; Palasantzas, G.; Kooi, B. J.

2014-02-15

The determination of the dynamic spring constant (k{sub d}) of atomic force microscopy cantilevers is of crucial importance for converting cantilever deflection to accurate force data. Indeed, the non-destructive, fast, and accurate measurement method of the cantilever dynamic spring constant by Sader et al. [Rev. Sci. Instrum. 83, 103705 (2012)] is confirmed here for plane geometry but surface modified cantilevers. It is found that the measured spring constants (k{sub eff}, the dynamic one k{sub d}), and the calculated (k{sub d,1}) are in good agreement within less than 10% error.

The Solar Constant: A Take Home Lab

ERIC Educational Resources Information Center

Eaton, B. G.; And Others

1977-01-01

Describes a method that uses energy from the sun, absorbed by aluminum discs, to melt ice, and allows the determination of the solar constant. The take-home equipment includes Styrofoam cups, a plastic syringe, and aluminum discs. (MLH)

Induction of antioxidant enzyme activities by a phenylurea derivative, EDU.

PubMed

Stevens, T M; Boswell, G A; Adler, R; Ackerman, N R; Kerr, J S

1988-10-01

Oxygen free radicals have the potential to mediate cell injury. Defenses against such radicals include the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX). The purposes of this study were (1) to develop an in vitro model using human cells in which to investigate a potential pharmacologic agent as an inducer of these antioxidant enzymes; (2) to investigate the phenylurea derivative N-[2-(2-oxo-1-imidazolindinyl)ethyl]-N-phenylurea (EDU) in this model with paraquat (PQ) serving as the positive control; and (3) to determine if induction of the antioxidant enzymes by EDU occurs in vivo. Human gingival fibroblasts (Gin-1) were used as the target cell in vitro; PQ and EDU, an inducer of SOD and CAT activities in plants, were evaluated as antioxidant enzyme inducers. Total SOD activity in Gin-1 cells increased 2-fold (p less than 0.05) in the presence of 1.0 mM PQ for 18-48 hr compared with untreated controls. Gin-1 cells incubated with 0.25-2.0 mM PQ for 24 hr had significantly increased total SOD (1.5 to 2.0-fold; p less than 0.05). CAT activity increased with 1.0 and 2.0 mM PQ (p less than 0.05). In the presence of PQ, GSH-PX activity decreased (p less than 0.05) in a concentration-dependent manner, indicating inactivation of this enzyme. No toxicity, indicated by lactate dehydrogenase released into the incubation medium, was noted at PQ concentrations below 5.0 mM. In the presence of 0.125-2.0 mM EDU, total SOD activity in Gin-1 cells significantly increased (1.5 to 2.0-fold; p less than 0.05). CAT activity significantly increased in a dose-dependent manner (p less than 0.05), while GSH-PX activity remained constant following exposure to 0.125-2.0 mM EDU. Intraperitoneal administration of EDU to rats twice a day for 2 days at 100 mg/kg induced SOD activity in heart, liver, and lung compared to controls (p less than 0.05). CAT activity increased in the liver 56% and in the lung 36% (p less than 0.05). GSH-PX activity

Description of plastic remains found in the stomach contents of the jumbo squid Dosidicus gigas landed in Ecuador during 2014.

PubMed

Rosas-Luis, Rigoberto

2016-12-15

Squids are active and opportunistic predators that feed on a wide range of prey. Their active movements in the water column and their voracity promote a high consumption of food. In the pelagic environment off Ecuador, marine pollution is characterized by plastic debris with a mainland origin, including plastics trash of fishing gears. The objective of this work was to describe the presence of plastic remains in the stomach contents of Dosidicus gigas caught off the coast of Ecuador. Results demonstrated that 12% of the stomachs contained plastic remains. These plastics were identified as multifilament of polyethylene lines and polyvinyl chloride remains. Findings of this work could be related to an increase in the discharge of solid materials in the water column, increasing the probability to be ingested by the jumbo squid. Copyright © 2016 Elsevier Ltd. All rights reserved.

Colossal dielectric constant up to gigahertz at room temperature

NASA Astrophysics Data System (ADS)

Krohns, S.; Lunkenheimer, P.; Kant, Ch.; Pronin, A. V.; Brom, H. B.; Nugroho, A. A.; Diantoro, M.; Loidl, A.

2009-03-01

The applicability of recently discovered materials with extremely high ("colossal") dielectric constants, required for future electronics, suffers from the fact that their dielectric constant ɛ' only is huge in a limited frequency range below about 1 MHz. In the present report, we show that the dielectric properties of a charge-ordered nickelate, La15/8Sr1/8NiO4, surpass those of other materials. Especially, ɛ' retains its colossal magnitude of >10 000 well into the gigahertz range.

Experimental determination of third-order elastic constants of diamond.

PubMed

Lang, J M; Gupta, Y M

2011-03-25

To determine the nonlinear elastic response of diamond, single crystals were shock compressed along the [100], [110], and [111] orientations to 120 GPa peak elastic stresses. Particle velocity histories and elastic wave velocities were measured by using laser interferometry. The measured elastic wave profiles were used, in combination with published acoustic measurements, to determine the complete set of third-order elastic constants. These constants represent the first experimental determination, and several differ significantly from those calculated by using theoretical models.

Rotational Spectra and Nuclear Quadrupole Coupling Constants of Iodoimidazoles

NASA Astrophysics Data System (ADS)

Cooper, Graham A.; Anderson, Cara J.; Medcraft, Chris; Legon, Anthony; Walker, Nick

2017-06-01

The microwave spectra of two isomers of iodoimidazole have been recorded and assigned with resolution of their nuclear quadrupole coupling constants. These constants have been analysed in terms of the conjugation between the lone pairs on the iodine atom and the aromatic π-bonding system, and the effect of this conjugation on the distribution of π-electron density in the ring. A comparison of these properties has been made between iodoimidazole and other 5- and 6-membered aromatic rings bonded to halogen atoms.

Multiphoton amplitude in a constant background field

NASA Astrophysics Data System (ADS)

Ahmad, Aftab; Ahmadiniaz, Naser; Corradini, Olindo; Kim, Sang Pyo; Schubert, Christian

2018-01-01

In this contribution, we present our recent compact master formulas for the multiphoton amplitudes of a scalar propagator in a constant background field using the worldline fomulation of quantum field theory. The constant field has been included nonperturbatively, which is crucial for strong external fields. A possible application is the scattering of photons by electrons in a strong magnetic field, a process that has been a subject of great interest since the discovery of astrophysical objects like radio pulsars, which provide evidence that magnetic fields of the order of 1012G are present in nature. The presence of a strong external field leads to a strong deviation from the classical scattering amplitudes. We explicitly work out the Compton scattering amplitude in a magnetic field, which is a process of potential relevance for astrophysics. Our final result is compact and suitable for numerical integration.

Gravity-independent constant force resistive exercise unit

NASA Technical Reports Server (NTRS)

Colosky, Jr., Paul E. (Inventor); Ruttley, Tara M. (Inventor)

2004-01-01

This invention describes a novel gravity-independent exercise unit designed for use in microgravity, or on the ground, as a means by which to counter muscle atrophy and bone degradation due to disuse or underuse. Modular resistive packs comprising constant torque springs provide constant force opposing the withdrawal of an exercise cable from the device. In addition to uses within the space program, the compact resistive packs of the CFREU allow the unit to be small enough for easy use as a home gym for personal use, or as a supplement for rehabilitation programs. Resistive packs may be changed conveniently out of the CFREU according to the desired exercise regimen. Thus, the resistive packs replace the need for expensive, heavy, and bulky traditional weight plates. The CFREU may be employed by hospitals, rehabilitation and physical therapy clinics, and other related professional businesses.

Juveniles' Motivations for Remaining in Prostitution

ERIC Educational Resources Information Center

Hwang, Shu-Ling; Bedford, Olwen

2004-01-01

Qualitative data from in-depth interviews were collected in 1990-1991, 1992, and 2000 with 49 prostituted juveniles remanded to two rehabilitation centers in Taiwan. These data are analyzed to explore Taiwanese prostituted juveniles' feelings about themselves and their work, their motivations for remaining in prostitution, and their difficulties…

Distinguishing mechanisms for alternans in cardiac cells using constant-diastolic-interval pacing

NASA Astrophysics Data System (ADS)

Cherry, Elizabeth M.

2017-09-01

Alternans, a proarrhythmic dynamical state in which cardiac action potentials alternate between long and short durations despite a constant pacing period, traditionally has been explained at the cellular level using nonlinear dynamics principles under the assumption that the action potential duration (APD) is determined solely by the time elapsed since the end of the previous action potential, called the diastolic interval (DI). In this scenario, APDs at a steady state should be the same provided that the preceding DIs are the same. Nevertheless, experiments attempting to eliminate alternans by dynamically adjusting the timing of pacing stimuli to keep the DI constant showed that alternans persisted, contradicting the traditional theory. It is now widely known that alternans also can arise from a different mechanism associated with intracellular calcium cycling. Our goal is to determine whether intracellular calcium dynamics can explain the experimental findings regarding the persistence of alternans despite a constant DI. For this, we use mathematical models capable of producing alternans through both voltage- and calcium-mediated mechanisms. We show that for voltage-driven alternans, action potentials elicited from a constant-DI protocol are always the same. However, in the case of calcium-driven alternans, the constant-DI protocol can result in alternans. Reducing the strength of the calcium instability progressively reduces and finally eliminates constant-DI alternans. Our findings suggest that screening for the presence of alternans using a constant-DI protocol has the potential for differentiating between voltage-driven and calcium-driven alternans.