effective world-sheet theory: Topics by Science.gov

Sample records for effective world-sheet theory

The generic world-sheet action of irrational conformal field theory

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

Clubok, K.; Halpern, M.B.

1995-05-01

We review developments in the world-sheet action formulation of the generic irrational conformal field theory, including the non-linear and the linearized forms of the action. These systems form a large class of spin-two gauged WZW actions which exhibit exotic gravitational couplings. Integrating out the gravitational field, we also speculate on a connection with sigma models.
World sheet instantons via the Myers effect and Script N = 1* quiver superpotentials

NASA Astrophysics Data System (ADS)

Hollowood, Timothy J.; Kumar, S. Prem

2002-10-01

In this note we explore the stringy interpretation of non-perturbative effects in Script N = 1* deformations of the Ak-1 quiver models. For certain types of deformations we argue that the massive vacua are described by Nk fractional D3-branes at the orbifold polarizing into k concentric 5-brane spheres each carrying fractional brane charge. The polarization of the D3-branes induces a polarization of D-instantons into string world-sheets wrapped on the Myers spheres. We show that the superpotentials in these models are indeed generated by these world-sheet instantons. We point out that for certain parameter values the condensates yield the exact superpotential for a relevant deformation of the Klebanov-Witten conifold theory.
World Population: Facts in Focus. World Population Data Sheet Workbook. Population Learning Series.

ERIC Educational Resources Information Center

Crews, Kimberly A.

This workbook teaches population analysis using world population statistics. To complete the four student activity sheets, the students refer to the included "1988 World Population Data Sheet" which lists nations' statistical data that includes population totals, projected population, birth and death rates, fertility levels, and the…
Glaciers and Ice Sheets As Analog Environments of Potentially Habitable Icy Worlds

PubMed Central

Garcia-Lopez, Eva; Cid, Cristina

2017-01-01

Icy worlds in the solar system and beyond have attracted a remarkable attention as possible habitats for life. The current consideration about whether life exists beyond Earth is based on our knowledge of life in terrestrial cold environments. On Earth, glaciers and ice sheets have been considered uninhabited for a long time as they seemed too hostile to harbor life. However, these environments are unique biomes dominated by microbial communities which maintain active biochemical routes. Thanks to techniques such as microscopy and more recently DNA sequencing methods, a great biodiversity of prokaryote and eukaryote microorganisms have been discovered. These microorganisms are adapted to a harsh environment, in which the most extreme features are the lack of liquid water, extremely cold temperatures, high solar radiation and nutrient shortage. Here we compare the environmental characteristics of icy worlds, and the environmental characteristics of terrestrial glaciers and ice sheets in order to address some interesting questions: (i) which are the characteristics of habitability known for the frozen worlds, and which could be compatible with life, (ii) what are the environmental characteristics of terrestrial glaciers and ice sheets that can be life-limiting, (iii) What are the microbial communities of prokaryotic and eukaryotic microorganisms that can live in them, and (iv) taking into account these observations, could any of these planets or satellites meet the conditions of habitability? In this review, the icy worlds are considered from the point of view of astrobiological exploration. With the aim of determining whether icy worlds could be potentially habitable, they have been compared with the environmental features of glaciers and ice sheets on Earth. We also reviewed some field and laboratory investigations about microorganisms that live in analog environments of icy worlds, where they are not only viable but also metabolically active. PMID:28804477
Glaciers and Ice Sheets As Analog Environments of Potentially Habitable Icy Worlds.

PubMed

Garcia-Lopez, Eva; Cid, Cristina

2017-01-01

Icy worlds in the solar system and beyond have attracted a remarkable attention as possible habitats for life. The current consideration about whether life exists beyond Earth is based on our knowledge of life in terrestrial cold environments. On Earth, glaciers and ice sheets have been considered uninhabited for a long time as they seemed too hostile to harbor life. However, these environments are unique biomes dominated by microbial communities which maintain active biochemical routes. Thanks to techniques such as microscopy and more recently DNA sequencing methods, a great biodiversity of prokaryote and eukaryote microorganisms have been discovered. These microorganisms are adapted to a harsh environment, in which the most extreme features are the lack of liquid water, extremely cold temperatures, high solar radiation and nutrient shortage. Here we compare the environmental characteristics of icy worlds, and the environmental characteristics of terrestrial glaciers and ice sheets in order to address some interesting questions: (i) which are the characteristics of habitability known for the frozen worlds, and which could be compatible with life, (ii) what are the environmental characteristics of terrestrial glaciers and ice sheets that can be life-limiting, (iii) What are the microbial communities of prokaryotic and eukaryotic microorganisms that can live in them, and (iv) taking into account these observations, could any of these planets or satellites meet the conditions of habitability? In this review, the icy worlds are considered from the point of view of astrobiological exploration. With the aim of determining whether icy worlds could be potentially habitable, they have been compared with the environmental features of glaciers and ice sheets on Earth. We also reviewed some field and laboratory investigations about microorganisms that live in analog environments of icy worlds, where they are not only viable but also metabolically active.
Strain tensor selection and the elastic theory of incompatible thin sheets.

PubMed

Oshri, Oz; Diamant, Haim

2017-05-01

The existing theory of incompatible elastic sheets uses the deviation of the surface metric from a reference metric to define the strain tensor [Efrati et al., J. Mech. Phys. Solids 57, 762 (2009)JMPSA80022-509610.1016/j.jmps.2008.12.004]. For a class of simple axisymmetric problems we examine an alternative formulation, defining the strain based on deviations of distances (rather than distances squared) from their rest values. While the two formulations converge in the limit of small slopes and in the limit of an incompressible sheet, for other cases they are found not to be equivalent. The alternative formulation offers several features which are absent in the existing theory. (a) In the case of planar deformations of flat incompatible sheets, it yields linear, exactly solvable, equations of equilibrium. (b) When reduced to uniaxial (one-dimensional) deformations, it coincides with the theory of extensible elastica; in particular, for a uniaxially bent sheet it yields an unstrained cylindrical configuration. (c) It gives a simple criterion determining whether an isometric immersion of an incompatible sheet is at mechanical equilibrium with respect to normal forces. For a reference metric of constant positive Gaussian curvature, a spherical cap is found to satisfy this criterion except in an arbitrarily narrow boundary layer.
Strain tensor selection and the elastic theory of incompatible thin sheets

NASA Astrophysics Data System (ADS)

Oshri, Oz; Diamant, Haim

2017-05-01

The existing theory of incompatible elastic sheets uses the deviation of the surface metric from a reference metric to define the strain tensor [Efrati et al., J. Mech. Phys. Solids 57, 762 (2009), 10.1016/j.jmps.2008.12.004]. For a class of simple axisymmetric problems we examine an alternative formulation, defining the strain based on deviations of distances (rather than distances squared) from their rest values. While the two formulations converge in the limit of small slopes and in the limit of an incompressible sheet, for other cases they are found not to be equivalent. The alternative formulation offers several features which are absent in the existing theory. (a) In the case of planar deformations of flat incompatible sheets, it yields linear, exactly solvable, equations of equilibrium. (b) When reduced to uniaxial (one-dimensional) deformations, it coincides with the theory of extensible elastica; in particular, for a uniaxially bent sheet it yields an unstrained cylindrical configuration. (c) It gives a simple criterion determining whether an isometric immersion of an incompatible sheet is at mechanical equilibrium with respect to normal forces. For a reference metric of constant positive Gaussian curvature, a spherical cap is found to satisfy this criterion except in an arbitrarily narrow boundary layer.
World-volume effective theory for higher-dimensional black holes.

PubMed

Emparan, Roberto; Harmark, Troels; Niarchos, Vasilis; Obers, Niels A

2009-05-15

We argue that the main feature behind novel properties of higher-dimensional black holes, compared to four-dimensional ones, is that their horizons can have two characteristic lengths of very different size. We develop a long-distance world-volume effective theory that captures the black hole dynamics at scales much larger than the short scale. In this limit the black hole is regarded as a blackfold: a black brane (possibly boosted locally) whose world volume spans a curved submanifold of the spacetime. This approach reveals black objects with novel horizon geometries and topologies more complex than the black ring, but more generally it provides a new organizing framework for the dynamics of higher-dimensional black holes.
Loop Variables in String Theory

NASA Astrophysics Data System (ADS)

Sathiapalan, B.

The loop variable approach is a proposal for a gauge-invariant generalization of the sigma-model renormalization group method of obtaining equations of motion in string theory. The basic guiding principle is space-time gauge invariance rather than world sheet properties. In essence it is a version of Wilson's exact renormalization group equation for the world sheet theory. It involves all the massive modes and is defined with a finite world sheet cutoff, which allows one to go off the mass-shell. On shell the tree amplitudes of string theory are reproduced. The equations are gauge-invariant off shell also. This paper is a self-contained discussion of the loop variable approach as well as its connection with the Wilsonian RG.
M theory through the looking glass: Tachyon condensation in the E{sub 8} heterotic string

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

Horava, Petr; Keeler, Cynthia A.

2008-03-15

We study the spacetime decay to nothing in string theory and M-theory. First we recall a nonsupersymmetric version of heterotic M-theory, in which bubbles of nothing--connecting the two E{sub 8} boundaries by a throat--are expected to be nucleated. We argue that the fate of this system should be addressed at weak string coupling, where the nonperturbative instanton instability is expected to turn into a perturbative tachyonic one. We identify the unique string theory that could describe this process: The heterotic model with one E{sub 8} gauge group and a singlet tachyon. We then use world sheet methods to study themore » tachyon condensation in the Neveu-Schwarz-Ramond formulation of this model, and show that it induces a world sheet super-Higgs effect. The main theme of our analysis is the possibility of making meaningful alternative gauge choices for world sheet supersymmetry, in place of the conventional superconformal gauge. We show in a version of unitary gauge how the world sheet gravitino assimilates the Goldstino and becomes dynamical. This picture clarifies recent results of Hellerman and Swanson. We also present analogs of R{sub {xi}} gauges, and note the importance of logarithmic conformal field theories in the context of tachyon condensation.« less
Electronic properties of T graphene-like C-BN sheets: A density functional theory study

NASA Astrophysics Data System (ADS)

Majidi, R.

2015-11-01

We have used density functional theory to study the electronic properties of T graphene-like C, C-BN and BN sheets. The planar T graphene with metallic property has been considered. The results show that the presence of BN has a considerable effect on the electronic properties of T graphene. The T graphene-like C-BN and BN sheets show semiconducting properties. The energy band gap is increased by enhancing the number of BN units. The possibility of opening and controlling band gap opens the door for T graphene in switchable electronic devices.
Nonlocal postbuckling analysis of graphene sheets with initial imperfection based on first order shear deformation theory

NASA Astrophysics Data System (ADS)

Soleimani, Ahmad; Naei, Mohammad Hasan; Mashhadi, Mahmoud Mosavi

In this paper, the first order shear deformation theory (FSDT) is used to investigate the postbuckling behavior of orthotropic single-layered graphene sheet (SLGS) under in-plane loadings. Nonlocal elasticity theory and von-Karman nonlinear model in combination with the isogeometric analysis (IGA) have been applied to study the postbuckling characteristics of SLGSs. In contrast to the classical model, the nonlocal continuum model developed in this work considers the size-effects on the postbuckling characteristics of SLGSs. FSDT takes into account effects of shear deformations through-the-thickness of plate. Geometric imperfection which is defined as a very small transverse displacement of the mid-plane is applied on undeformed nanoplate to create initial deviation in graphene sheet from being perfectly flat. Nonlinear governing equations of motion for SLGS are derived from the principle of virtual work and a variational formulation. At the end, the results are presented as the postbuckling equilibrium paths of SLGS. The influence of various parameters such as edge length, nonlocal parameter, compression ratio, boundary conditions and aspect ratio on the postbuckling path is investigated. The results of this work show the high accuracy of nonlocal FSDT-based analysis for postbuckling behavior of graphene sheets.
String scattering amplitudes and deformed cubic string field theory

NASA Astrophysics Data System (ADS)

Lai, Sheng-Hong; Lee, Jen-Chi; Lee, Taejin; Yang, Yi

2018-01-01

We study string scattering amplitudes by using the deformed cubic string field theory which is equivalent to the string field theory in the proper-time gauge. The four-string scattering amplitudes with three tachyons and an arbitrary string state are calculated. The string field theory yields the string scattering amplitudes evaluated on the world sheet of string scattering whereas the conventional method, based on the first quantized theory brings us the string scattering amplitudes defined on the upper half plane. For the highest spin states, generated by the primary operators, both calculations are in perfect agreement. In this case, the string scattering amplitudes are invariant under the conformal transformation, which maps the string world sheet onto the upper half plane. If the external string states are general massive states, generated by non-primary field operators, we need to take into account carefully the conformal transformation between the world sheet and the upper half plane. We show by an explicit calculation that the string scattering amplitudes calculated by using the deformed cubic string field theory transform into those of the first quantized theory on the upper half plane by the conformal transformation, generated by the Schwarz-Christoffel mapping.
Polar process and world climate /A brief overview/

NASA Technical Reports Server (NTRS)

Goody, R.

1980-01-01

A review is presented of events relating polar regions to the world climate, the mechanisms of sea ice and polar ice sheets, and of two theories of the Pleistocene Ice Ages. The sea ice which varies over time scales of one or two years and the polar ice sheets with time changes measured in tens or hundreds of thousands of years introduce two distinct time constants into global time changes; the yearly Arctic sea ice variations affect northern Europe and have some effect over the entire Northern Hemisphere; the ice-albedo coupling in the polar ice sheets is involved in major climatic events such as the Pleistocene ice ages. It is concluded that climate problems require a global approach including the atmosphere, the oceans, and the cryosphere.
A new approach to the linear theory of single-species tearing in two-dimensional quasi-neutral sheets

NASA Technical Reports Server (NTRS)

Brittnacher, M.; Quest, K. B.; Karimabadi, H.

1995-01-01

We have developed the linear theory of collisionless ion tearing in a two-dimensional magnetotail equilibrium for a single resonant species. We have solved the normal mode problem for tearing instability by an algorithm that employs particle-in-cell simulation to calculate the orbit integrals in the Maxwell-Vlasov eigenmode equation. The results of our single-species tearing analysis can be applied to ion tearing where electron effects are not included. We have calculated the tearing growth rate as a function of the magnetic field component B(sub n) normal to the current sheet for thick and thin current sheets, and we show that marginal stability occurs when the normal gyrofrequency Omega(sub n) is comparable to the Harris neutral sheet growth rate. A cross-tail B(sub y) component has little effect on the growth rate for B(sub y) approximately = B(sub n). Even in the limit B(sub y) much greater than B(sub n), the mode is strongly stabilized by B(sub n). We report than random pitch angle scattering can overcome the stabilizing effect of B(sub n) and drive the growth rate up toward the Harris neutral sheet (B(sub n) = 0) value when the pitch angle diffusion rate is comparable to Omega(sub n).
Maxwell's theory of eddy currents in thin conducting sheets, and applications to electromagnetic shielding and MAGLEV

NASA Astrophysics Data System (ADS)

Saslow, W. M.

1992-08-01

Using the example of a monopole that is spontaneously generated above a thin conducting sheet, the simplicity and power of Maxwell's 1872 theory of eddy currents in thin conducting sheets is illustrated. This theory employs a receding image construction, with a characteristic recession velocity v0=2/(μ0σd), where the sheet has conductivity σ and thickness d. A modern derivation of the theory, employing the magnetic scalar potential, is also presented, with explicit use of the uniqueness theorem. Also discussed are limitations on the theory of which Maxwell, living in a time before the discovery of the electron, could not have been aware. Previous derivations either have not appealed explicitly to the uniqueness theorem, or have employed the now unfamiliar current function, and are therefore either incomplete or inaccessible to the modern reader. After the derivation, two important examples considered by Maxwell are presented-a monopole moving above a thin conducting sheet, and a monopole above a rotating thin conducting sheet (Arago's disk)-and it is argued that the lift force thus obtained makes Maxwell the grandfather, if not the father, of eddy current MAGLEV transportation systems. An energy conservation argument is given to derive Davis's result that, for a magnet of arbitrary size and shape moving parallel to a thin conducting sheet at a characteristic height h, with velocity v, the ratio of drag force to lift force is equal to v0/v, provided that d≪δc, where δc =√2h/(μ0σv). If d≫δc, the eddy currents are confined to a thickness δc, leading to an increase in the dissipation and the drag by a factor of d/δc, so that the ratio of drag to lift force becomes proportional to √v'0/v, where v'0 = 2/(μ0σh). The case of a monopole fixed in position, but oscillating in strength (such as can be simulated by one end of a long, narrow, ac solenoid), is also treated. This is employed to obtain the results for an oscillating magnetic dipole whose moment
Origin of gauge invariance in string theory

NASA Technical Reports Server (NTRS)

Horowitz, G. T.; Strominger, A.

1986-01-01

A first quantization of the space-time embedding Chi exp mu and the world-sheet metric rho of the open bosonic string. The world-sheet metric rho decouples from S-matrix elements in 26 dimensions. This formulation of the theory naturally includes 26-dimensional gauge transformations. The gauge invariance of S-matrix elements is a direct consequence of the decoupling of rho. Second quantization leads to a string field Phi(Chi exp mu, rho) with a gauge-covariant equation of motion.
Covariant open bosonic string field theory on multiple D-branes in the proper-time gauge

NASA Astrophysics Data System (ADS)

Lee, Taejin

2017-12-01

We construct a covariant open bosonic string field theory on multiple D-branes, which reduces to a non-Abelian group Yang-Mills gauge theory in the zero-slope limit. Making use of the first quantized open bosonic string in the proper time gauge, we convert the string amplitudes given by the Polyakov path integrals on string world sheets into those of the second quantized theory. The world sheet diagrams generated by the constructed open string field theory are planar in contrast to those of the Witten's cubic string field theory. However, the constructed string field theory is yet equivalent to the Witten's cubic string field theory. Having obtained planar diagrams, we may adopt the light-cone string field theory technique to calculate the multi-string scattering amplitudes with an arbitrary number of external strings. We examine in detail the three-string vertex diagram and the effective four-string vertex diagrams generated perturbatively by the three-string vertex at tree level. In the zero-slope limit, the string scattering amplitudes are identified precisely as those of non-Abelian Yang-Mills gauge theory if the external states are chosen to be massless vector particles.
The intense world theory - a unifying theory of the neurobiology of autism.

PubMed

Markram, Kamila; Markram, Henry

2010-01-01

Autism covers a wide spectrum of disorders for which there are many views, hypotheses and theories. Here we propose a unifying theory of autism, the Intense World Theory. The proposed neuropathology is hyper-functioning of local neural microcircuits, best characterized by hyper-reactivity and hyper-plasticity. Such hyper-functional microcircuits are speculated to become autonomous and memory trapped leading to the core cognitive consequences of hyper-perception, hyper-attention, hyper-memory and hyper-emotionality. The theory is centered on the neocortex and the amygdala, but could potentially be applied to all brain regions. The severity on each axis depends on the severity of the molecular syndrome expressed in different brain regions, which could uniquely shape the repertoire of symptoms of an autistic child. The progression of the disorder is proposed to be driven by overly strong reactions to experiences that drive the brain to a hyper-preference and overly selective state, which becomes more extreme with each new experience and may be particularly accelerated by emotionally charged experiences and trauma. This may lead to obsessively detailed information processing of fragments of the world and an involuntarily and systematic decoupling of the autist from what becomes a painfully intense world. The autistic is proposed to become trapped in a limited, but highly secure internal world with minimal extremes and surprises. We present the key studies that support this theory of autism, show how this theory can better explain past findings, and how it could resolve apparently conflicting data and interpretations. The theory also makes further predictions from the molecular to the behavioral levels, provides a treatment strategy and presents its own falsifying hypothesis.
Experimental Study of Deformation and of Effective Width in Axially Loaded Sheet-stringer Panels

NASA Technical Reports Server (NTRS)

Ramberg, Walter; MCPHERSON ALBERT E; Levy, Sam

1939-01-01

The deformation of two sheet-stringer panels subjected to end compression under carefully controlled end conditions was measured at a number of points and at a number of loads, most of which were above the load at which the sheet had begun to buckle. The two panels were identical except for the sheet, which was 0.70-inch 24st alclad for specimen 1 and 0.025-inch 24st aluminum alloy for specimen 6. A technique was developed for attaching Tuckerman optical strain gauges to the sheet without disturbing the strain distribution in the sheet by the method of attachment. This technique was used to explore the strain distribution in the sheet at various loads. The twisting and the bending of the stringers was measured by means of pointers attached to the stringers. The shape of the buckles in the sheet of specimen 6 was recorded at two loads by means of plaster casts. The sheet and the stringer loads at failure are compared with the corresponding loads for five similar panels tested at the Navy Model Basin. A detailed comparison is made between the measured deformation of the buckled sheet and the deformation calculated from approximate theories for the deformation in a rectangular sheet with freely supported edges buckling under end compression advanced by Timoshenko, Frankland, and Marguerre. The measured effective width for the specimens is compared with the effective width given by nine different relations for effective width as a function of the edge stress divided by the buckling stress of the sheet. The analysis of the measured stringer deformation is confined to an application of Southwell's method of plotting deformation against deformation over load. It was concluded that the stringer failure in both specimens were due to an instability in which the stringer was simultaneously twisted and bent as a column.

Building Theories: The Three Worlds of Mathematics

ERIC Educational Resources Information Center

Tall, David

2004-01-01

In this commentary on Matthew Inglis' "Three Worlds and the Imaginary Sphere" (see EJ1106688), David Tall develops the theme that the building of theories is not an easy process. A theory in progress is a particularly delicate creation. Theories do not appear fully formed. There is a period of exploration and incubation that precedes the…
Magnetic field dissipation in D-sheets

NASA Technical Reports Server (NTRS)

Burlaga, L. F.; Scudder, J. D.

1973-01-01

The effects of magnetic field annihilation at a tangential or rotational discontinuity in a resistive plasma are examined. The magnetic field intensity profile depends on (1) the field intensities far from the current sheet (+ and - infinity), (2) the angle between the two intensities, and (3) the electrical resistivity. For a tangential discontinuity, the theory predicts a depression in B, centered at the discontinuity, and it predicts a monotonic transition. The theory provides satisfactory fits to the magnetic field intensity and proton temperature profiles observed for two extremely broad D-sheets in the solar wind. Assuming a diffusion time 10 days, one obtains effective resistivities or approximately = 3 x 10 to the 12th power and 2 x 10 to the 13th power emu for the D-sheets. Either resistivity at directional discontinuities is much lower than 10 to the 12th power emu or annihilation does not always occur at discontinuities.
The Intense World Theory – A Unifying Theory of the Neurobiology of Autism

PubMed Central

Markram, Kamila; Markram, Henry

2010-01-01

Autism covers a wide spectrum of disorders for which there are many views, hypotheses and theories. Here we propose a unifying theory of autism, the Intense World Theory. The proposed neuropathology is hyper-functioning of local neural microcircuits, best characterized by hyper-reactivity and hyper-plasticity. Such hyper-functional microcircuits are speculated to become autonomous and memory trapped leading to the core cognitive consequences of hyper-perception, hyper-attention, hyper-memory and hyper-emotionality. The theory is centered on the neocortex and the amygdala, but could potentially be applied to all brain regions. The severity on each axis depends on the severity of the molecular syndrome expressed in different brain regions, which could uniquely shape the repertoire of symptoms of an autistic child. The progression of the disorder is proposed to be driven by overly strong reactions to experiences that drive the brain to a hyper-preference and overly selective state, which becomes more extreme with each new experience and may be particularly accelerated by emotionally charged experiences and trauma. This may lead to obsessively detailed information processing of fragments of the world and an involuntarily and systematic decoupling of the autist from what becomes a painfully intense world. The autistic is proposed to become trapped in a limited, but highly secure internal world with minimal extremes and surprises. We present the key studies that support this theory of autism, show how this theory can better explain past findings, and how it could resolve apparently conflicting data and interpretations. The theory also makes further predictions from the molecular to the behavioral levels, provides a treatment strategy and presents its own falsifying hypothesis. PMID:21191475
Charting the landscape of supercritical string theory.

PubMed

Hellerman, Simeon; Swanson, Ian

2007-10-26

Special solutions of string theory in supercritical dimensions can interpolate in time between theories with different numbers of spacetime dimensions and different amounts of world sheet supersymmetry. These solutions connect supercritical string theories to the more familiar string duality web in ten dimensions and provide a precise link between supersymmetric and purely bosonic string theories. Dimension quenching and c duality appear to be natural concepts in string theory, giving rise to large networks of interconnected theories.
The Effective Width of Curved Sheet After Buckling

NASA Technical Reports Server (NTRS)

Wenzek, W A

1938-01-01

This report describes experiments made for the purpose of ascertaining the effective width of circularly curved sheet under pure flexural stress. A relation for the effective width of curved sheets is established. Experiments were made with circular cylinders compressed in longitudinal direction. The sheets were rigidly built in at the sides parallel to the axis of the cylinder.
Single-World Theory of the Extended Wigner's Friend Experiment

NASA Astrophysics Data System (ADS)

Sudbery, Anthony

2017-05-01

Frauchiger and Renner have recently claimed to prove that "Single-world interpretations of quantum theory cannot be self-consistent". This is contradicted by a construction due to Bell, inspired by Bohmian mechanics, which shows that any quantum system can be modelled in such a way that there is only one "world" at any time, but the predictions of quantum theory are reproduced. This Bell-Bohmian theory is applied to the experiment proposed by Frauchiger and Renner, and their argument is critically examined. It is concluded that it is their version of "standard quantum theory", incorporating state vector collapse upon measurement, that is not self-consistent.
An investigation of the astronomical theory of the ice ages using a simple climate-ice sheet model

NASA Technical Reports Server (NTRS)

Pollard, D.

1978-01-01

The astronomical theory of the Quaternary ice ages is incorporated into a simple climate model for global weather; important features of the model include the albedo feedback, topography and dynamics of the ice sheets. For various parameterizations of the orbital elements, the model yields realistic assessments of the northern ice sheet. Lack of a land-sea heat capacity contrast represents one of the chief difficulties of the model.
Thermoelectric properties of single-layered SnSe sheet.

PubMed

Wang, Fancy Qian; Zhang, Shunhong; Yu, Jiabing; Wang, Qian

2015-10-14

Motivated by the recent study of inspiring thermoelectric properties in bulk SnSe [Zhao et al., Nature, 2014, 508, 373] and the experimental synthesis of SnSe sheets [Chen et al., J. Am. Chem. Soc., 2013, 135, 1213], we have carried out systematic calculations for a single-layered SnSe sheet focusing on its stability, electronic structure and thermoelectric properties by using density functional theory combined with Boltzmann transport theory. We have found that the sheet is dynamically and thermally stable with a band gap of 1.28 eV, and the figure of merit (ZT) reaches 3.27 (2.76) along the armchair (zigzag) direction with optimal n-type carrier concentration, which is enhanced nearly 7 times compared to its bulk counterpart at 700 K due to quantum confinement effect. Furthermore, we designed four types of thermoelectric couples by assembling single-layered SnSe sheets with different transport directions and doping types, and found that their efficiencies are all above 13%, which are higher than those of thermoelectric couples made of commercial bulk Bi2Te3 (7%-8%), suggesting the great potential of single-layered SnSe sheets for heat-electricity conversion.
World Population and Beyond: A Teaching Strategy for Global Studies [And] Interchange. Population Education Newsletter. Vol. 7, No. 2, May 1978 [And] 1977 World Population Data Sheet.

ERIC Educational Resources Information Center

Clark, Leon E.; And Others

The unit contains a teacher's guide, student reading materials, and data sheets about a variety of worldwide demographic and economic variables. Designed for students in junior high through college, its goals are to encourage students to analyze the causes and consequences of world population and economic trends, and to detect interrelationships…
Analysis of low-dose radiation shield effectiveness of multi-gate polymeric sheets

NASA Astrophysics Data System (ADS)

Kim, S. C.; Lee, H. K.; Cho, J. H.

2014-07-01

Computed tomography (CT) uses a high dose of radiation to create images of the body. As patients are exposed to radiation during a CT scan, the use of shielding materials becomes essential in CT scanning. This study was focused on the radiation shielding materials used for patients during a CT scan. In this study, sheets were manufactured to shield the eyes and the thyroid, the most sensitive parts of the body, against radiation exposure during a CT scan. These sheets are manufactured using silicone polymers, barium sulfate (BaSO4) and tungsten, with the aim of making these sheets equally or more effective in radiation shielding and more cost-effective than lead sheets. The use of barium sulfate drew more attention than tungsten due to its higher cost-effectiveness. The barium sulfate sheets were coated to form a multigate structure by applying the maximum charge rate during the agitator and subsequent mixing processes and creating multilayered structures on the surface. To measure radiation shielding effectiveness, the radiation dose was measured around both eyes and the thyroid gland using sheets in three different thicknesses (1, 2 and 3 mm). Among the 1 and 2 mm sheets, the Pb sheets exhibited greater effectiveness in radiation shielding around both eyes, but the W sheets were more effective in radiation shielding around the thyroid gland. In the 3 mm sheets, the Pb sheet also attenuated a higher amount of radiation around both eyes while the W sheet was more effective around the thyroid gland. In conclusion, the sheets made from barium sulfate and tungsten proved highly effective in shielding against low-dose radiation in CT scans without causing ill-health effects, unlike lead.
Theory of buttressed marine ice sheet dynamics and its application to the assessment of tipping-point conditions

NASA Astrophysics Data System (ADS)

Pegler, S.

2017-12-01

Understanding the fate of the West Antarctic Ice Sheet is constrained by difficulties of resolving the buttressing effect of ice shelves and its dynamic response to grounding-line migration. This effect may be responsible for protecting a large majority of outlet glaciers in Antarctica against surging into the ocean. I present a theoretical methodology for assessing the positions and stability of grounding lines that incorporates closed-form, dynamic descriptions of ice-shelf buttressing and extensional (stretching) viscous stresses. The method is applied to assess the conditions for grounding-line tipping points. Such points are shown to produce abrupt `cliff-edge' transitions to runaway retreat, representing the so-called marine ice sheet instability. Depending on the bed profile, melt and calving rates, a tipping point can either lie very near to a local maximum in the bed topography or potentially far upstream of it, along a reverse bed. The model predictions for both wide and narrow embayments are validated by numerical simulations and laboratory experiments. A case study of Pine Island Glacier indicates the possibility for long-term stabilisation, with the analytical method affording an extensive exploration of scenarios. The theory also elucidates a mode of grounding-line migration controlled entirely by the determinants of the ice-shelf buttressing force, with a loss of sensitivity to basal conditions, contrasting with the conclusion from one-dimensional theory that the ice shelf is irrelevant. The results provide an interpretive framework for understanding grounding-line dynamics, its coupling with ice-shelf dynamics, an efficient exploration of parameter variation, and a complement to large-scale simulation.
Precision Sheet Metal. Progress Record and Theory Outline.

ERIC Educational Resources Information Center

Connecticut State Dept. of Education, Hartford. Div. of Vocational-Technical Schools.

This combination progress record and course outline is designed for use by individuals teaching a course in precision sheet metal. Included among the topics addressed in the course are the following: employment opportunities in metalworking, measurement and layout, orthographic projection, precision sheet metal drafting, simple layout, hand tools,…
Potential Climatic Effects on the Greenland Ice Sheet

NASA Technical Reports Server (NTRS)

Bindschadler, R. A.

1984-01-01

The Greenland Ice Sheet covers an area of 1,720,000 sq. km and contains approximately 2,600,000 cu km of ice. Most of the ice sheet receives an excess of snow accumulation over the amount of ice lost to wind, meltwater run-off or other ablative processes. The majority of mass loss occurs at the margin of the ice sheet as either surface melt, which flows into the sea or calving of icebergs from the tongues of outlet glaciers. Many estimates of these processes were published. An average of five published estimates is summarized. If these estimates are correct, then the Greenland Ice Sheet is in approximate equilibrium and contributes 490 cu km/a of fresh water to the North Atlantic and Arctic Oceans. Climate effects, ice sheet flow, and application of remote sensing to tracking of the ice sheet are discussed.
TOPICAL PROBLEMS: The phenomenological theory of world population growth

NASA Astrophysics Data System (ADS)

Kapitza, Sergei P.

1996-01-01

Of all global problems world population growth is the most significant. Demographic data describe this process in a concise and quantitative way in its past and present. Analysing this development it is possible by applying the concepts of systems analysis and synergetics, to work out a mathematical model for a phenomenological description of the global demographic process and to project its trends into the future. Assuming self-similarity as the dynamic principle of development, growth can be described practically over the whole of human history, assuming the growth rate to be proportional to the square of the number of people. The large parameter of the theory and the effective size of a coherent population group is of the order of 105 and the microscopic parameter of the phenomenology is the human lifespan. The demographic transition — a transition to a stabilised world population of some 14 billion in a foreseeable future — is a systemic singularity and is determined by the inherent pattern of growth of an open system, rather than by the lack of resources. The development of a quantitative nonlinear theory of the world population is of interest for interdisciplinary research in anthropology and demography, history and sociology, for population genetics and epidemiology, for studies in evolution of humankind and the origin of man. The model also provides insight into the stability of growth and the present predicament of humankind, and provides a setting for discussing the main global problems.
Covalent addition of chitosan to graphene sheets: Density functional theory explorations of quadrupole coupling constants

NASA Astrophysics Data System (ADS)

Mokhtari, Ali; Harismah, Kun; Mirzaei, Mahmoud

2015-12-01

Density functional theory (DFT) calculations have been performed to detect the stabilities and properties of chitosan-functionalized graphene and graphene-oxide structures (G-Chit and GO-Chit). The model systems with two different sizes of sheets have been optimized and the molecular and atomic properties have been evaluated for them. The results indicated that investigated G-Chit and GO-Chit structures could be considered as stable structures but with different properties. The properties for GO and GO-Chit structures are almost similar; however, they are different from the original G and G-Chit structures. The results also indicated that the properties could be also size-dependent, in which different molecular and atomic properties have been observed for the investigate G sheets.
Dynamics of a radially expanding liquid sheet: Experiments

NASA Astrophysics Data System (ADS)

Majumdar, Nayanika; Tirumkudulu, Mahesh

2017-11-01

A recent theory predicts that sinuous waves generated at the center of a radially expanding liquid sheet grow spatially even in absence of a surrounding gas phase. Unlike flat liquid sheets, the thickness of a radially expanding liquid sheet varies inversely with distance from the center of the sheet. To test the predictions of the theory, experiments were carried out on a horizontal, radially expanding liquid sheet formed by collision of a single jet on a solid impactor. The latter was placed on a speaker-vibrator with controlled amplitude and frequency. The growth of sinuous waves was determined by measuring the wave surface inclination angle using reflected laser light under both atmospheric and sub-atmospheric pressure conditions. It is shown that the measured growth rate matches with the predictions of the theory over a large range of Weber numbers for both pressure conditions suggesting that the thinning of the liquid sheet plays a dominant role in setting the growth rate of sinuous waves with minimal influence of the surrounding gas phase on its dynamics. IIT Bombay.
Equivalence Between Squirrel Cage and Sheet Rotor Induction Motor

NASA Astrophysics Data System (ADS)

Dwivedi, Ankita; Singh, S. K.; Srivastava, R. K.

2016-06-01

Due to topological changes in dual stator induction motor and high cost of its fabrication, it is convenient to replace the squirrel cage rotor with a composite sheet rotor. For an experimental machine, the inner and outer stator stampings are normally available whereas the procurement of rotor stampings is quite cumbersome and is not always cost effective. In this paper, the equivalence between sheet/solid rotor induction motor and squirrel cage induction motor has been investigated using layer theory of electrical machines, so as to enable one to utilize sheet/solid rotor in dual port experimental machines.
Using Grounded Theory to Understand the Recognition, Reflection on, Development, and Effects of Geography Teachers' Attitudes toward Regions around the World

ERIC Educational Resources Information Center

Lee, Dong-min

2018-01-01

This study attempts to illuminate the recognition, reflection, development, and effects of geography teachers' attitudes toward regions around the world (ATRAWs) using Straussian grounded theory. A total of 194 concepts were categorized into 18 categories, and three types were identified. The findings of this study show that geography teachers…
Effect of Temperature and Sheet Temper on Isothermal Solidification Kinetics in Clad Aluminum Brazing Sheet

NASA Astrophysics Data System (ADS)

Benoit, Michael J.; Whitney, Mark A.; Wells, Mary A.; Winkler, Sooky

2016-09-01

Isothermal solidification (IS) is a phenomenon observed in clad aluminum brazing sheets, wherein the amount of liquid clad metal is reduced by penetration of the liquid clad into the core. The objective of the current investigation is to quantify the rate of IS through the use of a previously derived parameter, the Interface Rate Constant (IRC). The effect of peak temperature and initial sheet temper on IS kinetics were investigated. The results demonstrated that IS is due to the diffusion of silicon (Si) from the liquid clad layer into the solid core. Reduced amounts of liquid clad at long liquid duration times, a roughened sheet surface, and differences in resolidified clad layer morphology between sheet tempers were observed. Increased IS kinetics were predicted at higher temperatures by an IRC model as well as by experimentally determined IRC values; however, the magnitudes of these values are not in good agreement due to deficiencies in the model when applied to alloys. IS kinetics were found to be higher for sheets in the fully annealed condition when compared with work-hardened sheets, due to the influence of core grain boundaries providing high diffusivity pathways for Si diffusion, resulting in more rapid liquid clad penetration.
Between Faith and Science: World Culture Theory and Comparative Education

ERIC Educational Resources Information Center

Carney, Stephen; Rappleye, Jeremy; Silova, Iveta

2012-01-01

World culture theory seeks to explain an apparent convergence of education through a neoinstitutionalist lens, seeing global rationalization in education as driven by the logic of science and the myth of progress. While critics have challenged these assumptions by focusing on local manifestations of world-level tendencies, such critique is…

Experimental Research on Just-World Theory: Problems, Developments, and Future Challenges

ERIC Educational Resources Information Center

Hafer, Carolyn L.; Begue, Laurent

2005-01-01

M. J. Lerner (1980) proposed that people need to believe in a just world; thus, evidence that the world is not just is threatening, and people have a number of strategies for reducing such threats. Early research on this idea, and on just-world theory more broadly, was reviewed in early publications (e.g., M. J. Lerner, 1980; M. J. Lerner & D. T.…
A nonlocal strain gradient model for dynamic deformation of orthotropic viscoelastic graphene sheets under time harmonic thermal load

NASA Astrophysics Data System (ADS)

Radwan, Ahmed F.; Sobhy, Mohammed

2018-06-01

This work presents a nonlocal strain gradient theory for the dynamic deformation response of a single-layered graphene sheet (SLGS) on a viscoelastic foundation and subjected to a time harmonic thermal load for various boundary conditions. Material of graphene sheets is presumed to be orthotropic and viscoelastic. The viscoelastic foundation is modeled as Kelvin-Voigt's pattern. Based on the two-unknown plate theory, the motion equations are obtained from the dynamic version of the virtual work principle. The nonlocal strain gradient theory is established from Eringen nonlocal and strain gradient theories, therefore, it contains two material scale parameters, which are nonlocal parameter and gradient coefficient. These scale parameters have two different effects on the graphene sheets. The obtained deflection is compared with that predicted in the literature. Additional numerical examples are introduced to illustrate the influences of the two length scale coefficients and other parameters on the dynamic deformation of the viscoelastic graphene sheets.
Dynamics of Radially Expanding Liquid Sheets

NASA Astrophysics Data System (ADS)

Majumdar, Nayanika; Tirumkudulu, Mahesh S.

2018-04-01

The process of atomization often involves ejecting thin liquid sheets at high speeds from a nozzle that causes the sheet to flap violently and break up into fine droplets. The flapping of the liquid sheet has long been attributed to the sheet's interaction with the surrounding gas phase. Here, we present experimental evidence to the contrary and show that the flapping is caused by the thinning of the liquid sheet as it spreads out from the nozzle exit. The measured growth rates of the waves agree remarkably well with the predictions of a recent theory that accounts for the sheet's thinning but ignores aerodynamic interactions. We anticipate these results to not only lead to more accurate predictions of the final drop-size distribution but also enable more efficient designs of atomizers.
Personality maturation around the world: a cross-cultural examination of social-investment theory.

PubMed

Bleidorn, Wiebke; Klimstra, Theo A; Denissen, Jaap J A; Rentfrow, Peter J; Potter, Jeff; Gosling, Samuel D

2013-12-01

During early adulthood, individuals from different cultures across the world tend to become more agreeable, more conscientious, and less neurotic. Two leading theories offer different explanations for these pervasive age trends: Five-factor theory proposes that personality maturation is largely determined by genetic factors, whereas social-investment theory proposes that personality maturation in early adulthood is largely the result of normative life transitions to adult roles. In the research reported here, we conducted the first systematic cross-cultural test of these theories using data from a large Internet-based sample of young adults from 62 nations (N = 884,328). We found strong evidence for universal personality maturation from early to middle adulthood, yet there were significant cultural differences in age effects on personality traits. Consistent with social-investment theory, results showed that cultures with an earlier onset of adult-role responsibilities were marked by earlier personality maturation.
Elastic effects on vibration of bilayer graphene sheets incorporating integrated VdWs interactions

NASA Astrophysics Data System (ADS)

Kamali, Kamran; Nazemnezhad, Reza; Zare, Mojtaba

2018-03-01

The following study addresses the free vibration analysis of a bilayer graphene sheet (BLGS) embedded in an elastic medium in the presence of shear and tensile-compressive effects of van der Waals (vdWs) interactions. To ascertain the contribution of each force, the effects are considered separately and simultaneously. To model the geometry of the BLGS, the sandwich plate theory and the Hamilton’s principle are considered to derive the governing equations of motion. The Harmonic differential quadrature method is applied to solve the coupled equations and obtain the natural frequencies and related mode shapes. The results reveal that the contribution of tensile-compressive modulus of elastic medium is the most in changing the frequency of BLGSs.
How Do Virtual World Experiences Bring about Learning? A Critical Review of Theories

ERIC Educational Resources Information Center

Loke, Swee-Kin

2015-01-01

While students do learn real-world knowledge and skills in virtual worlds, educators have yet to adequately theorise how students' virtual world experiences bring about this learning. This paper critically reviewed theories currently used to underpin empirical work in virtual worlds for education. In particular, it evaluated how applicable these…
Early Tests of Piagetian Theory Through World War II.

PubMed

Beins, Bernard C

2016-01-01

Psychologists recognized the importance of Jean Piaget's theory from its inception. Within a year of the appearance of his first book translated into English, The Language and Thought of the Child (J. Piaget, 1926) , it had been reviewed and welcomed; shortly thereafter, psychologists began testing the tenets of the theory empirically. The author traces the empirical testing of his theory in the 2 decades following publication of his initial book. A review of the published literature through the World War II era reveals that the research resulted in consistent failure to support the theoretical mechanisms that Piaget proposed. Nonetheless, the theory ultimately gained traction to become the bedrock of developmental psychology. Reasons for its persistence may include a possible lack of awareness by psychologists about the lack of empirical support, its breadth and complexity, and a lack of a viable alternate theory. As a result, the theory still exerts influence in psychology even though its dominance has diminished.
Provincialising the World Culture Theory Debate: Critical Insights from a Margin

ERIC Educational Resources Information Center

Takayama, Keita

2015-01-01

Neo-institutionalist theory of global "isomorphism", or so-called World Culture Theory (WCT), has been much debated in comparative education. One notable feature of the debate is that the vast majority of its participants belong to a handful of closely knit comparative education communities. Ironically enough then, a debate that…
Julius Edgar Lilienfeld Prize Lecture: The Higgs Boson, String Theory, and the Real World

NASA Astrophysics Data System (ADS)

Kane, Gordon

2012-03-01

In this talk I'll describe how string theory is exciting because it can address most, perhaps all, of the questions we hope to understand about our world: why quarks and leptons make up our world, what forces form our world, cosmology, parity violation, and much more. I'll explain why string theory is testable in basically the same ways as the rest of physics, and why much of what is written about that is misleading. String theory is already or soon being tested in several ways, including correctly predicting the recently observed Higgs boson properties and mass, and predictions for dark matter, LHC physics, cosmological history, and more, from work in the increasingly active subfield ``string phenomenology.''
Yang-Mills gauge conditions from Witten's open string field theory

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

Feng Haidong; Siegel, Warren

2007-02-15

We construct the Zinn-Justin-Batalin-Vilkovisky action for tachyons and gauge bosons from Witten's 3-string vertex of the bosonic open string without gauge fixing. Through canonical transformations, we find the off-shell, local, gauge-covariant action up to 3-point terms, satisfying the usual field theory gauge transformations. Perturbatively, it can be extended to higher-point terms. It also gives a new gauge condition in field theory which corresponds to the Feynman-Siegel gauge on the world-sheet.
Collisionless current sheet equilibria

NASA Astrophysics Data System (ADS)

Neukirch, T.; Wilson, F.; Allanson, O.

2018-01-01

Current sheets are important for the structure and dynamics of many plasma systems. In space and astrophysical plasmas they play a crucial role in activity processes, for example by facilitating the release of magnetic energy via processes such as magnetic reconnection. In this contribution we will focus on collisionless plasma systems. A sensible first step in any investigation of physical processes involving current sheets is to find appropriate equilibrium solutions. The theory of collisionless plasma equilibria is well established, but over the past few years there has been a renewed interest in finding equilibrium distribution functions for collisionless current sheets with particular properties, for example for cases where the current density is parallel to the magnetic field (force-free current sheets). This interest is due to a combination of scientific curiosity and potential applications to space and astrophysical plasmas. In this paper we will give an overview of some of the recent developments, discuss their potential applications and address a number of open questions.
On Compressible Vortex Sheets

NASA Astrophysics Data System (ADS)

Secchi, Paolo

2005-05-01

We introduce the main known results of the theory of incompressible and compressible vortex sheets. Moreover, we present recent results obtained by the author with J. F. Coulombel about supersonic compressible vortex sheets in two space dimensions. The problem is a nonlinear free boundary hyperbolic problem with two difficulties: the free boundary is characteristic and the Lopatinski condition holds only in a weak sense, yielding losses of derivatives. Under a supersonic condition that precludes violent instabilities, we prove an energy estimate for the boundary value problem obtained by linearization around an unsteady piecewise solution.
Effect of Cell Sheet Manipulation Techniques on the Expression of Collagen Type II and Stress Fiber Formation in Human Chondrocyte Sheets.

PubMed

Wongin, Sopita; Waikakul, Saranatra; Chotiyarnwong, Pojchong; Siriwatwechakul, Wanwipa; Viravaidya-Pasuwat, Kwanchanok

2018-03-01

Cell sheet technology is applied to human articular chondrocytes to construct a tissue-like structure as an alternative treatment for cartilage defect. The effect of a gelatin manipulator, as a cell sheet transfer system, on the quality of the chondrocyte sheets was investigated. The changes of important chondrogenic markers and stress fibers, resulting from the cell sheet manipulation, were also studied. The chondrocyte cell sheets were constructed with patient-derived chondrocytes using a temperature-responsive polymer and a gelatin manipulator as a transfer carrier. The properties of the cell sheets, including sizes, expression levels of collagen type II and I, and the localization of the stress fibers, were assessed and compared with those of the cell sheets harvested without the gelatin manipulator. Using the gelatin manipulator, the original size of the chondrocyte cell sheets was retained with abundant stress fibers, but with a decrease in the expression of collagen type II. Without the gelatin manipulator, although the cell shrinkage occurred, the cell sheet with suppressed stress fiber formation showed significantly higher levels of collagen type II. These results support our observations that stress fiber formation in chondrocyte cell sheets affected the production of chondrogenic markers. These densely packed tissue-like structures possessed a good chondrogenic activity, indicating their potential for use in autologous chondrocyte implantation to treat cartilage defects.
Mirage effect from thermally modulated transparent carbon nanotube sheets.

PubMed

Aliev, Ali E; Gartstein, Yuri N; Baughman, Ray H

2011-10-28

The single-beam mirage effect, also known as photothermal deflection, is studied using a free-standing, highly aligned carbon nanotube aerogel sheet as the heat source. The extremely low thermal capacitance and high heat transfer ability of these transparent forest-drawn carbon nanotube sheets enables high frequency modulation of sheet temperature over an enormous temperature range, thereby providing a sharp, rapidly changing gradient of refractive index in the surrounding liquid or gas. The advantages of temperature modulation using carbon nanotube sheets are multiple: in inert gases the temperature can reach > 2500 K; the obtained frequency range for photothermal modulation is ~100 kHz in gases and over 100 Hz in high refractive index liquids; and the heat source is transparent for optical and acoustical waves. Unlike for conventional heat sources for photothermal deflection, the intensity and phase of the thermally modulated beam component linearly depends upon the beam-to-sheet separation over a wide range of distances. This aspect enables convenient measurements of accurate values for thermal diffusivity and the temperature dependence of refractive index for both liquids and gases. The remarkable performance of nanotube sheets suggests possible applications as photo-deflectors and for switchable invisibility cloaks, and provides useful insights into their use as thermoacoustic projectors and sonar. Visibility cloaking is demonstrated in a liquid.
In situ Observations of Heliospheric Current Sheets Evolution

NASA Astrophysics Data System (ADS)

Liu, Yong; Peng, Jun; Huang, Jia; Klecker, Berndt

2017-04-01

We investigate the Heliospheric current sheet observation time difference of the spacecraft using the STEREO, ACE and WIND data. The observations are first compared to a simple theory in which the time difference is only determined by the radial and longitudinal separation between the spacecraft. The predictions fit well with the observations except for a few events. Then the time delay caused by the latitudinal separation is taken in consideration. The latitude of each spacecraft is calculated based on the PFSS model assuming that heliospheric current sheets propagate at the solar wind speed without changing their shapes from the origin to spacecraft near 1AU. However, including the latitudinal effects does not improve the prediction, possibly because that the PFSS model may not locate the current sheets accurately enough. A new latitudinal delay is predicted based on the time delay using the observations on ACE data. The new method improved the prediction on the time lag between spacecraft; however, further study is needed to predict the location of the heliospheric current sheet more accurately.
Exposure age and ice-sheet model constraints on Pliocene East Antarctic ice sheet dynamics.

PubMed

Yamane, Masako; Yokoyama, Yusuke; Abe-Ouchi, Ayako; Obrochta, Stephen; Saito, Fuyuki; Moriwaki, Kiichi; Matsuzaki, Hiroyuki

2015-04-24

The Late Pliocene epoch is a potential analogue for future climate in a warming world. Here we reconstruct Plio-Pleistocene East Antarctic Ice Sheet (EAIS) variability using cosmogenic nuclide exposure ages and model simulations to better understand ice sheet behaviour under such warm conditions. New and previously published exposure ages indicate interior-thickening during the Pliocene. An ice sheet model with mid-Pliocene boundary conditions also results in interior thickening and suggests that both the Wilkes Subglacial and Aurora Basins largely melted, offsetting increased ice volume. Considering contributions from West Antarctica and Greenland, this is consistent with the most recent IPCC AR5 estimate, which indicates that the Pliocene sea level likely did not exceed +20 m on Milankovitch timescales. The inception of colder climate since ∼3 Myr has increased the sea ice cover and inhibited active moisture transport to Antarctica, resulting in reduced ice sheet thickness, at least in coastal areas.
Postbuckling analysis of multi-layered graphene sheets under non-uniform biaxial compression

NASA Astrophysics Data System (ADS)

Farajpour, Ali; Arab Solghar, Alireza; Shahidi, Alireza

2013-01-01

In this article, the nonlinear buckling characteristics of multi-layered graphene sheets are investigated. The graphene sheet is modeled as an orthotropic nanoplate with size-dependent material properties. The graphene film is subjected by non-uniformly distributed in-plane load through its thickness. To include the small scale and the geometrical nonlinearity effects, the governing differential equations are derived based on the nonlocal elasticity theory in conjunction with the von Karman geometrical model. Explicit expressions for the postbuckling loads of single- and double-layered graphene sheets with simply supported edges under biaxial compression are obtained. For numerical results, six types of armchair and zigzag graphene sheets with different aspect ratio are considered. The present formulation and method of solution are validated by comparing the results, in the limit cases, with those available in the open literature. Excellent agreement between the obtained and available results is observed. Finally, the effects of nonlocal parameter, buckling mode number, compression ratio and non-uniform parameter on the postbuckling behavior of multi-layered graphene sheets are studied.
Theoretical analysis of sheet metal formability

NASA Astrophysics Data System (ADS)

Zhu, Xinhai

Sheet metal forming processes are among the most important metal-working operations. These processes account for a sizable proportion of manufactured goods made in industrialized countries each year. Furthermore, to reduce the cost and increase the performance of manufactured products, in addition to the environmental concern, more and more light weight and high strength materials have been used as a substitute to the conventional steel. These materials usually have limited formability, thus, a thorough understanding of the deformation processes and the factors limiting the forming of sound parts is important, not only from a scientific or engineering viewpoint, but also from an economic point of view. An extensive review of previous studies pertaining to theoretical analyses of Forming Limit Diagrams (FLDs) is contained in Chapter I. A numerical model to analyze the neck evolution process is outlined in Chapter II. With the use of strain gradient theory, the effect of initial defect profile on the necking process is analyzed. In the third chapter, the method proposed by Storen and Rice is adopted to analyze the initiation of localized neck and predict the corresponding FLDs. In view of the fact that the width of the localized neck is narrow, the deformation inside the neck region is constrained by the material in the neighboring homogeneous region. The relative rotation effect may then be assumed to be small and is thus neglected. In Chapter IV, Hill's 1948 yield criterion and strain gradient theory are employed to obtain FLDs, for planar anisotropic sheet materials by using bifurcation analysis. The effects of the strain gradient coefficient c and the material anisotropic parameters R's on the orientation of the neck and FLDs are analyzed in a systematic manner and compared with experiments. In Chapter V, Hill's 79 non-quadratic yield criterion with a deformation theory of plasticity is used along with bifurcation analyses to derive a general analytical
Nonperturbative corrections to 4D string theory effective actions from SL(2,Z) duality and supersymmetry.

PubMed

Robles-Llana, Daniel; Rocek, Martin; Saueressig, Frank; Theis, Ulrich; Vandoren, Stefan

2007-05-25

We find the D(-1)- and D1-brane instanton contributions to the hypermultiplet moduli space of type IIB string compactifications on Calabi-Yau threefolds. These combine with known perturbative and world sheet instanton corrections into a single modular invariant function that determines the hypermultiplet low-energy effective action.
Bayesian theories of conditioning in a changing world.

PubMed

Courville, Aaron C; Daw, Nathaniel D; Touretzky, David S

2006-07-01

The recent flowering of Bayesian approaches invites the re-examination of classic issues in behavior, even in areas as venerable as Pavlovian conditioning. A statistical account can offer a new, principled interpretation of behavior, and previous experiments and theories can inform many unexplored aspects of the Bayesian enterprise. Here we consider one such issue: the finding that surprising events provoke animals to learn faster. We suggest that, in a statistical account of conditioning, surprise signals change and therefore uncertainty and the need for new learning. We discuss inference in a world that changes and show how experimental results involving surprise can be interpreted from this perspective, and also how, thus understood, these phenomena help constrain statistical theories of animal and human learning.

Microwave effects on NiMoS and CoMoS single-sheet catalysts.

PubMed

Borges, I; Silva, Alexander M; Modesto-Costa, Lucas

2018-05-04

Single-sheet nanoclusters of MoS 2 , NiMoS or CoMoS are widely used in hydrodesulfurization (HDS) catalysis in the petroleum industry. In HDS reactions under microwave irradiation, experiments indirectly pointed out that for pristine MoS 2 reaction rates are accelerated because hot spots are generated on the catalyst bed. In this work, we investigated NiMoS and CoMoS isolated single-sheet substituted catalysts before and after thiophene adsorption focusing on quantifying the effect of microwave irradiation. For that purpose, density functional theory (DFT) molecular charge densities of each system were decomposed according to the distributed multipole analysis (DMA) of Stone. Site dipole values of each system were directly associated with a larger or smaller interaction with the microwave field according to a proposed general approach. We showed that microwave enhancement of HDS reaction rates can occur more efficiently in the CoMoS and NiMoS promoted clusters compared to pristine MoS 2 in the following order: CoMoS > NiMoS > MoS 2 . The atomic origin of the catalyst hot spots induced by microwaves was clearly established in the promoted clusters.
The effect of the neutral sheet structure of the interplanetary magnetic field on cosmic ray distribution in space

NASA Technical Reports Server (NTRS)

Alania, M. V.; Aslamazashvili, R. G.; Bochorishvili, T.; Djapiashvili, T. V.; Tkemaladze, V. S.

1985-01-01

Results of the numerical solution of the anistoropic diffusion equation are presented. The modulation depth of galactic cosmic rays is defined by the degree of curvature of the neutral current sheet in the heliosphere. The effect of the regular interplanetary magnetic field (IMF) on cosmic ray anisotropy in the period of solar activity minimum (in 1976) is analyzed by the data of the neutron super-monitors of the world network, and the heliolatitudinal gradient and cosmic ray diffusion coefficient are defined.
A Guide to Effective School Leadership Theories

ERIC Educational Resources Information Center

Lynch, Matthew

2012-01-01

Educational administrators know that leadership requires hundreds of judgments each day that require a sensitivity and understanding of various leadership strategies. Bridging the gap between the academic and practical world, "A Guide to Effective School Leadership Theories" provides an exploration of ten dominant leadership strategies to give…
Effects of mechanical strain on the performance of germanene sheets: Strength, failure behavior, and electronic structure

NASA Astrophysics Data System (ADS)

Ding, Ning; Wang, Huan; Liu, Long; Guo, Weimin; Chen, Xiangfeng; Wu, Chi-Man Lawrence

2018-02-01

As a two-dimensional material with a low-buckling structure, germanene has attracted considerable interest because of its excellent physical properties, such as massless Dirac fermions and quantum spin Hall effect. The mechanical characteristics of germanene are of the utmost importance when one is assessing its viability for nanodevices, especially for ones with defects. In this work, the stabilities, mechanical properties, and changes in electronic properties under mechanical strain for both pristine and defective germanene sheets were studied and analyzed with use of density functional theory. The mechanical properties of defect-free germanene exhibited obvious anisotropy along different directions. The mechanical properties of germanene sheets exhibited high sensitivity to the defect parameters, such as the linear density of vacancies, the width of the cracks, and the inflection angles caused by the grain boundaries. In addition, the applied mechanical strain changed the electronic properties of germanene to a large extent. The information obtained will be useful for the understanding and potential application of germanene.
An experimental study on particle effects in liquid sheets

NASA Astrophysics Data System (ADS)

Sauret, Alban; Troger, Anthony; Jop, Pierre

2017-06-01

Many industrial processes, such as surface coating or liquid transport in tubes, involve liquid sheets or thin films of suspensions. In these situations, the thickness of the liquid film becomes comparable to the particle size, which leads to unexpected dynamics. In addition, the classical constitutive rheological law for suspensions cannot be applied as the continuum approximation is no longer valid. Here, we consider experimentally a transient particle-laden liquid sheet that expands radially. We characterize the influence of the particles on the shape of the liquid film and the atomization process. We highlight that the presence of particles modifies the thickness and stability of the liquid sheet. Our study suggests that the influence of particles through capillary effects can modify significantly the dynamics of processes that involve suspensions and particles confined in liquid films.
Bending and buckling formulation of graphene sheets based on nonlocal simple first-order shear deformation theory

NASA Astrophysics Data System (ADS)

Golmakani, M. E.; Malikan, M.; Sadraee Far, M. N.; Majidi, H. R.

2018-06-01

This paper presents a formulation based on simple first-order shear deformation theory (S-FSDT) for large deflection and buckling of orthotropic single-layered graphene sheets (SLGSs). The S-FSDT has many advantages compared to the classical plate theory (CPT) and conventional FSDT such as needless of shear correction factor, containing less number of unknowns than the existing FSDT and strong similarities with the CPT. Governing equations and boundary conditions are derived based on Hamilton’s principle using the nonlocal differential constitutive relations of Eringen and von Kármán geometrical model. Numerical results are obtained using differential quadrature (DQ) method and the Newton–Raphson iterative scheme. Finally, some comparison studies are carried out to show the high accuracy and reliability of the present formulations compared to the nonlocal CPT and FSDT for different thicknesses, elastic foundations and nonlocal parameters.
Stabilization of Inviscid Vortex Sheets

NASA Astrophysics Data System (ADS)

Protas, Bartosz; Sakajo, Takashi

2017-11-01

In this study we investigate the problem of stabilizing inviscid vortex sheets via feedback control. Such models, expressed in terms of the Birkhoff-Rott equation, are often used to describe the Kevin-Helmholtz instability of shear layers and are known to be strongly unstable to small-scale perturbations. First, we consider the linear stability of a straight vortex sheet in the periodic setting with actuation in the form of an array of point vortices or sources located a certain distance away from the sheet. We establish conditions under which this system is controllable and observable. Next, using methods of the linear control theory, we synthesize a feedback control strategy which stabilizes a straight vortex sheet in the linear regime. Given the poor conditioning of the discretized problem, reliable solution of the resulting algebraic Riccati equation requires the use of high-precision arithmetic. Finally, we demonstrate that this control approach also succeeds in the nonlinear regime, provided the magnitude of the initial perturbation is sufficiently small.
Many-Worlds Interpretation of Quantum Theory and Mesoscopic Anthropic Principle

NASA Astrophysics Data System (ADS)

Kamenshchik, A. Yu.; Teryaev, O. V.

2008-10-01

We suggest to combine the Anthropic Principle with Many-Worlds Interpretation of Quantum Theory. Realizing the multiplicity of worlds it provides an opportunity of explanation of some important events which are assumed to be extremely improbable. The Mesoscopic Anthropic Principle suggested here is aimed to explain appearance of such events which are necessary for emergence of Life and Mind. It is complementary to Cosmological Anthropic Principle explaining the fine tuning of fundamental constants. We briefly discuss various possible applications of Mesoscopic Anthropic Principle including the Solar Eclipses and assembling of complex molecules. Besides, we address the problem of Time's Arrow in the framework of Many-World Interpretation. We suggest the recipe for disentangling of quantities defined by fundamental physical laws and by an anthropic selection.
Experimental realization of two-dimensional boron sheets

NASA Astrophysics Data System (ADS)

Feng, Baojie; Zhang, Jin; Zhong, Qing; Li, Wenbin; Li, Shuai; Li, Hui; Cheng, Peng; Meng, Sheng; Chen, Lan; Wu, Kehui

2016-06-01

A variety of two-dimensional materials have been reported in recent years, yet single-element systems such as graphene and black phosphorus have remained rare. Boron analogues have been predicted, as boron atoms possess a short covalent radius and the flexibility to adopt sp2 hybridization, features that favour the formation of two-dimensional allotropes, and one example of such a borophene material has been reported recently. Here, we present a parallel experimental work showing that two-dimensional boron sheets can be grown epitaxially on a Ag(111) substrate. Two types of boron sheet, a β12 sheet and a χ3 sheet, both exhibiting a triangular lattice but with different arrangements of periodic holes, are observed by scanning tunnelling microscopy. Density functional theory simulations agree well with experiments, and indicate that both sheets are planar without obvious vertical undulations. The boron sheets are quite inert to oxidization and interact only weakly with their substrate. We envisage that such boron sheets may find applications in electronic devices in the future.
Space Charge Effect in the Sheet and Solid Electron Beam

NASA Astrophysics Data System (ADS)

Song, Ho Young; Kim, Hyoung Suk; Ahn, Saeyoung

1998-11-01

We analyze the space charge effect of two different types of electron beam ; sheet and solid electron beam. Electron gun simulations are carried out using shadow and control grids for high and low perveance. Rectangular and cylindrical geometries are used for sheet and solid electron beam in planar and disk type cathode. The E-gun code is used to study the limiting current and space charge loading in each geometries.
Effect of a large-sized silicone sheet upon recovery of mastoid aeration after mastoidectomy.

PubMed

Kazama, Kyosuke; Takahashi, Haruo; Kaieda, Satoru; Iwanaga, Tetsu; Yamamoto-Fukuda, Tomomi; Yoshida, Haruo; Kumagami, Hidetaka; Takasaki, Kenji

2008-06-01

To evaluate the effect of our large-sized silicone sheet upon postoperative recovery of mastoid aeration in ears after surgery including mastoidectomy and soft-wall reconstruction (SWR). Retrospective chart review in a tertiary care center. Recovery of mastoid aeration was assessed by CT 4 to 12 months after surgery on 72 ears (69 patients), in which the silicone sheet covering from the eustachian tube (ET) to the mastoid was placed after SWR procedure with mastoidectomy were done for their chronic otitis media. Results were compared with those with a small silicone sheet. Recovery of mastoid aeration was significantly better in the large-silicone-sheet group than in the small-silicone-sheet group (chi(2) value = 11.7146, P = 0.0006). This preliminary study suggested that our large-sized silicone sheet may be effective for postoperative recovery of mastoid aeration even in ears operated with SWR procedure.
Theory of impossible worlds: Toward a physics of information

NASA Astrophysics Data System (ADS)

Buscema, Paolo Massimo; Sacco, Pier Luigi; Della Torre, Francesca; Massini, Giulia; Breda, Marco; Ferilli, Guido

2018-05-01

In this paper, we introduce an innovative approach to the fusion between datasets in terms of attributes and observations, even when they are not related at all. With our technique, starting from datasets representing independent worlds, it is possible to analyze a single global dataset, and transferring each dataset onto the others is always possible. This procedure allows a deeper perspective in the study of a problem, by offering the chance of looking into it from other, independent points of view. Even unrelated datasets create a metaphoric representation of the problem, useful in terms of speed of convergence and predictive results, preserving the fundamental relationships in the data. In order to extract such knowledge, we propose a new learning rule named double backpropagation, by which an auto-encoder concurrently codifies all the different worlds. We test our methodology on different datasets and different issues, to underline the power and flexibility of the Theory of Impossible Worlds.
Theory of impossible worlds: Toward a physics of information.

PubMed

Buscema, Paolo Massimo; Sacco, Pier Luigi; Della Torre, Francesca; Massini, Giulia; Breda, Marco; Ferilli, Guido

2018-05-01

In this paper, we introduce an innovative approach to the fusion between datasets in terms of attributes and observations, even when they are not related at all. With our technique, starting from datasets representing independent worlds, it is possible to analyze a single global dataset, and transferring each dataset onto the others is always possible. This procedure allows a deeper perspective in the study of a problem, by offering the chance of looking into it from other, independent points of view. Even unrelated datasets create a metaphoric representation of the problem, useful in terms of speed of convergence and predictive results, preserving the fundamental relationships in the data. In order to extract such knowledge, we propose a new learning rule named double backpropagation, by which an auto-encoder concurrently codifies all the different worlds. We test our methodology on different datasets and different issues, to underline the power and flexibility of the Theory of Impossible Worlds.
Effect of cryopreservation on proliferation and differentiation of periodontal ligament stem cell sheets.

PubMed

Li, Mengying; Feng, Cheng; Gu, Xiuge; He, Qin; Wei, Fulan

2017-04-17

Cryopreservation has been extensively applied to the long-term storage of a diverse range of biological materials. However, no comprehensive study is currently available on the cryopreservation of periodontal ligament stem cell (PDLSC) sheets which have been suggested as excellent transplant materials for periodontal tissue regeneration. The aim of this study is to investigate the effect of cryopreservation on the structural integrity and functional viability of PDLSC sheets. PDLSC sheets prepared from extracted human molars were divided into two groups: the cryopreservation group (cPDLSC sheets) and the freshly prepared control group (fPDLSC sheets). The cPDLSC sheets were cryopreserved in a solution consisting of 90% fetal bovine serum and 10% dimethyl sulfoxide for 3 months. Cell viability and cell proliferation rates of PDLSCs in both groups were evaluated by cell viability assay and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, respectively. The multilineage differentiation potentials of the cells were assessed by von Kossa staining and Oil Red O staining. The chromosomal stability was examined by karyotype analysis. Moreover, the cell sheets in each group were transplanted subcutaneously into the dorsal site of nude mice, after which Sirius Red staining was performed to analyze the efficiency of tissue regeneration. The PDLSCs derived from both groups of cell sheets showed no significant difference in their viability, proliferative capacities, and multilineage differentiation potentials, as well as chromosomal stability. Furthermore, transplantation experiments based on a mouse model demonstrated that the cPDLSC sheets were equally effective in generating viable osteoid tissues in vivo as their freshly prepared counterparts. In both cases, the regenerated tissues showed similar network patterns of bone-like matrix. Our results offer convincing evidence that cryopreservation does not alter the biological properties of PDLSC sheets
Ultraviolet photodetectors based on ZnO sheets: The effect of sheet size on photoresponse properties

NASA Astrophysics Data System (ADS)

Ghasempour Ardakani, Abbas; Pazoki, Meysam; Mahdavi, Seyed Mohammad; Bahrampour, Ali Reza; Taghavinia, Nima

2012-05-01

In this work, ultraviolet photodetectors based on electrodeposited ZnO sheet thin films were fabricated on a glass substrate. Before electrodeposition, a thin buffer layer of ZnO was deposited on the glass by pulsed laser deposition method. This layer not only acted as a nucleation site for ZnO sheet growth, but also made it possible to use cheap glass substrate instead of conventional fluorine-doped tin oxide (FTO) substrate. Our results showed that photoresponse properties of the photodetectors strongly depend on the sheet sizes. The smaller sheets exhibited enhanced photosensitivity, shortened fall times and decreased gain compared to larger ones. We showed that photodetectors based on ZnO sheets have a faster response than ones based on polycrystalline films. It was also shown that even less response time could be obtained by using comb-like electrodes instead of two-electrode.
Spiraling Cracks in Thin Sheets

NASA Astrophysics Data System (ADS)

Romero, Victor; Roman, Benoit; Cerda, Enrique

2008-03-01

A wide kind of everyday-life industrial products come in a thin package that needs to be torn open by the user, and the opening is not always easy. We built a simple setup to study crack propagation in thin sheets coupled with large out-of-plane displacement : A cylindrical tool is inserted in a straight incision in a thin sheet, and is pushed against the sheet perpendicularly to that incision, eventually propagating a crack. When the blunt tool is continually pushed against the lip, we found that the crack follows a very robust spiraling path. Experiments may be interpreted in terms of ``Spira Mirabilis'' (logarithmic spiral). Starting with crack theory argument, we will show that the early behavior of the cut path follows a portion of a logathmic spiral, and that the path tends to another spiral with a different pitch as the crack adds more turns. Our crack experiment illustrates the fact that thin sheets mechanics is deeply connected to geometry, and finally spirals characteristics allow us to measure material crack properties of the thin layer used.
Optimal swimming of a sheet.

PubMed

Montenegro-Johnson, Thomas D; Lauga, Eric

2014-06-01

Propulsion at microscopic scales is often achieved through propagating traveling waves along hairlike organelles called flagella. Taylor's two-dimensional swimming sheet model is frequently used to provide insight into problems of flagellar propulsion. We derive numerically the large-amplitude wave form of the two-dimensional swimming sheet that yields optimum hydrodynamic efficiency: the ratio of the squared swimming speed to the rate-of-working of the sheet against the fluid. Using the boundary element method, we show that the optimal wave form is a front-back symmetric regularized cusp that is 25% more efficient than the optimal sine wave. This optimal two-dimensional shape is smooth, qualitatively different from the kinked form of Lighthill's optimal three-dimensional flagellum, not predicted by small-amplitude theory, and different from the smooth circular-arc-like shape of active elastic filaments.
Non-Abelian semilocal strings in N=2 supersymmetric QCD

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

Shifman, M.; Yung, A.; Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg 188300

2006-06-15

We consider a benchmark bulk theory in four dimensions: N=2 supersymmetric QCD with the gauge group U(N) and N{sub f} flavors of fundamental matter hypermultiplets (quarks). The nature of the Bogomol'nyi-Prasad-Sommerfield (BPS) strings in this benchmark theory crucially depends on N{sub f}. If N{sub f}{>=}N and all quark masses are equal, it supports non-Abelian BPS strings which have internal (orientational) moduli. If N{sub f}>N these strings become semilocal, developing additional moduli {rho} related to (unlimited) variations of their transverse size. Using the U(2) gauge group with N{sub f}=3, 4 as an example, we derive an effective low-energy theory on themore » (two-dimensional) string world sheet. Our derivation is field theoretic, direct and explicit: we first analyze the Bogomol'nyi equations for string-geometry solitons, suggest an ansatz, and solve it at large {rho}. Then we use this solution to obtain the world-sheet theory. In the semiclassical limit our result confirms the Hanany-Tong conjecture, which rests on brane-based arguments, that the world-sheet theory is an N=2 supersymmetric U(1) gauge theory with N positively and N{sub e}=N{sub f}-N negatively charged matter multiplets and the Fayet-Iliopoulos term determined by the four-dimensional coupling constant. We conclude that the Higgs branch of this model is not lifted by quantum effects. As a result, such strings cannot confine. Our analysis of infrared effects, not seen in the Hanany-Tong consideration, shows that, in fact, the derivative expansion can make sense only provided that the theory under consideration is regularized in the infrared, e.g. by the quark mass differences. The world-sheet action discussed in this paper becomes a bona fide low-energy effective action only if {delta}m{sub AB}{ne}0.« less
A study of thin liquid sheet flows

NASA Technical Reports Server (NTRS)

Chubb, Donald L.; Calfo, Frederick D.; Mcconley, Marc W.; Mcmaster, Matthew S.; Afjeh, Abdollah A.

1993-01-01

This study was a theoretical and experimental investigation of thin liquid sheet flows in vacuum. A sheet flow created by a narrow slit of width, W, coalesces to a point at a distance, L, as a result of surface tension forces acting at the sheet edges. As the flow coalesces, the fluid accumulates in the sheet edges. The observed triangular shape of the sheet agrees with the calculated triangular result. Experimental results for L/W as a function of Weber number, We, agree with the calculated result, L/W = the sq. root of 8We. The edge cross sectional shape is found to oscillate from elliptic to 'cigar' like to 'peanut' like and then back to elliptic in the flow direction. A theoretical one-dimensional model was developed that yielded only elliptic solutions for the edge cross section. At the points where the elliptic shapes occur, there is agreement between theory and experiment.
One-loop Pfaffians and large-field inflation in string theory

NASA Astrophysics Data System (ADS)

Ruehle, Fabian; Wieck, Clemens

2017-06-01

We study the consistency of large-field inflation in low-energy effective field theories of string theory. In particular, we focus on the stability of Kähler moduli in the particularly interesting case where the non-perturbative superpotential of the Kähler sector explicitly depends on the inflaton field. This situation arises generically due to one-loop corrections to the instanton action. The field dependence of the modulus potential feeds back into the inflationary dynamics, potentially impairing slow roll. We distinguish between world-sheet instantons from Euclidean D-branes, which typically yield polynomial one-loop Pfaffians, and gaugino condensates, which can yield exponential or periodic corrections. In all scenarios successful slow-roll inflation imposes bounds on the magnitude of the one-loop correction, corresponding to constraints on possible compactifications. While we put a certain emphasis on Type IIB constructions with mobile D7-branes, our results seem to apply more generally.

Effect of Electron Beam Irradiation on the Tensile Properties of Carbon Nanotubes Sheets and Yarns

NASA Technical Reports Server (NTRS)

Williams, Tiffany S.; Miller, Sandi G.; Baker, James S.; McCorkle, Linda S.; Meador, Michael A.

2013-01-01

Carbon nanotube sheets and yarns were irradiated using electron beam (e-beam) energy to determine the effect of irradiation dose on the tensile properties. Results showed that a slight change in tensile strength occurred after irradiating as-received CNT sheets for 20 minutes, and a slight decrease in tensile strength as the irradiation time approached 90 minutes. On the other hand, the addition of small molecules to the CNT sheet surface had a greater effect on the tensile properties of e-beam irradiated CNT sheets. Some functionalized CNT sheets displayed up to a 57% increase in tensile strength following 90 minutes of e-beam exposure. In addition, as-received CNT yarns showed a significant increase in tensile strength as the irradiation time increased.
Physiotherapy exercise programmes: are instructional exercise sheets effective?

PubMed

Smith, Jo; Lewis, Jeremy; Prichard, Diana

2005-01-01

Effective compliance with physiotherapy exercises is only possible if patients remember the exercises accurately. The purpose of this study was to assess how well elderly in-patients remembered simple physiotherapy exercises, by comparing the ability to accurately reproduce a set of exercises in a group of patients that had received a written exercise sheet, with a group that had not. The study also aimed to investigate the relationship between memory for exercises and cognition. Sixty-four in-patients in an acute hospital were taught 3 exercises. Half of the subjects were randomised to receive exercise sheets to reinforce the teaching (Group 1). The rest of the subjects did not receive this memory aid (Group 2). Two to three days later subjects were asked to demonstrate their exercises. The accurate recall of the exercises was scored using a new assessment scale with a maximum score of 24. The mean exercise score was 17.19 for group 1 (SD = 5.91) and 16.24 for Group 2 (SD = 6.01). There was no significant difference in exercise score between groups (Mann Whitney U test p = 0.44). There was a statistically significant small positive correlation between exercise score and cognition (tau = 0.263). The study showed that older adult in-patients do not remember physiotherapy exercises effectively after a single teaching session and that their memory is not significantly improved by provision of an exercise sheet.
Forced tearing of ductile and brittle thin sheets.

PubMed

Tallinen, T; Mahadevan, L

2011-12-09

Tearing a thin sheet by forcing a rigid object through it leads to complex crack morphologies; a single oscillatory crack arises when a tool is driven laterally through a brittle sheet, while two diverging cracks and a series of concertinalike folds forms when a tool is forced laterally through a ductile sheet. On the other hand, forcing an object perpendicularly through the sheet leads to radial petallike tears in both ductile and brittle materials. To understand these different regimes we use a combination of experiments, simulations, and simple theories. In particular, we describe the transition from brittle oscillatory tearing via a single crack to ductile concertina tearing with two tears by deriving laws that describe the crack paths and wavelength of the concertina folds and provide a simple phase diagram for the morphologies in terms of the material properties of the sheet and the relative size of the tool.
Communication Fact Sheet.

ERIC Educational Resources Information Center

American Speech-Language-Hearing Association, Rockville, MD.

This brief fact sheet examines key aspects of communication, communication disabilities, and intervention. The fact sheet addresses the following questions: the nature of communication; communication disabilities (definitions of hearing impairments and speech and language impairments are given); effects of communication disabilities (factors…
Application technologies for effective utilization of advanced high strength steel sheets

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

Suehiro, Masayoshi, E-mail: suehiro.kp5.masayoshi@jp.nssmc.com

Recently, application of high strength steel sheets for automobiles has increased in order to meet a demand of light weighting of automobiles to reduce a carbon footprint while satisfying collision safety. The formability of steel sheets generally decreases with the increase in strength. Fracture and wrinkles tend to occur easily during forming. The springback phenomenon is also one of the issues which we should cope with, because it makes it difficult to obtain the desired shape after forming. Advanced high strength steel sheets with high formability have been developed in order to overcome these issues, and at the same timemore » application technologies have been developed for their effective utilization. These sheets are normally used for cold forming. As a different type of forming, hot forming technique has been developed in order to produce parts with ultra high strength. In this report, technologies developed at NSSMC in this field will be introduced.« less
Antifibrotic effect of dexamethasone/alginate-coated silicone sheet in the abraded middle ear mucosa.

PubMed

Jang, Chul Ho; Ahn, Seung Hyun; Kim, Geun Hyung

2016-12-01

Silicone sheet is a material which is commonly used in middle ear surgery to prevent the formation of adhesions between the tympanic membrane and the medial bony wall of the middle ear cavity. However, silicone sheet can induce a tight and hard fibrous capsule in the region of the stapes, and this is particularly common in cases of eustachian tube dysfunction. As a result of the fibrous encapsulation around the silicone sheet, postoperative aeration of the stapes can be interrupted causing poor hearing gain. In this study, we performed an in vitro and in vivo evaluation of the antifibrotic effects of a dexamethasone and alginate (Dx/alginate) coating on silicone sheet. The Dx/alginate-coated silicone sheets were fabricated using a plasma-treatment and coating method. The Dx/alginate-coated silicone sheets effectively limited in vitro fibroblast attachment and proliferation due to the controlled release of Dx, which can be modified by manipulation of the alginate coating. For the in-vivo evaluation, guinea pigs (albino, male, weighing 250g) were divided into two groups, with the control group (n=5) implanted with silicone sheet and the test group (n=5) receiving Dx/alginate-coated silicone sheet. Animals were sacrificed 3 weeks after implantation, and histological analysis was performed using hematoxylin and eosin (H&E) and immunohistochemical staining techniques. Dx/alginate-coated silicone sheets showed marked inhibition of fibrosis in both the in vitro and in vivo studies. Silicone sheet that incorporates a Dx/alginate coating can release Dx and inhibit fibrosis in the middle ear. This material could be utilized in middle ear surgery as a means of preserving proper aeration and hearing gain following ossiculoplasty. Copyright © 2016 Elsevier B.V. All rights reserved.
Density functional theory study of β-hairpins in antiparallel β-sheets, a new classification based upon H-bond topology.

PubMed

Roy, Dipankar; Pohl, Gabor; Ali-Torres, Jorge; Marianski, Mateusz; Dannenberg, J J

2012-07-10

We present a new classification of β-turns specific to antiparallel β-sheets based upon the topology of H-bond formation. This classification results from ONIOM calculations using B3LYP/D95** density functional theory and AM1 semiempirical calculations as the high and low levels, respectively. We chose acetyl(Ala)(6)NH(2) as a model system as it is the simplest all-alanine system that can form all the H-bonds required for a β-turn in a sheet. Of the 10 different conformations we have found, the most stable structures have C(7) cyclic H-bonds in place of the C(10) interactions specified in the classic definition. Also, the chiralities specified for residues i + 1 and i + 2 in the classic definition disappear when the structures are optimized using our techniques, as the energetic differences among the four diastereomers of each structure are not substantial for 8 of the 10 conformations.
Anchoring Effects in World University Rankings: Exploring Biases in Reputation Scores

ERIC Educational Resources Information Center

Bowman, Nicholas A.; Bastedo, Michael N.

2011-01-01

Despite ongoing debates about their uses and validity, university rankings are a popular means to compare institutions within a country and around the world. Anchoring theory suggests that these rankings may influence assessments of institutional reputation, and this effect may be particularly strong when a new rankings system is introduced. We…
Vibration responses of h-BN sheet to charge doping and external strain

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

Yang, Wei; Yang, Yu; Zheng, Fawei

2013-12-07

Based on density functional theory and density functional perturbation theory calculations, we systematically investigate the vibration responses of h-BN sheet to charge doping and external strains. It is found that under hole doping, the phonon frequencies of the ZO and TO branches at different wave vector q shift linearly with different slopes. Under electron doping, although the phonon frequencies shift irregularly, the shifting values are different at different phonon wave vectors. Interestingly, we find that external strain can restrain the irregular vibration responses of h-BN sheet to electron doping. The critical factor is revealed to be the relative position ofmore » the nearly free electron and boron p{sub z} states of h-BN sheet. Under external strains, the vibration responses of h-BN sheet are also found to be highly dependent on the phonon branches. Different vibration modes at different q points are revealed to be responsible for the vibration responses of h-BN sheet to charge doping and external strain. Our results point out a new way to detect the doping or strain status of h-BN sheet by measuring the vibration frequencies at different wave vector.« less
ISMIP6: Ice Sheet Model Intercomparison Project for CMIP6

NASA Technical Reports Server (NTRS)

Nowicki, S.

2015-01-01

ISMIP6 (Ice Sheet Model Intercomparison Project for CMIP6) targets the Cryosphere in a Changing Climate and the Future Sea Level Grand Challenges of the WCRP (World Climate Research Program). Primary goal is to provide future sea level contribution from the Greenland and Antarctic ice sheets, along with associated uncertainty. Secondary goal is to investigate feedback due to dynamic ice sheet models. Experiment design uses and augment the existing CMIP6 (Coupled Model Intercomparison Project Phase 6) DECK (Diagnosis, Evaluation, and Characterization of Klima) experiments. Additonal MIP (Model Intercomparison Project)- specific experiments will be designed for ISM (Ice Sheet Model). Effort builds on the Ice2sea, SeaRISE (Sea-level Response to Ice Sheet Evolution) and COMBINE (Comprehensive Modelling of the Earth System for Better Climate Prediction and Projection) efforts.
Using the Global Burden of Disease study to assist development of nation-specific fact sheets to promote prevention and control of hypertension and reduction in dietary salt: a resource from the World Hypertension League.

PubMed

Campbell, Norm R C; Lackland, Daniel T; Lisheng, Liu; Niebylski, Mark L; Nilsson, Peter M; Zhang, Xin-Hua

2015-03-01

Increased blood pressure and high dietary salt are leading risks for death and disability globally. Reducing the burden of both health risks are United Nations' targets for reducing noncommunicable disease. Nongovernmental organizations and individuals can assist by ensuring widespread dissemination of the best available facts and recommended interventions for both health risks. Simple but impactful fact sheets can be useful for informing the public, healthcare professionals, and policy makers. The World Hypertension League has developed fact sheets on dietary salt and hypertension but in many circumstances the greatest impact would be obtained from national-level fact sheets. This manuscript provides instructions and a template for developing fact sheets based on the Global Burden of Disease study and national survey data. ©2015 Wiley Periodicals, Inc.
Note on tachyon actions in string theory

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

Headrick, Matthew

2009-02-15

A number of spacetime fields in string theory (notably the metric, dilaton, bosonic and type 0 bulk closed-string tachyon, and bosonic open-string tachyon) have the following property: whenever the spacetime field configuration factorizes in an appropriate sense, the matter sector of the world-sheet theory factorizes into a tensor product of two decoupled theories. Since the beta functions for such a product theory necessarily also factorize, this property strongly constrains the form of the spacetime action encoding those beta functions. We show that this constraint alone--without needing actually to compute any of the beta functions--is sufficient to fix the form ofmore » the two-derivative action for the metric-dilaton system, as well as the potential for the bosonic open-string tachyon. We also show that no action consistent with this constraint exists for the closed-string tachyon coupled to the metric and dilaton.« less
Anti-adhesive effects of a newly developed two-layered gelatin sheet in dogs.

PubMed

Torii, Hiroko; Takagi, Toshitaka; Urabe, Mamoru; Tsujimoto, Hiroyuki; Ozamoto, Yuki; Miyamoto, Hiroe; Ikada, Yoshihito; Hagiwara, Akeo

2017-08-01

Adhesion after pelvic surgery causes infertility, ectopic pregnancy, and ileus or abdominal pain. The materials currently available for clinical use are insufficient. The purpose of this study was to develop an anti-adhesive material that overcomes the limitations of conventional anti-adhesive agents. The adhesion prevention effects of three methods - a two-layered sheet composed of gelatin film and gelatin sponge, Seprafilm and INTERCEED - were evaluated in 37 dogs. Anti-adhesive effects were investigated macroscopically and microscopically in a cauterized uterus adhesion model. Cell growth on the materials in vitro using human peritoneal mesothelial cells, fibroblasts and uterine smooth muscle cells were also evaluated. The two-layered gelatin sheet had significantly superior anti-adhesive effects compared to the conventional materials (Seprafilm and INTERCEED). A single-cell layer of mature mesothelium formed three weeks after surgery in the gelatin group. Peritoneum regeneration in the Seprafilm and INTERCEED groups was delayed and incomplete in the early phase. Little inflammation around the materials occurred and cell growth was significantly proliferated with the gelatin sheet. The anti-adhesive effects of a two-layered gelatin sheet were superior to conventional agents in a cauterized canine uterus model, demonstrating early regeneration of the peritoneum, little inflammation and material endurance. The newly developed two-layered gelatin sheet is a useful option as an anti-adhesive agent for deeply injured and hemorrhagic sites. © 2017 The Authors. Journal of Obstetrics and Gynaecology Research published by John Wiley & Sons Australia, Ltd on behalf of Japan Society of Obstetrics and Gynecology.
Restoration of uneven illumination in light sheet microscopy images.

PubMed

Uddin, Mohammad Shorif; Lee, Hwee Kuan; Preibisch, Stephan; Tomancak, Pavel

2011-08-01

Light microscopy images suffer from poor contrast due to light absorption and scattering by the media. The resulting decay in contrast varies exponentially across the image along the incident light path. Classical space invariant deconvolution approaches, while very effective in deblurring, are not designed for the restoration of uneven illumination in microscopy images. In this article, we present a modified radiative transfer theory approach to solve the contrast degradation problem of light sheet microscopy (LSM) images. We confirmed the effectiveness of our approach through simulation as well as real LSM images.
Moduli space potentials for heterotic non-Abelian flux tubes: Weak deformation

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

Shifman, M.; Yung, A.; Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg 188300

2010-09-15

We consider N=2 supersymmetric QCD with the U(N) gauge group (with no Fayet-Iliopoulos term) and N{sub f} flavors of massive quarks deformed by the mass term {mu} for the adjoint matter, W={mu}A{sup 2}, assuming that N{<=}N{sub f}<2N. This deformation breaks N=2 supersymmetry down to N=1. This theory supports non-Abelian flux tubes (strings) which are stabilized by W. They are referred to as F-term stabilized strings. We focus on the studies of such strings in the vacuum in which N squarks condense, at small {mu}, so that the Z{sub N} strings preserve, in a sense, their Bogomol'nyi-Prasad-Sommerfield nature. The (s)quark massesmore » are assumed to be nondegenerate. We calculate string tensions both in the classical and quantum regimes. Then we translate our results for the tensions in terms of the effective low-energy weighted CP(N{sub f}-1) model on the string world sheet. The bulk {mu} deformation makes this theory N=(0,2) supersymmetric heterotic weighted CP(N{sub f}-1) model in two dimensions. We find the deformation potential on the world sheet. This significantly expands the class of the heterotically deformed CP models emerging on the string world sheet compared to that suggested by Edalati and Tong. Among other things, we show that nonperturbative quantum effects in the bulk theory are exactly reproduced by the quantum effects in the world-sheet theory.« less
Good on paper: the gap between programme theory and real-world context in Pakistan's Community Midwife programme.

PubMed

Mumtaz, Z; Levay, A; Bhatti, A; Salway, S

2015-01-01

To understand why skilled birth attendance-an acknowledged strategy for reducing maternal deaths-has been effective in some settings but is failing in Pakistan and to demonstrate the value of a theory-driven approach to evaluating implementation of maternal healthcare interventions. Implementation research was conducted using an institutional ethnographic approach. National programme and local community levels in Pakistan. Observations, focus group discussions, and in-depth interviews were conducted with 38 Community Midwives (CMWs), 20 policymakers, 45 healthcare providers and 136 community members. A critical policy document review was conducted. National and local level data were brought together. Alignment of programme theory with real-world practice. Data revealed gaps between programme theory, assumptions and reality on the ground. The design of the programme failed to take into account: (1) the incongruity between the role of a midwife and dominant class and gendered norms that devalue such a role; (2) market and consumer behaviour that prevented CMWs from establishing private practices; (3) the complexity of public-private sector cooperation. Uniform deployment policies failed to consider existing provider density and geography. Greater attention to programme theory and the 'real-world' setting during design of maternal health strategies is needed to achieve consistent results in different contexts. © 2014 The Authors. BJOG An International Journal of Obstetrics and Gynaecology published by John Wiley & Sons Ltd on behalf of Royal College of Obstetricians and Gynaecologists.
Analytical and molecular dynamics studies on the impact loading of single-layered graphene sheet by fullerene

NASA Astrophysics Data System (ADS)

Hosseini-Hashemi, Shahrokh; Sepahi-Boroujeni, Amin; Sepahi-Boroujeni, Saeid

2018-04-01

Normal impact performance of a system including a fullerene molecule and a single-layered graphene sheet is studied in the present paper. Firstly, through a mathematical approach, a new contact law is derived to describe the overall non-bonding interaction forces of the "hollow indenter-target" system. Preliminary verifications show that the derived contact law gives a reliable picture of force field of the system which is in good agreements with the results of molecular dynamics (MD) simulations. Afterwards, equation of the transversal motion of graphene sheet is utilized on the basis of both the nonlocal theory of elasticity and the assumptions of classical plate theory. Then, to derive dynamic behavior of the system, a set including the proposed contact law and the equations of motion of both graphene sheet and fullerene molecule is solved numerically. In order to evaluate outcomes of this method, the problem is modeled by MD simulation. Despite intrinsic differences between analytical and MD methods as well as various errors arise due to transient nature of the problem, acceptable agreements are established between analytical and MD outcomes. As a result, the proposed analytical method can be reliably used to address similar impact problems. Furthermore, it is found that a single-layered graphene sheet is capable of trapping fullerenes approaching with low velocities. Otherwise, in case of rebound, the sheet effectively absorbs predominant portion of fullerene energy.
Understanding Recent Mass Balance Changes of the Greenland Ice Sheet

NASA Technical Reports Server (NTRS)

vanderVeen, Cornelius

2003-01-01

The ultimate goal of this project is to better understand the current transfer of mass between the Greenland Ice Sheet, the world's oceans and the atmosphere, and to identify processes controlling the rate of this transfer, to be able to predict with greater confidence future contributions to global sea level rise. During the first year of this project, we focused on establishing longer-term records of change of selected outlet glaciers, reevaluation of mass input to the ice sheet and analysis of climate records derived from ice cores, and modeling meltwater production and runoff from the margins of the ice sheet.
Effect of the material properties on the crumpling of a thin sheet.

PubMed

Habibi, Mehdi; Adda-Bedia, Mokhtar; Bonn, Daniel

2017-06-07

While simple at first glance, the dense packing of sheets is a complex phenomenon that depends on material parameters and the packing protocol. We study the effect of plasticity on the crumpling of sheets of different materials by performing isotropic compaction experiments on sheets of different sizes and elasto-plastic properties. First, we quantify the material properties using a dimensionless foldability index. Then, the compaction force required to crumple a sheet into a ball as well as the average number of layers inside the ball are measured. For each material, both quantities exhibit a power-law dependence on the diameter of the crumpled ball. We experimentally establish the power-law exponents and find that both depend nonlinearly on the foldability index. However the exponents that characterize the mechanical response and morphology of the crumpled materials are related linearly. A simple scaling argument explains this in terms of the buckling of the sheets, and recovers the relation between the crumpling force and the morphology of the crumpled structure. Our results suggest a new approach to tailor the mechanical response of the crumpled objects by carefully selecting their material properties.
Effects of wave shape on sheet flow sediment transport

USGS Publications Warehouse

Hsu, T.-J.; Hanes, D.M.

2004-01-01

A two-phase model is implemented to study the effects of wave shape on the transport of coarse-grained sediment in the sheet flow regime. The model is based on balance equations for the average mass, momentum, and fluctuation energy for both the fluid and sediment phases. Model simulations indicate that the responses of the sheet flow, such as the velocity profiles, the instantaneous bed shear stress, the sediment flux, and the total amount of the mobilized sediment, cannot be fully parameterized by quasi-steady free-stream velocity and may be correlated with the magnitude of local horizontal pressure gradient (or free-stream acceleration). A net sediment flux in the direction of wave advance is obtained for both skewed and saw-tooth wave shapes typical of shoaled and breaking waves. The model further suggests that at critical values of the horizontal pressure gradient, there is a failure event within the bed that mobilizes more sediment into the mobile sheet and enhances the sediment flux. Preliminary attempts to parameterize the total bed shear stress and the total sediment flux appear promising. Copyright 2004 by the American Geophysical Union.

Mesenchymal stem cell sheets exert anti-stenotic effects in a rat arterial injury model.

PubMed

Homma, Jun; Sekine, Hidekazu; Matsuura, Katsuhisa; Kobayashi, Eiji; Shimizu, Tatsuya

2018-05-04

Restenosis after catheter or surgical intervention substantially affects the prognosis of arterial occlusive disease. Mesenchymal stem cells (MSCs) may have anti-stenotic effects on injured arteries. MSC transplantation from the adventitial side of an artery is safer than endovascular transplantation but has not been extensively examined. In this study, a rat model of femoral artery injury was used to compare the anti-stenotic effects of transplanted cell sheets and transplanted cell suspensions. Rat adipose-derived stem cells (ASCs) were used as the source of MSCs. For both cell sheets and suspensions, 6×106 MSCs were transplanted on the day of arterial injury. MSC sheets attenuated neointimal hyperplasia more than MSC suspensions (intima-to-media ratio in haematoxylin/eosin-stained sections: 0.55±0.13 vs. 1.14±0.12; P<0.05). Cell engraftment (assessed by immunohistochemistry or bioluminescence imaging of luciferase-expressing cells), arterial re-endothelialisation (evaluated by immunohistochemical staining for rat endothelial cell antigen-1) and restriction of vascular smooth muscle cell proliferation in the neointima (double-staining of alpha-smooth muscle actin and phospho-histone H3) were greater when MSC sheets were applied than when MSC suspensions were used. In conclusion, MSC sheets exhibited better anti-stenotic and cell engraftment properties than MSC suspensions. MSC sheet transplantation from the adventitial side is a promising therapy for prevention of arterial restenosis.
The Svalbard-Barents Sea ice-sheet - Historical, current and future perspectives

NASA Astrophysics Data System (ADS)

Ingólfsson, Ólafur; Landvik, Jon Y.

2013-03-01

The history of research on the Late Quaternary Svalbard-Barents Sea ice sheet mirrors the developments of ideas and the shifts of paradigms in glacial theory over the past 150 years. Since the onset of scientific research there in the early 19th Century, Svalbard has been a natural laboratory where ideas and concepts have been tested, and played an important (but rarely acknowledged) role in the break-through of the Ice Age theory in the 1870's. The history of how the scientific perception of the Svalbard-Barents sea ice sheet developed in the mid-20th Century also tells a story of how a combination of fairly scattered and often contradictory observational data, and through both deductive and inductive reasoning, could outline a major ice sheet that had left but few tangible fingerprints. Since the 1980's, with increased terrestrial stratigraphical data, ever more marine geological evidence and better chronological control of glacial events, our perception of the Svalbard-Barents Sea ice sheet has changed. The first reconstructions depicted it as a static, concentric, single-domed ice sheet, with ice flowing from an ice divide over the central northern Barents Sea that expanded and declined in response to large-scale, Late Quaternary climate fluctuations, and which was more or less in tune with other major Northern Hemisphere ice sheets. We now increasingly perceive it as a very dynamic, multidomed ice sheet, controlled by climate fluctuations, relative sea-level change, as well as subglacial topography, substrate properties and basal temperature. In this respect, the Svalbard-Barents Sea ice sheet will increasingly hold the key for understanding the dynamics and processes of how marine-based ice sheets build-up and decay.
Theory and Practice: How Filming "Learning in the Real World" Helps Students Make the Connection

ERIC Educational Resources Information Center

Commander, Nannette Evans; Ward, Teresa E.; Zabrucky, Karen M.

2012-01-01

This article describes an assignment, titled "Learning in the Real World," designed for graduate students in a learning theory course. Students work in small groups to create high quality audio-visual films that present "real learning" through interviews and/or observations of learners. Students select topics relevant to theories we are discussing…
Effect of preparation methods on dispersion stability and electrochemical performance of graphene sheets

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

Chen, Li, E-mail: chenli1981@lut.cn; Li, Na; Zhang, Mingxia

Chemical exfoliation is one of the most important strategies for preparing graphene. The aggregation of graphene sheets severely prevents graphene from exhibiting excellent properties. However, there are no attempts to investigate the effect of preparation methods on the dispersity of graphene sheets. In this study, three chemical exfoliation methods, including Hummers method, modified Hummers method, and improved method, were used to prepare graphene sheets. The influence of preparation methods on the structure, dispersion stability in organic solvents, and electrochemical properties of graphene sheets were investigated. Fourier transform infrared microscopy, Raman spectra, transmission electron microscopy, and UV–vis spectrophotometry were employed tomore » analyze the structure of the as-prepared graphene sheets. The results showed that graphene prepared by improved method exhibits excellent dispersity and stability in organic solvents without any additional stabilizer or modifier, which is attributed to the completely exfoliation and regular structure. Moreover, cyclic voltammetric and electrochemical impedance spectroscopy measurements showed that graphene prepared by improved method exhibits superior electrochemical properties than that prepared by the other two methods. - Graphical abstract: Graphene oxides with different oxidation degree were obtained via three methods, and then graphene with different crystal structures were created by chemical reduction of exfoliated graphene oxides. - Highlights: • Graphene oxides with different oxidation degree were obtained via three oxidation methods. • The influence of oxidation methods on microstructure of graphene was investigated. • The effect of oxidation methods on dispersion stability of graphene was investigated. • The effect of oxidation methods on electrochemical properties of graphene was discussed.« less
Free-edge effects in a cylindrical sandwich panel with a flexible core and laminated composite face sheets

NASA Astrophysics Data System (ADS)

Afshin, M.; Sadighi, M.; Shakeri, M.

2010-12-01

In the present study, the static response of cylindrical sandwich panels with a flexible core is investigated. The face sheets are considered as composite laminates with a cross-ply lay-up and the core as a flexible elastic medium. The flexibility of the low-strength core leads to high stress concentrations in terms of peeling stresses between the face sheets and the core at edges of the sandwich panel. To take into account the compressibility of the core and to determine the free-edge stresses of sandwich structures accurately, the Reddy layerwise theory (LWT) is used in this paper. The paper outlines the mathematical formulation, along with a numerical study, of a cylindrical sandwich panel with two simply supported and two free edges under a transverse load. The formulation includes the derivation of field equations along with boundary conditions. A Levy-type solution procedure is performed to determine the distributions of stresses and strains. In the numerical study, first a comparison is made with results from the commercial finite-element software ANSYS to verify the LWT results. Finally, a parametric study is conducted, and the effect caused by varying different parameters, such as the radii of curvature and the core to face sheet thickness ratio, on the results are investigated. The results obtained demonstrate a good agreement between LWT and FEM solutions and show increasing interlaminar stresses in the free edge of the sandwich panel
connecting the dots between Greenland ice sheet surface melting and ice flow dynamics (Invited)

NASA Astrophysics Data System (ADS)

Box, J. E.; Colgan, W. T.; Fettweis, X.; Phillips, T. P.; Stober, M.

2013-12-01

This presentation is of a 'unified theory' in glaciology that first identifies surface albedo as a key factor explaining total ice sheet mass balance and then surveys a mechanistic self-reinforcing interaction between melt water and ice flow dynamics. The theory is applied in a near-real time total Greenland mass balance retrieval based on surface albedo, a powerful integrator of the competing effects of accumulation and ablation. New snowfall reduces sunlight absorption and increases meltwater retention. Melting amplifies absorbed sunlight through thermal metamorphism and bare ice expansion in space and time. By ';following the melt'; we reveal mechanisms linking existing science into a unified theory. Increasing meltwater softens the ice sheet in three ways: 1.) sensible heating given the water temperature exceeds that of the ice sheet interior; 2.) Some infiltrating water refreezes, transferring latent heat to the ice; 3.) Friction from water turbulence heats the ice. It has been shown that for a point on the ice sheet, basal lubrication increases ice flow speed to a time when an efficient sub-glacial drainage network develops that reduces this effect. Yet, with an increasing melt duration the point where the ice sheet glides on a wet bed increases inland to a larger area. This effect draws down the ice surface elevation, contributing to the ';elevation feedback'. In a perpetual warming scenario, the elevation feedback ultimately leads to ice sheet loss reversible only through much slower ice sheet growth in an ice age environment. As the inland ice sheet accelerates, the horizontal extension pulls cracks and crevasses open, trapping more sunlight, amplifying the effect of melt accelerated ice. As the bare ice area increases, the direct sun-exposed crevassed and infiltration area increases further allowing the ice warming process to occur more broadly. Considering hydrofracture [a.k.a. hydrofracking]; surface meltwater fills cracks, attacking the ice integrity
Triggering of explosive reconnection in a thick current sheet via current sheet compression: Less current sheet thinning, more temperature anisotropy

NASA Astrophysics Data System (ADS)

Shimizu, K.; Shinohara, I.; Fujimoto, M.

2016-12-01

Two-dimensional kinetic simulations of compression of thick current sheets are performed to see how it can lead to triggering of explosive magnetic reconnection. The current sheet under study is simply in a Harris-like anti-paralell and symmetric geometry. A one-dimensional pre-study shows that the compression is more effective to make the plasma anisotropy than to thin the current sheet width. When the lobe magnetic field is amplified by a factor of 2, the plasma temperature anisotropy inside the current sheet reaches 2 but the current sheet thickness is reduced only by 1/sqrt(2). If a current sheet thickness needs to be comparable to the ion inertial scale for reconnection triggering take place, as is widely and frequently mentioned in the research community, the initial thickness cannot be more than a few ion scale for reconnection to set-in. On the other hand, the temperature anisotropy of 2 can be significant for the triggering problem. Two-dimensional simulations show explosive magnetic reconnection to take place even when the initial current sheet thickness more than an order of magnitude thicker than the ion scale, indicating the resilient triggering drive supplied by the temperature anisotropy. We also discuss how the reconnection triggering capability of the temperature anisotropy boosted tearing mode for thick current sheets compares with the instabilities in the plane orthogonal to the reconnecting field.
Parental Acceptance and Rejection: Theory, Measures, and Research in the Arab World

ERIC Educational Resources Information Center

Ahmed, Ramadan A.; Rohner, Ronald P.; Khaleque, Abdul; Gielen, Uwe P.

2010-01-01

Purpose. The purpose of this article is to summarize the rich and growing body of research that draws from parental acceptance-rejection theory (PARTheory) and associated measures as used throughout the Arab world. Methodology. This body of work includes more than 100 studies that explore the reliability and validity of Arabic adaptations of…
Exactly solvable field theories of closed strings

NASA Astrophysics Data System (ADS)

Brézin, E.; Kazakov, V. A.

1990-02-01

Field theories of closed strings are shown to be exactly solvable for a central charge of matter fields c=1-6/m(m+1),m=1,2, 3, .... The two-point function χ(λ,N), in which λ is the cosmological constant and N-1 is the string coupling constant, obeys a scaling law χ(λ,N=N-(m+1/2)C((λc-λ)Nm/(m+1/2)) in the limit in which N-1 goes to zero and λ goes to a critical value λc we have determined the universal non-linear differential equation satisfied by the function C. From this equation it is found that a phase transition takes place for some finite value of the scaling parameter (λc-λ)Nm/(m+1/2); this transition is a ``condensation of handles'' on the world sheet, characterized by a divergence of the averaged genus of the world sheets. The cases m=2,3 are elaborated in more details, and the case m=1, which corresponds to the embedding of a bosonic string in -2 dimensions, is reduced to explicit quadratures. Permanent address: Cybernetics Council and Academy of Sciences, ul. Vavilova 40, SU-117 333 Moscow, USSR.
Plasma Sheet Circulation Pathways

NASA Technical Reports Server (NTRS)

Moore, Thomas E.; Delcourt, D. C.; Slinker, S. P.; Fedder, J. A.; Damiano, P.; Lotko, W.

2008-01-01

Global simulations of Earth's magnetosphere in the solar wind compute the pathways of plasma circulation through the plasma sheet. We address the pathways that supply and drain the plasma sheet, by coupling single fluid simulations with Global Ion Kinetic simulations of the outer magnetosphere and the Comprehensive Ring Current Model of the inner magnetosphere, including plasmaspheric plasmas. We find that the plasma sheet is supplied with solar wind plasmas via the magnetospheric flanks, and that this supply is most effective for northward IMF. For southward IMF, the innermost plasma sheet and ring current region are directly supplied from the flanks, with an asymmetry of single particle entry favoring the dawn flank. The central plasma sheet (near midnight) is supplied, as expected, from the lobes and polar cusps, but the near-Earth supply consists mainly of slowly moving ionospheric outflows for typical conditions. Work with the recently developed multi-fluid LFM simulation shows transport via plasma "fingers" extending Earthward from the flanks, suggestive of an interchange instability. We investigate this with solar wind ion trajectories, seeking to understand the fingering mechanisms and effects on transport rates.
A dynamic wicking technique for determining the effective pore radius of pregelatinized starch sheets.

PubMed

Kalogianni, E P; Savopoulos, T; Karapantsios, T D; Raphaelides, S N

2004-06-01

A dynamic wicking technique is employed for the first time for the determination of the effective mean pore radius of a thin-layer porous food: drum dried pregelatinized starch sheets. The technique consists of measuring the penetration rate of various n-alkanes in the porous matrix of the starch sheets and using this data to calculate the effective pore radius via the Washburn equation. Pore sizes in the order of a few nanometers have been determined in the starch sheets depending on the drum dryer's operating variables (drum rotation speed, steam pressure and starch feed concentration). The conditions for the application of the technique in porous foods are discussed as compared to the conditions for single capillaries and inorganic porous material measured in other studies.
Effects of electron pressure anisotropy on current sheet configuration

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

Artemyev, A. V., E-mail: aartemyev@igpp.ucla.edu; Angelopoulos, V.; Runov, A.

2016-09-15

Recent spacecraft observations in the Earth's magnetosphere have demonstrated that the magnetotail current sheet can be supported by currents of anisotropic electron population. Strong electron currents are responsible for the formation of very thin (intense) current sheets playing the crucial role in stability of the Earth's magnetotail. We explore the properties of such thin current sheets with hot isotropic ions and cold anisotropic electrons. Decoupling of the motions of ions and electrons results in the generation of a polarization electric field. The distribution of the corresponding scalar potential is derived from the electron pressure balance and the quasi-neutrality condition. Wemore » find that electron pressure anisotropy is partially balanced by a field-aligned component of this polarization electric field. We propose a 2D model that describes a thin current sheet supported by currents of anisotropic electrons embedded in an ion-dominated current sheet. Current density profiles in our model agree well with THEMIS observations in the Earth's magnetotail.« less
Ice sheet margins and ice shelves

NASA Technical Reports Server (NTRS)

Thomas, R. H.

1984-01-01

The effect of climate warming on the size of ice sheet margins in polar regions is considered. Particular attention is given to the possibility of a rapid response to warming on the order of tens to hundreds of years. It is found that the early response of the polar regions to climate warming would be an increase in the area of summer melt on the ice sheets and ice shelves. For sufficiently large warming (5-10C) the delayed effects would include the breakup of the ice shelves by an increase in ice drainage rates, particularly from the ice sheets. On the basis of published data for periodic changes in the thickness and melting rates of the marine ice sheets and fjord glaciers in Greenland and Antarctica, it is shown that the rate of retreat (or advance) of an ice sheet is primarily determined by: bedrock topography; the basal conditions of the grounded ice sheet; and the ice shelf condition downstream of the grounding line. A program of satellite and ground measurements to monitor the state of ice sheet equilibrium is recommended.
Anisotropic carrier mobility in single- and bi-layer C3N sheets

NASA Astrophysics Data System (ADS)

Wang, Xueyan; Li, Qingfang; Wang, Haifeng; Gao, Yan; Hou, Juan; Shao, Jianxin

2018-05-01

Based on the density functional theory combined with the Boltzmann transport equation with relaxation time approximation, we investigate the electronic structure and predict the carrier mobility of single- and bi-layer newly fabricated 2D carbon nitrides C3N. Although C3N sheets possess graphene-like planar hexagonal structure, the calculated carrier mobility is remarkably anisotropic, which is found mainly induced by the anisotropic effective masses and deformation potential constants. Importantly, we find that both the electron and hole mobilities are considerable high, for example, the hole mobility along the armchair direction of single-layer C3N sheets can arrive as high as 1.08 ×104 cm2 V-1 s-1, greatly larger than that of C2N-h2D and many other typical 2D materials. Owing to the high and anisotropic carrier mobility and appropriate band gap, single- and bi-layer semiconducting C3N sheets may have great potential applications in high performance electronic and optoelectronic devices.
A quantum theory account of order effects and conjunction fallacies in political judgments.

PubMed

Yearsley, James M; Trueblood, Jennifer S

2017-09-06

Are our everyday judgments about the world around us normative? Decades of research in the judgment and decision-making literature suggest the answer is no. If people's judgments do not follow normative rules, then what rules if any do they follow? Quantum probability theory is a promising new approach to modeling human behavior that is at odds with normative, classical rules. One key advantage of using quantum theory is that it explains multiple types of judgment errors using the same basic machinery, unifying what have previously been thought of as disparate phenomena. In this article, we test predictions from quantum theory related to the co-occurrence of two classic judgment phenomena, order effects and conjunction fallacies, using judgments about real-world events (related to the U.S. presidential primaries). We also show that our data obeys two a priori and parameter free constraints derived from quantum theory. Further, we examine two factors that moderate the effects, cognitive thinking style (as measured by the Cognitive Reflection Test) and political ideology.
Combinatorial effect of substratum properties on mesenchymal stem cell sheet engineering and subsequent multi-lineage differentiation.

PubMed

Chuah, Yon Jin; Zhang, Ying; Wu, Yingnan; Menon, Nishanth V; Goh, Ghim Hian; Lee, Ann Charlene; Chan, Vincent; Zhang, Yilei; Kang, Yuejun

2015-09-01

Cell sheet engineering has been exploited as an alternative approach in tissue regeneration and the use of stem cells to generate cell sheets has further showed its potential in stem cell-mediated tissue regeneration. There exist vast interests in developing strategies to enhance the formation of stem cell sheets for downstream applications. It has been proved that stem cells are sensitive to the biophysical cues of the microenvironment. Therefore we hypothesized that the combinatorial substratum properties could be tailored to modulate the development of cell sheet formation and further influence its multipotency. For validation, polydimethylsiloxane (PDMS) of different combinatorial substratum properties (including stiffness, roughness and wettability) were created, on which the human bone marrow derived mesenchymal stem cells (BMSCs) were cultured to form cell sheets with their multipotency evaluated after induced differentiation. The results showed that different combinatorial effects of these substratum properties were able to influence BMSC behavior such as adhesion, spreading and proliferation during cell sheet development. Collagen formation within the cell sheet was enhanced on substrates with lower stiffness, higher hydrophobicity and roughness, which further assisted the induced chondrogenesis and osteogenesis, respectively. These findings suggested that combinatorial substratum properties had profound effects on BMSC cell sheet integrity and multipotency, which had significant implications for future biomaterials and scaffold designs in the field of BMSC-mediated tissue regeneration. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
[Knowledge on Loose Sheets in the Context of fixed Theories. Theodor Leber's Research of Inflammation].

PubMed

Stahl, Dorina

2016-09-01

At the end of the nineteenth century, after twelve years of intensive research, the ophthalmologist Theodor Leber (1840-1917) established the chemotaxis of leukocytes as part of inflammation research. Although at the time his theory was smoothly enlisted into immunological research, up until now his name has been connected to chemotaxis only in the English-language literature. Leber was able to use his experimental system to develop a theory of the chemical attraction of the leukocytes during inflammation processes by the beginning of the 1880s, but his unconventional methodology-introducing chemically neutral contaminants in order to trigger inflammation in the eyes of rabbits-contradicted the basic bacteriological Denkstil (style of thought) of inflammation research at the time. Leber held fast to his research practice, which consisted of closely interlocking experimental and theoretical work. Only when an opening appeared in the bacteriological Denkstil was Leber able to transform his experimental observations, written on loose sheets of paper, into convincing evidence for his theory of inflammation. This micro-historical reconstruction of Leber's experimental and written work, based on his original lab protocols, opens up the research practice of a scientist who was not recognized by the established microbiological inflammation research of the time. Moreover, persistent factors in the generation of knowledge are revealed by connecting this micro-historical reconstruction with a macro-history analysis. Indeed Leber developed his specific paper technology in order to mobilise and stabilise the scientific findings gained through experiment because of the persistence of the bacteriological Denkstil.
Text World Theory and real world readers: From literature to life in a Belfast prison.

PubMed

Canning, Patricia

2017-05-01

Cognitive stylistics offers a range of frameworks for understanding (amongst other things) what producers of literary texts 'do' with language and how they 'do' it. Less prevalent, however, is an understanding of the ways in which these same frameworks offer insights into what readers 'do' (and how they 'do' it). Text World Theory (Werth, 1999; Gavins, 2007; Whiteley, 2011) has proved useful for understanding how and why readers construct mental representations engendered by the act of reading. However, research on readers' responses to literature has largely focused on an 'idealised' reader or an 'experimental' subject-reader often derived from within the academy and conducted using contrived or amended literary fiction. Moreover, the format of traditional book groups (participants read texts privately and discuss them at a later date) as well as online community forums such as Goodreads, means that such studies derive data from post-hoc, rather than real-time textual encounters and discussions. The current study is the first of its kind in analysing real-time reading contexts with real readers during a researcher-led literary project ('read.live.learn') in Northern Ireland's only female prison. In doing so, the study is unique in addressing experimental and post hoc bias. Using Text World Theory, the paper considers the personal and social impact of reader engagement in the talk of the participants. As such, it has three interrelated aims: to argue for the social and personal benefits of reading stylistically rich literature in real-time reading groups; to demonstrate the efficacy of stylistics for understanding how those benefits come about, and to demonstrate the inter-disciplinary value of stylistics, particularly its potential for traversing traditional research parameters.
Direct Laser Writing of Single-Material Sheets with Programmable Self-Rolling Capability

NASA Astrophysics Data System (ADS)

Bauhofer, Anton; KröDel, Sebastian; Bilal, Osama; Daraio, Chiara; Constantinescu, Andrei

Direct laser writing, a sub-class of two-photon polymerization, facilitates 3D-printing of single-material microstructures with inherent residual stresses. Here we show that controlled distribution of these stresses allows for fast and cost-effective fabrication of structures with programmable self-rolling capability. We investigate 2D sheets that evolve into versatile 3D structures. Precise control over the shape morphing potential is acquired through variations in geometry and writing parameters. Effects of capillary action and gravity were shown to be relevant for very thin sheets (thickness <1.5um) and have been analytically and experimentally quantified. In contrast to that, the deformations of sheets with larger thickness (>1.5um) are dominated by residual stresses and adhesion forces. The presented structures create local tensions up to 180MPa, causing rolling curvatures of 25E3m-1. A comprehensive analytical model that captures the relevant influence factors was developed based on laminate plate theory. The predicted curvature and directionality correspond well with the experimentally obtained data. Potential applications are found in drug encapsulation and particle traps for emulsions with differing surface energies. This work was supported by the Swiss National Science Foundation.
On spontaneous formation of current sheets: Untwisted magnetic fields

NASA Astrophysics Data System (ADS)

Bhattacharyya, R.; Low, B. C.; Smolarkiewicz, P. K.

2010-11-01

an effecting numerical resistivity. The principal results are related to the Parker theory of current-sheet formation and dissipation in the solar corona.

How to Do Things with Mouse Clicks: Applying Austin's Speech Act Theory to Explain Learning in Virtual Worlds

ERIC Educational Resources Information Center

Loke, Swee-Kin; Golding, Clinton

2016-01-01

This article addresses learning in desktop virtual worlds where students role play for professional education. When students role play in such virtual worlds, they can learn some knowledge and skills that are useful in the physical world. However, existing learning theories do not provide a plausible explanation of how performing non-verbal…
Electric field induced sheeting and breakup of dielectric liquid jets

NASA Astrophysics Data System (ADS)

Khoshnevis, Ahmad; Tsai, Scott S. H.; Esmaeilzadeh, Esmaeil

2014-01-01

We report experimental observations of the controlled deformation of a dielectric liquid jet subjected to a local high-voltage electrostatic field in the direction normal to the jet. The jet deforms to the shape of an elliptic cylinder upon application of a normal electrostatic field. As the applied electric field strength is increased, the elliptic cylindrical jet deforms permanently into a flat sheet, and eventually breaks-up into droplets. We interpret this observation—the stretch of the jet is in the normal direction to the applied electric field—qualitatively using the Taylor-Melcher leaky dielectric theory, and develop a simple scaling model that predicts the critical electric field strength for the jet-to-sheet transition. Our model shows a good agreement with experimental results, and has a form that is consistent with the classical drop deformation criterion in the Taylor-Melcher theory. Finally, we statistically analyze the resultant droplets from sheet breakup, and find that increasing the applied electric field strength improves droplet uniformity and reduces droplet size.
World Organisation for Animal Health

MedlinePlus

... Our members Delegates Key texts Basic texts Cooperation agreements Official Acts Resolutions and recommendations Final Reports of ... information: press releases, fact sheets, infographics… Partners Collaboration agreements with regional and world organisations of a public ...
Strings on complex multiplication tori and rational conformal field theory with matrix level

NASA Astrophysics Data System (ADS)

Nassar, Ali

Conformal invariance in two dimensions is a powerful symmetry. Two-dimensional quantum field theories which enjoy conformal invariance, i.e., conformal field theories (CFTs) are of great interest in both physics and mathematics. CFTs describe the dynamics of the world sheet in string theory where conformal symmetry arises as a remnant of reparametrization invariance of the world-sheet coordinates. In statistical mechanics, CFTs describe the critical points of second order phase transitions. On the mathematics side, conformal symmetry gives rise to infinite dimensional chiral algebras like the Virasoro algebra or extensions thereof. This gave rise to the study of vertex operator algebras (VOAs) which is an interesting branch of mathematics. Rational conformal theories are a simple class of CFTs characterized by a finite number of representations of an underlying chiral algebra. The chiral algebra leads to a set of Ward identities which gives a complete non-perturbative solution of the RCFT. Identifying the chiral algebra of an RCFT is a very important step in solving it. Particularly interesting RCFTs are the ones which arise from the compactification of string theory as sigma-models on a target manifold M. At generic values of the geometric moduli of M, the corresponding CFT is not rational. Rationality can arise at particular values of the moduli of M. At these special values of the moduli, the chiral algebra is extended. This interplay between the geometric picture and the algebraic description encoded in the chiral algebra makes CFTs/RCFTs a perfect link between physics and mathematics. It is always useful to find a geometric interpretation of a chiral algebra in terms of a sigma-model on some target manifold M. Then the next step is to figure out the conditions on the geometric moduli of M which gives a RCFT. In this thesis, we limit ourselves to the simplest class of string compactifications, i.e., strings on tori. As Gukov and Vafa proved, rationality selects
Manifold free multiple sheet superplastic forming

DOEpatents

Elmer, John W.; Bridges, Robert L.

2001-01-01

Fluid-forming compositions in a container attached to enclosed adjacent sheets are heated to relatively high temperatures to generate fluids (gases) that effect inflation of the sheets. Fluid rates to the enclosed space between the sheets can be regulated by the canal from the container. Inflated articles can be produced by a continuous, rather than batch-type, process.
Manifold free multiple sheet superplastic forming

DOEpatents

Elmer, John W.; Bridges, Robert L.

2004-01-13

Fluid-forming compositions in a container attached to enclosed adjacent sheets are heated to relatively high temperatures to generate fluids (gases) that effect inflation of the sheets. Fluid rates to the enclosed space between the sheets can be regulated by the canal from the container. Inflated articles can be produced by a continuous, rather than batch-type, process.
Keratinocyte cytoskeletal roles in cell sheet engineering

PubMed Central

2013-01-01

Background There is an increasing need to understand cell-cell interactions for cell and tissue engineering purposes, such as optimizing cell sheet constructs, as well as for examining adhesion defect diseases. For cell-sheet engineering, one major obstacle to sheet function is that cell sheets in suspension are fragile and, over time, will contract. While the role of the cytoskeleton in maintaining the structure and adhesion of cells cultured on a rigid substrate is well-characterized, a systematic examination of the role played by different components of the cytoskeleton in regulating cell sheet contraction and cohesion in the absence of a substrate has been lacking. Results In this study, keratinocytes were cultured until confluent and cell sheets were generated using dispase to remove the influence of the substrate. The effects of disrupting actin, microtubules or intermediate filaments on cell-cell interactions were assessed by measuring cell sheet cohesion and contraction. Keratin intermediate filament disruption caused comparable effects on cell sheet cohesion and contraction, when compared to actin or microtubule disruption. Interfering with actomyosin contraction demonstrated that interfering with cell contraction can also diminish cell cohesion. Conclusions All components of the cytoskeleton are involved in maintaining cell sheet cohesion and contraction, although not to the same extent. These findings demonstrate that substrate-free cell sheet biomechanical properties are dependent on the integrity of the cytoskeleton network. PMID:23442760
Teaching and Evaluating Instructor Effectiveness Using the Instructor Effectiveness Questionnaire and the Instructor Effectiveness Check Sheet Combination

ERIC Educational Resources Information Center

Phipps, Maurice L.; Hayashi, Aya; Lewandowski, April; Padgett, Allison H.

2005-01-01

This article describes the use of two linked instruments, the Instructor Effectiveness Check Sheet (IEC) and Instructor Effectiveness Questionnaire (IEQ). The use of an evaluation instrument during a course can enable improvements to be made--even with experienced instructors. Detail can be taken from the IEC and IEQ to find obvious and not so…
Text World Theory and real world readers: From literature to life in a Belfast prison

PubMed Central

Canning, Patricia

2017-01-01

Cognitive stylistics offers a range of frameworks for understanding (amongst other things) what producers of literary texts ‘do’ with language and how they ‘do’ it. Less prevalent, however, is an understanding of the ways in which these same frameworks offer insights into what readers ‘do’ (and how they ‘do’ it). Text World Theory (Werth, 1999; Gavins, 2007; Whiteley, 2011) has proved useful for understanding how and why readers construct mental representations engendered by the act of reading. However, research on readers’ responses to literature has largely focused on an ‘idealised’ reader or an ‘experimental’ subject-reader often derived from within the academy and conducted using contrived or amended literary fiction. Moreover, the format of traditional book groups (participants read texts privately and discuss them at a later date) as well as online community forums such as Goodreads, means that such studies derive data from post-hoc, rather than real-time textual encounters and discussions. The current study is the first of its kind in analysing real-time reading contexts with real readers during a researcher-led literary project (‘read.live.learn’) in Northern Ireland’s only female prison. In doing so, the study is unique in addressing experimental and post hoc bias. Using Text World Theory, the paper considers the personal and social impact of reader engagement in the talk of the participants. As such, it has three interrelated aims: to argue for the social and personal benefits of reading stylistically rich literature in real-time reading groups; to demonstrate the efficacy of stylistics for understanding how those benefits come about, and to demonstrate the inter-disciplinary value of stylistics, particularly its potential for traversing traditional research parameters. PMID:29278261
Predicting pulsar scintillation from refractive plasma sheets

NASA Astrophysics Data System (ADS)

Simard, Dana; Pen, Ue-Li

2018-07-01

The dynamic and secondary spectra of many pulsars show evidence for long-lived, aligned images of the pulsar that are stationary on a thin scattering sheet. One explanation for this phenomenon considers the effects of wave crests along sheets in the ionized interstellar medium, such as those due to Alfvén waves propagating along current sheets. If these sheets are closely aligned to our line of sight to the pulsar, high bending angles arise at the wave crests and a selection effect causes alignment of images produced at different crests, similar to grazing reflection off of a lake. Using geometric optics, we develop a simple parametrized model of these corrugated sheets that can be constrained with a single observation and that makes observable predictions for variations in the scintillation of the pulsar over time and frequency. This model reveals qualitative differences between lensing from overdense and underdense corrugated sheets: only if the sheet is overdense compared to the surrounding interstellar medium can the lensed images be brighter than the line-of-sight image to the pulsar, and the faint lensed images are closer to the pulsar at higher frequencies if the sheet is underdense, but at lower frequencies if the sheet is overdense.
Predicting Pulsar Scintillation from Refractive Plasma Sheets

NASA Astrophysics Data System (ADS)

Simard, Dana; Pen, Ue-Li

2018-05-01

The dynamic and secondary spectra of many pulsars show evidence for long-lived, aligned images of the pulsar that are stationary on a thin scattering sheet. One explanation for this phenomenon considers the effects of wave crests along sheets in the ionized interstellar medium, such as those due to Alfvén waves propagating along current sheets. If these sheets are closely aligned to our line-of-sight to the pulsar, high bending angles arise at the wave crests and a selection effect causes alignment of images produced at different crests, similar to grazing reflection off of a lake. Using geometric optics, we develop a simple parameterized model of these corrugated sheets that can be constrained with a single observation and that makes observable predictions for variations in the scintillation of the pulsar over time and frequency. This model reveals qualitative differences between lensing from overdense and underdense corrugated sheets: Only if the sheet is overdense compared to the surrounding interstellar medium can the lensed images be brighter than the line-of-sight image to the pulsar, and the faint lensed images are closer to the pulsar at higher frequencies if the sheet is underdense, but at lower frequencies if the sheet is overdense.
Engineering the work function of buckled boron α-sheet by lithium adsorption: a first-principles investigation.

PubMed

Zheng, Bing; Yu, Hai-tao; Xie, Ying; Lian, Yong-fu

2014-11-26

First-principles density functional theory calculations were performed to study the effect of Li adsorption on the structural and electronic properties, particularly the work function, of boron α-sheet. The calculated binding energies indicated that boron α-sheet could be well stabilized by the adsorption of Li atoms. Furthermore, the work functions of Li-adsorbed boron α-sheets were observed to decrease drastically with increasing Li coverage. The work functions are lower than that of Mg and even, for some of them, lower than that of Ca, indicating a considerable potential application of Li-adsorbed boron α-sheets as field-emission and electrode materials. Based on the calculated geometric and electronic structures, we discuss in details some possible aspects affecting the work function. The Li coverage dependence of the work functions of Li-adsorbed boron α-sheets was further confirmed by electrostatic potential analyses. The relationship between the work function variation and the Fermi and vacuum energy level shifts was also discussed, and we observed that the variation of the work function is primarily associated with the shift of the Fermi energy level. It is the surface dipole formed by the interaction between adatoms and substrate that should be responsible for the observed variation of the work function, whereas the increasing negative charge and rumpling for boron α-sheet only play minor roles. Additionally, the effect of Li adatoms on the work function of boron α-sheet was confirmed to be much stronger than that of graphene or a graphene double layer.
The Milankovitch theory and climate sensitivity. I - Equilibrium climate model solutions for the present surface conditions. II - Interaction between the Northern Hemisphere ice sheets and the climate system

NASA Technical Reports Server (NTRS)

Neeman, Binyamin U.; Ohring, George; Joseph, Joachim H.

1988-01-01

A seasonal climate model was developed to test the climate sensitivity and, in particular, the Milankovitch (1941) theory. Four climate model versions were implemented to investigate the range of uncertainty in the parameterizations of three basic feedback mechanisms: the ice albedo-temperature, the outgoing long-wave radiation-temperature, and the eddy transport-meridional temperature gradient. It was found that the differences between the simulation of the present climate by the four versions were generally small, especially for annually averaged results. The climate model was also used to study the effect of growing/shrinking of a continental ice sheet, bedrock sinking/uplifting, and sea level changes on the climate system, taking also into account the feedback effects on the climate of the building of the ice caps.
Investigation of the magnetic properties of Si-gradient steel sheet by comparison with 6.5%Si steel sheet

NASA Astrophysics Data System (ADS)

Hiratani, T.; Zaizen, Y.; Oda, Y.; Yoshizaki, S.; Senda, K.

2018-05-01

In this study, we investigated the magnetic properties of Si-gradient steel sheet produced by CVD (chemical vapor deposition) siliconizing process, comparing with 6.5% Si steel sheet. The Si-gradient steel sheet having silicon concentration gradient in the thickness direction, has larger hysteresis loss and smaller eddy current loss than the 6.5% Si steel sheet. In such a loss configuration, the iron loss of the Si-gradient steel sheet becomes lower than that of the 6.5% Si steel sheet at high frequencies. The experiment suggests that tensile stress is formed at the surface layer and compressive stress is formed at the inner layer in the Si gradient steel sheet. The magnetic anisotropy is induced by the internal stress and it is considered to affect the magnetization behavior of the Si-gradient steel sheet. The small eddy current loss of Si-gradient steel sheet can be explained as an effect of magnetic flux concentration on the surface layer.
Features analysis of five-element theory and its basal effects on construction of visceral manifestation theory.

PubMed

Ma, Zimi; Jia, Chunhua; Guo, Jin; Gu, Haorong; Miao, Yanhuan

2014-02-01

To study the Chinese ancient five-element theory, one of the philosophical foundations of Traditional Chinese Medicine (TCM) theory construction, from the perspective of comtemporary cognitive science, and to reveal the important functions of five-element theory in the construction of TCM theory. The basic effects of five-element theory in the construction of TCM theory are intensively expounded and proved from the following aspects: embodiment of five-element theory in cognizing the world, quasi axiom of five-element theory in essence, classification thery of family resemblance and deductive inference pattern of five-element theory, and the openness and expansibility of five-element theory. If five-element theory is considered a cognitive pattern or cognitive system related to culture, then there should be features of cognitive embodiment in the cognitive system. If five-element theory is regarded as a symbolic system, however, then there should be a quasi-axiom for the system, and inferential deduction. If, however, five-element theory is taken as a theoretical constructive metaphor, then there should be features of opening and expansibility for the metaphor. Based on five-element theory, this study provides a cognitive frame for the construction of TCM (a medicine that originated in China, and is characterized by holism and treatment based on pattern identification differentiation) theory with the function of constructing a concept base, thereby implying further research strategies. Useful information may be produced from the creative inferences obtained from the incorporation of five-element theory.
Functionalised graphene sheets as effective high dielectric constant fillers

NASA Astrophysics Data System (ADS)

Romasanta, Laura J.; Hernández, Marianella; López-Manchado, Miguel A.; Verdejo, Raquel

2011-08-01

A new functionalised graphene sheet (FGS) filled poly(dimethyl)siloxane insulator nanocomposite has been developed with high dielectric constant, making it well suited for applications in flexible electronics. The dielectric permittivity increased tenfold at 10 Hz and 2 wt.% FGS, while preserving low dielectric losses and good mechanical properties. The presence of functional groups on the graphene sheet surface improved the compatibility nanofiller/polymer at the interface, reducing the polarisation process. This study demonstrates that functionalised graphene sheets are ideal nanofillers for the development of new polymer composites with high dielectric constant values. PACS: 78.20.Ci, 72.80.Tm, 62.23.Kn
Physical properties of polyurethane plastic sheets produced from polyols from canola oil.

PubMed

Kong, Xiaohua; Narine, Suresh S

2007-07-01

Polyurethane (PUR) plastic sheets were prepared by reacting polyols synthesized from canola oil with aromatic diphenylmethane diisocyanate. The properties of the material were measured by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) as well as tensile properties measurements. The effect of stoichiometric balance (i.e., OH/NCO molar ratio) on the final properties was evaluated. The concentration of elastically active network chains (EANCs), nue, of the polymer networks was calculated using rubber elasticity theory. The glass transition temperatures (Tg) for the plastic sheets with OH/NCO molar ratios of 1.0/1.0, 1.0/1.1, and 1.0/1.2 were found to be 23, 41, and 43 degrees C, respectively. The kinetic studies of the degradation process of the PUR plastics showed three well-defined steps of degradation. The PUR plastic sheets with OH/NCO molar ratio 1.0/1.1 had the highest nue, lowest number-average molecule weight between cross-links, MC, and excellent mechanical properties, indicating that this is the optimum ratio in the PUR formulations.
Formation and interpretation of eskers beneath retreating ice sheets

NASA Astrophysics Data System (ADS)

Creyts, T. T.; Hewitt, I.

2017-12-01

The retreat of the ice sheets during the Pleistocene left large and spectacular subglacial features exposed. Understanding these features gives us insight into how the ice sheets retreated, how meltwater influenced retreat, and can help inform our understanding of potential future rates of ice sheet retreat. Among these features, eskers, long sinuous ridges primarily composed of clastic sediments, lack a detailed explanation of how surface melt rates and ice sheet retreat rates influence their growth and spatial distribution. Here, we develop a theory for esker formation based on the initial work of Rothlisberger modified for sediment transport and inclusion of surface meltwater forcing. The primary subglacial ingredients include water flow through subglacial tunnels with the addition of mass balances for sediment transport. We show how eskers when water flow slows below a critical stress for sediment motion. This implies that eskers are deposited in a localized region near the snout of the ice sheet. Our findings suggest that very long eskers form sequentially as the ice front retreats. The position of the esker follows the path of the channel mouth through time, which does not necessarily coincide with the instantaneous route of the feeding channel. However, in most cases, we expect those locations to be similar. The role of surface meltwater and the climatology associated with the forcing is crucial to the lateral spacing of the eskers. We predict that high surface melt rates lead to narrower catchments but that the greater extent of the ablation area means that channels are likely larger. At the same time, for a given channel size (and hence sediment flux), the size of a deposited esker depends on a margin retreat rate. Hence, the size of the eskers is related delicately to the balance between surface melt rates and margin retreat rates. We discuss how our theory can be combined with observed esker distributions to infer the relationship between these two rates
Stability of Thin Liquid Sheet Flows

NASA Technical Reports Server (NTRS)

McConley, Marc W.; Chubb, Donald L.; McMaster, Matthew S.; Afjeh, Abdollah A.

1997-01-01

A two-dimensional, linear stability analysis of a thin nonplanar liquid sheet flow in vacuum is carried out. A sheet flow created by a narrow slit of W and tau attains a nonplanar cross section as a consequence of cylinders forming on the sheet edge under the influence of surface tension forces. The region where these edge cylinders join the sheet is one of high curvature, and this is found to be the location where instability is most likely to occur. The sheet flow is found to be unstable, but with low growth rates for symmetric wave disturbances and high growth rates for antisymmetric disturbances. By combining the symmetric and antisymmetric disturbance modes, a wide range of stability characteristics is obtained. The product of unstable growth rate and flow time is proportional to the width-to-thickness ratio of the sift generating the sheet Three-dimensional effects can alter these results, particularly when the sheet length-to-width ratio is not much greater than unity.
Study of Microstructure and Mechanical Properties Effects on Workpiece Quality in Sheet Metal Extrusion Process

PubMed Central

Suriyapha, Chatkaew; Bubphachot, Bopit; Rittidech, Sampan

2015-01-01

Sheet metal extrusion is a metal forming process in which the movement of a punch penetrates a sheet metal surface and it flows through a die orifice; the extruded parts can be deflected to have an extrusion cavity and protrusion on the opposite side. Therefore, this process results in a narrow region of highly localized plastic deformation due to the formation and microstructure effect on the work piece. This research investigated the characteristics of the material-flow behavior during the formation and its effect on the microstructure of the extruded sheet metal using the finite element method (FEM). The actual parts and FEM simulation model were developed using a blank material made from AISI-1045 steel with a thickness of 5 mm; the material's behavior was determined subject to the punch penetration depths of 20%, 40%, 60%, and 80% of the sheet thickness. The results indicated the formation and microstructure effects on the sheet metal extrusion parts and defects. Namely, when increasing penetration, narrowing the die orifice the material flows through, the material was formed by extruding, and defects were visibility, and the microstructure of the material's grains' size was flat and very fine. Extrusion defects were not found in the control material flow. The region of highly localized plastic deformation affected the material gain and mechanical properties. The FEM simulation results agreed with the experimental results. Moreover, FEM could be investigated as a tool to decrease the cost and time in trial and error procedures. PMID:26229979

Experimental investigation of the stability of a moving radial liquid sheet

NASA Astrophysics Data System (ADS)

Paramati, Manjula; Tirumkudulu, Mahesh

2013-11-01

Experiments were conducted to understand the stability of moving radial liquid sheets formed by the head-on impingement of two co-linear water jets using laser induced fluorescence technique (LIF). Acoustic sinusoidal fluctuations were introduced at the jet impingement point and we measured the displacement of the center line of the liquid sheet (sinuous mode) and the thickness variation (varicose mode) of the disturbed liquid sheet. Our experiments show that the sinuous disturbances grow as they are convected outward in the radial direction even in the smooth regime (We < 800). In the absence of the acoustic forcing, the measured thickness has the expected 1/r dependence. Interestingly, we were unable to detect any thickness variation about the pre-stimulus values in the presence of acoustic forcing suggesting that the variation in the thickness is lower than the resolution of the technique (+/- 1 μm). The growth rates of the sinuous mode determined from the wave envelope matches with the prediction of a recent theory by Tirumkudulu and Paramati (Communicated to Phys. Of Fluids, 2013) which accounts for the inertia of the liquid phase and the surface tension force in a radial liquid sheet while neglecting the inertial effects due to the surrounding gas phase. The authors acknowledge the financial assistance from Indo-French Center for Pro- motion of Advanced Research and also Indian institute of technology Bombay.
Intercomparison of granular stress and turbulence models for unidirectional sheet flow applications

NASA Astrophysics Data System (ADS)

Chauchat, J.; Cheng, Z.; Hsu, T. J.

2016-12-01

The intergranular stresses are one of the key elements in two-phase sediment transport models. There are two main existing approaches, the kinetic theory of granular flows (Jenkins and Hanes, 1998; Hsu et al., 2004) and the phenomenological rheology such as the one proposed by Bagnold (Hanes and Bowen, 1985) or the μ(I) dense granular flow rheology (Revil-Baudard and Chauchat, 2013). Concerning the turbulent Reynolds stress, mixing length and k-ɛ turbulence models have been validated by previous studies (Revil-Baudard and Chauchat, 2013; Hsu et al., 2004). Recently, sedFoam was developed based on kinetic theory of granular flows and k-ɛ turbulence models (Cheng and Hsu, 2014). In this study, we further extended sedFoam by implementing the mixing length and the dense granular flow rheology by following Revil-Baudard and Chauchat (2013). This allows us to objectively compare the different combinations of intergranular stresses (kinetic theory or the dense granular flow rheology) and turbulence models (mixing length or k-ɛ) under unidirectional sheet flow conditions. We found that the calibrated mixing length and k-ɛ models predicts similar velocity and concentration profiles. The differences observed between the kinetic theory and the dense granular flow rheology requires further investigation. In particular, we hypothesize that the extended kinetic theory proposed by Berzi (2011) would probably improve the existing combination of the kinetic theory with a simple Coulomb frictional model in sedFoam. A semi-analytical solution proposed by Berzi and Fraccarollo(2013) for sediment transport rate and sheet layer thickness versus the Shields number is compared with the results obtained by using the dense granular flow rheology and the mixing length model. The results are similar which demonstrate that both the extended kinetic theory and the dense granular flow rheology can be used to model intergranular stresses under sheet flow conditions.
Functionalised graphene sheets as effective high dielectric constant fillers

PubMed Central

2011-01-01

A new functionalised graphene sheet (FGS) filled poly(dimethyl)siloxane insulator nanocomposite has been developed with high dielectric constant, making it well suited for applications in flexible electronics. The dielectric permittivity increased tenfold at 10 Hz and 2 wt.% FGS, while preserving low dielectric losses and good mechanical properties. The presence of functional groups on the graphene sheet surface improved the compatibility nanofiller/polymer at the interface, reducing the polarisation process. This study demonstrates that functionalised graphene sheets are ideal nanofillers for the development of new polymer composites with high dielectric constant values. PACS: 78.20.Ci, 72.80.Tm, 62.23.Kn PMID:21867505
Criticality and turbulence in a resistive magnetohydrodynamic current sheet

NASA Astrophysics Data System (ADS)

Klimas, Alexander J.; Uritsky, Vadim M.

2017-02-01

Scaling properties of a two-dimensional (2d) plasma physical current-sheet simulation model involving a full set of magnetohydrodynamic (MHD) equations with current-dependent resistivity are investigated. The current sheet supports a spatial magnetic field reversal that is forced through loading of magnetic flux containing plasma at boundaries of the simulation domain. A balance is reached between loading and annihilation of the magnetic flux through reconnection at the current sheet; the transport of magnetic flux from boundaries to current sheet is realized in the form of spatiotemporal avalanches exhibiting power-law statistics of lifetimes and sizes. We identify this dynamics as self-organized criticality (SOC) by verifying an extended set of scaling laws related to both global and local properties of the current sheet (critical susceptibility, finite-size scaling of probability distributions, geometric exponents). The critical exponents obtained from this analysis suggest that the model operates in a slowly driven SOC state similar to the mean-field state of the directed stochastic sandpile model. We also investigate multiscale correlations in the velocity field and find them numerically indistinguishable from certain intermittent turbulence (IT) theories. The results provide clues on physical conditions for SOC behavior in a broad class of plasma systems with propagating instabilities, and suggest that SOC and IT may coexist in driven current sheets which occur ubiquitously in astrophysical and space plasmas.
Criticality and turbulence in a resistive magnetohydrodynamic current sheet.

PubMed

Klimas, Alexander J; Uritsky, Vadim M

2017-02-01

Scaling properties of a two-dimensional (2d) plasma physical current-sheet simulation model involving a full set of magnetohydrodynamic (MHD) equations with current-dependent resistivity are investigated. The current sheet supports a spatial magnetic field reversal that is forced through loading of magnetic flux containing plasma at boundaries of the simulation domain. A balance is reached between loading and annihilation of the magnetic flux through reconnection at the current sheet; the transport of magnetic flux from boundaries to current sheet is realized in the form of spatiotemporal avalanches exhibiting power-law statistics of lifetimes and sizes. We identify this dynamics as self-organized criticality (SOC) by verifying an extended set of scaling laws related to both global and local properties of the current sheet (critical susceptibility, finite-size scaling of probability distributions, geometric exponents). The critical exponents obtained from this analysis suggest that the model operates in a slowly driven SOC state similar to the mean-field state of the directed stochastic sandpile model. We also investigate multiscale correlations in the velocity field and find them numerically indistinguishable from certain intermittent turbulence (IT) theories. The results provide clues on physical conditions for SOC behavior in a broad class of plasma systems with propagating instabilities, and suggest that SOC and IT may coexist in driven current sheets which occur ubiquitously in astrophysical and space plasmas.
A web-based fact sheet series for grandparents raising grandchildren and the professionals who serve them.

PubMed

Brintnall-Peterson, Mary; Poehlmann, Julie; Morgan, Kari; Shlafer, Rebecca

2009-04-01

To develop and evaluate a series of web-based fact sheets for grandparents raising grandchildren. The fact sheets focus on child development issues that grandparents may face when raising their grandchildren. The fact sheets were developed using research on attachment theory, child development, and the needs of grandparents raising grandchildren. The fact sheets can be viewed online or downloaded for free. Evaluation data for the fact sheets were gathered using an online survey. Results of the survey revealed that the fact sheets are used by grandparents and professionals. Respondents reported sharing the fact sheets with others and using them for personal use, in support groups, and as a general agency resource. The fact sheet series is a useful way to reach both grandparents and professionals working with this audience in a variety of settings. Modifications to the fact sheet series are suggested to address additional needs of grandparents raising grandchildren.
Transportation Secure Data Center: Real-World Data for Planning, Modeling, and Analysis (Fact Sheet)

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

Not Available

2014-01-01

This fact sheet describes the Transportation Secure Data Center (TSDC) - an NREL-operated resource that provides secure access to detailed GPS travel data for valuable research purposes in a way that protects original participant privacy.
Effect of gamma irradiation on the structural, mechanical and optical properties of polytetrafluoroethylene sheet

NASA Astrophysics Data System (ADS)

Mohammadian-Kohol, M.; Asgari, M.; Shakur, H. R.

2018-04-01

In this study, the effects of gamma radiation on the chemical structure, mechanical and optical properties of polytetrafluoroethylene (PTFE) sheet were investigated with various doses up to 12 kGy. The chemical changes in the structure were studied by FTIR spectroscopy. Also, effects of radiation on the different mechanical parameters such as Young's modulus, toughness, strain, and stress were studied at the maximum tolerable force and the fracture points. Furthermore, changing the various optical parameters such as absorption coefficient, Urbach energy, optical band gaps, refractive index, optical dispersion parameters and plasma resonance frequency were studied by UV-visible spectroscopy. Formation of a band at 1594 cm-1, which was belonged to double carbon bonds, indicated that chain-scission was occurred at 12 kGy gamma irradiation dose. As well, the mechanical results showed an increase in the elastic behavior of PTFE sheets and a decrease in the plastic behavior of it with absorbed dose increasing. Moreover, the results showed that gamma irradiation can effectively change the various optical properties of PTFE sheets due to different phenomena such as degradation of the main chains, occurring chain-scission, formation of free radicals and cross-linking in the polymer structure.
Sediment Vertical Flux in Unsteady Sheet Flows

NASA Astrophysics Data System (ADS)

Hsu, T.; Jenkins, J. T.; Liu, P. L.

2002-12-01

In models for sediment suspension, two different boundary conditions have been employed at the sediment bed. Either the sediment concentration is given or the vertical flux of sediment is specified. The specification of the latter is usually called the pick-up function. Recently, several developments towards a better understanding of the sediment bed boundary condition have been reported. Nielson et al (Coastal Engineering 2002, 45, p61-68) have indicated a better performance using the sediment vertical flux as the bed boundary condition in comparisons with experimental data. Also, Drake and Calantoni (Journal of Geophysical Research 2001, 106, C9, p19859-19868) have suggested that in the nearshore environment with its various unsteady flow conditions, the appropriate sediment boundary conditions of a large-scale morphology model must consider both the magnitude the free stream velocity and the acceleration of the flow. In this research, a small-scale sheet flow model based on the two-phase theory is implemented to further study these issues. Averaged two-phase continuum equations are presented for concentrated flows of sediment that are driven by strong, fully developed, unsteady turbulent shear flows over a mobile bed. The particle inter-granular stress is modeled using collisional granular flow theory and a two-equation closure for the fluid turbulence is adopted. In the context of the two-phase theory, sediment is transported through the sediment vertical velocity. Using the fully developed sediment phase continuity equation, it can be shown that the vertical velocity of the sediment must vanish when the flow reaches a steady state. In other words, in fully developed conditions, it is the unsteadiness of the flow that induces the vertical motion of the sediment and that changes the sediment concentration profile. Therefore, implementing a boundary condition based on sediment vertical flux is consistent with both the two-phase theory and with the observation
The world of epithelial sheets.

PubMed

Honda, Hisao

2017-06-01

An epithelium is a layer of closely connected cells covering the body or lining a body cavity. In this review, several fundamental questions are addressed regarding the epithelium. (i) While an epithelium functions as barrier against the external environment, how is barrier function maintained during its construction? (ii) What determines the apical and basal sides of epithelial layer? (iii) Is there any relationship between the apical side of the epithelium and the apical membrane of an epithelial cell? (iv) Why are hepatocytes (liver cells) called epithelial, even though they differ completely from column-like shape of typical epithelial cells? Keeping these questions in mind, multiple shapes of epithelia were considered, extracting a few of their elemental processes, and constructing a virtual world of epithelia by combining them. Epithelial cells were also classified into several types based on the number of apical domains of each cell. In addition, an intracellular organelle was introduced within epithelial cells, the vacuolar apical compartment (VAC), which is produced within epithelial cells surrounded by external cell matrix (ECM). The VAC interacts with areas of cell-cell contact of the cell surface membrane and is converted to apical membrane. The properties of VACs enable us to answer the initial questions posed above. Finally, the genetic and molecular mechanisms of epithelial morphogenesis are discussed. © 2017 Japanese Society of Developmental Biologists.
Nonlinear distortion of thin liquid sheets

NASA Astrophysics Data System (ADS)

Mehring, Carsten Ralf

Thin planar, annular and conical liquid sheets or films are analyzed, in a unified manner, by means of a reduced- dimension approach providing governing equations for the nonlinear motion of planar and swirling annular thin inviscid and incompressible liquid sheets in zero gravity and with axial disturbances only. Temporal analyses of periodically disturbed infinite sheets are considered, as well as spatial analyses of semi-infinite sheets modulated at the nozzle exit. Results on planar and swirling annular or conical sheets are presented for a zero density ambient gas. Here, conical sheets are obtained in the nearfield of the nozzle exit by considering sheets or films with swirl in excess of that needed to stabilize the discharging stream in its annular configuration. For nonswirling annular sheets a spatially and/or temporally constant gas-core pressure is assumed. A model extension considering the influence of aerodynamic effects on planar sheets is proposed. For planar and annular sheets, linear analyses of the pure initial- and pure boundary-value problem provide insight into the propagation characteristics of dilational and sinuous waves, the (linear) coupling between both wave modes, the stability limits for the annular configuration, as well as the appearance of particular waves on semi-infinite modulated sheets downstream from the nozzle exit. Nonlinear steady-state solutions for the conical configuration (without modulation) are illustrated. Comparison between nonlinear and linear numerical and linear analytical solutions for temporally or spatially developing sheets provides detailed information on the nonlinear distortion characteristics including nonlinear wave propagation and mode-coupling for all the considered geometric configurations and for a variety of parameter configurations. Sensitivity studies on the influence of Weber number, modulation frequency, annular radius, forcing amplitude and sheet divergence on breakup or collapse length and times
Development of tearing instability in a current sheet forming by sheared incompressible flow

NASA Astrophysics Data System (ADS)

Tolman, Elizabeth A.; Loureiro, Nuno F.; Uzdensky, Dmitri A.

2018-02-01

Sweet-Parker current sheets in high Lundquist number plasmas are unstable to tearing, suggesting they will not form in physical systems. Understanding magnetic reconnection thus requires study of the stability of a current sheet as it forms. Formation can occur due to sheared, sub-Alfvénic incompressible flows which narrow the sheet. Standard tearing theory (Furth et al. Phys. Fluids, vol. 6 (4), 1963, pp. 459-484, Rutherford, Phys. Fluids, vol. 16 (11), 1973, pp. 1903-1908, Coppi et al. Fizika Plazmy, vol. 2, 1976, pp. 961-966) is not immediately applicable to such forming sheets for two reasons: first, because the flow introduces terms not present in the standard calculation; second, because the changing equilibrium introduces time dependence to terms which are constant in the standard calculation, complicating the formulation of an eigenvalue problem. This paper adapts standard tearing mode analysis to confront these challenges. In an initial phase when any perturbations are primarily governed by ideal magnetohydrodynamics, a coordinate transformation reveals that the flow compresses and stretches perturbations. A multiple scale formulation describes how linear tearing mode theory (Furth et al. Phys. Fluids, vol. 6 (4), 1963, pp. 459-484, Coppi et al. Fizika Plazmy, vol. 2, 1976, pp. 961-966) can be applied to an equilibrium changing under flow, showing that the flow affects the separable exponential growth only implicitly, by making the standard scalings time dependent. In the nonlinear Rutherford stage, the coordinate transformation shows that standard theory can be adapted by adding to the stationary rates time dependence and an additional term due to the strengthening equilibrium magnetic field. Overall, this understanding supports the use of flow-free scalings with slight modifications to study tearing in a forming sheet.
Axisymmetric buckling of the circular graphene sheets with the nonlocal continuum plate model

NASA Astrophysics Data System (ADS)

Farajpour, A.; Mohammadi, M.; Shahidi, A. R.; Mahzoon, M.

2011-08-01

In this article, the buckling behavior of nanoscale circular plates under uniform radial compression is studied. Small-scale effect is taken into consideration. Using nonlocal elasticity theory the governing equations are derived for the circular single-layered graphene sheets (SLGS). Explicit expressions for the buckling loads are obtained for clamped and simply supported boundary conditions. It is shown that nonlocal effects play an important role in the buckling of circular nanoplates. The effects of the small scale on the buckling loads considering various parameters such as the radius of the plate and mode numbers are investigated.
Modeling the effect of doping on the catalyst-assisted growth and field emission properties of plasma-grown graphene sheet

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

Gupta, Neha; Sharma, Suresh C.; Sharma, Rinku

A theoretical model describing the effect of doping on the plasma-assisted catalytic growth of graphene sheet has been developed. The model accounts the charging rate of the graphene sheet, kinetics of all the plasma species, including the doping species, and the growth rate of graphene nuclei and graphene sheet due to surface diffusion, and accretion of ions on the catalyst nanoparticle. Using the model, it is observed that nitrogen and boron doping can strongly influence the growth and field emission properties of the graphene sheet. The results of the present investigation indicate that nitrogen doping results in reduced thickness andmore » shortened height of the graphene sheet; however, boron doping increases the thickness and height of the graphene sheet. The time evolutions of the charge on the graphene sheet and hydrocarbon number density for nitrogen and boron doped graphene sheet have also been examined. The field emission properties of the graphene sheet have been proposed on the basis of the results obtained. It is concluded that nitrogen doped graphene sheet exhibits better field emission characteristics as compared to undoped and boron doped graphene sheet. The results of the present investigation are consistent with the existing experimental observations.« less
A preliminary investigation of projectile shape effects in hypervelocity impact of a double-sheet structure

NASA Technical Reports Server (NTRS)

Morrison, R. H.

1972-01-01

Impact tests of a sphere and several cylinders of various masses and fineness ratios, all of aluminum, fired into an aluminum double-sheet structure at velocities near 7 km/sec, show that a cylinder, impacting in the direction of its axis, is considerably more effective as a penetrator than a sphere. Impacts of three cylinders of equal mass, but different fineness ratios, produced holes through the structures' rear sheet, whereas impact of a sphere of the same mass did not. Moreover, it was found that to prevent rear-sheet penetration, the mass of the 1/2-fineness-ratio cylinder had to be reduced by a factor greater than three. Further tests wherein the cylinder diameter was held constant while the cylinder length was systematically reduced showed that a cylinder with a fineness ratio of 0.07 and a mass of only 1/7 that of the sphere was still capable of producing a hole in the rear sheet.
The effects of strain and stress state in hot forming of mg AZ31 sheet

NASA Astrophysics Data System (ADS)

Sherek, Paul A.; Carpenter, Alexander J.; Hector, Louis G.; Krajewski, Paul E.; Carter, Jon T.; Lasceski, Joshua; Taleff, Eric M.

Wrought magnesium alloys, such as AZ31 sheet, are of considerable interest for light-weighting of vehicle structural components. The poor room-temperature ductility of AZ31 sheet has been a hindrance to forming the complex part shapes necessary for practical applications. However, the outstanding formability of AZ31 sheet at elevated temperature provides an opportunity to overcome that problem. Complex demonstration components have already been produced at 450°C using gas-pressure forming. Accurate simulations of such hot, gas-pressure forming will be required for the design and optimization exercises necessary if this technology is to be implemented commercially. We report on experiments and simulations used to construct the accurate material constitutive models necessary for finite-element-method simulations. In particular, the effects of strain and stress state on plastic deformation of AZ31 sheet at 450°C are considered in material constitutive model development. Material models are validated against data from simple forming experiments.
Observational support for the current sheet catastrophe model of substorm current disruption

NASA Technical Reports Server (NTRS)

Burkhart, G. R.; Lopez, R. E.; Dusenbery, P. B.; Speiser, T. W.

1992-01-01

The principles of the current sheet catastrophe models are briefly reviewed, and observations of some of the signatures predicted by the theory are presented. The data considered here include AMPTE/CCE observations of fifteen current sheet disruption events. According to the model proposed here, the root cause of the current disruption is some process, as yet unknown, that leads to an increase in the k sub A parameter. Possible causes for the increase in k sub A are discussed.
Capabilities and performance of the new generation ice-sheet model Elmer/Ice

NASA Astrophysics Data System (ADS)

Gagliardini, O.; Zwinger, T.; Durand, G.; Favier, L.; de Fleurian, B.; Gillet-chaulet, F.; Seddik, H.; Greve, R.; Mallinen, M.; Martin, C.; Raback, P.; Ruokolainen, J.; Schäfer, M.; Thies, J.

2012-12-01

Since the Fourth IPCC Assessment Report, and its conclusion about the inability of ice-sheet flow models to forecast the current increase of polar ice sheet discharge and associated contribution to sea-level rise, a huge development effort has been undertaken by the glaciological community. All around the world, models have been improved and, interestingly, a significant number of new ice-sheet models have emerged. Among them, the parallel finite-element model Elmer/Ice (based on the open-source multi-physics code Elmer) was one of the first full-Stokes models used to make projections of the future of the whole Greenland ice sheet for the coming two centuries. Originally developed to solve dedicated local ice flow problems of high mechanical and physical complexity, Elmer/Ice has today reached the maturity to solve larger scale problems, earning the status of an ice-sheet model. In this presentation, we summarise the almost 10 years of development performed by different groups. We present the components already included in Elmer/Ice, its numerical performance, selected applications, as well as developments planed for the future.
Reconnection at three dimensional magnetic null points: Effect of current sheet asymmetry

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

Wyper, P. F.; Jain, Rekha

2013-05-15

Asymmetric current sheets are likely to be prevalent in both astrophysical and laboratory plasmas with complex three dimensional (3D) magnetic topologies. This work presents kinematic analytical models for spine and fan reconnection at a radially symmetric 3D null (i.e., a null where the eigenvalues associated with the fan plane are equal) with asymmetric current sheets. Asymmetric fan reconnection is characterized by an asymmetric reconnection of flux past each spine line and a bulk flow of plasma across the null point. In contrast, asymmetric spine reconnection is characterized by the reconnection of an equal quantity of flux across the fan planemore » in both directions. The higher modes of spine reconnection also include localized wedges of vortical flux transport in each half of the fan. In this situation, two definitions for reconnection rate become appropriate: a local reconnection rate quantifying how much flux is genuinely reconnected across the fan plane and a global rate associated with the net flux driven across each semi-plane. Through a scaling analysis, it is shown that when the ohmic dissipation in the layer is assumed to be constant, the increase in the local rate bleeds from the global rate as the sheet deformation is increased. Both models suggest that asymmetry in the current sheet dimensions will have a profound effect on the reconnection rate and manner of flux transport in reconnection involving 3D nulls.« less
Greenland Ice Sheet Surface Temperature, Melt, and Mass Loss: 2000-2006

NASA Technical Reports Server (NTRS)

Hall, Dorothy K.; Williams, Richard S., Jr.; Luthcke, Scott B.; DiGirolamo, Nocolo

2007-01-01

Extensive melt on the Greenland Ice Sheet has been documented by a variety of ground and satellite measurements in recent years. If the well-documented warming continues in the Arctic, melting of the Greenland Ice Sheet will likely accelerate, contributing to sea-level rise. Modeling studies indicate that an annual or summer temperature rise of 1 C on the ice sheet will increase melt by 20-50% therefore, surface temperature is one of the most important ice-sheet parameters to study for analysis of changes in the mass balance of the ice-sheet. The Greenland Ice Sheet contains enough water to produce a rise in eustatic sea level of up to 7.0 m if the ice were to melt completely. However, even small changes (centimeters) in sea level would cause important economic and societal consequences in the world's major coastal cities thus it is extremely important to monitor changes in the ice-sheet surface temperature and to ultimately quantify these changes in terms of amount of sea-level rise. We have compiled a high-resolution, daily time series of surface temperature of the Greenland Ice Sheet, using the I-km resolution, clear-sky land-surface temperature (LST) standard product from the Moderate-Resolution Imaging Spectroradiometer (MODIS), from 2000 - 2006. We also use Gravity Recovery and Climate Experiment (GRACE) data, averaged over 10-day periods, to measure change in mass of the ice sheet as it melt and snow accumulates. Surface temperature can be used to determine frequency of surface melt, timing of the start and the end of the melt season, and duration of melt. In conjunction with GRACE data, it can also be used to analyze timing of ice-sheet mass loss and gain.

Effect of Brake Forming on the Strength of 24S-T Aluminum-alloy Sheet

NASA Technical Reports Server (NTRS)

Heimerl, George J; Woods, Walter

1946-01-01

Tests were made to determine the effect of brake forming on the strength of 24S-T aluminum alloy sheet that had been formed to an inside bend radius of three times the sheet thickness. The results for both directions of the grain of the material showed that the compressive yield stresses were appreciably increased, that the tensile yield stresses were moderately increased, that the ultimate tensile stresses were only slightly increased, that the elongations were considerably reduced, and that the shapes of the tensile and compressive stress-strain curves were markedly changed.
Effect of Punch Stroke on Deformation During Sheet Forming Through Finite Element

NASA Astrophysics Data System (ADS)

Akinlabi, Stephen; Akinlabi, Esther

2017-08-01

Forming is one of the traditional methods of making shapes, bends and curvature in metallic components during a fabrication process. Mechanical forming, in particular, employs the use of a punch, which is pressed against the sheet material to be deformed into a die by the application of an external force. This study reports on the finite element analysis of the effects of punch stroke on the resulting sheet deformation, which is directly a function of the structural integrity of the formed components for possible application in the automotive industry. The results show that punch stroke is directly proportional to the resulting bend angle of the formed components. It was further revealed that the developed plastic strain increases as the punch stroke increases.
Sheet Membrane Spacesuit Water Membrane Evaporator

NASA Technical Reports Server (NTRS)

Bue, Grant; Trevino, Luis; Zapata, Felipe; Dillion, Paul; Castillo, Juan; Vonau, Walter; Wilkes, Robert; Vogel, Matthew; Frodge, Curtis

2013-01-01

A document describes a sheet membrane spacesuit water membrane evaporator (SWME), which allows for the use of one common water tank that can supply cooling water to the astronaut and to the evaporator. Test data showed that heat rejection performance dropped only 6 percent after being subjected to highly contaminated water. It also exhibited robustness with respect to freezing and Martian atmospheric simulation testing. Water was allowed to freeze in the water channels during testing that simulated a water loop failure and vapor backpressure valve failure. Upon closing the backpressure valve and energizing the pump, the ice eventually thawed and water began to flow with no apparent damage to the sheet membrane. The membrane evaporator also serves to de-gas the water loop from entrained gases, thereby eliminating the need for special degassing equipment such as is needed by the current spacesuit system. As water flows through the three annular water channels, water evaporates with the vapor flowing across the hydrophobic, porous sheet membrane to the vacuum side of the membrane. The rate at which water evaporates, and therefore, the rate at which the flowing water is cooled, is a function of the difference between the water saturation pressure on the water side of the membrane, and the pressure on the vacuum side of the membrane. The primary theory is that the hydrophobic sheet membrane retains water, but permits vapor pass-through when the vapor side pressure is less than the water saturation pressure. This results in evaporative cooling of the remaining water.
A Text World Theory Approach to the Teaching of Short Stories in an EFL Context: A Pedagogical Stylistic Study

ERIC Educational Resources Information Center

Mohammadzadeh, Behbood

2017-01-01

The present study attempts to examine how the stylistic aspects of Text World Theory (TWT) can be used in Literature and Language Teaching classrooms in order to help students to improve their critical understanding and interpretation. The pedagogical stylistic application of this theory can enhance ELT students' language awareness, creative…
The effect of broken stringers on the stress intensity factor for a uniformly stiffened sheet containing a crack

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1973-01-01

A linear elastic stress analysis was made of a centrally cracked sheet stiffened by riveted, uniformly spaced and sized stringers. The stress intensity factor for the sheet and the load concentration factor for the most highly loaded stringer were determined for various numbers of broken stringers. A broken stringer causes the stress intensity factor to be very high when the crack tip is near the broken stringer, but causes little effect when the crack tip extends beyond several intact stringers. A broken stringer also causes an increase in the load concentration factor of the adjacent stringers. The calculated residual strengths and fatigue-crack-growth lives of a stiffened aluminum sheet with a broken stringer were only slightly less than a sheet with all intact stringers, and were still much higher than those of an unstiffened sheet.
Fact Sheets on Pesticides in Schools.

ERIC Educational Resources Information Center

National Coalition against the Misuse of Pesticides, Washington, DC.

This document consists of a collection of fact sheets about the use of pesticides in schools and how to reduce it. The sheets are: (1) "Alternatives to Using Pesticides in Schools: What Is Integrated Pest Management?"; (2) "Health Effects of 48 Commonly Used Pesticides in Schools"; (3) "The Schooling of State Pesticide…
Effects of transverse temperature field nonuniformity on stress in silicon sheet growth

NASA Technical Reports Server (NTRS)

Mataga, P. A.; Hutchinson, J. W.; Chalmers, B.; Bell, R. O.; Kalejs, J. P.

1987-01-01

Stress and strain rate distributions are calculated using finite element analysis for steady-state growth of thin silicon sheet temperature nonuniformities imposed in the transverse (sheet width) dimension. Significant reductions in residual stress are predicted to occur for the case where the sheet edge is cooled relative to its center provided plastic deformation with high creep rates is present.
Solution Conformations of Graphene Oxide Sheets, and Two-Dimensional Nanofluidics

NASA Astrophysics Data System (ADS)

Koltonow, Andrew R.

This work reports studies on the physical properties of collections of nanosheets. First, the configurations of graphene oxide sheets in solution are studied. Polarized optical microscopy reveals quickly and decisively that sheets remain flat and form lyotropic liquid crystals over a wide range of solvent conditions. When solvent conditions are inhospitable enough, sheets agglomerate into stacks rather crumpling upon themselves. Theory and simulation suggest that the crumpled state, which can be formed by compressing sheets, is metastable. This work might correct a persistent misunderstanding about the solution physics of graphene oxide. The other major area of study concerns the hydration layers in between lamellar stacks of exfoliated, restacked nanosheets. These layers comprise massive arrays of parallel two-dimensional nanofluidic channels, which exhibit enhanced unipolar ionic conductivity with counterions as the majority charge carriers. Based on the previously discovered graphene oxide nanofluidic platform, exfoliated vermiculite nanofluidic channels are constructed, which shuttle protons through the hydration channels by a Grotthuss mechanism, and which show superior thermal stability to graphene oxide. The 2D nanofluidics platform is also used to demonstrate "kirigami nanofluidics", where ion transport can be manipulated by cutting the film into specific shapes. This can give rise to ionic current rectification. The rectification effect is attributed to the size and shape mismatch of the concentration polarization zones developed at the inlets and outlets of the nanofluidic channels. The kirigami nanofluidic platform can be used to fabricate ionic diodes and other simple devices. This material platform is expected to be a useful tool for nanofluidics researchers, because it offers a way to carry out nanofluidic experiments quickly with minimal equipment and little expense.
Effect of Mantle Rheology on Viscous Heating induced during Ice Sheet Cycles

NASA Astrophysics Data System (ADS)

Huang, Pingping; Wu, Patrick; van der Wal, Wouter

2017-04-01

Hanyk et al. (2005) studied the viscous shear heating in the mantle induced by the surface loading and unloading of a parabolic-shaped Laurentide-size ice sheet. They found that for linear rheology, viscous heating is mainly concentrated below the ice sheet. The depth extent of the heating in the mantle is determined by the viscosity distribution. Also, the magnitude of viscous heating is significantly affected by the rate of ice thickness change. However, only one ice sheet has been considered in their work and the interactions between ice sheets and ocean loading have been neglected. Furthermore, only linear rheology has been considered, although they suggested that non-Newtonian rheology may have a stronger effect. Here we follow Hanyk et al. (2005) and computed the viscous dissipation for viscoelastic models using the finite element methodology of Wu (2004) and van der Wal et al. (2010). However, the global ICE6G model (Peltier et al. 2015) with realistic oceans is used here to provide the surface loading. In addition, viscous heating in non-linear rheology, composite rheology, in addition to linear rheology with uniform or VM5a profile are computed and compared. Our results for linear rheology mainly confirm the findings of Hanyk et al. (2005). For both non-linear and composite rheologies, viscous heating is also mainly distributed near and under the ice sheets, but, more concentrated; depending on the horizontal dimension of the ice sheet, it can extend into the lower mantle, but for some of the time, not as deep as that for linear rheology. For composite rheology, the viscous heating is dominated by the effect of non-linear relation between the stress and the strain. The ice history controls the time when the local maximum in viscous heating appears. However, the magnitude of the viscous heating is affected by mantle rheology as well as the ice loading. Due to viscosity stratification, the shape of the region with high viscous heating in model VM5a is a
A path model investigation of neurocognition, theory of mind, social competence, negative symptoms and real-world functioning in schizophrenia.

PubMed

Couture, Shannon M; Granholm, Eric L; Fish, Scott C

2011-02-01

Problems in real-world functioning are pervasive in schizophrenia and much recent effort has been devoted to uncovering factors which contribute to poor functioning. The goal of this study was to examine the role of four such factors: social cognition (theory of mind), neurocognition, negative symptoms, and functional capacity (social competence). 178 individuals with schizophrenia or schizoaffective disorder completed measures of theory of mind, neurocognition, negative symptoms, social competence, and self-reported functioning. Path models sought to determine the relationships among these variables. Theory of mind as indexed by the Hinting Task partially mediated the relationship between neurocognition and social competence, and negative symptoms and social competence demonstrated significant direct paths with self-reported functioning. Study results suggest theory of mind serves as an important mediator in addition to previously investigated social cognitive domains of emotional and social perception. The current study also highlights the need to determine variables which mediate the relationship between functional capacity and real-world functioning. Copyright © 2010 Elsevier B.V. All rights reserved.
Effective theories of universal theories

DOE PAGES

Wells, James D.; Zhang, Zhengkang

2016-01-20

It is well-known but sometimes overlooked that constraints on the oblique parameters (most notably S and T parameters) are generally speaking only applicable to a special class of new physics scenarios known as universal theories. The oblique parameters should not be associated with Wilson coefficients in a particular operator basis in the effective field theory (EFT) framework, unless restrictions have been imposed on the EFT so that it describes universal theories. Here, we work out these restrictions, and present a detailed EFT analysis of universal theories. We find that at the dimension-6 level, universal theories are completely characterized by 16more » parameters. They are conveniently chosen to be: 5 oblique parameters that agree with the commonly-adopted ones, 4 anomalous triple-gauge couplings, 3 rescaling factors for the h 3, hff, hV V vertices, 3 parameters for hV V vertices absent in the Standard Model, and 1 four-fermion coupling of order yf 2. Furthermore, all these parameters are defined in an unambiguous and basis-independent way, allowing for consistent constraints on the universal theories parameter space from precision electroweak and Higgs data.« less
Effective theories of universal theories

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

Wells, James D.; Zhang, Zhengkang

It is well-known but sometimes overlooked that constraints on the oblique parameters (most notably S and T parameters) are generally speaking only applicable to a special class of new physics scenarios known as universal theories. The oblique parameters should not be associated with Wilson coefficients in a particular operator basis in the effective field theory (EFT) framework, unless restrictions have been imposed on the EFT so that it describes universal theories. Here, we work out these restrictions, and present a detailed EFT analysis of universal theories. We find that at the dimension-6 level, universal theories are completely characterized by 16more » parameters. They are conveniently chosen to be: 5 oblique parameters that agree with the commonly-adopted ones, 4 anomalous triple-gauge couplings, 3 rescaling factors for the h 3, hff, hV V vertices, 3 parameters for hV V vertices absent in the Standard Model, and 1 four-fermion coupling of order yf 2. Furthermore, all these parameters are defined in an unambiguous and basis-independent way, allowing for consistent constraints on the universal theories parameter space from precision electroweak and Higgs data.« less
Theoretical investigation of calcium-decorated β12 boron sheet for hydrogen storage

NASA Astrophysics Data System (ADS)

Tang, Xiao; Gu, Yuantong; Kou, Liangzhi

2018-03-01

From first-principles calculations based on density functional theory, we find that the recently synthesized β12 boron sheet is a perfect candidate for calcium-decoration and hydrogen storage application. In contrast to graphene where defects are required to capture Ca, the naturally formed hexagonal hollow ring in β12 boron sheet provides the ideal site for Ca adsorption, and up to 6H2 molecules for each Ca atom can be captured with a desirable binding energy of ∼0.2 eV/H2. The gravimetric hydrogen density for Ca decorated boron sheet can reach up to 8.92 wt%. From the electronic analysis, it is found that both the orbital hybridizations and polarization mechanism play significant roles in H2 adsorption and storage.
Good on paper: the gap between programme theory and real-world context in Pakistan's Community Midwife programme

PubMed Central

Mumtaz, Z; Levay, A; Bhatti, A; Salway, S

2015-01-01

Objective To understand why skilled birth attendance—an acknowledged strategy for reducing maternal deaths—has been effective in some settings but is failing in Pakistan and to demonstrate the value of a theory-driven approach to evaluating implementation of maternal healthcare interventions. Design Implementation research was conducted using an institutional ethnographic approach. Setting and population National programme and local community levels in Pakistan. Methods Observations, focus group discussions, and in-depth interviews were conducted with 38 Community Midwives (CMWs), 20 policymakers, 45 healthcare providers and 136 community members. A critical policy document review was conducted. National and local level data were brought together. Main outcomes Alignment of programme theory with real-world practice. Results Data revealed gaps between programme theory, assumptions and reality on the ground. The design of the programme failed to take into account: (1) the incongruity between the role of a midwife and dominant class and gendered norms that devalue such a role; (2) market and consumer behaviour that prevented CMWs from establishing private practices; (3) the complexity of public–private sector cooperation. Uniform deployment policies failed to consider existing provider density and geography. Conclusions Greater attention to programme theory and the ‘real-world’ setting during design of maternal health strategies is needed to achieve consistent results in different contexts. PMID:25315837
Wave excited motion of a body floating on water confined between two semi-infinite ice sheets

NASA Astrophysics Data System (ADS)

Ren, K.; Wu, G. X.; Thomas, G. A.

2016-12-01

The wave excited motion of a body floating on water confined between two semi-infinite ice sheets is investigated. The ice sheet is treated as an elastic thin plate and water is treated as an ideal and incompressible fluid. The linearized velocity potential theory is adopted in the frequency domain and problems are solved by the method of matched eigenfunctions expansion. The fluid domain is divided into sub-regions and in each sub-region the velocity potential is expanded into a series of eigenfunctions satisfying the governing equation and the boundary conditions on horizontal planes including the free surface and ice sheets. Matching is conducted at the interfaces of two neighbouring regions to ensure the continuity of the pressure and velocity, and the unknown coefficients in the expressions are obtained as a result. The behaviour of the added mass and damping coefficients of the floating body with the effect of the ice sheets and the excitation force are analysed. They are found to vary oscillatorily with the wave number, which is different from that for a floating body in the open sea. The motion of the body confined between ice sheets is investigated, in particular its resonant behaviour with extremely large motion found to be possible under certain conditions. Standing waves within the polynya are also observed.
Quantitative confirmation of diffusion-limited oxidation theories

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

Gillen, K.T.; Clough, R.L.

1990-01-01

Diffusion-limited (heterogeneous) oxidation effects are often important for studies of polymer degradation. Such effects are common in polymers subjected to ionizing radiation at relatively high dose rate. To better understand the underlying oxidation processes and to aid in the planning of accelerated aging studies, it would be desirable to be able to monitor and quantitatively understand these effects. In this paper, we briefly review a theoretical diffusion approach which derives model profiles for oxygen surrounded sheets of material by combining oxygen permeation rates with kinetically based oxygen consumption expressions. The theory leads to a simple governing expression involving the oxygenmore » consumption and permeation rates together with two model parameters {alpha} and {beta}. To test the theory, gamma-initiated oxidation of a sheet of commercially formulated EPDM rubber was performed under conditions which led to diffusion-limited oxidation. Profile shapes from the theoretical treatments are shown to accurately fit experimentally derived oxidation profiles. In addition, direct measurements on the same EPDM material of the oxygen consumption and permeation rates, together with values of {alpha} and {beta} derived from the fitting procedure, allow us to quantitatively confirm for the first time the governing theoretical relationship. 17 refs., 3 figs.« less
Structure and luminescence properties of 10-BN sheets

NASA Astrophysics Data System (ADS)

Han, Wei-Qiang; Liu, Lijia; Sham, T. K.; Liu, Zhenxian

2012-10-01

Isotopic 10BN sheets were first prepared using graphene sheets as templates to react with 10B2O3. The edge-areas of BN sheets have much higher oxygen-doping ratios compared to other areas. The emission peak of X-ray excited optical luminescence spectra of the 10BN-sheets is broader and red-shifted because of the isotopic effect. A broad violet-blue emission at a wavelength centered at ~400 nm is assigned to the defect emission due to oxygen-doping and defects in the BN network.
Effects of auroral potential drops on plasma sheet dynamics

NASA Astrophysics Data System (ADS)

Xi, Sheng; Lotko, William; Zhang, Binzheng; Wiltberger, Michael; Lyon, John

2016-11-01

The reaction of the magnetosphere-ionosphere system to dynamic auroral potential drops is investigated using the Lyon-Fedder-Mobarry global model including, for the first time in a global simulation, the dissipative load of field-aligned potential drops in the low-altitude boundary condition. This extra load reduces the field-aligned current (j||) supplied by nightside reconnection dynamos. The system adapts by forcing the nightside X line closer to Earth, with a corresponding reduction in current lensing (j||/B = constant) at the ionosphere and additional contraction of the plasma sheet during substorm recovery and steady magnetospheric convection. For steady and moderate solar wind driving and with constant ionospheric conductance, the cross polar cap potential and hemispheric field-aligned current are lower by approximately the ratio of the peak field-aligned potential drop to the cross polar cap potential (10-15%) when potential drops are included. Hemispheric ionospheric Joule dissipation is less by 8%, while the area-integrated, average work done on the fluid by the reconnecting magnetotail field increases by 50% within |y| < 8 RE. Effects on the nightside plasma sheet include (1) an average X line 4 RE closer to Earth; (2) a 12% higher mean reconnection rate; and (3) dawn-dusk asymmetry in reconnection with a 17% higher rate in the premidnight sector.
Innovative technology: Slurry-phase biodegradation. Fact sheet (Final)

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

Not Available

1989-11-01

The fact sheet provides technology description, site characteristics affecting treatment feasibility, technology considerations, and technology status for Slurry Phase Biodegradation (SPB). The sheet describes how SPB is potentially effective in treating various organic contaminants.
Effect of Process Parameters on the Structure and Properties of Galvanized Sheets

NASA Astrophysics Data System (ADS)

Shukla, S. K.; Saha, B. B.; Triathi, B. D.; Avtar, Ram

2010-07-01

The effect of galvanizing parameters on the structure (spangle size and coating microstructure) and properties (formability and corrosion resistance) of galvanized sheets was studied in a hot dip process simulator (HDPS) in a conventional Pb bearing (0.08-0.10%) zinc bath by varying zinc bath Al level (0.10-0.28%), bath temperature (718-743 K), dipping time (1.5-3.5 s), wiping gas flow rate (200-450 lpm), nozzle distance (15-17 mm) and wiping delay time (0.1-2.1 s). Al level in the range of 0.18-0.24% in combination with dipping time of 1.5-2.5 s and bath temperature of 718-733 K results in superior formability ( E cv: ~9.3 mm) of the composite (thickness: 0.8 mm). High post-dip cooling rates (~25 K/s) suppress spangle growth (spangle size: ~2 mm). The spangle size of the GI sheet strongly influences the corrosion rate which increases from 5.8 to 9.2 mpy with a decrease in spangle size from 17.5 to 3 mm. By controlling the Al level (0.20%) in zinc bath and bath temperature (733 K), the corrosion rate of mini-spangle GI sheet can be controlled to a level of 5.5 mpy.

Loading direction-dependent shear behavior at different temperatures of single-layer chiral graphene sheets

NASA Astrophysics Data System (ADS)

Zhao, Yang; Dong, Shuhong; Yu, Peishi; Zhao, Junhua

2018-06-01

The loading direction-dependent shear behavior of single-layer chiral graphene sheets at different temperatures is studied by molecular dynamics (MD) simulations. Our results show that the shear properties (such as shear stress-strain curves, buckling strains, and failure strains) of chiral graphene sheets strongly depend on the loading direction due to the structural asymmetry. The maximum values of both the critical buckling shear strain and the failure strain under positive shear deformation can be around 1.4 times higher than those under negative shear deformation. For a given chiral graphene sheet, both its failure strain and failure stress decrease with increasing temperature. In particular, the amplitude to wavelength ratio of wrinkles for different chiral graphene sheets under shear deformation using present MD simulations agrees well with that from the existing theory. These findings provide physical insights into the origins of the loading direction-dependent shear behavior of chiral graphene sheets and their potential applications in nanodevices.
A first-principles study on adsorption behaviors of pristine and Li-decorated graphene sheets toward hydrazine molecules

NASA Astrophysics Data System (ADS)

Zeng, Huadong; Cheng, Xinlu; Wang, Wei

2018-03-01

The adsorption behaviors and properties of hydrazine (N2H4) molecules on pristine and Li-decorated graphene sheets were investigated by means of first-principles based on density functional theory. We systematically analyzed the optimal geometry, average binding energy, charge transfer, charge density difference and density of states of N2H4 molecules adsorbed on pristine and Li-decorated graphene sheets. It is found that the interaction between single N2H4 molecule and pristine graphene is weak physisorption with the low binding energy of -0.026 eV, suggesting that the pristine graphene sheet is insensitive to the presence of N2H4 molecule. However, it is markedly enhanced after lithium decoration with the high binding energy of -1.004 eV, verifying that the Li-decorated graphene sheet is significantly sensitive to detect N2H4 molecule. Meanwhile, the effects of the concentrations of N2H4 molecules on two different substrates were studied detailedly. For pristine graphene substrate, the average binding energy augments apparently with increasing the number of N2H4 molecules, which is mainly attributed to the van der Waals interactions and hydrogen bonds among N2H4 clusters. Li-decorated graphene sheet has still a strong affinity to N2H4 molecules despite the corresponding average binding energy emerges a contrary tendency. Overall, Li-decorated graphene sheet could be considered as a potential gas sensor in field of hydrazine molecules.
Wrinkling of a thin circular sheet bonded to a spherical substrate

PubMed Central

Kohn, Robert V.

2017-01-01

We consider a disc-shaped thin elastic sheet bonded to a compliant sphere. (Our sheet can slip along the sphere; the bonding controls only its normal displacement.) If the bonding is stiff (but not too stiff), the geometry of the sphere makes the sheet wrinkle to avoid azimuthal compression. The total energy of this system is the elastic energy of the sheet plus a (Winkler-type) substrate energy. Treating the thickness of the sheet h as a small parameter, we determine the leading-order behaviour of the energy as h tends to zero, and we give (almost matching) upper and lower bounds for the next-order correction. Our analysis of the leading-order behaviour determines the macroscopic deformation of the sheet; in particular, it determines the extent of the wrinkled region, and predicts the (non-trivial) radial strain of the sheet. The leading-order behaviour also provides insight about the length scale of the wrinkling, showing that it must be approximately independent of the distance r from the centre of the sheet (so that the number of wrinkles must increase with r). Our results on the next-order correction provide insight about how the wrinkling pattern should vary with r. Roughly speaking, they suggest that the length scale of wrinkling should not be exactly constant—rather, it should vary slightly, so that the number of wrinkles at radius r can be approximately piecewise constant in its dependence on r, taking values that are integer multiples of h−a with . This article is part of the themed issue ‘Patterning through instabilities in complex media: theory and applications’. PMID:28373380
Media Effects: Theory and Research.

PubMed

Valkenburg, Patti M; Peter, Jochen; Walther, Joseph B

2016-01-01

This review analyzes trends and commonalities among prominent theories of media effects. On the basis of exemplary meta-analyses of media effects and bibliometric studies of well-cited theories, we identify and discuss five features of media effects theories as well as their empirical support. Each of these features specifies the conditions under which media may produce effects on certain types of individuals. Our review ends with a discussion of media effects in newer media environments. This includes theories of computer-mediated communication, the development of which appears to share a similar pattern of reformulation from unidirectional, receiver-oriented views, to theories that recognize the transactional nature of communication. We conclude by outlining challenges and promising avenues for future research.
Effects of thermo-mechanical behavior and hinge geometry on folding response of shape memory polymer sheets

NASA Astrophysics Data System (ADS)

Mailen, Russell W.; Dickey, Michael D.; Genzer, Jan; Zikry, Mohammed

2017-11-01

Shape memory polymer (SMP) sheets patterned with black ink hinges change shape in response to external stimuli, such as absorbed thermal energy from an infrared (IR) light. The geometry of these hinges, including size, orientation, and location, and the applied thermal loads significantly influence the final folded shape of the sheet, but these variables have not been fully investigated. We perform a systematic study on SMP sheets to fundamentally understand the effects of single and double hinge geometries, hinge orientation and spacing, initial temperature, heat flux intensity, and pattern width on the folding behavior. We have developed thermo-viscoelastic finite element models to characterize and quantify the stresses, strains, and temperatures as they relate to SMP shape changes. Our predictions indicate that hinge orientation can be used to reduce the total bending angle, which is the angle traversed by the folding face of the sheet. Two parallel hinges increase the total bending angle, and heat conduction between the hinges affects the transient folding response. IR intensity and initial temperatures can also influence the transient folding behavior. These results can provide guidelines to optimize the transient folding response and the three-dimensional folded structure obtained from self-folding polymer origami sheets that can be applied for myriad applications.
Probing the interactions of phenol with oxygenated functional groups on curved fullerene-like sheets in activated carbon.

PubMed

Yin, Chun-Yang; Ng, Man-Fai; Goh, Bee-Min; Saunders, Martin; Hill, Nick; Jiang, Zhong-Tao; Balach, Juan; El-Harbawi, Mohanad

2016-02-07

The mechanism(s) of interactions of phenol with oxygenated functional groups (OH, COO and COOH) in nanopores of activated carbon (AC) is a contentious issue among researchers. This mechanism is of particular interest because a better understanding of the role of such groups in nanopores would essentially translate to advances in AC production and use, especially in regard to the treatment of organic-based wastewaters. We therefore attempt to shed more light on the subject by employing density functional theory (DFT) calculations in which fullerene-like models integrating convex or concave structure, which simulate the eclectic porous structures on AC surface, are adopted. TEM analysis, EDS mapping and Boehm titration are also conducted on actual phenol-adsorbed AC. Our results suggest the widely-reported phenomenon of decreased phenol uptake on AC due to increased concentration of oxygenated functional groups is possibly attributed to the increased presence of the latter on the convex side of the curved carbon sheets. Such a system effectively inhibits phenol from getting direct contact with the carbon sheet, thus constraining any available π-π interaction, while the effect of groups acting on the concave part of the curved sheet does not impart the same detriment.
An Imminent Revolution in Modeling Interactions of Ice Sheets With Climate

NASA Astrophysics Data System (ADS)

Hughes, T.

2008-12-01

Modeling continental ice sheets was inaugurated by meteorologists William Budd and Uwe Radok, with mathematician Richard Jenssen, in 1971. Their model calculated the thermal and mechanical regime using measured surface accumulation rates, temperatures, and elevations, and bed topography. This top-down approach delivered a basal thermal regime of temperatures or melting rates for an assumed basal geothermal heat flux. When Philippe Huybrechts and others incorporated time, largely unknownpast surface conditions had a major effect on present basal thermal conditions. This approach produced ice-sheet models with only a slow response to external forcing, whereas the glacial geological record and climate records from ice and ocean cores show that ice sheets can have rapid changes in size and shape independent of external forcing. These top-down models were wholly inadequate for reconstructing former ice sheets at the LGM for CLIMAP in 1981. Ice-sheet areas,elevations, and volumes provided the albedo, surface topography, and sea-surface area as input to climate models. A bottom-up model based on dated glacial geology was developed to provide the areal extent and basal thermal regime of ice sheets at the LGM. Basal thermal conditions determined ice-bed coupling and therefore the elevation of ice sheets. High convex ice surfaces for slow sheet flow lower about 20 percent when a frozen bed becomes thawed. As further basal melting drowns bedrock bumps that "pin" basal ice, the ice surface becomes concave in fast stream flow that ends as low floating ice shelves at marine ice margins. A revolution in modeling interactions between glaciation, climate, and sea level is driven by new Greenland and Antarctic data from Earth-orbiting satellites, airborne and surface traverses, and deep drilling. We anticipate continuous data acquisition of surface albedo, accumulation/ablation rates, elevations, velocities, and temperatures over a whole ice sheet, mapping basal thermal conditions
Status and ecological effects of the world's largest carnivores.

PubMed

Ripple, William J; Estes, James A; Beschta, Robert L; Wilmers, Christopher C; Ritchie, Euan G; Hebblewhite, Mark; Berger, Joel; Elmhagen, Bodil; Letnic, Mike; Nelson, Michael P; Schmitz, Oswald J; Smith, Douglas W; Wallach, Arian D; Wirsing, Aaron J

2014-01-10

Large carnivores face serious threats and are experiencing massive declines in their populations and geographic ranges around the world. We highlight how these threats have affected the conservation status and ecological functioning of the 31 largest mammalian carnivores on Earth. Consistent with theory, empirical studies increasingly show that large carnivores have substantial effects on the structure and function of diverse ecosystems. Significant cascading trophic interactions, mediated by their prey or sympatric mesopredators, arise when some of these carnivores are extirpated from or repatriated to ecosystems. Unexpected effects of trophic cascades on various taxa and processes include changes to bird, mammal, invertebrate, and herpetofauna abundance or richness; subsidies to scavengers; altered disease dynamics; carbon sequestration; modified stream morphology; and crop damage. Promoting tolerance and coexistence with large carnivores is a crucial societal challenge that will ultimately determine the fate of Earth's largest carnivores and all that depends upon them, including humans.
Sensitivity of an Antarctic Ice Sheet Model to Sub-Ice-Shelf Melting

NASA Astrophysics Data System (ADS)

Lipscomb, W. H.; Leguy, G.; Urban, N. M.; Berdahl, M.

2017-12-01

Theory and observations suggest that marine-based sectors of the Antarctic ice sheet could retreat rapidly under ocean warming and increased melting beneath ice shelves. Numerical models of marine ice sheets vary widely in sensitivity, depending on grid resolution and the parameterization of key processes (e.g., calving and hydrofracture). Here we study the sensitivity of the Antarctic ice sheet to ocean warming and sub-shelf melting in standalone simulations of the Community Ice Sheet Model (CISM). Melt rates either are prescribed based on observations and high-resolution ocean model output, or are derived from a plume model forced by idealized ocean temperature profiles. In CISM, we vary the model resolution (between 1 and 8 km), Stokes approximation (shallow-shelf, depth-integrated higher-order, or 3D higher-order) and calving scheme to create an ensemble of plausible responses to sub-shelf melting. This work supports a broader goal of building statistical and reduced models that can translate large-scale Earth-system model projections to changes in Antarctic ocean temperatures and ice sheet discharge, thus better quantifying uncertainty in Antarctic-sourced sea-level rise.
Sheet, ligament and droplet formation in swirling primary atomization

NASA Astrophysics Data System (ADS)

Shao, Changxiao; Luo, Kun; Chai, Min; Fan, Jianren

2018-04-01

We report direct numerical simulations of swirling liquid atomization to understand the physical mechanism underlying the sheet breakup of a non-turbulent liquid swirling jet which lacks in-depth investigation. The volume-of-fluid (VOF) method coupled with adapted mesh refinement (AMR) technique in GERRIS code is employed in the present simulation. The mechanisms of sheet, ligament and droplet formation are investigated. It is observed that the olive-shape sheet structure is similar to the experimental result qualitatively. The numerical results show that surface tension, pressure difference and swirling effect contribute to the contraction and extension of liquid sheet. The ligament formation is partially at the sheet rim or attributed to the extension of liquid hole. Especially, the movement of hairpin vortex exerts by an anti-radial direction force to the sheet surface and leads to the sheet thinness. In addition, droplet formation is attributed to breakup of ligament and central sheet.
Comprehension of hazard communication: effects of pictograms on safety data sheets and labels.

PubMed

Boelhouwer, Eric; Davis, Jerry; Franco-Watkins, Ana; Dorris, Nathan; Lungu, Claudiu

2013-09-01

The United Nations has proposed the Globally Harmonized System (GHS) of Classification and Labelling of Chemicals to make hazard communication more uniform and to improve comprehension. Two experiments were conducted to test whether the addition of hazard and precautionary pictograms to safety data sheets and product labels would improve the transfer of information to users compared to safety data sheets and product labels containing text only. Additionally, naïve users, workers, and experts were tested to determine any potential differences among users. The effect of adding pictograms to safety data sheets and labels was statistically significant for some conditions, but was not significant across all conditions. One benefit of the addition of pictograms was that the time to respond to the survey questions decreased when the pictograms were present for both the SDS and the labels. GHS format SDS and labels do provide benefits to users, but the system will need further enhancements and modifications to continue to improve the effectiveness of hazard communication. The final rule to modify the HCS to include the Globally Harmonized System (GHS) for the Classification and Labelling of Chemicals announced by OSHA (2012b) will change the information content of every chemical SDS and label used in commerce. This study suggests that the inclusion of GHS hazard pictograms and precautionary pictograms to SDS and labels may benefit the user. Copyright © 2013 National Safety Council and Elsevier Ltd. All rights reserved.
Observationally constrained projections of Antarctic ice sheet instability

NASA Astrophysics Data System (ADS)

Edwards, Tamsin; Ritz, Catherine; Durand, Gael; Payne, Anthony; Peyaud, Vincent; Hindmarsh, Richard

2015-04-01

Large parts of the Antarctic ice sheet lie on bedrock below sea level and may be vulnerable to a positive feedback known as Marine Ice Sheet Instability (MISI), a self-sustaining retreat of the grounding line triggered by oceanic or atmospheric changes. There is growing evidence MISI may be underway throughout the Amundsen Sea Embayment (ASE) of West Antarctica, induced by circulation of warm Circumpolar Deep Water. If this retreat is sustained the region could contribute up to 1-2 m to global mean sea level, and if triggered in other areas the potential contribution to sea level on centennial to millennial timescales could be two to three times greater. However, physically plausible projections of Antarctic MISI are challenging: numerical ice sheet models are too low in spatial resolution to resolve grounding line processes or else too computationally expensive to assess modelling uncertainties, and no dynamical models exist of the ocean-atmosphere-ice sheet system. Furthermore, previous numerical ice sheet model projections for Antarctica have not been calibrated with observations, which can reduce uncertainties. Here we estimate the probability of dynamic mass loss in the event of MISI under a medium climate scenario, assessing 16 modelling uncertainties and calibrating the projections with observed mass losses in the ASE from 1992-2011. We project losses of up to 30 cm sea level equivalent (SLE) by 2100 and 72 cm SLE by 2200 (95% credibility interval: CI). Our results are substantially lower than previous estimates. The ASE sustains substantial losses, 83% of the continental total by 2100 and 67% by 2200 (95% CI), but in other regions losses are limited by ice dynamical theory, observations, or a lack of projected triggers.
Effects of β-sheet crystals and a glycine-rich matrix on the thermal conductivity of spider dragline silk.

PubMed

Park, Jinju; Kim, Duckjong; Lee, Seung-Mo; Choi, Ji-Ung; You, Myungil; So, Hye-Mi; Han, Junkyu; Nah, Junghyo; Seol, Jae Hun

2017-03-01

We measured the thermal conductivity of Araneus ventricosus' spider dragline silk using a suspended microdevice. The thermal conductivity of the silk fiber was approximately 0.4Wm -1 K -1 at room temperature and gradually increased with an increasing temperature in a manner similar to that of other disordered crystals or proteins. In order to elucidate the effect of β-sheet crystals in the silk, thermal denaturation was used to reduce the quantity of the β-sheet crystals. A calculation with an effective medium approximation supported this measurement result showing that the thermal conductivity of β-sheet crystals had an insignificant effect on the thermal conductivity of SDS. Additionally, the enhancement of bonding strength in a glycine-rich matrix by atomic layer deposition did not increase the thermal conductivity. Thus, this study suggests that the disordered part of the glycine-rich matrix prevented the peptide chains from being coaxially extended via the cross-linking covalent bonds. Copyright © 2016 Elsevier B.V. All rights reserved.
GATEWAY Demonstrations: Exploring SSL Product Performance in the Real World

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

None

Fact sheet that outlines DOE's GATEWAY technology demonstration program, which evaluates high-performance SSL products for general illumination in a variety of real-world exterior and interior applications.
A World Apart? Bridging the Gap between Theory and Applied Social Gerontology

ERIC Educational Resources Information Center

Hendricks, Jon; Applebaum, Robert; Kunkel, Suzanne

2010-01-01

This article is based on the premise that there is inadequate attention to the link between theory and applied research in social gerontology. The article contends that applied research studies do not often or effectively employ a theoretical framework and that theory-based articles, including theory-based research, are not often focused on…
Pilot randomized trial of a volitional help sheet-based tool to increase leisure time physical activity in breast cancer survivors.

PubMed

Chapman, Janine; Fletcher, Chloe; Flight, Ingrid; Wilson, Carlene

2018-05-16

To develop and test a volitional help sheet-based tool to improve physical activity in breast cancer survivors compared to a standard self-generated implementation intention intervention. Pilot randomized trial conducted online over 3 months. Participants were randomized to an online volitional help sheet (n = 50) or implementation intention (n = 51) intervention. Measures were taken at baseline, 1 and 3 months. The main outcome measure was moderate-strenuous leisure time physical activity. Secondary outcomes were health-related quality of life and mood. Participants exposed to the volitional help sheet and implementation intention interventions showed similar effects after 1 month, with both groups reporting a significant increase in moderate-strenuous physical activity. After 3 months, the initial increase in physical activity was maintained by the volitional help sheet group, but not the implementation intention group. Improvements were also found for negative affect and emotional quality of life. While both interventions show promise in promoting physical activity in breast cancer survivors, the volitional help sheet may be more effective for facilitating lasting change and emotional well-being. Findings suggest that the volitional help sheet may have potential to offer a cost-effective contribution to consumer-led tertiary preventive health. Future research should test these initial findings in a definitive trial. Statement of contribution What is already known on this subject? Physical activity is important for optimizing health in breast cancer survivors. Despite this, physical activity in this cohort remains low. Theory-based strategies are needed to help breast cancer survivors independently manage and maintain regular physical activity over the long term. What does this study add? Online planning interventions can improve physical activity in breast cancer survivors. Volitional help sheets, but not implementation intentions, show sustained
Energized Oxygen : Speiser Current Sheet Bifurcation

NASA Astrophysics Data System (ADS)

George, D. E.; Jahn, J. M.

2017-12-01

A single population of energized Oxygen (O+) is shown to produce a cross-tail bifurcated current sheet in 2.5D PIC simulations of the magnetotail without the influence of magnetic reconnection. Treatment of oxygen in simulations of space plasmas, specifically a magnetotail current sheet, has been limited to thermal energies despite observations of and mechanisms which explain energized ions. We performed simulations of a homogeneous oxygen background, that has been energized in a physically appropriate manner, to study the behavior of current sheets and magnetic reconnection, specifically their bifurcation. This work uses a 2.5D explicit Particle-In-a-Cell (PIC) code to investigate the dynamics of energized heavy ions as they stream Dawn-to-Dusk in the magnetotail current sheet. We present a simulation study dealing with the response of a current sheet system to energized oxygen ions. We establish a, well known and studied, 2-species GEM Challenge Harris current sheet as a starting point. This system is known to eventually evolve and produce magnetic reconnection upon thinning of the current sheet. We added a uniform distribution of thermal O+ to the background. This 3-species system is also known to eventually evolve and produce magnetic reconnection. We add one additional variable to the system by providing an initial duskward velocity to energize the O+. We also traced individual particle motion within the PIC simulation. Three main results are shown. First, energized dawn- dusk streaming ions are clearly seen to exhibit sustained Speiser motion. Second, a single population of heavy ions clearly produces a stable bifurcated current sheet. Third, magnetic reconnection is not required to produce the bifurcated current sheet. Finally a bifurcated current sheet is compatible with the Harris current sheet model. This work is the first step in a series of investigations aimed at studying the effects of energized heavy ions on magnetic reconnection. This work differs
Education and World Order

ERIC Educational Resources Information Center

Jones, Phillip W.

2007-01-01

The impact on educational analysis of mainstream international relations (IR) theories is yet to realize its full potential. The problem of education in relation to the construction of world order is considered in relation to core developments in IR theory since the Second World War. In particular, the global architecture of education is seen as a…
Effects of rolling conditions on recrystallization microstructure and texture in magnetostrictive Fe-Ga-Al rolled sheets

NASA Astrophysics Data System (ADS)

Li, Jiheng; Liu, Yangyang; Li, Xiaojuan; Mu, Xing; Bao, Xiaoqian; Gao, Xuexu

2018-07-01

The effects of different rolling conditions on the microstructure and texture of primary and secondary recrystallization in magnetostrictive Fe82Ga9Al9+0.1at%NbC alloy sheets were investigated. After the primary recrystallization annealing at 850 °C for 5 min, the as-rolled sheets prepared by warm-cold rolling with an intermediate annealing, can be fully recrystallized, and obtain the homogeneous matrix in which the fine dispersed NbC precipitate particles are distributed. The primary recrystallization textures of sheets with different rolling conditions consist mostly of strong {1 0 0} textures, γ-fiber textures, {4 1 1}〈1 4 8〉 texture and weak Goss texture. In the primary recrystallized sheets prepared by warm-cold rolling with an intermediate annealing, the high energy grain boundaries and ∑9 boundaries have the highest proportion. After high temperature annealing, the secondary recrystallizations of Goss grains in these sheets are more complete, and the size of abnormal grown Goss grain is up to several centimeters, which results in the strongest Goss texture. Correspondingly, the largest magnetostriction of 183 ppm is observed. The sample prepared by warm-cold rolling with an intermediate annealing, has homogeneous primary matrix, special texture components and grain boundary distribution, all of which provide a better surrounding for the abnormal growth of Goss grains. This work indicates that the control of rolling conditions of Fe-Ga-Al alloy sheets is necessary to achieve the strong Goss texture and obtain a possible high magnetostriction if other appropriate conditions (stress, domain structure) are achieved.
Clouds enhance Greenland ice sheet meltwater runoff

PubMed Central

Van Tricht, K.; Lhermitte, S.; Lenaerts, J. T. M.; Gorodetskaya, I. V.; L'Ecuyer, T. S.; Noël, B.; van den Broeke, M. R.; Turner, D. D.; van Lipzig, N. P. M.

2016-01-01

The Greenland ice sheet has become one of the main contributors to global sea level rise, predominantly through increased meltwater runoff. The main drivers of Greenland ice sheet runoff, however, remain poorly understood. Here we show that clouds enhance meltwater runoff by about one-third relative to clear skies, using a unique combination of active satellite observations, climate model data and snow model simulations. This impact results from a cloud radiative effect of 29.5 (±5.2) W m−2. Contrary to conventional wisdom, however, the Greenland ice sheet responds to this energy through a new pathway by which clouds reduce meltwater refreezing as opposed to increasing surface melt directly, thereby accelerating bare-ice exposure and enhancing meltwater runoff. The high sensitivity of the Greenland ice sheet to both ice-only and liquid-bearing clouds highlights the need for accurate cloud representations in climate models, to better predict future contributions of the Greenland ice sheet to global sea level rise. PMID:26756470

Clouds enhance Greenland ice sheet meltwater runoff.

PubMed

Van Tricht, K; Lhermitte, S; Lenaerts, J T M; Gorodetskaya, I V; L'Ecuyer, T S; Noël, B; van den Broeke, M R; Turner, D D; van Lipzig, N P M

2016-01-12

The Greenland ice sheet has become one of the main contributors to global sea level rise, predominantly through increased meltwater runoff. The main drivers of Greenland ice sheet runoff, however, remain poorly understood. Here we show that clouds enhance meltwater runoff by about one-third relative to clear skies, using a unique combination of active satellite observations, climate model data and snow model simulations. This impact results from a cloud radiative effect of 29.5 (±5.2) W m(-2). Contrary to conventional wisdom, however, the Greenland ice sheet responds to this energy through a new pathway by which clouds reduce meltwater refreezing as opposed to increasing surface melt directly, thereby accelerating bare-ice exposure and enhancing meltwater runoff. The high sensitivity of the Greenland ice sheet to both ice-only and liquid-bearing clouds highlights the need for accurate cloud representations in climate models, to better predict future contributions of the Greenland ice sheet to global sea level rise.
Sv-map between type I and heterotic sigma models

NASA Astrophysics Data System (ADS)

Fan, Wei; Fotopoulos, A.; Stieberger, S.; Taylor, T. R.

2018-05-01

The scattering amplitudes of gauge bosons in heterotic and open superstring theories are related by the single-valued projection which yields heterotic amplitudes by selecting a subset of multiple zeta value coefficients in the α‧ (string tension parameter) expansion of open string amplitudes. In the present work, we argue that this relation holds also at the level of low-energy expansions (or individual Feynman diagrams) of the respective effective actions, by investigating the beta functions of two-dimensional sigma models describing world-sheets of open and heterotic strings. We analyze the sigma model Feynman diagrams generating identical effective action terms in both theories and show that the heterotic coefficients are given by the single-valued projection of the open ones. The single-valued projection appears as a result of summing over all radial orderings of heterotic vertices on the complex plane representing string world-sheet.
[The effect of colored syringes and a colored sheet on the incidence of syringe swaps during anesthetic management].

PubMed

Hirabayashi, Yoshihiro; Kawakami, Takayuki; Suzuki, Hideo; Igarashi, Takashi; Saitoh, Kazuhiko; Seo, Norimasa

2005-09-01

Syringe swap is an important problem in anesthetic care, causing harm to patients. We examined the effect of colored syringe and a colored sheet on the incidence of syringe swaps during anesthetic management. We determined the color code. The blue-syringe contains local anesthetics; yellow-syringe, sympathomimetic drugs; and white-syringe with a red label fixed opposite the scale, muscle relaxants. The colored sheet displays the photographs of the syringe with drug name, dose and volume. The colored syringe and colored sheet were supplied for use from February 2004. We compared the incidence of syringe swaps during the period from February 2004 to January 2005 with that from February 2003 to January 2004. Although five syringe swaps were recorded from February 2003 to January 2004, in 5901 procedures, we encountered no syringe swaps from February 2004 to January 2005, in 6078 procedures. The colored syringe and colored sheet significantly decreased the incidence of syringe swaps during anesthetic management (P <0.05). The use of the sheet together with colored syringes can prevent syringe swaps during anesthesia.
Quantum theory and human perception of the macro-world.

PubMed

Aerts, Diederik

2014-01-01

We investigate the question of 'why customary macroscopic entities appear to us humans as they do, i.e., as bounded entities occupying space and persisting through time', starting from our knowledge of quantum theory, how it affects the behavior of such customary macroscopic entities, and how it influences our perception of them. For this purpose, we approach the question from three perspectives. Firstly, we look at the situation from the standard quantum angle, more specifically the de Broglie wavelength analysis of the behavior of macroscopic entities, indicate how a problem with spin and identity arises, and illustrate how both play a fundamental role in well-established experimental quantum-macroscopical phenomena, such as Bose-Einstein condensates. Secondly, we analyze how the question is influenced by our result in axiomatic quantum theory, which proves that standard quantum theory is structurally incapable of describing separated entities. Thirdly, we put forward our new 'conceptual quantum interpretation', including a highly detailed reformulation of the question to confront the new insights and views that arise with the foregoing analysis. At the end of the final section, a nuanced answer is given that can be summarized as follows. The specific and very classical perception of human seeing-light as a geometric theory-and human touching-only ruled by Pauli's exclusion principle-plays a role in our perception of macroscopic entities as ontologically stable entities in space. To ascertain quantum behavior in such macroscopic entities, we will need measuring apparatuses capable of its detection. Future experimental research will have to show if sharp quantum effects-as they occur in smaller entities-appear to be ontological aspects of customary macroscopic entities. It remains a possibility that standard quantum theory is an incomplete theory, and hence incapable of coping ultimately with separated entities, meaning that a more general theory will be needed.
Outreach/education interface for Cryosphere models using the Virtual Ice Sheet Laboratory

NASA Astrophysics Data System (ADS)

Larour, E. Y.; Halkides, D. J.; Romero, V.; Cheng, D. L.; Perez, G.

2014-12-01

In the past decade, great strides have been made in the development of models capable of projecting the future evolution of glaciers and the polar ice sheets in a changing climate. These models are now capable of replicating some of the trends apparent in satellite observations. However, because this field is just now maturing, very few efforts have been dedicated to adapting these capabilities to education. Technologies that have been used in outreach efforts in Atmospheric and Oceanic sciences still have not been extended to Cryospheric Science. We present a cutting-edge, technologically driven virtual laboratory, geared towards outreach and k-12 education, dedicated to the polar ice sheets on Antarctica and Greenland, and their role as major contributors to sea level rise in coming decades. VISL (Virtual Ice Sheet Laboratory) relies on state-of-the art Web GL rendering of polar ice sheets, Android/iPhone and web portability using Javascript, as well as C++ simulations (back-end) based on the Ice Sheet System Model, the NASA model for simulating the evolution of polar ice sheets. Using VISL, educators and students can have an immersive experience into the world of polar ice sheets, while at the same exercising the capabilities of a state-of-the-art climate model, all of it embedded into an education experience that follows the new STEM standards for education.This work was performed at the California Institute of Technology's Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration's Cryosphere Science Program.
Prototypical model for tensional wrinkling in thin sheets

PubMed Central

Davidovitch, Benny; Schroll, Robert D.; Vella, Dominic; Adda-Bedia, Mokhtar; Cerda, Enrique A.

2011-01-01

The buckling and wrinkling of thin films has recently seen a surge of interest among physicists, biologists, mathematicians, and engineers. This activity has been triggered by the growing interest in developing technologies at ever-decreasing scales and the resulting necessity to control the mechanics of tiny structures, as well as by the realization that morphogenetic processes, such as the tissue-shaping instabilities occurring in animal epithelia or plant leaves, often emerge from mechanical instabilities of cell sheets. Although the most basic buckling instability of uniaxially compressed plates was understood by Euler more than two centuries ago, recent experiments on nanometrically thin (ultrathin) films have shown significant deviations from predictions of standard buckling theory. Motivated by this puzzle, we introduce here a theoretical model that allows for a systematic analysis of wrinkling in sheets far from their instability threshold. We focus on the simplest extension of Euler buckling that exhibits wrinkles of finite length—a sheet under axisymmetric tensile loads. The first study of this geometry, which is attributed to Lamé, allows us to construct a phase diagram that demonstrates the dramatic variation of wrinkling patterns from near-threshold to far-from-threshold conditions. Theoretical arguments and comparison to experiments show that the thinner the sheet is, the smaller is the compressive load above which the far-from-threshold regime emerges. This observation emphasizes the relevance of our analysis for nanomechanics applications. PMID:22042841
Theoretical predictions on the electronic structure and charge carrier mobility in 2D Phosphorus sheets

PubMed Central

Xiao, Jin; Long, Mengqiu; Zhang, Xiaojiao; Ouyang, Jun; Xu, Hui; Gao, Yongli

2015-01-01

We have investigated the electronic structure and carrier mobility of four types of phosphorous monolayer sheet (α-P, β-P,γ-P and δ-P) using density functional theory combined with Boltzmann transport method and relaxation time approximation. It is shown that α-P, β-P and γ-P are indirect gap semiconductors, while δ-P is a direct one. All four sheets have ultrahigh carrier mobility and show anisotropy in-plane. The highest mobility value is ~3 × 105 cm2V−1s−1, which is comparable to that of graphene. Because of the huge difference between the hole and electron mobilities, α-P, γ-P and δ-P sheets can be considered as n-type semiconductors, and β-P sheet can be considered as a p-type semiconductor. Our results suggest that phosphorous monolayer sheets can be considered as a new type of two dimensional materials for applications in optoelectronics and nanoelectronic devices. PMID:26035176
Crack propagation in aluminum sheets reinforced with boron-epoxy

NASA Technical Reports Server (NTRS)

Roderick, G. L.

1979-01-01

An analysis was developed to predict both the crack growth and debond growth in a reinforced system. The analysis was based on the use of complex variable Green's functions for cracked, isotropic sheets and uncracked, orthotropic sheets to calculate inplane and interlaminar stresses, stress intensities, and strain-energy-release rates. An iterative solution was developed that used the stress intensities and strain-energy-release rates to predict crack and debond growths, respectively, on a cycle-by-cycle basis. A parametric study was made of the effects of boron-epoxy composite reinforcement on crack propagation in aluminum sheets. Results show that the size of the debond area has a significant effect on the crack propagation in the aluminum. For small debond areas, the crack propagation rate is reduced significantly, but these small debonds have a strong tendency to enlarge. Debond growth is most likely to occur in reinforced systems that have a cracked metal sheet reinforced with a relatively thin composite sheet.
Ice stream activity scaled to ice sheet volume during Laurentide Ice Sheet deglaciation.

PubMed

Stokes, C R; Margold, M; Clark, C D; Tarasov, L

2016-02-18

The contribution of the Greenland and West Antarctic ice sheets to sea level has increased in recent decades, largely owing to the thinning and retreat of outlet glaciers and ice streams. This dynamic loss is a serious concern, with some modelling studies suggesting that the collapse of a major ice sheet could be imminent or potentially underway in West Antarctica, but others predicting a more limited response. A major problem is that observations used to initialize and calibrate models typically span only a few decades, and, at the ice-sheet scale, it is unclear how the entire drainage network of ice streams evolves over longer timescales. This represents one of the largest sources of uncertainty when predicting the contributions of ice sheets to sea-level rise. A key question is whether ice streams might increase and sustain rates of mass loss over centuries or millennia, beyond those expected for a given ocean-climate forcing. Here we reconstruct the activity of 117 ice streams that operated at various times during deglaciation of the Laurentide Ice Sheet (from about 22,000 to 7,000 years ago) and show that as they activated and deactivated in different locations, their overall number decreased, they occupied a progressively smaller percentage of the ice sheet perimeter and their total discharge decreased. The underlying geology and topography clearly influenced ice stream activity, but--at the ice-sheet scale--their drainage network adjusted and was linked to changes in ice sheet volume. It is unclear whether these findings can be directly translated to modern ice sheets. However, contrary to the view that sees ice streams as unstable entities that can accelerate ice-sheet deglaciation, we conclude that ice streams exerted progressively less influence on ice sheet mass balance during the retreat of the Laurentide Ice Sheet.
Description of the heterotic string solutions in U(N) supersymmetric QCD

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

Bolokhov, P. A.; Theoretical Physics Department, St. Petersburg State University, Ulyanovskaya 1, Peterhof, St. Petersburg, 198504; Shifman, M.

2009-04-15

We continue the study of heterotic non-Abelian Bogomol'nyi-Prasad-Sommerfield-saturated flux tubes (strings). Previously, such solutions were obtained [M. Shifman and A. Yung, Phys. Rev. D 77, 125016 (2008).] in a particular U(2) gauge theory: N=2 supersymmetric QCD deformed by superpotential terms of a special type breaking N=2 supersymmetry down to N=1. Here we generalize the previous results to U(N) gauge theories. As was suggested by Edalati and Tong [M. Edalati and D. Tong, J. High Energy Phys. 05 (2007) 005.], the string world-sheet theory is a heterotic N=(0,2) sigma model, with the CP(N-1) target space for bosonic fields and an extramore » right-handed fermion which couples to the fermion fields of the N=(2,2) CP(N-1) model. We derive the heterotic N=(0,2) world-sheet model directly from the U(N) bulk theory. Parameters of the bulk theory are related to those of the world-sheet theory. Qualitatively this relation turns out to be the same as in the U(2) case.« less
Analytical theory of neutral current sheets with a sheared magnetic field in collisionless relativistic plasma

NASA Astrophysics Data System (ADS)

Kocharovsky, V. V.; Kocharovsky, Vl V.; Martyanov, V. Yu; Nechaev, A. A.

2017-12-01

We derive and describe analytically a new wide class of self-consistent magnetostatic structures with sheared field lines and arbitrary energy distributions of particles. To do so we analyze superpositions of two planar current sheets with orthogonal magnetic fields and cylindrically symmetric momentum distribution functions, such that the magnetic field of one of them is directed along the symmetry axis of the distribution function of the other. These superpositions satisfy the pressure balance equation and allow one to construct configurations with an almost arbitrarily sheared magnetic field. We show that most of previously known current sheet families with sheared magnetic field lines are included in this novel class.
Residual stress measurement in silicon sheet by shadow moire interferometry

NASA Technical Reports Server (NTRS)

Kwon, Y.; Danyluk, S.; Bucciarelli, L.; Kalejs, J. P.

1987-01-01

A shadow moire interferometry technique has been developed to measure residual strain in thin silicon sheet. The curvature of a segment of sheet undergoing four-point bending is analyzed to include the applied bending moments, the in-plane residual stresses, and the 'end effect' of the sheet since it is of finite length. The technique is applied to obtain residual stress distributions for silicon sheet grown by the edge-defined film-fed growth technique.
71. PALMDALE WATER COMPANY, EASTWOOD MULTIPLEARCHED DAM: STRESS SHEET, SHEET ...

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

71. PALMDALE WATER COMPANY, EASTWOOD MULTIPLE-ARCHED DAM: STRESS SHEET, SHEET 3; DECEMBER 20, 1918. Littlerock Water District files. - Little Rock Creek Dam, Little Rock Creek, Littlerock, Los Angeles County, CA
Protein unfolding versus β-sheet separation in spider silk nanocrystals

NASA Astrophysics Data System (ADS)

Alam, Parvez

2014-03-01

In this communication a mechanism for spider silk strain hardening is proposed. Shear failure of β-sheet nanocrystals is the first failure mode that gives rise to the creation of smaller nanocrystals, which are of higher strength and stiffness. β-sheet unfolding requires more energy than nanocrystal separation in a shear mode of failure. As a result, unfolding occurs after the nanocrystals separate in shear. β-sheet unfolding yields a secondary strain hardening effect once the β-sheet conformation is geometrically stable and acts like a unidirectional fibre in a fibre reinforced composite. The mechanism suggested herein is based on molecular dynamics calculations of residual inter-β-sheet separation strengths against residual intra-β-sheet unfolding strengths.
A Statistical Model of the Magnetotail Neutral Sheet

NASA Astrophysics Data System (ADS)

Xiao, Sudong; Zhang, Tielong; Baumjohann, Wolfgang; Nakamura, Rumi; Ge, Yasong; Du, Aimin; Wang, Guoqiang; Lu, Quanming

2015-04-01

The neutral sheet of the magnetotail is characterized by weak magnetic field, strong cross tail current, and a reversal of the magnetic field direction across it. The dynamics of the earth's magnetosphere is greatly influenced by physical processes that occur near the neutral sheet. However, the exact position of the neutral sheet is variable in time. It is therefore essential to have a reliable estimate of the average position of the neutral sheet. Magnetic field data from ten years of Cluster, nineteen years of Geotail, four years of TC 1, and seven years of THEMIS observations have been incorporated to obtain a model of the magnetotail neutral sheet. All data in aberrated GSM (Geocentric Solar Magnetospheric) coordinate system are normalized to the same solar wind pressure condition. The shape and position of the neutral sheet, illustrated directly by the separator of positive and negative Bx on the YZ cross sections, are fitted with a displaced ellipse model. It is consistent with previous studies that the neutral sheet becomes curvier in the YZ cross section when the dipole tilt increases, yet our model shows the curviest neutral sheet compared with previous models. The new model reveals a hinging distance very close to 10 RE at a reference solar wind dynamic pressure of 2 nPa. We find that the earth dipole tilt angle not only affects the neutral sheet configuration in the YZ cross section but also in the XZ cross section. The neutral sheet becomes more tilting in the XZ cross section when the dipole tilt increases. The effect of an interplanetary magnetic field (IMF) penetration is studied, and an IMF By-related twisting of about 3° is found. Anticlockwise twisting of the neutral sheet is observed, looking along the downtail direction, for a positive IMF By, and clockwise twisting of the neutral sheet for a negative IMF By.
Ice sheets play important role in climate change

NASA Astrophysics Data System (ADS)

Clark, Peter U.; MacAyeal, Douglas R.; Andrews, John T.; Bartlein, Patrick J.

Ice sheets once were viewed as passive elements in the climate system enslaved to orbitally generated variations in solar radiation. Today, modeling results and new geologic records suggest that ice sheets actively participated in late-Pleistocene climate change, amplifying or driving significant variability at millennial as well as orbital timescales. Although large changes in global ice volume were ultimately caused by orbital variations (the Milankovitch hypothesis), once in existence, the former ice sheets behaved dynamically and strongly influenced regional and perhaps even global climate by altering atmospheric and oceanic circulation and temperature.Experiments with General Circulation Models (GCMs) yielded the first inklings of ice sheets' climatic significance. Manabe and Broccoli [1985], for example, found that the topographic and albedo effects of ice sheets alone explain much of the Northern Hemisphere cooling identified in paleoclimatic records of the last glacial maximum (˜21 ka).
Nonlinear breakup of liquid sheets

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

Jazayeri, S.A.; Li, X.

1997-07-01

Sprays formed from the disintegration of liquid sheets have extensive practical applications, ranging from chemical and pharmaceutical processes to power generation and propulsion systems. A knowledge of the liquid sheet breakup process is essential to the understanding of fundamental mechanism of liquid atomization and spray formation processes. The breakup of liquid sheets has been investigated in terms of hydrodynamic stability via linear analysis by Squire, Hagerty and Shea, Li, etc. nonlinear effect has been studied by Clark and Dombrowski up to the second order, and by Rangel and Sirignano through numerical simulation employing vortex discretization method. As shown by Taubmore » for the breakup of circular liquid jets, the closer to the breakup region, the higher the order of nonlinear analysis has to be for adequate description of the breakup behavior. As pointed out by Bogy, a nonlinear analysis up to the third order is generally sufficient to account for the inherent nonlinear nature of the breakup process. Therefore, a third-order nonlinear analysis has been carried out in this study to investigate the process of liquid sheet disruption preceding the spray formation.« less
Non-Classical Stress Concentration Behavior in a Radically Stretched Hyperelastic Sheet Containing a Circular Hole

NASA Technical Reports Server (NTRS)

Ko, William L.; Lung, Shun-Fat

2017-01-01

Non-classical stress concentration behavior in a stretched circular hyperelastic sheet (outer radius b = 10 in., thickness t = 0.0625 in.) containing a central hole (radius a = 0.5 in.) was analyzed. The hyperelastic sheet was subjected to different levels of remote radial stretchings. Nastran large-strain large-deformation analysis and the Blatz-Ko large deformation theory were used to calculate the equal-biaxial stress concentration factors K. The results show that the values of K calculated from the Blatz-Ko theory and Nastran are extremely close. Unlike the classical linear elasticity theory, which gives the constant K = 2 for the equal-biaxial stress field, the hyperelastic K values were found to increase with increased stretching and can exceed the value K = 6 at a remote radial extension ratio of 2.35. The present K-values compare fairly well with the K-values obtained by previous works. The effect of the hole-size on K-values was investigated. The values of K start to decrease from a hole radius a = 0.125 in. down to K = 1 (no stress concentration) as a shrinks to a = 0 in. (no hole). Also, the newly introduced stretch and strain magnification factors {K(sub ?),K(sub e) } are also material- and deformation-dependent, and can increase from linear levels of {1.0, 4.0} and reaching {3.07, 4.61}, respectively at a remote radial extension ratio of 2.35.
Effects of electric current on individual graphene oxide sheets combining in situ transmission electron microscopy and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Martín, Gemma; Varea, Aïda; Cirera, Albert; Estradé, Sònia; Peiró, Francesca; Cornet, Albert

2018-07-01

Graphene oxide (GO) is currently the object of extensive research because of its potential use in mass production of graphene-based materials, but also due to its tunability which holds great promise for new nanoscale electronic devices and sensors. To obtain a better understanding of the role of GO in electronic nano-devices, the elucidation of the effects of electrical current on a single GO sheet is of great interest. In this work, in situ transmission electron microscopy is used to study the effects of the electrical current flow through single GO sheets using an scanning tunneling microscope holder. In order to correlate the applied current with the structural properties of GO, Raman spectroscopy is carried out and data analysis is used to obtain information regarding the reduction grade and the disorder degree of the GO sheets before and after the application of current.
Effects of electric current on individual graphene oxide sheets combining in situ transmission electron microscopy and Raman spectroscopy.

PubMed

Martín, Gemma; Varea, Aïda; Cirera, Albert; Estradé, Sònia; Peiró, Francesca; Cornet, Albert

2018-04-17

Graphene oxide (GO) is currently the object of extensive research because of its potential use in mass production of graphene-based materials, but also due to its tunability which holds great promise for new nanoscale electronic devices and sensors. To obtain a better understanding of the role of GO in electronic nano-devices, the elucidation of the effects of electrical current on a single GO sheet is of great interest. In this work, in situ transmission electron microscopy is used to study the effects of the electrical current flow through single GO sheets using an scanning tunneling microscope holder. In order to correlate the applied current with the structural properties of GO, Raman spectroscopy is carried out and data analysis is used to obtain information regarding the reduction grade and the disorder degree of the GO sheets before and after the application of current.

Effects of flow sheet implementation on physician performance in the management of asthmatic patients.

PubMed

Ruoff, Gary

2002-01-01

This project focused on increasing compliance, in a large family practice group, with quality indicators for the management of asthma. The objective was to determine if use of a flow sheet incorporating the Global Initiative for Asthma (GINA) guidelines could improve compliance with those guidelines if the flow sheet was placed in patients' medical records. After review and selection of 14 clinical quality indicators, physicians in the practice implemented a flow sheet as an intervention. These flow sheets were inserted into the records of 122 randomly selected patients with asthma. Medical records were reviewed before the flow sheets were placed in the records, and again approximately 6 months later, to determine if there was a change in compliance with the quality indicators. Improvement of documentation was demonstrated in 13 of the 14 quality indicators. The results indicate that compliance with asthma management quality indicators can improve with the use of a flow sheet.
Ice sheet altimetry

NASA Technical Reports Server (NTRS)

Brooks, R. L.

1981-01-01

Generalized surface slopes were computed for the Antarctic and Greenland ice sheets by differencing plotted contour levels and dividing them by the distance between the contours. It was observed that more than 90% of the ice sheets have surface slopes less than 1%. Seasat test mode-1 Seasat altimeter measurements over Greenland were analyzed by comparisons with collinear and intersecting normal mode Seasat altimeter passes. Over the ice sheet, the computed surface elevations from test mode-1 measurements were consistently lower by about 45 m and the AGC levels were down by approximately 6 dB. No test mode-1 data were acquired over Antarctica. It is concluded that analysis of the existing altimeter data base over the two ice sheets is crucial in designing a future improved altimeter tracking capability. It is recommended that additional waveform retracking be performed to characterize ice sheet topography as a function of geographic area and elevation.
Microphase Separation Controlled Beta Sheet Crystallization Kinetics in Silk Fibroin Protein.

NASA Astrophysics Data System (ADS)

Hu, Xiao; Lu, Qiang; Kaplan, David; Cebe, Peggy

2009-03-01

We investigate the mechanism of isothermal crystallization kinetics of beta-sheet crystals in silk multiblock fibrous proteins. The Avrami analysis kinetic theory, for studies of synthetic polymer crystal growth, is for the first time extended to investigate protein self-assembly in beta-sheet rich Bombyx mori silk fibroin samples, using time-resolved Fourier transform infrared spectroscopy, differential scanning calorimetry and synchrotron real-time wide-angle X-ray scattering. Results indicate formation of beta sheet crystals in silk proteins is different from the 3-D spherulitic crystal growth found in synthetic homopolymers. Observations by scanning electron microscopy support the view that the protein structures vary during the different stages of crystal growth, and show a microphase separation pattern after chymotrypsin enzyme biodegradation. We present a model to explain the crystallization of the multiblock silk fibroin protein, by analogy to synthetic block copolymers. This model could be widely applicable in other proteins with multiblock (i.e., crystallizable and non-crystallizable) domains.
Pre-vascularization Enhances Therapeutic Effects of Human Mesenchymal Stem Cell Sheets in Full Thickness Skin Wound Repair.

PubMed

Chen, Lei; Xing, Qi; Zhai, Qiyi; Tahtinen, Mitchell; Zhou, Fei; Chen, Lili; Xu, Yingbin; Qi, Shaohai; Zhao, Feng

2017-01-01

Split thickness skin graft (STSG) implantation is one of the standard therapies for full thickness wound repair when full thickness autologous skin grafts (FTG) or skin flap transplants are inapplicable. Combined transplantation of STSG with dermal substitute could enhance its therapeutic effects but the results remain unsatisfactory due to insufficient blood supply at early stages, which causes graft necrosis and fibrosis. Human mesenchymal stem cell (hMSC) sheets are capable of accelerating the wound healing process. We hypothesized that pre-vascularized hMSC sheets would further improve regeneration by providing more versatile angiogenic factors and pre-formed microvessels. In this work, in vitro cultured hMSC cell sheets (HCS) and pre-vascularized hMSC cell sheets (PHCS) were implanted in a rat full thickness skin wound model covered with an autologous STSG. Results demonstrated that the HCS and the PHCS implantations significantly reduced skin contraction and improved cosmetic appearance relative to the STSG control group. The PHCS group experienced the least hemorrhage and necrosis, and lowest inflammatory cell infiltration. It also induced the highest neovascularization in early stages, which established a robust blood micro-circulation to support grafts survival and tissue regeneration. Moreover, the PHCS grafts preserved the largest amount of skin appendages, including hair follicles and sebaceous glands, and developed the smallest epidermal thickness. The superior therapeutic effects seen in PHCS groups were attributed to the elevated presence of growth factors and cytokines in the pre-vascularized cell sheet, which exerted a beneficial paracrine signaling during wound repair. Hence, the strategy of combining STSG with PHCS implantation appears to be a promising approach in regenerative treatment of full thickness skin wounds.
Alumna World, Inc. d/b/a Home Pro Information Sheet

EPA Pesticide Factsheets

Alumna World, Inc. d/b/a Home Pro (the Company) is located in Joplin, Missouri. The settlement involves renovation activities conducted at residential properties constructed prior to 1978, located in Carthage and Joplin, Missouri.
5. Historic American Buildings Survey Taken from drawing sheet, SHEET ...

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

5. Historic American Buildings Survey Taken from drawing sheet, SHEET #21, Showing the house as restored since Survey. (Dormer windows omitted as not authentic) - Samuel des Marest House, River Road, New Milford, Bergen County, NJ
Effect of Microstructure on Diffusional Solidification of 4343/3005/4343 Multi-Layer Aluminum Brazing Sheet

NASA Astrophysics Data System (ADS)

Tu, Yiyou; Tong, Zhen; Jiang, Jianqing

2013-04-01

The effect of microstructure on clad/core interactions during the brazing of 4343/3005/4343 multi-layer aluminum brazing sheet was investigated employing differential scanning calorimetry (DSC) and electron back-scattering diffraction (EBSD). The thickness of the melted clad layer gradually decreased during the brazing operation. It could be completely removed isothermally as a result of diffusional solidification at the brazing temperature. During the brazing cycle, the rate of loss of the melt in the brazing sheet, with small equiaxed grains' core layer, was higher than that with the core layer consisting of elongated large grains. The difference in microstructure affected the amount of liquid formed during brazing.
Psychosocial factors and theory in physical activity studies in minorities.

PubMed

Mama, Scherezade K; McNeill, Lorna H; McCurdy, Sheryl A; Evans, Alexandra E; Diamond, Pamela M; Adamus-Leach, Heather J; Lee, Rebecca E

2015-01-01

To summarize the effectiveness of interventions targeting psychosocial factors to increase physical activity (PA) among ethnic minority adults and explore theory use in PA interventions. Studies (N = 11) were identified through a systematic review and targeted African American/Hispanic adults, specific psychosocial factors, and PA. Data were extracted using a standard code sheet and the Theory Coding Scheme. Social support was the most common psychosocial factor reported, followed by motivational readiness, and self-efficacy, as being associated with increased PA. Only 7 studies explicitly reported using a theoretical framework. Future efforts should explore theory use in PA interventions and how integration of theoretical constructs, including psychosocial factors, increases PA.
Blanking and piercing theory, applications and recent experimental results

NASA Astrophysics Data System (ADS)

Zaid, Adnan l. O.

2014-06-01

Blanking and piercing are manufacturing processes by which certain geometrical shapes are sheared off a sheet metal. If the sheared off part is the one required, the processes referred to as blanking and if the remaining part in the sheet is the one required, the process is referred to as piercing. In this paper, the theory and practice of these processes are reviewed and discussed The main parameters affecting these processes are presented and discussed. These include: the radial clearance percentage, punch and die geometrical parameters, for example punch and die profile radii. The abovementioned parameters on the force and energy required to effect blanking together with their effect on the quality of the products are also presented and discussed. Recent experimental results together with photomacrographs and photomicrographs are also included and discussed. Finally, the effect of punch and die wear on the quality of the blanks is alsogiven and discussed.
Fuels planning: science synthesis and integration; environmental consequences fact sheet 05: prescriptions and fire effects

Treesearch

Melanie Miller

2004-01-01

Fuels planning: science synthesis and integration; environmental consequences fact sheet 5: prescriptions and fire effects. Miller, Melanie. 2004. Res. Note RMRS-RN-23-5-WWW. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 2 p. While our understanding of the causes for variation in postfire effects is increasing, burn...
Effects of Learning Style and Training Method on Computer Attitude and Performance in World Wide Web Page Design Training.

ERIC Educational Resources Information Center

Chou, Huey-Wen; Wang, Yu-Fang

1999-01-01

Compares the effects of two training methods on computer attitude and performance in a World Wide Web page design program in a field experiment with high school students in Taiwan. Discusses individual differences, Kolb's Experiential Learning Theory and Learning Style Inventory, Computer Attitude Scale, and results of statistical analyses.…
Snow and ice in a changing hydrological world.

USGS Publications Warehouse

Meier, M.F.

1983-01-01

Snow cover on land (especially in the Northern Hemisphere) and sea ice (especially in the Southern Hemisphere) vary seasonally, and this seasonal change has an important affect on the world climate because snow and sea ice reflect solar radiation efficiently and affect other heat flow processes between atmosphere and land or ocean. Glaciers, including ice sheets, store most of the fresh water on Earth, but change dimensions relatively slowly. There is no clear evidence that the glacier ice volume currently is declining, but more needs to be known about mountain glacier and ice sheet mass balances. -from Author
Effects of rotation on the nighttime brightness of overhead highway signs utilizing high intensity sheeting.

DOT National Transportation Integrated Search

1974-01-01

As an initial step in the establishment of guidelines for the use of high intensity sheeting on overhead signs, a pilot study was made to investigate the effect of rotation on the average nighttime brightness of signs utilizing this material. Rotatio...
The Effect of Varying Ultrafast Pulse Laser Energies on the Electrical Properties of Reduced Graphene Oxide Sheets in Solution

NASA Astrophysics Data System (ADS)

Ibrahim, Khaled H.; Irannejad, Mehrdad; Wales, Benjamin; Sanderson, Joseph; Musselman, Kevin P.; Yavuz, Mustafa

2018-02-01

Laser treatment of graphene oxide solution among other techniques is a well-established technique for producing reduced graphene sheets. However, production of high-quality ultra-low sheet resistance reduced graphene oxide (rGO) sheets in solution has been a challenge due to their high degree of randomness, defect-rich medium, and lack of controlability. Recent studies lack an in-depth analytic comparison of laser treatment parameters that yield the highest quality rGO sheets with a low defect ratio. Hence, in this study, we implement a comprehensive comparison of laser treatment parameters and their effect on the yielded rGO sheets from an electronic and physical standpoint. Ultra-low sheet resistance graphene oxide sheets were fabricated using ultrafast laser irradiation with different laser pulse energies in the range of 0.25-2 mJ. Laser treatment for 10 min using a pulse energy of 1 mJ resulted in an increase in the defect spacing, accompanied by a large red shift in the optical absorption of the C=C bond, indicating significant restoration of the s p 2 carbon bonds. These enhancements resulted in a significant reduction in the electrical resistance of the rGO flakes (up to 2 orders of magnitude), raising the electron mobility of the films produced using the irradiated graphene oxide a step closer to that of pristine graphene films. From this study, we can also deduce which exposure regimes result in the fabrication of quantum dots and continuous defect-free films.
Faculty Forum: Applying Motivation Theory to Real-World Problems

ERIC Educational Resources Information Center

Harpine, Elaine Clanton

2007-01-01

This article examines the effectiveness of incorporating an applied learning experience in an upper level undergraduate motivation theory class. In this 3-part course requirement, students (a) participated in a 2-hr field experience, (b) completed a homework assignment based on their participation, and (c) worked in groups to develop a deeper…
Analysis of Vibrational Harmonic Response for Printing Double-Sheet Detecting System via ANSYS

NASA Astrophysics Data System (ADS)

Guo, Qiang; Cai, Ji-Fei; Wang, Yan; Zhang, Yang

In order to explore the influence of the harmonic response of system vibration upon the stability of the double-sheet detector system, the mathematical model of vibrational system is established via the mechanical dynamic theory. Vibrational system of double-sheet detector is studied by theoretical modeling, and the dynamic simulation to obtain the amplitude/phase frequency response curve of the system based on ANSYS is completed to make a comparison with the theoretical results. It is shown that the theoretical value is basically consistent with that calculated through ANSYS. Conclusion vibrational characteristics of double-sheet detection system is obtained quickly and accurately, and propound solving measures by some crucial factors, such as the harmonic load, mass and stiffness, which will affect the vibration of the system, contribute to the finite element method is applied to the complex multiple-degree-of-freedom system.
Unifying Theories of Psychedelic Drug Effects

PubMed Central

Swanson, Link R.

2018-01-01

How do psychedelic drugs produce their characteristic range of acute effects in perception, emotion, cognition, and sense of self? How do these effects relate to the clinical efficacy of psychedelic-assisted therapies? Efforts to understand psychedelic phenomena date back more than a century in Western science. In this article I review theories of psychedelic drug effects and highlight key concepts which have endured over the last 125 years of psychedelic science. First, I describe the subjective phenomenology of acute psychedelic effects using the best available data. Next, I review late 19th-century and early 20th-century theories—model psychoses theory, filtration theory, and psychoanalytic theory—and highlight their shared features. I then briefly review recent findings on the neuropharmacology and neurophysiology of psychedelic drugs in humans. Finally, I describe recent theories of psychedelic drug effects which leverage 21st-century cognitive neuroscience frameworks—entropic brain theory, integrated information theory, and predictive processing—and point out key shared features that link back to earlier theories. I identify an abstract principle which cuts across many theories past and present: psychedelic drugs perturb universal brain processes that normally serve to constrain neural systems central to perception, emotion, cognition, and sense of self. I conclude that making an explicit effort to investigate the principles and mechanisms of psychedelic drug effects is a uniquely powerful way to iteratively develop and test unifying theories of brain function. PMID:29568270
Effects of bamboo charcoal on fouling and microbial diversity in a flat-sheet ceramic membrane bioreactor.

PubMed

Zhang, Wenjie; Liu, Xiaoning; Wang, Dunqiu; Jin, Yue

2017-11-01

Membrane fouling is a problem in full-scale membrane bioreactors. In this study, bamboo charcoal (BC) was evaluated for its efficacy in alleviating membrane fouling in flat-sheet membrane bioreactors treating municipal wastewater. The results showed that BC addition markedly improved treatment performance based on COD, NH 4 + -N, total nitrogen, and total phosphorus levels. Adding BC slowed the increase in the trans-membrane pressure rate and resulted in lower levels of soluble microbial products and extracellular polymeric substances detected in the flat-sheet membrane bioreactor. BC has a porous structure, and a large quantity of biomass was detected using scanning electron microscopy. The microbial community analysis results indicated that BC increased the microbial diversity and Aminomonas, Anaerofustis, uncultured Anaerolineaceae, Anaerolinea, and Anaerotruncus were found in higher abundances in the reactor with BC. BC addition is an effective method for reducing membrane fouling, and can be applied to full-scale flat-sheet membrane bioreactors to improve their function. Copyright © 2017 Elsevier Ltd. All rights reserved.
Effects of homogenization treatment on recrystallization behavior of 7150 aluminum sheet during post-rolling annealing

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

Guo, Zhanying; Department of Applied Science, University of Québec at Chicoutimi, Saguenay, QC G7H 2B1; Zhao, Gang

2016-04-15

The effects of two homogenization treatments applied to the direct chill (DC) cast billet on the recrystallization behavior in 7150 aluminum alloy during post-rolling annealing have been investigated using the electron backscatter diffraction (EBSD) technique. Following hot and cold rolling to the sheet, measured orientation maps, the recrystallization fraction and grain size, the misorientation angle and the subgrain size were used to characterize the recovery and recrystallization processes at different annealing temperatures. The results were compared between the conventional one-step homogenization and the new two-step homogenization, with the first step being pretreated at 250 °C. Al{sub 3}Zr dispersoids with highermore » densities and smaller sizes were obtained after the two-step homogenization, which strongly retarded subgrain/grain boundary mobility and inhibited recrystallization. Compared with the conventional one-step homogenized samples, a significantly lower recrystallized fraction and a smaller recrystallized grain size were obtained under all annealing conditions after cold rolling in the two-step homogenized samples. - Highlights: • Effects of two homogenization treatments on recrystallization in 7150 Al sheets • Quantitative study on the recrystallization evolution during post-rolling annealing • Al{sub 3}Zr dispersoids with higher densities and smaller sizes after two-step treatment • Higher recrystallization resistance of 7150 sheets with two-step homogenization.« less
Fluid Dynamic and Stability Analysis of a Thin Liquid Sheet

NASA Technical Reports Server (NTRS)

McMaster, Matthew S.

1992-01-01

Interest in thin sheet flows has recently been renewed due to their potential application in space radiators. Theoretical and experimental studies of the fluid dynamics and stability of thin liquid sheet flows have been carried out in this thesis. A computer program was developed to determine the cross-sectional shape of the edge cylinder given the cross-sectional area of the edge cylinder. A stability analysis was performed on a non-planer liquid sheet. A study was conducted to determine the effects of air resistance on the sheet.

Marginal Stability of Sweet–Parker Type Current Sheets at Low Lundquist Numbers

NASA Astrophysics Data System (ADS)

Shi, Chen; Velli, Marco; Tenerani, Anna

2018-06-01

Magnetohydrodynamic simulations have shown that a nonunique critical Lundquist number S c exists, hovering around S c ∼ 104, above which threshold Sweet–Parker type stationary reconnecting configurations become unstable to a fast tearing mode dominated by plasmoid generation. It is known that the flow along the sheet plays a stabilizing role, though a satisfactory explanation of the nonuniversality and variable critical Lundquist numbers observed is still lacking. Here we discuss this question using 2D linear MHD simulations and linear stability analyses of Sweet–Parker type current sheets in the presence of background stationary inflows and outflows at low Lundquist numbers (S ≤ 104). Simulations show that the inhomogeneous outflow stabilizes the current sheet by stretching the growing magnetic islands and at the same time evacuating the magnetic islands out of the current sheet. This limits the time during which fluctuations that begin at any given wavelength can remain unstable, rendering the instability nonexponential. We find that the linear theory based on the expanding-wavelength assumption works well for S larger than ∼1000. However, we also find that the inflow and location of the initial perturbation also affect the stability threshold.
Transporter for Treated Sheet Materials

NASA Technical Reports Server (NTRS)

Pollack, M., H.

1983-01-01

Plastic spacers keep parts separated during transport or storage. Cart with rods and spacers holds sheets with delicate finishes for storage or transport. Sheets supported vertically by rods, or horizontally. Spacers keep sheets separated. Designed to eliminate time and expense of tapping, wrapping, and sometimes refinishing aluminum sheets with delicate anodized finished.
Perforating Thin Metal Sheets

NASA Technical Reports Server (NTRS)

Davidson, M. E.

1985-01-01

Sheets only few mils thick bonded together, punched, then debonded. Three-step process yields perforated sheets of metal. (1): Individual sheets bonded together to form laminate. (2): laminate perforated in desired geometric pattern. (3): After baking, laminate separates into individual sheets. Developed for fabricating conductive layer on blankets that collect and remove ions; however, perforated foils have other applications - as conductive surfaces on insulating materials; stiffeners and conductors in plastic laminates; reflectors in antenna dishes; supports for thermal blankets; lightweight grille cover materials; and material for mockup of components.
Vocational Education and Training: A Major Shift in World Bank Policy.

ERIC Educational Resources Information Center

Foster, Phillip

1992-01-01

Comments on the World Bank's policy paper on vocational and technical education and training. Argues that past failures in establishing effective vocational and technical education were a result of not applying conventional neoclassical economic theory. Asserts that the World Bank's policy paper corrects this approach. (CFR)
The use of cell-sheet technique eliminates arrhythmogenicity of skeletal myoblast-based therapy to the heart with enhanced therapeutic effects.

PubMed

Narita, Takuya; Shintani, Yasunori; Ikebe, Chiho; Kaneko, Masahiro; Harada, Narumi; Tshuma, Nomathamsanqa; Takahashi, Kunihiko; Campbell, Niall G; Coppen, Steven R; Yashiro, Kenta; Sawa, Yoshiki; Suzuki, Ken

2013-09-20

Clinical application of skeletal myoblast transplantation has been curtailed due to arrhythmogenicity and inconsistent therapeutic benefits observed in previous studies. However, these issues may be solved by the use of a new cell-delivery mode. It is now possible to generate "cell-sheets" using temperature-responsive dishes without artificial scaffolds. This study aimed to validate the safety and efficacy of epicardial placement of myoblast-sheets (myoblast-sheet therapy) in treating heart failure. After coronary artery ligation in rats, the same numbers of syngeneic myoblasts were transplanted by intramyocardial injection or cell-sheet placement. Continuous radio-telemetry monitoring detected increased ventricular arrhythmias, including ventricular tachycardia, after intramyocardial injection compared to the sham-control, while these were abolished in myoblast-sheet therapy. This effect was conjunct with avoidance of islet-like cell-cluster formation that disrupts electrical conduction, and with prevention of increased arrhythmogenic substrates due to exaggerated inflammation. Persistent ectopic donor cells were found in the lung only after intramyocardial injection, strengthening the improved safety of myoblast-sheet therapy. In addition, myoblast-sheet therapy enhanced cardiac function, corresponding to a 9.2-fold increase in donor cell survival, compared to intramyocardial injection. Both methods achieved reduced infarct size, decreased fibrosis, attenuated cardiomyocyte hypertrophy, and increased neovascular formation, in association with myocardial upregulation of a group of relevant molecules. The pattern of these beneficial changes was similar between two methods, but the degree was more substantial after myoblast-sheet therapy. The cell-sheet technique enhanced safety and therapeutic efficacy of myoblast-based therapy, compared to the current method, thereby paving the way for clinical application. Copyright © 2012 Elsevier Ireland Ltd. All rights
Organizational Strategies to Increase Content Area Learning: Webbing, Pyramiding, and Think Sheets.

ERIC Educational Resources Information Center

Clewell, Suzanne; Haidemenos, Julie

A review of schema theory and memory research shows how the organization of text can affect comprehension and how three reading strategies can aid in improving student understanding of content area materials. The three strategies that help students remember information from the author's point of view are webbing, pyramiding, and think sheets. They…
Ice-sheet contributions to future sea-level change.

PubMed

Gregory, J M; Huybrechts, P

2006-07-15

Accurate simulation of ice-sheet surface mass balance requires higher spatial resolution than is afforded by typical atmosphere-ocean general circulation models (AOGCMs), owing, in particular, to the need to resolve the narrow and steep margins where the majority of precipitation and ablation occurs. We have developed a method for calculating mass-balance changes by combining ice-sheet average time-series from AOGCM projections for future centuries, both with information from high-resolution climate models run for short periods and with a 20km ice-sheet mass-balance model. Antarctica contributes negatively to sea level on account of increased accumulation, while Greenland contributes positively because ablation increases more rapidly. The uncertainty in the results is about 20% for Antarctica and 35% for Greenland. Changes in ice-sheet topography and dynamics are not included, but we discuss their possible effects. For an annual- and area-average warming exceeding 4.5+/-0.9K in Greenland and 3.1+/-0.8K in the global average, the net surface mass balance of the Greenland ice sheet becomes negative, in which case it is likely that the ice sheet would eventually be eliminated, raising global-average sea level by 7m.
An ice sheet model validation framework for the Greenland ice sheet

NASA Astrophysics Data System (ADS)

Price, Stephen F.; Hoffman, Matthew J.; Bonin, Jennifer A.; Howat, Ian M.; Neumann, Thomas; Saba, Jack; Tezaur, Irina; Guerber, Jeffrey; Chambers, Don P.; Evans, Katherine J.; Kennedy, Joseph H.; Lenaerts, Jan; Lipscomb, William H.; Perego, Mauro; Salinger, Andrew G.; Tuminaro, Raymond S.; van den Broeke, Michiel R.; Nowicki, Sophie M. J.

2017-01-01

We propose a new ice sheet model validation framework - the Cryospheric Model Comparison Tool (CmCt) - that takes advantage of ice sheet altimetry and gravimetry observations collected over the past several decades and is applied here to modeling of the Greenland ice sheet. We use realistic simulations performed with the Community Ice Sheet Model (CISM) along with two idealized, non-dynamic models to demonstrate the framework and its use. Dynamic simulations with CISM are forced from 1991 to 2013, using combinations of reanalysis-based surface mass balance and observations of outlet glacier flux change. We propose and demonstrate qualitative and quantitative metrics for use in evaluating the different model simulations against the observations. We find that the altimetry observations used here are largely ambiguous in terms of their ability to distinguish one simulation from another. Based on basin-scale and whole-ice-sheet-scale metrics, we find that simulations using both idealized conceptual models and dynamic, numerical models provide an equally reasonable representation of the ice sheet surface (mean elevation differences of < 1 m). This is likely due to their short period of record, biases inherent to digital elevation models used for model initial conditions, and biases resulting from firn dynamics, which are not explicitly accounted for in the models or observations. On the other hand, we find that the gravimetry observations used here are able to unambiguously distinguish between simulations of varying complexity, and along with the CmCt, can provide a quantitative score for assessing a particular model and/or simulation. The new framework demonstrates that our proposed metrics can distinguish relatively better from relatively worse simulations and that dynamic ice sheet models, when appropriately initialized and forced with the right boundary conditions, demonstrate a predictive skill with respect to observed dynamic changes that have occurred on
An ice sheet model validation framework for the Greenland ice sheet

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

Price, Stephen F.; Hoffman, Matthew J.; Bonin, Jennifer A.

We propose a new ice sheet model validation framework the Cryospheric Model Comparison Tool (CMCT) that takes advantage of ice sheet altimetry and gravimetry observations collected over the past several decades and is applied here to modeling of the Greenland ice sheet. We use realistic simulations performed with the Community Ice Sheet Model (CISM) along with two idealized, non-dynamic models to demonstrate the framework and its use. Dynamic simulations with CISM are forced from 1991 to 2013 using combinations of reanalysis-based surface mass balance and observations of outlet glacier flux change. We propose and demonstrate qualitative and quanti- tative metricsmore » for use in evaluating the different model simulations against the observations. We find 10 that the altimetry observations used here are largely ambiguous in terms of their ability to distinguish one simulation from another. Based on basin- and whole-ice-sheet scale metrics, the model initial condition as well as output from idealized and dynamic models all provide an equally reasonable representation of the ice sheet surface (mean elevation differences of <1 m). This is likely due to their short period of record, biases inherent to digital elevation models used for model initial conditions, and biases resulting from firn dynamics, which are not explicitly accounted for in the models or observations. On the other hand, we find that the gravimetry observations used here are able to unambiguously distinguish between simulations of varying complexity, and along with the CMCT, can provide a quantitative score for assessing a particular model and/or simulation. The new framework demonstrates that our proposed metrics can distinguish relatively better from relatively worse simulations and that dynamic ice sheet models, when appropriately initialized and forced with the right boundary conditions, demonstrate predictive skill with respect to observed dynamic changes occurring on Greenland over the past few
An ice sheet model validation framework for the Greenland ice sheet

PubMed Central

Price, Stephen F.; Hoffman, Matthew J.; Bonin, Jennifer A.; Howat, Ian M.; Neumann, Thomas; Saba, Jack; Tezaur, Irina; Guerber, Jeffrey; Chambers, Don P.; Evans, Katherine J.; Kennedy, Joseph H.; Lenaerts, Jan; Lipscomb, William H.; Perego, Mauro; Salinger, Andrew G.; Tuminaro, Raymond S.; van den Broeke, Michiel R.; Nowicki, Sophie M. J.

2018-01-01

We propose a new ice sheet model validation framework – the Cryospheric Model Comparison Tool (CmCt) – that takes advantage of ice sheet altimetry and gravimetry observations collected over the past several decades and is applied here to modeling of the Greenland ice sheet. We use realistic simulations performed with the Community Ice Sheet Model (CISM) along with two idealized, non-dynamic models to demonstrate the framework and its use. Dynamic simulations with CISM are forced from 1991 to 2013 using combinations of reanalysis-based surface mass balance and observations of outlet glacier flux change. We propose and demonstrate qualitative and quantitative metrics for use in evaluating the different model simulations against the observations. We find that the altimetry observations used here are largely ambiguous in terms of their ability to distinguish one simulation from another. Based on basin- and whole-ice-sheet scale metrics, we find that simulations using both idealized conceptual models and dynamic, numerical models provide an equally reasonable representation of the ice sheet surface (mean elevation differences of <1 m). This is likely due to their short period of record, biases inherent to digital elevation models used for model initial conditions, and biases resulting from firn dynamics, which are not explicitly accounted for in the models or observations. On the other hand, we find that the gravimetry observations used here are able to unambiguously distinguish between simulations of varying complexity, and along with the CmCt, can provide a quantitative score for assessing a particular model and/or simulation. The new framework demonstrates that our proposed metrics can distinguish relatively better from relatively worse simulations and that dynamic ice sheet models, when appropriately initialized and forced with the right boundary conditions, demonstrate predictive skill with respect to observed dynamic changes occurring on Greenland over the
An ice sheet model validation framework for the Greenland ice sheet.

PubMed

Price, Stephen F; Hoffman, Matthew J; Bonin, Jennifer A; Howat, Ian M; Neumann, Thomas; Saba, Jack; Tezaur, Irina; Guerber, Jeffrey; Chambers, Don P; Evans, Katherine J; Kennedy, Joseph H; Lenaerts, Jan; Lipscomb, William H; Perego, Mauro; Salinger, Andrew G; Tuminaro, Raymond S; van den Broeke, Michiel R; Nowicki, Sophie M J

2017-01-01

We propose a new ice sheet model validation framework - the Cryospheric Model Comparison Tool (CmCt) - that takes advantage of ice sheet altimetry and gravimetry observations collected over the past several decades and is applied here to modeling of the Greenland ice sheet. We use realistic simulations performed with the Community Ice Sheet Model (CISM) along with two idealized, non-dynamic models to demonstrate the framework and its use. Dynamic simulations with CISM are forced from 1991 to 2013 using combinations of reanalysis-based surface mass balance and observations of outlet glacier flux change. We propose and demonstrate qualitative and quantitative metrics for use in evaluating the different model simulations against the observations. We find that the altimetry observations used here are largely ambiguous in terms of their ability to distinguish one simulation from another. Based on basin- and whole-ice-sheet scale metrics, we find that simulations using both idealized conceptual models and dynamic, numerical models provide an equally reasonable representation of the ice sheet surface (mean elevation differences of <1 m). This is likely due to their short period of record, biases inherent to digital elevation models used for model initial conditions, and biases resulting from firn dynamics, which are not explicitly accounted for in the models or observations. On the other hand, we find that the gravimetry observations used here are able to unambiguously distinguish between simulations of varying complexity, and along with the CmCt, can provide a quantitative score for assessing a particular model and/or simulation. The new framework demonstrates that our proposed metrics can distinguish relatively better from relatively worse simulations and that dynamic ice sheet models, when appropriately initialized and forced with the right boundary conditions, demonstrate predictive skill with respect to observed dynamic changes occurring on Greenland over the past
An ice sheet model validation framework for the Greenland ice sheet

DOE PAGES

Price, Stephen F.; Hoffman, Matthew J.; Bonin, Jennifer A.; ...

2017-01-17

We propose a new ice sheet model validation framework the Cryospheric Model Comparison Tool (CMCT) that takes advantage of ice sheet altimetry and gravimetry observations collected over the past several decades and is applied here to modeling of the Greenland ice sheet. We use realistic simulations performed with the Community Ice Sheet Model (CISM) along with two idealized, non-dynamic models to demonstrate the framework and its use. Dynamic simulations with CISM are forced from 1991 to 2013 using combinations of reanalysis-based surface mass balance and observations of outlet glacier flux change. We propose and demonstrate qualitative and quanti- tative metricsmore » for use in evaluating the different model simulations against the observations. We find 10 that the altimetry observations used here are largely ambiguous in terms of their ability to distinguish one simulation from another. Based on basin- and whole-ice-sheet scale metrics, the model initial condition as well as output from idealized and dynamic models all provide an equally reasonable representation of the ice sheet surface (mean elevation differences of <1 m). This is likely due to their short period of record, biases inherent to digital elevation models used for model initial conditions, and biases resulting from firn dynamics, which are not explicitly accounted for in the models or observations. On the other hand, we find that the gravimetry observations used here are able to unambiguously distinguish between simulations of varying complexity, and along with the CMCT, can provide a quantitative score for assessing a particular model and/or simulation. The new framework demonstrates that our proposed metrics can distinguish relatively better from relatively worse simulations and that dynamic ice sheet models, when appropriately initialized and forced with the right boundary conditions, demonstrate predictive skill with respect to observed dynamic changes occurring on Greenland over the past few
An Ice Sheet Model Validation Framework for the Greenland Ice Sheet

NASA Technical Reports Server (NTRS)

Price, Stephen F.; Hoffman, Matthew J.; Bonin, Jennifer A.; Howat, Ian M.; Neumann, Thomas A.; Saba, Jack; Tezaur, Irina; Guerber, Jeffrey R.; Chambers, Don P.; Evans, Katherine J.;

2017-01-01

We propose a new ice sheet model validation framework - the Cryospheric Model Comparison Tool (CmCt) - that takes advantage of ice sheet altimetry and gravimetry observations collected over the past several decades and is applied here to modeling of the Greenland ice sheet. We use realistic simulations performed with the Community Ice Sheet Model (CISM) along with two idealized, non-dynamic models to demonstrate the framework and its use. Dynamic simulations with CISM are forced from 1991 to 2013, using combinations of reanalysis-based surface mass balance and observations of outlet glacier flux change. We propose and demonstrate qualitative and quantitative metrics for use in evaluating the different model simulations against the observations. We find that the altimetry observations used here are largely ambiguous in terms of their ability to distinguish one simulation from another. Based on basin-scale and whole-ice-sheet-scale metrics, we find that simulations using both idealized conceptual models and dynamic, numerical models provide an equally reasonable representation of the ice sheet surface (mean elevation differences of less than 1 meter). This is likely due to their short period of record, biases inherent to digital elevation models used for model initial conditions, and biases resulting from firn dynamics, which are not explicitly accounted for in the models or observations. On the other hand, we find that the gravimetry observations used here are able to unambiguously distinguish between simulations of varying complexity, and along with the CmCt, can provide a quantitative score for assessing a particular model and/or simulation. The new framework demonstrates that our proposed metrics can distinguish relatively better from relatively worse simulations and that dynamic ice sheet models, when appropriately initialized and forced with the right boundary conditions, demonstrate a predictive skill with respect to observed dynamic changes that have occurred

17. INTAKE PIER, BRIDGE STRESS SHEET, SHEET 8 OF 117, ...

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

17. INTAKE PIER, BRIDGE STRESS SHEET, SHEET 8 OF 117, 1920. - Sacramento River Water Treatment Plant Intake Pier & Access Bridge, Spanning Sacramento River approximately 175 feet west of eastern levee on river; roughly .5 mile downstream from confluence of Sacramento & American Rivers, Sacramento, Sacramento County, CA
The folding of acetyl(Ala)28NH2 and acetyl(Ala)40NH2 extended strand peptides into antiparallel β-sheets. A density functional theory study of β-sheets with β-turns.

PubMed

Ali-Torres, Jorge; Dannenberg, J J

2012-12-06

We report ONIOM calculations using B3LYP/D95** and AM1 on β-sheet formation from acetyl(Ala)(N)NH(2) (N = 28 or 40). The sheets contain from one to four β-turns for N = 28 and up to six for N = 40. We have obtained four types of geometrically optimized structures. All contain only β-turns. They differ from each other in the types of β-turns formed. The unsolvated sheets containing two turns are most stable. Aqueous solvation (using the SM5.2 and CPCM methods) reduces the stabilities of the folded structures compared to the extended strands.
Lateral dimension-dependent antibacterial activity of graphene oxide sheets.

PubMed

Liu, Shaobin; Hu, Ming; Zeng, Tingying Helen; Wu, Ran; Jiang, Rongrong; Wei, Jun; Wang, Liang; Kong, Jing; Chen, Yuan

2012-08-21

effectively isolate cells from environment. This study highlights the importance of tailoring the lateral dimension of GO sheets to optimize the application potential with minimal risks for environmental health and safety.
FDTD modeling of thin impedance sheets

NASA Technical Reports Server (NTRS)

Luebbers, Raymond; Kunz, Karl

1991-01-01

Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. It is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods. These sheets are characterized by a discontinuity in the tangential magnetic field on either side of the sheet but no discontinuity in tangential electric field. This continuity, or single valued behavior of the electric field, allows the sheet current to be expressed in terms of an impedance multiplying this electric field.
New directions in the science and technology of advanced sheet explosive formulations and the key energetic materials used in the processing of sheet explosives: Emerging trends.

PubMed

Talawar, M B; Jangid, S K; Nath, T; Sinha, R K; Asthana, S N

2015-12-30

This review presents the work carried out by the international community in the area of sheet explosive formulations and its applications in various systems. The sheet explosive is also named as PBXs and is a composite material in which solid explosive particles like RDX, HMX or PETN are dispersed in a polymeric matrix, forms a flexible material that can be rolled/cut into sheet form which can be applied to any complex contour. The designed sheet explosive must possess characteristic properties such as flexible, cuttable, water proof, easily initiable, and safe handling. The sheet explosives are being used for protecting tanks (ERA), light combat vehicle and futuristic infantry carrier vehicle from different attacking war heads etc. Besides, sheet explosives find wide applications in demolition of bridges, ships, cutting and metal cladding. This review also covers the aspects such as risks and hazard analysis during the processing of sheet explosive formulations, effect of ageing on sheet explosives, detection and analysis of sheet explosive ingredients and the R&D efforts of Indian researchers in the development of sheet explosive formulations. To the best of our knowledge, there has been no review article published in the literature in the area of sheet explosives. Copyright © 2015 Elsevier B.V. All rights reserved.
Effect of subglacial volcanism on changes in the West Antarctic Ice Sheet

NASA Technical Reports Server (NTRS)

Behrendt, John C.

1993-01-01

Rapid changes in the West Antarctic Ice Sheet (WAIS) may affect future global sea-level changes. Alley and Whillans note that 'the water responsible for separating the glacier from its bed is produced by frictional dissipation and geothermal heat,' but assume that changes in geothermal flux would ordinarily be expected to have slower effects than glaciological parameters. I suggest that episodic subglacial volcanism and geothermal heating may have significantly greater effects on the WAIS than is generally appreciated. The WAIS flows through the active, largely asiesmic West Antarctic rift system (WS), which defines the sub-sea-level bed of the glacier. Various lines of evidence summarized in Behrendt et al. (1991) indicate high heat flow and shallow asthenosphere beneath the extended, weak lithosphere underlying the WS and the WAIS. Behrendt and Cooper suggest a possible synergistic relation between Cenozoic tectonism, episodic mountain uplift and volcanism in the West Antarctic rift system, and the waxing and waning of the Antarctic ice sheet beginning about earliest Oligocene time. A few active volcanoes and late-Cenozoic volcanic rocks are exposed throughout the WS along both flanks, and geophysical data suggest their presence beneath the WAIS. No part of the rift system can be considered inactive. I propose that subglacial volcanic eruptions and ice flow across areas of locally (episodically?) high heat flow--including volcanically active areas--should be considered possibly to have a forcing effect on the thermal regime resulting in increased melting at the base of the ice streams.
Optimal Design of Sheet Pile Wall Embedded in Clay

NASA Astrophysics Data System (ADS)

Das, Manas Ranjan; Das, Sarat Kumar

2015-09-01

Sheet pile wall is a type of flexible earth retaining structure used in waterfront offshore structures, river protection work and temporary supports in foundations and excavations. Economy is an essential part of a good engineering design and needs to be considered explicitly in obtaining an optimum section. By considering appropriate embedment depth and sheet pile section it may be possible to achieve better economy. This paper describes optimum design of both cantilever and anchored sheet pile wall penetrating clay using a simple optimization tool Microsoft Excel ® Solver. The detail methodology and its application with examples are presented for cantilever and anchored sheet piles. The effects of soil properties, depth of penetration and variation of ground water table on the optimum design are also discussed. Such a study will help professional while designing the sheet pile wall penetrating clay.

The Efficacy of a Silicone Sheet in Postoperative Scar Management.

PubMed

Kim, Jin Sam; Hong, Joon Pio; Choi, Jong Woo; Seo, Dong Kyo; Lee, Eun Sook; Lee, Ho Seong

2016-09-01

Silicone gel sheeting has been introduced to prevent scarring, but objective evidence for its usefulness in scar healing is limited. Therefore, the authors' objective was to examine the effectiveness of silicone gel sheeting by randomly applying it to only unilateral scars from a bilateral hallux valgus surgery with symmetrical closure. In a prospective randomized, blinded, intraindividual comparison study, the silicone gel sheeting was applied to 1 foot of a hallux valgus incision scar (an experiment group) for 12 weeks upon removal of the stitches, whereas the symmetrical scar from the other foot was left untreated (a control group). The scars were evaluated at 4 and 12 weeks after the silicon sheet application. The Vancouver Scar Scale was used to measure the vascularity, pigmentation, pliability, height, and length of the scars. Adverse effects were also evaluated, and they included pain, itchiness, rash, erythema, and skin softening. At weeks 4 and 12, the experiment group scored significantly better on the Vancouver Scar Scale in all items, except length (P < .05 for all except the length of scar), compared with the control group. In all items, adverse effects of the experiment group were significantly lower than those of the control group at week 12, suggesting that direct attachment of the silicone sheet does not cause adverse effects (P < .05). To the authors' knowledge, this is one of the first models to minimize bias related to scar evaluation by using symmetrical scars. The early silicone sheet application did show a significant improvement in prevention of postoperative scarring.
Unified theory of effective interaction

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

Takayanagi, Kazuo, E-mail: k-takaya@sophia.ac.jp

2016-09-15

We present a unified description of effective interaction theories in both algebraic and graphic representations. In our previous work, we have presented the Rayleigh–Schrödinger and Bloch perturbation theories in a unified fashion by introducing the main frame expansion of the effective interaction. In this work, we start also from the main frame expansion, and present various nonperturbative theories in a coherent manner, which include generalizations of the Brandow, Brillouin–Wigner, and Bloch–Horowitz theories on the formal side, and the extended Krenciglowa–Kuo and the extended Lee–Suzuki methods on the practical side. We thus establish a coherent and comprehensive description of both perturbativemore » and nonperturbative theories on the basis of the main frame expansion.« less
Clouds enhance Greenland ice sheet mass loss

NASA Astrophysics Data System (ADS)

Van Tricht, Kristof; Gorodetskaya, Irina V.; L'Ecuyer, Tristan; Lenaerts, Jan T. M.; Lhermitte, Stef; Noel, Brice; Turner, David D.; van den Broeke, Michiel R.; van Lipzig, Nicole P. M.

2015-04-01

Clouds have a profound influence on both the Arctic and global climate, while they still represent one of the key uncertainties in climate models, limiting the fidelity of future climate projections. The potentially important role of thin liquid-containing clouds over Greenland in enhancing ice sheet melt has recently gained interest, yet current research is spatially and temporally limited, focusing on particular events, and their large scale impact on the surface mass balance remains unknown. We used a combination of satellite remote sensing (CloudSat - CALIPSO), ground-based observations and climate model (RACMO) data to show that liquid-containing clouds warm the Greenland ice sheet 94% of the time. High surface reflectivity (albedo) for shortwave radiation reduces the cloud shortwave cooling effect on the absorbed fluxes, while not influencing the absorption of longwave radiation. Cloud warming over the ice sheet therefore dominates year-round. Only when albedo values drop below ~0.6 in the coastal areas during summer, the cooling effect starts to overcome the warming effect. The year-round excess of energy due to the presence of liquid-containing clouds has an extensive influence on the mass balance of the ice sheet. Simulations using the SNOWPACK snow model showed not only a strong influence of these liquid-containing clouds on melt increase, but also on the increased sublimation mass loss. Simulations with the Community Earth System Climate Model for the end of the 21st century (2080-2099) show that Greenland clouds contain more liquid water path and less ice water path. This implies that cloud radiative forcing will be further enhanced in the future. Our results therefore urge the need for improving cloud microphysics in climate models, to improve future projections of ice sheet mass balance and global sea level rise.
The Reality of the Quantum World.

ERIC Educational Resources Information Center

Shimony, Abner

1988-01-01

Describes experiments used during recent history to explain the nature of the quantum world. Explains the essential elements of experiments using polarized light and magnetic flux. Illustrates differences between classical theories in physics and quantum theory. Shows how experiments in the microscopic and macroscopic world appear to support…
High-perveance W-band Sheet-beam Electron Gun Design

DTIC Science & Technology

2008-04-01

APR 2008 2. REPORT TYPE 3. DATES COVERED 00-00-2008 to 00-00-2008 4. TITLE AND SUBTITLE High -perveance W- band Sheet-beam Electron Gun Design 5a...8-98) Prescribed by ANSI Std Z39-18 10.1: High -perveance W- band Sheet-beam Electron Gun Design Khanh T. Nguyen1, John Pasour, Edward L. Wright1...effects due to cathode temperature are also included in the simulation. Keywords: Sheet beam; W- band ; electron gun; high perveance; amplifiers
Method for heating a glass sheet

DOEpatents

Boaz, Premakaran Tucker

1998-01-01

A method for heating a glass sheet includes the steps of heating a glass sheet to a first predetermined temperature and applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature to allow the glass sheet to be formed.
Clinching for sheet materials

PubMed Central

He, Xiaocong

2017-01-01

Abstract Latest developments in the clinching of sheet materials are reviewed in this article. Important issues are discussed, such as tool design, process parameters and joinability of some new lightweight sheet materials. Hybrid and modified clinching processes are introduced to a general reader. Several unaddressed issues in the clinching of sheet materials are identified. PMID:28656065
Liquid sheet radiator

NASA Technical Reports Server (NTRS)

Chubb, Donald L.; White, K. Alan, III

1987-01-01

A new external flow radiator concept, the liquid sheet radiator (LSR), is introduced. The LSR sheet flow is described and an expression for the length/width (l/w), ratio is presented. A linear dependence of l/w on velocity is predicted that agrees with experimental results. Specific power for the LSR is calculated and is found to be nearly the same as the specific power of a liquid droplet radiator, (LDR). Several sheet thicknesses and widths were experimentally investigated. In no case was the flow found to be unstable.
Method for heating a glass sheet

DOEpatents

Boaz, P.T.

1998-07-21

A method for heating a glass sheet includes the steps of heating a glass sheet to a first predetermined temperature and applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature to allow the glass sheet to be formed. 5 figs.
A world apart? Bridging the gap between theory and applied social gerontology.

PubMed

Hendricks, Jon; Applebaum, Robert; Kunkel, Suzanne

2010-06-01

This article is based on the premise that there is inadequate attention to the link between theory and applied research in social gerontology. The article contends that applied research studies do not often or effectively employ a theoretical framework and that theory-based articles, including theory-based research, are not often focused on questions related to applied social gerontology. We explore the extent to which theory and applied research could reasonably be expected to overlap, present data from an analysis of 5 years of articles in three leading journals, and posit some possible explanations for the current divide between theory and applied social gerontology research. We argue that the divide weakens research and inhibits the functions that theory can play in helping to organize the accumulation of knowledge, and we offer some suggestions about how the field can address this challenge, including changes to the journal review and submission process to reflect the importance of the link between theory and/or conceptual models and research, and an expansion of professional conference opportunities to link research and practice.
The Growth of Instabilities in Annular Liquid Sheets

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

Duke, Daniel J.; Honnery, Damon R; Soria, Julio

An annular liquid sheet surrounded by parallel co-flowing gas is an effective atomiser. However, the initial instabilities which determine the primary break-up of the liquid sheet are not well understood. Lack of agreement on the influence of the boundary conditions and the non-dimension scaling of the initial instability persists between theoretical stability analyses and experiments. To address this matter, we have undertaken an experimental parametric study of an aerodynamically-driven, non-swirling annular water sheet. The effects of sheet thickness, inner and outer gas-liquid momentum ratio were investigated over an order of magnitude variation in Reynolds and Weber number. From high-speed imagemore » correlation measurements in the near-nozzle region, we propose new empirical correlations for the frequency of the instability as a function of the total gas-liquid momentum ratio, with good non-dimensional collapse. From analysis of the instability velocity probability densities, we find two persistent and distinct superimposed instabilities with different growth rates. The first is a short-lived, rapidly saturating sawtooth-like instability. The second is a slower-growing stochastic instability which persists through the break-up of the sheet. The presence of multiple instabilities whose growth rates do not strongly correlate with the shear velocities may explain some of the discrepancies between experiments and stability analyses.« less
Psychosocial Factors and Theory in Physical Activity Studies in Minorities

PubMed Central

Mama, Scherezade K.; McNeill, Lorna H.; McCurdy, Sheryl A.; Evans, Alexandra E.; Diamond, Pamela M.; Adamus-Leach, Heather J.; Lee, Rebecca E.

2015-01-01

Objectives To summarize the effectiveness of interventions targeting psychosocial factors to increase physical activity (PA) among ethnic minority adults and explore theory use in PA interventions. Methods Studies (N = 11) were identified through a systematic review and targeted African American/Hispanic adults, specific psychosocial factors, and PA. Data were extracted using a standard code sheet and the Theory Coding Scheme. Results Social support was the most common psychosocial factor reported, followed by motivational readiness, and self-efficacy, as being associated with increased PA. Only 7 studies explicitly reported using a theoretical framework. Conclusions Future efforts should explore theory use in PA interventions and how integration of theoretical constructs, including psychosocial factors, increases PA. PMID:25290599
Dynamic of particle-laden liquid sheet

NASA Astrophysics Data System (ADS)

Sauret, Alban; Jop, Pierre; Troger, Anthony

2016-11-01

Many industrial processes, such as surface coating or liquid transport in tubes, involve liquid sheets or thin liquid films of suspensions. In these situations, the thickness of the liquid film becomes comparable to the particle size, which leads to unexpected dynamics. In addition, the classical constitutive rheological law cannot be applied as the continuum approximation is no longer valid. Here, we consider experimentally a transient free liquid sheet that expands radially. We characterize the influence of the particles on the shape of the liquid film as a function of time and the atomization process. We highlight that the presence of particles modifies the thickness and the stability of the liquid sheet. Our study suggests that the influence of particles through capillary effects can modify significantly the dynamics of processes that involve suspensions and particles confined in liquid films.
Brane-World Gravity.

PubMed

Maartens, Roy; Koyama, Kazuya

2010-01-01

The observable universe could be a 1+3-surface (the "brane") embedded in a 1+3+ d -dimensional spacetime (the "bulk"), with Standard Model particles and fields trapped on the brane while gravity is free to access the bulk. At least one of the d extra spatial dimensions could be very large relative to the Planck scale, which lowers the fundamental gravity scale, possibly even down to the electroweak (∼ TeV) level. This revolutionary picture arises in the framework of recent developments in M theory. The 1+10-dimensional M theory encompasses the known 1+9-dimensional superstring theories, and is widely considered to be a promising potential route to quantum gravity. At low energies, gravity is localized at the brane and general relativity is recovered, but at high energies gravity "leaks" into the bulk, behaving in a truly higher-dimensional way. This introduces significant changes to gravitational dynamics and perturbations, with interesting and potentially testable implications for high-energy astrophysics, black holes, and cosmology. Brane-world models offer a phenomenological way to test some of the novel predictions and corrections to general relativity that are implied by M theory. This review analyzes the geometry, dynamics and perturbations of simple brane-world models for cosmology and astrophysics, mainly focusing on warped 5-dimensional brane-worlds based on the Randall-Sundrum models. We also cover the simplest brane-world models in which 4-dimensional gravity on the brane is modified at low energies - the 5-dimensional Dvali-Gabadadze-Porrati models. Then we discuss co-dimension two branes in 6-dimensional models.
Effects of Changing Hot Rolling Direction on Microstructure, Texture and Mechanical Properties of Cu-2.7Be Sheets

NASA Astrophysics Data System (ADS)

Zhu, Daibo; Liu, Chuming; Yu, Haijun; Han, Tan

2018-03-01

A hot rolling scheme (cross-rolling and unidirectional rolling) was adopted to process Cu-2.7Be sheets used as multiplier dynodes in photomultiplier. The effects of changing rolling direction on microstructure, texture and mechanical properties were studied by a combination of XRD, EBSD and TEM. It was found that higher copper-type texture and lower brass texture intensity were obtained in the ultimately cross-rolling (CR) sheet compared with the unidirectional rolling (UR) sheet.The EBSD results indicated that the grain orientation from mainly < {101} > for UR sample turns to random for CR sample. Great enhancements in YS and UTS after unidirectional rolling were attributed to the massive and polygonal γ precipitates. The CR sample exhibited lower anisotropy, because of the increase of S and γ precipitates with spherical and tiny shape.
Role of ice sheet dynamics in the collapse of the early-Holocene Laurentide Ice Sheet

NASA Astrophysics Data System (ADS)

Matero, I. S. O.; Gregoire, L. J.; Cornford, S. L.; Ivanovic, R. F.

2017-12-01

The last stage of the deglaciation of the Laurentide Ice Sheet (LIS) during the early Holocene Thermal Maximum ( 9000 to 7000 years ago) provides an analogy and insight to the possible responses of contemporary ice sheets in a warming climate. What makes LIS particularly interesting is that meltwater from the collapse of an ice saddle over Hudson Bay was recently shown to be the primary forcing for the period of abrupt northern hemisphere cooling known as the 8.2 ka event. The evolution of the LIS during this period was likely influenced by its interaction with marginal lakes and the ocean, and its major ice stream, which exported ice towards Hudson Strait. Accurately simulating the early Holocene LIS evolution thus requires a model such as BISICLES, capable of accurately and efficiently resolving ice stream dynamics and grounding line migration thanks to the combined use of higher order physics and adaptive mesh refinement. We drive the BISICLES model using a positive degree day mass balance scheme with monthly precipitation and temperature from the HadCM3 climate model under climatic conditions from 10,000 to 8,000 years ago. We test the effect of varying the initial topographies and ice thicknesses from different timeslices in the ICE-6Gc reconstruction. We also test different parameterisations for the basal friction based on the thicknesses of the underlying sediments. These simulations evaluate the role of the Hudson Strait ice stream, ice sheet dynamics and interactions with the adjacent proglacial Lake Agassiz and North Atlantic Ocean in the collapse of the LIS. Our results highlight that the choice of parameterisation for basal friction has major effects on ice sheet dynamics and evolution.
Geometry of thin liquid sheet flows

NASA Technical Reports Server (NTRS)

Chubb, Donald L.; Calfo, Frederick D.; Mcconley, Marc W.; Mcmaster, Matthew S.; Afjeh, Abdollah A.

1994-01-01

Incompresible, thin sheet flows have been of research interest for many years. Those studies were mainly concerned with the stability of the flow in a surrounding gas. Squire was the first to carry out a linear, invicid stability analysis of sheet flow in air and compare the results with experiment. Dombrowski and Fraser did an experimental study of the disintegration of sheet flows using several viscous liquids. They also detected the formulation of holes in their sheet flows. Hagerty and Shea carried out an inviscid stability analysis and calculated growth rates with experimental values. They compared their calculated growth rates with experimental values. Taylor studied extensively the stability of thin liquid sheets both theoretically and experimentally. He showed that thin sheets in a vacuum are stable. Brown experimentally investigated thin liquid sheet flows as a method of application of thin films. Clark and Dumbrowski carried out second-order stability analysis for invicid sheet flows. Lin introduced viscosity into the linear stability analysis of thin sheet flows in a vacuum. Mansour and Chigier conducted an experimental study of the breakup of a sheet flow surrounded by high-speed air. Lin et al. did a linear stability analysis that included viscosity and a surrounding gas. Rangel and Sirignano carried out both a linear and nonlinear invisid stability analysis that applies for any density ratio between the sheet liquid and the surrounding gas. Now there is renewed interest in sheet flows because of their possible application as low mass radiating surfaces. The objective of this study is to investigate the fluid dynamics of sheet flows that are of interest for a space radiator system. Analytical expressions that govern the sheet geometry are compared with experimental results. Since a space radiator will operate in a vacuum, the analysis does not include any drag force on the sheet flow.
37 CFR 1.76 - Application data sheet.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 37 Patents, Trademarks, and Copyrights 1 2012-07-01 2012-07-01 false Application data sheet. 1.76... Application data sheet. (a) Application data sheet. An application data sheet is a sheet or sheets, that may... bibliographic data, arranged in a format specified by the Office. An application data sheet must be titled...
Microstructure evolution of a dissimilar junction interface between an Al sheet and a Ni-coated Cu sheet joined by magnetic pulse welding

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

Itoi, Takaomi, E-mail: itoi@faculty.chiba-u.jp

An Al sheet and a Ni-coated Cu sheet were lap joined by using magnetic pulse welding (MPW). Tensile tests were performed on the joined sheets, and a good lap joint was achieved at a discharge energy of > 0.9 kJ. The weld interface exhibited a wavy morphology and an intermediate layer along the weld interface. Microstructure observations of the intermediate layer revealed that the Ni coating region consisted of a Ni–Al binary amorphous alloy and that the Al sheet region contained very fine Al nanograins. Ni fragments indicative of unmelted residual Ni from the coating were also observed in partsmore » of the intermediate layer. Formation of these features can be attributed to localize melting and a subsequent high rate cooling of molten Al and Ni confined to the interface during the MPW process. In the absence of an oxide film, atomic-scale bonding was also achieved between the intermediate layer and the sheet surfaces after the collision. MPW utilises impact energy, which affects the sheet surfaces. From the obtained results, good lap joint is attributed to an increased contact area, the anchor effect, work hardening, the absence of an oxide film, and suppressed formation of intermetallic compounds at the interface. - Highlights: •Good lap joint of an Al sheet and a Ni-coated Cu sheet was achieved by using magnetic pulse welding. •A Ni–Al binary amorphous alloy was formed as an intermediate layer at weld interface. •Atomic-scale bonding was achieved between the intermediate layer and the sheet surfaces.« less
S U (2 ) Chern-Simons theory coupled to competing scalars

NASA Astrophysics Data System (ADS)

Pérez Ipiña, J. M.; Schaposnik, F. A.; Tallarita, G.

2018-06-01

We study a spontaneously broken S U (2 ) Chern-Simons-Higgs model coupled though a Higgs portal to an uncharged triplet scalar with a vacuum state competing with the Higgs one. We find vortexlike solutions to the field equations in different parameter space regions. Depending on the scalar coupling constants, we find a parameter region in which the competing order creates a halo about the Chern-Simons-Higgs vortex core, together with two other regions, one where no vortex solutions exist and the other where ordinary Chern-Simons-Higgs vortices can be found. We derive the low-energy theory for the moduli fields on the vortex world sheet and also discuss the connection of our results with those found in studies of competing orders in high-temperature superconductors.

Natural Curvature as Effective Confinement in Elastic Sheets

NASA Astrophysics Data System (ADS)

Albarran, Octavio; Katifori, Eleni; Goehring, Lucas

The wrinkling and folding transitions of thin elastic sheets have been extensively studied in the last decade. The exchange of energy from stretching to bending acts as a paradigm for a wide range of elastic instabilities, including the wrinkling of the gut, and the crinkling of leaves. In two dimensions this type of problem is typically considered by the model of an Euler-elastica in compressive confinement. We show that, even without any external forces, an elastic surface supported by a fluid can bend and wrinkle when it acquires a non-zero natural curvature. Locally, we will demonstrate how a preferential curvature can be related to an effective compression, and hence a confining force that can vary spatially. This suggests a simple experimental setup, where we have characterised a variety of wrinkle patterns that can be generated for different mechanical properties and natural curvatures.
The Folding of Acetyl(Ala)28NH2 and Acetyl(Ala)40NH2 Extended Strand Peptides into Antiparallel β-Sheets. A Density Functional Theory Study of β-Sheets with β-Turns

PubMed Central

Ali-Torres, Jorge

2012-01-01

We report ONIOM calculations using B3LYP/D95** and AM1 on β-sheet formation from acetyl(Ala)NNH2 (N=28 or 40). The sheets contain from one to four β-turns for N=28 and up to six for N=40. We have obtained four types of geometrically optimized structures. All contain only β-turns. They differ from each other in the types of β-turns formed. The unsolvated sheets containing two turns are most stable. Aqueous solvation (using the SM5.2 and CPCM methods) reduces the stabilities of the folded structures compared to the extended strands. PMID:23157432
ISMIP6 - initMIP: Greenland ice sheet model initialisation experiments

NASA Astrophysics Data System (ADS)

Goelzer, Heiko; Nowicki, Sophie; Payne, Tony; Larour, Eric; Abe Ouchi, Ayako; Gregory, Jonathan; Lipscomb, William; Seroussi, Helene; Shepherd, Andrew; Edwards, Tamsin

2016-04-01

Earlier large-scale Greenland ice sheet sea-level projections e.g. those run during ice2sea and SeaRISE initiatives have shown that ice sheet initialisation can have a large effect on the projections and gives rise to important uncertainties. This intercomparison exercise (initMIP) aims at comparing, evaluating and improving the initialization techniques used in the ice sheet modeling community and to estimate the associated uncertainties. It is the first in a series of ice sheet model intercomparison activities within ISMIP6 (Ice Sheet Model Intercomparison Project for CMIP6). The experiments are conceived for the large-scale Greenland ice sheet and are designed to allow intercomparison between participating models of 1) the initial present-day state of the ice sheet and 2) the response in two schematic forward experiments. The latter experiments serve to evaluate the initialisation in terms of model drift (forward run without any forcing) and response to a large perturbation (prescribed surface mass balance anomaly). We present and discuss first results of the intercomparison and highlight important uncertainties with respect to projections of the Greenland ice sheet sea-level contribution.
Sheet Metal Specialist 13-1. Military Curriculum Materials for Vocational and Technical Education.

ERIC Educational Resources Information Center

Chanute AFB Technical Training Center, IL.

This course, adapted from military curriculum materials for use in vocational and technical education, provides training in the theory and practice of sheet metal work. Designed for student self-instruction (such as a correspondence course), the text consists of four volumes. Volume 1 discusses shop mathematics, measurement and layout tools,…
An effective self-assessment based on concept map extraction from test-sheet for personalized learning

NASA Astrophysics Data System (ADS)

Liew, Keng-Hou; Lin, Yu-Shih; Chang, Yi-Chun; Chu, Chih-Ping

2013-12-01

Examination is a traditional way to assess learners' learning status, progress and performance after a learning activity. Except the test grade, a test sheet hides some implicit information such as test concepts, their relationships, importance, and prerequisite. The implicit information can be extracted and constructed a concept map for considering (1) the test concepts covered in the same question means these test concepts have strong relationships, and (2) questions in the same test sheet means the test concepts are relative. Concept map has been successfully employed in many researches to help instructors and learners organize relationships among concepts. However, concept map construction depends on experts who need to take effort and time for the organization of the domain knowledge. In addition, the previous researches regarding to automatic concept map construction are limited to consider all learners of a class, which have not considered personalized learning. To cope with this problem, this paper proposes a new approach to automatically extract and construct concept map based on implicit information in a test sheet. Furthermore, the proposed approach also can help learner for self-assessment and self-diagnosis. Finally, an example is given to depict the effectiveness of proposed approach.
BOOK REVIEW: Many Worlds?: Everett, Quantum Theory, and Reality Many Worlds?: Everett, Quantum Theory, and Reality

NASA Astrophysics Data System (ADS)

Wald, Robert M.

2011-04-01

Few, if any, issues in physics have engendered as much discussion as the measurement problem in quantum mechanics. It is generally agreed that the `normal' dynamical evolution of the state vector in quantum mechanics is given by a unitary map. The linearity of this map implies that the state vector will, in general, be found in a superposition of eigenstates of a given observable (or, similarly, that the density matrix describing a subsystem will not correspond to a definite value of this observable). However, when we make a measurement of an observable, we always obtain a define value—although it is impossible to predict with certainty which value will be obtained. The traditional response to this issue is to postulate that when a measurement is made, the wavefunction `collapses' to an eigenstate of the observable being measured, perhaps due to the inherent classicality of the measuring apparatus (Bohr), or to the consciousness of the observer (Wigner), or possibly to some modification of quantum dynamics that occurs even when observations are not being made. The main motivation for the Everett (`many worlds') interpretation is to avoid introducing any such collapse postulate. This volume commemorates the 50th anniversary of the publication of Everett's paper in 1957 and contains 20 original articles as well as the transcripts of several discussions that took place at meetings devoted to the Everett interpretation at Oxford University and the Perimeter Institute. The attractiveness of the Everett interpretation is very succinctly summarized by a sentence from Vaidman's contribution (p 582): `The collapse, with its randomness, non-locality and the lack of a well-defined moment of occurrence, is such an ugly scar on quantum theory, that I, along with many others, am ready to follow Everett and deny its existence.' But the main drawback of the interpretation is then equally succinctly stated in the next sentence: `The price is the many worlds interpretation, i
Sensitivities of Greenland ice sheet volume inferred from an ice sheet adjoint model

NASA Astrophysics Data System (ADS)

Heimbach, P.; Bugnion, V.

2009-04-01

We present a new and original approach to understanding the sensitivity of the Greenland ice sheet to key model parameters and environmental conditions. At the heart of this approach is the use of an adjoint ice sheet model. Since its introduction by MacAyeal (1992), the adjoint method has become widespread to fit ice stream models to the increasing number and diversity of satellite observations, and to estimate uncertain model parameters such as basal conditions. However, no attempt has been made to extend this method to comprehensive ice sheet models. As a first step toward the use of adjoints of comprehensive three-dimensional ice sheet models we have generated an adjoint of the ice sheet model SICOPOLIS of Greve (1997). The adjoint was generated by means of the automatic differentiation (AD) tool TAF. The AD tool generates exact source code representing the tangent linear and adjoint model of the nonlinear parent model provided. Model sensitivities are given by the partial derivatives of a scalar-valued model diagnostic with respect to the controls, and can be efficiently calculated via the adjoint. By way of example, we determine the sensitivity of the total Greenland ice volume to various control variables, such as spatial fields of basal flow parameters, surface and basal forcings, and initial conditions. Reliability of the adjoint was tested through finite-difference perturbation calculations for various control variables and perturbation regions. Besides confirming qualitative aspects of ice sheet sensitivities, such as expected regional variations, we detect regions where model sensitivities are seemingly unexpected or counter-intuitive, albeit ``real'' in the sense of actual model behavior. An example is inferred regions where sensitivities of ice sheet volume to basal sliding coefficient are positive, i.e. where a local increase in basal sliding parameter increases the ice sheet volume. Similarly, positive ice temperature sensitivities in certain parts
Microcomponent sheet architecture

DOEpatents

Wegeng, R.S.; Drost, M.K..; McDonald, C.E.

1997-03-18

The invention is a microcomponent sheet architecture wherein macroscale unit processes are performed by microscale components. The sheet architecture may be a single laminate with a plurality of separate microcomponent sections or the sheet architecture may be a plurality of laminates with one or more microcomponent sections on each laminate. Each microcomponent or plurality of like microcomponents perform at least one unit operation. A first laminate having a plurality of like first microcomponents is combined with at least a second laminate having a plurality of like second microcomponents thereby combining at least two unit operations to achieve a system operation. 14 figs.
Microcomponent sheet architecture

DOEpatents

Wegeng, Robert S.; Drost, M. Kevin; McDonald, Carolyn E.

1997-01-01

The invention is a microcomponent sheet architecture wherein macroscale unit processes are performed by microscale components. The sheet architecture may be a single laminate with a plurality of separate microcomponent sections or the sheet architecture may be a plurality of laminates with one or more microcomponent sections on each laminate. Each microcomponent or plurality of like microcomponents perform at least one unit operation. A first laminate having a plurality of like first microcomponents is combined with at least a second laminate having a plurality of like second microcomponents thereby combining at least two unit operations to achieve a system operation.
Aircraft Sheet Metal Practices; Sheet Metal Work 2: 9855.01.

ERIC Educational Resources Information Center

Dade County Public Schools, Miami, FL.

The course outline will serve as a guide to the 11th grade student interested in sheet metal occupations. Requiring 135 clock hours, the basic course covers orientation and techniques in aircraft sheet metal. Emphasis will be placed on the proper use of tools and machines, safety, fabrication methods, aircraft materials, basic layout, and special…
Formation of a wave on an ice-sheet above the dipole, moving in a fluid

NASA Astrophysics Data System (ADS)

Il'ichev, A. T.; Savin, A. A.; Savin, A. S.

2012-05-01

Theory of wave motions of a fluid with an ice-sheet was developed due to the necessity of solving of a number of problems of marine and land physics. The main attention in these investigations was focused on propagation and interaction of free waves, and also on appearance of waves under action of different loadings on the ice-sheet. From the other side, the problems dealing with waves on the fluid surface, free from the ice due to motion in the mass of the fluid of rigid bodies, has the known solutions. In this connection, it seems natural to disserminate the formulation and methods of such problems to the case of the fluid with the ice-sheet. In the present note we describe the character of formation of waves from the singularity, localized in the fluid of infinite depth beneath the ice-sheet. We use the example of the dipole, which models a cylinder in the infinite mass of the fluid. The character of the formation does not depend on the type of singularity. The ice-sheet is considered as a thin elastic plate of a constant width, floating on the water surface.
Ice shelf fracture parameterization in an ice sheet model

NASA Astrophysics Data System (ADS)

Sun, Sainan; Cornford, Stephen L.; Moore, John C.; Gladstone, Rupert; Zhao, Liyun

2017-11-01

Floating ice shelves exert a stabilizing force onto the inland ice sheet. However, this buttressing effect is diminished by the fracture process, which on large scales effectively softens the ice, accelerating its flow, increasing calving, and potentially leading to ice shelf breakup. We add a continuum damage model (CDM) to the BISICLES ice sheet model, which is intended to model the localized opening of crevasses under stress, the transport of those crevasses through the ice sheet, and the coupling between crevasse depth and the ice flow field and to carry out idealized numerical experiments examining the broad impact on large-scale ice sheet and shelf dynamics. In each case we see a complex pattern of damage evolve over time, with an eventual loss of buttressing approximately equivalent to halving the thickness of the ice shelf. We find that it is possible to achieve a similar ice flow pattern using a simple rule of thumb: introducing an enhancement factor ˜ 10 everywhere in the model domain. However, spatially varying damage (or equivalently, enhancement factor) fields set at the start of prognostic calculations to match velocity observations, as is widely done in ice sheet simulations, ought to evolve in time, or grounding line retreat can be slowed by an order of magnitude.
Radar attenuation and temperature within the Greenland Ice Sheet

USGS Publications Warehouse

MacGregor, Joseph A; Li, Jilu; Paden, John D; Catania, Ginny A; Clow, Gary D.; Fahnestock, Mark A; Gogineni, Prasad S.; Grimm, Robert E.; Morlighem, Mathieu; Nandi, Soumyaroop; Seroussi, Helene; Stillman, David E

2015-01-01

The flow of ice is temperature-dependent, but direct measurements of englacial temperature are sparse. The dielectric attenuation of radio waves through ice is also temperature-dependent, and radar sounding of ice sheets is sensitive to this attenuation. Here we estimate depth-averaged radar-attenuation rates within the Greenland Ice Sheet from airborne radar-sounding data and its associated radiostratigraphy. Using existing empirical relationships between temperature, chemistry, and radar attenuation, we then infer the depth-averaged englacial temperature. The dated radiostratigraphy permits a correction for the confounding effect of spatially varying ice chemistry. Where radar transects intersect boreholes, radar-inferred temperature is consistently higher than that measured directly. We attribute this discrepancy to the poorly recognized frequency dependence of the radar-attenuation rate and correct for this effect empirically, resulting in a robust relationship between radar-inferred and borehole-measured depth-averaged temperature. Radar-inferred englacial temperature is often lower than modern surface temperature and that of a steady state ice-sheet model, particularly in southern Greenland. This pattern suggests that past changes in surface boundary conditions (temperature and accumulation rate) affect the ice sheet's present temperature structure over a much larger area than previously recognized. This radar-inferred temperature structure provides a new constraint for thermomechanical models of the Greenland Ice Sheet.
Fuels planning: science synthesis and integration; environmental consequences fact sheet 01: Fire Effects Information System (FEIS)

Treesearch

Steve Sutherland

2004-01-01

The Fire Effects Information System (FEIS) provides accessible, up-to-date fire effects summaries, taken from current English-language literature, for almost 900 plant species, about 100 animal species, and 16 Kuchler plant communities found on the North American continent. This fact sheet discusses the development of FEIS and what is contained in the species summary....
Free Associations Mirroring Self- and World-Related Concepts: Implications for Personal Construct Theory, Psycholinguistics and Philosophical Psychology.

PubMed

Kuška, Martin; Trnka, Radek; Kuběna, Aleš A; Růžička, Jiří

2016-01-01

People construe reality by using words as basic units of meaningful categorization. The present theory-driven study applied the method of a free association task to explore how people express the concepts of the world and the self in words. The respondents were asked to recall any five words relating with the word world. Afterward they were asked to recall any five words relating with the word self. The method of free association provided the respondents with absolute freedom to choose any words they wanted. Such free recall task is suggested as being a relatively direct approach to the respondents' self- and world-related conceptual categories, without enormous rational processing. The results provide us, first, with associative ranges for constructs of the world and the self, where some associative dimensions are defined by semantic polarities in the meanings of peripheral categories (e.g., Nature vs. Culture). Second, our analysis showed that some groups of verbal categories that were associated with the words world and self are central, while others are peripheral with respect to the central position. Third, the analysis of category networks revealed that some categories play the role of a transmitter, mediating the pathway between other categories in the network.
Free Associations Mirroring Self- and World-Related Concepts: Implications for Personal Construct Theory, Psycholinguistics and Philosophical Psychology

PubMed Central

Kuška, Martin; Trnka, Radek; Kuběna, Aleš A.; Růžička, Jiří

2016-01-01

People construe reality by using words as basic units of meaningful categorization. The present theory-driven study applied the method of a free association task to explore how people express the concepts of the world and the self in words. The respondents were asked to recall any five words relating with the word world. Afterward they were asked to recall any five words relating with the word self. The method of free association provided the respondents with absolute freedom to choose any words they wanted. Such free recall task is suggested as being a relatively direct approach to the respondents’ self- and world-related conceptual categories, without enormous rational processing. The results provide us, first, with associative ranges for constructs of the world and the self, where some associative dimensions are defined by semantic polarities in the meanings of peripheral categories (e.g., Nature vs. Culture). Second, our analysis showed that some groups of verbal categories that were associated with the words world and self are central, while others are peripheral with respect to the central position. Third, the analysis of category networks revealed that some categories play the role of a transmitter, mediating the pathway between other categories in the network. PMID:27445940
13. Photograph of sheet 1 (index and title sheet) of ...

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

13. Photograph of sheet 1 (index and title sheet) of the Indiana State Highway Commission repair plans of 1969 for the Cicott Street Bridge. Photograph of a 24' by 36' print made from microfilm in the archives of the Indiana Department of Transportation in Indianapolis. - Cicott Street Bridge, Spanning Wabash River at State Road 25, Logansport, Cass County, IN
THE MAN MADE WORLD, A HIGH SCHOOL COURSE ON THE THEORIES AND TECHNIQUES WHICH CONTRIBUTE TO OUR TECHNOLOGICAL CIVILIZATION.

ERIC Educational Resources Information Center

Commission on Engineering Education, Washington, DC.

THIS STUDENTS' MANUAL FOR THE ENGINEERING CONCEPTS CURRICULUM PROJECT'S (ECCP) HIGH SCHOOL COURSE, "THE MAN MADE WORLD," IS THE THIRD DRAFT OF THE EXPERIMENTAL VERSION. THE MATERIAL WRITTEN BY SCIENTISTS, ENGINEERS, AND EDUCATORS, EMPHASIZES THE THEORIES AND TECHNIQUES WHICH CONTRIBUTE TO OUR TECHNOLOGICAL CIVILIZATION. RESOURCES OF THE MAN-MADE…
Three-dimensional CTOA and constraint effects during stable tearing in a thin-sheet material

NASA Technical Reports Server (NTRS)

Dawicke, D. S.; Newman, J. C., Jr.; Bigelow, C. A.

1995-01-01

A small strain theory, three-dimensional elastic-plastic finite element analysis was used to simulate fracture in thin sheet 2024-T3 aluminum alloy in the T-L orientation. Both straight and tunneled cracks were modeled. The tunneled crack front shapes as a function of applied stress were obtained from the fracture surface of tested specimens. The stable crack growth behavior was measured at the specimen surface as a function of applied stress. The fracture simulation modeled the crack tunneling and extension as a function of applied stress. The results indicated that the global constraint factor, alpha(sub g), initially dropped during stable crack growth. After peak applied stress was achieved, alpha(sub g) began to increase slightly. The effect of crack front shape on alpha(sub g) was small, but the crack front shape did greatly influence the local constraint and through-thickness crack-tip opening angle (CTOA) behavior. The surface values of CTOA for the tunneled crack front model agreed well with experimental measurements, showing the same initial decrease from high values during the initial 3mm of crack growth at the specimen's surface. At the same time, the interior CTOA values increased from low angles. After the initial stable tearing region, the CTOA was constant through the thickness. The three-dimensional analysis appears to confirm the potential of CTOA as a two-dimensional fracture criterion.
Adsorption of various types of amino acids on the graphene and boron-nitride nano-sheet, a DFT-D3 study

NASA Astrophysics Data System (ADS)

Zhiani, Rahele

2017-07-01

The binding properties of the adsorption of five different classes of amino acids, namely, alanine (Ala), arginine (Arg), asparagine (Asn), histidine (His) and cysteine (Cys) on the surface of the graphene (Gra) and the born-nitride (BN) nano-sheet structures were studied from molecular viewpoint using quantum mechanics methods. Density functional theory (DFT) and DFT-D3 calculations were carried out to investigate the electronic properties and the dispersion interaction of the amino acid/adsorbent complexes. Several parameters affecting the interactions between the amino acids and the adsorbent surfaces such as solvent effect, adsorption energy and separation distance were investigated. Findings show that Arg forms the most stable complexes with the graphene and the BN nano-sheet compare to the other amino acids used in this study. The observed frequency results which were related to the band gap energies were consistent with the above statement. Results exhibit that adsorption of the amino acids on the surface of the BN nano-sheet and the graphene accompanied with the release of the energy. Calculations show that there are no bonded interactions between the amino acids and adsorbent surfaces. The polarity of the BN nano-sheet provides the more affinity towards the amino acids. These results were proved by the quantum chemistry studies.

Thermomechanical processing of HAYNES alloy No. 188 sheet to improve creep strength

NASA Technical Reports Server (NTRS)

Klarstrom, D. L.

1978-01-01

Improvements in the low strain creep strength of HAYNES alloy No. 188 thin gauge sheet by means of thermomechanical processing were developed. Processing methods designed to develop a sheet with strong crystallographic texture after recrystallization and to optimize grain size were principally studied. The effects of thickness-to-grain diameter ratio and prestrain on low strain creep strength were also briefly examined. Results indicate that the most significant improvements were obtained in the sheets having a strong crystallographic texture. The low strain creep strength of the textured sheets was observed to be superior to that of standard production sheets in the 922 K to 1255 K temperature range. Tensile, stress rupture, fabricability, and surface stability properties of the experimental sheets were also measured and compared to property values reported for the baseline production sheets.
Insolation-driven 100,000-year glacial cycles and hysteresis of ice-sheet volume.

PubMed

Abe-Ouchi, Ayako; Saito, Fuyuki; Kawamura, Kenji; Raymo, Maureen E; Okuno, Jun'ichi; Takahashi, Kunio; Blatter, Heinz

2013-08-08

The growth and reduction of Northern Hemisphere ice sheets over the past million years is dominated by an approximately 100,000-year periodicity and a sawtooth pattern (gradual growth and fast termination). Milankovitch theory proposes that summer insolation at high northern latitudes drives the glacial cycles, and statistical tests have demonstrated that the glacial cycles are indeed linked to eccentricity, obliquity and precession cycles. Yet insolation alone cannot explain the strong 100,000-year cycle, suggesting that internal climatic feedbacks may also be at work. Earlier conceptual models, for example, showed that glacial terminations are associated with the build-up of Northern Hemisphere 'excess ice', but the physical mechanisms underpinning the 100,000-year cycle remain unclear. Here we show, using comprehensive climate and ice-sheet models, that insolation and internal feedbacks between the climate, the ice sheets and the lithosphere-asthenosphere system explain the 100,000-year periodicity. The responses of equilibrium states of ice sheets to summer insolation show hysteresis, with the shape and position of the hysteresis loop playing a key part in determining the periodicities of glacial cycles. The hysteresis loop of the North American ice sheet is such that after inception of the ice sheet, its mass balance remains mostly positive through several precession cycles, whose amplitudes decrease towards an eccentricity minimum. The larger the ice sheet grows and extends towards lower latitudes, the smaller is the insolation required to make the mass balance negative. Therefore, once a large ice sheet is established, a moderate increase in insolation is sufficient to trigger a negative mass balance, leading to an almost complete retreat of the ice sheet within several thousand years. This fast retreat is governed mainly by rapid ablation due to the lowered surface elevation resulting from delayed isostatic rebound, which is the lithosphere
The unique world of the Everett version of quantum theory

NASA Astrophysics Data System (ADS)

Squires, Euan J.

1988-03-01

We ask whether the basic Everett assumption, that there are no changes of the wavefunction other than those given by the Schrödinger equation, is compatible with experience. We conclude that it is, provided we allow the world of observation to be partially a creation of consciousness. The model suggests the possible existence of quantum paranormal effects.
Friction and lubrication modelling in sheet metal forming: Influence of lubrication amount, tool roughness and sheet coating on product quality

NASA Astrophysics Data System (ADS)

Hol, J.; Wiebenga, J. H.; Carleer, B.

2017-09-01

In the stamping of automotive parts, friction and lubrication play a key role in achieving high quality products. In the development process of new automotive parts, it is therefore crucial to accurately account for these effects in sheet metal forming simulations. This paper presents a selection of results considering friction and lubrication modelling in sheet metal forming simulations of a front fender product. For varying lubrication conditions, the front fender can either show wrinkling or fractures. The front fender is modelled using different lubrication amounts, tool roughness’s and sheet coatings to show the strong influence of friction on both part quality and the overall production stability. For this purpose, the TriboForm software is used in combination with the AutoForm software. The results demonstrate that the TriboForm software enables the simulation of friction behaviour for varying lubrication conditions, i.e. resulting in a generally applicable approach for friction characterization under industrial sheet metal forming process conditions.
Ice-Sheet Dynamics and Millennial-Scale Climate Variability in the North Atlantic across the Middle Pleistocene Transition (Invited)

NASA Astrophysics Data System (ADS)

Hodell, D. A.; Nicholl, J.

2013-12-01

During the Middle Pleistocene Transition (MPT), the climate system evolved from a more linear response to insolation forcing in the '41-kyr world' to one that was decidedly non-linear in the '100-kyr world'. Smaller ice sheets in the early Pleistocene gave way to larger ice sheets in the late Pleistocene with an accompanying change in ice sheet dynamics. We studied Sites U1308 (49° 52.7'N, 24° 14.3'W; 3871 m) and U1304 (53° 3.4'N, 33° 31.8'W; 3024 m) in the North Atlantic to determine how ice sheet dynamics and millennial-scale climate variability evolved as glacial boundary conditions changed across the MPT. The frequency of ice-rafted detritus (IRD) in the North Atlantic was greater during glacial stages prior to 650 ka (MIS 16), reflecting more frequent crossing of an ice volume threshold when the climate system spent more time in the 'intermediate ice volume' window, resulting in persistent millennial scale variability. The rarity of Heinrich Events containing detrital carbonate and more frequent occurrence of IRD events prior to 650 ka may indicate the presence of 'low-slung, slippery ice sheets' that flowed more readily than their post-MPT counterparts (Bailey et al., 2010). Ice volume surpassed a critical threshold across the MPT that permitted ice sheets to survive boreal summer insolation maxima, thereby increasing ice volume and thickness, lengthening glacial cycles, and activating the dynamical processes responsible for Laurentide Ice Sheet instability in the region of Hudson Strait (i.e., Heinrich events). The excess ice volume during post-MPT glacial maxima provided a large, unstable reservoir of freshwater to be released to the North Atlantic during glacial terminations with the potential to perturb Atlantic Meridional Overtunring Circulation. We speculate that orbital- and millennial-scale variability co-evolved across the MPT and the interaction of processes on orbital and suborbital time scales gave rise to the changing patterns of glacial
Effect of debond growth on stress-intensity factors in a cracked orthotropic sheet stiffened by a semi-infinite orthotropic sheet

NASA Technical Reports Server (NTRS)

Bigelow, C. A.

1986-01-01

Stress-intensity factors are determined for a cracked infinite sheet adhesively bonded to a stringer, and debonding of the adhesive layer is predicted. The stringer is modeled as a semi-infinite sheet. Adhesive nonlinearity is also included. Both the sheet and stringer are treated as homogeneous, orthotropic materials. A set of integral equations is formulated and solved to obtain the adhesive shear stresses and crack-tip stress-intensity factors. Adhesive debonding is predicted using a rupture criterion based on the combined adhesive stresses. When the crack is not under the stringer, the debond extends along the edge of the stringer. When the crack tip is beneath the stringer, the debond grows to the end of the crack, then along the edge of the stringer. Stress levels required for debond initiation decrease as the crack tip is moved beneath the stringer. With a nonlinear adhesive, the debond initiates at higher applied stress levels than in linear adhesive cases. Compared with the linear adhesive solution, modeling a nonlinear adhesive causes the stress-intensity factor to increase when the bond is assumed to remain intact but causes the stress-intensity factor to decrease when debonding is included.
Effective Field Theory on Manifolds with Boundary

NASA Astrophysics Data System (ADS)

Albert, Benjamin I.

In the monograph Renormalization and Effective Field Theory, Costello made two major advances in rigorous quantum field theory. Firstly, he gave an inductive position space renormalization procedure for constructing an effective field theory that is based on heat kernel regularization of the propagator. Secondly, he gave a rigorous formulation of quantum gauge theory within effective field theory that makes use of the BV formalism. In this work, we extend Costello's renormalization procedure to a class of manifolds with boundary and make preliminary steps towards extending his formulation of gauge theory to manifolds with boundary. In addition, we reorganize the presentation of the preexisting material, filling in details and strengthening the results.
Small-World Network Spectra in Mean-Field Theory

NASA Astrophysics Data System (ADS)

Grabow, Carsten; Grosskinsky, Stefan; Timme, Marc

2012-05-01

Collective dynamics on small-world networks emerge in a broad range of systems with their spectra characterizing fundamental asymptotic features. Here we derive analytic mean-field predictions for the spectra of small-world models that systematically interpolate between regular and random topologies by varying their randomness. These theoretical predictions agree well with the actual spectra (obtained by numerical diagonalization) for undirected and directed networks and from fully regular to strongly random topologies. These results may provide analytical insights to empirically found features of dynamics on small-world networks from various research fields, including biology, physics, engineering, and social science.
Knowledge synthesis of benefits and adverse effects of measles vaccination: the Lasbela balance sheet.

PubMed

Ledogar, Robert J; Fleming, John; Andersson, Neil

2009-10-14

In preparation for a cluster-randomized controlled trial of a community intervention to increase the demand for measles vaccination in Lasbela district of Pakistan, a balance sheet summarized published evidence on benefits and possible adverse effects of measles vaccination. The balance sheet listed: 1) major health conditions associated with measles; 2) the risk among the unvaccinated who contract measles; 3) the risk among the vaccinated; 4) the risk difference between vaccinated and unvaccinated; and 5) the likely net gain from vaccination for each condition. Two models revealed very different projections of net gain from measles vaccine. A Lasbela-specific combination of low period prevalence of measles among the unvaccinated, medium vaccination coverage and low vaccine efficacy rate, as revealed by the baseline survey, resulted in less-than-expected gains attributable to vaccination. Modelled on estimates where the vaccine had greater efficacy, the gains from vaccination would be more substantial. Specific local conditions probably explain the low rates among the unvaccinated while the high vaccine failure rate is likely due to weaknesses in the vaccination delivery system. Community perception of these realities may have had some role in household decisions about whether to vaccinate, although the major discouraging factor was inadequate access. The balance sheet may be useful as a communication tool in other circumstances, applied to up-to-date local evidence.
9. Photograph of sheet 1 (index and title sheet) of ...

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

9. Photograph of sheet 1 (index and title sheet) of the State Highway Department of Indiana repair plans of 1957 for the Cicott Street Bridge. Photograph of a 24' by 36' print made from microfilm in the archives of the Indiana Department of Transportation in Indianapolis. - Cicott Street Bridge, Spanning Wabash River at State Road 25, Logansport, Cass County, IN
FDTD modeling of thin impedance sheets

NASA Technical Reports Server (NTRS)

Luebbers, Raymond J.; Kunz, Karl S.

1991-01-01

Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. In this paper it is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods.
Modeling North American Ice Sheet Response to Changes in Precession and Obliquity

NASA Astrophysics Data System (ADS)

Tabor, C.; Poulsen, C. J.; Pollard, D.

2012-12-01

Milankovitch theory proposes that changes in insolation due to orbital perturbations dictate the waxing and waning of the ice sheets (Hays et al., 1976). However, variations in solar forcing alone are insufficient to produce the glacial oscillations observed in the climate record. Non-linear feedbacks in the Earth system likely work in concert with the orbital cycles to produce a modified signal (e.g. Berger and Loutre, 1996), but the nature of these feedbacks remain poorly understood. To gain a better understand of the ice dynamics and climate feedbacks associated with changes in orbital configuration, we use a complex Earth system model consisting of the GENESIS GCM and land surface model (Pollard and Thompson, 1997), the Pennsylvania State University ice sheet model (Pollard and DeConto, 2009), and the BIOME vegetation model (Kaplan et al., 2001). We began this study by investigating ice sheet sensitivity to a range of commonly used ice sheet model parameters, including mass balance and albedo, to optimize simulations for Pleistocene orbital cycles. Our tests indicate that choice of mass balance and albedo parameterizations can lead to significant differences in ice sheet behavior and volume. For instance, use of an insolation-temperature mass balance scheme (van den Berg, 2008) allows for a larger ice sheet response to orbital changes than the commonly employed positive degree-day method. Inclusion of a large temperature dependent ice albedo, representing phenomena such as melt ponds and dirty ice, also enhances ice sheet sensitivity. Careful tuning of mass balance and albedo parameterizations can help alleviate the problem of insufficient ice sheet retreat during periods of high summer insolation (Horton and Poulsen, 2007) while still accurately replicating the modern climate. Using our optimized configuration, we conducted a series of experiments with idealized transient orbits in an asynchronous coupling scheme to investigate the influence of obliquity and
Effect of Annealing on Mechanical Properties and Formability of Cold Rolled Thin Sheets of Fe-P P/M Alloys

NASA Astrophysics Data System (ADS)

Trivedi, Shefali; Ravi Kumar, D.; Aravindan, S.

2016-10-01

Phosphorus in steel is known to increase strength and hardness and decrease ductility. Higher phosphorus content (more than 0.05%), however, promotes brittle behavior due to segregation of Fe3P along the grain boundaries which makes further mechanical working of these alloys difficult. In this work, thin sheets of Fe-P alloys (with phosphorus in range of 0.1-0.35%) have been developed through processing by powder metallurgy followed by hot rolling and cold rolling. The effect of phosphorus content and annealing parameters (temperature and time) on microstructure, mechanical properties, formability in biaxial stretching and fracture behavior of the cold rolled and annealed sheets has been studied. A comparison has also been made between the properties of the sheets made through P/M route and the conventional cast route with similar phosphorus content. It has been shown that thin sheets of Fe-P alloys with phosphorous up to 0.35% possessing a good combination of strength and formability can be produced through rolling of billets of these alloys made through powder metallurgy technique without the problem of segregation.
van der Pauw's Theorem on Sheet Resistance

ERIC Educational Resources Information Center

Bolt, Michael

2017-01-01

The sheet resistance of a conducting material of uniform thickness is analogous to the resistivity of a solid material and provides a measure of electrical resistance. In 1958, L. J. van der Pauw found an effective method for computing sheet resistance that requires taking two electrical measurements from four points on the edge of a simply…
Hand-Drawn 'Weekly Information Sheets' Focus Teaching, Engage Students, and Improve Communication

NASA Astrophysics Data System (ADS)

Pound, K. S.

2016-12-01

Hand-drawn and lettered `Weekly Information Sheets' (WIS) were created on a weekly basis for an upper-level Sedimentology & Stratigraphy class. Use of these sheets resulted in improved work quality, attention to detail, communication skills, and overall engagement. The sheets were modeled on the work of Lynda Barry (https://www.drawnandquarterly.com/syllabus), and included a series of repeated elements: goofy/absurd newspaper clippings, marginally pertinent cartoon(s), a summary of the weeks activities / goals and lectures, as well as cartoon cat, mouse and penguin drawings with innane comments, quotes and general class reminders. The pedagogical aims for these weekly sheets were multifold. First, they were designed so that students could see the time and care I put in to the sheet - my hope was that this would show the time and care I expected them to put in to their work. Second, I wanted to create something students would take the time to read - despite this being a 400-level class, students are rarely diligent about reading a typewritten handout. Third, I wanted to have a vehicle for engaging them in the larger world, including ethical or moral dilemmas. Fourth, I wanted the students to reflectively consider the nature of communication in science. Finally, I wanted a mechanism to focus my thoughts on the teaching and learning for the upcoming week that went beyond simply reviewing my notes and activities. Student response to the WIS was positive; they read them, used them for organizing their class notes and exam review. Students arrived early for class on Mondays for the WIS - although I needed to give them time to read the sheet. Comparison with previous course offerings shows improvements in student communication skills (written reports, poster presentation) and overall achievement.
Religion, evolution, and mental health: attachment theory and ETAS theory.

PubMed

Flannelly, Kevin J; Galek, Kathleen

2010-09-01

This article reviews the historical origins of Attachment Theory and Evolutionary Threat Assessment Systems Theory (ETAS Theory), their evolutionary basis and their application in research on religion and mental health. Attachment Theory has been most commonly applied to religion and mental health in research on God as an attachment figure, which has shown that secure attachment to God is positively associated with psychological well-being. Its broader application to religion and mental health is comprehensively discussed by Kirkpatrick (2005). ETAS Theory explains why certain religious beliefs--including beliefs about God and life-after-death--should have an adverse association, an advantageous association, or no association at all with mental health. Moreover, it makes specific predictions to this effect, which have been confirmed, in part. The authors advocate the application of ETAS Theory in research on religion and mental health because it explains how religious and other beliefs related to the dangerousness of the world can directly affect psychiatric symptoms through their affects on specific brain structures.
Effect of temperature on the anisotropy of AZ31 magnesium alloy rolling sheet under high strain rate deformation

NASA Astrophysics Data System (ADS)

Liu, Yanyu; Mao, Pingli; Zhang, Feng; Liu, Zheng; Wang, Zhi

2018-04-01

In order to investigate the effect of temperature on the anisotropic behaviour of AZ31 magnesium alloy rolling sheet under high strain rate deformation, the Split Hopkinson Pressure Bar was used to analyse the dynamic mechanical properties of AZ31 magnesium alloy rolling sheet in three directions, rolling direction(RD), transverse direction (TD) and normal direction (ND). The texture of the rolling sheet was characterised by X-ray analysis and the microstructure prior and after high strain rate deformation was observed by optical microscope (OM). The results demonstrated that AZ31magnesium alloy rolling sheet has strong initial {0 0 0 2} texture, which resulted at the obvious anisotropy in high strain rate deformation at 20 °C. The anisotropy reflected in stress-strain curve, yield stress, peak stress and microstructure. The anisotropy became much weaker when the deformation temperature increased up to 250 °C. Continuing to increase the deformation temperature to 350 °C the anisotropy of AZ31 rolling sheet essentially disappeared. The decreasing tendency of anisotropy with increasing temperature was due to the fact that when the deformation temperature increased, the critical resolved shear stress (CRSS) for pyramidal 〈c + a〉 slip, which was the predominant slip mechanism for ND, decreased close to that of twinning, which was the predominant deformation mechanism for RD and TD. The deformation mechanism at different directions and temperatures and the Schmid factor (SF) at different directions were discussed in the present paper.
Linear Tidal Vestige Found in the WM Sheet

NASA Astrophysics Data System (ADS)

Lee, Jounghun; Kim, Suk; Rey, Soo-Chang

2018-06-01

We present a vestige of the linear tidal influence on the spin orientations of the constituent galaxies of the WM sheet discovered in the vicinity of the Virgo Cluster and the Local Void. The WM sheet is chosen as an optimal target since it has a rectangular parallelepiped-like shape whose three sides are in parallel with the supergalactic Cartesian axes. Determining three probability density functions of the absolute values of the supergalactic Cartesian components of the spin vectors of the WM sheet galaxies, we investigate their alignments with the principal directions of the surrounding large-scale tidal field. When the WM sheet galaxies located in the central region within the distance of 2 h ‑1 Mpc are excluded, the spin vectors of the remaining WM sheet galaxies are found to be weakly aligned, strongly aligned, and strongly anti-aligned with the minor, intermediate, and major principal directions of the surrounding large-scale tidal field, respectively. To examine whether or not the origin of the observed alignment tendency from the WM sheet is the linear tidal effect, we infer the eigenvalues of the linear tidal tensor from the axial ratios of the WM sheet with the help of the Zeldovich approximation and conduct a full analytic evaluation of the prediction of the linear tidal torque model for the three probability density functions. A detailed comparison between the analytical and the observational results reveals a good quantitative agreement not only in the behaviors but also in the amplitudes of the three probability density functions.
Horizontal electromagnetic casting of thin metal sheets

DOEpatents

Hull, John R.; Lari, Robert J.; Praeg, Walter F.; Turner, Larry R.

1987-01-01

Thin metal sheets are cast by magnetically suspending molten metal deposited within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled to form a solid metal sheet. Magnetic flux increases as the molten metal sheet moves downward and decreases as the molten metal sheet moves upward to stabilize the sheet and maintain it in equilibrium as it is linearly displaced and solidified by cooling gases. A conducting shield is electrically coupled to the molten metal sheet by means of either metal sheet engaging rollers or brushes on the solidified metal, and by means of an electrode in the vessel containing the molten metal thereby providing a return path for the eddy currents induced in the metal sheet by the AC coil generated magnetic flux. Variation in the geometry of the conducting shield allows the magnetic flux between the metal sheet and the conducting shield to be varied and the thickness in surface quality of the metal sheet to be controlled. Side guards provide lateral containment for the molten metal sheet and stabilize and shape the magnetic field while a leader sheet having electromagnetic characteristics similar to those of the metal sheet is used to start the casting process and precedes the molten metal sheet through the magnet and forms a continuous sheet therewith. The magnet may be either U-shaped with a single racetrack coil or may be rectangular with a pair of facing bedstead coils.
Horizontal electromagnetic casting of thin metal sheets

DOEpatents

Hull, John R.; Lari, Robert J.; Praeg, Walter F.; Turner, Larry R.

1988-01-01

Thin metal sheets are cast by magnetically suspending molten metal deposited within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled to form a solid metal sheet. Magnetic flux increases as the molten metal sheet moves downward and decreases as the molten metal sheet moves upward to stabilize the sheet and maintain it in equilibrium as it is linearly displaced and solidified by cooling gases. A conducting shield is electrically coupled to the molten metal sheet by means of either metal sheet engaging rollers or brushes on the solidified metal, and by means of an electrode in the vessel containing the molten metal thereby providing a return path for the eddy currents induced in the metal sheet by the AC coil generated magnetic flux. Variation in the geometry of the conducting shield allows the magnetic flux between the metal sheet and the conducting shield to be varied and the thickness in surface quality of the metal sheet to be controlled. Side guards provide lateral containment for the molten metal sheet and stabilize and shape the magnetic field while a leader sheet having electromagnetic characteristics similar to those of the metal sheet is used to start the casting process and precedes the molten metal sheet through the magnet and forms a continuous sheet therewith. The magnet may be either U-shaped with a single racetrack coil or may be rectangular with a pair of facing bedstead coils.

Physics and our View of the World

NASA Astrophysics Data System (ADS)

Hilgevoord, Jan

1994-11-01

Foreword; 1. Introduction JAN HILGEVOORD; 2. Questioning the answers GERARD T. HOOFT; 3. Theories of everything JOHN BARROW; 4. The scientific view of the world DENNIS DIEKS; 5. Enlarging the world ERNAN McMULLIN; 6. The world of empiricism BAS VAN FRAASSEN; 7. Has the scientific view of the world a special status compared with other views? PAUL FEYERABEND; 8. Quantum theory and our view of the world PAUL FEYERABEND; 9. Interpretation of science - science as interpretation BAS VAN FRAASSEN; 10. Problems in debates about physics and religion WILLEM DREES; 11. The mind of God PAUL DAVIES; 12. The sources of models for God: metaphysics or metaphor? MARY HESSE; 13. Discussion.
Collisionless reconnection in a quasi-neutral sheet near marginal stability

NASA Technical Reports Server (NTRS)

Pritchett, P. L.; Coroniti, F. V.; Pellat, R.; Karimabadi, H.

1989-01-01

Particle simulations are used to investigate the process of collisionless reconnection in a magnetotail configuration which includes a pressure gradient along the tail axis and tail flaring. In the absence of electron stabilization effects, the tearing mode is stabilized when the ion gyrofrequency in the normal field exceeds the growth rate in the corresponding one-dimensional current sheet. The presence of a low-frequency electromagnetic perturbation in the lobes can serve to destabilize a marginally stable current sheet by producing an extended neutral-sheet region which can then undergo reconnection. These results help to explain how X-type neutral lines, such as those associated with the onset of magnetospheric substorms, can be formed in the near-earth plasma sheet.
A Transient Initialization Routine of the Community Ice Sheet Model for the Greenland Ice Sheet

NASA Astrophysics Data System (ADS)

van der Laan, Larissa; van den Broeke, Michiel; Noël, Brice; van de Wal, Roderik

2017-04-01

The Community Ice Sheet Model (CISM) is to be applied in future simulations of the Greenland Ice Sheet under a range of climate change scenarios, determining the sensitivity of the ice sheet to individual climatic forcings. In order to achieve reliable results regarding ice sheet stability and assess the probability of future occurrence of tipping points, a realistic initial ice sheet geometry is essential. The current work describes and evaluates the development of a transient initialization routine, using NGRIP 18O isotope data to create a temperature anomaly field. Based on the latter, surface mass balance components runoff and precipitation are perturbed for the past 125k years. The precipitation and runoff fields originate from a downscaled 1 km resolution version of the regional climate model RACMO2.3 for the period 1961-1990. The result of the initialization routine is a present-day ice sheet with a transient memory of the last glacial-interglacial cycle, which will serve as the future runs' initial condition.
Basic in vitro experiment on the adhesive effects of sheet-type hemostatic agents used in combination with a liquid fibrin sealant.

PubMed

Ishii, Keiichi; Kawashima, Hideki; Hayama, Takuma; Mayabashira, Sumika; Oka, Shiro; Sugimoto, Toshikado

2011-11-01

Various hemostatic agents have been used quite effectively for hemostasis, as well as for providing effective adhesion during laparoscopic partial nephrectomies. In this study, we investigated the adhesiveness to the renal tissue of some sheet-type hemostatic agents used in combination with a liquid fibrin sealant. In Experiment A, component solutions of the fibrin glue (liquid fibrin sealant) were dripped onto a kite string placed annularly on a porcine kidney slice. Then, one of the sheet-type hemostats--namely, the collagen, gelatin, or cellulose hemostat--was placed on the slices, and a string scale was used to measure the force needed to pull the string apart vertically from the kidney slice. Twelve slices were used for each group, and the weight data were analyzed statistically. The tissue adhering to each sheet-type hemostatic agent was fixed in formalin and sliced and then examined by light microscopy after hematoxylin and eosin staining. In Experiment B, the solutions were dripped onto the sheet-type hemostatic agent placed first on the slice, and the force needed for pulling apart the hemostat sheet from the slice was similarly examined. The combination of fibrin glue plus a collagen hemostat was clearly superior in Experiment A, but the hemostat and renal tissue could be pulled apart more easily in Experiment B. These results showed that fibrin glue could not exert its expected adhesive effect unless it is used in combination with another hemostatic agent or is directly applied to renal tissue. It is important to obtain further comparative data among agents and select the appropriate agents, taking into consideration the type of surgery.
THE LANGUAGE LABORATORY--WORK SHEET.

ERIC Educational Resources Information Center

CROSBIE, KEITH

DESIGNED FOR TEACHERS AND ADMINISTRATORS, THIS WORK SHEET PROVIDES GENERAL AND SPECIFIC INFORMATION ABOUT THE PHILOSOPHY, TYPES, AND USES OF LANGUAGE LABORATORIES IN SECONDARY SCHOOL LANGUAGE PROGRAMS. THE FIRST SECTION DISCUSSES THE ADVANTAGES OF USING THE LABORATORY EFFECTIVELY TO REINFORCE AND CONSOLIDATE CLASSROOM LEARNING, AND MENTIONS SOME…
Wave-induced drift of large floating sheets

NASA Astrophysics Data System (ADS)

Christensen, K. H.; Weber, J. E.

In this article we study the wave-induced drift of large, flexible shallow floating objects, referred to as sheets. When surface waves propagate through a sheet, they provide a mean stress on the sheet, resulting in a mean drift. In response, the sheet generates an Ekman current. The drift velocity of the sheet is determined by (i) the wave-induced stress, (ii) the viscous stress due to the Ekman current, and (iii) the Coriolis force. The sheet velocity and the current beneath the sheet are determined for constant and depth-varying eddy viscosities.
Coding Instructions, Worksheets, and Keypunch Sheets for M.E.T.R.O.-APEX Simulation.

ERIC Educational Resources Information Center

Michigan Univ., Ann Arbor. Environmental Simulation Lab.

Compiled in this resource are coding instructions, worksheets, and keypunch sheets for use in the M.E.T.R.O.-APEX simulation, described in detail in documents ED 064 530 through ED 064 550. Air Pollution Exercise (APEX) is a computerized college and professional level "real world" simulation of a community with urban and rural problems, industrial…
46 CFR 232.4 - Balance sheet accounts.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 8 2010-10-01 2010-10-01 false Balance sheet accounts. 232.4 Section 232.4 Shipping... ACTIVITIES UNIFORM FINANCIAL REPORTING REQUIREMENTS Balance Sheet § 232.4 Balance sheet accounts. (a.... (b) Purpose of balance sheet accounts. The balance sheet accounts are intended to disclose the...
46 CFR 232.4 - Balance sheet accounts.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 8 2011-10-01 2011-10-01 false Balance sheet accounts. 232.4 Section 232.4 Shipping... ACTIVITIES UNIFORM FINANCIAL REPORTING REQUIREMENTS Balance Sheet § 232.4 Balance sheet accounts. (a.... (b) Purpose of balance sheet accounts. The balance sheet accounts are intended to disclose the...
Skill Sheets for Agricultural Mechanics.

ERIC Educational Resources Information Center

Iowa State Univ. of Science and Technology, Ames. Dept. of Agricultural Education.

This set of 33 skill sheets for agricultural mechanics was developed for use in high school and vocational school agricultural mechanics programs. Some sheets teach operational procedures while others are for simple projects. Each skill sheet covers a single topic and includes: (1) a diagram, (2) a step-by-step construction or operational…
Surface melt effects on Cryosat-2 elevation retrievals in the ablation zone of the Greenland ice sheet

NASA Astrophysics Data System (ADS)

Slater, T.; McMillan, M.; Shepherd, A.; Leeson, A.; Cornford, S. L.; Hogg, A.; Gilbert, L.; Muir, A. S.; Briggs, K.

2017-12-01

Over the past two decades, there has been an acceleration in the rate of mass losses from the Greenland ice sheet. This acceleration is, in part, attributed to an increasingly negative surface mass balance (SMB), linked to increasing melt water runoff rates due to enhanced surface melting. Understanding the past, present and future evolution in surface melting is central to ongoing monitoring of ice sheet mass balance and, in turn, to building realistic future projections. Currently, regional climate models are commonly used for this purpose, because direct in-situ observations are spatially and temporally sparse due to the logistics and resources required to collect such data. In particular, modelled SMB is used to estimate the extent and magnitude of surface melting, which influences (1) many geodetic mass balance estimates, and (2) snowpack microwave scattering properties. The latter is poorly understood and introduces uncertainty into radar altimeter estimates of ice sheet evolution. Here, we investigate the changes in CryoSat-2 waveforms and elevation measurements caused by the onset of surface melt in the summer months over the ablation zone of the Greenland ice sheet. Specifically, we use CryoSat-2 SARIn mode data acquired between 2011 and 2016, to characterise the effect of high variability in surface melt during this period, and to assess the associated impact on estimates of ice mass balance.
Airy acoustical-sheet spinner tweezers

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2016-09-01

The Airy acoustical beam exhibits parabolic propagation and spatial acceleration, meaning that the propagation bending angle continuously increases before the beam trajectory reaches a critical angle where it decays after a propagation distance, without applying any external bending force. As such, it is of particular importance to investigate its properties from the standpoint of acoustical radiation force, spin torque, and particle dynamics theories, in the development of novel particle sorting techniques and acoustically mediated clearing systems. This work investigates these effects on a two-dimensional (2D) circular absorptive structure placed in the field of a nonparaxial Airy "acoustical-sheet" (i.e., finite beam in 2D), for potential applications in surface acoustic waves and acousto-fluidics. Based on the characteristics of the acoustic field, the beam is capable of manipulating the circular cylindrical fluid cross-section and guides it along a transverse or parabolic trajectory. This feature of Airy acoustical beams could lead to a unique characteristic in single-beam acoustical tweezers related to acoustical sieving, filtering, and removal of particles and cells from a section of a small channel. The analysis developed here is based on the description of the nonparaxial Airy beam using the angular spectrum decomposition of plane waves in close association with the partial-wave series expansion method in cylindrical coordinates. The numerical results demonstrate the ability of the nonparaxial Airy acoustical-sheet beam to pull, propel, or accelerate a particle along a parabolic trajectory, in addition to particle confinement in the transverse direction of wave propagation. Negative or positive radiation force and spin torque causing rotation in the clockwise or the anticlockwise direction can occur depending on the nondimensional parameter ka (where k is the wavenumber and a is the radius) and the location of the cylinder in the beam. Applications in
Isometric immersions and self-similar buckling in elastic sheets.

NASA Astrophysics Data System (ADS)

Gemmer, John

The edges of torn elastic sheets and growing leaves often display hierarchical self-similar like buckling patterns. On the one hand, such complex, self similar patterns are usually associated with a competition between two distinct energy scales, e.g. elastic sheets with boundary conditions that preclude the possibility of relieving in plane strains, or at alloy-alloy interfaces between distinct crystal structures. On the other hand, within the non-Euclidean plate theory this complex morphology can be understood as low bending energy isometric immersions of hyperbolic Riemannian metrics. In particular, many growth patterns generate residual in-plane strains which can be entirely relieved by the sheet forming part of a surface of revolution or a helix. In this talk we will show that this complex morphology (i) arises from isometric immersions (ii) is driven by a competition between the two principal curvatures, rather than between bending and stretching. We identify the key role of branch-point (or monkey-saddle) singularities, in complex wrinkling patterns within the class of finite bending energy isometric immersions. Using these defects we will give an explicit construction of strain-free embeddings of hyperbolic surfaces that are fractal like and have lower elastic energy than their smooth counterparts US-Israel BSF Grant 2008432. NSF Grant DMS-0807501. NSF-RTG Grant DMS-1148284.
How might the North American ice sheet influence the northwestern Eurasian climate?

NASA Astrophysics Data System (ADS)

Beghin, P.; Charbit, S.; Dumas, C.; Kageyama, M.; Ritz, C.

2015-10-01

It is now widely acknowledged that past Northern Hemisphere ice sheets covering Canada and northern Europe at the Last Glacial Maximum (LGM) exerted a strong influence on climate by causing changes in atmospheric and oceanic circulations. In turn, these changes may have impacted the development of the ice sheets themselves through a combination of different feedback mechanisms. The present study is designed to investigate the potential impact of the North American ice sheet on the surface mass balance (SMB) of the Eurasian ice sheet driven by simulated changes in the past glacial atmospheric circulation. Using the LMDZ5 atmospheric circulation model, we carried out 12 experiments under constant LGM conditions for insolation, greenhouse gases and ocean. In these experiments, the Eurasian ice sheet is removed. The 12 experiments differ in the North American ice-sheet topography, ranging from a white and flat (present-day topography) ice sheet to a full-size LGM ice sheet. This experimental design allows the albedo and the topographic impacts of the North American ice sheet onto the climate to be disentangled. The results are compared to our baseline experiment where both the North American and the Eurasian ice sheets have been removed. In summer, the sole albedo effect of the American ice sheet modifies the pattern of planetary waves with respect to the no-ice-sheet case, resulting in a cooling of the northwestern Eurasian region. By contrast, the atmospheric circulation changes induced by the topography of the North American ice sheet lead to a strong decrease of this cooling. In winter, the Scandinavian and the Barents-Kara regions respond differently to the American ice-sheet albedo effect: in response to atmospheric circulation changes, Scandinavia becomes warmer and total precipitation is more abundant, whereas the Barents-Kara area becomes cooler with a decrease of convective processes, causing a decrease of total precipitation. The gradual increase of the
Sheet production apparatus for removing a crystalline sheet from the surface of a melt using gas jets located above and below the crystalline sheet

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

Kellerman, Peter L.; Thronson, Gregory D.

In one embodiment, a sheet production apparatus comprises a vessel configured to hold a melt of a material. A cooling plate is disposed proximate the melt and is configured to form a sheet of the material on the melt. A first gas jet is configured to direct a gas toward an edge of the vessel. A sheet of a material is translated horizontally on a surface of the melt and the sheet is removed from the melt. The first gas jet may be directed at the meniscus and may stabilize this meniscus or increase local pressure within the meniscus.
Transfer of fibroblast sheets cultured on thermoresponsive dishes with membranes.

PubMed

Kawecki, Marek; Kraut, Małgorzata; Klama-Baryła, Agnieszka; Łabuś, Wojciech; Kitala, Diana; Nowak, Mariusz; Glik, Justyna; Sieroń, Aleksander L; Utrata-Wesołek, Alicja; Trzebicka, Barbara; Dworak, Andrzej; Szweda, Dawid

2016-06-01

In cell or tissue engineering, it is essential to develop a support for cell-to-cell adhesion, which leads to the generation of cell sheets connected by extracellular matrix. Such supports must be hydrophobic and should result in a detachable cell sheet. A thermoresponsive support that enables the cultured cell sheet to detach using only a change in temperature could be an interesting alternative in regenerative medicine. The aim of this study was to evaluate plates covered with thermoresponsive polymers as supports for the formation of fibroblast sheets and to develop a damage-free procedure for cell sheet transfer with the use of membranes as transfer tools. Human skin fibroblasts were seeded on supports coated with a thermoresponsive polymer: commercial UpCell™ dishes (NUNC™) coated with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and dishes coated with thermoresponsive poly(tri(ethylene glycol) monoethyl ether methacrylate) (P(TEGMA-EE)). Confluent fibroblast sheets were effectively cultured and harvested from both commercial PNIPAM-coated dishes and laboratory P(TEGMA-EE)-coated dishes. To transfer a detached cell sheet, two membranes, Immobilon-P(®) and SUPRATHEL(®), were examined. The use of SUPRATHEL for relocating the cell sheets opens a new possibility for the clinical treatment of wounds. This study established the background for implementing thermoresponsive supports for transplanting in vitro cultured fibroblasts.
Endogenous Sheet-Averaged Tension Within a Large Epithelial Cell Colony.

PubMed

Dumbali, Sandeep P; Mei, Lanju; Qian, Shizhi; Maruthamuthu, Venkat

2017-10-01

Epithelial cells form quasi-two-dimensional sheets that function as contractile media to effect tissue shape changes during development and homeostasis. Endogenously generated intrasheet tension is a driver of such changes, but has predominantly been measured in the presence of directional migration. The nature of epithelial cell-generated forces transmitted over supracellular distances, in the absence of directional migration, is thus largely unclear. In this report, we consider large epithelial cell colonies which are archetypical multicell collectives with extensive cell-cell contacts but with a symmetric (circular) boundary. Using the traction force imbalance method (TFIM) (traction force microscopy combined with physical force balance), we first show that one can determine the colony-level endogenous sheet forces exerted at the midline by one half of the colony on the other half with no prior assumptions on the uniformity of the mechanical properties of the cell sheet. Importantly, we find that this colony-level sheet force exhibits large variations with orientation-the difference between the maximum and minimum sheet force is comparable to the average sheet force itself. Furthermore, the sheet force at the colony midline is largely tensile but the shear component exhibits significantly more variation with orientation. We thus show that even an unperturbed epithelial colony with a symmetric boundary shows significant directional variation in the endogenous sheet tension and shear forces that subsist at the colony level.
Effect of Time Dependent Bending of Current Sheets in Response to Generation of Plasma Jets and Reverse Currents

NASA Astrophysics Data System (ADS)

Frank, Anna

Magnetic reconnection is a basis for many impulsive phenomena in space and laboratory plasmas accompanied by effective transformation of magnetic energy. Reconnection processes usually occur in relatively thin current sheets (CSs), which separate magnetic fields of different or opposite directions. We report on recent observations of time dependent bending of CSs, which results from plasma dynamics inside the sheet. The experiments are carried out with the CS-3D laboratory device (Institute of General Physics RAS, Moscow) [1]. The CS magnetic structure with an X line provides excitation of the Hall currents and plasma acceleration from the X line to both side edges [2]. In the presence of the guide field By the Hall currents give rise to bending of the sheet: the peripheral regions located away from the X line are deflected from CS middle plane (z=0) in the opposite directions ±z [3]. We have revealed generation of reverse currents jy near the CS edges, i.e. the currents flowing in the opposite direction to the main current in the sheet [4]. There are strong grounds to believe that reverse currents are generated by the outflow plasma jets [5], accelerated inside the sheet and penetrated into the regions with strong normal magnetic field component Bz [4]. An impressive effect of sudden change in the sign of the CS bend has been disclosed recently, when analyzing distributions of plasma density [6] and current away from the X line, in the presence of the guide field By. The CS configuration suddenly becomes opposite from that observed at the initial stage, and this effect correlates well with generation of reverse currents. Consequently this effect can be related to excitation of the reverse Hall currents owing to generation of reverse currents jy in the CS. Hence it may be concluded that CSs may exhibit time dependent vertical z-displacements, and the sheet geometry depends on excitation of the Hall currents, acceleration of plasma jets and generation of reverse
Modification of β-Sheet Forming Peptide Hydrophobic Face: Effect on Self-Assembly and Gelation

PubMed Central

2016-01-01

β-Sheet forming peptides have attracted significant interest for the design of hydrogels for biomedical applications. One of the main challenges is the control and understanding of the correlations between peptide molecular structure, the morphology, and topology of the fiber and network formed as well as the macroscopic properties of the hydrogel obtained. In this work, we have investigated the effect that functionalizing these peptides through their hydrophobic face has on their self-assembly and gelation. Our results show that the modification of the hydrophobic face results in a partial loss of the extended β-sheet conformation of the peptide and a significant change in fiber morphology from straight to kinked. As a consequence, the ability of these fibers to associate along their length and form large bundles is reduced. These structural changes (fiber structure and network topology) significantly affect the mechanical properties of the hydrogels (shear modulus and elasticity). PMID:27089379
Effectiveness of Collaborative Learning with 3D Virtual Worlds

ERIC Educational Resources Information Center

Cho, Young Hoan; Lim, Kenneth Y. T.

2017-01-01

Virtual worlds have affordances to enhance collaborative learning in authentic contexts. Despite the potential of collaborative learning with a virtual world, few studies investigated whether it is more effective in student achievements than teacher-directed instruction. This study investigated the effectiveness of collaborative problem solving…

Soft collinear effective theory for gravity

NASA Astrophysics Data System (ADS)

Okui, Takemichi; Yunesi, Arash

2018-03-01

We present how to construct a soft collinear effective theory (SCET) for gravity at the leading and next-to-leading powers from the ground up. The soft graviton theorem and decoupling of collinear gravitons at the leading power are manifest from the outset in the effective symmetries of the theory. At the next-to-leading power, certain simple structures of amplitudes, which are completely obscure in Feynman diagrams of the full theory, are also revealed, which greatly simplifies calculations. The effective Lagrangian is highly constrained by effectively multiple copies of diffeomorphism invariance that are inevitably present in gravity SCET due to mode separation, an essential ingredient of any SCET. Further explorations of effective theories of gravity with mode separation may shed light on Lagrangian-level understandings of some of the surprising properties of gravitational scattering amplitudes. A gravity SCET with an appropriate inclusion of Glauber modes may serve as a powerful tool for studying gravitational scattering in the Regge limit.
Heat treatment effect on the electronic and magnetic structures of nanographene sheets investigated through electron spectroscopy and conductance measurements.

PubMed

Takashiro, Jun-ichi; Kudo, Yasuhiko; Kaneko, Satoshi; Takai, Kazuyuki; Ishii, Takafumi; Kyotani, Takashi; Enoki, Toshiaki; Kiguchi, Manabu

2014-04-28

The heat treatment effect on the electronic and magnetic structures of a disordered network of nanographene sheets has been investigated by in situ measurements of X-ray photoemission spectroscopy, near-edge X-ray absorption fine structure (NEXAFS), and electrical conductance, together with temperature-programmed desorption measurements. Oxygen-containing functional groups bonded to nanographene edges in the pristine sample are almost completely decomposed under heat treatment up to 1300-1500 K, resulting in the formation of edges primarily terminated by hydrogen. The removal of the oxygen-containing groups enhances the conductance owing to the decrease in the electron transport barriers between nanographene sheets. Heat treatment above 1500 K removes also the hydrogen atoms from the edges, promoting the successive fusion of nanographene sheets at the expense of edges. The decrease in the π* peak width in NEXAFS indicates the progress of the fusion reaction, that is, the extension of the π-conjugation, which agrees with the increase in the orbital susceptibility previously reported. The fusion leads to the formation of local π/sp(2) bridges between nanographene sheets and brings about an insulator-to-metal transition at 1500-1600 K, at which the bridge network becomes infinite. As for the magnetism, the intensity of the edge state peak in NEXAFS, which corresponds to the number of the spin-polarized edge states, decreases above 1500 K, though the effective edge-state spin density per edge state starts decreasing at approximately 200 K lower than the temperature of the edge state peak change. This disagreement indicates the development of antiferromagnetic short range ordering as a precursor of a spin glass state near the insulator-metal transition, at which the random network of inter-nanographene-sheet exchange interactions strengthened with the formation of the π/sp(2) bridges becomes infinite.
Ice-sheet thinning and acceleration at Camp Century, Greenlan

NASA Astrophysics Data System (ADS)

Colgan, W. T.

2017-12-01

Camp Century, Greenland (77.18 °N, 61.12 °W, 1900 m), is located approximately 150 km inland from the ice-sheet margin in Northwest Greenland. In-situ and remotely-sensed measurements of ice-sheet elevation at Camp Century exhibit a thinning trend between 1964 and the present. A comparison of 1966 and 2017 firn density profiles indicates that a portion of this ice-sheet thinning is attributable to increased firn compaction rate. In-situ measurements of increasing ice surface velocity over the 1977-2017 period indicate that enhanced horizontal divergence of ice flux is also contributing to ice dynamic thinning at Camp Century. This apparent ice dynamic thinning could potentially result from a migrating local flow divide or decreasing effective ice viscosity. In a shorter-term context, observations of decadal-scale ice-sheet thinning and acceleration at Camp Century highlights underappreciated transience in inland ice form and flow during the satellite era. In a longer-term context, these multi-decadal observations contrast with inferences of millennial-scale ice-sheet thickening and deceleration at Camp Century.
Fast imaging of live organisms with sculpted light sheets

NASA Astrophysics Data System (ADS)

Chmielewski, Aleksander K.; Kyrsting, Anders; Mahou, Pierre; Wayland, Matthew T.; Muresan, Leila; Evers, Jan Felix; Kaminski, Clemens F.

2015-04-01

Light-sheet microscopy is an increasingly popular technique in the life sciences due to its fast 3D imaging capability of fluorescent samples with low photo toxicity compared to confocal methods. In this work we present a new, fast, flexible and simple to implement method to optimize the illumination light-sheet to the requirement at hand. A telescope composed of two electrically tuneable lenses enables us to define thickness and position of the light-sheet independently but accurately within milliseconds, and therefore optimize image quality of the features of interest interactively. We demonstrated the practical benefit of this technique by 1) assembling large field of views from tiled single exposure each with individually optimized illumination settings; 2) sculpting the light-sheet to trace complex sample shapes within single exposures. This technique proved compatible with confocal line scanning detection, further improving image contrast and resolution. Finally, we determined the effect of light-sheet optimization in the context of scattering tissue, devising procedures for balancing image quality, field of view and acquisition speed.
Learning from Balance Sheet Visualization

ERIC Educational Resources Information Center

Tanlamai, Uthai; Soongswang, Oranuj

2011-01-01

This exploratory study examines alternative visuals and their effect on the level of learning of balance sheet users. Executive and regular classes of graduate students majoring in information technology in business were asked to evaluate the extent of acceptance and enhanced capability of these alternative visuals toward their learning…
Is ``the Theory of Everything'' Merely the Ultimate Ensemble Theory?

NASA Astrophysics Data System (ADS)

Tegmark, Max

1998-11-01

We discuss some physical consequences of what might be called "the ultimate ensemble theory,", where not only worlds corresponding to say different sets of initial data or different physical constants are considered equally real, but also worlds ruled by altogether different equations. The only postulate in this theory is that all structures that exist mathematically exist also physically, by which we mean that in those complex enough to contain self-aware substructures (SASs), these SASs will subjectively perceive themselves as existing in a physically "real" world. We find that it is far from clear that this simple theory, which has no free parameters whatsoever, is observationally ruled out. The predictions of the theory take the form of probability distributions for the outcome of experiments, which makes it testable. In addition, it may be possible to rule it out by comparing its a priori predictions for the observable attributes of nature (the particle masses, the dimensionality of spacetime, etc.) with what is observed.
Critical string from non-Abelian vortex in four dimensions

DOE PAGES

Shifman, M.; Yung, A.

2015-09-25

In a class of non-Abelian solitonic vortex strings supported in certain N = 2 super-Yang–Mills theories we search for the vortex which can behave as a critical fundamental string. We use the Polchinski–Strominger criterion of the ultraviolet completeness. We identify an appropriate four-dimensional bulk theory: it has the U(2) gauge group, the Fayet–Iliopoulos term and four flavor hypermultiplets. It supports semilocal vortices with the world-sheet theory for orientational (size) moduli described by the weighted CP(2,2) model. The latter is superconformal. Its target space is six-dimensional. The overall Virasoro central charge is critical. Lastly, we show that the world-sheet theory onmore » the vortex supported in this bulk model is the bona fide critical string.« less
The Physics of Ice Sheets

ERIC Educational Resources Information Center

Bassis, J. N.

2008-01-01

The great ice sheets in Antarctica and Greenland are vast deposits of frozen freshwater that contain enough to raise sea level by approximately 70 m if they were to completely melt. Because of the potentially catastrophic impact that ice sheets can have, it is important that we understand how ice sheets have responded to past climate changes and…
How effective is albedo modification (solar radiation management geoengineering) in preventing sea-level rise from the Greenland Ice Sheet?

NASA Astrophysics Data System (ADS)

Applegate, Patrick J.; Keller, Klaus

2015-08-01

Albedo modification (AM) is sometimes characterized as a potential means of avoiding climate threshold responses, including large-scale ice sheet mass loss. Previous work has investigated the effects of AM on total sea-level rise over the present century, as well as AM’s ability to reduce long-term (≫103 yr) contributions to sea-level rise from the Greenland Ice Sheet (GIS). These studies have broken new ground, but neglect important feedbacks in the GIS system, or are silent on AM’s effectiveness over the short time scales that may be most relevant for decision-making (<103 yr). Here, we assess AM’s ability to reduce GIS sea-level contributions over decades to centuries, using a simplified ice sheet model. We drive this model using a business-as-usual base temperature forcing scenario, as well as scenarios that reflect AM-induced temperature stabilization or temperature drawdown. Our model results suggest that (i) AM produces substantial near-term reductions in the rate of GIS-driven sea-level rise. However, (ii) sea-level rise contributions from the GIS continue after AM begins. These continued sea level rise contributions persist for decades to centuries after temperature stabilization and temperature drawdown begin, unless AM begins in the next few decades. Moreover, (iii) any regrowth of the GIS is delayed by decades or centuries after temperature drawdown begins, and is slow compared to pre-AM rates of mass loss. Combined with recent work that suggests AM would not prevent mass loss from the West Antarctic Ice Sheet, our results provide a nuanced picture of AM’s possible effects on future sea-level rise.
Moulin Migration and Development on the Greenland Ice Sheet

NASA Astrophysics Data System (ADS)

Chu, V. W.; Yang, L.

2017-12-01

Extensive river networks that terminate into moulins efficiently drain the surface of the Greenland ice sheet. These river moulins connect surface meltwater to englacial and subglacial drainage networks, where increased meltwater can enhance ice sliding dynamics. Previous moulin studies were limited to small geographic areas using field observations and/or high-resolution aerial/satellite imagery, or to medium-resolution satellite imagery for larger areas. In this study, high-resolution moulin maps created from WorldView-1/2/3 imagery near Russell Glacier in southwest Greenland show development of moulins and their migration between 2012 and 2015. Moulins are mapped and categorized as being located: in crevasse fields, along a single ice fracture, within drained lake basins, or having no visible formation mechanism. A majority of moulins mapped in 2015 (73%) are linked to moulins in 2012 and are analysed for their movement patterns and compared to ice velocity and strain rates. New moulins most commonly form in crevassed, thinner ice near the ice sheet edge, but significant quantities also develop at higher elevations (22% above 1300 m elevation).
Determining Beta Sheet Crystallinity in Fibrous Proteins by Thermal Analysis and Infrared Spectroscopy

NASA Astrophysics Data System (ADS)

Hu, Xiao; Kaplan, David; Cebe, Peggy

2007-03-01

We report a study of self-assembled beta pleated sheets in Bombyx mori silk fibroin films using thermal analysis and infrared spectroscopy. Crystallization of beta pleated sheets was effected either by heating the films above the glass transition temperature (Tg) and holding isothermally, or by exposure to methanol. The fractions of secondary structural components including random coils, alpha helices, beta pleated sheets, turns, and side chains, were evaluated using Fourier self-deconvolution (FSD) of the infrared absorbance spectra. As crystalline beta sheets form, the heat capacity increment from the TMDSC trace at Tg is systematically decreased and is linearly well correlated with beta sheet content determined from FSD. This analysis of beta sheet content can serve as an alternative to X-ray methods and may have wide applicability to other crystalline beta sheet forming proteins.
The mechanical behavior of cross-rolled beryllium sheet

NASA Technical Reports Server (NTRS)

Henkener, J. A.; Spiker, I. K.; Castner, W. L.

1992-01-01

In response to the failure of a conical section of the Insat C satellite during certification testing, the use of beryllium for payload structures, particularly in sheet product form, is being reevaluated. A test program was initiated to study the tensile, shear, and out-of-plane failure modes of beryllium cross-rolled sheet and to apply data to the development of an appropriate failure criterion. Tensile test results indicated that sanding the surface of beryllium sheet has no significant effect on yield strength but can produce a profound reduction in ultimate strength and results obtained by finite element analysis. Critical examination of these test results may contribute to the modification of a JSC policy for the use of beryllium in orbiter and payload structures.
Current status of solar cell performance of unconventional silicon sheets

NASA Technical Reports Server (NTRS)

Yoo, H. I.; Liu, J. K.

1981-01-01

It is pointed out that activities in recent years directed towards reduction in the cost of silicon solar cells for terrestrial photovoltaic applications have resulted in impressive advancements in the area of silicon sheet formation from melt. The techniques used in the process of sheet formation can be divided into two general categories. All approaches in one category require subsequent ingot wavering. The various procedures of the second category produce silicon in sheet form. The performance of baseline solar cells is discussed. The baseline process included identification marking, slicing to size, and surface treatment (etch-polishing) when needed. Attention is also given to the performance of cells with process variations, and the effects of sheet quality on performance and processing.
Scaling results for the liquid sheet radiator

NASA Technical Reports Server (NTRS)

Chubb, Donald L.; Calfo, Frederick D.

1989-01-01

Surface tension forces at the edges of a thin liquid (approx 100 micrometers) sheet flow result in a triangularly shaped sheet. Such a geometry is ideal for an external flow radiator. The experimental investigation of such sheet flows was extended to large sheets (width = 23.5 cm, length = 3.5 m). Experimental L/W results are greater than the calculated results. However, more experimental results are necessary for a complete comparison. The calculated emissivity of a sheet of Dow-Corning 705 silicone oil, which is low temperature (300-400 K) candidate for a liquid sheet radiator (LSR), is greater than 0.8 for sheet thicknesses greater than 100 micrometers.
Characteristics of the aluminum alloy sheets for forming and application examples

NASA Astrophysics Data System (ADS)

Uema, Naoyuki; Asano, Mineo

2013-12-01

In this paper, the characteristics and application examples of aluminum alloy sheets developed for automotive parts by Sumitomo Light Metal are described. For the automotive closure panels (ex., hood, back-door), an Al-Mg-Si alloy sheet having an excellent hemming performance was developed. The cause of the occurrence and the propagation of cracks by bending were considered to be the combined effect of the shear bands formed across several crystal grains and the micro-voids formed around the second phase particles. By reducing the shear band formation during bending by controlling the crystallographic texture, the Al-Mg-Si alloy sheets showed an excellent hemming performance. For the automotive outer panels (ex., roof, fender, trunk-lid), an Al-Mg alloy sheet, which has both a good hot blow formability and excellent surface appearance after hot blow forming was developed, and hot blow forming technology was put to practical use using this developed Al-Mg alloy sheet. For automotive heat insulators, a high ductile Al-Fe alloy sheet was developed. The heat insulator, which integrated several panels, was put into practical use using this developed Al-Fe alloy sheet. The textured sheet was often used as a heat insulator in order to reduce the thickness of the aluminum alloy sheet and obtain good press formability. The new textured sheet, which has both high rigidity and good press formability for heat insulators, was developed by FE analysis.
Two Eclipses, a Theory, and a World War

NASA Astrophysics Data System (ADS)

Batten, Alan H.

2015-01-01

Both the beginning and ending of World War I were signalled by total solar eclipses at which attempts were made to measure the deflection, predicted by Albert Einstein, of starlight passing close to the Sun. An American team led by W. W. Campbell and a German team led by E. F. Freundlich travelled to Russia to observe the eclipse of 1914 August 21. The Americans were foiled by the weather, and the Germans were interned as enemy aliens, so no successful measurements were made. British astronomers, led by A. S. Eddington, mounted two expeditions to observe the eclipse of 1919 May 29, one to Brazil, the other, with Eddington personally in charge, to an island off the west coast of Africa. The results, presented with much fanfare, appeared to constitute a spectacular confirmation of general relativity, although much debate surrounded the observations and their interpretation in later decades. The stories of Freundlich and Eddington intertwine not only with controversial questions about how best to make and to reduce the observations, but also with attitudes toward the war, notably the extreme anti-German sentiment that pervaded the countries of the western alliance, contrasted with the Quaker pacifism of Eddington himself; and also with differing attitudes to relativity among European and American astronomers. Eddington later played a role in bringing Freundlich to the United Kingdom after the rise of Hitler and the Nazis. Ironically, in later life, Freundlich became increasingly sceptical of general relativity and proposed a theory of proton-proton interaction to account for the cosmological red-shifts.
Flexible Structural-Health-Monitoring Sheets

NASA Technical Reports Server (NTRS)

Qing, Xinlin; Kuo, Fuo

2008-01-01

A generic design for a type of flexible structural-health-monitoring sheet with multiple sensor/actuator types and a method of manufacturing such sheets has been developed. A sheet of this type contains an array of sensing and/or actuation elements, associated wires, and any other associated circuit elements incorporated into various flexible layers on a thin, flexible substrate. The sheet can be affixed to a structure so that the array of sensing and/or actuation elements can be used to analyze the structure in accordance with structural-health-monitoring techniques. Alternatively, the sheet can be designed to be incorporated into the body of the structure, especially if the structure is made of a composite material. Customarily, structural-health monitoring is accomplished by use of sensors and actuators arrayed at various locations on a structure. In contrast, a sheet of the present type can contain an entire sensor/actuator array, making it unnecessary to install each sensor and actuator individually on or in a structure. Sensors of different types such as piezoelectric and fiber-optic can be embedded in the sheet to form a hybrid sensor network. Similarly, the traces for electric communication can be deposited on one or two layers as required, and an entirely separate layer can be employed to shield the sensor elements and traces.
Enhanced ice sheet melting driven by volcanic eruptions during the last deglaciation.

PubMed

Muschitiello, Francesco; Pausata, Francesco S R; Lea, James M; Mair, Douglas W F; Wohlfarth, Barbara

2017-10-24

Volcanic eruptions can impact the mass balance of ice sheets through changes in climate and the radiative properties of the ice. Yet, empirical evidence highlighting the sensitivity of ancient ice sheets to volcanism is scarce. Here we present an exceptionally well-dated annual glacial varve chronology recording the melting history of the Fennoscandian Ice Sheet at the end of the last deglaciation (∼13,200-12,000 years ago). Our data indicate that abrupt ice melting events coincide with volcanogenic aerosol emissions recorded in Greenland ice cores. We suggest that enhanced ice sheet runoff is primarily associated with albedo effects due to deposition of ash sourced from high-latitude volcanic eruptions. Climate and snowpack mass-balance simulations show evidence for enhanced ice sheet runoff under volcanically forced conditions despite atmospheric cooling. The sensitivity of past ice sheets to volcanic ashfall highlights the need for an accurate coupling between atmosphere and ice sheet components in climate models.
Sketching Designs Using the Five Design-Sheet Methodology.

PubMed

Roberts, Jonathan C; Headleand, Chris; Ritsos, Panagiotis D

2016-01-01

Sketching designs has been shown to be a useful way of planning and considering alternative solutions. The use of lo-fidelity prototyping, especially paper-based sketching, can save time, money and converge to better solutions more quickly. However, this design process is often viewed to be too informal. Consequently users do not know how to manage their thoughts and ideas (to first think divergently, to then finally converge on a suitable solution). We present the Five Design Sheet (FdS) methodology. The methodology enables users to create information visualization interfaces through lo-fidelity methods. Users sketch and plan their ideas, helping them express different possibilities, think through these ideas to consider their potential effectiveness as solutions to the task (sheet 1); they create three principle designs (sheets 2,3 and 4); before converging on a final realization design that can then be implemented (sheet 5). In this article, we present (i) a review of the use of sketching as a planning method for visualization and the benefits of sketching, (ii) a detailed description of the Five Design Sheet (FdS) methodology, and (iii) an evaluation of the FdS using the System Usability Scale, along with a case-study of its use in industry and experience of its use in teaching.
A panel method study of vortex sheets with special emphasis on sheets of axisymmetric geometry. M.S. Thesis

NASA Technical Reports Server (NTRS)

Sugioka, I.; Widnall, S. E.

1985-01-01

The self induced evolution of a vortex sheet was simulated by modeling the sheet using an integration of discrete elements of vorticity. Replacing small sections of a vortex sheet by flat panels of constant vorticity is found to reproduce more accurately the initial conditions for the Lagrangian simulation technique than replacement by point vortices. The flat panel method for the vortex sheet was then extended to model axisymmetric vortex sheets. The local and far field velocities induced by the axisymmetric panels were obtained using matched asymptotic analysis, and some of the uncertainties involved in other models of the axisymmetric vortex sheet have been eliminated. One important result of this analysis is the determination of the proper choice of core size for a circular vortex filament which may replace a section of an axisymmetric vortex sheet. Roll-up of both two dimensional and axisymmetric vortex sheets was computed using the panel methods developed in the report.

Ground-state Properties of Inhomogeneous Graphene Sheets

NASA Astrophysics Data System (ADS)

Polini, Marco

2009-03-01

When inter-valley scattering is weak and gauge fields due to e.g. ripples are neglected, doped and gated graphene sheets can be described using an envelope-function Hamiltonian with a new sublattice pseudospin degree-of freedom, an ultrarelativistic massless-Dirac free-fermion term, a pseudospin scalar disorder potential, and a non-relativistic instantaneous Coulombic interaction term. There is considerable evidence from experiment that this simplified description of a honeycomb lattice of Carbon atoms is usually a valid starting point for theories of those observables that depend solely on the electronic properties of π-electrons near the graphene Dirac point [1]. Although the use of this model simplifies the physics considerably it still leaves us with a many-body problem without translational invariance, which we do not know how to solve. In this talk we present a Kohn-Sham-Dirac density-functional-theory (DFT) scheme for graphene sheets that treats slowly-varying inhomogeneous scalar external potentials and electron-electron interactions on an equal footing [2]. The theory is able to account for the unusual property that the exchange-correlation contribution to chemical potential increases with carrier density in graphene [3,4]. Consequences of this property, and advantages and disadvantages of using the DFT approach to describe it, are discussed. The approach is illustrated by solving the Kohn-Sham-Dirac equations self-consistently for a model random potential describing charged point-like impurities located close to the graphene plane. The influence of electron-electron interactions on these non-linear screening calculations is discussed at length, in the light of recent experiments [5,6] reporting evidence for the presence of electron-hole puddles in nearly-neutral graphene sheets. [4pt] [1] A.K. Geim and K.S. Novoselov, Nature Mater. 6, 183 (2007); A.K. Geim and A.H. MacDonald, Phys. Today 60, 35 (2007); A.H. Castro Neto, F. Guinea, N.M.R. Peres, K
Ultrasonic superlensing jets and acoustic-fork sheets

NASA Astrophysics Data System (ADS)

Mitri, F. G.

2017-05-01

Focusing acoustical (and optical) beams beyond the diffraction limit has remained a major challenge in imaging instruments and systems, until recent advances on ;hyper; or ;super; lensing and higher-resolution imaging techniques have shown the counterintuitive violation of this rule under certain circumstances. Nonetheless, the proposed technologies of super-resolution acoustical focusing beyond the diffraction barrier require complex tools such as artificially engineered metamaterials, and other hardware equipment that may not be easily synthesized or manufactured. The present contribution therefore suggests a simple and reliable method of using a sound-penetrable circular cylinder lens illuminated by a nonparaxial Gaussian acoustical sheet (i.e. finite beam in 2D) to produce non-evanescent ultrasonic superlensing jets (or bullets) and acoustical 'snail-fork' shaped wavefronts with limited diffraction. The generalized (near-field) scattering theory for acoustical sheets of arbitrary wavefronts and incidence is utilized to synthesize the incident beam based upon the angular spectrum decomposition method and the multipole expansion method in cylindrical wave functions to compute the scattered pressure around the cylinder with particular emphasis on its physical properties. The results show that depending on the beam and lens parameters, a tight focusing (with dimensions much smaller than the beam waist) can be achieved. Subwavelength resolution can be also achieved by selecting a lens material with a speed of sound exceeding that of the host fluid medium. The ultrasonic superlensing jets provide the impetus to develop improved subwavelength microscopy and acoustical image-slicing systems, cell lysis and surgery, and photoacoustic imaging to name a few examples. Moreover, an acoustical fork-sheet generation may open innovative avenues in reconfigurable on-chip micro/nanoparticle tweezers and surface acoustic waves devices.
Chiral anomaly, Berry phase, and chiral kinetic theory from worldlines in quantum field theory

DOE PAGES

Mueller, Niklas; Venugopalan, Raju

2018-03-21

Here, we outline a novel chiral kinetic theory framework for systematic computations of the Chiral Magnetic Effect (CME) in ultrarelativistic heavy-ion collisions. The real part of the fermion determinant in the QCD effective action is expressed as a supersymmetric world-line action of spinning, colored, Grassmanian point particles in background gauge fields, with equations of motion that are covariant generalizations of the Bargmann-Michel-Telegdi and Wong equations. Berry’s phase is obtained in a consistent non-relativistic adiabatic limit. The chiral anomaly, in contrast, arises from the phase of the fermion determinant; its topological properties are therefore distinct from those of the Berry phase.more » We show that the imaginary contribution to the fermion determinant too can be expressed as a point particle world-line path integral and derive the corresponding anomalous axial vector current. Our results can be used to derive a covariant relativistic chiral kinetic theory including the effects of topological fluctuations that has overlap with classical-statistical simulations of the CME at early times and anomalous hydrodynamics at late times.« less
Chiral anomaly, Berry phase, and chiral kinetic theory from worldlines in quantum field theory

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

Mueller, Niklas; Venugopalan, Raju

Here, we outline a novel chiral kinetic theory framework for systematic computations of the Chiral Magnetic Effect (CME) in ultrarelativistic heavy-ion collisions. The real part of the fermion determinant in the QCD effective action is expressed as a supersymmetric world-line action of spinning, colored, Grassmanian point particles in background gauge fields, with equations of motion that are covariant generalizations of the Bargmann-Michel-Telegdi and Wong equations. Berry’s phase is obtained in a consistent non-relativistic adiabatic limit. The chiral anomaly, in contrast, arises from the phase of the fermion determinant; its topological properties are therefore distinct from those of the Berry phase.more » We show that the imaginary contribution to the fermion determinant too can be expressed as a point particle world-line path integral and derive the corresponding anomalous axial vector current. Our results can be used to derive a covariant relativistic chiral kinetic theory including the effects of topological fluctuations that has overlap with classical-statistical simulations of the CME at early times and anomalous hydrodynamics at late times.« less
The Effect of Solar Forcing on the Greenland Ice Sheet during the Holocene - A Model Study

NASA Astrophysics Data System (ADS)

Bügelmayer, Marianne; Roche, Didier; Renssen, Hans

2014-05-01

Abrupt climate changes did not only happen during glacials but also during interglacials such as the Holocene. Marine sediments provide evidence for the periodic occurrence of centennial-scale events with enhanced iceberg discharge during the past 11.000 years (Bond et al., 2001). These events were chronologically linked to reduced solar activity as reconstructed using cosmogenic isotopes (Bond et al., 2001), indicating that even an external forcing that is considered to be small, has a potential impact on climate due to several feedback mechanisms (Renssen et al., 2006). The interactions between climate and solar irradiance have been investigated using numerical models (e.g. Haigh, 1996; Renssen et al, 2006), but so far without dynamically computing the Greenland ice sheet and iceberg calving. Thus, the impact of solar variations on iceberg discharge and the underlying mechanisms have not been analysed so far. To analyse the effect of variations in solar activity on the Greenland ice sheet (GIS) and the iceberg calving, as well as possible feedback mechanisms that enhance the impact of the total solar irradiance, we use the earth system model of intermediate complexity (iLOVECLIM, Roche et al., 2013), coupled to the ice sheet/ice shelf model GRISLI (Ritz et al., 2001) and to a dynamic-thermodynamic iceberg module (Jongma et al., 2009, Bügelmayer et al., 2014) to perform transient experiments of the last 6000 years. The experiments are conducted applying reconstructed atmospheric greenhouse gas concentrations, volcanic aerosol loads, orbital parameters and variations in the total solar irradiance. We present the response of the coupled model to different solar irradiance scenarios to evaluate modeled GIS sensitivity to relatively modest variations in radiative forcing. Moreover, we investigate the dependence of the model results on the chosen model sensitivity. References: Bond, G., Kromer, B., Beer, J., Muscheler, R., Evans, M. N., Showers, W., … Bonani, G
Collisionless kinetic theory of oblique tearing instabilities

NASA Astrophysics Data System (ADS)

Baalrud, S. D.; Bhattacharjee, A.; Daughton, W.

2018-02-01

The linear dispersion relation for collisionless kinetic tearing instabilities is calculated for the Harris equilibrium. In contrast to the conventional 2D geometry, which considers only modes at the center of the current sheet, modes can span the current sheet in 3D. Modes at each resonant surface have a unique angle with respect to the guide field direction. Both kinetic simulations and numerical eigenmode solutions of the linearized Vlasov-Maxwell equations have recently revealed that standard analytic theories vastly overestimate the growth rate of oblique modes. We find that this stabilization is associated with the density-gradient-driven diamagnetic drift. The analytic theories miss this drift stabilization because the inner tearing layer broadens at oblique angles sufficiently far that the assumption of scale separation between the inner and outer regions of boundary-layer theory breaks down. The dispersion relation obtained by numerically solving a single second order differential equation is found to approximately capture the drift stabilization predicted by solutions of the full integro-differential eigenvalue problem. A simple analytic estimate for the stability criterion is provided.
Buckling and stretching of thin viscous sheets

NASA Astrophysics Data System (ADS)

O'Kiely, Doireann; Breward, Chris; Griffiths, Ian; Howell, Peter; Lange, Ulrich

2016-11-01

Thin glass sheets are used in smartphone, battery and semiconductor technology, and may be manufactured by producing a relatively thick glass slab and subsequently redrawing it to a required thickness. The resulting sheets commonly possess undesired centerline ripples and thick edges. We present a mathematical model in which a viscous sheet undergoes redraw in the direction of gravity, and show that, in a sufficiently strong gravitational field, buckling is driven by compression in a region near the bottom of the sheet, and limited by viscous resistance to stretching of the sheet. We use asymptotic analysis in the thin-sheet, low-Reynolds-number limit to determine the centerline profile and growth rate of such a viscous sheet.
Nitrotyrosine adsorption on defective graphene: A density functional theory study

NASA Astrophysics Data System (ADS)

Majidi, R.; Karami, A. R.

2015-06-01

We have applied density functional theory to study adsorption of nitrotyrosine on perfect and defective graphene sheets. The graphene sheets with Stone-Wales (SW) defect, pentagon-nonagon (5-9) single vacancy, and pentagon-octagon-pentagon (5-8-5) double vacancy were considered. The calculations of adsorption energy showed that nitrotyrosine presents a more strong interaction with defective graphene rather than with perfect graphene sheet. The order of interaction strength is: SW>5-9>5-8-5>perfect graphene. It is found that the electronic properties of perfect and defective graphene are sensitive to the presence of nitrotyrosine. Hence, graphene sheets can be considered as a good sensor for detection of nitrotyrosine molecule which is observed in connection with several human disorders, such as Parkinson's and Alzheimer's disease.
Kaluza-Klein two-brane-worlds cosmology at low energy

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

Feranie, S.; Arianto; Zen, Freddy P.

2010-04-15

We study two (4+n)-dimensional branes embedded in (5+n)-dimensional spacetime. Using the gradient expansion approximation, we find that the effective theory is described by (4+n)-dimensional scalar-tensor gravity with a specific coupling function. Based on this theory we investigate the Kaluza-Klein two-brane-worlds cosmology at low energy, in both the static and the nonstatic internal dimensions. In the case of the static internal dimensions, the effective gravitational constant in the induced Friedmann equation depends on the equations of state of the brane matter, and the dark radiation term naturally appears. In the nonstatic case we take a relation between the external and internalmore » scale factors of the form b(t)=a{sup {gamma}(t)} in which the brane world evolves with two scale factors. In this case, the induced Friedmann equation on the brane is modified in the effective gravitational constant and the term proportional to a{sup -4{beta}.} For dark radiation, we find {gamma}=-2/(1+n). Finally, we discuss the issue of conformal frames which naturally arises with scalar-tensor theories. We find that the static internal dimensions in the Jordan frame may become nonstatic in the Einstein frame.« less
Computer-Aided Light Sheet Flow Visualization

NASA Technical Reports Server (NTRS)

Stacy, Kathryn; Severance, Kurt; Childers, Brooks A.

1993-01-01

A computer-aided flow visualization process has been developed to analyze video images acquired from rotating and translating light sheet visualization systems. The computer process integrates a mathematical model for image reconstruction, advanced computer graphics concepts, and digital image processing to provide a quantitative and visual analysis capability. The image reconstruction model, based on photogrammetry, uses knowledge of the camera and light sheet locations and orientations to project two-dimensional light sheet video images into three-dimensional space. A sophisticated computer visualization package, commonly used to analyze computational fluid dynamics (CFD) data sets, was chosen to interactively display the reconstructed light sheet images, along with the numerical surface geometry for the model or aircraft under study. A description is provided of the photogrammetric reconstruction technique, and the image processing and computer graphics techniques and equipment. Results of the computer aided process applied to both a wind tunnel translating light sheet experiment and an in-flight rotating light sheet experiment are presented. The capability to compare reconstructed experimental light sheet images and CFD solutions in the same graphics environment is also demonstrated.
Computer-aided light sheet flow visualization

NASA Technical Reports Server (NTRS)

Stacy, Kathryn; Severance, Kurt; Childers, Brooks A.

1993-01-01

A computer-aided flow visualization process has been developed to analyze video images acquired from rotating and translating light sheet visualization systems. The computer process integrates a mathematical model for image reconstruction, advanced computer graphics concepts, and digital image processing to provide a quantitative and visual analysis capability. The image reconstruction model, based on photogrammetry, uses knowledge of the camera and light sheet locations and orientations to project two-dimensional light sheet video images into three-dimensional space. A sophisticated computer visualization package, commonly used to analyze computational fluid dynamics (CFD) data sets, was chosen to interactively display the reconstructed light sheet images, along with the numerical surface geometry for the model or aircraft under study. A description is provided of the photogrammetric reconstruction technique, and the image processing and computer graphics techniques and equipment. Results of the computer aided process applied to both a wind tunnel translating light sheet experiment and an in-flight rotating light sheet experiment are presented. The capability to compare reconstructed experimental light sheet images and CFD solutions in the same graphics environment is also demonstrated.
Comparison of Attachment theory and Cognitive-Motivational Structure theory.

PubMed

Malerstein, A J

2005-01-01

Attachment theory and Cognitive-Motivational Structure (CMS) are similar in most respects. They differ primarily in their proposal of when, during development, one's sense of the self and of the outside world are formed. I propose that the theories supplement each other after about age seven years--when Attachment theory's predictions of social function become unreliable, CMS theory comes into play.
Ohm's law for a current sheet

NASA Technical Reports Server (NTRS)

Lyons, L. R.; Speiser, T. W.

1985-01-01

The paper derives an Ohm's law for single-particle motion in a current sheet, where the magnetic field reverses in direction across the sheet. The result is considerably different from the resistive Ohm's law often used in MHD studies of the geomagnetic tail. Single-particle analysis is extended to obtain a self-consistency relation for a current sheet which agrees with previous results. The results are applicable to the concept of reconnection in that the electric field parallel to the current is obtained for a one-dimensional current sheet with constant normal magnetic field. Dissipated energy goes directly into accelerating particles within the current sheet.
49 CFR 236.338 - Mechanical locking required in accordance with locking sheet and dog chart.

Code of Federal Regulations, 2012 CFR

2012-10-01

... locking sheet and dog chart. 236.338 Section 236.338 Transportation Other Regulations Relating to... in accordance with locking sheet and dog chart. Mechanical locking shall be in accordance with locking sheet and dog chart currently in effect. ...
49 CFR 236.338 - Mechanical locking required in accordance with locking sheet and dog chart.

Code of Federal Regulations, 2014 CFR

2014-10-01

... locking sheet and dog chart. 236.338 Section 236.338 Transportation Other Regulations Relating to... in accordance with locking sheet and dog chart. Mechanical locking shall be in accordance with locking sheet and dog chart currently in effect. ...
49 CFR 236.338 - Mechanical locking required in accordance with locking sheet and dog chart.

Code of Federal Regulations, 2013 CFR

2013-10-01

... locking sheet and dog chart. 236.338 Section 236.338 Transportation Other Regulations Relating to... in accordance with locking sheet and dog chart. Mechanical locking shall be in accordance with locking sheet and dog chart currently in effect. ...
49 CFR 236.338 - Mechanical locking required in accordance with locking sheet and dog chart.

Code of Federal Regulations, 2011 CFR

2011-10-01

... locking sheet and dog chart. 236.338 Section 236.338 Transportation Other Regulations Relating to... in accordance with locking sheet and dog chart. Mechanical locking shall be in accordance with locking sheet and dog chart currently in effect. ...
49 CFR 236.338 - Mechanical locking required in accordance with locking sheet and dog chart.

Code of Federal Regulations, 2010 CFR

2010-10-01

... locking sheet and dog chart. 236.338 Section 236.338 Transportation Other Regulations Relating to... in accordance with locking sheet and dog chart. Mechanical locking shall be in accordance with locking sheet and dog chart currently in effect. ...
Effects of die quench forming on sheet thinning and 3-point bend testing of AA7075-T6

NASA Astrophysics Data System (ADS)

Kim, Samuel; Omer, Kaab; Rahmaan, Taamjeed; Butcher, Clifford; Worswick, Michael

2017-10-01

Lab-scaled AA7075 aluminum side impact beams were manufactured using the die quenching technique in which the sheet was solutionized and then quenched in-die during forming to a super saturated solid state. Sheet thinning measurements were taken at various locations throughout the length of the part and the effect of lubricant on surface scoring and material pick-up on the die was evaluated. The as-formed beams were subjected to a T6 aging treatment and then tested in three-point bending. Simulations were performed of the forming and mechanical testing experiments using the LS-DYNA finite element code. The thinning and mechanical response was predicted well.
Higher-derivative operators and effective field theory for general scalar-tensor theories

NASA Astrophysics Data System (ADS)

Solomon, Adam R.; Trodden, Mark

2018-02-01

We discuss the extent to which it is necessary to include higher-derivative operators in the effective field theory of general scalar-tensor theories. We explore the circumstances under which it is correct to restrict to second-order operators only, and demonstrate this using several different techniques, such as reduction of order and explicit field redefinitions. These methods are applied, in particular, to the much-studied Horndeski theories. The goal is to clarify the application of effective field theory techniques in the context of popular cosmological models, and to explicitly demonstrate how and when higher-derivative operators can be cast into lower-derivative forms suitable for numerical solution techniques.

Magneto-hydrodynamics of coupled fluid-sheet interface with mass suction and blowing

NASA Astrophysics Data System (ADS)

Ahmad, R.

2016-01-01

There are large number of studies which prescribe the kinematics of the sheet and ignore the sheet's mechanics. However, the current boundary layer analysis investigates the mechanics of both the electrically conducting fluid and a permeable sheet, which makes it distinct from the other studies in the literature. One of the objectives of the current study is to (i) examine the behaviour of magnetic field effect for both the surface and the electrically conducting fluid (ii) investigate the heat and mass transfer between a permeable sheet and the surrounding electrically conducting fluid across the hydro, thermal and mass boundary layers. Self-similar solutions are obtained by considering the RK45 technique. Analytical solution is also found for the stretching sheet case. The skin friction dual solutions are presented for various types of sheet. The influence of pertinent parameters on the dimensionless velocity, shear stress, temperature, mass concentration, heat and mass transfer rates on the fluid-sheet interface is presented graphically as well as numerically. The obtained results are of potential benefit for studying the electrically conducting flow over various soft surfaces such as synthetic plastics, soft silicone sheet and soft synthetic rubber sheet. These surfaces are easily deformed by thermal fluctuations or thermal stresses.
Low cost light-sheet microscopy for whole brain imaging

NASA Astrophysics Data System (ADS)

Kumar, Manish; Nasenbeny, Jordan; Kozorovitskiy, Yevgenia

2018-02-01

Light-sheet microscopy has evolved as an indispensable tool in imaging biological samples. It can image 3D samples at fast speed, with high-resolution optical sectioning, and with reduced photobleaching effects. These properties make light-sheet microscopy ideal for imaging fluorophores in a variety of biological samples and organisms, e.g. zebrafish, drosophila, cleared mouse brains, etc. While most commercial turnkey light-sheet systems are expensive, the existing lower cost implementations, e.g. OpenSPIM, are focused on achieving high-resolution imaging of small samples or organisms like zebrafish. In this work, we substantially reduce the cost of light-sheet microscope system while targeting to image much larger samples, i.e. cleared mouse brains, at single-cell resolution. The expensive components of a lightsheet system - excitation laser, water-immersion objectives, and translation stage - are replaced with an incoherent laser diode, dry objectives, and a custom-built Arduino-controlled translation stage. A low-cost CUBIC protocol is used to clear fixed mouse brain samples. The open-source platforms of μManager and Fiji support image acquisition, processing, and visualization. Our system can easily be extended to multi-color light-sheet microscopy.
Universal Rim Thickness in Unsteady Sheet Fragmentation.

PubMed

Wang, Y; Dandekar, R; Bustos, N; Poulain, S; Bourouiba, L

2018-05-18

Unsteady fragmentation of a fluid bulk into droplets is important for epidemiology as it governs the transport of pathogens from sneezes and coughs, or from contaminated crops in agriculture. It is also ubiquitous in industrial processes such as paint, coating, and combustion. Unsteady fragmentation is distinct from steady fragmentation on which most theoretical efforts have been focused thus far. We address this gap by studying a canonical unsteady fragmentation process: the breakup from a drop impact on a finite surface where the drop fluid is transferred to a free expanding sheet of time-varying properties and bounded by a rim of time-varying thickness. The continuous rim destabilization selects the final spray droplets, yet this process remains poorly understood. We combine theory with advanced image analysis to study the unsteady rim destabilization. We show that, at all times, the rim thickness is governed by a local instantaneous Bond number equal to unity, defined with the instantaneous, local, unsteady rim acceleration. This criterion is found to be robust and universal for a family of unsteady inviscid fluid sheet fragmentation phenomena, from impacts of drops on various surface geometries to impacts on films. We discuss under which viscous and viscoelastic conditions the criterion continues to govern the unsteady rim thickness.
Universal Rim Thickness in Unsteady Sheet Fragmentation

NASA Astrophysics Data System (ADS)

Wang, Y.; Dandekar, R.; Bustos, N.; Poulain, S.; Bourouiba, L.

2018-05-01

Unsteady fragmentation of a fluid bulk into droplets is important for epidemiology as it governs the transport of pathogens from sneezes and coughs, or from contaminated crops in agriculture. It is also ubiquitous in industrial processes such as paint, coating, and combustion. Unsteady fragmentation is distinct from steady fragmentation on which most theoretical efforts have been focused thus far. We address this gap by studying a canonical unsteady fragmentation process: the breakup from a drop impact on a finite surface where the drop fluid is transferred to a free expanding sheet of time-varying properties and bounded by a rim of time-varying thickness. The continuous rim destabilization selects the final spray droplets, yet this process remains poorly understood. We combine theory with advanced image analysis to study the unsteady rim destabilization. We show that, at all times, the rim thickness is governed by a local instantaneous Bond number equal to unity, defined with the instantaneous, local, unsteady rim acceleration. This criterion is found to be robust and universal for a family of unsteady inviscid fluid sheet fragmentation phenomena, from impacts of drops on various surface geometries to impacts on films. We discuss under which viscous and viscoelastic conditions the criterion continues to govern the unsteady rim thickness.
Dual circuit embossed sheet heat transfer panel

DOEpatents

Morgan, G.D.

1984-02-21

A heat transfer panel provides redundant cooling for fusion reactors or the like environment requiring low-mass construction. Redundant cooling is provided by two independent cooling circuits, each circuit consisting of a series of channels joined to inlet and outlet headers. The panel comprises a welded joinder of two full-size and two much smaller partial-size sheets. The first full-size sheet is embossed to form first portions of channels for the first and second circuits, as well as a header for the first circuit. The second full-sized sheet is then laid over and welded to the first full-size sheet. The first and second partial-size sheets are then overlaid on separate portions of the second full-sized sheet, and are welded thereto. The first and second partial-sized sheets are embossed to form inlet and outlet headers, which communicate with channels of the second circuit through apertures formed in the second full-sized sheet. 6 figs.
Dual-circuit embossed-sheet heat-transfer panel

DOEpatents

Morgan, G.D.

1982-08-23

A heat transfer panel provides redundant cooling for fusion reactors or the like environment requiring low-mass construction. Redundant cooling is provided by two independent cooling circuits, each circuit consisting of a series of channels joined to inlet and outlet headers. The panel comprises a welded joinder of two full-size and two much smaller partial-size sheets. The first full-size sheet is embossed for form first portions of channels for the first and second circuits, as well as a header for the first circuit. The second full-sized sheet is then laid over and welded to the first full-size sheet. The first and second partial-size sheets are then overlaid on separate portions of the second full-sized sheet, and are welded thereto. The first and second partial-sized sheets are embossed to form inlet and outlet headers, which communicate with channels of the second circuit through apertures formed in the second full-sized sheet.
Dual circuit embossed sheet heat transfer panel

DOEpatents

Morgan, Grover D.

1984-01-01

A heat transfer panel provides redundant cooling for fusion reactors or the like environment requiring low-mass construction. Redundant cooling is provided by two independent cooling circuits, each circuit consisting of a series of channels joined to inlet and outlet headers. The panel comprises a welded joinder of two full-size and two much smaller partial-size sheets. The first full-size sheet is embossed to form first portions of channels for the first and second circuits, as well as a header for the first circuit. The second full-sized sheet is then laid over and welded to the first full-size sheet. The first and second partial-size sheets are then overlaid on separate portions of the second full-sized sheet, and are welded thereto. The first and second partial-sized sheets are embossed to form inlet and outlet headers, which communicate with channels of the second circuit through apertures formed in the second full-sized sheet.
Interaction of reflected ions with the firehose marginally stable current sheet - Implications for plasma sheet convection

NASA Technical Reports Server (NTRS)

Pritchett, P. L.; Coroniti, F. V.

1992-01-01

The firehose marginally stable current sheet, which may model the flow away from the distant reconnection neutral line, assumes that the accelerated particles escape and never return to re-encounter the current region. This assumption fails on the earthward side where the accelerated ions mirror in the geomagnetic dipole field and return to the current sheet at distances up to about 30 R(E) down the tail. Two-dimensional particle simulations are used to demonstrate that the reflected ions drive a 'shock-like' structure in which the incoming flow is decelerated and the Bz field is highly compressed. These effects are similar to those produced by adiabatic choking of steady convection. Possible implications of this interaction for the dynamics of the tail are considered.
Single crystalline electronic structure and growth mechanism of aligned square graphene sheets

NASA Astrophysics Data System (ADS)

Yang, H. F.; Chen, C.; Wang, H.; Liu, Z. K.; Zhang, T.; Peng, H.; Schröter, N. B. M.; Ekahana, S. A.; Jiang, J.; Yang, L. X.; Kandyba, V.; Barinov, A.; Chen, C. Y.; Avila, J.; Asensio, M. C.; Peng, H. L.; Liu, Z. F.; Chen, Y. L.

2018-03-01

Recently, commercially available copper foil has become an efficient and inexpensive catalytic substrate for scalable growth of large-area graphene films for fundamental research and applications. Interestingly, despite its hexagonal honeycomb lattice, graphene can be grown into large aligned square-shaped sheets on copper foils. Here, by applying angle-resolved photoemission spectroscopy with submicron spatial resolution (micro-ARPES) to study the three-dimensional electronic structures of square graphene sheets grown on copper foils, we verified the high quality of individual square graphene sheets as well as their merged regions (with aligned orientation). Furthermore, by simultaneously measuring the graphene sheets and their substrate copper foil, we not only established the (001) copper surface structure but also discovered that the square graphene sheets' sides align with the ⟨110⟩ copper direction, suggesting an important role of copper substrate in the growth of square graphene sheets—which will help the development of effective methods to synthesize high-quality large-size regularly shaped graphene sheets for future applications. This work also demonstrates the effectiveness of micro-ARPES in exploring low-dimensional materials down to atomic thickness and sub-micron lateral size (e.g., besides graphene, it can also be applied to transition metal dichalcogenides and various van der Waals heterostructures)
Influence of temperature fluctuations on equilibrium
ice sheet volume

NASA Astrophysics Data System (ADS)

Bøgeholm Mikkelsen, Troels; Grinsted, Aslak; Ditlevsen, Peter

2018-01-01

Forecasting the future sea level relies on accurate modeling of the response of the Greenland and Antarctic ice sheets to changing temperatures. The surface mass balance (SMB) of the Greenland Ice Sheet (GrIS) has a nonlinear response to warming. Cold and warm anomalies of equal size do not cancel out and it is therefore important to consider the effect of interannual fluctuations in temperature. We find that the steady-state volume of an ice sheet is biased toward larger size if interannual temperature fluctuations are not taken into account in numerical modeling of the ice sheet. We illustrate this in a simple ice sheet model and find that the equilibrium ice volume is approximately 1 m SLE (meters sea level equivalent) smaller when the simple model is forced with fluctuating temperatures as opposed to a stable climate. It is therefore important to consider the effect of interannual temperature fluctuations when designing long experiments such as paleo-spin-ups. We show how the magnitude of the potential bias can be quantified statistically. For recent simulations of the Greenland Ice Sheet, we estimate the bias to be 30 Gt yr-1 (24-59 Gt yr-1, 95 % credibility) for a warming of 3 °C above preindustrial values, or 13 % (10-25, 95 % credibility) of the present-day rate of ice loss. Models of the Greenland Ice Sheet show a collapse threshold beyond which the ice sheet becomes unsustainable. The proximity of the threshold will be underestimated if temperature fluctuations are not taken into account. We estimate the bias to be 0.12 °C (0.10-0.18 °C, 95 % credibility) for a recent estimate of the threshold. In light of our findings it is important to gauge the extent to which this increased variability will influence the mass balance of the ice sheets.
A theoretical study on metal atom-modified BC3 sheets for effects of gas molecule adsorptions

NASA Astrophysics Data System (ADS)

Tang, Yanan; Cui, Xiao; Chen, Weiguang; Zhu, Dalei; Chai, Huaduo; Dai, Xianqi

2018-06-01

Based on the first-principle calculations, the chemical reactivity of transition metal (Fe, Co, Ni, and Cu) dopants within BC3 sheets toward toxic gas molecules (CO, NO, NO2, SO2, and HCN) is comparably investigated. First, the adsorbed gases on metal-modified BC3 sheets exhibit the different stability. Compared with other gases, the metal-modified BC3 substrates exhibit the stronger affinity toward the NO and NO2 molecules (> 1.0 eV), while the adsorbed HCN has the smallest adsorption energy, illustrating that the NO and NO2 as specific toxic gas molecule can be easily detected. Second, the adsorbed gas molecules can effectively regulate the electronic structure and magnetic property of BC3 systems. Fox example, the strong adsorption of NO and NO2 on Fe-modified BC3 systems exhibits non-magnetic property, yet these gases on Co modified BC3 systems exhibit the magnetic character. In addition, the adsorbed NO and SO2 can induce and turn the degree of magnetic moments of Ni- and Cu-modified BC3 systems. Therefore, the different kinds of adsorbed gases on metal-modified BC3 sheets can be distinguished through investigating the changed magnetic moments of system, which would provide important information for designing the functional BC3-based materials.
How could (should) we make contact between string/M-theory and our four-dimensional world, and associated LHC predictions?

NASA Astrophysics Data System (ADS)

Kane, Gordon

2015-12-01

String/M-theory is an exciting framework within which we try to understand our universe and its properties. Compactified string/M-theories address and offer solutions to almost every important question and issue in particle physics and particle cosmology. But earlier goals of finding a top-down “vacuum selection” principle and deriving the 4D theory have not yet been realized. Does that mean we should stop trying, as nearly all string theorists have? Or can we proceed in the historical way to make a few generic, robust assumptions not closely related to observables, and follow where they lead to testable predictions and explanations? Making only very generic assumptions is a significant issue. I discuss how to try to proceed with this approach, particularly in M-theory compactified on a 7D manifold of G2 holonomy. One goal is to understand our universe as a string/M-theory vacuum for its own sake, in the long tradition of trying to understand our world, and what that implies. In addition, understanding our vacuum may be a prelude to understanding its connection to the multiverse.
Five-dimensional fermionic Chern-Simons theory

NASA Astrophysics Data System (ADS)

Bak, Dongsu; Gustavsson, Andreas

2018-02-01

We study 5d fermionic CS theory with a fermionic 2-form gauge potential. This theory can be obtained from 5d maximally supersymmetric YM theory by performing the maximal topological twist. We put the theory on a five-manifold and compute the partition function. We find that it is a topological quantity, which involves the Ray-Singer torsion of the five-manifold. For abelian gauge group we consider the uplift to the 6d theory and find a mismatch between the 5d partition function and the 6d index, due to the nontrivial dimensional reduction of a selfdual two-form gauge field on a circle. We also discuss an application of the 5d theory to generalized knots made of 2d sheets embedded in 5d.
Monitoring Sand Sheets and Dunes

NASA Image and Video Library

2017-06-12

NASA's Mars Reconnaissance Orbiter (MRO) captured this crater featuring sand dunes and sand sheets on its floor. What are sand sheets? Snow fall on Earth is a good example of sand sheets: when it snows, the ground gets blanketed with up to a few meters of snow. The snow mantles the ground and "mimics" the underlying topography. Sand sheets likewise mantle the ground as a relatively thin deposit. This kind of environment has been monitored by HiRISE since 2007 to look for movement in the ripples covering the dunes and sheets. This is how scientists who study wind-blown sand can track the amount of sand moving through the area and possibly where the sand came from. Using the present environment is crucial to understanding the past: sand dunes, sheets, and ripples sometimes become preserved as sandstone and contain clues as to how they were deposited The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. [The original image scale is 25 centimeters (9.8 inches) per pixel (with 1 x 1 binning); objects on the order of 75 centimeters (29.5 inches) across are resolved.] North is up. https://photojournal.jpl.nasa.gov/catalog/PIA21757
Investigation of the Formability of TRIP780 Steel Sheets

NASA Astrophysics Data System (ADS)

Song, Yang

The formability of a metal sheet is dependent on its work hardening behaviour and its forming limits; and both aspects must be carefully determined in order to accurately simulate a particular forming process. This research aims to characterize the formability of a TRIP780 sheet steel using advanced experimental testing and analysis techniques. A series of flat rolling and tensile tests, as well as shear tests were conducted to determine the large deformation work hardening behaviour of this TRIP780 steel. Nakazima tests were carried out up to fracture to determine the forming limits of this sheet material. A highly-automated method for generating a robust FLC for sheet materials from DIC strain measurements was created with the help of finite element simulations, and evaluated against the conventional method. A correction algorithm that aims to compensate for the process dependent effects in the Nakazima test was implemented and tested with some success.
Dynamical and Physical Properties of a Post-Coronal Mass Ejection Current Sheet

NASA Technical Reports Server (NTRS)

Ko, Yuan-Kuen; Raymond, John C.; Lin, Jun; Lawrence, Gareth; Li, Jing; Fludra, Andrzej

2003-01-01

In the eruptive process of the Kopp-Pneuman type, the closed magnetic field is stretched by the eruption so much that it is usually believed to be " open " to infinity. Formation of the current sheet in such a configuration makes it possible for the energy in the coronal magnetic field to quickly convert into thermal and kinetic energies and cause significant observational consequences, such as growing postflare/CME loop system in the corona, separating bright flare ribbons in the chromosphere, and fast ejections of the plasma and the magnetic flux. An eruption on 2002 January 8 provides us a good opportunity to look into these observational signatures of and place constraints on the theories of eruptions. The event started with the expansion of a magnetic arcade over an active region, developed into a coronal mass ejection (CME), and left some thin streamer-like structures with successively growing loop systems beneath them. The plasma outflow and the highly ionized states of the plasma inside these streamer-like structures, as well as the growing loops beneath them, lead us to conclude that these structures are associated with a magnetic reconnection site, namely, the current sheet, of this eruptive process. We combine the data from the Ultraviolet Coronagraph Spectrometer, Large Angle and Spectrometric Coronagraph Experiment, EUV Imaging Telescope, and Coronal Diagnostic Spectrometer on board the Solar and Heliospheric Observatory, as well is from the Mauna Loa Solar Observatory Mark IV K-coronameter, to investigate the morphological and dynamical properties of this event, as well as the physical properties of the current sheet. The velocity and acceleration of the CME reached up to 1800 km/s and 1 km/sq s, respectively. The acceleration is found to occur mainly at the lower corona (<2.76 Solar Radius). The post-CME loop systems showed behaviors of both postflare loops (upward motion with decreasing speed) and soft X-ray giant arches (upward motion with constant
Twin-Mirrored-Galvanometer Laser-Light-Sheet Generator

NASA Technical Reports Server (NTRS)

Rhodes, David B.; Franke, John M.; Jones, Stephen B.; Leighty, Bradley D.

1991-01-01

Multiple, rotating laser-light sheets generated to illuminate flows in wind tunnels. Designed and developed to provide flexibility and adaptability to wide range of applications. Design includes capability to control size and location of laser-light sheet in real time, to generate horizontal or vertical sheets, to sweep sheet repeatedly through volume, to generate multiple sheets with controllable separation, and to rotate single or multiple laser-light sheets. Includes electronic equipment and laser mounted on adjustable-height platform. Twin-mirrored galvanometer unit supported by tripod to reduce vibration. Other possible applications include use in construction industry to align beams of building. Artistic or display applications also possible.
Calendering and Rolling of Viscoplastic Materials: Theory and Experiments

NASA Astrophysics Data System (ADS)

Mitsoulis, E.; Sofou, S.; Muliawan, E. B.; Hatzikiriakos, S. G.

2007-04-01

The calendering and rolling processes are used in a wide variety of industries for the production of rolled sheets or films of specific thickness and final appearance. The acquired final sheet thickness depends mainly on the rheological properties of the material. Materials which have been used in the present study are foodstuff (such as mozzarella cheese and flour-water dough) used in food processing. These materials are rheologically viscoplastic, obeying the Herschel-Bulkley model. The results give the final sheet thickness and the torque as a function of the roll speed. Theoretical analysis based on the Lubrication Approximation Theory (LAT) shows that LAT is a good predictive tool for calendering, where the sheet thickness is very small compared with the roll size. However, in rolling where this is not true, LAT does not hold, and a 2-D analysis is necessary.
New Modelling of Localized Necking in Sheet Metal Stretching

NASA Astrophysics Data System (ADS)

Bressan, José Divo

2011-01-01

Present work examines a new mathematical model to predict the onset of localized necking in the industrial processes of sheet metal forming such as biaxial stretching. Sheet metal formability is usually assessed experimentally by testing such as the Nakajima test to obtain the Forming Limit Curve, FLC, which is an essential material parameter necessary to numerical simulations by FEM. The Forming Limit Diagram or "Forming Principal Strain Map" shows the experimental FLC which is the plot of principal true strains in the sheet metal surface, ɛ1 and ɛ2, occurring at critical points obtained in laboratory formability tests or in the fabrication process. Two types of undesirable rupture mechanisms can occur in sheet metal forming products: localized necking and shear induced fracture. Therefore, two kinds of limit strain curves can be plotted: the local necking limit curve FLC-N and the shear fracture limit curve FLC-S. Localized necking is theoretically anticipated to initiate at a thickness defect ƒin = hib/hia inside the grooved sheet thickness hia, but only at the instability point of maximum load. The inception of grooving on the sheet surface evolves from instability point to localized necking and final rupture, during further sheet metal straining. Work hardening law is defined for a strain and strain rate material by the effective stress σ¯ = σo(1+βɛ¯)n???ɛM. The average experimental hardening law curve for tensile tests at 0°, 45° and 90°, assuming isotropic plasticity, was used to analyze the plasticity behavior during the biaxial stretching of sheet metals. Theoretical predicted curves of local necking limits are plotted in the positive quadrant of FPSM for different defect values ƒin and plasticity parameters. Limit strains are obtained from a software developed by the author. Some experimental results of forming limit curve obtained from experiments for IF steel sheets are compared with the theoretical predicted curves: the correlation is
Dynamic Antarctic ice sheet during the early to mid-Miocene

PubMed Central

DeConto, Robert M.; Pollard, David; Levy, Richard H.

2016-01-01

Geological data indicate that there were major variations in Antarctic ice sheet volume and extent during the early to mid-Miocene. Simulating such large-scale changes is problematic because of a strong hysteresis effect, which results in stability once the ice sheets have reached continental size. A relatively narrow range of atmospheric CO2 concentrations indicated by proxy records exacerbates this problem. Here, we are able to simulate large-scale variability of the early to mid-Miocene Antarctic ice sheet because of three developments in our modeling approach. (i) We use a climate–ice sheet coupling method utilizing a high-resolution atmospheric component to account for ice sheet–climate feedbacks. (ii) The ice sheet model includes recently proposed mechanisms for retreat into deep subglacial basins caused by ice-cliff failure and ice-shelf hydrofracture. (iii) We account for changes in the oxygen isotopic composition of the ice sheet by using isotope-enabled climate and ice sheet models. We compare our modeling results with ice-proximal records emerging from a sedimentological drill core from the Ross Sea (Andrill-2A) that is presented in a companion article. The variability in Antarctic ice volume that we simulate is equivalent to a seawater oxygen isotope signal of 0.52–0.66‰, or a sea level equivalent change of 30–36 m, for a range of atmospheric CO2 between 280 and 500 ppm and a changing astronomical configuration. This result represents a substantial advance in resolving the long-standing model data conflict of Miocene Antarctic ice sheet and sea level variability. PMID:26903645

Ice_Sheets_CCI: Essential Climate Variables for the Greenland Ice Sheet

NASA Astrophysics Data System (ADS)

Forsberg, R.; Sørensen, L. S.; Khan, A.; Aas, C.; Evansberget, D.; Adalsteinsdottir, G.; Mottram, R.; Andersen, S. B.; Ahlstrøm, A.; Dall, J.; Kusk, A.; Merryman, J.; Hvidberg, C.; Khvorostovsky, K.; Nagler, T.; Rott, H.; Scharrer, M.; Shepard, A.; Ticconi, F.; Engdahl, M.

2012-04-01

As part of the ESA Climate Change Initiative (www.esa-cci.org) a long-term project "ice_sheets_cci" started January 1, 2012, in addition to the existing 11 projects already generating Essential Climate Variables (ECV) for the Global Climate Observing System (GCOS). The "ice_sheets_cci" goal is to generate a consistent, long-term and timely set of key climate parameters for the Greenland ice sheet, to maximize the impact of European satellite data on climate research, from missions such as ERS, Envisat and the future Sentinel satellites. The climate parameters to be provided, at first in a research context, and in the longer perspective by a routine production system, would be grids of Greenland ice sheet elevation changes from radar altimetry, ice velocity from repeat-pass SAR data, as well as time series of marine-terminating glacier calving front locations and grounding lines for floating-front glaciers. The ice_sheets_cci project will involve a broad interaction of the relevant cryosphere and climate communities, first through user consultations and specifications, and later in 2012 optional participation in "best" algorithm selection activities, where prototype climate parameter variables for selected regions and time frames will be produced and validated using an objective set of criteria ("Round-Robin intercomparison"). This comparative algorithm selection activity will be completely open, and we invite all interested scientific groups with relevant experience to participate. The results of the "Round Robin" exercise will form the algorithmic basis for the future ECV production system. First prototype results will be generated and validated by early 2014. The poster will show the planned outline of the project and some early prototype results.
Infused polymers for cell sheet release

NASA Astrophysics Data System (ADS)

Juthani, Nidhi; Howell, Caitlin; Ledoux, Haylea; Sotiri, Irini; Kelso, Susan; Kovalenko, Yevgen; Tajik, Amanda; Vu, Thy L.; Lin, Jennifer J.; Sutton, Amy; Aizenberg, Joanna

2016-05-01

Tissue engineering using whole, intact cell sheets has shown promise in many cell-based therapies. However, current systems for the growth and release of these sheets can be expensive to purchase or difficult to fabricate, hindering their widespread use. Here, we describe a new approach to cell sheet release surfaces based on silicone oil-infused polydimethylsiloxane. By coating the surfaces with a layer of fibronectin (FN), we were able to grow mesenchymal stem cells to densities comparable to those of tissue culture polystyrene controls (TCPS). Simple introduction of oil underneath an edge of the sheet caused it to separate from the substrate. Characterization of sheets post-transfer showed that they retain their FN layer and morphology, remain highly viable, and are able to grow and proliferate normally after transfer. We expect that this method of cell sheet growth and detachment may be useful for low-cost, flexible, and customizable production of cellular layers for tissue engineering.
Infused polymers for cell sheet release

PubMed Central

Juthani, Nidhi; Howell, Caitlin; Ledoux, Haylea; Sotiri, Irini; Kelso, Susan; Kovalenko, Yevgen; Tajik, Amanda; Vu, Thy L.; Lin, Jennifer J.; Sutton, Amy; Aizenberg, Joanna

2016-01-01

Tissue engineering using whole, intact cell sheets has shown promise in many cell-based therapies. However, current systems for the growth and release of these sheets can be expensive to purchase or difficult to fabricate, hindering their widespread use. Here, we describe a new approach to cell sheet release surfaces based on silicone oil-infused polydimethylsiloxane. By coating the surfaces with a layer of fibronectin (FN), we were able to grow mesenchymal stem cells to densities comparable to those of tissue culture polystyrene controls (TCPS). Simple introduction of oil underneath an edge of the sheet caused it to separate from the substrate. Characterization of sheets post-transfer showed that they retain their FN layer and morphology, remain highly viable, and are able to grow and proliferate normally after transfer. We expect that this method of cell sheet growth and detachment may be useful for low-cost, flexible, and customizable production of cellular layers for tissue engineering. PMID:27189419
Infused polymers for cell sheet release.

PubMed

Juthani, Nidhi; Howell, Caitlin; Ledoux, Haylea; Sotiri, Irini; Kelso, Susan; Kovalenko, Yevgen; Tajik, Amanda; Vu, Thy L; Lin, Jennifer J; Sutton, Amy; Aizenberg, Joanna

2016-05-18

Tissue engineering using whole, intact cell sheets has shown promise in many cell-based therapies. However, current systems for the growth and release of these sheets can be expensive to purchase or difficult to fabricate, hindering their widespread use. Here, we describe a new approach to cell sheet release surfaces based on silicone oil-infused polydimethylsiloxane. By coating the surfaces with a layer of fibronectin (FN), we were able to grow mesenchymal stem cells to densities comparable to those of tissue culture polystyrene controls (TCPS). Simple introduction of oil underneath an edge of the sheet caused it to separate from the substrate. Characterization of sheets post-transfer showed that they retain their FN layer and morphology, remain highly viable, and are able to grow and proliferate normally after transfer. We expect that this method of cell sheet growth and detachment may be useful for low-cost, flexible, and customizable production of cellular layers for tissue engineering.
Coupled ice sheet-ocean modelling to investigate ocean driven melting of marine ice sheets in Antarctica

NASA Astrophysics Data System (ADS)

Jong, Lenneke; Gladstone, Rupert; Galton-Fenzi, Ben

2017-04-01

Ocean induced melting below the ice shelves of marine ice sheets is a major source of uncertainty for predictions of ice mass loss and Antarctica's resultant contribution to future sea level rise. The floating ice shelves provide a buttressing force against the flow of ice across the grounding line into the ocean. Thinning of these ice shelves due to an increase in melting reduces this force and can lead to an increase in the discharge of grounded ice. Fully coupled modelling of ice sheet-ocean interactions is key to improving understanding the influence of the Southern ocean on the evolution of the Antarctic ice sheet, and to predicting its future behaviour under changing climate conditions. Coupling of ocean and ice sheet models is needed to provide more realistic melt rates at the base of ice shelves and hence make better predictions of the behaviour of the grounding line and the shape of the ice-shelf cavity as the ice sheet evolves. The Framework for Ice Sheet - Ocean Coupling (FISOC) has been developed to provide a flexible platform for performing coupled ice sheet - ocean modelling experiments. We present preliminary results using FISOC to couple the Regional Ocean Modelling System (ROMS) with Elmer/Ice in idealised experiments Marine Ice Sheet-Ocean Model Intercomparison Project (MISOMIP). These experiments use an idealised geometry motivated by that of Pine Island glacier and the adjacent Amundsen Sea in West Antarctica, a region which has shown shown signs of thinning ice and grounding line retreat.
Intrinsic Dawn-Dusk Asymmetry of Magnetotail Thin Current Sheet

NASA Astrophysics Data System (ADS)

Lu, S.; Pritchett, P. L.; Angelopoulos, V.; Artemyev, A.

2017-12-01

Magnetic reconnection and its related phenomena (flux ropes, dipolarization fronts, bursty bulk flows, particle injections, etc.) occur more frequently on the duskside in the Earth's magnetotail. Magnetohydrodynamic simulations attributed the asymmetry to the nonuniform ionospheric conductance through global scale magnetosphere-ionosphere interaction. Hybrid simulations, on the other hand, found an alternative responsible mechanism: the Hall effect in the magnetotail thin current sheet, but left an open question: What is the physical origin of the asymmetric Hall effect? The answer could be the temperature difference on the two sides and/or the dawn-dusk transportation of magnetic flux and plasmas. In this work, we use 3-D particle-in-cell simulations to further explore the magnetotail dawn-dusk asymmetry. The magnetotail equilibrium contains a dipole magnetic field and a current sheet region. The simulation is driven by a symmetric and localized (in the y direction) high-latitude electric field, under which the current sheet thins with a decrease of Bz. During the same time, a dawn-dusk asymmetry is formed intrinsically in the thin current sheet, with a smaller Bz, a stronger Hall effect (indicated by the Hall electric field Ez), and a stronger cross-tail current jy on the duskside. The deep origin of the asymmetry is also shown to be dominated by the dawnward E×B drift of magnetic flux and plasmas. A direct consequence of this intrinsic dawn-dusk asymmetry is that it favors magnetotail reconnection and related phenomena to preferentially occur on the duskside.
Method for heating and forming a glass sheet

DOEpatents

Boaz, Premakaran Tucker

1997-01-01

A method for heating and forming a glass sheet includes the steps of heating a glass sheet to at least a first predetermined temperature, applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature, cooling an outer surface of the glass sheet to at least a third predetermined temperature and forming the glass sheet using forming rollers to a predetermined configuration.
Tunable electronic, electrical and optical properties of graphene oxide sheets by ion irradiation.

PubMed

Jayalakshmi, G; Saravanan, K; Panigrahi, B K; Sundaravel, B; Gupta, Mukul

2018-05-04

The tunable electronic, electrical and optical properties of graphene oxide (GO) sheets were investigated using a controlled reduction by 500 keV Ar + -ion irradiation. The carbon to oxygen ratio of the GO sheets upon the ion beam reduction has been estimated using resonant Rutherford backscattering spectrometry analyses and its effect on the electrical and optical properties of GO sheets has been studied using sheet resistance measurements and photoluminescence (PL) measurements. The restoration of sp 2 -hybridized carbon atoms within the sp 3 matrix is found to be increases with increasing the Ar + -ion fluences as evident from Fourier transform infrared, and x-ray absorption near-edge structure measurements. The decrease in the number of disorder-induced local density of states (LDOSs) within the π-π* gap upon the reduction causes the shifting of PL emission from near infra-red to blue region and decreases the sheet resistance. The improved electrical and optical properties of GO sheets were correlated to the decrease in the number of LDOSs within the π-π* gap. Our experimental investigations suggest ion beam irradiation is one of an effective approaches to reduce GO to RGO and to tailor its electronic, electrical and optical properties.
Tunable electronic, electrical and optical properties of graphene oxide sheets by ion irradiation

NASA Astrophysics Data System (ADS)

Jayalakshmi, G.; Saravanan, K.; Panigrahi, B. K.; Sundaravel, B.; Gupta, Mukul

2018-05-01

The tunable electronic, electrical and optical properties of graphene oxide (GO) sheets were investigated using a controlled reduction by 500 keV Ar+-ion irradiation. The carbon to oxygen ratio of the GO sheets upon the ion beam reduction has been estimated using resonant Rutherford backscattering spectrometry analyses and its effect on the electrical and optical properties of GO sheets has been studied using sheet resistance measurements and photoluminescence (PL) measurements. The restoration of sp 2-hybridized carbon atoms within the sp 3 matrix is found to be increases with increasing the Ar+-ion fluences as evident from Fourier transform infrared, and x-ray absorption near-edge structure measurements. The decrease in the number of disorder-induced local density of states (LDOSs) within the π-π* gap upon the reduction causes the shifting of PL emission from near infra-red to blue region and decreases the sheet resistance. The improved electrical and optical properties of GO sheets were correlated to the decrease in the number of LDOSs within the π-π* gap. Our experimental investigations suggest ion beam irradiation is one of an effective approaches to reduce GO to RGO and to tailor its electronic, electrical and optical properties.
The sea-level fingerprints of ice-sheet collapse during interglacial periods

NASA Astrophysics Data System (ADS)

Hay, Carling; Mitrovica, Jerry X.; Gomez, Natalya; Creveling, Jessica R.; Austermann, Jacqueline; E. Kopp, Robert

2014-03-01

Studies of sea level during previous interglacials provide insight into the stability of polar ice sheets in the face of global climate change. Commonly, these studies correct ancient sea-level highstands for the contaminating effect of isostatic adjustment associated with past ice age cycles, and interpret the residuals as being equivalent to the peak eustatic sea level associated with excess melting, relative to present day, of ancient polar ice sheets. However, the collapse of polar ice sheets produces a distinct geometry, or fingerprint, of sea-level change, which must be accounted for to accurately infer peak eustatic sea level from site-specific residual highstands. To explore this issue, we compute fingerprints associated with the collapse of the Greenland Ice Sheet, West Antarctic Ice Sheet, and marine sectors of the East Antarctic Ice Sheet in order to isolate regions that would have been subject to greater-than-eustatic sea-level change for all three cases. These fingerprints are more robust than those associated with modern melting events, when applied to infer eustatic sea level, because: (1) a significant collapse of polar ice sheets reduces the sensitivity of the computed fingerprints to uncertainties in the geometry of the melt regions; and (2) the sea-level signal associated with the collapse will dominate the signal from steric effects. We evaluate these fingerprints at a suite of sites where sea-level records from interglacial marine isotopes stages (MIS) 5e and 11 have been obtained. Using these results, we demonstrate that previously discrepant estimates of peak eustatic sea level during MIS5e based on sea-level markers in Australia and the Seychelles are brought into closer accord.
Sequentially bridged graphene sheets with high strength, toughness, and electrical conductivity

PubMed Central

Wan, Sijie; Li, Yuchen; Mu, Jiuke; Aliev, Ali E.; Fang, Shaoli; Kotov, Nicholas A.; Jiang, Lei; Cheng, Qunfeng; Baughman, Ray H.

2018-01-01

We here show that infiltrated bridging agents can convert inexpensively fabricated graphene platelet sheets into high-performance materials, thereby avoiding the need for a polymer matrix. Two types of bridging agents were investigated for interconnecting graphene sheets, which attach to sheets by either π–π bonding or covalent bonding. When applied alone, the π–π bonding agent is most effective. However, successive application of the optimized ratio of π–π bonding and covalent bonding agents provides graphene sheets with the highest strength, toughness, fatigue resistance, electrical conductivity, electromagnetic interference shielding efficiency, and resistance to ultrasonic dissolution. Raman spectroscopy measurements of stress transfer to graphene platelets allow us to decipher the mechanisms of property improvement. In addition, the degree of orientation of graphene platelets increases with increasing effectiveness of the bonding agents, and the interlayer spacing increases. Compared with other materials that are strong in all directions within a sheet, the realized tensile strength (945 MPa) of the resin-free graphene platelet sheets was higher than for carbon nanotube or graphene platelet composites, and comparable to that of commercially available carbon fiber composites. The toughness of these composites, containing the combination of π–π bonding and covalent bonding, was much higher than for these other materials having high strengths for all in-plane directions, thereby opening the path to materials design of layered nanocomposites using multiple types of quantitatively engineered chemical bonds between nanoscale building blocks. PMID:29735659
BRITICE-CHRONO and GLANAM: new exciting developments in the study of circum-North Atlantic ice sheets

NASA Astrophysics Data System (ADS)

Benetti, Sara; Clark, Chris D.; Petter Serjup, Hans

2013-04-01

This talk will present two newly funded projects on the reconstruction of former marine-based ice sheets bordering the North Atlantic Ocean and their effects on the surrounding continental margins. The NERC-funded BRITICE-CHRONO started in October 2012 and its consortium involves scientists from all over the UK with partners in Ireland, Canada and Norway. It aims to carry out a systematic campaign to collect and date material to constrain the timing and rates of change of the collapse of the former British-Irish Ice Sheet. This will be achieved by focussing on eight transects running from the shelf edge to a short distance onshore and acquiring marine and terrestrial samples for geochronometric dating. The sampling will be accomplished by two research cruises and eight fieldwork campaigns around UK and Ireland. The project will result in the world's best empirical reconstruction of a shrinking ice sheet, for use in improving ice sheet models, and to provide the long term context against which contemporary observations can be assessed. The FP7-funded Marie Curie Initial Training Networks GLANAM (Glaciated North Atlantic Margins) will start in April 2013 and aims at improving the career prospects and development of young researchers in both the public and private sector within the field of earth science, focusing specifically on North Atlantic glaciated margins. The training network comprises ten partner institutions, both academic and industrial, from Norway, UK and Denmark and will train eleven PhD and four postdoctoral researchers. The young scientists will perform multi-disciplinary research and receive training through three interconnected workpackages that collectively address knowledge gaps related to the glacial sedimentary depocentres on the North Atlantic margins. Filling these gaps will not only result in major new insights regarding glacial processes on continental margins in general, but critically will have particular impact on the exploitation of
The Steady Flow Resistance of Perforated Sheet Materials in High Speed Grazing Flows

NASA Technical Reports Server (NTRS)

Syed, Asif A.; Yu, Jia; Kwan, H. W.; Chien, E.; Jones, Michael G. (Technical Monitor)

2002-01-01

A study was conducted to determine the effects of high speed grazing air flow on the acoustic resistance of perforated sheet materials used in the construction of acoustically absorptive liners placed in commercial aircraft engine nacelles. Since DC flow resistance of porous sheet materials is known to be a major component of the acoustic resistance of sound suppression liners, the DC flow resistance of a set of perforated face-sheets and linear 'wiremesh' face-sheets was measured in a flow duct apparatus (up to Mach 0.8). Samples were fabricated to cover typical variations in perforated face-sheet parameters, such as hole diameter, porosity and sheet thickness, as well as those due to different manufacturing processes. The DC flow resistance data from perforated sheets were found to correlate strongly with the grazing flow Mach number and the face-sheet porosity. The data also show correlation against the boundary layer displacement thickness to hole-diameter ratio. The increase in resistance with grazing flow for punched aluminum sheets is in good agreement with published results up to Mach 0.4, but is significantly larger than expected above Mach 0.4. Finally, the tests demonstrated that there is a significant increase in the resistance of linear 'wiremesh' type face-sheet materials.
Validation of Modelled Ice Dynamics of the Greenland Ice Sheet using Historical Forcing

NASA Astrophysics Data System (ADS)

Hoffman, M. J.; Price, S. F.; Howat, I. M.; Bonin, J. A.; Chambers, D. P.; Tezaur, I.; Kennedy, J. H.; Lenaerts, J.; Lipscomb, W. H.; Neumann, T.; Nowicki, S.; Perego, M.; Saba, J. L.; Salinger, A.; Guerber, J. R.

2015-12-01

Although ice sheet models are used for sea level rise projections, the degree to which these models have been validated by observations is fairly limited, due in part to the limited duration of the satellite observation era and the long adjustment time scales of ice sheets. Here we describe a validation framework for the Greenland Ice Sheet applied to the Community Ice Sheet Model by forcing the model annually with flux anomalies at the major outlet glaciers (Enderlin et al., 2014, observed from Landsat/ASTER/Operation IceBridge) and surface mass balance (van Angelen et al., 2013, calculated from RACMO2) for the period 1991-2012. The ice sheet model output is compared to ice surface elevation observations from ICESat and ice sheet mass change observations from GRACE. Early results show promise for assessing the performance of different model configurations. Additionally, we explore the effect of ice sheet model resolution on validation skill.
Method for heating and forming a glass sheet

DOEpatents

Boaz, P.T.

1997-08-12

A method for heating and forming a glass sheet includes the steps of heating a glass sheet to at least a first predetermined temperature, applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature, cooling an outer surface of the glass sheet to at least a third predetermined temperature and forming the glass sheet using forming rollers to a predetermined configuration. 5 figs.
Isochronal Ice Sheet Model: a New Approach to Tracer Transport by Explicitly Tracing Accumulation Layers

NASA Astrophysics Data System (ADS)

Born, A.; Stocker, T. F.

2014-12-01

The long, high-resolution and largely undisturbed depositional record of polar ice sheets is one of the greatest resources in paleoclimate research. The vertical profile of isotopic and other geochemical tracers provides a full history of depositional and dynamical variations. Numerical simulations of this archive could afford great advances both in the interpretation of these tracers as well as to help improve ice sheet models themselves, as show successful implementations in oceanography and atmospheric dynamics. However, due to the slow advection velocities, tracer modeling in ice sheets is particularly prone to numerical diffusion, thwarting efforts that employ straightforward solutions. Previous attemps to circumvent this issue follow conceptually and computationally extensive approaches that augment traditional Eulerian models of ice flow with a semi-Lagrangian tracer scheme (e.g. Clarke et al., QSR, 2005). Here, we propose a new vertical discretization for ice sheet models that eliminates numerical diffusion entirely. Vertical motion through the model mesh is avoided by mimicking the real-world ice flow as a thinning of underlying layers (see figure). A new layer is added to the surface at equidistant time intervals (isochronally). Therefore, each layer is uniquely identified with an age. Horizontal motion follows the shallow ice approximation using an implicit numerical scheme. Vertical diffusion of heat which is physically desirable is also solved implicitly. A simulation of a two-dimensional section through the Greenland ice sheet will be discussed.
Fuels planning: science synthesis and integration; social issues fact sheet 07: The "laws" of effective public education about fire hazards

Treesearch

Rocky Mountain Research Station USDA Forest Service

2004-01-01

Within the past 10 years, breakthrough research has identified factors that are most important for effectively communicating about wildland fire hazards. This fact sheet discusses seven "Laws" of effective public communication that should be considered in any state-of-the-art education campaign.
A stable planar bilayer membrane of phospholipid supported by cellulose sheets.

PubMed

Setaka, M; Yamamoto, T; Sato, N; Yano, M; Kwan, T

1982-01-01

A new method is reported for preparing a thin planar membrane of 1,2-distearoylsn-glycero-3-phosphocholine and egg yolk lecithin-cholesterol (molar ratio of 1:1) between a pair of cellulose sheets. This technique, developed from the method of the multilayer planar membrane preparation (Setaka, M., et al. (1979) J. Biochem. 86, 355-362; 1619-1622; (1980) J. Biochem. 88, 1819-1829), consisted of three experimental processes. First, a phospholipid monolayer was prepared at an air-water interface, then taken up on a stretched cellulose sheet. A thin lipid membrane, supported from both sides by cellulose sheets, was constructed by combining two of these lipid monolayer-cellulose sheets. The permeability coefficient of the thin lipid membrane was estimated by removing the effect of two outer cellulose sheets, and this permeability was found to be larger than those of other model membranes of a lipid bilayer, indicating that the present lipid membrane is not a perfect single lipid bilayer. However, certain experimental evidence suggests that the bulk of the phospholipids formed a bilayer between the two cellulose sheets. Since this lipid membrane is particularily stable, larger membranes can be prepared by the present method than other planar bilayer membranes of lipid, which are usually constructed inside a pin hole in a thin teflon sheet.
Experimental formability analysis of bondal sandwich sheet

NASA Astrophysics Data System (ADS)

Kami, Abdolvahed; Banabic, Dorel

2018-05-01

Metal/polymer/metal sandwich sheets have recently attracted the interests of industries like automotive industry. These sandwich sheets have superior properties over single-layer metallic sheets including good sound and vibration damping and light weight. However, the formability of these sandwich sheets should be enhanced which requires more research. In this paper, the formability of Bondal sheet (DC06/viscoelastic polymer/DC06 sandwich sheet) was studied through different types of experiments. The mechanical properties of Bondal were determined by uniaxial tensile tests. Hemispherical punch stretching and hydraulic bulge tests were carried out to determine the forming limit diagram (FLD) of Bondal. Furthermore, cylindrical and square cup drawing tests were performed in dry and oil lubricated conditions. These tests were conducted at different blank holding forces (BHFs). An interesting observation about Bondal sheet deep drawing was obtaining of higher drawing depths at dry condition in comparison with oil-lubricated condition.
Trade-offs between robustness and small-world effect in complex networks

PubMed Central

Peng, Guan-Sheng; Tan, Suo-Yi; Wu, Jun; Holme, Petter

2016-01-01

Robustness and small-world effect are two crucial structural features of complex networks and have attracted increasing attention. However, little is known about the relation between them. Here we demonstrate that, there is a conflicting relation between robustness and small-world effect for a given degree sequence. We suggest that the robustness-oriented optimization will weaken the small-world effect and vice versa. Then, we propose a multi-objective trade-off optimization model and develop a heuristic algorithm to obtain the optimal trade-off topology for robustness and small-world effect. We show that the optimal network topology exhibits a pronounced core-periphery structure and investigate the structural properties of the optimized networks in detail. PMID:27853301

Development and evaluation of adsorption sheet (HD safe sheet-U) using active carbon for the purpose of the preventing the contamination diffusion of urinary excreted anticancer drug.

PubMed

Sato, Junya; Ohkubo, Haruka; Sasaki, Yuki; Yokoi, Makoto; Hotta, Yasunori; Kudo, Kenzo

2017-01-01

docetaxel. Furthermore, the quantities of adhesion in cytarabine, gemcitabine, doxorubicin, paclitaxel, and irinotecan were lower than determination limit. Active carbon might be effective in adsorbing urinary anticancer drugs. The active carbon sheet adsorbed urinary excreted anticancer drugs, and use of such sheets might prevent diffusion of contamination due to urinary excreted anticancer drugs.
Stampless fabrication of sheet bars using disposable templates

NASA Astrophysics Data System (ADS)

Smolentsev, V. P.; Safonov, S. V.; Smolentsev, E. V.; Fedonin, O. N.

2016-04-01

The article is devoted to the new method of small-scale fabrication of sheet bars. The procedure is performed by using disposable overlay templates, or those associated with a sheet, which parameters are obtained directly from the drawing. The proposed method used as a substitution of die cutting enables to intensify the preparatory technological process, which is particularly effective when launching the market-oriented items into production. It significantly increases the competitiveness of mechanical engineering and creates the conditions for technical support of present-day flexible production systems.
Effective theories and thresholds in particle physics

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

Gaillard, M.K.

1991-06-07

The role of effective theories in probing a more fundamental underlying theory and in indicating new physics thresholds is discussed, with examples from the standard model and more speculative applications to superstring theory. 38 refs.
Optimization of the excitation light sheet in selective plane illumination microscopy

PubMed Central

Gao, Liang

2015-01-01

Selective plane illumination microscopy (SPIM) allows rapid 3D live fluorescence imaging on biological specimens with high 3D spatial resolution, good optical sectioning capability and minimal photobleaching and phototoxic effect. SPIM gains its advantage by confining the excitation light near the detection focal plane, and its performance is determined by the ability to create a thin, large and uniform excitation light sheet. Several methods have been developed to create such an excitation light sheet for SPIM. However, each method has its own strengths and weaknesses, and tradeoffs must be made among different aspects in SPIM imaging. In this work, we present a strategy to select the excitation light sheet among the latest SPIM techniques, and to optimize its geometry based on spatial resolution, field of view, optical sectioning capability, and the sample to be imaged. Besides the light sheets discussed in this work, the proposed strategy is also applicable to estimate the SPIM performance using other excitation light sheets. PMID:25798312
Improvement of formability of high strength steel sheets in shrink flanging

NASA Astrophysics Data System (ADS)

Hamedon, Z.; Abe, Y.; Mori, K.

2016-02-01

In the shrinkage flanging, the wrinkling tends to occur due to compressive stress. The wrinkling will cause a difficulty in assembling parts, and severe wrinkling may leads to rupture of parts. The shrinkage flange of the ultra-high strength steel sheets not only defects the product by the occurrence of the wrinkling but also causes seizure and wear of the dies and shortens the life of dies. In the present study, a shape of a punch having gradual contact was optimized in order to prevent the wrinkling in shrinkage flanging of ultra-high strength steel sheets. The sheet was gradually bent from the corner of the sheet to reduce the compressive stress. The wrinkling in the shrink flanging of the ultra-high strength steel sheets was prevented by the punch having gradual contact. It was found that the punch having gradual contact is effective in preventing the occurrence of wrinkling in the shrinkage flanging.
Observational physics of mirror world

NASA Technical Reports Server (NTRS)

Khlopov, M. YA.; Beskin, G. M.; Bochkarev, N. E.; Pustilnik, L. A.; Pustilnik, S. A.

1989-01-01

The existence of the whole world of shadow particles, interacting with each other and having no mutual interactions with ordinary particles except gravity is a specific feature of modern superstring models, being considered as models of the theory of everything. The presence of shadow particles is the necessary condition in the superstring models, providing compensation of the asymmetry of left and right chirality states of ordinary particles. If compactification of additional dimensions retains the symmetry of left and right states, shadow world turns to be the mirror one, with particles and fields having properties strictly symmetrical to the ones of corresponding ordinary particles and fields. Owing to the strict symmetry of physical laws for ordinary and mirror particles, the analysis of cosmological evolution of mirror matter provides rather definite conclusions on possible effects of mirror particles in the universe. A general qualitative discussion of possible astronomical impact of mirror matter is given, in order to make as wide as possible astronomical observational searches for the effects of mirror world, being the unique way to test the existence of mirror partners of ordinary particles in the Nature.
A B-C-N hybrid porous sheet: an efficient metal-free visible-light absorption material.

PubMed

Lu, Ruifeng; Li, Feng; Salafranca, Juan; Kan, Erjun; Xiao, Chuanyun; Deng, Kaiming

2014-03-07

The polyphenylene network, known as porous graphene, is one of the most important and widely studied two-dimensional materials. As a potential candidate for photocatalysis and photovoltaic energy generation, its application has been limited by the low photocatalytic activity in the visible-light region. State-of-the-art hybrid density functional theory investigations are presented to show that an analogous B-C-N porous sheet outperforms the pristine polyphenylene network with significantly enhanced visible-light absorption. Compared with porous graphene, the calculated energy gap of the B-C-N hybrid crystal shrinks to 2.7 eV and the optical absorption peak remarkably shifts to the visible light region. The redox potentials of water splitting are well positioned in the middle of the band gap. Hybridizations among B_p, N_p and C_p orbitals are responsible for these findings. Valence and conduction band calculations indicate that the electrons and holes can be effectively separated, reducing charge recombination and improving the photoconversion efficiency. Moreover, the band gap and optical properties of the B-C-N hybrid porous sheet can be further finely engineered by external strain.
The Onset of Magnetic Reconnection: Tearing Instability in Current Sheets with a Guide Field

NASA Astrophysics Data System (ADS)

Daldorff, L. K. S.; Klimchuk, J. A.; Knizhnik, K. J.

2016-12-01

Magnetic reconnection is fundamental to many solar phenomena, ranging from coronal heating, to jets, to flares and CMEs. A poorly understood yet crucial aspect of reconnection is that it does not occur until magnetic stresses have built to sufficiently high levels for significant energy release. If reconnection were to happen too soon, coronal heating would be weak and flares would be small. As part of our program to study the onset conditions for magnetic reconnection, we have investigated the instability of current sheets to tearing. Surprisingly little work has been done on this problem for sheets that include a guide field, i.e., for which the field rotates by less than 180 degrees. This is the most common situation on the Sun. We present numerical 3D resistive MHD simulations of several sheets and show how the behaviour depends on the shear angle (rotation). We compare our results to the predictions of linear theory and discuss the nonlinear evolution in terms of plasmoid formation and the interaction of different oblique tearing modes. The relevance to the Sun is explained.
Disintegration of liquid sheets

NASA Technical Reports Server (NTRS)

Mansour, Adel; Chigier, Norman

1990-01-01

The development, stability, and disintegration of liquid sheets issuing from a two-dimensional air-assisted nozzle is studied. Detailed measurements of mean drop size and velocity are made using a phase Doppler particle analyzer. Without air flow the liquid sheet converges toward the axis as a result of surface tension forces. With airflow a quasi-two-dimensional expanding spray is formed. The air flow causes small variations in sheet thickness to develop into major disturbances with the result that disruption starts before the formation of the main break-up region. In the two-dimensional variable geometry air-blast atomizer, it is shown that the air flow is responsible for the formation of large, ordered, and small chaotic 'cell' structures.
Root-growth-inhibiting sheet

DOEpatents

Burton, Frederick G.; Cataldo, Dominic A.; Cline, John F.; Skiens, W. Eugene; Van Voris, Peter

1993-01-01

In accordance with this invention, a porous sheet material is provided at intervals with bodies of a polymer which contain a 2,6-dinitroaniline. The sheet material is made porous to permit free passage of water. It may be either a perforated sheet or a woven or non-woven textile material. A particularly desirable embodiment is a non-woven fabric of non-biodegradable material. This type of material is known as a "geotextile" and is used for weed control, prevention of erosion on slopes, and other landscaping purposes. In order to obtain a root repelling property, a dinitroaniline is blended with a polymer which is attached to the geotextile or other porous material.
Root-growth-inhibiting sheet

DOEpatents

Burton, F.G.; Cataldo, D.A.; Cline, J.F.; Skiens, W.E.; Van Voris, P.

1993-01-26

In accordance with this invention, a porous sheet material is provided at intervals with bodies of a polymer which contain a 2,6-dinitroaniline. The sheet material is made porous to permit free passage of water. It may be either a perforated sheet or a woven or non-woven textile material. A particularly desirable embodiment is a non-woven fabric of non-biodegradable material. This type of material is known as a geotextile'' and is used for weed control, prevention of erosion on slopes, and other landscaping purposes. In order to obtain a root repelling property, a dinitroaniline is blended with a polymer which is attached to the geotextile or other porous material.
16 CFR 460.13 - Fact sheets.

Code of Federal Regulations, 2012 CFR

2012-01-01

... heat flow. The higher the R-value, the greater the insulating power. Compare insulation R-values before... INSULATION § 460.13 Fact sheets. If you are a manufacturer, you must give retailers and installers fact sheets for the insulation products you sell to them. Each sheet must contain what is listed here. You can...
16 CFR 460.13 - Fact sheets.

Code of Federal Regulations, 2010 CFR

2010-01-01

... heat flow. The higher the R-value, the greater the insulating power. Compare insulation R-values before... INSULATION § 460.13 Fact sheets. If you are a manufacturer, you must give retailers and installers fact sheets for the insulation products you sell to them. Each sheet must contain what is listed here. You can...
16 CFR 460.13 - Fact sheets.

Code of Federal Regulations, 2014 CFR

2014-01-01

... heat flow. The higher the R-value, the greater the insulating power. Compare insulation R-values before... INSULATION § 460.13 Fact sheets. If you are a manufacturer, you must give retailers and installers fact sheets for the insulation products you sell to them. Each sheet must contain what is listed here. You can...
16 CFR 460.13 - Fact sheets.

Code of Federal Regulations, 2013 CFR

2013-01-01

... heat flow. The higher the R-value, the greater the insulating power. Compare insulation R-values before... INSULATION § 460.13 Fact sheets. If you are a manufacturer, you must give retailers and installers fact sheets for the insulation products you sell to them. Each sheet must contain what is listed here. You can...
16 CFR 460.13 - Fact sheets.

Code of Federal Regulations, 2011 CFR

2011-01-01

... heat flow. The higher the R-value, the greater the insulating power. Compare insulation R-values before... INSULATION § 460.13 Fact sheets. If you are a manufacturer, you must give retailers and installers fact sheets for the insulation products you sell to them. Each sheet must contain what is listed here. You can...
The effect of mesenchymal stem cell sheets on structural allograft healing of critical-sized femoral defects in mice

PubMed Central

Long, Teng; Zhu, Zhenan; Awad, Hani A.; Schwarz, Edward M.; Hilton, Matthew J.; Dong, Yufeng

2014-01-01

Structural bone allografts are widely used in the clinic to treat critical sized bone defects, despite lacking the osteoinductive characteristics of live autografts. To address this, we generated revitalized structural allografts wrapped with mesenchymal stem/progenitor cell (MSC) sheets, which were produced by expanding primary syngenic bone marrow derived cells on temperature-responsive plates, as a tissue engineered periosteum. In vitro assays demonstrated maintenance of the MSC phenotype in the sheets, suggesting that short-term culturing of MSC sheets is not detrimental. To test their efficacy in vivo, allografts wrapped with MSC sheets were transplanted into 4-mm murine femoral defects and compared to allografts with direct seeding of MSCs and allografts without cells. Evaluations consisted of x-ray plain radiography, 3D microCT, histology, and biomechanical testing at 4- and 6-weeks post-surgery. Our findings demonstrate that MSC sheets induce prolonged cartilage formation at the graft-host junction and enhanced bone callus formation, as well as graft-host osteointegration. Moreover, a large periosteal callus was observed spanning the allografts with MSC sheets, which partially mimics live autograft healing. Finally, biomechanical testing showed a significant increase in the structural and functional properties of MSC sheet grafted femurs. Taken together, MSC sheets exhibit enhanced osteogenicity during critical sized bone defect repair, demonstrating the feasibility of this tissue engineering solution for massive allograft healing. PMID:24393269
Electron distributions in the plasma sheet boundary layer - Time-of-flight effects

NASA Technical Reports Server (NTRS)

Onsager, T. G.; Thomsen, M. F.; Gosling, J. T.; Bame, S. J.

1990-01-01

The electron edge of the plasma sheet boundary layer lies lobeward of the ion edge. Measurements obtained near the electron edge of the boundary layer reveal low-speed cutoffs for earthward and tailward-flowing electrons. These cutoffs progress to lower speeds with deeper penetration into the boundary layer, and are consistently lower for the earthward-directed electrons than for the tailward-direction electrons. The cutoffs and their variation with distance from the edge of the boundary layer can be consistently interpreted in terms of a time-of-flight effect on recently reconnected magnetic field lines. The observed cutoff speeds are used to estimate the downtail location of the reconnection site.
Isostasy as a Driver of Paleo Retreat of the Greenland Ice Sheet

NASA Astrophysics Data System (ADS)

Robinson, A.; Tabone, I.; Alvarez-Solas, J.; Montoya, M.

2016-12-01

During glacial times, the Greenland ice sheet (GrIS) extended onto the continental shelf, and thus was much more directly affected by changing ocean temperatures through basal melt of the marine ice margins than it is today. The larger glacial ice sheet also induced lithospheric depression of several hundred meters in regions that are near sea level today. As the ice sheet retreated inland under interglacial climatic forcing, the regions significantly affected by local isostatic changes in elevation were exposed to much higher basal melt rates than they would have been given the present-day topography. Here we explore this effect using a hybrid ice sheet model that represents both grounded and floating ice, as well as local isostatic effects, and is driven by both atmospheric and oceanic temperature anomalies. We find that when transient oceanic forcing is included in the model, isostasy plays an important role in allowing oceanic melting to drive GrIS retreat in some regions. During the last interglacial, for example, this effect can account for a significant additional sea-level contribution, as well as an increase in the rate of sea-level rise. Our results highlight the importance of accounting for ice-ocean-lithosphere interactions in the past, in order to be able to properly reconstruct the evolution of the ice sheet, and for estimating its sensitivity to potential changes in climate in the future.
World Culture in the Capitalist World-System in Transition

ERIC Educational Resources Information Center

Griffiths, Tom G.; Arnove, Robert F.

2015-01-01

World culture theory (WCT) offers an explanatory framework for macro-level comparative analyses of systems of mass education, including their structures, accompanying policies and their curricular and pedagogical practices. WCT has contributed to broader efforts to overcome methodological nationalism in comparative research. In this paper, we…

Influence of nanotopography on periodontal ligament stem cell functions and cell sheet based periodontal regeneration

PubMed Central

Gao, Hui; Li, Bei; Zhao, Lingzhou; Jin, Yan

2015-01-01

Periodontal regeneration is an important part of regenerative medicine, with great clinical significance; however, the effects of nanotopography on the functions of periodontal ligament (PDL) stem cells (PDLSCs) and on PDLSC sheet based periodontal regeneration have never been explored. Titania nanotubes (NTs) layered on titanium (Ti) provide a good platform to study this. In the current study, the influence of NTs of different tube size on the functions of PDLSCs was observed. Afterward, an ectopic implantation model using a Ti/cell sheets/hydroxyapatite (HA) complex was applied to study the effect of the NTs on cell sheet based periodontal regeneration. The NTs were able to enhance the initial PDLSC adhesion and spread, as well as collagen secretion. With the Ti/cell sheets/HA complex model, it was demonstrated that the PDLSC sheets were capable of regenerating the PDL tissue, when combined with bone marrow mesenchymal stem cell (BMSC) sheets and HA, without the need for extra soluble chemical cues. Simultaneously, the NTs improved the periodontal regeneration result of the ectopically implanted Ti/cell sheets/HA complex, giving rise to functionally aligned collagen fiber bundles. Specifically, much denser collagen fibers, with abundant blood vessels as well as cementum-like tissue on the Ti surface, which well-resembled the structure of natural PDL, were observed in the NT5 and NT10 sample groups. Our study provides the first evidence that the nanotopographical cues obviously influence the functions of PDLSCs and improve the PDLSC sheet based periodontal regeneration size dependently, which provides new insight to the periodontal regeneration. The Ti/cell sheets/HA complex may constitute a good model to predict the effect of biomaterials on periodontal regeneration. PMID:26150714
Influence of nanotopography on periodontal ligament stem cell functions and cell sheet based periodontal regeneration.

PubMed

Gao, Hui; Li, Bei; Zhao, Lingzhou; Jin, Yan

2015-01-01

Periodontal regeneration is an important part of regenerative medicine, with great clinical significance; however, the effects of nanotopography on the functions of periodontal ligament (PDL) stem cells (PDLSCs) and on PDLSC sheet based periodontal regeneration have never been explored. Titania nanotubes (NTs) layered on titanium (Ti) provide a good platform to study this. In the current study, the influence of NTs of different tube size on the functions of PDLSCs was observed. Afterward, an ectopic implantation model using a Ti/cell sheets/hydroxyapatite (HA) complex was applied to study the effect of the NTs on cell sheet based periodontal regeneration. The NTs were able to enhance the initial PDLSC adhesion and spread, as well as collagen secretion. With the Ti/cell sheets/HA complex model, it was demonstrated that the PDLSC sheets were capable of regenerating the PDL tissue, when combined with bone marrow mesenchymal stem cell (BMSC) sheets and HA, without the need for extra soluble chemical cues. Simultaneously, the NTs improved the periodontal regeneration result of the ectopically implanted Ti/cell sheets/HA complex, giving rise to functionally aligned collagen fiber bundles. Specifically, much denser collagen fibers, with abundant blood vessels as well as cementum-like tissue on the Ti surface, which well-resembled the structure of natural PDL, were observed in the NT5 and NT10 sample groups. Our study provides the first evidence that the nanotopographical cues obviously influence the functions of PDLSCs and improve the PDLSC sheet based periodontal regeneration size dependently, which provides new insight to the periodontal regeneration. The Ti/cell sheets/HA complex may constitute a good model to predict the effect of biomaterials on periodontal regeneration.
21 CFR 880.5180 - Burn sheet.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Burn sheet. 880.5180 Section 880.5180 Food and... Burn sheet. (a) Identification. A burn sheet is a device made of a porous material that is wrapped aroung a burn victim to retain body heat, to absorb wound exudate, and to serve as a barrier against...
21 CFR 880.5180 - Burn sheet.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Burn sheet. 880.5180 Section 880.5180 Food and... Burn sheet. (a) Identification. A burn sheet is a device made of a porous material that is wrapped aroung a burn victim to retain body heat, to absorb wound exudate, and to serve as a barrier against...
21 CFR 880.5180 - Burn sheet.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Burn sheet. 880.5180 Section 880.5180 Food and... Burn sheet. (a) Identification. A burn sheet is a device made of a porous material that is wrapped aroung a burn victim to retain body heat, to absorb wound exudate, and to serve as a barrier against...
21 CFR 880.5180 - Burn sheet.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Burn sheet. 880.5180 Section 880.5180 Food and... Burn sheet. (a) Identification. A burn sheet is a device made of a porous material that is wrapped aroung a burn victim to retain body heat, to absorb wound exudate, and to serve as a barrier against...
21 CFR 880.5180 - Burn sheet.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Burn sheet. 880.5180 Section 880.5180 Food and... Burn sheet. (a) Identification. A burn sheet is a device made of a porous material that is wrapped aroung a burn victim to retain body heat, to absorb wound exudate, and to serve as a barrier against...
Oscillators and relaxation phenomena in Pleistocene climate theory

PubMed Central

Crucifix, Michel

2012-01-01

Ice sheets appeared in the northern hemisphere around 3 Ma (million years) ago and glacial–interglacial cycles have paced Earth's climate since then. Superimposed on these long glacial cycles comes an intricate pattern of millennial and sub-millennial variability, including Dansgaard–Oeschger and Heinrich events. There are numerous theories about these oscillations. Here, we review a number of them in order to draw a parallel between climatic concepts and dynamical system concepts, including, in particular, the relaxation oscillator, excitability, slow–fast dynamics and homoclinic orbits. Namely, almost all theories of ice ages reviewed here feature a phenomenon of synchronization between internal climate dynamics and astronomical forcing. However, these theories differ in their bifurcation structure and this has an effect on the way the ice age phenomenon could grow 3 Ma ago. All theories on rapid events reviewed here rely on the concept of a limit cycle excited by changes in the surface freshwater balance of the ocean. The article also reviews basic effects of stochastic fluctuations on these models, including the phenomenon of phase dispersion, shortening of the limit cycle and stochastic resonance. It concludes with a more personal statement about the potential for inference with simple stochastic dynamical systems in palaeoclimate science. PMID:22291227
Comparative evaluation of absorbable hemostats: advantages of fibrin-based sheets.

PubMed

Krishnan, Lissy K; Mohanty, Mira; Umashankar, P R; Lal, Arthur Vijayan

2004-11-01

Bioactive hemostats and wound dressings consist of either inherently active materials or act as delivery vehicles which contain such materials. Fibrin is a natural hemostat and scaffold, guiding the direction of wound contraction and closure. In order to improve the ease of application of liquid fibrin glue, we have made a freeze-dried form of polymerized fibrin that supports hemostasis and wound healing. The bleeding from the middle ear artery of rabbits was found to be arrested instantaneously on application of fibrin sheets, even when the animal was heparinized systemically. As the fibrin sheet was found to be fragile, gelatin was incorporated to the sheet and thus the mechanical stability was improved without compromising the hemostatic effect. The efficacy of the fabricated fibrin and fibrin-gelatin sheets to seal traumatized rat liver was compared with commercially available hemostats, Abgel (cross-linked gelatin) and Surgicel (cross-linked cellulose). Tissue compatibility of all the hemostats was studied by analyzing the liver tissue 15 days after application. While the hemostatic effect was best with fibrin and fibrin-gelatin sheets, both Surgicel and Abgel were not capable of arresting the bleeding quickly. Gross analysis of tissue on the 15th day of application, visibly, Abgel was not only degraded but resulted in severe adhesions of internal organs and histologically capsule formation around the implant was evident. Though Surgicel was also seen as cream soft material on the site of application that joined two pieces of liver, there was no adhesion of other internal organs and histologically, immune reaction and foreign-body-type giant cells were present in large amounts. Fibrin was not found grossly on application site whereas fibrin-gelatin was seen as a small white spot. Granulation tissue formation and cell migration into the fibrin-based sheets were evident, and therefore, fibrin-based sheets are not only efficient hemostats but showed optimum
Reconstructing the last Irish Ice Sheet 2: a geomorphologically-driven model of ice sheet growth, retreat and dynamics

NASA Astrophysics Data System (ADS)

Greenwood, Sarah L.; Clark, Chris D.

2009-12-01

The ice sheet that once covered Ireland has a long history of investigation. Much prior work focussed on localised evidence-based reconstructions and ice-marginal dynamics and chronologies, with less attention paid to an ice sheet wide view of the first order properties of the ice sheet: centres of mass, ice divide structure, ice flow geometry and behaviour and changes thereof. In this paper we focus on the latter aspect and use our new, countrywide glacial geomorphological mapping of the Irish landscape (>39 000 landforms), and our analysis of the palaeo-glaciological significance of observed landform assemblages (article Part 1), to build an ice sheet reconstruction yielding these fundamental ice sheet properties. We present a seven stage model of ice sheet evolution, from initiation to demise, in the form of palaeo-geographic maps. An early incursion of ice from Scotland likely coalesced with local ice caps and spread in a south-westerly direction 200 km across Ireland. A semi-independent Irish Ice Sheet was then established during ice sheet growth, with a branching ice divide structure whose main axis migrated up to 140 km from the west coast towards the east. Ice stream systems converging on Donegal Bay in the west and funnelling through the North Channel and Irish Sea Basin in the east emerge as major flow components of the maximum stages of glaciation. Ice cover is reconstructed as extending to the continental shelf break. The Irish Ice Sheet became autonomous (i.e. separate from the British Ice Sheet) during deglaciation and fragmented into multiple ice masses, each decaying towards the west. Final sites of demise were likely over the mountains of Donegal, Leitrim and Connemara. Patterns of growth and decay of the ice sheet are shown to be radically different: asynchronous and asymmetric in both spatial and temporal domains. We implicate collapse of the ice stream system in the North Channel - Irish Sea Basin in driving such asymmetry, since rapid
Collisionless kinetic theory of oblique tearing instabilities

DOE PAGES

Baalrud, S. D.; Bhattacharjee, A.; Daughton, W.

2018-02-15

The linear dispersion relation for collisionless kinetic tearing instabilities is calculated for the Harris equilibrium. In contrast to the conventional 2D geometry, which considers only modes at the center of the current sheet, modes can span the current sheet in 3D. Modes at each resonant surface have a unique angle with respect to the guide field direction. Both kinetic simulations and numerical eigenmode solutions of the linearized Vlasov-Maxwell equations have recently revealed that standard analytic theories vastly overestimate the growth rate of oblique modes. In this paper, we find that this stabilization is associated with the density-gradient-driven diamagnetic drift. Themore » analytic theories miss this drift stabilization because the inner tearing layer broadens at oblique angles sufficiently far that the assumption of scale separation between the inner and outer regions of boundary-layer theory breaks down. The dispersion relation obtained by numerically solving a single second order differential equation is found to approximately capture the drift stabilization predicted by solutions of the full integro-differential eigenvalue problem. Finally, a simple analytic estimate for the stability criterion is provided.« less
Collisionless kinetic theory of oblique tearing instabilities

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

Baalrud, S. D.; Bhattacharjee, A.; Daughton, W.

The linear dispersion relation for collisionless kinetic tearing instabilities is calculated for the Harris equilibrium. In contrast to the conventional 2D geometry, which considers only modes at the center of the current sheet, modes can span the current sheet in 3D. Modes at each resonant surface have a unique angle with respect to the guide field direction. Both kinetic simulations and numerical eigenmode solutions of the linearized Vlasov-Maxwell equations have recently revealed that standard analytic theories vastly overestimate the growth rate of oblique modes. In this paper, we find that this stabilization is associated with the density-gradient-driven diamagnetic drift. Themore » analytic theories miss this drift stabilization because the inner tearing layer broadens at oblique angles sufficiently far that the assumption of scale separation between the inner and outer regions of boundary-layer theory breaks down. The dispersion relation obtained by numerically solving a single second order differential equation is found to approximately capture the drift stabilization predicted by solutions of the full integro-differential eigenvalue problem. Finally, a simple analytic estimate for the stability criterion is provided.« less
Synergistic Effect between Ultra-Small Nickel Hydroxide Nanoparticles and Reduced Graphene Oxide sheets for the Application in High-Performance Asymmetric Supercapacitor.

PubMed

Liu, Yonghuan; Wang, Rutao; Yan, Xingbin

2015-06-08

Nanoscale electrode materials including metal oxide nanoparticles and two-dimensional graphene have been employed for designing supercapacitors. However, inevitable agglomeration of nanoparticles and layers stacking of graphene largely hamper their practical applications. Here we demonstrate an efficient co-ordination and synergistic effect between ultra-small Ni(OH)2 nanoparticles and reduced graphene oxide (RGO) sheets for synthesizing ideal electrode materials. On one hand, to make the ultra-small Ni(OH)2 nanoparticles work at full capacity as an ideal pseudocapacitive material, RGO sheets are employed as an suitable substrate to anchor these nanoparticles against agglomeration. As a consequence, an ultrahigh specific capacitance of 1717 F g(-1) at 0.5 A g(-1) is achieved. On the other hand, to further facilitate ion transfer within RGO sheets as an ideal electrical double layer capacitor material, the ultra-small Ni(OH)2 nanoparticles are introduced among RGO sheets as the recyclable sacrificial spacer to prevent the stacking. The resulting RGO sheets exhibit superior rate capability with a high capacitance of 182 F g(-1) at 100 A g(-1). On this basis, an asymmetric supercapacitor is assembled using the two materials, delivering a superior energy density of 75 Wh kg(-1) and an ultrahigh power density of 40 000 W kg(-1).
Synergistic Effect between Ultra-Small Nickel Hydroxide Nanoparticles and Reduced Graphene Oxide sheets for the Application in High-Performance Asymmetric Supercapacitor

PubMed Central

Liu, Yonghuan; Wang, Rutao; Yan, Xingbin

2015-01-01

Nanoscale electrode materials including metal oxide nanoparticles and two-dimensional graphene have been employed for designing supercapacitors. However, inevitable agglomeration of nanoparticles and layers stacking of graphene largely hamper their practical applications. Here we demonstrate an efficient co-ordination and synergistic effect between ultra-small Ni(OH)2 nanoparticles and reduced graphene oxide (RGO) sheets for synthesizing ideal electrode materials. On one hand, to make the ultra-small Ni(OH)2 nanoparticles work at full capacity as an ideal pseudocapacitive material, RGO sheets are employed as an suitable substrate to anchor these nanoparticles against agglomeration. As a consequence, an ultrahigh specific capacitance of 1717 F g−1 at 0.5 A g−1 is achieved. On the other hand, to further facilitate ion transfer within RGO sheets as an ideal electrical double layer capacitor material, the ultra-small Ni(OH)2 nanoparticles are introduced among RGO sheets as the recyclable sacrificial spacer to prevent the stacking. The resulting RGO sheets exhibit superior rate capability with a high capacitance of 182 F g−1 at 100 A g−1. On this basis, an asymmetric supercapacitor is assembled using the two materials, delivering a superior energy density of 75 Wh kg−1 and an ultrahigh power density of 40 000 W kg−1. PMID:26053847
Quality Control: (Material) Safety Data Sheets.

PubMed

Allen, Loyd V

2017-01-01

Safety Data Sheets (formerly Material Safety Data Sheets) are a system for cataloging information on chemicals, chemical compounds, and chemical mixtures and include instructions for the safe use and potential hazards associated with a particular material or product. At present, there are 16 sections of Safety Data Sheets, and these sections are discussed in this article. Two United States Pharmacopeia compounding-related chapters (<795> and <800>) refer to Safety Data Sheets, and this article provides a brief discussion on the terminology contained within those chapters. Copyright© by International Journal of Pharmaceutical Compounding, Inc.
Emittance Measurements for a Thin Liquid Sheet Flow

NASA Technical Reports Server (NTRS)

Englehart, Amy N.; McConley, Marc W.; Chubb, Donald L.

1996-01-01

The Liquid Sheet Radiator (LSR) is an external flow radiator that uses a triangular-shaped flowing liquid sheet as the radiating surface. It has potentially much lower mass than solid wall radiators such as pumped loop and heat pipe radiators, along with being nearly immune to micrometeoroid penetration. The LSR has an added advantage of simplicity. Surface tension causes a thin (100-300 microns) liquid sheet to coalesce to a point, causing the sheet flow to have a triangular shape. Such a triangular sheet is desirable since it allows for simple collection of the flow at a single point. A major problem for all external flow radiators is the requirement that the working fluid be of very low (approx. 10(sup -8) torr) vapor pressure to keep evaporative losses low. As a result, working fluids are limited to certain oils (such as used in diffusion pumps) for low temperatures (300-400 K) and liquid metals for higher temperatures. Previous research on the LSR has been directed at understanding the fluid mechanics of thin sheet flows and assessing the stability of such flows, especially with regard to the formation of holes in the sheet. Taylor studied extensively the stability of thin liquid sheets both theoretically and experimentally. He showed that thin sheets in a vacuum are stable. The latest research has been directed at determining the emittance of thin sheet flows. The emittance was calculated from spectral transmittance data for the Dow Corning 705 silicone oil. By experimentally setting up a sheet flow, the emittance was also determined as a function of measurable quantities, most importantly, the temperature drop between the top of the sheet and the temperature at the coalescence point of the sheet. Temperature fluctuations upstream of the liquid sheet were a potential problem in the analysis and were investigated.
Electromagnetic augmentation for casting of thin metal sheets

DOEpatents

Hull, John R.

1989-01-01

Thin metal sheets are cast by magnetically levitating molten metal deposited in a mold within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled by the water-cooled walls of the mold to form a solid metal sheet. A conducting shield is electrically coupled to the molten metal sheet to provide a return path for eddy currents induced in the metal sheet by the current in the AC conducting coils. In another embodiment, a DC conducting coil is coupled to the metal sheet for providing a direct current therein which interacts with the magnetic field to levitate the moving metal sheet. Levitation of the metal sheet in both molten and solid forms reduces its contact pressure with the mold walls while maintaining sufficient engagement therebetween to permit efficient conductive cooling by the mold through which a coolant fluid may be circulated. The magnetic fields associated with the currents in the aforementioned coils levitate the molten metal sheet while the mold provides for its lateral and vertical confinement. A leader sheet having electromagnetic characteristics similar to those of the molten metal sheet is used to start the casing process and precedes the molten metal sheet through the yoke/coil arrangement and mold and forms a continuous sheet therewith. The yoke/coil arrangement may be either U-shaped with a single racetrack coil or may be rectangular with a pair of spaced, facing bedstead coils.
Research on Al-alloy sheet forming formability during warm/hot sheet hydroforming based on elliptical warm bulging test

NASA Astrophysics Data System (ADS)

Cai, Gaoshen; Wu, Chuanyu; Gao, Zepu; Lang, Lihui; Alexandrov, Sergei

2018-05-01

An elliptical warm/hot sheet bulging test under different temperatures and pressure rates was carried out to predict Al-alloy sheet forming limit during warm/hot sheet hydroforming. Using relevant formulas of ultimate strain to calculate and dispose experimental data, forming limit curves (FLCS) in tension-tension state of strain (TTSS) area are obtained. Combining with the basic experimental data obtained by uniaxial tensile test under the equivalent condition with bulging test, complete forming limit diagrams (FLDS) of Al-alloy are established. Using a quadratic polynomial curve fitting method, material constants of fitting function are calculated and a prediction model equation for sheet metal forming limit is established, by which the corresponding forming limit curves in TTSS area can be obtained. The bulging test and fitting results indicated that the sheet metal FLCS obtained were very accurate. Also, the model equation can be used to instruct warm/hot sheet bulging test.
Modelling the climate and ice sheets of the mid-Pliocene warm period: a test of model dependency

NASA Astrophysics Data System (ADS)

Dolan, Aisling; Haywood, Alan; Lunt, Daniel; Hill, Daniel

2010-05-01

The mid-Pliocene warm period (MPWP; c. 3.0 - 3.3 million years ago) has been the subject of a large number of published studies during the last decade. It is an interval in Earth history, where conditions were similar to those predicted by climate models for the end of the 21st Century. Not only is it important to increase our understanding of the climate dynamics in a warmer world, it is also important to determine exactly how well numerical models can retrodict a climate significantly different from the present day, in order to have confidence in them for predicting the future climate. Previous General Circulation Model (GCM) simulations have indicated that MPWP mean annual surface temperatures were on average 2 to 3˚C warmer than the pre-industrial era. Coastal stratigraphy and benthic oxygen isotope records suggest that terrestrial ice volumes were reduced when compared to modern. Ice sheet modelling studies have supported this decrease in cryospheric extent. Generally speaking, both climate and ice sheet modelling studies have only used results from one numerical model when simulating the climate of the MPWP. However, recent projects such as PMIP (the Palaeoclimate Modelling Intercomparison Project) have emphasised the need to explore the dependency of past climate predictions on the specific climate model which is used. Here we present a comparison of MPWP climatologies produced by three atmosphere only GCMs from the Goddard Institute of Space Studies (GISS), the National Centre for Atmospheric Research (NCAR) and the Hadley Centre for Climate Prediction and Research (GCMAM3, CAM3-CLM and HadAM3 respectively). We focus on the ability of the GCMs to simulate climate fields needed to drive an offline ice sheet model to assess whether there are any significant differences between the climatologies. By taking the different temperature and precipitation predictions simulated by the three models as a forcing, and adopting GCM-specific topography, we have used the
On non-BPS effective actions of string theory

NASA Astrophysics Data System (ADS)

Hatefi, Ehsan

2018-05-01

We discuss some physical prospective of the non-BPS effective actions of type IIA and IIB superstring theories. By dealing with all complete three and four point functions, including a closed Ramond-Ramond string (in terms of both its field strength and its potential), gauge (scalar) fields as well as a real tachyon and under symmetry structures, we find various restricted world volume and bulk Bianchi identities. The complete forms of the non-BPS scattering amplitudes including their Chan-Paton factors are elaborated. All the singularity structures of the non-BPS amplitudes, their all order α ' higher-derivative corrections, their contact terms and various modified Bianchi identities are derived. Finally, we show that scattering amplitudes computed in different super-ghost pictures are compatible when suitable Bianchi identities are imposed on the Ramond-Ramond fields. Moreover, we argue that the higher-derivative expansion in powers of the momenta of the tachyon is universal.

Scaling results for the Liquid Sheet Radiator (LSR)

NASA Technical Reports Server (NTRS)

Chubb, Donald L.; Calfo, Frederick D.

1989-01-01

Surface tension forces at the edges of a thin liquid (approx. 100 micrometers) sheet flow result in a triangularly shaped sheet. Such a geometry is ideal for an external flow radiator. The experimental investigation of such sheet flows was extended to large sheets (width = W = 23.5 cm, length = L approx. = 3.5 m). Experimental L/W results are greater than the calculated results. However, more experimental results are necessary for a complete comparison. The calculated emissivity of a sheet of Dow-Corning 705 silicone oil, which is a low temperature (300 to 400K) candidate for a liquid sheet radiator (LSR), is greater than .8 for sheet thicknesses greater than 100 micrometers.
Notched strength of beryllium powder and ingot sheets.

NASA Technical Reports Server (NTRS)

Moss, R. G.

1972-01-01

The effects of notches in thin beryllium sheets were studied as functions of material variables and notch severity. Double edge notched samples having stress concentration factors of 1.0 to 15.4 were prepared by milling to size, etching, and electrical discharge machining the notches. Strength was not reduced greatly by sharp notches, and duller notches were more deleterious than sharp notches. The trend was for reduced strength for dull notches, increased strength for sharper notches, and reduced strength for very sharp notches. Differences in material purity or source of the sheet had little affect on notch sensitivity. The most important factors appear to be oxide content and directionality of the sheet microstructure; high oxide content and highly directional microstructure tend to give more notch sensitivity than low oxide content, and more bidirectional microstructure. Postulated causes of the change in notched/unnotched strength are given.
Effects of a wavy neutral sheet on cosmic ray anisotropies

NASA Technical Reports Server (NTRS)

Kota, J.; Jokipii, J. R.

1985-01-01

The first results of a three-dimensional numerical code calculating cosmic ray anisotropies is presented. The code includes diffusion, convection, adiabatic cooling, and drift in an interplanetary magnetic field model containing a wavy neutral sheet. The 3-D model can reproduce all the principal observations for a reasonable set of parameters.
Thermal properties of highly structured composite and aluminium sheets in an aerodynamic tunnel

NASA Astrophysics Data System (ADS)

Kulhavy, Petr; Egert, Josef

This article deals with the thermodynamic behaviour of heat shields - structured metal and composite plates. Experiments have been carried out in a wind tunnel with an additional heating, which simulates the heat source from engine or exhaust pipe and simultaneously the airflow generated during a car movement. The tested sheets with hexagonal structure were a standard commercial made of aluminium and a second manufactured by replication (lamination, diffusion) from glass fabric. The airflow in a parallel way along the sheets was analysed experimentally in order to determine the heat transfer efficiency between surfaces of sheets and surrounding airflow. The temperature on the sheets was chosen to observe the effects of different sheets material, various heat power and airflow velocity. During the experiment a thermal input below the sheets and airflow velocity through the tunnel have been changed. The thermal field distribution on the metal sheet is different than in case of composite sheet. For the composite material the thermal field distribution was more homogeneous. This article describe briefly also methods of obtaining real composite geometry based on scanned data and their reconstruction for using in some future numerical models.
Modeling of Firn Compaction for Estimating Ice-Sheet Mass Change from Observed Ice-Sheet Elevation Change

NASA Technical Reports Server (NTRS)

Li, Jun; Zwally, H. Jay

2011-01-01

Changes in ice-sheet surface elevation are caused by a combination of ice-dynamic imbalance, ablation, temporal variations in accumulation rate, firn compaction and underlying bedrock motion. Thus, deriving the rate of ice-sheet mass change from measured surface elevation change requires information on the rate of firn compaction and bedrock motion, which do not involve changes in mass, and requires an appropriate firn density to associate with elevation changes induced by recent accumulation rate variability. We use a 25 year record of surface temperature and a parameterization for accumulation change as a function of temperature to drive a firn compaction model. We apply this formulation to ICESat measurements of surface elevation change at three locations on the Greenland ice sheet in order to separate the accumulation-driven changes from the ice-dynamic/ablation-driven changes, and thus to derive the corresponding mass change. Our calculated densities for the accumulation-driven changes range from 410 to 610 kg/cu m, which along with 900 kg/cu m for the dynamic/ablation-driven changes gives average densities ranging from 680 to 790 kg/cu m. We show that using an average (or "effective") density to convert elevation change to mass change is not valid where the accumulation and the dynamic elevation changes are of opposite sign.
The Einstein equations on the 3-brane world

NASA Astrophysics Data System (ADS)

Shiromizu, Tetsuya; Maeda, Kei-Ichi; Sasaki, Misao

2000-07-01

We carefully investigate the gravitational equations of the brane world, in which all the matter forces except gravity are confined on the 3-brane in a 5-dimensional spacetime with Z2 symmetry. We derive the effective gravitational equations on the brane, which reduce to the conventional Einstein equations in the low energy limit. From our general argument we conclude that the first Randall-Sundrum-type theory predicts that the brane with a negative tension is an antigravity world and hence should be excluded from the physical point of view. Their second-type theory where the brane has a positive tension provides the correct signature of gravity. In this latter case, if the bulk spacetime is exactly anti-de Sitter spacetime, generically the matter on the brane is required to be spatially homogeneous because of the Bianchi identities. By allowing deviations from anti-de Sitter spacetime in the bulk, the situation will be relaxed and the Bianchi identities give just the relation between the Weyl tensor and the energy momentum tensor. In the present brane world scenario, the effective Einstein equations cease to be valid during an era when the cosmological constant on the brane is not well defined, such as in the case of the matter dominated by the potential energy of the scalar field.
Solar Energetic Particle Transport Near a Heliospheric Current Sheet

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

Battarbee, Markus; Dalla, Silvia; Marsh, Mike S., E-mail: mbattarbee@uclan.ac.uk

2017-02-10

Solar energetic particles (SEPs), a major component of space weather, propagate through the interplanetary medium strongly guided by the interplanetary magnetic field (IMF). In this work, we analyze the implications that a flat Heliospheric Current Sheet (HCS) has on proton propagation from SEP release sites to the Earth. We simulate proton propagation by integrating fully 3D trajectories near an analytically defined flat current sheet, collecting comprehensive statistics into histograms, fluence maps, and virtual observer time profiles within an energy range of 1–800 MeV. We show that protons experience significant current sheet drift to distant longitudes, causing time profiles to exhibitmore » multiple components, which are a potential source of confusing interpretations of observations. We find that variation of the current sheet thickness within a realistic parameter range has little effect on particle propagation. We show that the IMF configuration strongly affects the deceleration of protons. We show that in our model, the presence of a flat equatorial HCS in the inner heliosphere limits the crossing of protons into the opposite hemisphere.« less
Method for heating, forming and tempering a glass sheet

DOEpatents

Boaz, Premakaran Tucker; Sitzman, Gary W.

1998-01-01

A method for heating, forming and tempering a glass sheet including the steps of heating at least one glass sheet to at least a first predetermined temperature, applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature, forming the glass sheet to a predetermined configuration, and cooling an outer surface of the glass sheet to at least a third predetermined temperature to temper the glass sheet.
An electrically resistive sheet of glial cells for amplifying signals of neuronal extracellular recordings

PubMed Central

Matsumura, R.; Yamamoto, H.; Niwano, M.; Hirano-Iwata, A.

2016-01-01

Electrical signals of neuronal cells can be recorded non-invasively and with a high degree of temporal resolution using multielectrode arrays (MEAs). However, signals that are recorded with these devices are small, usually 0.01%–0.1% of intracellular recordings. Here, we show that the amplitude of neuronal signals recorded with MEA devices can be amplified by covering neuronal networks with an electrically resistive sheet. The resistive sheet used in this study is a monolayer of glial cells, supportive cells in the brain. The glial cells were grown on a collagen-gel film that is permeable to oxygen and other nutrients. The impedance of the glial sheet was measured by electrochemical impedance spectroscopy, and equivalent circuit simulations were performed to theoretically investigate the effect of covering the neurons with such a resistive sheet. Finally, the effect of the resistive glial sheet was confirmed experimentally, showing a 6-fold increase in neuronal signals. This technique feasibly amplifies signals of MEA recordings. PMID:27703279
The world, entanglement, and God: Quantum theory and the Christian doctrine of creation

NASA Astrophysics Data System (ADS)

Wegter-McNelly, Kirk Matthew

The adequacy of classical physics' mechanistic worldview is called into question by an "entanglement" interpretation of quantum nonlocal correlations, which suggests a relational holistic account of physical processes. Albert Einstein rejected the possibility of such behavior, but recent experiments confirm its existence in the world. The concept of entanglement provides an especially fruitful locus for appropriating quantum insights into theological reflection because it bridges two otherwise antithetical interpretations of the theory, the indeterministic "Copenhagen" version developed by Niels Bohr and the deterministic version later discovered by David Bohm. Entanglement also offers an opportunity to explore what Robert Russell has called the method of "mutual interaction," by which theology can play a legitimate heuristic role in scientific research programs even as it responds to scientific discoveries. The concept of entanglement offers rich possibilities for developing a theological program within which to situate an ecological, trinitarian understanding of creation. In particular, a theological appropriation of entanglement can strengthen an ecological approach such as that of Sallie McFague, who argues powerfully for the importance of naturalistic metaphors in crafting a cosmic vision of wholeness but whose use of "organic" metaphors does not entirely eliminate the specter of mechanism. Entanglement can also strengthen a trinitarian approach such as one finds in Wolfhart Pannenberg, whose relational understanding of creation remains mechanistic insofar as it depends primarily on classical rather than quantum field theory. According to the theological approach developed in this dissertation, a trinitarian relational God creates a universe that is entangled with itself and, as a result of the incarnation, also with God. Additionally, this theological perspective leads to the scientific prediction that no complete solution to the quantum measurement problem
Effect of en-glacial water on ice sheet temperatures in a warming climate - a model approach

NASA Astrophysics Data System (ADS)

Phillips, T. P.; Rajaram, H.; Steffen, K.

2009-12-01

Each summer, significant amount of melt is generated in the ablation zones of large glaciers and ice sheets. This melt does not run off on the surface of the glacier or ice sheet. In fact a significant fraction enters the glacier and flows through en-glacial and sub-glacial hydrologic systems. Correspondingly, the en-glacial and sub-glacial hydrologic systems are brought to a temperature close to the pressure melting point of ice. The thermal influence of these hydrologic processes is seldom incorporated in heat transfer models for glaciers and ice sheets. In a warming climate, as melt water generation is amplified, en-glacial and sub-glacial hydrologic processes can influence the thermal dynamics of an ice sheet significantly, a feedback which is missed in current models. Although the role of refreezing melt water in the firn of the accumulation zone is often accounted for to explain warmer near-surface temperatures, the role of melt water flow within a glacier is not considered in large ice sheet models. We propose a simple parameterization of the influence of en-glacial and sub-glacial hydrology on the thermal dynamics of ice sheets, in the form of a dual-column model. Our model basically modifies the classical Budd column model for temperature variations in ice sheets by introducing an interaction with an en-glacial column, where the temperature is brought to the melting point during the melt season, and winter-time refreezing is influenced by latent heat effects associated with water retained within the en-glacial and sub-glacial systems. A cryo-hydraulic heat exchange coefficient ς is defined, as a parameter that quantifies this interaction. The parameter ς is related to k/R^2, where R is the characteristic spacing between en-glacial passages. The general behavior of the dual-column model is influenced by the competition between cooling by horizontal advection and warming by cryo-hydraulic exchange. We present a dimensionless parameter to quantify this
A numerical study of magnetohydrodynamic transport of nanofluids over a vertical stretching sheet with exponential temperature-dependent viscosity and buoyancy effects

NASA Astrophysics Data System (ADS)

Akbar, Noreen Sher; Tripathi, Dharmendra; Khan, Zafar Hayat; Bég, O. Anwar

2016-09-01

In this paper, a mathematical study is conducted of steady incompressible flow of a temperature-dependent viscous nanofluid from a vertical stretching sheet under applied external magnetic field and gravitational body force effects. The Reynolds exponential viscosity model is deployed. Electrically-conducting nanofluids are considered which comprise a suspension of uniform dimension nanoparticles suspended in viscous base fluid. The nanofluid sheet is extended with a linear velocity in the axial direction. The Buonjiornio model is utilized which features Brownian motion and thermophoresis effects. The partial differential equations for mass, momentum, energy and species (nano-particle concentration) are formulated with magnetic body force term. Viscous and Joule dissipation effects are neglected. The emerging nonlinear, coupled, boundary value problem is solved numerically using the Runge-Kutta fourth order method along with a shooting technique. Graphical solutions for velocity, temperature, concentration field, skin friction and Nusselt number are presented. Furthermore stream function plots are also included. Validation with Nakamura's finite difference algorithm is included. Increasing nanofluid viscosity is observed to enhance temperatures and concentrations but to reduce velocity magnitudes. Nusselt number is enhanced with both thermal and species Grashof numbers whereas it is reduced with increasing thermophoresis parameter and Schmidt number. The model is applicable in nano-material manufacturing processes involving extruding sheets.
The effect of mesenchymal stem cell sheets on structural allograft healing of critical sized femoral defects in mice.

PubMed

Long, Teng; Zhu, Zhenan; Awad, Hani A; Schwarz, Edward M; Hilton, Matthew J; Dong, Yufeng

2014-03-01

Structural bone allografts are widely used in the clinic to treat critical sized bone defects, despite lacking the osteoinductive characteristics of live autografts. To address this, we generated revitalized structural allografts wrapped with mesenchymal stem/progenitor cell (MSC) sheets, which were produced by expanding primary syngenic bone marrow derived cells on temperature-responsive plates, as a tissue-engineered periosteum. In vitro assays demonstrated maintenance of the MSC phenotype in the sheets, suggesting that short-term culturing of MSC sheets is not detrimental. To test their efficacy in vivo, allografts wrapped with MSC sheets were transplanted into 4-mm murine femoral defects and compared to allografts with direct seeding of MSCs and allografts without cells. Evaluations consisted of X-ray plain radiography, 3D microCT, histology, and biomechanical testing at 4- and 6-weeks post-surgery. Our findings demonstrate that MSC sheets induce prolonged cartilage formation at the graft-host junction and enhanced bone callus formation, as well as graft-host osteointegration. Moreover, a large periosteal callus was observed spanning the allografts with MSC sheets, which partially mimics live autograft healing. Finally, biomechanical testing showed a significant increase in the structural and functional properties of MSC sheet grafted femurs. Taken together, MSC sheets exhibit enhanced osteogenicity during critical sized bone defect repair, demonstrating the feasibility of this tissue engineering solution for massive allograft healing. Copyright © 2013 Elsevier Ltd. All rights reserved.
Method for heating, forming and tempering a glass sheet

DOEpatents

Boaz, P.T.; Sitzman, G.W.

1998-10-27

A method for heating, forming and tempering a glass sheet is disclosed including the steps of heating at least one glass sheet to at least a first predetermined temperature, applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature, forming the glass sheet to a predetermined configuration, and cooling an outer surface of the glass sheet to at least a third predetermined temperature to temper the glass sheet. 2 figs.
Formability of Annealed Ni-Ti Shape Memory Alloy Sheet

NASA Astrophysics Data System (ADS)

Fann, K. J.; Su, J. Y.; Chang, C. H.

2018-03-01

Ni-Ti shape memory alloy has two specific properties, superelasiticity and shape memory effect, and thus is widely applied in diverse industries. To extend its application, this study attempts to investigate the strength and cold formability of its sheet blank, which is annealed at various temperatures, by hardness test and by Erichsen-like cupping test. As a result, the higher the annealing temperature, the lower the hardness, the lower the maximum punch load as the sheet blank fractured, and the lower the Erichsen-like index or the lower the formability. In general, the Ni-Ti sheet after annealing has an Erichsen-like index between 8 mm and 9 mm. This study has also confirmed via DSC that the Ni-Ti shape memory alloy possesses the austenitic phase and shows the superelasticity at room temperature.
Mechanochemical Modeling of Dynamic Microtubule Growth Involving Sheet-to-Tube Transition

PubMed Central

Ji, Xiang-Ying; Feng, Xi-Qiao

2011-01-01

Microtubule dynamics is largely influenced by nucleotide hydrolysis and the resultant tubulin configuration changes. The GTP cap model has been proposed to interpret the stabilizing mechanisms of microtubule growth from the view of hydrolysis effects. Besides, the growth of a microtubule involves the closure of a curved sheet at its growing end. The curvature conversion from the longitudinal direction to the circumferential direction also helps to stabilize the successive growth, and the curved sheet is referred to as the conformational cap. However, there still lacks theoretical investigation on the mechanical–chemical coupling growth process of microtubules. In this paper, we study the growth mechanisms of microtubules by using a coarse-grained molecular method. First, the closure process involving a sheet-to-tube transition is simulated. The results verify the stabilizing effect of the sheet structure and predict that the minimum conformational cap length that can stabilize the growth is two dimers. Then, we show that the conformational cap and the GTP cap can function independently and harmoniously, signifying the pivotal role of mechanical factors. Furthermore, based on our theoretical results, we describe a Tetris-like growth style of microtubules: the stochastic tubulin assembly is regulated by energy and harmonized with the seam zipping such that the sheet keeps a practically constant length during growth. PMID:22205994
Raman and AFM study of gamma irradiated plastic bottle sheets

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

Ali, Yasir; Kumar, Vijay; Dhaliwal, A. S.

2013-02-05

In this investigation, the effects of gamma irradiation on the structural properties of plastic bottle sheet are studied. The Plastic sheets were exposed with 1.25MeV {sup 60}Co gamma rays source at various dose levels within the range from 0-670 kGy. The induced modifications were followed by micro-Raman and atomic force microscopy (AFM). The Raman spectrum shows the decrease in Raman intensity and formation of unsaturated bonds with an increase in the gamma dose. AFM image displays rough surface morphology after irradiation. The detailed Raman analysis of plastic bottle sheets is presented here, and the results are correlated with the AFMmore » observations.« less
Ocean Tide Influences on the Antarctic and Greenland Ice Sheets

NASA Astrophysics Data System (ADS)

Padman, Laurie; Siegfried, Matthew R.; Fricker, Helen A.

2018-03-01

Ocean tides are the main source of high-frequency variability in the vertical and horizontal motion of ice sheets near their marine margins. Floating ice shelves, which occupy about three quarters of the perimeter of Antarctica and the termini of four outlet glaciers in northern Greenland, rise and fall in synchrony with the ocean tide. Lateral motion of floating and grounded portions of ice sheets near their marine margins can also include a tidal component. These tide-induced signals provide insight into the processes by which the oceans can affect ice sheet mass balance and dynamics. In this review, we summarize in situ and satellite-based measurements of the tidal response of ice shelves and grounded ice, and spatial variability of ocean tide heights and currents around the ice sheets. We review sensitivity of tide heights and currents as ocean geometry responds to variations in sea level, ice shelf thickness, and ice sheet mass and extent. We then describe coupled ice-ocean models and analytical glacier models that quantify the effect of ocean tides on lower-frequency ice sheet mass loss and motion. We suggest new observations and model developments to improve the representation of tides in coupled models that are used to predict future ice sheet mass loss and the associated contribution to sea level change. The most critical need is for new data to improve maps of bathymetry, ice shelf draft, spatial variability of the drag coefficient at the ice-ocean interface, and higher-resolution models with improved representation of tidal energy sinks.
More stereotypes, please! The limits of 'theory of mind' and the need for further studies on the complexity of real world social interactions.

PubMed

Andrews, Kristin

2017-01-01

I suggest that the Stereotype Rationality Hypothesis (Jussim 2012) is only partially right. I agree it is rational to rely on stereotypes, but in the complexity of real world social interactions, most of our individuating information invokes additional stereotypes. Despite assumptions to the contrary, there is reason to think theory of mind is not accurate, and social psychology's denial of stereotype accuracy led us toward mindreading/theory of mind - a less accurate account of how we understand other people.
A MoO2 sheet as a promising electrode material: ultrafast Li-diffusion and astonishing Li-storage capacity

NASA Astrophysics Data System (ADS)

Zhou, Yungang; Geng, Cheng

2017-03-01

The potential of MoO2 crystal as an electrode material is reported, and nanostructural MoO2 systems, including nanoparticles, nanospheres, nanobelts and nanowires, were synthesized and proved to be advanced electrode materials. A two-dimensional (2D) geometric structure represents an extreme of surface-to-volume ratio, and thus is more suitable as an electrode material in general. Stimulated by the recent fabrication of 2D MoO2, we adopted an ab initio molecular dynamics simulation and density functional theory calculation to study the stability and electrochemical properties of a MoO2 sheet. Identified by a phonon dispersion curve and potential energy curve calculations, the MoO2 sheet proved to be dynamically and thermally stable. After lithiation, similar to most promising 2D structures, we found that a Li atom can strongly adsorb on a MoO2 sheet, and the lithiated MoO2 sheet presented excellent metallic properties. Note that, compared with most promising 2D structures, we unexpectedly revealed that the diffusion barrier of the Li atom on the MoO2 sheet was much lower and the storage capacity of the MoO2 sheet was much larger. The calculated energy barrier for the diffusion of Li on the MoO2 sheet was only 75 meV, and, due to multilayer adsorption, the theoretical capacity of the MoO2 sheet can reach up to 2513 mA h g-1. Benefiting from general properties, such as strong Li-binding and excellent conductivity, and unique phenomena, such as ultrafast diffusion capacity and astonishing storage capacity, we highlight a new promising electrode material for the Li-ion battery.

Modelling the Climate - Greenland Ice Sheet Interaction in the Coupled Ice-sheet/Climate Model EC-EARTH - PISM

NASA Astrophysics Data System (ADS)

Yang, S.; Madsen, M. S.; Rodehacke, C. B.; Svendsen, S. H.; Adalgeirsdottir, G.

2014-12-01

Recent observations show that the Greenland ice sheet (GrIS) has been losing mass with an increasing speed during the past decades. Predicting the GrIS changes and their climate consequences relies on the understanding of the interaction of the GrIS with the climate system on both global and local scales, and requires climate model systems with an explicit and physically consistent ice sheet module. A fully coupled global climate model with a dynamical ice sheet model for the GrIS has recently been developed. The model system, EC-EARTH - PISM, consists of the EC-EARTH, an atmosphere, ocean and sea ice model system, and the Parallel Ice Sheet Model (PISM). The coupling of PISM includes a modified surface physical parameterization in EC-EARTH adapted to the land ice surface over glaciated regions in Greenland. The PISM ice sheet model is forced with the surface mass balance (SMB) directly computed inside the EC-EARTH atmospheric module and accounting for the precipitation, the surface evaporation, and the melting of snow and ice over land ice. PISM returns the simulated basal melt, ice discharge and ice cover (extent and thickness) as boundary conditions to EC-EARTH. This coupled system is mass and energy conserving without being constrained by any anomaly correction or flux adjustment, and hence is suitable for investigation of ice sheet - climate feedbacks. Three multi-century experiments for warm climate scenarios under (1) the RCP85 climate forcing, (2) an abrupt 4xCO2 and (3) an idealized 1% per year CO2 increase are performed using the coupled model system. The experiments are compared with their counterparts of the standard CMIP5 simulations (without the interactive ice sheet) to evaluate the performance of the coupled system and to quantify the GrIS feedbacks. In particular, the evolution of the Greenland ice sheet under the warm climate and its impacts on the climate system are investigated. Freshwater fluxes from the Greenland ice sheet melt to the Arctic
Kelvin-Helmholtz instability of a thin liquid sheet: Effect of the gas-boundary layer

NASA Astrophysics Data System (ADS)

Tirumkudulu, Mahesh

2017-11-01

It is well known that when a thin liquid sheet moves with respect to a surrounding gas phase, the liquid sheet is susceptible to the Kelvin-Helmholtz instability. Here, flow in both the liquid and the gas phases are assumed to be inviscid. In this work, we include exactly via a perturbation analysis, the influence of the growing boundary layer in the gas phase in the base flow and show that both temporal and spatial growth rates obtained from the linear stability analysis are significantly reduced due to the presence of the boundary layer. These results are in line with the simulation results of Lozano et al. and Tammisola et al.. We conclude with the implication of these results on the break-up of radially expanding liquid sheets. Funding from IIT Bombay, CSIR India, and Trinity College, Cambridge University is acknowledged.
Effect of Inductive Coil Geometry and Current Sheet Trajectory of a Conical Theta Pinch Pulsed Inductive Plasma Accelerator

NASA Technical Reports Server (NTRS)

Hallock, Ashley K.; Polzin, Kurt A.; Bonds, Kevin W.; Emsellem, Gregory D.

2011-01-01

Results are presented demonstrating the e ect of inductive coil geometry and current sheet trajectory on the exhaust velocity of propellant in conical theta pinch pulsed induc- tive plasma accelerators. The electromagnetic coupling between the inductive coil of the accelerator and a plasma current sheet is simulated, substituting a conical copper frustum for the plasma. The variation of system inductance as a function of plasma position is obtained by displacing the simulated current sheet from the coil while measuring the total inductance of the coil. Four coils of differing geometries were employed, and the total inductance of each coil was measured as a function of the axial displacement of two sep- arate copper frusta both having the same cone angle and length as the coil but with one compressed to a smaller size relative to the coil. The measured relationship between total coil inductance and current sheet position closes a dynamical circuit model that is used to calculate the resulting current sheet velocity for various coil and current sheet con gura- tions. The results of this model, which neglects the pinching contribution to thrust, radial propellant con nement, and plume divergence, indicate that in a conical theta pinch ge- ometry current sheet pinching is detrimental to thruster performance, reducing the kinetic energy of the exhausting propellant by up to 50% (at the upper bound for the parameter range of the study). The decrease in exhaust velocity was larger for coils and simulated current sheets of smaller half cone angles. An upper bound for the pinching contribution to thrust is estimated for typical operating parameters. Measurements of coil inductance for three di erent current sheet pinching conditions are used to estimate the magnetic pressure as a function of current sheet radial compression. The gas-dynamic contribution to axial acceleration is also estimated and shown to not compensate for the decrease in axial electromagnetic acceleration
The dynamics and shapes of a viscous sheet spreading on a moving liquid bath

NASA Astrophysics Data System (ADS)

Sebilleau, J.; Lebon, L.; Limat, L.; Quartier, L.; Receveur, M.

2010-10-01

We investigate the shape and dynamics of a floating viscous sheet formed by a jet falling on a static or moving bath under partial wetting conditions. For a static bath, the viscous sheet has a circular shape and spreads with a uniform thickness that is surprisingly larger than the static Langmuir equilibrium thickness. This thickening effect seems to be linked to a peculiarity of the oil used for the bath, which is in situation of total wetting on the sheet surface, and climbs the sheet a bit like a macroscopic "precursor film" that increases dissipation at the sheet perimeter. For a moving bath, the viscous sheet evolves from an ellipse to a ribbon, a transient remarkable pear shape being observed between these two states. A simple kinematic model of advection of the spreading sheet by the bath predicts very well the characteristics of the ribbon regime. Convected sheets whose shape is reminiscent of pendant drops in 2D are also observed at higher bath velocity, with interesting pinch off phenomena.
Energy information sheets

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

Not Available

1993-12-02

The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the general public. Written for the general public, the EIA publication Energy Information Sheets was developed to provide information on various aspects of fuel production, prices, consumption and capability. The information contained herein pertains to energy data as of December 1991. Additional information on related subject matter can be found in other EIA publications as referenced at the end of each sheet.
Weld Repair of Thin Aluminum Sheet

NASA Technical Reports Server (NTRS)

Beuyukian, C. S.; Mitchell, M. J.

1986-01-01

Weld repairing of thin aluminum sheets now possible, using niobium shield and copper heat sinks. Refractory niobium shield protects aluminum adjacent to hole, while copper heat sinks help conduct heat away from repair site. Technique limits tungsten/inert-gas (TIG) welding bombardment zone to melt area, leaving surrounding areas around weld unaffected. Used successfully to repair aluminum cold plates on Space Shuttle, Commercial applications, especially in sealing fractures, dents, and holes in thin aluminum face sheets or clad brazing sheet in cold plates, heat exchangers, coolers, and Solar panels. While particularly suited to thin aluminum sheet, this process also used in thicker aluminum material to prevent surface damage near weld area.
The Mediating Effect of World Assumptions on the Relationship between Trauma Exposure and Depression

ERIC Educational Resources Information Center

Lilly, Michelle M.; Valdez, Christine E.; Graham-Bermann, Sandra A.

2011-01-01

The association between trauma exposure and mental health-related challenges such as depression are well documented in the research literature. The assumptive world theory was used to explore this relationship in 97 female survivors of intimate partner violence (IPV). Participants completed self-report questionnaires that assessed trauma history,…
Cosmological perturbation theory in 1+1 dimensions

NASA Astrophysics Data System (ADS)

McQuinn, Matthew; White, Martin

2016-01-01

Many recent studies have highlighted certain failures of the standard Eulerian-space cosmological perturbation theory (SPT). Its problems include (1) not capturing large-scale bulk flows [leading to an Script O( 1) error in the 1-loop SPT prediction for the baryon acoustic peak in the correlation function], (2) assuming that the Universe behaves as a pressureless, inviscid fluid, and (3) treating fluctuations on scales that are non-perturbative as if they were. Recent studies have highlighted the successes of perturbation theory in Lagrangian space or theories that solve equations for the effective dynamics of smoothed fields. Both approaches mitigate some or all of the aforementioned issues with SPT. We discuss these physical developments by specializing to the simplified 1D case of gravitationally interacting sheets, which allows us to substantially reduces the analytic overhead and still (as we show) maintain many of the same behaviors as in 3D. In 1D, linear-order Lagrangian perturbation theory ("the Zeldovich approximation") is exact up to shell crossing, and we prove that nth-order Eulerian perturbation theory converges to the Zeldovich approximation as narrow ∞. In no 1D cosmology that we consider (including a CDM-like case and power-law models) do these theories describe accurately the matter power spectrum on any mildly nonlinear scale. We find that theories based on effective equations are much more successful at describing the dynamics. Finally, we discuss many topics that have recently appeared in the perturbation theory literature such as beat coupling, the shift and smearing of the baryon acoustic oscillation feature, and the advantages of Fourier versus configuration space. Our simplified 1D case serves as an intuitive review of these perturbation theory results.
Further Studies on the Effect of SiN x Refractive Index and Emitter Sheet Resistance on Potential-Induced Degradation

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

Oh, Jaewon; Dauksher, Bill; Bowden, Stuart

We present the impacts of silicon nitride (SiNx) antireflection coating refractive index and emitter sheet resistance on potential-induced degradation of the shunting type (PID-s). Previously, it has been shown that the cell becomes more PID-s-susceptible as the refractive index decreases or the emitter sheet resistance increases. To verify the effect of refractive index on PID-s, we fabricated cells with varying SiN x refractive index (1.87, 1.94, 2.05) on typical p-type base solar cells with ~60 Ω/sq emitters. However, none of these cells showed output power degradation, regardless of the refractive index. Further investigation of the emitter showed that the PID-smore » was suppressed at ~60 Ω/sq due to the extremely high surface phosphorus concentration (6 x 10 21 cm -3), as measured by secondary ion mass spectrometry. Furthermore, PID-s was observed on cells possessing a high emitter sheet resistance (~80 Ω/sq). In conclusion, the emitter surface phosphorus concentration plays an important role in determining PID-s susceptibility.« less
Further Studies on the Effect of SiN x Refractive Index and Emitter Sheet Resistance on Potential-Induced Degradation

DOE PAGES

Oh, Jaewon; Dauksher, Bill; Bowden, Stuart; ...

2017-01-11

We present the impacts of silicon nitride (SiNx) antireflection coating refractive index and emitter sheet resistance on potential-induced degradation of the shunting type (PID-s). Previously, it has been shown that the cell becomes more PID-s-susceptible as the refractive index decreases or the emitter sheet resistance increases. To verify the effect of refractive index on PID-s, we fabricated cells with varying SiN x refractive index (1.87, 1.94, 2.05) on typical p-type base solar cells with ~60 Ω/sq emitters. However, none of these cells showed output power degradation, regardless of the refractive index. Further investigation of the emitter showed that the PID-smore » was suppressed at ~60 Ω/sq due to the extremely high surface phosphorus concentration (6 x 10 21 cm -3), as measured by secondary ion mass spectrometry. Furthermore, PID-s was observed on cells possessing a high emitter sheet resistance (~80 Ω/sq). In conclusion, the emitter surface phosphorus concentration plays an important role in determining PID-s susceptibility.« less
Modeling the Alzheimer Abeta17-42 fibril architecture: tight intermolecular sheet-sheet association and intramolecular hydrated cavities.

PubMed

Zheng, Jie; Jang, Hyunbum; Ma, Buyong; Tsai, Chung-Jun; Nussinov, Ruth

2007-11-01

We investigate Abeta(17-42) protofibril structures in solution using molecular dynamics simulations. Recently, NMR and computations modeled the Abeta protofibril as a longitudinal stack of U-shaped molecules, creating an in-parallel beta-sheet and loop spine. Here we study the molecular architecture of the fibril formed by spine-spine association. We model in-register intermolecular beta-sheet-beta-sheet associations and study the consequences of Alzheimer's mutations (E22G, E22Q, E22K, and M35A) on the organization. We assess the structural stability and association force of Abeta oligomers with different sheet-sheet interfaces. Double-layered oligomers associating through the C-terminal-C-terminal interface are energetically more favorable than those with the N-terminal-N-terminal interface, although both interfaces exhibit high structural stability. The C-terminal-C-terminal interface is essentially stabilized by hydrophobic and van der Waals (shape complementarity via M35-M35 contacts) intermolecular interactions, whereas the N-terminal-N-terminal interface is stabilized by hydrophobic and electrostatic interactions. Hence, shape complementarity, or the "steric zipper" motif plays an important role in amyloid formation. On the other hand, the intramolecular Abeta beta-strand-loop-beta-strand U-shaped motif creates a hydrophobic cavity with a diameter of 6-7 A, allowing water molecules and ions to conduct through. The hydrated hydrophobic cavities may allow optimization of the sheet association and constitute a typical feature of fibrils, in addition to the tight sheet-sheet association. Thus, we propose that Abeta fiber architecture consists of alternating layers of tight packing and hydrated cavities running along the fibrillar axis, which might be possibly detected by high-resolution imaging.
Leveraging Cloud Technology to Provide a Responsive, Reliable and Scalable Backend for the Virtual Ice Sheet Laboratory Using the Ice Sheet System Model and Amazon's Elastic Compute Cloud

NASA Astrophysics Data System (ADS)

Perez, G. L.; Larour, E. Y.; Halkides, D. J.; Cheng, D. L. C.

2015-12-01

The Virtual Ice Sheet Laboratory(VISL) is a Cryosphere outreach effort byscientists at the Jet Propulsion Laboratory(JPL) in Pasadena, CA, Earth and SpaceResearch(ESR) in Seattle, WA, and the University of California at Irvine (UCI), with the goal of providing interactive lessons for K-12 and college level students,while conforming to STEM guidelines. At the core of VISL is the Ice Sheet System Model(ISSM), an open-source project developed jointlyat JPL and UCI whose main purpose is to model the evolution of the polar ice caps in Greenland and Antarctica. By using ISSM, VISL students have access tostate-of-the-art modeling software that is being used to conduct scientificresearch by users all over the world. However, providing this functionality isby no means simple. The modeling of ice sheets in response to sea and atmospheric temperatures, among many other possible parameters, requiressignificant computational resources. Furthermore, this service needs to beresponsive and capable of handling burst requests produced by classrooms ofstudents. Cloud computing providers represent a burgeoning industry. With majorinvestments by tech giants like Amazon, Google and Microsoft, it has never beeneasier or more affordable to deploy computational elements on-demand. This isexactly what VISL needs and ISSM is capable of. Moreover, this is a promisingalternative to investing in expensive and rapidly devaluing hardware.
ESTIMATION OF EFFECTIVE SHEAR STRESS WORKING ON FLAT SHEET MEMBRANE USING FLUIDIZED MEDIA IN MBRs

NASA Astrophysics Data System (ADS)

Zaw, Hlwan Moe; Li, Tairi; Nagaoka, Hiroshi; Mishima, Iori

This study was aimed at estimating effective shear stress working on flat sheet membrane by the addition of fluidized media in MBRs. In both of laboratory-scale aeration tanks with and without fluidized media, shear stress variations on membrane surface and water phase velocity variations were measured and MBR operation was conducted. For the evaluation of the effective shear stress working on membrane surface to mitigate membrane surface, simulation of trans-membrane pressure increase was conducted. It was shown that the time-averaged absolute value of shear stress was smaller in the reactor with fluidized media than without fluidized media. However, due to strong turbulence in the reactor with fluidized media caused by interaction between water-phase and media and also due to the direct interaction between membrane surface and fluidized media, standard deviation of shear stress on membrane surface was larger in the reactor with fluidized media than without media. Histograms of shear stress variation data were fitted well to normal distribution curves and mean plus three times of standard deviation was defined to be a maximum shear stress value. By applying the defined maximum shear stress to a membrane fouling model, trans-membrane pressure curve in the MBR experiment was simulated well by the fouling model indicting that the maximum shear stress, not time-averaged shear stress, can be regarded as an effective shear stress to prevent membrane fouling in submerged flat-sheet MBRs.
Heliospheric current sheet and effects of its interaction with solar cosmic rays

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

Malova, H. V., E-mail: hmalova@yandex.ru; Popov, V. Yu.; Grigorenko, E. E.

2016-08-15

The effects of interaction of solar cosmic rays (SCRs) with the heliospheric current sheet (HCS) in the solar wind are analyzed. A self-consistent kinetic model of the HCS is developed in which ions with quasiadiabatic dynamics can present. The HCS is considered an equilibrium embedded current structure in which two main plasma species with different temperatures (the low-energy background plasma of the solar wind and the higher energy SCR component) contribute to the current. The obtained results are verified by comparing with the results of numerical simulations based on solving equations of motion by the particle tracing method in themore » given HCS magnetic field with allowance for SCR particles. It is shown that the HCS is a relatively thin multiscale current configuration embedded in a thicker plasma layer. In this case, as a rule, the shear (tangential to the sheet current) component of the magnetic field is present in the HCS. Taking into account high-energy SCR particles in the HCS can lead to a change of its configuration and the formation of a multiscale embedded structure. Parametric family of solutions is considered in which the current balance in the HCS is provided at different SCR temperatures and different densities of the high-energy plasma. The SCR densities are determined at which an appreciable (detectable by satellites) HCS thickening can occur. Possible applications of this modeling to explain experimental observations are discussed.« less
Landform Formation Under Ice Sheets

NASA Astrophysics Data System (ADS)

Schoof, C. G.; Ng, F. S.; Hallet, B.

2004-12-01

We present a new mathematical model for the formation of subglacial landforms such as drumlins under a warm-based, soft-bedded ice sheet. At the heart of the model is a channelized drainage system in which smaller channels grow at the expense of larger ones, leading to the continuous creation and extinction of drainage paths, and to a spatially distributed imprint on the landscape. We demonstrate how interactions between such a drainage system, bed topography and ice flow can lead to the spontaneous formation of subglacial landforms, and discuss the effect of different sediment transport characteristics in the drainage system on the shape and migration of these landforms. This mathematical model is the first component of a study of landscape/ice-sheet self-organization, which is inspired and guided, in part, by new digital topographic data (LIDAR) that are revealing with unprecedented detail the striking grain of glacially scoured topography on length scales ranging from 0.5 to 20 km.
Design of the MISMIP+, ISOMIP+, and MISOMIP ice-sheet, ocean, and coupled ice sheet-ocean intercomparison projects

NASA Astrophysics Data System (ADS)

Asay-Davis, Xylar; Cornford, Stephen; Martin, Daniel; Gudmundsson, Hilmar; Holland, David; Holland, Denise

2015-04-01

The MISMIP and MISMIP3D marine ice sheet model intercomparison exercises have become popular benchmarks, and several modeling groups have used them to show how their models compare to both analytical results and other models. Similarly, the ISOMIP (Ice Shelf-Ocean Model Intercomparison Project) experiments have acted as a proving ground for ocean models with sub-ice-shelf cavities.As coupled ice sheet-ocean models become available, an updated set of benchmark experiments is needed. To this end, we propose sequel experiments, MISMIP+ and ISOMIP+, with an end goal of coupling the two in a third intercomparison exercise, MISOMIP (the Marine Ice Sheet-Ocean Model Intercomparison Project). Like MISMIP3D, the MISMIP+ experiments take place in an idealized, three-dimensional setting and compare full 3D (Stokes) and reduced, hydrostatic models. Unlike the earlier exercises, the primary focus will be the response of models to sub-shelf melting. The chosen configuration features an ice shelf that experiences substantial lateral shear and buttresses the upstream ice, and so is well suited to melting experiments. Differences between the steady states of each model are minor compared to the response to melt-rate perturbations, reflecting typical real-world applications where parameters are chosen so that the initial states of all models tend to match observations. The three ISOMIP+ experiments have been designed to to make use of the same bedrock topography as MISMIP+ and using ice-shelf geometries from MISMIP+ results produced by the BISICLES ice-sheet model. The first two experiments use static ice-shelf geometries to simulate the evolution of ocean dynamics and resulting melt rates to a quasi-steady state when far-field forcing changes in either from cold to warm or from warm to cold states. The third experiment prescribes 200 years of dynamic ice-shelf geometry (with both retreating and advancing ice) based on a BISICLES simulation along with similar flips between warm and
Capping Parallel β-Sheets of Acetyl(Ala)6NH2 with an Acetyl(Ala)5ProNH2 Can Arrest the Growth of the Sheet, Suggesting a Potential for Curtailing Amyloid Growth. An ONIOM and Density Functional Theory Study

PubMed Central

2015-01-01

We present ONIOM calculations using B3LYP/d95(d,p) as the high level and AM1 as the medium level on parallel β-sheets containing four strands of Ac-AAAAAA-NH2 capped with either Ac-AAPAAA-NH2 or Ac-AAAPAA-NH2. Because Pro can form H-bonds from only one side of the peptide linkage (that containing the C=O H-bond acceptor), only one of the two Pro-containing strands can favorably add to the sheet on each side. Surprisingly, when the sheet is capped with AAPAAA-NH2 at one edge, the interaction between the cap and sheet is slightly more stabilizing than that of another all Ala strand. Breaking down the interaction enthalpies into H-bonding and distortion energies shows the favorable interaction to be due to lower distortion energies in both the strand and the four-stranded sheet. Because another strand would be inhibited for attachment to the other side of the capping (Pro-containing) strand, we suggest the possible use of Pro residues in peptides designed to arrest the growth of many amyloids. PMID:24422496
Microcomponent chemical process sheet architecture

DOEpatents

Wegeng, Robert S.; Drost, M. Kevin; Call, Charles J.; Birmingham, Joseph G.; McDonald, Carolyn Evans; Kurath, Dean E.; Friedrich, Michele

1998-01-01

The invention is a microcomponent sheet architecture wherein macroscale unit processes are performed by microscale components. The sheet architecture may be a single laminate with a plurality of separate microcomponent sections or the sheet architecture may be a plurality of laminates with one or more microcomponent sections on each laminate. Each microcomponent or plurality of like microcomponents perform at least one chemical process unit operation. A first laminate having a plurality of like first microcomponents is combined with at least a second laminate having a plurality of like second microcomponents thereby combining at least two unit operations to achieve a system operation.
Tearing Instability of a Current Sheet Forming by Sheared Incompressible Flow

NASA Astrophysics Data System (ADS)

Tolman, Elizabeth; Loureiro, Nuno; Uzdensky, Dmitri

2017-10-01

Sweet-Parker current sheets are unstable to the tearing mode, suggesting they will not form in physical systems. Understanding magnetic reconnection thus requires study of the stability of a current sheet as it forms. Such formation can occur as a result of sheared, sub-Alfvénic incompressible flows into and along the sheet. This work presents an analysis of how tearing perturbations behave in a current sheet forming under the influence of such flows, beginning with a phase when the growth rate of the tearing mode is small and the behavior of perturbations is primarily governed by ideal MHD. Later, after the tearing growth rate becomes significant relative to the time scale of the driving flows, the flows cause a slight reduction in the tearing growth rate and wave vector of the dominant mode. Once the tearing mode enters the nonlinear regime, the flows accelerate the tearing growth slightly; during X-point collapse, the flows have negligible effect on the system behavior. This analysis allows greater understanding of reconnection in evolving systems and increases confidence in the application of tools developed in time-independent current sheets to changing current sheets. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship.
Urban ecology in a developing world: why advanced socioecological theory needs Africa.

PubMed

McHale, Melissa R; Bunn, David N; Pickett, Steward Ta; Twine, Wayne

2013-12-01

Socioecological theory, developed through the study of urban environments, has recently led to a proliferation of research focusing on comparative analyses of cities. This research emphasis has been concentrated in the more developed countries of the Northern Hemisphere (often referred to as the "Global North"), yet urbanization is now occurring mostly in the developing world, with the fastest rates of growth in sub-Saharan Africa. Countries like South Africa are experiencing a variety of land-cover changes that may challenge current assumptions about the differences between urban and rural environments and about the connectivity of these dynamic socioecological systems. Furthermore, questions concerning ecosystem services, landscape preferences, and conservation - when analyzed through rural livelihood frameworks - may provide insights into the social and ecological resilience of human settlements. Increasing research on urban development processes occurring in Africa, and on patterns of kinship and migration in the less developed countries of the "Global South", will advance a more comprehensive worldview of how future urbanization will influence the progress of sustainable societies.

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