Sample records for chain stretch transition

  1. Observing the chain stretch transition in a highly entangled polyisoprene melt using transient extensional rheometry

    DEFF Research Database (Denmark)

    Nielsen, Jens Kromann; Hassager, Ole; Rasmussen, Henrik K.


    We measure the viscoelastic properties of a highly entangled narrow molecular weight polyisoprene melt with approximately 280 entanglements per chain in steady and transient shear and in elongational flows. The storage and loss moduli of the melt are found to be well described by the Milner and M...


    Institute of Scientific and Technical Information of China (English)

    Lin-xi Zhang; De-lu Zhao


    When polyethylene chains are stretched, the chains are regarded as being confined in an infinite cylinder with decreasing diameter. The conformational properties of polyethylene chains confined in an infinite cylinder are investigated by using rotational isomeric state model. Using the average conformational energy and entropy and the average length, we can determine the elastic force f, or the fraction of the energy term to the total force fe/f, where fe=(б)/(б)/(б). Comparisons with experimental data are also made. The results of these microscopic calculations are discussed in terms of the macroscopic phenomena of rubber elasticity.

  3. The weak fundamental NH-stretching transition in amines (United States)

    Schrøder, Sidsel D.; Hansen, Anne S.; Wallberg, Jens H.; Nielsen, Anne R.; Du, Lin; Kjaergaard, Henrik G.


    Absolute intensities of NH-stretching fundamental and overtone transitions of gas phase aniline, methylamine, ethylamine, cyclopropylamine, methylethylamine, diethylamine and pyrrolidine have been measured with long path length conventional absorption spectroscopy. To support the assignments of NH-stretching transitions, transition frequencies and intensities were calculated with the local mode model using ab initio calculated local mode parameters and dipole moment functions obtained at the CCSD(T)-F12a/VDZ-F12 level of theory. For aniline, the absolute intensities of the NH-stretching transitions show the typical decrease of approximately an order of magnitude for each successive vibrational excitation. For methylamine, ethylamine, cyclopropylamine, methylethylamine, diethylamine and pyrrolidine, the observed absolute intensities of the fundamental NH-stretching transition is weak and of similar strength or even weaker than the corresponding first overtone transition. Characteristic for the amines with a normal fundamental intensity is a conjugated double bond next to the amine group.

  4. Stretching (United States)

    ... Loss Surgery? A Week of Healthy Breakfasts Shyness Stretching KidsHealth > For Teens > Stretching Print A A A ... full range of motion of the joints. continue Stretching Stretching used to be considered the main activity ...

  5. (Adiabatic) phase boundaries in a bistable chain with twist and stretch (United States)

    Zhao, Qingze; Purohit, Prashant K.


    Mass-spring chains with only extensional degrees of freedom have provided insights into the behavior of crystalline solids, including those capable of phase transitions. Here we add rotational degrees of freedom to the masses in a chain and study the dynamics of phase boundaries across which both the twist and stretch can jump. We solve impact and Riemann problems in the chain by numerical integration of the equations of motion and show that the solutions are analogous to those in a phase transforming rod whose stored energy function depends on both twist and stretch. From the dynamics of phase boundaries in the chain we extract a kinetic relation whose form is familiar from earlier studies involving chains with only extensional degrees of freedom. However, for some combinations of parameters characterizing the energy landscape of our springs we find propagating phase boundaries for which the rate of dissipation, as calculated using isothermal expressions for the driving force, is negative. This suggests that we cannot neglect the energy stored in the oscillations of the masses in the interpretation of the dynamics of mass-spring chains. Keeping this in mind we define a local temperature of our chain and show that it jumps across phase boundaries, but not across sonic waves. Hence, impact problems in our mass-spring chains are analogous to those on continuum thermoelastic bars with Mie-Gruneisen type constitutive laws. At the end of the paper we use our chain to shed some light on experiments involving yarns that couple twist and stretch to perform useful work in response to various stimuli.

  6. Structural Transitions in Supercoiled Stretched DNA (United States)

    v, Croquette


    Using magnetic micromanipulation techniques [Strick 96]( uc(T.R.) Strick, J.-F. Allemand, D. Bensimon, A. Bensimon) and uc(V.) Croquette, "The elasticity of a single supercoiled DNA molecule", Science, 271, 1835 (1996)., we have studied the mechanical properties (force versus extension) of single DNA molecules under a wide range of torsional stresses (supercoiling). We show that unwinding the DNA double helix leads to a phase separation between regular B-DNA and denaturation bubbles. The fraction of denatured molecule increases linearly with the degree of unwinding, beginning at a value of 1% unwinding. We have confirmed this denatured state by hybridization of homologous single-stranded DNA probes and by a chemical attack of the exposed bases. Surprisingly, when we overwind the molecule, the elasticity curves we obtain may also be interpreted by the coexistence of two phases, B-DNA and a new phase which we note P-DNA. The fraction of this new phase increases smoothly with overwinding, beginning at 3 % and continuing up to 300 %. Our results indicate that this new phase is four times more twisted that the standard B-DNA and is 1.75 times longer. Although the structure of this phase is not yet known, such a high twisting can only be attained if the sugar-phosphate backbones of the two strands are twisted closely while the bases are expelled outside of the molecule's core, in a structure reminiscent of the one proposed by Pauling. Indeed we have shown that this new phase is sensitive to chemical attack whereas the B-DNA is not. This new phase begins to appear on a molecule overwound by 3 % and stretched by a force of 5 pN, conditions typically encountered in vivo during gene transcription. This new phase may thus play a biological role biophysique-ADN>(for more details).

  7. Nonequilibrium Markov state modeling of the globule-stretch transition (United States)

    Knoch, Fabian; Speck, Thomas


    We describe a systematic approach to construct coarse-grained Markov state models from molecular dynamics data of systems driven into a nonequilibrium steady state. We apply this method to study the globule-stretch transition of a single tethered model polymer in shear flow. The folding and unfolding rates of the coarse-grained model agree with the original detailed model. We demonstrate that the folding and unfolding proceeds through the same narrow region of configuration space but along different cycles.

  8. Stochastic Simulation of a Full-Chain Reptation Model with Constraint Release, Chain-Length Fluctuations and Chain Stretching

    DEFF Research Database (Denmark)

    Neergaard, Jesper; Schieber, Jay D.


    A self-consistent reptation model that includes chain stretching, chain-length fluctuations, segment connectivity and constraint release is used to predict transient and steady flows. Quantitative comparisons are made with entangledsolution data. The model is able to capture quantitatively all fe...... for differentmolecular weight, the transient and steady-state behavior of the extinction angle, and the stress relaxation in cessation of steady shear flow....

  9. Polymer chain organization in tensile-stretched poly(ethylene oxide)-based polymer electrolytes (United States)

    Burba, Christopher M.; Woods, Lauren; Millar, Sarah Y.; Pallie, Jonathan


    Polymer chain orientation in tensile-stretched poly(ethylene oxide)-lithium trifluoromethanesulfonate polymer electrolytes are investigated with polarized infrared spectroscopy as a function of the degree of strain and salt composition (ether oxygen atom to lithium ion ratios of 20:1, 15:1, and 10:1). The 1359 and 1352 cm-1 bands are used to probe the crystalline PEO and P(EO)3LiCF3SO3 domains, respectively, allowing a direct comparison of chain orientation for the two phases. Two-dimensional correlation FT-IR spectroscopy indicates that the two crystalline domains align at the same rate as the polymer electrolytes are stretched. Quantitative measurements of polymer chain orientation obtained through dichroic infrared spectroscopy show that chain orientation predominantly occurs between strain values of 150% and 250%, regardless of salt composition investigated. There are few changes in chain orientation for either phase when the films are further elongated to a strain of 300%; however, the PEO domains are slightly more oriented at the high strain values. The spectroscopic data are consistent with stretching-induced melt-recrystallization of the unoriented crystalline domains in the solution-cast polymer films. Stretching the films pulls polymer chains from the crystalline domains, which subsequently recrystallize with the polymer helices parallel to the stretch direction. If lithium ion conduction in crystalline polymer electrolytes is viewed as consisting of two major components (facile intra-chain lithium ion conduction and slow helix-to-helix inter-grain hopping), then alignment of the polymer helices will affect the ion conduction pathways for these materials by reducing the number of inter-grain hops required to migrate through the polymer electrolyte. PMID:22184475

  10. Polymer chain organization in tensile-stretched poly(ethylene oxide)-based polymer electrolytes. (United States)

    Burba, Christopher M; Woods, Lauren; Millar, Sarah Y; Pallie, Jonathan


    Polymer chain orientation in tensile-stretched poly(ethylene oxide)-lithium trifluoromethanesulfonate polymer electrolytes are investigated with polarized infrared spectroscopy as a function of the degree of strain and salt composition (ether oxygen atom to lithium ion ratios of 20:1, 15:1, and 10:1). The 1359 and 1352 cm(-1) bands are used to probe the crystalline PEO and P(EO)(3)LiCF(3)SO(3) domains, respectively, allowing a direct comparison of chain orientation for the two phases. Two-dimensional correlation FT-IR spectroscopy indicates that the two crystalline domains align at the same rate as the polymer electrolytes are stretched. Quantitative measurements of polymer chain orientation obtained through dichroic infrared spectroscopy show that chain orientation predominantly occurs between strain values of 150% and 250%, regardless of salt composition investigated. There are few changes in chain orientation for either phase when the films are further elongated to a strain of 300%; however, the PEO domains are slightly more oriented at the high strain values. The spectroscopic data are consistent with stretching-induced melt-recrystallization of the unoriented crystalline domains in the solution-cast polymer films. Stretching the films pulls polymer chains from the crystalline domains, which subsequently recrystallize with the polymer helices parallel to the stretch direction. If lithium ion conduction in crystalline polymer electrolytes is viewed as consisting of two major components (facile intra-chain lithium ion conduction and slow helix-to-helix inter-grain hopping), then alignment of the polymer helices will affect the ion conduction pathways for these materials by reducing the number of inter-grain hops required to migrate through the polymer electrolyte.

  11. Treatment of Fluctuation Effects in Mean-field Models of Chain Stretching (United States)

    Douglas, Jack; Mansfield, Marc


    Many recent studies of chain stretching in block copolymer materials, polymer brushes, and many-arm stars have been formulated in terms of mean- field models, leading generally to power-law potentials describing the chain stretching arising from interchain and intrachain excluded volume interactions. This type of model has been highly successful, but fluctuation effects associated with finite chain length are often neglected in model calculations. We investigate whether fluctuation effects can be accounted for by reintroducing these effective pseudo-potentials into a path-integral description to calculate the chain streching. Numerical treatment of chain swelling with repulsive power-law potentials leads to universal scaling curves which are similar to those found for chain swelling due to excluded volume in polymer solutions. Density profiles are also calculated and the parabolic potential led to a density profile having a "foot" for finite chain lengths, as in measurements on polymer "brushes". Analytic calculations indicate a general relation between the polymer size exponent nu and the power of the potential which also holds for Hamiltonian dynamical systems and thus the 2/3 power law describing the strong segregation scaling of block copolymer lamellae with chain mass corresponds to Kepler's third law of planetary motion relating the orbital scale to its period.

  12. Molecular chain stretch is a multiaxial failure criterion for conventional and highly crosslinked UHMWPE. (United States)

    Bergström, J S; Rimnac, C M; Kurtz, S M


    The development of accurate theoretical failure, fatigue, and wear models for ultra-high molecular weight polyethylene (UHMWPE) is an important step towards better understanding the micromechanisms of the surface damage that occur in load bearing orthopaedic components and improving the lifetime of joint arthoplasties. Previous attempts to analytically predict the clinically observed damage, wear, and fatigue failure modes have met with limited success due to the complicated interaction between microstructural deformations and continuum level stresses. In this work, we examined monotonic uniaxial and multiaxial loading to failure of UHMWPE using eight failure criteria (maximum principal stress, Mises stress, Tresca stress, hydrostatic stress, Coulomb stress, maximum principal strain, Mises strain, and chain stretch). The quality of the predictions of the different models was assessed by comparing uniaxial tension and small punch test data at different rates with the failure model predictions. The experimental data were obtained for two conventional (unirradiated and gamma radiation sterilized in nitrogen) and two highly crosslinked (150kGy, remelted and annealed) UHMWPE materials. Of the different failures models examined, the chain stretch failure model was found to capture uniaxial and multiaxial failure data most accurately for all of the UHMWPE materials. In addition, the chain stretch failure criterion can readily be calculated for contemporary UHMWPE materials based on available uniaxial tension data. These results lay the foundation for future developments of damage and wear models capable of predicting multiaxial failure under cyclic loading conditions.

  13. Stretching and imaging of single DNA chains on a hydrophobic polymer surface made of amphiphilic alternating comb-copolymer. (United States)

    Liu, Rongrong; Wong, Sheau Tyug; Lau, Peggy Pei Zhi; Tomczak, Nikodem


    Functionalization of amine derivatized glass slides with a poly(maleic anhydride)-based comb-copolymer to facilitate stretching, aligning, and imaging of individual dsDNA chains is presented. The polymer-coated surface is hydrophobic due to the presence of the long alkyl side chains along the polymer backbone. The surface is also characterized by low roughness and a globular morphology. Stretched and aligned bacteriophage λ-DNA chains were obtained using a robust method based on stretching by a receding water meniscus at pH 7.8 without the need for small droplet volumes or precoating the surface with additional layers of (bio)molecules. Although the dye to DNA base pairs ratio did not influence substantially the stretching length distributions, a clear peak at stretching lengths close to the contour length of the dsDNA is visible at larger staining ratios.

  14. Vascular endothelial cell membranes differentiate between stretch and shear stress through transitions in their lipid phases. (United States)

    Yamamoto, Kimiko; Ando, Joji


    Vascular endothelial cells (ECs) respond to the hemodynamic forces stretch and shear stress by altering their morphology, functions, and gene expression. However, how they sense and differentiate between these two forces has remained unknown. Here we report that the plasma membrane itself differentiates between stretch and shear stress by undergoing transitions in its lipid phases. Uniaxial stretching and hypotonic swelling increased the lipid order of human pulmonary artery EC plasma membranes, thereby causing a transition from the liquid-disordered phase to the liquid-ordered phase in some areas, along with a decrease in membrane fluidity. In contrast, shear stress decreased the membrane lipid order and increased membrane fluidity. A similar increase in lipid order occurred when the artificial lipid bilayer membranes of giant unilamellar vesicles were stretched by hypotonic swelling, indicating that this is a physical phenomenon. The cholesterol content of EC plasma membranes significantly increased in response to stretch but clearly decreased in response to shear stress. Blocking these changes in the membrane lipid order by depleting membrane cholesterol with methyl-β-cyclodextrin or by adding cholesterol resulted in a marked inhibition of the EC response specific to stretch and shear stress, i.e., phosphorylation of PDGF receptors and phosphorylation of VEGF receptors, respectively. These findings indicate that EC plasma membranes differently respond to stretch and shear stress by changing their lipid order, fluidity, and cholesterol content in opposite directions and that these changes in membrane physical properties are involved in the mechanotransduction that activates membrane receptors specific to each force.

  15. Entropy Rate for Hidden Markov Chains with rare transitions



    We consider Hidden Markov Chains obtained by passing a Markov Chain with rare transitions through a noisy memoryless channel. We obtain asymptotic estimates for the entropy of the resulting Hidden Markov Chain as the transition rate is reduced to zero.

  16. Structural Transitions of a Twisted and Stretched DNA Molecule (United States)

    Léger, J. F.; Romano, G.; Sarkar, A.; Robert, J.; Bourdieu, L.; Chatenay, D.; Marko, J. F.


    We report results of a micromanipulation study of single double-helical DNA molecules at forces up to 150 pN. Depending on whether the DNA winding is allowed to relax, or held fixed, qualitatively different structural transitions are observed. By studying the transitions as a function of winding the different DNA structures underlying them are characterized; this allows us to report the first estimate of S-DNA helicity. A model is introduced to describe these transitions; in addition to B-DNA, we find that four DNA states are needed to describe the experiments.

  17. Absolute intensities of NH-stretching transitions in dimethylamine and pyrrole. (United States)

    Miller, Benjamin J; Du, Lin; Steel, Thomas J; Paul, Allanah J; Södergren, A Helena; Lane, Joseph R; Henry, Bryan R; Kjaergaard, Henrik G


    Vibrational spectra of vapor-phase dimethylamine (DMA) and pyrrole have been recorded in the 1000 to 13000 cm(-1) region using long path conventional spectroscopy techniques. We have focused on the absolute intensities of the NH-stretching fundamental and overtone transitions; Δν(NH) = 1-4 regions for DMA and the Δν(NH) = 1-3 regions for pyrrole. In the Δν(NH) = 1-3 regions for DMA, evidence of tunneling splitting associated with the NH-wagging mode is observed. For DMA, the fundamental NH-stretching transition intensity is weaker than the first NH-stretching overtone. Also, the fundamental NH-stretching transition in DMA is much weaker than the fundamental transition in pyrrole. We have used an anharmonic oscillator local mode model with ab initio calculated local mode parameters and dipole moment functions at the CCSD(T)/aug-cc-pVTZ level to calculate the NH-stretching intensities and explain this intensity anomaly in DMA.

  18. Markov chains with quasitoeplitz transition matrix: applications



    Application problems are investigated for the Markov chains with quasitoeplitz transition matrix. Generating functions of transient and steady state probabilities, first zero hitting probabilities and mean times are found for various particular cases, corresponding to some known patterns of feedback ( “warm-up,” “switch at threshold” etc.), Level depending dams and queue-depending queueing systems of both M/G/1 and MI/G/1 types with arbitrary random sizes of arriving and departing groups are ...

  19. Effects of Stretching Ratio and Temperature on Phase Transition of Melt-spun Poly (Vinylidene Fluoride) Fibers

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hua; REN Ping; ZHANG Guifang; XIAO Changfa


    The effects of stretching ratio and stretching temperature on phase transition of melt-spun poly ( vinylidene fluoride ) fibers were investigated and analyzed by using scanning electron microscopy, wide angle Xray diffraction, differential scanning calorimetry and Fourier transfer infrared spectroscopy. The β phase exists in the as-spun fiber. The β phase content increases as the stretching ratio increases. When the stretching temperature is lower than 100 ℃ , enhancing temperature is good for the transition of phase α to β. By contrast, when the stretching temperature is higher than 100 ℃ , enhancing temperature is unfavourable for the transition of phase α to β. Increasing the draw temperature increases the α-phase content.

  20. Effects of diaphragm stretching on posterior chain muscle kinematics and rib cage and abdominal excursion: a randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Francisco J. González-Álvarez


    Full Text Available ABSTRACT Background Few studies have explored the effects of stretching techniques on diaphragm and spine kinematics. Objective To determine whether the application of diaphragm stretching resulted in changes in posterior chain muscle kinematics and ribcage and abdominal excursion in healthy subjects. Method Eighty healthy adults were included in this randomized clinical trial. Participants were randomized into two groups: the experimental group, which received a diaphragmatic stretching technique, or the placebo group, which received a sham-ultrasound procedure. The duration of the technique, the position of participants, and the therapist who applied the technique were the same for both treatments. Participant assessment (cervical range of movement, lumbar flexibility, flexibility of the posterior chain, and rib cage and abdominal excursion was performed at baseline and immediately after the intervention by a blinded assessor. Results The mean between-group difference [95% CI] for the ribcage excursion after technique at xiphoid level was 2.48 [0.97 to 3.99], which shows significant differences in this outcome. The remaining between-group analysis showed significant differences in cervical extension, right and left flexion, flexibility of the posterior chain, and ribcage excursion at xiphoid level (p<0.05 in favor of the experimental group. Conclusion Diaphragm stretching generates a significant improvement in cervical extension, right and left cervical flexion, flexibility of the posterior chain, and ribcage excursion at xiphoid level compared to a placebo technique in healthy adults.

  1. Is remote stretching based on myofascial chains as effective as local exercise? A randomised-controlled trial. (United States)

    Wilke, J; Vogt, L; Niederer, D; Banzer, W


    Lower limb stretching based on myofascial chains has been demonstrated to increase cervical range of motion (ROM) in the sagittal plane. It is, however, unknown whether such remote exercise is as effective as local stretching. To resolve this research deficit, 63 healthy participants (36 ± 13 years, ♂32) were randomly assigned to one of three groups: remote stretching of the lower limb (LLS), local stretching of the cervical spine (CSS) or inactive control (CON). Prior (M1), immediately post (M2) and 5 min following intervention (M3), maximal cervical ROM was assessed. Non-parametric data analysis (Kruskal-Wallis tests and adjusted post hoc Dunn tests) revealed significant differences between the disposed conditions. With one exception (cervical spine rotation after CSS at M2, P > .05), both LLS and CSS increased cervical ROM compared to the control group in all movement planes and at all measurements (P  .05). Lower limb stretching based on myofascial chains induces similar acute improvements in cervical ROM as local exercise. Therapists might consequently consider its use in programme design. However, as the attained effects do not seem to be direction-specific, further research is warranted in order to provide evidence-based recommendations.

  2. Passive Repetitive Stretching for a Short Duration within a Week Increases Myogenic Regulatory Factors and Myosin Heavy Chain mRNA in Rats' Skeletal Muscles

    Directory of Open Access Journals (Sweden)

    Yurie Kamikawa


    Full Text Available Stretching is a stimulation of muscle growth. Stretching for hours or days has an effect on muscle hypertrophy. However, differences of continuous stretching and repetitive stretching to affect muscle growth are not well known. To clarify the difference of continuous and repetitive stretching within a short duration, we investigated the gene expression of muscle-related genes on stretched skeletal muscles. We used 8-week-old male Wistar rats ( for this study. Animals medial gastrocnemius muscle was stretched continuously or repetitively for 15 min daily and 4 times/week under anesthesia. After stretching, muscles were removed and total RNA was extracted. Then, reverse transcriptional quantitative real-time PCR was done to evaluate the mRNA expression of MyoD, myogenin, and embryonic myosin heavy chain (MyHC. Muscles, either stretched continuously or repetitively, increased mRNA expression of MyoD, myogenin, and embryonic MyHC more than unstretched muscles. Notably, repetitive stretching resulted in more substantial effects on embryonic MyHC gene expression than continuous stretching. In conclusion, passive stretching for a short duration within a week is effective in increasing myogenic factor expression, and repetitive stretching had more effects than continuous stretching for skeletal muscle on muscle growth. These findings are applicable in clinical muscle-strengthening therapy.

  3. Folding of a single polymer chain and phase transition

    Institute of Scientific and Technical Information of China (English)

    DING YanWei; ZHANG GuangZhao


    Using an ultra-sensitive differential scanning calorimetry (US-DSC), we have investigated the folding and aggregation behaviors of poly(N-isopropylacrylamide) (PNIPAM) chains in dilute and semidilute solutions. In the heating process, the intrachain folding and interchain aggregation simultaneously occur in the dilute solutions, and the ratio of intrachain folding increases with decreasing concentra-tion. In the semidilute solutions, PNIPAM chains show limited interchain aggregation with elevated temperature, because most of the PNIPAM chains have been collapsed at lower temperature. In an ex-tremely dilute solution, PNIPAM chains undergo a single folding transition in the heating process. By extrapolating heating rate and concentration to zero, we have obtained the phase transition tempera-ture (Ts) and enthalpy change (AHs) of the single chain folding. AHs is higher than that for a phase transition involving intrachain collapse and interchain aggregation, indicating that a single chain fold-ing can not be taken to be a macroscopic phase transition.

  4. Novel scenario of the folding transition of a single chain

    Energy Technology Data Exchange (ETDEWEB)

    Yoshikawa, Kenichi; Yoshinaga, Natsuhiko [Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)


    Unique characteristics of a single polymer chain with the effects of stiffness and charge are discussed. It has been well established that a flexible polymer chain undergoes a continuous transition from an elongated coil to a compact globule, corresponding to the transition between disordered gas-like and disordered liquid-like states. Here, we will show that a semiflexible chain exhibits a discrete transition from coil to compact states, corresponding to a disorder-order transition to an ordered crystalline state. We will propose a novel strategy to obtain various kinds of nano-ordered structures from single chains connecting a pair of chains of different stiffness. We will also discuss the effect of charge, putting emphasis on intramolecular segregation in a single polyelectrolyte chain.

  5. Markov chains with quasitoeplitz transition matrix

    Directory of Open Access Journals (Sweden)

    Alexander M. Dukhovny


    Full Text Available This paper investigates a class of Markov chains which are frequently encountered in various applications (e.g. queueing systems, dams and inventories with feedback. Generating functions of transient and steady state probabilities are found by solving a special Riemann boundary value problem on the unit circle. A criterion of ergodicity is established.

  6. A molecular simulation analysis of producing monatomic carbon chains by stretching ultranarrow graphene nanoribbons

    CERN Document Server

    Qi, Zenan; Zhou, Xiaozhou; Sun, Zehui; Park, Harold S; Wu, Hengan; 10.1088/0957-4484/21/26/265702


    Atomistic simulations were utilized to develop fundamental insights regarding the elongation process starting from ultranarrow graphene nanoribbons (GNRs) and resulting in monatomic carbon chains (MACCs). There are three key findings. First, we demonstrate that complete, elongated, and stable MACCs with fracture strains exceeding 100% can be formed from both ultranarrow armchair and zigzag GNRs. Second, we demonstrate that the deformation processes leading to the MACCs have strong chirality dependence. Specifically, armchair GNRs first form DNA-like chains, then develop into monatomic chains by passing through an intermediate configuration in which monatomic chain sections are separated by two-atom attachments. In contrast, zigzag GNRs form rope-ladder-like chains through a process in which the carbon hexagons are first elongated into rectangles; these rectangles eventually coalesce into monatomic chains through a novel triangle-pentagon deformation structure under further tensile deformation. Finally, we sho...

  7. Transient overshoot extensional rheology of long-chain branched polyethylenes: Experimental and numerical comparisons between filament stretching and cross-slot flow

    DEFF Research Database (Denmark)

    Hoyle, D.M.; Huang, Qian; Auhl, D.


    This work analyses the high-strain extensional behavior of long-chain branched polyethylenes, employing two novel extensional rheometer devices, the filament stretching rheometer and the cross-slot extensional rheometer. The filament stretching rheometer uses an active feedback loop to control...... the outflow centre line (named W-cusps). Using constitutive modeling of the observed transient overshoot in extension seen in the filament stretching rheometer and using finite element simulations we show that the overshoot explains the W-cusps seen in the cross-slot extensional rheometer, further confirming...

  8. Myosin heavy chain isoform composition and stretch activation kinetics in single fibres of Xenopus laevis iliofibularis muscle. (United States)

    Andruchova, Olena; Stephenson, Gabriela M M; Andruchov, Oleg; Stephenson, D George; Galler, Stefan


    Skeletal muscle is composed of specialized fibre types that enable it to fulfil complex and variable functional needs. Muscle fibres of Xenopus laevis, a frog formerly classified as a toad, were the first to be typed based on a combination of physiological, morphological, histochemical and biochemical characteristics. Currently the most widely accepted criterion for muscle fibre typing is the myosin heavy chain (MHC) isoform composition because it is assumed that variations of this protein are the most important contributors to functional diversity. Yet this criterion has not been used for classification of Xenopus fibres due to the lack of an effective protocol for MHC isoform analysis. In the present study we aimed to resolve and visualize electrophoretically the MHC isoforms expressed in the iliofibularis muscle of Xenopus laevis, to define their functional identity and to classify the fibres based on their MHC isoform composition. Using a SDS-PAGE protocol that proved successful with mammalian muscle MHC isoforms, we were able to detect five MHC isoforms in Xenopus iliofibularis muscle. The kinetics of stretch-induced force transients (stretch activation) produced by a fibre was strongly correlated with its MHC isoform content indicating that the five MHC isoforms confer different kinetics characteristics. Hybrid fibre types containing two MHC isoforms exhibited stretch activation kinetics parameters that were intermediate between those of the corresponding pure fibre types. These results clearly show that the MHC isoforms expressed in Xenopus muscle are functionally different thereby validating the idea that MHC isoform composition is the most reliable criterion for vertebrate skeletal muscle fibre type classification. Thus, our results lay the foundation for the unequivocal classification of the muscle fibres in the Xenopus iliofibularis muscle and for gaining further insights into skeletal muscle fibre diversity.

  9. Markov chains with quasitoeplitz transition matrix: first zero hitting

    Directory of Open Access Journals (Sweden)

    Alexander M. Dukhovny


    Full Text Available This paper continues the investigation of Markov Chains with a quasitoeplitz transition matrix. Generating functions of first zero hitting probabilities and mean times are found by the solution of special Riemann boundary value problems on the unit circle. Duality is discussed.

  10. Markov chain evaluation of acute postoperative pain transition states. (United States)

    Tighe, Patrick J; Bzdega, Matthew; Fillingim, Roger B; Rashidi, Parisa; Aytug, Haldun


    Previous investigations on acute postoperative pain dynamicity have focused on daily pain assessments, and so were unable to examine intraday variations in acute pain intensity. We analyzed 476,108 postoperative acute pain intensity ratings, which were clinically documented on postoperative days 1 to 7 from 8346 surgical patients using Markov chain modeling to describe how patients are likely to transition from one pain state to another in a probabilistic fashion. The Markov chain was found to be irreducible and positive recurrent, with no absorbing states. Transition probabilities ranged from 0.0031, for the transition from state 10 to state 1, to 0.69 for the transition from state 0 to state 0. The greatest density of transitions was noted in the diagonal region of the transition matrix, suggesting that patients were generally most likely to transition to the same pain state as their current state. There were also slightly increased probability densities in transitioning to a state of asleep or 0 from the current state. An examination of the number of steps required to traverse from a particular first pain score to a target state suggested that overall, fewer steps were required to reach a state of 0 (range 6.1-8.8 steps) or asleep (range 9.1-11) than were required to reach a mild pain intensity state. Our results suggest that using Markov chains is a feasible method for describing probabilistic postoperative pain trajectories, pointing toward the possibility of using Markov decision processes to model sequential interactions between pain intensity ratings, and postoperative analgesic interventions.

  11. Statistical significance test for transition matrices of atmospheric Markov chains (United States)

    Vautard, Robert; Mo, Kingtse C.; Ghil, Michael


    Low-frequency variability of large-scale atmospheric dynamics can be represented schematically by a Markov chain of multiple flow regimes. This Markov chain contains useful information for the long-range forecaster, provided that the statistical significance of the associated transition matrix can be reliably tested. Monte Carlo simulation yields a very reliable significance test for the elements of this matrix. The results of this test agree with previously used empirical formulae when each cluster of maps identified as a distinct flow regime is sufficiently large and when they all contain a comparable number of maps. Monte Carlo simulation provides a more reliable way to test the statistical significance of transitions to and from small clusters. It can determine the most likely transitions, as well as the most unlikely ones, with a prescribed level of statistical significance.

  12. Structural basis for the discrepancy of spectral behavior in C-H stretching band between steroids and long chain hydrocarbon compounds

    Institute of Scientific and Technical Information of China (English)

    徐怡庄; 陶靖; 许振华; 翁诗甫; 徐建平; 吴瑾光; 徐端夫; 徐光宪


    The discrepancies of the spectral behavior for the C-H stretching band between some long chain hydrocarbon compounds and steroids were investigated. At low temperature, the C-H stretching bands exhibit complex fine structure in steroids but remain simple in long chain hydrocarbon compounds. MM3 molecular mechanics calculation indicates that, for long chain hydrocarbon compounds, the C-H groups vibrate with large scale coupling. There exist a few bands where the C-H groups vibrate in synchronous and inphase mode. Thus the variations of dipole moment for these bands are enhanced and the intensities are obviously stronger than others and cover other band in the spectra. This is just the reason why the C-H stretching bands are simple even at low temperature environment. Nevertheless, for the steroids, the C-H stretching bands vibrate with local coupling mode. The synchronous enhancement effect does not occur, the differences of intensities for various modes are not as large as those in long chain hydrocarbo

  13. Maximum Entropy Estimation of Transition Probabilities of Reversible Markov Chains

    Directory of Open Access Journals (Sweden)

    Erik Van der Straeten


    Full Text Available In this paper, we develop a general theory for the estimation of the transition probabilities of reversible Markov chains using the maximum entropy principle. A broad range of physical models can be studied within this approach. We use one-dimensional classical spin systems to illustrate the theoretical ideas. The examples studied in this paper are: the Ising model, the Potts model and the Blume-Emery-Griffiths model.

  14. On Markov Chains Induced by Partitioned Transition Probability Matrices

    Institute of Scientific and Technical Information of China (English)

    Thomas KAIJSER


    Let S be a denumerable state space and let P be a transition probability matrix on S. If a denumerable set M of nonnegative matrices is such that the sum of the matrices is equal to P, then we call M a partition of P. Let K denote the set of probability vectors on S. With every partition M of P we can associate a transition probability function PM on K defined in such a way that if p ∈ K and M ∈ M are such that ‖pM‖ > 0, then, with probability ‖pM‖, the vector p is transferred to the vector pM/‖pM‖. Here ‖· ‖ denotes the l1-norm. In this paper we investigate the convergence in distribution for Markov chains generated by transition probability functions induced by partitions of transition probability matrices. The main motivation for this investigation is the application of the convergence results obtained to filtering processes of partially observed Markov chains with denumerable state space.

  15. Femtosecond laser pulse driven melting in gold nanorod aqueous colloidal suspension: identification of a transition from stretched to exponential kinetics. (United States)

    Li, Yuelin; Jiang, Zhang; Lin, Xiao-Min; Wen, Haidan; Walko, Donald A; Deshmukh, Sanket A; Subbaraman, Ram; Sankaranarayanan, Subramanian K R S; Gray, Stephen K; Ho, Phay


    Many potential industrial, medical, and environmental applications of metal nanorods rely on the physics and resultant kinetics and dynamics of the interaction of these particles with light. We report a surprising kinetics transition in the global melting of femtosecond laser-driven gold nanorod aqueous colloidal suspension. At low laser intensity, the melting exhibits a stretched exponential kinetics, which abruptly transforms into a compressed exponential kinetics when the laser intensity is raised. It is found the relative formation and reduction rate of intermediate shapes play a key role in the transition. Supported by both molecular dynamics simulations and a kinetic model, the behavior is traced back to the persistent heterogeneous nature of the shape dependence of the energy uptake, dissipation and melting of individual nanoparticles. These results could have significant implications for various applications such as water purification and electrolytes for energy storage that involve heat transport between metal nanorod ensembles and surrounding solvents.

  16. Polymer Stretching by Turbulence

    CERN Document Server

    Chertkov, M


    The stretching of a polymer chain by a large scale chaotic flow is considered. The steady state which emerges as a balance of the turbulent stretching and anharmonic resistance of the chain is quantitatively described, i.e. the dependency on the flow parameters (Lyapunov exponent statistics) and the chain characteristics (the number of beads and the inter-bead elastic potential) is made explicit. Implications for the drag reduction theory are discussed.

  17. Supply chains and energy security in a low carbon transition


    Hoggett, Richard; Bolton, Ronan; Candelise, Chiara; Kern, Florian; Mitchell, Catherine; Yan, Jinyue


    This special edition to be published in Applied Energy brings together a range of papers that explore the complex, multi-dimensional and inter-related issues associated with the supply or value chains that make up energy systems and how a focus on them can bring new insights for energy security in a low carbon transition.\\ud \\ud Dealing with the trilemma of maintaining energy security, reducing greenhouse gas emissions and maintaining affordability for economies and end users are key issues f...

  18. A resonant chain of four transiting, sub-Neptune planets (United States)

    Mills, Sean M.; Fabrycky, Daniel C.; Migaszewski, Cezary; Ford, Eric B.; Petigura, Erik; Isaacson, Howard


    Surveys have revealed many multi-planet systems containing super-Earths and Neptunes in orbits of a few days to a few months. There is debate whether in situ assembly or inward migration is the dominant mechanism of the formation of such planetary systems. Simulations suggest that migration creates tightly packed systems with planets whose orbital periods may be expressed as ratios of small integers (resonances), often in a many-planet series (chain). In the hundreds of multi-planet systems of sub-Neptunes, more planet pairs are observed near resonances than would generally be expected, but no individual system has hitherto been identified that must have been formed by migration. Proximity to resonance enables the detection of planets perturbing each other. Here we report transit timing variations of the four planets in the Kepler-223 system, model these variations as resonant-angle librations, and compute the long-term stability of the resonant chain. The architecture of Kepler-223 is too finely tuned to have been formed by scattering, and our numerical simulations demonstrate that its properties are natural outcomes of the migration hypothesis. Similar systems could be destabilized by any of several mechanisms, contributing to the observed orbital-period distribution, where many planets are not in resonances. Planetesimal interactions in particular are thought to be responsible for establishing the current orbits of the four giant planets in the Solar System by disrupting a theoretical initial resonant chain similar to that observed in Kepler-223.

  19. A resonant chain of four transiting, sub-Neptune planets. (United States)

    Mills, Sean M; Fabrycky, Daniel C; Migaszewski, Cezary; Ford, Eric B; Petigura, Erik; Isaacson, Howard


    Surveys have revealed many multi-planet systems containing super-Earths and Neptunes in orbits of a few days to a few months. There is debate whether in situ assembly or inward migration is the dominant mechanism of the formation of such planetary systems. Simulations suggest that migration creates tightly packed systems with planets whose orbital periods may be expressed as ratios of small integers (resonances), often in a many-planet series (chain). In the hundreds of multi-planet systems of sub-Neptunes, more planet pairs are observed near resonances than would generally be expected, but no individual system has hitherto been identified that must have been formed by migration. Proximity to resonance enables the detection of planets perturbing each other. Here we report transit timing variations of the four planets in the Kepler-223 system, model these variations as resonant-angle librations, and compute the long-term stability of the resonant chain. The architecture of Kepler-223 is too finely tuned to have been formed by scattering, and our numerical simulations demonstrate that its properties are natural outcomes of the migration hypothesis. Similar systems could be destabilized by any of several mechanisms, contributing to the observed orbital-period distribution, where many planets are not in resonances. Planetesimal interactions in particular are thought to be responsible for establishing the current orbits of the four giant planets in the Solar System by disrupting a theoretical initial resonant chain similar to that observed in Kepler-223.

  20. Conformation-specific spectroscopy of alkyl benzyl radicals: Effects of a radical center on the CH stretch infrared spectrum of an alkyl chain (United States)

    Korn, Joseph A.; Tabor, Daniel P.; Sibert, Edwin L.; Zwier, Timothy S.


    An important initial step in the combustion of gasoline and diesel fuels is the abstraction of hydrogen from alkylbenzenes to form resonance-stabilized alkyl benzyl radicals. This work uses, for the first time, double resonance spectroscopy methods to explore the conformation-specific vibronic and infrared spectroscopy of the α-ethylbenzyl (αEtBz) and α-propylbenzyl (αPrBz) radicals. Local mode Hamiltonian modeling enables assignment of the alkyl CH stretch IR spectra, accounting for Fermi resonance that complicates aliphatic alkyl CH stretch IR spectroscopy. The ground state conformational preferences of the ethyl and propyl chains are changed from those in the alkylbenzenes themselves, with global minima occurring for an in-plane orientation of the alkyl chain (trans) about its first dihedral angle (ϕf123, numbers are alkyl C atoms. C1 is CH radical site). This in-plane structure is the only observed conformer for the α-EtBz radical, while two conformers, tt and tg' share this orientation at the first dihedral, but differ in the second (ϕ1234) for the αPrBz radical. The in-plane orientation lowers the local site frequencies of the CH2 group stretches immediately adjacent to the benzylic radical site by about 50 cm-1 relative to those in pure alkyl chains or alkylbenzenes. This effect of the radical site is localized on the first CH2 group, with little effect on subsequent members of the alkyl chain. In the D1 excited electronic state, an out-of-plane orientation is preferred for the alkyl chains, leading to torsional mode Franck-Condon activity in the D0-D1 spectra that is both conformer-specific and diagnostic of the conformational change.

  1. Stretch marks (United States)

    Stretch marks can appear when there is rapid stretching of the skin. They are often seen when ... often disappear after the cause of the skin stretching is gone. Avoiding rapid weight gain helps reduce ...

  2. Influence of fast and slow alkali myosin light chain isoforms on the kinetics of stretch-induced force transients of fast-twitch type IIA fibres of rat. (United States)

    Andruchov, Oleg; Galler, Stefan


    This study contributes to understand the physiological role of slow myosin light chain isoforms in fast-twitch type IIA fibres of skeletal muscle. These isoforms are often attached to the myosin necks of rat type IIA fibres, whereby the slow alkali myosin light chain isoform MLC1s is much more frequent and abundant than the slow regulatory myosin light chain isoform MLC2s. In the present study, single-skinned rat type IIA fibres were maximally Ca(2+) activated and subjected to stepwise stretches for causing a perturbation of myosin head pulling cycles. From the time course of the resulting force transients, myosin head kinetics was deduced. Fibres containing MLC1s exhibited slower kinetics independently of the presence or absence of MLC2s. At the maximal MLC1s concentration of about 75%, the slowing was about 40%. The slowing effect of MLC1s is possibly due to differences in the myosin heavy chain binding sites of the fast and slow alkali MLC isoforms, which changes the rigidity of the myosin neck. Compared with the impact of myosin heavy chain isoforms in various fast-twitch fibre types, the influence of MLC1s on myosin head kinetics of type IIA fibres is much smaller. In conclusion, the physiological role of fast and slow MLC isoforms in type IIA fibres is a fine-tuning of the myosin head kinetics.

  3. Influence of chain topology and bond potential on the glass transition of polymer chains simulated with the bond fluctuation model

    Energy Technology Data Exchange (ETDEWEB)

    Freire, J J [Departamento de Ciencias y Tecnicas FisicoquImicas, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia (UNED), Senda del Rey 9, 28040 Madrid (Spain)], E-mail:


    The bond fluctuation model with a bond potential has been applied to investigation of the glass transition of linear chains and chains with a regular disposition of small branches. Cooling and subsequent heating curves are obtained for the chain energies and also for the mean acceptance probability of a bead jump. In order to mimic different trends to vitrification, a factor B gauging the strength of the bond potential with respect to the long-range potential (i.e. the intramolecular or intermolecular potential between indirectly bonded beads) has been introduced. (A higher value of B leads to a preference for the highest bond lengths and a higher total energy, implying a greater tendency to vitrify.) Different cases have been considered for linear chains: no long-range potential, no bond potential and several choices for B. Furthermore, two distinct values of B have been considered for alternate bonds in linear chains. In the case of the branched chains, mixed models with different values of B for bonds in the main chain and in the branches have also been investigated. The possible presence of ordering or crystallization has been characterized by calculating the collective light scattering function of the different samples after annealing at a convenient temperature below the onset of the abrupt change in the curves associated with a thermodynamic transition. It is concluded that ordering is inherited more efficiently in the systems with branched chains and also for higher values of B. The branched molecules with the highest B values in the main chain bonds exhibit two distinct transitions in the heating curves, which may be associated with two glass transitions. This behavior has been detected experimentally for chains with relatively long flexible branches.


    Institute of Scientific and Technical Information of China (English)

    Chi-bing Tan; Quan-ling Zhang; Shu-fan Zhang; Xia-yu Wang; Mao Xu


    The morphological features of a side-chain liquid crystalline polymer during the mesophase transitions were investigated by using the DSC technique. The polymer used was polyacrylate with mesogens of three benzene rings attached to the main chain through a flexible spacer. A special two-phase texture was observed in the transition temperature range. Similar to main-chain liquid crystalline polymers the transition process of the side-chain liquid crystalline polymer was composed of an initiation of the new phase at local places of the old phase matrix and a growth process of the new phase domains.

  5. Contribution of stretch to the change of activation properties of muscle fibers in the diaphragm at the transition from fetal to neonatal life.

    Directory of Open Access Journals (Sweden)

    David J Cannata


    Full Text Available The transition from fetal to postnatal life involves clearance of liquid from the lung and airways, and rapid formation of a functional residual capacity. Despite the importance of the diaphragm in this process, the impact on the mechanical and functional activity changes of its muscle fibers is not known. This study determined the contractile characteristics of individual ‘skinned’ diaphragm fibers from 70 days gestation to adulthood in sheep, and determined the impact of the transition from the in utero fetal status to (a, spontaneous air breathing; or (b mechanical ventilation - on passive tension and calcium- and strontium-activated properties of single fibers isolated from the diaphragm. Based on differential sensitivity to the divalent ions calcium (Ca2+ and strontium (Sr2+, all fibers in the fetal diaphragm were classified as ‘fast’, whereas fibers from the adult diaphragm exhibited a ‘hybrid’ phenotype wherein both ‘fast’ and ‘slow’ characteristics were present within each single fiber. Transition to the hybrid phenotype occurred at birth, was evident after 40 mins of spontaneous breathing, and could be induced by mechanical stretch of diaphragm fibers from near term foetuses (~147 days gestation. Applied stretch of fibers, achieved either by physical stretch of isolated fibres or mechanical ventilation of the fetus, significantly increased sensitivity to Ca2+ and Sr2+, maximum force generating capacity, and decreased passive tension in near-term and preterm fetuses. However, only fibers from near-term fetuses displayed a complete transition to a ‘hybrid’ activation profile., These findings suggest that activation properties of the diaphragm are changed by transition from a liquid to air-filled lung at birth, and that stretch induces physical changes of proteins determining the activation and elastic properties of the diaphragm. These changes may allow the diaphragm to meet the increased mechanical demands of


    Institute of Scientific and Technical Information of China (English)

    YUE Dequan; ZHANG Huachen; TU Fengsheng


    In this paper we consider a Markov chain model in an ATM network, which has been studied by Dag and Stavrakakis. On the basis of the iterative formulas obtained by Dag and Stavrakakis, we obtain the explicit analytical expression of the transition probability matrix. It is very simple to calculate the transition probabilities of the Markov chain by these expressions. In addition, we obtain some results about the structure of the transition probability matrix, which are helpful in numerical calculation and theoretical analysis.

  7. Deformation and concentration fluctuations under stretching in a polymer network with free chains. The ``butterfly`` effect; Fluctuations de deformation et de concentration sous etirement dans un reseau polymere contenant des chaines libres. L`effet ``papillon``

    Energy Technology Data Exchange (ETDEWEB)

    Ramzi, A.


    Small Angle Neutron Scattering gives access to concentration fluctuations of mobile labeled polymer chains embedded in a polymer network. At rest they appear progressively larger than for random mixing, with increasing ratio. Under uniaxial stretching, they decrease towards ideal mixing along the direction perpendicular to stretching, and can grow strongly along the parallel one, including the zero scattering vector q limit. This gives rise to intensity contours with double-winged patterns, in the shape of the figure `8`, or of `butterfly`. Random crosslinking and end-linking of monodisperse chains have both been studied. The strength of the `butterfly` effect increases with the molecular weight of the free chains, the crosslinking ratio, the network heterogeneity, and the elongation ratio. Eventually, the signal collapses on an `asymptotic` function I(q), of increasing correlation length with the elongation ratio. Deformation appears heterogeneous, maximal for soft areas, where the mobile chains localize preferentially. This could be due to spontaneous fluctuations, or linked to frozen fluctuations of the crosslink density. However, disagreement with the corresponding theoretical expressions makes it necessary to account for the spatial correlations of crosslink density, and their progressive unscreening as displayed by the asymptotic behavior. Networks containing pending labeled chains and free labeled stars lead to more precise understanding of the diffusion of free species and the heterogeneity of the deformation. It seems that the latter occurs even without diffusion for heterogeneous enough networks. In extreme cases (of the crosslinking parameters), the spatial correlations display on apparent fractal behavior, of dimensions 2 to 2.5, which is discussed here in terms of random clusters. 200 refs., 95 figs., 21 tabs., 10 appends.

  8. Collapse transitions in a flexible homopolymer chain: application of the Wang-Landau algorithm. (United States)

    Seaton, D T; Wüst, T; Landau, D P


    The thermodynamic behavior of a continuous homopolymer is described using the Wang-Landau algorithm for chain lengths up to N=561. The coil-globule and liquid-solid transitions are analyzed in detail with traditional thermodynamic and structural quantities. The behavior of the coil-globule transition is well within theoretical and computational predictions for all chain lengths, while the behavior of the liquid-solid transition is much more susceptible to finite-size effects. Certain "magic number" lengths (N=13,55,147,309,561) , whose minimal energy states offer unique icosahedral geometries, are discussed along with chains residing between these special cases. The low temperature behavior near the liquid-solid transition is rich in structural transformations for certain chain lengths, showing many similarities to the behavior of classical clusters with similar interaction potentials. General comments are made on this size dependent behavior and how it affects transition behavior in this model.

  9. Collapse transitions in a flexible homopolymer chain: Application of the Wang-Landau algorithm (United States)

    Seaton, D. T.; Wüst, T.; Landau, D. P.


    The thermodynamic behavior of a continuous homopolymer is described using the Wang-Landau algorithm for chain lengths up to N=561 . The coil-globule and liquid-solid transitions are analyzed in detail with traditional thermodynamic and structural quantities. The behavior of the coil-globule transition is well within theoretical and computational predictions for all chain lengths, while the behavior of the liquid-solid transition is much more susceptible to finite-size effects. Certain “magic number” lengths (N=13,55,147,309,561) , whose minimal energy states offer unique icosahedral geometries, are discussed along with chains residing between these special cases. The low temperature behavior near the liquid-solid transition is rich in structural transformations for certain chain lengths, showing many similarities to the behavior of classical clusters with similar interaction potentials. General comments are made on this size dependent behavior and how it affects transition behavior in this model.

  10. Prediction of Synchrostate Transitions in EEG Signals Using Markov Chain Models

    CERN Document Server

    Jamal, Wasifa; Oprescu, Ioana-Anastasia; Maharatna, Koushik


    This paper proposes a stochastic model using the concept of Markov chains for the inter-state transitions of the millisecond order quasi-stable phase synchronized patterns or synchrostates, found in multi-channel Electroencephalogram (EEG) signals. First and second order transition probability matrices are estimated for Markov chain modelling from 100 trials of 128-channel EEG signals during two different face perception tasks. Prediction accuracies with such finite Markov chain models for synchrostate transition are also compared, under a data-partitioning based cross-validation scheme.

  11. Translocation of Biopolymer Chain Through a Nanopore: Coil-Helix Transition

    Institute of Scientific and Technical Information of China (English)

    GU Fang; WANG Hai-Jun; HONG Xiao-Zhong; BA Xin-Wu


    @@ The translocation dynamics of a single biopolymer chain through a nanopore in a membrane is investigated by taking the coil-helix transition into account. Based on the changing of the free energy due to the coil-helix transition, the mean first passage time τ is obtained, and then the corresponding numerical simulations are presented under different conditions. It is shown that the coil helix transition can significantly shorten the translocation time of the biopolymer chain. In addition, we also discuss the scaling behaviour for τ with the chain length N and some related problems.


    Institute of Scientific and Technical Information of China (English)

    Chi-bing Tan; Shu-fan Zhang; Mao Xu


    The morphological changes of a side-chain liquid-crystalline polymethacrylate during isotropization and liquid-crystallization transitions were studied by means of polarizing microscopy. These transitions were found to be composed of the initiation of a new phase at local places of the old phase matrix and the growth of the new phase domains. The kinetics of the liquid-crystallization of the polymer from an isotropic melt to a smectic mesophase was also investigated. The isothermal process of the transition can be described by the Avrami equation. The values of the Avrami exponent were found to be around 2.6. which is lower than the value usually obtained for crystallization transition of polymers, but larger than that reported for liquid-crystallization transition of main-chain polymers. These results may indicate the difference in growth geometry of new phase during transition between crystallization and liquid-crystallization in general and between liquid-crystallization of main-chain and side-chain polymers. It was found that the liquidcrystallization of the used side-chain polymethacrylate may occur at small undercoolings with high transformation rate similar to that of main-chain polymers and small-molecule liquid crystals, while the crystallization of polymers can only proceed at large undercoolings. These phenomena can be explained by the idea that the surface free energy of nucleus during liquid-crystallization transition is less than that for crystallization, and evidence was obtained from analysis of the temperature dependence of the transformation rate.

  13. Coil-bridge transition in a single polymer chain as an unconventional phase transition: theory and simulation. (United States)

    Klushin, Leonid I; Skvortsov, Alexander M; Polotsky, Alexey A; Hsu, Hsiao-Ping; Binder, Kurt


    The coil-bridge transition in a self-avoiding lattice chain with one end fixed at height H above the attractive planar surface is investigated by theory and Monte Carlo simulation. We focus on the details of the first-order phase transition between the coil state at large height H ⩾ Htr and a bridge state at H ⩽ Htr, where Htr corresponds to the coil-bridge transition point. The equilibrium properties of the chain were calculated using the Monte Carlo pruned-enriched Rosenbluth method in the moderate adsorption regime at (H/Na)tr ⩽ 0.27 where N is the number of monomer units of linear size a. An analytical theory of the coil-bridge transition for lattice chains with excluded volume interactions is presented in this regime. The theory provides an excellent quantitative description of numerical results at all heights, 10 ⩽ H/a ⩽ 320 and all chain lengths 40 theory taking into account the effect of finite extensibility of the lattice chain in the strong adsorption regime at (H/Na)tr ⩾ 0.5 is presented. We discuss some unconventional properties of the coil-bridge transition: the absence of phase coexistence, two micro-phases involved in the bridge state, and abnormal behavior in the microcanonical ensemble.

  14. The isotropic-nematic phase transition of tangent hard-sphere chain fluids—Pure components

    NARCIS (Netherlands)

    Van Westen, T.; Oyarzun, B.; Vlugt, T.J.H.; Gross, J.


    An extension of Onsager's second virial theory is developed to describe the isotropic-nematic phase transition of tangent hard-sphere chain fluids. Flexibility is introduced by the rod-coil model. The effect of chain-flexibility on the second virial coefficient is described using an accurate, analyt

  15. First-order coil-to-flower transition of a polymer chain pinned near a stepwise external potential: Numerical, analytical, and scaling analysis (United States)

    Skvortsov, A. M.; Klushin, L. I.; van Male, J.; Leermakers, F. A. M.


    A polymer chain near a penetrable interface is studied in the Gaussian model, in the lattice random walk model and by a scaling analysis. The interface is modeled as an external potential u of a Heaviside step-function form. One end of the chain is fixed at a distance z0 away from this interface. When the end point is fixed in the high potential region, a first-order coil-to-flower transition takes place upon variation of the distance z0. Here, the flower has a strongly stretched stem from the grafting point towards the interface and, on top of it, a crown composed of the remaining segments in a (perturbed) coil conformation. The coil-to-flower transition is analyzed in terms of the Landau free energy. The order parameter is taken to be related to the fraction of segments residing in the energetically favorable region. Exact analytical expressions for the Landau function are obtained in the Gaussian model for any distances z0 and potential strength u. A phase diagram in the z0 versus u coordinates is constructed. It contains a line of the first-order phase transitions (binodal line) ending at a critical point z0=u=0, and two spinodal lines. Numerical results are obtained for several chain lengths in the lattice random walk model demonstrating the effects of finite extensibility on the position of the transition point. Excluded volume effects are analyzed within the scaling approach.

  16. Shift in membrane miscibility transition temperature upon addition of short-chain alcohols (United States)

    Schick, M.


    I consider the effect of a small concentration of a molecule, such as a short-chain alcohol, on the miscibility transition temperature of a giant plasma membrane vesicle. For concentrations sufficiently small such that the system can be treated as a dilute solution, the change in transition temperature is known to depend upon the extent of the molecule's partition into the coexisting liquid-disordered and liquid-ordered phases. Preferential partitioning into the former decreases the miscibility temperature, while preferential partitioning into the latter causes an increase. The analysis, combined with calculated values of the partition coefficient of saturated chains, illuminates the results of recent experiments on the change in miscibility transition temperatures with changing alcohol chain length, and makes several testable predictions.

  17. Frustrated Ferromagnetic Spin Chain near the Transition Point

    Institute of Scientific and Technical Information of China (English)

    ZHU Ren-Gui


    @@ The one-dimensional quantum spin-1/2 model with nearest-neighbor ferromagnetic and next-nearest-neighbor antiferromagnetic interaction is considered.The Hamiltonian is firstly rewritten in a form with rotated spin operators,then bosonized by using the linear spin wave approximation and then treated by using the Green function approach.An integral expression of the quantum correction to the classical ground state energy is derived.The critical behavior of the ground state energy in the vicinity of the transition point from the ferromagnetic to the singlet ground state is analyzed by numerical calculation and the result is-8γ2.%The one-dimensional quantum spin-1/2 model with nearest-neighbor ferromagnetic and next-nearest-neighbor antiferromagnetic interaction is considered. The Hamiltonian is firstly rewritten in a form with rotated spin operators, then bosonized by using the linear spin wave approximation and then treated by using the Green function approach. An integral expression of the quantum correction to the classical ground state energy is derived. The critical behavior of the ground state energy in the vicinity of the transition point from the ferromagnetic to the singlet ground state is analyzed by numerical calculation and the result is -8r2.

  18. Phase transitions of a single polymer chain: A Wang-Landau simulation study. (United States)

    Taylor, Mark P; Paul, Wolfgang; Binder, Kurt


    A single flexible homopolymer chain can assume a variety of conformations which can be broadly classified as expanded coil, collapsed globule, and compact crystallite. Here we study transitions between these conformational states for an interaction-site polymer chain comprised of N=128 square-well-sphere monomers with hard-sphere diameter sigma and square-well diameter lambdasigma. Wang-Landau sampling with bond-rebridging Monte Carlo moves is used to compute the density of states for this chain and both canonical and microcanonical analyses are used to identify and characterize phase transitions in this finite size system. The temperature-interaction range (i.e., T-lambda) phase diagram is constructed for lambda1.06 these two states are separated by an intervening collapsed globule phase and thus, with decreasing temperature a chain undergoes a continuous coil-globule (collapse) transition followed by a discontinuous globule-crystal (freezing) transition. For well diameters lambdamodel, that a collapsed globule state is unstable with respect to a solid phase for flexible polymers with sufficiently short-range monomer-monomer interactions.

  19. Markov-chain model of classified atomistic transition states for discrete kinetic Monte Carlo simulations. (United States)

    Numazawa, Satoshi; Smith, Roger


    Classical harmonic transition state theory is considered and applied in discrete lattice cells with hierarchical transition levels. The scheme is then used to determine transitions that can be applied in a lattice-based kinetic Monte Carlo (KMC) atomistic simulation model. The model results in an effective reduction of KMC simulation steps by utilizing a classification scheme of transition levels for thermally activated atomistic diffusion processes. Thermally activated atomistic movements are considered as local transition events constrained in potential energy wells over certain local time periods. These processes are represented by Markov chains of multidimensional Boolean valued functions in three-dimensional lattice space. The events inhibited by the barriers under a certain level are regarded as thermal fluctuations of the canonical ensemble and accepted freely. Consequently, the fluctuating system evolution process is implemented as a Markov chain of equivalence class objects. It is shown that the process can be characterized by the acceptance of metastable local transitions. The method is applied to a problem of Au and Ag cluster growth on a rippled surface. The simulation predicts the existence of a morphology-dependent transition time limit from a local metastable to stable state for subsequent cluster growth by accretion. Excellent agreement with observed experimental results is obtained.


    Institute of Scientific and Technical Information of China (English)

    Tisato Kajiyama; Daisuke Kawaguchi; Keiji Tanaka


    In this study, it was examined whether the dynamics of polymer chains at a surface is different from that in the bulk, and if so, to what extent they differ in terms of surface glass transition temperature and diffusion coefficient. Obtained results clearly indicate that surface chains can travel for a relatively large distance in comparison with the characteristic length scale of usual segmental motion even at a temperature below its bulk glass transition temperature, Tbg. This is consistent with our previous results that the surface glass transition temperature is much lower than the corresponding Tbg.Also, it was experimentally revealed that there was a gradient of molecular motion in the surface region.

  1. Negative compressibility and non-equivalence of two statistical ensembles in the escape transition of a polymer chain

    NARCIS (Netherlands)

    Skvortsov, A.M.; Klushin, L.I.; Leermakers, F.A.M.


    An end-tethered polymer chain compressed between two pistons undergoes an abrupt transition from a confined coil state to an inhomogeneous flowerlike conformation partially escaped from the gap. This phase transition is first order in the thermodynamic limit of infinitely long chains. A rigorous ana

  2. Effect of side-chain asymmetry on the intermolecular structure and order-disorder transition in alkyl-substituted polyfluorenes

    DEFF Research Database (Denmark)

    Knaapila, Matti; Stepanyan, R.; Torkkeli, M.;


    We study relations among the side-chain asymmetry, structure, and order-disorder transition (ODT) in hairy-rod-type poly(9,9-dihexylfluorene) (PF6) with two identical side chains and atactic poly(9-octyl-9-methyl-fluorene) (PF1-8) with two different side chains per repeat. PF6 and PF1-8 organize ...

  3. Self-Organized Growth, Structure, and Magnetism of Monatomic Transition-Metal Oxide Chains (United States)

    Ferstl, Pascal; Hammer, Lutz; Sobel, Christopher; Gubo, Matthias; Heinz, Klaus; Schneider, M. Alexander; Mittendorfer, Florian; Redinger, Josef


    We report on the self-organized growth of monatomic transition-metal oxide chains of (3 ×1 ) periodicity and unusual M O2 stoichiometry (M =Ni , Co, Fe, Mn) on Ir(100). We analyze their structural and magnetic properties by means of quantitative LEED, STM, and density functional theory (DFT) calculations. LEED analyses reveal a fascinating common atomic structure in which the transition-metal atoms sit above a missing-row structure of the surface and are coupled to the substrate only via oxygen atoms. This structure is confirmed by DFT calculations with structural parameters deviating by less than 1.7 pm. The DFT calculations predict that the NiO2 chains are nonmagnetic, CoO2 chains are ferromagnetic, while FeO2 and MnO2 are antiferromagnetic. All structures show only weak magnetic interchain coupling. Further, we demonstrate the growth of oxide chains of binary alloys of Co and Ni or Fe on Ir(100), which allows us to produce well-controlled ensembles of ferromagnetic chains of different lengths separated by nonmagnetic or antiferromagnetic segments.

  4. Geometrical and Anderson transitions in harmonic chains with constrained long-range couplings. (United States)

    Morais, P A; Andrade, J S; Nascimento, E M; Lyra, M L


    Low-dimensional systems with long-range couplings usually present phase transitions which are absent in the short-ranged counterpart model. In this work, we show that a harmonic chain with long-range couplings restricted by a cost function proportional to the chain length N exhibits two distinct phase transitions. In the present model, two sites at a distance r>1 are connected by a spring with probability 1/r(α) with the constraint that the total length of the non-nearest-neighbor couplings is limited to λN, where λ is a cost parameter. A geometrical phase transition is found at α=1.5 between a phase with a finite number of long-range couplings and a phase on which the number of long-range couplings is proportional to the system size. Further, the normal vibrational modes of this chain display a phase transition from delocalized to localized modes at a smaller value of α. Maximum effective disorder is reached at α=2 for which the frequency of the lowest vibrational mode exhibits a pronounced peak.

  5. Strong, Weak and Branching Bisimulation for Transition Systems and Markov Reward Chains: A Unifying Matrix Approach

    Directory of Open Access Journals (Sweden)

    Nikola Trčka


    Full Text Available We first study labeled transition systems with explicit successful termination. We establish the notions of strong, weak, and branching bisimulation in terms of boolean matrix theory, introducing thus a novel and powerful algebraic apparatus. Next we consider Markov reward chains which are standardly presented in real matrix theory. By interpreting the obtained matrix conditions for bisimulations in this setting, we automatically obtain the definitions of strong, weak, and branching bisimulation for Markov reward chains. The obtained strong and weak bisimulations are shown to coincide with some existing notions, while the obtained branching bisimulation is new, but its usefulness is questionable.

  6. Strong, Weak and Branching Bisimulation for Transition Systems and Markov Reward Chains: A Unifying Matrix Approach

    CERN Document Server

    Trčka, Nikola


    We first study labeled transition systems with explicit successful termination. We establish the notions of strong, weak, and branching bisimulation in terms of boolean matrix theory, introducing thus a novel and powerful algebraic apparatus. Next we consider Markov reward chains which are standardly presented in real matrix theory. By interpreting the obtained matrix conditions for bisimulations in this setting, we automatically obtain the definitions of strong, weak, and branching bisimulation for Markov reward chains. The obtained strong and weak bisimulations are shown to coincide with some existing notions, while the obtained branching bisimulation is new, but its usefulness is questionable.


    Institute of Scientific and Technical Information of China (English)

    LIU Xiaoping; HU Shiru; SHI Lianghe; XU Mao


    The kinetics of phase transitions including a transition between mesophases were studied for a main-chain thermotropic polyester by means of DSC and depolarizing transmittance techniques. The isothermal process of these transitions was found to be described by the Avrami equation to high conversions. The Avrami exponents n are about 2.4, 5.3 and 2.2 for liquid crystallization, transition between mesophases and crystallization from mesophase respectively. The liquid crystallization from isotropic liquid phase occurs at very low undercoolings with high transformation rate. This behavior is explained as the results of the smaller value of the surface free energy for mesophase than that for crystallites which is evidenced by the very weak temperature dependence of liquid crystallization rate.

  8. Interpretation of semiclassical transition moments through wave function expansion of dipole moment functions with applications to the OH stretching spectra of simple acids and alcohols. (United States)

    Takahashi, Hirokazu; Takahashi, Kaito; Yabushita, Satoshi


    Semiclassical description of molecular vibrations has provided us with various computational approximations and enhanced our conceptual understanding of quantum mechanics. In this study, the transition moments of the OH stretching fundamental and overtone intensities (Δv = 1-6) of some alcohols and acids are calculated by three kinds of semiclassical methods, correspondence-principle (CP) approximation, quasiclassical approximation, and uniform WKB approximation, and their respective transition moments are compared to those by the quantum theory. On the basis of the local mode picture, the one-dimensional potential energy curves and the dipole moment functions (DMFs) were obtained by density functional theory calculations and then fitted to Morse functions and sixth-order polynomials, respectively. It was shown that both the transition energies and the absorption intensities derived in the semiclassical methods reproduced their respective quantum values. In particular, the CP approximation reproduces the quantum transition moments if the formula given by Naccache is used for the action integral value. On the basis of these semiclassical results, we present a picture to understand the small variance in the overtone intensities of these acids and alcohols. Another important result is the ratios of semiclassical-to-quantum transition moment are almost independent of the applied molecules even with a great molecular variance of the DMFs, and they depend only on the nature of the semiclassical approximations and the quantum number. The difference between the semiclassical and quantum transition moments was analyzed in terms of a hitherto unrecognized concept that the Fourier expansion of the time dependent DMF in the CP treatment is a kind of the wave function expansion method using trigonometric functions as the quotient functions. For a Morse oscillator, we derive the analytic and approximate expressions of the quotient functions in terms of the bond displace

  9. A dynamical model for the full stretching curve of DNA

    CERN Document Server

    Fiasconaro, Alessandro


    We present a phenomenological dynamical model able to describe the stretching features of a length \\textit{vs} applied force DNA curve. As concerning the chain, the model grounds on the discrete worm-like chain model with the elastic modifications, which properly describes the elongation features at low and intermediate forces. At high forces the dynamics, developed under a double well potential with a cubic term, accounts for the narrow transition present in the DNA elongation (overstretching). An good agreement between simulation and experiment is obtained.

  10. Propagation of excitation in long 1D chains: Transition from regular quantum dynamics to stochastic dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Benderskii, V. A., E-mail: [Russian Academy of Sciences, Institute of Problems of Chemical Physics (Russian Federation); Kats, E. I., E-mail: [Russian Academy of Sciences, Landau Institute for Theoretical Physics (Russian Federation)


    The quantum dynamics problem for a 1D chain consisting of 2N + 1 sites (N Much-Greater-Than 1) with the interaction of nearest neighbors and an impurity site at the middle differing in energy and in coupling constant from the sites of the remaining chain is solved analytically. The initial excitation of the impurity is accompanied by the propagation of excitation over the chain sites and with the emergence of Loschmidt echo (partial restoration of the impurity site population) in the recurrence cycles with a period proportional to N. The echo consists of the main (most intense) component modulated by damped oscillations. The intensity of oscillations increases with increasing cycle number and matrix element C of the interaction of the impurity site n = 0 with sites n = {+-}1 (0 < C {<=} 1; for the remaining neighboring sites, the matrix element is equal to unity). Mixing of the components of echo from neighboring cycles induces a transition from the regular to stochastic evolution. In the regular evolution region, the wave packet propagates over the chain at a nearly constant group velocity, embracing a number of sites varying periodically with time. In the stochastic regime, the excitation is distributed over a number of sites close to 2N, with the populations varying irregularly with time. The model explains qualitatively the experimental data on ballistic propagation of the vibrational energy in linear chains of CH{sub 2} fragments and predicts the possibility of a nondissipative energy transfer between reaction centers associated with such chains.

  11. Quantum phase transition and von Neumann entropy of quasiperiodic Hubbard chains

    Institute of Scientific and Technical Information of China (English)

    Zhu Xuan; Tong Pei-Qing


    The half-filled Hubbard chains with the Fibonacci and Harper modulating site potentials are studied in a selfconsistent mean-field approximation.A new order parameter is introduced to describe a charge density order.We also calculate the yon Neumann entropy of the ground state.The results show that the yon Neumann entropy can identify a CDW/SDW (charge density wave/spin density wave) transition for quasiperiodic models.

  12. Accelerating the transition towards sustainability dynamics into supply chain relationship management and governance structures

    DEFF Research Database (Denmark)

    Govindan, Kannan; Seuring, Stefan; Zhu, Qinghua


    , sustainable, post-fossil carbon societies by working with all relevant stakeholders. This Special Volume of Journal of Cleaner Production is focused upon on diverse types of supply chain relationships, governance mechanisms, and innovations, which can foster effective and efficient sustainable supply chain......Stakeholders and competitive priorities drive profit and non-profit organizations towards the implementation of sustainability-related measures, in their internal operations, and in their supply chains planning. It is believed by some that investments in sustainability may help them to attain more...... successful futures by maintaining a healthy balance among economic, environmental, and social resources/dimensions. Consequently, some organizations have begun to integrate these dimensions in recent years. Researchers and practitioners are also working to accelerate the transition for more equitable...

  13. Tunable Crystal-to-Crystal Phase Transition in a Cadmium Halide Chain Polymer

    Directory of Open Access Journals (Sweden)

    Ulli Englert


    Full Text Available The chain polymer [{Cd(μ-X2py2}1∞] (X = Cl, Br; py = pyridine undergoes a fully reversible phase transition between a monoclinic low-temperature and an orthorhombic high-temperature phase. The transformation can be directly monitored in single crystals and can be confirmed for the bulk by powder diffraction. The transition temperature can be adjusted by tuning the composition of the mixed-halide phase: Transition temperatures between 175 K up to the decomposition of the material at ca. 350 K are accessible. Elemental analysis, ion chromatography and site occupancy refinements from single-crystal X-ray diffraction agree with respect to the stoichiometric composition of the samples.

  14. Enhancement of the superconducting transition temperature of MgB2 by a strain-induced bond-stretching mode softening. (United States)

    Pogrebnyakov, A V; Redwing, J M; Raghavan, S; Vaithyanathan, V; Schlom, D G; Xu, S Y; Li, Qi; Tenne, D A; Soukiassian, A; Xi, X X; Johannes, M D; Kasinathan, D; Pickett, W E; Wu, J S; Spence, J C H


    We report a systematic increase of the superconducting transition temperature T(c) with a biaxial tensile strain in MgB2 films to well beyond the bulk value. The tensile strain increases with the MgB2 film thickness, caused primarily by the coalescence of initially nucleated discrete islands (the Volmer-Weber growth mode.) The T(c) increase was observed in epitaxial films on SiC and sapphire substrates, although the T(c) values were different for the two substrates due to different lattice parameters and thermal expansion coefficients. We identified, by first-principles calculations, the underlying mechanism for the T(c) increase to be the softening of the bond-stretching E(2g) phonon mode, and we confirmed this conclusion by Raman scattering measurements. The result suggests that the E(2g) phonon softening is a possible avenue to achieve even higher T(c) in MgB2-related material systems.

  15. Stretch Sensor Device

    DEFF Research Database (Denmark)


    The invention relates to a method for determining stretch values and movement of body parts, e.g. a foot, by analysing stretch data from a stretch sensor. By analysing data from the stretch sensor it is possible to determine stretch samples which are associated with particular motion phases....... Thereby the stretch values determined from the stretch samples have a particular physical meaning since they are associated with particular motion phases....

  16. An exceptional series of phase transitions in hydrophobic amino acids with linear side chains

    Directory of Open Access Journals (Sweden)

    Carl Henrik Görbitz


    Full Text Available The solid-state phase transitions and intermediate structures of S-2-aminobutanoic acid (l-2-aminobutyric acid, S-2-aminopentanoic acid (l-norvaline, S-2-aminohexanoic acid (l-norleucine and l-methionine between 100 and 470 K, identified by differential scanning calorimetry, have been characterized in a comprehensive single-crystal X-ray diffraction investigation. Unlike other enantiomeric amino acids investigated until now, this group featuring linear side chains displays up to five distinct phases. The multiple transitions between them involve a number of different processes: alteration of the hydrogen-bond pattern, to our knowledge the first example of this observed for an amino acid, sliding of molecular bilayers, seen previously only for racemates and quasiracemates, concerted side-chain rearrangements and abrupt as well as gradual modifications of the side-chain disorder. Ordering of l-norleucine upon cooling even proceeds via an incommensurately modulated structure. l-Methionine has previously been described as being fully ordered at room temperature. An accurate refinement now reveals extensive disorder for both molecules in the asymmetric unit, while two previously unknown phases occur above room temperature.

  17. Effect of chain end group on surface glass transition temperature of thin polymer film (United States)

    Jiang, Xiqun; Yang, Chang Zheng; Tanaka, Keiji; Takahara, Atsushi; Kajiyama, Tisato


    Surface glass transition behaviors of proton end capped poly(2-vinylpyridine) (P2VP-H) and perfluoroalkyl end capped poly(2-vinylpyridine) (P2VP-C 2C 8F) thin films were investigated based on temperature-dependent lateral force microscopic (TDLFM) measurement. It is found that the species of chain end groups have significant influence on the surface glass transition temperature of the thin polymer film. For both samples, it is revealed that the surface glass transition temperatures decrease significantly in comparison to the bulk ones, and the magnitude order of reduction in surface Tg for P2VP-C 2C 8F is larger than that for P2VP-H. The apparent activation energy of surface α-relaxation calculated from the Arrhenius plot is ca. 292±40 and 212±40 kJ/mol for P2VP-H and P2VP-C 2C 8F, respectively, and is much smaller than the bulk one. The depression of the surface Tg for thin polymer films is explained by the excess free volume induced by the enrichment of chain end groups at the surface.

  18. Zero energy modes in a superconductor with ferromagnetic adatom chains and quantum phase transitions (United States)

    Čadež, Tilen; Sacramento, Pedro D.


    We study Majorana zero energy modes (MZEM) that occur in an s-wave superconducting surface, at the ends of a ferromagnetic (FM) chain of adatoms, in the presence of Rashba spin-orbit interaction (SOI) considering both non self-consistent and self-consistent superconducting order. We find that in the self-consistent solution, the average superconducting gap function over the adatom sites has a discontinuous drop with increasing exchange interaction at the same critical value where the topological phase transition occurs. We also study the MZEM for both treatments of superconducting order and find that the decay length is a linear function of the exchange coupling strength, chemical potential and superconducting order. For wider FM chains the MZEM occur at smaller exchange couplings and the slope of the decay length as a function of exchange coupling grows with chain width. Thus we suggest experimental detection of different delocalization of MZEM in chains of varying widths. We discuss similarities and differences between the MZEM for the two treatments of the superconducting order.

  19. Fluid Stretching as a Levy Process

    CERN Document Server

    Dentz, Marco; Borgne, Tanguy Le; de Barros, Felipe P J


    We uncover deformation dynamics that lead to power-law stretching of material lines in heterogeneous flow. This evidences the existence of a broad spectrum of algebraic stretching behaviors in fluids from sub- to superlinear beyond the linear (shear flow) and exponential (chaotic flow) elongation paradigms. Formulating fluid deformation in two-dimensional steady flow in stream-line coordinates, we show that stretching results from the non-linear coupling between Lagrangian shear deformation and velocity fluctuations. Casting the stretching process in the frame of a continuous time random walk, this coupling links the magnitude of elongation events to their persistence through the transit times of material strips. As a consequence, for broad transit time distributions stretching obeys Levy dynamics. We derive explicit expressions for the mean elongation which predict a broad range of power-law stretching behaviors depending on the velocity distribution and the relation between shear rate and velocity along str...

  20. Pulse and quench induced dynamical phase transition in a chiral multiferroic spin chain (United States)

    Azimi, M.; Sekania, M.; Mishra, S. K.; Chotorlishvili, L.; Toklikishvili, Z.; Berakdar, J.


    Quantum dynamics of magnetic order in a chiral multiferroic chain is studied. We consider two different scenarios: ultrashort terahertz excitations or a sudden electric field quench. Performing analytical and numerical exact diagonalization calculations, we trace the pulse induced spin dynamics and extract quantities that are relevant to quantum information processing. In particular, we analyze the dynamics of the system chirality, the von Neumann entropy, and the pairwise and many-body entanglement. If the characteristic frequencies of the generated states are noncommensurate, then a partial loss of pair concurrence occurs. Increasing the system size, this effect becomes even more pronounced. Many-particle entanglement and chirality are robust and persist in the incommensurate phase. To analyze the dynamical quantum transitions for the quenched and pulsed dynamics we combined the Weierstrass factorization technique for entire functions and the Lanczos exact diagonalization method. For a small system we obtained analytical results including the rate function of the Loschmidt echo. Exact numerical calculations for a system up to 40 spins confirm phase transition. Quench-induced dynamical transitions have been extensively studied recently. Here we show that related dynamical transitions can be achieved and controlled by appropriate electric field pulses.

  1. Stretching Safely and Effectively (United States)

    ... it safely and effectively. By Mayo Clinic Staff Stretching may take a back seat to your exercise routine. The main concern is exercising, not stretching, right? Not so fast. Stretching may help you: ...

  2. A new force-extension formula for stretched macromolecules and polymers based on the Ising model (United States)

    Chan, Yue; Haverkamp, Richard G.


    In this paper, we derive a new force-extension formula for stretched macromolecules and homogeneous polymer matrices. The Ising model arising from paramagnetism is employed, where the magnetic force is replaced by the external force, and the resistance energy is addressed in this model instead of the usual persistent length arising from the freely jointed chain and worm-like chain models. While the force-extension formula reveals the distinctive stretching features for stretched polymers, the resistance energy is found to increase almost linearly with the external force for our two polysaccharides stretching examples with and without ring conformational changes. In particular, a jump in the resistance energy which is caused by a conformational transition is investigated, and the gap between the jump determines the energy barrier between two conformational configurations. Our theoretical model matches well with experimental results undergoing no and single conformational transitions, and a Monte Carlo simulation has also been performed to ensure the correctness of the resistance energy. This technique might also be employed to determine the binding energy from other causes during molecular stretching and provide vital information for further theoretical investigations.

  3. Phase Transitions for Quantum Markov Chains Associated with Ising Type Models on a Cayley Tree (United States)

    Mukhamedov, Farrukh; Barhoumi, Abdessatar; Souissi, Abdessatar


    The main aim of the present paper is to prove the existence of a phase transition in quantum Markov chain (QMC) scheme for the Ising type models on a Cayley tree. Note that this kind of models do not have one-dimensional analogous, i.e. the considered model persists only on trees. In this paper, we provide a more general construction of forward QMC. In that construction, a QMC is defined as a weak limit of finite volume states with boundary conditions, i.e. QMC depends on the boundary conditions. Our main result states the existence of a phase transition for the Ising model with competing interactions on a Cayley tree of order two. By the phase transition we mean the existence of two distinct QMC which are not quasi-equivalent and their supports do not overlap. We also study some algebraic property of the disordered phase of the model, which is a new phenomena even in a classical setting.

  4. Granular chains with soft boundaries: Slowing the transition to quasi-equilibrium

    CERN Document Server

    Przedborski, Michelle; Sen, Surajit


    We present here a detailed numerical study of the dynamical behaviour of `soft' uncompressed grains in a granular chain where the grains interact via the intrinsically nonlinear Hertz force. It is well known that such a chain supports the formation of solitary waves (SWs). Here, however, the system response to the material properties of the grains and boundaries is further explored. In particular, we examine the details of the transition of the system from a SW phase to an equilibrium-like (or quasi-equilibrium) phase and for this reason we ignore the effects of dissipation in this study. We find that the soft walls slow the reflection of SWs at the boundaries of the system, which in turn slows the journey to quasi-equilibrium. Moreover, the increased grain-wall compression as the boundaries are softened results in fewer average grain-grain contacts at any given time in the quasi-equilibrium phase. These effects lead to increased kinetic energy fluctuations in the short term in softer systems. We conclude wit...

  5. Entanglement and quantum phase transition in alternating XY spin chain with next-nearest neighbouring interactions

    Institute of Scientific and Technical Information of China (English)

    Shan Chuan-Jia; Cheng Wei-Wen; Liu Tang-Kun; Huang Yan-Xia; Li nong


    By using the method of density-matrix renormalization-group to solve the different spin-spin correlation functions,the nearest-neighbouring entanglement (NNE) and the next-nearest-neighbouring entanglement (NNNE) of one-dimensional alternating Heisenberg XY spin chain are investigated in the presence of alternating the-nearestneighbouring interaction of exchange couplings,external magnetic fields and the next-nearest neighbouring interaction.For a dimerised ferromagnetic spin chain,the NNNE appears only above a critical dimerized interaction,meanwhile,the dimerized interaction a effects a quantum phase transition point and improves the NNNE to a large extent.We also study the effect of ferromagnetic or antiferromagnetic next-nearest neighbouring (NNN) interaction on the dynamics of NNE and NNNE.The ferromagnetic NNN interaction increases and shrinks the NNE below and above a critical frustrated interaction respectively,while the antiferromagnetic NNN interaction always reduces the NNE.The antiferromagnetic NNN interaction results in a large value of NNNE compared with the case where the NNN interaction is ferromagnetic.

  6. Kepler-223: A Resonant Chain of Four Transiting, Sub-Neptune Planets (United States)

    Mills, Sean; Fabrycky, Daniel C.; Migaszewski, Cezary; Ford, Eric B.; Petigura, Erik; Isaacson, Howard T.


    Surveys have revealed an abundance of multi-planet systems containing super-Earths and Neptunes in few-day to few-month orbits. Orbital periods of pairs of planets in the same system occasionally lie near, but generally not exactly on, ratios of small integers (resonances), allowing for the detection of the planets perturbing each other. There is debate whether in situ assembly or significant inward migration is the dominant mechanism of their formation. Simulations suggest migration creates tightly-packed, resonant systems, often in chains of resonance. Of the hundreds of multi-planet systems of sub-Neptunes, there is weak statistical enhancement near resonances, but no individual system has been identified that requires migration. Here we describe dynamical modeling of the system Kepler-223, which has a series of resonances among its four planets. We observe transit timing variations (TTVs), model them as resonant angle librations, and compute long-term stability, combining these analyses to constrain dynamical parameters and planetary masses. The detailed architecture of Kepler-223 is too finely tuned for formation by scattering, whereas numerical simulations demonstrate its properties are natural outcomes of the migration hypothesis. Similar systems could be destabilized by many mechanisms contributing to the observed period distribution. Planetesimal interactions in particular are thought to be responsible for establishing thecurrent orbits of the four giant planets in our own Solar System by disrupting a theoretical initial resonant chain like that actually observed in Kepler-223.

  7. Topological phase transition in a ladder of the dimerized Kitaev superconductor chains (United States)

    Zhou, Bo-Zhen; Zhou, Bin


    We investigate the topological properties of a ladder model of the dimerized Kitaev superconductor chains. The topological class of the system is determined by the relative phase θ between the inter- and intra-chain superconducting pairing. One topological class is the class BDI characterized by the ℤ index, and the other is the class D characterized by the ℤ2 index. For the two different topological classes, the topological phase diagrams of the system are presented by calculating two different topological numbers, i.e., the ℤ index winding number W and the ℤ2 index Majorana number ℳ, respectively. In the case of θ =0, the topological class belongs to the class BDI, multiple topological phase transitions accompanying the variation of the number of Majorana zero modes are observed. In the case of θ =π/2 it belongs to the class D. Our results show that for the given value of dimerization, the topologically nontrivial and trivial phases alternate with the variation of chemical potential. Project supported by the National Natural Science Foundation of China (Grant No. 11274102), the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-11-0960), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20134208110001).

  8. Electronic and magnetic properties of spiral spin-density-wave states in transition-metal chains (United States)

    Tanveer, M.; Ruiz-Díaz, P.; Pastor, G. M.


    The electronic and magnetic properties of one-dimensional (1D) 3 d transition-metal nanowires are investigated in the framework of density functional theory. The relative stability of collinear and noncollinear (NC) ground-state magnetic orders in V, Mn, and Fe monoatomic chains is quantified by computing the frozen-magnon dispersion relation Δ E (q ⃗) as a function of the spin-density-wave vector q ⃗. The dependence on the local environment of the atoms is analyzed by varying systematically the lattice parameter a of the chains. Electron correlation effects are explored by comparing local spin-density and generalized-gradient approximations to the exchange and correlation functional. Results are given for Δ E (q ⃗) , the local magnetic moments μ⃗i at atom i , the magnetization-vector density m ⃗(r ⃗) , and the local electronic density of states ρi σ(ɛ ) . The frozen-magnon dispersion relations are analyzed from a local perspective. Effective exchange interactions Ji j between the local magnetic moments μ⃗i and μ⃗j are derived by fitting the ab initio Δ E (q ⃗) to a classical 1D Heisenberg model. The dominant competing interactions Ji j at the origin of the NC magnetic order are identified. The interplay between the various Ji j is revealed as a function of a in the framework of the corresponding magnetic phase diagrams.

  9. The synthesis and characterization of organometallic copolymers with Mn-Re binuclear transition-metal group in the side chain

    Institute of Scientific and Technical Information of China (English)

    XU; Zhi; FENG; Gang; BAI; Zhifeng; MA; Yongqiang; CHANG; Weixing; LI; Jing


    Novel organometallic copolymers with Mn-Re binuclear transition-metal groups in the side chain are synthesized and characterized. The structure and properties of the copolymers are characterized by GPC, DSC, TG, NMR, FT-IR, UV-Vis spectra and elemental analysis. The glass transition temperature and UV-Vis spectra properties of these three organometallic copolymers are found to be different from the normal polystyrene. New synthetic strategy for the synthesis of organometallic copolymer is developed.

  10. Tuning the presence of dynamical phase transitions in a generalized X Y spin chain (United States)

    Divakaran, Uma; Sharma, Shraddha; Dutta, Amit


    We study an integrable spin chain with three spin interactions and the staggered field (λ ) while the latter is quenched either slowly [in a linear fashion in time (t ) as t /τ , where t goes from a large negative value to a large positive value and τ is the inverse rate of quenching] or suddenly. In the process, the system crosses quantum critical points and gapless phases. We address the question whether there exist nonanalyticities [known as dynamical phase transitions (DPTs)] in the subsequent real-time evolution of the state (reached following the quench) governed by the final time-independent Hamiltonian. In the case of sufficiently slow quenching (when τ exceeds a critical value τ1), we show that DPTs, of the form similar to those occurring for quenching across an isolated critical point, can occur even when the system is slowly driven across more than one critical point and gapless phases. More interestingly, in the anisotropic situation we show that DPTs can completely disappear for some values of the anisotropy term (γ ) and τ , thereby establishing the existence of boundaries in the (γ -τ ) plane between the DPT and no-DPT regions in both isotropic and anisotropic cases. Our study therefore leads to a unique situation when DPTs may not occur even when an integrable model is slowly ramped across a QCP. On the other hand, considering sudden quenches from an initial value λi to a final value λf, we show that the condition for the presence of DPTs is governed by relations involving λi,λf, and γ , and the spin chain must be swept across λ =0 for DPTs to occur.


    Institute of Scientific and Technical Information of China (English)

    Zhou-ting Jiang; Peng Xu; Ting-ting Sun


    The structural transition of a single polymer chain with chain length of 100,200 and 300 beads was investigated by parallel tempering MD simulation.Our simulation results can capture the structural change from random coil to orientationally ordered structure with decreasing temperature.The clear transition was observed on the curves of radius of gyration and global orientational order parameter P as the function of temperature,which demonstrated structural formation of a single polymer chain.The linear relationships between three components of square radius of gyration R2gx,R2gv,R2gz andglobal orientational order P can be obtained under the structurally transformational process.The slope of the linear relationship between x (or y-axis) component R2gx (or R2gy ) and P is negative,while that of R2gx as the function of P is positive.The absolute value of slope is proportional to the chain length.Once the single polymer chain takes the random coil or ordered configuration,the linear relationship is invalid.The conformational change was also analyzed on microscopic scale.The polymer chain can be treated as the construction of rigid stems connecting by flexible loops.The deviation from exponentially decreased behavior of stem length distribution becomes prominent,indicating a stiffening of the chain arises leading to more and more segments ending up in the trans state with decreasing temperature.The stem length Ntr is about 21 bonds indicating the polymer chain is ordered with the specific fold length.So,the simulation results,which show the prototype of a liquid-crystalline polymer chain,are helpful to understand the crystallization process of crystalline polymers.

  12. Time course of myosin heavy chain transitions in neonatal rats: importance of innervation and thyroid state (United States)

    Adams, G. R.; McCue, S. A.; Zeng, M.; Baldwin, K. M.


    During the postnatal period, rat limb muscles adapt to weight bearing via the replacement of embryonic (Emb) and neonatal (Neo) myosin heavy chains (MHCs) by the adult isoforms. Our aim was to characterize this transition in terms of the six MHC isoforms expressed in skeletal muscle and to determine the importance of innervation and thyroid hormone status on the attainment of the adult MHC phenotype. Neonatal rats were made hypothyroid via propylthiouracil (PTU) injection. In normal and PTU subgroups, leg muscles were unilaterally denervated at 15 days of age. The MHC profiles of plantaris (PLN) and soleus (Sol) muscles were determined at 7, 14, 23, and 30 days postpartum. At day 7, the Sol MHC profile was 55% type I, 30% Emb, and 10% Neo; in the PLN, the pattern was 60% Neo and 25% Emb. By day 30 the Sol and PLN had essentially attained an adult MHC profile in the controls. PTU augmented slow MHC expression in the Sol, whereas in the PLN it markedly repressed IIb MHC by retaining neonatal MHC expression. Denervation blunted the upregulation of IIb in the PLN and of Type I in the Sol and shifted the pattern to greater expression of IIa and IIx MHCs in both muscles. In contrast to previous observations, these findings collectively suggest that both an intact thyroid and innervation state are obligatory for the attainment of the adult MHC phenotype, particularly in fast-twitch muscles.

  13. Lattice stretching bistability and dynamic heterogeneity

    DEFF Research Database (Denmark)

    Christiansen, Peter Leth; Savin, A. V.; Zolotaryuk, A. V.


    A simple one-dimensional lattice model is suggested to describe the experimentally observed plateau in force-stretching diagrams for some macromolecules. This chain model involves the nearest-neighbor interaction of a Morse-like potential (required to have a saturation branch) and a harmonic second......-neighbor coupling. Under an external stretching applied to the chain ends, the intersite Morse-like potential results in the appearance of a double-well potential within each chain monomer, whereas the interaction between the second neighbors provides a homogeneous bistable (degenerate) ground state, at least...... stretched bonds with a double-well potential. This case allows us to explain the existence of a plateau in the force-extension diagram for DNA and α-helix protein. Finally, the soliton dynamics are studied in detail....


    Institute of Scientific and Technical Information of China (English)

    WAN Meixiang


    A physical model of series of the conductivity on chain and the interchain conductivity between chains is proposed to explain enhanced conductivity of stretched conducting polymers.This model suggests that the enhanced conductivity for stretched conducting polymers might be due to increasing of the interchain conductivity between chains along the elongation direction after drawing processes if the conductivity on chain is assumed much larger than that of the interchain conductivity between chains. According to this model, it is expected that the temperature dependence of conductivity measured by four-probe method for stretched conducting polymers is controlled by a variation of the interchain conductivity between chains with temperature, which can be used to explain that a metallic temperature dependence of conductivity for stretched conducting polymers is not observed although the conductivity along the elongation direction is enhanced by two or three orders of magnitude.

  15. Cardiomyopathy-related mutation (A30V) in mouse cardiac troponin T divergently alters the magnitude of stretch activation in α- and β-myosin heavy chain fibers. (United States)

    Mickelson, Alexis V; Gollapudi, Sampath K; Chandra, Murali


    The present study investigated the functional consequences of the human hypertrophic cardiomyopathy (HCM) mutation A28V in cardiac troponin T (TnT). The A28V mutation is located within the NH2 terminus of TnT, a region known to be important for full activation of cardiac thin filaments. The functional consequences of the A28V mutation in TnT remain unknown. Given how α- and β-myosin heavy chain (MHC) isoforms differently alter the functional effect of the NH2 terminus of TnT, we hypothesized that the A28V-induced effects would be differently modulated by α- and β-MHC isoforms. Recombinant wild-type mouse TnT (TnTWT) and the mouse equivalent of the human A28V mutation (TnTA30V) were reconstituted into detergent-skinned cardiac muscle fibers extracted from normal (α-MHC) and transgenic (β-MHC) mice. Dynamic and steady-state contractile parameters were measured in reconstituted muscle fibers. Step-like length perturbation experiments demonstrated that TnTA30V decreased the magnitude of the muscle length-mediated recruitment of new force-bearing cross bridges (ER) by 30% in α-MHC fibers. In sharp contrast, TnTA30V increased ER by 55% in β-MHC fibers. Inferences drawn from other dynamic contractile parameters suggest that directional changes in ER in TnTA30V + α-MHC and TnTA30V + β-MHC fibers result from a divergent impact on cross bridge-regulatory unit (troponin-tropomyosin complex) cooperativity. TnTA30V-mediated effects on Ca(2+)-activated maximal tension and instantaneous muscle fiber stiffness (ED) were also divergently affected by α- and β-MHC. Our study demonstrates that TnTA30V + α-MHC and TnTA30V + β-MHC fibers show contrasting contractile phenotypes; however, only the observations from β-MHC fibers are consistent with the clinical data for A28V in humans.

  16. First order quantum phase transitions of the XX spin-1/2 chain in a uniform transverse field

    Energy Technology Data Exchange (ETDEWEB)

    Pan Feng [Department of Physics, Liaoning Normal University, Dalian 116029 (China) and Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States)]. E-mail:; Ma Nan [Department of Physics, Liaoning Normal University, Dalian 116029 (China); Guan Xin [Department of Physics, Liaoning Normal University, Dalian 116029 (China); Draayer, J.P. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States)


    Quantum phase transitional behavior of a finite periodic XX spin-12 chain with nearest neighbor interaction in a uniform transverse field is studied based on the simple exact solutions. It is found that there are [N/2] level-crossing points in the ground state, where N is the periodic number of the system and [x] stands for the integer part of x, when the interaction strength and magnitude of the magnetic field satisfy certain conditions. The quantum phase transitional behavior in the thermodynamic is also studied.

  17. Effects of calcitriol, seocalcitol, and medium-chain triglyceride on a canine transitional cell carcinoma cell line

    DEFF Research Database (Denmark)

    Kaewsakhorn, T.; Kisseberth, W.C.; Capen, C.C.


    Background: Transitional cell carcinoma (TCC) in dogs is associated with high morbidity and mortality. Calcitriol and its analog seocalcitol, combined with medium-chain triglyceride (MCT), have potential for the treatment of this disease. Materials and Methods: TCC cells were treated with calcitr......Background: Transitional cell carcinoma (TCC) in dogs is associated with high morbidity and mortality. Calcitriol and its analog seocalcitol, combined with medium-chain triglyceride (MCT), have potential for the treatment of this disease. Materials and Methods: TCC cells were treated...... inhibited TCC cell growth via induction of cell cycle arrest and MCT enhanced this effect. Therefore, calcitriol and seocalcitol with MCT may have therapeutic potential for canine bladder cancer....

  18. Lamellar thickness transition of melt-crystallized polybuten-1 tetragonal phase: configurational change in chain folding directions

    Institute of Scientific and Technical Information of China (English)



    Lamellar crystal thickness lc of isotactic polybutene-1 (it-PB 1) have been investigated for crystal-lization in the melt over a wide range of crystallization temperature T from 40℃ to 90℃ by small angle X-ray scattering experiments and density measurements. The crystal thickness lc demonstrates two linear dependences on inverse supercooling and a transition from one dependence to the other has been observed around T =65~C. Each of the two dependences obeys the nucleation theory in the high and low supercooling ranges, respec-tively. Chain folding free energy q determined from the low supercooling range is larger than that determined from the high supercooling range. Possible mechanisms for the transition are discussed taking account of entropy of chain folding directions.

  19. Analysis on Saltwater Pearls Industry Ecological Value Chain and Its Global Value Chain Stretching in the World%我国海水珍珠产业生态价值链与GVC延伸情况分析

    Institute of Scientific and Technical Information of China (English)



    The paper has a careful study on the global value chain ( GVC ) extension in order to explore the mechanism situation of the sustainable development of saltwater pearl industry channels and approach embedded GVC.%对海水珍珠产业生态价值创造机理进行研究,并对海水珍珠全球价值链(GVC)延伸情况进行分析,以探寻海水珍珠产业持续发展的途径和嵌入GVC的方法.

  20. Stretching: Does It Help? (United States)

    Vardiman, Phillip; Carrand, David; Gallagher, Philip M.


    Stretching prior to activity is universally accepted as an important way to improve performance and help prevent injury. Likewise, limited flexibility has been shown to decrease functional ability and predispose a person to injuries. Although this is commonly accepted, appropriate stretching for children and adolescents involved with sports and…

  1. Stretch Band Exercise Program (United States)

    Skirka, Nicholas; Hume, Donald


    This article discusses how to use stretch bands for improving total body fitness and quality of life. A stretch band exercise program offers a versatile and inexpensive option to motivate participants to exercise. The authors suggest practical exercises that can be used in physical education to improve or maintain muscular strength and endurance,…

  2. Exact diagonalization for spin-1/2 chains and the first order quantum phase transitions of the XXX chain in a uniform transverse field (United States)

    Pan, Feng; Guan, Xin; Ma, Nan; Han, Wen-Juan; Draayer, J. P.


    A simple Mathematica code based on the differential realization of hard-core boson operators for finding exact solutions of the periodic-N spin-1/2 systems with or beyond nearest neighbor interactions is proposed; it can easily be used to study general spin-1/2 interaction systems. As an example, the code is applied to study XXX spin-1/2 chains with nearest neighbor interaction in a uniform transverse field. It shows that there are [N/2] level-crossing points in the ground state, where N is the periodic number of the system and [x] stands for the integer part of x, when the interaction strength and magnitude of the magnetic field satisfy certain conditions. The quantum phase transitional behavior in the ground state of the system in the thermodynamic limit is also studied.

  3. Exact diagonalization for spin-1/2 chains and the first order quantum phase transitions of the XXX chain in a uniform transverse field

    CERN Document Server

    Pan, Feng; Ma, Nan; Han, Wen-Juan; Draayer, J P; 10.1088/0953-8984/19/38/386208


    A simple Mathematica code based on the differential realization of hard-core boson operators for finding exact solutions of the periodic-N spin-1/2 systems with or beyond nearest neighbor interactions is proposed, which can easily be used to study general spin-1/2 interaction systems. As an example, The code is applied to study XXX spin-1/2 chain with nearest neighbor interaction in a uniform transverse field. It shows that there are [N/2] level-crossing points in the ground state, where N is the periodic number of the system and [x] stands for the integer part of x, when the interaction strength and magnitude of the magnetic field satisfy certain conditions. The quantum phase transitional behavior in the ground state of the system in the thermodynamic limit is also studied.

  4. Exact diagonalization for spin-1/2 chains and the first order quantum phase transitions of the XXX chain in a uniform transverse field

    Energy Technology Data Exchange (ETDEWEB)

    Pan Feng [Department of Physics, Liaoning Normal University, Dalian 116029 (China); Guan Xin [Department of Physics, Liaoning Normal University, Dalian 116029 (China); Ma Nan [Department of Physics, Liaoning Normal University, Dalian 116029 (China); Han Wenjuan [Department of Physics, Liaoning Normal University, Dalian 116029 (China); Draayer, J P [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States)


    A simple Mathematica code based on the differential realization of hard-core boson operators for finding exact solutions of the periodic-N spin-1/2 systems with or beyond nearest neighbor interactions is proposed; it can easily be used to study general spin-1/2 interaction systems. As an example, the code is applied to study XXX spin-1/2 chains with nearest neighbor interaction in a uniform transverse field. It shows that there are [N/2] level-crossing points in the ground state, where N is the periodic number of the system and [x] stands for the integer part of x, when the interaction strength and magnitude of the magnetic field satisfy certain conditions. The quantum phase transitional behavior in the ground state of the system in the thermodynamic limit is also studied.

  5. Obesity status transitions across the elementary years: Use of Markov chain modeling (United States)

    Overweight and obesity status transition probabilities using first-order Markov transition models applied to elementary school children were assessed. Complete longitudinal data across eleven assessments were available from 1,494 elementary school children (from 7,599 students in 41 out of 45 school...

  6. Dynein Light Intermediate Chain 2 Facilitates the Metaphase to Anaphase Transition by Inactivating the Spindle Assembly Checkpoint.

    Directory of Open Access Journals (Sweden)

    Sagar P Mahale

    Full Text Available The multi-functional molecular motor cytoplasmic dynein performs diverse essential roles during mitosis. The mechanistic importance of the dynein Light Intermediate Chain homologs, LIC1 and LIC2 is unappreciated, especially in the context of mitosis. LIC1 and LIC2 are believed to exist in distinct cytoplasmic dynein complexes as obligate subunits. LIC1 had earlier been reported to be required for metaphase to anaphase progression by inactivating the kinetochore-microtubule attachment-sensing arm of the spindle assembly checkpoint (SAC. However, the functional importance of LIC2 during mitosis remains elusive. Here we report prominent novel roles for the LIC2 subunit of cytoplasmic dynein in regulating the spindle assembly checkpoint. LIC2 depletion in mammalian cells led to prolonged metaphase arrest in the presence of an active SAC and also to stretched kinetochores, thus implicating it in SAC inactivation. Quantitative fluorescence microscopy of SAC components revealed accumulation of both attachment- and tension-sensing checkpoint proteins at metaphase kinetochores upon LIC2 depletion. These observations support a stronger and more diverse role in checkpoint inactivation for LIC2 in comparison to its close homolog LIC1. Our study uncovers a novel functional hierarchy during mitotic checkpoint inactivation between the closely related but homologous LIC subunits of cytoplasmic dynein. These subtle functional distinctions between dynein subpopulations could be exploited to study specific aspects of the spindle assembly checkpoint, which is a key mediator of fidelity in eukaryotic cell division.

  7. Quantum Phase Transitions in Alternating-Bond Mixed Diamond Chains with Spins 1 and 1/2 (United States)

    Hida, Kazuo; Takano, Ken'ichi; Suzuki, Hidenori


    We investigate the mixed diamond chain composed of spins 1 and 1/2 when the exchange interaction is alternatingly distorted. Depending on the strengths of frustration and distortion, this system has various ground states. Each ground state consists of an array of spin clusters separated by singlet dimers by virtue of an infinite number of local conservation laws. We determine the ground-state phase diagram by numerically analyzing each spin cluster. In particular, for strong distortions, we find an infinite series of quantum phase transitions using the cluster expansion method and conformal field theory. This leads to an infinite series of steps in the behavior of Curie constant and residual entropy.

  8. Gaussian phase transition and critical exponents in spin-1 bond-alternative Heisenberg chains (United States)

    Su, Yao Heng; Chen, Ai Min; Xiang, Chunhuan; Wang, Honglei; Xia, Cai-Juan; Wang, Jun


    The quantum Gaussian phase transition is investigated for the infinite spin-1 bond-alternative Heisenberg model in one spatial dimension. By using a tensor network representation with an infinite matrix product state approach, the ground state energy, bipartite entanglement entropy, non-local string order, and fidelity per lattice site are calculated to characterize the phase transition. At the quantum phase transition point, the scaling behavior of various physical observables with respect to the finite truncation dimension are discussed for the ground state wavefunctions. In addition, the central charge is extracted from the finite entanglement entropies and the finite correlation lengths. Furthermore, the various critical exponents of the string order are calculated. The characteristic critical exponents and the central charge determine the universality class of the phase transition.

  9. Magnetic transition in α-NaCuPO4 with Cu-O chains

    Directory of Open Access Journals (Sweden)

    Y. Wu


    Full Text Available The magnetic properties and specific heat have been studied on α-NaCuPO4, an analog of ion-battery material LiFePO4. A ferromagnetic-like transition at 23 K was observed for the first time by the isofield magnetization measurement and confirmed by isothermal magnetization below 23 K. The compound obeys Curie-Weiss law with an antiferromagentic coupling feature. A canted antiferromagentism was suggested to account for the ferromagnetic-like transition. The contribution from the orbital magnetic moment is found to be non-ignorable. Furthermore, specific heat shows that the magnetic transition is broadened and the critical temperature is enhanced under magnetic field, revealing a low dimensionality feature.

  10. Conformation of Organic Chain in Phase Transition of Hybrid(Cl2H25NH3)2MnCl4

    Institute of Scientific and Technical Information of China (English)

    GUO Liling; SUN Yubing; MEI Ao; DAI Yadong; LIU Hanxing


    The structural change in phase transition of hybrid(C12H25NH3)2MnCl4 was investigated.The temperature and the structures of the phase transition is investigated by thermal gravimetry(TG)and differential scanning calorimetry(DSC),infrared spectrum(IR)and X-ray diffraction(XRD).The results suggest that the phase transition is reversible and the structural change arises from the conformation change of the organic chain.The interlayer distance increases when the hybrid transforms from low temperature phase to high temperature phase.This is explained by the diffusion of gauche-bond along the organic chains and they move away from each other when the phase transition occurs.Combining the experimental data with theoretical calculation,we propose that organic chain of the hybrid in high temperature phase is the conformation of gauche-bond alternating with trans bond(noted as GTG'TGTG'TGTG'T).

  11. From Short Food Supply Chains to Sustainable Agriculture in Urban Food Systems: Food Democracy as a Vector of Transition

    Directory of Open Access Journals (Sweden)

    Yuna Chiffoleau


    Full Text Available In industrialized nations, local food networks have generally been analyzed through alternative food systems, in spite of the fact that they are much more diverse than this would imply. In France, ‘short food chains’ are both a continuation of a long tradition and a recent trend which now extends beyond activists, to consumers and producers as well. This paper will explore the conditions under which these chains can change the practices and knowledge of ordinary actors in urban food systems, from producers to urban consumers and policy-makers, in the area of agriculture and sustainability. It will consider the case study of the creation and development of an urban open-air market which has been analyzed using intervention research with input from economic sociology. We will highlight how personal relations, which are encouraged by a participatory context, support the evolution of practices and knowledge. We will also illustrate how a system of produce labelling has emerged as a mediation resource, and has increased changes as well as participation within the re-territorialization of the urban food system. By describing a concrete expression of food democracy which is spreading in France via a free collective trademark, and by showing its role in the transition of ‘ordinary’ actors towards a more sustainable agriculture, this paper will shine new light onto local food chains as well as traditional short food chains, and will call for more research on the subject.

  12. Places, Chains, and Plates: Governing Transitions in the Shrimp Aquaculture Production-Consumption System


    Lebel, L.; Lebel, P; Garden, P.; Dao, H. G.; Khrutmuang, S.; Nakayama, S


    The shrimp production-consumption system is governed by a diverse and dynamic array of actors each drawing on institutions at various levels, from local through national to international. But, for the most part, the politics of consumption (plates), chains, and places are disconnected. Instead, shrimp producers face a myriad of institutional and consumer demands and the sustainability of the shrimp aquaculture production-consumption system is not merely a technical problem to be solved by bet...

  13. Coil-helix transition of ι-carrageenan as a function of chain regularity

    NARCIS (Netherlands)

    Velde, F. van de; Rollema, H.S.; Grinberg, N.V.; Burova, T.V.; Grinberg, V.Ya.; Hans Tromp, R.


    A series of ι-carrageenans containing different amounts of v-carrageenan (0-23 monomer %) have been prepared from neutrally extracted carrageenan of Eucheuma denticulatum. v-Carrageenan is the biochemical precursor of ι-carrageenan. The conformational order-disorder transition and rheological proper

  14. Manufacturing of multilayer graphene oxide/poly(ethylene terephthalate) nanocomposites with tunable crystallinity, chain orientations and thermal transitions

    Energy Technology Data Exchange (ETDEWEB)

    Seyyed Monfared Zanjani, Jamal [Faculty of Engineering and Natural Sciences, Sabanci University, Orhanli, 34956 Tuzla, Istanbul (Turkey); Saner Okan, Burcu, E-mail: [Sabanci University Nanotechnology Research and Application Center, SUNUM, Orhanli, 34956 Tuzla, Istanbul (Turkey); Nanografen Nanotechnological Products Limited Company, GOSB Teknopark, Gebze 41430, Kocaeli (Turkey); Menceloglu, Yusuf [Faculty of Engineering and Natural Sciences, Sabanci University, Orhanli, 34956 Tuzla, Istanbul (Turkey); Nanografen Nanotechnological Products Limited Company, GOSB Teknopark, Gebze 41430, Kocaeli (Turkey)


    Thermally exfoliated graphene oxide (TEGO) reinforced polyethylene terephthalate (PET) nanocomposites with controlled crystallinity, chain conformations and thermo-mechanical properties were produced with very low TEGO weight fractions by a twin-screw compounding extruder. Tensile modulus was found to increase by 52% by the addition of 1 wt% TEGO. This significant increase in mechanical properties of PET nanocomposites was explained by well intercalation of PET chains through multi-layer graphene sheets and complete coverage of graphene surface by electrostatic interactions. An increase in the ratio of gauche and trans conformations in PET chains indicated that PET nanocomposites became more crystalline by increasing TEGO amount. Transmission electron microscopy observations showed the favorable interaction between TEGO sheets and PET matrix facilitating the dispersion and flattening of graphene sheets into polymeric matrix during elongation. The integration of 1 wt% TEGO sheets into PET matrix enhanced heat distortion temperature from 71 °C for neat specimen upto 91.6 °C at the constant stress of 0.45 MPa, and increased Vicat softening point from 76 °C upto 95 °C. Therefore, the failures of PET considerably reduced by improving short-term heat resistance and its softening properties between glass transition temperature and melting temperature by the incorporation of TEGO sheets. - Highlights: • 52% modulus improvement by the addition of 1 wt% graphene in PET. • Well-intercalation of PET chains through graphene sheets during compounding process. • Homogeneous graphene dispersion by favorable interactions between graphene and PET. • Enhancement in Heat distortion temperature and Vicat softening point of PET composite. • Considerable reduction in failures of PET by improving short-term heat resistance.

  15. Stationary-point approach to the phase transition of the classical XY chain with power-law interactions. (United States)

    Kastner, Michael


    The stationary points of the potential energy function V of the classical XY chain with power-law pair interactions (i.e., interactions decaying like r{-α} with the distance) are analyzed. For a class of "spinwave-type" stationary points, the asymptotic behavior of the Hessian determinant of V is computed analytically in the limit of large system size. The computation is based on the Toeplitz property of the Hessian and makes use of a Szegö-type theorem. The results serve to illustrate a recently discovered relation between phase transitions and the properties of stationary points of classical many-body potentials. In agreement with this relation, the exact phase transition potential energy of the model can be read off from the behavior of the Hessian determinant for exponents α between zero and one. For α between one and two, the phase transition is not manifest in the behavior of the determinant, and it might be necessary to consider larger classes of stationary points.

  16. Effect of the lipid chain melting transition on the stability of DSPE-PEG(2000) micelles. (United States)

    Kastantin, Mark; Ananthanarayanan, Badriprasad; Karmali, Priya; Ruoslahti, Erkki; Tirrell, Matthew


    Micellar nanoparticles are showing promise as carriers of diagnostic and therapeutic biofunctionality, leading to increased interest in their properties and behavior, particularly their size, shape, and stability. This work investigates the physical chemistry of micelles formed from DSPE-PEG(2000) monomers as it pertains to these properties. A melting transition in the lipid core of spheroidal DSPE-PEG(2000) micelles is observed as an endothermic peak at 12.8 degrees C upon heating in differential scanning calorimetry thermograms. Bulky PEG(2000) head groups prevent regular crystalline packing of lipids in both the low-temperature glassy and high-temperature fluid phases, as evidenced by wide-angle X-ray scattering. Equilibrium micelle geometry is spheroidal above and below the transition temperature, indicating that the entropic penalty to force the PEG brush into flat geometry is greater than the enthalpic benefit to the glassy core to pack in an extended configuration. Increased micelle stability is seen in the glassy phase with monomer desorption rates significantly lower than in the fluid phase. Activation energies for monomer desorption are 156+/-6.7 and 79+/-5.0 kJ/mol for the glassy and fluid phases, respectively. The observation of a glass transition that increases micelle stability but does not perturb micelle geometry is useful for the design of more effective biofunctional micelles.

  17. Stretching a Semiflexible Polymer in a Tube

    Directory of Open Access Journals (Sweden)

    Runhua Li


    Full Text Available How the statistical behavior of semiflexible polymer chains may be affected by force stretching and tube confinement is a classical unsolved problem in polymer physics. Based on the Odijk deflection theory and normal mode decomposition in terms of Fourier expansion, we have derived a new compact formula for the extension of a wormlike chain of finite length strongly confined in a tube and simultaneously stretched by an external force. We have also suggested a new deflection length, which together with the force-extension relation is valid for a very extended range of the tube-diameter/persistence-length ratio comparing to the classic Odijk theory. The newly derived formula has no adjustable fitting parameters for the whole deflection regime; in contrast, the classic Odijk length needs different prefactors to fit the free energy and average extension, respectively. Brownian dynamics simulations based on the Generalized Bead-Rod (GBR model were extensively performed, which justified the theoretical predictions.

  18. Free carboxylate stretching modes

    NARCIS (Netherlands)

    Oomens, J.; Steill, J. D.


    We report the first IR spectroscopic observation of carboxylate stretching modes in free space, i.e., in the complete absence of solvent or counterions. Gas-phase spectra of a series of benzoate anions have been recorded and compared to condensed-phase spectra, revealing the profound influence of th

  19. Field-Induced Multiple Reentrant Quantum Phase Transitions in Randomly Dimerized Antiferromagnetic S=1/2 Heisenberg Chains (United States)

    Hida, Kazuo


    The multiple reentrant quantum phase transitions in the S=1/2 antiferromagnetic Heisenberg chains with random bond alternation in the magnetic field are investigated by the density matrix renormalization group method combined with interchain mean field approximation. It is assumed that odd numbered bonds are antiferromagnetic with strength J and even numbered bonds can take the values JS and JW (JS > J > JW > 0) randomly with the probabilities p and 1- p, respectively. The pure version ( p=0 and 1) of this model has a spin gap but exhibits a field-induced antiferromagnetism in the presence of interchain coupling if Zeeman energy due to the magnetic field exceeds the spin gap. For 0 < p < 1, antiferromagnetism is induced by randomness at the small field region where the ground state is disordered due to the spin gap in the pure version. At the same time, this model exhibits randomness-induced plateaus at several values of magnetization. The antiferromagnetism is destroyed on the plateaus. As a consequence, we find a series of reentrant quantum phase transitions between transverse antiferromagnetic phases and disordered plateau phases with the increase of magnetic field for a moderate strength of interchain coupling. Above the main plateaus, the magnetization curve consists of a series of small plateaus and jumps between them. It is also found that antiferromagnetism is induced by infinitesimal interchain coupling at the jumps between the small plateaus. We conclude that this antiferromagnetism is supported by the mixing of low-lying excited states by the staggered interchain mean field even though the spin correlation function is short ranged in the ground state of each chain.

  20. Alkyl Chain Growth on a Transition Metal Center: How Does Iron Compare to Ruthenium and Osmium?

    Directory of Open Access Journals (Sweden)

    Mala A. Sainna


    Full Text Available Industrial Fischer-Tropsch processes involve the synthesis of hydrocarbons usually on metal surface catalysts. On the other hand, very few homogeneous catalysts are known to perform a Fischer-Tropsch style of reaction. In recent work, we established the catalytic properties of a diruthenium-platinum carbene complex, [(CpRu2(μ2-H (μ2-NHCH3(μ3-CPtCH3(P(CH332](COn+ with n = 0, 2 and Cp = η5-C5(CH35, and showed it to react efficiently by initial hydrogen atom transfer followed by methyl transfer to form an alkyl chain on the Ru-center. In particular, the catalytic efficiency was shown to increase after the addition of two CO molecules. As such, this system could be viewed as a potential homogeneous Fischer-Tropsch catalyst. Herein, we have engineered the catalytic center of the catalyst and investigated the reactivity of trimetal carbene complexes of the same type using iron, ruthenium and osmium at the central metal scaffold. The work shows that the reactivity should increase from diosmium to diruthenium to diiron; however, a non-linear trend is observed due to multiple factors contributing to the individual barrier heights. We identified all individual components of these reaction steps in detail and established the difference in reactivity of the various complexes.

  1. Quantum discord and quantum phase transition in the XXZ spin chain with three-site interaction (United States)

    Yang, Jing; Cong, Mei-Yan; Huang, Yan-Xia


    Pairwise quantum discord (QD) and entanglement of the three-qubit XXZ Heisenberg spin chain with two types of three-site interactions and an external magnetic field are investigated. Our study found that both entanglement and quantum discord could detect the quantum critical phenomena of this model. We were able to obtain a nonzero value of quantum discord even at high temperature with the increase of XZX+YZY or XZY-YZX three-site interaction, however, the cooperative effect of XZX+YZY and XZY-YZX interactions is more ideal. Furthermore, in contrast to XZY-YZX and XZX+YZY interactions, the cooperative effect of XZX+YZY and XZY-YZX three-site interactions is more efficient to enhance the maximum value of quantum discord. Likewise, the cooperative effect of XZX+YZY and XZY-YZX interactions is the most optimal to increase the range of magnetic field or anisotropy parameter where quantum discord maintains the maximum value.

  2. An informational transition in conditioned Markov chains: Applied to genetics and evolution. (United States)

    Zhao, Lei; Lascoux, Martin; Waxman, David


    In this work we assume that we have some knowledge about the state of a population at two known times, when the dynamics is governed by a Markov chain such as a Wright-Fisher model. Such knowledge could be obtained, for example, from observations made on ancient and contemporary DNA, or during laboratory experiments involving long term evolution. A natural assumption is that the behaviour of the population, between observations, is related to (or constrained by) what was actually observed. The present work shows that this assumption has limited validity. When the time interval between observations is larger than a characteristic value, which is a property of the population under consideration, there is a range of intermediate times where the behaviour of the population has reduced or no dependence on what was observed and an equilibrium-like distribution applies. Thus, for example, if the frequency of an allele is observed at two different times, then for a large enough time interval between observations, the population has reduced or no dependence on the two observed frequencies for a range of intermediate times. Given observations of a population at two times, we provide a general theoretical analysis of the behaviour of the population at all intermediate times, and determine an expression for the characteristic time interval, beyond which the observations do not constrain the population's behaviour over a range of intermediate times. The findings of this work relate to what can be meaningfully inferred about a population at intermediate times, given knowledge of terminal states.

  3. Stretching & Flexibility: An Interactive Encyclopedia of Stretching. [CD-ROM]. (United States)


    This CD-ROM offers 140 different stretches in full-motion video sequences. It focuses on the proper techniques for overall physical fitness, injury prevention and rehabilitation, and 23 different sports (e.g., golf, running, soccer, skiing, climbing, football, and baseball). Topics include stretching for sports; stretching awareness and education…

  4. Stretching the Border

    DEFF Research Database (Denmark)

    Horstmann, Alexander


    In this paper, I hope to add a complementary perspective to James Scott’s recent work on avoidance strategies of subaltern mountain people by focusing on what I call the refugee public. The educated Karen elite uses the space of exile in the Thai borderland to reconstitute resources and to re-ent......-based organizations succeed to stretch the border by establishing a firm presence that is supported by the international humanitarian economy in the refugee camps in Northwestern Thailand....

  5. Photo-Induced Phase Transitions to Liquid Crystal Phases: Influence of the Chain Length from C8E4 to C14E4

    Directory of Open Access Journals (Sweden)

    Simone Techert


    Full Text Available Photo-induced phase transitions are characterized by the transformation from phase A to phase B through the absorption of photons. We have investigated the mechanism of the photo-induced phase transitions of four different ternary systems CiE4/alkane (i with n = 8, 10, 12, 14; cyclohexane/H2O. We were interested in understanding the effect of chain length increase on the dynamics of transformation from the microemulsion phase to the liquid crystal phase. Applying light pump (pulse/x-ray probe (pulse techniques, we could demonstrate that entropy and diffusion control are the driving forces for the kind of phase transition investigated.

  6. Effect of stretching-induced changes in hydrodynamic screening on coil-stretch hysteresis of unentangled polymer solutions (United States)

    Prabhakar, Ranganathan; Sasmal, Chandi; Nguyen, Duc At; Sridhar, Tam; Prakash, J. Ravi


    Extensional rheometry and Brownian dynamics simulations of flexible polymer solutions confirm predictions based on blob concepts that coil-stretch hysteresis in extensional flows increases with concentration, reaching a maximum at the critical overlap concentration c* before progressively vanishing in the semidilute regime. These observations demonstrate that chain stretching strengthens intermolecular hydrodynamic screening in dilute solutions, but weakens it in semidilute solutions. Flow can thus strongly modify the concentration dependence of viscoelastic properties of polymer solutions.

  7. Optimal stretching of fluid for enhancing reaction growth (United States)

    Nevins, Thomas; Kelley, Douglas


    When a biological or chemical scalar grows in flowing fluid, the resulting reacted region is dependent on both the details of the flow, and the reaction kinetics. We simultaneously film reaction state and flow in a laboratory model of reactive mixing in order to examine reactive mixing in physical, time-dependent flows. Using the excitable Belousov-Zhabotinsky (BZ) reaction, we find an optimal stretching range in which the flow enhances reaction, but larger stretching causes reaction blowout. We observe the transition from flow mostly helping to mostly blowout is not associated with the transition to turbulence, and that stretching fields (closely related to finite-time Lyapunov exponents) inside the optimal range appear to have a large effect on reaction growth rate locally. We also present estimates of the optimal stretching for BZ, and hypothesize that it is a feature exclusive to excitable reactions.

  8. 可信链在Ad Hoc网络的传递%Transitive trusted chain in Ad Hoc networks

    Institute of Scientific and Technical Information of China (English)

    刘静; 王赜


    To further enhance the security of Ad Hoc networks, it presents a novel transitive trusted chain with Trusted Platform Module (TPM) in Ad Hoc networks. A scheme which extends the trusted relationships from the node of Ad Hoc networks to Ad Hoc networks as its design objective is proposed, and the trusted relationships between peers can be evaluated with a trusted model in Ad Hoc networks. Authenticated Routing for Ad hoc Networks (ARAN) is improved by introduction of trusted level and then it selects the routing of highest trusted level. The trusted transfer model in Ad Hoc networks is analyzed.%为了进一步提高Ad Hoc网络的安全性,提出一种利用可信平台模块传递信任链的方案.该方案以将信任关系从Ad Hoc网络节点扩展至Ad Hoc网络为设计目标,利用信任模型评估每个节点的信任度,在ARAN安全路由协议的基础上,结合信任度对ARAN安全路由协议进行了改进,选出一条可信度最高的路由,对可信链传递方案进行性能分析.

  9. Brand, Brand Stretching, and Brand Stretching Plan for JAC


    Chen, Lei


    With the consistent crisis of world economic, companies are encountering problems with their expansion. Introducing all new brands for expanding is hard to be accepted due to the high level of costs and risks. Using brand stretching as companies’ expansion strategy efficiently reduces the costs and risks today. Therefore, getting clear about brand stretching seems quite important for most companies nowadays. The objectives of this thesis is introducing brand stretching theory and making a...

  10. Sphere-to-rod transition of short-chain PEO-b-PDMS-b-PEO in aqueous solution induced by copolymer concentration

    Institute of Scientific and Technical Information of China (English)

    Xiao Li Zhan; Bi Chen; Qing Hua Zhang; Ling Min Yi


    A short-chain triblock copolymer EO9-DMS7-EO9 was synthesized by coupling reaction of allyl-terminated poly(ethylene oxide) and Si-H-terminated poly(dimethylsiloxane).The structure and purity of synthesized copolymer was carefully character-ized.Self-assembly behavior of EO9-DMS7-EO9 triblock copolymer in water was investigated.And it was found that along with the increase of copolymer concentration,morphology of self-assembled aggregates transits from sphere to rod.A plausible under-standing of the morphology transition for the investigated triblock copolymer was proposed.

  11. Capillary stretching of elastic fibers (United States)

    Protiere, Suzie; Stone, Howard A.; Duprat, Camille


    Fibrous media consisting of constrained flexible fibers can be found in many engineered systems (membranes in filters, woven textile, matted paper). When such materials interact with a liquid, the presence of liquid/air interfaces induces capillary forces that deform the fibers. To model this interaction we study the behaviour of a finite volume of liquid deposited on two parallel flexible fibers clamped at both ends. A tension along the fibers is imposed and may be varied. We show that the system undergoes various morphological changes as the interfiber distance, the elasticity and the tension of the fibers are varied. For a certain range of parameters, the liquid spreads along the fibers and pulls them together, leading to the ``zipping'' of the fibers. This capillary adhesion can then be enhanced or reduced by changing the tension within the fibers. We will show that balancing stretching and capillary forces allows the prediction of this transition as well as the conditions for which detachment of the fibers occurs. These results may be used to prevent the clogging of fibrous membranes or to optimize the capture of liquids.

  12. A statistical theory of coil-to-globule-to-coil transition of a polymer chain in a mixture of good solvents (United States)

    Budkov, Yu. A.; Kolesnikov, A. L.; Kalikin, N. N.; Kiselev, M. G.


    We present an off-lattice statistical model of a single polymer chain in mixed-solvent media. Taking into account the polymer conformational entropy, renormalization of solvent composition near the polymer backbone, the universal intermolecular excluded-volume and van der Waals interactions within the self-consistent field theory, the reentrant coil-to-globule-to-coil transition (co-nonsolvency) has been described in this paper. For convenience we split the system volume in two parts: the volume occupied by the polymer chain and the volume of bulk solution. Considering the equilibrium between two sub-volumes, the polymer solvation free energy as a function of radius of gyration and co-solvent mole fraction within internal polymer volume has been obtained. Minimizing the free energy of solvation with respect to its arguments, we show two qulitatively different regimes of co-nonsolvency. Namely, at sufficiently high temperature the reentrant coil-to-globule-to-coil transition proceeds smoothly. On the contrary, when the temperature drops below a certain threshold value a coil-globule transition occurs in the regime of first-order phase transition, i.e., discontinuous changes of the radius of gyration and the local co-solvent mole fraction near the polymer backbone. We show that, when the collapse of the polymer chain takes place, the entropy and enthalpy contributions to the solvation free energy of the globule strongly grow. From the first principles of statistical thermodynamics we confirm earlier speculations based on the MD simulations results that the co-nonsolvency is the essentially enthalpic-entropic effect and is caused by enthalpy-entropy compensation. We show that the temperature dependences of the solution heat capacity change due to the solvation of the polymer chain are in qualitative agreement with the differential scanning calorimetry data for PNIPAM in aqueous methanol.

  13. Assessing transition trajectories towards a sustainable energy system: A case study on the Dutch transition to climate-neutral transport fuel chains

    NARCIS (Netherlands)

    Suurs, R.A.A.; Hekkert, M.P.; Meeus, M.T.H.; Nieuwlaar, E.


    This paper proposes a method for the ex ante evaluation of technological trajectories. As a case we study the Dutch transport energy system and its transition to climate neutrality. Two technological trajectories are proposed: (i) a sequence of transition steps based on radical infrastructural chang

  14. Atomic Stretch: Optimally bounded real-time stretching and beyond

    DEFF Research Database (Denmark)

    Jensen, Rasmus Ramsbøl; Nielsen, Jannik Boll


    Atomic Stretch is a plugin for your preferred Adobe video editing tool, allowing real-time smooth and optimally bounded retarget-ting from and to any aspect ratio. The plugin allows preserving of high interest pixels through a protected region, attention redirection through color-modification, co......Atomic Stretch is a plugin for your preferred Adobe video editing tool, allowing real-time smooth and optimally bounded retarget-ting from and to any aspect ratio. The plugin allows preserving of high interest pixels through a protected region, attention redirection through color......-modification, countering barrelling effects through vertical stretching, and tracking of targets of interest....

  15. To stretch or not to stretch: the role of stretching in injury prevention and performance. (United States)

    McHugh, M P; Cosgrave, C H


    Stretching is commonly practiced before sports participation; however, effects on subsequent performance and injury prevention are not well understood. There is an abundance of literature demonstrating that a single bout of stretching acutely impairs muscle strength, with a lesser effect on power. The extent to which these effects are apparent when stretching is combined with other aspects of a pre-participation warm-up, such as practice drills and low intensity dynamic exercises, is not known. With respect to the effect of pre-participation stretching on injury prevention a limited number of studies of varying quality have shown mixed results. A general consensus is that stretching in addition to warm-up does not affect the incidence of overuse injuries. There is evidence that pre-participation stretching reduces the incidence of muscle strains but there is clearly a need for further work. Future prospective randomized studies should use stretching interventions that are effective at decreasing passive resistance to stretch and assess effects on subsequent injury incidence in sports with a high prevalence of muscle strains.

  16. Stretch-minimising stream surfaces

    KAUST Repository

    Barton, Michael


    We study the problem of finding stretch-minimising stream surfaces in a divergence-free vector field. These surfaces are generated by motions of seed curves that propagate through the field in a stretch minimising manner, i.e., they move without stretching or shrinking, preserving the length of their arbitrary arc. In general fields, such curves may not exist. How-ever, the divergence-free constraint gives rise to these \\'stretch-free\\' curves that are locally arc-length preserving when infinitesimally propagated. Several families of stretch-free curves are identified and used as initial guesses for stream surface generation. These surfaces are subsequently globally optimised to obtain the best stretch-minimising stream surfaces in a given divergence-free vector field. Our algorithm was tested on benchmark datasets, proving its applicability to incompressible fluid flow simulations, where our stretch-minimising stream surfaces realistically reflect the flow of a flexible univariate object. © 2015 Elsevier Inc. All rights reserved.

  17. Acute Muscle Stretching and Shoulder Position Sense


    Björklund, Martin; Djupsjöbacka, Mats; Crenshaw, Albert G.


    Context: Stretching is common among athletes as a potential method for injury prevention. Stretching-induced changes in the muscle spindle properties are a suggested mechanism, which may imply reduced proprioception after stretching; however, little is known of this association.

  18. Realization of Tapered Waveguide by Stretching the Rod Waveguide

    Institute of Scientific and Technical Information of China (English)

    XIA Ke-yu; YU Rong-jin; MENG Hua-mao


    By stretching the rod waveguide with different velocities in opposite directions,the tapered waveguide can be fabricated.In condition of taking no account of volume expansion caused by heating and under the assumptions of volume conservation,the rod waveguide can be stretched freely in the heated region without being stretched outside of the heated region. A model,which shows the relation of the transition shape and the two factors,that is the ratio of two velocity and the heated region length,is presented for the shape of the taper transition through mathematic deduction.Based on this model,a desired tapered waveguide can be fabricated.The tapered waveguide are widely used for fabricating tapered fiber couplers and sensors.In addition,the conclusion can be used for fabricating fused fiber coupler.

  19. Phase transitions and Heisenberg limited metrology in an Ising chain interacting with a single-mode cavity field

    DEFF Research Database (Denmark)

    Gammelmark, Søren; Mølmer, Klaus


    the Ising phase transition. Physical systems with first-order phase transitions are natural candidates for metrology and calibration purposes, and we apply filter theory to show that the sensitivity of the physical system to temperature and external fields reaches the 1/N Heisenberg limit....

  20. Soleus stretch reflex during cycling

    DEFF Research Database (Denmark)

    Grey, Michael James; Pierce, C. W.; Milner, T. E.


    The modulation and strength of the human soleus short latency stretch reflex was investigated by mechanically perturbing the ankle during an unconstrained pedaling task. Eight subjects pedaled at 60 rpm against a preload of 10 Nm. A torque pulse was applied to the crank at various positions during...... the crank cycle, producing ankle dorsiflexion perturbations of similar trajectory. The stretch reflex was greatest during the power phase of the crank cycle and was decreased to the level of background EMG during recovery. Matched perturbations were induced under static conditions at the same crank angle...... and background soleus EMG as recorded during the power phase of active pedaling. The magnitude of the stretch reflex was not statistically different from that during the static condition throughout the power phase of the movement. The results of this study indicate that the stretch reflex is not depressed during...

  1. Self-doping processes between planes and chains in the metal-to-superconductor transition of YBa2Cu3O6.9. (United States)

    Magnuson, M; Schmitt, T; Strocov, V N; Schlappa, J; Kalabukhov, A S; Duda, L-C


    The interplay between the quasi 1-dimensional CuO-chains and the 2-dimensional CuO2 planes of YBa(2)Cu(3)O(6+x) (YBCO) has been in focus for a long time. Although the CuO-chains are known to be important as charge reservoirs that enable superconductivity for a range of oxygen doping levels in YBCO, the understanding of the dynamics of its temperature-driven metal-superconductor transition (MST) remains a challenge. We present a combined study using x-ray absorption spectroscopy and resonant inelastic x-ray scattering (RIXS) revealing how a reconstruction of the apical O(4)-derived interplanar orbitals during the MST of optimally doped YBCO leads to substantial hole-transfer from the chains into the planes, i.e. self-doping. Our ionic model calculations show that localized divalent charge-transfer configurations are expected to be abundant in the chains of YBCO. While these indeed appear in the RIXS spectra from YBCO in the normal, metallic, state, they are largely suppressed in the superconducting state and, instead, signatures of Cu trivalent charge-transfer configurations in the planes become enhanced. In the quest for understanding the fundamental mechanism for high-Tc-superconductivity (HTSC) in perovskite cuprate materials, the observation of such an interplanar self-doping process in YBCO opens a unique novel channel for studying the dynamics of HTSC.

  2. Conformation of ceramide 6 molecules and chain-flip transitions in the lipid matrix of the outermost layer of mammalian skin, the stratum corneum (United States)

    Kiselev, M. A.


    Neutron diffraction from oriented multilamellar model stratum corneum (SC) membranes provides information on the internal nanostructure and hydration of the lipid bilayer. The main distinguishing feature of model SC membranes based on ceramide 6 is the extremely small intermembrane space (1 Å). The role of the fully extended (FE) conformation of ceramide 6 molecules in the organization of the nanostructure of the lipid matrix is discussed. The FE conformation gives rise to extremely strong intermembrane attractions (armature reinforcement), which tighten the adjacent bilayers to form steric contacts. Chain-flip transitions in the conformation of ceramide molecules account for structural alterations in native and model SC membranes upon their hydration.

  3. The NQR observation of spin-Peierls transition in an antiferromagnetic MX-chain complex [NiBr(chxn)2]Br2. (United States)

    Takaishi, Shinya; Tobu, Yasuhiro; Kitagawa, Hiroshi; Goto, Atsushi; Shimizu, Tadashi; Okubo, Takashi; Mitani, Tadaoki; Ikeda, Ryuichi


    81Br Nuclear quadrupole resonance (NQR) measurement was performed in an S = 1/2 one-dimensional Heisenberg antiferromagnetic metal complex [NiBr(chxn)2]Br2 (chxn: 1R,2R-diaminocyclohexane), having a halogen-bridged MX chain structure -Br-Ni3+-Br-Ni3+-Br-. Two 81Br NQR signals were observed below 40 K, while a single signal was observed above 130 K, showing the presence of two nonequivalent bridging Br sites below 40 K. This NQR result together with previously reported magnetic susceptibility and X-ray results indicate the occurrence of a transition into a spin-Peierls state between 40 and 130 K. This communication reports the first spin-Peierls transition in metal complexes in which pure d electrons contribute to the magnetism. In addition, we demonstrated a new experimental method for studying a spin-Peierls system.

  4. Fatty acid profile and composition of milk protein fraction in dairy cows fed long-chain unsaturated fatty acids during the transition period

    Directory of Open Access Journals (Sweden)

    Francisco Palma Rennó


    Full Text Available The objective of this study was to evaluate the utilization of different sources of unsaturated long-chain fatty acids in diets for dairy cows during the transition period and early lactation on the milk fatty acid profile and composition of the protein fraction. Thirty-six Holstein cows were divided into three groups, fed the following diets: control (C; soybean oil (SO; and calcium salts of long-chain unsaturated fatty acids (CS. The milk samples utilized for analysis were obtained weekly from parturition to twelve weeks of lactation; each one of the samples originated from two daily milkings. Milk composition and total nitrogen, non-protein nitrogen and non-casein nitrogen levels were analyzed. The cows receiving the diet with calcium salts had lower concentrations of non-protein nitrogen (%CP in milk compared with the animals fed the diet with soybean oil. There was a decrease in concentration of medium-chain fatty acids C12-C16, and a concomitant increase in concentrations of long-chain fatty acids >C18 in milk fat for the animals fed the diets CS and SO when compared with diet C. Soybean oil and CS diets increased milk-fat concentrations of the acids C18: 1 trans-11, C18: 2 cis-9, trans-11 and C18: 2 trans-10 cis-12 in relation to diet C. The utilization of sources of long-chain fatty acids in the diet of dairy cows increases the biological value of milk in early lactation due to higher concentrations of specific fatty acids such as CLA C18: 2cis-9, trans-11.

  5. Failure During Sheared Edge Stretching (United States)

    Levy, B. S.; van Tyne, C. J.


    Failure during sheared edge stretching of sheet steels is a serious concern, especially in advanced high-strength steel (AHSS) grades. The shearing process produces a shear face and a zone of deformation behind the shear face, which is the shear-affected zone (SAZ). A failure during sheared edge stretching depends on prior deformation in the sheet, the shearing process, and the subsequent strain path in the SAZ during stretching. Data from laboratory hole expansion tests and hole extrusion tests for multiple lots of fourteen grades of steel were analyzed. The forming limit curve (FLC), regression equations, measurement uncertainty calculations, and difference calculations were used in the analyses. From these analyses, an assessment of the primary factors that contribute to the fracture during sheared edge stretching was made. It was found that the forming limit strain with consideration of strain path in the SAZ is a major factor that contributes to the failure of a sheared edge during stretching. Although metallurgical factors are important, they appear to play a somewhat lesser role.

  6. Elastic Behavior of Polymer Chains

    Institute of Scientific and Technical Information of China (English)

    Teng Lu; Tao Chen; Hao-jun Liang


    The elastic behavior of the polymer chain was investigated in a three-dimensional off-lattice model. We sample more than 109 conformations of each kind of polymer chain by using a Monte Carlo algorithm, then analyze them with the non-Gaussian theory of rubberlike elasticity, and end with a statistical study. Through observing the effect of the chain flexibility and the stretching ratio on the mean-square end-to-end distance,the average energy, the average Helmholtz free energy, the elastic force, the contribution of energy to the elastic force, and the entropy contribution to elastic force of the polymer chain, we find that a rigid polymer chain is much easier to stretch than a flexible polymer chain. Also, a rigid polymer chain will become difficult to stretch only at a quite high stretching ratio because of the effect of the entropy contribution.These results of our simulation calculation may explain some of the macroscopic phenomena of polymer and biomacromolecular elasticity.

  7. Dynamics and supramolecular organization of the 1D spin transition polymeric chain compound [Fe(NH2trz)3](NO3)2. Muon spin relaxation. (United States)

    Garcia, Yann; Campbell, Stewart J; Lord, James S; Boland, Yves; Ksenofontov, Vadim; Gütlich, Philipp


    The thermal spin transition that occurs in the polymeric chain compound [Fe(NH(2)trz)3](NO3)2 above room temperature has been investigated by zero-field muon spin relaxation (microSR) over the temperature range approximately 8-402 K. The depolarization curves are best described by a Lorentzian and a Gaussian line that represent fast and slow components, respectively. The spin transition is associated with a hysteresis loop of width DeltaT = 34 K (T1/2 upward arrow = 346 K and T1/2 downward arrow = 312 K) that has been delineated by the temperature variation of the initial asymmetry parameter, in good agreement with previously published magnetic measurements. Zero-field and applied field (20-2000 Oe) microSR measurements show the presence of diamagnetic muon species and paramagnetic muonium radical species (A = 753 +/- 77 MHz) over the entire temperature range. Fast dynamics have been revealed in the high-spin state of [Fe(NH(2)trz)3](NO3)2 with the presence of a Gaussian relaxation mode that is mostly due to the dipolar interaction with static nuclear moments. This situation, where the muonium radicals are totally decoupled and not able to sense paramagnetic fluctuations, implies that the high-spin dynamics fall outside the muon time scale. Insights to the origin of the cooperative effects associated with the spin transition of [Fe(NH(2)trz)3](NO3)2 through muon implantation are presented.

  8. Effects of chronic Akt/mTOR inhibition by rapamycin on mechanical overload-induced hypertrophy and myosin heavy chain transition in masseter muscle. (United States)

    Umeki, Daisuke; Ohnuki, Yoshiki; Mototani, Yasumasa; Shiozawa, Kouichi; Fujita, Takayuki; Nakamura, Yoshiki; Saeki, Yasutake; Okumura, Satoshi


    To examine the effects of the Akt/mammalian target of rapamycin (mTOR) pathway on masseter muscle hypertrophy and myosin heavy chain (MHC) transition in response to mechanical overload, we analyzed the effects of bite-opening (BO) on the hypertrophy and MHC composition of masseter muscle of BO-rats treated or not treated with rapamycin (RAPA), a selective mTOR inhibitor. The masseter muscle weight in BO-rats was significantly greater than that in controls, and this increase was attenuated by RAPA treatment. Expression of slow-twitch MHC isoforms was significantly increased in BO-rats with/without RAPA treatment, compared with controls, but the magnitude of the increase was much smaller in RAPA-treated BO-rats. Phosphorylation of p44/42 MAPK (ERK1/2), which preserves fast-twitch MHC isoforms in skeletal muscle, was significantly decreased in BO-rats, but the decrease was abrogated by RAPA treatment. Calcineurin signaling is known to be important for masseter muscle hypertrophy and fast-to-slow MHC isoform transition, but expression of known calcineurin activity modulators was unaffected by RAPA treatment. Taken together, these results indicate that the Akt/mTOR pathway is involved in both development of masseter muscle hypertrophy and fast-to-slow MHC isoform transition in response to mechanical overload with inhibition of the ERK1/2 pathway and operates independently of the calcineurin pathway.

  9. Should Athletes Stretch before Exercise?

    Institute of Scientific and Technical Information of China (English)

    KarlB.Fields,MD; CraigM.Burnworth,MD; Martha Delaney·MA


    @@ KEY POINTS Traditional stretching routines performed during warm-up procedures before exercise can increase flexibility for a short time, but there is little scientific evidence that such routines can improve exercise performance, reduce delayed-onset muscular soreness, or prevent injuries.

  10. Iterated Stretching of Viscoelastic Jets (United States)

    Chang, Hsueh-Chia; Demekhin, Evgeny A.; Kalaidin, Evgeny


    We examine, with asymptotic analysis and numerical simulation, the iterated stretching dynamics of FENE and Oldroyd-B jets of initial radius r(sub 0), shear viscosity nu, Weissenberg number We, retardation number S, and capillary number Ca. The usual Rayleigh instability stretches the local uniaxial extensional flow region near a minimum in jet radius into a primary filament of radius [Ca(1 - S)/ We](sup 1/2)r(sub 0) between two beads. The strain-rate within the filament remains constant while its radius (elastic stress) decreases (increases) exponentially in time with a long elastic relaxation time 3We(r(sup 2, sub 0)/nu). Instabilities convected from the bead relieve the tension at the necks during this slow elastic drainage and trigger a filament recoil. Secondary filaments then form at the necks from the resulting stretching. This iterated stretching is predicted to occur successively to generate high-generation filaments of radius r(sub n), (r(sub n)/r(sub 0)) = square root of 2[r(sub n-1)/r(sub 0)](sup 3/2) until finite-extensibility effects set in.

  11. A Purposeful Dynamic Stretching Routine (United States)

    Leon, Craig; Oh, Hyun-Ju; Rana, Sharon


    Dynamic stretching, which involves moving parts of the body and gradually increases range of motion, speed of movement, or both through controlled, sport-specific movements, has become the popular choice of pre-exercise warm-up. This type of warm-up has evolved to encompass several variations, but at its core is the principle theme that preparing…

  12. Transient filament stretching rheometer II

    DEFF Research Database (Denmark)

    Kolte, Mette Irene; Rasmussen, Henrik K.; Hassager, Ole


    The Lagrangian sspecification is used to simulate the transient stretching filament rheometer. Simulations are performed for dilute PIB-solutions modeled as a four mode Oldroyd-B fluid and a semidilute PIB-solution modeled as a non-linear single integral equation. The simulations are compared...

  13. Design of Warped Stretch Transform (United States)

    Mahjoubfar, Ata; Chen, Claire Lifan; Jalali, Bahram


    Time stretch dispersive Fourier transform enables real-time spectroscopy at the repetition rate of million scans per second. High-speed real-time instruments ranging from analog-to-digital converters to cameras and single-shot rare-phenomena capture equipment with record performance have been empowered by it. Its warped stretch variant, realized with nonlinear group delay dispersion, offers variable-rate spectral domain sampling, as well as the ability to engineer the time-bandwidth product of the signal’s envelope to match that of the data acquisition systems. To be able to reconstruct the signal with low loss, the spectrotemporal distribution of the signal spectrum needs to be sparse. Here, for the first time, we show how to design the kernel of the transform and specifically, the nonlinear group delay profile dictated by the signal sparsity. Such a kernel leads to smart stretching with nonuniform spectral resolution, having direct utility in improvement of data acquisition rate, real-time data compression, and enhancement of ultrafast data capture accuracy. We also discuss the application of warped stretch transform in spectrotemporal analysis of continuous-time signals.

  14. A multiple length scale description of the mechanism of elastomer stretching

    DEFF Research Database (Denmark)

    Neuefeind, J.; Skov, Anne Ladegaard; Daniels, J. E.


    Conventionally, the stretching of rubber is modeled exclusively by rotations of segments of the embedded polymer chains; i.e. changes in entropy. However models have not been tested on all relevant length scales due to a lack of appropriate probes. Here we present a universal X-ray based method...... within the individual monomers, but among the contributions is also an elastic strain, acting between chains, which is 3-4 orders of magnitude smaller than the macroscopic strain, and of the opposite sign, i.e. extension of polymer chains in the direction perpendicular to the stretch. This may be due...

  15. Analysis of a filament stretching rheometer

    DEFF Research Database (Denmark)

    Kolte, Mette Irene; Rasmussen, Henrik K.; Hassager, Ole


    A finite element analysis of the stretching filament rheometer of Tirtaadmadja and Sridhar (1993) is presenetd. Simulations of the stretching of a filament of the polymet test solution, fluid A, between two plates are shown.......A finite element analysis of the stretching filament rheometer of Tirtaadmadja and Sridhar (1993) is presenetd. Simulations of the stretching of a filament of the polymet test solution, fluid A, between two plates are shown....

  16. Does Acute Static Stretching Reduce Muscle Power?


    Francis M. Kozub; Sameer A. Gohir; Alan Donnelly


    Context: Stretching is commonly used as a technique for injury prevention in the training and clinical setting. Recently, stretching in the warm-up has been shown to decrease several muscular performance variables, but the dose-response of this effect is unknown and moreover these stretching bouts are not representative of athletes during warm up procedures, as they are usually time consuming. Our findings may improve the understanding of the neuromuscular responses to stretching and help spo...

  17. Polymer network stretching during electrospinning (United States)

    Greenfeld, Israel; Arinstein, Arkadii; Fezzaa, Kamel; Rafailovich, Miriam; Zussman, Eyal


    Fast X-ray phase contrast imaging is used to observe the flow of a semi-dilute polyethylene oxide solution during electrospinning. Micron-size glass particles mixed in the polymer solution allow viewing of the jet flow field, and reveal a high-gradient flow that has both longitudinal and radial components that grow rapidly along the jet. The resulting hydrodynamic forces cause substantial longitudinal stretching and transversal contraction of the polymer network within the jet, as confirmed by random walk simulation and theoretical modeling. The polymer network therefore concentrates towards the jet center, and its conformation may transform from a free state to a fully-stretched state within a short distance from the jet start. We acknowledge the financial support of the United States - Israel Bi-National Science Foundation (grant 2006061).

  18. Reexamination of Nuclear Shape Transitions in Gadolinium and Dysprosium Isotopes Chains by Using the Geometric Collective Model

    Directory of Open Access Journals (Sweden)

    Khalaf A. M.


    Full Text Available The critical points of potential energy surface (PES’s of the limits of nuclear struc- ture harmonic oscillator, axially symmetric rotor and deformed -soft and discussed in framework of the general geometric collective model (GCM. Also the shape phase transitions linking the three dynamical symmetries are studied taking into account only three parameters in the PES’s. The model is tested for the case of 238 92 U , which shows a more prolate behavior. The optimized model parameters have been adjusted by fit- ting procedure using a simulated search program in order to reproduce the experimental excitation energies in the ground state band up to 6 + and the two neutron separation energies.

  19. Dansyl-labeled anionic amphiphile with a hexadecanoic carbon chain: synthesis and detection for shape transitions in organized molecular assemblies. (United States)

    Gao, Lining; Xia, Huiyun; Wang, Xiaoman; Li, Li; Chen, Huaxin


    The probing properties of a new fluorophore-labeled anionic surfactant, sodium 16-(N-dansyl)aminocetylate (16-DAN-ACA) were investigated systematically in molecular assemblies, especially in the transitions between micelles and vesicles. 16-DAN-ACA can efficiently differentiate the two different aggregate types in mixed cationic and anionic surfactant systems. The fluorescence anisotropy of 16-DAN-ACA was found to be sensitive for directly detecting the micellar growth in micelles containing oppositely charged surfactants; both cationic cetyltrimethylammonium bromide (CTAB) systems and anionic sodium dodecyl sulfate (SDS) systems were studied. The results indicated that the 16-DAN-ACA is a good fluorescent probe for differentiating the different aggregates, and even more can be used to detect the micellar growth.

  20. Modified "DMC" technique for stretching DNA molecules

    Institute of Scientific and Technical Information of China (English)


    A modified "dynamic molecular combing"(DMC)technique used for stretching double-strandedDNA is reported. DNA molecules were stretched on the silanized mica surface by thistechnique, its speed being precisely controlled with a computer. This approachcombinedthe precise DNA stretching method with high resolution AFM imaging at nanometer scale,thusmaking it useful for DNA alignment manipulation and subsequent gene research.

  1. Quantum phase transitions and string orders in the spin-1/2 Heisenberg-Ising alternating chain with Dzyaloshinskii-Moriya interaction. (United States)

    Liu, Guang-Hua; You, Wen-Long; Li, Wei; Su, Gang


    Quantum phase transitions (QPTs) and the ground-state phase diagram of the spin-1/2 Heisenberg-Ising alternating chain (HIAC) with uniform Dzyaloshinskii-Moriya (DM) interaction are investigated by a matrix-product-state (MPS) method. By calculating the odd- and even-string order parameters, we recognize two kinds of Haldane phases, i.e. the odd- and even-Haldane phases. Furthermore, doubly degenerate entanglement spectra on odd and even bonds are observed in odd- and even-Haldane phases, respectively. A rich phase diagram including four different phases, i.e. an antiferromagnetic (AF), AF stripe, odd- and even-Haldane phases, is obtained. These phases are found to be separated by continuous QPTs: the topological QPT between the odd- and even-Haldane phases is verified to be continuous and corresponds to conformal field theory with central charge c = 1; while the rest of the phase transitions in the phase diagram are found to be c = 1/2. We also revisit, with our MPS method, the exactly solvable case of HIAC model with DM interactions only on odd bonds and find that the even-Haldane phase disappears, but the other three phases, i.e. the AF, AF stripe and odd-Haldane phases, still remain in the phase diagram. We exhibit the evolution of the even-Haldane phase by tuning the DM interactions on the even bonds gradually.

  2. Industrial Upgrading in the Apparel Value Chain and the Role of Designer in the Transition: comparative analysis of Sri Lanka and Hong Kong

    Directory of Open Access Journals (Sweden)

    Sumith Gopura


    Full Text Available The apparel industry is a major export industry in Sri Lanka that depends upon labour intensive manufacturing. The Sri Lankan apparel industry is transitioning from Cut, Make, Trims (CMT assembly and Original Equipment Manufacturing (OEM to Original Design Manufacturing (ODM and Original Brand Manufacturing (OBM, experiencing the economic benefits of apparel product export. The transition relies on having expert professionals who can provide creative, commercial, technical, and leadership skills in the process. In order to identify the creative roles and responsibilities that can contribute to the industrial upgrading process in Sri Lanka, this paper first provides an analysis of the global apparel value chain and the journeys of the countries with newly industrialized economies (NIEs in the region. Second, a comparison of Hong Kong and Sri Lankan apparel industries contextualises the development of fashion design within each nation’s industry as a competitive advantage. In each country we examine three factors that demonstrate growth in fashion design: development of fashion design education; development of exportable own brands; and the establishment of local showcases to a global audience. The examples of both Hong Kong and Sri Lanka demonstrate the ways in which creative roles may act as a bridge between production and marketing networks, buyers and producers in maintaining and building industry value-adding for highly sophisticated and competitive fashion production systems. Although the Sri Lankan apparel industry has not progressed as far as Hong Kong in this arena, evidence suggests the industry is actively growing design capabilities

  3. Local stretch zeroing NMO correction (United States)

    Kazemi, N.; Siahkoohi, H. R.


    In this paper we present a new method of normal move-out (NMO) correction called local stretch zeroing (LSZ) method that avoids NMO stretch. The method eliminates the theoretical curves that generate interpolated data samples responsible for NMO stretch. Pre-correction time sampling interval is preserved by reassigning and zero padding of true data samples. The optimum mute zone selection feature of the LSZ method eliminates all interfering reflection events at far offsets. The resulted stacked section from the LSZ method contains generally higher frequency components than a normal stack, and preserves most of the shallow reflectors. The LSZ method requires that zero-offset width of the time gate, i.e. zero-offset time difference between two adjacent reflections, be larger than the dominant period. The major shortcoming of the method occurs when CMP data are over- or under-NMO corrected. Both synthetic and real world examples show the efficiency of the LSZ method over the conventional NMO (CNMO) correction. The method loses its superiority when CMP data are over- or under-NMO corrected.

  4. The Considere condition and rapid stretching of linear and branched polymer melts

    DEFF Research Database (Denmark)

    McKinley, Gareth H; Hassager, Ole


    to larger Hencky strains as the number of branches is increased. Numerical computations at finite Deborah numbers also show that there is an optimal range of deformation rates over which homogeneous extensions can be maintained to large strain. We also consider other rapid homogeneous stretching...... deformations, such as biaxial and planar stretching, and show that the degree of stabilization afforded by inclusion of material with long-chain branching is a sensitive function of the imposed mode of deformation....

  5. Linear Viscoelasticity, Reptation, Chain Stretching and Constraint Release

    DEFF Research Database (Denmark)

    Neergaard, Jesper; Schieber, Jay D.; Venerus, David C.


    A recently proposed self-consistent reptation model - alreadysuccessful at describing highly nonlinear shearing flows of manytypes using no adjustable parameters - is used here to interpretthe linear viscoelasticity of the same entangled polystyrenesolution. Using standard techniques, a relaxatio...

  6. Effects of poly (ethylene glycol) chains conformational transition on the properties of mixed DMPC/DMPE-PEG thin liquid films and monolayers. (United States)

    Georgiev, Georgi As; Sarker, Dipak K; Al-Hanbali, Othman; Georgiev, Georgi D; Lalchev, Zdravko


    Foam thin liquid films (TLF) and monolayers at the air-water interface formed by DMPC mixed with DMPE-bonded poly (ethylene glycol)s (DMPE-PEG(550), DMPE-PEG(2000) and DMPE-PEG(5000)) were obtained. The influence of both (i) PEG chain size (evaluated in terms of Mw) and mushroom-to-brush conformational transition and (ii) of the liposome/micelle ratio in the film-forming dispersions, on the interfacial properties of mixed DMPC/DMPE-PEG films was compared. Foam film studies demonstrated that DMPE-PEG addition to foam TLFs caused (i) delayed kinetics of film thinning and black spot expansion and (ii) film stabilization. At the mushroom-to-brush transition, due to steric repulsion increased DMPE-PEG films thickness reached 25 nm while pure DMPC films were only 8 nm thick Newton black films. It was possible to differentiate DMPE-PEG(2000/5000) from DMPE-PEG(550) by the ability to change foam TLF formation mechanism, which could be of great importance for "stealth" liposome design. Monolayer studies showed improved formation kinetics and equilibrium surface tension decrease for DMPE-PEG monolayers compared with DMPC pure films. SEM observations revealed "smoothing" and "sealing" of the defects in the solid-supported layer surface by DMPE-PEGs adsorption, which could explain DMPE-PEGs ability to stabilize TLFs and to decrease monolayer surface tension. All effects in monolayers, foam TLFs and solid-supported layers increased with the increase of PEG Mw and DMPE-PEG concentration. However, at the critical DMPE-PEG concentration (where mushroom-to-brush conformational transition occurred) maximal magnitude of the effects was reached, which only slightly changed at further DMPE-PEG content and micelle/liposome ratio increase.

  7. The amyloid stretch hypothesis: Recruiting proteins toward the dark side (United States)

    Esteras-Chopo, Alexandra; Serrano, Luis; de la Paz, Manuela López


    A detailed understanding of the molecular events underlying the conversion and self-association of normally soluble proteins into amyloid fibrils is fundamental to the identification of therapeutic strategies to prevent or cure amyloid-related disorders. Recent investigations indicate that amyloid fibril formation is not just a general property of the polypeptide backbone depending on external factors, but that it is strongly modulated by amino acid side chains. Here, we propose and address the validation of the premise that the amyloidogenicity of a protein is indeed localized in short protein stretches (amyloid stretch hypothesis). We demonstrate that the conversion of a soluble nonamyloidogenic protein into an amyloidogenic prone molecule can be triggered by a nondestabilizing six-residue amyloidogenic insertion in a particular structural environment. Interestingly enough, although the inserted amyloid sequences clearly cause the process, the protease-resistant core of the fiber also includes short adjacent sequences from the otherwise soluble globular domain. Thus, short amyloid stretches accessible for intermolecular interactions trigger the self-assembly reaction and pull the rest of the protein into the fibrillar aggregate. The reliable identification of such amyloidogenic stretches in proteins opens the possibility of using them as targets for the inhibition of the amyloid fibril formation process. PMID:16263932

  8. Effects of static stretching for 30 seconds and dynamic stretching on leg extension power. (United States)

    Yamaguchi, Taichi; Ishii, Kojiro


    The purposes of this study were to clarify the effects of static stretching for 30 seconds and dynamic stretching on leg extension power. Eleven healthy male students took part in this study. Each subject performed static stretching and dynamic stretching on the 5 muscle groups in the lower limbs and nonstretching on separate days. Leg extension power was measured before and after the static stretching, dynamic stretching, and nonstretching. No significant difference was found between leg extension power after static stretching (1788.5 +/- 85.7 W) and that after nonstretching (1784.8 +/- 108.4 W). On the other hand, leg extension power after dynamic stretching (2022.3 +/- 121.0 W) was significantly (p < 0.01) greater than that after nonstretching. These results suggest that static stretching for 30 seconds neither improves nor reduces muscular performance and that dynamic stretching enhances muscular performance.

  9. The stretch zone of automotive steel sheets

    Indian Academy of Sciences (India)

    Ľ Ambriško; L Pešek


    The paper deals with an experimental determination of the stretch zone dimensions in the notch tip in thin steel sheets. The stretch zone dimensions depend on steel grade, on the rolling direction as well as on the loading rate. Stretch zones were observed and measured on three steel grades. Fracture area and stretch zones were analysed by SEM. Stable crack growth was monitored by videoextensometry techniques on CT (Compact Tension) specimens. Specimens were loaded under two loading rates by eccentric tension, whereby the deformation in the notch surrounding area was recorded using a non-contact measurement–videoextensometry technique. Linear relation between the stretch zone dimensions was determined.

  10. Fuzzy Markov chains: uncertain probabilities



    We consider finite Markov chains where there are uncertainties in some of the transition probabilities. These uncertainties are modeled by fuzzy numbers. Using a restricted fuzzy matrix multiplication we investigate the properties of regular, and absorbing, fuzzy Markov chains and show that the basic properties of these classical Markov chains generalize to fuzzy Markov chains.

  11. Butterflies on the Stretched Horizon

    CERN Document Server

    Susskind, Leonard


    In this paper I return to the question of what kind of perturbations on Alice's side of an Einstein-Rosen bridge can send messages to Bob as he enters the horizon at the other end. By definition "easy" operators do not activate messages and "hard" operators do, but there are no clear criteria to identify the difference between easy and hard. In this paper I argue that the difference is related to the time evolution of a certain measure of computational complexity, associated with the stretched horizon of Alice's black hole. The arguments suggest that the AMPSS commutator argument is more connected with butterflies than with firewalls.

  12. Bending and stretching of plates

    CERN Document Server

    Mansfield, E H; Hemp, W S


    The Bending and Stretching of Plates deals with elastic plate theory, particularly on small- and large-deflexion theory. Small-deflexion theory concerns derivation of basic equations, rectangular plates, plates of various shapes, plates whose boundaries are amenable to conformal transformation, plates with variable rigidity, and approximate methods. Large-deflexion theory includes general equations and some exact solutions, approximate methods in large-deflexion theory, asymptotic large-deflexion theories for very thin plates. Asymptotic theories covers membrane theory, tension field theory, a

  13. Cavity approach for modeling and fitting polymer stretching

    CERN Document Server

    Massucci, Francesco Alessandro; Vicente, Conrad J Pérez


    The mechanical properties of molecules are today captured by single molecule manipulation experiments, so that polymer features are tested at a nanometric scale. Yet devising mathematical models to get further insight beyond the commonly studied force--elongation relation is typically hard. Here we draw from techniques developed in the context of disordered systems to solve models for single and double--stranded DNA stretching in the limit of a long polymeric chain. Since we directly derive the marginals for the molecule local orientation, our approach allows us to readily calculate the experimental elongation as well as other observables at wish. As an example, we evaluate the correlation length as a function of the stretching force. Furthermore, we are able to fit successfully our solution to real experimental data. Although the model is admittedly phenomenological, our findings are very sound. For single--stranded DNA our solution yields the correct (monomer) scale and, yet more importantly, the right pers...

  14. Multi-dimensional transition-metal coordination polymers of 4,4'-bipyridine-N,N'-dioxide: 1D chains and 2D sheets. (United States)

    Jia, Junhua; Blake, Alexander J; Champness, Neil R; Hubberstey, Peter; Wilson, Claire; Schröder, Martin


    Reaction of 4,4'-bipyridine -N, N' -dioxide (L) with a variety of transition-metal salts in MeOH affords a range of coordination polymer products. For the complexes [FeCl 3(mu-L)] infinity, 1, and ([Cu(L) 2(OHMe) 2(mu-L)].2PF 6. n(solv)) infinity, 2, 1D chain structures are observed, whereas ([Mn(mu-L) 3].2ClO 4) infinity, 3, and ([Cu(mu-L) 3].2BF 4) infinity, 4, both show 2D sheet architectures incorporating an unusual 3 (6)- hxl topology. The more common 4 (4)- sql topology is observed in [Cd(ONO 2) 2(mu-L) 2] infinity, 5, ([Cu(OHMe) 2(mu-L) 2].2ZrF 5) infinity, 6, ([Cu(L) 2(mu-L) 2].2EF 6) infinity ( 7 E = P; 8 E = Sb), and ([Et 4N][Cu(OHMe) 0.5(mu-L) 2(mu-FSiF 4F) 0.5].2SbF 6. n(solv)) infinity, 9. In 6, the [ZrF 5] (-) anion, formed in situ from [ZrF 6] (2-), forms 1D anionic chains ([ZrF 5] (-)) infinity of vertex-linked octahedra, and these chains thread through a pair of inclined polycatenated ([Cu(OHMe) 2(mu-L) 2] (2+)) infinity 4 (4)- sql grids to give a rare example of a triply intertwined coordination polymer. 9 also shows a 3D matrix structure with 4 (4)- sql sheets of stoichiometry ([Cu(L) 2] (2+)) infinity coordinatively linked by bridging [SiF 6] (2-) anions to give a structure of 5-c 4 (4).6 (6)- sqp topology. The mononuclear [Cu(L) 6].2BF 4 ( 10) and [Cd(L) 6].2NO 3 ( 11) and binuclear complexes [(Cu(L)(OH 2)) 2(mu-L) 2)].2SiF 6. n(solv), 12, are also reported. The majority of the coordination polymers are free of solvent and are nonporous. Thermal treatment of materials that do contain solvent results in structural disintegration of the complex structures giving no permanent porosity.

  15. Deregulation of mitochondrial functions provoked by long-chain fatty acid accumulating in long-chain 3-hydroxyacyl-CoA dehydrogenase and mitochondrial permeability transition deficiencies in rat heart--mitochondrial permeability transition pore opening as a potential contributing pathomechanism of cardiac alterations in these disorders. (United States)

    Cecatto, Cristiane; Hickmann, Fernanda H; Rodrigues, Marília D N; Amaral, Alexandre U; Wajner, Moacir


    Mitochondrial trifunctional protein and long-chain 3-hydroxyacyl-CoA dehydrogenase deficiencies are fatty acid oxidation disorders biochemically characterized by tissue accumulation of long-chain fatty acids and derivatives, including the monocarboxylic long-chain 3-hydroxy fatty acids (LCHFAs) 3-hydroxytetradecanoic acid (3HTA) and 3-hydroxypalmitic acid (3HPA). Patients commonly present severe cardiomyopathy for which the pathogenesis is still poorly established. We investigated the effects of 3HTA and 3HPA, the major metabolites accumulating in these disorders, on important parameters of mitochondrial homeostasis in Ca(2+) -loaded heart mitochondria. 3HTA and 3HPA significantly decreased mitochondrial membrane potential, the matrix NAD(P)H pool and Ca(2+) retention capacity, and also induced mitochondrial swelling. These fatty acids also provoked a marked decrease of ATP production reflecting severe energy dysfunction. Furthermore, 3HTA-induced mitochondrial alterations were completely prevented by the classical mitochondrial permeability transition (mPT) inhibitors cyclosporin A and ADP, as well as by ruthenium red, a Ca(2+) uptake blocker, indicating that LCHFAs induced Ca(2+)-dependent mPT pore opening. Milder effects only achieved at higher doses of LCHFAs were observed in brain mitochondria, implying a higher vulnerability of heart to these fatty acids. By contrast, 3HTA and docosanoic acids did not change mitochondrial homeostasis, indicating selective effects for monocarboxylic LCHFAs. The present data indicate that the major LCHFAs accumulating in mitochondrial trifunctional protein and long-chain 3-hydroxyacyl-CoA dehydrogenase deficiencies induce mPT pore opening, compromising Ca(2+) homeostasis and oxidative phosphorylation more intensely in the heart. It is proposed that these pathomechanisms may contribute at least in part to the severe cardiac alterations characteristic of patients affected by these diseases.

  16. Cell reorientation under cyclic stretching

    CERN Document Server

    Livne, Ariel; Geiger, Benjamin


    Mechanical cues from the extracellular microenvironment play a central role in regulating the structure, function and fate of living cells. Nevertheless, the precise nature of the mechanisms and processes underlying this crucial cellular mechanosensitivity remains a fundamental open problem. Here we provide a novel framework for addressing cellular sensitivity and response to external forces by experimentally and theoretically studying one of its most striking manifestations -- cell reorientation to a uniform angle in response to cyclic stretching of the underlying substrate. We first show that existing approaches are incompatible with our extensive measurements of cell reorientation. We then propose a fundamentally new theory that shows that dissipative relaxation of the cell's passively-stored, two-dimensional, elastic energy to its minimum actively drives the reorientation process. Our theory is in excellent quantitative agreement with the complete temporal reorientation dynamics of individual cells, measu...

  17. Stretching Folding Instability and Nanoemulsions

    CERN Document Server

    Chan, Chon U


    Here we show a folding-stretching instability in a microfluidic flow focusing device using silicon oil (100cSt) and water. The fluid dynamics video demonstrates an oscillating thread of oil focused by two co-flowing streams of water. We show several high-speed sequences of these oscillations with 30,000 frames/s. Once the thread is decelerated in a slower moving pool downstream an instability sets in and water-in-oil droplets are formed. We reveal the details of the pinch-off with 500,000 frames/s. The pinch-off is so repeatable that complex droplet patterns emerge. Some of droplets are below the resolution limit, thus smaller than 1 micrometer in diameter.

  18. Stretching Impacts Inflammation Resolution in Connective Tissue. (United States)

    Berrueta, Lisbeth; Muskaj, Igla; Olenich, Sara; Butler, Taylor; Badger, Gary J; Colas, Romain A; Spite, Matthew; Serhan, Charles N; Langevin, Helene M


    Acute inflammation is accompanied from its outset by the release of specialized pro-resolving mediators (SPMs), including resolvins, that orchestrate the resolution of local inflammation. We showed earlier that, in rats with subcutaneous inflammation of the back induced by carrageenan, stretching for 10 min twice daily reduced inflammation and improved pain, 2 weeks after carrageenan injection. In this study, we hypothesized that stretching of connective tissue activates local pro-resolving mechanisms within the tissue in the acute phase of inflammation. In rats injected with carrageenan and randomized to stretch versus no stretch for 48 h, stretching reduced inflammatory lesion thickness and neutrophil count, and increased resolvin (RvD1) concentrations within lesions. Furthermore, subcutaneous resolvin injection mimicked the effect of stretching. In ex vivo experiments, stretching of connective tissue reduced the migration of neutrophils and increased tissue RvD1 concentration. These results demonstrate a direct mechanical impact of stretching on inflammation-regulation mechanisms within connective tissue.

  19. Role of cyclic AMP sensor Epac1 in masseter muscle hypertrophy and myosin heavy chain transition induced by β2-adrenoceptor stimulation. (United States)

    Ohnuki, Yoshiki; Umeki, Daisuke; Mototani, Yasumasa; Jin, Huiling; Cai, Wenqian; Shiozawa, Kouichi; Suita, Kenji; Saeki, Yasutake; Fujita, Takayuki; Ishikawa, Yoshihiro; Okumura, Satoshi


    The predominant isoform of β-adrenoceptor (β-AR) in skeletal muscle is β2-AR and that in the cardiac muscle is β1-AR. We have reported that Epac1 (exchange protein directly activated by cAMP 1), a new protein kinase A-independent cAMP sensor, does not affect cardiac hypertrophy in response to pressure overload or chronic isoproterenol (isoprenaline) infusion. However, the role of Epac1 in skeletal muscle hypertrophy remains poorly understood. We thus examined the effect of disruption of Epac1, the major Epac isoform in skeletal muscle, on masseter muscle hypertrophy induced by chronic β2-AR stimulation with clenbuterol (CB) in Epac1-null mice (Epac1KO). The masseter muscle weight/tibial length ratio was similar in wild-type (WT) and Epac1KO at baseline and was significantly increased in WT after CB infusion, but this increase was suppressed in Epac1KO. CB treatment significantly increased the proportion of myosin heavy chain (MHC) IIb at the expense of that of MHC IId/x in both WT and Epac1KO, indicating that Epac1 did not mediate the CB-induced MHC isoform transition towards the faster isoform. The mechanism of suppression of CB-mediated hypertrophy in Epac1KO is considered to involve decreased activation of Akt signalling. In addition, CB-induced histone deacetylase 4 (HDAC4) phosphorylation on serine 246 mediated by calmodulin kinase II (CaMKII), which plays a role in skeletal muscle hypertrophy, was suppressed in Epac1KO. Our findings suggest that Epac1 plays a role in β2-AR-mediated masseter muscle hypertrophy, probably through activation of both Akt signalling and CaMKII/HDAC4 signalling.

  20. The purinergic component of human bladder smooth muscle cells’ proliferation and contraction under physiological stretch

    Energy Technology Data Exchange (ETDEWEB)

    Wazir, Romel; Luo, De-Yi; Tian, Ye; Yue, Xuan; Li, Hong; Wang, Kun-Jie, E-mail:


    Highlights: •Stretch induces proliferation and contraction. •Optimum applied stretch in vitro is 5% and 10% equibiaxial stretching respectively. •Expression of P2X1 and P2X2 is upregulated after application of stretch. •P2X2 is possibly more susceptible to stretch related changes. •Purinoceptors functioning may explain conditions with atropine resistance. -- Abstract: Objective: To investigate whether cyclic stretch induces proliferation and contraction of human smooth muscle cells (HBSMCs), mediated by P2X purinoceptor 1 and 2 and the signal transduction mechanisms of this process. Methods: HBSMCs were seeded on silicone membrane and stretched under varying parameters; (equibiaxial elongation: 2.5%, 5%, 10%, 15%, 20%, 25%), (Frequency: 0.05 Hz, 0.1 Hz, 0.2 Hz, 0.5 Hz, 1 Hz). 5-Bromo-2-deoxyuridine assay was employed for proliferative studies. Contractility of the cells was determined using collagen gel contraction assay. After optimal physiological stretch was established; P2X1 and P2X2 were analyzed by real time polymerase chain reaction and Western Blot. Specificity of purinoceptors was maintained by employing specific inhibitors; (NF023 for P2X1, and A317491for P2X2), in some experiments. Results: Optimum proliferation and contractility were observed at 5% and 10% equibiaxial stretching respectively, applied at a frequency of 0.1 Hz; At 5% stretch, proliferation increased from 0.837 ± 0.026 (control) to 1.462 ± 0.023%, p < 0.05. Mean contraction at 10% stretching increased from 31.7 ± 2.3%, (control) to 78.28 ±1.45%, p < 0.05. Expression of P2X1 and P2X2 was upregulated after application of stretch. Inhibition had effects on proliferation (1.232 ± 0.051, p < 0.05 NF023) and (1.302 ± 0.021, p < 0.05 A314791) while contractility was markedly reduced (68.24 ± 2.31, p < 0.05 NF023) and (73.2 ± 2.87, p < 0.05 A314791). These findings shows that mechanical stretch can promote magnitude-dependent proliferative and contractile modulation of HBSMCs in

  1. A multiple length scale description of the mechanism of elastomer stretching

    DEFF Research Database (Denmark)

    Neuefeind, J.; Skov, Anne Ladegaard; Daniels, J. E.;


    Conventionally, the stretching of rubber is modeled exclusively by rotations of segments of the embedded polymer chains; i.e. changes in entropy. However models have not been tested on all relevant length scales due to a lack of appropriate probes. Here we present a universal X-ray based method...

  2. Does Acute Static Stretching Reduce Muscle Power?

    Directory of Open Access Journals (Sweden)

    Francis M. Kozub


    Full Text Available Context: Stretching is commonly used as a technique for injury prevention in the training and clinical setting. Recently, stretching in the warm-up has been shown to decrease several muscular performance variables, but the dose-response of this effect is unknown and moreover these stretching bouts are not representative of athletes during warm up procedures, as they are usually time consuming. Our findings may improve the understanding of the neuromuscular responses to stretching and help sportsmen, coaches, physiotherapist and clinicians make decisions for integrating stretching as a part of warm up or rehabilitation treatment plan.Purpose: The aim of the present study was to examine whether acute static stretching is responsible for losses in isokinetic peak torque production and if it does, than which time of stretching effect muscle peak torque?Design: Randomized, counterbalanced, within-subjects experimental design.Setting: A university human project laboratory.Methods: Twenty (n=20 light to moderate young exercisers, male and female, from University of Limerick community, with an average age of 22.1±3.6 years, height of 175.6±5 cm, and weight of 73.1±9.9 kg, were randomly selected to take part in the study. Prior to the main study, volunteers attended the lab on two occasions to be familiarized with the knee extension protocol on the Con - trex isokinetic system and with the static stretching protocol. All participants than performed five additional static stretching protocols randomly, in non-consecutive training session. The stretching protocols were 0, 60,120, 180 and 180 with alternative pattern.Results: The results of the statistical analysis (P > 0.05 indicated that peak torque remained unchanged following the static stretching for 0-180 sec at 60 & 180° s−1 angular velocities.Conclusion: The findings suggest that an athletic stretching (shorter duration ranging from 0-180 sec does not produce decreases in peak torque. Athletes

  3. Stretching Probability Explorations with Geoboards (United States)

    Wheeler, Ann; Champion, Joe


    Students are faced with many transitions in their middle school mathematics classes. To build knowledge, skills, and confidence in the key areas of algebra and geometry, students often need to practice using numbers and polygons in a variety of contexts. Teachers also want students to explore ideas from probability and statistics. Teachers know…

  4. Stretching micropatterned cells on a PDMS membrane. (United States)

    Carpi, Nicolas; Piel, Matthieu


    Mechanical forces exerted on cells and/or tissues play a major role in numerous processes. We have developed a device to stretch cells plated on a PolyDiMethylSiloxane (PDMS) membrane, compatible with imaging. This technique is reproducible and versatile. The PDMS membrane can be micropatterned in order to confine cells or tissues to a specific geometry. The first step is to print micropatterns onto the PDMS membrane with a deep UV technique. The PDMS membrane is then mounted on a mechanical stretcher. A chamber is bound on top of the membrane with biocompatible grease to allow gliding during the stretch. The cells are seeded and allowed to spread for several hours on the micropatterns. The sample can be stretched and unstretched multiple times with the use of a micrometric screw. It takes less than a minute to apply the stretch to its full extent (around 30%). The technique presented here does not include a motorized device, which is necessary for applying repeated stretch cycles quickly and/or computer controlled stretching, but this can be implemented. Stretching of cells or tissue can be of interest for questions related to cell forces, cell response to mechanical stress or tissue morphogenesis. This video presentation will show how to avoid typical problems that might arise when doing this type of seemingly simple experiment.

  5. The escape transition of a polymer: A unique case of non-equivalence between statistical ensembles (United States)

    Dimitrov, D. I.; Klushin, L. I.; Skvortsov, A.; Milchev, A.; Binder, K.


    A flexible polymer chain under good solvent conditions, end-grafted on a flat repulsive substrate surface and compressed by a piston of circular cross-section with radius L may undergo the so-called “escape transition” when the height of the piston D above the substrate and the chain length N are in a suitable range. In this transition, the chain conformation changes from a quasi-two-dimensional self-avoiding walk of “blobs” of diameter D to an inhomogeneous “flower” state, consisting of a “stem” (stretched string of blobs extending from the grafting site to the piston border) and a “crown” outside of the confining piston. The theory of this transition is developed using a Landau free-energy approach, based on a suitably defined (global) order parameter and taking also effects due to the finite chain length N into account. The parameters of the theory are determined in terms of known properties of limiting cases (unconfined mushroom, chain confined between infinite parallel walls). Due to the non-existence of a local order parameter density, the transition has very unconventional properties (negative compressibility in equilibrium, non-equivalence between statistical ensembles in the thermodynamic limit, etc.). The reasons for this very unusual behavior are discussed in detail. Using Molecular Dynamics (MD) simulation for a simple bead-spring model, with N in the range 50 ≤ N ≤ 300 , a comprehensive study of both static and dynamic properties of the polymer chain was performed. Even though for the considered rather short chains the escape transition is still strongly rounded, the order parameter distribution does reveal the emerging transition clearly. Time autocorrelation functions of the order parameter and first passage times and their distribution indicate clearly the strong slowing down associated with the chain escape. The theory developed here is in good agreement with all these simulation results.

  6. Response of a single grafted polyethylene chain to simple shear flow: A Brownian dynamics simulation study (United States)

    Haliloglu, Turkan; Bahar, Ivet; Erman, Burak


    The behavior of a single polyethylene chain grafted to an impenetrable surface, under shear flow, is investigated using Brownian dynamics simulations. Both short-range conformational energies and excluded volume effects are included in the model. Simulations are performed in good and poor solvent conditions in order to explore the effect of solvent quality. The shear flow is represented by the superposition of a force profile increasing linearly with the distance from the surface. Distribution of rotational angles, chain dimensions, components of the radius of gyration, segment density distribution, average layer thickness, and average orientation of bond vectors with respect to flow direction are determined and compared with other studies. Above a certain value of the shear rate, a significant increase in chain dimensions is observed for both good and poor solvents, the transition from coiled to stretched state being sharper in poor solvent. In good solvent, chain dimensions along the two perpendicular directions to the flow direction diminish with increasing shear rate. On the other hand, in poor solvent, there is an overall expansion in chain dimensions in all directions at low shear rates, which is subsequently followed by the orientation and alignment of the chain along the direction of flow. The experimentally observed increase in chain dimensions normal to the flow field at low shear rates is evidenced for the first time by simulations.

  7. Stretching and injury prevention: an obscure relationship. (United States)

    Witvrouw, Erik; Mahieu, Nele; Danneels, Lieven; McNair, Peter


    It is generally accepted that increasing the flexibility of a muscle-tendon unit promotes better performances and decreases the number of injuries. Stretching exercises are regularly included in warm-up and cooling-down exercises; however, contradictory findings have been reported in the literature. Several authors have suggested that stretching has a beneficial effect on injury prevention. In contrast, clinical evidence suggesting that stretching before exercise does not prevent injuries has also been reported. Apparently, no scientifically based prescription for stretching exercises exists and no conclusive statements can be made about the relationship of stretching and athletic injuries. Stretching recommendations are clouded by misconceptions and conflicting research reports. We believe that part of these contradictions can be explained by considering the type of sports activity in which an individual is participating. Sports involving bouncing and jumping activities with a high intensity of stretch-shortening cycles (SSCs) [e.g. soccer and football] require a muscle-tendon unit that is compliant enough to store and release the high amount of elastic energy that benefits performance in such sports. If the participants of these sports have an insufficient compliant muscle-tendon unit, the demands in energy absorption and release may rapidly exceed the capacity of the muscle-tendon unit. This may lead to an increased risk for injury of this structure. Consequently, the rationale for injury prevention in these sports is to increase the compliance of the muscle-tendon unit. Recent studies have shown that stretching programmes can significantly influence the viscosity of the tendon and make it significantly more compliant, and when a sport demands SSCs of high intensity, stretching may be important for injury prevention. This conjecture is in agreement with the available scientific clinical evidence from these types of sports activities. In contrast, when the type

  8. Mechanical stretch induces mitochondria-dependent apoptosis in neonatal rat cardiomyocytes and G2/M accumulation in cardiac fibroblasts

    Institute of Scientific and Technical Information of China (English)

    Xu Dong LIAO; Xiao Hui WANG; Hai Jing JIN; Lan Ying CHEN; Quan CHEN


    Heart remodeling is associated with the loss of cardiomyocytes and increase of fibrous tissue owing to abnormal mechanical load in a number of heart disease conditions. In present study,a well-described in vitro sustained stretch model was employed to study mechanical stretch-induced responses in both neonatal cardiomyocytes and cardiac fibroblasts. Cardiomyocytes,but not cardiac fibroblasts,underwent mitochondria-dependent apoptosis as evidenced by cytochrome c (cyto c) and Smac/DIABLO release from mitochondria into cytosol accompanied by mitochondrial membrane potential (△ψm) reduction,indicative of mitochondrial permeability transition pore (PTP)opening. Cyclosporin A,an inhibitor of PTP,inhibited stretch-induced cyto c release,△ψm reduction and apoptosis,suggesting an important role of mitochondrial PTP in stretch-induced apoptosis. The stretch also resulted in increased expression of the pro-apoptotic Bcl-2 family proteins,including Bax and Bad,in cardiomyocytes,but not in fibroblasts. Bax was accumulated in mitochondria following stretch. Cell permeable Bid-BH3 peptide could induce and facilitate stretch-induced apoptosis and △ψm reduction in cardiomyocytes. These results suggest that Bcl-2 family proteins play an important role in coupling stretch signaling to mitochondrial death machinery,probably by targeting to PTP. Interestingly,the levels of p53 were increased at 12 h after stretch although we observed that Bax upregulation and apoptosis occurred as early as 1 h. Adenovirus delivered dominant negative p53 blocked Bax upregulation in cardiomyocytes but showed partial effect on preventing stretch-induced apoptosis,suggesting that p53 was only partially involved in mediating stretch-induced apoptosis. Furthermore,we showed that p21 was upregulated and cyclin B l was downregulated only in cardiac fibroblasts,which may be associated with G2/M accumulation in response to mechanical stretch.

  9. Springback Prediction and Optimization of Variable Stretch Force Trajectory in Three-dimensional Stretch Bending Process

    Institute of Scientific and Technical Information of China (English)

    TENG Fei; ZHANG Wanxi; LIANG Jicai; GAO Song


    Most of the existing studies use constant force to reduce springback while researching stretch force. However, variable stretch force can reduce springback more efficiently. The current research on springback prediction in stretch bending forming mainly focuses on artificial neural networks combined with the finite element simulation. There is a lack of springback prediction by support vector regression (SVR). In this paper, SVR is applied to predict springback inthe three-dimensional stretch bending forming process,and variable stretch force trajectory is optimized. Six parameters of variable stretch force trajectory are chosen as the input parameters of the SVR model. Sixty experiments generated by design of experiments (DOE) are carried out to train and test the SVR model. The experimental results confirm that the accuracy of the SVR model is higher than that of artificial neural networks. Based on this model, an optimization algorithm of variable stretch force trajectory using particle swarm optimization (PSO) is proposed. The springback amount is used as the objective function. Changes of local thickness are applied as the criterion of forming constraints. The objection and constraints are formulated by response surface models. The precision of response surface models is examined. Six different stretch force trajectories are employed to certify springback reduction in the optimum stretch force trajectory, which can efficiently reduce springback. This research proposes a new method of springback prediction using SVR and optimizes variable stretch force trajectory to reduce springback.

  10. Caspase-12 is involved in stretch-induced apoptosis mediated endoplasmic reticulum stress. (United States)

    Zhang, Qiang; Liu, Jianing; Chen, Shulan; Liu, Jing; Liu, Lijuan; Liu, Guirong; Wang, Fang; Jiang, Wenxin; Zhang, Caixia; Wang, Shuangyu; Yuan, Xiao


    It is well recognized that mandibular growth, which is caused by a variety of functional appliances, is considered to be the result of both neuromuscular and skeletal adaptations. Accumulating evidence has demonstrated that apoptosis plays an important role in the adaptation of skeletal muscle function. However, the underlying mechanism of apoptosis that is induced by stretch continues to be incompletely understood. Endoplasmic reticulum stress (ERS), a newly defined signaling pathway, initiates apoptosis. This study seeks to determine if caspase-12 is involved in stretch-induced apoptosis mediated endoplasmic reticulum stress in myoblast and its underlying mechanism. Apoptosis was assessed by Hochest staining, DAPI staining and annexin V binding and PI staining. ER chaperones, such as GRP78, CHOP and caspase-12, were determined by reverse transcription polymerase chain reaction (RT-PCR) and Western blot. Furthermore, caspase-12 inhibitor was used to value the mechanism of the caspase-12 pathway. Apoptosis of myoblast, which is subjected to cyclic stretch, was observed in a time-dependent manner. We found that GRP78 mRNA and protein were significantly increased and CHOP and caspase-12 were activated in myoblast that was exposed to cyclic stretch. Caspase-12 inhibition reduced stretch-induced apoptosis, and caspase-12 activated caspase-3 to induce apoptosis. We concluded that caspase-12 played an important role in stretch-induced apoptosis that is associated by endoplasmic reticulum stress by activating caspase-3.

  11. Static Versus Dynamic Stretching Effect on Agility Performance


    Troumbley, Patrick


    The purpose of this study was to compare effects of static and dynamic stretching on explosive agility movements, and to examine the effect of the interaction of dynamic and static stretching prior to explosive agility movements. Fourteen men and 10 women performed the different warm-up protocols, including no warm-up (NWU), static stretching (SS), dynamic stretching (DS), and dynamic stretching with static stretching (DS+SS). The T-Drill was used to assess agility. The results indicated n...

  12. Effect of modified hold-relax stretching and static stretching on hamstring muscle flexibility. (United States)

    Ahmed, Hashim; Iqbal, Amir; Anwer, Shahnawaz; Alghadir, Ahmad


    [Purpose] The aim of present study was to compare the effectiveness of modified hold-relax stretching and static stretching in improving the hamstring muscle flexibility. [Subjects and Methods] Forty-five male subjects with hamstring tightness were included in this study. The subjects were randomly placed into three groups: the modified hold-relax stretching, static stretching and control groups. The modified hold-relax stretching group performed 7 seconds of isometric contraction and then relaxed for 5 seconds, and this was repeated five times daily for five consecutive days. The static stretching group received 10 minutes of static stretching with the help of a pulley and weight system for five consecutive days. The control group received only moist heat for 20 minutes for five consecutive days. A baseline reading of passive knee extension (PKE) was taken prior to the intervention; rest measurements were taken immediate post intervention on day 1, day 3, day 5, and after a 1 week follow-up, i.e., at the 12th day. [Results] On comparing the baseline readings of passive knee extension (PKE), there was no difference noted between the three groups. On comparing the posttest readings on day 5 between the 3 groups, a significant difference was noted. However, post hoc analysis revealed an insignificant difference between the modified hold-relax stretching and static stretching groups. There was a significant difference between the static stretching and control groups and between the modified hold-relax stretching and control groups. [Conclusion] The results of this study indicate that both the modified hold-relax stretching technique and static stretching are equally effective, as there was no significant difference in improving the hamstring muscle flexibility between the two groups.

  13. Bias of purine stretches in sequenced chromosomes

    DEFF Research Database (Denmark)

    Ussery, David; Soumpasis, Dikeos Mario; Brunak, Søren


    We examined more than 700 DNA sequences (full length chromosomes and plasmids) for stretches of purines (R) or pyrimidines (Y) and alternating YR stretches; such regions will likely adopt structures which are different from the canonical B-form. Since one turn of the DNA helix is roughly 10 bp, we...... measured the fraction of each genome which contains purine (or pyrimidine) tracts of lengths of 10 by or longer (hereafter referred to as 'purine tracts'), as well as stretches of alternating pyrimidines/purine ('pyr/pur tracts') of the same length. Using this criteria, a random sequence would be expected......, in eukaryotes there is an abundance of long stretches of purines or alternating purine/pyrimidine tracts, which cannot be explained in this way; these sequences are likely to play an important role in eukaryotic chromosome organisation....

  14. Markov chains and decision processes for engineers and managers

    CERN Document Server

    Sheskin, Theodore J


    Markov Chain Structure and ModelsHistorical NoteStates and TransitionsModel of the WeatherRandom WalksEstimating Transition ProbabilitiesMultiple-Step Transition ProbabilitiesState Probabilities after Multiple StepsClassification of StatesMarkov Chain StructureMarkov Chain ModelsProblemsReferencesRegular Markov ChainsSteady State ProbabilitiesFirst Passage to a Target StateProblemsReferencesReducible Markov ChainsCanonical Form of the Transition MatrixTh

  15. Frequency chain to measure the 2S-8S/8D transitions in atomic hydrogen: measurement of the Rydberg constant in frequency unit; Chaine de frequence optique pour mesurer les transitions 2S-8S/8D dans l'atome d'hydrogene: mesure de la constante de Rydberg en unite de frequence

    Energy Technology Data Exchange (ETDEWEB)

    Nez, F


    The aim of this thesis is to make a pure measurement of the frequency of the 2S-8S/8D two-photon transition in atomic hydrogen. In that purpose we have built a frequency chain in which hydrogen frequencies are compared with the difference of two optical standards, the methane stabilized He-Ne laser (3.39 {mu}m) and the iodine stabilized He-Ne laser (633 nm). The radiation from a home made Ti-sapphire laser (TS2) at 778 nm is mixed, in a LiIO{sub 3} crystal, with the one of a auxiliary He-Ne laser at 3.39 {mu}m to produce a synthesized radiation at 633 nm. The frequency of the Ti-sapphire (TS1) laser used for the two photon excitation is 89 GHz away from the one of TS2. To compare these two lasers, we have used a Schottky diode. The two lasers and a microwave radiation at 89 GHz, produced by a Gunn diode, are focused on the Schottky diode. The Gunn diode is phase locked on an ultra-stable quartz oscillator. In this way, we have linked an optical frequency of atomic hydrogen to the cesium clock without interferometry. From our measurements, we have deduced a new value of the Rydberg constant: R{sub {infinity}} equals 109737.3156834 (24) cm{sup -1} with an uncertainty of 2.2 10{sup -11}. Our uncertainty is near the one of the Q.E.D calculations giving the theoretical values of the energy levels. This value, which is currently the most precise available, is in good agreement with the recent result obtained from the 1S-2S and 2S-4D transitions. (author)

  16. Comparison of two stretching methods and optimization of stretching protocol for the piriformis muscle. (United States)

    Gulledge, Brett M; Marcellin-Little, Denis J; Levine, David; Tillman, Larry; Harrysson, Ola L A; Osborne, Jason A; Baxter, Blaise


    Piriformis syndrome is an uncommon diagnosis for a non-discogenic form of sciatica whose treatment has traditionally focused on stretching the piriformis muscle (PiM). Conventional stretches include hip flexion, adduction, and external rotation. Using three-dimensional modeling, we quantified the amount of (PiM) elongation resulting from two conventional stretches and we investigated by use of a computational model alternate stretching protocols that would optimize PiM stretching. Seven subjects underwent three CT scans: one supine, one with hip flexion, adduction, then external rotation (ADD stretch), and one with hip flexion, external rotation, then adduction (ExR stretch). Three-dimensional bone models were constructed from the CT scans. PiM elongation during these stretches, femoral neck inclination, femoral head anteversion, and trochanteric anteversion were measured. A computer program was developed to map PiM length over a range of hip joint positions and was validated against the measured scans. ExR and ADD stretches elongated the PiM similarly by approximately 12%. Femoral head and greater trochanter anteversion influenced PiM elongation. Placing the hip joints in 115° of hip flexion, 40° of external rotation and 25° of adduction or 120° of hip flexion, 50° of external rotation and 30° of adduction increased PiM elongation by 30-40% compared to conventional stretches (15.1 and 15.3% increases in PiM muscle length, respectively). ExR and ADD stretches elongate the PiM similarly and therefore may have similar clinical effectiveness. The optimized stretches led to larger increases in PiM length and may be more easily performed by some patients due to increased hip flexion.

  17. Different Effects of Long- and Short-Chain Ceramides on the Gel-Fluid and Lamellar-Hexagonal Transitions of Phospholipids: A Calorimetric, NMR, and X-Ray Diffraction Study (United States)

    Sot, Jesús; Aranda, Francisco J.; Collado, M.-Isabel; Goñi, Félix M.; Alonso, Alicia


    The effects on dielaidoylphosphatidylethanolamine (DEPE) bilayers of ceramides containing different N-acyl chains have been studied by differential scanning calorimetry small angle x-ray diffraction and 31P-NMR spectroscopy. N-palmitoyl (Cer16), N-hexanoyl (Cer6), and N-acetyl (Cer2) sphingosines have been used. Both the gel-fluid and the lamellar-inverted hexagonal transitions of DEPE have been examined in the presence of the various ceramides in the 0-25 mol % concentration range. Pure hydrated ceramides exhibit cooperative endothermic order-disorder transitions at 93°C (Cer16), 60°C (Cer6), and 54°C (Cer2). In DEPE bilayers, Cer16 does not mix with the phospholipid in the gel phase, giving rise to high-melting ceramide-rich domains. Cer16 favors the lamellar-hexagonal transition of DEPE, decreasing the transition temperature. Cer2, on the other hand, is soluble in the gel phase of DEPE, decreasing the gel-fluid and increasing the lamellar-hexagonal transition temperatures, thus effectively stabilizing the lamellar fluid phase. In addition, Cer2 was peculiar in that no equilibrium could be reached for the Cer2-DEPE mixture above 60°C, the lamellar-hexagonal transition shifting with time to temperatures beyond the instrumental range. The properties of Cer6 are intermediate between those of the other two, this ceramide decreasing both the gel-fluid and lamellar-hexagonal transition temperatures. Temperature-composition diagrams have been constructed for the mixtures of DEPE with each of the three ceramides. The different behavior of the long- and short-chain ceramides can be rationalized in terms of their different molecular geometries, Cer16 favoring negative curvature in the monolayers, thus inverted phases, and the opposite being true of the micelle-forming Cer2. These differences may be at the origin of the different physiological effects that are sometimes observed for the long- and short-chain ceramides. PMID:15695626

  18. Effects of proprioceptive neuromuscular facilitation stretching and static stretching on maximal voluntary contraction. (United States)

    Miyahara, Yutetsu; Naito, Hisashi; Ogura, Yuji; Katamoto, Shizuo; Aoki, Junichiro


    This study was undertaken to investigate and compare the effects of proprioceptive neuromuscular facilitation (PNF) stretching and static stretching on maximal voluntary contraction (MVC). Thirteen male university students (age, 20 ± 1 years; height, 172.2 ± 4.6 cm; weight, 68.4 ± 6.7 kg; mean ± SD) completed 3 different conditions on 3 nonconsecutive days in randomized order: static stretching (SS), PNF stretching (PNF), and no stretching (control, CON). Each condition consisted of a 5-minute rest accompanied by one of the following activities: (a) control, (b) SS, or (c) PNF stretching. The hip flexion range of motion (ROM) was evaluated immediately before and after the activity. The MVC of knee flexion was then measured. Surface electromyography was recorded from the biceps femoris and vastus lateralis muscles during MVC tests and stretching. Although increases in ROM were significantly greater after PNF than after SS (p stretching increases ROM more than SS, PNF stretching and SS is detrimental to isometric maximal strength.

  19. How a single stretched polymer responds coherently to a minute oscillation in fluctuating environments: An entropic stochastic resonance

    CERN Document Server

    Kim, Won Kyu; 10.1063/1.4746118


    Within the cell, biopolymers are often situated in constrained, fluid environments, e.g., cytoskeletal networks, stretched DNAs in chromatin. It is of paramount importance to understand quantitatively how they, utilizing their flexibility, optimally respond to a minute signal, which is, in general, temporally fluctuating far away from equilibrium. To this end, we analytically study viscoelastic response and associated stochastic resonance in a stretched single semi-flexible chain to an oscillatory force or electric field. Including hydrodynamic interactions between chain segments, we evaluate dynamics of the polymer extension in coherent response to the force or field. We find power amplification factor of the response at a noise-strength (temperature) can attain the maximum that grows as the chain length increases, indicative of an entropic stochastic resonance (ESR). In particular for a charged chain under an electric field, we find that the maximum also occurs at an optimal chain length, a new feature of E...

  20. The Effect of a Helix-Coil Transition on the Extension Elasticity (United States)

    Buhot, Arnaud; Halperin, Avi


    The secondary structure of a polymer affects its deformation behavior in accordance with the Le Chatelier principle. An important example of such secondary structure is the alpha helix encountered in polypeptides. Similar structure was recently proposed for PEO in aqueous media. Our discussion concerns the coupling of the cooperative helix-coil transition and the extension elasticity. In particular, we analyze the extension of a long single chain by use of optical tweezers or AFM. We consider chains that exist in the coil-state when unperturbed. The transition nevertheless occurs because the extension favors the low entropy helical state. As a result, the corresponding force law exhibits a plateau. The analysis of this situation involves two ingredients: (I) the stretching free energy penalty for a rod-coil mutiblock copolymer (II) the entropy associated with the possible placements of the rod and coil blocks.

  1. Odd-even chain packing, molecular and thermal models for some long chain sodium(I) n-alkanoates (United States)

    Nelson, Peter N.; Ellis, Henry A.


    A homologous series of sodium(I) n-alkanoates, NaCnH2n-1O2, with chain lengths n = 8-18, inclusive, have been synthesized and their structural and thermal properties investigated via Fourier Transform Infrared and Solid State 13C NMR spectroscopies, X-ray powder diffraction, Thermogravimetry, Differential Scanning Calorimetry, Polarizing light microscopy and variable temperature Infrared spectroscopy. The measurements show that metal-carboxylate coordination is via asymmetric chelating bidentate bonding with extensive carboxyl group inter-molecular interactions in which four oxygen atoms are bonded tetrahedrally to a sodium atom. Furthermore, the compounds crystallize in a monoclinic crystal system with the hydrocarbon chains in the fully extended all-trans conformation, advancing along the c-axis. Moreover, the chains are packed as tilted (θ ∼ 63°), non-overlapping, tail-to-tail lamellar bilayers that are not in the same plane, within a lamellar. Though these compounds are nearly isostructural, there are subtle differences in the packing of the hydrocarbon chains in the crystal lattice, resulting in odd-even alternation in the terminal methyl group asymmetric stretching vibration and chemical shift. These differences arise from the relative vertical distances between hydrocarbon planes within the lamellar; such that, for odd-chain compounds, larger inter-planar distances result in less efficient packing in the crystal lattice and hence, lower inter-planar van der Waals interactions between hydrocarbon chains. Thermal traces, for all compounds, show several partially reversible solid-solid pre-melting transitions associated with different degrees of gauche conformers in the alkyl chains. The reversible gauche-trans isomerism, of the methylene groups, is kinetically controlled; hence, super-cooling of the melt and other transitions, are observed for all compounds. The kinetics of chain reversion follow the exponential law of nucleation, though complicated by

  2. An Analysis of Individual Stretching Programs of Intercollegiate Athletes. (United States)

    Levine, Michael; And Others


    To evaluate individual stretching programs of intercollegiate athletes, 238 athletes (164 male, 74 female) in ten sports were surveyed about their stretching practices. Almost all of the athletes stretched, but to varying degrees. Muscle groups stretched by the fewest athletes were the adductors, plantar flexors, hips, and neck. (Author/MT)

  3. Investigating the Microstructure of Slenderized Wool Fibers at Different Stretching Ratios by Raman Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    LIU Hong-ling; YU Wei-dong; ZHANG Yue-ting


    The molecular conformation and the microstructure of the slenderized wool fibers have been studied by the Raman spectroscopy. The typical bands analyzed in this paper include the amideⅠand amide Ⅲ regions, the C-C skeletal vibration region, and the S-S and C-S bond vibration regions. The experimental results show that ⅰ) the Raman spectroscopy can reveal the secondary structural transformation from α-helical to β-pleated sheet begin at the early stage of stretching; ⅱ) the stretching mechanism of wool fibers can be divided into two different mechanisms, I.e. The secondary structural transformation and the slippage of the polypeptide chain; and ⅲ) the stretching leads to the increasing of the amount of the disordered conformation and the decreasing of the amount of S-S bonds.

  4. Large deviations of Rouse polymer chain: First passage problem (United States)

    Cao, Jing; Zhu, Jian; Wang, Zuowei; Likhtman, Alexei E.


    The purpose of this paper is to investigate several analytical methods of solving first passage (FP) problem for the Rouse model, a simplest model of a polymer chain. We show that this problem has to be treated as a multi-dimensional Kramers' problem, which presents rich and unexpected behavior. We first perform direct and forward-flux sampling (FFS) simulations and measure the mean first-passage time τ(z) for the free end to reach a certain distance z away from the origin. The results show that the mean FP time is getting faster if the Rouse chain is represented by more beads. Two scaling regimes of τ(z) are observed, with transition between them varying as a function of chain length. We use these simulation results to test two theoretical approaches. One is a well known asymptotic theory valid in the limit of zero temperature. We show that this limit corresponds to fully extended chain when each chain segment is stretched, which is not particularly realistic. A new theory based on the well known Freidlin-Wentzell theory is proposed, where dynamics is projected onto the minimal action path. The new theory predicts both scaling regimes correctly, but fails to get the correct numerical prefactor in the first regime. Combining our theory with the FFS simulations leads us to a simple analytical expression valid for all extensions and chain lengths. One of the applications of polymer FP problem occurs in the context of branched polymer rheology. In this paper, we consider the arm-retraction mechanism in the tube model, which maps exactly on the model we have solved. The results are compared to the Milner-McLeish theory without constraint release, which is found to overestimate FP time by a factor of 10 or more.

  5. Stretch-activated channels in stretch-induced muscle damage: role in muscular dystrophy. (United States)

    Yeung, Ella W; Allen, David G


    1. Stretch-induced muscle injury results in the damage that causes reduced force and increased membrane permeability. This muscle damage is caused, in part, by ionic entry through stretch-activated channels and blocking these channels with Gd3+ or streptomycin reduces the force deficit associated with damage. 2. Dystrophin-deficient muscles are more susceptible to stretch-induced muscle injury and the recovery from injury can be incomplete. We have found that Na+ entry associated with stretch-induced injury is enhanced in dystrophin-deficient muscles and that blockers of stretch-activated channels are capable of preventing ionic entry and reducing muscle damage. 3. A model is presented that proposes links between stretch-induced injury, opening of stretch-activated channels, increased levels of intracellular ions and various forms of muscle damage. Although changes in Na+ accompany stretch-induced muscle injury, we believe that changes in Ca2+ probably have a more central role in the damage process.

  6. Movement and stretching imagery during flexibility training. (United States)

    Vergeer, Ineke; Roberts, Jenny


    The aim of this study was to examine the effect of movement and stretching imagery on increases in flexibility. Thirty volunteers took part in a 4 week flexibility training programme. They were randomly assigned to one of three groups: (1) movement imagery, where participants imagined moving the limb they were stretching; (2) stretching imagery, where participants imagined the physiological processes involved in stretching the muscle; and (3) control, where participants did not engage in mental imagery. Active and passive range of motion around the hip was assessed before and after the programme. Participants provided specific ratings of vividness and comfort throughout the programme. Results showed significant increases in flexibility over time, but no differences between the three groups. A significant relationship was found, however, between improved flexibility and vividness ratings in the movement imagery group. Furthermore, both imagery groups scored significantly higher than the control group on levels of comfort, with the movement imagery group also scoring significantly higher than the stretching imagery group. We conclude that the imagery had stronger psychological than physiological effects, but that there is potential for enhancing physiological effects by maximizing imagery vividness, particularly for movement imagery.

  7. What Protects Certain Nerves from Stretch Injury? (United States)

    Schraut, Nicholas B; Walton, Sharon; Bou Monsef, Jad; Shott, Susan; Serici, Anthony; Soulii, Lioubov; Amirouche, Farid; Gonzalez, Mark H; Kerns, James M


    The human tibial nerves is less prone to injury following joint arthroplasty compared with the peroneal nerves. Besides the anatomical distribution, other features may confer protection from stretch injury. We therefore examined the size, shape and connective tissue distribution for the two nerves. The tibial and peroneal nerves from each side of nine fresh human cadavers we reharvested mid-thigh. Proximal segments manually stretched 20%-25% were fixed in aldehyde, while the adjacent distal segments were fixed in their natural length. Paraffin sections stained by Masson's trichrome method for connective tissue were examined by light microscopy. Tibial nerves had 2X more fascicles compared with the peroneal, but the axonal content appeared similar. Analysis showed that neither nerve had a significant reduction in cross sectional area of the fascicles following stretch. However, fascicles from stretched tibial nerves become significantly more oval compared with those from unstretched controls and peroneal nerves. Tibial nerves had a greater proportion that was extrafascicular tissue (50-55%) compared with peroneal nerves (38%-42%). This epineurium was typically adipose tissue. Perineurial thickness in both nerves was directly related to fascicular size. Tibial nerves have several unique histological features associated with size, shape and tissue composition compared with the peroneal nerve. We suggest that more fascicles with their tightly bound perineurium and more robust epineurium afford protection against stretch injury. Mechanical studies should clarify how size and shape contribute to nerve protection and/or neurapraxia.

  8. Industrial Upgrading in the Apparel Value Chain and the Role of Designer in the Transition: comparative analysis of Sri Lanka and Hong Kong


    Sumith Gopura; Alice Payne; Laurie Buys


    The apparel industry is a major export industry in Sri Lanka that depends upon labour intensive manufacturing. The Sri Lankan apparel industry is transitioning from Cut, Make, Trims (CMT) assembly and Original Equipment Manufacturing (OEM) to Original Design Manufacturing (ODM) and Original Brand Manufacturing (OBM), experiencing the economic benefits of apparel product export. The transition relies on having expert professionals who can provide creative, commercial, technical, an...

  9. In situ ultra-small-angle X-ray scattering study under uniaxial stretching of colloidal crystals prepared by silica nanoparticles bearing hydrogen-bonding polymer grafts

    Directory of Open Access Journals (Sweden)

    Ryohei Ishige


    Full Text Available A molded film of single-component polymer-grafted nanoparticles (SPNP, consisting of a spherical silica core and densely grafted polymer chains bearing hydrogen-bonding side groups capable of physical crosslinking, was investigated by in situ ultra-small-angle X-ray scattering (USAXS measurement during a uniaxial stretching process. Static USAXS revealed that the molded SPNP formed a highly oriented twinned face-centered cubic (f.c.c. lattice structure with the [11−1] plane aligned nearly parallel to the film surface in the initial state. Structural analysis of in situ USAXS using a model of uniaxial deformation induced by rearrangement of the nanoparticles revealed that the f.c.c. lattice was distorted in the stretching direction in proportion to the macroscopic strain until the strain reached 35%, and subsequently changed into other f.c.c. lattices with different orientations. The lattice distortion and structural transition behavior corresponded well to the elastic and plastic deformation regimes, respectively, observed in the stress–strain curve. The attractive interaction of the hydrogen bond is considered to form only at the top surface of the shell and then plays an effective role in cross-linking between nanoparticles. The rearrangement mechanism of the nanoparticles is well accounted for by a strong repulsive interaction between the densely grafted polymer shells of neighboring particles.


    Institute of Scientific and Technical Information of China (English)

    B.Y. Sun; S.J. Yuan


    The principle of the stretch reducing process is analyzed and three models of pass design areestablished. The simulations are done about variables, such as, stress, strain, the stretches betweenthe stands, the size parameters of the steel tube, and the roll force parameters. According to itsproduct catalogs the system can automatically divide the pass series, formulate the rolling table,and simulate the basic technological parameters in the stretch reducing process. All modules areintegrated based on the developing environment of VB6. The system can draw simulation curvesand pass pictures. Three kinds of database including the material database, pass design database,and product database are devised using Microsoft Access, which can be directly edited, corrected,and searched.

  11. Exploration Supply Chain Simulation (United States)


    The Exploration Supply Chain Simulation project was chartered by the NASA Exploration Systems Mission Directorate to develop a software tool, with proper data, to quantitatively analyze supply chains for future program planning. This tool is a discrete-event simulation that uses the basic supply chain concepts of planning, sourcing, making, delivering, and returning. This supply chain perspective is combined with other discrete or continuous simulation factors. Discrete resource events (such as launch or delivery reviews) are represented as organizational functional units. Continuous resources (such as civil service or contractor program functions) are defined as enabling functional units. Concepts of fixed and variable costs are included in the model to allow the discrete events to interact with cost calculations. The definition file is intrinsic to the model, but a blank start can be initiated at any time. The current definition file is an Orion Ares I crew launch vehicle. Parameters stretch from Kennedy Space Center across and into other program entities (Michaud Assembly Facility, Aliant Techsystems, Stennis Space Center, Johnson Space Center, etc.) though these will only gain detail as the file continues to evolve. The Orion Ares I file definition in the tool continues to evolve, and analysis from this tool is expected in 2008. This is the first application of such business-driven modeling to a NASA/government-- aerospace contractor endeavor.

  12. Filament stretching rheometer: inertia compensation revisited

    DEFF Research Database (Denmark)

    Szabo, Peter; McKinley, Gareth H.


    The necessary inertia compensation used in the force balance for the filament stretching rheometer is derived for an arbitrary frame of reference. This enables the force balance to be used to extract correctly the extensional viscosity from measurements of the tensile force at either end of the e......The necessary inertia compensation used in the force balance for the filament stretching rheometer is derived for an arbitrary frame of reference. This enables the force balance to be used to extract correctly the extensional viscosity from measurements of the tensile force at either end...

  13. Depicting Vortex Stretching and Vortex Relaxing Mechanisms

    Institute of Scientific and Technical Information of China (English)

    符松; 李启兵; 王明皓


    Different from many existing studies on the paranetrization of vortices, we investigate the effectiveness of two new parameters for identifying the vortex stretching and vortex relaxing mechanisms. These parameters are invariants and identify three-dimensional flow structures only, i.e. they diminish in two-dimensional flows. This is also unlike the existing vortex identification approaches which deliver information in two-dimensional flows. The present proposals have been successfully applied to identify the stretching and relaxing vortices in compressible mixing layers and natural convection flows.

  14. Viscous Swirling Flow over a Stretching Cylinder

    Institute of Scientific and Technical Information of China (English)

    Tiegang FANG; ShanshanYAO


    We investigate a viscous How over a cylinder with stretching and torsional motion. There is an exact solution to the Navier-Stokes equations and there exists a unique solution for all the given values of the flow Reynolds number. The results show that velocity decays faster for a higher Reynolds number and the How penetrates shallower into the ambient Huid. All the velocity proHles decay algebraically to the ambient zero velocity.%We investigate a viscous flow over a cylinder with stretching and torsional motion.There is an exact solution to the Navier-Stokes equations and there exists a unique solution for all the given values of the flow Reynolds number.The results show that velocity decays faster for a higher Reynolds number and the flow penetrates shallower into the ambient fluid.All the velocity profiles decay algebraically to the ambient zero velocity.Exact solutions of the Navier-Stokes (NS) equations play important roles in the development of fluid mechanics.In the review articles,[1,2] Wang summarized the available exact solutions of the unsteady state and of the steady-state NS equations.Swirl flows have important engineering applications in many fields such as the cyclone for separation of solid,liquid and gas,swirl atomizers,swirl combustion devices,heat transfer enhancement and others.[3,4] A famous example of flows involving rotation or swirl is the rotating disk problem studied by von Karman.[5-8] The flow induced by a stretching boundary is also important in the extrusion processes in plastic and metal industries.[9-11] Crane[12] presented an exact solution of the two-dimensional NS equations for a stretching sheet problem with a closed analytical form.The stretching wall problem was extended by Wang[13]to a three-dimensional setting.The flow between two stretching disks was studied by Fang and Zhang recently.[14] The combined effects of disk stretching and rotation on the von Karman flow was investigated by Fang.[15] The flow inside a channel or a

  15. Stretching and folding mechanism in foams

    Energy Technology Data Exchange (ETDEWEB)

    Tufaile, Alberto [Escola de Artes, Ciencias e Humanidades, Soft Matter Laboratory, Universidade de Sao Paulo, 03828-000 Sao Paulo, SP (Brazil)], E-mail:; Pedrosa Biscaia Tufaile, Adriana [Escola de Artes, Ciencias e Humanidades, Soft Matter Laboratory, Universidade de Sao Paulo, 03828-000 Sao Paulo, SP (Brazil)


    We have described the stretching and folding of foams in a vertical Hele-Shaw cell containing air and a surfactant solution, from a sequence of upside-down flips. Besides the fractal dimension of the foam, we have observed the logistic growth for the soap film length. The stretching and folding mechanism is present during the foam formation, and this mechanism is observed even after the foam has reached its respective maximum fractal dimension. Observing the motion of bubbles inside the foam, large bubbles present power spectrum associated with random walk motion in both directions, while the small bubbles are scattered like balls in a Galton board.

  16. Stretched and overwound DNA forms a Pauling-like structure with exposed bases. (United States)

    Allemand, J F; Bensimon, D; Lavery, R; Croquette, V


    We investigate structural transitions within a single stretched and supercoiled DNA molecule. With negative supercoiling, for a stretching force >0.3 pN, we observe the coexistence of B-DNA and denatured DNA from sigma approximately -0.015 down to sigma = -1. Surprisingly, for positively supercoiled DNA (sigma > +0.037) stretched by 3 pN, we observe a similar coexistence of B-DNA and a new, highly twisted structure. Experimental data and molecular modeling suggest that this structure has approximately 2.62 bases per turn and an extension 75% larger than B-DNA. This structure has tightly interwound phosphate backbones and exposed bases in common with Pauling's early DNA structure [Pauling, L. & Corey, R. B. (1953), Proc. Natl. Acad. Sci. USA 39, 84-97] and an unusual structure proposed for the Pf1 bacteriophage [Liu, D. J. & Day, L. A. (1994) Science 265, 671-674].

  17. Alkyl CH Stretch Vibrations as a Probe of Conformational Preferences (United States)

    Sibert, Edwin L. Sibert, Iii; Buchanan, Evan G.; Zwier, Timothy S.


    Theoretical IR spectra of 1,2-diphenoxyethane (C_6H_5-O-CH_2-CH_2-O-C_6H_5 DPOE) and 1,2-diphenylethane (C_6H_5-CH_2-CH_2-C_6H_5 DPE) are presented and compared to results of single-conformation spectroscopy of jet cooled molecules. The theoretical transition energies and intensites are obtained from a model based on a local mode Hamiltonian that includes all local cubic stretch-bend couplings that are then projected onto the normal modes. The model parameters are obtained from density functional theory methods. Full dimensional calculations are compared to those of reduced dimensions that include anharmonic CH streches Fermi coupled to scissor modes. Excellent agreement is found. Scale factors of select terms in the reduced dimensional Hamiltonian are determined by fitting the theoretical Hamiltonian to the anti DPE spectrum. Using the same scaling, Hamiltonians for other conformers of the above molecules are generated and used to predict structures by comparing to experimentally determined spectra in the alkyl CH stretch region. The level patterns in the resulting spectra are elucidated in terms of the model parameters. The model results are extended to interpret the spectra of more complicated macrocycles containing multiple -CH_2CH_2- ethano bridges such as the dibenzo-15-crown-5 ether and 2,2,2-paracyclophane.

  18. Uncertainty quantification for Markov chain models. (United States)

    Meidani, Hadi; Ghanem, Roger


    Transition probabilities serve to parameterize Markov chains and control their evolution and associated decisions and controls. Uncertainties in these parameters can be associated with inherent fluctuations in the medium through which a chain evolves, or with insufficient data such that the inferential value of the chain is jeopardized. The behavior of Markov chains associated with such uncertainties is described using a probabilistic model for the transition matrices. The principle of maximum entropy is used to characterize the probability measure of the transition rates. The formalism is demonstrated on a Markov chain describing the spread of disease, and a number of quantities of interest, pertaining to different aspects of decision-making, are investigated.

  19. Management of Rail-transit Operational Materials Purchasing Based on Supply Chain%基于供应链的轨道交通运营物资采购管理研究

    Institute of Scientific and Technical Information of China (English)

    华宇虹; 李文兴


    以供应链理论为依托,对城市轨道交通运营物资采购管理问题进行了深入研究,明确了轨道交通运营企业在供应链中所处位置及运营物资采购管理过程中的矛盾和问题,提出了创新供应模式,加强供应商管理,协调企业内外部关系等优化措施.%Using supply chain theories, the paper studies in-depth the management of operational materials purchasing for urban rail-transit systems, ascertains the position of rail-transit operators within the supply chain as well as the conflicts and other problems in the purchasing process, and finally suggests optimizing measures such as innovating supply mode, strengthening supplier management and coordinating corporate internal and external relations.

  20. Filament stretching rheometry of polymer melts

    DEFF Research Database (Denmark)

    Hassager, Ole; Nielsen, Jens Kromann; Rasmussen, Henrik Koblitz


    The Filament Stretching Rheometry (FSR) method developed by Sridhar, McKinley and coworkers for polymer solutions has been extended to be used also for polymer melts. The design of a melt-FSR will be described and differences to conventional melt elongational rheometers will be pointed out. Results...

  1. Optical stretching on chip with acoustophoretic prefocusing

    DEFF Research Database (Denmark)

    Khoury Arvelo, Maria; Laub Busk, L.; Bruus, Henrik


    in the microchannel. Trapping and manipulation is demonstrated for dielectric beads. In addition, we show trapping, manipulation and stretching of red blood cells and vesicles, whereby we extract the elastic properties of these objects. Our design points towards the construction of a low-cost, high-throughput lab...

  2. Linear viscoelastic characterization from filament stretching rheometry

    DEFF Research Database (Denmark)

    Wingstrand, Sara Lindeblad; Alvarez, Nicolas J.; Hassager, Ole

    viscoelasticity well into the nonlinear regime. Therefore at present, complete rheological characterization of a material requires two apparatuses: a shear and an extensional rheometer. This work is focused on developing a linear viscoelastic protocol for the filament stretching rheometer (FSR) in order...

  3. The Storm and Nelson's model for polymer stretching revisited

    CERN Document Server

    Massucci, Francesco A; Vicente, Conrad Pérez


    The quite recent technological rise in molecular biology allowed single molecule manipulation experiments, where molecule stretching plays a primary role. In order to understand the experimental data, it is felt the urge of some physical and mathematical models to quantitatively express the mechanical properties of the observed molecules. In this paper we reconsider a simple phenomenological model which reproduces the behaviour of a molecule of double stranded DNA (dsDNA) under tension. The problem is easily solved via the cavity method both in the small forces range and in presence of overstretching transition, so that some properties such as bending stiffness and elasticity of dsDNA emerge in a very clear manner. Our theoretical findings are successfully fitted to real measurements and compared to Monte Carlo simulations, confirming the quality of the approach.

  4. The chain relation in sofic subshifts

    CERN Document Server

    Kazda, Alexandr


    The paper gives a characterisation of the chain relation of a sofic subshift. Every sofic subshift $\\Sigma$ can be described by a labelled graph $G$. Factorising $G$ in a suitable way we obtain the graph $G/_\\approx$ that offers insight into some properties of the original subshift. Using $G/_\\approx$ we describe first the chain relation in $\\Sigma$, then characterise chain-transitive sofic subshifts, chain-mixing sofic subshifts and finally the attractors of the subshift dynamic system. At the end we present (straightforward) algorithms deciding chain-transitivity and chain-mixing properties of a sofic subshift and listing all the attractors of the subshift system.

  5. Flexible-to-semiflexible chain crossover on the pressure-area isotherm of a lipid bilayer (United States)

    Krivonos, I. N.; Mukhin, S. I.


    We find theoretically that competition between ˜ K f q 4 and ˜ Qq 2 terms in the Fourier-transformed conformational energy of a single-lipid chain, in combination with interchain entropic repulsion in the hydrophobic part of the lipid (bi)layer, may cause a crossover on the bilayer pressure-area isotherm P( A)˜( A- A 0)-α. The crossover manifests itself in the transition from α = 5/3 to α = 3. Our microscopic model represents a single-lipid molecule as a worm-like chain with a finite irreducible cross-section area A 0, a flexural rigidity K f , and a stretching modulus Q in a parabolic potential with the self-consistent curvature B( A) formed by entropic interactions between hydrocarbon chains in the lipid layer. The crossover area A* obeys the relation Q/√ K f B( A*) ≈ 2. We predict a peculiar possibility of deducing the effective elastic moduli K f and Q of an individual hydrocarbon chain from the analysis of the isotherm with such a crossover. Also calculated is the crossover-related behavior of the area compressibility modulus K A , the equilibrium area per lipid A t , and the chain order parameter S(θ).

  6. Circuit topology of self-interacting chains: implications for folding and unfolding dynamics. (United States)

    Mugler, Andrew; Tans, Sander J; Mashaghi, Alireza


    Understanding the relationship between molecular structure and folding is a central problem in disciplines ranging from biology to polymer physics and DNA origami. Topology can be a powerful tool to address this question. For a folded linear chain, the arrangement of intra-chain contacts is a topological property because rearranging the contacts requires discontinuous deformations. Conversely, the topology is preserved when continuously stretching the chain while maintaining the contact arrangement. Here we investigate how the folding and unfolding of linear chains with binary contacts is guided by the topology of contact arrangements. We formalize the topology by describing the relations between any two contacts in the structure, which for a linear chain can either be in parallel, in series, or crossing each other. We show that even when other determinants of folding rate such as contact order and size are kept constant, this 'circuit' topology determines folding kinetics. In particular, we find that the folding rate increases with the fractions of parallel and crossed relations. Moreover, we show how circuit topology constrains the conformational phase space explored during folding and unfolding: the number of forbidden unfolding transitions is found to increase with the fraction of parallel relations and to decrease with the fraction of series relations. Finally, we find that circuit topology influences whether distinct intermediate states are present, with crossed contacts being the key factor. The approach presented here can be more generally applied to questions on molecular dynamics, evolutionary biology, molecular engineering, and single-molecule biophysics.

  7. Stretching an Elastic Loop: Crease, Helicoid, and Pop Out (United States)

    Morigaki, Yasuaki; Wada, Hirofumi; Tanaka, Yoshimi


    Under geometric constraints, a thin structure can respond to an external loading in an unexpected way. A paper strip that is looped and pulled can be used for simple experimentation of such a process. Here, we study this seemingly very simple phenomenon in detail by combing experiments and theory. We identify the three types of shape transitions, i.e., crease, helicoid, and pop out, from a stretched loop, and classify them in terms of parameters characterizing a ribbon geometry. We establish a transition-type diagram by compiling our extensive experimental data. Numerical simulations based on the Kirchhoff rod theory and scaling argument reveal that the pop-out transition is governed by a single characteristic length ξ ˜b2/h , where b and h are the ribbon's width and thickness, respectively. We also reveal the key roles of other physical effects such as the anisotropy of the bending elasticity and plastic deformations upon the shape selection mechanisms of a constraint ribbon.

  8. How to determine local stretching and tension in a flow-stretched DNA molecule

    DEFF Research Database (Denmark)

    Pedersen, Jonas Nyvold; Marie, Rodolphe; Kristensen, Anders


    We determine the nonuniform stretching of and tension in amega base pairs-long fragment of deoxyribonucleic acid (DNA) that is flow stretched in a nanofluidic chip. We use no markers, do not know the contour length of the DNA, and do not have the full DNA molecule inside our field of view. Instead......, we analyze the transverse thermal motion of the DNA. Tension at the center of the DNA adds up to 16 pN, giving almost fully stretched DNA. This method was devised for optical mapping of DNA, specifically, DNA denaturation patterns. It may be useful also for other studies, e.g., DNA......-protein interactions, specifically, their tension dependence. Generally, wherever long strands of DNA—e.g., native DNA extracted from human cells or bacteria—must be stretched with ease for inspection, this method applies....

  9. How to determine local stretching and tension in a flow-stretched DNA molecule (United States)

    Pedersen, Jonas N.; Marie, Rodolphe; Kristensen, Anders; Flyvbjerg, Henrik


    We determine the nonuniform stretching of and tension in a mega base pairs-long fragment of deoxyribonucleic acid (DNA) that is flow stretched in a nanofluidic chip. We use no markers, do not know the contour length of the DNA, and do not have the full DNA molecule inside our field of view. Instead, we analyze the transverse thermal motion of the DNA. Tension at the center of the DNA adds up to 16 pN, giving almost fully stretched DNA. This method was devised for optical mapping of DNA, specifically, DNA denaturation patterns. It may be useful also for other studies, e.g., DNA-protein interactions, specifically, their tension dependence. Generally, wherever long strands of DNA—e.g., native DNA extracted from human cells or bacteria—must be stretched with ease for inspection, this method applies.

  10. Falling chains (United States)

    Wong, Chun Wa; Yasui, Kosuke


    The one-dimensional fall of a folded chain with one end suspended from a rigid support and a chain falling from a resting heap on a table is studied. Because their Lagrangians contain no explicit time dependence, the falling chains are conservative systems. Their equations of motion are shown to contain a term that enforces energy conservation when masses are transferred between subchains. We show that Cayley's 1857 energy nonconserving solution for a chain falling from a resting heap is incorrect because it neglects the energy gained when a link leaves a subchain. The maximum chain tension measured by Calkin and March for the falling folded chain is given a simple if rough interpretation. Other aspects of the falling folded chain are briefly discussed.

  11. Observation of the widetilde{A} - widetilde{X} Electronic Transition of C_6-C_{10} Peroxy Radicals (United States)

    Kline, Neal D.; Miller, Terry A.


    The widetilde{A} - widetilde{X} electronic transition of straight chain C_6-C_{10} peroxy radicals and of the isooctyl peroxy radical have been observed and analyzed. These larger hydrocarbons are significant constituents of gasoline with heptane (octane rating of 0) and isooctane (2,2,4 trimethylpentane; octane rating of 100) being the two standards on which the octane rating scale is based. Spectra were obtained by abstraction of hydrogen atoms from the hydrocarbons using chlorine atoms. The origin and -OO stretch regions of the straight chain peroxy radicals are easily identifiable. It is relatively easy to uniquely identify hexyl peroxy, but differentiation among the spectra of the larger straight chain peroxy radicals has proven difficult. However, isooctyl peroxy is easily distinguished and the observation of the tertiary peroxy radical along with the primary and/or secondary peroxy radical(s) is discussed.

  12. Modeling aftershocks as a stretched exponential relaxation (United States)

    Mignan, A.


    The decay rate of aftershocks has been modeled as a power law since the pioneering work of Omori in the late nineteenth century. Although other expressions have been proposed in recent decades to describe the temporal behavior of aftershocks, the number of model comparisons remains limited. After reviewing the aftershock models published from the late nineteenth century until today, I solely compare the power law, pure exponential and stretched exponential expressions defined in their simplest forms. By applying statistical methods recommended recently in applied mathematics, I show that all aftershock sequences tested in three regional earthquake catalogs (Southern and Northern California, Taiwan) and with three declustering techniques (nearest-neighbor, second-order moment, window methods) follow a stretched exponential instead of a power law. These results infer that aftershocks are due to a simple relaxation process, in accordance with most other relaxation processes observed in Nature.

  13. The role of stretching in tendon injuries. (United States)

    Witvrouw, E; Mahieu, N; Roosen, P; McNair, P


    The function of tendons can be classified into two categories: tensile force transmission, and storage and release of elastic energy during locomotion. The action of tendons in storing and releasing energy is mainly seen in sports activities with stretch-shortening cycles (SSCs). The more intense the SSC movements are (jumping-like activities), the more frequently tendon problems are observed. High SSC movements impose high loads on tendons. Consequently, tendons that frequently deal with high SSC motion require a high energy-absorbing capacity to store and release this large amount of elastic energy. As the elasticity of tendon structures is a leading factor in the amount of stored energy, prevention and rehabilitation programmes for tendon injuries should focus on increasing this tendon elasticity in athletes performing high SSC movements. Recently, it has been shown that ballistic stretching can significantly increase tendon elasticity. These findings have important clinical implications for treatment and prevention of tendon injuries.

  14. How the Cloud Stretches the SOA Scope

    Directory of Open Access Journals (Sweden)

    Lakshmanan G


    Full Text Available In this article, we will describe how the enterprise serviceoriented-architecture (SOA scope is stretched with the advent of cloud computing. With the help of the case study of a fictitious global retailer, we will demonstrate the process for identifying cloud scenarios. Also, we will come across an emerging breed of distributed applications—both on-premise and in the Cloud—and discuss the integration considerations for building them.

  15. Ideal-Chain Collapse in Biopolymers

    CERN Document Server

    Neumann, R M


    A conceptual difficulty in the Hooke's-law description of ideal Gaussian polymer-chain elasticity is sometimes apparent in analyses of experimental data or in physical models designed to simulate the behavior of biopolymers. The problem, the tendency of a chain to collapse in the absence of external forces, is examined in the following examples: DNA-stretching experiments, gel electrophoresis, and protein folding. We demonstrate that the application of a statistical-mechanically derived repulsive force, acting between the chain ends, whose magnitude is proportional to the absolute temperature and inversely proportional to the scalar end separation removes this difficulty.

  16. Dynamics and structure of stretched flames

    Energy Technology Data Exchange (ETDEWEB)

    Law, C.K. [Princeton Univ., NJ (United States)


    This program aims to gain fundamental understanding on the structure, geometry, and dynamics of laminar premixed flames, and relate these understanding to the practical issues of flame extinction and stabilization. The underlying fundamental interest here is the recent recognition that the response of premixed flames can be profoundly affected by flame stretch, as manifested by flow nonuniformity, flame curvature, and flame/flow unsteadiness. As such, many of the existing understanding on the behavior of premixed flames need to be qualitatively revised. The research program consists of three major thrusts: (1) detailed experimental and computational mapping of the structure of aerodynamically-strained planar flames, with emphasis on the effects of heat loss, nonequidiffusion, and finite residence time on the flame thickness, extent of incomplete reaction, and the state of extinction. (2) Analytical study of the geometry and dynamics of stretch-affected wrinkled flame sheets in simple configurations, as exemplified by the Bunsen flame and the spatially-periodic flame, with emphasis on the effects of nonlinear stretch, the phenomena of flame cusping, smoothing, and tip opening, and their implications on the structure and burning rate of turbulent flames. (3) Stabilization and blowoff of two-dimensional inverted premixed and stabilization and determining the criteria governing flame blowoff. The research is synergistically conducted through the use of laser-based diagnostics, computational simulation of the flame structure with detailed chemistry and transport, and mathematical analysis of the flame dynamics.

  17. Gravity Waves from Chain Inflation

    CERN Document Server

    Ashoorioon, Amjad


    Chain inflation proceeds through a series of first order phase transitions, which can release considerable gravitational waves (GW). We demonstrate that bubble collisions can leave an observable signature for future high-frequency probes of GWs, such as advanced LIGO, LISA and BBO. A "smoking gun" for chain inflation would be wiggles in the spectrum (and consequently in the tensor spectral index) due to the multiple phase transitions. The spectrum could also be distinguished from a single first order phase transition by a small difference in the amplitude at low frequency. A second origin of GWs in chain inflation are tensor modes from quantum fluctuations; these GW can dominate and be observed on large scales. The consistency relation between scalar and tensor modes is different for chain inflation than for standard rolling models and is testable by Cosmic Microwave Background experiments. If inflation happened through a series of rapid tunnelings in the string landscape, future high frequency probes of GW c...

  18. Time-domain analysis of sub-micron transit region GaAs Gunn diodes for use in terahertz frequency multiplication chains (United States)

    Amir, F.; Farrington, N.; Mitchell, C.; Missous, M.


    Simulated RF time-domain characteristics for advanced Gunn diodes with hot electron injection and sub-micron transit region lengths for use at frequencies over 100GHz are reported. The physical models used have been developed in SILVACO and are compared to measured results. The devices measured were originally fabricated to investigate the feasibility of GaAs Gunn diode oscillators capable of operating at D-band frequencies and ultimately intended for use in high power (multi-mW) Terahertz sources (~0.6THz) when used in conjunction with novel Schottky diode frequency multiplier technology. The device models created using SILVACO are described and the DC and time-domain results presented. The simulations were used to determine the shortest transit region length capable of producing sustained oscillation. The operation of resonant disk second harmonic Gunn diode oscillators is also discussed and accurate electromagnetic models created using Ansoft High Frequency Structure Simulator presented. Novel methods for combining small-signal frequency-domain electromagnetic simulations with time-domain device simulations in order to account for the significant interactions between the diode and oscillator circuit are described.

  19. Effects of stretch and shortening on gene expression in intact myocardium. (United States)

    Haggart, Charles R; Ames, Elizabeth G; Lee, Jae K; Holmes, Jeffrey W


    Multiple cues have been suggested as the mechanical stimulus for the heart's hypertrophic response. Our work has previously suggested that the amount of cyclic shortening in cardiomyocytes controls myocyte shape and the amount of stretch controls myocyte size. To identify gene expression changes that occur in response to these mechanical perturbations, we used microarray analysis of papillary muscles cultured for 12 h at physiological or reduced levels of cyclic shortening and physiological or reduced mean stretch. Overall, genes related to extracellular matrix (ECM) were surprisingly prominent in our analysis. Connective tissue growth factor was among a small group of genes regulated by the amount of cyclic shortening regardless of the level of mean stretch, and many more ECM genes were regulated by shortening with reduced amounts of stretch. When we compared our results to gene expression data from an in vivo model of pressure overload (PO), which also decreases myocyte shortening, we found the genes that were commonly regulated in PO and our decreased shortening groups were most significantly enriched for ontology terms related to the ECM, followed by genes associated with mechanosensing and the cytoskeleton. The list of genes regulated in PO and our decreased shortening groups also includes genes known to change early in hypertrophy, such as myosin heavy chain 7, brain natriuretic peptide, and myosin binding protein C. We conclude that in intact myocardium, the amount of cyclic shortening may be an important regulator not only of myocyte genes classically associated with hypertrophy but also of ECM genes.

  20. Inducing uniform single-crystal like orientation in natural rubber with constrained uniaxial stretch. (United States)

    Zhou, Weiming; Meng, Lingpu; Lu, Jie; Wang, Zhen; Zhang, Wenhua; Huang, Ningdong; Chen, Liang; Li, Liangbin


    The effect of flow on crystallization is commonly attributed to entropic reduction, which is caused by stretch and orientation of polymer chains but overlooks the role of flow on final-state free energy. With the aid of in situ synchrotron radiation wide-angle X-ray diffraction (WAXD) and a homemade constrained uniaxial tensile testing machine, polycrystals possessing single-crystal-like orientation rather than uniaxial orientation are found during the constrained stretch of natural rubber, whereas the c-axis and a-axis align in the stretch direction (SD) and constrained direction (CD), respectively. Molecular dynamics simulation shows that aligning the a-axis of crystal nuclei in CD leads to the lowest free energy increase and favors crystal nucleation. This indicates that the nomenclature of strain-induced crystallization may not fully account for the nature of flow-induced crystallization (FIC) as strain mainly emphasizes the entropic reduction of initial melt, whereas stress rather than strain plays the dominant role in crystal deformation. The current work not only contributes to a comprehensive understanding of the mechanism of flow-induced crystallization but also demonstrates the potential application of constrained uniaxial tensile stretch for the creation of functional materials containing polycrystals that possess single-crystal-like orientation.


    Directory of Open Access Journals (Sweden)

    N. Vamsidhar


    Full Text Available Background: Flexibility is important in prevention of injury, muscular and postural imbalance more over the Hamstring flexibility has a lion share in sports performances and preventing DOMS. Stretching procedures increases the ROM by embarking on biomechanics and Neurologic and molecular mechanics. Hamstrings, the two joint muscle plays a crucial role in two joints integrity and also spine as they are in closed kinematic chain. The hamstring muscles represent the primary flexors of Knee. Hamstrings tightness results in Limits Knee extension when hip is flexed, Posterior Pelvic tilt, and flatten the lumbar spine. Methods: The subjects selected randomly and divided into two groups (Experimental group and control group.30 samples in One group applied with Static Stretch once a day for 3 repetitions 5 days a week for six weeks and 30 samples in other group applied with Hold relax technique once a day for 4 repetitions 5 days a week for six weeks. The knee joint range of motion was measured at the end of every week with Universal goniometer. Results: By comparing the means of Group – I, given Static Stretch and Group – II, given Hold relax Technique for six weeks implied that there is improvement of flexibility in Group – II and the ‘P’ value < 0.01 shows the difference is highly significant. Conclusion: This study concludes that the hold relax Technique method has proved to be better technique then the static stretch for improving hamstring flexibility.


    Institute of Scientific and Technical Information of China (English)

    Shao-feng Ran; Mao Xu


    The pore formation mechanism of β-crystalline polypropylene under stretching was investigated. The porosity of the samples increases rapidly with stretching, having a maximum at draw ratios around 2 and then decreases monotonically.An abrupt formation process of initial micropores at very low draw ratios was evidenced by in situ SAXS measurements. At the same time the phase transition from β-crystal to a-crystal proceeds slowly in the whole deformation process up to large draw ratios around 5. Comparative studies of a- and β-crystalline polypropylene samples before stretching indicate that in addition to difference in crystal forms the a- and β-crystalline polypropylene samples exhibit quite different morphological features. There are a lot of interfaces in β-crystalline polypropylene samples, which may have a lower density value and can be easily etched by argon ions and penetrated by small molecules. It was concluded from these experimental facts that the pore formation and crystal transition are two independent phenomena during the deformation of β-crystalline polypropylene samples, and phase transition from β-crystal to a-crystal could hardly be the origin of pore formation. A defect initiation mechanism was proposed to understand the pore formation behavior of β-crystalline polypropylenes.

  3. Unwrapping Chains

    CERN Document Server

    Cambou, A D; Hamm, E; Hanna, J A; Menon, N; Santangelo, C D; Walsh, L


    A loop of chain can move along its own tangents, maintaining a steady shape. An open-ended chain undergoing a nontrivial motion must change its shape. One consequence is that chains pulled around objects will fail to follow the contours of the objects, unwrapping themselves instead. This short note accompanies a fluid dynamics video submission (83068) to the APS DFD Gallery of Fluid Motion 2012.

  4. Falling chains

    CERN Document Server

    Wong, C W; Wong, Chun Wa; Yasui, Kosuke


    The one-dimensional falling motion of a bungee chain suspended from a rigid support and of a chain falling from a resting heap on a table is studied. Their Lagrangians are found to contain no explicit time dependence. As a result, these falling chains are conservative systems. Each of their Lagrange's equations of motion is shown to contain a term that enforces energy conservation when masses are transferred between subchains. We show in particular that Cayley's 1857 energy nonconserving solution for a chain falling from a resting heap is incorrect because it neglects the energy gained when the transferred link is emitted by the emitting subchain. The maximum chain tension measured by Calkin and March for the falling bungee chain is given a simple if rough interpretation. In the simplified one-dimensional treatment, the kinetic energy of the center of mass of the falling bungee chain is found to be converted by the chain tension at the rigid support into the internal kinetic energy of the chain. However, as t...

  5. Experimental Characterization of Stretch-Bending Formability of AHSS Sheets (United States)

    Kitting, Daniela; Ofenheimer, Aldo; Pauli, Heinrich; Till, Edwin T.


    Deformation conditions of combined stretching and bending are known to enhance material formability compared to forming conditions without bending (e.g. in-plane stretching). These phenomena can be observed for most conventional steel grades but is even more pronounced for Advanced High Strength Steel (AHSS) sheets. Consequently, there is an urgent need in industry to quantify the phenomena of enhanced material formability due to bending effects. In this work new stretch-bend test setups are presented which can be used in addition to the conventional Angular Stretch Bend Test to systematically investigate the influence of various stretch-bending deformation conditions on the formability of AHSS sheets.

  6. Consistency and Refinement for Interval Markov Chains

    DEFF Research Database (Denmark)

    Delahaye, Benoit; Larsen, Kim Guldstrand; Legay, Axel;


    Interval Markov Chains (IMC), or Markov Chains with probability intervals in the transition matrix, are the base of a classic specification theory for probabilistic systems [18]. The standard semantics of IMCs assigns to a specification the set of all Markov Chains that satisfy its interval...

  7. The Relevance of Stretch Intensity and Position: A Systematic Review

    Directory of Open Access Journals (Sweden)

    Nikos eApostolopoulos


    Full Text Available Stretching exercises to increase the range of motion (ROM of joints have been used by sports coaches and medical professionals for improving performance and rehabilitation. The ability of connective and muscular tissues to change their architecture in response to stretching is important for their proper function, repair and performance. Given the dearth of relevant data in the literature, this review examined two key elements of stretching: stretch intensity and stretch position; and their significance to ROM, delayed onset muscle soreness (DOMS, and inflammation in different populations. A search of three databases, Pub-Med, Google Scholar, and Cochrane Reviews, identified 152 articles, which were subsequently categorized into four groups; athletes (n = 24, clinical (n = 29, elderly (n = 12, and general population (n = 87. The use of different populations facilitated a wider examination of the stretching components and their effects. All 152 articles incorporated information regarding duration, frequency and stretch position, whereas only 79 referred to the intensity of stretching and 22 of these 79 studies were deemed high quality. It appears that the intensity of stretching is relatively under-researched, and the importance of body position and its influence on stretch intensity, is largely unknown. In conclusion, this review has highlighted areas for future research, including stretch intensity and position and their effect on musculo-tendinous tissue, in relation to the sensation of pain, delayed onset muscle soreness, inflammation, as well as muscle health and performance

  8. Does residual force enhancement increase with increasing stretch magnitudes? (United States)

    Hisey, Brandon; Leonard, Tim R; Herzog, Walter


    It is generally accepted that force enhancement in skeletal muscles increases with increasing stretch magnitudes. However, this property has not been tested across supra-physiological stretch magnitudes and different muscle lengths, thus it is not known whether this is a generic property of skeletal muscle, or merely a property that holds for small stretch magnitudes within the physiological range. Six cat soleus muscles were actively stretched with magnitudes varying from 3 to 24 mm at three different parts of the force-length relationship to test the hypothesis that force enhancement increases with increasing stretch magnitude, independent of muscle length. Residual force enhancement increased consistently with stretch amplitudes on the descending limb of the force-length relationship up to a threshold value, after which it reached a plateau. Force enhancement did not increase with stretch amplitude on the ascending limb of the force-length relationship. Passive force enhancement was observed for all test conditions, and paralleled the behavior of the residual force enhancement. Force enhancement increased with stretch magnitude when stretching occurred at lengths where there was natural passive force within the muscle. These results suggest that force enhancement does not increase unconditionally with increasing stretch magnitude, as is generally accepted, and that increasing force enhancement with stretch appears to be tightly linked to that part of the force-length relationship where there is naturally occurring passive force.

  9. Effects of cervical self-stretching on slow vital capacity. (United States)

    Han, Dongwook; Yoon, Nayoon; Jeong, Yeongran; Ha, Misook; Nam, Kunwoo


    [Purpose] This study investigated the effects of self-stretching of cervical muscles, because the accessory inspiratory muscle is considered to improve pulmonary function. [Subjects] The subjects were 30 healthy university students 19-21 years old who did not have any lung disease, respiratory dysfunction, cervical injury, or any problems upon cervical stretching. [Methods] Spirometry was used as a pulmonary function test to measure the slow vital capacity before and after stretching. The slow vital capacity of the experimental group was measured before and after cervical self-stretching. Meanwhile, the slow vital capacity of the control group, which did not perform stretching, was also measured before and after the intervention. [Results] The expiratory vital capacity, inspiratory reserve volume, and expiratory reserve volume of the experimental group increased significantly after the cervical self-stretching. [Conclusion] Self-stretching of the cervical muscle (i.e., the inspiratory accessory muscle) improves slow vital capacity.

  10. Refolding dynamics of stretched biopolymers upon force quench (United States)

    Hyeon, Changbong; Morrison, Greg; Pincus, David L.; Thirumalai, D.


    Single-molecule force spectroscopy methods can be used to generate folding trajectories of biopolymers from arbitrary regions of the folding landscape. We illustrate the complexity of the folding kinetics and generic aspects of the collapse of RNA and proteins upon force quench by using simulations of an RNA hairpin and theory based on the de Gennes model for homopolymer collapse. The folding time, τF, depends asymmetrically on δfS = f S − f m and δf Q = f m − f Q where f S (f Q) is the stretch (quench) force and f m is the transition midforce of the RNA hairpin. In accord with experiments, the relaxation kinetics of the molecular extension, R(t), occurs in three stages: A rapid initial decrease in the extension is followed by a plateau and finally, an abrupt reduction in R(t) occurs as the native state is approached. The duration of the plateau increases as λ = τ Q/τ F decreases (where τ Q is the time in which the force is reduced from f S to f Q). Variations in the mechanisms of force-quench relaxation as λ is altered are reflected in the experimentally measurable time-dependent entropy, which is computed directly from the folding trajectories. An analytical solution of the de Gennes model under tension reproduces the multistage stage kinetics in R(t). The prediction that the initial stages of collapse should also be a generic feature of polymers is validated by simulation of the kinetics of toroid (globule) formation in semiflexible (flexible) homopolymers in poor solvents upon quenching the force from a fully stretched state. Our findings give a unified explanation for multiple disparate experimental observations of protein folding. PMID:19915145

  11. 基于"Stretching"技术的QPSO算法%QPSO Algorithm Based on Stretching Technique

    Institute of Scientific and Technical Information of China (English)

    于敏; 孙俊; 须文波; 江家宝



  12. Experimental realization of suspended atomic chains composed of different atomic species

    Energy Technology Data Exchange (ETDEWEB)

    Bettini, Jefferson; Ugarte, Daniel [Laboratorio Nacional de Luz Sincrotron (LNLS), Campinas, SP (Brazil); Sato, Fernando; Galvao, Douglas Soares [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Inst. de Fisica Gleb Wataghin; Coura, Pablo Zimmerman; Dantas, Socrates de Oliveira [Universidade Federal de Juiz de Fora (UFJF), MG (Brazil). Inst. de Ciencias Exatas. Dept. de Fisica


    We report high resolution transmission electron microscopy (HRTEM) and molecular dynamics results of the first experimental test of suspended atomic chains composed of different atomic species formed from spontaneous stretching of metallic nanowires. (author)

  13. The effect of chain bending on the photophysical properties of conjugated polymers. (United States)

    Hestand, Nicholas J; Spano, Frank C


    The impact of chain bending on the photophysical properties of emissive conjugated polymers (CPs) is studied theoretically using Holstein-style Hamiltonians which treat vibronic coupling involving the ubiquitous vinyl/ring stretching mode nonadiabatically. The photophysical impact of chain bending is already evident at the level of an effective Frenkel Hamiltonian, where the positive exciton band curvature in CPs translates to negative excitonic coupling between monomeric units, as in J-aggregates. It is shown that the absorption and photoluminescence (PL) spectral line shapes respond very differently to chain bending. The misalignment of monomeric transition dipole moments with bending selectively attenuates the 0-0 PL peak intensity while leaving the 0-1 intensity practically unchanged, a property which is ultimately due to the uniquely coherent nature of the 0-0 peak. Hence, the 0-0/0-1 PL ratio, as well as the radiative decay rate, decrease with chain bending, effects that are more pronounced at lower temperatures where exciton coherence extends over a larger portion of the chain. Increasing temperature and/or static disorder reduces the exciton coherence number, Ncoh, thereby reducing the sensitivity to bending. In marked contrast, the absorption vibronic progression is far less sensitive to morphological changes, even at low temperatures, and is mainly responsive to the exciton bandwidth. The above results also hold when using a more accurate 1D semiconductor Hamiltonian which allows for electron-hole separation along the CP chain. The findings may suggest unique ways of controlling the radiative properties of conjugated polymer chains useful in applications such as organic light emitting diodes (OLEDs) and low-temperature sensors.

  14. Establishment and evaluation of a multi-system chain transitional care programme for postpartum pelvic floor training%产后盆底功能训练的延续护理模式构建及效果评价

    Institute of Scientific and Technical Information of China (English)

    霍然; 王惠珍; 石兰萍; 张巍颖; 吴震云; 陈学丽


    Objective To build a multi-system chain transitional care programme for postpartum pelvic floor training and test its effect.Methods By a prospective randomized controlled trial,the study group (n=60) received a multi-system chain transitional care programme which consisted of ward nurse,home visiting doctor,post-natal care clinic doctor,pelvic floor doctor and pelvic floor nurse.The control group(n=60) received routine care.The pelvic floor muscle strength,sexual function and patient satisfaction of baseline,on the 42th days,3rd months and 6th months were compared between two groups by short-term follow-up.Results There was no difference in baseline consisting of age,gestational weeks,birth weight and so on between groups.Participants in the study group had significantly better improvement and score in pelvic floor muscle strength,sexual thoughts,sexual arousal,sexual psychopathy and problems affecting sexual function.There was no difference in score of sexual pleasure and ejaculation time between two groups.Conclusions This study was an original effort to establish and evaluate a multi-system chain transitional care program for postpartum pelvic floor training.Results demonstrated that this transitional care was effective in improving pelvic floor function.%目的 构建产后盆底功能训练的延续护理模式并检验其效果.方法 采用前瞻性随机对照实验,延续护理60例接受病房责任护士-家庭访视医生-产后保健门诊医生-盆底诊疗中心医生-盆底诊疗中心护士构成的延续护理服务,对照组60例接受传统护理服务.随访和比较2组的基线情况,42 d、3个月和6个月盆底肌肌力、性功能和患者满意度.结果 2组在年龄、孕周、新生儿体质量等基线情况上比较差异无统计学意义.延续护理组在盆底肌肌力改善、性欲、性唤起、性心理和性行为异常症状上得分,以及患者满意度均优于对照组,差异有统计学意义.2组在性高潮和性

  15. Finite stretching of an annular plate. (United States)

    Biricikoglu, V.; Kalnins, A.


    The problem of the finite stretching of an annular plate which is bonded to a rigid inclusion at its inner edge is considered. The material is assumed to be isotropic and incompressible with a Mooney-type constitutive law. It is shown that the inclusion of the effect of the transverse normal strain leads to a rapid variation in thickness which is confined to a narrow edge zone. The explicit solutions to the boundary layer equations, which govern the behavior of the plate near the edges, are presented.

  16. Wind effects on a stretched membrane heliostat

    Energy Technology Data Exchange (ETDEWEB)

    Bienkiewicz, B. (Colorado State Univ., Fort Collins, CO (United States). Dept. of Civil Engineering)


    Wind effects on stretched membrane heliostat were investigated in a boundary layer wind tunnel. The membrane response was measured at stow and representative operational conditions. It was found that both at the stow and operational conditions the mean response was much higher than the rms response. At stow conditions the largest response occurred near the leading edge of the membrane, while the rms response was the largest at the membrane center point. For the operational conditions, the largest mean and rms responses were found at the membrane centerpoint. The membrane response was significantly reduced by the membrane focusing induced through the internal underpressure.

  17. Force-clamp analysis techniques reveal stretched exponential unfolding kinetics in ubiquitin

    CERN Document Server

    Lannon, Herbert; Brujic, Jasna


    Force-clamp spectroscopy reveals the unfolding and disulfide bond rupture times of single protein molecules as a function of the stretching force, point mutations and solvent conditions. The statistics of these times reveal whether the protein domains are independent of one another, the mechanical hierarchy in the polyprotein chain, and the functional form of the probability distribution from which they originate. It is therefore important to use robust statistical tests to decipher the correct theoretical model underlying the process. Here we develop multiple techniques to compare the well-established experimental data set on ubiquitin with existing theoretical models as a case study. We show that robustness against filtering, agreement with a maximum likelihood function that takes into account experimental artifacts, the Kuiper statistic test and alignment with synthetic data all identify the Weibull or stretched exponential distribution as the best fitting model. Our results are inconsistent with recently ...

  18. Polarized actin structural dynamics in response to cyclic uniaxial stretch (United States)

    Huang, Lawrence; Helmke, Brian P.


    Endothelial cell (EC) alignment to directional flow or stretch supports anti-inflammatory functions, but mechanisms controlling polarized structural adaptation in response to physical cues remain unclear. This study aimed to determine whether factors associated with early actin edge ruffling implicated in cell polarization are prerequisite for stress fiber (SF) reorientation in response to cyclic uniaxial stretch. Time-lapse analysis of EGFP-actin in confluent ECs showed that onset of either cyclic uniaxial or equibiaxial stretch caused a non-directional increase in edge ruffling. Edge activity was concentrated in a direction perpendicular to the stretch axis after 60 min, consistent with the direction of SF alignment. Rho-kinase inhibition caused reorientation of both stretch-induced edge ruffling and SF alignment parallel to the stretch axis. Arp2/3 inhibition attenuated stretch-induced cell elongation and disrupted polarized edge dynamics and microtubule organizing center reorientation, but it had no effect on the extent of SF reorientation. Disrupting localization of p21-activated kinase (PAK) did not prevent stretch-induced SF reorientation, suggesting that this Rac effector is not critical in regulating stretch-induced cytoskeletal remodeling. Overall, these results suggest that directional edge ruffling is not a primary mechanism that guides SF reorientation in response to stretch; the two events are coincident but not causal. PMID:25821527

  19. Curved Piezoelectric Actuators for Stretching Optical Fibers (United States)

    Allison, Sidney G.; Shams, Qamar A.; Fox, Robert L.


    Assemblies containing curved piezoceramic fiber composite actuators have been invented as means of stretching optical fibers by amounts that depend on applied drive voltages. Piezoceramic fiber composite actuators are conventionally manufactured as sheets or ribbons that are flat and flexible, but can be made curved to obtain load-carrying ability and displacement greater than those obtainable from the flat versions. In the primary embodiment of this invention, piezoceramic fibers are oriented parallel to the direction of longitudinal displacement of the actuators so that application of drive voltage causes the actuator to flatten, producing maximum motion. Actuator motion can be transmitted to the optical fiber by use of hinges and clamp blocks. In the original application of this invention, the optical fiber contains a Bragg grating and the purpose of the controlled stretching of the fiber is to tune the grating as part of a small, lightweight, mode-hop-free, rapidly tunable laser for demodulating strain in Bragg-grating strain-measurement optical fibers attached to structures. The invention could also be used to apply controllable tensile force or displacement to an object other than an optical fiber.

  20. Rounded stretched exponential for time relaxation functions. (United States)

    Powles, J G; Heyes, D M; Rickayzen, G; Evans, W A B


    A rounded stretched exponential function is introduced, C(t)=exp{(tau(0)/tau(E))(beta)[1-(1+(t/tau(0))(2))(beta/2)]}, where t is time, and tau(0) and tau(E) are two relaxation times. This expression can be used to represent the relaxation function of many real dynamical processes, as at long times, t>tau(0), the function converges to a stretched exponential with normalizing relaxation time, tau(E), yet its expansion is even or symmetric in time, which is a statistical mechanical requirement. This expression fits well the shear stress relaxation function for model soft soft-sphere fluids near coexistence, with tau(E)Cole-Cole plots for dielectric and shear stress relaxation (both the modulus and viscosity forms). It is shown that both the dielectric spectra and dynamic shear modulus imaginary parts approach the real axis with a slope equal to 0 at high frequency, whereas the dynamic viscosity has an infinite slope in the same limit. This indicates that inertial effects at high frequency are best discerned in the modulus rather than the viscosity Cole-Cole plot. As a consequence of the even expansion in time of the shear stress relaxation function, the value of the storage modulus derived from it at very high frequency exceeds that in the infinite frequency limit (i.e., G(infinity)).

  1. Stretching and relaxation of malaria-infected red blood cells. (United States)

    Ye, Ting; Phan-Thien, Nhan; Khoo, Boo Cheong; Lim, Chwee Teck


    The invasion of red blood cells (RBCs) by malaria parasites is a complex dynamic process, in which the infected RBCs gradually lose their deformability and their ability to recover their original shape is greatly reduced with the maturation of the parasites. In this work, we developed two types of cell model, one with an included parasite, and the other without an included parasite. The former is a representation of real malaria-infected RBCs, in which the parasite is treated as a rigid body. In the latter, where the parasite is absent, the membrane modulus and viscosity are elevated so as to produce the same features present in the parasite model. In both cases, the cell membrane is modeled as a viscoelastic triangular network connected by wormlike chains. We studied the transient behaviors of stretching deformation and shape relaxation of malaria-infected RBCs based on these two models and found that both models can generate results in agreement with those of previously published studies. With the parasite maturation, the shape deformation becomes smaller and smaller due to increasing cell rigidity, whereas the shape relaxation time becomes longer and longer due to the cell's reduced ability to recover its original shape.

  2. The relation between stretched-exponential relaxation and the vibrational density of states in glassy disordered systems (United States)

    Cui, Bingyu; Milkus, Rico; Zaccone, Alessio


    Amorphous solids or glasses are known to exhibit stretched-exponential decay over broad time intervals in several of their macroscopic observables: intermediate scattering function, dielectric relaxation modulus, time-dependent elastic modulus, etc. This behaviour is prominent especially near the glass transition. In this Letter we show, on the example of dielectric relaxation, that stretched-exponential relaxation is intimately related to the peculiar lattice dynamics of glasses. By reformulating the Lorentz model of dielectric matter in a more general form, we express the dielectric response as a function of the vibrational density of states (DOS) for a random assembly of spherical particles interacting harmonically with their nearest-neighbours. Surprisingly we find that near the glass transition for this system (which coincides with the Maxwell rigidity transition in this model), the dielectric relaxation is perfectly consistent with stretched-exponential behaviour with Kohlrausch exponents 0.56 stretched-exponential relaxation can be traced back to soft modes (boson-peak) in the DOS.

  3. Effects of stretching the scalene muscles on slow vital capacity. (United States)

    Lee, Juncheol; Hwang, Sehee; Han, Seungim; Han, Dongwook


    [Purpose] The purpose of this study was to examine whether stretching of the scalene muscles would improve slow vital capacity (SVC). [Subjects and Methods] The subjects of this study were 20 healthy female students to whom the study's methods and purpose were explained and their agreement for participation was obtained. The SVC was measured using spirometry (Pony FX, COSMED Inc., Italy). The intervention used was stretching of the scalene muscles. Stretching was carried out for 15 min, 10 times at per each portion of scalene muscles: the anterior, middle, and posterior parts. [Results] Expiratory vital capacity (EVC) and tidal volume (Vt) noticeably increased after stretching. However, there were no changes in any of the SVC items in the control group. [Conclusion] This study demonstrated that stretching of the scalene muscles can effectively improve SVC. In particular, we confirmed that stretching of the scalene muscles was effective in increasing EVC and Vt, which are items of SVC.

  4. Effects of stretching the scalene muscles on slow vital capacity (United States)

    Lee, Juncheol; Hwang, Sehee; Han, Seungim; Han, Dongwook


    [Purpose] The purpose of this study was to examine whether stretching of the scalene muscles would improve slow vital capacity (SVC). [Subjects and Methods] The subjects of this study were 20 healthy female students to whom the study’s methods and purpose were explained and their agreement for participation was obtained. The SVC was measured using spirometry (Pony FX, COSMED Inc., Italy). The intervention used was stretching of the scalene muscles. Stretching was carried out for 15 min, 10 times at per each portion of scalene muscles: the anterior, middle, and posterior parts. [Results] Expiratory vital capacity (EVC) and tidal volume (Vt) noticeably increased after stretching. However, there were no changes in any of the SVC items in the control group. [Conclusion] This study demonstrated that stretching of the scalene muscles can effectively improve SVC. In particular, we confirmed that stretching of the scalene muscles was effective in increasing EVC and Vt, which are items of SVC. PMID:27390425

  5. Análise da transição entre dias secos e chuvosos por meio da cadeia de Markov de terceira ordem Analysis of the transition between dry and wet days through third-order Markov chains

    Directory of Open Access Journals (Sweden)

    Thadeu Keller Filho


    Full Text Available O objetivo deste trabalho foi verificar se as ocorrências de dias secos e chuvosos são condicionalmente dependentes da seqüência dos três dias secos e chuvosos anteriores, numa zona pluviometricamente homogênea, por meio da cadeia não-homogênea de Markov de terceira ordem. Os resultados mostraram que as probabilidades diárias de transição podem ser adequadamente estimadas, com base em dados agregados bimestralmente, seguidas de interpolação por meio de funções sinusoidais. Além disso, evidenciou-se que, naquela zona, as ocorrências diárias de chuva são condicionalmente dependentes da seqüência de dias secos e chuvosos nos três dias anteriores. A cadeia não-homogênea de Markov de terceira ordem é um importante instrumento para a análise da dependência entre as seqüências de dias secos e chuvosos em determinadas regiões.The aim of this work was to verify if the occurrence of dry and wet days are conditionally dependent on the sequences of the dry and wet three preceding days, in a rainfall homogeneous area, using the nonhomogeneous third-order Markov chains. The results showed that daily transition probabilities can be properly estimated from two-month aggregate data, and then adjusted by means of sinusoidal functions. Besides, it was evidenced that everyday rain events in that area are conditionally dependent on the sequences of the dry and wet three days previous to occurrences. The third-order nonhomogeneous Markov chains are an important instrument for the analysis of the dependence between sequences of dry and wet days in certain areas.

  6. Effects of three different stretching techniques on vertical jumping performance. (United States)

    Kirmizigil, Berkiye; Ozcaldiran, Bahtiyar; Colakoglu, Muzaffer


    The aim of this study was to evaluate 3 different flexibility techniques: (a) ballistic stretching (BS), (b) proprioceptive neuromuscular facilitation stretching (PNF) + BS, and (c) PNF + static stretching (SS) on vertical jump (VJ) performance and to determine the most appropriate stretching method during warm-up period before explosive force disciplines. One hundred voluntary male athletes participated in this study. All subjects performed aerobic warm-up (5-minute jog) followed by BS (5 seconds for each stretching exercise), PNF + BS (PNF performed followed by 5 seconds of BS), and PNF + SS (PNF performed followed by 30 seconds of SS) treatment protocol, respectively in the same day. Each stretching treatment was applied for 4 sets bilaterally. In all stretching treatments, lumbar extensor, gluteus maximus, and hamstring muscles were stretched with a single stretching exercise. After a 2-minute brief rest period, participants performed 3 trials of VJ test followed by one of the treatment protocols. Vertical jump performance was evaluated by countermovement jump (CMJ). Participants were divided into 3 groups according to their flexibility and prejump performances after warm-up. For each individual group and the whole group, after all treatments, differences in CMJ values were obtained (p ≤ 0.05). Ballistic stretching increased the VJ performance in the groups with low and average flexibility, poor prejumping performance, and also in the whole group (p ≤ 0.05). Proprioceptive neuromuscular facilitation stretching + BS affected VJ performance in the group of participants with high flexibility (p ≤ 0.05). Proprioceptive neuromuscular facilitation + SS decreased VJ performance in groups of participants with high flexibility, moderate, and high prejumping performance and in whole group (p ≤ 0.05). Ballistic stretching method increased VJ height, therefore seems to be more suitable than PNF + SS and PNF + BS before events that rely on explosive power as a part

  7. The Process Analysis of the Roller Stretching for Wool Slenderization

    Institute of Scientific and Technical Information of China (English)

    刘洪玲; 于伟东; 章悦庭


    A theoretical estimation for the multiple-drawing has been derived under the consideration of fiber length distribution for the wool fiber stretching system. The functions of the roller drawing system and the parameters in stretching process have also been analyzed. The theoretical algorithms have been verified by the experimental results and can be used for the estimation of fiber length and its distribution after the stretching.

  8. Acute effect of different stretching methods on isometric muscle strength


    Gabriel Vasconcellos de Lima Costa e Silva; Anderson Luiz Bezerra da Silveira; Fabrízio Di Masi; Cláudio Melibeu Bentes; Maria do Socorro Cirilo de Sousa; Jefferson da Silva Novaes

    2014-01-01 This study investigated the acute effect of static stretching methods (SS) and proprioceptive neuromuscular facilitation (PNF) on the static muscle strength (SMS). Eleven young male subjects with strength training experience, performed 3 tests with a 48h interval between them, randomly selected, where each one subject carried out all procedures: a) hand grip without stretching; b) hand grip preceded by static stretching of wrist flexor...

  9. Effects of stretching the scalene muscles on slow vital capacity


    Lee, Juncheol; Hwang, Sehee; Han, Seungim; Han, Dongwook


    [Purpose] The purpose of this study was to examine whether stretching of the scalene muscles would improve slow vital capacity (SVC). [Subjects and Methods] The subjects of this study were 20 healthy female students to whom the study’s methods and purpose were explained and their agreement for participation was obtained. The SVC was measured using spirometry (Pony FX, COSMED Inc., Italy). The intervention used was stretching of the scalene muscles. Stretching was carried out for 15 min, 10 ti...

  10. Effects of cervical self-stretching on slow vital capacity


    Han, Dongwook; Yoon, Nayoon; Jeong, Yeongran; Ha, Misook; Nam, Kunwoo


    [Purpose] This study investigated the effects of self-stretching of cervical muscles, because the accessory inspiratory muscle is considered to improve pulmonary function. [Subjects] The subjects were 30 healthy university students 19–21 years old who did not have any lung disease, respiratory dysfunction, cervical injury, or any problems upon cervical stretching. [Methods] Spirometry was used as a pulmonary function test to measure the slow vital capacity before and after stretching. The slo...

  11. Cyclic stretch induces upregulation of endothelin-1 with keratinocytes in vitro: Possible role in mechanical stress-induced hyperpigmentation

    Energy Technology Data Exchange (ETDEWEB)

    Kurita, Masakazu, E-mail: [Department of Plastic Surgery, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka-shi, Tokyo 181-8611 (Japan); Okazaki, Mutsumi [Department of Plastic and Reconstructive Surgery, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8510 (Japan); Fujino, Takashi [Department of Pathology, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka-shi, Tokyo 181-8611 (Japan); Takushima, Akihiko; Harii, Kiyonori [Department of Plastic Surgery, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka-shi, Tokyo 181-8611 (Japan)


    Highlights: {yields} Influence of cyclic stretch on melanogenetic paracrine cytokines was investigated. {yields} Keratinocyte-derived endothelin-1 was upregulated with cyclic stretch. {yields} Degree of upregulation increases dose-dependently. {yields} This upregulation possibly plays a role in the pathogenesis of pigmented disorders. -- Abstract: The aim of this study was to investigate the possible pathological relation between mechanical stress and hyperpigmentation. We did this by investigating the influence of cyclic stretch on the expression of keratinocyte- and fibroblast-derived melanogenetic paracrine cytokines in vitro. Using primary human keratinocytes and fibroblasts, alterations of mRNA expression of melanogenetic paracrine cytokines due to cyclic stretch were investigated using a real-time polymerase chain reaction (PCR). The cytokines included basic fibroblast growth factor (bFGF), stem cell factor (SCF), granulocyte/macrophage colony-stimulating factor, interleukin-1{alpha}, and endothelin-1 (ET-1) for keratinocytes and bFGF, SCF, and hepatocyte growth factor for fibroblasts. The dose dependence of keratinocyte-derived ET-1 upregulation was further investigated using real-time PCR and an enzyme-linked immunosorbent assay. We also investigated the effects of cyclic stretch on the proliferation and differentiation of keratinocytes. Among the melanogenetic paracrine cytokines investigated, keratinocyte-derived ET-1 was consistently upregulated in all four cell lines. The degree of upregulation increased with the degree of the length and frequency of the stretch; in contrast, cell number and differentiation markers showed no obvious alterations with cyclic stretch. Keratinocyte-derived ET-1 upregulation possibly plays a significant role in the pathogenesis of pigmented disorders, such as friction melanosis, caused by mechanical stress.

  12. Reconstructing multiple free energy pathways of DNA stretching from single molecule experiments. (United States)

    Frey, Eric W; Li, Jingqiang; Wijeratne, Sithara S; Kiang, Ching-Hwa


    Free energy landscapes provide information on the dynamics of proteins and nucleic acid folding. It has been demonstrated that such landscapes can be reconstructed from single molecule force measurement data using Jarzynski's equality, which requires only stretching data. However, when the process is reversible, the Crooks fluctuation theorem combines both stretch and relaxation force data for the analysis and can offer more rapid convergence of free energy estimates of different states. Here we demonstrate that, similar to Jarzynski's equality, the Crooks fluctuation theorem can be used to reconstruct the full free energy landscapes. In addition, when the free energy landscapes exhibit multiple folding pathways, one can use Jarzynski's equality to reconstruct individual free energy pathways if the experimental data show distinct work distributions. We applied the method to reconstruct the overstretching transition of poly(dA) to demonstrate that the nonequilibrium work theorem combined with single molecule force measurements provides a clear picture of the free energy landscapes.

  13. 600 Volt Stretched Lens Array for Solar Electric Propulsion Project (United States)

    National Aeronautics and Space Administration — ENTECH, Auburn, NASA, and others have recently developed a new space photovoltaic array called the Stretched Lens Array (SLA), offering unprecedented performance...


    Directory of Open Access Journals (Sweden)

    Jacqueline Amorin Anchieta Borges da Silva, Isabel Cristina Taranto e Fernanda Piasecki


    Full Text Available Nowadays, there are many opportunities for the society to live a healthful and long life. At the same time, never people was so sedentary and without harmony. Without a healthy body and with “an occupied mind” the human loses exactly what more it needs: the disposal to produce, to coexist and to live a good life. In this context, the present research aimed to revise some terms related to labor gymnastics, which is focused in the prevention of risks related to hours of working and in the reduction of muscular tension levels that may be originated during a day of work. Thus, the present study will make a differentiation between the use of stretching and flexionament during labor gymnastic sessions.

  15. Modeling Aftershocks as a Stretched Exponential Relaxation

    CERN Document Server

    Mignan, Arnaud


    The decay rate of aftershocks has been modeled as a power law since the pioneering work of Omori in the late nineteenth century. Considered the second most fundamental empirical law after the Gutenberg-Richter relationship, the power law paradigm has rarely been challenged by the seismological community. By taking a view of aftershock research not biased by prior conceptions of Omori power law decay and by applying statistical methods recommended in applied mathematics, I show that all aftershock sequences tested in three regional earthquake catalogs (Southern and Northern California, Taiwan) and with three declustering techniques (nearest-neighbor, second-order moment, window methods) follow a stretched exponential instead of a power law. These results infer that aftershocks are due to a simpler relaxation process than originally thought, in accordance with most other relaxation processes observed in Nature.

  16. Configurational statistics of confined polymer chains

    Energy Technology Data Exchange (ETDEWEB)

    Lohse, David John


    The work on confined chain statistics is reviewed. The work on the general statistics is discussed first, and then some of the theories for the applications of statistics are considered. Two methods for determining the general statistics of a confined chain are discussed. The first is the method of images. The second method involves the use of differential equations. In a specific case the statistics of the unconfined chain are chosen to be defined by the Gaussian real chain distribution. The confinement is provided by two parallel walls. The distribution for the four possible types of chains, bridges (tie chains), loops, cilia (dangling chain ends), and floating (unattached) chains, are derived. These statistics are then applied to two polymer systems in which the confinement is due to internal surfaces, semicrystalline polymers and block copolymers. Both systems are modelled by chains between two walls for a number of morphologies. Mechanical properties are calculated for both systems and for block copolymers swelling is also considered. The main result of this work is that there are two effects which determine the behavior of the chains in these systems. The first is the effect of the confinement which operates on all the chains, since the mode of attachment is not important. The confinement reduces the number of configurations available to the chains. This effect is larger the closer the walls are, relative to the length and stiffness of the chains. The second effect operates only on bridges, since it requires that the ends of the chain be attached to different walls. This is the inherent elastic nature of the bridge, which means that the number of configurations is reduced when it is stretched beyond its equilibrium length. All the behavior calculated here can be explained by these two effects.

  17. Refolding dynamics of stretched biopolymers upon force quench

    CERN Document Server

    Hyeon, Changbong; Pincus, David L; Thirumalai, D


    Single molecule force spectroscopy methods can be used to generate folding trajectories of biopolymers from arbitrary regions of the folding landscape. We illustrate the complexity of the folding kinetics and generic aspects of the collapse of RNA and proteins upon force quench, using simulations of an RNA hairpin and theory based on the de Gennes model for homopolymer collapse. The folding time, $\\tau_F$, depends asymmetrically on $\\delta f_S = f_S - f_m$ and $\\delta f_Q = f_m - f_Q$ where $f_S$ ($f_Q$) is the stretch (quench) force, and $f_m$ is the transition mid-force of the RNA hairpin. In accord with experiments, the relaxation kinetics of the molecular extension, $R(t)$, occurs in three stages: a rapid initial decrease in the extension is followed by a plateau, and finally an abrupt reduction in $R(t)$ that occurs as the native state is approached. The duration of the plateau increases as $\\lambda =\\tau_Q/\\tau_F$ decreases (where $\\tau_Q$ is the time in which the force is reduced from $f_S$ to $f_Q$). ...


    Directory of Open Access Journals (Sweden)

    Meena .V


    Full Text Available Background: Osteoarthritis (OA is a degenerative joint disease and one of the major public health problem that causesfunctional impairment and reduced quality of life. To compare the effectiveness of PNF Hold relax stretching versus Static stretching on pain and flexibility of hamstring following moist heat in individuals with knee osteoarthritis. Hamstring tightness is the major problem in knee osteoarthritis individuals. Therefore the need of study is comparing the effectiveness of PNF Hold relax stretching versus static stretching on pain and flexibility of hamstrings following moist heat in knee osteoarthritis participants. Determining the effects of PNF Hold relax stretching versus Static stretching along with moist heat on pain and hamstring flexibility by VAS and Active knee extension range of motion in knee osteoarthritis individuals. Methods: 30 subjects with symptoms of knee osteoarthritis were randomly distributed into 2 groups 15 in each group. PNF Hold relax stretching along with moist heat is compared to Static stretching along with moist heat. Pain was measured by Visual Analogue Scale (VAS and hamstring flexibility by Active knee Extension Range of Motion (AKEROM by universal goniometer. Measurements are taken pre and post intervention. Results: The results indicated PNF Hold relax stretching along with moist heat showed a statistically significant improvement in pain (p<0.05 and improvement in hamstring flexibility (p<0.05 when compared to Static stretching along with moist heat. Conclusion: Subjects with PNF Hold relax stretching along with moist heat showed significant improvement in pain reduction and improving hamstring flexibility than Static stretching along with moist heat.


    Directory of Open Access Journals (Sweden)

    Shamik Bhattacharjee


    Full Text Available Background: Healthy individuals, to ease and accomplish their activities of daily living they need flexible body without any tightness in the muscles, particularly those used for a definite function. Cooling soft tissues in a lengthened position after stretching has been shown to promote more lasting increases in soft tissue length and minimize post stretch muscle soreness. There are less documented studies which compared modified proprioceptive neuromuscular facilitation (PNF stretch over passive manual stretch with cold application commonly after the interventions. Methods: Thirty high school going healthy students were divided into two groups- Group I received Passive Manual stretching (n=15 and Group II received modified PNF stretching (n=15 and both groups received cold application after the interventions for 10 minutes commonly for 5 days. ROM was taken on day 1, day 5 and day 7. Results: After day 7, Group II with Modified PNF stretching along with cold application showed a significant increase in range of motion tested with active knee extension test (AKET. Conclusion: Modified PNF stretching is considered to be the effective intervention in increasing and maintaining ROM in AKET over passive manual stretching with cold applications commonly after the interventions.

  20. Effects of stretching on upper-body muscular performance. (United States)

    Torres, Earlando M; Kraemer, William J; Vingren, Jakob L; Volek, Jeff S; Hatfield, Disa L; Spiering, Barry A; Ho, Jen Yu; Fragala, Maren S; Thomas, Gwendolyn A; Anderson, Jeffrey M; Häkkinen, Keijo; Maresh, Carl M


    The purpose of this investigation was to examine the influence of upper-body static stretching and dynamic stretching on upper-body muscular performance. Eleven healthy men, who were National Collegiate Athletic Association Division I track and field athletes (age, 19.6 +/- 1.7 years; body mass, 93.7 +/- 13.8 kg; height, 183.6 +/- 4.6 cm; bench press 1 repetition maximum [1RM], 106.2 +/- 23.0 kg), participated in this study. Over 4 sessions, subjects participated in 4 different stretching protocols (i.e., no stretching, static stretching, dynamic stretching, and combined static and dynamic stretching) in a balanced randomized order followed by 4 tests: 30% of 1 RM bench throw, isometric bench press, overhead medicine ball throw, and lateral medicine ball throw. Depending on the exercise, test peak power (Pmax), peak force (Fmax), peak acceleration (Amax), peak velocity (Vmax), and peak displacement (Dmax) were measured. There were no differences among stretch trials for Pmax, Fmax, Amax, Vmax, or Dmax for the bench throw or for Fmax for the isometric bench press. For the overhead medicine ball throw, there were no differences among stretch trials for Vmax or Dmax. For the lateral medicine ball throw, there was no difference in Vmax among stretch trials; however, Dmax was significantly larger (p static and dynamic condition compared to the static-only condition. In general, there was no short-term effect of stretching on upper-body muscular performance in young adult male athletes, regardless of stretch mode, potentially due to the amount of rest used after stretching before the performances. Since throwing performance was largely unaffected by static or dynamic upper-body stretching, athletes competing in the field events could perform upper-body stretching, if enough time were allowed before the performance. However, prior studies on lower-body musculature have demonstrated dramatic negative effects on speed and power. Therefore, it is recommended that a dynamic

  1. Chain Gang (United States)


    6 August 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a chain of clustered and battered craters. These were formed by secondary impact. That is, somewhere to the south (beyond the bottom of this image), a large impact crater formed. When this occurred, material ejected from the crater was thrown tens to hundreds of kilometers away. This material then impacted the martian surface, forming clusters and chains of smaller craters. Location near: 15.8oN, 35.6oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Northern Spring


    Institute of Scientific and Technical Information of China (English)

    QIAN Renyuan; SHEN Jingshu


    Rubber of high molar mass, like cis-polybutadiene, shows a stress peak on the engineering stress-strain curve during stretching at room temperature. In this work cispolybutadiene samples were swollen in a poor solvent, CHCla/EtOH (1/1 v/v), for different times. It was found that both the initial modulus and the stress peak on stretching decreased in magnitude with increasing swelling time and the peak disappeared entirely after1 hour of swelling. On further swelling the initial modulus increased somewhat and a small stress peak re-appeared after swelling for 2 h. The disappearance of the stress peak after swelling is interpreted as the result of disruption of cohesional entanglements present in the initial rubber sample. The re-appearance of a small stress peak and the increase of modulus on further swelling are interpreted as being of the same nature as the phenomenon of anti-plasticization. It is the result of forming some new cohesional entanglements of larger binding energies through longer range chain segmental motions excited after the disruption of the previously existing cohesional entanglements in the rubber. Thus an understanding of the stress peak on stretching a high molar mass rubber and the phenomenon of anti-plasticization on molecular level has been put forward.

  3. Deletion of the huntingtin polyglutamine stretch enhances neuronal autophagy and longevity in mice.

    Directory of Open Access Journals (Sweden)

    Shuqiu Zheng


    Full Text Available Expansion of a stretch of polyglutamine in huntingtin (htt, the protein product of the IT15 gene, causes Huntington's disease (HD. Previous investigations into the role of the polyglutamine stretch (polyQ in htt function have suggested that its length may modulate a normal htt function involved in regulating energy homeostasis. Here we show that expression of full-length htt lacking its polyglutamine stretch (DeltaQ-htt in a knockin mouse model for HD (Hdh(140Q/DeltaQ, reduces significantly neuropil mutant htt aggregates, ameliorates motor/behavioral deficits, and extends lifespan in comparison to the HD model mice (Hdh(140Q/+. The rescue of HD model phenotypes is accompanied by the normalization of lipofuscin levels in the brain and an increase in the steady-state levels of the mammalian autophagy marker microtubule-associate protein 1 light chain 3-II (LC3-II. We also find that DeltaQ-htt expression in vitro increases autophagosome synthesis and stimulates the Atg5-dependent clearance of truncated N-terminal htt aggregates. DeltaQ-htt's effect on autophagy most likely represents a gain-of-function, as overexpression of full-length wild-type htt in vitro does not increase autophagosome synthesis. Moreover, Hdh(DeltaQ/DeltaQ mice live significantly longer than wild-type mice, suggesting that autophagy upregulation may be beneficial both in diseases caused by toxic intracellular aggregate-prone proteins and also as a lifespan extender in normal mammals.

  4. Combined IR/NIR and density functional theory calculations analysis of the solvent effects on frequencies and intensities of the fundamental and overtones of the C ═ O stretching vibrations of acetone and 2-hexanone. (United States)

    Chen, Yujing; Morisawa, Yusuke; Futami, Yoshisuke; Czarnecki, Mirosław A; Wang, Hai-Shui; Ozaki, Yukihiro


    Vibrational overtone studies primarily focus on X-H stretching overtone transitions, where X is an atom like C, O, N, or S. In contrast, the studies on the C ═ O stretching overtones are very scattered. To advance the research in this field, we measured the fundamental, first, and second overtones of the C ═ O stretching vibration of acetone and 2-hexanone in n-hexane, CCl4, and CHCl3, as well as in the vapor phase using FT-IR/FT-NIR spectroscopy. Density functional theory (DFT) calculations have also been performed to help the assignment of the C ═ O stretching bands and to guide interpretation of the experimental results. It was found that the wavenumbers, absorption intensities, and oscillator strengths of the C ═ O stretching bands show marked solvent dependence. In the fundamental and the first overtone regions, the intensities of the C ═ O stretching vibration were found to be pronouncedly more intense than those of the C-H stretching vibration. In the second overtone region, the intensities of the C-H stretching vibration are comparable to those of the C ═ O stretching vibration. The theoretical and observed decrease in integrated intensity upon going from the fundamental to the first overtone of the C ═ O stretching vibration is around 50, which is significantly larger than those of the O-H, C-H, and S-H stretching vibration. Both the calculated and experimental results suggest that excessive weakness in the C ═ O stretching overtone was shown to be a result of both a low anharmonicity and a substantial reduction in the oscillator strength. These results provide new insight into our understanding of the C ═ O stretching vibration.

  5. Stretched exponential relaxation and ac universality in disordered dielectrics

    DEFF Research Database (Denmark)

    Milovanov, Alexander V.; Rypdal, Kristoffer; Juul Rasmussen, Jens


    are stretched exponential character of dielectric relaxation, power-law power spectral density, and anomalous dependence of ac conduction coefficient on frequency. We propose a self-consistent model of dielectric relaxation in which the relaxations are described by a stretched exponential decay function...

  6. The stretch reflex and the contributions of C David Marsden

    Directory of Open Access Journals (Sweden)

    Kalyan B Bhattacharyya


    Full Text Available The stretch reflex or myotatic reflex refers to the contraction of a muscle in response to its passive stretching by increasing its contractility as long as the stretch is within physiological limits. For ages, it was thought that the stretch reflex was of short latency and it was synonymous with the tendon reflex, subserving the same spinal reflex arc. However, disparities in the status of the two reflexes in certain clinical situations led Marsden and his collaborators to carry out a series of experiments that helped to establish that the two reflexes had different pathways. That the two reflexes are dissociated has been proved by the fact that the stretch reflex and the tendon reflex, elicited by stimulation of the same muscle, have different latencies, that of the stretch reflex being considerably longer. They hypothesized that the stretch reflex had a transcortical course before it reached the spinal motor neurons for final firing. Additionally, the phenomenon of stimulus-sensitive cortical myoclonus lent further evidence to the presence of the transcortical loop where the EEG correlate preceded the EMG discharge. This concept has been worked out by later neurologists in great detail , and the general consensus is that indeed, the stretch reflex is endowed with a conspicuous transcortical component.

  7. Acute nerve stretch and the compound motor action potential

    Directory of Open Access Journals (Sweden)

    Wolfe Jacob


    Full Text Available Abstract In this paper, the acute changes in the compound motor action potential (CMAP during mechanical stretch were studied in hamster sciatic nerve and compared to the changes that occur during compression. In response to stretch, the nerve physically broke when a mean force of 331 gm (3.3 N was applied while the CMAP disappeared at an average stretch force of 73 gm (0.73 N. There were 5 primary measures of the CMAP used to describe the changes during the experiment: the normalized peak to peak amplitude, the normalized area under the curve (AUC, the normalized duration, the normalized velocity and the normalized velocity corrected for the additional path length the impulses travel when the nerve is stretched. Each of these measures was shown to contain information not available in the others. During stretch, the earliest change is a reduction in conduction velocity followed at higher stretch forces by declines in the amplitude of the CMAP. This is associated with the appearance of spontaneous EMG activity. With stretch forces Multiple means of predicting when a change in the CMAP suggests a significant stretch are discussed and it is clear that a multifactorial approach using both velocity and amplitude parameters is important. In the case of pure compression, it is only the amplitude of the CMAP that is critical in predicting which changes in the CMAP are associated with significant compression.

  8. Does Postexercise Static Stretching Alleviate Delayed Muscle Soreness? (United States)

    Buroker, Katherine C.; Schwane, James A.


    Because many experts recommend stretching after exercise to relieve muscle soreness, 23 subjects performed a 30-minute step test to induce delayed muscle soreness. There was neither temporary relief of pain immediately after stretching nor a reduction in pain during the 3-day postexercise period. (Author/SM)

  9. Microscopic theory of light-induced deformation in amorphous side-chain azobenzene polymers. (United States)

    Toshchevikov, V; Saphiannikova, M; Heinrich, G


    We propose a microscopic theory of light-induced deformation of side-chain azobenzene polymers taking into account the internal structure of polymer chains. Our theory is based on the fact that interaction of chromophores with the polarized light leads to the orientation anisotropy of azobenzene macromolecules which is accompanied by the appearance of mechanical stress. It is the first microscopic theory which provides the value of the light-induced stress larger than the yield stress. This result explains a possibility for the inscription of surface relief gratings in glassy side-chain azobenzene polymers. For some chemical architectures, elongation of a sample demonstrates a nonmonotonic behavior with the light intensity and can change its sign (a stretched sample starts to be uniaxially compressed), in agreement with experiments. Using a viscoplastic approach, we show that the irreversible strain of a sample, which remains after the light is switched off, decreases with increasing temperature and can disappear at certain temperature below the glass transition temperature. This theoretical prediction is also confirmed by recent experiments.

  10. Bruxism: Is There an Indication for Muscle-Stretching Exercises? (United States)

    Gouw, Simone; de Wijer, Anton; Creugers, Nico Hj; Kalaykova, Stanimira I

    Bruxism is a common phenomenon involving repetitive activation of the masticatory muscles. Muscle-stretching exercises are a recommended part of several international guidelines for musculoskeletal disorders and may be effective in management of the jaw muscle activity that gives rise to bruxism. However, most studies of muscle-stretching exercises have mainly focused on their influence on performance (eg, range of motion, coordination, and muscle strength) of the limb or trunk muscles of healthy individuals or individuals with sports-related injuries. Very few have investigated stretching of the human masticatory muscles and none muscle-stretching exercises in the management of (sleep) bruxism. This article reviews the literature on muscle-stretching exercises and their potential role in the management of sleep bruxism or its consequences in the musculoskeletal system.

  11. Acute effect of different stretching methods on isometric muscle strength

    Directory of Open Access Journals (Sweden)

    Gabriel Vasconcellos de Lima Costa e Silva


    This study investigated the acute effect of static stretching methods (SS and proprioceptive neuromuscular facilitation (PNF on the static muscle strength (SMS. Eleven young male subjects with strength training experience, performed 3 tests with a 48h interval between them, randomly selected, where each one subject carried out all procedures: a hand grip without stretching; b hand grip preceded by static stretching of wrist flexors muscles; c hand grip preceded by PNF stretching of wrist flexors muscles. The Shapiro-Wilk test verified the normality of data, and a one-way ANOVA with repeated measures, followed by Tukey’s post hoc test, evaluated the differences between the groups. The significance was set at p 0.05. In conclusion, both stretching methods had caused negative effects on isometric strength, reducing its levels.

  12. Stretching and injury prevention in football: current perspectives. (United States)

    Stojanovic, Marko D; Ostojic, Sergej M


    Stretching exercises are regularly recommended as a part of football-training sessions and in preparation for competition. There is little sound empirical evidence, however, to substantiate the role of stretching exercises and consequently increased flexibility on injury prevention in football. Furthermore, in the last decade or so, fundamental research has shed some light on the biomechanical adaptation of the muscle-tendon unit following different stretching protocols, improving knowledge about the topic and enabling better understanding of the stretching-injury relationship. The purpose of this review is to examine the literature on the role of stretching and/or increased flexibility on injury prevention in football, with presented results analyzed in the context of the up-to-date basic science research evidence.

  13. Extended linear chain compounds

    CERN Document Server

    Linear chain substances span a large cross section of contemporary chemistry ranging from covalent polymers, to organic charge transfer com­ plexes to nonstoichiometric transition metal coordination complexes. Their commonality, which coalesced intense interest in the theoretical and exper­ imental solid state physics/chemistry communities, was based on the obser­ vation that these inorganic and organic polymeric substrates exhibit striking metal-like electrical and optical properties. Exploitation and extension of these systems has led to the systematic study of both the chemistry and physics of highly and poorly conducting linear chain substances. To gain a salient understanding of these complex materials rich in anomalous aniso­ tropic electrical, optical, magnetic, and mechanical properties, the conver­ gence of diverse skills and talents was required. The constructive blending of traditionally segregated disciplines such as synthetic and physical organic, inorganic, and polymer chemistry, crystallog...

  14. Pre-exercise stretching does not impact upon running economy. (United States)

    Hayes, Philip R; Walker, Adrian


    Pre-exercise stretching has been widely reported to reduce performance in tasks requiring maximal or near-maximal force or torque. The purpose of this study was to compare the effects of 3 different pre-exercise stretching routines on running economy. Seven competitive male middle and long-distance runners (mean +/- SD) age: 32.5 +/- 7.7 years; height: 175.0 +/- 8.8 cm; mass: 67.8 +/- 8.6 kg; V(.-)O2max: 66.8 +/- 7.0 ml x kg(-1) x min(-1)) volunteered to participate in this study. Each participant completed 4 different pre-exercise conditions: (a) a control condition, (b) static stretching, (c) progressive static stretching, and (d) dynamic stretching. Each stretching routine consisted of 2 x 30-second stretches for each of 5 exercises. Dependent variables measured were sit and reach test before and after each pre-exercise routine, running economy (ml x kg(-1) x km(-1)), and steady-state oxygen uptake (ml x kg(-1) x min(-1)), which were measured during the final 3 minutes of a 10-minute run below lactate threshold. All 3 stretching routines resulted in an increase in the range of movement (p = 0.008). There was no change in either running economy (p = 0.915) or steady-state V(.-)O2 (p = 0.943). The lack of change in running economy was most likely because it was assessed after a period of submaximal running, which may have masked any effects from the stretching protocols. Previously reported reductions in performance have been attributed to reduced motor unit activation, presumably IIX. In this study, these motor units were likely not to have been recruited; this may explain the unimpaired performance. This study suggests that pre-exercise stretching has no impact upon running economy or submaximal exercise oxygen cost.

  15. On the origin of stretched exponential (Kohlrausch) relaxation kinetics in the room temperature luminescence decay of colloidal quantum dots. (United States)

    Bodunov, E N; Antonov, Yu A; Simões Gamboa, A L


    The non-exponential room temperature luminescence decay of colloidal quantum dots is often well described by a stretched exponential function. However, the physical meaning of the parameters of the function is not clear in the majority of cases reported in the literature. In this work, the room temperature stretched exponential luminescence decay of colloidal quantum dots is investigated theoretically in an attempt to identify the underlying physical mechanisms associated with the parameters of the function. Three classes of non-radiative transition processes between the excited and ground states of colloidal quantum dots are discussed: long-range resonance energy transfer, multiphonon relaxation, and contact quenching without diffusion. It is shown that multiphonon relaxation cannot explain a stretched exponential functional form of the luminescence decay while such dynamics of relaxation can be understood in terms of long-range resonance energy transfer to acceptors (molecules, quantum dots, or anharmonic molecular vibrations) in the environment of the quantum dots acting as energy-donors or by contact quenching by acceptors (surface traps or molecules) distributed statistically on the surface of the quantum dots. These non-radiative transition processes are assigned to different ranges of the stretching parameter β.

  16. On the origin of stretched exponential (Kohlrausch) relaxation kinetics in the room temperature luminescence decay of colloidal quantum dots (United States)

    Bodunov, E. N.; Antonov, Yu. A.; Simões Gamboa, A. L.


    The non-exponential room temperature luminescence decay of colloidal quantum dots is often well described by a stretched exponential function. However, the physical meaning of the parameters of the function is not clear in the majority of cases reported in the literature. In this work, the room temperature stretched exponential luminescence decay of colloidal quantum dots is investigated theoretically in an attempt to identify the underlying physical mechanisms associated with the parameters of the function. Three classes of non-radiative transition processes between the excited and ground states of colloidal quantum dots are discussed: long-range resonance energy transfer, multiphonon relaxation, and contact quenching without diffusion. It is shown that multiphonon relaxation cannot explain a stretched exponential functional form of the luminescence decay while such dynamics of relaxation can be understood in terms of long-range resonance energy transfer to acceptors (molecules, quantum dots, or anharmonic molecular vibrations) in the environment of the quantum dots acting as energy-donors or by contact quenching by acceptors (surface traps or molecules) distributed statistically on the surface of the quantum dots. These non-radiative transition processes are assigned to different ranges of the stretching parameter β.

  17. Acute effects of different stretching durations on passive torque, mobility, and isometric muscle force. (United States)

    Matsuo, Shingo; Suzuki, Shigeyuki; Iwata, Masahiro; Banno, Yasuhiro; Asai, Yuji; Tsuchida, Wakako; Inoue, Takayuki


    Static stretching is widely applied in various disciplines. However, the acute effects of different durations of stretching are unclear. Therefore, this study was designed to investigate the acute effects of different stretching durations on muscle function and flexibility, and provide an insight into the optimal duration of static stretching. This randomized crossover trial included 24 healthy students (17 men and 7 women) who stretched their right hamstrings for durations of 20, 60, 180, and 300 seconds in a random order. The following outcomes were assessed using an isokinetic dynamometer as markers of lower-limb function and flexibility: static passive torque (SPT), dynamic passive torque (DPT), stiffness, straight leg raise (SLR), and isometric muscle force. Static passive torque was significantly decreased after all stretching durations (p stretching compared with that after 20-second stretching, and stiffness decreased significantly after 180- and 300-second stretching (p stretching (p stretching durations (p stretching than after 20-second stretching and higher after 300-second stretching than after 60-second stretching (p stretching durations (p stretching is associated with a decrease in SPT but an increase in SLR. Over 180 seconds of stretching was required to decrease DPT and stiffness, but isometric muscle force decreased regardless of the stretching duration. In conclusion, these results indicate that longer durations of stretching are needed to provide better flexibility.

  18. Phase behaviour of polyethylene knotted ring chains

    Institute of Scientific and Technical Information of China (English)

    Wen Xiao-Hui; Zhang Lin-Xi; Xia A-Gen; Chen Hong-Ping


    The phase behaviour of polyethylene knotted ring chains is investigated by using molecular dynamics simulations.In this paper, we focus on the collapse of the polyethylene knotted ring chain, and also present the results of linear and ring chains for comparison. At high temperatures, a fully extensive knot structure is observed. The mean-square radius of gyration per bond〈S2〉/(Nb2)and the shape factor(δ*)depend on not only the chain length but also the knot type.With temperature decreasing, chain collapse is observed, and the collapse temperature decreases with the chain length increasing. The actual collapse transition can be determined by the specific heat capacity Cv, and the knotted ring chain undergoes gas-liquid-solid-like transition directly. The phase transition of a knotted ring chain is only one-stage collapse, which is different from the polyethylene linear and ring chains. This investigation can provide some insights into the statistical properties of knotted polymer chains.

  19. Effects of contract-relax vs static stretching on stretch-induced strength loss and length-tension relationship

    DEFF Research Database (Denmark)

    Balle, S S; Magnusson, S P; McHugh, M P


    The purpose of this study was to determine the acute effects of contract-relax stretching (CRS) vs static stretching (SS) on strength loss and the length-tension relationship. We hypothesized that there would be a greater muscle length-specific effect of CRS vs SS. Isometric hamstring strength...... was measured in 20 healthy people at four knee joint angles (90°, 70°, 50°, 30°) before and after stretching. One leg received SS, the contralateral received CRS. Both stretching techniques resulted in significant strength loss, which was most apparent at short muscle lengths [SS: P = 0.025; stretching × angle...... P stretching × angle P stretch-induced strength loss was greater (P = 0.015) after CRS (11...

  20. Modeling the effect of intercalators on the high-force stretching behavior of DNA

    CERN Document Server

    Schakenraad, Koen; Biebricher, Andreas; Wuite, Gijs; Storm, Cornelis; van der Schoot, Paul


    DNA is structurally and mechanically altered by the binding of intercalator molecules. Intercalation strongly affects the force-extension behavior of DNA, in particular the overstretching transition. We present a statistical model that captures all relevant findings of recent force-extension experiments. Two predictions from our model are presented. The first suggests the existence of a novel hyper-stretching regime in the presence of intercalators and the second, a linear dependence of the overstretching force on intercalator concentration, is verified by re-analyzing available experimental data. Our model pins down the physical principles that govern intercalated DNA mechanics, providing a predictive understanding of its limitations and possibilities.

  1. Nucleation of liquid droplets and voids in a stretched Lennard-Jones fcc crystal. (United States)

    Baidakov, Vladimir G; Tipeev, Azat O


    The method of molecular dynamics simulation has been used to investigate the phase decay of a metastable Lennard-Jones face-centered cubic crystal at positive and negative pressures. It is shown that at high degrees of metastability, crystal decay proceeds through the spontaneous formation and growth of new-phase nuclei. It has been found that there exists a certain boundary temperature. Below this temperature, the crystal phase disintegrates as the result of formation of voids, and above, as a result of formation of liquid droplets. The boundary temperature corresponds to the temperature of cessation of a crystal-liquid phase equilibrium when the melting line comes in contact with the spinodal of the stretched liquid. The results of the simulations are interpreted in the framework of classical nucleation theory. The thermodynamics of phase transitions in solids has been examined with allowance for the elastic energy of stresses arising owing to the difference in the densities of the initial and the forming phases. As a result of the action of elastic forces, at negative pressures, the boundary of the limiting superheating (stretching) of a crystal approaches the spinodal, on which the isothermal bulk modulus of dilatation becomes equal to zero. At the boundary of the limiting superheating (stretching), the shape of liquid droplets and voids is close to the spherical one.

  2. Wavelet stretch correction%子波拉伸校正

    Institute of Scientific and Technical Information of China (English)

    黄文锋; 李宏兵; 姚逢昌; 李国平; 张佳佳


    依赖于偏移距的反射波调谐是AVO分析的不利因素.无论动校正还是偏移,都会引起子波拉伸、频谱向低频移动.在频率域对动校正或偏移后的地震数据进行反拉伸校正是本文消除子波拉伸采用的方法.从射线参数时距方程出发推导的地震映射压缩因子与反射角存在较精确的余弦关系.角度道中动校正或偏移子波拉伸因子是反射角余弦的倒数.用无拉伸子波频谱除以拉伸子波频谱得到反频谱压缩算子,对动校正或偏移后存在子波拉伸的角度道应用反频谱压缩算子,操作简单易行.薄层模型试验和实际地震资料处理表明角度道校正方法能够消除子波拉伸畸变,展宽频谱,补偿地震资料动校正或偏移过程中丢失的高频成分,提高大角度的分辨率和保真度,改善AVO分析.%Offset-dependent tuning includes seismic imaging tuning, NMO stretch, and migration stretch. Seismic imaging tuning caused by compression of reflectivity inheres in seismic record. Either NMO stretch or migration stretch is the wavelet stretch which arises in the seismic processing. They are adverse factors for AVO analysis. The goal of dynamic correction or migration is to modify the time difference measured at the mid- and the far-offset trace to that at the near-offset trace. Either dynamic correction or migration stretches the compressed reflectivity, but brings wavelet stretch and corresponding spectral compression at the same time. The method of removing wavelet stretch proposed in this article is to do anti-stretch correction on the seismic data after dynamic correction or migration in frequency domain. The compression factor of seismic imaging tuning deduced from the parametric ray equations is related closely to the cosine of the refection angle. In offset traces after dynamic correction or migration, the wavelet stretch factor which varies with time and velocity is nonstationary. The shallow reflection at the far


    Directory of Open Access Journals (Sweden)

    ORK Nilay


    Full Text Available Product variability of manufactured leather goods such as garment leathers could be closely related to the wear comfort because each material forming the garments are affected the comfort properties of the products. Considering the significant demand to elastic woven stretch fabrics and the advantages provided to leather goods like allowing easy body movements, well-fitting and keeping the shape make the use of stretch fabrics focus in interest. In this study, the performance properties of stretch leathers, leathers and spandex fabrics were presented and the differences between the characteristic properties of the leathers were described. For this purpose, physical characteristics of leathers were investigated in terms of thickness, weight, drape ability, stiffness, bending stiffness, air and water vapor permeability. The drape ability, stiffness and bending stiffness properties were significantly affected by the stretch fabrics laminated on the suede side of the leathers. The drape ability, stiffness and bending values were increased due to the implementation of stretch fabrics. There was no significant difference between the air permeability values of the leathers prior and after the implementation of stretch fabrics in contrast to water vapor permeability. The results of this study showed that the aesthetic behavior of clothing materials such as drape and stiffness properties as well as water vapor permeability was mainly affected from the implementation of the stretch fabrics.

  4. Translational vibrations between chains of hydrogen-bonded molecules in solid-state aspirin form I (United States)

    Takahashi, Masae; Ishikawa, Yoichi


    We perform dispersion-corrected first-principles calculations, and far-infrared (terahertz) spectroscopic experiments at 4 K, to examine translational vibrations between chains of hydrogen-bonded molecules in solid-state aspirin form I. The calculated frequencies and relative intensities reproduce the observed spectrum to accuracy of 11 cm-1 or less. The stronger one of the two peaks assigned to the translational mode includes the stretching vibration of the weak hydrogen bond between the acetyl groups of a neighboring one-dimensional chain. The calculation of aspirin form II performed for comparison gives the stretching vibration of the weak hydrogen bond in one-dimensional chain.

  5. Large-deviation statistics of vorticity stretching in isotropic turbulence. (United States)

    Johnson, Perry L; Meneveau, Charles


    A key feature of three-dimensional fluid turbulence is the stretching and realignment of vorticity by the action of the strain rate. It is shown in this paper, using the cumulant-generating function, that the cumulative vorticity stretching along a Lagrangian path in isotropic turbulence obeys a large deviation principle. As a result, the relevant statistics can be described by the vorticity stretching Cramér function. This function is computed from a direct numerical simulation data set at a Taylor-scale Reynolds number of Re(λ)=433 and compared to those of the finite-time Lyapunov exponents (FTLE) for material deformation. As expected, the mean cumulative vorticity stretching is slightly less than that of the most-stretched material line (largest FTLE), due to the vorticity's preferential alignment with the second-largest eigenvalue of strain rate and the material line's preferential alignment with the largest eigenvalue. However, the vorticity stretching tends to be significantly larger than the second-largest FTLE, and the Cramér functions reveal that the statistics of vorticity stretching fluctuations are more similar to those of the largest FTLE. In an attempt to relate the vorticity stretching statistics to the vorticity magnitude probability density function in statistically stationary conditions, a model Kramers-Moyal equation is constructed using the statistics encoded in the Cramér function. The model predicts a stretched-exponential tail for the vorticity magnitude probability density function, with good agreement for the exponent but significant difference (35%) in the prefactor.

  6. Energy Method in Stretch Reducing Process of Steel Tube

    Institute of Scientific and Technical Information of China (English)

    ZHANG Fang-ping; SUN Bin-yu; WANG Jian-mei


    According to the theories for stretch reducing process and steel tube plastic deformation,the energy method was used To mesh the rolled deformation zone of the steel tube into the upper limit elements,and an admissible velocity field was constructed to deduce a series of formulas of the inner virtual power consumption of deformed bodies.The rolling force during the stretch reducing process could be obtained by optimizing the upper limit power,which could provide guidelines for a proper choice of the stretch reducing process and devices for steel tube companies,as well as new products and devices.

  7. DNA analysis by single molecule stretching in nanofluidic biochips

    DEFF Research Database (Denmark)

    Abad, E.; Juarros, A.; Retolaza, A.


    Stretching single DNA molecules by confinement in nanofluidic channels has attracted a great interest during the last few years as a DNA analysis tool. We have designed and fabricated a sealed micro/nanofluidic device for DNA stretching applications, based on the use of the high throughput Nano......-DNA stained with the fluorescent dye YOYO-1 were stretched in the nanochannel array and the experimental results were analysed to determine the extension factor of the DNA in the chip and the geometrical average of the nanochannel inner diameter. The determination of the extension ratio of the chip provides...

  8. Temperature Field for Improving Internal Quality of Stretched Round Billet

    Institute of Scientific and Technical Information of China (English)

    QIU Ping; XIAO Hong


    Based on the rigid-plastic theory, using a coupled thermomechanieal model, the stretching process of a cir-cular section billet is simulated by means of FEM software Deform-2D. Through the distribution of internal stress fields of stretched round billet, it is found that the shear stress field is the main factor to induce Mannesmann's effect. The simulation results show that a reasonable distribution of the temperature field may improve the internal quality of the circular section billet in the stretching process.

  9. Conformational Transitions (United States)

    Czerminski, Ryszard; Roitberg, Adrian; Choi, Chyung; Ulitsky, Alexander; Elber, Ron


    Two computational approaches to study plausible conformations of biological molecules and the transitions between them are presented and discussed. The first approach is a new search algorithm which enhances the sampling of alternative conformers using a mean field approximation. It is argued and demonstrated that the mean field approximation has a small effect on the location of the minima. The method is a combination of the LES protocol (Locally Enhanced Sampling) and simulated annealing. The LES method was used in the past to study the diffusion pathways of ligands from buried active sites in myoglobin and leghemoglobin to the exterior of the protein. The present formulation of LES and its implementation in a Molecular Dynamics program is described. An application for side chain placement in a tetrapeptide is presented. The computational effort associated with conformational searches using LES grows only linearly with the number of degrees of freedom, whereas in the exact case the computational effort grows exponentially. Such saving is of course associated with a mean field approximation. The second branch of studies pertains to the calculation of reaction paths in large and flexible biological systems. An extensive mapping of minima and barriers for two different tetrapeptides is calculated from the known minima and barriers of alanine tetrapeptide which we calculated recently.1 The tetrapeptides are useful models for the formation of secondary structure elements since they are the shortest possible polymers of this type which can still form a complete helical turn. The tetrapeptides are isobutyryl-val(χ1=60)-ala-ala and isobutyryl-val(χ1=-60)-ala-ala. Properties of the hundreds of minima and of the hundreds intervening barriers are discussed. Estimates for thermal transition times between the many conformers (and times to explore the complete phase space) are calculated and compared. It is suggested that the most significant effect of the side chain size is

  10. Effects of contract-relax vs static stretching on stretch-induced strength loss and length-tension relationship. (United States)

    Balle, S S; Magnusson, S P; McHugh, M P


    The purpose of this study was to determine the acute effects of contract-relax stretching (CRS) vs static stretching (SS) on strength loss and the length-tension relationship. We hypothesized that there would be a greater muscle length-specific effect of CRS vs SS. Isometric hamstring strength was measured in 20 healthy people at four knee joint angles (90°, 70°, 50°, 30°) before and after stretching. One leg received SS, the contralateral received CRS. Both stretching techniques resulted in significant strength loss, which was most apparent at short muscle lengths [SS: P = 0.025; stretching × angle P stretching × angle P stretch-induced strength loss was greater (P = 0.015) after CRS (11.7%) vs SS (3.7%). The muscle length effect on strength loss was not different between CRS and SS (stretching × angle × stretching technique P = 0.43). Contrary to the hypothesis, CRS did not result in a greater shift in the length-tension relationship, and in fact, resulted in greater overall strength loss compared with SS. These results support the use of SS for stretching the hamstrings.

  11. The Invariance Principle for p-(→θ) Chain

    Institute of Scientific and Technical Information of China (English)

    Di He HU; Zheng Yan XIAO


    There are two parts in this paper. In the first part we construct the Maxkov chain in random environment(MCRE), the skew product Markov chain and p-(→θ) chain from a random transition matrix and a two-dimensional probability distribution, and in the second part we prove that the invariance principle for p-(→θ) chain, a more complex non-homogeneons Markov chain, is true under some reasonable conditions. This result is more powerful.

  12. Realistic searches on stretched exponential networks

    Indian Academy of Sciences (India)

    Parogama Sen


    We consider navigation or search schemes on networks which have a degree distribution of the form () ∝ exp(−). In addition, the linking probability is taken to be dependent on social distances and is governed by a parameter . The searches are realistic in the sense that not all search chains can be completed. An estimate of = ρ/d, where is the success rate and d the dynamic path length, shows that for a network of nodes, ∝ - in general. Dynamic small world effect, i.e., ≃ 0 is shown to exist in a restricted region of the - plane.

  13. Epithelial cell stretching and luminal acidification lead to a retarded development of stria vascularis and deafness in mice lacking pendrin.

    Directory of Open Access Journals (Sweden)

    Hyoung-Mi Kim

    Full Text Available Loss-of-function mutations of SLC26A4/pendrin are among the most prevalent causes of deafness. Deafness and vestibular dysfunction in the corresponding mouse model, Slc26a4(-/-, are associated with an enlargement and acidification of the membranous labyrinth. Here we relate the onset of expression of the HCO(3 (- transporter pendrin to the luminal pH and to enlargement-associated epithelial cell stretching. We determined expression with immunocytochemistry, cell stretching by digital morphometry and pH with double-barreled ion-selective electrodes. Pendrin was first expressed in the endolymphatic sac at embryonic day (E 11.5, in the cochlear hook-region at E13.5, in the utricle and saccule at E14.5, in ampullae at E16.5, and in the upper turn of the cochlea at E17.5. Epithelial cell stretching in Slc26a4(-/- mice began at E14.5. pH changes occurred first in the cochlea at E15.5 and in the endolymphatic sac at E17.5. At postnatal day 2, stria vascularis, outer sulcus and Reissner's membrane epithelial cells, and utricular and saccular transitional cells were stretched, whereas sensory cells in the cochlea, utricle and saccule did not differ between Slc26a4(+/- and Slc26a4(-/- mice. Structural development of stria vascularis, including vascularization, was retarded in Slc26a4(-/- mice. In conclusion, the data demonstrate that the enlargement and stretching of non-sensory epithelial cells precedes luminal acidification in the cochlea and the endolymphatic sac. Stretching and luminal acidification may alter cell-to-cell communication and lead to the observed retarded development of stria vascularis, which may be an important step on the path to deafness in Slc26a4(-/- mice, and possibly in humans, lacking functional pendrin expression.

  14. High-Resolution Infrared Spectroscopy Slit-Jet Cooled Hydroxymethyl Radical (CH_2OH): CH Symmetric Stretching Mode (United States)

    Wang, Fang; Chang, Chih-Hsuan; Nesbitt, David


    Hydroxymethyl radical (CH_2OH) plays an important role in combustion and environmental chemistry as a reactive intermediate. Reisler's group published the first rotationally resolved spectroscopy of CH_2OH with determined band origins for fundamental CH symmetric stretch state, CH asymmetric stretch state and OH stretch state, respectively. Here CH_2OH was first studied via sub-Doppler infrared spectroscopy in a slit-jet supersonic discharge expansion source. Rotationally resolved direct absorption spectra in the CH symmetric stretching mode were recorded. As a result of the low rotational temperature and sub-Doppler linewidths, the tunneling splittings due to the large amplitude of COH torsion slightly complicate the spectra. Each of the ground vibration state and the CH symmetric stretch state includes two levels. One level, with a 3:1 nuclear spin statistic ratio for Ka=0+/Ka=1+, is labeled as ``+". The other tunneling level, labeled as ``-", has Ka=0-/Ka=1- states with 1:3 nuclear spin statistics. Except for the Ka=0+ ← 0+ band published before, more bands (Ka=1+ ← 1+, Ka=0- ← 0- and Ka=1- ← 1-) were identified. The assigned transitions were fit to a Watson A-reduced symmetric top Hamiltonian to improve the accuracy of the band origin of CH symmetric state. The rotational parameters for both ground and CH symmetric stretch state were well determined. L. Feng, J. Wei and H. Reisler, J. Phys. Chem. A, Vol. 108. M. A. Roberts, E. N. Sharp-Williams and D. J. Nesbitt, J. Phys. Chem. A 2013, 117, 7042-7049

  15. EMG and peak force responses to PNF stretching and the relationship between stretching-induced force deficits and bilateral deficits



    [Purpose] The aim of the present study was to investigate the possibility of an interaction between stretching induced deficit (SFD) and bilateral deficits (BLD) during maximal voluntary isometric hand flexion under PNF stretch and no-stretch conditions through measurement of EMG and force production. [Subjects and Methods] Ten physically active male Caucasian students (age, 24.1±2.38 years; body mass, 79.48±11.40 kg; height, 174.15±0.8 cm) volunteered to participate in this study. EMG and fo...

  16. Radiology's value chain. (United States)

    Enzmann, Dieter R


    A diagnostic radiology value chain is constructed to define its main components, all of which are vulnerable to change, because digitization has caused disaggregation of the chain. Some components afford opportunities to improve productivity, some add value, while some face outsourcing to lower labor cost and to information technology substitutes, raising commoditization risks. Digital image information, because it can be competitive at smaller economies of scale, allows faster, differential rates of technological innovation of components, initiating a centralization-to-decentralization technology trend. Digitization, having triggered disaggregation of radiology's professional service model, may soon usher in an information business model. This means moving from a mind-set of "reading images" to an orientation of creating and organizing information for greater accuracy, faster speed, and lower cost in medical decision making. Information businesses view value chain investments differently than do small professional services. In the former model, producing a better business product will extend image interpretation beyond a radiologist's personal fund of knowledge to encompass expanding external imaging databases. A follow-on expansion with integration of image and molecular information into a report will offer new value in medical decision making. Improved interpretation plus new integration will enrich and diversify radiology's key service products, the report and consultation. A more robust, information-rich report derived from a "systems" and "computational" radiology approach will be facilitated by a transition from a professional service to an information business. Under health care reform, radiology will transition its emphasis from volume to greater value. Radiology's future brightens with the adoption of a philosophy of offering information rather than "reads" for decision making. Staunchly defending the status quo via turf wars is unlikely to constitute a

  17. Measurement of Reversed Extension Flow using the Filament Stretch Rheometer

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.; Skov, Anne Ladegaard; Nielsen, Jens Kromann;


    The measurement of material functions with reversed extension flow is demonstrated using the Filament Stretching Rheometer (FSR). This includes startup of uniaxial elongational flow (potentially until steady state) followed by biaxial squeezing, and large amplitude oscillatory elongation (LAOE). ...

  18. Myoelectric silence following unopposed passive stretch in normal man. (United States)

    Angel, R W; Waxman, S G; Kocsis, J D


    The response to unopposed passive muscle stretch applied during sustained contraction was studied in normal man. When the subject did not resist the stretching force, the initial response was a brief cessation of EMG activity in the elongated muscle. The myoelectric silence was observed repeatedly in muscles of the upper and lower limbs. The response to passive stretch is discussed in relation to the lengthening reaction and the inverse myotatic reflex. The silent period observed under these experimental conditions is unlikely to be caused by Renshaw inhibition, a pause in spindle afferent discharge, or activity of the group II afferent reflex pathway. Possible mechanisms include autogenetic inhibition and a stretch-evoked decrease of fusimotor activity.

  19. Effects of Static Stretching and Playing Soccer on Knee Laxity

    NARCIS (Netherlands)

    Baumgart, Christian; Gokeler, Alli; Donath, Lars; Hoppe, Matthias W.; Freiwald, Juergen


    Objective: This study investigated exercise-induced effects of static stretching and playing soccer on anterior tibial translation (ATT) of the knee joint. Design: Randomized controlled trial. Setting: University biomechanics laboratory. Participants: Thirty-one athletes were randomly assigned into

  20. 600 Volt Stretched Lens Array for Solar Electric Propulsion Project (United States)

    National Aeronautics and Space Administration — Over the past six years, ENTECH, Auburn, NASA, and other organizations have developed a new space photovoltaic array called the Stretched Lens Array (SLA), which...

  1. Saturation of Zeldovich stretch-twist-fold map dynamos (United States)

    Seta, Amit; Bhat, Pallavi; Subramanian, Kandaswamy


    > value is determined by the relative importance of the increased diffusion versus the reduced stretching. These saturation properties are akin to the range of possibilities that have been discussed in the context of fluctuation dynamos.

  2. Guidelines for Stretch Flanging Advanced High Strength Steels (United States)

    Sriram, S.; Chintamani, J.


    Advanced High Strength Steels (AHSS) are currently being considered for use in closure and structural panels in the automotive industry because of their high potential for affordable weight reduction and improved performance. AHSS such as dual phase steels are currently being used in some vehicle platforms. From a manufacturing perspective, stretch flanging during stamping is an important deformation mode requiring careful consideration of geometry and the die process. This paper presents some geometric and process guidelines for stretch flanging AHSS. Hole expansion experiments were conducted to determine the failure limit for a sheared edge condition. Effects of punching clearance, prestrain and prior strain path on hole expansion were explored in these experiments. In addition, dynamic explicit FE calculations using LS-DYNA were also conducted for a typical stretch flange by varying some key geometric parameters. The experimental and FEA results were then analyzed to yield process and geometric guidelines to enable successful stretch flanging of AHSS.

  3. Damage percolation during stretch flange forming of aluminum alloy sheet (United States)

    Chen, Zengtao; Worswick, Michael J.; Keith Pilkey, A.; Lloyd, David J.


    A multi-scale finite element (FE)-damage percolation model was employed to simulate stretch flange forming of aluminum alloys AA5182 and AA5754. Material softening and strain gradients were captured using a Gurson-based FE model. FE results were then fed into the so-called damage percolation code, from which the damage development was modelled within measured microstructures. The formability of the stretch flange samples was predicted based upon the onset of catastrophic failure triggered by profuse void coalescence within the measured second-phase particle field. Damage development is quantified in terms of crack and void areal fractions, and compared to metallographic results obtained from interrupted stretch flange specimens. Parametric study is conducted on the effect of void nucleation strain in the prediction of formability of stretch flanges to "calibrate" proper nucleation strains for both alloys.

  4. A New Tool to Assess the Perception of Stretching Intensity. (United States)

    Freitas, Sandro R; Vaz, João R; Gomes, Luis; Silvestre, Rui; Hilário, Edgar; Cordeiro, Nuno; Carnide, Filomena; Pezarat-Correia, Pedro; Mil-Homens, Pedro


    This study aimed to develop a valid and reliable scale to assess the perception of stretching intensity below and above the maximal range of motion. Experiments were conducted through a passive leg extension angle-torque assessment to healthy population (n = 90). In the study's first phase, the visual, numerical, and description of the stretching intensity scale (SIS) components were developed. The visual analog scale (VAS) score, absolute magnitude estimation (AME) score, and verbal stretching intensity symptom descriptors were assessed for different stretching intensities. In the second phase, the SIS was tested for validity, reliability, scale production, and estimation properties as well as responsiveness to stretching. In the first phase, a high correlation was found between SIS score and range of motion (ROM), as well as SIS and torque in both submaximal (intraclass correlation coefficient [ICC] = 0.89-0.99, r = 0.88-0.99) and supramaximal (ICC = 0.75-0.86, r = 0.68-0.88) stretching intensities. The AME and VAS scores fitted well in an exponential model for submaximal stretching intensities (y = 14.829e, ICC = 0.97 [0.83-0.99], r = 0.98), and in a linear model for supramaximal stretching intensities (y = 0.7667x - 25.751, ICC = 0.97 [0.89-0.99], r = 0.9594). For the second phase, a high correlation was found between SIS score and ROM (r = 0.70-0.76, ICC = 0.76-0.85), as well as SIS and torque (r = 0.62-0.88, ICC = 0.57-0.85). The interday reliability was high to produce (r = 0.70, ICC = 0.70 [0.50-0.83]) or estimate (r = 0.89, ICC = 0.89 [0.82-0.93]) stretching intensities. The acute stretching effects on ROM and passive torque were detectable using the SIS. It is expected a high application in assessing the stretch intensity using the SIS in future studies and practical interventions.

  5. Spontaneous Enhancement of Packing Regularity of Spherical Microdomains in the Body-Centered Cubic Lattice upon Uniaxial Stretching of Elastomeric Triblock Copolymers

    Directory of Open Access Journals (Sweden)

    Shinichi Sakurai


    Full Text Available Block copolymers forming glassy spheres in the matrix of rubbery chains can exhibit elastomeric properties. It is well known that the spherical microdomains are arranged in the body-center cubic (bcc lattice. However, recently, we have found packing in the face-centered cubic (fcc lattice, which is easily transformed into the bcc lattice upon uniaxial stretching. In the same time, the packing regularity of the spheres in the bcc lattice was found to be enhanced for samples completely recovered from the stretched state. This reminds us that a cycle of stretching-and-releasing plays an important role from analogy of densification of the packing in granules upon shaking. In the current paper, we quantify the enhancement of packing regularity of spherical microdomains in the bcc lattice upon uniaxial stretching of the same elastomeric triblock copolymer as used in our previous work by conducting small-angle X-ray scattering (SAXS measurements using high brilliant synchrotron radiation. Isotropically circular rings of the lattice peaks observed for the unstretched sample turned into deformed ellipsoidal rings upon the uniaxial stretching, with sharpening of the peaks in the direction parallel to the stretching direction and almost disappearing of the peaks in the perpendicular direction. By quantitatively analyzing the SAXS results, it was found that the packing regularity of the spherical microdomains was enhanced in the parallel direction while it was spoiled in the perpendicular direction under the stretched state. The enhanced regularity of packing was unchanged even if the stretching load was completely removed.


    Institute of Scientific and Technical Information of China (English)

    SUN Zhenhua; DING Mengxian; FENG Zhiliu


    The structure of polyimide from 1,4-bis (3', 4'-dicarboxyphenoxy ) benzene and 4,4'-oxydianiline film specimens before and after hot stretching has been investigated by WAXD, DSC and FTIR. As evidenced by both the WAXD and DSC results, it could be believed that strain induced crystallization did take place after hot stretching. Meanwhile, shifting position and splitting of some band peaks existed on the FTIR spectrograms were explained in terms of the close packing of chains and the changes of inter-molecular charge-transfer interaction between imide groups and aromatic groups upon crystallization.


    Directory of Open Access Journals (Sweden)



    Full Text Available Despite the great success, seminal Huxley's sliding filament model broadly fails to explain the steady state behavior of stretched activated skeletal muscles. Here, a new self-consistent solution to the fundamental kinetic equation for the distribution of actin-myosin linkages (cross-bridges is proposed in light of the generalized thermodynamic theory of fluctuations, thus substituting the transition state theory traditionally used for the transition rates. The unified description for mechanism of the force output in both shortening and stretching regimes is attributed to the interplay between the uniformly-state distributed, thermodynamically equilibrated myosin heads attached to actin filaments and asymmetrically-state distributed, mechanically equilibrated rotating myosin heads. The crossover between two steady regimes is associated with a reconstruction of the cross-bridge domains and change their attach-detach rates, leaving unchanged basic mechanical characteristics. Theory suggests a unified generic force-velocity equation, using only a single combination of the cross-bridge parameters for each regime, while Huxley's approach (1957 as well as its subsequent modifications, requires four adjustable parameters to fit the same data.

  8. Efficacy of hamstring stretching programs in schoolchildren. A systematic review

    Directory of Open Access Journals (Sweden)

    Carlos-Alberto BECERRA FERNANDEZ


    Full Text Available The main purpose of the present review was to examine the scientific literature on the effects of physical education-based stretching programs on hamstring extensibility in schoolchildren aged 6-11 years. For this purpose relevant studies were searched from ten electronic databases dated up through May 2015. Of the 25 potentially relevant articles identified and retrieved for more detailed evaluation, only eight studies were included in the present review because they met the inclusion criteria. The overall results showed that incorporating hamstring stretching as a part of physical education classes produces a significant improvement in the scores of the tests: straight leg raise and classic sit-and-reach, for the experimental groups, but not for control groups. Stretching programs can be included in Physical Education classes, specifically during the warm-up and the cool down periods in order to improve hamstring extensibility. Although it seems that the stretching exercises in the warm-up period could be less effective in gaining flexibility in school children. Studies that use a stretching volume between 4 and 7 minutes per session and 2-4 training classes per week, obtain statistically significant improvements on the levels of hamstring flexibility in the experimental groups. However, after a five-week detraining period, children revert back to their initial flexibility levels. Therefore, it seems appropriate that physical education teachers should implement stretching programs to improve the students´ flexibility during the Physical Education classes.

  9. A model of cytoskeletal reorientation in response to substrate stretching

    Directory of Open Access Journals (Sweden)

    Lazopoulos K.A.


    Full Text Available Living adherent cells change their orientation in response to substrate stretching such that their cytoskeletal components reorganize in a new direction. To study this phenomenon, we model the cytoskeleton as a planar system of elastic cables and struts both pinned at their endpoints to a flat flexible substrate. Tensed (pre-strained cables represent acting stress fibers, whereas compression-bearing struts represent microtubules. We assume that in response to uniaxial substrate stretching the model reorients and deforms into a new configuration that minimizes its total potential energy. Using the Maxwell's global stability criterion, we find global minima configurations during static extension and compression of the substrate. Based on these results, we predict reorientation during cyclic stretching of the substrate. We find that in response to cyclic stretching cells either reorient transversely to the direction of stretching, or exhibit multiple configurations symmetrically distributed relative to the direction of stretching. These predictions are consistent with experimental data on living cells from the literature.

  10. Unsteady Viscous Flow over an Expanding Stretching Cylinder

    Institute of Scientific and Technical Information of China (English)

    方铁钢; 章骥; 钟永芳; 陶华


    We study the viscous How over an expanding stretching cylinder. The solution is exact to the Navier-Stokes equations. The stretching velocity of the cylinder is proportional to the axial distance from the origin and decreases with time. There exists a unique solution for the How with all the studied values of Reynolds number and the unsteadiness parameter. Reversal Hows exist for an expanding stretching cylinder. The velocity decays faster for a larger Reynolds number and a more rapidly expanding cylinder.%We study the viscous flow over an expanding stretching cylinder.The solution is exact to the Navier-Stokes equations.The stretching velocity of the cylinder is proportional to the axial distance from the origin and decreases with time.There exists a unique solution for the flow with all the studied values of Reynolds number and the unsteadiness parameter.Reversal flows exist for an expanding stretching cylinder.The velocity decays faster for a larger Reynolds number and a more rapidly expanding cylinder.

  11. Pectoral stretching program for women undergoing radiotherapy for breast cancer. (United States)

    Lee, T S; Kilbreath, S L; Refshauge, K M; Pendlebury, S C; Beith, J M; Lee, M J


    Surgery and radiotherapy commonly cause adverse musculoskeletal problems, particularly loss of strength and range of motion, in the upper quadrant of breast cancer patients. Few well-designed studies have investigated whether these impairments can be prevented. Stretching is an effective technique for increasing range of motion, hence the aim of this study was to investigate whether a stretching program reduced acute musculoskeletal impairments in patients undergoing radiotherapy for breast cancer. Sixty-four women were recruited prior to commencement of radiotherapy following breast cancer surgery. Participants were randomised to either a control or stretch group. Participants in both groups were reviewed by the physical therapist on a weekly basis for approximately 6 weeks, and were given general information about skin care and lymphedema. The control group received no advice about exercise. The stretch group received instruction on low-load, prolonged pectoral stretches, which were to be performed daily and were checked at weekly visits. Shoulder range of motion, strength, arm circumference, and quality of life measurements were taken prior to, and at completion of radiotherapy, and at 7 months after radiotherapy. There was no difference in any outcome between groups. Breast symptoms increased for both groups during radiotherapy, without loss of strength or range of movement. The incidence of lymphedema during the study was low for both groups and did not differ between groups. The pectoral stretching program did not influence the outcomes measured because the symptoms reported by patients were not a consequence of contracture.

  12. The influence of chain stretching on the phase behavior of multiblock copolymer and comb copolymer melts

    NARCIS (Netherlands)

    Angerman, HJ; ten Brinke, G


    The subject of this paper is inspired by microphase-separated copolymer melts in which a small-scale structure is present inside one of the phases of a large-scale structure. Such a situation can arise in a diblock copolymer melt, if one of the blocks of the diblock is in itself a multiblock copolym

  13. Reflection on the role of the Dutch government in sustainable supply chains. New phase in the transition of sustainable products; Reflectie op rol overheid bij verduurzaming productketens. Nieuwe fase in transitie naar duurzame producten

    Energy Technology Data Exchange (ETDEWEB)

    Vermeulen, W. [Copernicus Instituut voor Duurzame Ontwikkeling en Innovatie, Universiteit Utrecht, Utrecht (Netherlands); Kok, M.; Van Oorschot, M. [Planbureau voor de Leefomgeving PBL, Den Haag (Netherlands)


    This article is based on an exploratory study which analyses some of the earliest multi-actor sustainable supply chain governance systems in order to answer the key research questions: Which strategies and instruments do governments - national and supranational - apply in advancing sustainable production and consumption in global supply chains; and What is known about the effectiveness of these strategies and instruments? The study focuses on two supply chains with the longest history of addressing imports from developing countries (tropical timber and coffee). These two supply chains are compared with two supply chains that are gaining increasing attention: - cocoa and tea. The study shows that the two most 'mature' global sustainable supply chains are market led in issuing voluntary certification and that buying certified products is starting to become mainstream and increasingly effective. The sustainable supply chains for tea and cocoa are more recent developments but may develop faster because of the lessons learnt in sustainable supply chains developed earlier. [Dutch] Het marktaandeei van meerdere duurzame producten is inmiddels het nichestadium ontstegen. Die verduurzaming wordt door de overheid primair gezien als een verantwoordelijkheid van de maatschappelijke partners (bedrijfsleven, burgers en belangenorganisaties). Hierbij speelt de overheid slechts een begeleidende rol vanuit de zijlijn. Naarmate de marktaandelen verder toenemen is vanwege tekortkomingen in de markt reflectie op die rol nodig. Als illustratie wordt in dit artikel ingegaan op ontwikkelingen in twee productketens: koffie en hout.

  14. The effect of warm-up, static stretching and dynamic stretching on hamstring flexibility in previously injured subjects.

    LENUS (Irish Health Repository)

    O'Sullivan, Kieran


    BACKGROUND: Warm-up and stretching are suggested to increase hamstring flexibility and reduce the risk of injury. This study examined the short-term effects of warm-up, static stretching and dynamic stretching on hamstring flexibility in individuals with previous hamstring injury and uninjured controls. METHODS: A randomised crossover study design, over 2 separate days. Hamstring flexibility was assessed using passive knee extension range of motion (PKE ROM). 18 previously injured individuals and 18 uninjured controls participated. On both days, four measurements of PKE ROM were recorded: (1) at baseline; (2) after warm-up; (3) after stretch (static or dynamic) and (4) after a 15-minute rest. Participants carried out both static and dynamic stretches, but on different days. Data were analysed using Anova. RESULTS: Across both groups, there was a significant main effect for time (p < 0.001). PKE ROM significantly increased with warm-up (p < 0.001). From warm-up, PKE ROM further increased with static stretching (p = 0.04) but significantly decreased after dynamic stretching (p = 0.013). The increased flexibility after warm-up and static stretching reduced significantly (p < 0.001) after 15 minutes of rest, but remained significantly greater than at baseline (p < 0.001). Between groups, there was no main effect for group (p = 0.462), with no difference in mean PKE ROM values at any individual stage of the protocol (p > 0.05). Using ANCOVA to adjust for the non-significant (p = 0.141) baseline difference between groups, the previously injured group demonstrated a greater response to warm-up and static stretching, however this was not statistically significant (p = 0.05). CONCLUSION: Warm-up significantly increased hamstring flexibility. Static stretching also increased hamstring flexibility, whereas dynamic did not, in agreement with previous findings on uninjured controls. The effect of warm-up and static stretching on flexibility was greater in those with reduced

  15. The effect of warm-up, static stretching and dynamic stretching on hamstring flexibility in previously injured subjects

    Directory of Open Access Journals (Sweden)

    Murray Elaine


    Full Text Available Abstract Background Warm-up and stretching are suggested to increase hamstring flexibility and reduce the risk of injury. This study examined the short-term effects of warm-up, static stretching and dynamic stretching on hamstring flexibility in individuals with previous hamstring injury and uninjured controls. Methods A randomised crossover study design, over 2 separate days. Hamstring flexibility was assessed using passive knee extension range of motion (PKE ROM. 18 previously injured individuals and 18 uninjured controls participated. On both days, four measurements of PKE ROM were recorded: (1 at baseline; (2 after warm-up; (3 after stretch (static or dynamic and (4 after a 15-minute rest. Participants carried out both static and dynamic stretches, but on different days. Data were analysed using Anova. Results Across both groups, there was a significant main effect for time (p 0.05. Using ANCOVA to adjust for the non-significant (p = 0.141 baseline difference between groups, the previously injured group demonstrated a greater response to warm-up and static stretching, however this was not statistically significant (p = 0.05. Conclusion Warm-up significantly increased hamstring flexibility. Static stretching also increased hamstring flexibility, whereas dynamic did not, in agreement with previous findings on uninjured controls. The effect of warm-up and static stretching on flexibility was greater in those with reduced flexibility post-injury, but this did not reach statistical significance. Further prospective research is required to validate the hypothesis that increased flexibility improves outcomes. Trial Registration ACTRN12608000638336

  16. Stretching Rubber, Stretching Minds: a polymer physics lab for teaching entropy

    CERN Document Server

    Brzinski, Theodore A


    Entropy is a difficult concept to teach using real-world examples. Unlike temperature, pressure, volume, or work, it's not a quantity which most students encounter in their day-to-day lives. Even the way entropy is often qualitatively described, as a measure of disorder, is incomplete and can be misleading. In an effort to address these obstacles, we have developed a simple laboratory activity, the stretching of an elastic rubber sheet, intended to give students hands-on experience with the concepts of entropy, temperature and work in both adiabatic and quasistatic processes. We present two versions of the apparatus: a double-lever system, which may be reproduced with relatively little cost, and a commercial materials testing system, which provides students experience with scientific instrumentation that is used in research.

  17. Enhancing Crystallinity and Orientation by Hot-Stretching to Improve the Mechanical Properties of Electrospun Partially Aligned Polyacrylonitrile (PAN Nanocomposites

    Directory of Open Access Journals (Sweden)

    Xiaoxiao Hou


    Full Text Available Partially aligned polyacrylonitrile (PAN-based nanofibers were electrospun from PAN and PAN/single-walled carbon nanotubes (SWNTs in a solution of dimethylformamide (DMF to make the nanofiber composites. The as-spun nanofibers were then hot-stretched in the oven to enhance its orientation and crystallinity. With the introduction of SWNTs and by the hot-stretched process, the mechanical properties will be enhanced correspondingly. Scanning electron microscopy (SEM, transmission electron microscopy (TEM, X-ray scattering (XRD, differential scanning calorimetry (DSC, and the tensile test were used to characterize the microstructure and performances of the nanofibers. The orientation and crystallinity of the as-spun and hot-stretched nanofibers confirmed by X-ray have increased. Differential scanning calorimetry showed that the glass transition temperature of PAN increased about 3 °C by an addition of 0.75 wt% SWNTs indicating a strong interfacial interaction between PAN and SWNTs. The tensile strength and the modulus of the nanofibers increased revealing significant load transfer across the nanotube-matrix interface. For PAN nanofibers, the improved fiber alignment, orientation and crystallinity resulted in enhanced mechanical properties, such as the tensile strength and modulus of the nanofibers. It was concluded that the hot-stretched nanofiber and the PAN/SWNTs nanofibers can be used as a potential precursor to produce high-performance nanocomposites.

  18. Progression of articular cartilage degeneration after application of muscle stretch. (United States)

    Dias, Carolina Náglio Kalil; Renner, Adriana Frias; dos Santos, Anderson Amaro; Vasilceac, Fernando Augusto; Mattiello, Stela Márcia


    The aim of study was to evaluate the progression of the ankle articular cartilage alterations after a post-immobilization muscle stretching. Twenty-nine Wistar rats were separated into five groups: C--control, S--stretched, SR--stretch recovery, IS--immobilized and stretched, and ISR--immobilized stretched recovery. The immobilization was maintained for 4 weeks and the left ankle was then stretched manually through a full dorsal flexion for 10 times for 60 s with a 30 s interval between each 60 s period, 7 days/week for 3 weeks. The recovery period was of 7 weeks. At the end of the experiment, the left ankles were removed, processed in paraffin, and stained in hematoxylin-eosin and safranin O. Two blinded observers evaluated the articular cartilage using the Mankin grading system (cellularity, chondrocyte cloning, and proteoglycan content) through light microscopy, and performed the morphometry (cellularity, total thickness, non-calcified thickness, and calcified thickness measures). Both the Mankin grading system and the morphometric analysis showed that the ISR group presented the most increased cellularity among the groups. The IS and SR groups showed the highest proteoglycan loss, and the ISR group showed the same content of proteoglycan observed in the C group. No significant differences were found in the chondrocyte cloning, the total cartilage thickness, the non-calcified cartilage thickness, and the calcified cartilage thickness among the groups. The results suggest that the cartilage can recover the proteoglycan loss caused by immobilization and stretching, probably because of the increased chondrocyte density. Therefore, the ankle articular cartilage responded as to repair the metabolic deficits.

  19. Cβ-H stretching vibration as a new probe for conformation of n-propanol in gaseous and liquid states. (United States)

    Yu, Yuanqin; Wang, Yuxi; Hu, Naiyin; Lin, Ke; Zhou, Xiaoguo; Liu, Shilin


    The development of potential probes to identify molecular conformation is essential in organic and biological chemistry. In this work, we investigated a site-specific C-H stretching vibration as a conformational probe for a model compound, 1,1,3,3,3-deuterated n-propanol (CD3CH2CD2OH), using stimulated photoacoustic Raman spectroscopy in the gas phase and conventional spontaneous Raman spectroscopy in the liquid state. Along with quantum chemistry calculations, the experiment shows that the CH2 symmetric stretching mode at the β-carbon position is very sensitive to the conformational structure of n-propanol and can serve as a new probe for all five of its conformers. Compared with the O-H stretching vibration, a well-established conformational sensor for n-propanol, the Cβ-H stretching vibration presented here shows better conformational resolution in the liquid state. Furthermore, using this probe, we investigated the conformational preference of n-propanol in pure liquid and in dilute water solution. It is revealed that in pure liquid, n-propanol molecules prefer the trans-OH conformation, and in dilute water solution, this preference is enhanced, indicating that the water molecules play a role of further stabilizing the trans-OH n-propanol conformers. This leads to conformational evolution that n-propanol molecules with gauche-OH structure are transferred to the trans-OH structure upon diluting with water. These results not only provide important information on structures of n-propanol in different environments, but also demonstrate the potential of the C-H stretching vibration as a new tool for conformational analysis. This is especially important when considering that hydrocarbon chains are structural units in organic and biological molecules.

  20. The adsorption-desorption transition of double-stranded DNA interacting with an oppositely charged dendrimer induced by multivalent anions. (United States)

    Jiang, Yangwei; Zhang, Dong; Zhang, Yaoyang; Deng, Zhenyu; Zhang, Linxi


    The adsorption-desorption transition of DNA in DNA-dendrimer solutions is observed when high-valence anions, such as hexavalent anions, are added to the DNA-dendrimer solutions. In the DNA-dendrimer solutions with low-valence anions, dendrimers bind tightly with the V-shaped double-stranded DNA. When high-valence anions, such as pentavalent or hexavalent anions, are added to the DNA-dendrimer solutions, the double-stranded DNA chains can be stretched straightly and the dendrimers are released from the double-stranded DNA chains. In fact, adding high-valence anions to the solutions can change the charge spatial distribution in the DNA-dendrimer solutions, and weaken the electrostatic interactions between the positively charged dendrimers and the oppositely charged DNA chains. Adsorption-desorption transition of DNA is induced by the overcharging of dendrimers. This investigation is capable of helping us understand how to control effectively the release of DNA in gene/drug delivery because an effective gene delivery for dendrimers includes non-covalent DNA-dendrimer binding and the effective release of DNA in gene therapy.

  1. Learning phase transitions by confusion

    CERN Document Server

    van Nieuwenburg, Evert P L; Huber, Sebastian D


    Classifying phases of matter is a central problem in physics. For quantum mechanical systems, this task can be daunting owing to the exponentially large Hilbert space. Thanks to the available computing power and access to ever larger data sets, classification problems are now routinely solved using machine learning techniques. Here, we propose to use a neural network based approach to find phase transitions depending on the performance of the neural network after training it with deliberately incorrectly labelled data. We demonstrate the success of this method on the topological phase transition in the Kitaev chain, the thermal phase transition in the classical Ising model, and the many-body-localization transition in a disordered quantum spin chain. Our method does not depend on order parameters, knowledge of the topological content of the phases, or any other specifics of the transition at hand. It therefore paves the way to a generic tool to identify unexplored phase transitions.

  2. Formation of helical ion chains

    CERN Document Server

    Nigmatullin, Ramil; De Chiara, Gabriele; Morigi, Giovanna; Plenio, Martin B; Retzker, Alex


    We study the nonequilibrium dynamics of the linear to zigzag structural phase transition exhibited by an ion chain confined in a trap with periodic boundary conditions. The transition is driven by reducing the transverse confinement at a finite quench rate, which can be accurately controlled. This results in the formation of zigzag domains oriented along different transverse planes. The twists between different domains can be stabilized by the topology of the trap and under laser cooling the system relaxes to a helical chain with possibly nonzero winding number. Molecular dynamics simulations are used to obtain a large sample of possible trajectories for different quench rates. The scaling of the average winding number with different quench rates is compared to the prediction of the Kibble-Zurek theory, and a good quantitative agreement is found.

  3. Stretching Fibroblasts Remodels Fibronectin and Alters Cancer Cell Migration (United States)

    Ao, Mingfang; Brewer, Bryson M.; Yang, Lijie; Franco Coronel, Omar E.; Hayward, Simon W.; Webb, Donna J.; Li, Deyu


    Most investigations of cancer-stroma interactions have focused on biochemical signaling effects, with much less attention being paid to biophysical factors. In this study, we investigated the role of mechanical stimuli on human prostatic fibroblasts using a microfluidic platform that was adapted for our experiments and further developed for both repeatable performance among multiple assays and for compatibility with high-resolution confocal microscopy. Results show that mechanical stretching of normal tissue-associated fibroblasts (NAFs) alters the structure of secreted fibronectin. Specifically, unstretched NAFs deposit and assemble fibronectin in a random, mesh-like arrangement, while stretched NAFs produce matrix with a more organized, linearly aligned structure. Moreover, the stretched NAFs exhibited an enhanced capability for directing co-cultured cancer cell migration in a persistent manner. Furthermore, we show that stretching NAFs triggers complex biochemical signaling events through the observation of increased expression of platelet derived growth factor receptor α (PDGFRα). A comparison of these behaviors with those of cancer-associated fibroblasts (CAFs) indicates that the observed phenotypes of stretched NAFs are similar to those associated with CAFs, suggesting that mechanical stress is a critical factor in NAF activation and CAF genesis.

  4. Stretch-regulated Exocytosis/Endocytosis in Bladder Umbrella Cells (United States)

    Truschel, Steven T.; Wang, Edward; Ruiz, Wily G.; Leung, Som-Ming; Rojas, Raul; Lavelle, John; Zeidel, Mark; Stoffer, David; Apodaca, Gerard


    The epithelium of the urinary bladder must maintain a highly impermeable barrier despite large variations in urine volume during bladder filling and voiding. To study how the epithelium accommodates these volume changes, we mounted bladder tissue in modified Ussing chambers and subjected the tissue to mechanical stretch. Stretching the tissue for 5 h resulted in a 50% increase in lumenal surface area (from ∼2900 to 4300 μm2), exocytosis of a population of discoidal vesicles located in the apical cytoplasm of the superficial umbrella cells, and release of secretory proteins. Surprisingly, stretch also induced endocytosis of apical membrane and 100% of biotin-labeled membrane was internalized within 5 min after stretch. The endocytosed membrane was delivered to lysosomes and degraded by a leupeptin-sensitive pathway. Last, we show that the exocytic events were mediated, in part, by a cyclic adenosine monophosphate, protein kinase A-dependent process. Our results indicate that stretch modulates mucosal surface area by coordinating both exocytosis and endocytosis at the apical membrane of umbrella cells and provide insight into the mechanism of how mechanical forces regulate membrane traffic in nonexcitable cells. PMID:11907265


    Directory of Open Access Journals (Sweden)

    Bergun MERİÇ


    Full Text Available The aim of this study was to determine the effects of static and dynamic stretching protocols on agility performance in warm-up sessions. Twenty-three football players (mean ± SD age = 15,04± 0,77 years; weight = 62,35± 6,48kg; height = 1,73± 0,06cm participated to this study from Kocaeli Amateur Football League. Three different warm-up protocols were applied to the players every 48 hours. The first protocol was a general warm-up consisting of 5 minutes jogging with no stretching (GWU+NS, the second protocol was GWU with dynamic stretching (GWU+DS and the third protocol was GWU with static stretching (GWU+SS respectively. In the GWU+DS and GWU+SS protocols, 10 different movements were worked out with 12-15 repetitions in 30 seconds for each muscle group. Following each protocols, the players applied an agility performance test. SPSS (17.0 program used to compare the data obtained from 3 protocols and between two of them. In result, there were no statistically differences between NS and SS protocols (p>0.05. However, statistically difference was seen between DS and SS protocols and between DS and NS protocols (p<0.05. The warm up protocols consist of dynamic stretching exercises before agility activities should be preferred to have better performance.

  6. Sub-Doppler Spectroscopy by Use of Microwave Sidebands of CO2 Laser Lines Applied to the C-O Stretching Fundamental Band of Methanol

    Directory of Open Access Journals (Sweden)

    Kojiro Takagi


    Full Text Available Microwave sidebands of CO2 laser lines were used as an infrared source in infrared microwave double resonance spectroscopy and infrared saturation spectroscopy to study the C -O stretching fundamental band of methanol. In the former application, rotational lines in the vCO = 1 state have been observed with good signal to noise ratios and physical processes involved in this method have been discussed. In the latter method, (vt, A/E, K = (2, A, 4 sequence transitions in the C-O stretching fundamental band have been identified and term values for the (2, A, 4 levels in the vCO = 1 state have been determined.

  7. Analysis of the carbonyl group stretching vibrations in some structural fragments of poly-3-hydroxybutyrate

    CERN Document Server

    Pitsevich, George A; Doroshenko, Iryna


    The structure and the medium effects exerted on the spectral characteristics of the carbonyl group stretching vibrations in some structural fragments of poly-3-hydroxybutyrate have been analyzed. Calculations of the equilibrium configurations and IR spectra were carried out using the Gaussian program set in the approximation B3LYP/cc-pVDZ. It has been shown that typical bending of the poly-3-hydroxybutyrate chain is observed with an increase in the number of structural units. In order to explain the difference between the calculated and experimental frequencies of the C=O group stretching vibrations, the calculations of the potential energy curve associated with variations in the length of C=O bond and the subsequent numerical solution of a one-dimensional vibrational Schr\\"odinger equation have been performed. The medium effects have been taken into account within the scope of a polarizable continuum model. Owing to the inclusion of the above-mentioned factors, which affect frequencies of the carbonyl groups...

  8. Acute effects of two different stretching techniques on isokinetic strength and power


    Ayala, F.; De Ste Croix, M; Sainz de Baranda, P.; Santonja, F.


    Objectives: To examine and compare the acute effects of short duration static and dynamic lower-limb stretching routines on the knee flexor and extensor peak torque and mean power during maximal concentric and eccentric muscle actions. Method: Forty-nine active adults completed the following intervention protocols on separate days: non-stretching, static stretching and dynamic stretching. After the stretching or control intervention, concentric and eccentric isokinetic peak torque and mean...

  9. Cell volume and membrane stretch independently control K+ channel activity

    DEFF Research Database (Denmark)

    Bomholtz, Sofia Hammami; Willumsen, Niels J; Olsen, Hervør L;


    A number of potassium channels including members of the KCNQ family and the Ca(2+) activated IK and SK, but not BK, are strongly and reversibly regulated by small changes in cell volume. It has been argued that this general regulation is mediated through sensitivity to changes in membrane stretch....... To test this hypothesis we have studied the regulation of KCNQ1 and BK channels after expression in Xenopus oocytes. Results from cell-attached patch clamp studies (approximately 50 microm(2) macropatches) in oocytes expressing BK channels demonstrate that the macroscopic volume-insensitive BK current...... was not affected by membrane stretch. The results indicate that (1) activation of BK channels by local membrane stretch is not mimicked by membrane stress induced by cell swelling, and (2) activation of KCNQ1 channels by cell volume increase is not mediated by local tension in the cell membrane. We conclude...

  10. Stretching Behavior of Red Blood Cells at High Strain Rates (United States)

    Mancuso, Jordan; Ristenpart, William


    Most work on the mechanical behavior of red blood cells (RBCs) has focused on simple shear flows. Relatively little work has examined RBC deformations in the physiologically important extensional flow that occurs at the entrance to a constriction. In particular, previous work suggests that RBCs rapidly stretch out and then retract upon entering the constriction, but to date no model predicts this behavior for the extremely high strain rates typically experienced there. In this work, we use high speed video to perform systematic measurements of the dynamic stretching behavior of RBCs as they enter a microfluidic constriction. We demonstrate that a simple viscoelastic model captures the observed stretching dynamics, up to strain rates as high as 1000 s-1. The results indicate that the effective elastic modulus of the RBC membrane at these strain rates is an order of magnitude larger than moduli measured by micropipette aspiration or other low strain rate techniques.

  11. Convective flow of sisko fluid over a bidirectional stretching sheet

    CERN Document Server

    Munir, Asif; Khan, Masood


    The present investigation discusses the flow and heat transfer characteristics of a steady three dimensional Sisko fluid. The flow is induced due to bidirectional stretching sheet. The influence of power-law index and stretching ratio on flow and heat transfer is studied thoroughly. Governing partial differential equations are reduced to coupled ordinary differential equations by suitable similarity variable. The resulting equations are then solved numerically by shooting method using adaptive Runge Kutta algorithm in combination with Broyden's method in the domain . The numerical results for the velocity and temperature fields are graphically presented and effects of the relevant parameters are discussed in detail. Moreover, the skin-friction coefficient and local Nusselt number for different values of the power-law index and stretching ratio are presented through tabulated data. The numerical results are verified with the results obtained by HAM. Additionally, the results are also validated with previously ...

  12. Effects of static stretching on 1-mile uphill run performance. (United States)

    Lowery, Ryan P; Joy, Jordan M; Brown, Lee E; Oliveira de Souza, Eduardo; Wistocki, David R; Davis, Gregory S; Naimo, Marshall A; Zito, Gina A; Wilson, Jacob M


    It is previously demonstrated that static stretching was associated with a decrease in running economy and distance run during a 30-minute time trial in trained runners. Recently, the detrimental effects of static stretching on economy were found to be limited to the first few minutes of an endurance bout. However, economy remains to be studied for its direct effects on performance during shorter endurance events. The aim of this study was to investigate the effects of static stretching on 1-mile uphill run performance, electromyography (EMG), ground contact time (GCT), and flexibility. Ten trained male distance runners aged 24 ± 5 years with an average VO2max of 64.9 ± 6.5 mL·kg-1·min-1 were recruited. Subjects reported to the laboratory on 3 separate days interspersed by 72 hours. On day 1, anthropometrics and V[Combining Dot Above]O2max were determined on a motor-driven treadmill. On days 2 and 3, subjects performed a 5-minute treadmill warm-up and either performed a series of 6 lower-body stretches for three 30-second repetitions or sat still for 10 minutes. Time to complete a 1-mile run under stretching and nonstretching conditions took place in randomized order. For the performance run, subjects were instructed to run as fast as possible at a set incline of 5% until a distance of 1 mile was completed. Flexibility from the sit and reach test, EMG, GCT, and performance, determined by time to complete the 1-mile run, were recorded after each condition. Time to complete the run was significantly less (6:51 ± 0:28 minutes) in the nonstretching condition as compared with the stretching condition (7:04 ± 0:32 minutes). A significant condition-by-time interaction for muscle activation existed, with no change in the nonstretching condition (pre 91.3 ± 11.6 mV to post 92.2 ± 12.9 mV) but increased in the stretching condition (pre 91.0 ± 11.6 mV to post 105.3 ± 12.9 mV). A significant condition-by-time interaction for GCT was also present, with no changes in

  13. Stretching to prevent musculoskeletal injuries. An approach to workplace wellness. (United States)

    Gartley, Rosanna M; Prosser, J Lynn


    A pre-shift stretching protocol to reduce employee injuries was initiated at a beverage company and a tin mill in the northeastern United States. The primary goal of this study was to determine the effects of a pre-shift stretching program on work-related musculoskeletal injuries. A secondary goal was to evaluate daily participation compliance during the 90-day program. Data on employee injuries during the stretching program were collected and compared to injury events during the same time period 1 year earlier. Comparison to injury events of the total eligible population during the study time frame was also included. Results of this pilot program in terms of injury rate reduction and participant compliance are promising. Study results may be useful for employers considering implementing similar programs and also suggest the need for further study in this area.

  14. Transcription upregulation via force-induced direct stretching of chromatin (United States)

    Tajik, Arash; Zhang, Yuejin; Wei, Fuxiang; Sun, Jian; Jia, Qiong; Zhou, Wenwen; Singh, Rishi; Khanna, Nimish; Belmont, Andrew S.; Wang, Ning


    Mechanical forces play critical roles in the function of living cells. However, the underlying mechanisms of how forces influence nuclear events remain elusive. Here, we show that chromatin deformation as well as force-induced transcription of a green fluorescent protein (GFP)-tagged bacterial-chromosome dihydrofolate reductase (DHFR) transgene can be visualized in a living cell by using three-dimensional magnetic twisting cytometry to apply local stresses on the cell surface via an Arg-Gly-Asp-coated magnetic bead. Chromatin stretching depended on loading direction. DHFR transcription upregulation was sensitive to load direction and proportional to the magnitude of chromatin stretching. Disrupting filamentous actin or inhibiting actomyosin contraction abrogated or attenuated force-induced DHFR transcription, whereas activating endogenous contraction upregulated force-induced DHFR transcription. Our findings suggest that local stresses applied to integrins propagate from the tensed actin cytoskeleton to the LINC complex and then through lamina-chromatin interactions to directly stretch chromatin and upregulate transcription.

  15. Dynamic Contractility and Efficiency Impairments in Stretch-Shortening Cycle Are Stretch-Load-Dependent After Training-Induced Muscle Damage

    NARCIS (Netherlands)

    Vaczi, Mark; Racz, Levente; Hortobagyi, Tibor; Tihanyi, Jozsef


    Vaczi, M, Racz, L, Hortobagyi, T, and Tihanyi, J. Dynamic contractility and efficiency impairments in stretch-shortening cycle are stretch-load-dependent after training-induced muscle damage. J Strength Cond Res 27(8): 2171-2179, 2013To determine the acute task and stretch-load dependency of neuromu

  16. The acute effects of dynamic and ballistic stretching on vertical jump height, force, and power. (United States)

    Jaggers, Jason R; Swank, Ann M; Frost, Karen L; Lee, Chong D


    Stretching before performance is a common practice among athletes in hopes of increasing performance and reducing the risk of injury. However, cumulative results indicate a negative impact of static stretching and proprioceptive neuromuscular facilitation (PNF) on performance; thus, there is a need for evaluating other stretching strategies for effective warm-up. The purpose of this study was to compare the differences between two sets of ballistic stretching and two sets of a dynamic stretching routine on vertical jump performance. Twenty healthy male and female college students between the ages of 22 and 34 (24.8 +/- 3 years) volunteered to participate in this study. All subjects completed three individual testing sessions on three nonconsecutive days. On each day, the subjects completed one of three treatments (no stretch, ballistic stretch, and dynamic stretch). Intraclass reliability was determined using the data obtained from each subject. A paired samples t-test revealed no significant difference in jump height, force, or power when comparing no stretch with ballistic stretch. A significant difference was found on jump power when comparing no stretch with dynamic stretch, but no significant difference was found for jump height or force. Statistics showed a very high reliability when measuring jump height, force, and power using the Kistler Quattro Jump force plate. It seems that neither dynamic stretching nor ballistic stretching will result in an increase in vertical jump height or force. However, dynamic stretching elicited gains in jump power poststretch.

  17. EMG and peak force responses to PNF stretching and the relationship between stretching-induced force deficits and bilateral deficits. (United States)

    Cengiz, Asim


    [Purpose] The aim of the present study was to investigate the possibility of an interaction between stretching induced deficit (SFD) and bilateral deficits (BLD) during maximal voluntary isometric hand flexion under PNF stretch and no-stretch conditions through measurement of EMG and force production. [Subjects and Methods] Ten physically active male Caucasian students (age, 24.1±2.38 years; body mass, 79.48±11.40 kg; height, 174.15±0.8 cm) volunteered to participate in this study. EMG and force measurements of the subjects were recorded during either unilateral or bilateral 3-second maximal voluntary isometric hand flexion (MVC) against a force transducer. The paired sample t-test was used to examine the significance of differences among several conditions. Pearson product-moment correlation was used to evaluate the associations between different parameters. [Results] Stretching-induced deficits correlated with bilateral deficits in both force (r=0.85) and iEMG (r=0.89). PNF stretching caused significant decrements in the bilateral and unilateral conditions for both the right and left sides. [Conclusion] Since both force and iEMG decreases were observed in most measurements; it suggests there is a neural mechanism behinnd both the BLD and the SFD.

  18. Structure of low-stretch methane nonpremixed flames

    Energy Technology Data Exchange (ETDEWEB)

    Han, Bai; Ibarreta, Alfonso F.; Sung, Chih-Jen; T' ien, James S. [Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106 (United States)


    The present study experimentally and numerically investigates the structure associated with extremely low-stretch ({proportional_to}2 s{sup -1}) gaseous nonpremixed flames. The study of low-stretch flames aims to improve our fundamental understanding of the flame radiation effects on flame response and extinction limits. Low-stretch flames are also relevant to fire safety in reduced-gravity environments and to large buoyant fires, where localized areas of low stretch are attainable. In this work, ultra-low-stretch flames are established in normal gravity by bottom burning of a methane/nitrogen mixture discharged from a porous spherically symmetric burner of large radius of curvature. The large thickness of the resulting nonpremixed flame allows detailed mapping of the flame structure. Several advanced nonintrusive optical diagnostics are used to study the flame structure. Gas phase temperatures are measured by Raman scattering, while the burner surface temperatures are obtained by IR imaging. In addition, OH-PLIF and chemiluminescence imaging techniques are used to help characterize the extent of the flame reaction zone. These experimental results allow direct comparison with a quasi-one-dimensional numerical model including detailed chemistry, thermodynamic/transport properties, and radiation treatment. In addition, the radiative interactions between the flame and porous burner (modeled as a gray surface) are accounted for in the present model. The numerical modeling is demonstrated to be able to simulate the low-stretch flame structure. Using the current model, the extinction limits under different conditions are also examined. The computational results are consistent with experimental observations. (author)

  19. Can Treadmill Perturbations Evoke Stretch Reflexes in the Calf Muscles?

    Directory of Open Access Journals (Sweden)

    Lizeth H Sloot

    Full Text Available Disinhibition of reflexes is a problem amongst spastic patients, for it limits a smooth and efficient execution of motor functions during gait. Treadmill belt accelerations may potentially be used to measure reflexes during walking, i.e. by dorsal flexing the ankle and stretching the calf muscles, while decelerations show the modulation of reflexes during a reduction of sensory feedback. The aim of the current study was to examine if belt accelerations and decelerations of different intensities applied during the stance phase of treadmill walking can evoke reflexes in the gastrocnemius, soleus and tibialis anterior in healthy subjects. Muscle electromyography and joint kinematics were measured in 10 subjects. To determine whether stretch reflexes occurred, we assessed modelled musculo-tendon length and stretch velocity, the amount of muscle activity, as well as the incidence of bursts or depressions in muscle activity with their time delays, and co-contraction between agonist and antagonist muscle. Although the effect on the ankle angle was small with 2.8±1.0°, the perturbations caused clear changes in muscle length and stretch velocity relative to unperturbed walking. Stretched muscles showed an increasing incidence of bursts in muscle activity, which occurred after a reasonable electrophysiological time delay (163-191 ms. Their amplitude was related to the muscle stretch velocity and not related to co-contraction of the antagonist muscle. These effects increased with perturbation intensity. Shortened muscles showed opposite effects, with a depression in muscle activity of the calf muscles. The perturbations only slightly affected the spatio-temporal parameters, indicating that normal walking was retained. Thus, our findings showed that treadmill perturbations can evoke reflexes in the calf muscles and tibialis anterior. This comprehensive study could form the basis for clinical implementation of treadmill perturbations to functionally

  20. Graphs: Associated Markov Chains



    In this research paper, weighted / unweighted, directed / undirected graphs are associated with interesting Discrete Time Markov Chains (DTMCs) as well as Continuous Time Markov Chains (CTMCs). The equilibrium / transient behaviour of such Markov chains is studied. Also entropy dynamics (Shannon entropy) of certain structured Markov chains is investigated. Finally certain structured graphs and the associated Markov chains are studied.

  1. Simulation of stretch in non-uniform filaments

    DEFF Research Database (Denmark)

    Szabo, Peter; Clasen, Christian; McKinley, Gareth H.

    We consider the rapid stretching of a liquid lament under the action of a constant imposed tensile force. This problem was rst considered experimentally by Matta and Tytus (1990). A liquid bridge formed from a dilute polymer solution is established between two cylindrical disks. The upper disk...... numerically using FENE type models and two alternative kinematic descriptions. The axisymmetric lament is described by a Lagrangian approach based on an average stretch of axial elements (see Renardy (1990)). A noslip boundary condition is imposed indirectly at the end-plates according to a method described...

  2. Magnetohydrodynamics stagnation point flow towards a stretching vertical sheet (United States)

    Ishak, A.; Nazar, R.; Pop, I.


    The analysis of steady two-dimensional stagnation point flow of an incompressible viscous and electrically conducting fluid, subject to a transverse uniform magnetic field, over a vertical stretching sheet is investigated when the sheet is stretched in its own plane with a velocity and a temperature proportional to the distance from the stagnation point. It is shown that the basic partial differential equations reduce to similarity equations. This is followed by a direct numerical solution of the resulting boundary value problem using a very efficient finite-difference method. Discussions are made to trace among them the physically realistic solution. Tables 5, Figs 13, Refs 17.

  3. Stretch Polytetrafluoroethylene Grafts for Hemodialysis Angioaccess: Three-year Experience

    Directory of Open Access Journals (Sweden)

    Al Dayel Adel


    Full Text Available We report the results of 90 stretch polytetrafluoroethylene (PTFE grafts in 78 chronic renal failure patients over a 3-year period from 1995-1998. The grafts were used as primary access in 15% of the patients. The cumulative patency was 63.3% and there were no complications in 48.8% of the cases. Infection was encountered in 15.5% and thrombosis in 31.1% of the grafts. Intimal hyperplasia, venous anastomotic stenosis, improper puncture technique and subclavian vein stenosis were the major causes of failure of grafts. We conclude that stretch PTFE grafts as angioaccesses may provide good patency and durability.

  4. Surface effects on the mechanical elongation of AuCu nanowires: De-alloying and the formation of mixed suspended atomic chains

    Energy Technology Data Exchange (ETDEWEB)

    Lagos, M. J. [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, R. Sergio B. de Holanda 777, 13083-859 Campinas-SP (Brazil); Laboratório Nacional de Nanotecnologia-LNNANO, 13083-970 Campinas-SP (Brazil); Autreto, P. A. S.; Galvao, D. S., E-mail:; Ugarte, D. [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, R. Sergio B. de Holanda 777, 13083-859 Campinas-SP (Brazil); Bettini, J. [Laboratório Nacional de Nanotecnologia-LNNANO, 13083-970 Campinas-SP (Brazil); Sato, F.; Dantas, S. O. [Departamento de Física, ICE, Universidade Federal de Juiz de Fora, 36036-330 Juiz de Fora-MG (Brazil)


    We report here an atomistic study of the mechanical deformation of Au{sub x}Cu{sub (1−x)} atomic-size wires (nanowires (NWs)) by means of high resolution transmission electron microscopy experiments. Molecular dynamics simulations were also carried out in order to obtain deeper insights on the dynamical properties of stretched NWs. The mechanical properties are significantly dependent on the chemical composition that evolves in time at the junction; some structures exhibit a remarkable de-alloying behavior. Also, our results represent the first experimental realization of mixed linear atomic chains (LACs) among transition and noble metals; in particular, surface energies induce chemical gradients on NW surfaces that can be exploited to control the relative LAC compositions (different number of gold and copper atoms). The implications of these results for nanocatalysis and spin transport of one-atom-thick metal wires are addressed.

  5. a First-Principles Model of Fermi Resonance in the Alkyl CH Stretch Region: Application to Hydronaphthalenes, Indanes, and Cyclohexane (United States)

    Sibert, Edwin; Kidwell, Nathanael; Zwier, Timothy S.


    The infrared (IR) spectroscopy of the alkyl CH stretch region (2750-3000 cm-1) of a series of bicyclic hydrocarbons and free radicals has been studied under supersonic expansion cooling in the gas phase, and compared with a theoretical model that describes the local mode stretch-bend Fermi resonance interactions. The double resonance method of fluorescence-dip infrared (FDIR) spectroscopy was used on the stable molecules 1,2-dihydronaphthalene, 1,4-dihydronaphthalene, tetralin, indene, and indane using the S_0-S_1 origin transition as a monitor of transitions. Resonant ion-dip infrared (RIDIR) spectra were recorded for the trihydronaphthyl (THN) and inden-2-yl methyl (I2M) radicals. The previously developed model Hamiltonian [J. Chem. Phys. 138 064308 (2013)] incorporates cubic stretch-bend coupling with parameters obtained from density functional theory methods. Full dimensional calculations are compared to reduced dimensional Hamiltonian results in which anharmonic CH streches and CH_2 scissor modes are Fermi coupled. Excellent agreement between theoretical results is found. Scale factors of select terms in the reduced dimensional Hamiltonian, obtained by fitting the theoretical Hamiltonian predictions to the experimental spectra, are found to be similar to previous work. The resulting Hamiltonian predicts successfully all the major spectral features considered in this study. A simplified model is introduced in which the CH_2 groups are decoupled. This model enables the assignment of many of the spectral features. The model results are extended to describe the CH stretch spectrum of the chair and twist-boat conformers of cyclohexane. The chair conformer is used to illustrate the shortcomings of the CH_2 coupling model.

  6. Citation distribution of individual scientist: approximations of stretch exponential distribution with power law tails

    CERN Document Server

    Garanina, O S


    A multi-parametric family of stretch exponential distributions with various power law tails is introduced and is shown to describe adequately the empirical distributions of scientific citation of individual authors. The four-parametric families are characterized by a normalization coefficient in the exponential part, the power exponent in the power-law asymptotic part, and the coefficient for the transition between the above two parts. The distribution of papers of individual scientist over citations of these papers is studied. Scientists are selected via total number of citations in three ranges: 102-103, 103-104, and 104-105 of total citations. We study these intervals for physicists in ISI Web of Knowledge. The scientists who started their scientific publications after 1980 were taken into consideration only. It is detected that the power coefficient in the stretch exponent starts from one for low-cited authors and has to trend to smaller values for scientists with large number of citation. At the same tim...

  7. Nematic Liquid Crystal Alignment Behaviors between Crossed Stretched Miropolymer Filaments with Anchoring Effects (United States)

    Fujikake, Hideo; Murashige, Takeshi; Sato, Hiroto; Kikuchi, Hiroshi; Kurita, Taiichiro; Sato, Fumio


    We observed the molecular alignment of a liquid crystal (LC) induced by crossing two stretched micropolymer filaments between glass substrates and confirmed its light modulation property. The two microfilaments, which were extracted from a cellulose cloth by stretching it in advance, had surface molecular alignment and stabilized nematic LC alignment between the microfilaments crossed with a small angle. In the fabricated LC cell, a spatially-uniform LC planar alignment is achieved in the area of a filament interval of less than 60 μm. By polarizing microscopy observation of the isotropic-to-nematic wetting transition of the LC material between the polymer filaments, it was confirmed that the stable LC alignment area is formed by the surface anchoring of the filaments. When external voltages were applied to the obtained uniformed alignment LC area, a characteristic periodic electrooptic property was confirmed on the basis of electrically-controlled birefringence under the alignment control of the in-plane anchoring of the filaments.

  8. Revisiting Causality in Markov Chains

    CERN Document Server

    Shojaee, Abbas


    Identifying causal relationships is a key premise of scientific research. The growth of observational data in different disciplines along with the availability of machine learning methods offers the possibility of using an empirical approach to identifying potential causal relationships, to deepen our understandings of causal behavior and to build theories accordingly. Conventional methods of causality inference from observational data require a considerable length of time series data to capture cause-effect relationship. We find that potential causal relationships can be inferred from the composition of one step transition rates to and from an event. Also known as Markov chain, one step transition rates are a commonly available resource in different scientific disciplines. Here we introduce a simple, effective and computationally efficient method that we termed 'Causality Inference using Composition of Transitions CICT' to reveal causal structure with high accuracy. We characterize the differences in causes,...


    Institute of Scientific and Technical Information of China (English)

    Meng-bo Luo; Ying-cai Chen; Jian-hua Huang; Jian-min Xu


    The conformational entropy S and free energy F were calculated by exact enumeration of polysilane chain up to 23 segments with excluded volume (EV) and long-range van der Waals (VW) interaction. A nonlinear relation between SEV+VW and chain length n was found though SEV was found to vary linearly with n. We found that the second-order transition temperature of polysilane chain with VW interaction increases with the increase of chain length, while that of polysilane chain without VW interaction is chain length independent. Moreover, the free energies FEV+VW and FEV are both linearly related with n, and FEV+VW<FEV for all temperatures.``


    Directory of Open Access Journals (Sweden)

    Elvis Luke Fernandez


    Full Text Available Introduction: Low back pain has a significant impact on the individual’s family, socio-economic status, occupation, health system, community. Stretching is included as a part of treatment regimen for low back pain. Much controversy exists on the type of stretching technique and parameters which would prove beneficial to improve flexibility. Aim of the study was to compare the efficacy of active stretching over passive stretching, on the functional performance among patients with low back pain. Materials and method: 52 subjects with mechanical low back pains in the age group of 20-50 were enrolled for the study. Flexibility measurement and Oswestry Low Back Pain Disability Index was used as the primary outcome measure. Flexibility of Iliopsoas was measured using the modified Thomas test; Flexibility of Hamstring was measured using the active knee extension test. The subjects underwent 7 days of therapy sessions, after 7 days of therapy the individuals where re-assessed for flexibility and they were asked to fill the Oswestry Low Back Pain Disability Questionnaire. Results: 52 subjects were enrolled in the study, of which 36 subjects completed the study, among them 18 subjects in the control group and 18 subjects in intervention group. For independent groups paired t-test was used. Using the paired sample t-test significant difference was measured between the pre and post of the intervention group and control groups a significant difference of .001 was achieved in both the groups (P=.001. Discussion: The results of the present study prove that both active and passive stretching is beneficial in improving the flexibility of tight muscles in the lower limbs. Also both active stretching and passive stretching has a profound effect on the functional aspect in patients suffering with low back pain. Conclusion: The result of present study conveys that both active and passive stretch is helpful in improving the flexibility in the major muscle groups of

  11. Effects on hamstring muscle extensibility, muscle activity, and balance of different stretching techniques. (United States)

    Lim, Kyoung-Il; Nam, Hyung-Chun; Jung, Kyoung-Sim


    [Purpose] The purpose of this study was to investigate the effects of two different stretching techniques on range of motion (ROM), muscle activation, and balance. [Subjects] For the present study, 48 adults with hamstring muscle tightness were recruited and randomly divided into three groups: a static stretching group (n=16), a PNF stretching group (n=16), a control group (n=16). [Methods] Both of the stretching techniques were applied to the hamstring once. Active knee extension angle, muscle activation during maximum voluntary isometric contraction (MVC), and static balance were measured before and after the application of each stretching technique. [Results] Both the static stretching and the PNF stretching groups showed significant increases in knee extension angle compared to the control group. However, there were no significant differences in muscle activation or balance between the groups. [Conclusion] Static stretching and PNF stretching techniques improved ROM without decrease in muscle activation, but neither of them exerted statistically significant effects on balance.

  12. Acute effects of three different stretching protocols on the wingate test performance. (United States)

    Franco, Bruno L; Signorelli, Gabriel R; Trajano, Gabriel S; Costa, Pablo B; de Oliveira, Carlos G


    The purpose of this study was to examine the acute effects of different stretching exercises on the performance of the traditional Wingate test (WT). Fifteen male participants performed five WT; one for familiarization (FT), and the remaining four after no stretching (NS), static stretching (SS), dynamic stretching (DS), and proprioceptive neuromuscular facilitation (PNF). Stretches were targeted for the hamstrings, quadriceps, and calf muscles. Peak power (PP), mean power (MP), and the time to reach PP (TP) were calculated. The MP was significantly lower when comparing the DS (7.7 ± 0.9 W/kg) to the PNF (7.3 ± 0.9 W/kg) condition (p stretching providing the lowest result. A consistent increase of TP was observed after all stretching exercises when compared to NS. The results suggest the type of stretching, or no stretching, should be considered by those who seek higher performance and practice sports that use maximal anaerobic power.

  13. Examining flow-flame interaction and the characteristic stretch rate in vortex-driven combustion dynamics using PIV and numerical simulation

    KAUST Repository

    Hong, Seunghyuck


    In this paper, we experimentally investigate the combustion dynamics in lean premixed flames in a laboratory scale backward-facing step combustor in which flame-vortex driven dynamics are observed. A series of tests was conducted using propane/hydrogen/air mixtures for various mixture compositions at the inlet temperature ranging from 300K to 500K and at atmospheric pressure. Pressure measurements and high speed particle image velocimetry (PIV) are used to generate pressure response curves and phase-averaged vorticity and streamlines as well as the instantaneous flame front, respectively, which describe unsteady flame and flow dynamics in each operating regime. This work was motivated in part by our earlier study where we showed that the strained flame consumption speed Sc can be used to collapse the pressure response curves over a wide range of operating conditions. In previous studies, the stretch rate at which Sc was computed was determined by trial and error. In this study, flame stretch is estimated using the instantaneous flame front and velocity field from the PIV measurement. Independently, we also use computed strained flame speed and the experimental data to determine the characteristic values of stretch rate near the mode transition points at which the flame configuration changes. We show that a common value of the characteristic stretch rate exists across all the flame configurations. The consumption speed computed at the characteristic stretch rate captures the impact of different operating parameters on the combustor dynamics. These results suggest that the unsteady interactions between the turbulent flow and the flame dynamics can be encapsulated in the characteristic stretch rate, which governs the critical flame speed at the mode transitions and thereby plays an important role in determining the stability characteristics of the combustor. © 2013 The Combustion Institute.

  14. Buckling a Semiflexible Polymer Chain under Compression

    Directory of Open Access Journals (Sweden)

    Ekaterina Pilyugina


    Full Text Available Instability and structural transitions arise in many important problems involving dynamics at molecular length scales. Buckling of an elastic rod under a compressive load offers a useful general picture of such a transition. However, the existing theoretical description of buckling is applicable in the load response of macroscopic structures, only when fluctuations can be neglected, whereas membranes, polymer brushes, filaments, and macromolecular chains undergo considerable Brownian fluctuations. We analyze here the buckling of a fluctuating semiflexible polymer experiencing a compressive load. Previous works rely on approximations to the polymer statistics, resulting in a range of predictions for the buckling transition that disagree on whether fluctuations elevate or depress the critical buckling force. In contrast, our theory exploits exact results for the statistical behavior of the worm-like chain model yielding unambiguous predictions about the buckling conditions and nature of the buckling transition. We find that a fluctuating polymer under compressive load requires a larger force to buckle than an elastic rod in the absence of fluctuations. The nature of the buckling transition exhibits a marked change from being distinctly second order in the absence of fluctuations to being a more gradual, compliant transition in the presence of fluctuations. We analyze the thermodynamic contributions throughout the buckling transition to demonstrate that the chain entropy favors the extended state over the buckled state, providing a thermodynamic justification of the elevated buckling force.

  15. Electrohydrodynamic direct-writing microfiber patterns under stretching (United States)

    Zheng, Gaofeng; Sun, Lingling; Wang, Xiang; Wei, Jin; Xu, Lei; Liu, Yifang; Zheng, Jianyi; Liu, Juan


    In this paper, the rheology and deposition behaviors of electrohydrodynamic direct-write (EDW) jet under stretching tension are studied. The EDW jet is stretched into tightened state by the drag force from moving collector, when moving speed of collector is higher than deposition velocity of jet. The drag force from the moving collector provides an extra force to stretch the charged jet, which promotes the stability and decreases the diameter of direct-written fiber. The whipping and bending motion of jet can be overcome by the drag force, and then, straight orderly fibers are direct-written along the trajectory of collector. The falling jet would be also deviated from the extension line of spinneret by the drag force. As the collector velocity increases from 10 to 1000 mm/s, the average line width of direct-written microfiber decreases from 18.89 to 0.89 µm. The thickness of microfiber ranges from 100 nm to 1.5 µm. The moving collector leads to large deviation of charged jet. The tightened charged jet has good resistance against the interference of charge repulsion force, which helps to direct-write orderly nanofiber. During the EDW process, the mechanical stretching force had provided an excellent function to control the morphology and deposition pattern of micro-/nanofiber.


    Institute of Scientific and Technical Information of China (English)

    Zhu Jun; Cheng Yan; Chen Xiang-rong; Gou Qing-quan


    A four-parameter nonlinear model is introduced to the description of theX - Y stretching modes of XY6 octahedral molecules in the electronicground state. We here only apply it to the calculations of S--Fstretches of SF6 molecule. The model calculations appear to describethe observed data well, and predict some new vibrational bands ataccurate energies not yet observed.

  17. Automation of a single-DNA molecule stretching device

    DEFF Research Database (Denmark)

    Sørensen, Kristian Tølbøl; Lopacinska, Joanna M.; Tommerup, Niels


    We automate the manipulation of genomic-length DNA in a nanofluidic device based on real-time analysis of fluorescence images. In our protocol, individual molecules are picked from a microchannel and stretched with pN forces using pressure driven flows. The millimeter-long DNA fragments free...

  18. OH stretching frequencies in systems with intramolecular hydrogen bonds

    DEFF Research Database (Denmark)

    Spanget-Larsen, Jens; Hansen, Bjarke Knud Vilster; Hansen, Poul Erik


    OH stretching wavenumbers were investigated for 30 species with intramolecularly hydrogen bonded hydroxyl groups, covering the range from 3600 to ca. 1900 cm-1. Theoretical wavenumbers were predicted with B3LYP/6-31G(d) density functional theory using the standard harmonic approximation, as well...

  19. Effects of Warm-Up Stretching Exercises on Sprint Performance (United States)

    Makaruk, Hubert; Makaruk, Beata; Kedra, Stanislaw


    Study aim: To assess direct effects of warm-up consisting of static and dynamic stretching exercises on sprint results attained by students differing in sprint performance. Material and methods: A group of 24 male and 19 female physical education students, including 12 and 9 sprinters, respectively. They performed warm-ups consisting of dynamic…

  20. Transient filament stretching rheometer I: force balance analysis

    DEFF Research Database (Denmark)

    Szabo, Peter


    The filament stretching device which is used increasingly as an apparatus for measuring extensional properties of polymeric liquids isanalysed. A force balance that includes the effects of inertia and surface tension is derived.The force balance may be used to correct for the effects of inertia...

  1. Partly Imidized Polyamic Acid and Its Uniaxial Stretched Polyimide Films

    Institute of Scientific and Technical Information of China (English)

    MA Peng-chang; HOU Yong


    Partly imidized polyamic acid(PAA) has been used to prepare high performance polyimide films.The behaviors of two polyamic acids derived from pyromellitic dianhydride(PMDA)/4,4'-oxydianiline(ODA) and 3,Y,4,4'-biphenyltetracarboxylic diahhydride(BPDA)/paraphenylenediamine(PPD) containing dehydrating agents composed of acetic anhydride and a tertiary amine as the catalyst were investigated.The gel point was dependent on imidization degree in despite of temperature and the molar ratio of catalyst to acetic acid.Imdization content was about 35% for PMDA/ODA and about 22% for BPDA/PPD.The effect of catalyst on imidization possessed an order of triethylamine>3-methylpyridine>pyridine>isoquinoline>2-methylpyridine.The stretching of the films greatly reduced the coefficient of linear thermal expansion(CTE) either in the longitudinal direction or transversal direction.Compared to the film from polyamic acid,the partly imidized film had greater stretching ratio,so that the uniaxial stretched polyimide film from partly imidized PAA had higher tensile strength and tensile modulus,but lower elongation in the stretching direction.

  2. Stretching of DNA confined in nanochannels with charged walls (United States)

    Manneschi, Chiara; Fanzio, Paola; Angeli, Elena; Repetto, Luca; Valbusa, Ugo


    There is currently a growing interest in control of stretching of DNA inside nanoconfined regions due to the possibility to analyze and manipulate single biomolecules for applications such as DNA mapping and barcoding, which are based on stretching the DNA in a linear fashion. In the present work, we couple Finite Element Methods and Monte Carlo simulations in order to study the conformation of DNA molecules confined in nanofluidic channels with neutral and charged walls. We find that the electrostatic forces become more and more important when lowering the ionic strength of the solution. The influence of the nanochannel cross section geometry is also studied by evaluating the DNA elongation in square, rectangular, and triangular channels. We demonstrate that coupling electrostatically interacting walls with a triangular geometry is an efficient way to stretch DNA molecules at the scale of hundreds of nanometers. The paper reports experimental observations of λ-DNA molecules in poly(dimethylsiloxane) nanochannels filled with solutions of different ionic strength. The results are in good agreement with the theoretical predictions, confirming the crucial role of the electrostatic repulsion of the constraining walls on the molecule stretching. PMID:25553196

  3. Anharmonic bend-stretch coupling in neat liquid water

    NARCIS (Netherlands)

    Lindner, Joerg; Cringus, Dan; Pshenichnikov, Maxim S.; Voehringer, Peter


    Femtosecond mid-IR spectroscopy is used to study the vibrational relaxation dynamics in neat liquid water. By exciting the bending vibration and probing the stretching mode, it is possible to reliably determine the bending and librational lifetimes of water. The anharmonic coupling between the bendi

  4. Structural information from OH stretching frequencies monohydric saturated alcohols

    NARCIS (Netherlands)

    Maas, J.H. van der; Lutz, E.T.G.


    Infrared data have been recorded of the hydroxyl stretching band for about 70 monohydric saturated alcohols in dilute carbon tetrachloride solution. The wavenumber maximum, the half-bandwidth and the band pattern could be related to the structure of the molecules. Not only primary, secondary and ter

  5. Mediators of Yoga and Stretching for Chronic Low Back Pain

    Directory of Open Access Journals (Sweden)

    Karen J. Sherman


    Full Text Available Although yoga is an effective treatment for chronic low back pain, little is known about the mechanisms responsible for its benefits. In a trial comparing yoga to intensive stretching and self-care, we explored whether physical (hours of back exercise/week, cognitive (fear avoidance, body awareness, and self-efficacy, affective (psychological distress, perceived stress, positive states of mind, and sleep, and physiological factors (cortisol, DHEA mediated the effects of yoga or stretching on back-related dysfunction (Roland-Morris Disability Scale (RDQ. For yoga, 36% of the effect on 12-week RDQ was mediated by increased self-efficacy, 18% by sleep disturbance, 9% by hours of back exercise, and 61% by the best combination of all possible mediators (6 mediators. For stretching, 23% of the effect was mediated by increased self-efficacy, 14% by days of back exercise, and 50% by the best combination of all possible mediators (7 mediators. In open-ended questions, ≥20% of participants noted the following treatment benefits: learning new exercises (both groups, relaxation, increased awareness, and the benefits of breathing (yoga, benefits of regular practice (stretching. Although both self-efficacy and hours of back exercise were the strongest mediators for each intervention, compared to self-care, qualitative data suggest that they may exert their benefits through partially distinct mechanisms.

  6. Mediators of yoga and stretching for chronic low back pain. (United States)

    Sherman, Karen J; Wellman, Robert D; Cook, Andrea J; Cherkin, Daniel C; Ceballos, Rachel M


    Although yoga is an effective treatment for chronic low back pain, little is known about the mechanisms responsible for its benefits. In a trial comparing yoga to intensive stretching and self-care, we explored whether physical (hours of back exercise/week), cognitive (fear avoidance, body awareness, and self-efficacy), affective (psychological distress, perceived stress, positive states of mind, and sleep), and physiological factors (cortisol, DHEA) mediated the effects of yoga or stretching on back-related dysfunction (Roland-Morris Disability Scale (RDQ)). For yoga, 36% of the effect on 12-week RDQ was mediated by increased self-efficacy, 18% by sleep disturbance, 9% by hours of back exercise, and 61% by the best combination of all possible mediators (6 mediators). For stretching, 23% of the effect was mediated by increased self-efficacy, 14% by days of back exercise, and 50% by the best combination of all possible mediators (7 mediators). In open-ended questions, ≥20% of participants noted the following treatment benefits: learning new exercises (both groups), relaxation, increased awareness, and the benefits of breathing (yoga), benefits of regular practice (stretching). Although both self-efficacy and hours of back exercise were the strongest mediators for each intervention, compared to self-care, qualitative data suggest that they may exert their benefits through partially distinct mechanisms.

  7. Habituation of lower leg stretch responses in Parkinson's disease. (United States)

    Bloem, B R; van Vugt, J P; Beckley, D J; Remler, M P; Roos, R A


    In young healthy subjects, initially large stretch responses in leg muscles are progressively attenuated following a series of identical postural perturbations. We have studied whether this habituation of stretch responses is impaired in Parkinson's disease. Ten patients and 10 elderly controls received 10 serial 'toe-up' rotational perturbations (amplitude 10 degrees) while standing on a supporting forceplate. We recorded posturally destabilizing medium latency (ML) stretch responses from the medial gastrocnemius muscle. Functional habituation across the first few trials occurred in patients, but not in elderly controls. The rate of habituation was influenced by the size of the response to the first perturbation. This observation explained the absence of habituation in elderly subjects because their responses during the first few trials were much smaller compared to patients. These results suggest that habituation of lower leg stretch responses is unimpaired in Parkinson's disease. The presence of initially large and 'unpracticed' responses may partially explain why Parkinson patients fall in response to unexpected postural disturbances that commonly occur in daily life.

  8. Sport stretching : Effect on passive muscle stiffness of short hamstrings

    NARCIS (Netherlands)

    Halbertsma, JPK; vanBolhuis, AI; Goeken, LNH


    Objective: To evaluate the effects of one 10-minute stretch on muscle stiffness in subjects with short hamstrings. Design: Randomized control trial. Setting: Laboratory for human movement sciences in the department of rehabilitation of a university hospital. Subjects: Sixteen students from the Depar

  9. Viscoelastic properties of vascular endothelial cells exposed to uniaxial stretch (United States)

    Osterday, Kathryn; Chew, Thomas; Loury, Phillip; Haga, Jason; Del Alamo, Juan C.; Chien, Shu


    Vascular endothelial cells (VECs) line the interior of blood vessels and regulate a variety of functions in the cardiovascular system. It is widely accepted that VECs will remodel themselves in response to mechanical stimuli, but few studies have analyzed the mechanical properties of these cells under stretch. We hypothesize that uniaxial stretch will cause an anisotropic realignment of actin filaments, and a change in the viscoelastic properties of the cell. To test this hypothesis, VECs were grown on a thin, transparent membrane mounted on a microscope. The membrane was stretched, consequently stretching the cells. Time-lapse sequences of the cells were taken every hour with a time resolution of 10 Hz. The random trajectories of intracellular endogenous particles were tracked using in-house algorithms. These trajectories were analyzed using a novel particle tracking microrheology formulation that takes into account the anisotropy of the cytoplasm of VECs. Supported by NSF CBET-1055697 CAREER Award (JCA) and NIH grants BRP HL064382 (SC), 1R01 HL080518 (SC).

  10. Searching for transit timing variations in transiting exoplanet systems

    CERN Document Server

    Hrudková, Marie; Benn, Chris; Pollacco, Don; Gibson, Neale; Joshi, Yogesh; Harmanec, Petr; Tulloch, Simon


    Searching for transit timing variations in the known transiting exoplanet systems can reveal the presence of other bodies in the system. Here we report such searches for two transiting exoplanet systems, TrES-1 and WASP-2. Their new transits were observed with the 4.2m William Herschel Telescope located on La Palma, Spain. In a continuing programme, three consecutive transits were observed for TrES-1, and one for WASP-2 during September 2007. We used the Markov Chain Monte Carlo simulations to derive transit times and their uncertainties. The resulting transit times are consistent with the most recent ephemerides and no conclusive proof of additional bodies in either system was found.

  11. The CC stretching band ν6 of allene- d4 (United States)

    Plíva, J.; Rousan, K.; Polo, S. R.


    The infrared spectrum of C 3D 4 was measured in the region of the paralled band of the CC stretching vibration ν6 centered at ν0 = 1920.2332 cm -1 on a high-resolution Fourier transform spectrometer and deconvolved to a linewidth of ˜ {1}/{2} of the Doppler width (˜0.0023 cm -1). The high resolution reveals the presence of strong perturbations in the K = 4 and K = 8 to 12 levels of the ν6 upper state. For a quantitative treatment of the observed transitions, a Hamiltonian matrix including six different perturbing states was constructed and used to refine the 6 spectroscopic constants of the ν6 state and 20 of the constants for the perturbing states. Measurement of the hot band ν6 + ν11 - ν11 whose band center is at 1916.200 cm -1 yielded the anharmonic constant x6,11 = -4.033 cm -1.

  12. Study of Transition Strategy of Clothing Export Enterprises Based on the Perspective of Industry Chain%基于产业链视角的服装出口企业转型策略研究

    Institute of Scientific and Technical Information of China (English)



    当今服装行业的竞争已经从简单的企业间的竞争,转变成为产应链之间的竞争,产应链体系的建设对于企业的市场快速反应、成本控制、产品开发等构成的企业综合竞争力提升具有重要意义,发达国家服装企业非常注重对产应链的建设和完善。本文基于产业链视角分析了我国服装出口企业经营中存在的问题,并提出了相应的转型发展建议。%Competition in today's clothing industry has become competition between industry chain from simple competition between enterprises.The construction of industry chain is very important for clothing export enterprises to enhance rapid response to market, cost control, product development, and so on. Clothing enterprises in developed countries focus on construction and improvement of industry chain.This paper analyzes the existing problems of Chinese export business from the perspective of industry chain, and proposes the corresponding transformation countermeasures.

  13. Dipalmitoyl-phosphatidylcholine biosynthesis is induced by non-injurious mechanical stretch in a model of alveolar type II cells. (United States)

    Pantazi, Despoina; Kitsiouli, Eirini; Karkabounas, Athanasios; Trangas, Theoni; Nakos, George; Lekka, Marilena E


    Dipalmitoylphosphatidylcholine, (DP-PtdCho), the major phospholipid component of lung surfactant is biosynthesized via a de novo pathway, the last step of which is catalyzed by CDP-choline:cholinephosphotransferase (CPT) and two remodeling steps: a deacylation and a reacylation one, catalyzed by an acidic, Ca²⁺-independent phospholipase A₂ (aiPLA₂) and a lyso-phosphatidylcholine acyltransferase (LPCAT), respectively. The aim of our study was to investigate whether a low magnitude, non-injurious static mode of mechanical stretch can induce phosphatidylcholine (PtdCho) biosynthesis and its remodeling to DP-PtdCho in the A549 cell-line, a model of alveolar type II cells. The deformation of A549 cells did not cause any release of lactate dehydrogenase, or phospholipids into the cell culture supernatants. An increase in PtdCho levels was observed after 1 h of static stretching, especially among the DP-PtdCho molecular species, as indicated by targeted lipidomics approach and site-directed fatty acyl-chain analysis. Moreover, although sphingomyelin (CerPCho) levels were unaffected, the DP-PtdCho/CerPCho ratio increased. Induction was observed in CPT, LPCAT and aiPLA₂ enzymatic activities and gene expression. Finally, incubation of the cells with MJ33 suppressed aiPLA₂ activity and DP-PtdCho production. Our data suggest that mild static mechanical stretch can promote the biosynthesis of PtdCho and its remodeling to DP-PtdCho in lung epithelial cells. Thus, low magnitude stretch could contribute to protective mechanisms rather than to injurious ones.

  14. Acute effect of different stretching methods on Illinois agility test in soccer players. (United States)

    Amiri-Khorasani, Mohammadtaghi; Sahebozamani, Mansour; Tabrizi, Kourosh G; Yusof, Ashril B


    The purpose of this study was to examine the effects of static, dynamic, and the combination of static and dynamic stretching within a pre-exercise warm-up on the Illinois agility test (IAT) in soccer players. Nineteen professional soccer players (age = 22.5 ± 2.5 years, height = 1.79 ± 0.003 m, body mass = 74.8 ± 10.9 kg) were tested for agility performance using the IAT after different warm-up protocols consisting of static, dynamic, combined stretching, and no stretching. The players were subgrouped into less and more experienced players (5.12 ± 0.83 and 8.18 ± 1.16 years, respectively). There were significant decreases in agility time after no stretching, among no stretching vs. static stretching; after dynamic stretching, among static vs. dynamic stretching; and after dynamic stretching, among dynamic vs. combined stretching during warm-ups for the agility: mean ± SD data were 14.18 ± 0.66 seconds (no stretch), 14.90 ± 0.38 seconds (static), 13.95 ± 0.32 seconds (dynamic), and 14.50 ± 0.35 seconds (combined). There was significant difference between less and more experienced players after no stretching and dynamic stretching. There was significant decrease in agility time following dynamic stretching vs. static stretching in both less and more experienced players. Static stretching does not appear to be detrimental to agility performance when combined with dynamic warm-up for professional soccer players. However, dynamic stretching during the warm-up was most effective as preparation for agility performance. The data from this study suggest that more experienced players demonstrate better agility skills due to years of training and playing soccer.

  15. The effectiveness of manual stretching in the treatment of plantar heel pain: a systematic review

    Directory of Open Access Journals (Sweden)

    Parish Ben


    Full Text Available Abstract Background Plantar heel pain is a commonly occurring foot complaint. Stretching is frequently utilised as a treatment, yet a systematic review focusing only on its effectiveness has not been published. This review aimed to assess the effectiveness of stretching on pain and function in people with plantar heel pain. Methods Medline, EMBASE, CINAHL, AMED, and The Cochrane Library were searched from inception to July 2010. Studies fulfilling the inclusion criteria were independently assessed, and their quality evaluated using the modified PEDro scale. Results Six studies including 365 symptomatic participants were included. Two compared stretching with a control, one study compared stretching to an alternative intervention, one study compared stretching to both alternative and control interventions, and two compared different stretching techniques and durations. Quality rating on the modified Pedro scale varied from two to eight out of a maximum of ten points. The methodologies and interventions varied significantly between studies, making meta-analysis inappropriate. Most participants improved over the course of the studies, but when stretching was compared to alternative or control interventions, the changes only reached statistical significance in one study that used a combination of calf muscle stretches and plantar fascia stretches in their stretching programme. Another study comparing different stretching techniques, showed a statistically significant reduction in some aspects of pain in favour of plantar fascia stretching over calf stretches in the short term. Conclusions There were too few studies to assess whether stretching is effective compared to control or other interventions, for either pain or function. However, there is some evidence that plantar fascia stretching may be more effective than Achilles tendon stretching alone in the short-term. Appropriately powered randomised controlled trials, utilizing validated outcome

  16. 中国煤电能源供应链风险关系及风险评价测度研究%Research on Risk Sources Transitive Relation of Coal -Electricity Supply Chain and Risk Evaluation in China

    Institute of Scientific and Technical Information of China (English)

    谭忠富; 刘平阔


    煤电能源供应链的风险管理问题是保障中国能源安全的重要基石。本文针对中国煤电能源供应链的绩效和风险管理,研究了煤电能源供应链风险管理的风险评价测度问题。基于供应链部门关系的界定,利用价值驱动树方法对风险源传递关系进行梳理,构建中国煤电能源供应链指标体系(C -ES-CRMIS)。通过社会问卷调查的方式收集样本,进行主成分分析,建立结构方程模型(SEM );为测量指标权重,对风险因子载荷分析、二级因子路径系数进行计算;基于指标相关性的指标权重确定方法(CRIT-IC ),得到煤炭供应链风险评价测度模型(C-ESCRE )。结果表明:现阶段,中国煤电能源供应链的主要风险源为政策风险、意外灾害和市场需求风险。节点企业可根据测度模型,对其供应链风险进行评价分析。最后进行了案例分析,以期为政府宏观调控、供应链协同管理以及企业内部控制提供参考。%Risk management of Coal -Electricity supply chain is an important cornerstone for China's energy security . With respect to the performance and risk management of Coal -Electricity supply chain risk management in China , this article is focused on the issues of Coal-Electricity supply chain risk evaluation . Based on defining the relationships among the supply chain sectors , using Value Driver Tree to sort out the risk sources , Coal-Electricity Supply Chain Risk Management Index System is built . Social questionnaires samples are collected to introduce a principal component analysis , and Structural Equation Modeling is employed . With respect to the weight of index , the factor loading and the path coefficient of risks are discussed at the same time . According to the Criteria Importance Through Intercriteria Correlation method , a model of Coal -Electricity supply chain risk evaluation is built . The results show that :currently

  17. Logistic chain modelling

    NARCIS (Netherlands)

    Slats, P.A.; Bhola, B.; Evers, J.J.M.; Dijkhuizen, G.


    Logistic chain modelling is very important in improving the overall performance of the total logistic chain. Logistic models provide support for a large range of applications, such as analysing bottlenecks, improving customer service, configuring new logistic chains and adapting existing chains to n

  18. Health supply chain management. (United States)

    Zimmerman, Rolf; Gallagher, Pat


    This chapter gives an educational overview of: * The actual application of supply chain practice and disciplines required for service delivery improvement within the current health environment. * A rationale for the application of Supply Chain Management (SCM) approaches to the Health sector. * The tools and methods available for supply chain analysis and benchmarking. * Key supply chain success factors.

  19. Helical Inversion of Gel Fibrils by Elongation of Perfluoroalkyl Chains as Studied by Vibrational Circular Dichroism. (United States)

    Sato, Hisako; Yajima, Tomoko; Yamagishi, Akihiko


    Vibrational circular dichroism (VCD) spectroscopy was applied to gelation by a chiral low-molecular mass weight gelator, N,N'-diperfluoroalkanoyl-1,2-trans-diaminocyclohexane. Attention was focused on the winding effects of (-CF2 )n chains on the gelating ability. For this purpose, a series of gelators were synthesized with perfluoroalkyl chains of different length (n = 6-8). When gelation was studied using acetonitrile as a solvent, the fibrils took different morphologies, depending on the chain length: twisted saddle-like ribbon or helical ribbon from fibril (n = 6) and a helical ribbon from platelet (n = 8). The signs of VCD peaks assigned to the couplet of C=O stretching and to the C-F stretching were also dependent on n, indicating that a gelator molecule changed conformation on elongating perfluoroalkyl chains. A model is proposed for the aggregation modes in fibrils. Chirality 28:361-364, 2016. © 2016 Wiley Periodicals, Inc.

  20. Fluidization, resolidification, and reorientation of the endothelial cell in response to slow tidal stretches. (United States)

    Krishnan, Ramaswamy; Canovic, Elizabeth Peruski; Iordan, Andreea L; Rajendran, Kavitha; Manomohan, Greeshma; Pirentis, Athanassios P; Smith, Michael L; Butler, James P; Fredberg, Jeffrey J; Stamenovic, Dimitrije


    Mechanical stretch plays an important role in regulating shape and orientation of the vascular endothelial cell. This morphological response to stretch is basic to angiogenesis, neovascularization, and vascular homeostasis, but mechanism remains unclear. To elucidate mechanisms, we used cell mapping rheometry to measure traction forces in primary human umbilical vein endothelial cells subjected to periodic uniaxial stretches. Onset of periodic stretch of 10% strain amplitude caused a fluidization response typified by attenuation of traction forces almost to zero. As periodic stretch continued, the prompt fluidization response was followed by a slow resolidification response typified by recovery of the traction forces, but now aligned along the axis perpendicular to the imposed stretch. Reorientation of the cell body lagged reorientation of the traction forces, however. Together, these observations demonstrate that cellular reorientation in response to periodic stretch is preceded by traction attenuation by means of cytoskeletal fluidization and subsequent traction recovery transverse to the stretch direction by means of cytoskeletal resolidification.

  1. A systematic literature review of the relationship between stretching and athletic injury prevention. (United States)

    Lewis, Julia


    Athletic-related injuries are a major cause for healthcare visits and financial burden for an otherwise healthy population of adults. The purpose of this article was to investigate the effects of stretching on injury prevention and to determine whether current stretching guidelines are beneficial for athletes. A systematic review of the literature was conducted through searching MEDLINE and CINAHL on topics related to stretching and injury prevention. Current belief is that stretching reduces injury incidence and that it should be performed prior to athletic activities. An examination of 11 articles provided inconclusive outcomes regarding the positive effect of stretching on injury prevention. A sport or activity-specific tailored stretch and warm-up program yielded the best outcomes in relation to preventing injuries. Direct negative effects of stretching were not identified; therefore, the application of stretching should be performed on an individual basis.

  2. Acute Effects of Static and Proprioceptive Neuromuscular Facilitation Stretching on Muscle Strength and Power Output


    Marek, Sarah M; Cramer, Joel T; Fincher, A. Louise; Massey, Laurie L; Dangelmaier, Suzanne M; Purkayastha, Sushmita; Fitz, Kristi A; Culbertson, Julie Y


    Context: Stretching is commonly used as a technique for injury prevention in the clinical setting. Our findings may improve the understanding of the neuromuscular responses to stretching and help clinicians make decisions for rehabilitation progression and return to play.

  3. Acute effects of two different stretching techniques on isokinetic strength and power

    Directory of Open Access Journals (Sweden)

    F. Ayala


    Conclusions: Short pre-exercise static and dynamic lower-limb stretching routines did not elicit stretching-induce reductions or improvements in knee flexor and knee extensor isokinetic concentric and eccentric strength. In addition, the findings of the current study support the claim that dynamic stretching may be preferable to static stretching as part of a warm-up designed to prepare for physical activity.

  4. Vacuum response to cosmic stretching: accelerated Universe and prevention of singularity


    Novikov, E. A.


    Spacetime stretching is included in the general relativity alongside with the spacetime curvature. Response of the vacuum to cosmic stretching is considered as macroscopic quantum effect. This effect explains the accelerated expansion of the Universe without resorting to Plank scale. For negative stretching (collapse) the same effect can prevent formation of singularity. Stretching effect can be important for a variety of cosmic phenomena, including collisions of galaxies and local collapses.

  5. Flame Stretch Analysis in Diffusion Flames with Inert Gas

    Institute of Scientific and Technical Information of China (English)

    Ay Su; Ying-Chieh Liu


    Experimental investigations of impinging flame with fuel mixed with non-reaction gas were conducted.According to the observations of combustion test and temperature measurement, the non-reaction gas might dilute the local concentration of fuel in the diffusion process. The shape of the flame was symmetrical due to the flame stretch force. Results show that the conical flame might be de-structured by the addition of inert gas in pure methane fuel. The impinging flame became shorter and bluer as nitrogen was added to the fuel. The conditions of N2/CH4 equal to 1/2 and 1/1 show a wider plane in the YZ plane. The effect of inert gas overcomes the flame stretch and destroys the symmetrical column flame as well as the cold flow. Nitrogen addition also enhances the diffusion rate and combustion efficiency.

  6. Stretching and imaging studies of single DNA molecules

    Institute of Scientific and Technical Information of China (English)


    DNA molecules were stretched on silanized mica surface with the molecular combing technique, and detected with fluorescence microscopy and atomic force microscopy. Meantime, DNA molecules were stretched with a modified dynamic molecular combing technique and studied with atomic force microscopy. The results indicate that, compared with the dynamic molecular combing technique, the modified dynamic molecular combing technique has advantages of less-sample demand and less contamination to sample; as compared with the molecular combing technique, it has better aligning effect and reproducibility. Combination of this kind of DNA molecular manipulating technique with the single DNA molecule detecting technique by atomic force microscopy and fluorescence microscopy will play an important role in the basic research of molecular dynamics and the application of gene research.

  7. Development of Stretched wire measurement bench at IDDL, DAVV Indore (United States)

    Gehlot, Mona; Mishra, G.


    A stretched wire magnetic measurement bench is under development at IDDL, DAVV, Indore. In this method a multistrend wire consisting of N turns is stretched inside the undulator to measure the field integrals of the undulators. The wire moved with constant velocity of translation measures the first integral of the undulator field. The cross motion of the wire at the undulator ends measures the second field integral. The measurement accuracy depends on the wire conditions and material properties. In this paper we follow an analytical approach to find the voltage fluctuations due to wire vibrations during the field measurement. It is shown that the voltage fluctuations depend on undulator gap, magnitude of the impulse on the wire. The mass density and the length of the wire also cause sizeable voltage fluctuations. The analytical derived expression is analysed to optimize system parameters for minimum errors during the measurement.

  8. Effect of passive muscle stretching in osteoarthritis of the hip. (United States)

    Leivseth, G; Torstensson, J; Reikerås, O


    1. Twenty-five minute daily muscle stretching, perpendicular to the fibre direction of the adductor muscles without movement of the hip, was performed in patients with osteoarthritis of the hip. 2. Before and after treatment hip abduction was measured and muscle biopsies were taken for analysis of fibre cross-sectional areas of type 1 and type 2 fibres as well as adenosine 5'-triphosphate, creatine phosphate and glycogen contents. 3. From the results it is concluded that passive muscle stretching leads to a significant increase in hip abduction of 8.3 degrees (P less than 0.05). There was also a significant increase of type 1 and type 2 fibre cross-sectional area and of glycogen content after the treatment period (P less than 0.05), but the concentrations of adenosine 5'-triphosphate and creatine phosphate did not change significantly.

  9. Research on Methods of Processing Transit IC Card Information and Constructing Transit OD Matrix (United States)

    Han, Xiuhua; Li, Jin; Peng, Han

    Transit OD matrix is of vital importance when planning urban transit system. Traditional transit OD matrix constructing method needs a large range of spot check survey. It is expensive and needs long cycle time to process information. Recently transit IC card charging systems have been widely applied in big cities. Being processed reasonably, transit passenger information stored in IC card database can turn into information resource. It will reduce survey cost a lot. The concept of transit trip chain is put forward in this paper. According to the characteristics of closed transit trip chain, it discusses how to process IC card information and construct transit OD matrix. It also points out that urban transit information platform and data warehouse should be constructed, and how to integrate IC card information.

  10. Quantum Fluids of Self-Assembled Chains of Polar Molecules at Finite Temperature

    Institute of Scientific and Technical Information of China (English)

    ZHU Kun-Yan; TAN Lei; GAO Xiang; WANG Daw-Wei


    The finite temperature properties of self-assembled dipole chains of polar molecules in strongly confined pancake traps are investigated.The single-chain vibrations at finite temperature,which become important for long chains in a strongly interacting regime,are found to lower the transition temperature and to shift the chain distribution by less than 10%.We also propose experimental parameters to observe such quantum phase transition.

  11. The Acute Effects of Static Stretching on Speed and Agility Performance Depend on Stretch Duration and Conditioning Level. (United States)

    Avloniti, Alexandra; Chatzinikolaou, Athanasios; Fatouros, Ioannis G; Avloniti, Christina; Protopapa, Maria; Draganidis, Dimitrios; Stampoulis, Theodoros; Leontsini, Diamanda; Mavropalias, George; Gounelas, George; Kambas, Antonios


    Avloniti, A, Chatzinikolaou, A, Fatouros, IG, Avloniti, C, Protopapa, M, Draganidis, D, Stampoulis, T, Leontsini, D, Mavropalias, G, Gounelas, G, and Kambas, A. The acute effects of static stretching on speed and agility performance depend on stretch duration and conditioning level. J Strength Cond Res 30(10): 2767-2773, 2016-Although static stretching (SS) is an integral part of physical preparation before training and competition, its usefulness in regards to power performance improvement has been questioned. The aim of this study was to investigate the effect of 6 SS durations on speed and agility performance. According to a cross-over design, 34 trained men (age, 20.5 ± 1.4 years; height, 1.81 ± 0.2 m; weight, 77.2 ± 2.6 kg; body fat, 8.2 ± 2.6%) participated in a control session (no stretch) and 6 experimental conditions (10, 15, 20, 30, 40, and 60 seconds) performed in a randomized order. Performance in speed (10 and 20 m) and agility (T-test) was measured after the control and experimental conditions. Static stretching, consisting of stretches for hip extensors, hip adductors, knee extensors, knee flexors, and ankle sole flexors, was performed after light cardiovascular exercise (8 minutes). A 1-way repeated-measures analysis of variance showed that speed was improved only by SS of short duration (15/20 seconds), whereas agility remained unaffected by all SS trials. When participants' speed and agility level was taken into account, it was revealed that only those of moderate performance demonstrated an improved speed (in 15- and 20-second trials) and agility (in 10- and 15-second trials) performance. These results suggest that short-duration SS protocols induce an acute improvement of speed and agility performance, whereas longer-duration SS protocols have neither positive nor negative effect. Furthermore, it seems that individuals of lower speed and agility performance level are more likely to benefit by a short-duration SS protocol.

  12. Gravitational Entropy and String Bits on the Stretched Horizon

    CERN Document Server

    Halyo, E


    We show that the entropy of Schwarzschild black holes in any dimension can be described by a gas of free string bits at the stretched horizon. The number of string bits is equal to the black hole entropy and energy dependent. For an asymptotic observer the bit gas is at the Hawking temperature. We show that the same description is also valid for de Sitter space--times in any dimension.

  13. Cardiac mechanosensitivity and stretch-activated ion channels. (United States)

    Bett, G C; Sachs, F


    Mechanosensitivity is a ubiquitous property of cells, and mechanosensitive ion channels (MSCs) are hypothesized to be the transducers. In the heart, MSCs are likely to account for changes in beating rate as a function of filling and for initiating stretch-induced arrhythmias (for example, following a myocardial infarction). Pharmacological agents that affect MSCs may provide a new class of antiarrhythmic drugs. © 1997, Elsevier Science Inc. (Trends Cardiovasc Med 1997;7:4-8).

  14. Centrifugal stretching of 170Hf in the interacting boson model

    Directory of Open Access Journals (Sweden)

    Werner V.


    Full Text Available We present the results of a recent experiment to deduce lifetimes of members of the ground state rotational band of 170Hf, which show the effect of centrifugal stretching in this deformed isotope. Results are compared to the geometrical confined beta-soft(CBS rotor model, as well as to the interacting boson model (IBM. Two methods to correct for effects due to the finite valence space within the IBM are proposed.

  15. The effects of strain heating in lithospheric stretching models (United States)

    Stanton, M.; Hodge, D.; Cozzarelli, F.


    The deformation by stretching of a continental type lithosphere has been formulated so that the problem can be solved by a continuum mechanical approach. The deformation, stress state, and temperature distribution are constrained to satisfy the physical laws of conservation of mass, energy, momentum, and an experimentally defined rheological response. The conservation of energy equation including a term of strain energy dissipation is given. The continental lithosphere is assumed to have the rheology of an isotropic, incompressible, nonlinear viscous, two layered solid.

  16. Effect of Stretching--Setting Treatment on Dyeing Behavior of Wool

    Institute of Scientific and Technical Information of China (English)



    Changes of dyeing behavior of wool after stretching - setting treatment are studied.Effects of stretching - setting on wool structure are analyzed.It is concluded that stretching - setting treatment not only reduces wool diameter and increases wool length,but also brings about low-temperature dyeing of wool.

  17. Can Stretching Prior to Exercise and Sports Improve Performance and Prevent Injury? (United States)

    Bracko, Michael R.


    Examines data from research on stretching as it relates to enhanced performance and injury prevention so that fitness, exercise, and sports performance professionals can make informed decisions about stretching programs for clients. The paper notes that stretching is a misunderstood component of fitness and sports training. Few studies show…

  18. Vibrational Spectroscopy of CH/CD Stretches in Propadiene: An Algebraic Approach

    Institute of Scientific and Technical Information of China (English)

    Joydeep Choudhury; Nirmal Kumar Sarkar; Srinivasa Rao Kaxumuri; Ramendu Bhattacharjee


    Using Hamiltonian based on Lie algebraic method, the stretching vibrational modes of C3H4 and C3D4 molecules are calculated up to higher overtones. The model appears to describe C-H and C-D stretching modes with less number of parameters. The locality parameter ξ confirms the highly local behaviour of the stretching modes of these molecules.

  19. Finite Element Simulation of the Stretch-Forming of Aircraft Skins

    NARCIS (Netherlands)

    Wisselink, H.H.; Boogaard, van den A.H.


    In the aerospace industry stretch forming is often used to produce skin parts. During stretch forming a sheet is clamped at two sides and stretched over a die, such that the sheet gets the shape of the die. However for complex shapes it is necessary to use expensive intermediate heat-treatments in o

  20. Chaperones in Polyglutamine Aggregation: Beyond the Q-Stretch (United States)

    Kuiper, E. F. E.; de Mattos, Eduardo P.; Jardim, Laura B.; Kampinga, Harm H.; Bergink, Steven


    Expanded polyglutamine (polyQ) stretches in at least nine unrelated proteins lead to inherited neuronal dysfunction and degeneration. The expansion size in all diseases correlates with age at onset (AO) of disease and with polyQ protein aggregation, indicating that the expanded polyQ stretch is the main driving force for the disease onset. Interestingly, there is marked interpatient variability in expansion thresholds for a given disease. Between different polyQ diseases the repeat length vs. AO also indicates the existence of modulatory effects on aggregation of the upstream and downstream amino acid sequences flanking the Q expansion. This can be either due to intrinsic modulation of aggregation by the flanking regions, or due to differential interaction with other proteins, such as the components of the cellular protein quality control network. Indeed, several lines of evidence suggest that molecular chaperones have impact on the handling of different polyQ proteins. Here, we review factors differentially influencing polyQ aggregation: the Q-stretch itself, modulatory flanking sequences, interaction partners, cleavage of polyQ-containing proteins, and post-translational modifications, with a special focus on the role of molecular chaperones. By discussing typical examples of how these factors influence aggregation, we provide more insight on the variability of AO between different diseases as well as within the same polyQ disorder, on the molecular level. PMID:28386214

  1. The different muscle-energetics during shortening and stretch. (United States)

    Jarosch, Robert


    The helical shape of the thin filaments causes their passive counterclockwise rotation during muscle stretch that increases tensile stress and torque at first by unwinding and then by winding up the four anchoring Z-filaments. This means storage of energy in the series elastic Z-filaments and a considerable decrease of the liberated energy of heat and work to (h-w(ap)), where h is the heat energy and w(ap) the stretch energy induced from outside by an apparatus. The steep thin filament helix with an inclination angle of 70° promotes the passive rotation during stretch, but impedes the smooth sliding of shortening by increased friction and production of frictional heat. The frictional heat may be produced by the contact with the myosin cross-bridges: (1) when they passively snap on drilling thin filaments from cleft to cleft over a distance 2 × 2.7 nm = 5.4 nm between the globular actin monomers in one groove, causing stepwise motion; or (2) when they passively cycle from one helical groove to the next (distance 36 nm). The latter causes more heat and may take place on rotating thin filaments without an effective forward drilling ("idle rotation"), e.g., when they produce "unexplained heat" at the beginning of an isometric tetanus. In an Appendix to this paper the different states of muscle are defined. The function of its most important components is described and rotation model and power-stroke model of muscular contraction is compared.

  2. Torsion and CO-stretching vibration interactions in methanol (United States)

    Duan, Yun-Bo; Yuan, Shuping; Wang, Rubin; Mukhopadhyay, I.


    A model Hamiltonian is constructed to investigate the vibration-torsion-rotational interaction in methanol. The model Hamiltonian is based on the formulation of reduction of Hamiltonian, in which the CO-stretching mode ν8, the large-amplitude torsion mode ν12 and the three degrees of freedom that correspond to the overall rotation of the molecule, are considered simultaneously. This Hamiltonian is used to carry out an analysis of already published data for CH 3OH with vco ⩽ 1 (the CO-stretching vibrational quantum number), vt ⩽ 4 (the torsional quantum number), and J ⩽ 5 (the overall rotational quantum number). The relative locations of the CO-stretch vibrational ground state and the fundamental state are well reproduced for torsional states with vt ⩽ 4 and J ⩽ 5. An effective potential energy surface that describes ν8 and ν12 modes is obtained from this analysis. The present analyses show that a variety of resonance interactions can affect states for energies larger than 1100 cm -1.

  3. Fibril orientation redistribution induced by stretching of cellulose nanofibril hydrogels

    Energy Technology Data Exchange (ETDEWEB)

    Josefsson, Gabriella; Gamstedt, E. Kristofer [The Ångström Laboratory, Department of Engineering Sciences, Division of Applied Mechanics, Uppsala University, Box 534, SE-751 21 Uppsala (Sweden); Ahvenainen, Patrik [Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 University of Helsinki (Finland); Mushi, Ngesa Ezekiel [Department of Fiber and Polymer Technology, Royal Institute of Technology (KTH), SE-100 44 Stockholm (Sweden)


    The mechanical performance of materials reinforced by cellulose nanofibrils is highly affected by the orientation of these fibrils. This paper investigates the nanofibril orientation distribution of films of partly oriented cellulose nanofibrils. Stripes of hydrogel films were subjected to different amount of strain and, after drying, examined with X-ray diffraction to obtain the orientation of the nanofibrils in the films, caused by the stretching. The cellulose nanofibrils had initially a random in-plane orientation in the hydrogel films and the strain was applied to the films before the nanofibrils bond tightly together, which occurs during drying. The stretching resulted in a reorientation of the nanofibrils in the films, with monotonically increasing orientation towards the load direction with increasing strain. Estimation of nanofibril reorientation by X-ray diffraction enables quantitative comparison of the stretch-induced orientation ability of different cellulose nanofibril systems. The reorientation of nanofibrils as a consequence of an applied strain is also predicted by a geometrical model of deformation of nanofibril hydrogels. Conversely, in high-strain cold-drawing of wet cellulose nanofibril materials, the enhanced orientation is promoted by slipping of the effectively stiff fibrils.

  4. Stretch fast dynamo mechanism via conformal mapping in Riemannian manifolds (United States)

    Garcia de Andrade, L. C.


    Two new analytical solutions of the self-induction equation in Riemannian manifolds are presented. The first represents a twisted magnetic flux tube or flux rope in plasma astrophysics, where the rotation of the flow implies that the poloidal field is amplified from toroidal field, in the spirit of dynamo theory. The value of the amplification depends on the Frenet torsion of the magnetic axis of the tube. Actually this result illustrates the Zeldovich stretch, twist, and fold method to generate dynamos from straight and untwisted ropes. Based on the fact that this problem was previously handled, using a Riemannian geometry of twisted magnetic flux ropes [Phys Plasmas 13, 022309 (2006)], investigation of a second dynamo solution, conformally related to the Arnold kinematic fast dynamo, is obtained. In this solution, it is shown that the conformal effect on the fast dynamo metric enhances the Zeldovich stretch, and therefore a new dynamo solution is obtained. When a conformal mapping is performed in an Arnold fast dynamo line element, a uniform stretch is obtained in the original line element.

  5. Stretch-sensitive paresis and effort perception in hemiparesis. (United States)

    Vinti, Maria; Bayle, Nicolas; Hutin, Emilie; Burke, David; Gracies, Jean-Michel


    In spastic paresis, stretch applied to the antagonist increases its inappropriate recruitment during agonist command (spastic co-contraction). It is unknown whether antagonist stretch: (1) also affects agonist recruitment; (2) alters effort perception. We quantified voluntary activation of ankle dorsiflexors, effort perception, and plantar flexor co-contraction during graded dorsiflexion efforts at two gastrocnemius lengths. Eighteen healthy (age 41 ± 13) and 18 hemiparetic (age 54 ± 12) subjects performed light, medium and maximal isometric dorsiflexion efforts with the knee flexed or extended. We determined dorsiflexor torque, Root Mean Square EMG and Agonist Recruitment/Co-contraction Indices (ARI/CCI) from the 500 ms peak voluntary agonist recruitment in a 5-s maximal isometric effort in tibialis anterior, soleus and medial gastrocnemius. Subjects retrospectively reported effort perception on a 10-point visual analog scale. During gastrocnemius stretch in hemiparetic subjects, we observed: (1) a 25 ± 7 % reduction of tibialis anterior voluntary activation (maximum reduction 98 %; knee extended vs knee flexed; p = 0.007, ANOVA); (2) an increase in dorsiflexion effort perception (p = 0.03, ANCOVA). Such changes did not occur in healthy subjects. Effort perception depended on tibialis anterior recruitment only (βARI(TA) = 0.61, p perception, an additional incentive to evaluate and treat this phenomenon.

  6. A discrete electromechanical model for human cardiac tissue: effects of stretch-activated currents and stretch conditions on restitution properties and spiral wave dynamics.

    Directory of Open Access Journals (Sweden)

    Louis D Weise

    Full Text Available We introduce an electromechanical model for human cardiac tissue which couples a biophysical model of cardiac excitation (Tusscher, Noble, Noble, Panfilov, 2006 and tension development (adjusted Niederer, Hunter, Smith, 2006 model with a discrete elastic mass-lattice model. The equations for the excitation processes are solved with a finite difference approach, and the equations of the mass-lattice model are solved using Verlet integration. This allows the coupled problem to be solved with high numerical resolution. Passive mechanical properties of the mass-lattice model are described by a generalized Hooke's law for finite deformations (Seth material. Active mechanical contraction is initiated by changes of the intracellular calcium concentration, which is a variable of the electrical model. Mechanical deformation feeds back on the electrophysiology via stretch-activated ion channels whose conductivity is controlled by the local stretch of the medium. We apply the model to study how stretch-activated currents affect the action potential shape, restitution properties, and dynamics of spiral waves, under constant stretch, and dynamic stretch caused by active mechanical contraction. We find that stretch conditions substantially affect these properties via stretch-activated currents. In constantly stretched medium, we observe a substantial decrease in conduction velocity, and an increase of action potential duration; whereas, with dynamic stretch, action potential duration is increased only slightly, and the conduction velocity restitution curve becomes biphasic. Moreover, in constantly stretched medium, we find an increase of the core size and period of a spiral wave, but no change in rotation dynamics; in contrast, in the dynamically stretching medium, we observe spiral drift. Our results may be important to understand how altered stretch conditions affect the heart's functioning.

  7. Sustainable Supply Chain Design

    DEFF Research Database (Denmark)

    Bals, Lydia; Tate, Wendy

    to implement TBL goals across the supply chain. In supply chain design, the classic economic perspective still dominates, although the idea of the TBL is more widely disseminated. The purpose of this research is to add to the sustainable supply chain management literature (SSCM) research agenda......A significant conceptual and practical challenge is how to integrate triple bottom line (TBL; including economic, social and environmental) sustainability into global supply chains. Although this integration is necessary to slow down global resource depletion, understanding is limited of how...... by incorporating the physical chain, and the (information and financial) support chains into supply chain design. This manuscript tackles issues of what the chains are designed for and how they are designed structurally. Four sustainable businesses are used as illustrative case examples of innovative supply chain...

  8. Chain-reaction crash on a highway in high visibility (United States)

    Nagatani, Takashi


    We study the chain-reaction crash (multiple-vehicle collision) in high-visibility condition on a highway. In the traffic situation, drivers control their vehicles by both gear-changing and braking. Drivers change the gears according to the headway and brake according to taillights of the forward vehicle. We investigate whether or not the first collision induces the chain-reaction crash numerically. It is shown that dynamic transitions occur from no collisions, through a single collision, to multiple collisions with decreasing the headway. Also, we find that the dynamic transition occurs from the finite chain reaction to the infinite chain reaction when the headway is less than the critical value. We compare the multiple-vehicle collisions in high-visibility with that in low-visibility. We derive the transition points and the region maps for the chain-reaction crash in high visibility.

  9. Document Ranking Based upon Markov Chains. (United States)

    Danilowicz, Czeslaw; Balinski, Jaroslaw


    Considers how the order of documents in information retrieval responses are determined and introduces a method that uses a probabilistic model of a document set where documents are regarded as states of a Markov chain and where transition probabilities are directly proportional to similarities between documents. (Author/LRW)

  10. Optical behavior of the conjugated polymer MEH-PPV thin films stretched in bi-layer dwetting by an unstable layer (United States)

    Chen, Po-Tsun; Yang, Arnold C.-M.


    Molecular packing and chain conformation play important roles in the optoelectronic performance of conjugated polymer thin films. It has been shown that by virtue of stretching via dewetting, the photoluminescence (PL) efficiencies of rarefied MEH-PPV thin films may be dramatically enhanced. To result similar effects in the stable non-diluted pristine MEH-PPV thin films, bi-layer dewetting was attempted in samples of MEH-PPV thin films (˜7nm) covered by one layer of polystyrene (PS) (˜40nm) that dewetted in toluene vapor to form droplets (height ˜300 nm) and ultrathin residual layer (˜3nm) on the substrate. The instability was initiated from the PS layer in which small pinholes first emerged upon the intake of the solvent vapor. The pinholes then expanded and deepened into the underlying MEH-PPV, forcing the conjugated film to dewet. As a result of the stretching induced by the dewetting, the PL peak blue-shifted 20 nm to 540 nm and the intensity was enhanced around 10 times. Revealed by the position-sensitive confocal PL data, the huge enhancement came from both the droplet and residual layer, caused by molecular separation and stretching. Electroluminescence devices are being made based on these stretched MEH-PPV films.

  11. Ca{sup 2+} influx and ATP release mediated by mechanical stretch in human lung fibroblasts

    Energy Technology Data Exchange (ETDEWEB)

    Murata, Naohiko [Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya 466-8550 (Japan); Ito, Satoru, E-mail: [Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya 466-8550 (Japan); Furuya, Kishio [Mechanobiology Laboratory, Nagoya University Graduate School of Medicine, Nagoya 466-8550 (Japan); Takahara, Norihiro [Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya 466-8550 (Japan); Naruse, Keiji [Department of Cardiovascular Physiology, Okayama University Graduate School of Medicine, Okayama 700-8558 (Japan); Aso, Hiromichi; Kondo, Masashi [Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya 466-8550 (Japan); Sokabe, Masahiro [Mechanobiology Laboratory, Nagoya University Graduate School of Medicine, Nagoya 466-8550 (Japan); Hasegawa, Yoshinori [Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya 466-8550 (Japan)


    Highlights: • Uniaxial stretching activates Ca{sup 2+} signaling in human lung fibroblasts. • Stretch-induced intracellular Ca{sup 2+} elevation is mainly via Ca{sup 2+} influx. • Mechanical strain enhances ATP release from fibroblasts. • Stretch-induced Ca{sup 2+} influx is not mediated by released ATP or actin cytoskeleton. - Abstract: One cause of progressive pulmonary fibrosis is dysregulated wound healing after lung inflammation or damage in patients with idiopathic pulmonary fibrosis and severe acute respiratory distress syndrome. The mechanical forces are considered to regulate pulmonary fibrosis via activation of lung fibroblasts. In this study, the effects of mechanical stretch on the intracellular Ca{sup 2+} concentration ([Ca{sup 2+}]{sub i}) and ATP release were investigated in primary human lung fibroblasts. Uniaxial stretch (10–30% in strain) was applied to fibroblasts cultured in a silicone chamber coated with type I collagen using a stretching apparatus. Following stretching and subsequent unloading, [Ca{sup 2+}]{sub i} transiently increased in a strain-dependent manner. Hypotonic stress, which causes plasma membrane stretching, also transiently increased the [Ca{sup 2+}]{sub i}. The stretch-induced [Ca{sup 2+}]{sub i} elevation was attenuated in Ca{sup 2+}-free solution. In contrast, the increase of [Ca{sup 2+}]{sub i} by a 20% stretch was not inhibited by the inhibitor of stretch-activated channels GsMTx-4, Gd{sup 3+}, ruthenium red, or cytochalasin D. Cyclic stretching induced significant ATP releases from fibroblasts. However, the stretch-induced [Ca{sup 2+}]{sub i} elevation was not inhibited by ATP diphosphohydrolase apyrase or a purinergic receptor antagonist suramin. Taken together, mechanical stretch induces Ca{sup 2+} influx independently of conventional stretch-sensitive ion channels, the actin cytoskeleton, and released ATP.

  12. A comparison of assisted and unassisted proprioceptive neuromuscular facilitation techniques and static stretching. (United States)

    Maddigan, Meaghan E; Peach, Ashley A; Behm, David G


    A comparison of assisted and unassisted proprioceptive neuromuscular facilitation techniques and static stretching. J Strength Cond Res 26(5): 1238-1244, 2012-Proprioceptive neuromuscular facilitation (PNF) stretching often requires a partner. Straps are available allowing an individual to perform PNF stretching alone. It is not known if a strap provides similar improvements in the range of motion (ROM) as partner-assisted PNF or static stretching. The purpose of this study was to compare assisted and unassisted (with a strap) PNF stretching and static stretching. Hip joint ROM, reaction time (RT), and movement time (MT) were measured prestretching and poststretching. Thirteen recreationally active adults participated in this study. The participants were subjected to 5 different stretch interventions in a random order on separate days. Stretch conditions included unassisted PNF stretching using (a) isometric, (b) concentric, and (c) eccentric contractions with a stretch strap, (d) partner-assisted isometric PNF, and (e) static stretching. The RT, MT, dynamic, active, passive hip flexion angle, and angular velocity with dynamic hip flexion were measured before and after the intervention. The ROM improved (p < 0.05) 2.6, 2.7, and 5.4%, respectively, with dynamic, active static, and passive static ROM, but there was no significant difference between the stretching protocols. There was a main effect for time (p < 0.05) with all stretching conditions negatively impacting dynamic angular velocity (9.2%). Although there was no significant effect on RT, MT showed a negative main effect for time (p < 0.05) slowing 3.4%. In conclusion, it was found that all 3 forms of active stretching provided similar improvements in the ROM and poststretching performance decrements in MT and angular velocity. Thus, individuals can implement PNF stretching techniques with a partner or alone with a strap to improve ROM, but athletes should not use these techniques before important

  13. Markov chains for testing redundant software (United States)

    White, Allan L.; Sjogren, Jon A.


    A preliminary design for a validation experiment has been developed that addresses several problems unique to assuring the extremely high quality of multiple-version programs in process-control software. The procedure uses Markov chains to model the error states of the multiple version programs. The programs are observed during simulated process-control testing, and estimates are obtained for the transition probabilities between the states of the Markov chain. The experimental Markov chain model is then expanded into a reliability model that takes into account the inertia of the system being controlled. The reliability of the multiple version software is computed from this reliability model at a given confidence level using confidence intervals obtained for the transition probabilities during the experiment. An example demonstrating the method is provided.

  14. Contraction-specific differences in maximal muscle power during stretch-shortening cycle movements in elderly males and females

    DEFF Research Database (Denmark)

    Caserotti, Paolo; Aagaard, Per; Simonsen, Erik Bruun;


    Aging, muscle power, stretch-shortening cycle, eccentric muscle actions, concentric contractions......Aging, muscle power, stretch-shortening cycle, eccentric muscle actions, concentric contractions...

  15. Numerical Investigation on Mixing Efficiency and Exponential Fluid Stretching in Chaotic Mixing

    Institute of Scientific and Technical Information of China (English)

    王林翔; 陈鹰; 范毓润; 路甬祥


    The stretching and folding of fluid element during chaotic mixing field is studied using numerical method. The chaotic mixing process is caused by periodic secondary flow in a twisted curved pipe. Using the nonlinear discrete velocity field as the dynamical system, the present study connects the fluid particle's stretching along its trajectory in one period to a linearized time-varying variational equation. After numerical approximation of the variational equation, fluid stretching is calculated on the whole cross section. The stretching distribution shows an exponential fluid stretching and folding, which indicates an excellent mixing performance.

  16. Numerical Investigation on Mixing Efficiency and Exponential Fluid Stretching in Chaotic Mixing

    Institute of Scientific and Technical Information of China (English)


    The stretching and folding of fluid element during chaotic mixing field isstudied using numerical method. The chaotic mixing process is caused byperiodicsecondary flow in a twisted curved pipe. Using the nonlinear discrete velocity field as thedynamical system, the present study connects the fluid particle's stretching along itstrajectory in one period to a linearized time-varying variational equation. After numericalapproximation of the variational equation, fluid stretching is calculated on the whole crosssection. The stretching distribution shows an exponential fluid stretching and folding,which indicates an excellent mixing performance.

  17. Relaxation pathways of the OD stretch fundamental of HOD in liquid H2O (United States)

    Miguel, Beatriz; Zúñiga, José; Requena, Alberto; Bastida, Adolfo


    The molecular dynamics with quantum transitions method is used to study the vibrational relaxation of the OD stretching mode of HOD dissolved in liquid H2O water at 303 K. All the vibrational modes of the solute and solvent molecules that participate in the relaxation process are described by quantum mechanics, while the rotational and translational degrees of freedom are treated classically. A modification of the water intramolecular SPC/E (Simple Point Charge/Extended) force field providing vibrational frequencies in solution closer to the experimental values is proposed to analyze the influence of the vibrational energy gaps on the relaxation channels. The relaxation times obtained are in satisfactory agreement with experimental values. The energy transfer during the relaxation process alters significantly the H-bond network around the HOD molecule. The analysis of the vibrational transitions during the relaxation process reveals a complex mechanism which involves the participation of both intra- and intermolecular channels and provides a compromise for the different interpretations of the experimental data reported for this system in recent years.

  18. Effects of effort and EMG levels on short-latency stretch reflex modulation after varying background muscle contractions. (United States)

    Ogiso, K; McBride, J M; Finni, T; Komi, P V


    It is known that the short-latency stretch reflex (SLSR) is modulated by the background muscle activity when it is elicited at matched torque levels. This study was designed to examine the effects of muscle contraction types before a stretch perturbation on SLSR in the human soleus muscle (SOL) when SLSR was elicited at the same levels of effort and at matched electromyographic (EMG) activity levels. A mechanical stretch perturbation was applied to the calf muscles when the ankle joint reached a ninety degree tibio-tarsal joint angle after the muscles performed an isometric (pre-ISO), shortening (pre-SHO) and lengthening contraction (pre-LEN). Subjects were seated on an ankle ergometer chair and developed 0%, 10%, 20%, 30%, 40%, 50%, 60% and 70% ankle joint torque (AJT) of maximum voluntary isometric plantar flexion contraction at 80 degrees in pre-SHO, at 90 degrees in pre-ISO and at 100 degrees in pre-LEN. After that, isometric or dynamic contractions started, and the subjects were asked to maintain effort levels as, needed, to maintain the target torque levels until the end of the stretch. They relaxed their muscles fully after the stretch. This chain of processes was consecutively repeated 10 times. EMG signals obtained from SOL were averaged after they were high-pass filtered and full-wave rectified. Some major findings resulted: (1) there were no differences in SLSR area in the active muscle between pre-ISO and pre-SHO, whereas its waveform was steeper in pre-ISO than in pre-SHO. (2) SLSR p-to-p amplitude and waveform were larger and steeper in the active muscle than in the relaxed one in all conditions, whereas they were independent of the effort levels once the muscle was activated. This led to steady SLSR modulation in response to the background muscle contraction in the active muscle regardless of whether the SLSR was elicited at matched AJT or EMG activity levels. These findings suggest that SLSR is closely related to the muscle spindle sensitivity

  19. A stretch/compress scheme for a high temporal resolution detector for the magnetic recoil spectrometer time (MRSt) (United States)

    Hilsabeck, T. J.; Frenje, J. A.; Hares, J. D.; Wink, C. W.


    A time-resolved detector concept for the magnetic recoil spectrometer for time-resolved measurements of the NIF neutron spectrum is presented. The measurement is challenging due to the time spreading of the recoil protons (or deuterons) as they transit an energy dispersing magnet system. Ions arrive at the focal plane of the magnetic spectrometer over an interval of tens of nanoseconds. We seek to measure the time-resolved neutron spectrum with 20 ps precision by manipulating an electron signal derived from the ions. A stretch-compress scheme is employed to remove transit time skewing while simultaneously reducing the bandwidth requirements for signal recording. Simulation results are presented along with design concepts for structures capable of establishing the required electromagnetic fields.

  20. The effect of static, ballistic, and proprioceptive neuromuscular facilitation stretching on vertical jump performance. (United States)

    Bradley, Paul S; Olsen, Peter D; Portas, Matthew D


    The purpose of this study was to compare the acute effects of different modes of stretching on vertical jump performance. Eighteen male university students (age, 24.3 +/- 3.2 years; height, 181.5 +/- 11.4 cm; body mass, 78.1 +/- 6.4 kg; mean +/- SD) completed 4 different conditions in a randomized order, on different days, interspersed by a minimum of 72 hours of rest. Each session consisted of a standard 5-minute cycle warm-up, accompanied by one of the subsequent conditions: (a) control, (b) 10-minute static stretching, (c) 10-minute ballistic stretching, or (d) 10-minute proprioceptive neuromuscular facilitation (PNF) stretching. The subjects performed 3 trials of static and countermovement jumps prior to stretching and poststretching at 5, 15, 30, 45, and 60 minutes. Vertical jump height decreased after static and PNF stretching (4.0% and 5.1%, p ballistic stretching (2.7%, p > 0.05). However, jumping performance had fully recovered 15 minutes after all stretching conditions. In conclusion, vertical jump performance is diminished for 15 minutes if performed after static or PNF stretching, whereas ballistic stretching has little effect on jumping performance. Consequently, PNF or static stretching should not be performed immediately prior to an explosive athletic movement.

  1. Acute effects of the different intensity of static stretching on flexibility and isometric muscle force. (United States)

    Kataura, Satoshi; Suzuki, Shigeyuki; Matsuo, Shingo; Hatano, Genki; Iwata, Masahiro; Yokoi, Kazuaki; Tsuchida, Wakako; Banno, Yasuhiro; Asai, Yuji


    In various fields, static stretching is commonly performed to improve flexibility, whereas the acute effects of different stretch intensities are unclear. Therefore, we investigated the acute effects of different stretch intensities on flexibility and muscle force. Eighteen healthy participants (nine men, nine women) performed 180-s static stretches of the right hamstrings at 80%, 100%, and 120% of maximum tolerable intensity without stretching pain, in random order. The following outcomes were assessed as markers of lower limb function and flexibility: static passive torque (SPT), range of motion (ROM), passive joint (muscle-tendon) stiffness, passive torque at onset of pain (PT), and isometric muscle force. SPT was significantly decreased after all stretching intensities (p stretching at 100% and 120% intensity, ROM and PT were significantly increased after stretching (p stretching at 100% and 120% than at 80%, and passive stiffness was significantly lower after 120% than after 80% (p stretching and the relative change for SPT (p stretching at greater intensity is more effective for increasing ROM and decreasing passive muscle-tendon stiffness.

  2. Mechanical stretching for tissue engineering: two-dimensional and three-dimensional constructs. (United States)

    Riehl, Brandon D; Park, Jae-Hong; Kwon, Il Keun; Lim, Jung Yul


    Mechanical cell stretching may be an attractive strategy for the tissue engineering of mechanically functional tissues. It has been demonstrated that cell growth and differentiation can be guided by cell stretch with minimal help from soluble factors and engineered tissues that are mechanically stretched in bioreactors may have superior organization, functionality, and strength compared with unstretched counterparts. This review explores recent studies on cell stretching in both two-dimensional (2D) and three-dimensional (3D) setups focusing on the applications of stretch stimulation as a tool for controlling cell orientation, growth, gene expression, lineage commitment, and differentiation and for achieving successful tissue engineering of mechanically functional tissues, including cardiac, muscle, vasculature, ligament, tendon, bone, and so on. Custom stretching devices and lab-specific mechanical bioreactors are described with a discussion on capabilities and limitations. While stretch mechanotransduction pathways have been examined using 2D stretch, studying such pathways in physiologically relevant 3D environments may be required to understand how cells direct tissue development under stretch. Cell stretch study using 3D milieus may also help to develop tissue-specific stretch regimens optimized with biochemical feedback, which once developed will provide optimal tissue engineering protocols.

  3. Mechanical Stretching for Tissue Engineering: Two-Dimensional and Three-Dimensional Constructs (United States)

    Riehl, Brandon D.; Park, Jae-Hong; Kwon, Il Keun


    Mechanical cell stretching may be an attractive strategy for the tissue engineering of mechanically functional tissues. It has been demonstrated that cell growth and differentiation can be guided by cell stretch with minimal help from soluble factors and engineered tissues that are mechanically stretched in bioreactors may have superior organization, functionality, and strength compared with unstretched counterparts. This review explores recent studies on cell stretching in both two-dimensional (2D) and three-dimensional (3D) setups focusing on the applications of stretch stimulation as a tool for controlling cell orientation, growth, gene expression, lineage commitment, and differentiation and for achieving successful tissue engineering of mechanically functional tissues, including cardiac, muscle, vasculature, ligament, tendon, bone, and so on. Custom stretching devices and lab-specific mechanical bioreactors are described with a discussion on capabilities and limitations. While stretch mechanotransduction pathways have been examined using 2D stretch, studying such pathways in physiologically relevant 3D environments may be required to understand how cells direct tissue development under stretch. Cell stretch study using 3D milieus may also help to develop tissue-specific stretch regimens optimized with biochemical feedback, which once developed will provide optimal tissue engineering protocols. PMID:22335794

  4. On the Fabrication, Characterization and Mechanical Properties of Melt-Stretched Stochastic Honeycombs (United States)

    Hostetter, Megan

    This thesis presents a new type of polypropylene (PP) cellular material fabricated through a simple melt-stretching process. Stochastic honeycombs have an open cell, random honeycomb structure, with webs oriented perpendicular to built-in skins. This process has the advantage that, for example, PP pellets can be turned into a sandwich panel in one step. It was demonstrated that despite the randomness in the web structure, the out-of-plane compressive strength of stochastic honeycombs was repeatable, and exceeded that of commercial PP foams and was comparable to commercial PP honeycombs. The key material properties required to produce an this architecture were shown to be a high melt strength and a high viscosity, branched polymer. The viscosity was shown to affect the total length of the webs in cross-section and the relative partitioning of material through the skin, transition region and webs. Web thickness was affected by the areal density of the polymer during fabrication. Mechanical testing methods were adapted from ASTM standards for honeycombs, and the fabrication method was advanced from a manual to a machine controlled process. Stochastic honeycombs were shown to buckle elastically, plastically, and fracture after the peak strength. Elastic and plastic buckling were dominant at lower densities, and plastic buckling and fracture at higher densities. A thin-plate buckling model for the strength of stochastic honeycombs was developed and verified experimentally. The crystallinity of the polymer affected the tensile strength and stiffness, having a linear effect on the buckling strength. The architecture was composed of webs bound on both sides and webs bound on one side and free on the other. A greater fraction of bound webs increased the strength of the structure in the buckling model. A fabrication study showed that melt-stretching the polymer at higher strain rates increased the connectivity and fraction of bound webs. Additionally, higher density led to a

  5. The Global Value Chain

    DEFF Research Database (Denmark)

    Sørensen, Olav Jull

    The conference paper aims to develop the global value chain concept by including corporate internal value adding activities and competition to the basic framework in order to turn the global value chain into a strategic management tool......The conference paper aims to develop the global value chain concept by including corporate internal value adding activities and competition to the basic framework in order to turn the global value chain into a strategic management tool...

  6. Acute changes in hamstrings musculo-articular dissipative properties induced by cyclic and static stretching. (United States)

    Nordez, A; McNair, P; Casari, P; Cornu, C


    This study was designed to measure changes in musculo-articular dissipative properties related to viscosity that were induced by passive cyclic and static stretching. Musculo-articular dissipative properties were assessed by calculating a dissipation coefficient using potential elastic energies stored and restituted during cyclic stretching. Eight subjects performed five passive knee extensions/flexions cycles on a Biodex dynamometer at 5 degrees . s (-1) to 80 % of their maximal range of motion before and after a static stretching protocol. Electromyographic activity from the hamstring muscles was monitored and remained constant during cyclic stretching and after static stretching (p > 0.05). The dissipation coefficient decreased during cyclic stretching (- 28.8 +/- 6.0 %, p musculo-articular dissipative properties were primarily affected by a single cycle of motion, and were not influenced by static stretching procedures. The decrease in dissipation coefficient following cyclic motion indicates that the musculo-articular system displays thixotropic behavior.

  7. Effect of static stretching on prevention of injuries for military recruits. (United States)

    Amako, Masatoshi; Oda, Takaaki; Masuoka, Kazunori; Yokoi, Hiromichi; Campisi, Paolo


    This prospective study was designed to evaluate whether static stretching can prevent training-related injuries in Japan Ground Self-Defense Force military recruits. A total of 901 recruits between 1996 and 1998 were divided into two groups. Of which, 518 recruits were assigned to the stretching group and practiced static stretching before and after each physical training session. The control subjects (383 recruits in the nonstretching group) did not stretch statically prior to exercise. The static stretching consisted of 18 exercises. We collected injury data from medical records and assessed the incidence and the location of injury. The total injury rate was almost the same between two groups; however, the incidences of muscle/tendon injury and low back pain were significantly lower in the stretching group (p stretching decreased the incidence of muscle-related injuries but did not prevent bone or joint injuries.

  8. Thermo-mechanical simulation of liquid-supported stretch blow molding (United States)

    Zimmer, J.; Stommel, M.


    Stretch blow molding is the well-established plastics forming method to produce Polyehtylene therephtalate (PET) bottles. An injection molded preform is heated up above the PET glass transition temperature (Tg˜85°C) and subsequently inflated by pressurized air into a closed cavity. In the follow-up filling process, the resulting bottle is filled with the final product. A recently developed modification of the process combines the blowing and filling stages by directly using the final liquid product to inflate the preform. In a previously published paper, a mechanical simulation and successful evaluation of this liquid-driven stretch blow molding process was presented. In this way, a realistic process parameter dependent simulation of the preform deformation throughout the forming process was enabled, whereas the preform temperature evolution during forming was neglected. However, the formability of the preform is highly reduced when the temperature sinks below Tg during forming. Experimental investigations show temperature-induced failure cases due to the fast heat transfer between hot preform and cold liquid. Therefore, in this paper, a process dependent simulation of the temperature evolution during processing to avoid preform failure is presented. For this purpose, the previously developed mechanical model is used to extract the time dependent thickness evolution. This information serves as input for the heat transfer simulation. The required material parameters are calibrated from preform cooling experiments recorded with an infrared-camera. Furthermore, the high deformation ratios during processing lead to strain induced crystallization. This exothermal reaction is included into the simulation by extracting data from preform measurements at different stages of deformation via Differential Scanning Calorimetry (DSC). Finally, the thermal simulation model is evaluated by free forming experiments, recorded by a high-speed infrared camera.

  9. Thermo-mechanical simulation of liquid-supported stretch blow molding

    Energy Technology Data Exchange (ETDEWEB)

    Zimmer, J.; Stommel, M. [Chair of Polymer Materials, Saarland University, Saarbruecken, Germany, – (Germany)


    Stretch blow molding is the well-established plastics forming method to produce Polyehtylene therephtalate (PET) bottles. An injection molded preform is heated up above the PET glass transition temperature (Tg∼85°C) and subsequently inflated by pressurized air into a closed cavity. In the follow-up filling process, the resulting bottle is filled with the final product. A recently developed modification of the process combines the blowing and filling stages by directly using the final liquid product to inflate the preform. In a previously published paper, a mechanical simulation and successful evaluation of this liquid-driven stretch blow molding process was presented. In this way, a realistic process parameter dependent simulation of the preform deformation throughout the forming process was enabled, whereas the preform temperature evolution during forming was neglected. However, the formability of the preform is highly reduced when the temperature sinks below Tg during forming. Experimental investigations show temperature-induced failure cases due to the fast heat transfer between hot preform and cold liquid. Therefore, in this paper, a process dependent simulation of the temperature evolution during processing to avoid preform failure is presented. For this purpose, the previously developed mechanical model is used to extract the time dependent thickness evolution. This information serves as input for the heat transfer simulation. The required material parameters are calibrated from preform cooling experiments recorded with an infrared-camera. Furthermore, the high deformation ratios during processing lead to strain induced crystallization. This exothermal reaction is included into the simulation by extracting data from preform measurements at different stages of deformation via Differential Scanning Calorimetry (DSC). Finally, the thermal simulation model is evaluated by free forming experiments, recorded by a high-speed infrared camera.

  10. Serum Free Light Chains (United States)

    ... or of one of its component parts – a kappa or lambda light chain, or rarely, a heavy chain. Traditionally, plasma cell ... protein (M-protein) production and to calculate a kappa/lambda free light chain ratio. If the protein electrophoresis test is abnormal, ...

  11. Unilateral Plantar Flexors Static-Stretching Effects on Ipsilateral and Contralateral Jump Measures

    Directory of Open Access Journals (Sweden)

    Josinaldo Jarbas da Silva, David George Behm, Willy Andrade Gomes, Fernando Henrique Domingues de Oliveira Silva, Enrico Gori Soares, Érica Paes Serpa, Guanis de Barros Vilela Junior, Charles Ricardo Lopes, Paulo Henrique Marchetti


    Full Text Available The aim of this study was to evaluate the acute effects of unilateral ankle plantar flexors static-stretching (SS on the passive range of movement (ROM of the stretched limb, surface electromyography (sEMG and single-leg bounce drop jump (SBDJ performance measures of the ipsilateral stretched and contralateral non-stretched lower limbs. Seventeen young men (24 ± 5 years performed SBDJ before and after (stretched limb: immediately post-stretch, 10 and 20 minutes and non-stretched limb: immediately post-stretch unilateral ankle plantar flexor SS (6 sets of 45s/15s, 70-90% point of discomfort. SBDJ performance measures included jump height, impulse, time to reach peak force, contact time as well as the sEMG integral (IEMG and pre-activation (IEMGpre-activation of the gastrocnemius lateralis. Ankle dorsiflexion passive ROM increased in the stretched limb after the SS (pre-test: 21 ± 4° and post-test: 26.5 ± 5°, p < 0.001. Post-stretching decreases were observed with peak force (p = 0.029, IEMG (P<0.001, and IEMGpre-activation (p = 0.015 in the stretched limb; as well as impulse (p = 0.03, and jump height (p = 0.032 in the non-stretched limb. In conclusion, SS effectively increased passive ankle ROM of the stretched limb, and transiently (less than 10 minutes decreased muscle peak force and pre-activation. The decrease of jump height and impulse for the non-stretched limb suggests a SS-induced central nervous system inhibitory effect.

  12. Stretching Effects: High-intensity & Moderate-duration vs. Low-intensity & Long-duration. (United States)

    Freitas, S R; Vaz, J R; Bruno, P M; Andrade, R; Mil-Homens, P


    This study examined whether a high-intensity, moderate-duration bout of stretching would produce the same acute effects as a low-intensity, long-duration bout of stretching. 17 volunteers performed 2 knee-flexor stretching protocols: a high-intensity stretch (i. e., 100% of maximum tolerable passive torque) with a moderate duration (243.5 ± 69.5-s); and a low-intensity stretch (50% of tolerable passive torque) with a long duration (900-s). Passive torque at a given sub-maximal angle, peak passive torque, maximal range of motion (ROM), and muscle activity were assessed before and after each stretching protocol (at intervals of 1, 30 and 60 min). The maximal ROM and tolerable passive torque increased for all time points following the high-intensity stretching (p0.05). 1 min post-stretching, the passive torque decreased in both protocols, but to a greater extent in the low-intensity protocol. 30 min post-test, torque returned to baseline for the low-intensity protocol and had increased above the baseline for the high-intensity stretches. The following can be concluded: 1) High-intensity stretching increases the maximal ROM and peak passive torque compared to low-intensity stretching; 2) low-intensity, long-duration stretching is the best way to acutely decrease passive torque; and 3) high-intensity, moderate-duration stretching increases passive torque above the baseline 30 min after stretching.

  13. Phase Transition in Loop Quantum Gravity

    CERN Document Server

    Mäkelä, Jarmo


    We point out that with a specific counting of states loop quantum gravity implies that black holes perform a phase transition at a certain characteristic temperature $T_C$. In this phase transition the punctures of the spin network on the stretched horizon of the black hole jump, in effect, from the vacuum to the excited states. The characteristic temperature $T_C$ may be regarded as the lowest possible temperature of the hole. From the point of view of a distant observer at rest with respect to the hole the characteristic temperature $T_C$ corresponds to the Hawking temperature of the hole.

  14. Generalized crested products of Markov chains

    CERN Document Server

    D'Angeli, Daniele


    We define a finite Markov chain, called generalized crested product, which naturally appears as a generalization of the first crested product of Markov chains. A complete spectral analysis is developed and the $k$-step transition probability is given. It is important to remark that this Markov chain describes a more general version of the classical Ehrenfest diffusion model. As a particular case, one gets a generalization of the classical Insect Markov chain defined on the ultrametric space. Finally, an interpretation in terms of representation group theory is given, by showing the correspondence between the spectral decomposition of the generalized crested product and the Gelfand pairs associated with the generalized wreath product of permutation groups.

  15. Force-Degradation Pattern of Six Different Orthodontic Elastomeric Chains

    Directory of Open Access Journals (Sweden)

    AH Mirhashemi


    Full Text Available Objective: An ideal orthodontic force system should exert continuous light force. Thus, many efforts have been made to improve the memory characteristics of elastomeric chains. The aim of this study was to compare elastomeric chains (ECs claimed by their manufacturers to offer high memory with traditional ones according to their force-extension diagrams.Materials and Methods: In this in-vitro study, ECs were divided into six groups, each containing 40 pieces of chain, from three brands (American Orthodontics, GAC and Ortho-Technology. Each brand was divided into two groups with respect to their claimed characteristics (with or without memory. Each sample was stretched to twice its original length and kept constant in 37°C distilled water. Force-extension diagrams were drawn by universal testing machine at 0,1,8,24,72 hours and 1, 2, 4-week intervals. Additionally, the amounts of elongation required to deliver 200 g force were calculated. To compare the results, ANOVA and Tukey tests were performed.Results: Force-decay rate was significantly different between traditional and memory chains (p<0.05. For traditional chains, there was a substantial decay in force in the first hour and 30-40% of the force was retained at 4 weeeks. The memory chains demonstrated more constant force and retained 60% of the force. The maximum amount of elongation required to deliver 200 g force belonged to American Orthodontics memory chains (61.9% after 24hr and the minimum to Ortho-Technology ECs (23.4% initially.Conclusion: Memory chains exhibited superior mechanical properties compared to traditional ones. For delivering the same force, memory chains required more elongation. Memory chains of GAC and American Orthodontics showed better characteristics among all chains.

  16. Resistance training vs. static stretching: effects on flexibility and strength. (United States)

    Morton, Sam K; Whitehead, James R; Brinkert, Ronald H; Caine, Dennis J


    Morton, SK, Whitehead, JR, Brinkert, RH, and Caine, DJ. Resistance training vs. static stretching: Effects on flexibility and strength. J Strength Cond Res 25(12): 3391-3398, 2011-The purpose of this study was to determine how full-range resistance training (RT) affected flexibility and strength compared to static stretching (SS) of the same muscle-joint complexes in untrained adults. Volunteers (n = 25) were randomized to an RT or SS training group. A group of inactive volunteers (n = 12) served as a convenience control group (CON). After pretesting hamstring extension, hip flexion and extension, shoulder extension flexibility, and peak torque of quadriceps and hamstring muscles, subjects completed 5-week SS or RT treatments in which the aim was to stretch or to strength train the same muscle-joint complexes over similar movements and ranges. Posttests of flexibility and strength were then conducted. There was no difference in hamstring flexibility, hip flexion, and hip extension improvement between RT and SS, but both were superior to CON values. There were no differences between groups on shoulder extension flexibility. The RT group was superior to the CON in knee extension peak torque, but there were no differences between groups on knee flexion peak torque. The results of this preliminary study suggest that carefully constructed full-range RT regimens can improve flexibility as well as the typical SS regimens employed in conditioning programs. Because of the potential practical significance of these results to strength and conditioning programs, further studies using true experimental designs, larger sample sizes, and longer training durations should be conducted with the aim of confirming or disproving these results.

  17. Ultrafast quantitative time-stretch imaging flow cytometry of phytoplankton (United States)

    Lai, Queenie T. K.; Lau, Andy K. S.; Tang, Anson H. L.; Wong, Kenneth K. Y.; Tsia, Kevin K.


    Comprehensive quantification of phytoplankton abundance, sizes and other parameters, e.g. biomasses, has been an important, yet daunting task in aquatic sciences and biofuel research. It is primarily because of the lack of effective tool to image and thus accurately profile individual microalgae in a large population. The phytoplankton species are highly diversified and heterogeneous in terms of their sizes and the richness in morphological complexity. This fact makes time-stretch imaging, a new ultrafast real-time optical imaging technology, particularly suitable for ultralarge-scale taxonomic classification of phytoplankton together with quantitative image recognition and analysis. We here demonstrate quantitative imaging flow cytometry of single phytoplankton based on quantitative asymmetric-detection time-stretch optical microscopy (Q-ATOM) - a new time-stretch imaging modality for label-free quantitative phase imaging without interferometric implementations. Sharing the similar concept of Schlieren imaging, Q-ATOM accesses multiple phase-gradient contrasts of each single phytoplankton, from which the quantitative phase profile is computed. We employ such system to capture, at an imaging line-scan rate of 11.6 MHz, high-resolution images of two phytoplankton populations (scenedesmus and chlamydomonas) in ultrafast microfluidic flow (3 m/s). We further perform quantitative taxonomic screening analysis enabled by this technique. More importantly, the system can also generate quantitative phase images of single phytoplankton. This is especially useful for label-free quantification of biomasses (e.g. lipid droplets) of the particular species of interest - an important task adopted in biofuel applications. Combining machine learning for automated classification, Q-ATOM could be an attractive platform for continuous and real-time ultralarge-scale single-phytoplankton analysis.

  18. Elastography Study of Hamstring Behaviors during Passive Stretching.

    Directory of Open Access Journals (Sweden)

    Guillaume Le Sant

    Full Text Available The mechanical properties of hamstring muscles are usually inferred from global passive torque/angle relationships, in combination with adjoining tissues crossing the joint investigated. Shear modulus measurement provides an estimate of changes in muscle-tendon stiffness and passive tension. This study aimed to assess the passive individual behavior of each hamstring muscle in different stretching positions using shear wave elastography.The muscle shear modulus of each hamstring muscle was measured during a standardized slow passive knee extension (PKE, 80% of maximal range of motion on eighteen healthy male volunteers. Firstly, we assessed the reliability of the measurements. Results were good for semitendinosus (ST, CV: 8.9%-13.4%, semimembranosus (SM, CV: 10.3%-11.2% and biceps femoris long-head (BF-lh, CV: 8.6%-13.3%, but not for biceps femoris short-head (BF-sh, CV: 20.3%-44.9%. Secondly, we investigated each reliable muscle in three stretch positions: 70°, 90° and 110° of hip flexion. The results showed different values of shear modulus for the same amount of perceived stretch, with the highest measurements in the high-flexed hip situation. Moreover, individual muscles displayed different values, with values increasing or BF-lh, SM and ST, respectively. The inter-subject variability was 35.3% for ST, 27.4% for SM and 30.2% for BF-lh.This study showed that the hip needs to be high-flexed to efficiently tension the hamstrings, and reports a higher muscle-tendon stress tolerance at 110° of hip angle. In addition muscles have different passive behaviors, and future works will clarify if it can be linked with rate of injury.

  19. The effect of large amplitude motions on the transition frequency redshift in hydrogen bonded complexes

    DEFF Research Database (Denmark)

    Mackeprang, Kasper; Kjærgaard, Henrik Grum; Salmi, Teemu


    -stretching transition. The model accurately predicts the transition wavenumbers of the vibrations in water dimer compared to experimental values and provides a physical picture that explains the redshift of the hydrogen bonded OH-oscillator. We find that it is unnecessary to include all six intermolecular modes...

  20. Stretched flow of Carreau nanofluid with convective boundary condition

    Indian Academy of Sciences (India)

    T Hayat; M Waqas; S A Shehzad; A Alsaedi


    The steady laminar boundary layer flow of Carreau nanofluid over a stretching sheet is investigated. Effects of Brownian motion and thermophoresis are present. Heat transfer is characterized using convective boundary condition at the sheet. The governing partial differential equations are reduced into a set of nonlinear ordinary differential equations through suitable transformations. Results of velocity, temperature and concentration fields are computed via homotopic procedure. Numerical values of skin-friction coefficient, local Nusselt and Sherwood numbers are computed and discussed. A comparative study with existing solutions in a limiting sense is made.

  1. Muon anomalous magnetic moment due to the brane stretching effect

    CERN Document Server

    Sawa, K


    We investigate the contribution of extra dimensions to muon anomalous magnetic moment using a 6-dimensional model. The approach analyzes the extent to which small brane fluctuations influence the magnetic moment. In particular, we assume that the fluctuations are static in time, which add the new potential terms to the schr{\\"o}dinger equation through the induced vierbein. This paper shows that the fluctuations result in the brane stretching effect due to the negative tension. The effect would be a capable of reproducing the appropriate order for the recent BNL measurements of the muon (g-2) deviation.

  2. HSZ 220 and 260 steel with excellent stretch formability

    Energy Technology Data Exchange (ETDEWEB)

    Hartmann, G.; Heckelmann, I.; Menne, M. [Thyssenkrupp Stahl AG, Duisburg (Germany)


    As has been shown in the stretch forming and deep drawing tests, the newly developed HSZ steels are particularly suitable for the production of large exposed car body parts, such as roofs, doors and hoods. They are rather unfavourable for applications required higher drawing depths. Owing to its excellent strain hardening behaviour and a relatively high yield strength, the HSZ steel grades exhibits a good dent resistance. For weight reduction purposes, it is possible to replace soft aluminium-killed steels or IF steels by HSZ steels with reduced sheet thicknesses. If corrosion protection is required, HSZ grades are also available electrogalvanized. (orig.)

  3. Excitation energy transfer in partly ordered polymer films differing in donor and acceptor transition moments orientation (United States)

    Synak, A.; Bojarski, P.; Sadownik, M.; Kułak, L.; Gryczynski, I.; Grobelna, B.; Rangełowa-Jankowska, S.; Jankowski, D.; Kubicki, A.


    Based on spectroscopic measurements selected properties of nonradiative Förster energy transport are studied in uniaxially stretched polyvinyl alcohol thin films for three systems differing in donor and acceptor transition moments orientation relative to the axis of stretching. In particular, donor - acceptor emission anisotropy spectra yield completely different regularities for these systems in uniaxially stretched films, whereas they are similar in unstretched films. In particular it is shown that acceptor fluorescence can be either strongly polarized after nonradiative energy transfer in stretched films or depolarized depending on the angular distribution of acceptor transition moments in the matrix. Donor and acceptor emission anisotropy decays exhibit similar regularities to those of steady-state measurements. The obtained results are analyzed with the help of Monte Carlo simulations.

  4. Structural Origins of Martian Pit Chains (United States)

    Wyrick, D.; Ferrill, D. A.; Morris, A. P.; Colton, S. L.; Sims, D. W.


    Pit craters are circular to elliptical depressions found in alignments (chains), which in many cases coalesce into linear troughs, and are common on the surface of Mars. Pit craters lack an elevated rim, ejecta deposits, or lava flows that are associated with impact craters or calderas. It is generally agreed that these features are formed by collapse into a subsurface cavity. Hypotheses regarding the formation of pit crater chains require development of a substantial subsurface void to accommodate collapse of the overlying sediments. Suggested mechanisms of formation include: collapsed lava tubes, dike swarms, collapsed magma chamber, karst dissolution, fissuring beneath loose material, and dilational faulting. The research described here is intended to constrain current interpretations of pit crater chain formation by analyzing their distribution and morphology. The western hemisphere of Mars was systematically mapped using Mars Orbiter Camera (MOC) images to generate ArcView Geographic Information System (GIS) coverages. All visible pit crater chains were mapped, including their orientations and associations with other structures. We found that pit chains commonly occur in areas that show regional extension or local fissuring. There is a strong correlation between pit chains and fault-bounded grabens. Frequently, there are transitions along strike from (i) visible faulting to (ii) faults and pits to (iii) pits alone. We performed a detailed quantitative analysis of pit crater morphology using MOC narrow angle images, Thermal Emission Imaging System (THEMIS) visual images and Mars Orbiter Laser Altimeter (MOLA) data. This allowed us to interpret a pattern of pit chain evolution and calculate pit depth, slope, and volume. The information collected in the study was then compared with non-Martian examples of pit chains and physical analog models. We evaluated the various mechanisms for pit chain development based on the data collected and conclude that dilational

  5. Gushing metal chain (United States)

    Belyaev, Alexander; Sukhanov, Alexander; Tsvetkov, Alexander


    This article addresses the problem in which a chain falls from a glass from some height. This phenomenon demonstrates a paradoxical rise of the chain over the glass. To explain this effect, an initial hypothesis and an appropriate theory are proposed for calculating the steady fall parameters of the chain. For this purpose, the modified Cayley's problem of falling chain given its rise due to the centrifugal force of upward inertia is solved. Results show that the lift caused by an increase in linear density at the part of chain where it is being bent (the upper part) is due to the convergence of the chain balls to one another. The experiments confirm the obtained estimates of the lifting chain.

  6. Markov chain for estimating human mitochondrial DNA mutation pattern (United States)

    Vantika, Sandy; Pasaribu, Udjianna S.


    The Markov chain was proposed to estimate the human mitochondrial DNA mutation pattern. One DNA sequence was taken randomly from 100 sequences in Genbank. The nucleotide transition matrix and mutation transition matrix were estimated from this sequence. We determined whether the states (mutation/normal) are recurrent or transient. The results showed that both of them are recurrent.

  7. Asymptotics of Markov Kernels and the Tail Chain

    CERN Document Server

    Resnick, Sidney I


    An asymptotic model for extreme behavior of certain Markov chains is the "tail chain". Generally taking the form of a multiplicative random walk, it is useful in deriving extremal characteristics such as point process limits. We place this model in a more general context, formulated in terms of extreme value theory for transition kernels, and extend it by formalizing the distinction between extreme and non-extreme states. We make the link between the update function and transition kernel forms considered in previous work, and we show that the tail chain model leads to a multivariate regular variation property of the finite-dimensional distributions under assumptions on the marginal tails alone.

  8. Memory Chain in a Chaotic Autoassociative Neural Network

    Institute of Scientific and Technical Information of China (English)

    FAN Hong; WANG Zhi-jie; ZHANG Jue


    Memory chain is observed in a chaotic autoassociative neural network. The network recalls first stored pattern from a fragment of a memory, stays at this pattern for a while, transits to the second stored pattern that overlaps with the first recalled pattern.Then it stays at the second recalled pattern for a while, transits to the third stored pattern that overlaps with the second recalled pattern, and so on. Thus a memory chain is generated. The memory chain ends with the pattern that overlaps no other stored patten. This phenomenon is similar to the way of recalling process of human beings in some respects.

  9. Tactile spatial acuity is reduced by skin stretch at the human wrist. (United States)

    Cody, Frederick W J; Idrees, Raheel; Spilioti, Diamantina X; Poliakoff, Ellen


    The skin is an elastic organ that is continuously distorted as our limbs move. The hypothesis that the precision of human tactile localisation is reduced when the skin is stretched, with concurrent expansion of receptive fields (RFs) was tested. Locognosic acuity over the dorsal wrist area was quantified during application of background stretch by (a) Wrist-Bend (skin stretch combined with non-cutaneous proprioceptor activation) and (b) Skin-Pull (skin stretch alone). Participants identified the perceived direction (distal or proximal) of brief test stimuli, applied along a 7-point linear array, relative to a central reference locus. Performance was significantly reduced during the large amplitude compared to the small amplitude of tonic skin stretch, but there was no effect of stretch mode (Wrist-Bend, Skin-Pull), nor was the effect of stretch amplitude modulated by the mode of stretch. Locognosic acuity was poorer than baseline accuracy for the large amplitude skin stretches, for both application modes, but did not differ significantly from baseline for either of the small amplitude stretches. We interpret these observations as corroborating the long-held assumption that tactile localisation is primarily dependent upon the RF dimensions, and associated innervation densities, of regional touch units. The finding that performance was reduced to a similar extent under Skin-Pull and Wrist-Bend conditions suggests that non-cutaneous proprioceptors had rather little tonic modulatory effect.

  10. Acute Effects of Different Agonist and Antagonist Stretching Arrangements on Static and Dynamic Range of Motion (United States)

    Amiri-Khorasani, Mohammadtaghi; Kellis, Eleftherios


    Background: Traditionally, stretching exercises are considered as basic components of warm up aiming to prepare the musculoskeletal system for performance and to prevent injuries. Objectives: The purpose of this study was to examine the effects of different agonist and antagonist stretching arrangements within a pre-exercise warm-up on hip static (SROM) and dynamic range of motion (DROM). Materials and Methods: Sixty trained male subjects (Mean ± SD: height, 177.38 ± 6.92 cm; body mass, 68.4 ± 10.22 kg; age, 21.52 ± 1.17 years) volunteered to participate in this study. SROM was measured by V-sit test and DROM captured by a motion analysis system before and after (i) static stretching for both hip flexor and extensor muscles (SFSE), (ii) dynamic stretching for both hip flexor and extensor muscles (DFDE), (iii) static stretching for the hip flexors and dynamic stretching for hip extensors (SFDE), and (iv) dynamic stretching for the hip flexors and static stretching for hip extensors (DFSE). Results: DFSE showed a significantly higher increase in DROM and SROM than the remainder of the stretching protocols (P < 0.05). There were significant differences between DFDE with SFSE and SFDE (P < 0.05) and SFSE showed significant increase as compared to SFDE (P < 0.05). Conclusions: In conclusion, DFSE is probably the best stretching arrangement due to producing more post activation potentiation on agonist muscles and less muscle stiffness in antagonist muscles. PMID:26715975

  11. Effects of contraction intensity on muscle fascicle and stretch reflex behavior in the human triceps surae. (United States)

    Cronin, Neil J; Peltonen, Jussi; Ishikawa, Masaki; Komi, Paavo V; Avela, Janne; Sinkjaer, Thomas; Voigt, Michael


    The aims of this study were to examine changes in the distribution of a stretch to the muscle fascicles with changes in contraction intensity in the human triceps surae and to relate fascicle stretch responses to short-latency stretch reflex behavior. Thirteen healthy subjects were seated in an ankle ergometer, and dorsiflexion stretches (8 degrees ; 250 degrees /s) were applied to the triceps surae at different moment levels (0-100% of maximal voluntary contraction). Surface EMG was recorded in the medial gastrocnemius, soleus, and tibialis anterior muscles, and ultrasound was used to measure medial gastrocnemius and soleus fascicle lengths. At low forces, reflex amplitudes increased despite a lack of change or even a decrease in fascicle stretch velocities. At high forces, lower fascicle stretch velocities coincided with smaller stretch reflexes. The results revealed a decline in fascicle stretch velocity of over 50% between passive conditions and maximal force levels in the major muscles of the triceps surae. This is likely to be an important factor related to the decline in stretch reflex amplitudes at high forces. Because short-latency stretch reflexes contribute to force production and stiffness regulation of human muscle fibers, a reduction in afferent feedback from muscle spindles could decrease the efficacy of human movements involving the triceps surae, particularly where high force production is required.

  12. The carpal stretch test at the rheumatoid wrist. (United States)

    Shimizu, Hiroyuki; Beppu, Moroe; Matsusita, Kazuhiko; Arai, Takeshi; Yoshida, Noriyuki


    The purpose of this study was to evaluate the radiographic changes of the carpus for rheumatoid wrists in patients who underwent the Sauvé-Kapandji procedure by examining the clinical results and comparing pre- and postoperative radiographic measurements. We studied 43 wrists in 37 patients who showed vertical laxity in the radiocarpal and midcarpal joint on preoperative carpal stretch test. Pain was improved in all patients and the forearm rotation angles of the wrist were significantly improved after the operation. The carpal collapse ratio was significantly reduced after the operation. The carpal collapse reduction rate was significantly greater in the group with than that in the group without midcarpal joint vertical laxity on the carpal stretch test. Although the Sauvé-Kapandji procedure was not sufficiently effective in preventing carpal collapse, it did have a protective effect against ulnar carpal shift. The results of our study showed that vertical laxity of the midcarpal joint was the risk factor of the carpal collapse after Sauvé-Kapandji procedure.

  13. Dynamic rotation and stretch tensors from a dynamic polar decomposition (United States)

    Haller, George


    The local rigid-body component of continuum deformation is typically characterized by the rotation tensor, obtained from the polar decomposition of the deformation gradient. Beyond its well-known merits, the polar rotation tensor also has a lesser known dynamical inconsistency: it does not satisfy the fundamental superposition principle of rigid-body rotations over adjacent time intervals. As a consequence, the polar rotation diverts from the observed mean material rotation of fibers in fluids, and introduces a purely kinematic memory effect into computed material rotation. Here we derive a generalized polar decomposition for linear processes that yields a unique, dynamically consistent rotation component, the dynamic rotation tensor, for the deformation gradient. The left dynamic stretch tensor is objective, and shares the principal strain values and axes with its classic polar counterpart. Unlike its classic polar counterpart, however, the dynamic stretch tensor evolves in time without spin. The dynamic rotation tensor further decomposes into a spatially constant mean rotation tensor and a dynamically consistent relative rotation tensor that is objective for planar deformations. We also obtain simple expressions for dynamic analogues of Cauchy's mean rotation angle that characterize a deforming body objectively.

  14. Fluid Flow and Heat Transfer over a Permeable Stretching Cylinder

    Directory of Open Access Journals (Sweden)

    K Vajravelu


    Full Text Available In this paper, we analyze the effects of thermo-physical properties on the axisymmetric flow of a viscous fluid induced by a stretching cylinder in the presence of internal heat generation/absorption. It is assumed that the cylinder is stretched in the axial direction with a linear velocity and the surface temperature of the cylinder is subjected to vary linearly. Here, the temperature dependent thermo-physical properties namely, the fluid viscosity and the fluid thermal conductivity are respectively assumed to vary as an inverse function of the temperature and a linear function of the temperature. The governing system of partial differential equations is converted into a system of coupled non-linear ordinary differential equations with variable coefficients. The resulting system is solved numerically using a second order finite difference scheme known as the Keller-box method. The governing equations of the problem show that the flow and heat transfer characteristics depend on six parameters, namely the curvature parameter, fluid viscosity parameter, injection/suction parameter, variable thermal conductivity parameter, heat source/sink parameter and the Prandtl number. The numerical values obtained for the velocity, temperature, skin friction, and the Nusselt number are presented through graphs and tables for several sets of values of the pertinent parameters. The results obtained for the flow and heat transfer characteristics reveal many interesting behaviors that warrant further study on the axisymmetric flow phenomena. Comparisons with the available results in the literature are presented as special cases.

  15. Extension by faulting, stretching and magma intrusion in Ethiopia (United States)

    Bastow, I. D.; Keir, D.


    The 2001-2004 Ethiopia Afar Geoscientific Lithospheric Experiment showed that high seismic wavespeed, dense, mafic crustal intrusions exist beneath many zones of Quaternary magmatism in the Main Ethiopian rift, and that crustal thinning is minimal. From these observations, a consensus quickly emerged that extension presently occurs not by ductile stretching and brittle faulting but by magma intrusion. Striking InSAR images and accompanying seismic data from the 2005 Afar diking episode provided further compelling evidence in support of the magma assisted rifting hypothesis. Patterns of mantle seismic anisotropy, constrained by a combination of body and surface-wave analysis showed that melt intrusion likely also plays an important role in accommodating extension at greater depths in the extending plate. Evidence from further north in Afar, however, where crustal thickness decreases abruptly into the Danakil Depression, is not so easily explained by the magma assisted rifting hypothesis. Subsidence of the newly forming margin towards and below sea level, and eruption of voluminous basalt flows, is likely the result of late-stage thinning of the heavily intruded, weakened plate just before the onset of seafloor spreading. Faulting, stretching and magma intrusion are thus each important, but at different times during breakup. Combining, not isolating, these mechanisms of strain in new rifting models and appreciating how plate strength varies during rifting is essential in developing a clearer understanding of the incomplete geological record that documents continental breakup over time.

  16. Hacking the code of amyloid formation: the amyloid stretch hypothesis. (United States)

    Pastor, M Teresa; Esteras-Chopo, Alexandra; Serrano, Luis


    Many research efforts in the last years have been directed towards understanding the factors determining protein misfolding and amyloid formation. Protein stability and amino acid composition have been identified as the two major factors in vitro. The research of our group has been focused on understanding the relationship between amino acid sequence and amyloid formation. Our approach has been the design of simple model systems that reproduce the biophysical properties of natural amyloids. An amyloid sequence pattern was extracted that can be used to detect amyloidogenic hexapeptide stretches in proteins. We have added evidence supporting that these amyloidogenic stretches can trigger amyloid formation by nonamyloidogenic proteins. Some experimental results in other amyloid proteins will be analyzed under the conclusions obtained in these studies. Our conclusions together with evidences from other groups suggest that amyloid formation is the result of the interplay between a decrease of protein stability, and the presence of highly amyloidogenic regions in proteins. As many of these results have been obtained in vitro, the challenge for the next years will be to demonstrate their validity in in vivo systems.

  17. Saturation of Zeldovich Stretch-Twist-Fold Map Dynamos

    CERN Document Server

    Seta, Amit; Subramanian, Kandaswamy


    Zeldovich's stretch-twist fold (STF) dynamo provided a breakthrough in conceptual understanding of fast dynamos, including fluctuation or small scale dynamos. We study the evolution and saturation behaviour of two types of Baker's map dynamos, which have been used to model Zeldovich's STF dynamo process. Using such maps allows one to analyze dynamos at much higher magnetic Reynolds numbers $R_M$ as compared to direct numerical simulations. In the 2-strip map dynamo there is constant constructive folding while the 4-strip map dynamo also allows the possibility of field reversal. Incorporating a diffusive step parameterised by $R_M$, we find that the magnetic field $B(x)$ is amplified only above a critical $R_M=R_{crit} \\sim 4$ for both types of dynamos. We explore the saturation of these dynamos in 3 ways; by a renormalized decrease of the effective $R_M$ (Case I) or due to a decrease in the efficiency of field amplification by stretching (Case II), or a combination of both effects (Case III). For Case I, we s...

  18. Sustainable Transition

    DEFF Research Database (Denmark)

    Hansen, Ole Erik; Søndergård, Bent


    transition processes. Where. Addresses design processes aimed at sustainable transition enacted in complex social settings, socio-technical systems involving many different actors and agendas. How. The chapter outlines a conceptual and analytic framework for a reflexive design practice for sustainability...... including the perspective of structural changes (transition of socio-technical systems and social practices) and Design as metadesign; an reflexivity on contextual framework of the design practice (regimes/design spaces)....

  19. Beyond the nearest-neighbor Zimm-Bragg model for helix-coil transition in peptides. (United States)

    Murza, Adrian; Kubelka, Jan


    The nearest-neighbor (micro = 1) variant of the Zimm and Bragg (ZB) model has been extensively used to describe the helix-coil transition in biopolymers. In this work, we investigate the helix-coil transition for a 21-residue alanine peptide (AP) with the ZB model up to fourth nearest neighbor (micro = 1, 2, 3, and 4). We use a matrix approach that takes into account combinations of any number of helical stretches of any length and therefore gives the exact statistical weight of the chain within the assumptions of the ZB model. The parameters of the model are determined by fitting the temperature-dependent circular dichroism and Fourier transform infrared experimental spectra of the AP. All variants of the model fit the experimental data, thus giving similar results in terms of the macroscopic observables, such as temperature-dependent fractional helicity. However, the resulting microscopic parameters, such as distributions of the individual residue helical probabilities and free energy surfaces, vary significantly depending on the variant of the model. Overall, the mean residue enthalpy and entropy (in the absolute value) both increase with micro, but combined yield essentially the same "effective" value of the ZB propagation parameters for all micro. Greater helical probabilities for individual residues are predicted for larger micro, in particular, near the center of the sequence. The ZB nucleation parameters increase with increasing micro, which results in a lower free energy barrier to helix nucleation and lower apparent "cooperativity" of the transition. The significance of the long-range interactions for the predictions of ZB model for helix-coil transition, the calculated model parameters and the limitations of the model are discussed.

  20. The Carry-Over Effects of Diathermy and Stretching in Developing Hamstring Flexibility. (United States)

    Draper, David O; Miner, Lisa; Knight, Kenneth L; Ricard, Mark D


    OBJECTIVE: To compare the effects of low-load, short-duration stretching with or without high-intensity, pulsed short-wave diathermy on hamstring flexibility. DESIGN AND SETTING: We used a single-blind, repeated-measures design (pretest and posttest for all treatments) that included a placebo. The 3 independent variables were treatment mode, pretest and posttest measurements, and day. Treatment mode had 3 levels: diathermy and stretching, stretching alone, and control. The dependent variable was range of motion. Subjects were randomly assigned to the diathermy and stretching, stretching-only, or control group. Subjects were treated and tested each day (at approximately the same time) for 5 days, with a follow-up test administered 72 hours later. Hamstring flexibility was tested using a sit-and-reach box before and after each treatment. Diathermy and stretching subjects received a 15-minute diathermy treatment on the right hamstring at a setting of 7000 pulses per second, with an average pulse width of 95 μsec. Stretching-only subjects received a 15-minute sham diathermy treatment. Both diathermy and stretching and stretching-only subjects then performed three 30-second stretches (short duration) before being retested. Control subjects lay prone for 15 minutes before being retested. SUBJECTS: Thirty-seven healthy college students (11 men, 26 women, age = 20.46 +/- 1.74 years) volunteered. MEASUREMENTS: Hamstring flexibility was measured using a sit-and-reach box before and after each treatment. RESULTS: The average increases in hamstring flexibility over the 5 treatment days for the diathermy and stretching, stretching-only, and control groups were 6.06 cm (19.6%), 5.27 cm (19.7%), and 3.38 cm (10.4%), respectively. Three days later (after no treatment), the values for the diathermy and stretching, stretching-only, and control groups were 8.27 cm (26.7%), 6.83 cm (25.3%), and 4.15 cm (14.2%), respectively. No significant differences in hamstring flexibility were

  1. The Role of Structure in the Protein Dynamical Transition

    CERN Document Server

    He, Yunfen


    The protein dynamical transition is investigated as a function of protein structure using terahertz time domain spectroscopy (THz-TDS). Measurements performed for native state and denatured hen egg white lysozyme (HEWL) show that protein structure is not necessary for the dynamical transition. We find the temperature dependence follows activated behavior and there is no evidence of a fragile to strong transition. Measurements of short chain poly alanine show a dynamical transition down to penta-alanine, however no transition is observed for di-alanine or tri-alanine. These measurements demonstrate that the temperature dependence arises strictly from the interaction of the side chains with the solvent. The lack of a transition for shorter chain polypeptides may indicate the temperature dependence arises from a net ordering of the adjacent water which scales with the length of the polypeptide chain.

  2. Side chain polysiloxanes with phthalocyanine moieties

    Directory of Open Access Journals (Sweden)

    T. Ganicz


    Full Text Available Side chain polysiloxane with 5-(pentyloxy-3-methyloxy-9,10,16,17,23,24-hexakis(octenyloxyphthalocyanine moieties is synthesized by hydrosilylation reaction. The phase behavior and thermooptical properties of the polysiloxane and starting 2-(pent-4-enyloxy-3-methyloxy-9,10,16,17,23,24-hexakis(octenyloxyphthalocyanine is examined by POM (Polarizing optical microscopy, TOA (thermooptical analysis, DSC (differential scanning calorimetry, AFM (atomic force microscopy and SAXS (small angle X-ray scattering studies. The effect of the attachment of phthalocyanine to polysiloxane chains over phase transitions and phase morphology is discussed in details.

  3. Supply Chain Management og Supply Chain costing

    DEFF Research Database (Denmark)

    Nielsen, Steen; Mortensen, Ole


    Formålet med denne artikel er at belyse de muligheder som ligger i at integrere virksomhedens økonomiske styring med begrebet Supply Chain Management (SCM). Dette søges belyst ved først at beskrive den teoretiske ramme, hvori SCM indgår. Herefter analyseres begrebet Supply Chain Costing (SCC) som...... Århus. Et resultat er, at via begrebet Supply Chain Costing skabes der mulighed for at måle logistikkædens aktiviteter i kr./øre. Anvendelsen af denne information har også strategisk betydning for at kunne vælge kunde og leverandør. Ved hjælp af integrationen skabes der også helt nye mulighed...

  4. Understanding the Chain Fountain

    CERN Document Server

    Biggins, John Simeon


    If a chain is initially at rest in a beaker at a height h1 above the ground, and the end of the chain is pulled over the rim of the beaker and down towards the ground and then released, the chain will spontaneously "flow" out of the beaker under gravity. Furthermore, if h1 is sufficient, the beads do not simply drag over the edge of the beaker but form a fountain reaching a height h2 above it. We show that the formation of a fountain requires that the beads come into motion not only by being pulled upwards by the part of the chain immediately above the pile, but also by being pushed upwards by an anomalous reaction force from the pile of stationary chain. We propose possible origins for this force, argue that its magnitude will be proportional to the square of the chain velocity, and predict and verify experimentally that h2 is proportional to h1.

  5. The Effects of Hamstring Stretching on Leg Rotation during Knee Extension. (United States)

    Kimura, Atsushi


    [Purpose] This study investigated the effects of hamstring stretching on leg rotation during active knee extension. [Subjects] Subjects were 100 bilateral legs of 50 healthy women without articular disease. [Methods] Hamstring hardness, leg rotation and muscle activities of the knee extensors during active knee extension were measured before and after hamstring stretching. [Results] Hamstring hardness was significantly decreased after hamstring stretching. The leg rotation angle, variation in leg rotation angle, variation in leg external rotation angle, and muscle activities of the vastus lateralis and rectus femoris were significantly increased after hamstring stretching. A moderate positive correlation was found between variation in leg rotation and variation in muscle hardness in hamstring. [Conclusion] Leg rotation during active knee extension was increased by hamstring stretching. Hamstring stretching would be effective as a pretreatment for restoring proper leg rotation when knee extension is conducted as a therapeutic exercise.

  6. The acute effects of static and ballistic stretching on vertical jump performance in trained women. (United States)

    Unick, Jessica; Kieffer, H Scott; Cheesman, Wendy; Feeney, Anna


    Traditionally stretching has been included as part of a warm-up that precedes athletic participation. However, there is mixed evidence as to whether stretching actually enhances or hinders athletic performance. Therefore, the purpose of this study was to examine the acute effects of static (SS) and ballistic stretching (BS) on vertical jump (VJ) performance and to investigate whether power was altered at 15 and 30 minutes after stretching. Sixteen actively trained women performed a series of vertical jumps (countermovement and drop jumps) after an initial nonstretching (NS) session and after participating in BS and SS sessions that were conducted in a balanced and randomized order. The results indicated that there was no significant difference (p ballistic stretching, elapsed time, or initial flexibility scores. This suggests that stretching prior to competition may not negatively affect the performance of trained women.

  7. Food supply chains


    Zhou, Qian


    The dissertation analyses food waste in global supply chain. From the related managerial literature, the process of supply chain operation, from agriculture, manufacturing, warehouses, retailers to customers are explained clearly. Then the reasons and characteristics of food wastes in any point of food supply chain are analyzed. From some case studies and questionnaire investigation, some corresponding methods to reduce food waste are put forward in the following. Lastly, in terms of method s...

  8. Supply chain components

    Directory of Open Access Journals (Sweden)

    Vieraşu, T.


    Full Text Available In this article I will go through three main logistics components, which are represented by: transportation, inventory and facilities, and the three secondary logistical components: information, production location, price and how they determine performance of any supply chain. I will discuss then how these components are used in the design, planning and operation of a supply chain. I will also talk about some obstacles a supply chain manager may encounter.

  9. Effects of chain length and Au spin-orbit coupling on 3(pi pi*) emission from bridging Cn2- units: theoretical characterization of spin-forbidden radiative transitions in metal-capped one-dimensional carbon chains [H3PAu(C[triple bond]C)nAuPH3]. (United States)

    Cao, Zexing; Zhang, Qianer


    Density functional theory and CASSCF calculations have been used to optimize the geometries of binuclear gold(I) complexes [H(3)PAu(C[triple bond]C)(n)AuPH(3)] (n=1-6) in their ground states and selected lowest energy (3)(pi pi*) excited states. Vertical excitation energies obtained by time-dependent density functional calculations for the spin-forbidden singlet-triplet transitions have exponential-decay size dependence. The predicted singlet-triplet splitting limit of [H(3)PAu(C[triple bond]C)(proportional/variant)AuPH(3)] is about 8317 cm(-1). Calculated singlet-triplet transition energies are in reasonable agreement with available experimental observations. The effect of the heavy atom Au spin-orbit coupling on the (3)(pi pi*) emission of these metal-capped one-dimensional carbon allotropes has been investigated by MRCI calculations. The contribution of the spin- and dipole-allowed singlet excited state to the spin-orbit-coupling wave function of the (3)(pi pi*) excited state makes the low-lying acetylenic triplet excited states become sufficiently allowed so as to appear in both electronic absorption and emission.

  10. Comparing the effects of 3 weeks of upper-body vibration training, vibration and stretching, and stretching alone on shoulder flexibility in college-aged men. (United States)

    Ferguson, Steven L; Kim, Eonho; Seo, Dong-Il; Bemben, Michael G


    This study compared the effects of 3 weeks of upper-body vibration training, vibration and stretching, and stretching alone on shoulder flexibility in college-aged men. Twenty-one men were randomly assigned to vibration-stretching (VS; n = 8), vibration only (VO; n = 6), or stretching only (SO; n = 7) groups that trained 3 times per week for 3 weeks. All 3 groups performed 9 total sets of 30-second stretches. The VS group performed four 30-second upper-body vibration exercises and five 30-second upper-body stretching exercises. The VO group performed nine 30-second upper-body vibration exercises. The SO group performed nine 30-second upper-body stretching exercises. Shoulder flexion (SF), shoulder extension (SE), and shoulder transverse extension (STE) were assessed by a Leighton Flexometer and back scratch tests bilaterally (BSR, BSL) were measured via tape measure. A 1-way analysis of variance (ANOVA) evaluated groups at baseline and a 2-way repeated-measures ANOVA evaluated the interventions over time. At baseline, there were no group differences in age, height, or weight. There was a significant (p flexibility outcome variable (SF: +6.1%, +3.9%, +3.4%; SE: +8.9%, +13.5%, +26.9%; STE: +12.8%, +8.7%, +24.3%; BSR: +4.4 cm, +3.4 cm, +3.1 cm; BSL: +3.6 cm, +2.3 cm, +6.1 cm) for SO, VO, and VS, respectively. Shoulder extension was the only variable that showed a significant (p training, alone or combined with stretching, is a viable alternative to a standard stretching routine when attempting to increase shoulder flexibility. Adding vibration training to a flexibility regimen may improve the likelihood of regularly performing flexibility sessions because of increased variety.

  11. Stretching training affects erythrocyte rheological properties and anaerobic performance in healthy young males


    Toprak, Emine Kılıç; Koçak, Fatma Ünver; Erken, Gülten; Küçükatay, Melek Bor


    INTRODUCTION: Stretching exercise training is used to improve flexibility and performance. This study aimed to investigate the short and long-term effects of stretching exercise on flexibility, performance, red blood cell (RBC) deformability and aggregation. METHODS: 7 young male subjects (mean age 20.71±0.52 years) participated to the study. Stretching protocol consisted of 3 repetitions for 60 seconds, 3 days/week, 6 weeks. Blood samples were obtained before and immediately after the stretc...

  12. Effects of passive static stretching on blood glucose levels in patients with type 2 diabetes mellitus


    Park, Seong Hoon


    [Purpose] This study determined the effects of passive static stretching on blood glucose levels in patients with type 2 diabetes. [Subjects] Fifteen patients (8 males and 7 females) with type 2 diabetes were recruited and randomly assigned to the control group or passive static stretching group. [Methods] Glycated hemoglobin was measured before and after the 8-week training period. [Results] Glycated hemoglobin levels decreased significantly in the passive static stretching group, and there ...

  13. The effects of passive stretching plus vibration on strength and activation of the plantar flexors. (United States)

    Miller, Jonathan D; Herda, Trent J; Trevino, Michael A; Mosier, Eric M


    This study examined the effects of passive stretching only (PS+CON) and passive stretching with the addition of continuous vibration (VIB) during post-passive stretching tests (PS+VIB) on peak torque (PT), percent voluntary inactivation (%VI), single stimulus twitch torque (TTSINGLE), and doublet stimuli twitch torque (TTDOUBLET) of the plantar flexors at a short (20° plantar flexion (PF)) and long muscle length (15° dorsiflexion (DF)). Fourteen healthy men (age = 22 ± 3 years) performed isometric maximal voluntary contractions at PF and DF, and passive range of motion (PROM) assessments before and after 8 × 30-s passive stretches without (PS+CON) or with VIB (PS+VIB) administered continuously throughout post-passive stretching tests. The passive properties of the muscle tendon unit were assessed pre- and post-passive stretching via PROM, passive torque (PASSTQ), and musculotendinous stiffness (MTS) measurements. PT, TTSINGLE, and TTDOUBLET decreased, whereas, %VI increased following passive stretching at PF and DF (P stretching during both trials (P stretching-induced force/torque deficit and increases in %VI were evident following passive stretching at short and long muscle lengths. Although not statistically significant, effect size calculations suggested large and moderate differences in the absolute changes in PT (Cohen's d = 1.14) and %VI (Cohen's d = 0.54) from pre- to post-passive stretching between treatments, with PS+VIB having greater decreases of PT and higher %VI than PS+CON. The decrement in PT following passive stretching may be primarily neural in origin.

  14. Lewis lung carcinoma regulation of mechanical stretch-induced protein synthesis in cultured myotubes. (United States)

    Gao, Song; Carson, James A


    Mechanical stretch can activate muscle and myotube protein synthesis through mammalian target of rapamycin complex 1 (mTORC1) signaling. While it has been established that tumor-derived cachectic factors can induce myotube wasting, the effect of this catabolic environment on myotube mechanical signaling has not been determined. We investigated whether media containing cachectic factors derived from Lewis lung carcinoma (LLC) can regulate the stretch induction of myotube protein synthesis. C2C12 myotubes preincubated in control or LLC-derived media were chronically stretched. Protein synthesis regulation by anabolic and catabolic signaling was then examined. In the control condition, stretch increased mTORC1 activity and protein synthesis. The LLC treatment decreased basal mTORC1 activity and protein synthesis and attenuated the stretch induction of protein synthesis. LLC media increased STAT3 and AMP-activated protein kinase phosphorylation in myotubes, independent of stretch. Both stretch and LLC independently increased ERK1/2, p38, and NF-κB phosphorylation. In LLC-treated myotubes, the inhibition of ERK1/2 and p38 rescued the stretch induction of protein synthesis. Interestingly, either leukemia inhibitory factor or glycoprotein 130 antibody administration caused further inhibition of mTORC1 signaling and protein synthesis in stretched myotubes. AMP-activated protein kinase inhibition increased basal mTORC1 signaling activity and protein synthesis in LLC-treated myotubes, but did not restore the stretch induction of protein synthesis. These results demonstrate that LLC-derived cachectic factors can dissociate stretch-induced signaling from protein synthesis through ERK1/2 and p38 signaling, and that glycoprotein 130 signaling is associated with the basal stretch response in myotubes.

  15. Force enhancement during and following muscle stretch of maximal voluntarily activated human quadriceps femoris. (United States)

    Hahn, Daniel; Seiberl, Wolfgang; Schwirtz, Ansgar


    Force enhancement during and following muscle stretch has been observed for electrically and voluntarily activated human muscle. However, especially for voluntary contractions, the latter observation has only been made for adductor pollicis and the ankle joint muscles, but not for large muscles like quadriceps femoris. Therefore, the aim of this study was to investigate the effects of active muscle stretch on force production for maximal voluntary contractions of in vivo human quadriceps femoris (n = 15). Peak torques during and torques at the end of stretch, torques following stretch, and passive torques following muscle deactivation were compared to the isometric torques at corresponding muscle length. In addition, muscle activation of rectus femoris, vastus medialis and vastus lateralis was obtained using surface EMG. Stretches with different amplitudes (15, 25 and 35 degrees at a velocity of 60 degrees s(-1)) were performed on the plateau region and the descending limb of the force-length relation in a random order. Data analysis showed four main results: (1) peak torques did not occur at the end of the stretch, but torques at the end of the stretch exceeded the corresponding isometric torque; (2) there was no significant force enhancement following muscle stretch, but a small significant passive force enhancement persisted for all stretch conditions; (3) forces during and following stretch were independent of stretch amplitude; (4) muscle activation during and following muscle stretch was significantly reduced. In conclusion, although our results showed passive force enhancement, we could not provide direct evidence that there is active force enhancement in voluntarily activated human quadriceps femoris.

  16. Supply chain planning classification (United States)

    Hvolby, Hans-Henrik; Trienekens, Jacques; Bonde, Hans


    Industry experience a need to shift in focus from internal production planning towards planning in the supply network. In this respect customer oriented thinking becomes almost a common good amongst companies in the supply network. An increase in the use of information technology is needed to enable companies to better tune their production planning with customers and suppliers. Information technology opportunities and supply chain planning systems facilitate companies to monitor and control their supplier network. In spite if these developments, most links in today's supply chains make individual plans, because the real demand information is not available throughout the chain. The current systems and processes of the supply chains are not designed to meet the requirements now placed upon them. For long term relationships with suppliers and customers, an integrated decision-making process is needed in order to obtain a satisfactory result for all parties. Especially when customized production and short lead-time is in focus. An effective value chain makes inventory available and visible among the value chain members, minimizes response time and optimizes total inventory value held throughout the chain. In this paper a supply chain planning classification grid is presented based current manufacturing classifications and supply chain planning initiatives.

  17. Thermal Entanglement of Anisotropic XY Chains in a Transverse Field

    Institute of Scientific and Technical Information of China (English)

    ZHAI Xiao-Yue; TONG Pei-Qing


    By using the concept of concurrence, we numerically investigate the thermal entanglement between any two nearest-neighbour spins in uniform and periodic anisotropic XY chains in a transverse field at finite temperature T. It is found that the entanglement has more than one critical temperatures on some parameter regions for uniform and periodic chains. We also discuss the behaviour of the thermal entanglement at the vicinity of quantum phase transition of periodic anisotropic XY chains and find that all the derivatives (δ)λC have similar behaviour as that of the uniform chain.

  18. Acute decrease in the stiffness of resting muscle belly due to static stretching. (United States)

    Taniguchi, K; Shinohara, M; Nozaki, S; Katayose, M


    The purpose of the study was to examine the acute effect of static stretching exercise on the resting stiffness of gastrocnemius muscle belly. Ten healthy young adults performed standing wall stretching in dorsiflexion for 1 min at a time and repeated five times. Before and after stretching, the shear modulus was measured in medial and lateral heads of the resting gastrocnemius muscle with ultrasound shear-wave elastography. After the stretching, dorsiflexion range of motion (ROM) of the ankle joint increased (P stretching, shear modulus decreased (P stretching across muscle heads. The decrease in shear modulus returned in 20 min after stretching. In the comparison group of 10 additional subjects, the standing intervention without stretching had no influence on these measures. There was a negative correlation between dorsiflexion ROM and shear modulus in either head before and after stretching. The results demonstrate the transient decreases in the stiffness of the resting gastrocnemius muscle belly and indicate that joint flexibility is greater in individuals with lower resting stiffness of the muscle belly.

  19. Stretching-induced nanostructures on shape memory polyurethane films and their regulation to osteoblasts morphology. (United States)

    Xing, Juan; Ma, Yufei; Lin, Manping; Wang, Yuanliang; Pan, Haobo; Ruan, Changshun; Luo, Yanfeng


    Programming such as stretching, compression and bending is indispensible to endow polyurethanes with shape memory effects. Despite extensive investigations on the contributions of programming processes to the shape memory effects of polyurethane, less attention has been paid to the nanostructures of shape memory polyurethanes surface during the programming process. Here we found that stretching could induce the reassembly of hard domains and thereby change the nanostructures on the film surfaces with dependence on the stretching ratios (0%, 50%, 100%, and 200%). In as-cast polyurethane films, hard segments sequentially assembled into nano-scale hard domains, round or fibrillar islands, and fibrillar apophyses. Upon stretching, the islands packed along the stretching axis to form reoriented fibrillar apophyses along the stretching direction. Stretching only changed the chemical patterns on polyurethane films without significantly altering surface roughness, with the primary composition of fibrillar apophyses being hydrophilic hard domains. Further analysis of osteoblasts morphology revealed that the focal adhesion formation and osteoblasts orientation were in accordance with the chemical patterns of the underlying stretched films, which corroborates the vital roles of stretching-induced nanostructures in regulating osteoblasts morphology. These novel findings suggest that programming might hold great potential for patterning polyurethane surfaces so as to direct cellular behavior. In addition, this work lays groundwork for guiding the programming of shape memory polyurethanes to produce appropriate nanostructures for predetermined medical applications.

  20. Effects of hamstring stretching on passive muscle stiffness vary between hip flexion and knee extension maneuvers. (United States)

    Miyamoto, N; Hirata, K; Kanehisa, H


    The purpose of this study was to examine whether the effects of hamstring stretching on the passive stiffness of each of the long head of the biceps femoris (BFl), semitendinosus (ST), and semimembranosus (SM) vary between passive knee extension and hip flexion stretching maneuvers. In 12 male subjects, before and after five sets of 90 s static stretching, passive lengthening measurements where knee or hip joint was passively rotated to the maximal range of motion (ROM) were performed. During the passive lengthening, shear modulus of each muscle was measured by ultrasound shear wave elastography. Both stretching maneuvers significantly increased maximal ROM and decreased passive torque at a given joint angle. Passive knee extension stretching maneuver significantly reduced shear modulus at a given knee joint angle in all of BFl, ST, and SM. In contrast, the stretching effect by passive hip flexion maneuver was significant only in ST and SM. The present findings indicate that the effects of hamstring stretching on individual passive muscles' stiffness vary between passive knee extension and hip flexion stretching maneuvers. In terms of reducing the muscle stiffness of BFl, stretching of the hamstring should be performed by passive knee extension rather than hip flexion.