Science.gov

Sample records for high curvature regions

  1. Evidence of Cholesterol Accumulated in High Curvature Regions: Implication ot the Curvature Elastic Energy for Lipid Mixtures

    SciTech Connect

    Wang,W.; Yang, L.; Huang, H.

    2007-01-01

    Recent experiments suggested that cholesterol and other lipid components of high negative spontaneous curvature facilitate membrane fusion. This is taken as evidence supporting the stalk-pore model of membrane fusion in which the lipid bilayers go through intermediate structures of high curvature. How do the high-curvature lipid components lower the free energy of the curved structure? Do the high-curvature lipid components modify the average spontaneous curvature of the relevant monolayer, thereby facilitate its bending, or do the lipid components redistribute in the curved structure so as to lower the free energy? This question is fundamental to the curvature elastic energy for lipid mixtures. Here we investigate the lipid distribution in a monolayer of a binary lipid mixture before and after bending, or more precisely in the lamellar, hexagonal, and distorted hexagonal phases. The lipid mixture is composed of 2:1 ratio of brominated di18:0PC and cholesterol. Using a newly developed procedure for the multiwavelength anomalous diffraction method, we are able to isolate the bromine distribution and reconstruct the electron density distribution of the lipid mixture in the three phases. We found that the lipid distribution is homogenous and uniform in the lamellar and hexagonal phases. But in the distorted hexagonal phase, the lipid monolayer has nonuniform curvature, and cholesterol almost entirely concentrates in the high curvature region. This finding demonstrates that the association energies between lipid molecules vary with the curvature of membrane. Thus, lipid components in a mixture may redistribute under conditions of nonuniform curvature, such as in the stalk structure. In such cases, the spontaneous curvature depends on the local lipid composition and the free energy minimum is determined by lipid distribution as well as curvature.

  2. Curvature sensor using a highly birefringent photonic crystal fiber with two asymmetric hole regions in a Sagnac interferometer.

    PubMed

    Frazão, Orlando; Baptista, José M; Santos, José L; Roy, Philippe

    2008-05-01

    A curvature sensor based on a highly birefringent (Hi-Bi) photonic crystal fiber inserted into a Sagnac interferometer is demonstrated. For this purpose, a novel Hi-Bi photonic crystal fiber was designed and fabricated. Half of the microstructured region of the photonic crystal fiber was composed by large diameter holes, while the other half contained small diameter holes. Because of this geometry, the fiber core was shifted from the center and high birefringence appears in the optical fiber. Curvature was applied for three different fiber directions for a range of 0.6-5 m(-1). Temperature and longitudinal strain was also characterized for constant curvature. The configuration showed insensitivity to these two physical parameters.

  3. Effect of geometrical and flow parameters on high-effectiveness region of film cooling. [effect of wall curvature on length of the core region

    NASA Technical Reports Server (NTRS)

    Braum, W. H.

    1974-01-01

    Previous analyses for an inviscid jet injected into a stream and the turbulent mixing region which forms between jet and stream are used to find the extent of the core region in a cooling film by calculating the growth of the turbulent boundary layer on the downstream wall. The core is a region of nearly perfect effectiveness which ends at the intersection of the boundary layer and the mixing region. The calculations show that the most important geometrical factor bearing on the length of the core is the curvature of the wall. When the radius of curvature is large, the boundary layer remains thin and the core is long. The effects of Reynolds number, total-pressure difference between film and stream, and lateral position of the downstream wall are also investigated. The step configuration is shown to have a longer core than the slot for the same flow conditions.

  4. First Investigation on the Magnetic Curvature Distribution in the Magnetic Diffusion Region

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Shen, C.; Liu, Z.; Marchaudon, A.; Rong, Z.

    2015-12-01

    We report first results of magnetic curvature distribution in the diffusion region of a unique magnetic reconnection event. This event is exceptional since all four Cluster spacecraft are crossing the diffusion region. Magnetic curvature analysis shows that magnetic field lines are sharply curved with high curvature in the inner outflow regions between the two Hall regions and display nearly coplanar features of antiparallel reconnection. Combination of the decrease in curvature radius of magnetic field lines and the increase in electron gyro-radius induces curvature pitch angle scattering of initially trapped electrons, resulting in an isotropic electron distribution. In Hall regions, magnetic curvature decreases corresponding obviously to the presence of Y-directed Hall fields, which implies that the stress of reconnected field is released here, in agreement with whistler mediated-reconnection. The value and direction of curvature radius are not well organized due to the fluctuating Hall fields resulting from the temporal dynamical reconnection.Same analysis will be applied to MMS data to investigate the fine magnetic structure in diffusion region.

  5. Conservation of DNA curvature signals in regulatory regions of prokaryotic genes

    PubMed Central

    Jáuregui, Ruy; Abreu-Goodger, Cei; Moreno-Hagelsieb, Gabriel; Collado-Vides, Julio; Merino, Enrique

    2003-01-01

    DNA curvature plays a well-characterized role in many transcriptional regulation mechanisms. We present evidence for the conservation of curvature signals in putative regulatory regions of several archaeal and eubacterial genomes. Genes with highly curved upstream regions were identified in orthologous groups, based on the annotations of the Cluster of Orthologous Groups of proteins (COG) database. COGs possessing a significant number of genes with curvature signals were analyzed, and conserved properties were found in several cases. Curvature signals related to regulatory sites, previously described in single organisms, were located in a broad spectrum of bacterial genomes. Global regulatory proteins, such as HU, IHF and FIS, known to bind to curved DNA and to be autoregulated, were found to present conserved DNA curvature signals in their regulatory regions, emphasizing the fact that structural parameters of the DNA molecule are conserved elements in the process of transcriptional regulation of some systems. It is currently an open question whether these diverse systems are part of an integrated global regulatory response in different microorganisms. PMID:14627810

  6. Curvature in Arabidopsis inflorescence stems is limited to the region of amyloplast displacement.

    PubMed

    Weise, S E; Kuznetsov, O A; Hasenstein, K H; Kiss, J Z

    2000-06-01

    Gravitropic sensing in stems and stem-like organs is hypothesized to occur in the endodermis. However, since the endodermis runs the entire length of the stem, the precise site of gravisensing has been difficult to define. In this investigation of gravisensitivity in inflorescence stems of Arabidopsis, we positioned stems in a high gradient magnetic field (HGMF) on a rotating clinostat. Approximately 40% of the young, wild-type (WT) inflorescences, for all positions tested, curved toward the HGMF in the vicinity of the stem exposed to the field. In contrast, when the wedge was placed in the basal region of older inflorescence stems, no curvature was observed. As a control, the HGMF was applied to a starchless mutant, and 5% of the stems curved toward the field. Microscopy of the endodermis in the WT showed amyloplast displacement in the vicinity of the HGMF. Additional structural studies demonstrated that the basal region of WT stems experienced amyloplast displacement and, therefore, suggest this region is capable of gravity perception. However, increased lignification likely prevented curvature in the basal region. The lack of apical curvature after basal amyloplast displacement indicates that gravity perception in the base is not transmitted to the apex. Thus, these results provide evidence that the signal (and thus, response) resulting from perception in Arabidopsis inflorescence stems is spatially restricted.

  7. Curvature in Arabidopsis inflorescence stems is limited to the region of amyloplast displacement

    NASA Technical Reports Server (NTRS)

    Weise, S. E.; Kuznetsov, O. A.; Hasenstein, K. H.; Kiss, J. Z.

    2000-01-01

    Gravitropic sensing in stems and stem-like organs is hypothesized to occur in the endodermis. However, since the endodermis runs the entire length of the stem, the precise site of gravisensing has been difficult to define. In this investigation of gravisensitivity in inflorescence stems of Arabidopsis, we positioned stems in a high gradient magnetic field (HGMF) on a rotating clinostat. Approximately 40% of the young, wild-type (WT) inflorescences, for all positions tested, curved toward the HGMF in the vicinity of the stem exposed to the field. In contrast, when the wedge was placed in the basal region of older inflorescence stems, no curvature was observed. As a control, the HGMF was applied to a starchless mutant, and 5% of the stems curved toward the field. Microscopy of the endodermis in the WT showed amyloplast displacement in the vicinity of the HGMF. Additional structural studies demonstrated that the basal region of WT stems experienced amyloplast displacement and, therefore, suggest this region is capable of gravity perception. However, increased lignification likely prevented curvature in the basal region. The lack of apical curvature after basal amyloplast displacement indicates that gravity perception in the base is not transmitted to the apex. Thus, these results provide evidence that the signal (and thus, response) resulting from perception in Arabidopsis inflorescence stems is spatially restricted.

  8. Curvature in Arabidopsis inflorescence stems is limited to the region of amyloplast displacement

    NASA Technical Reports Server (NTRS)

    Weise, S. E.; Kuznetsov, O. A.; Hasenstein, K. H.; Kiss, J. Z.

    2000-01-01

    Gravitropic sensing in stems and stem-like organs is hypothesized to occur in the endodermis. However, since the endodermis runs the entire length of the stem, the precise site of gravisensing has been difficult to define. In this investigation of gravisensitivity in inflorescence stems of Arabidopsis, we positioned stems in a high gradient magnetic field (HGMF) on a rotating clinostat. Approximately 40% of the young, wild-type (WT) inflorescences, for all positions tested, curved toward the HGMF in the vicinity of the stem exposed to the field. In contrast, when the wedge was placed in the basal region of older inflorescence stems, no curvature was observed. As a control, the HGMF was applied to a starchless mutant, and 5% of the stems curved toward the field. Microscopy of the endodermis in the WT showed amyloplast displacement in the vicinity of the HGMF. Additional structural studies demonstrated that the basal region of WT stems experienced amyloplast displacement and, therefore, suggest this region is capable of gravity perception. However, increased lignification likely prevented curvature in the basal region. The lack of apical curvature after basal amyloplast displacement indicates that gravity perception in the base is not transmitted to the apex. Thus, these results provide evidence that the signal (and thus, response) resulting from perception in Arabidopsis inflorescence stems is spatially restricted.

  9. High-Curvature Nanostructuring Enhances Probe Display for Biomolecular Detection.

    PubMed

    De Luna, Phil; Mahshid, Sahar S; Das, Jagotamoy; Luan, Binquan; Sargent, Edward H; Kelley, Shana O; Zhou, Ruhong

    2017-02-08

    High-curvature electrodes facilitate rapid and sensitive detection of a broad class of molecular analytes. These sensors have reached detection limits not attained using bulk macroscale materials. It has been proposed that immobilized DNA probes are displayed at a high deflection angle on the sensor surface, which allows greater accessibility and more efficient hybridization. Here we report the first use of all-atom molecular dynamics simulations coupled with electrochemical experiments to explore the dynamics of single-stranded DNA immobilized on high-curvature versus flat surfaces. We find that high-curvature structures suppress DNA probe aggregation among adjacent probes. This results in conformations that are more freely accessed by target molecules. The effect observed is amplified in the presence of highly charged cations commonly used in electrochemical biosensing. The results of the simulations agree with experiments that measure the degree of hybridization in the presence of mono-, di-, and trivalent cations. On high-curvature structures, hybridization current density increases as positive charge increases, whereas on flat electrodes, the trivalent cations cause aggregation due to electrostatic overscreening, which leads to decreased current density and less sensitive detection.

  10. Plan curvature and landslide probability in regions dominated by earth flows and earth slides

    USGS Publications Warehouse

    Ohlmacher, G.C.

    2007-01-01

    Damaging landslides in the Appalachian Plateau and scattered regions within the Midcontinent of North America highlight the need for landslide-hazard mapping and a better understanding of the geomorphic development of landslide terrains. The Plateau and Midcontinent have the necessary ingredients for landslides including sufficient relief, steep slope gradients, Pennsylvanian and Permian cyclothems that weather into fine-grained soils containing considerable clay, and adequate precipitation. One commonly used parameter in landslide-hazard analysis that is in need of further investigation is plan curvature. Plan curvature is the curvature of the hillside in a horizontal plane or the curvature of the contours on a topographic map. Hillsides can be subdivided into regions of concave outward plan curvature called hollows, convex outward plan curvature called noses, and straight contours called planar regions. Statistical analysis of plan-curvature and landslide datasets indicate that hillsides with planar plan curvature have the highest probability for landslides in regions dominated by earth flows and earth slides in clayey soils (CH and CL). The probability of landslides decreases as the hillsides become more concave or convex. Hollows have a slightly higher probability for landslides than noses. In hollows landslide material converges into the narrow region at the base of the slope. The convergence combined with the cohesive nature of fine-grained soils creates a buttressing effect that slows soil movement and increases the stability of the hillside within the hollow. Statistical approaches that attempt to determine landslide hazard need to account for the complex relationship between plan curvature, type of landslide, and landslide susceptibility. ?? 2007 Elsevier B.V. All rights reserved.

  11. First In Situ Evidence of Electron Pitch Angle Scattering Due to Magnetic Field Line Curvature in the Ion Diffusion Region

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Shen, C.; Marchaudon, A.; Rong, Z.; Lavraud, B.; Fazakerley, A. N.; Yao, Z.; Mihaljcic, B.; Ji, Y.

    2016-12-01

    Theory predicts that the first adiabatic invariant of a charged particle may be violated in a region of highly curved field lines, leading to significant pitch angle scattering for particles whose gyroradius are comparable to the radius of the magnetic field line curvature. This scattering generates more isotropic particle distribution functions, with important impacts on the presence or absence of plasma instabilities. Using magnetic curvature analysis (MCA) based on multipoint Cluster spacecraft observations, we present the first investigation of magnetic curvature in the vicinity of an ion diffusion region where reconnected field lines are highly curved. Electrons at energies > 8 keV show a clear pitch angle ordering between bidirectional or trapped distribution in surrounding regions, while we show that in the more central part of the ion diffusion region electrons above such energies become isotropic. By contrast, colder electrons ( 1 keV) retain their bidirectional character throughout the diffusion regions. The calculated adiabatic parameter for these electrons is in agreement with theory. This study provides the first observational evidence for particle pitch angle scattering due to magnetic field lines with well characterized curvature in a space plasma.

  12. First in situ evidence of electron pitch angle scattering due to magnetic field line curvature in the Ion diffusion region

    NASA Astrophysics Data System (ADS)

    Zhang, Y. C.; Shen, C.; Marchaudon, A.; Rong, Z. J.; Lavraud, B.; Fazakerley, A.; Yao, Z.; Mihaljcic, B.; Ji, Y.; Ma, Y. H.; Liu, Z. X.

    2016-05-01

    Theory predicts that the first adiabatic invariant of a charged particle may be violated in a region of highly curved field lines, leading to significant pitch angle scattering for particles whose gyroradius are comparable to the radius of the magnetic field line curvature. This scattering generates more isotropic particle distribution functions, with important impacts on the presence or absence of plasma instabilities. Using magnetic curvature analysis based on multipoint Cluster spacecraft observations, we present the first investigation of magnetic curvature in the vicinity of an ion diffusion region where reconnected field lines are highly curved. Electrons at energies > 8 keV show a clear pitch angle ordering between bidirectional and trapped distribution in surrounding regions, while we show that in the more central part of the ion diffusion region electrons above such energies become isotropic. By contrast, colder electrons (~1 keV) retain their bidirectional character throughout the diffusion regions. The calculated adiabatic parameter K2 for these electrons is in agreement with theory. This study provides the first observational evidence for particle pitch angle scattering due to magnetic field lines with well characterized curvature in a space plasma.

  13. Ocular dimensions, corneal thickness, and corneal curvature in quarter horses with hereditary equine regional dermal asthenia.

    PubMed

    Badial, Peres R; Cisneros-Àlvarez, Luis Emiliano; Brandão, Cláudia Valéria S; Ranzani, José Joaquim T; Tomaz, Mayana A R V; Machado, Vania M; Borges, Alexandre S

    2015-09-01

    The aim of this study was to compare ocular dimensions, corneal curvature, and corneal thickness between horses affected with hereditary equine regional dermal asthenia (HERDA) and unaffected horses. Five HERDA-affected quarter horses and five healthy control quarter horses were used. Schirmer's tear test, tonometry, and corneal diameter measurements were performed in both eyes of all horses prior to ophthalmologic examinations. Ultrasonic pachymetry was performed to measure the central, temporal, nasal, dorsal, and ventral corneal thicknesses in all horses. B-mode ultrasound scanning was performed on both eyes of each horse to determine the dimensions of the ocular structures and to calculate the corneal curvature. Each corneal region examined in this study was thinner in the affected group compared with the healthy control group. However, significant differences in corneal thickness were only observed for the central and dorsal regions. HERDA-affected horses exhibited significant increases in corneal curvature and corneal diameter compared with unaffected animals. The ophthalmologic examinations revealed mild corneal opacity in one eye of one affected horse and in both eyes of three affected horses. No significant between-group differences were observed for Schirmer's tear test, intraocular pressure, or ocular dimensions. Hereditary equine regional dermal asthenia-affected horses exhibit decreased corneal thickness in several regions of the cornea, increased corneal curvature, increased corneal diameter, and mild corneal opacity. Additional research is required to determine whether the increased corneal curvature significantly impacts the visual accuracy of horses with HERDA. © 2014 American College of Veterinary Ophthalmologists.

  14. The HOPS/Class C Vps Complex Tethers High-Curvature Membranes via a Direct Protein-Membrane Interaction.

    PubMed

    Ho, Ruoya; Stroupe, Christopher

    2016-10-01

    Membrane tethering is a physical association of two membranes before their fusion. Many membrane tethering factors have been identified, but the interactions that mediate inter-membrane associations remain largely a matter of conjecture. Previously, we reported that the homotypic fusion and protein sorting/Class C vacuolar protein sorting (HOPS/Class C Vps) complex, which has two binding sites for the yeast vacuolar Rab GTPase Ypt7p, can tether two low-curvature liposomes when both membranes bear Ypt7p. Here, we show that HOPS tethers highly curved liposomes to Ypt7p-bearing low-curvature liposomes even when the high-curvature liposomes are protein-free. Phosphorylation of the curvature-sensing amphipathic lipid-packing sensor (ALPS) motif from the Vps41p HOPS subunit abrogates tethering of high-curvature liposomes. A HOPS complex without its Vps39p subunit, which contains one of the Ypt7p binding sites in HOPS, lacks tethering activity, though it binds high-curvature liposomes and Ypt7p-bearing low-curvature liposomes. Thus, HOPS tethers highly curved membranes via a direct protein-membrane interaction. Such high-curvature membranes are found at the sites of vacuole tethering and fusion. There, vacuole membranes bend sharply, generating large areas of vacuole-vacuole contact. We propose that HOPS localizes via the Vps41p ALPS motif to these high-curvature regions. There, HOPS binds via Vps39p to Ypt7p in an apposed vacuole membrane. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  15. A novel setup for wafer curvature measurement at very high heating rates.

    PubMed

    Islam, T; Zechner, J; Bernardoni, M; Nelhiebel, M; Pippan, R

    2017-02-01

    The curvature evolution of a thin film layer stack containing a top Al layer is measured during temperature cycles with very high heating rates. The temperature cycles are generated by means of programmable electrical power pulses applied to miniaturized polysilicon heater systems embedded inside a semiconductor chip and the curvature is measured by a fast wafer curvature measurement setup. Fast temperature cycles with heating duration of 100 ms are created to heat the specimen up to 270 °C providing an average heating rate of 2500 K/s. As a second approach, curvature measurement utilizing laser scanning Doppler vibrometry is also demonstrated which verifies the results obtained from the fast wafer curvature measurement setup. Film stresses calculated from the measured curvature values compare well to literature results, indicating that the new method can be used to measure curvature during fast temperature cycling.

  16. A novel setup for wafer curvature measurement at very high heating rates

    NASA Astrophysics Data System (ADS)

    Islam, T.; Zechner, J.; Bernardoni, M.; Nelhiebel, M.; Pippan, R.

    2017-02-01

    The curvature evolution of a thin film layer stack containing a top Al layer is measured during temperature cycles with very high heating rates. The temperature cycles are generated by means of programmable electrical power pulses applied to miniaturized polysilicon heater systems embedded inside a semiconductor chip and the curvature is measured by a fast wafer curvature measurement setup. Fast temperature cycles with heating duration of 100 ms are created to heat the specimen up to 270 °C providing an average heating rate of 2500 K/s. As a second approach, curvature measurement utilizing laser scanning Doppler vibrometry is also demonstrated which verifies the results obtained from the fast wafer curvature measurement setup. Film stresses calculated from the measured curvature values compare well to literature results, indicating that the new method can be used to measure curvature during fast temperature cycling.

  17. Internal curvature signal and noise in low- and high-level vision

    PubMed Central

    Grabowecky, Marcia; Kim, Yee Joon; Suzuki, Satoru

    2011-01-01

    How does internal processing contribute to visual pattern perception? By modeling visual search performance, we estimated internal signal and noise relevant to perception of curvature, a basic feature important for encoding of three-dimensional surfaces and objects. We used isolated, sparse, crowded, and face contexts to determine how internal curvature signal and noise depended on image crowding, lateral feature interactions, and level of pattern processing. Observers reported the curvature of a briefly flashed segment, which was presented alone (without lateral interaction) or among multiple straight segments (with lateral interaction). Each segment was presented with no context (engaging low-to-intermediate-level curvature processing), embedded within a face context as the mouth (engaging high-level face processing), or embedded within an inverted-scrambled-face context as a control for crowding. Using a simple, biologically plausible model of curvature perception, we estimated internal curvature signal and noise as the mean and standard deviation, respectively, of the Gaussian-distributed population activity of local curvature-tuned channels that best simulated behavioral curvature responses. Internal noise was increased by crowding but not by face context (irrespective of lateral interactions), suggesting prevention of noise accumulation in high-level pattern processing. In contrast, internal curvature signal was unaffected by crowding but modulated by lateral interactions. Lateral interactions (with straight segments) increased curvature signal when no contextual elements were added, but equivalent interactions reduced curvature signal when each segment was presented within a face. These opposing effects of lateral interactions are consistent with the phenomena of local-feature contrast in low-level processing and global-feature averaging in high-level processing. PMID:21209356

  18. Active optics for high-dynamic variable curvature mirrors.

    PubMed

    Hugot, Emmanuel; Ferrari, Marc; Lemaitre, Gérard R; Madec, Fabrice; Vives, Sébastien; Chardin, Elodie; Le Mignant, David; Cuby, Jean-Gabriel

    2009-10-01

    Variable curvature mirrors of large amplitude are designed by using finite element analysis. The specific case studied reaches at least a 800 mum sag with an optical quality better than lambda/5 over a 120 mm clear aperture. We highlight the geometrical nonlinearity and the plasticity effect.

  19. Management of High-Grade Penile Curvature Associated With Hypospadias in Children

    PubMed Central

    Moscardi, Paulo R. M.; Gosalbez, Rafael; Castellan, Miguel Alfedo

    2017-01-01

    Penile curvature is a frequent feature associated with hypospadias with also a great variability of severity among each patient. While the low-grade curvature (<30°) can be relatively easily corrected by simple techniques like penile degloving and dorsal plication, severe cases often demand more complex maneuvers to manage it. A great number of surgical techniques have been developed to adequately correct curvatures greater than 30°; however, each one of them should be individualized to different patients and local conditions encountered. In this article, we will review the evaluation of the pediatric patient with penile curvature associated with hypospadias with a special attention to high-grade cases, their management, indications for surgical treatment, and several surgical options for their definitive treatment. PMID:28929092

  20. High bending curvature withstanding one-dimensional angle sensor with fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Jang, Minsu; Kim, Ockchul; Yang, Sungwook; Kim, Jinseok

    2017-04-01

    We report on the development of an angle sensor which can measure at high bending curvature. Unlike the other sensors, the novel angle sensor can be durable and flexible. The sensors consist of one fiber Bragg grating (FBG) fiber which is located in the middle of each sensor, and are fabricated in varying thickness to confirm the relation between the distance of the center of the angle sensor to the core of the FBG node and the radii of curvature at which the sensor can measure. The thinnest sensor has the thickness of 200 μm and can measure at the bending radius of 5 mm. However, its angle measurement error is the largest with 1.25°, because of high sensitivity. Regulating the thickness of sensor, the angles at high curvatures can be measured reliably.

  1. Classification and quantification of leaf curvature

    PubMed Central

    Liu, Zhongyuan; Jia, Liguo; Mao, Yanfei; He, Yuke

    2010-01-01

    Various mutants of Arabidopsis thaliana deficient in polarity, cell division, and auxin response are characterized by certain types of leaf curvature. However, comparison of curvature for clarification of gene function can be difficult without a quantitative measurement of curvature. Here, a novel method for classification and quantification of leaf curvature is reported. Twenty-two mutant alleles from Arabidopsis mutants and transgenic lines deficient in leaf flatness were selected. The mutants were classified according to the direction, axis, position, and extent of leaf curvature. Based on a global measure of whole leaves and a local measure of four regions in the leaves, the curvature index (CI) was proposed to quantify the leaf curvature. The CI values accounted for the direction, axis, position, and extent of leaf curvature in all of the Arabidopsis mutants grown in growth chambers. Comparison of CI values between mutants reveals the spatial and temporal variations of leaf curvature, indicating the strength of the mutant alleles and the activities of the corresponding genes. Using the curvature indices, the extent of curvature in a complicated genetic background becomes quantitative and comparable, thus providing a useful tool for defining the genetic components of leaf development and to breed new varieties with leaf curvature desirable for the efficient capture of sunlight for photosynthesis and high yields. PMID:20400533

  2. Classification and quantification of leaf curvature.

    PubMed

    Liu, Zhongyuan; Jia, Liguo; Mao, Yanfei; He, Yuke

    2010-06-01

    Various mutants of Arabidopsis thaliana deficient in polarity, cell division, and auxin response are characterized by certain types of leaf curvature. However, comparison of curvature for clarification of gene function can be difficult without a quantitative measurement of curvature. Here, a novel method for classification and quantification of leaf curvature is reported. Twenty-two mutant alleles from Arabidopsis mutants and transgenic lines deficient in leaf flatness were selected. The mutants were classified according to the direction, axis, position, and extent of leaf curvature. Based on a global measure of whole leaves and a local measure of four regions in the leaves, the curvature index (CI) was proposed to quantify the leaf curvature. The CI values accounted for the direction, axis, position, and extent of leaf curvature in all of the Arabidopsis mutants grown in growth chambers. Comparison of CI values between mutants reveals the spatial and temporal variations of leaf curvature, indicating the strength of the mutant alleles and the activities of the corresponding genes. Using the curvature indices, the extent of curvature in a complicated genetic background becomes quantitative and comparable, thus providing a useful tool for defining the genetic components of leaf development and to breed new varieties with leaf curvature desirable for the efficient capture of sunlight for photosynthesis and high yields.

  3. A high-precision calculation method for interface normal and curvature on an unstructured grid

    NASA Astrophysics Data System (ADS)

    Ito, Kei; Kunugi, Tomoaki; Ohno, Shuji; Kamide, Hideki; Ohshima, Hiroyuki

    2014-09-01

    In the volume-of-fluid algorithm, the calculations of the interface normal and curvature are crucially important for accurately simulating interfacial flows. However, few methods have been proposed for the high-precision interface calculation on an unstructured grid. In this paper, the authors develop a height function method that works appropriately on an unstructured grid. In the process, the definition of the height function is discussed, and the high-precision calculation method of the interface normal is developed to meet the necessary condition for a second-order method. This new method has highly reduced computational cost compared with a conventional high-precision method because the interface normal calculation is completed by solving relatively simple algebraic equations. The curvature calculation method is also discussed and the approximated quadric curve of an interface is employed to calculate the curvature. Following a basic verification, the developed height function method is shown to successfully provide superior calculation accuracy and highly reduced computational cost compared with conventional calculation methods in terms of the interface normal and curvature. In addition, the height function method succeeds in calculating accurately the slotted-disk revolution problem and the oscillating drop on unstructured grids. Therefore, the developed height function method is confirmed to be an efficient technique for the high-precision numerical simulation of interfacial flows on an unstructured grid.

  4. Highly sensitive curvature sensor based on asymmetrical twin core fiber and multimode fiber

    NASA Astrophysics Data System (ADS)

    Wu, Yue; Pei, Li; Jin, Wenxing; Jiang, Youchao; Yang, Yuguang; Shen, Ya; Jian, Shuisheng

    2017-07-01

    A highly sensitive curvature sensor based on asymmetrical twin core fiber (TCF) and multimode fiber (MMF) is proposed and experimentally demonstrated. By applying the coupled-mode theory and equivalent refractive index model, we theoretically analyze the uncoupled feature of the TCF and the relationship between peak wavelength and the curvature. Two segments of MMF used as beam splitter and combiner are embedded on the two ends of the TCF, and the extinction ratio of the comb transmission spectrum is about 15 dB. The experimental result shows that the curvature sensitivity of the sensor can be achieved as high as 103.35 nm/m-1 ranging from 0.24 m-1 to 0.6 m-1, and the strain sensitivity is up to -4.01 pm/με in the range from 0 μεto 1400 με. The simultaneous detection of the curvature and strain can be realized. The temperature sensitivity is 0.431 nm/°C in the range from 40 °C to 70 °C. This fiber sensor exhibits the advantages of low cost, easy and repeated fabrication, and high sensitivity.

  5. In-fiber directional coupler for high-sensitivity curvature measurement.

    PubMed

    Guzman-Sepulveda, J R; May-Arrioja, D A

    2013-05-20

    A curvature fiber optic sensor using a two-core fiber (TCF) is proposed and demonstrated. The TCF is designed to operate as a directional coupler with one core located exactly at the center of the fiber and the other off-axis, but close to the center of the fiber. This design allows straightforward splicing of the TCF to single mode fibers (SMF), and alignment of the off-axis core is not strictly required for optimum operation. The sensor is fabricated by simply splicing a 5 cm long section of TCF between two SMF sections, which provides a sinusoidal spectral response. When the fiber is bent, the coupling parameters are modified due to stress-optic and effective length effects, effectively blue-shifting the sinusoidal spectral response of the sensor and allowing for the measurement of curvature. The sensor exhibits linear response and a sensitivity of -137.87 nm/m(-1) for curvature ranging from 0 to 0.27 m(-1), making it suitable to measure small curvatures with high sensitivity.

  6. Tuning the Nanostructure of Highly Functionalized Silica Using Amphiphilic Organosilanes: Curvature Agent Effects.

    PubMed

    Besnard, Romain; Arrachart, Guilhem; Cambedouzou, Julien; Pellet-Rostaing, Stéphane

    2016-05-10

    The self-assembly of amino-undecyl-triethoxysilane (AUT) as micelles in water is considered. The behavior of acid/AUT systems is governed by a complete proton transfer from the acid to the amine, leading to the formation of an ammonium headgroup. This moiety is responsible for the bending of the interface between the organic core of the micelles and the surrounding water. By playing with the size of the acid used as curvature agent, the amphiphilic behavior of the organosilane molecule may be adjusted. We follow the aggregation as the curvature agent size increases. This approach constitutes an efficient and original method in order to tune the nanostructure of highly functionalized silica at the early stage of the elaboration. Small-angle X-ray scattering, wet scanning transmission electron microscopy, dynamic light scattering, and complementary characterization techniques indicate that hybrid organic-inorganic planar objects and vesicles are obtained for smaller curvature agents. Increasing the size of the curvature agent results in a transition of the aggregation geometry from vesicles to cylindrical direct micelles, finally leading to nanofibers organized in a 2D hexagonal network resembling a "reverse MCM-41 structure". A geometrical molecular self-assembly model is finally proposed, considering the dimensions of the surfactant tail and those of the head groups.

  7. Integrating 3D seismic curvature and curvature gradient attributes for fracture characterization: Methodologies and interpretational implications

    SciTech Connect

    Gao, Dengliang

    2013-03-01

    In 3D seismic interpretation, curvature is a popular attribute that depicts the geometry of seismic reflectors and has been widely used to detect faults in the subsurface; however, it provides only part of the solutions to subsurface structure analysis. This study extends the curvature algorithm to a new curvature gradient algorithm, and integrates both algorithms for fracture detection using a 3D seismic test data set over Teapot Dome (Wyoming). In fractured reservoirs at Teapot Dome known to be formed by tectonic folding and faulting, curvature helps define the crestal portion of the reservoirs that is associated with strong seismic amplitude and high oil productivity. In contrast, curvature gradient helps better define the regional northwest-trending and the cross-regional northeast-trending lineaments that are associated with weak seismic amplitude and low oil productivity. In concert with previous reports from image logs, cores, and outcrops, the current study based on an integrated seismic curvature and curvature gradient analysis suggests that curvature might help define areas of enhanced potential to form tensile fractures, whereas curvature gradient might help define zones of enhanced potential to develop shear fractures. In certain fractured reservoirs such as at Teapot Dome where faulting and fault-related folding contribute dominantly to the formation and evolution of fractures, curvature and curvature gradient attributes can be potentially applied to differentiate fracture mode, to predict fracture intensity and orientation, to detect fracture volume and connectivity, and to model fracture networks.

  8. Electron microscopy mapping of pBR322 DNA curvature. Comparison with theoretical models.

    PubMed Central

    Muzard, G; Théveny, B; Révet, B

    1990-01-01

    A map of local curvature of the pBR322 DNA has been established by electron microscopy analysis of linearized plasmid molecules. To determine their polarity these molecules are one end labelled with an avidin-ferritin-biotin complex and the images are digitized. Local curvature is calculated from two mathematical treatments of the DNA trajectory and expressed in term of a mean dinucleotide wedge angle. Eight regions of curvature are distinguished. The four main regions of curvature have a high content of phased AA runs. The experimental curvature map is compared to theoretical maps of curvature obtained from four available models for DNA curvature. Images Fig. 2. PMID:2323339

  9. Formation, Stability, and Mobility of One-Dimensional Lipid Bilayer on High Curvature Substrates

    SciTech Connect

    Huang, J; Martinez, J; Artyukhin, A; Sirbuly, D; Wang, Y; Ju, J W; Stroeve, P; Noy, A

    2007-03-23

    Curved lipid membranes are ubiquitous in living systems and play an important role in many biological processes. To understand how curvature and lipid composition affect membrane formation and fluidity we have assembled and studied mixed 1,2-Dioleoyl-sn-Glycero-3-Phosphocholine (DOPC) and 1,2-Dioleoyl-sn-Glycero-3-Phosphoethanolamine (DOPE) supported lipid bilayers on amorphous silicon nanowires with controlled diameters ranging from 20 nm to 200 nm. Addition of cone-shaped DOPE molecules to cylindrical DOPC molecules promotes vesicle fusion and bilayer formation on smaller diameter nanowires. Our experiments demonstrate that nanowire-supported bilayers are mobile, exhibit fast recovery after photobleaching, and have low concentration of defects. Lipid diffusion coefficients in these high-curvature tubular membranes are comparable to the values reported for flat supported bilayers and increase with decreasing nanowire diameter.

  10. Highly sensitive curvature sensor based on long period fiber grating with alternately splicing multiple single/multimode structure

    NASA Astrophysics Data System (ADS)

    Hu, Qihao; Zhang, Shuo; Yang, Wenlei; Geng, Tao; Sun, Weimin; Sun, Cuiting; Jin, Xiren; Yuan, Libo

    2017-09-01

    A highly sensitive curvature sensor made of a novel long period fiber grating (LPFG) is presented and experimentally demonstrated. It is constructed by splicing multiple single mode fibers (SMFs) and multi-mode fibers (MMFs) alternately (MS/MA). The measurement result shows that it has a high sensitivity of -22.4 nm/m-1 in the range from 0.223 m-1 to 4.358 m-1. It can measure curvature on all direction due to the symmetric structure. The proposed sensor was also insensitive to the temperature, whose temperature sensitivity was around -0.015 nm/°C in the range from 40 °C to 200 °C. The advantages of high curvature sensitivity and low temperature sensitivity make it has a great potential to measure curvature in practical application with high resolutions.

  11. Analysis of Fundus Shape in Highly Myopic Eyes by Using Curvature Maps Constructed from Optical Coherence Tomography

    PubMed Central

    Miyake, Masahiro; Yamashiro, Kenji; Akagi-Kurashige, Yumiko; Oishi, Akio; Tsujikawa, Akitaka; Hangai, Masanori; Yoshimura, Nagahisa

    2014-01-01

    Purpose To evaluate fundus shape in highly myopic eyes using color maps created through optical coherence tomography (OCT) image analysis. Methods We retrospectively evaluated 182 highly myopic eyes from 113 patients. After obtaining 12 lines of 9-mm radial OCT scans with the fovea at the center, the Bruch’s membrane line was plotted and its curvature was measured at 1-µm intervals in each image, which was reflected as a color topography map. For the quantitative analysis of the eye shape, mean absolute curvature and variance of curvature were calculated. Results The color maps allowed staphyloma visualization as a ring of green color at the edge and as that of orange-red color at the bottom. Analyses of mean and variance of curvature revealed that eyes with myopic choroidal neovascularization tended to have relatively flat posterior poles with smooth surfaces, while eyes with chorioretinal atrophy exhibited a steep, curved shape with an undulated surface (P<0.001). Furthermore, eyes with staphylomas and those without clearly differed in terms of mean curvature and the variance of curvature: 98.4% of eyes with staphylomas had mean curvature ≥7.8×10−5 [1/µm] and variance of curvature ≥0.26×10−8 [1/µm]. Conclusions We established a novel method to analyze posterior pole shape by using OCT images to construct curvature maps. Our quantitative analysis revealed that fundus shape is associated with myopic complications. These values were also effective in distinguishing eyes with staphylomas from those without. This tool for the quantitative evaluation of eye shape should facilitate future research of myopic complications. PMID:25259853

  12. Radius of curvature changes in spontaneous improvement of foveoschisis in highly myopic eyes.

    PubMed

    Hoang, Quan V; Chen, Ching-Lung; Garcia-Arumi, Jose; Sherwood, Pamela R; Chang, Stanley

    2016-02-01

    Myopic foveoschisis is the splitting of retinal layers overlying staphyloma in highly myopic patients that can lead to vision loss. We assess possible contributing mechanisms to the formation of foveoschisis by examining two cases of spontaneous improvement of myopic foveoschisis and employ a radius of curvature (ROC) measure to track posterior scleral curvature over time. A retrospective, non-comparative case series was performed and optical coherence tomography images were analysed. Retinal pigment epithelial layer ROC was calculated from manually segmented images through the posterior scleral curvature apex. Two cases of myopic foveoschisis with foveal detachments in the left eye (OS) were studied. Both patients had high myopia (either <-10 D or >30 mm in axial length). One case occurred in a treatment-naive patient who improved after 4 months of observation. On initial presentation, OS posterior scleral ROC was 12.35 mm and decreased to 12.15 mm at the time of resolution. The other case occurred in a patient who was followed for 7 years, had previously underwent pars plana vitrectomy and removal of epiretinal membrane, experienced recurrence of foveoschisis and then spontaneously improved without further posterior segment surgery. There was an uncomplicated cataract extraction in the interim. Posterior scleral ROC was 4.05 mm on presentation, 4.10 during recurrence, 3.55 mm after cataract extraction and 3.75 mm at resolution. Spontaneous improvement of myopic foveoschisis may be due to changes in tractional forces from the internal limiting membrane, cortical vitreous or staphyloma or, alternatively, from a delayed or fluctuant recovery course after intervention. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  13. Visualization of Secondary Flow Development in High Aspect Ratio Channels with Curvature

    NASA Technical Reports Server (NTRS)

    Meyer, Michael L.; Giuliani, James E.

    1994-01-01

    The results of an experimental project to visually examine the secondary flow structure that develops in curved, high aspect-ratio rectangular channels are presented. The results provide insight into the fluid dynamics within high aspect ratio channels. A water flow test rig constructed out of plexiglass, with an adjustable aspect ratio, was used for these experiments. Results were obtained for a channel geometry with a hydraulic diameter of 10.6 mm (0.417 in.), an aspect ratio of 5.0, and a hydraulic radius to curvature radius ratio of 0.0417. Flow conditions were varied to achieve Reynolds numbers up to 5,100. A new particle imaging velocimetry technique was developed which could resolve velocity information from particles entering and leaving the field of view. Time averaged secondary flow velocity vectors, obtained using this velocimetry technique, are presented for 30 degrees, 60 degrees, and 90 degrees into a 180 degrees bend and at a Reynolds number of 5,100. The secondary flow results suggest the coexistence of both the classical curvature induced vortex pair flow structure and the eddies seen in straight turbulent channel flow.

  14. A high-order curvature compensation technique for bandgap voltage reference using subthreshold MOSFETs

    NASA Astrophysics Data System (ADS)

    Adl, Ahmad-Hossein; El-Sankary, Kamal; El-Masry, Ezz

    2010-07-01

    A bandgap voltage reference with high-order curvature compensation is presented in this study. It exploits subtraction and derivative equalisation of currents generated from two complementary NMOS and PMOS bandgap references (BGRs) using subthreshold MOSFETs. By equating the derivative with respect to temperature of the two currents, generated by the complementary bandgaps, and subtracting these currents, an accurate high-order curvature compensation is achieved. To overcome problems due to the limited input common-mode range of opamps used in BGRs, a transimpedance amplifier with new accurate current compensation that tracks the temperature variation is proposed. This bandgap is implemented using the 0.18 μm CMOS process with a supply voltage as low as 0.7 V. At 0.8 V power supply and an output reference voltage of 386 mV, the proposed circuit achieves a temperature coefficient of 19 ppm/°C from 0 to 130°C. The power consumption is 119 μW and the power supply reduction ratio is 24 dB at 1 kHz.

  15. Mesoscale simulations of curvature-inducing protein partitioning on lipid bilayer membranes in the presence of mean curvature fields

    NASA Astrophysics Data System (ADS)

    Liu, Jin; Tourdot, Richard; Ramanan, Vyas; Agrawal, Neeraj J.; Radhakrishanan, Ravi

    2012-06-01

    The membrane-surface migration of curvature-inducing proteins in response to membrane curvature gradients has been investigated using Monte Carlo simulations of a curvilinear membrane model based on the Helfrich Hamiltonian. Consistent with theoretical and experimental data, we find the proteins that generate curvature can also sense the background membrane curvature, wherein they preferentially partition to the high curvature regions. The partitioning strength depends linearly on local membrane curvature and the slope (or the coupling constant) of the partitioning probability versus mean curvature depends on the membrane bending rigidity and instantaneous curvature field caused by different proteins. Our simulation study allows us to quantitatively characterize and identify the important factors affecting the coupling constant (slope), which may be difficult to determine in experiments. Furthermore, the membrane model is used to study budding of vesicles where it is found that in order to stabilize a mature vesicle with a stable 'neck-region' (or stable membrane overhangs), the area (extent) of the intrinsic curvature region needs to exceed a threshold-critical value. The migration and partitioning of curvature-inducing proteins in a budding vesicle with a stable neck (with a characteristic negative value of the Gaussian curvature) is investigated.

  16. Mesoscale simulations of curvature-inducing protein partitioning on lipid bilayer membranes in the presence of mean curvature fields.

    PubMed

    Liu, Jin; Tourdot, Richard; Ramanan, Vyas; Agrawal, Neeraj J; Radhakrishanan, Ravi

    2012-06-01

    The membrane-surface migration of curvature-inducing proteins in response to membrane curvature gradients has been investigated using Monte Carlo simulations of a curvilinear membrane model based on the Helfrich Hamiltonian. Consistent with theoretical and experimental data, we find the proteins that generate curvature can also sense the background membrane curvature, wherein they preferentially partition to the high curvature regions. The partitioning strength depends linearly on local membrane curvature and the slope (or the coupling constant) of the partitioning probability versus mean curvature depends on the membrane bending rigidity and instantaneous curvature field caused by different proteins. Our simulation study allows us to quantitatively characterize and identify the important factors affecting the coupling constant (slope), which may be difficult to determine in experiments. Furthermore, the membrane model is used to study budding of vesicles where it is found that in order to stabilize a mature vesicle with a stable 'neck-region' (or stable membrane overhangs), the area (extent) of the intrinsic curvature region needs to exceed a threshold-critical value. The migration and partitioning of curvature-inducing proteins in a budding vesicle with a stable neck (with a characteristic negative value of the Gaussian curvature) is investigated.

  17. High energy green nanosecond and picosecond pulse delivery through a negative curvature fiber for precision micro-machining.

    PubMed

    Jaworski, Piotr; Yu, Fei; Carter, Richard M; Knight, Jonathan C; Shephard, Jonathan D; Hand, Duncan P

    2015-04-06

    In this paper we present an anti-resonant guiding, low-loss Negative Curvature Fiber (NCF) for the efficient delivery of high energy short (ns) and ultrashort (ps) pulsed laser light in the green spectral region. The fabricated NCF has an attenuation of 0.15 dB/m and 0.18 dB/m at 532 nm and 515 nm respectively, and provided robust transmission of nanosecond and picosecond pulses with energies of 0.57 mJ (10.4 kW peak power) and 30 µJ (5 MW peak power) respectively. It provides single-mode, stable (low bend-sensitivity) output and maintains spectral and temporal properties of the source laser beam. The practical application of fiber-delivered pulses has been demonstrated in precision micro-machining and marking of metals and glass.

  18. Adaptive region-growing with maximum curvature strategy for tumor segmentation in 18F-FDG PET

    NASA Astrophysics Data System (ADS)

    Tan, Shan; Li, Laquan; Choi, Wookjin; Kang, Min Kyu; D'Souza, Warren D.; Lu, Wei

    2017-07-01

    Accurate tumor segmentation in PET is crucial in many oncology applications. We developed an adaptive region-growing (ARG) algorithm with a maximum curvature strategy (ARG_MC) for tumor segmentation in PET. The ARG_MC repeatedly applied a confidence connected region-growing algorithm with increasing relaxing factor f. The optimal relaxing factor (ORF) was then determined at the transition point on the f-volume curve, where the volume just grew from the tumor into the surrounding normal tissues. The ARG_MC along with five widely used algorithms were tested on a phantom with 6 spheres at different signal to background ratios and on two clinic datasets including 20 patients with esophageal cancer and 11 patients with non-Hodgkin lymphoma (NHL). The ARG_MC did not require any phantom calibration or any a priori knowledge of the tumor or PET scanner. The identified ORF varied with tumor types (mean ORF  =  9.61, 3.78 and 2.55 respectively for the phantom, esophageal cancer, and NHL datasets), and varied from one tumor to another. For the phantom, the ARG_MC ranked the second in segmentation accuracy with an average Dice similarity index (DSI) of 0.86, only slightly worse than Daisne’s adaptive thresholding method (DSI  =  0.87), which required phantom calibration. For both the esophageal cancer dataset and the NHL dataset, the ARG_MC had the highest accuracy with an average DSI of 0.87 and 0.84, respectively. The ARG_MC was robust to parameter settings and region of interest selection, and it did not depend on scanners, imaging protocols, or tumor types. Furthermore, the ARG_MC made no assumption about the tumor size or tumor uptake distribution, making it suitable for segmenting tumors with heterogeneous FDG uptake. In conclusion, the ARG_MC was accurate, robust and easy to use, it provides a highly potential tool for PET tumor segmentation in clinic.

  19. Fold-and-thrust belt curvature in the Fars region, eastern Zagros, achieved by variable thrust slip vectors and fault block rotations

    NASA Astrophysics Data System (ADS)

    Edey, Alex; Allen, Mark B.

    2017-04-01

    Many fold-and-thrust belts are curved in plan view, but the origins of this curvature are debated. Understanding which mechanism(s) is appropriate is important to constrain the behaviour of the lithosphere during compressional deformation. Here we analyse the active deformation of the Fars Arc region in the eastern part of the Zagros, Iran, including slip vectors of 92 earthquakes, published GPS and palaeomagnetism data, and the distributions of young and/or active folds. The fold-and-thrust belt in the Fars Arc shows pronounced curvature, convex southwards. Folds trends vary from NW-SE in the west to ENE-WSW in the east. The GPS-derived velocity field shows NNE to SSW convergence, towards the foreland on the Arabian Plate, without dispersion. Earthquake slip vectors are highly variable, spanning a range of azimuths from SW to SSE in an Arabian Plate reference frame. The full variation of azimuths occurs within small (10s of km) sub-regions, but this variation is superimposed on a radial pattern, whereby slip vectors tend to be parallel to the regional topographic gradient. Given the lack of variation in the GPS vectors, we conclude that the Fars Arc is not curved as a result of gravitational spreading over the adjacent foreland, but as a result of deformation being restricted at tectonic boundaries at the eastern and western margins of the Arc. Fault blocks and folds within the Fars Arc, each 20-40 km long, rotate about vertical axes to achieve the overall curvature, predominantly clockwise in the west and counter-clockwise in the east. Active folds of different orientations may intersect and produce dome-and-basin interference patterns, without the need for a series of separate deformation phases of different stress orientations. The Fars Arc clearly contrasts with the Himalayas, where both GPS and earthquake slip vectors display radial patterns towards the foreland, and gravitational spreading is a viable mechanism for producing fold-and-thrust belt curvature.

  20. Mesoscale simulations of curvature-inducing protein partitioning on lipid bilayer membranes in the presence of mean curvature fields

    PubMed Central

    Liu, Jin; Tourdot, Richard; Ramanan, Vyas; Agrawal, Neeraj J.; Radhakrishanan, Ravi

    2015-01-01

    The membrane-surface migration of curvature-inducing proteins in response to membrane curvature gradients has been investigated using Monte Carlo simulations of a curvilinear membrane model based on the Helfrich Hamiltonian. Consistent with theoretical and experimental data, we find the proteins that generate curvature can also sense the background membrane curvature, wherein they preferentially partition to the high curvature regions. The partitioning strength depends linearly on local membrane curvature and the slope (or the coupling constant) of the partitioning probability versus mean curvature depends on the membrane bending rigidity and instantaneous curvature field caused by different proteins. Our simulation study allows us to quantitatively characterize and identify the important factors affecting the coupling constant (slope), which may be difficult to determine in experiments. Furthermore, the membrane model is used to study budding of vesicles where it is found that in order to stabilize a mature vesicle with a stable ‘neck-region’ (or stable membrane overhangs), the area (extent) of the intrinsic curvature region needs to exceed a threshold-critical value. The migration and partitioning of curvature-inducing proteins in a budding vesicle with a stable neck (with a characteristic negative value of the Gaussian curvature) is investigated. PMID:26500377

  1. High beam headlamp use rates: Effects of rurality, proximity of other traffic, and roadway curvature.

    PubMed

    Reagan, Ian J; Brumbelow, Matthew L; Flannagan, Michael J; Sullivan, John M

    2017-10-03

    The few observational studies of the prevalence of high beam use indicate the rate of high beam use is about 25% when vehicles are isolated from other vehicles on unlit roads. Recent studies were limited to 2-lane rural roads and used measurement methods that likely overestimated use. The current study examined factors associated with the rate of high beam use of isolated vehicles on a variety of roadways in the Ann Arbor, Michigan area. Twenty observation sites were categorized as urban, rural, or on a rural/urban boundary and selected to estimate the effects of street lighting, road curvature, and direction of travel relative to the city on high beam use. Sites were selected in pairs so that a majority of traffic passing one site also passed through the other. Measurement of high beams relied on video data recorded for 2 nights at each site, and the video data also were used to derive a precise measure of the proximity of other traffic. Nearly 3,200 isolated vehicles (10 s or longer from other vehicles) were observed, representing 1,500-plus vehicle pairs. Across the sample, 18% of the vehicles used high beams. Seventy-three percent of the 1,500-plus vehicle pairs used low beams at each paired site, whereas 9% used high beams at both sites. Vehicles at rural sites and sites at the boundaries of Ann Arbor were more likely to use high beams than vehicles at urban sites, but use in rural areas compared with rural/urban boundary areas did not vary significantly. Rates at all sites were much lower than expected, ranging from 0.9 to 52.9%. High beam use generally increased with greater time between subject vehicles and leading vehicles and vehicles in the opposing lane. There were mixed findings associated with street lighting, road curvature, and direction of travel relative to the city. Maximizing visibility available to drivers from headlights includes addressing the substantial underuse of high beam headlamps. Advanced technologies such as high beam assist, which

  2. Curvature and the Visual Perception of Shape: Theory on Information along Object Boundaries and the Minima Rule Revisited

    ERIC Educational Resources Information Center

    Lim, Ik Soo; Leek, E. Charles

    2012-01-01

    Previous empirical studies have shown that information along visual contours is known to be concentrated in regions of high magnitude of curvature, and, for closed contours, segments of negative curvature (i.e., concave segments) carry greater perceptual relevance than corresponding regions of positive curvature (i.e., convex segments). Lately,…

  3. Curvature and the Visual Perception of Shape: Theory on Information along Object Boundaries and the Minima Rule Revisited

    ERIC Educational Resources Information Center

    Lim, Ik Soo; Leek, E. Charles

    2012-01-01

    Previous empirical studies have shown that information along visual contours is known to be concentrated in regions of high magnitude of curvature, and, for closed contours, segments of negative curvature (i.e., concave segments) carry greater perceptual relevance than corresponding regions of positive curvature (i.e., convex segments). Lately,…

  4. Penile curvature: an update for management from 20 years experience in a high volume centre.

    PubMed

    Sasso, Francesco; Vittori, Matteo; D'Addessi, Alessandro; Bassi, Pier Francesco

    2016-09-26

    Our aim was to review the literature and discuss about penile curvature in order to have an update for management after 20 years experience in the field.Penile curvature may be congenital or acquired. Congenital penile curvature is a relatively uncommon condition that may present in late adolescent or early adult life. The incidence is estimated to be 0.6 %. On the other side, acquired penile curvature has an overall prevalence of 0.5-13%. Three main factors seem to increase the risk of developing an acquired penile curvature, often related to Peyronie's disease: penile traumatism, genetic and familiar conditions and a history of diseases of the genital tract. In treating Peyronie's disease, no medical therapy is fully effective, and surgery remains the gold standard in cases of severe deformity and/or erectile disfunction. Peyronie's disease is associated with significant psychological stress for patients and their partners. Appropriate treatment should be individualized and tailored to the patient's goals and expectations. There is not the 'best' surgical technique and outcomes are satisfactory when proper treatment decisions are made.

  5. Design of anamorphic magnification high-numerical aperture objective for extreme ultraviolet lithography by curvatures combination method.

    PubMed

    Liu, Yan; Li, Yanqiu; Cao, Zhen

    2016-06-20

    An anamorphic magnification extreme ultraviolet (EUV) lithographic objective could increase the size of the exposure field at a wafer in the orthogonal scanning direction to improve the throughput of the lithographic system. In this paper, we present a curvatures combination method for an anamorphic magnification EUV lithographic objective with high numerical aperture (NA). This method achieves an anamorphic magnification initial structure by use of the double-curvature surfaces, which are formed by combining the curvatures of the corresponding surfaces into two coaxial spherical systems. A series of control measures is taken to design the two coaxial spherical systems for ensuring the rationalities of the initial structure and the surfaces after combining. The image quality of the anamorphic initial structure is optimized by a gradual optimization process. Finally, as an example, we design an Mx1/4 and My1/8 anamorphic magnification EUV lithographic objective with the presented design method. This objective achieves 0.5 NA and a 26  mm×16.5  mm exposure field at the wafer. The wavefront error RMS reaches 0.06λ (λ=13.5  nm), and the distortion is less than 2.8 nm. The design result proves the availability of the curvatures combination method.

  6. Influence of Hamstring Muscles Extensibility on Spinal Curvatures and Pelvic Tilt in Highly Trained Cyclists

    PubMed Central

    Muyor, José M.; Alacid, Fernando; López-Miñarro, Pedro A.

    2011-01-01

    The purpose of this study was to determine the influence of hamstring muscles extensibility in standing, maximal trunk flexion with knees extended and on the bicycle in lower handlebar-hands position of highly trained cyclists. Ninety-six cyclists were recruited for the study (mean ± SD, age: 30.36 ± 5.98 years). Sagittal spinal curvatures and pelvic tilt were measured in the standing position, maximal trunk flexion with knees extended (sit-and-reach test) and while sitting on a bicycle in lower handlebar-hand position using a Spinal Mouse system. Hamstring muscles extensibility was determined in both legs by passive straight leg raise test (PSLR). The sample was divided into three groups according to PSLR angle: (1) reduced extensibility (PSLR < 80º; n = 30), (2) moderate hamstring extensibility group (PSLR = 80º – 90º; n = 35), and (3) high hamstring extensibility (PSLR = > 90º; n = 31). ANOVA analysis showed significant differences among groups for thoracic (p < 0.001) and pelvic tilt (p < 0.001) angles in the sit-and-reach test. No differences were found between groups for standing and on the bicycle position. Post hoc analysis showed significant differences in all pairwise comparisons for thoracic angle (p < 0.01) and pelvic angle (p < 0.001) in the sit-and-reach test. No differences were found in lumbar angle in any posture. In conclusion, the hamstring muscles extensibility influence the thoracic and pelvic postures when maximal trunk flexion with knees extended is performed, but not when cyclists are seated on their bicycles PMID:23486997

  7. Aligning and measuring the curvature and thickness of high-precision lens

    NASA Astrophysics Data System (ADS)

    Wu, Kun-Huan; Chang, Shenq-Tsong; Hsu, Ming-Ying; Huang, Ting-Ming; Hsu, Wei-Yao; Tseng, Shih-Feng

    2015-09-01

    The radius of curvature is one of the most important specifications for spherical optics [1]. There are several methods and devices currently on the market that can be used to measure it, including optical level, non-contact laser interferometer (Interferometer), a probe-contact profiler (Profilometer), the centering machine and three-point contact ball diameter meter (Spherometer). The amount that can be measured with a radius of curvature of the lens aperture range depends on the interferometer standard lens f / number and lens of R / number (radius of curvature divided by the clear aperture of the spherical surface ratio between them). Unfortunately, for lens with diameter greater than 300 mm, the device is limited by the size of the holding fixture lenses or space. This paper aims to provide a novel surface contour detection method and machine, named "CMM spherometry by probe compensation," to measure the radius and thickness of the curvature of the optical surface by a coordinate measurement machine (CMM). In order to obtain more accurate optimization results, we used probe and temperature compensation to discuss the effect. The trace samples and the measurement results of CMM and the centering machine, which has top and bottom autocollimators, are compared.

  8. Design and characterization of dual-curvature 1.5-dimensional high-intensity focused ultrasound phased-array transducer.

    PubMed

    Chen, Gin-Shin; Lin, Che-Yu; Jeong, Jong Seob; Cannata, Jonathan M; Lin, Win-Li; Chang, Hsu; Shung, K Kirk

    2012-01-01

    A dual-curvature focused ultrasound phased-array transducer with a symmetric control has been developed for noninvasive ablative treatment of tumors. The 1.5-D array was constructed in-house and the electro-acoustic conversion efficiency was measured to be approximately 65%. In vitro experiments demonstrated that the array uses 256 independent elements to achieve 2-D wide-range high-intensity electronic focusing.

  9. Forman curvature for complex networks

    NASA Astrophysics Data System (ADS)

    Sreejith, R. P.; Mohanraj, Karthikeyan; Jost, Jürgen; Saucan, Emil; Samal, Areejit

    2016-06-01

    We adapt Forman’s discretization of Ricci curvature to the case of undirected networks, both weighted and unweighted, and investigate the measure in a variety of model and real-world networks. We find that most nodes and edges in model and real networks have a negative curvature. Furthermore, the distribution of Forman curvature of nodes and edges is narrow in random and small-world networks, while the distribution is broad in scale-free and real-world networks. In most networks, Forman curvature is found to display significant negative correlation with degree and centrality measures. However, Forman curvature is uncorrelated with clustering coefficient in most networks. Importantly, we find that both model and real networks are vulnerable to targeted deletion of nodes with highly negative Forman curvature. Our results suggest that Forman curvature can be employed to gain novel insights on the organization of complex networks.

  10. Experimental analysis of the effect of vegetation on flow and bed shear stress distribution in high-curvature bends

    NASA Astrophysics Data System (ADS)

    Termini, Donatella

    2016-12-01

    The cross-sectional circulation, which develops in meandering bends, exerts an important role in velocity and the boundary shear stress redistributions. This paper considers the effect of vegetation on cross-sectional flow and bed shear distribution along a high-curvature bend. The analysis is conducted with the aid of data collected in a large-amplitude meandering flume during a reference experiment without vegetation and an experiment with vegetation on the bed. The results show that the presence of vegetation modifies the curvature-induced flow pattern and the directionality of turbulent structures. In fact, in the presence of vegetation, the turbulent structures tend to develop within and between the vegetated elements. The pattern of cross-sectional flow, modified by the presence of vegetation, affects the bed shear stress distribution along the bend so that the core of the highest value of the bed shear stress does not reach the outer bank.

  11. A flexure-based steerable needle: high curvature with reduced tissue damage.

    PubMed

    Swaney, Philip J; Burgner, Jessica; Gilbert, Hunter B; Webster, Robert J

    2013-04-01

    In the quest to design higher curvature bevel-steered needles, kinked bevel-tips have been one of the most successful approaches yet proposed. However, the price to be paid for enhancing steerability in this way has been increased tissue damage, since the prebent tip cuts a local helical path into tissue when axially rotated. This is problematic when closed-loop control is desired, because the controller will typically require the needle to rotate rapidly, and it is particularly problematic when duty cycling (i.e., continual needle spinning) is used to adjust curvature. In this paper, we propose a new flexure-based needle tip design that provides the enhanced steerability of kinked bevel-tip needles, while simultaneously minimizing tissue damage.

  12. A Flexure-Based Steerable Needle: High Curvature With Reduced Tissue Damage

    PubMed Central

    Burgner, Jessica; Gilbert, Hunter B.; Webster, Robert J.

    2013-01-01

    In the quest to design higher curvature bevel-steered needles, kinked bevel-tips have been one of the most successful approaches yet proposed. However, the price to be paid for enhancing steerability in this way has been increased tissue damage, since the prebent tip cuts a local helical path into tissue when axially rotated. This is problematic when closed-loop control is desired, because the controller will typically require the needle to rotate rapidly, and it is particularly problematic when duty cycling (i.e., continual needle spinning) is used to adjust curvature. In this paper, we propose a new flexure-based needle tip design that provides the enhanced steerability of kinked bevel-tip needles, while simultaneously minimizing tissue damage. PMID:23204267

  13. Curvature adaptive optics and low light imaging

    NASA Astrophysics Data System (ADS)

    Ftaclas, C.; Chun, M.; Kuhn, J.; Ritter, J.

    We review the basic approach of curvature adaptive optics (AO) and show how its many advantages arise. A curvature wave front sensor (WFS) measures exactly what a curvature deformable mirror (DM) generates. This leads to the computational and operational simplicity of a nearly diagonal control matrix. The DM automatically reconstructs the wave front based on WFS curvature measurements. Thus, there is no formal wave front reconstruction. This poses an interesting challenge to post-processing of AO images. Physical continuity of the DM and the reconstruction of phase from wave front curvature data assure that each actuated region of the DM corrects local phase, tip-tilt and focus. This gain in per-channel correction efficiency, combined with the need for only one pixel per channel detector reads in the WFS allows the use of photon counting detectors for wave front sensing. We note that the use of photon counting detectors implies penalty-free combination of correction channels either in the WFS or on the DM. This effectively decouples bright and faint source performance in that one no longer predicts the other. The application of curvature AO to the low light moving target detection problem, and explore the resulting challenges to components and control systems. Rapidly moving targets impose high-speed operation posing new requirements unique to curvature components. On the plus side, curvature wave front sensors, unlike their Shack-Hartmann counterparts, are tunable for optimum sensitivity to seeing and we are examining autonomous optimization of the WFS to respond to rapid changes in seeing.

  14. Curvature Cosmology

    NASA Astrophysics Data System (ADS)

    Crawford, David F.

    Curvature Cosmology proposes a new cosmological model very different from, and more elegant than, the Big-Bang Theory. Curvature Cosmology is based on two major hypotheses that Hubble redshift is due to an interaction of photons with curved spacetime and that there is a pressure that acts to stabilise expansion and provides a static, stable universe. The main focus of this book is to describe these two hypotheses in detail and to examine all relevant cosmological data in the context of this new model of the universe. This model proposes that, though evolution of stars and galaxies is evident, the statistical properties of the universe are the same at all places and at all times. In short, the universe is ageless, has no defined beginning (unlike the Big-Bang model), and carries no evidence of expansion, despite the changeability of its components. Curvature Cosmology calls for a paradigm shift in current cosmology and requires at least basic (if not more complex) knowledge of past and current cosmological models and equations.

  15. A hybrid 3D region growing and 4D curvature analysis-based automatic abdominal blood vessel segmentation through contrast enhanced CT

    NASA Astrophysics Data System (ADS)

    Maklad, Ahmed S.; Matsuhiro, Mikio; Suzuki, Hidenobu; Kawata, Yoshiki; Niki, Noboru; Shimada, Mitsuo; Iinuma, Gen

    2017-03-01

    In abdominal disease diagnosis and various abdominal surgeries planning, segmentation of abdominal blood vessel (ABVs) is a very imperative task. Automatic segmentation enables fast and accurate processing of ABVs. We proposed a fully automatic approach for segmenting ABVs through contrast enhanced CT images by a hybrid of 3D region growing and 4D curvature analysis. The proposed method comprises three stages. First, candidates of bone, kidneys, ABVs and heart are segmented by an auto-adapted threshold. Second, bone is auto-segmented and classified into spine, ribs and pelvis. Third, ABVs are automatically segmented in two sub-steps: (1) kidneys and abdominal part of the heart are segmented, (2) ABVs are segmented by a hybrid approach that integrates a 3D region growing and 4D curvature analysis. Results are compared with two conventional methods. Results show that the proposed method is very promising in segmenting and classifying bone, segmenting whole ABVs and may have potential utility in clinical use.

  16. Curvature sensor based on a Fabry-Perot interferometer

    NASA Astrophysics Data System (ADS)

    Monteiro, Catarina; Ferreira, Marta S.; Kobelke, Jens; Schuster, Kay; Bierlich, Jörg; Frazão, Orlando

    2016-05-01

    A curvature sensor based on a Fabry-Perot interferometer is proposed. A capillary tube of silica is fusion spliced between two single mode fibers, producing a Fabry-Perot cavity. The light propagates in air, when passing through the capillary tube. Two different cavities are subjected to curvature and temperature. The cavity with shorter length shows insensitivity to both measurands. The larger cavity shows two operating regions for curvature measurement, where a linear response is shown, with a maximum sensitivity of 18.77pm/m-1 for the high curvature radius range. When subjected to temperature, the sensing head produces a similar response for different curvature radius, with a sensitivity of 0.87pm/°C.

  17. 3D curvature of muscle fascicles in triceps surae.

    PubMed

    Rana, Manku; Hamarneh, Ghassan; Wakeling, James M

    2014-12-01

    Muscle fascicles curve along their length, with the curvatures occurring around regions of high intramuscular pressure, and are necessary for mechanical stability. Fascicles are typically considered to lie in fascicle planes that are the planes visualized during dissection or two-dimensional (2D) ultrasound scans. However, it has previously been predicted that fascicles must curve in three-dimensional (3D) and thus the fascicle planes may actually exist as 3D sheets. 3D fascicle curvatures have not been explored in human musculature. Furthermore, if the fascicles do not lie in 2D planes, then this has implications for architectural measures that are derived from 2D ultrasound scans. The purpose of this study was to quantify the 3D curvatures of the muscle fascicles and fascicle sheets within the triceps surae muscles and to test whether these curvatures varied among different contraction levels, muscle length, and regions within the muscle. Six male subjects were tested for three torque levels (0, 30, and 60% maximal voluntary contraction) and four ankle angles (-15, 0, 15, and 30° plantar flexion), and fascicles were imaged using 3D ultrasound techniques. The fascicle curvatures significantly increased at higher ankle torques and shorter muscle lengths. The fascicle sheet curvatures were of similar magnitude to the fascicle curvatures but did not vary between contractions. Fascicle curvatures were regionalized within each muscle with the curvature facing the deeper aponeuroses, and this indicates a greater intramuscular pressure in the deeper layers of muscles. Muscle architectural measures may be in error when using 2D images for complex geometries such as the soleus.

  18. Effect of the collision-induced trajectory curvature on molecular line shifts in the visible region of the spectrum

    NASA Astrophysics Data System (ADS)

    Bykov, A. D.; Lavrent'eva, N. N.; Sinitsa, L. N.

    1992-09-01

    The paper is concerned with the effect of trajectory curvature in calculations of the vibrational-rotational lines of molecules. The first-order term of the interruption function is calculated using exact solutions of classical dynamic equations. A universal function for two reduced arguments is obtained which is independent of the potential parameter and initial collision conditions; the function is capable of accounting for actual trajectories. Errors resulting from the use of a linear trajectory model are estimated for water vapor and methane expanded by various gases.

  19. Curvature, Hydrogen, Q

    SciTech Connect

    Wallace, John Paul; Myneni, Ganapati Rao; Pike, Robert

    2011-03-31

    The manufacturing of niobium SRF accelerator cavities is plagued by a mobile point defect, hydrogen. For efficient accelerator operation, niobium must function at both high electric and magnetic fields, and is compromised if magnetic impurities are located in the surface regions of the material. The finding that trace hydrogen in niobium can produce structures with magnetic properties is a feature that is not acceptable for a high performance cavity. X-ray diffraction has proved to be the key tool in assessing irreversible process damage to the niobium substrate. In future generations of accelerators, niobium will actually be merely the substrate for more effective superconductors that will allow for more efficient operation. The substrate analogy to the silicon wafer industry is useful since for niobium it may be possible to avoid some of the mistakes made in silicon technology. Because hydrogen attacks niobium on a number of different size scales, there is an inherent complexity in the trouble sources. There are also features in cavity design that are benign, such as local curvature considerations, requiring a fully non symmetric analysis of current flow to be appreciated.

  20. Curvature, Hydrogen, Q

    SciTech Connect

    John Paul Wallace, Ganapati Rao Myneni, and Robert Pike

    2011-03-01

    The manufacturing of niobium SRF accelerator cavities is plagued by a mobile point defect, hydrogen. For efficient accelerator operation, niobium must function at both high electric and magnetic fields, and is compromised if magnetic impurities are located in the surface regions of the material. The finding that trace hydrogen in niobium can produce structures with magnetic properties is a feature that is not acceptable for a high performance cavity. X-ray diffraction has proved to be the key tool in assessing irreversible process damage to the niobium substrate. In future generations of accelerators, niobium will actually be merely the substrate for more effective superconductors that will allow for more efficient operation. The substrate analogy to the silicon wafer industry is useful since for niobium it may be possible to avoid some of the mistakes made in silicon technology. Because hydrogen attacks niobium on a number of different size scales, there is an inherent complexity in the trouble sources. There are also features in cavity design that are benign, such as local curvature considerations, requiring a fully non symmetric analysis of current flow to be appreciated.

  1. Image curvature correction and cosmic removal for high-throughput dispersive Raman spectroscopy.

    PubMed

    Zhao, Jun

    2003-11-01

    A key factor determining the sensitivity of a Raman spectrometer is the usable detection area, which is the product of the usable slit width and the height. For the majority of process Raman samples, the larger the sampling area is, the more the scattered Raman signal can be gathered. On a multi-channel-detector-based dispersive spectrometer, a given spectral resolution limits the slit width. Extending the slit height using a straight slit usually causes the image to be curved on the detector due to optical effects. If left untreated, the curved slit image will degrade the peak shape and spectral resolution; therefore, the slit height must also be kept small if this negative effect is to be avoided. The mechanism of the curvature formation was analyzed for an on-axis-lens-based spectrograph, and a correction technique was developed to generate a straight slit image on the charge-coupled device (CCD). This allowed a large portion of the CCD height to be used without degrading the spectral resolution. A large fiber bundle was usable instead of a single small core fiber, generating significant increase in collected signal strength in clear or translucent samples. The straight image also enabled a new cosmic spike removal method, wherein the CCD image was divided into multiple strips, and a comparison among them allowed the identification and removal of cosmic spikes in a single CCD integration. On the contrary, many existing cosmic removal methods rely on comparison of multiple sequentially acquired spectra, potentially introducing artifacts, particularly when the spectral features are changing.

  2. Spacetime curvature and the Higgs stability during inflation.

    PubMed

    Herranen, M; Markkanen, T; Nurmi, S; Rajantie, A

    2014-11-21

    It has been claimed that the electroweak vacuum may be unstable during inflation due to large fluctuations of the order H in the case of a high inflationary scale as suggested by BICEP2. We compute the standard model Higgs effective potential including UV-induced curvature corrections at one-loop level. We find that for a high inflationary scale a large curvature mass is generated due to renormalization group running of nonminimal coupling ξ, which either stabilizes the potential against fluctuations for ξEW≳6×10(-2), or destabilizes it for ξEW≲2×10(-2) when the generated curvature mass is negative. Only in the narrow intermediate region may the effect of the curvature mass be significantly smaller.

  3. Curvature Interaction in Collective Space

    NASA Astrophysics Data System (ADS)

    Herrmann, Richard

    2012-12-01

    For the Riemannian space, built from the collective coordinates used within nuclear models, an additional interaction with the metric is investigated, using the collective equivalent to Einstein's curvature scalar. The coupling strength is determined using a fit with the AME2003 ground state masses. An extended finite-range droplet model including curvature is introduced, which generates significant improvements for light nuclei and nuclei in the trans-fermium region.

  4. Defining the free-energy landscape of curvature-inducing proteins on membrane bilayers

    PubMed Central

    Tourdot, Richard W.; Ramakrishnan, N.; Radhakrishnan, Ravi

    2015-01-01

    Curvature-sensing and curvature-remodeling proteins, such as Amphiphysin, Epsin, and Exo70, are known to reshape cell membranes, and this remodeling event is essential for key biophysical processes such as tubulation, exocytosis, and endocytosis. Curvature-inducing proteins can act as curvature sensors; they aggregate to membrane regions matching their intrinsic curvature; as well as induce curvature in cell membranes to stabilize emergent high curvature, nonspherical, structures such as tubules, discs, and caveolae. A definitive understanding of the interplay between protein recruitment and migration, the evolution of membrane curvature, and membrane morphological transitions is emerging but remains incomplete. Here, within a continuum framework and using the machinery of Monte Carlo simulations, we introduce and compare three free-energy methods to delineate the free-energy landscape of curvature-inducing proteins on bilayer membranes. We demonstrate the utility of the Widom test particle (or field) insertion methodology in computing the excess chemical potentials associated with curvature-inducing proteins on the membrane—in particular, we use this method to track the onset of morphological transitions in the membrane at elevated protein densities. We validate this approach by comparing the results from the Widom method with those of thermodynamic integration and Bennett acceptance ratio methods. Furthermore, the predictions from the Widom method have been tested against analytical calculations of the excess chemical potential at infinite dilution. Our results are useful in precisely quantifying the free-energy landscape, and also in determining the phase boundaries associated with curvature-induction, curvature-sensing, and morphological transitions. This approach can be extended to studies exploring the role of thermal fluctuations and other external (control) variables, such as membrane excess area, in shaping curvature-mediated interactions on bilayer

  5. Defining the free-energy landscape of curvature-inducing proteins on membrane bilayers

    NASA Astrophysics Data System (ADS)

    Tourdot, Richard W.; Ramakrishnan, N.; Radhakrishnan, Ravi

    2014-08-01

    Curvature-sensing and curvature-remodeling proteins, such as Amphiphysin, Epsin, and Exo70, are known to reshape cell membranes, and this remodeling event is essential for key biophysical processes such as tubulation, exocytosis, and endocytosis. Curvature-inducing proteins can act as curvature sensors; they aggregate to membrane regions matching their intrinsic curvature; as well as induce curvature in cell membranes to stabilize emergent high curvature, nonspherical, structures such as tubules, discs, and caveolae. A definitive understanding of the interplay between protein recruitment and migration, the evolution of membrane curvature, and membrane morphological transitions is emerging but remains incomplete. Here, within a continuum framework and using the machinery of Monte Carlo simulations, we introduce and compare three free-energy methods to delineate the free-energy landscape of curvature-inducing proteins on bilayer membranes. We demonstrate the utility of the Widom test particle (or field) insertion methodology in computing the excess chemical potentials associated with curvature-inducing proteins on the membrane—in particular, we use this method to track the onset of morphological transitions in the membrane at elevated protein densities. We validate this approach by comparing the results from the Widom method with those of thermodynamic integration and Bennett acceptance ratio methods. Furthermore, the predictions from the Widom method have been tested against analytical calculations of the excess chemical potential at infinite dilution. Our results are useful in precisely quantifying the free-energy landscape, and also in determining the phase boundaries associated with curvature-induction, curvature-sensing, and morphological transitions. This approach can be extended to studies exploring the role of thermal fluctuations and other external (control) variables, such as membrane excess area, in shaping curvature-mediated interactions on bilayer

  6. Pre-compensation for continuous-path running trajectory error in high-speed machining of parts with varied curvature features

    NASA Astrophysics Data System (ADS)

    Jia, Zhenyuan; Song, Dening; Ma, Jianwei; Gao, Yuanyuan

    2017-01-01

    Parts with varied curvature features play increasingly critical roles in engineering, and are often machined under high-speed continuous-path running mode to ensure the machining efficiency. However, the continuous-path running trajectory error is significant during high-feed-speed machining, which seriously restricts the machining precision for such parts with varied curvature features. In order to reduce the continuous-path running trajectory error without sacrificing the machining efficiency, a pre-compensation method for the trajectory error is proposed. Based on the formation mechanism of the continuous-path running trajectory error analyzed, this error is estimated in advance by approximating the desired toolpath with spline curves. Then, an iterative error pre-compensation method is presented. By machining with the regenerated toolpath after pre-compensation instead of the uncompensated toolpath, the continuous-path running trajectory error can be effectively decreased without the reduction of the feed speed. To demonstrate the feasibility of the proposed pre-compensation method, a heart curve toolpath that possesses varied curvature features is employed. Experimental results indicate that compared with the uncompensated processing trajectory, the maximum and average machining errors for the pre-compensated processing trajectory are reduced by 67.19% and 82.30%, respectively. An easy to implement solution for high efficiency and high precision machining of the parts with varied curvature features is provided.

  7. A major QTL controls susceptibility to spinal curvature in the curveback guppy

    PubMed Central

    2011-01-01

    Background Understanding the genetic basis of heritable spinal curvature would benefit medicine and aquaculture. Heritable spinal curvature among otherwise healthy children (i.e. Idiopathic Scoliosis and Scheuermann kyphosis) accounts for more than 80% of all spinal curvatures and imposes a substantial healthcare cost through bracing, hospitalizations, surgery, and chronic back pain. In aquaculture, the prevalence of heritable spinal curvature can reach as high as 80% of a stock, and thus imposes a substantial cost through production losses. The genetic basis of heritable spinal curvature is unknown and so the objective of this work is to identify quantitative trait loci (QTL) affecting heritable spinal curvature in the curveback guppy. Prior work with curveback has demonstrated phenotypic parallels to human idiopathic-type scoliosis, suggesting shared biological pathways for the deformity. Results A major effect QTL that acts in a recessive manner and accounts for curve susceptibility was detected in an initial mapping cross on LG 14. In a second cross, we confirmed this susceptibility locus and fine mapped it to a 5 cM region that explains 82.6% of the total phenotypic variance. Conclusions We identify a major QTL that controls susceptibility to curvature. This locus contains over 100 genes, including MTNR1B, a candidate gene for human idiopathic scoliosis. The identification of genes associated with heritable spinal curvature in the curveback guppy has the potential to elucidate the biological basis of spinal curvature among humans and economically important teleosts. PMID:21269476

  8. Porous membrane with high curvature, three-dimensional heat-resistance skeleton: a new and practical separator candidate for high safety lithium ion battery

    PubMed Central

    Shi, Junli; Xia, Yonggao; Yuan, Zhizhang; Hu, Huasheng; Li, Xianfeng; Zhang, Huamin; Liu, Zhaoping

    2015-01-01

    Separators with high reliability and security are in urgent demand for the advancement of high performance lithium ion batteries. Here, we present a new and practical porous membrane with three-dimension (3D) heat-resistant skeleton and high curvature pore structure as a promising separator candidate to facilitate advances in battery safety and performances beyond those obtained from the conventional separators. The unique material properties combining with the well-developed structural characteristics enable the 3D porous skeleton to own several favorable properties, including superior thermal stability, good wettability with liquid electrolyte, high ion conductivity and internal short-circuit protection function, etc. which give rise to acceptable battery performances. Considering the simply and cost-effective preparation process, the porous membrane is deemed to be an interesting direction for the future lithium ion battery separator. PMID:25653104

  9. Porous membrane with high curvature, three-dimensional heat-resistance skeleton: a new and practical separator candidate for high safety lithium ion battery.

    PubMed

    Shi, Junli; Xia, Yonggao; Yuan, Zhizhang; Hu, Huasheng; Li, Xianfeng; Zhang, Huamin; Liu, Zhaoping

    2015-02-05

    Separators with high reliability and security are in urgent demand for the advancement of high performance lithium ion batteries. Here, we present a new and practical porous membrane with three-dimension (3D) heat-resistant skeleton and high curvature pore structure as a promising separator candidate to facilitate advances in battery safety and performances beyond those obtained from the conventional separators. The unique material properties combining with the well-developed structural characteristics enable the 3D porous skeleton to own several favorable properties, including superior thermal stability, good wettability with liquid electrolyte, high ion conductivity and internal short-circuit protection function, etc. which give rise to acceptable battery performances. Considering the simply and cost-effective preparation process, the porous membrane is deemed to be an interesting direction for the future lithium ion battery separator.

  10. Single Lipid Molecule Dynamics on Supported Lipid Bilayers with Membrane Curvature

    PubMed Central

    Cheney, Philip P.; Weisgerber, Alan W.; Feuerbach, Alec M.; Knowles, Michelle K.

    2017-01-01

    The plasma membrane is a highly compartmentalized, dynamic material and this organization is essential for a wide variety of cellular processes. Nanoscale domains allow proteins to organize for cell signaling, endo- and exocytosis, and other essential processes. Even in the absence of proteins, lipids have the ability to organize into domains as a result of a variety of chemical and physical interactions. One feature of membranes that affects lipid domain formation is membrane curvature. To directly test the role of curvature in lipid sorting, we measured the accumulation of two similar lipids, 1,2-Dihexadecanoyl-sn-glycero-3-phosphoethanolamine (DHPE) and hexadecanoic acid (HDA), using a supported lipid bilayer that was assembled over a nanopatterned surface to obtain regions of membrane curvature. Both lipids studied contain 16 carbon, saturated tails and a head group tag for fluorescence microscopy measurements. The accumulation of lipids at curvatures ranging from 28 nm to 55 nm radii was measured and fluorescein labeled DHPE accumulated more than fluorescein labeled HDA at regions of membrane curvature. We then tested whether single biotinylated DHPE molecules sense curvature using single particle tracking methods. Similar to groups of fluorescein labeled DHPE accumulating at curvature, the dynamics of single molecules of biotinylated DHPE was also affected by membrane curvature and highly confined motion was observed. PMID:28294967

  11. Regional High School Senior Survey.

    ERIC Educational Resources Information Center

    Day, Philip R., Jr.

    In order to identify the educational needs and aspirations of graduating high school seniors in the service region of the University of Maine at Augusta, a survey instrument was designed and administered to 1,950 seniors at 19 institutions. In all, 1,744 completed surveys were returned, a 92 percent response rate. The data are sub-grouped into…

  12. Spatial curvature endgame: Reaching the limit of curvature determination

    NASA Astrophysics Data System (ADS)

    Leonard, C. Danielle; Bull, Philip; Allison, Rupert

    2016-07-01

    Current constraints on spatial curvature show that it is dynamically negligible: |ΩK|≲5 ×10-3 (95% C.L.). Neglecting it as a cosmological parameter would be premature however, as more stringent constraints on ΩK at around the 10-4 level would offer valuable tests of eternal inflation models and probe novel large-scale structure phenomena. This precision also represents the "curvature floor," beyond which constraints cannot be meaningfully improved due to the cosmic variance of horizon-scale perturbations. In this paper, we discuss what future experiments will need to do in order to measure spatial curvature to this maximum accuracy. Our conservative forecasts show that the curvature floor is unreachable—by an order of magnitude—even with Stage IV experiments, unless strong assumptions are made about dark energy evolution and the Λ CDM parameter values. We also discuss some of the novel problems that arise when attempting to constrain a global cosmological parameter like ΩK with such high precision. Measuring curvature down to this level would be an important validation of systematics characterization in high-precision cosmological analyses.

  13. An in-fiber Mach-Zehnder interferometer based on dual side-hole fiber for highly sensitive measurement of curvature

    NASA Astrophysics Data System (ADS)

    Ouyang, Xiaowei; Guo, Huiyong; Zheng, Zhou; Ding, Liyun; Zhou, Ai

    2017-04-01

    An in-fiber Mach-Zehnder interferometer (MZI) based on dual side-hole fiber (DSHF) was demonstrated for highly sensitive measurement of curvature. The MZI-based bending sensor is fabricated by fusion splicing a piece of DSHF in between two standard single mode fibers (SMF) with cladding alignment. Due to the existence of the two air holes and the asymmetrical cross-section of the DSHF, the DSHF-based MZI is a core-cladding interferometer which is sensitive to directional bending. The bending characteristics are investigated experimentally within the curvature range of 0-8.172m-1. The bending sensitivities of the sensor are respectively 1.464 nm/m-1 and -1.394 nm/m-1 at their two opposite bending directions.

  14. Cell descent caused by boundary curvature of a high topographical structure for a device that changes cell density

    NASA Astrophysics Data System (ADS)

    Okutani, Chihiro; Wagatsuma, Akira; Mabuchi, Kunihiko; Hoshino, Takayuki

    2017-06-01

    Noninvasive techniques of controlling cell migration on substrates are widely useful for tissue engineering. However, the cell migration controls of previous studies were not enough for collecting cells locally. To solve this problem, in this work, we report the C2C12 mouse myoblast cell migration difference (descend or be repelled) by changing the curvature of the boundary of a topographical structure when the cells move from a flat surface to the boundary. 69% of the cells coming across a round boundary — the curvature radius of which was 50 µm — descended into the hole. In contrast, no cells descended into a groove with a linear boundary. Moreover, we demonstrated the cell spatial density change from the difference at the boundary. This finding will provide a new device that will enable us to manipulate spatial cell density noninvasively for tissue engineering.

  15. On the Weyl curvature hypothesis

    SciTech Connect

    Stoica, Ovidiu Cristinel

    2013-11-15

    The Weyl curvature hypothesis of Penrose attempts to explain the high homogeneity and isotropy, and the very low entropy of the early universe, by conjecturing the vanishing of the Weyl tensor at the Big-Bang singularity. In previous papers it has been proposed an equivalent form of Einstein’s equation, which extends it and remains valid at an important class of singularities (including in particular the Schwarzschild, FLRW, and isotropic singularities). Here it is shown that if the Big-Bang singularity is from this class, it also satisfies the Weyl curvature hypothesis. As an application, we study a very general example of cosmological models, which generalizes the FLRW model by dropping the isotropy and homogeneity constraints. This model also generalizes isotropic singularities, and a class of singularities occurring in Bianchi cosmologies. We show that the Big-Bang singularity of this model is of the type under consideration, and satisfies therefore the Weyl curvature hypothesis. -- Highlights: •The singularities we introduce are described by finite geometric/physical objects. •Our singularities have smooth Riemann and Weyl curvatures. •We show they satisfy Penrose’s Weyl curvature hypothesis (Weyl=0 at singularities). •Examples: FLRW, isotropic singularities, an extension of Schwarzschild’s metric. •Example: a large class of singularities which may be anisotropic and inhomogeneous.

  16. Membrane curvature at a glance

    PubMed Central

    McMahon, Harvey T.; Boucrot, Emmanuel

    2015-01-01

    ABSTRACT Membrane curvature is an important parameter in defining the morphology of cells, organelles and local membrane subdomains. Transport intermediates have simpler shapes, being either spheres or tubules. The generation and maintenance of curvature is of central importance for maintaining trafficking and cellular functions. It is possible that local shapes in complex membranes could help to define local subregions. In this Cell Science at a Glance article and accompanying poster, we summarize how generating, sensing and maintaining high local membrane curvature is an active process that is mediated and controlled by specialized proteins using general mechanisms: (i) changes in lipid composition and asymmetry, (ii) partitioning of shaped transmembrane domains of integral membrane proteins or protein or domain crowding, (iii) reversible insertion of hydrophobic protein motifs, (iv) nanoscopic scaffolding by oligomerized hydrophilic protein domains and, finally, (v) macroscopic scaffolding by the cytoskeleton with forces generated by polymerization and by molecular motors. We also summarize some of the discoveries about the functions of membrane curvature, where in addition to providing cell or organelle shape, local curvature can affect processes like membrane scission and fusion as well as protein concentration and enzyme activation on membranes. PMID:25774051

  17. Spatial curvature falsifies eternal inflation

    SciTech Connect

    Kleban, Matthew; Schillo, Marjorie E-mail: mls604@nyu.edu

    2012-06-01

    Inflation creates large-scale cosmological density perturbations that are characterized by an isotropic, homogeneous, and Gaussian random distribution about a locally flat background. Even in a flat universe, the spatial curvature measured within one Hubble volume receives contributions from long wavelength perturbations, and will not in general be zero. These same perturbations determine the Cosmic Microwave Background (CMB) temperature fluctuations, which are O(10{sup −5}). Consequently, the low-l multipole moments in the CMB temperature map predict the value of the measured spatial curvature Ω{sub k}. On this basis we argue that a measurement of |Ω{sub k}| > 10{sup −4} would rule out slow-roll eternal inflation in our past with high confidence, while a measurement of Ω{sub k} < −10{sup −4} (which is positive curvature, a locally closed universe) rules out false-vacuum eternal inflation as well, at the same confidence level. In other words, negative curvature (a locally open universe) is consistent with false-vacuum eternal inflation but not with slow-roll eternal inflation, and positive curvature falsifies both. Near-future experiments will dramatically extend the sensitivity of Ω{sub k} measurements and constitute a sharp test of these predictions.

  18. Studying Biomolecule Localization by Engineering Bacterial Cell Wall Curvature

    PubMed Central

    Renner, Lars D.; Eswaramoorthy, Prahathees; Ramamurthi, Kumaran S.; Weibel, Douglas B.

    2013-01-01

    In this article we describe two techniques for exploring the relationship between bacterial cell shape and the intracellular organization of proteins. First, we created microchannels in a layer of agarose to reshape live bacterial cells and predictably control their mean cell wall curvature, and quantified the influence of curvature on the localization and distribution of proteins in vivo. Second, we used agarose microchambers to reshape bacteria whose cell wall had been chemically and enzymatically removed. By combining microstructures with different geometries and fluorescence microscopy, we determined the relationship between bacterial shape and the localization for two different membrane-associated proteins: i) the cell-shape related protein MreB of Escherichia coli, which is positioned along the long axis of the rod-shaped cell; and ii) the negative curvature-sensing cell division protein DivIVA of Bacillus subtilis, which is positioned primarily at cell division sites. Our studies of intracellular organization in live cells of E. coli and B. subtilis demonstrate that MreB is largely excluded from areas of high negative curvature, whereas DivIVA localizes preferentially to regions of high negative curvature. These studies highlight a unique approach for studying the relationship between cell shape and intracellular organization in intact, live bacteria. PMID:24391905

  19. Sculpting membranes: a mechanism of curvature generation by proteins

    NASA Astrophysics Data System (ADS)

    Campelo, Felix

    2010-03-01

    A wide spectrum of intracellular processes is dependent on the ability of cells to dynamically regulate membrane shape. Membrane bending by proteins is necessary for the generation of intracellular transport carriers and for the maintenance of otherwise intrinsically unstable regions of high membrane curvature in cell organelles. Understanding the mechanisms by which proteins curve membranes is therefore of primary importance. Crescent shaped N-BAR domains containing amphipathic helices can induce membrane curvature by two mechanisms: the scaffolding mechanism due to the very shape of the BAR dimer, and the hydrophobic insertion mechanism by which small shallow inclusions penetrate the membrane matrix and act as a wedge changing the local membrane curvature. We will focus on this latter mechanism, and study it from a quantitative point of view. We use an elastic model of the lipid bilayer, taking into account the internal strains and stresses generated by the presence of an inclusion. We show that large membrane curvatures found in in vitro experiments can be ascribed to this mechanism, and that shallow insertions are more powerful curvature generators than lipids.

  20. Sorting of Lipids and Proteins in Membrane Curvature Gradients

    PubMed Central

    Tian, A.; Baumgart, T.

    2009-01-01

    The sorting of lipids and proteins in cellular trafficking pathways is a process of central importance in maintaining compartmentalization in eukaryotic cells. However, the mechanisms behind these sorting phenomena are currently far from being understood. Among several mechanistic suggestions, membrane curvature has been invoked as a means to segregate lipids and proteins in cellular sorting centers. To assess this hypothesis, we investigate the sorting of lipid analog dye trace components between highly curved tubular membranes and essentially flat membranes of giant unilamellar vesicles. Our experimental findings indicate that intracellular lipid sorting, contrary to frequent assumptions, is unlikely to occur by lipids fitting into membrane regions of appropriate curvature. This observation is explained in the framework of statistical mechanical lattice models that show that entropy, rather than curvature energy, dominates lipid distribution in the absence of strongly preferential lateral intermolecular interactions. Combined with previous findings of curvature induced phase segregation, we conclude that lipid cooperativity is required to enable efficient sorting. In contrast to lipid analog dyes, the peripheral membrane binding protein Cholera toxin subunit B is effectively curvature-sorted. The sorting of Cholera toxin subunit B is rationalized by statistical models. We discuss the implications of our findings for intracellular sorting mechanisms. PMID:19348750

  1. Novel alleles of the VERNALIZATION1 genes in wheat are associated with modulation of DNA curvature and flexibility in the promoter region.

    PubMed

    Muterko, Alexandr; Kalendar, Ruslan; Salina, Elena

    2016-01-27

    In wheat, the vernalization requirement is mainly controlled by the VRN genes. Different species of hexaploid and tetraploid wheat are widely used as genetic source for new mutant variants and alleles for fundamental investigations and practical breeding programs. In this study, VRN-A1 and VRN-B1 were analysed for 178 accessions representing six tetraploid wheat species (Triticum dicoccoides, T. dicoccum, T. turgidum, T. polonicum, T. carthlicum, T. durum) and five hexaploid species (T. compactum, T. sphaerococcum, T. spelta, T. macha, T. vavilovii). Novel allelic variants in the promoter region of VRN-A1 and VRN-B1 were identified based on the change in curvature and flexibility of the DNA molecules. The new variants of VRN-A1 (designated as Vrn-A1a.2, Vrn-A1b.2 - Vrn-A1b.6 and Vrn-A1i) were found to be widely distributed in hexaploid and tetraploid wheat, and in fact were predominant over the known VRN-A1 alleles. The greatest diversity of the new variants of VRN-B1 (designated as VRN-B1.f, VRN-B1.s and VRN-B1.m) was found in the tetraploid and some hexaploid wheat species. For the first time, minor differences within the sequence motif known as the VRN-box of VRN1 were correlated with wheat growth habit. Thus, vrn-A1b.3 and vrn-A1b.4 were revealed in winter wheat in contrast to Vrn-A1b.2, Vrn-A1b.5, Vrn-A1b.6 and Vrn-A1i. It was found that single nucleotide mutation in the VRN-box can influence the vernalization requirement and growth habit of wheat. Our data suggest that both the A-tract and C-rich segment within the VRN-box contribute to its functionality, and provide a new view of the hypothesised role of the VRN-box in regulating transcription of the VRN1 genes. Specifically, it is proposed that combination of mutations in this region can modulate vernalization sensitivity and flowering time of wheat. New allelic variants of the VRN-A1 and VRN-B1 genes were identified in hexaploid and tetraploid wheat. Mutations in A-tract and C-rich segments within the VRN

  2. Helical Microfilaments with Alternating Imprinted Intrinsic Curvatures.

    PubMed

    Silva, Pedro Emanuel Santos; Godinho, Maria Helena

    2017-03-01

    There has been an intense research for developing techniques that can produce filaments with helical shapes, given the widespread of potential applications. In this work, how helices with different curvatures can be precisely imprinted in microfilaments is shown. It is also shown that using this technique, it is possible to produce, in a single fiber, helices with different curvatures. This striking and innovative behavior is observed when one side of the stretched filaments is irradiated with UV light, modifying the mechanical properties at surface. Upon release, the regions with higher curvature start to curl first, while regions with lower intrinsic curvature remain stretched until start to curl later. The results presented here can be important to understand why structures adopt a helical shape in general, which can be of interest in nanotechnology, biomolecular science, or even to understand why plant filaments curl. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Curvature in solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Wenxia; Hasinska, Kathy; Seabaugh, Matt; Swartz, Scott; Lannutti, John

    At this point in history, curvature is inherent to the laminated components that comprise solid oxide fuel cells (SOFCs). Surprisingly, however, this fact has never been previously quantified in the literature. In addition, potential curvature changes associated with NiO reduction and re-oxidation during operation have not been investigated. In this report, an optical profilometer was employed to non-destructively quantify the surface curvature or cracking behavior observed on a large scale in industrially manufactured cells. This provides insights into the challenges that the component materials face as well as additional appreciation for why, in spite of a concerted effort to commercialize SOFC power generation, all currently manufactured SOFC stacks fail. Our results demonstrate that cracked electrolyte areas (caused by differential sintering) are flatter than uncracked regions. The height of the electrolyte surface ranged from 86 to 289 μm above the baseline following sintering. Reduction typically results in increases in curvature of up to 214 μm. Initial crack density appears to affect curvature evolution during reduction; the higher the crack density, the smaller the curvature increase following reduction at 600 °C. In general, however, we observed that the electrolyte layer is remarkably resistant to further cracking during these typographic changes. Following oxidation at 750 °C, large changes in curvature (up to 280 μm) are noted that appear to be related to the strength of the bond between the electrolyte and the underlying anode.

  4. Relaxation and curvature-induced molecular flows within multicomponent membranes

    NASA Astrophysics Data System (ADS)

    Morris, Richard G.

    2014-06-01

    The quantitative understanding of membranes is still rooted in work performed in the 1970s by Helfrich and others, concerning amphiphilic bilayers. However, most biological membranes contain a wide variety of nonamphiphilic molecules too. Drawing analogy with the physics of nematic-non-nematic mixtures, we present a dynamical (out-of-equilibrium) description of such multicomponent membranes. The approach combines nematohydrodynamics in the linear regime and a proper use of (differential-) geometry. The main result is to demonstrate that one can obtain equations describing a cross-diffusion effect (similar to the Soret and Dufour effects) between curvature and the (in-membrane) flow of amphiphilic molecules relative to nonamphiphilic ones. Surprisingly, the shape of a membrane relaxes according to a simple heat equation in the mean curvature, a process that is accompanied by a simultaneous boost to the diffusion of amphiphiles away from regions of high curvature. The model also predicts the inverse process, by which the forced bending of a membrane induces a flow of amphiphilic molecules towards areas of high curvature. In principle, numerical values for the relevant diffusion coefficients should be verifiable by experiment.

  5. Relaxation and curvature-induced molecular flows within multicomponent membranes.

    PubMed

    Morris, Richard G

    2014-06-01

    The quantitative understanding of membranes is still rooted in work performed in the 1970s by Helfrich and others, concerning amphiphilic bilayers. However, most biological membranes contain a wide variety of nonamphiphilic molecules too. Drawing analogy with the physics of nematic-non-nematic mixtures, we present a dynamical (out-of-equilibrium) description of such multicomponent membranes. The approach combines nematohydrodynamics in the linear regime and a proper use of (differential-) geometry. The main result is to demonstrate that one can obtain equations describing a cross-diffusion effect (similar to the Soret and Dufour effects) between curvature and the (in-membrane) flow of amphiphilic molecules relative to nonamphiphilic ones. Surprisingly, the shape of a membrane relaxes according to a simple heat equation in the mean curvature, a process that is accompanied by a simultaneous boost to the diffusion of amphiphiles away from regions of high curvature. The model also predicts the inverse process, by which the forced bending of a membrane induces a flow of amphiphilic molecules towards areas of high curvature. In principle, numerical values for the relevant diffusion coefficients should be verifiable by experiment.

  6. From voxel to curvature

    NASA Astrophysics Data System (ADS)

    Monga, Olivier; Ayache, Nicholas; Sander, Peter T.

    1991-09-01

    Modern medical image techniques, such as magnetic resonance image (MRI) or x-ray computed tomography provide three dimensional images of internal structures of the body, usually by means of a stack of tomographic images. The first stage in the automatic analysis of such data is 3-D edge detection1,2 which provides points corresponding to the boundaries of the surfaces forming the 3-D structure. The next stage is to characterize the local geometry of these surfaces in order to extract points or lines on which registration and/or tracking procedures can rely.3,4,5,6 This paper presents a pipeline of processes which define a hierarchical description of the second order differential characteristics of the surfaces. The focus is on the theoretical coherence of these levels of representation. Using uncertainty, a link is established between the edge detection and the local surface approximation by addressing the uncertainties inherent to edge detection in 2-D or 3-D images; and how to incorporate these uncertainties into the computation of local geometric models. In particular, calculate the uncertainty of edge location, direction, and magnitude for the 3-D Deriche operator is calculated.1,2 Statistical results are then used as a solid theoretical foundation on which to base subsequent computations, such as the determination of local surface curvature using local geometric models for surface segmentation. From the local fitting, for each edge point the mean and Gaussian curvature, principal curvatures and directions, curvature singularities, lines of curvature singularities, and covariance matrices defining the uncertainties are calculated. Experimental results for real data using two 3-D scanner images of the same organ taken at different positions demonstrate the stability of the mean and Gaussian curvatures. Experimental results for real data showing the determination of local curvature extremes of surfaces extracted from MR images are presented.

  7. Effects of streamline curvature on separation prediction

    NASA Astrophysics Data System (ADS)

    Arolla, Sunil K.; Durbin, Paul A.

    2009-11-01

    In this study, the effects of streamline curvature on prediction of flow separation are investigated. The geometry is a circulation control airfoil, a high-lift configuration that has been under extensive research for more than two decades. A tangential jet is blown over a thick, rounded trailing edge, using the Coanda effect to delay separation. An attempt is made to understand, through numerical simulations, the dynamics of turbulent separation and reattachment on the Coanda surface. Highly curved, attached recirculation regions are seen to form. A physics based curvature correction proposed by Pettersson-Reif et al. (1999) is used in conjunction with ζ-f turbulence model. The chord-based Reynolds number is Re = 10^6. Two jet momentum coefficients of Cμ=0.03 and 0.1 are computed. In this paper, comparisons between the computed and experimental pressure distributions, velocity profiles and the position of flow detachment are presented. Comparisons with other closures such as Menter's SST model are also discussed.

  8. Fiber Fabry-Perot interferometer for curvature sensing

    NASA Astrophysics Data System (ADS)

    Monteiro, Catarina S.; Ferreira, Marta S.; Silva, Susana O.; Kobelke, Jens; Schuster, Kay; Bierlich, Jörg; Frazão, Orlando

    2016-12-01

    A curvature sensor based on an Fabry-Perot (FP) interferometer was proposed. A capillary silica tube was fusion spliced between two single mode fibers, producing an FP cavity. Two FP sensors with different cavity lengths were developed and subjected to curvature and temperature. The FP sensor with longer cavity showed three distinct operating regions for the curvature measurement. Namely, a linear response was shown for an intermediate curvature radius range, presenting a maximum sensitivity of 68.52 pm/m-1. When subjected to temperature, the sensing head produced a similar response for different curvature radii, with a sensitivity varying from 0.84 pm/°C to 0.89 pm/°C, which resulted in a small cross-sensitivity to temperature when the FP sensor was subjected to curvature. The FP cavity with shorter length presented low sensitivity to curvature.

  9. Curvature and torsion in growing actin networks

    NASA Astrophysics Data System (ADS)

    Shaevitz, Joshua W.; Fletcher, Daniel A.

    2008-06-01

    Intracellular pathogens such as Listeria monocytogenes and Rickettsia rickettsii move within a host cell by polymerizing a comet-tail of actin fibers that ultimately pushes the cell forward. This dense network of cross-linked actin polymers typically exhibits a striking curvature that causes bacteria to move in gently looping paths. Theoretically, tail curvature has been linked to details of motility by considering force and torque balances from a finite number of polymerizing filaments. Here we track beads coated with a prokaryotic activator of actin polymerization in three dimensions to directly quantify the curvature and torsion of bead motility paths. We find that bead paths are more likely to have low rather than high curvature at any given time. Furthermore, path curvature changes very slowly in time, with an autocorrelation decay time of 200 s. Paths with a small radius of curvature, therefore, remain so for an extended period resulting in loops when confined to two dimensions. When allowed to explore a three-dimensional (3D) space, path loops are less evident. Finally, we quantify the torsion in the bead paths and show that beads do not exhibit a significant left- or right-handed bias to their motion in 3D. These results suggest that paths of actin-propelled objects may be attributed to slow changes in curvature, possibly associated with filament debranching, rather than a fixed torque.

  10. Curvature and torsion in growing actin networks

    PubMed Central

    Shaevitz, Joshua W; Fletcher, Daniel A

    2011-01-01

    Intracellular pathogens such as Listeria monocytogenes and Rickettsia rickettsii move within a host cell by polymerizing a comet-tail of actin fibers that ultimately pushes the cell forward. This dense network of cross-linked actin polymers typically exhibits a striking curvature that causes bacteria to move in gently looping paths. Theoretically, tail curvature has been linked to details of motility by considering force and torque balances from a finite number of polymerizing filaments. Here we track beads coated with a prokaryotic activator of actin polymerization in three dimensions to directly quantify the curvature and torsion of bead motility paths. We find that bead paths are more likely to have low rather than high curvature at any given time. Furthermore, path curvature changes very slowly in time, with an autocorrelation decay time of 200 s. Paths with a small radius of curvature, therefore, remain so for an extended period resulting in loops when confined to two dimensions. When allowed to explore a three-dimensional (3D) space, path loops are less evident. Finally, we quantify the torsion in the bead paths and show that beads do not exhibit a significant left- or right-handed bias to their motion in 3D. These results suggest that paths of actin-propelled objects may be attributed to slow changes in curvature, possibly associated with filament debranching, rather than a fixed torque. PMID:18560043

  11. The dark side of curvature

    SciTech Connect

    Barenboim, Gabriela; Martínez, Enrique Fernández; Mena, Olga; Verde, Licia E-mail: enfmarti@mppmu.mpg.de E-mail: liciaverde@icc.ub.edu

    2010-03-01

    Geometrical tests such as the combination of the Hubble parameter H(z) and the angular diameter distance d{sub A}(z) can, in principle, break the degeneracy between the dark energy equation of state parameter w(z), and the spatial curvature Ω{sub k} in a direct, model-independent way. In practice, constraints on these quantities achievable from realistic experiments, such as those to be provided by Baryon Acoustic Oscillation (BAO) galaxy surveys in combination with CMB data, can resolve the cosmic confusion between the dark energy equation of state parameter and curvature only statistically and within a parameterized model for w(z). Combining measurements of both H(z) and d{sub A}(z) up to sufficiently high redshifts z ∼ 2 and employing a parameterization of the redshift evolution of the dark energy equation of state are the keys to resolve the w(z)−Ω{sub k} degeneracy.

  12. Probing the very high energy  γ-ray spectral curvature in the blazar PG 1553+113 with the MAGIC telescopes

    SciTech Connect

    Aleksi , J.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Bangale, P.; Barrio, J. A.; Becerra Gonzalez, J.; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Lotto, B.; de Ona Wilhelmi, E.; Delgado Mendez, C.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher, D.; Elsaesser, D.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; Garcia Lopez, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Godinovi , N.; Gonzalez Munoz, A.; Gozzini, S. R.; Hadasch, D.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hildebrand, D.; Hose, J.; Hrupec, D.; Idec, W.; Kadenius, V.; Kellermann, H.; Knoetig, M. L.; Kodani, K.; Konno, Y.; Krause, J.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; Longo, F.; Lopez, M.; Lopez-Coto, R.; Lopez-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martinez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Nilsson, K.; Nishijima, K.; Noda, K.; Orito, R.; Overkemping, A.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Persic, M.; Poutanen, J.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribo, M.; Rico, J.; Rodriguez Garcia, J.; Rugamer, S.; Saito, T.; Saito, K.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Sillanpaa, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Stamerra, A.; Steinbring, T.; Storz, J.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzi , T.; Tescaro, D.; Teshima, M.; Thaele, J.; Tibolla, O.; Torres, D. F.; Toyama, T.; Treves, A.; Vogler, P.; Will, M.; Zanin, R.; Collaboration), (The M.; D'Ammando, F.; Buson, S.; Lahteenmaki, A.; Tornikoski, M.; Hovatta, T.; Readhead, A. C. S.; Max-Moerbeck, W.; Richards, J. L.

    2015-05-13

    PG 1553+113 is a very high energy (VHE, E > 100 GeV) γ-ray emitter classified as a BL Lac object. Its redshift is constrained by intergalactic absorption lines in the range 0.4 < z < 0.58. The MAGIC telescopes have monitored the source's activity since 2005. In early 2012, PG 1553+113 was found in a high state, and later, in April of the same year, the source reached its highest VHE flux state detected so far. Simultaneous observations carried out in X-rays during 2012 April show similar flaring behaviour. In contrast, the γ-ray flux at E < 100 GeV observed by Fermi-LAT is compatible with steady emission. Here, in this paper, a detailed study of the flaring state is presented. The VHE spectrum shows clear curvature, being well fitted either by a power law with an exponential cut-off or by a log-parabola. A simple power-law fit hypothesis for the observed shape of the PG 1553+113 VHE γ-ray spectrum is rejected with a high significance (fit probability P = 2.6 × 10-6). The observed curvature is compatible with the extragalactic background light (EBL) imprint predicted by current generation EBL models assuming a redshift z ~ 0.4. New constraints on the redshift are derived from the VHE spectrum. These constraints are compatible with previous limits and suggest that the source is most likely located around the optical lower limit, z = 0.4, based on the detection of Lyα absorption. Lastly, we find that the synchrotron self-Compton model gives a satisfactory description of the observed multiwavelength spectral energy distribution during the flare.

  13. Probing the very high energy γ-ray spectral curvature in the blazar PG 1553+113 with the MAGIC telescopes

    NASA Astrophysics Data System (ADS)

    Aleksić, J.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Bangale, P.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Caneva, G.; de Lotto, B.; de Oña Wilhelmi, E.; Delgado Mendez, C.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher, D.; Elsaesser, D.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadasch, D.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hildebrand, D.; Hose, J.; Hrupec, D.; Idec, W.; Kadenius, V.; Kellermann, H.; Knoetig, M. L.; Kodani, K.; Konno, Y.; Krause, J.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Nilsson, K.; Nishijima, K.; Noda, K.; Orito, R.; Overkemping, A.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Persic, M.; Poutanen, J.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Rügamer, S.; Saito, T.; Saito, K.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Stamerra, A.; Steinbring, T.; Storz, J.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Tibolla, O.; Torres, D. F.; Toyama, T.; Treves, A.; Vogler, P.; Will, M.; Zanin, R.; MAGIC Collaboration; D'Ammando, F.; Buson, S.; Lähteenmäki, A.; Tornikoski, M.; Hovatta, T.; Readhead, A. C. S.; Max-Moerbeck, W.; Richards, J. L.

    2015-07-01

    PG 1553+113 is a very high energy (VHE, E > 100 GeV) γ-ray emitter classified as a BL Lac object. Its redshift is constrained by intergalactic absorption lines in the range 0.4 < z < 0.58. The MAGIC telescopes have monitored the source's activity since 2005. In early 2012, PG 1553+113 was found in a high state, and later, in April of the same year, the source reached its highest VHE flux state detected so far. Simultaneous observations carried out in X-rays during 2012 April show similar flaring behaviour. In contrast, the γ-ray flux at E < 100 GeV observed by Fermi-LAT is compatible with steady emission. In this paper, a detailed study of the flaring state is presented. The VHE spectrum shows clear curvature, being well fitted either by a power law with an exponential cut-off or by a log-parabola. A simple power-law fit hypothesis for the observed shape of the PG 1553+113 VHE γ-ray spectrum is rejected with a high significance (fit probability P = 2.6 × 10-6). The observed curvature is compatible with the extragalactic background light (EBL) imprint predicted by current generation EBL models assuming a redshift z ˜ 0.4. New constraints on the redshift are derived from the VHE spectrum. These constraints are compatible with previous limits and suggest that the source is most likely located around the optical lower limit, z = 0.4, based on the detection of Lyα absorption. Finally, we find that the synchrotron self-Compton model gives a satisfactory description of the observed multiwavelength spectral energy distribution during the flare.

  14. Probing the very high energy  γ-ray spectral curvature in the blazar PG 1553+113 with the MAGIC telescopes

    DOE PAGES

    Aleksi , J.; Ansoldi, S.; Antonelli, L. A.; ...

    2015-05-13

    PG 1553+113 is a very high energy (VHE, E > 100 GeV) γ-ray emitter classified as a BL Lac object. Its redshift is constrained by intergalactic absorption lines in the range 0.4 < z < 0.58. The MAGIC telescopes have monitored the source's activity since 2005. In early 2012, PG 1553+113 was found in a high state, and later, in April of the same year, the source reached its highest VHE flux state detected so far. Simultaneous observations carried out in X-rays during 2012 April show similar flaring behaviour. In contrast, the γ-ray flux at E < 100 GeV observedmore » by Fermi-LAT is compatible with steady emission. Here, in this paper, a detailed study of the flaring state is presented. The VHE spectrum shows clear curvature, being well fitted either by a power law with an exponential cut-off or by a log-parabola. A simple power-law fit hypothesis for the observed shape of the PG 1553+113 VHE γ-ray spectrum is rejected with a high significance (fit probability P = 2.6 × 10-6). The observed curvature is compatible with the extragalactic background light (EBL) imprint predicted by current generation EBL models assuming a redshift z ~ 0.4. New constraints on the redshift are derived from the VHE spectrum. These constraints are compatible with previous limits and suggest that the source is most likely located around the optical lower limit, z = 0.4, based on the detection of Lyα absorption. Lastly, we find that the synchrotron self-Compton model gives a satisfactory description of the observed multiwavelength spectral energy distribution during the flare.« less

  15. Curvature Sorting of Peripheral Proteins on Solid-Supported Wavy Membranes

    PubMed Central

    Hsieh, Wan-Ting; Hsu, Chih-Jung; Capraro, Benjamin R.; Wu, Tingting; Chen, Chi-Mon; Yang, Shu; Baumgart, Tobias

    2013-01-01

    Cellular membrane deformation and the associated redistribution of membrane-bound proteins are important aspects of membrane function. Current model membrane approaches for studying curvature sensing are limited to positive curvatures, and often require complex and delicate experimental setups. To overcome these challenges, we fabricated a wavy substrate imposing a range of curvatures onto an adhering lipid bilayer membrane. We examined the curvature sorting of several peripheral proteins binding to the wavy membrane and observed them to partition into distinct regions of curvature. Furthermore, single molecule imaging experiments suggested that curvature sensing of proteins on low-curvature substrates requires cooperative interactions. PMID:22881196

  16. Automated drumlin shape and volume estimation using high resolution LiDAR imagery (Curvature Based Relief Separation): A test from the Wadena Drumlin Field, Minnesota

    NASA Astrophysics Data System (ADS)

    Yu, Peter; Eyles, Nick; Sookhan, Shane

    2015-10-01

    Resolving the origin(s) of drumlins and related megaridges in areas of megascale glacial lineations (MSGL) left by paleo-ice sheets is critical to understanding how ancient ice sheets interacted with their sediment beds. MSGL is now linked with fast-flowing ice streams but there is a broad range of erosional and depositional models. Further progress is reliant on constraining fluxes of subglacial sediment at the ice sheet base which in turn is dependent on morphological data such as landform shape and elongation and most importantly landform volume. Past practice in determining shape has employed a broad range of geomorphological methods from strictly visualisation techniques to more complex semi-automated and automated drumlin extraction methods. This paper reviews and builds on currently available visualisation, semi-automated and automated extraction methods and presents a new, Curvature Based Relief Separation (CBRS) technique; for drumlin mapping. This uses curvature analysis to generate a base level from which topography can be normalized and drumlin volume can be derived. This methodology is tested using a high resolution (3 m) LiDAR elevation dataset from the Wadena Drumlin Field, Minnesota, USA, which was constructed by the Wadena Lobe of the Laurentide Ice Sheet ca. 20,000 years ago and which as a whole contains 2000 drumlins across an area of 7500 km2. This analysis demonstrates that CBRS provides an objective and robust procedure for automated drumlin extraction. There is strong agreement with manually selected landforms but the method is also capable of resolving features that were not detectable manually thereby considerably expanding the known population of streamlined landforms. CBRS provides an effective automatic method for visualisation of large areas of the streamlined beds of former ice sheets and for modelling sediment fluxes below ice sheets.

  17. Curvature and the visual perception of shape: theory on information along object boundaries and the minima rule revisited.

    PubMed

    Lim, Ik Soo; Leek, E Charles

    2012-07-01

    Previous empirical studies have shown that information along visual contours is known to be concentrated in regions of high magnitude of curvature, and, for closed contours, segments of negative curvature (i.e., concave segments) carry greater perceptual relevance than corresponding regions of positive curvature (i.e., convex segments). Lately, Feldman and Singh (2005, Psychological Review, 112, 243-252) proposed a mathematical derivation to yield information content as a function of curvature along a contour. Here, we highlight several fundamental errors in their derivation and in its associated implementation, which are problematic in both mathematical and psychological senses. Instead, we propose an alternative mathematical formulation for information measure of contour curvature that addresses these issues. Additionally, unlike in previous work, we extend this approach to 3-dimensional (3D) shape by providing a formal measure of information content for surface curvature and outline a modified version of the minima rule relating to part segmentation using curvature in 3D shape. Copyright 2012 APA, all rights reserved.

  18. Nonlocal Curvature Flows

    NASA Astrophysics Data System (ADS)

    Chambolle, Antonin; Morini, Massimiliano; Ponsiglione, Marcello

    2015-12-01

    This paper aims at building a unified framework to deal with a wide class of local and nonlocal translation-invariant geometric flows. We introduce a class of nonlocal generalized mean curvatures and prove the existence and uniqueness for the level set formulation of the corresponding geometric flows. We then introduce a class of generalized perimeters, whose first variation is an admissible generalized curvature. Within this class, we implement a minimizing movements scheme and we prove that it approximates the viscosity solution of the corresponding level set PDE. We also describe several examples and applications. Besides recovering and presenting in a unified way existence, uniqueness, and approximation results for several geometric motions already studied and scattered in the literature, the theory developed in this paper also allows us to establish new results.

  19. Curvature constraints from the causal entropic principle

    SciTech Connect

    Bozek, Brandon; Albrecht, Andreas; Phillips, Daniel

    2009-07-15

    Current cosmological observations indicate a preference for a cosmological constant that is drastically smaller than what can be explained by conventional particle physics. The causal entropic principle (Bousso et al.) provides an alternative approach to anthropic attempts to predict our observed value of the cosmological constant by calculating the entropy created within a causal diamond. We have extended this work to use the causal entropic principle to predict the preferred curvature within the 'multiverse'. We have found that values larger than {rho}{sub k}=40{rho}{sub m} are disfavored by more than 99.99% peak value at {rho}{sub {lambda}}=7.9x10{sup -123} and {rho}{sub k}=4.3{rho}{sub m} for open universes. For universes that allow only positive curvature or both positive and negative curvature, we find a correlation between curvature and dark energy that leads to an extended region of preferred values. Our universe is found to be disfavored to an extent depending on the priors on curvature. We also provide a comparison to previous anthropic constraints on open universes and discuss future directions for this work.

  20. Curvature Effect on Hemodynamic Conditions at the Inner Bend of the Carotid Siphon and its Relation to Aneurysm Formation

    PubMed Central

    Lauric, Alexandra; Hippelheuser, James; Safain, Mina G.; Malek, Adel M.

    2014-01-01

    Although high-impact hemodynamic forces are thought to lead to cerebral aneurysmal change, little is known about the aneurysm formation on the inner aspect of vascular bends such as the internal carotid artery (ICA) siphon where wall shear stress (WSS) is expected to be low. This study evaluates the effect of vessel curvature and hemodynamics on aneurysm formation along the inner carotid siphon. Catheter 3D-rotational angiographic volumes of 35 ICA (10 aneurysms, 25 controls) were evaluated in 3D for radius of curvature and peak curvature of the siphon bend, followed by univariate statistical analysis. Computational fluid dynamic (CFD) simulations were performed on patient-derived models after aneurysm removal and on synthetic variants of increasing curvature. Peak focal siphon curvature was significantly higher in aneurysm bearing ICAs (0.36±0.045 vs. 0.30±0.048 mm−1, p=0.003), with no difference in global radius of curvature (p=0.36). In CFD simulations, increasing parametric curvature tightness (from 5 to 3 mm radius) resulted in dramatic increase of WSS and WSS gradient magnitude (WSSG) on the inner wall of the bend. In patient-derived data, the location of aneurysms coincided with regions of low WSS (<4 Pa) flanked by high WSS and WSSG peaks. WSS peaks correlated with the aneurysm neck. In contrast, control siphon bends displayed low, almost constant, WSS and WSSG profiles with little spatial variation. High bend curvature induces dynamically fluctuating high proximal WSS and WSSG followed by regions of flow stasis and recirculation, leading to local conditions known to induce destructive vessel wall remodeling and aneurysmal initiation. PMID:25062932

  1. Asymptotic behavior of curvature of surface elements in isotropic turbulence

    NASA Technical Reports Server (NTRS)

    Girimaji, S. S.

    1991-01-01

    The asymptotic behavior of the curvature of material elements in turbulence is investigated using Lagrangian velocity-gradient time series obtained from direct numerical simulations of isotropic turbulence. Several material-element ensembles of different initial curvatures and shapes are studied. It is found that, at long times, the (first five) moments of the logarithm of characteristic curvature and shape factor asymptote to values that are independent of the initial curvature or shape. This evidence strongly suggests that the asymptotic pdf's of the curvature and shape of material elements are stationary and independent of initial conditions. Irrespective of initial curvature or shape, the asymptotic shape of a material surface is cylindrical with a high probability.

  2. Experiments in Transitional Boundary Layers With Emphasis on High Free-Stream Disturbance Level, Surface Concave Curvature and Strong Favorable Streamwise Pressure Gradient Effects

    NASA Technical Reports Server (NTRS)

    Simon, T. W.; Volino, R. J.

    2007-01-01

    Experiments on boundary layer transition with flat, concave and convex walls and various levels of free-stream disturbance and with zero and strong streamwise acceleration have been conducted. Measurements of both fluid mechanics and heat transfer processes were taken. Examples are profiles of mean velocity and temperature; Reynolds normal and shear stresses; turbulent streamwise and cross-stream heat fluxed; turbulent Prandtl number; and streamwise variations of wall skin friction and heat transfer coefficient values. Free-stream turbulence levels were varied over the range from about 0.3 percent to about 8 percent. The effects of curvature on the onset of transition under low disturbance conditions are clear; concave curvature leads to an earlier and more rapid transition and the opposite is true for convex curvature This was previously known but little documentation of the transport processes in the flow was available

  3. Improving the Sensitivity of Astronomical Curvature Wavefront Sensor Using Dual-Stroke Curvature

    NASA Astrophysics Data System (ADS)

    Guyon, Olivier; Blain, Celia; Takami, Hideki; Hayano, Yutaka; Hattori, Masayuki; Watanabe, Makoto

    2008-06-01

    Curvature wavefront sensors measure wavefront phase aberration by acquiring two intensity images on either side of the pupil plane. Low-order adaptive optics (AO) systems using curvature wavefront sensing (CWFS) have proved to be highly efficient for astronomical applications: they are more sensitive, use fewer detector elements, and achieve, for the same number of actuators, higher Strehl ratios than AO systems using more traditional Shack-Hartmann wavefront sensors. In higher-order systems, however, curvature wavefront sensors lose sensitivity to low spatial frequencies wavefront aberrations. This effect, often described as “noise propagation,” limits the usefulness of curvature wavefront sensing for high-order AO systems and/or large telescopes. In this paper, we first explain how this noise propagation effect occurs and then show that this limitation can be overcome by acquiring four defocused images of the pupil instead of two. This solution can be implemented without significant technology development and can run with a simple linear wavefront reconstruction algorithm at >kHz speed. We have successfully demonstrated in the laboratory that the four conjugation planes can be sequentially obtained at >kHz speed using a speaker-vibrating membrane assembly commonly used in current curvature AO systems. Closed loop simulations show that implementing this scheme is equivalent to making the guide star 1 to 1.5 magnitude brighter for the configuration tested (188 actuator elements on 8-m telescope). Higher sensitivity gains are expected on curvature systems with higher number of actuators.

  4. Hysteresis compensation technique for POF curvature sensors

    NASA Astrophysics Data System (ADS)

    Leal, Arnaldo G.; Frizera, Anselmo; Pontes, Maria José

    2017-04-01

    Polymer optical fibers (POF) have higher strain limits, fracture toughness and flexibility in bend if compared to glass optical fibers. These characteristics enable the application of POFs as curvature sensors. However, the polymer is a viscoelastic material, which does not have a constant response with stress or strain. For this reason, a curvature sensor based on POF may present high hysteresis. This paper proposes a dynamic compensation technique based on the angular velocity of the sensor. Results show a hysteresis up to 10 times lower. Furthermore, it results on a simple calibration equation, which can be applied in real-time measurements.

  5. Self-assembly of a filament by curvature-inducing proteins

    NASA Astrophysics Data System (ADS)

    Kwiecinski, James; Chapman, S. Jonathan; Goriely, Alain

    2017-04-01

    We explore a simplified macroscopic model of membrane shaping by means of curvature-sensing BAR proteins. Equations describing the interplay between the shape of a freely floating filament in a fluid and the adhesion kinetics of proteins are derived from mechanical principles. The constant curvature solutions that arise from this system are studied using weakly nonlinear analysis. We show that the stability of the filament's shape is completely characterized by the parameters associated with protein recruitment and establish that in the bistable regime, proteins aggregate on the filament forming regions of high and low curvatures. This pattern formation is then followed by phase-coarsening that resolves on a time-scale dependent on protein diffusion and drift across the filament, which contend to smooth and maintain the pattern respectively. The model is generalized for multiple species of BAR proteins and we show that the stability of the assembled shape is determined by a competition between proteins attaching on opposing sides.

  6. Curvature-induced expulsion of actomyosin bundles during cytokinetic ring contraction

    PubMed Central

    Huang, Junqi; Chew, Ting Gang; Kamnev, Anton; Martin, Douglas S; Carter, Nicholas J; Cross, Robert Anthony; Oliferenko, Snezhana; Balasubramanian, Mohan K

    2016-01-01

    Many eukaryotes assemble a ring-shaped actomyosin network that contracts to drive cytokinesis. Unlike actomyosin in sarcomeres, which cycles through contraction and relaxation, the cytokinetic ring disassembles during contraction through an unknown mechanism. Here we find in Schizosaccharomyces japonicus and Schizosaccharomyces pombe that, during actomyosin ring contraction, actin filaments associated with actomyosin rings are expelled as micron-scale bundles containing multiple actomyosin ring proteins. Using functional isolated actomyosin rings we show that expulsion of actin bundles does not require continuous presence of cytoplasm. Strikingly, mechanical compression of actomyosin rings results in expulsion of bundles predominantly at regions of high curvature. Our work unprecedentedly reveals that the increased curvature of the ring itself promotes its disassembly. It is likely that such a curvature-induced mechanism may operate in disassembly of other contractile networks. DOI: http://dx.doi.org/10.7554/eLife.21383.001 PMID:27734801

  7. Curvature of wave streamlines

    NASA Astrophysics Data System (ADS)

    Berry, M. V.

    2013-10-01

    Wave streamlines are integral curves of the local wavevector (phase gradient). An exact formula is derived, giving the curvature of streamlines as the component transverse to the local wavevector of the gradient of the logarithm of the local wavenumber. The formula is applied to quantum particles moving in a potential and classical light in the presence of a refractive-index gradient. Three limiting regimes are encompassed. The first is geometrical, in which the bending of streamlines arises solely from the classical force or optical index gradient. The second and third limits concern singularities in the pattern of wave streamlines, of two types: optical vortices, near which the streamlines are asymptotically circular, and phase saddles, near which the streamlines are asymptotically hyperbolic.

  8. Curvature-processing network in macaque visual cortex.

    PubMed

    Yue, Xiaomin; Pourladian, Irene S; Tootell, Roger B H; Ungerleider, Leslie G

    2014-08-19

    Our visual environment abounds with curved features. Thus, the goal of understanding visual processing should include the processing of curved features. Using functional magnetic resonance imaging in behaving monkeys, we demonstrated a network of cortical areas selective for the processing of curved features. This network includes three distinct hierarchically organized regions within the ventral visual pathway: a posterior curvature-biased patch (PCP) located in the near-foveal representation of dorsal V4, a middle curvature-biased patch (MCP) located on the ventral lip of the posterior superior temporal sulcus (STS) in area TEO, and an anterior curvature-biased patch (ACP) located just below the STS in anterior area TE. Our results further indicate that the processing of curvature becomes increasingly complex from PCP to ACP. The proximity of the curvature-processing network to the well-known face-processing network suggests a possible functional link between them.

  9. Curvature-processing network in macaque visual cortex

    PubMed Central

    Yue, Xiaomin; Pourladian, Irene S.; Tootell, Roger B. H.; Ungerleider, Leslie G.

    2014-01-01

    Our visual environment abounds with curved features. Thus, the goal of understanding visual processing should include the processing of curved features. Using functional magnetic resonance imaging in behaving monkeys, we demonstrated a network of cortical areas selective for the processing of curved features. This network includes three distinct hierarchically organized regions within the ventral visual pathway: a posterior curvature-biased patch (PCP) located in the near-foveal representation of dorsal V4, a middle curvature-biased patch (MCP) located on the ventral lip of the posterior superior temporal sulcus (STS) in area TEO, and an anterior curvature-biased patch (ACP) located just below the STS in anterior area TE. Our results further indicate that the processing of curvature becomes increasingly complex from PCP to ACP. The proximity of the curvature-processing network to the well-known face-processing network suggests a possible functional link between them. PMID:25092328

  10. Curvature-driven lateral segregation of membrane constituents in Golgi cisternae

    NASA Astrophysics Data System (ADS)

    Derganc, Jure

    2007-12-01

    Lateral segregation of mobile membrane constituents (e.g. lipids, proteins or membrane domains) into the regions of their preferred curvature relaxes stresses in the membrane. The equilibrium distribution of the constituents in the membrane is thus a balance between the gains in the membrane elastic energy and the segregation-induced loss of entropy. The membrane in the Golgi cisternae is particularly susceptible to the curvature-driven segregation because it possesses two very different curvatures—the highly curved membrane in the cisternal rims and the flat membrane in the cisternal sides. In this work, we calculate the extent of lateral segregation in the Golgi cisternae in the case where the segregation is driven by the Helfrich bending energy. It is assumed that the membrane bending constant and spontaneous curvature depend on the local membrane composition. A simple analytical expression for the extent of the lateral segregation is derived. The results show that the segregation depends on the ratio between the bending constant and the thermal energy, the difference of the preferred curvatures of the constituents and the sizes of the constituents. Applying the model to a typical Golgi cisterna, it was found that entropy can effectively limit the extent of the curvature-driven lateral segregation.

  11. Controllable curvature from planar polymer sheets in response to light.

    PubMed

    Hubbard, Amber M; Mailen, Russell W; Zikry, Mohammed A; Dickey, Michael D; Genzer, Jan

    2017-02-24

    The ability to change shape and control curvature in 3D structures starting from planar sheets can aid in assembly and add functionality to an object. Herein, we convert planar sheets of shape memory polymers (SMPs) into 3D objects with controllable curvature by dictating where the sheets shrink. Ink patterned on the surface of the sheet absorbs infrared (IR) light, resulting in localized heating, and the material shrinks locally wherever the temperature exceeds the activation temperature, Ta. We introduce two different mechanisms for controlling curvature within SMP sheets. The 'direct' mechanism uses localized shrinkage to induce curvature only in regions patterned with ink. The 'indirect' mechanism uses localized shrinkage in regions patterned with ink to induce curvature in neighboring regions without ink through a balance of internal stresses. Finite element analysis predicts the final shape of the polymer sheets with excellent qualitative agreement with experimental studies. Results from this study show that curvature can be controlled by the distribution and darkness of the ink pattern on the polymer sheet. Additionally, we utilize the direct and indirect curvature mechanisms to demonstrate the formation and actuation of gripper devices, which represent the potential utility of this approach.

  12. On nonlinear higher spin curvature

    NASA Astrophysics Data System (ADS)

    Manvelyan, Ruben; Mkrtchyan, Karapet; Rühl, Werner; Tovmasyan, Murad

    2011-05-01

    We present the first nonlinear term of the higher spin curvature which is covariant with respect to deformed gauge transformations that are linear in the field. We consider the case of spin 3 after presenting spin 2 as an example, and then construct the general spin s quadratic term of the de Wit-Freedman curvature.

  13. Controlling Hamiltonian chaos via Gaussian curvature.

    PubMed

    Oloumi, A; Teychenné, D

    1999-12-01

    We present a method allowing one to partly stabilize some chaotic Hamiltonians which have two degrees of freedom. The purpose of the method is to avoid the regions of V(q(1),q(2)) where its Gaussian curvature becomes negative. We show the stabilization of the Hénon-Heiles system, over a wide area, for the critical energy E=1/6. Total energy of the system varies only by a few percent.

  14. Generalization of Seidel astigmatism and Petzval curvature.

    PubMed

    Gaj, M

    1966-06-01

    In a paper probably to be published in Optika i Spektroskopiya the wave aberration for sagittal focus for the arbitrary surface of rotational symmetry has been carried out on the base of the astigmatic beam invariant D(s) = nu(s)d(s). The resulting expression for the wave aberration has been reformulated into three terms which, in the Seidel region, go over into astigmatism (the first) and into the Petzval curvature (the second) while the third disappears.

  15. Curvature dependence of the interfacial heat and mass transfer coefficients

    NASA Astrophysics Data System (ADS)

    Glavatskiy, K. S.; Bedeaux, D.

    2014-03-01

    Nucleation is often accompanied by heat transfer between the surroundings and a nucleus of a new phase. The interface between two phases gives an additional resistance to this transfer. For small nuclei the interfacial curvature is high, which affects not only equilibrium quantities such as surface tension, but also the transport properties. In particular, high curvature affects the interfacial resistance to heat and mass transfer. We develop a framework for determining the curvature dependence of the interfacial heat and mass transfer resistances. We determine the interfacial resistances as a function of a curvature. The analysis is performed for a bubble of a one-component fluid and may be extended to various nuclei of multicomponent systems. The curvature dependence of the interfacial resistances is important in modeling transport processes in multiphase systems.

  16. Influenza virus A M2 protein generates negative Gaussian membrane curvature necessary for budding and scission

    PubMed Central

    Schmidt, Nathan W.; Mishra, Abhijit; Wang, Jun; DeGrado, William F.; Wong, Gerard C. L.

    2013-01-01

    The M2 protein is a multi-functional protein, which plays several roles in the replication cycle of the influenza A virus. Here we focus on its ability to promote budding of the mature virus from the cell surface. Using high resolution small angle X-ray scattering we show that M2 can restructure lipid membranes into bicontinuous cubic phases which are rich in negative Gaussian curvature (NGC). The active generation of negative Gaussian membrane curvature by M2 is essential to influenza virus budding. M2 has been observed to colocalize with the region of high NGC at the neck of a bud. The structural requirements for scission are even more stringent than those for budding, as the neck must be considerably smaller than the virus during ‘pinch off’. Consistent with this, the amount of NGC in the induced cubic phases suggests that M2 proteins can generate high curvatures comparable to those on a neck with size 10x smaller than a spherical influenza virus. Similar experiments on variant proteins containing different M2 domains show that the cytoplasmic amphipathic helix is necessary and sufficient for NGC generation. Mutations to the helix which reduce its amphiphilicity and are known to diminish budding attenuated NGC generation. An M2 construct comprising the membrane interactive domains, the transmembrane helix and the cytoplasmic helix, displayed enhanced ability to generate NGC, suggesting that other domains cooperatively promote membrane curvature. These studies establish the importance of M2-induced negative Gaussian curvature during budding and suggest that antagonizing this curvature is a viable anti-influenza strategy. PMID:23962302

  17. CUTEX: CUrvature Thresholding EXtractor

    NASA Astrophysics Data System (ADS)

    Molinari, S.; Schisano, E.; Faustini, F.; Pestalozzi, M.; di Giorgio, A. M.; Liu, S.

    2017-08-01

    CuTEx analyzes images in the infrared bands and extracts sources from complex backgrounds, particularly star-forming regions that offer the challenges of crowding, having a highly spatially variable background, and having no-psf profiles such as protostars in their accreting phase. The code is composed of two main algorithms, the first an algorithm for source detection, and the second for flux extraction. The code is originally written in IDL language and it was exported in the license free GDL language. CuTEx could be used in other bands or in scientific cases different from the native case. This software is also available as an on-line tool from the Multi-Mission Interactive Archive web pages dedicated to the Herschel Observatory.

  18. Astronomical redshifts of highly ionized regions

    NASA Astrophysics Data System (ADS)

    Hansen, Peter M.

    2014-07-01

    Astronomical or cosmological redshifts are an observable property of extragalactic objects and have historically been wholly attributed to the recessional velocity of that object. The question of other, or intrinsic, components of the redshift has been highly controversial since it was first proposed. This paper investigates one theoretical source of intrinsic redshift that has been identified. The highly ionized regions of Active Galactic Nuclei (AGN) and Quasi-Stellar Objects (QSO) are, by definition, plasmas. All plasmas have electromagnetic scattering characteristics that could contribute to the observed redshift. To investigate this possibility, one region of a generalized AGN was selected, the so called Broad Line Region (BLR). Even though unresolvable with current instrumentation, physical estimates of this region have been published for years in the astronomical literature. These data, selected and then averaged, are used to construct an overall model that is consistent with the published data to within an order of magnitude. The model is then subjected to a theoretical scattering investigation. The results suggest that intrinsic redshifts, derivable from the characteristics of the ambient plasma, may indeed contribute to the overall observed redshift of these objects.

  19. Cosmic curvature and condensation

    NASA Technical Reports Server (NTRS)

    Harwit, Martin

    1992-01-01

    It is shown that the universe may consist of a patchwork of domains with different Riemann curvature constants k = 0, +/-1. Features of a phase transition in which flat space breaks up in a transition 2k0 - k(-) + k(+) with initial scale factors R(-) = R(+) are postulated and explored. It is shown that such a transition is energetically permitted, has the equivalent of a Curie temperature, and can lead in a natural way to the formation of voids and galaxies. It is predicted that, if the ambient universe on average is well fitted by a purely k(-) space, with only occasional domains of k(+) containing galaxies, a density parameter of (A(z sub c + 1)) super -1 should be expected, where z sub c represents the redshift of the earliest objects to have condensed, and A takes on values ranging from about 5 to 3. Present observations of quasars would suggest a density of about 0.03 or 0.05, respectively, but it could be lower if earlier condensation took place.

  20. Animal Fascioliasis: Perspectives from high altitudinal regions.

    PubMed

    Lyngdoh, Damanbha; Sharma, Sunil; Roy, Bishnupada; Tandon, Veena

    2016-12-15

    The parasitic flukes of the genus Fasciola (Platyhelminthes: Trematoda: Digenea) cause fascioliasis or liver-rot disease in ruminant livestock in tropical and sub-tropical regions of the world. Classically, two species of Fasciola- F. hepatica and F. gigantica, are universally recognized as taxonomically valid species. Our survey studies on ovid and bovid animals including yak and mithun from high altitudinal mountainous regions in Northeast India revealed the occurrence of Fasciola gigantica and also Fasciola sp.- an intermediate form, at altitudes between 5000 and 14,085 feet above sea level (asl). Two morphotypes- F. hepatica - like and F. gigantica - like, of Fasciola species were reported from the high altitudinal areas of Northeast India; most of these locales constitute new-locality and first records for the occurrence of these liver flukes.

  1. EAU guidelines on penile curvature.

    PubMed

    Hatzimouratidis, Konstantinos; Eardley, Ian; Giuliano, François; Hatzichristou, Dimitrios; Moncada, Ignacio; Salonia, Andrea; Vardi, Yoram; Wespes, Eric

    2012-09-01

    Penile curvature can be congenital or acquired. Acquired curvature is secondary due to La Peyronie (Peyronie's) disease. To provide clinical guidelines on the diagnosis and treatment of penile curvature. A systematic literature search on the epidemiology, diagnosis, and treatment of penile curvature was performed. Articles with the highest evidence available were selected and formed the basis for assigning levels of evidence and grades of recommendations. The pathogenesis of congenital penile curvature is unknown. Peyronie's disease is a poorly understood connective tissue disorder most commonly attributed to repetitive microvascular injury or trauma during intercourse. Diagnosis is based on medical and sexual histories, which are sufficient to establish the diagnosis. Physical examination includes assessment of palpable nodules and penile length. Curvature is best documented by a self-photograph or pharmacologically induced erection. The only treatment option for congenital penile curvature is surgery based on plication techniques. Conservative treatment for Peyronie's disease is associated with poor outcomes. Pharmacotherapy includes oral potassium para-aminobenzoate, intralesional treatment with verapamil, clostridial collagenase or interferon, topical verapamil gel, and iontophoresis with verapamil and dexamethasone. They can be efficacious in some patients, but none of these options carry a grade A recommendation. Steroids, vitamin E, and tamoxifen cannot be recommended. Extracorporeal shock wave treatment and penile traction devices may only be used to treat penile pain and reduce penile deformity, respectively. Surgery is indicated when Peyronie's disease is stable for at least 3 mo. Tunical shortening procedures, especially plication techniques, are the first treatment options. Tunical lengthening procedures are preferred in more severe curvatures or in complex deformities. Penile prosthesis implantation is recommended in patients with erectile dysfunction

  2. Highlighting High Performance: Whitman Hanson Regional High School; Whitman, Massachusetts

    SciTech Connect

    Not Available

    2006-06-01

    This brochure describes the key high-performance building features of the Whitman-Hanson Regional High School. The brochure was paid for by the Massachusetts Technology Collaborative as part of their Green Schools Initiative. High-performance features described are daylighting and energy-efficient lighting, indoor air quality, solar and wind energy, building envelope, heating and cooling systems, water conservation, and acoustics. Energy cost savings are also discussed.

  3. Compound curvature laser window development

    NASA Technical Reports Server (NTRS)

    Verhoff, Vincent G.

    1993-01-01

    The NASA Lewis Research Center has developed and implemented a unique process for forming flawless compound curvature laser windows. These windows represent a major part of specialized, nonintrusive laser data acquisition systems used in a variety of compressor and turbine research test facilities. This report summarizes the main aspects of compound curvature laser window development. It is an overview of the methodology and the peculiarities associated with the formulation of these windows. Included in this discussion is new information regarding procedures for compound curvature laser window development.

  4. Sigma models with negative curvature

    NASA Astrophysics Data System (ADS)

    Alonso, Rodrigo; Jenkins, Elizabeth E.; Manohar, Aneesh V.

    2016-05-01

    We construct Higgs Effective Field Theory (HEFT) based on the scalar manifold Hn, which is a hyperbolic space of constant negative curvature. The Lagrangian has a non-compact O (n , 1) global symmetry group, but it gives a unitary theory as long as only a compact subgroup of the global symmetry is gauged. Whether the HEFT manifold has positive or negative curvature can be tested by measuring the S-parameter, and the cross sections for longitudinal gauge boson and Higgs boson scattering, since the curvature (including its sign) determines deviations from Standard Model values.

  5. Sigma models with negative curvature

    DOE PAGES

    Alonso, Rodrigo; Jenkins, Elizabeth E.; Manohar, Aneesh V.

    2016-03-16

    Here, we construct Higgs Effective Field Theory (HEFT) based on the scalar manifold Hn, which is a hyperbolic space of constant negative curvature. The Lagrangian has a non-compact O(n, 1) global symmetry group, but it gives a unitary theory as long as only a compact subgroup of the global symmetry is gauged. Whether the HEFT manifold has positive or negative curvature can be tested by measuring the S-parameter, and the cross sections for longitudinal gauge boson and Higgs boson scattering, since the curvature (including its sign) determines deviations from Standard Model values.

  6. Spatial Control of Epsin-induced Clathrin Assembly by Membrane Curvature*♦

    PubMed Central

    Holkar, Sachin S.; Kamerkar, Sukrut C.; Pucadyil, Thomas J.

    2015-01-01

    Epsins belong to the family of highly conserved clathrin-associated sorting proteins that are indispensable for clathrin-mediated endocytosis, but their precise functions remain unclear. We have developed an assay system of budded supported membrane tubes displaying planar and highly curved membrane surfaces to analyze intrinsic membrane curvature preference shown by clathrin-associated sorting proteins. Using real-time fluorescence microscopy, we find that epsin preferentially partitions to and assembles clathrin on highly curved membrane surfaces. Sorting of epsin to regions of high curvature strictly depends on binding to phosphatidylinositol 4,5-bisphosphate. Fluorescently labeled clathrins rapidly assemble as foci, which in turn cluster epsin, while maintaining tube integrity. Clathrin foci grow in intensity with a typical time constant of ∼75 s, similar to the time scales for coated pit formation seen in cells. Epsin therefore effectively senses membrane curvature to spatially control clathrin assembly. Our results highlight the potential role of membrane curvature in orchestrating the myriad molecular interactions necessary for the success of clathrin-mediated membrane budding. PMID:25837255

  7. Spatial Control of Epsin-induced Clathrin Assembly by Membrane Curvature.

    PubMed

    Holkar, Sachin S; Kamerkar, Sukrut C; Pucadyil, Thomas J

    2015-06-05

    Epsins belong to the family of highly conserved clathrin-associated sorting proteins that are indispensable for clathrin-mediated endocytosis, but their precise functions remain unclear. We have developed an assay system of budded supported membrane tubes displaying planar and highly curved membrane surfaces to analyze intrinsic membrane curvature preference shown by clathrin-associated sorting proteins. Using real-time fluorescence microscopy, we find that epsin preferentially partitions to and assembles clathrin on highly curved membrane surfaces. Sorting of epsin to regions of high curvature strictly depends on binding to phosphatidylinositol 4,5-bisphosphate. Fluorescently labeled clathrins rapidly assemble as foci, which in turn cluster epsin, while maintaining tube integrity. Clathrin foci grow in intensity with a typical time constant of ∼75 s, similar to the time scales for coated pit formation seen in cells. Epsin therefore effectively senses membrane curvature to spatially control clathrin assembly. Our results highlight the potential role of membrane curvature in orchestrating the myriad molecular interactions necessary for the success of clathrin-mediated membrane budding. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  8. Influence of Coanda surface curvature on performance of bladeless fan

    NASA Astrophysics Data System (ADS)

    Li, Guoqi; Hu, Yongjun; Jin, Yingzi; Setoguchi, Toshiaki; Kim, Heuy Dong

    2014-10-01

    The unique Coanda surface has a great influence on the performance of bladeless fan. However, there is few studies to explain the relationship between the performance and Coanda surface curvature at present. In order to gain a qualitative understanding of effect of the curvature on the performance of bladeless fan, numerical studies are performed in this paper. Firstly, three-dimensional numerical simulation is done by Fluent software. For the purpose to obtain detailed information of the flow field around the Coanda surface, two-dimensional numerical simulation is also conducted. Five types of Coanda surfaces with different curvature are designed, and the flow behaviour and the performance of them are analyzed and compared with those of the prototype. The analysis indicates that the curvature of Coanda surface is strongly related to blowing performance, It is found that there is an optimal curvature of Coanda surfaces among the studied models. Simulation result shows that there is a special low pressure region. With increasing curvature in Y direction, several low pressure regions gradually enlarged, then begin to merge slowly, and finally form a large area of low pressure. From the analyses of streamlines and velocity angle, it is found that the magnitude of the curvature affects the flow direction and reasonable curvature can induce fluid flow close to the wall. Thus, it leads to that the curvature of the streamlines is consistent with that of Coanda surface. Meanwhile, it also causes the fluid movement towards the most suitable direction. This study will provide useful information to performance improvements of bladeless fans.

  9. The Influenza Hemagglutinin Fusion Domain Is an Amphipathic Helical Hairpin That Functions by Inducing Membrane Curvature*

    PubMed Central

    Smrt, Sean T.; Draney, Adrian W.; Lorieau, Justin L.

    2015-01-01

    The highly conserved N-terminal 23 residues of the hemagglutinin glycoprotein, known as the fusion peptide domain (HAfp23), is vital to the membrane fusion and infection mechanism of the influenza virus. HAfp23 has a helical hairpin structure consisting of two tightly packed amphiphilic helices that rest on the membrane surface. We demonstrate that HAfp23 is a new class of amphipathic helix that functions by leveraging the negative curvature induced by two tightly packed helices on membranes. The helical hairpin structure has an inverted wedge shape characteristic of negative curvature lipids, with a bulky hydrophobic region and a relatively small hydrophilic head region. The F3G mutation reduces this inverted wedge shape by reducing the volume of its hydrophobic base. We show that despite maintaining identical backbone structures and dynamics as the wild type HAfp23, the F3G mutant has an attenuated fusion activity that is correlated to its reduced ability to induce negative membrane curvature. The inverted wedge shape of HAfp23 is likely to play a crucial role in the initial stages of membrane fusion by stabilizing negative curvature in the fusion stalk. PMID:25398882

  10. A novel and small curvature sensor based on butterfly-shape Mach-Zehnder interferometer

    NASA Astrophysics Data System (ADS)

    Chen, Mao-qing; Zhao, Yong; Lv, Ri-qing; Xia, Feng

    2017-04-01

    A novel hollow-core fiber (HCF) curvature sensor based on a tapered HCF sandwiched between two single mode fibers (Butterfly-Shape Structure) is proposed and experimentally demonstrated. The collapsed region around the first fusion interface excites the high-order modes, and the butterfly shape couples the high-order modes back into the core and interferes with the fundamental mode in the second fusion interface. Simulation of the butterfly-shape structure is carried out using the beam propagation method to determine an optimized size of sensing element. The experimental results show that the variation of the interference spectrum light intensity is almost linearly proportional to the change of curvature, and the curvature sensitivity and resolution of the proposed sensor can be up to -10.9041dB / m-1 and 0.000917m-1 respectively in the range from 0.387 to 1.285 m-1. The proposed curvature sensor is compact size, high sensitive, and inexpensive.

  11. Geometrical interpretation and curvature distribution in nanocarbons

    NASA Astrophysics Data System (ADS)

    Gupta, Sanju; Saxena, Avadh

    2011-04-01

    Despite extensive research on microscopic structure and physical property characterization of advanced nanocarbon systems, they have not been viewed as topologically distinct nanoscale materials with various geometries (curvature). This work is motivated by our recent work [S. Gupta and A. Saxena, J. Raman Spectrosc. 40, 1127 (2009)] where we introduced the notion of "global" topology for novel nanocarbons and provided systematic trends by monitoring the phonon spectra via resonance Raman spectroscopy, which led to the paradigm of curvature/topology → property → functionality relationship in these materials. Here we determined the distribution of the mean (H) and Gaussian (K) curvatures as pertinent observables for geometric characterization taking into account the observed geometrical parameters, that is, radius, polar, azimuthal, or conical angle associated with tubular (single, double-, and multi-walled nanotubes; K = 0), spherical (hypo- and hyperfullerenes; K > 0) and complex (helical nanoribbons and nanotori/nanorings; K < 0) nanocarbon geometries to quantify the interplay of intrinsic surface curvature and topology, wherein global topology of the overall sp2-bonded carbon (sp2C) constrains local topology of the constituent carbon rings. We also studied various other structures such as catenoid and saddle-shaped surfaces as interesting nanocarbons. We compared these results with highly oriented pyrolytic graphite and monolayer graphene as layered and planar systems, respectively. Moreover, nanocarbons discussed herein are their derivatives. Curvature leads to nonlinearity that manifests itself in some form of symmetry breaking which can be extrapolated to topological variation due to nanoscale defects. Thus it may either close/open the bandgap leading to the introduction of new Raman spectroscopy signatures and optical absorption peaks, changes in mechanical properties, electrical behavior, and electronic density of states and possibly inducing magnetism

  12. High Plains regional ground-water study

    USGS Publications Warehouse

    Dennehy, Kevin F.

    2000-01-01

    Over the last 25 years, industry and government have made large financial investments aimed at improving water quality across the Nation. Significant progress has been made; however, many water-quality concerns remain. In 1991, the U.S. Geological Survey (USGS) began implementing a full-scale National Water-Quality Assessment Program to provide consistent and scientifically sound information for managing the Nation's water resources. The goals of the NAWQA Program are to (1) describe current water-quality conditions for a large part of the Nation's freshwater streams and aquifers, (2) describe how water quality is changing over time, and (3) improve our understanding of the primary natural and human factors affecting water quality. Assessing the quality of water in every location in the Nation would not be practical; therefore, NAWQA Program studies are conducted within a set of areas called study units (fig. 1). These study units are composed of more than 50 important river and aquifer systems that represent the diverse geography, water resources, and land and water uses of the Nation. The High Plains Regional Ground-Water Study is one such study area, designed to address issues relevant to the High Plains Aquifer system while supplementing water-quality information collected in other study units across the Nation. Implementation of the NAWQA Program for the High Plains Regional Ground-Water Study area began in 1998.

  13. Effect of curvature on domain wall motion in elliptical nanorings

    NASA Astrophysics Data System (ADS)

    Kaya, Fikriye Idil; Bickel, Jessica; Aidala, Katherine

    2014-03-01

    Understanding domain wall (DW) motion in ferromagnetic nanostructures is important to realize proposed magnetic data storage and logic devices. We investigate the effect of curvature on DW pinning and motion by studying elliptical rings using micromagnetic simulations. Elliptical rings with constant width have varying curvature, with the lowest curvature at the minor axis, and the greatest curvature at the major axis. DWs can be created at any angular position within the ellipse by the application of an appropriate uniform magnetic field. However, only some of these positions are stable when the field is removed. We study the stability and depinning of the DWs by applying a slowly increasing elliptical magnetic field to determine the magnitude of the field at which the DWs begin to move. By varying the major to minor axis ratio, we examine the effect of curvature on DW pinning. A larger field is required to move DWs in regions of higher curvature (near the major axis) than lower curvature (near the minor axis). Overall, we see that increasing the major to minor axis ratio of elliptical nanorings requires increasing field strength to depin the DWs along the major axis. Work supported in part by NSF DMR-1207924 and NSF CMMI-1025020. Simulations performed at the CNS computational facilities at Harvard University, a member of the NNIN supported by NSF Award No. ECS-0335765.

  14. Influence of Global and Local Membrane Curvature on Mechanosensitive Ion Channels: A Finite Element Approach

    PubMed Central

    Bavi, Omid; Cox, Charles D.; Vossoughi, Manouchehr; Naghdabadi, Reza; Jamali, Yousef; Martinac, Boris

    2016-01-01

    Mechanosensitive (MS) channels are ubiquitous molecular force sensors that respond to a number of different mechanical stimuli including tensile, compressive and shear stress. MS channels are also proposed to be molecular curvature sensors gating in response to bending in their local environment. One of the main mechanisms to functionally study these channels is the patch clamp technique. However, the patch of membrane surveyed using this methodology is far from physiological. Here we use continuum mechanics to probe the question of how curvature, in a standard patch clamp experiment, at different length scales (global and local) affects a model MS channel. Firstly, to increase the accuracy of the Laplace’s equation in tension estimation in a patch membrane and to be able to more precisely describe the transient phenomena happening during patch clamping, we propose a modified Laplace’s equation. Most importantly, we unambiguously show that the global curvature of a patch, which is visible under the microscope during patch clamp experiments, is of negligible energetic consequence for activation of an MS channel in a model membrane. However, the local curvature (RL < 50) and the direction of bending are able to cause considerable changes in the stress distribution through the thickness of the membrane. Not only does local bending, in the order of physiologically relevant curvatures, cause a substantial change in the pressure profile but it also significantly modifies the stress distribution in response to force application. Understanding these stress variations in regions of high local bending is essential for a complete understanding of the effects of curvature on MS channels. PMID:26861405

  15. Influence of Global and Local Membrane Curvature on Mechanosensitive Ion Channels: A Finite Element Approach.

    PubMed

    Bavi, Omid; Cox, Charles D; Vossoughi, Manouchehr; Naghdabadi, Reza; Jamali, Yousef; Martinac, Boris

    2016-02-05

    Mechanosensitive (MS) channels are ubiquitous molecular force sensors that respond to a number of different mechanical stimuli including tensile, compressive and shear stress. MS channels are also proposed to be molecular curvature sensors gating in response to bending in their local environment. One of the main mechanisms to functionally study these channels is the patch clamp technique. However, the patch of membrane surveyed using this methodology is far from physiological. Here we use continuum mechanics to probe the question of how curvature, in a standard patch clamp experiment, at different length scales (global and local) affects a model MS channel. Firstly, to increase the accuracy of the Laplace's equation in tension estimation in a patch membrane and to be able to more precisely describe the transient phenomena happening during patch clamping, we propose a modified Laplace's equation. Most importantly, we unambiguously show that the global curvature of a patch, which is visible under the microscope during patch clamp experiments, is of negligible energetic consequence for activation of an MS channel in a model membrane. However, the local curvature (RL < 50) and the direction of bending are able to cause considerable changes in the stress distribution through the thickness of the membrane. Not only does local bending, in the order of physiologically relevant curvatures, cause a substantial change in the pressure profile but it also significantly modifies the stress distribution in response to force application. Understanding these stress variations in regions of high local bending is essential for a complete understanding of the effects of curvature on MS channels.

  16. Do adult men with untreated ventral penile curvature have adverse outcomes?

    PubMed

    Menon, Vani; Breyer, Benjamin; Copp, Hillary L; Baskin, Laurence; Disandro, Michael; Schlomer, Bruce J

    2016-02-01

    Congenital ventral penile curvature without hypospadias is often treated surgically in childhood. The history of untreated ventral curvature is unknown. This study's aim was to examine the association of untreated ventral penile curvature with various sexual and psychosexual outcomes. An electronic survey was advertised to men older than 18 years on Facebook. Men with possible ventral penile curvature identified themselves by choosing sketches that most closely represented their anatomy. Outcomes assessed included: Sexual Health Inventory for Men, difficulty of intercourse because of curvature, International Prostate Symptom Score, Penile Perception Score, psychosexual milestones, paternity, infertility, sitting to urinate, and the CDC HRQOL-4 module. Among participants, 81 out of 684 men (11.8%) reported untreated ventral penile curvature. Participants with self-reported curvature noted more difficulty with intercourse because of curvature (4.5 vs 4.9, p < 0.001), more unhealthy mental days (8.6 vs 6.2, p = 0.02), and increased dissatisfaction with penile self-perception compared with men without reported curvature (8.6 vs 9.5, p < 0.001). Men with possible untreated ventral curvature reported worse penile perception scores, more mentally unhealthy days, and increased difficulty with intercourse secondary to curvature compared with men without curvature. A limitation to this study is selection bias; responses collected were self-reported from survey volunteers. Additionally, the question identifying ventral penile curvature is not validated but performed well in pretesting. Most questions were from validated surveys, but some were modeled after validated surveys and/or contained high face validity types of questions. Men with possible untreated ventral penile curvature reported more dissatisfaction with penile appearance, increased difficulty with intercourse, and more unhealthy mental days. Given high success rates, low complications, and improved outcomes after

  17. Do adult men with untreated ventral penile curvature have adverse outcomes?

    PubMed Central

    Menon, Vani; Breyer, Benjamin; Copp, Hillary L.; Baskin, Laurence; Disandro, Michael; Schlomer, Bruce J.

    2016-01-01

    Summary Introduction Congenital ventral penile curvature without hypospadias is often treated surgically in childhood. The history of untreated ventral curvature is unknown. Objective This study’s aim was to examine the association of untreated ventral penile curvature with various sexual and psychosexual outcomes. Study design An electronic survey was advertised to men older than 18 years on Facebook. Men with possible ventral penile curvature identified themselves by choosing sketches that most closely represented their anatomy. Outcomes assessed included: Sexual Health Inventory for Men, difficulty of intercourse because of curvature, International Prostate Symptom Score, Penile Perception Score, psychosexual milestones, paternity, infertility, sitting to urinate, and the CDC HRQOL-4 module. Results Among participants, 81 out of 684 men (11.8%) reported untreated ventral penile curvature. Participants with self-reported curvature noted more difficulty with intercourse because of curvature (4.5 vs 4.9, p < 0.001), more unhealthy mental days (8.6 vs 6.2, p = 0.02), and increased dissatisfaction with penile self-perception compared with men without reported curvature (8.6 vs 9.5, p < 0.001). Discussion Men with possible untreated ventral curvature reported worse penile perception scores, more mentally unhealthy days, and increased difficulty with intercourse secondary to curvature compared with men without curvature. A limitation to this study is selection bias; responses collected were self-reported from survey volunteers. Additionally, the question identifying ventral penile curvature is not validated but performed well in pretesting. Most questions were from validated surveys, but some were modeled after validated surveys and/or contained high face validity types of questions. Conclusion Men with possible untreated ventral penile curvature reported more dissatisfaction with penile appearance, increased difficulty with intercourse, and more unhealthy mental

  18. Magnetophoretic Induction of Root Curvature

    NASA Technical Reports Server (NTRS)

    Hasenstein, Karl H.

    1997-01-01

    The last year of the grant period concerned the consolidation of previous experiments to ascertain that the theoretical premise apply not just to root but also to shoots. In addition, we verified that high gradient magnetic fields do not interfere with regular cellular activities. Previous results have established that: (1) intracellular magnetophoresis is possible; and (2) HGMF lead to root curvature. In order to investigate whether HGMF affect the assembly and/or organization of structural proteins, we examined the arrangement of microtubules in roots exposed to HGMF. The cytoskeletal investigations were performed with fomaldehyde-fixed, nonembedded tissue segments that were cut with a vibratome. Microtubules (MTs) were stained with rat anti-yeast tubulin (YOL 1/34) and DTAF-labeled antibody against rat IgG. Microfilaments (MFs) were visualized by incubation in rhodamine-labeled phalloidin. The distribution and arrangement of both components of the cytoskeleton were examined with a confocal microscope. Measurements of growth rates and graviresponse were done using a video-digitizer. Since HGMF repel diamagnetic substances including starch-filled amyloplasts and most The second aspect of the work includes studies of the effect of cytoskeletal inhibitors on MTs and MFs. The analysis of the effect of micotubular inhibitors on the auxin transport in roots showed that there is very little effect of MT-depolymerizing or stabilizing drugs on auxin transport. This is in line with observations that application of such drugs is not immediately affecting the graviresponsiveness of roots.

  19. LPG-based sensor for curvature and vibration

    NASA Astrophysics Data System (ADS)

    Nascimento, I. M.; Chesini, G.; Baptista, J. M.; Cordeiro, Cristiano M. B.; Jorge, P. A. S.

    2016-05-01

    A long-period grating (LPG) written on a standard single mode fiber is investigated as a curvature and vibration sensor. It is demonstrated a high sensitivity to applied curvature and the possibility to monitor vibration in a wide range of frequencies from 30 Hz to 2000 Hz. The system was tested using an intensity based interrogation scheme with the LPG sensor operating in the curvature regime. Results have shown a reproducible frequency discrimination in the 30 Hz to 2000 Hz, with resolutions between 11 mHz and 913 mHz. Frequency retrieval could be performed independent of temperature up to 86 °C.

  20. A highly amyloidogenic region of hen lysozyme.

    PubMed

    Frare, Erica; Polverino De Laureto, Patrizia; Zurdo, Jesús; Dobson, Christopher M; Fontana, Angelo

    2004-07-23

    Amyloid fibrils obtained after incubating hen egg-white lysozyme (HEWL) at pH 2.0 and 65 degrees C for extended periods of time have been found to consist predominantly of fragments of the protein corresponding to residues 49-100, 49-101, 53-100 and 53-101, derived largely from the partial acid hydrolysis of Asp-X peptide bonds. These internal fragments of HEWL encompass part of the beta-domain and all the residues forming the C-helix in the native protein, and contain two internal disulfide bridges Cys64-Cys80 and Cys76-Cys94. The complementary protein fragments, including helices A, B and D of the native protein, are not significantly incorporated into the network of fibrils, but remain largely soluble, in agreement with their predicted lower propensities to aggregate. Further analysis of the properties of different regions of HEWL to form amyloid fibrils was carried out by studying fragments produced by limited proteolysis of the protein by pepsin. Here, we show that only fragment 57-107, but not fragment 1-38/108-129, is able to generate well-defined amyloid fibrils under the conditions used. This finding is of particular importance, as the beta-domain and C-helix of the highly homologous human lysozyme have been shown to unfold locally in the amyloidogenic variant D67H, which is associated with the familial cases of systemic amyloidosis linked to lysozyme deposition. The identification of the highly amyloidogenic character of this region of the polypeptide chain provides strong support for the involvement of partially unfolded species in the initiation of the aggregation events that lead to amyloid deposition in clinical disease.

  1. Curvature modulates the self-assembly of amphiphilic molecules.

    PubMed

    Tian, Falin; Luo, Yu; Zhang, Xianren

    2010-10-14

    In this work, we used lattice Monte Carlo simulations and theoretical model calculations to show how the self-assembly of adsorbed amphiphilic molecules is affected by the local curvature of solid surfaces. It is found that, beyond a critical curvature value, solid surface geometry governs the spatial ordering of aggregates and may induce the morphological transitions. The simulation results show how the curvature of solid surfaces modulates the distribution of aggregates: the anisotropy in local curvature along and perpendicular to the cylindrical surfaces tends to generate orientationally ordered cylindrical micelles. To account for the morphological transitions induced by the local curvature of solid surfaces, we constructed a theoretical model which includes the Helfrich bending energy, the deformation energy of aggregates induced by solid surfaces, and the adsorption energy. The model calculations indicate that on highly curved solid surfaces the bending energy for bilayer structure sharply increases with surface curvature, which in turn induces the morphological transition from bilayer to cylindrical structure. Our results suggest that the local curvature provides a means of controlling the spatial organization of amphiphilic molecules.

  2. Static optical designs for Wavefront Curvature Sensing

    NASA Astrophysics Data System (ADS)

    Bharmal, Nazim A.

    2006-06-01

    A bulk optic is presented, the Parallel Output Beamsplitter, which allows simultaneous imaging of two planes either side of the focus using static imaging optics. The POB is used to create novel optical configurations for Wavefront Curvature Sensing and two designs are presented. The first is suited to small-amplitude aberration measurements in situations where compactness, a large field of view, and high optical throughput are desirable. A laboratory experiment using a POB to make such a wavefront sensor was undertaken, and results are presented. The second design is a conceptual idea which offers image-scale invariant imaging of two planes whose conjugation satisfies the requirements of a conventional Wavefront Curvature Sensor concept.

  3. Intrinsically disordered proteins drive membrane curvature

    PubMed Central

    Busch, David J.; Houser, Justin R.; Hayden, Carl C.; Sherman, Michael B.; Lafer, Eileen M.; Stachowiak, Jeanne C.

    2015-01-01

    Assembly of highly curved membrane structures is essential to cellular physiology. The prevailing view has been that proteins with curvature-promoting structural motifs, such as wedge-like amphipathic helices and crescent-shaped BAR domains, are required for bending membranes. Here we report that intrinsically disordered domains of the endocytic adaptor proteins, Epsin1 and AP180 are highly potent drivers of membrane curvature. This result is unexpected since intrinsically disordered domains lack a well-defined three-dimensional structure. However, in vitro measurements of membrane curvature and protein diffusivity demonstrate that the large hydrodynamic radii of these domains generate steric pressure that drives membrane bending. When disordered adaptor domains are expressed as transmembrane cargo in mammalian cells, they are excluded from clathrin-coated pits. We propose that a balance of steric pressure on the two surfaces of the membrane drives this exclusion. These results provide quantitative evidence for the influence of steric pressure on the content and assembly of curved cellular membrane structures. PMID:26204806

  4. Intrinsically disordered proteins drive membrane curvature

    NASA Astrophysics Data System (ADS)

    Busch, David J.; Houser, Justin R.; Hayden, Carl C.; Sherman, Michael B.; Lafer, Eileen M.; Stachowiak, Jeanne C.

    2015-07-01

    Assembly of highly curved membrane structures is essential to cellular physiology. The prevailing view has been that proteins with curvature-promoting structural motifs, such as wedge-like amphipathic helices and crescent-shaped BAR domains, are required for bending membranes. Here we report that intrinsically disordered domains of the endocytic adaptor proteins, Epsin1 and AP180 are highly potent drivers of membrane curvature. This result is unexpected since intrinsically disordered domains lack a well-defined three-dimensional structure. However, in vitro measurements of membrane curvature and protein diffusivity demonstrate that the large hydrodynamic radii of these domains generate steric pressure that drives membrane bending. When disordered adaptor domains are expressed as transmembrane cargo in mammalian cells, they are excluded from clathrin-coated pits. We propose that a balance of steric pressure on the two surfaces of the membrane drives this exclusion. These results provide quantitative evidence for the influence of steric pressure on the content and assembly of curved cellular membrane structures.

  5. Intrinsically disordered proteins drive membrane curvature.

    PubMed

    Busch, David J; Houser, Justin R; Hayden, Carl C; Sherman, Michael B; Lafer, Eileen M; Stachowiak, Jeanne C

    2015-07-24

    Assembly of highly curved membrane structures is essential to cellular physiology. The prevailing view has been that proteins with curvature-promoting structural motifs, such as wedge-like amphipathic helices and crescent-shaped BAR domains, are required for bending membranes. Here we report that intrinsically disordered domains of the endocytic adaptor proteins, Epsin1 and AP180 are highly potent drivers of membrane curvature. This result is unexpected since intrinsically disordered domains lack a well-defined three-dimensional structure. However, in vitro measurements of membrane curvature and protein diffusivity demonstrate that the large hydrodynamic radii of these domains generate steric pressure that drives membrane bending. When disordered adaptor domains are expressed as transmembrane cargo in mammalian cells, they are excluded from clathrin-coated pits. We propose that a balance of steric pressure on the two surfaces of the membrane drives this exclusion. These results provide quantitative evidence for the influence of steric pressure on the content and assembly of curved cellular membrane structures.

  6. 2D dynamic studies combined with the surface curvature analysis to predict Arias Intensity amplification

    NASA Astrophysics Data System (ADS)

    Torgoev, Almaz; Havenith, Hans-Balder

    2016-07-01

    A 2D elasto-dynamic modelling of the pure topographic seismic response is performed for six models with a total length of around 23.0 km. These models are reconstructed from the real topographic settings of the landslide-prone slopes situated in the Mailuu-Suu River Valley, Southern Kyrgyzstan. The main studied parameter is the Arias Intensity (Ia, m/sec), which is applied in the GIS-based Newmark method to regionally map the seismically-induced landslide susceptibility. This method maps the Ia values via empirical attenuation laws and our studies investigate a potential to include topographic input into them. Numerical studies analyse several signals with varying shape and changing central frequency values. All tests demonstrate that the spectral amplification patterns directly affect the amplification of the Ia values. These results let to link the 2D distribution of the topographically amplified Ia values with the parameter called as smoothed curvature. The amplification values for the low-frequency signals are better correlated with the curvature smoothed over larger spatial extent, while those values for the high-frequency signals are more linked to the curvature with smaller smoothing extent. The best predictions are provided by the curvature smoothed over the extent calculated according to Geli's law. The sample equations predicting the Ia amplification based on the smoothed curvature are presented for the sinusoid-shape input signals. These laws cannot be directly implemented in the regional Newmark method, as 3D amplification of the Ia values addresses more problem complexities which are not studied here. Nevertheless, our 2D results prepare the theoretical framework which can potentially be applied to the 3D domain and, therefore, represent a robust basis for these future research targets.

  7. Curvature generation in nematic surfaces

    NASA Astrophysics Data System (ADS)

    Mostajeran, Cyrus

    2015-06-01

    In recent years there has been a growing interest in the study of shape formation using modern responsive materials that can be preprogrammed to undergo spatially inhomogeneous local deformations. In particular, nematic liquid crystalline solids offer exciting possibilities in this context. Considerable recent progress has been made in achieving a variety of shape transitions in thin sheets of nematic solids by engineering isolated points of concentrated Gaussian curvature using topological defects in the nematic director field across textured surfaces. In this paper, we consider ways of achieving shape transitions in thin sheets of nematic glass by generation of nonlocalized Gaussian curvature in the absence of topological defects in the director field. We show how one can blueprint any desired Gaussian curvature in a thin nematic sheet by controlling the nematic alignment angle across the surface and highlight specific patterns which present feasible initial targets for experimental verification of the theory.

  8. Measurement of radius of curvature of spherical optical surfaces with small curvature and aperture by optical profiler

    NASA Astrophysics Data System (ADS)

    Ma, Shuang; Yi, Shengzhen; Chen, Shenghao; Wang, Zhanshan

    2014-11-01

    Monochromatic energy multilayer Kirkpatrick-Baez microscope is one of key diagnostic tools for researches on inertial confinement fusion. It is composed by two orthogonal concave spherical mirrors with small curvature and aperture, and produce the image of an object by collecting X-rays in each orthogonal direction, independently. Accurate measurement of radius of curvature of concave spherical mirrors is very important to achieve its design optical properties including imaging quality, optical throughput and energy resolution. However, it is difficult to measure the radius of curvature of spherical optical surfaces with small curvature and aperture by conventional methods, for the produced reflective intensity of glass is too low to correctly test. In this paper, we propose an improved measuring method of optical profiler to accomplish accurate measurement of radius of curvature of spherical optical surfaces with small curvature and aperture used in the monochromatic energy multilayer Kirkpatrick-Baez microscope. Firstly, we use a standard super-smooth optical flat to calibrate reference mirror before each experiment. Following, deviation of central position between measurement area and interference pattern is corrected by the theory of Newton's rings, and the zero-order fringe position is derived from the principle of interference in which surface roughness has minimum values in the position of zero light path difference. Measured results by optical profiler show the low relative errors and high repeatability. Eventually, an imaging experiment of monochromatic energy multilayer Kirkpatrick-Baez microscope determines the measurement accuracy of radius of curvature.

  9. Amplification of curvature perturbations in cyclic cosmology

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Liu, Zhi-Guo; Piao, Yun-Song

    2010-12-01

    We analytically and numerically show that through the cycles with nonsingular bounce, the amplitude of curvature perturbation on a large scale will be amplified and the power spectrum will redden. In some sense, this amplification will eventually destroy the homogeneity of the background, which will lead to the ultimate end of cycles of the global universe. We argue that for the model with increasing cycles, it might be possible that a fissiparous multiverse will emerge after one or several cycles, in which the cycles will continue only at corresponding local regions.

  10. Amplification of curvature perturbations in cyclic cosmology

    SciTech Connect

    Zhang Jun; Liu Zhiguo; Piao Yunsong

    2010-12-15

    We analytically and numerically show that through the cycles with nonsingular bounce, the amplitude of curvature perturbation on a large scale will be amplified and the power spectrum will redden. In some sense, this amplification will eventually destroy the homogeneity of the background, which will lead to the ultimate end of cycles of the global universe. We argue that for the model with increasing cycles, it might be possible that a fissiparous multiverse will emerge after one or several cycles, in which the cycles will continue only at corresponding local regions.

  11. The Induction of Negative Curvature as a Mechanism of Cell Toxicity by Amyloidogenic Peptides

    PubMed Central

    Smith, Pieter E. S.; Brender, Jeffrey R.; Ramamoorthy, Ayyalusamy

    2009-01-01

    The death of insulin-producing β-cells is a key step in the pathogenesis of type 2 diabetes. The amyloidogenic peptide Islet Amyloid Polypeptide (IAPP, also known as amylin) has been shown to disrupt β-cell membranes leading to β-cell death. Despite the strong evidence linking IAPP to the destruction of β-cell membrane integrity and cell death, the mechanism of IAPP toxicity is poorly understood. In particular, the effect of IAPP on the bilayer structure has largely been uncharacterized. In this study, we have determined the effect of the amyloidogenic and toxic hIAPP1-37 peptide and the non-toxic and non-amyloidogenic rIAPP1-37 peptide on membranes by a combination of DSC and solid-state NMR spectroscopy. We also characterized the toxic but largely non-amyloidogenic rIAPP1-19 and hIAPP1-19 fragments. DSC shows that both amyloidogenic (hIAPP1-37) and largely non-amyloidogenic (hIAPP1-19 and rIAPP1-19) toxic versions of the peptide strongly favor the formation of negative curvature in lipid bilayers, while the non-toxic full-length rat IAPP1-37 peptide does not. This result was confirmed by solid-state NMR spectroscopy which shows that in bicelles composed of regions of high curvature and low curvature, non-toxic rIAPP1-37 binds to the regions of low curvature while toxic rIAPP1-19 binds to regions of high curvature. Similarly, solid-state NMR spectroscopy shows that the toxic rIAPP1-19 peptide significantly disrupts the lipid bilayer structure, whereas the non-toxic rIAPP1-37 does not have a significant effect. These results indicate IAPP may induce the formation of pores by the induction of excess membrane curvature and can be used to guide the design of compounds that can prevent the cell-toxicity of IAPP. This mechanism may be important to understand the toxicity of other amyloidogenic proteins. Our solid-state NMR results also demonstrate the possibility of using bicelles to measure the affinity of biomolecules for negatively or positively curved regions of

  12. Nanoscale Membrane Curvature detected by Polarized Localization Microscopy

    NASA Astrophysics Data System (ADS)

    Kelly, Christopher; Maarouf, Abir; Woodward, Xinxin

    Nanoscale membrane curvature is a necessary component of countless cellular processes. Here we present Polarized Localization Microscopy (PLM), a super-resolution optical imaging technique that enables the detection of nanoscale membrane curvature with order-of-magnitude improvements over comparable optical techniques. PLM combines the advantages of polarized total internal reflection fluorescence microscopy and fluorescence localization microscopy to reveal single-fluorophore locations and orientations without reducing localization precision by point spread function manipulation. PLM resolved nanoscale membrane curvature of a supported lipid bilayer draped over polystyrene nanoparticles on a glass coverslip, thus creating a model membrane with coexisting flat and curved regions and membrane radii of curvature as small as 20 nm. Further, PLM provides single-molecule trajectories and the aggregation of curvature-inducing proteins with super-resolution to reveal the correlated effects of membrane curvature, dynamics, and molecular sorting. For example, cholera toxin subunit B has been observed to induce nanoscale membrane budding and concentrate at the bud neck. PLM reveals a previously hidden and critical information of membrane topology.

  13. Curvature-induced geometrical frustration in magnetic systems

    SciTech Connect

    Saxena, A.; Dandoloff, R.

    1997-05-01

    We study classical Heisenberg spins in the continuum limit (i.e., the nonlinear {sigma} model) on an elastic two-dimensional manifold with at least one nonconstant principal curvature. If the corresponding Euler-Lagrange equations support a soliton solution, the nonconstant curvature of the geometry induces geometrical frustration in the region of the soliton which is relieved by a deformation of the manifold in the region of the soliton. We illustrate these results on an elliptic cylinder where we find an elastic soliton in terms of the variable ellipticity along the axis of the cylinder. {copyright} {ital 1997} {ital The American Physical Society}

  14. Raft Formation in Lipid Bilayers Coupled to Curvature

    PubMed Central

    Sadeghi, Sina; Müller, Marcus; Vink, Richard L.C.

    2014-01-01

    We present computer simulations of a membrane in which the local composition is coupled to the local membrane curvature. At high temperatures (i.e., above the temperature of macroscopic phase separation), finite-sized transient domains are observed, reminiscent of lipid rafts. The domain size is in the range of hundred nanometers, and set by the membrane elastic properties. These findings are in line with the notion of the membrane as a curvature-induced microemulsion. At low temperature, the membrane phase separates. The transition to the phase-separated regime is continuous and belongs to the two-dimensional Ising universality class when the coupling to curvature is weak, but becomes first-order for strong curvature-composition coupling. PMID:25296311

  15. Holonomy Attractor Connecting Spaces of Different Curvature Responsible for ``Anomalies''

    NASA Astrophysics Data System (ADS)

    Binder, Bernd

    2009-03-01

    In this lecture paper we derive Magic Angle Precession (MAP) from first geometric principles. MAP can arise in situations, where precession is multiply related to spin, linearly by time or distance (dynamic phase, rolling, Gauss law) and transcendentally by the holonomy loop path (geometric phase). With linear spin-precession coupling, gyroscopes can be spun up and down to very high frequencies via low frequency holonomy control induced by external accelerations, which provides for extreme coupling strengths or "anomalies" that can be tested by the powerball or gyrotwister device. Geometrically, a gyroscopic manifold with spherical metric is tangentially aligned to a precession wave channel with conic or hyperbolic metric (like the relativistic Thomas precession). Transporting triangular spin/precession vector relations across the tangential boundary of contact with SO(3) Lorentz symmetry, we get extreme vector currents near the attractor fixed points in precession phase space, where spin currents remain intact while crossing the contact boundaries between regions of different curvature signature (-1, 0, +1). The problem can be geometrically solved by considering a curvature invariant triangular condition, which holds on surfaces with different curvature that are in contact and locally parallel. In this case two out of three angles are identical, whereas the third angle is different due to holonomy. If we require that the side length ratio corresponding to these angles are invariant we get a geodesic chaotic attractor, which is a cosine map cos(x)˜Mx in parameter space providing for fixed points, limit cycle bifurcations, and singularities. The situation could be quite natural and common in the context of vector currents in curved spacetime and gauge theories. MAP could even be part of the electromagnetic interaction, where the electric charge is the geometric U(1) precession spin current and gauge potential with magnetic effects given by extra rotations under the

  16. Curvature of co-links uncovers hidden thematic layers in the World Wide Web.

    PubMed

    Eckmann, Jean-Pierre; Moses, Elisha

    2002-04-30

    Beyond the information stored in pages of the World Wide Web, novel types of "meta-information" are created when pages connect to each other. Such meta-information is a collective effect of independent agents writing and linking pages, hidden from the casual user. Accessing it and understanding the interrelation between connectivity and content in the World Wide Web is a challenging problem [Botafogo, R. A. & Shneiderman, B. (1991) in Proceedings of Hypertext (Assoc. Comput. Mach., New York), pp. 63-77 and Albert, R. & Barabási, A.-L. (2002) Rev. Mod. Phys. 74, 47-97]. We demonstrate here how thematic relationships can be located precisely by looking only at the graph of hyperlinks, gleaning content and context from the Web without having to read what is in the pages. We begin by noting that reciprocal links (co-links) between pages signal a mutual recognition of authors and then focus on triangles containing such links, because triangles indicate a transitive relation. The importance of triangles is quantified by the clustering coefficient [Watts, D. J. & Strogatz, S. H. (1999) Nature (London) 393, 440-442], which we interpret as a curvature [Bridson, M. R. & Haefliger, A. (1999) Metric Spaces of Non-Positive Curvature (Springer, Berlin)]. This curvature defines a World Wide Web landscape whose connected regions of high curvature characterize a common topic. We show experimentally that reciprocity and curvature, when combined, accurately capture this meta-information for a wide variety of topics. As an example of future directions we analyze the neural network of Caenorhabditis elegans, using the same methods.

  17. Curvature of co-links uncovers hidden thematic layers in the World Wide Web

    PubMed Central

    Eckmann, Jean-Pierre; Moses, Elisha

    2002-01-01

    Beyond the information stored in pages of the World Wide Web, novel types of “meta-information” are created when pages connect to each other. Such meta-information is a collective effect of independent agents writing and linking pages, hidden from the casual user. Accessing it and understanding the interrelation between connectivity and content in the World Wide Web is a challenging problem [Botafogo, R. A. & Shneiderman, B. (1991) in Proceedings of Hypertext (Assoc. Comput. Mach., New York), pp. 63–77 and Albert, R. & Barabási, A.-L. (2002) Rev. Mod. Phys. 74, 47–97]. We demonstrate here how thematic relationships can be located precisely by looking only at the graph of hyperlinks, gleaning content and context from the Web without having to read what is in the pages. We begin by noting that reciprocal links (co-links) between pages signal a mutual recognition of authors and then focus on triangles containing such links, because triangles indicate a transitive relation. The importance of triangles is quantified by the clustering coefficient [Watts, D. J. & Strogatz, S. H. (1999) Nature (London) 393, 440–442], which we interpret as a curvature [Bridson, M. R. & Haefliger, A. (1999) Metric Spaces of Non-Positive Curvature (Springer, Berlin)]. This curvature defines a World Wide Web landscape whose connected regions of high curvature characterize a common topic. We show experimentally that reciprocity and curvature, when combined, accurately capture this meta-information for a wide variety of topics. As an example of future directions we analyze the neural network of Caenorhabditis elegans, using the same methods. PMID:11972019

  18. Curvature of co-links uncovers hidden thematic layers in the World Wide Web

    NASA Astrophysics Data System (ADS)

    Eckmann, Jean-Pierre; Moses, Elisha

    2002-04-01

    Beyond the information stored in pages of the World Wide Web, novel types of "meta-information" are created when pages connect to each other. Such meta-information is a collective effect of independent agents writing and linking pages, hidden from the casual user. Accessing it and understanding the interrelation between connectivity and content in the World Wide Web is a challenging problem [Botafogo, R. A. & Shneiderman, B. (1991) in Proceedings of Hypertext (Assoc. Comput. Mach., New York), pp. 63-77 and Albert, R. & Barabási, A.-L. (2002) Rev. Mod. Phys. 74, 47-97]. We demonstrate here how thematic relationships can be located precisely by looking only at the graph of hyperlinks, gleaning content and context from the Web without having to read what is in the pages. We begin by noting that reciprocal links (co-links) between pages signal a mutual recognition of authors and then focus on triangles containing such links, because triangles indicate a transitive relation. The importance of triangles is quantified by the clustering coefficient [Watts, D. J. & Strogatz, S. H. (1999) Nature (London) 393, 440-442], which we interpret as a curvature [Bridson, M. R. & Haefliger, A. (1999) Metric Spaces of Non-Positive Curvature (Springer, Berlin)]. This curvature defines a World Wide Web landscape whose connected regions of high curvature characterize a common topic. We show experimentally that reciprocity and curvature, when combined, accurately capture this meta-information for a wide variety of topics. As an example of future directions we analyze the neural network of Caenorhabditis elegans, using the same methods.

  19. Space Curvature and the "Heavy Banana 'Paradox.'"

    ERIC Educational Resources Information Center

    Gruber, Ronald P.; And Others

    1991-01-01

    Two ways to visually enhance the concept of space curvature are described. Viewing space curvature as a meterstick contraction and the heavy banana "paradox" are discussed. The meterstick contraction is mathematically explained. (KR)

  20. Space Curvature and the "Heavy Banana 'Paradox.'"

    ERIC Educational Resources Information Center

    Gruber, Ronald P.; And Others

    1991-01-01

    Two ways to visually enhance the concept of space curvature are described. Viewing space curvature as a meterstick contraction and the heavy banana "paradox" are discussed. The meterstick contraction is mathematically explained. (KR)

  1. Curvature-induced lipid segregation

    NASA Astrophysics Data System (ADS)

    Zheng, Bin; Meng, Qing-Tian; B. Selinger Robin, L.; V. Selinger, Jonathan; Ye, Fang-Fu

    2015-06-01

    We investigate how an externally imposed curvature influences lipid segregation on two-phase-coexistent membranes. We show that the bending-modulus contrast of the two phases and the curvature act together to yield a reduced effective line tension. On largely curved membranes, a state of multiple domains (or rafts) forms due to a mechanism analogous to that causing magnetic-vortex formation in type-II superconductors. We determine the criterion for such a multi-domain state to occur; we then calculate respectively the size of the domains formed on cylindrically and spherically curved membranes. Project supported by the Hundred-Talent Program of the Chinese Academy of Sciences (FY) and the National Science Foundation of USA via Grant DMR-1106014 (RLBS, JVS).

  2. Quantum complexity and negative curvature

    NASA Astrophysics Data System (ADS)

    Brown, Adam R.; Susskind, Leonard; Zhao, Ying

    2017-02-01

    As time passes, once simple quantum states tend to become more complex. For strongly coupled k -local Hamiltonians, this growth of computational complexity has been conjectured to follow a distinctive and universal pattern. In this paper we show that the same pattern is exhibited by a much simpler system—classical geodesics on a compact two-dimensional geometry of uniform negative curvature. This striking parallel persists whether the system is allowed to evolve naturally or is perturbed from the outside.

  3. Curvatures Estimation in Orientation Selection

    DTIC Science & Technology

    1991-01-31

    than is-obtained in length-tuning measurements . Hence, over a limited range, increasing the size or gain of the small RF has a similar effect . The...the remaining larger, lower curvature units to represent the curve. An indirect test involves measuring the time for the effect to set in, with and...31Jan 91 By, Steen .Zcke * ax . Cnadr tDistribution/ Steen .Zcke *MaxS. ynaer ~ Availability Codes Dist Special Computer Vision and Robotics Laboratory

  4. Curvature-Driven Lipid Sorting in Biomembranes

    PubMed Central

    Callan-Jones, Andrew; Sorre, Benoit; Bassereau, Patricia

    2011-01-01

    It has often been suggested that the high curvature of transport intermediates in cells may be a sufficient means to segregate different lipid populations based on the relative energy costs of forming bent membranes. In this review, we present in vitro experiments that highlight the essential physics of lipid sorting at thermal equilibrium: It is driven by a trade-off between bending energy, mixing entropy, and interactions between species. We collect evidence that lipid sorting depends strongly on lipid–lipid and protein–lipid interactions, and hence on the underlying composition of the membrane and on the presence of bound proteins. PMID:21421916

  5. Spacetime Curvature and Higgs Stability after Inflation.

    PubMed

    Herranen, M; Markkanen, T; Nurmi, S; Rajantie, A

    2015-12-11

    We investigate the dynamics of the Higgs field at the end of inflation in the minimal scenario consisting of an inflaton field coupled to the standard model only through the nonminimal gravitational coupling ξ of the Higgs field. Such a coupling is required by renormalization of the standard model in curved space, and in the current scenario also by vacuum stability during high-scale inflation. We find that for ξ≳1, rapidly changing spacetime curvature at the end of inflation leads to significant production of Higgs particles, potentially triggering a transition to a negative-energy Planck scale vacuum state and causing an immediate collapse of the Universe.

  6. Disformal invariance of curvature perturbation

    SciTech Connect

    Motohashi, Hayato; White, Jonathan E-mail: jwhite@post.kek.jp

    2016-02-01

    We show that under a general disformal transformation the linear comoving curvature perturbation is not identically invariant, but is invariant on superhorizon scales for any theory that is disformally related to Horndeski's theory. The difference between disformally related curvature perturbations is found to be given in terms of the comoving density perturbation associated with a single canonical scalar field. In General Relativity it is well-known that this quantity vanishes on superhorizon scales through the Poisson equation that is obtained on combining the Hamiltonian and momentum constraints, and we confirm that a similar result holds for any theory that is disformally related to Horndeski's scalar-tensor theory so long as the invertibility condition for the disformal transformation is satisfied. We also consider the curvature perturbation at full nonlinear order in the unitary gauge, and find that it is invariant under a general disformal transformation if we assume that an attractor regime has been reached. Finally, we also discuss the counting of degrees of freedom in theories disformally related to Horndeski's.

  7. Substrate curvature regulates cell migration

    NASA Astrophysics Data System (ADS)

    He, Xiuxiu; Jiang, Yi

    2017-06-01

    Cell migration is essential in many aspects of biology. Many basic migration processes, including adhesion, membrane protrusion and tension, cytoskeletal polymerization, and contraction, have to act in concert to regulate cell migration. At the same time, substrate topography modulates these processes. In this work, we study how substrate curvature at micrometer scale regulates cell motility. We have developed a 3D mechanical model of single cell migration and simulated migration on curved substrates with different curvatures. The simulation results show that cell migration is more persistent on concave surfaces than on convex surfaces. We have further calculated analytically the cell shape and protrusion force for cells on curved substrates. We have shown that while cells spread out more on convex surfaces than on concave ones, the protrusion force magnitude in the direction of migration is larger on concave surfaces than on convex ones. These results offer a novel biomechanical explanation to substrate curvature regulation of cell migration: geometric constrains bias the direction of the protrusion force and facilitates persistent migration on concave surfaces.

  8. Substrate curvature regulates cell migration.

    PubMed

    He, Xiuxiu; Jiang, Yi

    2017-05-23

    Cell migration is essential in many aspects of biology. Many basic migration processes, including adhesion, membrane protrusion and tension, cytoskeletal polymerization, and contraction, have to act in concert to regulate cell migration. At the same time, substrate topography modulates these processes. In this work, we study how substrate curvature at micrometer scale regulates cell motility. We have developed a 3D mechanical model of single cell migration and simulated migration on curved substrates with different curvatures. The simulation results show that cell migration is more persistent on concave surfaces than on convex surfaces. We have further calculated analytically the cell shape and protrusion force for cells on curved substrates. We have shown that while cells spread out more on convex surfaces than on concave ones, the protrusion force magnitude in the direction of migration is larger on concave surfaces than on convex ones. These results offer a novel biomechanical explanation to substrate curvature regulation of cell migration: geometric constrains bias the direction of the protrusion force and facilitates persistent migration on concave surfaces.

  9. Clinical workflow for spinal curvature measurement with portable ultrasound

    NASA Astrophysics Data System (ADS)

    Tabanfar, Reza; Yan, Christina; Kempston, Michael; Borschneck, Daniel; Ungi, Tamas; Fichtinger, Gabor

    2016-03-01

    PURPOSE: Spinal curvature monitoring is essential in making treatment decisions in scoliosis. Monitoring entails radiographic examinations, however repeated ionizing radiation exposure has been shown to increase cancer risk. Ultrasound does not emit ionizing radiation and is safer for spinal curvature monitoring. We investigated a clinical sonography protocol and challenges associated with position-tracked ultrasound in spinal curvature measurement in scoliosis. METHODS: Transverse processes were landmarked along each vertebra using tracked ultrasound snapshots. The transverse process angle was used to determine the orientation of each vertebra. We tested our methodology on five patients in a local pediatric scoliosis clinic, comparing ultrasound to radiographic curvature measurements. RESULTS: Despite strong correlation between radiographic and ultrasound curvature angles in phantom studies, we encountered new challenges in the clinical setting. Our main challenge was differentiating transverse processes from ribs and other structures during landmarking. We observed up to 13° angle variability for a single vertebra and a 9.85° +/- 10.81° difference between ultrasound and radiographic Cobb angles for thoracic curvatures. Additionally, we were unable to visualize anatomical landmarks in the lumbar region where soft tissue depth was 25-35mm. In volunteers with large Cobb angles (greater than 40° thoracic and 60° lumbar), we observed spinal protrusions resulting in incomplete probe-skin contact and partial ultrasound images not suitable for landmarking. CONCLUSION: Spinal curvature measurement using tracked ultrasound is viable on phantom spine models. In the clinic, new challenges were encountered which must be resolved before a universal sonography protocol can be developed.

  10. Machine Learning Models for Detection of Regions of High Model Form Uncertainty in RANS

    NASA Astrophysics Data System (ADS)

    Ling, Julia; Templeton, Jeremy

    2015-11-01

    Reynolds Averaged Navier Stokes (RANS) models are widely used because of their computational efficiency and ease-of-implementation. However, because they rely on inexact turbulence closures, they suffer from significant model form uncertainty in many flows. Many RANS models make use of the Boussinesq hypothesis, which assumes a non-negative, scalar eddy viscosity that provides a linear relation between the Reynolds stresses and the mean strain rate. In many flows of engineering relevance, this eddy viscosity assumption is violated, leading to inaccuracies in the RANS predictions. For example, in near wall regions, the Boussinesq hypothesis fails to capture the correct Reynolds stress anisotropy. In regions of flow curvature, the linear relation between Reynolds stresses and mean strain rate may be inaccurate. This model form uncertainty cannot be quantified by simply varying the model parameters, as it is rooted in the model structure itself. Machine learning models were developed to detect regions of high model form uncertainty. These machine learning models consisted of binary classifiers that predicted, on a point-by-point basis, whether or not key RANS assumptions were violated. These classifiers were trained and evaluated for their sensitivity, specificity, and generalizability on a database of canonical flows.

  11. Nonlinear Sorting, Curvature Generation, and Crowding of Endophilin N-BAR on Tubular Membranes

    PubMed Central

    Zhu, Chen; Das, Sovan L.; Baumgart, Tobias

    2012-01-01

    The curvature of biological membranes is controlled by membrane-bound proteins. For example, during endocytosis, the sorting of membrane components, vesicle budding, and fission from the plasma membrane are mediated by adaptor and accessory proteins. Endophilin is a peripherally binding membrane protein that functions as an endocytic accessory protein. Endophilin's membrane tubulation capacity is well known. However, to understand the thermodynamic and mechanical aspects of endophilin function, experimental measurements need to be compared to quantitative theoretical models. We present measurements of curvature sorting and curvature generation of the endophilin A1 N-BAR domain on tubular membranes pulled from giant unilamellar vesicles. At low concentration, endophilin functions primarily as a membrane curvature sensor; at high concentrations, it also generates curvature. We determine the spontaneous curvature induced by endophilin and observe sigmoidal curvature/composition coupling isotherms that saturate at high membrane tensions and protein solution concentrations. The observation of saturation is supported by a strong dependence of lateral diffusion coefficients on protein density on the tether membrane. We develop a nonlinear curvature/composition coupling model that captures our experimental observations. Our model predicts a curvature-induced phase transition among two states with varying protein density and membrane curvature. This transition could act as a switch during endocytosis. PMID:22768939

  12. Calculation of Scale-Dependent Curvatures of Geological Surfaces

    NASA Astrophysics Data System (ADS)

    Bergbauer, S.; Mukerji, T.; Pollard, D. D.; Hennings, P. H.

    2001-12-01

    A comparison between a spectral and a factorial kriging analysis is presented for the calculation of scale -dependent normal surface curvatures. Knowledge of scale -dependent curvatures of geological surfaces plays an important role in quantitative structural geology. Often, curvature analyses of geological surfaces, such as horizon tops, are performed to estimate the strain resulting from deformation. The final shape of the horizon, however, is a superposition of natural structures of different sizes ranging from the grain scale to the basin scale. Performing a curvature analysis on the raw data often leads to patchy, un-interpretable surface curvatures. Separating the surface curvature of the overall structure from the curvature of minor surface undulations can therefore be crucial in any quantitative structural analysis that uses the absolute value of surface curvature. The two methods are applied to a seismically mapped and depth-converted horizon of domal structures from the North Sea to investigate their applicability in a sub-surface context. For the spectral analysis the surface is transformed into a discrete frequency spectrum. When the overall curvature of the horizon is of interest, only the low-frequency components of the spectrum are used for the curvature analysis. The frequency bin width is determined such that only those frequencies that make up the overall surface structure are used, and that aliasing is minimized. The remaining high-frequency spectrum can be added back to address quantitatively the alias introduced by this filtering. In geostatistical factorial kriging analyses, the spatial covariance (variogram) is estimated from the data, and modeled as a sum of independent factors with different ranges. Short range variogram factors correspond to high frequency spectral components of the surface while long range factors contribute low frequency components. Using the modeled variogram, factorial kriging filters out the desired long range

  13. On the determination of curvature and dynamical dark energy

    SciTech Connect

    Virey, J-M; Taxil, P; Talon-Esmieu, D; Ealet, A; Tilquin, A E-mail: talon@cppm.in2p3.fr E-mail: taxil@cpt.univ-mrs.fr

    2008-12-15

    Constraining simultaneously the dark energy (DE) equation of state and the curvature of the universe is difficult due to strong degeneracies. To circumvent this problem when analyzing data it is usual to assume flatness to constrain the DE or, conversely, to assume that the DE is a cosmological constant to constrain the curvature. In this paper, we quantify the impact of such assumptions with an eye to future large surveys. We simulate future data for type Ia supernovae, the cosmic microwave background and baryon acoustic oscillations for a large range of fiducial cosmologies allowing a small spatial curvature. We take into account a possible time evolution of DE through a parameterized equation of state: w(a) = w{sub 0}+(1-a)w{sub a}. We then fit the simulated data with a wrong assumption on the curvature or on the DE parameters. For a fiducial {Lambda}CDM cosmology, if flatness is incorrectly assumed in the fit and if the true curvature is within the ranges 0.01<{Omega}{sub k}<0.03 and -0.07<{Omega}{sub k}<-0.01, one will be led to conclude erroneously that an evolving DE is present, even with high statistics. On the other hand, models with curvature and dynamical DE can be confused with a flat {Lambda}CDM model when the fit ignores a possible DE evolution. We find that, in the future, with high statistics, such risks of confusion should be limited, but they are still possible, and biases in the cosmological parameters might be important. We conclude by recalling that, in the future, it will be mandatory to perform some complete multi-probe analyses, leaving the DE parameters as well as the curvature as free parameters.

  14. Lumen irregularity dominates the relationship between mechanical stress condition, fibrous-cap thickness, and lumen curvature in carotid atherosclerotic plaque.

    PubMed

    Teng, Zhongzhao; Sadat, Umar; Ji, Guangyu; Zhu, Chengcheng; Young, Victoria E; Graves, Martin J; Gillard, Jonathan H

    2011-03-01

    High mechanical stress condition over the fibrous cap (FC) has been widely accepted as a contributor to plaque rupture. The relationships between the stress, lumen curvature, and FC thickness have not been explored in detail. In this study, we investigate lumen irregularity-dependent relationships between mechanical stress conditions, local FC thickness (LT(FC)), and lumen curvature (LC(lumen)). Magnetic resonance imaging slices of carotid plaque from 100 patients with delineated atherosclerotic components were used. Two-dimensional structure-only finite element simulations were performed for the mechanical analysis, and maximum principal stress (stress-P₁) at all integral nodes along the lumen was obtained. LT(FC) and LC(lumen) were computed using the segmented contour. The lumen irregularity (L-δir) was defined as the difference between the largest and the smallest lumen curvature. The results indicated that the relationship between stress-P₁, LT(FC), and LC(lumen) is largely dependent on L-δir. When L-δir ≥ .31 (irregular lumen), stress-P₁ strongly correlated with lumen curvature and had a weak/no correlation with local FC thickness, and in 73.4% of magnetic resonance (MR) slices, the critical stress (maximum of stress-P₁ over the diseased region) was found at the site where the lumen curvature was large. When L-δir ≤ 0.28 (relatively round lumen), stress-P₁ showed a strong correlation with local FC thickness but weak/no correlation with lumen curvature, and in 71.7% of MR slices, the critical stress was located at the site of minimum FC thickness. Using lumen irregularity as a method of identifying vulnerable plaque sites by referring to the lumen shape is a novel and simple method, which can be used for mechanics-based plaque vulnerability assessment.

  15. Intensity modulated SMF cascaded tapers with a hollow core PCF based microcavity for curvature sensing

    NASA Astrophysics Data System (ADS)

    Dass, Sumit; Narayan Dash, Jitendra; Jha, Rajan

    2016-03-01

    We propose a highly sensitive curvature sensor based on cascaded single mode fiber (SMF) tapers with a microcavity. The microcavity is created by splicing a small piece of hollow core photonic crystal fiber (HCPCF) at the end of an SMF to obtain a sharp interference pattern. Experimental results show that two SMF tapers enhance the curvature sensitivity of the system and by changing the tapering parameters of the second taper, the curvature sensitivity of the system can be tailored, together with the fringe contrast of the interference pattern. A maximum curvature sensitivity of 10.4 dB/m-1 is observed in the curvature range 0 to 1 m-1 for a second taper diameter of 18 μm. The sensing setup is highly stable and shows very low temperature sensitivity. As the interrogation is intensity based, a low cost optical power meter can be utilized to determine the curvature.

  16. Long-time behavior of material-surface curvature in isotropic turbulence

    NASA Technical Reports Server (NTRS)

    Girimaji, S. S.

    1992-01-01

    The behavior at large times of the curvature of material elements in turbulence is investigated using Lagrangian velocity-gradient time series obtained from direct numerical simulations of isotropic turbulence. The main objectives are: to study the asymptotic behavior of the pdf curvature as a function of initial curvature and shape; and to establish whether the curvature of an initially plane material element goes to a stationary probability distribution. The evidence available in the literature about the asymptotic curvature-pdf of initially flat surfaces is ambiguous, and the conjecture is that it is quasi-stationary. In this work several material-element ensembles of different initial curvatures and shapes are studied. It is found that, at long times the moments of the logarithm of curvature are independent of the initial pdf of curvature. This, it is argued, supports the view that the curvature attains a stationary distribution at long times. It is also shown that, irrespective of initial shape or curvature, the shape of any material element at long times is cylindrical with a high probability.

  17. Detonation Front Curvatures and Detonation Rates

    NASA Astrophysics Data System (ADS)

    Lauderbach, Lisa M.; Lorenz, K. Thomas; Lee, Edward L.; Souers, P. Clark

    2015-06-01

    We have normalized the LLNL library of detonation front curvatures by dividing lags by the edge lag and radii by the edge radius. We then fit the normalized data to the equation L = AR2 + BR8, where L is the normalized lag and R is the normalized radius. We attribute the quadratic term to thermal processes and the 8th-power term to shock processes. We compare the % of the quadratic term J at the edge with detonation rates obtained from the size effect. One class of results is made up of fine-grained, uniform explosives with large lags, where a low detonation rate leads to a high J and vice versa. This provides a rough way of estimating unknown rates if the unknown explosive is of high quality. The other, equally-large class contains rough-grained materials, often with small lags and small radii. These have curves that do not fit the equation but superfically often look quadratic. Some HMX and PETN curvatures even show a ``sombrero'' effect. Code models show that density differences of 0.03 g/cc in ram-pressed parts can cause pseudo-quadratic curves and even sombreros. Modeling is used to illustrate J at the lowest and highest possible detonation rates. This work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  18. Turning maneuvers in sharks: Predicting body curvature from axial morphology.

    PubMed

    Porter, Marianne E; Roque, Cassandra M; Long, John H

    2009-08-01

    Given the diversity of vertebral morphologies among fishes, it is tempting to propose causal links between axial morphology and body curvature. We propose that shape and size of the vertebrae, intervertebral joints, and the body will more accurately predict differences in body curvature during swimming rather than a single meristic such as total vertebral number alone. We examined the correlation between morphological features and maximum body curvature seen during routine turns in five species of shark: Triakis semifasciata, Heterodontus francisci, Chiloscyllium plagiosum, Chiloscyllium punctatum, and Hemiscyllium ocellatum. We quantified overall body curvature using three different metrics. From a separate group of size-matched individuals, we measured 16 morphological features from precaudal vertebrae and the body. As predicted, a larger pool of morphological features yielded a more robust prediction of maximal body curvature than vertebral number alone. Stepwise linear regression showed that up to 11 features were significant predictors of the three measures of body curvature, yielding highly significant multiple regressions with r(2) values of 0.523, 0.537, and 0.584. The second moment of area of the centrum was always the best predictor, followed by either centrum length or transverse height. Ranking as the fifth most important variable in three different models, the body's total length, fineness ratio, and width were the most important non-vertebral morphologies. Without considering the effects of muscle activity, these correlations suggest a dominant role for the vertebral column in providing the passive mechanical properties of the body that control, in part, body curvature during swimming. (c) 2009 Wiley-Liss, Inc.

  19. Salvage penile curvature correction surgery.

    PubMed

    Hsieh, Cheng-Hsing; Chen, Heng-Shuen; Lee, Wen-Yuan; Chen, Kuo-Liang; Chang, Chao-Hsiang; Hsu, Geng-Long

    2010-01-01

    It is commonly believed that coarser suture materials should be used to provide sufficient tenacity in surgery for penile curvature correction. We report our 15-year experience of fine sutures in a second operation in 31 patients who underwent prior curvature correction elsewhere with coarser sutures, resulting in recurrent penile curvature. Suture materials used in prior surgeries in these patients were either 2-0 or 3-0 nylon sutures. In this series, all 31 patients underwent a modified Nesbit procedure at the level of the collagen bundles using finer sutures. Prior to July 1998, 10 men underwent salvage surgery using 4-0 polyglactin sutures. Thereafter, we adapted 6-0 nylon sutures for another 21 patients. We categorized the patients into the polyglactin (n = 10) and nylon (n = 21) groups respectively. Overall, 29 patients were available for follow-up while using the abridged 5-item version of the International Index of Erectile Function (IIEF-5) scoring system, with 21 patients in the nylon group. We have found cavernosography a practical and reliable method to objectively assess penile morphology in these patients. The penile morphology both subjectively and objectively was excellent in all patients, except for 1 in each group. Erectile function restoration showed a trend of satisfaction in the polyglactin group and based on IIEF-5 was significantly improved in the nylon group (14.2 ± 3.6 vs 21.9 ± 2.1, n = 20, P < .001). These results suggest that in penile tunical surgery, fine sutures such as 6-0 nylon may result in better penile morphology and functional outcomes.

  20. The Effect of Arterial Curvature on Blood Flow in Arterio-Venous Fistulae: Realistic Geometries and Pulsatile Flow.

    PubMed

    Grechy, L; Iori, F; Corbett, R W; Gedroyc, W; Duncan, N; Caro, C G; Vincent, P E

    2017-07-26

    Arterio-Venous Fistulae (AVF) are regarded as the "gold standard" method of vascular access for patients with End-Stage Renal Disease (ESRD) who require haemodialysis. However, up to 60% of AVF do not mature, and hence fail, as a result of Intimal Hyperplasia (IH). Unphysiological flow and oxygen transport patterns, associated with the unnatural and often complex geometries of AVF, are believed to be implicated in the development of IH. Previous studies have investigated the effect of arterial curvature on blood flow in AVF using idealized planar AVF configurations and non-pulsatile inflow conditions. The present study takes an important step forwards by extending this work to more realistic non-planar brachiocephalic AVF configurations with pulsatile inflow conditions. Results show that forming an AVF by connecting a vein onto the outer curvature of an arterial bend does not, necessarily, suppress unsteady flow in the artery. This finding is converse to results from a previous more idealized study. However, results also show that forming an AVF by connecting a vein onto the inner curvature of an arterial bend can suppress exposure to regions of low wall shear stress and hypoxia in the artery. This finding is in agreement with results from a previous more idealized study. Finally, results show that forming an AVF by connecting a vein onto the inner curvature of an arterial bend can significantly reduce exposure to high WSS in the vein. The results are important, as they demonstrate that in realistic scenarios arterial curvature can be leveraged to reduce exposure to excessively low/high levels of WSS and regions of hypoxia in AVF. This may in turn reduce rates of IH and hence AVF failure.

  1. Curvature Continuous and Bounded Path Planning for Fixed-Wing UAVs.

    PubMed

    Wang, Xiaoliang; Jiang, Peng; Li, Deshi; Sun, Tao

    2017-09-19

    Unmanned Aerial Vehicles (UAVs) play an important role in applications such as data collection and target reconnaissance. An accurate and optimal path can effectively increase the mission success rate in the case of small UAVs. Although path planning for UAVs is similar to that for traditional mobile robots, the special kinematic characteristics of UAVs (such as their minimum turning radius) have not been taken into account in previous studies. In this paper, we propose a locally-adjustable, continuous-curvature, bounded path-planning algorithm for fixed-wing UAVs. To deal with the curvature discontinuity problem, an optimal interpolation algorithm and a key-point shift algorithm are proposed based on the derivation of a curvature continuity condition. To meet the upper bound for curvature and to render the curvature extrema controllable, a local replanning scheme is designed by combining arcs and Bezier curves with monotonic curvature. In particular, a path transition mechanism is built for the replanning phase using minimum curvature circles for a planning philosophy. Numerical results demonstrate that the analytical planning algorithm can effectively generate continuous-curvature paths, while satisfying the curvature upper bound constraint and allowing UAVs to pass through all predefined waypoints in the desired mission region.

  2. Curvature Continuous and Bounded Path Planning for Fixed-Wing UAVs

    PubMed Central

    Jiang, Peng; Li, Deshi; Sun, Tao

    2017-01-01

    Unmanned Aerial Vehicles (UAVs) play an important role in applications such as data collection and target reconnaissance. An accurate and optimal path can effectively increase the mission success rate in the case of small UAVs. Although path planning for UAVs is similar to that for traditional mobile robots, the special kinematic characteristics of UAVs (such as their minimum turning radius) have not been taken into account in previous studies. In this paper, we propose a locally-adjustable, continuous-curvature, bounded path-planning algorithm for fixed-wing UAVs. To deal with the curvature discontinuity problem, an optimal interpolation algorithm and a key-point shift algorithm are proposed based on the derivation of a curvature continuity condition. To meet the upper bound for curvature and to render the curvature extrema controllable, a local replanning scheme is designed by combining arcs and Bezier curves with monotonic curvature. In particular, a path transition mechanism is built for the replanning phase using minimum curvature circles for a planning philosophy. Numerical results demonstrate that the analytical planning algorithm can effectively generate continuous-curvature paths, while satisfying the curvature upper bound constraint and allowing UAVs to pass through all predefined waypoints in the desired mission region. PMID:28925960

  3. Amino Terminal Region of Dengue Virus NS4A Cytosolic Domain Binds to Highly Curved Liposomes.

    PubMed

    Hung, Yu-Fu; Schwarten, Melanie; Hoffmann, Silke; Willbold, Dieter; Sklan, Ella H; Koenig, BerndW

    2015-07-21

    Dengue virus (DENV) is an important human pathogen causing millions of disease cases and thousands of deaths worldwide. Non-structural protein 4A (NS4A) is a vital component of the viral replication complex (RC) and plays a major role in the formation of host cell membrane-derived structures that provide a scaffold for replication. The N-terminal cytoplasmic region of NS4A(1-48) is known to preferentially interact with highly curved membranes. Here, we provide experimental evidence for the stable binding of NS4A(1-48) to small liposomes using a liposome floatation assay and identify the lipid binding sequence by NMR spectroscopy. Mutations L6E;M10E were previously shown to inhibit DENV replication and to interfere with the binding of NS4A(1-48) to small liposomes. Our results provide new details on the interaction of the N-terminal region of NS4A with membranes and will prompt studies of the functional relevance of the curvature sensitive membrane anchor at the N-terminus of NS4A.

  4. Bimodal spectrum for the curvature fluctuations of bilayer vesicles: pure bending plus hybrid curvature-dilation modes.

    PubMed

    Rodríguez-García, R; Arriaga, L R; Mell, M; Moleiro, L H; López-Montero, I; Monroy, F

    2009-03-27

    We study thermal undulations of giant bilayer vesicles by flickering spectroscopy. The experimental fluctuation spectra are scrutinized in view of the classical Helfrich theory. Pure bending modes are revealed to be unable to predict the large fluctuations systematically found at a high wave vector. Hybrid curvature-dilational modes are then invoked as a more efficient mode of motion in producing high curvatures. A bimodal spectrum of the thermal undulations has been theoretically developed for the shell-like topology. Reconciliation between experiments and theory is achieved when this bimodal spectrum is considered.

  5. Measurement of curvature and twist of a deformed object using digital holography

    SciTech Connect

    Chen Wen; Quan Chenggen; Cho Jui Tay

    2008-05-20

    Measurement of curvature and twist is an important aspect in the study of object deformation. In recent years, several methods have been proposed to determine curvature and twist of a deformed object using digital shearography. Here we propose a novel method to determine the curvature and twist of a deformed object using digital holography and a complex phasor. A sine/cosine transformation method and two-dimensional short time Fourier transform are proposed subsequently to process the wrapped phase maps. It is shown that high-quality phase maps corresponding to curvature and twist can be obtained. An experiment is conducted to demonstrate the validity of the proposed method.

  6. Mirror with thermally controlled radius of curvature

    DOEpatents

    Neil, George R.; Shinn, Michelle D.

    2010-06-22

    A radius of curvature controlled mirror for controlling precisely the focal point of a laser beam or other light beam. The radius of curvature controlled mirror provides nearly spherical distortion of the mirror in response to differential expansion between the front and rear surfaces of the mirror. The radius of curvature controlled mirror compensates for changes in other optical components due to heating or other physical changes. The radius of curvature controlled mirror includes an arrangement for adjusting the temperature of the front surface and separately adjusting the temperature of the rear surface to control the radius of curvature. The temperature adjustment arrangements can include cooling channels within the mirror body or convection of a gas upon the surface of the mirror. A control system controls the differential expansion between the front and rear surfaces to achieve the desired radius of curvature.

  7. Characterizing repulsive gravity with curvature eigenvalues

    NASA Astrophysics Data System (ADS)

    Luongo, Orlando; Quevedo, Hernando

    2014-10-01

    Repulsive gravity has been investigated in several scenarios near compact objects by using different intuitive approaches. Here, we propose an invariant method to characterize regions of repulsive gravity, associated to black holes and naked singularities. Our method is based upon the behavior of the curvature tensor eigenvalues, and leads to an invariant definition of a repulsion radius. The repulsion radius determines a physical region, which can be interpreted as a repulsion sphere, where the effects due to repulsive gravity naturally arise. Further, we show that the use of effective masses to characterize repulsion regions can lead to coordinate-dependent results whereas, in our approach, repulsion emerges as a consequence of the spacetime geometry in a completely invariant way. Our definition is tested in the spacetime of an electrically charged Kerr naked singularity and in all its limiting cases. We show that a positive mass can generate repulsive gravity if it is equipped with an electric charge or an angular momentum. We obtain reasonable results for the spacetime regions contained inside the repulsion sphere whose size and shape depend on the value of the mass, charge and angular momentum. Consequently, we define repulsive gravity as a classical relativistic effect by using the geometry of spacetime only.

  8. Generalized Boussinesq-Scriven surface fluid model with curvature dissipation for liquid surfaces and membranes.

    PubMed

    Aguilar Gutierrez, Oscar F; Herrera Valencia, Edtson E; Rey, Alejandro D

    2017-10-01

    Curvature dissipation is relevant in synthetic and biological processes, from fluctuations in semi-flexible polymer solutions, to buckling of liquid columns, tomembrane cell wall functioning. We present a micromechanical model of curvature dissipation relevant to fluid membranes and liquid surfaces based on a parallel surface parameterization and a stress constitutive equation appropriate for anisotropic fluids and fluid membranes.The derived model, aimed at high curvature and high rate of change of curvature in liquid surfaces and membranes, introduces additional viscous modes not included in the widely used 2D Boussinesq-Scriven rheological constitutive equation for surface fluids.The kinematic tensors that emerge from theparallel surface parameterization are the interfacial rate of deformation and the surface co-rotational Zaremba-Jaumann derivative of the curvature, which are used to classify all possibledissipative planar and non-planar modes. The curvature dissipation function that accounts for bending, torsion and twist rates is derived and analyzed under several constraints, including the important inextensional bending mode.A representative application of the curvature dissipation model to the periodic oscillation in nano-wrinkled outer hair cells show how and why curvature dissipation decreases with frequency, and why the 100kHz frequency range is selected. These results contribute to characterize curvature dissipation in membranes and liquid surfaces. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Computer simulation of flagellar movement VIII: coordination of dynein by local curvature control can generate helical bending waves.

    PubMed

    Brokaw, Charles J

    2002-10-01

    Computer simulations have been carried out with a model flagellum that can bend in three dimensions. A pattern of dynein activation in which regions of dynein activity propagate along each doublet, with a phase shift of approximately 1/9 wavelength between adjacent doublets, will produce a helical bending wave. This pattern can be termed "doublet metachronism." The simulations show that doublet metachronism can arise spontaneously in a model axoneme in which activation of dyneins is controlled locally by the curvature of each outer doublet microtubule. In this model, dyneins operate both as sensors of curvature and as motors. Doublet metachronism and the chirality of the resulting helical bending pattern are regulated by the angular difference between the direction of the moment and sliding produced by dyneins on a doublet and the direction of the controlling curvature for that doublet. A flagellum that is generating a helical bending wave experiences twisting moments when it moves against external viscous resistance. At high viscosities, helical bending will be significantly modified by twist unless the twist resistance is greater than previously estimated. Spontaneous doublet metachronism must be modified or overridden in order for a flagellum to generate the planar bending waves that are required for efficient propulsion of spermatozoa. Planar bending can be achieved with the three-dimensional flagellar model by appropriate specification of the direction of the controlling curvature for each doublet. However, experimental observations indicate that this "hard-wired" solution is not appropriate for real flagella. Copyright 2002 Wiley-Liss, Inc.

  10. a Curvature Based Adaptive Neighborhood for Individual Point Cloud Classification

    NASA Astrophysics Data System (ADS)

    He, E.; Chen, Q.; Wang, H.; Liu, X.

    2017-09-01

    As a key step in 3D scene analysis, point cloud classification has gained a great deal of concerns in the past few years. Due to the uneven density, noise and data missing in point cloud, how to automatically classify the point cloud with a high precision is a very challenging task. The point cloud classification process typically includes the extraction of neighborhood based statistical information and machine learning algorithms. However, the robustness of neighborhood is limited to the density and curvature of the point cloud which lead to a label noise behavior in classification results. In this paper, we proposed a curvature based adaptive neighborhood for individual point cloud classification. Our main improvement is the curvature based adaptive neighborhood method, which could derive ideal 3D point local neighborhood and enhance the separability of features. The experiment result on Oakland benchmark dataset shows that the proposed method can effectively improve the classification accuracy of point cloud.

  11. Waterfall field in hybrid inflation and curvature perturbation

    SciTech Connect

    Gong, Jinn-Ouk; Sasaki, Misao E-mail: misao@yukawa.kyoto-u.ac.jp

    2011-03-01

    We study carefully the contribution of the waterfall field to the curvature perturbation at the end of hybrid inflation. In particular we clarify the parameter dependence analytically under reasonable assumptions on the model parameters. After calculating the mode function of the waterfall field, we use the δN formalism and confirm the previously obtained result that the power spectrum is very blue with the index 4 and is absolutely negligible on large scales. However, we also find that the resulting curvature perturbation is highly non-Gaussian and hence we calculate the bispectrum. We find that the bispectrum is at leading order independent of momentum and exhibits its peak at the equilateral limit, though it is unobservably small on large scales. We also present the one-point probability distribution function of the curvature perturbation.

  12. Dynamic lumbar curvature measurement in acute and chronic low back pain sufferers.

    PubMed

    Williams, Jonathan Mark; Haq, Inam; Lee, Raymond Y

    2012-11-01

    (1) To determine the reliability of a novel fiber-optic method to dynamically measure lumbar curvature in low back pain (LBP) sufferers, and (2) to investigate the dynamic lumbar curvature in acute and chronic LBP sufferers. Cross-sectional study. Physiotherapy clinic. Acute (n=20) and chronic (n=20) LBP sufferers recruited from general practitioner and therapist referrals. Not applicable. A fiber-optic device was used to measure curvature through time during flexion, lifting, and extension movements. Repeated-measures reliability for curvature-time curves was tested using coefficients of multiple correlation (CMCs) and root mean square error, and for peak curvature values intraclass correlation coefficients (ICCs) and mean absolute errors were used. Acute and chronic LBP groups were compared using peak curvatures and sequencing of curvature change. The fiber-optic method was shown to be highly reliable in measuring both whole lumbar and lower lumbar curvature with CMC values >.81 and ICC values >.99. Chronic LBP sufferers displayed greater peak curvatures during flexion and lifting for the whole lumbar spine and lifting for the lower lumbar spine. The sequencing behavior demonstrated that the quartile of movement associated with the greatest curvature change was the second for flexion and lifting and first and second for extension across both groups. No significant differences in sequencing were demonstrated between the 2 groups. This method is reliable for dynamic lumbar curvature measurement in back pain sufferers and is a viable option for clinicians. Acute LBP sufferers display less kyphosis during flexion and lifting. Sequencing of curvature change is similar across the 2 groups. Copyright © 2012 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  13. Radius of curvature controlled mirror

    DOEpatents

    Neil, George R.; Rathke, John Wickham; Schultheiss, Thomas John; Shinn, Michelle D.; Dillon-Townes, Lawrence A.

    2006-01-17

    A controlled radius of curvature mirror assembly comprising: a distortable mirror having a reflective surface and a rear surface; and in descending order from the rear surface; a counter-distortion plate; a flow diverter having a flow diverter aperture at the center thereof; a flow return plate having a flow return aperture at the center thereof; a thermal isolation plate having a thermal isolation plate aperture at the center thereof and a flexible heater having a rear surface and a flexible heater aperture at the center thereof; a double walled tube defining a coolant feed chamber and a coolant return chamber; said coolant feed chamber extending to and through the flow diverter aperture and terminating at the counter-distortion plate and the coolant return chamber extending to and through the thermal isolation backplate and terminating at the flow diverter; and a coolant feed and a coolant return exit at the rear of said flexible heater.

  14. Protein-Induced Membrane Curvature Alters Local Membrane Tension

    PubMed Central

    Rangamani, Padmini; Mandadap, Kranthi K.; Oster, George

    2014-01-01

    Adsorption of proteins onto membranes can alter the local membrane curvature. This phenomenon has been observed in biological processes such as endocytosis, tubulation, and vesiculation. However, it is not clear how the local surface properties of the membrane, such as membrane tension, change in response to protein adsorption. In this article, we show that the partial differential equations arising from classical elastic model of lipid membranes, which account for simultaneous changes in shape and membrane tension due to protein adsorption in a local region, cannot be solved for nonaxisymmetric geometries using straightforward numerical techniques; instead, a viscous-elastic formulation is necessary to fully describe the system. Therefore, we develop a viscous-elastic model for inhomogeneous membranes of the Helfrich type. Using the newly available viscous-elastic model, we find that the lipids flow to accommodate changes in membrane curvature during protein adsorption. We show that, at the end of protein adsorption process, the system sustains a residual local tension to balance the difference between the actual mean curvature and the imposed spontaneous curvature. We also show that this change in membrane tension can have a functional impact such as altered response to pulling forces in the presence of proteins. PMID:25099814

  15. Three-dimensional ultrasound palmprint recognition using curvature methods

    NASA Astrophysics Data System (ADS)

    Iula, Antonio; Nardiello, Donatella

    2016-05-01

    Palmprint recognition systems that use three-dimensional (3-D) information of the palm surface are the most recently explored techniques to overcome some two-dimensional palmprint difficulties. These techniques are based on light structural imaging. In this work, a 3-D ultrasound palmprint recognition system is proposed and evaluated. Volumetric images of a region of the human hand are obtained by moving an ultrasound linear array along its elevation direction and one by one acquiring a number of B-mode images, which are then grouped in a 3-D matrix. The acquisition time was contained in about 5 s. Much information that can be exploited for 3-D palmprint recognition is extracted from the ultrasound volumetric images, including palm curvature and other under-skin information as the depth of the various traits. The recognition procedure developed in this work is based on the analysis of the principal curvatures of palm surface, i.e., mean curvature image, Gaussian curvature image, and surface type. The proposed method is evaluated by performing verification and identification experiments. Preliminary results have shown that the proposed system exhibits an acceptable recognition rate. Further possible improvements of the proposed technique are finally highlighted and discussed.

  16. Determining wave direction using curvature parameters.

    PubMed

    de Queiroz, Eduardo Vitarelli; de Carvalho, João Luiz Baptista

    2016-01-01

    The curvature of the sea wave was tested as a parameter for estimating wave direction in the search for better results in estimates of wave direction in shallow waters, where waves of different sizes, frequencies and directions intersect and it is difficult to characterize. We used numerical simulations of the sea surface to determine wave direction calculated from the curvature of the waves. Using 1000 numerical simulations, the statistical variability of the wave direction was determined. The results showed good performance by the curvature parameter for estimating wave direction. Accuracy in the estimates was improved by including wave slope parameters in addition to curvature. The results indicate that the curvature is a promising technique to estimate wave directions.•In this study, the accuracy and precision of curvature parameters to measure wave direction are analyzed using a model simulation that generates 1000 wave records with directional resolution.•The model allows the simultaneous simulation of time-series wave properties such as sea surface elevation, slope and curvature and they were used to analyze the variability of estimated directions.•The simultaneous acquisition of slope and curvature parameters can contribute to estimates wave direction, thus increasing accuracy and precision of results.

  17. [The relationship between upper airway curvature and obstructive sleep apnea and hypopnea syndrome].

    PubMed

    Zhu, Min; Lu, Xiao-feng; Shi, Hui-min

    2007-08-01

    The fluid flow through curved tubes has characteristics that an increase in the curvature induces pressure losses as well as higher resistance in the same region. The purpose of this study is to analyze the relationship between upper airway curvature and obstructive sleep apnea and hypopnea syndrome(OSAHS). 18 male OSAHS patients were paired by age with 18 males with no snoring. The mean AHI was 58.8. The supine lateral cephalometric films were obtained from CT and analysed using curvature software. Data were presented as mean and paired t test was conducted using SPSS10.0 software package. Correlative analysis was performed to indicate the relationship between BMI and AHI, curvature and BMI, respectively. The airway curvature was significantly different between the two groups(P<0.01). The curvature radius was significantly correlative with BMI (P<0.01), but not with AHI(P>0.05). Upper airway curvature was related significantly to the pathogenesis of OSAHS. An increase of curvature on anterior wall of velopharynx in OSAHS patients can change the pressure and resistance distribution in upper airway.

  18. High School Attrition Rates Across Texas Education Service Center Regions

    ERIC Educational Resources Information Center

    Johnson, Roy

    2008-01-01

    The examination of historical trend data on the number and percent of students lost from public school enrollment prior to graduation from high school is becoming increasingly important since distinct trends are emerging on a regional basis. This study examines regional trends in Texas on the number and percent of students lost from public high…

  19. Streamline curvature effects on turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Wilcox, D. C.; Chambers, T. L.

    1976-01-01

    A theoretical tool has been developed for predicting, in a nonempirical manner, effects of streamline curvature and coordinate-system rotation on turbulent boundary layers. The second-order closure scheme developed by Wilcox and Traci has been generalized for curved streamline flow and for flow in a rotating coordinate system. A physically based straightforward argument shows that curvature/rotation primarily affects the turbulent mixing energy; the argument yields suitable curvature/rotation terms which are added to the mixing-energy equation. Singular-perturbation solutions valid in the wall layer of a curved-wall boundary layer and a fully developed rotating channel flow demonstrate that, with the curvature/rotation terms, the model predicts the curved-wall and the rotating coordinate system laws of the wall. Results of numerical computations of curved-wall boundary layers and of rotating channel flow show that curvature/rotation effects can be computed accurately with second-order closure.

  20. Importance of plan curvature in watershed modeling

    NASA Astrophysics Data System (ADS)

    Boll, J.; Ribail, J.; Zhao, M.

    2016-12-01

    A hillslope's hydrologic response to precipitation events is largely controlled by the topographic features of a given hillslope, specifically the profile and plan curvature. Many models simplify hillslope topography and ignore the curvature properties, and some use alternate measures such as a topographic index or the hillslope width function. Models that ignore curvature properties may be calibrated to produce the statistically acceptable integrated response of runoff at a watershed outlet, but incorporating these properties is necessary to model accurately hydrologic processes such as surface flow, erosion, subsurface lateral flow, location of runoff generation and drainage response. In this study, we evaluated the sensitivity of rainfall-runoff modelling to profile and plan curvature in two models. In the first model, the Water Erosion Prediction Project (WEPP) model, hillslope uses a representative width to the hillslope by dividing the drainage area by the average surface channel length. Profile curvature is preserved with a limited spatial resolution due to the number of overland flow elements. In the second model, the distributed Soil Moisture Routing (SMR) model, the geographic information system uses the D8 algorithm to capture profile and plan curvature. Sensitivity to topographic features was tested for three profile curvatures (convex, concave, straight) combined with three plan curvatures (diverging, converging, uniform) resulting in a total of nine hillslopes. Each hillslope was subjected to different rainfall events to detect threshold behavior for when topographic features cannot be ignored. Our findings indicate that concave and convex plan curvature need to be included when subsurface flow processes are the dominant flow process for surface flow runoff generation. We present thresholds for acceptable cases when profile and plan curvature can be simplified in larger spatial hydrologic units.

  1. Negative voltage bandgap reference with multilevel curvature compensation technique

    NASA Astrophysics Data System (ADS)

    Xi, Liu; Qian, Liu; Xiaoshi, Jin; Yongrui, Zhao; Lee, Jong-Ho

    2016-05-01

    A novel high-order curvature compensation negative voltage bandgap reference (NBGR) based on a novel multilevel compensation technique is introduced. Employing an exponential curvature compensation (ECC) term with many high order terms in itself, in a lower temperature range (TR) and a multilevel curvature compensation (MLCC) term in a higher TR, a flattened and better effect of curvature compensation over the TR of 165 °C (-40 to 125 °C) is realised. The MLCC circuit adds two convex curves by using two sub-threshold operated NMOS. The proposed NBGR implemented in the Central Semiconductor Manufacturing Corporation (CSMC) 0.5 μm BCD technology demonstrates an accurate voltage of -1.183 V with a temperature coefficient (TC) as low as 2.45 ppm/°C over the TR of 165 °C at a -5.0 V power supply; the line regulation is 3 mV/V from a -5 to -2 V supply voltage. The active area of the presented NBGR is 370 × 180 μm2. Project supported by the Fund of Liaoning Province Education Department (No. L2013045).

  2. The impact of surface area, volume, curvature, and Lennard-Jones potential to solvation modeling.

    PubMed

    Nguyen, Duc D; Wei, Guo-Wei

    2017-01-05

    This article explores the impact of surface area, volume, curvature, and Lennard-Jones (LJ) potential on solvation free energy predictions. Rigidity surfaces are utilized to generate robust analytical expressions for maximum, minimum, mean, and Gaussian curvatures of solvent-solute interfaces, and define a generalized Poisson-Boltzmann (GPB) equation with a smooth dielectric profile. Extensive correlation analysis is performed to examine the linear dependence of surface area, surface enclosed volume, maximum curvature, minimum curvature, mean curvature, and Gaussian curvature for solvation modeling. It is found that surface area and surfaces enclosed volumes are highly correlated to each other's, and poorly correlated to various curvatures for six test sets of molecules. Different curvatures are weakly correlated to each other for six test sets of molecules, but are strongly correlated to each other within each test set of molecules. Based on correlation analysis, we construct twenty six nontrivial nonpolar solvation models. Our numerical results reveal that the LJ potential plays a vital role in nonpolar solvation modeling, especially for molecules involving strong van der Waals interactions. It is found that curvatures are at least as important as surface area or surface enclosed volume in nonpolar solvation modeling. In conjugation with the GPB model, various curvature-based nonpolar solvation models are shown to offer some of the best solvation free energy predictions for a wide range of test sets. For example, root mean square errors from a model constituting surface area, volume, mean curvature, and LJ potential are less than 0.42 kcal/mol for all test sets. © 2016 Wiley Periodicals, Inc.

  3. Localized tearing modes in the magnetotail driven by curvature effects

    NASA Technical Reports Server (NTRS)

    Sundaram, A. K.; Fairfield, D. H.

    1995-01-01

    The stability of collisionless tearing modes is examined in the presence of curvature drift resonances and the trapped particle effects. A kinetic description for both electrons and ions is employed to investigate the stability of a two-dimensional equilibrium model. The main features of the study are to treat the ion dynamics properly by incorporating effects associated with particle trajectories in the tail fields and to include the linear coupling of trapped particle modes. Generalized dispersion relations are derived in several parameter regimes by considering two important sublayers of the reconnecting region. For a typical choice of parameters appropriate to the current sheet region, we demonstrate that localized tearing modes driven by ion curvature drift resonance effects are excited in the current sheet region with growth time of the order of a few seconds. Also, we examine nonlocal characteristics of tearing modes driven by curvature effects and show that modes growing in a fraction of a second arise when mode widths are larger than the current sheet width. Further, we show that trapped particle effects, in an interesting frequency regime, significantly enhance the growth rate of the tearing mode. The relevance of this theory for substorm onset phase and other features of the substorms is briefly discussed.

  4. Programming curvature using origami tessellations

    NASA Astrophysics Data System (ADS)

    Dudte, Levi H.; Vouga, Etienne; Tachi, Tomohiro; Mahadevan, L.

    2016-05-01

    Origami describes rules for creating folded structures from patterns on a flat sheet, but does not prescribe how patterns can be designed to fit target shapes. Here, starting from the simplest periodic origami pattern that yields one-degree-of-freedom collapsible structures--we show that scale-independent elementary geometric constructions and constrained optimization algorithms can be used to determine spatially modulated patterns that yield approximations to given surfaces of constant or varying curvature. Paper models confirm the feasibility of our calculations. We also assess the difficulty of realizing these geometric structures by quantifying the energetic barrier that separates the metastable flat and folded states. Moreover, we characterize the trade-off between the accuracy to which the pattern conforms to the target surface, and the effort associated with creating finer folds. Our approach enables the tailoring of origami patterns to drape complex surfaces independent of absolute scale, as well as the quantification of the energetic and material cost of doing so.

  5. Ionic liquid tunes microemulsion curvature.

    PubMed

    Liu, Liping; Bauduin, Pierre; Zemb, Thomas; Eastoe, Julian; Hao, Jingcheng

    2009-02-17

    Middle-phase microemulsions formed from cationic dioctadecyldimethylammonium chloride (DODMAC), anionic sodium dodecylsulfate (SDS), n-butanol, and n-heptane were studied. An ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), was employed as the electrolyte in the aqueous media instead of inorganic salts usually used in microemulsion formulation. Studies have been carried out as a function of the concentrations of [bmim][BF4], n-butanol, total surfactant (cDODMAC+SDS), and temperature on the phase behavior and the ultralow interfacial tensions in which the anionic component is present in excess in the catanionic film. Ultralow interfacial tension measurements confirmed the formation of middle-phase microemulsions and the necessary conditions for stabilizing middle-phase microemulsions. Electrical conductivity, small-angle X-ray scattering (SAXS), and small-angle neutron scattering (SANS) experiments were also performed, indicating that the typical heptane domain size has an average radius of 360 A and the ionic liquid induces softening of the charged catanionic film. Most interestingly, the IL concentration (cIL) is shown to act as an effective interfacial curvature-control parameter, representing a new approach to tuning the formulation of microemulsions and emulsions. The results expand the potential uses of ILs but also point to the design of new ILs that may achieve superefficient control over interfacial and self-assembly systems.

  6. Curvature function and coarse graining

    NASA Astrophysics Data System (ADS)

    Díaz-Marín, Homero; Zapata, José A.

    2010-12-01

    A classic theorem in the theory of connections on principal fiber bundles states that the evaluation of all holonomy functions gives enough information to characterize the bundle structure (among those sharing the same structure group and base manifold) and the connection up to a bundle equivalence map. This result and other important properties of holonomy functions have encouraged their use as the primary ingredient for the construction of families of quantum gauge theories. However, in these applications often the set of holonomy functions used is a discrete proper subset of the set of holonomy functions needed for the characterization theorem to hold. We show that the evaluation of a discrete set of holonomy functions does not characterize the bundle and does not constrain the connection modulo gauge appropriately. We exhibit a discrete set of functions of the connection and prove that in the abelian case their evaluation characterizes the bundle structure (up to equivalence), and constrains the connection modulo gauge up to "local details" ignored when working at a given scale. The main ingredient is the Lie algebra valued curvature function F_S (A) defined below. It covers the holonomy function in the sense that exp {F_S (A)} = Hol(l= partial S, A).

  7. Curvature function and coarse graining

    SciTech Connect

    Diaz-Marin, Homero; Zapata, Jose A.

    2010-12-15

    A classic theorem in the theory of connections on principal fiber bundles states that the evaluation of all holonomy functions gives enough information to characterize the bundle structure (among those sharing the same structure group and base manifold) and the connection up to a bundle equivalence map. This result and other important properties of holonomy functions have encouraged their use as the primary ingredient for the construction of families of quantum gauge theories. However, in these applications often the set of holonomy functions used is a discrete proper subset of the set of holonomy functions needed for the characterization theorem to hold. We show that the evaluation of a discrete set of holonomy functions does not characterize the bundle and does not constrain the connection modulo gauge appropriately. We exhibit a discrete set of functions of the connection and prove that in the abelian case their evaluation characterizes the bundle structure (up to equivalence), and constrains the connection modulo gauge up to ''local details'' ignored when working at a given scale. The main ingredient is the Lie algebra valued curvature function F{sub S}(A) defined below. It covers the holonomy function in the sense that expF{sub S}(A)=Hol(l={partial_derivative}S,A).

  8. Soliton curvatures of surfaces and spaces

    SciTech Connect

    Konopelchenko, B.G.

    1997-01-01

    An intrinsic geometry of surfaces and three-dimensional Riemann spaces is discussed. In the geodesic coordinates the Gauss equation for two-dimensional Riemann spaces (surfaces) is reduced to the one-dimensional Schr{umlt o}dinger equation, where the Gaussian curvature plays a role of potential. The use of this fact provides an infinite set of explicit expressions for curvature and metric of surface. A special case is governed by the KdV equation for the Gaussian curvature. Integrable dynamics of curvature via the KdV equation, higher KdV equations, and 2+1-dimensional integrable equations with breaking solitons is considered. For a special class of three-dimensional Riemann spaces the relation between metric and scalar curvature is given by the two-dimensional stationary Schr{umlt o}dinger or perturbed string equations. This provides us an infinite family of Riemann spaces with explicit scalar curvature and metric. Particular class of spaces and their integrable evolutions are described by the Nizhnik{endash}Veselov{endash}Novikov equation and its higher analogs. Surfaces and three-dimensional Riemann spaces with large curvature and slow dependence on the variable are considered. They are associated with the Burgers and Kadomtsev{endash}Petviashvili equations, respectively. {copyright} {ital 1997 American Institute of Physics.}

  9. Mapping High-Frequency Waves in the Reconnection Diffusion Region

    NASA Astrophysics Data System (ADS)

    Viberg, H.; Khotyaintsev, Y. V.; Vaivads, A.; Andre, M.

    2012-12-01

    We study the occurrence of high frequency waves, between the electron cyclotron and plasma frequency, in a reconnection diffusion region in the Earth's magnetotail at a distance of about 19 RE from the Earth. Most of the wave activity is concentrated in the separatrix regions, with no significant activity observed in the inflow and outflow regions. Different types of waves are observed at the outer part of the separatrix region depending on the plasma characteristics in the inflow region. For the cold ~100 eV lobe plasma in the inflow we observe Langmuir waves which are generated by the bump-on-tail instability of a several keV electron beam propagating in the cold background plasma. For the hotter ~1 keV inflow plasma, which is similar to the plasmasheet population, electron cyclotron waves are observed in this region, most probably generated by low energy (several tens of eV) electron beams. Deeper into the separatrix region (closer to the current sheet), we observe mostly electrostatic solitary waves (ESWs) in association with two counter-streaming electron beams: low energy beam towards the X-line, and high energy beam away from the X-line. Observations of HF waves provide important information about electron dynamics in the diffusion region, and allow for precise mapping of kinetic boundaries.

  10. Double-strand conformation polymorphism (DSCP) analysis of the mitochondrial control region generates highly variable markers for population studies in a social insect.

    PubMed

    Atkinson, L; Adams, E S

    1997-11-01

    Genetic markers were obtained for the termite Nasutitermes corniger by DSCP (double-strand conformation polymorphism) analysis of PCR-amplified mitochondrial control region DNA. This procedure revealed twenty-one haplotypes in forty-four colonies, whereas a restriction fragment length polymorphism analysis detected only nine haplotypes. Sequence analysis of DSCP fragments of contrasting mobilities suggests that the electrophoretic haplotypes are caused by DNA curvature in this highly AT-rich region. DSCP markers showed that some termite colonies contained maternally unrelated queens, each of which produced worker offspring. This pattern is consistent with nest founding by unrelated queens. Due to the availability of conserved primers for the mtDNA control region, DSCP analysis may readily reveal comparatively high levels of variation in a wide variety of organisms.

  11. Intracellular magnetophoresis of amyloplasts and induction of root curvature

    NASA Technical Reports Server (NTRS)

    Kuznetsov, O. A.; Hasenstein, K. H.

    1996-01-01

    High-gradient magnetic fields (HGMFs) were used to induce intracellular magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the gap edge between two permanent magnets. In the vicinity of the tip of the wedge the dynamic factor of the magnetic field, delta(H2/2), was about 10(9) Oe2.cm-1, which subjected the amyloplasts to a force comparable to that of gravity. When roots of 2-d-old seedlings of flax (Linum usitatissimum L.) were positioned vertically and exposed to an HGMF, curvature away from the wedge was transient and lasted approximately 1 h. Average curvature obtained after placing magnets, wedge and seedlings on a 1-rpm clinostat for 2 h was 33 +/- 5 degrees. Roots of horizontally placed control seedlings without rotation curved about 47 +/- 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. Microscopy showed displacement of amyloplasts in vitro and in vivo. Studies with Arabidopsis thaliana (L.) Heynh. showed that the wild type responded to HGMFs but the starchless mutant TC7 did not. The data indicate that a magnetic force can be used to study the gravisensing and response system of roots.

  12. Intracellular magnetophoresis of amyloplasts and induction of root curvature.

    PubMed

    Kuznetsov, O A; Hasenstein, K H

    1996-01-01

    High-gradient magnetic fields (HGMFs) were used to induce intracellular magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the gap edge between two permanent magnets. In the vicinity of the tip of the wedge the dynamic factor of the magnetic field, delta(H2/2), was about 10(9) Oe2.cm-1, which subjected the amyloplasts to a force comparable to that of gravity. When roots of 2-d-old seedlings of flax (Linum usitatissimum L.) were positioned vertically and exposed to an HGMF, curvature away from the wedge was transient and lasted approximately 1 h. Average curvature obtained after placing magnets, wedge and seedlings on a 1-rpm clinostat for 2 h was 33 +/- 5 degrees. Roots of horizontally placed control seedlings without rotation curved about 47 +/- 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. Microscopy showed displacement of amyloplasts in vitro and in vivo. Studies with Arabidopsis thaliana (L.) Heynh. showed that the wild type responded to HGMFs but the starchless mutant TC7 did not. The data indicate that a magnetic force can be used to study the gravisensing and response system of roots.

  13. Symmetric curvature descriptors for label-free analysis of DNA

    PubMed Central

    Buzio, Renato; Repetto, Luca; Giacopelli, Francesca; Ravazzolo, Roberto; Valbusa, Ugo

    2014-01-01

    High-resolution microscopy techniques such as electron microscopy, scanning tunnelling microscopy and atomic force microscopy represent well-established, powerful tools for the structural characterization of adsorbed DNA molecules at the nanoscale. Notably, the analysis of DNA contours allows mapping intrinsic curvature and flexibility along the molecular backbone. This is particularly suited to address the impact of the base-pairs sequence on the local conformation of the strands and plays a pivotal role for investigations relating the inherent DNA shape and flexibility to other functional properties. Here, we introduce novel chain descriptors aimed to characterize the local intrinsic curvature and flexibility of adsorbed DNA molecules with unknown orientation. They consist of stochastic functions that couple the curvatures of two nanosized segments, symmetrically placed on the DNA contour. We show that the fine mapping of the ensemble-averaged functions along the molecular backbone generates characteristic patterns of variation that highlight all pairs of tracts with large intrinsic curvature or enhanced flexibility. We demonstrate the practical applicability of the method for DNA chains imaged by atomic force microscopy. Our approach paves the way for the label-free comparative analysis of duplexes, aimed to detect nanoscale conformational changes of physical or biological relevance in large sample numbers. PMID:25248631

  14. Origins of chemoreceptor curvature sorting in Escherichia coli

    PubMed Central

    Draper, Will; Liphardt, Jan

    2017-01-01

    Bacterial chemoreceptors organize into large clusters at the cell poles. Despite a wealth of structural and biochemical information on the system's components, it is not clear how chemoreceptor clusters are reliably targeted to the cell pole. Here, we quantify the curvature-dependent localization of chemoreceptors in live cells by artificially deforming growing cells of Escherichia coli in curved agar microchambers, and find that chemoreceptor cluster localization is highly sensitive to membrane curvature. Through analysis of multiple mutants, we conclude that curvature sensitivity is intrinsic to chemoreceptor trimers-of-dimers, and results from conformational entropy within the trimer-of-dimers geometry. We use the principles of the conformational entropy model to engineer curvature sensitivity into a series of multi-component synthetic protein complexes. When expressed in E. coli, the synthetic complexes form large polar clusters, and a complex with inverted geometry avoids the cell poles. This demonstrates the successful rational design of both polar and anti-polar clustering, and provides a synthetic platform on which to build new systems. PMID:28322223

  15. Intracellular magnetophoresis of amyloplasts and induction of root curvature

    NASA Technical Reports Server (NTRS)

    Kuznetsov, O. A.; Hasenstein, K. H.

    1996-01-01

    High-gradient magnetic fields (HGMFs) were used to induce intracellular magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the gap edge between two permanent magnets. In the vicinity of the tip of the wedge the dynamic factor of the magnetic field, delta(H2/2), was about 10(9) Oe2.cm-1, which subjected the amyloplasts to a force comparable to that of gravity. When roots of 2-d-old seedlings of flax (Linum usitatissimum L.) were positioned vertically and exposed to an HGMF, curvature away from the wedge was transient and lasted approximately 1 h. Average curvature obtained after placing magnets, wedge and seedlings on a 1-rpm clinostat for 2 h was 33 +/- 5 degrees. Roots of horizontally placed control seedlings without rotation curved about 47 +/- 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. Microscopy showed displacement of amyloplasts in vitro and in vivo. Studies with Arabidopsis thaliana (L.) Heynh. showed that the wild type responded to HGMFs but the starchless mutant TC7 did not. The data indicate that a magnetic force can be used to study the gravisensing and response system of roots.

  16. Magnetic curvature effects on plasma interchange turbulence

    SciTech Connect

    Li, B. Liao, X.; Sun, C. K.; Ou, W.; Liu, D.; Gui, G.; Wang, X. G.

    2016-06-15

    The magnetic curvature effects on plasma interchange turbulence and transport in the Z-pinch and dipole-like systems are explored with two-fluid global simulations. By comparing the transport levels in the systems with a different magnetic curvature, we show that the interchange-mode driven transport strongly depends on the magnetic geometry. For the system with large magnetic curvature, the pressure and density profiles are strongly peaked in a marginally stable state and the nonlinear evolution of interchange modes produces the global convective cells in the azimuthal direction, which lead to the low level of turbulent convective transport.

  17. Impact of curvature on topological defects

    NASA Astrophysics Data System (ADS)

    Mesarec, L.; Góźdź, W.; Iglič, A.; Kralj, S.

    2017-01-01

    We analyze the impact of extrinsic and intrinsic curvature on positions of topological defects (TDs) in two-dimensional (2D) nematic films. We demonstrate that both these curvature contributions are commonly present and are expected to be weighted by comparable elastic constants. A simple Landau-de Gennes approach in terms of tensor nematic order parameter is used to numerically demonstrate impact of the curvatures on position of TDs on 2D ellipsoidal nematic shells. In particular, in oblate ellipsoids the extrinsic and intrinsic elastic terms enforce conflicting tendencies to positions of TDs.

  18. End-Stopping Predicts Curvature Tuning along the Ventral Stream.

    PubMed

    Ponce, Carlos R; Hartmann, Till S; Livingstone, Margaret S

    2017-01-18

    Neurons in primate inferotemporal cortex (IT) are clustered into patches of shared image preferences. Functional imaging has shown that these patches are activated by natural categories (e.g., faces, body parts, and places), artificial categories (numerals, words) and geometric features (curvature and real-world size). These domains develop in the same cortical locations across monkeys and humans, which raises the possibility of common innate mechanisms. Although these commonalities could be high-level template-based categories, it is alternatively possible that the domain locations are constrained by low-level properties such as end-stopping, eccentricity, and the shape of the preferred images. To explore this, we looked for correlations among curvature preference, receptive field (RF) end-stopping, and RF eccentricity in the ventral stream. We recorded from sites in V1, V4, and posterior IT (PIT) from six monkeys using microelectrode arrays. Across all visual areas, we found a tendency for end-stopped sites to prefer curved over straight contours. Further, we found a progression in population curvature preferences along the visual hierarchy, where, on average, V1 sites preferred straight Gabors, V4 sites preferred curved stimuli, and many PIT sites showed a preference for curvature that was concave relative to fixation. Our results provide evidence that high-level functional domains may be mapped according to early rudimentary properties of the visual system. The macaque occipitotemporal cortex contains clusters of neurons with preferences for categories such as faces, body parts, and places. One common question is how these clusters (or "domains") acquire their cortical position along the ventral stream. We and other investigators previously established an fMRI-level correlation among these category domains, retinotopy, and curvature preferences: for example, in inferotemporal cortex, face- and curvature-preferring domains show a central visual field bias

  19. End-Stopping Predicts Curvature Tuning along the Ventral Stream

    PubMed Central

    Hartmann, Till S.; Livingstone, Margaret S.

    2017-01-01

    Neurons in primate inferotemporal cortex (IT) are clustered into patches of shared image preferences. Functional imaging has shown that these patches are activated by natural categories (e.g., faces, body parts, and places), artificial categories (numerals, words) and geometric features (curvature and real-world size). These domains develop in the same cortical locations across monkeys and humans, which raises the possibility of common innate mechanisms. Although these commonalities could be high-level template-based categories, it is alternatively possible that the domain locations are constrained by low-level properties such as end-stopping, eccentricity, and the shape of the preferred images. To explore this, we looked for correlations among curvature preference, receptive field (RF) end-stopping, and RF eccentricity in the ventral stream. We recorded from sites in V1, V4, and posterior IT (PIT) from six monkeys using microelectrode arrays. Across all visual areas, we found a tendency for end-stopped sites to prefer curved over straight contours. Further, we found a progression in population curvature preferences along the visual hierarchy, where, on average, V1 sites preferred straight Gabors, V4 sites preferred curved stimuli, and many PIT sites showed a preference for curvature that was concave relative to fixation. Our results provide evidence that high-level functional domains may be mapped according to early rudimentary properties of the visual system. SIGNIFICANCE STATEMENT The macaque occipitotemporal cortex contains clusters of neurons with preferences for categories such as faces, body parts, and places. One common question is how these clusters (or “domains”) acquire their cortical position along the ventral stream. We and other investigators previously established an fMRI-level correlation among these category domains, retinotopy, and curvature preferences: for example, in inferotemporal cortex, face- and curvature-preferring domains show a

  20. Membrane curvature regulates ligand-specific membrane sorting of GPCRs in living cells.

    PubMed

    Rosholm, Kadla R; Leijnse, Natascha; Mantsiou, Anna; Tkach, Vadym; Pedersen, Søren L; Wirth, Volker F; Oddershede, Lene B; Jensen, Knud J; Martinez, Karen L; Hatzakis, Nikos S; Bendix, Poul Martin; Callan-Jones, Andrew; Stamou, Dimitrios

    2017-07-01

    The targeted spatial organization (sorting) of Gprotein-coupled receptors (GPCRs) is essential for their biological function and often takes place in highly curved membrane compartments such as filopodia, endocytic pits, trafficking vesicles or endosome tubules. However, the influence of geometrical membrane curvature on GPCR sorting remains unknown. Here we used fluorescence imaging to establish a quantitative correlation between membrane curvature and sorting of three prototypic class A GPCRs (the neuropeptide Y receptor Y2, the β1 adrenergic receptor and the β2 adrenergic receptor) in living cells. Fitting of a thermodynamic model to the data enabled us to quantify how sorting is mediated by an energetic drive to match receptor shape and membrane curvature. Curvature-dependent sorting was regulated by ligands in a specific manner. We anticipate that this curvature-dependent biomechanical coupling mechanism contributes to the sorting, trafficking and function of transmembrane proteins in general.

  1. A quantum chemistry study of curvature effects on boron nitride nanotubes/nanosheets for gas adsorption.

    PubMed

    Sha, Haoyan; Faller, Roland

    2016-07-20

    Quantum chemistry calculations were performed to investigate the effect of the surface curvature of a Boron Nitride (BN) nanotube/nanosheet on gas adsorption. Curved boron nitride layers with different curvatures interacting with a number of different gases including noble gases, oxygen, and water on both their convex and concave sides of the surface were studied using density functional theory (DFT) with a high level dispersion corrected functional. Potential energy surfaces of the gas molecules interacting with the selected BN surfaces were investigated. In addition, the charge distribution and electrostatic potential contour of the selected BN surfaces are discussed. The results reveal how the curvature of the BN surfaces affects gas adsorption. In particular, small curvatures lead to a slight difference in the physisorption energy, while large curvatures present distinct potential energy surfaces, especially for the short-range repulsion.

  2. Non-perturbative approach for curvature perturbations in stochastic δ N formalism

    SciTech Connect

    Fujita, Tomohiro; Kawasaki, Masahiro; Tada, Yuichiro E-mail: kawasaki@icrr.u-tokyo.ac.jp

    2014-10-01

    In our previous paper [1], we have proposed a new algorithm to calculate the power spectrum of the curvature perturbations generated in inflationary universe with use of the stochastic approach. Since this algorithm does not need the perturbative expansion with respect to the inflaton fields on super-horizon scale, it works even in highly stochastic cases. For example, when the curvature perturbations are very large or the non-Gaussianities of the curvature perturbations are sizable, the perturbative expansion may break down but our algorithm enables to calculate the curvature perturbations. We apply it to two well-known inflation models, chaotic and hybrid inflation, in this paper. Especially for hybrid inflation, while the potential is very flat around the critical point and the standard perturbative computation is problematic, we successfully calculate the curvature perturbations.

  3. Turbine component casting core with high resolution region

    DOEpatents

    Kamel, Ahmed; Merrill, Gary B.

    2014-08-26

    A hollow turbine engine component with complex internal features can include a first region and a second, high resolution region. The first region can be defined by a first ceramic core piece formed by any conventional process, such as by injection molding or transfer molding. The second region can be defined by a second ceramic core piece formed separately by a method effective to produce high resolution features, such as tomo lithographic molding. The first core piece and the second core piece can be joined by interlocking engagement that once subjected to an intermediate thermal heat treatment process thermally deform to form a three dimensional interlocking joint between the first and second core pieces by allowing thermal creep to irreversibly interlock the first and second core pieces together such that the joint becomes physically locked together providing joint stability through thermal processing.

  4. The High Latitude D Region During Electron Precipitation Events

    NASA Technical Reports Server (NTRS)

    Hargreaves, J. K.; Collis, P. N.; Korth, A.

    1984-01-01

    The fluxes of energetic electrons entering the high-latitude atmosphere during auroral radio absorption events and their effect on the electron density in the auroral D region are discussed. An attempt was made to calculate the radio absorption during precipitation events from the fluxes of energetic electrons measured at geosynchronous orbit, and then to consider the use of absorption measurements to indicate the magnetospheric particle fluxes, the production rates, and electron densities in the D region.

  5. Reposition sense of lumbar curvature with flexed and asymmetric lifting postures.

    PubMed

    Wilson, Sara E; Granata, Kevin P

    2003-03-01

    Reposition sense of lumbar curvature was assessed as a function of trunk flexion, trunk asymmetry, and target lumbar curvature using a repeated-measures design and an active-active proprioception paradigm. The objectives of the research were to measure the ability of the subjects to sense and control the lumbar curvature in different lifting postures and to see if error in the lumbar curvature would increase in high-risk postures. The risk of low back disorders (LBDs) is related to trunk posture, with greater risk reported in flexed and asymmetric trunk positions. Spinal posture, including trunk position and lumbar lordosis, influences spinal stability. Hence, the ability to accurately sense and control spinal curvature may be an important factor in the control of LBD risk. Eleven subjects were trained to assume specified lumbar curvatures using visual feedback. The ability of the subjects to reproduce this curvature without feedback was then assessed. This procedure was repeated for different trunk postures, including flexion and asymmetry, and with different target lumbar curvatures. These measurements demonstrated reposition error was increased in flexed trunk positions but was unchanged with trunk asymmetry. This increase in reposition error with flexion was diminished when the target posture and lumbar curvature were highly flexed and kyphotic. This research suggests that it may be difficult to control spinal curvature in flexed positions, leading to an increased risk of injury. For jobs in which flexed working postures are unavoidable, therefore, it is important to minimize potentially unstable events such as slipping or shifting loads to avoid injury.

  6. Mean curvature flow of a hyperbolic surface

    SciTech Connect

    Ovchinnikov, Yu. N.; Sigal, I. M.

    2011-12-15

    A four-parameter family of self-similar solutions is obtained to the mean curvature flow equation for a surface. This family is shown to be stable with respect to a small deformation of a hyperbolic surface. At time instant t*, a singular point is formed within a finite time interval, that is accompanied by a change in the topology of the surface. The solution is continued beyond the singular point. A relationship between the parameters describing the hyperbolic surface before and after the change in the surface topology is obtained. A particular case is analyzed when the unperturbed surface is a cylinder. A cylindrical surface is weakly unstable with respect to a perturbation in the form of a 'wide neck.' At the final stage of the development of the neck when its transverse size becomes much less than the cylinder radius at large distances from the neck, the surface flow in a wide region in the neighborhood of the neck is described by a universal two-parameter family of self-similar solutions. These solutions are stable with respect to small perturbations of the surface.

  7. Glauber theory and the quantum coherence of curvature inhomogeneities

    NASA Astrophysics Data System (ADS)

    Giovannini, Massimo

    2017-02-01

    The curvature inhomogeneities are systematically scrutinized in the framework of the Glauber approach. The amplified quantum fluctuations of the scalar and tensor modes of the geometry are shown to be first-order coherent while the interference of the corresponding intensities is larger than in the case of Bose–Einstein correlations. After showing that the degree of second-order coherence does not suffice to characterize unambiguously the curvature inhomogeneities, we argue that direct analyses of the degrees of third- and fourth-order coherence are necessary to discriminate between different correlated states and to infer more reliably the statistical properties of the large-scale fluctuations. We speculate that the moments of the multiplicity distributions of the relic phonons might be observationally accessible thanks to new generations of instruments able to count the single photons of the Cosmic Microwave Background in the THz region.

  8. Detonation front curvatures and detonation rates

    NASA Astrophysics Data System (ADS)

    Lauderbach, Lisa M.; Lorenz, K. Thomas; Lee, Edward L.; Souers, P. Clark

    2017-01-01

    Many detonation front curvatures are reviewed. Most are of the Shock Dynamics type, which are described as a combination of quadratic and 8th power-of-the-radius curves. The integrated fraction of the 8th power curve is taken as a measure of curvature, which we are able to relate to the logarithm of the detonation rate. This provides a means of estimating the rates of some unknown explosives from the curvature. Using the edge lag divided by the radius is an even better way. A second group of curvatures are almost or purely quadratic. This is probably not associated with density gradients but may be caused by low sound speeds. A final group of "sombreros" show curvy fronts for ideal explosives, which appear to be caused by density gradients.

  9. Anisotropic Membrane Curvature Sensing by Amphipathic Peptides

    PubMed Central

    Gómez-Llobregat, Jordi; Elías-Wolff, Federico; Lindén, Martin

    2016-01-01

    Many proteins and peptides have an intrinsic capacity to sense and induce membrane curvature, and play crucial roles for organizing and remodeling cell membranes. However, the molecular driving forces behind these processes are not well understood. Here, we describe an approach to study curvature sensing by simulating the interactions of single molecules with a buckled lipid bilayer. We analyze three amphipathic antimicrobial peptides, a class of membrane-associated molecules that specifically target and destabilize bacterial membranes, and find qualitatively different sensing characteristics that would be difficult to resolve with other methods. Our findings provide evidence for direction-dependent curvature sensing mechanisms in amphipathic peptides and challenge existing theories of hydrophobic insertion. The buckling approach is generally applicable to a wide range of curvature-sensing molecules, and our results provide strong motivation to develop new experimental methods to track position and orientation of membrane proteins. PMID:26745422

  10. Role of feature curvature in contact guidance

    PubMed Central

    Mathur, Anurag; Moore, Simon W.; Sheetz, Michael P.; Hone, James

    2012-01-01

    This study examines the role of feature curvature in cellular topography sensing. To separate the effects of feature size and curvature, we have developed a method to fabricate grooved substrates whose radius of curvature (r) is varied from under 10 nm to 400 nm, while all other dimensions are kept constant. With increasing r up to 200 nm, mouse embryonic fibroblasts increased their spread area, but reduced their polarization (aspect ratio). Interestingly, on features with an r of 200 and 400 nm - where there was very little effect on spreading area and polarization - we find that internal structures such as stress fibers are nevertheless still strongly aligned to the topography. These findings are of importance to studies of both tissue engineering and curvature sensing proteins. PMID:22426288

  11. Gravitational energy in quadratic-curvature gravities.

    PubMed

    Deser, S; Tekin, Bayram

    2002-09-02

    We define energy (E) and compute its values for gravitational systems involving terms quadratic in curvature. There are significant differences, both conceptually and concretely, from Einstein theory. For D=4, all purely quadratic models admit constant curvature vacua with arbitrary Lambda, and E is the "cosmological" Abbott-Deser (AD) expression; instead, E always vanishes in flat, Lambda=0, background. For combined Einstein-quadratic curvature systems without explicit Lambda-term vacuum must be flat space, and E has the usual Arnowitt-Deser-Misner form. A Lambda-term forces unique de Sitter vacuum, with E the sum of contributions from Einstein and quadratic parts to the AD form. We also discuss the effects on energy definition of higher curvature terms and of higher dimension.

  12. Spline-Based Smoothing of Airfoil Curvatures

    NASA Technical Reports Server (NTRS)

    Li, W.; Krist, S.

    2008-01-01

    Constrained fitting for airfoil curvature smoothing (CFACS) is a splinebased method of interpolating airfoil surface coordinates (and, concomitantly, airfoil thicknesses) between specified discrete design points so as to obtain smoothing of surface-curvature profiles in addition to basic smoothing of surfaces. CFACS was developed in recognition of the fact that the performance of a transonic airfoil is directly related to both the curvature profile and the smoothness of the airfoil surface. Older methods of interpolation of airfoil surfaces involve various compromises between smoothing of surfaces and exact fitting of surfaces to specified discrete design points. While some of the older methods take curvature profiles into account, they nevertheless sometimes yield unfavorable results, including curvature oscillations near end points and substantial deviations from desired leading-edge shapes. In CFACS as in most of the older methods, one seeks a compromise between smoothing and exact fitting. Unlike in the older methods, the airfoil surface is modified as little as possible from its original specified form and, instead, is smoothed in such a way that the curvature profile becomes a smooth fit of the curvature profile of the original airfoil specification. CFACS involves a combination of rigorous mathematical modeling and knowledge-based heuristics. Rigorous mathematical formulation provides assurance of removal of undesirable curvature oscillations with minimum modification of the airfoil geometry. Knowledge-based heuristics bridge the gap between theory and designers best practices. In CFACS, one of the measures of the deviation of an airfoil surface from smoothness is the sum of squares of the jumps in the third derivatives of a cubicspline interpolation of the airfoil data. This measure is incorporated into a formulation for minimizing an overall deviation- from-smoothness measure of the airfoil data within a specified fitting error tolerance. CFACS has been

  13. Curvature Analysis of Cardiac Excitation Wavefronts

    DTIC Science & Technology

    2013-04-01

    computational cardiac-cell network accurately reproduces a particular kind of cardiac arrhythmia , such as ventricular fibrillation. Curvature Analysis of Cardiac...network accurately reproduces a particular kind of cardiac arrhythmia , such as ventricular fibrillation. Index Terms Cardiac excitation waves...isopotentials, Bézier curves, curvature, cardiac arrhythmia and fibrillation Ç 1 INTRODUCTION AN estimated 81,000,000 American adults, more than onein three

  14. Curvature tensors unified field equations on SEXn

    NASA Astrophysics Data System (ADS)

    Chung, Kyung Tae; Lee, Il Young

    1988-09-01

    We study the curvature tensors and field equations in the n-dimensional SE manifold SEXn. We obtain several basic properties of the vectors S λ and U λ and then of the SE curvature tensor and its contractions, such as a generalized Ricci identity, a generalized Bianchi identity, and two variations of the Bianchi identity satisfied by the SE Einstein tensor. Finally, a system of field equations is discussed in SEXn and one of its particular solutions is constructed and displayed.

  15. Instant curvature measurement for microcantilever sensors

    SciTech Connect

    Jeon, Sangmin; Thundat, Thomas

    2004-08-09

    A multiple-point deflection technique has been developed for the instant measurement of microcantilever curvature. Eight light-emitting diodes are focused on various positions of a gold-coated silicon cantilever through optical fibers, and temperature change or chemical adsorption induces cantilever bending. The deflection at each point on the cantilever is measured with subnanometer precision by a position-sensitive detector, and thus the curvature of the cantilever is obtained.

  16. Investigation of the curvature induction and membrane localization of the influenza virus M2 protein using static and off-magic-angle spinning solid-state nuclear magnetic resonance of oriented bicelles.

    PubMed

    Wang, Tuo; Hong, Mei

    2015-04-07

    A wide variety of membrane proteins induce membrane curvature for function; thus, it is important to develop new methods to simultaneously determine membrane curvature and protein binding sites in membranes with multiple curvatures. We introduce solid-state nuclear magnetic resonance (NMR) methods based on magnetically oriented bicelles and off-magic-angle spinning (OMAS) to measure membrane curvature and the binding site of proteins in mixed-curvature membranes. We demonstrate these methods on the influenza virus M2 protein, which not only acts as a proton channel but also mediates virus assembly and membrane scission. An M2 peptide encompassing the transmembrane (TM) domain and an amphipathic helix, M2(21-61), was studied and compared with the TM peptide (M2TM). Static (31)P NMR spectra of magnetically oriented 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) bicelles exhibit a temperature-independent isotropic chemical shift in the presence of M2(21-61) but not M2TM, indicating that the amphipathic helix confers the ability to generate a high-curvature phase. Two-dimensional (2D) (31)P spectra indicate that this high-curvature phase is associated with the DHPC bicelle edges, suggestive of the structure of budding viruses from the host cell. (31)P- and (13)C-detected (1)H relaxation times of the lipids indicate that the majority of M2(21-61) is bound to the high-curvature phase. Using OMAS experiments, we resolved the (31)P signals of lipids with identical headgroups based on their distinct chemical shift anisotropies. On the basis of this resolution, 2D (1)H-(31)P correlation spectra show that the amide protons in M2(21-61) correlate with the DMPC but not DHPC (31)P signal of the bicelle, indicating that a small percentage of M2(21-61) partitions into the planar region of the bicelles. These results show that the amphipathic helix induces high membrane curvature and localizes the protein to this phase, in good

  17. Investigation of the Curvature Induction and Membrane Localization of the Influenza Virus M2 Protein Using Static and Off-Magic-Angle Spinning Solid-State NMR of Oriented Bicelles

    PubMed Central

    Wang, Tuo; Hong, Mei

    2015-01-01

    A wide variety of membrane proteins induce membrane curvature for function, thus it is important to develop new methods to simultaneously determine membrane curvature and protein binding sites in membranes with multiple curvatures. We introduce solid-state NMR methods based on magnetically oriented bicelles and off-magic-angle spinning (OMAS) to measure membrane curvature and the binding site of proteins in mixed-curvature membranes. We demonstrate these methods on the influenza virus M2 protein, which not only acts as a proton channel but also mediates virus assembly and membrane scission. An M2 peptide encompassing the transmembrane (TM) domain and an amphipathic helix, M2(21-61), was studied and compared with the TM peptide (M2TM). Static 31P NMR spectra of magnetically oriented DMPC/DHPC bicelles exhibit a temperature-independent isotropic chemical shift in the presence of M2(21-61) but not M2TM, indicating that the amphipathic helix confers the peptide with the ability to generate a high-curvature phase. 2D 31P spectra indicate that this high-curvature phase is associated with the DHPC bicelle edges, suggestive of the structure of budding viruses from the host cell. 31P- and 13C-detected 1H relaxation times of the lipids indicate that the majority of M2(21-61) is bound to the high-curvature phase. Using OMAS experiments, we resolved the 31P signals of lipids with identical headgroups based on their distinct chemical shift anisotropies. Based on this resolution, 2D 1H-31P correlation spectra show that the amide protons in M2(21-61) correlate with the DMPC but not the DHPC 31P signal of the bicelle, indicating that a small percentage of M2(21-61) partitions into the planar region of the bicelles. These results show that the M2 amphipathic helix induces high membrane curvature and localizes the protein to this phase, in excellent agreement with the membrane-scission function of the protein. These bicelle-based relaxation and OMAS solid-state NMR techniques are

  18. Regions of High Excitation in the Nebula around Eta Carinae

    NASA Astrophysics Data System (ADS)

    Martin, J. C.; Davidson, K.

    2005-05-01

    The circumstellar environment around Eta Carinae is polluted by a complicated field of ejecta which is the product of several historic eruptions. At least two regions are uniquely characterized by narrow high excitation emission features: the Wiegelt Knots and Strontium "Filament." We have produced the first sub-arcsecond spatial maps of high excitation emission from individual spectral features within a few arcseconds of the central star. These maps provide helpful insights into the general shape of these regions, their probable origins, and the excitation mechanism which powers them.

  19. Spherical gravitational curvature boundary-value problem

    NASA Astrophysics Data System (ADS)

    Šprlák, Michal; Novák, Pavel

    2016-08-01

    Values of scalar, vector and second-order tensor parameters of the Earth's gravitational field have been collected by various sensors in geodesy and geophysics. Such observables have been widely exploited in different parametrization methods for the gravitational field modelling. Moreover, theoretical aspects of these quantities have extensively been studied and well understood. On the other hand, new sensors for observing gravitational curvatures, i.e., components of the third-order gravitational tensor, are currently under development. As the gravitational curvatures represent new types of observables, their exploitation for modelling of the Earth's gravitational field is a subject of this study. Firstly, the gravitational curvature tensor is decomposed into six parts which are expanded in terms of third-order tensor spherical harmonics. Secondly, gravitational curvature boundary-value problems defined for four combinations of the gravitational curvatures are formulated and solved in spectral and spatial domains. Thirdly, properties of the corresponding sub-integral kernels are investigated. The presented mathematical formulations reveal some important properties of the gravitational curvatures and extend the so-called Meissl scheme, i.e., an important theoretical framework that relates various parameters of the Earth's gravitational field.

  20. Nonadditive Compositional Curvature Energetics of Lipid Bilayers

    NASA Astrophysics Data System (ADS)

    Sodt, A. J.; Venable, R. M.; Lyman, E.; Pastor, R. W.

    2016-09-01

    The unique properties of the individual lipids that compose biological membranes together determine the energetics of the surface. The energetics of the surface, in turn, govern the formation of membrane structures and membrane reshaping processes, and thus they will underlie cellular-scale models of viral fusion, vesicle-dependent transport, and lateral organization relevant to signaling. The spontaneous curvature, to the best of our knowledge, is always assumed to be additive. We describe observations from simulations of unexpected nonadditive compositional curvature energetics of two lipids essential to the plasma membrane: sphingomyelin and cholesterol. A model is developed that connects molecular interactions to curvature stress, and which explains the role of local composition. Cholesterol is shown to lower the number of effective Kuhn segments of saturated acyl chains, reducing lateral pressure below the neutral surface of bending and favoring positive curvature. The effect is not observed for unsaturated (flexible) acyl chains. Likewise, hydrogen bonding between sphingomyelin lipids leads to positive curvature, but only at sufficient concentration, below which the lipid prefers negative curvature.

  1. The role of curvature in entanglement

    NASA Astrophysics Data System (ADS)

    Buck, Gregory

    2015-10-01

    Which tangles more readily: curly hair or straight hair? A perhaps natural thought, supported by some theoretical evidence, is to associate curvature and entanglement, and assume that they would grow together-that an increase in one fosters an increase in the other. However we have biological examples such as DNA in the chromosome, and mechanical examples such as coiled telephone cords, in which much more curvature is employed than is required for the packing, and in which tangling is presumably detrimental. We offer a resolution to this conundrum. We show, that at least for simple but generally applicable models, the relationship between curvature and entanglement is subtle: if we keep filament density constant and increase curvature, the entanglement initially increases, passes through a maximum, then decreases, so there is a regime where increasing curvature increases entanglement, and there is also a regime where increasing curvature decreases entanglement. This has implications for filament packing in many circumstances, and in particular for the compaction structure of DNA in the cell-it provides a straightforward argument for the view that one purpose of DNA coiling and supercoiling is to inhibit entanglement. It also tells us to expect that wavy hair-neither the straightest nor the curliest-tangles most readily.

  2. Nonadditive Compositional Curvature Energetics of Lipid Bilayers.

    PubMed

    Sodt, A J; Venable, R M; Lyman, E; Pastor, R W

    2016-09-23

    The unique properties of the individual lipids that compose biological membranes together determine the energetics of the surface. The energetics of the surface, in turn, govern the formation of membrane structures and membrane reshaping processes, and thus they will underlie cellular-scale models of viral fusion, vesicle-dependent transport, and lateral organization relevant to signaling. The spontaneous curvature, to the best of our knowledge, is always assumed to be additive. We describe observations from simulations of unexpected nonadditive compositional curvature energetics of two lipids essential to the plasma membrane: sphingomyelin and cholesterol. A model is developed that connects molecular interactions to curvature stress, and which explains the role of local composition. Cholesterol is shown to lower the number of effective Kuhn segments of saturated acyl chains, reducing lateral pressure below the neutral surface of bending and favoring positive curvature. The effect is not observed for unsaturated (flexible) acyl chains. Likewise, hydrogen bonding between sphingomyelin lipids leads to positive curvature, but only at sufficient concentration, below which the lipid prefers negative curvature.

  3. Anisotropic Cosmology and Curvature Invariants.

    NASA Astrophysics Data System (ADS)

    Skea, James E. F.

    greater when non-axisymmetric cosmologies are considered. In the limit where the particle production is switched on at the Planck time (t _{rm Pl}), isotropisation is found to occur at _{Omega } 10^5 t_ {rm Pl}, compatible with restrictions on anistropy at that time. Particle production is not found to isotropise Bianchi VIII and IX cosmologies. In Part 3, we study the structure of various curvature invariants and, following a suggestion by Karlhede, we investigate their relationship to horizons in particular space-times. (Abstract shortened by UMI.).

  4. High resolution regional seismic attenuation tomography in eastern Tibetan Plateau and adjacent regions

    NASA Astrophysics Data System (ADS)

    Bao, Xueyang; Sandvol, Eric; Ni, James; Hearn, Thomas; Chen, Yongshun John; Shen, Yang

    2011-08-01

    The Q of regional seismic phases Lg and Pg within the crust is assumed as a proxy for crustal Qβ and Qα, which is used as a constraint of crustal rheology. We measure regional-phase Q of the eastern Tibetan Plateau and adjacent areas. This method eliminates contributions from source and site responses and is an improvement on the Two-Station Method (TSM). We have generated tomographic images of crustal attenuation anomalies with resolution as high as 1°. In general we observe low Q in the northernmost portions of the Tibetan Plateau and high Q in the more tectonically stable regions such as the interior of the Qaidam basin. The calculated site responses appear to correlate with topography or sediment thickness. Furthermore the relationship between earthquake magnitudes and calculated source terms suggest that the RTM method effectively removes the source response and may be used as an alternative to source magnitude.

  5. High beta and second stability region transport and stability analysis

    SciTech Connect

    Not Available

    1990-06-12

    This document summarizes progress made on the research of high beta and second region transport and stability. In the area second stability region studies we report on an investigation of the possibility of second region access in the center of TFTR supershots.'' The instabilities found may coincide with experimental observation. Significant progress has been made on the resistive stability properties of high beta poloidal supershot'' discharges. For these studies profiles were taken from the TRANSP transport analysis code which analyzes experimental data. Invoking flattening of the pressure profile on mode rational surfaces causes tearing modes to persist into the experimental range of interest. Further, the experimental observation of the modes seems to be consistent with the predictions of the MHD model. In addition, code development in several areas has proceeded.

  6. Distorted Plane Waves on Manifolds of Nonpositive Curvature

    NASA Astrophysics Data System (ADS)

    Ingremeau, Maxime

    2017-03-01

    We will consider the high frequency behaviour of distorted plane waves on manifolds of nonpositive curvature which are Euclidean or hyperbolic near infinity, under the assumption that the curvature is negative close to the trapped set of the geodesic flow and that the topological pressure associated to half the unstable Jacobian is negative. We obtain a precise expression for distorted plane waves in the high frequency limit, similar to the one in Guillarmou and Naud (Am J Math 136:445-479, 2014) in the case of convex co-compact manifolds. In particular, we will show {L_{loc}^∞} bounds on distorted plane waves that are uniform with frequency. We will also show a small-scale equidistribution result for the real part of distorted plane waves, which implies sharp bounds for the volume of their nodal sets.

  7. Cam radius of curvature modification for improved manufacturability

    SciTech Connect

    Doughty, S.

    1995-12-31

    The design of IC engine cams using the popular polynomial design techniques often results in very high accelerations (and associated high contact forces) as the follower approaches the base circle. In those same parts of the cam action, the cam radius of curvature is likely to change signs, going from convex to concave, and this leads to manufacturing difficulties. When the cam is concave, the radius of the grinding wheel that can be used in manufacture is controlled by the minimum concave radius of curvature of the cam, and this is often much smaller than the wheel size that would result in most economic production. Further, the arc of contact is extended, resulting in loss of coolant flow and rapid loss of wheel dress. A solution is presented, based on substituting a convex circular arc to replace a segment of the cam profile including the concavity. The ramifications of such a modification with regard to the follower motion is also presented.

  8. Strong curvature effects in Neumann wave problems

    SciTech Connect

    Willatzen, M.; Pors, A.; Gravesen, J.

    2012-08-15

    Waveguide phenomena play a major role in basic sciences and engineering. The Helmholtz equation is the governing equation for the electric field in electromagnetic wave propagation and the acoustic pressure in the study of pressure dynamics. The Schroedinger equation simplifies to the Helmholtz equation for a quantum-mechanical particle confined by infinite barriers relevant in semiconductor physics. With this in mind and the interest to tailor waveguides towards a desired spectrum and modal pattern structure in classical structures and nanostructures, it becomes increasingly important to understand the influence of curvature effects in waveguides. In this work, we demonstrate analytically strong curvature effects for the eigenvalue spectrum of the Helmholtz equation with Neumann boundary conditions in cases where the waveguide cross section is a circular sector. It is found that the linear-in-curvature contribution originates from parity symmetry breaking of eigenstates in circular-sector tori and hence vanishes in a torus with a complete circular cross section. The same strong curvature effect is not present in waveguides subject to Dirichlet boundary conditions where curvature contributions contribute to second-order in the curvature only. We demonstrate this finding by considering wave propagation in a circular-sector torus corresponding to Neumann and Dirichlet boundary conditions, respectively. Results for relative eigenfrequency shifts and modes are determined and compared with three-dimensional finite element method results. Good agreement is found between the present analytical method using a combination of differential geometry with perturbation theory and finite element results for a large range of curvature ratios.

  9. Strong curvature effects in Neumann wave problems

    NASA Astrophysics Data System (ADS)

    Willatzen, M.; Pors, A.; Gravesen, J.

    2012-08-01

    Waveguide phenomena play a major role in basic sciences and engineering. The Helmholtz equation is the governing equation for the electric field in electromagnetic wave propagation and the acoustic pressure in the study of pressure dynamics. The Schrödinger equation simplifies to the Helmholtz equation for a quantum-mechanical particle confined by infinite barriers relevant in semiconductor physics. With this in mind and the interest to tailor waveguides towards a desired spectrum and modal pattern structure in classical structures and nanostructures, it becomes increasingly important to understand the influence of curvature effects in waveguides. In this work, we demonstrate analytically strong curvature effects for the eigenvalue spectrum of the Helmholtz equation with Neumann boundary conditions in cases where the waveguide cross section is a circular sector. It is found that the linear-in-curvature contribution originates from parity symmetry breaking of eigenstates in circular-sector tori and hence vanishes in a torus with a complete circular cross section. The same strong curvature effect is not present in waveguides subject to Dirichlet boundary conditions where curvature contributions contribute to second-order in the curvature only. We demonstrate this finding by considering wave propagation in a circular-sector torus corresponding to Neumann and Dirichlet boundary conditions, respectively. Results for relative eigenfrequency shifts and modes are determined and compared with three-dimensional finite element method results. Good agreement is found between the present analytical method using a combination of differential geometry with perturbation theory and finite element results for a large range of curvature ratios.

  10. CURVATURE-DRIFT INSTABILITY FAILS TO GENERATE PULSAR RADIO EMISSION

    SciTech Connect

    Kaganovich, Alexander; Lyubarsky, Yuri

    2010-10-01

    The curvature-drift instability has long been considered as a viable mechanism for pulsar radio emission. We reconsidered this mechanism by finding an explicit solution describing the propagation of short electromagnetic waves in a plasma flow along curved magnetic field lines. We show that even though the waves could be amplified, the amplification factor remains very close to unity; therefore, this mechanism is unable to generate high brightness temperature emission from initial weak fluctuations.

  11. Instability in bacterial populations and the curvature tensor

    NASA Astrophysics Data System (ADS)

    Melgarejo, Augusto; Langoni, Laura; Ruscitti, Claudia

    2016-09-01

    In the geometry associated with equilibrium thermodynamics the scalar curvature Rs is a measure of the volume of correlation, and therefore the singularities of Rs indicates the system instabilities. We explore the use of a similar approach to study instabilities in non-equilibrium systems and we choose as a test example, a colony of bacteria. In this regard we follow the proposal made by Obata et al. of using the curvature tensor for studying system instabilities. Bacterial colonies are often found in nature in concentrated biofilms, or other colony types, which can grow into spectacular patterns visible under the microscope. For instance, it is known that a decrease of bacterial motility with density can promote separation into bulk phases of two coexisting densities; this is opposed to the logistic law for birth and death that allows only a single uniform density to be stable. Although this homogeneous configuration is stable in the absence of bacterial interactions, without logistic growth, a density-dependent swim speed v(ρ) leads to phase separation via a spinodal instability. Thus we relate the singularities in the curvature tensor R to the spinodal instability, that is the appearance of regions of different densities of bacteria.

  12. Evaluation of Spatial Anisotropy by Curvature Analysis of Elliptical Targets

    PubMed Central

    Aleci, Carlo; Piana, Giulio; Anselmino, Franco

    2010-01-01

    Spatial relationship perception (SRP), defined as the function able to detect the difference between the perceived extent of a shape along the x/y cardinal coordinates, has been investigated in 42 eyes of 21 emmetropic subjects by means of a psychophysical test conceived on purpose. Aiming to the highest sensibility and since curvature detection is reckoned as an hyperacuity, elliptical stimuli have been chosen to measure the spatial relationship anisotropy (SRA) in the visual system. Observers turned out to be able to detect curvature differences along the elliptical contour as low as 33.6 sec arc, which in terms of SRP means an aspect ratio (i.e. the ratio between the height and the width of the ellipse) as low as 1.0022-1.0035. By comparing these results with those obtained in previous investigations from other curvature discrimination tasks, it is argued that recognition threshold is conditioned by the amount of space anisotropy of the visual system. Indeed, in about half of the recruited subjects, vertical/horizontal anisotropy is found to a certain extent and such SRA correlates with the recognition threshold (r= 0.69, p<0.01). There is direct evidence of visual spatial distortion and in particular increased anisotropy in neuro-ophtalmological diseases such as hemianopia and around scotomatous regions in the visual field. Thence, apart from theoretical considerations in physiological field, results collected in this study may be regarded as normative data for future clinical investigations. PMID:20802805

  13. Encoding Gaussian curvature in glassy and elastomeric liquid crystal solids

    PubMed Central

    Mostajeran, Cyrus; Ware, Taylor H.; White, Timothy J.

    2016-01-01

    We describe shape transitions of thin, solid nematic sheets with smooth, preprogrammed, in-plane director fields patterned across the surface causing spatially inhomogeneous local deformations. A metric description of the local deformations is used to study the intrinsic geometry of the resulting surfaces upon exposure to stimuli such as light and heat. We highlight specific patterns that encode constant Gaussian curvature of prescribed sign and magnitude. We present the first experimental results for such programmed solids, and they qualitatively support theory for both positive and negative Gaussian curvature morphing from flat sheets on stimulation by light or heat. We review logarithmic spiral patterns that generate cone/anti-cone surfaces, and introduce spiral director fields that encode non-localized positive and negative Gaussian curvature on punctured discs, including spherical caps and spherical spindles. Conditions are derived where these cap-like, photomechanically responsive regions can be anchored in inert substrates by designing solutions that ensure compatibility with the geometric constraints imposed by the surrounding media. This integration of such materials is a precondition for their exploitation in new devices. Finally, we consider the radial extension of such director fields to larger sheets using nematic textures defined on annular domains. PMID:27279777

  14. Autonomic straightening after gravitropic curvature of cress roots

    NASA Technical Reports Server (NTRS)

    Stankovic, B.; Volkmann, D.; Sack, F. D.

    1998-01-01

    Few studies have documented the response of gravitropically curved organs to a withdrawal of a constant gravitational stimulus. The effects of stimulus withdrawal on gravitropic curvature were studied by following individual roots of cress (Lepidium sativum L.) through reorientation and clinostat rotation. Roots turned to the horizontal curved down 62 degrees and 88 degrees after 1 and 5 h, respectively. Subsequent rotation on a clinostat for 6 h resulted in root straightening through a loss of gravitropic curvature in older regions and through new growth becoming aligned closer to the prestimulus vertical. However, these roots did not return completely to the prestimulus vertical, indicating the retention of some gravitropic response. Clinostat rotation shifted the mean root angle -36 degrees closer to the prestimulus vertical, regardless of the duration of prior horizontal stimulation. Control roots (no horizontal stimulation) were slanted at various angles after clinostat rotation. These findings indicate that gravitropic curvature is not necessarily permanent, and that the root retains some commitment to its equilibrium orientation prior to gravitropic stimulation.

  15. Autonomic Straightening after Gravitropic Curvature of Cress Roots1

    PubMed Central

    Stanković, Bratislav; Volkmann, Dieter; David Sack, Fred

    1998-01-01

    Few studies have documented the response of gravitropically curved organs to a withdrawal of a constant gravitational stimulus. The effects of stimulus withdrawal on gravitropic curvature were studied by following individual roots of cress (Lepidium sativum L.) through reorientation and clinostat rotation. Roots turned to the horizontal curved down 62° and 88° after 1 and 5 h, respectively. Subsequent rotation on a clinostat for 6 h resulted in root straightening through a loss of gravitropic curvature in older regions and through new growth becoming aligned closer to the prestimulus vertical. However, these roots did not return completely to the prestimulus vertical, indicating the retention of some gravitropic response. Clinostat rotation shifted the mean root angle −36° closer to the prestimulus vertical, regardless of the duration of prior horizontal stimulation. Control roots (no horizontal stimulation) were slanted at various angles after clinostat rotation. These findings indicate that gravitropic curvature is not necessarily permanent, and that the root retains some commitment to its equilibrium orientation prior to gravitropic stimulation. PMID:9662531

  16. Gravitropic curvature of maize roots is not preceded by rootcap asymmetry

    NASA Technical Reports Server (NTRS)

    Sack, F. D.; Hasenstein, K. H.; Blair, A.

    1990-01-01

    We tested whether the first response to gravistimulation is an asymmetry in the root tip that results from differential growth of the rootcap itself. The displacement of markers on the rootcap surface of maize (Zea mays L. cv. Merit) roots was quantified from videotaped images using customized software. The method was sensitive enough to detect marker displacements down to 15 microns and root curvature as early as 8 min after gravistimulation. No differential growth of the upper and lower sides of the cap occurred before or during root curvature. Fewer than a third of all gravistimulated roots developed an asymmetrical outline of the root tip after curvature had started, and this asymmetry did not occur in the rootcap itself. Our data support the view that the regions of gravitropic sensing and curvature are spatially separate during all phases of gravitropism in maize roots.

  17. High Plains Regional Ground-water Study web site

    USGS Publications Warehouse

    Qi, Sharon L.

    2000-01-01

    Now available on the Internet is a web site for the U.S. Geological Survey's (USGS) National Water-Quality Assessment (NAWQA) Program- High Plains Regional Ground-Water Study. The purpose of the web site is to provide public access to a wide variety of information on the USGS investigation of the ground-water resources within the High Plains aquifer system. Typical pages on the web site include the following: descriptions of the High Plains NAWQA, the National NAWQA Program, the study-area setting, current and past activities, significant findings, chemical and ancillary data (which can be downloaded), listing and access to publications, links to other sites about the High Plains area, and links to other web sites studying High Plains ground-water resources. The High Plains aquifer is a regional aquifer system that underlies 174,000 square miles in parts of eight States (Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming). Because the study area is so large, the Internet is an ideal way to provide project data and information on a near real-time basis. The web site will be a collection of living documents where project data and information are updated as it becomes available throughout the life of the project. If you have an interest in the High Plains area, you can check this site periodically to learn how the High Plains NAWQA activities are progressing over time and access new data and publications as they become available.

  18. Actin filament curvature biases branching direction

    NASA Astrophysics Data System (ADS)

    Wang, Evan; Risca, Viviana; Chaudhuri, Ovijit; Chia, Jia-Jun; Geissler, Phillip; Fletcher, Daniel

    2012-02-01

    Actin filaments are key components of the cellular machinery, vital for a wide range of processes ranging from cell motility to endocytosis. Actin filaments can branch, and essential in this process is a protein complex known as the Arp2/3 complex, which nucleate new ``daughter'' filaments from pre-existing ``mother'' filaments by attaching itself to the mother filament. Though much progress has been made in understanding the Arp2/3-actin junction, some very interesting questions remain. In particular, F-actin is a dynamic polymer that undergoes a wide range of fluctuations. Prior studies of the Arp2/3-actin junction provides a very static notion of Arp2/3 binding. The question we ask is how differently does the Arp2/3 complex interact with a straight filament compared to a bent filament? In this study, we used Monte Carlo simulations of a surface-tethered worm-like chain to explore possible mechanisms underlying the experimental observation that there exists preferential branch formation by the Arp2/3 complex on the convex face of a curved filament. We show that a fluctuation gating model in which Arp2/3 binding to the actin filament is dependent upon a rare high-local-curvature shape fluctuation of the filament is consistent with the experimental data.

  19. Determination of slope, curvature, and twist from a single shearography fringe pattern using derivative-based regularized phase tracker

    NASA Astrophysics Data System (ADS)

    Deepan, Balakrishnan; Quan, Chenggen; Tay, Cho Jui

    2016-12-01

    A fringe analysis algorithm for determination of slope, curvature, and twist from a single fringe pattern in digital speckle-shearing interferometry is proposed. A method for estimation of biased curvature and twist maps from fringe orientation and fringe density maps is employed. The curvature and twist maps obtained are further processed by B-spline interpolation to achieve high quality curvature and twist maps. A derivative-based regularized phase tracker (RPT) utilizes these predetermined curvature and twist maps for determination of a slope map from a single shearography fringe pattern. The proposed model requires less computational time and it overcomes the limitations of the RPT model. The method is validated with an experimental fringe pattern. The results show that this method is robust against speckle noise and it is able to retrieve accurate slope, curvature, and twist maps from a single shearography fringe pattern.

  20. High dispersion observations of selected regions in the Orion Nebula

    NASA Astrophysics Data System (ADS)

    Boeshaar, G. O.; Harvel, C. A.; Mallama, A. D.; Perry, P. M.; Thompson, R. W.; Turnrose, B.

    High resolution spectral observations were made of several regions of the Orion Nebula near theta (2) Ori A using the IUE. The positions were selected using a moderate spatial resolution map from a previous low dispersion IUE survery of this section of the nebula. With the SWP and LWR cameras, 28 pectra were obtained of the bright bar, three Taylor-Munch cloudlets, and several surrounding locations. Emission lines of He, C, N, O, Mg, and Si allow a characterization of these cloudlets and of the gas in and around the bar. Small aperture observations provide radial velocity information for the ultraviolet emission of these features. These data show ionization variations from region to region and are suggestive of stellar wind interactions between the cloudlets and theta(2) Ori A.

  1. Lipids, curvature, and nano-medicine*

    PubMed Central

    Mouritsen, Ole G

    2011-01-01

    The physical properties of the lamellar lipid-bilayer component of biological membranes are controlled by a host of thermodynamic forces leading to overall tensionless bilayers with a conspicuous lateral pressure profile and build-in curvature-stress instabilities that may be released locally or globally in terms of morphological changes. In particular, the average molecular shape and the propensity of the different lipid and protein species for forming non-lamellar and curved structures are a source of structural transitions and control of biological function. The effects of different lipids, sterols, and proteins on membrane structure are discussed and it is shown how one can take advantage of the curvature-stress modulations brought about by specific molecular agents, such as fatty acids, lysolipids, and other amphiphilic solutes, to construct intelligent drug-delivery systems that function by enzymatic triggering via curvature. Practical applications: The simple concept of lipid molecular shape and how it impacts on the structure of lipid aggregates, in particular the curvature and curvature stress in lipid bilayers and liposomes, can be exploited to construct liposome-based drug-delivery systems, e.g., for use as nano-medicine in cancer therapy. Non-lamellar-forming lysolipids and fatty acids, some of which may be designed to be prodrugs, can be created by phospholipase action in diseased tissues thereby providing for targeted drug release and proliferation of molecular entities with conical shape that break down the permeability barrier of the target cells and may hence enhance efficacy. PMID:22164124

  2. Seismic Curvature Estimation Based on Combining Gradient Structure Tensor and Multi-window

    NASA Astrophysics Data System (ADS)

    Wang, X.; Zhao, H.; Chen, W.

    2016-12-01

    Geometric attribute, which can be extracted from seismic exploration data, is one of the most important kinds of seismic attributes. Curvature attribute is one of the most useful geometric attribute in 3D seismic data interpretation. It is proved that curvature is related to fault, fracture and oil-gas production. However, curvature attribute is obtained by calculate the partial derivatives of the dip of seismic events. Therefore, estimating dips with high precision is very important. We propose one seismic dip estimating method based on combining gradient structure tensor and multi-window technology, and estimate curvature based on this estimated dips. Firstly, we obtain instantaneous amplitude(IA) and instantaneous phase(IP) through complex trace analysis. Secondly, we construct gradient structural tensor(GST) is based on IP, and do eigendecomposition on GST to estimated seismic dips precisely. Meanwhile, we also utilize multi-window technology to promote estimating precision of seismic dips. Finally, we compute structure curvature (include most-negative curvature, most-positive curvature and so on) based on estimated seismic dips. We verify the effectiveness and precision of our method by apply our method to one synthetic seismic data and two real 3D field data.

  3. Biplanar measurement of thoracolumbar curvature in older adults using an electromagnetic tracking device.

    PubMed

    Singh, Devinder K; Bailey, Martin; Lee, Raymond

    2010-01-01

    Singh DK, Bailey M, Lee R. Biplanar measurement of thoracolumbar curvature in older adults using an electromagnetic tracking device. To develop a new biplanar method of thoracolumbar curvature measurement by using an electromagnetic tracking device and to study the effects of aging on the thoracolumbar curvature. Cross-sectional study. Human movement laboratory. Healthy (N=52, 26 younger and 26 older) volunteers. Not applicable. An electromagnetic tracking device was used to trace the thoracolumbar curvature by recording the positions of the spinous processes of the spine. The coordinates of the curvature were fitted with polynomial equations, and the magnitudes of thoracic kyphosis, lumbar lordosis, and lateral thoracic and lumbar curves were determined. The present technique was shown to be highly reliable in measuring thoracolumbar curvature with an intraclass correlation coefficient of more than .90. The mean thoracic kyphosis (-46.95 degrees +/-11.41 degrees ) in the older adults was significantly larger than that in the younger adults (-38.82 degrees +/-9.86 degrees ) (P<.01). However, there were no significant differences in lumbar lordosis and lateral curvatures between the 2 subject groups. The present study provided evidence of an increase in thoracic kyphosis in older adults. The method of measurement presented in this study was found to provide reliable biplanar data that will be useful in a clinical setting. Copyright (c) 2010 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  4. Mammalian phospholipid homeostasis: evidence that membrane curvature elastic stress drives homeoviscous adaptation in vivo.

    PubMed

    Dymond, Marcus K

    2016-08-01

    Several theories of phospholipid homeostasis have postulated that cells regulate the molecular composition of their bilayer membranes, such that a common biophysical membrane parameter is under homeostatic control. Two commonly cited theories are the intrinsic curvature hypothesis, which states that cells control membrane curvature elastic stress, and the theory of homeoviscous adaptation, which postulates cells control acyl chain packing order (membrane order). In this paper, we present evidence from data-driven modelling studies that these two theories correlate in vivo. We estimate the curvature elastic stress of mammalian cells to be 4-7 × 10(-12) N, a value high enough to suggest that in mammalian cells the preservation of membrane order arises through a mechanism where membrane curvature elastic stress is controlled. These results emerge from analysing the molecular contribution of individual phospholipids to both membrane order and curvature elastic stress in nearly 500 cellular compositionally diverse lipidomes. Our model suggests that the de novo synthesis of lipids is the dominant mechanism by which cells control curvature elastic stress and hence membrane order in vivo These results also suggest that cells can increase membrane curvature elastic stress disproportionately to membrane order by incorporating polyunsaturated fatty acids into lipids. © 2016 The Author(s).

  5. Mammalian phospholipid homeostasis: evidence that membrane curvature elastic stress drives homeoviscous adaptation in vivo

    PubMed Central

    2016-01-01

    Several theories of phospholipid homeostasis have postulated that cells regulate the molecular composition of their bilayer membranes, such that a common biophysical membrane parameter is under homeostatic control. Two commonly cited theories are the intrinsic curvature hypothesis, which states that cells control membrane curvature elastic stress, and the theory of homeoviscous adaptation, which postulates cells control acyl chain packing order (membrane order). In this paper, we present evidence from data-driven modelling studies that these two theories correlate in vivo. We estimate the curvature elastic stress of mammalian cells to be 4–7 × 10−12 N, a value high enough to suggest that in mammalian cells the preservation of membrane order arises through a mechanism where membrane curvature elastic stress is controlled. These results emerge from analysing the molecular contribution of individual phospholipids to both membrane order and curvature elastic stress in nearly 500 cellular compositionally diverse lipidomes. Our model suggests that the de novo synthesis of lipids is the dominant mechanism by which cells control curvature elastic stress and hence membrane order in vivo. These results also suggest that cells can increase membrane curvature elastic stress disproportionately to membrane order by incorporating polyunsaturated fatty acids into lipids. PMID:27534697

  6. Geometrical membrane curvature as an allosteric regulator of membrane protein structure and function.

    PubMed

    Tonnesen, Asger; Christensen, Sune M; Tkach, Vadym; Stamou, Dimitrios

    2014-01-07

    Transmembrane proteins are embedded in cellular membranes of varied lipid composition and geometrical curvature. Here, we studied for the first time the allosteric effect of geometrical membrane curvature on transmembrane protein structure and function. We used single-channel optical analysis of the prototypic transmembrane β-barrel α-hemolysin (α-HL) reconstituted on immobilized single small unilamellar liposomes of different diameter and therefore curvature. Our data demonstrate that physiologically abundant geometrical membrane curvatures can enforce a dramatic allosteric regulation (1000-fold inhibition) of α-HL permeability. High membrane curvatures (1/diameter ~1/40 nm(-1)) compressed the effective pore diameter of α-HL from 14.2 ± 0.8 Å to 11.4 ± 0.6 Å. This reduction in effective pore area (~40%) when combined with the area compressibility of α-HL revealed an effective membrane tension of ~50 mN/m and a curvature-imposed protein deformation energy of ~7 kBT. Such substantial energies have been shown to conformationally activate, or unfold, β-barrel and α-helical transmembrane proteins, suggesting that membrane curvature could likely regulate allosterically the structure and function of transmembrane proteins in general. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  7. Membrane tension controls the assembly of curvature-generating proteins

    NASA Astrophysics Data System (ADS)

    Simunovic, Mijo; Voth, Gregory A.

    2015-05-01

    Proteins containing a Bin/Amphiphysin/Rvs (BAR) domain regulate membrane curvature in the cell. Recent simulations have revealed that BAR proteins assemble into linear aggregates, strongly affecting membrane curvature and its in-plane stress profile. Here, we explore the opposite question: do mechanical properties of the membrane impact protein association? By using coarse-grained molecular dynamics simulations, we show that increased surface tension significantly impacts the dynamics of protein assembly. While tensionless membranes promote a rapid formation of long-living linear aggregates of N-BAR proteins, increase in tension alters the geometry of protein association. At high tension, protein interactions are strongly inhibited. Increasing surface density of proteins leads to a wider range of protein association geometries, promoting the formation of meshes, which can be broken apart with membrane tension. Our work indicates that surface tension may play a key role in recruiting proteins to membrane-remodelling sites in the cell.

  8. Curvature effects in carbon nanomaterials: Exohedral versus endohedral supercapacitors

    SciTech Connect

    Huang, Jingsong; Sumpter, Bobby G; Meunier, Vincent; Gogotsi, Yury G.; Yushin, Gleb; Portet, Cristelle

    2010-01-01

    Capacitive energy storage mechanisms in nanoporous carbon supercapacitors hinge on endohedral interactions in carbon materials with macro-, meso-, and micropores that have negative surface curvature. In this article, we show that because of the positive curvature found in zero-dimensional carbon onions or one-dimensional carbon nanotube arrays, exohedral interactions cause the normalized capacitance to increase with decreasing particle size or tube diameter, in sharp contrast to the behavior of nanoporous carbon materials. This finding is in good agreement with the trend of recent experimental data. Our analysis suggests that electrical energy storage can be improved by exploiting the highly curved surfaces of carbon nanotube arrays with diameters on the order of 1 nm.

  9. Curvature effects on carbon nanomaterials: Exohedral versus endhohedral supercapacitors

    SciTech Connect

    Huang, J; Sumpter, B. G.; Meunier, V.; Yushin, G.; Portet, C.; Gogotsi, Y.

    2011-01-31

    Capacitive energy storage mechanisms in nanoporous carbon supercapacitors hinge on endohedral interactions in carbon materials with macro-, meso-, and micropores that have negative surface curvature. In this article, we show that because of the positive curvature found in zero-dimensional carbon onions or one-dimensional carbon nanotube arrays, exohedral interactions cause the normalized capacitance to increase with decreasing particle size or tube diameter, in sharp contrast to the behavior of nanoporous carbon materials. This finding is in good agreement with the trend of recent experimental data. Our analysis suggests that electrical energy storage can be improved by exploiting the highly curved surfaces of carbon nanotube arrays with diameters on the order of 1 nm.

  10. Couple sex therapy for dysfunctions associated with congenital penile curvature.

    PubMed

    Zukerman, Z; Goldberg, I; Neri, A; Ovadia, J

    1988-05-01

    Three couples presented to our clinic with congenital ventral curvature of the penis resulting in unconsummated marriage in 2 cases and dyspareunia in 1. Intensive sex therapy was initiated, including use of vaginal dilators for vaginismus and dyspareunia, sex education, sensate focus exercises, and sexual techniques and methods to increase communication. Two highly motivated couples succeeded in having painless, normal, pleasurable sexual relations after short-term sex therapy. The problems of couple 3 were compounded by the wife's admitted lesbianism. However, this patient insisted on corrective surgery for her husband but she divorced him shortly thereafter. This nonsurgical approach for the treatment of sexual dysfunction secondary to penile curvature appears to be effective in selected cases. When corrective surgery is undertaken sex therapy is recommended to reinforce the operative results.

  11. DNA Origami with Complex Curvatures in Three-Dimensional Space

    SciTech Connect

    Han, Dongran; Pal, Suchetan; Nangreave, Jeanette; Deng, Zhengtao; Liu, Yan; Yan, Hao

    2011-04-14

    We present a strategy to design and construct self-assembling DNA nanostructures that define intricate curved surfaces in three-dimensional (3D) space using the DNA origami folding technique. Double-helical DNA is bent to follow the rounded contours of the target object, and potential strand crossovers are subsequently identified. Concentric rings of DNA are used to generate in-plane curvature, constrained to 2D by rationally designed geometries and crossover networks. Out-of-plane curvature is introduced by adjusting the particular position and pattern of crossovers between adjacent DNA double helices, whose conformation often deviates from the natural, B-form twist density. A series of DNA nanostructures with high curvature—such as 2D arrangements of concentric rings and 3D spherical shells, ellipsoidal shells, and a nanoflask—were assembled.

  12. Relationship between peptide amino acid sequence and membrane curvature generation

    NASA Astrophysics Data System (ADS)

    Schmidt, Nathan; Kuo, David; Hwee Lai, Ghee; Mishra, Abhijit; Wong, Gerard

    2012-02-01

    Amphipathic peptides and amphipathic domains in proteins can perturb and restructure biological membranes. For example, it is believed that the cationic, amphipathic motif found in membrane active antimicrobial peptides (AMPs) is responsible for their membrane disruption mechanisms of action. And ApoA-I, the main apolipoprotein in high density lipoprotein contains a series of amphipathic α-helical repeats which are responsible for its lipid associating properties. We use small angle x-ray scattering (SAXS) to investigate the interaction of model cell membranes with prototypical AMPs and consensus peptides derived from the helical structural motif of ApoA-I. The relationship between peptide sequence and the peptide-induced changes in membrane curvature and topology is examined. By comparing the membrane rearrangement and corresponding phase behavior induced by these two distinct classes of membrane restructuring peptides we will discuss the role of amino acid sequence on membrane curvature generation.

  13. On the curvature effect of thin membranes

    NASA Astrophysics Data System (ADS)

    Wang, Duo; Jiao, Xiangmin; Conley, Rebecca; Glimm, James

    2013-01-01

    We investigate the curvature effect of a thin, curved elastic interface that separates two subdomains and exerts a pressure due to a curvature effect. This pressure, which we refer to as interface pressure, is similar to the surface tension in fluid mechanics. It is important in some applications, such as the canopy of parachutes, biological membranes of cells, balloons, airbags, etc., as it partially balances a pressure jump between the two sides of an interface. In this paper, we show that the interface pressure is equal to the trace of the matrix product of the curvature tensor and the Cauchy stress tensor in the tangent plane. We derive the theory for interfaces in both 2-D and 3-D, and present numerical discretizations for computing the quality over triangulated surfaces.

  14. Cosmic curvature from de Sitter equilibrium cosmology.

    PubMed

    Albrecht, Andreas

    2011-10-07

    I show that the de Sitter equilibrium cosmology generically predicts observable levels of curvature in the Universe today. The predicted value of the curvature, Ω(k), depends only on the ratio of the density of nonrelativistic matter to cosmological constant density ρ(m)(0)/ρ(Λ) and the value of the curvature from the initial bubble that starts the inflation, Ω(k)(B). The result is independent of the scale of inflation, the shape of the potential during inflation, and many other details of the cosmology. Future cosmological measurements of ρ(m)(0)/ρ(Λ) and Ω(k) will open up a window on the very beginning of our Universe and offer an opportunity to support or falsify the de Sitter equilibrium cosmology.

  15. HEREDITARY DISTAL FORELEG CURVATURE IN THE RABBIT

    PubMed Central

    Pearce, Louise

    1960-01-01

    An inwardly directed curvature of the distal segment of both forelegs of the rabbit has been described. The condition was detected at 2 to 3 weeks of age, developed rapidly, and reached its final and permanent stage at 2 to 3 months of age. Only the distal epiphysis of the ulna was primarily affected and this in the form of a massive chondrodystrophic lesion accompanied by a progressive curvature of the shaft. The curvature of the growing radius was a secondary effect due to the firm, immovable, anatomical connection of the ulna and radius. The positional changes of the wrist and paw were likewise effects secondary to the changed form of the ulna and radius. The bowing abnormality occurred only in certain families of pure bred Beveren, Belgian, French Silver, and Dutch rabbits and was found to be inherited. The mode of inheritance was on the basis of a single recessive unit factor (5). PMID:13733755

  16. Principal curvature for infrared small target detection

    NASA Astrophysics Data System (ADS)

    Zhao, Yao; Pan, Haibin; Du, Changping; Zheng, Yao

    2015-03-01

    Small target detection in infrared image with complex background and low signal-noise ratio is an important and difficult task in the infrared target tracking system. In this paper, a principal curvature-based method is proposed. The principal curvatures of target pixels are negative and their absolute values are larger than that of background pixels and noise pixels in a Gaussian-blurred infrared image. The proposed filter takes a composite function of the curvatures for detection. An approximate model is also built for optimizing the parameters. Experimental results show that the proposed algorithm is effective and adaptable for infrared small target detection in complex background. Compared with several popular methods, the proposed algorithm demonstrates significant improvement on detection performance in terms of the parameters of signal clutter ratio gain, background suppression factor and ROC.

  17. Evaluating an impact origin for Mercury's high-magnesium region

    NASA Astrophysics Data System (ADS)

    Frank, Elizabeth A.; Potter, Ross W. K.; Abramov, Oleg; James, Peter B.; Klima, Rachel L.; Mojzsis, Stephen J.; Nittler, Larry R.

    2017-03-01

    During its four years in orbit around Mercury, the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft's X-ray Spectrometer revealed a large geochemical terrane in the northern hemisphere that hosts the highest Mg/Si, S/Si, Ca/Si, and Fe/Si and lowest Al/Si ratios on the planet. Correlations with low topography, thin crust, and a sharp northern topographic boundary led to the proposal that this high-Mg region is the remnant of an ancient, highly degraded impact basin. Here we use a numerical modeling approach to explore the feasibility of this hypothesis and evaluate the results against multiple mission-wide data sets and resulting maps from MESSENGER. We find that an 3000 km diameter impact basin easily exhumes Mg-rich mantle material but that the amount of subsequent modification required to hide basin structure is incompatible with the strength of the geochemical anomaly, which is also present in maps of Gamma Ray and Neutron Spectrometer data. Consequently, the high-Mg region is more likely to be the product of high-temperature volcanism sourced from a chemically heterogeneous mantle than the remains of a large impact event.Plain Language SummaryDuring its four years in orbit around Mercury, chemical measurements from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft revealed a large <span class="hlt">region</span> of unusual composition relative to the rest of the planet. Its elevated magnesium abundance, in particular, led to the name of the "<span class="hlt">high</span>-magnesium <span class="hlt">region</span>" (HMR). <span class="hlt">High</span> magnesium abundance in rock can be an indicator of its origin, such as <span class="hlt">high</span>-temperature volcanism. Although the HMR covers approximately 15% of Mercury's surface, its origin is not obvious. It does roughly correspond to a depression with thin crust, which previously led to the hypothesis that it is an ancient impact crater that was large enough to excavate mantle material, which, in rocky planets</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1110757G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1110757G"><span>A <span class="hlt">high</span> resolution <span class="hlt">regional</span> paleoclimate experiment over the Iberian Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gomez-Navarro, J. J.; Montavez, J. P.; Jerez, S.; Jimenez-Guerrero, P.; Garcia-Valero, J. A.; Gonzalez-Rouco, J. F.</p> <p>2009-04-01</p> <p>During the last years the use of paleoclimate simulations with models of different complexity has become an usual tool in paleoclimate studies. Progress in understanding climate variability leans on simulation and reconstruction efforts. Exercises blending both approaches present a great potential for answering questions relevant for both the simulation and reconstruction of past climate, and depend on the specific peculiarities of proxies and methods involved in climate reconstructions, as well as on the realism and limitations of model simulations. Most of paleoclimate integrations available in the literature covering the last millennium have been performed with relative rough resolution which does not allow to analyze <span class="hlt">regional</span> climate features that can be of interest in the context of proxies evidence. In this work we present a new <span class="hlt">high</span> resolution (30 km) <span class="hlt">regional</span> climate simulation over the Iberian Peninsula of the last five centuries and two extensions to the future for the A2 and B2 SRES scenarios. The <span class="hlt">regional</span> simulations were performed with a climate version of the MM5 model coupled to the Noah LSM. The driving conditions used follow the Erik1 experiment, performed with the ECHO-G global circulation model. The results indicate that the seasonal modes of variation for near surface air temperature and precipitation obtained within the <span class="hlt">regional</span> paleoclimate experiment are consistent with the obtained using the observational databases and equivalent to <span class="hlt">regional</span> climate integrations driven by reanalysis data. On the other hand, the main modes of variation show strong signals in historical periods such as the Maunder and Dalton Minimum. Finally, some preliminary comparisons between the global and the <span class="hlt">regional</span> model against tree ring temperature reconstructions are also reported in this contribution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA064302','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA064302"><span>Ray <span class="hlt">Curvature</span> and Refraction of Wave Packets.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1978-09-01</p> <p>1!~~~~~ _ ‘ AD AOM 302 FLORIDA STATE UNIV TALLAHASSEE DEPT OF OCEANOGRAPHY FIG B/3 RAY <span class="hlt">CURVATURE</span> AND REFRACTION OF WAVE PACKETS. (U) SEP 78 .J E...BREEDING N00014—77—C—0329 UNCLASSIFIED TR JE6 3 NL _ _ _ rwii__ _ ~iU ir!I I -~~ RAYOJR\\1L~[UREAND REFRACI ION OF WAVE F1~\\CKET~S ~y J. Ernest Breeding...01 29 014 -~ Technical Report No. JEB-3 Department of Oceanography • Florida State University RAY <span class="hlt">CURVATURE</span> AND REFRACTION OF WAVE PACKETS b O G • J</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750023410','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750023410"><span>NASTRAN modifications for recovering strains and <span class="hlt">curvatures</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hennrich, C. W.</p> <p>1975-01-01</p> <p>Modifications to the NASTRAN structural analysis computer program are described. The modifications allow the recovery of strain and <span class="hlt">curvature</span> data for the general two-dimensional elements, in addition to the usual stress data. Option features allow the transformation of the strain/<span class="hlt">curvature</span> (or stress) data to a common coordinate system and representation at the grid points of the structural model rather than at the conventional element center locations. Usage information is provided which will allow present users of NASTRAN to easily utilize the new capability.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhRvL.108w8103I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhRvL.108w8103I"><span>Cholesterol Mediates Membrane <span class="hlt">Curvature</span> during Fusion Events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ivankin, Andrey; Kuzmenko, Ivan; Gidalevitz, David</p> <p>2012-06-01</p> <p>Biomembranes undergo extensive shape changes as they perform vital cellular functions. The mechanisms by which lipids and proteins control membrane <span class="hlt">curvature</span> remain unclear. We use x-ray reflectivity, grazing incidence x-ray diffraction, and epifluorescence microscopy to study binding of HIV-1 glycoprotein gp41’s membrane-bending domain to DPPC/cholesterol monolayers of various compositions at the air-liquid interface. The results offer a new insight into how membrane <span class="hlt">curvature</span> could be regulated by cholesterol during fusion of the viral lipid envelope and the host cell membranes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030020911','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030020911"><span>Equal-<span class="hlt">Curvature</span> X-Ray Telescopes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Saha, Timo T.; Zhang, William</p> <p>2002-01-01</p> <p>We introduce a new type of x-ray telescope design; an Equal-<span class="hlt">Curvature</span> telescope. We simply add a second order axial sag to the base grazing incidence cone-cone telescope. The radius of <span class="hlt">curvature</span> of the sag terms is the same on the primary surface and on the secondary surface. The design is optimized so that the on-axis image spot at the focal plane is minimized. The on-axis RMS (root mean square) spot diameter of two studied telescopes is less than 0.2 arc-seconds. The off-axis performance is comparable to equivalent Wolter type 1 telescopes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1390219','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1390219"><span><span class="hlt">Curvature</span> suppresses the Rayleigh-Taylor instability</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Trinh, Philippe H.; Kim, Hyoungsoo; Hammoud, Naima; Howell, Peter D.; Chapman, S. Jonathan; Stone, Howard A.</p> <p>2014-05-01</p> <p>The dynamics of a thin liquid #12;lm on the underside of a curved cylindrical substrate is studied. The evolution of the liquid layer is investigated as the #12;lm thickness and the radius of <span class="hlt">curvature</span> of the substrate are varied. A dimensionless parameter (a modi#12;ed Bond number) that incorporates both geometric parameters, gravity, and surface tension is identified, and allows the observations to be classified according to three different flow regimes: stable films, films with transient growth of perturbations followed by decay, and unstable films. Experiments and theory confirm that, below a critical value of the Bond number, <span class="hlt">curvature</span> of the substrate suppresses the Rayleigh-Taylor instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...827...99T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...827...99T"><span><span class="hlt">High</span> Spatial Resolution Fe XII Observations of Solar Active <span class="hlt">Regions</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Testa, Paola; De Pontieu, Bart; Hansteen, Viggo</p> <p>2016-08-01</p> <p>We use UV spectral observations of active <span class="hlt">regions</span> with the Interface <span class="hlt">Region</span> Imaging Spectrograph (IRIS) to investigate the properties of the coronal Fe xii 1349.4 Å emission at unprecedented <span class="hlt">high</span> spatial resolution (˜0.33″). We find that by using appropriate observational strategies (i.e., long exposures, lossless compression), Fe xii emission can be studied with IRIS at <span class="hlt">high</span> spatial and spectral resolution, at least for <span class="hlt">high</span>-density plasma (e.g., post-flare loops and active <span class="hlt">region</span> moss). We find that upper transition <span class="hlt">region</span> (TR; moss) Fe xii emission shows very small average Doppler redshifts ({v}{{D}} ˜ 3 km s-1) as well as modest non-thermal velocities (with an average of ˜24 km s-1 and the peak of the distribution at ˜15 km s-1). The observed distribution of Doppler shifts appears to be compatible with advanced three-dimensional radiative MHD simulations in which impulsive heating is concentrated at the TR footpoints of a hot corona. While the non-thermal broadening of Fe xii 1349.4 Å peaks at similar values as lower resolution simultaneous Hinode Extreme Ultraviolet Imaging Spectrometer (EIS) measurements of Fe xii 195 Å, IRIS observations show a previously undetected tail of increased non-thermal broadening that might be suggestive of the presence of subarcsecond heating events. We find that IRIS and EIS non-thermal line broadening measurements are affected by instrumental effects that can only be removed through careful analysis. Our results also reveal an unexplained discrepancy between observed 195.1/1349.4 Å Fe xii intensity ratios and those predicted by the CHIANTI atomic database.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006IAUJD...4E...3T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006IAUJD...4E...3T"><span>Analysis Of The <span class="hlt">High</span> Temperature <span class="hlt">Region</span> In Be Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Torres, A. F.; Ringuelet, A. E.</p> <p>2006-08-01</p> <p>The <span class="hlt">High</span> Temperature <span class="hlt">Region</span> (HTR) that surrounds the photospheres of Be stars is studied in order to derive observational constraints for modelling Be stars, in particular for the <span class="hlt">region</span> where superionization takes place. 50 Be stars, representative of a considerable range of temperature, were chosen. From archival, <span class="hlt">high</span>-dispersion IUE spectra, different lines that originate in the HTR <span class="hlt">region</span> were considered, namely the resonance lines of Si IV, C IV and Al III, and He II λ 1640. Equivalent widths (corrected for photospheric contribution), optical depths, atom columns and expansion velocities were measured. From this observational data several correlations between different observables were obtained. These correlations permit us to discuss the geometry, density distribution and heat input of the lines formation <span class="hlt">regions</span> (LFRs). The major results can be summarised as follows: 1) The circumstellar material contributes to the resonance lines of Si IV, C IV, Al III and to the He II λ 1640 at all inclination angles. 2) In Si IV, C IV and Al III the equivalent widths have a tendency to increase in objects with <span class="hlt">high</span> rotational velocities. 3) Si IV and C IV equivalent widths are also correlated to the kinetic energy of the expansion velocity. This means that dissipation of mechanical energy is one of the heating mechanisms. 4)On the basis of the expansion velocities and the line profiles, we establish a sequence for the LFRs: The LFR of He II is at the base of the wind and the closest to the central star. The LFRs of Si IV and C IV are inmersed in the stellar wind. The LFR of Al III is an interface between the HTR and the cool envelope. The analysis followed in this work is completely model-independent. Consequently, these results could be useful to decide which are the facts that are to be considered when modelling Be stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19259211','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19259211"><span>Frequency analysis of wavefront <span class="hlt">curvature</span> sensing: optimum propagation distance and multi-z wavefront <span class="hlt">curvature</span> sensing.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fengjie, Xi; Zongfu, Jiang; Xiaojun, Xu; Jing, Hou; Zejin, Liu</p> <p>2009-03-02</p> <p>In this paper we determine the optimum propagation distance between measurement planes and the plane of the lens in a wavefront <span class="hlt">curvature</span> sensor with the diffraction optics approach. From the diffraction viewpoint, the measured wavefront aberration can be decomposed into Fourier harmonics at various frequencies. The <span class="hlt">curvature</span> signal produced by a single harmonic is analyzed with the wave propagation transfer function approach, which is the frequency analysis of wavefront <span class="hlt">curvature</span> sensing. The intensity of the <span class="hlt">curvature</span> signal is a sine function of the product of the propagation distance and the squared frequency. To maximize the <span class="hlt">curvature</span> signal, the optimum propagation distance is proposed as one quarter of the Talbot length at the critical frequency (average power point at which the power spectrum density is the average power spectrum density). Following the determination of the propagation distance, the intensity of the <span class="hlt">curvature</span> signal varies sinusoidally with the squared frequencies, vanishing at some higher frequency bands just like a comb filter. To cover these insensitive bands, wavefront <span class="hlt">curvature</span> sensing with dual propagation distances or with multi-propagation distances is proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JETPL..94..824K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JETPL..94..824K"><span><span class="hlt">Curvature</span>-dependent excitation propagation in cultured cardiac tissue</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kadota, S.; Kay, M. W.; Magome, N.; Agladze, K.</p> <p>2012-02-01</p> <p>The geometry of excitation wave front may play an important role on the propagation block and spiral wave formation. The wave front which is bent over the critical value due to interaction with the obstacles may partially cease to propagate and appearing wave breaks evolve into rotating waves or reentry. This scenario may explain how reentry spontaneously originates in a heart. We studied <span class="hlt">highly</span> curved excitation wave fronts in the cardiac tissue culture and found that in the conditions of normal, non-inhibited excitability the <span class="hlt">curvature</span> effects do not play essential role in the propagation. Neither narrow isthmuses nor sharp corners of the obstacles, being classical objects for production of extremely curved wave front, affect non-inhibited wave propagation. The <span class="hlt">curvature</span>-related phenomena of the propagation block and wave detachment from the obstacle boundary were observed only after partial suppression of the sodium channels with Lidocaine. Computer simulations confirmed the experimental observations. The explanation of the observed phenomena refers to the fact that the heart tissue is made of finite size cells so that <span class="hlt">curvature</span> radii smaller than the cardiomyocyte size loses sense, and in non-inhibited tissue the single cell is capable to transmit excitation to its neighbors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6814297','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6814297"><span><span class="hlt">Curvature</span>-driven instabilities in the Elmo Bumpy Torus (EBT)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Abe, H.; Spong, D.A.; Antonsen, T.M. Jr.; Tsang, K.T.; Nguyen, K.T.</p> <p>1982-01-01</p> <p><span class="hlt">Curvature</span>-driven instabilities are analyzed for an EBT configuration which consists of plasma interacting with a hot electron ring whose drift frequencies are larger than the growth rates predicted from conventional magnetohydrodynamic (MHD) theory. Stability criteria are obtained for five possible modes: the conventional hot electron interchange, a <span class="hlt">high</span>-frequency hot electron interchange (at frequencies greater than the ion-cyclotron frequency), a compressional instability, a background plasma interchange, and an interacting pressure-driven interchange. A wide parameter regime for stable operation is found, which, however, severely deteriorates for a band of intermediate mode numbers. Finite Larmor radius effects can eliminate this deterioration; moreover, all short-wavelength <span class="hlt">curvature</span>-driven modes are stabilized if the hot electron Larmor radius rho/sub h/ satisfies (kappa/sub perpendicular/rho/sub h/)/sup 2/ > 2..delta../(R..beta../sub h/(1 + P'/sub parallel//P'/sub perpendicular/)), where kappa/sub perpendicular/ is the transverse wavenumber, ..delta.. is the ring half-width, R is the mid-plane radius of <span class="hlt">curvature</span>, ..beta../sub h/ is the hot electron beta value, and P' is the pressure gradient. Resonant wave-particle instabilities predicted by a new low frequency variational principle show that a variety of remnant instabilities may still persist.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19751668','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19751668"><span>Bending stiffness depends on <span class="hlt">curvature</span> of ternary lipid mixture tubular membranes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tian, Aiwei; Capraro, Benjamin R; Esposito, Cinzia; Baumgart, Tobias</p> <p>2009-09-16</p> <p>Lipid and protein sorting and trafficking in intracellular pathways maintain cellular function and contribute to organelle homeostasis. Biophysical aspects of membrane shape coupled to sorting have recently received increasing attention. Here we determine membrane tube bending stiffness through measurements of tube radii, and demonstrate that the stiffness of ternary lipid mixtures depends on membrane <span class="hlt">curvature</span> for a large range of lipid compositions. This observation indicates amplification by <span class="hlt">curvature</span> of cooperative lipid demixing. We show that <span class="hlt">curvature</span>-induced demixing increases upon approaching the critical <span class="hlt">region</span> of a ternary lipid mixture, with qualitative differences along two roughly orthogonal compositional trajectories. Adapting a thermodynamic theory earlier developed by M. Kozlov, we derive an expression that shows the renormalized bending stiffness of an amphiphile mixture membrane tube in contact with a flat reservoir to be a quadratic function of <span class="hlt">curvature</span>. In this analytical model, the degree of sorting is determined by the ratio of two thermodynamic derivatives. These derivatives are individually interpreted as a driving force and a resistance to <span class="hlt">curvature</span> sorting. We experimentally show this ratio to vary with composition, and compare the model to sorting by spontaneous <span class="hlt">curvature</span>. Our results are likely to be relevant to the molecular sorting of membrane components in vivo.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1610806E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1610806E"><span>Testing the <span class="hlt">regionalization</span> of a SVAT model for a <span class="hlt">region</span> with <span class="hlt">high</span> observation density</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eiermann, Sven; Thies, Boris; Bendix, Jörg</p> <p>2014-05-01</p> <p>The variable soil moisture is an important quantity in weather and climate investigations, because it has an essential influence on the energy exchange between the land surface and the atmosphere. However the recording of soil moisture in <span class="hlt">high</span> spatio-temporal resolution is problematic. The planned Tandem-L mission of the German Aerospace Center (DLR) with an innovative L-band radar on board provides the opportunity to get daily soil moisture data at a spatial resolution of 50 meters. Within the Helmholtz Alliance Remote Sensing and Earth System Dynamics this data is planned to be used to <span class="hlt">regionalize</span> a Soil Vegetation Atmosphere Transfer Model, in order to analyze the energy flux and the gas exchange and to improve the prediction of the water exchange between soil, vegetation and atmosphere. As investigation areas selected <span class="hlt">regions</span> of the TERENO (TERrestrial ENviromental Observatoria) test sites and, later on, a <span class="hlt">region</span> in South Ecuador will be used, for which data for the model initialization and validation are available. The reason for testing the method for the TERENO test sites first is the good data basis as a result of the already established <span class="hlt">high</span> observation density there. The poster will present the methods being used for the model adaptation for the TERENO test sites and discuss the improvements achieved by these methods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A24D..08B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A24D..08B"><span>Evaluation of a <span class="hlt">High</span>-Resolution <span class="hlt">Regional</span> Climate Ensemble</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bruyere, C. L.; Tye, M. R.; Keellings, D.; Jaye, A.</p> <p>2014-12-01</p> <p>A <span class="hlt">high</span>-resolution <span class="hlt">Regional</span> Climate Ensemble is used to investigate the limits of predictability of climate simulations, with a focus on <span class="hlt">high</span>-impact weather. A diverse set of approaches are being applied to examine the impact of the different physics parameterizations on the simulated climate and <span class="hlt">high</span>-impact weather statistics and to determine the physics combinations that result in realistic scenarios. In this paper we focus on the ensemble members' ability to correctly simulate current climate variability in terms of: 1) extreme temperature and precipitation over different <span class="hlt">regions</span>, and 2) tropical cyclone statistics. A twenty-four member physics ensemble of climate simulations has been generated using the state-of-the-art Weather Research and Forecasting Model (Skamarock et al. 2008). The ensemble model has been run over an extended North American domain of approximately 25° S to 70° N and from the African coast to the East Pacific, and at sufficient resolution to capture <span class="hlt">high</span>-impact weather events. Skamarock, W., J. B. Klemp, J. Dudhia, D. O. Gill, D. Barker, M. G. Duda, X. Huang, and W. Wang, 2008: A Description of the Advanced Research WRF Version 3. NCAR Technical Note NCAR/TN-475+STR. Boulder, CO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21430079','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21430079"><span>Diaphragm <span class="hlt">curvature</span> modulates the relationship between muscle shortening and volume displacement.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Greybeck, Brad J; Wettergreen, Matthew; Hubmayr, Rolf D; Boriek, Aladin M</p> <p>2011-07-01</p> <p>During physiological spontaneous breathing maneuvers, the diaphragm displaces volume while maintaining <span class="hlt">curvature</span>. However, with maximal diaphragm activation, <span class="hlt">curvature</span> decreases sharply. We tested the hypotheses that the relationship between diaphragm muscle shortening and volume displacement (VD) is nonlinear and that <span class="hlt">curvature</span> is a determinant of such a relationship. Radiopaque markers were surgically placed on three neighboring muscle fibers in the midcostal <span class="hlt">region</span> of the diaphragm in six dogs. The three-dimensional locations were determined using biplanar fluoroscopy and diaphragm VD, <span class="hlt">curvature</span>, and muscle shortening were computed in the prone and supine postures during spontaneous breathing (SB), spontaneous inspiration efforts after airway occlusion at lung volumes ranging from functional residual capacity (FRC) to total lung capacity, and during bilateral maximal phrenic nerve stimulation at those same lung volumes. In supine dogs, diaphragm VD was approximately two- to three-fold greater during maximal phrenic nerve stimulation than during SB. The contribution of muscle shortening to VD nonlinearly increases with level of diaphragm activation independent of posture. During submaximal diaphragm activation, the contribution is essentially linear due to constancy of diaphragm <span class="hlt">curvature</span> in both the prone and supine posture. However, the sudden loss of <span class="hlt">curvature</span> during maximal bilateral phrenic nerve stimulation at muscle shortening values greater than 40% (ΔL/L(FRC)) causes a nonlinear increase in the contribution of muscle shortening to diaphragm VD, which is concomitant with a nonlinear change in diaphragm <span class="hlt">curvature</span>. We conclude that the nonlinear relationship between diaphragm muscle shortening and its VD is, in part, due to a loss of its <span class="hlt">curvature</span> at extreme muscle shortening.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014OptCo.312...23B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014OptCo.312...23B"><span>Myopic aberrations: Simulation based comparison of <span class="hlt">curvature</span> and Hartmann Shack wavefront sensors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Basavaraju, Roopashree M.; Akondi, Vyas; Weddell, Stephen J.; Budihal, Raghavendra Prasad</p> <p>2014-02-01</p> <p>In comparison with a Hartmann Shack wavefront sensor, the <span class="hlt">curvature</span> wavefront sensor is known for its higher sensitivity and greater dynamic range. The aim of this study is to numerically investigate the merits of using a <span class="hlt">curvature</span> wavefront sensor, in comparison with a Hartmann Shack (HS) wavefront sensor, to analyze aberrations of the myopic eye. Aberrations were statistically generated using Zernike coefficient data of 41 myopic subjects obtained from the literature. The <span class="hlt">curvature</span> sensor is relatively simple to implement, and the processing of extra- and intra-focal images was linearly resolved using the Radon transform to provide Zernike modes corresponding to statistically generated aberrations. Simulations of the HS wavefront sensor involve the evaluation of the focal spot pattern from simulated aberrations. Optical wavefronts were reconstructed using the slope geometry of Southwell. Monte Carlo simulation was used to find critical parameters for accurate wavefront sensing and to investigate the performance of HS and <span class="hlt">curvature</span> sensors. The performance of the HS sensor is <span class="hlt">highly</span> dependent on the number of subapertures and the <span class="hlt">curvature</span> sensor is largely dependent on the number of Zernike modes used to represent the aberration and the effective propagation distance. It is shown that in order to achieve <span class="hlt">high</span> wavefront sensing accuracy while measuring aberrations of the myopic eye, a simpler and cost effective <span class="hlt">curvature</span> wavefront sensor is a reliable alternative to a <span class="hlt">high</span> resolution HS wavefront sensor with a large number of subapertures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......114N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......114N"><span>Molecular line tracers of <span class="hlt">high</span>-mass star forming <span class="hlt">regions</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nagy, Zsofia</p> <p>2013-09-01</p> <p><span class="hlt">High</span>-mass stars influence their environment in different ways including feedback via their far-UV radiation and mechanical feedback via shocks and stellar winds. The penetration of FUV photons into molecular clouds creates Photon Dominated <span class="hlt">Regions</span> (PDRs) with different chemical layers where the mainly ionized medium changes into mainly molecular. Different chemical layers in PDRs are traced by different species observable at sub-mm and far-infrared wavelengths. In this thesis we present results from two molecular line surveys. One of them is the James Clerk Maxwell Telescope (JCMT) Spectral Legacy Survey (SLS) toward the luminous (>10^7 L_Sun), massive (~10^6 M_Sun), and distant (11.4 kpc) star-forming <span class="hlt">region</span> W49A. The SLS images a 2x2 arcminute field around W49A in the 330-373 GHz frequency range. The detected molecular lines reveal a complex chemistry and the importance of FUV-irradiation and shocks in the heating and chemistry of the <span class="hlt">region</span>. The other line survey presented in this thesis is part of the HEXOS (Herschel observations of EXtra-Ordinary Sources) key program using the Herschel Space Observatory and is toward the nearby (~420 pc) prototypical edge-on Orion Bar PDR and the dense molecular condensation Orion S. Reactive ions, such as CH+, SH+, and CO+, detected as a part of this line survey trace the warm (~500-1000 K) surface <span class="hlt">region</span> of PDRs. Spectroscopic data from the HIFI and PACS instruments of Herschel give constraints on the chemistry and excitation of reactive ions in these <span class="hlt">regions</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711692D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711692D"><span><span class="hlt">Regional</span> <span class="hlt">High</span>-resolution Coupled Atmosphere Ocean Modelling in the North Sea <span class="hlt">Region</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dumenil-Gates, Lydia; Bülow, Katharina; Ganske, Anette; Heinrich, Hartmut; Klein, Birgit; Klein, Holger; Möller, Jens; Rosenhagen, Gudrun; Schade, Nils; Hüttl-Kabus, Sabine; Tinz, Birger</p> <p>2015-04-01</p> <p>The analysis of climate projections in the North Sea area is one of the research tasks of the research programme KLIWAS of the German Federal Ministry of Transport and Digital Infrastructure. A multi-model ensemble of three coupled <span class="hlt">regional</span> atmosphere-ocean models was set up comprising very <span class="hlt">high</span> resolution simulations for the German coastal <span class="hlt">regions</span> of the North Sea and the Baltic to represent the complex land-sea-atmosphere conditions in the <span class="hlt">region</span>. The ensemble consists of simulations made in cooperation with the Swedish Meteorological and Hydrological Institute, the Climate Service Centre and the Max-Planck-Institute for the period of 1950 to 2100. The KLIWAS project thereby adds coupled models to the band-width of possible future climate conditions in the atmosphere as given by the ENSEMBLES project, which were also analyzed. The coupled results are evaluated for present-day climate using a North Sea climatology of maritime conditions at a matching <span class="hlt">high</span> resolution. In the future climate, while air and water temperatures will rise to the year 2100, the mean wind speed does not show a significant trend, but large decadal variability. The frequency of occurrence of westerly wind directions increases in the majority of simulations and results in an increase of significant wave height in the eastern parts of the North Sea. In an interdisciplinary approach, these results are used to provide <span class="hlt">regional</span> to local information for the development of adaptation strategies for the estuary, and climate-proofing of infrastructure in the wider context of the project.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1187056','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1187056"><span>Stagnation <span class="hlt">Region</span> Heat Transfer Augmentation at Very <span class="hlt">High</span> Turbulence Levels</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ames, Forrest; Kingery, Joseph E.</p> <p>2015-06-17</p> <p>A database for stagnation <span class="hlt">region</span> heat transfer has been extended to include heat transfer measurements acquired downstream from a new <span class="hlt">high</span> intensity turbulence generator. This work was motivated by gas turbine industry heat transfer designers who deal with heat transfer environments with increasing Reynolds numbers and very <span class="hlt">high</span> turbulence levels. The new mock aero-combustor turbulence generator produces turbulence levels which average 17.4%, which is 37% higher than the older turbulence generator. The increased level of turbulence is caused by the reduced contraction ratio from the liner to the exit. Heat transfer measurements were acquired on two large cylindrical leading edge test surfaces having a four to one range in leading edge diameter (40.64 cm and 10.16 cm). Gandvarapu and Ames [1] previously acquired heat transfer measurements for six turbulence conditions including three grid conditions, two lower turbulence aero-combustor conditions, and a low turbulence condition. The data are documented and tabulated for an eight to one range in Reynolds numbers for each test surface with Reynolds numbers ranging from 62,500 to 500,000 for the large leading edge and 15,625 to 125,000 for the smaller leading edge. The data show augmentation levels of up to 136% in the stagnation <span class="hlt">region</span> for the large leading edge. This heat transfer rate is an increase over the previous aero-combustor turbulence generator which had augmentation levels up to 110%. Note, the rate of increase in heat transfer augmentation decreases for the large cylindrical leading edge inferring only a limited level of turbulence intensification in the stagnation <span class="hlt">region</span>. The smaller cylindrical leading edge shows more consistency with earlier stagnation <span class="hlt">region</span> heat transfer results correlated on the TRL (Turbulence, Reynolds number, Length scale) parameter. The downstream <span class="hlt">regions</span> of both test surfaces continue to accelerate the flow but at a much lower rate than the leading edge. Bypass transition occurs</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711209B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711209B"><span>A <span class="hlt">high</span>-resolution <span class="hlt">regional</span> reanalysis for the European CORDEX <span class="hlt">region</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bollmeyer, Christoph; Keller, Jan; Ohlwein, Christian; Wahl, Sabrina</p> <p>2015-04-01</p> <p>Within the Hans-Ertel-Centre for Weather Research (HErZ), the climate monitoring branch concentrates efforts on the assessment and analysis of <span class="hlt">regional</span> climate in Germany and Europe. In joint cooperation with DWD (German Weather Service), a <span class="hlt">high</span>-resolution reanalysis system based on the COSMO model has been developed. Reanalyses gain more and more importance as a source of meteorological information for many purposes and applications. Several global reanalyses projects (e.g., ERA, MERRA, CSFR, JMA9) produce and verify these data sets to provide time series as long as possible combined with a <span class="hlt">high</span> data quality. Due to a spatial resolution down to 50-70km and 3-hourly temporal output, they are not suitable for small scale problems (e.g., <span class="hlt">regional</span> climate assessment, meso-scale NWP verification, input for subsequent models such as river runoff simulations, renewable energy applications). The implementation of <span class="hlt">regional</span> reanalyses based on a limited area model along with a data assimilation scheme is able to generate reanalysis data sets with <span class="hlt">high</span> spatio-temporal resolution. The work presented here focuses on two <span class="hlt">regional</span> reanalyses for Europe and Germany. The European reanalysis COSMO-REA6 matches the CORDEX EURO-11 specifications, albeit at a higher spatial resolution, i.e., 0.055° (6km) instead of 0.11° (12km). Nested into COSMO-REA6 is COSMO-REA2, a convective-scale reanalysis with 2km resolution for Germany. COSMO-REA6 comprises the assimilation of observational data using the existing nudging scheme of COSMO and is complemented by a special soil moisture analysis and boundary conditions given by ERA-Interim data. COSMO-REA2 also uses the nudging scheme complemented by a latent heat nudging of radar information. The reanalysis data set currently covers 17 years (1997-2013) for COSMO-REA6 and 4 years (2010-2013) for COSMO-REA2 with a very large set of output variables and a <span class="hlt">high</span> temporal output step of hourly 3D-fields and quarter-hourly 2D-fields. The evaluation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002SPIE.4684..883N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002SPIE.4684..883N"><span>Determination of biplane geometry and centerline <span class="hlt">curvature</span> in vascular imaging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nazareth, Daryl; Hoffmann, Kenneth R.; Walczak, Alan; Dmochowski, Jacek; Guterman, Lee R.; Rudin, Stephen; Bednarek, Daniel R.</p> <p>2002-05-01</p> <p>Three-dimensional (3-D) vessel trees can provide useful visual and quantitative information during interventional procedures. To calculate the 3-D vasculature from biplane images, the transformation relating the imaging systems (i.e., the rotation matrix R and the translation vector t) must be determined. We have developed a technique to calculate these parameters, which requires only the identification of approximately corresponding vessel <span class="hlt">regions</span> in the two images. Initial estimates of R and t are generated based on the gantry angles, and then refined using an optimization technique. The objective function to be minimized is determined as follows. For each endpoint of each vessel in the first image, an epipolar line in the second image is generated. The intersection points between these two epipolar lines and the corresponding vessel centerline in the second image are determined. The vessel arclength between these intersection points is calculated as a fraction of the entire vessel <span class="hlt">region</span> length in the image. This procedure is repeated for every vessel in each image. The value of the objective function is calculated from the sum of these fractions, and is smallest when the total fractional arclength is greatest. The 3-D vasculature is obtained from the optimal R and t using triangulation, and vessel <span class="hlt">curvature</span> is then determined. This technique was evaluated using simulated curves and vessel centerlines obtained from clinical images, and provided rotational, magnification and relative <span class="hlt">curvature</span> errors of 1 degree(s), 1% and 14% respectively. Accurate 3-D and <span class="hlt">curvature</span> measures may be useful in clinical decision making, such as in assessing vessel tortuousity and access, during interventional procedures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5399291','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5399291"><span>Strong <span class="hlt">curvature</span> singularities and causal simplicity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Krolak, A. )</p> <p>1992-02-01</p> <p>Techniques of differential topology in Lorentzian manifolds developed by Geroch, Hawking, and Penrose are used to rule out a class of locally naked strong <span class="hlt">curvature</span> singularities in strongly causal space-times. This result yields some support to the validity of Penrose's strong cosmic censorship hypothesis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3234936','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3234936"><span>Membrane <span class="hlt">Curvature</span> Sensing by Amphipathic Helices</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Jensen, Martin Borch; Bhatia, Vikram Kjøller; Jao, Christine C.; Rasmussen, Jakob Ewald; Pedersen, Søren L.; Jensen, Knud J.; Langen, Ralf; Stamou, Dimitrios</p> <p>2011-01-01</p> <p>Preferential binding of proteins on curved membranes (membrane <span class="hlt">curvature</span> sensing) is increasingly emerging as a general mechanism whereby cells may effect protein localization and trafficking. Here we use a novel single liposome fluorescence microscopy assay to examine a common sensing motif, the amphipathic helix (AH), and provide quantitative measures describing and distinguishing membrane binding and sensing behavior. By studying two AH-containing proteins, α-synuclein and annexin B12, as well as a range of AH peptide mutants, we reveal that both the hydrophobic and hydrophilic faces of the helix greatly influence binding and sensing. Although increased hydrophobic and electrostatic interactions with the membrane both lead to greater densities of bound protein, the former yields membrane <span class="hlt">curvature</span>-sensitive binding, whereas the latter is not <span class="hlt">curvature</span>-dependent. However, the relative contributions of both components determine the sensing of AHs. In contrast, charge density in the lipid membrane seems important primarily in attracting AHs to the membrane but does not significantly influence sensing. These observations were made possible by the ability of our assay to distinguish within our samples liposomes with and without bound protein as well as the density of bound protein. Our findings suggest that the description of membrane <span class="hlt">curvature</span>-sensing requires consideration of several factors such as short and long range electrostatic interactions, hydrogen bonding, and the volume and structure of inserted hydrophobic residues. PMID:21953452</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28804159','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28804159"><span>Geodesic <span class="hlt">curvature</span> driven surface microdomain formation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Adkins, Melissa R; Zhou, Y C</p> <p>2017-09-15</p> <p>Lipid bilayer membranes are not uniform and clusters of lipids in a more ordered state exist within the generally disorder lipid milieu of the membrane. These clusters of ordered lipids microdomains are now referred to as lipid rafts. Recent reports attribute the formation of these microdomains to the geometrical and molecular mechanical mismatch of lipids of different species on the boundary. Here we introduce the geodesic <span class="hlt">curvature</span> to characterize the geometry of the domain boundary, and develop a geodesic <span class="hlt">curvature</span> energy model to describe the formation of these microdomains as a result of energy minimization. Our model accepts the intrinsic geodesic <span class="hlt">curvature</span> of any binary lipid mixture as an input, and will produce microdomains of the given geodesic <span class="hlt">curvature</span> as demonstrated by three sets of numerical simulations. Our results are in contrast to the surface phase separation predicted by the classical surface Cahn-Hilliard equation, which tends to generate large domains as a result of the minimizing line tension. Our model provides a direct and quantified description of the structure inhomogeneity of lipid bilayer membrane, and can be coupled to the investigations of biological processes on membranes for which such inhomogeneity plays essential roles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4500997','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4500997"><span>Graph <span class="hlt">Curvature</span> for Differentiating Cancer Networks</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sandhu, Romeil; Georgiou, Tryphon; Reznik, Ed; Zhu, Liangjia; Kolesov, Ivan; Senbabaoglu, Yasin; Tannenbaum, Allen</p> <p>2015-01-01</p> <p>Cellular interactions can be modeled as complex dynamical systems represented by weighted graphs. The functionality of such networks, including measures of robustness, reliability, performance, and efficiency, are intrinsically tied to the topology and geometry of the underlying graph. Utilizing recently proposed geometric notions of <span class="hlt">curvature</span> on weighted graphs, we investigate the features of gene co-expression networks derived from large-scale genomic studies of cancer. We find that the <span class="hlt">curvature</span> of these networks reliably distinguishes between cancer and normal samples, with cancer networks exhibiting higher <span class="hlt">curvature</span> than their normal counterparts. We establish a quantitative relationship between our findings and prior investigations of network entropy. Furthermore, we demonstrate how our approach yields additional, non-trivial pair-wise (i.e. gene-gene) interactions which may be disrupted in cancer samples. The mathematical formulation of our approach yields an exact solution to calculating pair-wise changes in <span class="hlt">curvature</span> which was computationally infeasible using prior methods. As such, our findings lay the foundation for an analytical approach to studying complex biological networks. PMID:26169480</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27588858','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27588858"><span>Photon Drag Effect due to Berry <span class="hlt">Curvature</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kurosawa, Hiroyuki; Sawada, Kei; Ohno, Seigo</p> <p>2016-08-19</p> <p>A theoretical investigation reveals that the photon drag effect (PDE) is induced in a grating slab with deformation by the Berry <span class="hlt">curvature</span> in phase space. It drifts the momentum of light, and gives asymmetric PDE signals in momentum space. Large PDE signals are observed even near the Γ point. This characteristic agrees well with our theoretical results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JCoPh.345..260A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JCoPh.345..260A"><span>Geodesic <span class="hlt">curvature</span> driven surface microdomain formation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adkins, Melissa R.; Zhou, Y. C.</p> <p>2017-09-01</p> <p>Lipid bilayer membranes are not uniform and clusters of lipids in a more ordered state exist within the generally disorder lipid milieu of the membrane. These clusters of ordered lipids microdomains are now referred to as lipid rafts. Recent reports attribute the formation of these microdomains to the geometrical and molecular mechanical mismatch of lipids of different species on the boundary. Here we introduce the geodesic <span class="hlt">curvature</span> to characterize the geometry of the domain boundary, and develop a geodesic <span class="hlt">curvature</span> energy model to describe the formation of these microdomains as a result of energy minimization. Our model accepts the intrinsic geodesic <span class="hlt">curvature</span> of any binary lipid mixture as an input, and will produce microdomains of the given geodesic <span class="hlt">curvature</span> as demonstrated by three sets of numerical simulations. Our results are in contrast to the surface phase separation predicted by the classical surface Cahn-Hilliard equation, which tends to generate large domains as a result of the minimizing line tension. Our model provides a direct and quantified description of the structure inhomogeneity of lipid bilayer membrane, and can be coupled to the investigations of biological processes on membranes for which such inhomogeneity plays essential roles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJGMM..1350002B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJGMM..1350002B"><span>Riemann <span class="hlt">curvature</span> of a boosted spacetime geometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Battista, Emmanuele; Esposito, Giampiero; Scudellaro, Paolo; Tramontano, Francesco</p> <p>2016-10-01</p> <p>The ultrarelativistic boosting procedure had been applied in the literature to map the metric of Schwarzschild-de Sitter spacetime into a metric describing de Sitter spacetime plus a shock-wave singularity located on a null hypersurface. This paper evaluates the Riemann <span class="hlt">curvature</span> tensor of the boosted Schwarzschild-de Sitter metric by means of numerical calculations, which make it possible to reach the ultrarelativistic regime gradually by letting the boost velocity approach the speed of light. Thus, for the first time in the literature, the singular limit of <span class="hlt">curvature</span>, through Dirac’s δ distribution and its derivatives, is numerically evaluated for this class of spacetimes. Moreover, the analysis of the Kretschmann invariant and the geodesic equation shows that the spacetime possesses a “scalar <span class="hlt">curvature</span> singularity” within a 3-sphere and it is possible to define what we here call “boosted horizon”, a sort of elastic wall where all particles are surprisingly pushed away, as numerical analysis demonstrates. This seems to suggest that such “boosted geometries” are ruled by a sort of “antigravity effect” since all geodesics seem to refuse to enter the “boosted horizon” and are “reflected” by it, even though their initial conditions are aimed at driving the particles toward the “boosted horizon” itself. Eventually, the equivalence with the coordinate shift method is invoked in order to demonstrate that all δ2 terms appearing in the Riemann <span class="hlt">curvature</span> tensor give vanishing contribution in distributional sense.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3166612','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3166612"><span>Efficient CT Metal Artifact Reduction Based on Fractional-Order <span class="hlt">Curvature</span> Diffusion</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhang, Yi; Pu, Yi-Fei; Hu, Jin-Rong; Liu, Yan; Chen, Qing-Li; Zhou, Ji-Liu</p> <p>2011-01-01</p> <p>We propose a novel metal artifact reduction method based on a fractional-order <span class="hlt">curvature</span> driven diffusion model for X-ray computed tomography. Our method treats projection data with metal <span class="hlt">regions</span> as a damaged image and uses the fractional-order <span class="hlt">curvature</span>-driven diffusion model to recover the lost information caused by the metal <span class="hlt">region</span>. The numerical scheme for our method is also analyzed. We use the peak signal-to-noise ratio as a reference measure. The simulation results demonstrate that our method achieves better performance than existing projection interpolation methods, including linear interpolation and total variation. PMID:21941593</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27828505','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27828505"><span>Infrared glass-based negative-<span class="hlt">curvature</span> anti-resonant fibers fabricated through extrusion.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gattass, Rafael R; Rhonehouse, Daniel; Gibson, Daniel; McClain, Collin C; Thapa, Rajesh; Nguyen, Vinh Q; Bayya, Shyam S; Weiblen, R Joseph; Menyuk, Curtis R; Shaw, L Brandon; Sanghera, Jasbinder S</p> <p>2016-10-31</p> <p>Negative <span class="hlt">curvature</span> fibers have been gaining attention as fibers for <span class="hlt">high</span> power infrared light. Currently, these fibers have been made of silica glass and infrared glasses solely through stack and draw. Infrared glasses' lower softening point presents the opportunity to perform low-temperature processing methods such as direct extrusion of pre-forms. We demonstrate an infrared-glass based negative <span class="hlt">curvature</span> fiber fabricated through extrusion. The fiber shows record low losses in 9.75 - 10.5 µm range (which overlaps with the CO<sub>2</sub> emission bands). We show the fiber's lowest order mode and measure the numerical aperture in the longwave infrared transmission band. The possibility to directly extrude a negative <span class="hlt">curvature</span> fiber with no penalties in losses is a strong motivation to think beyond the limitations of stack-and-draw to novel shapes for negative <span class="hlt">curvature</span> fibers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MS%26E..231a2083J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MS%26E..231a2083J"><span>Optimization research of sextant fan baffle <span class="hlt">curvature</span> radius in shell and tube heat exchanger</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jin, M.; Liu, H. J.; Wang, X. Y.</p> <p>2017-09-01</p> <p>For a <span class="hlt">high</span> shell side pressure drop of the conventional segmental baffles in shell and tube heat exchanger, a novel sextant fan baffle was put forward. To research the influence of baffle <span class="hlt">curvature</span> radius of the sextant fan baffled shell and tube heat exchanger (SFTHX) on the shell side pressure drop, the heat transfer coefficient and the comprehensive heat transfer performance, six different <span class="hlt">curvature</span> radius baffles were numerically simulated and experimental studied in this paper. Based on the numerically simulation results, under the same inlet flow conditions, a better comprehensive heat transfer performance can be found in SFTHX with the baffle <span class="hlt">curvature</span> radius of 1 D, which is higher by 0.84-6.85% more than that of the others. Moreover, the experimental investigation data of SFTHX with baffle <span class="hlt">curvature</span> radius of 1 D indicates that the numerically simulation can well predict the flow and heat transfer characteristics with the experiment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T51A2857R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T51A2857R"><span>Seismological Constraints on Fault Plane <span class="hlt">Curvature</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reynolds, K.</p> <p>2015-12-01</p> <p>The down-dip geometry of seismically active normal faults is not well known. Many examples of normal faults with down-dip <span class="hlt">curvature</span> exist, such as listric faults revealed in cross-section or in seismic reflection data, or the exposed domes of core complexes. However, it is not understood: (1) whether curved faults fail in earthquakes, and (2) if those faults have generated earthquakes, is the <span class="hlt">curvature</span> a primary feature of the rupture or due to later modification of the plane? Even if an event is surface-rupturing, because of the limited depth-extent over which observations can be made, it is difficult to reliably constrain the change in dip with depth (if any) and therefore the fault <span class="hlt">curvature</span>. Despite the uncertainty in seismogenic normal fault geometries, published slip inversions most commonly use planar fault models. We investigate the seismological constraints on normal fault geometry using a forward-modelling approach and present a seismological technique for determining down-dip geometry. We demonstrate that complexity in the shape of teleseismic body waveforms may be used to investigate the presence of down-dip fault plane <span class="hlt">curvature</span>. We have applied this method to a catalogue of continental and oceanic normal faulting events. Synthetic models demonstrate that the shapes of SH waveforms at along-strike stations are particularly sensitive to fault plane geometry. It is therefore important to consider the azimuthal station coverage before modelling an event. We find that none of the data require significant down-dip <span class="hlt">curvature</span>, although the modelling results for some events remain ambiguous. In some cases we can constrain that the down-dip fault geometry is within 20° of planar.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4735656','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4735656"><span>Mean cortical <span class="hlt">curvature</span> reflects cytoarchitecture restructuring in mild traumatic brain injury</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>King, Jace B.; Lopez-Larson, Melissa P.; Yurgelun-Todd, Deborah A.</p> <p>2016-01-01</p> <p>In the United States alone, the number of persons living with the enduring consequences of traumatic brain injuries is estimated to be between 3.2 and 5 million. This number does not include individuals serving in the United States military or seeking care at Veterans Affairs hospitals. The importance of understanding the neurobiological consequences of mild traumatic brain injury (mTBI) has increased with the return of veterans from conflicts overseas, many of who have suffered this type of brain injury. However, identifying the neuroanatomical <span class="hlt">regions</span> most affected by mTBI continues to prove challenging. The aim of this study was to assess the use of mean cortical <span class="hlt">curvature</span> as a potential indicator of progressive tissue loss in a cross-sectional sample of 54 veterans with mTBI compared to 31 controls evaluated with MRI. It was hypothesized that mean cortical <span class="hlt">curvature</span> would be increased in veterans with mTBI, relative to controls, due in part to cortical restructuring related to tissue volume loss. Mean cortical <span class="hlt">curvature</span> was assessed in 60 bilateral <span class="hlt">regions</span> (31 sulcal, 29 gyral). Of the 120 <span class="hlt">regions</span> investigated, nearly 50% demonstrated significantly increased mean cortical <span class="hlt">curvature</span> in mTBI relative to controls with 25% remaining significant following multiple comparison correction (all, pFDR < .05). These differences were most prominent in deep gray matter <span class="hlt">regions</span> of the cortex. Additionally, significant relationships were found between mean cortical <span class="hlt">curvature</span> and gray and white matter volumes (all, p < .05). These findings suggest potentially unique patterns of atrophy by <span class="hlt">region</span> and indicate that changes in brain microstructure due to mTBI are sensitive to measures of mean <span class="hlt">curvature</span>. PMID:26909332</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhL.109b3504D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhL.109b3504D"><span>Stress compensation for arbitrary <span class="hlt">curvature</span> control in vanadium dioxide phase transition actuators</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dong, Kaichen; Lou, Shuai; Choe, Hwan Sung; Liu, Kai; You, Zheng; Yao, Jie; Wu, Junqiao</p> <p>2016-07-01</p> <p>Due to its thermally driven structural phase transition, vanadium dioxide (VO2) has emerged as a promising material for micro/nano-actuators with superior volumetric work density, actuation amplitude, and repetition frequency. However, the <span class="hlt">high</span> initial <span class="hlt">curvature</span> of VO2 actuators severely obstructs the actuation performance and application. Here, we introduce a "seesaw" method of fabricating tri-layer cantilevers to compensate for the residual stress and realize nearly arbitrary <span class="hlt">curvature</span> control of VO2 actuators. By simply adjusting the thicknesses of the individual layers, cantilevers with positive, zero, or negative <span class="hlt">curvatures</span> can be engineered. The actuation amplitude can be decoupled from the <span class="hlt">curvature</span> and controlled independently as well. Based on the experimentally measured residual stresses, we demonstrate sub-micron thick VO2 actuators with nearly zero final <span class="hlt">curvature</span> and a <span class="hlt">high</span> actuation amplitude simultaneously. This "seesaw" method can be further extended to the <span class="hlt">curvature</span> engineering of other microelectromechanical system multi-layer structures where large stress-mismatch between layers are inevitable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22590610','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22590610"><span>Stress compensation for arbitrary <span class="hlt">curvature</span> control in vanadium dioxide phase transition actuators</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dong, Kaichen E-mail: wuj@berkeley.edu; Lou, Shuai; Choe, Hwan Sung; Yao, Jie; Wu, Junqiao E-mail: wuj@berkeley.edu; Liu, Kai; You, Zheng</p> <p>2016-07-11</p> <p>Due to its thermally driven structural phase transition, vanadium dioxide (VO{sub 2}) has emerged as a promising material for micro/nano-actuators with superior volumetric work density, actuation amplitude, and repetition frequency. However, the <span class="hlt">high</span> initial <span class="hlt">curvature</span> of VO{sub 2} actuators severely obstructs the actuation performance and application. Here, we introduce a “seesaw” method of fabricating tri-layer cantilevers to compensate for the residual stress and realize nearly arbitrary <span class="hlt">curvature</span> control of VO{sub 2} actuators. By simply adjusting the thicknesses of the individual layers, cantilevers with positive, zero, or negative <span class="hlt">curvatures</span> can be engineered. The actuation amplitude can be decoupled from the <span class="hlt">curvature</span> and controlled independently as well. Based on the experimentally measured residual stresses, we demonstrate sub-micron thick VO{sub 2} actuators with nearly zero final <span class="hlt">curvature</span> and a <span class="hlt">high</span> actuation amplitude simultaneously. This “seesaw” method can be further extended to the <span class="hlt">curvature</span> engineering of other microelectromechanical system multi-layer structures where large stress-mismatch between layers are inevitable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003JSG....25..277B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003JSG....25..277B"><span>How to calculate normal <span class="hlt">curvatures</span> of sampled geological surfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bergbauer, Stephan; Pollard, David D.</p> <p>2003-02-01</p> <p><span class="hlt">Curvature</span> has been used both to describe geological surfaces and to predict the distribution of deformation in folded or domed strata. Several methods have been proposed in the geoscience literature to approximate the <span class="hlt">curvature</span> of surfaces; however we advocate a technique for the exact calculation of normal <span class="hlt">curvature</span> for single-valued gridded surfaces. This technique, based on the First and Second Fundamental Forms of differential geometry, allows for the analytical calculation of the magnitudes and directions of principal <span class="hlt">curvatures</span>, as well as Gaussian and mean <span class="hlt">curvature</span>. This approach is an improvement over previous methods to calculate surface <span class="hlt">curvatures</span> because it avoids common mathematical approximations, which introduce significant errors when calculated over sloped horizons. Moreover, the technique is easily implemented numerically as it calculates <span class="hlt">curvatures</span> directly from gridded surface data (e.g. seismic or GPS data) without prior surface triangulation. In geological <span class="hlt">curvature</span> analyses, problems arise because of the sampled nature of geological horizons, which introduces a dependence of calculated <span class="hlt">curvatures</span> on the sample grid. This dependence makes <span class="hlt">curvature</span> analysis without prior data manipulation problematic. To ensure a meaningful <span class="hlt">curvature</span> analysis, surface data should be filtered to extract only those surface wavelengths that scale with the feature under investigation. A <span class="hlt">curvature</span> analysis of the top-Pennsylvanian horizon at Goose Egg dome, Wyoming shows that sampled surfaces can be smoothed using a moving average low-pass filter to extract <span class="hlt">curvature</span> information associated with the true morphology of the structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/112335','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/112335"><span>Effects of corotating interaction <span class="hlt">regions</span> on ULYSSES <span class="hlt">high</span> energy particles</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Droege, W.; Kunow, H.; Raviart, A.</p> <p>1995-09-01</p> <p>Since June 1992 the Kiel Electron Telescope on board ULYSSES measures variations of more than 10% in the fluxes of <span class="hlt">high</span> energy H and He showing a periodicity of about 26 days in coincidence with the passage of corotating interaction <span class="hlt">regions</span>. (CIR). At low energies MeV protons are accelerated at the shocks of the CIRs. These effects are observed up to <span class="hlt">high</span> southern latitudes, where the signature of a CIR is no longer visible in plasma or magnetic field data. After passing over the south polar cap ULYSSES has now returned to the solar equator and climbs up to the north pole. In this paper we study the relative intensity variations with latitude and the latitude dependence at solar distances smaller than ever studied before.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6280G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6280G"><span>Modelization of <span class="hlt">highly</span> nonlinear waves in coastal <span class="hlt">regions</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gouin, Maïté; Ducrozet, Guillaume; Ferrant, Pierre</p> <p>2015-04-01</p> <p>The proposed work deals with the development of a <span class="hlt">highly</span> non-linear model for water wave propagation in coastal <span class="hlt">regions</span>. The accurate modelization of surface gravity waves is of major interest in ocean engineering, especially in the field of marine renewable energy. These marine structures are intended to be settled in coastal <span class="hlt">regions</span> where the effect of variable bathymetry may be significant on local wave conditions. This study presents a numerical model for the wave propagation with complex bathymetry. It is based on <span class="hlt">High</span>-Order Spectral (HOS) method, initially limited to the propagation of non-linear wave fields over flat bottom. Such a model has been developed and validated at the LHEEA Lab. (Ecole Centrale Nantes) over the past few years and the current developments will enlarge its application range. This new numerical model will keep the interesting numerical properties of the original pseudo-spectral approach (convergence, efficiency with the use of FFTs, …) and enable the possibility to propagate <span class="hlt">highly</span> non-linear wave fields over long time and large distance. Different validations will be provided in addition to the presentation of the method. At first, Bragg reflection will be studied with the proposed approach. If the Bragg condition is satisfied, the reflected wave generated by a sinusoidal bottom patch should be amplified as a result of resonant quadratic interactions between incident wave and bottom. Comparisons will be provided with experiments and reference solutions. Then, the method will be used to consider the transformation of a non-linear monochromatic wave as it propagates up and over a submerged bar. As the waves travel up the front slope of the bar, it steepens and <span class="hlt">high</span> harmonics are generated due to non-linear interactions. Comparisons with experimental data will be provided. The different test cases will assess the accuracy and efficiency of the method proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9799E..1XL','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9799E..1XL"><span>State switching in <span class="hlt">regions</span> of <span class="hlt">high</span> modal density</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lopp, Garrett K.; Kauffman, Jeffrey L.</p> <p>2016-04-01</p> <p>Performance of piezoelectric-based, semi-active vibration reduction approaches has been studied extensively in the past decade. Originally analyzed with single-degree-of-freedom systems, these approaches have been extended to multi-mode vibration reduction. However, the accompanying analysis typically assumes well-separated modes, which is often not the case for plate structures. Because the semi-active approaches induce a shift in the structural resonance frequency (at least temporarily), targeting a specific mode for vibration reduction can actually lead to additional vibration in an adjacent mode. This paper presents an analysis using a simplified model of a two-degree-of-freedom mass-spring-damper system with lightly-coupled masses to achieve two closely-spaced modes. This investigation is especially applicable to the resonance frequency detuning approach previously proposed to reduce vibrations caused by transient excitation in turbomachinery blades where <span class="hlt">regions</span> of <span class="hlt">high</span> modal density exist. More generally, this paper addresses these effects of stiffness state switches in frequency ranges containing <span class="hlt">regions</span> of <span class="hlt">high</span> modal density and subject to frequency sweep excitation. Of the approaches analyzed, synchronized switch damping on an inductor offers the greatest vibration reduction performance, whereas resonance frequency detuning and state switching each yield similar performance. Additionally, as the relative distance between resonance peaks decreases, the performance for the vibration reduction methods approaches that of a single-degree-of-freedom system; however, there are distances between these resonant peaks that diminish vibration reduction potential.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.3351V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.3351V"><span>How to map soil carbon stocks in <span class="hlt">highly</span> urbanized <span class="hlt">regions</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vasenev, V. I.; Stoorvogel, J. J.</p> <p>2012-04-01</p> <p>Soil organic carbon (SOC) is the largest carbon stock in terrestrial ecosystems and the capacity for carbon sequestration is a widely accepted soil function. For land-use planning and decision making the <span class="hlt">regional</span> analysis of SOC stocks and their spatial variability is an important and challenging task that receives increasing attention. Quite a few studies focus on mapping the carbon stocks in natural and agricultural areas using digital soil mapping (DSM) techniques. Although urban areas remain almost neglected. The urban environment provides a number of specific features and processes that influence soil formation and functioning: soil sealing, functional zoning and settlement history. This not only results in a considerable urban SOC (especially in the subsoil), but also results in a unique spatial variability of SOC stocks at short distance. In contrast to the often gradual changes in natural areas, urban soils may exhibit abrupt changes due to the anthropogenic influence. Thus implementation of standard DSM methodology will result in extremely <span class="hlt">high</span> nuggets and correspondingly low prediction accuracy. Besides, traditional regression kriging, widely-used for the case when legacy data is lacking, is often based on the correlation between SOC and dominating soil forming factors (climate, relief, parent material and vegetation). Although in urban conditions, anthropogenic influence itself turns out to be a predominant soil-forming factor. The spatial heterogeneity of urban soil carbon stocks is further complicated by a specific profile distribution with possible second SOC maximum, referred to cultural layer. Importance of urban SOC as well as specifics of urban environment requires for a specific approach to map urban SOC as part of <span class="hlt">regional</span> analysis. Moscow <span class="hlt">region</span> with its variability of bioclimatic conditions and <span class="hlt">high</span> urbanization level (10 % from the total area) was chosen as an interesting case study. Random soil sampling in different soil zones (4) and land</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGP...112...74T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGP...112...74T"><span>Inequalities for scalar <span class="hlt">curvature</span> of pseudo-Riemannian submanifolds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tripathi, Mukut Mani; Gülbahar, Mehmet; Kılıç, Erol; Keleş, Sadık</p> <p>2017-02-01</p> <p>Some basic inequalities, involving the scalar <span class="hlt">curvature</span> and the mean <span class="hlt">curvature</span>, for a pseudo-Riemannian submanifold of a pseudo-Riemannian manifold are obtained. We also find inequalities for spacelike submanifolds. Equality cases are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27015103','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27015103"><span>The geometric <span class="hlt">curvature</span> of the lumbar spine during restricted and unrestricted squats.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hebling Campos, Mário; Furtado Alaman, Laizi I; Seffrin-Neto, Aldo A; Vieira, Carlos A; Costa de Paula, Marcelo; Barbosa de Lira, Claudio A</p> <p>2017-06-01</p> <p>The main purpose of this study was to analyze the behavior of the geometric <span class="hlt">curvature</span> of the lumbar spine during restricted and unrestricted squats, using a novel investigative method. The rationale for our hypothesis is that the lumbar <span class="hlt">curvature</span> has different patterns at different spine levels depending on the squat technique used. Spine motion was collected via stereo-photogrammetric analysis in nineteen participants (11 males, 8 females). The reconstructed spine points at the upright neutral position and at the deepest position of the squat exercise were projected onto the sagittal plane of the trunk, a polynomial was fitted to the data, and were quantified the two-dimensional geometric <span class="hlt">curvature</span> at lower, central and higher lumbar levels, besides the inclination of trunk and lumbosacral <span class="hlt">region</span>, the overall geometric <span class="hlt">curvature</span> and overall angle of the lumbar spine. The mean values for each variable were analysed with paired t-test (P<0.05). The lumbar presents a flexion from upright neutral posture to deepest point of the movement, but for the lower lumbar the flexion is less intense if the knees travel anteriorly past the toes. The trunk and the lumbosacral <span class="hlt">region</span> lean forward in both squat techniques and these effects are also reduced in unrestricted squats. The data collected in the study are evidence that during barbell squats the lumbar <span class="hlt">curvature</span> has different patterns at different spinal levels depending on the exercise technique. The lower lumbar spine appears to be less overloaded during unrestricted squats.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15..209K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15..209K"><span><span class="hlt">High</span> Resolution <span class="hlt">Regional</span> Climate Modeling for Lebanon, Eastern Mediterranean Coast</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Katurji, Marwan; Soltanzadeh, Iman; Kuhnlein, Meike; Zawar-Reza, Peyman</p> <p>2013-04-01</p> <p>The Eastern Mediterranean coast consists of Lebanon, Palestine, Syria, Israel and a small part of southern Turkey. The <span class="hlt">region</span> lies between latitudes 30 degrees S and 40 degrees N, which makes its climate affected by westerly propagating wintertime cyclones spinning off mid-latitude troughs (December, January and February), while during summer (June, July and August) the area is strongly affected by the sub-tropical anti-cyclonic belt as a result of the descending air of the Hadley cell circulation system. The area is considered to be in a transitional zone between tropical to mid-latitude climate regimes, and having a coastal topography up to 3000 m in elevation (like in the Western Ranges of Lebanon), which emphasizes the complexity of climate variability in this area under future predictions of climate change. This research incorporates both <span class="hlt">regional</span> climate numerical simulations, Tropical Rainfall Measuring Mission (TRMM) satellite derived and surface rain gauge rainfall data to evaluate the <span class="hlt">Regional</span> Climate Model (RegCM) version 4 ability to represent both the mean and variance of observed precipitation in the Eastern Mediterranean <span class="hlt">Region</span>, with emphasis on the Lebanese coastal terrain and mountain ranges. The adopted methodology involves dynamically down scaling climate data from reanalysis synoptic files through a double nesting procedure. The retrospective analysis of 13 years with both 50 and 10 km spatial resolution allows for the assessment of the model results on both a climate scale and specific <span class="hlt">high</span> intensity precipitating events. The spatial averaged mean bias error in precipitation rate for the rainy season predicted by RegCM 50 and 10 km resolution grids was 0.13 and 0.004 mm hr-1 respectively. When correlating RegCM and TRMM precipitation rate for the domain covering Lebanon's coastal mountains, the root mean square error (RMSE) for the mean quantities over the 13-year period was only 0.03, while the RMSE for the standard deviation was higher by one</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26040401','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26040401"><span>Femoral <span class="hlt">curvature</span> variability in modern humans using three-dimensional quadric surface fitting.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chapman, Tara; Sholukha, Victor; Semal, Patrick; Louryan, Stéphane; Rooze, Marcel; Van Sint Jan, Serge</p> <p>2015-12-01</p> <p>This study analysed femoral <span class="hlt">curvature</span> in a population from Belgium in conjunction with other morphological characteristics by the use of three-dimensional (3D) quadric surfaces (QS) modelled from the bone surface. 3D models were created from computed tomography data of 75 femoral modern human bones. Anatomical landmarks (ALs) were palpated in specific bony areas of the femur (shaft, condyles, neck and head). QS were then created from the surface vertices which enclose these ALs. The diaphyseal shaft was divided into five QS shapes to analyse <span class="hlt">curvature</span> in different parts of the shaft. Femoral bending differs in different parts of the diaphyseal shaft. The greatest degree of <span class="hlt">curvature</span> was found in the distal shaft (mean 4.5° range 0.2°-10°) followed by the proximal (mean 4.4° range 1.5°-10.2°), proximal intermediate (mean 3.7° range 0.9°-7.9°) and distal intermediate (mean 1.8° range 0.2°-5.6°) shaft sections. The proximal and distal angles were significantly more bowed than the intermediate proximal and the intermediate distal angle. There was no significant difference between the proximal and distal angle. No significant correlations were found between morphological characteristics and femoral <span class="hlt">curvature</span>. An extremely large variability of femoral <span class="hlt">curvature</span> with several bones displaying very <span class="hlt">high</span> or low degrees of femoral <span class="hlt">curvature</span> was also found. 3D QS fitting enables the creation of accurate models which can discriminate between different patterns in similar <span class="hlt">curvatures</span> and demonstrates there is a clear difference between <span class="hlt">curvature</span> in different parts of the shaft.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26330889','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26330889"><span>Laser triangulation measurements of scoliotic spine <span class="hlt">curvatures</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Čelan, Dušan; Jesenšek Papež, Breda; Poredoš, Primož; Možina, Janez</p> <p>2015-01-01</p> <p>The main purpose of this research was to develop a new method for differentiating between scoliotic and healthy subjects by analysing the <span class="hlt">curvatures</span> of their spines in the cranio-caudal view. The study included 247 subjects with physiological <span class="hlt">curvatures</span> of the spine and 28 subjects with clinically confirmed scoliosis. The <span class="hlt">curvature</span> of the spine was determined by a computer analysis of the surface of the back, measured with a non-invasive, 3D, laser-triangulation system. The determined spinal curve was represented in the transversal plane, which is perpendicular to the line segment that was defined by the initial point and the end point of the spinal curve. This was achieved using a rotation matrix. The distances between the extreme points in the antero-posterior (AP) and left-right (LR) views were calculated in relation to the length of the spine as well as the quotient of these two values LR/AP. All the measured parameters were compared between the scoliotic and control groups using the Student's t-Test in case of normal data and Kruskal-Wallis test in case of non-normal data. Besides, a comprehensive diagram representing the distances between the extreme points in the AP and LR views was introduced, which clearly demonstrated the direction and the size of the thoracic and lumbar spinal <span class="hlt">curvatures</span> for each individual subject. While the distances between the extreme points of the spine in the AP view were found to differ only slightly between the groups (p = 0.1), the distances between the LR extreme points were found to be significantly greater in the scoliosis group, compared to the control group (p < 0.001). The quotient LR/AP was statistically significantly different in both groups (p < 0.001). The main innovation of the presented method is the ability to differentiate a scoliotic subject from a healthy subject by assessing the <span class="hlt">curvature</span> of the spine in the cranio-caudal view. Therefore, the proposed method could be useful for human posture</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25851418','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25851418"><span><span class="hlt">Curvature</span> sensing MARCKS-ED peptides bind to membranes in a stereo-independent manner.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yan, Lei; de Jesus, Armando Jerome; Tamura, Ryo; Li, Victoria; Cheng, Kui; Yin, Hang</p> <p>2015-07-01</p> <p>Membrane <span class="hlt">curvature</span> and lipid composition plays a critical role in interchanging of matter and energy in cells. Peptide <span class="hlt">curvature</span> sensors are known to activate signaling pathways and promote molecular transport across cell membranes. Recently, the 25-mer MARCKS-ED peptide, which is derived from the effector domain of the myristoylated alanine-rich C kinase substrate protein, has been reported to selectively recognize <span class="hlt">highly</span> curved membrane surfaces. Our previous studies indicated that the naturally occurring L-MARCKS-ED peptide could simultaneously detect both phosphatidylserine and <span class="hlt">curvature</span>. Here, we demonstrate that D-MARCKS-ED, composed by unnatural D-amino acids, has the same activities as its enantiomer, L-MARCKS-ED, as a <span class="hlt">curvature</span> and lipid sensor. An atomistic molecular dynamics simulation suggests that D-MARCKS-ED may change from linear to a boat conformation upon binding to the membrane. Comparable enhancement of fluorescence intensity was observed between D- and L-MARCKS-ED peptides, indicating similar binding affinities. Meanwhile, circular dichroism spectra of D- and L-MARCKS-ED are almost symmetrical both in the presence and absence of liposomes. These results suggest similar behavior of artificial D- and natural L-MARCKS-ED peptides when binding to curved membranes. Our studies may contribute to further understanding of how MARCKS-ED senses membrane <span class="hlt">curvature</span> as well as provide a new direction to develop novel membrane <span class="hlt">curvature</span> probes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.3955W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.3955W"><span>Developing a <span class="hlt">high</span>-resolution <span class="hlt">regional</span> atmospheric reanalysis for Australia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>White, Christopher; Fox-Hughes, Paul; Su, Chun-Hsu; Jakob, Dörte; Kociuba, Greg; Eisenberg, Nathan; Steinle, Peter; Harris, Rebecca; Corney, Stuart; Love, Peter; Remenyi, Tomas; Chladil, Mark; Bally, John; Bindoff, Nathan</p> <p>2017-04-01</p> <p>A dynamically consistent, long-term atmospheric reanalysis can be used to support <span class="hlt">high</span>-quality assessments of environmental risk and likelihood of extreme events. Most reanalyses are presently based on coarse-scale global systems that are not suitable for <span class="hlt">regional</span> assessments in fire risk, water and natural resources, amongst others. The Australian Bureau of Meteorology is currently working to close this gap by producing a <span class="hlt">high</span>-resolution reanalysis over the Australian and New Zealand <span class="hlt">region</span> to construct a sequence of atmospheric conditions at sub-hourly intervals over the past 25 years from 1990. The Australia reanalysis consists of a convective-scale analysis nested within a 12 km <span class="hlt">regional</span>-scale reanalysis, which is bounded by a coarse-scale ERA-Interim reanalysis that provides the required boundary and initial conditions. We use an unchanging atmospheric modelling suite based on the UERRA system used at the UK Met Office and the more recent version of the Bureau of Meteorology's operational numerical prediction model used in ACCESS-R (Australian Community Climate and Earth-System Simulator-<span class="hlt">Regional</span> system). An advanced (4-dimensional variational) data assimilation scheme is used to optimally combine model physics with multiple observations from aircrafts, sondes, surface observations and satellites to create a best estimate of state of the atmosphere over a 6-hour moving window. This analysis is in turn used to drive a higher-resolution (1.5 km) downscaling model over selected subdomains within Australia, currently eastern New South Wales and Tasmania, with the capability to support this anywhere in the Australia-New Zealand domain. The temporal resolution of the gridded analysis fields for both the <span class="hlt">regional</span> and higher-resolution subdomains are generally one hour, with many fields such as 10 m winds and 2 m temperatures available every 10 minutes. The reanalysis also produces many other variables that include wind, temperature, moisture, pressure, cloud cover</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016CG.....93...36M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016CG.....93...36M"><span>Feature tracking in <span class="hlt">high</span>-resolution <span class="hlt">regional</span> climate data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Massey, Neil R.</p> <p>2016-08-01</p> <p>In this paper, a suite of algorithms are presented which facilitate the identification and tracking of storm-indicative features, such as mean sea-level pressure minima, in <span class="hlt">high</span> resolution <span class="hlt">regional</span> climate data. The methods employ a hierarchical triangular mesh, which is tailored to the <span class="hlt">regional</span> climate data by only subdividing triangles, from an initial icosahedron, within the domain of the data. The <span class="hlt">regional</span> data is then regridded to this triangular mesh at each level of the grid, producing a compact representation of the data at numerous resolutions. Storm indicative features are detected by first subtracting the background field, represented by a low resolution version of the data, which occurs at a lower level in the mesh. Anomalies from this background field are detected, as feature objects, at a mesh level which corresponds to the spatial scale of the feature being detected and then refined to the highest mesh level. These feature objects are expanded to an outer contour and overlapping objects are merged. The centre points of these objects are tracked across timesteps by applying an optimisation scheme which uses five hierarchical rules. Objects are added to tracks based on the highest rule in the scheme they pass and, if two objects pass the same rule, the cost of adding the object to the track. An object exchange scheme ensures that adding an object to a track is locally optimal. An additional track optimisation phase is performed which exchanges segments between tracks and merges tracks to obtain a globally optimal track set. To validate the suite of algorithms they are applied to the ERA-Interim reanalysis dataset and compared to other storm-indicative feature tracking algorithms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121.2669V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121.2669V"><span>Electrodynamic structure of the morning <span class="hlt">high</span>-latitude trough <span class="hlt">region</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vanhamäki, H.; Aikio, A.; Voiculescu, M.; Juusola, L.; Nygrén, T.; Kuula, R.</p> <p>2016-03-01</p> <p>We describe the electrodynamics of a postmidnight, <span class="hlt">high</span>-latitude ionospheric trough, observed with the European Incoherent Scatter radar in northern Scandinavia on 24-25 June 2003 around 22:00-02:30 UT during quiet conditions. The UHF radar made meridian scans with a 30 min cadence resulting in nine cross sections of ionospheric parameters. The F <span class="hlt">region</span> electric field was also determined with the tristatic system. Ionospheric equivalent currents, calculated from ground magnetometer data, mostly show an electrojet-like current that is reasonably uniform in the longitudinal direction. Combined analysis of the conductances and equivalent current with a local Kamide-Richmond-Matsushita (KRM) method yields the ionospheric electric field and field-aligned current (FAC) in a 2-D (latitude-longitude) area around the radar. We conclude that the most likely scenario is one where the trough is initially created poleward of the auroral oval by downward FAC that evacuates the F <span class="hlt">region</span>, but as the trough moves to lower latitudes during the early morning hours, it becomes colocated with the westward electrojet. There the electron density further decreases due to increased recombination caused by enhanced ion temperature, which in turn is brought about by a larger convection speed. Later in the morning the convection speed decreases and the trough is filled by increasing photoionization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16486802','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16486802"><span>Constraining inverse-<span class="hlt">curvature</span> gravity with supernovae.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mena, Olga; Santiago, José; Weller, Jochen</p> <p>2006-02-03</p> <p>We show that models of generalized modified gravity, with inverse powers of the <span class="hlt">curvature</span>, can explain the current accelerated expansion of the Universe without resorting to dark energy and without conflicting with solar system experiments. We have solved the Friedmann equations for the full dynamical range of the evolution of the Universe and performed a detailed analysis of supernovae data in the context of such models that results in an excellent fit. If we further include constraints on the current expansion of the Universe and on its age, we obtain that the matter content of the Universe is 0.07<or=omegam<or=0.21 (95% C.L.). Hence the inverse-<span class="hlt">curvature</span> gravity models considered cannot explain the dynamics of the Universe just with a baryonic matter component.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930035197&hterms=Aachen&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DAachen','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930035197&hterms=Aachen&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DAachen"><span>Streamline <span class="hlt">curvature</span> in supersonic shear layers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kibens, V.</p> <p>1992-01-01</p> <p>Results of an experimental investigation in which a curved shear layer was generated between supersonic flow from a rectangular converging/diverging nozzle and the freestream in a series of open channels with varying radii of <span class="hlt">curvature</span> are reported. The shear layers exhibit unsteady large-scale activity at supersonic pressure ratios, indicating increased mixing efficiency. This effect contrasts with supersonic flow in a straight channel, for which no large-scale vortical structure development occurs. <span class="hlt">Curvature</span> must exceed a minimum level before it begins to affect the dynamics of the supersonic shear layer appreciably. The curved channel flows are compared with reference flows consisting of a free jet, a straight channel, and wall jets without sidewalls on a flat and a curved plate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhRvE..80e1904G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhRvE..80e1904G"><span>Effect of intrinsic <span class="hlt">curvature</span> on semiflexible polymers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghosh, Surya K.; Singh, Kulveer; Sain, Anirban</p> <p>2009-11-01</p> <p>Recently many important biopolymers have been found to possess intrinsic <span class="hlt">curvature</span>. Tubulin protofilaments in animal cells, FtsZ filaments in bacteria and double stranded DNA are examples. We examine how intrinsic <span class="hlt">curvature</span> influences the conformational statistics of such polymers. We give exact results for the tangent-tangent spatial correlation function C(r)=⟨t̂(s).t̂(s+r)⟩ , both in two and three dimensions. Contrary to expectation, C(r) does not show any oscillatory behavior, rather decays exponentially and the effective persistence length has strong length dependence for short polymers. We also compute the distribution function P(R) of the end to end distance R and show how curved chains can be distinguished from wormlike chains using loop formation probability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1390219-curvature-suppresses-rayleigh-taylor-instability','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1390219-curvature-suppresses-rayleigh-taylor-instability"><span><span class="hlt">Curvature</span> suppresses the Rayleigh-Taylor instability</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Trinh, Philippe H.; Kim, Hyoungsoo; Hammoud, Naima; ...</p> <p>2014-05-20</p> <p>We studied the dynamics of a thin liquid film on the underside of a curved cylindrical substrate. The evolution of the liquid layer is investigated as the film thickness and the radius of <span class="hlt">curvature</span> of the substrate are varied. A dimensionless parameter (a modified Bond number) that incorporates both geometric parameters, gravity, and surface tension is identified, and allows the observations to be classified according to three different flow regimes: stable films, films with transient growth of perturbations followed by decay, and unstable films. We found that the experiments and theory confirm that, below a critical value of the Bondmore » number, <span class="hlt">curvature</span> of the substrate suppresses the Rayleigh-Taylor instability.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/867311','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/867311"><span>Tube <span class="hlt">curvature</span> measuring probe and method</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Sokol, George J.</p> <p>1990-01-01</p> <p>The present invention is directed to a probe and method for measuring the radius of <span class="hlt">curvature</span> of a bend in a section of tubing. The probe includes a member with a pair of guide means, one located at each end of the member. A strain gauge is operatively connected to the member for detecting bending stress exrted on the member as the probe is drawn through and in engagement with the inner surface of a section of tubing having a bend. The method of the present invention includes steps utilizing a probe, like the aforementioned probe, which can be made to detect bends only in a single plane when having a fixed orientation relative the section of tubing to determine the maximum radius of <span class="hlt">curvature</span> of the bend.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhTea..54..416M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhTea..54..416M"><span>Measuring Intrinsic <span class="hlt">Curvature</span> of Space with Electromagnetism</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mabin, Mason; Becker, Maria; Batelaan, Herman</p> <p>2016-10-01</p> <p>The concept of curved space is not readily observable in everyday life. The educational movie "Sphereland" attempts to illuminate the idea. The main character, a hexagon, has to go to great lengths to prove that her world is in fact curved. We present an experiment that demonstrates a new way to determine if a two-dimensional surface, the 2-sphere, is curved. The behavior of an electric field, placed on a spherical surface, is shown to be related to the intrinsic Gaussian <span class="hlt">curvature</span>. This approach allows students to gain some understanding of Einstein's theory of general relativity, which relates the <span class="hlt">curvature</span> of spacetime to the presence of mass and energy. Additionally, an opportunity is provided to investigate the dimensionality of Gauss's law.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930035197&hterms=aachen&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Daachen','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930035197&hterms=aachen&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Daachen"><span>Streamline <span class="hlt">curvature</span> in supersonic shear layers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kibens, V.</p> <p>1992-01-01</p> <p>Results of an experimental investigation in which a curved shear layer was generated between supersonic flow from a rectangular converging/diverging nozzle and the freestream in a series of open channels with varying radii of <span class="hlt">curvature</span> are reported. The shear layers exhibit unsteady large-scale activity at supersonic pressure ratios, indicating increased mixing efficiency. This effect contrasts with supersonic flow in a straight channel, for which no large-scale vortical structure development occurs. <span class="hlt">Curvature</span> must exceed a minimum level before it begins to affect the dynamics of the supersonic shear layer appreciably. The curved channel flows are compared with reference flows consisting of a free jet, a straight channel, and wall jets without sidewalls on a flat and a curved plate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22525712','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22525712"><span>Cosmological signatures of anisotropic spatial <span class="hlt">curvature</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pereira, Thiago S.; Marugán, Guillermo A. Mena; Carneiro, Saulo E-mail: mena@iem.cfmac.csic.es</p> <p>2015-07-01</p> <p>If one is willing to give up the cherished hypothesis of spatial isotropy, many interesting cosmological models can be developed beyond the simple anisotropically expanding scenarios. One interesting possibility is presented by shear-free models in which the anisotropy emerges at the level of the <span class="hlt">curvature</span> of the homogeneous spatial sections, whereas the expansion is dictated by a single scale factor. We show that such models represent viable alternatives to describe the large-scale structure of the inflationary universe, leading to a kinematically equivalent Sachs-Wolfe effect. Through the definition of a complete set of spatial eigenfunctions we compute the two-point correlation function of scalar perturbations in these models. In addition, we show how such scenarios would modify the spectrum of the CMB assuming that the observations take place in a small patch of a universe with anisotropic <span class="hlt">curvature</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21163517','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21163517"><span>Effects of corotating interaction <span class="hlt">regions</span> on Ulysses <span class="hlt">high</span> energy particles</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Droege, W.; Kunow, H.; Heber, B.; Mueller-Mellin, R.; Sierks, H.; Wibberenz, G.; Raviart, A.; Ducros, R.; Ferrando, P.; Rastoin, C.; Paizis, C.; Gosling, J. T.</p> <p>1996-07-20</p> <p>We investigate the intensity variation of low energy ({approx}6-23 MeV/N) heliospheric ions and of galactic protons (250-2200 MeV) observed by the Kiel Electron Telescope onboard the Ulysses spacecraft associated with Corotating Interaction <span class="hlt">Regions</span> (CIR) from mid-1992 to end of June 1995. This period covers Ulysses' transit to <span class="hlt">high</span> southern latitudes, the south polar pass, return to the solar equator and ascent to the north pole up to 70 deg. We find that the flux of <span class="hlt">high</span> energy protons exhibits a periodicity of about 26 days with a relative intensity variation of 10%. At latitudes below {approx}50 deg. the recurrent variations of galactic protons are in coincidence with the passage of CIRs and enhancements of low energies protons and alpha particles which are accelerated at the shocks of the CIRs. The modulation of galactic protons is observed up to <span class="hlt">high</span> southern latitudes, where the signatures of a CIR are no longer visible in plasma or magnetic field data. The periodicity does not depend on latitude and its phase apparently remains constant during Ulysses' pass over the south pole as well as through the solar equator.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/575572','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/575572"><span>Effects of corotating interaction <span class="hlt">regions</span> on Ulysses <span class="hlt">high</span> energy particles</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Droege, W.; Kunow, H.; Heber, B.; Mueller-Mellin, R.; Sierks, H.; Wibberenz, G.; Raviart, A.; Ducros, R.; Ferrando, P.; Rastoin, C.; Gosling, J.T.</p> <p>1996-07-01</p> <p>We investigate the intensity variation of low energy ({approximately}6{endash}23MeV/N) heliospheric ions and of galactic protons (250{endash}2200 MeV) observed by the Kiel Electron Telescope onboard the Ulysses spacecraft associated with Corotating Interaction <span class="hlt">Regions</span> (CIR) from mid-1992 to end of June 1995. This period covers Ulysses{close_quote} transit to <span class="hlt">high</span> southern latitudes, the south polar pass, return to the solar equator and ascent to the north pole up to 70{degree}. We find that the flux of <span class="hlt">high</span> energy protons exhibits a periodicity of about 26 days with a relative intensity variation of 10{percent}. At latitudes below {approximately}50{degree} the recurrent variations of galactic protons are in coincidence with the passage of CIRs and enhancements of low energies protons and alpha particles which are accelerated at the shocks of the CIRs. The modulation of galactic protons is observed up to <span class="hlt">high</span> southern latitudes, where the signatures of a CIR are no longer visible in plasma or magnetic field data. The periodicity does not depend on latitude and its phase apparently remains constant during Ulysses{close_quote} pass over the south pole as well as through the solar equator. {copyright} {ital 1996 American Institute of Physics.}</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991PhLA..155..459A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991PhLA..155..459A"><span>Breeding <span class="hlt">curvature</span> from extended gauge covariance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aldrovandi, R.</p> <p>1991-05-01</p> <p>Independence between spacetime and “internal” space in gauge theories is related to the adjoint-covariant behaviour of the gauge potential. The usual gauge scheme is modified to allow a coupling between both spaces. Gauging spacetime translations produce field equations similar to Einstein equations. A <span class="hlt">curvature</span>-like quantity of mixed differential-algebraic character emerges. Enlarged conservation laws are present, pointing to the presence of an covariance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhTea..54..572W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhTea..54..572W"><span><span class="hlt">Curvature</span> of spacetime: A simple student activity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wood, Monika; Smith, Warren; Jackson, Matthew</p> <p>2016-12-01</p> <p>The following is a description of an inexpensive and simple student experiment for measuring the differences between the three types of spacetime topology—Euclidean (flat), Riemann (spherical), and Lobachevskian (saddle) <span class="hlt">curvatures</span>. It makes use of commonly available tools and materials, and requires only a small amount of construction. The experiment applies to astronomical topics such as gravity, spacetime, general relativity, as well as geometry and mathematics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015OptEn..54b5103Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015OptEn..54b5103Z"><span>Carbon-fiber-reinforced polymer variable-<span class="hlt">curvature</span> mirror used for optical zoom imaging: prototype design and experimental demonstration</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Hui; Fan, Xuewu; Pang, Zhihai; Ren, Guorui; Wang, Wei; Xie, Yongjie; Ma, Zhen; Du, Yunfei; Su, Yu; Wei, Jingxuan</p> <p>2015-02-01</p> <p>In recent years, optical zoom imaging without moving elements has received much attention. The key to realizing this technique lies in the design of the variable-<span class="hlt">curvature</span> mirror (VCM). To obtain enough optical magnification, the VCM should be able to change its radius of <span class="hlt">curvature</span> over a wide range. In other words, the VCM must be able to provide a large sagittal variation, which requires the mirror material to be robust during <span class="hlt">curvature</span> variation, require little force to deform, and have <span class="hlt">high</span> ultimate strength. Carbon-fiber-reinforced polymer (CFRP) satisfies all these requirements and is suitable for fabricating such a VCM. Therefore, in this research, a CFRP prototype VCM has been designed, fabricated, and tested. With a diameter of 100 mm, a thickness of 2 mm, and an initial radius of <span class="hlt">curvature</span> of 1740 mm, this VCM can provide a maximum 23-μm sagittal variation and a minimum and maximum radius of <span class="hlt">curvature</span> of 1705 and 1760 mm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvL.119h0602M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvL.119h0602M"><span>Lower Bounding Diffusion Constant by the <span class="hlt">Curvature</span> of Drude Weight</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Medenjak, Marko; Karrasch, Christoph; Prosen, Tomaž</p> <p>2017-08-01</p> <p>We establish a general connection between ballistic and diffusive transport in systems where the ballistic contribution in the canonical ensemble vanishes. A lower bound on the Green-Kubo diffusion constant is derived in terms of the <span class="hlt">curvature</span> of the ideal transport coefficient, the Drude weight, with respect to the filling parameter. As an application, we explicitly determine the lower bound on the <span class="hlt">high</span>-temperature diffusion constant in the anisotropic spin-1 /2 Heisenberg chain for anisotropy parameters Δ ≥1 , thus, settling the question of whether or not the transport is subdiffusive. Additionally, the lower bound is shown to saturate the diffusion constant for a certain classical integrable model.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6521572','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6521572"><span><span class="hlt">Curvature</span> effects on heat transfer in the free jet boundary</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Diggs, I.W.; Kim, K.H.</p> <p>1982-10-01</p> <p>The Coanda effect, which is known to exist in flows associated with velocity discontinuities around airfoils, may include the effects of <span class="hlt">high</span> temperature and thermal radiation. A physical interpretation of the steady, two-dimensional incompressible flowfield for such cases, and the boundary conditions which apply, are presented. It is found that the radiative boundary layer displays a sensitivity to <span class="hlt">curvature</span> that grows more pronounced as Reynolds number value increases. Attention is given to flow behavior for the cases of the predominance of conduction and of radiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982NIMPR.198..337T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982NIMPR.198..337T"><span>A momentum calculation for charged tracks with minute <span class="hlt">curvature</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Treadwell, Elliott</p> <p>1982-07-01</p> <p>ADJUST is a calculational method written in A.N.S.I. Fortran IV to correct the momenta of charged tracks with minute radius of <span class="hlt">curvature</span> and large fractional momentum error [ K<0.0014 (GeV/ c) -1 and Δp/ p⩾0.30]. Single application of the method to straight tracks eliminates remeasurements and avoids creating additional biases against <span class="hlt">high</span> multiplicity events ( NCH>8 tracks). Although ADJUST originated from the analysis of bubble-chamber events, the method is not restricted to bubble-chamber data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4573980','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4573980"><span>Multiple Manifold Clustering Using <span class="hlt">Curvature</span> Constrained Path</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Babaeian, Amir; Bayestehtashk, Alireza; Bandarabadi, Mojtaba</p> <p>2015-01-01</p> <p>The problem of multiple surface clustering is a challenging task, particularly when the surfaces intersect. Available methods such as Isomap fail to capture the true shape of the surface near by the intersection and result in incorrect clustering. The Isomap algorithm uses shortest path between points. The main draw back of the shortest path algorithm is due to the lack of <span class="hlt">curvature</span> constrained where causes to have a path between points on different surfaces. In this paper we tackle this problem by imposing a <span class="hlt">curvature</span> constraint to the shortest path algorithm used in Isomap. The algorithm chooses several landmark nodes at random and then checks whether there is a <span class="hlt">curvature</span> constrained path between each landmark node and every other node in the neighborhood graph. We build a binary feature vector for each point where each entry represents the connectivity of that point to a particular landmark. Then the binary feature vectors could be used as a input of conventional clustering algorithm such as hierarchical clustering. We apply our method to simulated and some real datasets and show, it performs comparably to the best methods such as K-manifold and spectral multi-manifold clustering. PMID:26375819</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22314835','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22314835"><span>Superintegrable systems on spaces of constant <span class="hlt">curvature</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gonera, Cezary Kaszubska, Magdalena</p> <p>2014-07-15</p> <p>Construction and classification of two-dimensional (2D) superintegrable systems (i.e. systems admitting, in addition to two global integrals of motion guaranteeing the Liouville integrability, the third global and independent one) defined on 2D spaces of constant <span class="hlt">curvature</span> and separable in the so-called geodesic polar coordinates are presented. The method proposed is applicable to any value of <span class="hlt">curvature</span> including the case of Euclidean plane, sphere and hyperbolic plane. The main result is a generalization of Bertrand’s theorem on 2D spaces of constant <span class="hlt">curvature</span> and covers most of the known separable and superintegrable models on such spaces (in particular, the so-called Tremblay–Turbiner–Winternitz (TTW) and Post–Winternitz (PW) models which have recently attracted some interest). -- Highlights: •Classifying 2D superintegrable, separable (polar coordinates) systems on S{sup 2}, R{sup 2}, H{sup 2}. •Construction of radial, angular potentials leading to superintegrability. •Generalization of Bertrand’s theorem covering known models, e.g. Higgs, TTW, PW, and Coulomb.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDG19010N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDG19010N"><span>Stiffness Modulation of Rayed Fins by <span class="hlt">Curvature</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nguyen, Khoi; Yu, Ning; Venkadesan, Madhusudhan; Bandi, Mahesh; Mandre, Shreyas</p> <p>2016-11-01</p> <p>Fishes with rayed fins comprise over 99% of all extant fish species. Multifunctional use of fins, from propulsion to station holding, requires substantial modulation of stiffness. We propose that fishes stiffen the fin by curving it transverse to its length. This effect is similar to stiffening a dollar bill by curling it because of <span class="hlt">curvature</span>-induced coupling of out-of-plane bending with in-plane stretching. Unlike a piece of paper, rayed fins are a composite of rays and membranes. We model this as parallel elastic beams (rays) with springy interconnections (membranes). Our analysis shows that the key parameters stiffening the fin are the ray anisotropy to bending, the misalignment of principal bending directions of adjacent rays, and the membrane elasticity. The composite fin stiffens when the principal bending directions of adjacent rays are misaligned due to fin <span class="hlt">curvature</span>, which necessarily causes the membrane to stretch. Unlike a homogenous thin sheet, composite rayed structures are able to mimic <span class="hlt">curvature</span>-induced stiffening by using misaligned rays even if the fin appears geometrically flat. Preliminary radiographic evidence from the rays of fish fins supports such a mechanism. Funding by Human Frontier Science Program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860045543&hterms=time+curvature&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dtime%2Bcurvature','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860045543&hterms=time+curvature&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dtime%2Bcurvature"><span>Effects of wall <span class="hlt">curvature</span> on turbulence statistics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moser, R. D.; Moin, P.</p> <p>1985-01-01</p> <p>A three-dimensional, time-dependent, direct numerical simulation of low-Reynolds number turbulent flow in a mildly curved channel was performed, and the results examined to determine the mechanism by which <span class="hlt">curvature</span> affects wall-bounded turbulent shear flows. A spectral numerical method with about one-million modes was employed, and no explicit subgrid scale model was used. The effects of <span class="hlt">curvature</span> on this flow were determined by comparing the concave and convex sides of the channel. The observed effects are consistent with experimental observations for mild <span class="hlt">curvature</span>. The most significant difference in the turbulence statistics between the concave and convex sides is in the Reynolds shear stress. This is accompanied by significant differences in the terms of the Reynolds shear stress balance equations. In addition, it was found that stationary Taylor-Goertler vortices were present and that they had a significant effect on the flow by contributing to the mean Reynolds shear stress, and by enhancing the difference between the wall shear stresses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.......197G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......197G"><span><span class="hlt">Regional</span> Climate Modeling over the Glaciated <span class="hlt">Regions</span> of the Canadian <span class="hlt">High</span> Arctic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gready, Benjamin P.</p> <p></p> <p>The Canadian Arctic Islands (CAI) contain the largest concentration of terrestrial ice outside of the continental ice sheets. Mass loss from this <span class="hlt">region</span> has recently increased sharply due to above average summer temperatures. Thus, increasing the understanding of the mechanisms responsible for mass loss from this <span class="hlt">region</span> is critical. Previously, <span class="hlt">Regional</span> Climate Models (RCMs) have been utilized to estimate climatic balance over Greenland and Antarctica. This method offers the opportunity to study a full suite of climatic variables over extensive spatially distributed grids. However, there are doubts of the applicability of such models to the CAI, given the relatively complex topography of the CAI. To test RCMs in the CAI, the polar version of the <span class="hlt">regional</span> climate model MM5 was run at <span class="hlt">high</span> resolution over Devon Ice Cap. At low altitudes, residuals (computed through comparisons with in situ measurements) in the net radiation budget were driven primarily by residuals in net shortwave (NSW) radiation. Residuals in NSW are largely due to inaccuracies in modeled cloud cover and modeled albedo. Albedo on glaciers and ice sheets is oversimplified in Polar MM5 and its successor, the Polar version of the Weather Research and Forecast model (Polar WRF), and is an obvious place for model improvement. Subsequently, an inline parameterization of albedo for Polar WRF was developed as a function of the depth, temperature and age of snow. The parameterization was able to reproduce elevation gradients of seasonal mean albedo derived from satellite albedo measurements (MODIS MOD10A1 daily albedo), on the western slope of the Greenland Ice Sheet for three years. Feedbacks between modelled albedo and modelled surface energy budget components were identified. The shortwave radiation flux feeds back positively with changes to albedo, whereas the longwave, turbulent and ground energy fluxes all feed back negatively, with a maximum combined magnitude of two thirds of the shortwave feedback</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24867633','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24867633"><span>The effect of anterior cruciate ligament injury on bone <span class="hlt">curvature</span>: exploratory analysis in the KANON trial.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hunter, D J; Lohmander, L S; Makovey, J; Tamez-Peña, J; Totterman, S; Schreyer, E; Frobell, R B</p> <p>2014-07-01</p> <p>Investigate the 5-year longitudinal changes in bone <span class="hlt">curvature</span> after acute anterior cruciate ligament (ACL) injury, and identify predictors of such changes. In the KANON-trial (ISRCTN 84752559), 111/121 young active adults with an acute ACL tear to a previously un-injured knee had serial 1.5 T MR images from baseline (within 5 weeks from injury) to 5 years after injury. Of these, 86 had ACL reconstruction (ACLR) performed early or delayed, 25 were treated with rehabilitation alone. Measures of articulating bone <span class="hlt">curvature</span> were obtained from computer-assisted segmentation of MR images. <span class="hlt">Curvature</span> (mm(-1)) was determined for femur, tibia, medial/lateral femur, trochlea, medial/lateral tibia. Age, sex, treatment, BMI, meniscal injury, osteochondral fracture on baseline MR images were tested for association. Over 5 years, <span class="hlt">curvature</span> decreased in each <span class="hlt">region</span> (P < 0.001) suggesting flattening of convex shapes and increased concavity of concave shapes. A higher BMI was associated with flattening of the femur (P = 0.03), trochlea (P = 0.007) and increasing concavity of the lateral tibia (LT) (P = 0.011). ACLR, compared to rehabilitation alone, was associated with flatter <span class="hlt">curvature</span> in the femur (P < 0.001), medial femoral condyle (P = 0.006) and trochlea (P = 0.003). Any meniscal injury at baseline was associated with a more flattened <span class="hlt">curvature</span> in the femur (P = 0.038), trochlea (P = 0.039), lateral femoral condyle (P = 0.034) and increasing concavity of the LT (P = 0.048). ACL injury is associated with significant changes in articulating bone <span class="hlt">curvature</span> over a 5 year period. Higher BMI, baseline meniscal injury and undergoing ACL reconstruction (as distinct from undergoing rehabilitation alone) are all associated with flattening of the articulating bone. Copyright © 2014 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26546679','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26546679"><span>Sar1 GTPase Activity Is Regulated by Membrane <span class="hlt">Curvature</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hanna, Michael G; Mela, Ioanna; Wang, Lei; Henderson, Robert M; Chapman, Edwin R; Edwardson, J Michael; Audhya, Anjon</p> <p>2016-01-15</p> <p>The majority of biosynthetic secretory proteins initiate their journey through the endomembrane system from specific subdomains of the endoplasmic reticulum. At these locations, coated transport carriers are generated, with the Sar1 GTPase playing a critical role in membrane bending, recruitment of coat components, and nascent vesicle formation. How these events are appropriately coordinated remains poorly understood. Here, we demonstrate that Sar1 acts as the <span class="hlt">curvature</span>-sensing component of the COPII coat complex and highlight the ability of Sar1 to bind more avidly to membranes of <span class="hlt">high</span> <span class="hlt">curvature</span>. Additionally, using an atomic force microscopy-based approach, we further show that the intrinsic GTPase activity of Sar1 is necessary for remodeling lipid bilayers. Consistent with this idea, Sar1-mediated membrane remodeling is dramatically accelerated in the presence of its guanine nucleotide-activating protein (GAP), Sec23-Sec24, and blocked upon addition of guanosine-5'-[(β,γ)-imido]triphosphate, a poorly hydrolysable analog of GTP. Our results also indicate that Sar1 GTPase activity is stimulated by membranes that exhibit elevated <span class="hlt">curvature</span>, potentially enabling Sar1 membrane scission activity to be spatially restricted to <span class="hlt">highly</span> bent membranes that are characteristic of a bud neck. Taken together, our data support a stepwise model in which the amino-terminal amphipathic helix of GTP-bound Sar1 stably penetrates the endoplasmic reticulum membrane, promoting local membrane deformation. As membrane bending increases, Sar1 membrane binding is elevated, ultimately culminating in GTP hydrolysis, which may destabilize the bilayer sufficiently to facilitate membrane fission. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6869I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6869I"><span>Alterations in braided rivers' morphology: a typology for <span class="hlt">Curvature</span> Subcarpathians (Romania)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ioana-Toroimac, Gabriela; Zaharia, Liliana; Ciobotaru, Nicu</p> <p>2015-04-01</p> <p>The morphology of braided rivers was altered by human pressures in the last century in Europe. Rivers from <span class="hlt">Curvature</span> Subcarpathians have the highest sediment charges in Romania, therefore it seems relevant to evaluate the status of their braided sectors. Therefore, the aim of this work is to carry out an inventory of river morphology alterations suffered by braided rivers in <span class="hlt">Curvature</span> Subcarpathians and to establish a typology based on indicators for channel adjustments and artificiality. For channel adjustments, we calculated the length of the braided sectors, the width of the active-channels and the length of banks covered by a riparian forest for 1900-2011 interval, in GIS. For artificiality, we counted dams, weirs, bridges, as well as artificial banks length for 2011 time horizon. The results indicate a diminishing braiding activity: all the rivers narrowed their braided active-channel (30-70% of the mean width); the majority suffered fluvial metamorphosis, transforming partially into single channels (0-75% of the braided sector length in 1900); artificial banks vary from 0 to 40% of the initial braided sector. We distinguished three main types of braided rivers based on morphological alterations. Type 1 includes rivers with human interventions and important braiding retraction, both upstream and downstream; a sub-type characterises by riparian forest lining the downstream metamorphosed reach; most rivers are in the south-western part of the studied <span class="hlt">region</span>; the most demonstrative examples are Prahova and Ialomiţa rivers. Type 2 corresponds to rivers with important retraction upstream, without important values of artificiality; most demonstrative is Râmna River. Type 3 regroups rivers with a low level of channel adjustments and artificiality; actually, they had and still have the highest braiding activity in the studied <span class="hlt">region</span>; they are located in the north-eastern part; typical examples are Putna and Şuşiţa rivers. As a discussion, the variations of active</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C51G..02C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C51G..02C"><span>Unraveling glacier change signals in <span class="hlt">high</span>-mountain <span class="hlt">regions</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Collier, S. E.; Moelg, T.; Sauter, T.</p> <p>2016-12-01</p> <p>A key challenge for the climatological and glaciological communities is the detection and attribution of climate change, which is the effort to decompose environmental signals into an anthropogenic component and a component due to internal modes of atmospheric variability, such as climate oscillations. This challenge is especially great in <span class="hlt">high</span>-mountain <span class="hlt">regions</span>, where observational data are sparse but environmental changes such as glacier retreat have the potential to strongly impact human populations. Using a case study of Kilimanjaro in East Africa, we employ an interdisciplinary approach to unraveling recent climate and glacier-change signals, combining sub-kilometer resolution atmospheric simulations, in situ measurements, and physically based glacier mass balance modelling over a decadal period. We use these datasets to assess the impact of the El Niño Southern Oscillation and the Indian Ocean Zonal Mode, as well as interactions between them, on large- and local-glacier-scale atmospheric conditions and therefore drivers of glacier change. Elucidating the present-day impact of internal climate variability at <span class="hlt">high</span> altitudes is key for understanding local phenomena and will permit more accurate assessments of external forcing factors, including future projections.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820043791&hterms=streaming&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dstreaming','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820043791&hterms=streaming&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dstreaming"><span>Free-streaming radiation in cosmological models with spatial <span class="hlt">curvature</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilson, M. L.</p> <p>1982-01-01</p> <p>The effects of spatial <span class="hlt">curvature</span> on radiation anisotropy are examined for the standard Friedmann-Robertson-Walker model universes. The effect of <span class="hlt">curvature</span> is found to be very important when considering fluctuations with wavelengths comparable to the horizon. It is concluded that the behavior of radiation fluctuations in models with spatial <span class="hlt">curvature</span> is quite different from that in spatially flat models, and that models with negative <span class="hlt">curvature</span> are most strikingly different. It is therefore necessary to take the <span class="hlt">curvature</span> into account in careful studies of the anisotropy of the microwave background.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JAMTP..58...31P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JAMTP..58...31P"><span>Influence of the size and wall <span class="hlt">curvature</span> of nanopores on the gas distribution pattern in them</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Psakh'e, S. G.; Zol'nikov, K. P.; Korchuganov, A. V.; Kryzhevich, D. S.; Grinyaev, Yu. V.</p> <p>2017-01-01</p> <p>The behavior of hydrogen molecules in carbon nanopores of different shapes (slit-shaped, cylindrical, and spherical) is investigated using the molecular dynamics method. It is shown that an adsorbed molecular layer with increased density is formed near the nanopore walls, and dynamic equilibrium is established between this layer and the gas in the central <span class="hlt">region</span> of the nanopore. The distribution of the density of gas molecules over the cross section is found to depend on the size and wall <span class="hlt">curvature</span> of nanopores: with a reduction in the nanopore size, the density of the adsorbate increases more rapidly in spherical nanopores, whose walls are characterized by greater mean <span class="hlt">curvature</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100032963','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100032963"><span>Impact of <span class="hlt">High</span> Resolution SST Data on <span class="hlt">Regional</span> Weather Forecasts</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jedlovec, Gary J.; Case, Jonathon; LaFontaine, Frank; Vazquez, Jorge; Mattocks, Craig</p> <p>2010-01-01</p> <p>Past studies have shown that the use of coarse resolution SST products such as from the real-time global (RTG) SST analysis[1] or other coarse resolution once-a-day products do not properly portray the diurnal variability of fluxes of heat and moisture from the ocean that drive the formation of low level clouds and precipitation over the ocean. For example, the use of <span class="hlt">high</span> resolution MODIS SST composite [2] to initialize the Advanced Research Weather Research and Forecast (WRF) (ARW) [3] has been shown to improve the prediction of sensible weather parameters in coastal <span class="hlt">regions</span> [4][5}. In an extend study, [6] compared the MODIS SST composite product to the RTG SST analysis and evaluated forecast differences for a 6 month period from March through August 2007 over the Florida coastal <span class="hlt">regions</span>. In a comparison to buoy data, they found that that the MODIS SST composites reduced the bias and standard deviation over that of the RTG data. These improvements led to significant changes in the initial and forecasted heat fluxes and the resulting surface temperature fields, wind patterns, and cloud distributions. They also showed that the MODIS composite SST product, produced for the Terra and Aqua satellite overpass times, captured a component of the diurnal cycle in SSTs not represented in the RTG or other one-a-day SST analyses. Failure to properly incorporate these effects in the WRF initialization cycle led to temperature biases in the resulting short term forecasts. The forecast impact was limited in some situations however, due to composite product inaccuracies brought about by data latency during periods of long-term cloud cover. This paper focuses on the forecast impact of an enhanced MODIS/AMSR-E composite SST product designed to reduce inaccuracies due data latency in the MODIS only composite product.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatCo...6E8753O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatCo...6E8753O"><span>Unusually <span class="hlt">high</span> soil nitrogen oxide emissions influence air quality in a <span class="hlt">high</span>-temperature agricultural <span class="hlt">region</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oikawa, P. Y.; Ge, C.; Wang, J.; Eberwein, J. R.; Liang, L. L.; Allsman, L. A.; Grantz, D. A.; Jenerette, G. D.</p> <p>2015-11-01</p> <p>Fertilized soils have large potential for production of soil nitrogen oxide (NOx=NO+NO2), however these emissions are difficult to predict in <span class="hlt">high</span>-temperature environments. Understanding these emissions may improve air quality modelling as NOx contributes to formation of tropospheric ozone (O3), a powerful air pollutant. Here we identify the environmental and management factors that regulate soil NOx emissions in a <span class="hlt">high</span>-temperature agricultural <span class="hlt">region</span> of California. We also investigate whether soil NOx emissions are capable of influencing <span class="hlt">regional</span> air quality. We report some of the highest soil NOx emissions ever observed. Emissions vary nonlinearly with fertilization, temperature and soil moisture. We find that a <span class="hlt">regional</span> air chemistry model often underestimates soil NOx emissions and NOx at the surface and in the troposphere. Adjusting the model to match NOx observations leads to elevated tropospheric O3. Our results suggest management can greatly reduce soil NOx emissions, thereby improving air quality.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4659929','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4659929"><span>Unusually <span class="hlt">high</span> soil nitrogen oxide emissions influence air quality in a <span class="hlt">high</span>-temperature agricultural <span class="hlt">region</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Oikawa, P. Y.; Ge, C.; Wang, J.; Eberwein, J. R.; Liang, L. L.; Allsman, L. A.; Grantz, D. A.; Jenerette, G. D.</p> <p>2015-01-01</p> <p>Fertilized soils have large potential for production of soil nitrogen oxide (NOx=NO+NO2), however these emissions are difficult to predict in <span class="hlt">high</span>-temperature environments. Understanding these emissions may improve air quality modelling as NOx contributes to formation of tropospheric ozone (O3), a powerful air pollutant. Here we identify the environmental and management factors that regulate soil NOx emissions in a <span class="hlt">high</span>-temperature agricultural <span class="hlt">region</span> of California. We also investigate whether soil NOx emissions are capable of influencing <span class="hlt">regional</span> air quality. We report some of the highest soil NOx emissions ever observed. Emissions vary nonlinearly with fertilization, temperature and soil moisture. We find that a <span class="hlt">regional</span> air chemistry model often underestimates soil NOx emissions and NOx at the surface and in the troposphere. Adjusting the model to match NOx observations leads to elevated tropospheric O3. Our results suggest management can greatly reduce soil NOx emissions, thereby improving air quality. PMID:26556236</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26556236','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26556236"><span>Unusually <span class="hlt">high</span> soil nitrogen oxide emissions influence air quality in a <span class="hlt">high</span>-temperature agricultural <span class="hlt">region</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Oikawa, P Y; Ge, C; Wang, J; Eberwein, J R; Liang, L L; Allsman, L A; Grantz, D A; Jenerette, G D</p> <p>2015-11-10</p> <p>Fertilized soils have large potential for production of soil nitrogen oxide (NOx=NO+NO2), however these emissions are difficult to predict in <span class="hlt">high</span>-temperature environments. Understanding these emissions may improve air quality modelling as NOx contributes to formation of tropospheric ozone (O3), a powerful air pollutant. Here we identify the environmental and management factors that regulate soil NOx emissions in a <span class="hlt">high</span>-temperature agricultural <span class="hlt">region</span> of California. We also investigate whether soil NOx emissions are capable of influencing <span class="hlt">regional</span> air quality. We report some of the highest soil NOx emissions ever observed. Emissions vary nonlinearly with fertilization, temperature and soil moisture. We find that a <span class="hlt">regional</span> air chemistry model often underestimates soil NOx emissions and NOx at the surface and in the troposphere. Adjusting the model to match NOx observations leads to elevated tropospheric O3. Our results suggest management can greatly reduce soil NOx emissions, thereby improving air quality.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.H13H1511H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.H13H1511H"><span>Multiscale Lagrangian Statistics of <span class="hlt">Curvature</span> Angle in Direct Numerical Simulation of Pore-Scale Turbulence</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>He, X.; Kadoch, B.; Apte, S.; Farge, M.; Schneider, K.</p> <p>2016-12-01</p> <p>Direct Numerical Simulations (DNS) of flow through a periodic face centered cubic (FCC) unit cell at Reynolds numbers of 300, 500 and 1000 are conducted to investigate porescale turbulent flow physics. The simulations are performed using a fictitious domain approach [Apte et al, J. Comp. Physics 2009], which uses non-body conforming Cartesian grids. The flowfield involves <span class="hlt">regions</span> of rapid acceleration and decelerations, separated flow and jet-impingement like flow features. Lagrangian statistics of scale dependent <span class="hlt">curvature</span> angle and acceleration are calculated by tracking a large number of fluid particle trajectories. For isotropic turbulence, it has been shown [Bos et al. 2015, PRL] that the mean <span class="hlt">curvature</span> angle varies linearly with time initially, reaches an inertial range and asymptotes to a value of π /2 at long times, corresponding to the decorrelation and equipartition of the cosine of the <span class="hlt">curvature</span> angle. Similar trends are observed at early times for turbulence in porous medium; however, the mean <span class="hlt">curvature</span> angle asymptotes to a value larger than π /2, due to the effect of confinement on the fluid particle trajectories that result in preferred directions at large times. A Monte-Carlo based stochastic model to predict the long-time behavior of <span class="hlt">curvature</span> angles is developed. It is shown to correctly predict an angle larger than π /2 at large times consistent with the Lagrangian statistics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE10158E..1DF','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE10158E..1DF"><span>A few mode fiber <span class="hlt">curvature</span> sensor based on two spherical-shape structures modal interferometer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fu, Xinghu; Wang, Siwen; Zhang, Shunyang; Liu, Qin; Li, Qifeng; Xie, Haiyang; Fu, Guangwei; Bi, Weihong; Li, Yanjun</p> <p>2016-10-01</p> <p>In order to improve the equilibrium between fiber sensor performance and cost, a <span class="hlt">curvature</span> sensor based on Few Mode Fiber(FMF) is proposed. A length of FMF is spliced with waist enlarge between two Single mode Fibers(SMFs) to form two spherical- shape structure. Fiber core mode interfere with clad mode due to the excite and couple function of spherical-shape structure, respectively. The phase difference between the cladding and core <span class="hlt">regions</span> of the fiber changes with the external strain increase, and then the interference spectrum changes. Two sensors with different length of FMF are fabricated, and the transmission spectrum are obtained. The result shows the optical power at certain wavelength is increasing with the <span class="hlt">curvature</span> increasing. When the <span class="hlt">curvature</span> range is 0 0.42m-1 and the FMF is 5.7cm, the <span class="hlt">curvature</span> sensitivity can be 11.22dB/m-1. When the FMF is 5.9cm, the <span class="hlt">curvature</span> sensitivity can be climbed to 14.08dB/m-1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013IJGMM..1050044R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013IJGMM..1050044R"><span>On the Riemann <span class="hlt">Curvature</span> Operators in Randers Spaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rafie-Rad, M.</p> <p>2013-05-01</p> <p>The Riemann <span class="hlt">curvature</span> in Riemann-Finsler geometry can be regarded as a collection of linear operators on the tangent spaces. The algebraic properties of these operators may be linked to the geometry and the topology of the underlying space. The principal <span class="hlt">curvatures</span> of a Finsler space (M, F) at a point x are the eigenvalues of the Riemann <span class="hlt">curvature</span> operator at x. They are real functions κ on the slit tangent manifold TM0. A principal <span class="hlt">curvature</span> κ(x, y) is said to be isotropic (respectively, quadratic) if κ(x, y)/F(x, y) is a function of x only (respectively, κ(x, y) is quadratic with respect to y). On the other hand, the Randers metrics are the most popular and prominent metrics in pure and applied disciplines. Here, it is proved that if a Randers metric admits an isotropic principal <span class="hlt">curvature</span>, then F is of isotropic S-<span class="hlt">curvature</span>. The same result is also established for F to admit a quadratic principal <span class="hlt">curvature</span>. These results extend Shen's verbal results about Randers metrics of scalar flag <span class="hlt">curvature</span> K = K(x) as well as those Randers metrics with quadratic Riemann <span class="hlt">curvature</span> operator. The Riemann <span class="hlt">curvature</span> Rik may be broken into two operators Rik and Jik. The isotropic and quadratic principal <span class="hlt">curvature</span> are characterized in terms of the eigenvalues of R and J.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3334380','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3334380"><span>A Novel Quantitative Measure of Breast <span class="hlt">Curvature</span> Based on Catenary</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lee, Juhun; Chen, Si; Reece, Gregory P.; Crosby, Melissa A.; Beahm, Elisabeth K.</p> <p>2012-01-01</p> <p>Quantitative, objective measurements of breast <span class="hlt">curvature</span> computed from clinical photographs could be used to investigate factors that impact reconstruction and facilitate surgical planning. This paper introduces a novel quantitative measure of breast <span class="hlt">curvature</span> based on catenary. A catenary curve is used to approximate the overall <span class="hlt">curvature</span> of the breast contour, and the <span class="hlt">curvature</span> measure is extracted from the catenary curve. The catenary curve was verified by comparing its length, the area enclosed by the curve, and the <span class="hlt">curvature</span> measure from the catenary curve to those from manual tracings of the breast contour. The evaluation of the proposed analysis employed untreated and postoperative clinical photographs of women who were undergoing tissue expander/implant (TE/Implant) reconstruction. Logistic regression models were developed to distinguish between the <span class="hlt">curvature</span> of breasts undergoing TE/Implant reconstruction and that of untreated breasts based on the <span class="hlt">curvature</span> measure and patient variables (age and body mass index). The relationships between the <span class="hlt">curvature</span> measures of untreated breasts and patient variables were also investigated. The catenary curve approximates breast <span class="hlt">curvature</span> reliably. The <span class="hlt">curvature</span> measure contains useful information for quantifying the <span class="hlt">curvature</span> differences between breasts undergoing TE/Implant reconstruction and untreated breasts, and identifying the effect of patient variables on the breast shape. PMID:22271826</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22271826','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22271826"><span>A novel quantitative measure of breast <span class="hlt">curvature</span> based on catenary.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, Juhun; Chen, Si; Reece, Gregory P; Crosby, Melissa A; Beahm, Elisabeth K; Markey, Mia K</p> <p>2012-04-01</p> <p>Quantitative, objective measurements of breast <span class="hlt">curvature</span> computed from clinical photographs could be used to investigate factors that impact reconstruction and facilitate surgical planning. This paper introduces a novel quantitative measure of breast <span class="hlt">curvature</span> based on catenary. A catenary curve is used to approximate the overall <span class="hlt">curvature</span> of the breast contour, and the <span class="hlt">curvature</span> measure is extracted from the catenary curve. The catenary curve was verified by comparing its length, the area enclosed by the curve, and the <span class="hlt">curvature</span> measure from the catenary curve to those from manual tracings of the breast contour. The evaluation of the proposed analysis employed untreated and postoperative clinical photographs of women who were undergoing tissue expander/implant (TE/Implant) reconstruction. Logistic regression models were developed to distinguish between the <span class="hlt">curvature</span> of breasts undergoing TE/Implant reconstruction and that of untreated breasts based on the <span class="hlt">curvature</span> measure and patient variables (age and body mass index). The relationships between the <span class="hlt">curvature</span> measures of untreated breasts and patient variables were also investigated. The catenary curve approximates breast <span class="hlt">curvature</span> reliably. The <span class="hlt">curvature</span> measure contains useful information for quantifying the <span class="hlt">curvature</span> differences between breasts undergoing TE/Implant reconstruction and untreated breasts, and identifying the effect of patient variables on the breast shape.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26590553','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26590553"><span><span class="hlt">Curvature</span> inducing macroion condensation driven shape changes of fluid vesicles.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sreeja, K K; Ipsen, John H; Sunil Kumar, P B</p> <p>2015-11-21</p> <p>We study the effect of <span class="hlt">curvature</span> inducing macroion condensation on the shapes of charged deformable fluid interfaces using dynamically triangulated Monte Carlo simulations. In the weak electrostatic coupling regime, surface charges are weakly screened and the conformations of a vesicle, with fixed spherical topology, depend on the charge-charge interaction on the surface. While in the strong coupling regime, condensation driven <span class="hlt">curvature</span> induction plays a dominant role in determining the conformations of these surfaces. Condensation itself is observed to be dependent on the induced <span class="hlt">curvature</span>, with larger induced <span class="hlt">curvatures</span> favoring increased condensation. We show that both <span class="hlt">curvature</span> generation and <span class="hlt">curvature</span> sensing, induced by the interplay of electrostatics and <span class="hlt">curvature</span> energy, contribute to determination of the vesicle configurations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDKP1056S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDKP1056S"><span>Optimal Spatial Scale for <span class="hlt">Curvature</span> Calculations in Multiphase Flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Senecal, Jacob; Owkes, Mark</p> <p>2016-11-01</p> <p>In gas-liquid flows, the surface tension force often controls the dynamics of the flow and an accurate calculation of this force is necessary for predictive simulations. The surface tension force is directly proportional to the <span class="hlt">curvature</span> of the gas-liquid interface, making accurate <span class="hlt">curvature</span> calculations an essential consideration. Multiple methods have been developed to calculate the <span class="hlt">curvature</span> of volume of fluid (VoF) interface capturing schemes, such as the height function method. These methods have been extensively tested. However, the impact of the scale or size of computational stencil on which the <span class="hlt">curvature</span> is computed, has not been correlated with the rate at which interface perturbations relax under the surface tension force. In this work, the effect of varying the scale on which the <span class="hlt">curvature</span> is computed has been tested and quantified. An optimal <span class="hlt">curvature</span> scale is identified that leads to accurate and converging <span class="hlt">curvatures</span>, and accurate timescales for surface tension induced, interface dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18002425','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18002425"><span>Investigation of catheter <span class="hlt">curvature</span> and genetic algorithms in conductance catheter optimization.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thaijiam, C; Gale, T J</p> <p>2007-01-01</p> <p>Catheter <span class="hlt">curvature</span> affects accuracy of intra-ventricular blood volume measurement when using conductance catheter techniques, especially with irregular geometries, such as in the right ventricle. To investigate this effect, we present results from using different curved catheter configurations and different numbers of electrodes in a simple Finite Element model. It was found that there is an apparent increase in accuracy with <span class="hlt">curvature</span>, due to greater linearity in the field in the <span class="hlt">region</span> of the measurement electrodes, which are located farther from the source electrodes as <span class="hlt">curvature</span> increases. Also, optimization using Genetic Algorithms is presented as a method to find the optimal distribution of measurement electrodes. We plan to extend these results to develop improved electrode configurations for using in blood volume measurement in the right ventricle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23948838','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23948838"><span>Does the presence of a vertical barrier influence sagittal spinal <span class="hlt">curvature</span> or range of motion in young females?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Williams, Jonathan M; Theobald, Peter S; Jones, Michael D</p> <p>2014-01-01</p> <p>Lifting presents a significant risk for the development of low back pain. It is not known what effect lifting from a supermarket shopping trolley has on sagittal spinal <span class="hlt">curvature</span>. The aim of this study is to determine the effect of lifting from a shopping trolley on sagittal spinal <span class="hlt">curvature</span>. Fifteen female subjects (height 1.67 ± 0.04 m, weight 64.3 ± 5.0 kg) completed lifts of 9 kg from a shopping trolley and a surface matched for height whilst sagittal spinal <span class="hlt">curvature</span> was measured using Qualysis motion analysis system. Seven retro-reflective markers were placed along spine with angle between three markers representing <span class="hlt">regional</span> <span class="hlt">curvature</span>. No constraints on lifting technique were instigated. Results demonstrate no difference in sagittal range of motion or spinal <span class="hlt">curvature</span> across the two lifts. A small but significant difference in knee flexion angle was observed. These results demonstrate that the chosen lifting strategy was not influenced by the constraint imposed by the shopping trolley. Furthermore the function of knee flexion did not result in change in sagittal <span class="hlt">curvature</span> during the lifts. Lifting from a shopping trolley has no effect of sagittal spinal <span class="hlt">curvature</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT........72R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT........72R"><span>Plasma simulations of emission line <span class="hlt">regions</span> in <span class="hlt">high</span> energy environments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Richardson, Chris T.</p> <p></p> <p>This dissertation focuses on understanding two different, but in each case extreme, astrophysical environments: the Crab Nebula and emission line galaxies. These relatively local objects are well constrained by observations and are test cases of phenomena seen at <span class="hlt">high</span>-z where detailed observations are rare. The tool used to study these objects is the plasma simulation code known as Cloudy. The introduction provides a brief summary of relevant physical concepts in nebular astrophysics and presents the basic features and assumptions of Cloudy. The first object investigated with Cloudy, the Crab Nebula, is a nearby supernova remnant that previously has been subject to photoionization modeling to reproduce the ionized emission seen in the nebula's filamentary structure. However, there are still several unanswered questions: (1) What excites the H2 emitting gas? (2) How much mass is in the molecular component? (3) How did the H2 form? (4) What is nature of the dust grains? A large suite of observations including long slit optical and NIR spectra over ionized, neutral and molecular gas in addition to HST and NIR ground based images constrain a particularly bright <span class="hlt">region</span> of H2 emission, Knot 51, which exhibits a <span class="hlt">high</span> excitation temperature of ˜3000 K. Simulations of K51 revealed that only a trace amount of H2 is needed to reproduce the observed emission and that H2 forms through an uncommon nebular process known as associative detachment. The final chapters of this dissertation focus on interpreting the narrow line <span class="hlt">region</span> (NLR) in low-z emission line galaxies selected by a novel technique known as mean field independent component analysis (MFICA). A mixture of starlight and radiation from an AGN excites the gas present in galaxies. MFICA separates galaxies over a wide range of ionization into subsets of pure AGN and pure star forming galaxies allowing simulations to reveal the properties responsible for their observed variation in ionization. Emission line ratios can</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810485B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810485B"><span>Extraction of "best fit circles" on 3D meshes based on discrete <span class="hlt">curvatures</span>: application to impact craters detection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beguet, Florian; Bali, Sarah; Christoff, Nicole; Jorda, Laurent; Viseur, Sophie; Bouley, Sylvain; Manolova, Agata; Mari, Jean-Luc</p> <p>2016-04-01</p> <p>Impact craters is a typical feature observed at the surface of most bodies in the solar system: terrestrial planets, their satellites, asteroids and even possibly cometary nuclei exhibit impact craters. Their spatial density yields the estimation of the age of the surface, a key parameter required for subsequent geological studies. With the development of interplanetary missions, a large number of solar system objects have been mapped at a <span class="hlt">high</span> spatial resolution, emphasizing the need for new automatic methods of crater detection and counting. In this work, we present such a method using a new approach based on the analysis of reconstructed 3D meshes instead of 2D images. The robust extraction of feature areas on surface objects embedded in 3D, like circular shapes, is a challenging problem. Classical approaches generally rely on image processing and template matching on a 2D flat projection of the 3D object (for instance a <span class="hlt">high</span>-resolution picture). In this paper, we propose a full 3D method that mainly relies on <span class="hlt">curvature</span> analysis. Mean and Gaussian <span class="hlt">curvatures</span> are estimated on the surface. They are used to label vertices that belong to concave parts corresponding to specific pits on the surface. Centers are located in the targeted surface <span class="hlt">regions</span>, corresponding to potential crater features. Then "best fit circles" are extracted, based on the rims of the circular shapes. They consist in closed lines exclusively composed of edges of the initial mesh. This approach has been applied to the detection of craters on the asteroid Vesta. Keywords: geometric modeling, 3D meshes, shape recognition, mesh processing, discrete <span class="hlt">curvatures</span>, asteroids, crater detection, geology, geomorphology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3169039','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3169039"><span>Temporal changes in greenspace in a <span class="hlt">highly</span> urbanized <span class="hlt">region</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Dallimer, Martin; Tang, Zhiyao; Bibby, Peter R.; Brindley, Paul; Gaston, Kevin J.; Davies, Zoe G.</p> <p>2011-01-01</p> <p>The majority of the world's population now lives in towns and cities, and urban areas are expanding faster than any other land-use type. In response to this phenomenon, two opposing arguments have emerged: whether cities should ‘sprawl’ into the wider countryside, or ‘densify’ through the development of existing urban greenspace. However, these greenspaces are increasingly recognized as being central to the amelioration of urban living conditions, supporting biodiversity conservation and ecosystem service provision. Taking the <span class="hlt">highly</span> urbanized <span class="hlt">region</span> of England as a case study, we use data from a variety of sources to investigate the impact of national-level planning policy on temporal patterns in the extent of greenspace in cities. Between 1991 and 2006, greenspace showed a net increase in all but one of 13 cities. However, the majority of this gain occurred prior to 2001, and greenspace has subsequently declined in nine cities. Such a dramatic shift in land use coincides with policy reforms in 2000, which favoured densification. Here, we illustrate the dynamic and policy-responsive nature of urban land use, thereby highlighting the need for a detailed investigation of the trade-offs associated with different mechanisms of urban densification to optimize and secure the diverse benefits associated with greenspaces. PMID:21429910</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5762520','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5762520"><span><span class="hlt">High</span> altitude plume emissions in atmospheric-window <span class="hlt">region</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sharma, R.D.; Bakshi, P.; Sindoni, J.</p> <p>1989-02-01</p> <p>Quantum-Mechanical Spectator model (Impulse Approximation) is used to calculate the cross section for rotation-vibration excitation of CO during collision with atomic oxygen at relative velocity (energy) of 5 (1.3), 8 (3.3), 11 (5.3), and 14 km/s (10.2 eV). The calculation is carried out for initial CO vibrational level v=o and rotational levels J=O and J=10 and final vibrational levels v'=o - 6 and final rotational levels up to J'=100. It is shown that the final results are almost independent of the initial rotational level. The rotational distribution in the final vibrational levels is rather flat and cannot be described by a Maxwell-Boltzmann distribution. The final rotation-vibration distributions are translated into relative emission in the 4.7-micron <span class="hlt">region</span>. The emitted radiation from each level shows an R-branch bandhead around 4.4 microns with P-branch extending beyond 6 microns. It is expected that carbon dioxide and water generated by the plumes at <span class="hlt">high</span> altitudes, upon collision with atomic oxygen, would also emit band infrared radiation around 6, 4.3, and 2.7 microns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007PhDT.......175D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007PhDT.......175D"><span><span class="hlt">High</span> resolution studies of complex solar active <span class="hlt">regions</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deng, Na</p> <p></p> <p>Flares and Coronal Mass Ejections (CMEs) are energetic events, which can even impact the near-Earth environment and are the principal source of space weather. Most of them originate in solar active <span class="hlt">regions</span>. The most violent events are produced in sunspots with a complex magnetic field topology. Studying their morphology and dynamics is helpful in understanding the energy accumulation and release mechanisms for flares and CMEs, which are intriguing problems in solar physics. The study of complex active <span class="hlt">regions</span> is based on <span class="hlt">high</span>-resolution observations from space missions and new instruments at the Big Bear Solar Observatory (BBSO). Adaptive optics (AO) in combination with image restoration techniques (speckle masking imaging) can achieve improved image quality and a spatial resolution (about 100 km on the solar surface) close to the diffraction limit of BBSO's 65 cm vacuum telescope. Dopplergrams obtained with a two-dimensional imaging spectrometer combined with horizontal flow maps derived with Local Correlation Tracking (LCT) provide precise measurements of the three-dimensional velocity field in sunspots. Magnetic field measurements from ground- and space-based instruments complement these data. At the outset of this study, the evolution and morphology of a typical round sunspot are described in some detail. The sunspot was followed from disk center to the limb, thus providing some insight into the geometry of the magnetic flux system. Having established a benchmark for a stable sunspot, the attention is turned to changes of the sunspot structure associated with flares and CMEs. Rapid penumbral decay and the strengthening of sunspot umbrae are manifestations of photospheric magnetic field changes after a flare. These sudden intensity changes are interpreted as a result of magnetic reconnection during the flare, which causes the magnetic field lines to be turned from more inclined to more vertical. Strong photospheric shear flows along the flaring magnetic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SPIE.9678E..07Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SPIE.9678E..07Z"><span>Annular force based variable <span class="hlt">curvature</span> mirror aiming to realize non-moving element optical zooming</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Hui; Xie, Xiaopeng; Wei, Jingxuan; Ren, Guorui; Pang, Zhihai; Xu, Liang</p> <p>2015-10-01</p> <p>Recently, a new kind of optical zooming technique in which no moving elements are involved has been paid much attention. The elimination of moving elements makes optical zooming suitable for applications which has exacting requirements in space, power cost and system stability. The mobile phone and the space-borne camera are two typical examples. The key to realize non-moving elements optical zooming lies in the introduction of variable <span class="hlt">curvature</span> mirror (VCM) whose radius of <span class="hlt">curvature</span> could be changed dynamically. When VCM is about to be used to implement optical zoom imaging, two characteristics should be ensured. First, VCM has to provide large enough saggitus variation in order to obtain a big magnification ratio. Second, after the radius of <span class="hlt">curvature</span> has been changed, the corresponding surface figure accuracy should still be maintained superior to a threshold level to make the <span class="hlt">high</span> quality imaging possible. In this manuscript, based on the elasticity theory, the physical model of the annular force based variable <span class="hlt">curvature</span> mirror is established and numerically analyzed. The results demonstrate that when the annular force is applied at the half-the-aperture position, the actuation force is reduced and a smaller actuation force is required to generate the saggitus variation and thus the maintenance of surface figure accuracy becomes easier during the variation of radius of <span class="hlt">curvature</span>. Besides that, a prototype VCM, whose diameter and thickness are 100mm and 3mm respectively, have been fabricated and the maximum saggitus variation that could be obtained approaches more than 30 wavelengths. At the same time, the degradation of surface figure accuracy is weakly correlated to the <span class="hlt">curvature</span> radius variation. Keywords: optical zooming; variable <span class="hlt">curvature</span> mirror; surface figure accuracy; saggitus;</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AIPC.1252..868Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AIPC.1252..868Z"><span>A Method of Springback Prediction and Tool Shape Compensation for Multi-<span class="hlt">curvature</span> Sheet Metal Bending</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Chi; Liao, Juan; Zhu, Yin; Chen, Zhenjiao</p> <p>2010-06-01</p> <p>Advanced <span class="hlt">High</span> Strength Steels (AHSS) are used increasingly in automobile structure parts to reduce the vehicle weight while keeping the safety standard. But their <span class="hlt">high</span> values of the ratio of strength to Young's modulus cause more springback problems. A method of calculating the compensated tool shape for complex bending shapes is proposed in this paper. The method is composed of 3 steps: firstly the cross-section profile of a part was discretized into points and their corresponding <span class="hlt">curvatures</span>; then an analytic algorithm based on plastic bending theory is applied to calculate the compensated <span class="hlt">curvatures</span> of each point; finally, a numerical algorithm based on differential geometry is used to construct the tool shape according to the compensated <span class="hlt">curvatures</span> of each point. A wave-shaped AHSS part with three different <span class="hlt">curvatures</span> had been used to evaluate this method. The experimental results showed that the max <span class="hlt">curvature</span> variance between the actual bending parts and desired shape is less than 4%, which is satisfying for most engineering applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9784E..0MK','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9784E..0MK"><span>Sinogram smoothing and interpolation via alternating projections onto the slope and <span class="hlt">curvature</span> constraints</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karimi, Davood; Ward, Rabab K.</p> <p>2016-03-01</p> <p>Reducing the radiation dose in computed tomography (CT) requires reducing the number or the energy of the photons that pass through the patient's body. An image reconstructed from such noisy or undersampled measurements will contain much noise and artifacts that can significantly reduce the diagnostic value of the image. Effective sinogram denoising or interpolation can reduce these noise and artifacts. In this paper, we present a novel approach to sinogram smoothing and interpolation. The proposed method iteratively estimates the local slope and <span class="hlt">curvature</span> of the sinogam and forces the sinogram to follow the estimated slope and <span class="hlt">curvature</span>. This is performed by projection onto the set of constraints that define the slope and the <span class="hlt">curvature</span>. The constraints on the slope and <span class="hlt">curvature</span> correspond to very simple convex sets. Projection onto these sets have simple analytical solutions. Moreover, these operations are <span class="hlt">highly</span> parallelizable because the equations defining the slope and <span class="hlt">curvature</span> constraints for all the points in a sinogram can be summarized as five convex sets, regardless of the length of the sinogram. We apply the proposed method on simulated and real data and examine its effect on the quality of the reconstructed image. Our results show that the proposed method is <span class="hlt">highly</span> effective and can lead to a substantial improvement in the quality of the images reconstructed from noisy sinogram measurements. A comparison with the K-SVD denoising algorithm shows that the proposed algorithm achieves better results. We suggest that the proposed method can be a useful tool for low-dose CT.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26997615','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26997615"><span>Numerical analysis of corneal <span class="hlt">curvature</span> dynamics based on Corvis tonometer images.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kasprzak, Henryk; Boszczyk, Agnieszka</p> <p>2016-05-01</p> <p>The paper presents numerical analysis of corneal <span class="hlt">curvature</span> distribution, based on Corvis ST images. It was shown that a new approach to analysis of corneal <span class="hlt">curvature</span> from tonometer images enables a better description and understanding of processes during fast corneal deformation. Ten healthy volunteers participated in nine repeated measurements on one eye. 90 sequences of images were processed with software written in Matlab, with the use of the Image Processing Toolbox. Time-spatial distribution of the local <span class="hlt">curvature</span> distribution of the corneal profile was obtained for each and every measurement. Some new <span class="hlt">curvature</span> parameters were proposed and analyzed. A <span class="hlt">high</span> repeatability for individual subjects was obtained for the proposed parameters. For four of these new parameters, the ICC coefficients were higher than 0.85. The ICC value for the calculated <span class="hlt">curvature</span> of the cornea before deformation reaches 0.989. Such <span class="hlt">high</span> repeatability of the proposed new parameters can be useful in examination and differentiation of corneas due to their geometrical and biomechanical properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21408895','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21408895"><span>Solitons in curved space of constant <span class="hlt">curvature</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Batz, Sascha; Peschel, Ulf</p> <p>2010-05-15</p> <p>We consider spatial solitons as, for example, self-confined optical beams in spaces of constant <span class="hlt">curvature</span>, which are a natural generalization of flat space. Due to the symmetries of these spaces we are able to define respective dynamical parameters, for example, velocity and position. For positively curved space we find stable multiple-hump solitons as a continuation from the linear modes. In the case of negatively curved space we show that no localized solution exists and a bright soliton will always decay through a nonlinear tunneling process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApPhL.111h1602D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApPhL.111h1602D"><span>Zero <span class="hlt">curvature</span>-surface driven small objects</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dou, Xiaoxiao; Li, Shanpeng; Liu, Jianlin</p> <p>2017-08-01</p> <p>In this study, we investigate the spontaneous migration of small objects driven by surface tension on a catenoid, formed by a layer of soap constrained by two rings. Although the average <span class="hlt">curvature</span> of the catenoid is zero at each point, the small objects always migrate to the position near the ring. The force and energy analyses have been performed to uncover the mechanism, and it is found that the small objects distort the local shape of the liquid film, thus making the whole system energetically favorable. These findings provide some inspiration to design microfluidics, aquatic robotics, and miniature boats.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AIPC.1477...73L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AIPC.1477...73L"><span>Double <span class="hlt">curvature</span> mirrors for linear concentrators</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lance, Tamir; Ackler, Harold; Finot, Marc</p> <p>2012-10-01</p> <p>Skyline Solar's medium concentration photovoltaic system uses quasi-parabolic mirrors and one axis tracking. Improvements in levelized cost of energy can be achieved by effective management of non-uniformity of the flux line on the panels. To reduce non uniformity of the flux line due to mirror to mirror gaps, Skyline developed a dual <span class="hlt">curvature</span> mirror that stretches the flux line along the panel. Extensive modeling and experiments have been conducted to analyze the impact of this new design and to optimize the design.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26469619','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26469619"><span>Steering electromagnetic beams with conical <span class="hlt">curvature</span> singularities.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Yong-Liang; Dong, Xian-Zi; Zheng, Mei-Ling; Zhao, Zhen-Sheng; Duan, Xuan-Ming</p> <p>2015-10-15</p> <p>We describe how the transformation-optics technique can be used to design an effective medium mimicking the conical <span class="hlt">curvature</span> singularity. Anholonomic coordinate transformation gives rise to linear topological defects that break the rotational symmetry. The bending and splitting of the optical beams are found analytically and numerically, depending on the incident direction and the topological charge. Beyond their practical applications to omnidirectional beam steering for photonics, our findings set forth an attractive realm to simulate the relevant physical phenomena in the optical laboratory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16832447','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16832447"><span><span class="hlt">Curvature</span> sensor for ocular wavefront measurement.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Díaz-Doutón, Fernando; Pujol, Jaume; Arjona, Montserrat; Luque, Sergio O</p> <p>2006-08-01</p> <p>We describe a new wavefront sensor for ocular aberration determination, based on the <span class="hlt">curvature</span> sensing principle, which adapts the classical system used in astronomy for the living eye's measurements. The actual experimental setup is presented and designed following a process guided by computer simulations to adjust the design parameters for optimal performance. We present results for artificial and real young eyes, compared with the Hartmann-Shack estimations. Both methods show a similar performance for these cases. This system will allow for the measurement of higher order aberrations than the currently used wavefront sensors in situations in which they are supposed to be significant, such as postsurgery eyes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24991828','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24991828"><span>Lipidation of the autophagy proteins LC3 and GABARAP is a membrane-<span class="hlt">curvature</span> dependent process.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dancourt, Julia; Melia, Thomas J</p> <p>2014-08-01</p> <p>The phagophore membrane is <span class="hlt">highly</span> curved along the rim of the open cup, suggesting that the molecular mechanisms governing its formation and growth could rely on membrane <span class="hlt">curvature</span>-dependent events. To this end, we recently reported that lipidation of the LC3 protein family is facilitated on <span class="hlt">highly</span> curved membranes in vitro. We further showed that the conjugating enzyme ATG3 contains an amphipathic helix that is responsible for this membrane <span class="hlt">curvature</span> dependency, and that the maintenance of this amphipathic structure is essential for ATG3 function in vivo.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JChPh.140w4506S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JChPh.140w4506S"><span><span class="hlt">Curvature</span> induced phase stability of an intensely heated liquid</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sasikumar, Kiran; Liang, Zhi; Cahill, David G.; Keblinski, Pawel</p> <p>2014-06-01</p> <p>We use non-equilibrium molecular dynamics simulations to study the heat transfer around intensely heated solid nanoparticles immersed in a model Lennard-Jones fluid. We focus our studies on the role of the nanoparticle <span class="hlt">curvature</span> on the liquid phase stability under steady-state heating. For small nanoparticles we observe a stable liquid phase near the nanoparticle surface, which can be at a temperature well above the boiling point. Furthermore, for particles with radius smaller than a critical radius of 2 nm we do not observe formation of vapor even above the critical temperature. Instead, we report the existence of a stable fluid <span class="hlt">region</span> with a density much larger than that of the vapor phase. We explain the stability in terms of the Laplace pressure associated with the formation of a vapor nanocavity and the associated effect on the Gibbs free energy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24125229','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24125229"><span>Thermodynamic <span class="hlt">curvature</span> for attractive and repulsive intermolecular forces.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>May, Helge-Otmar; Mausbach, Peter; Ruppeiner, George</p> <p>2013-09-01</p> <p>The thermodynamic <span class="hlt">curvature</span> scalar R for the Lennard-Jones system is evaluated in phase space, including vapor, liquid, and solid state. We paid special attention to the investigation of R along vapor-liquid, liquid-solid, and vapor-solid equilibria. Because R is a measure of interaction strength, we traced out the line R=0 dividing the phase space into <span class="hlt">regions</span> with effectively attractive (R<0) or repulsive (R>0) interactions. Furthermore, we analyzed the dependence of R on the strength of attraction applying a perturbation ansatz proposed by Weeks-Chandler-Anderson. Our results show clearly a transition from R>0 (for poorly repulsive interaction) to R<0 when loading attraction in the intermolecular potential.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017OptLT..92..138Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017OptLT..92..138Z"><span>In-fiber modal interferometer for simultaneous measurement of <span class="hlt">curvature</span> and temperature based on hollow core fiber</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Yong; Cai, Lu; Li, Xue-gang</p> <p>2017-07-01</p> <p>An in-fiber modal interferometer is presented and experimentally demonstrated for simultaneous measurement of <span class="hlt">curvature</span> and temperature. The sensing part is fabricated by splicing single mode fiber (SMF) and hollow core fiber (HCF) via two abrupt tapered joints. Light couples to the wall of HCF due to the collapse in abrupt taper <span class="hlt">region</span> and then modal interference occurs among multiple modes. Not only intensity but also wavelength of the dip around 1556 nm linearly responses to the <span class="hlt">curvature</span> and temperature change thus a sensitivity matrix could be built to demodulate both <span class="hlt">curvature</span> and temperature simultaneously. In addition, the interference dip around 1540 nm performs a decrease trend and the highest <span class="hlt">curvature</span> sensitivity of 5.05 dB/m-1 is achieved in a wide range from 0.765 m-1 to 3.423 m-1.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4646232','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4646232"><span>Membrane <span class="hlt">Curvature</span>-sensing and <span class="hlt">Curvature</span>-inducing Activity of Islet Amyloid Polypeptide and Its Implications for Membrane Disruption*♦</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kegulian, Natalie C.; Sankhagowit, Shalene; Apostolidou, Melania; Jayasinghe, Sajith A.; Malmstadt, Noah; Butler, Peter C.; Langen, Ralf</p> <p>2015-01-01</p> <p>Islet amyloid polypeptide (IAPP) is a 37-amino acid amyloid protein intimately associated with pancreatic islet β-cell dysfunction and death in type II diabetes. In this study, we combine spectroscopic methods and microscopy to investigate α-helical IAPP-membrane interactions. Using light scattering and fluorescence microscopy, we observe that larger vesicles become smaller upon treatment with human or rat IAPP. Electron microscopy shows the formation of various <span class="hlt">highly</span> curved structures such as tubules or smaller vesicles in a membrane-remodeling process, and spectrofluorometric detection of vesicle leakage shows disruption of membrane integrity. This effect is stronger for human IAPP than for the less toxic rat IAPP. From CD spectra in the presence of different-sized vesicles, we also uncover the membrane <span class="hlt">curvature</span>-sensing ability of IAPP and find that it transitions from inducing to sensing membrane <span class="hlt">curvature</span> when lipid negative charge is decreased. Our in vivo EM images of immunogold-labeled rat IAPP and human IAPP show both forms to localize to mitochondrial cristae, which contain not only locally curved membranes but also phosphatidylethanolamine and cardiolipin, lipids with <span class="hlt">high</span> spontaneous negative <span class="hlt">curvature</span>. Disruption of membrane integrity by induction of membrane <span class="hlt">curvature</span> could apply more broadly to other amyloid proteins and be responsible for membrane damage observed in other amyloid diseases as well. PMID:26283787</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22189764','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22189764"><span>Mechanisms underlying rhythmic locomotion: interactions between activation, tension and body <span class="hlt">curvature</span> waves.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Jun; Friesen, W Otto; Iwasaki, Tetsuya</p> <p>2012-01-15</p> <p>Undulatory animal locomotion arises from three closely related propagating waves that sweep rostrocaudally along the body: activation of segmental muscles by motoneurons (MNs), strain of the body wall, and muscle tension induced by activation and strain. Neuromechanical models that predict the relative propagation speeds of neural/muscle activation, muscle tension and body <span class="hlt">curvature</span> can reveal crucial underlying control features of the central nervous system and the power-generating mechanisms of the muscle. We provide an analytical explanation of the relative speeds of these three waves based on a model of neuromuscular activation and a model of the body-fluid interactions for leech anguilliform-like swimming. First, we deduced the motoneuron spike frequencies that activate the muscle and the resulting muscle tension during swimming in intact leeches from muscle bending moments. Muscle bending moments were derived from our video-recorded kinematic motion data by our body-fluid interaction model. The phase relationships of neural activation and muscle tension in the strain cycle were then calculated. Our study predicts that the MN activation and body <span class="hlt">curvature</span> waves have roughly the same speed (the ratio of <span class="hlt">curvature</span> to MN activation speed ≈0.84), whereas the tension wave travels about twice as fast. The <span class="hlt">high</span> speed of the tension wave resulting from slow MN activation is explained by the multiplicative effects of MN activation and muscle strain on tension development. That is, the product of two slower waves (activation and strain) with appropriate amplitude, bias and phase can generate a tension wave with twice the propagation speed of the factors. Our study predicts that (1) the bending moment required for swimming is achieved by minimal MN spike frequency, rather than by minimal muscle tension; (2) MN activity is greater in the mid-body than in the head and tail <span class="hlt">regions</span>; (3) inhibitory MNs not only accelerate the muscle relaxation but also reduce the intrinsic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28736221','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28736221"><span>Scaffold <span class="hlt">curvature</span>-mediated novel biomineralization process originates a continuous soft tissue-to-bone interface.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Paris, Michael; Götz, Andreas; Hettrich, Inga; Bidan, Cécile M; Dunlop, John W C; Razi, Hajar; Zizak, Ivo; Hutmacher, Dietmar W; Fratzl, Peter; Duda, Georg N; Wagermaier, Wolfgang; Cipitria, Amaia</p> <p>2017-09-15</p> <p>A myriad of shapes are found in biological tissues, often naturally evolved to fulfill a particular function. In the field of tissue engineering, substrate geometry influences cell behavior and tissue formation in vitro, yet little is known how this translates to an in vivo scenario. Here we investigate scaffold <span class="hlt">curvature</span>-induced tissue growth, without additional growth factors or cells, in an ovine animal model. We show that soft tissue formation follows a <span class="hlt">curvature</span>-driven tissue growth model. The <span class="hlt">highly</span> organized endogenous soft matrix, potentially under mechanical strain, leads to a non-standard form of biomineralization, whereby the pre-existing organic matrix is mineralized without collagen remodeling and without an intermediate cartilage ossification phase. Micro- and nanoscale characterization of the tissue microstructure using histology, backscattered electron (BSE) and second-harmonic generation (SHG) imaging and synchrotron small angle X-ray scattering (SAXS) revealed (i) continuous collagen fibers across the soft-hard tissue interface on the tip of mineralized cones, and (ii) bone remodeling by basic multicellular units (BMUs) in <span class="hlt">regions</span> adjacent to the native cortical bone. Thus, features of soft tissue-to-bone interface resembling the insertion sites of ligaments and tendons into bone were created, using a scaffold that did not mimic the structural or biological gradients across such a complex interface at its mature state. This study provides fundamental knowledge for biomimetic scaffold design in the fields of bone regeneration and soft tissue-to-bone interface tissue engineering. Geometry influences cell behavior and tissue formation in vitro. However, little is known how this translates to an in vivo scenario. Here we investigate the influence of scaffold mean surface <span class="hlt">curvature</span> on in vivo tissue growth using an ovine animal model. Based on a multiscale tissue microstructure characterization, we show a seamless integration of soft tissue into newly</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3244339','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3244339"><span>Mechanisms underlying rhythmic locomotion: interactions between activation, tension and body <span class="hlt">curvature</span> waves</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Chen, Jun; Friesen, W. Otto; Iwasaki, Tetsuya</p> <p>2012-01-01</p> <p>SUMMARY Undulatory animal locomotion arises from three closely related propagating waves that sweep rostrocaudally along the body: activation of segmental muscles by motoneurons (MNs), strain of the body wall, and muscle tension induced by activation and strain. Neuromechanical models that predict the relative propagation speeds of neural/muscle activation, muscle tension and body <span class="hlt">curvature</span> can reveal crucial underlying control features of the central nervous system and the power-generating mechanisms of the muscle. We provide an analytical explanation of the relative speeds of these three waves based on a model of neuromuscular activation and a model of the body–fluid interactions for leech anguilliform-like swimming. First, we deduced the motoneuron spike frequencies that activate the muscle and the resulting muscle tension during swimming in intact leeches from muscle bending moments. Muscle bending moments were derived from our video-recorded kinematic motion data by our body–fluid interaction model. The phase relationships of neural activation and muscle tension in the strain cycle were then calculated. Our study predicts that the MN activation and body <span class="hlt">curvature</span> waves have roughly the same speed (the ratio of <span class="hlt">curvature</span> to MN activation speed ≈0.84), whereas the tension wave travels about twice as fast. The <span class="hlt">high</span> speed of the tension wave resulting from slow MN activation is explained by the multiplicative effects of MN activation and muscle strain on tension development. That is, the product of two slower waves (activation and strain) with appropriate amplitude, bias and phase can generate a tension wave with twice the propagation speed of the factors. Our study predicts that (1) the bending moment required for swimming is achieved by minimal MN spike frequency, rather than by minimal muscle tension; (2) MN activity is greater in the mid-body than in the head and tail <span class="hlt">regions</span>; (3) inhibitory MNs not only accelerate the muscle relaxation but also reduce</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JHyd..448...80B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JHyd..448...80B"><span>Bias correction of <span class="hlt">high</span> resolution <span class="hlt">regional</span> climate model data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Berg, P.; Feldmann, H.; Panitz, H.-J.</p> <p>2012-07-01</p> <p>SummaryBias correction of varying complexity - from simple scaling and additive corrections to more advanced histogram equalisation (HE) corrections - is applied to <span class="hlt">high</span> resolution (7 km) <span class="hlt">regional</span> climate model (RCM) simulations. The aim of the study is to compare different methods that are easily implemented and applied to the data, and to assess the applicability and impact of the bias correction depending on the type of bias. The model bias is determined by comparison to a new gridded <span class="hlt">high</span> resolution (1 km) data set of temperature and precipitation, which is also used as reference for the corrections. The performance of the different methods depends on the type of bias of the model, and on the investigated statistic. Whereas simpler methods correct the first moment of the distributions, they can have adverse effects on higher moments. The HE method corrects also higher moments, but approximations of the transfer function are necessary when applying the method to other data than the calibration data. Here, an empirical transfer function with linear fits to the tails is compared to a version where the complete function is approximated by a linear fit. The latter is thus limited to corrections of the first and second moments of the distribution. While making the transfer function more generally applicable, these approximations also limit the performance of the HE method. For the current model biases, the linear approximation is found suitable for precipitation, but for temperature it is not able to correct the whole distribution. The lower performance of the linear correction is most pronounced in summer, and is likely due to a difference in skewness between the model and observational data. Further limitations of the HE method are due to the need for long time series in order to have robust distributions for calculating the transfer function. Theoretical approximations of the required length of the calibration period were performed by using different sampling</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11541075','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11541075"><span>Magnetophoretic induction of <span class="hlt">curvature</span> in coleoptiles and hypocotyls.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kuznetsov, O A; Hasenstein, K H</p> <p>1997-11-01</p> <p>Coleoptiles of barley (Hordeum vulgare) were positioned in a <span class="hlt">high</span> gradient magnetic field (HGMF, dynamic factor gradient of H(2)/2 of 10(9)-10(10) Oe2 cm-1), generated by a ferromagnetic wedge in a uniform magnetic field and rotated on a 1 rpm clinostat. After 4 h 90% of coleoptiles had curved toward the HGMF. The cells affected by HGMF showed clear intracellular displacement of amyloplasts. Coleoptiles in a magnetic field next to a non-ferromagnetic wedge showed no preferential <span class="hlt">curvature</span>. The small size of the area of nonuniformity of the HGMF allowed mapping of the sensitivity of the coleoptiles by varying the initial position of the wedge relative to the coleoptile apex. When the ferromagnetic wedge was placed 1 mm below the coleoptile tip only 58% of the coleoptiles curved toward the wedge indicating that the cells most sensitive to intracellular displacement of amyloplasts and thus gravity sensing are confined to the top 1 mm portion of barley coleoptiles. Similar experiments with tomato hypocotyls (Lycopersicum esculentum) also resulted in <span class="hlt">curvature</span> toward the HGMF. The data strongly support the amyloplast-based gravity-sensing system in higher plants and the usefulness of HGMF to substitute gravity in shoots.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040089309&hterms=Barley&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DBarley','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040089309&hterms=Barley&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DBarley"><span>Magnetophoretic induction of <span class="hlt">curvature</span> in coleoptiles and hypocotyls</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kuznetsov, O. A.; Hasenstein, K. H.</p> <p>1997-01-01</p> <p>Coleoptiles of barley (Hordeum vulgare) were positioned in a <span class="hlt">high</span> gradient magnetic field (HGMF, dynamic factor gradient of H(2)/2 of 10(9)-10(10) Oe2 cm-1), generated by a ferromagnetic wedge in a uniform magnetic field and rotated on a 1 rpm clinostat. After 4 h 90% of coleoptiles had curved toward the HGMF. The cells affected by HGMF showed clear intracellular displacement of amyloplasts. Coleoptiles in a magnetic field next to a non-ferromagnetic wedge showed no preferential <span class="hlt">curvature</span>. The small size of the area of nonuniformity of the HGMF allowed mapping of the sensitivity of the coleoptiles by varying the initial position of the wedge relative to the coleoptile apex. When the ferromagnetic wedge was placed 1 mm below the coleoptile tip only 58% of the coleoptiles curved toward the wedge indicating that the cells most sensitive to intracellular displacement of amyloplasts and thus gravity sensing are confined to the top 1 mm portion of barley coleoptiles. Similar experiments with tomato hypocotyls (Lycopersicum esculentum) also resulted in <span class="hlt">curvature</span> toward the HGMF. The data strongly support the amyloplast-based gravity-sensing system in higher plants and the usefulness of HGMF to substitute gravity in shoots.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040089309&hterms=tomato&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dtomato','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040089309&hterms=tomato&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dtomato"><span>Magnetophoretic induction of <span class="hlt">curvature</span> in coleoptiles and hypocotyls</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kuznetsov, O. A.; Hasenstein, K. H.</p> <p>1997-01-01</p> <p>Coleoptiles of barley (Hordeum vulgare) were positioned in a <span class="hlt">high</span> gradient magnetic field (HGMF, dynamic factor gradient of H(2)/2 of 10(9)-10(10) Oe2 cm-1), generated by a ferromagnetic wedge in a uniform magnetic field and rotated on a 1 rpm clinostat. After 4 h 90% of coleoptiles had curved toward the HGMF. The cells affected by HGMF showed clear intracellular displacement of amyloplasts. Coleoptiles in a magnetic field next to a non-ferromagnetic wedge showed no preferential <span class="hlt">curvature</span>. The small size of the area of nonuniformity of the HGMF allowed mapping of the sensitivity of the coleoptiles by varying the initial position of the wedge relative to the coleoptile apex. When the ferromagnetic wedge was placed 1 mm below the coleoptile tip only 58% of the coleoptiles curved toward the wedge indicating that the cells most sensitive to intracellular displacement of amyloplasts and thus gravity sensing are confined to the top 1 mm portion of barley coleoptiles. Similar experiments with tomato hypocotyls (Lycopersicum esculentum) also resulted in <span class="hlt">curvature</span> toward the HGMF. The data strongly support the amyloplast-based gravity-sensing system in higher plants and the usefulness of HGMF to substitute gravity in shoots.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..MARX37013S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MARX37013S"><span>Particles and <span class="hlt">curvatures</span> in nematic liquid crystals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Serra, Francesca; Luo, Yimin; Yang, Shu; Kamien, Randall D.; Stebe, Kathleen J.</p> <p></p> <p>Elastic interactions in anisotropic fluids can be harnessed to direct particle interactions. A strategy to smoothly manipulate the director field in nematic liquid crystals is to vary the topography of the bounding surfaces. A rugged landscape with peaks and valleys create local deformations of the director field which can interact with particles in solution. We study this complex interaction in two different settings. The first consists of an array of shallow pores in a poly-dimethyl-siloxane (PDMS) membrane, whose <span class="hlt">curvature</span> can be tuned either by swelling the PDMS membrane or by mechanical stretching. The second is a set of grooves with wavy walls, fabricated by photolithography, with various parameters of <span class="hlt">curvature</span> and shapes. In this contexts we study how the motion of colloidal particles in nematic liquid crystals can be influenced by their interaction with the peaks and valleys of the bottom substrate or of the side walls. Particles with different associated topological defects (hedgehogs or Saturn rings) behave differently as they interact with the topographical features, favoring the docking on peaks or valleys. These experimental systems are also ideal to study the ``lock and key'' mechanism of particles in holes and to investigate a possible route for particle sorting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25113914','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25113914"><span>ODE/PDE analysis of corneal <span class="hlt">curvature</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Płociniczak, Lukasz; Griffiths, Graham W; Schiesser, William E</p> <p>2014-10-01</p> <p>The starting point for this paper is a nonlinear, two-point boundary value ordinary differential equation (BVODE) that defines corneal <span class="hlt">curvature</span> according to a static force balance. A numerical solution to the BVODE is computed by first converting the BVODE to a parabolic partial differential equation (PDE) by adding an initial value (t, pseudo-time) derivative to the BVODE. A numerical solution to the PDE is then computed by the method of lines (MOL) with the calculation proceeding to a sufficiently large value of t such that the derivative in t reduces to essentially zero. The PDE solution at this point is also the solution for the BVODE. This procedure is implemented in R (an open source scientific programming system) and the programming is discussed in some detail. A series approximation to the solution is derived from which an estimate for the rate of convergence is obtained. This is compared to a fitted exponential model. Also, two linear approximations are derived, one of which leads to a closed form solution. Both provide solutions very close to that obtained from the full nonlinear model. An estimate for the cornea radius of <span class="hlt">curvature</span> is also derived. The paper concludes with a discussion of the features of the solution to the ODE/PDE system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/813334','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/813334"><span>Brane Localized <span class="hlt">Curvature</span> for Warped Gravitons</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rizzo, Thomas G.</p> <p>2003-06-26</p> <p>We study the effects of including brane localized <span class="hlt">curvature</span> terms in the Randall-Sundrum (RS) model of the hierarchy. This leads to the existence of brane localized kinetic terms for the graviton. Such terms can be induced by brane and bulk quantum effects as well as Higgs-<span class="hlt">curvature</span> mixing on the brane. We derive the modified spectrum of Kaluza-Klein (KK) gravitons and their couplings to 4-dimensional fields in the presence of these terms. We find that the masses and couplings of the KK gravitons have considerable dependence on the size of the brane localized terms; the weak-scale phenomenology of the model is consequently modified . In particular, the weak-scale spin-2 graviton resonances which generically appear in the RS model may be significantly lighter than previously assumed. However, they may avoid detection as their widths may be too narrow to be observable at colliders. In the contact interaction limit, for a certain range of parameters, the experimental reach for the scale of the theory is independent of the size of the boundary terms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/300046','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/300046"><span>Kinetic information from detonation front <span class="hlt">curvature</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Souers, P. C., LLNL</p> <p>1998-06-15</p> <p>The time constants for time-dependent modeling may be estimated from reaction zone lengths, which are obtained from two sources One is detonation front <span class="hlt">curvature</span>, where the edge lag is close to being a direct measure The other is the Size Effect, where the detonation velocity decreases with decreasing radius as energy is lost to the cylinder edge A simple theory that interlocks the two effects is given A differential equation for energy flow in the front is used, the front is described by quadratic and sixth-power radius terms The quadratic <span class="hlt">curvature</span> comes from a constant power source of energy moving sideways to the walls Near the walls, the this energy rises to the total energy of detonation and produces the sixth-power term The presence of defects acting on a short reaction zone can eliminate the quadratic part while leaving the wall portion of the cuvature A collection of TNT data shows that the reaction zone increases with both the radius and the void fraction</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22224273','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22224273"><span>Vortex motion on surfaces of small <span class="hlt">curvature</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dorigoni, Daniele Dunajski, Maciej Manton, Nicholas S.</p> <p>2013-12-15</p> <p>We consider a single Abelian Higgs vortex on a surface Σ whose Gaussian <span class="hlt">curvature</span> K is small relative to the size of the vortex, and analyse vortex motion by using geodesics on the moduli space of static solutions. The moduli space is Σ with a modified metric, and we propose that this metric has a universal expansion, in terms of K and its derivatives, around the initial metric on Σ. Using an integral expression for the Kähler potential on the moduli space, we calculate the leading coefficients of this expansion numerically, and find some evidence for their universality. The expansion agrees to first order with the metric resulting from the Ricci flow starting from the initial metric on Σ, but differs at higher order. We compare the vortex motion with the motion of a point particle along geodesics of Σ. Relative to a particle geodesic, the vortex experiences an additional force, which to leading order is proportional to the gradient of K. This force is analogous to the self-force on bodies of finite size that occurs in gravitational motion. -- Highlights: •We study an Abelian Higgs vortex on a surface with small <span class="hlt">curvature</span>. •A universal expansion for the moduli space metric is proposed. •We numerically check the universality at low orders. •Vortex motion differs from point particle motion because a vortex has a finite size. •Moduli space geometry has similarities with the geometry arising from Ricci flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JHEP...03..033A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JHEP...03..033A"><span>Emergent gravity in spaces of constant <span class="hlt">curvature</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alvarez, Orlando; Haddad, Matthew</p> <p>2017-03-01</p> <p>In physical theories where the energy (action) is localized near a submanifold of a constant <span class="hlt">curvature</span> space, there is a universal expression for the energy (or the action). We derive a multipole expansion for the energy that has a finite number of terms, and depends on intrinsic geometric invariants of the submanifold and extrinsic invariants of the embedding of the submanifold. This is the second of a pair of articles in which we try to develop a theory of emergent gravity arising from the embedding of a submanifold into an ambient space equipped with a quantum field theory. Our theoretical method requires a generalization of a formula due to by Hermann Weyl. While the first paper discussed the framework in Euclidean (Minkowski) space, here we discuss how this framework generalizes to spaces of constant sectional <span class="hlt">curvature</span>. We focus primarily on anti de Sitter space. We then discuss how such a theory can give rise to a cosmological constant and Planck mass that are within reasonable bounds of the experimental values.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28141519','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28141519"><span><span class="hlt">Curvature</span> Filters Efficiently Reduce Certain Variational Energies.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gong, Yuanhao; Sbalzarini, Ivo F</p> <p>2017-04-01</p> <p>In image processing, the rapid approximate solution of variational problems involving generic data-fitting terms is often of practical relevance, for example in real-time applications. Variational solvers based on diffusion schemes or the Euler-Lagrange equations are too slow and restricted in the types of data-fitting terms. Here, we present a filter-based approach to reduce variational energies that contain generic data-fitting terms, but are restricted to specific regularizations. Our approach is based on reducing the regularization part of the variational energy, while guaranteeing non-increasing total energy. This is applicable to regularization-dominated models, where the data-fitting energy initially increases, while the regularization energy initially decreases. We present fast discrete filters for regularizers based on Gaussian <span class="hlt">curvature</span>, mean <span class="hlt">curvature</span>, and total variation. These pixel-local filters can be used to rapidly reduce the energy of the full model. We prove the convergence of the resulting iterative scheme in a greedy sense, and we show several experiments to demonstrate applications in image-processing problems involving regularization-dominated variational models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3286980','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3286980"><span>Actin filament <span class="hlt">curvature</span> biases branching direction</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Risca, Viviana I.; Wang, Evan B.; Chaudhuri, Ovijit; Chia, Jia Jun; Geissler, Phillip L.; Fletcher, Daniel A.</p> <p>2012-01-01</p> <p>Mechanical cues affect many important biological processes in metazoan cells, such as migration, proliferation, and differentiation. Such cues are thought to be detected by specialized mechanosensing molecules linked to the cytoskeleton, an intracellular network of protein filaments that provide mechanical rigidity to the cell and drive cellular shape change. The most abundant such filament, actin, forms branched networks nucleated by the actin-related protein (Arp) 2/3 complex that support or induce membrane protrusions and display adaptive behavior in response to compressive forces. Here we show that filamentous actin serves in a mechanosensitive capacity itself, by biasing the location of actin branch nucleation in response to filament bending. Using an in vitro assay to measure branching from curved sections of immobilized actin filaments, we observed preferential branch formation by the Arp2/3 complex on the convex face of the curved filament. To explain this behavior, we propose a fluctuation gating model in which filament binding or branch nucleation by Arp2/3 occur only when a sufficiently large, transient, local <span class="hlt">curvature</span> fluctuation causes a favorable conformational change in the filament, and we show with Monte Carlo simulations that this model can quantitatively account for our experimental data. We also show how the branching bias can reinforce actin networks in response to compressive forces. These results demonstrate how filament <span class="hlt">curvature</span> can alter the interaction of cytoskeletal filaments with regulatory proteins, suggesting that direct mechanotransduction by actin may serve as a general mechanism for organizing the cytoskeleton in response to force. PMID:22308368</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26620715','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26620715"><span>Impact of alterations in target vessel <span class="hlt">curvature</span> on branch durability after endovascular repair of thoracoabdominal aortic aneurysms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sylvan, Joshua; Brier, Corey; Wolski, Katherine; Yanof, Jeffrey; Goel, Vikash; Kuramochi, Yuki; Eagleton, Matthew J</p> <p>2016-03-01</p> <p>The aim of this study was to evaluate <span class="hlt">curvature</span> and its effect on the durability of visceral and renal branches in patients undergoing endovascular repair of thoracoabdominal aortic aneurysms (TAAAs) with fenestrated/branched endovascular aneurysm repair (F/B-EVAR). Quantitative branch vessel <span class="hlt">curvature</span> assessment on branches arising from reinforced fenestrations was performed for 168 patients undergoing F/B-EVAR for type II and type III TAAAs. Preoperative and postoperative centerline coordinates were obtained using iNtuition (TeraRecon, Foster City, Calif) and exported into MATLAB (The MathWorks, Inc, Natick, Mass) based on thin-slice computed tomography imaging. Spline interpolation was applied to the centerline coordinates and resampled at 100 equally spaced points, and <span class="hlt">curvature</span> calculations (κ, mm(-1)) were applied. Global and maximal <span class="hlt">curvatures</span> for each of the target vessels were measured and categorized by severity. Categories for <span class="hlt">curvature</span> were 0 to 0.05 mm(-1) (low), 0.05 to 0.1 mm(-1) (medium), 0.1 to 0.15 mm(-1) (<span class="hlt">high</span>), and >0.15 mm(-1) (extreme) for global <span class="hlt">curvature</span> and 0 to 0.2 mm(-1), 0.2 to 0.4 mm(-1), 0.4 to 0.6 mm(-1), and >0.6 mm(-1), respectively, for maximum <span class="hlt">curvature</span>. <span class="hlt">Curvature</span> variances were assessed for an association with vessel patency and need for reintervention. There were 558 vessels that underwent analysis based on repairs involving 650 vessels, whereby 92 vessels were excluded as they were treated with an external helical branch (58 celiac arteries and 34 superior mesenteric arteries). There was a significant difference found before and after F/B-EVAR for the global celiac artery <span class="hlt">curvature</span> (median difference, -0.01; P < .001), global left renal artery <span class="hlt">curvature</span> (median, -0.01; P = .014), maximum left renal artery <span class="hlt">curvature</span> (median, 0.05; P < .001), and maximum right renal artery <span class="hlt">curvature</span> (median, 0.03; P = .009). Maximum artery <span class="hlt">curvature</span> was found to have shifted distally in all vessels postoperatively; 37 adverse events (AEs) were</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21454894','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21454894"><span><span class="hlt">HIGH</span>-ENTROPY POLAR <span class="hlt">REGIONS</span> AROUND THE FIRST PROTOSTARS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Turk, Matthew J.; Norman, Michael L.; Abel, Tom</p> <p>2010-12-20</p> <p>We report on simulations of the formation of the first stars in the universe, where we identify <span class="hlt">regions</span> of hot atomic gas (f{sub H{sub 2}}< 10{sup -6}) at densities above 10{sup -14} g cm{sup -3}, heated to temperatures ranging between 3000 and 8000 K. Within this temperature range atomic hydrogen is unable to cool effectively. We describe the kinetic and thermal characteristics of these <span class="hlt">regions</span> and investigate their origin. We find that these <span class="hlt">regions</span>, while small in total mass fraction of the cloud, may be dynamically important over the accretion timescale for the central clump in the cloud, particularly as a chemical, rather than a radiative, mechanism for clearing the polar <span class="hlt">regions</span> of the accretion disk of material and terminating accretion along these directions. These inherently three-dimensional effects stress the need for multi-dimensional calculations of protostellar accretion for reliable predictions of the masses of the very first stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22351705','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22351705"><span>The influence of saddle-shaped annuloplasty on leaflet <span class="hlt">curvature</span> in patients with ischaemic mitral regurgitation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vergnat, Mathieu; Levack, Melissa M; Jassar, Arminder S; Jackson, Benjamin M; Acker, Michael A; Woo, Y Joseph; Gorman, Robert C; Gorman, Joseph H</p> <p>2012-09-01</p> <p>Reports indicate that repair procedures for ischaemic mitral regurgitation (IMR) are less durable than previously thought. Repair failure has been shown to be stress related. Leaflet <span class="hlt">curvature</span> is the major determinant of valve stress. Theoretical and animal experiments have shown that saddle-shaped annuloplasty optimizes leaflet <span class="hlt">curvature</span> when compared with standard flat ring annuloplasty. Despite this, the influence of the ring shape on leaflet <span class="hlt">curvature</span> has not been described in patients with IMR. This study uses real-time three-dimensional echocardiography (rt-3DE) to assess the influence of the ring shape on leaflet <span class="hlt">curvature</span>. Rt-3DE was performed in 21 patients with IMR after placement of either a flat (n = 10, CE-Physio, Edwards) or saddle-shaped (n = 11, Profile 3D, Medtronic) annuloplasty ring. A combination of commercially available and customized software was used to measure multiple leaflet <span class="hlt">curvature</span> parameters across all <span class="hlt">regions</span> of the mitral valve. Independently of the shape of the annuloplasty ring, all patients were subject to the same degree of annular undersizing. Patients who received saddle-shaped annuloplasty rings had greater leaflet <span class="hlt">curvature</span> in all six mitral valve leaflet <span class="hlt">regions</span> (A1 = 0.36 ± 0.10, A2 = 0.53 ± 0.13, A3 = 0.47 ± 0.13, P1 = 0.35 ± 0.23, P2 = 0.53 ± 0.34, P3 = 0.42 ± 0.20 cm(-2)) compared with patients who received flat annuloplasty rings (A1 = 0.16 ± 0.11, A2 = 0.18 ± 0.09, A3 = 0.16 ± 0.11, P1 = 0.20 ± 0.17, P2 = 0.21 ± 0.11, P3 = 0.18 ± 0.13 cm(-2)). These differences were statistically significant in all <span class="hlt">regions</span> except the P1 <span class="hlt">region</span>. Saddle-shaped annuloplasty rings increase leaflet <span class="hlt">curvature</span> compared with flat rings in patients with IMR. As a result, saddle-shaped annuloplasty may decrease leaflet stress and potentially increases the durability of the repair in patients with IMR.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3679405','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3679405"><span>Quantifying Membrane <span class="hlt">Curvature</span> Generation of Drosophila Amphiphysin N-BAR Domains</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Heinrich, Michael C.; Capraro, Benjamin R.; Tian, Aiwei; Isas, Jose M.; Langen, Ralf; Baumgart, Tobias</p> <p>2012-01-01</p> <p>Biological membrane functions are coupled to membrane <span class="hlt">curvature</span>, the regulation of which often involves membrane-associated proteins. The membrane-binding N-terminal amphipathic helix-containing BIN/Amphiphysin/Rvs (N-BAR) domain of amphiphysin is implicated in <span class="hlt">curvature</span> generation and maintenance. Improving the mechanistic understanding of membrane <span class="hlt">curvature</span> regulation by N-BAR domains requires quantitative experimental characterization. We have measured tube pulling force modulation by the N-BAR domain of Drosophila amphiphysin (DA-N-BAR) bound to tubular membranes pulled from micropipette-aspirated giant vesicles. We observed that fluorescently-labeled DA-N-BAR showed significantly higher protein density on tubules compared to the connected low-<span class="hlt">curvature</span> vesicle membrane. Furthermore, we found the equilibrium tube pulling force to be systematically dependent on the aqueous solution concentration of DA-N-BAR, thereby providing the first quantitative assessment of spontaneous <span class="hlt">curvature</span> generation. At sufficiently <span class="hlt">high</span> protein concentrations, pulled tubes required no external force to maintain mechanical equilibrium, in agreement with the qualitative spontaneous tubulation previously reported for amphiphysin. PMID:23772271</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15273879','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15273879"><span>Congenital penile <span class="hlt">curvature</span>: long-term results of operative treatment using the plication procedure.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, S-S; Meng, E; Chuang, F-P; Yen, C-Y; Chang, S-Y; Yu, D-S; Sun, G-H</p> <p>2004-09-01</p> <p>To determine the long-term outcome, effectiveness and patient satisfaction of congenital penile <span class="hlt">curvature</span> correction by plication of tunica albuginea. From January 1992 to January 2002, 106 young patients underwent surgical correction of congenital penile <span class="hlt">curvature</span> by corporeal plication. Indications for operation were difficult or impossible vaginal penetration and cosmetic problems. The technique of corporeal plication consists of placing longitudinal plication sutures of 2-zero braided polyester on the convex side of the <span class="hlt">curvature</span> until the <span class="hlt">curvature</span> is corrected when erection is artificially induced. Results of this procedure were obtained by retrospective chart reviews and questionnaires via mail. Long-term follow-up ranged from 11 to 132 (mean 69.3) months and data were available for 68 patients. Penile straightening was excellent in 62 patients (91 %) and good with less than 15 degree of residual <span class="hlt">curvature</span> in 6 patients (9 %). Sixty-seven patients reported no change in erectile rigidity or maintenance postoperatively, while 1 described early detumescence. Shortening of the penis without functional problems was noted by 26 patients (38 %). Thirty-Five patients (51 %) reported feeling palpable indurations (suture knots) on the penis. Temporary numbness of glans penis was described in 3 patients. Overall, 60 patients were very satisfied, 6 satisfied, 2 unsatisfied. Corporeal plication is an effective and durable procedure with a <span class="hlt">high</span> rate of patient satisfaction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/44947','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/44947"><span>Detection of zones of abnormal strains in structures using Gaussian <span class="hlt">curvature</span> analysis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lisle, R.J.</p> <p>1994-12-01</p> <p>Whereas some folds, such as those produced by flexural slip, do not theoretically entail strain within the folded surfaces, any surface involving double <span class="hlt">curvature</span> (such as domes and saddles) cannot form without some stretching or contraction of the bedding. Whether straining of the surfaces is required during folding depends on the three-dimensional fold shape and, in particular, on the Gaussian <span class="hlt">curvature</span> at points on the folded surface. Using this as a basis, I present a method for detecting zones of anomalously <span class="hlt">high</span> strain in oil-field structures from Gaussian <span class="hlt">curvature</span> analysis (GCA) of natural structures. The new method of GCA is suitable for analyzing surfaces that have been mapped seismically. A Gaussian <span class="hlt">curvature</span> map of the structure is a principal outcome of the analysis and can be used to predict the density of strain-related subseismic structures, such as small-scale fracturing. The Goose Egg dome, near Casper, Wyoming, is analyzed and provides an example of GCA. In this structure, a relationship is observed between fracture densities and Gaussian <span class="hlt">curvature</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008SPIE.7375E..3HQ','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008SPIE.7375E..3HQ"><span>Determination of <span class="hlt">curvature</span> and twist of deformed object by digital holographic interferometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Quan, C.; Chen, W.; Tay, C. J.</p> <p>2008-11-01</p> <p>This paper describes a feasibility study of digital holographic interferometry for the measurement of <span class="hlt">curvature</span> and twist of a deformed object. Measurement of <span class="hlt">curvature</span> and twist is an important aspect in experimental mechanics. Numerous methods have been proposed to determine the <span class="hlt">curvature</span> and twist by using digital shearography. We proposed a novel method to determine <span class="hlt">curvature</span> and twist based on digital holography (DH) and complex phasor (CP). In the conventional methods, phase difference between the first and second states is obtained directly by digital phase subtraction (DPS) and Fourier transform is then employed to extract phase maps. In this study, CP method is proposed to improve the quality of phase maps corresponding to second-order derivatives. Subsequently, sine/cosine transformation and short time Fourier transform (STFT) are employed to process the wrapped phase maps. An experiment is conducted on a clamped circular plate under a point load at centre. The experimental results show that the proposed method is valid and able to obtain <span class="hlt">high</span> quality phase maps corresponding to <span class="hlt">curvature</span> and twist of a deformed object.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982OptEn..21..721K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982OptEn..21..721K"><span>Family Of Grating Techniques Of Slope And <span class="hlt">Curvature</span> Measurements For Static And Dynamic Flexure Of Plates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kao, T. Y.; Chiang, F. P.</p> <p>1982-08-01</p> <p>A family of optical methods are developed for the measurement of slope and <span class="hlt">curvature</span> of flexed plate surfaces. Slope and <span class="hlt">curvature</span> contour fringes are generated by using gratings as filters in the light path emerging from the flexed surface. General field equations are derived for gratings placed anywhere in the field. Depending upon the pitch and the position and the number of gratings used, a variety of techniques are obtained for the contouring of slopes or <span class="hlt">curvatures</span>. When a low density grating is used, the resulting shadowgram yields slope contour fringes if it is placed at the real focal plane of the field lens. Otherwise, the shadow gram fringes are not slope contours. However, slope contours can be obtained if a double-exposure technique or a double grating is used to generate the moire fringes. If a grating of sufficiently <span class="hlt">high</span> frequency is used, the resulting pattern is a <span class="hlt">curvature</span> pattern, for which a monochromatic light source is needed. A successive plotting method is also proposed for <span class="hlt">curvature</span> contouring whereby white light and a grating of arbi-trary pitch can be used. The methods are verified by a series of experiments using cantilever beams and clamped circular plates. Applications to a variety of other problems, including flexure wave propagation, are also demonstrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3991310','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3991310"><span>Multi-scale <span class="hlt">curvature</span> for automated identification of glaciated mountain landscapes☆</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Prasicek, Günther; Otto, Jan-Christoph; Montgomery, David R.; Schrott, Lothar</p> <p>2014-01-01</p> <p>Erosion by glacial and fluvial processes shapes mountain landscapes in a long-recognized and characteristic way. Upland valleys incised by fluvial processes typically have a V-shaped cross-section with uniform and moderately steep slopes, whereas glacial valleys tend to have a U-shaped profile with a changing slope gradient. We present a novel <span class="hlt">regional</span> approach to automatically differentiate between fluvial and glacial mountain landscapes based on the relation of multi-scale <span class="hlt">curvature</span> and drainage area. Sample catchments are delineated and multiple moving window sizes are used to calculate per-cell <span class="hlt">curvature</span> over a variety of scales ranging from the vicinity of the flow path at the valley bottom to catchment sections fully including valley sides. Single-scale <span class="hlt">curvature</span> can take similar values for glaciated and non-glaciated catchments but a comparison of multi-scale <span class="hlt">curvature</span> leads to different results according to the typical cross-sectional shapes. To adapt these differences for automated classification of mountain landscapes into areas with V- and U-shaped valleys, <span class="hlt">curvature</span> values are correlated with drainage area and a new and simple morphometric parameter, the Difference of Minimum <span class="hlt">Curvature</span> (DMC), is developed. At three study sites in the western United States the DMC thresholds determined from catchment analysis are used to automatically identify 5 × 5 km quadrats of glaciated and non-glaciated landscapes and the distinctions are validated by field-based geological and geomorphological maps. Our results demonstrate that DMC is a good predictor of glacial imprint, allowing automated delineation of glacially and fluvially incised mountain landscapes. PMID:24748703</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24748703','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24748703"><span>Multi-scale <span class="hlt">curvature</span> for automated identification of glaciated mountain landscapes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Prasicek, Günther; Otto, Jan-Christoph; Montgomery, David R; Schrott, Lothar</p> <p>2014-03-15</p> <p>Erosion by glacial and fluvial processes shapes mountain landscapes in a long-recognized and characteristic way. Upland valleys incised by fluvial processes typically have a V-shaped cross-section with uniform and moderately steep slopes, whereas glacial valleys tend to have a U-shaped profile with a changing slope gradient. We present a novel <span class="hlt">regional</span> approach to automatically differentiate between fluvial and glacial mountain landscapes based on the relation of multi-scale <span class="hlt">curvature</span> and drainage area. Sample catchments are delineated and multiple moving window sizes are used to calculate per-cell <span class="hlt">curvature</span> over a variety of scales ranging from the vicinity of the flow path at the valley bottom to catchment sections fully including valley sides. Single-scale <span class="hlt">curvature</span> can take similar values for glaciated and non-glaciated catchments but a comparison of multi-scale <span class="hlt">curvature</span> leads to different results according to the typical cross-sectional shapes. To adapt these differences for automated classification of mountain landscapes into areas with V- and U-shaped valleys, <span class="hlt">curvature</span> values are correlated with drainage area and a new and simple morphometric parameter, the Difference of Minimum <span class="hlt">Curvature</span> (DMC), is developed. At three study sites in the western United States the DMC thresholds determined from catchment analysis are used to automatically identify 5 × 5 km quadrats of glaciated and non-glaciated landscapes and the distinctions are validated by field-based geological and geomorphological maps. Our results demonstrate that DMC is a good predictor of glacial imprint, allowing automated delineation of glacially and fluvially incised mountain landscapes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25375290','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25375290"><span>Engineering <span class="hlt">curvature</span> in graphene ribbons using ultrathin polymer films.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Chunyu; Koslowski, Marisol; Strachan, Alejandro</p> <p>2014-12-10</p> <p>We propose a method to induce <span class="hlt">curvature</span> in graphene nanoribbons in a controlled manner using an ultrathin thermoset polymer in a bimaterial strip setup and test it via molecular dynamics (MD) simulations. Continuum mechanics shows that <span class="hlt">curvature</span> develops to release the residual stress caused by the chemical and thermal shrinkage of the polymer during processing and that this <span class="hlt">curvature</span> increases with decreasing film thickness; however, significant deformation is only achieved for ultrathin polymer films. Quite surprisingly, explicit MD simulations of the curing and annealing processes show that the predicted trend not just continues down to film thicknesses of 1-2 nm but that the <span class="hlt">curvature</span> development is enhanced significantly in such ultrathin films due to surface tension effects. This combination of effects leads to very large <span class="hlt">curvatures</span> of over 0.14 nm(-1) that can be tuned via film thickness. This provides a new avenue to engineer <span class="hlt">curvature</span> and, thus, electromagnetic properties of graphene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22788740','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22788740"><span>Superficial tunica albuginea excision, using geometric principles, for the correction of congenital penile <span class="hlt">curvature</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kuehhas, Franklin Emmanuel; Egydio, Paulo Henrique</p> <p>2012-12-01</p> <p>Study Type--Therapy (practise pattern survey) Level of Evidence 3b. What's known on the subject? and What does the study add? Congenital penile deviation has become a relatively frequent finding due to a greater awareness of the problem among patients and physicians. Since the first surgical correction for congenital penile <span class="hlt">curvature</span> was performed, many modifications have been implemented to overcome the disadvantages of the standard procedure and to improve functional results. Among the possible side effects of the original technique are postoperative erectile dysfunction, the development of painful nodules at the suture sites ('dog ears'), alteration of cutaneous sensibility and significant penile shortening. This study presents a novel approach for the correction of congenital penile <span class="hlt">curvature</span>. We modified the conventional Nesbit technique by applying superficial tunica albuginea excisions, according to the geometric principles of the Egydio technique. • To report our experience with a new technique for the correction of congenital penile <span class="hlt">curvature</span> based on geometric principles. • Between January 2006 and March 2011, 211 men with congenital penile <span class="hlt">curvature</span> underwent our modified Nesbit technique. • The technique consists of an objectivation of the degree of <span class="hlt">curvature</span> and distribution of the bending force by multiple, small, superficial, elliptical excisions of the tunica albuginea. • The overall success rate was 99.1%. • A residual <span class="hlt">curvature</span> of less than 20° was reported in 5% (n = 11) of the cases; none of these patients opted for further surgical correction. • Residual <span class="hlt">curvature</span> of up to 30° was observed in 0.9% (n = 2); these patients underwent a reoperation. • Acquiring or regaining the ability to perform sexual intercourse brought major relief and <span class="hlt">high</span> rates of satisfaction and self-esteem. • No recurrence of a ventral <span class="hlt">curvature</span> occurred. • Our modified Nesbit technique, consisting of superficial tunica albuginea excision according to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADP012018','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADP012018"><span><span class="hlt">Curvature</span> and Tangency Handles for Control of Convex Cubic Shapes</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2000-01-01</p> <p>looked at A-splines constructed with segments of singular al- gebraic cubics, which are just rational cubics, with new, geometrically more meaningful...contact interpolation , and <span class="hlt">curvatures</span> at three prescribed points, see Figures 1-4. Curve and Surface Design: Saint-Malo 1999 91 Pierre-Jean Laurent...<span class="hlt">curvature</span> at one contact point. §2. Barycentric Coordinates and <span class="hlt">Curvature</span> at the Endpoints The general algebraic cubic in cartesian coordinates x, y is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010SPIE.7990E..0SZ','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010SPIE.7990E..0SZ"><span>The <span class="hlt">curvature</span> measurement of Sagnac loop based on PMF</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Yu; Jin, Yongxing; Gong, Huaping; Wang, Jianfeng</p> <p>2010-12-01</p> <p>An optical fiber <span class="hlt">curvature</span> sensor is fabricated by using a short section of polarization maintaining fiber (PMF) as the sensing component spliced in an optical fiber Sagnac loop. The length of the sensing element for the <span class="hlt">curvature</span> sensing is about 142 mm. The sensitivity of the <span class="hlt">curvature</span> measurement of 0.0344 m-1/pm is achieved experimentally. The propose sensor is more convenient and simply than that of photonic crystal fiber (PCF).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4611641','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4611641"><span>Wrinkles and splay conspire to give positive disclinations negative <span class="hlt">curvature</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Matsumoto, Elisabetta A.; Vega, Daniel A.; Pezzutti, Aldo D.; García, Nicolás A.; Chaikin, Paul M.; Register, Richard A.</p> <p>2015-01-01</p> <p>Recently, there has been renewed interest in the coupling between geometry and topological defects in crystalline and striped systems. Standard lore dictates that positive disclinations are associated with positive Gaussian <span class="hlt">curvature</span>, whereas negative disclinations give rise to negative <span class="hlt">curvature</span>. Here, we present a diblock copolymer system exhibiting a striped columnar phase that preferentially forms wrinkles perpendicular to the underlying stripes. In free-standing films this wrinkling behavior induces negative Gaussian <span class="hlt">curvature</span> to form in the vicinity of positive disclinations. PMID:26420873</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020066658&hterms=Radius&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DRadius','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020066658&hterms=Radius&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DRadius"><span>Radius of <span class="hlt">Curvature</span> of Off-Axis Paraboloids</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Robinson, Brian; Reardon, Patrick; Hadaway, James; Geary, Joseph; Russell, Kevin (Technical Monitor)</p> <p>2002-01-01</p> <p>We present several methods for measuring the vertex radius of <span class="hlt">curvature</span> of off-axis paraboloidal mirrors. One is based on least-squares fitting of interferometer output, one on comparison of sagittal and tangential radii of <span class="hlt">curvature</span>, and another on measurement of displacement of the nulled test article from the ideal reference wave. Each method defines radius of <span class="hlt">curvature</span> differently and, as a consequence, produces its own sort of errors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.3635D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.3635D"><span>From the Bay of Biscay to the <span class="hlt">High</span> Atlas: completing the anisotropic characterization of the westernmost Mediterranean <span class="hlt">region</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Diaz, Jordi; Gallart, Josep</p> <p>2014-05-01</p> <p>The knowledge of the anisotropic properties beneath the Iberian Peninsula and Northern Morocco has been dramatically changed since late 2007 with the analysis of the data provided by the dense TopoIberia-Iberarray broad-band seismic network, the increasing number of permanent stations operating in Morocco, Portugal and Spain and the contribution of smaller scale/higher resolution experiments. The first TopoIberia deployment in the Betics-Alboran zone has evidenced a spectacular rotation of the fast polarization direction (FPD) along the Gibraltar arc following the <span class="hlt">curvature</span> of the Rif-Betic chain, from roughly N65E beneath the Betics to close to N65W beneath the Rif chain. (Díaz et al, 2010). This result, confirmed latter on by the analysis of the PICASSO experiment data (Miller et al., 2013), has been interpreted as an evidence of mantle flow deflected around the <span class="hlt">high</span> velocity slab identified by tomographic methods beneath the Gibraltar Arc. Data from the second TopoIberia deployment and from additional deployments in the Moroccan Meseta and the western <span class="hlt">High</span> Atlas, allowed expanding the investigated area and obtaining a larger scale image of the mantle flow around the <span class="hlt">region</span>. Diaz et al. (2014) have shown that SW Portugal and the western <span class="hlt">High</span> Atlas <span class="hlt">regions</span> have a small degree of anisotropy and a large number of "null" measurements, which suggest the presence of vertical flow in the mantle associated to small-scale edge-driven convective cells. The rather uniform N100ºE FPD retrieved beneath the Variscan Central Iberian Massif is consistent with global mantle flow models taking into account contributions of surface plate motion, density variations and net lithosphere rotation. The last Iberarray deployment covers the northern part of the Iberian Peninsula and has been coeval with the deployment of a similar seismic network in southern France in the framework of the Pyrope project. Even if data from short term experiments in the Pyrenees and northern Iberia have</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19810016266','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19810016266"><span>Principal normal <span class="hlt">curvature</span> of surfaces. [electromagnetic scattering and the geometrical theory of diffraction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schmidt, R. F.</p> <p>1981-01-01</p> <p>Certain principal normal <span class="hlt">curvatures</span> of differential geometry were developed for use in <span class="hlt">curvature</span> matrices associated with the asymptotic solution of electromagnetic diffraction problems. The effort is directed toward microwave antenna simulations and <span class="hlt">high</span> speed digital computer analysis of radiometric instruments used to obtain soil moisture, sea state, salinity and temperature data. It is shown that the methods used to develop the principal normal <span class="hlt">curvatures</span> for paraboloid, hyperboloid, ellipsoid, sphere, and cone can be applied to other radiometer geometries such as the parabolic torus, even though the surface parameterizations are different. It is concluded that deployable offset geometries, distorted by rotational forces and solar loads may be analyzed by similar means given a suitable surface description.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012mgm..conf.1376R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012mgm..conf.1376R"><span>A Direct Estimate of the Spatial <span class="hlt">Curvature</span> of the Universe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rosquist, Kjell; Samuelsson, Lars</p> <p></p> <p>The main idea of this contribution is to calculate the average spatial <span class="hlt">curvature</span> directly from the observed mass distribution of the universe. In short, our philosophy is that the <span class="hlt">curvature</span> of the universe is generated solely by the matter it contains. Although this may seem as self-evident in the context of general relativity, the usual practice in cosmology is rather to use a top-down approach in which the <span class="hlt">curvature</span> is calculated indirectly using a prescribed matter distribution as a source of the Einstein equations. By contrast, our approach may be seen as part of a bottom-up approach. In practical terms, we first calculate the far field spatial <span class="hlt">curvature</span> generated by an isolated matter distribution which is in arbitrary motion. At this stage we obtain the result that the sign of the spatial <span class="hlt">curvature</span> is necessarily positive. For the spatial <span class="hlt">curvature</span> generated by multiple sources we show that it is sufficient to use linearized theory to compute the leading contributions. In the matter dominated era the spatial <span class="hlt">curvature</span> is then seen to be generated by local sources at small redshifts. This fact makes it possible to calculate the total spatial <span class="hlt">curvature</span> just by summing up the contributions from the observed discrete mass distribution. A crude estimate gives a very small value for the <span class="hlt">curvature</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003OptLT..35...31M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003OptLT..35...31M"><span>Fringes of equal tangential inclination by <span class="hlt">curvature</span>-induced birefringence</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Medhat, M.; Hendawy, N. I.; Zaki, A. A.</p> <p>2003-02-01</p> <p>A new kind of interference fringes, fringes of equal tangential inclination by <span class="hlt">curvature</span>-induced birefringence, is presented. These are two-beam interference fringes produced by bending a thin sheet of birefringent material into a part of an exact cylinder such that the <span class="hlt">curvature</span> is constant. Due to this <span class="hlt">curvature</span> there is a uniform birefringence being induced. The change in birefringence induced by applying different radii of <span class="hlt">curvatures</span> to a Fortepan sheet is measured. The stored (fixed) or natural birefringence of this sheet is deduced.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6104184','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6104184"><span>Plane wave gravitons, <span class="hlt">curvature</span> singularities and string physics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Brooks, R. . Center for Theoretical Physics)</p> <p>1991-03-21</p> <p>This paper discusses bounded (compactifying) potentials arising from a conspiracy between plane wave graviton and dilaton condensates. So are string propagation and supersymmetry in spacetimes with <span class="hlt">curvature</span> singularities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhyS...91j5001C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhyS...91j5001C"><span>Evolving extrinsic <span class="hlt">curvature</span> and the cosmological constant problem</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Capistrano, Abraão J. S.; Cabral, Luis A.</p> <p>2016-10-01</p> <p>The concept of smooth deformation of Riemannian manifolds associated with the extrinsic <span class="hlt">curvature</span> is explained and applied to the Friedmann-Lemaître-Robertson-Walker cosmology. We show that such deformation can be derived from the Einstein-Hilbert-like dynamical principle may produce an observable effect in the sense of Noether. As a result, we show how the extrinsic <span class="hlt">curvature</span> compensates both quantitative and qualitative differences between the cosmological constant Λ and the vacuum energy {ρ }{vac} obtaining the observed upper bound for the cosmological constant problem at electroweak scale. The topological characteristics of the extrinsic <span class="hlt">curvature</span> are discussed showing that the produced extrinsic scalar <span class="hlt">curvature</span> is an evolving dynamical quantity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JCAP...06..002M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JCAP...06..002M"><span>Evolution of the <span class="hlt">curvature</span> perturbations during warm inflation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matsuda, Tomohiro</p> <p>2009-06-01</p> <p>This paper considers warm inflation as an interesting application of multi-field inflation. Delta-N formalism is used for the calculation of the evolution of the <span class="hlt">curvature</span> perturbations during warm inflation. Although the perturbations considered in this paper are decaying after the horizon exit, the corrections to the <span class="hlt">curvature</span> perturbations sourced by these perturbations can remain and dominate the <span class="hlt">curvature</span> perturbations at large scales. In addition to the typical evolution of the <span class="hlt">curvature</span> perturbations, inhomogeneous diffusion rate is considered for warm inflation, which may lead to significant non-Gaussianity of the spectrum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6802731','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6802731"><span>Inconsistency of scale invariant <span class="hlt">curvature</span> coupled to gravity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zoller, D.</p> <p>1990-01-01</p> <p>We show that the scale invariant <span class="hlt">curvature</span> action for paths, the point particle version of Polyakov's extrinsic <span class="hlt">curvature</span> action for surfaces, does not couple consistently to gravity. Although the <span class="hlt">curvature</span> action for paths yields a massless representation of the Poincare group with fixed helicity and so potentially provides a description of single photons and gravitons, the inconsistent coupling to gravity apparently suggests such a description is not viable. We present a physical interpretation of the inconsistency in terms of the non-localizability of the photon and point out a conceptual kinship between the local symmetry of the <span class="hlt">curvature</span> theory and the local supersymmetry of a spinning particle or spinning string. 11 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22757541','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22757541"><span>The <span class="hlt">curvature</span> index and synchronization of dynamical systems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Yen-Sheng; Chang, Chien-Cheng</p> <p>2012-06-01</p> <p>We develop a quantity, named the <span class="hlt">curvature</span> index, for dynamical systems. This index is defined as the limit of the average <span class="hlt">curvature</span> of the trajectory during evolution, which measures the bending of the curve on an attractor. The <span class="hlt">curvature</span> index has the ability to differentiate the topological change of an attractor, as its alterations exhibit the structural changes of a dynamical system. Thus, the <span class="hlt">curvature</span> index may indicate thresholds of some synchronization regimes. The Rössler system and a time-delay system are simulated to demonstrate the effectiveness of the index, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AMTM...36...44B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AMTM...36...44B"><span>Multi-scale <span class="hlt">curvature</span> tensor analysis of machined surfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bartkowiak, Tomasz; Brown, Christopher</p> <p>2016-12-01</p> <p>This paper demonstrates the use of multi-scale <span class="hlt">curvature</span> analysis, an areal new surface characterization technique for better understanding topographies, for analyzing surfaces created by conventional machining and grinding. <span class="hlt">Curvature</span>, like slope and area, changes with scale of observation, or calculation, on irregular surfaces, therefore it can be used for multi-scale geometric analysis. <span class="hlt">Curvatures</span> on a surface should be indicative of topographically dependent behavior of a surface and <span class="hlt">curvatures</span> are, in turn, influenced by the processing and use of the surface. <span class="hlt">Curvatures</span> have not been well characterized previously. <span class="hlt">Curvature</span> has been used for calculations in contact mechanics and for the evaluation of cutting edges. In the current work two parts were machined and then one of them was ground. The surface topographies were measured with a scanning laser confocal microscope. Plots of <span class="hlt">curvatures</span> as a function of position and scale are presented, and the means and standard deviations of principal <span class="hlt">curvatures</span> are plotted as a function of scale. Statistical analyses show the relations between <span class="hlt">curvature</span> and these two manufacturing processes at multiple scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004NIMPA.533...37P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004NIMPA.533...37P"><span>Beam test results of CMS RPCs at <span class="hlt">high</span> eta <span class="hlt">region</span> under <span class="hlt">high</span>-radiation environment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Park, S.; Ahn, S. H.; Bahk, S. Y.; Hong, B.; Hong, S. J.; Kang, D. H.; Kang, T. I.; Kim, T. J.; Kim, Y. J.; Kim, Y. U.; Koo, D. G.; Lee, H. W.; Lee, K. S.; Lee, S. J.; Lim, J. K.; Moon, D. H.; Nam, S. K.; Oh, J. K.; Park, W. J.; Rhee, J. T.; Ryu, M. S.; Shim, H. H.; Sim, K. S.</p> <p>2004-11-01</p> <p>The Compact Muon Solenoid (CMS) forward resistivity plate chambers (RPCs) at the <span class="hlt">high</span> eta <span class="hlt">region</span> must be operated in presence of a radiation-induced rate as <span class="hlt">high</span> as 1 kHz /cm2. It is still unknown if the RPCs coated with linseed oil can be operated under such a <span class="hlt">high</span>-radiation environment over the lifetime of CMS. Non-oiled RPCs may be one of the options since phenolic or melamine-coated bakelite is chemically stabler than linseed oil. We have constructed oiled and non-oiled RPCs at the <span class="hlt">high</span> eta <span class="hlt">region</span> of CMS using phenolic bakelite and tested them in the Gamma Irradiation Facility at CERN. While both RPCs show the same characteristics in the efficiency and the strip multiplicity, the non-oiled RPC generates an intrinsic noise rate of 50 Hz /cm2, compared to only 5 Hz /cm2 for the oiled RPC, both at 10.0 kV which is about 100 V above the 95 % knee of the efficiency curve.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19970016638&hterms=starch&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dstarch','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19970016638&hterms=starch&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dstarch"><span>Induction of Plant <span class="hlt">Curvature</span> by Magnetophoresis and Cytoskeletal Changes during Root Graviresponse</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hasenstein, Karl H.; Kuznetsov, Oleg A.; Blancaflor, Eilson B.</p> <p>1996-01-01</p> <p><span class="hlt">High</span> gradient magnetic fields (HGMF) induce <span class="hlt">curvature</span> in roots and shoots. It is considered that this response is likely to be based on the intracellular displacement of bulk starch (amyloplasts) by the ponderomotive force generated by the HGMF. This process is called magnetophoresis. The differential elongation during the <span class="hlt">curvature</span> along the concave and convex flanks of growing organs may be linked to the microtubular and/or microfilament cytoskeleton. The possible existence of an effect of the HGMF on the cytoskeleton was tested for, but none was found. The application of cytoskeletal stabilizers or depolymerizers showed that neither microtubules, nor microfilaments, are involved in the graviresponse.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JAP...121l5301F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JAP...121l5301F"><span><span class="hlt">Curvature</span> effect on the surface topography evolution during oxidation at small scale</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fang, Xufei; Li, Yan; Feng, Xue</p> <p>2017-03-01</p> <p>We use <span class="hlt">high</span> temperature scanning probe microscopy (SPM) to in situ and real time characterize the evolution of surface topography of metals during oxidation. A nanoindentation method was used to create nanoindents as markers to pinpoint the locations where the evolution of the surface topography was studied. The SPM images reveal that during oxidation, the originally sharp tip of the indented pits exhibits a chamfering and flattening effect, suggesting that the tip <span class="hlt">curvature</span> affects the surface topography evolution at the nanoscale/sub-microscale during the oxidation process. A model is proposed to explain the experimental result by considering the surface diffusion as well as the <span class="hlt">curvature</span> effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24617997','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24617997"><span>Hair <span class="hlt">curvature</span>: a natural dialectic and review.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nissimov, Joseph N; Das Chaudhuri, Asit Baran</p> <p>2014-08-01</p> <p>Although hair forms (straight, curly, wavy, etc.) are present in apparently infinite variations, each fibre can be reduced to a finite sequence of tandem segments of just three types: straight, bent/curly, or twisted. Hair forms can thus be regarded as resulting from genetic pathways that induce, reverse or modulate these basic <span class="hlt">curvature</span> modes. However, physical interconversions between twists and curls demonstrate that strict one-to-one correspondences between them and their genetic causes do not exist. Current hair-<span class="hlt">curvature</span> theories do not distinguish between bending and twisting mechanisms. We here introduce a multiple papillary centres (MPC) model which is particularly suitable to explain twisting. The model combines previously known features of hair cross-sectional morphology with partially/completely separated dermal papillae within single follicles, and requires such papillae to induce differential growth rates of hair cortical material in their immediate neighbourhoods. The MPC model can further help to explain other, poorly understood, aspects of hair growth and morphology. Separate bending and twisting mechanisms would be preferentially affected at the major or minor ellipsoidal sides of fibres, respectively, and together they exhaust the possibilities for influencing hair-form phenotypes. As such they suggest dialectic for hair-<span class="hlt">curvature</span> development. We define a natural-dialectic (ND) which could take advantage of speculative aspects of dialectic, but would verify its input data and results by experimental methods. We use this as a top-down approach to first define routes by which hair bending or twisting may be brought about and then review evidence in support of such routes. In particular we consider the wingless (Wnt) and mammalian target of rapamycin (mTOR) pathways as paradigm pathways for molecular hair bending and twisting mechanisms, respectively. In addition to the Wnt canonical pathway, the Wnt/Ca(2+) and planar cell polarity (PCP) pathways</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=140650','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=140650"><span>The curved DNA structure in the 5′-upstream <span class="hlt">region</span> of the light-responsive genes: its universality, binding factor and function for cyanobacterial psbA transcription</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Asayama, Munehiko; Kato, Hideki; Shibato, Junko; Shirai, Makoto; Ohyama, Takashi</p> <p>2002-01-01</p> <p>A unique DNA <span class="hlt">curvature</span>, the CIT, has been found in the 5′-upstream <span class="hlt">region</span> of the psbA2 gene, which exhibits basal, light-responsive and circadian rhythmic transcription, in a unicellular photosynthetic cyanobacterium, Microcystis aeruginosa K-81. In this study, we report the universality of <span class="hlt">curvatures</span> found in 5′-upstream <span class="hlt">regions</span> in the psbA family and the function of the <span class="hlt">curvature</span> in gene expression. Intrinsic <span class="hlt">curvatures</span> were identified within 1000 bp upstream from the psbA genes in another cyanobacterium, a red alga and in plants (monocot and dicot). Mutagenized <span class="hlt">curvatures</span> were constructed and confirmed to have disrupted architecture by gel electrophoresis and atomic force microscopy. Relatively small amounts but light-responsive transcripts of psbA2 were observed in cyanobacterial transformants harboring the mutagenized <span class="hlt">curvature</span> under light/dark and light/<span class="hlt">high</span>-light conditions. This shows that the <span class="hlt">curvature</span> is important for basal transcription. In vitro primer extension and DNA mobility shift assay revealed that factors which might bind to the <span class="hlt">region</span> upstream from the bending center contribute to the effective basal transcription of psbA2. PMID:12409456</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18479112','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18479112"><span>Modulation of the spontaneous <span class="hlt">curvature</span> and bending rigidity of lipid membranes by interfacially adsorbed amphipathic peptides.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zemel, Assaf; Ben-Shaul, Avinoam; May, Sylvio</p> <p>2008-06-12</p> <p>Amphipathic alpha-helical peptides are often ascribed an ability to induce <span class="hlt">curvature</span> stress in lipid membranes. This may lead directly to a bending deformation of the host membrane, or it may promote the formation of defects that involve <span class="hlt">highly</span> curved lipid layers present in membrane pores, fusion intermediates, and solubilized peptide-micelle complexes. The driving force is the same in all cases: peptides induce a spontaneous <span class="hlt">curvature</span> in the host lipid layer, the sign of which depends sensitively on the peptide's structural properties. We provide a quantitative account for this observation on the basis of a molecular-level method. To this end, we consider a lipid membrane with peptides interfacially adsorbed onto one leaflet at <span class="hlt">high</span> peptide-to-lipid ratio. The peptides are modeled generically as rigid cylinders that interact with the host membrane through a perturbation of the conformational properties of the lipid chains. Through the use of a molecular-level chain packing theory, we calculate the elastic properties, that is, the spontaneous <span class="hlt">curvature</span> and bending stiffness, of the peptide-decorated lipid membrane as a function of the peptide's insertion depth. We find a positive spontaneous <span class="hlt">curvature</span> (preferred bending of the membrane away from the peptide) for small penetration depths of the peptide. At a penetration depth roughly equal to half-insertion into the hydrocarbon core, the spontaneous <span class="hlt">curvature</span> changes sign, implying negative spontaneous <span class="hlt">curvature</span> (preferred bending of the membrane toward the peptide) for large penetration depths. Despite thinning of the membrane upon peptide insertion, we find an increase in the bending stiffness. We discuss these findings in terms of how the peptide induces elastic stress.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ExFl...52..963B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ExFl...52..963B"><span>Local <span class="hlt">curvature</span> measurements of a lean, partially premixed swirl-stabilised flame</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bayley, Alan E.; Hardalupas, Yannis; Taylor, Alex M. K. P.</p> <p>2012-04-01</p> <p>A swirl-stabilised, lean, partially premixed combustor operating at atmospheric conditions has been used to investigate the local <span class="hlt">curvature</span> distributions in lifted, stable and thermoacoustically oscillating CH4-air partially premixed flames for bulk cold-flow Reynolds numbers of 15,000 and 23,000. Single-shot OH planar laser-induced fluorescence has been used to capture instantaneous images of these three different flame types. Use of binary thresholding to identify the reactant and product <span class="hlt">regions</span> in the OH planar laser-induced fluorescence images, in order to extract accurate flame-front locations, is shown to be unsatisfactory for the examined flames. The Canny-Deriche edge detection filter has also been examined and is seen to still leave an unacceptable quantity of artificial flame-fronts. A novel approach has been developed for image analysis where a combination of a non-linear diffusion filter, Sobel gradient and threshold-based curve elimination routines have been used to extract traces of the flame-front to obtain local <span class="hlt">curvature</span> distributions. A visual comparison of the effectiveness of flame-front identification is made between the novel approach, the threshold binarisation filter and the Canny-Deriche filter. The novel approach appears to most accurately identify the flame-fronts. Example histograms of the <span class="hlt">curvature</span> for six flame conditions and of the total image area are presented and are found to have a broader range of local flame <span class="hlt">curvatures</span> for increasing bulk Reynolds numbers. Significantly positive values of mean <span class="hlt">curvature</span> and marginally positive values of skewness of the histogram have been measured for one lifted flame case, but this is generally accounted for by the effect of flame brush <span class="hlt">curvature</span>. The mean local flame-front <span class="hlt">curvature</span> reduces with increasing axial distance from the burner exit plane for all flame types. These changes are more pronounced in the lifted flames but are marginal for the thermoacoustically oscillating flames. It is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009MNRAS.399.1650M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009MNRAS.399.1650M"><span>Relic HII <span class="hlt">regions</span> and radiative feedback at <span class="hlt">high</span> redshifts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mesinger, Andrei; Bryan, Greg L.; Haiman, Zoltán</p> <p>2009-11-01</p> <p>Ultraviolet (UV) radiation from early astrophysical sources could have a large impact on subsequent star formation in nearby protogalaxies, and in general on the progress of cosmological reionization. Theoretical arguments based on the absence of metals in the early Universe suggest that the first stars were likely massive, bright, yet short-lived, with lifetimes of a few million years. Here we study the radiative feedback arising from such stars using hydrodynamical simulations with transient UV backgrounds (UVBs) and persistent Lyman-Werner backgrounds (LWBs) of varying intensity. We extend our prior work in Mesinger et al., by studying a more typical <span class="hlt">region</span> whose protogalaxies form at lower redshifts, z ~ 13-20, in the epoch likely preceding the bulk of reionization. We confirm our previous results that feedback in the relic HII <span class="hlt">regions</span> resulting from such transient radiation is itself transient. Feedback effects dwindle away after ~30 per cent of the Hubble time, and the same critical specific intensity of JUV ~ 0.1 × 10-21ergs-1cm-2Hz-1sr-1 separates positive and negative feedback regimes. This suggests that overall feedback is fairly insensitive to the large-scale environment, overdensity and redshift-dependent halo parameters, and can accurately be modelled in this regime with just the intensity of the impinging UVB. Additionally, we discover a second episode of eventual positive feedback in haloes which have not yet collapsed when their progenitor <span class="hlt">regions</span> were exposed to the transient UVB. When exposed to the transient UVB, this gas suffers relatively little density depletion but a significant enhancement of the molecular hydrogen abundance, thus resulting in net positive feedback. This eventual positive feedback appears in all runs, regardless of the strength of the UVB. However, this feedback regime is very sensitive to the presence of Lyman-Werner radiation, and notable effects disappear under fairly modest background intensities of JLW >~ 10-3 × 10</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27821339','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27821339"><span>Experimental study of the heated contact line <span class="hlt">region</span> for a pure fluid and binary fluid mixture in microgravity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nguyen, Thao T T; Kundan, Akshay; Wayner, Peter C; Plawsky, Joel L; Chao, David F; Sicker, Ronald J</p> <p>2017-02-15</p> <p>Understanding the dynamics of phase change heat and mass transfer in the three-phase contact line <span class="hlt">region</span> is a critical step toward improving the efficiency of phase change processes. Phase change becomes especially complicated when a fluid mixture is used. In this paper, a wickless heat pipe was operated on the International Space Station (ISS) to study the contact line dynamics of a pentane/isohexane mixture. Different interfacial <span class="hlt">regions</span> were identified, compared, and studied. Using <span class="hlt">high</span> resolution (50×), interference images, we calculated the <span class="hlt">curvature</span> gradient of the liquid-vapor interface at the contact line <span class="hlt">region</span> along the edges of the heat pipe. We found that the <span class="hlt">curvature</span> gradient in the evaporation <span class="hlt">region</span> increases with increasing heat flux magnitude and decreasing pentane concentration. The <span class="hlt">curvature</span> gradient for the mixture case is larger than for the pure pentane case. The difference between the two cases increases as pentane concentration decreases. Our data showed that the <span class="hlt">curvature</span> gradient profile within the evaporation section is separated into two <span class="hlt">regions</span> with the boundary between the two corresponding to the location of a thick, liquid, "central drop" <span class="hlt">region</span> at the point of maximum internal local heat flux. We found that the <span class="hlt">curvature</span> gradients at the central drop and on the flat surfaces where condensation begins are one order of magnitude smaller than the gradients in the corner meniscus indicating the driving forces for fluid flow are much larger in the corners.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JOpt...18j5002N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JOpt...18j5002N"><span>Mach-Zehnder interferometer based on tapered PCF with an up-tapered joint for <span class="hlt">curvature</span>, strain and temperature interrogation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Narayan Dash, Jitendra; Jha, Rajan</p> <p>2016-10-01</p> <p>We propose a Mach-Zehnder interferometric sensor based on tapered Photonic Crystal Fiber (PCF) with up-tapered collapsed <span class="hlt">region</span> for measurement of parameters such as <span class="hlt">curvature</span>, strain and temperature. The up-tapered collapsed <span class="hlt">region</span> helps in excitation of the cladding modes in PCF and these modes interfere with each other at the tapered <span class="hlt">region</span> of PCF which is completely collapsed. Three tapered PCFs with varying geometry are fabricated and their effect on <span class="hlt">curvature</span> sensitivity is analyzed. Experimental results show that the proposed sensor has a <span class="hlt">curvature</span> sensitivity of 7.56 nm m-1 with negligible hysteresis effect. Moreover, the proposed sensor shows a strain sensitivity of 1.6 pm/μɛ along with a maximum temperature sensitivity of 51.6 pm °C-1. In addition to this, the response of the interference pattern to all these parameters is found to be linear.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040090415&hterms=Cucumbers&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DCucumbers','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040090415&hterms=Cucumbers&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DCucumbers"><span>Rapid, bilateral changes in growth rate and <span class="hlt">curvature</span> during gravitropism of cucumber hypocotyls: implications for mechanism of growth control</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cosgrove, D. J.</p> <p>1990-01-01</p> <p>The growth response of etiolated cucumber (Cucumis sativus L.) hypocotyls to gravitropic stimulation was examined by means of time-lapse photography and <span class="hlt">high</span>-resolution analysis of surface expansion and <span class="hlt">curvature</span>. In comparison with video analysis, the technique described here has five- to 20-fold better resolution; moreover, the mathematical fitting method (cubic splines) allows direct estimation of local and integrated <span class="hlt">curvature</span>. After switching seedlings from a vertical to horizontal position, both upper and lower surfaces of the stem reacted after a lag of about 11 min with a two- to three-fold increase in surface expansion rate on the lower side and a cessation of expansion, or slight compression, on the upper surface. This growth asymmetry was initiated simultaneously along the length of the hypocotyl, on both upper and lower surfaces, and did not migrate basipetally from the apex. Later stages in the gravitropic response involved a complex reversal of the growth asymmetry, with the net result being a basipetal migration of the curved <span class="hlt">region</span>. This secondary growth reversal may reflect oscillatory and/or self-regulatory behaviour of growing cells. With some qualifications, the kinetics and pattern of growth response are consistent with a mechanism involving hormone redistribution, although they do not prove such a mechanism. The growth kinetics require a growth mechanism which can be stimulated by two- to three-fold or completely inhibited within a few minutes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040090415&hterms=time+curvature&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtime%2Bcurvature','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040090415&hterms=time+curvature&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtime%2Bcurvature"><span>Rapid, bilateral changes in growth rate and <span class="hlt">curvature</span> during gravitropism of cucumber hypocotyls: implications for mechanism of growth control</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cosgrove, D. J.</p> <p>1990-01-01</p> <p>The growth response of etiolated cucumber (Cucumis sativus L.) hypocotyls to gravitropic stimulation was examined by means of time-lapse photography and <span class="hlt">high</span>-resolution analysis of surface expansion and <span class="hlt">curvature</span>. In comparison with video analysis, the technique described here has five- to 20-fold better resolution; moreover, the mathematical fitting method (cubic splines) allows direct estimation of local and integrated <span class="hlt">curvature</span>. After switching seedlings from a vertical to horizontal position, both upper and lower surfaces of the stem reacted after a lag of about 11 min with a two- to three-fold increase in surface expansion rate on the lower side and a cessation of expansion, or slight compression, on the upper surface. This growth asymmetry was initiated simultaneously along the length of the hypocotyl, on both upper and lower surfaces, and did not migrate basipetally from the apex. Later stages in the gravitropic response involved a complex reversal of the growth asymmetry, with the net result being a basipetal migration of the curved <span class="hlt">region</span>. This secondary growth reversal may reflect oscillatory and/or self-regulatory behaviour of growing cells. With some qualifications, the kinetics and pattern of growth response are consistent with a mechanism involving hormone redistribution, although they do not prove such a mechanism. The growth kinetics require a growth mechanism which can be stimulated by two- to three-fold or completely inhibited within a few minutes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25014827','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25014827"><span><span class="hlt">Curvature</span> effects in thin magnetic shells.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gaididei, Yuri; Kravchuk, Volodymyr P; Sheka, Denis D</p> <p>2014-06-27</p> <p>A magnetic energy functional is derived for an arbitrary curved thin shell on the assumption that the magnetostatic effects can be reduced to an effective easy-surface anisotropy; it can be used for solving both static and dynamic problems. General static solutions are obtained in the limit of a strong anisotropy of both signs (easy-surface and easy-normal cases). It is shown that the effect of the <span class="hlt">curvature</span> can be treated as the appearance of an effective magnetic field, which is aligned along the surface normal for the case of easy-surface anisotropy and is tangential to the surface for the case of easy-normal anisotropy. In general, the existence of such a field excludes the solutions that are strictly tangential or strictly normal to the surface. As an example, we consider static equilibrium solutions for a cone surface magnetization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21502666','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21502666"><span>Hawking temperature of constant <span class="hlt">curvature</span> black holes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cai Ronggen; Myung, Yun Soo</p> <p>2011-05-15</p> <p>The constant <span class="hlt">curvature</span> (CC) black holes are higher dimensional generalizations of Banados-Teitelboim-Zanelli black holes. It is known that these black holes have the unusual topology of M{sub D-1}xS{sup 1}, where D is the spacetime dimension and M{sub D-1} stands for a conformal Minkowski spacetime in D-1 dimensions. The unusual topology and time-dependence for the exterior of these black holes cause some difficulties to derive their thermodynamic quantities. In this work, by using a globally embedding approach, we obtain the Hawking temperature of the CC black holes. We find that the Hawking temperature takes the same form when using both the static and global coordinates. Also, it is identical to the Gibbons-Hawking temperature of the boundary de Sitter spaces of these CC black holes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvB..95b4515L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvB..95b4515L"><span>Band geometry, Berry <span class="hlt">curvature</span>, and superfluid weight</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liang, Long; Vanhala, Tuomas I.; Peotta, Sebastiano; Siro, Topi; Harju, Ari; Törmä, Päivi</p> <p>2017-01-01</p> <p>We present a theory of the superfluid weight in multiband attractive Hubbard models within the Bardeen-Cooper-Schrieffer (BCS) mean-field framework. We show how to separate the geometric contribution to the superfluid weight from the conventional one, and that the geometric contribution is associated with the interband matrix elements of the current operator. Our theory can be applied to systems with or without time-reversal symmetry. In both cases the geometric superfluid weight can be related to the quantum metric of the corresponding noninteracting systems. This leads to a lower bound on the superfluid weight given by the absolute value of the Berry <span class="hlt">curvature</span>. We apply our theory to the attractive Kane-Mele-Hubbard and Haldane-Hubbard models, which can be realized in ultracold atom gases. Quantitative comparisons are made to state of the art dynamical mean-field theory and exact diagonalization results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21254117','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21254117"><span>Nonminimal coupling of perfect fluids to <span class="hlt">curvature</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bertolami, Orfeu; Lobo, Francisco S. N.; Paramos, Jorge</p> <p>2008-09-15</p> <p>In this work, we consider different forms of relativistic perfect fluid Lagrangian densities that yield the same gravitational field equations in general relativity (GR). A particularly intriguing example is the case with couplings of the form [1+f{sub 2}(R)]L{sub m}, where R is the scalar <span class="hlt">curvature</span>, which induces an extra force that depends on the form of the Lagrangian density. It has been found that, considering the Lagrangian density L{sub m}=p, where p is the pressure, the extra-force vanishes. We argue that this is not the unique choice for the matter Lagrangian density, and that more natural forms for L{sub m} do not imply the vanishing of the extra force. Particular attention is paid to the impact on the classical equivalence between different Lagrangian descriptions of a perfect fluid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25969523','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25969523"><span><span class="hlt">High</span> radon areas in the Walloon <span class="hlt">region</span> of Belgium.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tondeur, F; Cinelli, G; Dehandschutter, B</p> <p>2015-06-01</p> <p>Indoor radon data from Southern Belgium are organised in 35 geological units (GUs), most of which are homogeneous with respect to the radon risk. The percentage of cases above the reference level (400 Bq m(-3); 300 Bq m(-3) in the future) is calculated for these GUs from the observations and from the log-normal distribution fitted to the data. Affected areas are defined as areas with more than 1 % of houses above the reference level. In the north of the <span class="hlt">region</span>, the old Palaeozoic basement is generally covered by Silesian, Cretaceous and Tertiary rocks, which are unaffected. The affected areas here are hot spots associated with specific Palaeozoic outcrops. In the south, there is generally no cover above Palaeozoic formations, which are often radon affected. The affected areas of Ardenne and Condroz dominate this part, but unaffected areas occur like Famenne and Gaume. About 48 % of the Walloon <span class="hlt">region</span> is expected to be radon affected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20868540','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20868540"><span><span class="hlt">High</span> fertility <span class="hlt">regions</span> in Bangladesh: a marriage cohort analysis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Islam, Sabina; Islam, Mohammad Amirul; Padmadas, Sabu S</p> <p>2010-11-01</p> <p>Bangladesh represents one of the few countries in south Asia where the pace of fertility decline has been unprecedented over the last three decades. Although there has been significant reduction in fertility levels at the national level, <span class="hlt">regional</span> variations continue to persist, especially in Sylhet and Chittagong where the total fertility rates are well above the country average. Using data from three consecutive Bangladesh Demographic and Health Surveys (BDHSs) this paper assesses how fertility patterns in Sylhet and Chittagong differ from the rest of Bangladesh through a marriage cohort analysis of the parity progression ratios, and examines the factors determining the transition rates to higher parity in these two <span class="hlt">regions</span>. Three cohorts of women are identified: those married during 1965-1974, 1975-84 and 1985-94. The results show that the probability that a woman from the recent cohort in Sylhet or Chittagong who had a third birth will have a fourth birth is nearly twice that of her counterpart in other <span class="hlt">regions</span>. Social characteristics such as education, occupation, religion and residence have no effect on fertility in Sylhet and Chittagong. Additional period-specific analyses using the 2007 BDHS data show that women in Sylhet are considerably more likely to have a third or fourth birth sooner than those in other divisions, especially Khulna. The findings call for specific family planning policy interventions in Sylhet and Chittagong ensuring gender equity, promoting female education and delaying entry into marriage and childbearing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=Radius&pg=7&id=EJ723753','ERIC'); return false;" href="http://eric.ed.gov/?q=Radius&pg=7&id=EJ723753"><span>Measurement of the Earth's Radius Based on Historical Evidence of Its <span class="hlt">Curvature</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Roura, Pere; Josep, Calbo</p> <p>2005-01-01</p> <p>Probably the most direct observation of the Earth's <span class="hlt">curvature</span> is how objects appear from over the horizon when we approach them and disappear as we get further away from them. Similarly, the portion of a <span class="hlt">high</span> object (a building or a mountain) that is visible depends on the height of the site where the observation is made. Based upon these very…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=%22References+to%22+AND+Physics&pg=6&id=EJ723753','ERIC'); return false;" href="https://eric.ed.gov/?q=%22References+to%22+AND+Physics&pg=6&id=EJ723753"><span>Measurement of the Earth's Radius Based on Historical Evidence of Its <span class="hlt">Curvature</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Roura, Pere; Josep, Calbo</p> <p>2005-01-01</p> <p>Probably the most direct observation of the Earth's <span class="hlt">curvature</span> is how objects appear from over the horizon when we approach them and disappear as we get further away from them. Similarly, the portion of a <span class="hlt">high</span> object (a building or a mountain) that is visible depends on the height of the site where the observation is made. Based upon these very…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EL....10939002E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EL....10939002E"><span>Directional dependence of the local estimation of H0 and the nonperturbative effects of primordial <span class="hlt">curvature</span> perturbations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Enea Romano, Antonio; Andrés Vallejo, Sergio</p> <p>2015-02-01</p> <p>Recent measurements of the cosmic microwave background (CMB) radiation have shown an apparent tension with the present value of the Hubble parameter inferred from local observations of supernovae, which look closer, i.e. brighter, than what is expected in a homogeneous model with a value of H0 equal to the one estimated from CMB observations. We examine the possibility that such a discrepancy is the consequence of the presence of a local inhomogeneity seeded by primordial <span class="hlt">curvature</span> perturbations, finding that a negative peak of the order of less than two standard deviations could allow to fit low-redshift supernovae observations without the need of using a value of the Hubble parameter different from H0CMB. The type of inhomogeneity we consider does not modify the distance to the last scattering, making it compatible with the constraints of the PLANCK mission data. The effect on the luminosity distance is in fact localized around the <span class="hlt">region</span> in space where the transition between different values of the <span class="hlt">curvature</span> perturbations occurs, producing a local decrease, while the distance outside the inhomogeneity is not affected. Our calculation is fully relativistic and nonperturbative, and for this reason shows important effects which were missed in the previous investigations using relativistic perturbations or Newtonian approximations, because the structures seeded by primordial <span class="hlt">curvature</span> perturbations can be today <span class="hlt">highly</span> nonlinear, and relativist Doppler terms cannot be neglected. Because of these effects the correction to the luminosity distance necessary to explain observations is associated to a compensated structure which involves both an underdense central <span class="hlt">region</span> and an overdense outer shell, ensuring that the distance to the last scattering surface is unaffected. Comparison with studies of local structure based on galaxy surveys analysis reveals that the density profile we find could in fact be compatible with the one obtained for the same <span class="hlt">region</span> of sky where</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009MSSP...23.1223C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009MSSP...23.1223C"><span>Novel Laplacian scheme and multiresolution modal <span class="hlt">curvatures</span> for structural damage identification</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cao, Maosen; Qiao, Pizhong</p> <p>2009-05-01</p> <p>Modal <span class="hlt">curvature</span> is more sensitive to structural damage than directly measured mode shape, and the standard Laplace operator is commonly used to acquire the modal <span class="hlt">curvatures</span> from the mode shapes. However, the standard Laplace operator is very prone to noise, which often leads to the degraded modal <span class="hlt">curvatures</span> incapable of identifying damage. To overcome this problem, a novel Laplacian scheme is proposed, from which an improved damage identification algorithm is developed. The proposed step-by-step procedures in the algorithm include: (1) By progressively upsampling the standard Laplace operator, a new Laplace operator is constructed, from which a Laplace operator array is formed; (2) by applying the Laplace operator array to the retrieved mode shape of a damaged structure, the multiresolution <span class="hlt">curvature</span> mode shapes are produced, on which the damage trait, previously shadowed under the standard Laplace operator, can be revealed by a ridge of multiresolution modal <span class="hlt">curvatures</span>; (3) a Gaussian filter is then incorporated into the new Laplace operator to produce a more versatile Laplace operator with properties of both the smoothness and differential capabilities, in which the damage feature is effectively strengthened; and (4) a smoothened nonlinear energy operator is introduced to further enhance the damage feature by eliminating the trend interference of the multiresolution modal <span class="hlt">curvatures</span>, and it results in a significantly improved damage trait. The proposed algorithm is tested using the data generated by an analytical crack beam model, and its applicability is validated with an experimental program of a delaminated composite beam using scanning laser vibrometer (SLV) to acquire mode shapes. The results are compared in each step, showing increasing degree of improvement for damage effect. Numerical and experimental results demonstrate that the proposed novel Laplacian scheme provides a promising damage identification algorithm, which exhibits apparent advantages (e</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhRvE..89c2811A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhRvE..89c2811A"><span>Topological implications of negative <span class="hlt">curvature</span> for biological and social networks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Albert, Réka; DasGupta, Bhaskar; Mobasheri, Nasim</p> <p>2014-03-01</p> <p>Network measures that reflect the most salient properties of complex large-scale networks are in <span class="hlt">high</span> demand in the network research community. In this paper we adapt a combinatorial measure of negative <span class="hlt">curvature</span> (also called hyperbolicity) to parametrized finite networks, and show that a variety of biological and social networks are hyperbolic. This hyperbolicity property has strong implications on the higher-order connectivity and other topological properties of these networks. Specifically, we derive and prove bounds on the distance among shortest or approximately shortest paths in hyperbolic networks. We describe two implications of these bounds to crosstalk in biological networks, and to the existence of central, influential neighborhoods in both biological and social networks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhyE...84...98P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhyE...84...98P"><span>Modelling the nonlinear behaviour of double walled carbon nanotube based resonator with <span class="hlt">curvature</span> factors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Patel, Ajay M.; Joshi, Anand Y.</p> <p>2016-10-01</p> <p>This paper deals with the nonlinear vibration analysis of a double walled carbon nanotube based mass sensor with <span class="hlt">curvature</span> factor or waviness, which is doubly clamped at a source and a drain. Nonlinear vibrational behaviour of a double-walled carbon nanotube excited harmonically near its primary resonance is considered. The double walled carbon nanotube is harmonically excited by the addition of an excitation force. The modelling involves stretching of the mid plane and damping as per phenomenon. The equation of motion involves four nonlinear terms for inner and outer tubes of DWCNT due to the curved geometry and the stretching of the central plane due to the boundary conditions. The vibrational behaviour of the double walled carbon nanotube with different surface deviations along its axis is analyzed in the context of the time response, Poincaré maps and Fast Fourier Transformation diagrams. The appearance of instability and chaos in the dynamic response is observed as the <span class="hlt">curvature</span> factor on double walled carbon nanotube is changed. The phenomenon of Periodic doubling and intermittency are observed as the pathway to chaos. The <span class="hlt">regions</span> of periodic, sub-harmonic and chaotic behaviour are clearly seen to be dependent on added mass and the <span class="hlt">curvature</span> factors in the double walled carbon nanotube. Poincaré maps and frequency spectra are used to explicate and to demonstrate the miscellany of the system behaviour. With the increase in the <span class="hlt">curvature</span> factor system excitations increases and results in an increase of the vibration amplitude with reduction in excitation frequency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JCoPh.281..285O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JCoPh.281..285O"><span>A mesh-decoupled height function method for computing interface <span class="hlt">curvature</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Owkes, Mark; Desjardins, Olivier</p> <p>2015-01-01</p> <p>In this paper, a mesh-decoupled height function method is proposed and tested. The method is based on computing height functions within columns that are not aligned with the underlying mesh and have variable dimensions. Because they are decoupled from the computational mesh, the columns can be aligned with the interface normal vector, which is found to improve the <span class="hlt">curvature</span> calculation for under-resolved interfaces where the standard height function method often fails. A computational geometry toolbox is used to compute the heights in the complex geometry that is formed at the intersection of the computational mesh and the columns. The toolbox reduces the complexity of the problem to a series of straightforward geometric operations using simplices. The proposed scheme is shown to compute more accurate <span class="hlt">curvatures</span> than the standard height function method on coarse meshes. A combined method that uses the standard height function where it is well defined and the proposed scheme in under-resolved <span class="hlt">regions</span> is tested. This approach achieves accurate and robust <span class="hlt">curvatures</span> for under-resolved interface features and second-order converging <span class="hlt">curvatures</span> for well-resolved interfaces.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008SPIE.6915E..2KP','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008SPIE.6915E..2KP"><span>Automatic segmentation of lung parenchyma based on <span class="hlt">curvature</span> of ribs using HRCT images in scleroderma studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prasad, M. N.; Brown, M. S.; Ahmad, S.; Abtin, F.; Allen, J.; da Costa, I.; Kim, H. J.; McNitt-Gray, M. F.; Goldin, J. G.</p> <p>2008-03-01</p> <p>Segmentation of lungs in the setting of scleroderma is a major challenge in medical image analysis. Threshold based techniques tend to leave out lung <span class="hlt">regions</span> that have increased attenuation, for example in the presence of interstitial lung disease or in noisy low dose CT scans. The purpose of this work is to perform segmentation of the lungs using a technique that selects an optimal threshold for a given scleroderma patient by comparing the <span class="hlt">curvature</span> of the lung boundary to that of the ribs. Our approach is based on adaptive thresholding and it tries to exploit the fact that the <span class="hlt">curvature</span> of the ribs and the <span class="hlt">curvature</span> of the lung boundary are closely matched. At first, the ribs are segmented and a polynomial is used to represent the ribs' <span class="hlt">curvature</span>. A threshold value to segment the lungs is selected iteratively such that the deviation of the lung boundary from the polynomial is minimized. A Naive Bayes classifier is used to build the model for selection of the best fitting lung boundary. The performance of the new technique was compared against a standard approach using a simple fixed threshold of -400HU followed by regiongrowing. The two techniques were evaluated against manual reference segmentations using a volumetric overlap fraction (VOF) and the adaptive threshold technique was found to be significantly better than the fixed threshold technique.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4017297','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4017297"><span>Molecular Modeling of Lipid Membrane <span class="hlt">Curvature</span> Induction by a Peptide: More than Simply Shape</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sodt, Alexander J.; Pastor, Richard W.</p> <p>2014-01-01</p> <p>Molecular dynamics simulations of an amphipathic helix embedded in a lipid bilayer indicate that it will induce substantial positive <span class="hlt">curvature</span> (e.g., a tube of diameter 20 nm at 16% surface coverage). The induction is twice that of a continuum model prediction that only considers the shape of the inclusion. The discrepancy is explained in terms of the additional presence of specific interactions described only by the molecular model. The conclusion that molecular shape alone is insufficient to quantitatively model <span class="hlt">curvature</span> is supported by contrasting molecular and continuum models of lipids with large and small headgroups (choline and ethanolamine, respectively), and of the removal of a lipid tail (modeling a lyso-lipid). For the molecular model, <span class="hlt">curvature</span> propensity is analyzed by computing the derivative of the free energy with respect to bending. The continuum model predicts that the inclusion will soften the bilayer near the headgroup <span class="hlt">region</span>, an effect that may weaken <span class="hlt">curvature</span> induction. The all-atom predictions are consistent with experimental observations of the degree of tubulation by amphipathic helices and variation of the free energy of binding to liposomes. PMID:24806928</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24806928','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24806928"><span>Molecular modeling of lipid membrane <span class="hlt">curvature</span> induction by a peptide: more than simply shape.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sodt, Alexander J; Pastor, Richard W</p> <p>2014-05-06</p> <p>Molecular dynamics simulations of an amphipathic helix embedded in a lipid bilayer indicate that it will induce substantial positive <span class="hlt">curvature</span> (e.g., a tube of diameter 20 nm at 16% surface coverage). The induction is twice that of a continuum model prediction that only considers the shape of the inclusion. The discrepancy is explained in terms of the additional presence of specific interactions described only by the molecular model. The conclusion that molecular shape alone is insufficient to quantitatively model <span class="hlt">curvature</span> is supported by contrasting molecular and continuum models of lipids with large and small headgroups (choline and ethanolamine, respectively), and of the removal of a lipid tail (modeling a lyso-lipid). For the molecular model, <span class="hlt">curvature</span> propensity is analyzed by computing the derivative of the free energy with respect to bending. The continuum model predicts that the inclusion will soften the bilayer near the headgroup <span class="hlt">region</span>, an effect that may weaken <span class="hlt">curvature</span> induction. The all-atom predictions are consistent with experimental observations of the degree of tubulation by amphipathic helices and variation of the free energy of binding to liposomes. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=369082','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=369082"><span>Rearrangements of <span class="hlt">highly</span> polymorphic <span class="hlt">regions</span> near telomeres of Saccharomyces cerevisiae.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Horowitz, H; Thorburn, P; Haber, J E</p> <p>1984-01-01</p> <p>We have examined the mitotic and meiotic properties of telomeric <span class="hlt">regions</span> in various laboratory strains of yeast. Using a sequence (Y probe) derived from a cloned yeast telomere (J. Szostak and E. Blackburn, Cell 29:245-255, 1982), we found that various strains of Saccharomyces cerevisiae show extensive polymorphisms of restriction endonuclease fragment length. Some of the variation in the lengths of telomeric fragments appears to be under the control of a small number of genes. When DNA from various strains was digested with endonuclease KpnI, nearly all of the fragments homologous to the Y probe were found to be of different size. The pattern of fragments in different strains was extremely variable, with a greater degree of polymorphism than that observed for fragments containing the mobile TY1 element. Tetrad analysis of haploid meiotic segregants from diploids heterozygous for many different Y-homologous KpnI fragments revealed that most of them exhibited Mendelian (2:0) segregation. However, only a small proportion of these fragments displayed the obligate 2:2 parental segregation expected of simple allelic variants at the same chromosome end. From the segregations of these fragments, we concluded that some yeast telomeres lack a Y-homologous sequence and that the chromosome arms containing a Y-homologous sequence are different among various yeast strains. <span class="hlt">Regions</span> near yeast telomeres frequently undergo rearrangement. Among eight tetrads from three different diploids, we have found three novel Y-homologous restriction fragments that appear to have arisen during meiosis. In all three cases, the appearance of a new fragment was accompanied by the loss of another band. In one of these cases, the rearrangement leading to a novel fragment arose in an isogenic diploid, in which both homologous chromosomes should have been identical. Among these same tetrads we also found examples of apparent mitotic gene conversions and mitotic recombination involving telemetric</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080004442','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080004442"><span>Coherent gradient sensing method and system for measuring surface <span class="hlt">curvature</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rosakis, Ares J. (Inventor); Singh, Ramen P. (Inventor); Kolawa, Elizabeth (Inventor); Moore, Jr., Nicholas R. (Inventor)</p> <p>2000-01-01</p> <p>A system and method for determining a <span class="hlt">curvature</span> of a specularly reflective surface based on optical interference. Two optical gratings are used to produce a spatial displacement in an interference field of two different diffraction components produced by one grating from different diffraction components produced by another grating. Thus, the <span class="hlt">curvature</span> of the surface can be determined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGP...114..109S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGP...114..109S"><span>Gaussian and mean <span class="hlt">curvatures</span> for discrete asymptotic nets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schief, W. K.</p> <p>2017-04-01</p> <p>We propose discretisations of Gaussian and mean <span class="hlt">curvatures</span> of surfaces parametrised in terms of asymptotic coordinates and examine their relevance in the context of integrable discretisations of classical classes of surfaces and their underlying integrable systems. We also record discrete analogues of the classical relation between the Gaussian <span class="hlt">curvature</span> of hyperbolic surfaces and the torsion of their asymptotic lines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6828813','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6828813"><span>Effects of <span class="hlt">curvature</span> on asymmetric steady states in catalyst particles</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lucier, B J</p> <p>1981-02-01</p> <p>The effects of <span class="hlt">curvature</span> on steady states of chemical catalytic reactions are investigated by studying the cases of the catalytic particle being a spherical or cylindrical shell. Existence and stability of solutions are studied. It is shown that the solutions converge to the solutions for the catalytic slab when the <span class="hlt">curvature</span> goes to 0 in each case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.206.1327D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.206.1327D"><span>An analytical approach to estimate <span class="hlt">curvature</span> effect of coseismic deformations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dong, Jie; Sun, Wenke; Zhou, Xin; Wang, Rongjiang</p> <p>2016-08-01</p> <p>We present an analytical approach to compute the <span class="hlt">curvature</span> effect by the new analytical solutions of coseismic deformation derived for the homogeneous sphere model. We consider two spheres with different radii: one is the same as earth and the other with a larger radius can approximate a half-space model. Then, we calculate the coseismic displacements for the two spheres and define the relative percentage of the displacements as the <span class="hlt">curvature</span> effect. The near-field <span class="hlt">curvature</span> effect is defined relative to the maximum coseismic displacement. The results show that the maximum <span class="hlt">curvature</span> effect is about 4 per cent for source depths of less than 100 km, and about 30 per cent for source depths of less than 600 km. For the far-field <span class="hlt">curvature</span> effect, we define it relative to the observing point. The <span class="hlt">curvature</span> effect is extremely large and sometimes exceeds 100 per cent. Moreover, this new approach can be used to estimate any planet's <span class="hlt">curvature</span> effect quantitatively. For a smaller sphere, such as the Moon, the <span class="hlt">curvature</span> effect is much larger than that of the Earth, with an inverse ratio to the earth's radius.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28584714','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28584714"><span>The development of <span class="hlt">curvature</span> in the porcine radioulna.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pantinople, Jess; McCabe, Kyle; Henderson, Keith; Richards, Hazel L; Milne, Nick</p> <p>2017-01-01</p> <p>Long bone <span class="hlt">curvature</span> in animal limbs has long been a subject of interest and much work has explored why long bones should be curved. However, the 'when' and 'how' of <span class="hlt">curvature</span> development is poorly understood. It has been shown that the rat tibia fails to attain its normal <span class="hlt">curvature</span> if the action of muscles is removed early in life, but it is not clear if this is because the <span class="hlt">curvature</span> fails to develop or if the bone becomes straighter without the action of muscles. No studies have examined the development of bone <span class="hlt">curvature</span> in a normally developing quadruped, so this study tracks the course of <span class="hlt">curvature</span> formation in the radioulna in a series of growing pigs. We also histologically examined the epiphyseal growth plates of these bones to determine if they contribute to the formation of <span class="hlt">curvature</span>. In all three epiphyseal plates examined, the proliferative zone is thicker and more densely populated with chondrocytes on the cranial (convex) side than the caudal (concave) side. Frost's chondral modelling theory would suggest that the cranial side of the bone is under more compression than the caudal side, and we conclude that this is due to the action of triceps extending the elbow by pulling on the olecranon process. These results support the idea that bone <span class="hlt">curvature</span> is an adaptation to habitual loading, where longitudinal loads acting on the curved bone cause bending strains that counter the bending resulting from the habitual muscle action.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUSM.T51A..10M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUSM.T51A..10M"><span>Surface <span class="hlt">Curvature</span> in Island Groups and Discontinuous Cratonic Structures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McDowell, M. S.</p> <p>2002-05-01</p> <p>The Canadian Archipelago includes eight major islands and a host of smaller ones. They are separated by water bodies, of varying widths attributable to glacial activity and ocean currents. Land form varies from relatively rugged mountains (~2000 m) in eastern, glacial, islands, to low lying western, similar to the continental topography adjacent. The Arctic <span class="hlt">region</span> is thought to have been low average elevation before the Pleistocene. To a picture puzzler, it all looks like it fit together. Experimentally cutting apart the islands from large scale maps shows that the rough edges match fairly well. However, when those independent pieces are sutured together, without restraint, as in free air, the fit is far better. Far more importantly, they consistently form a noticeably concave surface. This tendency is not at all apparent in flat surface or computer screen manipulation; the pieces need to be "hand joined" or on a molded surface to allow the assembly to freely form as it will. Fitting together the coastlines above 60 \\deg north, from 120 \\deg west to 45 \\deg east, and comparing the resulting contracted area to the original, obtains an 8 percent area reduction. The <span class="hlt">curvature</span> "humps" a trial planar section of 15 cms by 1.6 cm, a substantial difference in the radius of <span class="hlt">curvature</span>. If you rashly suggest applying that formula globally, the resulting sphere would have a surface area of 4.7 x108,(down from 5 x108), and therefore radius of 6117 km, down from 6400, which is a rather preposterous conclusion. As nobody would believe it, I tested the idea elsewhere. The Huronian succession of six named cratons is adjacent on the south. I cut this map apart, too, and fit it together, once again getting a <span class="hlt">curvature</span>, this time more pronounced. I am trying it with the Indonesian Archipelago, although this area has volcanic complications, and with Precambrian Basins in western Australia and Nimibia, Africa. Indications are - an essentially similar pattern of fit, but non uniform</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040141915&hterms=video+movement+detection&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dvideo%2Bmovement%2Bdetection','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040141915&hterms=video+movement+detection&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dvideo%2Bmovement%2Bdetection"><span>Robust pupil center detection using a <span class="hlt">curvature</span> algorithm</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhu, D.; Moore, S. T.; Raphan, T.; Wall, C. C. (Principal Investigator)</p> <p>1999-01-01</p> <p>Determining the pupil center is fundamental for calculating eye orientation in video-based systems. Existing techniques are error prone and not robust because eyelids, eyelashes, corneal reflections or shadows in many instances occlude the pupil. We have developed a new algorithm which utilizes <span class="hlt">curvature</span> characteristics of the pupil boundary to eliminate these artifacts. Pupil center is computed based solely on points related to the pupil boundary. For each boundary point, a <span class="hlt">curvature</span> value is computed. Occlusion of the boundary induces characteristic peaks in the <span class="hlt">curvature</span> function. <span class="hlt">Curvature</span> values for normal pupil sizes were determined and a threshold was found which together with heuristics discriminated normal from abnormal <span class="hlt">curvature</span>. Remaining boundary points were fit with an ellipse using a least squares error criterion. The center of the ellipse is an estimate of the pupil center. This technique is robust and accurately estimates pupil center with less than 40% of the pupil boundary points visible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11539343','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11539343"><span>Nastic <span class="hlt">curvatures</span> of wheat coleoptiles that develop in true microgravity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Heathcote, D G; Chapman, D K; Brown, A H</p> <p>1995-07-01</p> <p>Dark-grown wheat coleoptiles developed strong <span class="hlt">curvatures</span> within 5 h of being transferred in orbit from a 1 g centrifuge to microgravity during an experiment flown on the IML-1 shuttle mission. The curving tendency was strongest in seedlings that were immature, with coleoptiles shorter than 10 mm at the time of transfer. The <span class="hlt">curvature</span> direction was non-random, and directed away from the caryopsis (the coleptile face adjacent to the caryopsis becoming convex). The <span class="hlt">curvatures</span> were most marked in the basal third of the coleoptiles, contrasting with phototropic responses, which occur in the apical third. We interpret these <span class="hlt">curvatures</span> as being nastic, and related to the <span class="hlt">curvatures</span> commonly reported to occur during clinostat rotation treatments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1096316','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1096316"><span>Effects of Iris Surface <span class="hlt">Curvature</span> on Iris Recognition</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Thompson, Joseph T; Flynn, Patrick J; Bowyer, Kevin W; Santos-Villalobos, Hector J</p> <p>2013-01-01</p> <p>To focus on objects at various distances, the lens of the eye must change shape to adjust its refractive power. This change in lens shape causes a change in the shape of the iris surface which can be measured by examining the <span class="hlt">curvature</span> of the iris. This work isolates the variable of iris <span class="hlt">curvature</span> in the recognition process and shows that differences in iris <span class="hlt">curvature</span> degrade matching ability. To our knowledge, no other work has examined the effects of varying iris <span class="hlt">curvature</span> on matching ability. To examine this degradation, we conduct a matching experiment across pairs of images with varying degrees of iris <span class="hlt">curvature</span> differences. The results show a statistically signi cant degradation in matching ability. Finally, the real world impact of these ndings is discussed</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040089744&hterms=Wheat&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DWheat','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040089744&hterms=Wheat&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DWheat"><span>Nastic <span class="hlt">curvatures</span> of wheat coleoptiles that develop in true microgravity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Heathcote, D. G.; Chapman, D. K.; Brown, A. H.</p> <p>1995-01-01</p> <p>Dark-grown wheat coleoptiles developed strong <span class="hlt">curvatures</span> within 5 h of being transferred in orbit from a 1 g centrifuge to microgravity during an experiment flown on the IML-1 shuttle mission. The curving tendency was strongest in seedlings that were immature, with coleoptiles shorter than 10 mm at the time of transfer. The <span class="hlt">curvature</span> direction was non-random, and directed away from the caryopsis (the coleptile face adjacent to the caryopsis becoming convex). The <span class="hlt">curvatures</span> were most marked in the basal third of the coleoptiles, contrasting with phototropic responses, which occur in the apical third. We interpret these <span class="hlt">curvatures</span> as being nastic, and related to the <span class="hlt">curvatures</span> commonly reported to occur during clinostat rotation treatments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvE..95a2702F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvE..95a2702F"><span>Effect of <span class="hlt">curvature</span> on cholesteric liquid crystals in toroidal geometries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fialho, Ana R.; Bernardino, Nelson R.; Silvestre, Nuno M.; Telo da Gama, Margarida M.</p> <p>2017-01-01</p> <p>The confinement of liquid crystals inside curved geometries leads to exotic structures, with applications ranging from biosensors to optical switches and privacy windows. Here we study how <span class="hlt">curvature</span> affects the alignment of a cholesteric liquid crystal. We model the system on the mesoscale using the Landau-de Gennes model. Our study was performed in three stages, analyzing different curved geometries from cylindrical walls and pores, to toroidal domains, in order to isolate the <span class="hlt">curvature</span> effects. Our results show that the stresses introduced by the <span class="hlt">curvature</span> influence the orientation of the liquid crystal molecules, and cause distortions in the natural periodicity of the cholesteric that depend on the radius of <span class="hlt">curvature</span>, on the pitch, and on the dimensions of the system. In particular, the cholesteric layers of toroidal droplets exhibit a symmetry breaking not seen in cylindrical pores and that is driven by the additional <span class="hlt">curvature</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040089744&hterms=time+curvature&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtime%2Bcurvature','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040089744&hterms=time+curvature&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtime%2Bcurvature"><span>Nastic <span class="hlt">curvatures</span> of wheat coleoptiles that develop in true microgravity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Heathcote, D. G.; Chapman, D. K.; Brown, A. H.</p> <p>1995-01-01</p> <p>Dark-grown wheat coleoptiles developed strong <span class="hlt">curvatures</span> within 5 h of being transferred in orbit from a 1 g centrifuge to microgravity during an experiment flown on the IML-1 shuttle mission. The curving tendency was strongest in seedlings that were immature, with coleoptiles shorter than 10 mm at the time of transfer. The <span class="hlt">curvature</span> direction was non-random, and directed away from the caryopsis (the coleptile face adjacent to the caryopsis becoming convex). The <span class="hlt">curvatures</span> were most marked in the basal third of the coleoptiles, contrasting with phototropic responses, which occur in the apical third. We interpret these <span class="hlt">curvatures</span> as being nastic, and related to the <span class="hlt">curvatures</span> commonly reported to occur during clinostat rotation treatments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040141915&hterms=eyelash&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Deyelash','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040141915&hterms=eyelash&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Deyelash"><span>Robust pupil center detection using a <span class="hlt">curvature</span> algorithm</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhu, D.; Moore, S. T.; Raphan, T.; Wall, C. C. (Principal Investigator)</p> <p>1999-01-01</p> <p>Determining the pupil center is fundamental for calculating eye orientation in video-based systems. Existing techniques are error prone and not robust because eyelids, eyelashes, corneal reflections or shadows in many instances occlude the pupil. We have developed a new algorithm which utilizes <span class="hlt">curvature</span> characteristics of the pupil boundary to eliminate these artifacts. Pupil center is computed based solely on points related to the pupil boundary. For each boundary point, a <span class="hlt">curvature</span> value is computed. Occlusion of the boundary induces characteristic peaks in the <span class="hlt">curvature</span> function. <span class="hlt">Curvature</span> values for normal pupil sizes were determined and a threshold was found which together with heuristics discriminated normal from abnormal <span class="hlt">curvature</span>. Remaining boundary points were fit with an ellipse using a least squares error criterion. The center of the ellipse is an estimate of the pupil center. This technique is robust and accurately estimates pupil center with less than 40% of the pupil boundary points visible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800016222&hterms=Bakshi&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DBakshi','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800016222&hterms=Bakshi&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DBakshi"><span><span class="hlt">High</span>-latitude E and F <span class="hlt">region</span> ionospheric predictions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hunsucker, R. D.; Allen, R.; Argo, P. E.; Babcock, R.; Bakshi, P.; Lund, D.; Matsushita, S.; Smith, G.; Shirochkov, A. V.; Wortham, G.</p> <p>1979-01-01</p> <p>The physical processes and morphology of the <span class="hlt">high</span> latitude E and F layers are discussed. The existence and adequacy of models, and features to be included are examined, as well as reliability of ionospheric predictions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800016222&hterms=argos&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dargos','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800016222&hterms=argos&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dargos"><span><span class="hlt">High</span>-latitude E and F <span class="hlt">region</span> ionospheric predictions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hunsucker, R. D.; Allen, R.; Argo, P. E.; Babcock, R.; Bakshi, P.; Lund, D.; Matsushita, S.; Smith, G.; Shirochkov, A. V.; Wortham, G.</p> <p>1979-01-01</p> <p>The physical processes and morphology of the <span class="hlt">high</span> latitude E and F layers are discussed. The existence and adequacy of models, and features to be included are examined, as well as reliability of ionospheric predictions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2890417','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2890417"><span>Structural and micro-anatomical changes in vertebrae associated with idiopathic-type spinal <span class="hlt">curvature</span> in the curveback guppy model</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2010-01-01</p> <p>Background The curveback lineage of guppy is characterized by heritable idiopathic-type spinal <span class="hlt">curvature</span> that develops during growth. Prior work has revealed several important developmental similarities to the human idiopathic scoliosis (IS) syndrome. In this study we investigate structural and histological aspects of the vertebrae that are associated with spinal <span class="hlt">curvature</span> in the curveback guppy and test for sexual dimorphism that might explain a female bias for severe curve magnitudes in the population. Methods Vertebrae were studied from whole-mount skeletal specimens of curved and non-curved adult males and females. A series of ratios were used to characterize structural aspects of each vertebra. A three-way analysis of variance tested for effects of sex, <span class="hlt">curvature</span>, vertebral position along the spine, and all 2-way interactions (i.e., sex and <span class="hlt">curvature</span>, sex and vertebra position, and vertebra position and <span class="hlt">curvature</span>). Histological analyses were used to characterize micro-architectural changes in affected vertebrae and the intervertebral <span class="hlt">region</span>. Results In curveback, vertebrae that are associated with <span class="hlt">curvature</span> demonstrate asymmetric shape distortion, migration of the intervertebral ligament, and vertebral thickening on the concave side of <span class="hlt">curvature</span>. There is sexual dimorphism among curved individuals such that for several vertebrae, females have more slender vertebrae than do males. Also, in the <span class="hlt">region</span> of the spine where lordosis typically occurs, curved and non-curved females have a reduced width at the middle of their vertebrae, relative to males. Conclusions Based on similarities to human spinal <span class="hlt">curvatures</span> and to animals with induced curves, the concave-convex biases described in the guppy suggest that there is a mechanical component to curve pathogenesis in curveback. Because idiopathic-type <span class="hlt">curvature</span> in curveback is primarily a sagittal deformity, it is structurally more similar to Scheuermann kyphosis than IS. Anatomical differences between teleosts and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20087620','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20087620"><span>Dissipative <span class="hlt">curvature</span> fluctuations in bilayer vesicles: Coexistence of pure-bending and hybrid <span class="hlt">curvature</span>-compression modes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Arriaga, L R; Rodríguez-García, R; López-Montero, I; Farago, B; Hellweg, T; Monroy, F</p> <p>2010-01-01</p> <p>We have studied the relaxation dynamics of shape fluctuations in unilamellar lipid vesicles by neutron spin echo (NSE). The presence of a hybrid <span class="hlt">curvature</span>-compression mode coexisting with the usual bending one has been revealed in the experimental relaxation functions at <span class="hlt">high</span> q . Differently to the conventional relaxation approximately q (3) typical for bending modes, the hybrid mode was found to relax as approximately q (2) , which is compatible with a dissipation mechanism arising from intermonolayer friction. Complementary data obtained from flickering spectroscopy (FS) in giant unilamellar vesicles confirm the existence of both modes coexisting together. By combining NSE and FS data we have depicted the experimental bimodal dispersion diagram, which is found compatible with theoretical predictions for reliable values of the material parameters. From the present data two conventional dynamical methods (NSE and FS) have been shown to be suitable for measuring intermonolayer friction coefficients in bilayer vesicles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6248644','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6248644"><span>Anisotropy of <span class="hlt">high</span>-latitude nighttime F <span class="hlt">region</span> irregularities</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Livingston, R.C.; Rino, C.L.; Owen, J.; Tsunoda, R.T.</p> <p>1982-12-01</p> <p>The anisotropy of intermediate-scale, F <span class="hlt">region</span> irregularities in the nighttime auroral zone is described. The study is based upon spaced-receiver phase scintillation measurements made with the Wideband satellite at Poker Flat, Alaska. A systematic dependence of irregularity anisotropy with local time and magnetic latitude is observed, suggesting convective control. Sheetlike irregularities are confined to the zone of east-west drift near the equatorward boundary of the auroral zone, and at the flow reversal, or Harang discontinuity, the cross-field extension of the sheets is reduced. The extension of rodlike irregularities, which are observed poleward of the zonal convection boundary, also shows apparent convection dominance. Mechanisms for convection control of the anisotropy are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A34C..05L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A34C..05L"><span>Using <span class="hlt">High</span> Resolution <span class="hlt">Regional</span> Climate Models to Quantify the Snow Albedo Feedback in a <span class="hlt">Region</span> of Complex Terrain</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Letcher, T.; Minder, J. R.</p> <p>2015-12-01</p> <p><span class="hlt">High</span> resolution <span class="hlt">regional</span> climate models are used to characterize and quantify the snow albedo feedback (SAF) over the complex terrain of the Colorado Headwaters <span class="hlt">region</span>. Three pairs of 7-year control and pseudo global warming simulations (with horizontal grid spacings of 4, 12, and 36 km) are used to study how the SAF modifies the <span class="hlt">regional</span> climate response to a large-scale thermodynamic perturbation. The SAF substantially enhances warming within the Headwaters domain, locally as much as 5 °C in <span class="hlt">regions</span> of snow loss. The SAF also increases the inter-annual variability of the springtime warming within Headwaters domain under the perturbed climate. Linear feedback analysis is used quantify the strength of the SAF. The SAF attains a maximum value of 4 W m-2 K-1 during April when snow loss coincides with strong incoming solar radiation. On sub-seasonal timescales, simulations at 4 km and 12 km horizontal grid-spacing show good agreement in the strength and timing of the SAF, whereas a 36km simulation shows greater discrepancies that are tired to differences in snow accumulation and ablation caused by smoother terrain. An analysis of the <span class="hlt">regional</span> energy budget shows that transport by atmospheric motion acts as a negative feedback to <span class="hlt">regional</span> warming, damping the effects of the SAF. On the mesoscale, this transport causes non-local warming in locations with no snow. The methods presented here can be used generally to quantify the role of the SAF in other <span class="hlt">regional</span> climate modeling experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28718229','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28718229"><span>Comparison Of Pre-Operative <span class="hlt">Curvature</span> With Postoperative <span class="hlt">Curvature</span> In Root Canals Treated With K-3 Rotary Systems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nagi, Sana Ehsen; Khan, Farhan Raza</p> <p>2017-01-01</p> <p>With root canal treatment, the organic debris and micro-organisms from pulp space is removed and an ideal canal preparation is achieved that is conducive of hermetic obturation. The purpose of this study was to correlate the pre-operative canal <span class="hlt">curvature</span> with the postoperative <span class="hlt">curvature</span> in human extracted teeth prepared with K-3 rotary systems. The root canal preparation was carried out on extracted human molars and premolars using K-3 endodontic rotary files. A pre and post-operative image of the teeth using digital radiograph were taken in order to compare pre and post-operative canal <span class="hlt">curvature</span>. The images were saved in an images retrieval system (Gendex software, USA). Change in the canal <span class="hlt">curvature</span> was measured using the software measuring tool (Vixwin software, USA). Student paired t-test and Pearson correlation test was applied at 0.05 level of significance. There is a statistically significant difference between pre-operative and post-operative canal <span class="hlt">curvature</span> (p-value <0.001) and a strong positive correlation (91% correlation) between pre-operative and post-operative canal <span class="hlt">curvature</span> in teeth prepared with the K-3 rotary files. A significant difference between pre and post instrumentation <span class="hlt">curvature</span> was found. Degree of canal <span class="hlt">curvature</span> was not correlated with time taken for canal preparation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23347831','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23347831"><span>Effect of amino acid distribution of amphipathic helical peptide derived from human apolipoprotein A-I on membrane <span class="hlt">curvature</span> sensing.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tanaka, Masafumi; Takamura, Yuki; Kawakami, Toru; Aimoto, Saburo; Saito, Hiroyuki; Mukai, Takahiro</p> <p>2013-03-01</p> <p>Amphipathic helix, which senses membrane <span class="hlt">curvature</span>, is of growing interest. Here we explore the effect of amino acid distribution of amphipathic helical peptide derived from the C-terminal <span class="hlt">region</span> (residues 220-241) of human apolipoprotein (apo) A-I on membrane <span class="hlt">curvature</span> sensing. This peptide preferred a curved membrane in a manner similar to full-length apoA-I, although its model peptide did not sense membrane <span class="hlt">curvature</span>. Substitution of several residues both on the polar and non-polar faces of the amphipathic helix had no significant effect on sensing, suggestive of the elaborate molecular architecture in the C-terminal helical <span class="hlt">region</span> of apoA-I to exert lipid efflux function. Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26153704','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26153704"><span>Synaptobrevin transmembrane domain influences exocytosis by perturbing vesicle membrane <span class="hlt">curvature</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chang, Che-Wei; Jackson, Meyer B</p> <p>2015-07-07</p> <p>Membrane fusion requires that nearly flat lipid bilayers deform into shapes with very <span class="hlt">high</span> <span class="hlt">curvature</span>. This makes membrane bending a critical force in determining fusion mechanisms. A lipid bilayer will bend spontaneously when material is distributed asymmetrically between its two monolayers, and its spontaneous <span class="hlt">curvature</span> (C0) will influence the stability of curved fusion intermediates. Prior work on Ca(2+)-triggered exocytosis revealed that fusion pore lifetime (τ) varies with vesicle content (Q), and showed that this relation reflects membrane bending energetics. Lipids that alter C0 change the dependence of τ on Q. These results suggested that the greater stability of an initial exocytotic fusion pore associated with larger vesicles reflects the need to bend more membrane during fusion pore dilation. In this study, we explored the possibility of manipulating C0 by mutating the transmembrane domain (TMD) of the vesicle membrane protein synaptobrevin 2 (syb2). Amperometric measurements of exocytosis in mouse chromaffin cells revealed that syb2 TMD mutations altered the relation between τ and Q. The effects of these mutations showed a striking periodicity, changing sign as the structural perturbation moved through the inner and outer leaflets. Some glycine and charge mutations also influenced the dependence of τ on Q in a manner consistent with expected changes in C0. These results suggest that side chains in the syb2 TMD influence the kinetics of exocytosis by perturbing the packing of the surrounding lipids. The present results support the view that membrane bending occurs during fusion pore expansion rather than during fusion pore formation. This supports the view of an initial fusion pore through two relatively flat membranes formed by protein. Copyright © 2015 Biophysical Society. Published by Elsevier Inc. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25562190','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25562190"><span>Using hidden Markov models to characterize termite traveling behavior in tunnels with different <span class="hlt">curvatures</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sim, SeungWoo; Kang, Seung-Ho; Lee, Sang-Hee</p> <p>2015-02-01</p> <p>Subterranean termites live underground and build tunnel networks to obtain food and nesting space. After obtaining food, termites return to their nests to transfer it. The efficiency of termite movement through the tunnels is directly connected to their survival. Tunnels should therefore be optimized to ensure <span class="hlt">highly</span> efficient returns. An optimization factor that strongly affects movement efficiency is tunnel <span class="hlt">curvature</span>. In the present study, we investigated traveling behavior in tunnels with different <span class="hlt">curvatures</span>. We then characterized traveling behavior at the level of the individual using hidden Markov models (HMMs) constructed from the experimental data. To observe traveling behavior, we designed 5-cm long artificial tunnels that had different <span class="hlt">curvatures</span>. The tunnels had widths (W) of 2, 3, or 4mm, and the linear distances between the two ends of the tunnels were (D) 20, 30, 40, or 50mm. <span class="hlt">High</span> values of D indicate low <span class="hlt">curvature</span>. We systematically observed the traveling behavior of Coptotermes formosanus shiraki and Reticulitermes speratus kyushuensis and measured the time (τ) required for a termite to pass through the tunnel. Using HMM models, we calculated τ for different tunnels and compared the results with the τ of real termites. We characterized the traveling behavior in terms of transition probability matrices (TPM) and emission probability matrices (EPM) of HMMs. We briefly discussed the construction of a sinusoidal-like tunnels in relation to the energy required for termites to pass through tunnels and provided suggestions for the development of more sophisticated HMMs to better understand termite foraging behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012APS..MARV40007K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012APS..MARV40007K"><span>Using Surface <span class="hlt">Curvature</span> to Control the Dimerization of a Surface-Active Protein</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kurylowicz, Martin; Giuliani, Maximiliano; Dutcher, John</p> <p>2012-02-01</p> <p>Understanding the influence of surface geometry on adsorbed proteins promises new possibilities in biophysics, such as topographical catalysis, molecular recognition of geometric cues, and modulations of oligomerization or ligand binding. We have created nano-textured hydrophobic surfaces that are stable in buffer by spin coating polystyrene (PS) nanoparticles (NPs) to form patchy NP monolayers on a PS substrate, yielding flat and <span class="hlt">highly</span> curved areas on the same sample. Moreover, we have separated surface chemistry from texture by floating a 10 nm thick film of monodisperse PS onto the NP-functionalized surface. Using Single Molecule Force Spectroscopy we have compared in situ the distribution of detachment lengths for proteins on curved surfaces to that measured on flat surfaces. We have shown that β-Lactoglobulin (β-LG), a surface-active protein which helps to stabilize oil droplets in milk, forms dimers on both flat PS surfaces and surfaces with a radius of <span class="hlt">curvature</span> of 100 nm, whereas β-LG monomers exist for more <span class="hlt">highly</span> curved surfaces with radii of <span class="hlt">curvature</span> of 25 and 40 nm. It is surprising that rather large radii of <span class="hlt">curvature</span> have such a strong influence on proteins whose radius is only ˜2 nm. Furthermore, the transition from dimer to monomer with changes in surface <span class="hlt">curvature</span> offers promising applications for proteins whose function can be modified by their oligomerization state.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995SSRv...72..297M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995SSRv...72..297M"><span>Elemental Abundances in Corotating Interaction <span class="hlt">Regions</span> at <span class="hlt">High</span> Solar Latitudes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maclennan, C. G.; Lanzerotti, L. J.</p> <p>1995-04-01</p> <p>Throughout 1993, as the Ulysses spacecraft traveled from ˜23° to ˜45° south heliolatitude, the HI-SCALE instrument on the spacecraft measured a recurrent series of enhanced particle fluxes with a recurrence period of ˜26.5 days. These particles are accelerated from a background seed population by the corotating interaction <span class="hlt">regions</span> (CIRs) associated with a southern solar polar coronal hole. Using the Wart detector telescope of the HI-SCALE instrument, we have analyzed the elemental abundances of C, N, O, and Fe relative to He for 0.5 4.0 MeV/nucl ions and Ne, Mg, and Si for 1.0 4.0 MeV/nucl ions in the CIRs. We compare the relative abundances to some previous measurements reported from 1 A.U. as well as with solar photosphere abundances. We note that HI-SCALE measurements of the heliolatitude dependence of the oxygen abundance and spectrum as reported by Lanzerottiet al. (1994) suggest that a substantial fraction of the seed population for the CIR-accelerated oxygen is likely to be the anomalous oxygen component of the cosmic rays.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23020396','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23020396"><span>Micro glass ball embedded gels to study cell mechanobiological responses to substrate <span class="hlt">curvatures</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, Sang Joo; Yang, Shengyuan</p> <p>2012-09-01</p> <p>The effects of substrate stiffness on cell behaviors have been extensively studied; however, the effects of substrate <span class="hlt">curvature</span> are not well documented. The <span class="hlt">curvature</span> of the surface to which cells adhere can have profound effects on cell behaviors. To reveal these cell mechanobiological responses to substrate <span class="hlt">curvatures</span>, here we introduce a novel, unique, simple, and flexible class of substrates, polyacrylamide gels embedded with micro glass balls ranging in diameter from 5 μm to 2 mm, to culture cells. NIH-3T3 fibroblasts were cultured on these glass ball embedded gels. Morphologies of cells growing on glass balls were analyzed by using an optical microscope and a 3D confocal laser scanning microscope. The cell behaviors on micro cylindrical glass tubes having similar diameters to the glass balls were also compared. It is observed that the fibroblasts were sensitive to the <span class="hlt">curvatures</span> of the glass balls. Significant differences in cell attachment rate, migration speed, and morphology were noted for cells cultured on glass balls of diameters at or below 500 μm, compared to those on glass balls of larger diameters. Cell spread area increased as a function of the ball diameter with three different slopes in the three distinct <span class="hlt">regions</span> depending on the ball diameter. To the best of our knowledge, this is the first experimental attempt to study cell responses to spherically shaped substrates. These cell culture experiments imply that this class of substrates, micro glass ball embedded gels, can be useful tools to study cell mechanobiological responses to substrate <span class="hlt">curvatures</span>, related cell and tissue engineering researches, and biomedical applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27419660','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27419660"><span>Anisotropic surface functionalization of Au nanorods driven by molecular architecture and <span class="hlt">curvature</span> effects.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Solveyra, Estefania Gonzalez; Tagliazucchi, Mario; Szleifer, Igal</p> <p>2016-10-06</p> <p>This work suggests a novel strategy to coat the caps and body of Au-nanorods (Au-NRs) with end-grafted polymer layers of different compositions by taking advantage of the different <span class="hlt">curvature</span> of these two <span class="hlt">regions</span>. A molecular theory was used to theoretically investigate the effect of local <span class="hlt">curvature</span> and molecular architecture (intramolecular connectivity of the monomers) on the adsorption of polymer mixtures on cylindrical (Au-NR body) and spherical (Au-NR caps) surfaces. The adsorption process was systematically studied as a function of the backbone length, number and position of branches, quality of the solvent and total number of monomers of the polymer molecules in the mixture. The balance between repulsive forces and polymer-surface and polymer-polymer attractions governs the amount and composition of the adsorbed layer. This balance is in turn modulated by the architecture of the polymers, the <span class="hlt">curvature</span> of the surface and the competition between the different polymers in the mixture for the available area. As a result, the equilibrium composition of the polymer layer on spheres and cylinders of the same radius differs, and in turn departs from that of the bulk solution. <span class="hlt">Curvature</span> plays a major role: the available volume at a given distance from the surface is larger for spherical surfaces than for cylindrical ones, therefore the surface density of the bulkier (more branched) polymer in the mixture is larger on the Au-NR caps than on the Au-NR body. These results suggest that the combination of <span class="hlt">curvature</span> at the nanoscale and tailored molecular architecture can confer anisotropic nanoparticles with spatially enriched domains and, therefore, lead to nanoconstructs with directional chemical interactions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27806741','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27806741"><span><span class="hlt">High</span>-risk <span class="hlt">regions</span> and outbreak modelling of tularemia in humans.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Desvars-Larrive, A; Liu, X; Hjertqvist, M; Sjöstedt, A; Johansson, A; Rydén, P</p> <p>2017-02-01</p> <p>Sweden reports large and variable numbers of human tularemia cases, but the <span class="hlt">high</span>-risk <span class="hlt">regions</span> are anecdotally defined and factors explaining annual variations are poorly understood. Here, <span class="hlt">high</span>-risk <span class="hlt">regions</span> were identified by spatial cluster analysis on disease surveillance data for 1984-2012. Negative binomial regression with five previously validated predictors (including predicted mosquito abundance and predictors based on local weather data) was used to model the annual number of tularemia cases within the <span class="hlt">high</span>-risk <span class="hlt">regions</span>. Seven <span class="hlt">high</span>-risk <span class="hlt">regions</span> were identified with annual incidences of 3·8-44 cases/100 000 inhabitants, accounting for 56·4% of the tularemia cases but only 9·3% of Sweden's population. For all <span class="hlt">high</span>-risk <span class="hlt">regions</span>, most cases occurred between July and September. The regression models explained the annual variation of tularemia cases within most <span class="hlt">high</span>-risk <span class="hlt">regions</span> and discriminated between years with and without outbreaks. In conclusion, tularemia in Sweden is concentrated in a few <span class="hlt">high</span>-risk <span class="hlt">regions</span> and shows <span class="hlt">high</span> annual and seasonal variations. We present reproducible methods for identifying tularemia <span class="hlt">high</span>-risk <span class="hlt">regions</span> and modelling tularemia cases within these <span class="hlt">regions</span>. The results may help health authorities to target populations at risk and lay the foundation for developing an early warning system for outbreaks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26808459','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26808459"><span>Programming <span class="hlt">curvature</span> using origami tessellations.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dudte, Levi H; Vouga, Etienne; Tachi, Tomohiro; Mahadevan, L</p> <p>2016-05-01</p> <p>Origami describes rules for creating folded structures from patterns on a flat sheet, but does not prescribe how patterns can be designed to fit target shapes. Here, starting from the simplest periodic origami pattern that yields one-degree-of-freedom collapsible structures-we show that scale-independent elementary geometric constructions and constrained optimization algorithms can be used to determine spatially modulated patterns that yield approximations to given surfaces of constant or varying <span class="hlt">curvature</span>. Paper models confirm the feasibility of our calculations. We also assess the difficulty of realizing these geometric structures by quantifying the energetic barrier that separates the metastable flat and folded states. Moreover, we characterize the trade-off between the accuracy to which the pattern conforms to the target surface, and the effort associated with creating finer folds. Our approach enables the tailoring of origami patterns to drape complex surfaces independent of absolute scale, as well as the quantification of the energetic and material cost of doing so.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6848769','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6848769"><span>Cosmological spatial <span class="hlt">curvature</span> probed by microwave polarization</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Matzner, R.A.; Tolman, B.W.</p> <p>1982-11-15</p> <p>If there is a large-scale anisotropy in the expansion of the universe, the microwave background radiation is expected to be linearly polarized. This communication shows that spatial <span class="hlt">curvature</span> is capable of rotating the polarization of the microwaves relative to its direction at last scattering, which is directly correlated with the expansion anisotropy (and so also the observed intensity anisotropy). In Friedmann-Robertson-Walker models of the universe with additional small expansion anisotropy, the observed rotation relative to the intensity anisotropy would be appreciable and constant over the celestial sphere in the closed (type IX) model, but in the flat and open models, it must either vanish (types I and V) or vary ina complicated way over the celestial sphere (type VII/sub h/). These facts suggest a clear observational test of the closure of the universe. Also, an ambiguity inherent in the homogeneity of the universe does not allow prediction of the direction of rotation; thus homogeneous universes possess a property which might be called ''handedness.''</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22375770','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22375770"><span>BICEP2, the <span class="hlt">curvature</span> perturbation and supersymmetry</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lyth, David H.</p> <p>2014-11-01</p> <p>The tensor fraction r ≅ 0.16 found by BICEP2 corresponds to a Hubble parameter H ≅ 1.0 × 10{sup 14} GeV during inflation. This has two implications for the (single-field) slow-roll inflation hypothesis. First, the inflaton perturbation must account for much more than 10% of the <span class="hlt">curvature</span> perturbation ζ, which barring fine-tuning means that it accounts for practically all of it. It follows that a curvaton-like mechanism for generating ζ requires an alternative to slow roll such as k-inflation. Second, accepting slow-roll inflation, the excursion of the inflaton field is at least of order Planck scale. As a result, the flatness of the inflaton presumably requires a shift symmetry. I point out that if such is the case, the resulting potential is likely to have at least approximately the quadratic form suggested in 1983 by Linde, which is known to be compatible with the observed r as well as the observed spectral index n{sub s}. The shift symmetry does not require supersymmetry. Also, the big H may rule out a GUT by restoring the symmetry and producing fatal cosmic strings. The absence of a GUT would correspond to the absence of superpartners for the Standard Model particles, which indeed have yet to be found at the LHC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.5837K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.5837K"><span>Nonlinear diffusion filtering influenced by mean <span class="hlt">curvature</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kollár, Michal; Mikula, Karol; Čunderlík, Róbert</p> <p>2016-04-01</p> <p>The presentation introduces a new nonlinear diffusion filtering method on closed surfaces such as a sphere, ellipsoid or the Earth's surface. Our new model extends the regularized surface Perona-Malik model by including a local extrema detector based on a mean <span class="hlt">curvature</span> of processed data. The model is thus represented by a nonlinear diffusion equation which filters noise while preserves main edges, local extrema and details important for a correct interpretation of data. We define a surface finite-volume method to approximate numerically the nonlinear parabolic partial differential equation on a closed surface. The closed surface is approximated by a polyhedral surface created by planar triangles representing subdivision of an initial icosahedron grid and we use a piece-wise linear approximation of a solution in space and the backward Euler time discretization. Numerical experiments present nonlinear diffusion filtering of artificial data and real measurements, namely the GOCE satellite observations. They aim to point out a main advantage of the new nonlinear model which, on the contrary of Perona-Malik model, preserves local extremal values of filtered data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GReGr..48..142Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GReGr..48..142Z"><span>Cosmic acceleration from matter-<span class="hlt">curvature</span> coupling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zaregonbadi, Raziyeh; Farhoudi, Mehrdad</p> <p>2016-10-01</p> <p>We consider f( {R,T} ) modified theory of gravity in which, in general, the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar and the trace of the energy-momentum tensor. We indicate that in this type of the theory, the coupling energy-momentum tensor is not conserved. However, we mainly focus on a particular model that matter is minimally coupled to the geometry in the metric formalism and wherein, its coupling energy-momentum tensor is also conserved. We obtain the corresponding Raychaudhuri dynamical equation that presents the evolution of the kinematic quantities. Then for the chosen model, we derive the behavior of the deceleration parameter, and show that the coupling term can lead to an acceleration phase after the matter dominated phase. On the other hand, the <span class="hlt">curvature</span> of the universe corresponds with the deviation from parallelism in the geodesic motion. Thus, we also scrutinize the motion of the free test particles on their geodesics, and derive the geodesic deviation equation in this modified theory to study the accelerating universe within the spatially flat FLRW background. Actually, this equation gives the relative accelerations of adjacent particles as a measurable physical quantity, and provides an elegant tool to investigate the timelike and the null structures of spacetime geometries. Then, through the null deviation vector, we find the observer area-distance as a function of the redshift for the chosen model, and compare the results with the corresponding results obtained in the literature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21541460','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21541460"><span>Gradient expansion, <span class="hlt">curvature</span> perturbations, and magnetized plasmas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Giovannini, Massimo; Rezaei, Zahra</p> <p>2011-04-15</p> <p>The properties of magnetized plasmas are always investigated under the hypothesis that the relativistic inhomogeneities stemming from the fluid sources and from the geometry itself are sufficiently small to allow for a perturbative description prior to photon decoupling. The latter assumption is hereby relaxed and predecoupling plasmas are described within a suitable expansion where the inhomogeneities are treated to a given order in the spatial gradients. It is argued that the (general relativistic) gradient expansion shares the same features of the drift approximation, customarily employed in the description of cold plasmas, so that the two schemes are physically complementary in the large-scale limit and for the low-frequency branch of the spectrum of plasma modes. The two-fluid description, as well as the magnetohydrodynamical reduction, is derived and studied in the presence of the spatial gradients of the geometry. Various solutions of the coupled system of evolution equations in the anti-Newtonian regime and in the quasi-isotropic approximation are presented. The relation of this analysis to the so-called separate universe paradigm is outlined. The evolution of the magnetized <span class="hlt">curvature</span> perturbations in the nonlinear regime is addressed for the magnetized adiabatic mode in the plasma frame.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20122931','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20122931"><span>BAR domains, amphipathic helices and membrane-anchored proteins use the same mechanism to sense membrane <span class="hlt">curvature</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Madsen, K L; Bhatia, V K; Gether, U; Stamou, D</p> <p>2010-05-03</p> <p>The internal membranes of eukaryotic cells are all twists and bends characterized by <span class="hlt">high</span> <span class="hlt">curvature</span>. During recent years it has become clear that specific proteins sustain these <span class="hlt">curvatures</span> while others simply recognize membrane shape and use it as "molecular information" to organize cellular processes in space and time. Here we discuss this new important recognition process termed membrane <span class="hlt">curvature</span> sensing (MCS). First, we review a new fluorescence-based experimental method that allows characterization of MCS using measurements on single vesicles and compare it to sensing assays that use bulk/ensemble liposome samples of different mean diameter. Next, we describe two different MCS protein motifs (amphipathic helices and BAR domains) and suggest that in both cases <span class="hlt">curvature</span> sensitive membrane binding results from asymmetric insertion of hydrophobic amino acids in the lipid membrane. This mechanism can be extended to include the insertion of alkyl chain in the lipid membrane and consequently palmitoylated and myristoylated proteins are predicted to display similar <span class="hlt">curvature</span> sensitive binding. Surprisingly, in all the aforementioned cases, MCS is predominantly mediated by a higher density of binding sites on curved membranes instead of higher affinity as assumed so far. Finally, we integrate these new insights into the debate about which motifs are involved in sensing versus induction of membrane <span class="hlt">curvature</span> and what role MCS proteins may play in biology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28914316','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28914316"><span>Negative Gaussian <span class="hlt">curvature</span> induces significant suppression of thermal conduction in carbon crystals.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Zhongwei; Chen, Jie; Li, Baowen</p> <p>2017-09-28</p> <p>From the mathematic category of surface Gaussian <span class="hlt">curvature</span>, carbon allotropes can be classified into three types: zero <span class="hlt">curvature</span>, positive <span class="hlt">curvature</span>, and negative <span class="hlt">curvature</span>. By performing Green-Kubo equilibrium molecular dynamics simulations, we found that surface <span class="hlt">curvature</span> has a significant impact on the phonon vibration and thermal conductivity (κ) of carbon crystals. When curving from zero <span class="hlt">curvature</span> to negative or positive <span class="hlt">curvature</span> structures, κ is reduced by several orders of magnitude. Interestingly, we found that κ of negatively curved carbon crystals exhibits a monotonic dependence on <span class="hlt">curvature</span>. Through phonon mode analysis, we show that <span class="hlt">curvature</span> induces remarkable phonon softening in phonon dispersion, which results in the reduction of phonon group velocity and flattening of phonon band structure. Furthermore, the <span class="hlt">curvature</span> was found to induce phonon mode hybridization, leading to the suppression of phonon relaxation time. Our study provides physical insight into thermal transport in <span class="hlt">curvature</span> materials, and will be valuable in the modulation of phonon activity through surface <span class="hlt">curvature</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22250772','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22250772"><span>On 3-gauge transformations, 3-<span class="hlt">curvatures</span>, and Gray-categories</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wang, Wei</p> <p>2014-04-15</p> <p>In the 3-gauge theory, a 3-connection is given by a 1-form A valued in the Lie algebra g, a 2-form B valued in the Lie algebra h, and a 3-form C valued in the Lie algebra l, where (g,h,l) constitutes a differential 2-crossed module. We give the 3-gauge transformations from one 3-connection to another, and show the transformation formulae of the 1-<span class="hlt">curvature</span> 2-form, the 2-<span class="hlt">curvature</span> 3-form, and the 3-<span class="hlt">curvature</span> 4-form. The gauge configurations can be interpreted as smooth Gray-functors between two Gray 3-groupoids: the path 3-groupoid P{sub 3}(X) and the 3-gauge group G{sup L} associated to the 2-crossed module L, whose differential is (g,h,l). The derivatives of Gray-functors are 3-connections, and the derivatives of lax-natural transformations between two such Gray-functors are 3-gauge transformations. We give the 3-dimensional holonomy, the lattice version of the 3-<span class="hlt">curvature</span>, whose derivative gives the 3-<span class="hlt">curvature</span> 4-form. The covariance of 3-<span class="hlt">curvatures</span> easily follows from this construction. This Gray-categorical construction explains why 3-gauge transformations and 3-<span class="hlt">curvatures</span> have the given forms. The interchanging 3-arrows are responsible for the appearance of terms with the Peiffer commutator (, )</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4386559','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4386559"><span>Cervical cancer screening coverage in a <span class="hlt">high</span>-incidence <span class="hlt">region</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Navarro, Cibelli; da Fonseca, Allex Jardim; Sibajev, Alexander; Souza, Camila Iasmim de Andrade; Araújo, Daniela Souza; Teles, Daniele Aparecida de Freitas; de Carvalho, Stéphanie Gomes Lins; Cavalcante, Kyldery Wendell Moura; Rabelo, Wendell Lima</p> <p>2015-01-01</p> <p>OBJECTIVE To analyze the coverage of a cervical cancer screening program in a city with a <span class="hlt">high</span> incidence of the disease in addition to the factors associated with non-adherence to the current preventive program. METHODS A cross-sectional study based on household surveys was conducted. The sample was composed of women between 25 and 59 years of age of the city of Boa Vista, RR, Northern Brazil who were covered by the cervical cancer screening program. The cluster sampling method was used. The dependent variable was participation in a women’s health program, defined as undergoing at least one Pap smear in the 36 months prior to the interview; the explanatory variables were extracted from individual data. A generalized linear model was used. RESULTS 603 women were analyzed, with an mean age of 38.2 years (SD = 10.2). Five hundred and seventeen women underwent the screening test, and the prevalence of adherence in the last three years was up to 85.7% (95%CI 82.5;88.5). A <span class="hlt">high</span> per capita household income and recent medical consultation were associated with the lower rate of not being tested in multivariate analysis. Disease ignorance, causes, and prevention methods were correlated with chances of non-adherence to the screening system; 20.0% of the women were reported to have undergone opportunistic and non-routine screening. CONCLUSIONS The informed level of coverage is <span class="hlt">high</span>, exceeding the level recommended for the control of cervical cancer. The preventive program appears to be opportunistic in nature, particularly for the most vulnerable women (with low income and little information on the disease). Studies on the diagnostic quality of cervicovaginal cytology and therapeutic schedules for positive cases are necessary for understanding the barriers to the control of cervical cancer. PMID:25741655</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA564091','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA564091"><span><span class="hlt">High</span>-Resolution <span class="hlt">Regional</span> Phase Attenuation Models of the Iranian Plateau and Zagros (Postprint)</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2012-05-12</p> <p>National Laboratory2 14. ABSTRACT Development of <span class="hlt">high</span>-resolution seismic attenuation models of the Iranian Plateau and the Zagros Mountains is...undertaken. Previous studies have suggested a complexity in crustal and uppermost mantle seismic attenuation structure as well as <span class="hlt">regional</span> phase...propagation characteristics beneath much of the Iranian Plateau and the surrounding <span class="hlt">regions</span>. <span class="hlt">Regional</span> seismic phases show strong lateral variability in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22092387','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22092387"><span>HYDROGEN FLUORIDE IN <span class="hlt">HIGH</span>-MASS STAR-FORMING <span class="hlt">REGIONS</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Emprechtinger, M.; Monje, R. R.; Lis, D. C.; Phillips, T. G.; Van der Tak, F. F. S.; Van der Wiel, M. H. D.; Neufeld, D.; Ceccarelli, C.</p> <p>2012-09-10</p> <p>Hydrogen fluoride (HF) has been established to be an excellent tracer of molecular hydrogen in diffuse clouds. In denser environments, however, the HF abundance has been shown to be approximately two orders of magnitude lower. We present Herschel/HIFI observations of HF J = 1-0 toward two <span class="hlt">high</span>-mass star formation sites, NGC 6334 I and AFGL 2591. In NGC 6334 I the HF line is seen in absorption in foreground clouds and the source itself, while in AFGL 2591 HF is partially in emission. We find an HF abundance with respect to H{sub 2} of 1.5 Multiplication-Sign 10{sup -8} in the diffuse foreground clouds, whereas in the denser parts of NGC 6334 I we derive a lower limit on the HF abundance of 5 Multiplication-Sign 10{sup -10}. Lower HF abundances in dense clouds are most likely caused by freezeout of HF molecules onto dust grains in <span class="hlt">high</span>-density gas. In AFGL 2591, the view of the hot core is obstructed by absorption in the massive outflow, in which HF is also very abundant (3.6 Multiplication-Sign 10{sup -8}) due to the desorption by sputtering. These observations provide further evidence that the chemistry of interstellar fluorine is controlled by freezeout onto gas grains.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24980977','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24980977"><span><span class="hlt">Curvature</span> of the localized surface plasmon resonance peak.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Peng; Liedberg, Bo</p> <p>2014-08-05</p> <p>Localized surface plasmon resonance (LSPR) occurring in noble metal nanoparticles (e.g., Au) is a widely used phenomenon to report molecular interactions. Traditional LSPR sensors typically monitor shifts in the peak position or extinction in response to local refractive index changes in the close vicinity of the nanoparticle surface. The ability to resolve minute shifts/extinction changes is to a large extent limited by instrumental noise. A new strategy to evaluate LSPR responses utilizing changes in the shape of the extinction spectrum (the <span class="hlt">curvature</span>) is proposed. The response of <span class="hlt">curvature</span> to refractive index changes is investigated theoretically using Mie theory and an analytical expression relating the <span class="hlt">curvature</span> to the refractive index is presented. The experimentally derived <span class="hlt">curvatures</span> for 13 nm spherical gold nanoparticles (AuNPs) exposed to solvents with different bulk refractive indices confirm the theoretical predictions. Moreover, both the calculated and experimental findings suggest that the <span class="hlt">curvature</span> is approximately a linear function of refractive index in regimes relevant to bio and chemical sensing. We demonstrate that <span class="hlt">curvature</span> is superior over peak shift and extinction both in terms of signal-to-noise (S/N) ratio and reliability of LSPR sensors. With a <span class="hlt">curvature</span>, one could readily monitor submonolayer adsorption of a low molecular weight thiol molecule (M(w) = 458.6) onto 13 nm AuNPs. It is also worthwhile mentioning that <span class="hlt">curvature</span> is virtually insensitive to instrumental instabilities and artifacts occurring during measurement. Instabilities such as baseline tilt and shift, shift in peak position as well as sharp spikes/steps in the extinction spectra do not induce artifacts in the sensorgrams of <span class="hlt">curvature</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21452743','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21452743"><span>WEAK LINE QUASARS AT <span class="hlt">HIGH</span> REDSHIFT: EXTREMELY <span class="hlt">HIGH</span> ACCRETION RATES OR ANEMIC BROAD-LINE <span class="hlt">REGIONS</span>?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shemmer, Ohad; Trakhtenbrot, Benny; Netzer, Hagai; Anderson, Scott F.; Brandt, W. N.; Schneider, Donald P.; Diamond-Stanic, Aleksandar M.; Fan Xiaohui; Lira, Paulina; Plotkin, Richard M.; Richards, Gordon T.; St