Character displacement and the evolution of niche complementarity in a model biofilm community

PubMed Central

Ellis, Crystal N; Traverse, Charles C; Mayo-Smith, Leslie; Buskirk, Sean W; Cooper, Vaughn S

2015-01-01

Colonization of vacant environments may catalyze adaptive diversification and be followed by competition within the nascent community. How these interactions ultimately stabilize and affect productivity are central problems in evolutionary ecology. Diversity can emerge by character displacement, in which selection favors phenotypes that exploit an alternative resource and reduce competition, or by facilitation, in which organisms change the environment and enable different genotypes or species to become established. We previously developed a model of long-term experimental evolution in which bacteria attach to a plastic bead, form a biofilm, and disperse to a new bead. Here, we focus on the evolution of coexisting mutants within a population of Burkholderia cenocepacia and how their interactions affected productivity. Adaptive mutants initially competed for space, but later competition declined, consistent with character displacement and the predicted effects of the evolved mutations. The community reached a stable equilibrium as each ecotype evolved to inhabit distinct, complementary regions of the biofilm. Interactions among ecotypes ultimately became facilitative and enhanced mixed productivity. Observing the succession of genotypes within niches illuminated changing selective forces within the community, including a fundamental role for genotypes producing small colony variants that underpin chronic infections caused by B. cenocepacia. PMID:25494960

The time-course of lexical activation in Japanese morphographic word recognition: evidence for a character-driven processing model.

PubMed

Miwa, Koji; Libben, Gary; Dijkstra, Ton; Baayen, Harald

2014-01-01

This lexical decision study with eye tracking of Japanese two-kanji-character words investigated the order in which a whole two-character word and its morphographic constituents are activated in the course of lexical access, the relative contributions of the left and the right characters in lexical decision, the depth to which semantic radicals are processed, and how nonlinguistic factors affect lexical processes. Mixed-effects regression analyses of response times and subgaze durations (i.e., first-pass fixation time spent on each of the two characters) revealed joint contributions of morphographic units at all levels of the linguistic structure with the magnitude and the direction of the lexical effects modulated by readers' locus of attention in a left-to-right preferred processing path. During the early time frame, character effects were larger in magnitude and more robust than radical and whole-word effects, regardless of the font size and the type of nonwords. Extending previous radical-based and character-based models, we propose a task/decision-sensitive character-driven processing model with a level-skipping assumption: Connections from the feature level bypass the lower radical level and link up directly to the higher character level.

Interspecific aggression, not interspecific mating, drives character displacement in the wing coloration of male rubyspot damselflies (Hetaerina)

PubMed Central

Drury, J. P.; Grether, G. F.

2014-01-01

Traits that mediate intraspecific social interactions may overlap in closely related sympatric species, resulting in costly between-species interactions. Such interactions have principally interested investigators studying the evolution of reproductive isolation via reproductive character displacement (RCD) or reinforcement, yet in addition to reproductive interference, interspecific trait overlap can lead to costly between-species aggression. Previous research on rubyspot damselflies (Hetaerina spp.) demonstrated that sympatric shifts in male wing colour patterns and competitor recognition reduce interspecific aggression, supporting the hypothesis that agonistic character displacement (ACD) drove trait shifts. However, a recent theoretical model shows that RCD overshadows ACD if the same male trait is used for both female mate recognition and male competitor recognition. To determine whether female mate recognition is based on male wing coloration in Hetaerina, we conducted a phenotype manipulation experiment. Compared to control males, male H. americana with wings manipulated to resemble a sympatric congener (H. titia) suffered no reduction in mating success. Thus, female mate recognition is not based on species differences in male wing coloration. Experimental males did, however, experience higher interspecific fighting rates and reduced survival compared to controls. These results greatly strengthen the case for ACD and highlight the mechanistic distinction between ACD and RCD. PMID:25339724

Molecular signatures of selection on reproductive character displacement of flower color in Phlox drummondii.

PubMed

Hopkins, Robin; Levin, Donald A; Rausher, Mark D

2012-02-01

Character displacement, which arises when species diverge in sympatry to decrease competition for resources or reproductive interference, has been observed in a wide variety of plants and animals. A classic example of reproductive character displacement, presumed to be caused by reinforcing selection, is flower-color variation in the native Texas wildflower Phlox drummondii. Here, we use population genetic analyses to investigate molecular signatures of selection on flower-color variation in this species. First, we quantify patterns of neutral genetic variation across the range of P. drummondii to demonstrate that restricted gene flow and genetic drift cannot explain the pattern of flower-color divergence in this species. There is evidence of extensive gene flow across populations with different flower colors, suggesting selection caused flower-color divergence. Second, analysis of sequence variation in the genes underlying this divergence reveals a signature of a selective sweep in one of the two genes, further indicating selection is responsible for divergence in sympatry. The lack of a signature of selection at the second locus does not necessarily indicate a lack of selection on this locus but instead brings attention to the uncertainty in depending on molecular signatures to identify selection. © 2011 The Author(s). Evolution© 2011 The Society for the Study of Evolution.

Character displacement and the evolution of niche complementarity in a model biofilm community.

PubMed

Ellis, Crystal N; Traverse, Charles C; Mayo-Smith, Leslie; Buskirk, Sean W; Cooper, Vaughn S

2015-02-01

Colonization of vacant environments may catalyze adaptive diversification and be followed by competition within the nascent community. How these interactions ultimately stabilize and affect productivity are central problems in evolutionary ecology. Diversity can emerge by character displacement, in which selection favors phenotypes that exploit an alternative resource and reduce competition, or by facilitation, in which organisms change the environment and enable different genotypes or species to become established. We previously developed a model of long-term experimental evolution in which bacteria attach to a plastic bead, form a biofilm, and disperse to a new bead. Here, we focus on the evolution of coexisting mutants within a population of Burkholderia cenocepacia and how their interactions affected productivity. Adaptive mutants initially competed for space, but later competition declined, consistent with character displacement and the predicted effects of the evolved mutations. The community reached a stable equilibrium as each ecotype evolved to inhabit distinct, complementary regions of the biofilm. Interactions among ecotypes ultimately became facilitative and enhanced mixed productivity. Observing the succession of genotypes within niches illuminated changing selective forces within the community, including a fundamental role for genotypes producing small colony variants that underpin chronic infections caused by B. cenocepacia. © 2014 The Author(s). Evolution published by Wiley Periodicals, Inc. on behalf of The Society for the Study of Evolution.

Design and analysis of a 3D Elliptical Micro-Displacement Motion Stage

NASA Astrophysics Data System (ADS)

Lin, Jieqiong; Zhao, Dongpo; Lu, Mingming; Zhou, Jiakang

2017-12-01

Micro-displacement motion stage driven by piezoelectric actuator has a significant demand in the field of ultra-precision machining in recent years, while the design of micro-displacement motion stage plays an important role to realize a large displacement output and high precision control. Thus, a 3D elliptical micro-displacement motion stage driven by three PZT actuators has been developed. Firstly, the 3D elliptical trajectory of this motion stage could be adjusted through the form of the PZT actuators input signal. Then, the desired trajectory was obtained by adjusting the micro displacement of the motion stage in 3D elliptical space. Finally, the trajectory simulation and the finite element simulation were applied in this motion stage. The experimental results shown that, the output displacement of the three directions under the input force of the 1600N were 14μm, 16μm and 74μm, respectively. And the first three modes were 1471.6Hz, 2698.4Hz and 2803.4Hz, respectively. Analysis and experiments were carried out to verify the performance, result proved that a large output displacement and high precision control could be obtained.

Quantitative analysis of the orthodontic and orthopedic effects of maxillary traction.

PubMed

Baumrind, S; Korn, E L; Isaacson, R J; West, E E; Molthen, R

1983-11-01

This article analyzes differences in displacement of ANS and of the upper first molar when different vectors of force are delivered to the maxilla in non-full-banded Phase I mixed-dentition treatment of Class II malocclusion. The sample is identical to that for which we have previously reported differences in change in several key measures of mandibular and facial shape. It includes a cervical-traction group, a high-pull-to-upper-molar group, a modified-activator group, and an untreated Class II control group. Using newly developed computer-conducted procedures, which are described, we have been able to partition the orthodontic and orthopedic components of upper molar displacement and also to isolate treatment effects from those attributable to spontaneous growth and development. In the region of ANS, small but statistically significant and clinically meaningful differences were noted between treatments. When the intercurrent effects of growth and development had been factored out (Table III), orthopedic distal displacement of ANS was significantly greater in the high-pull and cervical groups than in the activator group. Orthopedic downward displacement of ANS was seen to be significantly greater in the cervical group than in the high-pull and activator groups. In the region of the first molar cusp, mean distal displacement of the tooth as an orthopedic effect was found to be almost identical in the cervical and high-pull groups (although variability was greater in the cervical group), but the mean orthodontic effect was significantly greater in the high-pull group than in the cervical group. In the cervical group, where relatively light forces were used for relatively long treatment periods on average, more of the total distal displacement of the upper molar was of an orthopedic character than of an orthodontic character. Conversely, in the high-pull group, in which relatively heavier forces tended to be used for briefer treatment periods, most of the distal displacement at the upper molar was of an orthodontic character. These observations are contrary to expectations from conventional orthodontic theory. In the activator-treated group, roughly equal components of the treatment-associated distal displacement of the upper molar were of the orthodontic and orthopedic types. As concerns changes in the vertical direction in the region of the molar cusp, significant intrusion of both the orthopedic and orthodontic types was seen in the high-pull sample as compared to each of the other groups examined.(ABSTRACT TRUNCATED AT 400 WORDS)

Testing the role of interspecific competition in the evolutionary origin of elevational zonation: an example with Buarremon brush-finches (Aves, Emberizidae) in the neotropical mountains.

PubMed

Cadena, Carlos Daniel

2007-05-01

Interspecific competition might drive the evolution of ecological niches and result in pairs of formerly competing species segregating along ecological gradients following a process of character displacement. This mechanism has been proposed to account for replacement of related species along gradients of elevation in many areas of the world, but the fundamental issue of whether competition is responsible for the origin of elevational replacements has not been tested. To test hypotheses about the role of interspecific competition in the origin of complementary elevational ranges, I combined molecular phylogenetics, phylogeography, and population genetic analyses on Buarremon torquatus and B. brunneinucha (Aves, Emberizidae), whose patterns of elevational distribution suggest character displacement or ecological release. The hypothesis that elevational distributions in these species changed in opposite directions as a result of competition is untenable because: (1) a historical expansion of the range of B. brunneinucha into areas occupied by B. torquatus was not accompanied by a shift in the elevational range of the former species; (2) when B. brunneinucha colonized the range of B. torquatus, lineages of the latter distributions had already diverged; and (3) historical trends in effective population size do not suggest populations with elevational ranges abutting those of putative competitors have declined as would be expected if competition caused range contractions. However, owing to uncertainty in coalescent estimates of historical population sizes, the hypothesis that some populations of B. torquatus have declined cannot be confidently rejected, which suggests asymmetric character displacement might have occurred. I suggest that the main role of competition in elevational zonation may be to act as a sorting mechanism that allows the coexistence along mountain slopes only of ecologically similar species that differ in elevational distributions prior to attaining sympatry. The contrasting biogeographic histories of B. brunneinucha and B. torquatus illustrate how present-day ecological interactions can have recent origins, and highlights important challenges for testing the hypothesis of character displacement in the absence of data on population history and robust reconstructions of the evolution of traits and geographic ranges.

Theory of morphological transformation of viral capsid shell during the maturation process in the HK97 bacteriophage and similar viruses

NASA Astrophysics Data System (ADS)

Konevtsova, O. V.; Lorman, V. L.; Rochal, S. B.

2016-05-01

We consider the symmetry and physical origin of collective displacement modes playing a crucial role in the morphological transformation during the maturation of the HK97 bacteriophage and similar viruses. It is shown that the experimentally observed hexamer deformation and pentamer twist in the HK97 procapsid correspond to the simplest irreducible shear strain mode of a spherical shell. We also show that the icosahedral faceting of the bacteriophage capsid shell is driven by the simplest irreducible radial displacement field. The shear field has the rotational icosahedral symmetry group I while the radial field has the full icosahedral symmetry Ih. This difference makes their actions independent. The radial field sign discriminates between the icosahedral and the dodecahedral shapes of the faceted capsid shell, thus making the approach relevant not only for the HK97-like viruses but also for the parvovirus family. In the frame of the Landau-Ginzburg formalism we propose a simple phenomenological model valid for the first reversible step of the HK97 maturation process. The calculated phase diagram illustrates the discontinuous character of the virus shape transformation. The characteristics of the virus shell faceting and expansion obtained in the in vitro and in vivo experiments are related to the decrease in the capsid shell thickness and to the increase of the internal capsid pressure.

Hydrogen bond effects on compressional behavior of isotypic minerals: high-pressure polymorphism of cristobalite-like Be(OH) 2

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

Shelton, Hannah; Barkley, Madison C.; Downs, Robert T.

2016-05-31

Three isotypic crystals, SiO 2 (α-cristobalite), ε-Zn(OH) 2 (wülfingite), and Be(OH) 2 (β-behoite), with topologically identical frameworks of corner-connected tetrahedra, undergo displacive compression-driven phase transitions at similar pressures (1.5–2.0 GPa), but each transition is characterized by a different mechanism resulting in different structural modifications. In this study, we report the crystal structure of the high-pressure γ-phase of beryllium hydroxide and compare it with the high-pressure structures of the other two minerals. In Be(OH) 2, the transition from the ambient β-behoite phase with the orthorhombic space group P2 12 12 1 and ambient unit cell parameters a = 4.5403(4) Å, bmore » = 4.6253(5) Å, c = 7.0599(7) Å, to the high-pressure orthorhombic γ-polymorph with space group Fdd2 and unit cell parameters (at 5.3(1) GPa) a = 5.738(2) Å, b = 6.260(3) Å, c = 7.200(4) Å takes place between 1.7 and 3.6 GPa. This transition is essentially second order, is accompanied by a negligible volume discontinuity, and exhibits both displacive and reversible character. The mechanism of the phase transition results in a change to the hydrogen bond connectivities and rotation of the BeO 4 tetrahedra.« less

Reinforcement and a cline in mating behaviour evolve in response to secondary contact and hybridization in shield-back katydids (Orthoptera: Tettigoniidae).

PubMed

Cole, J A

2016-09-01

In a dispersal-limited species that has evolved reproductive character displacement at a contact zone, a cline in mating behaviour may result if gene flow diffuses alleles out of the contact zone into allopatric populations. Prior work has found such a clinal pattern in the shield-back katydid Aglaothorax morsei, in which the male calling songs in a sympatric population have a displaced, short interpulse interval that increases in length with increasing distance from the contact zone. In this study, molecular phylogenetic and female preference data show that (1) sympatric populations result from secondary contact, (2) hybridization in sympatry has resulted in unidirectional mitochondrial introgression and (3) female preferences are consistent with reproductive character displacement and could generate a cline in mating behaviour. These data together suggest a history of reinforcement, generally considered rare in acoustically communicating insects; thus, Aglaothorax represents an important example of a rarely documented evolutionary process. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

Free-piston regenerative hot gas hydraulic engine

NASA Technical Reports Server (NTRS)

Beremand, D. G. (Inventor)

1980-01-01

A displacer piston which is driven pneumatically by a high-pressure or low-pressure gas is included in a free-piston regenerative hydraulic engine. Actuation of the displacer piston circulates the working fluid through a heater, a regenerator and a cooler. The present invention includes an inertial mass such as a piston or a hydraulic fluid column to effectively store and supply energy during portions of the cycle. Power is transmitted from the working fluid to a hydraulic fluid across a diaphragm or lightweight piston to achieve a hydraulic power out-put. The displacer piston of the present invention may be driven pneumatically, hydraulically or electromagnetically. In addition, the displacer piston and the inertial mass of the present invention may be positioned on the same side of the diaphragm member or may be separated by the diaphragm member.

Theoretical modeling of a gas clearance phase regulation mechanism for a pneumatically-driven split-Stirling-cycle cryocooler

NASA Astrophysics Data System (ADS)

Zhang, Cun-quan; Zhong, Cheng

2015-03-01

The concept of a new type of pneumatically-driven split-Stirling-cycle cryocooler with clearance-phase-adjustor is proposed. In this implementation, the gap between the phase-adjusting part and the cylinder of the spring chamber is used, instead of dry friction acting on the pneumatically-driven rod to control motion damping of the displacer and to adjust the phase difference between the compression piston and displacer. It has the advantages of easy damping adjustment, low cost, and simplified manufacturing and assembly. A theoretical model has been established to simulate its dynamic performance. The linear compressor is modeled under adiabatic conditions, and the displacement of the compression piston is experimentally rectified. The working characteristics of the compressor motor and the principal losses of cooling, including regenerator inefficiency loss, solid conduction loss, shuttle loss, pump loss and radiation loss, are taken into account. The displacer motion was modeled as a single-degree-of-freedom (SDOF) forced system. A set of governing equations can be solved numerically to simulate the cooler's performance. The simulation is useful for understanding the physical processes occurring in the cooler and for predicting the cooler's performance.

Applying Thiessen Polygon Catchment Areas and Gridded Population Weights to Estimate Conflict-Driven Population Changes in South Sudan

NASA Astrophysics Data System (ADS)

Jordan, L.

2017-10-01

Recent violence in South Sudan produced significant levels of conflict-driven migration undermining the accuracy and utility of both national and local level population forecasts commonly used in demographic estimates, public health metrics and food security proxies. This article explores the use of Thiessen Polygons and population grids (Gridded Population of the World, WorldPop and LandScan) as weights for estimating the catchment areas for settlement locations that serve large populations of internally displaced persons (IDP), in order to estimate the county-level in- and out-migration attributable to conflict-driven displacement between 2014-2015. Acknowledging IDP totals improves internal population estimates presented by global population databases. Unlike other forecasts, which produce spatially uniform increases in population, accounting for displaced population reveals that 15 percent of counties (n = 12) increased in population over 20 percent, and 30 percent of counties (n = 24) experienced zero or declining population growth, due to internal displacement and refugee out-migration. Adopting Thiessen Polygon catchment zones for internal migration estimation can be applied to other areas with United Nations IDP settlement data, such as Yemen, Somalia, and Nigeria.

ScatterType: a reading CAPTCHA resistant to segmentation attack

NASA Astrophysics Data System (ADS)

Baird, Henry S.; Riopka, Terry P.

2004-12-01

A reading-based CAPTCHA designed to resist character-segmentation attacks, called 'ScatterType,' is described. Its challenges are pseudorandomly synthesized images of text strings rendered in machine-print typefaces: within each image, characters are fragmented using horizontal and vertical cuts, and the fragments are scattered by vertical and horizontal displacements. This scattering is designed to defeat all methods known to us for automatic segmentation into characters. As in the BaffleText CAPTCHA, English-like but unspellable text-strings are used to defend against known-dictionary attacks. In contrast to the PessimalPrint and BaffleText CAPTCHAs (and others), no physics-based image degradations, occlusions, or extraneous patterns are employed. We report preliminary results from a human legibility trial with 57 volunteers that yielded 4275 CAPTCHA challenges and responses. ScatterType human legibility remains remarkably high even on extremely degraded cases. We speculate that this is due to Gestalt perception abilities assisted by style-specific (here, typeface-specific) consistency among primitive shape features of character fragments. Although recent efforts to automate style-consistent perceptual skills have reported progress, the best known methods do not yet pose a threat to ScatterType. The experimental data also show that subjective rating of difficulty is strongly (and usefully) correlated with illegibility. In addition, we present early insights emerging from these data as we explore the ScatterType design space -- choice of typefaces, 'words', cut positioning, and displacements -- with the goal of locating regimes in which ScatterType challenges remain comfortably legible to almost all people but strongly resist mahine-vision methods for automatic segmentation into characters.

ScatterType: a reading CAPTCHA resistant to segmentation attack

NASA Astrophysics Data System (ADS)

Baird, Henry S.; Riopka, Terry P.

2005-01-01

A reading-based CAPTCHA designed to resist character-segmentation attacks, called 'ScatterType,' is described. Its challenges are pseudorandomly synthesized images of text strings rendered in machine-print typefaces: within each image, characters are fragmented using horizontal and vertical cuts, and the fragments are scattered by vertical and horizontal displacements. This scattering is designed to defeat all methods known to us for automatic segmentation into characters. As in the BaffleText CAPTCHA, English-like but unspellable text-strings are used to defend against known-dictionary attacks. In contrast to the PessimalPrint and BaffleText CAPTCHAs (and others), no physics-based image degradations, occlusions, or extraneous patterns are employed. We report preliminary results from a human legibility trial with 57 volunteers that yielded 4275 CAPTCHA challenges and responses. ScatterType human legibility remains remarkably high even on extremely degraded cases. We speculate that this is due to Gestalt perception abilities assisted by style-specific (here, typeface-specific) consistency among primitive shape features of character fragments. Although recent efforts to automate style-consistent perceptual skills have reported progress, the best known methods do not yet pose a threat to ScatterType. The experimental data also show that subjective rating of difficulty is strongly (and usefully) correlated with illegibility. In addition, we present early insights emerging from these data as we explore the ScatterType design space -- choice of typefaces, 'words', cut positioning, and displacements -- with the goal of locating regimes in which ScatterType challenges remain comfortably legible to almost all people but strongly resist mahine-vision methods for automatic segmentation into characters.

"They may be pixels, but they're MY pixels:" developing a metric of character attachment in role-playing video games.

PubMed

Lewis, Melissa L; Weber, René; Bowman, Nicholas David

2008-08-01

This paper proposes a new and reliable metric for measuring character attachment (CA), the connection felt by a video game player toward a video game character. Results of construct validity analyses indicate that the proposed CA scale has a significant relationship with self-esteem, addiction, game enjoyment, and time spent playing games; all of these relationships are predicted by theory. Additionally, CA levels for role-playing games differ significantly from CA levels of other character-driven games.

Selection on male sex pheromone composition contributes to butterfly reproductive isolation

PubMed Central

Bacquet, P. M. B.; Brattström, O.; Wang, H.-L.; Allen, C. E.; Löfstedt, C.; Brakefield, P. M.; Nieberding, C. M.

2015-01-01

Selection can facilitate diversification by inducing character displacement in mate choice traits that reduce the probability of maladaptive mating between lineages. Although reproductive character displacement (RCD) has been demonstrated in two-taxa case studies, the frequency of this process in nature is still debated. Moreover, studies have focused primarily on visual and acoustic traits, despite the fact that chemical communication is probably the most common means of species recognition. Here, we showed in a large, mostly sympatric, butterfly genus, a strong pattern of recurrent RCD for predicted male sex pheromone composition, but not for visual mate choice traits. Our results suggest that RCD is not anecdotal, and that selection for divergence in male sex pheromone composition contributed to reproductive isolation within the Bicyclus genus. We propose that selection may target olfactory mate choice traits as a more common sensory modality to ensure reproductive isolation among diverging lineages than previously envisaged. PMID:25740889

Morphospaces of functionally analogous traits show ecological separation between birds and pterosaurs.

PubMed

Chan, Nicholas R

2017-10-25

Birds originated and radiated in the presence of another group of flying vertebrates, the pterosaurs. Opinion is divided as to whether birds competitively displaced pterosaurs from small-body size niches or whether the two groups coexisted with little competition. Previous studies of Mesozoic birds and pterosaurs compared measurements of homologous limb bones to test these hypotheses. However, these characters probably reflect differing ancestries rather than ecologies. Here, competition and ecological separation were tested for using multivariate analyses of functionally equivalent morphological characters. As well as using characters from the fore- and hindlimbs, these analyses also included measurements of the lower jaw. The results of this study indicate that pterosaurs had relatively longer jaws, shorter metatarsals and shorter brachial regions compared with birds of similar size. Contrary to the results of previous studies, the distal wing was not important for separating the two clades in morphospace owing to the inclusion of the primary feathers in this unit. The differences found here indicate ecological separation based on differences in size, locomotory features and feeding adaptations. Thus, instead of one group displacing the other, birds and pterosaurs appear to have adopted distinctive ecological strategies throughout their period of coexistence. © 2017 The Author(s).

Gene flow during glacial habitat shifts facilitates character displacement in a Neotropical flycatcher radiation.

PubMed

Chattopadhyay, Balaji; Garg, Kritika M; Gwee, Chyi Yin; Edwards, Scott V; Rheindt, Frank E

2017-09-01

Pleistocene climatic fluctuations are known to be an engine of biotic diversification at higher latitudes, but their impact on highly diverse tropical areas such as the Andes remains less well-documented. Specifically, while periods of global cooling may have led to fragmentation and differentiation at colder latitudes, they may - at the same time - have led to connectivity among insular patches of montane tropical habitat with unknown consequences on diversification. In the present study we utilized ~5.5 kb of DNA sequence data from eight nuclear loci and one mitochondrial gene alongside diagnostic morphological and bioacoustic markers to test the effects of Pleistocene climatic fluctuations on diversification in a complex of Andean tyrant-flycatchers of the genus Elaenia. Population genetic and phylogenetic approaches coupled with coalescent simulations demonstrated disparate levels of gene flow between the taxon chilensis and two parapatric Elaenia taxa predominantly during the last glacial period but not thereafter, possibly on account of downward shifts of montane forest habitat linking the populations of adjacent ridges. Additionally, morphological and bioacoustic analyses revealed a distinct pattern of character displacement in coloration and vocal traits between the two sympatric taxa albiceps and pallatangae, which were characterized by a lack of gene flow. Our study demonstrates that global periods of cooling are likely to have facilitated gene flow among Andean montane Elaenia flycatchers that are more isolated from one another during warm interglacial periods such as the present era. We also identify a hitherto overlooked case of plumage and vocal character displacement, underpinning the complexities of gene flow patterns caused by Pleistocene climate change across the Andes.

Investigation of Creep Properties in RAINBOW High Displacement Actuators

NASA Technical Reports Server (NTRS)

Haertling, Gene; Furman, Eugene; Li, Guang; Barron, Bret; Moon, Youngwoo

1997-01-01

Results from this study on fatigue in Rainbow and Cerambow actuators show that these high displacement actuators have definite fatigue rates and lifetimes depending upon (1) the amount of displacement generated, (2) how hard they are driven electrically, and (3) the microstructure (grain size) of the ceramic material. Lifetimes for some actuators were on the order of 10(exp 7) cycles at near dc (1 Hz) frequencies while others still retained up to 74% of their displacement at 2.1 x 10(exp 7) Hz.

Reciprocating magnetic refrigerator employing tandem porous matrices within a reciprocating displacer

NASA Technical Reports Server (NTRS)

Johnson, D. L. (Inventor)

1985-01-01

Disclosed is a method and apparatus for a magnetic refrigeration system. A continuously reciprocating displacer houses at least a pair of paramagnetic substances each of which is alternately driven into and out of a magnetic field. Two separate bidirectional pumping systems flow helium gas through the displacer and through both paramagnetic substances to create heat exchange conditions at two separate temperature extremes.

A Theoretical Model to Predict Both Horizontal Displacement and Vertical Displacement for Electromagnetic Induction-Based Deep Displacement Sensors

PubMed Central

Shentu, Nanying; Zhang, Hongjian; Li, Qing; Zhou, Hongliang; Tong, Renyuan; Li, Xiong

2012-01-01

Deep displacement observation is one basic means of landslide dynamic study and early warning monitoring and a key part of engineering geological investigation. In our previous work, we proposed a novel electromagnetic induction-based deep displacement sensor (I-type) to predict deep horizontal displacement and a theoretical model called equation-based equivalent loop approach (EELA) to describe its sensing characters. However in many landslide and related geological engineering cases, both horizontal displacement and vertical displacement vary apparently and dynamically so both may require monitoring. In this study, a II-type deep displacement sensor is designed by revising our I-type sensor to simultaneously monitor the deep horizontal displacement and vertical displacement variations at different depths within a sliding mass. Meanwhile, a new theoretical modeling called the numerical integration-based equivalent loop approach (NIELA) has been proposed to quantitatively depict II-type sensors’ mutual inductance properties with respect to predicted horizontal displacements and vertical displacements. After detailed examinations and comparative studies between measured mutual inductance voltage, NIELA-based mutual inductance and EELA-based mutual inductance, NIELA has verified to be an effective and quite accurate analytic model for characterization of II-type sensors. The NIELA model is widely applicable for II-type sensors’ monitoring on all kinds of landslides and other related geohazards with satisfactory estimation accuracy and calculation efficiency. PMID:22368467

A theoretical model to predict both horizontal displacement and vertical displacement for electromagnetic induction-based deep displacement sensors.

PubMed

Shentu, Nanying; Zhang, Hongjian; Li, Qing; Zhou, Hongliang; Tong, Renyuan; Li, Xiong

2012-01-01

Deep displacement observation is one basic means of landslide dynamic study and early warning monitoring and a key part of engineering geological investigation. In our previous work, we proposed a novel electromagnetic induction-based deep displacement sensor (I-type) to predict deep horizontal displacement and a theoretical model called equation-based equivalent loop approach (EELA) to describe its sensing characters. However in many landslide and related geological engineering cases, both horizontal displacement and vertical displacement vary apparently and dynamically so both may require monitoring. In this study, a II-type deep displacement sensor is designed by revising our I-type sensor to simultaneously monitor the deep horizontal displacement and vertical displacement variations at different depths within a sliding mass. Meanwhile, a new theoretical modeling called the numerical integration-based equivalent loop approach (NIELA) has been proposed to quantitatively depict II-type sensors' mutual inductance properties with respect to predicted horizontal displacements and vertical displacements. After detailed examinations and comparative studies between measured mutual inductance voltage, NIELA-based mutual inductance and EELA-based mutual inductance, NIELA has verified to be an effective and quite accurate analytic model for characterization of II-type sensors. The NIELA model is widely applicable for II-type sensors' monitoring on all kinds of landslides and other related geohazards with satisfactory estimation accuracy and calculation efficiency.

A novel piezostack-driven jetting dispenser with corner-filleted flexure hinge and high-frequency performance

NASA Astrophysics Data System (ADS)

Bu, Zhenxiang; Lin, Siying; Huang, Xiang; Li, Anlin; Wu, Dezhi; Zhao, Yang; Luo, Zhiwei; Wang, Lingyun

2018-07-01

This paper presents a new jetting dispenser which is applicable to high-frequency microelectronic packaging. In order to achieve high frequency glue jetting and improve the stability of jetting dispensers, we redesign a novel displacement amplifying mechanism, and a new on–off valve jetting dispenser driven by piezoelectric actuators is developed. Firstly, the core part of this jetting dispenser—the displacement amplifying mechanism with a corner-filleted flexure hinge—is proposed and a comparison with the previous structure is carried out; then the characteristic dimensional parameters of the amplifying mechanism are determined by theoretical calculation and finite element analysis. Secondly, a prototype of the dispenser with the displacement amplifying mechanism is fabricated based on the determined parameters. We use a laser displacement sensor to test the displacement of the needle, and a maximum amplifying displacement output of 367 µm is obtained under an applied 200 V to the piezoelectric actuator, which is consistent with the simulation result and meets the requirement of high displacement output. Thirdly, we build an integrated testing system. Mixed glycerol/ethanol is chosen as the experimental dispensing glue, and the experiment and analysis of a droplet diameter are conducted. A higher jetting frequency of 400 Hz and a smaller droplet diameter of 525 µm are achieved with the glycerol/ethanol mixture, and the characteristics of consistency and temperature influencing the droplet diameter are verified by experiments.

Prediction of pile set-up for Ohio soils.

DOT National Transportation Integrated Search

2011-02-01

ODOT typically uses small diameter driven pipe piles for bridge foundations. When a pile is driven into the subsurface, it disturbs and displaces the soil. As the soil surrounding the pile recovers from the installation disturbance, a time dependant ...

Extant ape dental topography and its implications for reconstructing the emergence of early Homo.

PubMed

Berthaume, Michael A; Schroer, Kes

2017-11-01

Dental topography reflects diet accurately in several extant and extinct mammalian clades. However, dental topographic dietary reconstructions have high success rates only when closely related taxa are compared. Given the dietary breadth that exists among extant apes and likely existed among fossil hominins, dental topographic values from many species and subspecies of great apes are necessary for making dietary inferences about the hominin fossil record. Here, we present the results of one metric of dental topography, Dirichlet normal energy (DNE), for seven groups of great apes (Pongo pygmaeus pygmaeus, Pan paniscus, Pan troglodytes troglodytes and schweinfurthii, Gorilla gorilla gorilla, Gorilla beringei graueri and beringei). Dirichlet normal energy was inadequate at differentiating folivores from frugivores, but was adequate at predicting which groups had more fibrous diets among sympatric African apes. Character displacement analyses confirmed there is substantial dental topographic and relative molar size (M 1 :M 2 ratio; length, width, and area) divergence in sympatric apes when compared to their allopatric counterparts, but character displacement is only present in relative molar size when DNE is also considered. Presence of character displacement is likely due to indirect competition over similar food resources. Assuming similar ecological conditions in the Plio-Pleistocene, the derived masticatory apparatuses of the robust australopiths and early Homo may be due to indirect competition over dietary resources between the taxa, causing dietary niche partitioning. Our results imply that dental topography cannot be used to predict dietary categories in fossil hominins without consideration of ecological factors, such as dietary and geographic overlap. In addition, our results may open new avenues for understanding the community compositions of early hominins and the formation of specific ecological niches among hominin taxa. Copyright © 2017 Elsevier Ltd. All rights reserved.

Allochronic speciation, secondary contact, and reproductive character displacement in periodical cicadas (Hemiptera: Magicicada spp.): genetic, morphological, and behavioural evidence.

PubMed

Cooley, J R; Simon, C; Marshall, D C; Slon, K; Ehrhardt, C

2001-03-01

Periodical cicadas have proven useful in testing a variety of ecological and evolutionary hypotheses because of their unusual life history, extraordinary abundance, and wide geographical range. Periodical cicadas provide the best examples of synchronous periodicity and predator satiation in the animal kingdom, and are excellent illustrations of habitat partitioning (by the three morphologically distinct species groups), incipient species (the year classes or broods), and cryptic species (a newly discovered 13-year species, Magicicada neotredecim). They are particularly useful for exploring questions regarding speciation via temporal isolation, or allochronic speciation. Recently, data were presented that provided strong support for an instance of allochronic speciation by life-cycle switching. This speciation event resulted in the formation of a new 13-year species from a 17-year species and led to secondary contact between two formerly separated lineages, one represented by the new 13-year cicadas (and their 17-year ancestors), and the other represented by the pre-existing 13-year cicadas. Allozyme frequency data, mitochondrial DNA (mtDNA), and abdominal colour were shown to be correlated genetic markers supporting the life-cycle switching/allochronic speciation hypothesis. In addition, a striking pattern of reproductive character displacement in male call pitch and female pitch preference between the two 13-year species was discovered. In this paper we report a strong association between calling song pitch and mtDNA haplotype for 101 individuals from a single locality within the M. tredecim/M. neotredecim contact zone and a strong association between abdomen colour and mtDNA haplotype. We conclude by reviewing proposed mechanisms for allochronic speciation and reproductive character displacement.

Purpose-Driven Leadership: Defining, Defending and Sustaining a School's Purpose

ERIC Educational Resources Information Center

Holloman, Harold L., Jr.; Rouse, William A., Jr.; Farrington, Vernon

2007-01-01

Purpose-driven leadership is a constructive leadership model that challenges an organization to: define its purpose, maintain integrity, encourage character, prevent burnout and sustain vitality. The model incorporates "best practice language" and the tools needed to foster a meaningful discourse. As school leaders strive to define, defend, and…

Divergence in the calling songs between sympatric and allopatric populations of the southern wood cricket Gryllus fultoni (Orthoptera: Gryllidae).

PubMed

Jang, Y; Gerhardt, H C

2006-03-01

In the eastern United States the wood cricket Gryllus fultoni (Orthoptera: Gryllidae) occurs in sympatry with G. vernalis in an area between eastern Kansas and west of the Appalachian Mountains. Calling songs were recorded from 13 sympatric and allopatric localities. Both field and laboratory recordings showed that chirp rate (CR) and pulse rate (PR) overlapped extensively between allopatric populations of G. fultoni and sympatric populations of G. vernalis; by contrast, there was little or no overlap in these variables between sympatric populations of these two species. Divergence in PR and CR between the two species was thus greater in areas of sympatry than in areas of allopatry. Our field and laboratory studies of G. fultoni calling songs thus demonstrate the pattern expected of character displacement and support the genetic assumptions of this hypothesis. Other possible explanations for the sympatric divergence such as ecological character displacement and clinal variation are discussed.

Volatile anesthetic binding to proteins is influenced by solvent and aliphatic residues.

PubMed

Streiff, John H; Jones, Keith A

2008-10-01

The main objective of this work was to characterize VA binding sites in multiple anesthetic target proteins. A computational algorithm was used to quantify the solvent exclusion and aliphatic character of amphiphilic pockets in the structures of VA binding proteins. VA binding sites in the protein structures were defined as the pockets with solvent exclusion and aliphatic character that exceeded minimum values observed in the VA binding sites of serum albumin, firefly luciferase, and apoferritin. We found that the structures of VA binding proteins are enriched in these pockets and that the predicted binding sites were consistent with experimental determined binding locations in several proteins. Autodock3 was used to dock the simulated molecules of 1,1,1,2,2-pentafluoroethane, difluoromethyl 1,1,1,2-tetrafluoroethyl ether, and sevoflurane and the isomers of halothane and isoflurane into these potential binding sites. We found that the binding of the various VA molecules to the amphiphilic pockets is driven primarily by VDW interactions and to a lesser extent by weak hydrogen bonding and electrostatic interactions. In addition, the trend in Delta G binding values follows the Meyer-Overton rule. These results suggest that VA potencies are related to the VDW interactions between the VA ligand and protein target. It is likely that VA bind to sites with a high degree of solvent exclusion and aliphatic character because aliphatic residues provide favorable VDW contacts and weak hydrogen bond donors. Water molecules occupying these sites maintain pocket integrity, associate with the VA ligand, and diminish the unfavorable solvation enthalpy of the VA. Water molecules displaced into the bulk by the VA ligand may provide an additional favorable enthalpic contribution to VA binding. Anesthesia is a component of many health related procedures, the outcomes of which could be improved with a better understanding of the molecular targets and mechanisms of anesthetic action.

Prediction of pile set-up for Ohio soils : executive summary report.

DOT National Transportation Integrated Search

2011-02-01

ODOT typically uses small diameter driven pipe piles for bridge foundations. When a pile is driven into the subsurface, it disturbs and displaces the soil. As the soil surrounding the pile recovers from the installation disturbance, a time dependant ...

Split-Stirling-cycle displacer linear-electric drive

NASA Technical Reports Server (NTRS)

Ackermann, R. A.; Bhate, S. K.; Byrne, D. V.

1983-01-01

The retrofit of a 1/4-W split-Stirling cooler with a linear driven on the displacer was achieved and its performance characterized. The objective of this work was to demonstrate that a small linear motor could be designed to meet the existing envelope specifications of the cooler and that an electric linear drive on the displacer could improve the cooler's reliability and performance. The paper describes the characteristics of this motor and presents cooler test results.

Character convergence under competition for nutritionally essential resources.

PubMed

Fox, Jeremy W; Vasseur, David A

2008-11-01

Resource competition is thought to drive divergence in resource use traits (character displacement) by generating selection favoring individuals able to use resources unavailable to others. However, this picture assumes nutritionally substitutable resources (e.g., different prey species). When species compete for nutritionally essential resources (e.g., different nutrients), theory predicts that selection drives character convergence. We used models of two species competing for two essential resources to address several issues not considered by existing theory. The models incorporated either slow evolutionary change in resource use traits or fast physiological or behavioral change. We report four major results. First, competition always generates character convergence, but differences in resource requirements prevent competitors from evolving identical resource use traits. Second, character convergence promotes coexistence. Competing species always attain resource use traits that allow coexistence, and adaptive trait change stabilizes the ecological equilibrium. In contrast, adaptation in allopatry never preadapts species to coexist in sympatry. Third, feedbacks between ecological dynamics and trait dynamics lead to surprising dynamical trajectories such as transient divergence in resource use traits followed by subsequent convergence. Fourth, under sufficiently slow trait change, ecological dynamics often drive one of the competitors to near extinction, which would prevent realization of long-term character convergence in practice.

ADAPT: The Agent Development and Prototyping Testbed.

PubMed

Shoulson, Alexander; Marshak, Nathan; Kapadia, Mubbasir; Badler, Norman I

2014-07-01

We present ADAPT, a flexible platform for designing and authoring functional, purposeful human characters in a rich virtual environment. Our framework incorporates character animation, navigation, and behavior with modular interchangeable components to produce narrative scenes. The animation system provides locomotion, reaching, gaze tracking, gesturing, sitting, and reactions to external physical forces, and can easily be extended with more functionality due to a decoupled, modular structure. The navigation component allows characters to maneuver through a complex environment with predictive steering for dynamic obstacle avoidance. Finally, our behavior framework allows a user to fully leverage a character's animation and navigation capabilities when authoring both individual decision-making and complex interactions between actors using a centralized, event-driven model.

Are Children Really Inferior Goods? Evidence from Displacement-Driven Income Shocks

ERIC Educational Resources Information Center

Lindo, Jason M.

2010-01-01

This paper explores the causal link between income and fertility by analyzing women's fertility response to the large and permanent income shock generated by a husband's job displacement. I find that the shock reduces total fertility, suggesting that the causal effect of income on fertility is positive. A model that incorporates the time cost of…

Gender Transformations and Colonial Displacements in Laura Antillano's "Tuna de mar"

ERIC Educational Resources Information Center

Reid, Alana

2015-01-01

This paper examines the trajectories of two characters in Laura Antillano's short story, "Tuna de mar" (1991), as they navigate interrelated systems of power and attempt to position themselves closer to, or further away from, the margins. Set in the late eighteenth century, the tale features a female protagonist who escapes prostitution…

Non-convergent ordering and displacive phase transition in pigeonite: in situ HT XRD study

NASA Astrophysics Data System (ADS)

Cámara, F.; Carpenter, M. A.; Domeneghetti, M. C.; Tazzoli, V.

A natural Ca-rich pigeonite (En47Fs43Wo10), free of augite exsolution products, was studied by in situ high-temperature single-crystal X-ray diffraction. The sample, monoclinic P21/c (a=9.719(7) Å, b=8.947(9) Å, c=5.251(3) Å, β=108.49(5), V=433.0(6) Å3), was annealed up to 1000 °C to induce a phase transition from P21/c to C2/c symmetry. Complete single-crystal X-ray diffraction data collections were carried out in situ at 650, 750, 850 and 950 °C after the crystal had reached equilibrium for the Fe-Mg intracrystalline exchange reaction at each temperature. The variation, with increasing temperature, of lattice parameters, of intensity of hkl reflections with h + k=2n + 1 (which vanish at high temperature) and of some geometrical parameters from structure refinement, showed that the displacive phase transition P21/cC2/c was continuous in character. This contrasts with the first-order character for the HT phase transition in pigeonite containing significantly less calcium.

Species diversity driven by morphological and ecological disparity: a case study of comparative seed morphology and anatomy across a large monocot order

PubMed Central

Benedict, John C.; Smith, Selena Y.; Specht, Chelsea D.; Collinson, Margaret E.; Leong-Škorničková, Jana; Parkinson, Dilworth Y.; Marone, Federica

2016-01-01

Phenotypic variation can be attributed to genetic heritability as well as biotic and abiotic factors. Across Zingiberales, there is a high variation in the number of species per clade and in phenotypic diversity. Factors contributing to this phenotypic variation have never been studied in a phylogenetic or ecological context. Seeds of 166 species from all eight families in Zingiberales were analyzed for 51 characters using synchrotron based 3D X-ray tomographic microscopy to determine phylogenetically informative characters and to understand the distribution of morphological disparity within the order. All families are distinguishable based on seed characters. Non-metric multidimensional scaling analyses show Zingiberaceae occupy the largest seed morphospace relative to the other families, and environmental analyses demonstrate that Zingiberaceae inhabit both temperate and tropical regions, while other Zingiberales are almost exclusively tropical. Temperate species do not cluster in morphospace nor do they share a common suite of character states. This suggests that the diversity seen is not driven by adaptation to temperate niches; rather, the morphological disparity seen likely reflects an underlying genetic plasticity that allowed Zingiberaceae to repeatedly colonize temperate environments. The notable morphoanatomical variety in Zingiberaceae seeds may account for their extraordinary ecological success and high species diversity as compared to other Zingiberales. PMID:27594701

The influence of familiar characters and other appealing images on young children's preference for low-quality objects.

PubMed

Danovitch, Judith H; Mills, Candice M

2017-09-01

This study examines the factors underlying young children's preference for products bearing a familiar character's image. Three-year-olds (N = 92) chose between low-quality objects with images on or near the objects and high-quality objects without images. Children showed stronger preferences for damaged objects bearing images of a preferred familiar character than for objects bearing images of a preferred colour star, and they showed weak preferences for damaged objects with the character near, but not on, the object. The results suggest that children's preference for low-quality products bearing character images is driven by prior exposure to characters, and not only by the act of identifying a favourite. Statement of contribution What is already known on this subject? Children are exposed to characters in the media and on products such as clothing and school supplies. Products featuring familiar characters appeal to preschool children, even if they are of low quality. What does this study add? Three-year-olds prefer damaged objects with an image of a favourite character over plain undamaged objects. Children's preference is not solely a function of having identified a favourite image or of attentional cues. © 2017 The British Psychological Society.

High speed displacement measurement based on electro-magnetic induction applied to electromagnetically driven ring expansion

NASA Astrophysics Data System (ADS)

Han, Xiaotao; Wu, Jiawei; Huang, Lantao; Qiu, Lei; Chen, Qi; Cao, Quanliang; Herlach, Fritz; Li, Liang

2017-11-01

Investigating the mechanism of electromagnetic forming (EMF) becomes a hot topic in the field of metal forming. The high speed up to 200 m/s in EMF makes it a real challenge to capture the forming process. To this end, a new method for measuring displacement at high speed based on electromagnetic induction has been developed. Specifically this is used to measure the displacement of an expanding metal ring driven by a pulsed magnetic field; this is one of the basic EMF processes. The new method is simple and practical, and it combines high-speed response with adequate precision. The new measurement system consists of a printed circuit board (PCB) and a Rogowski probe. Eleven coaxial annular detecting probes are arranged in the PCB plate to acquire induced voltage at different positions, and a Rogowski probe is used to measure the current in the driving coil. The displacement of the ring is deduced by analyzing the output voltages of the detecting probes and the Rogowski probe. The feasibility of the method is verified by comparing the results with pictures from a high speed camera taken simultaneously.

Disentangling Ancient Interactions: A New Extinct Passerine Provides Insights on Character Displacement among Extinct and Extant Island Finches

PubMed Central

Rando, Juan Carlos; Alcover, Josep Antoni; Illera, Juan Carlos

2010-01-01

Background Evolutionary studies of insular biotas are based mainly on extant taxa, although such biotas represent artificial subsets of original faunas because of human-caused extinctions of indigenous species augmented by introduced exotic taxa. This makes it difficult to obtain a full understanding of the history of ecological interactions between extant sympatric species. Morphological bill variation of Fringilla coelebs and F. teydea (common and blue chaffinches) has been previously studied in the North Atlantic Macaronesian archipelagos. Character displacement between both species has been argued to explain bill sizes in sympatry. However, this explanation is incomplete, as similar patterns of bill size have been recorded in F. coelebs populations from islands with and without F. teydea. Methodology/Principal Findings The discovery of a new extinct species in Tenerife (Canary Islands), here named Carduelis aurelioi n. sp. (slender-billed greenfinch), provides the opportunity to study ancient ecological interactions among Macaronesian finches. To help understand the evolutionary histories of forest granivores in space and time, we have performed a multidisciplinary study combining: (1) morphological analyses and radiocarbon dating (11,460±60 yr BP) of the new taxon and, (2) molecular divergence among the extant finch species and populations in order to infer colonization times (1.99 and 1.09 My for F. teydea and F. coelebs respectively). Conclusion/Significance C. aurelioi, F. coelebs and F. teydea co-habited in Tenerife for at least one million years. The unique anatomical trends of the new species, namely chaffinch-like beak and modified hind and forelimbs, reveal that there was a process of divergence of resource competition traits among the three sympatric finches. The results of our study, combined with the presence of more extinct greenfinches in other Macaronesian islands with significant variation in their beak sizes, suggests that the character displacement has influenced patterns of divergence in bill size and shape on other Macaronesian islands as well. PMID:20886036

Integrate-and-fire models with an almost periodic input function

NASA Astrophysics Data System (ADS)

Kasprzak, Piotr; Nawrocki, Adam; Signerska-Rynkowska, Justyna

2018-02-01

We investigate leaky integrate-and-fire models (LIF models for short) driven by Stepanov and μ-almost periodic functions. Special attention is paid to the properties of the firing map and its displacement, which give information about the spiking behavior of the considered system. We provide conditions under which such maps are well-defined and are uniformly continuous. We show that the LIF models with Stepanov almost periodic inputs have uniformly almost periodic displacements. We also show that in the case of μ-almost periodic drives it may happen that the displacement map is uniformly continuous, but is not μ-almost periodic (and thus cannot be Stepanov or uniformly almost periodic). By allowing discontinuous inputs, we extend some previous results, showing, for example, that the firing rate for the LIF models with Stepanov almost periodic input exists and is unique. This is a starting point for the investigation of the dynamics of almost-periodically driven integrate-and-fire systems.

Performance-Driven Hybrid Full-Body Character Control for Navigation and Interaction in Virtual Environments

NASA Astrophysics Data System (ADS)

Mousas, Christos; Anagnostopoulos, Christos-Nikolaos

2017-06-01

This paper presents a hybrid character control interface that provides the ability to synthesize in real-time a variety of actions based on the user's performance capture. The proposed methodology enables three different performance interaction modules: the performance animation control that enables the direct mapping of the user's pose to the character, the motion controller that synthesizes the desired motion of the character based on an activity recognition methodology, and the hybrid control that lies within the performance animation and the motion controller. With the methodology presented, the user will have the freedom to interact within the virtual environment, as well as the ability to manipulate the character and to synthesize a variety of actions that cannot be performed directly by him/her, but which the system synthesizes. Therefore, the user is able to interact with the virtual environment in a more sophisticated fashion. This paper presents examples of different scenarios based on the three different full-body character control methodologies.

Phylogeography and diversification history of the day-gecko genus Phelsuma in the Seychelles islands.

PubMed

Rocha, Sara; Posada, David; Harris, D James

2013-01-05

Lying in a shallow continental shelf cyclically affected by oscillating sea levels since the Miocene, the Seychelles islands are particularly interesting for evolutionary studies. Recent molecular studies are generating an emerging picture of the origin of its biota, yet very little is known regarding their phylogeographic structure or on the factors promoting diversification within the archipelago. Here we aimed to obtain a detailed depiction of the genetic structure and evolution of one of the most widespread vertebrate groups in the archipelago: the day-geckos of the genus Phelsuma. In parallel, we aimed to infer divergence times between species and subspecies, testing a long-standing hypothesis that argues for different time since sympatry between species as the cause of their different morphological differentiation across the archipelago. Molecular data corroborated the existence of two main lineages, corresponding to the two currently recognized species. Divergences between species likely date back to the Mio-Pliocene, while more recent, Pleistocenic, divergences are suggested within each species. Populations from outer islands share mtDNA haplotypes with inner island populations, suggesting very recent dispersals (or introductions). We found no evidence of current gene flow between species, but results pointed to the possibility of gene flow between (now allopatric) subspecies. Time estimates suggest a synchronous divergence within each species (between island groups). The geographic patterns of genetic variation agree with previous taxonomic subdivisions within each species and the origin of outer islands populations is clearly tracked. The similar intraspecific divergence time estimates obtained suggest that the differential body-size differentiation between species within each group of islands may be driven by factors other than character displacement proportional to time since sympatry, as previously suggested. These factors could include different habitats/resources available within each island group, niche differentiation and/or character displacement. We also bring again into consideration the hypothesis of body size being influenced by the distribution of native vegetation and social systems within this group, although it remains to be tested. Our results highlight not only the necessity of clarifying the role of ecology and interspecific interactions in this group's morphological diversification and community assemblage, but also the importance of co-evolutionary mechanisms and their importance for appropriate conservation of island biodiversity. Further, we provide a detailed description of the phylogeographic structure of these taxa across these islands, which still remain poorly characterized in this respect.

Mrs. Squandertime

NASA Astrophysics Data System (ADS)

Anstey, Josephine; Pape, Dave

2013-03-01

In this paper we discuss Mrs. Squandertime, a real-time, persistent simulation of a virtual character, her living room, and the view from her window, designed to be a wall-size, projected art installation. Through her large picture window, the eponymous Mrs. Squandertime watches the sea: boats, clouds, gulls, the tide going in and out, people on the sea wall. The hundreds of images that compose the view are drawn from historical printed sources. The program that assembles and animates these images is driven by weather, time, and tide data constantly updated from a real physical location. The character herself is rendered photographically in a series of slowly dissolving stills which correspond to the character's current behavior.

Microgravity Investigation of Capillary Driven Imbibition

NASA Astrophysics Data System (ADS)

Dushin, V. R.; Nikitin, V. F.; Smirnov, N. N.; Skryleva, E. I.; Tyurenkova, V. V.

2018-05-01

The goal of the present paper is to investigate the capillary driven filtration in porous media under microgravity conditions. New mathematical model that allows taking into account the blurring of the front due to the instability of the displacement that is developing at the front is proposed. The constants in the mathematical model were selected on the basis of the experimental data on imbibition into unsaturated porous media under microgravity conditions. The flow under the action of a combination of capillary forces and a constant pressure drop or a constant flux is considered. The effect of capillary forces and the type of wettability of the medium on the displacement process is studied. A criterion in which case the capillary effects are insignificant and can be neglected is established.

Conflict, displacement and health in the Middle East.

PubMed

Mowafi, Hani

2011-01-01

Displacement is a hallmark of modern humanitarian emergencies. Displacement itself is a traumatic event that can result in illness or death. Survivors face challenges including lack of adequate shelter, decreased access to health services, food insecurity, loss of livelihoods, social marginalisation as well as economic and sexual exploitation. Displacement takes many forms in the Middle East and the Arab World. Historical conflicts have resulted in long-term displacement of Palestinians. Internal conflicts have driven millions of Somalis and Sudanese from their homes. Iraqis have been displaced throughout the region by invasion and civil strife. In addition, large numbers of migrants transit Middle Eastern countries or live there illegally and suffer similar conditions as forcibly displaced people. Displacement in the Middle East is an urban phenomenon. Many displaced people live hidden among host country populations in poor urban neighbourhoods - often without legal status. This represents a challenge for groups attempting to access displaced populations. Furthermore, health information systems in host countries often do not collect data on displaced people, making it difficult to gather data needed to target interventions towards these vulnerable populations. The following is a discussion of the health impacts of conflict and displacement in the Middle East. A review was conducted of published literature on migration and displacement in the region. Different cases are discussed with an emphasis on the recent, large-scale and urban displacement of Iraqis to illustrate aspects of displacement in this region.

Study on the Evaluation Method for Fault Displacement: Probabilistic Approach Based on Japanese Earthquake Rupture Data - Principal fault displacements -

NASA Astrophysics Data System (ADS)

Kitada, N.; Inoue, N.; Tonagi, M.

2016-12-01

The purpose of Probabilistic Fault Displacement Hazard Analysis (PFDHA) is estimate fault displacement values and its extent of the impact. There are two types of fault displacement related to the earthquake fault: principal fault displacement and distributed fault displacement. Distributed fault displacement should be evaluated in important facilities, such as Nuclear Installations. PFDHA estimates principal fault and distributed fault displacement. For estimation, PFDHA uses distance-displacement functions, which are constructed from field measurement data. We constructed slip distance relation of principal fault displacement based on Japanese strike and reverse slip earthquakes in order to apply to Japan area that of subduction field. However, observed displacement data are sparse, especially reverse faults. Takao et al. (2013) tried to estimate the relation using all type fault systems (reverse fault and strike slip fault). After Takao et al. (2013), several inland earthquakes were occurred in Japan, so in this time, we try to estimate distance-displacement functions each strike slip fault type and reverse fault type especially add new fault displacement data set. To normalized slip function data, several criteria were provided by several researchers. We normalized principal fault displacement data based on several methods and compared slip-distance functions. The normalized by total length of Japanese reverse fault data did not show particular trend slip distance relation. In the case of segmented data, the slip-distance relationship indicated similar trend as strike slip faults. We will also discuss the relation between principal fault displacement distributions with source fault character. According to slip distribution function (Petersen et al., 2011), strike slip fault type shows the ratio of normalized displacement are decreased toward to the edge of fault. However, the data set of Japanese strike slip fault data not so decrease in the end of the fault. This result indicates that the fault displacement is difficult to appear at the edge of the fault displacement in Japan. This research was part of the 2014-2015 research project `Development of evaluating method for fault displacement` by the Secretariat of Nuclear Regulation Authority (NRA), Japan.

Species diversity driven by morphological and ecological disparity: a case study of comparative seed morphology and anatomy across a large monocot order.

PubMed

Benedict, John C; Smith, Selena Y; Specht, Chelsea D; Collinson, Margaret E; Leong-Škorničková, Jana; Parkinson, Dilworth Y; Marone, Federica

2016-01-01

Phenotypic variation can be attributed to genetic heritability as well as biotic and abiotic factors. Across Zingiberales, there is a high variation in the number of species per clade and in phenotypic diversity. Factors contributing to this phenotypic variation have never been studied in a phylogenetic or ecological context. Seeds of 166 species from all eight families in Zingiberales were analyzed for 51 characters using synchrotron based 3D X-ray tomographic microscopy to determine phylogenetically informative characters and to understand the distribution of morphological disparity within the order. All families are distinguishable based on seed characters. Non-metric multidimensional scaling analyses show Zingiberaceae occupy the largest seed morphospace relative to the other families, and environmental analyses demonstrate that Zingiberaceae inhabit both temperate and tropical regions, while other Zingiberales are almost exclusively tropical. Temperate species do not cluster in morphospace nor do they share a common suite of character states. This suggests that the diversity seen is not driven by adaptation to temperate niches; rather, the morphological disparity seen likely reflects an underlying genetic plasticity that allowed Zingiberaceae to repeatedly colonize temperate environments. The notable morphoanatomical variety in Zingiberaceae seeds may account for their extraordinary ecological success and high species diversity as compared to other Zingiberales. © The Authors 2016. Published by Oxford University Press on behalf of the Annals of Botany Company.

High-rate real-time GPS network at Parkfield: Utility for detecting fault slip and seismic displacements

USGS Publications Warehouse

Langbein, J.; Bock, Y.

2004-01-01

A network of 13 continuous GPS stations near Parkfield, California has been converted from 30 second to 1 second sampling with positions of the stations estimated in real-time relative to a master station. Most stations are near the trace of the San Andreas fault, which exhibits creep. The noise spectra of the instantaneous 1 Hz positions show flicker noise at high frequencies and change to frequency independence at low frequencies; the change in character occurs between 6 to 8 hours. Our analysis indicates that 1-second sampled GPS can estimate horizontal displacements of order 6 mm at the 99% confidence level from a few seconds to a few hours. High frequency GPS can augment existing measurements in capturing large creep events and postseismic slip that would exceed the range of existing creepmeters, and can detect large seismic displacements. Copyright 2004 by the American Geophysical Union.

Brownian self-driven particles on the surface of a sphere

NASA Astrophysics Data System (ADS)

Apaza, Leonardo; Sandoval, Mario

2017-08-01

We present the dynamics of overdamped Brownian self-propelled particles moving on the surface of a sphere. The effect of self-propulsion on the diffusion of these particles is elucidated by determining their angular (azimuthal and polar) mean-square displacement. Short- and long-times analytical expressions for their angular mean-square displacement are offered. Finally, the particles' steady marginal angular probability density functions are also elucidated.

Toehold strand displacement-driven assembly of G-quadruplex DNA for enzyme-free and non-label sensitive fluorescent detection of thrombin.

PubMed

Xu, Yunying; Zhou, Wenjiao; Zhou, Ming; Xiang, Yun; Yuan, Ruo; Chai, Yaqin

2015-02-15

Based on a new signal amplification strategy by the toehold strand displacement-driven cyclic assembly of G-quadruplex DNA, the development of an enzyme-free and non-label aptamer sensing approach for sensitive fluorescent detection of thrombin is described. The target thrombin associates with the corresponding aptamer of the partial dsDNA probes and liberates single stranded initiation sequences, which trigger the toehold strand displacement assembly of two G-quadruplex containing hairpin DNAs. This toehold strand displacement reaction leads to the cyclic reuse of the initiation sequences and the production of DNA assemblies with numerous G-quadruplex structures. The fluorescent dye, N-Methyl mesoporphyrin IX, binds to these G-quadruplex structures and generates significantly amplified fluorescent signals to achieve highly sensitive detection of thrombin down to 5 pM. Besides, this method shows high selectivity towards the target thrombin against other control proteins. The developed thrombin sensing method herein avoids the modification of the probes and the involvement of any enzyme or nanomaterial labels for signal amplification. With the successful demonstration for thrombin detection, our approach can be easily adopted to monitor other target molecules in a simple, low-cost, sensitive and selective way by choosing appropriate aptamer/ligand pairs. Copyright © 2014 Elsevier B.V. All rights reserved.

Chemistry, Characterization and Processing of IMC Curing Polymers.

DTIC Science & Technology

1983-07-01

example, nitronium hexafluorosilicate (Ref- erence 110), nitronium hexafluorophosphate (Reference 111) and nitronium trifluorometh- anesulfonate(triflate...CCLtoo) "C The dilithio compound underwent lithium -halogen exchange instead of displacement with bromophenylacetylene (Reference 129) due to the...positive character of the bromine on l-bromo-2-phenylacetylene. The reaction product of the lithium -bromine exchange reaction ൭ was identified as 1,4

A Study of Displacement in Jean Rhys' Novel "Wide Sargasso Sea"

ERIC Educational Resources Information Center

Jamal, Inna Malissa bte Che; Singh, Hardev Kaur A/P Jujar; Mani, Manimangai

2014-01-01

"Wide Sargasso Sea," by Jean Rhys, is a novel filled with tragedy; two characters in conflict meet in circumstances not in their best interests but rather for other people. This novel is an illustration of the mad woman in the novel "Jane Eyre," by Charlotte Bronte, as the story of her life before madness is told in the novel…

Selection for niche differentiation in plant communities increases biodiversity effects.

PubMed

Zuppinger-Dingley, Debra; Schmid, Bernhard; Petermann, Jana S; Yadav, Varuna; De Deyn, Gerlinde B; Flynn, Dan F B

2014-11-06

In experimental plant communities, relationships between biodiversity and ecosystem functioning have been found to strengthen over time, a fact often attributed to increased resource complementarity between species in mixtures and negative plant-soil feedbacks in monocultures. Here we show that selection for niche differentiation between species can drive this increasing biodiversity effect. Growing 12 grassland species in test monocultures and mixtures, we found character displacement between species and increased biodiversity effects when plants had been selected over 8 years in species mixtures rather than in monocultures. When grown in mixtures, relative differences in height and specific leaf area between plant species selected in mixtures (mixture types) were greater than between species selected in monocultures (monoculture types). Furthermore, net biodiversity and complementarity effects were greater in mixtures of mixture types than in mixtures of monoculture types. Our study demonstrates a novel mechanism for the increase in biodiversity effects: selection for increased niche differentiation through character displacement. Selection in diverse mixtures may therefore increase species coexistence and ecosystem functioning in natural communities and may also allow increased mixture yields in agriculture or forestry. However, loss of biodiversity and prolonged selection of crops in monoculture may compromise this potential for selection in the longer term.

Electronic structure of the benzene dimer cation

NASA Astrophysics Data System (ADS)

Pieniazek, Piotr A.; Krylov, Anna I.; Bradforth, Stephen E.

2007-07-01

The benzene and benzene dimer cations are studied using the equation-of-motion coupled-cluster model with single and double substitutions for ionized systems. The ten lowest electronic states of the dimer at t-shaped, sandwich, and displaced sandwich configurations are described and cataloged based on the character of the constituent fragment molecular orbitals. The character of the states, bonding patterns, and important features of the electronic spectrum are explained using qualitative dimer molecular orbital linear combination of fragment molecular orbital framework. Relaxed ground state geometries are obtained for all isomers. Calculations reveal that the lowest energy structure of the cation has a displaced sandwich structure and a binding energy of 20kcal/mol, while the t-shaped isomer is 6kcal/mol higher. The calculated electronic spectra agree well with experimental gas phase action spectra and femtosecond transient absorption in liquid benzene. Both sandwich and t-shaped structures feature intense charge resonance bands, whose location is very sensitive to the interfragment distance. Change in the electronic state ordering was observed between σ and πu states, which correlate to the B˜ and C˜ bands of the monomer, suggesting a reassignment of the local excitation peaks in the gas phase experimental spectrum.

Research regarding the influence of driving-wires length change on positioning precision of a robotic arm

NASA Astrophysics Data System (ADS)

Ciofu, C.; Stan, G.

2016-08-01

The paper emphasise positioning precision of an elephant's trunk robotic arm which has joints driven by wires with variable length while operating The considered 5 degrees of freedom robotic arm has a particular structure of joint that makes possible inner actuation with wire-driven mechanism. We analyse solely the length change of wires as a consequence due inner winding and unwinding on joints for certain values of rotational angles. Variations in wires length entail joint angular displacements. We analyse positioning precision by taking into consideration equations from inverse kinematics of the elephant's trunk robotic arm. The angular displacements of joints are considered into computational method after partial derivation of positioning equations. We obtain variations of wires length at about tenths of micrometers. These variations employ angular displacements which are about minutes of sexagesimal degree and, thus, define positioning precision of elephant's trunk robotic arms. The analytical method is used for determining aftermath design structure of an elephant's trunk robotic arm with inner actuation through wires on positioning precision. Thus, designers could take suitable decisions on accuracy specifications limits of the robotic arm.

How Japanese language has been used and transformed--focused on social-cultural context and the use in communication.

PubMed

Hidaka, Tomoo

2010-06-01

In this paper I address that flexibility and vagueness of mimic word, especially Gitai-go, can provide the communication with tension leading us to the continuous process of meaning construction, focused on the history of Japanese characters as the core of mimic words. I present that Hiragana, as the character for Gitai-go, was started to use by people viewed as of no public authority such as women at that time while Kanji had a position as an official characters. As unofficial character, Hiragana was received and transformed by common people as the character which is more flexible and vague suited to express persons' experience than Kanji. Most of Gitai-go is written in Hiragana, and people can also create original and personalized one based on their experience. We can be driven by necessity to search the meanings of Gitai-go when we meet unknown one, through its vagueness. This undifferentiated nature and indefinite feature of Gitai-go provide us with tension of communication.

Utilization of optical tracking to validate a software-driven isocentric approach to robotic couch movements for proton radiotherapy.

PubMed

Hsi, Wen C; Law, Aaron; Schreuder, Andreas N; Zeidan, Omar A

2014-08-01

An optical tracking and positioning system (OTPS) was developed to validate the software-driven isocentric (SDI) approach to control the six-degrees-of-freedom movement of a robotic couch. The SDI approach to movements rotating around a predefined isocenter, referred to as a GeoIso, instead of a mechanical pivot point was developed by the robot automation industry. With robotic couch-sag corrections for weight load in a traditional SDI approach, movements could be accurately executed for a GeoIso located within a 500 mm cubic volume on the couch for treatments. The accuracy of SDI movement was investigated using the OTPS. The GeoIso was assumed to align with the proton beam isocenter (RadIso) for gantry at the reference angle. However, the misalignment between GeoIso and RadIso was quantitatively investigated by measuring the displacements at various couch angles for a target placed at the RadIso at an initial couch angle. When circular target displacements occur on a plane, a relative isocenter shift (RIS) correction could be applied in the SDI movement to minimize target displacements. Target displacements at a fixed gantry angle without and with RIS correction were measured for 12 robotic couches. Target displacements for various gantry angles were performed on three couches in gantry rooms to study the gantry-induced RadIso shift. The RIS correction can also be applied for the RadIso shift. A new SDI approach incorporating the RIS correction with the couch sag is described in this study. In parallel, the accuracy of SDI translation movements for various weight loads of patients on the couch was investigated during positioning of patients for proton prostate treatments. For a fixed gantry angle, measured target displacements without RIS correction for couch rotations in the horizontal plane varied from 4 to 20 mm. However, measured displacements perpendicular to couch rotation plane were about 2 mm for all couches. Extracted misalignments of GeoIso and RadIso in the horizontal plane were about 10 mm for one couch and within 3 mm for the rest of couches. After applying the RIS correction, the residual target displacements for couch rotations were within 0.5 mm to RadIso for all couches. For various gantry angles, measured target location for each angle was within 0.5 mm to its excepted location by the preset RadIso shift. Measured target displacements for ± 30° of couch rotations were within 0.5 mm for gantry angles at 0° and 180°. Overall, nearly 85% of couch movements were within 0.5 mm in the horizontal plane and 0.7 mm vector distance from required displacements. The authors present an optical tracking methodology to quantify for software-driven isocentric movements of robotic couches. By applying proper RIS correction for misaligned GeoIso and RadIso for each couch, and the RadIso shifts for a moving gantry, residual target displacements for isocentric couch movements around the actual RadIso can be reduced to submillimeter tolerance.

Utilization of optical tracking to validate a software-driven isocentric approach to robotic couch movements for proton radiotherapy

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

Hsi, Wen C., E-mail: Wen.Hsi@Mclaren.org, E-mail: Wenchien.hsi@sphic.org.cn; Zeidan, Omar A., E-mail: omar.zeidan@orlandohealth.com; Law, Aaron

Purpose: An optical tracking and positioning system (OTPS) was developed to validate the software-driven isocentric (SDI) approach to control the six-degrees-of-freedom movement of a robotic couch. Methods: The SDI approach to movements rotating around a predefined isocenter, referred to as a GeoIso, instead of a mechanical pivot point was developed by the robot automation industry. With robotic couch-sag corrections for weight load in a traditional SDI approach, movements could be accurately executed for a GeoIso located within a 500 mm cubic volume on the couch for treatments. The accuracy of SDI movement was investigated using the OTPS. The GeoIso wasmore » assumed to align with the proton beam isocenter (RadIso) for gantry at the reference angle. However, the misalignment between GeoIso and RadIso was quantitatively investigated by measuring the displacements at various couch angles for a target placed at the RadIso at an initial couch angle. When circular target displacements occur on a plane, a relative isocenter shift (RIS) correction could be applied in the SDI movement to minimize target displacements. Target displacements at a fixed gantry angle without and with RIS correction were measured for 12 robotic couches. Target displacements for various gantry angles were performed on three couches in gantry rooms to study the gantry-induced RadIso shift. The RIS correction can also be applied for the RadIso shift. A new SDI approach incorporating the RIS correction with the couch sag is described in this study. In parallel, the accuracy of SDI translation movements for various weight loads of patients on the couch was investigated during positioning of patients for proton prostate treatments. Results: For a fixed gantry angle, measured target displacements without RIS correction for couch rotations in the horizontal plane varied from 4 to 20 mm. However, measured displacements perpendicular to couch rotation plane were about 2 mm for all couches. Extracted misalignments of GeoIso and RadIso in the horizontal plane were about 10 mm for one couch and within 3 mm for the rest of couches. After applying the RIS correction, the residual target displacements for couch rotations were within 0.5 mm to RadIso for all couches. For various gantry angles, measured target location for each angle was within 0.5 mm to its excepted location by the preset RadIso shift. Measured target displacements for ±30° of couch rotations were within 0.5 mm for gantry angles at 0° and 180°. Overall, nearly 85% of couch movements were within 0.5 mm in the horizontal plane and 0.7 mm vector distance from required displacements. Conclusions: The authors present an optical tracking methodology to quantify for software-driven isocentric movements of robotic couches. By applying proper RIS correction for misaligned GeoIso and RadIso for each couch, and the RadIso shifts for a moving gantry, residual target displacements for isocentric couch movements around the actual RadIso can be reduced to submillimeter tolerance.« less

Multiple-degree-of-freedom vehicle

DOEpatents

Borenstein, Johann

1995-01-01

A multi-degree-of-freedom vehicle employs a compliant linkage to accommodate the need for a variation in the distance between drive wheels or drive systems which are independently steerable and drivable. The subject vehicle is provided with rotary encodes to provide signals representative of the orientation of the steering pivot associated with each such drive wheel or system, and a linear encoder which issues a signal representative of the fluctuations in the distance between the drive elements. The wheels of the vehicle are steered and driven in response to the linear encoder signal, there being provided a controller system for minimizing the fluctuations in the distance. The controller system is a software implementation of a plurality of controllers, operating at the chassis level and at the vehicle level. A trajectory interpolator receives x-displacement, y-displacement, and .theta.-displacement signals and produces to the vehicle level controller trajectory signals corresponding to interpolated control signals. The x-displacement, y-displacement, and .theta.-displacement signals are received from a human operator, via a manipulable joy stick.

Distinguishing thrust sequences in gravity-driven fold and thrust belts

NASA Astrophysics Data System (ADS)

Alsop, G. I.; Weinberger, R.; Marco, S.

2018-04-01

Piggyback or foreland-propagating thrust sequences, where younger thrusts develop in the footwalls of existing thrusts, are generally assumed to be the typical order of thrust development in most orogenic settings. However, overstep or 'break-back' sequences, where later thrusts develop above and in the hangingwalls of earlier thrusts, may potentially form during cessation of movement in gravity-driven mass transport deposits (MTDs). In this study, we provide a detailed outcrop-based analysis of such an overstep thrust sequence developed in an MTD in the southern Dead Sea Basin. Evidence that may be used to discriminate overstep thrusting from piggyback thrust sequences within the gravity-driven fold and thrust belt includes upright folds and forethrusts that are cut by younger overlying thrusts. Backthrusts form ideal markers that are also clearly offset and cut by overlying younger forethrusts. Portions of the basal detachment to the thrust system are folded and locally imbricated in footwall synclines below forethrust ramps, and these geometries also support an overstep sequence. However, new 'short-cut' basal detachments develop below these synclines, indicating that movement continued on the basal detachment rather than it being abandoned as in classic overstep sequences. Further evidence for 'synchronous thrusting', where movement on more than one thrust occurs at the same time, is provided by displacement patterns on sequences of thrust ramp imbricates that systematically increases downslope towards the toe of the MTD. Older thrusts that initiate downslope in the broadly overstep sequence continue to move and therefore accrue greater displacements during synchronous thrusting. Our study provides a template to help distinguish different thrust sequences in both orogenic settings and gravity-driven surficial systems, with displacement patterns potentially being imaged in seismic sections across offshore MTDs.

Vertical and horizontal surface displacements near Jakobshavn Isbræ driven by melt-induced and dynamic ice loss

NASA Astrophysics Data System (ADS)

Nielsen, Karina; Khan, Shfaqat A.; Spada, Giorgio; Wahr, John; Bevis, Michael; Liu, Lin; van Dam, Tonie

2013-04-01

We analyze Global Positioning System (GPS) time series of relative vertical and horizontal surface displacements from 2006 to 2012 at four GPS sites located between ˜5 and ˜150 km from the front of Jakobshavn Isbræ (JI) in west Greenland. Horizontal displacements during 2006-2010 at KAGA, ILUL, and QEQE, relative to the site AASI, are directed toward north-west, suggesting that the main mass loss signal is located near the frontal portion of JI. The directions of the observed displacements are supported by modeled displacements, derived from NASA's Airborne Topographic Mapper (ATM) surveys of surface elevations from 2006, 2009, and 2010. However, horizontal displacements during 2010-2012 at KAGA and ILUL are directed more towards the west suggesting a change in the spatial distribution of the ice mass loss. In addition, we observe an increase in the uplift rate during 2010-2012 as compared to 2006-2010. The sudden change in vertical and horizontal displacements is due to enhanced melt-induced ice loss in 2010 and 2012.

Numerical simulation and comparison of two ventilation methods for a restaurant - displacement vs mixed flow ventilation

NASA Astrophysics Data System (ADS)

Chitaru, George; Berville, Charles; Dogeanu, Angel

2018-02-01

This paper presents a comparison between a displacement ventilation method and a mixed flow ventilation method using computational fluid dynamics (CFD) approach. The paper analyses different aspects of the two systems, like the draft effect in certain areas, the air temperatureand velocity distribution in the occupied zone. The results highlighted that the displacement ventilation system presents an advantage for the current scenario, due to the increased buoyancy driven flows caused by the interior heat sources. For the displacement ventilation case the draft effect was less prone to appear in the occupied zone but the high heat emissions from the interior sources have increased the temperature gradient in the occupied zone. Both systems have been studied in similar conditions, concentrating only on the flow patterns for each case.

Research on influence factor about the dynamic characteristic of armored vehicle hydraulic-driven fan system

NASA Astrophysics Data System (ADS)

Chao, Zhiqiang; Mao, Feiyue; Liu, Xiangbo; Li, Huaying; Han, Shousong

2017-01-01

In view of the large power of armored vehicle cooling system, the demand for high fan speed control and energy saving, this paper expounds the basic composition and principle of hydraulic-driven fan system and establishes the mathematical model of the system. Through the simulation analysis of different parameters, such as displacement of motor and working volume of fan system, the influences of performance parameters on the dynamic characteristic of hydraulic-driven fan system are obtained, which can provide theoretical guidance for system optimization design.

Environmental determinism, and not interspecific competition, drives morphological variability in Australasian warblers (Acanthizidae).

PubMed

García-Navas, Vicente; Rodríguez-Rey, Marta; Marki, Petter Z; Christidis, Les

2018-04-01

Interspecific competition is thought to play a key role in determining the coexistence of closely related species within adaptive radiations. Competition for ecological resources can lead to different outcomes from character displacement to, ultimately, competitive exclusion. Accordingly, divergent natural selection should disfavor those species that are the most similar to their competitor in resource use, thereby increasing morphological disparity. Here, we examined ecomorphological variability within an Australo-Papuan bird radiation, the Acanthizidae, which include both allopatric and sympatric complexes. In addition, we investigated whether morphological similarities between species are related to environmental factors at fine scale (foraging niche) and/or large scale (climate). Contrary to that predicted by the competition hypothesis, we did not find a significant correlation between the morphological similarities found between species and their degree of range overlap. Comparative modeling based on both a priori and data-driven identification of selective regimes suggested that foraging niche is a poor predictor of morphological variability in acanthizids. By contrast, our results indicate that climatic conditions were an important factor in the formation of morphological variation. We found a significant negative correlation between species scores for PC1 (positively associated to tarsus length and tail length) and both temperature and precipitation, whereas PC2 (positively associated to bill length and wing length) correlated positively with precipitation. In addition, we found that species inhabiting the same region are closer to each other in morphospace than to species outside that region regardless of genus to which they belong or its foraging strategy. Our results indicate that the conservative body form of acanthizids is one that can work under a wide variety of environments (an all-purpose morphology), and the observed interspecific similarity is probably driven by the common response to environment.

Coseismic and Postseismic Deformation Following the 2011 Mw 9.0 Tohoku Earthquake and its Mw 7.9 Aftershock: Searching for Fault-localized Relaxation of Coseismic Stress Increments

NASA Astrophysics Data System (ADS)

Wang, F.; Bevis, M. G.; Blewitt, G.; Gomez, D.

2017-12-01

We study the postseismic transient displacements following the 2011 Mw 9.0 Tohoku earthquake using the Nevada Geodetic Laboratory's daily and 5-minute interval PPP solutions for 1,272 continuous GPS stations in Japan, with particular emphasis on the early transient displacements of these stations. One significant complication is the Mw 7.9 aftershock that occurred just 29.3 minutes after the main shock, since the coseismic (and postseismic) displacements driven by the aftershock are superimposed on the postseismic transients driven by the main shock. We address the question of whether or not the stresses induced by the Mw 9.0 main shock were relaxed by any major faults within Japan. The notion is that significant stress relaxation which is localized on a fault system should be manifested in the spatial pattern of the postseismic transient displacement field in the vicinity of that system. This would provide a basis for distinguishing between faults that engage in stick-slip behavior and those that creep instead. The distinction is important in that it has implications for the seismic risk associated with upper plate faulting. We will make the case that we do detect localized fault creeping in response to the coseismic stress field produced by the Mw 9 event.

Natural ventilation of buildings: opposing wind and buoyancy

NASA Astrophysics Data System (ADS)

Linden, Paul; Hunt, Gary

1998-11-01

The use of natural ventilation in buildings is an attractive way to reduce energy usage thereby reducing costs and CO2 emissions. Generally, it is necessary to remove excess heat from a building and the designer can use the buoyancy forces associated with the above ambient temperatures within the building to drive a flow - 'stack' ventilation. The most efficient mode is displacement ventilation where warm air accumulates near the top of the building and flows out through upper level vents and cooler air flows in at lower levels. Ventilation will also be driven between these lower and upper openings by the wind. We report on laboratory modeling and theory which investigates the effects of an opposing wind on stack ventilation driven by a constant source of heat within a space under displacement ventilation. We show that there is a critical wind speed, expressed in dimensionless terms as a critical Froude number, above which displacement ventilation is replaced by (less efficient) mixing ventilation with reversed flow. Below this critical speed, displacement ventilation, in which the interior has a two-layer stratification, is maintained. The criterion for the change in ventilation mode is derived from general considerations of mixing efficiencies in stratified flows. We conclude that even when wind effects might appear to be dominant, the inhibition of mixing by the stable stratification within the space ensures that stack ventilation can operate over a wide range of apparently adverse conditions.

A universal model for predicting human migration under climate change: examining future sea level rise in Bangladesh

NASA Astrophysics Data System (ADS)

Frankel Davis, Kyle; Bhattachan, Abinash; D’Odorico, Paolo; Suweis, Samir

2018-06-01

Climate change is expected to impact the habitability of many places around the world in significant and unprecedented ways in the coming decades. While previous studies have provided estimates of populations potentially exposed to various climate impacts, little work has been done to assess the number of people that may actually be displaced or where they will choose to go. Here we modify a diffusion-based model of human mobility in combination with population, geographic, and climatic data to estimate the sources, destinations, and flux of potential migrants as driven by sea level rise (SLR) in Bangladesh in the years 2050 and 2100. Using only maps of population and elevation, we predict that 0.9 million people (by year 2050) to 2.1 million people (by year 2100) could be displaced by direct inundation and that almost all of this movement will occur locally within the southern half of the country. We also find that destination locations should anticipate substantial additional demands on jobs (594 000), housing (197 000), and food (783 × 109 calories) by mid-century as a result of those displaced by SLR. By linking the sources of migrants displaced by SLR with their likely destinations, we demonstrate an effective approach for predicting climate-driven migrant flows, especially in data-limited settings.

Comments on baseline correction of digital strong-motion data: Examples from the 1999 Hector Mine, California, earthquake

USGS Publications Warehouse

Boore, D.M.; Stephens, C.D.; Joyner, W.B.

2002-01-01

Residual displacements for large earthquakes can sometimes be determined from recordings on modern digital instruments, but baseline offsets of unknown origin make it difficult in many cases to do so. To recover the residual displacement, we suggest tailoring a correction scheme by studying the character of the velocity obtained by integration of zeroth-order-corrected acceleration and then seeing if the residual displacements are stable when the various parameters in the particular correction scheme are varied. For many seismological and engineering purposes, however, the residual displacement are of lesser importance than ground motions at periods less than about 20 sec. These ground motions are often recoverable with simple baseline correction and low-cut filtering. In this largely empirical study, we illustrate the consequences of various correction schemes, drawing primarily from digital recordings of the 1999 Hector Mine, California, earthquake. We show that with simple processing the displacement waveforms for this event are very similar for stations separated by as much as 20 km. We also show that a strong pulse on the transverse component was radiated from the Hector Mine earthquake and propagated with little distortion to distances exceeding 170 km; this pulse leads to large response spectral amplitudes around 10 sec.

Data-driven train set crash dynamics simulation

NASA Astrophysics Data System (ADS)

Tang, Zhao; Zhu, Yunrui; Nie, Yinyu; Guo, Shihui; Liu, Fengjia; Chang, Jian; Zhang, Jianjun

2017-02-01

Traditional finite element (FE) methods are arguably expensive in computation/simulation of the train crash. High computational cost limits their direct applications in investigating dynamic behaviours of an entire train set for crashworthiness design and structural optimisation. On the contrary, multi-body modelling is widely used because of its low computational cost with the trade-off in accuracy. In this study, a data-driven train crash modelling method is proposed to improve the performance of a multi-body dynamics simulation of train set crash without increasing the computational burden. This is achieved by the parallel random forest algorithm, which is a machine learning approach that extracts useful patterns of force-displacement curves and predicts a force-displacement relation in a given collision condition from a collection of offline FE simulation data on various collision conditions, namely different crash velocities in our analysis. Using the FE simulation results as a benchmark, we compared our method with traditional multi-body modelling methods and the result shows that our data-driven method improves the accuracy over traditional multi-body models in train crash simulation and runs at the same level of efficiency.

A cryocooler for applications requiring low magnetic and mechanical interference

NASA Technical Reports Server (NTRS)

Zimmerman, J. E.; Daney, D. E.; Sullivan, D. B.

1983-01-01

A very low-power, low-interference Stirling cryocooler is being developed based on principles and techniques described in several previous publications over the last four years. It differs in several important details from those built previously. It uses a tapered displacer based upon an analytical optimization procedure. The displacer is driven by an auxiliary piston and cylinder (rather than by mechanical linkage) using some of the working fluid itself to provide the driving force. This provides smooth, vibration-free motion, and, more importantly, allows complete mechanical and spatial separation of the cryostat from the pressure-wave generator. Either of two different pressure-wave generators can be used. One is a non-contaminating, unlubricated ceramic piston and cylinder. The other is a compressed-air-operated rubber diaphragm with motor-driven valves to cycle the pressure between appropriate limits.

Variation in sperm displacement and its association with accessory gland protein loci in Drosophila melanogaster.

PubMed

Clark, A G; Aguadé, M; Prout, T; Harshman, L G; Langley, C H

1995-01-01

Genes that influence mating and/or fertilization success may be targets for strong natural selection. If females remate frequently relative to the duration of sperm storage and rate of sperm use, sperm displacement may be an important component of male reproductive success. Although it has long been known that mutant laboratory stocks of Drosophila differ in sperm displacement, the magnitude of the naturally occurring genetic variation in this character has not been systematically quantified. Here we report the results of a screen for variation in sperm displacement among 152 lines of Drosophilia melanogaster that were made homozygous for second and/or third chromosomes recovered from natural populations. Sperm displacement was assayed by scoring the progeny of cn;bw females that had been mated sequentially to cn;bw and tested males in either order. Highly significant differences were seen in both the ability to displace sperm that is resident in the female's reproductive tract and in the ability to resist displacement by subsequent sperm. Most lines exhibited nearly complete displacement, having nearly all progeny sired by the second male, but several lines had as few as half the progeny fathered by the second male. Lines that were identified in the screen for naturally occurring variation in sperm displacement were also characterized for single-strand conformation polymorphisms (SSCP) at seven accessory gland protein (Acp) genes, Glucose dehydrogenase (Gld), and Esterase-6 (Est-6). Acp genes encode proteins that are in some cases known to be transmitted to the female in the seminal fluid and are likely candidates for genes that might mediate the phenomenon of sperm displacement. Significant associations were found between particular Acp alleles at four different loci (Acp26Aa/Ab, Acp29B, Acp36DE and Acp53E) and the ability of males to resist displacement by subsequent sperm. There was no correlation between the ability to displace resident sperm and the ability to resist being displaced by subsequent sperm. This lack of correlation, and the association of Acp alleles with resisting subsequent sperm only, suggests that different mechanisms mediate the two components of sperm displacement.

On-Chip Fluorescence Switching System for Constructing a Rewritable Random Access Data Storage Device.

PubMed

Nguyen, Hoang Hiep; Park, Jeho; Hwang, Seungwoo; Kwon, Oh Seok; Lee, Chang-Soo; Shin, Yong-Beom; Ha, Tai Hwan; Kim, Moonil

2018-01-10

We report the development of on-chip fluorescence switching system based on DNA strand displacement and DNA hybridization for the construction of a rewritable and randomly accessible data storage device. In this study, the feasibility and potential effectiveness of our proposed system was evaluated with a series of wet experiments involving 40 bits (5 bytes) of data encoding a 5-charactered text (KRIBB). Also, a flexible data rewriting function was achieved by converting fluorescence signals between "ON" and "OFF" through DNA strand displacement and hybridization events. In addition, the proposed system was successfully validated on a microfluidic chip which could further facilitate the encoding and decoding process of data. To the best of our knowledge, this is the first report on the use of DNA hybridization and DNA strand displacement in the field of data storage devices. Taken together, our results demonstrated that DNA-based fluorescence switching could be applicable to construct a rewritable and randomly accessible data storage device through controllable DNA manipulations.

Fuel Delivery System.

DTIC Science & Technology

1996-07-24

to fuel tank 27 aboard 23 test torpedo 26. Pressure switch 19B operates to close solenoid 24 valve 22A and concurrently open solenoid valve 22D...leading to a pump explosion. The boost pump 4 is driven by its 11 motor 14B and positive displacement pump 1 by its respective 12 motor 14A. Pressure ... switch 19A monitors the head pressure 13 created by the boost pump 4 and it will shut off the motor 14A of 14 the positive displacement pump 1 if

Flash signal evolution in Photinus fireflies: character displacement and signal exploitation in a visual communication system.

PubMed

Stanger-Hall, Kathrin F; Lloyd, James E

2015-03-01

Animal communication is an intriguing topic in evolutionary biology. In this comprehensive study of visual signal evolution, we used a phylogenetic approach to study the evolution of the flash communication system of North American fireflies. The North American firefly genus Photinus contains 35 described species with simple ON-OFF visual signals, and information on habitat types, sympatric congeners, and predators. This makes them an ideal study system to test hypotheses on the evolution of male and female visual signal traits. Our analysis of 34 Photinus species suggests two temporal pattern generators: one for flash duration and one for flash intervals. Reproductive character displacement was a main factor for signal divergence in male flash duration among sympatric Photinus species. Male flash pattern intervals (i.e., the duration of the dark periods between signals) were positively correlated with the number of sympatric Photuris fireflies, which include predators of Photinus. Females of different Photinus species differ in their response preferences to male traits. As in other communication systems, firefly male sexual signals seem to be a compromise between optimizing mating success (sexual selection) and minimizing predation risk (natural selection). An integrative model for Photinus signal evolution is proposed. © 2015 The Author(s).

Effect of Allylic Groups on SN2 Reactivity

PubMed Central

2015-01-01

The activating effects of the benzyl and allyl groups on SN2 reactivity are well-known. 6-Chloromethyl-6-methylfulvene, also a primary, allylic halide, reacts 30 times faster with KI/acetone than does benzyl chloride at room temperature. The latter result, as well as new experimental observations, suggests that the fulvenyl group is a particularly activating allylic group in SN2 reactions. Computational work on identity SN2 reactions, e.g., chloride– displacing chloride– and ammonia displacing ammonia, shows that negatively charged SN2 transition states (tss) are activated by allylic groups according to the Galabov–Allen–Wu electrostatic model but with the fulvenyl group especially effective at helping to delocalize negative charge due to some cyclopentadienide character in the transition state (ts). In contrast, the triafulvenyl group is deactivating. However, the positively charged SN2 transition states of the ammonia reactions are dramatically stabilized by the triafulvenyl group, which directly conjugates with a reaction center having SN1 character in the ts. Experiments and calculations on the acidities of a variety of allylic alcohols and carboxylic acids support the special nature of the fulvenyl group in stabilizing nearby negative charge and highlight the ability of fulvene species to dramatically alter the energetics of processes even in the absence of direct conjugation. PMID:24977317

Habitat segregation and ecological character displacement in cryptic African malaria mosquitoes

PubMed Central

Tene Fossog, Billy; Ayala, Diego; Acevedo, Pelayo; Kengne, Pierre; Ngomo Abeso Mebuy, Ignacio; Makanga, Boris; Magnus, Julie; Awono-Ambene, Parfait; Njiokou, Flobert; Pombi, Marco; Antonio-Nkondjio, Christophe; Paupy, Christophe; Besansky, Nora J; Costantini, Carlo

2015-01-01

Understanding how divergent selection generates adaptive phenotypic and population diversification provides a mechanistic explanation of speciation in recently separated species pairs. Towards this goal, we sought ecological gradients of divergence between the cryptic malaria vectors Anopheles coluzzii and An. gambiae and then looked for a physiological trait that may underlie such divergence. Using a large set of occurrence records and eco-geographic information, we built a distribution model to predict the predominance of the two species across their range of sympatry. Our model predicts two novel gradients along which the species segregate: distance from the coastline and altitude. Anopheles coluzzii showed a ‘bimodal’ distribution, predominating in xeric West African savannas and along the western coastal fringe of Africa. To test whether differences in salinity tolerance underlie this habitat segregation, we assessed the acute dose–mortality response to salinity of thirty-two larval populations from Central Africa. In agreement with its coastal predominance, Anopheles coluzzii was overall more tolerant than An. gambiae. Salinity tolerance of both species, however, converged in urban localities, presumably reflecting an adaptive response to osmotic stress from anthropogenic pollutants. When comparing degree of tolerance in conjunction with levels of syntopy, we found evidence of character displacement in this trait. PMID:25926878

On the Morphological Description of Tracheal and Esophageal Displacement and Its Phylogenetic Distribution in Avialae

PubMed Central

Klingler, Jeremy J.

2016-01-01

This research examines the evolution and phylogenetic distribution of a peculiar and often overlooked character seen in birds, herein called tracheal and esophageal displacement. Tracheal and esophageal displacement refers to an asymmetrically situated trachea and/or esophagus along the length of the neck. This contrasts with what would be perceived as the “normal” (midsagittal) placement of these organs, wherein the two organs are situated along the ventral midline of the neck with no deviation. A total of forty-two bird species were examined (thirty-six of which came from dissections whereas six came from comments from previous literature or personal observations), as well as turtles, lizards, crocodylians, and mammals. This study found that essentially all birds have a laterally displaced trachea and/or esophagus. Lizards and mammals were seen to have normal, midsagittally placed tracheae and esophagi. Crocodylians were interesting in that alligators were defined by a normally situated trachea and esophagus whereas some crocodiles were characterized by displacement. In birds, the displacement may occur gradually along the neck, or it may happen immediately upon exiting the oropharynx. Displacement of these organs in birds is the result of a heavily modified neck wherein muscles that restrict mobility of the trachea and esophagus in lizards, alligators, and mammals (e.g., m. episternocleidomastoideus, m. omohyoideus, and m. sternohyoideus) no longer substantially restrict positions of the trachea and esophagus in birds. Rather, these muscles are modified in ways which may assist with making tracheal movements. The implications of this study may provide interesting insights for future comparisons in extinct taxa. PMID:27648952

DNA logic gate based on metallo-toehold strand displacement.

PubMed

Deng, Wei; Xu, Huaguo; Ding, Wei; Liang, Haojun

2014-01-01

DNA is increasingly being used as an ideal material for the construction of nanoscale structures, circuits, and machines. Toehold-mediated DNA strand displacement reactions play a very important role in these enzyme-free constructions. In this study, the concept of metallo-toehold was utilized to further develop a mechanism for strand displacement driven by Ag+ ions, in which the intercalation of cytosine-cytosine mismatched base pairs on the toeholds provides additional control by varying of the concentration of Ag+ ions. The characteristics of displacement reaction in response to different concentration of Ag+ ions are investigated by fluorescence spectral and non-denaturing polyacrylamide gel electrophoresis. The reaction can successfully occur when the concentration of Ag+ ions is suitabe; excess Ag+ ions block the reaction. Furthermore, the displacement reaction can be tuned and controlled most efficiently under the condition of two C:C mismatched base pairs placed on the six-nt toehold. Based on our research, a mechanism was developed to construct Boolean logic gate AND and OR by employing strand displacement reaction as a tool, Ag+ and Hg2+ as input.

Instability of displacement of Oldroyd-B fluid by air in a Hele-Shaw cell

NASA Astrophysics Data System (ADS)

Daripa, Prabir

2014-03-01

We study the displacement of an Oldroyd-B fluid in a Hele-Shaw cell when driven by air. In particular, we explicitly obtain an analytical expression for the growth rate of instability which depends on the relaxation and retardation (time) constants, denoted by λ, and λ1 respectively, appearing in the Oldroyd-B constitutive relations. When these two constants are zero, we recover the classical Saffman-Taylor result for a Newtonian liquid displaced by air. Our results show that this displacement process is more unstable than the case when a Newtonian fluid is displaced by air. The analytical results are plotted and compared with numerical results on this unstable displacement process available in the literature. The agreement is found to be excellent. In particular, results show that the non-Newtonian case (i.e., Oldroyd-B) is more unstable than the Newtonian case. Supported by an NPRP Grant # 08-777-1-141 from the Qatar National Research Fund (a member of the Qatar Foundation). The statements made herein are solely the responsibility of the author.

High-displacement spiral piezoelectric actuators

NASA Astrophysics Data System (ADS)

Mohammadi, F.; Kholkin, A. L.; Jadidian, B.; Safari, A.

1999-10-01

A high-displacement piezoelectric actuator, employing spiral geometry of a curved piezoelectric strip is described. The monolithic actuators are fabricated using a layered manufacturing technique, fused deposition of ceramics, which is capable of prototyping electroceramic components with complex shapes. The spiral actuators (2-3 cm in diameter) consisted of 4-5 turns of a lead zirconate titanate ceramic strip with an effective length up to 28 cm. The width was varied from 0.9 to 1.75 mm with a height of 3 mm. When driven by the electric field applied across the width of the spiral wall, the tip of the actuator was found to displace in both radial and tangential directions. The tangential displacement of the tip was about 210 μm under the field of 5 kV/cm. Both the displacement and resonant frequency of the spirals could be tailored by changing the effective length and wall width. The blocking force of the actuator in tangential direction was about 1 N under the field of 5 kV/cm. These properties are advantageous for high-displacement low-force applications where bimorph or monomorph actuators are currently employed.

Varieties of virtualization

NASA Technical Reports Server (NTRS)

Ellis, Stephen R.

1991-01-01

Natural environments have a content, i.e., the objects in them; a geometry, i.e., a pattern of rules for positioning and displacing the objects; and a dynamics, i.e., a system of rules describing the effects of forces acting on the objects. Human interaction with most common natural environments has been optimized by centuries of evolution. Virtual environments created through the human-computer interface similarly have a content, geometry, and dynamics, but the arbitrary character of the computer simulation creating them does not insure that human interaction with these virtual environments will be natural. The interaction, indeed, could be supernatural but it also could be impossible. An important determinant of the comprehensibility of a virtual environment is the correspondence between the environmental frames of reference and those associated with the control of environmental objects. The effects of rotation and displacement of control frames of reference with respect to corresponding environmental references differ depending upon whether perceptual judgement or manual tracking performance is measured. The perceptual effects of frame of reference displacement may be analyzed in terms of distortions in the process of virtualizing the synthetic environment space. The effects of frame of reference displacement and rotation have been studied by asking subjects to estimate exocentric direction in a virtual space.

Spin-orbit driven magnetic insulating state with J eff=1/2 character in a 4d oxide

DOE PAGES

Calder, S.; Li, Ling; Okamoto, Satoshi; ...

2015-11-30

The unusual magnetic and electronic ground states of 5d iridates has been shown to be driven by intrinsically enhanced spin-orbit coupling (SOC). The influence of appreciable but reduced SOC in creating the manifested magnetic insulating states in 4d oxides is less clear, with one hurdle being the existence of such compounds. Here we present experimental and theoretical results on Sr 4RhO 6 that reveal SOC dominated behavior. Neutron measurements show the octahedra are both spatially separated and locally ideal, making the electronic ground state susceptible to alterations by SOC. Magnetic ordering is observed with a similar structure to an analogousmore » J eff=1/2 Mott iridate. We consider the underlying role of SOC in this rhodate with density functional theory and x-ray absorption spectroscopy and find a magnetic insulating ground state with J eff =1/2 character.The unusual magnetic and electronic ground states of 5d iridates have been shown to be driven by intrinsically enhanced spin-orbit coupling (SOC). The influence of appreciable but reduced SOC in creating the manifested magnetic insulating states in 4d oxides is less clear, with one hurdle being the existence of such compounds. Here, we present experimental and theoretical results on Sr 4RhO 6 that reveal SOC dominated behavior. Neutron measurements show the octahedra are both spatially separated and locally ideal, making the electronic ground state susceptible to alterations by SOC. Magnetic ordering is observed with a similar structure to an analogous J eff=1/2 Mott iridate. We consider the underlying role of SOC in this rhodate with density functional theory and x-ray absorption spectroscopy, and find a magnetic insulating ground state with J eff=12 character.« less

What Controls the "Off/On Switch" in the Toehold-Mediated Strand Displacement Reaction on DNA Conjugated Gold Nanoparticles?

PubMed

Yao, Dongbao; Wang, Bei; Xiao, Shiyan; Song, Tingjie; Huang, Fujian; Liang, Haojun

2015-06-30

In DNA dynamic nanotechnology, a toehold-mediated DNA strand-displacement reaction has demonstrated its capability in building complex autonomous system. In most cases, the reaction is performed in pure DNA solution that is essentially a one-phase system. In the present work, we systematically investigated the reaction in a heterogeneous media, in which the strand that implements a displacing action is conjugated on gold nanoparticles. By monitoring the kinetics of spherical nucleic acid (SNA) assembly driven by toehold-mediated strand displacement reaction, we observed significant differences, i.e., the abrupt jump in behavior of an "off/on switch", in the reaction rate when the invading toehold was extended to eight bases from seven bases. These phenomena are attributed to the effect of steric hindrance arising from the high density of invading strand conjugated to AuNPs. Based on these studies, an INHIBIT logic gate presenting good selectivity was developed.

Apparatus for the conversion of power strokes of a random sequence and of random lengths of strokes into potential energy

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

Elkuch, E.

1984-01-17

The apparatus comprises at least one positive displacement pump, which is driven by the sea waves. The quantity of delivery of this pump is adjustable in accordance with the lengths of strokes made by the ocean waves. This is made possible in that the positive displacement pump comprises pistons having different volume displacements. The height of the incoming waves is measured by a membrane box connected to a transducer which generates signals such that only that piston of the plurality of pistons is made to operate, which has by design a volume displacement which gives the optimal recovery of themore » energy of the ocean waves. The or these pistons pump a working fluid into a storage vessel, which allows the generation of peak load as well as base load electrical energy.« less

Small hydraulic turbine drives

NASA Technical Reports Server (NTRS)

Rostafinski, W. A.

1970-01-01

Turbine, driven by the fluid being pumped, requires no external controls, is completely integrated into the flow system, and has bearings which utilize the main fluid for lubrication and cooling. Torque capabilities compare favorably with those developed by positive displacement hydraulic motors.

Pneumatic pressure wave generator provides economical, simple testing of pressure transducers

NASA Technical Reports Server (NTRS)

Gaal, A. E.; Weldon, T. P.

1967-01-01

Testing device utilizes the change in pressure about a bias or reference pressure level produced by displacement of a center-driven piston in a closed cylinder. Closely controlled pneumatic pressure waves allow testing under dynamic conditions.

Real-time physics-based 3D biped character animation using an inverted pendulum model.

PubMed

Tsai, Yao-Yang; Lin, Wen-Chieh; Cheng, Kuangyou B; Lee, Jehee; Lee, Tong-Yee

2010-01-01

We present a physics-based approach to generate 3D biped character animation that can react to dynamical environments in real time. Our approach utilizes an inverted pendulum model to online adjust the desired motion trajectory from the input motion capture data. This online adjustment produces a physically plausible motion trajectory adapted to dynamic environments, which is then used as the desired motion for the motion controllers to track in dynamics simulation. Rather than using Proportional-Derivative controllers whose parameters usually cannot be easily set, our motion tracking adopts a velocity-driven method which computes joint torques based on the desired joint angular velocities. Physically correct full-body motion of the 3D character is computed in dynamics simulation using the computed torques and dynamical model of the character. Our experiments demonstrate that tracking motion capture data with real-time response animation can be achieved easily. In addition, physically plausible motion style editing, automatic motion transition, and motion adaptation to different limb sizes can also be generated without difficulty.

Current-driven plasma acceleration versus current-driven energy dissipation. I - Wave stability theory

NASA Technical Reports Server (NTRS)

Kelly, A. J.; Jahn, R. G.; Choueiri, E. Y.

1990-01-01

The dominant unstable electrostatic wave modes of an electromagnetically accelerated plasma are investigated. The study is the first part of a three-phase program aimed at characterizing the current-driven turbulent dissipation degrading the efficiency of Lorentz force plasma accelerators such as the MPD thruster. The analysis uses a kinetic theory that includes magnetic and thermal effects as well as those of an electron current transverse to the magnetic field and collisions, thus combining all the features of previous models. Analytical and numerical solutions allow a detailed description of threshold criteria, finite growth behavior, destabilization mechanisms and maximized-growth characteristics of the dominant unstable modes. The lower hybrid current-driven instability is implicated as dominant and was found to preserve its character in the collisional plasma regime.

On Displacement Height, from Classical to Practical Formulation: Stress, Turbulent Transport and Vorticity Considerations

NASA Astrophysics Data System (ADS)

Sogachev, Andrey; Kelly, Mark

2016-03-01

Displacement height ( d) is an important parameter in the simple modelling of wind speed and vertical fluxes above vegetative canopies, such as forests. Here we show that, aside from implicit definition through a (displaced) logarithmic profile, accepted formulations for d do not consistently predict flow properties above a forest. Turbulent transport can affect the displacement height, and is an integral part of what is called the roughness sublayer. We develop a more general approach for estimation of d, through production of turbulent kinetic energy and turbulent transport, and show how previous stress-based formulations for displacement height can be seen as simplified cases of a more general definition including turbulent transport. Further, we also give a simplified and practical form for d that is in agreement with the general approach, exploiting the concept of vortex thickness scale from mixing-layer theory. We assess the new and previous displacement height formulations by using flow statistics derived from the atmospheric boundary-layer Reynolds-averaged Navier-Stokes model SCADIS as well as from wind-tunnel observations, for different vegetation types and flow regimes in neutral conditions. The new formulations tend to produce smaller d than stress-based forms, falling closer to the classic logarithmically-defined displacement height. The new, more generally defined, displacement height appears to be more compatible with profiles of components of the turbulent kinetic energy budget, accounting for the combined effects of turbulent transport and shear production. The Coriolis force also plays a role, introducing wind-speed dependence into the behaviour of the roughness sublayer; this affects the turbulent transport, shear production, stress, and wind speed, as well as the displacement height, depending on the character of the forest. We further show how our practical (`mixing-layer') form for d matches the new turbulence-based relation, as well as correspondence to previous (stress-based) formulations.

Fiber optic sensing system

NASA Technical Reports Server (NTRS)

Adamovsky, Grigory (Inventor)

1991-01-01

A fiber optic interferometer utilizes a low coherence light emitting diode (LED) laser as a light source which is filtered and driven at two RF frequencies, high and low, that are specific to the initial length of the resonator chamber. A displacement of a reflecting mirror changes the length traveled by the nonreferencing signal. The low frequency light undergoes destructive interference which reduces the average intensity of the wave while the high frequency light undergoes constructive interference which increases the average intensity of the wave. The ratio of these two intensity measurements is proportional to the displacement incurred.

Two dimensional modeling of elastic wave propagation in solids containing cracks with rough surfaces and friction - Part I: Theoretical background.

PubMed

Aleshin, Vladislav; Delrue, Steven; Trifonov, Andrey; Bou Matar, Olivier; Van Den Abeele, Koen

2018-01-01

Our study aims at the creation of a numerical toolbox that describes wave propagation in samples containing internal contacts (e.g. cracks, delaminations, debondings, imperfect intergranular joints) of known geometry with postulated contact interaction laws including friction. The code consists of two entities: the contact model and the solid mechanics module. Part I of the paper concerns the modeling of internal contacts (called cracks for brevity), while part II is related to the integration of the developed contact model into a solid mechanics module that allows the description of wave propagation processes. The contact model is used to produce normal and tangential load-displacement relationships, which in turn are used by the solid mechanics module as boundary conditions at the internal contacts. Due to friction, the tangential reaction curve is hysteretic and memory-dependent. In addition, it depends on the normal reaction curve. An essential feature of the proposed contact model is that it takes into account the roughness of the contact faces. On one hand, accounting for roughness makes the contact model more complicated since it gives rise to a partial slip regime when some parts on the contact area experience slip and some do not. On the other hand, as we will show, the concept of contact surfaces covered by asperities receding under load makes it possible to formulate a consistent contact model that provides nonlinear load-displacement relationships for any value of the drive displacements and their histories. This is a strong advantage, since this way, the displacement-driven model allows for a simple explicit procedure of data exchange with the solid mechanics module, while more traditional flat-surface contacts driven by loads generate a complex iterative procedure. More specifically, the proposed contact model is based on the previously developed method of memory diagrams that allows one to automatically obtain memory-dependent solutions to frictional contact problems in the particular case of partial slip. Here we extend the solution onto cases of total sliding and contact loss which is possible while using the displacement-driven formulation. The method requires the knowledge of the normal contact response obtained in our case as a result of statistical consideration of roughness of contact faces. Copyright © 2017 Elsevier B.V. All rights reserved.

A wireless laser displacement sensor node for structural health monitoring.

PubMed

Park, Hyo Seon; Kim, Jong Moon; Choi, Se Woon; Kim, Yousok

2013-09-30

This study describes a wireless laser displacement sensor node that measures displacement as a representative damage index for structural health monitoring (SHM). The proposed measurement system consists of a laser displacement sensor (LDS) and a customized wireless sensor node. Wireless communication is enabled by a sensor node that consists of a sensor module, a code division multiple access (CDMA) communication module, a processor, and a power module. An LDS with a long measurement distance is chosen to increase field applicability. For a wireless sensor node driven by a battery, we use a power control module with a low-power processor, which facilitates switching between the sleep and active modes, thus maximizing the power consumption efficiency during non-measurement and non-transfer periods. The CDMA mode is also used to overcome the limitation of communication distance, which is a challenge for wireless sensor networks and wireless communication. To evaluate the reliability and field applicability of the proposed wireless displacement measurement system, the system is tested onsite to obtain the required vertical displacement measurements during the construction of mega-trusses and an edge truss, which are the primary structural members in a large-scale irregular building currently under construction. The measurement values confirm the validity of the proposed wireless displacement measurement system and its potential for use in safety evaluations of structural elements.

Subnanometer Motion of Cargoes Driven by Thermal Gradients Along Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Barreiro, Amelia; Rurali, Riccardo; Hernández, Eduardo R.; Moser, Joel; Pichler, Thomas; Forró, László; Bachtold, Adrian

2008-05-01

An important issue in nanoelectromechanical systems is developing small electrically driven motors. We report on an artificial nanofabricated motor in which one short carbon nanotube moves relative to another coaxial nanotube. A cargo is attached to an ablated outer wall of a multiwalled carbon nanotube that can rotate and/or translate along the inner nanotube. The motion is actuated by imposing a thermal gradient along the nanotube, which allows for subnanometer displacements, as opposed to an electromigration or random walk effect.

Plasma-driven ultrashort bunch diagnostics

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

Dornmair, I.; Schroeder, C. B.; Floettmann, K.

2016-06-10

Ultrashort electron bunches are crucial for an increasing number of applications, however, diagnosing their longitudinal phase space remains a challenge. We propose a new method that harnesses the strong electric fields present in a laser driven plasma wakefield. By transversely displacing driver laser and witness bunch, a streaking field is applied to the bunch. This field maps the time information to a transverse momentum change and, consequently, to a change of transverse position. We illustrate our method with simulations where we achieve a time resolution in the attosecond range.

Computational Design of Animated Mechanical Characters

NASA Astrophysics Data System (ADS)

Coros, Stelian; Thomaszewski, Bernhard; DRZ Team Team

2014-03-01

A factor key to the appeal of modern CG movies and video-games is that the virtual worlds they portray place no bounds on what can be imagined. Rapid manufacturing devices hold the promise of bringing this type of freedom to our own world, by enabling the fabrication of physical objects whose appearance, deformation behaviors and motions can be precisely specified. In order to unleash the full potential of this technology however, computational design methods that create digital content suitable for fabrication need to be developed. In recent work, we presented a computational design system that allows casual users to create animated mechanical characters. Given an articulated character as input, the user designs the animated character by sketching motion curves indicating how they should move. For each motion curve, our framework creates an optimized mechanism that reproduces it as closely as possible. The resulting mechanisms are attached to the character and then connected to each other using gear trains, which are created in a semi-automated fashion. The mechanical assemblies generated with our system can be driven with a single input driver, such as a hand-operated crank or an electric motor, and they can be fabricated using rapid prototyping devices.

Kinematic GPS Analysis Gives New Insights on the Origin of the Very-Long-Period Seismic Signals at Miyake-Jima Volcano during the Caldera Formation

NASA Astrophysics Data System (ADS)

Munekane, H.; Oikawa, J.; Kobayashi, T.

2014-12-01

Miyake-jima is an active basaltic stratovolcano that is located 200km south of Tokyo, Japan. Its eruption event in 2000 was remarkable in that the large caldera was formed at the summit in approximately one month. During the caldera forming stage, very-long-period (VLP) seismic pulse waves with a duration of about 50-s that were accompanied by the step-like inflation were repeatedly recorded. Based on the broadband seismometer data, the piston model is proposed in which a vertical piston of solid materials in the conduit is intermittently sucked into the magma chamber located 3-5 km beneath the edific. In this study, we used the kinematic displacements from the continuous GPS observation to obtain additonal insights on the source mechanism of the pulse waves. 　We calculated the kinematic displacements of 15 GPS stations on Miyake-jima that were in operation at that time at 30 sec interval. Then we extracted the displacements associated with each event using 20-hour time window centered at the occurrence of the event, and stacked the whole time series to obtain mean displacement time series. The obtained time series contain: 1) step-like displacements associated with the pulse waves, 2) exponential decay following the events with time constant of approximately half-day, and 3) steady linear displacements indicating continuous contraction of the edifice. The type one displacements can be attributed to the simultaneous inflation of an mogi-type spherical pressure source located at the depth of 3.6 km under the edifice, and the opening of the nearby vertical dike whose top is at the depth of 2.3 km. The type two displacements can be interpreted as the pressure adjustment at the type one source by the outflow of the magma driven by the pressure difference between the type one source and surrounding area. The type three displacements can be interpreted as the steady outflow of the magma from the type one source. The above results support the ``piston model'' for the source of the pulse waves. However, it seems that the pressure increases by the collapse of the piston are not adjusted by the steady magma outflow as the ``piston model'' suggests but by the pressure-driven magma outflow. The steady magma outflow instead seems to be responsible for the long-term shrinkage of the edifice observed at that period.

Nanometer-scale displacement sensing using self-mixing interferometry with a correlation-based signal processing technique

NASA Astrophysics Data System (ADS)

Hast, J.; Okkonen, M.; Heikkinen, H.; Krehut, L.; Myllylä, R.

2006-06-01

A self-mixing interferometer is proposed to measure nanometre-scale optical path length changes in the interferometer's external cavity. As light source, the developed technique uses a blue emitting GaN laser diode. An external reflector, a silicon mirror, driven by a piezo nanopositioner is used to produce an interference signal which is detected with the monitor photodiode of the laser diode. Changing the optical path length of the external cavity introduces a phase difference to the interference signal. This phase difference is detected using a signal processing algorithm based on Pearson's correlation coefficient and cubic spline interpolation techniques. The results show that the average deviation between the measured and actual displacements of the silicon mirror is 3.1 nm in the 0-110 nm displacement range. Moreover, the measured displacements follow linearly the actual displacement of the silicon mirror. Finally, the paper considers the effects produced by the temperature and current stability of the laser diode as well as dispersion effects in the external cavity of the interferometer. These reduce the sensor's measurement accuracy especially in long-term measurements.

Comparison of microtweezers based on three lateral thermal actuator configurations

NASA Astrophysics Data System (ADS)

Luo, J. K.; Flewitt, A. J.; Spearing, S. M.; Fleck, N. A.; Milne, W. I.

2005-06-01

Thermal actuator-based microtweezers with three different driving configurations have been designed, fabricated and characterized. Finite element analysis has been used to model the device performance. It was found that one configuration of microtweezer, based on two lateral bimorph thermal actuators, has a small displacement (tip opening of the tweezers) and a very limited operating power range. An alternative configuration consisting of two horizontal hot bars with separated beams as the arms can deliver a larger displacement with a much-extended operating power range. This structure can withstand a higher temperature due to the wider beams used, and has flexible arms for increased displacement. Microtweezers driven by a number of chevron structures in parallel have similar maximum displacements but at a cost of higher power consumption. The measured temperature of the devices confirms that the device with the chevron structure can deliver the largest displacement for a given working temperature, while the bimorph thermal actuator design has the highest operating temperature at the same power due to its thin hot arm, and is prone to structural failure.

Sympatry Predicts Spot Pigmentation Patterns and Female Association Behavior in the Livebearing Fish Poeciliopsis baenschi

PubMed Central

Roth-Monzón, Andrea J.; Scott, Laura E.; Camargo, Ashley A.; Clark, Eliza I.; Schott, Eric E.; Johnson, Jerald B.

2017-01-01

In this study, we explored the possibility that differences in pigmentation patterns among populations of the fish Poeciliopsis baenschi were associated with the presence or absence of the closely related species P. turneri. If reproductive character displacement is responsible, spotting patterns in these two species should diverge in sympatry, but not allopatry. We predicted that female P. baenschi from sympatric sites should show a preference for associating with conspecifics vs. heterospecific males, but females from allopatric sites should show no such preferences. To evaluate these predictions, we compared spotting patterns and female association behaviors in populations of P. baenschi from Central Mexico. We found that both of our predictions were supported. Poeciliopsis baenschi that co-occured with P. turneri had spotting patterns significantly different than their counterparts from allopatric sites. Using a simultaneous choice test of video presentations of males, we also found that female P. baenschi from populations that co-occured with P. turneri spent significantly more time with males of their own species than with P. turneri males. In contrast, females from allopatric populations of P. baenschi showed no differences in the amount of time they spent with either conspecific or heterospecific males. Together, our results are consistent with the hypothesis that reproductive character displacement may be responsible for behavioral and spotting pattern differences in these populations of P. baenschi. PMID:28107407

Method and device for producing a tactile display using an electrorheological fluid

NASA Technical Reports Server (NTRS)

Garner, H. Douglas (Inventor)

1996-01-01

A tactile display device utilizes an electrorheological fluid to activate a plurality of tactile dots. A voltage is selectively produced uniformly across an electrorheological fluid flowing between a common ground electrode and a plurality of conductive dot electrodes, thereby producing an increase in the fluid's viscosity to the extent that fluid flow between the two electrodes is restricted. The flow restriction produces a build-up of electrorheological fluid in a corresponding dot actuator chamber. The resulting pressure increase in the chamber displaces an elastic diaphragm fixed to a display surface to form a lump which can be perceived by the reader as one dot in a Braille character cell. A flow regulation system provides a continually pressurized flow system and provides for free flow of the electrorheological fluid through the plurality of dot actuator chambers when they are not activated. The device is adaptable to printed circuit techniques and can simultaneously display tactile dots representative of a full page of Braille characters stored on a medium such as a tape cassette or to display tactile dots representative of non-Braille data appearing on a computer monitor or contained on another data storage medium. In an alternate embodiment, the elastic diaphragm drives a plurality of spring-loaded pins provided with positive stops to maintain consistent displacements of the pins in both their actuated and nonactuated positions.

Tactile display device using an electrorheological fluid

NASA Technical Reports Server (NTRS)

Garner, H. Douglas (Inventor)

1994-01-01

A tactile display device utilizes an electrorheological fluid to activate a plurality of tactile dots. A voltage is selectively produced uniformly across an electrorheological fluid flowing between a common ground electrode and a plurality of conductive dot electrodes, thereby producing an increase in the fluid's viscosity to the extent that fluid flow between the two electrodes is restricted. The flow restriction produces a build-up of electrorheological fluid in a corresponding dot actuator chamber. The resulting pressure increase in the chamber displaces an elastic diaphragm fixed to a display surface to form a lump which can be perceived by the reader as one dot in a Braille character cell. A flow regulation system provides a continually pressurized flow system and provides for free flow of the electrorheological fluid through the plurality of dot actuator chambers when they are not activated. The device is adaptable to printed circuit techniques and can simultaneously display tactile dots representative of a full page of Braille characters stored on a medium such as a tape cassette or to display tactile dots representative of non-Braille data appearing on a computer monitor or contained on another data storage medium. In an alternate embodiment, the elastic diaphragm drives a plurality of spring-loaded pins provided with positive stops to maintain consistent displacements of the pins in both their actuated and nonactuated positions.

Science Education in the United States.

ERIC Educational Resources Information Center

Champagne, Audrey B.

1997-01-01

Discusses science education in the United States, which is in the midst of an unprecedented reform movement driven by national standards developed with support from the federal government. These standards are redefining the character of science education from kindergarten to the post-graduate education of scientists and science teachers. The new…

"Wireless": Some Facts and Figures from a Corpus-Driven Study

ERIC Educational Resources Information Center

Rizzo, Camino Rea

2009-01-01

"Wireless" is the word selected to illustrate a model of analysis designed to determine the specialized character of a lexical unit. "Wireless" belongs to the repertoire of specialized vocabulary automatically extracted from a corpus of telecommunication engineering English (TEC). This paper describes the procedure followed in the analysis which…

Volcano dome dynamics at Mount St. Helens: Deformation and intermittent subsidence monitored by seismicity and camera imagery pixel offsets

USGS Publications Warehouse

Salzer, Jacqueline T.; Thelen, Weston A.; James, Mike R.; Walter, Thomas R.; Moran, Seth C.; Denlinger, Roger P.

2016-01-01

The surface deformation field measured at volcanic domes provides insights into the effects of magmatic processes, gravity- and gas-driven processes, and the development and distribution of internal dome structures. Here we study short-term dome deformation associated with earthquakes at Mount St. Helens, recorded by a permanent optical camera and seismic monitoring network. We use Digital Image Correlation (DIC) to compute the displacement field between successive images and compare the results to the occurrence and characteristics of seismic events during a 6 week period of dome growth in 2006. The results reveal that dome growth at Mount St. Helens was repeatedly interrupted by short-term meter-scale downward displacements at the dome surface, which were associated in time with low-frequency, large-magnitude seismic events followed by a tremor-like signal. The tremor was only recorded by the seismic stations closest to the dome. We find a correlation between the magnitudes of the camera-derived displacements and the spectral amplitudes of the associated tremor. We use the DIC results from two cameras and a high-resolution topographic model to derive full 3-D displacement maps, which reveals internal dome structures and the effect of the seismic activity on daily surface velocities. We postulate that the tremor is recording the gravity-driven response of the upper dome due to mechanical collapse or depressurization and fault-controlled slumping. Our results highlight the different scales and structural expressions during growth and disintegration of lava domes and the relationships between seismic and deformation signals.

Flexural Behavior of GFRP Tubes Filled with Magnetically Driven Concrete

PubMed Central

Xie, Fang; Chen, Ju; Dong, Xinlong; Feng, Bing

2018-01-01

Experimental investigation of GFRP (glass fiber reinforced polymer) tubes that were filled with magnetically driven concrete was carried out to study the flexural behavior of specimens under bending. Specimens having different cross section and lengths were tested. The test specimens were fabricated by filling magnetically driven concrete into the GFRP tubes and the concrete was vibrated using magnetic force. Specimens vibrated using vibrating tube were also tested for comparison. In addition, specimens having steel reinforcing bars and GFRP bars were both tested to study the effect of reinforcing bars on the magnetically driven concrete. The load-displacement curves, load-strain curves, failure mode, and ultimate strengths of test specimens were obtained. Design methods for the flexural stiffness of test specimens were also discussed in this study. PMID:29316732

Flexural Behavior of GFRP Tubes Filled with Magnetically Driven Concrete.

PubMed

Xie, Fang; Chen, Ju; Dong, Xinlong; Feng, Bing

2018-01-08

Experimental investigation of GFRP (glass fiber reinforced polymer) tubes that were filled with magnetically driven concrete was carried out to study the flexural behavior of specimens under bending. Specimens having different cross section and lengths were tested. The test specimens were fabricated by filling magnetically driven concrete into the GFRP tubes and the concrete was vibrated using magnetic force. Specimens vibrated using vibrating tube were also tested for comparison. In addition, specimens having steel reinforcing bars and GFRP bars were both tested to study the effect of reinforcing bars on the magnetically driven concrete. The load-displacement curves, load-strain curves, failure mode, and ultimate strengths of test specimens were obtained. Design methods for the flexural stiffness of test specimens were also discussed in this study.

The Design Fabrication Installation & Evaluation of the Balance Probe Monitor for Large Centrifuges at a National Laboratory Facility.

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

Gallegos, Jonathan Michael

Balance Probe Monitors were designed, fabricated, installed, and evaluated at Sandia National Laboratories (SNL) for the 22,600 g kg (50,000 g lb) direct drive electromotor driven large centrifuges. These centrifuges provide a high onset/decay rate g environment. The Balance Probe Monitor is physically located near a centrifuge’s Capacitance Probe, a crucial sensor for the centrifuge’s sustainability. The Balance Probe Monitor will validate operability of the centrifuge. Most importantly, it is used for triggering a kill switch under the condition that the centrifuge displacement value exceeds allowed tolerances. During operational conditions, the Capacitance Probe continuously detects the structural displacement of themore » centrifuge and an adjoining AccuMeasure 9000 translates this displacement into an output voltage.« less

Non-local sub-characteristic zones of influence in unsteady interactive boundary-layers

NASA Technical Reports Server (NTRS)

Rothmayer, A. P.

1992-01-01

The properties of incompressible, unsteady, interactive, boundary layers are examined for a model hypersonic boundary layer and internal flow past humps or, equivalently, external flow past short-scaled humps. Using a linear high frequency analysis, it is shown that the domains of dependence within the viscous sublayer may be a strong function of position within the sublayer and may be strongly influenced by the pressure displacement interaction, or the prescribed displacement condition. Detailed calculations are presented for the hypersonic boundary layer. This effect is found to carry over directly to the fully viscous problem as well as the nonlinear problem. In the fully viscous problem, the non-local character of the domains of dependence manifests itself in the sub-characteristics. Potential implications of the domain of dependence structure on finite difference computations of unsteady boundary layers are briefly discussed.

Micro-heterogeneity of Cellulosic Fiber Biopolymer Prepared from Corn Hulls

USDA-ARS?s Scientific Manuscript database

Z-trim is a zero calorie cellulosic fiber biopolymer produced from corn hulls. The micro-structural heterogeneities of Z-trim biopolymer were investigated by monitoring the thermally driven displacements of well-dispersed micro-spheres via video fluorescence microscopy named multiple-particle track...

Micro-Heterogeneity of Cellulosic Fiber Biopolymer Prepared from Corn Hulls

USDA-ARS?s Scientific Manuscript database

Z-trim is a zero calorie cellulosic fiber biopolymer produced from corn hulls. The micro-structural heterogeneities of Z-trim biopolymer were investigated by monitoring the thermally driven displacements of well-dispersed micro-spheres via video fluorescence microscopy named multiple-particle track...

Brownian motion of a self-propelled particle.

PubMed

ten Hagen, B; van Teeffelen, S; Löwen, H

2011-05-18

Overdamped Brownian motion of a self-propelled particle is studied by solving the Langevin equation analytically. On top of translational and rotational diffusion, in the context of the presented model, the 'active' particle is driven along its internal orientation axis. We calculate the first four moments of the probability distribution function for displacements as a function of time for a spherical particle with isotropic translational diffusion, as well as for an anisotropic ellipsoidal particle. In both cases the translational and rotational motion is either unconfined or confined to one or two dimensions. A significant non-Gaussian behaviour at finite times t is signalled by a non-vanishing kurtosis γ(t). To delimit the super-diffusive regime, which occurs at intermediate times, two timescales are identified. For certain model situations a characteristic t(3) behaviour of the mean-square displacement is observed. Comparing the dynamics of real and artificial microswimmers, like bacteria or catalytically driven Janus particles, to our analytical expressions reveals whether their motion is Brownian or not.

Ultra-precise micro-motion stage for optical scanning test

NASA Astrophysics Data System (ADS)

Chen, Wen; Zhang, Jianhuan; Jiang, Nan

2009-05-01

This study aims at the application of optical sensing technology in a 2D flexible hinge test stage. Optical fiber sensor which is manufactured taking advantage of the various unique properties of optical fiber, such as good electric insulation properties, resistance of electromagnetic disturbance, sparkless property and availability in flammable and explosive environment, has lots of good properties, such as high accuracy and wide dynamic range, repeatable, etc. and is applied in 2D flexible hinge stage driven by PZT. Several micro-bending structures are designed utilizing the characteristics of the flexible hinge stage. And through experiments, the optimal micro-bending tooth structure and the scope of displacement sensor trip under this optimal micro-bending tooth structure are derived. These experiments demonstrate that the application of optical fiber displacement sensor in 2D flexible hinge stage driven by PZT substantially broadens the dynamic testing range and improves the sensitivity of this apparatus. Driving accuracy and positioning stability are enhanced as well. [1,2

Compliant displacement-multiplying apparatus for microelectromechanical systems

DOEpatents

Kota, Sridhar; Rodgers, M. Steven; Hetrick, Joel A.

2001-01-01

A pivotless compliant structure is disclosed that can be used to increase the geometric advantage or mechanical advantage of a microelectromechanical (MEM) actuator such as an electrostatic comb actuator, a capacitive-plate electrostatic actuator, or a thermal actuator. The compliant structure, based on a combination of interconnected flexible beams and cross-beams formed of one or more layers of polysilicon or silicon nitride, can provide a geometric advantage of from about 5:1 to about 60:1 to multiply a 0.25-3 .mu.m displacement provided by a short-stroke actuator so that such an actuator can be used to generate a displacement stroke of about 10-34 .mu.m to operate a ratchet-driven MEM device or a microengine. The compliant structure has less play than conventional displacement-multiplying devices based on lever arms and pivoting joints, and is expected to be more reliable than such devices. The compliant structure and an associated electrostatic or thermal actuator can be formed on a common substrate (e.g. silicon) using surface micromachining.

GMTIFS: cryogenic rotary mechanisms for the GMT Integral-Field Spectrograph

NASA Astrophysics Data System (ADS)

Hart, John; Espeland, Brady; Bloxham, Gabe; Boz, Robert; Bundy, Dave; Davies, John; Fordham, Bart; Herald, Nick; Sharp, Rob; Vaccarella, Annino; Vest, Colin

2016-07-01

A representative range of the rotary mechanisms proposed for use in GMTIFS is described. All are driven by cryogenically rated stepper motors. For each mechanism, angular position is measured by means of eddy current sensors arranged to function as a resolver. These measure the linear displacement of a decentered aluminum alloy target in two orthogonal directions, from which angular position is determined as a function of the displacement ratio. Resolver function and performance is described. For each mechanism, the mechanical design is described and the adequacy of positioning repeatability assessed. Options for improvement are discussed.

Measurement and interpretation of threshold stress intensity factors for steels in high-pressure hydrogen gas.

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

Dadfarnia, Mohsen; Nibur, Kevin A.; San Marchi, Christopher W.

2010-07-01

Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. The sustained load cracking procedures are generally consistent with those in ASME Article KD-10 of Section VIII Division 3 of the Boiler and Pressure Vessel Code, which was recently published to guide design of high-pressure hydrogen vessels. Three definitions of threshold were established for the two test methods: K{sub THi}* is the maximum applied stress intensity factor for which no crack extension was observed under constant displacement; K{sub THa} ismore » the stress intensity factor at the arrest position for a crack that extended under constant displacement; and K{sub JH} is the stress intensity factor at the onset of crack extension under rising displacement. The apparent crack initiation threshold under constant displacement, K{sub THi}*, and the crack arrest threshold, K{sub THa}, were both found to be non-conservative due to the hydrogen exposure and crack-tip deformation histories associated with typical procedures for sustained-load cracking tests under constant displacement. In contrast, K{sub JH}, which is measured under concurrent rising displacement and hydrogen gas exposure, provides a more conservative hydrogen-assisted fracture threshold that is relevant to structural components in which sub-critical crack extension is driven by internal hydrogen gas pressure.« less

Measurement and interpretation of threshold stress intensity factors for steels in high-pressure hydrogen gas.

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

Nibur, Kevin A.

2010-11-01

Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. The sustained load cracking procedures are generally consistent with those in ASME Article KD-10 of Section VIII Division 3 of the Boiler and Pressure Vessel Code, which was recently published to guide design of high-pressure hydrogen vessels. Three definitions of threshold were established for the two test methods: K{sub THi}* is the maximum applied stress intensity factor for which no crack extension was observed under constant displacement; K{sub THa} ismore » the stress intensity factor at the arrest position for a crack that extended under constant displacement; and K{sub JH} is the stress intensity factor at the onset of crack extension under rising displacement. The apparent crack initiation threshold under constant displacement, K{sub THi}*, and the crack arrest threshold, K{sub THa}, were both found to be non-conservative due to the hydrogen exposure and crack-tip deformation histories associated with typical procedures for sustained-load cracking tests under constant displacement. In contrast, K{sub JH}, which is measured under concurrent rising displacement and hydrogen gas exposure, provides a more conservative hydrogen-assisted fracture threshold that is relevant to structural components in which sub-critical crack extension is driven by internal hydrogen gas pressure.« less

Adaptive dynamics of competition for nutritionally complementary resources: character convergence, displacement, and parallelism.

PubMed

Vasseur, David A; Fox, Jeremy W

2011-10-01

Consumers acquire essential nutrients by ingesting the tissues of resource species. When these tissues contain essential nutrients in a suboptimal ratio, consumers may benefit from ingesting a mixture of nutritionally complementary resource species. We investigate the joint ecological and evolutionary consequences of competition for complementary resources, using an adaptive dynamics model of two consumers and two resources that differ in their relative content of two essential nutrients. In the absence of competition, a nutritionally balanced diet rarely maximizes fitness because of the dynamic feedbacks between uptake rate and resource density, whereas in sympatry, nutritionally balanced diets maximize fitness because competing consumers with different nutritional requirements tend to equalize the relative abundances of the two resources. Adaptation from allopatric to sympatric fitness optima can generate character convergence, divergence, and parallel shifts, depending not on the degree of diet overlap but on the match between resource nutrient content and consumer nutrient requirements. Contrary to previous verbal arguments that suggest that character convergence leads to neutral stability, coadaptation of competing consumers always leads to stable coexistence. Furthermore, we show that incorporating costs of consuming or excreting excess nonlimiting nutrients selects for nutritionally balanced diets and so promotes character convergence. This article demonstrates that resource-use overlap has little bearing on coexistence when resources are nutritionally complementary, and it highlights the importance of using mathematical models to infer the stability of ecoevolutionary dynamics.

Analysis of Driven Pile Capacity within Pre-Bored Soil : Research Project Capsule

DOT National Transportation Integrated Search

2017-10-01

Pre-boring is a method used to facilitate large displacement pile driving in hard/dense soils (see Figure 1). By pre-boring a pilot hole, the end bearing and side friction within the pre-bored zone are reduced, thus aiding pile driving installation. ...

What Does It Mean to Be Educated?

ERIC Educational Resources Information Center

Hurley, J. Casey

2011-01-01

In this article, the author states that it is widely thought that understanding, imagination, strong character, courage, humility, and generosity are the six virtues of the educated person. He stresses that today's schools are driven by a definition that says educated people are those who score high on standardized tests. This definition is…

Harry Potter: Agency or Addiction?

ERIC Educational Resources Information Center

Mills, Alice

2010-01-01

This article considers limitations on agency for characters in the Harry Potter novels, in particular, how far they are driven by an addictive yearning for their beloved dead. As well as Harry's yearning for his dead parents, Dumbledore's guilt, Snape's longing and Slughorn's craving can be read as evidence of addiction rather than love, while the…

Women's Vantage Points and New Realities: A Philosophic Viewing.

ERIC Educational Resources Information Center

Greene, Maxine

Women who are able to acknowledge their distinctive perceptions and to relate them to their lives are the ones most likely to expose the oppressiveness of a power-driven society. Nathaniel Hawthorne's fictional character, Hester Prynne ("The Scarlet Letter") illustrates a crucial theme: a woman's faculty for critical awareness and her ability to…

Self-driven visible-blind photodetector based on ferroelectric perovskite oxides

NASA Astrophysics Data System (ADS)

Li, Jian-kun; Ge, Chen; Jin, Kui-juan; Du, Jian-yu; Yang, Jing-ting; Lu, Hui-bin; Yang, Guo-zhen

2017-04-01

Ultraviolet photodetectors have attracted considerable interest for a variety of applications in health, industry, and science areas. Self-driven visible-blind photodetectors represent an appealing type of sensor, due to the reduced size and high flexibility. In this work, we employed BaTiO3 (BTO) single crystals with a bandgap of 3.2 eV for the realization of a self-driven ultraviolet detector, by utilizing the ferroelectric properties of BTO. We found that the sign of the photocurrent can be reversed by flipping the ferroelectric polarization, which makes the photodetector suitable for electrical manipulation. The photoelectric performance of this photodetector was systematically investigated in terms of rectification character, stability of short-circuit photocurrent, spectral response, and transient photoelectric response. Particularly, the self-driven photodetectors based on BTO showed an ultrafast response time about 200 ps. It is expected that the present work can provide a route for the design of photodetectors based on ferroelectric oxides.

How fluctuating competition and phenotypic plasticity mediate species divergence.

PubMed

Pfennig, David W; Murphy, Peter J

2002-06-01

Causal evidence linking resource competition to species divergence is scarce. In this study, we coupled field observations with experiments to ask if the degree of character displacement reflects the intensity of competition between two closely related spadefoot toads (Spea bombifrons and S. multiplicata). Tadpoles of both species develop into either a small-headed omnivorous morph, which feeds mostly on detritus, or a large-headed carnivorous morph, which specializes on and whose phenotype is induced by fairy shrimp. Previously, we found that S. multiplicata are inferior competitors for fairy shrimp and are less likely to develop into carnivores in sympatry with S. bombifrons. We compared four key trophic characters in S. multiplicata across natural ponds where the frequency of S. bombifrons varied. We found that S. multiplicata became increasingly more omnivore-like as the relative abundance of S. bombifrons increased. Moreover, in controlled laboratory populations, S. multiplicata became increasingly more omnivore-like and S. bombifrons became increasingly more carnivore-like as we increased the relative abundance of the other species. Phenotypic plasticity helped mediate this divergence: S. multiplicata became increasingly less likely to eat shrimp and develop into carnivores in the presence of S. bombifrons, a superior predator on shrimp. However, divergence also reflected differences in canalized traits: When reared under common conditions, S. multiplicata tadpoles became increasingly less likely to produce carnivores as their natal pond decreased in elevation. Presumably, this pattern reflected selection against carnivores in lower-elevation ponds, because S. bombifrons became increasingly more common with decreasing elevation. Local genetic adaptation to the presence of S. bombifrons was remarkably fine grained, with differences in carnivore production detected between populations a few kilometers apart. Our results suggest that the degree of character displacement potentially reflects the intensity of competition between interacting species and that both phenotypic plasticity and fine-scale genetic differentiation can mediate this response. Moreover, these results provide causal evidence linking resource competition to species divergence.

Processing and characterization of oval piezoelectric actuators

NASA Astrophysics Data System (ADS)

Jadidian, B.; Allahverdi, M.; Mohammadi, F.; Safari, A.

2002-03-01

The processing and characterization of piezoelectric actuators with oval geometry are presented. The monolithic actuators were fabricated using the fused deposition of ceramic process. The minor diameter of the ovals varied between 2 and 14 mm and their major diameter, wall thickness, and width were 20, 0.85, and 7 mm, respectively. When driven under electric field, the actuators expanded along their minor diameter. The static and dynamic displacements of ˜7 and ˜5.6 μm were observed at 850 V(dc) and 100 V(ac). The static displacement of the ovals varied almost linearly with voltage and did not change under the application of external load in the range of 1-15 N. However, both dynamic displacement and resonant frequency of the ovals varied, with a maximum of 42 μm and 38 Hz, respectively, under 13 N load.

Axisymmetric flows from fluid injection into a confined porous medium

NASA Astrophysics Data System (ADS)

Guo, Bo; Zheng, Zhong; Celia, Michael A.; Stone, Howard A.

2016-02-01

We study the axisymmetric flows generated from fluid injection into a horizontal confined porous medium that is originally saturated with another fluid of different density and viscosity. Neglecting the effects of surface tension and fluid mixing, we use the lubrication approximation to obtain a nonlinear advection-diffusion equation that describes the time evolution of the sharp fluid-fluid interface. The flow behaviors are controlled by two dimensionless groups: M, the viscosity ratio of displaced fluid relative to injected fluid, and Γ, which measures the relative importance of buoyancy and fluid injection. For this axisymmetric geometry, the similarity solution involving R2/T (where R is the dimensionless radial coordinate and T is the dimensionless time) is an exact solution to the nonlinear governing equation for all times. Four analytical expressions are identified as asymptotic approximations (two of which are new solutions): (i) injection-driven flow with the injected fluid being more viscous than the displaced fluid (Γ ≪ 1 and M < 1) where we identify a self-similar solution that indicates a parabolic interface shape; (ii) injection-driven flow with injected and displaced fluids of equal viscosity (Γ ≪ 1 and M = 1), where we find a self-similar solution that predicts a distinct parabolic interface shape; (iii) injection-driven flow with a less viscous injected fluid (Γ ≪ 1 and M > 1) for which there is a rarefaction wave solution, assuming that the Saffman-Taylor instability does not occur at the reservoir scale; and (iv) buoyancy-driven flow (Γ ≫ 1) for which there is a well-known self-similar solution corresponding to gravity currents in an unconfined porous medium [S. Lyle et al. "Axisymmetric gravity currents in a porous medium," J. Fluid Mech. 543, 293-302 (2005)]. The various axisymmetric flows are summarized in a Γ-M regime diagram with five distinct dynamic behaviors including the four asymptotic regimes and an intermediate regime. The implications of the regime diagram are discussed using practical engineering projects of geological CO2 sequestration, enhanced oil recovery, and underground waste disposal.

Modifying landscape connectivity by reducing wind driven sediment redistribution, northern Chihuahuan Desert, USA

USDA-ARS?s Scientific Manuscript database

Shrub encroachment into perennial grasslands is occurring in many arid and semi-arid parts of the world. As shrubs displace perennial grasslands, bare patches coalesce to enhance soil erosion and sediment fluxes by wind and water transport. Reducing the connectedness of these sediment transport path...

Multiple-particle tracking study of the microheterogeneity of beta-glucan-rich hydrocolloidal extractive suspensions

USDA-ARS?s Scientific Manuscript database

Nutrim-10 is a newly developed food product containing the dietary of soluble fiber ß-glucan. The micro-structural heterogeneities of Nutrim-10 suspensions were investigated by monitoring the thermally driven displacements of well-dispersed microspheres via video fluorescence microscopy. By comparin...

Shell Tectonics: A Mechanical Model for Strike-slip Displacement on Europa

NASA Technical Reports Server (NTRS)

Rhoden, Alyssa Rose; Wurman, Gilead; Huff, Eric M.; Manga, Michael; Hurford, Terry A.

2012-01-01

We introduce a new mechanical model for producing tidally-driven strike-slip displacement along preexisting faults on Europa, which we call shell tectonics. This model differs from previous models of strike-slip on icy satellites by incorporating a Coulomb failure criterion, approximating a viscoelastic rheology, determining the slip direction based on the gradient of the tidal shear stress rather than its sign, and quantitatively determining the net offset over many orbits. This model allows us to predict the direction of net displacement along faults and determine relative accumulation rate of displacement. To test the shell tectonics model, we generate global predictions of slip direction and compare them with the observed global pattern of strike-slip displacement on Europa in which left-lateral faults dominate far north of the equator, right-lateral faults dominate in the far south, and near-equatorial regions display a mixture of both types of faults. The shell tectonics model reproduces this global pattern. Incorporating a small obliquity into calculations of tidal stresses, which are used as inputs to the shell tectonics model, can also explain regional differences in strike-slip fault populations. We also discuss implications for fault azimuths, fault depth, and Europa's tectonic history.

Characterization of piezoelectric device for implanted pacemaker energy harvesting

NASA Astrophysics Data System (ADS)

Jay, Sunny; Caballero, Manuel; Quinn, William; Barrett, John; Hill, Martin

2016-10-01

Novel implanted cardiac pacemakers that are powered by energy harvesters driven by the cardiac motion and have a 40 year lifetime are currently under development. To satisfy space constraints and energy requirements of the device, silicon-based MEMS energy harvesters are being developed in the EU project (MANpower1). Such MEMS harvesters for vibration frequencies below 50 Hz have not been widely reported. In this paper, an analytical model and a 3D finite element model (FEM) to predict displacement and open circuit voltage, validated through experimental analysis using an off-the-shelf low frequency energy harvester, are presented. The harvester was excited through constant amplitude sinusoidal base displacement over a range of 20 to 70 Hz passing through its first mode natural frequency at 47 Hz. At resonance both models predict displacements with an error of less than 2% when compared to the experimental result. Comparing the two models, the application of the experimentally measured damping ratio differs for accurate displacement prediction and the differences in symmetry in the measured and modelled displacement and voltage data around the resonance frequency indicate the two piezoelectric voltage models use different fundamental equations.

Linear or Rotary Actuator Using Electromagnetic Driven Hammer as Prime Mover

NASA Technical Reports Server (NTRS)

McMahan, Bert K. (Inventor); Sesler, Joshua J. (Inventor); Paine, Matthew T. (Inventor); McMahan, Mark C. (Inventor); Paine, Jeffrey S. N. (Inventor); Smith, Byron F. (Inventor)

2018-01-01

We claim a hammer driven actuator that uses the fast-motion, low-force characteristics of an electro-magnetic or similar prime mover to develop kinetic energy that can be transformed via a friction interface to produce a higher-force, lower-speed linear or rotary actuator by using a hammering process to produce a series of individual steps. Such a system can be implemented using a voice-coil, electro-mechanical solenoid or similar prime mover. Where a typical actuator provides limited range of motion or low force, the range of motion of a linear or rotary impact driven motor can be configured to provide large displacements which are not limited by the characteristic dimensions of the prime mover.

Applicability of steady models for hot-star winds

NASA Technical Reports Server (NTRS)

Owocki, Stanley P.; Poe, Clint H.; Castor, John I.

1990-01-01

Non-Sobolev models of radiatively driven stellar winds based on a pure-absorption approximation do not have a well-defined steady state. Here the implications of this for flow time-dependence are examined, showing that, under such circumstances, instabilities in the flow attain an absolute character that leads to intrinsic variability. In this case, steady solutions are inherently inapplicable because they do not represent physically realizable states. However, for actual hot-star winds, driving is principally by scattering, not pure absorption. In practice, the relatively weak force associated with slight asymmetries in the diffuse, scattered radiation field may play a crucial role in breaking the solution degeneracy and reducing the instability from an absolute to an advective character.

Dual roles of f electrons in mixing Al 3 p character into d -orbital conduction bands for lanthanide and actinide dialuminides

DOE PAGES

Altman, Alison B.; Pemmaraju, C. D.; Alayoglu, Selim; ...

2018-01-15

Correlated electron phenomena in lanthanide and actinide materials are driven by a complex interplay between the f and d orbitals. Here in this study, aluminum K-edge x-ray absorption spectroscopy and density functional theory calculations are used to evaluate the electronic structure of the dialuminides, MAl 2 (M = Ce, Sm, Eu, Yb, Lu, U, and Pu). The results show how the energy and occupancy of the 4f or 5f orbitals impacts mixing of Al 3p character into the 5d or 6d conduction bands, which has implications for understanding the magnetic and structural properties of correlated electron systems.

Real-time sub-Ångstrom imaging of reversible and irreversible conformations in rhodium catalysts and graphene

NASA Astrophysics Data System (ADS)

Kisielowski, Christian; Wang, Lin-Wang; Specht, Petra; Calderon, Hector A.; Barton, Bastian; Jiang, Bin; Kang, Joo H.; Cieslinski, Robert

2013-07-01

The dynamic responses of a rhodium catalyst and a graphene sheet are investigated upon random excitation with 80 kV electrons. An extraordinary electron microscope stability and resolution allow studying temporary atom displacements from their equilibrium lattice sites into metastable sites across projected distances as short as 60 pm. In the rhodium catalyst, directed and reversible atom displacements emerge from excitations into metastable interstitial sites and surface states that can be explained by single atom trajectories. Calculated energy barriers of 0.13 eV and 1.05 eV allow capturing single atom trapping events at video rates that are stabilized by the Rh [110] surface corrugation. Molecular dynamics simulations reveal that randomly delivered electrons can also reversibly enhance the sp3 and the sp1 characters of the sp2-bonded carbon atoms in graphene. The underlying collective atom motion can dynamically stabilize characteristic atom displacements that are unpredictable by single atom trajectories. We detect three specific displacements and use two of them to propose a path for the irreversible phase transformation of a graphene nanoribbon into carbene. Collectively stabilized atom displacements greatly exceed the thermal vibration amplitudes described by Debye-Waller factors and their measured dose rate dependence is attributed to tunable phonon contributions to the internal energy of the systems. Our experiments suggest operating electron microscopes with beam currents as small as zepto-amperes/nm2 in a weak-excitation approach to improve on sample integrity and allow for time-resolved studies of conformational object changes that probe for functional behavior of catalytic surfaces or molecules.

Neural division of labor in reading is constrained by culture: A training study of reading Chinese characters

PubMed Central

Zhao, Jingjing; Wang, Xiaoyi; Frost, Stephen J.; Sun, Wan; Fang, Shin-Yi; Mencl, W. Einar; Pugh, Kenneth R.; Shu, Hua; Rueckl, Jay G.

2014-01-01

Word reading in alphabetic language involves a cortical system with multiple components whose division of labor depends on the transparency of the writing system. To gain insight about the division of labor between phonology and semantics subserving word reading in Chinese, a deep non-alphabetic writing system, fMRI was used to investigate the effects of phonological and semantic training on the cortical circuitry for oral naming of Chinese characters. In a training study, we examined whether a training task that differentially focused readers' attention on the phonological or semantic properties of a Chinese character changes the patterns of cortical activation that was evoked by that character in a subsequent naming task. Our imaging results corroborate that the cortical regions underlying reading in Chinese largely overlaps the left-hemisphere reading system responsible for reading in alphabetic languages, with some cortical regions in the left-hemisphere uniquely recruited for reading in Chinese. However, in contrast to findings from studies of English word naming, we observed considerable overlap in the neural activation patterns associated with phonological and semantic training on naming Chinese characters, which we suggest may reflect a balanced neural division of labor between phonology and semantics in Chinese character reading. The equitable division of labor for Chinese reading might be driven by the special statistical structure of the writing system, which includes equally systematic mappings in the correspondences between written forms and their pronunciations and meanings. PMID:24607883

E-Drama: Facilitating Online Role-Play Using an AI Actor and Emotionally Expressive Characters

ERIC Educational Resources Information Center

Zhang, Li; Gillies, Marco; Dhaliwal, Kulwant; Gower, Amanda; Robertson, Dale; Crabtree, Barry

2009-01-01

This paper describes a multi-user role-playing environment, referred to as "e-drama", which enables groups of people to converse online, in scenario driven virtual environments. The starting point of this research, is an existing application known as "edrama", a 2D graphical environment in which users are represented by static…

Seismic displacement of gently-sloping coastal and marine sediment under multidirectional earthquake loading

USGS Publications Warehouse

Kayen, Robert E.

2017-01-01

Gentle sediment-laden slopes are typical of the onshore coastal zone and offshore continental shelf and slope. Coastal sediment are commonly young weakly consolidated materials that are well stratified, have low strength, and can mobilize shear displacements at low levels of stress. Seismically-driven plastic displacements of these sediment pose a hazard to coastal cities, buried onshore utilities, and offshore infrastructure like harbor protection and outfalls. One-dimensional rigid downslope-directed Newmark sliding block analyses have been used to predict earthquake deformations generally on steeper slopes that are modeled as frictional materials. This study probes the effect of multidirectional earthquake motions on inertial displacements of gently sloping ground of the coastal and offshore condition where soft-compliant soil is expected. Toward that objective, this investigation seeks to understand the effect on Newmark-type displacements of [1] multidirectional earthquake shaking and [2] soil compliance. In order to model multidirectional effects, the earthquake motions are rotated into the local slope strike- and dip-components. On gently sloping ground, including the strike component of motion always results in a larger and more accurate shear stress vector. Strike motions are found to contribute to downslope deformations on any declivity. Compliant response of the soil mass also influences the plastic displacements. The magnitude of seismic displacements can be estimated with a simplified model using only the estimated soil yield-acceleration (ky) and the peak ground velocity (Vmax) of the earthquake motions. Compliance effects can be effectively mapped using the concept of Plastic Displacement Response Spectra (PDRS).

Imaging Correlations in Heterodyne Spectra for Quantum Displacement Sensing

NASA Astrophysics Data System (ADS)

Pontin, A.; Lang, J. E.; Chowdhury, A.; Vezio, P.; Marino, F.; Morana, B.; Serra, E.; Marin, F.; Monteiro, T. S.

2018-01-01

The extraordinary sensitivity of the output field of an optical cavity to small quantum-scale displacements has led to breakthroughs such as the first detection of gravitational waves and of the motions of quantum ground-state cooled mechanical oscillators. While heterodyne detection of the output optical field of an optomechanical system exhibits asymmetries which provide a key signature that the mechanical oscillator has attained the quantum regime, important quantum correlations are lost. In turn, homodyning can detect quantum squeezing in an optical quadrature but loses the important sideband asymmetries. Here we introduce and experimentally demonstrate a new technique, subjecting the autocorrelators of the output current to filter functions, which restores the lost heterodyne correlations (whether classical or quantum), drastically augmenting the useful information accessible. The filtering even adjusts for moderate errors in the locking phase of the local oscillator. Hence we demonstrate the single-shot measurement of hundreds of different field quadratures allowing the rapid imaging of detailed features from a simple heterodyne trace. We also obtain a spectrum of hybrid homodyne-heterodyne character, with motional sidebands of combined amplitudes comparable to homodyne. Although investigated here in a thermal regime, the method's robustness and generality represents a promising new approach to sensing of quantum-scale displacements.

Imaging Correlations in Heterodyne Spectra for Quantum Displacement Sensing.

PubMed

Pontin, A; Lang, J E; Chowdhury, A; Vezio, P; Marino, F; Morana, B; Serra, E; Marin, F; Monteiro, T S

2018-01-12

The extraordinary sensitivity of the output field of an optical cavity to small quantum-scale displacements has led to breakthroughs such as the first detection of gravitational waves and of the motions of quantum ground-state cooled mechanical oscillators. While heterodyne detection of the output optical field of an optomechanical system exhibits asymmetries which provide a key signature that the mechanical oscillator has attained the quantum regime, important quantum correlations are lost. In turn, homodyning can detect quantum squeezing in an optical quadrature but loses the important sideband asymmetries. Here we introduce and experimentally demonstrate a new technique, subjecting the autocorrelators of the output current to filter functions, which restores the lost heterodyne correlations (whether classical or quantum), drastically augmenting the useful information accessible. The filtering even adjusts for moderate errors in the locking phase of the local oscillator. Hence we demonstrate the single-shot measurement of hundreds of different field quadratures allowing the rapid imaging of detailed features from a simple heterodyne trace. We also obtain a spectrum of hybrid homodyne-heterodyne character, with motional sidebands of combined amplitudes comparable to homodyne. Although investigated here in a thermal regime, the method's robustness and generality represents a promising new approach to sensing of quantum-scale displacements.

Integrated modeling and analysis of the multiple electromechanical couplings for the direct driven feed system in machine tools

NASA Astrophysics Data System (ADS)

Yang, Xiaojun; Lu, Dun; Liu, Hui; Zhao, Wanhua

2018-06-01

The complicated electromechanical coupling phenomena due to different kinds of causes have significant influences on the dynamic precision of the direct driven feed system in machine tools. In this paper, a novel integrated modeling and analysis method of the multiple electromechanical couplings for the direct driven feed system in machine tools is presented. At first, four different kinds of electromechanical coupling phenomena in the direct driven feed system are analyzed systematically. Then a novel integrated modeling and analysis method of the electromechanical coupling which is influenced by multiple factors is put forward. In addition, the effects of multiple electromechanical couplings on the dynamic precision of the feed system and their main influencing factors are compared and discussed, respectively. Finally, the results of modeling and analysis are verified by the experiments. It finds out that multiple electromechanical coupling loops, which are overlapped and influenced by each other, are the main reasons of the displacement fluctuations in the direct driven feed system.

Multiferroicity in an organic charge-transfer salt that is suggestive of electric-dipole-driven magnetism

NASA Astrophysics Data System (ADS)

Lunkenheimer, Peter; Müller, Jens; Krohns, Stephan; Schrettle, Florian; Loidl, Alois; Hartmann, Benedikt; Rommel, Robert; de Souza, Mariano; Hotta, Chisa; Schlueter, John A.; Lang, Michael

2012-09-01

Multiferroics, showing simultaneous ordering of electrical and magnetic degrees of freedom, are remarkable materials as seen from both the academic and technological points of view. A prominent mechanism of multiferroicity is the spin-driven ferroelectricity, often found in frustrated antiferromagnets with helical spin order. There, as for conventional ferroelectrics, the electrical dipoles arise from an off-centre displacement of ions. However, recently a different mechanism, namely purely electronic ferroelectricity, where charge order breaks inversion symmetry, has attracted considerable interest. Here we provide evidence for ferroelectricity, accompanied by antiferromagnetic spin order, in a two-dimensional organic charge-transfer salt, thus representing a new class of multiferroics. We propose a charge-order-driven mechanism leading to electronic ferroelectricity in this material. Quite unexpectedly for electronic ferroelectrics, dipolar and spin order arise nearly simultaneously. This can be ascribed to the loss of spin frustration induced by the ferroelectric ordering. Hence, here the spin order is driven by the ferroelectricity, in marked contrast to the spin-driven ferroelectricity in helical magnets.

Implementing Nonlinear Feedback Controllers Using DNA Strand Displacement Reactions.

PubMed

Sawlekar, Rucha; Montefusco, Francesco; Kulkarni, Vishwesh V; Bates, Declan G

2016-07-01

We show how an important class of nonlinear feedback controllers can be designed using idealized abstract chemical reactions and implemented via DNA strand displacement (DSD) reactions. Exploiting chemical reaction networks (CRNs) as a programming language for the design of complex circuits and networks, we show how a set of unimolecular and bimolecular reactions can be used to realize input-output dynamics that produce a nonlinear quasi sliding mode (QSM) feedback controller. The kinetics of the required chemical reactions can then be implemented as enzyme-free, enthalpy/entropy driven DNA reactions using a toehold mediated strand displacement mechanism via Watson-Crick base pairing and branch migration. We demonstrate that the closed loop response of the nonlinear QSM controller outperforms a traditional linear controller by facilitating much faster tracking response dynamics without introducing overshoots in the transient response. The resulting controller is highly modular and is less affected by retroactivity effects than standard linear designs.

Nonlinear cavity optomechanics with nanomechanical thermal fluctuations

PubMed Central

Leijssen, Rick; La Gala, Giada R.; Freisem, Lars; Muhonen, Juha T.; Verhagen, Ewold

2017-01-01

Although the interaction between light and motion in cavity optomechanical systems is inherently nonlinear, experimental demonstrations to date have allowed a linearized description in all except highly driven cases. Here, we demonstrate a nanoscale optomechanical system in which the interaction between light and motion is so large (single-photon cooperativity C0≈103) that thermal motion induces optical frequency fluctuations larger than the intrinsic optical linewidth. The system thereby operates in a fully nonlinear regime, which pronouncedly impacts the optical response, displacement measurement and radiation pressure backaction. Specifically, we measure an apparent optical linewidth that is dominated by thermo-mechanically induced frequency fluctuations over a wide temperature range, and show that in this regime thermal displacement measurements cannot be described by conventional analytical models. We perform a proof-of-concept demonstration of exploiting the nonlinearity to conduct sensitive quadratic readout of nanomechanical displacement. Finally, we explore how backaction in this regime affects the mechanical fluctuation spectra. PMID:28685755

Hydraulically actuated fuel injector including a pilot operated spool valve assembly and hydraulic system using same

DOEpatents

Shafer, Scott F.

2002-01-01

The present invention relates to hydraulic systems including hydraulically actuated fuel injectors that have a pilot operated spool valve assembly. One class of hydraulically actuated fuel injectors includes a solenoid driven pilot valve that controls the initiation of the injection event. However, during cold start conditions, hydraulic fluid, typically engine lubricating oil, is particularly viscous and is often difficult to displace through the relatively small drain path that is defined past the pilot valve member. Because the spool valve typically responds slower than expected during cold start due to the difficulty in displacing the relatively viscous oil, accurate start of injection timing can be difficult to achieve. There also exists a greater difficulty in reaching the higher end of the cold operating speed range. Therefore, the present invention utilizes a fluid evacuation valve to aid in displacement of the relatively viscous oil during cold start conditions.

Displaceable Spur Gear Torque Controlled Driver and Method

NASA Technical Reports Server (NTRS)

Cook, Joseph S., Jr. (Inventor)

1996-01-01

Methods and apparatus are provided for a torque driver including a laterally displaceable gear support member to carry an output spur gear. A biasing assembly biases the output spur gear into engagement with a pinion to which is applied an input torque greater than a desired output torque limit for a threaded fastener such as a nut or screw. A coiled output linkage connects the output spur gear with a fastener adaptor which may be a socket for a nut. A gear tooth profile provides a separation force that overcomes the bias to limit torque at the desired torque limit. Multiple fasteners may be rotated simultaneously to a desired torque limit if additional output spur gears are provided. A gauged selector mechanism is provided to laterally displace multiple driven members for fasteners arranged in differing configurations. The torque limit is selectably adjustable and may be different for fasteners within the same fastener configuration.

Tracking control of a spool displacement in a direct piezoactuator-driven servo valve system

NASA Astrophysics Data System (ADS)

Han, Chulhee; Hwang, Yong-Hoon; Choi, Seung-Bok

2017-03-01

This paper presents tracking control performances of a piezostack direct drive valve (PDDV) operated at various temperatures. As afirst step, a spool valve and valve system are designed operated by the piezoactuator. After briefly describing about operating principle, an experimental apparatus to investigate the effect of temperaturs on the performances is set up. Subsequently, the PDDV is installed in a large-size heat chamber equipped with electric circuits and sensors. A classical proportional-integral-derivative (PID) controller is designed and applied to control the spool displacement. In addition, a fuzzt algorithm is integrated with the PID controller to enhace performance of the proposed valve system. The tracking performance of a spool displacement is tested by increasing the teperature and exciting frequency up to 150°C and 200 Hz, respectively. It is shown that the tracking performance heavily depends on both the operating temperature and the excitation frequency.

Symmetry-Driven Atomic Rearrangement at a Brownmillerite-Perovskite Interface

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

Meyer, Tricia L.; Jeen, Hyoungjeen; Gao, Xiang

2015-12-15

To those investigating new interfacial phenomena, symmetry mismatch is of immense interest. The interfacial and bulk microstructure of the brownmillerite–perovskite interface is probed using detailed transmission electron microscopy. Unique asymmetric displacements of the tetrahedra at the interface are observed, signifying a compensation mechanism for lattice and symmetry mismatch at the interface.

Improvements In Ball-Screw Linear Actuators

NASA Technical Reports Server (NTRS)

Iskenderian, Theodore; Joffe, Benjamin; Summers, Robert

1996-01-01

Report describes modifications of design of type of ball-screw linear actuator driven by dc motor, with linear-displacement feedback via linear variable-differential transformer (LVDT). Actuators used to position spacecraft engines to direct thrust. Modifications directed toward ensuring reliable and predictable operation during planned 12-year cruise and interval of hard use at end of cruise.

Long-term kinematics and sediment flux of an active earthflow, Eel River, California

Treesearch

B. H. Mackey; J. J. Roering; J. A. McKean

2009-01-01

Although earthflows are the dominant erosion mechanism in many mountainous landscapes, estimates of long-term earthflow-driven sediment flux remain elusive because landslide displacement data are typically limited to contemporary time periods. Combining high-resolution topography from airborne LiDAR (light detection and ranging), total station surveying, orthorectified...

Field driven magnetic racetrack memory accompanied with the interfacial Dzyaloshinskii-Moriya interaction

NASA Astrophysics Data System (ADS)

Kim, June-Seo; Lee, Hyeon-Jun; Hong, Jung-Il; You, Chun-Yeol

2018-06-01

The in-plane magnetic field pulse driven domain wall motion on a perpendicularly magnetized nanowire is numerically investigated by performing micromagnetic simulations and magnetic domain wall dynamics are evaluated analytically with one-dimensional collective coordinate models including the interfacial Dzyaloshinskii-Moriya interaction. With the action of the precession torque, the chirality and the magnetic field direction dependent displacements of the magnetic domain walls are clearly observed. In order to move Bloch type and Neel type domain walls, a longitudinal and a transverse in-plane magnetic field pulse are required, respectively. The domain wall type (Bloch or Neel) can easily be determined by the dynamic motion of the domain walls under the applied pulse fields. By applying a temporally asymmetric in-plane field pulse and successive notches in the perpendicularly magnetized nanowire strip line with a proper interval, the concept of racetrack memory based on the synchronous displacements of the chirality dependent multiple domain walls is verified to be feasible. Requirement of multiple domain walls with homogeneous chirality is achieved with the help of Dzyaloshinskii-Moriya interaction.

Digital control of magnetic bearings in a cryogenic cooler

NASA Technical Reports Server (NTRS)

Feeley, J.; Law, A.; Lind, F.

1990-01-01

This paper describes the design of a digital control system for control of magnetic bearings used in a spaceborne cryogenic cooler. The cooler was developed by Philips Laboratories for the NASA Goddard Space Flight Center. Six magnetic bearing assemblies are used to levitate the piston, displacer, and counter-balance of the cooler. The piston and displacer are driven by linear motors in accordance with Stirling cycle thermodynamic principles to produce the desired cooling effect. The counter-balance is driven by a third linear motor to cancel motion induced forces that would otherwise be transmitted to the spacecraft. An analog control system is currently used for bearing control. The purpose of this project is to investigate the possibilities for improved performance using digital control. Areas for potential improvement include transient and steady state control characteristics, robustness, reliability, adaptability, alternate control modes, size, weight, and cost. The present control system is targeted for the Intel 80196 microcontroller family. The eventual introduction of application specific integrated circuit (ASIC) technology to this problem may produce a unique and elegant solution both here and in related industrial problems.

Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO 3

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

Chen, F.; Zhu, Y.; Liu, S.

The dynamical processes associated with electric field manipulation of the polarization in a ferroelectric remain largely unknown but fundamentally determine the speed and functionality of ferroelectric materials and devices. Here we apply subpicosecond duration, single-cycle terahertz pulses as an ultrafast electric field bias to prototypical BaTiO 3 ferroelectric thin films with the atomic-scale response probed by femtosecond x-ray-scattering techniques. We show that electric fields applied perpendicular to the ferroelectric polarization drive large-amplitude displacements of the titanium atoms along the ferroelectric polarization axis, comparable to that of the built-in displacements associated with the intrinsic polarization and incoherent across unit cells. Thismore » effect is associated with a dynamic rotation of the ferroelectric polarization switching on and then off on picosecond time scales. These transient polarization modulations are followed by long-lived vibrational heating effects driven by resonant excitation of the ferroelectric soft mode, as reflected in changes in the c-axis tetragonality. The ultrafast structural characterization described here enables a direct comparison with first-principles-based molecular-dynamics simulations, with good agreement obtained.« less

Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO 3

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

Chen, F.; Zhu, Y.; Liu, S.

The dynamical processes associated with electric field manipulation of the polarization in a ferroelectric remain largely unknown but fundamentally determine the speed and functionality of ferroelectric materials and devices. Here in this paper we apply subpicosecond duration, single-cycle terahertz pulses as an ultrafast electric field bias to prototypical BaTiO 3 ferroelectric thin films with the atomic-scale response probed by femtosecond x-ray-scattering techniques. We show that electric fields applied perpendicular to the ferroelectric polarization drive large-amplitude displacements of the titanium atoms along the ferroelectric polarization axis, comparable to that of the built-in displacements associated with the intrinsic polarization and incoherent acrossmore » unit cells. This effect is associated with a dynamic rotation of the ferroelectric polarization switching on and then off on picosecond time scales. These transient polarization modulations are followed by long-lived vibrational heating effects driven by resonant excitation of the ferroelectric soft mode, as reflected in changes in the c-axis tetragonality. The ultrafast structural characterization described here enables a direct comparison with first-principles-based molecular-dynamics simulations, with good agreement obtained.« less

Ultrafast terahertz-field-driven ionic response in ferroelectric BaTiO 3

DOE PAGES

Chen, F.; Zhu, Y.; Liu, S.; ...

2016-11-22

The dynamical processes associated with electric field manipulation of the polarization in a ferroelectric remain largely unknown but fundamentally determine the speed and functionality of ferroelectric materials and devices. Here in this paper we apply subpicosecond duration, single-cycle terahertz pulses as an ultrafast electric field bias to prototypical BaTiO 3 ferroelectric thin films with the atomic-scale response probed by femtosecond x-ray-scattering techniques. We show that electric fields applied perpendicular to the ferroelectric polarization drive large-amplitude displacements of the titanium atoms along the ferroelectric polarization axis, comparable to that of the built-in displacements associated with the intrinsic polarization and incoherent acrossmore » unit cells. This effect is associated with a dynamic rotation of the ferroelectric polarization switching on and then off on picosecond time scales. These transient polarization modulations are followed by long-lived vibrational heating effects driven by resonant excitation of the ferroelectric soft mode, as reflected in changes in the c-axis tetragonality. The ultrafast structural characterization described here enables a direct comparison with first-principles-based molecular-dynamics simulations, with good agreement obtained.« less

Stochastic epidemic outbreaks: why epidemics are like lasers

NASA Astrophysics Data System (ADS)

Schwartz, Ira B.; Billings, Lora

2004-05-01

Many diseases, such as childhood diseases, dengue fever, and West Nile virus, appear to oscillate randomly as a function of seasonal environmental or social changes. Such oscillations appear to have a chaotic bursting character, although it is still uncertain how much is due to random fluctuations. Such bursting in the presence of noise is also observed in driven lasers. In this talk, I will show how noise can excite random outbreaks in simple models of seasonally driven outbreaks, as well as lasers. The models for both population dynamics will be shown to share the same class of underlying topology, which plays a major role in the cause of observed stochastic bursting.

Data-driven event-by-event respiratory motion correction using TOF PET list-mode centroid of distribution

NASA Astrophysics Data System (ADS)

Ren, Silin; Jin, Xiao; Chan, Chung; Jian, Yiqiang; Mulnix, Tim; Liu, Chi; E Carson, Richard

2017-06-01

Data-driven respiratory gating techniques were developed to correct for respiratory motion in PET studies, without the help of external motion tracking systems. Due to the greatly increased image noise in gated reconstructions, it is desirable to develop a data-driven event-by-event respiratory motion correction method. In this study, using the Centroid-of-distribution (COD) algorithm, we established a data-driven event-by-event respiratory motion correction technique using TOF PET list-mode data, and investigated its performance by comparing with an external system-based correction method. Ten human scans with the pancreatic β-cell tracer 18F-FP-(+)-DTBZ were employed. Data-driven respiratory motions in superior-inferior (SI) and anterior-posterior (AP) directions were first determined by computing the centroid of all radioactive events during each short time frame with further processing. The Anzai belt system was employed to record respiratory motion in all studies. COD traces in both SI and AP directions were first compared with Anzai traces by computing the Pearson correlation coefficients. Then, respiratory gated reconstructions based on either COD or Anzai traces were performed to evaluate their relative performance in capturing respiratory motion. Finally, based on correlations of displacements of organ locations in all directions and COD information, continuous 3D internal organ motion in SI and AP directions was calculated based on COD traces to guide event-by-event respiratory motion correction in the MOLAR reconstruction framework. Continuous respiratory correction results based on COD were compared with that based on Anzai, and without motion correction. Data-driven COD traces showed a good correlation with Anzai in both SI and AP directions for the majority of studies, with correlation coefficients ranging from 63% to 89%. Based on the determined respiratory displacements of pancreas between end-expiration and end-inspiration from gated reconstructions, there was no significant difference between COD-based and Anzai-based methods. Finally, data-driven COD-based event-by-event respiratory motion correction yielded comparable results to that based on Anzai respiratory traces, in terms of contrast recovery and reduced motion-induced blur. Data-driven event-by-event respiratory motion correction using COD showed significant image quality improvement compared with reconstructions with no motion correction, and gave comparable results to the Anzai-based method.

Data-driven event-by-event respiratory motion correction using TOF PET list-mode centroid of distribution.

PubMed

Ren, Silin; Jin, Xiao; Chan, Chung; Jian, Yiqiang; Mulnix, Tim; Liu, Chi; Carson, Richard E

2017-06-21

Data-driven respiratory gating techniques were developed to correct for respiratory motion in PET studies, without the help of external motion tracking systems. Due to the greatly increased image noise in gated reconstructions, it is desirable to develop a data-driven event-by-event respiratory motion correction method. In this study, using the Centroid-of-distribution (COD) algorithm, we established a data-driven event-by-event respiratory motion correction technique using TOF PET list-mode data, and investigated its performance by comparing with an external system-based correction method. Ten human scans with the pancreatic β-cell tracer 18 F-FP-(+)-DTBZ were employed. Data-driven respiratory motions in superior-inferior (SI) and anterior-posterior (AP) directions were first determined by computing the centroid of all radioactive events during each short time frame with further processing. The Anzai belt system was employed to record respiratory motion in all studies. COD traces in both SI and AP directions were first compared with Anzai traces by computing the Pearson correlation coefficients. Then, respiratory gated reconstructions based on either COD or Anzai traces were performed to evaluate their relative performance in capturing respiratory motion. Finally, based on correlations of displacements of organ locations in all directions and COD information, continuous 3D internal organ motion in SI and AP directions was calculated based on COD traces to guide event-by-event respiratory motion correction in the MOLAR reconstruction framework. Continuous respiratory correction results based on COD were compared with that based on Anzai, and without motion correction. Data-driven COD traces showed a good correlation with Anzai in both SI and AP directions for the majority of studies, with correlation coefficients ranging from 63% to 89%. Based on the determined respiratory displacements of pancreas between end-expiration and end-inspiration from gated reconstructions, there was no significant difference between COD-based and Anzai-based methods. Finally, data-driven COD-based event-by-event respiratory motion correction yielded comparable results to that based on Anzai respiratory traces, in terms of contrast recovery and reduced motion-induced blur. Data-driven event-by-event respiratory motion correction using COD showed significant image quality improvement compared with reconstructions with no motion correction, and gave comparable results to the Anzai-based method.

Kinematics and dynamics of salt movement driven by sub-salt normal faulting and supra-salt sediment accumulation - combined analogue experiments and analytical calculations

NASA Astrophysics Data System (ADS)

Warsitzka, Michael; Kukowski, Nina; Kley, Jonas

2017-04-01

In extensional sedimentary basins, the movement of ductile salt is mainly controlled by the vertical displacement of the salt layer, differential loading due to syn-kinematic deposition, and tectonic shearing at the top and the base of the salt layer. During basement normal faulting, salt either tends to flow downward to the basin centre driven by its own weight or it is squeezed upward due to differential loading. In analogue experiments and analytical models, we address the interplay between normal faulting of the sub-salt basement, compaction and density inversion of the supra-salt cover and the kinematic response of the ductile salt layer. The analogue experiments consist of a ductile substratum (silicone putty) beneath a denser cover layer (sand mixture). Both layers are displaced by normal faults mimicked through a downward moving block within the rigid base of the experimental apparatus and the resulting flow patterns in the ductile layer are monitored and analysed. In the computational models using an analytical approximative solution of the Navier-Stokes equation, the steady-state flow velocity in an idealized natural salt layer is calculated in order to evaluate how flow patterns observed in the analogue experiments can be translated to nature. The analytical calculations provide estimations of the prevailing direction and velocity of salt flow above a sub-salt normal fault. The results of both modelling approaches show that under most geological conditions salt moves downwards to the hanging wall side as long as vertical offset and compaction of the cover layer are small. As soon as an effective average density of the cover is exceeded, the direction of the flow velocity reverses and the viscous material is squeezed towards the elevated footwall side. The analytical models reveal that upward flow occurs even if the average density of the overburden does not exceed the density of salt. By testing various scenarios with different layer thicknesses, displacement rate or lithological parameters of the cover, our models suggest that the reversal of material flow usually requires vertical displacements between 700 and 2000 m. The transition from downward to upward flow occurs at smaller fault displacements, if the initial overburden thickness and the overburden density are high and if sedimentation rate keeps pace with the displacement rate of the sub-salt normal fault.

Creolizing Educational Practices

ERIC Educational Resources Information Center

Gordon, Jane Anna

2018-01-01

Author Jane Anna Gordon begins this commentary by saying that early in her academic career she was struck by the dual character of schools as places that can damage and waste the human potential of some on one hand, and that can and should be put in the service of liberation on the other. She writes that this point was driven home to her through…

Military Operations: The Harmful Effects of Hubris Influenced Leaders

DTIC Science & Technology

2013-05-20

grandeur, arrogance and narcissism , endangers operational objectives as well as negatively influences current and future strategic objectives. The...leader driven by the dangerous illusion of personal grandeur, arrogance and narcissism , endangers operational objectives as well as negatively...streak of narcissism without mediation or opposition. In order for the consequence of hubris to occur, a leader must possess the underlying character

Integrating Digital Technology in an Intensive, Fully Online College Course for Japanese Beginning Learners: A Standards-Based, Performance-Driven Approach

ERIC Educational Resources Information Center

Sato, Eriko; Chen, Julian Cheng Chiang; Jourdain, Sarah

2017-01-01

The development of distance learning courses for less commonly taught languages (LCTLs) often meets with instructional challenges, especially for Asian LCTLs with their distinct non-Roman characters and structures. This study documents the implementation of a fully online, elementary Japanese course at Stony Brook University. The curriculum was…

Neural division of labor in reading is constrained by culture: a training study of reading Chinese characters.

PubMed

Zhao, Jingjing; Wang, Xiaoyi; Frost, Stephen J; Sun, Wan; Fang, Shin-Yi; Mencl, W Einar; Pugh, Kenneth R; Shu, Hua; Rueckl, Jay G

2014-04-01

Word reading in alphabetic language involves a cortical system with multiple components whose division of labor depends on the transparency of the writing system. To gain insight about the neural division of labor between phonology and semantics subserving word reading in Chinese, a deep non-alphabetic writing system, functional magnetic resonance imaging (fMRI) was used to investigate the effects of phonological and semantic training on the cortical circuitry for oral naming of Chinese characters. In a training study, we examined whether a training task that differentially focused readers' attention on the phonological or semantic properties of a Chinese character changes the patterns of cortical activation that was evoked by that character in a subsequent naming task. Our imaging results corroborate that the cortical regions underlying reading in Chinese largely overlap the left-hemisphere reading system responsible for reading in alphabetic languages, with some cortical regions in the left-hemisphere uniquely recruited for reading in Chinese. However, in contrast to findings from studies of English word naming, we observed considerable overlap in the neural activation patterns associated with phonological and semantic training on naming Chinese characters, which we suggest may reflect a balanced neural division of labor between phonology and semantics in Chinese character reading. The equitable division of labor for Chinese reading might be driven by the special statistical structure of the writing system, which includes equally systematic mappings in the correspondences between written forms and their pronunciations and meanings. Copyright © 2014 Elsevier Ltd. All rights reserved.

Normal and anomalous diffusion in fluctuations of dust concentration nearby emission source

NASA Astrophysics Data System (ADS)

Szczurek, Andrzej; Maciejewska, Monika; Wyłomańska, Agnieszka; Sikora, Grzegorz; Balcerek, Michał; Teuerle, Marek

2018-02-01

Particulate matter (PM) is an important component of air. Nowadays, major attention is payed to fine dust. It has considerable environmental impact, including adverse effect on human health. One of important issues regarding PM is the temporal variation of its concentration. The variation contains information about factors influencing this quantity in time. The work focuses on the character of PM concentration dynamics indoors, in the vicinity of emission source. The objective was to recognize between the homogeneous or heterogeneous dynamics. The goal was achieved by detecting normal and anomalous diffusion in fluctuations of PM concentration. For this purpose we used anomalous diffusion exponent, β which was derived from Mean Square Displacement (MSD) analysis. The information about PM concentration dynamics may be used to design sampling strategy, which serves to attain representative information about PM behavior in time. The data analyzed in this work was collected from single-point PM concentration monitoring in the vicinity of seven emission sources in industrial environment. In majority of cases we observed heterogeneous character of PM concentration dynamics. It confirms the complexity of interactions between the emission sources and indoor environment. This result also votes against simplistic approach to PM concentration measurement indoors, namely their occasional character, short measurement periods and long term averaging.

Frictional and hydraulic behaviour of carbonate fault gouge during fault reactivation - An experimental study

NASA Astrophysics Data System (ADS)

Delle Piane, Claudio; Giwelli, Ausama; Clennell, M. Ben; Esteban, Lionel; Nogueira Kiewiet, Melissa Cristina D.; Kiewiet, Leigh; Kager, Shane; Raimon, John

2016-10-01

We present a novel experimental approach devised to test the hydro-mechanical behaviour of different structural elements of carbonate fault rocks during experimental re-activation. Experimentally faulted core plugs were subject to triaxial tests under water saturated conditions simulating depletion processes in reservoirs. Different fault zone structural elements were created by shearing initially intact travertine blocks (nominal size: 240 × 110 × 150 mm) to a maximum displacement of 20 and 120 mm under different normal stresses. Meso-and microstructural features of these sample and the thickness to displacement ratio characteristics of their deformation zones allowed to classify them as experimentally created damage zones (displacement of 20 mm) and fault cores (displacement of 120 mm). Following direct shear testing, cylindrical plugs with diameter of 38 mm were drilled across the slip surface to be re-activated in a conventional triaxial configuration monitoring the permeability and frictional behaviour of the samples as a function of applied stress. All re-activation experiments on faulted plugs showed consistent frictional response consisting of an initial fast hardening followed by apparent yield up to a friction coefficient of approximately 0.6 attained at around 2 mm of displacement. Permeability in the re-activation experiments shows exponential decay with increasing mean effective stress. The rate of permeability decline with mean effective stress is higher in the fault core plugs than in the simulated damage zone ones. It can be concluded that the presence of gouge in un-cemented carbonate faults results in their sealing character and that leakage cannot be achieved by renewed movement on the fault plane alone, at least not within the range of slip measureable with our apparatus (i.e. approximately 7 mm of cumulative displacement). Additionally, it is shown that under sub seismic slip rates re-activated carbonate faults remain strong and no frictional weakening was observed during re-activation.

Thermally Driven Electronic Topological Transition in FeTi

NASA Astrophysics Data System (ADS)

Yang, F. C.; Muñoz, J. A.; Hellman, O.; Mauger, L.; Lucas, M. S.; Tracy, S. J.; Stone, M. B.; Abernathy, D. L.; Xiao, Yuming; Fultz, B.

2016-08-01

Ab initio molecular dynamics, supported by inelastic neutron scattering and nuclear resonant inelastic x-ray scattering, showed an anomalous thermal softening of the M5- phonon mode in B 2 -ordered FeTi that could not be explained by phonon-phonon interactions or electron-phonon interactions calculated at low temperatures. A computational investigation showed that the Fermi surface undergoes a novel thermally driven electronic topological transition, in which new features of the Fermi surface arise at elevated temperatures. The thermally induced electronic topological transition causes an increased electronic screening for the atom displacements in the M5- phonon mode and an adiabatic electron-phonon interaction with an unusual temperature dependence.

The Ural-Herirud transcontinental postcollisional strike-slip fault and its role in the formation of the Earth's crust

NASA Astrophysics Data System (ADS)

Leonov, Yu. G.; Volozh, Yu. A.; Antipov, M. P.; Kheraskova, T. N.

2015-11-01

The paper considers the morphology, deep structure, and geodynamic features of the Ural-Herirud postorogenic strike-slip fault (UH fault), along which the Moho (the "M") shifts along the entire axial zone of the Ural Orogen, then further to the south across the Scythian-Turan Plate to the Herirud sublatitudinal fault in Afghanistan. The postcollisional character of dextral displacements along the Ural-Herirud fault and its Triassic-Jurassic age are proven. We have estimated the scale of displacements and made an attempt to make a paleoreconstruction, illustrating the relationship between the Variscides of the Urals and the Tien Shan before tectonic displacements. The analysis of new data includes the latest generation of 1: 200000 geological maps and the regional seismic profiling data obtained in the most elevated part of the Urals (from the seismic profile of the Middle Urals in the north to the Uralseis seismic profile in the south), as well as within the sedimentary cover of the Turan Plate, from Mugodzhary to the southern boundaries of the former water area of the Aral Sea. General typomorphic signs of transcontinental strike-slip fault systems are considered and the structural model of the Ural-Herirud postcollisional strike-slip fault is presented.

Structural peculiarities of the sedimentary cover of the MAR crest depressions (5°-8°N) in the Equatorial Atlantics

NASA Astrophysics Data System (ADS)

Skolotnev, S. G.; Tsukanov, N. V.; Turko, N. N.; Peyve, A. A.

2003-04-01

The analysis of the bottom relief structure investigated with multibeam SIMRAD 12S and sedimentary cover of depressions investigeted with PARASAUND in the MAR crest zone near Sierra-Leone Fault (22 Cruise of the RV "Akademik Nikolay Strachov", and 10 Cruise of the RV "Akademik Ioffe") point on the complicated character of the tectonic activity distribution in this region. The left-lateral displacements of the rift velley and the absence of transform faults are typical for this region. Two extremely deep rift depressions (up to 5000 m) are located in the rift valley: one on 5°54'N latitude (Markov depression) and the other on 5°46'N latitude. About 40 m sediments cover their bottom. On contary, in the depression located parallel to the rift valley directly to the west from the two mentioned rift depressions the sedimentary cover is absent and bottom has very dissected, apparently volcanic, relief. In the MAR crest zone in 20 miles to the south-west from the Markov and 5°46'N depressions one can see a system of depressions oriented both parallel and oblique to the rift valley. There are filled by the sediments of different thickness. The sedimentary cover of these depressions often is tired and deformed by diapir and horst uplifts. Dredging data show, that basalts, which represent, according to their petro-geo-chemical characteristics the enriched MORB basalts and alkaline basalts compose these uplifts. Irregular distribution and character of composition of the sediments in the depressions of crest zone of the MAR segment under consideration along with high volcanic activity outside the axial spreding zone show that tectonic and volcanic activity in this area are distributed all over the crest zone. The complicated character of this activity is obviosly caused by two reasons. From one hand it may be a deep mantle plum, as inferred from basalt composition and from the other hand it may be the lithosphere blocks displacements along the left-lateral strike slips.

Formation and acceleration of uniformly filled ellipsoidal electron bunches obtained via space-charge-driven expansion from a cesium-telluride photocathode

NASA Astrophysics Data System (ADS)

Piot, P.; Sun, Y.-E.; Maxwell, T. J.; Ruan, J.; Secchi, E.; Thangaraj, J. C. T.

2013-01-01

We report the experimental generation, acceleration, and characterization of a uniformly filled electron bunch obtained via space-charge-driven expansion (often referred to as “blow-out regime”) in an L-band (1.3-GHz) radiofrequency photoinjector. The beam is photoemitted from a cesium-telluride semiconductor photocathode using a short (<200fs) ultraviolet laser pulse. The produced electron bunches are characterized with conventional diagnostics and the signatures of their ellipsoidal character are observed. We especially demonstrate the production of ellipsoidal bunches with charges up to ˜0.5nC corresponding to a ˜20-fold increase compared to previous experiments with metallic photocathodes.

Cycling chair: a novel vehicle for the lower limbs disabled

NASA Astrophysics Data System (ADS)

Takahashi, Takayuki; Nishiyyama, Yuuki; Ozawa, Yukiko; Nakano, Eiji; Handa, Yasunobu

2005-12-01

The goal of our research is to develop a practical vehicle for lower limbs disabled to improve their mobility and health. The most significant mechanical character of the proposed vehicle is that it is driven by the lower limbs of the disabled themselves. We call it as Cycling Chair. Disuse of the lower limbs leads many subsidiary issues on health, deteriorating the whole-body circulation, it is the most serious problem, cases so-called the disuse syndrome. The proposed Cycling Chair solves those problems by using the leg-driven mechanism. In this paper, the mechanism of the Cycling Chair and the way to drive the chair by paraplegics are discussed. Some experimental results are also presented.

A Coupled Model of Stress-Driven Frictional Afterslip and Viscoelastic Relaxation Following the 2011 Tohoku-oki Earthquake

NASA Astrophysics Data System (ADS)

Fukuda, J.; Johnson, K. M.

2017-12-01

Postseismic deformation following the 2011 Mw9.0 Tohoku-oki earthquake has been captured by both on-land GNSS and seafloor GPS/Acoustic networks. Previous studies have shown that the observed postseismic displacements can be reproduced as the sum of contributions from viscoelastic relaxation of coseismic stress changes in the upper mantle and afterslip on the plate interface surrounding the coseismic rupture. In most previous studies, viscoelastic relaxation and afterslip were modeled separately and afterslip was estimated kinematically. In this study, we develop a mechanical model of postseismic deformation in which afterslip and viscoelastic relaxation are driven by coseismic stress perturbations and are mechanically coupled. We assume that afterslip is governed by a rate-strengthening friction law that is characterized with a friction parameter (a-b)*sigma, where a-b represents the rate dependence of steady-state friction and sigma is the effective normal stress. Viscoelastic relaxation of the upper mantle is modeled with a biviscous Burgers rheology that is characterized with the steady-state and transient viscosities. We calculate the evolution of afterslip and viscoelastic relaxation using stress changes computed from an assumed coseismic slip model as the initial condition. We examine the effects of the friction parameters, mantle viscosities, elastic thickness of the slab and upper plate, and coseismic slip distribution on the model prediction and explore the range of the parameters that can fit the observed postseismic displacements. We find that the vertical postseismic displacements are particularly sensitive to these parameters. Our modeling results indicate that the on-land postseismic deformation is dominated by afterslip, whereas the seafloor postseismic deformation is dominated by viscoelastic relaxation. We also examine if afterslip overlaps regions that ruptured seismically during M6.3-7.2 earthquakes between 2003 and 2010. We find that significant overlap between afterslip and the historical M6.3-7.2 coseismic rupture areas are required to fit the horizontal postseismic displacements.

Evidence of displacement-driven maturation along the San Cristobal Trough transform plate boundary

NASA Astrophysics Data System (ADS)

Neely, James S.; Furlong, Kevin P.

2018-03-01

The San Cristobal Trough (SCT), formed by the tearing of the Australia plate as it subducts under the Pacific plate near the Solomon Islands, provides an opportunity to study the transform boundary development process. Recent seismicity (2013-2016) along the 280 km long SCT, known as a Subduction-Transform Edge Propagator (STEP) fault, highlights the tearing process and ongoing development of the plate boundary. The region's earthquakes reveal two key characteristics. First, earthquakes at the western terminus of the SCT, which we interpret to indicate the Australia plate tearing, display disparate fault geometries. These events demonstrate that plate tearing is accommodated via multiple intersecting planes rather than a single through-going fault. Second, the SCT hosts sequences of Mw ∼7 strike-slip earthquakes that migrate westward through a rapid succession of events. Sequences in 1993 and 2015 both began along the eastern SCT and propagated west, but neither progression ruptured into or nucleated a large earthquake within the region near the tear. Utilizing b-value and Coulomb Failure Stress analyses, we examine these along-strike variations in the SCT's seismicity. b-Values are highest along the youngest, western end of the SCT and decrease with increasing distance from the tear. This trend may reflect increasing strain localization with increasing displacement. Coulomb Failure Stress analyses indicate that the stress conditions were conducive to continued western propagation of the 1993 and 2015 sequences suggesting that the unruptured western SCT may have fault geometries or properties that inhibit continued rupture. Our results indicate a displacement-driven fault maturation process. The multi-plane Australia plate tearing likely creates a western SCT with diffuse strain accommodated along a network of disorganized faults. After ∼90 km of cumulative displacement (∼900,000 yr of plate motion), strain localizes and faults align, allowing the SCT to host large earthquakes.

Bevel gear driver and method having torque limit selection

NASA Technical Reports Server (NTRS)

Cook, Joseph S., Jr. (Inventor)

1994-01-01

This invention comprises a torque drive mechanism utilizing axially translatable, mutually engageable transmission members having mating crown gears, driven and driving members with a three-element drive train being biased together by resilient means or by a fluid actuator system, the apparatus being operable to transmit a precisely controlled degree of torque to a driven member. The apparatus is applicable for use in hand tools and as a replacement for impact torque drivers, torque wrenches, motorized screw drivers, or the like, wherein the applied torque must be precisely controlled or limited. The bevel torque drive includes a drive gear which is axially displaceable and rotatable within cylindrical driver housing, a rotatable intermediate gear, and an output gear. Key rotationally secures displaceable gear with respect to input shaft but permits axial movement therebetween. A thrust bearing is preferably connected to the lower end of shaft for support to reduce play and friction between shaft and a transmission joint disc during rotation of the gear train. Coaxially mounted coiled spring is footed against displaceable gear for biasing the displaceable gear toward and into engagement with the intermediate gear for driving intermediate gear and output gear. Torque control is achieved by the use of straight or spiral beveled gears which are of configurations adapted to withdraw from mutual engagement upon the torque exceeding a predetermined limit. The novel, advantageous features of the invention include the configuration of the mating, crown gear sets and the axially translatable, slidable drive gear. The mechanism is capable of transmitting a high degree of torque within a narrow, compact transmission housing. The compact size and narrow, elongated configuration of the housing is particularly applicable for use in hand tools and in multiple torque driver mechanisms in which it is necessary to drive multiple fasteners which are located in close proximity. Prior torque drivers such as 'click-type' torque wrenches do not actually limit torque application but only provide an audible warning that the limit has been reached.

Beyond the bucket: testing the effect of experimental design on rate and sequence of decay

NASA Astrophysics Data System (ADS)

Gabbott, Sarah; Murdock, Duncan; Purnell, Mark

2016-04-01

Experimental decay has revealed the potential for profound biases in our interpretations of exceptionally preserved fossils, with non-random sequences of character loss distorting the position of fossil taxa in phylogenetic trees. By characterising these sequences we can rewind this distortion and make better-informed interpretations of the affinity of enigmatic fossil taxa. Equally, rate of character loss is crucial for estimating the preservation potential of phylogentically informative characters, and revealing the mechanisms of preservation themselves. However, experimental decay has been criticised for poorly modeling 'real' conditions, and dismissed as unsophisticated 'bucket science'. Here we test the effect of a differing experimental parameters on the rate and sequence of decay. By doing so, we can test the assumption that the results of decay experiments are applicable to informing interpretations of exceptionally preserved fossils from diverse preservational settings. The results of our experiments demonstrate the validity of using the sequence of character loss as a phylogenetic tool, and sheds light on the extent to which environment must be considered before making decay-informed interpretations, or reconstructing taphonomic pathways. With careful consideration of experimental design, driven by testable hypotheses, decay experiments are robust and informative - experimental taphonomy needn't kick the bucket just yet.

Mind-modelling with corpus stylistics in David Copperfield

PubMed Central

Mahlberg, Michaela

2015-01-01

We suggest an innovative approach to literary discourse by using corpus linguistic methods to address research questions from cognitive poetics. In this article, we focus on the way that readers engage in mind-modelling in the process of characterisation. The article sets out our cognitive poetic model of characterisation that emphasises the continuity between literary characterisation and real-life human relationships. The model also aims to deal with the modelling of the author’s mind in line with the modelling of the minds of fictional characters. Crucially, our approach to mind-modelling is text-driven. Therefore we are able to employ corpus linguistic techniques systematically to identify textual patterns that function as cues triggering character information. In this article, we explore our understanding of mind-modelling through the characterisation of Mr. Dick from David Copperfield by Charles Dickens. Using the CLiC tool (Corpus Linguistics in Cheshire) developed for the exploration of 19th-century fiction, we investigate the textual traces in non-quotations around this character, in order to draw out the techniques of characterisation other than speech presentation. We show that Mr. Dick is a thematically and authorially significant character in the novel, and we move towards a rigorous account of the reader’s modelling of authorial intention. PMID:29708113

Mind-modelling with corpus stylistics in David Copperfield.

PubMed

Stockwell, Peter; Mahlberg, Michaela

2015-05-01

We suggest an innovative approach to literary discourse by using corpus linguistic methods to address research questions from cognitive poetics. In this article, we focus on the way that readers engage in mind-modelling in the process of characterisation. The article sets out our cognitive poetic model of characterisation that emphasises the continuity between literary characterisation and real-life human relationships. The model also aims to deal with the modelling of the author's mind in line with the modelling of the minds of fictional characters. Crucially, our approach to mind-modelling is text-driven. Therefore we are able to employ corpus linguistic techniques systematically to identify textual patterns that function as cues triggering character information. In this article, we explore our understanding of mind-modelling through the characterisation of Mr. Dick from David Copperfield by Charles Dickens. Using the CLiC tool (Corpus Linguistics in Cheshire) developed for the exploration of 19th-century fiction, we investigate the textual traces in non-quotations around this character, in order to draw out the techniques of characterisation other than speech presentation. We show that Mr. Dick is a thematically and authorially significant character in the novel, and we move towards a rigorous account of the reader's modelling of authorial intention.

Floral and Vegetative Morphometrics of Five Pleurothallis (Orchidaceae) Species: Correlation with Taxonomy, Phylogeny, Genetic Variability and Pollination Systems

PubMed Central

BORBA, EDUARDO L.; SHEPHERD, GEORGE J.; BERG, CÁSSIO VAN DEN; SEMIR, JOÃO

2002-01-01

Morphometric analyses of vegetative and floral characters were conducted in 21 populations of five Pleurothallis (Orchidaceae) species occurring in Brazilian ‘campo rupestre’ vegetation. A phylogenetic analysis of this species group was also carried out using nuclear ribosomal DNA internal transcribed spacers (ITS1 and ITS2). Results of the ordination and cluster analyses agree with species’ delimitation revealed by taxonomic and allozyme studies. The groups formed in ordination analysis correspond to the pollinator groups determined in a previous pollination study. Relationships among the species in the cluster analysis using only vegetative characters are similar to those found in a previous allozyme study, but those indicated by cluster analysis using only floral characters differ. These results support the hypothesis that floral similarities are due to convergence driven by similar pollination mechanisms, and therefore floral traits may not be good indicators of phylogenetic relationships in this group. The results of the phylogenetic analysis support this conclusion to some extent. There is no correlation between genetic (allozyme) and morphological variability in the populations nor in the way this variability is distributed among conspecific populations. We describe a new subspecies of Pleurothallis ochreata based on differences in vegetative and chemical characters as well as geographic distribution. Absence of differentiation in floral characters, attraction of the same pollinator species, interfertility and genetic similarity support the argument for subspecific rather than specific status. PMID:12197519

Enhanced oil displacement by nanofluid's structural disjoining pressure in model fractured porous media.

PubMed

Zhang, Hua; Ramakrishnan, T S; Nikolov, Alex; Wasan, Darsh

2018-02-01

Nanofluids for improved oil recovery has been demonstrated through laboratory corefloods. Despite numerous experimental studies, little is known about the efficacy of nanofluids in fractured systems. Here, we present studies of nanofluid injection in fractured porous media (both water-wet and oil-wet) formed by sintering borosilicate glass-beads around a dissolvable substrate. The fracture inside the porous medium is characterized and visualized using a high resolution X-ray microtomography. Based on a simple displacement theory, the nanofluid injection is conducted at a rate where structural disjoining pressure driven oil recovery is operational. An additional 23.8% oil was displaced using nanofluid after brine injection with an overall recovery efficiency of 90.4% provided the matrix was in its native wettability state. But only 6% additional oil was displaced by nanofluid following brine injection when the bead-pack was rendered oil-wet. Nanofluids appear to be a good candidate for enhanced oil recovery (EOR) in fractured water-wet to weakly water-wet media but not necessarily for strongly oil-wet systems. Our laboratory studies enable us to understand limitations of nanofluids for improving oil recovery in fractured media. Copyright © 2017 Elsevier Inc. All rights reserved.

High Precision Piezoelectric Linear Motors for Operations at Cryogenic Temperatures and Vacuum

NASA Technical Reports Server (NTRS)

Wong, D.; Carman, G.; Stam, M.; Bar-Cohen, Y.; Sen, A.; Henry, P.; Bearman, G.; Moacanin, J.

1995-01-01

The use of an electromechanical device for optically positioning a mirror system during the pre-project phase of the Pluto Fast Flyby mission was evaluated at JPL. The device under consideration was a piezoelectric driven linear motor functionally dependent upon a time varying electric field which induces displacements ranging from submicrons to millimeters with positioning accuracy within nanometers.

The Role of Testimony in Young Children's Solution of a Gravity-Driven Invisible Displacement Task

ERIC Educational Resources Information Center

Bascandziev, Igor; Harris, Paul L.

2010-01-01

Previous research has shown that young children make a perseverative, gravity-oriented, error when asked to predict the final location of a ball dropped down an S-shaped opaque tube (Hood, 1995). We asked if providing children with verbal information concerning the role that the tubes play, in determining the ball's trajectory would improve their…

Climate driven changes in Engelmann spruce stands at timberline in the La Sal Mountains

Treesearch

James F. Fowler; Steven Overby; Barb Smith

2012-01-01

Due to global warming spruce-fir forest and associated vegetation may experience elevational displacement and altered species composition at the timberline-treeline ecotone. These forests and their component species are predicted to migrate upslope and thus landscape features such as timberline and treeline may move upslope as well. Prior to this study, baseline data...

Particle image velocimetry for the Surface Tension Driven Convection Experiment using a particle displacement tracking technique

NASA Technical Reports Server (NTRS)

Wernet, Mark P.; Pline, Alexander D.

1991-01-01

The Surface Tension Driven Convection Experiment (STDCE) is a Space Transportation System flight experiment to study both transient and steady thermocapillary fluid flows aboard the USML-1 Spacelab mission planned for 1992. One of the components of data collected during the experiment is a video record of the flow field. This qualitative data is then quantified using an all electronic, two-dimensional particle image velocimetry technique called particle displacement tracking (PDT) which uses a simple space domain particle tracking algorithm. The PDT system is successful in producing velocity vector fields from the raw video data. Application of the PDT technique to a sample data set yielded 1606 vectors in 30 seconds of processing time. A bottom viewing optical arrangement is used to image the illuminated plane, which causes keystone distortion in the final recorded image. A coordinate transformation was incorporated into the system software to correct this viewing angle distortion. PDT processing produced 1.8 percent false identifications, due to random particle locations. A highly successful routine for removing the false identifications was also incorporated, reducing the number of false identifications to 0.2 percent.

Design and experimental research of a novel inchworm type piezo-driven rotary actuator with the changeable clamping radius.

PubMed

Zhao, Hongwei; Fu, Lu; Ren, Luquan; Huang, Hu; Fan, Zunqiang; Li, Jianping; Qu, Han

2013-01-01

In this paper, a novel piezo-driven rotary actuator with the changeable clamping radius is developed based on the inchworm principle. This actuator mainly utilizes three piezoelectric actuators, a flexible gripper, a clamping block, and a rotor to achieve large stroke rotation with high resolution. The design process of the flexible gripper consisting of the driving unit and the clamping unit is described. Lever-type mechanisms were used to amplify the micro clamping displacements. The amplifying factor and parasitic displacement of the lever-type mechanism in the clamping unit was analyzed theoretically and experimentally. In order to investigate the rotation characteristics of the actuator, a series of experiments was carried out. Experimental results indicate that the actuator can rotate at a speed of 77,488 μrad/s with a driving frequency of 167 Hz. The rotation resolution and maximum load torque of the actuator are 0.25 μrad and 37 N mm, respectively. The gripper is movable along the z direction based on an elevating platform, and the clamping radius can change from 10.6 mm to 25 mm. Experimental results confirm that the actuator can achieve different rotation speeds by changing the clamping radius.

Particle image velocimetry for the surface tension driven convection experiment using a particle displacement tracking technique

NASA Technical Reports Server (NTRS)

Wernet, Mark P.; Pline, Alexander D.

1991-01-01

The Surface Tension Driven Convection Experiment (STDCE) is a Space Transportation System flight experiment to study both transient and steady thermocapillary fluid flows aboard the USML-1 Spacelab mission planned for 1992. One of the components of data collected during the experiment is a video record of the flow field. This qualitative data is then quantified using an all electronic, two-dimensional particle image velocimetry technique called particle displacement tracking (PDT) which uses a simple space domain particle tracking algorithm. The PDT system is successful in producing velocity vector fields from the raw video data. Application of the PDT technique to a sample data set yielded 1606 vectors in 30 seconds of processing time. A bottom viewing optical arrangement is used to image the illuminated plane, which causes keystone distortion in the final recorded image. A coordinate transformation was incorporated into the system software to correct this viewing angle distortion. PDT processing produced 1.8 percent false identifications, due to random particle locations. A highly successful routine for removing the false identifications was also incorporated, reducing the number of false identifications to 0.2 percent.

Bedrock displacements in Greenland manifest ice mass variations, climate cycles and climate change

PubMed Central

Bevis, Michael; Wahr, John; Khan, Shfaqat A.; Madsen, Finn Bo; Brown, Abel; Willis, Michael; Kendrick, Eric; Knudsen, Per; Box, Jason E.; van Dam, Tonie; Caccamise, Dana J.; Johns, Bjorn; Nylen, Thomas; Abbott, Robin; White, Seth; Miner, Jeremy; Forsberg, Rene; Zhou, Hao; Wang, Jian; Wilson, Terry; Bromwich, David; Francis, Olivier

2012-01-01

The Greenland GPS Network (GNET) uses the Global Positioning System (GPS) to measure the displacement of bedrock exposed near the margins of the Greenland ice sheet. The entire network is uplifting in response to past and present-day changes in ice mass. Crustal displacement is largely accounted for by an annual oscillation superimposed on a sustained trend. The oscillation is driven by earth’s elastic response to seasonal variations in ice mass and air mass (i.e., atmospheric pressure). Observed vertical velocities are higher and often much higher than predicted rates of postglacial rebound (PGR), implying that uplift is usually dominated by the solid earth’s instantaneous elastic response to contemporary losses in ice mass rather than PGR. Superimposed on longer-term trends, an anomalous ‘pulse’ of uplift accumulated at many GNET stations during an approximate six-month period in 2010. This anomalous uplift is spatially correlated with the 2010 melting day anomaly. PMID:22786931

Multi-level partnerships to promote health services among internally displaced in eastern Burma.

PubMed

Mahn, M; Maung, C; Oo, E K Shwe; Smith, L; Lee, C I; Whichard, E; Neumann, C; Richards, A K; Mullany, L C; Kuiper, H; Lee, T J

2008-01-01

Ethnic populations in eastern Burma are the target of military policies that result in forced labour, destruction of food supplies, and massive forced displacement. Despite international assistance to Burmese refugees along the Thai-Burma border, traditional humanitarian models have failed to reach these internally displaced persons (IDPs) within Burma. Nevertheless, through the cultivation of a model (cross border local-global partnerships) 300,000 IDPs in eastern Burma now receive critical health services where, otherwise, there would be none. We describe key elements of the partnership model's genesis in eastern Burma. The role of the local partner, Backpack Health Worker Team (BPHWT), is highlighted for its indigenous access to the IDP populations and its maintenance of programmatic autonomy. These local elements are potentiated by international support for technical assistance, training, resources, and advocacy. International policy and investment should prioritize support of locally-driven health initiatives that utilize local-global partnerships to reach not only IDPs but also other war-torn or traditionally inaccessible populations worldwide.

A mathematical description of a growing cell colony based on the mechanical bidomain model

NASA Astrophysics Data System (ADS)

Auddya, Debabrata; Roth, Bradley J.

2017-03-01

The mechanical bidomain model is used to describe a colony of cells growing on a substrate. Analytical expressions are derived for the intracellular and extracellular displacements. Mechanotransduction events are driven by the difference between the displacements in the two spaces, corresponding to the force acting on integrins. The equation for the displacement consists of two terms: one proportional to the radius that is the same in the intracellular and extracellular spaces (the monodomain term) and one that is proportional to a modified Bessel function that is responsible for mechanotransduction (the bidomain term). The model predicts that mechanotransduction occurs within a few length constants of the colony’s edge, and an expression for the length constant contains the intracellular and extracellular shear moduli and the spring constant of the integrins coupling the two spaces. The model predictions are qualitatively consistent with experiments on human embryonic stem cell colonies, in which differentiation is localized near the edge.

Field Test of Driven Pile Group under Lateral Loading

NASA Astrophysics Data System (ADS)

Gorska, Karolina; Rybak, Jaroslaw; Wyjadlowski, Marek

2017-12-01

All the geotechnical works need to be tested because the diversity of soil parameters is much higher than in other fields of construction. Horizontal load tests are necessary to determine the lateral capacity of driven piles subject to lateral load. Various load tests were carried out altogether on the test field in Kutno (Poland). While selecting the piles for load tests, different load combinations were taken into account. The piles with diverse length were chosen, on the basis of the previous tests of their length and integrity. The subsoil around the piles consisted of mineral soils: clays and medium compacted sands with the density index ID>0.50. The pile heads were free. The points of support of the “base” to which the dial gauges (displacement sensors) were fastened were located at the distance of 0.7 m from the side surface of the pile loaded laterally. In order to assure the independence of measurement, additional control (verifying) geodetic survey of the displacement of the piles subject to the load tests was carried out (by means of the alignment method). The trial load was imposed in stages by means of a hydraulic jack. The oil pressure in the actuator was corrected by means of a manual pump in order to ensure the constant value of the load in the on-going process of the displacement of the pile under test. On the basis of the obtained results it is possible to verify the numerical simulations of the behaviour of piles loaded by a lateral force.

A systematic review of resilience and mental health outcomes of conflict-driven adult forced migrants

PubMed Central

2014-01-01

Background The rising global burden of forced migration due to armed conflict is increasingly recognised as an important issue in global health. Forced migrants are at a greater risk of developing mental disorders. However, resilience, defined as the ability of a person to successfully adapt to or recover from stressful and traumatic experiences, has been highlighted as a key potential protective factor. This study aimed to review systematically the global literature on the impact of resilience on the mental health of adult conflict-driven forced migrants. Methodology Both quantitative and qualitative studies that reported resilience and mental health outcomes among forcibly displaced persons (aged 18+) by way of exploring associations, links, pathways and causative mechanisms were included. Fourteen bibliographic databases and seven humanitarian study databases/websites were searched and a four stage screening process was followed. Results Twenty three studies were included in the final review. Ten qualitative studies identified highlighted family and community cohesion, family and community support, individual personal qualities, collective identity, supportive primary relationships and religion. Thirteen quantitative studies were identified, but only two attempted to link resilience with mental disorders, and three used a specific resilience measure. Over-reliance on cross-sectional designs was noted. Resilience was generally shown to be associated with better mental health in displaced populations, but the evidence on this and underlying mechanisms was limited. Discussion The review highlights the need for more epidemiological and qualitative evidence on resilience in forcibly displaced persons as a potential avenue for intervention development, particularly in resource-poor settings. PMID:25177360

Rapid evolution of troglomorphic characters suggests selection rather than neutral mutation as a driver of eye reduction in cave crabs.

PubMed

Klaus, Sebastian; Mendoza, José C E; Liew, Jia Huan; Plath, Martin; Meier, Rudolf; Yeo, Darren C J

2013-04-23

This study asked whether reductive traits in cave organisms evolve at a slower pace (suggesting neutral evolution under relaxed selection) than constructive changes, which are likely to evolve under directional selection. We investigated 11 subterranean and seven surface populations of Sundathelphusa freshwater crabs on Bohol Island, Philippines, and examined constructive traits associated with improved food finding in darkness (increased leg and setae length) and reductive traits (reduced cornea size and eyestalk length). All changes occurred rapidly, given that the age of the most recent common ancestor was estimated to be 722-271 ka based on three mitochondrial markers. In order to quantify the speed of character change, we correlated the degree of morphological change with genetic distances between surface and subterranean individuals. The temporal pattern of character change following the transition to subterranean life was indistinguishable for constructive and reductive traits, characterized by an immediate onset and rapid evolutionary change. We propose that the evolution of these reductive traits-just like constructive traits-is most likely driven by strong directional selection.

Amorphization driven by defect-induced mechanical instability.

PubMed

Jiang, Chao; Zheng, Ming-Jie; Morgan, Dane; Szlufarska, Izabela

2013-10-11

Using ab initio molecular dynamics simulations, we perform a comparative study of the defect accumulation process in silicon carbide (SiC) and zirconium carbide (ZrC). Interestingly, we find that the fcc Si sublattice in SiC spontaneously and gradually collapses following the continuous introduction of C Frenkel pairs (FPs). Above a critical amorphization dose of ~0.33 displacements per atom (dpa), the pair correlation function exhibits no long-range order. In contrast, the fcc Zr sublattice in ZrC remains structurally stable against C sublattice displacements up to the highest dose of 1.0 dpa considered. Consequently, ZrC cannot be amorphized by the accumulation of C FPs. We propose defect-induced mechanical instability as the key mechanism driving the amorphization of SiC under electron irradiation.

Reproductive interference and fecundity affect competitive interactions of sibling species with low mating barriers: experimental and theoretical evidence.

PubMed

Gebiola, M; Kelly, S E; Velten, L; Zug, R; Hammerstein, P; Giorgini, M; Hunter, M S

2017-12-01

When allopatric species with incomplete prezygotic isolation come into secondary contact, the outcome of their interaction is not easily predicted. The parasitoid wasp Encarsia suzannae (iES), infected by Cardinium inducing cytoplasmic incompatibility (CI), and its sibling species E. gennaroi (EG), not infected by bacterial endosymbionts, may have diverged because of the complementary action of CI and asymmetric hybrid incompatibilities. Whereas postzygotic isolation is now complete because of sterility of F1 hybrid progeny, prezygotic isolation is still incipient. We set up laboratory population cage experiments to evaluate the outcome of the interaction between ES and EG in two pairwise combinations: iES vs EG and cured ES (cES, where Cardinium was removed with antibiotics) vs EG. We also built a theoretical model aimed at exploring the role of life-history differences and asymmetric mating on competitive outcomes. In three of four cages in each treatment, ES dominated the interaction. We found evidence for reproductive interference, driven by asymmetric mating preferences, that gave a competitive edge to ES, the species that better discriminated against heterospecifics. However, we did not find the fecundity cost previously shown to be associated with Cardinium infection in iES. The model largely supported the experimental results. The finding of only a slight competitive edge of ES over EG in population cages suggests that in a more heterogeneous environment the species could coexist. This is supported by evidence that the two species coexist in sympatry, where preliminary data suggest reproductive character displacement may have reinforced postzygotic isolation.

Comparison of 3D displacements of screw-retained zirconia implant crowns into implants with different internal connections with respect to screw tightening.

PubMed

Rebeeah, Hanadi A; Yilmaz, Burak; Seidt, Jeremy D; McGlumphy, Edwin; Clelland, Nancy; Brantley, William

2018-01-01

Internal conical implant-abutment connections without horizontal platforms may lead to crown displacement during screw tightening and torque application. This displacement may affect the proximal contacts and occlusion of the definitive prosthesis. The purpose of this in vitro study was to evaluate the displacement of custom screw-retained zirconia single crowns into a recently introduced internal conical seal implant-abutment connection in 3D during hand and torque driver screw tightening. Stereolithic acrylic resin models were printed using computed tomography data from a patient missing the maxillary right central incisor. Two different internal connection implant systems (both ∼11.5 mm) were placed in the edentulous site in each model using a surgical guide. Five screw-retained single zirconia computer-aided design and computer-aided manufacturing (CAD-CAM) crowns were fabricated for each system. A pair of high-resolution digital cameras was used to record the relationship of the crown to the model. The crowns were tightened according to the manufacturers' specifications using a torque driver, and the cameras recorded their relative position again. Three-dimensional image correlation was used to measure and compare crown positions, first hand tightened and then torque driven. The displacement test was repeated 3 times for each crown. Commercial image correlation software was used to extract the data and compare the amount of displacement vertically, mesiodistally, and buccolingually. Repeated-measures ANOVA calculated the relative displacements for all 5 specimens for each implant for both crown screw hand tightening and after applied torque. A Student t test with Bonferroni correction was used for pairwise comparison of interest to determine statistical differences between the 2 implants (α=.05). The mean vertical displacements were statistically higher than the mean displacements in the mesiodistal and buccolingual directions for both implants (P<.001). Mean displacements in all directions were statistically significant between iterations for both implants (P<.001). No statistically significant differences were found for displacements between implants at different directions and at different iterations (P>.05). Within the limitations of this in vitro study, screw-retained zirconia crowns tended to displace in all 3 directions, with the highest mean displacement in the vertical direction at iteration 1. However, the amount of displacement of crowns between the 2 different implants was statistically insignificant for all directions and iterations. Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Electrical current nanogeneration driven by spontaneous nanofluidic oscillations.

PubMed

Gimenez, R; Mercuri, M; Berli, C L A; Bellino, M G

2018-02-15

Exploiting natural phenomena is a central route for providing electricity to sustainably drive wearable electronics. Here we report a nano-scale water-driven energy generator that produces tiny electrical currents from spontaneous wetting-drying oscillations in mesoporous thin films. The system was fabricated with a wormlike mesoporous silica film, which was packed in between Cu and silicon contacts. The nanogenerator runs autonomously when a water droplet is laid over the film close to the Cu electrode, as water infiltration into the film under the electrode produces a direct-current. Wetting-drying cycles, which are spontaneously triggered by water evaporation, are perfectly correlated to the generated electrical current. The autonomous water displacement through the film yields a sustained energy conversion until the droplet reservoir vanishes. This novel water-driven nanogenerator opens new alternatives for versatile, mobile and cost-effective self-powering of nanosystems and nanodevices.

Protein dynamics as seen by (quasi) elastic neutron scattering.

PubMed

Magazù, S; Mezei, F; Falus, P; Farago, B; Mamontov, E; Russina, M; Migliardo, F

2017-01-01

Elastic and quasielastic neutron scattering studies proved to be efficient probes of the atomic mean square displacement (MSD), a fundamental parameter for the characterization of the motion of individual atoms in proteins and its evolution with temperature and compositional environment. We present a technical overview of the different types of experimental situations and the information quasi-elastic neutron scattering approaches can make available. In particular, MSD can crucially depend on the time scale over which the averaging (building of the "mean") takes place, being defined by the instrumental resolution. Due to their high neutron scattering cross section, hydrogen atoms can be particularly sensitively observed with little interference by the other atoms in the sample. A few examples, including new data, are presented for illustration. The incoherent character of neutron scattering on hydrogen atoms restricts the information obtained to the self-correlations in the motion of individual atoms, simplifying at the same time the data analysis. On the other hand, the (often overlooked) exploration of the averaging time dependent character of MSD is crucial for unambiguous interpretation and can provide a wealth of information on micro- and nanoscale atomic motion in proteins. By properly exploiting the broad range capabilities of (quasi)elastic neutron scattering techniques to deliver time dependent characterization of atomic displacements, they offer a sensitive, direct and simple to interpret approach to exploration of the functional activity of hydrogen atoms in proteins. Partial deuteration can add most valuable selectivity by groups of hydrogen atoms. "This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo". Copyright © 2016 Elsevier B.V. All rights reserved.

Thermally Driven Electronic Topological Transition in FeTi

DOE PAGES

Yang, F. C.; Muñoz, J. A.; Hellman, O.; ...

2016-08-08

In this paper, ab initio molecular dynamics, supported by inelastic neutron scattering and nuclear resonant inelastic x-ray scattering, showed an anomalous thermal softening of the M 5 - phonon mode in B2-ordered FeTi that could not be explained by phonon-phonon interactions or electron-phonon interactions calculated at low temperatures. A computational investigation showed that the Fermi surface undergoes a novel thermally driven electronic topological transition, in which new features of the Fermi surface arise at elevated temperatures. Finally, the thermally induced electronic topological transition causes an increased electronic screening for the atom displacements in the M 5 - phonon mode andmore » an adiabatic electron-phonon interaction with an unusual temperature dependence.« less

An optimized strain demodulation method for PZT driven fiber Fabry-Perot tunable filter

NASA Astrophysics Data System (ADS)

Sheng, Wenjuan; Peng, G. D.; Liu, Yang; Yang, Ning

2015-08-01

An optimized strain-demodulation-method based on piezo-electrical transducer (PZT) driven fiber Fabry-Perot (FFP) filter is proposed and experimentally demonstrated. Using a parallel processing mode to drive the PZT continuously, the hysteresis effect is eliminated, and the system demodulation rate is increased. Furthermore, an AC-DC compensation method is developed to address the intrinsic nonlinear relationship between the displacement and voltage of PZT. The experimental results show that the actual demodulation rate is improved from 15 Hz to 30 Hz, the random error of the strain measurement is decreased by 95%, and the deviation between the test values after compensation and the theoretical values is less than 1 pm/με.

Sterilisation in the laboratory autoclave using direct air displacement by steam.

PubMed Central

Everall, P H; Morris, C A; Yarnell, R

1978-01-01

A device using a steam injection funnel is described by means of which air can be driven quickly and surely from an autoclave load. It is simple and inexpensive, necessitates no changes in the working routine of a microbiology laboratory, and does not interfere with the operation of the autoclave in its normal mode. Images Fig. 1 Fig. 3 PMID:344345

Current Status and Future Challenges in Risk-Based Radiation Engineering

NASA Technical Reports Server (NTRS)

Pellish, Jonathan A.

2017-01-01

This presentation covers the basis and challenges for radiation effects in electronic systems. The three main types of radiation effects in electronics are: 1) total ionizing dose (TID), 2) total non-ionizing dose (TNID) / displacement damage dose (DDD), and 3) single-event effect (SEE). Some content on relevant examples of effects, current concerns, and possible environmental model-driven solutions are also included.

Stochastic Epidemic Outbreaks, or Why Epidemics Behave Like Lasers

NASA Astrophysics Data System (ADS)

Schwartz, Ira; Billings, Lora; Bollt, Erik; Carr, Thomas

2004-03-01

Many diseases, such childhood diseases, dengue fever, and West Nile virus, appear to oscillate randomly as a function of seasonal environmental or social changes. Such oscillations appear to have a chaotic bursting character, although it is still uncertain how much is due to random fluctuations. Such bursting in the presence of noise is also observed in driven lasers. In this talk, I will show how noise can excite random outbreaks in simple models of seasonally driven outbreaks, as well as lasers. The models for both population dynamics will be shown to share the same class of underlying topology, which plays a major role in the cause of observed stochastic bursting. New tools for predicting stcohastic outbreaks will be presented.

Canal wall planning by engine-driven nickel-titanium instruments, compared with stainless-steel hand instrumentation.

PubMed

Tucker, D M; Wenckus, C S; Bentkover, S K

1997-03-01

Twenty-two mesial roots of extracted human mandibular molars were divided into two groups based on root curvature and length. The mesiolingual canals were instrumented using either Flexofiles in a step-back anticurvature filing method, or they were instrumented with engine-driven 0.02 taper nickel-titanium files. Ground sections were prepared at 1-, 2.5-, and 5-mm levels from the working length. The mesiobuccal canal was used as an uninstrumented control for predentin character. Digitizing software was used to calculate the instrumented portion as a percentage of the total canal perimeter. The results indicated no significant difference in overall canal wall planning between the two groups and no significant difference at each of the three levels.

A comparison of Data Driven models of solving the task of gender identification of author in Russian language texts for cases without and with the gender deception

NASA Astrophysics Data System (ADS)

Sboev, A.; Moloshnikov, I.; Gudovskikh, D.; Rybka, R.

2017-12-01

In this work we compare several data-driven approaches to the task of author’s gender identification for texts with or without gender imitation. The data corpus has been specially gathered with crowdsourcing for this task. The best models are convolutional neural network with input of morphological data (fl-measure: 88%±3) for texts without imitation, and gradient boosting model with vector of character n-grams frequencies as input data (f1-measure: 64% ± 3) for texts with gender imitation. The method to filter the crowdsourced corpus using limited reference sample of texts to increase the accuracy of result is discussed.

The hydrophilic-to-hydrophobic transition in glassy silica is driven by the atomic topology of its surface

NASA Astrophysics Data System (ADS)

Yu, Yingtian; Krishnan, N. M. Anoop; Smedskjaer, Morten M.; Sant, Gaurav; Bauchy, Mathieu

2018-02-01

The surface reactivity and hydrophilicity of silicate materials are key properties for various industrial applications. However, the structural origin of their affinity for water remains unclear. Here, based on reactive molecular dynamics simulations of a series of artificial glassy silica surfaces annealed at various temperatures and subsequently exposed to water, we show that silica exhibits a hydrophilic-to-hydrophobic transition driven by its silanol surface density. By applying topological constraint theory, we show that the surface reactivity and hydrophilic/hydrophobic character of silica are controlled by the atomic topology of its surface. This suggests that novel silicate materials with tailored reactivity and hydrophilicity could be developed through the topological nanoengineering of their surface.

Visible-Light-Driven BiOI-Based Janus Micromotor in Pure Water.

PubMed

Dong, Renfeng; Hu, Yan; Wu, Yefei; Gao, Wei; Ren, Biye; Wang, Qinglong; Cai, Yuepeng

2017-02-08

Light-driven synthetic micro-/nanomotors have attracted considerable attention due to their potential applications and unique performances such as remote motion control and adjustable velocity. Utilizing harmless and renewable visible light to supply energy for micro-/nanomotors in water represents a great challenge. In view of the outstanding photocatalytic performance of bismuth oxyiodide (BiOI), visible-light-driven BiOI-based Janus micromotors have been developed, which can be activated by a broad spectrum of light, including blue and green light. Such BiOI-based Janus micromotors can be propelled by photocatalytic reactions in pure water under environmentally friendly visible light without the addition of any other chemical fuels. The remote control of photocatalytic propulsion by modulating the power of visible light is characterized by velocity and mean-square displacement analysis of optical video recordings. In addition, the self-electrophoresis mechanism has been confirmed for such visible-light-driven BiOI-based Janus micromotors by demonstrating the effects of various coated layers (e.g., Al 2 O 3 , Pt, and Au) on the velocity of motors. The successful demonstration of visible-light-driven Janus micromotors holds a great promise for future biomedical and environmental applications.

Relationships of Cetacea (Artiodactyla) among mammals: increased taxon sampling alters interpretations of key fossils and character evolution.

PubMed

Spaulding, Michelle; O'Leary, Maureen A; Gatesy, John

2009-09-23

Integration of diverse data (molecules, fossils) provides the most robust test of the phylogeny of cetaceans. Positioning key fossils is critical for reconstructing the character change from life on land to life in the water. We reexamine relationships of critical extinct taxa that impact our understanding of the origin of Cetacea. We do this in the context of the largest total evidence analysis of morphological and molecular information for Artiodactyla (661 phenotypic characters and 46,587 molecular characters, coded for 33 extant and 48 extinct taxa). We score morphological data for Carnivoramorpha, Creodonta, Lipotyphla, and the raoellid artiodactylan Indohyus and concentrate on determining which fossils are positioned along stem lineages to major artiodactylan crown clades. Shortest trees place Cetacea within Artiodactyla and close to Indohyus, with Mesonychia outside of Artiodactyla. The relationships of Mesonychia and Indohyus are highly unstable, however--in trees only two steps longer than minimum length, Mesonychia falls inside Artiodactyla and displaces Indohyus from a position close to Cetacea. Trees based only on data that fossilize continue to show the classic arrangement of relationships within Artiodactyla with Cetacea grouping outside the clade, a signal incongruent with the molecular data that dominate the total evidence result. Integration of new fossil material of Indohyus impacts placement of another extinct clade Mesonychia, pushing it much farther down the tree. The phylogenetic position of Indohyus suggests that the cetacean stem lineage included herbivorous and carnivorous aquatic species. We also conclude that extinct members of Cetancodonta (whales+hippopotamids) shared a derived ability to hear underwater sounds, even though several cetancodontans lack a pachyostotic auditory bulla. We revise the taxonomy of living and extinct artiodactylans and propose explicit node and stem-based definitions for the ingroup.

Stereovision-based integrated system for point cloud reconstruction and simulated brain shift validation.

PubMed

Yang, Xiaochen; Clements, Logan W; Luo, Ma; Narasimhan, Saramati; Thompson, Reid C; Dawant, Benoit M; Miga, Michael I

2017-07-01

Intraoperative soft tissue deformation, referred to as brain shift, compromises the application of current image-guided surgery navigation systems in neurosurgery. A computational model driven by sparse data has been proposed as a cost-effective method to compensate for cortical surface and volumetric displacements. We present a mock environment developed to acquire stereoimages from a tracked operating microscope and to reconstruct three-dimensional point clouds from these images. A reconstruction error of 1 mm is estimated by using a phantom with a known geometry and independently measured deformation extent. The microscope is tracked via an attached tracking rigid body that facilitates the recording of the position of the microscope via a commercial optical tracking system as it moves during the procedure. Point clouds, reconstructed under different microscope positions, are registered into the same space to compute the feature displacements. Using our mock craniotomy device, realistic cortical deformations are generated. When comparing our tracked microscope stereo-pair measure of mock vessel displacements to that of the measurement determined by the independent optically tracked stylus marking, the displacement error was [Formula: see text] on average. These results demonstrate the practicality of using tracked stereoscopic microscope as an alternative to laser range scanners to collect sufficient intraoperative information for brain shift correction.

Universality Results for Multi-layer Radial Hele-Shaw Flows

NASA Astrophysics Data System (ADS)

Daripa, Prabir; Gin, Craig; Daripa Research Team

2014-03-01

Saffman-Taylor instability is a well known viscosity driven instability of an interface separating two immiscible fluids. We study linear stability of this displacement process in multi-layer radial Hele-Shaw geometry involving an arbitrary number of immiscible fluid phases. Universal stability results have been obtained and applied to design displacement processes that are considerably less unstable than the pure Saffman-Taylor case. In particular, we derive universal formula which gives specific values of the viscosities of the fluid layers corresponding to smallest unstable band. Other similar universal results will also be presented. The talk is based on ongoing work. Supported by an NPRP Grant # 08-777-1-141 from the Qatar National Research Fund (a member of the Qatar Foundation). The statements made herein are solely the responsibility of the authors.

Modeling the Impact of Deformation on Unstable Miscible Displacements in Porous Media

NASA Astrophysics Data System (ADS)

Santillán, D.; Cueto-Felgueroso, L.

2014-12-01

Coupled flow and geomechanics is a critical research challenge in engineering and the geosciences. The simultaneous flow of two or more fluids with different densities or viscosities through deformable media is ubiquitous in environmental, industrial, and biological processes, including the removal of non-aqueous phase liquids from underground water bodies, the geological storage of CO2, and current challenges in energy technologies, such as enhanced geothermal systems, unconventional hydrocarbon resources or enhanced oil recovery techniques. Using numerical simulation, we study the interplay between viscous-driven flow instabilities (viscous fingering) and rock mechanics, and elucidate the structure of the displacement patterns as a function of viscosity contrast, injection rate and rock mechanical properties. Finally, we discuss the role of medium deformation on transport and mixing processes in porous media.

Interface instabilities during displacements of two miscible fluids in a vertical pipe

NASA Astrophysics Data System (ADS)

Scoffoni, J.; Lajeunesse, E.; Homsy, G. M.

2001-03-01

We study experimentally the downward vertical displacement of one miscible fluid by another in a vertical pipe at sufficiently high velocities for diffusive effects to be negligible. For certain viscosity ratios and flow rates, the interface between the two fluids can destabilize. We determine the dimensionless flow rate Uc above which the instability is triggered and its dependence on the viscous ratio M, resulting in a stability map Uc=Uc(M). Two different instability modes have been observed: an asymmetric "corkscrew" mode and an axisymmetric one. We remark that the latter is always eventually disturbed by "corkscrew" type instabilities. We speculate that these instabilities are driven by the viscosity stratification and are analogous to those already observed in core annular flows of immiscible fluids.

Influence of Grid Reinforcement Placed In Masonry Bed Joints on Its Flexural Strength

NASA Astrophysics Data System (ADS)

Piekarczyk, Adam

2017-10-01

The paper presents the test results of the flexural strength of masonry when plane of failure is perpendicular to the bed joints. Comparison tests of unreinforced specimens and specimens reinforced with steel wire, glass and basalt fibre grids applied in masonry bed joints showed the higher flexural strength and crack resistance of masonry reinforced in this manner and so loaded. Reinforced masonry exposed plastic character after cracking allow for large horizontal displacements and transfer the considerable loads perpendicular to their surface. The strengthening of masonry was observed in most tests of reinforced specimens leading to occurrence of the maximum load in after cracking phase.

[Proletariat and migrant: free for subordination].

PubMed

Alves De Souza, G A

1986-01-01

Using information taken from experiences in Bahia, Brazil, this study attempts to show how the historic process of proletarianization changes in character and level of radicalism at certain moments in the process of the emergence and development of capitalism, thus producing significant changes in migratory patterns. Special focus is given on how the migratory flux in rural Bahia has been more intense in the last 50 years, altering subsequent spacial displacements of population. At the same time, the form of collective organization of production of the salaried classes in both the rural and town areas have been redefined, thus turning migrations into expressive mediation mechanisms in constitution of an eminently urban society.

Observation of band gaps in the gigahertz range and deaf bands in a hypersonic aluminum nitride phononic crystal slab

NASA Astrophysics Data System (ADS)

Gorisse, M.; Benchabane, S.; Teissier, G.; Billard, C.; Reinhardt, A.; Laude, V.; Defaÿ, E.; Aïd, M.

2011-06-01

We report on the observation of elastic waves propagating in a two-dimensional phononic crystal composed of air holes drilled in an aluminum nitride membrane. The theoretical band structure indicates the existence of an acoustic band gap centered around 800 MHz with a relative bandwidth of 6.5% that is confirmed by gigahertz optical images of the surface displacement. Further electrical measurements and computation of the transmission reveal a much wider attenuation band that is explained by the deaf character of certain bands resulting from the orthogonality of their polarization with that of the source.

A New Chanidae (Ostariophysii: Gonorynchiformes) from the Cretaceous of Brazil with Affinities to Laurasian Gonorynchiforms from Spain

PubMed Central

Amaral, Cesar R. L.; Brito, Paulo M.

2012-01-01

Based on specimens originally referred to as “Dastilbe minor”, a nomem-nudum, we describe a new genus of Chanidae †Nanaichthys longipinnus nov. gen. and sp. which exhibits several diagnostic characters such as the absence of orbitosphenoid and basisphenoid, anteriorly displaced quadrate-mandibular articulation, laterally expanded supraneurals, an acute angle between the preopercular limbs, expansion at the angle between the preopercular limbs, and a curved maxillary articular process. Its occurrence and supposed relationship within the Chanidae reinforce the influence of the Mediterranean Tethys over the Gondwanan main rift system prior to the Aptian/Albian highstands. PMID:22629376

The Influence of the External Signal Modulation Waveform and Frequency on the Performance of a Photonic Forced Oscillator.

PubMed

Sánchez-Castro, Noemi; Palomino-Ovando, Martha Alicia; Estrada-Wiese, Denise; Valladares, Nydia Xcaret; Del Río, Jesus Antonio; de la Mora, Maria Beatriz; Doti, Rafael; Faubert, Jocelyn; Lugo, Jesus Eduardo

2018-05-21

Photonic crystals have been an object of interest because of their properties to inhibit certain wavelengths and allow the transmission of others. Using these properties, we designed a photonic structure known as photodyne formed by two porous silicon one-dimensional photonic crystals with an air defect between them. When the photodyne is illuminated with appropriate light, it allows us to generate electromagnetic forces within the structure that can be maximized if the light becomes localized inside the defect region. These electromagnetic forces allow the microcavity to oscillate mechanically. In the experiment, a chopper was driven by a signal generator to modulate the laser light that was used. The driven frequency and the signal modulation waveform (rectangular, sinusoidal or triangular) were changed with the idea to find optimal conditions for the structure to oscillate. The microcavity displacement amplitude, velocity amplitude and Fourier spectrum of the latter and its frequency were measured by means of a vibrometer. The mechanical oscillations are modeled and compared with the experimental results and show good agreement. For external frequency values of 5 Hz and 10 Hz, the best option was a sinusoidal waveform, which gave higher photodyne displacements and velocity amplitudes. Nonetheless, for an external frequency of 15 Hz, the best option was the rectangular waveform.

The Influence of the External Signal Modulation Waveform and Frequency on the Performance of a Photonic Forced Oscillator

PubMed Central

Sánchez-Castro, Noemi; Palomino-Ovando, Martha Alicia; Estrada-Wiese, Denise; Valladares, Nydia Xcaret; del Río, Jesus Antonio; Doti, Rafael; Faubert, Jocelyn; Lugo, Jesus Eduardo

2018-01-01

Photonic crystals have been an object of interest because of their properties to inhibit certain wavelengths and allow the transmission of others. Using these properties, we designed a photonic structure known as photodyne formed by two porous silicon one-dimensional photonic crystals with an air defect between them. When the photodyne is illuminated with appropriate light, it allows us to generate electromagnetic forces within the structure that can be maximized if the light becomes localized inside the defect region. These electromagnetic forces allow the microcavity to oscillate mechanically. In the experiment, a chopper was driven by a signal generator to modulate the laser light that was used. The driven frequency and the signal modulation waveform (rectangular, sinusoidal or triangular) were changed with the idea to find optimal conditions for the structure to oscillate. The microcavity displacement amplitude, velocity amplitude and Fourier spectrum of the latter and its frequency were measured by means of a vibrometer. The mechanical oscillations are modeled and compared with the experimental results and show good agreement. For external frequency values of 5 Hz and 10 Hz, the best option was a sinusoidal waveform, which gave higher photodyne displacements and velocity amplitudes. Nonetheless, for an external frequency of 15 Hz, the best option was the rectangular waveform. PMID:29883393

Ultrafast Charge Transfer of a Valence Double Hole in Glycine Driven Exclusively by Nuclear Motion

NASA Astrophysics Data System (ADS)

Li, Zheng; Vendrell, Oriol; Santra, Robin

2015-10-01

We explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K -shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we find that the double hole is transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. The nuclear displacements along specific vibrational modes are of the order of 15% of a typical chemical bond between carbon, oxygen, and nitrogen atoms and about 30% for bonds involving hydrogen atoms. The time required for the hole transfer corresponds to less than half a vibrational period of the involved nuclear modes. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. It also indicates that in x-ray imaging experiments, in which ionization is unavoidable, valence electron redistribution caused by nuclear dynamics might be much faster than previously anticipated. Thus, non-Born-Oppenheimer effects may affect the apparent electron densities extracted from such measurements.

Theoretical and experimental research on machine tool servo system for ultra-precision position compensation on CNC lathe

NASA Astrophysics Data System (ADS)

Ma, Zhichao; Hu, Leilei; Zhao, Hongwei; Wu, Boda; Peng, Zhenxing; Zhou, Xiaoqin; Zhang, Hongguo; Zhu, Shuai; Xing, Lifeng; Hu, Huang

2010-08-01

The theories and techniques for improving machining accuracy via position control of diamond tool's tip and raising resolution of cutting depth on precise CNC lathes have been extremely focused on. A new piezo-driven ultra-precision machine tool servo system is designed and tested to improve manufacturing accuracy of workpiece. The mathematical model of machine tool servo system is established and the finite element analysis is carried out on parallel plate flexure hinges. The output position of diamond tool's tip driven by the machine tool servo system is tested via a contact capacitive displacement sensor. Proportional, integral, derivative (PID) feedback is also implemented to accommodate and compensate dynamical change owing cutting forces as well as the inherent non-linearity factors of the piezoelectric stack during cutting process. By closed loop feedback controlling strategy, the tracking error is limited to 0.8 μm. Experimental results have shown the proposed machine tool servo system could provide a tool positioning resolution of 12 nm, which is much accurate than the inherent CNC resolution magnitude. The stepped shaft of aluminum specimen with a step increment of cutting depth of 1 μm is tested, and the obtained contour illustrates the displacement command output from controller is accurately and real-time reflected on the machined part.

On the impact of self-clearing on electroactive polymer (EAP) actuators

NASA Astrophysics Data System (ADS)

Ahmed, Saad; Ounaies, Zoubeida; Lanagan, Michael T.

2017-10-01

Electroactive polymer (EAP)-based actuators have large potential for a wide array of applications; however, their practical implementation is still a challenge because of the requirement of high driving voltage, which most often leads to premature defect-driven electrical breakdown. Polymer-based capacitors have the ability to clear defects with partial electrical breakdown and subsequent removal of a localized electrode section near the defect. In this study, this process, which is known as self-clearing, is adopted for EAP technologies. We report a methodical approach to self-clear an EAP, more specifically P(VDF-TrFE-CTFE) terpolymer, to delay premature defect-driven electrical breakdown of the terpolymer actuators at high operating electric fields. Breakdown results show that electrical breakdown strength is improved up to 18% in comparison to a control sample after self-clearing. Furthermore, the electromechanical performance in terms of blocked force and free displacement of P(VDF-TrFE-CTFE) terpolymer-based bending actuators are examined after self-clearing and precleared samples show improved blocked force, free displacement and maximum sustainable electric field compared to control samples. The study demonstrates that controlled self-clearing of EAPs improves the breakdown limit and reliability of the EAP actuators for practical applications without impeding their electromechanical performance.

Ultrafast Charge Transfer of a Valence Double Hole in Glycine Driven Exclusively by Nuclear Motion.

PubMed

Li, Zheng; Vendrell, Oriol; Santra, Robin

2015-10-02

We explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K-shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we find that the double hole is transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. The nuclear displacements along specific vibrational modes are of the order of 15% of a typical chemical bond between carbon, oxygen, and nitrogen atoms and about 30% for bonds involving hydrogen atoms. The time required for the hole transfer corresponds to less than half a vibrational period of the involved nuclear modes. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. It also indicates that in x-ray imaging experiments, in which ionization is unavoidable, valence electron redistribution caused by nuclear dynamics might be much faster than previously anticipated. Thus, non-Born-Oppenheimer effects may affect the apparent electron densities extracted from such measurements.

Vertical and horizontal surface displacements near Jakobshavn Isbræ driven by melt-induced and dynamic ice loss

NASA Astrophysics Data System (ADS)

Khan, S. A.; Nielsen, K.; Wahr, J. M.; Bevis, M. G.; Liu, L.; Spada, G.; van Dam, T. M.

2012-12-01

We analyze Global Positioning System (GPS) time series of relative vertical and horizontal displacements from 2009-2011, at four GPS sites located between 5 and 150 km from the front of Jakobshavn Isbræ (JI). The horizontal displacements at KAGA, ILUL, and QEQE, relative to the site AASI, are directed towards east-north-east, suggesting that the main mass loss signal is south-east of these sites. The directions of the observed displacements are supported by modelled displacements, derived from NASA's Airborne Topographic Mapper (ATM) surveys of surface elevations from 2006 to 2011. The agreement between the observed and modelled relative displacements is 0.8 mm or better, which suggests that the mass loss estimate of JI is well captured. In 2010, we observe a rapid increase in the uplift at all four sites. This uplift anomaly, defined as the deviation at 2010.75 from the 2006-2009.75 trend is estimated to 8.8 +/- 2.4 mm (KAGA), 9.3 +/- 2.2 mm (ILUL), 5.1 +/- 2.0 mm (QEQE), and 6.1 +/- 2.3 mm (AASI). The relative large anomalies at the sites QEQE and AASI, located ~150 km from the front of JI, suggests that the uplift anomalies are caused by a large wide-spread melt-induced ice loss. The relatively low uplift anomaly at KAGA, located only 5 km from the front, indicates that there has been a dramatic decrease in dynamic-induced ice loss near the front of JI. This is supported by elevation changes derived from ATM measurements between 2010 and 2011, where we observe an elevation increase in the flow direction of up to 10 m at the frontal part of JI.

Quasi-static displacement calibration system for a “Violin-Mode” shadow-sensor intended for Gravitational Wave detector suspensions

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

Lockerbie, N. A.; Tokmakov, K. V.

This paper describes the design of, and results from, a calibration system for optical linear displacement (shadow) sensors. The shadow sensors were designed to detect “Violin-Mode” (VM) resonances in the 0.4 mm diameter silica fibre suspensions of the test masses/mirrors of Advanced Laser Interferometer Gravitational Wave Observatory gravitational wave interferometers. Each sensor illuminated the fibre under test, so as to cast its narrow shadow onto a “synthesized split photodiode” detector, the shadow falling over adjacent edges of the paired photodiodes. The apparatus described here translated a vertically orientated silica test fibre horizontally through a collimated Near InfraRed illuminating beam, whilstmore » simultaneously capturing the separate DC “shadow notch” outputs from each of the paired split photodiode detectors. As the ratio of AC to DC photocurrent sensitivities to displacement was known, a calibration of the DC response to quasi-static shadow displacement allowed the required AC sensitivity to vibrational displacement to be found. Special techniques are described for generating the required constant scan rate for the test fibre using a DC motor-driven stage, for removing “jitter” at such low translation rates from a linear magnetic encoder, and so for capturing the two shadow-notch signals at each micrometre of the test fibre's travel. Calibration, across the four detectors of this work, gave a vibrational responsivity in voltage terms of (9.45 ± 1.20) MV (rms)/m, yielding a VM displacement sensitivity of (69 ± 13) pm (rms)/√Hz, at 500 Hz, over the required measuring span of ±0.1 mm.« less

The nonlinear bending response of thin-walled laminated composite cylinders

NASA Technical Reports Server (NTRS)

Fuchs, Hannes P.; Hyer, Michael W.

1992-01-01

The geometrically nonlinear Donnell shell theory is applied to the problem of stable bending of thin-walled circular cylinders. Responses are computed for cylinders with a radius-to-thickness ratio of 50 and length-to-radius ratios of 1 and 5. Four laminated composite cylinders and an aluminum cylinder are considered. Critical moment estimates are presented for short cylinders for which compression-type buckling behavior is important, and for very long cylinders for which the cross-section flattening, i.e., Brazier effect, is important. A finite element analysis is used to estimate the critical end rotation in addition to establishing the range of validity of the prebuckling analysis. The radial displacement response shows that the character of the boundary layer is significantly influenced by the geometric nonlinearities. Application of a first ply failure analysis using the maximum stress criterion suggests that in nearly all instances material failure occurs before buckling. Failure of the composite cylinders can be attributed to fiber breakage. Striking similarities are seen between the prebuckling displacements of the bending problem and axial compression problem for short cylinders.

Thermal diffusivity determination using heterodyne phase insensitive transient grating spectroscopy

NASA Astrophysics Data System (ADS)

Dennett, Cody A.; Short, Michael P.

2018-06-01

The elastic and thermal transport properties of opaque materials may be measured using transient grating spectroscopy (TGS) by inducing and monitoring periodic excitations in both reflectivity and surface displacement. The "phase grating" response encodes both properties of interest, but complicates quantitative analysis by convolving temperature dynamics with surface displacement dynamics. Thus, thermal transport characteristics are typically determined using the "amplitude grating" response to isolate the surface temperature dynamics. However, this signal character requires absolute heterodyne phase calibration and contains no elastic property information. Here, a method is developed by which phase grating TGS measurements may be consistently analyzed to determine thermal diffusivity with no prior knowledge of the expected properties. To demonstrate this ability, the wavelength-dependent 1D effective thermal diffusivity of pure germanium is measured using this type of response and found to be consistent with theoretical predictions made by solving the Boltzmann transport equation. This ability to determine the elastic and thermal properties from a single set of TGS measurements will be particularly advantageous for new in situ implementations of the technique being used to study dynamic materials systems.

A programming language for composable DNA circuits

PubMed Central

Phillips, Andrew; Cardelli, Luca

2009-01-01

Recently, a range of information-processing circuits have been implemented in DNA by using strand displacement as their main computational mechanism. Examples include digital logic circuits and catalytic signal amplification circuits that function as efficient molecular detectors. As new paradigms for DNA computation emerge, the development of corresponding languages and tools for these paradigms will help to facilitate the design of DNA circuits and their automatic compilation to nucleotide sequences. We present a programming language for designing and simulating DNA circuits in which strand displacement is the main computational mechanism. The language includes basic elements of sequence domains, toeholds and branch migration, and assumes that strands do not possess any secondary structure. The language is used to model and simulate a variety of circuits, including an entropy-driven catalytic gate, a simple gate motif for synthesizing large-scale circuits and a scheme for implementing an arbitrary system of chemical reactions. The language is a first step towards the design of modelling and simulation tools for DNA strand displacement, which complements the emergence of novel implementation strategies for DNA computing. PMID:19535415

A 10 deg K triple-expansion Stirling-cycle cryocooler

NASA Technical Reports Server (NTRS)

Newman, W.; Keung, C. S.

1983-01-01

The design of a triple expansion closed cycle Stirling cryocooler optimized for a cooling load of 50 mW at 10 K is described. The cooler was designed with the objectives of low power, low weight, compactness, low mechanical motion, low electromagnetic noise, and low output temperature fluctuations. The design employs a direct drive linear motion piston motor and a triple expansion free displacer. Piston motion is controlled by feedback from an optical position transducer. Mechanical vibrations are attenuated with a passive resonant counterbalance. Electromagnetic noise is attenuated with layered high permeability magnetic shielding. The regenerators move with the displacer within a thin titanium cold finger. The piston and displacer oscillate at 8.33 Hz on bearings and seals of reinforced Teflon. The cooler is designed to provide the desired 50 mW of cooling at 10 K with a power input of less than 100 W. The piston can be driven at a greater stroke to produce up to 200 mW of cooling with an input power of 250 W. A lead and copper cold tip heat exchanger will limit temperature fluctuations to within 0.01 K.

A programming language for composable DNA circuits.

PubMed

Phillips, Andrew; Cardelli, Luca

2009-08-06

Recently, a range of information-processing circuits have been implemented in DNA by using strand displacement as their main computational mechanism. Examples include digital logic circuits and catalytic signal amplification circuits that function as efficient molecular detectors. As new paradigms for DNA computation emerge, the development of corresponding languages and tools for these paradigms will help to facilitate the design of DNA circuits and their automatic compilation to nucleotide sequences. We present a programming language for designing and simulating DNA circuits in which strand displacement is the main computational mechanism. The language includes basic elements of sequence domains, toeholds and branch migration, and assumes that strands do not possess any secondary structure. The language is used to model and simulate a variety of circuits, including an entropy-driven catalytic gate, a simple gate motif for synthesizing large-scale circuits and a scheme for implementing an arbitrary system of chemical reactions. The language is a first step towards the design of modelling and simulation tools for DNA strand displacement, which complements the emergence of novel implementation strategies for DNA computing.

Post seismic deformation associated with the 1992 Mω=7.3 Landers earthquake, southern California

USGS Publications Warehouse

Savage, J.C.; Svarc, J.L.

1997-01-01

Following the 1992 Mω=7.3 Landers earthquake, a linear array of 10 geodetic monuments at roughly 5-km spacing was established across the Emerson fault segment of the Landers rupture. The array trends perpendicular to the local strike of the fault segment and extends about 30 km on either side of it. The array was surveyed by Global Positioning System 0.034, 0.048, 0.381, 1.27, 1.88, 2.60, and 3.42 years after the Landers earthquake to measure both the spatial and temporal character of the postearthquake relaxation. The temporal behavior is described roughly by a short-term (decay time 84±23 days) exponential relaxation superimposed upon an apparently linear trend. Because the linear trend represents motions much more rapid than the observed preseismic motions, we attribute that trend to a slower (decay time greater than 5 years) postseismic relaxation, the curvature of which cannot be resolved in the short run (3.4 years) of postseismic data. About 100 mm of right-lateral displacement and 50 mm of fault-normal displacement accumulated across the geodetic array in the 3.4-year interval covered by the postseismic surveys. Those displacements are attributed to postseismic, right-lateral slip in the depth interval 10 to 30 km on the downward extension of the rupture trace. The right-lateral slip amounted to about 1 m directly beneath the geodetic array, and the fault-normal displacement is apparently primarily a consequence of the curvature of the rupture. These conclusions are based upon dislocation models fit to the observed deformation. However, no dislocation model was found with rms residuals as small as the expected observational error.

Transparent actuator made with few layer graphene electrode and dielectric elastomer, for variable focus lens

NASA Astrophysics Data System (ADS)

Hwang, Taeseon; Kwon, Hyeok-Yong; Oh, Joon-Suk; Hong, Jung-Pyo; Hong, Seung-Chul; Lee, Youngkwan; Ryeol Choi, Hyouk; Jin Kim, Kwang; Hossain Bhuiya, Mainul; Nam, Jae-Do

2013-07-01

A transparent dielectric elastomer actuator driven by few-layer-graphene (FLG) electrode was experimentally investigated. The electrodes were made of graphene, which was dispersed in N-methyl-pyrrolidone. The transparent actuator was fabricated from developed FLG electrodes. The FLG electrode with its sheet resistance of 0.45 kΩ/sq (80 nm thick) was implemented to mask silicone elastomer. The developed FLG-driven actuator exhibited an optical transparency of over 57% at a wavenumber of 600 nm and produced bending displacement performance ranging from 29 to 946 μm as functions of frequency and voltage. The focus variation was clearly demonstrated under actuation to study its application-feasibility in variable focus lens and various opto-electro-mechanical devices.

Discrimination of shot-noise-driven Poisson processes by external dead time - Application of radioluminescence from glass

NASA Technical Reports Server (NTRS)

Saleh, B. E. A.; Tavolacci, J. T.; Teich, M. C.

1981-01-01

Ways in which dead time can be used to constructively enhance or diminish the effects of point processes that display bunching in the shot-noise-driven doubly stochastic Poisson point process (SNDP) are discussed. Interrelations between photocount bunching arising in the SNDP and the antibunching character arising from dead-time effects are investigated. It is demonstrated that the dead-time-modified count mean and variance for an arbitrary doubly stochastic Poisson point process can be obtained from the Laplace transform of the single-fold and joint-moment-generating functions for the driving rate process. The theory is in good agreement with experimental values for radioluminescence radiation in fused silica, quartz, and glass, and the process has many applications in pulse, particle, and photon detection.

Stability of Buoyancy-Driven Gas Flow: Visualization of Coherent and Incoherent Gas Flow Patterns and Capillary Trapping

NASA Astrophysics Data System (ADS)

Geistlinger, H. W.; Samani, S.; Pohlert, M.; Jia, R.; Lazik, D.

2009-12-01

There are several mechanisms by which the CO2 can be stored: (1) In hydrodynamic trapping, the buoyant CO2 remains as a mobile fluid but is prevented from flowing back to the surface by an impermeable cap rock. (2) In solution trapping, CO2 dissolves into the brine, possibly enhanced by gravity instabilities due to the larger density of the brine-CO2 liquid mixture. (3) In mineral trapping, geochemical binding to the rock due to mineral precipitation. (4) In capillary trapping, the CO2 phase is disconnected into a coherent, mobile phase and an incoherent, immobile (trapped) phase. Recent analytical and numerical investigations [Juanes et al., 2006, 2009; Hesse et al., 2007 ] of buoyant-driven CO2-plume along a sloped aquifer are based on the following conceptual process model: (1) During the injection period, the less wetting CO2 displaces the more wetting brine in a drainage-like process. It is assumed that no capillary trapping occurs and that the CO2-network is coherent and driven both by the injection pressure and the buoyant pressure. Because of this coherence assumption a generalized Darcy-law can be used for the dynamics of the mobile, gaseous CO2-phase. (2) After injection the buoyant CO2 migrates laterally and upward, and water displaces CO2 at the trailing edge of the plume in an imbibition-like process. During this process, there are several physical mechanisms by which the water can displace the CO2 [Lenormand et al., 1983]. In addition to piston-type displacement, core-annular flow (also called: cooperative pore-body filling) may occur, i.e. the wetting phase moves along the walls and under certain conditions the CO2-core flow becomes unstable (snap-off). For water wet rocks, snap-off is the dominant mechanism [Al-Futaisi and Patzek, 2003; Valvatne and Blunt, 2004]. There seems to be consensus that the capillary trapping mechanism has a huge impact on the migration and distribution of CO2 which, in turn, affects the effectiveness of the other sequestration mechanisms. In order to investigate the stability of buoyancy-driven gas flow and the transition between coherent flow, incoherent flow, and their correlation to capillary trapping, we conducted high-resolution optical bench scale experiments. We observed a grain-size (dk) - and flow-rate (Q) dependent transition from incoherent to coherent flow. Based on core-annular flow (= cooperative pore-body filling), we propose a dynamic stability criterion that could describe our experimental results. Our experimental results for vertical gas flow support the experimental results by Lenormand et al. [1983] obtained for horizontal flow, if one takes into account that gravity leads to more unstable flow conditions. Our main results, which are in strong contradiction to the accepted conceptual model of the sloped aquifer, are: (1) Capillary Trapping can already occur during injection and at the front of the plume [Lazik et al., 2008] (2) Gas clusters or bubbles can be mobile (incoherent gas flow) and immobile (capillary trapping), and (3) Incoherent gas flow can not be described by a generalized Darcy law [Geistlinger et al., 2006, 2009].

Motion of the surface of the human tympanic membrane measured with stroboscopic holography

PubMed Central

Cheng, Jeffrey Tao; Aarnisalo, Antti A.; Harrington, Ellery; Hernandez-Montes, Maria del Socorro; Furlong, Cosme; Merchant, Saumil N.; Rosowski, John J.

2010-01-01

Sound-induced motion of the surface of the human tympanic membrane (TM) was studied by stroboscopic holographic interferometery, which measures the amplitude and phase of the displacement at each of about 40000 points on the surface of the TM. Measurements were made with tonal stimuli of 0.5, 1, 4 and 8 kHz. The magnitude and phase of the sinusoidal displacement of the TM at each driven frequency were derived from the fundamental Fourier component of the raw displacement data computed from stroboscopic holograms of the TM recorded at eight stimulus phases. The correlation between the Fourier estimates and measured motion data was generally above 0.9 over the entire TM surface. We used three data presentations: (i) Plots of the phasic displacements along a single chord across the surface of the TM, (ii) Phasic surface maps of the displacement of the entire TM surface, and (iii) Plots of the Fourier derived amplitude and phase-angle of the surface displacement along four diameter lines that define and bisect each of the four quadrants of the TM. These displays led to some common conclusions: At 0.5 and 1 kHz, the entire TM moved roughly in-phase with some small phase delay apparent between local areas of maximal displacement in the posterior half of the TM. At 4 and 8 kHz, the motion of the TM became more complicated with multiple local displacement maxima arranged in rings around the manubrium. The displacements at most of these maxima were roughly in-phase, while some moved out-of-phase. Superposed on this in- and out-of-phase behavior were significant cyclic variations in phase with location of less than 0.2 cycles or occasionally rapid half-cycle step-like changes in phase. The high frequency displacement amplitude and phase maps discovered in this study can not be explained by any single wave motion, but are consistent with a combination of low and higher order modal motions plus some small traveling-wave-like components. The observations of the dynamics of TM surface motion from this study will help us better understand the sound-receiving function of the TM and how it couples sound to the ossicular chain and inner ear. PMID:20034549

Shock wave oscillation driven by turbulent boundary layer fluctuations

NASA Technical Reports Server (NTRS)

Plotkin, K. J.

1972-01-01

Pressure fluctuations due to the interaction of a shock wave with a turbulent boundary layer were investigated. A simple model is proposed in which the shock wave is convected from its mean position by velocity fluctuations in the turbulent boundary layer. Displacement of the shock is assumed limited by a linear restoring mechanism. Predictions of peak root mean square pressure fluctuation and spectral density are in excellent agreement with available experimental data.

Disconnect unit

NASA Technical Reports Server (NTRS)

Alexander, P., Jr.; Mcdougal, A. R. (Inventor)

1973-01-01

A squib-actuated disconnect is characterized by an expandable collet axially extended from a first tension member for receiving in locking engagement a protuberance axially extended from a second tension member. A gas-driven retainer of an annular configuration is also locked in for supporting the collet in locking engagement with the protuberance. The protuberance is axially displaced in response to a firing of an associated squib for thus accommodating a disengagement of the protuberance and the collet.

Theory-Driven Models for Correcting Fight or Flight Imbalance in Gulf War Illness

DTIC Science & Technology

2011-09-01

testing on software • Performed static and dynamic analysis on safety code Research Interests To understand how the nervous system operates, how...dynamics of these systems to reset control of the HPA-immune axis to normal. We have completed the negotiation of sub-awards to the CFIDS Association...We propose that severe physical or psychological insult to the endocrine and immune systems can displace these from a normal regulatory equilibrium

Vibration Problems of Rotating Machinery due to Coupling Misalignments

DTIC Science & Technology

1988-05-01

driven couplings in which parallel but radially offset shafts are Joined, quite often through speed increasing or decreasing wheel ratios; 3) flexible...specified as offset or total indicator runout (TIR). Offset is defined as the amount one shaft is physically displaced from its *truely" aligned...position when measured from the other 0 shaft. Total indicator runout is the difference in dial indicator readings taken in a particular plane when the

Forced imbibition through model porous media

NASA Astrophysics Data System (ADS)

Odier, Celeste; Levache, Bertrand; Bartolo, Denis

2016-11-01

A number of industrial and natural process ultimately rely on two-phase flow in heterogeneous media. One of the most prominent example is oil recovery which has driven fundamental and applied research in this field for decades. Imbibition occurs when a wetting fluid displaces an immiscible fluid e.g. in a porous media. Using model microfluidic experiment we control both the geometry and wetting properties of the heterogenous media, and show that the typical front propagation picture fails when imbibition is forced and the displacing fluid is less viscous than the non-wetting fluid. We identify and quantitatively characterize four different flow regimes at the pore scale yielding markedly different imbibition patterns at large scales. In particular we will discuss the transition from a conventional 2D-front propagation scenario to a regime where the meniscus dynamics is an intrinsically 3D process.

Controlling Viscous Fingering Using Time-Dependent Strategies

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

Stone, Howard; Zheng, Zhong; Kim, Hyoungsoo

Control and stabilization of viscous fingering of immiscible fluids impacts a wide variety of pressure-driven multiphase flows. Here, we report theoretical and experimental results on time-dependent control strategy by manipulating the gap thickness b(t) in a lifting Hele-Shaw cell in the power-law form b(t) = b 1t 1/7. Experimental results show good quantitative agreement with the predictions of linear stability analysis. Furthermore, by choosing the value of a single time-independent control parameter we can either totally suppress the viscous fingering instability or maintain a series of non-splitting viscous fingers during the fluid displacement process. Besides the gap thickness of amore » Hele-Shaw cell, in principle, time-dependent control strategies can also be placed on the injection rate, viscosity of the displaced fluid, and interfacial tensions between the two fluids.« less

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

Costa, Liborio I., E-mail: liborio78@gmail.com

A new Markov Chain Monte Carlo method for simulating the dynamics of particle systems characterized by hard-core interactions is introduced. In contrast to traditional Kinetic Monte Carlo approaches, where the state of the system is associated with minima in the energy landscape, in the proposed method, the state of the system is associated with the set of paths traveled by the atoms and the transition probabilities for an atom to be displaced are proportional to the corresponding velocities. In this way, the number of possible state-to-state transitions is reduced to a discrete set, and a direct link between the Montemore » Carlo time step and true physical time is naturally established. The resulting rejection-free algorithm is validated against event-driven molecular dynamics: the equilibrium and non-equilibrium dynamics of hard disks converge to the exact results with decreasing displacement size.« less

Universality Results for Multi-phase Hele-Shaw Flows

NASA Astrophysics Data System (ADS)

Daripa, Prabir

2013-03-01

Saffman-Taylor instability is a well known viscosity driven instability of an interface separating two immiscible fluids. We study linear stability of displacement processes in a Hele-Shaw cell involving an arbitrary number of immiscible fluid phases. This is a problem involving many interfaces. Universal stability results have been obtained for this multi-phase immiscible flow in the sense that the results hold for arbitrary number of interfaces. These stability results have been applied to design displacement processes that are considerably less unstable than the pure Saffman-Taylor case. In particular, we derive universal formula which gives specific values of the viscosities of the fluid layers corresponding to smallest unstable band. Other similar universal results will also be presented. The talk is based on the following paper. This work was supported by the Qatar National Research Fund (a member of The Qatar Foundation).

Controlling Viscous Fingering Using Time-Dependent Strategies

DOE PAGES

Stone, Howard; Zheng, Zhong; Kim, Hyoungsoo

2015-10-20

Control and stabilization of viscous fingering of immiscible fluids impacts a wide variety of pressure-driven multiphase flows. Here, we report theoretical and experimental results on time-dependent control strategy by manipulating the gap thickness b(t) in a lifting Hele-Shaw cell in the power-law form b(t) = b 1t 1/7. Experimental results show good quantitative agreement with the predictions of linear stability analysis. Furthermore, by choosing the value of a single time-independent control parameter we can either totally suppress the viscous fingering instability or maintain a series of non-splitting viscous fingers during the fluid displacement process. Besides the gap thickness of amore » Hele-Shaw cell, in principle, time-dependent control strategies can also be placed on the injection rate, viscosity of the displaced fluid, and interfacial tensions between the two fluids.« less

Pathways to substance-related disorder: a structural model approach exploring the influence of temperament, character, and childhood adversity in a national cohort of prisoners.

PubMed

Lukasiewicz, Michael; Neveu, Xavier; Blecha, Lisa; Falissard, Bruno; Reynaud, Michel; Gasquet, Isabelle

2008-01-01

Using Cloninger's model of personality, we aimed to specify the relative influence of the more biologically determined variables, temperament and character and more environmentally driven influence, childhood adversity in the development of addiction; and to compare patterns found among alcoholics with those found among drug addicts. We studied a group of prisoners, at a high risk of substance abuse and past history of childhood adversity. Using a stratified random strategy we selected (i) 23 prisons among the different types of prison in France, (ii) 998 prisoners. Each prisoner was assessed by two psychiatrists--one junior, using a structured interview (MINI 5 plus), and one senior, completing the procedure with an open clinical interview. At the end of the interview the clinicians met and agreed on a list of diagnoses. Cloninger's Temperament and Character Inventory was used to measure personality. Structural equations models, which have been advocated to disentangle the respective influence of complex risk factors, were used. The "novelty seeking" temperament was a crucial vulnerability factor, for both alcoholics and drug addicts, in the same proportion. Character and childhood adversity played a significant part only in the development of drug abuse. In a prison population, a common biological loaded factor, novelty seeking is found both at the core of alcohol- and drug-related disorder whereas environmentally loaded factors play a greater role in drug problems.

Discrete and morphometric traits reveal contrasting patterns and processes in the macroevolutionary history of a clade of scorpions.

PubMed

Mongiardino Koch, N; Ceccarelli, F S; Ojanguren-Affilastro, A A; Ramírez, M J

2017-04-01

Many palaeontological studies have investigated the evolution of entire body plans, generally relying on discrete character-taxon matrices. In contrast, macroevolutionary studies performed by neontologists have mostly focused on morphometric traits. Although these data types are very different, some studies have suggested that they capture common patterns. Nonetheless, the tests employed to support this claim have not explicitly incorporated a phylogenetic framework and may therefore be susceptible to confounding effects due to the presence of common phylogenetic structure. We address this question using the scorpion genus Brachistosternus Pocock 1893 as case study. We make use of a time-calibrated multilocus molecular phylogeny, and compile discrete and traditional morphometric data sets, both capturing the overall morphology of the organisms. We find that morphospaces derived from these matrices are significantly different, and that the degree of discordance cannot be replicated by simulations of random character evolution. Moreover, we find strong support for contrasting modes of evolution, with discrete characters being congruent with an 'early burst' scenario whereas morphometric traits suggest species-specific adaptations to have driven morphological evolution. The inferred macroevolutionary dynamics are therefore contingent on the choice of character type. Finally, we confirm that metrics of correlation fail to detect these profound differences given common phylogenetic structure in both data sets, and that methods incorporating a phylogenetic framework and accounting for expected covariance should be favoured. © 2017 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2017 European Society For Evolutionary Biology.

Nonlinear optimal control policies for buoyancy-driven flows in the built environment

NASA Astrophysics Data System (ADS)

Nabi, Saleh; Grover, Piyush; Caulfield, Colm

2017-11-01

We consider optimal control of turbulent buoyancy-driven flows in the built environment, focusing on a model test case of displacement ventilation with a time-varying heat source. The flow is modeled using the unsteady Reynolds-averaged equations (URANS). To understand the stratification dynamics better, we derive a low-order partial-mixing ODE model extending the buoyancy-driven emptying filling box problem to the case of where both the heat source and the (controlled) inlet flow are time-varying. In the limit of a single step-change in the heat source strength, our model is consistent with that of Bower et al.. Our model considers the dynamics of both `filling' and `intruding' added layers due to a time-varying source and inlet flow. A nonlinear direct-adjoint-looping optimal control formulation yields time-varying values of temperature and velocity of the inlet flow that lead to `optimal' time-averaged temperature relative to appropriate objective functionals in a region of interest.

Effect of bromine-dopant on radiation-driven Rayleigh-Taylor instability in plastic foil

NASA Astrophysics Data System (ADS)

Xu, Binbin; Ma, Yanyun; Yang, Xiaohu; Tang, Wenhui; Ge, Zheyi; Zhao, Yuan; Ke, Yanzhao; Kawata, Shiego

2017-10-01

Effects of bromine (Br) dopant on the growth of radiation-driven ablative Rayleigh-Taylor instability (RTI) in plastic foils are studied by radiation hydrodynamics simulations and theoretical analysis. It is found that the Br-dopant in plastic foil reduces the seed of ablative RTI. The main reasons of the reduction are attributed to the smaller oscillation amplitude of ablative Richtmyer-Meshkov instability (RMI) induced by the smaller post-shock sound speed, and the smaller oscillation frequency of ablative RMI induced by the smaller ablation velocity and blow-off plasma velocity. The Br-dopant also decreases the linear growth rate of ablative RTI due to the smaller acceleration. Treating the perturbation growth as a function of foil’s displacement, the perturbation growth would increase in Br-doped foil at the phase of ablative RTI, which is attributed to the decrease of the ablation velocity and the density gradient scale length. The results are helpful for further understanding the influence of high-Z dopant on the radiation-driven ablative RTI.

Artificial muscles driven by the cooperative actuation of electrochemical molecular machines. Persistent discrepancies and challenges

NASA Astrophysics Data System (ADS)

Otero

2017-10-01

Here we review the persisting conceptual discrepancies between different research groups working on artificial muscles based on conducting polymers and other electroactive material. The basic question is if they can be treated as traditional electro-mechanical (physical) actuators driven by electric fields and described by some adaptation of their physical models or if, replicating natural muscles, they are electro-chemo-mechanical actuators driven by electrochemical reaction of the constitutive molecular machines: the polymeric chains. In that case the charge consumed by the reaction will control the volume variation of the muscular material and the motor displacement, following the basic and single Faraday's laws: the charge consumed by the reaction determines the number of exchanged ions and solvent, the film volume variation to lodge/expel them and the amplitude of the movement. Deviations from the linear relationships are due to the osmotic exchange of solvent and to the presence of parallel reactions from the electrolyte, which originate creeping effects. Challenges and limitations are underlined.

MEMS tactile display: from fabrication to characterization

NASA Astrophysics Data System (ADS)

Miki, Norihisa; Kosemura, Yumi; Watanabe, Junpei; Ishikawa, Hiroaki

2014-03-01

We report fabrication and characterization of MEMS-based tactile display that can display users various tactile information, such as Braille codes and surface textures. The display consists of 9 micro-actuators that are equipped with hydraulic displacement amplification mechanism (HDAM) to achieve large enough displacement to stimulate the human tactile receptors. HDAM encapsulates incompressible liquids. We developed a liquid encapsulation process, which we termed as Bonding-in-Liquid Technique, where bonding with a UV-curable resin in glycerin is conducted in the liquid, which prevented interfusion of air bubbles and deformation of the membrane during the bonding. HDAM successfully amplified the displacement generated by piezoelectric actuators by a factor of 6. The display could virtually produce "rough" and "smooth" surfaces, by controlling the vibration frequency, displacement, and the actuation periods of an actuator until the adjacent actuator was driven. We introduced a sample comparison method to characterize the surfaces, which involves human tactile sensation. First, we prepared samples whose mechanical properties are known. We displayed a surface texture to the user by controlling the parameters and then, the user selects a sample that has the most similar surface texture. By doing so, we can correlate the parameters with the mechanical properties of the sample as well as find the sets of the parameters that can provide similar tactile information to many users. The preliminary results with respect to roughness and hardness is presented.

Spatial instability of the rift in the St. Paul multifault transform fracture system, Atlantic Ocean

NASA Astrophysics Data System (ADS)

Sokolov, S. Yu.; Zaraiskaya, Yu. A.; Mazarovich, A. O.; Efimov, V. N.; Sokolov, N. S.

2016-05-01

The structure of the acoustic basement of the eastern part of the St. Paul multifault transform fracture system hosts rift paleovalleys and a paleonodal depression that mismatch the position of the currently active zones. This displacement zone, which is composed of five fault troughs, is unstable in terms of the position of the rift segments, which jumped according to redistribution of stresses. The St. Paul system is characterized by straightening of the transform transition between two remote segments of the Mid-Atlantic Ridge (MAR). The eastern part of the system contains anomalous bright-spot-like reflectors on the flattened basement, which is a result of atypical magmatism, that forms the standard ridge relief of the acoustic basement. Deformations of the acoustic basement have a presedimentation character. The present-day deformations with lower amplitude in comparison to the basement are accompanied by acoustic brightening of the sedimentary sequence. The axial Bouguer anomalies in the east of the system continue to the north for 120 km from the active segments of the St. Paul system. Currently seismically active segments of the spreading system are characterized by increasing amplitudes of the E-W displacement along the fault troughs. Cross-correlation of the lengths of the active structural elements of the MAR zone (segments of the ridge and transform fracture zones of displacement) indicates that, statistically, the multifault transform fracture system is a specific type of oceanic strike-slip faults.

Piezoelectric pushers for active vibration control of rotating machinery

NASA Technical Reports Server (NTRS)

Palazzolo, A. B.; Kascak, A. F.; Lin, R. R.; Montague, J.; Alexander, R. M.

1989-01-01

The active control of rotordynamic vibrations and stability by magnetic bearings and electromagnetic shakers was discussed extensively in the literature. These devices, though effective, are usually large in volume and add significant weight to the stator. The use of piezoelectric pushers may provide similar degrees of effectiveness in light, compact packages. Analyses are contained which extend quadratic regulator, pole placement and derivative feedback control methods to the prescribed displacement character of piezoelectric pushers. The structural stiffness of the pusher is also included in the theory. Tests are currently being conducted at NASA Lewis Research Center with piezoelectric pusher-based active vibration control. Results performed on the NASA test rig as preliminary verification of the related theory are presented.

Biomimetics and the case of the remarkable ragworms.

PubMed

Hesselberg, Thomas

2007-08-01

Biomimetics is a rapidly growing field both as an academic and as an applied discipline. This paper gives a short introduction to the current status of the discipline before it describes three approaches to biomimetics: the mechanism-driven, which is based on the study of a specific mechanism; the focused organism-driven, which is based on the study of one function in a model organism; and the integrative organism-driven approach, where multiple functions of a model organism provide inspiration. The first two are established approaches and include many modern studies and the famous biomimetic discoveries of Velcro and the Lotus-Effect, whereas the last approach is not yet well recognized. The advantages of the integrative organism-driven approach are discussed using the ragworms as a case study. A morphological and locomotory study of these marine polychaetes reveals their biomimetic potential, which includes using their ability to move in slippery substrates as inspiration for novel endoscopes, using their compound setae as models for passive friction structures and using their three gaits, slow crawling, fast crawling, and swimming as well as their rapid burrowing technique to provide inspiration for the design of displacement pumps and multifunctional robots.

Biomimetics and the case of the remarkable ragworms

NASA Astrophysics Data System (ADS)

Hesselberg, Thomas

2007-08-01

Biomimetics is a rapidly growing field both as an academic and as an applied discipline. This paper gives a short introduction to the current status of the discipline before it describes three approaches to biomimetics: the mechanism-driven, which is based on the study of a specific mechanism; the focused organism-driven, which is based on the study of one function in a model organism; and the integrative organism-driven approach, where multiple functions of a model organism provide inspiration. The first two are established approaches and include many modern studies and the famous biomimetic discoveries of Velcro and the Lotus-Effect, whereas the last approach is not yet well recognized. The advantages of the integrative organism-driven approach are discussed using the ragworms as a case study. A morphological and locomotory study of these marine polychaetes reveals their biomimetic potential, which includes using their ability to move in slippery substrates as inspiration for novel endoscopes, using their compound setae as models for passive friction structures and using their three gaits, slow crawling, fast crawling, and swimming as well as their rapid burrowing technique to provide inspiration for the design of displacement pumps and multifunctional robots.

The AGN-driven shock in NGC 4472

NASA Astrophysics Data System (ADS)

Gendron-Marsolais, Marie-Lou; Kraft, Ralph P.; Bogdan, Akos; Forman, William R.; Hlavacek-Larrondo, Julie; Jones, Christine; Nulsen, Paul; Randall, Scott W.; Roediger, Elke

2016-04-01

Chandra observations of most cool core clusters of galaxies have revealed large cavities where the inflation of the jet-driven radio bubbles displace the cluster gas. In a few cases, outburst shocks, likely driven by cavity inflation, are detected in the ambient gas. AGN-driven shocks may be key to balancing the radiative losses as shocks will increase the entropy of, and thereby heat, the diffuse gas. We will present initial results on deep Chandra observations of the nearby (D=17 Mpc) early-type massive elliptical galaxy NGC 4472, the most optically luminous galaxy in the local Universe, lying on the outskirts of the Virgo cluster. The X-ray observations show clear cavities in the X-ray emission at the position of the radio lobes, and rings of enhanced X-ray emission just beyond the lobes. We will present results from our analysis to determine whether the lobes are inflating supersonically or are rising buoyantly. We will compare the energy and power of this AGN outburst with previous powerful radio outbursts in clusters and groups to determine whether this outburst lies on the same scaling relations or whether it represents a new category of outburst.

External radioactive markers for PET data-driven respiratory gating in positron emission tomography.

PubMed

Büther, Florian; Ernst, Iris; Hamill, James; Eich, Hans T; Schober, Otmar; Schäfers, Michael; Schäfers, Klaus P

2013-04-01

Respiratory gating is an established approach to overcoming respiration-induced image artefacts in PET. Of special interest in this respect are raw PET data-driven gating methods which do not require additional hardware to acquire respiratory signals during the scan. However, these methods rely heavily on the quality of the acquired PET data (statistical properties, data contrast, etc.). We therefore combined external radioactive markers with data-driven respiratory gating in PET/CT. The feasibility and accuracy of this approach was studied for [(18)F]FDG PET/CT imaging in patients with malignant liver and lung lesions. PET data from 30 patients with abdominal or thoracic [(18)F]FDG-positive lesions (primary tumours or metastases) were included in this prospective study. The patients underwent a 10-min list-mode PET scan with a single bed position following a standard clinical whole-body [(18)F]FDG PET/CT scan. During this scan, one to three radioactive point sources (either (22)Na or (18)F, 50-100 kBq) in a dedicated holder were attached the patient's abdomen. The list mode data acquired were retrospectively analysed for respiratory signals using established data-driven gating approaches and additionally by tracking the motion of the point sources in sinogram space. Gated reconstructions were examined qualitatively, in terms of the amount of respiratory displacement and in respect of changes in local image intensity in the gated images. The presence of the external markers did not affect whole-body PET/CT image quality. Tracking of the markers led to characteristic respiratory curves in all patients. Applying these curves for gated reconstructions resulted in images in which motion was well resolved. Quantitatively, the performance of the external marker-based approach was similar to that of the best intrinsic data-driven methods. Overall, the gain in measured tumour uptake from the nongated to the gated images indicating successful removal of respiratory motion was correlated with the magnitude of the respiratory displacement of the respective tumour lesion, but not with lesion size. Respiratory information can be assessed from list-mode PET/CT through PET data-derived tracking of external radioactive markers. This information can be successfully applied to respiratory gating to reduce motion-related image blurring. In contrast to other previously described PET data-driven approaches, the external marker approach is independent of tumour uptake and thereby applicable even in patients with poor uptake and small tumours.

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

Juanes, Ruben

The overarching goal of this project was to develop a new continuum theory of multiphase flow in porous media. The theory follows a phase-field modeling approach, and therefore has a sound thermodynamical basis. It is a phenomenological theory in the sense that its formulation is driven by macroscopic phenomena, such as viscous instabilities during multifluid displacement. The research agenda was organized around a set of hypothesis on hitherto unexplained behavior of multiphase flow. All these hypothesis are nontrivial, and testable. Indeed, a central aspect of the project was testing each hypothesis by means of carefully-designed laboratory experiments, therefore probing themore » validity of the proposed theory. The proposed research places an emphasis on the fundamentals of flow physics, but is motivated by important energy-driven applications in earth sciences, as well as microfluidic technology.« less

Kinematic analysis of crank -cam mechanism of process equipment

NASA Astrophysics Data System (ADS)

Podgornyj, Yu I.; Skeeba, V. Yu; Martynova, T. G.; Pechorkina, N. S.; Skeeba, P. Yu

2018-03-01

This article discusses how to define the kinematic parameters of a crank-cam mechanism. Using the mechanism design, the authors have developed a calculation model and a calculation algorithm that allowed the definition of kinematic parameters of the mechanism, including crank displacements, angular velocities and acceleration, as well as driven link (rocker arm) angular speeds and acceleration. All calculations were performed using the Mathcad mathematical package. The results of the calculations are reported as numerical values.

Ellipsoidal Brownian self-driven particles in a magnetic field

NASA Astrophysics Data System (ADS)

Fan, Wai-Tong Louis; Pak, On Shun; Sandoval, Mario

2017-03-01

We study the two-dimensional Brownian dynamics of an ellipsoidal paramagnetic microswimmer moving at a low Reynolds number and subject to a magnetic field. Its corresponding mean-square displacement, showing the effect of a particles's shape, activity, and magnetic field on the microswimmer's diffusion, is analytically obtained. Comparison between analytical and computational results shows good agreement. In addition, the effect of self-propulsion on the transition time from anisotropic to isotropic diffusion of the ellipse is investigated.

Analytical Prediction of Motor Component Vibrations Driven by Acoustic Combustion Instability

DTIC Science & Technology

1976-02-01

27"V 1Sy 1 2 oiihedr41 Symmetry .. .. . ., . . C-28 3 SPCD Bulk Data Card Format ......... . . .. .- 29 4 CYJOIN Bulk Data Card Format...analysis, the loads, the values of enforced displacements, and the temperatures may vary from element to element. The SPCD bulk data card (Figure 3) is...Static loads for vech suhc’: -e are spcified with LOAD, ’TEMPERATURE (LOAD), or DE .-I, oiectic.-,!•. Enforced deformations may be specified on SPCD

Flow regimes for fluid injection into a confined porous medium

DOE PAGES

Zheng, Zhong; Guo, Bo; Christov, Ivan C.; ...

2015-02-24

We report theoretical and numerical studies of the flow behaviour when a fluid is injected into a confined porous medium saturated with another fluid of different density and viscosity. For a two-dimensional configuration with point source injection, a nonlinear convection–diffusion equation is derived to describe the time evolution of the fluid–fluid interface. In the early time period, the fluid motion is mainly driven by the buoyancy force and the governing equation is reduced to a nonlinear diffusion equation with a well-known self-similar solution. In the late time period, the fluid flow is mainly driven by the injection, and the governingmore » equation is approximated by a nonlinear hyperbolic equation that determines the global spreading rate; a shock solution is obtained when the injected fluid is more viscous than the displaced fluid, whereas a rarefaction wave solution is found when the injected fluid is less viscous. In the late time period, we also obtain analytical solutions including the diffusive term associated with the buoyancy effects (for an injected fluid with a viscosity higher than or equal to that of the displaced fluid), which provide the structure of the moving front. Numerical simulations of the convection–diffusion equation are performed; the various analytical solutions are verified as appropriate asymptotic limits, and the transition processes between the individual limits are demonstrated.« less

Identifying Time Periods of Minimal Thermal Gradient for Temperature-Driven Structural Health Monitoring

PubMed Central

Reilly, John; Glisic, Branko

2018-01-01

Temperature changes play a large role in the day to day structural behavior of structures, but a smaller direct role in most contemporary Structural Health Monitoring (SHM) analyses. Temperature-Driven SHM will consider temperature as the principal driving force in SHM, relating a measurable input temperature to measurable output generalized strain (strain, curvature, etc.) and generalized displacement (deflection, rotation, etc.) to create three-dimensional signatures descriptive of the structural behavior. Identifying time periods of minimal thermal gradient provides the foundation for the formulation of the temperature–deformation–displacement model. Thermal gradients in a structure can cause curvature in multiple directions, as well as non-linear strain and stress distributions within the cross-sections, which significantly complicates data analysis and interpretation, distorts the signatures, and may lead to unreliable conclusions regarding structural behavior and condition. These adverse effects can be minimized if the signatures are evaluated at times when thermal gradients in the structure are minimal. This paper proposes two classes of methods based on the following two metrics: (i) the range of raw temperatures on the structure, and (ii) the distribution of the local thermal gradients, for identifying time periods of minimal thermal gradient on a structure with the ability to vary the tolerance of acceptable thermal gradients. The methods are tested and validated with data collected from the Streicker Bridge on campus at Princeton University. PMID:29494496

Role of the AP2 β-Appendage Hub in Recruiting Partners for Clathrin-Coated Vesicle Assembly

PubMed Central

Burtey, Anne; Praefcke, Gerrit J. K; Peak-Chew, Sew-Yeu; Mills, Ian G; Benmerah, Alexandre; McMahon, Harvey T

2006-01-01

Adaptor protein complex 2 α and β-appendage domains act as hubs for the assembly of accessory protein networks involved in clathrin-coated vesicle formation. We identify a large repertoire of β-appendage interactors by mass spectrometry. These interact with two distinct ligand interaction sites on the β-appendage (the “top” and “side” sites) that bind motifs distinct from those previously identified on the α-appendage. We solved the structure of the β-appendage with a peptide from the accessory protein Eps15 bound to the side site and with a peptide from the accessory cargo adaptor β-arrestin bound to the top site. We show that accessory proteins can bind simultaneously to multiple appendages, allowing these to cooperate in enhancing ligand avidities that appear to be irreversible in vitro. We now propose that clathrin, which interacts with the β-appendage, achieves ligand displacement in vivo by self-polymerisation as the coated pit matures. This changes the interaction environment from liquid-phase, affinity-driven interactions, to interactions driven by solid-phase stability (“matricity”). Accessory proteins that interact solely with the appendages are thereby displaced to areas of the coated pit where clathrin has not yet polymerised. However, proteins such as β-arrestin (non-visual arrestin) and autosomal recessive hypercholesterolemia protein, which have direct clathrin interactions, will remain in the coated pits with their interacting receptors. PMID:16903783

Proposed design modifications to reduce risk of operating rotary field mowers.

PubMed

White, K L; Wells, L G; Shearer, S A; Piercy, L R

2000-11-01

The primary objective of this project was to reduce risk of injury associated with operating a rotary mower driven by a tractor power take-off (PTO) by developing and evaluating design improvements and determining their economic feasibility. Researchers have concluded that alteration of machinery design has a greater impact on the reduction of accidents than safety training. Implementation of an Operator Presence Sensing System (OPSS) and removal of the PTO are the two injury-reducing, engineering modifications evaluated by this research. Hydraulic power allows this to occur by providing dynamic braking, few moving parts (removal of the PTO), and controllable power. A hydraulic circuit was developed to power the mower and to enable an OPSS. Tractor hydraulics were simulated using a hydraulic training bench. Two mower configurations were tested: 6.55 cm3 rev(-1) (0.4 in.3 rev(-1)) displacement motor with a 0.748 kg blade and 47.5 cm3 rev(-1) (2.9 in.3 rev(-1)) displacement motor with a 9.4 kg blade. A PTO-driven rotary mower was not used to test the circuit due to spatial and safety limitations of the hydraulic training bench. Results from the first mower configuration verified the concepts behind the hydraulic circuit. The second configuration verified the OPSS and indicated the applicability of the circuit to a rotary mower.

Identifying Time Periods of Minimal Thermal Gradient for Temperature-Driven Structural Health Monitoring.

PubMed

Reilly, John; Glisic, Branko

2018-03-01

Temperature changes play a large role in the day to day structural behavior of structures, but a smaller direct role in most contemporary Structural Health Monitoring (SHM) analyses. Temperature-Driven SHM will consider temperature as the principal driving force in SHM, relating a measurable input temperature to measurable output generalized strain (strain, curvature, etc.) and generalized displacement (deflection, rotation, etc.) to create three-dimensional signatures descriptive of the structural behavior. Identifying time periods of minimal thermal gradient provides the foundation for the formulation of the temperature-deformation-displacement model. Thermal gradients in a structure can cause curvature in multiple directions, as well as non-linear strain and stress distributions within the cross-sections, which significantly complicates data analysis and interpretation, distorts the signatures, and may lead to unreliable conclusions regarding structural behavior and condition. These adverse effects can be minimized if the signatures are evaluated at times when thermal gradients in the structure are minimal. This paper proposes two classes of methods based on the following two metrics: (i) the range of raw temperatures on the structure, and (ii) the distribution of the local thermal gradients, for identifying time periods of minimal thermal gradient on a structure with the ability to vary the tolerance of acceptable thermal gradients. The methods are tested and validated with data collected from the Streicker Bridge on campus at Princeton University.

Orbital Dimer Model for the Spin-Glass State in Y 2 Mo 2 O 7

DOE PAGES

Thygesen, Peter M. M.; Paddison, Joseph A. M.; Zhang, Ronghuan; ...

2017-02-08

The formation of a spin glass generally requires that magnetic exchange interactions are both frustrated and disordered. Consequently, the origin of spin-glass behavior in Y 2Mo 2O 7-in which magnetic Mo 4+ ions occupy a frustrated pyrochlore lattice with minimal compositional disorder-has been a longstanding question. Here, we use neutron and x-ray pair-distribution function (PDF) analysis to develop a disorder model that resolves apparent incompatibilities between previously reported PDF, extended x-rayabsorption fine structure spectroscopy, and NMR studies, and provides a new and physical explanation of the exchange disorder responsible for spin-glass formation. We show that Mo 4+ ions displace accordingmore » to a local "two-in-two-out" rule on each Mo 4 tetrahedron, driven by orbital dimerization of Jahn-Teller active Mo 4+ ions. Long-range orbital order is prevented by the macroscopic degeneracy of dimer coverings permitted by the pyrochlore lattice. Cooperative O 2- displacements yield a distribution of Mo-O-Mo angles, which in turn introduces disorder into magnetic interactions. In conclusion, our study demonstrates experimentally how frustration of atomic displacements can assume the role of compositional disorder in driving a spin-glass transition.« less

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

Thygesen, Peter M. M.; Paddison, Joseph A. M.; Zhang, Ronghuan

The formation of a spin glass generally requires that magnetic exchange interactions are both frustrated and disordered. Consequently, the origin of spin-glass behavior in Y 2Mo 2O 7-in which magnetic Mo 4+ ions occupy a frustrated pyrochlore lattice with minimal compositional disorder-has been a longstanding question. Here, we use neutron and x-ray pair-distribution function (PDF) analysis to develop a disorder model that resolves apparent incompatibilities between previously reported PDF, extended x-rayabsorption fine structure spectroscopy, and NMR studies, and provides a new and physical explanation of the exchange disorder responsible for spin-glass formation. We show that Mo 4+ ions displace accordingmore » to a local "two-in-two-out" rule on each Mo 4 tetrahedron, driven by orbital dimerization of Jahn-Teller active Mo 4+ ions. Long-range orbital order is prevented by the macroscopic degeneracy of dimer coverings permitted by the pyrochlore lattice. Cooperative O 2- displacements yield a distribution of Mo-O-Mo angles, which in turn introduces disorder into magnetic interactions. In conclusion, our study demonstrates experimentally how frustration of atomic displacements can assume the role of compositional disorder in driving a spin-glass transition.« less

Orbital Dimer Model for the Spin-Glass State in Y_{2}Mo_{2}O_{7}.

PubMed

Thygesen, Peter M M; Paddison, Joseph A M; Zhang, Ronghuan; Beyer, Kevin A; Chapman, Karena W; Playford, Helen Y; Tucker, Matthew G; Keen, David A; Hayward, Michael A; Goodwin, Andrew L

2017-02-10

The formation of a spin glass generally requires that magnetic exchange interactions are both frustrated and disordered. Consequently, the origin of spin-glass behavior in Y_{2}Mo_{2}O_{7}-in which magnetic Mo^{4+} ions occupy a frustrated pyrochlore lattice with minimal compositional disorder-has been a longstanding question. Here, we use neutron and x-ray pair-distribution function (PDF) analysis to develop a disorder model that resolves apparent incompatibilities between previously reported PDF, extended x-ray-absorption fine structure spectroscopy, and NMR studies, and provides a new and physical explanation of the exchange disorder responsible for spin-glass formation. We show that Mo^{4+} ions displace according to a local "two-in-two-out" rule on each Mo_{4} tetrahedron, driven by orbital dimerization of Jahn-Teller active Mo^{4+} ions. Long-range orbital order is prevented by the macroscopic degeneracy of dimer coverings permitted by the pyrochlore lattice. Cooperative O^{2-} displacements yield a distribution of Mo-O-Mo angles, which in turn introduces disorder into magnetic interactions. Our study demonstrates experimentally how frustration of atomic displacements can assume the role of compositional disorder in driving a spin-glass transition.

Thermal noise and optomechanical features in the emission of a membrane-coupled compound cavity laser diode.

PubMed

Baldacci, Lorenzo; Pitanti, Alessandro; Masini, Luca; Arcangeli, Andrea; Colangelo, Francesco; Navarro-Urrios, Daniel; Tredicucci, Alessandro

2016-08-19

We demonstrate the use of a compound optical cavity as linear displacement detector, by measuring the thermal motion of a silicon nitride suspended membrane acting as the external mirror of a near-infrared Littrow laser diode. Fluctuations in the laser optical power induced by the membrane vibrations are collected by a photodiode integrated within the laser, and then measured with a spectrum analyzer. The dynamics of the membrane driven by a piezoelectric actuator is investigated as a function of air pressure and actuator displacement in a homodyne configuration. The high Q-factor (~3.4 · 10(4) at 8.3 · 10(-3) mbar) of the fundamental mechanical mode at ~73 kHz guarantees a detection sensitivity high enough for direct measurement of thermal motion at room temperature (~87 pm RMS). The compound cavity system here introduced can be employed as a table-top, cost-effective linear displacement detector for cavity optomechanics. Furthermore, thanks to the strong optical nonlinearities of the laser compound cavity, these systems open new perspectives in the study of non-Markovian quantum properties at the mesoscale.

The Syrian public health and humanitarian crisis: A 'displacement' in global governance?

PubMed

Akbarzada, Sumaira; Mackey, Tim K

2018-07-01

Ongoing failure by the international community to resolve the Syrian conflict has led to destruction of critical infrastructure. This includes the collapse of the Syrian health system, leaving millions of internally displaced persons (IDPs) in urgent need of healthcare services. As the conflict intensifies, IDP populations are suffering from infectious and non-communicable disease risks, poor maternal and child health outcomes, trauma, and mental health issues, while healthcare workers continually exit the country. Healthcare workers who remain face significant challenges, including systematic attacks on healthcare facilities and conditions that severely inhibit healthcare delivery and assistance. Within this conflict-driven public health crisis, the most susceptible population is arguably the IDP. Though the fundamental 'right to health' is a recognised international legal principle, its application is inadequate due to limited recognition by the UN Security Council and stymied global governance by the broader international community. These factors have also negatively impacted other vulnerable groups other than IDPs, such as refugees and ethnic minorities, who may or may not be displaced. Hence, this article reviews the current Syrian conflict, assesses challenges with local and global governance for IDPs, and explores potential governance solutions needed to address this health and humanitarian crisis.

Fluid-structural dynamics of ground-based and microgravity caloric tests

NASA Technical Reports Server (NTRS)

Kassemi, M.; Oas, J. G.; Deserranno, Dimitri

2005-01-01

Microgravity caloric tests aboard the 1983 SpaceLab1 mission produced nystagmus results with an intensity comparable to those elicited during post- and pre- flight tests, thus contradicting the basic premise of Barany's convection hypothesis for caloric stimulation. In this work, we present a dynamic fluid structural analysis of the caloric stimulation of the lateral semicircular canal based on two simultaneous driving forces for the endolymphatic flow: natural convection driven by the temperature-dependent density variation in the bulk fluid and expansive convection caused by direct volumetric displacement of the endolymph during the thermal irrigation. Direct numerical simulations indicate that on earth, the natural convection mechanism is dominant. But in the microgravity environment of orbiting spacecraft, where buoyancy effects are mitigated, expansive convection becomes the sole mechanism for producing cupular displacement. A series of transient 1 g and microgravity case studies are presented to delineate the differences between the dynamics of the 1 g and microgravity endolymphatic flows. The impact of these different flow dynamics on the endolymph-cupula fluid-structural interactions is also analyzed based on the time evolutions of cupular displacement and velocity and the transcupular pressure differences.

Fluid-structural dynamics of ground-based and microgravity caloric tests.

PubMed

Kassemi, M; Oas, J G; Deserranno, Dimitri

2005-01-01

Microgravity caloric tests aboard the 1983 SpaceLab1 mission produced nystagmus results with an intensity comparable to those elicited during post- and pre- flight tests, thus contradicting the basic premise of Barany's convection hypothesis for caloric stimulation. In this work, we present a dynamic fluid structural analysis of the caloric stimulation of the lateral semicircular canal based on two simultaneous driving forces for the endolymphatic flow: natural convection driven by the temperature-dependent density variation in the bulk fluid and expansive convection caused by direct volumetric displacement of the endolymph during the thermal irrigation. Direct numerical simulations indicate that on earth, the natural convection mechanism is dominant. But in the microgravity environment of orbiting spacecraft, where buoyancy effects are mitigated, expansive convection becomes the sole mechanism for producing cupular displacement. A series of transient 1 g and microgravity case studies are presented to delineate the differences between the dynamics of the 1 g and microgravity endolymphatic flows. The impact of these different flow dynamics on the endolymph-cupula fluid-structural interactions is also analyzed based on the time evolutions of cupular displacement and velocity and the transcupular pressure differences.

Thermal noise and optomechanical features in the emission of a membrane-coupled compound cavity laser diode

PubMed Central

Baldacci, Lorenzo; Pitanti, Alessandro; Masini, Luca; Arcangeli, Andrea; Colangelo, Francesco; Navarro-Urrios, Daniel; Tredicucci, Alessandro

2016-01-01

We demonstrate the use of a compound optical cavity as linear displacement detector, by measuring the thermal motion of a silicon nitride suspended membrane acting as the external mirror of a near-infrared Littrow laser diode. Fluctuations in the laser optical power induced by the membrane vibrations are collected by a photodiode integrated within the laser, and then measured with a spectrum analyzer. The dynamics of the membrane driven by a piezoelectric actuator is investigated as a function of air pressure and actuator displacement in a homodyne configuration. The high Q-factor (~3.4 · 104 at 8.3 · 10−3 mbar) of the fundamental mechanical mode at ~73 kHz guarantees a detection sensitivity high enough for direct measurement of thermal motion at room temperature (~87 pm RMS). The compound cavity system here introduced can be employed as a table-top, cost-effective linear displacement detector for cavity optomechanics. Furthermore, thanks to the strong optical nonlinearities of the laser compound cavity, these systems open new perspectives in the study of non-Markovian quantum properties at the mesoscale. PMID:27538586

High-order harmonic generation driven by inhomogeneous plasmonics fields spatially bounded: influence on the cut-off law

NASA Astrophysics Data System (ADS)

Neyra, E.; Videla, F.; Ciappina, M. F.; Pérez-Hernández, J. A.; Roso, L.; Lewenstein, M.; Torchia, G. A.

2018-03-01

We study high-order harmonic generation (HHG) in model atoms driven by plasmonic-enhanced fields. These fields result from the illumination of plasmonic nanostructures by few-cycle laser pulses. We demonstrate that the spatial inhomogeneous character of the laser electric field, in a form of Gaussian-shaped functions, leads to an unexpected relationship between the HHG cutoff and the laser wavelength. Precise description of the spatial form of the plasmonic-enhanced field allows us to predict this relationship. We combine the numerical solutions of the time-dependent Schrödinger equation (TDSE) with the plasmonic-enhanced electric fields obtained from 3D finite element simulations. We additionally employ classical simulations to supplement the TDSE outcomes and characterize the extended HHG spectra by means of their associated electron trajectories. A proper definition of the spatially inhomogeneous laser electric field is instrumental to accurately describe the underlying physics of HHG driven by plasmonic-enhanced fields. This characterization opens up new perspectives for HHG control with various experimental nano-setups.

The effect of stereochemistry on the thermodynamic characteristics of the binding of fenoterol stereoisomers to the β2-adrenoceptor

PubMed Central

Jozwiak, Krzysztof; Toll, Lawrence; Jimenez, Lucita; Woo, Anthony Yiu-Ho; Xiao, Rui-Ping; Wainer, Irving W.

2010-01-01

The binding thermodynamics of the stereoisomers of fenoterol, (R,R')-, (S,S')- , (R,S')-, and (S,R')-fenoterol, to the β2-adrenergic receptor (β2-AR) have been determined. The experiments utilized membranes obtained from HEK cells stably transfected with cDNA encoding human β2-AR. Competitive displacement studies using [3H]CGP-12177 as the marker ligand were conducted at 4°, 15°, 25°, 30° and 37°C, the binding affinities calculated and the standard enthalpic (ΔH°) and standard entropic (ΔS°) contribution to the standard free energy change (ΔG°) associated with the binding process determined through the construction of van't Hoff plots. The results indicate that the binding of (S,S')- and (S,R')-fenoterol were predominately enthalpy-driven processes while the binding of (R,R')- and (R,S')-fenoterol were entropy-driven. All of the fenoterol stereoisomers are full agonists of the β2-AR, and, therefore, the results of this study are inconsistent with the previously described “thermodynamic agonist-antagonist discrimination”, in which the binding of an agonist to the β-AR is entropy-driven and the binding of an antagonist is enthalpy driven. In addition, the data demonstrate that the chirality of the carbon atom containing the β-hydroxyl group of the fenoterol molecule (the β-OH carbon) is a key factor in the determination of whether the binding process will be enthalpy-driven or entropy-driven. When the configuration at the β-OH carbon is S the binding process is enthalpy-driven while the R configuration produces an entropy-driven process. PMID:20144591

The effect of stereochemistry on the thermodynamic characteristics of the binding of fenoterol stereoisomers to the beta(2)-adrenoceptor.

PubMed

Jozwiak, Krzysztof; Toll, Lawrence; Jimenez, Lucita; Woo, Anthony Yiu-Ho; Xiao, Rui-Ping; Wainer, Irving W

2010-06-01

The binding thermodynamics of the stereoisomers of fenoterol, (R,R')-, (S,S')-, (R,S')-, and (S,R')-fenoterol, to the beta(2)-adrenergic receptor (beta(2)-AR) have been determined. The experiments utilized membranes obtained from HEK cells stably transfected with cDNA encoding human beta(2)-AR. Competitive displacement studies using [(3)H]CGP-12177 as the marker ligand were conducted at 4, 15, 25, 30 and 37 degrees C, the binding affinities calculated and the standard enthalpic (DeltaH degrees ) and standard entropic (DeltaS degrees ) contribution to the standard free energy change (DeltaG degrees ) associated with the binding process determined through the construction of van't Hoff plots. The results indicate that the binding of (S,S')- and (S,R')-fenoterol were predominately enthalpy-driven processes while the binding of (R,R')- and (R,S')-fenoterol were entropy-driven. All of the fenoterol stereoisomers are full agonists of the beta(2)-AR, and, therefore, the results of this study are inconsistent with the previously described "thermodynamic agonist-antagonist discrimination", in which the binding of an agonist to the beta-AR is entropy-driven and the binding of an antagonist is enthalpy-driven. In addition, the data demonstrate that the chirality of the carbon atom containing the beta-hydroxyl group of the fenoterol molecule (the beta-OH carbon) is a key factor in the determination of whether the binding process will be enthalpy-driven or entropy-driven. When the configuration at the beta-OH carbon is S the binding process is enthalpy-driven while the R configuration produces an entropy-driven process. Published by Elsevier Inc.

Programmable Regulation of DNA Conjugation to Gold Nanoparticles via Strand Displacement.

PubMed

Zhang, Cheng; Wu, Ranfeng; Li, Yifan; Zhang, Qiang; Yang, Jing

2017-10-31

Methods for conjugating DNA to gold nanoparticles (AuNPs) have recently attracted considerable attention. The ability to control such conjugation in a programmable way is of great interest. Here, we have developed a logic-based method for manipulating the conjugation of thiolated DNA species to AuNPs via cascading DNA strand displacement. Using this method, several logic-based operation systems are established and up to three kinds of DNA signals are introduced at the same time. In addition, a more sensitive catalytic logic-based operation is also achieved based on an entropy-driven process. In the experiment, all of the DNA/AuNPs conjugation results are verified by agrose gel. This strategy promises great potential for automatically conjugating DNA stands onto label-free gold nanoparticles and can be extended to constructing DNA/nanoparticle devices for applications in diagnostics, biosensing, and molecular robotics.

Shape and Displacement Fluctuations in Soft Vesicles Filled by Active Particles

PubMed Central

Paoluzzi, Matteo; Di Leonardo, Roberto; Marchetti, M. Cristina; Angelani, Luca

2016-01-01

We investigate numerically the dynamics of shape and displacement fluctuations of two-dimensional flexible vesicles filled with active particles. At low concentration most of the active particles accumulate at the boundary of the vesicle where positive particle number fluctuations are amplified by trapping, leading to the formation of pinched spots of high density, curvature and pressure. At high concentration the active particles cover the vesicle boundary almost uniformly, resulting in fairly homogeneous pressure and curvature, and nearly circular vesicle shape. The change between polarized and spherical shapes is driven by the number of active particles. The center-of-mass of the vesicle performs a persistent random walk with a long time diffusivity that is strongly enhanced for elongated active particles due to orientational correlations in their direction of propulsive motion. In our model shape-shifting induces directional sensing and the cell spontaneously migrate along the polarization direction. PMID:27678166

Electron-Beam Dynamics for an Advanced Flash-Radiography Accelerator

DOE PAGES

Ekdahl, Carl

2015-11-17

Beam dynamics issues were assessed for a new linear induction electron accelerator being designed for multipulse flash radiography of large explosively driven hydrodynamic experiments. Special attention was paid to equilibrium beam transport, possible emittance growth, and beam stability. Especially problematic would be high-frequency beam instabilities that could blur individual radiographic source spots, low-frequency beam motion that could cause pulse-to-pulse spot displacement, and emittance growth that could enlarge the source spots. Furthermore, beam physics issues were examined through theoretical analysis and computer simulations, including particle-in-cell codes. Beam instabilities investigated included beam breakup, image displacement, diocotron, parametric envelope, ion hose, and themore » resistive wall instability. The beam corkscrew motion and emittance growth from beam mismatch were also studied. It was concluded that a beam with radiographic quality equivalent to the present accelerators at Los Alamos National Laboratory will result if the same engineering standards and construction details are upheld.« less

Hydrodynamic Fingering Instability Induced by a Precipitation Reaction

NASA Astrophysics Data System (ADS)

Nagatsu, Y.; Ishii, Y.; Tada, Y.; De Wit, A.

2014-07-01

We experimentally demonstrate that a precipitation reaction at the miscible interface between two reactive solutions can trigger a hydrodynamic instability due to the buildup of a locally adverse mobility gradient related to a decrease in permeability. The precipitate results from an A +B→C type of reaction when a solution containing one of the reactants is injected into a solution of the other reactant in a porous medium or a Hele-Shaw cell. Fingerlike precipitation patterns are observed upon displacement, the properties of which depend on whether A displaces B or vice versa. A mathematical modeling of the underlying mobility profile confirms that the instability originates from a local decrease in mobility driven by the localized precipitation. Nonlinear simulations of the related reaction-diffusion-convection model reproduce the properties of the instability observed experimentally. In particular, the simulations suggest that differences in diffusivity between A and B may contribute to the asymmetric characteristics of the fingering precipitation patterns.

Aphanius arakensis, a new species of tooth-carp (Actinopterygii, Cyprinodontidae) from the endorheic Namak Lake basin in Iran.

PubMed

Teimori, Azad; Esmaeili, Hamid Reza; Gholami, Zeinab; Zarei, Neda; Reichenbacher, Bettina

2012-01-01

A new species of tooth-carp, Aphanius arakensissp. n., is described from the Namak Lake basin in Iran. The new species is distinguished by the congeners distributed in Iran by the following combination of characters: 10-12 anal fin rays, 28-32 lateral line scales, 10-13 caudal peduncle scales, 8-10 gill rakers, 12-19, commonly 15-16, clearly defined flank bars in males, a more prominent pigmentation along the flank added by relatively big blotches in the middle and posterior flank segments in females, a short but high antirostrum of the otolith that has a wide excisura, and a ventral rim with some small, drop-like processes, and 19 molecular apomorphies (17 transitions, two transversions) in the cytochrome b gene. It was suggested based on the phylogenetic analysis that the new species is sister to Aphanius sophiae from the Kor River and that Aphanius farsicus from the Maharlu Lake basin is sister to Aphanius arakensis plus Aphanius sophiae. A noticeable feature of the Aphanius diversity in Iran is the conservatism of the external morphology as well as morphometric and meristic characters, while distinctive differences are present in genetic characters, otolith morphology, and male color pattern. Transformation of the latter was probably driven by sexual selection.

Chemical communication, sexual selection, and introgression in wall lizards.

PubMed

MacGregor, Hannah E A; Lewandowsky, Rachel A M; d'Ettorre, Patrizia; Leroy, Chloé; Davies, Noel W; While, Geoffrey M; Uller, Tobias

2017-10-01

Divergence in communication systems should influence the likelihood that individuals from different lineages interbreed, and consequently shape the direction and rate of hybridization. Here, we studied the role of chemical communication in hybridization, and its contribution to asymmetric and sexually selected introgression between two lineages of the common wall lizard (Podarcis muralis). Males of the two lineages differed in the chemical composition of their femoral secretions. Chemical profiles provided information regarding male secondary sexual characters, but the associations were variable and inconsistent between lineages. In experimental contact zones, chemical composition was weakly associated with male reproductive success, and did not predict the likelihood of hybridization. Consistent with these results, introgression of chemical profiles in a natural hybrid zone resembled that of neutral nuclear genetic markers overall, but one compound in particular (tocopherol methyl ether) matched closely the introgression of visual sexual characters. These results imply that associations among male chemical profiles, sexual characters, and reproductive success largely reflect transient and environmentally driven effects, and that genetic divergence in chemical composition is largely neutral. We therefore suggest that femoral secretions in wall lizards primarily provide information about residency and individual identity rather than function as sexual signals. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

Geographic variation in advertisement calls of a Microhylid frog - testing the role of drift and ecology.

PubMed

Lee, Ko-Huan; Shaner, Pei-Jen L; Lin, Yen-Po; Lin, Si-Min

2016-05-01

Acoustic signals for mating are important traits that could drive population differentiation and speciation. Ecology may play a role in acoustic divergence through direct selection (e.g., local adaptation to abiotic environment), constraint of correlated traits (e.g., acoustic traits linked to another trait under selection), and/or interspecific competition (e.g., character displacement). However, genetic drift alone can also drive acoustic divergence. It is not always easy to differentiate the role of ecology versus drift in acoustic divergence. In this study, we tested the role of ecology and drift in shaping geographic variation in the advertisement calls of Microhyla fissipes. We examined three predictions based on ecological processes: (1) the correlation between temperature and call properties across M. fissipes populations; (2) the correlation between call properties and body size across M. fissipes populations; and (3) reproductive character displacement (RCD) in call properties between M. fissipes populations that are sympatric with and allopatric to a congener M. heymonsi. To test genetic drift, we examined correlations among call divergence, geographic distance, and genetic distance across M. fissipes populations. We recorded the advertisement calls from 11 populations of M. fissipes in Taiwan, five of which are sympatrically distributed with M. heymonsi. We found geographic variation in both temporal and spectral properties of the advertisement calls of M. fissipes. However, the call properties were not correlated with local temperature or the callers' body size. Furthermore, we did not detect RCD. By contrast, call divergence, geographic distance, and genetic distance between M. fissipes populations were all positively correlated. The comparisons between phenotypic Q st (P st) and F st values did not show significant differences, suggesting a role of drift. We concluded that genetic drift, rather than ecological processes, is the more likely driver for the geographic variation in the advertisement calls of M. fissipes.

Development of a Compact Efficient Cooling Pump for Space Suit Life Support Systems

NASA Technical Reports Server (NTRS)

vanBoeyen, Roger W.; Reeh, Jonathan A.; Trevino, Luis

2008-01-01

With the increasing demands placed on extravehicular activity (EVA) for the International Space Station (ISS) assembly and maintenance, along with planned lunar and Martian missions, the need for increased human productivity and capability becomes ever more critical. This is most readily achieved by reduction in space suit weight and volume, and increased hardware reliability, durability, and operating lifetime. Considerable progress has been made with each successive generation of space suit design; from the Apollo A7L suit, to the current Shuttle Extravehicular Mobile Unit (EMU) suit, and the next generation Constellation Space Suit Element (CSSE). However, one area of space suit design which has continued to lag is the fluid pump used to drive the water cooling loop of the Primary Life Support System (PLSS). The two main types of fluid pumps typically used in space applications are rotodynamic pumps (pumping is achieved through a rotary vaned impeller) and displacement pumps (which includes rotary and diaphragm pumps). The rotating and moving parts found in the pumps and electric motor add significantly to the susceptibility to wear and friction, thermal mismatch, and complexity of the pumps. Electric motor-driven pumps capable of achieving high operational reliability are necessarily large, heavy, and energy inefficient. This report describes a development effort conducted for NASA by Lynntech, Inc., who recently demonstrated the feasibility of an electrochemically-driven fluid cooling pump. With no electric motor and minimal lightweight components, an electrochemically-driven pump is expected to be significantly smaller, lighter and achieve a longer life time than conventional rotodynamic and displacement pumps. By employing sulfonated polystyrene-based proton exchange membranes, rather than conventional Nafion membranes, a significant reduction in the actuator power consumption was demonstrated. It was also demonstrated that these membranes possess the necessary mechanical strength, durability, and temperature range for long life space operation. The preliminary design for a Phase II prototype pump compares very favorably to the fluid cooling pumps currently used in space suit portable life support systems (PLSS). Characteristics of the electrochemically-driven pump are described and the benefits of the technology as a replacement for electric motor pumps in mechanically pumped single-phase fluid loops (MPFLs) is discussed.

Crustal displacements due to continental water loading

USGS Publications Warehouse

Van Dam, T.; Wahr, J.; Milly, P.C.D.; Shmakin, A.B.; Blewitt, G.; Lavallee, D.; Larson, K.M.

2001-01-01

The effects of long-wavelength (> 100 km), seasonal variability in continental water storage on vertical crustal motions are assessed. The modeled vertical displacements (??rM) have root-mean-square (RMS) values for 1994-1998 as large as 8 mm, with ranges up to 30 mm, and are predominantly annual in character. Regional strains are on the order of 20 nanostrain for tilt and 5 nanostrain for horizontal deformation. We compare ??rM with observed Global Positioning System (GPS) heights (??rO) (which include adjustments to remove estimated effects of atmospheric pressure and annual tidal and non-tidal ocean loading) for 147 globally distributed sites. When the ??rO time series are adjusted by ??rM, their variances are reduced, on average, by an amount equal to the variance of the ??rM. Of the ??rO time series exhibiting a strong annual signal, more than half are found to have an annual harmonic that is in phase and of comparable amplitude with the annual harmonic in the ??rM. The ??rM time series exhibit long-period variations that could be mistaken for secular tectonic trends or post-glacial rebound when observed over a time span of a few years.

The geophysical character of southern Alaska - Implications for crustal evolution

USGS Publications Warehouse

Saltus, R.W.; Hudson, T.L.; Wilson, Frederic H.

2007-01-01

The southern Alaska continental margin has undergone a long and complicated history of plate convergence, subduction, accretion, and margin-parallel displacements. The crustal character of this continental margin is discernible through combined analysis of aeromagnetic and gravity data with key constraints from previous seismic interpretation. Regional magnetic data are particularly useful in defining broad geophysical domains. One of these domains, the south Alaska magnetic high, is the focus of this study. It is an intense and continuous magnetic high up to 200 km wide and ∼1500 km long extending from the Canadian border in the Wrangell Mountains west and southwest through Cook Inlet to the Bering Sea shelf. Crustal thickness beneath the south Alaska magnetic high is commonly 40–50 km. Gravity analysis indicates that the south Alaska magnetic high crust is dense. The south Alaska magnetic high spatially coincides with the Peninsular and Wrangellia terranes. The thick, dense, and magnetic character of this domain requires significant amounts of mafic rocks at intermediate to deep crustal levels. In Wrangellia these mafic rocks are likely to have been emplaced during Middle and (or) Late Triassic Nikolai Greenstone volcanism. In the Peninsular terrane, the most extensive period of mafic magmatism now known was associated with the Early Jurassic Talkeetna Formation volcanic arc. Thus the thick, dense, and magnetic character of the south Alaska magnetic high crust apparently developed as the response to mafic magmatism in both extensional (Wrangellia) and subduction-related arc (Peninsular terrane) settings. The south Alaska magnetic high is therefore a composite crustal feature. At least in Wrangellia, the crust was probably of average thickness (30 km) or greater prior to Triassic mafic magmatism. Up to 20 km (40%) of its present thickness may be due to the addition of Triassic mafic magmas. Throughout the south Alaska magnetic high, significant crustal growth was caused by the addition of mafic magmas at intermediate to deep crustal levels.

Relationships of Cetacea (Artiodactyla) Among Mammals: Increased Taxon Sampling Alters Interpretations of Key Fossils and Character Evolution

PubMed Central

Spaulding, Michelle; O'Leary, Maureen A.; Gatesy, John

2009-01-01

Background Integration of diverse data (molecules, fossils) provides the most robust test of the phylogeny of cetaceans. Positioning key fossils is critical for reconstructing the character change from life on land to life in the water. Methodology/Principal Findings We reexamine relationships of critical extinct taxa that impact our understanding of the origin of Cetacea. We do this in the context of the largest total evidence analysis of morphological and molecular information for Artiodactyla (661 phenotypic characters and 46,587 molecular characters, coded for 33 extant and 48 extinct taxa). We score morphological data for Carnivoramorpha, †Creodonta, Lipotyphla, and the †raoellid artiodactylan †Indohyus and concentrate on determining which fossils are positioned along stem lineages to major artiodactylan crown clades. Shortest trees place Cetacea within Artiodactyla and close to †Indohyus, with †Mesonychia outside of Artiodactyla. The relationships of †Mesonychia and †Indohyus are highly unstable, however - in trees only two steps longer than minimum length, †Mesonychia falls inside Artiodactyla and displaces †Indohyus from a position close to Cetacea. Trees based only on data that fossilize continue to show the classic arrangement of relationships within Artiodactyla with Cetacea grouping outside the clade, a signal incongruent with the molecular data that dominate the total evidence result. Conclusions/Significance Integration of new fossil material of †Indohyus impacts placement of another extinct clade †Mesonychia, pushing it much farther down the tree. The phylogenetic position of †Indohyus suggests that the cetacean stem lineage included herbivorous and carnivorous aquatic species. We also conclude that extinct members of Cetancodonta (whales + hippopotamids) shared a derived ability to hear underwater sounds, even though several cetancodontans lack a pachyostotic auditory bulla. We revise the taxonomy of living and extinct artiodactylans and propose explicit node and stem-based definitions for the ingroup. PMID:19774069

The Role of the Oculomotor System in Updating Visual-Spatial Working Memory across Saccades.

PubMed

Boon, Paul J; Belopolsky, Artem V; Theeuwes, Jan

2016-01-01

Visual-spatial working memory (VSWM) helps us to maintain and manipulate visual information in the absence of sensory input. It has been proposed that VSWM is an emergent property of the oculomotor system. In the present study we investigated the role of the oculomotor system in updating of spatial working memory representations across saccades. Participants had to maintain a location in memory while making a saccade to a different location. During the saccade the target was displaced, which went unnoticed by the participants. After executing the saccade, participants had to indicate the memorized location. If memory updating fully relies on cancellation driven by extraretinal oculomotor signals, the displacement should have no effect on the perceived location of the memorized stimulus. However, if postsaccadic retinal information about the location of the saccade target is used, the perceived location will be shifted according to the target displacement. As it has been suggested that maintenance of accurate spatial representations across saccades is especially important for action control, we used different ways of reporting the location held in memory; a match-to-sample task, a mouse click or by making another saccade. The results showed a small systematic target displacement bias in all response modalities. Parametric manipulation of the distance between the to-be-memorized stimulus and saccade target revealed that target displacement bias increased over time and changed its spatial profile from being initially centered on locations around the saccade target to becoming spatially global. Taken together results suggest that we neither rely exclusively on extraretinal nor on retinal information in updating working memory representations across saccades. The relative contribution of retinal signals is not fixed but depends on both the time available to integrate these signals as well as the distance between the saccade target and the remembered location.

Putative floral brood-site mimicry, loss of autonomous selfing, and reduced vegetative growth are significantly correlated with increased diversification in Asarum (Aristolochiaceae).

PubMed

Sinn, Brandon T; Kelly, Lawrence M; Freudenstein, John V

2015-08-01

The drivers of angiosperm diversity have long been sought and the flower-arthropod association has often been invoked as the most powerful driver of the angiosperm radiation. We now know that features that influence arthropod interactions cannot only affect the diversification of lineages, but also expedite or constrain their rate of extinction, which can equally influence the observed asymmetric richness of extant angiosperm lineages. The genus Asarum (Aristolochiaceae; ∼100 species) is widely distributed in north temperate forests, with substantial vegetative and floral divergence between its three major clades, Euasarum, Geotaenium, and Heterotropa. We used Binary-State Speciation and Extinction Model (BiSSE) Net Diversification tests of character state distributions on a Maximum Likelihood phylogram and a Coalescent Bayesian species tree, inferred from seven chloroplast markers and nuclear rDNA, to test for signal of asymmetric diversification, character state transition, and extinction rates of floral and vegetative characters. We found that reduction in vegetative growth, loss of autonomous self-pollination, and the presence of putative fungal-mimicking floral structures are significantly correlated with increased diversification in Asarum. No significant difference in model likelihood was identified between symmetric and asymmetric rates of character state transitions or extinction. We conclude that the flowers of the Heterotropa clade may have converged on some aspects of basidiomycete sporocarp morphology and that brood-site mimicry, coupled with a reduction in vegetative growth and the loss of autonomous self-pollination, may have driven diversification within Asarum. Copyright © 2015 Elsevier Inc. All rights reserved.

Otoliths of Five Extant Species of the Annual Killifish Nothobranchius from the East African Savannah

PubMed Central

Reichenbacher, Bettina; Reichard, Martin

2014-01-01

This study presents, for the first time, a comprehensive dataset that documents the range of inter- and intraspecific otolith variation in aplocheiloid killifish, based on a total of 86 individuals representing five extant species of Nothobranchius PETERS, 1868, from East Africa: the sympatric pairs N. rubripinnis SEEGERS, 1986 and N. ruudwildekampi COSTA, 2009 (Eastern Tanzania), and N. orthonotus (PETERS, 1844) and N. furzeri JUBB, 1971 (Southern Mozambique), and two isolated populations of N. korthausae MEINKEN, 1973 (Eastern Tanzania). Otolith characters were analysed based on SEM images, and otolith morphometry was conducted using uni- and multivariate statistics. Two ancient clades of probably Early to Middle Miocene age in eastern Tanzania and southern Mozambique can be recognized based on otolith morphologies, which is consistent with previous work based on molecular data. The distinctive sulcus morphologies in the otoliths of sympatric species may be linked to species-specific hearing capabilities, perhaps constituting a case of character displacement in an area of secondary sympatry. The otoliths of the studied species of Nothobranchius are diagnostic at the species level, even in the case of closely related species diagnosable otherwise only by minor differences in coloration. The two populations of N. korthausae also displayed some differences in their otolith characters. The new data may facilitate future recognition of fossil species of Nothobranchius. As no fossil remains of extant aplocheiloid killifishes have yet been described, the discovery of fossil otoliths of Nothobranchius would significantly advance understanding of the evolutionary history of this interesting group of fishes. PMID:25383789

Neutronics Assessments for a RIA Fragmentation Line Beam Dump Concept

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

Boles, J L; Reyes, S; Ahle, L E

Heavy ion and radiation transport calculations are in progress for conceptual beam dump designs for the fragmentation line of the proposed Rare Isotope Accelerator (RIA). Using the computer code PHITS, a preliminary design of a motor-driven rotating wheel beam dump and adjacent downstream multipole has been modeled. Selected results of these calculations are given, including neutron and proton flux in the wheel, absorbed dose and displacements per atom in the hub materials, and heating from prompt radiation and from decay heat in the multipole.

Laser Doppler measurements of laminar and turbulent flow in a pipe bend

NASA Technical Reports Server (NTRS)

Enayet, M. M.; Gibson, M. M.; Taylor, A. M. K. P.; Yianneskis, M.

1982-01-01

The streamwise components of velocity in the flow through a ninety degree bend of circular cross section for which the ratio of radius of curvature to diameter is 2.8 were measured. The development of strong pressure driven secondary flow in the form of a pair of counter rotating vortices in the steamwise direction is shown. Refractive index matching at the fluid wall interface was not employed; the displacement of the measurement volume due to refraction is allowed for in simple geometrical calculations.

Ellipsoidal Brownian self-driven particles in a magnetic field

NASA Astrophysics Data System (ADS)

Sandoval, Mario; Wai-Tong, Fan; Shun Pak, On

We study the two-dimensional Brownian dynamics of an ellipsoidal paramagnetic microswimmer moving at low Reynolds number and subject to a magnetic field. Its corresponding mean-square displacement showing the effect of particles's shape, activity, and magnetic field on the microswimmer's diffusion is analytically obtained. A comparison among analytical and computational results is also made and we obtain good agreement. Additionally, the effect of self-propulsion on the transition time from anisotropic to isotropic diffusion of the ellipse is also elucidated. CONACYT GRANT: CB 2014/237848.

Single reflector interference spectrometer and drive system therefor

NASA Technical Reports Server (NTRS)

Schindler, R. A. (Inventor)

1974-01-01

In a Fourier interference spectrometer of the doublepass retroreflector type, a single mirror is employed in the path of both split beams of an incoming ray to cause them to double back through separate retroreflectors. Changes in optical path length are achieved by linear displacement of both retroreflectors using a motor driven lead screw on one for large, low frequency changes, a moving-coil actuator on the other for smaller, mid-frequency changes and a piezoelectric actuator on one of these two for small, high frequency changes.

Surface deformation in volcanic rift zones

USGS Publications Warehouse

Pollard, D.D.; Delaney, P.T.; Duffield, W.A.; Endo, E.T.; Okamura, A.T.

1983-01-01

The principal conduits for magma transport within rift zones of basaltic volcanoes are steeply dipping dikes, some of which feed fissure eruptions. Elastic displacements accompanying a single dike emplacement elevate the flanks of the rift relative to a central depression. Concomitant normal faulting may transform the depression into a graben thus accentuating the topographic features of the rift. If eruption occurs the characteristic ridge-trough-ridge displacement profile changes to a single ridge, centered at the fissure, and the erupted lava alters the local topography. A well-developed rift zone owes its structure and topography to the integrated effects of many magmatic rifting events. To investigate this process we compute the elastic displacements and stresses in a homogeneous, two-dimensional half-space driven by a pressurized crack that may breach the surface. A derivative graphical method permits one to estimate the three geometric parameters of the dike (height, inclination, and depth-to-center) and the mechanical parameter (driving pressure/rock stiffness) from a smoothly varying displacement profile. Direct comparison of measured and theoretical profiles may be used to estimate these parameters even if inelastic deformation, notably normal faulting, creates discontinuities in the profile. Geological structures (open cracks, normal faults, buckles, and thrust faults) form because of stresses induced by dike emplacement and fissure eruption. Theoretical stress states associated with dilation of a pressurized crack are used to interpret the distribution and orientation of these structures and their role in rift formation. ?? 1983.

In vivo feasibility of real-time monitoring of focused ultrasound surgery (FUS) using harmonic motion imaging (HMI).

PubMed

Maleke, Caroline; Konofagou, Elisa E

2010-01-01

In this study, the Harmonic Motion Imaging for Focused Ultrasound (HMIFU) technique is applied to monitor changes in mechanical properties of tissues during thermal therapy in a transgenic breast cancer mouse model in vivo. An HMIFU system, composed of a 4.5-MHz focused ultrasound (FUS) and a 3.3-MHz phased-array imaging transducer, was mechanically moved to image and ablate the entire tumor. The FUS transducer was driven by an amplitude-modulated (AM) signal at 15 Hz. The acoustic intensity ( I(spta)) was equal to 1050 W/cm(2) at the focus. A digital low-pass filter was used to filter out the spectrum of the FUS beam and its harmonics prior to displacement estimation. The resulting axial displacement was estimated using 1-D cross-correlation on the acquired RF signals. Results from two mice with eight lesions formed in each mouse (16 lesions total) showed that the average peak-to-peak displacement amplitude before and after lesion formation was respectively equal to 17.34 +/- 1.34 microm and 10.98 +/- 1.82 microm ( p < 0.001). Cell death was also confirmed by hematoxylin and eosin histology. HMI displacement can be used to monitor the relative tissue stiffness changes in real time during heating so that the treatment procedure can be performed in a time-efficient manner. The HMIFU system may, therefore, constitute a cost-efficient and reliable alternative for real-time monitoring of thermal ablation.

The Neuro-Mechanical Processes That Underlie Goal-Directed Medio-Lateral APA during Gait Initiation.

PubMed

Honeine, Jean-Louis; Schieppati, Marco; Crisafulli, Oscar; Do, Manh-Cuong

2016-01-01

Gait initiation (GI) involves passing from bipedal to unipedal stance. It requires a rapid movement of the center of foot pressure (CoP) towards the future swing foot and of the center of mass (CoM) in the direction of the stance foot prior to the incoming step. This anticipatory postural adjustment (APA) allows disengaging the swing leg from the ground and establishing favorable conditions for stepping. This study aimed to describe the neuro-mechanical process that underlies the goal-directed medio-lateral (ML) APA. We hypothesized that controlled knee flexion of the stance leg contributes to the initial ML displacement of the CoP and to the calibration of the first step. Fourteen subjects initiated gait starting from three different initial stance widths of 15 cm (Small), 30 cm (Medium), and 45 cm (Large). Optoelectronic, force platform and electromyogram (EMG) measurements were performed. During APA, soleus activity diminished bilaterally, while tibialis anterior (TA) activity increased, more so in the stance leg than in the swing leg, and to a larger extent with increasing initial stance width. Knee flexion of the stance leg was observed during APA and correlated with the ML CoP displacement towards the swing leg. ML CoP and CoM displacements during APA increased with increasing stance width. The activity of stance-leg TA was correlated with the degree of knee flexion. Swing-leg tensor fasciae latae (TFL) was also active during APA. Across subjects, when stance-leg tibialis activity was low, TFL activity was large and vice versa. The modulation of the ML CoP position during APA allowed the gravity-driven torque to place the CoM just lateral to the stance foot during step execution. Accordingly, the gravity-driven torque, the ML CoM velocity during step execution, and the step width at foot contact (FC) were lower in the Small and greater in the Large condition. Consequently, the position of the stepping foot at FC remained close to the sagittal plane in all three conditions. Conclusively, coordinated activation of hip abductors and ankle dorsiflexors during APA displaces the CoP towards the swing leg, and sets the contact position for the swing foot.

The Neuro-Mechanical Processes That Underlie Goal-Directed Medio-Lateral APA during Gait Initiation

PubMed Central

Honeine, Jean-Louis; Schieppati, Marco; Crisafulli, Oscar; Do, Manh-Cuong

2016-01-01

Gait initiation (GI) involves passing from bipedal to unipedal stance. It requires a rapid movement of the center of foot pressure (CoP) towards the future swing foot and of the center of mass (CoM) in the direction of the stance foot prior to the incoming step. This anticipatory postural adjustment (APA) allows disengaging the swing leg from the ground and establishing favorable conditions for stepping. This study aimed to describe the neuro-mechanical process that underlies the goal-directed medio-lateral (ML) APA. We hypothesized that controlled knee flexion of the stance leg contributes to the initial ML displacement of the CoP and to the calibration of the first step. Fourteen subjects initiated gait starting from three different initial stance widths of 15 cm (Small), 30 cm (Medium), and 45 cm (Large). Optoelectronic, force platform and electromyogram (EMG) measurements were performed. During APA, soleus activity diminished bilaterally, while tibialis anterior (TA) activity increased, more so in the stance leg than in the swing leg, and to a larger extent with increasing initial stance width. Knee flexion of the stance leg was observed during APA and correlated with the ML CoP displacement towards the swing leg. ML CoP and CoM displacements during APA increased with increasing stance width. The activity of stance-leg TA was correlated with the degree of knee flexion. Swing-leg tensor fasciae latae (TFL) was also active during APA. Across subjects, when stance-leg tibialis activity was low, TFL activity was large and vice versa. The modulation of the ML CoP position during APA allowed the gravity-driven torque to place the CoM just lateral to the stance foot during step execution. Accordingly, the gravity-driven torque, the ML CoM velocity during step execution, and the step width at foot contact (FC) were lower in the Small and greater in the Large condition. Consequently, the position of the stepping foot at FC remained close to the sagittal plane in all three conditions. Conclusively, coordinated activation of hip abductors and ankle dorsiflexors during APA displaces the CoP towards the swing leg, and sets the contact position for the swing foot. PMID:27642280

Reconciling Pre- and Co-Seismic Deformation at Megathrusts: Tohoku Informing Cascadia

NASA Astrophysics Data System (ADS)

Furlong, K. P.; Govers, R. M.

2013-12-01

One of the outstanding goals of earthquake science is to effectively anticipate the earthquake characteristics of a future event - magnitude, rupture area, slip history - through the judicious application of models that use observations of inter-earthquake deformation and the history of earthquakes along that plate boundary segment. The series of great earthquakes over the past decade since the 2004 Mw 9.2 Sumatra earthquake have demonstrated both the sobering reality that our current models of subduction zone earthquake genesis are insufficient but more positively have provided a wealth of data and observations that can be used to develop improved framework models of the lithospheric behavior through the earthquake cycle in subduction zones. Some of the issues that recent observations raise are straightforward, while others imply aspects of the subduction process that have not been previously considered important. Based on observations of a range of great earthquakes since 2004, and with a particular focus on the 2011 Mw 9.0 Tohoku event we can identify a suite of key issues that include: (1) Patterns of inter-seismic deformation (strain accumulation) are not simply the converse of the co-seismic elastic strain release. (2) Deformation of the slab during the earthquake cycle is a common occurrence and its role in buffering upper-plate deformation is a key consideration in the potential tsunamigenic character of a subduction system. (3) Rates of pre-earthquake deformation (e.g. observed upper-plate GPS displacements) and inferred slip deficit accumulation on the megathrust are inconsistent with co-seismic displacements/fault slip and recurrence intervals. (4) Patterns of megathrust locked patches, degrees of coupling and other parameterizations that are used to define earthquake potential have only a loose agreement with the actual patterns of slip and moment release seen in the ensuing great earthquake. Simple elastic models do provide a general agreement between processes along the megathrust and observations regionally - i.e. with such models (e.g. Okada-type solutions) we find reasonable agreement among geodetic and seismologic models. In assessing sensitivities in our preliminary modeling, we find that depending on the strength and rheologic considerations in the model, similar patterns of displacement in the upper plate in the typical observing zones (on-shore, ~ 100+ km from trench) can have significantly different displacement effects in the vicinity of the earthquake rupture and trench - the areas most critical to tsunamigenesis and assessing earthquake magnitude. Also although it is perhaps reassuring to see that there is general agreement between the seismologically determined finite fault models (FFM) and the observed surface deformation; this information after-the-fact does not tell us why the slip deficit accumulated as it did. Here we report on improved (numerical) models of the strain accumulation and release cycle in megathrust zones that better incorporate variations in rheology, the effects of plate boundary character (pre- and co-seismic), and the relationships between pre-earthquakes observed deformation and co-seismic rupture characteristics.

Investigation of Cracks Found in Helicopter Longerons

NASA Technical Reports Server (NTRS)

Newman, John A.; Baughman, James M.; Wallace, Terryl A.

2009-01-01

Four cracked longerons, containing a total of eight cracks, were provided for study. Cracked regions were cut from the longerons. Load was applied to open the cracks, enabling crack surface examination. Examination revealed that crack propagation was driven by fatigue loading in all eight cases. Fatigue crack initiation appears to have occurred on the top edge of the longerons near geometric changes that affect component bending stiffness. Additionally, metallurigical analysis has revealed a local depletion in alloying elements in the crack initiation regions that may be a contributing factor. Fatigue crack propagation appeared to be initially driven by opening-mode loading, but at a crack length of approximately 0.5 inches (12.7 mm), there is evidence of mixed-mode crack loading. For the longest cracks studied, shear-mode displacements destroyed crack-surface features of interest over significant portions of the crack surfaces.

Investigation of Helicopter Longeron Cracks

NASA Technical Reports Server (NTRS)

Newman, John A.; Baughman, James; Wallace, Terryl A.

2009-01-01

Four cracked longerons, containing a total of eight cracks, were provided for study. Cracked regions were cut from the longerons. Load was applied to open the cracks, enabling crack surface examination. Examination revealed that crack propagation was driven by fatigue loading in all eight cases. Fatigue crack initiation appears to have occurred on the top edge of the longerons near geometric changes that affect component bending stiffness. Additionally, metallurgical analysis has revealed a local depletion in alloying elements in the crack initiation regions that may be a contributing factor. Fatigue crack propagation appeared to be initially driven by opening-mode loading, but at a crack length of approximately 0.5 inches (12.7 mm), there is evidence of mixed-mode crack loading. For the longest cracks studied, shear-mode displacements destroyed crack-surface features of interest over significant portions of the crack surfaces.

Microelectromechanical dual-mass resonator structure

DOEpatents

Dyck, Christopher W.; Allen, James J.; Huber, Robert J.

2002-01-01

A dual-mass microelectromechanical (MEM) resonator structure is disclosed in which a first mass is suspended above a substrate and driven to move along a linear or curved path by a parallel-plate electrostatic actuator. A second mass, which is also suspended and coupled to the first mass by a plurality of springs is driven by motion of the first mass. Various modes of operation of the MEM structure are possible, including resonant and antiresonant modes, and a contacting mode. In each mode of operation, the motion induced in the second mass can be in the range of several microns up to more than 50 .mu.m while the first mass has a much smaller displacement on the order of one micron or less. The MEM structure has applications for forming microsensors that detect strain, acceleration, rotation or movement.

Combustion mode switching with a turbocharged/supercharged engine

DOEpatents

Mond, Alan; Jiang, Li

2015-09-22

A method for switching between low- and high-dilution combustion modes in an internal combustion engine having an intake passage with an exhaust-driven turbocharger, a crankshaft-driven positive displacement supercharger downstream of the turbocharger and having variable boost controllable with a supercharger bypass valve, and a throttle valve downstream of the supercharger. The current combustion mode and mass air flow are determined. A switch to the target combustion mode is commanded when an operating condition falls within a range of predetermined operating conditions. A target mass air flow to achieve a target air-fuel ratio corresponding to the current operating condition and the target combustion mode is determined. The degree of opening of the supercharger bypass valve and the throttle valve are controlled to achieve the target mass air flow. The amount of residual exhaust gas is manipulated.

Evaluation of image deblurring methods via a classification metric

NASA Astrophysics Data System (ADS)

Perrone, Daniele; Humphreys, David; Lamb, Robert A.; Favaro, Paolo

2012-09-01

The performance of single image deblurring algorithms is typically evaluated via a certain discrepancy measure between the reconstructed image and the ideal sharp image. The choice of metric, however, has been a source of debate and has also led to alternative metrics based on human visual perception. While fixed metrics may fail to capture some small but visible artifacts, perception-based metrics may favor reconstructions with artifacts that are visually pleasant. To overcome these limitations, we propose to assess the quality of reconstructed images via a task-driven metric. In this paper we consider object classification as the task and therefore use the rate of classification as the metric to measure deblurring performance. In our evaluation we use data with different types of blur in two cases: Optical Character Recognition (OCR), where the goal is to recognise characters in a black and white image, and object classification with no restrictions on pose, illumination and orientation. Finally, we show how off-the-shelf classification algorithms benefit from working with deblurred images.

A manifold learning approach to data-driven computational materials and processes

NASA Astrophysics Data System (ADS)

Ibañez, Ruben; Abisset-Chavanne, Emmanuelle; Aguado, Jose Vicente; Gonzalez, David; Cueto, Elias; Duval, Jean Louis; Chinesta, Francisco

2017-10-01

Standard simulation in classical mechanics is based on the use of two very different types of equations. The first one, of axiomatic character, is related to balance laws (momentum, mass, energy, …), whereas the second one consists of models that scientists have extracted from collected, natural or synthetic data. In this work we propose a new method, able to directly link data to computers in order to perform numerical simulations. These simulations will employ universal laws while minimizing the need of explicit, often phenomenological, models. They are based on manifold learning methodologies.

Imine-based [2]catenanes in water.

PubMed

Caprice, Kenji; Pupier, Marion; Kruve, Anneli; Schalley, Christoph A; Cougnon, Fabien B L

2018-02-07

We report the efficient condensation of imine-based macrocycles from dialdehyde A and aliphatic diamines B n in pure water. Within the libraries, we identified a family of homologous amphiphilic [2]catenanes, whose self-assembly is primarily driven by the hydrophobic effect. The length and odd-even character of the diamine alkyl linker dictate both the yield and the conformation of the [2]catenanes, whose particular thermodynamic stability further shifts the overall equilibrium in favour of imine condensation. These findings highlight the role played by solvophobic effects in the self-assembly of complex architectures.

Inverse energy cascades in three-dimensional turbulence

NASA Technical Reports Server (NTRS)

Hossain, Murshed

1991-01-01

Fully three-dimensional magnetohydrodynamic (MHD) turbulence at large kinetic and low magnetic Reynolds numbers is considered in the presence of a strong uniform magnetic field. It is shown by numerical simulation of a model of MHD that the energy inverse cascades to longer length scales when the interaction parameter is large. While the steady-state dynamics of the driven problem is three-dimensional in character, the behavior has resemblance to two-dimensional hydrodynamics. These results have implications in turbulence theory, MHD power generator, planetary dynamos, and fusion reactor blanket design.

Electronic states of the Cu 3O 1217- model cluster

NASA Astrophysics Data System (ADS)

Chen, Xue-an; Chen, Zhi-fang; Heng, Fu; Tang, Youqi; Ye, Xue-qi; Zhu, Min-hui

1991-03-01

The Fenske-Hall molecular orbital calculations were performed on the model cluster Cu 3O 1217-. The calculated results revealed that the major contribution to the electronic states near the Fermi level comes from the orbitals of Cu 3d and O 2p, with dominantly oxygen p character, and the oxidation beyond the Cu 2+ state does not lead to Cu 3+ but to O - state. There exists the strong covalent bonding between copper and neighboring oxygen ions, especially between the chain Cu(1) and bridge O(4) ions. The slight displacement of O(4) along the c-axis toward Cu(2) can result in a decrease in the HOMO-LUMO gap and a strengthening of the chain-plane coupling.

Numerical Simulation of Nonperiodic Rail Operation Diagram Characteristics

PubMed Central

Qian, Yongsheng; Wang, Bingbing; Zeng, Junwei; Wang, Xin

2014-01-01

This paper succeeded in utilizing cellular automata (CA) model to simulate the process of the train operation under the four-aspect color light system and getting the nonperiodic diagram of the mixed passenger and freight tracks. Generally speaking, the concerned models could simulate well the situation of wagon in preventing trains from colliding when parking and restarting and of the real-time changes the situation of train speeds and displacement and get hold of the current train states in their departures and arrivals. Finally the model gets the train diagram that simulates the train operation in different ratios of the van and analyzes some parameter characters in the process of train running, such as time, speed, through capacity, interval departing time, and departing numbers. PMID:25435863

Kinetically-Driven Phase Transformation during Lithiation in Copper Sulfide Nanoflakes

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

He, Kai; Yao, Zhenpeng; Hwang, Sooyeon

Two-dimensional (2D) transition metal chalcogenides have been widely studied and utilized as electrode materials for lithium ion batteries due to their unique layered structures to accommodate reversible lithium insertion. Real-time observation and mechanistic understanding of the phase transformations during lithiation of these materials are critically important for improving battery performance by controlling structures and reaction pathways. Here, we use in situ transmission electron microscopy methods to study the structural, morphological, and chemical evolutions in individual copper sulfide (CuS) nanoflakes during lithiation. We report a highly kinetically driven phase transformation in which lithium ions rapidly intercalate into the 2D van dermore » Waals-stacked interlayers in the initial stage, and further lithiation induces the Cu extrusion via a displacement reaction mechanism that is different from the typical conversion reactions. Density functional theory calculations have confirmed both the thermodynamically favored and the kinetically driven reaction pathways. Lastly, our findings elucidate the reaction pathways of the Li/CuS system under nonequilibrium conditions and provide valuable insight into the atomistic lithiation mechanisms of transition metal sulfides in general.« less

Kinetically-Driven Phase Transformation during Lithiation in Copper Sulfide Nanoflakes

DOE PAGES

He, Kai; Yao, Zhenpeng; Hwang, Sooyeon; ...

2017-08-11

Two-dimensional (2D) transition metal chalcogenides have been widely studied and utilized as electrode materials for lithium ion batteries due to their unique layered structures to accommodate reversible lithium insertion. Real-time observation and mechanistic understanding of the phase transformations during lithiation of these materials are critically important for improving battery performance by controlling structures and reaction pathways. Here, we use in situ transmission electron microscopy methods to study the structural, morphological, and chemical evolutions in individual copper sulfide (CuS) nanoflakes during lithiation. We report a highly kinetically driven phase transformation in which lithium ions rapidly intercalate into the 2D van dermore » Waals-stacked interlayers in the initial stage, and further lithiation induces the Cu extrusion via a displacement reaction mechanism that is different from the typical conversion reactions. Density functional theory calculations have confirmed both the thermodynamically favored and the kinetically driven reaction pathways. Lastly, our findings elucidate the reaction pathways of the Li/CuS system under nonequilibrium conditions and provide valuable insight into the atomistic lithiation mechanisms of transition metal sulfides in general.« less

Prediction of gravity-driven fingering in porous media

NASA Astrophysics Data System (ADS)

Beljadid, Abdelaziz; Cueto-Felgueroso, Luis; Juanes, Ruben

2017-11-01

Gravity-driven displacement of one fluid by another in porous media is often subject to a hydrodynamic instability, whereby fluid invasion takes the form of preferential flow paths-examples include secondary oil migration in reservoir rocks, and infiltration of rainfall water in dry soil. Here, we develop a continuum model of gravity-driven two-phase flow in porous media within the phase-field framework (Cueto-Felgueroso and Juanes, 2008). We employ pore-scale physics arguments to design the free energy of the system, which notably includes a nonlinear formulation of the high-order (square-gradient) term based on equilibrium considerations in the direction orthogonal to gravity. This nonlocal term plays the role of a macroscopic surface tension, which exhibits a strong link with capillary pressure. Our theoretical analysis shows that the proposed model enforces that fluid saturations are bounded between 0 and 1 by construction, therefore overcoming a serious limitation of previous models. Our numerical simulations show that the proposed model also resolves the pinning behavior at the base of the infiltration front, and the asymmetric behavior of the fingers at material interfaces observed experimentally.

Mean apparent propagator (MAP) MRI: a novel diffusion imaging method for mapping tissue microstructure.

PubMed

Özarslan, Evren; Koay, Cheng Guan; Shepherd, Timothy M; Komlosh, Michal E; İrfanoğlu, M Okan; Pierpaoli, Carlo; Basser, Peter J

2013-09-01

Diffusion-weighted magnetic resonance (MR) signals reflect information about underlying tissue microstructure and cytoarchitecture. We propose a quantitative, efficient, and robust mathematical and physical framework for representing diffusion-weighted MR imaging (MRI) data obtained in "q-space," and the corresponding "mean apparent propagator (MAP)" describing molecular displacements in "r-space." We also define and map novel quantitative descriptors of diffusion that can be computed robustly using this MAP-MRI framework. We describe efficient analytical representation of the three-dimensional q-space MR signal in a series expansion of basis functions that accurately describes diffusion in many complex geometries. The lowest order term in this expansion contains a diffusion tensor that characterizes the Gaussian displacement distribution, equivalent to diffusion tensor MRI (DTI). Inclusion of higher order terms enables the reconstruction of the true average propagator whose projection onto the unit "displacement" sphere provides an orientational distribution function (ODF) that contains only the orientational dependence of the diffusion process. The representation characterizes novel features of diffusion anisotropy and the non-Gaussian character of the three-dimensional diffusion process. Other important measures this representation provides include the return-to-the-origin probability (RTOP), and its variants for diffusion in one- and two-dimensions-the return-to-the-plane probability (RTPP), and the return-to-the-axis probability (RTAP), respectively. These zero net displacement probabilities measure the mean compartment (pore) volume and cross-sectional area in distributions of isolated pores irrespective of the pore shape. MAP-MRI represents a new comprehensive framework to model the three-dimensional q-space signal and transform it into diffusion propagators. Experiments on an excised marmoset brain specimen demonstrate that MAP-MRI provides several novel, quantifiable parameters that capture previously obscured intrinsic features of nervous tissue microstructure. This should prove helpful for investigating the functional organization of normal and pathologic nervous tissue. Copyright © 2013 Elsevier Inc. All rights reserved.

The Structural Consequences of Big Data-Driven Education.

PubMed

Zeide, Elana

2017-06-01

Educators and commenters who evaluate big data-driven learning environments focus on specific questions: whether automated education platforms improve learning outcomes, invade student privacy, and promote equality. This article puts aside separate unresolved-and perhaps unresolvable-issues regarding the concrete effects of specific technologies. It instead examines how big data-driven tools alter the structure of schools' pedagogical decision-making, and, in doing so, change fundamental aspects of America's education enterprise. Technological mediation and data-driven decision-making have a particularly significant impact in learning environments because the education process primarily consists of dynamic information exchange. In this overview, I highlight three significant structural shifts that accompany school reliance on data-driven instructional platforms that perform core school functions: teaching, assessment, and credentialing. First, virtual learning environments create information technology infrastructures featuring constant data collection, continuous algorithmic assessment, and possibly infinite record retention. This undermines the traditional intellectual privacy and safety of classrooms. Second, these systems displace pedagogical decision-making from educators serving public interests to private, often for-profit, technology providers. They constrain teachers' academic autonomy, obscure student evaluation, and reduce parents' and students' ability to participate or challenge education decision-making. Third, big data-driven tools define what "counts" as education by mapping the concepts, creating the content, determining the metrics, and setting desired learning outcomes of instruction. These shifts cede important decision-making to private entities without public scrutiny or pedagogical examination. In contrast to the public and heated debates that accompany textbook choices, schools often adopt education technologies ad hoc. Given education's crucial impact on individual and collective success, educators and policymakers must consider the implications of data-driven education proactively and explicitly.

A Study on a Microwave-Driven Smart Material Actuator

NASA Technical Reports Server (NTRS)

Choi, Sang H.; Chu, Sang-Hyon; Kwak, M.; Cutler, A. D.

2001-01-01

NASA s Next Generation Space Telescope (NGST) has a large deployable, fragmented optical surface (greater than or = 2 8 m in diameter) that requires autonomous correction of deployment misalignments and thermal effects. Its high and stringent resolution requirement imposes a great deal of challenge for optical correction. The threshold value for optical correction is dictated by lambda/20 (30 nm for NGST optics). Control of an adaptive optics array consisting of a large number of optical elements and smart material actuators is so complex that power distribution for activation and control of actuators must be done by other than hard-wired circuitry. The concept of microwave-driven smart actuators is envisioned as the best option to alleviate the complexity associated with hard-wiring. A microwave-driven actuator was studied to realize such a concept for future applications. Piezoelectric material was used as an actuator that shows dimensional change with high electric field. The actuators were coupled with microwave rectenna and tested to correlate the coupling effect of electromagnetic wave. In experiments, a 3x3 rectenna patch array generated more than 50 volts which is a threshold voltage for 30-nm displacement of a single piezoelectric material. Overall, the test results indicate that the microwave-driven actuator concept can be adopted for NGST applications.

Off-Angle Iris Correction Methods

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

Santos-Villalobos, Hector J; Thompson, Joseph T; Karakaya, Mahmut

In many real world iris recognition systems obtaining consistent frontal images is problematic do to inexperienced or uncooperative users, untrained operators, or distracting environments. As a result many collected images are unusable by modern iris matchers. In this chapter we present four methods for correcting off-angle iris images to appear frontal which makes them compatible with existing iris matchers. The methods include an affine correction, a retraced model of the human eye, measured displacements, and a genetic algorithm optimized correction. The affine correction represents a simple way to create an iris image that appears frontal but it does not accountmore » for refractive distortions of the cornea. The other method account for refraction. The retraced model simulates the optical properties of the cornea. The other two methods are data driven. The first uses optical flow to measure the displacements of the iris texture when compared to frontal images of the same subject. The second uses a genetic algorithm to learn a mapping that optimizes the Hamming Distance scores between off-angle and frontal images. In this paper we hypothesize that the biological model presented in our earlier work does not adequately account for all variations in eye anatomy and therefore the two data-driven approaches should yield better performance. Results are presented using the commercial VeriEye matcher that show that the genetic algorithm method clearly improves over prior work and makes iris recognition possible up to 50 degrees off-angle.« less

Design, fabrication, and implementation of thermally driven outdoor testing devices for building joint sealants.

PubMed

White, C C; Tan, K T; O'Brien, E P; Hunston, D L; Chin, J W; Williams, R S

2011-02-01

The paper describes the development, implementation, and testing of two thermally driven outdoor exposure instruments. These devices are unique in their ability to impose field generated thermally induced strain on sealant specimens while monitoring their resulting load and displacement. The instruments combine a fixed wood and steel supporting frame with a moving polyvinyl chloride frame, and employ differences in the coefficients of thermal expansion between the supporting frame and moving frame to induce strain on the sealant specimens. Two different kinds of instruments have been fabricated, "winter/tension" and "winter/compression" designs. In the winter/tension design, the thermally induced dimensional change is directly transferred to the specimens; while in the winter/compression design, the samples are loaded in an opposite direction with the dimensional change. Both designs are instrumented to monitor load and displacement and are built so that the strain on the specimen does not exceed ±25% over the range of temperatures expected in Gaithersburg, MD. Additionally, a weather station is colocated with the device to record environmental conditions in 1 min intervals. This combination of weather information with mechanical property data enables a direct link between environmental conditions and the corresponding sealant response. The reliability and effectiveness of these instruments are demonstrated with a typical sealant material. The results show that the instruments work according to the design criteria and provide a meaningful quantitative platform to monitor the mechanical response of sealant exposed to outdoor weathering.

Torsional actuator motor using solid freeform fabricated PZT ceramics

NASA Astrophysics Data System (ADS)

Kim, Chulho; Wu, Carl C. M.; Bender, Barry

2004-07-01

A torsional actuator has been developed at NRL utilizing the high piezoelectric shear coefficient, d15. This torsional actuator uses an even number of alternately poled segments of electroactive PZT. Under an applied electric field, the torsional actuator produces large angular displacement and a high torque. The solid freeform fabrication technique of the laminated object manufacturing (LOM) is used for rapid prototyping of torsional actuator with potential cost and time saving. First step to demonstrate the feasibility of the LOM technique for the torsional actuator device fabrication is to make near net shape segments. We report a prototype PZT torsional actuator using LOM prepared PZT-5A segments. Fabrication processes and test results are described. The torsional actuator PZT-5A tube has dimensions of 13 cm long, 2.54 cm OD and 1.9 cm ID. Although the piezoelectric strain is small, it may be converted into large displacement via accumulation of the small single cycle displacements over many cycles using AC driving voltage such as with a rotary 'inchworm' actuator or an ultrasonic rotary motor. A working prototype of a full-cycle motor driven by the piezoelectric torsional actuator has been achieved. The rotational speed is 1,200 rpm under 200 V/cm field at the resonant frequency of 4.5 kHz.

The duality of ocean acidification as a resource and a stressor.

PubMed

Connell, Sean D; Doubleday, Zoë A; Foster, Nicole R; Hamlyn, Sarah B; Harley, Christopher D G; Helmuth, Brian; Kelaher, Brendan P; Nagelkerken, Ivan; Rodgers, Kirsten L; Sarà, Gianluca; Russell, Bayden D

2018-05-01

Ecologically dominant species often define ecosystem states, but as human disturbances intensify, their subordinate counterparts increasingly displace them. We consider the duality of disturbance by examining how environmental drivers can simultaneously act as a stressor to dominant species and as a resource to subordinates. Using a model ecosystem, we demonstrate that CO 2 -driven interactions between species can account for such reversals in dominance; i.e., the displacement of dominants (kelp forests) by subordinates (turf algae). We established that CO 2 enrichment had a direct positive effect on productivity of turfs, but a negligible effect on kelp. CO 2 enrichment further suppressed the abundance and feeding rate of the primary grazer of turfs (sea urchins), but had an opposite effect on the minor grazer (gastropods). Thus, boosted production of subordinate producers, exacerbated by a net reduction in its consumption by primary grazers, accounts for community change (i.e., turf displacing kelp). Ecosystem collapse, therefore, is more likely when resource enrichment alters competitive dominance of producers, and consumers fail to compensate. By recognizing such duality in the responses of interacting species to disturbance, which may stabilize or exacerbate change, we can begin to understand how intensifying human disturbances determine whether or not ecosystems undergo phase shifts. © 2018 by the Ecological Society of America.

Gravity-driven postseismic deformation following the Mw 6.3 2009 L’Aquila (Italy) earthquake

PubMed Central

Albano, Matteo; Barba, Salvatore; Saroli, Michele; Moro, Marco; Malvarosa, Fabio; Costantini, Mario; Bignami, Christian; Stramondo, Salvatore

2015-01-01

The present work focuses on the postseismic deformation observed in the region of L’Aquila (central Italy) following the Mw 6.3 earthquake that occurred on April 6, 2009. A new, 16-month-long dataset of COSMO-SkyMed SAR images was analysed using the Persistent Scatterer Pairs interferometric technique. The analysis revealed the existence of postseismic ground subsidence in the mountainous rocky area of Mt Ocre ridge, contiguous to the sedimentary plain that experienced coseismic subsidence. The postseismic subsidence was characterized by displacements of 10 to 35 mm along the SAR line of sight. In the Mt Ocre ridge, widespread morphological elements associated with gravitational spreading have been previously mapped. We tested the hypothesis that the postseismic subsidence of the Mt Ocre ridge compensates the loss of equilibrium induced by the nearby coseismic subsidence. Therefore, we simulated the coseismic and postseismic displacement fields via the finite element method. We included the gravitational load and fault slip and accounted for the geometrical and rheological characteristics of the area. We found that the elastoplastic behaviour of the material under gravitational loading best explains the observed postseismic displacement. These findings emphasize the role of gravity in the postseismic processes at the fault scale. PMID:26553120

Body size as a primary determinant of ecomorphological diversification and the evolution of mimicry in the lampropeltinine snakes (Serpentes: Colubridae).

PubMed

Pyron, R Alexander; Burbrink, F T

2009-10-01

Evolutionary correlations between functionally related character suites are expected as a consequence of coadaptation due to physiological relationships between traits. However, significant correlations may also exist between putatively unrelated characters due to shared relationships between those traits and underlying variables, such as body size. Although such patterns are often dismissed as simple body size scaling, this presumption may overlook important evolutionary patterns of diversification. If body size is the primary determinant of potential diversity in multiple unrelated characters, the observed differentiation of species may be governed by variability in body size, and any biotic or abiotic constraints on the diversification thereof. Here, we demonstrate that traits related to both predatory specialization (gape and diet preference) and predatory avoidance (the development of Batesian mimicry) are phylogenetically correlated in the North American snake tribe Lampropeltini. This is apparently due to shared relationships between those traits and adult body size, suggesting that size is the primary determinant of ecomorphological differentiation in the lampropeltinines. Diversification in body size is apparently not linked to climatic or environmental factors, and may have been driven by interspecific interactions such as competition. Additionally, we find the presence of a 'key zone' for the development of both rattle- and coral snake mimicry; only small snakes feeding primarily on ectothermic prey develop mimetic colour patterns, in or near the range of venomous model species.

Aphanius arakensis, a new species of tooth-carp (Actinopterygii, Cyprinodontidae) from the endorheic Namak Lake basin in Iran

PubMed Central

Teimori, Azad; Esmaeili, Hamid Reza; Gholami, Zeinab; Zarei, Neda; Reichenbacher, Bettina

2012-01-01

Abstract A new species of tooth-carp, Aphanius arakensis sp. n., is described from the Namak Lake basin in Iran. The new species is distinguished by the congeners distributed in Iran by the following combination of characters: 10–12 anal fin rays, 28–32 lateral line scales, 10–13 caudal peduncle scales, 8–10 gill rakers, 12–19, commonly 15–16, clearly defined flank bars in males, a more prominent pigmentation along the flank added by relatively big blotches in the middle and posterior flank segments in females, a short but high antirostrum of the otolith that has a wide excisura, and a ventral rim with some small, drop-like processes, and 19 molecular apomorphies (17 transitions, two transversions) in the cytochrome b gene. It was suggested based on the phylogenetic analysis that the new species is sister to Aphanius sophiae from the Kor River and that Aphanius farsicus from the Maharlu Lake basin is sister to Aphanius arakensis plus Aphanius sophiae. A noticeable feature of the Aphanius diversity in Iran is the conservatism of the external morphology as well as morphometric and meristic characters, while distinctive differences are present in genetic characters, otolith morphology, and male color pattern. Transformation of the latter was probably driven by sexual selection. PMID:22936871

Data-driven non-linear elasticity: constitutive manifold construction and problem discretization

NASA Astrophysics Data System (ADS)

Ibañez, Ruben; Borzacchiello, Domenico; Aguado, Jose Vicente; Abisset-Chavanne, Emmanuelle; Cueto, Elias; Ladeveze, Pierre; Chinesta, Francisco

2017-11-01

The use of constitutive equations calibrated from data has been implemented into standard numerical solvers for successfully addressing a variety problems encountered in simulation-based engineering sciences (SBES). However, the complexity remains constantly increasing due to the need of increasingly detailed models as well as the use of engineered materials. Data-Driven simulation constitutes a potential change of paradigm in SBES. Standard simulation in computational mechanics is based on the use of two very different types of equations. The first one, of axiomatic character, is related to balance laws (momentum, mass, energy,\\ldots ), whereas the second one consists of models that scientists have extracted from collected, either natural or synthetic, data. Data-driven (or data-intensive) simulation consists of directly linking experimental data to computers in order to perform numerical simulations. These simulations will employ laws, universally recognized as epistemic, while minimizing the need of explicit, often phenomenological, models. The main drawback of such an approach is the large amount of required data, some of them inaccessible from the nowadays testing facilities. Such difficulty can be circumvented in many cases, and in any case alleviated, by considering complex tests, collecting as many data as possible and then using a data-driven inverse approach in order to generate the whole constitutive manifold from few complex experimental tests, as discussed in the present work.

Excited state conformational dynamics in carotenoids: dark intermediates and excitation energy transfer.

PubMed

Beck, Warren F; Bishop, Michael M; Roscioli, Jerome D; Ghosh, Soumen; Frank, Harry A

2015-04-15

A consideration of the excited state potential energy surfaces of carotenoids develops a new hypothesis for the nature of the conformational motions that follow optical preparation of the S2 (1(1)Bu(+)) state. After an initial displacement from the Franck-Condon geometry along bond length alternation coordinates, it is suggested that carotenoids pass over a transition-state barrier leading to twisted conformations. This hypothesis leads to assignments for several dark intermediate states encountered in femtosecond spectroscopic studies. The Sx state is assigned to the structure reached upon the onset of torsional motions near the transition state barrier that divides planar and twisted structures on the S2 state potential energy surface. The X state, detected recently in two-dimensional electronic spectra, corresponds to a twisted structure well past the barrier and approaching the S2 state torsional minimum. Lastly, the S(∗) state is assigned to a low lying S1 state structure with intramolecular charge transfer character (ICT) and a pyramidal conformation. It follows that the bent and twisted structures of carotenoids that are found in photosynthetic light-harvesting proteins yield excited-state structures that favor the development of an ICT character and optimized energy transfer yields to (bacterio)chlorophyll acceptors. Copyright © 2015 Elsevier Inc. All rights reserved.

Observations of changes in waveform character induced by the 1999 Mw7.6 Chi-Chi earthquake

USGS Publications Warehouse

Chen, K.H.; Furumura, T.; Rubinstein, J.; Rau, R.-J.

2011-01-01

We observe changes in the waveforms of repeating earthquakes in eastern Taiwan following the 1999 Mw7.6 Chi-Chi earthquake, while their recurrence intervals appear to be unaffected. There is a clear reduction in waveform similarity and velocity changes indicated by delayed phases at the time of the Chi-Chi event. These changes are limited to stations in and paths that cross the 70 × 100 km region surrounding the Chi-Chi source area, the area where seismic intensity and co-seismic surface displacements were largest. This suggests that damage at the near-surface is responsible for the observed waveform changes. Delays are largest in the late S-wave coda, reaching approximately 120 ms. This corresponds to a path averaged Swave velocity reduction of approximately 1%. There is also evidence that damage in the fault-zone caused changes in waveform character at sites in the footwall, where source-receiver paths propagate either along or across the rupture. The reduction in waveform similarity persists through the most recent repeating event in our study (November 15, 2007), indicating that the subsurface damage induced by the Chi-Chi earthquake did not fully heal within the first 8 years following the Chi-Chi earthquake.

Observations of changes in waveform character induced by the 1999 M w7.6 Chi-Chi earthquake

USGS Publications Warehouse

Chen, K.H.; Furumura, T.; Rubinstein, J.; Rau, R.-J.

2011-01-01

We observe changes in the waveforms of repeating earthquakes in eastern Taiwan following the 1999 Mw7.6 Chi-Chi earthquake, while their recurrence intervals appear to be unaffected. There is a clear reduction in waveform similarity and velocity changes indicated by delayed phases at the time of the Chi-Chi event. These changes are limited to stations in and paths that cross the 70 ?? 100 km region surrounding the Chi-Chi source area, the area where seismic intensity and co-seismic surface displacements were largest. This suggests that damage at the near-surface is responsible for the observed waveform changes. Delays are largest in the late S-wave coda, reaching approximately 120 ms. This corresponds to a path averaged S wave velocity reduction of approximately 1%. There is also evidence that damage in the fault-zone caused changes in waveform character at sites in the footwall, where source-receiver paths propagate either along or across the rupture. The reduction in waveform similarity persists through the most recent repeating event in our study (November 15, 2007), indicating that the subsurface damage induced by the Chi-Chi earthquake did not fully heal within the first 8 years following the Chi-Chi earthquake. ?? 2011 by the American Geophysical Union.

Robust Control of a Cable-Driven Soft Exoskeleton Joint for Intrinsic Human-Robot Interaction.

PubMed

Jarrett, C; McDaid, A J

2017-07-01

A novel, cable-driven soft joint is presented for use in robotic rehabilitation exoskeletons to provide intrinsic, comfortable human-robot interaction. The torque-displacement characteristics of the soft elastomeric core contained within the joint are modeled. This knowledge is used in conjunction with a dynamic system model to derive a sliding mode controller (SMC) to implement low-level torque control of the joint. The SMC controller is experimentally compared with a baseline feedback-linearised proportional-derivative controller across a range of conditions and shown to be robust to un-modeled disturbances. The torque controller is then tested with six healthy subjects while they perform a selection of activities of daily living, which has validated its range of performance. Finally, a case study with a participant with spastic cerebral palsy is presented to illustrate the potential of both the joint and controller to be used in a physiotherapy setting to assist clinical populations.

Nanoporous-Gold-Based Hybrid Cantilevered Actuator Dealloyed and Driven by A Modified Rotary Triboelectric Nanogenerator

PubMed Central

Li, Xuequan; Liu, Mengmeng; Huang, Baisheng; Liu, Hong; Hu, Weiguo; Shao, Li-Hua; Wang, Zhong Lin

2016-01-01

We firstly designed an electrochemical system for dealloying to synthesize nanoporous gold (NPG) and also driving the novel NPG based actuator by utilizing a modified rotary triboelectric nanogenerator (TENG). Compared to the previous reported TENG whose outputs decline due to temperature rising resulting from electrodes friction, the modified TENG with a cooling system has stable output current and voltage increased by 14% and 20%, respectively. The novel cantilevered hybrid actuator characterised by light-weight (ca. 3 mg) and small volume (ca. 30 mm × 2 mm × 10 μm) is driven by a microcontroller modulated TENG with the displacement of 2.2 mm, which is about 106 times larger than that of traditional cantilever using planar surfaces. The energy conversion efficiencies defined as the energy consumed during dealloying and actuation compared with the output of TENG are 47% and 56.7%, respectively. PMID:27063987

Curvature-driven bubbles or droplets on the spiral surface

NASA Astrophysics Data System (ADS)

Li, Shanpeng; Liu, Jianlin; Hou, Jian

2016-11-01

Directional motion of droplets or bubbles can often be observed in nature and our daily life, and this phenomenon holds great potential in many engineering areas. The study shows that droplets or bubbles can be driven to migrate perpetually on some special substrates, such as the Archimedean spiral, the logarithmic spiral and a cantilever sheet in large deflection. It is found that a bubble approaches or deviates from the position with highest curvature of the substrate, when it is on the concave or convex side. This fact is helpful to explain the repelling water capability of Nepenthes alata. Based on the force and energy analysis, the mechanism of the bubble migration is well addressed. These findings pave a new way to accurately manipulate droplet or bubble movement, which bring inspirations to the design of microfluidic and water harvesting devices, as well as oil displacement and ore filtration.

Development of a Compact, Efficient Cooling Pump for Space Suit Life Support Systems

NASA Technical Reports Server (NTRS)

van Boeyen, Roger; Reeh, Jonathan; Trevino, Luis

2009-01-01

A compact, low-power electrochemically-driven fluid cooling pump is currently being developed by Lynntech, Inc. With no electric motor and minimal lightweight components, the pump is significantly lighter than conventional rotodynamic and displacement pumps. Reliability and robustness is achieved with the absence of rotating or moving components (apart from the bellows). By employing sulfonated polystyrene-based proton exchange membranes, rather than conventional Nafion membranes, a significant reduction in the actuator power consumption was demonstrated. Lynntech also demonstrated that these membranes possess the necessary mechanical strength, durability, and temperature range for long life space operation. The preliminary design for a Phase II prototype pump compares very favorably to the fluid cooling pumps currently used in space suit primary life support systems (PLSSs). Characteristics of the electrochemically-driven pump are described and the benefits of the technology as a replacement for electric motor pumps in mechanically pumped single-phase fluid loops is discussed.

Two-Dimensional Micro-/Nanoradian Angle Generator with High Resolution and Repeatability Based on Piezo-Driven Double-Axis Flexure Hinge and Three Capacitive Sensors.

PubMed

Tan, Xinran; Zhu, Fan; Wang, Chao; Yu, Yang; Shi, Jian; Qi, Xue; Yuan, Feng; Tan, Jiubin

2017-11-19

This study presents a two-dimensional micro-/nanoradian angle generator (2D-MNAG) that achieves high angular displacement resolution and repeatability using a piezo-driven flexure hinge for two-dimensional deflections and three capacitive sensors for output angle monitoring and feedback control. The principal error of the capacitive sensor for precision microangle measurement is analyzed and compensated for; so as to achieve a high angle output resolution of 10 nrad (0.002 arcsec) and positioning repeatability of 120 nrad (0.024 arcsec) over a large angular range of ±4363 μrad (±900 arcsec) for the 2D-MNAG. The impact of each error component, together with the synthetic error of the 2D-MNAG after principal error compensation are determined using Monte Carlo simulation for further improvement of the 2D-MNAG.

Two-Dimensional Micro-/Nanoradian Angle Generator with High Resolution and Repeatability Based on Piezo-Driven Double-Axis Flexure Hinge and Three Capacitive Sensors

PubMed Central

Tan, Xinran; Zhu, Fan; Wang, Chao; Yu, Yang; Shi, Jian; Qi, Xue; Yuan, Feng; Tan, Jiubin

2017-01-01

This study presents a two-dimensional micro-/nanoradian angle generator (2D-MNAG) that achieves high angular displacement resolution and repeatability using a piezo-driven flexure hinge for two-dimensional deflections and three capacitive sensors for output angle monitoring and feedback control. The principal error of the capacitive sensor for precision microangle measurement is analyzed and compensated for; so as to achieve a high angle output resolution of 10 nrad (0.002 arcsec) and positioning repeatability of 120 nrad (0.024 arcsec) over a large angular range of ±4363 μrad (±900 arcsec) for the 2D-MNAG. The impact of each error component, together with the synthetic error of the 2D-MNAG after principal error compensation are determined using Monte Carlo simulation for further improvement of the 2D-MNAG. PMID:29156595

Fluid-Driven Deformation of a Soft Porous Medium

NASA Astrophysics Data System (ADS)

Lutz, Tyler; Wilen, Larry; Wettlaufer, John

2017-11-01

Viscous drag forces resisting the flow of fluid through a soft porous medium are maintained by restoring forces associated with deformations in the solid matrix. We describe experimental measurements of the deformation of foam under a pressure-driven flow of water along a single axis. Image analysis techniques allow tracking of the foam displacement while pressure sensors allow measurement of the fluid pressure. Experiments are performed for a series of different pressure heads ranging from 10 to 90 psi, and the results are compared to theory. This work builds on previous measurements of the fluid-induced deformation of a bed of soft hydrogel spheres. Compared to the hydrogel system, foams have the advantage that the constituents of the porous medium do not rearrange during an experiment, but they have the disadvantage of having a high friction coefficient with any boundaries. We detail strategies to characterize and mitigate the effects of friction on the observed foam deformations.

Ankle morphology amplifies calcaneus movement relative to triceps surae muscle shortening.

PubMed

Csapo, R; Hodgson, J; Kinugasa, R; Edgerton, V R; Sinha, S

2013-08-15

The present study investigated the mechanical role of the dorsoventral curvature of the Achilles tendon in the conversion of the shortening of the plantarflexor muscles into ankle joint rotation. Dynamic, sagittal-plane magnetic resonance spin-tagged images of the ankle joint were acquired in six healthy subjects during both passive and active plantarflexion movements driven by a magnetic resonance compatible servomotor-controlled foot-pedal device. Several points on these images were tracked to determine the 1) path and deformation of the Achilles tendon, 2) ankle's center of rotation, and 3) tendon moment arms. The degree of mechanical amplification of joint movement was calculated as the ratio of the displacements of the calcaneus and myotendinous junction. In plantarflexion, significant deflection of the Achilles tendon was evident in both the passive (165.7 ± 7.4°; 180° representing a straight tendon) and active trials (166.9 ± 8.8°). This bend in the dorsoventral direction acts to move the Achilles tendon closer to the ankle's center of rotation, resulting in an ∼5% reduction of moment arm length. Over the entire range of movement, the overall displacement of the calcaneus exceeded the displacement of the myotendinous junction by ∼37%, with the mechanical gains being smaller in dorsi- and larger in plantarflexed joint positions. This is the first study to assess noninvasively and in vivo using MRI the curvature of the Achilles tendon during both passive and active plantarflexion movements. The dorsoventral tendon curvature amplifies the shortening of the plantarflexor muscles, resulting in a greater displacement of the tendon's insertion into the calcaneus compared with its origin.

VAB Sway Investigation

NASA Technical Reports Server (NTRS)

Youngquist, Robert c.; Ihlefeld, Curtis M.; Lane, John E.; Starr, Stanley O.

2013-01-01

The Vehicle Assembly Building (VAB) was constructed in the mid-1960s to house the Saturn V moon rocket while it was being assembled. Designed to withstand hurricanes and tropical storms, the V AB has a foundation consisting of 30,000 cubic yards of concrete strengthened by 4,225 steel rods driven 160 feet into limestone bedrock. The goal of the VAB Sway Investigation, which began collecting data in April 201 0 and ended in November 2012, was to quantify the displacement or sway of the VAB as a function of wind loading.

Software for System for Controlling a Magnetically Levitated Rotor

NASA Technical Reports Server (NTRS)

Morrison, Carlos R. (Inventor)

2004-01-01

In a rotor assembly having a rotor supported for rotation by magnetic bearings, a processor controlled by software or firmware controls the generation of force vectors that position the rotor relative to its bearings in a 'bounce' mode in which the rotor axis is displaced from the principal axis defined between the bearings and a 'tilt' mode in which the rotor axis is tilted or inclined relative to the principal axis. Waveform driven perturbations are introduced to generate force vectors that excite the rotor in either the 'bounce' or 'tilt' modes.

System for Controlling a Magnetically Levitated Rotor

NASA Technical Reports Server (NTRS)

Morrison, Carlos R. (Inventor)

2006-01-01

In a rotor assembly having a rotor supported for rotation by magnetic bearings, a processor controlled by software or firmware controls the generation of force vectors that position the rotor relative to its bearings in a "bounce" mode in which the rotor axis is displaced from the principal axis defined between the bearings and a "tilt" mode in which the rotor axis is tilted or inclined relative to the principal axis. Waveform driven perturbations are introduced to generate force vectors that excite the rotor in either the "bounce" or "tilt" modes.

Biologically inspired design of feedback control systems implemented using DNA strand displacement reactions.

PubMed

Foo, Mathias; Sawlekar, Rucha; Kulkarni, Vishwesh V; Bates, Declan G

2016-08-01

The use of abstract chemical reaction networks (CRNs) as a modelling and design framework for the implementation of computing and control circuits using enzyme-free, entropy driven DNA strand displacement (DSD) reactions is starting to garner widespread attention in the area of synthetic biology. Previous work in this area has demonstrated the theoretical plausibility of using this approach to design biomolecular feedback control systems based on classical proportional-integral (PI) controllers, which may be constructed from CRNs implementing gain, summation and integrator operators. Here, we propose an alternative design approach that utilises the abstract chemical reactions involved in cellular signalling cycles to implement a biomolecular controller - termed a signalling-cycle (SC) controller. We compare the performance of the PI and SC controllers in closed-loop with a nonlinear second-order chemical process. Our results show that the SC controller outperforms the PI controller in terms of both performance and robustness, and also requires fewer abstract chemical reactions to implement, highlighting its potential usefulness in the construction of biomolecular control circuits.

Subharmonic generation, chaos, and subharmonic resurrection in an acoustically driven fluid-filled cavity.

PubMed

Cantrell, John H; Adler, Laszlo; Yost, William T

2015-02-01

Traveling wave solutions of the nonlinear acoustic wave equation are obtained for the fundamental and second harmonic resonances of a fluid-filled cavity. The solutions lead to the development of a non-autonomous toy model for cavity oscillations. Application of the Melnikov method to the model equation predicts homoclinic bifurcation of the Smale horseshoe type leading to a cascade of period doublings with increasing drive displacement amplitude culminating in chaos. The threshold value of the drive displacement amplitude at tangency is obtained in terms of the acoustic drive frequency and fluid attenuation coefficient. The model prediction of subharmonic generation leading to chaos is validated from acousto-optic diffraction measurements in a water-filled cavity using a 5 MHz acoustic drive frequency and from the measured frequency spectrum in the bifurcation cascade regime. The calculated resonant threshold amplitude of 0.2 nm for tangency is consistent with values estimated for the experimental set-up. Experimental evidence for the appearance of a stable subharmonic beyond chaos is reported.

Measurement of elasto-plastic deformations by speckle interferometry

NASA Astrophysics Data System (ADS)

Bova, Marco; Bruno, Luigi; Poggialini, Andrea

2010-09-01

In the paper the authors present an experimental equipment for elasto-plastic characterization of engineering materials by tensile tests. The stress state is imposed to a dog bone shaped specimen by a testing machine fixed on the optical table and designed for optimizing the performance of a speckle interferometer. All three displacement components are measured by a portable speckle interferometer fed by three laser diodes of 50 mW, by which the deformations of a surface of about 6×8 mm2 can be fully analyzed in details. All the equipment is driven by control electronics designed and realized on purpose, by which it is possible to accurately modify the intensity of the illumination sources, the position of a PZT actuator necessary for applying phase-shifting procedure, and the overall displacement applied to the specimen. The experiments were carried out in National Instrument LabVIEW environment, while the processing of the experimental data in Wolfram Mathematica environment. The paper reports the results of the elasto-plastic characterization of a high strength steel specimen.

Modeling thermal spike driven reactions at low temperature and application to zirconium carbide radiation damage

NASA Astrophysics Data System (ADS)

Ulmer, Christopher J.; Motta, Arthur T.

2017-11-01

The development of TEM-visible damage in materials under irradiation at cryogenic temperatures cannot be explained using classical rate theory modeling with thermally activated reactions since at low temperatures thermal reaction rates are too low. Although point defect mobility approaches zero at low temperature, the thermal spikes induced by displacement cascades enable some atom mobility as it cools. In this work a model is developed to calculate "athermal" reaction rates from the atomic mobility within the irradiation-induced thermal spikes, including both displacement cascades and electronic stopping. The athermal reaction rates are added to a simple rate theory cluster dynamics model to allow for the simulation of microstructure evolution during irradiation at cryogenic temperatures. The rate theory model is applied to in-situ irradiation of ZrC and compares well at cryogenic temperatures. The results show that the addition of the thermal spike model makes it possible to rationalize microstructure evolution in the low temperature regime.

Semi-Active Control of Precast RC Columns under Seismic Action

NASA Astrophysics Data System (ADS)

Caterino, Nicola; Spizzuoco, Mariacristina

2017-10-01

This work is inspired by the idea of dissipating seismic energy at the base of prefabricated RC columns via semi-active (SA) variable dampers exploiting the base rocking. It was performed a wide numerical campaign to investigate the seismic behaviour of a pre-cast RC column with a variable base restraint. The latter is based on the combined use of a hinge, elastic springs, and magnetorheological (MR) dampers remotely controlled according to the instantaneous response of the structural component. The MR devices are driven by a SA control algorithm purposely written to modulate the dissipative capability so as to reduce base bending moment without causing excessive displacement at the top. The proposed strategy results to be really promising, since the base restraint relaxation, that favours the base moment demand reduction, is accompanied by a high enhancement of the dissipated energy due to rocking that can be even able to reduce top displacement in respect to the “fixed base rotation” conditions.

Post-Disaster Fertility: Hurricane Katrina and the Changing Racial Composition of New Orleans

PubMed Central

Seltzer, Nathan; Nobles, Jenna

2017-01-01

Large-scale climate events can have enduring effects on population size and composition. Natural disasters affect population fertility through multiple mechanisms, including displacement, demand for children, and reproductive care access. Fertility effects, in turn, influence the size and composition of new birth cohorts, extending the reach of climate events across generations. We study these processes in New Orleans during the decade spanning Hurricane Katrina. We combine census data, ACS data, and vital statistics data to describe fertility in New Orleans and seven comparison cities. Following Katrina, displacement contributed to a 30% decline in birth cohort size. Black fertility fell, and remained 4% below expected values through 2010. By contrast, white fertility increased by 5%. The largest share of births now occurs to white women. These fertility differences—beyond migration-driven population change—generate additional pressure on the renewal of New Orleans as a city in which the black population is substantially smaller in the disaster’s wake. PMID:29200546

Post-Disaster Fertility: Hurricane Katrina and the Changing Racial Composition of New Orleans.

PubMed

Seltzer, Nathan; Nobles, Jenna

2017-06-01

Large-scale climate events can have enduring effects on population size and composition. Natural disasters affect population fertility through multiple mechanisms, including displacement, demand for children, and reproductive care access. Fertility effects, in turn, influence the size and composition of new birth cohorts, extending the reach of climate events across generations. We study these processes in New Orleans during the decade spanning Hurricane Katrina. We combine census data, ACS data, and vital statistics data to describe fertility in New Orleans and seven comparison cities. Following Katrina, displacement contributed to a 30% decline in birth cohort size. Black fertility fell, and remained 4% below expected values through 2010. By contrast, white fertility increased by 5%. The largest share of births now occurs to white women. These fertility differences-beyond migration-driven population change-generate additional pressure on the renewal of New Orleans as a city in which the black population is substantially smaller in the disaster's wake.

Attenuation of the NMR signal in a field gradient due to stochastic dynamics with memory

NASA Astrophysics Data System (ADS)

Lisý, Vladimír; Tóthová, Jana

2017-03-01

The attenuation function S(t) for an ensemble of spins in a magnetic-field gradient is calculated by accumulation of the phase shifts in the rotating frame resulting from the displacements of spin-bearing particles. The found S(t), expressed through the particle mean square displacement, is applicable for any kind of stationary stochastic motion of spins, including their non-markovian dynamics with memory. The known expressions valid for normal and anomalous diffusion are obtained as special cases in the long time approximation. The method is also applicable to the NMR pulse sequences based on the refocusing principle. This is demonstrated by describing the Hahn spin echo experiment. The attenuation of the NMR signal is also evaluated providing that the random motion of particle is modeled by the generalized Langevin equation with the memory kernel exponentially decaying in time. The models considered in our paper assume massive particles driven by much smaller particles.

Hydrodynamic fingering instability induced by a precipitation reaction

NASA Astrophysics Data System (ADS)

De Wit, Anne; Nagatsu, Yuichiro

2014-05-01

We experimentally demonstrate that a precipitation reaction at the miscible interface between two reactive solutions can trigger a hydrodynamic instability due to the build-up of a locally adverse mobility gradient related to a decrease in permeability. The precipitate results from an A+B → C type of reaction when a solution containing one of the reactant is injected into a solution of the other reactant in a porous medium or a Hele-Shaw cell. Finger-like precipitation patterns are observed upon displacement, the properties of which depend on whether A displaces B or vice-versa. A mathematical modeling of the underlying mobility profile in the cell reconstructed on the basis of one-dimensional reaction-diffusion concentration profiles confirms that the instability originates from a local decrease in mobility driven by the precipitation. Nonlinear simulations of the related reaction-diffusion-convection model reproduce the properties of the instability observed experimentally. In particular, the simulations suggest that differences in diffusivity between A and B may contribute to the asymmetric characteristics of the fingering precipitation patterns.

The structural response of unsymmetrically laminated composite cylinders

NASA Technical Reports Server (NTRS)

Butler, T. A.; Hyer, M. W.

1989-01-01

The responses of an unsymmetrically laminated fiber-reinforced composite cylinder to an axial compressive load, a torsional load, and the temperature change associated with cooling from the processing temperature to the service temperature are investigated. These problems are considered axisymmetric and the response is studied in the context of linear elastic material behavior and geometrically linear kinematics. Four different laminates are studied: a general unsymmetric laminate; two unsymmetric but more conventional laminates; and a conventional quasi-isotropic symmetric laminate. The responses based on closed-form solutions for different boundary conditions are computed and studied in detail. Particular emphasis is directed at understanding the influence of elastic couplings in the laminates. The influence of coupling decreased from a large effect in the general unsymmetric laminate, to practically no effect in the quasi-isotropic laminate. For example, the torsional loading of the general unsymmetric laminate resulted in a radial displacement. The temperature change also caused a significant radial displacement to occur near the ends of the cylinder. On the other hand, the more conventional unsymmetric laminate and the quasi-isotropic cylinder did not deform radially when subjected to a torsional load. From the results obtained, it is clear the degree of elastic coupling can be controlled and indeed designed into a cylinder, the degree and character of the coupling being dictated by the application.

Crustal Displacements Due to Continental Water Loading

NASA Technical Reports Server (NTRS)

vanDam, T.; Wahr, J.; Milly, P. C. D.; Shmakin, A. B.; Blewitt, G.; Lavallee, D.; Larson, K. M.

2001-01-01

The effects of long-wavelength (> 100 km), seasonal variability in continental water storage on vertical crustal motions are assessed. The modeled vertical displacements (delta-r(sub M)) have root-mean-square (RMS) values for 1994-1998 as large as 8 mm with ranges up to 30 mm, and are predominantly annual in character. Regional strains are on the order of 20 nanostrain for tilt and 5 nanostrain for horizontal deformation. We compare delta-r(sub M) with observed Global Positioning System (GPS) heights (delta-r(sub O)) (which include adjustments to remove estimated effects of atmospheric pressure and annual tidal and non-tidal ocean loading) for 147 globally distributed sites. When the delta-r(sub O) time series are adjusted by delta-r(sub M), their variances are reduced, on average, by an amount equal to the variance of the delta-r(sub M). Of the delta-r(sub O) time series exhibiting a strong annual signal, more than half are found to have an annual harmonic that is in phase and of comparable amplitude with the annual harmonic in the delta-r(sub M). The delta-r(sub M) time series exhibit long-period variations that could be mistaken for secular tectonic trends or post-glacial rebound when observed over a time span of a few years.

Electrically Tunable Energy Bandgap in Dual-Gated Ultra-Thin Black Phosphorus Field Effect Transistors

NASA Astrophysics Data System (ADS)

Yan, Shi-Li; Xie, Zhi-Jian; Chen, Jian-Hao; Taniguchi, Takashi; Watanabe, Kenji

2017-03-01

The energy bandgap is an intrinsic character of semiconductors, which largely determines their properties. The ability to continuously and reversibly tune the bandgap of a single device during real time operation is of great importance not only to device physics but also to technological applications. Here we demonstrate a widely tunable bandgap of few-layer black phosphorus (BP) by the application of vertical electric field in dual-gated BP field-effect transistors. A total bandgap reduction of 124 meV is observed when the electrical displacement field is increased from 0.10V/nm to 0.83V/nm. Our results suggest appealing potential for few-layer BP as a tunable bandgap material in infrared optoelectronics, thermoelectric power generation and thermal imaging.

Analysis of photopole data reduction models

NASA Technical Reports Server (NTRS)

Cheek, James B.

1987-01-01

An analysis of the total impulse obtained from a buried explosive charge can be calculated from displacement versus time points taken from successive film frames of high speed motion pictures of the explosive event. The indicator of that motion is a pole and baseplate (photopole), which is placed on or within the soil overburden. Here, researchers are concerned with the precision of the impulse calculation and ways to improve that precision. Also examined here is the effect of each initial condition on the curve fitting process. It is shown that the zero initial velocity criteria should not be applied due to the linear acceleration versus time character of the cubic power series. The applicability of the new method to photopole data records whose early time motions are obscured is illustrated.

Agonistic character displacement in social cognition of advertisement signals.

PubMed

Pasch, Bret; Sanford, Rachel; Phelps, Steven M

2017-03-01

Interspecific aggression between sibling species may enhance discrimination of competitors when recognition errors are costly, but proximate mechanisms mediating increased discriminative ability are unclear. We studied behavioral and neural mechanisms underlying responses to conspecific and heterospecific vocalizations in Alston's singing mouse (Scotinomys teguina), a species in which males sing to repel rivals. We performed playback experiments using males in allopatry and sympatry with a dominant heterospecific (Scotinomys xerampelinus) and examined song-evoked induction of egr-1 in the auditory system to examine how neural tuning modulates species-specific responses. Heterospecific songs elicited stronger neural responses in sympatry than in allopatry, despite eliciting less singing in sympatry. Our results refute the traditional neuroethological concept of a matched filter and instead suggest expansion of sensory sensitivity to mediate competitor recognition in sympatry.

First record of Viannaiidae (Nematoda: Trichostrongylina) in fossorial rodents (Ctenomys spp.) from Central Argentina, with description of a new genus and species.

PubMed

Serrano, Paula Carolina; Digiani, María Celina

2016-09-14

A new genus and species of Viannaiidae (Trichostrongylina, Heligmosomoidea), Ischilinema baldoi n. gen. et sp. is described parasitizing two species of tuco-tucos, Ctenomys bergi and Ctenomys rosendopascuali (Rodentia, Hystricomorpha, Ctenomyidae) from Córdoba province, Central Argentina. No helminths were previously known from these two host species. The new genus is defined by the following characters: synlophe with 15 continuous ridges subequal in size, presence of left cuticular dilatation, a gap between ridges 1' and 2', bursa asymmetrical with dorsal ray hypertrophied and displaced to the right, and spicules not twisted. This is the first record of Viannaiidae from the Ctenomyidae, enlarging the host range of these parasites to five out of the 12 extant families of caviomorphs.

Orbital and spin dynamics of intraband electrons in quantum rings driven by twisted light.

PubMed

Quinteiro, G F; Tamborenea, P I; Berakdar, J

2011-12-19

We theoretically investigate the effect that twisted light has on the orbital and spin dynamics of electrons in quantum rings possessing sizable Rashba spin-orbit interaction. The system Hamiltonian for such a strongly inhomogeneous light field exhibits terms which induce both spin-conserving and spin-flip processes. We analyze the dynamics in terms of the perturbation introduced by a weak light field on the Rasha electronic states, and describe the effects that the orbital angular momentum as well as the inhomogeneous character of the beam have on the orbital and the spin dynamics.

Prediction of nonlinear evolution character of energetic-particle-driven instabilities

DOE PAGES

Duarte, Vinicius N.; Berk, H. L.; Gorelenkov, N. N.; ...

2017-03-17

A general criterion is proposed and found to successfully predict the emergence of chirping oscillations of unstable Alfvénic eigenmodes in tokamak plasma experiments. The model includes realistic eigenfunction structure, detailed phase-space dependences of the instability drive, stochastic scattering and the Coulomb drag. The stochastic scattering combines the effects of collisional pitch angle scattering and micro-turbulence spatial diffusion. Furthermore, the latter mechanism is essential to accurately identify the transition between the fixed-frequency mode behavior and rapid chirping in tokamaks and to resolve the disparity with respect to chirping observation in spherical and conventional tokamaks.

Prediction of nonlinear evolution character of energetic-particle-driven instabilities

NASA Astrophysics Data System (ADS)

Duarte, V. N.; Berk, H. L.; Gorelenkov, N. N.; Heidbrink, W. W.; Kramer, G. J.; Nazikian, R.; Pace, D. C.; Podestà, M.; Tobias, B. J.; Van Zeeland, M. A.

2017-05-01

A general criterion is proposed and found to successfully predict the emergence of chirping oscillations of unstable Alfvénic eigenmodes in tokamak plasma experiments. The model includes realistic eigenfunction structure, detailed phase-space dependences of the instability drive, stochastic scattering and the Coulomb drag. The stochastic scattering combines the effects of collisional pitch angle scattering and micro-turbulence spatial diffusion. The latter mechanism is essential to accurately identify the transition between the fixed-frequency mode behavior and rapid chirping in tokamaks and to resolve the disparity with respect to chirping observation in spherical and conventional tokamaks.

The geology of the Oceanographer Transform: The ridge-transform intersection

NASA Astrophysics Data System (ADS)

Karson, J. A.; Fox, P. J.; Sloan, H.; Crane, K. T.; Kidd, W. S. F.; Bonatti, E.; Stroup, J. B.; Fornari, D. J.; Elthon, D.; Hamlyn, P.; Casey, J. F.; Gallo, D. G.; Needham, D.; Sartori, R.

1984-06-01

Seven dives in the submersible ALVIN and four deep-towed (ANGUS) camera lowerings have been made at the eastern ridge-transform intersection of the Oceanographer Transform with the axis of the Mid-Atlantic Ridge. These data constrain our understanding of the processes that create and shape the distinctive morphology that is characteristic of slowly-slipping ridge-transform-ridge plate boundaries. Although the geological relationships observed in the rift valley floor in the study area are similar to those reported for the FAMOUS area, we observe a distinct change in the character of the rift valley floor with increasing proximity to the transform. Over a distance of approximately ten kilometers the volcanic constructional terrain becomes increasingly more disrupted by faulting and degraded by mass wasting. Moreover, proximal to the transform boundary, faults with orientations oblique to the trend of the rift valley are recognized. The morphology of the eastern rift valley wall is characterized by inward-facing scarps that are ridge-axis parallel, but the western rift valley wall, adjacent to the active transform zone, is characterized by a complex fault pattern defined by faults exhibiting a wide range of orientations. However, even for transform parallel faults no evidence for strike-slip displacement is observed throughout the study area and evidence for normal (dip-slip) displacement is ubiquitous. Basalts, semi-consolidated sediments (chalks, debris slide deposits) and serpentinized ultramafic rocks are recovered from localities within or proximal to the rift valley. The axis of accretion-principal transform displacement zone intersection is not clearly established, but appears to be located along the E-W trending, southern flank of the deep nodal basin that defines the intersection of the transform valley with the rift floor.

Water Displacement in Oil-Wet Tight Reservoirs by Dynamic Network Simulation

NASA Astrophysics Data System (ADS)

Wang, Y.; Li, M.; Chen, M.

2017-12-01

Pore network simulation is an effective tool for studying the multiphase flow in porous media. Based on the topological information and pore-throat size distribution obtained from the analysis of Scanning Electron Microscope (SEM) and constant-rate mercury injection (CRMI) for tight cores (composed by micro-nano scale throats and micro scale pores), a simple cubic (SC) pore-throat network was built with equilateral triangular cross-section throats and cubic bodies. Rules for oil and water movement and redistribution were devised in accordance with the physics process at pore-throat scale. Water flooding from oil-saturated under irreducible water were simulated by considering the changing displacement rate and viscosity ratio at the slightly oil-wet condition (the static contact angle ranges between π/2 to 2π/3). Different from the double pressure field algorithm, a single pressure field which solved by using successive over relaxation method was used with the flow of irreducible water in corners was ignored while its swilling was take into consideration. Dynamic of displacement fronts, relative permeability curves and residual oil saturation were obtained. It showed that there were obviously snap-off at low capillary number (Nc<10-5) and fingering at high capillary number (Nc<10-4) even at a favorable viscosity ratio (M=1). The magnitude of viscosity ratio effect on relative permeability depended largely on the capillary number, which the effect wasn't noticeable for a high capillary number. For residual oil saturation Sor, it showed that Sor decreased with the increase of capillary number at different viscosity ratio. Changing of residual oil saturation from simulation was in good agreement with the experimental results in a certain range, which indicated that this network model could be used to character the water flooding in tight reservoirs.

Using cGPS to estimate the magma budget for Soufrière Hills volcano, Montserrat, West Indies

NASA Astrophysics Data System (ADS)

Collinson, Amy; Neuberg, Jurgen; Pascal, Karen

2017-04-01

For over 20 years, Soufrière Hills Volcano, Montserrat has been in a state of volcanic unrest. Intermittent periods of dome building have been punctuated by explosive eruptions and dome collapse events, endangering the lives of the inhabitants of the island. The last episode of active magma extrusion was in February 2010, and the last explosive event (ash venting) in March 2012. Despite a lack of recent eruptive activity, the volcano continues to emit significant volumes of SO2 and shows an ongoing trend of island inflation as indicated by cGPS. Through the aid of three-dimensional numerical modelling, using a finite element method, we model the cGPS data to explore the potential sources of the ongoing island deformation. We consider both magmatic (dykes and chambers) and tectonic sources which result in entirely different interpretations: Whilst a magmatic source suggests the possibility for further eruption, a tectonic source may indicate cessation of volcanic activity. We investigate the effects that different sources (shapes, characters and depths) have on the surface displacement. We demonstrate that whilst a tectonic contribution cannot be completely discounted, the dominant source is magmatic. Consequently, we define a best-fit model which we use to assess the source volume change, and therefore, the potential current magma budget. Based on the similarity in the relative displacement between the cGPS stations at every episode of the eruption, we assume that the displacement for all Phases and Pauses can be explained by the same basic source. Therefore, we interpret the cGPS data with our source model for all the preceding Pauses and Phases to estimate the magma budget feeding the entire eruption. Subsequently, we derive important insights into the potential future eruptive behaviour of the volcano.

D Model Visualization Enhancements in Real-Time Game Engines

NASA Astrophysics Data System (ADS)

Merlo, A.; Sánchez Belenguer, C.; Vendrell Vidal, E.; Fantini, F.; Aliperta, A.

2013-02-01

This paper describes two procedures used to disseminate tangible cultural heritage through real-time 3D simulations providing accurate-scientific representations. The main idea is to create simple geometries (with low-poly count) and apply two different texture maps to them: a normal map and a displacement map. There are two ways to achieve models that fit with normal or displacement maps: with the former (normal maps), the number of polygons in the reality-based model may be dramatically reduced by decimation algorithms and then normals may be calculated by rendering them to texture solutions (baking). With the latter, a LOD model is needed; its topology has to be quad-dominant for it to be converted to a good quality subdivision surface (with consistent tangency and curvature all over). The subdivision surface is constructed using methodologies for the construction of assets borrowed from character animation: these techniques have been recently implemented in many entertainment applications known as "retopology". The normal map is used as usual, in order to shade the surface of the model in a realistic way. The displacement map is used to finish, in real-time, the flat faces of the object, by adding the geometric detail missing in the low-poly models. The accuracy of the resulting geometry is progressively refined based on the distance from the viewing point, so the result is like a continuous level of detail, the only difference being that there is no need to create different 3D models for one and the same object. All geometric detail is calculated in real-time according to the displacement map. This approach can be used in Unity, a real-time 3D engine originally designed for developing computer games. It provides a powerful rendering engine, fully integrated with a complete set of intuitive tools and rapid workflows that allow users to easily create interactive 3D contents. With the release of Unity 4.0, new rendering features have been added, including DirectX 11 support. Real-time tessellation is a technique that can be applied by using such technology. Since the displacement and the resulting geometry are calculated by the GPU, the time-based execution cost of this technique is very low.

The Role of the Oculomotor System in Updating Visual-Spatial Working Memory across Saccades

PubMed Central

Boon, Paul J.; Belopolsky, Artem V.; Theeuwes, Jan

2016-01-01

Visual-spatial working memory (VSWM) helps us to maintain and manipulate visual information in the absence of sensory input. It has been proposed that VSWM is an emergent property of the oculomotor system. In the present study we investigated the role of the oculomotor system in updating of spatial working memory representations across saccades. Participants had to maintain a location in memory while making a saccade to a different location. During the saccade the target was displaced, which went unnoticed by the participants. After executing the saccade, participants had to indicate the memorized location. If memory updating fully relies on cancellation driven by extraretinal oculomotor signals, the displacement should have no effect on the perceived location of the memorized stimulus. However, if postsaccadic retinal information about the location of the saccade target is used, the perceived location will be shifted according to the target displacement. As it has been suggested that maintenance of accurate spatial representations across saccades is especially important for action control, we used different ways of reporting the location held in memory; a match-to-sample task, a mouse click or by making another saccade. The results showed a small systematic target displacement bias in all response modalities. Parametric manipulation of the distance between the to-be-memorized stimulus and saccade target revealed that target displacement bias increased over time and changed its spatial profile from being initially centered on locations around the saccade target to becoming spatially global. Taken together results suggest that we neither rely exclusively on extraretinal nor on retinal information in updating working memory representations across saccades. The relative contribution of retinal signals is not fixed but depends on both the time available to integrate these signals as well as the distance between the saccade target and the remembered location. PMID:27631767

Identifying the time scale of synchronous movement: a study on tropical snakes.

PubMed

Lindström, Tom; Phillips, Benjamin L; Brown, Gregory P; Shine, Richard

2015-01-01

Individual movement is critical to organismal fitness and also influences broader population processes such as demographic stochasticity and gene flow. Climatic change and habitat fragmentation render the drivers of individual movement especially critical to understand. Rates of movement of free-ranging animals through the landscape are influenced both by intrinsic attributes of an organism (e.g., size, body condition, age), and by external forces (e.g., weather, predation risk). Statistical modelling can clarify the relative importance of those processes, because externally-imposed pressures should generate synchronous displacements among individuals within a population, whereas intrinsic factors should generate consistency through time within each individual. External and intrinsic factors may vary in importance at different time scales. In this study we focused on daily displacement of an ambush-foraging snake from tropical Australia (the Northern Death Adder Acanthophis praelongus), based on a radiotelemetric study. We used a mixture of spectral representation and Bayesian inference to study synchrony in snake displacement by phase shift analysis. We further studied autocorrelation in fluctuations of displacement distances as "one over f noise". Displacement distances were positively autocorrelated with all considered noise colour parameters estimated as >0. We show how the methodology can reveal time scales of particular interest for synchrony and found that for the analysed data, synchrony was only present at time scales above approximately three weeks. We conclude that the spectral representation combined with Bayesian inference is a promising approach for analysis of movement data. Applying the framework to telemetry data of A. praelongus, we were able to identify a cut-off time scale above which we found support for synchrony, thus revealing a time scale where global external drivers have a larger impact on the movement behaviour. Our results suggest that for the considered study period, movement at shorter time scales was primarily driven by factors at the individual level; daily fluctuations in weather conditions had little effect on snake movement.

Evaluation of a silicon 5 MHz p–n diode actuator with a laterally vibrating extensional mode

NASA Astrophysics Data System (ADS)

Miyazaki, Fumito; Baba, Kazuki; Tanigawa, Hiroshi; Furutsuka, Takashi; Suzuki, Kenichiro

2018-05-01

In this paper, we describe p–n diode actuators that are laterally driven by the force induced in a depletion layer. The previously reported p–n diode actuators have been vertically driven. Because the resonant frequency depends on the thickness of the vibrating plate, the integration of resonators with different frequencies on a chip has been difficult. The resonators in this work are driven laterally by using length-extensional vibration. We have developed a compact model based on an analytical expression, in which p–n diode actuators are driven by the forces induced by the spread of the depletion layer. The deflection generated by the p–n diode actuators was proportional to the ratio of the depletion layer width to the resonator thickness as well as the position of the p–n junction. Good agreement of experimental results with the theory was confirmed by comparing the measured values for silicon p–n diode rectangular-plate actuators fabricated using a silicon-on-insulator (SOI) substrate. The displacement amplitude of the actuators was proportional to the DC bias, while the resonant frequency was independent of the DC bias. The latter characteristic is very different from that of widely used electrostatic actuators. Although the amplitude of the actuator measured in this work was very small, it is expected that the amplitude will increase greatly by increasing the doping of the p–n diode actuators.

CA-LOD: Collision Avoidance Level of Detail for Scalable, Controllable Crowds

NASA Astrophysics Data System (ADS)

Paris, Sébastien; Gerdelan, Anton; O'Sullivan, Carol

The new wave of computer-driven entertainment technology throws audiences and game players into massive virtual worlds where entire cities are rendered in real time. Computer animated characters run through inner-city streets teeming with pedestrians, all fully rendered with 3D graphics, animations, particle effects and linked to 3D sound effects to produce more realistic and immersive computer-hosted entertainment experiences than ever before. Computing all of this detail at once is enormously computationally expensive, and game designers as a rule, have sacrificed the behavioural realism in favour of better graphics. In this paper we propose a new Collision Avoidance Level of Detail (CA-LOD) algorithm that allows games to support huge crowds in real time with the appearance of more intelligent behaviour. We propose two collision avoidance models used for two different CA-LODs: a fuzzy steering focusing on the performances, and a geometric steering to obtain the best realism. Mixing these approaches allows to obtain thousands of autonomous characters in real time, resulting in a scalable but still controllable crowd.

Optical design of GaN nanowire arrays for photocatalytic applications

NASA Astrophysics Data System (ADS)

Winnerl, Julia; Hudeczek, Richard; Stutzmann, Martin

2018-05-01

GaN nanowire (NW) arrays are interesting candidates for photocatalytic applications due to their high surface-to-volume ratio and their waveguide character. The integration of GaN NW arrays on GaN-based light emitting diodes (LEDs), serving as a platform for electrically driven NW-based photocatalytic devices, enables an efficient coupling of the light from the planar LED to the GaN NWs. Here, we present a numerical study of the influence of the NW geometries, i.e., the NW diameter, length, and period, and the illumination wavelength on the transmission of GaN NW arrays on transparent substrates. A detailed numerical analysis reveals that the transmission characteristics for large periods are determined by the waveguide character of the single NW, whereas for dense GaN NW arrays inter-wire coupling and diffraction effects originating from the periodic arrangement of the GaN NWs dominate the transmission. The numerically simulated results are confirmed by experimental transmission measurements. We also investigate the influence of a dielectric NW shell and of the surrounding medium on the transmission characteristics of a GaN NW array.

Floral and mating system divergence in secondary sympatry: testing an alternative hypothesis to reinforcement in Clarkia.

PubMed

Briscoe Runquist, Ryan D; Moeller, David A

2014-01-01

Reproductive character displacement (RCD) is often an important signature of reinforcement when partially cross-compatible taxa meet in secondary sympatry. In this study, floral evolution is examined during the Holocene range expansion of Clarkia xantiana subsp. parviflora from eastern Pleistocene refugia to a western zone of sympatry with its sister taxon, subsp. xantiana. Floral divergence between the two taxa is greater in sympatry than allopatry. The goal was to test an alternative hypothesis to reinforcement - that floral divergence of sympatric genotypes is simply a by-product of adaptation to pollination environments that differ between the allopatric and sympatric portions of the subspecies' range. Floral trait data from two common garden studies were used to examine floral divergence between sympatric and allopatric regions and among phylogeographically defined lineages. In natural populations of C. x. parviflora, the magnitude of pollen limitation and reproductive assurance were quantified across its west-to-east range. Potted sympatric and allopatric genotypes were also reciprocally translocated between geographical regions to distinguish between the effects of floral phenotype versus contrasting pollinator environments on reproductive ecology. Sympatric populations are considerably smaller flowered with reduced herkogamy. Pollen limitation and the reproductive assurance value of selfing are greater in sympatric than in allopatric populations. Most significantly, reciprocal translocation experiments showed these differences in reproductive ecology cannot be attributed to contrasting pollinator environments between the sympatric and allopatric regions, but instead reflect the effects of flower size on pollinator attraction. Floral evolution occurred during the westward range expansion of parviflora, particularly in the zone of sympatry with xantiana. No evidence was found that strongly reduced flower size in sympatric parviflora (and RCD between parviflora and xantiana) is due to adaptation to limited pollinator availability. Rather, floral divergence appears to have been driven by other factors, such as interactions with congenerics in secondary sympatry.

Look who's talking! Facial appearance can bias source monitoring.

PubMed

Nash, Robert A; Bryer, Olwen M; Schlaghecken, Friederike

2010-05-01

When we see a stranger's face we quickly form impressions of his or her personality, and expectations of how the stranger might behave. Might these intuitive character judgements bias source monitoring? Participants read headlines "reported" by a trustworthy- and an untrustworthy-looking reporter. Subsequently, participants recalled which reporter provided each headline. Source memory for likely-sounding headlines was most accurate when a trustworthy-looking reporter had provided the headlines. Conversely, source memory for unlikely-sounding headlines was most accurate when an untrustworthy-looking reporter had provided the headlines. This bias appeared to be driven by the use of decision criteria during retrieval rather than differences in memory encoding. Nevertheless, the bias was apparently unrelated to variations in subjective confidence. These results show for the first time that intuitive, stereotyped judgements of others' appearance can bias memory attributions analogously to the biases that occur when people receive explicit information to distinguish sources. We suggest possible real-life consequences of these stereotype-driven source-monitoring biases.

Wide operating window spin-torque majority gate towards large-scale integration of logic circuits

NASA Astrophysics Data System (ADS)

Vaysset, Adrien; Zografos, Odysseas; Manfrini, Mauricio; Mocuta, Dan; Radu, Iuliana P.

2018-05-01

Spin Torque Majority Gate (STMG) is a logic concept that inherits the non-volatility and the compact size of MRAM devices. In the original STMG design, the operating range was restricted to very small size and anisotropy, due to the exchange-driven character of domain expansion. Here, we propose an improved STMG concept where the domain wall is driven with current. Thus, input switching and domain wall propagation are decoupled, leading to higher energy efficiency and allowing greater technological optimization. To ensure majority operation, pinning sites are introduced. We observe through micromagnetic simulations that the new structure works for all input combinations, regardless of the initial state. Contrary to the original concept, the working condition is only given by threshold and depinning currents. Moreover, cascading is now possible over long distances and fan-out is demonstrated. Therefore, this improved STMG concept is ready to build complete Boolean circuits in absence of external magnetic fields.

Irrationality and Quasiperiodicity in Driven Nonlinear Systems

NASA Astrophysics Data System (ADS)

Cubero, David; Casado-Pascual, Jesús; Renzoni, Ferruccio

2014-05-01

We analyze the relationship between irrationality and quasiperiodicity in nonlinear driven systems. To that purpose, we consider a nonlinear system whose steady-state response is very sensitive to the periodic or quasiperiodic character of the input signal. In the infinite time limit, an input signal consisting of two incommensurate frequencies will be recognized by the system as quasiperiodic. We show that this is, in general, not true in the case of finite interaction times. An irrational ratio of the driving frequencies of the input signal is not sufficient for it to be recognized by the nonlinear system as quasiperiodic, resulting in observations which may differ by several orders of magnitude from the expected quasiperiodic behavior. Thus, the system response depends on the nature of the irrational ratio, as well as the observation time. We derive a condition for the input signal to be identified by the system as quasiperiodic. Such a condition also takes into account the sub-Fourier response of the nonlinear system.

Role of activity in human dynamics

NASA Astrophysics Data System (ADS)

Zhou, T.; Kiet, H. A. T.; Kim, B. J.; Wang, B.-H.; Holme, P.

2008-04-01

The human society is a very complex system; still, there are several non-trivial, general features. One type of them is the presence of power-law-distributed quantities in temporal statistics. In this letter, we focus on the origin of power laws in rating of movies. We present a systematic empirical exploration of the time between two consecutive ratings of movies (the interevent time). At an aggregate level, we find a monotonous relation between the activity of individuals and the power law exponent of the interevent time distribution. At an individual level, we observe a heavy-tailed distribution for each user, as well as a negative correlation between the activity and the width of the distribution. We support these findings by a similar data set from mobile phone text-message communication. Our results demonstrate a significant role of the activity of individuals on the society-level patterns of human behavior. We believe this is a common character in the interest-driven human dynamics, corresponding to (but different from) the universality classes of task-driven dynamics.

The evolution of fabric with displacement in natural brittle faults

NASA Astrophysics Data System (ADS)

Mittempergher, S.; Di Toro, G.; Gratier, J.; Aretusini, S.; Boullier-Bertrand, A.

2011-12-01

In experiments performed at room temperature on gouges, a characteristic clast size distribution (CSD) is produced with increasing strain, and shear localization is documented to begin after few millimetres of sliding. But in natural faults active at depth in the crust, mechanical processes are associated with fluid-rock interactions, which might control the deformation and strength recovery. We aim to investigate the microstructural, geochemical and mineralogical evolution of low-displacement faults with increasing shear strain. The faults (cataclasite- and pseudotachylyte-bearing) are hosted in tonalite and were active at 9-11 km and 250-300°C. The samples were collected on a large glacier-polished outcrop, where major faults (accommodating up to 4300 mm of displacement) exploit pre-existing magmatic joints and are connected by a network of secondary fractures and faults (accommodating up to 500 mm of displacement) breaking intact tonalite. We performed optical and cathodoluminescence (CL) microscope, Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS), Rietveld X-Ray Powder Diffraction and microprobe chemical analysis in deformation zones of secondary faults with various offsets in order to evaluate the transfer of chemical species between dissolution zones and protected zones. Image analysis techniques were applied on SEM-BSE and optical microscope images to compute the CSD in samples, which experienced an increasing amount of strain. The secondary fractures are up to 5 mm thick. Within the first 20 mm of displacement, shear localizes along Y and R1 surfaces and a cataclastic foliation develops. The CSD evolves from a fractal dimension D of 1.3 in fractures without visible displacement to values above 2 after the first 500 mm of displacement. Chemical maps and CL images indicate that the foliation in cataclasite results from the rotation and fragmentation of clasts, with dissolution of quartz and passive concentration of Ti oxides and titanite in the foliation planes. The cataclasites are cemented by pervasive precipitation of K-feldspar plagues and idiomorphic, randomly oriented, epidote and chlorite. We conclude that the textures of these small displacement (< 500 mm) faults are controlled by brittle processes (fracture propagation and cataclastic comminution) similar to those reproduced in friction experiments performed on granite gouge (e.g., Beeler et al., 1996; Logan, 2007). Then progressively, stress driven fluid-rock reactions develop as fracturing and grain size reduction allows the kinetics of these reactions to be more efficient and fracture interconnection allows fluid infiltration. Healing of microfractures and fault rock cementation caused a rapid posteismic recovery of fault strength. References Beeler, N.M., Tullis, T.E., Blanpied, L., Weeks, J.D., 1996. Frictional behaviour of large displacement experimental faults. Journal of Geophysical Research 101, B4, 8697-8715. Logan, J.M., 2007. The progression from damage to localization of displacement observed in laboratory testing of porous rocks, in Lewis, H., and Couples, G.D. (eds.) The relationship between damage and localization. Geological Society of London Special Publication 289, 75-87.

Relations between overturning length scales at the Spanish planetary boundary layer

NASA Astrophysics Data System (ADS)

López, Pilar; Cano, José L.

2016-04-01

We analyze the behavior of the maximum Thorpe displacement (dT)max and the Thorpe scale LTat the atmospheric boundary layer (ABL), extending previous research with new data and improving our studies related to the novel use of the Thorpe method applied to ABL. The maximum Thorpe displacements vary between -900 m and 950 m for the different field campaigns. The maximum Thorpe displacement is always greater under convective conditions than under stable ones, independently of its sign. The Thorpe scale LT ranges between 0.2 m and 680 m for the different data sets which cover different stratified mixing conditions (turbulence shear-driven and convective regions). The Thorpe scale does not exceed several tens of meters under stable and neutral stratification conditions related to instantaneous density gradients. In contrast, under convective conditions, Thorpe scales are relatively large, they exceed hundreds of meters which may be related to convective bursts. We analyze the relation between (dT)max and the Thorpe scale LT and we deduce that they verify a power law. We also deduce that there is a difference in exponents of the power laws for convective conditions and shear-driven conditions. These different power laws could identify overturns created under different mechanisms. References Cuxart, J., Yagüe, C., Morales, G., Terradellas, E., Orbe, J., Calvo, J., Fernández, A., Soler, M., Infante, C., Buenestado, P., Espinalt, Joergensen, H., Rees, J., Vilà, J., Redondo, J., Cantalapiedra, I. and Conangla, L.: Stable atmospheric boundary-layer experiment in Spain (Sables 98). A report, Boundary-Layer Meteorology, 96, 337-370, 2000. Dillon, T. M.: Vertical Overturns: A Comparison of Thorpe and Ozmidov Length Scales, J. Geophys. Res., 87(C12), 9601-9613, 1982. Itsweire, E. C.: Measurements of vertical overturns in stably stratified turbulent flow, Phys. Fluids, 27(4), 764-766, 1984. Kitade, Y., Matsuyama, M. and Yoshida, J.: Distribution of overturn induced by internal tides and Thorpe scale in Uchiura Bay, Journal of Oceanography, 59, 845-850, 2003. López P., Cano J. L., Cano D. and Tijera M.: Thorpe method applied to planetary boundary layer data, Il Nuovo Cimento, 31C(5-6), 881-892, 2008. DOI: 10.1393/ncc/i2009-10338-3. Lorke A. and Wüest A.: Probability density of displacement and overturning length scales under diverse stratification, J. Geophys. Res., 107 (C12), 3214-3225, 2002. Piera, J., Roget, E. and Catalan, J.: Turbulent patch identification in microstructure profiles: a method based on wavelet denoising and Thorpe displacement analysis, J. Atmospheric and Oceanic Technology, 19, 1390-1402, 2002. Piera, J.: Signal processing of microstructure profiles: integrating turbulent spatial scales in aquatic ecological modelling, Ph. D. Thesis, Gerona University, Spain, 2004. Smyth, W. D. and Moum, J. N.: Length scales of turbulence in stably stratified mixing layers, Phys. Fluids., 12, 1327-1342, 2000. Thorpe, S.A.: Turbulence and Mixing in a Scottish Loch, Philos. Trans. R. Soc. London (Ser. A), 286(1334), 125-18, 1977.

Kinematics of polygonal fault systems: observations from the northern North Sea

NASA Astrophysics Data System (ADS)

Wrona, Thilo; Magee, Craig; Jackson, Christopher A.-L.; Huuse, Mads; Taylor, Kevin G.

2017-12-01

Layer-bound, low-displacement normal faults, arranged into a broadly polygonal pattern, are common in many sedimentary basins. Despite having constrained their gross geometry, we have a relatively poor understanding of the processes controlling the nucleation and growth (i.e. the kinematics) of polygonal fault systems. In this study we use high-resolution 3-D seismic reflection and borehole data from the northern North Sea to undertake a detailed kinematic analysis of faults forming part of a seismically well-imaged polygonal fault system hosted within the up to 1000 m thick, Early Palaeocene-to-Middle Miocene mudstones of the Hordaland Group. Growth strata and displacement-depth profiles indicate faulting commenced during the Eocene to early Oligocene, with reactivation possibly occurring in the late Oligocene to middle Miocene. Mapping the position of displacement maxima on 137 polygonal faults suggests that the majority (64%) nucleated in the lower 500 m of the Hordaland Group. The uniform distribution of polygonal fault strikes in the area indicates that nucleation and growth were not driven by gravity or far-field tectonic extension as has previously been suggested. Instead, fault growth was likely facilitated by low coefficients of residual friction on existing slip surfaces, and probably involved significant layer-parallel contraction (strains of 0.01-0.19) of the host strata. To summarize, our kinematic analysis provides new insights into the spatial and temporal evolution of polygonal fault systems.

Real-time Focused Ultrasound Surgery (FUS) Monitoring Using Harmonic Motion Imaging (HMI)

NASA Astrophysics Data System (ADS)

Maleke, Caroline; Konofagou, Elisa E.

2009-04-01

Monitoring changes in tissue mechanical properties to optimally control thermal exposure is important in thermal therapies. The amplitude-modulated (AM) harmonic motion imaging (HMI) for focused ultrasound (HMIFU) technique is a radiation force technique, which has the capability of tracking tissue stiffness during application of an oscillatory force. The feasibility of HMIFU for assessing mechanical tissue properties has been previously demonstrated. In this paper, a confocal transducer, combining a 4.5 MHz FUS transducer and a 3.3 MHz phased array imaging transducer, was used. The FUS transducer was driven by AM wave at 15 Hz with an acoustic intensity (Ispta) was equal to 1050 W/cm2. A lowpass digital filter was used to remove the spectrum of the higher power beam prior to displacement estimation. The resulting axial tissue displacement was estimated using 1D cross-correlation with a correlation window of 2 mm and a 92.5% overlap. A thermocouple was also used to measure the temperature near the ablated region. 2D HMI-images from six-bovine-liver specimens indicated the onset of coagulation necrosis through changes in amplitude displacement after coagulation due to its simultaneous probing and heating capability. The HMI technique can thus be used to monitor temperature-related stiffness changes of tissues during thermal therapies in real-time, i.e., without interrupting or modifying the treatment protocol.

Applying a pelvic corrective force induces forced use of the paretic leg and improves paretic leg EMG activities of individuals post-stroke during treadmill walking.

PubMed

Hsu, Chao-Jung; Kim, Janis; Tang, Rongnian; Roth, Elliot J; Rymer, William Z; Wu, Ming

2017-10-01

To determine whether applying a mediolateral corrective force to the pelvis during treadmill walking would enhance muscle activity of the paretic leg and improve gait symmetry in individuals with post-stroke hemiparesis. Fifteen subjects with post-stroke hemiparesis participated in this study. A customized cable-driven robotic system based over a treadmill generated a mediolateral corrective force to the pelvis toward the paretic side during early stance phase. Three different amounts of corrective force were applied. Electromyographic (EMG) activity of the paretic leg, spatiotemporal gait parameters and pelvis lateral displacement were collected. Significant increases in integrated EMG of hip abductor, medial hamstrings, soleus, rectus femoris, vastus medialis and tibialis anterior were observed when pelvic corrective force was applied, with pelvic corrective force at 9% of body weight inducing greater muscle activity than 3% or 6% of body weight. Pelvis lateral displacement was more symmetric with pelvic corrective force at 9% of body weight. Applying a mediolateral pelvic corrective force toward the paretic side may enhance muscle activity of the paretic leg and improve pelvis displacement symmetry in individuals post-stroke. Forceful weight shift to the paretic side could potentially force additional use of the paretic leg and improve the walking pattern. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Local structural behavior of PbZr0.5Ti0.5O3 during electric field application via in situ pair distribution function study

NASA Astrophysics Data System (ADS)

Zhao, Changhao; Hou, Dong; Chung, Ching-Chang; Yu, Yingying; Liu, Wenfeng; Li, Shengtao; Jones, Jacob L.

2017-11-01

The local structural behavior of PbZr0.5Ti0.5O3 (PZT 50/50) ceramics during application of an electric field was investigated using pair distribution function (PDF) analysis. In situ synchrotron total scattering was conducted, and the PDFs were calculated from the Fourier transform of the total scattering data. The PDF refinement of the zero-field data suggests a local-structure model with [001] Ti-displacement and negligible Zr-displacement. The directional PDFs at different field amplitudes indicate the bond-length distribution of the nearest Pb-B (B = Zr/Ti) pair changes significantly with the field. The radial distribution functions (RDFs) of a model for polarization rotation were calculated. The calculated and the experimental RDFs are consistent. This result suggests the changes in Pb-B bond-length distribution could be dominantly caused by polarization rotation. Peak fitting of the experimental RDFs was also conducted. The peak position trends with increasing field are mostly in agreement with the calculation result of the polarization rotation model. The area ratio of the peaks in the experimental RDFs also changed with field amplitude, indicating that Zr atoms have a detectable displacement driven by the electric field. Our study provides an experimental observation of the behaviors of PZT 50/50 under field at a local scale which supports the polarization rotation mechanism.

Power strain imaging based on vibro-elastography techniques

NASA Astrophysics Data System (ADS)

Wen, Xu; Salcudean, S. E.

2007-03-01

This paper describes a new ultrasound elastography technique, power strain imaging, based on vibro-elastography (VE) techniques. With this method, tissue is compressed by a vibrating actuator driven by low-pass or band-pass filtered white noise, typically in the 0-20 Hz range. Tissue displacements at different spatial locations are estimated by correlation-based approaches on the raw ultrasound radio frequency signals and recorded in time sequences. The power spectra of these time sequences are computed by Fourier spectral analysis techniques. As the average of the power spectrum is proportional to the squared amplitude of the tissue motion, the square root of the average power over the range of excitation frequencies is used as a measure of the tissue displacement. Then tissue strain is determined by the least squares estimation of the gradient of the displacement field. The computation of the power spectra of the time sequences can be implemented efficiently by using Welch's periodogram method with moving windows or with accumulative windows with a forgetting factor. Compared to the transfer function estimation originally used in VE, the computation of cross spectral densities is not needed, which saves both the memory and computational times. Phantom experiments demonstrate that the proposed method produces stable and operator-independent strain images with high signal-to-noise ratio in real time. This approach has been also tested on a few patient data of the prostate region, and the results are encouraging.

Unique self-assembly properties of a bridge-shaped protein dimer with quantum dots

NASA Astrophysics Data System (ADS)

Wang, Jianhao; Jiang, Pengju; Gao, Liqian; Yu, Yongsheng; Lu, Yao; Qiu, Lin; Wang, Cheli; Xia, Jiang

2013-09-01

How protein-protein interaction affects protein-nanoparticle self-assembly is the key to the understanding of biomolecular coating of nanoparticle in biological fluids. However, the relationship between protein shape and its interaction with nanoparticles is still under-exploited because of lack of a well-conceived binding system and a method to detect the subtle change in the protein-nanoparticle assemblies. Noticing this unresolved need, we cloned and expressed a His-tagged SpeA protein that adopts a bridge-shaped dimer structure, and utilized a high-resolution capillary electrophoresis method to monitor assembly formation between the protein and quantum dots (QDs, 5 nm in diameter). We observed that the bridge-shaped structure rendered a low SpeA:QD stoichiometry at saturation. Also, close monitoring of imidazole (Im) displacement of surface-bound protein revealed a unique two-step process. High-concentration Im could displace surface-bound SpeA protein and form a transient QD-protein intermediate, through a kinetically controlled displacement process. An affinity-driven equilibrium step then followed, resulting in re-assembling of the QD-protein complex in about 1 h. Through a temporarily formed intermediate, Im causes a rearrangement of His-tagged proteins on the surface. Thus, our work showcases that the synergistic interplay between QD-His-tag interaction and protein-protein interaction can result in unique properties of protein-nanoparticle assembly for the first time.

Real-time Focused Ultrasound Surgery (FUS) Monitoring Using Harmonic Motion Imaging (HMI)

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

Maleke, Caroline; Konofagou, Elisa E.; Department of Radiology, Columbia University, New York, NY

2009-04-14

Monitoring changes in tissue mechanical properties to optimally control thermal exposure is important in thermal therapies. The amplitude-modulated (AM) harmonic motion imaging (HMI) for focused ultrasound (HMIFU) technique is a radiation force technique, which has the capability of tracking tissue stiffness during application of an oscillatory force. The feasibility of HMIFU for assessing mechanical tissue properties has been previously demonstrated. In this paper, a confocal transducer, combining a 4.5 MHz FUS transducer and a 3.3 MHz phased array imaging transducer, was used. The FUS transducer was driven by AM wave at 15 Hz with an acoustic intensity (I{sub spta}) wasmore » equal to 1050 W/cm{sup 2}. A lowpass digital filter was used to remove the spectrum of the higher power beam prior to displacement estimation. The resulting axial tissue displacement was estimated using 1D cross-correlation with a correlation window of 2 mm and a 92.5% overlap. A thermocouple was also used to measure the temperature near the ablated region. 2D HMI-images from six-bovine-liver specimens indicated the onset of coagulation necrosis through changes in amplitude displacement after coagulation due to its simultaneous probing and heating capability. The HMI technique can thus be used to monitor temperature-related stiffness changes of tissues during thermal therapies in real-time, i.e., without interrupting or modifying the treatment protocol.« less

Amplitude-modulated ultrasound radiation force combined with phase-sensitive optical coherence tomography for shear wave elastography

NASA Astrophysics Data System (ADS)

Nguyen, Thu-Mai; Song, Shaozhen; Arnal, Bastien; Wong, Emily Y.; Shen, Tueng T.; Wang, Ruikang K.; O'Donnell, Matthew

2015-03-01

Tissue stiffness can be measured from the propagation speed of shear waves. Acoustic radiation force (ARF) can generate shear waves by focusing ultrasound in tissue for ~100 μs. Safety considerations and electronics abilities limit ultrasound pressures. We previously presented shear wave elastography combining ARF and phase-sensitive optical coherence tomography (PhS-OCT) [1]. Here, we use amplitude-modulated ARF to enhance shear wave signal-to-noise ratio (SNR) at low pressures. Experiments were performed on tissue-mimicking phantoms. ARF was applied using a single-element transducer, driven by a 7.5 MHz, 3-ms, sine wave modulated in amplitude by a linear-swept frequency (1 to 7 kHz). Pressures between 1 to 3 MPa were tested. Displacements were tracked using PhS-OCT and numerically compressed using pulse compression methods detailed in previous work [2]. SNR was compared to that of 200-μs bursts. Stiffness maps were reconstructed using time-of-flight computations. 200-μs bursts give barely detectable displacements at 1 MPa (3.7 dB SNR). Pulse compression gives 36.2 dB at 1.5 MPa. In all cases with detectable displacements, shear wave speeds were determined in 5%-gelatin and 10%-gelatin phantoms and compared to literature values. Applicability to ocular tissues (cornea, intraocular lens) is under investigation.

Eye movements reveal the time-course of anticipating behaviour based on complex, conflicting desires.

PubMed

Ferguson, Heather J; Breheny, Richard

2011-05-01

The time-course of representing others' perspectives is inconclusive across the currently available models of ToM processing. We report two visual-world studies investigating how knowledge about a character's basic preferences (e.g. Tom's favourite colour is pink) and higher-order desires (his wish to keep this preference secret) compete to influence online expectations about subsequent behaviour. Participants' eye movements around a visual scene were tracked while they listened to auditory narratives. While clear differences in anticipatory visual biases emerged between conditions in Experiment 1, post-hoc analyses testing the strength of the relevant biases suggested a discrepancy in the time-course of predicting appropriate referents within the different contexts. Specifically, predictions to the target emerged very early when there was no conflict between the character's basic preferences and higher-order desires, but appeared to be relatively delayed when comprehenders were provided with conflicting information about that character's desire to keep a secret. However, a second experiment demonstrated that this apparent 'cognitive cost' in inferring behaviour based on higher-order desires was in fact driven by low-level features between the context sentence and visual scene. Taken together, these results suggest that healthy adults are able to make complex higher-order ToM inferences without the need to call on costly cognitive processes. Results are discussed relative to previous accounts of ToM and language processing. Copyright © 2011 Elsevier B.V. All rights reserved.

Novel Function of the Fanconi Anemia Group J or RECQ1 Helicase to Disrupt Protein-DNA Complexes in a Replication Protein A-stimulated Manner*

PubMed Central

Sommers, Joshua A.; Banerjee, Taraswi; Hinds, Twila; Wan, Bingbing; Wold, Marc S.; Lei, Ming; Brosh, Robert M.

2014-01-01

Understanding how cellular machinery deals with chromosomal genome complexity is an important question because protein bound to DNA may affect various cellular processes of nucleic acid metabolism. DNA helicases are at the forefront of such processes, yet there is only limited knowledge how they remodel protein-DNA complexes and how these mechanisms are regulated. We have determined that representative human RecQ and Fe-S cluster DNA helicases are potently blocked by a protein-DNA interaction. The Fanconi anemia group J (FANCJ) helicase partners with the single-stranded DNA-binding protein replication protein A (RPA) to displace BamHI-E111A bound to duplex DNA in a specific manner. Protein displacement was dependent on the ATPase-driven function of the helicase and unique properties of RPA. Further biochemical studies demonstrated that the shelterin proteins TRF1 and TRF2, which preferentially bind the telomeric repeat found at chromosome ends, effectively block FANCJ from unwinding the forked duplex telomeric substrate. RPA, but not the Escherichia coli single-stranded DNA-binding protein or shelterin factor Pot1, stimulated FANCJ ejection of TRF1 from the telomeric DNA substrate. FANCJ was also able to displace TRF2 from the telomeric substrate in an RPA-dependent manner. The stimulation of helicase-catalyzed protein displacement is also observed with the DNA helicase RECQ1, suggesting a conserved functional interaction of RPA-interacting helicases. These findings suggest that partnerships between RPA and interacting human DNA helicases may greatly enhance their ability to dislodge proteins bound to duplex DNA, an activity that is likely to be highly relevant to their biological roles in DNA metabolism. PMID:24895130

A Multi-Mode Shock Tube for Investigation of Blast-Induced Traumatic Brain Injury

PubMed Central

Reneer, Dexter V.; Hisel, Richard D.; Hoffman, Joshua M.; Kryscio, Richard J.; Lusk, Braden T.

2011-01-01

Abstract Blast-induced mild traumatic brain injury (bTBI) has become increasingly common in recent military conflicts. The mechanisms by which non-impact blast exposure results in bTBI are incompletely understood. Current small animal bTBI models predominantly utilize compressed air-driven membrane rupture as their blast wave source, while large animal models use chemical explosives. The pressure-time signature of each blast mode is unique, making it difficult to evaluate the contributions of the different components of the blast wave to bTBI when using a single blast source. We utilized a multi-mode shock tube, the McMillan blast device, capable of utilizing compressed air- and compressed helium-driven membrane rupture, and the explosives oxyhydrogen and cyclotrimethylenetrinitramine (RDX, the primary component of C-4 plastic explosives) as the driving source. At similar maximal blast overpressures, the positive pressure phase of compressed air-driven blasts was longer, and the positive impulse was greater, than those observed for shockwaves produced by other driving sources. Helium-driven shockwaves more closely resembled RDX blasts, but by displacing air created a hypoxic environment within the shock tube. Pressure-time traces from oxyhydrogen-driven shockwaves were very similar those produced by RDX, although they resulted in elevated carbon monoxide levels due to combustion of the polyethylene bag used to contain the gases within the shock tube prior to detonation. Rats exposed to compressed air-driven blasts had more pronounced vascular damage than those exposed to oxyhydrogen-driven blasts of the same peak overpressure, indicating that differences in blast wave characteristics other than peak overpressure may influence the extent of bTBI. Use of this multi-mode shock tube in small animal models will enable comparison of the extent of brain injury with the pressure-time signature produced using each blast mode, facilitating evaluation of the blast wave components contributing to bTBI. PMID:21083431

Light-Driven Polymeric Bimorph Actuators

NASA Technical Reports Server (NTRS)

Adamovsky, Gregory; Sarkisov, Sergey S.; Curley, Michael J.

2009-01-01

Light-driven polymeric bimorph actuators are being developed as alternatives to prior electrically and optically driven actuators in advanced, highly miniaturized devices and systems exemplified by microelectromechanical systems (MEMS), micro-electro-optical-mechanical systems (MEOMS), and sensor and actuator arrays in smart structures. These light-driven polymeric bimorph actuators are intended to satisfy a need for actuators that (1) in comparison with the prior actuators, are simpler and less power-hungry; (2) can be driven by low-power visible or mid-infrared light delivered through conventional optic fibers; and (3) are suitable for integration with optical sensors and multiple actuators of the same or different type. The immediate predecessors of the present light-driven polymeric bimorph actuators are bimorph actuators that exploit a photorestrictive effect in lead lanthanum zirconate titanate (PLZT) ceramics. The disadvantages of the PLZT-based actuators are that (1) it is difficult to shape the PLZT ceramics, which are hard and brittle; (2) for actuation, it is necessary to use ultraviolet light (wavelengths < 380 nm), which must be generated by use of high-power, high-pressure arc lamps or lasers; (3) it is difficult to deliver sufficient ultraviolet light through conventional optical fibers because of significant losses in the fibers; (4) the response times of the PLZT actuators are of the order of several seconds unacceptably long for typical applications; and (5) the maximum mechanical displacements of the PLZT-based actuators are limited to those characterized by low strains beyond which PLZT ceramics disintegrate because of their brittleness. The basic element of a light-driven bimorph actuator of the present developmental type is a cantilever beam comprising two layers, at least one of which is a polymer that exhibits a photomechanical effect (see figure). The dominant mechanism of the photomechanical effect is a photothermal one: absorption of light energy causes heating, which, in turn, causes thermal expansion.

A multi-mode shock tube for investigation of blast-induced traumatic brain injury.

PubMed

Reneer, Dexter V; Hisel, Richard D; Hoffman, Joshua M; Kryscio, Richard J; Lusk, Braden T; Geddes, James W

2011-01-01

Blast-induced mild traumatic brain injury (bTBI) has become increasingly common in recent military conflicts. The mechanisms by which non-impact blast exposure results in bTBI are incompletely understood. Current small animal bTBI models predominantly utilize compressed air-driven membrane rupture as their blast wave source, while large animal models use chemical explosives. The pressure-time signature of each blast mode is unique, making it difficult to evaluate the contributions of the different components of the blast wave to bTBI when using a single blast source. We utilized a multi-mode shock tube, the McMillan blast device, capable of utilizing compressed air- and compressed helium-driven membrane rupture, and the explosives oxyhydrogen and cyclotrimethylenetrinitramine (RDX, the primary component of C-4 plastic explosives) as the driving source. At similar maximal blast overpressures, the positive pressure phase of compressed air-driven blasts was longer, and the positive impulse was greater, than those observed for shockwaves produced by other driving sources. Helium-driven shockwaves more closely resembled RDX blasts, but by displacing air created a hypoxic environment within the shock tube. Pressure-time traces from oxyhydrogen-driven shockwaves were very similar those produced by RDX, although they resulted in elevated carbon monoxide levels due to combustion of the polyethylene bag used to contain the gases within the shock tube prior to detonation. Rats exposed to compressed air-driven blasts had more pronounced vascular damage than those exposed to oxyhydrogen-driven blasts of the same peak overpressure, indicating that differences in blast wave characteristics other than peak overpressure may influence the extent of bTBI. Use of this multi-mode shock tube in small animal models will enable comparison of the extent of brain injury with the pressure-time signature produced using each blast mode, facilitating evaluation of the blast wave components contributing to bTBI.

[Comparison of TTR and CMV promoters in vivo and in vitro via a secreted luciferase reporter system].

PubMed

Luo, Shun-Tao; Tian, Wen-Hong; Wang, Gang; Dong, Xiao-Yan; Yang, Li; Wu, Xiao-Bing

2009-11-01

GLuc (Gaussia luciferase) is a secreted luciferase with high sensitivity. In this study, we primarily compared expression character of PTTR with that of PCMV, relied on easy secretion, high sensitivity and simple and fast detection of GLuc. We firstly constructed two plasmids pAAV2-neo-TTR-GLuc and pAAV2-neo-CMV-GLuc. Then, 4 cell lines were transfected with the two plasmids in aid of Lipofectamine 2000, including Huh7 and HepG2, which are derived from liver cells, as well as HEK293 and HeLaS3 cells, which are non-liver cell lines. We monitored the expression of GLuc in the supernatant of these cell cultures at different time points post-transfection. Furthermore, we injected the two plasmids with different doses into BALB/c mice by the means of hydrodynamic delivery and monitored the GLuc expression in vivo with 2.5 microl tail tip blood since 2 h post-injection. The cell assay results suggested that the expression of GLuc driven by CMV promoter was significantly higher than that of GLuc driven by TTR promoter. And, the luciferase activity of GLuc driven by CMV promoter was 50-300 times higher than that of GLuc driven by TTR promoter in HEK293 and HeLaS3 cell lines, but less than 10 times higher than that of GLuc driven by TTR promoter in the HepG2 and Huh7 cell lines, indicating the relative liver-specificity of TTR promoter. In the animal assay, the higher luciferase activity was determined in CMV promoter group than in TTR promoter group at different doses of the two plasmids. But the expression patterns for the two promoters differed obviously. The expression of GLuc driven by CMV promoter reached the maximum 10 hours post-injection and declined rapidly; while the expression of GLuc driven by TTR promoter reached the maximum 48 hours after delivery, and declined very slowly. These results implied that PTTR could keep expression of driven gene in a long time although its expression intensity is lower than PCMV's. Thus, it is more suitable for maintaining longer expression of target genes in liver.

Investigating the feasibility of a BCI-driven robot-based writing agent for handicapped individuals

NASA Astrophysics Data System (ADS)

Syan, Chanan S.; Harnarinesingh, Randy E. S.; Beharry, Rishi

2014-07-01

Brain-Computer Interfaces (BCIs) predominantly employ output actuators such as virtual keyboards and wheelchair controllers to enable handicapped individuals to interact and communicate with their environment. However, BCI-based assistive technologies are limited in their application. There is minimal research geared towards granting disabled individuals the ability to communicate using written words. This is a drawback because involving a human attendant in writing tasks can entail a breach of personal privacy where the task entails sensitive and private information such as banking matters. BCI-driven robot-based writing however can provide a safeguard for user privacy where it is required. This study investigated the feasibility of a BCI-driven writing agent using the 3 degree-of- freedom Phantom Omnibot. A full alphanumerical English character set was developed and validated using a teach pendant program in MATLAB. The Omnibot was subsequently interfaced to a P300-based BCI. Three subjects utilised the BCI in the online context to communicate words to the writing robot over a Local Area Network (LAN). The average online letter-wise classification accuracy was 91.43%. The writing agent legibly constructed the communicated letters with minor errors in trajectory execution. The developed system therefore provided a feasible platform for BCI-based writing.

Chapter 18: Variable Frequency Drive Evaluation Protocol. The Uniform Methods Project: Methods for Determining Energy Efficiency Savings for Specific Measures

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

Romberger, Jeff

An adjustable-speed drive (ASD) includes all devices that vary the speed of a rotating load, including those that vary the motor speed and linkage devices that allow constant motor speed while varying the load speed. The Variable Frequency Drive Evaluation Protocol presented here addresses evaluation issues for variable-frequency drives (VFDs) installed on commercial and industrial motor-driven centrifugal fans and pumps for which torque varies with speed. Constant torque load applications, such as those for positive displacement pumps, are not covered by this protocol.

Non-linear vibrational response of Ge and SiC membranes

NASA Astrophysics Data System (ADS)

Zhou, L. Q.; Colston, G.; Pearce, M. J.; Prince, R. G.; Myronov, M.; Leadley, D. R.; Trushkevych, O.; Edwards, R. S.

2017-07-01

Characterisation of membranes produced for use as micro-electro-mechanical systems using vibrational techniques can give a measure of their behaviour and suitability for operation in different environments. Two membranes are studied here: germanium (Ge) and cubic silicon carbide (3C-SiC) on a silicon (Si) substrate. When driven at higher displacements, the membranes exhibit self-protecting behaviour. The resonant vibration amplitude is limited to a maximum value of around 10 nm, through dissipation of energy via higher harmonic vibrations. This is observed for both materials, despite their different Young's moduli and defect densities.

Electroactive Polymers as Artificial Muscles - Reality and Challenges

NASA Technical Reports Server (NTRS)

Bar-Cohen, Y.

2001-01-01

Electroactive Polymers (EAPs) are emerging as effective displacement actuators. These materials offer the closest resemblance of biological muscle potentially enabling unique capabilities changing the paradigm about robots construction. Under a NASA task, several EAP driven mechanisms were developed including dust wiper, gripper, and robotic arm EAP are inducing a low actuation force limiting the applications that can use their current capability. In recognition of this limitation a series of international forums were established including SPIE conference, Webhub, Newsletter, and Newsgroup. A challenge was posed to the EAP community to have an arm wrestling between robot that is equipped with EAP actuators and human.

A rack-mounted precision waveguide-below-cutoff attenuator with an absolute electronic readout

NASA Technical Reports Server (NTRS)

Cook, C. C.

1974-01-01

A coaxial precision waveguide-below-cutoff attenuator is described which uses an absolute (unambiguous) electronic digital readout of displacement in inches in addition to the usual gear driven mechanical counter-dial readout in decibels. The attenuator is rack-mountable and has the input and output RF connectors in a fixed position. The attenuation rate for 55, 50, and 30 MHz operation is given along with a discussion of sources of errors. In addition, information is included to aid the user in making adjustments on the attenuator should it be damaged or disassembled for any reason.

Pressure-driven laminar flow switching for rapid exchange of solution environment around surface adhered biological particles

PubMed Central

Allen, Peter B.; Milne, Graham; Doepker, Byron R.; Chiu, Daniel T.

2010-01-01

This paper describes a technique for rapidly exchanging the solution environment near a surface by displacing laminar flow fluid streams using sudden changes in applied pressure. The method employs off-chip solenoid valves to induce pressure changes, which is important in keeping the microfluidic design simple and the operation of the system robust. The performance of this technique is characterized using simulation and validated with experiments. This technique adds to the microfluidic tool box that is currently available for manipulating the solution environment around biological particles and molecules. PMID:20221560

High Aspect-Ratio Neural Probes using Conventional Blade Dicing

NASA Astrophysics Data System (ADS)

Goncalves, S. B.; Ribeiro, J. F.; Silva, A. F.; Correia, J. H.

2016-10-01

Exploring deep neural circuits has triggered the development of long penetrating neural probes. Moreover, driven by brain displacement, the long neural probes require also a high aspect-ratio shafts design. In this paper, a simple and reproducible method of manufacturing long-shafts neural probes using blade dicing technology is presented. Results shows shafts up to 8 mm long and 200 µm wide, features competitive to the current state-of-art, being its outline simply accomplished by a single blade dicing program. Therefore, conventional blade dicing presents itself as a viable option to manufacture long neural probes.

Numerical analysis and experimental research of the rubber boot of the joint drive vehicle

NASA Astrophysics Data System (ADS)

Ziobro, Jan

2016-04-01

The article presents many numerical studies and experimental research of the drive rubber boot of the joint drive vehicle. Performance requirements have been discussed and the required coefficients of the mathematical model for numerical simulation have been determined. The behavior of living in MSC.MARC environment was examined. In the analysis the following have been used: hyperplastic two-parameter model of the Mooney-Rivlin material, large displacements procedure, safe contact condition, friction on the sides of the boots. 3D numerical model of the joint bootwas analyzed under influence of the forces: tensile, compressive, centrifugal and angular. Numerous results of studies have been presented. An appropriate test stand was built and comparison of the results of the numerical analysis and the results of experimental studies was made. Numerous requests and recommendations for utilitarian character have been presented.

Effect of causal and acausal filters on elastic and inelastic response spectra

USGS Publications Warehouse

Boore, D.M.; Akkar, Sinan

2003-01-01

With increasing interest in displacement spectra and long-period motions, it is important to check the sensitivity of both elastic and inelastic response spectra to the filtering that is often necessary to remove long period artifacts, even from many modern digital recordings. Using two records of very different character from the M=7.1, 1999 Hector Mine, California, earthquake, we find that the response spectra can be sensitive to the corner periods used in causal filtering, even for oscillator periods much less than the filter corner periods. The effect is most pronounced for inelastic response spectra, where the ratio of response spectra computed from accelerations filtered at 25 and 200 sec can be close to a factor of 2 for oscillator periods less than 5 sec. Published in 2003 by John Wiley and Sons, Ltd.

Stick-slip behavior in a continuum-granular experiment.

PubMed

Geller, Drew A; Ecke, Robert E; Dahmen, Karin A; Backhaus, Scott

2015-12-01

We report moment distribution results from a laboratory experiment, similar in character to an isolated strike-slip earthquake fault, consisting of sheared elastic plates separated by a narrow gap filled with a two-dimensional granular medium. Local measurement of strain displacements of the plates at 203 spatial points located adjacent to the gap allows direct determination of the event moments and their spatial and temporal distributions. We show that events consist of spatially coherent, larger motions and spatially extended (noncoherent), smaller events. The noncoherent events have a probability distribution of event moment consistent with an M(-3/2) power law scaling with Poisson-distributed recurrence times. Coherent events have a log-normal moment distribution and mean temporal recurrence. As the applied normal pressure increases, there are more coherent events and their log-normal distribution broadens and shifts to larger average moment.

Diffusive and subdiffusive dynamics of indoor microclimate: a time series modeling.

PubMed

Maciejewska, Monika; Szczurek, Andrzej; Sikora, Grzegorz; Wyłomańska, Agnieszka

2012-09-01

The indoor microclimate is an issue in modern society, where people spend about 90% of their time indoors. Temperature and relative humidity are commonly used for its evaluation. In this context, the two parameters are usually considered as behaving in the same manner, just inversely correlated. This opinion comes from observation of the deterministic components of temperature and humidity time series. We focus on the dynamics and the dependency structure of the time series of these parameters, without deterministic components. Here we apply the mean square displacement, the autoregressive integrated moving average (ARIMA), and the methodology for studying anomalous diffusion. The analyzed data originated from five monitoring locations inside a modern office building, covering a period of nearly one week. It was found that the temperature data exhibited a transition between diffusive and subdiffusive behavior, when the building occupancy pattern changed from the weekday to the weekend pattern. At the same time the relative humidity consistently showed diffusive character. Also the structures of the dependencies of the temperature and humidity data sets were different, as shown by the different structures of the ARIMA models which were found appropriate. In the space domain, the dynamics and dependency structure of the particular parameter were preserved. This work proposes an approach to describe the very complex conditions of indoor air and it contributes to the improvement of the representative character of microclimate monitoring.

Mechanosensation is evolutionarily tuned to locomotor mechanics

PubMed Central

Aiello, Brett R.; Westneat, Mark W.; Hale, Melina E.

2017-01-01

The biomechanics of animal limbs has evolved to meet the functional demands for movement associated with different behaviors and environments. Effective movement relies not only on limb mechanics but also on appropriate mechanosensory feedback. By comparing sensory ability and mechanics within a phylogenetic framework, we show that peripheral mechanosensation has evolved with limb biomechanics, evolutionarily tuning the neuromechanical system to its functional demands. We examined sensory physiology and mechanics of the pectoral fins, forelimb homologs, in the fish family Labridae. Labrid fishes exhibit extraordinary morphological and behavioral diversity and use pectoral fin-based propulsion with fins ranging in shape from high aspect ratio (AR) wing-like fins to low AR paddle-like fins. Phylogenetic character analysis demonstrates that high AR fins evolved independently multiple times in this group. Four pairs of species were examined; each included a plesiomorphic low AR and a high AR species. Within each species pair, the high AR species demonstrated significantly stiffer fin rays in comparison with the low AR species. Afferent sensory nerve activity was recorded during fin ray bending. In all cases, afferents of stiffer fins were more sensitive at lower displacement amplitudes, demonstrating mechanosensory tuning to fin mechanics and a consistent pattern of correlated evolution. We suggest that these data provide a clear example of parallel evolution in a complex neuromechanical system, with a strong link between multiple phenotypic characters: pectoral fin shape, swimming behavior, fin ray stiffness, and mechanosensory sensitivity. PMID:28396411

A comparison of long-baseline strain data and fault creep records obtained near Hollister, California

USGS Publications Warehouse

Slater, L.E.; Burford, R.O.

1979-01-01

A comparison of creepmeter records from nine sites along a 12-km segment of the Calaveras fault near Hollister, California and long-baseline strain changes for nine lines in the Hollister multiwavelength distance-measuring (MWDM) array has established that episodes of large-scale deformation both preceded and accompanied periods of creep activity monitored along the fault trace during 1976. A concept of episodic, deep-seated aseismic slip that contributes to loading and subsequent aseismic failure of shallow parts of the fault plane seems attractive, implying that the character of aseismic slip sensed along the surface trace may be restricted to a relatively shallow (~ 1-km) region on the fault plane. Preliminary results from simple dislocation models designed to test the concept demonstrate that extending the time-histories and amplitudes of creep events sensed along the fault trace to depths of up to 10 km on the fault plane cannot simulate adequately the character and amplitudes of large-scale episodic movements observed at points more than 1 km from the fault. Properties of a 2-3-km-thick layer of unconsolidated sediments present in Hollister Valley, combined with an essentially rigid-block behavior in buried basement blocks, might be employed in the formulation of more appropriate models that could predict patterns of shallow fault creep and large-scale displacements much more like those actually observed. ?? 1979.

Rogue waves in a multistable system.

PubMed

Pisarchik, Alexander N; Jaimes-Reátegui, Rider; Sevilla-Escoboza, Ricardo; Huerta-Cuellar, G; Taki, Majid

2011-12-30

Clear evidence of rogue waves in a multistable system is revealed by experiments with an erbium-doped fiber laser driven by harmonic pump modulation. The mechanism for the rogue wave formation lies in the interplay of stochastic processes with multistable deterministic dynamics. Low-frequency noise applied to a diode pump current induces rare jumps to coexisting subharmonic states with high-amplitude pulses perceived as rogue waves. The probability of these events depends on the noise filtered frequency and grows up when the noise amplitude increases. The probability distribution of spike amplitudes confirms the rogue wave character of the observed phenomenon. The results of numerical simulations are in good agreement with experiments.

Restricted amide rotation with steric hindrance induced multiple conformations

NASA Astrophysics Data System (ADS)

Krishnan, V. V.; Vazquez, Salvador; Maitra, Kalyani; Maitra, Santanu

2017-12-01

The Csbnd N bond character is dependent directly upon the resonance-contributor structure population driven by the delocalized nitrogen lone-pair of electrons. In the case of N, N-dibenzyl-ortho-toluamide (o-DBET), the molecule adopts subpopulations of conformers with distinct NMR spectral features, particularly at low temperatures. This conformational adaptation is unique to o-DBET, while the corresponding meta- and para- forms do not show such behavior. Variable-temperature (VT) NMR, two-dimensional exchange spectroscopy (EXSY), and qualitative molecular modeling studies are used to demonstrate how multiple competing interactions such as restricted amide rotation and steric hindrance effects can lead to versatile molecular adaptations in the solution state.

Theoretical regime diagrams for thermally driven flows in a beta-plane channel in the presence of variable gravity

NASA Technical Reports Server (NTRS)

Geisler, J. E.; Fowlis, W. W.

1980-01-01

The effect of a power law gravity field on baroclinic instability is examined, with a focus on the case of inverse fifth power gravity, since this is the power law produced when terrestrial gravity is simulated in spherical geometry by a dielectric force. Growth rates are obtained of unstable normal modes as a function of parameters of the problem by solving a second order differential equation numerically. It is concluded that over the range of parameter space explored, there is no significant change in the character of theoretical regime diagrams if the vertically averaged gravity is used as parameter.

Evolution of aminoacyl-tRNA synthetases--analysis of unique domain architectures and phylogenetic trees reveals a complex history of horizontal gene transfer events.

PubMed

Wolf, Y I; Aravind, L; Grishin, N V; Koonin, E V

1999-08-01

Phylogenetic analysis of aminoacyl-tRNA synthetases (aaRSs) of all 20 specificities from completely sequenced bacterial, archaeal, and eukaryotic genomes reveals a complex evolutionary picture. Detailed examination of the domain architecture of aaRSs using sequence profile searches delineated a network of partially conserved domains that is even more elaborate than previously suspected. Several unexpected evolutionary connections were identified, including the apparent origin of the beta-subunit of bacterial GlyRS from the HD superfamily of hydrolases, a domain shared by bacterial AspRS and the B subunit of archaeal glutamyl-tRNA amidotransferases, and another previously undetected domain that is conserved in a subset of ThrRS, guanosine polyphosphate hydrolases and synthetases, and a family of GTPases. Comparison of domain architectures and multiple alignments resulted in the delineation of synapomorphies-shared derived characters, such as extra domains or inserts-for most of the aaRSs specificities. These synapomorphies partition sets of aaRSs with the same specificity into two or more distinct and apparently monophyletic groups. In conjunction with cluster analysis and a modification of the midpoint-rooting procedure, this partitioning was used to infer the likely root position in phylogenetic trees. The topologies of the resulting rooted trees for most of the aaRSs specificities are compatible with the evolutionary "standard model" whereby the earliest radiation event separated bacteria from the common ancestor of archaea and eukaryotes as opposed to the two other possible evolutionary scenarios for the three major divisions of life. For almost all aaRSs specificities, however, this simple scheme is confounded by displacement of some of the bacterial aaRSs by their eukaryotic or, less frequently, archaeal counterparts. Displacement of ancestral eukaryotic aaRS genes by bacterial ones, presumably of mitochondrial origin, was observed for three aaRSs. In contrast, there was no convincing evidence of displacement of archaeal aaRSs by bacterial ones. Displacement of aaRS genes by eukaryotic counterparts is most common among parasitic and symbiotic bacteria, particularly the spirochaetes, in which 10 of the 19 aaRSs seem to have been displaced by the respective eukaryotic genes and two by the archaeal counterpart. Unlike the primary radiation events between the three main divisions of life, that were readily traceable through the phylogenetic analysis of aaRSs, no consistent large-scale bacterial phylogeny could be established. In part, this may be due to additional gene displacement events among bacterial lineages. Argument is presented that, although lineage-specific gene loss might have contributed to the evolution of some of the aaRSs, this is not a viable alternative to horizontal gene transfer as the principal evolutionary phenomenon in this gene class.

Numerical methods for coupled fracture problems

NASA Astrophysics Data System (ADS)

Viesca, Robert C.; Garagash, Dmitry I.

2018-04-01

We consider numerical solutions in which the linear elastic response to an opening- or sliding-mode fracture couples with one or more processes. Classic examples of such problems include traction-free cracks leading to stress singularities or cracks with cohesive-zone strength requirements leading to non-singular stress distributions. These classical problems have characteristic square-root asymptotic behavior for stress, relative displacement, or their derivatives. Prior work has shown that such asymptotics lead to a natural quadrature of the singular integrals at roots of Chebyhsev polynomials of the first, second, third, or fourth kind. We show that such quadratures lead to convenient techniques for interpolation, differentiation, and integration, with the potential for spectral accuracy. We further show that these techniques, with slight amendment, may continue to be used for non-classical problems which lack the classical asymptotic behavior. We consider solutions to example problems of both the classical and non-classical variety (e.g., fluid-driven opening-mode fracture and fault shear rupture driven by thermal weakening), with comparisons to analytical solutions or asymptotes, where available.

An adaptive liquid microlens driven by a ferrofluidic transducer

NASA Astrophysics Data System (ADS)

Xiao, Wenjia; Hardt, Steffen

2010-05-01

Ferrofluids behave superparamagnetically and can be manipulated by external magnetic fields, providing numerous applications in microfluidic systems. In this paper, an adaptive liquid microlens driven by a ferrofluidic actuator is presented. The microlens consists of a cylindrical well filled with a lens liquid connected to a microchannel containing a ferrofluid plug. When the ferrofluid plug is moved back and forth by an external magnetic field, the lens liquid is displaced, forming a liquid lens with an adaptive focus in the cylindrical well. The focal length of the lens can be changed from infinity to the scale of the radius of the cylindrical well, leading to a high optical power compared to conventional liquid lenses utilizing liquid crystals or electrowetting. The lens curvature is reversibly tunable without hysteresis when the ferrofluid plug moves with a speed below a specific threshold value. The lens can be acted on by a magnetic field of about 100 mT which can be generated by microcoils requiring much lower voltages than the electrowetting principle.

Bio-inspired piezoelectric linear motor driven by a single-phase harmonic wave with an asymmetric stator.

PubMed

Pan, Qiaosheng; Miao, Enming; Wu, Bingxuan; Chen, Weikang; Lei, Xiujun; He, Liangguo

2017-07-01

A novel, bio-inspired, single-phase driven piezoelectric linear motor (PLM) using an asymmetric stator was designed, fabricated, and tested to avoid mode degeneracy and to simplify the drive mechanism of a piezoelectric motor. A piezoelectric transducer composed of two piezoelectric stacks and a displacement amplifier was used as the driving element of the PLM. Two simple and specially designed claws performed elliptical motion. A numerical simulation was performed to design the stator and determine the feasibility of the design mechanism of the PLM. Moreover, an experimental setup was built to validate the working principles, as well as to evaluate the performance, of the PLM. The prototype motor outputs a no-load speed of 233.7 mm/s at a voltage of 180 V p-p and a maximum thrust force of 2.3 N under a preload of 10 N. This study verified the feasibility of the proposed design and provided a method to simplify the driving harmonic signal and structure of PLMs.

Geographic distribution of the invasive cattle tick Rhipicephalus microplus, a country-wide survey in Benin.

PubMed

De Clercq, E M; Vanwambeke, S O; Sungirai, M; Adehan, S; Lokossou, R; Madder, M

2012-12-01

The cattle tick Rhipicephalus microplus is currently invading the West African region, and little information is available on the spread of this exotic tick in this region. We set out a country-wide field survey to determine its current distribution in Benin. Ticks were collected on cattle from 106 farms selected by random sampling covering all regions of the country. Rhipicephalus annulatus was found on 70 % of all farms, R. decoloratus on 42 %, R. geigyi on 58 %, and R. microplus on 49 %. There is a clear geographic separation between the indigenous Rhipicephalus species and R. microplus. Rhipicephalus annulatus occurs mainly in the northern departments, but it was also observed in lower numbers in locations in the south. The presence of R. decoloratus is limited to the northern region, and in most locations, this tick makes up a small proportion of the collected ticks. The tick R. geigyi tends to be dominant, but occurs only in the four northern departments. The observations concerning R. microplus are entirely different, this species occurs in the southern and central region. The results of this survey confirm the invasive character and displacement properties of R. microplus, since in less than a decade it has colonized more than half of the country and has displaced indigenous ticks of the same genus in many of the sampled locations.

Hydration structure of the α-chymotrypsin substrate binding pocket: the impact of constrained geometry

NASA Astrophysics Data System (ADS)

Carey, Christina; Cheng, Yuen-Kit; Rossky, Peter J.

2000-08-01

The concave substrate binding pocket of α-chymotrypsin binds specifically hydrophobic side chains. In order to understand the hydration structure present in the absence of substrate, and elucidate the character of the solvent displaced on binding, molecular dynamics computer simulation of the solvent in a fully hydrated protein has been carried out and analyzed. The pocket is found to be characterized in terms of a mixed polar and apolar macromolecular surface. It is shown that the simulated solvent structure within it is spatially consistent with that seen via crystallography. The solvent structure is energetically characterized by large losses in hydrogen bonding among solvent molecules except at the mouth of the pocket where exposure to bulk-like solvent is possible. The loss in hydrogen bonding is attributed to the highly constrained geometry available to the solvent, preventing formation of a hydrogen bonding network, with only partial compensation by interactions with the macromolecular surface. The solvent displacement concomitant with substrate binding will therefore be associated with a large enthalpic driving force. This result is at the extreme of a continuum of variable cases of "hydrophobic" hydration, which differ most basically in surface curvature. These range from convex solute surfaces, inducing clathrate-like structures, with negligible hydrogen bond loss, to flat surfaces with significant interfacial loss, to the present concave case with hydrogen bonding losses exceeding 50%.

A set of alternative explanations to account for the deformation field at Montserrat, West Indies

NASA Astrophysics Data System (ADS)

Collinson, Amy; Neuberg, Jurgen; Pascal, Karen

2015-04-01

For almost 20 years, Soufrière Hills Volcano, Monsterrat, has been in a state of volcanic unrest. Intermittent periods of dome building have been punctuated by explosive eruptions and dome collapse events, endangering the lives of the inhabitants of the island. To date, there have been numerous phases to the activity, with the current activity designated Pause 5. There has not been any active magma extrusion since February 2010, and the last significant explosive (ash-venting) event occurred in March 2012. However, the volcano continues to emit an average of 374t/d SO2 and shows signs of deformation. Current observations indicate a line lengthening between several pairs of GPS stations across the island, suggesting an overall inflation of Montserrat. Through the use of three-dimensional numerical modelling using a finite element method, we explore the potential sources of this deformation, ranging from an inflating magma chamber or dyke - suggesting ongoing volcanic activity, to the existence of an active left-lateral strike-slip fault - which may indicate cessation of volcanic activity. We show the effect of different dyke sources (shapes, characters and depths) on the surface displacement. Furthermore, through the inclusion of topographic data, we investigate how the topography may affect the displacement pattern at the surface. Alternatively, we determine how much fault slip would be required in order to derive the deformation observed.

Glasslike dynamical behavior of the plastocyanin hydration water

NASA Astrophysics Data System (ADS)

Bizzarri, Anna Rita; Paciaroni, Alessandro; Cannistraro, Salvatore

2000-09-01

The dynamical behavior of water around plastocyanin has been investigated in a wide temperature range by molecular dynamics simulation. The mean square displacements of water oxygen atoms show, at long times, a tα trend for all temperatures. Below 150 K, α is constant and equal to 1; at higher temperatures it drops to a value significantly smaller than 1, and thereafter decreases with increasing temperature. The occurrence of such an anomalous diffusion matches the onset of the dynamical transition observed in the protein. The intermediate scattering function of water is characterized, at high temperature, by a stretched exponential decay evolving, at low temperature, toward a two step relaxation behavior, which becomes more evident on increasing the exchanged wave vector q. Both the mean square displacements and the intermediate scattering functions show, beyond the ballistic regime, a plateau, which progressively extends for longer times as long as the temperature is lowered, such behavior reflecting trapping of water molecules within a cage formed by the nearest neighbors. At low temperature, a low frequency broad inelastic peak is observed in the dynamical structure factor of hydration water; such an excess of vibrational modes being reminiscent of the boson peak, characteristic of disordered, amorphous systems. All these features, which are typical of complex systems, can be traced back to the glassy character of the hydration water and suggest a dynamical coupling occurring at the macromolecule-solvent interface.

Hydrogen bond effects on compressional behavior of isotypic minerals: high-pressure polymorphism of cristobalite-like Be(OH) 2

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

Shelton, Hannah; Barkley, Madison C.; Downs, Robert T.

2016-05-31

Three isotypic crystals, SiO 2 (α-cristobalite), ε-Zn(OH) 2 (wülfingite), and Be(OH) 2 (β-behoite), with topologically identical frameworks of corner-connected tetrahedra, undergo displacive compression drivenphase transitions at similar pressures (1.5–2.0 GPa), but each transition is characterized by a different mechanism resulting in different structural modifications. In this study, we report the crystal structure of the high pressure γ-phase of beryllium hydroxide and compare it with the high pressure structures of the other two minerals. In Be(OH) 2, the transition from the ambient β-behoite phase with the orthorhombic space group P2 12 12 1 and ambient unit cell parameters a = 4.5403(4)more » Å, b = 4.6253(5) Å, c = 7.0599(7) Å, to the high pressure orthorhombic γ-polymorph with space group Fdd2 and unit cell parameters (at 5.3(1) GPa) a = 5.738(2) Å, b = 6.260(3) Å, c = 7.200(4) Å takes place between 1.7 and 3.6 GPa. This transition is essentially second order, is accompanied by a negligible volume discontinuity, and exhibits both displacive and reversible character. The mechanism of the phase transition results in a change to the hydrogen bond connectivities and rotation of the BeO 4 tetrahedra.« less

Engineering an Insulating Ferroelectric Superlattice with a Tunable Band Gap from Metallic Components

DOE PAGES

Ghosh, Saurabh; Borisevich, Albina Y.; Pantelides, Sokrates T.

2017-10-25

The recent discovery of “polar metals” with ferroelectriclike displacements offers the promise of designing ferroelectrics with tunable energy gaps by inducing controlled metal-insulator transitions. Here in this work, we employ first-principles calculations to design a metallic polar superlattice from nonpolar metal components and show that controlled intermixing can lead to a true insulating ferroelectric with a tunable band gap. We consider a 2/2 superlattice made of two centrosymmetric metallic oxides, La 0.75Sr 0.25MnO 3 and LaNiO 3, and show that ferroelectriclike displacements are induced. The ferroelectriclike distortion is found to be strongly dependent on the carrier concentration (Sr content). Further,more » we show that a metal-to-insulator (MI) transition is feasible in this system via disproportionation of the Ni sites. Such a disproportionation and, hence, a MI transition can be driven by intermixing of transition metal ions between Mn and Ni layers. Finally, as a result, the energy gap of the resulting ferroelectric can be tuned by varying the degree of intermixing in the experimental fabrication method.« less

Engineering an Insulating Ferroelectric Superlattice with a Tunable Band Gap from Metallic Components

NASA Astrophysics Data System (ADS)

Ghosh, Saurabh; Borisevich, Albina Y.; Pantelides, Sokrates T.

2017-10-01

The recent discovery of "polar metals" with ferroelectriclike displacements offers the promise of designing ferroelectrics with tunable energy gaps by inducing controlled metal-insulator transitions. Here we employ first-principles calculations to design a metallic polar superlattice from nonpolar metal components and show that controlled intermixing can lead to a true insulating ferroelectric with a tunable band gap. We consider a 2 /2 superlattice made of two centrosymmetric metallic oxides, La0.75 Sr0.25 MnO3 and LaNiO3 , and show that ferroelectriclike displacements are induced. The ferroelectriclike distortion is found to be strongly dependent on the carrier concentration (Sr content). Further, we show that a metal-to-insulator (MI) transition is feasible in this system via disproportionation of the Ni sites. Such a disproportionation and, hence, a MI transition can be driven by intermixing of transition metal ions between Mn and Ni layers. As a result, the energy gap of the resulting ferroelectric can be tuned by varying the degree of intermixing in the experimental fabrication method.

Transient aging in fractional Brownian and Langevin-equation motion.

PubMed

Kursawe, Jochen; Schulz, Johannes; Metzler, Ralf

2013-12-01

Stochastic processes driven by stationary fractional Gaussian noise, that is, fractional Brownian motion and fractional Langevin-equation motion, are usually considered to be ergodic in the sense that, after an algebraic relaxation, time and ensemble averages of physical observables coincide. Recently it was demonstrated that fractional Brownian motion and fractional Langevin-equation motion under external confinement are transiently nonergodic-time and ensemble averages behave differently-from the moment when the particle starts to sense the confinement. Here we show that these processes also exhibit transient aging, that is, physical observables such as the time-averaged mean-squared displacement depend on the time lag between the initiation of the system at time t=0 and the start of the measurement at the aging time t(a). In particular, it turns out that for fractional Langevin-equation motion the aging dependence on t(a) is different between the cases of free and confined motion. We obtain explicit analytical expressions for the aged moments of the particle position as well as the time-averaged mean-squared displacement and present a numerical analysis of this transient aging phenomenon.

Tough Nanocomposite Ionogel-based Actuator Exhibits Robust Performance

NASA Astrophysics Data System (ADS)

Liu, Xinhua; He, Bin; Wang, Zhipeng; Tang, Haifeng; Su, Teng; Wang, Qigang

2014-10-01

Ionogel electrolytes can be fabricated for electrochemical actuators with many desirable advantages, including direct low-voltage control in air, high electrochemical and thermal stability, and complete silence during actuation. However, the demands for active actuators with above features and load-driving ability remain a challenge; much work is necessary to enhance the mechanical strength of electrolyte materials. Herein, we describe a cross-linked supramolecular approach to prepare tough nanocomposite gel electrolytes from HEMA, BMIMBF4, and TiO2 via self-initiated UV polymerization. The tough and stable ionogels are emerging to fabricate electric double-layer capacitor-like soft actuators, which can be driven by electrically induced ion migration. The ionogel-based actuator shows a displacement response of 5.6 mm to the driving voltage of 3.5 V. After adding the additional mass weight of the same as the actuator, it still shows a large displacement response of 3.9 mm. Furthermore, the actuator can not only work in harsh temperature environments (100°C and -10°C) but also realize the goal of grabbing an object by adjusting the applied voltage.

Design and testing of a novel piezoelectric micro-motor actuated by asymmetrical inertial impact driving principle.

PubMed

Zeng, Ping; Sun, Shujie; Li, Li'an; Xu, Feng; Cheng, Guangming

2014-03-01

In this paper, an asymmetrical inertial impact driving principle is first proposed, and accordingly a novel piezoelectrically actuated linear micro-motor is developed. It is driven by the inertial impact force generated by piezoelectric smart cantilever (PSC) with asymmetrical clamping locations during a driving cycle. When the PSC is excited by typical harmonic voltage signals, different equivalent stiffness will be induced due to its asymmetrical clamping locations when it is vibrating back and forth, leading to a tiny displacement difference on the two opposite directions in a cycle, and then the accumulation of tiny displacement difference will allow directional movements. A prototype of the proposed motor has been developed and investigated by means of experimental tests. The motion and dynamics characteristics of the prototype are well studied. The experimental results demonstrate that the resolution of the micro-motor is 0.02 μm, the maximum velocity is 16.87 mm/s, and the maximum loading capacity can reach up to 1 kg with a voltage of 100 V and 35 Hz.

Engineering an Insulating Ferroelectric Superlattice with a Tunable Band Gap from Metallic Components

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

Ghosh, Saurabh; Borisevich, Albina Y.; Pantelides, Sokrates T.

The recent discovery of “polar metals” with ferroelectriclike displacements offers the promise of designing ferroelectrics with tunable energy gaps by inducing controlled metal-insulator transitions. Here in this work, we employ first-principles calculations to design a metallic polar superlattice from nonpolar metal components and show that controlled intermixing can lead to a true insulating ferroelectric with a tunable band gap. We consider a 2/2 superlattice made of two centrosymmetric metallic oxides, La 0.75Sr 0.25MnO 3 and LaNiO 3, and show that ferroelectriclike displacements are induced. The ferroelectriclike distortion is found to be strongly dependent on the carrier concentration (Sr content). Further,more » we show that a metal-to-insulator (MI) transition is feasible in this system via disproportionation of the Ni sites. Such a disproportionation and, hence, a MI transition can be driven by intermixing of transition metal ions between Mn and Ni layers. Finally, as a result, the energy gap of the resulting ferroelectric can be tuned by varying the degree of intermixing in the experimental fabrication method.« less

Tough nanocomposite ionogel-based actuator exhibits robust performance.

PubMed

Liu, Xinhua; He, Bin; Wang, Zhipeng; Tang, Haifeng; Su, Teng; Wang, Qigang

2014-10-20

Ionogel electrolytes can be fabricated for electrochemical actuators with many desirable advantages, including direct low-voltage control in air, high electrochemical and thermal stability, and complete silence during actuation. However, the demands for active actuators with above features and load-driving ability remain a challenge; much work is necessary to enhance the mechanical strength of electrolyte materials. Herein, we describe a cross-linked supramolecular approach to prepare tough nanocomposite gel electrolytes from HEMA, BMIMBF4, and TiO2 via self-initiated UV polymerization. The tough and stable ionogels are emerging to fabricate electric double-layer capacitor-like soft actuators, which can be driven by electrically induced ion migration. The ionogel-based actuator shows a displacement response of 5.6 mm to the driving voltage of 3.5 V. After adding the additional mass weight of the same as the actuator, it still shows a large displacement response of 3.9 mm. Furthermore, the actuator can not only work in harsh temperature environments (100°C and -10°C) but also realize the goal of grabbing an object by adjusting the applied voltage.

Tough Nanocomposite Ionogel-based Actuator Exhibits Robust Performance

PubMed Central

Liu, Xinhua; He, Bin; Wang, Zhipeng; Tang, Haifeng; Su, Teng; Wang, Qigang

2014-01-01

Ionogel electrolytes can be fabricated for electrochemical actuators with many desirable advantages, including direct low-voltage control in air, high electrochemical and thermal stability, and complete silence during actuation. However, the demands for active actuators with above features and load-driving ability remain a challenge; much work is necessary to enhance the mechanical strength of electrolyte materials. Herein, we describe a cross-linked supramolecular approach to prepare tough nanocomposite gel electrolytes from HEMA, BMIMBF4, and TiO2 via self-initiated UV polymerization. The tough and stable ionogels are emerging to fabricate electric double-layer capacitor-like soft actuators, which can be driven by electrically induced ion migration. The ionogel-based actuator shows a displacement response of 5.6 mm to the driving voltage of 3.5 V. After adding the additional mass weight of the same as the actuator, it still shows a large displacement response of 3.9 mm. Furthermore, the actuator can not only work in harsh temperature environments (100°C and −10°C) but also realize the goal of grabbing an object by adjusting the applied voltage. PMID:25327414

Critical dimensional linewidth calibration using UV microscope and laser interferometry

NASA Astrophysics Data System (ADS)

Li, Qi; Gao, Si-tian; Li, Wei; Lu, Ming-zhen; Zhang, Ming-kai

2013-10-01

In order to calibrate the critical dimensional (CD) uncertainty of lithography masks in semiconductor manufacturing, NIM is building a two dimensional metrological UV microscope which has traceable measurement ability for nanometer linewidths and pitches. The microscope mainly consists of UV light receiving components, piezoelectric ceramics (PZT) driven stage and interferometer calibration framework. In UV light receiving components they include all optical elements on optical path. The UV light originates from Köhler high aperture transmit/reflect illumination sources; then goes through objective lens to UV splitting optical elements; after that, one part of light attains UV camera for large range calibration, the other part of light passes through a three dimensional adjusted pinhole and is collected by PMT for nanoscale scanning. In PZT driven stage, PZT stick actuators with closed loop control are equipped to push/pull a flexural hinge based platform. The platform has a novel designed compound flexural hinges which nest separate X, Y direction moving mechanisms within one layer but avoiding from mutual cross talk, besides this, the hinges also contain leverage structures to amplify moving distance. With these designs, the platform can attain 100 μm displacement ranges as well as 1 nm resolution. In interferometer framework a heterodyne multi-pass interferometer is mounted on the platform, which measures X-Y plane movement and Z axis rotation, through reference mirror mounted on objective lens tube and Zerodur mirror mounted on PZT platform, the displacement is traced back to laser wavelength. When development is finished, the apparatus can offer the capability to calibrate one dimensional linewidths and two dimensional pitches ranging from 200nm to 50μm with expanded uncertainty below 20nm.

Mid-Holocene climates of the Americas: A dynamical response to changed seasonality

USGS Publications Warehouse

Harrison, S.P.; Kutzbach, J.-E.; Liu, Z.; Bartlein, P.J.; Otto-Bliesner, B.; Muhs, D.; Prentice, I.C.; Thompson, R.S.

2003-01-01

Simulations of the climatic response to mid-Holocene (6 ka BP) orbital forcing with two coupled ocean-atmosphere models (FOAM and CSM) show enhancement of monsoonal precipitation in parts of the American Southwest, Central America and northern-most South America during Northern Hemisphere summer. The enhanced onshore flow that brings precipitation into Central America is caused by a northward displacement of the inter-tropical convergence zone, driven by cooling of the equatorial and warming of the northern subtropical and mid-latitude ocean. Ocean feedbacks also enhance precipitation over the American Southwest, although the increase in monsoon precipitation there is largely driven by increases in land-surface temperature. The northward shift in the equatorial precipitation band that causes enhanced precipitation in Central America and the American Southwest has a negative feedback effect on monsoonal precipitation in northern South America. The simulations demonstrate that mid-Holocene aridity in the mid-continent of North America is dynamically linked to the orbitally induced enhancement of the summer monsoon in the American Southwest, with a spatial structure (wet in the Southwest and dry in the mid-continent) similar to that found in strong monsoon years today. Changes in winter precipitation along the west coast of North America, in Central America and along the Gulf Coast, caused by southward-displacement of the westerly storm tracks, indicate that changes in the Northern Hemisphere winter monsoon also play a role in regional climate changes during the mid-Holocene. Although the simulations with FOAM and CSM differ in detail, the general mechanisms and patterns are common to both. The model results thus provide a coherent dynamical explanation for regional patterns of increased or decreased aridity shown by vegetation, lake status and aeolian data from the Americas.

Stretching morphogenesis of the roof plate and formation of the central canal.

PubMed

Kondrychyn, Igor; Teh, Cathleen; Sin, Melvin; Korzh, Vladimir

2013-01-01

Neurulation is driven by apical constriction of actomyosin cytoskeleton resulting in conversion of the primitive lumen into the central canal in a mechanism driven by F-actin constriction, cell overcrowding and buildup of axonal tracts. The roof plate of the neural tube acts as the dorsal morphogenetic center and boundary preventing midline crossing by neural cells and axons. The roof plate zebrafish transgenics expressing cytosolic GFP were used to study and describe development of this structure in vivo for a first time ever. The conversion of the primitive lumen into the central canal causes significant morphogenetic changes of neuroepithelial cells in the dorsal neural tube. We demonstrated that the roof plate cells stretch along the D-V axis in parallel with conversion of the primitive lumen into central canal and its ventral displacement. Importantly, the stretching of the roof plate is well-coordinated along the whole spinal cord and the roof plate cells extend 3× in length to cover 2/3 of the neural tube diameter. This process involves the visco-elastic extension of the roof place cytoskeleton and depends on activity of Zic6 and the Rho-associated kinase (Rock). In contrast, stretching of the floor plate is much less extensive. The extension of the roof plate requires its attachment to the apical complex of proteins at the surface of the central canal, which depends on activity of Zic6 and Rock. The D-V extension of the roof plate may change a range and distribution of morphogens it produces. The resistance of the roof plate cytoskeleton attenuates ventral displacement of the central canal in illustration of the novel mechanical role of the roof plate during development of the body axis.

Stretching Morphogenesis of the Roof Plate and Formation of the Central Canal

PubMed Central

Kondrychyn, Igor; Teh, Cathleen; Sin, Melvin; Korzh, Vladimir

2013-01-01

Background Neurulation is driven by apical constriction of actomyosin cytoskeleton resulting in conversion of the primitive lumen into the central canal in a mechanism driven by F-actin constriction, cell overcrowding and buildup of axonal tracts. The roof plate of the neural tube acts as the dorsal morphogenetic center and boundary preventing midline crossing by neural cells and axons. Methodology/Principal Findings The roof plate zebrafish transgenics expressing cytosolic GFP were used to study and describe development of this structure in vivo for a first time ever. The conversion of the primitive lumen into the central canal causes significant morphogenetic changes of neuroepithelial cells in the dorsal neural tube. We demonstrated that the roof plate cells stretch along the D–V axis in parallel with conversion of the primitive lumen into central canal and its ventral displacement. Importantly, the stretching of the roof plate is well-coordinated along the whole spinal cord and the roof plate cells extend 3× in length to cover 2/3 of the neural tube diameter. This process involves the visco-elastic extension of the roof place cytoskeleton and depends on activity of Zic6 and the Rho-associated kinase (Rock). In contrast, stretching of the floor plate is much less extensive. Conclusions/Significance The extension of the roof plate requires its attachment to the apical complex of proteins at the surface of the central canal, which depends on activity of Zic6 and Rock. The D–V extension of the roof plate may change a range and distribution of morphogens it produces. The resistance of the roof plate cytoskeleton attenuates ventral displacement of the central canal in illustration of the novel mechanical role of the roof plate during development of the body axis. PMID:23409159

Spreading of nanofluids driven by the structural disjoining pressure gradient.

PubMed

Chengara, Anoop; Nikolov, Alex D; Wasan, Darsh T; Trokhymchuk, Andrij; Henderson, Douglas

2004-12-01

This paper discusses the role of the structural disjoining pressure exerted by nanoparticles on the spreading of a liquid film containing these particles. The origin of the structural disjoining pressure in a confined geometry is due to the layering of the particles normal to the confining plane and has already been traced to the net increase in the entropy of the system in previous studies. In a recent paper, Wasan and Nikolov (Nature, 423 (2003) 156) pointed out that the structural component of the disjoining pressure is strong enough to move a liquid wedge; this casts a new light on many applications-most notably, detergency. While the concept of spreading driven by the disjoining pressure is not new, the importance of the structural disjoining pressure arises from its long-range nature (as compared to the van der Waals' force), making it an important component of the overall force balance near the contact line. In this paper, we report on a parametric study of the spreading phenomena by examining the effects of nanoparticle size, concentration and polydispersity on the displacement of an oil-aqueous interface with the aqueous bulk containing nanoparticles. The solution of the extended Laplace-Young equations for the profile of the meniscus yields the position of the nominal contact line under the action of the structural disjoining pressure. Simulations show that the displacement of the contact line is greater with a high nanoparticle volume fraction, small particles for the same volume fraction, monodispersed (in size) particles rather than polydispersed particles and when the resisting capillary pressure is small, i.e., when the interfacial tension is low and/or the radius of the dispersed phase drop/bubble is large.

Direct Numerical Simulation of Low Capillary Number Pore Scale Flows

NASA Astrophysics Data System (ADS)

Esmaeilzadeh, S.; Soulaine, C.; Tchelepi, H.

2017-12-01

The arrangement of void spaces and the granular structure of a porous medium determines multiple macroscopic properties of the rock such as porosity, capillary pressure, and relative permeability. Therefore, it is important to study the microscopic structure of the reservoir pores and understand the dynamics of fluid displacements through them. One approach for doing this, is direct numerical simulation of pore-scale flow that requires a robust numerical tool for prediction of fluid dynamics and a detailed understanding of the physical processes occurring at the pore-scale. In pore scale flows with a low capillary number, Eulerian multiphase methods are well-known to produce additional vorticity close to the interface. This is mainly due to discretization errors which lead to an imbalance of capillary pressure and surface tension forces that causes unphysical spurious currents. At the pore scale, these spurious currents can become significantly stronger than the average velocity in the phases, and lead to unphysical displacement of the interface. In this work, we first investigate the capability of the algebraic Volume of Fluid (VOF) method in OpenFOAM for low capillary number pore scale flow simulations. Afterward, we compare VOF results with a Coupled Level-Set Volume of Fluid (CLSVOF) method and Iso-Advector method. It has been shown that the former one reduces the VOF's unphysical spurious currents in some cases, and both are known to capture interfaces sharper than VOF. As the conclusion, we will investigate that whether the use of CLSVOF or Iso-Advector will lead to less spurious velocities and more accurate results for capillary driven pore-scale multiphase flows or not. Keywords: Pore-scale multiphase flow, Capillary driven flows, Spurious currents, OpenFOAM

A repulsive magnetic force driven translation micromirror

NASA Astrophysics Data System (ADS)

Xue, Yuan; Zuo, Hui; He, Siyuan

2017-10-01

This paper presents a repulsive magnetic force driven micromirror with large displacement and high surface quality which well solves the limitation of the previous design, i.e. large variation in translation starting position and low repeatability, caused by the touching points between the moving film and substrate before and in operation. The new design utilizes a driving mechanism, i.e. permanent magnet ring above and electromagnet underneath the moving film, to lift the moving film from touching the substrate and generate a repulsive magnetic force (instead of attractive force in the previous design) to push the moving film up and away from the substrate for translation. Due to the touching, the previous design has to pre-oscillate for 20-30 min at 1 Hz before usage (after resting for a few hours) to reduce the starting position variation from ~15 µm to 3-4 µm. Even after the pre-oscillation, the repeatability is still low, which is 14.2% because of the touching in operation. In the design presented in this paper, the touching between the moving film and the substrate is completely eliminated before and in operation. As a result, the starting position of the translating mirror is constant each time and the repeatability is  <1%. In addition, this design does not need the residual stress gradient to curve up the moving film. The maximum displacement of 144 µm can be achieved when 140 mA current is applied on the electromagnet. As an application, the micromirror is used as the movable mirror in a Michelson interferometer to measure the wavelength of a laser beam. The result shows a measurement accuracy of 2.19% for a 532 nm laser beam.

Stress loading from viscous flow in the lower crust and triggering of aftershocks following the 1994 Northridge, California, earthquake

USGS Publications Warehouse

Deng, J.; Hudnut, K.; Gurnis, M.; Hauksson, E.

1999-01-01

Following the M(w) 6.7 Northridge earthquake, significant postseismic displacements were resolved with GPS. Using a three-dimensional viscoelastic model, we suggest that this deformation is mainly driven by viscous flow in the lower crust. Such flow can transfer stress to the upper crust and load the rupture zone of the main shock at a decaying rate. Most aftershocks within the rupture zone, especially those that occurred after the first several weeks of the main shock, may have been triggered by continuous stress loading from viscous flow. The long-term decay time of aftershocks (about 2 years) approximately matches the decay of viscoelastic loading, and thus is controlled by the viscosity of the lower crust. Our model provides a physical interpretation of the observed correlation between aftershock decay rate and surface heat flow.Following the Mw 6.7 Northridge earthquake, significant postseismic displacements were resolved with GPS. Using a three-dimensional viscoelastic model, we suggest that this deformation is mainly driven by viscous flow in the lower crust. Such flow can transfer stress to the upper crust and load the rupture zone of the main shock at a decaying rate. Most aftershocks within the rupture zone, especially those that occurred after the first several weeks of the main shock, may have been triggered by continuous stress loading from viscous flow. The long-term decay time of aftershocks (about 2 years) approximately matches the decay of viscoelastic loading, and thus is controlled by the viscosity of the lower crust. Our model provides a physical interpretation of the observed correlation between aftershock decay rate and surface heat flow.

Design and modeling of magnetically driven electric-field sensor for non-contact DC voltage measurement in electric power systems.

PubMed

Wang, Decai; Li, Ping; Wen, Yumei

2016-10-01

In this paper, the design and modeling of a magnetically driven electric-field sensor for non-contact DC voltage measurement are presented. The magnetic drive structure of the sensor is composed of a small solenoid and a cantilever beam with a cylindrical magnet mounted on it. The interaction of the magnet and the solenoid provides the magnetic driving force for the sensor. Employing magnetic drive structure brings the benefits of low driving voltage and large vibrating displacement, which consequently results in less interference from the drive signal. In the theoretical analyses, the capacitance calculation model between the wire and the sensing electrode is built. The expression of the magnetic driving force is derived by the method of linear fitting. The dynamical model of the magnetic-driven cantilever beam actuator is built by using Euler-Bernoulli theory and distributed parameter method. Taking advantage of the theoretical model, the output voltage of proposed sensor can be predicted. The experimental results are in good agreement with the theoretical results. The proposed sensor shows a favorable linear response characteristic. The proposed sensor has a measuring sensitivity of 9.87 μV/(V/m) at an excitation current of 37.5 mA. The electric field intensity resolution can reach 10.13 V/m.

Numerical study of acoustophoretic motion of particles in a PDMS microchannel driven by surface acoustic waves.

PubMed

Nama, Nitesh; Barnkob, Rune; Mao, Zhangming; Kähler, Christian J; Costanzo, Francesco; Huang, Tony Jun

2015-06-21

We present a numerical study of the acoustophoretic motion of particles suspended in a liquid-filled PDMS microchannel on a lithium niobate substrate acoustically driven by surface acoustic waves. We employ a perturbation approach where the flow variables are divided into first- and second-order fields. We use impedance boundary conditions to model the PDMS microchannel walls and we model the acoustic actuation by a displacement function from the literature based on a numerical study of piezoelectric actuation. Consistent with the type of actuation, the obtained first-order field is a horizontal standing wave that travels vertically from the actuated wall towards the upper PDMS wall. This is in contrast to what is observed in bulk acoustic wave devices. The first-order fields drive the acoustic streaming, as well as the time-averaged acoustic radiation force acting on suspended particles. We analyze the motion of suspended particles driven by the acoustic streaming drag and the radiation force. We examine a range of particle diameters to demonstrate the transition from streaming-drag-dominated acoustophoresis to radiation-force-dominated acoustophoresis. Finally, as an application of our numerical model, we demonstrate the capability to tune the position of the vertical pressure node along the channel width by tuning the phase difference between two incoming surface acoustic waves.

Aseismic creep along the North Anatolian Fault quantified by coupling microstructural strain and chemical analyses

NASA Astrophysics Data System (ADS)

Kaduri, Maor; Gratier, Jean-Pierre; Renard, François; Çakir, Ziyadin; Lasserre, Cécile

2017-04-01

In the last decade aseismic creep has been noted as one of the key processes along tectonic plate boundaries. It contributes to the energy budget during the seismic cycle, delaying or triggering the occurrence of large earthquakes. Several major continental active faults show spatial alternation of creeping and locked segments. A great challenge is to understand which parameters control the transition from seismic to aseismic deformation in fault zones, such as the lithology, the degree of deformation from damage rocks to gouge, and the stress driven fault architecture transformations at all scales. The present study focuses on the North Anatolian Fault (Turkey) and characterizes the mechanisms responsible for the partition between seismic and aseismic deformation. Strain values were calculated using various methods, e.g. Fry, R-φs from microstructural measurements in gouge and damage samples collected on more than 30 outcrops along the fault. Maps of mineral composition were reconstructed from microprobe measurements of gouge and damage rock microstructure, in order to calculate the relative mass changes due to stress driven processes during deformation. Strain values were extracted, in addition to the geometrical properties of grain orientation and size distribution. Our data cover subsamples in the damage zones that were protected from deformation and are reminiscent of the host rock microstructure and composition, and subsamples that were highly deformed and recorded both seismic and aseismic deformations. Increase of strain value is linked to the evolution of the orientation of the grains from random to sheared sub-parallel and may be related to various parameters: (1) relative mass transfer increase with increasing strain indicating how stress driven mass transfer processes control aseismic creep evolution with time; (2) measured strain is strongly related with the initial lithology and with the evolution of mineral composition: monomineralic rocks are stronger (less deformed) than polymineralic ones; (3) strain measurements allow to evaluate the cumulated geological displacement accommodated by aseismic creep and the relative ratio between seismic and aseismic displacement for each section of an active fault. These relations allow to quantify more accurately the aseismic creep processes and their evolution with time along the North Anatolian Fault which are controlled by a superposition of two kinds of mechanisms: (1) stress driven mass transfer (pressure solution and metamorphism) that control local and regional mass transfer and associated rheology evolution and (2) grain boundary sliding along weak mineral interfaces (initially weak minerals or more often transformed by deformation-related reactions).

Excitation of high frequency pressure driven modes in non-axisymmetric equilibrium at high βpol in PBX-M

NASA Astrophysics Data System (ADS)

Sesnic, S.; Holland, A.; Kaita, R.; Kaye, S. M.; Okabayashi, M.; Takahashi, H.; Asakura, N.; Bell, R. E.; Bernabei, S.; Chance, M. S.; Duperrex, P.-A.; Fonck, R. J.; Gammel, G. M.; Greene, G. J.; Hatcher, R. E.; Jardin, S. C.; Jiang, T.; Kessel, C. E.; Kugel, H. W.; Leblanc, B.; Levinton, F. M.; Manickam, J.; Ono, M.; Paul, S. F.; Powell, E. T.; Qin, Y.; Roberts, D. W.; Sauthoff, N. R.

1993-12-01

High frequency pressure driven modes have been observed in high poloidal beta discharges in the Princeton Beta Experiment Modification (PBX-M). These modes are excited in a non-axisymmetric equilibrium characterized by a large, low frequency mt = 1/nt = 1 island, and they are capable of expelling fast ions. The modes reside on or very close to the q = 1 surface and have mode numbers with either mh = nh or (less probably) mh/nh = mh/(mh-1), with mh varying between 3 and 10. Occasionally these modes are simultaneously localized in the vicinity of the ml = 2/nl = 1 island. The high frequency modes near the q = 1 surface also exhibit a ballooning character, being significantly stronger on the large major radius side of the plasma. When a large mt = 1/nt = 1 island is present, the mode is poloidally localized in the immediate vicinity of the X point of the island. The modes occur exclusively in high beta beam heated discharges and are likely to be driven by the beam ions. They can thus be a manifestation of either a toroidicity induced shear Alfven eigenmode (TAE) at q = (2mh+1)/2nh, a kinetic ballooning mode, or some other type of pressure driven (high β) mode. Most of the data are consistent with the theoretical predictions for the TAE gap mode. Since the high frequency modes in PBX-M, however, are found exclusively on or in the immediate neighbourhood of magnetic surfaces with low rational numbers (q = 1, 2,...), other possibilities are not excluded

Precessionally driven dynamos in ellipsoidal geometry

NASA Astrophysics Data System (ADS)

Ernst-Hullermann, J.; Harder, H.; Hansen, U.

2013-12-01

Precession was suggested as an alternative driving mechanism for Earth's and planetary magnetic fields by Bullard in 1949. Recent estimates of the thermal and electrical conductivity of Earth's core even show that the energy budget for buoyancy driven dynamos might be very tight. Therefore it seems worth to consider precession at least as an additional if not the only source of energy for the geodynamo. We are going to investigate precessionally driven dynamos by the use of a Finite Volume code. As precession drives a flow only due to the movement of the boundaries the shape of the container is essential for the character of the flow. In planets, it is much more effective to drive a precessional flow by the pressure differences induced by the topography of the precessing body rather than by viscous coupling to the walls. Numerical simulations are the only method offering the possibility to investigate the influence of the topography since laboratory experiments normally are constrained by the predetermined geometry of the vessel. We discuss how ellipticity of the planets can be included in our simulations by the use of a non-orthogonal grid. We will show that even laminar precession-driven flows are capable to generate a magnetic field. Most of the magnetic energy of this dynamos resides in the outer viscous boundary layer. While at lower Ekman number the kinematic dynamos also have magnetic fields located in the bulk, these diminish in the full magneto-hydrodynamic case. The laminar dynamos may not scale to Earth-like parameters. Nevertheless, with our new method we have the possibility to explore the parameter space much more systematically.

Excitations and relaxation dynamics in multiferroic GeV4S8 studied by terahertz and dielectric spectroscopy

NASA Astrophysics Data System (ADS)

Reschke, S.; Wang, Zhe; Mayr, F.; Ruff, E.; Lunkenheimer, P.; Tsurkan, V.; Loidl, A.

2017-10-01

We report on THz time-domain spectroscopy on multiferroic GeV4S8 , which undergoes orbital ordering at a Jahn-Teller transition at 30.5 K and exhibits antiferromagnetic order below 14.6 K. The THz experiments are complemented by dielectric experiments at audio and radio frequencies. We identify a low-lying excitation close to 0.5 THz, which is only weakly temperature dependent and probably corresponds to a molecular excitation within the electronic level scheme of the V4 clusters. In addition, we detect complex temperature-dependent behavior of a low-lying phononic excitation, closely linked to the onset of orbitally driven ferroelectricity. In the high-temperature cubic phase, which is paramagnetic and orbitally disordered, this excitation is of relaxational character becomes an overdamped Lorentzian mode in the orbitally ordered phase below the Jahn-Teller transition, and finally appears as well-defined phonon excitation in the antiferromagnetic state. Abrupt changes in the real and imaginary parts of the complex dielectric permittivity show that orbital ordering appears via a structural phase transition with strong first-order character and that the onset of antiferromagnetic order is accompanied by significant structural changes, which are of first-order character, too. Dielectric spectroscopy documents that at low frequencies, significant dipolar relaxations are present in the orbitally ordered, paramagnetic phase only. In contrast to the closely related GaV4S8 , this relaxation dynamics that most likely mirrors coupled orbital and polar fluctuations does not seem to be related to the dynamic processes detected in the THz regime.

Nearshore wave-induced cyclical flexing of sea cliffs

USGS Publications Warehouse

Adams, P.N.; Storlazzi, C.D.; Anderson, R. Scott

2005-01-01

[1] Evolution of a tectonically active coast is driven by geomorphically destructive energy supplied by ocean waves. Wave energy is episodic and concentrated; sea cliffs are battered by the geomorphic wrecking ball every 4-25 s. We measure the response of sea cliffs to wave assault by sensing the ground motion using near-coastal seismometers. Sea cliffs respond to waves in two distinct styles. High-frequency motion (20 Hz) reflects the natural frequency of the sea cliff as it rings in response to direct wave impact. Low-frequency motion in the 0.1-0.05 Hz (10-20 s) band consistently agrees with the dominant nearshore wave period. Integrating microseismic velocities suggests 50 ??m and 10 ??m displacements in horizontal and vertical directions, respectively. Displacement ellipsoids exhibit simultaneous downward and seaward sea cliff motion with each wave. Video footage corroborates the downward sea cliff flex in response to the imposed water load on the wave cut platform. Gradients in displacement amplitudes documented using multiple seismometers suggest longitudinal and shear strain of the flexing sea cliff on the order of 0.5-4 ?? strains during each wave loading cycle. As this sea cliff flexure occurs approximately 3 million times annually, it has the potential to fatigue the rock through cyclical loading. Local sea cliff retreat rates of 10 cm/yr imply that a given parcel of rock is flexed through roughly 109 cycles of increasing amplitude before exposure to direct wave attack at the cliff face. Copyright 2005 by the American Geophysical Union.

Contaminants in ventilated filling boxes

NASA Astrophysics Data System (ADS)

Bolster, D. T.; Linden, P. F.

While energy efficiency is important, the adoption of energy-efficient ventilation systems still requires the provision of acceptable indoor air quality. Many low-energy systems, such as displacement or natural ventilation, rely on temperature stratification within the interior environment, always extracting the warmest air from the top of the room. Understanding buoyancy-driven convection in a confined ventilated space is key to understanding the flow that develops with many of these modern low-energy ventilation schemes. In this work we study the transport of an initially uniformly distributed passive contaminant in a displacement-ventilated space. Representing a heat source as an ideal sourced of buoyancy, analytical and numerical models are developed that allow us to compare the average efficiency of contaminant removal between traditional mixing and modern low-energy systems. A set of small-scale analogue laboratory experiments was also conducted to further validate our analytical and numerical solutions.We find that on average traditional and low-energy ventilation methods are similar with regard to pollutant flushing efficiency. This is because the concentration being extracted from the system at any given time is approximately the same for both systems. However, very different vertical concentration gradients exist. For the low-energy system, a peak in contaminant concentration occurs at the temperature interface that is established within the space. This interface is typically designed to sit at some intermediate height in the space. Since this peak does not coincide with the extraction point, displacement ventilation does not offer the same benefits for pollutant flushing as it does for buoyancy removal.

Integrated system for point cloud reconstruction and simulated brain shift validation using tracked surgical microscope

NASA Astrophysics Data System (ADS)

Yang, Xiaochen; Clements, Logan W.; Luo, Ma; Narasimhan, Saramati; Thompson, Reid C.; Dawant, Benoit M.; Miga, Michael I.

2017-03-01

Intra-operative soft tissue deformation, referred to as brain shift, compromises the application of current imageguided surgery (IGS) navigation systems in neurosurgery. A computational model driven by sparse data has been used as a cost effective method to compensate for cortical surface and volumetric displacements. Stereoscopic microscopes and laser range scanners (LRS) are the two most investigated sparse intra-operative imaging modalities for driving these systems. However, integrating these devices in the clinical workflow to facilitate development and evaluation requires developing systems that easily permit data acquisition and processing. In this work we present a mock environment developed to acquire stereo images from a tracked operating microscope and to reconstruct 3D point clouds from these images. A reconstruction error of 1 mm is estimated by using a phantom with a known geometry and independently measured deformation extent. The microscope is tracked via an attached tracking rigid body that facilitates the recording of the position of the microscope via a commercial optical tracking system as it moves during the procedure. Point clouds, reconstructed under different microscope positions, are registered into the same space in order to compute the feature displacements. Using our mock craniotomy device, realistic cortical deformations are generated. Our experimental results report approximately 2mm average displacement error compared with the optical tracking system. These results demonstrate the practicality of using tracked stereoscopic microscope as an alternative to LRS to collect sufficient intraoperative information for brain shift correction.

Effects of trunk-to-head rotation on the labyrinthine responses of rat reticular neurons.

PubMed

Barresi, M; Grasso, C; Bruschini, L; Berrettini, S; Manzoni, D

2012-11-08

Vestibulospinal reflexes elicited by head displacement become appropriate for body stabilization owing to the integration of neck input by the cerebellar anterior vermis. Due to this integration, the preferred direction of spinal motoneurons' responses to animal tilt rotates by the same angle and by the same direction as the head over the body, which makes it dependent on the direction of body displacement rather than on head displacement. It is known that the cerebellar control of spinal motoneurons involves the reticular formation. Since the preferred directions of corticocerebellar units' responses to animal tilt are tuned by neck rotation, as occuring in spinal motoneurons, we investigated whether a similar tuning can be observed also in the intermediate station of reticular formation. In anaesthetized rats, the activity of neurons in the medullary reticular formation was recorded during wobble of the whole animal at 0.156 Hz, a stimulus that tilted the animal's head by a constant amplitude (5°), in a direction rotating clockwise or counter clockwise over the horizontal plane. The response gain and the direction of tilt eliciting the maximal activity were evaluated with the head and body axes aligned and during a maintained body-to-head displacement of 5-20° over the horizontal plane, in either direction. We found that the neck displacement modified the response gain and/or the average activity of most of the responsive neurons. Rotation of the response direction was observed only in a minor percentage of the recorded neurons. The modifications of reticular neurons' responses were different from those observed in the P-cells of the cerebellar anterior vermis, which rarely showed gain and activity changes and often exhibited a rotation of their response directions. In conclusion, reticular neurons take part in the neck tuning of vestibulospinal reflexes by transforming a head-driven sensory input into a body-centred postural response. The present findings prompt re-evaluation of the role played by the reticular neurons and the cerebellum in vestibulospinal reflexes. Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

Languages of the heart: the biomedical and the metaphorical in American fiction.

PubMed

Oldfield, Benjamin J; Jones, David S

2014-01-01

The role of heart disease in American fiction has received less attention from scholars of literature, history, and medicine than have portrayals of tuberculosis, cancer, or HIV/AIDS, despite the fact that heart disease topped mortality charts for most of the 20th century. This article surveys manifestations of coronary artery disease in popular works of 20th-century American fiction to trace how authors and their protagonists grappled with the disease while knowledge of pathophysiology and therapeutics evolved. Countering Susan Sontag's mechanistic vision of patient encounters-where disease is absent of metaphor-we pair popular fiction with concurrent historical analysis to show that the proliferation of technological narratives of cardiac therapeutics could not displace the deeply symbolic nature of characters' encounters with heart disease. Because of the limited ability of the biomedical narrative to convey the meanings of disease and treatments, doctors and patients need to communicate through the rich possibilities of metaphor.

Pressure Dependence of the Peierls Stress in Aluminum

NASA Astrophysics Data System (ADS)

Dang, Khanh; Spearot, Douglas

2018-03-01

The effect of pressure applied normal to the {111} slip plane on the Peierls stress in Al is studied via atomistic simulations. Edge, screw, 30°, and 60° straight dislocations are created using the Volterra displacement fields for isotropic elasticity. For each dislocation character angle, the Peierls stress is calculated based on the change in the internal energy, which is an invariant measure of the dislocation driving force. It is found that the Peierls stress for dislocations under zero pressure is in general agreement with previous results. For screw and 60° dislocations, the Peierls stress versus pressure relationship has maximum values associated with stacking fault widths that are multiples of the Peierls period. For the edge dislocation, the Peierls stress decreases with increasing pressure from tension to compression. Compared with the Mendelev potential, the Peierls stress calculated from the Mishin potential is more sensitive to changes in pressure.

Levers and linkages: mechanical trade-offs in a power-amplified system.

PubMed

Anderson, Philip S L; Claverie, Thomas; Patek, S N

2014-07-01

Mechanical redundancy within a biomechanical system (e.g., many-to-one mapping) allows morphologically divergent organisms to maintain equivalent mechanical outputs. However, most organisms depend on the integration of more than one biomechanical system. Here, we test whether coupled mechanical systems follow a pattern of amplification (mechanical changes are congruent and evolve toward the same functional extreme) or independence (mechanisms evolve independently). We examined the correlated evolution and evolutionary pathways of the coupled four-bar linkage and lever systems in mantis shrimp (Stomatopoda) ultrafast raptorial appendages. We examined models of character evolution in the framework of two divergent groups of stomatopods-"smashers" (hammer-shaped appendages) and "spearers" (bladed appendages). Smashers tended to evolve toward force amplification, whereas spearers evolved toward displacement amplification. These findings show that coupled biomechanical systems can evolve synergistically, thereby resulting in functional amplification rather than mechanical redundancy. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

Diversity spurs diversification in ecological communities

PubMed Central

Calcagno, Vincent; Jarne, Philippe; Loreau, Michel; Mouquet, Nicolas; David, Patrice

2017-01-01

Diversity is a fundamental, yet threatened, property of ecological systems. The idea that diversity can itself favour diversification, in an autocatalytic process, is very appealing but remains controversial. Here, we study a generalized model of ecological communities and investigate how the level of initial diversity influences the possibility of evolutionary diversification. We show that even simple models of intra- and inter-specific ecological interactions can predict a positive effect of diversity on diversification: adaptive radiations may require a threshold number of species before kicking-off. We call this phenomenon DDAR (diversity-dependent adaptive radiations) and identify mathematically two distinct pathways connecting diversity to diversification, involving character displacement and the positive diversity-productivity relationship. Our results may explain observed delays in adaptive radiations at the macroscale and diversification patterns reported in experimental microbial communities, and shed new light on the dynamics of ecological diversity, the diversity-dependence of diversification rates, and the consequences of biodiversity loss. PMID:28598423

Raman and infrared spectroscopic investigations of a ferroelastic phase transition in B a2ZnTe O6 double perovskite

NASA Astrophysics Data System (ADS)

Moreira, Roberto L.; Lobo, Ricardo P. S. M.; Ramos, Sérgio L. L. M.; Sebastian, Mailadil T.; Matinaga, Franklin M.; Righi, Ariete; Dias, Anderson

2018-05-01

The low-temperature vibrational properties of B a2ZnTe O6 double-perovskite ceramics obtained by the solid-state route were investigated by Raman scattering and Fourier-transform infrared reflectivity. We found that this material undergoes a reversible ferroelastic phase transition at around 140 K, well compatible with a recently proposed rhombohedral-to-monoclinic structural change that would occur below 165 K. Complementary calorimetric measurements showed that the phase transition has a first-order character, with an entropy jump compatible with a displacive mechanism. The vibrational spectra show clearly the splitting of the doubly degenerate E modes into nondegenerate representations of the low-symmetry phase. In particular, the lowest-frequency Raman mode presents soft-mode behavior and splits below the critical temperature, confirming the in-plane ferroelastic deformation in the low-temperature phase.

Diversity spurs diversification in ecological communities

NASA Astrophysics Data System (ADS)

Calcagno, Vincent; Jarne, Philippe; Loreau, Michel; Mouquet, Nicolas; David, Patrice

2017-06-01

Diversity is a fundamental, yet threatened, property of ecological systems. The idea that diversity can itself favour diversification, in an autocatalytic process, is very appealing but remains controversial. Here, we study a generalized model of ecological communities and investigate how the level of initial diversity influences the possibility of evolutionary diversification. We show that even simple models of intra- and inter-specific ecological interactions can predict a positive effect of diversity on diversification: adaptive radiations may require a threshold number of species before kicking-off. We call this phenomenon DDAR (diversity-dependent adaptive radiations) and identify mathematically two distinct pathways connecting diversity to diversification, involving character displacement and the positive diversity-productivity relationship. Our results may explain observed delays in adaptive radiations at the macroscale and diversification patterns reported in experimental microbial communities, and shed new light on the dynamics of ecological diversity, the diversity-dependence of diversification rates, and the consequences of biodiversity loss.

Morphological divergence in a continental adaptive radiation: South American ovenbirds of the genus Cinclodes

USGS Publications Warehouse

Rader, Jonathan A.; Dillon, Michael E.; Chesser, R. Terry; Sabat, Pablo; Martinez del Rio, Carlos

2015-01-01

Cinclodes is an ecologically diverse genus of South American passerine birds and represents a case of continental adaptive radiation along multiple axes. We investigated morphological diversification in Cinclodes using a comprehensive set of morphometric measurements of study skins. Principal component analysis identified 2 primary axes of morphological variation: one describing body size and a second capturing differences in wing-tip shape and toe length. Phylogenetic analyses of the first principal component suggest an early divergence ofCinclodes into 2 main clades characterized by large and small body sizes. We suggest that 2 morphological outliers within these main clades (C. antarcticus and C. palliatus) may be cases of island gigantism and that a third (C. patagonicus) may reflect ecological character displacement. Despite its ecological and physiological diversity, the genus Cinclodes does not appear to show morphological diversity beyond what is typical of other avian genera.

What makes the difference in perovskite titanates?

NASA Astrophysics Data System (ADS)

Bussmann-Holder, Annette; Roleder, Krystian; Ko, Jae-Hyeon

2018-06-01

We have investigated in detail the lattice dynamics of five different perovskite titanates ATiO3 (A = Ca, Sr, Ba, Pb, Eu) where the A sites are occupied by +2 ions. In spite of the largely ionic character of these ions, the properties of these compounds differ substantially. They range from order/disorder like, to displacive ferroelectric, quantum paraelectric, and antiferromagnetic. All compounds crystallize in the cubic structure at high temperature and undergo structural phase transitions to tetragonal symmetry, partly followed by further transitions to lower symmetries. Since the TiO6 moiety is the essential electronic and structural unit, the question arises, what makes the significant difference between them. It is shown that the lattice dynamics of these compounds are very different, and that mode-mode coupling effects give rise to many distinct properties. In addition, the oxygen ion nonlinear polarizability plays a key role since it dominates the anharmonicity of these perovskites and determines the structural instability.

Diversity spurs diversification in ecological communities.

PubMed

Calcagno, Vincent; Jarne, Philippe; Loreau, Michel; Mouquet, Nicolas; David, Patrice

2017-06-09

Diversity is a fundamental, yet threatened, property of ecological systems. The idea that diversity can itself favour diversification, in an autocatalytic process, is very appealing but remains controversial. Here, we study a generalized model of ecological communities and investigate how the level of initial diversity influences the possibility of evolutionary diversification. We show that even simple models of intra- and inter-specific ecological interactions can predict a positive effect of diversity on diversification: adaptive radiations may require a threshold number of species before kicking-off. We call this phenomenon DDAR (diversity-dependent adaptive radiations) and identify mathematically two distinct pathways connecting diversity to diversification, involving character displacement and the positive diversity-productivity relationship. Our results may explain observed delays in adaptive radiations at the macroscale and diversification patterns reported in experimental microbial communities, and shed new light on the dynamics of ecological diversity, the diversity-dependence of diversification rates, and the consequences of biodiversity loss.

Geophysical investigations in the Bi'r Idimah-Wadi Wassat area, Saudi Arabia, Part One

USGS Publications Warehouse

Allen, R.V.; Davis, W.E.

1969-01-01

The area is near latitude 18°20'N., longitude 44°20'E, about 20 Km south of Bi'r Idirah (Fig. 1). Most of the area lies in a wadi bounded by low hills that reach elevations near 1250 meters and rise as ranch as 50 meters above the wadi floor. The gossan is exposed in the wadi and near the crests of a few hills in the southern part of the surveyed area. It is underlain by andesite porphyry and greenstone intruded by granitic rocks, and appears to have been displaced laterally by faulting in the central part of the area. An inclined test hole north of the offset cut massive pyrite between depths 98 and 141 feet, 250 and 260 feet, and between depths 299 and 351 feet. This test and the character of the gossan suggest that the mineralized zone continues southward for a considerable distance.

Devil's staircase and the absence of chaos in the dc- and ac-driven overdamped Frenkel-Kontorova model

NASA Astrophysics Data System (ADS)

Sokolović, I.; Mali, P.; Odavić, J.; Radošević, S.; Medvedeva, S. Yu.; Botha, A. E.; Shukrinov, Yu. M.; Tekić, J.

2017-08-01

The devil's staircase structure arising from the complete mode locking of an entirely nonchaotic system, the overdamped dc+ac driven Frenkel-Kontorova model with deformable substrate potential, was observed. Even though no chaos was found, a hierarchical ordering of the Shapiro steps was made possible through the use of a previously introduced continued fraction formula. The absence of chaos, deduced here from Lyapunov exponent analyses, can be attributed to the overdamped character and the Middleton no-passing rule. A comparative analysis of a one-dimensional stack of Josephson junctions confirmed the disappearance of chaos with increasing dissipation. Other common dynamic features were also identified through this comparison. A detailed analysis of the amplitude dependence of the Shapiro steps revealed that only for the case of a purely sinusoidal substrate potential did the relative sizes of the steps follow a Farey sequence. For nonsinusoidal (deformed) potentials, the symmetry of the Stern-Brocot tree, depicting all members of particular Farey sequence, was seen to be increasingly broken, with certain steps being more prominent and their relative sizes not following the Farey rule.

A three-dimensional movie of structural changes in bacteriorhodopsin.

PubMed

Nango, Eriko; Royant, Antoine; Kubo, Minoru; Nakane, Takanori; Wickstrand, Cecilia; Kimura, Tetsunari; Tanaka, Tomoyuki; Tono, Kensuke; Song, Changyong; Tanaka, Rie; Arima, Toshi; Yamashita, Ayumi; Kobayashi, Jun; Hosaka, Toshiaki; Mizohata, Eiichi; Nogly, Przemyslaw; Sugahara, Michihiro; Nam, Daewoong; Nomura, Takashi; Shimamura, Tatsuro; Im, Dohyun; Fujiwara, Takaaki; Yamanaka, Yasuaki; Jeon, Byeonghyun; Nishizawa, Tomohiro; Oda, Kazumasa; Fukuda, Masahiro; Andersson, Rebecka; Båth, Petra; Dods, Robert; Davidsson, Jan; Matsuoka, Shigeru; Kawatake, Satoshi; Murata, Michio; Nureki, Osamu; Owada, Shigeki; Kameshima, Takashi; Hatsui, Takaki; Joti, Yasumasa; Schertler, Gebhard; Yabashi, Makina; Bondar, Ana-Nicoleta; Standfuss, Jörg; Neutze, Richard; Iwata, So

2016-12-23

Bacteriorhodopsin (bR) is a light-driven proton pump and a model membrane transport protein. We used time-resolved serial femtosecond crystallography at an x-ray free electron laser to visualize conformational changes in bR from nanoseconds to milliseconds following photoactivation. An initially twisted retinal chromophore displaces a conserved tryptophan residue of transmembrane helix F on the cytoplasmic side of the protein while dislodging a key water molecule on the extracellular side. The resulting cascade of structural changes throughout the protein shows how motions are choreographed as bR transports protons uphill against a transmembrane concentration gradient. Copyright © 2016, American Association for the Advancement of Science.

Orbital transfer vehicle oxygen turbopump technology. Volume 1: Design, fabrication, and hydrostatic bearing testing

NASA Technical Reports Server (NTRS)

Buckmann, P. S.; Hayden, W. R.; Lorenc, S. A.; Sabiers, R. L.; Shimp, N. R.

1990-01-01

The design, fabrication, and initial testing of a rocket engine turbopump (TPA) for the delivery of high pressure liquid oxygen using hot oxygen for the turbine drive fluid are described. This TPA is basic to the dual expander engine which uses both oxygen and hydrogen as working fluids. Separate tasks addressed the key issue of materials for this TPA. All materials selections emphasized compatibility with hot oxygen. The OX TPA design uses a two-stage centrifugal pump driven by a single-stage axial turbine on a common shaft. The design includes ports for three shaft displacement/speed sensors, various temperature measurements, and accelerometers.

Phasing operator for two oscillators in classical field

NASA Technical Reports Server (NTRS)

Kim, Jong-Jean; Koo, Je-Hwan; Bae, Dong-Jae

1993-01-01

The origin of Dicke cooperative states was studied by considering two harmonic oscillators driven by a common field of radiation. The origin is assumed for superradiance in a system of molecules where no mutual interactions exist, but all of the molecules encounter the same field of radiation. A phasing operator as Phi(sub Nu) equals D(alpha) + P(sub Nu)D(alpha), where D(alpha) is the displacing operator and P(sub Nu) the projection operator for constant energy Nu for two oscillators, was derived. The eigenstates of the phasing operator Phi are found to show a finite correlation as in the Dicke cooperative states.

Precise-spike-driven synaptic plasticity: learning hetero-association of spatiotemporal spike patterns.

PubMed

Yu, Qiang; Tang, Huajin; Tan, Kay Chen; Li, Haizhou

2013-01-01

A new learning rule (Precise-Spike-Driven (PSD) Synaptic Plasticity) is proposed for processing and memorizing spatiotemporal patterns. PSD is a supervised learning rule that is analytically derived from the traditional Widrow-Hoff rule and can be used to train neurons to associate an input spatiotemporal spike pattern with a desired spike train. Synaptic adaptation is driven by the error between the desired and the actual output spikes, with positive errors causing long-term potentiation and negative errors causing long-term depression. The amount of modification is proportional to an eligibility trace that is triggered by afferent spikes. The PSD rule is both computationally efficient and biologically plausible. The properties of this learning rule are investigated extensively through experimental simulations, including its learning performance, its generality to different neuron models, its robustness against noisy conditions, its memory capacity, and the effects of its learning parameters. Experimental results show that the PSD rule is capable of spatiotemporal pattern classification, and can even outperform a well studied benchmark algorithm with the proposed relative confidence criterion. The PSD rule is further validated on a practical example of an optical character recognition problem. The results again show that it can achieve a good recognition performance with a proper encoding. Finally, a detailed discussion is provided about the PSD rule and several related algorithms including tempotron, SPAN, Chronotron and ReSuMe.

Precise-Spike-Driven Synaptic Plasticity: Learning Hetero-Association of Spatiotemporal Spike Patterns

PubMed Central

Yu, Qiang; Tang, Huajin; Tan, Kay Chen; Li, Haizhou

2013-01-01

A new learning rule (Precise-Spike-Driven (PSD) Synaptic Plasticity) is proposed for processing and memorizing spatiotemporal patterns. PSD is a supervised learning rule that is analytically derived from the traditional Widrow-Hoff rule and can be used to train neurons to associate an input spatiotemporal spike pattern with a desired spike train. Synaptic adaptation is driven by the error between the desired and the actual output spikes, with positive errors causing long-term potentiation and negative errors causing long-term depression. The amount of modification is proportional to an eligibility trace that is triggered by afferent spikes. The PSD rule is both computationally efficient and biologically plausible. The properties of this learning rule are investigated extensively through experimental simulations, including its learning performance, its generality to different neuron models, its robustness against noisy conditions, its memory capacity, and the effects of its learning parameters. Experimental results show that the PSD rule is capable of spatiotemporal pattern classification, and can even outperform a well studied benchmark algorithm with the proposed relative confidence criterion. The PSD rule is further validated on a practical example of an optical character recognition problem. The results again show that it can achieve a good recognition performance with a proper encoding. Finally, a detailed discussion is provided about the PSD rule and several related algorithms including tempotron, SPAN, Chronotron and ReSuMe. PMID:24223789

Design and Optimization of a Hybrid-Driven Waist Rehabilitation Robot

PubMed Central

Zi, Bin; Yin, Guangcai; Zhang, Dan

2016-01-01

In this paper a waist rehabilitation robot driven by cables and pneumatic artificial muscles (PAMs) has been conceptualized and designed. In the process of mechanism design, the human body structure, the waist movement characteristics, and the actuators’ driving characteristics are the main considerable factors to make the hybrid-driven waist rehabilitation robot (HWRR) cost-effective, safe, flexible, and well-adapted. A variety of sensors are chosen to measure the position and orientation of the recovery patient to ensure patient safety at the same time as the structure design. According to the structure specialty and function, the HWRR is divided into two independent parallel robots: the waist twist device and the lower limb traction device. Then these two devices are analyzed and evaluated, respectively. Considering the characters of the human body in the HWRR, the inverse kinematics and statics are studied when the waist and the lower limb are considered as a spring and link, respectively. Based on the inverse kinematics and statics, the effect of the contraction parameter of the PAM is considered in the optimization of the waist twist device, and the lower limb traction device is optimized using particle swarm optimization (PSO) to minimize the global conditioning number over the feasible workspace. As a result of the optimization, an optimal rehabilitation robot design is obtained and the condition number of the Jacobian matrix over the feasible workspace is also calculated. PMID:27983626

Design and Optimization of a Hybrid-Driven Waist Rehabilitation Robot.

PubMed

Zi, Bin; Yin, Guangcai; Zhang, Dan

2016-12-14

In this paper a waist rehabilitation robot driven by cables and pneumatic artificial muscles (PAMs) has been conceptualized and designed. In the process of mechanism design, the human body structure, the waist movement characteristics, and the actuators' driving characteristics are the main considerable factors to make the hybrid-driven waist rehabilitation robot (HWRR) cost-effective, safe, flexible, and well-adapted. A variety of sensors are chosen to measure the position and orientation of the recovery patient to ensure patient safety at the same time as the structure design. According to the structure specialty and function, the HWRR is divided into two independent parallel robots: the waist twist device and the lower limb traction device. Then these two devices are analyzed and evaluated, respectively. Considering the characters of the human body in the HWRR, the inverse kinematics and statics are studied when the waist and the lower limb are considered as a spring and link, respectively. Based on the inverse kinematics and statics, the effect of the contraction parameter of the PAM is considered in the optimization of the waist twist device, and the lower limb traction device is optimized using particle swarm optimization (PSO) to minimize the global conditioning number over the feasible workspace. As a result of the optimization, an optimal rehabilitation robot design is obtained and the condition number of the Jacobian matrix over the feasible workspace is also calculated.

Topometry optimization of sheet metal structures for crashworthiness design using hybrid cellular automata

NASA Astrophysics Data System (ADS)

Mozumder, Chandan K.

The objective in crashworthiness design is to generate plastically deformable energy absorbing structures which can satisfy the prescribed force-displacement (FD) response. The FD behavior determines the reaction force, displacement and the internal energy that the structure should withstand. However, attempts to include this requirement in structural optimization problems remain scarce. The existing commercial optimization tools utilize models under static loading conditions because of the complexities associated with dynamic/impact loading. Due to the complexity of a crash event and the consequent time required to numerically analyze the dynamic response of the structure, classical methods (i.e., gradient-based and direct) are not well developed to solve this undertaking. This work presents an approach under the framework of the hybrid cellular automaton (HCA) method to solve the above challenge. The HCA method has been successfully applied to nonlinear transient topology optimization for crashworthiness design. In this work, the HCA algorithm has been utilized to develop an efficient methodology for synthesizing shell-based sheet metal structures with optimal material thickness distribution under a dynamic loading event using topometry optimization. This method utilizes the cellular automata (CA) computing paradigm and nonlinear transient finite element analysis (FEA) via ls-dyna. In this method, a set field variables is driven to their target states by changing a convenient set of design variables (e.g., thickness). These rules operate locally in cells within a lattice that only know local conditions. The field variables associated with the cells are driven to a setpoint to obtain the desired structure. This methodology is used to design for structures with controlled energy absorption with specified buckling zones. The peak reaction force and the maximum displacement are also constrained to meet the desired safety level according to passenger safety regulations. Design for prescribed FD response by minimizing the error between the actual response and desired FD curve is implemented. With the use of HCA rules, manufacturability constraints (e.g., rolling) and structures which can be manufactured by special techniques, such as, tailor-welded blanks (TWB), have also been implemented. This methodology is applied to shock-absorbing structural components for passengers in a crashing vehicle. These results are compared to previous designs showing the benefits of the method introduced in this work.

Evolutionary Determinants of Cancer

PubMed Central

Greaves, Mel

2015-01-01

‘Nothing in biology makes sense except in the light of evolution’ Th. Dobzhansky, 1973 Our understanding of cancer is being transformed by exploring clonal diversity, drug resistance and causation within an evolutionary framework. The therapeutic resilience of advanced cancer is a consequence of its character as complex, dynamic and adaptive ecosystem engendering robustness, underpinned by genetic diversity and epigenetic plasticity. The risk of mutation-driven escape by self-renewing cells is intrinsic to multicellularity but is countered by multiple restraints facilitating increasing complexity and longevity of species. But our own has disrupted this historical narrative by rapidly escalating intrinsic risk. Evolutionary principles illuminate these challenges and provide new avenues to explore for more effective control. PMID:26193902

Investigation of Vibrational Control of the Bridgman Crystal Growth Technique

NASA Technical Reports Server (NTRS)

Fedoseyev, Alexandre I.; Alexander, J. I. D.; Feigelson, R. S.; Zharikov, E. V.; Ostrogorsky, A. G.; Marin, C.; Volz, M. P.; Kansa, E. J.; Friedman, M. J.

2001-01-01

The character of natural buoyant convection in rigidly contained inhomogeneous fluids can be drastically altered by vibrating the container. Vibrations are expected to play a crucial influence on heat and mass transfer onboard the International Space Station (ISS). It is becoming evident that substantial vibrations will exist on the ISS in the wide frequency spectrum. In general, vibrational flows are very complex and governed by many parameters. In many terrestrial crystal growth situations, convective transport of heat and constituent components is dominated by buoyancy driven convection arising from compositional and thermal gradients. Thus, it may be concluded that vibro-convective flow can potentially be used to influence and even control transport in some crystal growth situations.

Ion pairing and phase behaviour of an asymmetric restricted primitive model of ionic liquids

NASA Astrophysics Data System (ADS)

Lu, Hongduo; Li, Bin; Nordholm, Sture; Woodward, Clifford E.; Forsman, Jan

2016-12-01

An asymmetric restricted primitive model (ARPM) of electrolytes is proposed as a simple three parameter (charge q, diameter d, and charge displacement b) model of ionic liquids and solutions. Charge displacement allows electrostatic and steric interactions to operate between different centres, so that orientational correlations arise in ion-ion interactions. In this way the ionic system may have partly the character of a simple ionic fluid/solid and of a polar fluid formed from ion pairs. The present exploration of the system focuses on the ion pair formation mechanism, the relative concentration of paired and free ions and the consequences for the cohesive energy, and the tendency to form fluid or solid phase. In contrast to studies of similar (though not identical) models in the past, we focus on behaviours at room temperature. By MC and MD simulations of such systems composed of monovalent ions of hard-sphere (or essentially hard-sphere) diameter equal to 5 Å and a charge displacement ranging from 0 to 2 Å from the hard-sphere origin, we find that ion pairing dominates for b larger than 1 Å. When b exceeds about 1.5 Å, the system is essentially a liquid of dipolar ion pairs with a small presence of free ions. We also investigate dielectric behaviours of corresponding liquids, composed of purely dipolar species. Many basic features of ionic liquids appear to be remarkably consistent with those of our ARPM at ambient conditions, when b is around 1 Å. However, the rate of self-diffusion and, to a lesser extent, conductivity is overestimated, presumably due to the simple spherical shape of our ions in the ARPM. The relative simplicity of our ARPM in relation to the rich variety of new mechanisms and properties it introduces, and to the numerical simplicity of its exploration by theory or simulation, makes it an essential step on the way towards representation of the full complexity of ionic liquids.

Ion pairing and phase behaviour of an asymmetric restricted primitive model of ionic liquids.

PubMed

Lu, Hongduo; Li, Bin; Nordholm, Sture; Woodward, Clifford E; Forsman, Jan

2016-12-21

An asymmetric restricted primitive model (ARPM) of electrolytes is proposed as a simple three parameter (charge q, diameter d, and charge displacement b) model of ionic liquids and solutions. Charge displacement allows electrostatic and steric interactions to operate between different centres, so that orientational correlations arise in ion-ion interactions. In this way the ionic system may have partly the character of a simple ionic fluid/solid and of a polar fluid formed from ion pairs. The present exploration of the system focuses on the ion pair formation mechanism, the relative concentration of paired and free ions and the consequences for the cohesive energy, and the tendency to form fluid or solid phase. In contrast to studies of similar (though not identical) models in the past, we focus on behaviours at room temperature. By MC and MD simulations of such systems composed of monovalent ions of hard-sphere (or essentially hard-sphere) diameter equal to 5 Å and a charge displacement ranging from 0 to 2 Å from the hard-sphere origin, we find that ion pairing dominates for b larger than 1 Å. When b exceeds about 1.5 Å, the system is essentially a liquid of dipolar ion pairs with a small presence of free ions. We also investigate dielectric behaviours of corresponding liquids, composed of purely dipolar species. Many basic features of ionic liquids appear to be remarkably consistent with those of our ARPM at ambient conditions, when b is around 1 Å. However, the rate of self-diffusion and, to a lesser extent, conductivity is overestimated, presumably due to the simple spherical shape of our ions in the ARPM. The relative simplicity of our ARPM in relation to the rich variety of new mechanisms and properties it introduces, and to the numerical simplicity of its exploration by theory or simulation, makes it an essential step on the way towards representation of the full complexity of ionic liquids.

Edentulism, beaks, and biomechanical innovations in the evolution of theropod dinosaurs.

PubMed

Lautenschlager, Stephan; Witmer, Lawrence M; Altangerel, Perle; Rayfield, Emily J

2013-12-17

Maniraptoriformes, the speciose group of derived theropod dinosaurs that ultimately gave rise to modern birds, display a diverse and remarkable suite of skeletal adaptations. Apart from the evolution of flight, a large-scale change in dietary behavior appears to have been one of the main triggers for specializations in the bauplan of these derived theropods. Among the different skeletal specializations, partial or even complete edentulism and the development of keratinous beaks form a recurring and persistent trend in from the evolution of derived nonavian dinosaurs. Therizinosauria is an enigmatic maniraptoriform clade, whose members display these and other osteological characters thought to be correlated with the shift from carnivory to herbivory. This makes therizinosaurians prime candidates to assess the functional significance of these morphological characters. Based on a highly detailed biomechanical model of Erlikosaurus andrewsi, a therizinosaurid from the Upper Cretaceous of Mongolia, different morphological configurations incorporating soft-tissue structures, such as a keratinous rhamphotheca, are evaluated for their biomechanical performance. Our results indicate that the development of beaks and the presence of a keratinous rhamphotheca would have helped to dissipate stress and strain, making the rostral part of the skull less susceptible to bending and displacement, and this benefit may extend to other vertebrate clades that possess rhamphothecae. Keratinous beaks, paralleled by edentulism, thus represent an evolutionary innovation developed early in derived theropods to enhance cranial stability, distinct to postulated mass-saving benefits associated with the origin of flight.

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

Yazdani, Ahmad, E-mail: Yazdania@modares.ac.ir; Shadrokh, Zohreh; Department of Physics, University of Shahrood, P.O. Box 316-36155, Shahrood

Highlights: • Opto-crystalline character of the composition of Cu{sub 2}S and S{sub 2}Sn was considered. • The formation Cu{sub 2}SnS{sub 3} is strongly related to phase separation at interface. • The entanglement of phases is strongly due to the chemical bond competition. • The suggested fluctuation region is approved by PL spectra. • Reconstruction and cluster formation is evident by formation of flat-spiral flowers. - Abstract: Optical character of crystal structure of the composition of two different semiconducting metallic sulfides, Cu{sub 2}S and S{sub 2}Sn, in pure phase formation of the ternary chalcogenide Cu{sub 2}SnS{sub 3} was considered. Because ofmore » the difficulties related to the phase separation at the definite Eutectic temperature for the composite formation, which is evident in optical absorption fluctuations, solvothermal synthesis in the intermediate temperature range 180–220 °C seems convenient where tetragonal crystal structure is investigated by XRD. Absorption fluctuations below E = E{sub g} were more pronounced for the lower limit case (180 °C) reflected in a sharp peak located at 1.48 eV on S1 as seen in UV-PL measurement. The characteristic behavior of the interface, resulting in the reconstruction and cluster formation due to the offset of bond rupturing displacement of atomic positions, is in favor of aggregation instead of agglomeration, which is evident by formation of small flat-spiral flowers in SEM images.« less

Edentulism, beaks, and biomechanical innovations in the evolution of theropod dinosaurs

PubMed Central

Lautenschlager, Stephan; Witmer, Lawrence M.; Altangerel, Perle; Rayfield, Emily J.

2013-01-01

Maniraptoriformes, the speciose group of derived theropod dinosaurs that ultimately gave rise to modern birds, display a diverse and remarkable suite of skeletal adaptations. Apart from the evolution of flight, a large-scale change in dietary behavior appears to have been one of the main triggers for specializations in the bauplan of these derived theropods. Among the different skeletal specializations, partial or even complete edentulism and the development of keratinous beaks form a recurring and persistent trend in from the evolution of derived nonavian dinosaurs. Therizinosauria is an enigmatic maniraptoriform clade, whose members display these and other osteological characters thought to be correlated with the shift from carnivory to herbivory. This makes therizinosaurians prime candidates to assess the functional significance of these morphological characters. Based on a highly detailed biomechanical model of Erlikosaurus andrewsi, a therizinosaurid from the Upper Cretaceous of Mongolia, different morphological configurations incorporating soft-tissue structures, such as a keratinous rhamphotheca, are evaluated for their biomechanical performance. Our results indicate that the development of beaks and the presence of a keratinous rhamphotheca would have helped to dissipate stress and strain, making the rostral part of the skull less susceptible to bending and displacement, and this benefit may extend to other vertebrate clades that possess rhamphothecae. Keratinous beaks, paralleled by edentulism, thus represent an evolutionary innovation developed early in derived theropods to enhance cranial stability, distinct to postulated mass-saving benefits associated with the origin of flight. PMID:24297877

Thermodynamics of interactions between mammalian cytochromes P450 and b5.

PubMed

Yablokov, Evgeny; Florinskaya, Anna; Medvedev, Alexei; Sergeev, Gennady; Strushkevich, Natallia; Luschik, Alexander; Shkel, Tatsiana; Haidukevich, Irina; Gilep, Andrei; Usanov, Sergey; Ivanov, Alexis

2017-04-01

Cytochromes P450 (CYPs) play an important role in the metabolism of xenobiotics and various endogenous substrates. Being a crucial component of the microsomal monooxygenase system, CYPs are involved in numerous protein-protein interactions. However, mechanisms underlying molecular interactions between components of the monooxygenase system still need better characterization. In this study thermodynamic parameters of paired interactions between mammalian CYPs and cytochromes b5 (CYB5) have been evaluated using a Surface Plasmon Resonance (SPR) based biosensor Biacore 3000. Analysis of 18 pairs of CYB5-CYP complexes formed by nine different isoforms of mammalian CYPs and two isoforms of human CYB5 has shown that thermodynamically these complexes can be subdivided into enthalpy-driven and entropy-driven groups. Formation of the enthalpy-driven complexes was observed in the case of microsomal CYPs allosterically regulated by CYB5 (CYB5A-CYP3A4, CYB5A-CYP3A5, CYB5A-CYP17A1). The entropy-driven complexes were formed when CYB5 had no effect on the CYP activity (CYB5A-CYP51A1, CYB5A-CYP1B1, CYB5B-CYP11A1). Results of this study suggest that such interactions determining protein clustering are indirectly linked to the monooxygenase functioning. Positive ΔH values typical for such interactions may be associated with displacement of the solvation shells of proteins upon clustering. CYB5-CYP complex formation accompanied by allosteric regulation of CYP activity by CYB5 is enthalpy-dependent. Copyright © 2017 Elsevier Inc. All rights reserved.

Binding the Mammalian High Mobility Group Protein AT-hook 2 to AT-Rich Deoxyoligonucleotides: Enthalpy-Entropy Compensation

PubMed Central

Joynt, Suzanne; Morillo, Victor; Leng, Fenfei

2009-01-01

HMGA2 is a DNA minor-groove binding protein. We previously demonstrated that HMGA2 binds to AT-rich DNA with very high binding affinity where the binding of HMGA2 to poly(dA-dT)2 is enthalpy-driven and to poly(dA)poly(dT) is entropy-driven. This is a typical example of enthalpy-entropy compensation. To further study enthalpy-entropy compensation of HMGA2, we used isothermal-titration-calorimetry to examine the interactions of HMGA2 with two AT-rich DNA hairpins: 5′-CCAAAAAAAAAAAAAAAGCCCCCGCTTTTTTTTTTTTTTTGG-3′ (FL-AT-1) and 5′-CCATATATATATATATAGCCCCCGCTATATATATATATATGG-3′ (FL-AT-2). Surprisingly, we observed an atypical isothermal-titration-calorimetry-binding curve at low-salt aqueous solutions whereby the apparent binding-enthalpy decreased dramatically as the titration approached the end. This unusual behavior can be attributed to the DNA-annealing coupled to the ligand DNA-binding and is eliminated by increasing the salt concentration to ∼200 mM. At this condition, HMGA2 binding to FL-AT-1 is entropy-driven and to FL-AT-2 is enthalpy-driven. Interestingly, the DNA-binding free energies for HMGA2 binding to both hairpins are almost temperature independent; however, the enthalpy-entropy changes are dependent on temperature, which is another aspect of enthalpy-entropy compensation. The heat capacity change for HMGA2 binding to FL-AT-1 and FL-AT-2 are almost identical, indicating that the solvent displacement and charge-charge interaction in the coupled folding/binding processes for both binding reactions are similar. PMID:19450485

Global Confinement, Sawtooth Mixing, and Stochastic Diffusion Ripple Loss of Fast ICRF-driven H+ Minority Ions in TFTR

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

Petrov, M.P.; Bell, R.; Budny, R.V.

1998-07-01

This paper presents studies of ICRF-driven H+ minority ions in TFTR (Tokamak Fusion Test Reator) deuterium plasmas using primarily passive Ho flux detection in the energy range of 0.2-1.0 MeV with some corroborating active (lithium pellet charge exchange) measurements. It is shown that in the passive mode the main donors for the neutralization of H+ ions in this energy range are C5+ ions. The measured effective H+ tail temperatures range from 0.15 MeV at an ICRF power of 2 MW to 0.35 MeV at 6 MW. Analysis of the ICRF-driven H+ ion energy balance has been performed on the basismore » of the dependence of effective H+ temperatures on the plasma parameters. The analysis showed that H+ confinement times are comparable with their slowing-down times and tended to decrease with increasing ICRF power. Radial redistribution of ICRF-driven H+ ions was detected when giant sawtooth crashes occurred during the ICRF heating. The redistribution affected ions with energy below 0.7-0.8 MeV. The sawtooth crashes displace H+ ions outward along the plasma major radius into the stochastic ripple diffusion domain were those ions are lost in about 10 milliseconds. These observations are consistent with the model of the redistribution of energetic particles developed previously to explain the results of deuterium-tritium alpha-particle redistribution due to sawteeth observed in TFTR. The experimental data are also consistent with ORBIT code simulations of H+ stochastic ripple diffusion losses.« less

Diversification and spatial structuring in the mutualism between Ficus septica and its pollinating wasps in insular South East Asia.

PubMed

Rodriguez, Lillian Jennifer; Bain, Anthony; Chou, Lien-Siang; Conchou, Lucie; Cruaud, Astrid; Gonzales, Regielene; Hossaert-McKey, Martine; Rasplus, Jean-Yves; Tzeng, Hsy-Yu; Kjellberg, Finn

2017-08-29

Interspecific interactions have long been assumed to play an important role in diversification. Mutualistic interactions, such as nursery pollination mutualisms, have been proposed as good candidates for diversification through co-speciation because of their intricate nature. However, little is known about how speciation and diversification proceeds in emblematic nursery pollination systems such as figs and fig wasps. Here, we analyse diversification in connection with spatial structuring in the obligate mutualistic association between Ficus septica and its pollinating wasps throughout the Philippines and Taiwan. Ceratosolen wasps pollinating F. septica are structured into a set of three vicariant black coloured species, and a fourth yellow coloured species whose distribution overlaps with those of the black species. However, two black pollinator species were found to co-occur on Lanyu island. Microsatellite data on F. septica indicates the presence of three gene pools that broadly mirrors the distribution of the three black clades. Moreover, receptive fig odours, the specific message used by pollinating wasps to locate their host tree, varied among locations. F. septica and its black pollinator clades exhibited similar geographic structuring. This could be due originally to geographic barriers leading to isolation, local adaptation, and finally co-structuring. Nevertheless, the co-occurrence of two black pollinator species on Lanyu island suggests that the parapatric distribution of the black clades is now maintained by the inability of migrating individuals of black pollinators to establish populations outside their range. On the other hand, the distribution of the yellow clade strongly suggests an initial case of character displacement followed by subsequent range extension: in our study system, phenotypic or microevolutionary plasticity has allowed the yellow clade to colonise hosts presenting distinct odours. Hence, while variation in receptive fig odours allows specificity in the interaction, this variation does not necessarily lead to coevolutionary plant-insect diversification. Globally, our results evidence evolutionary plasticity in the fig-fig wasp mutualism. This is the first documentation of the presence of two distinct processes in pollinating fig wasp diversification on a host species: the formation of vicariant species and the co-occurrence of other species over large parts of their ranges probably made possible by character displacement.

Spontaneous transition of replacive to displacive growth of dolomite in burial dolomitization, and of serpentine in serpentinization

NASA Astrophysics Data System (ADS)

Merino, E.; Canals, A.

2011-12-01

Burial dolostones consist of huge volumes of dolomite that has replaced limestone volume for volume, with patches < 10 meters across of thin, equidistant "zebra" veins that are displacive. Characteristically, the contact between the two dolomite types is, under the microscope, seamless. This has long puzzled carbonate petrologists, who have mistaken the displacive dolomite veins for "void-filling cements" and therefore expect a sharp contact between the two dolomite types. The replacive dolomite forms not by dissolution-precipitation as usually assumed, but by dolomite-growth-driven pressure solution of the host calcite -- if the host is sufficiently viscous, or rigid. The local stress induced by the dolomite growth self-adjusts automatically so as to force the rates of dolomite growth and calcite pressure-solution to be mutually equal at each moment of the replacement. That is why replacement is always isovolumetric. But the dolomite-for-calcite replacement is self-accelerating via Ca2+ (each replacement increment releases Ca2+, which increases the activity product for dolomite and thus the rate of the next replacement increment, and so on), and crystalline carbonates are non-newtonian solids of the softening kind (as shown experimentally, Heard & Raleigh 1972). Thus, when the dolomite-for-calcite replacement becomes fast enough to reduce the local rock viscosity sufficiently, and if aqueous Mg2+ has not run out by then, the replacive growth will inevitably, and seamlessly, transition to displacive growth. This is when incipient zebra veins start to form. Each vein interacts with its neighbors via the induced stress they exert on each other, which leads to a "weeding" feedback that pressure dissolves some veins (the ones that find themselves too close to their neighbors), leaving the surviving ones more equidistant than before. Dolomitic zebra veins, or "rhythmites", are a good example of syntaxial veins. The same process and feedbacks, via Mg2+ instead of via Ca2+, take place in the serpentinization of ultrabasic rocks, leading also to displacive zebra veins of serpentine in seamless contact with the host, replacive serpentine. The origin of the dolomite zebra veins above turns out to have a serendipitous proof. The same feedback that causes the dolomite-for-calcite replacement to self-accelerate exponentially, raises the pore-fluid Ca2+ concentration also exponentially. Consequently, when the rheological replacement-to-displacement transition takes place, the displacive dolomite is growing under such a huge Ca2+ concentration that some Ca2+, even as submicroscopic calcitic slivers, is forced to substitute for Mg2+ in the structure of the growing dolomite, deforming and curving it. This is why the displacive zebra veins always consist of dolomite crystals that are curved, called saddle dolomite. It also explains why some calcite forms right after the dolomite veins stop growing, as a cement and/or back-replacing dolomite.

On the role of horizontal displacements in the exhumation of high pressure metamorphic rocks

NASA Astrophysics Data System (ADS)

Brun, J.-P.; Tirel, C.; Philippon, M.; Burov, E.; Faccenna, C.; Gueydan, F.; Lebedev, S.

2012-04-01

High pressure metamorphic rocks exposed in the core of many mountain belts correspond to various types of upper crustal materials that have been buried to mantle depths and, soon after, brought back to surface at mean displacement rates up to few cm/y, comparable to those of plate boundaries. The vertical component of HP rock exhumation velocity back to surface is commonly well constrained by pressure estimates from petrology and geochronological data whereas the horizontal component remains generally difficult or impossible to estimate. Consequently, most available models, if not all, attempt to simulate exhumation with a minimal horizontal component of displacement. Such models, require that the viscosity of HP rocks is low and/or the erosion rate large -i.e. at least equal to the rate of exhumation. However, in some regions like the Aegean, where the exhumation of blueschists and eclogites is driven by slab rollback, it can be shown that the horizontal component of exhumation related displacement, obtained from map view restoration, is 5 to 7 times larger than the vertical one, deduced from metamorphic pressure estimates. Using finite element models performed with FLAMAR, we show that such a situation simply results from the subduction of small continental blocks (< 500km) that stimulate subduction rollback. The continental block is dragged downward and sheared off the downgoing mantle slab by buoyancy force. Exhumation of the crustal block occurs through a one step Caterpillar-type walk, with the block's tail slipping along a basal décollement, approaching the head and making a large buckle, which then unrolls at surface as soon as the entire block is delaminated. Finally, the crustal block emplaces at surface in the space created by trench retreat. This process of exhumation requires neither rheological weakening of HP rocks nor high rates of erosion.

The Implications of Strike-Slip Earthquake Source Properties on the Transform Boundary Development Process

NASA Astrophysics Data System (ADS)

Neely, J. S.; Huang, Y.; Furlong, K.

2017-12-01

Subduction-Transform Edge Propagator (STEP) faults, produced by the tearing of a subducting plate, allow us to study the development of a transform plate boundary and improve our understanding of both long-term geologic processes and short-term seismic hazards. The 280 km long San Cristobal Trough (SCT), formed by the tearing of the Australia plate as it subducts under the Pacific plate near the Solomon and Vanuatu subduction zones, shows along-strike variations in earthquake behaviors. The segment of the SCT closest to the tear rarely hosts earthquakes > Mw 6, whereas the SCT sections more than 80 - 100 km from the tear experience Mw7 earthquakes with repeated rupture along the same segments. To understand the effect of cumulative displacement on SCT seismicity, we analyze b-values, centroid-time delays and corner frequencies of the SCT earthquakes. We use the spectral ratio method based on Empirical Green's Functions (eGfs) to isolate source effects from propagation and site effects. We find high b-values along the SCT closest to the tear with values decreasing with distance before finally increasing again towards the far end of the SCT. Centroid time-delays for the Mw 7 strike-slip earthquakes increase with distance from the tear, but corner frequency estimates for a recent sequence of Mw 7 earthquakes are approximately equal, indicating a growing complexity in earthquake behavior with distance from the tear due to a displacement-driven transform boundary development process (see figure). The increasing complexity possibly stems from the earthquakes along the eastern SCT rupturing through multiple asperities resulting in multiple moment pulses. If not for the bounding Vanuatu subduction zone at the far end of the SCT, the eastern SCT section, which has experienced the most displacement, might be capable of hosting larger earthquakes. When assessing the seismic hazard of other STEP faults, cumulative fault displacement should be considered a key input in determining potential earthquake size.

Molecular dynamics simulations study of nano bubble attachment at hydrophobic surfaces

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

Jin, Jiaqi; Dang, Liem X.; Miller, Jan D.

Bubble attachment phenomena are examined using Molecular Dynamics Simulations (MDS) for the first time. The simulation involves a nitrogen nano bubble containing 906 nitrogen molecules in a water phase with 74,000 water molecules at molybdenite surfaces. During a simulation period of 1 ns, film rupture and displacement occurs. The attached nanobubble at the hydrophobic molybdenite face surface results in a contact angle of about 90º. This spontaneous attachment is due to a “water exclusion zone” at the molybdenite face surface and can be explained by a van der Waals (vdW) attractive force, as discussed in the literature. In contrast, themore » film is stable at the hydrophilic quartz (001) surface and the bubble does not attach. Contact angles determined from MD simulations are reported, and these results agree well with experimental and MDS sessile drop results. In this way, film stability and bubble attachment are described with respect to interfacial water structure for surfaces of different polarity. Interfacial water molecules at the hydrophobic molybdenite face surface have relatively weak interactions with the surface when compared to the hydrophilic quartz (001) surface, as revealed by the presence of a 3 Å “water exclusion zone” at the molybdenite/water interface. The molybdenite armchair-edge and zigzag-edge surfaces show a comparably slow process for film rupture and displacement when compared to the molybdenite face surface, which is consistent with their relatively weak hydrophobic character.« less

Effects of the earthquake of March 27, 1964, on the Alaska Railroad: Chapter D in The Alaska earthquake, March 27, 1964: effects on transportation, communications, and utilities

USGS Publications Warehouse

McCulloch, David S.; Bonilla, Manuel G.

1970-01-01

In the 1964 Alaska earthquake, the federally owned Alaska Railroad sustained damage of more than $35 million: 54 percent of the cost for port facilities; 25 percent, roadbed and track; 9 percent, buildings and utilities; 7 percent, bridges and culverts; and 5 percent, landslide removal. Principal causes of damage were: (1) landslides, landslide-generated waves, and seismic sea waves that destroyed costly port facilities built on deltas; (2) regional tectonic subsidence that necessitated raising and armoring 22 miles of roadbed made susceptible to marine erosion; and (3), of greatest importance in terms of potential damage in seismically active areas, a general loss of strength experienced by wet waterlaid unconsolidated granular sediments (silt to coarse gravel) that allowed embankments to settle and enabled sediments to undergo fiowlike displacement toward topographic depressions, even in fiat-lying areas. The term “landspreading” is proposed for the lateral displacement and distension of mobilized sediments; landspreading appears to have resulted largely from liquefaction. Because mobilization is time dependent and its effects cumulative, the long duration of strong ground motion (timed as 3 to 4 minutes) along the southern 150 miles of the rail line made landspreading an important cause of damage. Sediments moved toward natural and manmade topographic depressions (stream valleys, gullies, drainage ditches, borrow pits, and lakes). Stream widths decreased, often about 20 inches but at some places by as much as 6.5 feet, and sediments moved upward beneath stream channels. Landspreading toward streams and even small drainage ditches crushed concrete and metal culverts. Bridge superstructures were compressed and failed by lateral buckling, or more commonly were driven into, through, or over bulkheads. Piles and piers were torn free of superstructures by moving sediments, crowded toward stream channels, and lifted in the center. The lifted piles arched the superstructures. Vertical pile displacement was independent of the depth of the pile penetration in the sediment and thus was due to vertical movement of the sediments, rather than to differential compaction. The fact that bridge piles were carried laterally without notable tilting suggests that mobilization exceeded pile depths, which averaged about 20 feet. Field observations, largely duplicated by vibrated sandbox models of stream channels, suggest that movement was distributed throughout the sediments, rather than restricted to finite failure surfaces. Landspreading generated stress that produced cracks in the ground surface adjacent to depressions. The distribution of this stress controlled the crack patterns: tension cracks parallel to straight or concave streambanks, shear cracks intersecting at 45° to 70° on convex banks where there was some component of radial spreading, and orthogonal cracks on the insides of tight meander bends or islands where spreading was omnidirectional. Ground cracks of these kinds commonly extended 500 feet, and occasionally about 1,000 feet, back from streams, which indicates that landspreading occurred over large areas. In areas of landspreading, highway and railroad embankments, pavements, and rails were pulled apart endways and were displaced laterally if they lay at an angle to the direction of sediment displacement. Sediment movement commonly skewed bridges that crossed streams obliquely. The maximum horizontal skew was 10 feet. Embankment settlement, nearly universal in areas of landspreading, also occurred in areas where there was no evidence for widespread loss of strength in the unconsolidated sediments. In the latter areas embankments themselves clearly caused the loss of bearing strength in the underlying sediment. In both areas, settlement was accompanied by the formation of ground cracks approximately parallel to the embankment in the adjacent sediments. Sediment-laden ground water was discharged from the cracks, and extreme local settlements (as much as 6 ft) were associated with large discharges. Landspreading was accompanied by transient horizontal displacement of the ground that pounded bridge ends with slight or considerable force. The deck of a 105-foot bridge was repeatedly arched up off its piles by transient compression. Bridges may also have developed high horizontal accelerations. One bridge deck, driven through its bulkhead, appears to have had an acceleration of at least 1.1 to 1.7 g; however, most evidence for high accelerations is ambiguous. Limited standard penetration data show that landspreading damage was not restricted to soft sediments. Some bridges were severely damaged by displacement of piles driven in sediments classified as compact and dense. Total thickness of unconsolidated sediments strongly controlled the degree of damage. In areas underlain by wet water-laid sediments the degree of damage to uniformly designed and built wooden railroad bridges shows a closer correlation with total sediment thickness at the bridge site than with the grain size of the material in which the piles were driven. Local geology and physiography largely controlled the kind, distribution, and severity of damage to the railroad. This relationship is so clear that maps of surficial geology and physiography of damaged areas of the rail belt show that only a few geologic-physiographic units serve to identify these areas: 1. Bedrock and glacial till on bedrock. No foundation displacements, but ground vibration increased toward the area of maximum strain-energy release. 2. Glacial outwash terraces. Landspreading and damage ranged from none where the water table was low and the terrace undissected to severe where the water table was near the surface and the terrace dissected by streams. 3. Inactive flood plains. Landspreading, ground cracking, flooding by ejected ground water, and damage were generally slight but increased to severe toward lower, wetter active flood plains or river channels. 4. Active flood plains. Landspreading, ground cracking, and flooding were nearly universal and were greater than on adjacent inactive flood plains. 5. Fan deltas. Radial downhill spreading and ground cracking were considerable near the lower edges of the fan deltas and were accompanied by ground-water discharge. Landslides were common from edges of deltas. Damage, landspreading, ground crack-ing, vibration, and flooding by ground water generally increased with (1) increasing thickness of unconsolidated sediments, (2) decreasing depth to the water table, (3) proximity to topographic depressions, and (4) proximity to the area of maximum strain-energy release.

The role of theory-driven graphic warning labels in motivation to quit: a qualitative study on perceptions from low-income, urban smokers.

PubMed

Mead, Erin L; Cohen, Joanna E; Kennedy, Caitlin E; Gallo, Joseph; Latkin, Carl A

2015-02-07

Use of communication theories in the development of pictorial health warning labels (graphic warning labels) for cigarette packaging might enhance labels' impact on motivation to quit, but research has been limited, particularly among low socioeconomic status (SES) populations in the U.S. This qualitative study explored perceptions of theory-based graphic warning labels and their role in motivation to quit among low-income smokers. A cross-sectional qualitative study was conducted with 25 low-income adult smokers in Baltimore, Maryland, who were purposively sampled from a community-based source population. Semi-structured, in-depth interviews were conducted from January to February 2014. Participants were asked about the motivational impact of 12 labels falling into four content categories: negative depictions of the health effects of smoking to smokers and others, and positive depictions of the benefits of quitting to smokers and others. Data were coded using a combined inductive/deductive approach and analyzed thematically through framework analysis. Labels depicting negative health effects to smokers were identified as most motivational, followed by labels depicting negative health effects to others. Reasons included perceived severity of and susceptibility to the effects, negative emotional reactions (such as fear), and concern for children. Labels about the benefits of quitting were described as motivational because of their hopefulness, characters as role models, and desire to improve family health. Reasons why labels were described as not motivational included lack of impact on perceived severity/susceptibility, low credibility, and fatalistic attitudes regarding the inevitability of disease. Labels designed to increase risk perceptions from smoking might be significant sources of motivation for low SES smokers. Findings suggest innovative theory-driven approaches for the design of labels, such as using former smokers as role models, contrasting healthy and unhealthy characters, and socially-oriented labels, might motivate low SES smokers to quit.

Off-axis fishbone-like instability and excitation of resistive wall modes in JT-60U and DIII-D

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

Okabayashi, M.; Solomon, W. M.; Budny, R. V.

2011-05-15

An energetic-particle (EP)-driven ''off-axis-fishbone-like mode (OFM)'' often triggers a resistive wall mode (RWM) in JT-60U and DIII-D devices, preventing long-duration high-{beta}{sub N} discharges. In these experiments, the EPs are energetic ions (70-85 keV) injected by neutral beams to produce high-pressure plasmas. EP-driven bursting events reduce the EP density and the plasma rotation simultaneously. These changes are significant in high-{beta}{sub N} low-rotation plasmas, where the RWM stability is predicted to be strongly influenced by the EP precession drift resonance and by the plasma rotation near the q=2 surface (kinetic effects). Analysis of these effects on stability with a self-consistent perturbation tomore » the mode structure using the MARS-K code showed that the impact of EP losses and rotation drop is sufficient to destabilize the RWM in low-rotation plasmas, when the plasma rotation normalized by Alfven frequency is only a few tenths of a percent near the q=2 surface. The OFM characteristics are very similar in JT-60U and DIII-D, including nonlinear mode evolution. The modes grow initially like a classical fishbone, and then the mode structure becomes strongly distorted. The dynamic response of the OFM to an applied n=1 external field indicates that the mode retains its external kink character. These comparative studies suggest that an energetic particle-driven 'off-axis-fishbone-like mode' is a new EP-driven branch of the external kink mode in wall-stabilized plasmas, analogous to the relationship of the classical fishbone branch to the internal kink mode.« less

Plume meander and dispersion in a stable boundary layer

NASA Astrophysics Data System (ADS)

Hiscox, April L.; Miller, David R.; Nappo, Carmen J.

2010-11-01

Continuous lidar measurements of elevated plume dispersion and corresponding micrometeorology data are analyzed to establish the relationship between plume behavior and nocturnal boundary layer dynamics. Contrasting nights of data from the JORNADA field campaign in the New Mexico desert are analyzed. The aerosol lidar measurements were used to separate the plume diffusion (plume spread) from plume meander (displacement). Mutiresolution decomposition was used to separate the turbulence scale (<90 s) from the submesoscale (>90 s). Durations of turbulent kinetic energy stationarity and the wind steadiness were used to characterize the local scale and submesoscale turbulence. Plume meander, driven by submesoscale wind motions, was responsible for most of the total horizontal plume dispersion in weak and variable winds and strong stability. This proportion was reduced in high winds (i.e., >4 m s-1), weakly stable conditions but remained the dominant dispersion mechanism. The remainder of the plume dispersion in all cases was accounted for by internal spread of the plume, which is a small eddy diffusion process driven by turbulence. Turbulence stationarity and the wind steadiness are demonstrated to be closely related to plume diffusion and plume meander, respectively.

Development of a broadband reflectivity diagnostic for laser driven shock compression experiments

DOE PAGES

Ali, S. J.; Bolme, C. A.; Collins, G. W.; ...

2015-04-16

Here, a normal-incidence visible and near-infrared shock wave optical reflectivity diagnostic was constructed to investigate changes in the optical properties of materials under dynamic laser compression. Documenting wavelength- and time-dependent changes in the optical properties of laser-shock compressed samples has been difficult, primarily due to the small sample sizes and short time scales involved, but we succeeded in doing so by broadening a series of time delayed 800-nm pulses from an ultrafast Ti:sapphire laser to generate high-intensity broadband light at nanosecond time scales. This diagnostic was demonstrated over the wavelength range 450–1150 nm with up to 16 time displaced spectramore » during a single shock experiment. Simultaneous off-normal incidence velocity interferometry (velocity interferometer system for any reflector) characterized the sample under laser-compression and also provided an independent reflectivity measurement at 532 nm wavelength. The shock-driven semiconductor-to-metallic transition in germanium was documented by the way of reflectivity measurements with 0.5 ns time resolution and a wavelength resolution of 10 nm.« less

Wind-driven currents in a shallow lake or sea

NASA Technical Reports Server (NTRS)

Goldstein, M. E.; Gedney, R. T.

1971-01-01

For shallow lakes and seas such as the great lakes (especially Lake Erie) where the depth is not much greater than the Ekman depth, the usual Ekman dynamics cannot be used to predict the wind driven currents. The necessary extension to include shallow bodies of water, given by Welander, leads to a partial differential equation for the surface displacement which in turn determines all other flow quantities. A technique for obtaining exact analytical solutions to Welander's equation for bodies of water with large class of bottom topographies which may or may not contain islands is given. It involves applying conformal mapping methods to an extension of Welander's equation into the complex plane. When the wind stress is constant (which is the usual assumption for lakes) the method leads to general solutions which hold for bodies of water of arbitrary shape (the shape appears in the solutions through a set of constants which are the coefficients in the Laurent expansion of a mapping of the particular lake geometry). The method is applied to an elliptically shaped lake and a circular lake containing an eccentrically located circular island.

Ultrafast electronic dynamics driven by nuclear motion

NASA Astrophysics Data System (ADS)

Vendrell, Oriol

2016-05-01

The transfer of electrical charge on a microscopic scale plays a fundamental role in chemistry, in biology, and in technological applications. In this contribution, we will discuss situations in which nuclear motion plays a central role in driving the electronic dynamics of photo-excited or photo-ionized molecular systems. In particular, we will explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K-shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we will illustrate how the double hole can be transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. We thank the Hamburg Centre for Ultrafast Imaging and the Volkswagen Foundation for financial support.

Design and implementation of a novel rotary micropositioning system driven by linear voice coil motor.

PubMed

Xu, Qingsong

2013-05-01

Limited-angle rotary micropositioning stages are required in precision engineering applications where an ultrahigh-precision rotational motion within a restricted range is needed. This paper presents the design, fabrication, and control of a compliant rotary micropositioning stage dedicated to the said applications. To tackle the challenge of achieving both a large rotational range and a compact size, a new idea of multi-stage compound radial flexure is proposed. A compact rotary stage is devised to deliver an over 10° rotational range while possessing a negligible magnitude of center shift. The stage is driven by a linear voice coil motor and its output motion is measured by laser displacement sensors. Analytical models are derived to facilitate the parametric design, which is validated by conducting finite element analysis. The actuation and sensing issues are addressed to guarantee the stage performance. A prototype is fabricated and a proportional-integral-derivative control is implemented to achieve a precise positioning. Experimental results demonstrate a resolution of 2 μrad over 10° rotational range as well as a low level of center shift of the rotary micropositioning system.

SPH Modelling of Sea-ice Pack Dynamics

NASA Astrophysics Data System (ADS)

Staroszczyk, Ryszard

2017-12-01

The paper is concerned with the problem of sea-ice pack motion and deformation under the action of wind and water currents. Differential equations describing the dynamics of ice, with its very distinct mateFfigrial responses in converging and diverging flows, express the mass and linear momentum balances on the horizontal plane (the free surface of the ocean). These equations are solved by the fully Lagrangian method of smoothed particle hydrodynamics (SPH). Assuming that the ice behaviour can be approximated by a non-linearly viscous rheology, the proposed SPH model has been used to simulate the evolution of a sea-ice pack driven by wind drag stresses. The results of numerical simulations illustrate the evolution of an ice pack, including variations in ice thickness and ice area fraction in space and time. The effects of different initial ice pack configurations and of different conditions assumed at the coast-ice interface are examined. In particular, the SPH model is applied to a pack flow driven by a vortex wind to demonstrate how well the Lagrangian formulation can capture large deformations and displacements of sea ice.

Strain-rate and temperature-driven transition in the shear transformation zone for two-dimensional amorphous solids

NASA Astrophysics Data System (ADS)

Cao, Penghui; Park, Harold S.; Lin, Xi

2013-10-01

We couple the recently developed self-learning metabasin escape algorithm, which enables efficient exploration of the potential energy surface (PES), with shear deformation to elucidate strain-rate and temperature effects on the shear transformation zone (STZ) characteristics in two-dimensional amorphous solids. In doing so, we report a transition in the STZ characteristics that can be obtained through either increasing the temperature or decreasing the strain rate. The transition separates regions having two distinct STZ characteristics. Specifically, at high temperatures and high strain rates, we show that the STZs have characteristics identical to those that emerge from purely strain-driven, athermal quasistatic atomistic calculations. At lower temperatures and experimentally relevant strain rates, we use the newly coupled PES + shear deformation method to show that the STZs have characteristics identical to those that emerge from a purely thermally activated state. The specific changes in STZ characteristics that occur in moving from the strain-driven to thermally activated STZ regime include a 33% increase in STZ size, faster spatial decay of the displacement field, a change in the deformation mechanism inside the STZ from shear to tension, a reduction in the stress needed to nucleate the first STZ, and finally a notable loss in characteristic quadrupolar symmetry of the surrounding elastic matrix that has previously been seen in athermal, quasistatic shear studies of STZs.

A Compact and Low-Cost MEMS Loudspeaker for Digital Hearing Aids.

PubMed

Sang-Soo Je; Rivas, F; Diaz, R E; Jiuk Kwon; Jeonghwan Kim; Bakkaloglu, B; Kiaei, S; Junseok Chae

2009-10-01

A microelectromechanical-systems (MEMS)-based electromagnetically actuated loudspeaker to reduce form factor, cost, and power consumption, and increase energy efficiency in hearing-aid applications is presented. The MEMS loudspeaker has multilayer copper coils, an NiFe soft magnet on a thin polyimide diaphragm, and an NdFeB permanent magnet on the perimeter. The coil impedance is measured at 1.5 Omega, and the resonant frequency of the diaphragm is located far from the audio frequency range. The device is driven by a power-scalable, 0.25-mum complementary metal-oxide semiconductor class-D SigmaDelta amplifier stage. The class-D amplifier is formed by a differential H-bridge driven by a single bit, pulse-density-modulated SigmaDelta bitstream at a 1.2-MHz clock rate. The fabricated MEMS loudspeaker generates more than 0.8-mum displacement, equivalent to 106-dB sound pressure level (SPL), with 0.13-mW power consumption. Driven by the SigmaDelta class-D amplifier, the MEMS loudspeaker achieves measured 65-dB total harmonic distortion (THD) with a measurement uncertainty of less than 10%. Energy-efficient and cost-effective advanced hearing aids would benefit from further miniaturization via MEMS technology. The results from this study appear very promising for developing a compact, mass-producible, low-power loudspeaker with sufficient sound generation for hearing-aid applications.

Displacement of polarons by vibrational modes in doped conjugated polymers

NASA Astrophysics Data System (ADS)

Anderson, M.; Ramanan, C.; Fontanesi, C.; Frick, A.; Surana, S.; Cheyns, D.; Furno, M.; Keller, T.; Allard, S.; Scherf, U.; Beljonne, D.; D'Avino, G.; von Hauff, E.; Da Como, E.

2017-10-01

Organic pi-conjugated polymers are deemed to be soft materials with strong electron-phonon coupling, which results in the formation of polarons, i.e., charge carriers dressed by self-localized distortion of the nuclei. Universal signatures for polarons are optical resonances below the band gap and intense vibrational modes (IVMs), both found in the infrared (IR) spectral region. Here, we study p -doped conjugated homo- and copolymers by combining first-principles modelling and optical spectroscopy from the far-IR to the visible. Polaronic IVMs are found to feature absorption intensities comparable to purely electronic transitions and, most remarkably, show only loose resemblance to the Raman or IR-active modes of the neutral polymer. The IVM frequency is dramatically scaled down (up to 50%) compared to the backbone carbon-stretching modes in the pristine polymers. The very large intensity of IVMs is associated with displacement of the excess positive charge along the backbone driven by specific vibrational modes. We propose a quantitative picture for the identification of these polaron shifting modes that solely based on structural information, directly correlates with their IR intensity. This finding finally discloses the elusive microscopic mechanism behind the huge IR intensity of IVMs in doped polymeric semiconductors.

3D active stabilization system with sub-micrometer resolution.

PubMed

Kursu, Olli; Tuukkanen, Tuomas; Rahkonen, Timo; Vähäsöyrinki, Mikko

2012-01-01

Stable positioning between a measurement probe and its target from sub- to few micrometer scales has become a prerequisite in precision metrology and in cellular level measurements from biological tissues. Here we present a 3D stabilization system based on an optoelectronic displacement sensor and custom piezo-actuators driven by a feedback control loop that constantly aims to zero the relative movement between the sensor and the target. We used simulations and prototyping to characterize the developed system. Our results show that 95% attenuation of movement artifacts is achieved at 1 Hz with stabilization performance declining to ca. 70% attenuation at 10 Hz. Stabilization bandwidth is limited by mechanical resonances within the displacement sensor that occur at relatively low frequencies, and are attributable to the sensor's high force sensitivity. We successfully used brain derived micromotion trajectories as a demonstration of complex movement stabilization. The micromotion was reduced to a level of ∼1 µm with nearly 100 fold attenuation at the lower frequencies that are typically associated with physiological processes. These results, and possible improvements of the system, are discussed with a focus on possible ways to increase the sensor's force sensitivity without compromising overall system bandwidth.