The generalized added mass revised
NASA Astrophysics Data System (ADS)
De Wilde, Juray
2007-05-01
The reformulation of the generalized or apparent added mass presented by De Wilde [Phys. Fluids 17, 113304 (2005)] neglects the presence of a drag-type force in the gas and solid phase momentum equations. Reformulating the generalized added mass accounting for the presence of a drag-type force, an apparent drag force appears next to the apparent distribution of the filtered gas phase pressure gradient over the phases already found by De Wilde in the above-cited reference. The reformulation of the generalized added mass and the evaluation of a linear wave propagation speed test then suggest a generalized added mass type closure approach to completely describe filtered gas-solid momentum transfer, that is, including both the filtered drag force and the correlation between the solid volume fraction and the gas phase pressure gradient.
Metabolic rate of carrying added mass: a function of walking speed, carried mass and mass location.
Schertzer, Eliran; Riemer, Raziel
2014-11-01
The effort of carrying additional mass at different body locations is important in ergonomics and in designing wearable robotics. We investigate the metabolic rate of carrying a load as a function of its mass, its location on the body and the subject's walking speed. Novel metabolic rate prediction equations for walking while carrying loads at the ankle, knees and back were developed based on experiments where subjects walked on a treadmill at 4, 5 or 6km/h bearing different amounts of added mass (up to 2kg per leg and 22kg for back). Compared to previously reported equations, ours are 7-69% more accurate. Results also show that relative cost for carrying a mass at a distal versus a proximal location changes with speed and mass. Contrary to mass carried on the back, mass attached to the leg cannot be modeled as an increase in body mass.
Creating images by adding masses to gravitational point lenses
NASA Astrophysics Data System (ADS)
Sète, Olivier; Luce, Robert; Liesen, Jörg
2015-04-01
A well-studied maximal gravitational point lens construction of S. H. Rhie produces images of a light source using deflector masses. The construction arises from a circular, symmetric deflector configuration on masses (producing only images) by adding a tiny mass in the center of the other mass positions (and reducing all the other masses a little bit). In a recent paper we studied this "image creating effect" from a purely mathematical point of view (Sète, Luce & Liesen, Comput. Methods Funct. Theory 15(1), 2014). Here we discuss a few consequences of our findings for gravitational microlensing models. We present a complete characterization of the effect of adding small masses to these point lens models, with respect to the number of images. In particular, we give several examples of maximal lensing models that are different from Rhie's construction and that do not share its highly symmetric appearance. We give generally applicable conditions that allow the construction of maximal point lenses on masses from maximal lenses on masses.
Proposed Framework for Determining Added Mass of Orion Drogue Parachutes
NASA Technical Reports Server (NTRS)
Fraire, Usbaldo, Jr.; Dearman, James; Morris, Aaron
2011-01-01
The Crew Exploration Vehicle (CEV) Parachute Assembly System (CPAS) project is executing a program to qualify a parachute system for a next generation human spacecraft. Part of the qualification process involves predicting parachute riser tension during system descent with flight simulations. Human rating the CPAS hardware requires a high degree of confidence in the simulation models used to predict parachute loads. However, uncertainty exists in the heritage added mass models used for loads predictions due to a lack of supporting documentation and data. Even though CPAS anchors flight simulation loads predictions to flight tests, extrapolation of these models outside the test regime carries the risk of producing non-bounding loads. A set of equations based on empirically derived functions of skirt radius is recommended as the simplest and most viable method to test and derive an enhanced added mass model for an inflating parachute. This will increase confidence in the capability to predict parachute loads. The selected equations are based on those published in A Simplified Dynamic Model of Parachute Inflation by Dean Wolf. An Ames 80x120 wind tunnel test campaign is recommended to acquire the reefing line tension and canopy photogrammetric data needed to quantify the terms in the Wolf equations and reduce uncertainties in parachute loads predictions. Once the campaign is completed, the Wolf equations can be used to predict loads in a typical CPAS Drogue Flight test. Comprehensive descriptions of added mass test techniques from the Apollo Era to the current CPAS project are included for reference.
Added mass in human swimmers: age and gender differences.
Caspersen, Cecilie; Berthelsen, Petter A; Eik, Mari; Pâkozdi, Csaba; Kjendlie, Per-Ludvik
2010-08-26
In unstationary swimming (changing velocity), some of the water around the swimmer is set in motion. This can be thought of as an added mass (M(a)) of water. The purpose of this study was to find added mass on human swimmers and investigate the effect of shape and body size. Thirty subjects were connected to a 2.8m long bar with handles, attached with springs (stiffness k = 318 N/m) and a force cell. By oscillating this system vertically and registering the period of oscillations it was possible to find the added mass of the swimmer, given the known masses of the bar and swimmer. Relative added mass (M(a)%) for boys, women and men were, respectively, 26.8 +/- 2.9%, 23.6 +/- 1.6% and 26.8 +/- 2.3% of the subjects total mass. This study reported significantly lower added mass (p < 0.001) and relative added mass (p < 0.002) for women compared to men, which indicate that the possible body shape differences between genders may be an important factor for determining added mass. Boys had significantly lower (p < 0.001) added mass than men. When added mass was scaled for body size there were no significant differences (p = 0.996) between boys and men, which indicated that body size is an important factor that influences added mass. The added mass in this study seems to be lower and within a smaller range than previously reported (Klauck, 1999; Eik et al., 2008). It is concluded that the added mass in human swimmers, in extended gliding position, is approximately 1/4 of the subjects' body mass.
Heavy quark potential from deformed AdS5 models
NASA Astrophysics Data System (ADS)
Zhang, Zi-qiang; Hou, De-fu; Chen, Gang
2017-04-01
In this paper, we investigate the heavy quark potential in some holographic QCD models. The calculation relies on a modified renormalization scheme mentioned in a previous work of Albacete et al. After studying the heavy quark potential in Pirner-Galow model and Andreev-Zakharov model, we extend the discussion to a general deformed AdS5 case. It is shown that the obtained potential is negative definite for all quark-antiquark separations, differs from that using the usual renormalization scheme.
Higgs mechanism and the added-mass effect.
Krishnaswami, Govind S; Phatak, Sachin S
2015-04-08
In the Higgs mechanism, mediators of the weak force acquire masses by interacting with the Higgs condensate, leading to a vector boson mass matrix. On the other hand, a rigid body accelerated through an inviscid, incompressible and irrotational fluid feels an opposing force linearly related to its acceleration, via an added-mass tensor. We uncover a striking physical analogy between the two effects and propose a dictionary relating them. The correspondence turns the gauge Lie algebra into the space of directions in which the body can move, encodes the pattern of gauge symmetry breaking in the shape of an associated body and relates symmetries of the body to those of the scalar vacuum manifold. The new viewpoint is illustrated with numerous examples, and raises interesting questions, notably on the fluid analogues of the broken symmetry and Higgs particle, and the field-theoretic analogue of the added mass of a composite body.
Higgs mechanism and the added-mass effect
Krishnaswami, Govind S.; Phatak, Sachin S.
2015-01-01
In the Higgs mechanism, mediators of the weak force acquire masses by interacting with the Higgs condensate, leading to a vector boson mass matrix. On the other hand, a rigid body accelerated through an inviscid, incompressible and irrotational fluid feels an opposing force linearly related to its acceleration, via an added-mass tensor. We uncover a striking physical analogy between the two effects and propose a dictionary relating them. The correspondence turns the gauge Lie algebra into the space of directions in which the body can move, encodes the pattern of gauge symmetry breaking in the shape of an associated body and relates symmetries of the body to those of the scalar vacuum manifold. The new viewpoint is illustrated with numerous examples, and raises interesting questions, notably on the fluid analogues of the broken symmetry and Higgs particle, and the field-theoretic analogue of the added mass of a composite body. PMID:27547077
Massive quiver matrix models for massive charged particles in AdS
Asplund, Curtis T.; Denef, Frederik; Dzienkowski, Eric
2016-01-11
Here, we present a new class of N = 4 supersymmetric quiver matrix models and argue that it describes the stringy low-energy dynamics of internally wrapped D-branes in four-dimensional anti-de Sitter (AdS) flux compactifications. The Lagrangians of these models differ from previously studied quiver matrix models by the presence of mass terms, associated with the AdS gravitational potential, as well as additional terms dictated by supersymmetry. These give rise to dynamical phenomena typically associated with the presence of fluxes, such as fuzzy membranes, internal cyclotron motion and the appearance of confining strings. We also show how these models can be obtained by dimensional reduction of four-dimensional supersymmetric quiver gauge theories on a three-sphere.
Massive quiver matrix models for massive charged particles in AdS
Asplund, Curtis T.; Denef, Frederik; Dzienkowski, Eric
2016-01-11
Here, we present a new class of N = 4 supersymmetric quiver matrix models and argue that it describes the stringy low-energy dynamics of internally wrapped D-branes in four-dimensional anti-de Sitter (AdS) flux compactifications. The Lagrangians of these models differ from previously studied quiver matrix models by the presence of mass terms, associated with the AdS gravitational potential, as well as additional terms dictated by supersymmetry. These give rise to dynamical phenomena typically associated with the presence of fluxes, such as fuzzy membranes, internal cyclotron motion and the appearance of confining strings. We also show how these models can bemore » obtained by dimensional reduction of four-dimensional supersymmetric quiver gauge theories on a three-sphere.« less
Rotational-Mode-Shape-Based Added Mass Identification Using Wavelet Packet Transform
NASA Astrophysics Data System (ADS)
Rajendran, Prakash; Sivakumar, Srinivasan M.
2015-05-01
A novel approach is proposed in this article that the combination of rotational mode shape with wavelet packet transform can detect the relatively small added mass (damage) location and its intensity in a beam structure. The rotational mode shapes of added mass state are obtained from a finite element model and used as input in wavelet analysis to capture signatures arising from even small damage in the beam. The proposed algorithm is able to clearly identify single and multiple added mass locations and their intensities in a cantilever beam. It is also tested with noise-contaminated signals to show its feasibility in practical situations.
Octopus-inspired drag cancelation by added mass pumping
NASA Astrophysics Data System (ADS)
Weymouth, Gabriel; Giorgio-Serchi, Francesco
2016-11-01
Recent work has shown that when an immersed body suddenly changes its size, such as a deflating octopus during rapid escape jetting, the body experiences large forces due to the variation of added-mass energy. We extend this line of research by investigating a spring-mass oscillator submerged in quiescent fluid subject to periodic changes in its volume. This system isolates the ability of the added-mass thrust to cancel the bluff body resistance (having no jet flow to confuse the analysis) and moves closer to studying how these effects would work in a sustained propulsion case by studying periodic shape-change instead of a "one-shot" escape maneuver. With a combination of analytical, numerical, and experimental results, we show that the recovery of added-mass kinetic energy can be used to completely cancel the drag of the fluid, driving the onset of sustained oscillations with amplitudes as large as four times the average body radius. Moreover, these results are fairly independent of the details of the shape-change kinematics as long as the Stokes number and shape-change number are large. In addition, the effective pumping frequency range based on parametric oscillator analysis is shown to predict large amplitude response region observed in the numerics and experiments.
Adding immigrants to microsimulation models.
Duleep, Harriet Orcutt; Dowhan, Daniel J
2008-01-01
Forecasts of the financial status of Social Security's Old-Age, Survivors, and Disability Insurance (OASDI) programs and forecasts of the effects of various OASDI policy options on Americans would be improved if information about the earnings and labor force behavior of various population subgroups were included in projection models. Focusing on the projection of immigrant earnings, this article proffers a conceptual basis for incorporating immigration into microsimulation models. Key results from research on immigrant earnings, as described in the first article in this trilogy--"Research on Immigrant Earnings"--are linked to methods for forecasting individual earnings in microsimulation models. The research on immigrant earnings also inspires new methods for forecasting earnings in microsimulation models as well as the projection of immigrant emigration. Forecasting immigrant earnings and emigration is discussed in the context of a "closed system"--that is, forecasts are only made for a given population, which is represented in the base sample of the microsimulation model. The third article in our trilogy--"Incorporating Immigrant Flows into Microsimulation Models"--explores how to project immigrant earnings in the context of an "open system," which includes future immigrants.
Silva, Diana F.; Selfridge, J. Eva; Lu, Jianghua; E, Lezi; Roy, Nairita; Hutfles, Lewis; Burns, Jeffrey M.; Michaelis, Elias K.; Yan, ShiDu; Cardoso, Sandra M.; Swerdlow, Russell H.
2013-01-01
Bioenergetic dysfunction occurs in Alzheimer's disease (AD) and mild cognitive impairment (MCI), a clinical syndrome that frequently precedes symptomatic AD. In this study, we modeled AD and MCI bioenergetic dysfunction by transferring mitochondria from MCI, AD and control subject platelets to mtDNA-depleted SH-SY5Y cells. Bioenergetic fluxes and bioenergetics-related infrastructures were characterized in the resulting cytoplasmic hybrid (cybrid) cell lines. Relative to control cybrids, AD and MCI cybrids showed changes in oxygen consumption, respiratory coupling and glucose utilization. AD and MCI cybrids had higher ADP/ATP and lower NAD+/NADH ratios. AD and MCI cybrids exhibited differences in proteins that monitor, respond to or regulate cell bioenergetic fluxes including HIF1α, PGC1α, SIRT1, AMPK, p38 MAPK and mTOR. Several endpoints suggested mitochondrial mass increased in the AD cybrid group and probably to a lesser extent in the MCI cybrid group, and that the mitochondrial fission–fusion balance shifted towards increased fission in the AD and MCI cybrids. As many of the changes we observed in AD and MCI cybrid models are also seen in AD subject brains, we conclude reduced bioenergetic function is present during very early AD, is not brain-limited and induces protean retrograde responses that likely have both adaptive and mal-adaptive consequences. PMID:23740939
Thermo-mechanical phase-shift determination in Coriolis mass-flowmeters with added masses
NASA Astrophysics Data System (ADS)
Ghayesh, Mergen H.; Amabili, Marco; Païdoussis, Michael P.
2012-10-01
The aim of this paper is to develop an approximate analytical solution for phase-shift (and thus mass flow) prediction along the length of the measuring tube of a Coriolis mass-flowmeter. A single, straight measuring tube is considered; added masses at the sensor and excitation locations are included in the model, and thus in the equation of motion. The measuring tube is excited harmonically by an electromagnetic driver. Taking into account thermal effects, the equation of motion is derived through use of the extended Hamilton's principle and constitutive relations. The equation of motion is discretized into a set of ordinary differential equations via Galerkin's technique. The method of multiple timescales is applied to the set of resultant equations, and the equations of order one and epsilon are obtained analytically for the system at primary resonance. The solution of the equation of motion is obtained by satisfying the solvability condition (making the solution of order epsilon free of secular terms). The flow-related phase-shift in the driver-induced tube vibration is measured at two symmetrically located points on either side of the mid-length of the tube. The analytical results for the phase-shift are compared to those obtained numerically. The effect of system parameters on the measured phase-shift is discussed. It is shown that the measured phase-shift depends on the mass flow rate, of course, but it is also affected by the magnitude of the added sensor mass and location, and the temperature change; nevertheless, the factors investigated do not induce a zero phase-shift.
Revisiting the thermodynamic relations in AdS /CMT models
NASA Astrophysics Data System (ADS)
Hyun, Seungjoon; Park, Sang-A.; Yi, Sang-Heon
2017-03-01
Motivated by the recent unified approach to the Smarr-like relation of anti-de Sitter (AdS) planar black holes in conjunction with the quasilocal formalism on conserved charges, we revisit the quantum statistical and thermodynamic relations of hairy AdS planar black holes. By extending the previous results, we identify the hairy contribution in the bulk and show that the holographic computation can be improved so that it is consistent with the bulk computation. We argue that the first law can be retained in its universal form and that the relation between the on-shell renormalized Euclidean action and its free energy interpretation in gravity may also be undeformed even with the hairy contribution in hairy AdS black holes.
NASA Astrophysics Data System (ADS)
Farahani, Hassan H.; Ditmar, Pavel; Inácio, Pedro; Didova, Olga; Gunter, Brian; Klees, Roland; Guo, Xiang; Guo, Jing; Sun, Yu; Liu, Xianglin; Zhao, Qile; Riva, Riccardo
2017-01-01
We present a high resolution model of the linear trend in the Earth's mass variations based on DMT-2 (Delft Mass Transport model, release 2). DMT-2 was produced primarily from K-Band Ranging (KBR) data of the Gravity Recovery And Climate Experiment (GRACE). It comprises a time series of monthly solutions complete to spherical harmonic degree 120. A novel feature in its production was the accurate computation and incorporation of stochastic properties of coloured noise when processing KBR data. The unconstrained DMT-2 monthly solutions are used to estimate the linear trend together with a bias, as well as annual and semi-annual sinusoidal terms. The linear term is further processed with an anisotropic Wiener filter, which uses full noise and signal covariance matrices. Given the fact that noise in an unconstrained model of the trend is reduced substantially as compared to monthly solutions, the Wiener filter associated with the trend is much less aggressive compared to a Wiener filter applied to monthly solutions. Consequently, the trend estimate shows an enhanced spatial resolution. It allows signals in relatively small water bodies, such as Aral sea and Ladoga lake, to be detected. Over the ice sheets, it allows for a clear identification of signals associated with some outlet glaciers or their groups. We compare the obtained trend estimate with the ones from the CSR-RL05 model using (i) the same approach based on monthly noise covariance matrices and (ii) a commonly-used approach based on the DDK-filtered monthly solutions. We use satellite altimetry data as independent control data. The comparison demonstrates a high spatial resolution of the DMT-2 linear trend. We link this to the usage of high-accuracy monthly noise covariance matrices, which is due to an accurate computation and incorporation of coloured noise when processing KBR data. A preliminary comparison of the linear trend based on DMT-2 with that computed from GSFC_global_mascons_v01 reveals, among
Value-added logistics: the answer to mass customization.
Verwoerd, W
1999-11-01
Value added logistics: A new concept or just new terminology? If you read Today and Tomorrow you will notice that Henry Ford used postponed manufacturing to save on transportation costs: On one railway-wagon he could ship either three T-Fords or the parts for seven T-Fords. This is one of the reasons he build several assembly plants in the United States and in Europe (Dagenham, UK; Koln, Germany; and Amsterdam). Although this concept has existed for more than 70 years, I found out that it is still quite unknown. Thanks to information technology, it is becoming more powerful. This opens large possibilities for mass customization.
Added mass and damping on an oscillating surface-piercing circular column with a circular footing
Chung, J.S.
1994-12-31
Added mass and damping on a vertical, surface-piercing, circular cylinder or column with a submerged sharp-cornered circular floating, oscillating in water of finite and infinite depths are measured using a planar motion mechanism. The model is made of aluminum, and the outer diameters of the column and footing are 26.67 cm and 60.96 cm, and their lengths are 90.17 cm and 22.86 cm, respectively. The bodies were forced to oscillate sinusoidally with small amplitudes, for several submergences below a free surface. The added-mass and wave-damping coefficients are shown to be influenced strongly by the free-surface effect and are presented as a function of water depth, frequency and direction of oscillation and of depth of submergence from the free surface. For the vertical oscillation close to the free surface, negative added mass values are measured, and the predictions of the added mass by a 3-D diffraction theory are 10--20% lower than the experimental values at the model submergences tested. The experimental added mass coefficient values for the horizontal oscillation and the wave damping coefficients for the vertical oscillation in finite depth differ more than 100% from the corresponding 3-D theory prediction at a certain at-sea operational frequency range. This set of data provides further experimental information for the improvement of theoretical predictions.
AdS5×S(5) mirror model as a string sigma model.
Arutyunov, Gleb; van Tongeren, Stijn J
2014-12-31
Doing a double Wick rotation in the world sheet theory of the light cone AdS5×S(5) superstring results in an inequivalent, so-called mirror theory that plays a central role in the field of integrability in the AdS-CFT correspondence. We show that this mirror theory can be interpreted as the light cone theory of a free string on a different background. This background is related to dS5×H(5) by a double T-duality, and has hidden supersymmetry. The geometry can also be extracted from an integrable deformation of the AdS5×S(5) sigma model, and we prove the observed mirror duality of these deformed models at the bosonic level as a byproduct. While we focus on AdS5×S(5), our results apply more generally.
NASA Technical Reports Server (NTRS)
Butler, Thomas G.
1987-01-01
Methods of modeling mass for bars are surveyed. A method for extending John Archer's concept of consistent mass beyond just translational inertia effects is included. Recommendations are given for various types of modeling situations.
Free vibrations of circular cylindrical shells with a small added concentrated mass
NASA Astrophysics Data System (ADS)
Leizerovich, G. S.; Seregin, S. V.
2016-09-01
The effect of a small added mass on the frequency and shape of free vibrations of a thin shell is studied using shallow shell theory. The proposed mathematical model assumes that mass asymmetry even in a linear formulation leads to coupled radial flexural vibrations. The interaction of shape-generating waves is studied using modal equations obtained by the Bubnov-Galerkin method. Splitting of the flexural frequency spectrum is found, which is caused not only by the added mass but also by the wave-formation parameters of the shell. The ranges of the relative lengths and shell thicknesses are determined in which the interaction of flexural and radial vibrations can be neglected.
NASA Astrophysics Data System (ADS)
Piñeirua, M.; Godoy-Diana, R.; Thiria, B.
2015-08-01
In this Rapid Communication, we address a crucial point regarding the description of moderate to high Reynolds numbers aquatic swimmers. For decades, swimming animals have been classified in two different families of propulsive mechanisms based on the Reynolds number: the resistive swimmers, using local friction to produce the necessary thrust force for locomotion at low Reynolds number, and the reactive swimmers, lying in the high Reynolds range, and using added mass acceleration (described by perfect fluid theory). However, inertial swimmers are also systems that dissipate energy, due to their finite size, therefore involving strong resistive contributions, even for high Reynolds numbers. Using a complete model for the hydrodynamic forces, involving both reactive and resistive contributions, we revisit here the physical mechanisms responsible for the thrust production of such swimmers. We show, for instance, that the resistive part of the force balance is as crucial as added mass effects in the modeling of the thrust force, especially for elongated species. The conclusions brought by this work may have significant contributions to the understanding of complex swimming mechanisms, especially for the future design of artificial swimmers.
Piñeirua, M; Godoy-Diana, R; Thiria, B
2015-08-01
In this Rapid Communication, we address a crucial point regarding the description of moderate to high Reynolds numbers aquatic swimmers. For decades, swimming animals have been classified in two different families of propulsive mechanisms based on the Reynolds number: the resistive swimmers, using local friction to produce the necessary thrust force for locomotion at low Reynolds number, and the reactive swimmers, lying in the high Reynolds range, and using added mass acceleration (described by perfect fluid theory). However, inertial swimmers are also systems that dissipate energy, due to their finite size, therefore involving strong resistive contributions, even for high Reynolds numbers. Using a complete model for the hydrodynamic forces, involving both reactive and resistive contributions, we revisit here the physical mechanisms responsible for the thrust production of such swimmers. We show, for instance, that the resistive part of the force balance is as crucial as added mass effects in the modeling of the thrust force, especially for elongated species. The conclusions brought by this work may have significant contributions to the understanding of complex swimming mechanisms, especially for the future design of artificial swimmers.
Maniaci, D. C.; Li, Y.
2012-04-01
This paper describes a recent study to investigate the applicability of a horizontal-axis wind turbine (HAWT) structural dynamics and unsteady aerodynamics analysis program (FAST and AeroDyn respectively) to modeling the forces on marine hydrokinetic (MHK) turbines. It summarizes the added mass model that has been added to AeroDyn. The added mass model only includes flow acceleration perpendicular to the rotor disc, and ignores added mass forces caused by blade deflection. A model of the National Renewable Energy Laboratory's (NREL) Unsteady Aerodynamics Experiment (UAE) Phase VI wind turbine was analyzed using FAST and AeroDyn with sea water conditions and the new added mass model. The results of this analysis exhibited a 3.6% change in thrust for a rapid pitch case and a slight change in amplitude and phase of thrust for a case with 30 degrees of yaw.
Maniaci, D. C.; Li, Y.
2011-10-01
This paper describes a recent study to investigate the applicability of a horizontal-axis wind turbine (HAWT) structural dynamics and unsteady aerodynamics analysis program (FAST and AeroDyn respectively) to modeling the forces on marine hydrokinetic (MHK) turbines. This paper summarizes the added mass model that has been added to AeroDyn. The added mass model only includes flow acceleration perpendicular to the rotor disc, and ignores added mass forces caused by blade deflection. A model of the National Renewable Energy Laboratory's (NREL) Unsteady Aerodynamics Experiment (UAE) Phase VI wind turbine was analyzed using FAST and AeroDyn with sea water conditions and the new added mass model. The results of this analysis exhibited a 3.6% change in thrust for a rapid pitch case and a slight change in amplitude and phase of thrust for a case with 30{sup o} of yaw.
AdS black disk model for small-x DIS
NASA Astrophysics Data System (ADS)
Cornalba, Lorenzo; Costa, Miguel S.; Penedones, João
2011-05-01
Using the approximate conformal invariance of QCD at high energies we consider a simple AdS black disk model to describe saturation in DIS. Deep inside saturation the structure functions have the same power law scaling, FT˜FL˜x-ω, where ω is related to the expansion rate of the black disk with energy. Furthermore, the ratio FL/FT is given by the universal value 1+ω/3+ω, independently of the target.
Adding interventions to mass measles vaccinations in India
Verguet, Stéphane; Morris, Shaun K; Sharma, Jitendar K; Ram, Usha; Gauvreau, Cindy; Jones, Edward; Jha, Prabhat; Jit, Mark
2016-01-01
Abstract Objective To quantify the impact on mortality of offering a hypothetical set of technically feasible, high-impact interventions for maternal and child survival during India’s 2010–2013 measles supplementary immunization activity. Methods We developed Lives Saved Tool models for 12 Indian states participating in the supplementary immunization, based on state- and sex-specific data on mortality from India’s Million Deaths Study and on health services coverage from Indian household surveys. Potential add-on interventions were identified through a literature review and expert consultations. We quantified the number of lives saved for a campaign offering measles vaccine alone versus a campaign offering measles vaccine with six add-on interventions (nutritional screening and complementary feeding for children, vitamin A and zinc supplementation for children, multiple micronutrient and calcium supplementation in pregnancy, and free distribution of insecticide-treated bednets). Findings The measles vaccination campaign saved an estimated 19 016 lives of children younger than 5 years. A hypothetical campaign including measles vaccine with add-on interventions was projected to save around 73 900 lives (range: 70 200–79 300), preventing 73 700 child deaths (range: 70 000–79 000) and 300 maternal deaths (range: 200–400). The most effective interventions in the whole package were insecticide-treated bednets, measles vaccine and preventive zinc supplementation. Girls accounted for 66% of expected lives saved (12 712/19 346) for the measles vaccine campaign, and 62% of lives saved (45 721/74 367) for the hypothetical campaign including add-on interventions. Conclusion In India, a measles vaccination campaign including feasible, high-impact interventions could substantially increase the number of lives saved and mitigate gender-related inequities in child mortality. PMID:27843161
Measuring Teacher Quality with Value-Added Modeling
ERIC Educational Resources Information Center
Marder, Michael
2012-01-01
Using computers to evaluate teachers based on student test scores is more difficult than it seems. Value-added modeling is a genuinely serious attempt to grapple with the difficulties. Value-added modeling carries the promise of measuring teacher quality automatically and objectively, and improving school systems at minimal cost. The essence of…
Using School Lotteries to Evaluate the Value-Added Model
ERIC Educational Resources Information Center
Deutsch, Jonah
2013-01-01
There has been an active debate in the literature over the validity of value-added models. In this study, the author tests the central assumption of value-added models that school assignment is random relative to expected test scores conditional on prior test scores, demographic variables, and other controls. He uses a Chicago charter school's…
Full Adaptive Optics Images of ADS 9731 and MU Cassiopeiae: Orbits and Masses
NASA Astrophysics Data System (ADS)
Drummond, Jack D.; Christou, Julian C.; Fugate, Robert Q.
1995-09-01
The double double ADS 9731 and the nearby Population II astrometric binary μ Cas have been imaged with full adaptive optics employed at the 1.5 m telescope belonging to the USAF Phillips Laboratory's Starfire Optical Range near Albuquerque, New Mexico. On 1994 May 4 at a wavelength of 0.85 μm, the Δmag values and separations for ADS 9731 components AB were observed to be 2.19 and 1".27, 0.90 and 1".55 for CD, and 0.40 and 14".8 between A and C. Combining these observations with earlier ones, we have obtained circular, highly inclined, long-period (834 and 1230 yr) preliminary orbits for both pairs and derived their masses along with other astrophysical quantities. However, consideration of stellar evolutionary models leads to a disagreement in the derived distance to the system (108.1 pc) and/or masses, which will perhaps be resolved by subsequent orbital refinement. The first ever real-time images at short wavelengths (<1 μm) of the faint companion to the astrometric binary μ Cas A component were easily made at 0.85 microns on 1994 August 28 and October 22, with movement noted between the two dates. The Δmag value was determined to be 4.9±0.1, and the separation on the two dates was 0".73 and 0".66. Combining our measurements with astrometric data from both Sproul and Allegheny Observatories, we make a simultaneous fit for a new master orbit and find masses of 0.742±0.059 and 0.173±0.011 Msun for A and B, respectively. From further analysis we derive a presumably primordial helium abundance f6r μ Cas of Y = 0.24±0.07 for an assumed age of 1010 yr and the latest measured metallicity of Z = 0.0021.
Value-Added Models for the Pittsburgh Public Schools
ERIC Educational Resources Information Center
Johnson, Matthew; Lipscomb, Stephen; Gill, Brian; Booker, Kevin; Bruch, Julie
2012-01-01
At the request of Pittsburgh Public Schools (PPS) and the Pittsburgh Federation of Teachers (PFT), Mathematica has developed value-added models (VAMs) that aim to estimate the contributions of individual teachers, teams of teachers, and schools to the achievement growth of their students. The authors' work in estimating value-added in Pittsburgh…
The Use of Stereotypes in Mass Media Advertising: Blacks in Magazine, Newspaper and Television Ads.
ERIC Educational Resources Information Center
Culley, James D.; Bennett, Rex
A brief review of the literature on the use of black stereotypes in mass media advertising, and the results of a current study in this area are presented. Data were gathered by analysis of 1,536 ads in six general interest magazines and 4,371 ads in the New York Times over a one month period, and 368 television commercials on three networks over a…
A note on physical mass and the thermodynamics of AdS-Kerr black holes
McInnes, Brett; Ong, Yen Chin E-mail: yenchin.ong@nordita.org
2015-11-01
As with any black hole, asymptotically anti-de Sitter Kerr black holes are described by a small number of parameters, including a ''mass parameter'' M that reduces to the AdS-Schwarzschild mass in the limit of vanishing angular momentum. In sharp contrast to the asymptotically flat case, the horizon area of such a black hole increases with the angular momentum parameter a if one fixes M; this appears to mean that the Penrose process in this case would violate the Second Law of black hole thermodynamics. We show that the correct procedure is to fix not M but rather the ''physical'' mass E=M/(1−a{sup 2}/L{sup 2}){sup 2}; this is motivated by the First Law. For then the horizon area decreases with a. We recommend that E always be used as the mass in physical processes: for example, in attempts to ''over-spin'' AdS-Kerr black holes.
Expression profiles for macrophage alternative activation genes in AD and in mouse models of AD
Colton, Carol A; Mott, Ryan T; Sharpe, Hayley; Xu, Qing; Van Nostrand, William E; Vitek, Michael P
2006-01-01
Background Microglia are associated with neuritic plaques in Alzheimer disease (AD) and serve as a primary component of the innate immune response in the brain. Neuritic plaques are fibrous deposits composed of the amyloid beta-peptide fragments (Abeta) of the amyloid precursor protein (APP). Numerous studies have shown that the immune cells in the vicinity of amyloid deposits in AD express mRNA and proteins for pro-inflammatory cytokines, leading to the hypothesis that microglia demonstrate classical (Th-1) immune activation in AD. Nonetheless, the complex role of microglial activation has yet to be fully explored since recent studies show that peripheral macrophages enter an "alternative" activation state. Methods To study alternative activation of microglia, we used quantitative RT-PCR to identify genes associated with alternative activation in microglia, including arginase I (AGI), mannose receptor (MRC1), found in inflammatory zone 1 (FIZZ1), and chitinase 3-like 3 (YM1). Results Our findings confirmed that treatment of microglia with anti-inflammatory cytokines such as IL-4 and IL-13 induces a gene profile typical of alternative activation similar to that previously observed in peripheral macrophages. We then used this gene expression profile to examine two mouse models of AD, the APPsw (Tg-2576) and Tg-SwDI, models for amyloid deposition and for cerebral amyloid angiopathy (CAA) respectively. AGI, MRC1 and YM1 mRNA levels were significantly increased in the Tg-2576 mouse brains compared to age-matched controls while TNFα and NOS2 mRNA levels, genes commonly associated with classical activation, increased or did not change, respectively. Only TNFα mRNA increased in the Tg-SwDI mouse brain. Alternative activation genes were also identified in brain samples from individuals with AD and were compared to age-matched control individuals. In AD brain, mRNAs for TNFα, AGI, MRC1 and the chitinase-3 like 1 and 2 genes (CHI3L1; CHI3L2) were significantly increased
Teacher Effects, Value-Added Models, and Accountability
ERIC Educational Resources Information Center
Konstantopoulos, Spyros
2014-01-01
Background: In the last decade, the effects of teachers on student performance (typically manifested as state-wide standardized tests) have been re-examined using statistical models that are known as value-added models. These statistical models aim to compute the unique contribution of the teachers in promoting student achievement gains from grade…
Matrix model maps and reconstruction of AdS supergravity interactions
Cremonini, Sera; Mello Koch, Robert de; Jevicki, Antal
2008-05-15
We consider the question of reconstructing (cubic) SUGRA interactions in AdS/CFT. The method we introduce is based on the matrix model maps (MMP) which were previously successfully employed at the linearized level. The strategy is to start with the map for 1/2 BPS configurations, which is exactly known (to all orders) in the Hamiltonian framework. We then use the extension of the matrix model map with the corresponding Ward identities to completely specify the interaction. A central point in this construction is the nonvanishing of off-shell interactions (even for highest-weight states)
Matrix model maps in AdS/CFT correspondence
Donos, Aristomenis; Jevicki, Antal; Rodrigues, Joao P.
2005-12-15
We discuss an extension of a map between BPS states and free fermions. The extension involves states associated with a full two matrix problem which are constructed using a sequence of integral equations. A two parameter set of matrix model eigenstates is then related to states in SUGRA. Their wave functions are characterized by nontrivial dependence on the radial coordinate of AdS and of the Sphere, respectively. A kernel defining a one to one map between these states is then constructed.
He, Qing Mao, Xinhua Chu, Dongliang
2015-07-15
This study proposes an optimized frequency adjustment method that uses a micro-cantilever beam-based piezoelectric vibration generator based on a combination of added mass and capacitance. The most important concept of the proposed method is that the frequency adjustment process is divided into two steps: the first is a rough adjustment step that changes the size of the mass added at the end of cantilever to adjust the frequency in a large-scale and discontinuous manner; the second step is a continuous but short-range frequency adjustment via the adjustable added capacitance. Experimental results show that when the initial natural frequency of a micro piezoelectric vibration generator is 69.8 Hz, then this natural frequency can be adjusted to any value in the range from 54.2 Hz to 42.1 Hz using the combination of the added mass and the capacitance. This method simply and effectively matches a piezoelectric vibration generator’s natural frequency to the vibration source frequency.
Evaluating Value-Added Models for Teacher Accountability. Monograph
ERIC Educational Resources Information Center
McCaffrey, Daniel F.; Lockwood, J. R.; Koretz, Daniel M.; Hamilton, Laura S.
2003-01-01
Value-added modeling (VAM) to estimate school and teacher effects is currently of considerable interest to researchers and policymakers. Recent reports suggest that VAM demonstrates the importance of teachers as a source of variance in student outcomes. Policymakers see VAM as a possible component of education reform through improved teacher…
Value-Added Models: What the Experts Say
ERIC Educational Resources Information Center
Amrein-Beardsley, Audrey; Pivovarova, Margarita; Geiger, Tray J.
2016-01-01
Being an expert involves explaining how things are supposed to work, and, perhaps more important, why things might not work as supposed. In this study, researchers surveyed scholars with expertise in value-added models (VAMs) to solicit their opinions about the uses and potential of VAMs for teacher-level accountability purposes (for example, in…
NASA Astrophysics Data System (ADS)
Gentilini, C.; Marzani, A.; Mazzotti, M.
2013-01-01
The structural characterization of tie-rods is crucial for the safety assessments of historical buildings. The main parameters that characterize the behavior of tie-rods are the tensile force, the modulus of elasticity of the material and the rotational stiffness at both restraints. Several static, static-dynamic and pure dynamic nondestructive methods have been proposed in the last decades to identify such parameters. However, none of them is able to characterize all the four mentioned parameters. To fill this gap, in this work a procedure based on dynamic testing, added masses and genetic algorithms (GA) is proposed. The identification is driven by GA where the objective function is a metric of the discrepancy between the experimentally determined (by dynamic impact testing) and the numerically computed (by a fast and reliable finite element formulation) frequencies of vibration of some modified systems obtained from the tie-rod by adding a concentrated mass in specific positions. It is shown by a comprehensive numerical testing campaign in which several cases spanning from short, low-stressed, and almost hinged tie-rods to long, high-tensioned, and nearly clamped tie-rods, that the proposed strategy is reliable in the identification of the four unknowns. Finally, the procedure has been applied to characterize a metallic tie-rod located in Palazzo Paleotti, Bologna (Italy).
NASA Astrophysics Data System (ADS)
Amabili, M.; Garziera, R.; Carra, S.
2005-12-01
This paper completes a study of Amabili and Garziera [2000, Vibrations of circular cylindrical shells with nonuniform constraints, elastic bed and added mass; Part I: empty and fluid-filled shells. J. Fluids Struct. 14, 669 690; 2002a, Vibrations of circular cylindrical shells with nonuniform constraints, elastic bed and added mass; Part II: shells containing or immersed in axial flow. J. Fluids Struct. 16, 31 51; 2002b, Vibrations of circular cylindrical shells with nonuniform constraints, elastic bed and added mass; Part III: steady viscous effects on shells conveying fluid. J. Fluids Struct. 16, 795 809] by adding the effect of rotary inertia of added masses to the DIVA code, based on the Rayleigh Ritz method and developed to study free vibrations of circular cylindrical shells with nonuniform boundary conditions, added masses, partial elastic bed, initial pre-stress, conveying flow or immersed in axial flow. The effect of rotary inertia has also been evaluated by commercial FEM software and experiments in order to validate the DIVA code. Calculations and experiments show that the effect of rotary inertia of added masses is generally negligible, except for additional local modes; this is in contrast with what has been found for thin plates, due to the geometric stiffness of the circular cylindrical shell.
Realistic Mobility Modeling for Vehicular Ad Hoc Networks
NASA Astrophysics Data System (ADS)
Akay, Hilal; Tugcu, Tuna
2009-08-01
Simulations used for evaluating the performance of routing protocols for Vehicular Ad Hoc Networks (VANET) are mostly based on random mobility and fail to consider individual behaviors of the vehicles. Unrealistic assumptions about mobility produce misleading results about the behavior of routing protocols in real deployments. In this paper, a realistic mobility modeling tool, Mobility for Vehicles (MOVE), which considers the basic mobility behaviors of vehicles, is proposed for a more accurate evaluation. The proposed model is tested against the Random Waypoint (RWP) model using AODV and OLSR protocols. The results show that the mobility model significantly affects the number of nodes within the transmission range of a node, the volume of control traffic, and the number of collisions. It is shown that number of intersections, grid size, and node density are important parameters when dealing with VANET performance.
Lifshitz from AdS at finite temperature and top down models
NASA Astrophysics Data System (ADS)
Korovin, Yegor; Skenderis, Kostas; Taylor, Marika
2013-11-01
We construct analytically an asymptotically Lifshitz black brane with dynamical exponent z = 1 + ∈ 2 in an Einstein-Proca model, where ∈ is a small parameter. In previous work we showed that the holographic dual QFT is a deformation of a CFT by the time component of a vector operator and the parameter ∈ is the corresponding deformation parameter. In the black brane background this operator additionally acquires a vacuum expectation value. We explain how the QFT Ward identity associated with Lifshitz invariance leads to a conserved mass and compute analytically the thermodynamic quantities showing that they indeed take the form implied by Lifshitz invariance. In the second part of the paper we consider top down Lifshitz models with dynamical exponent close to one and show that they can be understood in terms of vector deformations of conformal field theories. However, in all known cases, both the conformal field theory and its Lifshitz deformations have modes that violate the Breitenlohner-Freedman bound.
Ground-based observations and AD HOC models
NASA Astrophysics Data System (ADS)
Ground based observations of B stars in the visible, the infrared, and the radio region are described along with the ad hoc models proposed to interpret them. It is shown that these observations refer essentially to the photosphere and to the regions of the outer atmosphere where the gas is cool and at low velocity. The characteristics of the variability of the continuous and line spectrum are examined in general and in the cases of individual stars. Finally, linear polarization in the B stars is discussed.
Adding the Long-Term Perspective: Tien Shan's Glacier Mass Change during 1961-2012
NASA Astrophysics Data System (ADS)
Farinotti, D.; Longuevergne, L.; Moholdt, G.; Duethmann, D.; Bolch, T.; Vorogushyn, S.; Guntner, A.; Gafurov, A.
2014-12-01
The Tien Shan, Central Asia's major mountain range, has recently been the focus of a series of studies targeting changes in meteorological variables, glacier mass and extent, as well as runoff. Reviews have repeatedly highlighted the importance of glacier melt for total runoff on the one hand, but the scarcity of direct glaciological observation on the other. At the regional to global scale, the lack of such direct observations has been tackled by using remotely sensed products such as satellite gravimetry and altimetry, but the covered time frame is typically in the order of one decade, thus hampering robust assessments. Here, an ensemble of approaches based on the Gravity Recovery and Climate Experiment (GRACE), the Ice, Cloud and land Elevation Satellite (ICESat), and in-situ glacier mass balance measurements is used for estimating glacier mass changes in the Tien Shan during the last decade, and for validating a glacier mass balance model that we subsequently use for reconstructing a continuous mass balance time series over the last half-century. The model ensemble is designed to take into account a wide range of uncertainty sources including often-neglected differences such as data sources or model structure. We cross-validate our different approaches during the period 2003-2009, and find an average glacier mass change of -6.1±4.4 Gt/a, thus confirming previously published estimates. We use the glaciological modelling approach to extend our estimates over the period 1961-2012, and gain insights in the spatial and temporal evolution of the regional glacier melt. Estimated melt rates are in turn used for assessing the contribution of glacier melt to the total runoff of major hydrological basins, and indicate that the contribution from glaciers has likely been overestimated in a series of previous studies.
In silico strain optimization by adding reactions to metabolic models.
Correia, Sara; Rocha, Miguel
2012-07-24
Nowadays, the concerns about the environment and the needs to increase the productivity at low costs, demand for the search of new ways to produce compounds with industrial interest. Based on the increasing knowledge of biological processes, through genome sequencing projects, and high-throughput experimental techniques as well as the available computational tools, the use of microorganisms has been considered as an approach to produce desirable compounds. However, this usually requires to manipulate these organisms by genetic engineering and/ or changing the enviromental conditions to make the production of these compounds possible. In many cases, it is necessary to enrich the genetic material of those microbes with hereologous pathways from other species and consequently adding the potential to produce novel compounds. This paper introduces a new plug-in for the OptFlux Metabolic Engineering platform, aimed at finding suitable sets of reactions to add to the genomes of selected microbes (wild type strain), as well as finding complementary sets of deletions, so that the mutant becomes able to overproduce compounds with industrial interest, while preserving their viability. The necessity of adding reactions to the metabolic model arises from existing gaps in the original model or motivated by the productions of new compounds by the organism. The optimization methods used are metaheuristics such as Evolutionary Algorithms and Simulated Annealing. The usefulness of this plug-in is demonstrated by a case study, regarding the production of vanillin by the bacterium E. coli.
Investigation on fluid added mass effect in the modal response of a pump-turbine runner
NASA Astrophysics Data System (ADS)
Y He, L.; He, Y.; Y Luo, Y.; Wang, Z. W.
2013-12-01
With the improvement of technology and manufacturing level of hydraulic turbine, there is a trend to increase the power concentration of the units. As a consequence, heads, fluid velocities and rotational speeds are higher which lead to larger hydraulic excitation forces on the structures. Accordingly, vibration and high stress levels will arise, which may cause fatigue damage. Therefore, how to predict the natural frequencies and mode shapes of the runner during the design stage is of paramount importance. In this paper, numerical simulation to analyze the influence of the surrounding water in a pump-turbine runner modal has been carried out by using finite element method. The modal behavior of the runner in air and in water has been calculated. In addition, the added mass effect by comparing the natural frequencies and mode shapes in both cases has been determined. The results show that, due to the added mass effect of the surrounding water, natural frequencies are considerably reduced. The frequency reduction ratio (FRR) varies in a range of 0.06~0.43, depending on the mode shapes. Vibration amplitude and complexity of modes are the two main factors that affect the reduction ratio of runner natural frequencies. For the FRR of in-phase (IP) mode shapes, the vibration amplitude of each mode is considered to be the dominant reason. It is clear that the FRR decreases as the nodal diameter (ND) increases (except for 0ND). While for counter-phase (CP) mode shapes, with the frequency increases, the runner modes will become more and more complex, as a result of which, the FRR increases.
Electrospray ionization mass spectrometric detection of low polar compounds by adding NaAuCl4.
Moriwaki, Hiroshi
2016-11-01
Liquid chromatography electrospray ionization mass spectrometry (LC/ESI/MS) has been widely used for various analyses. However, it is difficult to use LC/ESI/MS for the analysis of low polar compounds, such as polycyclic aromatic hydrocarbons. It is well known that AuCl4(-) ion decomposes to AuCl3 by heating, and AuCl3 is a strong π-electrophilic Lewis acid. Low polar compounds (pyrene, benzo[a]pyrene, perylene, benzo[ghi]perylene, dibenzothiophene and p-dimethoxybenzene) were detected by ESI/MS in the positive ion mode by adding NaAuCl4 . The low polar compound interacts with AuCl3 formed at the ESI interface, and undergoes electron transfer to AuCl3 . The radical cation of the low polar compound was then detected by MS. In addition, the LC/ESI/MS determination of polycyclic aromatic hydrocarbons by the post-column addition of NaAuCl4 was studied. © 2016 The Authors Journal of Mass Spectrometry Published by John Wiley & Sons Ltd.
Supersymmetric model with Dirac neutrino masses
Marshall, Gardner; McCaskey, Mathew; Sher, Marc
2010-03-01
New models have recently been proposed in which a second Higgs doublet couples only to the lepton doublets and right-handed neutrinos, yielding Dirac neutrino masses. The vacuum value of this second 'nu-Higgs' doublet is made very small by means of a very softly-broken Z{sub 2} or U(1) symmetry. The latter is technically natural and avoids fine-tuning and very light scalars. We consider a supersymmetric version of this model, in which two additional doublets are added to the minimal supersymmetric standard model (MSSM). If kinematically allowed, the decay of the heavy MSSM scalar into charged nu-Higgs scalars will yield dilepton events which can be separated from the W-pair background. In addition, the nu-Higgsinos can lead to very dramatic tetralepton, pentalepton, and hexalepton events which have negligible background and can be detected at the LHC and the Tevatron.
Spatial and temporal distribution of mass loss from the Greenland Ice Sheet since AD 1900.
Kjeldsen, Kristian K; Korsgaard, Niels J; Bjørk, Anders A; Khan, Shfaqat A; Box, Jason E; Funder, Svend; Larsen, Nicolaj K; Bamber, Jonathan L; Colgan, William; van den Broeke, Michiel; Siggaard-Andersen, Marie-Louise; Nuth, Christopher; Schomacker, Anders; Andresen, Camilla S; Willerslev, Eske; Kjær, Kurt H
2015-12-17
The response of the Greenland Ice Sheet (GIS) to changes in temperature during the twentieth century remains contentious, largely owing to difficulties in estimating the spatial and temporal distribution of ice mass changes before 1992, when Greenland-wide observations first became available. The only previous estimates of change during the twentieth century are based on empirical modelling and energy balance modelling. Consequently, no observation-based estimates of the contribution from the GIS to the global-mean sea level budget before 1990 are included in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Here we calculate spatial ice mass loss around the entire GIS from 1900 to the present using aerial imagery from the 1980s. This allows accurate high-resolution mapping of geomorphic features related to the maximum extent of the GIS during the Little Ice Age at the end of the nineteenth century. We estimate the total ice mass loss and its spatial distribution for three periods: 1900-1983 (75.1 ± 29.4 gigatonnes per year), 1983-2003 (73.8 ± 40.5 gigatonnes per year), and 2003-2010 (186.4 ± 18.9 gigatonnes per year). Furthermore, using two surface mass balance models we partition the mass balance into a term for surface mass balance (that is, total precipitation minus total sublimation minus runoff) and a dynamic term. We find that many areas currently undergoing change are identical to those that experienced considerable thinning throughout the twentieth century. We also reveal that the surface mass balance term shows a considerable decrease since 2003, whereas the dynamic term is constant over the past 110 years. Overall, our observation-based findings show that during the twentieth century the GIS contributed at least 25.0 ± 9.4 millimetres of global-mean sea level rise. Our result will help to close the twentieth-century sea level budget, which remains crucial for evaluating the reliability of models used to
Spatial and temporal distribution of mass loss from the Greenland Ice Sheet since AD 1900
NASA Astrophysics Data System (ADS)
Kjeldsen, Kristian K.; Korsgaard, Niels J.; Bjørk, Anders A.; Khan, Shfaqat A.; Box, Jason E.; Funder, Svend; Larsen, Nicolaj K.; Bamber, Jonathan L.; Colgan, William; van den Broeke, Michiel; Siggaard-Andersen, Marie-Louise; Nuth, Christopher; Schomacker, Anders; Andresen, Camilla S.; Willerslev, Eske; Kjær, Kurt H.
2015-12-01
The response of the Greenland Ice Sheet (GIS) to changes in temperature during the twentieth century remains contentious, largely owing to difficulties in estimating the spatial and temporal distribution of ice mass changes before 1992, when Greenland-wide observations first became available. The only previous estimates of change during the twentieth century are based on empirical modelling and energy balance modelling. Consequently, no observation-based estimates of the contribution from the GIS to the global-mean sea level budget before 1990 are included in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Here we calculate spatial ice mass loss around the entire GIS from 1900 to the present using aerial imagery from the 1980s. This allows accurate high-resolution mapping of geomorphic features related to the maximum extent of the GIS during the Little Ice Age at the end of the nineteenth century. We estimate the total ice mass loss and its spatial distribution for three periods: 1900-1983 (75.1 ± 29.4 gigatonnes per year), 1983-2003 (73.8 ± 40.5 gigatonnes per year), and 2003-2010 (186.4 ± 18.9 gigatonnes per year). Furthermore, using two surface mass balance models we partition the mass balance into a term for surface mass balance (that is, total precipitation minus total sublimation minus runoff) and a dynamic term. We find that many areas currently undergoing change are identical to those that experienced considerable thinning throughout the twentieth century. We also reveal that the surface mass balance term shows a considerable decrease since 2003, whereas the dynamic term is constant over the past 110 years. Overall, our observation-based findings show that during the twentieth century the GIS contributed at least 25.0 ± 9.4 millimetres of global-mean sea level rise. Our result will help to close the twentieth-century sea level budget, which remains crucial for evaluating the reliability of models used to
Preferential survival in models of complex ad hoc networks
NASA Astrophysics Data System (ADS)
Kong, Joseph S.; Roychowdhury, Vwani P.
2008-05-01
There has been a rich interplay in recent years between (i) empirical investigations of real-world dynamic networks, (ii) analytical modeling of the microscopic mechanisms that drive the emergence of such networks, and (iii) harnessing of these mechanisms to either manipulate existing networks, or engineer new networks for specific tasks. We continue in this vein, and study the deletion phenomenon in the web by the following two different sets of websites (each comprising more than 150,000 pages) over a one-year period. Empirical data show that there is a significant deletion component in the underlying web networks, but the deletion process is not uniform. This motivates us to introduce a new mechanism of preferential survival (PS), where nodes are removed according to the degree-dependent deletion kernel, D(k)∝k, with α≥0. We use the mean-field rate equation approach to study a general dynamic model driven by Preferential Attachment (PA), Double PA (DPA), and a tunable PS (i.e., with any α>0), where c nodes ( c<1) are deleted per node added to the network, and verify our predictions via large-scale simulations. One of our results shows that, unlike in the case of uniform deletion (i.e., where α=0), the PS kernel when coupled with the standard PA mechanism, can lead to heavy-tailed power-law networks even in the presence of extreme turnover in the network. Moreover, a weak DPA mechanism, coupled with PS, can help to make the network even more heavy-tailed, especially in the limit when deletion and insertion rates are almost equal, and the overall network growth is minimal. The dynamics reported in this work can be used to design and engineer stable ad hoc networks and explain the stability of the power-law exponents observed in real-world networks.
Syrian hamster tumor model to study oncolytic Ad5-based vectors.
Dhar, Debanjan; Toth, Karoly; Wold, William S M
2012-01-01
Oncolytic (replicating) adenovirus (Ad) vectors are emerging as a promising form of a cancer therapy agent. There has been a need for an appropriate animal model to study oncolytic Ad since human Ad -replication is usually species specific. We have shown that Syrian (golden) hamsters are an appropriate animal model to study human Ad5-based vectors. Syrian hamsters are immunocompetent, and they allow human Ad5 replication in normal tissues as well as in Syrian hamster cancer cells. The development of the Syrian hamster as a model to study oncolytic Ad vectors has opened avenues to explore the role of host immune response and preexisting immunity in Ad vector efficacy and toxicity/biodistribution following Ad vector administration. Since most of the normal tissues in the Syrian hamster are permissive for human Ad5 replication, Ad vectors can be studied in the context of orthotopic cancer model developed in Syrian hamsters.
Model of the world oil market with an OPEC cartel. [1980 AD to 2040 AD
Alsmiller, R.G. Jr.; Horwedel, J.E.; Marshalla, R.A.; Nesbitt, D.M.; Haas, S.M.
1984-08-01
A world oil market model (WOM) with OPEC treated as a Stackelberg cartel has been developed within the framework of the Generalized Equilibrium Modeling System (GEMS) that is available from Decision Focus, Inc. The US sector of the model is represented by a Liquid Fuels Supply model that was presented previously. The WOM model is described and results obtained with the model for the period 1980 to 2040 are presented. For comparative purposes, results obtained with the model when OPEC is treated as a competitive producer are also presented. By comparing the world oil price as a function of time from the two calculations, the influence that OPEC may have on the oil market by exploiting all of its market power is quantified. The world oil price as obtained with the WOM model is also compared with world oil price projections from a variety of sources. 22 references, 9 figures, 2 tables.
Modeling Interplanetary Coronal Mass Ejections
NASA Technical Reports Server (NTRS)
Riley, Pete
2004-01-01
Heliospheric models of Coronal Mass Ejection (CME) propagation and evolution provide an important insight into the dynamics of CMEa and are a valuable tool for interpreting interplanetary in situ observations. Moreover, they represent a virtual laboratory for exploring conditions and regions of space that are not conveniently or currently accessible by spacecraft. In this review I summarize recent advances in modeling the properties and evolution of CMEs in the solar wind. In particular, I will focus on: (1) the types of ICME models; (2) the boundary conditions that are imposed, (3) the role of the ambient solar wind; (4) predicting new phenomena; and (5) distinguishing between competing CME initiation mechanisms. I will conclude by discussing what topics will likely be important for models to address in the future.
Model of neutrino effective masses
Dinh Nguyen Dinh; Nguyen Thi Hong Van; Nguyen Anh Ky; Phi Quang Van
2006-10-01
It is shown that an effective (nonrenormalizable) coupling of lepton multiplets to scalar triplets in the 331 model with sterile/exotic neutrinos, can be a good way for generating neutrino masses of different types. The method is simple and avoids radiative/loop calculations which, sometimes, are long and complicated. Basing on some astrophysical arguments it is also stated that the scale of SU(3){sub L} symmetry breaking is at TeV scale, in agreement with earlier investigations. Or equivalently, starting from this symmetry breaking scale we could have sterile/exotic neutrinos with mass of a few keV's which could be used to explain several astrophysical and cosmological puzzles, such as the dark matter, the fast motion of the observed pulsars, the re-ionization of the Universe, etc.
Assessing the TARES as an ethical model for antismoking ads.
Lee, Seow Ting; Cheng, I-Huei
2010-01-01
This study examines the ethical dimensions of public health communication, with a focus on antismoking public service announcements (PSAs). The content analysis of 826 television ads from the U.S. Centers for Disease Control and Prevention's (CDC) Media Campaign Resource Center is an empirical testing of Baker and Martinson's (2001) TARES Test that directly examines persuasive messages for truthfulness, authenticity, respect, equity, and social responsibility. In general, the antismoking ads score highly on ethicality. There are significant relationships between ethicality and message attributes (thematic frame, emotion appeal, source, and target audience). Ads that portrayed smoking as damaging to health and socially unacceptable score lower in ethicality than ads that focus on tobacco industry manipulation, addiction, dangers of secondhand smoke, and cessation. Emotion appeals of anger and sadness are associated with higher ethicality than shame and humor appeals. Ads targeting teen/youth audiences score lower on ethicality than ads targeting adult and general audiences. There are significant differences in ethicality based on source; ads produced by the CDC rate higher in ethicality than other sources. Theoretical implications and practical recommendations are discussed.
AdS Black Disk Model for Small-x Deep Inelastic Scattering
NASA Astrophysics Data System (ADS)
Cornalba, Lorenzo; Costa, Miguel S.; Penedones, João
2010-08-01
Using the approximate conformal invariance of QCD at high energies we consider a simple anti-de Sitter black disk model to describe saturation in deep inelastic scattering. Deep inside saturation the structure functions have the same power law scaling, FT˜FL˜x-ω, where ω is related to the expansion rate of the black disk with energy. Furthermore, the ratio FL/FT is given by the universal value (1+ω)/(3+ω), independently of the target. For γ*-γ* scattering at high energies we obtain explicit expressions and ratios for the total cross sections of transverse and longitudinal photons in terms of the single parameter ω.
Rossi, Stefano; Colazza, Alessandra; Petrarca, Maurizio; Castelli, Enrico; Cappa, Paolo; Krebs, Hermano Igo
2013-01-01
We are designing a pediatric exoskeletal ankle robot (pediatric Anklebot) to promote gait habilitation in children with Cerebral Palsy (CP). Few studies have evaluated how much or whether the unilateral loading of a wearable exoskeleton may have the unwanted effect of altering significantly the gait. The purpose of this study was to evaluate whether adding masses up to 2.5 kg, the estimated overall added mass of the mentioned device, at the knee level alters the gait kinematics. Ten healthy children and eight children with CP, with light or mild gait impairment, walked wearing a knee brace with several masses. Gait parameters and lower-limb joint kinematics were analyzed with an optoelectronic system under six conditions: without brace (natural gait) and with masses placed at the knee level (0.5, 1.0, 1.5, 2.0, 2.5 kg). T-tests and repeated measures ANOVA tests were conducted in order to find noteworthy differences among the trial conditions and between loaded and unloaded legs. No statistically significant differences in gait parameters for both healthy children and children with CP were observed in the five “with added mass” conditions. We found significant differences among “natural gait” and “with added masses” conditions in knee flexion and hip extension angles for healthy children and in knee flexion angle for children with CP. This result can be interpreted as an effect of the mechanical constraint induced by the knee brace rather than the effect associated with load increase. The study demonstrates that the mechanical constraint induced by the brace has a measurable effect on the gait of healthy children and children with CP and that the added mass up to 2.5 kg does not alter the lower limb kinematics. This suggests that wearable devices weighing 25 N or less will not noticeably modify the gait patterns of the population examined here. PMID:24023822
NASA Astrophysics Data System (ADS)
Guo, X. L.; Wang, L.; Wang, J.; Wang, S. Y.; Liu, Y. Y.; Sun, S.
2014-01-01
The Injector-II of ADS project will include two cryomodules, each of which consists of eight HWR cavities and nine SC solenoid magnets. A test cryomodule (TCM1) containing one HWR cavity and two SC magnets was developed for verification of related technique at the first stage. The TCM1 cryostat was designed by Shanghai Institute of Applied Physics of Chinese Academy of Sciences (SINAP, CAS). The cold mass support assembly in the test cryomodule should accommodate the unbalanced loads induced by each cold mass assembly, the deformation induced by thermal shrinkage, and the thermal stress between different materials. In order to validate the structure design, coupled thermal and mechanical analysis on the cold mass support assembly was performed. The temperature, deformation and stress of the cold mass support assembly were obtained. The results effectively provide the guideline for the design and improvement of the cold mass support assembly.
Inverse magnetic catalysis in the soft-wall model of AdS/QCD
NASA Astrophysics Data System (ADS)
Li, Danning; Huang, Mei; Yang, Yi; Yuan, Pei-Hung
2017-02-01
Magnetic effects on chiral phase transition have been investigated in a modified soft-wall AdS/QCD model, in which the dilaton field is taken to be negative at the ultraviolet region and positive at the infrared region as in Phys. Rev. D 93 (2016) 101901 and JHEP 04 (2016) 036. The magnetic field is introduced into the background geometry by solving the Einstein-Maxwell system. After embedding the magnetized background geometry into the modified soft-wall model, the magnetic field dependent behavior of chiral condensate is worked out numerically. It is found that, in the chiral limit, the chiral phase transition remains as a second order at finite magnetic field B, while the symmetry restoration temperature and chiral condensate decrease with the increasing of magnetic field in small B region. When including finite quark mass effect, the phase transition turns to be a crossover one, and the transition temperature still decreases with increasing magnetic field B when B is not very large. In this sense, inverse magnetic catalysis effect is observed in this modified soft-wall AdS/QCD model.
NASA Astrophysics Data System (ADS)
An, Song; Faltinsen, Odd M.
2013-05-01
Forced harmonic heave motions of horizontally submerged and perforated rectangular plates are studied experimentally and numerically at both a deep and shallow submergence. The steady-state vertical forces are expressed in terms of added mass and damping coefficients. The numerical results are partly obtained by combining potential flow with linear free-surface conditions and a nonlinear viscous pressure loss condition at the mean oscillatory plate position. A domain decomposition technique is applied with a boundary element method in the inner domain and an analytical representation of the velocity potential in the outer domain. A drag term accounts for the vortex shedding at the outer plate edges. The numerically predicted Keulegan-Carpenter number dependent heave added mass and damping coefficients agree reasonably with experimental values, in particular for the deeper submergence.
A study on the characteristic behavior of mass inclusions added to a poro-elastic layer
NASA Astrophysics Data System (ADS)
Idrisi, Kamal; Johnson, Marty E.; Theurich, Daniel; Carneal, James P.
2010-09-01
Heterogeneous (HG) blankets consist of a layer of poro-elastic media with small embedded masses that replicate the behavior of a distributed mass-spring-damper system. The concept of an HG blanket used to control the sound transmission through an aircraft double-panel system has already been developed and cited in the present literature. However, deficiencies in methodical property control exist; therefore, the prime objective of this research is to provide a simple method to predict and control material properties of the heterogeneous blankets through alteration of mass and stiffness parameters. Mass inclusion size, shape, and placement were varied. If optimized heterogeneous (HG) blankets targeted to specific applications are to be successfully developed, control of these parameters is necessary. This research offers a detailed analysis of the behavior of the mass inclusions, highlighting controlled stiffness variation of the mass-spring-damper systems inside the HG blanket. Characteristic parameters of the HG blanket like the "footprint," "effective area," and the "mass interaction distance" are defined and confirmed through mathematical calculations and experimental results. A novel, empirical approach to predict the natural frequency of different mass shapes embedded in porous media was derived and experimentally verified for many different types of porous media, including melamine foam, polyurethane, and polyamide. A maximum error of 8% existed for all the predictions made in this document.
Unification of gauge couplings in radiative neutrino mass models
NASA Astrophysics Data System (ADS)
Hagedorn, Claudia; Ohlsson, Tommy; Riad, Stella; Schmidt, Michael A.
2016-09-01
We investigate the possibility of gauge coupling unification in various radiative neutrino mass models, which generate neutrino masses at one- and/or two-loop level. Renormalization group running of gauge couplings is performed analytically and numerically at one- and two-loop order, respectively. We study three representative classes of radiative neutrino mass models: (I) minimal ultraviolet completions of the dimension-7 Δ L = 2 operators which generate neutrino masses at one- and/or two-loop level without and with dark matter candidates, (II) models with dark matter which lead to neutrino masses at one-loop level and (III) models with particles in the adjoint representation of SU(3). In class (I), gauge couplings unify in a few models and adding dark matter amplifies the chances for unification. In class (II), about a quarter of the models admits gauge coupling unification. In class (III), none of the models leads to gauge coupling unification. Regarding the scale of unification, we find values between 1014 GeV and 1016 GeV for models belonging to class (I) without dark matter, whereas models in class (I) with dark matter as well as models of class (II) prefer values in the range 5·1010 - 5·1014 GeV.
Imaging of Cells and Tissues with Mass Spectrometry: Adding Chemical Information to Imaging
Zimmerman, Tyler A.; Monroe, Eric B.; Tucker, Kevin R.; Rubakhin, Stanislav S.; Sweedler, Jonathan V.
2009-01-01
Techniques that map the distribution of compounds in biological tissues can be invaluable in addressing a number of critical questions in biology and medicine. One of the newest methods, mass spectrometric imaging, has enabled investigation of spatial localization for a variety of compounds ranging from atomics to proteins. The ability of mass spectrometry to detect and differentiate a large number of unlabeled compounds makes the approach amenable to the study of complex biological tissues. This chapter focuses on recent advances in the instrumentation and sample preparation protocols that make mass spectrometric imaging of biological samples possible, including strategies for both tissue and single cell imaging using the following mass spectrometric ionization methods: matrix-assisted laser desorption/ionization, secondary ion, electrospray and desorption electrospray. PMID:19118682
Value-Added Models of Assessment: Implications for Motivation and Accountability
ERIC Educational Resources Information Center
Anderman, Eric M.; Anderman, Lynley H.; Yough, Michael S.; Gimbert, Belinda G.
2010-01-01
In this article, we examine the relations of value-added models of measuring academic achievement to student motivation. Using an achievement goal orientation theory perspective, we argue that value-added models, which focus on the progress of individual students over time, are more closely aligned with research on student motivation than are more…
Interpreting incremental value of markers added to risk prediction models.
Pencina, Michael J; D'Agostino, Ralph B; Pencina, Karol M; Janssens, A Cecile J W; Greenland, Philip
2012-09-15
The discrimination of a risk prediction model measures that model's ability to distinguish between subjects with and without events. The area under the receiver operating characteristic curve (AUC) is a popular measure of discrimination. However, the AUC has recently been criticized for its insensitivity in model comparisons in which the baseline model has performed well. Thus, 2 other measures have been proposed to capture improvement in discrimination for nested models: the integrated discrimination improvement and the continuous net reclassification improvement. In the present study, the authors use mathematical relations and numerical simulations to quantify the improvement in discrimination offered by candidate markers of different strengths as measured by their effect sizes. They demonstrate that the increase in the AUC depends on the strength of the baseline model, which is true to a lesser degree for the integrated discrimination improvement. On the other hand, the continuous net reclassification improvement depends only on the effect size of the candidate variable and its correlation with other predictors. These measures are illustrated using the Framingham model for incident atrial fibrillation. The authors conclude that the increase in the AUC, integrated discrimination improvement, and net reclassification improvement offer complementary information and thus recommend reporting all 3 alongside measures characterizing the performance of the final model.
The added value of high-resolution climate modeling of the Greenland Ice Sheet
NASA Astrophysics Data System (ADS)
van de Berg, Willem Jan; van Meijgaard, Erik; van Ulft, Bert; Machguth, Horst; Noël, Brice; van den Broeke, Michiel
2016-04-01
The local surface mass balance (SMB) of glaciers and ice sheets is to a very high extent related to topography. Subsequently, spatial variability in the SMB is also related to the spatial scales in the topography. The typical topographic length scales on the Greenland Ice Sheet are from several to over hundred kilometers. Therefore, regional climate models with resolutions between 5 and 25 kilometers normally capture the SMB of the Greenland Ice Sheet well. In this study, we analyze the added value of high-resolution regional climate simulations compared to statistical downscaling. For this aim, the regional climate model RACMO2 has been run for South Greenland for the period 2007-2014 using resolutions of 60, 20, 6.6 and 2.2 kilometer. Modeled and downscaled SMB from these four simulations are analyzed and evaluated against ablation observations. Our results show that the strong correlation of runoff to elevation makes statistical downscaling a robust tool to refine modeled spatial SMB patterns. However, only high-resolution climate modeling can improve the physical representation of the SMB in lower ablation zone, because the summertime interaction between the warm air over the tundra and the colder air over the ice sheet starts to be resolved. As a result, the runoff in the lower ablation zone is more enhanced compared to lower resolution simulations and statistical downscaled SMB.
Strategies for fitting nonlinear ecological models in R, AD Model Builder, and BUGS
Bolker, Benjamin M.; Gardner, Beth; Maunder, Mark; Berg, Casper W.; Brooks, Mollie; Comita, Liza; Crone, Elizabeth; Cubaynes, Sarah; Davies, Trevor; de Valpine, Perry; Ford, Jessica; Gimenez, Olivier; Kéry, Marc; Kim, Eun Jung; Lennert-Cody, Cleridy; Magunsson, Arni; Martell, Steve; Nash, John; Nielson, Anders; Regentz, Jim; Skaug, Hans; Zipkin, Elise
2013-01-01
1. Ecologists often use nonlinear fitting techniques to estimate the parameters of complex ecological models, with attendant frustration. This paper compares three open-source model fitting tools and discusses general strategies for defining and fitting models. 2. R is convenient and (relatively) easy to learn, AD Model Builder is fast and robust but comes with a steep learning curve, while BUGS provides the greatest flexibility at the price of speed. 3. Our model-fitting suggestions range from general cultural advice (where possible, use the tools and models that are most common in your subfield) to specific suggestions about how to change the mathematical description of models to make them more amenable to parameter estimation. 4. A companion web site (https://groups.nceas.ucsb.edu/nonlinear-modeling/projects) presents detailed examples of application of the three tools to a variety of typical ecological estimation problems; each example links both to a detailed project report and to full source code and data.
Adding ecosystem function to agent-based land use models
Yadav, V.; Del Grosso, S.J.; Parton, W.J.; Malanson, G.P.
2015-01-01
The objective of this paper is to examine issues in the inclusion of simulations of ecosystem functions in agent-based models of land use decision-making. The reasons for incorporating these simulations include local interests in land fertility and global interests in carbon sequestration. Biogeochemical models are needed in order to calculate such fluxes. The Century model is described with particular attention to the land use choices that it can encompass. When Century is applied to a land use problem the combinatorial choices lead to a potentially unmanageable number of simulation runs. Century is also parameter-intensive. Three ways of including Century output in agent-based models, ranging from separately calculated look-up tables to agents running Century within the simulation, are presented. The latter may be most efficient, but it moves the computing costs to where they are most problematic. Concern for computing costs should not be a roadblock. PMID:26191077
ASC-AD penetration modeling FY05 status report.
Kistler, Bruce L.; Ostien, Jakob T.; Chiesa, Michael L.; Bhutani, Nipun; Ohashi, Yuki; Marin, Esteban B.; Korellis, John S.; Settgast, Randy; Antoun, Bonnie R.
2006-04-01
Sandia currently lacks a high fidelity method for predicting loads on and subsequent structural response of earth penetrating weapons. This project seeks to test, debug, improve and validate methodologies for modeling earth penetration. Results of this project will allow us to optimize and certify designs for the B61-11, Robust Nuclear Earth Penetrator (RNEP), PEN-X and future nuclear and conventional penetrator systems. Since this is an ASC Advanced Deployment project the primary goal of the work is to test, debug, verify and validate new Sierra (and Nevada) tools. Also, since this project is part of the V&V program within ASC, uncertainty quantification (UQ), optimization using DAKOTA [1] and sensitivity analysis are an integral part of the work. This project evaluates, verifies and validates new constitutive models, penetration methodologies and Sierra/Nevada codes. In FY05 the project focused mostly on PRESTO [2] using the Spherical Cavity Expansion (SCE) [3,4] and PRESTO Lagrangian analysis with a preformed hole (Pen-X) methodologies. Modeling penetration tests using PRESTO with a pilot hole was also attempted to evaluate constitutive models. Future years work would include the Alegra/SHISM [5] and AlegrdEP (Earth Penetration) methodologies when they are ready for validation testing. Constitutive models such as Soil-and-Foam, the Sandia Geomodel [6], and the K&C Concrete model [7] were also tested and evaluated. This report is submitted to satisfy annual documentation requirements for the ASC Advanced Deployment program. This report summarizes FY05 work performed in the Penetration Mechanical Response (ASC-APPS) and Penetration Mechanics (ASC-V&V) projects. A single report is written to document the two projects because of the significant amount of technical overlap.
Adding value through accelerator mass spectrometry-enabled first in human studies.
Seymour, Mark A
2016-12-01
Accelerator mass spectrometry (AMS) is an ultra-sensitive technique for the analysis of radiocarbon. It is applicable to bioanalysis of any (14) C-labelled analyte and any sample type. The increasing body of data generated using LC+AMS indicates that the methodology is robust and reliable, and capable of meeting the same validation criteria as conventional bioanalytical techniques. Because it is a tracer technique, AMS is capable of discriminating between an administered radiolabelled dose and endogenous compound or non-radiolabelled compound administered separately. This paper discusses how it can be used to enhance the design of first in human (FIH) clinical studies and generate significant additional data, including: fundamental pharmacokinetics (CL and V), absolute bioavailability, mass balance, routes and rates of excretion, metabolic fate (including first-pass metabolism, identification of biliary metabolites and quantitative data to address metabolite safety testing issues), and tissue disposition of parent compound and metabolites. Because the (14) C-labelled microtracer dose is administered at the same time as a pharmacologically relevant non-radiolabelled dose, there is no concern about dose-linearity. However the mass of the microtracer dose itself is negligible and therefore does not affect the outcome of the FIH study. The addition of microtracer doses to a FIH study typically requires little additional expense, apart from the AMS analytics, making the approach cost-effective. It can also save significant time, compared to conventional approaches, and, by providing reliable human in vivo data as early as possible, prevent unnecessary expenditure later in drug development.
ERIC Educational Resources Information Center
Lincove, Jane Arnold; Osborne, Cynthia; Dillon, Amanda; Mills, Nicholas
2014-01-01
Despite questions about validity and reliability, the use of value-added estimation methods has moved beyond academic research into state accountability systems for teachers, schools, and teacher preparation programs (TPPs). Prior studies of value-added measurement for TPPs test the validity of researcher-designed models and find that measuring…
Rethinking Teacher Evaluation: A Conversation about Statistical Inferences and Value-Added Models
ERIC Educational Resources Information Center
Callister Everson, Kimberlee; Feinauer, Erika; Sudweeks, Richard R.
2013-01-01
In this article, the authors provide a methodological critique of the current standard of value-added modeling forwarded in educational policy contexts as a means of measuring teacher effectiveness. Conventional value-added estimates of teacher quality are attempts to determine to what degree a teacher would theoretically contribute, on average,…
Adding Missing-Data-Relevant Variables to FIML-Based Structural Equation Models
ERIC Educational Resources Information Center
Graham, John W.
2003-01-01
Conventional wisdom in missing data research dictates adding variables to the missing data model when those variables are predictive of (a) missingness and (b) the variables containing missingness. However, it has recently been shown that adding variables that are correlated with variables containing missingness, whether or not they are related to…
Bifurcation and Spike Adding Transition in Chay-Keizer Model
NASA Astrophysics Data System (ADS)
Lu, Bo; Liu, Shenquan; Liu, Xuanliang; Jiang, Xiaofang; Wang, Xiaohui
Electrical bursting is an activity which is universal in excitable cells such as neurons and various endocrine cells, and it encodes rich physiological information. As burst delay identifies that the signal integration has reached the threshold at which it can generate an action potential, the number of spikes in a burst may have essential physiological implications, and the transition of bursting in excitable cells is associated with the bifurcation phenomenon closely. In this paper, we focus on the transition of the spike count per burst of the pancreatic β-cells within a mathematical model and bifurcation phenomenon in the Chay-Keizer model, which is utilized to simulate the pancreatic β-cells. By the fast-slow dynamical bifurcation analysis and the bi-parameter bifurcation analysis, the local dynamics of the Chay-Keizer system around the Bogdanov-Takens bifurcation is illustrated. Then the variety of the number of spikes per burst is discussed by changing the settings of a single parameter and bi-parameter. Moreover, results on the number of spikes within a burst are summarized in ISIs (interspike intervals) sequence diagrams, maximum and minimum, and the number of spikes under bi-parameter value changes.
2015-10-01
AWARD NUMBER: W81XWH-13-1-0253 TITLE: Brain and Plasma Molecular Characterization of the Pathogenic TBI-AD Interrelationship in Mouse Models ... brain and plasma responses in mouse models of TBI, AD and other neurodegenerative conditions (Abdullah et al., 2014; Abdullah et al., 2013; Crawford...identify age/time-dependent expression of brain proteins and lipids in mouse models of AD (PSAPP and hTau) and of mTBI (single and repetitive mTBI in hTau
Autoimmune Manifestations in the 3xTg-AD Model of Alzheimer's Disease
Marchese, Monica; Cowan, David; Head, Elizabeth; Ma, Donglai; Karimi, Khalil; Ashthorpe, Vanessa; Kapadia, Minesh; Zhao, Hui; Davis, Paulina; Sakic, Boris
2015-01-01
Background Immune system activation is frequently reported in patients with Alzheimer's disease (AD). However, it remains unknown whether this is a cause, a consequence, or an epiphenomenon of brain degeneration. Objective The present study examines whether immunological abnormalities occur in a well-established murine AD model and if so, how they relate temporally to behavioral deficits and neuropathology. Methods A broad battery of tests was employed to assess behavioral performance and autoimmune/inflammatory markers in 3xTg-AD (AD) mice and wild type controls from 1.5 to 12 months of age. Results Aged AD mice displayed severe manifestations of systemic autoimmune/inflammatory disease, as evidenced by splenomegaly, hepatomegaly, elevated serum levels of anti-nuclear/anti-dsDNA antibodies, low hematocrit, and increased number of double-negative T splenocytes. However, anxiety-related behavior and altered spleen function were evident as early as 2 months of age, thus preceding typical AD-like brain pathology. Moreover, AD mice showed altered olfaction and impaired “cognitive” flexibility in the first 6 months of life, suggesting mild cognitive impairment-like manifestations before general learning/memory impairments emerged at an older age. Interestingly, all of these features were present in 3xTg-AD mice prior to significant amyloid-β or tau pathology. Conclusion The results indicate that behavioral deficits in AD mice develop in parallel with systemic autoimmune/inflammatory disease. These changes antedate AD-like neuropathology, thus supporting a causal link between autoimmunity and aberrant behavior. Consequently, 3xTg-AD mice may be a useful model in elucidating the role of immune system in the etiology of AD. PMID:24150111
Battery Performance Modelling ad Simulation: a Neural Network Based Approach
NASA Astrophysics Data System (ADS)
Ottavianelli, Giuseppe; Donati, Alessandro
2002-01-01
This project has developed on the background of ongoing researches within the Control Technology Unit (TOS-OSC) of the Special Projects Division at the European Space Operations Centre (ESOC) of the European Space Agency. The purpose of this research is to develop and validate an Artificial Neural Network tool (ANN) able to model, simulate and predict the Cluster II battery system's performance degradation. (Cluster II mission is made of four spacecraft flying in tetrahedral formation and aimed to observe and study the interaction between sun and earth by passing in and out of our planet's magnetic field). This prototype tool, named BAPER and developed with a commercial neural network toolbox, could be used to support short and medium term mission planning in order to improve and maximise the batteries lifetime, determining which are the future best charge/discharge cycles for the batteries given their present states, in view of a Cluster II mission extension. This study focuses on the five Silver-Cadmium batteries onboard of Tango, the fourth Cluster II satellite, but time restrains have allowed so far to perform an assessment only on the first battery. In their most basic form, ANNs are hyper-dimensional curve fits for non-linear data. With their remarkable ability to derive meaning from complicated or imprecise history data, ANN can be used to extract patterns and detect trends that are too complex to be noticed by either humans or other computer techniques. ANNs learn by example, and this is why they can be described as an inductive, or data-based models for the simulation of input/target mappings. A trained ANN can be thought of as an "expert" in the category of information it has been given to analyse, and this expert can then be used, as in this project, to provide projections given new situations of interest and answer "what if" questions. The most appropriate algorithm, in terms of training speed and memory storage requirements, is clearly the Levenberg
Fermion masses and mixing in general warped extra dimensional models
NASA Astrophysics Data System (ADS)
Frank, Mariana; Hamzaoui, Cherif; Pourtolami, Nima; Toharia, Manuel
2015-06-01
We analyze fermion masses and mixing in a general warped extra dimensional model, where all the Standard Model (SM) fields, including the Higgs, are allowed to propagate in the bulk. In this context, a slightly broken flavor symmetry imposed universally on all fermion fields, without distinction, can generate the full flavor structure of the SM, including quarks, charged leptons and neutrinos. For quarks and charged leptons, the exponential sensitivity of their wave functions to small flavor breaking effects yield hierarchical masses and mixing as it is usual in warped models with fermions in the bulk. In the neutrino sector, the exponential wave-function factors can be flavor blind and thus insensitive to the small flavor symmetry breaking effects, directly linking their masses and mixing angles to the flavor symmetric structure of the five-dimensional neutrino Yukawa couplings. The Higgs must be localized in the bulk and the model is more successful in generalized warped scenarios where the metric background solution is different than five-dimensional anti-de Sitter (AdS5 ). We study these features in two simple frameworks, flavor complimentarity and flavor democracy, which provide specific predictions and correlations between quarks and leptons, testable as more precise data in the neutrino sector becomes available.
Relativistic mean-field mass models
NASA Astrophysics Data System (ADS)
Peña-Arteaga, D.; Goriely, S.; Chamel, N.
2016-10-01
We present a new effort to develop viable mass models within the relativistic mean-field approach with density-dependent meson couplings, separable pairing and microscopic estimations for the translational and rotational correction energies. Two interactions, DD-MEB1 and DD-MEB2, are fitted to essentially all experimental masses, and also to charge radii and infinite nuclear matter properties as determined by microscopic models using realistic interactions. While DD-MEB1 includes the σ, ω and ρ meson fields, DD-MEB2 also considers the δ meson. Both mass models describe the 2353 experimental masses with a root mean square deviation of about 1.1 MeV and the 882 measured charge radii with a root mean square deviation of 0.029 fm. In addition, we show that the Pb isotopic shifts and moments of inertia are rather well reproduced, and the equation of state in pure neutron matter as well as symmetric nuclear matter are in relatively good agreement with existing realistic calculations. Both models predict a maximum neutron-star mass of more than 2.6 solar masses, and thus are able to accommodate the heaviest neutron stars observed so far. However, the new Lagrangians, like all previously determined RMF models, present the drawback of being characterized by a low effective mass, which leads to strong shell effects due to the strong coupling between the spin-orbit splitting and the effective mass. Complete mass tables have been generated and a comparison with other mass models is presented.
Voice Communications over 802.11 Ad Hoc Networks: Modeling, Optimization and Call Admission Control
NASA Astrophysics Data System (ADS)
Xu, Changchun; Xu, Yanyi; Liu, Gan; Liu, Kezhong
Supporting quality-of-service (QoS) of multimedia communications over IEEE 802.11 based ad hoc networks is a challenging task. This paper develops a simple 3-D Markov chain model for queuing analysis of IEEE 802.11 MAC layer. The model is applied for performance analysis of voice communications over IEEE 802.11 single-hop ad hoc networks. By using the model, we finish the performance optimization of IEEE MAC layer and obtain the maximum number of voice calls in IEEE 802.11 ad hoc networks as well as the statistical performance bounds. Furthermore, we design a fully distributed call admission control (CAC) algorithm which can provide strict statistical QoS guarantee for voice communications over IEEE 802.11 ad hoc networks. Extensive simulations indicate the accuracy of the analytical model and the CAC scheme.
Quantum self-consistency of AdS×Σ brane models
NASA Astrophysics Data System (ADS)
Flachi, Antonino; Pujolàs, Oriol
2003-07-01
Continuing our previous work, we consider a class of higher dimensional brane models with the topology of AdSD1+1×Σ, where Σ is a one-parameter compact manifold and two branes of codimension one are located at the orbifold fixed points. We consider a setup where such a solution arises from Einstein-Yang-Mills theory and evaluate the one-loop effective potential induced by gauge fields and by a generic bulk scalar field. We show that this type of brane model resolves the gauge hierarchy between the Planck and electroweak scales through redshift effects due to the warp factor a=e-πkr. The value of a is then fixed by minimizing the effective potential. We find that, as in the Randall-Sundrum case, the gauge field contribution to the effective potential stabilizes the hierarchy without fine-tuning as long as the Laplacian ΔΣ on Σ has a zero eigenvalue. Scalar fields can stabilize the hierarchy depending on the mass and the nonminimal coupling. We also address the quantum self-consistency of the solution, showing that the classical brane solution is not spoiled by quantum effects.
Internal structure of charged AdS black holes
NASA Astrophysics Data System (ADS)
Bhattacharjee, Srijit; Sarkar, Sudipta; Virmani, Amitabh
2016-06-01
When an electrically charged black hole is perturbed, its inner horizon becomes a singularity, often referred to as the Poisson-Israel mass inflation singularity. Ori constructed a model of this phenomenon for asymptotically flat black holes, in which the metric can be determined explicitly in the mass inflation region. In this paper we implement the Ori model for charged AdS black holes. We find that the mass function inflates faster than the flat space case as the inner horizon is approached. Nevertheless, the mass inflation singularity is still a weak singularity: Although spacetime curvature becomes infinite, tidal distortions remain finite on physical objects attempting to cross it.
Thearle, Marie S.; Krakoff, Jonathan; Votruba, Susanne B.
2015-01-01
Context: Body fat-free mass (FFM), energy expenditure (EE), and respiratory quotient (RQ) are known predictors of daily food intake. Because FFM largely determines EE, it is unclear whether body composition per se or the underlying metabolism drives dietary intake. Objective: The objective of the study was to test whether 24-hour measures of EE and RQ and their components influence ad libitum food intake independently of FFM. Design and Participants: One hundred seven healthy individuals (62 males/45 females, 84 Native Americans/23 whites; age 33 ± 8 y; body mass index 33 ± 8 kg/m2; body fat 31% ± 8%) had 24-hour measures of EE in a whole-room indirect calorimeter during energy balance, followed by 3 days of ad libitum food intake using computerized vending machine systems. Body composition was estimated by dual-energy x-ray absorptiometry. Main Outcome Measures: FFM, 24-hour EE, RQ, spontaneous physical activity, sleeping EE (sleeping metabolic rate), awake and fed thermogenesis, and ad libitum food intake (INTAKE) were measured. Results: Higher 24-hour RQ (P < .001, partial R2 = 16%) and EE (P = .01, partial R2 = 7%), but not FFM (P = .65), were independent predictors of INTAKE. Mediation analysis demonstrated that 24-hour EE is responsible for 80% of the FFM effect on INTAKE (44.5 ± 16.9 kcal ingested per kilogram of FFM, P= .01), whereas the unique effect due to solely FFM was negligible (10.6 ± 23.2, P = .65). Spontaneous physical activity (r = 0.33, P = .001), but not sleeping metabolic rate (P = .71), positively predicted INTAKE, whereas higher awake and fed thermogenesis determined greater INTAKE only in subjects with a body mass index of 29 kg/m2 or less (r = 0.44, P = .01). Conclusions: EE and RQ, rather than FFM, independently determine INTAKE, suggesting that competitive energy-sensing mechanisms driven by the preferential macronutrient oxidation and total energy demands may regulate food intake. PMID:26086330
Four mass coupled oscillator guitar model.
Popp, John E
2012-01-01
Coupled oscillator models have been used for the low frequency response (50 to 250 Hz) of a guitar. These 2 and 3 mass models correctly predict measured resonance frequency relationships under various laboratory boundary conditions, but did not always represent the true state of a guitar in the players' hands. The model presented has improved these models in three ways, (1) a fourth oscillator includes the guitar body, (2) plate stiffnesses and other fundamental parameters were measured directly and effective areas and masses used to calculate the responses, including resonances and phases, directly, and (3) one of the three resultant resonances varies with neck and side mass and can also be modeled as a bar mode of the neck and body. The calculated and measured resonances and phases agree reasonably well.
Higgs boson masses in supersymmetric models
Berger, M.S.
1991-04-01
Imposing supersymmetry on a Higgs potential constrains the parameters that define the potential. In supersymmetric extensions to the stranded model containing only Higgs SU(2){sub L} doublets there exist Higgs boson mass sum rules and bounds on the Higgs masses at tree level. The prescription for renormalizing these sum rules is derived. An explicit calculation is performed in the minimal supersymmetric extension to the standard model (MSSM). In this model at tree level the mass sum rule is M{sub H}{sup 2} + M{sub h}{sup 2} = M{sub A}{sup 2} + M{sub Z}{sup 2}. The results indicate that large corrections to the sum rules may arise from heavy matter fields, e.g. a heavy top quark. Squarks significantly heavier than their fermionic partners contribute large contributions when mixing occurs in the squark sector. These large corrections result from squark-Higgs couplings that become large in this limit. Contributions to individual Higgs boson masses that are quadratic in the squark masses cancel in the sum rule. Thus the naturalness constraint on Higgs boson masses is hidden in the combination of Higgs boson masses that comprise the sum rule. 39 refs., 13 figs.
Delft Mass Transport model DMT-2
NASA Astrophysics Data System (ADS)
Ditmar, Pavel; Hashemi Farahani, Hassan; Inacio, Pedro; Klees, Roland; Zhao, Qile; Guo, Jing; Liu, Xianglin; Sun, Yu; Riva, Ricardo; Ran, Jiangjun
2013-04-01
Gravity Recovery And Climate Experiment (GRACE) satellite mission has enormously extended our knowledge of the Earth's system by allowing natural mass transport of various origin to be quantified. This concerns, in particular, the depletion and replenishment of continental water stocks; shrinking of polar ice sheets; deformation of the Earth's crust triggered by large earthquakes, and isostatic adjustment processes. A number of research centers compute models of temporal gravity field variations and mass transport, using GRACE data as input. One of such models - Delft Mass Transport model - is being produced at the Delft University of Technology in collaboration with the GNSS Research Center of Wuhan University. A new release of this model, DMT-2, has been produced on the basis of a new (second) release of GRACE level-1b data. This model consists of a time-series of monthly solutions spanning a time interval of more than 8 years, starting from Feb. 2003. Each solution consists of spherical harmonic coefficients up to degree 120. Both unconstrained and optimally filtered solutions are obtained. The most essential improvements of the DMT-2 model, as compared to its predecessors (DMT-1 and DMT-1b), are as follows: (i) improved estimation and elimination of low-frequency noise in GRACE data, so that strong mass transport signals are not damped; (ii) computation of accurate stochastic models of data noise for each month individually with a subsequent application of frequency-dependent data weighting, which allows statistically optimal solutions to be compiled even if data noise is colored and gradually changes in time; (iii) optimized estimation of accelerometer calibration parameters; (iv) incorporation of degree 1 coefficients estimated with independent techniques; (v) usage of state-of-the-art background models to de-alias GRACE data from rapid mass transport signals (this includes the EOT11a model of ocean tides and the latest release of the AOD1B product describing
The Pleiades mass function: Models versus observations
NASA Astrophysics Data System (ADS)
Moraux, E.; Kroupa, P.; Bouvier, J.
2004-10-01
Two stellar-dynamical models of binary-rich embedded proto-Orion-Nebula-type clusters that evolve to Pleiades-like clusters are studied with an emphasis on comparing the stellar mass function with observational constraints. By the age of the Pleiades (about 100 Myr) both models show a similar degree of mass segregation which also agrees with observational constraints. This thus indicates that the Pleiades is well relaxed and that it is suffering from severe amnesia. It is found that the initial mass function (IMF) must have been indistinguishable from the standard or Galactic-field IMF for stars with mass m ≲ 2 M⊙, provided the Pleiades precursor had a central density of about 104.8 stars/pc3. A denser model with 105.8 stars/pc3 also leads to reasonable agreement with observational constraints, but owing to the shorter relaxation time of the embedded cluster it evolves through energy equipartition to a mass-segregated condition just prior to residual-gas expulsion. This model consequently preferentially loses low-mass stars and brown dwarfs (BDs), but the effect is not very pronounced. The empirical data indicate that the Pleiades IMF may have been steeper than the Salpeter for stars with m⪆ 2 M⊙.
Banks, J.W. Henshaw, W.D. Kapila, A.K. Schwendeman, D.W.
2016-01-15
We describe an added-mass partitioned (AMP) algorithm for solving fluid–structure interaction (FSI) problems involving inviscid compressible fluids interacting with nonlinear solids that undergo large rotations and displacements. The computational approach is a mixed Eulerian–Lagrangian scheme that makes use of deforming composite grids (DCG) to treat large changes in the geometry in an accurate, flexible, and robust manner. The current work extends the AMP algorithm developed in Banks et al. [1] for linearly elasticity to the case of nonlinear solids. To ensure stability for the case of light solids, the new AMP algorithm embeds an approximate solution of a nonlinear fluid–solid Riemann (FSR) problem into the interface treatment. The solution to the FSR problem is derived and shown to be of a similar form to that derived for linear solids: the state on the interface being fundamentally an impedance-weighted average of the fluid and solid states. Numerical simulations demonstrate that the AMP algorithm is stable even for light solids when added-mass effects are large. The accuracy and stability of the AMP scheme is verified by comparison to an exact solution using the method of analytical solutions and to a semi-analytical solution that is obtained for a rotating solid disk immersed in a fluid. The scheme is applied to the simulation of a planar shock impacting a light elliptical-shaped solid, and comparisons are made between solutions of the FSI problem for a neo-Hookean solid, a linearly elastic solid, and a rigid solid. The ability of the approach to handle large deformations is demonstrated for a problem of a high-speed flow past a light, thin, and flexible solid beam.
Kong, Yan; Li, Ke; Fu, Tingting; Wan, Chao; Zhang, Dongdong; Song, Hang; Zhang, Yao; Liu, Na; Gan, Zhenji; Yuan, Liudi
2016-01-01
Alzheimer's disease (AD) is a prevalent neurodegenerative disorder characterized by β amyloid (Aβ) deposition and neurofibril tangles. It has been reported that a bioflavonoid, quercetin, could ameliorate AD phenotypes in C. elegans and mice. However, the mechanism underlying the ameliorative effect of quercetin is not fully understood yet. Drosophila models could recapitulate AD-like phenotypes, such as shortened lifespan, impaired locomotive ability as well as defects in learning and memory. So in this study, we investigated the effects of quercetin on AD in Drosophila model and explored the underlying mechanisms. We found quercetin could effectively intervene in AD pathogenesis in vivo. Mechanism study showed quercetin could restore the expression of genes perturbed by Aβ accumulation, such as those involved in cell cycle and DNA replication. Cyclin B, an important cell cycle protein, was chosen to test whether it participated in the AD ameliorative effects of quercetin. We found that cyclin B RNAi in the brain could alleviate AD phenotypes. Taken together, the current study suggested that the neuroprotective effects of quercetin were mediated at least partially by targeting cell cycle-related proteins. PMID:27626494
Kong, Yan; Li, Ke; Fu, Tingting; Wan, Chao; Zhang, Dongdong; Song, Hang; Zhang, Yao; Liu, Na; Gan, Zhenji; Yuan, Liudi
2016-10-18
Alzheimer's disease (AD) is a prevalent neurodegenerative disorder characterized by β amyloid (Aβ) deposition and neurofibril tangles. It has been reported that a bioflavonoid, quercetin, could ameliorate AD phenotypes in C. elegans and mice. However, the mechanism underlying the ameliorative effect of quercetin is not fully understood yet. Drosophila models could recapitulate AD-like phenotypes, such as shortened lifespan, impaired locomotive ability as well as defects in learning and memory. So in this study, we investigated the effects of quercetin on AD in Drosophila model and explored the underlying mechanisms. We found quercetin could effectively intervene in AD pathogenesis in vivo. Mechanism study showed quercetin could restore the expression of genes perturbed by Aβ accumulation, such as those involved in cell cycle and DNA replication. Cyclin B, an important cell cycle protein, was chosen to test whether it participated in the AD ameliorative effects of quercetin. We found that cyclin B RNAi in the brain could alleviate AD phenotypes. Taken together, the current study suggested that the neuroprotective effects of quercetin were mediated at least partially by targeting cell cycle-related proteins.
Leptonic color models from Z{sub 8} orbifolded AdS/CFT
Babu, K. S.; Kephart, Thomas W.; Paes, Heinrich
2008-06-01
We study orbifold compactifications of the type IIB superstring on AdS{sub 5}xS{sup 5}/{gamma}, where {gamma} is the Abelian group Z{sub 8}, which can lead to non-supersymmetric three and four family models based on quartification. In particular, we focus on two models, one fully quartified model and one a model with two trinification families and one quartification family, which reduces to the standard model with a minimal leptonic color sector.
Ocular Changes in TgF344-AD Rat Model of Alzheimer's Disease
Tsai, Yuchun; Lu, Bin; Ljubimov, Alexander V.; Girman, Sergey; Ross-Cisneros, Fred N.; Sadun, Alfredo A.; Svendsen, Clive N.; Cohen, Robert M.; Wang, Shaomei
2014-01-01
Purpose. Alzheimer's disease (AD) is the most common neurodegenerative disorder characterized by progressive decline in learning, memory, and executive functions. In addition to cognitive and behavioral deficits, vision disturbances have been reported in early stage of AD, well before the diagnosis is clearly established. To further investigate ocular abnormalities, a novel AD transgenic rat model was analyzed. Methods. Transgenic (Tg) rats (TgF344-AD) heterozygous for human mutant APPswe/PS1ΔE9 and age-matched wild type (WT) rats, as well as 20 human postmortem retinal samples from both AD and healthy donors were used. Visual function in the rodent was analyzed using the optokinetic response. Immunohistochemistry on retinal and brain sections was used to detect various markers including amyloid-β (Aβ) plaques. Results. As expected, Aβ plaques were detected in the hippocampus, cortex, and retina of Tg rats. Plaque-like structures were also found in two AD human whole-mount retinas. The choroidal thickness was significantly reduced in both Tg rat and in AD human eyes when compared with age-matched controls. Tg rat eyes also showed hypertrophic retinal pigment epithelial cells, inflammatory cells, and upregulation of complement factor C3. Although visual acuity was lower in Tg than in WT rats, there was no significant difference in the retinal ganglion cell number and retinal vasculature. Conclusions. Further studies are needed to elucidate the significance and mechanisms of this pathological change and luminance threshold recording from the superior colliculus. PMID:24398104
The Promise and Peril of Using Value-Added Modeling to Measure Teacher Effectiveness. Research Brief
ERIC Educational Resources Information Center
RAND Corporation, 2004
2004-01-01
Value-added modeling offers the possibility of estimating the effects of teachers and schools on student performance, a potentially important contribution in the current environment of concern for accountability in education. These techniques, however, are susceptible to a number of sources of bias, depending on decisions about how the modeling is…
Giving a Structural Framework for Ohio's Value-Added Model: What All Educators Should Know?
ERIC Educational Resources Information Center
Quattrochi, David P.; Chapman, Paul E.
2010-01-01
A qualitative case study of one rural elementary school in Ohio examined how faculty, administrators, students, and parents experienced Ohio's Value-added model. The findings generated from looking at planning and professional development to implementation of the model generated a close- up of a successful approach to helping teachers use multiple…
ERIC Educational Resources Information Center
Brady, Michael P.; Heiser, Lawrence A.; McCormick, Jazarae K.; Forgan, James
2016-01-01
High-stakes standardized student assessments are increasingly used in value-added evaluation models to connect teacher performance to P-12 student learning. These assessments are also being used to evaluate teacher preparation programs, despite validity and reliability threats. A more rational model linking student performance to candidates who…
NASA Astrophysics Data System (ADS)
Kremer, K.; Simpson, G.; Girardclos, S.
2012-04-01
Steep continental margins are known to collapse, producing submarine landslides that can generate Tsunamis. At smaller scale, the same can happen in lake basins. Lake sediments are excellent archives of such events. The study of mass movement deposits in lake sediments allows a better knowledge of past natural hazards in intracontinental regions at historic and prehistoric timescales. In Lake Geneva (Switzerland-France), more than 100 km of high resolution seismic reflection profiles reveal two distinct sequences in the lakes' late Holocene sedimentation history. The first sequence consists mainly of a succession of five large lens-shaped seismic units (A to E), characterized by transparent/chaotic seismic facies with irregular lower boundaries, interpreted as mass-movement deposits. These units are interbedded with parallel, continuous and strong amplitude reflections, interpreted as the 'background' lake sediment. The largest and most recent unit (E) is 5 m thick, covers an area of 50 km2 and has an estimated minimum volume of 0.25 km3, making it the largest sub-lacustrine mass-movement unit in Switzerland. The second sediment sequence consists of 5 m of 'background' seismic facies with parallel geometry, varying at small scale between chaotic/transparent and continuous, high amplitude reflections, which is interpreted as alternating turbidite and hemipelagic layers, respectively. Four 10 m long sediment cores confirm the seismic interpretation and show that the 5 m thick deposit can be described as a co-genetic debrite turbidite (Talling et al., 2004). Radiocarbon dating of plant macro-remains reveals that the unit E deposit may be linked to the Tauredunum rockslide of 563 AD in Rhone delta area. The induced sediment failure in the Rhone delta triggered a tsunami wave destroying parts of the Geneva Burgudian city and other villages at the lake borders as described in historical records. Numerical simulations, based on the shallow water equations, performed here
A model-driven approach to qualitatively assessing the added value of community coalitions.
Herman, Elizabeth Jane; Keller, Adrienne; Davis, Adam; Ehrensberger, Ryan; Telleen, Sharon; Kurz, Richard; Nesvold, Jill Heins; Findley, Sally; Bryant-Stephens, Tyra; Benson, Mindy; Fierro, Leslie
2011-02-01
Community-based coalitions are commonly formed to plan and to carry out public health interventions. The literature includes evaluations of coalition structure, composition, and functioning; evaluations of community-level changes achieved through coalition activities; and the association between coalition characteristics and various indicators of success. Little information is available on the comparative advantage or "added value" of conducting public health interventions through coalitions as opposed to less structured collaborative mechanisms. This paper describes a qualitative, iterative process carried out with site representatives of the Controlling Asthma in American Cities Project (CAACP) to identify outcomes directly attributable to coalitions. The process yielded 2 complementary sets of results. The first were criteria that articulated and limited the concept of "added value of coalitions". The criteria included consensus definitions, an organizing figure, a logic model, and inclusion/exclusion criteria. The second set of results identified site-specific activities that met the definitional criteria and were, by agreement, examples of CAACP coalitions' added value. Beyond the specific findings relevant to the added value of coalitions in this project, the use of a social ecological model to identify the components of added value and the placement of those components within a logic model specific to coalitions should provide useful tools for those planning and assessing coalition-based projects.
John Day Tailrace MASS2 Hydraulic Modeling
Rakowski, Cynthia L.; Richmond, Marshall C.
2003-06-03
Recent biological results for the Juvenile Bypass System at John Jay Lock and Dam have raised concerns about the hydraulic conditions that are created in the tailrace under different project operations. This Memorandum for Record discusses the development and application of a truncated MASS2 model in the John Day tailrace.
NASA Astrophysics Data System (ADS)
Kluiving, Sjoerd; Bekkema, Marijke; Roymans, Nico; van Mourik, Jan
2015-04-01
Long-term archaeological data gathering in the southern Netherlands may deliver an unprecedented regional comparison that could be exemplary for the Pleistocene sand areas of the Northwest European Plain. On a micro-scale level, it has become clear that Bronze Age (2000-800 BC) and Iron Age (800-12 BC) farmers intensively used the landscape, resulting in a relatively dense distribution pattern of settlements all over the ridges and planes of the cover sand landscape. However, this agricultural use of the landscape related to the "celtic field" system led to a process of soil degradation by increased acidification during which Umbric Podzols gradually transformed into Carbic Podzols that could no longer be used as farmland. According to established "models," this process of "secondary podzolization" particularly affected those sections of the landscape that were dominated by dry sandy soils with a low loam content (loam = clay and silt, between c. 10% and 20%). In the Late Iron Age (250-12 BC), the changing soil conditions resulted in a dramatic shift in the habitation pattern that clearly manifests itself in the Roman period (12 BC-410 AD); on the local scale, the habitation moved from the degenerated soils to nearby areas with better soil conditions (higher loam content), which became more densely inhabited now than in the Bronze Age/Early Iron Age (2000-500 BC). The introduction of new land management (in the later Iron Age, and also by Romans) could also have been important for soil degradation. The areas where the Roman period settlements concentrated became also the areas where we can find the early medieval habitation (447-751 AD) and where the Plaggic Anthrosols started to develop in the late medieval period (1270-1500 AD). This poster is based on the analysis of soil properties. Measured loam values of soil samples (n=181) in Veldhoven, southern Netherlands, are in agreement with the described model that the plaggen cover is located on soils containing high
Ong, Daniel; Wijaya, Linda; Laws, Simon M.; Taddei, Kevin; Newman, Morgan; Lardelli, Michael; Martins, Ralph N.; Verdile, Giuseppe
2013-01-01
We investigated the guinea pig, Cavia porcellus, as a model for Alzheimer’s disease (AD), both in terms of the conservation of genes involved in AD and the regulatory responses of these to a known AD risk factor - high cholesterol intake. Unlike rats and mice, guinea pigs possess an Aβ peptide sequence identical to human Aβ. Consistent with the commonality between cardiovascular and AD risk factors in humans, we saw that a high cholesterol diet leads to up-regulation of BACE1 (β-secretase) transcription and down-regulation of ADAM10 (α-secretase) transcription which should increase release of Aβ from APP. Significantly, guinea pigs possess isoforms of AD-related genes found in humans but not present in mice or rats. For example, we discovered that the truncated PS2V isoform of human PSEN2, that is found at raised levels in AD brains and that increases γ-secretase activity and Aβ synthesis, is not uniquely human or aberrant as previously believed. We show that PS2V formation is up-regulated by hypoxia and a high-cholesterol diet while, consistent with observations in humans, Aβ concentrations are raised in some brain regions but not others. Also like humans, but unlike mice, the guinea pig gene encoding tau, MAPT, encodes isoforms with both three and four microtubule binding domains, and cholesterol alters the ratio of these isoforms. We conclude that AD-related genes are highly conserved and more similar to human than the rat or mouse. Guinea pigs represent a superior rodent model for analysis of the impact of dietary factors such as cholesterol on the regulation of AD-related genes. PMID:23805206
Sangani, A.S. ); Zhang, D.Z.; Prosperetti, A. )
1991-12-01
The motion of bubbles dispersed in a liquid when a small-amplitude oscillatory motion is imposed on the mixture is examined in the limit of small frequency and viscosity. Under these conditions, for bubbles with a stress-free surface, the motion can be described in terms of added mass and viscous force coefficients. For bubbles contaminated with surface-active impurities, the introduction of a further coefficient to parametrize the Basset force is necessary. These coefficients are calculated numerically for random configurations of bubbles by solving the appropriate multibubble interaction problem exactly using a method of multipole expansion. Results obtained by averaging over several configurations are presented. Comparison of the results with those for periodic arrays of bubbles shows that these coefficients are, in general, relatively insensitive to the detailed spatial arrangement of the bubbles. On the basis of this observation, it is possible to estimate them via simple formulas derived analytically for dilute periodic arrays. The effect of surface tension and density of bubbles (or rigid particles in the case where the no-slip boundary condition is applicable) is also examined and found to be rather small.
NASA Astrophysics Data System (ADS)
Ruiz Chavarria, Gerardo; Lopez Sanchez, Erick Javier
2016-11-01
The motion of particles in a fluid is an open problem. The main difficulty arises from the fact that hydrodynamical forces acting on a particle depend on the flow properties. In addition, the form and the size of particles must be taken into account. In this work we present numerical results of the particle transport in a periodic driving flow in a channel flushing into an open domain. To study the transport of particles we solve the equation of motion for a spherical particle in which we include the drag, the gravity, the buoyancy, the added mass and the history force. Additionally we include the corrections for a particle of finite size. For solving this equation a knowledge of the velocity field is required. To obtain the velocity field we solve the Navier Stokes and the continuity equations with a finite volume method. In the flow under study a vorticity dipole and a spanwise vortex are present, both have an important influence on the motion of particles. The dipole enhances displacement of particles because flow between vortices behaves like a jet and the spanwise vortex produces the lifting and deposition of particles from/to the bottom. We observe clustering of particles both into the channel and in the open domain as observed in coastal systems. The authors acknowledge DGAPA-UNAM by support under project PAPIIT IN115315 "Ondas y estructuras coherentes en dinámica de fluidos".
Value-Added Model (VAM) Research for Educational Policy: Framing the Issue
ERIC Educational Resources Information Center
Amrein-Beardsley, Audrey; Collins, Clarin; Polasky, Sarah A.; Sloat, Edward F.
2013-01-01
In this manuscript, the guest editors of the EPAA Special Issue on "Value-Added Model (VAM) Research for Educational Policy" (1) introduce the background and policy context surrounding the increased use of VAMs for teacher evaluation and accountability purposes across the United States; (2) summarize the five research papers and one…
Elementary School Data Issues for Value-Added Models: Implications for Research
ERIC Educational Resources Information Center
Isenberg, Eric; Teh, Bing-ru; Walsh, Elias
2015-01-01
Researchers often presume that it is better to use administrative data from grades 4 and 5 than data from grades 6 through 8 for conducting research on teacher effectiveness that uses value-added models because (1) elementary school teachers teach all subjects to their students in self-contained classrooms and (2) classrooms are more homogenous at…
Accounting for Co-Teaching: A Guide for Policymakers and Developers of Value-Added Models
ERIC Educational Resources Information Center
Isenberg, Eric; Walsh, Elias
2015-01-01
We outline the options available to policymakers for addressing co-teaching in a value-added model. Building on earlier work, we propose an improvement to a method of accounting for co-teaching that treats co-teachers as teams, with each teacher receiving equal credit for co-taught students. Hock and Isenberg (2012) described a method known as the…
The Sensitivity of Value-Added Modeling to the Creation of a Vertical Score Scale
ERIC Educational Resources Information Center
Briggs, Derek C.; Weeks, Jonathan P.
2009-01-01
The purpose of this study was to evaluate the sensitivity of growth and value-added modeling to the way an underlying vertical score scale has been created. Longitudinal item-level data were analyzed with both student- and school-level identifiers for the entire state of Colorado between 2003 and 2006. Eight different vertical scales were…
Methods for Accounting for Co-Teaching in Value-Added Models. Working Paper
ERIC Educational Resources Information Center
Hock, Heinrich; Isenberg, Eric
2012-01-01
Isolating the effect of a given teacher on student achievement (value-added modeling) is complicated when the student is taught the same subject by more than one teacher. We consider three methods, which we call the Partial Credit Method, Teacher Team Method, and Full Roster Method, for estimating teacher effects in the presence of co-teaching.…
What Are Error Rates for Classifying Teacher and School Performance Using Value-Added Models?
ERIC Educational Resources Information Center
Schochet, Peter Z.; Chiang, Hanley S.
2013-01-01
This article addresses likely error rates for measuring teacher and school performance in the upper elementary grades using value-added models applied to student test score gain data. Using a realistic performance measurement system scheme based on hypothesis testing, the authors develop error rate formulas based on ordinary least squares and…
Adding thermal and granularity effects to the effective density fluid model.
Williams, Kevin L
2013-05-01
Previously, an effective density fluid model (EDFM) was developed by the author [J. Acoust. Soc. Am. 110, 2276-2281 (2001)] for unconsolidated granular sediments and applied to sand. The model is a simplification of the full Biot porous media model. Here two additional effects are added to the EDFM model: heat transfer between the liquid and solid at low frequencies and the granularity of the medium at high frequencies. The frequency range studied is 100 Hz-1 MHz. The analytical sound speed and attenuation expressions obtained have no free parameters. The resulting model is compared to ocean data.
An Ad-Hoc Adaptive Pilot Model for Pitch Axis Gross Acquisition Tasks
NASA Technical Reports Server (NTRS)
Hanson, Curtis E.
2012-01-01
An ad-hoc algorithm is presented for real-time adaptation of the well-known crossover pilot model and applied to pitch axis gross acquisition tasks in a generic fighter aircraft. Off-line tuning of the crossover model to human pilot data gathered in a fixed-based high fidelity simulation is first accomplished for a series of changes in aircraft dynamics to provide expected values for model parameters. It is shown that in most cases, for this application, the traditional crossover model can be reduced to a gain and a time delay. The ad-hoc adaptive pilot gain algorithm is shown to have desirable convergence properties for most types of changes in aircraft dynamics.
Biogeochemical modeling at mass extinction boundaries
NASA Technical Reports Server (NTRS)
Rampino, M. R.; Caldeira, K. G.
1991-01-01
The causes of major mass extinctions is a subject of considerable interest to those concerned with the history and evolution of life on earth. The primary objectives of the proposed plan of research are: (1) to develop quantitative time-dependent biogeochemical cycle models, coupled with an ocean atmosphere in order to improve the understanding of global scale physical, chemical, and biological processes that control the distribution of elements important for life at times of mass extinctions; and (2) to develop a comprehensive data base of the best available geochemical, isotopic, and other relevant geologic data from sections across mass extinction boundaries. These data will be used to constrain and test the biogeochemical model. These modeling experiments should prove useful in: (1) determining the possible cause(s) of the environmental changes seen at bio-event boundaries; (2) identifying and quantifying little-known feedbacks among the oceans, atmosphere, and biosphere; and (3) providing additional insights into the possible responses of the earth system to perturbations of various timescales. One of the best known mass extinction events marks the Cretaceous/Tertiary (K/T) boundary (66 Myr ago). Data from the K/T boundary are used here to constrain a newly developed time-dependent biogeochemical cycle model that is designed to study transient behavior of the earth system. Model results predict significant fluctuations in ocean alkalinity, atmospheric CO2, and global temperatures caused by extinction of calcareous plankton and reduction in the sedimentation rates of pelagic carbonates and organic carbon. Oxygen-isotome and other paleoclimatic data from K/T time provide some evidence that such climatic fluctuations may have occurred, but stabilizing feedbacks may have acted to reduce the ocean alkalinity and carbon dioxide fluctuations.
Modelling of Medium Access Control (MAC) Protocols for Mobile Ad-Hoc Networks
2005-06-01
Slot IP Internet Protocol LAN Local Area Network MAC Medium Access Control MACAW Medium Access Protocol for Wireless LANs MANET Mobile Ad-hoc...Unforced state – It waits after entering the state until it is invoked by another process or an interrupt. It is in dark grey on this report, and red ... green in OPNET. A MAC process model is built for general initialisations of the MAC module, and to invoke the selected MAC protocol process model
Annealed Importance Sampling for Neural Mass Models
Penny, Will; Sengupta, Biswa
2016-01-01
Neural Mass Models provide a compact description of the dynamical activity of cell populations in neocortical regions. Moreover, models of regional activity can be connected together into networks, and inferences made about the strength of connections, using M/EEG data and Bayesian inference. To date, however, Bayesian methods have been largely restricted to the Variational Laplace (VL) algorithm which assumes that the posterior distribution is Gaussian and finds model parameters that are only locally optimal. This paper explores the use of Annealed Importance Sampling (AIS) to address these restrictions. We implement AIS using proposals derived from Langevin Monte Carlo (LMC) which uses local gradient and curvature information for efficient exploration of parameter space. In terms of the estimation of Bayes factors, VL and AIS agree about which model is best but report different degrees of belief. Additionally, AIS finds better model parameters and we find evidence of non-Gaussianity in their posterior distribution. PMID:26942606
A neural mass model of spectral responses in electrophysiology
Moran, R.J.; Kiebel, S.J.; Stephan, K.E.; Reilly, R.B.; Daunizeau, J.; Friston, K.J.
2007-01-01
We present a neural mass model of steady-state membrane potentials measured with local field potentials or electroencephalography in the frequency domain. This model is an extended version of previous dynamic causal models for investigating event-related potentials in the time-domain. In this paper, we augment the previous formulation with parameters that mediate spike-rate adaptation and recurrent intrinsic inhibitory connections. We then use linear systems analysis to show how the model's spectral response changes with its neurophysiological parameters. We demonstrate that much of the interesting behaviour depends on the non-linearity which couples mean membrane potential to mean spiking rate. This non-linearity is analogous, at the population level, to the firing rate–input curves often used to characterize single-cell responses. This function depends on the model's gain and adaptation currents which, neurobiologically, are influenced by the activity of modulatory neurotransmitters. The key contribution of this paper is to show how neuromodulatory effects can be modelled by adding adaptation currents to a simple phenomenological model of EEG. Critically, we show that these effects are expressed in a systematic way in the spectral density of EEG recordings. Inversion of the model, given such non-invasive recordings, should allow one to quantify pharmacologically induced changes in adaptation currents. In short, this work establishes a forward or generative model of electrophysiological recordings for psychopharmacological studies. PMID:17632015
Diffractive deep inelastic scattering in an AdS/CFT inspired model: A phenomenological study
Betemps, M. A.; Goncalves, V. P.; Santana Amaral, J. T. de
2010-05-01
The analytical treatment of the nonperturbative QCD dynamics is one of the main open questions of the strong interactions. Currently, it is only possible to get some qualitative information about this regime considering other QCD-like theories, as, for example, the N=4 super Yang-Mills theory, where one can perform calculations in the nonperturbative limit of large 't Hooft coupling using the anti-de Sitter space/conformal field theory (AdS/CFT). Recently, the high energy scattering amplitude was calculated in the AdS/CFT approach, applied to deep-inelastic scattering and confronted with the F{sub 2} HERA data. In this work we extend the nonperturbative AdS/CFT inspired model for diffractive processes and compare its predictions with a perturbative approach based on the Balitsky-Kovchegov equation. We demonstrate that the AdS/CFT inspired model is not able to describe the current F{sub 2}{sup D(3)} HERA data and predicts a similar behavior to that from the Balitsky-Kovchegov equation in the range 10{sup -7} < or approx. x{sub P} < or approx. 10{sup -4}. At smaller values of x{sub P} the diffractive structure function is predicted to be energy independent.
Improving Mass Balance Modeling of Benchmark Glaciers
NASA Astrophysics Data System (ADS)
van Beusekom, A. E.; March, R. S.; O'Neel, S.
2009-12-01
The USGS monitors long-term glacier mass balance at three benchmark glaciers in different climate regimes. The coastal and continental glaciers are represented by Wolverine and Gulkana Glaciers in Alaska, respectively. Field measurements began in 1966 and continue. We have reanalyzed the published balance time series with more modern methods and recomputed reference surface and conventional balances. Addition of the most recent data shows a continuing trend of mass loss. We compare the updated balances to the previously accepted balances and discuss differences. Not all balance quantities can be determined from the field measurements. For surface processes, we model missing information with an improved degree-day model. Degree-day models predict ablation from the sum of daily mean temperatures and an empirical degree-day factor. We modernize the traditional degree-day model as well as derive new degree-day factors in an effort to closer match the balance time series and thus better predict the future state of the benchmark glaciers. For subsurface processes, we model the refreezing of meltwater for internal accumulation. We examine the sensitivity of the balance time series to the subsurface process of internal accumulation, with the goal of determining the best way to include internal accumulation into balance estimates.
ERIC Educational Resources Information Center
Lenkeit, Jenny
2013-01-01
Educational effectiveness research often appeals to "value-added models (VAM)" to gauge the impact of schooling on student learning net of the effect of student background variables. A huge amount of cross-sectional studies do not, however, meet VAM's requirement for longitudinal data. "Contextualised attainment models (CAM)"…
Comparing the F-Spin Mass Model to Other Nuclear Mass Models
NASA Astrophysics Data System (ADS)
Porter, William; Nystrom, Andrew; Aprahamian, Ani
2016-09-01
Nuclear masses and binding energies play an important role in nuclear science and the applications of nuclear science such as nuclear astrophysics. The reliable prediction of nuclear masses far from stability are particularly important for a better understanding of the rapid neutron capture process. We are exploring the implementation of a semi-empirical mass model based on the concept of F-spin in nuclei. This model incorporates the evolution of shape in various regions of the chart of nuclides. Here, with the intent of better predicting nuclear binding energies near the bounds of our experimental knowledge, the F-Spin mass model uses a 9 parameter quadratic equation dependent on the third projection of F-Spin and proton number to evaluate the microscopic portion of all nuclear binding energies. We divide the known 2317 isotopes into 14 different zones for fitting purposes, we are able to generate predictions for nuclear masses in the order of 324 keV. The F-Spin model implied shapes are then compared with a number of other mass models to determine the variations in nuclear structure. This work is supported by the National Science Foundation under Contract PHY-1205412.
Mass Modelling of dwarf Spheroidal Galaxies
NASA Astrophysics Data System (ADS)
Klimentowski, Jarosław; Łokas, Ewa L.; Kazantzidis, Stelios; Prada, Francisco; Mayer, Lucio; Mamon, Gary A.
2008-05-01
We study the origin and properties of unbound stars in the kinematic samples of dwarf spheroidal galaxies. For this purpose we have run a high resolution N-body simulation of a two-component dwarf galaxy orbiting in a Milky Way potential. We create mock kinematic data sets by observing the dwarf in different directions. When the dwarf is observed along the tidal tails the kinematic samples are strongly contaminated by unbound stars from the tails. However, most of the unbound stars can be removed by the method of interloper rejection proposed by den Hartog & Katgert. We model the velocity dispersion profiles of the cleaned-up kinematic samples using solutions of the Jeans equation. We show that even for such a strongly stripped dwarf the Jeans analysis, when applied to cleaned samples, allows us to reproduce the mass and mass-to-light ratio of the dwarf with accuracy typically better than 25%.
Full vector archaeomagnetic data and Bayesian modelling for 1300 to 1750 AD
NASA Astrophysics Data System (ADS)
Schnepp, E.; Lanos, P.; Chauvin, A.
2009-04-01
The data base of geomagnetic palaeointensities obtained from archaeological artefacts is poor and very scattered for Western and Central Europe. High precision palaeointensities have been determined from a single archaeological site in Lübeck (Germany) where a sequence of 25 bread-oven-floors has been preserved in a bakery from medieval times until today. Age dating confines the time interval from about 1300 AD to about 1750 AD. Palaeomagnetic directions have been determined from each oven-floor (Schnepp et al., JGR, 2003). Palaeointensity was measured from selected specimens with the double-heating Thellier method and reliable palaeointensity results have been obtained. Tests for thermoremanent magnetisation anisotropy have been performed, but did not show a significant change, while a cooling rate correction was not necessary. 22 mean palaeointensity values derived from the oven-floors show maxima in the 15th and early 17th century AD, followed by a decrease of palaeointensity of about 25% until 1750 AD. The Thellier experiments provided also new characteristic remanent magnetisation directions which were included in the data set. Mean directions have been recalculated. Palaeointensity together with the directions represent a record of about 450 years full vector secular variation. From this full vector data set a secular variation curve has been calculated using a Bayesian modelling taking dating errors, all errors on the field vector and stratigraphy into account. A smooth curve with an error envelope was obtained which compares very well with the gufm1 geomagnetic model (Jackson et al., Phil. Trans. R. Soc. Lond. A, 2000) obtained from historical observations starting at 1600 AD. Comparison of the marginal curve obtained for palaeointensity with a selected data set of archaeomagnetic intensities from Western and Central Europe will be discussed.
Modelling tsunami sedimentation associated with the AD 1755 event in Algarve (Portugal)
NASA Astrophysics Data System (ADS)
Costa, P. J. M.; Gelfenbaum, G. R.; La Selle, S.; Costas, S.; Andrade, C.; Cascalho, J.; Freitas, M. C.
2015-12-01
Numerical models of tsunami inundation and sedimentation can provide useful insights into the dynamics of palaeotsunamis. We applied a coupled field data and numerical modelling approach for the AD1755 tsunami, the most destructive tsunami to affect the Atlantic coast of Europe in historical times. At Salgados, a lowland on the south coast of Portugal, tsunami deposits from AD1755 mostly consist of massive or normally-graded, landward thinning layers of shell-rich sand with an erosive base within the mud-dominated lowlands. Landward of the foredune, the AD1755 deposit is roughly 10cm thick and thins in the landward and alongshore directions. It is possible to ascribe the sediment source of this deposit to the dune and/or beach based on mineralogical and grain-size comparisons with modern surface samples. The present dune crest height is 6 m above MSL (mean sea level) near the seasonally-closed inlet of the lagoon, and rises alongshore towards the west up to 17m above MSL. From the combination of the spatial distribution of the deposit thickness landward of the sloping dune, and GPR data, which shows an erosional surface at approximately 6m above MSL, we infer that the maximum tsunami water level at the coast was between 6 and 10m. Regional tsunami historical records, however, suggest higher heights, up to 12m above MSL at the coast. We simulated tsunami inundation and sediment transport using Delft3D to examine these discrepancies. A 1D cross shore model was used to test flow height controls on deposit thickness and also to identify the sediment source of the AD1755 deposit. Four possible sediment sources were tested (nearshore, beach, dune and lagoon) using synthetic, long-period waves to simulate the AD1755 tsunami. The combination of geological studies with numerical modeling of inundation and sediment transport produces a better description of the AD1755 tsunami and its effects in coastal areas in the Algarve that will contribute to better hazard assessments.
Mass and power modeling of communication satellites
NASA Technical Reports Server (NTRS)
Price, Kent M.; Pidgeon, David; Tsao, Alex
1991-01-01
Analytic estimating relationships for the mass and power requirements for major satellite subsystems are described. The model for each subsystem is keyed to the performance drivers and system requirements that influence their selection and use. Guidelines are also given for choosing among alternative technologies which accounts for other significant variables such as cost, risk, schedule, operations, heritage, and life requirements. These models are intended for application to first order systems analyses, where resources do not warrant detailed development of a communications system scenario. Given this ground rule, the models are simplified to 'smoothed' representation of reality. Therefore, the user is cautioned that cost, schedule, and risk may be significantly impacted where interpolations are sufficiently different from existing hardware as to warrant development of new devices.
ERIC Educational Resources Information Center
Newton, Xiaoxia A.; Darling-Hammond, Linda; Haertel, Edward; Thomas, Ewart
2010-01-01
Recent policy interest in tying student learning to teacher evaluation has led to growing use of value-added methods for assessing student learning gains linked to individual teachers. VAM analyses rely on complex assumptions about the roles of schools, multiple teachers, student aptitudes and efforts, homes and families in producing measured…
Mass Transfer Model of Desulfurization in the Electroslag Remelting Process
NASA Astrophysics Data System (ADS)
Hou, Dong; Jiang, Zhou-Hua; Dong, Yan-Wu; Li, Yang; Gong, Wei; Liu, Fu-Bin
2017-02-01
Experimental and theoretical studies have been carried out to investigate the effects of the slag on desulfurization during the electroslag remelting (ESR) process with a focus of developing a mass transfer model to understand the mechanism of desulfurization. Stainless steel 1Cr21Ni5Ti was used as the electrode and remelted with two different kinds of slags using a 50-kg ESR furnace. The contents of sulfur along the axial direction of product ingots were analyzed. It was found that the sulfur content of 350 ppm in the electrode is reduced to 71 to 95 ppm in the ingot by remelting with the slag containing 5 wt pct of CaO, and lowered more to 47 to 59 ppm with another slag having 20 wt pct CaO. On the basis of the penetration and film theories, the theoretical model developed in this work well elucidates the kinetics of desulfurization revealing the mechanism of sulfur transfer during the ESR process. The calculation results obtained from the model agree well with the experimental results. The model indicates that when sulfur content in electrode is given, there is a corresponding minimum value of sulfur content in the ingot due to the kinetics limit. This lowest sulfur content cannot be further reduced even with increasing L S (sulfur distribution coefficient between metal and slag phases) or decreasing sulfur content in the slag. Constant addition of extra amount of CaO to the molten slag with the increase of sulfur content in the slag during the remelting process can improve the macrosegregation of sulfur distributed along the axial direction of ESR ingots. Since the rate-determining steps of the sulfur mass transfer lie in the metal phase, adding calcium as deoxidizer can change mass transfer of sulfur and thus promote desulfurization further during the ESR process.
Thermodynamic MHD Modeling of Coronal Mass Ejections
NASA Astrophysics Data System (ADS)
Linker, Jon A.; Lionello, R.; Mikic, Z.; Riley, P.; Titov, V.
2007-05-01
Coronal mass ejections (CMEs) disrupt the large-scale coronal magnetic field and propel plasma and magnetic flux outward into interplanetary space. The most energetic CMEs typically originate from active regions on the Sun. Accurately modeling active regions while also capturing the entire corona requires MHD models that include energy transport (radiative losses,anisotropic thermal conduction, and coronal heating) in the transition region and solar corona. We refer to this as the thermodynamic MHD model. The more accurate representation of energy flow in the thermodynamic MHD model allows us to to compute simulated EUV and X-ray emission as would be observed from spacecraft such as SOHO, STEREO, and Hinode. With this approach, theorists no longer get to argue what emission they think their favorite model's magnetic field evolution implies; we can actually go compute the emission and compare with observations. As an example, we show a simulation of the May 12, 1997 CME, and compare the simulated emission with observations from the actual event of dimming regions, postflare loops, and reformation of loops near the northern polar coronal hole. Work supported by NASA, NSF and the Center for Integrated Space Weather Modeling (an NSF Science and Technology Center).
NASA Technical Reports Server (NTRS)
Hibbard, William L.; Dyer, Charles R.; Paul, Brian E.
1994-01-01
The VIS-AD data model integrates metadata about the precision of values, including missing data indicators and the way that arrays sample continuous functions, with the data objects of a scientific programming language. The data objects of this data model form a lattice, ordered by the precision with which they approximate mathematical objects. We define a similar lattice of displays and study visualization processes as functions from data lattices to display lattices. Such functions can be applied to visualize data objects of all data types and are thus polymorphic.
Concentrated mass effects on the flutter of a composite advanced turboprop model
NASA Technical Reports Server (NTRS)
Ramsey, J. K.; Kaza, K. R. V.
1986-01-01
The effects on bending-torsion flutter due to the addition of a concentrated mass to an advanced turboprop model blade with rigid hub are studied. Specifically the effects of the magnitude and location of added mass on the natural frequencies, mode shapes, critical interblade phase angle, and flutter Mach number are analytically investigated. The flutter of a propfan model is shown to be sensitive to the change in mass distribution. Static unbalance effects, like those for fixed wings, were shown to occur as the concentrated mass was moved from the leading edge to the trailing edge with the exception of one mass location. Mass balancing is also inferred to be a feasible method for increasing the flutter speed.
A Leasing Model to Deal with Partial Failures in Mobile Ad Hoc Networks
NASA Astrophysics Data System (ADS)
Gonzalez Boix, Elisa; van Cutsem, Tom; Vallejos, Jorge; de Meuter, Wolfgang; D'Hondt, Theo
In mobile ad hoc networks (MANETs) many partial failures are the result of temporary network partitions due to the intermittent connectivity of mobile devices. Some of these failures will be permanent and require application-level failure handling. However, it is impossible to distinguish a permanent from a transient failure. Leasing provides a solution to this problem based on the temporal restriction of resources. But to date no leasing model has been designed specifically for MANETs. In this paper, we identify three characteristics required for a leasing model to be usable in a MANET, discuss the issues with existing leasing models and then propose the leased object references model, which integrates leasing with remote object references. In addition, we describe an implementation of the model in the programming language AmbientTalk. Leased object references provide an extensible framework that allows programmers to express their own leasing patterns and enables both lease holders (clients) and lease grantors (services) to deal with permanent failures.
Homoclinic Spike adding in a neuronal model in the presence of noise
NASA Astrophysics Data System (ADS)
Fuwape, Ibiyinka; Neiman, Alexander; Shilnikov, Andrey
2008-03-01
We study the influence of noise on a spike adding transitions within the bursting activity in a Hodgkin-Huxley-type model of the leech heart interneuron. Spike adding in this model occur via homoclinic bifurcation of a saddle periodic orbit. Although narrow chaotic regions are observed near bifurcation transition, overall bursting dynamics is regular and is characterized by a constant number of spikes per burst. Experimental studies, however, show variability of bursting patterns whereby number of spikes per burst varies randomly. Thus, introduction of external synaptic noise is a necessary step to account for variability of burst durations observed experimentally. We show that near every such transition the neuron is highly sensitive to random perturbations that lead to and enhance broadly the regions of chaotic dynamics of the cell. For each spike adding transition there is a critical noise level beyond which the dynamics of the neuron becomes chaotic throughout the entire region of the given transition. Noise-induced chaotic dynamics is characterized in terms of the Lyapunov exponents and the Shannon entropy and reflects variability of firing patterns with various numbers of spikes per burst, traversing wide range of the neuron's parameters
Better Galactic mass models through chemistry
NASA Astrophysics Data System (ADS)
Sanderson, Robyn Ellyn; Wetzel, Andrew; Hopkins, Philip F.; Sharma, Sanjib
2017-01-01
With the upcoming release of the Gaia catalog and the many multiplexed spectroscopic surveys on the horizon, we are rapidly moving into a new data-driven era in the study of the Milky Way's stellar halo. When combined, these data sets will give us a many-dimensional view of stars in accreted structures in the halo that includes both dynamical information about their orbits and chemical information about their formation histories. Using simulated data from the state-of-the-art Latte simulations of Milky-Way-like galaxies, which include hydrodynamics, feedback, and chemical evolution in a cosmological setting using the FIRE physics model, we demonstrate that while dynamical information alone can be used to constrain models of the Galactic mass distribution in the halo, including the extra dimensions provided by chemical abundances can improve these constraints as well as assist in untangling different accreted components.
Constraints on tachyon inflationary models with an AdS/CFT correspondence
NASA Astrophysics Data System (ADS)
Bouabdallaoui, Zahra; Errahmani, Ahmed; Bouhmadi-López, Mariam; Ouali, Taoufik
2016-12-01
To study the effect of the anti-de Sitter/conformal field theory correspondence (AdS/CFT) on the primordial inflationary era, we consider a universe filled with a tachyon field in a slow-roll regime. In this context, the background and perturbative parameters characterizing the inflationary era are related to the standard one by correction terms. We show a clear agreement between the theoretical prediction and the observational data for the above-mentioned model. The main results of our work are illustrated for an exponential potential. We show that, for a suitable conformal anomaly coefficient, AdS/CFT correspondence might leave its imprints on the spectrum of the gravitational waves amplitude with a tensor to scalar ratio, r , of the perturbations compatible with Planck data.
A model-free method for mass spectrometer response correction
NASA Astrophysics Data System (ADS)
Shykoff, Barbara E.; Swanson, Harvey T.
1987-11-01
A new method for correction of mass spectrometer output signals is described. Response-time distortion is reduced independently of any model of mass spectrometer behavior. The delay of the system is found first from the cross-correlation function of a step change and its response. A two-sided time-domain digital correction filter (deconvolution filter) is generated next from the same step response data using a regression procedure. Other data are corrected using the filter and delay. The mean squared error between a step response and a step is reduced considerably more after the use of a deconvolution filter than after the application of a second-order model correction. O2 consumption and CO2 production values calculated from data corrupted by a simulated dynamic process return to near the uncorrupted values after correction. Although a clean step response or the ensemble average of several responses contaminated with noise is needed for the generation of the filter, random noise of magnitude not above 0.5 percent added to the response to be corrected does not impair the correction severely.
Neutrino mass models and CP violation
Joshipura, Anjan S.
2011-10-06
Theoretical ideas on the origin of (a) neutrino masses (b) neutrino mass hierarchies and (c) leptonic mixing angles are reviewed. Topics discussed include (1) symmetries of neutrino mass matrix and their origin (2) ways to understand the observed patterns of leptonic mixing angles and (3)unified description of neutrino masses and mixing angles in grand unified theories.
Final report for the ASC gas-powder two-phase flow modeling project AD2006-09.
Evans, Gregory Herbert; Winters, William S.
2007-01-01
This report documents activities performed in FY2006 under the ''Gas-Powder Two-Phase Flow Modeling Project'', ASC project AD2006-09. Sandia has a need to understand phenomena related to the transport of powders in systems. This report documents a modeling strategy inspired by powder transport experiments conducted at Sandia in 2002. A baseline gas-powder two-phase flow model, developed under a companion PEM project and implemented into the Sierra code FUEGO, is presented and discussed here. This report also documents a number of computational tests that were conducted to evaluate the accuracy and robustness of the new model. Although considerable progress was made in implementing the complex two-phase flow model, this project has identified two important areas that need further attention. These include the need to compute robust compressible flow solutions for Mach numbers exceeding 0.35 and the need to improve conservation of mass for the powder phase. Recommendations for future work in the area of gas-powder two-phase flow are provided.
Turbulent motion of mass flows. Mathematical modeling
NASA Astrophysics Data System (ADS)
Eglit, Margarita; Yakubenko, Alexander; Yakubenko, Tatiana
2016-04-01
New mathematical models for unsteady turbulent mass flows, e.g., dense snow avalanches and landslides, are presented. Such models are important since most of large scale flows are turbulent. In addition to turbulence, the two other important points are taken into account: the entrainment of the underlying material by the flow and the nonlinear rheology of moving material. The majority of existing models are based on the depth-averaged equations and the turbulent character of the flow is accounted by inclusion of drag proportional to the velocity squared. In this paper full (not depth-averaged) equations are used. It is assumed that basal entrainment takes place if the bed friction equals the shear strength of the underlying layer (Issler D, M. Pastor Peréz. 2011). The turbulent characteristics of the flow are calculated using a three-parameter differential model (Lushchik et al., 1978). The rheological properties of moving material are modeled by one of the three types of equations: 1) Newtonian fluid with high viscosity, 2) power-law fluid and 3) Bingham fluid. Unsteady turbulent flows down long homogeneous slope are considered. The flow dynamical parameters and entrainment rate behavior in time as well as their dependence on properties of moving and underlying materials are studied numerically. REFERENCES M.E. Eglit and A.E. Yakubenko, 2014. Numerical modeling of slope flows entraining bottom material. Cold Reg. Sci. Technol., 108, 139-148 Margarita E. Eglit and Alexander E. Yakubenko, 2016. The effect of bed material entrainment and non-Newtonian rheology on dynamics of turbulent slope flows. Fluid Dynamics, 51(3) Issler D, M. Pastor Peréz. 2011. Interplay of entrainment and rheology in snow avalanches; a numerical study. Annals of Glaciology, 52(58), 143-147 Lushchik, V.G., Paveliev, A.A. , and Yakubenko, A.E., 1978. Three-parameter model of shear turbulence. Fluid Dynamics, 13, (3), 350-362
Kassouf, Nick; Syed, Sara; Larner, Joanne; Amlôt, Richard
2017-01-01
The UK’s Initial Operational Response (IOR) is a revised process for the medical management of mass casualties potentially contaminated with hazardous materials. A critical element of the IOR is the introduction of immediate, on-scene disrobing and decontamination of casualties to limit the adverse health effects of exposure. Ad hoc cleansing of the skin with dry absorbent materials has previously been identified as a potential means of facilitating emergency decontamination. The purpose of this study was to evaluate the in vitro oil and water absorbency of a range of materials commonly found in the domestic and clinical environments and to determine the effectiveness of a small, but representative selection of such materials in skin decontamination, using an established ex vivo model. Five contaminants were used in the study: methyl salicylate, parathion, diethyl malonate, phorate and potassium cyanide. In vitro measurements of water and oil absorbency did not correlate with ex vivo measurements of skin decontamination. When measured ex vivo, dry decontamination was consistently more effective than a standard wet decontamination method (“rinse-wipe-rinse”) for removing liquid contaminants. However, dry decontamination was ineffective against particulate contamination. Collectively, these data confirm that absorbent materials such as wound dressings and tissue paper provide an effective, generic capability for emergency removal of liquid contaminants from the skin surface, but that wet decontamination should be used for non-liquid contaminants. PMID:28152053
Kassouf, Nick; Syed, Sara; Larner, Joanne; Amlôt, Richard; Chilcott, Robert P
2017-01-01
The UK's Initial Operational Response (IOR) is a revised process for the medical management of mass casualties potentially contaminated with hazardous materials. A critical element of the IOR is the introduction of immediate, on-scene disrobing and decontamination of casualties to limit the adverse health effects of exposure. Ad hoc cleansing of the skin with dry absorbent materials has previously been identified as a potential means of facilitating emergency decontamination. The purpose of this study was to evaluate the in vitro oil and water absorbency of a range of materials commonly found in the domestic and clinical environments and to determine the effectiveness of a small, but representative selection of such materials in skin decontamination, using an established ex vivo model. Five contaminants were used in the study: methyl salicylate, parathion, diethyl malonate, phorate and potassium cyanide. In vitro measurements of water and oil absorbency did not correlate with ex vivo measurements of skin decontamination. When measured ex vivo, dry decontamination was consistently more effective than a standard wet decontamination method ("rinse-wipe-rinse") for removing liquid contaminants. However, dry decontamination was ineffective against particulate contamination. Collectively, these data confirm that absorbent materials such as wound dressings and tissue paper provide an effective, generic capability for emergency removal of liquid contaminants from the skin surface, but that wet decontamination should be used for non-liquid contaminants.
Spin Matrix theory: a quantum mechanical model of the AdS/CFT correspondence
NASA Astrophysics Data System (ADS)
Harmark, Troels; Orselli, Marta
2014-11-01
We introduce a new quantum mechanical theory called Spin Matrix theory (SMT). The theory is interacting with a single coupling constant g and is based on a Hilbert space of harmonic oscillators with a spin index taking values in a Lie (super)algebra representation as well as matrix indices for the adjoint representation of U( N). We show that SMT describes super-Yang-Mills theory (SYM) near zero-temperature critical points in the grand canonical phase diagram. Equivalently, SMT arises from non-relativistic limits of SYM. Even though SMT is a non-relativistic quantum mechanical theory it contains a variety of phases mimicking the AdS/CFT correspondence. Moreover, the g → ∞ limit of SMT can be mapped to the supersymmetric sector of string theory on AdS5 × S 5. We study SU(2) SMT in detail. At large N and low temperatures it is a theory of spin chains that for small g resembles planar gauge theory and for large g a non-relativistic string theory. When raising the temperature a partial deconfinement transition occurs due to finite- N effects. For sufficiently high temperatures the partially deconfined phase has a classical regime. We find a matrix model description of this regime at any coupling g. Setting g = 0 it is a theory of N 2 + 1 harmonic oscillators while for large g it becomes 2 N harmonic oscillators.
Uncertainties of mass extrapolations in Hartree-Fock-Bogoliubov mass models
NASA Astrophysics Data System (ADS)
Goriely, S.; Capote, R.
2014-05-01
Some 27 Hartree-Fock-Bogoliubov (HFB) mass models have been developed by the Brussels-Montreal collaboration. Each of these models has been obtained with different model prescriptions or corresponds to a significantly different minimum in the parameter space. The corresponding uncertainties in the mass extrapolation are discussed. In addition, for each of these models, uncertainties associated with local variations of the model parameters exist. Those are estimated for the HFB-24 mass model using a variant of the backward-forward Monte Carlo method to propagate the uncertainties on the masses of exotic nuclei far away from the experimentally known regions. The resulting uncertainties are found to be significantly lower than those arising from the 27 HFB mass models. In addition, the derived correlations between the calculated masses and between model parameters are analyzed.
Liu, ChunMei; Yuan, HaiRong; Zou, DeXun; Liu, YanPing; Zhu, BaoNing; Li, XiuJin
2015-01-01
This research applied sodium hydroxide (NaOH) pretreatment and trace elements to improve biomethane production when using corn stover for anaerobic digestion. Full-factor experimental tests identified the best combination of trace elements with the NaOH pretreatment, indicating that the best combination was with 1.0, 0.4, and 0.4 mg·L−1·d−1 of elements Fe, Co, and Ni, respectively. The cumulative biomethane production adding NaOH pretreatment and trace elements was 11,367 mL; total solid bioconversion rate was 55.7%, which was 41.8%–62.2% higher than with NaOH-pretreatment alone and 22.2%–56.3% higher than with untreated corn stover. The best combination was obtained 5–9 days shorter than T90 and maintained good system operation stability. Only a fraction of the trace elements in the best combination was present in the resulting solution; more than 85% of the total amounts added were transferred into the solid fraction. Adding 0.897 g of Fe, 0.389 g of Co, and 0.349 g of Ni satisfied anaerobic digestion needs and enhanced biological activity at the beginning of the operation. The results showed that NaOH pretreatment and adding trace elements improve corn stover biodegradability and enhance biomethane production. PMID:26137469
NASA Astrophysics Data System (ADS)
Anninos, Dionysios; Li, Wei; Padi, Megha; Song, Wei; Strominger, Andrew
2009-03-01
Three dimensional topologically massive gravity (TMG) with a negative cosmological constant -l-2 and positive Newton constant G admits an AdS3 vacuum solution for any value of the graviton mass μ. These are all known to be perturbatively unstable except at the recently explored chiral point μl = 1. However we show herein that for every value of μl ≠ 3 there are two other (potentially stable) vacuum solutions given by SL(2,Bbb R) × U(1)-invariant warped AdS3 geometries, with a timelike or spacelike U(1) isometry. Critical behavior occurs at μl = 3, where the warping transitions from a stretching to a squashing, and there are a pair of warped solutions with a null U(1) isometry. For μl > 3, there are known warped black hole solutions which are asymptotic to warped AdS3. We show that these black holes are discrete quotients of warped AdS3 just as BTZ black holes are discrete quotients of ordinary AdS3. Moreover new solutions of this type, relevant to any theory with warped AdS3 solutions, are exhibited. Finally we note that the black hole thermodynamics is consistent with the hypothesis that, for μl > 3, the warped AdS3 ground state of TMG is holographically dual to a 2D boundary CFT with central charges c_R-formula and c_L-formula.
NASA Astrophysics Data System (ADS)
Song, Wei; Anninos, Dionysios; Li, Wei; Padi, Megha; Strominger, Andrew
2009-03-01
Three dimensional topologically massive gravity (TMG) with a negative cosmological constant -ell-2 and positive Newton constant G admits an AdS3 vacuum solution for any value of the graviton mass μ. These are all known to be perturbatively unstable except at the recently explored chiral point μell = 1. However we show herein that for every value of μell ≠ 3 there are two other (potentially stable) vacuum solutions given by SL(2,Bbb R) × U(1)-invariant warped AdS3 geometries, with a timelike or spacelike U(1) isometry. Critical behavior occurs at μell = 3, where the warping transitions from a stretching to a squashing, and there are a pair of warped solutions with a null U(1) isometry. For μell > 3, there are known warped black hole solutions which are asymptotic to warped AdS3. We show that these black holes are discrete quotients of warped AdS3 just as BTZ black holes are discrete quotients of ordinary AdS3. Moreover new solutions of this type, relevant to any theory with warped AdS3 solutions, are exhibited. Finally we note that the black hole thermodynamics is consistent with the hypothesis that, for μell > 3, the warped AdS3 ground state of TMG is holographically dual to a 2D boundary CFT with central charges c_R-formula and c_L-formula.
A mass transfer model of bauxite formation
Soler, J.M.; Lasaga, A.C.
1996-12-01
The formation of bauxite due to weathering of a granitic protolith has been simulated by means of a one-dimensional flow and reaction model based on the mass transfer principle. The model couples mineral dissolution and precipitation reactions, speciation in solution, and advective solute transport in a porous medium. A very important aspect of the modeling study is the use of mineral reaction rates determined experimentally in the laboratory. The important effects of solution saturation state and pH have been incorporated into the kinetic rate laws governing the heterogeneous reactions. The values of these parameters have been obtained from the scientific literature to guarantee that realistic reaction rates are used in the simulations. Albite and quartz are the minerals that make up the parent rock in the model. Gibbsite, kaolinite, and a Na-mica (as a surrogate for smectite) are the secondary minerals that have been taken into account. Long-term simulations (>1 Ma) have been run, and the formation of a bauxitic profile, with an upper gibbsite-rich and a lower kaolinite-rich zone, is predicted. In early stages of the process (up to a few hundreds of thousands of years), both gibbsite and kaolinite precipitate directly from solution as a consequence of albite dissolution. In later stages, the bulk of gibbsite precipitation derives from the incongruent dissolution of kaolinite, while kaolinite precipitation is still caused by the dissolution of albite. This is also reflected by the formation of two reaction fronts in the profile. These results are compared with weathering sequences from the Los Pijiguaos bauxite deposit, Venezuela. The overlap between the gibbsite and kaolinite zones and the replacement of kaolinite by gibbsite are consistent with model calculations. 59 refs., 22 figs., 1 tab.
The value of adding optics to ecosystem models: a case study
NASA Astrophysics Data System (ADS)
Fujii, M.; Boss, E.; Chai, F.
2007-05-01
matter to the modeled properties. Coupling explicit optics to an ecosystem model provides several advantages in generating: (1) a more accurate subsurface light-field, which is important for light sensitive biogeochemical processes such as photosynthesis and photo-oxidation, (2) added constraints on model parameters that help to reduce uncertainties in ecosystem model simulations, and (3) model output which is comparable to basic remotely-sensed properties. In addition, the coupling of biogeochemical models and optics paves the road for future assimilation of ocean color and in-situ measured optical properties into the models.
Knechtle, Beat; Senn, Oliver; Imoberdorf, Reinhard; Joleska, Irena; Wirth, Andrea; Knechtle, Patrizia; Rosemann, Thomas
2010-01-01
We investigated in 11 female ultra-runners during a 100 km ultra-run, the association between fluid intake and prevalence of exercise-associated hyponatremia in a cross-sectional study. Athletes drank ad libitum and recorded their fluid intake. They competed at 8.0 (1.0) km/h and finished within 762 (91) min. Fluid intake was 4.1 (1.3) L during the race, equal to 0.3 (0.1) L/h. Body mass decreased by 1.5 kg (p< 0.01); pre race body mass was related to speed in the race (r = -0.78, p< 0.05); and change (Delta) in body mass was not associated with speed in the race. Change in body mass was positively (r = 0.70; p< 0.05), and Delta urinary specific gravity negatively (r = -0.67; p< 0.05), correlated to Delta percent total body water. Changes in body mass were not related to fluid intake during the race. Fluid intake was not correlated to running speed and showed no association with either Delta percent total body water nor Delta [Na] in plasma. Fluid intake showed no relationship with both Delta haematocrit and Delta plasma volume. No exercise-associated hyponatremia occurred. Female ultra- runners consuming fluids ad libitum during the race experienced no fluid overload, and ad libitum drinking protects against exercise-associated hyponatremia. The reported higher incidence of exercise-associated hyponatremia in women is not really a gender effect but due to women being more prone to overdrink.
Homoclinic chaos in axisymmetric Bianchi-IX cosmological models with an ad hoc quantum potential
Correa, G. C.; Stuchi, T. J.; Joras, S. E.
2010-04-15
In this work we study the dynamics of the axisymmetric Bianchi-IX cosmological model with a term of quantum potential added. As it is well known, this class of Bianchi-IX models is homogeneous and anisotropic with two scale factors, A(t) and B(t), derived from the solution of Einstein's equation for general relativity. The model we use in this work has a cosmological constant and the matter content is dust. To this model we add a quantum-inspired potential that is intended to represent short-range effects due to the general relativistic behavior of matter in small scales and play the role of a repulsive force near the singularity. We find that this potential restricts the dynamics of the model to positive values of A(t) and B(t) and alters some qualitative and quantitative characteristics of the dynamics studied previously by several authors. We make a complete analysis of the phase space of the model finding critical points, periodic orbits, stable/unstable manifolds using numerical techniques such as Poincare section, numerical continuation of orbits, and numerical globalization of invariant manifolds. We compare the classical and the quantum models. Our main result is the existence of homoclinic crossings of the stable and unstable manifolds in the physically meaningful region of the phase space [where both A(t) and B(t) are positive], indicating chaotic escape to inflation and bouncing near the singularity.
NASA Astrophysics Data System (ADS)
Cvetič, Mirjam; Papadimitriou, Ioannis
2016-12-01
We construct the holographic dictionary for both running and constant dilaton solutions of the two dimensional Einstein-Maxwell-Dilaton theory that is obtained by a circle reduction from Einstein-Hilbert gravity with negative cosmological constant in three dimensions. This specific model ensures that the dual theory has a well defined ultraviolet completion in terms of a two dimensional conformal field theory, but our results apply qualitatively to a wider class of two dimensional dilaton gravity theories. For each type of solutions we perform holographic renormalization, compute the exact renormalized one-point functions in the presence of arbitrary sources, and derive the asymptotic symmetries and the corresponding conserved charges. In both cases we find that the scalar operator dual to the dilaton plays a crucial role in the description of the dynamics. Its source gives rise to a matter conformal anomaly for the running dilaton solutions, while its expectation value is the only non trivial observable for constant dilaton solutions. The role of this operator has been largely overlooked in the literature. We further show that the only non trivial conserved charges for running dilaton solutions are the mass and the electric charge, while for constant dilaton solutions only the electric charge is non zero. However, by uplifting the solutions to three dimensions we show that constant dilaton solutions can support non trivial extended symmetry algebras, including the one found by Compère, Song and Strominger [1], in agreement with the results of Castro and Song [2]. Finally, we demonstrate that any solution of this specific dilaton gravity model can be uplifted to a family of asymptotically AdS2 × S 2 or conformally AdS2 × S 2 solutions of the STU model in four dimensions, including non extremal black holes. The four dimensional solutions obtained by uplifting the running dilaton solutions coincide with the so called `subtracted geometries', while those obtained
Discounting testimony with the argument ad hominem and a Bayesian congruent prior model.
Bhatia, Jaydeep-Singh; Oaksford, Mike
2015-09-01
When directed to ignore evidence of a witness's previous bad character because of a violation of the rules of evidence, are jurors' beliefs still affected? The intuition is that they will be because in everyday argumentation, fallacies, like the ad hominem, are effective argumentative strategies. An ad hominem argument (against the person) undermines a conclusion by questioning the character of the proposer. This intuition divides current theories of argumentation. According to pragmadialectical theory (e.g., Van Eemeren & Grootendorst, 2004), procedural rules exactly like the rules of evidence are part of our cognitive resources for evaluating arguments. If one of these rules is violated, an argument should be treated as a fallacy and so it should not alter someone's belief in the conclusion. Some recent experiments investigating how reasonable these arguments are perceived to be seem to support this account (van Eemeren, Garssen, & Meuffels, 2009). These experiments are critiqued from the perspective of the relevance (Walton, 2009, 2010) and epistemic (Hahn & Oaksford, 2006, 2007; Oaksford & Hahn, 2004) approaches to argumentation. An experiment investigates the predictions of these approaches for a graded belief change version of van Eemeren et al.'s (2009) experiment, and the results are modeled using a Bayesian congruent prior model. These results cannot be explained by the pragmadialectical approach and show that in everyday argument people are extremely sensitive to the epistemic relevance of evidence. Moreover, it seems highly unlikely that this can be switched off in more formal contexts such as the courtroom.
Khan, M Badruzzaman; Khan, Mohd Moshahid; Khan, Andleeb; Ahmed, Md Ejaz; Ishrat, Tauheed; Tabassum, Rizwana; Vaibhav, Kumar; Ahmad, Ajmal; Islam, Fakhrul
2012-12-01
Oxidative stress is involved in Alzheimer's disease (AD)-type neurodegeneration with cognitive impairment (AD-TNDCI) as well as age related cognitive deficit. The present study was designed to investigate the pre-treatment effects of naringenin (NAR), a polyphenolic compound on cognitive dysfunction, oxidative stress in the hippocampus, and hippocampal neuron injury in a rat model of AD-TNDCI. The rats were pre-treated with NAR at a selective dose (50mg/kg, orally) for 2 weeks followed by intracerebroventricular-streptozotocin (ICV-STZ) (3mg/kg; 5μl per site) injection bilaterally. Behavioral alterations were monitored after 2 weeks from the lesion using passive avoidance test and Morris water maze paradigm. Three weeks after the lesion, the rats were sacrificed for measuring non-enzymatic [4-hydroxynonenal (4-HNE), malonaldehyde (MDA), thiobarbituric reactive substances (TBARS), hydrogen peroxide (H(2)O(2)), protein carbonyl (PC), reduced glutathione (GSH)] content and enzymatic [glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT) and Na(+)/K(+)-ATPase] activity in the hippocampus, and expression of choline acetyltransferase (ChAT) positive neuron, and histopathology of hippocampal neurons. The non-enzymatic level and enzymatic activity was significantly increased and decreased, respectively, with striking impairments in spatial learning and memory, loss of ChAT positive neuron and severe damage to hippocampal neurons in the rat induced by ICV-STZ. These abnormalities were significantly improved by NAR pre-treatment. The study suggests that NAR can protect against cognitive deficits, neuronal injury and oxidative stress induced by ICV-STZ, and may be used as a potential agent in treatment of neurodegenerative diseases such as AD-TNDCI.
ERIC Educational Resources Information Center
Hutchison-Lupardus, Tammy R.; Hatfield, Timothy E.; Snyder, Jennifer E.
2012-01-01
This problem-based learning project addressed the need to improve the construction and implementation of value-added teacher evaluation policies and instruments. State officials are constructing value-added teacher evaluation models due to accountability initiatives, while ignoring the holes and problems in its implementation. The team's…
ERIC Educational Resources Information Center
Koedel, Cory; Betts, Julian R.
2011-01-01
Value-added modeling continues to gain traction as a tool for measuring teacher performance. However, recent research questions the validity of the value-added approach by showing that it does not mitigate student-teacher sorting bias (its presumed primary benefit). Our study explores this critique in more detail. Although we find that estimated…
ERIC Educational Resources Information Center
Karl, Andrew T.; Yang, Yan; Lohr, Sharon L.
2013-01-01
Value-added models have been widely used to assess the contributions of individual teachers and schools to students' academic growth based on longitudinal student achievement outcomes. There is concern, however, that ignoring the presence of missing values, which are common in longitudinal studies, can bias teachers' value-added scores.…
SOA-based model for value-added ITS services delivery.
Herrera-Quintero, Luis Felipe; Maciá-Pérez, Francisco; Marcos-Jorquera, Diego; Gilart-Iglesias, Virgilio
2014-01-01
Integration is currently a key factor in intelligent transportation systems (ITS), especially because of the ever increasing service demands originating from the ITS industry and ITS users. The current ITS landscape is made up of multiple technologies that are tightly coupled, and its interoperability is extremely low, which limits ITS services generation. Given this fact, novel information technologies (IT) based on the service-oriented architecture (SOA) paradigm have begun to introduce new ways to address this problem. The SOA paradigm allows the construction of loosely coupled distributed systems that can help to integrate the heterogeneous systems that are part of ITS. In this paper, we focus on developing an SOA-based model for integrating information technologies (IT) into ITS to achieve ITS service delivery. To develop our model, the ITS technologies and services involved were identified, catalogued, and decoupled. In doing so, we applied our SOA-based model to integrate all of the ITS technologies and services, ranging from the lowest-level technical components, such as roadside unit as a service (RSUAAS), to the most abstract ITS services that will be offered to ITS users (value-added services). To validate our model, a functionality case study that included all of the components of our model was designed.
SOA-Based Model for Value-Added ITS Services Delivery
Herrera-Quintero, Luis Felipe; Maciá-Pérez, Francisco; Marcos-Jorquera, Diego; Gilart-Iglesias, Virgilio
2014-01-01
Integration is currently a key factor in intelligent transportation systems (ITS), especially because of the ever increasing service demands originating from the ITS industry and ITS users. The current ITS landscape is made up of multiple technologies that are tightly coupled, and its interoperability is extremely low, which limits ITS services generation. Given this fact, novel information technologies (IT) based on the service-oriented architecture (SOA) paradigm have begun to introduce new ways to address this problem. The SOA paradigm allows the construction of loosely coupled distributed systems that can help to integrate the heterogeneous systems that are part of ITS. In this paper, we focus on developing an SOA-based model for integrating information technologies (IT) into ITS to achieve ITS service delivery. To develop our model, the ITS technologies and services involved were identified, catalogued, and decoupled. In doing so, we applied our SOA-based model to integrate all of the ITS technologies and services, ranging from the lowest-level technical components, such as roadside unit as a service (RSUAAS), to the most abstract ITS services that will be offered to ITS users (value-added services). To validate our model, a functionality case study that included all of the components of our model was designed. PMID:25019101
NASA Astrophysics Data System (ADS)
Schueller, Felix; Förster, Kristian; Hanzer, Florian; Huttenlau, Matthias; Marzeion, Ben; Strasser, Ulrich; Achleitner, Stefan; Kirnbauer, Robert
2015-04-01
Glacier and snow runoff in high alpine regions is an essential process in hydrological research for its high relevance on lower altitude areas and hydro-power generation. MUSICALS II (Multiscale Snow/Icemelt Discharge Simulations into Alpine Reservoirs) seeks to identify and quantify water availability and runoff in alpine headwater catchments. The focus is on future changes due to glacier retreat, altering the multi-day and seasonal runoff available for hydropower operations. Our aim is to investigate and improve runoff forecasts by coupling the semi-distributed hydrological model HQSim with a simple glacier evolution model. The glacier model MMBM (Marzeion Mass Balance Model) with its statistical nature allows for fast modelling of the dynamical properties of glaciers. We present the design of the coupled hydrological application for different hydro power headwater catchments in Tyrol. The capabilities of the glacier model to simulate the selected glaciers is shown. Simulated discharge with the original and the coupled model are compared to downstream gauge measurements. Using the multi-objective optimization algorithm AMALGAM (A Multi-ALgorithm, Genetically Adaptive Multiobjective model), we optimize the glacier module parameters fully automatically. The results show the improvements in runoff modelling for past periods, when altering of glaciated catchment parts is considered. This indicates consideration of this process is mandatory for simulating future developments.
NASA Astrophysics Data System (ADS)
Günther, Uwe; Zhuk, Alexander; Bezerra, Valdir B.; Romero, Carlos
2005-08-01
We study multi-dimensional gravitational models with scalar curvature nonlinearities of types R-1 and R4. It is assumed that the corresponding higher dimensional spacetime manifolds undergo a spontaneous compactification to manifolds with a warped product structure. Special attention has been paid to the stability of the extra-dimensional factor spaces. It is shown that for certain parameter regions the systems allow for a freezing stabilization of these spaces. In particular, we find for the R-1 model that configurations with stabilized extra dimensions do not provide a late-time acceleration (they are AdS), whereas the solution branch which allows for accelerated expansion (the dS branch) is incompatible with stabilized factor spaces. In the case of the R4 model, we obtain that the stability region in parameter space depends on the total dimension D = dim(M) of the higher dimensional spacetime M. For D > 8 the stability region consists of a single (absolutely stable) sector which is shielded from a conformal singularity (and an antigravity sector beyond it) by a potential barrier of infinite height and width. This sector is smoothly connected with the stability region of a curvature-linear model. For D < 8 an additional (metastable) sector exists which is separated from the conformal singularity by a potential barrier of finite height and width so that systems in this sector are prone to collapse into the conformal singularity. This second sector is not smoothly connected with the first (absolutely stable) one. Several limiting cases and the possibility of inflation are discussed for the R4 model.
A model for stealth coronal mass ejections
NASA Astrophysics Data System (ADS)
Lynch, B. J.; Masson, S.; Li, Y.; DeVore, C. R.; Luhmann, J. G.; Antiochos, S. K.; Fisher, G. H.
2016-11-01
Stealth coronal mass ejections (CMEs) are events in which there are almost no observable signatures of the CME eruption in the low corona but often a well-resolved slow flux rope CME observed in the coronagraph data. We present results from a three-dimensional numerical magnetohydrodynamics (MHD) simulation of the 1-2 June 2008 slow streamer blowout CME that Robbrecht et al. (2009) called "the CME from nowhere." We model the global coronal structure using a 1.4 MK isothermal solar wind and a low-order potential field source surface representation of the Carrington Rotation 2070 magnetogram synoptic map. The bipolar streamer belt arcade is energized by simple shearing flows applied in the vicinity of the helmet streamer's polarity inversion line. The flows are large scale and impart a shear typical of that expected from the differential rotation. The slow expansion of the energized helmet streamer arcade results in the formation of a radial current sheet. The subsequent onset of expansion-induced flare reconnection initiates the stealth CME while gradually releasing the stored magnetic energy. We present favorable comparisons between our simulation results and the multiviewpoint SOHO-LASCO (Large Angle and Spectrometric Coronagraph) and STEREO-SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) coronagraph observations of the preeruption streamer structure and the initiation and evolution of the stealth streamer blowout CME.
2002-06-01
Elizabeth Royer described the Ad Hoc On-Demand Distance Vector (AODV) routing protocol as “providing quick and efficient route establishment between...Network.” Thesis, Naval Postgraduate School, December 2000. 8. Das, Samir R., Perkins, Charles E., and Royer, Elizabeth M. “ The Ad-hoc On-Demand...Lidong. “Securing Ad Hoc Networks.” Paper Cornell University, Itaca, New York, NY. 16. Corson , Scott S., and Macker, J. “Mobile Ad Hoc
Assessing the effect of adding interactive modeling to the geoscience curriculum
NASA Astrophysics Data System (ADS)
Castillo, A.; Marshall, J.; Cardenas, M.
2013-12-01
Technology and computer models enhance the learning experience when appropriately utilized. Moreover, learning is significantly improved when effective visualization is combined with models of processes allowing for inquiry-based problem solving. Still, hands-on experiences in real scenarios result in better contextualization of related problems compared to virtual laboratories. Therefore, the role of scientific visualization, technology, and computer modeling is to enhance, not displace, the learning experience by supplementing real-world problem solving and experiences, although in some circumstances, they can adequately serve to take the place of reality. The key to improving scientific education is to embrace an inquiry-based approach that favorably uses technology. This study will attempt to evaluate the effect of adding interactive modeling to the geological sciences curriculum. An assessment tool, designed to assess student understanding of physical hydrology, was used to evaluate a curriculum intervention based on student learning with a data- and modeling-driven approach using COMSOL Multiphysics software. This intervention was implemented in an upper division and graduate physical hydrology course in fall 2012. Students enrolled in the course in fall 2011 served as the control group. Interactive modeling was added to the curriculum in fall 2012 to replace the analogous mathematical modeling done by hand in fall 2011. Pre- and post-test results were used to assess and report its effectiveness. Student interviews were also used to probe student reactions to both the experimental and control curricula. The pre- and post-tests asked students to describe the significant processes in the hydrological cycle and describe the laws governing these processes. Their ability to apply their knowledge in a real-world problem was also assessed. Since the pre- and post-test data failed to meet the assumption of normality, a non-parametric Kruskal-Wallis test was run to
How One School Implements and Experiences Ohio's Value-Added Model: A Case Study
ERIC Educational Resources Information Center
Quattrochi, David
2009-01-01
Ohio made value-added law in 2003 and incorporated value-added assessment to its operating standards for teachers and administrators in 2006. Value-added data is used to determine if students are making a year's growth at the end of each school year. Schools and districts receive a rating of "Below Growth, Met Growth, or Above Growth" on…
Christensen, Kirstine L; Hedemann, Mette S; Jørgensen, Henry; Stagsted, Jan; Knudsen, Knud Erik B
2012-07-06
Genetically identical cloned pigs should in principle eliminate biological variation and provide more pronounced effects when subjected to, e.g., dietary interventions, but little is known about how phenotype and phenotypic variation is affected by cloning. Therefore, an investigation of the metabolome of cloned pigs compared to normal control pigs was performed to elucidate the variation and possible differences in the metabolic phenotypes during a dietary intervention. A total of 19 control pigs and 17 cloned pigs were given the same high-energy dense diet either ad libitum or in a restricted manner (60% of ad libitum) for ∼6 months, and plasma was subjected to liquid chromatography-mass spectrometry nontargeted metabolomics and biochemical analyses. Low systemic levels of IGF-1 could indicate altered growth conditions and energy metabolism in cloned pigs. In response to ad libitum feeding, clones had a decreased energy intake and lower weight gain compared to controls, and plasma lipid profiles were changed accordingly. Elevated lactate and decreased creatine levels implied an increased anaerobic metabolism in ad libitum fed clones. Less interindividual variation between cloned pigs was however not established, suggesting a strong role for epigenetics and/or the gut microbiota to develop variation.
Non-Equilibrium Ionization Modeling of Coronal Mass Ejections
NASA Astrophysics Data System (ADS)
Rimple, Remington; Murphy, Nicholas Arnold; Shen, Chengcai
2017-01-01
Coronal Mass Ejections, or CMEs, are solar events that eject plasma and magnetic flux into interplanetary space. Contemporary sources have noted that the onset of CMEs are caused by some instability of the coronal magnetic field, and further allows heating of plasma upon expansion. Additionally, plasma that leaves the lower solar corona does not remain in ionization equilibrium due to the rapid expansion of plasma. We investigate the evolution of charge states of CME plasma using non-equilibrium ionization (NEI) modeling. These NEI models include radiative cooling and serve as baseline studies for special cases where no heat is being added to the plasma. Each of the simulated CMEs have initial conditions characteristic of active regions. Various function inputs, such as initial temperature, density and final velocity, allow us to examine the influence of certain parameters on the charge state evolution. The results of our project show that plasma originating from active regions display charge state evolutions substantially dependent on initial density and temperature. The CMEs starting with higher plasma density often show an abundance of lower charge states above the freeze-in height. Simulations starting from higher temperatures often show abundance peaks at charge states with closed electron shells.
NASA Astrophysics Data System (ADS)
Quareni, Francesca; Moretti, Roberto; Piochi, Monica; Chiodini, Giovanni
2007-03-01
The last eruptive event at Mount Vesuvius occurred in 1944 A.D., ending a cycle of continuous eruptive activity started with the sub-Plinian event of 1631 A.D. The aim of this research is (1) to model the thermal evolution of the volcanic system from 1631 A.D. up to the present and (2) to investigate the possible process leading the volcano to the current state of quiescence. A finite element software is employed to solve the time-dependent energy equation and obtain the thermal field in the volcanic edifice and the surrounding medium. Volcanological, petrological, and geophysical constraints are used to define the crustal structure beneath the volcanic edifice, the magma supply system active since 1631 A.D., and the physico-chemical conditions of magma. Thermodynamic properties of magma and wall rocks have been evaluated from well-established thermo-chemical compilations and data from the literature. It is shown that heat transfer due to magma degassing is required in addition to the heat conduction in order to obtain transient depth-temperature fields consistent with geochemical observations, high crustal magnetization, and rigid behavior of the shallow crust as indicated by geophysical data. Surface data of carbon dioxide soil flux coming out from the Mount Vesuvius crater are taken to constrain such an additional heat flux. The agreement between modeled and measured temperatures at the crater since 1944 A.D. proves the consistency of the model. It is concluded that the present state of quiescence of Mount Vesuvius is mostly a consequence of the absence of magma supply from the deep reservoir into the shallower system. This allows the cooling of residual magma left within the volcanic conduit and the transition from continuous eruptive activity to the condition of conduit obstruction. In this scenario, the hydrothermal system may have developed subsequent to the cooling of the magma within the conduit. Our findings are a direct consequence of the high
Integrated modelling requires mass collaboration (Invited)
NASA Astrophysics Data System (ADS)
Moore, R. V.
2009-12-01
add, “and are the plans sustainable?” To return to the present, although, it is now possible to ask the first question and obtain an answer through linked modelling; we are still at a very early stage and the associated uncertainties are large. The process of linking and running linked systems is not yet the simple, reliable process needed for widespread uptake. At this point, it is useful to look back over the development process which has taken us from paper maps to GIS and Google Maps; it was the result of tens of thousands of PhD and MSc projects over forty years. During the development of the OpenMI, it was quickly appreciated that to transform integrated modelling from something possible in a research lab to something that had the ease of use and reliability of Google Maps would require a similar process but on a far greater scale; one far larger than any single organisation or state could support. A dramatic change to the research and development process would be needed. Using the OpenMI Association’s strategy as an example, the presentation will describe how through openness, sharing and mass collaboration made possible by inexpensive communications and computing power and adoption of a minimum set of standards, the innovation and enterprise of thousands of individuals across the world can be brought to bear upon the problems.
The Will, Skill, Tool Model of Technology Integration: Adding Pedagogy as a New Model Construct
ERIC Educational Resources Information Center
Knezek, Gerald; Christensen, Rhonda
2015-01-01
An expansion of the Will, Skill, Tool Model of Technology Integration to include teacher's pedagogical style is proposed by the authors as a means of advancing the predictive power for level of classroom technology integration to beyond 90%. Suggested advantages to this expansion include more precise identification of areas to be targeted for…
Ad Hoc modeling, expert problem solving, and R&T program evaluation
NASA Technical Reports Server (NTRS)
Silverman, B. G.; Liebowitz, J.; Moustakis, V. S.
1983-01-01
A simplified cost and time (SCAT) analysis program utilizing personal-computer technology is presented and demonstrated in the case of the NASA-Goddard end-to-end data system. The difficulties encountered in implementing complex program-selection and evaluation models in the research and technology field are outlined. The prototype SCAT system described here is designed to allow user-friendly ad hoc modeling in real time and at low cost. A worksheet constructed on the computer screen displays the critical parameters and shows how each is affected when one is altered experimentally. In the NASA case, satellite data-output and control requirements, ground-facility data-handling capabilities, and project priorities are intricately interrelated. Scenario studies of the effects of spacecraft phaseout or new spacecraft on throughput and delay parameters are shown. The use of a network of personal computers for higher-level coordination of decision-making processes is suggested, as a complement or alternative to complex large-scale modeling.
Binder, H; Sauerbrei, W
2010-03-30
When global techniques, based on fractional polynomials (FPs), are employed for modeling potentially nonlinear effects of several continuous covariates on a response, accessible model equations are obtained. However, local features might be missed. Therefore, a procedure is introduced, which systematically checks model fits, obtained by the multivariable fractional polynomial (MFP) approach, for overlooked local features. Statistically significant local polynomials are then parsimoniously added. This approach, called MFP + L, is seen to result in an effective control of the Type I error with respect to the addition of local components in a small simulation study with univariate and multivariable settings. Prediction performance is compared with that of a penalized regression spline technique. In a setting unfavorable for FPs, the latter outperforms the MFP approach, if there is much information in the data. However, the addition of local features reduces this performance difference. There is only a small detrimental effect in settings where the MFP approach performs better. In an application example with children's respiratory health data, fits from the spline-based approach indicate many local features, but MFP + L adds only few significant features, which seem to have good support in the data. The proposed approach may be expected to be superior in settings with local features, but retains the good properties of the MFP approach in a large number of settings where global functions are sufficient.
Stochastic modeling of uncertain mass characteristics in rigid body dynamics
NASA Astrophysics Data System (ADS)
Richter, Lanae A.; Mignolet, Marc P.
2017-03-01
This paper focuses on the formulation, assessment, and application of a modeling strategy of uncertainty on the mass characteristics of rigid bodies, i.e. mass, position of center of mass, and inertia tensor. These characteristics are regrouped into a 4×4 matrix the elements of which are represented as random variables with joint probability density function derived following the maximum entropy framework. This stochastic model is first shown to satisfy all properties expected of the mass and tensor of inertia of rigid bodies. Its usefulness and computational efficiency are next demonstrated on the behavior of a rigid body in pure rotation exhibiting significant uncertainty in mass distribution.
Improving Accuracy in Arrhenius Models of Cell Death: Adding a Temperature-Dependent Time Delay.
Pearce, John A
2015-12-01
The Arrhenius formulation for single-step irreversible unimolecular reactions has been used for many decades to describe the thermal damage and cell death processes. Arrhenius predictions are acceptably accurate for structural proteins, for some cell death assays, and for cell death at higher temperatures in most cell lines, above about 55 °C. However, in many cases--and particularly at hyperthermic temperatures, between about 43 and 55 °C--the particular intrinsic cell death or damage process under study exhibits a significant "shoulder" region that constant-rate Arrhenius models are unable to represent with acceptable accuracy. The primary limitation is that Arrhenius calculations always overestimate the cell death fraction, which leads to severely overoptimistic predictions of heating effectiveness in tumor treatment. Several more sophisticated mathematical model approaches have been suggested and show much-improved performance. But simpler models that have adequate accuracy would provide useful and practical alternatives to intricate biochemical analyses. Typical transient intrinsic cell death processes at hyperthermic temperatures consist of a slowly developing shoulder region followed by an essentially constant-rate region. The shoulder regions have been demonstrated to arise chiefly from complex functional protein signaling cascades that generate delays in the onset of the constant-rate region, but may involve heat shock protein activity as well. This paper shows that acceptably accurate and much-improved predictions in the simpler Arrhenius models can be obtained by adding a temperature-dependent time delay. Kinetic coefficients and the appropriate time delay are obtained from the constant-rate regions of the measured survival curves. The resulting predictions are seen to provide acceptably accurate results while not overestimating cell death. The method can be relatively easily incorporated into numerical models. Additionally, evidence is presented
Chen, Yanxing; Liang, Zhihou; Blanchard, Julie; Dai, Chun-Ling; Sun, Shenggang; Lee, Moon H; Grundke-Iqbal, Inge; Iqbal, Khalid; Liu, Fei; Gong, Cheng-Xin
2013-04-01
Alzheimer's disease (AD) can be divided into sporadic AD (SAD) and familial AD (FAD). Most AD cases are sporadic and result from multiple etiologic factors, including environmental, genetic, and metabolic factors, whereas FAD is caused by mutations in the presenilins or amyloid-β (Aβ) precursor protein (APP) genes. A commonly used animal model for AD is the 3xTg-AD transgenic mouse model, which harbors mutated presenilin 1, APP, and tau genes and thus represents a model of FAD. There is an unmet need in the field to characterize animal models representing different AD mechanisms, so that potential drugs for SAD can be evaluated preclinically in these animal models. A mouse model generated by intracerebroventricular (icv) administration of streptozocin (STZ), the icv-STZ mouse, shows many aspects of SAD. In this study, we compared the non-cognitive and cognitive behaviors as well as biochemical and immunohistochemical alterations between the icv-STZ mouse and the 3xTg-AD mouse. We found that both mouse models showed increased exploratory activity as well as impaired learning and spatial memory. Both models also demonstrated neuroinflammation, altered synaptic proteins and insulin/IGF-1 (insulin-like growth factor-1) signaling, and increased hyperphosphorylated tau in the brain. The most prominent brain abnormality in the icv-STZ mouse was neuroinflammation, and in the 3xTg-AD mouse it was elevation of hyperphosphorylated tau. These observations demonstrate the behavioral and neuropathological similarities and differences between the icv-STZ mouse and the 3xTg-AD mouse models and will help guide future studies using these two mouse models for the development of AD drugs.
Haddix, Michelle L.; Magrini-Bair, Kim; Evans, Robert J.; Conant, Richard T.; Wallenstein, Matthew D.; Morris, Sherri J.; Calderón, Francisco; Paul, Eldor A.
2016-12-01
Soil organic matter (SOM) is extremely complex. It is composed of hundreds of different organic substances and it has been difficult to quantify these diverse substances in a dynamic-ecosystem functioning standpoint. Analytical pyrolysis has been used to compare chemical differences between soils, but its ability to measure the absolute amount of a specific compound in the soil is still in question. Our objective was to assess whether utilizing pyrolysis-molecular beam mass spectroscopy (py-MBMS) to define the signature of known reference compounds (adenine, indole, palmitic acid, etc.) and biological samples (chitin, fungi, cellulose, etc.) separately and when added to whole soils it was possible to make py-MBMS more quantitative. Reference compounds, spanning a wide variety of compound categories, and biological samples, expected to be present in SOM, were added to three soils from Colorado, Ohio, and Massachusetts that have varying total C, % clay, and clay type. Py-MBMS, a rapid analysis technique originally developed to analyze complex biomolecules, flash pyrolyzes soil organic matter to form products that are often considered characteristic of the original molecular structure. Samples were pyrolyzed at 550 degrees C by py-MBMS. All samples were weighed and %C and %N determined both before and after pyrolysis to evaluate mass loss, C loss, and N loss for the samples.An average relationship of r2 = 0.76 (P = 0.005) was found for the amount of cellulose added to soil at 25, 50, and 100% of soil C relative to the ion intensity of select mass/charge of the compound.There was a relationship of r2 = 0.93 (P < 0.001) for the amount of indole added to soil at 25, 50, and 100% of soil C and the ion intensity of the associated mass variables (mass/charge). Comparing spectra of pure compounds with the spectra of the compounds added to soil and isolated clay showed that interference could occur based on soil type and compound with the Massachusetts soil with high C (55
Vandal, Milene; White, Philip J; Tournissac, Marine; Tremblay, Cyntia; St-Amour, Isabelle; Drouin-Ouellet, Janelle; Bousquet, Melanie; Traversy, Marie-Thérèse; Planel, Emmanuel; Marette, Andre; Calon, Frederic
2016-07-01
The sharp rise in the incidence of Alzheimer's disease (AD) at an old age coincides with a reduction in energy metabolism and core body temperature. We found that the triple-transgenic mouse model of AD (3×Tg-AD) spontaneously develops a lower basal body temperature and is more vulnerable to a cold environment compared with age-matched controls. This was despite higher nonshivering thermogenic activity, as evidenced by brown adipose tissue norepinephrine content and uncoupling protein 1 expression. A 24-hour exposure to cold (4 °C) aggravated key neuropathologic markers of AD such as: tau phosphorylation, soluble amyloid beta concentrations, and synaptic protein loss in the cortex of 3×Tg-AD mice. Strikingly, raising the body temperature of aged 3×Tg-AD mice via exposure to a thermoneutral environment improved memory function and reduced amyloid and synaptic pathologies within a week. Our results suggest the presence of a vicious cycle between impaired thermoregulation and AD-like neuropathology, and it is proposed that correcting thermoregulatory deficits might be therapeutic in AD.
Nuclear Mass Datasets and Models at nuclearmasses.org
This online repository for nuclear mass information allows nuclear researchers to upload their own mass values, store then, share them with colleagues, and, in turn, visualize and analyze the work of others. The Resources link provides access to published information or tools on other websites. The Contributions page is where users will find software, documents, experimental mass data sets, and theoretical mass models that have been uploaded for sharing with the scientific community.
Discounting Testimony with the Argument Ad Hominem and a Bayesian Congruent Prior Model
ERIC Educational Resources Information Center
Bhatia, Jaydeep-Singh; Oaksford, Mike
2015-01-01
When directed to ignore evidence of a witness's previous bad character because of a violation of the rules of evidence, are jurors' beliefs still affected? The intuition is that they will be because in everyday argumentation, fallacies, like the ad hominem, are effective argumentative strategies. An ad hominem argument (against the person)…
Comments on single-mass models of vocal fold vibration
McGowan, Richard S.; Howe, Michael S.
2010-01-01
Proposed mechanisms for single-mass oscillation in the vocal tract are examined critically. There are two areas that distinguish single-mass models: in the sophistication of the air flow modeling near the oscillator and whether or not oscillation depends on acoustic feedback. Two recent models that do not depend on acoustic feedback are examined in detail. One model that depends on changing flow separation points is extended with approximate calculations. PMID:21117717
NASA Astrophysics Data System (ADS)
Chapman, Erik W.; Hofmann, Eileen E.; Patterson, Donna L.; Fraser, William R.
2010-04-01
Factors that control variability in energy density of Antarctic krill ( Euphausia superba) populations, and the consequences of this variability for growth and fledging mass of Adélie penguin ( Pygoscelis adeliae) chicks, were investigated using an individual-based energetics model. Lipid content as a function of sex/maturity stage and season was used to calculate the energy density of krill ingested by chicks. Simulations tested the influence of variability in krill size-class distribution, sex-ratio, length-at-maturity, and the timing of spawning on krill population energy density and penguin chick fledging mass. Of the parameters included in simulations, variability in the timing of krill spawning had the greatest influence on predicted Adélie penguin fledging mass, with fledging mass decreasing from 3.30 to 2.92 kg when peak spawning was shifted from early December to early March. Adélie penguin chicks that fledge from colonies along the western Antarctic Peninsula (wAP) and survive to recruit into the breeding population are 0.117 kg heavier than those that do not survive to breed. Thus, it appears that small differences in fledging mass potentially have significant implications for Adélie penguin chick survivorship. Therefore, the timing of krill spawning may have important consequences for Adélie penguins, and other top-predator species, that may time critical activities to coincide with a period of dependable prey availability with maximum energy density.
NASA Astrophysics Data System (ADS)
Baumgardt, H.
2017-01-01
We have determined the masses and mass-to-light ratios of 50 Galactic globular clusters by comparing their velocity dispersion and surface brightness profiles against a large grid of 900 N-body simulations of star clusters of varying initial concentration, size and central black hole mass fraction. Our models follow the evolution of the clusters under the combined effects of stellar evolution and two-body relaxation allowing us to take the effects of mass segregation and energy equipartition between stars self-consistently into account. For a subset of 16 well-observed clusters, we also derive their kinematic distances. We find an average mass-to-light ratio of Galactic globular clusters of
Ellis, Wade C; Lewis, Charlotte R; Openshaw, Anna P; Farnsworth, Paul B
2016-09-01
We demonstrate the effectiveness of using hydrogen-doped argon as the support gas for the dielectric barrier discharge (DBD) ambient desorption/ionization (ADI) source in mass spectrometry. Also, we explore the chemistry responsible for the signal enhancement observed when using both hydrogen-doped argon and hydrogen-doped helium. The hydrogen-doped argon was tested for five analytes representing different classes of molecules. Addition of hydrogen to the argon plasma gas enhanced signals for gas-phase analytes and for analytes coated onto glass slides in positive and negative ion mode. The enhancements ranged from factors of 4 to 5 for gas-phase analytes and factors of 2 to 40 for coated slides. There was no significant increase in the background. The limit of detection for caffeine was lowered by a factor of 79 using H2/Ar and 2 using H2/He. Results are shown that help explain the fundamental differences between the pure-gas discharges and those that are hydrogen-doped for both argon and helium. Experiments with different discharge geometries and grounding schemes indicate that observed signal enhancements are strongly dependent on discharge configuration. Graphical Abstract ᅟ.
NASA Astrophysics Data System (ADS)
Ellis, Wade C.; Lewis, Charlotte R.; Openshaw, Anna P.; Farnsworth, Paul B.
2016-09-01
We demonstrate the effectiveness of using hydrogen-doped argon as the support gas for the dielectric barrier discharge (DBD) ambient desorption/ionization (ADI) source in mass spectrometry. Also, we explore the chemistry responsible for the signal enhancement observed when using both hydrogen-doped argon and hydrogen-doped helium. The hydrogen-doped argon was tested for five analytes representing different classes of molecules. Addition of hydrogen to the argon plasma gas enhanced signals for gas-phase analytes and for analytes coated onto glass slides in positive and negative ion mode. The enhancements ranged from factors of 4 to 5 for gas-phase analytes and factors of 2 to 40 for coated slides. There was no significant increase in the background. The limit of detection for caffeine was lowered by a factor of 79 using H2/Ar and 2 using H2/He. Results are shown that help explain the fundamental differences between the pure-gas discharges and those that are hydrogen-doped for both argon and helium. Experiments with different discharge geometries and grounding schemes indicate that observed signal enhancements are strongly dependent on discharge configuration.
NASA Astrophysics Data System (ADS)
Chen, Xin; Liu, Li; Zhou, Sida; Yue, Zhenjiang
2016-09-01
Reduced order models(ROMs) based on the snapshots on the CFD high-fidelity simulations have been paid great attention recently due to their capability of capturing the features of the complex geometries and flow configurations. To improve the efficiency and precision of the ROMs, it is indispensable to add extra sampling points to the initial snapshots, since the number of sampling points to achieve an adequately accurate ROM is generally unknown in prior, but a large number of initial sampling points reduces the parsimony of the ROMs. A fuzzy-clustering-based adding-point strategy is proposed and the fuzzy clustering acts an indicator of the region in which the precision of ROMs is relatively low. The proposed method is applied to construct the ROMs for the benchmark mathematical examples and a numerical example of hypersonic aerothermodynamics prediction for a typical control surface. The proposed method can achieve a 34.5% improvement on the efficiency than the estimated mean squared error prediction algorithm and shows same-level prediction accuracy.
The simultaneous mass and energy evaporation (SM2E) model.
Choudhary, Rehan; Klauda, Jeffery B
2016-01-01
In this article, the Simultaneous Mass and Energy Evaporation (SM2E) model is presented. The SM2E model is based on theoretical models for mass and energy transfer. The theoretical models systematically under or over predicted at various flow conditions: laminar, transition, and turbulent. These models were harmonized with experimental measurements to eliminate systematic under or over predictions; a total of 113 measured evaporation rates were used. The SM2E model can be used to estimate evaporation rates for pure liquids as well as liquid mixtures at laminar, transition, and turbulent flow conditions. However, due to limited availability of evaporation data, the model has so far only been tested against data for pure liquids and binary mixtures. The model can take evaporative cooling into account and when the temperature of the evaporating liquid or liquid mixture is known (e.g., isothermal evaporation), the SM2E model reduces to a mass transfer-only model.
First Gogny-Hartree-Fock-Bogoliubov Nuclear Mass Model
Goriely, S.; Hilaire, S.; Girod, M.; Peru, S.
2009-06-19
We present the first Gogny-Hartree-Fock-Bogoliubov (HFB) model which reproduces nuclear masses with an accuracy comparable with the best mass formulas. In contrast with the Skyrme-HFB nuclear-mass models, an explicit and self-consistent account of all the quadrupole correlation energies are included within the 5D collective Hamiltonian approach. The final rms deviation with respect to the 2149 measured masses is 798 keV. In addition, the new Gogny force is shown to predict nuclear and neutron matter properties in agreement with microscopic calculations based on realistic two- and three-body forces.
Modeling Brain Resonance Phenomena Using a Neural Mass Model
Spiegler, Andreas; Knösche, Thomas R.; Schwab, Karin; Haueisen, Jens; Atay, Fatihcan M.
2011-01-01
Stimulation with rhythmic light flicker (photic driving) plays an important role in the diagnosis of schizophrenia, mood disorder, migraine, and epilepsy. In particular, the adjustment of spontaneous brain rhythms to the stimulus frequency (entrainment) is used to assess the functional flexibility of the brain. We aim to gain deeper understanding of the mechanisms underlying this technique and to predict the effects of stimulus frequency and intensity. For this purpose, a modified Jansen and Rit neural mass model (NMM) of a cortical circuit is used. This mean field model has been designed to strike a balance between mathematical simplicity and biological plausibility. We reproduced the entrainment phenomenon observed in EEG during a photic driving experiment. More generally, we demonstrate that such a single area model can already yield very complex dynamics, including chaos, for biologically plausible parameter ranges. We chart the entire parameter space by means of characteristic Lyapunov spectra and Kaplan-Yorke dimension as well as time series and power spectra. Rhythmic and chaotic brain states were found virtually next to each other, such that small parameter changes can give rise to switching from one to another. Strikingly, this characteristic pattern of unpredictability generated by the model was matched to the experimental data with reasonable accuracy. These findings confirm that the NMM is a useful model of brain dynamics during photic driving. In this context, it can be used to study the mechanisms of, for example, perception and epileptic seizure generation. In particular, it enabled us to make predictions regarding the stimulus amplitude in further experiments for improving the entrainment effect. PMID:22215992
Models of Neutrino Masses: Anarchy versus Hierarchy
NASA Astrophysics Data System (ADS)
Altarelli, Guido; Feruglio, Ferruccio; Masina, Isabella
2003-01-01
We present a quantitative study of the ability of models with different levels of hierarchy to reproduce the solar neutrino solutions, in particular the LA solution. As a flexible testing ground we consider models based on SU(5) × U(1)F. In this context, we have made statistical simulations of models with different patterns from anarchy to various types of hierarchy: normal hierarchical models with and without automatic suppression of the 23 (sub)determinant and inverse hierarchy models. We find that, not only for the LOW or VO solutions, but even in the LA case, the hierarchical models have a significantly better success rate than those based on anarchy. The normal hierarchy and the inverse hierarchy models have comparable performances in models with see-saw dominance, while the inverse hierarchy models are particularly good in the no see-saw versions. As a possible distinction between these categories of models, the inverse hierarchy models favour a maximal solar mixing angle and their rate of success drops dramatically as the mixing angle decreases, while normal hierarchy models are far more stable in this respect.
Modeling and Performance Simulation of the Mass Storage Network Environment
NASA Technical Reports Server (NTRS)
Kim, Chan M.; Sang, Janche
2000-01-01
This paper describes the application of modeling and simulation in evaluating and predicting the performance of the mass storage network environment. Network traffic is generated to mimic the realistic pattern of file transfer, electronic mail, and web browsing. The behavior and performance of the mass storage network and a typical client-server Local Area Network (LAN) are investigated by modeling and simulation. Performance characteristics in throughput and delay demonstrate the important role of modeling and simulation in network engineering and capacity planning.
NASA Astrophysics Data System (ADS)
Morales, Jose F.; Samtleben, Henning
2003-06-01
We review recent work on the holographic duals of type II and heterotic matrix string theories described by warped AdS3 supergravities. In particular, we compute the spectra of Kaluza-Klein primaries for type I, II supergravities on warped AdS3 × S7 and match them with the primary operators in the dual two-dimensional gauge theories. The presence of non-trivial warp factors and dilaton profiles requires a modification of the familiar dictionary between masses and 'scaling' dimensions of fields and operators. We present these modifications for the general case of domain wall/QFT correspondences between supergravities on warped AdSd+1 × Sq geometries and super Yang-Mills theories with 16 supercharges.
A Robust Deep Model for Improved Classification of AD/MCI Patients
Li, Feng; Tran, Loc; Thung, Kim-Han; Ji, Shuiwang; Shen, Dinggang; Li, Jiang
2015-01-01
Accurate classification of Alzheimer’s Disease (AD) and its prodromal stage, Mild Cognitive Impairment (MCI), plays a critical role in possibly preventing progression of memory impairment and improving quality of life for AD patients. Among many research tasks, it is of particular interest to identify noninvasive imaging biomarkers for AD diagnosis. In this paper, we present a robust deep learning system to identify different progression stages of AD patients based on MRI and PET scans. We utilized the dropout technique to improve classical deep learning by preventing its weight co-adaptation, which is a typical cause of over-fitting in deep learning. In addition, we incorporated stability selection, an adaptive learning factor, and a multi-task learning strategy into the deep learning framework. We applied the proposed method to the ADNI data set and conducted experiments for AD and MCI conversion diagnosis. Experimental results showed that the dropout technique is very effective in AD diagnosis, improving the classification accuracies by 5.9% on average as compared to the classical deep learning methods. PMID:25955998
Mammographic mass detection based on extended concentric morphology model
NASA Astrophysics Data System (ADS)
Li, Yanfeng; Chen, Houjin
2014-01-01
Breast cancer occurs with high frequency among women. In most cases, the main early signs appear as mass and calcification. Distinguishing masses from normal tissues is still a challenging work as mass varies with shapes, margins and sizes. In this paper, a novel method for mass detection in mammograms was presented. First, morphology operators are employed to locate mass candidates. Then anisotropic diffusion was applied to make mass region display better multiple concentric layers (MCL). Finally an extended concentric morphology model (ECMM) criterion combining MCL criterion and template matching was proposed to detect masses. This method was examined on 170 images from Digital Database for Screening Mammography (DDSM) database. The detection rate is 93.92% at 1.88 false positives per image (FPs/I), demonstrating the effectiveness of the proposed method.
NASA Astrophysics Data System (ADS)
Longcope, D. W.; Klimchuk, J. A.
2015-11-01
Aspects of solar flare dynamics, such as chromospheric evaporation and flare light curves, have long been studied using one-dimensional models of plasma dynamics inside a static flare loop, subjected to some energy input. While extremely successful at explaining the observed characteristics of flares, all such models so far have specified energy input ad hoc, rather than deriving it self-consistently. There is broad consensus that flares are powered by magnetic energy released through reconnection. Recent work has generalized Petschek’s basic reconnection scenario, topological change followed by field line retraction and shock heating, to permit its inclusion in a one-dimensional flare loop model. Here we compare the gas dynamics driven by retraction and shocking to those from more conventional static loop models energized by ad hoc source terms. We find significant differences during the first minute, when retraction leads to larger kinetic energies and produces higher densities at the loop top, while ad hoc heating tends to rarify the loop top. The loop-top density concentration is related to the slow magnetosonic shock, characteristic of Petschek’s model, but persists beyond the retraction phase occurring in the outflow jet. This offers an explanation for observed loop-top sources of X-ray and EUV emission, with advantages over that provided by ad hoc heating scenarios. The cooling phases of the two models are, however, notably similar to one another, suggesting that observations at that stage will yield little information on the nature of energy input.
Conserved charges in timelike warped AdS3 spaces
NASA Astrophysics Data System (ADS)
Donnay, L.; Fernández-Melgarejo, J. J.; Giribet, G.; Goya, A.; Lavia, E.
2015-06-01
We consider the timelike version of warped anti-de Sitter space (WAdS), which corresponds to the three-dimensional section of the Gödel solution of four-dimensional cosmological Einstein equations. This geometry presents closed timelike curves (CTCs), which are inherited from its four-dimensional embedding. In three dimensions, this type of solution can be supported without matter provided the graviton acquires mass. Here, among the different ways to consistently give mass to the graviton in three dimensions, we consider the parity-even model known as new massive gravity (NMG). In the bulk of timelike WAdS3 space, we introduce defects that, from the three-dimensional point of view, represent spinning massive particlelike objects. For this type of source, we investigate the definition of quasilocal gravitational energy as seen from infinity, far beyond the region where the CTCs appear. We also consider the covariant formalism applied to NMG to compute the mass and the angular momentum of spinning particlelike defects and compare the result with the one obtained by means of the quasilocal stress tensor. We apply these methods to special limits in which the WAdS3 solutions coincide with locally AdS3 and locally AdS2×R spaces. Finally, we make some comments about the asymptotic symmetry algebra of asymptotically WAdS3 spaces in NMG.
Mass loss in 2D rotating stellar models
Lovekin, Caterine; Deupree, Bob
2010-10-05
Radiatively driven mass loss is an important factor in the evolution of massive stars . The mass loss rates depend on a number of stellar parameters, including the effective temperature and luminosity. Massive stars are also often rapidly rotating, which affects their structure and evolution. In sufficiently rapidly rotating stars, both the effective temperature and radius vary significantly as a function of latitude, and hence mass loss rates can vary appreciably between the poles and the equator. In this work, we discuss the addition of mass loss to a 2D stellar evolution code (ROTORC) and compare evolution sequences with and without mass loss. Preliminary results indicate that a full 2D calculation of mass loss using the local effective temperature and luminosity can significantly affect the distribution of mass loss in rotating main sequence stars. More mass is lost from the pole than predicted by 1D models, while less mass is lost at the equator. This change in the distribution of mass loss will affect the angular momentum loss, the surface temperature and luminosity, and even the interior structure of the star. After a single mass loss event, these effects are small, but can be expected to accumulate over the course of the main sequence evolution.
Air Mass Considerations in Fog Optical Modeling.
1981-02-01
military forces are increasingly relying on new sophis - ticated weapons systems which employ electro-optical (EO) sensors or systems in their principles of...infrared extinction coefficients. Several authors (Stewart,10 Turner et all’) have shown that models which depend upon visibility alone can lead to...Extinction by Fog, TR-77-9, Technology Laboratory, Physical Science Directorate, Redstone Arsenal, AL 11R. E. Turner et al, 1978, Model Development for E-O
Testing galaxy formation models with galaxy stellar mass functions
NASA Astrophysics Data System (ADS)
Lim, S. H.; Mo, H. J.; Lan, T.-W.; Ménard, B.
2017-01-01
We compare predictions of a number of empirical models and numerical simulations of galaxy formation to the conditional stellar mass functions of galaxies in groups of different masses obtained recently by Lan et al. to test how well different models accommodate the data. The observational data clearly prefer a model in which star formation in low-mass haloes changes behaviour at a characteristic redshift zc ˜ 2. There is also tentative evidence that this characteristic redshift depends on environment, becoming zc ˜ 4 in regions that eventually evolve into rich clusters of galaxies. The constrained model is used to understand how galaxies form and evolve in dark matter haloes, and to make predictions for other statistical properties of the galaxy population, such as the stellar mass functions of galaxies at high z, the star formation, and stellar mass assembly histories in dark matter haloes. A comparison of our model predictions with those of other empirical models shows that different models can make vastly different predictions, even though all of them are tuned to match the observed stellar mass functions of galaxies.
Radiative neutrino mass model with degenerate right-handed neutrinos
NASA Astrophysics Data System (ADS)
Kashiwase, Shoichi; Suematsu, Daijiro
2016-03-01
The radiative neutrino mass model can relate neutrino masses and dark matter at a TeV scale. If we apply this model to thermal leptogenesis, we need to consider resonant leptogenesis at that scale. It requires both finely degenerate masses for the right-handed neutrinos and a tiny neutrino Yukawa coupling. We propose an extension of the model with a U(1) gauge symmetry, in which these conditions are shown to be simultaneously realized through a TeV scale symmetry breaking. Moreover, this extension can bring about a small quartic scalar coupling between the Higgs doublet scalar and an inert doublet scalar which characterizes the radiative neutrino mass generation. It also is the origin of the Z_2 symmetry which guarantees the stability of dark matter. Several assumptions which are independently supposed in the original model are closely connected through this extension.
Mass storage system reference model, Version 4
NASA Technical Reports Server (NTRS)
Coleman, Sam (Editor); Miller, Steve (Editor)
1993-01-01
The high-level abstractions that underlie modern storage systems are identified. The information to generate the model was collected from major practitioners who have built and operated large storage facilities, and represents a distillation of the wisdom they have acquired over the years. The model provides a common terminology and set of concepts to allow existing systems to be examined and new systems to be discussed and built. It is intended that the model and the interfaces identified from it will allow and encourage vendors to develop mutually-compatible storage components that can be combined to form integrated storage systems and services. The reference model presents an abstract view of the concepts and organization of storage systems. From this abstraction will come the identification of the interfaces and modules that will be used in IEEE storage system standards. The model is not yet suitable as a standard; it does not contain implementation decisions, such as how abstract objects should be broken up into software modules or how software modules should be mapped to hosts; it does not give policy specifications, such as when files should be migrated; does not describe how the abstract objects should be used or connected; and does not refer to specific hardware components. In particular, it does not fully specify the interfaces.
ERIC Educational Resources Information Center
Educational Researcher, 2015
2015-01-01
The purpose of this statement is to inform those using or considering the use of value-added models (VAM) about their scientific and technical limitations in the evaluation of educators and programs that prepare teachers. The statement briefly reviews the background and current context of using VAM for evaluations, enumerates specific psychometric…
ERIC Educational Resources Information Center
Davison, Kimberlee Kaye Callister
2012-01-01
The purpose of this study was to examine the potential for using propensity score-based matching methods to estimate teacher contributions to student learning. Value-added models are increasingly used in teacher accountability systems in the United States in spite of ongoing qualms about the validity of teacher quality estimates resulting from…
NASA Astrophysics Data System (ADS)
Anabalón, Andrés; Astefanesei, Dumitru; Choque, David
2016-11-01
We construct exact hairy AdS soliton solutions in Einstein-dilaton gravity theory. We examine their thermodynamic properties and discuss the role of these solutions for the existence of first order phase transitions for hairy black holes. The negative energy density associated to hairy AdS solitons can be interpreted as the Casimir energy that is generated in the dual filed theory when the fermions are antiperiodic on the compact coordinate.
Modeling rapidly disseminating infectious disease during mass gatherings.
Chowell, Gerardo; Nishiura, Hiroshi; Viboud, Cécile
2012-12-07
We discuss models for rapidly disseminating infectious diseases during mass gatherings (MGs), using influenza as a case study. Recent innovations in modeling and forecasting influenza transmission dynamics at local, regional, and global scales have made influenza a particularly attractive model scenario for MG. We discuss the behavioral, medical, and population factors for modeling MG disease transmission, review existing model formulations, and highlight key data and modeling gaps related to modeling MG disease transmission. We argue that the proposed improvements will help integrate infectious-disease models in MG health contingency plans in the near future, echoing modeling efforts that have helped shape influenza pandemic preparedness plans in recent years.
Neutrino masses in the left right supersymmetric model
NASA Astrophysics Data System (ADS)
Frank, M.
2002-08-01
We show that in a left-right supersymmetric model with a Higgs structure that supports the see-saw mechanism, the neutrinos get additional contributions to their masses at one loop level. The mechanism responsible is analogous to the Grossman-Haber see-saw mechanism, but the additional mass terms are proportional to the mass difference of the right-handed sneutrinos. We show that the data on both the solar and the atmospheric neutrinos can be accommodated by either two almost degenerate right-handed sneutrinos, or two heavy sneutrino with different, but still relatively small, mass splittings. We discuss the implications of this result for the masses and mixings of the heavy sneutrinos, and the soft-breaking parameters of the left-right supersymmetric model.
Modelling Mass Movements for Planetary Studies
NASA Technical Reports Server (NTRS)
Bulmer, M. H.; Glaze, L.; Barnouin-Jha, O.; Murphy, W.; Neumann, G.
2002-01-01
Use of an empirical model in conjunction with data from the Chaos Jumbles rock avalanches constrain to first order their flow behavior, and provide a method to interpret rock/debris avalanche emplacement on Mars. Additional information is contained in the original extended abstract.
A novel observer design method for neural mass models
NASA Astrophysics Data System (ADS)
Liu, Xian; Miao, Dong-Kai; Gao, Qing; Xu, Shi-Yun
2015-09-01
Neural mass models can simulate the generation of electroencephalography (EEG) signals with different rhythms, and therefore the observation of the states of these models plays a significant role in brain research. The structure of neural mass models is special in that they can be expressed as Lurie systems. The developed techniques in Lurie system theory are applicable to these models. We here provide a new observer design method for neural mass models by transforming these models and the corresponding error systems into nonlinear systems with Lurie form. The purpose is to establish appropriate conditions which ensure the convergence of the estimation error. The effectiveness of the proposed method is illustrated by numerical simulations. Project supported by the National Natural Science Foundation of China (Grant Nos. 61473245, 61004050, and 51207144).
ERIC Educational Resources Information Center
Troncoso, Patricio; Pampaka, Maria; Olsen, Wendy
2016-01-01
School value-added studies have largely demonstrated the effects of socioeconomic and demographic characteristics of the schools and the pupils on performance in standardised tests. Traditionally, these studies have assessed the variation coming only from the schools and the pupils. However, recent studies have shown that the analysis of academic…
Thierry, Anne-Mathilde; Ropert-Coudert, Yan; Raclot, Thierry
2013-01-01
Study of physiological mechanisms can help us to understand how animals respond to changing environmental conditions. In particular, stress hormones (i.e. glucocorticoids, such as corticosterone) are described as mediating resource allocation, allowing animals to adjust their physiology and behaviour to predictable and unpredictable changes in the environment. In this study, we investigated the effects of an experimental increase in baseline corticosterone levels on the breeding effort and the reproductive output of chick-rearing male Adélie penguins (Pygoscelis adeliae). The number of chicks per nest, their body mass, and their size were monitored throughout the study. Direct observations allowed measurement of the time spent foraging at sea and caring for the young on the nest. At the end of the treatment, blood samples were collected for isotope analysis. Although all birds raised at least one chick, reproductive output was decreased by 42% in corticosterone-treated birds compared with control birds. The increase in corticosterone levels during the guard stage did not affect the mass of surviving chicks or the brood mass at fledging. Corticosterone-treated males spent on average 21% more time at the nest than control birds. However, the duration of foraging trips was similar between both groups. In addition, the similarity of isotopic signatures suggests that both groups foraged at similar locations and ingested the same prey species. The detailed on-land behaviour of birds should be examined in further studies to clarify the possible links between corticosterone levels, brooding time, and reproductive output. Understanding the relationships between glucocorticoids, fitness, and ultimately population dynamics is fundamental to enabling conservation physiology as a discipline to be successful in helping to manage species of conservation concern. PMID:27293591
ACCURATE LOW-MASS STELLAR MODELS OF KOI-126
Feiden, Gregory A.; Chaboyer, Brian; Dotter, Aaron
2011-10-10
The recent discovery of an eclipsing hierarchical triple system with two low-mass stars in a close orbit (KOI-126) by Carter et al. appeared to reinforce the evidence that theoretical stellar evolution models are not able to reproduce the observational mass-radius relation for low-mass stars. We present a set of stellar models for the three stars in the KOI-126 system that show excellent agreement with the observed radii. This agreement appears to be due to the equation of state implemented by our code. A significant dispersion in the observed mass-radius relation for fully convective stars is demonstrated; indicative of the influence of physics currently not incorporated in standard stellar evolution models. We also predict apsidal motion constants for the two M dwarf companions. These values should be observationally determined to within 1% by the end of the Kepler mission.
Relativistic electromagnetic mass models in spherically symmetric spacetime
NASA Astrophysics Data System (ADS)
Maurya, S. K.; Gupta, Y. K.; Ray, Saibal; Chatterjee, Vikram
2016-10-01
Under the static spherically symmetric Einstein-Maxwell spacetime of embedding class one we explore possibility of constructing electromagnetic mass model where mass and other physical parameters have purely electromagnetic origin (Lorentz in Proc. Acad. Sci. Amst. 6, 1904). This work is in continuation of our earlier investigation of Maurya et al. (Eur. Phys. J. C 75:389, 2015a) where we developed an algorithm and found out three new solutions of electromagnetic mass model. In the present work we consider different metric potentials ν and λ and have analyzed them in a systematic way. It is observed that some of the previous solutions related to electromagnetic mass model are nothing but special cases of the presently obtained generalized solution set. We further verify the solution set and especially show that these are extremely applicable in the case of compact stars.
Analytical model of peptide mass cluster centres with applications
Wolski, Witold E; Farrow, Malcolm; Emde, Anne-Katrin; Lehrach, Hans; Lalowski, Maciej; Reinert, Knut
2006-01-01
Background The elemental composition of peptides results in formation of distinct, equidistantly spaced clusters across the mass range. The property of peptide mass clustering is used to calibrate peptide mass lists, to identify and remove non-peptide peaks and for data reduction. Results We developed an analytical model of the peptide mass cluster centres. Inputs to the model included, the amino acid frequencies in the sequence database, the average length of the proteins in the database, the cleavage specificity of the proteolytic enzyme used and the cleavage probability. We examined the accuracy of our model by comparing it with the model based on an in silico sequence database digest. To identify the crucial parameters we analysed how the cluster centre location depends on the inputs. The distance to the nearest cluster was used to calibrate mass spectrometric peptide peak-lists and to identify non-peptide peaks. Conclusion The model introduced here enables us to predict the location of the peptide mass cluster centres. It explains how the location of the cluster centres depends on the input parameters. Fast and efficient calibration and filtering of non-peptide peaks is achieved by a distance measure suggested by Wool and Smilansky. PMID:16995952
Keswani, Sundeep G; Balaji, Swathi; Katz, Anna B; King, Alice; Omar, Khaled; Habli, Mounira; Klanke, Charles; Crombleholme, Timothy M
2015-03-01
Intrauterine growth restriction (IUGR) due to placental insufficiency is a leading cause of perinatal complications for which there is no effective prenatal therapy. We have previously demonstrated that intraplacental injection of adenovirus-mediated insulin-like growth factor-1 (Ad-IGF-1) corrects fetal weight in a murine IUGR model induced by mesenteric uterine artery branch ligation. This study investigated the effect of intraplacental Ad-IGF-1 gene therapy in a rabbit model of naturally occurring IUGR (runt) due to placental insufficiency, which is similar to the human IUGR condition with onset in the early third trimester, brain sparing, and a reduction in liver weight. Laparotomy was performed on New Zealand White rabbits on day 21 of 30 days of gestation and litters were divided into five groups: Control (first position)+phosphate-buffered saline (PBS), control+Ad-IGF-1, runt (third position)+PBS, runt+Ad-IGF-1, and runt+Ad-LacZ. The effect of IGF-1 gene therapy on fetal, placental, liver, heart, lung, and musculoskeletal weights of the growth-restricted pups was examined. Protein expression after gene transfer was seen along the maternal-fetal placenta interface (n=12) 48 hr after gene therapy. There was minimal gene transfer detected in the pups or maternal organs. At term, compared with the normally grown first-position control, the runted third-position pups demonstrated significantly lower fetal, placental, liver, lung, and musculoskeletal weights. The fetal, liver, and musculoskeletal weights were restored to normal by intraplacental Ad-IGF-1 gene therapy (p<0.01), with no change in the placental weight. Intraplacental gene therapy is a novel strategy for the treatment of IUGR caused by placental insufficiency that takes advantage of an organ that will be discarded at birth. Development of nonviral IGF-1 gene delivery using placenta-specific promoters can potentially minimize toxicity to the mother and fetus and facilitate clinical translation of
Kinetic model of mass exchange with dynamic Arrhenius transition rates
NASA Astrophysics Data System (ADS)
Hristopulos, Dionissios T.; Muradova, Aliki
2016-02-01
We study a nonlinear kinetic model of mass exchange between interacting grains. The transition rates follow the Arrhenius equation with an activation energy that depends dynamically on the grain mass. We show that the activation parameter can be absorbed in the initial conditions for the grain masses, and that the total mass is conserved. We obtain numerical solutions of the coupled, nonlinear, ordinary differential equations of mass exchange for the two-grain system, and we compare them with approximate theoretical solutions in specific neighborhoods of the phase space. Using phase plane methods, we determine that the system exhibits regimes of diffusive and growth-decay (reverse diffusion) kinetics. The equilibrium states are determined by the mass equipartition and separation nullcline curves. If the transfer rates are perturbed by white noise, numerical simulations show that the system maintains the diffusive and growth-decay regimes; however, the noise can reverse the sign of equilibrium mass difference. Finally, we present theoretical analysis and numerical simulations of a system with many interacting grains. Diffusive and growth-decay regimes are established as well, but the approach to equilibrium is considerably slower. Potential applications of the mass exchange model involve coarse-graining during sintering and wealth exchange in econophysics.
ERIC Educational Resources Information Center
Ferrão, Maria Eugénia; Couto, Alcino Pinto
2014-01-01
This article focuses on the use of a value-added approach for promoting school improvement. It presents yearly value-added estimates, analyses their stability over time, and discusses the contribution of this methodological approach for promoting school improvement programmes in the Portuguese system of evaluation. The value-added model is applied…
Lu, Li; Gong, Xu; Tan, Li
2015-03-01
A fast screening method was established for the simultaneous determination of 24 sedative hypnotics illegally added in improving sleep health foods by high performance liquid chromatography-ion trap mass spectrometry (HPLC-IT MS). The method was based on the sonication assisted extraction of the improving sleep health food samples using methanol. The extract was then filtrated with 0.45 µm filter membrane and the filtrate was separated on a Phenomenex Luna C18 column with isocratic elution at a flow rate of 0.3 mL/min. A binary mobile phase was 0.05% (v/v) formic acid (solvent A)-methanol/acetonitrile (15:25, v/v, solvent B). The electrospray ionization (ESI) source in positive ion mode or negative ion mode was used to scan MS1-MS3 spectra for the 24 sedative hypnotics. The MS2 and MS3 spectra were used for qualitative analysis of samples. The calibration graphs were linear in their concentration ranges with the correlation coefficients (r2) more than 0.999. The limits of detection (LODs) were 4.0-446.6 µg/L. The recoveries for all the drugs in the improving sleep health foods were 88.6%-110.3% with the relative standard deviations no more than 9.8% at three spiked levels. Twenty-seven batches of the improving sleep health foods were tested. Melatonin was found in eighteen batches. The method is fast, specific, sensitive, easy and suitable for fast screening of 24 sedative hypnotics illegally added in improving sleep health foods.
Light, Heather R; Tsanzi, Embedzayi; Gigliotti, Joseph; Morgan, Keri; Tou, Janet C
2009-06-01
Caloric sweetened beverages have been suggested to be a major dietary contributor to weight gain, particularly among adolescents. Dietary recommendations are for moderating intakes of added sugars; however, the question remains whether certain types of sugars should be limited. The objective of this study was to determine the effect of drinking different caloric sweetened beverages on the development of adiposity, metabolic, and endocrine disorders. Young (age 28 days) female Sprague-Dawley rats (n = 8-9 rats/group) were randomly assigned to drink either deionized distilled water (ddH2O) or ddH2O sweetened with 13% (w/v) glucose, sucrose, fructose or high fructose corn syrup 55 (HFCS-55) for 8 weeks. Rats drinking caloric sweetened solutions failed to completely compensate for liquid calories ingested by reducing their consumption of solid food. This resulted in greater total energy intake compared to the ddH2O control; however, there was no significant difference in total energy intake between rats drinking sucrose, fructose or HFCS-55. Of the different caloric sweeteners, only rats drinking HFCS-55 had greater (P < 0.05) final body weights and fat mass compared to the rats drinking ddH2O or glucose solution. This may have occurred because drinking HFCS-55 solution promoted a faster body weight gain. Adiposity induced by caloric sweetened water was not accompanied by metabolic disorders indicated by the absence of dyslipidemia and no differences in fasting serum glucose, insulin or C-peptide among the treatment groups. However, rats drinking HFCS-55 showed lengthened estrous cycles due to prolonged estrus. Based on this study, the type of caloric sweetener added to beverages should be considered when making dietary recommendation for reducing excess body weight and related health risk.
Longcope, D. W.; Klimchuk, J. A.
2015-11-10
Aspects of solar flare dynamics, such as chromospheric evaporation and flare light curves, have long been studied using one-dimensional models of plasma dynamics inside a static flare loop, subjected to some energy input. While extremely successful at explaining the observed characteristics of flares, all such models so far have specified energy input ad hoc, rather than deriving it self-consistently. There is broad consensus that flares are powered by magnetic energy released through reconnection. Recent work has generalized Petschek’s basic reconnection scenario, topological change followed by field line retraction and shock heating, to permit its inclusion in a one-dimensional flare loop model. Here we compare the gas dynamics driven by retraction and shocking to those from more conventional static loop models energized by ad hoc source terms. We find significant differences during the first minute, when retraction leads to larger kinetic energies and produces higher densities at the loop top, while ad hoc heating tends to rarify the loop top. The loop-top density concentration is related to the slow magnetosonic shock, characteristic of Petschek’s model, but persists beyond the retraction phase occurring in the outflow jet. This offers an explanation for observed loop-top sources of X-ray and EUV emission, with advantages over that provided by ad hoc heating scenarios. The cooling phases of the two models are, however, notably similar to one another, suggesting that observations at that stage will yield little information on the nature of energy input.
... need sugar to function properly. Added sugars contribute zero nutrients but many added calories that can lead to extra pounds or even obesity, thereby reducing heart health. If you think of your daily calorie needs as a budget, you want to “spend” ...
ERIC Educational Resources Information Center
UCLA IDEA, 2012
2012-01-01
Value added measures (VAM) uses changes in student test scores to determine how much "value" an individual teacher has "added" to student growth during the school year. Some policymakers, school districts, and educational advocates have applauded VAM as a straightforward measure of teacher effectiveness: the better a teacher,…
Study on the constitutive model for jointed rock mass.
Xu, Qiang; Chen, Jianyun; Li, Jing; Zhao, Chunfeng; Yuan, Chenyang
2015-01-01
A new elasto-plastic constitutive model for jointed rock mass, which can consider the persistence ratio in different visual angle and anisotropic increase of plastic strain, is proposed. The proposed the yield strength criterion, which is anisotropic, is not only related to friction angle and cohesion of jointed rock masses at the visual angle but also related to the intersection angle between the visual angle and the directions of the principal stresses. Some numerical examples are given to analyze and verify the proposed constitutive model. The results show the proposed constitutive model has high precision to calculate displacement, stress and plastic strain and can be applied in engineering analysis.
Mass and heat transfer model of Tubular Solar Still
Ahsan, Amimul; Fukuhara, Teruyuki
2010-07-15
In this paper, a new mass and heat transfer model of a Tubular Solar Still (TSS) was proposed incorporating various mass and heat transfer coefficients taking account of the humid air properties inside the still. The heat balance of the humid air and the mass balance of the water vapor in the humid air were formulized for the first time. As a result, the proposed model enabled to calculate the diurnal variations of the temperature, water vapor density and relative humidity of the humid air, and to predict the hourly condensation flux besides the temperatures of the water, cover and trough, and the hourly evaporation flux. The validity of the proposed model was verified using the field experimental results carried out in Fukui, Japan and Muscat, Oman in 2008. The diurnal variations of the calculated temperatures and water vapor densities had a good agreement with the observed ones. Furthermore, the proposed model can predict the daily and hourly production flux precisely. (author)
Model-Based Systems Engineering Approach to Managing Mass Margin
NASA Technical Reports Server (NTRS)
Chung, Seung H.; Bayer, Todd J.; Cole, Bjorn; Cooke, Brian; Dekens, Frank; Delp, Christopher; Lam, Doris
2012-01-01
When designing a flight system from concept through implementation, one of the fundamental systems engineering tasks ismanaging the mass margin and a mass equipment list (MEL) of the flight system. While generating a MEL and computing a mass margin is conceptually a trivial task, maintaining consistent and correct MELs and mass margins can be challenging due to the current practices of maintaining duplicate information in various forms, such as diagrams and tables, and in various media, such as files and emails. We have overcome this challenge through a model-based systems engineering (MBSE) approach within which we allow only a single-source-of-truth. In this paper we describe the modeling patternsused to capture the single-source-of-truth and the views that have been developed for the Europa Habitability Mission (EHM) project, a mission concept study, at the Jet Propulsion Laboratory (JPL).
Renormalization of a two-loop neutrino mass model
Babu, K. S.; Julio, J.
2014-01-01
We analyze the renormalization group structure of a radiative neutrino mass model consisting of a singly charged and a doubly charged scalar fields. Small Majorana neutrino masses are generated by the exchange of these scalars via two-loop diagrams. We derive boundedness conditions for the Higgs potential and show how they can be satisfied to energies up to the Planck scale. Combining boundedness and perturbativity constraints with neutrino oscillation phenomenology, new limits on the masses and couplings of the charged scalars are derived. These in turn lead to lower limits on the branching ratios for certain lepton flavor violating (LFV) processes such as μ→eγ, μ→3e and μ – e conversion in nuclei. Improved LFV measurements could test the model, especially in the case of inverted neutrino mass hierarchy where these are more prominent.
Model independent explorations of Majorana neutrino mass origins
NASA Astrophysics Data System (ADS)
Jenkins, James Phearl, Jr.
The recent observation of nonzero neutrino mass is the first concrete indication of physics beyond the Standard Model. Their properties, unique among the other fermions, leads naturally to the idea of a Majorana neutrino mass term. Despite the strong theoretical prejudice toward this concept, it must be tested experimentally. This is indeed possible in the context of next generation experiments. Unfortunately, the scale of neutrino mass generation may be too large to explore directly, but useful information may still be extracted from independent experimental channels. Here I survey various model independent probes of Majorana neutrino mass origins. A brief introduction to the concepts relevant to the analysis is followed by a discussion of the physical ranges of neutrino mass and mixing parameters within the context of standard and non-standard interactions. Armed with this, I move on to systematically analyze the properties of radiatively generated neutrino masses induced by nonrenormalizable lepton number violating effective operators of mass dimensions five through eleven. By fitting these to the observed light mass scale, I extract predictions for neutrino mixing as well as neutrinoless double beta decay, rare meson/tau decays and collider phenomenology. I find that many such models are already constrained by current data and many more will be probed in the near future. I then move on demonstrate the utility of a low scale see saw mechanism via a viable 3+2+1 sterile neutrino model that satisfies all oscillation data as well as solves problems associated with supernova kicks and heavy element nucleosynthesis. From this I extract predictions for tritium and neutrinoless double beta decay searches. This is supplemented throughout by descriptions of practical limitations in addition to suggestions for future work.
An equivalent viscoelastic model for rock mass with parallel joints
NASA Astrophysics Data System (ADS)
Li, Jianchun; Ma, Guowei; Zhao, Jian
2010-03-01
An equivalent viscoelastic medium model is proposed for rock mass with parallel joints. A concept of "virtual wave source (VWS)" is proposed to take into account the wave reflections between the joints. The equivalent model can be effectively applied to analyze longitudinal wave propagation through discontinuous media with parallel joints. Parameters in the equivalent viscoelastic model are derived analytically based on longitudinal wave propagation across a single rock joint. The proposed model is then verified by applying identical incident waves to the discontinuous and equivalent viscoelastic media at one end to compare the output waves at the other end. When the wavelength of the incident wave is sufficiently long compared to the joint spacing, the effect of the VWS on wave propagation in rock mass is prominent. The results from the equivalent viscoelastic medium model are very similar to those determined from the displacement discontinuity method. Frequency dependence and joint spacing effect on the equivalent viscoelastic model and the VWS method are discussed.
Models of material ejection. [of solar coronal mass
NASA Technical Reports Server (NTRS)
Steinolfson, R. S.
1990-01-01
Some recently developed models related to the formation of a coronal mass ejection (CME) are reviewed. The models individually consider the stability of a prominence, the eruption of a coupled prominence and CME configuration with driven reconnection below the prominence, magnetic arcade equilibrium, and coronal evolution due to shear motion. No effort is made to critique the various models. Their relevance to actual observed material ejections will ultimately be determined by detailed comparison with present and future observations.
The Higgs boson mass in minimal Technicolor models
Doff, A.; Natale, A. A.
2010-11-12
Recently a Minimal and an Ultraminimal Technicolor models were proposed where the presence of TC fermions in other representations than the fundamental one led to viable models without conflict with the known value for the measured S parameter. In this work we apply the results of [5] to compute the masses of the Higgs boson in the case of the Minimal and Ultraminimal Technicolor models.
Kitazawa, Masashi; Cheng, David; Laferla, Frank M
2009-03-01
Excess copper exposure is thought to be linked to the development of Alzheimer's disease (AD) neuropathology. However, the mechanism by which copper affects the CNS remains unclear. To investigate the effect of chronic copper exposure on both beta-amyloid and tau pathologies, we treated young triple transgenic (3xTg-AD) mice with 250 ppm copper-containing water for a period of 3 or 9 months. Copper exposure resulted in altered amyloid precursor protein processing; increased accumulation of the amyloid precursor protein and its proteolytic product, C99 fragment, along with increased generation of amyloid-beta peptides and oligomers. These changes were found to be mediated via up-regulation of BACE1 as significant increases in BACE1 levels and deposits were detected around plaques in mice following copper exposure. Furthermore, tau pathology within hippocampal neurons was exacerbated in copper-exposed 3xTg-AD group. Increased tau phosphorylation was closely correlated with aberrant cdk5/p25 activation, suggesting a role for this kinase in the development of copper-induced tau pathology. Taken together, our data suggest that chronic copper exposure accelerates not only amyloid pathology but also tau pathology in a mouse model of AD.
Impact of mass generation for spin-1 mediator simplified models
NASA Astrophysics Data System (ADS)
Bell, Nicole F.; Cai, Yi; Leane, Rebecca K.
2017-01-01
In the simplified dark matter models commonly studied, the mass generation mechanism for the dark fields is not typically specified. We demonstrate that the dark matter interaction types, and hence the annihilation processes relevant for relic density and indirect detection, are strongly dictated by the mass generation mechanism chosen for the dark sector particles, and the requirement of gauge invariance. We focus on the class of models in which fermionic dark matter couples to a spin-1 vector or axial-vector mediator. However, in order to generate dark sector mass terms, it is necessary in most cases to introduce a dark Higgs field and thus a spin-0 scalar mediator will also be present. In the case that all the dark sector fields gain masses via coupling to a single dark sector Higgs field, it is mandatory that the axial-vector coupling of the spin-1 mediator to the dark matter is non-zero; the vector coupling may also be present depending on the charge assignments. For all other mass generation options, only pure vector couplings between the spin-1 mediator and the dark matter are allowed. If these coupling restrictions are not obeyed, unphysical results may be obtained such as a violation of unitarity at high energies. These two-mediator scenarios lead to important phenomenology that does not arise in single mediator models. We survey two-mediator dark matter models which contain both vector and scalar mediators, and explore their relic density and indirect detection phenomenology.
Simulation of the blowing snow flux in Adélie Land, Antarctica, by a regional climate model
NASA Astrophysics Data System (ADS)
Gallée, Hubert; Amory, Charles; Agosta, Cécile
2016-04-01
The parameterization of blowing snow in the regional climate model MAR (Modèle Atmosphérique Régional) has been tested. The model is set-up over Adélie Land, Antarctica, with a fine horizontal resolution (5 km) and an improved vertical resolution near the surface (lowest level is now situated 0.15 m above the surface). The domain of the model covers the steepest slopes of Adélie Land, on an area of 500 times 500 km2. Simulations last 2 summer months (December 2010 and January 2011). The influence of model parameterizations on the simulated wind speed, relative humidity and horizontal blowing snow flux near the surface is assessed. It is found that model parameters influencing turbulence and in particular the parameterization of the roughness length are the main contributors to the sensitivity of the above-mentioned model variables. Therefore model sensitivity tests to various parameterizations of the roughness length are performed, allowing to define a new parameterization of the roughness length depending on snow erosion by the wind.
The value of adding optics to ecosystem models: a case study
NASA Astrophysics Data System (ADS)
Fujii, M.; Boss, E.; Chai, F.
2007-10-01
Many ecosystem models have been developed to study the ocean's biogeochemical properties, but most of these models use simple formulations to describe light penetration and spectral quality. Here, an optical model is coupled with a previously published ecosystem model that explicitly represents two phytoplankton (picoplankton and diatoms) and two zooplankton functional groups, as well as multiple nutrients and detritus. Surface ocean color fields and subsurface light fields are calculated by coupling the ecosystem model with an optical model that relates biogeochemical standing stocks with inherent optical properties (absorption, scattering); this provides input to a commercially available radiative transfer model (Ecolight). We apply this bio-optical model to the equatorial Pacific upwelling region, and find the model to be capable of reproducing many measured optical properties and key biogeochemical processes in this region. Our model results suggest that non-algal particles largely contribute to the total scattering or attenuation (>50% at 660 nm) but have a much smaller contribution to particulate absorption (<20% at 440 nm), while picoplankton dominate the total phytoplankton absorption (>95% at 440 nm). These results are consistent with the field observations. In order to achieve such good agreement between data and model results, however, key model parameters, for which no field data are available, have to be constrained. Sensitivity analysis of the model results to optical parameters reveals a significant role played by colored dissolved organic matter through its influence on the quantity and quality of the ambient light. Coupling explicit optics to an ecosystem model provides advantages in generating: (1) a more accurate subsurface light-field, which is important for light sensitive biogeochemical processes such as photosynthesis and photo-oxidation, (2) additional constraints on model parameters that help to reduce uncertainties in ecosystem model
Hobi, Martina L.; Ginzler, Christian
2012-01-01
Digital surface models (DSMs) are widely used in forest science to model the forest canopy. Stereo pairs of very high resolution satellite and digital aerial images are relatively new and their absolute accuracy for DSM generation is largely unknown. For an assessment of these input data two DSMs based on a WorldView-2 stereo pair and a ADS80 DSM were generated with photogrammetric instruments. Rational polynomial coefficients (RPCs) are defining the orientation of the WorldView-2 satellite images, which can be enhanced with ground control points (GCPs). Thus two WorldView-2 DSMs were distinguished: a WorldView-2 RPCs-only DSM and a WorldView-2 GCP-enhanced RPCs DSM. The accuracy of the three DSMs was estimated with GPS measurements, manual stereo-measurements, and airborne laser scanning data (ALS). With GCP-enhanced RPCs the WorldView-2 image orientation could be optimised to a root mean square error (RMSE) of 0.56 m in planimetry and 0.32 m in height. This improvement in orientation allowed for a vertical median error of −0.24 m for the WorldView-2 GCP-enhanced RPCs DSM in flat terrain. Overall, the DSM based on ADS80 images showed the highest accuracy of the three models with a median error of 0.08 m over bare ground. As the accuracy of a DSM varies with land cover three classes were distinguished: herb and grass, forests, and artificial areas. The study suggested the ADS80 DSM to best model actual surface height in all three land cover classes, with median errors <1.1 m. The WorldView-2 GCP-enhanced RPCs model achieved good accuracy, too, with median errors of −0.43 m for the herb and grass vegetation and −0.26 m for artificial areas. Forested areas emerged as the most difficult land cover type for height modelling; still, with median errors of −1.85 m for the WorldView-2 GCP-enhanced RPCs model and −1.12 m for the ADS80 model, the input data sets evaluated here are quite promising for forest canopy modelling. PMID:22778645
Homogenization limit for a multiband effective mass model in heterostructures
Morandi, O.
2014-06-15
We study the homogenization limit of a multiband model that describes the quantum mechanical motion of an electron in a quasi-periodic crystal. In this approach, the distance among the atoms that constitute the material (lattice parameter) is considered a small quantity. Our model include the description of materials with variable chemical composition, intergrowth compounds, and heterostructures. We derive the effective multiband evolution system in the framework of the kp approach. We study the well posedness of the mathematical problem. We compare the effective mass model with the standard kp models for uniform and non-uniforms crystals. We show that in the limit of vanishing lattice parameter, the particle density obtained by the effective mass model, converges to the exact probability density of the particle.
Molar mass distribution and solubility modeling of asphaltenes
Yarranton, H.W.; Masliyah, J.H.
1996-12-01
Attempts to model asphaltene solubility with Scatchard-Hildebrand theory were hampered by uncertainty in molar volume and solubility parameter distribution within the asphaltenes. By considering asphaltenes as a series of polyaromatic hydrocarbons with randomly distributed associated functional groups, molar volume and solubility parameter distributions are calculated from experimental measurements of molar mass and density. The molar mass distribution of Athabasca asphaltenes is determined from interfacial tension and vapor pressure osmometry measurements together with plasma desorption mass spectrometry determinations from the literature. Asphaltene densities are calculated indirectly from mixtures of known concentration of asphaltene in toluene. Asphaltene density, molar volume, and solubility parameter are correlated with molar mass. Solid-liquid equilibrium calculations based on solubility theory and the asphaltene property correlations successfully predict experimental data for both the precipitation point and the amount of precipitated asphaltenes in toluene-hexane solvent mixtures.
Lumped mass modelling for the dynamic analysis of aircraft structures
NASA Technical Reports Server (NTRS)
Abu-Saba, Elias G.; Shen, Ji Yao; Mcginley, William M.; Montgomery, Raymond C.
1992-01-01
Aircraft structures may be modelled by lumping the masses at particular strategic points and the flexibility or stiffness of the structure is obtained with reference to these points. Equivalent moments of inertia for the section at these positions are determined. The lumped masses are calculated based on the assumption that each point will represent the mass spread on one half of the space on each side. Then these parameters are used in the differential equation of motion and the eigen characteristics are determined. A comparison is made with results obtained by other established methods. The lumped mass approach in the dynamic analysis of complicated structures provides an easier means of predicting the dynamic characteristics of these structures. It involves less computer time and avoids computational errors that are inherent in the numerical solution of complicated systems.
Quigg, Chris
2007-12-05
In the classical physics we inherited from Isaac Newton, mass does not arise, it simply is. The mass of a classical object is the sum of the masses of its parts. Albert Einstein showed that the mass of a body is a measure of its energy content, inviting us to consider the origins of mass. The protons we accelerate at Fermilab are prime examples of Einsteinian matter: nearly all of their mass arises from stored energy. Missing mass led to the discovery of the noble gases, and a new form of missing mass leads us to the notion of dark matter. Starting with a brief guided tour of the meanings of mass, the colloquium will explore the multiple origins of mass. We will see how far we have come toward understanding mass, and survey the issues that guide our research today.
Fermion masses in the economical 3-3-1 model
Dong, P. V.; Huong, Tr. T.; Huong, D. T.; Long, H. N.
2006-09-01
We show that, in frameworks of the economical 3-3-1 model, all fermions get masses. At the tree level, one up-quark and two down-quarks are massless, but the one-loop corrections give all quarks the consistent masses. This conclusion is in contradiction to the previous analysis in which the third scalar triplet has been introduced. This result is based on the key properties of the model: First, there are three quite different scales of vacuum expectation values: {omega}{approx}O(1) TeV, v{approx_equal}246 GeV, and u{approx}O(1) GeV. Second, there exist two types of Yukawa couplings with different strengths: the lepton-number conserving couplings h's and the lepton-number violating ones s's satisfying the condition in which the second are much smaller than the first ones: s<
Detailed OFDM Modeling in Network Simulation of Mobile Ad Hoc Networks
2003-01-01
Ptolemy II as the design environment, some of the widely used models of computation for control system design — continuous time...closer to reality. The Ptolemy approach is similar to the approach used in this thesis. Our method of integrating heterogeneous models to...errors by mapping it to a BER value. Notice that, the simulated receiver SINR from the model is used instead of the model BER because of the
NASA Astrophysics Data System (ADS)
Mark, Bryan G.; Seltzer, Geoffrey O.
2005-11-01
We use a combination of aerial photogrammetry, satellite imagery, and differential GPS mapping to quantify the volume of ice lost between AD 1962 and 1999 from three glaciers on Nevado Queshque in the Cordillera Blanca, Perú (˜10°S). The largest averaged surface lowering (thinning) occurred in the southwest aspect (22 m) and the least in the eastern aspect (5 m). A heuristic sensitivity analysis indicates that 9.3 W m -2 was required to melt the total observed ice loss and this can be explained by sensible heat transfer related to a temperature rise of 1 °C, combined with a latent heat decrease related to a 0.14 g kg -1 increase in specific humidity. A first-difference analysis of temperature records from 29 stations in the Cordillera Blanca shows an average rising trend of 0.26 °C per decade over the 37 year interval, more than adequate to supply the hypothesized sensible heat transfer. A simple transmittivity model within a digital elevation model indicates solar radiation related to altered cloudiness was not a predominant climatic forcing. The distribution of glacier area with altitude calculated with the digital terrain model explains the observed asymmetrical ice melt.
NASA Astrophysics Data System (ADS)
Nicolaou, Georgios; Yamauchi, Masatoshi; Wieser, Martin; Barabash, Stas; Fedorov, Andrei
2016-04-01
Mass separation and particularly distinction between atomic ions and molecular ions are essential in understanding a wide range of plasma environments, with each consisted of different species with various properties. In this study we present the optimization results of light-weight (about 2 kg) magnetic mass analyzers with high g-factor for Rosetta (Ion Composition Analyser: ICA) and for Mars Express and Venus Express (Ion Mass Analyser: IMA). For the instrument's optimization we use SIMION, a 3D ion tracing software in which we can trace particle beams of several energies and directions, passing through the instrument's units. We first reproduced ICA and IMA results, which turned out to be different from simple models for low energy (< 100 eV). We then change the mechanical structure of several units of the instrument and we quantify the new mass resolution achieved with each change. Our goal is to find the optimal instrument's structure, which will allow us to achieve a proper mass resolution to distinguish atomic nitrogen from atomic oxygen for the purposes of a future magnetospheric mission.
Optimal Filtering in Mass Transport Modeling From Satellite Gravimetry Data
NASA Astrophysics Data System (ADS)
Ditmar, P.; Hashemi Farahani, H.; Klees, R.
2011-12-01
Monitoring natural mass transport in the Earth's system, which has marked a new era in Earth observation, is largely based on the data collected by the GRACE satellite mission. Unfortunately, this mission is not free from certain limitations, two of which are especially critical. Firstly, its sensitivity is strongly anisotropic: it senses the north-south component of the mass re-distribution gradient much better than the east-west component. Secondly, it suffers from a trade-off between temporal and spatial resolution: a high (e.g., daily) temporal resolution is only possible if the spatial resolution is sacrificed. To make things even worse, the GRACE satellites enter occasionally a phase when their orbit is characterized by a short repeat period, which makes it impossible to reach a high spatial resolution at all. A way to mitigate limitations of GRACE measurements is to design optimal data processing procedures, so that all available information is fully exploited when modeling mass transport. This implies, in particular, that an unconstrained model directly derived from satellite gravimetry data needs to be optimally filtered. In principle, this can be realized with a Wiener filter, which is built on the basis of covariance matrices of noise and signal. In practice, however, a compilation of both matrices (and, therefore, of the filter itself) is not a trivial task. To build the covariance matrix of noise in a mass transport model, it is necessary to start from a realistic model of noise in the level-1B data. Furthermore, a routine satellite gravimetry data processing includes, in particular, the subtraction of nuisance signals (for instance, associated with atmosphere and ocean), for which appropriate background models are used. Such models are not error-free, which has to be taken into account when the noise covariance matrix is constructed. In addition, both signal and noise covariance matrices depend on the type of mass transport processes under
Keswani, Sundeep G.; Balaji, Swathi; Katz, Anna B.; King, Alice; Omar, Khaled; Habli, Mounira; Klanke, Charles
2015-01-01
Abstract Intrauterine growth restriction (IUGR) due to placental insufficiency is a leading cause of perinatal complications for which there is no effective prenatal therapy. We have previously demonstrated that intraplacental injection of adenovirus-mediated insulin-like growth factor-1 (Ad-IGF-1) corrects fetal weight in a murine IUGR model induced by mesenteric uterine artery branch ligation. This study investigated the effect of intraplacental Ad-IGF-1 gene therapy in a rabbit model of naturally occurring IUGR (runt) due to placental insufficiency, which is similar to the human IUGR condition with onset in the early third trimester, brain sparing, and a reduction in liver weight. Laparotomy was performed on New Zealand White rabbits on day 21 of 30 days of gestation and litters were divided into five groups: Control (first position)+phosphate-buffered saline (PBS), control+Ad-IGF-1, runt (third position)+PBS, runt+Ad-IGF-1, and runt+Ad-LacZ. The effect of IGF-1 gene therapy on fetal, placental, liver, heart, lung, and musculoskeletal weights of the growth-restricted pups was examined. Protein expression after gene transfer was seen along the maternal–fetal placenta interface (n=12) 48 hr after gene therapy. There was minimal gene transfer detected in the pups or maternal organs. At term, compared with the normally grown first-position control, the runted third-position pups demonstrated significantly lower fetal, placental, liver, lung, and musculoskeletal weights. The fetal, liver, and musculoskeletal weights were restored to normal by intraplacental Ad-IGF-1 gene therapy (p<0.01), with no change in the placental weight. Intraplacental gene therapy is a novel strategy for the treatment of IUGR caused by placental insufficiency that takes advantage of an organ that will be discarded at birth. Development of nonviral IGF-1 gene delivery using placenta-specific promoters can potentially minimize toxicity to the mother and fetus and facilitate clinical
ApoE-directed therapeutics rapidly clear β-amyloid and reverse deficits in AD mouse models.
Cramer, Paige E; Cirrito, John R; Wesson, Daniel W; Lee, C Y Daniel; Karlo, J Colleen; Zinn, Adriana E; Casali, Brad T; Restivo, Jessica L; Goebel, Whitney D; James, Michael J; Brunden, Kurt R; Wilson, Donald A; Landreth, Gary E
2012-03-23
Alzheimer's disease (AD) is associated with impaired clearance of β-amyloid (Aβ) from the brain, a process normally facilitated by apolipoprotein E (apoE). ApoE expression is transcriptionally induced through the action of the nuclear receptors peroxisome proliferator-activated receptor gamma and liver X receptors in coordination with retinoid X receptors (RXRs). Oral administration of the RXR agonist bexarotene to a mouse model of AD resulted in enhanced clearance of soluble Aβ within hours in an apoE-dependent manner. Aβ plaque area was reduced more than 50% within just 72 hours. Furthermore, bexarotene stimulated the rapid reversal of cognitive, social, and olfactory deficits and improved neural circuit function. Thus, RXR activation stimulates physiological Aβ clearance mechanisms, resulting in the rapid reversal of a broad range of Aβ-induced deficits.
Physical Scalar Mass Particles in the 331 Model
Ravinez, O.; Diaz, H.; Romero, D.
2007-10-26
We get to diagonalize the mass matrix considering all terms in the scalar lagrangian sector, given in the SU(3)xSU(3)xU(1) model cited below. This will let us in the future realize the phenomenological consequences.
Dissociation and Mass Transfer Coefficients for Ammonia Volatilization Models
Technology Transfer Automated Retrieval System (TEKTRAN)
Process-based models are being used to predict ammonia emissions from manure sources, but their accuracy has not been fully evaluated for cattle manure. Laboratory trials were conducted to measure the dissociation and mass transfer coefficients for ammonia volatilization from media of buffered ammon...
False Vacuum in the Supersymmetric Mass Varying Neutrino Model
Tanimoto, Morimitsu
2009-04-17
We discuss the vacuum structure of the scalar potential in a supersymmetric Mass Varying Neutrinos model. The observed dark energy density is identified with the false vacuum energy and the dark energy scale of order (10{sup -3} eV){sup 4} is understood by gravitationally suppressed supersymmetry breaking scale, F(TeV{sup 2})/M{sub pl}.
Political Socialization and Mass Media Use: A Reverse Causality Model.
ERIC Educational Resources Information Center
Tan, Alexis S.
A reverse causality model treating mass media use for public affairs information as a result rather than as a cause of political behavior was tested utilizing surveys of 190 Mexican-American, 176 black, and 225 white adults. The criterion variable used in each sample was frequency of television and newspaper use for public affairs information. The…
OVERVIEW AND STATUS OF LAKE MICHIGAN MASS BALANCE MODELLING PROJECT
With most of the data available from the Lake Michigan Mass Balance Project field program, the modeling efforts have begun in earnest. The tributary and atmospheric load estimates are or will be completed soon, so realistic simulations for calibration are beginning. A Quality Ass...
Disambiguating seesaw models using invariant mass variables at hadron colliders
NASA Astrophysics Data System (ADS)
Dev, P. S. Bhupal; Kim, Doojin; Mohapatra, Rabindra N.
2016-01-01
We propose ways to distinguish between different mechanisms behind the collider signals of TeV-scale seesaw models for neutrino masses using kinematic endpoints of invariant mass variables. We particularly focus on two classes of such models widely discussed in literature: (i) Standard Model extended by the addition of singlet neutrinos and (ii) Left-Right Symmetric Models. Relevant scenarios involving the same "smoking-gun" collider signature of dilepton plus dijet with no missing transverse energy differ from one another by their event topology, resulting in distinctive relationships among the kinematic endpoints to be used for discerning them at hadron colliders. These kinematic endpoints are readily translated to the mass parameters of the on-shell particles through simple analytic expressions which can be used for measuring the masses of the new particles. A Monte Carlo simulation with detector effects is conducted to test the viability of the proposed strategy in a realistic environment. Finally, we discuss the future prospects of testing these scenarios at the √{s}=14 and 100 TeV hadron colliders.
CHEMICAL MASS BALANCE MODEL: EPA-CMB8.2
The Chemical Mass Balance (CMB) method has been a popular approach for receptor modeling of ambient air pollutants for over two decades. For the past few years the U.S. Environmental Protection Agency's Office of Research and Development (ORD) and Office of Air Quality Plannin...
Disambiguating seesaw models using invariant mass variables at hadron colliders
Dev, P. S. Bhupal; Kim, Doojin; Mohapatra, Rabindra N.
2016-01-19
Here, we propose ways to distinguish between different mechanisms behind the collider signals of TeV-scale seesaw models for neutrino masses using kinematic endpoints of invariant mass variables. We particularly focus on two classes of such models widely discussed in literature: (i) Standard Model extended by the addition of singlet neutrinos and (ii) Left-Right Symmetric Models. Relevant scenarios involving the same "smoking-gun" collider signature of dilepton plus dijet with no missing transverse energy differ from one another by their event topology, resulting in distinctive relationships among the kinematic endpoints to be used for discerning them at hadron colliders. Furthermore, these kinematic endpoints are readily translated to the mass parameters of the on-shell particles through simple analytic expressions which can be used for measuring the masses of the new particles. We also conducted a Monte Carlo simulation with detector effects in order to test the viability of the proposed strategy in a realistic environment. Finally, we discuss the future prospects of testing these scenarios at themore » $$\\sqrt{s}$$ = 14 and 100TeV hadron colliders.« less
Disambiguating seesaw models using invariant mass variables at hadron colliders
Dev, P. S. Bhupal; Kim, Doojin; Mohapatra, Rabindra N.
2016-01-19
Here, we propose ways to distinguish between different mechanisms behind the collider signals of TeV-scale seesaw models for neutrino masses using kinematic endpoints of invariant mass variables. We particularly focus on two classes of such models widely discussed in literature: (i) Standard Model extended by the addition of singlet neutrinos and (ii) Left-Right Symmetric Models. Relevant scenarios involving the same "smoking-gun" collider signature of dilepton plus dijet with no missing transverse energy differ from one another by their event topology, resulting in distinctive relationships among the kinematic endpoints to be used for discerning them at hadron colliders. Furthermore, these kinematic endpoints are readily translated to the mass parameters of the on-shell particles through simple analytic expressions which can be used for measuring the masses of the new particles. We also conducted a Monte Carlo simulation with detector effects in order to test the viability of the proposed strategy in a realistic environment. Finally, we discuss the future prospects of testing these scenarios at the $\\sqrt{s}$ = 14 and 100TeV hadron colliders.
False vacuum in the supersymmetric mass varying neutrinos model
Takahashi, Ryo; Tanimoto, Morimitsu
2008-02-15
We present detailed analyses of the vacuum structure of the scalar potential in a supersymmetric mass varying neutrinos model. The observed dark energy density is identified with false vacuum energy and the dark energy scale of order (10{sup -3} eV){sup 4} is understood by the gravitationally suppressed supersymmetry breaking scale, F(TeV){sup 2}/M{sub Pl}, in the model. The vacuum expectation values of sneutrinos should be tiny in order that the model works. Some decay processes of superparticles into an acceleron and sterile neutrino are also discussed in the model.
The fermion mass hierarchy in models with warped extra dimensions and a bulk Higgs
NASA Astrophysics Data System (ADS)
Archer, Paul R.
2012-09-01
The phenomenological implications of allowing the Higgs to propagate in both AdS5 and a class of asymptotically AdS spaces are considered. Without tuning, the vacuum expectation value (VEV) of the Higgs is peaked towards the IR tip of the space and hence such a scenario still offers a potential resolution to the gauge-hierarchy problem. When the exponent of the Higgs VEV is approximately two and one assumes order one Yukawa couplings, then the fermion Dirac mass term is found to range from ~ 10-5 eV to ~ 200 GeV in approximate agreement with the observed fermion masses. However, this result is sensitive to the exponent of the Higgs VEV, which is a free parameter. This paper offers a number of phenomenological and theoretical motivations for considering an exponent of two to be the optimal value. In particular, the exponent is bounded from below by the Breitenlohner-Freedman bound and the requirement that the dual theory resolves the gauge hierarchy problem. While, in the model considered, if the exponent is too large, electroweak symmetry may not be broken. In addition, the holographic method is used to demonstrate, in generality, that the flatter the Higgs VEV, the smaller the contribution to the electroweak T parameter. In addition, the constraints from a large class of gauge mediated and scalar mediated flavour changing neutral currents, will be at minimal values for flatter Higgs VEVs. Some initial steps are taken to investigate the physical scalar degrees of freedom that arise from a mixing between the W 5 /Z 5 components and the Higgs components.
A mass transfer model for VOC emission from silage
NASA Astrophysics Data System (ADS)
Hafner, Sasha D.; Montes, Felipe; Rotz, C. Alan
2012-07-01
Silage has been shown to be an important source of emissions of volatile organic compounds (VOCs), which contribute to the formation of ground-level ozone. Measurements have shown that environmental conditions and silage properties strongly influence emission rates, making it difficult to assess the contribution of silage in VOC emission inventories. In this work, we present an analytical convection-diffusion-dispersion model for predicting emission of VOCs from silage. It was necessary to incorporate empirical relationships from wind tunnel trials for the response of mass transfer parameters to surface air velocity and silage porosity. The resulting model was able to accurately predict the effect of temperature on ethanol emission in wind tunnel trials, but it over-predicted alcohol and aldehyde emission measured using a mass balance approach from corn silage samples outdoors and within barns. Mass balance results confirmed that emission is related to gas-phase porosity, but the response to air speed was not clear, which was contrary to wind tunnel results. Mass balance results indicate that alcohol emission from loose silage on farms may approach 50% of the initial mass over six hours, while relative losses of acetaldehyde will be greater.
An Agent-based Model Simulation of Multiple Collaborating Mobile Ad Hoc Networks (MANET)
2011-06-01
RESULTS: Agent Learning Profiles Discounted Positive Reinforcement Learning Learning and Forgetting Forgetting is triggered by task conditions that...disable rational and deliberate mental models –forcing the agent to ignore (or forget) routine processes. Positive reinforcement is earned by an...deliberate behavior of agents as rational entities (model-based functions). 6.Experiment with positive reinforcement learning (with incremental gain over
NASA Astrophysics Data System (ADS)
Yuan, Xing
2016-06-01
This is the second paper of a two-part series on introducing an experimental seasonal hydrological forecasting system over the Yellow River basin in northern China. While the natural hydrological predictability in terms of initial hydrological conditions (ICs) is investigated in a companion paper, the added value from eight North American Multimodel Ensemble (NMME) climate forecast models with a grand ensemble of 99 members is assessed in this paper, with an implicit consideration of human-induced uncertainty in the hydrological models through a post-processing procedure. The forecast skill in terms of anomaly correlation (AC) for 2 m air temperature and precipitation does not necessarily decrease over leads but is dependent on the target month due to a strong seasonality for the climate over the Yellow River basin. As there is more diversity in the model performance for the temperature forecasts than the precipitation forecasts, the grand NMME ensemble mean forecast has consistently higher skill than the best single model up to 6 months for the temperature but up to 2 months for the precipitation. The NMME climate predictions are downscaled to drive the variable infiltration capacity (VIC) land surface hydrological model and a global routing model regionalized over the Yellow River basin to produce forecasts of soil moisture, runoff and streamflow. And the NMME/VIC forecasts are compared with the Ensemble Streamflow Prediction method (ESP/VIC) through 6-month hindcast experiments for each calendar month during 1982-2010. As verified by the VIC offline simulations, the NMME/VIC is comparable to the ESP/VIC for the soil moisture forecasts, and the former has higher skill than the latter only for the forecasts at long leads and for those initialized in the rainy season. The forecast skill for runoff is lower for both forecast approaches, but the added value from NMME/VIC is more obvious, with an increase of the average AC by 0.08-0.2. To compare with the observed
Improved Nuclear Reactor and Shield Mass Model for Space Applications
NASA Technical Reports Server (NTRS)
Robb, Kevin
2004-01-01
New technologies are being developed to explore the distant reaches of the solar system. Beyond Mars, solar energy is inadequate to power advanced scientific instruments. One technology that can meet the energy requirements is the space nuclear reactor. The nuclear reactor is used as a heat source for which a heat-to-electricity conversion system is needed. Examples of such conversion systems are the Brayton, Rankine, and Stirling cycles. Since launch cost is proportional to the amount of mass to lift, mass is always a concern in designing spacecraft. Estimations of system masses are an important part in determining the feasibility of a design. I worked under Michael Barrett in the Thermal Energy Conversion Branch of the Power & Electric Propulsion Division. An in-house Closed Cycle Engine Program (CCEP) is used for the design and performance analysis of closed-Brayton-cycle energy conversion systems for space applications. This program also calculates the system mass including the heat source. CCEP uses the subroutine RSMASS, which has been updated to RSMASS-D, to estimate the mass of the reactor. RSMASS was developed in 1986 at Sandia National Laboratories to quickly estimate the mass of multi-megawatt nuclear reactors for space applications. In response to an emphasis for lower power reactors, RSMASS-D was developed in 1997 and is based off of the SP-100 liquid metal cooled reactor. The subroutine calculates the mass of reactor components such as the safety systems, instrumentation and control, radiation shield, structure, reflector, and core. The major improvements in RSMASS-D are that it uses higher fidelity calculations, is easier to use, and automatically optimizes the systems mass. RSMASS-D is accurate within 15% of actual data while RSMASS is only accurate within 50%. My goal this summer was to learn FORTRAN 77 programming language and update the CCEP program with the RSMASS-D model.
Adding Abstraction and Reuse to a Network Modelling Tool Using the Reuseware Composition Framework
NASA Astrophysics Data System (ADS)
Johannes, Jendrik; Fernández, Miguel A.
Domain-specific modelling (DSM) environments enable experts in a certain domain to actively participate in model-driven development. Developing DSM environments need to be cost-efficient, since they are only used by a limited group of domain experts. Different model-driven technologies promise to allow this cost-efficient development. [1] presented experiences in developing a DSM environment for telecommunication network modelling. There, challenges were identified that need to be addressed by other new modelling technologies. In this paper, we now present the results of addressing one of theses challenges - abstraction and reuse support - with the Reuseware Composition Framework. We show how we identified the abstraction and reuse features required in the telecommunication DSM environment in a case study and extended the existing environment with these features using Reuseware. We discuss the advantages of using this technology and propose a process for further improving the abstraction and reuse capabilities of the DSM environment in the future.
A dynamic CSTT model for the effects of added nutrients in Loch Creran, a shallow fjord
NASA Astrophysics Data System (ADS)
Laurent, Céline; Tett, Paul; Fernandes, Teresa; Gilpin, Linda; Jones, Ken
2006-07-01
Despite a tendency for the complexity of physical-biological models to increase, simple coupled models remain useful for some applications and can provide insights into crucial links between physical and biological processes. This argument is illustrated with an account of a simple 3-box model intended to help assess the capacity of fjords to assimilate nutrients from fish farms. The model, a dynamic version of the UK "Comprehensive Studies Task Team" (CSTT) steady-state model for eutrophication, was applied to Loch Creran (Scottish Western Highlands) and was implemented using Stella 8 and tested using historical data from 1975 (before the installation of a salmon farm) and field data collected in 2003, during the period of operation of the farm. The model's biological state variables are chlorophyll, dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP), and it includes a simple run-off model to convert rainfall into river discharge. The physical processes involved in exchange between the loch and the adjacent waters of the Firth of Lorne were parameterised as a constant daily exchange rate. Between 1975 and 2003, local inputs of nutrient increased but, despite this, there was little apparent increase in nutrient concentrations in the loch, and observed chlorophyll concentrations decreased substantially. Model simulations of chlorophyll and DIN agreed well with observations in 1975, as did DIN simulations in 2003. However, simulated chlorophyll was overestimated in 2003. Some of the agreement between observations and simulations come from the use of observed boundary conditions to force the model. However, even when boundary conditions are subtracted from simulations and observations, the simulations in most cases retain a significant correlation with observations, demonstrating that the model's 'interior' processes do add to its ability to replicate conditions in the loch.
Shell-model calculations of nuclei around mass 130
NASA Astrophysics Data System (ADS)
Teruya, E.; Yoshinaga, N.; Higashiyama, K.; Odahara, A.
2015-09-01
Shell-model calculations are performed for even-even, odd-mass, and doubly-odd nuclei of Sn, Sb, Te, I, Xe, Cs, and Ba isotopes around mass 130 using the single-particle space made up of valence nucleons occupying the 0 g7 /2 ,1 d5 /2 ,2 s1 /2 ,0 h11 /2 , and 1 d3 /2 orbitals. The calculated energies and electromagnetic transitions are compared with the experimental data. In addition, several typical isomers in this region are investigated.
Are the numbers adding up? Exploiting discrepancies among complementary population models
Stenglein, Jennifer L; Zhu, Jun; Clayton, Murray K; Van Deelen, Timothy R
2015-01-01
Large carnivores are difficult to monitor because they tend to be sparsely distributed, sensitive to human activity, and associated with complex life histories. Consequently, understanding population trend and viability requires conservationists to cope with uncertainty and bias in population data. Joint analysis of combined data sets using multiple models (i.e., integrated population model) can improve inference about mechanisms (e.g., habitat heterogeneity and food distribution) affecting population dynamics. However, unobserved or unobservable processes can also introduce bias and can be difficult to quantify. We developed a Bayesian hierarchical modeling approach for inference on an integrated population model that reconciles annual population counts with recruitment and survival data (i.e., demographic processes). Our modeling framework is flexible and enables a realistic form of population dynamics by fitting separate density-dependent responses for each demographic process. Discrepancies estimated from shared parameters among different model components represent unobserved additions (i.e., recruitment or immigration) or removals (i.e., death or emigration) when annual population counts are reliable. In a case study of gray wolves in Wisconsin (1980–2011), concordant with policy changes, we estimated that a discrepancy of 0% (1980–1995), −2% (1996–2002), and 4% (2003–2011) in the annual mortality rate was needed to explain annual growth rate. Additional mortality in 2003–2011 may reflect density-dependent mechanisms, changes in illegal killing with shifts in wolf management, and nonindependent censoring in survival data. Integrated population models provide insights into unobserved or unobservable processes by quantifying discrepancies among data sets. Our modeling approach is generalizable to many population analysis needs and allows for identifying dynamic differences due to external drivers, such as management or policy changes. PMID:25691964
Deconfinement and chiral transition in AdS/QCD wall models supplemented with a magnetic field
NASA Astrophysics Data System (ADS)
Dudal, David; Granado, Diego R.; Mertens, Thomas G.
2017-03-01
We discuss the phenomenon of (inverse) magnetic catalysis for both the deconfinement and chiral transition. We discriminate between the hard and soft wall model, which we suitably generalize to include a magnetic field. Our findings show a critical deconfinement temperature going down, in contrast with the chiral restoration temperature growing with increasing magnetic field. This is at odds with contemporary lattice data, so the quest for a holographic QCD model capable of capturing inverse magnetic catalysis in the chiral sector remains open.
Are the numbers adding up? Exploiting discrepancies among complementary population models.
Stenglein, Jennifer L; Zhu, Jun; Clayton, Murray K; Van Deelen, Timothy R
2015-01-01
Large carnivores are difficult to monitor because they tend to be sparsely distributed, sensitive to human activity, and associated with complex life histories. Consequently, understanding population trend and viability requires conservationists to cope with uncertainty and bias in population data. Joint analysis of combined data sets using multiple models (i.e., integrated population model) can improve inference about mechanisms (e.g., habitat heterogeneity and food distribution) affecting population dynamics. However, unobserved or unobservable processes can also introduce bias and can be difficult to quantify. We developed a Bayesian hierarchical modeling approach for inference on an integrated population model that reconciles annual population counts with recruitment and survival data (i.e., demographic processes). Our modeling framework is flexible and enables a realistic form of population dynamics by fitting separate density-dependent responses for each demographic process. Discrepancies estimated from shared parameters among different model components represent unobserved additions (i.e., recruitment or immigration) or removals (i.e., death or emigration) when annual population counts are reliable. In a case study of gray wolves in Wisconsin (1980-2011), concordant with policy changes, we estimated that a discrepancy of 0% (1980-1995), -2% (1996-2002), and 4% (2003-2011) in the annual mortality rate was needed to explain annual growth rate. Additional mortality in 2003-2011 may reflect density-dependent mechanisms, changes in illegal killing with shifts in wolf management, and nonindependent censoring in survival data. Integrated population models provide insights into unobserved or unobservable processes by quantifying discrepancies among data sets. Our modeling approach is generalizable to many population analysis needs and allows for identifying dynamic differences due to external drivers, such as management or policy changes.
Enhancement and modeling of microparticle-added Rhizopus oryzae lactic acid production.
Coban, Hasan Bugra; Demirci, Ali
2016-02-01
Lactic acid has a wide industrial application area and can be produced by fungal strains. However, excessive bulk growth form of fungi during the fermentations is a major problem, which limits the fermentation performance. Microparticles are excellent tools to prevent bulk fungal growth and provide homogenized fermentation broth to increase uniformity and the prediction performance of the models. Therefore, in this study, addition of aluminum oxide and talcum microparticles into fermentations was evaluated to enhance the production of lactic acid by Rhizopus oryzae. The results showed that the bulk fungal growth was prevented and the lactic acid concentration increased from 6.02 to 13.88 and 24.01 g/L, when 15 g/L of aluminum oxide or 10 g/L of talcum was used, respectively, in the shake-flask fermentations. Additionally, substrate concentration, pH, and agitation were optimized in the bioreactors using response surface methodology, and optimum values were determined as 126 g/L of glucose, 6.22 pH, and 387 rpm, respectively. Under these conditions, lactic acid production further increased to 75.1 ± 1.5 g/L with 10 g/L of talcum addition. Also, lactic acid production and glucose consumption in the batch fermentation were successfully modeled with modified Gompertz model and modified logistic model. RMSE and MAE values for lactic acid production were calculated as 2.279 and 1.498 for the modified Gompertz model; 3.6 and 4.056 for the modified logistic model. Additionally, modified logistic model predicted glucose consumption with -2.088 MAE and 2.868 RMSE, whereas these values were calculated as 2.035 and 3.946 for the modified Gompertz model.
ERIC Educational Resources Information Center
Orsini, Larry L.; Hudack, Lawrence R.; Zekan, Donald L.
1999-01-01
The value-added statement (VAS), relatively unknown in the United States, is used in financial reports by many European companies. Saint Bonaventure University (New York) has adapted a VAS to make it appropriate for not-for-profit universities by identifying stakeholder groups (students, faculty, administrators/support personnel, creditors, the…
Use of Numerical Models as Data Proxies for Approximate Ad-Hoc Query Processing
Kamimura, R; Abdulla, G; Baldwin, C; Critchlow, T; Lee, B; Lozares, I; Musick, R; Tang, N
2003-05-19
As datasets grow beyond the gigabyte scale, there is an increasing demand to develop techniques for dealing/interacting with them. To this end, the DataFoundry team at the Lawrence Livermore National Laboratory has developed a software prototype called Approximate Adhoc Query Engine for Simulation Data (AQSim). The goal of AQSim is to provide a framework that allows scientists to interactively perform adhoc queries over terabyte scale datasets using numerical models as proxies for the original data. The advantages of this system are several. The first is that by storing only the model parameters, each dataset occupies a smaller footprint compared to the original, increasing the shelf-life of such datasets before they are sent to archival storage. Second, the models are geared towards approximate querying as they are built at different resolutions, allowing the user to make the tradeoff between model accuracy and query response time. This allows the user greater opportunities for exploratory data analysis. Lastly, several different models are allowed, each focusing on a different characteristic of the data thereby enhancing the interpretability of the data compared to the original. The focus of this paper is on the modeling aspects of the AQSim framework.
Models of neutrino mass, mixing and CP violation
NASA Astrophysics Data System (ADS)
King, Stephen F.
2015-12-01
In this topical review we argue that neutrino mass and mixing data motivates extending the Standard Model (SM) to include a non-Abelian discrete flavour symmetry in order to accurately predict the large leptonic mixing angles and {C}{P} violation. We begin with an overview of the SM puzzles, followed by a description of some classic lepton mixing patterns. Lepton mixing may be regarded as a deviation from tri-bimaximal mixing, with charged lepton corrections leading to solar mixing sum rules, or tri-maximal lepton mixing leading to atmospheric mixing rules. We survey neutrino mass models, using a roadmap based on the open questions in neutrino physics. We then focus on the seesaw mechanism with right-handed neutrinos, where sequential dominance (SD) can account for large lepton mixing angles and {C}{P} violation, with precise predictions emerging from constrained SD (CSD). We define the flavour problem and discuss progress towards a theory of favour using GUTs and discrete family symmetry. We classify models as direct, semidirect or indirect, according to the relation between the Klein symmetry of the mass matrices and the discrete family symmetry, in all cases focussing on spontaneous {C}{P} violation. Finally we give two examples of realistic and highly predictive indirect models with CSD, namely an A to Z of flavour with Pati-Salam and a fairly complete A 4 × SU(5) SUSY GUT of flavour, where both models have interesting implications for leptogenesis.
Baxter, Sally L; Allard, Denise E; Crowl, Christopher; Sherwood, Nina Tang
2014-08-01
Autosomal-dominant hereditary spastic paraplegia (AD-HSP) is a crippling neurodegenerative disease for which effective treatment or cure remains unknown. Victims experience progressive mobility loss due to degeneration of the longest axons in the spinal cord. Over half of AD-HSP cases arise from loss-of-function mutations in spastin, which encodes a microtubule-severing AAA ATPase. In Drosophila models of AD-HSP, larvae lacking Spastin exhibit abnormal motor neuron morphology and function, and most die as pupae. Adult survivors display impaired mobility, reminiscent of the human disease. Here, we show that rearing pupae or adults at reduced temperature (18°C), compared with the standard temperature of 24°C, improves the survival and mobility of adult spastin mutants but leaves wild-type flies unaffected. Flies expressing human spastin with pathogenic mutations are similarly rescued. Additionally, larval cooling partially rescues the larval synaptic phenotype. Cooling thus alleviates known spastin phenotypes for each developmental stage at which it is administered and, notably, is effective even in mature adults. We find further that cold treatment rescues larval synaptic defects in flies with mutations in Flower (a protein with no known relation to Spastin) and mobility defects in flies lacking Kat60-L1, another microtubule-severing protein enriched in the CNS. Together, these data support the hypothesis that the beneficial effects of cold extend beyond specific alleviation of Spastin dysfunction, to at least a subset of cellular and behavioral neuronal defects. Mild hypothermia, a common neuroprotective technique in clinical treatment of acute anoxia, might thus hold additional promise as a therapeutic approach for AD-HSP and, potentially, for other neurodegenerative diseases.
A mass transfer model of ammonia volatilisation from anaerobic digestate
Whelan, M.J.; Everitt, T.; Villa, R.
2010-10-15
Anaerobic digestion (AD) is becoming increasingly popular for treating organic waste. The methane produced can be burned to generate electricity and the digestate, which is high in mineral nitrogen, can be used as a fertiliser. In this paper we evaluate potential losses of ammonia via volatilisation from food waste anaerobic digestate using a closed chamber system equipped with a sulphuric acid trap. Ammonia losses represent a pollution source and, over long periods could reduce the agronomic value of the digestate. Observed ammonia losses from the experimental system were linear with time. A simple non-steady-state partitioning model was developed to represent the process. After calibration, the model was able to describe the behaviour of ammonia in the digestate and in the trap very well. The average rate of volatilisation was approximately 5.2 g N m{sup -2} week{sup -1}. The model was used to extrapolate the findings of the laboratory study to a number of AD storage scenarios. The simulations highlight that open storage of digestate could result in significant losses of ammonia to the atmosphere. Losses are predicted to be relatively minor from covered facilities, particularly if depth to surface area ratio is high.
A radiative model of quark masses with binary tetrahedral symmetry
NASA Astrophysics Data System (ADS)
Natale, Alexander
2017-01-01
A radiative model of quark and lepton masses utilizing the binary tetrahedral (T‧) flavor symmetry, or horizontal symmetry, is proposed which produces the first two generation of quark masses through their interactions with vector-like quarks that carry charges under an additional U (1). By softly-breaking the T‧ to a residual Z4 through the vector-like quark masses, a CKM mixing angle close to the Cabibbo angle is produced. In order to generate the cobimaximal neutrino oscillation pattern (θ13 ≠ 0 ,θ23 = π / 4 ,δCP = ± π / 2) and protect the horizontal symmetry from arbitrary corrections in the lepton sector, there are automatically two stabilizing symmetries in the dark sector. Several benchmark cases where the correct relic density is achieved in a multi-component DM scenario, as well as the potential collider signatures of the vector-like quarks are discussed.
Systematics of Coupling Flows in AdS Backgrounds
Goldberger, Walter D.; Rothstein, Ira Z.
2003-03-18
We give an effective field theory derivation, based on the running of Planck brane gauge correlators, of the large logarithms that arise in the predictions for low energy gauge couplings in compactified AdS}_5 backgrounds, including the one-loop effects of bulk scalars, fermions, and gauge bosons. In contrast to the case of charged scalars coupled to Abelian gauge fields that has been considered previously in the literature, the one-loop corrections are not dominated by a single 4D Kaluza-Klein mode. Nevertheless, in the case of gauge field loops, the amplitudes can be reorganized into a leading logarithmic contribution that is identical to the running in 4D non-Abelian gauge theory, and a term which is not logarithmically enhanced and is analogous to a two-loop effect in 4D. In a warped GUT model broken by the Higgs mechanism in the bulk,we show that the matching scale that appears in the large logarithms induced by the non-Abelian gauge fields is m_{XY}^2/k where m_{XY} is the bulk mass of the XY bosons and k is the AdS curvature. This is in contrast to the UV scale in the logarithmic contributions of scalars, which is simply the bulk mass m. Our results are summarized in a set of simple rules that can be applied to compute the leading logarithmic predictions for coupling constant relations within a given warped GUT model. We present results for both bulk Higgs and boundary breaking of the GUT gauge
Investigation of modified AD/RANS models for wind turbine wake predictions in large wind farm
NASA Astrophysics Data System (ADS)
Tian, L. L.; Zhu, W. J.; Shen, W. Z.; Sørensen, J. N.; Zhao, N.
2014-06-01
Average power losses due to multiple wind turbine wakes in the large offshore wind farm is studied in this paper using properly modified k-ω SST turbulence models. The numerical simulations are carried out by the actuator disc methodology implemented in the flow solver EllipSys3D. In these simulations, the influence of different inflow conditions such as wind direction sectors are considered and discussed. Comparisons with measurements in terms of wake speed ratio and the corresponding power outputs show that the modified turbulence models had significant improvements; especially the SST-Csust model reflects the best ability in predicting the wake defect. The investigations of various inflow angles reveal that the agreement between predicted and measured data is improved for the wider sector case than the narrow case because of the wind direction uncertainty.
Model uniform core criteria for mass casualty triage.
2011-06-01
There is a need for model uniform core criteria for mass casualty triage because disasters frequently cross jurisdictional lines and involve responders from multiple agencies who may be using different triage tools. These criteria (Tables 1-4) reflect the available science, but it is acknowledged that there are significant research gaps. When no science was available, decisions were formed by expert consensus derived from the available triage systems. The intent is to ensure that providers at a mass-casualty incident use triage methodologies that incorporate these core principles in an effort to promote interoperability and standardization. At a minimum, each triage system must incorporate the criteria that are listed below. Mass casualty triage systems in use can be modified using these criteria to ensure interoperability. The criteria include general considerations, global sorting, lifesaving interventions, and assignment of triage categories. The criteria apply only to providers who are organizing multiple victims in a discrete geographic location or locations, regardless of the size of the incident. They are classified by whether they were derived through available direct scientific evidence, indirect scientific evidence, expert consensus, and/or are used in multiple existing triage systems. These criteria address only primary triage and do not consider secondary triage. For the purposes of this document the term triage refers to mass-casualty triage and provider refers to any person who assigns primary triage categories to victims of a mass-casualty incident.
ERIC Educational Resources Information Center
Poff, Raymond
Outdoor programs can offset initial investment costs in services and products by developing integrated program areas. The experience of Outdoors Unlimited, a recently created kayaking program at Brigham Young University (Utah), is provided as a model. The purchase of 11 kayaks for rental was followed by the introduction of retail sales, repair…
Edwards, Joel; Othman, Maazuza; Burn, Stewart; Crossin, Enda
2016-10-01
The collection of source separated kerbside municipal FW (SSFW) is being incentivised in Australia, however such a collection is likely to increase the fuel and time a collection truck fleet requires. Therefore, waste managers need to determine whether the incentives outweigh the cost. With literature scarcely describing the magnitude of increase, and local parameters playing a crucial role in accurately modelling kerbside collection; this paper develops a new general mathematical model that predicts the energy and time requirements of a collection regime whilst incorporating the unique variables of different jurisdictions. The model, Municipal solid waste collect (MSW-Collect), is validated and shown to be more accurate at predicting fuel consumption and trucks required than other common collection models. When predicting changes incurred for five different SSFW collection scenarios, results show that SSFW scenarios require an increase in fuel ranging from 1.38% to 57.59%. There is also a need for additional trucks across most SSFW scenarios tested. All SSFW scenarios are ranked and analysed in regards to fuel consumption; sensitivity analysis is conducted to test key assumptions.
NASA Astrophysics Data System (ADS)
Murphy, Maurice; McGovern, Eugene; Pavia, Sara
2013-02-01
Historic Building Information Modelling (HBIM) is a novel prototype library of parametric objects, based on historic architectural data and a system of cross platform programmes for mapping parametric objects onto point cloud and image survey data. The HBIM process begins with remote collection of survey data using a terrestrial laser scanner combined with digital photo modelling. The next stage involves the design and construction of a parametric library of objects, which are based on the manuscripts ranging from Vitruvius to 18th century architectural pattern books. In building parametric objects, the problem of file format and exchange of data has been overcome within the BIM ArchiCAD software platform by using geometric descriptive language (GDL). The plotting of parametric objects onto the laser scan surveys as building components to create or form the entire building is the final stage in the reverse engineering process. The final HBIM product is the creation of full 3D models including detail behind the object's surface concerning its methods of construction and material make-up. The resultant HBIM can automatically create cut sections, details and schedules in addition to the orthographic projections and 3D models (wire frame or textured) for both the analysis and conservation of historic objects, structures and environments.
Historic Building Information Modelling - Adding Intelligence to Laser and Image Based Surveys
NASA Astrophysics Data System (ADS)
Murphy, M.; McGovern, E.; Pavia, S.
2011-09-01
Historic Building Information Modelling (HBIM) is a novel prototype library of parametric objects based on historic data and a system of cross platform programmes for mapping parametric objects onto a point cloud and image survey data. The HBIM process begins with remote collection of survey data using a terrestrial laser scanner combined with digital photo modelling. The next stage involves the design and construction of a parametric library of objects, which are based on the manuscripts ranging from Vitruvius to 18th century architectural pattern books. In building parametric objects, the problem of file format and exchange of data has been overcome within the BIM ArchiCAD software platform by using geometric descriptive language (GDL). The plotting of parametric objects onto the laser scan surveys as building components to create or form the entire building is the final stage in the reverse engin- eering process. The final HBIM product is the creation of full 3D models including detail behind the object's surface concerning its methods of construction and material make-up. The resultant HBIM can automatically create cut sections, details and schedules in addition to the orthographic projections and 3D models (wire frame or textured).
A probabilistic dynamic energy model for ad-hoc wireless sensors network with varying topology
NASA Astrophysics Data System (ADS)
Al-Husseini, Amal
In this dissertation we investigate the behavior of Wireless Sensor Networks (WSNs) from the degree distribution and evolution perspective. In specific, we focus on implementation of a scale-free degree distribution topology for energy efficient WSNs. WSNs is an emerging technology that finds its applications in different areas such as environment monitoring, agricultural crop monitoring, forest fire monitoring, and hazardous chemical monitoring in war zones. This technology allows us to collect data without human presence or intervention. Energy conservation/efficiency is one of the major issues in prolonging the active life WSNs. Recently, many energy aware and fault tolerant topology control algorithms have been presented, but there is dearth of research focused on energy conservation/efficiency of WSNs. Therefore, we study energy efficiency and fault-tolerance in WSNs from the degree distribution and evolution perspective. Self-organization observed in natural and biological systems has been directly linked to their degree distribution. It is widely known that scale-free distribution bestows robustness, fault-tolerance, and access efficiency to system. Fascinated by these properties, we propose two complex network theoretic self-organizing models for adaptive WSNs. In particular, we focus on adopting the Barabasi and Albert scale-free model to fit into the constraints and limitations of WSNs. We developed simulation models to conduct numerical experiments and network analysis. The main objective of studying these models is to find ways to reducing energy usage of each node and balancing the overall network energy disrupted by faulty communication among nodes. The first model constructs the wireless sensor network relative to the degree (connectivity) and remaining energy of every individual node. We observed that it results in a scale-free network structure which has good fault tolerance properties in face of random node failures. The second model considers
Neural masses and fields in dynamic causal modeling
Moran, Rosalyn; Pinotsis, Dimitris A.; Friston, Karl
2013-01-01
Dynamic causal modeling (DCM) provides a framework for the analysis of effective connectivity among neuronal subpopulations that subtend invasive (electrocorticograms and local field potentials) and non-invasive (electroencephalography and magnetoencephalography) electrophysiological responses. This paper reviews the suite of neuronal population models including neural masses, fields and conductance-based models that are used in DCM. These models are expressed in terms of sets of differential equations that allow one to model the synaptic underpinnings of connectivity. We describe early developments using neural mass models, where convolution-based dynamics are used to generate responses in laminar-specific populations of excitatory and inhibitory cells. We show that these models, though resting on only two simple transforms, can recapitulate the characteristics of both evoked and spectral responses observed empirically. Using an identical neuronal architecture, we show that a set of conductance based models—that consider the dynamics of specific ion-channels—present a richer space of responses; owing to non-linear interactions between conductances and membrane potentials. We propose that conductance-based models may be more appropriate when spectra present with multiple resonances. Finally, we outline a third class of models, where each neuronal subpopulation is treated as a field; in other words, as a manifold on the cortical surface. By explicitly accounting for the spatial propagation of cortical activity through partial differential equations (PDEs), we show that the topology of connectivity—through local lateral interactions among cortical layers—may be inferred, even in the absence of spatially resolved data. We also show that these models allow for a detailed analysis of structure–function relationships in the cortex. Our review highlights the relationship among these models and how the hypothesis asked of empirical data suggests an appropriate
Modeling the mass balance of the Wolverine Glacier Alaska USA using the PTAA model
NASA Astrophysics Data System (ADS)
Korn, D.
2010-12-01
Glaciers in Alaska have been increasingly losing mass over the last several decades. This trend is especially apparent in South-Central Alaska where many glaciers are undergoing rapid changes and contributing substantially to rising sea levels (Arendt et al., 2002). It is important to understand the rates at which these glaciers are losing mass as well as the important climatic drivers to better prepare for what the future holds in this region and the rest of the world. This work compares glacier mass balance data modeled through the Precipitation-Temperature Area Altitude (PTAA) mass balance model for the Wolverine Glacier in the Kenai Peninsula in South-Central Alaska to observed data from the USGS “benchmark” glacier program in order to help validate the model. The mass balance data are also correlated with climate data in order to understand the main climatic drivers of the glacier mass balance in this region.
Updated Delft Mass Transport model DMT-2: computation and validation
NASA Astrophysics Data System (ADS)
Hashemi Farahani, Hassan; Ditmar, Pavel; Inacio, Pedro; Klees, Roland; Guo, Jing; Guo, Xiang; Liu, Xianglin; Zhao, Qile; Didova, Olga; Ran, Jiangjun; Sun, Yu; Tangdamrongsub, Natthachet; Gunter, Brian; Riva, Ricardo; Steele-Dunne, Susan
2014-05-01
A number of research centers compute models of mass transport in the Earth's system using primarily K-Band Ranging (KBR) data from the Gravity Recovery And Climate Experiment (GRACE) satellite mission. These models typically consist of a time series of monthly solutions, each of which is defined in terms of a set of spherical harmonic coefficients up to degree 60-120. One of such models, the Delft Mass Transport, release 2 (DMT-2), is computed at the Delft University of Technology (The Netherlands) in collaboration with Wuhan University. An updated variant of this model has been produced recently. A unique feature of the computational scheme designed to compute DMT-2 is the preparation of an accurate stochastic description of data noise in the frequency domain using an Auto-Regressive Moving-Average (ARMA) model, which is derived for each particular month. The benefits of such an approach are a proper frequency-dependent data weighting in the data inversion and an accurate variance-covariance matrix of noise in the estimated spherical harmonic coefficients. Furthermore, the data prior to the inversion are subject to an advanced high-pass filtering, which makes use of a spatially-dependent weighting scheme, so that noise is primarily estimated on the basis of data collected over areas with minor mass transport signals (e.g., oceans). On the one hand, this procedure efficiently suppresses noise, which are caused by inaccuracies in satellite orbits and, on the other hand, preserves mass transport signals in the data. Finally, the unconstrained monthly solutions are filtered using a Wiener filter, which is based on estimates of the signal and noise variance-covariance matrices. In combination with a proper data weighting, this noticeably improves the spatial resolution of the monthly gravity models and the associated mass transport models.. For instance, the computed solutions allow long-term negative trends to be clearly seen in sufficiently small regions notorious
Soft walls in dynamic AdS /QCD and the technidilaton
NASA Astrophysics Data System (ADS)
Evans, Nick; Jones, Peter; Scott, Marc
2015-11-01
Dynamic AdS /QCD is a modification of AdS /QCD that includes the running of the anomalous dimension of the q ¯q quark bilinear and in which the generation of the constituent quark mass plays the role of an IR wall. The model allows one to move away smoothly from the controlled spectrum of the N =2 super Yang-Mills theory of the D3/probe-D7 system to more QCD-like theories with chiral symmetry breaking. We investigate soft wall behavior in the model that gives Regge trajectories with Mn,s 2˜n ,s . To achieve these behaviors requires the quark's constituent mass to fall peculiarly sharply in the IR so that meson physics is sensitive to renormalization group (RG) scales well below the quark's on-shell mass. Including soft wall behavior in models of walking gauge dynamics breaks the near conformal symmetry which is present above the quark on-shell mass which can generate a large mass for the technidilaton like state. We conclude that the meson spectrum is rather sensitive to the IR decoupling.
Neutrino mass model with S3 symmetry and seesaw interplay
NASA Astrophysics Data System (ADS)
Pramanick, Soumita; Raychaudhuri, Amitava
2016-12-01
We develop a seesaw model for neutrino masses and mixing with an S3×Z3 symmetry. It involves an interplay of type-I and type-II seesaw contributions of which the former is subdominant. The S3×Z3 quantum numbers of the fermion and scalar fields are chosen such that the type-II seesaw generates a mass matrix which incorporates the atmospheric mass splitting and sets θ23=π /4 . The solar splitting and θ13 are absent, while the third mixing angle can achieve any value, θ120. Specific choices of θ120 are of interest, e.g., 35.3° (tribimaximal), 45.0° (bimaximal), 31.7° (golden ratio), and 0° (no solar mixing). The role of the type-I seesaw is to nudge all the above into the range indicated by the data. The model results in novel interrelationships between these quantities due to their common origin, making it readily falsifiable. For example, normal (inverted) ordering is associated with θ23 in the first (second) octant. C P violation is controlled by phases in the right-handed neutrino Majorana mass matrix, Mν R . In their absence, only normal ordering is admissible. When Mν R is complex, the Dirac C P phase, δ , can be large, i.e., ˜±π /2 , and inverted ordering is also allowed. The preliminary results from T2K and NOVA which favor normal ordering and δ ˜-π /2 are indicative, in this model, of a lightest neutrino mass of 0.05 eV or more.
Herbst, Antje; Diethelm, Katharina; Cheng, Guo; Alexy, Ute; Icks, Andrea; Buyken, Anette E
2011-07-01
Dietary factors, especially during early childhood, have been discussed as potentially critical for the development of childhood overweight. This study evaluated associations between added sugar intake during early childhood and BMI and body fat at age 7 y. Analysis was based on data from 216 participants of the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study. Life-course plots were constructed to evaluate the association between added sugar intake at different ages (0.5, 1, 1.5, and 2 y) and BMI SD score (BMI-SDS) and % body fat (%BF) at age 7 y. Multivariable analyses were performed for the periods identified as critical for later BMI and body fat. Added sugar intake at age 1 y and the change in intake levels during the second year of life emerged as potentially critical. At age 1 y, a higher total added sugar intake was related to a lower BMI-SDS at age 7 y [adjusted β ± SE: -0.116 ± 0.057 BMI-SDS/percent energy (%En) added sugar; P = 0.04]. Conversely, an increase in total added sugar in the second year of life (Δ%En between age 1 and 2 y) tended to be associated with a higher BMI-SDS (adjusted β ± SE: 0.074 ± 0.043 BMI-SDS/Δ%En added sugar; P = 0.09). No associations were observed with %BF. In conclusion, added sugar intake at low intake levels during early childhood does not appear to be critical for BMI and body fat at age 7 y. However, detrimental effects on BMI development may emerge when added sugar intakes are increased to higher levels.
Modeling and Simulation of Variable Mass, Flexible Structures
NASA Technical Reports Server (NTRS)
Tobbe, Patrick A.; Matras, Alex L.; Wilson, Heath E.
2009-01-01
The advent of the new Ares I launch vehicle has highlighted the need for advanced dynamic analysis tools for variable mass, flexible structures. This system is composed of interconnected flexible stages or components undergoing rapid mass depletion through the consumption of solid or liquid propellant. In addition to large rigid body configuration changes, the system simultaneously experiences elastic deformations. In most applications, the elastic deformations are compatible with linear strain-displacement relationships and are typically modeled using the assumed modes technique. The deformation of the system is approximated through the linear combination of the products of spatial shape functions and generalized time coordinates. Spatial shape functions are traditionally composed of normal mode shapes of the system or even constraint modes and static deformations derived from finite element models of the system. Equations of motion for systems undergoing coupled large rigid body motion and elastic deformation have previously been derived through a number of techniques [1]. However, in these derivations, the mode shapes or spatial shape functions of the system components were considered constant. But with the Ares I vehicle, the structural characteristics of the system are changing with the mass of the system. Previous approaches to solving this problem involve periodic updates to the spatial shape functions or interpolation between shape functions based on system mass or elapsed mission time. These solutions often introduce misleading or even unstable numerical transients into the system. Plus, interpolation on a shape function is not intuitive. This paper presents an approach in which the shape functions are held constant and operate on the changing mass and stiffness matrices of the vehicle components. Each vehicle stage or component finite element model is broken into dry structure and propellant models. A library of propellant models is used to describe the
Nolte, Heinrich W; Noakes, Timothy D; van Vuuren, Bernard
2011-11-01
The extent to which humans need to replace fluid losses during exercise remains contentious despite years of focused research. The primary objective was to evaluate ad libitum drinking on hydration status to determine whether body mass loss can be used as an accurate surrogate for changes in total body water (TBW) during exercise. Data were collected during a 14.6-km route march (wet bulb globe temperature of 14.1°C ). 18 subjects with an average age of 26 ± 2.5 (SD) years participated. Their mean ad libitum total fluid intake was 2.1 ± 1.4 litres during the exercise. Predicted sweat rate was 1.289 ± 0.530 l/h. There were no significant changes (p>0.05) in TBW, urine specific gravity or urine osmolality despite an average body mass loss (p<0.05) of 1.3 ± 0.45 kg during the march. Core temperature rose as a function of marching speed and was unrelated to the % change in body mass. This suggests that changes in mass do not accurately predict changes in TBW (r=-0.16) because either the body mass loss during exercise includes losses other than water or there is an endogenous body water source that is released during exercise not requiring replacement during exercise, or both. Ad libitum water replacement between 65% and 70% of sweat losses maintained safe levels of hydration during the experiment. The finding that TBW was protected by ad libitum drinking despite approximately 2% body mass loss suggests that the concept of 'voluntary dehydration' may require revision.
Modelling of heat and mass transfer processes in neonatology.
Ginalski, Maciej K; Nowak, Andrzej J; Wrobel, Luiz C
2008-09-01
This paper reviews some of our recent applications of computational fluid dynamics (CFD) to model heat and mass transfer problems in neonatology and investigates the major heat and mass transfer mechanisms taking place in medical devices such as incubators and oxygen hoods. This includes novel mathematical developments giving rise to a supplementary model, entitled infant heat balance module, which has been fully integrated with the CFD solver and its graphical interface. The numerical simulations are validated through comparison tests with experimental results from the medical literature. It is shown that CFD simulations are very flexible tools that can take into account all modes of heat transfer in assisting neonatal care and the improved design of medical devices.
Modeling mass drug treatment and resistant filaria disease transmission
NASA Astrophysics Data System (ADS)
Fuady, A. M.; Nuraini, N.; Soewono, E.; Tasman, H.; Supriatna, A. K.
2014-03-01
It has been indicated that a long term application of combined mass drug treatment may contribute to the development of drug resistance in lymphatic filariasis. This phenomenon is not well understood due to the complexity of filaria life cycle. In this paper we formulate a mathematical model for the spread of mass drug resistant in a filaria endemic region. The model is represented in a 13-dimensional Host-Vector system. The basic reproductive ratio of the system which is obtained from the next generation matrix, and analysis of stability of both the disease free equilibrium and the coexistence equilibria are shown. Numerical simulation for long term dynamics for possible field conditions is also shown.
Characterization of a model Phillips catalyst by mass spectrometry.
Di Croce, Pascal Gabriel; Aubriet, Frédéric; Chéty-Gimondo, Rachel; Muller, Jean-François; Grange, Paul
2004-01-01
A model Phillips catalyst for ethylene polymerization, prepared by spin coating a Cr(III)(Cr(acac)3) precursor on a silicon wafer, was submitted to an oxidative activation. Laser ablation Fourier transform mass spectrometry provided direct information on molecular species at the silicon wafer surface during activation. At 350 degrees C the chromium precursor was degraded, while chromium oxide species were formed. The chromium concentration decreased with temperature. The activated model catalyst was active for ethylene polymerization. Using complementary techniques (Fourier transform infrared spectroscopy, laser desorption/ionization mass spectrometry), the polymer was identified as crystalline polyethylene. After 1 h of polymerization at 160 degrees C, dome-like structures were observed by atomic force microscopy. Their morphologies were constituted of regions of parallel aligned lamellae of polymer.
Mass concentration in a nonlocal model of clonal selection.
Busse, J-E; Gwiazda, P; Marciniak-Czochra, A
2016-10-01
Self-renewal is a constitutive property of stem cells. Testing the cancer stem cell hypothesis requires investigation of the impact of self-renewal on cancer expansion. To better understand this impact, we propose a mathematical model describing the dynamics of a continuum of cell clones structured by the self-renewal potential. The model is an extension of the finite multi-compartment models of interactions between normal and cancer cells in acute leukemias. It takes a form of a system of integro-differential equations with a nonlinear and nonlocal coupling which describes regulatory feedback loops of cell proliferation and differentiation. We show that this coupling leads to mass concentration in points corresponding to the maxima of the self-renewal potential and the solutions of the model tend asymptotically to Dirac measures multiplied by positive constants. Furthermore, using a Lyapunov function constructed for the finite dimensional counterpart of the model, we prove that the total mass of the solution converges to a globally stable equilibrium. Additionally, we show stability of the model in the space of positive Radon measures equipped with the flat metric (bounded Lipschitz distance). Analytical results are illustrated by numerical simulations.
Krick, Julian; Ackerman, Josef Daniel
2015-03-07
The particle capture efficiency, η, of systems that remove suspended particles from ambient flow (e.g. suspension feeding, abiotic pollination) has been studied using static collectors in steady flows. Particle deposition on collectors moving due to fluid flow remains largely unknown, despite its ecological relevance. We used numerical modeling to simulate particle deposition on a 2D circular cylinder subject to flow-induced oscillation in a cross flow. Using parameter values relevant to wind pollination and other natural biological systems, we examined the influence of the direction, amplitude and frequency of the oscillation, the Stokes number (Stk=0.01-5, characterizing particle behavior), as well as the Reynolds number (Re=662 and 3309, characterizing flow regime) in steady and unsteady flow, on η. The numerical model was validated with empirical results for parts of the parameter space. Particle capture occurred via "inertial impaction", "direct interception" and "leeward deposition", as well as via a new mechanism, "collector chasing" for moving collectors. The η of an oscillating cylinder varied significantly relative to a static cylinder, depending on the parameters used, and on the magnitude of a numerical error that caused loss of particles. This variance of η was due to a change in relative momentum between the particle and the moving collector, which depends on Re, Stk and the oscillation parameters. Collector oscillation transverse to oncoming flow direction strongly increased η, whereas collector motion parallel to flow had little effect on capture efficiency. The oscillation also changed leeward capture significantly in some cases. For most conditions, however, leeward deposition was small. Results suggest that collector motion could have significant influence on the particle capture efficiency of natural systems, which indicates the need to incorporate these ecologically more relevant findings into current models. Empirical studies, however
Ad-hoc model acquisition for combat simulation in urban terrain
NASA Astrophysics Data System (ADS)
Bulatov, Dimitri; Solbrig, Peter; Wernerus, Peter
2012-10-01
Situation awareness in complex urban environments is an important component for a successful task fulfillment both in military and civil area of applications. In the first area, the fields of deployment of the members of the North Atlantic Alliance have been changed, in the past two decades, from the originally assigned task of acting as national and allied defense forces within the partners' own borders to out-of-area missions under conditions of an asymmetric conflict. Because of its complicated structure, urban terrain represents a particular difficulty of military missions such as patrolling. In the civil field of applications, police and rescue forces are also often strongly dependent on a local visibility and accessibility analysis. However, the process of decision-taking within a short time and under enormous pressure can be extensively trained in an environment that is tailored to the concrete situation. The contribution of this work consists of context-based modeling of urban terrain that can be then integrated into simulation software, for example, Virtual Battlespace 2 (VBS2). The input of our procedure is made up by the airborne sensor data, collected either by an active or a passive sensor. The latter is particularly important if the application is time-critical or the area to be explored is small. After description of our procedure for urban terrain modeling with a detailed focus on the recent innovations, the main steps of model integration into simulation software will be presented and two examples of missions for military and civil applications that can be easily created with VBS2 will be given.
Silva, Daniel Paiva; Varela, Sara; Nemésio, André; De Marco, Paulo
2015-01-01
Orchid bees compose an exclusive Neotropical pollinators group, with bright body coloration. Several of those species build their own nests, while others are reported as nest cleptoparasites. Here, the objective was to evaluate whether the inclusion of a strong biotic interaction, such as the presence of a host species, improved the ability of species distribution models (SDMs) to predict the geographic range of the cleptoparasite species. The target species were Aglae caerulea and its host species Eulaema nigrita. Additionally, since A. caerulea is more frequently found in the Amazon rather than the Cerrado areas, a secondary objective was to evaluate whether this species is increasing or decreasing its distribution given South American past and current climatic conditions. SDMs methods (Maxent and Bioclim), in addition with current and past South American climatic conditions, as well as the occurrences for A. caerulea and E. nigrita were used to generate the distribution models. The distribution of A. caerulea was generated with and without the inclusion of the distribution of E. nigrita as a predictor variable. The results indicate A. caerulea was barely affected by past climatic conditions and the populations from the Cerrado savanna could be at least 21,000 years old (the last glacial maximum), as well as the Amazonian ones. On the other hand, in this study, the inclusion of the host-cleptoparasite interaction complex did not statistically improve the quality of the produced models, which means that the geographic range of this cleptoparasite species is mainly constrained by climate and not by the presence of the host species. Nonetheless, this could also be caused by unknown complexes of other Euglossini hosts with A. caerulea, which still are still needed to be described by science. PMID:26069956
Pion Form Factor in Chiral Limit of Hard-Wall AdS/QCD Model
Anatoly Radyushkin; Hovhannes Grigoryan
2007-12-01
We develop a formalism to calculate form factor and charge density distribution of pion in the chiral limit using the holographic dual model of QCD with hard-wall cutoff. We introduce two conjugate pion wave functions and present analytic expressions for these functions and for the pion form factor. They allow to relate such observables as the pion decay constant and the pion charge electric radius to the values of chiral condensate and hard-wall cutoff scale. The evolution of the pion form factor to large values of the momentum transfer is discussed, and results are compared to existing experimental data.
ERIC Educational Resources Information Center
Isenberg, Eric; Hock, Heinrich
2011-01-01
This report presents the value-added models that will be used to measure school and teacher effectiveness in the District of Columbia Public Schools (DCPS) in the 2010-2011 school year. It updates the earlier technical report, "Measuring Value Added for IMPACT and TEAM in DC Public Schools." The earlier report described the methods used…
Liu, Ming; Xu, Yang; Mohammed, Abdul-Wahid
2016-01-01
Limited communication resources have gradually become a critical factor toward efficiency of decentralized large scale multi-agent coordination when both system scales up and tasks become more complex. In current researches, due to the agent’s limited communication and observational capability, an agent in a decentralized setting can only choose a part of channels to access, but cannot perceive or share global information. Each agent’s cooperative decision is based on the partial observation of the system state, and as such, uncertainty in the communication network is unavoidable. In this situation, it is a major challenge working out cooperative decision-making under uncertainty with only a partial observation of the environment. In this paper, we propose a decentralized approach that allows agents cooperatively search and independently choose channels. The key to our design is to build an up-to-date observation for each agent’s view so that a local decision model is achievable in a large scale team coordination. We simplify the Dec-POMDP model problem, and each agent can jointly work out its communication policy in order to improve its local decision utilities for the choice of communication resources. Finally, we discuss an implicate resource competition game, and show that, there exists an approximate resources access tradeoff balance between agents. Based on this discovery, the tradeoff between real-time decision-making and the efficiency of cooperation using these channels can be well improved. PMID:26727504
Vector condensate and AdS soliton instability induced by a magnetic field
NASA Astrophysics Data System (ADS)
Cai, Rong-Gen; Li, Li; Li, Li-Fang; Wu, You
2014-01-01
We continue to study the holographic p-wave superconductor model in the Einstein-Maxwell-complex vector field theory with a non-minimal coupling between the complex vector field and the Maxwell field. In this paper we work in the AdS soliton background which describes a conformal field theory in the confined phase and focus on the probe approximation. We find that an applied magnetic field can lead to the condensate of the vector field and the AdS soliton instability. As a result, a vortex lattice structure forms in the spatial directions perpendicular to the applied magnetic field. As a comparison, we also discuss the vector condensate in the Einstein-SU(2) Yang-Mills theory and find that in the setup of the present paper, the Einstein-Maxwell-complex vector field model is a generalization of the SU(2) model in the sense that the vector field has a general mass and gyromagnetic ratio.
Guo, Xiao-dan; Sun, Guang-long; Zhou, Ting-ting; Xu, Xin; Zhu, Zhi-yuan; Rukachaisirikul, Vatcharin; Hu, Li-hong; Shen, Xu
2016-01-01
Aim: Streptozotocin (STZ) is widely used to induce oxidative damage and to impair glucose metabolism, apoptosis, and tau/Aβ pathology, eventually leading to cognitive deficits in both in vitro and in vivo models of Alzheimer's disease (AD). In this study, we constructed a cell-based platform using STZ to induce stress conditions mimicking the complicated pathologies of AD in vitro, and evaluated the anti-amyloid effects of a small molecule, N-(1,3-benzodioxol-5-yl)-2-[5-chloro-2-methoxy(phenylsulfonyl)anilino]acetamide (LX2343) in the amelioration of cognitive deficits in AD model mice. Methods: Cell-based assays for screening anti-amyloid compounds were established by assessing Aβ accumulation in HEK293-APPsw and CHO-APP cells, and Aβ clearance in primary astrocytes and SH-SY5Y cells after the cells were treated with STZ in the presence of the test compounds. Autophagic flux was observed using confocal laser scanning microscopy. APP/PS1 transgenic mice were administered LX2343 (10 mg·kg−1·d−1, ip) for 100 d. After LX2343 administration, cognitive ability of the mice was evaluated using Morris water maze test, and senile plaques in the brains were detected using Thioflavine S staining. ELISA assay was used to evaluate Aβ and sAPPβ levels, while Western blot analysis was used to measure the signaling proteins in both cell and animal brains. Results: LX2343 (5–20 μmol/L) dose-dependently decreased Aβ accumulation in HEK293-APPsw and CHO-APP cells, and promoted Aβ clearance in SH-SY5Y cells and primary astrocytes. The anti-amyloid effects of LX2343 were attributed to suppressing JNK-mediated APPThr668 phosphorylation, thus inhibiting APP cleavage on one hand, and inhibiting BACE1 enzymatic activity with an IC50 value of 11.43±0.36 μmol/L, on the other hand. Furthermore, LX2343 acted as a non-ATP competitive PI3K inhibitor to negatively regulate AKT/mTOR signaling, thus promoting autophagy, and increasing Aβ clearance. Administration of LX2343 in APP
NASA Astrophysics Data System (ADS)
Lien, Vidar S.; Hjøllo, Solfrid S.; Skogen, Morten D.; Svendsen, Einar; Wehde, Henning; Bertino, Laurent; Counillon, Francois; Chevallier, Matthieu; Garric, Gilles
2016-03-01
The Nordic Seas is a hotspot both in terms of climate related processes, such as Atlantic-Arctic heat exchange, and natural marine resources. A sustainable management of the marine resources within the Nordic Seas, including the co-existence between fisheries and petroleum industries, requires detailed information on the state of the ocean within an operational framework and beyond what is obtainable from observations only. Numerical ocean models applying data assimilation techniques are utilized to address this need. Subsequently, comprehensive comparisons between model results and observations are required in order to assess the model performance. Here, we apply a set of objective statistics to quantitatively assess the added value of data assimilation in numerical ocean models that are currently used operationally. The results indicate that the inclusion of data assimilation improves the model performance both in terms of hydrographic properties and volume and heat transports. Furthermore, we find that increasing the resolution towards eddy resolving resolution performs similarly to coarser resolution models applying data assimilation in shelf areas.
Extending JAGS: a tutorial on adding custom distributions to JAGS (with a diffusion model example).
Wabersich, Dominik; Vandekerckhove, Joachim
2014-03-01
We demonstrate how to add a custom distribution into the general-purpose, open-source, cross-platform graphical modeling package JAGS ("Just Another Gibbs Sampler"). JAGS is intended to be modular and extensible, and modules written in the way laid out here can be loaded at runtime as needed and do not interfere with regular JAGS functionality when not loaded. Writing custom extensions requires knowledge of C++, but installing a new module can be highly automatic, depending on the operating system. As a basic example, we implement a Bernoulli distribution in JAGS. We further present our implementation of the Wiener diffusion first-passage time distribution, which is freely available at https://sourceforge.net/projects/jags-wiener/ .
Modeling of Fluctuating Mass Flux in Variable Density Flows
NASA Technical Reports Server (NTRS)
So, R. M. C.; Mongia, H. C.; Nikjooy, M.
1983-01-01
The approach solves for both Reynolds and Favre averaged quantities and calculates the scalar pdf. Turbulent models used to close the governing equations are formulated to account for complex mixing and variable density effects. In addition, turbulent mass diffusivities are not assumed to be in constant proportion to turbulent momentum diffusivities. The governing equations are solved by a combination of finite-difference technique and Monte-Carlo simulation. Some preliminary results on simple variable density shear flows are presented. The differences between these results and those obtained using conventional models are discussed.
Shell model approach for nuclei with mass around 220
NASA Astrophysics Data System (ADS)
Kaiura, Yukiko; Yoshinaga, Naotaka; Higashiyama, Koji
2014-09-01
Ra and Th isotopes with mass around 220 belonging to a transitional region between spherical and deformed regions have fascinated our interest from the past. In particular, since a large number of negative parity states are observed in low-lying states, collective octupole correlations are supposed to be important. In this talk we report the nuclear structure of Po, Rn, Ra and Th isotopes in terms of the pair truncated shell model, the basic ingredients of which consist of nuclear collective models. The 208Pb is considered as the doubly-magic core. The conventional pairing plus quadrupole interaction is employed. Energy levels and electric transitions are compared between theory and experiment.
Model-independent analysis of quark mass matrices
Choudhury, D.; Sarkar, U.
1989-06-01
In view of the apparent inconsistency of the Stech, Fritzsch-Stech, and Fritzsch-Shin models and only marginal agreement of the Fritzsch and modified Fritzsch-Stech models with recent data on /ital B//sub /ital d///sup 0/-/bar B/ /sub /ital d///sup 0/ mixing, we analyze the general quark mass matrices for three generations. Phenomenological considerations restrict the range of parameters involved to different sectors. In the present framework, the constraints corresponding to various /ital Ansa/$/ital uml/---/ital tze/ have been discussed.
An overview of the Lake Michigan Mass Balance models were provided (eutrophication/nutrients, atrazine, mercury, and PCBs) with emphasis on the PCB model post-audit and forecast for Lake Trout. Provided were modeling construct, model description, and primary results. An assessm...
Neural mass model-based tracking of anesthetic brain states.
Kuhlmann, Levin; Freestone, Dean R; Manton, Jonathan H; Heyse, Bjorn; Vereecke, Hugo E M; Lipping, Tarmo; Struys, Michel M R F; Liley, David T J
2016-06-01
Neural mass model-based tracking of brain states from electroencephalographic signals holds the promise of simultaneously tracking brain states while inferring underlying physiological changes in various neuroscientific and clinical applications. Here, neural mass model-based tracking of brain states using the unscented Kalman filter applied to estimate parameters of the Jansen-Rit cortical population model is evaluated through the application of propofol-based anesthetic state monitoring. In particular, 15 subjects underwent propofol anesthesia induction from awake to anesthetised while behavioral responsiveness was monitored and frontal electroencephalographic signals were recorded. The unscented Kalman filter Jansen-Rit model approach applied to frontal electroencephalography achieved reasonable testing performance for classification of the anesthetic brain state (sensitivity: 0.51; chance sensitivity: 0.17; nearest neighbor sensitivity 0.75) when compared to approaches based on linear (autoregressive moving average) modeling (sensitivity 0.58; nearest neighbor sensitivity: 0.91) and a high performing standard depth of anesthesia monitoring measure, Higuchi Fractal Dimension (sensitivity: 0.50; nearest neighbor sensitivity: 0.88). Moreover, it was found that the unscented Kalman filter based parameter estimates of the inhibitory postsynaptic potential amplitude varied in the physiologically expected direction with increases in propofol concentration, while the estimates of the inhibitory postsynaptic potential rate constant did not. These results combined with analysis of monotonicity of parameter estimates, error analysis of parameter estimates, and observability analysis of the Jansen-Rit model, along with considerations of extensions of the Jansen-Rit model, suggests that the Jansen-Rit model combined with unscented Kalman filtering provides a valuable reference point for future real-time brain state tracking studies. This is especially true for studies of
Automatic Determination of the Conic Coronal Mass Ejection Model Parameters
NASA Technical Reports Server (NTRS)
Pulkkinen, A.; Oates, T.; Taktakishvili, A.
2009-01-01
Characterization of the three-dimensional structure of solar transients using incomplete plane of sky data is a difficult problem whose solutions have potential for societal benefit in terms of space weather applications. In this paper transients are characterized in three dimensions by means of conic coronal mass ejection (CME) approximation. A novel method for the automatic determination of cone model parameters from observed halo CMEs is introduced. The method uses both standard image processing techniques to extract the CME mass from white-light coronagraph images and a novel inversion routine providing the final cone parameters. A bootstrap technique is used to provide model parameter distributions. When combined with heliospheric modeling, the cone model parameter distributions will provide direct means for ensemble predictions of transient propagation in the heliosphere. An initial validation of the automatic method is carried by comparison to manually determined cone model parameters. It is shown using 14 halo CME events that there is reasonable agreement, especially between the heliocentric locations of the cones derived with the two methods. It is argued that both the heliocentric locations and the opening half-angles of the automatically determined cones may be more realistic than those obtained from the manual analysis
Modeling rapid mass movements using the shallow water equations
NASA Astrophysics Data System (ADS)
Hergarten, S.; Robl, J.
2014-11-01
We propose a new method to model rapid mass movements on complex topography using the shallow water equations in Cartesian coordinates. These equations are the widely used standard approximation for the flow of water in rivers and shallow lakes, but the main prerequisite for their application - an almost horizontal fluid table - is in general not satisfied for avalanches and debris flows in steep terrain. Therefore, we have developed appropriate correction terms for large topographic gradients. In this study we present the mathematical formulation of these correction terms and their implementation in the open source flow solver GERRIS. This novel approach is evaluated by simulating avalanches on synthetic and finally natural topographies and the widely used Voellmy flow resistance law. The results are tested against analytical solutions and the commercial avalanche model RAMMS. The overall results are in excellent agreement with the reference system RAMMS, and the deviations between the different models are far below the uncertainties in the determination of the relevant fluid parameters and involved avalanche volumes in reality. As this code is freely available and open source, it can be easily extended by additional fluid models or source areas, making this model suitable for simulating several types of rapid mass movements. It therefore provides a valuable tool assisting regional scale natural hazard studies.
Modelling Mass Casualty Decontamination Systems Informed by Field Exercise Data
Egan, Joseph R.; Amlôt, Richard
2012-01-01
In the event of a large-scale chemical release in the UK decontamination of ambulant casualties would be undertaken by the Fire and Rescue Service (FRS). The aim of this study was to track the movement of volunteer casualties at two mass decontamination field exercises using passive Radio Frequency Identification tags and detection mats that were placed at pre-defined locations. The exercise data were then used to inform a computer model of the FRS component of the mass decontamination process. Having removed all clothing and having showered, the re-dressing (termed re-robing) of casualties was found to be a bottleneck in the mass decontamination process during both exercises. Computer simulations showed that increasing the capacity of each lane of the re-robe section to accommodate 10 rather than five casualties would be optimal in general, but that a capacity of 15 might be required to accommodate vulnerable individuals. If the duration of the shower was decreased from three minutes to one minute then a per lane re-robe capacity of 20 might be necessary to maximise the throughput of casualties. In conclusion, one practical enhancement to the FRS response may be to provide at least one additional re-robe section per mass decontamination unit. PMID:23202768
Modeling the chemistry of plasma polymerization using mass spectrometry.
Ihrig, D F; Stockhaus, J; Scheide, F; Winkelhake, Oliver; Streuber, Oliver
2003-04-01
The goal of the project is a solvent free painting shop. The environmental technologies laboratory is developing processes of plasma etching and polymerization. Polymerized thin films are first-order corrosion protection and primer for painting. Using pure acetylene we get very nice thin films which were not bonded very well. By using air as bulk gas it is possible to polymerize, in an acetylene plasma, well bonded thin films which are stable first-order corrosion protections and good primers. UV/Vis spectroscopy shows nitrogen oxide radicals in the emission spectra of pure nitrogen and air. But nitrogen oxide is fully suppressed in the presence of acetylene. IR spectroscopy shows only C=O, CH(2) and CH(3) groups but no nitrogen species. With the aid of UV/Vis spectra and the chemistry of ozone formation it is possible to define reactive traps and steps, molecule depletion and processes of proton scavenging and proton loss. Using a numerical model it is possible to evaluate these processes and to calculate theoretical mass spectra. Adjustment of theoretical mass spectra to real measurements leads to specific channels of polymerization which are driven by radicals especially the acetyl radical. The estimated theoretical mass spectra show the specific channels of these chemical processes. It is possible to quantify these channels. This quantification represents the mass flow through this chemical system. With respect to these chemical processes it is possible to have an idea of pollutant production processes.
Modelling mass casualty decontamination systems informed by field exercise data.
Egan, Joseph R; Amlôt, Richard
2012-10-16
In the event of a large-scale chemical release in the UK decontamination of ambulant casualties would be undertaken by the Fire and Rescue Service (FRS). The aim of this study was to track the movement of volunteer casualties at two mass decontamination field exercises using passive Radio Frequency Identification tags and detection mats that were placed at pre-defined locations. The exercise data were then used to inform a computer model of the FRS component of the mass decontamination process. Having removed all clothing and having showered, the re-dressing (termed re-robing) of casualties was found to be a bottleneck in the mass decontamination process during both exercises. Computer simulations showed that increasing the capacity of each lane of the re-robe section to accommodate 10 rather than five casualties would be optimal in general, but that a capacity of 15 might be required to accommodate vulnerable individuals. If the duration of the shower was decreased from three minutes to one minute then a per lane re-robe capacity of 20 might be necessary to maximise the throughput of casualties. In conclusion, one practical enhancement to the FRS response may be to provide at least one additional re-robe section per mass decontamination unit.
Oreopoulos, Lazaros; Norris, Peter M.
2010-03-14
The overarching goal of the project was to improve the transfer of solar and thermal radiation in the most sophisticated computer tools that are currently available for climate studies, namely Global Climate Models (GCMs). This transfer can be conceptually separated into propagation of radiation under cloudy and under cloudless conditions. For cloudless conditions, the factors that affect radiation propagation are gaseous absorption and scattering, aerosol particle absorption and scattering and surface albedo and emissivity. For cloudy atmospheres the factors are the various cloud properties such as cloud fraction, amount of cloud condensate, the size of the cloud particles, and morphological cloud features such as cloud vertical location, cloud horizontal and vertical inhomogeneity and cloud shape and size. The project addressed various aspects of the influence of the above contributors to atmospheric radiative transfer variability. In particular, it examined: (a) the quality of radiative transfer for cloudless and non-complex cloudy conditions for a substantial number of radiation algorithms used in current GCMs; (b) the errors in radiative fluxes from neglecting the horizontal variabiity of cloud extinction; (c) the statistical properties of cloud horizontal and vertical cloud inhomogeneity that can be incorporated into radiative transfer codes; (d) the potential albedo effects of changes in the particle size of liquid clouds; (e) the gaseous radiative forcing in the presence of clouds; and (f) the relative contribution of clouds of different sizes to the reflectance of a cloud field. To conduct the research in the various facets of the project, data from both the DOE ARM project and other sources were used. The outcomes of the project will have tangible effects on how the calculation of radiative energy will be approached in future editions of GCMs. With better calculations of radiative energy in GCMs more reliable predictions of future climate states will be
Model Atmospheres From Very Low Mass Stars to Brown Dwarfs
NASA Astrophysics Data System (ADS)
Allard, F.; Homeier, D.; Freytag, B.
2011-12-01
Since the discovery of brown dwarfs in 1994, and the discovery of dust cloud formation in the latest Very Low Mass Stars (VLMs) and Brown Dwarfs (BDs) in 1996, the most important challenge in modeling their atmospheres as become the understanding of cloud formation and advective mixing. For this purpose, we have developed radiation hydrodynamic 2D model atmosphere simulations to study the formation of forsterite dust in presence of advection, condensation, and sedimentation across the M-L-T VLMs to BDs sequence (Teff = 2800 K to 900 K, Freytag et al. 2010). We discovered the formation of gravity waves as a driving mechanism for the formation of clouds in these atmospheres, and derived a rule for the velocity field versus atmospheric depth and Teff, which is relatively insensitive to gravity. This rule has been used in the construction of the new model atmosphere grid, BT-Settl, to determine the micro-turbulence velocity, the diffusion coefficient, and the advective mixing of molecules as a function of depth. This new model grid of atmospheres and synthetic spectra has been computed for 100,000 K > Teff > 400 K, 5.5 > logg > -0.5, and [M/H]= +0.5 to -1.5, and the reference solar abundances of Asplund et al. (2009). We found that the new solar abundances allow an improved (close to perfect) reproduction of the photometric and spectroscopic VLMs properties, and, for the first time, a smooth transition between stellar and substellar regimes -- unlike the transition between the NextGen models from Hauschildt et al. 1999a,b, and the AMES-Dusty models from Allard et al. 2001. In the BDs regime, the BT-Settl models propose an improved explanation for the M-L-T spectral transition. In this paper, we therefore present the new BT-Settl model atmosphere grid, which explains the entire transition from the stellar to planetary mass regimes.
NASA Astrophysics Data System (ADS)
Fotso-Nguemo, Thierry C.; Vondou, Derbetini A.; Pokam, Wilfried M.; Djomou, Zéphirin Yepdo; Diallo, Ismaïla; Haensler, Andreas; Tchotchou, Lucie A. Djiotang; Kamsu-Tamo, Pierre H.; Gaye, Amadou T.; Tchawoua, Clément
2017-02-01
In this paper, the regional climate model REMO is used to investigate the added value of downscaling low resolutions global climate models (GCMs) and the climate change projections over Central Africa. REMO was forced by two GCMs (EC-Earth and MPI-ESM), for the period from 1950 to 2100 under the Representative Concentration Pathway 8.5 scenario. The performance of the REMO simulations for current climate is compared first with REMO simulation driven by ERA-Interim reanalysis, then by the corresponding GCMs in order to determine whether REMO outputs are able to effectively lead to added value at local scale. We found that REMO is generally able to better represent some aspects of the rainfall inter-annual variability, the daily rainfall intensity distribution as well as the intra-seasonal variability of the Central African monsoon, though few biases are still evident. It is also found that the boundary conditions strongly influences the spatial distribution of seasonal 2-m temperature and rainfall. From the analysis of the climate change signal from the present period 1976-2005 to the future 2066-2095, we found that all models project a warming at the end of the twenty-first century although the details of the climate change differ between REMO and the driving GCMs, specifically in REMO where we observe a general decrease in rainfall. This rainfall decrease is associated with delayed onset and anticipated recession of the Central African monsoon and a shortening of the rainy season. Small-scales variability of the climate change signal for 2-m temperature are usually smaller than that of the large-scales climate change part. For rainfall however, small-scales induce change of about 70% compared to the present climate statistics.
Parthsarathy, Vadivel; Hölscher, Christian
2013-01-01
Neurogenesis is a life long process, but the rate of cell proliferation and differentiation decreases with age. In Alzheimer's patients, along with age, the presence of Aβ in the brain inhibits this process by reducing stem cell proliferation and cell differentiation. GLP-1 is a growth factor that has neuroprotective properties. GLP1 receptors are present on neuronal progenitor cells, and the GLP-1 analogue liraglutide has been shown to increase cell proliferation in an Alzheimer's disease (AD) mouse model. Here we investigated acute and chronic effects of liraglutide on progenitor cell proliferation, neuroblast differentiation and their subsequent differentiation into neurons in wild type and APP/PS-1 mice at different ages. APP/PS1 and their littermate controls, aged 3, 6, 12, 15 months were injected acutely or chronically with 25 nmol/kg liraglutide. Acute treatment with liraglutide showed an increase in cell proliferation in APP/PS1 mice, but not in controls whereas chronic treatment increased cell proliferation at all ages (BrdU and Ki67 markers). Moreover, numbers of immature neurons (DCX) were increased in both acute and chronic treated animals at all ages. Most newly generated cells differentiated into mature neurons (NeuN marker). A significant increase was observed with chronically treated 6, 12, 15 month APP/PS1 and WT groups. These results demonstrate that liraglutide, which is currently on the market as a treatment for type 2 diabetes (Victoza(TM)), increases neurogenesis, which may have beneficial effects in neurodegenerative disorders like AD.
NASA Astrophysics Data System (ADS)
Pałko, Krzysztof J.; Rogalski, Andrzej; Zieliński, Krzysztof; Glapiński, Jarosław; Kozarski, Maciej; Pałko, Tadeusz; Darowski, Marek
2007-01-01
Ventilation of the lungs involves the exchange of gases during inhalation and exhalation causing the movement of respiratory gases between alveolars and the atmosphere as a result of a pressure drop between alveolars and the atmosphere. During artificial ventilation what is most important is to keep specific mechanical parameters of the lungs such as total compliance of the respiratory system
Mesenchymal Stem Cells Preserve Working Memory in the 3xTg-AD Mouse Model of Alzheimer's Disease.
Ruzicka, Jiri; Kulijewicz-Nawrot, Magdalena; Rodrigez-Arellano, Jose Julio; Jendelova, Pavla; Sykova, Eva
2016-01-25
The transplantation of stem cells may have a therapeutic effect on the pathogenesis and progression of neurodegenerative disorders. In the present study, we transplanted human mesenchymal stem cells (MSCs) into the lateral ventricle of a triple transgenic mouse model of Alzheimer's disease (3xTg-AD) at the age of eight months. We evaluated spatial reference and working memory after MSC treatment and the possible underlying mechanisms, such as the influence of transplanted MSCs on neurogenesis in the subventricular zone (SVZ) and the expression levels of a 56 kDa oligomer of amyloid β (Aβ*56), glutamine synthetase (GS) and glutamate transporters (Glutamate aspartate transporter (GLAST) and Glutamate transporter-1 (GLT-1)) in the entorhinal and prefrontal cortices and the hippocampus. At 14 months of age we observed the preservation of working memory in MSC-treated 3xTg-AD mice, suggesting that such preservation might be due to the protective effect of MSCs on GS levels and the considerable downregulation of Aβ*56 levels in the entorhinal cortex. These changes were observed six months after transplantation, accompanied by clusters of proliferating cells in the SVZ. Since the grafted cells did not survive for the whole experimental period, it is likely that the observed effects could have been transiently more pronounced at earlier time points than at six months after cell application.
Comparison of Cone Model Parameters for Halo Coronal Mass Ejections
NASA Astrophysics Data System (ADS)
Na, Hyeonock; Moon, Y.-J.; Jang, Soojeong; Lee, Kyoung-Sun; Kim, Hae-Yeon
2013-11-01
Halo coronal mass ejections (HCMEs) are a major cause of geomagnetic storms, hence their three-dimensional structures are important for space weather. We compare three cone models: an elliptical-cone model, an ice-cream-cone model, and an asymmetric-cone model. These models allow us to determine three-dimensional parameters of HCMEs such as radial speed, angular width, and the angle [ γ] between sky plane and cone axis. We compare these parameters obtained from three models using 62 HCMEs observed by SOHO/LASCO from 2001 to 2002. Then we obtain the root-mean-square (RMS) error between the highest measured projection speeds and their calculated projection speeds from the cone models. As a result, we find that the radial speeds obtained from the models are well correlated with one another ( R > 0.8). The correlation coefficients between angular widths range from 0.1 to 0.48 and those between γ-values range from -0.08 to 0.47, which is much smaller than expected. The reason may be the different assumptions and methods. The RMS errors between the highest measured projection speeds and the highest estimated projection speeds of the elliptical-cone model, the ice-cream-cone model, and the asymmetric-cone model are 376 km s-1, 169 km s-1, and 152 km s-1. We obtain the correlation coefficients between the location from the models and the flare location ( R > 0.45). Finally, we discuss strengths and weaknesses of these models in terms of space-weather application.
Sterile particles from the flavor gauge model of masses
NASA Astrophysics Data System (ADS)
Smetana, Adam
2013-04-01
Our motivation is to study a dynamics which has the ambition to underlie models of the electroweak symmetry breaking via the condensation of known fermions. The right-handed neutrinos and the seesaw mechanism are necessary ingredients for viability of this scenario. The existence of right-handed neutrinos follows from theoretical consistence of a model based on dynamical flavor gauge symmetry breaking. The model is defined by a particular flavor representation setting of electroweakly charged fermions. Only finite number of versions of the model exists. They differ by the number and the flavor structure of the right-handed neutrino sector. We choose for inspection one of them, the non-minimal version with right-handed neutrinos in one sextet and four anti-triplet flavor representations. We show that a Majorana pairing of the sextet right-handed neutrinos is responsible for the flavor symmetry breaking and for the seesaw pattern of the neutrino mass matrix. The dynamically generated neutrino mass matrix spontaneously breaks the lepton number and the chiral sterility symmetry of the right-handed neutrino sector. As a result, a spectrum of majorons, neutrino composites, manifests. We study main characteristics of both massive sterile neutrinos and majorons.
Multiphase, multicomponent numerical model of bioventing with nonequilibrium mass exchange
Lang, J.R.; Rathfelder, K.M.; Abriola, L.M.
1995-12-31
A numerical model is presented that has been specifically designed to simulate the combined processes of soil vapor extraction and enhanced bioremediation known as bioventing. In this model, equations describing multiphase flow, multicomponent advective diffusive transport, and biodegradation are coupled. An entrapped organic residual, mobile gas and aqueous phases, and a reactive biophase are modeled. Components include n organic contaminants, oxygen, nitrogen, and water. Rate-limited mass exchange between the phases is simulated using linear driving force expressions. These expressions model volatilization and dissolution of the entrapped organic residual, rate-limited transport between the gas and aqueous phases, and rate-limited transport to the biophase. Monod-type kinetic expressions are employed to describe biophase utilization of substrates, the electron acceptor, and a limiting nutrient, as well as the growth of the microbial population. The coupled nonlinear governing equations are solved using a set iterative finite element method. Numerical simulations are presented for one-dimensional bench-scale column studies. These simulations illustrate the potential importance of biological degradation in the remediation of systems that are subject to mass transfer limitations.
Running-mass inflation model and primordial black holes
Drees, Manuel; Erfani, Encieh E-mail: erfani@th.physik.uni-bonn.de
2011-04-01
We revisit the question whether the running-mass inflation model allows the formation of Primordial Black Holes (PBHs) that are sufficiently long-lived to serve as candidates for Dark Matter. We incorporate recent cosmological data, including the WMAP 7-year results. Moreover, we include ''the running of the running'' of the spectral index of the power spectrum, as well as the renormalization group ''running of the running'' of the inflaton mass term. Our analysis indicates that formation of sufficiently heavy, and hence long-lived, PBHs still remains possible in this scenario. As a by-product, we show that the additional term in the inflaton potential still does not allow significant negative running of the spectral index.
Modelling aeolian sand transport using a dynamic mass balancing approach
NASA Astrophysics Data System (ADS)
Mayaud, Jerome R.; Bailey, Richard M.; Wiggs, Giles F. S.; Weaver, Corinne M.
2017-03-01
Knowledge of the changing rate of sediment flux in space and time is essential for quantifying surface erosion and deposition in desert landscapes. Whilst many aeolian studies have relied on time-averaged parameters such as wind velocity (U) and wind shear velocity (u*) to determine sediment flux, there is increasing field evidence that high-frequency turbulence is an important driving force behind the entrainment and transport of sand. At this scale of analysis, inertia in the saltation system causes changes in sediment transport to lag behind de/accelerations in flow. However, saltation inertia has yet to be incorporated into a functional sand transport model that can be used for predictive purposes. In this study, we present a new transport model that dynamically balances the sand mass being transported in the wind flow. The 'dynamic mass balance' (DMB) model we present accounts for high-frequency variations in the horizontal (u) component of wind flow, as saltation is most strongly associated with the positive u component of the wind. The performance of the DMB model is tested by fitting it to two field-derived (Namibia's Skeleton Coast) datasets of wind velocity and sediment transport: (i) a 10-min (10 Hz measurement resolution) dataset; (ii) a 2-h (1 Hz measurement resolution) dataset. The DMB model is shown to outperform two existing models that rely on time-averaged wind velocity data (e.g. Radok, 1977; Dong et al., 2003), when predicting sand transport over the two experiments. For all measurement averaging intervals presented in this study (10 Hz-10 min), the DMB model predicted total saltation count to within at least 0.48%, whereas the Radok and Dong models over- or underestimated total count by up to 5.50% and 20.53% respectively. The DMB model also produced more realistic (less 'peaky') time series of sand flux than the other two models, and a more accurate distribution of sand flux data. The best predictions of total sand transport are achieved using
Dynamical mass modeling of dispersion-supported dwarf galaxies
NASA Astrophysics Data System (ADS)
Wolf, Joseph
The currently favored cold dark matter cosmology (LCDM) has had much success in reproducing the large scale structure of the universe. However, on smaller scales there are some possible discrepancies when attempting to match galactic observations with properties of halos in dissipationless LCDM simulations. One advantageous method to test small scale simulations with observations is through dynamical mass modeling of nearby dwarf spheroidal galaxies (dSphs). The stellar tracers of dSphs are dispersion-supported, which poses a significant challenge in accurately deriving mass profiles. Unlike rotationally-supported galaxies, the dynamics of which can be well-approximated by one-dimensional physics, modeling dispersion-supported systems given only line-of-sight data results in a well-known degeneracy between the mass profile and the velocity dispersion anisotropy. The core of this dissertation is rooted in a new advancement which we have discovered: the range of solutions allowed by the mass-anisotropy degeneracy varies as a function of radius, with a considerable minimal near the deprojected half-light radius of almost all observed dispersion-supported galaxies. This finding allows for a wide range of applications in galaxy formation scenarios to be explored in an attempt to address, amongst other hypotheses, whether the LCDM framework needs to be modified in order to reproduce observations on the small scale. This thesis is comprised of both the derivation of this finding, and its applicability to all dispersion-supported systems, ranging from dwarfs galaxies consisting of a few hundred stars to systems of 'intracluster light', containing over a trillion stars. Rarely does one have the privilege of working with systems that span such a large range in luminosity (or any intrinsic property) in a short graduate career. Although the large applicability of this scale-free finding allows for discussion in many subfields, this thesis will mainly focus on one topic: dwarf
SPUF - a simple polyurethane foam mass loss and response model.
Hobbs, Michael L.; Lemmon, Gordon H.
2003-07-01
A Simple PolyUrethane Foam (SPUF) mass loss and response model has been developed to predict the behavior of unconfined, rigid, closed-cell, polyurethane foam-filled systems exposed to fire-like heat fluxes. The model, developed for the B61 and W80-0/1 fireset foam, is based on a simple two-step mass loss mechanism using distributed reaction rates. The initial reaction step assumes that the foam degrades into a primary gas and a reactive solid. The reactive solid subsequently degrades into a secondary gas. The SPUF decomposition model was implemented into the finite element (FE) heat conduction codes COYOTE [1] and CALORE [2], which support chemical kinetics and dynamic enclosure radiation using 'element death.' A discretization bias correction model was parameterized using elements with characteristic lengths ranging from 1-mm to 1-cm. Bias corrected solutions using the SPUF response model with large elements gave essentially the same results as grid independent solutions using 100-{micro}m elements. The SPUF discretization bias correction model can be used with 2D regular quadrilateral elements, 2D paved quadrilateral elements, 2D triangular elements, 3D regular hexahedral elements, 3D paved hexahedral elements, and 3D tetrahedron elements. Various effects to efficiently recalculate view factors were studied -- the element aspect ratio, the element death criterion, and a 'zombie' criterion. Most of the solutions using irregular, large elements were in agreement with the 100-{micro}m grid-independent solutions. The discretization bias correction model did not perform as well when the element aspect ratio exceeded 5:1 and the heated surface was on the shorter side of the element. For validation, SPUF predictions using various sizes and types of elements were compared to component-scale experiments of foam cylinders that were heated with lamps. The SPUF predictions of the decomposition front locations were compared to the front locations determined from real-time X
Gholami, Behnood; Norton, Isaiah; Eberlin, Livia S; Agar, Nathalie Y R
2013-05-01
Current clinical practice involves classification of biopsied or resected tumor tissue based on a histopathological evaluation by a neuropathologist. In this paper, we propose a method for computer-aided histopathological evaluation using mass spectrometry imaging. Specifically, mass spectrometry imaging can be used to acquire the chemical composition of a tissue section and, hence, provides a framework to study the molecular composition of the sample while preserving the morphological features in the tissue. The proposed classification framework uses statistical modeling to identify the tumor type associated with a given sample. In addition, if the tumor type for a given tissue sample is unknown or there is a great degree of uncertainty associated with assigning the tumor type to one of the known tumor models, then the algorithm rejects the given sample without classification. Due to the modular nature of the proposed framework, new tumor models can be added without the need to retrain the algorithm on all existing tumor models.
Thermodynamic models for bounding pressurant mass requirements of cryogenic tanks
NASA Technical Reports Server (NTRS)
Vandresar, Neil T.; Haberbusch, Mark S.
1994-01-01
Thermodynamic models have been formulated to predict lower and upper bounds for the mass of pressurant gas required to pressurize a cryogenic tank and then expel liquid from the tank. Limiting conditions are based on either thermal equilibrium or zero energy exchange between the pressurant gas and initial tank contents. The models are independent of gravity level and allow specification of autogenous or non-condensible pressurants. Partial liquid fill levels may be specified for initial and final conditions. Model predictions are shown to successfully bound results from limited normal-gravity tests with condensable and non-condensable pressurant gases. Representative maximum collapse factor maps are presented for liquid hydrogen to show the effects of initial and final fill level on the range of pressurant gas requirements. Maximum collapse factors occur for partial expulsions with large final liquid fill fractions.
NASA Astrophysics Data System (ADS)
Muller, J. R.; Harding, D. J.
2005-05-01
Within the Puget Sound region of Washington State, several lines of geological evidence suggest that the largest upper-crustal earthquake within the past 2500 years occurred on the Seattle fault system in A.D. 900. Constraining the rupture characteristics of this event is of singular importance in evaluating the upper-bound seismic hazard and tsunami threat posed by upper-crustal (non-subduction) earthquakes to the Puget Lowland region. It is only possible to model the fault geometry, slip distribution, and moment magnitude of this earthquake with a data set of the surface elevation changes caused by this event. Due to the historic age of this earthquake, we use elevations of an uplifted marine terrace, digitally extracted from LIDAR images, as a novel source of coseismic surface deformation data for this event. Ideal for this forested region, LIDAR images, acquired via airborne laser swath mapping (ALSM), offer a drastic improvement over earlier topographic mapping techniques due to its improved resolution and its ability to measure the ground surface beneath dense vegetative cover. The LIDAR images reveal a single uplifted terrace, dated to 1000 cal yr B.P. near Restoration Point, that is morphologically continuous along the southern shoreline of Bainbridge Island and is visible at comparable elevations within a 25 km by 12 km region encompassing coastlines of West Seattle, Bremerton, East Bremerton, Port Orchard, and Waterman Point. Considering sea level changes since A.D. 900, the maximum uplift magnitudes of shoreline inner edges approach nine meters and are located at the southernmost coastline of Bainbridge Island and the northern tip of Waterman Point, while tilt magnitudes are modest - approaching 0.1 degrees. Although the terrace is locally offset and tilted near the Toe Jam Hill and Waterman north-dipping, reverse fault scarps, the regional uplift pattern is a doubly-plunging antiform with steepened north limb, consistent with its location directly above
Local monitoring of post-treatment drinking water using bench-top mass spectrometers could identify target compounds in a mass spectral library. However, a terrorist might seek to incite greater hysteria by injecting or infusing a mixture of unanticipated compounds of unknown tox...
ON THE SINGLE-MASS MODEL OF THE VOCAL FOLDS
Howe, M. S.; McGowan, R. S.
2010-01-01
SUMMARY An analysis is made of the fluid-structure interactions necessary to support self-sustained oscillations of a single-mass mechanical model of the vocal folds subject to a nominally steady subglottal overpressure. The single-mass model of Fant and Flanagan is re-examined and an analytical representation of vortex shedding during ‘voiced speech’ is proposed that promotes cooperative, periodic excitation of the folds by the glottal flow. Positive feedback that sustains glottal oscillations is shown to occur during glottal contraction, when the flow separates from the ‘trailing edge’ of the glottis producing a low pressure ‘suction’ force that tends to pull the folds together. Details are worked out for flow that can be regarded as locally two-dimensional in the glottal region. Predictions of free-streamline theory are used to model the effects of quasi-static variations in the separation point on the glottal wall. Numerical predictions are presented to illustrate the waveform of the sound radiated towards the mouth from the glottis. The theory is easily modified to include feedback on the glottal flow of standing acoustic waves, both in the vocal tract beyond the glottis and in the subglottal region. PMID:20419082
A Unified Model of Low Mass X-ray Binaries
NASA Astrophysics Data System (ADS)
Balucinska-Church, M.; Church, M.
2014-07-01
We present a unified physical model of Low Mass X-ray Binaries explaining the basic Atoll and Z-track types of source. In all LMXB with luminosity above 1-2.10^{37} erg/s, we have a new fundamental result that the temperature of the Comptonizing ADC corona equals that of the neutron star, i.e. there is thermal equilibrium. This equilibrium explains the properties of the basic Banana State of Atoll sources. Below this luminosity, equilibrium breaks down, T_ADC rising towards 100 keV by an unknown heating mechanism, explaining the Island State. Above 5.10^{37} erg/s flaring begins in the GX-Atolls which we show is unstable nuclear burning. Above 1.10^{38} erg/s, LMXB are seen as Z-track sources. Flaring in these and the GX-Atolls occurs when the mass accretion rate to the neutron star falls to the critical value for unstable nuclear burning on the star. Below 2.10^{37} erg/s, a different unstable burning: X-ray bursting, takes over. We show that the Normal Branch of the Z-track consists simply of increasing mass accretion rate, as is the Banana State in Atolls. In the Horizontal Branch, a measured, strongly increasing radiation pressure of the neutron star disrupts the inner disk launching the relativistic jets seen on this branch.
Constraining models of accretion outbursts in low-mass YSOs}
NASA Astrophysics Data System (ADS)
Ninan, J. P.; Ojha, D. K.; Ghosh, S. K.; Bhatt, B. C.
Young low-mass stars, which are still undergoing accretion, have been found to undergo sudden outbursts in short period of time. They are believed to be due to sudden increase of typically ˜2 orders of magnitude in mass infall rate. Classically these objects are classified as FUors and EXors. FUors undergo long duration outbursts for several decades of typical magnitude δ m ˜ 4-5, while EXors undergo short duration outbursts for few months to years of typical magnitude δ m ˜ 2-3 and they might occur repeatedly. From the number count of FUors, it is estimated that every low-mass stars, on a minimum, undergo FUors kind of outburst in its early life. We present our study on three such rare outbursts in optical and near-infrared wavebands using long-term observations with 2-m Himalayan Chandra Telescope and 2-m IUCAA Girawali Observatory telescope. Using the current available models and the constrains on it, we can deduce to understand the physical process driving the outburst.
Neural mass model parameter identification for MEG/EEG
NASA Astrophysics Data System (ADS)
Kybic, Jan; Faugeras, Olivier; Clerc, Maureen; Papadopoulo, Théo
2007-03-01
Electroencephalography (EEG) and magnetoencephalography (MEG) have excellent time resolution. However, the poor spatial resolution and small number of sensors do not permit to reconstruct a general spatial activation pattern. Moreover, the low signal to noise ratio (SNR) makes accurate reconstruction of a time course also challenging. We therefore propose to use constrained reconstruction, modeling the relevant part of the brain using a neural mass model: There is a small number of zones that are considered as entities, neurons within a zone are assumed to be activated simultaneously. The location and spatial extend of the zones as well as the interzonal connection pattern can be determined from functional MRI (fMRI), diffusion tensor MRI (DTMRI), and other anatomical and brain mapping observation techniques. The observation model is linear, its deterministic part is known from EEG/MEG forward modeling, the statistics of the stochastic part can be estimated. The dynamics of the neural model is described by a moderate number of parameters that can be estimated from the recorded EEG/MEG data. We explicitly model the long-distance communication delays. Our parameters have physiological meaning and their plausible range is known. Since the problem is highly nonlinear, a quasi-Newton optimization method with random sampling and automatic success evaluation is used. The actual connection topology can be identified from several possibilities. The method was tested on synthetic data as well as on true MEG somatosensory-evoked field (SEF) data.
Using bioprocess stoichiometry to build a plant-wide mass balance based steady-state WWTP model.
Ekama, G A
2009-05-01
Steady-state models are useful for design of wastewater treatment plants (WWTPs) because they allow reactor sizes and interconnecting flows to be simply determined from explicit equations in terms of unit operation performance criteria. Once the overall WWTP scheme is established and the main system defining parameters of the individual unit operations estimated, dynamic models can be applied to the connected unit operations to refine their design and evaluate their performance under dynamic flow and load conditions. To model anaerobic digestion (AD) within plant-wide WWTP models, not only COD and nitrogen (N) but also carbon (C) fluxes entering the AD need to be defined. Current plant-wide models, like benchmark simulation model No 2 (BSM2), impose a C flux at the AD influent. In this paper, the COD and N mass balance steady-state models of activated sludge (AS) organics degradation, nitrification and denitrification (ND) and anaerobic (AD) and aerobic (AerD) digestion of wastewater sludge are extended and linked with bioprocess transformation stoichiometry to form C, H, O, N, chemical oxygen demand (COD) and charge mass balance based models so that also C (and H and O) can be tracked through the whole WWTP. By assigning a stoichiometric composition (x, y, z and a in C(x)H(y)O(z)N(a)) to each of the five main influent wastewater organic fractions and ammonia, these, and the products generated from them via the biological processes, are tracked through the WWTP. The model is applied to two theoretical case study WWTPs treating the same raw wastewater (WW) to the same final sludge residual biodegradable COD. It is demonstrated that much useful information can be generated with the relatively simple steady-state models to aid WWTP layout design and track the different products exiting the WWTP via the solid, liquid and gas streams, such as aerobic versus anaerobic digestion of waste activated sludge, N loads in recycle streams, methane production for energy recovery
Modelling the mass migration phenomena in partially frozen heat pipes
Keddy, M.D.; Merrigan, M.A.; Critchley, E.
1993-11-01
Liquid metal heat pipes operated at power throughputs well below their design point and with sink temperatures below the freezing temperature of the working fluid may fail as a result of the working fluid migrating to a cold region within the pipe, freezing there, and not returning to the evaporator section. Eventually, sufficient working fluid inventory may be lost to the cold region to cause a local dry-out condition in the evaporator. A joint experimental and analytical effort by the Air Force Phillips Laboratory and Los Alamos National Laboratory is underway to investigate this phenomena. This paper presents an analytical model developed to describes this phenomena. The model provides for analytic determination of heat pipe temperature profiles, freeze-front locations and mass migration rates.
Induced Monoculture in Axelrod Model with Clever Mass Media
NASA Astrophysics Data System (ADS)
Rodríguez, Arezky H.; Del Castillo-Mussot, M.; Vázquez, G. J.
A new model is proposed, in the context of Axelrod's model for the study of cultural dissemination, to include an external vector field (VF) which describes the effects of mass media on social systems. The VF acts over the whole system and it is characterized by two parameters: a nonnull overlap with each agent in the society and a confidence value of its information. Beyond a threshold value of the confidence, there is induced monocultural globalization of the system lined up with the VF. Below this value, the multicultural states are unstable and certain homogenization of the system is obtained in opposite line up according to that we have called negative publicity effect. Three regimes of behavior for the spread process of the VF information as a function of time are reported.
An ice-cream cone model for coronal mass ejections
NASA Astrophysics Data System (ADS)
Xue, X. H.; Wang, C. B.; Dou, X. K.
2005-08-01
In this study, we use an ice-cream cone model to analyze the geometrical and kinematical properties of the coronal mass ejections (CMEs). Assuming that in the early phase CMEs propagate with near-constant speed and angular width, some useful properties of CMEs, namely the radial speed (v), the angular width (α), and the location at the heliosphere, can be obtained considering the geometrical shapes of a CME as an ice-cream cone. This model is improved by (1) using an ice-cream cone to show the near real configuration of a CME, (2) determining the radial speed via fitting the projected speeds calculated from the height-time relation in different azimuthal angles, (3) not only applying to halo CMEs but also applying to nonhalo CMEs.
Mass transport measurements and modeling for chemical vapor infiltration
Starr, T.L.; Chiang, D.Y.; Fiadzo, O.G.; Hablutzel, N.
1997-12-01
This project involves experimental and modeling investigation of densification behavior and mass transport in fiber preforms and partially densified composites, and application of these results to chemical vapor infiltration (CVI) process modeling. This supports work on-going at ORNL in process development for fabrication of ceramic matrix composite (CMC) tubes. Tube-shaped composite preforms are fabricated at ORNL with Nextel{trademark} 312 fiber (3M Corporation, St. Paul, MN) by placing and compressing several layers of braided sleeve on a tubular mandrel. In terms of fiber architecture these preforms are significantly different than those made previously with Nicalon{trademark} fiber (Nippon Carbon Corp., Tokyo, Japan) square weave cloth. The authors have made microstructure and permeability measurements on several of these preforms and a few partially densified composites so as to better understand their densification behavior during CVI.
Nakajima, Akira; Aoyama, Yuki; Shin, Eun-Joo; Nam, Yunsung; Kim, Hyoung-Chun; Nagai, Taku; Yokosuka, Akihito; Mimaki, Yoshihiro; Yokoi, Tsuyoshi; Ohizumi, Yasushi; Yamada, Kiyofumi
2015-08-01
Alzheimer's disease (AD), the most common form of dementia among the elderly, is characterized by the progressive decline of cognitive function. Increasing evidence indicates that the production and accumulation of amyloid β (Aβ), particularly soluble Aβ oligomers, is central to the pathogenesis of AD. Our recent studies have demonstrated that nobiletin, a polymethoxylated flavone from citrus peels, ameliorates learning and memory impairment in olfactory-bulbectomized mice, amyloid precursor protein transgenic mice, NMDA receptor antagonist-treated mice, and senescence-accelerated mouse prone 8. Here, we present evidence that this natural compound improves cognitive impairment and reduces soluble Aβ levels in a triple transgenic mouse model of AD (3XTg-AD) that progressively develops amyloid plaques, neurofibrillary tangles, and cognitive impairments. Treatment with nobiletin (30 mg/kg) for 3 months reversed the impairment of short-term memory and recognition memory in 3XTg-AD mice. Our ELISA analysis also showed that nobiletin reduced the levels of soluble Aβ1-40 in the brain of 3XTg-AD mice. Furthermore, nobiletin reduced ROS levels in the hippocampus of 3XTg-AD as well as wild-type mice. These results suggest that this natural compound has potential to become a novel drug for the treatment and prevention of AD.
Ensemble Modeling of the 23 July 2012 Coronal Mass Ejection
NASA Astrophysics Data System (ADS)
Cash, M. D.; Biesecker, D. A.; Pizzo, V.; Koning, C. A.; Millward, G.; Arge, C. N.; Henney, C. J.; Odstrcil, D.
2015-10-01
On 23 July 2012 a significant and rapid coronal mass ejection (CME) was detected in situ by the Solar Terrestrial Relations Observatory (STEREO) A. This CME was unusual due to its extremely brief Sun-to-1 AU transit time of less than 21 h and its exceptionally high impact speed of 2246 km/s. If this CME had been Earth directed, it would have produced a significant geomagnetic storm with potentially serious consequences. To protect our ground- and space-based assets, there is a clear need to accurately forecast the arrival times of such events using realistic input parameters and models run in near real time. Using Wang-Sheely-Arge (WSA)-Enlil, the operational model currently employed at the NOAA Space Weather Prediction Center, we investigate the sensitivity of the 23 July CME event to model input parameters. Variations in the initial CME speed, angular width, and direction, as well as the ambient solar wind background, are investigated using an ensemble approach to study the effect on the predicted arrival time of the CME at STEREO A. Factors involved in the fast transit time of this large CME are discussed, and potential improvements to modeling such events with the WSA-Enlil model are presented.
Periodic mass extinctions and the Planet X model reconsidered
NASA Astrophysics Data System (ADS)
Whitmire, Daniel P.
2016-01-01
The 27 Myr period in the fossil extinction record has been confirmed in modern data bases dating back 500 Myr, which is twice the time interval of the original analysis from 30 years ago. The surprising regularity of this period has been used to reject the Nemesis model. A second model based on the Sun's vertical Galactic oscillations has been challenged on the basis of an inconsistency in period and phasing. The third astronomical model originally proposed to explain the periodicity is the Planet X model in which the period is associated with the perihelion precession of the inclined orbit of a trans-Neptunian planet. Recently, and unrelated to mass extinctions, a trans-Neptunian super-Earth planet has been proposed to explain the observation that the inner Oort cloud objects Sedna and 2012VP113 have perihelia that lie near the ecliptic plane. In this Letter, we reconsider the Planet X model in light of the confluence of the modern palaeontological and outer Solar system dynamical evidence.
Treviño-Garza, Consuelo; Estrada-Zúñiga, Cynthia M.; Mancillas-Adame, Leonardo; Villarreal-Martínez, Laura; Villarreal-Pérez, Jesús Z.; Rodríguez-Balderrama, Isaías; Montes-Tapia, Fernando F.; de la O. Cavazos, Manuel E.
2016-01-01
Objective: Most adipose tissue programming is realized in early life. Also, the postnatal three months, rather than the later phases of infancy, may be more relevant in the development of an adverse cardiometabolic risk profile. The adipokines phenotype, as a predictor of early-life weight gain, has been recently explored in cord blood. To determine whether in addition to leptin levels in cord samples, adiponectin, interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), resistin, plasminogen activator inhibitor-1 (PAI-1), and tumor necrosis factor alpha (TNF-α) levels improve weight gain prediction during the first three months of life. Methods: Adiponectin, IL-6, MCP-1, leptin, resistin, PAI-1, and TNF-α were measured by multiplex immunoassay in a subsample of 86 healthy term newborns. Results: Leptin levels significantly predicted weight gain at 3 months of follow-up (r2=0.09, p=0.006). In the multivariate analysis, including additional adipokines in the model, stepwise or all at once, did not increase the prediction of weight gain after the first three months of life. Conclusion: Adding adiponectin, IL-6, MCP-1, resistin, PAI-1, and TNF-α to the prediction model of weight gain in healthy newborns did not prove to be useful. It is probable that their relative contribution to weight gain is not important. Only leptin was relevant as a predictor of weight gain at the 3-month endpoint. PMID:27087431
NASA Astrophysics Data System (ADS)
Torma, Csaba; Giorgi, Filippo; Coppola, Erika
2015-05-01
We present an analysis of the added value (AV) of downscaling via regional climate model (RCM) nesting with respect to the driving global climate models (GCMs). We analyze ensembles of driving GCM and nested RCM (two resolutions, 0.44° and 0.11°) simulations for the late 20th and late 21st centuries from the CMIP5, EURO-CORDEX, and MED-CORDEX experiments, with a focus on the Alpine region. Different metrics of AV are investigated, measuring aspects of precipitation where substantial AV can be expected in mountainous terrains: spatial pattern of mean precipitation, daily precipitation intensity distribution, and daily precipitation extremes tails. Comparison with a high-quality, fine-scale (5 km) gridded observational data set shows substantial AV of RCM downscaling for all metrics selected, and results are mostly improved compared to the driving GCMs also when the RCM fields are upscaled at the scale of the GCM resolution. We also find consistent improvements in the high-resolution (0.11°) versus medium-resolution (0.44°) RCM simulations. Finally, we find that the RCM downscaling substantially modulates the GCM-produced precipitation change signal in future climate projections, particularly in terms of fine-scale spatial pattern associated with the complex topography of the region. Our results thus point to the important role that high-resolution nested RCMs can play in the study of climate change over areas characterized by complex topographical features.
Howey, Meghan C. L.; Palace, Michael W.; McMichael, Crystal H.
2016-01-01
Building monuments was one way that past societies reconfigured their landscapes in response to shifting social and ecological factors. Understanding the connections between those factors and monument construction is critical, especially when multiple types of monuments were constructed across the same landscape. Geospatial technologies enable past cultural activities and environmental variables to be examined together at large scales. Many geospatial modeling approaches, however, are not designed for presence-only (occurrence) data, which can be limiting given that many archaeological site records are presence only. We use maximum entropy modeling (MaxEnt), which works with presence-only data, to predict the distribution of monuments across large landscapes, and we analyze MaxEnt output to quantify the contributions of spatioenvironmental variables to predicted distributions. We apply our approach to co-occurring Late Precontact (ca. A.D. 1000–1600) monuments in Michigan: (i) mounds and (ii) earthwork enclosures. Many of these features have been destroyed by modern development, and therefore, we conducted archival research to develop our monument occurrence database. We modeled each monument type separately using the same input variables. Analyzing variable contribution to MaxEnt output, we show that mound and enclosure landscape suitability was driven by contrasting variables. Proximity to inland lakes was key to mound placement, and proximity to rivers was key to sacred enclosures. This juxtaposition suggests that mounds met local needs for resource procurement success, whereas enclosures filled broader regional needs for intergroup exchange and shared ritual. Our study shows how MaxEnt can be used to develop sophisticated models of past cultural processes, including monument building, with imperfect, limited, presence-only data. PMID:27330115
NASA Astrophysics Data System (ADS)
Ditmar, Pavel; Hashemi Farahani, Hassan; Encarnação, João.
2010-05-01
The satellite gravity mission GRACE (Gravity Recovery And Climate Experiment), which was launched in 2002, offers a unique opportunity to monitor tiny variations of the Earth's gravity and associated mass transport from space. In particular, the redistribution of water in the Earth's system can be traced in this way, which is critical for monitoring key climate indicators such as ice-sheet mass balance, terrestrial water-storage change, sea-level rise, and ocean circulation. Unfortunately, mass transport models based on GRACE data suffer from along-track artifacts. In order to suppress these artifacts, various filtering algorithms are applied to unconstrained GRACE-based models at the post-processing stage. However, any filtering not only suppresses noise but also distorts signals. Therefore, it is important to study the precise origin of the along-track artifacts in an attempt to mitigate them already at the level of unconstrained solutions. We identify two major causes of along-track artifacts: (1) the presence of low-frequency noise in GRACE data and (2) the observation principle of the GRACE satellite mission, which results in a poor sensitivity of the collected inter-satellite ranging data to the East-West gradient of the gravity field. According to our studies, an increased level of noise at low frequencies can be mostly explained by inaccuracies in the estimated orbits of GRACE satellites. To suppress this type of noise, we propose: (i) to use more advanced orbit determination procedures that allow deficiencies of available force models to be mitigated; (ii) to apply proper data weighting in the frequency domain, so that that the influence of frequencies with a large noise level is downweighted. As far as East-West gradients are concerned, we find it important to use the statistically optimal combination of GRACE inter-satellite ranging data with other observations (particularly, absolute positions of GRACE and CHAMP satellites). The added value of each of
Charge-to-Mass Dispersion Methods in Knockout-Ablation Fragmentation Models
NASA Astrophysics Data System (ADS)
Townsend, Lawrence; Burton, Krista; de Wet, Wouter
2014-09-01
Breakup of high-energy heavy ions in nuclear collisions is an important process in space radiation transport, shielding and risk assessment since the secondary particles produced by these collisions have ranges greater than their parent nucleus, and are damaging to humans and spacecraft components. This work uses a quantum-mechanical optical potential knockout-ablation model to estimate these collision cross sections in order to investigate differences in isotope and element production cross sections as a result of utilizing two different models of charge-to mass ratios for the projectile prefragments produced by the abrasion/knockout process. One model commonly used, a hypergeometric model, assumes that the distribution of abraded nucleons is completely uncorrelated. However, it permits some unrealistic distributions, such as removing all neutrons in the knockout stage, while leaving all protons intact. Another model, developed for use with a classical geometric, clean-cut abrasion model, is based upon the zero point vibrations of the giant dipole resonance of the fragmenting nucleus. In this work we compare fragment production cross section predictions using the two charge dispersion models with published experimental data. Breakup of high-energy heavy ions in nuclear collisions is an important process in space radiation transport, shielding and risk assessment since the secondary particles produced by these collisions have ranges greater than their parent nucleus, and are damaging to humans and spacecraft components. This work uses a quantum-mechanical optical potential knockout-ablation model to estimate these collision cross sections in order to investigate differences in isotope and element production cross sections as a result of utilizing two different models of charge-to mass ratios for the projectile prefragments produced by the abrasion/knockout process. One model commonly used, a hypergeometric model, assumes that the distribution of abraded nucleons is
Value Added in English Schools
ERIC Educational Resources Information Center
Ray, Andrew; McCormack, Tanya; Evans, Helen
2009-01-01
Value-added indicators are now a central part of school accountability in England, and value-added information is routinely used in school improvement at both the national and the local levels. This article describes the value-added models that are being used in the academic year 2007-8 by schools, parents, school inspectors, and other…
Modeling of Protein Binary Complexes Using Structural Mass Spectrometry Data
Amisha Kamal,J.; Chance, M.
2008-01-01
In this article, we describe a general approach to modeling the structure of binary protein complexes using structural mass spectrometry data combined with molecular docking. In the first step, hydroxyl radical mediated oxidative protein footprinting is used to identify residues that experience conformational reorganization due to binding or participate in the binding interface. In the second step, a three-dimensional atomic structure of the complex is derived by computational modeling. Homology modeling approaches are used to define the structures of the individual proteins if footprinting detects significant conformational reorganization as a function of complex formation. A three-dimensional model of the complex is constructed from these binary partners using the ClusPro program, which is composed of docking, energy filtering, and clustering steps. Footprinting data are used to incorporate constraints--positive and/or negative--in the docking step and are also used to decide the type of energy filter--electrostatics or desolvation--in the successive energy-filtering step. By using this approach, we examine the structure of a number of binary complexes of monomeric actin and compare the results to crystallographic data. Based on docking alone, a number of competing models with widely varying structures are observed, one of which is likely to agree with crystallographic data. When the docking steps are guided by footprinting data, accurate models emerge as top scoring. We demonstrate this method with the actin/gelsolin segment-1 complex. We also provide a structural model for the actin/cofilin complex using this approach which does not have a crystal or NMR structure.
Transformation of chloroform in model treatment wetlands: from mass balance to microbial analysis.
Chen, Yi; Wen, Yue; Zhou, Junwei; Zhou, Qi; Vymazal, Jan; Kuschk, Peter
2015-05-19
Chloroform is one of the common disinfection byproducts, which is not susceptible to degradation and poses great health concern. In this study, the chloroform removal efficiencies and contributions of sorption, microbial degradation, plant uptake, and volatilization were evaluated in six model constructed wetlands (CWs). The highest chloroform removal efficiency was achieved in litter-added CWs (99%), followed by planted (46-54%) and unplanted CWs (39%). Mass balance study revealed that sorption (73.5-81.2%) and microbial degradation (17.6-26.2%) were the main chloroform removal processes in litter-added CWs, and that sorption (53.6-66.1%) and plant uptake (25.3-36.2%) were the primary contributors to chloroform removal in planted CWs. Around 60% of chloroform got accumulated in the roots after plant uptake, and both transpiration and gas-phase transport were expected to be the drivers for the plant uptake. Sulfate-reducing bacteria and methanogens were found to be the key microorganisms for chloroform biodegradation through cometabolic dechlorination, and positive correlations were observed between functional genes (dsrA, mcrA) and biodegradation rates. Overall, this study suggests that wetland is an efficient ecosystem for sustainable chloroform removal, and that plant and litter can enhance the removal performance through root uptake and microbial degradation stimulation, respectively.
Rawat, Vivek K; Vidal-de-Miguel, Guillermo; Hogan, Christopher J
2015-10-21
Low field ion mobility spectrometry-mass spectrometry (IMS-MS) techniques exhibit low orthogonality, as inverse mobility often scales with mass to charge ratio. This inadequacy can be mitigated by adding vapor dopants, which may cluster with analyte ions and shift their mobilities by amounts independent of both mass and mobility of the ion. It is therefore important to understand the interactions of vapor dopants with ions, to better quantify the extent of dopant facilitated mobility shifts. Here, we develop predictive models of vapor dopant facilitated mobility shifts, and compare model calculations to measurements of mobility shifts for peptide ions exposed to variable gas phase concentrations of isopropanol. Mobility measurements were made at atmospheric pressure and room temperature using a recently developed transversal modulation ion mobility spectrometer (TMIMS). Results are compared to three separate models, wherein mobility shifts due to vapor dopants are attributed to changes in gas composition and (I) no vapor dopant uptake is assumed, (II) site-specific dopant uptake by the ion is assumed (approximated via a Langmuir adsorption model), and (III) site-unspecific dopant uptake by the ion is assumed (approximated via a classical nucleation model). We find that mobility shifts in peptide ions are in excellent agreement with model II, site-specific binding predictions. Conversely, mobility shifts of tetraalkylammonium ions from previous measurements were compared with these models and best agreement was found with model III predictions, i.e. site-unspecific dopant uptake.
Force Limited Random Vibration Test of TESS Camera Mass Model
NASA Technical Reports Server (NTRS)
Karlicek, Alexandra; Hwang, James Ho-Jin; Rey, Justin J.
2015-01-01
The Transiting Exoplanet Survey Satellite (TESS) is a spaceborne instrument consisting of four wide field-of-view-CCD cameras dedicated to the discovery of exoplanets around the brightest stars. As part of the environmental testing campaign, force limiting was used to simulate a realistic random vibration launch environment. While the force limit vibration test method is a standard approach used at multiple institutions including Jet Propulsion Laboratory (JPL), NASA Goddard Space Flight Center (GSFC), European Space Research and Technology Center (ESTEC), and Japan Aerospace Exploration Agency (JAXA), it is still difficult to find an actual implementation process in the literature. This paper describes the step-by-step process on how the force limit method was developed and applied on the TESS camera mass model. The process description includes the design of special fixtures to mount the test article for properly installing force transducers, development of the force spectral density using the semi-empirical method, estimation of the fuzzy factor (C2) based on the mass ratio between the supporting structure and the test article, subsequent validating of the C2 factor during the vibration test, and calculation of the C.G. accelerations using the Root Mean Square (RMS) reaction force in the spectral domain and the peak reaction force in the time domain.
MODELS OF NEPTUNE-MASS EXOPLANETS: EMERGENT FLUXES AND ALBEDOS
Spiegel, David S.; Burrows, Adam; Ibgui, Laurent; Hubeny, Ivan; Milsom, John A. E-mail: burrows@astro.princeton.ed E-mail: hubeny@as.arizona.ed
2010-01-20
There are now many known exoplanets with Msin i within a factor of 2 of Neptune's, including the transiting planets GJ 436b and HAT-P-11b. Planets in this mass range are different from their more massive cousins in several ways that are relevant to their radiative properties and thermal structures. By analogy with Neptune and Uranus, they are likely to have metal abundances that are an order of magnitude or more greater than those of larger, more massive planets. This increases their opacity, decreases Rayleigh scattering, and changes their equation of state. Furthermore, their smaller radii mean that fluxes from these planets are roughly an order of magnitude lower than those of otherwise identical gas giant planets. Here, we compute a range of plausible radiative equilibrium models of GJ 436b and HAT-P-11b. In addition, we explore the dependence of generic Neptune-mass planets on a range of physical properties, including their distance from their host stars, their metallicity, the spectral type of their stars, the redistribution of heat in their atmospheres, and the possible presence of additional optical opacity in their upper atmospheres.
Solutions of free higher spins in AdS
NASA Astrophysics Data System (ADS)
Lü, H.; Shao, Kai-Nan
2011-11-01
We consider free massive and massless higher integer spins in AdS backgrounds in general D dimensions. We obtain the solutions corresponding to the highest-weight state of the spin-ℓ representations of the SO (2 , D - 1) isometry groups. The solution for the spin-ℓ field is expressed recursively in terms of that for the spin- (ℓ - 1). Thus starting from the explicit spin-0, all the higher-spin solutions can be obtained. These solutions allow us to derive the generalized Breitenlohner-Freedman bound, and analyze the asymptotic falloffs. In particular, solutions with negative mass square in general have falloffs slower than those of the Schwarzschild AdS black holes in the AdS boundaries.
NASA Astrophysics Data System (ADS)
Lee, Y. H.; Adams, P. J.; Shindell, D. T.
2014-09-01
The TwO-Moment Aerosol Sectional microphysics model (TOMAS) has been integrated into the state-of-the-art general circulation model, GISS ModelE2. TOMAS has the flexibility to select a size resolution as well as the lower size cutoff. A computationally efficient version of TOMAS is used here, which has 15 size bins covering 3 nm to 10 μm aerosol dry diameter. For each bin, it simulates the total aerosol number concentration and mass concentrations of sulphate, pure elementary carbon (hydrophobic), mixed elemental carbon (hydrophilic), hydrophobic organic matter, hydrophilic organic matter, sea salt, mineral dust, ammonium, and aerosol-associated water. This paper provides a detailed description of the ModelE2-TOMAS model and evaluates the model against various observations including aerosol precursor gas concentrations, aerosol mass and number concentrations, and aerosol optical depths. Additionally, global budgets in ModelE2-TOMAS are compared with those of other global aerosol models, and the TOMAS model is compared to the default aerosol model in ModelE2, which is a bulk aerosol model. Overall, the ModelE2-TOMAS predictions are within the range of other global aerosol model predictions, and the model has a reasonable agreement with observations of sulphur species and other aerosol components as well as aerosol optical depth. However, ModelE2-TOMAS (as well as the bulk aerosol model) cannot capture the observed vertical distribution of sulphur dioxide over the Pacific Ocean possibly due to overly strong convective transport. The TOMAS model successfully captures observed aerosol number concentrations and cloud condensation nuclei concentrations. Anthropogenic aerosol burdens in the bulk aerosol model running in the same host model as TOMAS (ModelE2) differ by a few percent to a factor of 2 regionally, mainly due to differences in aerosol processes including deposition, cloud processing, and emission parameterizations. Larger differences are found for naturally
Lumped mass formulations for modeling flexible body systems
NASA Technical Reports Server (NTRS)
Rampalli, Rajiv
1989-01-01
The efforts of Mechanical Dynamics, Inc. in obtaining a general formulation for flexible bodies in a multibody setting are discussed. The efforts being supported by MDI, both in house and externally are summarized. The feasibility of using lumped mass approaches to modeling flexibility in a multibody dynamics context is examined. The kinematics and kinetics for a simple system consisting of two rigid bodies connected together by an elastic beam are developed in detail. Accuracy, efficiency and ease of use using this approach are some of the issues that are then looked at. The formulation is then generalized to a superelement containing several nodes and connecting several bodies. Superelement kinematics and kinetics equations are developed. The feasibility and effectiveness of the method is illustrated by the use of some examples illustrating phenomena common in the context of spacecraft motions.
Simulating tidal evolution and encounters with mass-spring models
NASA Astrophysics Data System (ADS)
Quillen, Alice C.; Frouard, Julien; Ebinger, Cynthia; Giannella, David; Efroimsky, Michael; Shaw, John
2016-05-01
We have recently found that we can directly simulate tidal spin down of viscoelastic objects using damped springs within an N-body code. But there is a 30% discrepancy between the torque analytically predicted and that numerically measured and we still have not identified the cause!Close tidal encounters among large planetesimals and moons were more common than impacts. Using a mass spring model within an N-body simulation, we simulate the deformation of the surface caused by a close tidal encounter and find tidal encounters can induce sufficient stress on the surface to cause brittle failure of an icy crust. Simulated fractures can extend a large fraction of the radius of body. Strong tidal encounters may be responsible for the formation of long graben complexes and chasmata in ancient terrain of icy moons such as Dione, Tethys, Ariel and Charon.
DiskJockey: Protoplanetary disk modeling for dynamical mass derivation
NASA Astrophysics Data System (ADS)
Czekala, Ian
2016-03-01
DiskJockey derives dynamical masses for T Tauri stars using the Keplerian motion of their circumstellar disks, applied to radio interferometric data from the Atacama Large Millimeter Array (ALMA) and the Submillimeter Array (SMA). The package relies on RADMC-3D (ascl:1202.015) to perform the radiative transfer of the disk model. DiskJockey is designed to work in a parallel environment where the calculations for each frequency channel can be distributed to independent processors. Due to the computationally expensive nature of the radiative synthesis, fitting sizable datasets (e.g., SMA and ALMA) will require a substantial amount of CPU cores to explore a posterior distribution in a reasonable timeframe.
System Modeling of Lunar Oxygen Production: Mass and Power Requirements
NASA Technical Reports Server (NTRS)
Steffen, Christopher J.; Freeh, Joshua E.; Linne, Diane L.; Faykus, Eric W.; Gallo, Christopher A.; Green, Robert D.
2007-01-01
A systems analysis tool for estimating the mass and power requirements for a lunar oxygen production facility is introduced. The individual modeling components involve the chemical processing and cryogenic storage subsystems needed to process a beneficiated regolith stream into liquid oxygen via ilmenite reduction. The power can be supplied from one of six different fission reactor-converter systems. A baseline system analysis, capable of producing 15 metric tons of oxygen per annum, is presented. The influence of reactor-converter choice was seen to have a small but measurable impact on the system configuration and performance. Finally, the mission concept of operations can have a substantial impact upon individual component size and power requirements.
Dynamical Models to Infer the Core Mass Fraction of Venus
NASA Astrophysics Data System (ADS)
Quintana, Elisa V.; Barclay, Thomas
2016-10-01
The uncompressed density of Venus is just a few percent lower than Earth's, however the nature of the interior core structure of Venus remains unclear. Employing state-of-the-art dynamical formation models that allow both accretion and collisional fragmentation, we perform hundreds of simulations of terrestrial planet growth around the Sun in the presence of the giant planets. For both Earth and Venus analogs, we quantify the iron-silicate ratios, water/volatile abundances and specific impact energies of all collisions that lead to their formation. Preliminary results suggest that the distributions of core mass fraction and water content are comparable among the Earth and Venus analogs, suggesting that Earth and Venus may indeed have formed with similar structures and compositions.
ERIC Educational Resources Information Center
Lopez-Martin, Esther; Kuosmanen, Timo; Gaviria, Jose Luis
2014-01-01
Value-added models are considered one of the best alternatives not only for accountability purposes but also to improve the school system itself. The estimates provided by these models measure the contribution of schools to students' academic progress, once the effect of other factors outside school control are eliminated. The functional form for…
Mass-conserving method of characteristics for streamflow modeling
Sikonia, W.G.
1989-01-01
A robust numerical model is presented for the computation of unsteady streamflow on steep river slopes. The one-dimensional model uses the method of characteristics on a specified space-time grid to solve the Saint-Venant equations. An additional continuity equation requirement on each space-time element provides greatly improved conservation of mass over traditional implementations of the method of characteristics on a fixed grid. The space-time geometry of the problem is described in a finite element setting. Hermite interpolation of channel parameters is used to avoid numerical difficulties that may occur with steep slopes due to discontinuities in the derivatives of data such as channel top width. Manning 's equation for friction slope can be modified by a factor to make the slope more appropriate for steep rivers. The standard Manning 's friction slope can also be used, if preferred. The computer model is not restricted to steep slopes, and applies as well to gently sloping streams. Two numerical examples support the mathematical approach and computational algorithm. (USGS)
Mass-conserving method of characteristics for streamflow modeling
Sikonia, William G.
1992-01-01
A robust numerical model is presented for the computation of unsteady streamflow on steep river slopes. The one-dimensional model uses the method of characteristics on a specified space-time grid to solve the Saint-Venant equations. An additional continuity equation requirement on each space-time element provides greatly improved conservation of mass over traditional implementations of the method of characteristics on a fixed grid. The space-time geometry of the problem is described in a finite element setting. Hermite interpolation of channel parameters is used to avoid numerical difficulties that may occur with steep slopes due to discontinuities in the derivatives of data such as channel top width. Manning's equation for friction slope can be modified by a factor to make the slope more appropriate for steep rivers. The standard Manning's friction slope can also be used, if preferred. The computer model is not restricted to steep slopes, and applies as well to gently sloping streams. Two numerical examples support the mathematical approach and computational algorithm.
Mass-spring model of a self-pulsating drop.
Antoine, Charles; Pimienta, Véronique
2013-12-03
Self-pulsating sessile drops are a striking example of the richness of far-from-equilibrium liquid/liquid systems. The complex dynamics of such systems is still not fully understood, and simple models are required to grasp the mechanisms at stake. In this article, we present a simple mass-spring mechanical model of the highly regular drop pulsations observed in Pimienta, V.; Brost, M.; Kovalchuk, N.; Bresch, S.; Steinbock, O. Complex shapes and dynamics of dissolving drops of dichloromethane. Angew. Chem., Int. Ed. 2011, 50, 10728-10731. We introduce an effective time-dependent spreading coefficient that sums up all of the forces (due to evaporation, solubilization, surfactant transfer, coffee ring effect, solutal and thermal Marangoni flows, drop elasticity, etc.) that pull or push the edge of a dichloromethane liquid lens, and we show how to account for the periodic rim breakup. The model is examined and compared against experimental observations. The spreading parts of the pulsations are very rapid and cannot be explained by a constant positive spreading coefficient or superspreading.
Modeling the Motion of an Increasing Mass System
ERIC Educational Resources Information Center
Kunkel, William; Harrington, Randal
2010-01-01
Problems on the dynamics of changing mass systems often call for the more general form of Newton's second law Fnet = dp/dt. These problems usually involve situations where the mass of the system decreases, such as in rocket propulsion. In contrast, this experiment examines a system where the mass "increases" at a constant rate and the net force…
Traveling waves for the mass in mass model of granular chains
Kevrekidis, Panayotis G.; Stefanov, Atanas G.; Xu, Haitao
2016-06-03
In this work, we consider the mass in mass (or mass with mass) system of granular chains, namely, a granular chain involving additionally an internal (or, respectively, external) resonator. For these chains, we rigorously establish that under suitable “anti-resonance” conditions connecting the mass of the resonator and the speed of the wave, bell-shaped traveling-wave solutions continue to exist in the system, in a way reminiscent of the results proven for the standard granular chain of elastic Hertzian contacts. Finally, we also numerically touch upon settings, where the conditions do not hold, illustrating, in line also with recent experimental work, that non-monotonic waves bearing non-vanishing tails may exist in the latter case.
Traveling waves for the mass in mass model of granular chains
Kevrekidis, Panayotis G.; Stefanov, Atanas G.; Xu, Haitao
2016-06-03
In this work, we consider the mass in mass (or mass with mass) system of granular chains, namely, a granular chain involving additionally an internal (or, respectively, external) resonator. For these chains, we rigorously establish that under suitable “anti-resonance” conditions connecting the mass of the resonator and the speed of the wave, bell-shaped traveling-wave solutions continue to exist in the system, in a way reminiscent of the results proven for the standard granular chain of elastic Hertzian contacts. Finally, we also numerically touch upon settings, where the conditions do not hold, illustrating, in line also with recent experimental work, thatmore » non-monotonic waves bearing non-vanishing tails may exist in the latter case.« less
Subgrid models for mass and thermal diffusion in turbulent mixing
Sharp, David H; Lim, Hyunkyung; Li, Xiao - Lin; Gilmm, James G
2008-01-01
We are concerned with the chaotic flow fields of turbulent mixing. Chaotic flow is found in an extreme form in multiply shocked Richtmyer-Meshkov unstable flows. The goal of a converged simulation for this problem is twofold: to obtain converged solutions for macro solution features, such as the trajectories of the principal shock waves, mixing zone edges, and mean densities and velocities within each phase, and also for such micro solution features as the joint probability distributions of the temperature and species concentration. We introduce parameterized subgrid models of mass and thermal diffusion, to define large eddy simulations (LES) that replicate the micro features observed in the direct numerical simulation (DNS). The Schmidt numbers and Prandtl numbers are chosen to represent typical liquid, gas and plasma parameter values. Our main result is to explore the variation of the Schmidt, Prandtl and Reynolds numbers by three orders of magnitude, and the mesh by a factor of 8 per linear dimension (up to 3200 cells per dimension), to allow exploration of both DNS and LES regimes and verification of the simulations for both macro and micro observables. We find mesh convergence for key properties describing the molecular level of mixing, including chemical reaction rates between the distinct fluid species. We find results nearly independent of Reynolds number for Re 300, 6000, 600K . Methodologically, the results are also new. In common with the shock capturing community, we allow and maintain sharp solution gradients, and we enhance these gradients through use of front tracking. In common with the turbulence modeling community, we include subgrid scale models with no adjustable parameters for LES. To the authors' knowledge, these two methodologies have not been previously combined. In contrast to both of these methodologies, our use of Front Tracking, with DNS or LES resolution of the momentum equation at or near the Kolmogorov scale, but without resolving the
NASA Astrophysics Data System (ADS)
Malik, Sham S.
2017-04-01
The fission fragment mass distribution followed by neutron emission is studied for the 208Pb (18O , f) reaction using the asymmetric two centre shell model. The measured mass distribution spectrum reveals new kind of systematics on shell structure and leads to an improved understanding of structure effects in nuclear fission. A detailed investigation of shell effects both in potential and cranking mass parameter has been carried out for explaining the observed fine structure dips (i.e., less probable distributions) corresponding to shell closure (Z = 50 and/or N = 82) of fission fragments and their complementary partners. The available energy states for the decay process are obtained by solving the Schrödinger equation and found that first-five eigenstates are sufficient in reproducing the observed mass distribution spectrum. An outcome of the asymmetric two centre shell model also completely favours the observed claim that ;the total number of emitted neutrons between correlated pairs of fission fragments should not exceed 6;. A complete observed spectrum is obtained by adding the mass distribution yields of all 6-neutron emission channels. This suggests a possible importance of extending these calculations to get new insight into an understanding of the dynamical behaviour of fragment formation in the fission process.
Device-Level Models Using Multi-Valley Effective Mass
NASA Astrophysics Data System (ADS)
Baczewski, Andrew D.; Frees, Adam; Gamble, John King; Gao, Xujiao; Jacobson, N. Tobias; Mitchell, John A.; Montaño, Inès; Muller, Richard P.; Nielsen, Erik
2015-03-01
Continued progress in quantum electronics depends critically on the availability of robust device-level modeling tools that capture a wide range of physics and effective mass theory (EMT) is one means of building such models. Recent developments in multi-valley EMT show quantitative agreement with more detailed atomistic tight-binding calculations of phosphorus donors in silicon (Gamble, et. al., arXiv:1408.3159). Leveraging existing PDE solvers, we are developing a framework in which this multi-valley EMT is coupled to an integrated device-level description of several experimentally active qubit technologies. Device-level simulations of quantum operations will be discussed, as well as the extraction of process matrices at this level of theory. The authors gratefully acknowledge support from the Sandia National Laboratories Truman Fellowship Program, which is funded by the Laboratory Directed Research and Development (LDRD) Program. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Security Administration under contract DE-AC04-94AL85000.
[Mass-balance ecopath model of Belbu Gulf ecosystem].
Chen, Zuozhi; Qiu, Yongsong; Jia, Xiaoping
2006-06-01
Based on the investigation of fishery resources and eco-environment in the Beibu Gulf of northern South China Sea from October 1997 to May 1999, and with EwE software, a mass-balance ecopath model of Beibu Gulf ecosystem was constructed, which consisted of 16 functional groups (boxes) including marine mammals and seabirds, each representing the organisms with similar roles in the food web, and covered the main trophic flow in Beibu Gulf ecosystem. The food web in Beibu Gulf ecosystem was dominated by detrital path, and benthic invertebrate played a significant role in transferring energy from detritus to higher trophic levels. Phytoplankton was the primary producer, and the fractional trophic levels ranged from 1.00 to 4.04, with marine mammals occupying the highest trophic level. By using network analysis, the system network was mapped into a linear food chain, and six discrete trophic levels were found, with a mean transfer efficiency of 12.3% from detritus, and 12.2% from primary producer within the ecosystem. The biomass density of commercially utilized species estimated by the model was 8.7 t x km(-2), and the bioproduction only accounted for 1.81% of the net primary production, which indicated that the system was still in developing status and instable.
Orientifolded locally AdS3 geometries
NASA Astrophysics Data System (ADS)
Loran, F.; Sheikh-Jabbari, M. M.
2011-01-01
Continuing the analysis of [Loran F and Sheikh-Jabbari M M 2010 Phys. Lett. B 693 184-7], we classify all locally AdS3 stationary axi-symmetric unorientable solutions to AdS3 Einstein gravity and show that they are obtained by applying certain orientifold projection on AdS3, BTZ or AdS3 self-dual orbifold, respectively, O-AdS3, O-BTZ and O-SDO geometries. Depending on the orientifold fixed surface, the O-surface, which is either a space-like 2D plane or a cylinder, or a light-like 2D plane or a cylinder, one can distinguish four distinct cases. For the space-like orientifold plane or cylinder cases, these geometries solve AdS3 Einstein equations and are hence locally AdS3 everywhere except at the O-surface, where there is a delta-function source. For the light-like cases, the geometry is a solution to Einstein equations even at the O-surface. We discuss the causal structure for static, extremal and general rotating O-BTZ and O-SDO cases as well as the geodesic motion on these geometries. We also discuss orientifolding Poincaré patch AdS3 and AdS2 geometries as a way to geodesic completion of these spaces and comment on the 2D CFT dual to the O-geometries.
NASA Astrophysics Data System (ADS)
Sempreviva, A. M.
2009-04-01
The EC FP6 Marie Curie Training Network "ModObs" http://www.modobs.windeng.net addresses the improvement of atmospheric boundary layer (ABL) models to investigate the interplay of processes at different temporal and spatial scales, and to explore the added value from new observation techniques. The overall goal is to bring young scientists to work together with experienced researchers in developing a better interaction amongst scientific communities of modelers and experimentalists, using a comprehensive approach to "Climate Change", "Clean Energy assessment" and "Environmental Policies", issues. This poster describes the work in progress of ten students, funded by the network, under the supervision of a team of scientists within atmospheric physics, engineering and satellite remote sensing and end-users such as companies in the private sector, all with the appropriate expertise to integrate the most advanced research methods and techniques in the following topics. MODELING: GLOBAL-TO-MESO SCALE: Analytical and process oriented numerical models will be used to study the interaction between the atmosphere and the ocean on a regional scale. Initial results indicate an interaction between the intensity of polar lows and the subsurface warm core often present in the Nordic Seas (11). The presence of waves, mainly swell, influence the MABL fluxes and turbulence structure. The regional and global wave effect on the atmosphere will be also studied and quantified (7) MESO-SCALE: Applicability of the planetary boundary layer (PBL) parametrizations in the meso-scale WRF model to marine atmospheric boundary layer (MABL) over the North Sea is investigated. The most suitable existing PBL parametrization will be additionally improved and used for downscaling North Sea past and future climates (2). Application of the meso-scale model (MM5 and WRF) for the wind energy in off-shore and coastal area. Set-up of the meso-scale model, post-processing and verification of the data from
Mass transfer model for two-layer TBP oxidation reactions
Laurinat, J.E.
1994-09-28
To prove that two-layer, TBP-nitric acid mixtures can be safely stored in the canyon evaporators, it must be demonstrated that a runaway reaction between TBP and nitric acid will not occur. Previous bench-scale experiments showed that, at typical evaporator temperatures, this reaction is endothermic and therefore cannot run away, due to the loss of heat from evaporation of water in the organic layer. However, the reaction would be exothermic and could run away if the small amount of water in the organic layer evaporates before the nitric acid in this layer is consumed by the reaction. Provided that there is enough water in the aqueous layer, this would occur if the organic layer is sufficiently thick so that the rate of loss of water by evaporation exceeds the rate of replenishment due to mixing with the aqueous layer. This report presents measurements of mass transfer rates for the mixing of water and butanol in two-layer, TBP-aqueous mixtures, where the top layer is primarily TBP and the bottom layer is comprised of water or aqueous salt solution. Mass transfer coefficients are derived for use in the modeling of two-layer TBP-nitric acid oxidation experiments. Three cases were investigated: (1) transfer of water into the TBP layer with sparging of both the aqueous and TBP layers, (2) transfer of water into the TBP layer with sparging of just the TBP layer, and (3) transfer of butanol into the aqueous layer with sparging of both layers. The TBP layer was comprised of 99% pure TBP (spiked with butanol for the butanol transfer experiments), and the aqueous layer was comprised of either water or an aluminum nitrate solution. The liquid layers were air sparged to simulate the mixing due to the evolution of gases generated by oxidation reactions. A plastic tube and a glass frit sparger were used to provide different size bubbles. Rates of mass transfer were measured using infrared spectrophotometers provided by SRTC/Analytical Development.
Impact of plant shoot architecture on leaf cooling: a coupled heat and mass transfer model
Bridge, L. J.; Franklin, K. A.; Homer, M. E.
2013-01-01
Plants display a range of striking architectural adaptations when grown at elevated temperatures. In the model plant Arabidopsis thaliana, these include elongation of petioles, and increased petiole and leaf angles from the soil surface. The potential physiological significance of these architectural changes remains speculative. We address this issue computationally by formulating a mathematical model and performing numerical simulations, testing the hypothesis that elongated and elevated plant configurations may reflect a leaf-cooling strategy. This sets in place a new basic model of plant water use and interaction with the surrounding air, which couples heat and mass transfer within a plant to water vapour diffusion in the air, using a transpiration term that depends on saturation, temperature and vapour concentration. A two-dimensional, multi-petiole shoot geometry is considered, with added leaf-blade shape detail. Our simulations show that increased petiole length and angle generally result in enhanced transpiration rates and reduced leaf temperatures in well-watered conditions. Furthermore, our computations also reveal plant configurations for which elongation may result in decreased transpiration rate owing to decreased leaf liquid saturation. We offer further qualitative and quantitative insights into the role of architectural parameters as key determinants of leaf-cooling capacity. PMID:23720538
NASA Astrophysics Data System (ADS)
Schoöner, Wolfgang; Böhm, Reinhard
2007-10-01
Stepwise linear regression models were calibrated against the measured mass balance of glaciers in the Austrian Alps for the prediction of specific annual net balance and summer balance from climatological and topographical input data. For estimation of winter mass balance, a simple ratio between the amount of winter precipitation and the measured winter balance was used. A ratio with a mean value of 2.0 and a standard deviation of 0.44 was derived from the sample of measured winter balances. Climate input data were taken from the HISTALP database which offers a homogenized data source that is outstanding in terms of its spatial and temporal coverage. Data from the Austrian glacier inventory were used as topographical input data. From the group of possible predictors summer air temperature, winter precipitation, summer snow precipitation and continentality (as defined from seasonal temperature variation) were selected as climatological driving forces in addition to lowest glacier elevation and area-weighted mean glacier elevation as topographical driving forces. Summer temperature explains 60% of the variance of summer mass balance and 39% of the variance of annual mass balance. Additional factors increase the explained variance by 22% for summer and 31% for annual net balance. The calibrated mass-balance model was used to reconstruct the mass balance of Hintereisferner and Vernagtferner back to 1800. Whereas the model performs well for Hintereisferner, it fails for some sub-periods for Vernagtferner due to the complicated flow dynamics of the glacier.
Jobson, Harvey E.; Keefer, Thomas N.
1979-01-01
A coupled flow-temperature model has been developed and verified for a 27.9-km reach of the Chattahoochee River between Buford Dam and Norcross, Ga. Flow in this reach of the Chattahoochee is continuous but highly regulated by Buford Dam, a flood-control and hydroelectric facility located near Buford, Ga. Calibration and verification utilized two sets of data collected under highly unsteady discharge conditions. Existing solution techniques, with certain minor improvements, were applied to verify the existing technology of flow and transport modeling. The linear, implicit finite-difference flow model was calibrated by use of a depth profile obtained at steady low flow and unsteady flow data obtained in March 1976. During the calibration period, the model was generally able to reproduce observed stages to within 0.15 m and discharges at less than 100 m 3 /s, to within 5 percent. Peak discharges of about 200 m 3 /s were under-estimated by about 20 percent. During the verification period, October 1975, the flow model reproduced observed stage changes to within about 0.15 m, and its timing and over-all performance was considered to be very good. Dye was added to the upstream end of the river reach at a constant rate while the river flow was highly unsteady. The numerical solution of either the conservative or nonconservative form of the mass-transport equation did an excellent job of simulating the observed concentrations of dye in the river. The temperature model was capable of predicting temperature changes through this reach of as large as 5.8?C with a RMS (root-mean-square) error of 0.32?C in October 1975 and 0.20?C in March 1976. Hydropulsation has a significant effect on the water temperature below Buford Dam. These effects are very complicated because they are quite dependent on the timing of the release with respect to both the time of day and past releases.
Coset construction of AdS particle dynamics
NASA Astrophysics Data System (ADS)
Heinze, Martin; Jorjadze, George; Megrelidze, Luka
2017-01-01
We analyze the dynamics of the AdSN+1 particle realized on the coset SO(2, N)/SO (1,N). Hamiltonian reduction provides the physical phase space in terms of the coadjoint orbit obtained by boosting a timelike element of 𝔰𝔬(2, N). We show equivalence of this approach to geometric quantization and to the SO(N) covariant oscillator description, for which the boost generators entail a complicated operator ordering. As an alternative scheme, we introduce dual oscillator variables and derive their algebra at the classical and the quantum levels. This simplifies the calculations of the commutators for the boost generators and leads to unitary irreducible representations of 𝔰𝔬(2, N) for all admissible values of the mass parameter. We furthermore discuss an SO(N) covariant supersymmetric extension of the oscillator quantization, with its realization for superparticles in AdS2 and AdS3 given by recent works.
Mass Distribution and Bar Formation in Growing Disk Galaxy Models
NASA Astrophysics Data System (ADS)
Berrier, Joel C.; Sellwood, J. A.
2016-11-01
We report idealized simulations that mimic the growth of galaxy disks embedded in responsive halos and bulges. The disks manifested an almost overwhelming tendency to form strong bars that we found very difficult to prevent. We found that fresh bars formed in growing disks after we had destroyed the original, indicating that bar formation also afflicts continued galaxy evolution, and not just the early stages of disk formation. This behavior raises still more insistently the previously unsolved question of how some galaxies avoid bars. Since our simulations included only collisionless star and halo particles, our findings may apply to gas-poor galaxies only; however, the conundrum persists for the substantial unbarred fraction of those galaxies. Our original objective was to study how internal dynamics rearranged the distribution of mass in the disk as a generalization of our earlier study with rigid spherical components. With difficulty, we were able to construct some models that were not strongly influenced by bars, and found that halo compression and angular momentum exchange with the disk did not alter our earlier conclusion that spiral activity is largely responsible for creating smooth density profiles and rotation curves.
A mass-flow model of ammonia emissions from UK livestock production
NASA Astrophysics Data System (ADS)
Webb, J.; Misselbrook, T. H.
This paper describes a mass-flow approach to estimating ammonia (NH 3) emissions from livestock production at the national scale. NH 3 is emitted from a pool of ammoniacal-N (TAN) in livestock excreta. This pool is not added to during manure management, but is depleted by losses as gaseous emissions and leachate and by immobilization in litter. At each stage of manure management, a proportion of TAN will be lost, mainly as NH 3, and the rest passed on to the next stage. This approach enables rapid and easy estimation of the consequences of abatement at one stage of manure management (upstream) on NH 3 losses at later stages of manure management (downstream). Such a model facilitates scenario analysis of abatement options and cost-curve production. Model output is most sensitive to variation in estimates of the length of the housing period for cattle. Thus, the collation of accurate data on factors such as the length of the housing period and other 'activity' data, are as important in compiling accurate inventories of national emissions as improving the accuracy of emission factors. Priorities for research should be to accurately quantify the relationship between NH 3 emissions from livestock buildings and the proportion of the day those buildings are occupied, and to characterize and quantify the transformations of N that take place during storage of litter-based manures.
ERIC Educational Resources Information Center
Franco, M. Suzanne; Seidel, Kent
2014-01-01
Value-added approaches for attributing student growth to teachers often use weighted estimates of building-level factors based on "typical" schools to represent a range of community, school, and other variables related to teacher and student work that are not easily measured directly. This study examines whether such estimates are likely…
General structure of democratic mass matrix of quark sector in E6 model
NASA Astrophysics Data System (ADS)
Ciftci, R.; ćiftci, A. K.
2016-03-01
An extension of the Standard Model (SM) fermion sector, which is inspired by the E6 Grand Unified Theory (GUT) model, might be a good candidate to explain a number of unanswered questions in SM. Existence of the isosinglet quarks might explain great mass difference of bottom and top quarks. Also, democracy on mass matrix elements is a natural approach in SM. In this study, we have given general structure of Democratic Mass Matrix (DMM) of quark sector in E6 model.
A global biogeochemical mass balance model for vanadium
Hope, B.K.
1995-12-31
Vanadium is a major trace metal in fossil fuels and combustion of these materials provides a significant source of vanadium in the environment. Close correlation exists between atmospheric vanadium concentration and fuel consumption, so that atmospheric vanadium pentoxide has been used as an indicator of human industrial activity. Little vanadium is retained in refined oil products, and vanadium contamination occurs as fallout from refining operations and burning of residual oils. This is the major cause for the approximate doubling of the environmental flux of vanadium as a result of human activity; other sources are products of coal combustion, leachates, and effluents from mining and milling of uranium and titanium. It was estimated in 1975 that the injection of vanadium into the atmosphere from anthropogenic sources equaled the input from natural sources. Such evidence that environmental levels of vanadium are increasing has raised concern over the injection of vanadium into the atmosphere from anthropogenic sources. A simple global mass balance model was developed to demonstrate the influence of anthropogenic vanadium on the global distribution of this trace metal. Vanadium in particulate emissions owing to man`s industrial activities were estimated to comprise {approx} 53% of total atmosphere vanadium loading and exceeded natural continental or volcanogenic dust by only a narrow margin. Oceanic deposition of vanadium adhering to anthropogenic particles was estimated to comprise {approx} 5% of total ocean vanadium loading. There is no suggestion that these inputs of anthropogenic vanadium pose a significant global environmental threat. It is entirely possible, however, that anthropogenic vanadium inputs could pose an environmental hazard given a more restricted area and a specific set of unfavorable circumstances.
Kinematics and mass modelling of M33: Hα observations
NASA Astrophysics Data System (ADS)
Kam, Z. S.; Carignan, C.; Chemin, L.; Amram, P.; Epinat, B.
2015-06-01
As part of a long-term project to revisit the kinematics and dynamics of the large disc galaxies of the Local Group, we present the first deep, wide-field (˜42 arcmin × 56 arcmin) 3D-spectroscopic survey of the ionized gas disc of Messier 33. Fabry-Perot interferometry has been used to map its Hα distribution and kinematics at unprecedented angular resolution (≲3 arcsec) and resolving power (˜12 600), with the 1.6 m telescope at the Observatoire du Mont Mégantic. The ionized gas distribution follows a complex, large-scale spiral structure, unsurprisingly coincident with the already-known spiral structures of the neutral and molecular gas discs. The kinematical analysis of the velocity field shows that the rotation centre of the Hα disc is distant from the photometric centre by ˜168 pc (sky-projected distance) and that the kinematical major-axis position angle and disc inclination are in excellent agreement with photometric values. The Hα rotation curve agrees very well with the H I rotation curves for 0 < R < 6.5 kpc, but the Hα velocities are 10-20 km s-1 higher for R > 6.5 kpc. The reason for this discrepancy is not well understood. The velocity dispersion profile is relatively flat around 16 km s-1, which is at the low end of velocity dispersions of nearby star-forming galactic discs. A strong relation is also found between the Hα velocity dispersion and the Hα intensity. Mass models were obtained using the Hα rotation curve but, as expected, the dark matter halo's parameters are not very well constrained since the optical rotation curve only extends out to 8 kpc.
NASA Astrophysics Data System (ADS)
Aas, Kjetil S.; Dunse, Thorben; Collier, Emily; Schuler, Thomas V.; Berntsen, Terje K.; Kohler, Jack; Luks, Bartłomiej
2016-05-01
In this study we simulate the climatic mass balance of Svalbard glaciers with a coupled atmosphere-glacier model with 3 km grid spacing, from September 2003 to September 2013. We find a mean specific net mass balance of -257 mm w.e. yr-1, corresponding to a mean annual mass loss of about 8.7 Gt, with large interannual variability. Our results are compared with a comprehensive set of mass balance, meteorological, and satellite measurements. Model temperature biases of 0.19 and -1.9 °C are found at two glacier automatic weather station sites. Simulated climatic mass balance is mostly within about 100 mm w.e. yr-1 of stake measurements, and simulated winter accumulation at the Austfonna ice cap shows mean absolute errors of 47 and 67 mm w.e. yr-1 when compared to radar-derived values for the selected years 2004 and 2006. Comparison of modeled surface height changes from 2003 to 2008, and satellite altimetry reveals good agreement in both mean values and regional differences. The largest deviations from observations are found for winter accumulation at Hansbreen (up to around 1000 mm w.e. yr-1), a site where sub-grid topography and wind redistribution of snow are important factors. Comparison with simulations using 9 km grid spacing reveal considerable differences on regional and local scales. In addition, 3 km grid spacing allows for a much more detailed comparison with observations than what is possible with 9 km grid spacing. Further decreasing the grid spacing to 1 km appears to be less significant, although in general precipitation amounts increase with resolution. Altogether, the model compares well with observations and offers possibilities for studying glacier climatic mass balance on Svalbard both historically as well as based on climate projections.
The Capra Research Program for Modelling Extreme Mass Ratio Inspirals
NASA Astrophysics Data System (ADS)
Thornburg, Jonathan
2011-02-01
Suppose a small compact object (black hole or neutron star) of mass m orbits a large black hole of mass M ≫ m. This system emits gravitational waves (GWs) that have a radiation-reaction effect on the particle's motion. EMRIs (extreme-mass-ratio inspirals) of this type will be important GW sources for LISA. To fully analyze these GWs, and to detect weaker sources also present in the LISA data stream, will require highly accurate EMRI GW templates. In this article I outline the ``Capra'' research program to try to model EMRIs and calculate their GWs ab initio, assuming only that m ≪ M and that the Einstein equations hold. Because m ≪ M the timescale for the particle's orbit to shrink is too long for a practical direct numerical integration of the Einstein equations, and because this orbit may be deep in the large black hole's strong-field region, a post-Newtonian approximation would be inaccurate. Instead, we treat the EMRI spacetime as a perturbation of the large black hole's ``background'' (Schwarzschild or Kerr) spacetime and use the methods of black-hole perturbation theory, expanding in the small parameter m/M. The particle's motion can be described either as the result of a radiation-reaction ``self-force'' acting in the background spacetime or as geodesic motion in a perturbed spacetime. Several different lines of reasoning lead to the (same) basic O(m/M) ``MiSaTaQuWa'' equations of motion for the particle. In particular, the MiSaTaQuWa equations can be derived by modelling the particle as either a point particle or a small Schwarzschild black hole. The latter is conceptually elegant, but the former is technically much simpler and (surprisingly for a nonlinear field theory such as general relativity) still yields correct results. Modelling the small body as a point particle, its own field is singular along the particle worldline, so it's difficult to formulate a meaningful ``perturbation'' theory or equations of motion there. Detweiler and Whiting found
Coronas-Sámano, G; Portillo, W; Beltrán Campos, V; Medina-Aguirre, G I; Paredes, R G; Diaz-Cintra, S
2014-07-14
Alzheimer׳s disease (AD) is characterized by a number of alterations including those in cognition and olfaction. An early symptom of AD is decreased olfactory ability, which may affect odor-guided behaviors. To test this possibility we evaluated alterations in sexual incentive motivation, sexual olfactory preference, sexual olfactory discrimination, nursing-relevant olfactory preference and olfactory discrimination in female mice. We tested 3xTg-AD (a triple transgenic model, which is a "knock in" of PS1M146V, APPSwe, and tauP300L) and wild type (WT) female mice when receptive (estrous) and non-receptive (anestrous). Subjects were divided into three groups of different ages: (1) 4-5 months, (2) 10-11 months, and (3) 16-18 months. In the sexual incentive motivation task, the receptive 3xTg-AD females showed no preference for a sexually active male at any age studied, in contrast to the WT females. In the sexual olfactory preference test, the receptive WT females were able to identify sexually active male secretions at all ages, but the oldest (16-18 months old) 3xTg-AD females could not. In addition, the oldest 3xTg-AD females showed no preference for nursing-relevant odors in dam secretions and were unable to discriminate between cinnamon and strawberry odors, indicating olfactory alterations. Thus, the present study suggests that the olfactory deficits in this mouse model are associated with changes in sexual incentive motivation and discrimination of food-related odors.
Dynamic Models of Instruments Using Rotating Unbalanced Masses
NASA Technical Reports Server (NTRS)
Hung, John Y.; Gallaspy, Jason M.; Bishop, Carlee A.
1998-01-01
The motion of telescopes, satellites, and other flight bodies have been controlled by various means in the past. For example, gimbal mounted devices can use electric motors to produce pointing and scanning motions. Reaction wheels, control moment gyros, and propellant-charged reaction jets are other technologies that have also been used. Each of these methods has its advantages, but all actuator systems used in a flight environment face the challenges of minimizing weight, reducing energy consumption, and maximizing reliability. Recently, Polites invented and patented the Rotating Unbalanced Mass (RUM) device as a means for generation scanning motion on flight experiments. RUM devices together with traditional servomechanisms have been successfully used to generate various scanning motions: linear, raster, and circular. The basic principle can be described: A RUM rotating at constant angular velocity exerts a cyclic centrifugal force on the instrument or main body, thus producing a periodic scanning motion. A system of RUM devices exerts no reaction forces on the main body, requires very little energy to rotate the RUMS, and is simple to construct. These are significant advantages over electric motors, reaction wheels, and control moment gyroscopes. Although the RUM device very easily produces scanning motion, an auxiliary control system has been required to maintain the proper orientation, or pointing of the main body. It has been suggested that RUM devices can be used to control pointing dynamics, as well as generate the desired periodic scanning motion. The idea is that the RUM velocity will not be kept constant, but will vary over the period of one RUM rotation. The thought is that the changing angular velocity produces a centrifugal force having time-varying magnitude and direction. The scope of this ongoing research project is to study the pointing control concept, and recommend a direction of study for advanced pointing control using only RUM devices. This
Diffusion and chaos from near AdS2 horizons
NASA Astrophysics Data System (ADS)
Blake, Mike; Donos, Aristomenis
2017-02-01
We calculate the thermal diffusivity D = κ/c ρ and butterfly velocity v B in holographic models that flow to AdS2 × R d fixed points in the infra-red. We show that both these quantities are governed by the same irrelevant deformation of AdS2 and hence establish a simple relationship between them. When this deformation corresponds to a universal dilaton mode of dimension Δ = 2 then this relationship is always given by D = v B 2 /(2 πT).
Warping, extra dimensions, and a slice of AdSd
NASA Astrophysics Data System (ADS)
McDonald, Kristian L.
2010-01-01
Inspired by the Randall-Sundrum framework we consider a number of phenomenologically relevant model-building questions on a slice of compactified AdSd for d>5. Such spaces are interesting as they enable one to realize the weak scale via warping. We perform the Kaluza-Klein (KK) reduction for gravitons and bulk vectors in these spaces, and for the case of AdS6 consider the KK spectrum of gauge scalars. We further obtain the KK towers for bulk fermions on a slice of AdS7 and AdS9 and show that the Randall-Sundrum approach to flavor generalizes to these spaces with the localization of chiral zero-mode fermions controlled by their bulk Dirac mass parameters. However, for the phenomenologically interesting case where the transverse radius is R-1˜TeV, we show that bulk standard model fields are not viable due to a resulting volume suppression of the gauge-coupling constants. A similar suppression occurs for the case of UV localization. Thus it seems that the standard model fields should be confined to the infrared brane in such spaces. Sterile fields and extended gauge sectors may propagate in the bulk, with the gauge-coupling volume suppression experienced by the latter motivating a weak coupling to standard model fields. We also discuss some issues regarding the effective 4D theory description in these spaces.
Implications of improved Higgs mass calculations for supersymmetric models.
Buchmueller, O; Dolan, M J; Ellis, J; Hahn, T; Heinemeyer, S; Hollik, W; Marrouche, J; Olive, K A; Rzehak, H; de Vries, K J; Weiglein, G
We discuss the allowed parameter spaces of supersymmetric scenarios in light of improved Higgs mass predictions provided by FeynHiggs 2.10.0. The Higgs mass predictions combine Feynman-diagrammatic results with a resummation of leading and subleading logarithmic corrections from the stop/top sector, which yield a significant improvement in the region of large stop masses. Scans in the pMSSM parameter space show that, for given values of the soft supersymmetry-breaking parameters, the new logarithmic contributions beyond the two-loop order implemented in FeynHiggs tend to give larger values of the light CP-even Higgs mass, [Formula: see text], in the region of large stop masses than previous predictions that were based on a fixed-order Feynman-diagrammatic result, though the differences are generally consistent with the previous estimates of theoretical uncertainties. We re-analyse the parameter spaces of the CMSSM, NUHM1 and NUHM2, taking into account also the constraints from CMS and LHCb measurements of [Formula: see text]and ATLAS searches for [Formula: see text] events using 20/fb of LHC data at 8 TeV. Within the CMSSM, the Higgs mass constraint disfavours [Formula: see text], though not in the NUHM1 or NUHM2.
Perry, Russell W.; Plumb, John M.; Huntington, Charles
2015-01-01
To estimate the parameters that govern mass- and temperature-dependent growth, we conducted a meta-analysis of existing growth data from juvenile Chinook Salmon Oncorhynchus tshawytscha that were fed an ad libitum ration of a pelleted diet. Although the growth of juvenile Chinook Salmon has been well studied, research has focused on a single population, a narrow range of fish sizes, or a narrow range of temperatures. Therefore, we incorporated the Ratkowsky model for temperature-dependent growth into an allometric growth model; this model was then fitted to growth data from 11 data sources representing nine populations of juvenile Chinook Salmon. The model fit the growth data well, explaining 98% of the variation in final mass. The estimated allometric mass exponent (b) was 0.338 (SE = 0.025), similar to estimates reported for other salmonids. This estimate of b will be particularly useful for estimating mass-standardized growth rates of juvenile Chinook Salmon. In addition, the lower thermal limit, optimal temperature, and upper thermal limit for growth were estimated to be 1.8°C (SE = 0.63°C), 19.0°C (SE = 0.27°C), and 24.9°C (SE = 0.02°C), respectively. By taking a meta-analytical approach, we were able to provide a growth model that is applicable across populations of juvenile Chinook Salmon receiving an ad libitum ration of a pelleted diet.
Predictive model for radiatively induced neutrino masses and mixings with dark matter.
Gustafsson, Michael; No, Jose M; Rivera, Maximiliano A
2013-05-24
A minimal extension of the standard model to naturally generate small neutrino masses and provide a dark matter candidate is proposed. The dark matter particle is part of a new scalar doublet field that plays a crucial role in radiatively generating neutrino masses. The symmetry that stabilizes the dark matter also suppresses neutrino masses to appear first at three-loop level. Without the need of right-handed neutrinos or other very heavy new fields, this offers an attractive explanation of the hierarchy between the electroweak and neutrino mass scales. The model has distinct verifiable predictions for the neutrino masses, flavor mixing angles, colliders, and dark matter signals.
NASA Astrophysics Data System (ADS)
Callebaut, Nele; Gubser, Steven S.; Samberg, Andreas; Toldo, Chiara
2015-11-01
We study segmented strings in flat space and in AdS 3. In flat space, these well known classical motions describe strings which at any instant of time are piecewise linear. In AdS 3, the worldsheet is composed of faces each of which is a region bounded by null geodesics in an AdS 2 subspace of AdS 3. The time evolution can be described by specifying the null geodesic motion of kinks in the string at which two segments are joined. The outcome of collisions of kinks on the worldsheet can be worked out essentially using considerations of causality. We study several examples of closed segmented strings in AdS 3 and find an unexpected quasi-periodic behavior. We also work out a WKB analysis of quantum states of yo-yo strings in AdS 5 and find a logarithmic term reminiscent of the logarithmic twist of string states on the leading Regge trajectory.
The Spatial Resolution of Mass Distributions Required For Forward Gravity Field Modelling
NASA Astrophysics Data System (ADS)
Kuhn, M.
In forward gravity field modelling all parameters can be derived from the Earth's mass distribution using Newton's law of gravitation. Now more and more information on the Earth's mass distribution is available such, as fine digital elevation models, dig- ital density models and models of the crustal thickness. Apart from the theoretical restriction that the Earth's mass distribution will never be completely known, this con- tribution studies the spatial resolution of different mass distributions of the Earth's crust in view of deriving gravity field quantities in a forward model with a given accu- racy. Here the influence of the topographic masses, mass anomalies above the geoid, compensation masses and crustal mass anomalies below the geoid will be studied by the spherical harmonic expansion of their corresponding potential effect. Using New- ton's law, these spherical harmonic expansions can be expressed directly by that of height, depth or density of the corresponding mass distributions. This representation is well suited to study the spectral sensitivity of different mass distributions on gravity field quantities. Numerical results will be presented in order to give an optimal data spacing required to forward model the gravity field of the Earth to a desired accuracy.
EVOLUTIONARY MODELS OF SUPER-EARTHS AND MINI-NEPTUNES INCORPORATING COOLING AND MASS LOSS
Howe, Alex R.; Burrows, Adam E-mail: burrows@astro.princeton.edu
2015-08-01
We construct models of the structural evolution of super-Earth- and mini-Neptune-type exoplanets with H{sub 2}–He envelopes, incorporating radiative cooling and XUV-driven mass loss. We conduct a parameter study of these models, focusing on initial mass, radius, and envelope mass fractions, as well as orbital distance, metallicity, and the specific prescription for mass loss. From these calculations, we investigate how the observed masses and radii of exoplanets today relate to the distribution of their initial conditions. Orbital distance and the initial envelope mass fraction are the most important factors determining planetary evolution, particularly radius evolution. Initial mass also becomes important below a “turnoff mass,” which varies with orbital distance, with mass–radius curves being approximately flat for higher masses. Initial radius is the least important parameter we study, with very little difference between the hot start and cold start limits after an age of 100 Myr. Model sets with no mass loss fail to produce results consistent with observations, but a plausible range of mass-loss scenarios is allowed. In addition, we present scenarios for the formation of the Kepler-11 planets. Our best fit to observations of Kepler-11b and Kepler-11c involves formation beyond the snow line, after which they moved inward, circularized, and underwent a reduced degree of mass loss.
MULTI-DIMENSIONAL MODELS FOR DOUBLE DETONATION IN SUB-CHANDRASEKHAR MASS WHITE DWARFS
Moll, R.; Woosley, S. E.
2013-09-10
Using two-dimensional and three-dimensional simulations, we study the ''robustness'' of the double detonation scenario for Type Ia supernovae, in which a detonation in the helium shell of a carbon-oxygen white dwarf induces a secondary detonation in the underlying core. We find that a helium detonation cannot easily descend into the core unless it commences (artificially) well above the hottest layer calculated for the helium shell in current presupernova models. Compressional waves induced by the sliding helium detonation, however, robustly generate hot spots which trigger a detonation in the core. Our simulations show that this is true even for non-axisymmetric initial conditions. If the helium is ignited at multiple points, then the internal waves can pass through one another or be reflected, but this added complexity does not defeat the generation of the hot spot. The ignition of very low-mass helium shells depends on whether a thermonuclear runaway can simultaneously commence in a sufficiently large region.
Applying a model of orographic precipitation to improve mass balance modeling of the Juneau Icefield
NASA Astrophysics Data System (ADS)
Roth, Aurora
Mass loss from glaciers in Southeast Alaska is expected to alter downstream environmental conditions such as streamflow patterns, riverine and coastal ecological systems, and ocean properties. To investigate these potential changes under future climate scenarios, accurate climate data are needed to drive glacier mass balance models. However, assessing and modeling precipitation in mountainous regions remains a major challenge in glacier mass balance modeling. We have used a linear theory of orographic precipitation model (LT model) to downscale precipitation from both the Weather Research and Forecasting (WRF) model and the European Centre for Medium-Range Weather Forecasts interim reanalysis (ERA-Interim) to the Juneau Icefield, one of the largest icefields in North America (4149 km2), over the period 1979-2013. The LT model is physically-based, combining airflow dynamics and simple cloud microphysics to simulate precipitation in complex terrain. Cloud microphysics is parameterized as a function of user-defined snow and rain fall speeds which are then used to calculate the cloud time delay, tau, at every time step. We established a model reference run using literature values of snow fall speed and rain fall speed. The model was run using a 1 km digital elevation model and 6 hour timesteps. Due to a lack of precipitation observations, we validated the model with point net accumulation observations along an 8.5 km transect on Taku glacier, one of the largest and best-studied outlet glaciers of the icefield. The observations occurred in late July of 1998, 2004, 2005, 2010, and 2011. We extracted the snow portion from the modeled precipitation and accounted for melt using a temperature-index model prior to comparing results to the observations. The latter was necessary since the observations were taken when substantial melt of the winter snow cover had occurred. The results of the reference run show reasonable agreement with the available glaciological observations (r
IMPROVED MODELING OF THE MASS DISTRIBUTION OF DISK GALAXIES BY THE EINASTO HALO MODEL
Chemin, Laurent; De Blok, W. J. G.; Mamon, Gary A. E-mail: edeblok@ast.uct.ac.za
2011-10-15
Analysis of the rotation curves (RCs) of spiral galaxies provides an efficient diagnostic for studying the properties of dark matter halos and their relations with baryonic material. Since the cored pseudo-isothermal (Iso) model usually provides a better description of observed RCs than does the cuspy Navarro-Frenk-White (NFW) model, there have been concerns that the {Lambda}CDM primordial density fluctuation spectrum may not be the correct one. We have modeled the RCs of galaxies from The H I Nearby Galaxy Survey (THINGS) with the Einasto halo model, which has emerged as the best-fitting model of the halos arising in dissipationless cosmological N-body simulations. We find that the RCs are significantly better fit with the Einasto halo than with either Iso or NFW halo models. In our best-fit Einasto models, the radius of density slope -2 and the density at this radius are highly correlated. The Einasto index, which controls the overall shape of the density profile, is near unity on average for intermediate and low mass halos. This is not in agreement with the predictions from {Lambda}CDM simulations. The indices of the most massive halos are in rough agreement with those cosmological simulations and appear correlated with the halo virial mass. We find that a typical Einasto density profile declines more strongly in its outermost parts than any of the Iso or NFW models whereas it is relatively shallow in its innermost regions. The core nature of those regions of halos thus extends the cusp-core controversy found for the NFW model with low surface density galaxies to the Einasto halo with more massive galaxies like those of THINGS. The Einasto concentrations decrease as a function of halo mass, in agreement with trends seen in numerical simulations. However, they are generally smaller than values expected for simulated Einasto halos. We thus find that, so far, the Einasto halo model provides the best match to the observed RCs and can therefore be considered as a new
NASA Astrophysics Data System (ADS)
Taktakishvili, A.; Pulkkinen, A.; MacNeice, P. J.; Kuznetsova, M. M.; Hesse, M.; Odstrcil, D.
2010-12-01
The largest geomagnetic storms are caused by the solar coronal mass ejections (CMEs). In our previous paper (Taktakishvili et al., [2009]) we reported the results of modeling 14 selected well observed strong halo CME events using the WSA/ENLIL cone model combination. In that study the cone model input parameters were obtained from white-light coronagraph images of the CME events using the analytical method developed by Xie et al [ 2004 ]. This work verified that coronagraph input gives reasonably good results for the CME arrival time prediction. Recently Pulkkinen et al., [2009] developed a novel method for automatic determination of cone model parameters. This approach combines standard image processing techniques and a novel inversion routine to derive the cone parameters. The present work extends our previous studies by addressing more CME events. The approach in this paper is different from our previous study: we started from addressing 36 particularly strong geomagnetic storms, then tried to associate them with particular CMEs using SOHO/LASCO catalogue, and finally modeled these CMEs using WSA/ENLIL cone model. This approach is addressing space weather forecasting and operational needs. We employed both analytical and automatic methods to determine cone model input parameters. We examined the CME arrival times and magnitude of impact at 1 AU for both techniques. The results of the simulations were compared with the ACE satellite observations. This comparison demonstrated that WSA/ENLIL model combination with coronograph input gives reasonably good results for the CME arrival times for this set of "geo-effective" CME events as well. References: Taktakishvili, A., M. Kuznetsova, P. Macneice, M. Hesse, L. Rastaetter, A. Pulkkinen, A. Chulaki and D. Odstrci (2009), Validation of the coronal mass ejection predictions at the Earth orbit estimated by ENLIL heliosphere cone model, Space Weather,7, S03004,doi10.1029/2008SW000448. Xie, H., L. Ofman, and G. Lawrence
Farside lunar gravity from a mass point model
NASA Technical Reports Server (NTRS)
Ananda, M.
1975-01-01
A mass point representation of the lunar gravity field was determined from the long-period orbital variations of the Apollo 15 and 16 subsatellites and Lunar Orbiter V. A radial acceleration contour map, evaluated at 100 km altitude from the lunar surface, shows that the nearside is in close agreement with the result derived from the line of sight method by Muller and Sjogren. The farside map shows the highland regions as broad positive gravity anomaly areas and the basins such as Korolev, Hertzsprung, Moscoviense, Mendeleev, and Tsiolkovsky as localized, negative gravity anomaly regions. The farside map has a first-order agreement with the result derived from the harmonic field method by Ferrari. The mass points analysis indicates that the nearside is almost all negative gravity anomaly regions except for the known positive mass anomaly basins (mascons) and the farside is almost all positive gravity anomaly regions except for some localized negative areas near the basins.
NASA Astrophysics Data System (ADS)
Hiemstra, Tjisse; Van Riemsdijk, Willem H.
2009-08-01
A multisite surface complexation (MUSIC) model for ferrihydrite (Fh) has been developed. The surface structure and composition of Fh nanoparticles are described in relation to ion binding and surface charge development. The site densities of the various reactive surface groups, the molar mass, the mass density, the specific surface area, and the particle size are quantified. As derived theoretically, molecular mass and mass density of nanoparticles will depend on the types of surface groups and the corresponding site densities and will vary with particle size and surface area because of a relatively large contribution of the surface groups in comparison to the mineral core of nanoparticles. The nano-sized (˜2.6 nm) particles of freshly prepared 2-line Fh as a whole have an increased molar mass of M ˜ 101 ± 2 g/mol Fe, a reduced mass density of ˜3.5 ± 0.1 g/cm 3, both relatively to the mineral core. The specific surface area is ˜650 m 2/g. Six-line Fh (5-6 nm) has a molar mass of M ˜ 94 ± 2 g/mol, a mass density of ˜3.9 ± 0.1 g/cm 3, and a surface area of ˜280 ± 30 m 2/g. Data analysis shows that the mineral core of Fh has an average chemical composition very close to FeOOH with M ˜ 89 g/mol. The mineral core has a mass density around ˜4.15 ± 0.1 g/cm 3, which is between that of feroxyhyte, goethite, and lepidocrocite. These results can be used to constrain structural models for Fh. Singly-coordinated surface groups dominate the surface of ferrihydrite (˜6.0 ± 0.5 nm -2). These groups can be present in two structural configurations. In pairs, the groups either form the edge of a single Fe-octahedron (˜2.5 nm -2) or are present at a single corner (˜3.5 nm -2) of two adjacent Fe octahedra. These configurations can form bidentate surface complexes by edge- and double-corner sharing, respectively, and may therefore respond differently to the binding of ions such as uranyl, carbonate, arsenite, phosphate, and others. The relatively low PZC of
Mode Selection Techniques in Variable Mass Flexible Body Modeling
NASA Technical Reports Server (NTRS)
Quiocho, Leslie J.; Ghosh, Tushar K.; Frenkel, David; Huynh, An
2010-01-01
In developing a flexible body spacecraft simulation for the Launch Abort System of the Orion vehicle, when a rapid mass depletion takes place, the dynamics problem with time varying eigenmodes had to be addressed. Three different techniques were implemented, with different trade-offs made between performance and fidelity. A number of technical issues had to be solved in the process. This paper covers the background of the variable mass flexibility problem, the three approaches to simulating it, and the technical issues that were solved in formulating and implementing them.
Constraints on texture zero and cofactor zero models for neutrino mass
Whisnant, K.; Liao, Jiajun; Marfatia, D.
2014-06-24
Imposing a texture or cofactor zero on the neutrino mass matrix reduces the number of independent parameters from nine to seven. Since five parameters have been measured, only two independent parameters would remain in such models. We find the allowed regions for single texture zero and single cofactor zero models. We also find strong similarities between single texture zero models with one mass hierarchy and single cofactor zero models with the opposite mass hierarchy. We show that this correspondence can be generalized to texture-zero and cofactor-zero models with the same homogeneous costraints on the elements and cofactors.
NASA Astrophysics Data System (ADS)
Ehrlich, R.
2016-12-01
Evidence is presented in support of an unconventional 3 + 3 model of the neutrino mass eigenstates with specific m2 > 0 and m2 < 0 masses. The two large m2 > 0 masses of the model were originally suggested based on a SN 1987A analysis, and they were further supported by several dark matter fits. The new evidence for one of the m2 > 0 mass values comes from an analysis of published data from the three most precise tritium β - decay experiments. The KATRIN experiment by virtue of a unique 3-part signature should either confirm or reject the model in its entirety.
Consumption of Mass Communication--Construction of a Model on Information Consumption Behaviour.
ERIC Educational Resources Information Center
Sepstrup, Preben
A general conceptual model on the consumption of information is introduced. Information as the output of the mass media is treated as a product, and a model on the consumption of this product is developed by merging elements from consumer behavior theory and mass communication theory. Chapter I gives basic assumptions about the individual and the…
A Communication Model for Teaching a Course in Mass Media and Society.
ERIC Educational Resources Information Center
Crumley, Wilma; Stricklin, Michael
Many professors of mass media and society courses have relied on a teaching model implying that students are sponges soaking up information. A more appropriate model invites concern with an active audience, transaction, the interpersonal mass media mix, a general systems approach, and process and change--in other words, utilization of current and…
NASA Astrophysics Data System (ADS)
Fontanot, Fabio; De Lucia, Gabriella; Hirschmann, Michaela; Bruzual, Gustavo; Charlot, Stéphane; Zibetti, Stefano
2017-02-01
In this paper, we investigate the implications of the integrated galaxy-wide stellar initial mass function (IGIMF) approach in the framework of the semi-analytical model GAEA (GAlaxy Evolution and Assembly), which features a detailed treatment of chemical enrichment and stellar feedback. The IGIMF provides an analytic description of the dependence of the stellar IMF shape on the rate of star formation in galaxies. We find that our model with a universal IMF predicts a rather flat [α/Fe]-stellar mass relation. The model assuming the IGIMF, instead, is able to reproduce the observed increase of α-enhancement with stellar mass, in agreement with previous studies. This is mainly due to the fact that massive galaxies are characterized by larger star formation rates at high redshift, leading to stronger α-enhancement with respect to low-mass galaxies. At the same time, the IGIMF hypothesis does not affect significantly the trend for shorter star formation time-scales for more massive galaxies. We argue that in the IGIMF scenario the [α/Fe] ratios are good tracers of the highest star formation events. The final stellar masses and mass-to-light ratio of our model massive galaxies are larger than those estimated from the synthetic photometry assuming a universal IMF, providing a self-consistent interpretation of similar recent results, based on dynamical analysis of local early-type galaxies.
Pawlosky, Robert J; Kemper, Martin F; Kashiwaya, Yoshihero; King, M Todd; Mattson, Mark P; Veech, Richard L
2017-01-18
In patients with Alzheimer's disease (AD) and in a triple transgenic (3xTgAD) mouse model of AD low glucose metabolism in the brain precedes loss of memory and cognitive decline. The metabolism of ketones in the brain by-passes glycolysis and therefore may correct several deficiencies that are associated with glucose hypometabolism. A dietary supplement composed of an ester of D-β-hydroxybutyrate and R-1,3 butane diol referred to as ketone ester (KE) was incorporated into a rodent diet and fed to 3xTgAD mice for 8 months. At 16.5 months of age animals were euthanized and brains dissected. Analyses were carried out on the hippocampus and frontal cortex for glycolytic and TCA (Tricarboxylic Acid) cycle intermediates, amino acids, oxidized lipids and proteins, and enzymes. There were higher concentrations of D-β-hydroxybutyrate in the hippocampus of KE-fed mice where there were also higher concentrations of TCA cycle and glycolytic intermediates and the energy-linked biomarker, n-acetyl aspartate compared to controls. In the hippocampi of control-fed animals the free mitochondrial [NAD(+) ]/[NADH] ratio were highly oxidized, whereas, in KE-fed animals the mitochondria were reduced. Also, the levels of oxidized protein and lipids were lower and the energy of ATP hydrolysis was greater compared to controls. 3xTgAD mice maintained on a KE-supplemented diet had higher concentrations of glycolytic and TCA cycle metabolites, a more reduced mitochondrial redox potential, and lower amounts of oxidized lipids and proteins in their hippocampi compared to controls. The KE offers a potential therapy to counter fundamental metabolic deficits common to patients and transgenic models. This article is protected by copyright. All rights reserved.
NASA Astrophysics Data System (ADS)
Alexander, Patrick M.; Tedesco, Marco; Schlegel, Nicole-Jeanne; Luthcke, Scott B.; Fettweis, Xavier; Larour, Eric
2016-06-01
Improving the ability of regional climate models (RCMs) and ice sheet models (ISMs) to simulate spatiotemporal variations in the mass of the Greenland Ice Sheet (GrIS) is crucial for prediction of future sea level rise. While several studies have examined recent trends in GrIS mass loss, studies focusing on mass variations at sub-annual and sub-basin-wide scales are still lacking. At these scales, processes responsible for mass change are less well understood and modeled, and could potentially play an important role in future GrIS mass change. Here, we examine spatiotemporal variations in mass over the GrIS derived from the Gravity Recovery and Climate Experiment (GRACE) satellites for the January 2003-December 2012 period using a "mascon" approach, with a nominal spatial resolution of 100 km, and a temporal resolution of 10 days. We compare GRACE-estimated mass variations against those simulated by the Modèle Atmosphérique Régionale (MAR) RCM and the Ice Sheet System Model (ISSM). In order to properly compare spatial and temporal variations in GrIS mass from GRACE with model outputs, we find it necessary to spatially and temporally filter model results to reproduce leakage of mass inherent in the GRACE solution. Both modeled and satellite-derived results point to a decline (of -178.9 ± 4.4 and -239.4 ± 7.7 Gt yr-1 respectively) in GrIS mass over the period examined, but the models appear to underestimate the rate of mass loss, especially in areas below 2000 m in elevation, where the majority of recent GrIS mass loss is occurring. On an ice-sheet-wide scale, the timing of the modeled seasonal cycle of cumulative mass (driven by summer mass loss) agrees with the GRACE-derived seasonal cycle, within limits of uncertainty from the GRACE solution. However, on sub-ice-sheet-wide scales, some areas exhibit significant differences in the timing of peaks in the annual cycle of mass change. At these scales, model biases, or processes not accounted for by models related
The evolution of massive stars including mass loss - Presupernova models and explosion
NASA Technical Reports Server (NTRS)
Woosley, S. E.; Langer, Norbert; Weaver, Thomas A.
1993-01-01
The evolution of massive stars of 35, 40, 60, and 85 solar masses is followed through all stages of nuclear burning to the point of Fe core collapse. Critical nuclear reaction and mass-loss rates are varied. Efficient mass loss during the Wolf-Rayet (WR) stage is likely to lead to final masses as small as 4 solar masses. For a reasonable parameterization of the mass loss, there may be convergence of all WR stars, both single and in binaries, to a narrow band of small final masses. Our representative model, a 4.25 solar-mass WR presupernova derived from a 60 solar mass star, is followed through a simulated explosion, and its explosive nucleosynthesis and light curve are determined. Its properties are similar to those observed in Type Ib supernovae. The effects of the initial mass and mass loss on the presupernova structure of small mass WR models is also explored. Important properties of the presupernova star and its explosion can only be obtained by following the complete evolution starting on the main sequence.
Development of Parametric Mass and Volume Models for an Aerospace SOFC/Gas Turbine Hybrid System
NASA Technical Reports Server (NTRS)
Tornabene, Robert; Wang, Xiao-yen; Steffen, Christopher J., Jr.; Freeh, Joshua E.
2005-01-01
In aerospace power systems, mass and volume are key considerations to produce a viable design. The utilization of fuel cells is being studied for a commercial aircraft electrical power unit. Based on preliminary analyses, a SOFC/gas turbine system may be a potential solution. This paper describes the parametric mass and volume models that are used to assess an aerospace hybrid system design. The design tool utilizes input from the thermodynamic system model and produces component sizing, performance, and mass estimates. The software is designed such that the thermodynamic model is linked to the mass and volume model to provide immediate feedback during the design process. It allows for automating an optimization process that accounts for mass and volume in its figure of merit. Each component in the system is modeled with a combination of theoretical and empirical approaches. A description of the assumptions and design analyses is presented.
RSMASS: A preliminary reactor/shield mass model for SDI applications
Marshall, A.C.
1986-08-01
A simple mathematical model (RSMASS) has been developed to provide rapid estimates of reactor and shield masses for space-based reactor power systems. Approximations are used rather than correlations or detailed calculations to estimate the reactor fuel mass and the masses of the moderator, structure, reflector, pressure vessel, miscellaneous components, and the reactor shield. The fuel mass is determined either by neutronics limits, specific power limits, or fuel burnup limits - whichever yields the largest mass. RSMASS requires the reactor power and energy, 24 reactor parameters, and 20 shield parameters to be specified. This parametric approach should provide good mass estimates for a very broad range of reactor types. Reactor and shield masses calculated by RSMASS were found to be in good agreement with the masses obtained from detailed calculations.
Modeling the effect of sleep regulation on a neural mass model.
Costa, Michael Schellenberger; Born, Jan; Claussen, Jens Christian; Martinetz, Thomas
2016-08-01
In mammals, sleep is categorized by two main sleep stages, rapid eye movement (REM) and non-REM (NREM) sleep that are known to fulfill different functional roles, the most notable being the consolidation of memory. While REM sleep is characterized by brain activity similar to wakefulness, the EEG activity changes drastically with the emergence of K-complexes, sleep spindles and slow oscillations during NREM sleep. These changes are regulated by circadian and ultradian rhythms, which emerge from an intricate interplay between multiple neuronal populations in the brainstem, forebrain and hypothalamus and the resulting varying levels of neuromodulators. Recently, there has been progress in the understanding of those rhythms both from a physiological as well as theoretical perspective. However, how these neuromodulators affect the generation of the different EEG patterns and their temporal dynamics is poorly understood. Here, we build upon previous work on a neural mass model of the sleeping cortex and investigate the effect of those neuromodulators on the dynamics of the cortex and the corresponding transition between wakefulness and the different sleep stages. We show that our simplified model is sufficient to generate the essential features of human EEG over a full day. This approach builds a bridge between sleep regulatory networks and EEG generating neural mass models and provides a valuable tool for model validation.
Increases in body mass of rats during spaceflight: models and measurements.
Wade, C E; Ortiz, R M; Baer, L A
2000-11-01
To test the hypothesis that the body mass of rats is increased during spaceflight, we developed two models from the literature and obtained mass measurements during spaceflight. From studies of centrifugation (hypergravity), there is a reduction in body mass of rats dependent on the exposure gravity level. From data in 18 publications on rats subjected to hypergravity by centrifugation, we developed a model that predicted a 27% increase in body mass during the microgravity of spaceflight. Following spaceflight, with an increase in gravity on return to Earth, there is a reduction in body mass of rats for over 3 d. We related the reduction in body mass after spaceflight to the time after landing that mass measurements were made. From data in 23 publications on rats returning from spaceflight, we developed a model that predicted a 19% increase in body mass during spaceflight. Measurement of body mass of rats on days 6 and 10 of spaceflight found a 7 and 9% increase compared with ground control animals. The increase in body mass during spaceflight suggests that the rat may provide a viable model for metabolic studies in which changes during spaceflight may be predicted in part by ground-based hypergravity studies.
Gabbita, S. Prasad; Johnson, Ming F.; Kobritz, Naomi; Eslami, Pirooz; Poteshkina, Aleksandra; Varadarajan, Sridhar; Turman, John; Zemlan, Frank; Harris-White, Marni E.
2015-01-01
Cytokines such as TNFα can polarize microglia/macrophages into different neuroinflammatory types. Skewing of the phenotype towards a cytotoxic state is thought to impair phagocytosis and has been described in Alzheimer’s Disease (AD). Neuroinflammation can be perpetuated by a cycle of increasing cytokine production and maintenance of a polarized activation state that contributes to AD progression. In this study, 3xTgAD mice, age 6 months, were treated orally with 3 doses of the TNFα modulating compound isoindolin-1,3 dithione (IDT) for 10 months. We demonstrate that IDT is a TNFα modulating compound both in vitro and in vivo. Following long-term IDT administration, mice were assessed for learning & memory and tissue and serum were collected for analysis. Results demonstrate that IDT is safe for long-term treatment and significantly improves learning and memory in the 3xTgAD mouse model. IDT significantly reduced paired helical filament tau and fibrillar amyloid accumulation. Flow cytometry of brain cell populations revealed that IDT increased the infiltrating neutrophil population while reducing TNFα expression in this population. IDT is a safe and effective TNFα and innate immune system modulator. Thus small molecule, orally bioavailable modulators are promising therapeutics for Alzheimer’s disease. PMID:26436670
Cristallo, S.; Straniero, O.; Piersanti, L.; Gobrecht, D.
2015-08-15
We present a new set of models for intermediate-mass asymptotic giant branch (AGB) stars (4.0, 5.0, and 6.0 M{sub ⊙}) at different metallicities (−2.15 ≤ [Fe/H] ≤ +0.15). This set integrates the existing models for low-mass AGB stars (1.3 ≤ M/M{sub ⊙} ≤ 3.0) already included in the FRUITY database. We describe the physical and chemical evolution of the computed models from the main sequence up to the end of the AGB phase. Due to less efficient third dredge up episodes, models with large core masses show modest surface enhancements. This effect is due to the fact that the interpulse phases are short and, therefore, thermal pulses (TPs) are weak. Moreover, the high temperature at the base of the convective envelope prevents it from deeply penetrating the underlying radiative layers. Depending on the initial stellar mass, the heavy element nucleosynthesis is dominated by different neutron sources. In particular, the s-process distributions of the more massive models are dominated by the {sup 22}Ne(α,n){sup 25}Mg reaction, which is efficiently activated during TPs. At low metallicities, our models undergo hot bottom burning and hot third dredge up. We compare our theoretical final core masses to available white dwarf observations. Moreover, we quantify the influence intermediate-mass models have on the carbon star luminosity function. Finally, we present the upgrade of the FRUITY web interface, which now also includes the physical quantities of the TP-AGB phase for all of the models included in the database (ph-FRUITY)
NASA Astrophysics Data System (ADS)
Cristallo, S.; Straniero, O.; Piersanti, L.; Gobrecht, D.
2015-08-01
We present a new set of models for intermediate-mass asymptotic giant branch (AGB) stars (4.0, 5.0, and 6.0 M⊙) at different metallicities (-2.15 ≤ [Fe/H] ≤ +0.15). This set integrates the existing models for low-mass AGB stars (1.3 ≤ M/M⊙ ≤ 3.0) already included in the FRUITY database. We describe the physical and chemical evolution of the computed models from the main sequence up to the end of the AGB phase. Due to less efficient third dredge up episodes, models with large core masses show modest surface enhancements. This effect is due to the fact that the interpulse phases are short and, therefore, thermal pulses (TPs) are weak. Moreover, the high temperature at the base of the convective envelope prevents it from deeply penetrating the underlying radiative layers. Depending on the initial stellar mass, the heavy element nucleosynthesis is dominated by different neutron sources. In particular, the s-process distributions of the more massive models are dominated by the 22Ne(α,n)25Mg reaction, which is efficiently activated during TPs. At low metallicities, our models undergo hot bottom burning and hot third dredge up. We compare our theoretical final core masses to available white dwarf observations. Moreover, we quantify the influence intermediate-mass models have on the carbon star luminosity function. Finally, we present the upgrade of the FRUITY web interface, which now also includes the physical quantities of the TP-AGB phase for all of the models included in the database (ph-FRUITY).
Washburn, J.F.; Kaszeta, F.E.; Simmons, C.S.; Cole, C.R.
1980-07-01
This report presents the results of the development of a one-dimensional radionuclide transport code, MMT2D (Multicomponent Mass Transport), for the AEGIS Program. Multicomponent Mass Transport is a numerical solution technique that uses the discrete-parcel-random-wald (DPRW) method to directly simulate the migration of radionuclides. MMT1D accounts for: convection;dispersion; sorption-desorption; first-order radioactive decay; and n-membered radioactive decay chains. Comparisons between MMT1D and an analytical solution for a similar problem show that: MMT1D agrees very closely with the analytical solution; MMT1D has no cumulative numerical dispersion like that associated with solution techniques such as finite differences and finite elements; for current AEGIS applications, relatively few parcels are required to produce adequate results; and the power of MMT1D is the flexibility of the code in being able to handle complex problems for which analytical solution cannot be obtained. Multicomponent Mass Transport (MMT1D) codes were developed at Pacific Northwest Laboratory to predict the movement of radiocontaminants in the saturated and unsaturated sediments of the Hanford Site. All MMT models require ground-water flow patterns that have been previously generated by a hydrologic model. This report documents the computer code and operating procedures of a third generation of the MMT series: the MMT differs from previous versions by simulating the mass transport processes in systems with radionuclide decay chains. Although MMT is a one-dimensional code, the user is referred to the documentation of the theoretical and numerical procedures of the three-dimensional MMT-DPRW code for discussion of expediency, verification, and error-sensitivity analysis.
Exact Mass-Coupling Relation for the Homogeneous Sine-Gordon Model.
Bajnok, Zoltán; Balog, János; Ito, Katsushi; Satoh, Yuji; Tóth, Gábor Zsolt
2016-05-06
We derive the exact mass-coupling relation of the simplest multiscale quantum integrable model, i.e., the homogeneous sine-Gordon model with two mass scales. The relation is obtained by comparing the perturbed conformal field theory description of the model valid at short distances to the large distance bootstrap description based on the model's integrability. In particular, we find a differential equation for the relation by constructing conserved tensor currents, which satisfy a generalization of the Θ sum rule Ward identity. The mass-coupling relation is written in terms of hypergeometric functions.
Equilibrium models of mass distribution and collisional lifetimes of asteroids
NASA Technical Reports Server (NTRS)
Williams, David R.; Wetherill, George
1993-01-01
An understanding of the steady state distribution expected in the present day asteroid belt is important to our understanding of the collisional evolution of the asteroids and their physical properties. We have extended earlier work to show that, in the absence of gravity, a simple power law distribution as a function of mass with constant exponent will give an equilibrium distribution of asteroids for all bodies much smaller than the largest asteroids. This result holds for realistic fragmentation mechanisms and is independent of the physical properties of the asteroids. Inclusion of the effects of gravity on disruption and fragmentation of asteroids precludes an analytic solution to this problem, and rules out a simple power law distribution. We are currently calculating numerical solutions in order to determine the expected steady state mass distribution in the asteroid belt.
Modeling of body mass index by Newton's second law.
Canessa, Enrique
2007-10-21
Since laws of physics exists in nature, their possible relationship to terrestrial growth is introduced. By considering the human body as a dynamic system of variable mass (and volume), growing under a gravity field, it is shown how natural laws may influence the vertical growth of humans. This approach makes sense because the non-linear percentile curves of different aspects of human physical growth from childhood to adolescence can be described in relation to physics laws independently of gender and nationality. Analytical relations for the dependence of stature, measured mass (weight), growth velocity (and their mix as the body mass index) on age are deduced with a set of common statistical parameters which could relate environmental, genetics and metabolism and different aspects of physical growth on earth. A relationship to the monotone smoothing using functional data analysis to estimate growth curves and its derivatives is established. A preliminary discussion is also presented on horizontal growth in an essentially weightless environment (i.e., aquatic) with a connection to the Laird-Gompertz formula for growth.
ERIC Educational Resources Information Center
Lee, Yi-Hsuan; Hsieh, Yi-Chuan; Hsu, Chia-Ning
2011-01-01
This study intends to investigate factors affecting business employees' behavioral intentions to use the e-learning system. Combining the innovation diffusion theory (IDT) with the technology acceptance model (TAM), the present study proposes an extended technology acceptance model. The proposed model was tested with data collected from 552…
NASA Technical Reports Server (NTRS)
Taktakishvili, A.; Pulkkinen, A.; MacNeice, P.; Kuznetsova, M.; Hesse, M.; Odstrcil, D.
2011-01-01
In our previous paper we reported the results of modeling of 14 selected well -observed strong halo coronal mass ejection (CME) events using the WSA -ENLIL cone model combination. Cone model input parameters were obtained from white light coronagraph images of the CME events using the analytical method developed by Xie et al. This work verified that coronagraph input gives reasonably good results for the CME arrival time prediction. In contrast to Taktakishvili et al., where we started the analysis by looking for clear CME signatures in the data and then proceeded to model the interplanetary consequences at 1 AU, in the present paper we start by generating a list of observed geomagnetic storm events and then work our way back to remote solar observations and carry out the corresponding CME modeling. The approach used in this study is addressing space weather forecasting and operational needs. We analyzed 36 particularly strong geomagnetic storms, then tried to associate them with particular CMEs using SOHO/LASCO catalogue, and finally modeled these CMEs using WSA-ENLIL cone model. Recently, Pulkkinen et al. developed a novel method for automatic determination of cone model parameters. We employed both analytical and automatic methods to determine cone model input parameters. We examined the CME arrival times and magnitude of impact at 1 AU for both techniques. The results of the simulations are compared with the ACE satellite observations. This comparison demonstrated that WSA -ENLIL model combination with coronagraph input gives reasonably good results for the CME arrival times for this set of 'geoeffective" CME events as well.
A hydrodynamical model for the explosion of a neutron star just below the minimum mass
NASA Technical Reports Server (NTRS)
Colpi, Monica; Shapiro, Stuart L.; Teukolsky, Saul A.
1993-01-01
The instability of a neutron star at the minimum mass is investigated using a hydrodynamical model to follow the evolution of the unstable star. A detailed analysis of the linear stability of the equilibrium configurations near the minimum mass is performed by solving the radial eigenvalue problem for the fundamental mode. The minimum mass configuration M(mmc) of 0.196 solar mass is found to be stable to small perturbations. Stability to radial perturbations is lost only at a lower critical mass of 0.16 solar mass, corresponding to about 0.8 M(mmc). It is shown that a simple dynamical model constructed using a 3-polytrope equation of state for hot dense matter reproduces the key dynamical features of the instability in the explosion phase.
Coffeng, Luc E; Truscott, James E; Farrell, Sam H; Turner, Hugo C; Sarkar, Rajiv; Kang, Gagandeep; de Vlas, Sake J; Anderson, Roy M
2017-03-01
The predictions of two mathematical models of the transmission dynamics of Ascaris lumbricoides and hookworm infection and the impact of mass drug administration (MDA) are compared, using data from India. One model has an age structured partial differential equation (PDE) deterministic framework for the distribution of parasite numbers per host and sexual mating. The second model is an individual-based stochastic model. Baseline data acquired prior to treatment are used to estimate key transmission parameters, and forward projections are made, given the known MDA population coverage. Predictions are compared with observed post-treatment epidemiological patterns. The two models could equally well predict the short-term impact of deworming on A. lumbricoides and hookworm infection levels, despite being fitted to different subsets and/or summary statistics of the data. As such, the outcomes give confidence in their use as aids to policy formulation for the use of PCT to control A. lumbricoides and hookworm infection. The models further largely agree in a qualitative sense on the added benefit of semi-annual vs. annual deworming and targeting of the entire population vs. only children, as well as the potential for interruption of transmission. Further, this study also illustrates that long-term predictions are sensitive to modelling assumptions about which age groups contribute most to transmission, which depends on human demography and age-patterns in exposure and contribution to the environmental reservoir of infection, the latter being notoriously difficult to empirically quantify.
Investigation of Sorption Mass Transfer Models Using Synthetic Soils
1996-12-01
distributions of two or more materials and sizes. We tested the ability of the model to simulate the behavior of these systems and to fit system...for groundwater pollutants and improved clean-up operations are possible. New models developed for this purpose require rigorous testing using media of...be made to test model validity. Research Obiectives: The purpose of this experimental study is to test a theory that relates sorption rate to geometry
Tachyon inflation in an AdS braneworld with backreaction
NASA Astrophysics Data System (ADS)
Bilić, Neven; Dimitrijevic, Dragoljub D.; Djordjevic, Goran S.; Milosevic, Milan
2017-02-01
We analyze the inflationary scenario based on the tachyon field coupled with the radion of the second Randall-Sundrum model (RSII). The tachyon Lagrangian is derived from the dynamics of a 3-brane moving in the five-dimensional bulk. The AdS5 geometry of the bulk is extended to include the radion. Using the Hamiltonian formalism we find four nonlinear field equations supplemented by the modified Friedmann equations of the RSII braneworld cosmology. After a suitable rescaling we reduce the parameters of our model to only one free parameter related to the brane tension and the AdS5 curvature. We solve the equations numerically assuming a reasonably wide range of initial conditions determined by physical considerations. Varying the free parameter and initial conditions we confront our results with the Planck 2015 data.
NASA Astrophysics Data System (ADS)
Akashi, Haruaki; Yoshinaga, Tomokazu
2013-09-01
Ozone zero phenomena in an atmospheric pressure oxygen dielectric barrier discharges have been one of the major problems during a long time operation of ozone generators. But it is also known that the adding a small amount of nitrogen makes the recover from the ozone zero phenomena. To make clear the mechanism of recovery, authors have been simulated the discharges with using the results of Ref. 3. As a result, the recovery process can be seen and ozone density increased. It is found that the most important species would be nitrogen atoms. The reaction of nitrogen atoms and oxygen molecules makes oxygen atoms which is main precursor species of ozone. This generation of oxygen atoms is effective to increase ozone. The dependence of oxygen atom density (nO) and nitrogen atom density (nN) ratio was examined in this paper. In the condition of low nN/nO ratio case, generation of nitrogen oxide is low, and the quenching of ozone by the nitrogen oxide would be low. But in the high ratio condition, the quenching of ozone by nitrogen oxide would significant. This work was supported by KAKENHI(23560352).
Hedrick, Valisa E; Zoellner, Jamie M; Jahren, A Hope; Woodford, Natalie A; Bostic, Joshua N; Davy, Brenda M
2015-01-01
Background: An objective measure of added sugar (AS) and sugar-sweetened beverage (SSB) intake is needed. The δ13C value of finger-stick blood is a novel validated biomarker of AS/SSB intake; however, nonsweetener corn products and animal protein also carry a δ13C value similar to AS sources, which may affect blood δ13C values. The δ15N value of blood has been proposed as a “correction factor” for animal protein intake. Objectives: The objectives were to 1) identify foods associated with δ13C and δ15N blood values, 2) determine the contribution of nonsweetener corn to the diet relative to AS intake, and 3) determine if the dual-isotope model (δ13C and δ15N) is a better predictor of AS/SSB intake than δ13C alone. Methods: A cross-sectional sample of southwest Virginian adults (n = 257; aged 42 ± 15 y; 74% overweight/obese) underwent dietary intake assessments and provided finger-stick blood samples, which were analyzed for δ13C and δ15N values by using natural abundance stable isotope mass spectrometry. Statistical analyses included ANOVAs, paired-samples t tests, and multiple linear regressions. Results: The mean ± SD daily AS intake was 88 ± 59 g and nonsweetener corn intake was 13 ± 13 g. The mean δ13C value was −19.1 ± 0.9‰, which was significantly correlated with AS and SSB intakes (r = 0.32 and 0.39, respectively; P ≤ 0.01). The δ13C value and nonsweetener corn intake and the δ15N value and animal protein intake were not correlated. AS intake was significantly greater than nonsweetener corn intake (mean difference = 76.2 ± 57.2 g; P ≤ 0.001). The δ13C value was predictive of AS/SSB intake (β range: 0.28–0.35; P ≤ 0.01); however, δ15N was not predictive and minimal increases in R2 values were observed when the δ15N value was added to the model. Conclusions: The data do not provide evidence that the dual-isotope method is superior for predicting AS/SSB intakes within a southwest Virginian population. Our results support
Implications of general lepton mass matrices in the standard model on me e
NASA Astrophysics Data System (ADS)
Sharma, Samandeep; Ahuja, Gulsheen; Gupta, Manmohan
2016-12-01
Within the framework of the standard model (SM), using the facility of weak basis (WB) transformations, the general Dirac neutrino mass matrix and the charged lepton mass matrix can essentially be considered as texture two zero mass matrices. Using type I seesaw formula for Majorana neutrino mass matrix, our analysis yields lower bounds me e≳0.001 eV for normal mass ordering and me e≳0.08 eV for inverted mass ordering, the latter being tantalizingly close to the expected outcome of the ongoing experiments. Interestingly, for inverted mass ordering, me e is largely independent of variation of mass m3, whereas, for normal mass ordering with m1 in the range 0.0001 eV-0.01 eV, the bound on parameter me e gets further sharpened and one obtains me e within the band 0.014-0.042 eV. Further, noting that a particular set of texture four zero quark mass matrices has been shown to be a unique viable option for the description of quark mixing data, an analysis of similar mass matrices in the lepton sector has also been carried out to obtain bounds for the parameter me e with interesting consequences.
Effects of Rate-Limited Mass Transfer on Modeling Vapor Intrusion with Aerobic Biodegradation.
Chen, Yiming; Hou, Deyi; Lu, Chunhui; Spain, Jim C; Luo, Jian
2016-09-06
Most of the models for simulating vapor intrusion accept the local equilibrium assumption for multiphase concentration distributions, that is, concentrations in solid, liquid and vapor phases are in equilibrium. For simulating vapor transport with aerobic biodegradation controlled by counter-diffusion processes, the local equilibrium assumption combined with dual-Monod kinetics and biomass decay may yield near-instantaneous behavior at steady state. The present research investigates how predicted concentration profiles and fluxes change as interphase mass transfer resistances are increased for vapor intrusion with aerobic biodegradation. Our modeling results indicate that the attenuation coefficients for cases with and without mass transfer limitations can be significantly different by orders of magnitude. Rate-limited mass transfer may lead to larger overlaps of contaminant vapor and oxygen concentrations, which cannot be simulated by instantaneous reaction models with local equilibrium mass transfer. In addition, the contaminant flux with rate-limited mass transfer is much smaller than that with local equilibrium mass transfer, indicating that local equilibrium mass transfer assumption may significantly overestimate the biodegradation rate and capacity for mitigating vapor intrusion through the unsaturated zone. Our results indicate a strong research need for field tests to examine the validity of local equilibrium mass transfer, a widely accepted assumption in modeling vapor intrusion.
Dynamical Calculation of Θ+ Mass and Decay width in the Quark Model
NASA Astrophysics Data System (ADS)
Rostampour, M.; Saadat, H.; Farahani, H.
2012-08-01
In this paper we study the mass splitting and the decay width of pentaquark (Θ+) at the ground states in the framework of flux tube, quark delocalization and color screening model. We consider the pentaquark as diquark-triquark configuration and obtained closer values of mass splitting and the decay width of Θ+ to the experimental data.
Neutrino masses and oscillations in an unconventional model of lepton number violation
NASA Astrophysics Data System (ADS)
Tamvakis, K.; Vergados, J. D.
1985-06-01
Radiatively generated neutrino masses are studied in the framework of a simple model which predicts large mixings for neutrinos independently of the actual value of neutrino masses. The associated phenomenology of neutrino oscillations is analysed in detail. Other lepton violating processes are also discussed.
Optimization of Coronal Mass Ejection Ensemble Forecasting Using WSA-ENLIL with Coned Model
2013-03-01
I. Introduction .....................................................................................................................1 II...Figure 1: Image of a CME eruption associated with the largest modern solar flare recorded (~ X28) that occurred 4 November 2003 from LASCO C2. (NASA...WITH CONED MODEL I. Introduction Coronal Mass Ejections (CMEs) are the largest explosions in the solar system, ejecting up to 1013 kg of mass with
Modeling of Heat and Mass Transfer in Fusion Welding
Zhang, Wei
2011-01-01
In fusion welding, parts are joined together by melting and subsequent solidification. Although this principle is simple, complex transport phenomena take place during fusion welding, and they determine the final weld quality and performance. The heat and mass transfer in the weld pool directly affect the size and shape of the pool, the solidification microstructure, the formation of weld defects such as porosity and humping, and the temperature distribution in the fusion zone and heat-affected zone (HAZ). Furthermore, the temperature evolution affects the kinetics and extent of various solid-state phase transformations, which in turn determine the final weld microstructure and mechanical properties. The formation of residual stresses and distortion originates from the thermal expansion and contraction during welding heating and cooling, respectively.
Mass-Conserved Phase Field Models for Binary Fluids
2011-01-01
substrate [27], a wide variety of diffusive and diffusion -less solid -state phase transitions [10, 39], dislo- cation modeling in microstructure...has been proven effective in the numerical solution of the incompressible field phase model [32, 33]. Scheme based on a pressure-stabilization method...of the transient solution , the next set of figures (Figures 10-13) portrait the solutions up to nearly quasi-static states. The phase behavior
A computational model to generate simulated three-dimensional breast masses
Sisternes, Luis de; Brankov, Jovan G.; Zysk, Adam M.; Wernick, Miles N.; Schmidt, Robert A.; Nishikawa, Robert M.
2015-02-15
Purpose: To develop algorithms for creating realistic three-dimensional (3D) simulated breast masses and embedding them within actual clinical mammograms. The proposed techniques yield high-resolution simulated breast masses having randomized shapes, with user-defined mass type, size, location, and shape characteristics. Methods: The authors describe a method of producing 3D digital simulations of breast masses and a technique for embedding these simulated masses within actual digitized mammograms. Simulated 3D breast masses were generated by using a modified stochastic Gaussian random sphere model to generate a central tumor mass, and an iterative fractal branching algorithm to add complex spicule structures. The simulated masses were embedded within actual digitized mammograms. The authors evaluated the realism of the resulting hybrid phantoms by generating corresponding left- and right-breast image pairs, consisting of one breast image containing a real mass, and the opposite breast image of the same patient containing a similar simulated mass. The authors then used computer-aided diagnosis (CAD) methods and expert radiologist readers to determine whether significant differences can be observed between the real and hybrid images. Results: The authors found no statistically significant difference between the CAD features obtained from the real and simulated images of masses with either spiculated or nonspiculated margins. Likewise, the authors found that expert human readers performed very poorly in discriminating their hybrid images from real mammograms. Conclusions: The authors’ proposed method permits the realistic simulation of 3D breast masses having user-defined characteristics, enabling the creation of a large set of hybrid breast images containing a well-characterized mass, embedded within real breast background. The computational nature of the model makes it suitable for detectability studies, evaluation of computer aided diagnosis algorithms, and
Systematic U(1 ) B - L extensions of loop-induced neutrino mass models with dark matter
NASA Astrophysics Data System (ADS)
Ho, Shu-Yu; Toma, Takashi; Tsumura, Koji
2016-08-01
We study the gauged U(1 ) B - L extensions of the models for neutrino masses and dark matter. In this class of models, tiny neutrino masses are radiatively induced through the loop diagrams, while the origin of the dark matter stability is guaranteed by the remnant of the gauge symmetry. Depending on how the lepton number conservation is violated, these models are systematically classified. We present complete lists for the one-loop Z2 and the two-loop Z3 radiative seesaw models as examples of the classification. The anomaly cancellation conditions in these models are also discussed.
Langseth, Brian J.; Jones, Michael L.; Riley, Stephen C.
2014-01-01
Ecopath with Ecosim (EwE) is a widely used modeling tool in fishery research and management. Ecopath requires a mass-balanced snapshot of a food web at a particular point in time, which Ecosim then uses to simulate changes in biomass over time. Initial inputs to Ecopath, including estimates for biomasses, production to biomass ratios, consumption to biomass ratios, and diets, rarely produce mass balance, and thus ad hoc changes to inputs are required to balance the model. There has been little previous research of whether ad hoc changes to achieve mass balance affect Ecosim simulations. We constructed an EwE model for the offshore community of Lake Huron, and balanced the model using four contrasting but realistic methods. The four balancing methods were based on two contrasting approaches; in the first approach, production of unbalanced groups was increased by increasing either biomass or the production to biomass ratio, while in the second approach, consumption of predators on unbalanced groups was decreased by decreasing either biomass or the consumption to biomass ratio. We compared six simulation scenarios based on three alternative assumptions about the extent to which mortality rates of prey can change in response to changes in predator biomass (i.e., vulnerabilities) under perturbations to either fishing mortality or environmental production. Changes in simulated biomass values over time were used in a principal components analysis to assess the comparative effect of balancing method, vulnerabilities, and perturbation types. Vulnerabilities explained the most variation in biomass, followed by the type of perturbation. Choice of balancing method explained little of the overall variation in biomass. Under scenarios where changes in predator biomass caused large changes in mortality rates of prey (i.e., high vulnerabilities), variation in biomass was greater than when changes in predator biomass caused only small changes in mortality rates of prey (i.e., low
Models for predicting the mass of lime fruits by some engineering properties.
Miraei Ashtiani, Seyed-Hassan; Baradaran Motie, Jalal; Emadi, Bagher; Aghkhani, Mohammad-Hosein
2014-11-01
Grading fruits based on mass is important in packaging and reduces the waste, also increases the marketing value of agricultural produce. The aim of this study was mass modeling of two major cultivars of Iranian limes based on engineering attributes. Models were classified into three: 1-Single and multiple variable regressions of lime mass and dimensional characteristics. 2-Single and multiple variable regressions of lime mass and projected areas. 3-Single regression of lime mass based on its actual volume and calculated volume assumed as ellipsoid and prolate spheroid shapes. All properties considered in the current study were found to be statistically significant (ρ < 0.01). The results indicated that mass modeling of lime based on minor diameter and first projected area are the most appropriate models in the first and the second classifications, respectively. In third classification, the best model was obtained on the basis of the prolate spheroid volume. It was finally concluded that the suitable grading system of lime mass is based on prolate spheroid volume.
NASA Astrophysics Data System (ADS)
Shkolnik, I. M.; Efimov, S. V.
2013-12-01
Decadal long simulations of atmospheric circulation in the high latitudes have been carried out using a multiscale atmospheric modeling system that consists of MGO global and regional atmospheric models with respective resolutions of 200, 50 and 25 km in the horizontal. The detailed analysis of extratropical cyclone activity including activity of polar mesocyclones has been conducted for the winter season using an advanced cyclone identification and tracking scheme. To enhance the applicability of high-resolution regional atmospheric modeling in the context of detailed general atmospheric circulation analysis, an end-to-end approach for cyclone trajectory calculation on a unified global and regional grid has been proposed. It has been shown that increasing modeling resolution in the high latitudes allows one to more realistically simulate the activity of baroclinic waves and the thermal regime of the Arctic troposphere. The statistical structure of cyclonic activity has been investigated depending on the spatial resolution of the modeling system and compared with that in the reanalyses and satellite-derived analyses. The performance of the atmospheric models in the simulation of extreme cyclones is evaluated.
Cubical Mass-Spring Model design based on a tensile deformation test and nonlinear material model.
San-Vicente, Gaizka; Aguinaga, Iker; Tomás Celigüeta, Juan
2012-02-01
Mass-Spring Models (MSMs) are used to simulate the mechanical behavior of deformable bodies such as soft tissues in medical applications. Although they are fast to compute, they lack accuracy and their design remains still a great challenge. The major difficulties in building realistic MSMs lie on the spring stiffness estimation and the topology identification. In this work, the mechanical behavior of MSMs under tensile loads is analyzed before studying the spring stiffness estimation. In particular, the performed qualitative and quantitative analysis of the behavior of cubical MSMs shows that they have a nonlinear response similar to hyperelastic material models. According to this behavior, a new method for spring stiffness estimation valid for linear and nonlinear material models is proposed. This method adjusts the stress-strain and compressibility curves to a given reference behavior. The accuracy of the MSMs designed with this method is tested taking as reference some soft-tissue simulations based on nonlinear Finite Element Method (FEM). The obtained results show that MSMs can be designed to realistically model the behavior of hyperelastic materials such as soft tissues and can become an interesting alternative to other approaches such as nonlinear FEM.
Mass and metallicity requirement in stellar models for galactic chemical evolution applications
NASA Astrophysics Data System (ADS)
Côté, Benoit; West, Christopher; Heger, Alexander; Ritter, Christian; O'Shea, Brian W.; Herwig, Falk; Travaglio, Claudia; Bisterzo, Sara
2016-12-01
We used a one-zone chemical evolution model to address the question of how many masses and metallicities are required in grids of massive stellar models in order to ensure reliable galactic chemical evolution predictions. We used a set of yields that includes seven masses between 13 and 30 M⊙, 15 metallicities between 0 and 0.03 in mass fraction, and two different remnant mass prescriptions. We ran several simulations where we sampled subsets of stellar models to explore the impact of different grid resolutions. Stellar yields from low- and intermediate-mass stars and from Type Ia supernovae have been included in our simulations, but with a fixed grid resolution. We compared our results with the stellar abundances observed in the Milky Way for O, Na, Mg, Si, Ca, Ti, and Mn. Our results suggest that the range of metallicity considered is more important than the number of metallicities within that range, which only affects our numerical predictions by about 0.1 dex. We found that our predictions at [Fe/H] ≲ -2 are very sensitive to the metallicity range and the mass sampling used for the lowest metallicity included in the set of yields. Variations between results can be as high as 0.8 dex. At higher [Fe/H], we found that the required number of masses depends on the element of interest and on the remnant mass prescription. With a monotonic remnant mass prescription where every model explodes as a core-collapse supernova, the mass resolution induces variations of 0.2 dex on average. But with a remnant mass prescription that includes islands of non-explodability, the mass resolution can cause variations of about 0.2-0.7 dex depending on the choice of the lower limit of the metallicity range. With such a remnant mass prescription, explosive or non-explosive models can be missed if not enough masses are selected, resulting in over- or underestimations of the mass ejected by massive stars.
Composition of Meridiani Hematite-rich Spherules: A Mass-Balance Mixing-Model Approach
NASA Astrophysics Data System (ADS)
Jolliff, B. L.; Athena Science Team
2005-03-01
A mass-balance model using APXS data and microscopic images indicates that the composition of spherules ("blueberries"), found at the Meridiani site by the Mars Exploration Rover Opportunity and thought to be concretions, contain ~45-60 wt% hematite.
Tabares Velasco, P. C.
2011-04-01
This presentation discusses estimating heat and mass transfer processes in green roof systems: current modeling capabilities and limitations. Green roofs are 'specialized roofing systems that support vegetation growth on rooftops.'
Aoki phases in the lattice Gross-Neveu model with flavored mass terms
Creutz, Michael; Kimura, Taro; Misumi, Tatsuhiro
2011-05-01
We investigate the parity-broken phase structure for staggered and naive fermions in the Gross-Neveu model as a toy model of QCD. We consider a generalized staggered Gross-Neveu model including two types of four-point interactions. We use generalized mass terms to split the doublers for both staggered and naive fermions. The phase boundaries derived from the gap equations show that the mass splitting of tastes results in an Aoki phase both in the staggered and naive cases. We also discuss the continuum limit of these models and explore taking the chirally symmetric limit by fine-tuning a mass parameter and two-coupling constants. This supports the idea that in lattice QCD we can derive one- or two-flavor staggered fermions by tuning the mass parameter, which are likely to be less expensive than Wilson fermions in QCD simulation.
NASA Technical Reports Server (NTRS)
Campbell, William J.; Short, Nicholas M., Jr.; Roelofs, Larry H.; Dorfman, Erik
1991-01-01
A methodology for optimizing organization of data obtained by NASA earth and space missions is discussed. The methodology uses a concept based on semantic data modeling techniques implemented in a hierarchical storage model. The modeling is used to organize objects in mass storage devices, relational database systems, and object-oriented databases. The semantic data modeling at the metadata record level is examined, including the simulation of a knowledge base and semantic metadata storage issues. The semantic data model hierarchy and its application for efficient data storage is addressed, as is the mapping of the application structure to the mass storage.
Kim, Bo-Yeon; Lee, Ji-Young; Ha, Sang-Do
2011-04-01
Response surface methodology was used to determine growth characteristics and to develop a predictive model to describe specific growth rates of Bacillus cereus in wet noodles containing a combination of ethanol (0 to 2% [vol/wt]) and vitamin B(1) (0 to 2 g/liter). B. cereus F4810/72, which produces an emetic toxin, was used in this study. The noodles containing B. cereus were incubated at 10°C. The growth curves were fitted to the modified Gompertz equation using nonlinear regression, and the growth rate values from the curves were used to establish the predictive model using a response surface methodology quadratic polynomial equation as a function of concentrations of ethanol and vitamin B(1). The model was shown to fit the data very well (r(2) = 0.9505 to 0.9991) and could be used to accurately predict growth rates. The quadratic polynomial model was validated, and the predicted growth rate values were in good agreement with the experimental values. The polynomial model was found to be an appropriate secondary model for growth rate (GR) and lag time (LT) based on the correlation of determination (r(2) = 0.9899 for GR, 0.9782 for LT), bias factor (B(f) = 1.006 for GR, 0.992 for LT), and accuracy factor (A(f) = 1.024 for GR, 1.011 for LT). Thus, this model holds great promise for use in predicting the growth of B. cereus in fresh wet noodles using only the bacterial concentration, an important contribution to the manufacturing of safe products.
Halo Coronal Mass Ejections: Comparing Observations and Models
NASA Technical Reports Server (NTRS)
Gilbert, Holly; Orlove, Matthew; SaintCyr, O.; Mays, L.; Gopalswamy, N.
2011-01-01
Since 1996, the SOHO LASCO coronagraphs have detected "halo" CMEs that appear to be directed toward Earth, but information about the size and speed of these events seen face-on has been limited. From a single vantage point along the Sun-Earth line, the primary limitation has been ambiguity in fitting the cone model (or other forward-modeling techniques, e.g., Thernisian et al., 2006). But in the past few years, the STEREO mission has provided a view of Earth-directed events from the side. These events offer the opportunity to compare measurements (width and speed) of halo CMEs observed by STEREO with models that derive halo CME properties. We report here results of such a comparison on a large sample of LASCO CMEs in the STEREO era.
LM-3: A High-resolution Lake Michigan Mass Balance Water Quality Model
This report is a user’s manual that describes the high-resolution mass balance model known as LM3. LM3 has been applied to Lake Michigan to describe the transport and fate of atrazine, PCB congeners, and chloride in that system. The model has also been used to model eutrophicat...
AN OVERVIEW OF NEUTRINO MASSES AND MIXING IN SO(10) MODELS.
CHEN,M.C.MAHANTHAPPA,K.T.
2003-06-05
We review in this talk various SUSY SO(10) models. Specifically, we discuss how small neutrino masses are generated in and generic predictions of different SO(10) models. A comparison of the predictions of these models for sin{sup 2} {theta}{sub 13}is given.
An explicit SU(12) family and flavor unification model with natural fermion masses and mixings
Albright, Carl H.; Feger, Robert P.; Kephart, Thomas W.
2012-07-01
We present an SU(12) unification model with three light chiral families, avoiding any external flavor symmetries. The hierarchy of quark and lepton masses and mixings is explained by higher dimensional Yukawa interactions involving Higgs bosons that contain SU(5) singlet fields with VEVs about 50 times smaller than the SU(12) unification scale. The presented model has been analyzed in detail and found to be in very good agreement with the observed quark and lepton masses and mixings.
A new methodology to test galaxy formation models using the dependence of clustering on stellar mass
NASA Astrophysics Data System (ADS)
Campbell, David J. R.; Baugh, Carlton M.; Mitchell, Peter D.; Helly, John C.; Gonzalez-Perez, Violeta; Lacey, Cedric G.; Lagos, Claudia del P.; Simha, Vimal; Farrow, Daniel J.
2015-09-01
We present predictions for the two-point correlation function of galaxy clustering as a function of stellar mass, computed using two new versions of the GALFORM semi-analytic galaxy formation model. These models make use of a high resolution, large volume N-body simulation, set in the 7-year Wilkinson Microwave Anisotropy Probe cosmology. One model uses a universal stellar initial mass function (IMF), while the other assumes different IMFs for quiescent star formation and bursts. Particular consideration is given to how the assumptions required to estimate the stellar masses of observed galaxies (such as the choice of IMF, stellar population synthesis model, and dust extinction) influence the perceived dependence of galaxy clustering on stellar mass. Broad-band spectral energy distribution fitting is carried out to estimate stellar masses for the model galaxies in the same manner as in observational studies. We show clear differences between the clustering signals computed using the true and estimated model stellar masses. As such, we highlight the importance of applying our methodology to compare theoretical models to observations. We introduce an alternative scheme for the calculation of the merger time-scales for satellite galaxies in GALFORM, which takes into account the dark matter subhalo information from the simulation. This reduces the amplitude of small-scale clustering. The new merger scheme offers improved or similar agreement with observational clustering measurements, over the redshift range 0 < z < 0.7. We find reasonable agreement with clustering measurements from the Galaxy and Mass Assembly Survey, but find larger discrepancies for some stellar mass ranges and separation scales with respect to measurements from the Sloan Digital Sky Survey and the VIMOS Public Extragalactic Redshift Survey, depending on the GALFORM model used.
Yoshida, Kenichiro; Nishidate, Izumi
2014-01-01
To rapidly derive a result for diffuse reflectance from a multilayered model that is equivalent to that of a Monte-Carlo simulation (MCS), we propose a combination of a layered white MCS and the adding-doubling method. For slabs with various scattering coefficients assuming a certain anisotropy factor and without absorption, we calculate the transition matrices for light flow with respect to the incident and exit angles. From this series of precalculated transition matrices, we can calculate the transition matrices for the multilayered model with the specific anisotropy factor. The relative errors of the results of this method compared to a conventional MCS were less than 1%. We successfully used this method to estimate the chromophore concentration from the reflectance spectrum of a numerical model of skin and in vivo human skin tissue. PMID:25426319
[Determination of Virtual Surgery Mass Point Spring Model Parameters Based on Genetic Algorithms].
Chen, Ying; Hu, Xuyi; Zhu, Qiguang
2015-12-01
Mass point-spring model is one of the commonly used models in virtual surgery. However, its model parameters have no clear physical meaning, and it is hard to set the parameter conveniently. We, therefore, proposed a method based on genetic algorithm to determine the mass-spring model parameters. Computer-aided tomography (CAT) data were used to determine the mass value of the particle, and stiffness and damping coefficient were obtained by genetic algorithm. We used the difference between the reference deformation and virtual deformation as the fitness function to get the approximate optimal solution of the model parameters. Experimental results showed that this method could obtain an approximate optimal solution of spring parameters with lower cost, and could accurately reproduce the effect of the actual deformation model as well.
Modeling The GRB Host Galaxy Mass Distribution: Are GRBs Unbiased Tracers of Star Formation?
Kocevski, Daniel; West, Andrew A.; Modjaz, Maryam; /UC, Berkeley, Astron. Dept.
2009-08-03
We model the mass distribution of long gamma-ray burst (GRB) host galaxies given recent results suggesting that GRBs occur in low metallicity environments. By utilizing measurements of the redshift evolution of the mass-metallicity (M-Z) relationship for galaxies, along with a sharp host metallicity cut-off suggested by Modjaz and collaborators, we estimate an upper limit on the stellar mass of a galaxy that can efficiently produce a GRB as a function of redshift. By employing consistent abundance indicators, we find that sub-solar metallicity cut-offs effectively limit GRBs to low stellar mass spirals and dwarf galaxies at low redshift. At higher redshifts, as the average metallicity of galaxies in the Universe falls, the mass range of galaxies capable of hosting a GRB broadens, with an upper bound approaching the mass of even the largest spiral galaxies. We compare these predicted limits to the growing number of published GRB host masses and find that extremely low metallicity cut-offs of 0.1 to 0.5 Z{sub {circle_dot}} are effectively ruled out by a large number of intermediate mass galaxies at low redshift. A mass function that includes a smooth decrease in the efficiency of producing GRBs in galaxies of metallicity above 12+log(O/H){sub KK04} = 8.7 can, however, accommodate a majority of the measured host galaxy masses. We find that at z {approx} 1, the peak in the observed GRB host mass distribution is inconsistent with the expected peak in the mass of galaxies harboring most of the star formation. This suggests that GRBs are metallicity biased tracers of star formation at low and intermediate redshifts, although our model predicts that this bias should disappear at higher redshifts due to the evolving metallicity content of the universe.
Alternative model of the Antonov problem: Generalization with the presence of a mass spectrum
NASA Astrophysics Data System (ADS)
Velazquez, L.; García, S. Gómez; Guzmán, F.
2009-01-01
We extend the quasiergodic model proposed as an alternative version of the Antonov isothermal model [L. Velazquez and F. Guzman, Phys. Rev. E 68, 066116 (2003)] by including the incidence of a mass spectrum. We propose an iterative procedure inspired by the Newton-Raphson method to solve the resulting nonlinear structure equations. As an example of application, we assume the existence of a mass spectrum with a standard Salpeter form, dN=Cdm/mα . We analyze consequences of this realistic ingredient on the system thermodynamical behavior and perform a quantitative description of the mass segregation effect.
Comments on "Two-mass models of the vocal cords for natural sounding voice synthesis".
Nudelman, H B; Hoyt, B D
1989-05-01
Koizumi et al. [J. Acoust. Soc. Am. 82, 1179-1192 (1987)] have proposed a way to incorporate mucosal waves into previous two-mass mechanical models of the vocal folds. This was accomplished by allowing the mass of the masses to vary with time. The equations of motion Koizumi et al. used to mathematically describe this model neglected terms from the time rate of change of momentum of Newton's second law. In this letter, approximations of the magnitude of this term indicate that it must not be neglected.
Improvement of filament-protection circuitry in a Finnigan model 251 mass spectrometer
Wildman, J.D.
1986-01-01
As delivered from Finnigan MAT, the emission current of the Leybold-Heraeus model IM210 ionization vacuum gage on a model 251 isotope ratio mass spectrometer can turn on as soon as the ' PUMP ON ' switch is depressed, before a good vacuum in the mass spectrometer is attained. The filament in the source of the mass spectrometer may turn on at the same time, thereby shortening its life or burning it out if the vacuum is poor. This design flaw can be corrected by a simple modification of the electronic circuitry. (Author 's abstract)
Model of Mass Transfer in Liquid-Liquid Extraction in a Turbulent Forward Flow
NASA Astrophysics Data System (ADS)
Laptev, A. G.; Farakhov, T. M.; Dudarovskaya, O. G.
2015-01-01
A mathematical description of the process of mass transfer in a continuous phase in the turbulent motion of two mutually insoluble liquids has been obtained on the basis of an assigned law of damping of turbulent pulsations in the boundary layer. The basic parameters of the model have been found in terms of the hydraulic resistance of a droplet in motion. Consideration has been given to the use of the mathematical mass-transfer model in apparatuses with mixing devices. Agreement has been shown between results of calculation of mass-transfer coefficients and experimental data.
Higgs masses and stability in the standard and the two Higgs doublet models
Juarez W, S. R.; Morales C, D.; Kielanowski, P.
2010-07-29
Within the framework of the standard model (SM) of elementary particles and the two Higgs doublet extension to this model (2DHM), we obtained analytical and numerical solutions for the gauge couplings, the vacuum expectation values (VEV) of the Higgs fields, the quark Yukawa couplings and quark masses, the quartic Higgs couplings, and the running Higgs masses, considering the renormalization group equations. The bounds on the SM Higgs running mass have been fixed, and the region of validity of the SM was determined through it, at the one and two loop approximations, using the triviality and stability conditions for the Higgs quartic coupling {lambda}{sub H}.
Canellas, E; Vera, P; Domeño, C; Alfaro, P; Nerín, C
2012-04-27
Acrylic adhesives are used to manufacture multilayer laminates that are used in food packaging to form the geometric shape of the package as well as to stick labels on the packages. Once applied on the packaging adhesives can supply potential migrants that could endanger the packaged food. Adhesives are complex matrices where intentionally and non intentionally added substances are present, but the identification of the migrants is required by law. In this study atmospheric pressure gas chromatography coupled to a quadrupole hyphenated to a time of flight mass spectrometer (APGC-MS/Q-TOF) has been explored for identification of unknowns coming from three different acrylic adhesives. The results are compared to those obtained by conventional GC-MS-Q (quadrupole). Sixteen compounds were identified by GC-MS/Q and five of them were confirmed by APGC-MS/Q-TOF as their molecular ions were found. Moreover, additional three new compounds were identified and their structure was elucidated working with the spectra obtained by APGC-MS/Q-TOF. This finding was very relevant as these compounds were biocides suspected to be allergenic and cytotoxic in humans. Migration studies were carried out using Tenax as solid food simulant and the results showed that the three acrylic adhesives tested in this work were safe for being used in food packaging materials since the migration of compounds previously identified was below the limit established in the current legislation.
ERIC Educational Resources Information Center
Collier, Geoffrey L.; Ogden, R. Todd
2004-01-01
The Wing-Kristofferson model (A. M. Wing & A. B. Kristofferson, (1973a, 1973b) decomposes the variance of isochronous finger tapping into 2 components: a central clock component and a peripheral motor component. The method assumes that there is no drift in the intertap intervals. A new method is introduced that further decomposes the clock…
Supersymmetric AdS_6 solutions of type IIB supergravity
NASA Astrophysics Data System (ADS)
Kim, Hyojoong; Kim, Nakwoo; Suh, Minwoo
2015-10-01
We study the general requirement for supersymmetric AdS_6 solutions in type IIB supergravity. We employ the Killing spinor technique and study the differential and algebraic relations among various Killing spinor bilinears to find the canonical form of the solutions. Our result agrees precisely with the work of Apruzzi et al. (JHEP 1411:099, 2014), which used the pure spinor technique. Hoping to identify the geometry of the problem, we also computed four-dimensional theory through the dimensional reduction of type IIB supergravity on AdS_6. This effective action is essentially a non-linear sigma model with five scalar fields parametrizing {SL}(3,{R})/{SO}(2,1), modified by a scalar potential and coupled to Einstein gravity in Euclidean signature. We argue that the scalar potential can be explained by a subgroup CSO(1,1,1) subset {SL}(3,{R}) in a way analogous to gauged supergravity.
The simulation of 3D mass models in 2D digital mammography and breast tomosynthesis
Shaheen, Eman De Keyzer, Frederik; Bosmans, Hilde; Ongeval, Chantal Van; Dance, David R.; Young, Kenneth C.
2014-08-15
Purpose: This work proposes a new method of building 3D breast mass models with different morphological shapes and describes the validation of the realism of their appearance after simulation into 2D digital mammograms and breast tomosynthesis images. Methods: Twenty-five contrast enhanced MRI breast lesions were collected and each mass was manually segmented in the three orthogonal views: sagittal, coronal, and transversal. The segmented models were combined, resampled to have isotropic voxel sizes, triangularly meshed, and scaled to different sizes. These masses were referred to as nonspiculated masses and were then used as nuclei onto which spicules were grown with an iterative branching algorithm forming a total of 30 spiculated masses. These 55 mass models were projected into 2D projection images to obtain mammograms after image processing and into tomographic sequences of projection images, which were then reconstructed to form 3D tomosynthesis datasets. The realism of the appearance of these mass models was assessed by five radiologists via receiver operating characteristic (ROC) analysis when compared to 54 real masses. All lesions were also given a breast imaging reporting and data system (BIRADS) score. The data sets of 2D mammography and tomosynthesis were read separately. The Kendall's coefficient of concordance was used for the interrater observer agreement assessment for the BIRADS scores per modality. Further paired analysis, using the Wilcoxon signed rank test, of the BIRADS assessment between 2D and tomosynthesis was separately performed for the real masses and for the simulated masses. Results: The area under the ROC curves, averaged over all observers, was 0.54 (95% confidence interval [0.50, 0.66]) for the 2D study, and 0.67 (95% confidence interval [0.55, 0.79]) for the tomosynthesis study. According to the BIRADS scores, the nonspiculated and the spiculated masses varied in their degrees of malignancy from normal (BIRADS 1) to highly
Mass balances for a biological life support system simulation model
NASA Technical Reports Server (NTRS)
Volk, Tyler; Rummel, John D.
1987-01-01
Design decisions to aid the development of future space based biological life support systems (BLSS) can be made with simulation models. The biochemistry stoichiometry was developed for: (1) protein, carbohydrate, fat, fiber, and lignin production in the edible and inedible parts of plants; (2) food consumption and production of organic solids in urine, feces, and wash water by the humans; and (3) operation of the waste processor. Flux values for all components are derived for a steady state system with wheat as the sole food source. The large scale dynamics of a materially closed (BLSS) computer model is described in a companion paper. An extension of this methodology can explore multifood systems and more complex biochemical dynamics while maintaining whole system closure as a focus.
NASA Astrophysics Data System (ADS)
Peßenteiner, Stefanie; Van Beek, Rens; Sutanudjaja, Edwin; Bierkens, Marc
2015-04-01
With growing populations, economic expansion, and rising standards of living the demand for water is increasing across the globe. Demographic developments and a changing climate will further aggravate the pressure on global water resources. In the EU FP7 project EartH2Observe in-situ data, earth observations, and models will be assimilated to provide a comprehensive reanalysis of the global water resources system, accounting for all components of the global water cycle including information on the impacts of human activities, e.g., through water consumption and man-made reservoirs. Synthesizing as many sources of information as possible bears great potential to improve global water balance estimates and to consequently allow for consistent and informed decisions in water management. One of the modelling suites participating in EartH2Observe is the global hydrological model PCR-GLOBWB (Van Beek et al., 2011) which already accounts for anthropogenic perturbations in the water cycle. Here we present an extensive validation of the latest model version PCR-GLOBWB 2.0 (Sutanudjaja et al., 2014) which comprises dynamic withdrawal, allocation and consumptive use of ground- and surface water resources, irrigation, return flows of unconsumed water to surface water and groundwater resources, and more than 6000 reservoirs of the GRanD database. This study presents the first step towards a full reanalysis merging earth observations, in-situ data and models. We focus on human activities altering the hydrologic cycle over the past 30 years by evaluating PCR-GLOBWB 'natural' and 'humanly-modified' simulations in 0.5°× 0.5° spatial and daily temporal resolution. To this end our model is forced with the newly available WFDEI (WATCH Forcing Data methodology applied to ERA-Interim data) data set. PCR-GLOBWB 2.0 simulations of river discharge, water abstraction and water use are validated against observations from the Global Runoff Data Centre as well as available national and
A class of three-loop models with neutrino mass and dark matter
NASA Astrophysics Data System (ADS)
Chen, Chian-Shu; McDonald, Kristian L.; Nasri, Salah
2014-06-01
We study a class of three-loop models for neutrino mass in which dark matter plays a key role in enabling the mass diagram. The simplest models in this class have Majorana dark matter and include the proposal of Krauss, Nasri and Trodden; we identify the remaining related models, including the viable colored variants. The next-to-simplest models use either more multiplets and/or a slight modification of the loop-diagram, and predict inert N-tuplet scalar dark matter.
Neutrino masses, leptogenesis, and dark matter in a hybrid seesaw model
Gu Peihong; Hirsch, M.; Valle, J. W. F.
2009-02-01
We suggest a hybrid seesaw model where relatively light right-handed neutrinos give no contribution to neutrino mass matrix due to a special symmetry. This allows their Yukawa couplings to the standard model particles to be relatively strong, so that the standard model Higgs boson can decay dominantly to a left- and a right-handed neutrino, leaving another stable right-handed neutrino as cold dark matter. In our model neutrino masses arise via the type-II seesaw mechanism, the Higgs triplet scalars being also responsible for the generation of the matter-antimatter asymmetry via the leptogenesis mechanism.
Kovac, Andrej; Somikova, Zuzana; Zilka, Norbert; Novak, Michal
2014-02-01
Alzheimer's disease (AD) is still being recognized today as an unmet medical need. Currently, there is no cure and early preclinical diagnostic assay available for AD. Therefore much attention is now being directed at the development of novel methods for quantitative determination of AD biomarkers in the cerebrospinal fluid (CSF). Here, we describe the liquid chromatography-tandem mass spectrometry method for determination of 5-hydroxytryptamine (SER), 5-hydroxyindoleacetic acid (5-HIAA), homovanilic acid (HVA), noradrenaline (NADR), adrenaline (ADR), dopamine (DA), glutamic acid (Glu), γ-aminobutyric acid (GABA), 3,4-dihydroxyphenylacetic acid (DOPAC) and histamine (HIS) in cerebrospinal fluid (CSF) from the rat model for human tauopathy. The benzoyl chloride was used as pre-column derivatization reagents. Neurotransmitters and metabolites were analysed on ultra performance liquid chromatography (UPLC) on C18 column in combination with tandem mass spectrometry. The method is simple, highly sensitive and showed excellent linearity with regression coefficients higher than 0.99. The accuracy was in a range of 93-113% for all analytes. The inter-day precision (n=5 days), expressed as %RSD, was in a range 2-10% for all analytes. Using this method we detected significant changes of CSF levels of two important neurotransmitters/metabolites, ADR and 5-HIAA, which correlates with progression of neurodegeneration in our animal model.
2010-05-01
Alternative diversity, difficulties in selecting metrics and measuring performance, and other factors make the Analysis of Alternatives (AoA) difficult...particularly difficult because of the intangible nature of many important benefits. The current work addresses the need to improve the use of benefits in AoA...research focuses on the use of KVA and “Real Options” models in identifying, valuing, maintaining, and exercising options in military decision -making
NASA Astrophysics Data System (ADS)
Agosta, Cécile; Favier, Vincent; Krinner, Gerhard; Gallée, Hubert; Fettweis, Xavier; Genthon, Christophe
2013-12-01
About 75 % of the Antarctic surface mass gain occurs over areas below 2,000 m asl, which cover 40 % of the grounded ice-sheet. As the topography is complex in many of these regions, surface mass balance modelling is highly dependent on horizontal resolution, and studying the impact of Antarctica on the future rise in sea level requires physical approaches. We have developed a computationally efficient, physical downscaling model for high-resolution (15 km) long-term surface mass balance (SMB) projections. Here, we present results of this model, called SMHiL (surface mass balance high-resolution downscaling), which was forced with the LMDZ4 atmospheric general circulation model to assess Antarctic SMB variability in the twenty first and the twenty second centuries under two different scenarios. The higher resolution of SMHiL better reproduces the geographical patterns of SMB and increase significantly the averaged SMB over the grounded ice-sheet for the end of the twentieth century. A comparison with more than 3200 quality-controlled field data shows that LMDZ4 and SMHiL reproduce the observed values equally well. Nevertheless, field data below 2,000 m asl are too scarce to efficiently show the added value of SMHiL and measuring the SMB in these undocumented areas should be a future scientific priority. Our results suggest that running LMDZ4 at a finer resolution (15 km) may give a future increase in SMB in Antarctica that is about 30 % higher than by using its standard resolution (60 km) due to the higher increase in precipitation in coastal areas at 15 km. However, a part (˜15 %) of these discrepancies could be an artefact from SMHiL since it neglects the foehn effect and likely overestimates the precipitation increase. Future changes in the Antarctic SMB at low elevations will result from the competition between higher snow accumulation and runoff. For this reason, developing downscaling models is crucial to represent processes in sufficient detail and correctly
NASA Astrophysics Data System (ADS)
Namwong, Lawit; Authayanun, Suthida; Saebea, Dang; Patcharavorachot, Yaneeporn; Arpornwichanop, Amornchai
2016-11-01
Proton-conducting solid oxide electrolysis cells (SOEC-H+) are a promising technology that can utilize carbon dioxide to produce syngas. In this work, a detailed electrochemical model was developed to predict the behavior of SOEC-H+ and to prove the assumption that the syngas is produced through a reversible water gas-shift (RWGS) reaction. The simulation results obtained from the model, which took into account all of the cell voltage losses (i.e., ohmic, activation, and concentration losses), were validated using experimental data to evaluate the unknown parameters. The developed model was employed to examine the structural and operational parameters. It is found that the cathode-supported SOEC-H+ is the best configuration because it requires the lowest cell potential. SOEC-H+ operated favorably at high temperatures and low pressures. Furthermore, the simulation results revealed that the optimal S/C molar ratio for syngas production, which can be used for methanol synthesis, is approximately 3.9 (at a constant temperature and pressure). The SOEC-H+ was optimized using a response surface methodology, which was used to determine the optimal operating conditions to minimize the cell potential and maximize the carbon dioxide flow rate.
Parametric Mass Modeling for Mars Entry, Descent and Landing System Analysis Study
NASA Technical Reports Server (NTRS)
Samareh, Jamshid A.; Komar, D. R.
2011-01-01
This paper provides an overview of the parametric mass models used for the Entry, Descent, and Landing Systems Analysis study conducted by NASA in FY2009-2010. The study examined eight unique exploration class architectures that included elements such as a rigid mid-L/D aeroshell, a lifting hypersonic inflatable decelerator, a drag supersonic inflatable decelerator, a lifting supersonic inflatable decelerator implemented with a skirt, and subsonic/supersonic retro-propulsion. Parametric models used in this study relate the component mass to vehicle dimensions and mission key environmental parameters such as maximum deceleration and total heat load. The use of a parametric mass model allows the simultaneous optimization of trajectory and mass sizing parameters.
Mass modeling of fig (Ficus carica L.) fruit with some physical characteristics.
Shahbazi, Feizollah; Rahmati, Satar
2013-03-01
Horticultural crops with the similar weight and uniform shape are in high demand in terms of marketing value, which are used as food. For proper design of grading systems, important relationships among the mass and other properties of fruits such as length, width, thickness, volumes, and projected areas must be known. The aim of this research was to measure and present some physical properties of fig fruits. In addition, Linear, Quadratic, S-curve, and Power models are used for mass predication of fig fruits based on measured physical properties. The results showed that all measured physical properties were statistically significant at the 1% probability level. For mass predication of fig fruits, the best and the worst models were obtained based on criteria projected area and thickness of the fruits with determination coefficients (R (2)) of 0.984 and 0.664, respectively. At last, from economical standpoint, mass modeling of fig fruits based on first projected area is recommended.
Möller, Marco; Obleitner, Friedrich; Reijmer, Carleen H; Pohjola, Veijo A; Głowacki, Piotr; Kohler, Jack
2016-05-27
Large-scale modeling of glacier mass balance relies often on the output from regional climate models (RCMs). However, the limited accuracy and spatial resolution of RCM output pose limitations on mass balance simulations at subregional or local scales. Moreover, RCM output is still rarely available over larger regions or for longer time periods. This study evaluates the extent to which it is possible to derive reliable region-wide glacier mass balance estimates, using coarse resolution (10 km) RCM output for model forcing. Our data cover the entire Svalbard archipelago over one decade. To calculate mass balance, we use an index-based model. Model parameters are not calibrated, but the RCM air temperature and precipitation fields are adjusted using in situ mass balance measurements as reference. We compare two different calibration methods: root mean square error minimization and regression optimization. The obtained air temperature shifts (+1.43°C versus +2.22°C) and precipitation scaling factors (1.23 versus 1.86) differ considerably between the two methods, which we attribute to inhomogeneities in the spatiotemporal distribution of the reference data. Our modeling suggests a mean annual climatic mass balance of -0.05 ± 0.40 m w.e. a(-1) for Svalbard over 2000-2011 and a mean equilibrium line altitude of 452 ± 200 m above sea level. We find that the limited spatial resolution of the RCM forcing with respect to real surface topography and the usage of spatially homogeneous RCM output adjustments and mass balance model parameters are responsible for much of the modeling uncertainty. Sensitivity of the results to model parameter uncertainty is comparably small and of minor importance.
Uhl, Felix; Walewski, Łukasz; Forbert, Harald; Marx, Dominik
2014-09-14
The so-called “particles-on-a-sphere” (POS) model has been introduced a while ago in order to describe in simple terms large-amplitude motion of polyatomic hydrides, XH{sub n}. The POS model of protonated methane, CH{sub 5}{sup +}, has been shown to capture well the essence of the fluxional nature of this enigmatic floppy molecule. Here, we extend this model to the POSflex force field by adding flexibility to the C–H bonds, which are constrained to a common fixed bond length in the original model. This makes the present model extremely efficient for computer simulation, including path integral molecular dynamics in order to assess the crucial quantum effects on nuclear motion at low temperatures. Moreover, the POSflex force field can be conveniently used to study microsolvation effects upon combining it with intermolecular pair potentials to account for solute-solvent interactions. Upon computing static properties as well as thermal and quantum fluctuation effects at ambient and low temperatures, respectively, it is shown that the POSflex model is very well suited to describe the structural properties of bare CH{sub 5}{sup +}, including hydrogen scrambling and thus fluxionality in the first place. The far- to mid-infrared spectrum up to the bending band is roughly described, whereas the model fails to account for the well-structured stretching band by construction.
Uhl, Felix; Walewski, Łukasz; Forbert, Harald; Marx, Dominik
2014-09-14
The so-called "particles-on-a-sphere" (POS) model has been introduced a while ago in order to describe in simple terms large-amplitude motion of polyatomic hydrides, XH(n). The POS model of protonated methane, CH₅⁺, has been shown to capture well the essence of the fluxional nature of this enigmatic floppy molecule. Here, we extend this model to the POSflex force field by adding flexibility to the C-H bonds, which are constrained to a common fixed bond length in the original model. This makes the present model extremely efficient for computer simulation, including path integral molecular dynamics in order to assess the crucial quantum effects on nuclear motion at low temperatures. Moreover, the POSflex force field can be conveniently used to study microsolvation effects upon combining it with intermolecular pair potentials to account for solute-solvent interactions. Upon computing static properties as well as thermal and quantum fluctuation effects at ambient and low temperatures, respectively, it is shown that the POSflex model is very well suited to describe the structural properties of bare CH₅⁺, including hydrogen scrambling and thus fluxionality in the first place. The far- to mid-infrared spectrum up to the bending band is roughly described, whereas the model fails to account for the well-structured stretching band by construction.
NASA Astrophysics Data System (ADS)
Hertog, Thomas
2004-12-01
We review some properties of N=8 gauged supergravity in four dimensions with modified, but AdS invariant boundary conditions on the m2 = -2 scalars. There is a one-parameter class of asymptotic conditions on these fields and the metric components, for which the full AdS symmetry group is preserved. The generators of the asymptotic symmetries are finite, but acquire a contribution from the scalar fields. For a large class of such boundary conditions, we find there exist black holes with scalar hair that are specified by a single conserved charge. Since Schwarschild-AdS is a solution too for all boundary conditions, this provides an example of black hole non-uniqueness. We also show there exist solutions where smooth initial data evolve to a big crunch singularity. This opens up the possibility of using the dual conformal field theory to obtain a fully quantum description of the cosmological singularity, and we report on a preliminary study of this.
Mass balances for a biological life support system simulation model
NASA Technical Reports Server (NTRS)
Volk, Tyler; Rumel, John D.
1987-01-01
Design decisions to aid the development of future space-based biological life support systems (BLSS) can be made with simulation models. Here the biochemical stoichiometry is developed for: (1) protein, carbohydrate, fat, fiber, and lignin production in the edible and inedible parts of plants; (2) food consumption and production of organic solids in urine, feces, and wash water by the humans; and (3) operation of the waste processor. Flux values for all components are derived for a steady-state system with wheat as the sole food source.
Bessel functions in mass action modeling of memories and remembrances
NASA Astrophysics Data System (ADS)
Freeman, Walter J.; Capolupo, Antonio; Kozma, Robert; Olivares del Campo, Andrés; Vitiello, Giuseppe
2015-10-01
Data from experimental observations of a class of neurological processes (Freeman K-sets) present functional distribution reproducing Bessel function behavior. We model such processes with couples of damped/amplified oscillators which provide time dependent representation of Bessel equation. The root loci of poles and zeros conform to solutions of K-sets. Some light is shed on the problem of filling the gap between the cellular level dynamics and the brain functional activity. Breakdown of time-reversal symmetry is related with the cortex thermodynamic features. This provides a possible mechanism to deduce lifetime of recorded memory.
The AdS/QCD Correspondence and Exclusive Processes
Brodsky, Stanley J.; de Teramond, Guy F.; Deur, Alexandre; /Jefferson Lab
2010-08-25
The AdS/CFT correspondence between theories in AdS space and conformal field theories in physical space-time provides an analytic, semi-classical, color-confining model for strongly-coupled QCD. The soft-wall AdS/QCD model modified by a positive-sign dilaton metric leads to a remarkable one-parameter description of nonperturbative hadron dynamics at zero quark mass, including a zero-mass pion and a Regge spectrum of linear trajectories with the same slope in orbital angular momentum L and radial quantum number n for both mesons and baryons. One also predicts the form of the non-perturbative effective coupling {alpha}{sub s}{sup AdS}(q) and its {beta}-function which agrees with the effective coupling {alpha}{sub ga} extracted from the Bjorken sum rule. Light-front holography, which connects the fifth-dimensional coordinate of AdS space z to an invariant impact separation variable {zeta}, allows one to compute the analytic form of the frame-independent light-front wavefunctions, the fundamental entities which encode hadron properties as well as decay constants, form factors, deeply virtual Compton scattering, exclusive heavy hadron decays and other exclusive scattering amplitudes. One thus obtains a relativistic description of hadrons in QCD at the amplitude level with dimensional counting for hard exclusive reactions at high momentum transfer. As specific examples we discuss the behavior of the pion and nucleon form factors in the space-like and time-like regions. We also review the phenomenology of exclusive processes including some anomalous empirical results.
Improving the XAJ Model on the Basis of Mass-Energy Balance
NASA Astrophysics Data System (ADS)
Fang, Yuanghao; Corbari, Chiara; Zhang, Xingnan; Mancini, Marco
2014-11-01
The Xin’anjiang(XAJ) model is a conceptual model developed by the group led by Prof. Ren-Jun Zhao, which takes the pan evaporation as one of its input and then computes the effective evapotranspiration (ET) of the catchment by mass balance. Such scheme can ensure a good performance of discharge simulation but has obvious defects, one of which is that the effective ET is spatially-constant over the computation unit, neglecting the spatial variation of variables that influence the effective ET and therefore the simulation of ET and SM by the XAJ model, comparing with discharge, is less reliable. In this study, The XAJ model was improved to employ both energy and mass balance to compute the ET following the energy-mass balance scheme of FEST-EWB. model.
Improving the XAJ Model on the Basis of Mass-Energy Balance
NASA Astrophysics Data System (ADS)
Fang, Yuanhao; Corbari, Chiara; Zhang, Xingnan; Mancini, Marco
2014-11-01
Introduction: The Xin'anjiang(XAJ) model is a conceptual model developed by the group led by Prof. Ren-Jun Zhao, which takes the pan evaporation as one of its input and then computes the effective evapotranspiration (ET) of the catchment by mass balance. Such scheme can ensure a good performance of discharge simulation but has obvious defects, one of which is that the effective ET is spatially-constant over the computation unit, neglecting the spatial variation of variables that influence the effective ET and therefore the simulation of ET and SM by the XAJ model, comparing with discharge, is less reliable. In this study, The XAJ model was improved to employ both energy and mass balance to compute the ET following the energy-mass balance scheme of FEST-EWB. model.
From Mindless Masses to Small Groups: Conceptualizing Collective Behavior in Crowd Modeling
2015-01-01
Computer simulations are increasingly used to monitor and predict behavior at large crowd events, such as mass gatherings, festivals and evacuations. We critically examine the crowd modeling literature and call for future simulations of crowd behavior to be based more closely on findings from current social psychological research. A systematic review was conducted on the crowd modeling literature (N = 140 articles) to identify the assumptions about crowd behavior that modelers use in their simulations. Articles were coded according to the way in which crowd structure was modeled. It was found that 2 broad types are used: mass approaches and small group approaches. However, neither the mass nor the small group approaches can accurately simulate the large collective behavior that has been found in extensive empirical research on crowd events. We argue that to model crowd behavior realistically, simulations must use methods which allow crowd members to identify with each other, as suggested by self-categorization theory. PMID:26388685
A Plasmaspheric Mass Density Model and Constraints on its Heavy Ion Concentration
NASA Technical Reports Server (NTRS)
Berube, D.; Moldwin, M. B.; Green, J. L.
2004-01-01
The first empirical model of the equatorial mass density of the plasmasphere is constructed using ground-based ULF wave diagnostics. Plasmaspheric mass density between L=l.7 and L=3.2 has been determined using over 5200 hours of data from pairs of stations in the MEASURE array of ground magnetometers. The least-squares fit to the data as a function of L shows that mass density falls logarithmically with L. Average ion mass as a function of L is also estimated by combining the mass density model with plasmaspheric electron density profiles determined from the IMAGE Radio Plasma Imager (RPI). Additionally, we use the RPI electron density database to examine how the average ion mass changes under different levels of geomagnetic activity. We find that average ion mass is greatest under the most disturbed conditions. This result indicates that heavy ion concentrations are enhanced during large geomagnetic disturbances, and therefore play an important role in storm-time plasmaspheric dynamics. The average ion mass is also used to constrain the concentrations of He(+) and O(+). Estimates of the He(+) concentration determined this way can be useful for interpreting IMAGE Extreme Ultraviolet Imager (EUV) images.
An open-source library for the numerical modeling of mass-transfer in solid oxide fuel cells
NASA Astrophysics Data System (ADS)
Novaresio, Valerio; García-Camprubí, María; Izquierdo, Salvador; Asinari, Pietro; Fueyo, Norberto
2012-01-01
the simulation of the steady state mass and momentum transport in a multi-species gas mixture, possibly in a porous medium. The software is particularly designed to be used as the mass-transport library for the modeling of solid oxide fuel cells (SOFC). When supplemented with other sub-models, such as thermal and charge-transport ones, it allows the prediction of the cell polarization curve and hence the cell performance. Solution method: Standard finite volume method (FVM) is used for solving all the conservation equations. The pressure-velocity coupling is solved using the SIMPLE algorithm (possibly adding a porous drag term if required). The mass transport can be calculated using different alternative models, namely Fick, Maxwell-Stefan or dusty gas model. The code adopts a segregated method to solve the resulting linear system of equations. The different regions of the SOFC, namely gas channels, electrodes and electrolyte, are solved independently, and coupled through boundary conditions. Restrictions: When extremely large species fluxes are considered, current implementation of the Neumann and Robin boundary conditions do not avoid negative values of molar and/or mass fractions, which finally end up with numerical instability. However this never happened in the documented runs. Eventually these boundary conditions could be reformulated to become more robust. Running time: From seconds to hours depending on the mesh size and number of species. For example, on a 64 bit machine with Intel Core Duo T8300 and 3 GBytes of RAM, the provided test run requires less than 1 second.
Wu, Xiaoli; Kosaraju, Jayasankar; Zhou, Wei; Tam, Kin Yip
2017-03-15
Amyloid β (Aβ) peptide aggregating to form a neurotoxic plaque, leading to cognitive deficits, is believed to be one of the plausible mechanisms for Alzheimer's disease (AD). Inhibiting Aβ aggregation is supposed to offer a neuroprotective effect to ameliorate AD. A previous report has shown that SLM, a carbazole-based fluorophore, binds to Aβ to inhibit the aggregation. However, it is not entirely clear whether the inhibition of Aβ aggregation alone would lead to the anticipated neuroprotective effects. In the current study, we intended to examine the protective action of SLM against Aβ-induced neurotoxicity in vitro and to evaluate if SLM can decrease the cognitive and behavioral deficits observed in triple transgenic AD mouse model (3xTg-AD). In the in vitro study, neurotoxicity induced by Aβ42 in human neuroblastoma (SH-SY5Y) cells was found to be reduced through the treatment with SLM. In the in vivo study, following one month SLM intraperitoneal injection (1, 2, and 4 mg/kg), 3xTg-AD mice were tested on Morris water maze (MWM) and Y-maze for their cognitive ability and sacrificed for biochemical estimations. Results show that SLM treatment improved the learning and memory ability in 3xTg-AD mice in MWM and Y-maze tasks. SLM also mitigated the amyloid burden by decreasing brain Aβ40 and Aβ42 levels and reduced tau phosphorylation, glycogen synthase kinase-3β activity, and neuro-inflammation. From our observations, SLM shows neuroprotection in SH-SY5Y cells against Aβ42 and also in 3xTg-AD mouse model by mitigating the pathological features and behavioral impairments.
Investigation of the mass distribution of a detailed seated male finite element model.
Vavalle, Nicholas A; Thompson, A Bradley; Hayes, Ashley R; Moreno, Daniel P; Stitzel, Joel D; Gayzik, F Scott
2014-06-01
Accurate mass distribution in computational human body models is essential for proper kinematic and kinetic simulations. The purpose of this study was to investigate the mass distribution of a 50th percentile male (M50) full body finite element model (FEM) in the seated position. The FEM was partitioned into 10 segments, using segment planes constructed from bony landmarks per the methods described in previous research studies. Body segment masses and centers of gravity (CGs) of the FEM were compared with values found from these studies, which unlike the present work assumed homogeneous body density. Segment masses compared well to literature while CGs showed an average deviation of 6.0% to 7.0% when normalized by regional characteristic lengths. The discrete mass distribution of the FEM appears to affect the mass and CGs of some segments, particularly those with low-density soft tissues. The locations of the segment CGs are provided in local coordinate systems, thus facilitating comparison with other full body FEMs and human surrogates. The model provides insights into the effects of inhomogeneous mass on the location of body segment CGs.
Performance and Mass Modeling Subtleties in Closed-Brayton-Cycle Space Power Systems
NASA Technical Reports Server (NTRS)
Barrett, Michael J.; Johnson, Paul K.
2006-01-01
A number of potential NASA missions could benefit from closed-Brayton-cycle (CBC) power conversion systems. The human and robotic mission power applications include spacecraft, surface base, and rover scenarios. Modeling of CBC subsystems allows system engineers, mission planners and project managers to make informed decisions regarding power conversion system characteristics and capabilities. To promote thorough modeling efforts, a critical review of CBC modeling techniques is presented. Analysis of critical modeling elements, component influences and cycle sensitivities is conducted. The analysis leads to quantitative results addressing projections on converter efficiency and overall power conversion system mass. Even moderate modeling errors are shown to easily over-predict converter efficiencies by 30% and underestimate mass estimates by 20%. Both static and dynamic modeling regimes are evaluated. Key considerations in determining model fidelity requirements are discussed. Conclusions and recommendations are presented that directly address ongoing modeling efforts in solar and nuclear space power systems.
Performance and Mass Modeling Subtleties in Closed-Brayton-Cycle Space Power Systems
NASA Technical Reports Server (NTRS)
Barrett, Michael J.; Johnson, Paul K.
2005-01-01
A number of potential NASA missions could benefit from closed-Brayton-cycle (CBC) power conversion systems. The human and robotic mission power applications include spacecraft, surface base, and rover scenarios. Modeling of CBC subsystems allows system engineers, mission planners and project managers to make informed decisions regarding power conversion system characteristics and capabilities. To promote thorough modeling efforts, a critical review of CBC modeling techniques is presented. Analysis of critical modeling elements, component influences and cycle sensitivities is conducted. The analysis leads to quantitative results addressing projections on converter efficiency and overall power conversion system mass. Even moderate modeling errors are shown to easily over-predict converter efficiencies by 30 percent and underestimate mass estimates by 20 percent. Both static and dynamic modeling regimes are evaluated. Key considerations in determining model fidelity requirements are discussed. Conclusions and recommendations are presented that directly address ongoing modeling efforts in solar and nuclear space power systems.
NASA Astrophysics Data System (ADS)
Abdol Rahim, A. H.; Tijani, Alhassan Salami; Kamarudin, S. K.; Hanapi, S.
2016-03-01
Polymer electrolyte membrane electrolyzer (PEME) is a candidate for advanced engineering technology. There are many polymer electrolyte membrane fuel cell (PEMFC) models that have been reported, but none regarding PEME. This paper presents state of the art mass transport models applied to PEME, a detailed literature review of these models and associate methods have been conducted. PEME models are typically developed using analytical, semi empirical and mechanistic techniques that are based on their state and spatial dimensions. Methods for developing the PEME models are introduced and briefly explained. Furthermore the model cell voltage of PEME, which consists of Nernst voltage, ohmic over potential, activation over potential, and diffusion over potential is discussed with focus on mass transport modeling. This paper also presents current issues encountered with PEME model.
Yu, Mi Hye; Kim, Hae Ri; Kim, Bo Ram; Park, Eun-Joo; Kim, Hoe Suk; Han, Joon Koo; Choi, Byung Ihn
2016-01-01
Objective To investigate whether high-intensity focused ultrasound (HIFU) combined with microbubbles enhances the therapeutic effects of chemotherapy. Materials and Methods A pancreatic cancer xenograft model was established using BALB/c nude mice and luciferase-expressing human pancreatic cancer cells. Mice were randomly assigned to five groups according to treatment: control (n = 10), gemcitabine alone (GEM; n = 12), HIFU with microbubbles (HIFU + MB, n = 11), combined HIFU and gemcitabine (HIGEM; n = 12), and HIGEM + MB (n = 13). After three weekly treatments, apoptosis rates were evaluated using the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay in two mice per group. Tumor volume and bioluminescence were monitored using high-resolution 3D ultrasound imaging and in vivo bioluminescence imaging for eight weeks in the remaining mice. Results The HIGEM + MB group showed significantly higher apoptosis rates than the other groups (p < 0.05) and exhibited the slowest tumor growth. From week 5, the tumor-volume-ratio relative to the baseline tumor volume was significantly lower in the HIGEM + MB group than in the control, GEM, and HIFU + MB groups (p < 0.05). Despite visible distinction, the HIGEM and HIGEM + MB groups showed no significant differences. Conclusion High-intensity focused ultrasound combined with microbubbles enhances the therapeutic effects of gemcitabine chemotherapy in a pancreatic cancer xenograft model. PMID:27587968
= 4 supersymmetric Yang-Mills theories in AdS3
NASA Astrophysics Data System (ADS)
Kuzenko, Sergei M.; Tartaglino-Mazzucchelli, Gabriele
2014-05-01
For all types of = 4 anti-de Sitter (AdS) supersymmetry in three dimensions, we construct manifestly supersymmetric actions for Abelian vector multiplets and explain how to extend the construction to the non-Abelian case. Manifestly = 4 supersymmetric Yang-Mills (SYM) actions are explicitly given in the cases of (2,2) and critical (4,0) AdS supersymmetries. The = 4 vector multiplets and the corresponding actions are then reduced to (2,0) AdS superspace, in which only = 2 supersymmetry is manifest. Using the off-shell structure of the = 4 vector multiplets, we provide complete = 4 SYM actions in (2,0) AdS superspace for all types of = 4 AdS supersymmetry. In the case of (4,0) AdS supersymmetry, which admits a Euclidean counterpart, the resulting = 2 action contains a Chern-Simons term proportional to q/r, where r is the radius of AdS 3 and q is the R-charge of a chiral scalar superfield. The R-charge is a linear inhomogeneous function of X, an expectation value of the = 4 Cotton superfield. Thus our results explain the mysterious structure of = 4 supersymmetric Yang-Mills theories on S 3 discovered in arXiv:1401.7952. In the case of (3,1) AdS supersymmetry, which has no Euclidean counterpart, the SYM action contains both a Chern-Simons term and a chiral mass-like term. In the case of (2,2) AdS supersymmetry, which admits a Euclidean counterpart, the SYM action has no Chern-Simons and chiral mass-like terms.
NASA Astrophysics Data System (ADS)
Herve, Gwenael; Chauvin, Annick; Lanos, Philippe
2014-05-01
At the regional scale, the dispersion between archaeomagnetic data and especially archaeointensities suggests that some of them may be biased. As a consequence, it appears necessary to perform a selection of available data before to compute mean regional secular variation curves or geomagnetic models. However the definition of suitable selection criteria is not obvious and we need to know how to manage "old" data acquired during the 60-70s. The Western Europe directional and intensity data set from 1500 BC to 200 AD allows to discuss these issues. It has recently been enhanced by 39 new archaeodirections and 23 new archaeointensities (Hervé et al., 2013a and 2013b data sets and 5 unpublished data). First, the whole Western Europe data set was selected but the strong dispersion restricted the accuracy and the reliability of the new Western Europe secular variation curves at Paris. The causes of the dispersion appear different between archaeodirections and archaeointensities. In the directional data set, the main problem comes from some age errors in the oldest published data. Since their publication their archaeological dating may have changed of 50 years or more. For intensity data that were acquired much more recently, the dispersion mainly results from the use of unreliable archaeointensity protocols. We propose a weighting approach based on the number of specimens and the use of pTRM-checks, anisotropy and cooling rate corrections. Only 63% of available archaeodirections and 32% of archaeointensities were used to build the new Western Europe secular variation curves from 1500 BC to 200 AD. These curves reveal that selecting the reference data avoids wrong estimations of the shape of the secular variation curves, the secular variation rate, the dating of archaeomagnetic jerks... Finally, it is worth pointing out that current geomagnetic global models take into account almost all the data that we decided to reject. It could partly explain why their predictions at
2014-01-01
Background Noopept (N-phenyl-acetyl-L-prolylglycine ethyl ester) was constructed as a dipeptide analog of the standard cognition enhancer, piracetam. Our previous experiments have demonstrated the cognition restoring effect of noopept in several animal models of Alzheimer disease (AD). Noopept was also shown to prevent ionic disbalance, excitotoxicity, free radicals and pro-inflammatory cytokines accumulation, and neurotrophine deficit typical for different kinds of brain damages, including AD. In this study, we investigated the neuroprotective action of noopept on cellular model of AD, Aβ25–35-induced toxicity in PC12 cells and revealed the underlying mechanisms. Results The neuroprotective effect of noopept (added to the medium at 10 μM concentration, 72 hours before Аβ25–35) was studied on Аβ25–35-induced injury (5 μM for 24 h) in PC12 cells. The ability of drug to protect the impairments of cell viability, calcium homeostasis, ROS level, mitochondrial function, tau phosphorylation and neurite outgrowth caused by Аβ25–35 were evaluated. Following the exposure of PC12 cells to Аβ25–35 an increase of the level of ROS, intracellular calcium, and tau phosphorylation at Ser396 were observed; these changes were accompanied by a decrease in cell viability and an increase of apoptosis. Noopept treatment before the amyloid-beta exposure improved PC12 cells viability, reduced the number of early and late apoptotic cells, the levels of intracellular reactive oxygen species and calcium and enhanced the mitochondrial membrane potential. In addition, pretreatment of PC12 cell with noopept significantly attenuated tau hyperphosphorylation at Ser396 and ameliorated the alterations of neurite outgrowth evoked by Аβ25–35. Conclusions Taken together, these data provide evidence that novel cognitive enhancer noopept protects PC12 cell against deleterious actions of Aβ through inhibiting the oxidative damage and calcium overload as well as suppressing
Hachisu, Izumi; Kato, Mariko; Saio, Hideyuki; Nomoto, Ken'ichi E-mail: mariko@educ.cc.keio.ac.jp E-mail: nomoto@astron.s.u-tokyo.ac.jp
2012-01-01
Recent observations of Type Ia supernovae (SNe Ia) suggest that some of the progenitor white dwarfs (WDs) had masses up to 2.4-2.8 M{sub Sun }, highly exceeding the Chandrasekhar mass limit. We present a new single degenerate model for SN Ia progenitors, in which the WD mass possibly reaches 2.3-2.7 M{sub Sun }. Three binary evolution processes are incorporated: optically thick winds from mass-accreting WDs, mass stripping from the binary companion star by the WD winds, and WDs being supported by differential rotation. The WD mass can increase by accretion up to 2.3 (2.7) M{sub Sun} from the initial value of 1.1 (1.2) M{sub Sun }, consistent with high-luminosity SNe Ia, such as SN 2003fg, SN 2006gz, SN 2007if, and SN 2009dc. There are three characteristic mass ranges of exploding WDs. In the extreme massive case, differentially rotating WDs explode as an SN Ia soon after the WD mass exceeds 2.4 M{sub Sun} because of a secular instability at T/|W| {approx} 0.14. For the mid-mass range of M{sub WD} = 1.5-2.4 M{sub Sun }, it takes some time (spinning-down time) until carbon is ignited to induce an SN Ia explosion after the WD mass has reached maximum, because it needs a loss or redistribution of angular momentum. For the lower mass case of rigidly rotating WDs, M{sub WD} = 1.38-1.5 M{sub Sun }, the spinning-down time depends on the timescale of angular momentum loss from the WD. The difference in the spinning-down time may produce the 'prompt' and 'tardy' components. We also suggest that the very bright super-Chandrasekhar mass SNe Ia are born in a low-metallicity environment.
Josberger, Edward G.; Bidlake, William R.
2010-01-01
The long-term USGS measurement and reporting of mass balance at South Cascade Glacier was assisted in balance years 2006 and 2007 by a new mass balance model. The model incorporates a temperature-index melt computation and accumulation is modeled from glacier air temperature and gaged precipitation at a remote site. Mass balance modeling was used with glaciological measurements to estimate dates and magnitudes of critical mass balance phenomena. In support of the modeling, a detailed analysis was made of the "glacier cooling effect" that reduces summer air temperature near the ice surface as compared to that predicted on the basis of a spatially uniform temperature lapse rate. The analysis was based on several years of data from measurements of near-surface air temperature on the glacier. The 2006 and 2007 winter balances of South Cascade Glacier, computed with this new, model-augmented methodology, were 2.61 and 3.41 mWE, respectively. The 2006 and 2007 summer balances were -4.20 and -3.63 mWE, respectively, and the 2006 and 2007 net balances were -1.59 and -0.22 mWE. PDF version of a presentation on the mass balance of South Cascade Glacier in Washington state. Presented at the American Geophysical Union Fall Meeting 2010.
Modeling of heat and mass transfer in lateritic building envelopes
NASA Astrophysics Data System (ADS)
Meukam, Pierre; Noumowe, Albert
2005-12-01
The aim of the present work is to investigate the behavior of building envelopes made of local lateritic soil bricks subjected to different climatic conditions. The building envelopes studied in this work consist of lateritic soil bricks with incorporation of natural pozzolan or sawdust in order to obtain small thermal conductivity and low-density materials. In order to describe coupled heat and moisture transfer in wet porous materials, the coupled equations were solved by the introduction of diffusion coefficients. A numerical model HMtrans, developed for prediction of heat and moisture transfer in multi-layered building components, was used to simulate the temperature, water content and relative humidity profiles within the building envelopes. The results allow the prediction of the duration of the exposed building walls to the local weather conditions. They show that the durability of building envelopes made of lateritic soil bricks with incorporation of natural pozzolan or sawdust is not strongly affected by the climatic conditions in tropical and equatorial areas.
NASA Astrophysics Data System (ADS)
Tripathi, D.; Dey, T. K.
2016-04-01
The measurement of superconducting levitation force between permanent magnet and polycrystalline samples of pure and MgB2 added with starch, polystyrene (PS) and multiwall carbon nanotube (MWCNT) have been performed under zero field cooling (ZFC) condition at 20 K in both descending and ascending modes. For this, the bulk pellets were synthesized by conventional solid state sintering technique. The XRD data indicate well developed MgB2 phase. However, a decrease in lattice parameter 'a = b' have been observed for doped MgB2 samples. Superconducting transition temperature of MgB2 also decreases with starch/PS/MWCNT addition. Unlike MWCNT, the addition of starch/polystyrene is found to enhance the levitation force of MgB2 superconductor. The levitation force between PM and investigated pellets in ZFC condition is explained well in terms of the updated version of modified frozen image model and the magnetic moment originated due to vertical motion of the superconductors have been estimated. It may be noted that except for MWCNT, addition of starch/PS in MgB2 improves the magnetic moment generated by vertical movement of pure MgB2. However, this improvement is more pronounced for 1 wt.% of PS added MgB2, which indicates more flux trapping and hence better levitation properties in 1 wt.% of PS added MgB2. The vertical stiffness estimated for pure and starch/PS/MWCNT doped MgB2 samples indicate that the levitation force are more sensitive in the region close to the PM.
NASA Astrophysics Data System (ADS)
Aquila, V.; Swartz, W. H.; Waugh, D. W.; Colarco, P. R.; Pawson, S.; Polvani, L. M.; Stolarski, R. S.
2016-07-01
Satellite instruments show a cooling of global stratospheric temperatures over the whole data record (1979-2014). This cooling is not linear and includes two descending steps in the early 1980s and mid-1990s. The 1979-1995 period is characterized by increasing concentrations of ozone-depleting substances (ODSs) and by the two major volcanic eruptions of El Chichón (1982) and Mount Pinatubo (1991). The 1995-present period is characterized by decreasing ODS concentrations and by the absence of major volcanic eruptions. Greenhouse gas (GHG) concentrations increase over the whole time period. In order to isolate the roles of different forcing agents in the global stratospheric temperature changes, we performed a set of simulations using the NASA Goddard Earth Observing System Chemistry-Climate Model with prescribed sea surface temperatures. We find that in our model simulations the cooling of the stratosphere from 1979 to present is mostly driven by changes in GHG concentrations in the middle and upper stratosphere and by GHG and ODS changes in the lower stratosphere. While the cooling trend caused by increasing GHGs is roughly constant over the satellite era, changing ODS concentrations cause a significant stratospheric cooling only up to the mid-1990s, when they start to decrease because of the implementation of the Montreal Protocol. Sporadic volcanic events and the solar cycle have a distinct signature in the time series of stratospheric temperature anomalies but do not play a statistically significant role in the long-term trends from 1979 to 2014. Several factors combine to produce the step-like behavior in the stratospheric temperatures: in the lower stratosphere, the flattening starting in the mid-1990s is due to the decrease in ozone-depleting substances; Mount Pinatubo and the solar cycle cause the abrupt steps through the aerosol-associated warming and the volcanically induced ozone depletion. In the middle and upper stratosphere, changes in solar